EP2401789B1 - Method for producing flexible metal contacts - Google Patents

Description

The invention relates to methods for producing flexible electrical and / or thermal metal contacts for connecting electrical, electronic or thermal components, such contacts and their use for compensating mechanical and / or thermal stresses in an electrical, electronic or thermal component.

An essential element of electrical, electronic and thermal components is the contacting. The contacting establishes the physical connection between the material in the "heart" of the component (which is responsible for the desired effect of the component) and the "outside world". The structure of such a contact is in Fig. 1 shown schematically.

The material 1 within the component provides for the actual effect of the component. This may be, for example, an electrical resistance, a diode material, a capacitor, a piezoelectric crystal, or a thermoelectric leg. The naming as the material should not be limited to a single material at this point, it may well involve several materials, composites or other "building units". It is relevant, also within the meaning of the invention, that the material 1 must be traversed by an electric current and / or a heat flow in order to fulfill its purpose in the overall structure.

Exactly this coupling of the electrical and / or heat flow can now turn out to be limiting for the performance characteristics of the component. A common construction is in Fig. 1 shown. The material 1 is connected on at least two sides via the contacts 4 and 5 with the leads 6 and 7 respectively. The layers 2 and 3 are intended to symbolize an intermediate layer (barrier material, solder, adhesion promoter or the like) which may be necessary between the material 1 and the contacts 4 and 5 . However, these intermediate layers may well be omitted or even multiple layers, depending on the specific structure of the component. The pairs belonging to each other segments 2/3, 4/5, 6/7 can, but need not be identical. Ultimately, this also depends on the specific structure and the application, as well as the flow direction of electrical current or heat flow through the structure.

The important role now comes to contacts 4 and 5 . These provide a close connection between material and supply line. If the contacts are bad, high losses occur here, which can severely limit the performance of the component. For this Reason the contacts are often also pressed onto the material. The contacts are therefore exposed to a strong mechanical stress. This mechanical load increases as soon as increased (or even lowered) temperatures or / and thermal changes play a role. The thermal expansion of the materials installed in the component inevitably leads to mechanical stress, which in extreme cases can lead to a failure of the component by a tearing of the contact.

To prevent this, the contacts used must have a certain flexibility and spring properties, so that such thermal stresses can be compensated.

A sheet of metal or metal plate is usually not soft or flexible enough to meet the requirements.

In the case of thermoelectric ketrischen components, which are operated in a sometimes quite large (several hundred Kelvin) temperature gradient, the use of such "buffering" contacts from the literature is known. So describes N. Eisner, Mat. Res. Soc. Symp. Proc. 1991, 234, 167 , the use of flexible metal plates for contacting in thermoelectric generators.

EP-A-0 901 191 relates to an electrical connection of a woven mesh. The fabric consists of parallel conductive metal filaments that are cross-interwoven with non-conductive filaments. The fabric is embedded in a resin matrix. It is stated that the conductive tissue can be deformed.

US 2006/0094269 relates to an electrical contact and a method for its production. The contact is made of a woven or perforated metal sheet that can be deformed into a desired shape using elastic deformation and plastic deformation. A folded or unfolded layer structure can be formed. The metal mesh is formed so that no further support elements are required.

The contacts described are not yet sufficiently flexible and adaptable to extreme temperature fluctuations for all applications.

Object of the present invention is to provide a method for producing flexible electrical and / or thermal metal contacts for connecting electrical, electronic or thermal components, the flexible or resilient contacts leads, which show a favorable property spectrum especially for thermoelectric applications.

The object is achieved by a method for producing flexible electrical and / or thermal metal contacts for connecting electrical, electronic or thermal components, in which compressed metal fiber web with a mean fiber diameter in the range of 1 to 500 microns by rolling under cold deformation to fiberboard.

It has now been found that can be produced by rolling of fine non-wovens very dense fiberboard, which have a high thermal and electrical conductivity in the component and also mechanically very stable, but at the same time soft (ie pressure yielding or resilient) and are flexible enough to compensate for thermal and mechanical stresses.

Depending on the purpose, different metals can be used. Of course, particularly preferred are conventional contacting metals such as copper, silver, gold, aluminum, iron or steels, but in principle the method is applicable to any metallic conductive material. According to one embodiment of the invention, the metal is Cu, Ag, Au, Fe, Ni, Pt, Al or alloys thereof.

In the metal nonwovens, the average fiber diameter is 1 to 500 μm, preferably 10 to 100 μm, in particular 40 to 80 μm. The metal nonwovens preferably have a greater extent in two spatial directions than in the third spatial direction, so that they are flat nonwovens. The metal contacts to be produced preferably have an average diameter or a thickness in the range of 100 μm to 10 mm.

Structured or unstructured (in the sense of the fiber direction) nonwovens can be used as starting materials. Of course, the fabric density has an influence on the result, but basically there are no restrictions on the area density or the like.

There is also no limitation on the surface texture of the single fiber. Although a rough fiber surface quickly leads to a dense toothing in the product, but also a fleece made of smooth fibers can be easily processed and compacted.

The metal fiber webs can be folded one or more times before densification to form thicker fleece layers, metal fiber nonwovens of different metals can be combined into a layer composite. Even nonwovens with different orientation can be stacked. As a rule, nonwovens have one or two preferred directions. Superimposed or successive layers can show the same preferred direction, or the preferred directions can form an angle to each other in the individual layers. For example, a unidirectional metal fiber fleece can be laid alternately in the longitudinal and transverse directions.

The manufacturing process itself is preferably based on a metal fiber fleece. This can be z. B. can be used directly for compaction. But it is also possible to fold the fleece several times before compaction (like a newspaper), and then to compact. In this way, thicker and closely interlocked contact plates are obtained. In principle, it is also possible first to perform a folding after a first compacting step and then to compact it again (and repeat the process several times if necessary), but this normally leads to a poorer toothing of these individual layers due to the smoother surface of the once compacted material.

Since the compaction during rolling is a directed process, ultimately also the orientation of the workpiece plays a role, especially since even the fleece itself sometimes has a preferred orientation of the fiber. A successive "crosswise" compaction in two mutually perpendicular spatial directions therefore seems most favorable for a close and dense toothing.

The rolling can be done in a simple rolling device, but also using multiple parallel or serially inserted rollers. The rollers can have both a smooth and a structured surface. The latter may be advantageous if a certain surface roughness in the product is desired.

Optionally, the cold working may be combined with heating or cooling to adapt the processing properties of the respective metals to the particular rolling process, depending on the fiber thickness.

The processes can also be used for continuous and discontinuous production.

The invention also relates to flexible electrical and / or thermal metal contacts made of fiberboard obtainable by the method described above.

These metal contacts are preferably used to compensate for mechanical and / or thermal stresses in an electrical, electronic or thermal component. In particular, the mechanical and / or thermal stresses which may occur under operating conditions are compensated.

The fiberboard or metal contacts can be used in a variety of applications where good thermal and / or electrical conductivity is required. Preferred fields of application are thermoelectrics, magnetocalorics, electronic components such as capacitors, fuel cells, transformers, batteries, electric generators, the photovoltaic or system combinations thereof. The component is particularly preferably a thermoelectric generator or a Peltier element.

The invention will be explained in more detail by the following example.

example 1

A copper fleece with a wire thickness of 60 μm was transferred by rolling into a fiber board. It was compressed from an initial thickness of 4.5 mm to 0.9 mm.

Example 2

A copper cloth with a fiber diameter of 60 μm and a weight per unit area of 1700 g / m ^{2 was transferred} by rolling into a fiber board. It was compressed from a starting thickness of 6.0 mm to 1.4 mm.

Claims (10)

1. A method for producing flexible electrical and/or thermal metal contacts for connecting electrical, electronic or thermal components in which metal fiber nonwovens with an average fiber diameter in the range from 1 to 500 µm are compacted by rolling involving cold working to form fibrous sheets.
2. The method according to claim 1, wherein the average fiber diameter is 10 to 100 µm.
3. The method according to either of claims 1 and 2, wherein the metal is selected from Cu, Ag, Au, Fe, Ni, Pt, Al and alloys thereof.
4. The method according to one of claims 1 to 3, wherein the metal contacts have an average diameter or a thickness in the range from 100 µm to 10 mm.
5. The method according to one of claims 1 to 4, wherein the metal fiber nonwovens are folded one or more times before compaction, to form thicker nonwoven coverings.
6. The method according to one of claims 1 to 5, wherein metal fiber nonwovens of at least two different metals are laid one on top of the other and this composite is compacted.
7. The method according to one of claims 1 to 6, wherein the compaction is performed successively in two spatial directions that are perpendicular to each other.
8. A flexible electrical and/or thermal metal contact comprising fibrous sheets, obtainable by a method according to one of claims 1 to 7.
9. The use of metal contacts according to claim 8 to compensate for mechanical and/or thermal stresses in an electrical, electronic or thermal component.
10. The use according to claim 9, wherein the component is a thermoelectric generator or a Peltier element.

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