NL2011267C2

NL2011267C2 - Method for manufacturing a product.

Info

Publication number: NL2011267C2
Application number: NL2011267A
Authority: NL
Inventors: Jan Marc Wielant; Roger Arthur Jules Ghislain Hubert
Original assignee: Onderzoekscentrum Voor Aanwending Van Staal N V
Priority date: 2013-08-05
Filing date: 2013-08-05
Publication date: 2015-02-09
Also published as: WO2015018820A1

Abstract

The invention pertains to a method for manufacturing a product, comprising the following steps: providing a electrically conductive substrate having a receiving surface, arranging said substrate in a bath containing an electrolyte that comprises Zn2+-ions and OH--ions, thereby bringing the electrolyte into contact with the receiving surface, depositing from said electrolyte a nanostructure deposit onto the receiving surface, said nanostructure deposit comprising zinc oxide and/or zinc hydroxide nanostructures that generally extend substantially perpendicular from the receiving surface, thereby forming a zinc oxide and/or zinc hydroxide with interstices being present between the nanostructures, which interstices extend to the outer surface of the nanostructure deposit away from the receiving surface, stopping said deposition of said nanostructure deposit before said interstices are filled by the nanostructures, applying a layer of material onto the nanostructure deposit and the receiving surface, with said material at least partially penetrating into the interstices between the nanostructures.

Description

Method for manufacturing a product

The invention pertains to a method for manufacturing a product.

Nowadays, many products comprise at least one component that is made of a substrate that is provided with a layer of a different material. For example, such components are covered with e.g. a metal coating, a paint, a resin, one or more polymers, a thermoplastic material, a thermosetting material, a reinforced plastic, a rubber or a ceramic coating. Furthermore, products may comprise glued components, with a layer of glue between the components that are joined.

For such components, the adhesion between the substrate and the layer that is provided on it can be an important point of attention. Insufficient adhesion can lead to various defects, from an unattractive appearance to failure of the product. For some materials that are used for layers on components, for example fluorocarbon polymers such as polytetrafluoroethylene (PTFE), it is generally difficult to obtain a good adherence to substrates, almost regardless of the type and/or chemistry of the material of the substrate.

Various methods of altering the adhesion properties of an interface between a substrate and a layer thereon have been proposed. Often, such methods are related to increasing the roughness of the surface of the substrate onto which the layer is to be applied, for example by sanding the surface of the substrate or by controlled deposition or growth of microstructures on the surface of the substrate. A rough surface increases the surface area of the substrate which can result in a higher contact area between the substrate and the applied layer and a higher physicochemical interaction. Also, it can provide mechanical interlocking between the material of the substrate and the material of the layer. It is known to provide the surface substrate with a roughness at a micrometer scale or even at nanometer scale to achieve this.

For example, W097/49549 discloses a process for producing PTFE dielectric boards on metal plate, in which one of the deposited layers is a layer of copper having a microcrystalline dendritic structure. This dendritic structure is then covered with a thin layer of copper and a thin layer of zinc, after which a PTFE-layer is applied.

The problem with providing roughness to the surface of the substrate at nanometer scale is that the process to apply this nanometer scale roughness is hardly compatible with many industrial production processes. In industrial production processes (for example industrial processes for the production of copper foil or steel) the different processing steps typically take less then a minute or even just a few seconds. However, applying a nanostructure deposit on the surface of a substrate by known deposition methods such as physical vapour deposition, hydrothermal methods or flame treatments, generally take at least several minutes up to multiple hours. Furthermore, due to the nature of these known deposition processes and the specific process conditions they require, incorporating such a known process into an industrial manufacturing process would strongly increase the complexity of the industrial manufacturing process. Therefore, it is problematic to incorporate such known deposition methods in industrial production lines, for example in production lines for manufacturing steel or for manufacturing copper foils for electric components such as printed circuit boards.

The invention aims to provide a method for manufacturing a product having a layer that is adherent to a substrate.

This object is achieved with the method according to claim 1.

In the method according to claim 1, first a substrate is provided. This substrate has an exposed receiving surface. The receiving surface is the part of the surface which in the final product will be provided with a layer of material such as a metal coating, a paint, a resin, a polymer, a thermoplastic material, a thermosetting material, a reinforced plastic, a rubber or a ceramic coating. In the method according to the invention, the adhesion properties of this receiving surface are modified.

The receiving surface can be the entire exposed surface of the substrate or just a part thereof.

In order to increase the roughness of the receiving surface at nanometer scale, a nanostructure deposit is applied to the receiving surface of the substrate.

In accordance with the invention, this is done by arranging the substrate in a bath that contains an electrolyte that, at least during the deposition step, comprises Zn2+-ions and OH" -ions. The electrolyte can be arranged any suitable receptacle or container. Arranging the substrate in the bath brings the exposed receiving surface and the electrolyte in contact with each other.

It is possible that the Zn2+-ions and OH" - ions are present in the electrolyte before the electrolyte is put into the receptacle or container, and/or before the substrate is arranged in the bath of electrolyte. Alternatively or in addition, Zn2+-ions and OH" - ions are formed in the electrolyte after the electrolyte is put into the receptacle or container, and/or after the substrate is arranged in the bath of electrolyte, e.g. due to dissolution of a part of the substrate, the coating of the substrate if such coating is present, or an electrode and/or one or more physicochemical reactions. For example, the Zn2+-ions and/or OH" - ions can be initially present in the electrolyte in the form of precursors.

From this electrolyte, a nanostructure deposit is deposited onto the receiving surface of the substrate. The deposited nanostructure deposit comprises nanostructures of zinc oxide and/or zinc hydroxide. These nanostructures of zinc oxide and/or zinc hydroxide have a first end and a second end that is located opposite said first end. At their first end, the nanostructures have a base that is attached to the receiving surface. At their second end, the nanostructures have a tip at a distance from the receiving surface.

The nanostructures generally extend in a direction substantially perpendicular to the receiving surface. “Substantially perpendicular” means that the enclosed angle between a nanostructure, as seen from its base to its tip, and the receiving surface at the location at which the base of the nanostructure is attached to the receiving surface, is between 50° and 90° (90° being perpendicular to the receiving surface). Preferably, the enclosed angle between a nanostructure, as seen from its base to its tip, and the receiving surface, is between 60° and 90°, optionally between 75° and 90°. “Generally” means that at least 60% of the deposited nanostructures have such an orientation relative to the receiving surface.

Typically, the suitable zinc oxide and/or zinc hydroxide individual nanostructures have at least one dimension, such as a diameter and/or length, that is less than 1 pm, optionally a few hundreds of nanometers, for example between 200 and 900 nanometers. The zinc oxide and/or zinc hydroxide individual nanostructures can have a variety of shapes, for example nanowires, nanopillars, nanocones, nanocolumns, nanorods, and/or nanodendrites.

The zinc oxide and/or zinc hydroxide nanostructure deposit that is formed by the deposition from the electrolyte has nanostructures with interstices being present between the nanostructures. These interstices extend to the outer surface of the nanostructure deposit away from the receiving surface.

One of the parameters that is generally used in the art to characterize the morphology of nanostructure deposits is the packing density. The packing density of the nanostructure deposit indicates how much of the total surface area of the receiving surface is covered by the bases of the nanostructures. As in accordance with the invention, interstices are present between the nanostructures, the packing density of the nanostructure deposit according to the invention is likely to be relatively low. Optionally, the packing density is between about 10% to about 70%, for example between about 30% and about 60%.

It is possible that the nanostructure deposit comprises nanostructures that are spaced apart from the other nanostructures. If this is the case, the interstice between two adjacent nanostructures extends all the way to the receiving surface. Alternatively or in addition, it is possible that the nanostructure deposit comprises nanostructures that are agglomerated with each other on the side of the receiving surface, but not on the side of the tips of the nanostructures.

It is possible that some nanostructures are agglomerated at their tips with one or more adjacent nanostructures. However, it is not desirable that a large percentage of the nanostructures (e.g. more than 60%) are agglomerated with each other on the side of the tips of adjacent nanostructures as this is thought to have a detrimental effect on the adhesion between the receiving surface and the layer that is applied onto it.

Zinc oxide nanostructure deposits as such are known for example for electrical or optical applications, e.g. in LED’s or solar cells. However, the zinc oxide and/or zinc hydroxide nanostructure deposit according to the invention has a different morphology than zinc oxide nanostructure deposits that are generally used in electrical or optical applications. In the nanostructure deposit according to the invention, the nanostructure deposit has a lower packing density and is much thinner than the nanostructure deposits that are generally used for electrical or optical applications.

In accordance with the invention, the deposition of the nanostructure deposit is stopped before the interstices are filled by the zinc oxide and/or zinc hydroxide nanostructures by the agglomeration of the nanostructures, in particular the agglomeration of the nanostructures on the side of the tips of the nanostructures. Stopping the deposition in time ensures a good nanometer scale roughness of the receiving surface of the substrate.

After the deposition of the nanostructure deposit has stopped, a layer of material is applied onto the nanostructure deposit which is present on the receiving surface. In accordance with the invention, the material of this layer at least partly penetrates into the interstices between the zinc oxide and/or zinc hydroxide nanostructures. It is not required that all interstices are entirely filled by the material of the applied layer. Some interstices may be filled partly or even not at all.

In case an interstice extends all the way to the receiving surface, the material of the applied layer may contact the receiving surface.

It was found that when applying the method according to the invention, the nanostructure deposit of zinc oxide and/or zinc hydroxide nanostructures to the receiving surface generally improves the adhesion between the receiving surface and the layer of material that is applied to the substrate at the location of the receiving surface, over the nanostructure deposit. It was also observed that this improvement in adhesion can be obtained by a very quick deposition of the nanostructure deposit.

Generally, in the method according to the invention, the deposition of the nanostructure deposit does not have to take any longer than a few seconds in order for improved adhesion properties of the receiving surface to occur. In some experiments, improved adhesion properties were already measured for substrates onto which the deposition of the nanostructure deposit lasted one a second or less.

Because the method according to the invention allows to improve the adhesion properties of the receiving surface within a short period of time, the method according to the invention can be incorporated in high speed production processes that for example have process times of 1 minute or less for each process step, such as processes for producing copper foils (as e.g. are used in the manufacture of electronic components such as printed circuit boards) or processes for the production of galvanized products. In such processing lines, an additional processing unit can be arranged in which the method according to the invention is carried out.

Furthermore, it was surprising to find that the improvement of the adhesion occurred without further measures to strengthen the bond between the zinc oxide and/or zinc hydroxide nanostructures and the receiving surface, e.g. by baking or other thermal treatment, as is sometimes used in the art to secure zinc oxide and/or zinc hydroxide nanostructures onto the substrate on which they are provided. The zinc oxide and/or zinc hydroxide nanostructures that are deposited on the receiving surface in accordance with the invention show generally strong adherence to the receiving surface. Furthermore, it was found that zinc oxide and/or zinc hydroxide nanostructures as deposited in accordance with the invention have a good resistance against high temperatures, better than for example the thin layer of zinc as applied in accordance with W097/49549. This is very useful in for example the production of electrical components such as printed circuit boards, as this often involves production steps that are carried out at elevated temperatures and pressures, for example in an autoclave.

It is noted that the improvement of the adhesion also occurs when the material of the receiving surface and/or the material of the layer that is provided over the nanostructure deposit is not zinc.

Optionally, the deposition of the nanostructure deposit is carried out by electrodeposition or by electroless deposition. In case the deposition of the nanostructure deposit is carried out by electrodeposition, at least the receiving surface of the substrate is electrically conductive, and/or at least electrically conductive under the process conditions that are present during the deposition of the nanostructure deposit.

Optionally, the substrate is electrically conductive, at least under the process conditions that are present during the deposition of the nanostructure deposit.

Optionally, the deposition time, which is the time it takes to deposit the nanostructure deposit, is about 0.1 seconds to about 5 minutes. In a possible embodiment, the deposition time is about 0.1 seconds to about 180 seconds. In a further possible embodiment, the deposition time is about 0.1 seconds to about 1 minute. In a further possible embodiment, the deposition time is about 0.2 seconds to about 50 seconds. In a further possible embodiment, the deposition time is about 0.2 seconds to about 20 seconds. In a further possible embodiment, the deposition time is about 0.5 seconds to about 10 seconds. In a further possible embodiment, the deposition time is about 3 seconds to about 8 seconds. In a further possible embodiment, the deposition time is about 20 seconds to about 40 seconds. In a further possible embodiment, the deposition time is about 0.1 seconds to about 10 seconds.

The selection of the optimal deposition time is to be made on the basis of process parameters like the materials of the receiving surface, the material of the layer that is provided over the nanostructure deposit, the intended use of the product that is manufactures, the potential or current that is applied in case of deposition of the nanostructure deposit by means of electrodeposition, the temperature at which the deposition takes place and the concentration of the Zn2+-ions and OH' - ions in the electrolyte during the deposition.

It is noted that generally the shorter deposition times as indicated above are sufficient to obtain improvement of the adhesion properties of the receiving surface. Sometimes, the longer deposition times can be desired as these may produce a nanostructure deposit that may have additional advantageous properties, such as better durability or better corrosion resistance. However, when the deposition time is significantly longer than indicated above, the improvement of the adhesion properties of the receiving surface could decrease and/or maybe even finally disappear.

It has been observed that nanostructure deposits comprising a large percentage of nanostructures that extend in a direction substantially perpendicular to the receiving surface, generally show good improvement of adhesion properties of the receiving surface. The direction of the receiving surface in this respect has to be regarded at the location at which the nanostructure’s base is attached to it, so taking into account the microstructure of the receiving surface. “Substantially perpendicular” means that the enclosed angle between a nanostructure, as seen from its base to its tip, and the receiving surface at the location at which the base of the nanostructure is attached to the receiving surface, is between 50° and 90° (90° being perpendicular to the receiving surface). Preferably, the enclosed angle between a nanostructure, as seen from its base to its tip, and the receiving surface, is between 60° and 90°, optionally between 75° and 90°.

So, apparently, the adhesion improvement that is observed is not just due to the increased roughness of the receiving surface at nanometer scale, but the direction in which the zinc oxide and/or zinc hydroxide nanostructures extend relative to the receiving surface at or near the base of that nanostructure apparently also plays a role. This may be related to the type and/or direction of the mechanical stresses that are for example exerted on the nanostructures during the performance of adhesion tests or when the substrate is used for example in a product. Maybe the zinc oxide or zinc hydroxide nanostructures are more effective when they are subjected to tension or compression than when they are subjected to bending.

In a possible embodiment, the substrate that is used is a metal substrate. Optionally the metal substrate is of copper, stainless steel or galvanized steel. An example of a metal substrate is copper foil.

In a possible embodiment, the receiving surface is of copper, a copper alloy, steel (e.g. stainless steel or carbon steel), zinc or a zinc alloy, aluminum or aluminum alloy. For example, the receiving surface can be of zinc, a zinc alloy, aluminum or aluminum alloy when the substrate is a galvanized steel, e.g. a batch galvanized steel, an electrogalvanized steel or hot dip galvanized steel, or a steel, e.g. a carbon steel, provided with metal coating such as an aluminum coating, a zinc-aluminum coating, an aluminum-zinc coating, a zinc-iron alloy coating, a zinc-aluminum-magnesium coating or a aluminum-silicon coating. The receiving surface can be subjected to a treatment before the nanostructure deposit is deposited, for example a treatment in which oxides (for example copper oxides) are formed on the receiving surface.

In a possible embodiment, the material of the layer that is applied onto the nanostructure deposit is a metal, a glue (for example an adhesive resin), a polymer, a paint, an electrically insulating material, a ceramic and/or a plastic (for example a reinforced plastic). In case the material of the layer that is applied onto the nanostructure deposit is a metal, the material can for example be a zinc, zinc alloy, aluminum or aluminum alloy that is applied as a coating onto the substrate.

In a possible embodiment, the substrate is made of a single material. In a different embodiment, the substrate comprises a base material that has a coating applied to it. The coating optionally forms the receiving surface or a part thereof, making that the material of the receiving surface is entirely or partly different from the base material of the substrate. Alternatively or in addition to both these embodiments, the material of the receiving surface and/or the substrate may be supported by a support material that is different from the material of the receiving surface and/or the material of the substrate. It is possible that the substrate comprises multiple layers of material already prior to carrying out the method according to the invention.

It is possible that the method according to the invention is carried out multiple times on the same substrate. In such an embodiment, the layer of material that has been deposited on the nanostructure deposit forms the receiving surface in a subsequent performance of the method according to the invention.

Optionally, the material of the layer that is applied onto the nanostructure deposit is an fluorocarbon polymer, for example PTFE. Experiments have shown that with the method according to the invention, a significant improvement in het adhesion of a PTFE-layer onto an adhesion structure can be obtained.

In a possible embodiment, the receiving surface is made of copper and the material of the layer that is applied onto the nanostructure deposit is PTFE. Experiments have shown very good results for the obtained adhesion between a copper receiving surface (for example on a copper foil substrate) and a PTFE layer.

In a possible embodiment, the Zn2+ - ions in the electrolyte originate from aqueous solution of one or more of ZnCI2, Zn(N03)2, Zn(CH3COO)2. Alternatively, the Zn2+ - ions in the electrolyte originate from dissolved zinc coming from a zinc substrate, a zinc coated substrate a zinc alloy substrate, a zinc alloy coated substrate and/or a zinc electrode.

In a possible embodiment, the OH' - ions in the electrolyte originate from hydroxides (e.g. NaOH), from the cathodic reduction of one or more oxidizing agents, for example 02, 03, peroxides such as H202, nitrates such as Zn(N03)2, hypochlorates such as Zn(OCI)2, persulfates and/or from one ore more salts for example Zn(CH3COO)2.

In a possible embodiment, when the deposition of the zinc oxide and/or zinc hydroxide nanostructure deposit is carried out by electrodeposition or electroless deposition, the electrolyte is an aqueous solution, comprising: - ZnCI2 and H202, or - ZnCI2, saturated with oxygen, or - hydrated Zn(N03)2.

In a possible embodiment, electroless deposition of zinc oxide and/or zinc hydroxide nanostructures is used in the method according to the invention to form the nanostructure deposit on the receiving surface. In such an embodiment, for example an electrogalvanized steel substrate is used. For example due to presence of an oxidizing agent in the electrolyte (for example H202) in combination with the zinc of the electrogalvanized substrate, a spontaneous reaction will start that comprises the following steps:

In a first step, the zinc is oxidized (Zn —► Zn2+ + 2e) and the oxidizing agent (for example H202) is reduced (H202 + 2e' —► 20FT). Together, this results in the following redox reaction: Zn + H202 —► Zn2+ + 20H'.

In a subsequent step, due to a high pH at the surface of the substrate, spontaneously a zinc hydroxide deposit is formed: Zn2+ + 20H' —► Zn(OH)2.

In a possible further subsequent step, the hydroxide deposit may be dehydrated: Zn(OH)2 -» ZnO + H20.

In a possible embodiment, electrodeposition of zinc oxide and/or zinc hydroxide nanostructures is used in the method according to the invention to form the nanostructure deposit on the receiving surface.

In such an embodiment, the deposition process is initiated by applying a cathodic potential on the substrate material. If an oxidizing agent is present in the electrolyte (for example H202), the cathodic potential preferably reduces the oxidizing agent, which results in the formation of OH-ions, for example due to this reaction: H202 + 2e' —► 20H'.

Alternatively or in addition, other oxidizing agents than H202 are present. For example, oxygen is used as an oxidizing agent. This leads to following reaction: 02 + 2H20 + 4 e' --> 4 OH'. Oxygen can be introduced into the electrolyte for example by oxygen bubbling or air bubbling.

As another example, nitrate can be used as an oxidizer. In that case, the following reaction occurs: N03~ + H20 + 2 e' --> N02” +20H". OH' can also be formed when a salt (for example Zn(CH3COO)2) is added to water or to an aqueous solution. For example, then the following hydrolysis reaction may occur: Zn(CH3COO)2 + 2H20 -» Zn2+ + 2CH3COOH + 20H".

The subsequent reaction step or steps can be the same as for electroless deposition, so first, due to a high pH at the surface of the substrate, spontaneously a zinc hydroxide deposit is formed: Zn2+ + 20H' —► Zn(OH)2.

In a possible further subsequent step, the hydroxide deposit may be dehydrated: Zn(OH)2 -► ZnO + H20.

In a possible embodiment, the electrolyte comprises one or more additives, for example a shape controlling agent, a complexing agent (for example ethylenediaminetetraacetic acid (EDTA)), corrosion inhibitor, and/or surfactant. Optionally, one or more of these additives are deposited onto the receiving surface, either before, after or during the deposition of the nanostructure deposit of zinc oxide and/or zinc hydroxide nanostructures. The deposition of such an additive can contribute to the further optimization and/or tailoring of the properties of the receiving surface, the nanostructure deposit and/or the layer that is deposited onto the nanostructure deposit, and/or the bonding between any two of those. Optionally, the electrolyte may contain a pH adjusting agent in the form of an acid or base to adjust the pH of the solution.

Experiments have shown that the concentration of Zn2+-ions and OH' -ions in the electrolyte is a relevant process parameter, as it has an influence on the deposition speed of the nanostructure deposit onto the receiving surface and also on the shape of the nanostructures that are formed.

Experiments have shown that in embodiments of the invention wherein the electrolyte is an aqueous solution comprising ZnCI2, a concentration of ZnCI2 between about 1 mM and about 100 mM, preferably between about 2 mM and about 60 mM, allows to obtain a nanostructure deposit in accordance with the invention. In a particular embodiment, a concentration of ZnCI2 between about 2 mM and about 10 mM, optionally between about 3 mM and about 5 mM, is used.

In a different embodiment, a concentration between about 15mM and about 65 mM, optionally between about 20mM and about 60mM, optionally between about 30 and about 50 mM, optionally between about 35 mM and about 45 mM, is used.

Furthermore, experiments have shown that in embodiments of the invention wherein the electrolyte is an aqueous solution comprising H202, a concentration of H202 between about 10 mM and about 100 mM allows to obtain a nanostructure deposit in accordance with the invention. In a particular embodiment, the concentration of H202 is between about 15 mM and about 50 mM, optionally between about 20 mM and about 40 mM.

In a possible embodiment, the deposition of the nanostructure deposit is carried out at a temperature between about 40°C and about 98°C, optionally between about 65 °C and about 95°C, optionally between about 80°C and about 90°C.

In a possible embodiment wherein the deposition of the nanostructure deposit is carried out by electrodeposition, the electrodeposition is carried out potentiostatically. In such an embodiment, the potential that is applied to the substrate during the electrodeposition, as is determined versus a saturated calomel electrode, is preferably between about -0.5V and about -2.5V versus a saturated calomel electrode, preferably between about -1V and about -2V, optionally between about -1.2V and about - 1.8V. In a particular embodiment, the potential is between about -1.3V and about -1.5V. In a different embodiment, the potential is between about -1,6V and about -1,8V. The potential of a saturated calomel electrode versus a standard hydrogen electrode is +0.244 V.

In a possible embodiment, the deposition of the nanostructure is carried out galvanostatically by electrodeposition, the current density that is applied between the receiving surface of the substrate and an anode (e.g. platinum or metal coated titanium (DSA)) is between about 0.0001 A/cm2and about 10 A/cm2, preferably between about 0.001 A/cm2and about 1 A/cm2. In a particular variant of this embodiment, the current is between about 0.005 A/cm2 and about 0.5 A/cm2. The receiving surface, optionally the entire substrate, acts as a cathode in this set-up.

In a possible embodiment, the deposition of the nanostructure deposit is carried out in about 0.1 seconds to about 5 minutes, preferably in about 0.1 seconds to about 180 seconds, optionally in about 0.1 seconds to about 1 minute, optionally in about 0.2 seconds to about 50 seconds, optionally in about 0.2 seconds to about 20 seconds, optionally in about 0.5 seconds to about 10 seconds, optionally in about 3 seconds to about 8 seconds, optionally between about 20 seconds and about 40 seconds, optionally in about 0.1 seconds to about 10 seconds, and the electrolyte is an aqueous solution comprising ZnCI2, wherein the concentration of ZnCI2is between about 15mM and about 65 mM, optionally between about 20mM and about 60mM, optionally between about 30 mM and about 50 mM, optionally between about 35 mM and about 45 mM, and the electrolyte further comprises H202, wherein the concentration of H202 is between about 10 mM and about 100 mM, optionally between about 15 mM and about 50 mM, optionally between about 20 mM and about 40 mM.

Optionally, in this embodiment, the deposition of the nanostructure deposit is carried out at a temperature between about 80°C and about 90°C.

Optionally, in this embodiment, either at the temperature mentioned above or not, the deposition of the nanostructure deposit is carried out by electrodeposition and the potential that is applied to the substrate during the electrodeposition, as is determined versus a saturated calomel electrode, is between about -1 V and about -2 V, optionally between about -1.2 V and about -1.8 V, for example between about -1.3 V and about -1.5 V or between about -1.6 V and about -1.8 V.

Optionally, in this embodiment, either carried out with or without the optional features mentioned in the previous paragraphs, the receiving surface is of copper or stainless steel.

Optionally, in this embodiment, either carried out with or without the optional features mentioned in the previous paragraphs, the material of the layer that is applied onto the nanostructure deposit is an epoxy, an acrylic or acrylate material, a polyimide or PTFE.

In a first possible variant of the embodiment described above, the deposition of the nanostructure deposit is carried out in in about 0.1 seconds to about 1 minute, and the electrolyte is an aqueous solution comprising ZnCI2, wherein the concentration of ZnCI2 is between about 30 mM and about 50 mM, and the electrolyte further comprises H202, wherein the concentration of H202 is between about 15 mM and about 50 mM. In this variant, the deposition of the nanostructure deposit is carried out at a temperature between about 80°C and about 90°C. In this variant, the deposition of the nanostructure deposit is carried out by electrodeposition and the potential that is applied to the substrate during the electrodeposition, as is determined versus a saturated calomel electrode is between about -1.2 V and about - 1.8 V, for example between about -1.3 V and about -1.5 V or between about -1.6 V and about -1.8 V. In this first variant, the receiving surface is preferably of copper or stainless steel and the material of the layer that is applied onto the nanostructure deposit preferably is an epoxy, an acrylic or acrylate material.

In a second possible variant of the embodiment described above, the deposition of the nanostructure deposit is carried out in in about 0.1 seconds to about 1 minute, and the electrolyte is an aqueous solution comprising ZnCI2, wherein the concentration of ZnCI2 is between about 35 mM and about 45 mM, and the electrolyte further comprises H202, wherein the concentration of H202 is between about 20 mM and about 40 mM. In this variant, the deposition of the nanostructure deposit is carried out at a temperature between about 80°C and about 90°. In this variant, the deposition of the nanostructure deposit is carried out by electrodeposition and the potential that is applied to the substrate during the electrodeposition, as is determined versus a saturated calomel electrode is between about -1.6V and about -1,8V. In this second variant, the receiving surface preferably is of copper and the material of the layer that is applied onto the nanostructure deposit preferably is an acrylic or acrylate material.

In a third possible variant of the embodiment described above, the deposition of the nanostructure is carried out in in about 0.1 seconds to about 10 seconds, and the electrolyte is an aqueous solution comprising ZnCI2, wherein the concentration of ZnCI2 is between about 35 mM and about 45 mM, and the electrolyte further comprises H202, wherein the concentration of H202 is between about 20 mM and about 40 mM. In this variant, the deposition of the nanostructure is carried out at a temperature between about 80°C and about 85°. In this variant, the deposition of the nanostructure is carried out by electrodeposition and the current that is applied during the electrodeposition is between about 0.005 A/cm2 and about 0.5 A/cm2. In this third variant, the receiving surface preferably is of copper and the material of the layer that is applied onto the combination of the adhesion surface and the nanostructure preferably is epoxy, polyimide or PTFE.

The invention further pertains to products that can be manufactured by the method according to the invention. A first example of such a product is an electrical component, comprising: - a substrate having a receiving surface, which receiving surface is made of an electrically conductive material, - on said receiving surface and attached thereto, a nanostructure deposit comprising nanostructures of zinc oxide and/or zinc hydroxide, which nanostructures have a first end and a second end that is located opposite said first end, wherein the nanostructures have a base at their first end that is attached to the receiving surface and a tip at a distance from the receiving surface at their second end, which nanostructures generally extend in a direction substantially perpendicular to the receiving surface, which nanostructure deposit has interstices between the nanostructures, which interstices extend to the outer surface of the nanostructure deposit away from the receiving surface, - a layer of material, for example electrically insulating material, which is present on the nanostructure deposit, said material of said layer at least partially penetrating into the interstices between the zinc oxide and/or zinc hydroxide nanostructures. A second example of such a product is a printed circuit board, comprising: - a copper foil, which copper foil has a receiving surface, - on said receiving surface and attached thereto, a nanostructure deposit comprising nanostructures of zinc oxide and/or zinc hydroxide, which nanostructures have a first end and a second end that is located opposite said first end, wherein the nanostructures have a base at their first end that is attached to the receiving surface and a tip at a distance from the receiving surface at their second end, which nanostructures generally extend in a direction substantially perpendicular to the receiving surface, which nanostructure deposit has interstices between the nanostructures, which interstices extend to the outer surface of the nanostructure deposit away from the receiving surface - a layer of electrically insulating material which is present on the nanostructure deposit, said material of said layer at least partially penetrating into the interstices between the zinc oxide and/or zinc hydroxide nanostructures.

Optionally, in such a printed circuit board, the electrically insulating material is PTFE. A third example of such a product is metal component, comprising: - a substrate which is made of stainless steel or a carbon steel optionally having a coating that comprises zinc and/or aluminum, which substrate has a receiving surface, - on said receiving surface and attached thereto, a nanostructure deposit comprising nanostructures of zinc oxide and/or zinc hydroxide, which nanostructures have a first end and a second end that is located opposite said first end, wherein the nanostructures have a base at their first end that is attached to the receiving surface and a tip at a distance from the receiving surface at their second end, which nanostructures generally extend in a direction substantially perpendicular to the receiving surface, which nanostructure deposit has interstices between the nanostructures, which interstices extend to the outer surface of the nanostructure deposit away from the receiving surface - a layer of material which is present on the nanostructure deposit, said material of said layer at least partially penetrating into the interstices between the zinc oxide and/or zinc hydroxide nanostructures.

Optionally, in such a metal component, the material of the layer that is applied onto the nanostructure deposit is a metal, a glue for example an adhesive resin, a polymer, a paint, an electrically insulating material and/or a plastic.

The invention will be described in more detail below under reference to the drawing, in which in a non-limiting manner exemplary embodiments of the invention will be shown.

The drawing shows in:

Fig. 1 : an example of a substrate, before carrying out the method according to the invention,

Fig. 2: the substrate of fig. 1 in a bath of electrolyte according to the invention,

Fig. 3: a nanostructure deposit according to the invention, deposited on the receiving surface of the substrate,

Fig. 4: the substrate, the nanostructure deposit according to the invention with a layer of material applied to it,

Fig. 4a: a detail of the receiving surface before and after deposition of the nanostructure deposit,

Fig. 5: a schematic representation of an industrial process for manufacturing copper foil, Fig. 6: a process set up for carrying out the method according to the invention,

Fig. 7: the compared results of T-peel tests carried out on different test specimens,

Fig. 8: the results of T-peel tests on further test specimens,

Fig. 9: the results of pull-off tests on different test specimens,

Fig. 10: the results of pull-off tests on further test specimens Fig. 11: the results of pull-off tests on more further test specimens,

Fig. 12: a schematical cross section of a part of a product that can be made using the method according to the invention,

Fig. 13: a schematical cross section of a part of a product that can be made using the method according to the invention.

Figures 1,2, 3, and 4 show in a schematic way several stages of the method according to the invention.

Fig. 1 shows a substrate 1 prior to carrying out the method according to the invention. The substrate 1 in the example of fig. 1 is a strip of metal, but alternatively the substrate can have a different shape and/or be made of a different material. The substrate is for example made of copper, stainless steel or galvanized steel (for example hot dip galvanized steel or electrogalvanized steel). The substrate can be made of a single material, but optionally it comprises a base material that has a coating applied to it, resulting in a material for the receiving surface that is different from the base material of the substrate. Alternatively or in addition, the material of the receiving surface may be supported by a support material that is different from the material of the receiving surface. For example, if a copper foil (for example of the type that is used in the production of electrical components, e.g. printed circuit boards) is subjected to the method according to the invention, the receiving surface will be of copper. It is however possible that during processing of the copper foil using the method of the invention, the copper foil is supported by a support. This support can be for example made of a plastic or a metal.

The substrate 1 of fig. 1 has an exposed receiving surface 2. The receiving surface 2 can be the entire exposed outer surface of the substrate 1, or a part of it. In case the receiving surface is just a part of the exposed outer surface of the substrate 1, optionally, the rest of the exposed outer surface is shielded such that the formation of a zinc oxide and/or zinc hydroxide nanostructure deposit on it is prevented.

Optionally, the substrate is cleaned (e.g. ultrasonically, for example in a mixture of ethanol and methanol or in an alkaline cleaning solution) before proceeding further with the method according to the invention.

Fig. 2 shows a stage in the method according to the invention. Here, the substrate 1 with the exposed receiving surface 2 is arranged in a container or receptacle 5 that contains an electrolyte 6. The container or receptacle 5 is preferably made of a material that is chemically inert to the electrolyte 6 that is used in the method according to the invention. The electrolyte 6 contains Zn2+ - ions 7, which are schematically indicated by circles in fig. 2. The electrolyte 6 also contains OH' - ions 8, which are schematically indicated by squares in fig. 2. The exposed receiving surface 2 of the substrate 1 is in contact with the electrolyte 6.

The deposition of zinc oxide and/or zinc hydroxide nanostructures from the electrolyte 6 onto the receiving surface 2 of the substrate can be effected in different ways, for example by electroless deposition or by electrodeposition.

In case electrodeposition is chosen for effecting the deposition of zinc oxide and/or zinc hydroxide nanostructures, at least one counter electrode 10 is provided, which counter electrode 10 is in contact with the electrolyte 6. The counter electrode is for example a platinum or coated titanium electrode. An electric potential is then applied between the counter electrode 10 and the substrate 1, by means of a power supply 11 that is connected by electrical connection wires 12 to the electrode 10 and to the substrate 1. Optionally, an additional electrode can be provided (not shown) to operate as a reference electrode. For example, the additional electrode can be a saturated calomel electrode. The additional electrode is in contact with the electrolyte and connected to the power supply 11.

In case of electroless deposition, no counter electrode 10 or power supply 11 is required.

The Zn2+-ions 7 in the electrolyte 6 may originate for example from a zinc electrode or from a dissolved zinc salt. For example, source of the Zn2+- ions 7 in the electrolyte is an aqueous solution of one or more of ZnCI2, Zn(N03)2, or Zn(CH3COO)2. Alternatively, the Zn2+ - ions in the electrolyte originate from dissolved zinc coming from a zinc substrate, a zinc coated substrate a zinc alloy substrate, a zinc alloy coated substrate and/or a zinc electrode.

The OFT - ions 8 in the electrolyte 6 for example originate from a combination of water and one or more of 02, 03, peroxides (e.g. H202), nitrates, hypochlorites, persulfates or organic salts (e.g. Zn(CH3COO)2). In case the source of the OFT - ions 8 in the electrolyte 6 originate from oxygen (02), the oxygen can be introduced into the electrolyte e.g. by bubbling air or oxygen gas.

Examples of suitable electrolytes include aqueous solutions comprising for example ZnCI2 and FH202, or ZnCI2 with oxygen and air bubbling, or Zn(N03)2.

The electrolyte may comprise one or additives, e.g. a corrosion inhibitor or a surfactant. Optionally, material from one or more of the additives is deposited on the receiving surface along with the zinc oxide or zinc hydroxide nanostructures in order to influence the properties of the receiving surface, the nanostructure deposit and/or the layer on the nanostructure deposit. Optionally, the electrolyte may contain an acid or base to adjust the pFH of the solution.

The Zn2+-ions 7 and the OFT - ions 8 in the electrolyte 6 react with each other to form Zn(OFI)2, which then decomposes into zinc oxide (ZnO) and water (Fl20). The zinc oxide and/or zinc hydroxide is precipitated in the form of zinc oxide and/or zinc hydroxide nanostructures onto the exposed receiving surface 2 of the substrate 1 that is arranged in the electrolyte 6.

According to the invention, the process conditions of the deposition of the zinc oxide and/or zinc hydroxide nanostructures are chosen such that the nanostructures that are formed have a first end and a second end that is located opposite said first end, wherein the nanostructures have a base at their first end that is attached to the receiving surface and a tip at a distance from the receiving surface at their second end, which nanostructures generally extend in a direction substantially perpendicular to the receiving surface.

The process conditions are such that the nanostructures together form a nanostructure deposit with interstices being present between the nanostructures, which interstices extend to the outer surface of the nanostructure deposit away from the receiving surface,

Concentration of the Zn2+ - ions, concentration of the OH' - ions, temperature, and in case electrodeposition is used to deposit the nanostructure deposit onto the receiving surface, the electric potential or electric current that is applied in case of electrodeposition are relevant process parameters that influence the speed at which the nanostructures are deposited and the final morphology of the nanostructures and the nanostructure deposit.

In a different embodiment, a concentration between about 15mM and about 65 mM, optionally between about 20mM and about 60mM, optionally between about 30 mM and about 50 mM, optionally between about 35 mM and about 45 mM, is used.

In a possible embodiment wherein the deposition of the nanostructure deposit is carried out by electrodeposition, the potential that is applied to the substrate, as determined versus a saturated calomel electrode, during the electrodeposition is between about -0.5V and about -2.5V, preferably between about -1V and about -2V, optionally between about -1.2V and about -1.8V. In a particular embodiment, the potential is between about -1.3V and about -1.5V. In a different embodiment, the potential is between about -1.6V and about -1.8V.

In a possible embodiment, the process parameters mentioned above are applied as follows: the deposition of the nanostructure deposit is carried out in about 0.1 seconds to about 5 minutes, preferably in about 0.1 seconds to about 180 seconds, optionally in about 0.1 seconds to about 1 minute, optionally in about 0.2 seconds to about 50 seconds, optionally in about 0.2 seconds to about 20 seconds, optionally in about 0.5 seconds to about 10 seconds, optionally in about 3 seconds to about 8 seconds, optionally in about 20 seconds to about 40 seconds, optionally in about 0.1 seconds to about 10 seconds, and the electrolyte is an aqueous solution comprising ZnCI2, wherein the concentration of ZnCI2is between about 15mM and about 65 mM, optionally between about 20mM and about 60mM, optionally between about 30 mM and about 50 mM, optionally between about 35 mM and about 45 mM, and the electrolyte further comprises H202, wherein the concentration of H202 is between about 10 mM and about 100 mM, optionally between about 15 mM and about 50 mM, optionally between about 20 mM and about 40 mM.

Optionally, in this embodiment, the deposition of the nanostructure deposit is carried out at a temperature between about 80°C and about 90°.

Optionally, in this embodiment, either at the temperature mentioned above or not, the deposition of the nanostructure deposit is carried out by electrodeposition and the potential that is applied during the electrodeposition is between about -1V and about -2V, optionally between about -1,2V and about -1,8V, for example between about -1,3V and about -1,5V or between about -1,6V and about -1,8V.

Fig. 3 schematically shows deposited zinc oxide and/or zinc hydroxide nanostructures 21 onto the receiving surface 2 of the substrate 1. The zinc oxide and/or zinc hydroxide nanostructures 21 together form a nanostructure deposit 20 that covers at least a part of the receiving surface 2.

The nanostructures 21 have a tip 22 and a base 23. The base 23 is attached to the receiving surface 2. The tip 22 is located at the opposite end of the nanostructure 21, at a distance from the receiving surface 2. The nanostructures 21 extend in a direction away from the receiving surface 2 (when seen from base 23 to tip 22). Generally, the nanostructures 21 extend substantially perpendicular to the receiving surface 2.

The packing density of the nanostructures 21 within the nanostructure deposit 20 is relatively low, preferably between about 10% and about 70%. Interstices 25 are present between adjacent nanostructures 21. These interstices 25 extend to the outer surface 24 of the nanostructure deposit 20, on the side away from the receiving surface 2. This outer surface 24 is indicated by a dashed line in fig. 3.

As can be seen in fig. 3, the interstices 25 may extend all the way to the receiving surface 2. This is however not necessary. Figure 3 also shows some nanostructures that have agglomerated at their base with adjacent nanostructures, but that still have interstices between them closer to the tip.

This type of nanostructure deposit allows to be deposited quickly. For example, the deposition of the nanostructure deposit in accordance with the invention can be carried out in about 0.1 seconds to about 5 minutes, or even in about 0.1 seconds to about 180 seconds. In a possible embodiment, the deposition time is about 0.1 seconds to about 1 minute. In a further possible embodiment, the deposition time is about 0.2 seconds to about 50 seconds.

In a further possible embodiment, the deposition time is about 0.2 seconds to about 20 seconds. In a further possible embodiment, the deposition time is about 0.5 seconds to about 10 seconds. In a further possible embodiment, the deposition time is about 3 seconds to about 8 seconds. In a further possible embodiment, the deposition time is about 20 seconds to about 40 seconds. In a further possible embodiment, the deposition time is about 0.1 seconds to 10 seconds.

Fig. 4 schematically shows a further stage in the method according to the invention. A layer 30 of material is applied over the combination of the nanostructure deposit 20 and the receiving surface 2 of the substrate 1.

The material of the layer 30 extends into the interstices 25 between the zinc oxide and/or zinc hydroxide nanostructures 21. The material of the layer 30 may or may not extend into the entire depth of an interstice, and may or may not be in contact with the receiving surface 2 between the nanostructures 21 of the nanostructure deposit.

The material of the layer for example is a metal (e.g. a protective metal coating), a glue ( e.g. an adhesive resin), a paint, a polymer, an electrically insulating material and/or a plastic (e.g. an amorphous fluorocarbon polymer, for example PTFE).

For example, the adhesion between a copper receiving surface (for example of a substrate of copper foil) and a layer of PFTE has shown to be good when the method according to the invention was applied.

Fig. 4a shows a detail of the receiving surface before (top) and after (bottom) the deposition of the nanostructure deposit.

As can be seen in fig. 4a, the receiving surface 2 has a roughness, which makes that on micrometer scale the receiving surface 2 is not flat. In accordance with the invention, the nanostructures 21 generally extend in a direction substantially perpendicular to the receiving surface at the location where the base of the nanostructure is attached to the receiving surface. The enclosed angle a between a nanostructure 21, as seen from its base to its tip, and the receiving surface 2 at the location at which the base of the nanostructure is attached to the receiving surface determines whether a nanostructure 21 extends substantially perpendicular to the receiving surface or not. So, the micrometer scale roughness of the receiving surface is taken into account when determining the enclosed angle a between the receiving surface 2 and the nanostructure 21.

In accordance with the invention, the enclosed angle a is between 50° and 90° (90° being perpendicular to the receiving surface). Preferably, the enclosed angle between a nanostructure, as seen from its base to its tip, and the receiving surface, is between 60° and 90°, optionally between 75° and 90°. At least 60% of the deposited nanostructures have such an orientation relative to the receiving surface.

Fig. 5 shows a schematic representation of an industrial process for manufacturing copper foil.

In this process, a reservoir 50 with electrolyte is provided. This reservoir 50 is in fluid communication with composition adjustment tank 51, in which the composition of the electrolyte is adjusted to meet the requirements of the process.

From the composition adjustment tank 51, the electrolyte flows to electrodeposition cell 53 via electrolyte supply line 52 in the direction of arrow A.

The electrodeposition cell 53 comprises electrolyte bath 60, which contains a quantity of electrolyte 56. In the bath, an anode 55 is provided. A rotatable cathode drum 54 extends into the electrolyte. An electric potential or electrical current is applied to the anode and/or cathode, so that an electrodeposition process takes place in which copper is deposited onto the rotatable cathode drum. The deposited copper is then removed from the rotatable cathode drum 54 as it rotated, resulting in a copper film 58, which is then collected onto roll 59.

The electrolyte is returned from the bath 60 to the reservoir 50.

This process can be carried out in a continuous way.

Fig. 6 shows a process set up for carrying out the method according to the invention, which could for example be integrated into the process as shown in fig. 5.

In the process set up of fig. 6, a copper foil 58 is transported over guide rolls 61, 62, 63 in the direction of the arrows as shown in fig. 6. A bath 64 with electrolyte 65 is provided through which the copper foil 58 passes. In case of electroless deposition of the nanostructure deposit, no electrodes have to be provided.

However, when electrodeposition is applied, anode 66 is provided in the bath 65, such that it is in contact with the electrolyte 65. A power supply 67 can be electrically connected to the anode 66 and the guide drum 62. The guide drum 62 is in electrical contact with the copper foil 58 and therewith an electrical potential or electric current can be applied between the anode 66 and the copper foil 58, so the desired nanostructure deposit of zinc oxide and/or zinc hydroxide nanostructures can be deposited onto the copper foil.

The set up of fig. 6 can for example be arranged between the rotatable cathodic drum 54 and the roll 59 of fig. 5.

The set up of fig. 6 can alternatively be integrated into different industrial manufacturing processes, for example in an industrial process for electrogalvanisation of foil, sheets or strips that are coiled after the galvanisation.

Fig. 7 shows the compared results of T-peel tests carried out on different test specimens. Process parameters were different for each test specimen, so that their effect on the measured peel strength could be assessed.

The test specimens that were tested here comprised two copper substrates, with a layer of glue between them. Both copper substrates were provided with a nanostructure deposit according to the invention. So, for both substrates, the material of the receiving surface was copper. The layer of material that was applied over the combination of the receiving surface an the nanostructure deposit was the glue between them. In this test, the glue was an acrylate, having a thickness of about 40 pm. The deposition of the nanostructure deposit on the copper substrates was carried out by electrodeposition.

On these test specimens, a T-peel test in accordance with EN ISO 11339 was carried out. In such a peel test, loose ends of the substrates are gripped and brought at an angle of 180° relative to each other. Then, force is exerted on the loose ends of the substrates and the layer are separated from each other by pulling on the loose ends of the substrates. The force required to achieve this separation is recorded.

The process parameters for applying the nanostructure deposit to the substrates of the test specimens were as follows (potential versus saturated calomel electrode):

Test specimen no. 1 was used as a reference specimen. No deposition of a nanostructure deposit according to the invention took place. The acrylate layer was applied at the copper receiving surface in a conventional way, after cleaning the receiving surfaces of the substrates with a mixture of ethanol and methanol.

Test specimens no. 2, 3, and 4 received a nanostructure deposit in accordance with the invention, with zinc oxide and/or zinc hydroxide nanostructures with interstices between adjacent nanostructures 21, as can be seen in the pictures of the morphology incorporated in fig. 7. The light grey “dots” that are visible on the darker grey background are the nanostructures.

Test specimen no. 5 comprises a rapidly deposited nanostructure deposit of zinc oxide and/or zinc hydroxide nanostructures. However, the nanostructures of test specimen no. 5 have a different morphology than the nanostructures according to the invention, as can be seen in the picture of the morphology incorporated in fig. 7. In the flake-like morphology of specimen no. 5 in fig. 7, a large percentage of the nanostructures does not extend substantially perpendicularly to the receiving surface. Also, the nanostructures in test specimen no. 5 are relatively large with generally both length and width being over 1 pm.

The measured peel force as indicated on the y-axis of fig. 7 is in N/mm2. The peel force is the amount of force that is required to separate the copper substrates from each other by pulling on the loose ends, and therewith the amount of force that is required to overcome the adhesion between the glue and at least one of the copper substrates. The higher the peel force, the better the adhesion between the acrylate glue and the substrate.

Fig. 7 shows that already with a deposition time of just 5 seconds for the nanostructure deposit having the nanostructures, the adhesion between the copper layer and the acrylate glue layer is better than in the reference test specimen, in which no zinc oxide and/or zinc hydroxide nanostructures are present on the receiving surface.

Fig. 7 also shows that when instead of zinc oxide and/or zinc hydroxide nanostructures in accordance with the invention, larger nanostructures that do not extend substantially perpendicular to the receiving surface are present on the receiving surface, the adhesion between the copper layer and the acrylate glue layer is worse than in the reference test specimen.

Fig. 8 shows the results of T-peel tests on different test specimens.

The test specimens that were tested here comprised two copper substrates, with a layer of glue between them. Both copper substrates were provided with a nanostructure deposit in according to the invention. So, for both substrates, the material of the receiving surface was copper. The layer of material that was applied over the combination of the receiving surface an the nanostructure deposit was the glue between them. In this test, the glue was an acrylate, having a thickness of about 40 pm. The deposition of the nanostructure deposit on the copper substrates was carried out by electrodeposition.

The process parameters for applying the nanostructure deposit were process temperature 82°C, potential -1.4V versus a saturated calomel electrode, concentration ZnCI2 4mM, concentration H2O220mM. The deposition time for depositing the nanostructure deposit of the zinc oxide and/or zinc hydroxide nanostructures was varied amongst the test specimens. The deposition times that were used were: 5 seconds, 30 seconds, 60 seconds, 180 seconds.

In fig. 8a and fig. 8b, the recorded force required for pulling the copper substrate away from each other is shown on the y-axis of the graph. The horizontal line indicated as “reference sample” in fig. 8 gives the T-peel force for a test specimen without the zinc oxide and/or zinc hydroxide nanostructure deposit according to the invention, with the acrylate glue layer being applied onto the copper receiving surfaces in a conventional way.

Fig. 8a shows the situation where the nanostructure deposits were applied to a receiving surface on the smooth side of the copper foil substrates. The smooth side is the side of the copper foil that faces towards the rotatable cathodic drum in the manufacturing process (see fig. 5). Fig. 8b shows the situation where the nanostructure deposits were applied to a receiving surface on the rough side of the copper foil substrates. The rough side is the side of the copper foil that faces away from the rotatable cathodic drum in the manufacturing process (see fig. 5).

The peel force is the amount of force that is required to separate the copper substrates of the test specimens from each other by pulling on the loose ends and therewith the amount of force that is required to overcome the adhesion between the glue and at least one of the copper substrates. The higher the peel force, the better the adhesion between the acrylate glue and the substrates.

Fig. 8 shows that for all test specimens, the adhesion between the copper substrate and the acrylate glue was better than the reference test specimen, in which no zinc oxide and/or zinc hydroxide nanostructures are present on the receiving surface.

Fig. 8 also shows that the improved adhesion was already obtained at a deposition time of just 5 seconds. Furthermore, under these process conditions, for the deposition on the smooth side (fig. 8a) there first seems to be an optimal deposition time for the nanostructure deposit, over which the effect in relation to the improved adhesion seems to decrease.

Fig. 9 shows the results of pull-off tests on different test specimens.

The pull-off test was carried out in accordance with ISO 4624. In such a pull-off test, an aluminum cylinder called a “dolly” is glued to a test specimen. Then, after the glue has hardened, the dolly is pulled off the test specimen in a direction perpendicular to the surface of the test specimen. The force required to separate the dolly from the substrate is recorded.

In the tests of which fig. 9 shows the results, a stainless steel substrate was provided with a nanostructure deposit according to the invention. Also, a stainless steel reference sample was provided that did not have the nanostructure deposit. Glue was applied to the test specimen as the layer of material on the nanostructure deposit in accordance with the invention. On the reference sample, the glue was applied to the stainless steel test specimen directly. The reference sample was cleaned with a mixture of ethanol and methanol before the glue was applied. The glue used for all test specimens in this test was 3M Scotch-Weld epoxy adhesive DP490.

For the test specimens having the nanostructure deposit in accordance with the invention, the process parameters for applying the nanostructure deposit were: process temperature 82°C, potential -1.4V versus a saturated calomel electrode, concentration ZnCI2 4mM, concentration H2O220mM. The deposition time for depositing the nanostructure deposit of the zinc oxide and/or zinc hydroxide nanostructures was varied amongst the test specimens. The deposition times that were used were: 5 seconds, 30 seconds, 60 seconds, 180 seconds.

In fig. 9, the recorded force required for pulling loose the dolly from the stainless steel substrate (“pull off strength”) is shown on the y-axis. The horizontal line indicated as “reference sample” in fig. 9 gives the pull-off strength for a test specimen without the zinc oxide and/or zinc hydroxide nanostructure deposit according to the invention, with the glue applied directly on the stainless steel substrate.

Fig. 9 shows that in the test specimen that was subjected to a deposition time of 5 seconds, the adhesion between stainless steel and glue is similar to the reference test specimen, but that for higher deposition times the adhesion between stainless steel and glue is better than in the reference sample. It was observed that in test specimens in which the deposition times for the nanostructure deposit were over 30 seconds, cohesive failure of the glue layer occurred, instead of adhesive failure.

Furthermore, a similar test was carried out as was described in relation to fig. 9, but now the process parameters for depositing the nanostructure deposit were chosen differently. The results of this test are shown in fig. 10.

In this test, four samples were provided with a nanostructure deposit according to the invention. One reference sample was provided that did not have a nanostructure deposit. The test specimens were of stainless steel, and glue was applied to the test specimen as the layer of material on the nanostructure deposit. On the reference sample, the glue was applied to the stainless steel test specimen directly. The glue used here was 3M Scotch-Weld epoxy adhesive DP490.

The process conditions for applying the nanostructure deposit were: process temperature 85°C, potential -1.7V versus a saturated calomel electrode, concentration ZnCI2 40 mM, concentration H20220-40 mM. The deposition time for depositing the nanostructure deposit of the zinc oxide and/or zinc hydroxide nanostructures was varied amongst the test specimens. The deposition times that were used were: 0.5 seconds, 1 second, 2 seconds, 8 seconds.

The measured pull-off strengths are shown in fig. 10.

In the test specimens with deposition times of 1 second and more, cohesive failure of the glue layer occurred, instead of adhesive failure.

So, with these process conditions for depositing the nanostructure deposit, improved adhesion is already reached at deposition times of 0.5 seconds.

Fig. 11 shows the results of pull-off tests on different test specimens.

The pull-off test was carried out in accordance with ISO 4624. In such a pull-off test, a “dolly” is glued to a test specimen. Then, after the glued has hardened, the dolly is pulled off the test specimen in a direction perpendicular to the surface of the test specimen. The force required to pull the dolly loose is recorded.

In the tests of which fig. 11 shows the results, an electrogalvanized steel substrate was provided with a nanostructure deposit according to the invention. Also, an electrogalvanized steel reference sample was provided that did not have the nanostructure deposit. Glue was applied to the test specimen as the layer of material on the nanostructure deposit. On the reference sample, the glue was directly applied to the electrogalvanized test specimen. The glue used here was 3M Scotch-Weld acrylic adhesive DP810.

For the test specimens having the nanostructure deposit in accordance with the invention, the process parameters for applying the nanostructure deposit were: process temperature 82°C, concentration ZnCI2 4mM, concentration H2O220mM. No potential was applied, as the nanostructures were deposited using electroless deposition. The deposition time for depositing the nanostructure deposit of the zinc oxide and/or zinc hydroxide nanostructures was varied amongst the test specimens. The deposition times that were used were: 2 seconds, 1 minute, 2 minutes, 5 minutes and 10 minutes.

In fig. 11, the recorded force required for pulling loose the dolly from the electrogalvanized steel substrate (“pull off strength”) is shown on the y-axis. The horizontal line indicated as “reference sample” in fig. 11 gives the pull-off strength for a test specimen without the zinc oxide and/or zinc hydroxide nanostructure deposit according to the invention, with the glue applied directly on the electrogalvanized steel substrate.

Fig. 11 shows that for a deposition time of 2 seconds, the adhesion between electrogalvanized steel and glue already better than in the reference test specimen. However, if the deposition time was too long (as shown in the test specimen where the deposition of the nanostructure deposit was 10 minutes), the adhesion between the electrogalvanized steel and glue could become worse than in the reference sample. This probably is due to the increased agglomeration of the nanostructures at longer deposition times.

Table A (below) shows the results of further peel tests performed on different copper test specimens. In these test specimens, the receiving surface was made of copper and was bonded to a support made of a material selected from various materials that are commonly used in the manuafacturing of printed circuit boards as prepreg compounds, in particular epoxy, polyimide and PTFE.

The peel tests were carried out in accordance with ISO 1464. In such a peel test, a support of prepreg material having a thickness of at least 0.5 mm is pressed onto a copper foil substrate and hardened in an autoclave at high temperature and pressure. Then, after the prepreg material had hardened, the foil was peeled from the prepreg. The force required to separate the copper foil and the prepreg is recorded.

In the tests of which table A shows the results, a copper foil with a thickness of 18 pm was provided with a nanostructure according to the invention. Also, a copper reference sample was provided that did not have the nanostructure. On the reference sample, the prepreg layer was applied to the copper foil directly, after ethanol/methanol cleaning.

The prepregs used for these tests were: epoxy, PTFE and polyimide.

For the test specimens having the nanostructure in accordance with the invention, the process parameters for applying the nanostructure were: process temperature 80-85°C, current density 0.01 A/cm2, concentration ZnCI2 40mM, concentration H202 20mM. The deposition time for depositing the nanostructure deposit of the zinc oxide and/or zinc hydroxide nanostructures was 5 seconds.

In table A, the recorded force required for separating the copper foil from the prepreg layers are summarized. Copper foils having various microroughnesses between 1.8 and 7.2 pm were provided with prepreg material and tested. Also, copper foils with the same roughnesses were provided with a nanostructure deposit according to the invention and then with prepreg material and tested. Tabel A shows the results of the peel tests.

As shown in the table, for almost all prepreg materials used in the test specimens (epoxy, PTFE and polyimide) a significant enhancement of adhesion was achieved compared to the copper foils that were not provided with a nanostructure deposit in accordance with the invention. The most striking results were obtained for PTFE, which is known as a weakly adhering material. These results show that adhesion improvement can be achieved by applying the method according to the invention, and that it can be applied for many different materials and combinations of materials.

Table A

Figures 12 and 13 show schematical cross sections of parts of products that can be made using the method according to the invention, e.g. an electrical component, a printed circuit board or an metal component.

In fig. 12, the product comprises a substrate 1 that is provided with a coating 3. The substrate is for example made of steel and the coating is for example a metal coating comprising zinc and/or aluminum, or a ceramic coating. The coating 3 has a receiving surface 2. In case the product is an electrical component e.g. a printed circuit board, the receiving surface is electrically conductive. In case of a printed circuit board, the receiving surface is made of copper, in particular of copper foil.

On said receiving surface and attached thereto, a nanostructure deposit 20 is present comprising nanostructures 21 of zinc oxide and/or zinc hydroxide, which nanostructures have a first end and a second end that is located opposite said first end, wherein the nanostructures have a base at their first end that is attached to the receiving surface and a tip at a distance from the receiving surface at their second end, which nanostructures generally extend in a direction substantially perpendicular to the receiving surface.

The nanostructure deposit is shown enlarged with respect tot the other dimensions in fig. 12, because otherwise it would not be visible. The nanostructure deposit 20 comprises nanostructures 21 with interstices 25 being present between the nanostructures 21, which interstices extend to the outer surface of the nanostructure deposit away from the receiving surface 2.

The product of fig. 12 further comprises a layer 30 of material which is present on the combination of the receiving surface 2 and the nanostructure deposit 20. The material of this layer 30 at least partly penetrates into the interstices between the zinc oxide and/or zinc hydroxide nanostructures 21. In case the product is a printed circuit board, the material of this layer 30 may be electrically insulating.

Fig. 13 shows a product that is similar to the one shown in fig. 12, only in fig. 13 there is no coating 3 on the substrate 1. The receiving surface 2 is in fig. 13 made of the same material as the substrate, e.g. of copper foil in case the product is a printed circuit board.

Claims

A method of manufacturing a product, the method comprising the steps of: - providing a substrate, which substrate has an exposed receiving surface, applying the substrate to a bath, which bath contains an electrolyte containing Zn 2+ ions and OH 'ions, bringing the electrolyte into contact with the exposed receiving surface while the substrate is in the bath, depositing a nanostructure deposit from the electrolyte on the receiving surface of the substrate, the nanostructure depositing nanostructures of zinc oxide and / or zinc hydroxide, which nanostructures have a first end and a second end that is opposite the first end, the nanostructures having a base at their first end attached to the receiving surface and a remote tip from the receiving surface at their second end, which nanostructures are essentially in one direction extend substantially perpendicular to the receiving surface, thereby forming a zinc oxide and / or zinc hydroxide nanostructure deposit with spaces present between the nanostructures, which spaces extend to the outer surface of the nanostructure deposit away from the receiving surface, terminating the deposition of the nanostructure deposit before the spaces are filled by the zinc oxide and / or zinc hydroxide nanostructures, - applying a layer of material to the nanostructure deposit, the material of the layer penetrating at least partially into the spaces between the zinc oxide and / or zinc hydroxide nanostructures.

The method of claim 1, wherein the deposition of the nanostructure deposition is carried out in about 0.1 seconds to about 5 minutes, preferably in about 0.1 seconds to about 180 seconds, possibly in about 0.1 seconds to about 1 minute, possibly in about 0.2 seconds up to about 50 seconds, possibly in about 0.2 seconds to about 20 seconds, possible in about 0.5 seconds to about 10 seconds, possible in about 3 seconds to about 8 seconds, possibly in about 20 seconds to about 40 seconds, possibly in about 0.1 seconds up to about 10 seconds.

The method according to any of the preceding claims, wherein the deposition of the nanostructure deposit is performed by electroless deposition, or wherein the receiving surface is electrically conductive at least during the deposition of the nanostructure deposit and the deposition of the nanostructure deposit is carried out by electrodeposition.

Method according to one of the preceding claims, wherein the zinc oxide and / or zinc hydroxide nanostructures have at least a dimension that is smaller than 1 µm - possibly several hundred nanometers, for example between 200 and 900 nanometers -, and possibly in the form of nanowires , nano pillars, nano cones, nano columns, nano bars and / or nano dendrites.

The method of any one of the preceding claims, wherein the packing density of the nanostructure deposit is between about 10% and about 70%, possibly between about 30% and about 60%.

Method according to one of the preceding claims, wherein the substrate used is a metal substrate, the metal substrate possibly being copper, stainless steel, galvanized steel, for example hot-dip galvanized steel or electro-galvanized steel.

A method according to any one of the preceding claims, wherein the substrate is a substrate of carbon steel which is at least partially provided with a metal coating and wherein the material of the receiving surface is one of zinc, zinc alloy, aluminum or aluminum alloy, possibly with the metals coating is a zinc coating, an aluminum coating, a zinc-aluminum coating, a zinc-iron coating, an aluminum-zinc coating, a zinc-aluminum-magnesium coating or an aluminum-silicon coating.

A method according to any one of the preceding claims, wherein the material of the layer applied to the nanostructure deposit, a metal, an adhesive, for example an adhesive resin, a paint, a polymer, an electrically insulating material, a ceramic and / or a plastic is, for example, a reinforced plastic.

The method of claim 8, wherein the material of the layer applied to the nanostructure deposit is a fluorocarbon polymer, optionally PTFE, or an acrylate, polyurethane, epoxy, or polyimide.

The method of any one of the preceding claims, wherein the receiving surface is made of copper and the material of the layer applied to the nanostructure deposit is PTFE.

A method according to any one of the preceding claims, wherein the Zn 2+ ions in the electrolyte originate from an aqueous solution of one or more of ZnCl 2, Zn (NO 3) 2, Zn (CH 3 COO) 2, or from dissolved zinc from a zinc substrate , a zinc coated substrate, a substrate of a zinc alloy, a substrate with a coating of a zinc alloy and / or a zinc electrode.

12. A method according to any one of the preceding claims, wherein the OH 'ions in the electrolyte originate from hydroxides, for example NaOH, from the cathodic reduction of one or more oxidizing agents, for example 02 or, 03, peroxides for example H 2 O 2, nitrates for example Zn (NO 3 ) 2, hypochlorites, for example, Zn (OCI) 2, persulfates and / or from one or more organic salts Zn (CH 3 COO) 2.

A method according to any one of the preceding claims, wherein the electrolyte comprises one or more additives, for example a shape control agent, a complexing agent, a corrosion inhibitor, an acidity adjusting agent and / or a surfactant.

The method of claim 3, wherein the electrolyte is an aqueous solution comprising: ZnCl 2 and H 2 O 2, or ZnCl 2, saturated with oxygen, or hydrated Zn (NO 3) 2.

The method of any one of the preceding claims, wherein the electrolyte is an aqueous solution comprising ZnCl 2, wherein the concentration of ZnCl 2 is between approximately 1 mM and approximately 100 mM, possibly between approximately 2 mM and approximately 60 mM, possibly between approximately 2 mM and approximately 10 mM, possibly between approximately 3 mM and approximately 5 mM, possibly between approximately 15 mM and approximately 65 mM, possibly between approximately 20 mM and approximately 60 mM, possibly between approximately 30 mM and approximately 50 mM, possibly between approximately 35 mM and approximately 45 mM.

A method according to any one of the preceding claims, wherein the electrolyte is an aqueous solution comprising H 2 O 2, wherein the concentration of H 2 O 2 is between about 10 mM and about 100 mM, possibly between about 15 mM and about 50 mM, possibly between about 20 mM and about 40 mM.

The method of any one of the preceding claims, wherein the deposition of the nanostructure deposition is carried out at a temperature between about 40 ° C and about 98 ° C, possibly between about 65 ° C and about 95 ° C, possibly between about 80 ° C and about 90 ° C, possibly between 80 ° C and 85 ° C.

A method according to claim 3, wherein the deposition of the nanostructure deposition is carried out by electrodeposition and wherein the potential as determined versus a saturated calomel electrode used during the electrodeposition is between approximately -0.5V and approximately -2.5V, preferably between approximately - 1V and approximately -2V, possibly between approximately -1.2V and approximately -1.8V, possibly between approximately -1.3V and approximately -1.5V, possibly between approximately -1.6V and approximately -1.8V.

A method according to claim 3, wherein the deposition of the nanostructure deposition is performed by electrodeposition and wherein the current density applied between the receiving surface and an anode, for example a platinum or metal-coated titanium anode, is between approximately 0.0001 A / cm 2 and approximately 10 A / cm2, possibly between approximately 0.001 A / cm2 and approximately 1 A / cm2, possibly between approximately 0.005 A / cm2 and approximately 0.5 A / cm2.

The method of any one of the preceding claims, wherein the deposition of the nanostructure deposit is performed in about 0.1 seconds to about 5 minutes, preferably in about 0.1 seconds to about 180 seconds, possibly in about 0.1 seconds to about 1 minute, possibly in about 0.2 seconds to about 50 seconds, possibly in about 0.2 seconds to about 20 seconds, possibly in about 0.5 seconds to about 10 seconds, possibly in about 3 seconds to about 8 seconds, possibly in about 20 seconds to about 40 seconds, possibly in about 0.1 seconds to about 10 seconds, and wherein the electrolyte is an aqueous solution comprising ZnCl 2, wherein the concentration of ZnCl 2 is between about 15 mM and about 65 mM, possibly between about 20 mM and about 60 mM, possibly between about 30 mM and about 50 mM, possibly between about 35 mM and about 45 mM, and wherein the electrolyte further comprises H 2 O 2, wherein the H 2 O 2 concentration is between approximately 10 mM and approximately 100 mM, possibly between approximately 15 mM and approximately 50 mM, possibly between approximately 20 mM and approximately 40 mM

The method of claim 20, wherein the nanostructure deposition is performed at a temperature between about 80 ° C and about 90 ° C.

A method according to claim 20 or claim 21, wherein the deposition of the nanostructure deposition is performed by electrodeposition and wherein the potential as determined versus a saturated calomel electrode used during the electrodeposition is between approximately -0.5V and approximately -2.5V, preferably between approximately -1V and approximately -2V, possibly between approximately -1.2V and approximately -1.8V, possibly between approximately -1.3V and approximately -1.5V, possibly between approximately -1.6V and approximately -1.8V.

The method of any one of claims 20 to 22, wherein the receiving surface is copper or stainless steel.

The method of any one of claims 20 to 23, wherein the layer material applied to the nanostructure deposit is an epoxy, an acrylic or acrylate material, a polyimide or PTFE.

An electrical component, comprising: - a substrate, which substrate has an exposed receiving surface, which receiving surface is of an electrically conductive material, on the receiving surface and attached thereto, a nanostructure deposit comprising nanostructures of zinc oxide and / or zinc hydroxide, which nanostructures a first have an end and a second end opposite the first end, wherein the nanostructures have a base at their first end attached to the receiving surface and a tip remote from the receiving surface at their second end, which nanostructures are substantially in a direction extending substantially perpendicular to the receiving surface, which nanostructure deposit becomes spaces present between the nanostructures, which spaces extend to the outer surface of the nanostructure deposit away from the receiving surface, - a layer of material, for example electrically insulating material present on the nanostructure deposit, the material of the layer penetrating at least partially into the spaces between the zinc oxide and / or zinc hydroxide nanostructures.

A printed circuit board comprising a copper foil, which copper foil has an exposed receiving surface, on the receiving surface and attached thereto, a nanostructure deposit comprising nanostructures of zinc oxide and / or zinc hydroxide, which nanostructures have a first end and a second end that faces the first end, the nanostructures having a base at their first end attached to the receiving surface and a remote tip from the receiving surface at their second end, which nanostructures extend substantially in a direction substantially perpendicular to the receiving surface, nanostructure deposit has spaces that are present between the nanostructures, which spaces extend to the outer surface of the nanostructure deposit away from the receiving surface, - a layer of electrically insulating material that is present on the nanostructure deposit, the material of the la ag at least partially penetrates into the spaces between the zinc oxide and / or zinc hydroxide nanostructures.

The printed circuit board of claim 26, wherein the material of the layer is PTFE.

A metal component comprising: a substrate made of stainless steel or carbon steel possibly with a coating comprising zinc and / or aluminum, which substrate has an exposed receiving surface, on the receiving surface and attached thereto, a nanostructure deposit comprising nanostructures of zinc oxide and / or comprises zinc hydroxide, which nanostructures have a first end and a second end that is opposite the first end, the nanostructures having a base at their first end which is attached to the receiving surface and a tip remote from the receiving surface at their second end, which nanostructures extend substantially in a direction substantially perpendicular to the receiving surface, which nanostructure deposit becomes spaces present between the nanostructures, which spaces extend to the outer surface of the nanostructure deposit away from the receiving surface, - a layer of material, for example electrically insulating material present on the nanostructure deposit, the material of the layer penetrating at least partly into the spaces between the zinc oxide and / or zinc hydroxide nanostructures.

A metal component according to claim 28, wherein the material of the layer present on the nanostructure deposit is a metal, an adhesive for example an adhesive resin, a paint, a polymer, an electrically insulating material and / or a plastic for example a reinforced plastic .