JP2018162367A - Metal laminated structure - Google Patents

Abstract

Kind Code: A1 A metal laminate structure is provided which is excellent in thermal conductivity and exhibits little deterioration of the thermal conductivity over time. A metal laminate structure comprising a plurality of metal layers and a thermally conductive layer sandwiched between the metal layers, the thermally conductive layer containing water, a surfactant, and a sodium salt. body. According to this metal laminate structure, the heat conductive layer sandwiched between the metal layers contains water, a surfactant, and a sodium salt to improve the heat conductivity and improve the heat conductivity. Deterioration over time can be reduced. Sodium salts include sodium lactate and sodium phosphite. [Selection drawing] Fig. 2

Description

  The present disclosure relates to a metal laminate structure. The present disclosure particularly relates to a metal laminated structure that is excellent in thermal conductivity and has little deterioration over time in the thermal conductivity.

  Many electronic and electrical devices such as LEDs, solar cells, windmill power generation elements, semiconductor elements, automobile motors, and electronic control elements for internal combustion engines generate heat during use. Controlling this heat generation not only affects product performance and the like, but is also affecting energy saving and the maintenance of the global environment. This trend is further strengthened as the operating speed of electronic and electrical equipment is increasing. Therefore, it is desired to efficiently release the heat generated from the electronic / electric equipment.

  However, it is not always clear what factors are important for releasing heat generated from electronic / electrical equipment from electronic / electrical equipment. Therefore, there is a tendency to focus on the development of high thermal conductivity materials. However, this alone is not enough to improve the thermal control technology.

  Thus, focusing on how heat conductive materials are used, it has been studied to perform heat control. The heat conducting material is generally used by being sandwiched between a heat generation source and a heat cooling source. There are contact interfaces between the heat generating source and the heat conducting material, and between the heat conducting material and the heat cooling source. A contact thermal resistance is generated at the contact interface.

  The thermally conductive material itself has thermal resistance. In the case where the contact thermal resistance is significantly smaller than the thermal resistance of the heat conducting material itself, the contact thermal resistance is not substantially a problem. However, when the heat conductive material is thin, the heat resistance due to the heat conductive material becomes small, and therefore, the influence of the contact heat resistance becomes relatively large in the entire system of the heat generation source-heat conductive material-thermal cooling source. For this reason, it is important to study the contact thermal resistance, and attempts have been made to reduce the contact thermal resistance.

  For example, Patent Document 1 discloses a heat radiator in which a thermally conductive filler is contained in a flexible matrix resin.

JP-A-6-252572

  Since the viscosity of the matrix resin disclosed in Patent Document 1 is not sufficiently low, the wettability to the metal contact interface is low and the contact thermal resistance is high. It is conceivable to improve the wettability of the matrix resin to the metal contact interface by using water and a surfactant together. However, the present inventor has a problem that contact thermal resistance deteriorates with time due to water evaporation. Found.

  The present disclosure has been made in order to solve the above-described problems, and an object of the present disclosure is to provide a metal laminated structure that is excellent in thermal conductivity and has little deterioration over time in the thermal conductivity.

In order to achieve the above-mentioned object, the present inventor has intensively studied and completed the metal laminated structure of the present disclosure. The summary is as follows.
<1> a plurality of metal layers;
A thermally conductive layer sandwiched between the metal layers;
With
The heat conductive layer contains water, a surfactant, and a sodium salt;
Metal laminated structure.

  According to the present disclosure, the thermal conductive layer sandwiched between the metal layers contains water, a surfactant, and a sodium salt, thereby reducing the thermal contact resistance and the time of the thermal contact resistance. A metal laminated structure with little deterioration can be provided.

FIG. 1 is a graph showing the effect of the type of material between aluminum plates on the contact thermal resistance with respect to a laminate of aluminum plates. FIG. 2 is a graph showing a change with time of contact thermal resistance with respect to a laminate of aluminum plates. FIG. 3 is a cross-sectional view illustrating a form of a contact interface of a metal laminated structure including a crosslinked silicone rubber sandwiched between two aluminum plates. FIG. 4 is a graph showing the relationship between contact pressure and thermal resistance for Reference Examples 4 to 6.

  Hereinafter, an embodiment of a metal laminated structure according to the present disclosure will be described in detail. In addition, embodiment shown below does not limit the metal laminated structure which concerns on this indication.

For example, when an aluminum plate having a high thermal conductivity (thermal conductivity: 240 Wm ⁻¹ K ⁻¹ ) is laminated, the heat transfer coefficient between the aluminum plates is remarkably low. For example, even when a pressure of 0.01 to 1 MPa is applied between the aluminum plates, the heat transfer coefficient between the aluminum plates is 0.54 to 0.84 Wm ⁻¹ K ⁻¹ . The same applies to the copper plate. For example, even when a pressure of 0.01 to ¹ MPa is applied to a copper plate (thermal conductivity: 403 Wm ⁻¹ K ⁻¹ ), the heat transfer coefficient between the copper plates is 0.38 to 0.80 Wm ⁻¹ K ⁻¹ . . Thus, even if a sufficient pressure (0.3 MPa) is applied between the metal plates, it is not easy to obtain a good heat transfer coefficient. Moreover, it is not easy to always apply a pressure of 0.3 MPa or more between the metal plates.

  Thus, although the heat conductivity of the metal plate alone is high, when a plurality of metal plates are laminated, the heat transfer coefficient between the metal plates is remarkably low. This is because when a plurality of metal plates are laminated, the contact area between them is small.

  When a heat radiating component is attached to the electronic / electrical device, a laminated structure of a heat generation source side metal-heat conduction layer-cooling source side metal is formed. Therefore, not only the improvement of the thermal conductivity of the heat source side metal and the cooling source side metal, but also the contact between the heat source side metal and the heat conduction layer and between the heat conduction layer and the cooling source side metal. Improvement of contact thermal resistance that reflects the area is essential.

  The contact thermal resistance of the metal laminate structure of the present disclosure is substantially zero. The knowledge for obtaining such contact thermal resistance will be described below.

  When the heat conduction layer is brought into physical contact with the heat generation source side metal and / or the cooling source side metal, the contact surfaces may be flattened and smoothed to improve the contact area and reduce the contact thermal resistance. is important. However, even if the surface roughness is 0.5 μm or less in Ra, it is inevitable that a gap is generated at the contact interface.

  Even if the contact surface is flattened and smoothed, the heat generation source side metal, the cooling source side metal, and the surface of the heat conductive layer always have damage or unevenness depending on the contact method and the number of times. To do. As a result, it is not easy to increase the contact area ratio at the contact interface between the heat generation source side metal and the heat conduction layer and between the cooling source side metal and the heat conduction layer to 1% or more.

  The damage or unevenness described above is unavoidable even when a low-abrasion material is used. The metal laminated structure of the present disclosure includes a heat conductive layer so that the contact thermal resistance can be reduced even if damage or unevenness exists in the contact interface. The heat conduction layer promotes heat conduction between the heat generation source side metal and the heat conduction layer and between the cooling source side metal and the heat conduction layer.

  FIG. 1 is a graph showing the effect of the type of substance between aluminum plates on the contact thermal resistance value for a laminate of aluminum plates. As can be seen from FIG. 1, when water is present between the aluminum plates, the thermal resistance value of the laminate of the aluminum plates can be reduced.

Therefore, the heat conductive layer of the laminated structure of the generation source side metal-heat conductive layer-cooling source side metal contains water as a main component to reduce the contact thermal resistance. Water has a small molecular weight and a large specific heat (4.217 Jg ⁻¹ K ⁻¹ ). Since water penetrates into the gaps at the contact interface to improve heat conduction, the influence of the contact interface roughness and contact pressure on the contact thermal resistance can be significantly reduced.

  FIG. 2 is a graph showing a change with time of contact thermal resistance with respect to a laminate of aluminum plates. As can be seen from FIG. 2, when the heat conductive layer contains only water, the contact thermal resistance value of the laminate deteriorates (increases) with time. This is thought to be because water evaporates over time.

  The heat conductive layer of the laminated structure of the source-side metal-heat conductive layer-cooling source-side metal contains an additive in addition to water, and suppresses the temporal change of the contact thermal resistance value. Additives are surfactants and builders. Surfactant and builder suppress water evaporation and prevent bubbles from remaining at the contact interface.

  As described above, it is possible to obtain a metal laminated structure having excellent thermal conductivity and small deterioration with time of the thermal conductivity by containing the water, the surfactant, and the builder. They found out.

  The configuration of the metal laminated structure of the present disclosure based on these findings will be described next.

(Metal layer)
The metal laminated structure of the present disclosure includes a plurality of metal layers. Typically, it includes two metal layers, but is not limited to this. Three or more metal layers may be provided as long as a heat conductive layer described later is sandwiched between the metal layers.

  Since metal generally has higher thermal conductivity than other materials, the type of metal layer is not limited. Metals include alloys. Since aluminum and copper have a particularly high thermal conductivity among metals, the metal layer is preferably made of aluminum or copper. The metal layer may be made of an aluminum alloy or a copper alloy.

  The metal laminated structure includes a plurality of metal layers, but the individual metal layers may not be the same type. For example, when two metal layers are provided, one metal layer may be made of an aluminum alloy and the other metal layer may be made of a copper alloy.

(Thermal conduction layer)
The heat conductive layer is sandwiched between the metal layers. The heat conductive layer contains water, a surfactant, and a builder. A heat conductive layer is a low-viscosity solution medium in which these inclusions coexist. Hereinafter, these inclusions will be described.

(water)
Water is the main component of the heat conduction layer. As for water content, 70 mass% or more is preferable with respect to the whole heat conductive layer. When the water content is 70% by mass or more, the contact thermal resistance between the metal layers can be sufficiently reduced. Further, the contact thermal resistance is hardly changed by the pressure (contact pressure) applied between the metal layers by water. Furthermore, the contact thermal resistance is difficult to change depending on the distance between the metal layers due to water.

  From the viewpoint of lowering contact thermal resistance and contact pressure independence and inter-metal distance independence of contact thermal resistance, the water content is more preferably 85% by mass or more, and even more preferably 90% by mass or more. . On the other hand, the water content is preferably 99.88% by mass or less. If water content is 99.88 mass% or less, a heat conductive layer can contain additive, ie, surfactant, a builder, etc. required amount.

  The water may be distilled water or ion exchange water, or heavy water. The water may be a combination of distilled water, ion exchange water, and heavy water.

(Surfactant)
The surfactant reduces the viscosity of water and suppresses water evaporation. Examples of such surfactants include cationic surfactants, nonionic surfactants, anionic surfactants, and amphoteric surfactants.

  The content of the surfactant is preferably 0.1% by mass or more. If the content of the surfactant is 0.1% by mass or more, the viscosity of water is lowered and the evaporation of water is easily suppressed. From the viewpoint of reducing the viscosity of water and suppressing the evaporation of water, the content of the surfactant is more preferably 1% by mass or more, and even more preferably 10% by mass or more.

  On the other hand, the surfactant content is preferably 30% by mass or less. If the content of the surfactant is 30% by mass or less, the content of water will not be excessively decreased due to the excessive amount of the surfactant. As a result, the contact thermal resistance can be sufficiently reduced by water. From the viewpoint of ensuring a decrease in contact thermal resistance due to water, the content of the surfactant is more preferably 25% by mass or less, and even more preferably 20% by mass or less.

  Cationic surfactants include single-chain trimethyl higher saturated alkylammonium halides, one-chain trimethyl higher unsaturated alkylammonium halides, two-chain dimethyl higher saturated alkylammonium halides, one-chain trimethyl higher Saturated alkylammonium halide, 1-chain trimethyl higher unsaturated alkylammonium hydroxide, 2-chain dimethyl higher saturated alkylammonium hydroxide, 2-chain dimethyl higher unsaturated alkylammonium halide, 3-chain methyl higher saturated alkyl Ammonium halogenides, 3-chain methyl higher unsaturated alkylammonium halides, 1-chain triphenyl higher alkyl phosphonium halides, 1-chain triphenyl higher alkyl phosphonium hydroxide Alkylbenzyldimethylammonium salt, phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine, tetrabutylphosphonium bromide, tetraoctylphosphonium bromide, tetrabutylammonium hobromide, tetraoctylammonium bromide, oleyl sulfate triethanol Examples include amines, diphenyldioctyl phosphate bromide, and triethanolamine.

Nonionic surfactants include polyoxyethylene alkyl ether RO (CH ₂ CH ₂ O) _m H, fatty acid sorbitan ester, alkyl polyglucoside, fatty acid diethanolamide RCON (CH ₂ CH ₂ OH) ₂ , alkyl monoglyceryl ether ROCH ₂ CH (OH) CH ₂ OH and the like.

  Examples of anionic surfactants include 6-octylamino-1,3,5-triazine-4-thiol-2-thionatrium salt, 6-octylamino-1,3,5-triazine-4-thiol-2- Thiocalium salt, 6-triethoxysilylpropylamino-1,3,5-triazine-2-thiol-2-thiocalium salt, 6-triethoxysilylpropylamino-1,3,5-triazine-2, 4- Diaminoethylamine, 6-triethoxysilylpropylamino-1,3,5-triazine-2, 4-dihydrazine, saturated alkylbenzene sulfonate, saturated alkyl, monoalkyl acid salt, alkyl polyoxyethylene sulfate, triazine trithiol Examples include monosodium and sodium isostearyl sulfate.

Examples of amphoteric surfactants include alkyl dimethylamine oxide R (CH ₃ ) ₂ NO and alkyl carboxybetaine R (CH ₃ ) ₂ N ⁺ CH ₂ COO ⁻ .

(builder)
The builder suppresses evaporation of water by coexisting with the surfactant, and as a result, suppresses deterioration of contact thermal resistance with time. Further, the builder promotes the contact between the heat conductive layer and the metal layer surface, suppresses the bubbles from remaining on the metal surface, and contributes to the reduction of the contact thermal resistance.

  The builder content is preferably 0.1% by mass or more. If the builder content is 0.1% by mass or more, it becomes easy to suppress water evaporation, and it is easy to suppress bubbles from adhering to the metal surface. From the viewpoint of water evaporation suppression and bubble adhesion suppression, the builder content is more preferably 1% by mass or more, and even more preferably 5% by mass or more.

  On the other hand, the builder content is preferably 10% by mass or less. If the builder content is 10% by mass or less, the builder content becomes excessive, so that the water content does not decrease excessively. As a result, the contact thermal resistance can be sufficiently reduced by water. From the viewpoint of ensuring a decrease in contact thermal resistance due to water, the content of the surfactant is more preferably 8% by mass or less.

  Builders include: carboxymethylcellulose, polyethylene glycol, polyvinyl alcohol, sodium nitrate, sodium sulfite, sodium hyposulfite, ammonium sulfite, ammonium carbonate, sodium phosphate, ammonium phosphate, sodium silicate, ammonium silicate, sodium lactate, phosphorus phosphite Examples include acid soda, ammonium phosphite, sodium nitrate, sodium nitrite, ethylenediaminetetraacetic acid, ethylenediamine, ammonium ethylenediaminetetraacetate, and decyltriethylene glycol.

  From the viewpoint of water evaporation suppression, sodium salts are preferable, and among them, sodium lactate and sodium phosphite are particularly preferable.

  Although not bound by theory, it is considered that the deterioration of contact thermal resistance with time is suppressed for the following reason. Surfactants and builders, especially sodium salts, especially sodium lactate and sodium phosphite, facilitate the unimolecularization and clustering of hydrogen-bonded water clusters, and energy transfer between multiple metal layers This is considered to occur.

(Surface stabilizer)
The heat conductive layer essentially contains water, a surfactant, and a builder as described above. In addition to these, the heat conductive layer may optionally contain a surface stabilizer. The surface stabilizer suppresses corrosion or the like of the surface of the metal layer, and suppresses deterioration of the surface of the metal layer.

  The content of the surface stabilizer is preferably 0.1% by mass or more. When the content of the surface stabilizer is 0.1% by mass or more, corrosion of the surface of the metal layer is easily suppressed. From the viewpoint of suppressing the corrosion of the surface of the metal layer, the content of the surface stabilizer is more preferably 1% by mass or more, and further preferably 2% by mass or more.

  On the other hand, the content of the surface stabilizer is preferably 5% by mass or less. If content of a surface stabilizer is 5 mass% or less, the effect of the metal laminated structure of this indication will not be reduced. From the viewpoint of not reducing the effect of the metal laminated structure of the present disclosure, the surface stabilization content is more preferably 3% by mass or less.

(Deformation)
The metal laminate structure of the present disclosure may be modified as follows in the configuration requirements. A heat conductive sheet may be included inside the heat conductive layer. The inside of the heat conductive layer means that water, a surfactant, and a builder are provided on at least one surface of the heat conductive sheet. From the viewpoint of ensuring thermal conductivity, it is preferable that water, a surfactant, and a builder are provided on both sides of the thermal conductive sheet. The builder is preferably a sodium salt.

  Examples of the heat conductive sheet include a heat conductive composite silicone rubber sheet. A polyimide-bonded thermally conductive composite silicone rubber sheet may be obtained by molecularly bonding polyimide to at least one surface in the stacking direction of the thermally conductive composite silicone rubber sheet.

  As long as water, a surfactant, and a builder are provided on at least one surface of the heat conductive sheet, a plurality of heat conductive sheets may be provided.

  Hereinafter, the metal laminated structure of the present disclosure will be described more specifically with reference to examples. In addition, the metal laminated structure of this indication is not limited to these.

(Experiment A)
Samples of the metal laminated structures of Examples 1 and 2, Comparative Examples 1 to 3, and Reference Example 1 were prepared, and the influence of the type of the heat conductive layer on the temporal deterioration of the contact thermal resistance was evaluated.

Example 1
Two metal blocks made of aluminum alloy were prepared. A metal block is a metal layer of a metal laminated structure. The thermal conductivity of these metal blocks was 139 Wm ⁻¹ K ⁻¹ . The surface roughness of these metal blocks was 0.025 μm in Ra.

  On the surface of one metal block, the raw material of the heat conductive layer was dropped with a dropper. The raw materials were 96.69 g of water, 0.001 g of triazine trithiol monosodium as an anionic surfactant, 2.1 g of sodium isostearyl sulfate, and 1 of sodium lactate (sodium salt) as a builder. .2g was prepared. In addition, the raw material of this mixture was used as the heat conductive layer raw material 1.

The dripping amount of the heat conductive layer raw material 1 was 20 mg / 4.84 cm ² . Thus, when the raw material dripped on the surface of the metal block was leveled with a glass rod and the overflow was wiped off, 8 to 12 mg (target value: 10 mg) of the raw material could be applied. Next, a sample of the metal laminate structure of Example 1 was manufactured by superimposing the other metal block on one metal block onto which the raw material was dropped.

(Example 2)
A sample of the metal laminated structure of Example 2 was prepared in the same manner as in Example 1 except that the raw material for the heat conductive layer was prepared with the following composition. The raw materials are 99.0 g of pure water, as a cationic surfactant, 0.8 g of oleyl sulfate triethanolamine, as a builder, 0.1 g of sodium phosphite (sodium salt), and as a surface stabilizer And 0.1 g resorcin. In addition, the raw material of this mixture was used as the heat conductive layer raw material 2.

(Comparative Example 1)
A sample of the metal laminate structure of Comparative Example 1 was prepared in the same manner as in Example 1 except that the heat conductive layer was prepared by blending 95 g of pure water and 5 g of liquid detergent for kitchen. In addition, the raw material of the heat conductive layer used when producing the sample of the comparative example 1 was the heat conductive layer raw material 3.

(Comparative Example 2)
A metal laminated structure of Comparative Example 2 was produced in the same manner as in Example 1 except that a heat dissipation compound (product number: G746) manufactured by Shin-Etsu Chemical Co., Ltd. was used as the heat conductive layer. This heat radiation compound contains silicone oil and an inorganic heat radiation material (alumina fine particles having a particle size of 1 μm or less). Moreover, the thermal conductivity of this heat dissipation compound is 1.9 Wm ⁻¹ K ⁻¹ . This heat radiation compound was used as the heat conductive layer raw material 4.

(Comparative Example 3)
A metal laminated structure of Comparative Example 3 was produced in the same manner as in Example 1 except that only the pure water was used as the raw material for the heat conductive layer. In addition, the raw material of only pure water was used as the heat conductive layer raw material 5.

(Reference Example 1)
As Reference Example 1, a metal laminated structure having no heat conductive layer was prepared. The two metal blocks are the same as those used in Example 1. The interval between the two metal blocks was within 0.5 nm.

  In addition, it shows in Table 1 about the mixing | blending of the raw materials 1-5 of the heat conductive layer demonstrated so far. Table 1 also shows the composition of raw materials 6 to 7 to be described.

(Evaluation)

  The thermal characteristics (contact thermal resistance, thermal resistance, and thermal conductivity) of the samples thus prepared were evaluated. A constant pressure is applied in the sample stacking direction, one metal block is heated, and the other metal block is cooled.

Contact thermal resistance R _c (mKW ⁻¹ ) between the metal block (metal layer) and the thermal conductive layer having a thickness L _x (10 ⁻³ m), and thermal resistance R _s (mKW ⁻¹ ) of the thermal conductive layer The total thermal resistance R _t (mKW ⁻¹ ) consisting of the sum of However, A is a cross-sectional area of a heat conductive layer. ΔT is the difference between the surface temperature T ₇ of the surface temperature T ₁ of the other of the metal block of the one metal block. Φ (W) is calculated from the voltage E _{1 of the} heater connected to one metal block and the current i (voltage E _{2 of the} fractionator / resistance value R _{o of the} shunt). In addition, the surface temperature of a metal block means the temperature of the surface at the side of the heat conductive layer of a metal block (metal layer).
R _t = A _x ΔT / Φ Equation 1

When the thickness L _x of the heat conduction layer is changed (1.0, 2.0, and 3.0 mm) and the thickness L _x is plotted on the horizontal axis and the total thermal resistance R _t is plotted on the vertical axis, In addition, the relationship represented by the following expression 2 is established.
R _t = aL _x + b (2)

In Equation 2, when the contact thermal resistance R _c is subtracted from the intercept b and the contact thermal resistance R _c is subtracted from the total thermal resistance R _t , the thermal resistance R _s of the heat conductive layer is obtained. Further, the thermal conductivity λ (Wm ⁻¹ K ⁻¹ ) of the heat conductive layer can be obtained by dividing the thickness L _x of the heat conductive layer by the thermal resistance R _s .

  The results thus obtained are shown in Table 2.

  As can be seen from Tables 1 and 2, when the heat conductive layer contains a sodium salt, that is, sodium lactate or sodium phosphite, the contact thermal resistance is stable at a low value. This is considered to be because hydrogen lactate or sodium phosphite facilitates unimolecularization and clustering of water-bonded water clusters, and energy transfer occurs between the two metal blocks.

  In addition, the following can be seen from Tables 1 and 2. In the sample of Reference Example 1, there is physical contact obtained by contact pressure between the metal blocks. In the vicinity of physical contact, the distance between the metal blocks is within 0.5 nm, and heat is transferred by phonon vibration. In the sample of Reference Example 1, in addition to physical vibration, oxygen and nitrogen molecules collide with the metal block surface to exchange energy between the metal blocks.

  In the sample of Comparative Example 3, the heat conduction layer is water, and water is a hydrogen-bonded molecule. Therefore, between the metal blocks, the water molecule obtains energy from the metal block having a high temperature, and becomes a metal block having a low temperature. Release energy (heat dissipation). However, since water evaporates over time, the contact thermal resistance increases accordingly.

  In the sample of Comparative Example 2, since the commercially available heat dissipation compound contains silicone oil and an inorganic heat dissipation material (alumina particles having a particle size of 1 μm or less), the thermal conductivity is better than water at the initial stage of heating. Deterioration with time is small. However, the heat dissipation compound has low wettability with the metal block and high contact thermal resistance.

(Experiment B)
Samples of the metal laminated structures of Examples 3 to 4, Comparative Examples 4 to 5, and Reference Example 2 were prepared, and the influence of contact pressure (pressure applied in the metal layer lamination direction) on contact thermal resistance was evaluated. did.

(Example 3)
A sample of the metal laminate structure of Example 4 was produced in the same manner as in Example 1 except that the contact pressure was 0.01 to 0.30 MPa.

Example 4
A sample of the metal laminate structure of Example 4 was produced in the same manner as in Example 2 except that the contact pressure was 0.01 to 0.30 MPa.

(Comparative Example 4)
A sample of the metal laminate structure of Comparative Example 4 was produced in the same manner as Comparative Example 1 except that the contact pressure was 0.01 to 0.30 MPa.

(Comparative Example 5)
A sample of the metal laminate structure of Comparative Example 5 was produced in the same manner as Comparative Example 2 except that the contact pressure was 0.01 to 0.30 MPa.

(Reference Example 2)
A sample of the metal laminate structure of Reference Example 2 was produced in the same manner as Reference Example 1 except that the contact pressure was 0.01 to 0.30 MPa.
(Evaluation)

  The thermal characteristics of the sample thus prepared were evaluated in the same manner as the sample of Experiment A. The results are shown in Table 3.

  As can be seen from Table 3, the contact thermal resistance is greatly affected by the contact pressure in the sample of Comparative Example 5 using a commercially available heat dissipation compound and the sample of Reference Example 2 having no heat conduction layer. On the other hand, in the samples of Examples 3 and 4 and Comparative Example 4 in which the heat conductive layer contains a surfactant, it can be confirmed that the contact thermal resistance is hardly affected by the contact pressure. It was.

(Experiment C)
Samples of the metal laminated structures of Example 5, Comparative Examples 6 to 7, and Reference Example 3 were prepared, and the influence of the contact interface surface roughness (metal block surface roughness) on the contact thermal resistance was evaluated. .

(Example 5)
A sample of the metal laminate structure of Example 5 was produced in the same manner as in Example 1 except that the surface roughness Ra of one metal block and the raw material of the heat conduction layer were as follows.

  The surface roughness Ra of one metal block is set to 0.010 ± 0.01 μm, 0.020 ± 0.0 μm, 0.05 ± 0.01 μm, 0.10 ± 0.01 μm, and 0.30 ± 0.0. It was set to 01 μm.

  The raw materials are 98.2 g of pure water, 1.5 g of diphenyldioctyl phosphate bromide as the cationic surfactant, 0.3 g of triethanolamine, and 0.2 g of sodium hyposulfite as the builder. It was made. In addition, the raw material of this mixture was used as the heat conductive layer raw material 6.

(Comparative Example 6)
A sample of the metal laminate structure of Comparative Example 6 was produced in the same manner as Comparative Example 1 except that the surface roughness Ra of one metal block and the raw material of the heat conduction layer were as follows.

  The surface roughness Ra of one metal block is set to 0.010 ± 0.01 μm, 0.020 ± 0.0 μm, 0.05 ± 0.01 μm, 0.10 ± 0.01 μm, and 0.30 ± 0.0. It was set to 01 μm.

  The raw materials were 97.5 g of ion-exchanged water, 0.3 g of triazine trithiol monosodium as a cationic surfactant, and 2 g of decyltriethylene glycol and 2 of ethylenediaminetetraacetic acid (EDTA) as a builder. 0.0 g was prepared. In addition, the raw material produced by this mixing was used as the heat conductive layer raw material 7.

(Comparative Example 7)
The surface roughness Ra of one metal block is set to 0.010 ± 0.01 μm, 0.020 ± 0.0 μm, 0.05 ± 0.01 μm, 0.10 ± 0.01 μm, and 0.30 ± 0.0. A sample of the metal laminate structure of Comparative Example 7 was produced in the same manner as Comparative Example 1 except that the thickness was 01 μm.

(Comparative Example 8)
The surface roughness Ra of one metal block is 0.010 ± 0.01 μm, 0.025 ± 0.0 μm, 0.05 ± 0.01 μm, 0.10 ± 0.01 μm, and 0.30 ± 0.0. A sample of the metal laminated structure of Comparative Example 8 was produced in the same manner as Comparative Example 2 except that the thickness was 01 μm.

(Reference Example 3)
The surface roughness Ra of one metal block is 0.010 ± 0.01 μm, 0.020 ± 0.0 μm, 0.05 ± 0.01 μm, 0.10 ± 0.01 μm, and 0.30 ± 0.01 μm A metal laminate structure of Reference Example 3 was produced in the same manner as Reference Example 1 except that the above was changed.
(Evaluation)

  The thermal characteristics of the sample thus prepared were evaluated in the same manner as the sample of Experiment A. The results are shown in Table 4.

  As can be seen from Table 4, in the sample of Comparative Example 8 using a commercially available heat radiation compound and the sample of Reference Example 3 having no heat conduction layer, the contact thermal resistance is greatly affected by the surface roughness. . On the other hand, in the samples of Example 5 and Comparative Examples 6 and 7 in which the heat conductive layer contains a surfactant, it was confirmed that the contact thermal resistance was hardly affected by the surface roughness. did it.

(Experiment D)
Samples of the metal laminated structures of Reference Examples 4 to 6 were prepared, and the influence of the contact form of the crosslinked silicone rubber sheet with the metal block on the thermal resistance of the crosslinked silicone rubber was evaluated.

  FIG. 3 is a cross-sectional view illustrating a form of a contact interface of a metal laminated structure including a crosslinked silicone rubber sandwiched between two aluminum plates. FIG. 3A is an explanatory view showing a cross-sectional structure of a metal laminated structure manufactured as Reference Example 4. FIG. FIG. 3B is an explanatory view showing a cross-sectional structure of a metal laminated structure produced as Reference Example 5. FIG. 3C is an explanatory view showing a cross-sectional structure of a metal laminated structure produced as Reference Example 6.

  The thermal resistance of the crosslinked silicone rubbers of Reference Examples 4 to 6 was measured. The procedure for the measurement is as described for the evaluation of the sample of Example 1. The measurement results are shown in FIG. FIG. 4 is a graph showing the relationship between contact pressure and thermal resistance for Reference Examples 4 to 6. 4, (a) is Reference Example 4 ((a) in FIG. 3), (b) is Reference Example 5 ((b) in FIG. 3), and (c) is Reference Example 6 (((3) in FIG. 3)). The thermal resistance of c)) is shown.

  In the metal laminated structure of Reference Example 4, as shown in FIG. 3A, the boundary 12a between one metal block 10 and the crosslinked silicone rubber 20, and the other metal block 10 and crosslinked silicone rubber 20 are used. And a boundary 14a.

  In the metal laminated structure of Reference Example 4, the metal block 10 and the crosslinked silicone rubber 20 are in physical contact at any boundary. Therefore, as shown in FIG. 4A, the thermal resistance of the crosslinked silicone rubber 20 of Reference Example 4 changes in a wave shape. Although not bound by theory, it is considered that the expansion / contraction occurs near the boundaries 12a and 14a due to the change of the contact pressure. The physical contact is contact by intermolecular force.

  In the metal laminated structure of Reference Example 5, as shown in FIG. 3B, one metal block 10 and the crosslinked silicone rubber 20 are in physical contact at a boundary 12b. The other metal block 10 and the crosslinked silicone rubber 20 are in chemical contact (chemical bonding) at the boundary 14b.

  As described above, when one of the boundary 12b and the boundary 14b is in chemical contact, as shown in FIG. 4B, the thermal resistance value of the crosslinked silicone rubber 20 is not affected by the contact pressure and is constant. It becomes.

  In the metal laminated structure of Reference Example 6, as shown in FIG. 3C, one metal block 10 and the crosslinked silicone rubber 20 are in chemical contact at a boundary 12c. The other metal block 10 and the crosslinked silicone rubber 20 are in chemical contact at the boundary 14c.

  Thus, when the metal block 10 and the crosslinked silicone rubber 20 are in chemical contact at both the boundary 12c and the boundary 14c, as shown in FIG. The thermal resistance becomes low.

  From these facts, it was confirmed that it is important to be in chemical contact at the interface in order to realize stable heat conduction with a low thermal resistance without being affected by the use environment.

(Experiment E)
Samples of the metal laminated structures of Comparative Examples 9 to 11 were prepared, and the influence on the contact thermal resistance value was evaluated when a heat conductive sheet was included in the heat conductive layer. That is, when a heat conductive layer including water, a surfactant, and a builder was formed on the surface of the heat conductive sheet, the influence on the total heat resistance was evaluated.

(Comparative Example 9)
Two metal blocks made of aluminum alloy were prepared. A metal block is a metal layer of a metal laminated structure. The thermal conductivity of these metal blocks was 139 Wm ⁻¹ K ⁻¹ . The surface roughness of these metal blocks was 0.025 μm in Ra.

  Moreover, the heat conductive composite silicone rubber sheet was prepared as a heat conductive sheet. The heat conductive composite silicone rubber sheet is 100 phr of silicone rubber (product number: SH851) manufactured by Toray Industries, Inc., 0.6 phr of silicone rubber (product number: RC-4) manufactured by Toray Industries, Ltd., and Showa Denko K.K. Alumina manufactured (product number: AS-30, particle size: 30 μm) was blended in 200 phr. The crosslinking conditions were 160 ° C., 3 MPa, and 30 minutes. The thickness of the heat conductive composite silicone rubber sheet was 0.175 mm.

The heat conductive layer raw material 7 was applied to one surface of the heat conductive composite silicon rubber sheet in the same manner as in Example 1. And one metal block was piled up. Moreover, the heat conductive layer raw material 7 was apply | coated to the other surface of a heat conductive composite silicon rubber sheet in the same way as the case of one surface. And the other metal block was piled up and the sample of the metal laminated structure of the comparative example 9 was produced. The coating amount of the heat conductive layer raw material 7 was 10 mg / 4.84 cm ² on one surface and the other surface, respectively.

(Comparative Example 10)
A sample of the metal laminate structure of Comparative Example 10 was prepared in the same manner as Comparative Example 9 except that the heat conductive sheet was a polyimide-bonded heat conductive composite silicone rubber sheet.

  As the polyimide, Kapton (registered trademark) (product number: 250EN) having a thickness of 25 μm was used.

  The polyimide-bonded thermally conductive composite silicone rubber sheet was prepared by molecularly bonding polyimide to one surface of the same type of sheet as the thermally conductive composite silicone rubber sheet used in Comparative Example 9. The thickness of the polyimide-bonded thermally conductive composite silicone rubber sheet was 0.2 mm.

(Comparative Example 11)
A sample of the metal laminate structure of Comparative Example 11 was produced in the same manner as Comparative Example 10 except that the heat conductive layer raw material 7 was not applied.
(Evaluation)

  The thermal characteristics of the sample thus prepared were evaluated in the same manner as the sample of Experiment A. The results are shown in Table 5.

As can be seen from Table 5, in the sample of Comparative Example 11 without the heat conducting layer, the total thermal resistance is reduced from 0.421 × 10 ³ m ² KW ⁻¹ to 0.360 × 10 ³ m ² KW ⁻¹ . It is greatly affected by the contact pressure. On the other hand, in the sample of Comparative Example 9 in which the heat conductive layer contains a surfactant, the total thermal resistance is substantially constant at 0.215 to 0.216 × 10 ³ m ² KW ^−1. Yes, the total thermal resistance is almost unaffected by the contact pressure. Further, in the sample of Comparative Example 10 in which the heat conductive layer contains a surfactant, the total thermal resistance is 0.341 × 10 ³ m ² KW ⁻¹ to 0.333 × 10 ³ m ² KW ^−. Although it is slightly reduced to ¹ , the rate of decrease is 2.4%, which is a practically acceptable range.

(Experiment F)
When the metal laminated structures of Examples 6 to 8 and Comparative Examples 12 to 14 were prepared and 1 to 3 heat conductive sheets were provided inside the heat conductive layer, the influence on the total thermal resistance was evaluated. That is, when a heat conductive layer including water, a surfactant, and a builder was formed on the surface of the heat conductive sheet, the influence on the total heat resistance was evaluated.

(Example 6)
The heat conductive layer raw material was changed to heat conductive layer raw material 6, and 600 phr of Showa Denko Co., Ltd. alumina (product number: AS-30, particle size: 30 μm), which was the heat conductive sheet raw material, was blended. Except for the above, a sample of the metal laminate structure of Example 6 was produced in the same manner as in Comparative Example 9.

(Comparative Example 12)
A sample of the metal laminate structure of Comparative Example 12 was produced in the same manner as in Example 6 except that there was no thermal conductive layer.

(Example 7)
Comparative Example 10 except that two heat conductive sheets were used, and 600 phr of alumina (product number: AS-30, particle size: 30 μm) manufactured by Showa Denko Co., Ltd., which is the raw material of the heat conductive sheet, was blended. Thus, a metal laminated structure of Example 7 was produced. A heat conductive layer was also formed between the polyimide-bonded silicone rubber sheets.

(Comparative Example 13)
A sample of the metal laminate structure of Comparative Example 13 was produced in the same manner as in Example 7 except that there was no thermal conductive layer.

(Example 8)
A sample of the metal laminated structure of Example 8 was produced in the same manner as in Example 7 except that the number of heat conductive sheets was three.

(Comparative Example 14)
A sample of the metal laminate structure of Comparative Example 14 was produced in the same manner as in Example 8 except that there was no thermal conductive layer.
(Evaluation)

  The thermal characteristics of the sample thus prepared were evaluated in the same manner as the sample of Experiment A. The results are shown in Table 6.

  As can be seen from Table 6, it was confirmed by the heat conductive layer that the total thermal resistance was not dependent on the contact pressure when the contact pressure was approximately 0.05 MPa or more. In the absence of a heat conducting layer, the total thermal resistance decreases with increasing contact pressure. Thus, it was confirmed that the contact pressure when the total thermal resistance was lowered was considerably larger than the contact pressure allowed in the usage environment of the laminated metal structure. When the contact pressure is increased, the size of the components increases, and it has been confirmed that it is difficult to employ a metal laminated structure without a heat conductive sheet with small components such as an inverter and an LED.

  As a result, particularly from Table 2, the effect of the metal laminated structure of the present disclosure was confirmed.

10 Metal block 20 Cross-linked silicone rubber 12a, 14a, 12b, 14b, 12c, 14c

Claims (1)

Multiple metal layers;
A thermally conductive layer sandwiched between the metal layers;
With
The heat conductive layer contains water, a surfactant, and a sodium salt;
Metal laminated structure.

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