EP3191249A1

EP3191249A1 - Method for shortening the process time during the soldering of electric or electronic components by means of electromagnetic induction heating

Info

Publication number: EP3191249A1
Application number: EP15763876.8A
Authority: EP
Inventors: André Jenrich
Original assignee: FEW Fahrzeugelektrikwerk GmbH and Co KG
Current assignee: FEW Fahrzeugelektrikwerk GmbH and Co KG
Priority date: 2014-09-12
Filing date: 2015-09-10
Publication date: 2017-07-19
Also published as: MX390608B; DE102015003086A1; US20170297130A1; DE202015002764U1; WO2016038144A1; CN107073617A; MX2017003154A

Abstract

The invention relates to a method for shortening the process time during the soldering of electric or electronic components by means of electromagnetic induction heating, in particular the soldering of electric contact elements to solder connection surfaces that are applied to a non-metallic substrate, in particular a pane of glass. According to the invention, an electric contact element is first produced, designed as a solder foot, made of a material with an iron-nickel or iron-chromium alloy base. Subsequently, a lead-free connecting material is applied to the solder foot. After the solder foot has been positioned on the respective solder connection surface, the solder foot is inductively heated by means of high frequency energy with increased heating of the solder foot material and reduced heating of the silver-containing material of the respective solder connection surface. The soldering stage is completed after a time of <10 s, in particular within a time of <4 to 6s. The invention also relates to a contact element in the form of a special solder foot.

Description

Process for shortening the process time during soldering of electrical or electronic components by means of electromagnetic induction heating

description

The invention relates to a process for shortening the process time when soldering electrical or electronic components by means of electromagnetic

Induction heating, in particular the soldering of electrical

Contact elements with solder pads, which are applied to a non-metallic substrate, in particular a glass sheet, as well as

Contact element for this.

From DE 102004057630 B3 a method for soldering a plurality of electrical connections is already known, in which contact elements are to be soldered with arranged on a non-metallic disc solder pads.

In the previously known method, an inductive soldering process is used. In this regard, one of an electrically powered

Loop or coil comprehensive and in the area of several solder pads overlapping soldering tool radiated a magnetic field with a vorgefernen frequency to the solder joints to heat them by induction, the size and shape of the soldering tool is sized with the loop or coil depending on the area on the plurality are arranged in a soldering simultaneously aufheizende solder joints.

The frequency of the AC voltage applied to the loop or coil is adjusted to the connection geometry and is set to a maximum of 150 kHz. Specifically, the frequency of the magnetic field is between 5 and 150 kHz.

The teaching according to DE 102004057630 B3 is based on the recognition that in experiments of inductive soldering with frequencies in the range between 700 and 900 kHz no satisfactory results have been achieved. It has been found that the solder pattern pads on the wafer surface, which consist of a baked thick film of relatively high silver screen print paste, overheat and dissipate a great deal of heat while at the same time not sufficiently heating the components to be soldered. The reason given is that the conductor structure or its material has a high absorption for the inductively registered high-frequency waves. When using high frequencies, the heating does not go into the depth range of a body, or only very slowly, but stays on its surface, which is called a so-called skin effect.

Accordingly, deviating from knowledge of the device manufacturers the

Frequency of the induced waves in inductive soldering significantly reduced, in a range <150 kHz. With this frequency, the penetration depth of the magnetic field is to be increased. A disadvantage is pointed out in DE 102004057630 B3 that an increased electrical power is to be provided, since the relatively low-frequency radiation undergoes comparatively high transmission losses in the air gap and disk body. In this respect, it is necessary to work with a higher field strength of the low-frequency magnetic field.

From DE 20203202 Ul is an electrical connection, in particular crimp or crimp connection, for at least one of a disc of a

Means of transport, in particular of a motor vehicle, electrical equipment to be arranged, e.g. an antenna, previously known. The electrical connection comprises at least one essentially flat soldering pad to be soldered onto the pane and at least one crimping part, in particular crimp, which is in connection with the soldering pad by welding or soldering and which defines at least one electrical cable in the crimping connection.

According to the local solution, the connection between the soldering pad and the crimping part is designed in the form of at least one connecting part, wherein the connecting part is designed such that the crimping part can be bent back into the area of the soldering pad and / or beyond the area of the soldering pad.

DE 102006047764 AI discloses a lead-free solder with improved properties at temperatures of> 150 ° C. The lead-free solder is based on an Sn-In-Ag solder alloy containing between 88 to 98.5 wt% Sn, between 1 and 10 wt% In, between 0.5 to 3.5 wt% Ag, between 0 to 1% by weight of Cu and a doping with a crystallization modifier,

in particular a maximum of 100 ppm neodymium. This lot should be a good one

Compatibility with regard to the luting agent used and have a high fatigue strength. DE 202011 100906 Ul shows an electrical connection element for

Contacting a conductive structure on a flat support by means of a thermosubstantial bonding material, wherein on its, remote from the conductive structure side, means for fixing a conductor are arranged. The connection element is as Lötfuß

formed, which has a, at least approximately eight or circular ring shape. Preferably, the soldering foot of the known type consists of several, interlocking circular rings or circular ring segments. However, it has been found that in such a connection element in the field of

interlocking circular rings or circular ring segments in an inductive soldering process, a high concentration of the electromagnetic field is produced, resulting in overheating of the glass structure during soldering on a

corresponding busbar of the glass and thus to their

Destruction leads.

From the above, it is an object of the invention, a further developed process for process time reduction during soldering electrical or

electronic components by means of electromagnetic induction heating, in particular the soldering of electrical contact elements with

Solder pads located on a non-metallic substrate,

Specifically, a glass pane are applied to specify, in which it succeeds with classic frequencies optimal heating of the

soldering object to accomplish in an inductive manner, without

Gegenkontaktflächen an excessive heating subject to the associated adverse effects of the used

non-metallic substrates, especially when this substrate is a glass sheet, e.g. a vehicle window is.

In addition, it is an object of the invention, an evolved

Indicate contact element for soldering by means of electromagnetic induction heating, which helps to avoid local overheating during the soldering process, thus allowing a uniform heating of the soldering partners.

The solution of the object of the invention is achieved by the teaching

Definition according to claim 1 or 9, wherein the dependent claims

represent at least expedient refinements and developments. The invention goes back to the basic knowledge of the principle of induction heating for the purpose of soldering. Due to the possibility of partial heating during induction soldering can solder joints

Workpieces are executed, which may be heated briefly and only at the solder joint. Thus, inductive soldering basically offers the advantage that unwanted influences on the structure and the strength of adjacent zones are avoided.

The basic principle of induction soldering uses the knowledge that electrical conductors through which an alternating current flows create an electromagnetic field around them, which oscillates around the zero point with a phase shift analogous to the frequency of the alternating current. If an electrically conductive body is brought in the vicinity of this current-carrying conductor, then a voltage is induced therein, which also causes an alternating current, the so-called secondary alternating current.

This induced alternating current is 180 ° out of phase with the

Primary current. If sufficient current is sufficient, the second conductor or workpiece, in the present case the soldering foot, is heated by the heat generated by the current. The heat energy can be at non-ferromagnetic

Materials are determined by Newton's law.

The current-carrying primary conductor is referred to as an inductor. The shape of the inductor is adapted to the shape of the workpiece section to be heated, in particular the soldering foot.

It is possible to use both inducing Einwindige inductors as well as mehrwindige inductor coils with n turns, in the latter case, the secondary current in the workpiece proportional to the

Number of turns increases and reaches n times the value of the primary current.

The induced currents predominantly flow only at the surface of the conductor. The heat energy generated in an inductively heated metallic body is thus accumulated in its surface layer, the thickness of which depends on the frequency and on the electrical and magnetic properties of the material. The relevant skin effect is due to the fact that an alternating current flowing in a conductor also generates eddy currents through self-induction in its interior, which are directed counter to the primary current. Through this resulting overlay arises inside the conductor a higher resistance, which causes a concentration of the current at the surface of the conductor. With increasing frequency, this effect increases, so that at high frequencies only a very thin

Surface layer of the conductor is flowed through. This also has the consequence that the effective resistance increases significantly with increasing frequency compared to its DC resistance. Furthermore, the current density from the surface to the inside of the conductor decreases after an e-function. Related to the inductive heating so it can be seen that the introduced into an inductor workpiece also behaves like a current-carrying conductor.

Regardless of the problems of the skin effect, a significant advantage of induction heating over other thermal heating methods is the fact that the heat is instantaneous

Workpiece itself is generated. So it does not need to be transmitted by convection, radiation and / or heat conduction, which basically allows high Aufheizgeschwind ig opportunities.

Will be a ferromagnetic material for the material to be soldered

used, then added to the heat energy, the through

Re-magnetization arises as a result of the constantly changing electromagnetic field

According to the invention, the prejudice of the art has been overcome, which consists in the case of soldering of metallic soldering feet on electrical contact elements with solder pads as possible no high frequencies to use to overheating the solder pads

Avoid, otherwise too much heat is dissipated and only one

insufficient heating of the components to be soldered is the result.

According to the invention it has been recognized that in the formation of electrical contact elements, in particular solder feet, made of a material of an iron-nickel or iron-chromium alloy, even at high frequencies

extremely rapid heating of the ferromagnetic elements is given by higher eddy current losses. Since the solder pads, which usually consist of a silver-containing thick-film material, represent a much better electrical conductor, the amount of energy converted there by induction is significantly lower, so that in the desired very short process time, a fast and sufficient heating of the solder pad materials, but only a slight warming of the respective solder pad occurs. Thus, only little energy is conducted to the substrate, in particular the glass used, so that thermal stresses caused by the soldering process can be avoided.

Another advantage arises when according to the invention

Process a lead-free compound material, in particular a lead-free solder, is used for the soldering process.

In the case of lead-free solders, to replace the ductility of the missing lead, adaptation of the thermal expansion coefficients of the glass sheet and solder foot material is achieved by replacing the copper in the solder foot material, in particular by an iron-nickel or iron-chromium alloy. Just such an alloy material leads to the particularly advantageous effect of higher eddy current losses with faster and

More intense heating, so that there are multiple benefits, under the said aspect of the thermal expansion coefficient and the desired process time reduction during soldering.

Surprisingly, the proposed process control and the application of high frequency energy in a range of around 900 kHz does not adversely affect or damage the silver layer material of the solder pads located on the disk.

In a further development of the method according to the invention, the process control can be configured such that a short-term first inductive

Heating step followed by a short cooling phase, followed by another inductive heating phase followed. Such a cycle can also be executed several times, within the very short total process time. Such process control significantly increases the shear strength of the achieved solder joint.

The electrical contact element used according to the invention is used for

Contacting a on a flat support, in particular the mentioned glass located conductive structure, these in turn consisting of a silver thick film. As already mentioned, the carrier or the substrate is preferably a pane of safety glass, in particular for use in motor vehicle technology. The conductive structure is an electrically conductive structure, for example in the form of an antenna or heating conductor arrangement, which can be realized by screen printing. In particular, unleaded solder, which is located on the side of the electrical connection element which is free of a wire end sleeve or a similar means for fastening a flexible conductor, is used as connection means.

The contact element, designed as a soldering foot, has one, at least

Approximate shape of number eight or an approximate circular shape. The soldering foot is flat and consists of an iron-nickel or iron-chromium alloy.

According to the invention, the soldering foot consists of a plurality of non-intermeshing or non-touching, i. spaced circular surfaces, circular rings or circular ring segments. Between the circular surfaces there is a connecting surface piece which is used to fix a connection means, e.g. a wire end sleeve is used.

The connecting material may be preferred as Lötzinn-Ronde on the

Contact element are applied on one side.

Preferably, the contact element, ie the soldering foot, consists of FeCr ₂ 8 or FeNi ₂₉ Coi ₇ .

The lead-free solder comprises, at least as a component, the following alloys: Bi ₅₇ Sn ₄₂ Agi, Bi ₅₇ Sn ₄₀ AG _3, SnAg. ₃ ₈ Cu ₀ .7 or Sn ₅₅ Bi ₄₄ Agi.

By the choice of material of the electrical contact member results in a coefficient of expansion that is very close to the coefficient of expansion of automotive glass panes, about 9xl0 ^"6 K. Potential or residual stresses are distributed through the particular form of Lötfußes in the glass and absorbed by the glass material without that there is a risk of impairment or destruction.

For example, the soldering foot in the form of a quasi-elongated "eight" has a length of about 20 mm and one each end-side outer diameter of approx. 6 mm with a material thickness of approx. 0.8 mm. It is within the meaning of the embodiment of the invention to modify the mentioned form of Lötfußes also to an exploded double night, without leaving the theory of the invention. The connecting surface piece has a length of about 9 mm.

It has surprisingly been found that in particular the

proposed surface shape of the contact element of an optimal inductive heating in terms of the desired rapid heating and reducing the process time is sufficient, with the avoidance of adverse

stray electromagnetic fields at least one of the surface sides of the soldering foot has a circumferential radius of e.g. Has 0.2 mm.

In exemplary experiments for soldering iron-nickel-containing or stainless steel contact elements or soldering feet, a process time reduction of> 50% compared to inductive soldering of copper-containing materials could be detected. If one compares the proposed inductive soldering with a classical resistance soldering of the electrical contact elements, then the process time of 12 to 15 seconds during inductive soldering is shortened to about 4 to 6 seconds.

The inventive method is summarized by the steps of creating an electrical contact element, designed as Lötfuß

characterized in that the contact element material is based on an iron-nickel or iron-chromium alloy. Furthermore, a lead-free bonding material is applied to the contact element, i. applied the soldering foot. in the

Connection is carried out by positioning the soldering foot on the respective

Lötanschlussfläche, which preferably consists of a silver thick-layer material and which is located on a glass sheet.

Subsequently, an inductive heating of the soldering foot by means of

high-frequency energy with resulting increased heating of the

Solder foot material and only reduced heating of the silver-containing material of the respective solder pad. The soldering step is completed after a very short time, in particular a time <10 seconds, preferably in particular in a time of 4 to 6 seconds. The electrical connection element according to the invention, ie the specially trained soldering foot, will be explained in more detail using an exemplary embodiment and with the aid of figures.

Hereby show:

Fig. 1 is a side view of the soldering foot with exemplary dimensioning in

Scale 8: 1;

Fig. 2 is a plan view of the contact element of Fig. 1; 3 shows a detailed view A according to FIG. 1 and FIG. 4 shows a narrow side view of the soldering foot.

The electrical connection element shown in the figures is designed as Lötfuß and consists of two circular surface segments 1; Second

Between the circular surface segments 1; 2 is a connecting surface piece 3. In the plan view of Fig. 2 therefore has the Lötfuß the shape of a quasi-expanded "eight" with two, not intermeshing

Circular surface segments 1; 2 and the connecting surface piece 3.

Preferably, a conductor or a conductor end sleeve (not shown) is provided in the area of the joining surface piece 3, e.g. fixed by welding or soldering.

In the area of the circular surface segments 1; 2 protrusions 4 are formed on the underside of the soldering foot, which are for example embossed beads.

These projections 4 rest on the surface of the structure during the soldering process and form a defined one with an exemplary height of 0.3 mm

Soldering gap.

In sleeve-like holes 5, the solder is cohesively fixed, so that a corresponding prefabrication of the soldering foot including solder can be done in a simple manner. In order to avoid disadvantageous electromagnetic stray fields or a field concentration, at least one of the surface sides of the soldering foot is provided with a circumferential radius 6 of, for example, 0.2 mm.

The dimensions shown in Figs. 1 and 2 are merely exemplary, i. Without limiting the teaching of the invention to understand.

The connecting surface piece 3 may have a crank 7 with the exemplary radius R = 0.8 mm.

Decisive is a taper 8 such that the width of the connecting surface piece 3 is smaller than the diameter of the corresponding

Circular area segment 1; 2. In the example shown, the width of the connecting surface piece 3 is 4 mm; however, the diameter of the

Circular surface segments 1; 2 6 mm.

Claims

claims

1. A method for process time reduction in the soldering of electrical or electronic components by means of electromagnetic induction heating, in particular the soldering of electrical contact elements with

Solder pads located on a non-metallic substrate,

in particular a glass pane are applied,

with the following steps:

- Creation of an electrical contact element, designed as Lötfuß, made of a material of an iron-nickel or iron-chromium alloy;

Applying a lead-free bonding material to the soldering foot;

Positioning the solder foot on the respective solder pad;

inductive heating of the soldering foot by means of high-frequency energy with increased heating of the Lötfußmaterials and reduced heating of the material of the respective solder pad;

Completion of the soldering step after a time <10 s, preferably 4 to 6 s.

2. The method according to claim 1,

characterized in that

the high-frequency energy is in the range of 700 to 1500 kHz, in particular at substantially 900 kHz.

3. Method according to one of the preceding claims,

characterized in that

the bonding material or solder consists of a lead-free material, in particular Bi ₅₇ Sn ₄₂ Agi, Bi ₅₇ Sn ₄₀ AG3, SnAG3.sCuo.7 or Sn ₅₅ Bi ₄₄ Agi.

4. Method according to one of the preceding claims,

characterized in that

a soldering foot is used, which consists of at least two, not

interdigitated, by a connecting surface piece spaced circular surfaces, circular rings, circular ring segments or circular surface segments, wherein the soldering foot preferably outside of the connecting surface piece has projections for forming a defined soldering gap.

5. An electrical connection element for contacting a surface-mounted conductive structure by means of a thermosolid bonding material, wherein on its of the conductive Structure facing away from means are arranged for fixing a conductor, further, the connection element is designed as a soldering foot, which has an approximate shape of an eight,

characterized in that

the soldering foot of at least two, not interlocking, by a

Connecting surface piece (3) spaced circular surfaces, circular rings,

Circular segments or circular surface segments (1, 2) consists.

6. Electrical connection element according to claim 5,

characterized in that

the soldering foot preferably has projections (4) outside of the connecting surface piece (3) to form a defined soldering gap.

7. Electrical connection element according to claim 5 or 6,

characterized in that

the means for fixing the conductor in or on the connecting surface piece (3) is located.

8. Electrical connection element according to one of claims 5 to 7, characterized in that

the thermal-cohesive bonding material on one side of the

Connecting element is applied and there occupies a surface which is smaller than the circular or annular surface (1, 2).

9. Electrical connection element according to claim 8,

characterized in that

the connecting material is designed as a solder-wire blank which is arranged at least partially in a recess (5) or bore in the area of the respective circular or annular surface (1; 2).

10. Electrical connection element according to one of claims 5 to 9, characterized in that

the connection element consists of an iron-nickel or iron-chromium alloy or a mixture thereof.