EP1771596A1 - CONDUCTIVE MATERIAL COMPRISING AN Me-DLC HARD MATERIAL COATING - Google Patents

Abstract

The invention relates to a conductive material consisting of an alloy that contains copper, for use as a plug-in or clip connection. Said material comprises a cover layer that is deposited on at least some sections of the contact surface, said layer consisting at least of a support layer and an adhesive layer. The anti-friction layer has a carbon content greater or less than 40 and less than or equal to 70 atomic percent.

Description

Copper-containing material with Me-DLC hard coating

Technical area

The invention relates to a conductive material made of a copper-containing alloy for use as a plug or Klemm¬ connection according to the preamble of claim 1. Further, a contact piece according to claim 18, and a semifinished product according to claim 19 or a band or profile according to claim 20 ,

State of the art

Copper-containing conductive materials are also known from the prior art, such as the good suitability of copper materials for the application of galvanic layers for Ober¬ surface refinement. On the other hand, PVD, CVD or PVD / CVD layers have hitherto been used little on the relatively soft copper materials, since, for example, in the case of a sliding stress with high load, as can occur when mounting plug-in or clamped connections, the layer In the base material is pressed or breaks and many used for the tool coating layer system too high a coefficient of friction (for example, the carbides WC, or Cr _x Cy have a coefficient of friction of about 0.5 and greater), have too high roughness or poor electrical conductivity which makes them unsuitable for such an application.

DE 1 802 932 discloses a high-frequency plasma method for coating electrical contacts with carbide wear protection layers. Similar to DE 3011694, wherein inter alia the application of a galvanic adhesive layer on various hardened or hardened metallic Werk¬ materials and an adjoining PVD coating in High-frequency plasma is described in which, inter alia, a carbide hard material layer is deposited. This achieves good electrical conductivity and increased wear protection, but the carbide coating results in a relatively high coefficient of friction.

From DE 4421144 coated tools are known in which a hard material layer of metal carbide and then a free carbon-containing ReibminderungsSchicht is applied to tungsten carbide base to increase the service life.

Presentation of the invention

The invention is based on the object to provide a copper-containing control material, in which the disadvantages of the prior art are avoided and better electrical properties and a better service life and sliding behavior compared to conventionally coated materials are achieved.

This object is achieved by the inventive features in the characterizing part of claim 1.

By using according to the invention modified carbon-containing sliding or hard coatings having a carbon content of greater than or equal to 40 but less than or equal to 70 atomic percent, which are deposited on copper or copper alloys, it is possible the hardness of the surface and thus the To increase the wear and abrasion resistance of the materials without significantly changing their excellent electrical properties. The carbon content is understood as meaning the content of carbide-bound and free carbon which, together with the carbide former and additional optional elements added to 100%. In this case, a hard layer having defined tribological and electrical properties is deposited with a method as described in more detail below, which leads to an extension of the service life of the guide materials. The layers are slightly less hard than conventional hard carbides, for example, but significantly harder than the carrier material and thus protect it against abrasive wear. Surprisingly, these layers better protect the carrier material in plug-in and clamping applications than conventional hard-coating systems, wherein a support layer may additionally be provided for applications with high surface pressure. In the case of existing hard coatings, this could also be attributed to the relatively low coefficient of friction, which has advantageous effects, for example when used in a plug connection, since this simultaneously reduces the insertion forces and prevents scratching of a possibly uncoated counterpart.

It is precisely these properties that make such layers suitable for applications in vehicle or aircraft construction or in all applications in which continuous loads due to vibrations, oscillations or the like may also occur in conjunction with shock loads. Due to the higher stability compared to conventional copper conductive materials, dysfunctional or even function-preventing phenomena of surface fatigue at joints which can occur due to the relatively low strength of the copper or of the previously coated copper materials are avoided. Furthermore, it is also possible to effectively prevent triboxidation phenomena which occur at elevated working temperatures and are frequently the cause of the failure of such plug and clamp connections. On the following copper-containing alloys coated according to the invention, a marked improvement in the load-bearing capacity could be ascertained up to now when used as push-in and clamp connections: copper, bronze, brass or nickel silver. However, similar improvements are expected when using other base materials such as CuBe and other alloys, or when used for other applications.

Furthermore, it may also be advantageous to use galvanically coated conductive materials. Examples of these are Cr, Ni or CrNi layers, which are applied before the support layer.

Due to the low deposition temperatures, plasma CVD, PVD or PVD / CVD hybrid processes are particularly suitable for the deposition of Me-DLC layers for the coating of, for example, hardenable copper materials.

However, with conventional free carbon-containing layers described, for example, in DE 4421144, or Me-DLC layers described in US Pat. No. 4,992,153 or DE10018143 (DLC stands for "diamond-like carbon"), sufficient conductivity could not be afforded and, as is the case with known carbide layers, insufficient protection against Surprisingly, only by adjusting the carbon content to greater than or equal to 40 but less than or equal to 70 atomic percent could a substantial improvement in conductivity be achieved equal to 50 but less than or equal to 60 atomic percent. By applying an additional support layer comprising at least one metal Me from the elements of subgroups IV, V, and VI of the Periodic Table of the Elements (ie Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) or aluminum or Si included, could further impressions even at very high loads are avoided. Stütz¬ layers have proven to be particularly advantageous in addition to the metallic phase and a non-metal such as C, N, B, or 0 or the HartstoffVerbin¬ containing the metals with these non-metals. Merely by way of example here are the backing layer systems TiN or Ti / TiN (ie, a metallic titanium layer with an adjoining Titannitridhartschicht), CrN or Cr / CrN, Cr _x C _γ or Cr / Cr _x C _y, Cr _x (CN) _γ or Cr / Cr _x (CN) _y , TiAl or TiAlN and TiAl / TiAlN mentioned.

However, depending on the application, it should be noted that the support layer has a minimum layer thickness. This depends above all on the surface pressure occurring depending on the application. For example, with a low surface pressure even with layer thicknesses of 0.5 .mu.m, a sufficient supporting effect of the DLC layer could be achieved, while with a support layer of 0.3 .mu.m, the supporting effect was no longer sufficient. In general, however, a layer thickness of at least 1 to about 3 microns is recommended. For applications in which particularly high surface pressures occur, larger layer thicknesses, for example 6 μm, may also be advantageous.

In addition, between the support layer and the sliding layer, a metallic intermediate layer with or without a graded transition, or directly a transition layer, for example in the form of a gradient layer with increasing carbon content towards the sliding layer, can be applied become .

The DLC overlay itself is therefore advantageously carried out as follows: Directly on the support layer, a metallic intermediate layer comprising at least one metal Me from the elements of the IV, V, VI subgroup, Al or Si deposited. Preferably, an intermediate layer of the elements Cr or Ti is used, which have been found to be particularly suitable for this purpose. However, it is also possible to use nitridic, carbidic, boridic or oxidic interlayers, or interlayers, which are a mixture of one or more metals with one or more of the said non-metals, which, if required, can be used even on a metallic base layer with or without graded Transition can be constructed. When the carbon-lubricant layer is applied directly to the adhesion layer, this intermediate step can be omitted if the adhesion layer itself consists of a metal or a compound suitable as an adhesion-promoting layer.

On this, or alternatively directly, without an intermediate layer, a transition layer, in particular in the form of a gradient layer, preferably adjoins, in the course of which, perpendicular to the workpiece surface, the metal content decreases and the C content increases. The increase in the carbon can be effected by increasing possibly different carbide phases, by increasing the free carbon, or by a mixture of such phases with the metallic phase of the intermediate layer. As is known to the person skilled in the art, the thickness of the gradient layer can be adjusted by setting suitable process ramps. The increase of the C-content or decrease of the metallic phase can take place continuously or stepwise, furthermore, at least in one part of the gradient layer, a sequence of metal-rich and C-type metals can also be obtained. rich individual layers for further degradation of SchichtSpannun¬ conditions are provided. For example, it can be based on a MeC layer, which is applied for example by sputtering, and the proportion of free carbon by adding a carbon-containing reactive gas continuously or gradually increased. For tungsten carbide-based layers, for example, a ratio of about 50: 1 to about 2: 1 of the carbide bound to the free carbon has proved favorable. Similar dependencies could also be found for layers based on chromium carbide, tantalum carbide or molybdenum carbide.

As a result of the mentioned embodiments of the gradient layer, the material properties (for example modulus of elasticity, structure etc.) of the support layer and the DLC layer are substantially continuously adapted to each other and thus the risk of crack formation along an otherwise occurring metal or Si / DLC interface counteracted.

The conclusion of the DLC sliding layer can be made by switching off the sputtering and / or bias supply upon reaching a defined flow of the carbon-containing process gas or upon reaching a certain pressure. Another possibility is to keep the coating parameters constant during the last process phase in order to keep the properties of the outer functional layer constant over a desired minimum layer thickness.

The hardness of the entire carbon layer is set to a value greater than 0.8 GPa, preferably greater than or equal to 10 GPa, and even at layer thicknesses> 1 .mu.m, preferably> 2 .mu.m, an adhesive strength is better on a steel test specimen having a hardness of about 60 HRC or equal to HF 3, but preferably equal to HF 1 according to VDI 3824 sheet 4 is achieved. Measurements of the contact resistance of inventive DLC layers revealed Values between δ = 0.1 mΩ and δ = 90 mΩ, whereby values between 0.5 mΩ and 10 mΩ are preferably set, since on the one hand δ values of less than 0.5 mΩ can only be achieved by substantial additions of noble metals, whereby the production costs increase significantly and on the other hand, for some applications, a contact resistance of more than 10 mΩ is already too high.

At the same time, the present carbon layer is characterized by the low friction coefficients typical for Me carbon, preferably μ <0.2 in the pencil / Scheib test, with a layer roughness of R _a = 0.01-0.04; R ₂ DIN <0.8 preferably <0.5.

The growth rate is about 1-3 μm / h and depends, in addition to the process parameters, also on the loading and mounting. In particular, this affects whether the parts to be coated 1-, 2- or 3-turn, on magnetic brackets, or clamped or plugged attached. Also, the total mass and plasma transmittance of the supports is important, for example, with lightly constructed brackets, e.g. achieved by using storage plates, instead of plates made of solid material, higher growth rates and an overall better layer quality. The layer stress can be at 0.8 GPa and thus in the usual range of hard DLC layers. Furthermore, such layers, with a slightly lower hardness (9 to 15 GPa), a significantly lower coefficient of friction on the insertion forces occurring reduced.

Furthermore, these properties can be achieved by adding, for example by co-sputtering, evaporation, alloying to the target materials or the like, small amounts of the elements -S

Ag, Au, Cu, Fe, Ir, Mo, Ni, Pd, Pt, Os, Rh, Ru, W and / or their alloys are improved and / or stabilized against corrosion / oxidation. If it is desired to achieve particularly good conductive properties, it is advantageous to provide a residual metal content of at least 30 to at most 60%, preferably between 40 and 50%, in the final layer package.

Due to the excellent mechanical properties of such metal-containing DLC layers, these can also be used advantageously, if in addition a Lager¬ function of the coated Leitwerkstoffs is desired. For example, such control materials can be advantageously used for bearings which simultaneously serve to transmit electrical signals.

Examples and experiments

In the following the invention will be described with reference to various embodiments. All Me-DLC layers or support layers were at temperatures of less than 250 ° C on copper materials, in a, as in DE 100 18 143 under Figure 1 and related description [0076] to [0085] modified, Balzers BAI 830 C Produktionsanläge , isolated. For this purpose, in all coatings, a pretreatment was carried out using a heating and etching process known from process example 1 above using a low-voltage arc. The correspondingly designated passages of the above disclosure will become an integral part of the present application.

Comparative Example 1

In this case, a metal-containing DLC sliding layer on a CuSnδ bronze in the final, ie outer layer area was formed by means of chromium adhesion layer, but applied without additional support layer. After the above-mentioned pretreatment, a chromium adhesion layer was first applied as in process example 1 of DE 100 18 143.

Subsequently, with activated Cr targets, six WC targets with a power of 1 kW each were activated and both target types were run simultaneously for 2 min. At the same time, the power of the WC targets is increased from 1 kW to 3.5 kW in 2 minutes while maintaining the Ar flow. At the same time, the negative substrate voltage on the components is ramped up from 0 V applied at the end of the Cr adhesion layer to 300 V in 2 minutes. The 300 V are reached when the WC targets are running at full power. Subsequently, the Cr targets are switched off. The WC targets are run for 6 minutes at constant Ar flow and 3.5 kW power, then the acetylene gas flow is increased to 200 sccm in 11 minutes and held constant for 60 minutes at the parameters described in Table 1. Subsequently, the coating process is stopped.

Table 1) Coating parameter 1 - metal-containing DLC layer

River Argon 115 sccm

Flow of acetylene 200 sccrα

Bias voltage -300 V

Coil voltage upper coil 6 A

Coil voltage lower coil 0 A

Tare output 6 x 3.5 kW

Example 2

Differs from Example 1 in that the acetylene gas flow in the last stage of the process in 5 min. only increased to 80 sccm and held there for 60 minutes.

Example 3

Differs from Example 1 in that the acetylene gas flow in the last process phase in 2 min. increased to 30 sccm and held there for 60 minutes constant.

Comparative Example 4

Differs from Example 1 in that no acetylene added in the last stage of the process and the WC targets are operated after switching off the Cr targets, 60 min at constant Ar flow. Example 5

For Example 5, a CrN support layer was first deposited and then applied to Example 3 a Me-DLC conductive layer on the support layer. The deposition of the CrN supporting layer was carried out in accordance with the parameters given in Table 5), in which case a low-voltage arc discharge ignited in the central axis between a hot cathode and an auxiliary anode was additionally operated to increase the plasma density.

Table 5) Coating parameters CrN support layer

Example 6

For Example 6, a chromium adhesion layer was first applied as in Example 1. The subsequent WC-containing functional layer was doped with Ag.

For activated Cr targets, four WC targets each with 1 kW power are activated and both target types are simultaneously run for 2 minutes, whereby the power of the WC targets is 1 kW within 2 minutes with the Ar flow remaining constant is increased to 3.5 kW. Two silver targets also incorporated in the coating system are ignited simultaneously with the WC targets and their power increased from 0 to 1 kW in the same period. At the same time, the negative substrate voltage on the components is ramped up from 0 V applied at the end of the Cr adhesion layer to 300 V in 2 minutes. Subsequently, the Cr targets are switched off. The WC and Ag targets are operated together for 6 min at constant Ar flow, then the Acetylengasfluss in 2 min. increased to 30 sccm and during the last coating phase the parameters according to Table 6 were kept constant for 60 minutes.

Table 6) Coating parameters metal-containing cover layer

River Argon 115 sccm

Flow of acetylene 30 sccm

Bias voltage -300 V

Coil voltage upper coil 6 A

Coil voltage lower coil 0 A

Target power WC 4 x 3.5 kW

Target power Ag 2 x 1 kW

Assessment of the layers

As can be seen from Table 7, layers of the prior art, as described in Comparative Examples 1 and 4, have a relatively high contact resistance. Example 1 is a typical example of an a-C: H: Me or Me-DLC layer, with a strongly increasing C-content towards the surface. Example 4 represents a carbide layer, without appreciable amounts of free carbon. The indicated measured values were determined by averaging at 5 different measuring points in each case 10 s after application of a contact weight of 100 g. The tip of the Kontakt¬ weight consists of gold with a diameter of 3 mm. The determination of the individual value was confirmed by a preceding and subsequent reference measurement of gold.

The frictional force of the connectors was determined on a macro wear test bench for

DLC plug standard plug

(tinned)

Sample geometry rider on flat rider on flat

Diameter of the rider 4 mm 4 mm

Contact area 0.3 mm ² 0.3 mm ²

Test atmosphere dry dry

Frequency 1 cycle in 2.5 s 1 cycle in 2.5 s

Test duration 3000 cycles 25 cycles

Normal force 20 N 5 N

Friction travel 3 mm 3 mm

The indication of the frictional force after a defined number of cycles shows the frictional wear of the sample. The tinned standard plug has a friction force of 1000 πiN after 25 cycles. Increasing the number of cycles to more than 30 leads to complete destruction. The values for DLC coated connectors are in the third column.

Surprisingly, it was found in the experiments that layers whose proportion of free carbon is in an intermediate range (Examples 2 to 3), have a significantly lower contact resistance. This low Contact resistance was also maintained when applying an additional CrN support layer as indicated in Example 5. By co-sputtering Ag as described in Example 6, the contact resistance could be further lowered.

Table 7) Contact resistance and frictional force of different DLC layers:

Claims

claims 1. Conducting material made of a copper-containing alloy for use as a plug or clamp connection with a deposited at least on parts of the contact surface cover layer, which consists of at least an adhesive layer and a carbon-containing sliding layer, characterized in that the sliding layer has a carbon content of greater than or equal to 40 and less than or equal to 70 atomic percent. Second conductive material according to claim 1, characterized in that the sliding layer is a hard layer and diamond-like carbon comprises. 3. Conducting material according to claim 1, characterized in that the sliding layer additionally comprises at least one metal Me from the elements of the IV, V, and VI subgroup of the Periodic Table of the Elements (ie Ti, Zr, Hf; V, Nb, Ta; Cr, Mo , W) or Si. 4. Guide material according to claim 3, characterized in that the sliding layer contains a metal carbide and a metal carbide layer deposited thereon with a content of free carbon increasing against the surface. 5. Guide material according to claim 4, characterized in that the metal carbide is a carbide of Subgroup IV, V, and VI of the Periodic Table of the Elements, preferably tantalum, molybdenum, chromium or tungsten carbide. 6. Conductive material according to one of the preceding claims, characterized in that between the adhesive layer and the sliding layer, a support layer is provided, or the adhesive layer is designed as a support layer. 7. Guide material according to claim 6, characterized in that the support layer comprises at least one metal Me from the elements of the IV, V, and VI subgroup of the Periodic Table of the Elements (ie Ti, Zr, Hf; V, Nb, Ta; Cr, Mo, W) or aluminum or Si. 8. Guide material according to claim 6, characterized in that the support layer additionally or exclusively one or more hard material compounds comprising at least one metal Me and at least one non-metal, the metal of at least one of the elements of the IV, V, and VI subgroup of the PSE (ie Ti , Zr, Hf, V, Nb, Ta, Cr, Mo, W), aluminum or Si and the non-metal is at least one of the elements C, N, B or O, but preferably contains carbon. 9. Guide material according to one of claims 6 to 8, characterized in that between the support layer and the sliding layer, a transition layer is applied. 10. Guide material according to claim 9, characterized in that the transition layer of at least one metal Me from the elements of IV, V, and VI Subgroup of the Periodic Table of the Elements (ie Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) or aluminum or Si. 11. Guide material according to claim 9, characterized in that the transition layer is a gradient layer, wherein the C content of the transition layer increases toward the sliding layer. 12. Guide material according to one of the preceding claims, characterized in that the adhesive layer and / or the backing layer preferably but at least the overlay contains small amounts of one or more of the following elements and / or their alloys: Ag, Au, Cu, Fe ₇ Ir, Mo, Ni, Pd, Pt, Os, Rh, Ru, W. 13. Guide material according to one of claims 6 to 11, characterized in that the layer thickness of the support layer is between 0.5 and 6 microns, preferably between 1 to 3 microns. 14. Conductive material according to one of the preceding claims, characterized in that the contact resistance between 0.1 to 90 mΩ, preferably between 0.5 and 10 mΩ. 15. Conductive material according to claim 1, characterized in that the copper-containing alloy is copper, bronze, brass or nickel silver. 16. Guide material according to claim 1, characterized in that the copper-containing alloy is electroplated precoated. 17. Guide material according to claim 1, characterized in that the copper-containing alloy with a Cr of a Ni or a CrNi alloy is electroplated precoated. 18. Electrical contact piece which comprises a control material according to one of the preceding claims or consists thereof. 19. An electrically conductive semi-finished product with at least one contact piece according to claim 18. 20. Electrically conductive tape or profile with at least one contact piece according to claim 19.