JP2005251762A - Tin coated electrical connector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrical conductor (10) having a copper base substrate (12) coated with a tin base coating layer (14) and to suppress diffusion of copper from the substrate (12) into the coating layer (14) and consequential formation of a brittle tin/copper intermetallic compound. <P>SOLUTION: In this invention, a barrier layer (16) is interposed between the substrate (12) and the coating layer (14). The barrier layer (16) contains nickel of 20% to 40%, by weight, and is preferably predominantly composed of copper. In one embodiment, an intermetallic compound layer (38) selected from the group (Cu-Ni)<SB>3</SB>Sn, (Cu-Ni)<SB>6</SB>Sn<SB>5</SB>, Cu<SB>3</SB>Sn, Cu<SB>6</SB>Sn<SB>5</SB>is disposed between the barrier layer (16) and the tin base coating layer (14). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tin-coated copper-based electrical connector having a reduced production rate of a copper / tin intermetallic compound. More particularly, a barrier layer containing 20% to 40% nickel by weight is provided between the connector substrate and the coating. Alternatively, the barrier layer contains a copper / tin intermetallic compound.

  Electrical connectors such as sockets and plugs are generally formed from a copper-based alloy substrate that provides good electrical conductivity. When an electrical connector is exposed to high temperatures during operation, such as under an automobile bonnet, the substrate is formed from a copper-based alloy that has high strength and stress relaxation resistance.

  Stress relaxation resistance is pre-loaded with 80% yield strength set percent in cantilever mode on strip samples as per ASTM (American Society for Testing and Materials) specifications. Is recorded as a percentage of the residual stress after. The strip is then heated to 125 ° C., typically for a specified long time, typically up to 3000 hours, and retested periodically. The higher the residual stress in each retest, the better the utility of the particular composition for spring applications.

  In order to reduce high temperature damage of copper based substrates and to improve solderability, a coating layer is often applied to the substrate. Exemplary coating layers include nickel, palladium / nickel alloys, tin and tin alloys. Tin is often used to minimize the price.

At high temperatures, copper diffuses from the substrate and combines with tin to form intermetallic compounds such as Cu ₆ Sn ₅ and Cu ₃ Sn. The formation of intermetallic compounds reduces the amount of unreacted or free tin on the surface. This will exacerbate the electrical, corrosion and other performance characteristics.

It is known to interpose a barrier layer between a copper-based substrate and a tin-based coating layer to reduce the formation of copper / tin intermetallic compounds. Publications by Kay et al. Appearing in Transactions of the Institute of Metal Finishing, Volume 59 (1979), page 169 include tin / nickel, copper / It is disclosed that barrier layers such as nickel, cobalt and iron as well as tin and alloys such as nickel / iron are placed between the copper base substrate and the tin coating to reduce the formation of intermetallic compounds. .

  While effective, these barriers do not inhibit the formation of intermetallic compounds that are forced to be used under automobile hoods that leave only a minimal amount of free tin after 3000 hours exposure to 125 ° C.

  Accordingly, an object of the present invention is to interpose a barrier layer between the copper base substrate and the tin base coating that reduces the rate of formation of the copper / tin intermetallic compound.

  A feature of the present invention is that in one embodiment, the barrier layer is an alloy having 20% to 40% nickel by weight. Nickel may be combined with copper, iron or tin. Another feature of the present invention is that the thickness of this barrier layer is between 0.2 microns and 10% of the total thickness of the member.

  In one alternative embodiment of the present invention, the barrier layer is formed by providing alternating layers of different metals and then diffusing the layers to produce a predetermined alloy.

  In a second alternative embodiment of the invention, the barrier layer is presaturated with a nickel / tin intermetallic compound.

  One advantage of the barrier layer of the present invention is that a sufficient thickness of free tin remains on the surface of the member after high temperature exposure to maintain the integrity of the coating layer.

  According to the present invention, a composite material having a copper or copper-based alloy substrate is provided. Tin or a tin-based alloy covers this part of the substrate. The barrier layer is interposed between the substrate and the tin or tin base alloy. The barrier layer contains 20% to 40% nickel by weight and has a thickness of 0.2μ to 5μ.

  The above objects, features and advantages will become more apparent from the specification and the following drawings:

  FIG. 1 illustrates a composite material 10 useful as an electrical connector component. Such members include sockets and plugs. The composite material 10 is particularly useful as a member for electrical connectors that are exposed to high temperatures in excess of 75 ° C., either intermittently or continuously, as under an automobile hood.

  The composite material 10 has a copper or copper base alloy substrate 12 and a tin or tin base alloy coating 14 covering at least a portion of the substrate 12. “Base” is used in its conventional sense in the metallurgical field, meaning that the alloy contains at least 50% by weight of the base component.

  A barrier layer 16 is interposed between the substrate 12 and the coating layer 14. The barrier layer 16 contains 10% to 70% nickel by weight and has a thickness from 0.2μ to 10% of the total thickness of the composite material 10.

  Preferably, the nickel content of the barrier layer 16 is 20 wt% to 40 wt%, more preferably 25 wt% to 35 wt%. A preferred thickness range for the barrier layer 16 is 0.2 to 5 microns, and a most preferred thickness range is 0.2 to 1.5 microns.

  The substrate 12 is formed from copper or a copper base alloy. Preferably, the copper alloy substrate has an electrical conductivity greater than about 25% IACS (IACS means conductivity as defined by the International Annealed Copper Standard and “pure” copper at 20 ° C. Graded as having 100% IACS). Most preferably, the electrical conductivity of the substrate is above about 35% IACS.

  Substrate 12 has a room temperature yield strength above about 344.7 MPa (50 ksi), and preferably above about 448.2 MPa (65 ksi).

  A suitable alloy is copper alloy C7025 having a composition of 2% to 4.8% nickel by weight, 0.2% to 1.4% silicon, 0.05% to 0.045% magnesium and the balance copper; A copper alloy C194 having a composition of 2.1% to 2.6% iron, 0.05% to 0.20% zinc, 0.015% to 0.15% phosphorus and the balance copper by weight; and As a copper alloy C197 having a composition of 0.3% to 1.2% iron by weight, 0.1% to 0.4% phosphorus, 0.01% to 0.2% magnesium and the balance copper Includes those directed by the Copper Development Association.

  The tin-based coating 14 is applied by any conventional method such as electrodeposition, hot dipping, electroless chemical plating, vapor deposition or cladding. In the case of electrodeposition, the coating layer is either matte or glossy. The electrodeposited layer may be reflowed to improve surface appearance and reduce wrinkles in the plating, thereby improving performance in the solderability of the coating and contact characteristics in connector applications .

The tin-based coating layer may be a tin alloy such as a tin / lead-based solder containing 1% to 99% tin by weight. Tin compounds may be used. Compounds that may be added to the tin-based matrix as particulates are silicon carbide, aluminum oxide, silica (SiO ₂ ), carbon black, graphite, tungsten carbide, molybdenum disulfide, and polytetrafluoroethylene (“Teflon®). ", A trademark of DuPont, Wilmington, DE).

  The thickness of the tin base coating layer 14 is 0.5 μm to 10 μm, preferably 0.75 μm to 1.5 μm. A preferred coating is electrodeposited matte tin that is later reflowed by heating to a temperature above the melting point of tin. Heating is any suitable method, for example, in a hydrocarbon type reducing atmosphere; in some other suitable atmosphere such as air, nitrogen or other inert gas; induction furnace; infrared heating; or hot oil Dipping in;

  The barrier layer 16 has a minimum thickness of about 0.2 microns. Below this thickness, copper diffuses from the substrate 12 through defects in the barrier layer 16, leading to an increase in the rate of formation of intermetallic compounds.

  The maximum thickness of the barrier layer 16 is about 10% of the total thickness of the composite material 10, and is preferably less than about 5% of the total thickness of the composite material 10. The minimum barrier thickness depends on how the tin base layer 14 is provided. Tin-based coatings applied by electrodeposition require a thin barrier thickness layer closer to the specified minimum thickness. Dip coating requires a relatively thick coating that is closer to the maximum thickness specified to compensate for erosion of the barrier layer when immersed in molten tin for dip coating.

  For connector applications, the substrate 12 has a minimum thickness that is effective to withstand the forces associated with insertion and removal. Typically, this minimum thickness is on the order of at least 50μ, more preferably on the order of 200μ to 500μ.

  The maximum barrier layer thickness is on the order of 5μ. Above this thickness, the barrier layer begins to affect both the electrical conductivity and yield strength of the composite material 10. Since the copper / nickel alloy has a relatively low electrical conductivity, the effect of the barrier layer is preferably minimized.

  A preferred barrier layer thickness is 0.2 to 5 microns. A more preferred thickness range for the barrier layer is from 0.2μ to 1.5μ.

  The barrier layer contains 20% to 40% nickel by weight. If the nickel content is less than 20%, the barrier layer 16 is not effective in reducing the rate of formation of intermetallic compounds. If the nickel content exceeds 40%, the electrical conductivity of the barrier layer decreases and the rate of formation of intermetallic compounds increases as shown in FIG.

  FIG. 2 graphically illustrates the relationship between the rate of formation of intermetallic compounds in the nickel / copper binary barrier layer and the nickel content. When the barrier layer is 100% copper, the reference point 18 has a surprisingly small difference in production rate compared to 100% nickel, reference point 20.

The production rate of intermetallic compounds was measured by fluorescent X-ray analysis. The total tin thickness was first measured (M ₁ ). Unreacted tin was then removed by chemical stripping. Next, the amount of tin remaining was measured (M ₂ ), and the difference between M ₁ and M ₂ was the amount of free tin remaining.

  The intermetallic compound formation rate is greatest when the barrier layer has a composition of about 8 wt.% Nickel and the remaining copper (reference point 22). At higher amounts, from 10% by weight of nickel, the rate of formation of intermetallic compounds is less than that of pure nickel or pure copper barrier layers. At 20% to 40% by weight, the intermetallic compound formation rate is a minimum of 24.

  The present inventors have deduced from FIG. 2 that when the nickel content exceeds 40% by weight, the formation rate of intermetallic compounds increases and the electrical conductivity decreases. Therefore, in the barrier layer 16 consisting essentially of nickel and copper, the nickel content of the barrier layer is preferably 20% to 40% by weight.

  In one embodiment, the barrier layer 16 is a binary alloy containing nickel, and the remaining components of the alloy are preferably selected from the group consisting of tin, iron, cobalt and copper. Combining copper with nickel is most preferred because this combination has the lowest intermetallic growth rate.

  Instead, the barrier layer 16 is one selected from the group consisting of tin, copper, iron, zinc, cobalt, indium, mixtures thereof and optionally tungsten, chromium, vanadium, manganese and phosphorus in addition to nickel. Alternatively, it may be a ternary or higher alloy containing more elements.

  An alloy containing 15% to 40% by weight of cobalt in place of nickel with the alloying additives specified above is also believed to be satisfactory. The preferred amount of cobalt is the same as specified above for nickel.

The barrier layer is applied to all or a portion of the substrate 12 by any suitable means including hot dipping, deposition or electrodeposition. Electrodeposition is preferred for ease of deposition and control of the barrier layer thickness. A copper-weight percent 20-40% nickel barrier layer may be deposited from an aqueous citrate electrolyte. The electrolyte is an aqueous solution containing 30-80 g of nickel per liter, 7-35 g of copper per liter, and 80-320 g of sodium citrate dihydrate per liter. The solution is heated to a temperature between 40 ° C and 70 ° C for use. Along with stainless steel suitable as the anode, the substrate is immersed in the electrolyte as the cathode. A current of 30 to 120 milliamperes / cm ² is applied to the entire electrolyte. After about 0.5 to 2 minutes, a barrier layer having a nominal thickness of 0.3 to 2.5 is deposited.

  The barrier layer should be relatively smooth as opposed to having a small hump. This is because small humped coatings increase the surface area of the interface between the substrate and tin, which leads to an increased rate of formation of intermetallic compounds. Cosmetically, the smooth barrier layer increases the gloss of the reflowed tin coating layer.

  The effectiveness of the copper / nickel barrier layer 16 is improved by adding one or more refining compounds to the electrolyte. These refining compounds include benzotriazole (BTA), glue, protein, thiourea, sulfone compounds and chloride ion donors such as nickel chloride. The refining compound is effective in reducing the porosity and roughness of the deposited barrier layer and can also provide a barrier layer having a finer grain structure.

  Decreasing the porosity of the barrier layer reduces the diffusion rate of tin and copper. The reduced roughness of the barrier layer reduces the area of the interface between the barrier layer and the substrate and between the barrier layer and the coating, which leads to a decrease in copper and tin diffusion rates. Modifying the crystal grain structure to increase the fineness of the grain leads to a denser intermetallic compound structure and effectively reduces the growth rate of the intermetallic compound.

  Preferably, about 10 ppm to about 1000 ppm of the refining compound is added to the electrolyte to achieve the desired reduction in porosity and roughness and lead to a finer particle structure. In a preferred embodiment, the refining compound is 50 ppm to 100 ppm BTA.

  Instead, the barrier layer 16 is mechanically distorted, eg, by rolling, or heat treated, eg, by heating, to modify the grain structure of the barrier layer prior to deposition of the tin-based coating.

  In one exemplary process, after depositing a copper / nickel barrier layer on the substrate, the barrier layer / substrate composite is annealed to a temperature of 300 ° C. to 500 ° C. for 30 minutes to 120 minutes. . In order to minimize the oxidation of the complex, the annealing is carried out in an inert or reducing atmosphere such as cracked ammonia (96% nitrogen and 4% hydrogen by volume). The annealed composite is then passed through a roll mill at room temperature (about 20 ° C.) and undergoes a 10% to 20% thickness reduction.

  In addition to providing a finer grain structure or preferred crystal orientation, annealing and rolling, either individually or in combination, increase the hardness of certain copper alloys through work hardening and precipitation aging. This curing is particularly effective when forming an electrical connector. One exemplary alloy suitable for the substrate for this process is copper alloy C194.

  Instead, thermal processing by annealing improves the bendability of the composite material. Annealing is believed to relieve the stress that would be present in the electrodeposited copper / nickel barrier layer.

  The tin base coating layer 14 is then applied by conventional means on at least a portion of the barrier layer 16.

  When the barrier layer is a co-adhering alloy of two or more metals, it is often difficult to accurately control the alloy composition. FIG. 3 illustrates how to achieve more precise control over the composition of the barrier layer 16.

  The alloy components are deposited sequentially. A first layer 26 of one alloy component, for example nickel, is deposited to the desired thickness. A second alloy component is then deposited as the second layer 28. The second layer 28 may be copper, for example. The thickness of the first layer 26 and the second layer 28 is effective to provide the desired amounts of the first and second components. The layers may be used as a barrier layer either as deposited or after diffusion.

  Layers 26, 28 are deposited by any suitable method, such as electrolytically, electroless plating, chemical vapor deposition, or plasma deposition. Multiple layers of the same material may be deposited. For example, the first layer 16, the third layer 30, and the fifth layer 34 may be the first component, and the second layer 28, the fourth layer 32, and the sixth layer 36 may be the second component. Multiple thin layers provide a more uniform barrier layer 16 after diffusion.

  When the first component is nickel and the second component is copper, diffusing to a homogeneous nickel level of about 20% to 40% by weight is performed at a temperature of 750 ° C. to 850 ° C. for 12 minutes to 72 minutes. This can be achieved by heating.

  The third layer 30 may constitute the third component. For example, when the first component is nickel and the second component is copper, the third component may be tin. Then, the fourth layer 32 may constitute a fourth component, such as silver, silicon, aluminum, zinc, iron, chromium, manganese, cobalt, vanadium, indium or phosphorus.

  Any combination of elements may be so combined. In order to limit the formation of intermetallic compounds, the barrier layer contains 20% to 40% nickel after diffusion.

  The innermost first layer 26 has a thickness of less than 1.25 micron (50 microinches), preferably 0.05 micron (2 microinches) to 0.5 micron (20 microinches) thick ( flash). The flash may be any metal, but is preferably copper or nickel. The flash has the effect of leveling the surface to mask surface irregularities in the substrate and reducing the area of the interface available for diffusion.

  The flush also minimizes the effect of the alloying components in the substrate on the barrier layer deposition.

  The layer need not be an element. One or more layers may constitute a binary or higher alloy. For example, the first layer may be Ni + X and the second layer may be Cu + Y. When heated, X and Y may combine with each other or with copper and nickel to form an effective intermetallic compound in the barrier layer. For example, X can be Si forming nickel silicide.

  Any number of layers may be repeated any number of times. It is not necessary to repeat the same sequence of layers over and over, only that the combined thickness of all layers provides the desired barrier layer composition when all layers are deposited. The multilayer is then diffused to provide the barrier layer 16 with the desired homogeneity.

  The thickness of the tin coating layer decreases rapidly when first heated. At the same time, a copper-tin intermetallic compound is rapidly formed in the barrier layer. When the barrier layer is saturated with a copper / tin intermetallic compound, the rate of decrease in tin thickness decreases rapidly.

According to another aspect of the present invention, the barrier layer 16 may be a high initial concentration of intermetallic compound, one of (Cu—Ni) ₃ Sn, (Cu—Ni) ₆ Sn ₅ , Cu ₃ Sn and Cu ₆ Sn ₅ . Formed to contain as one or more. This barrier layer saturated with the intermetallic compound appears to significantly reduce the expression of additional intermetallic compounds through sacrificing a portion of the tin layer.

In a preferred embodiment, as illustrated in FIG. 4, the intermetallic compound layer 38 is disposed between the barrier layer 16 and the tin layer 14. The intermetallic layer 38 appears to be effective in inhibiting the collapse of the tin layer 14 over any suitable barrier layer 16. Preferably, the barrier layer 16 is a copper / nickel alloy having about 20% to about 40% nickel by weight. The barrier layer 16 has a thickness of about 0.25 microns to about 1.25 microns (10 to about 50 microinches). The intermetallic layer 38, which is deposited by any suitable method, such as vapor deposition or electroplating, either as a co-deposition or as separate layers that are later diffused together as described above. Intermetallic layer 38 has a thickness of about 100 angstroms to about 10,000 angstroms, preferably about 200 angstroms to about 1000 angstroms.
The advantages of the barrier layer of the present invention will become more apparent from the following examples.

(Example 1)
Cu-20% Ni
Fe
Ni
Cu
Copper alloy C194 coupon coated with 30 microinches (0.75μ) of a specific barrier layer selected from the group of, and copper alloys C194 and C710 without a barrier layer (with a nominal electrical conductivity of 6.5% IACS) A nominal coupon of 80% copper by weight and 20% nickel was coated with 40 microinches (1μ) of matte tin by electrodeposition.

  The coupon was then heated to a temperature between 125 ° C and 175 ° C for up to 250 hours. Contact resistance was measured by utilizing a gold probe and a method similar to ASTM methods B539-80 and B667-80. The contact resistance expressed in milliohms as a function of aging temperature and aging time is presented in Table 1 and FIG.

  As illustrated in FIG. 3, low contact resistance was achieved under most test conditions with a copper / nickel barrier layer. The high contact resistance in the copper / nickel barrier layer after aging at 175 ° C. for 100 hours is considered exceptional on the test.

  The residual amount of free tin, the portion of tin that was not converted to the copper / tin intermetallic compound, was measured by fluorescent X-ray analysis and recorded in μ. The thickness in microinches is shown in parentheses. As summarized in Table 2 and illustrated in FIG. 4, a large volume of free tin residue was achieved under most test conditions with a copper-nickel barrier layer.

  The copper alloy C710 control coupon without the barrier layer had low contact resistance and a large volume of free tin. However, the C710 substrate has an electrical conductivity that is too low for use as an electrical connector in an automobile under bonnet applications.

(Example 2)
Copper alloy C194 coupons were coated with a barrier layer of 1 μ (40 microinches) copper-30 wt% nickel alloy and then with 1.25 μ (50 microinches) matte tin. The matte tin was later reflowed. Both the barrier layer and matte tin were electrolytically deposited. The barrier layer copper and nickel were deposited simultaneously.
The control was a copper alloy C194 coupon that was electrolytically coated with matte tin that was later reflowed. The control lacked a barrier layer.

  The test coupons and controls were then aged at 125 ° C. for 2000 hours. The thickness of the intermetallic compound layer (IMC) expressed in microinches was then measured and recorded as a function of the square root of the number of hours aged. The test coupon results are shown in FIG. 7 by reference line 40 and the control coupon results by reference line 42. The thickness of the intermetallic compound with an aging time exceeding 2000 hours is extrapolated from the graph.

(Example 3)
FIG. 8 is a 2000 × magnification illustrating the copper / tin intermetallic compound that develops when the substrate / barrier layer is not subjected to thermal or mechanical processing in a copper alloy C194 substrate / copper-30% nickel / tin plate system. FIG. Intermetallics were exposed by selectively chemically removing residual tin. Intermetallic compounds consist of rapidly growing spheroids.

  FIG. 9 appears when the substrate is mechanically distorted by rolling prior to tin deposition in a copper alloy C715 substrate (nominal composition: 30% nickel by weight and the remaining copper) / tin plate system 1 is a photomicrograph at 2000X magnification illustrating a copper / tin intermetallic compound. Intermetallics were exposed by selectively chemically removing residual tin. Intermetallics consist of flattened obelisks that grow relatively slowly. Preferably, the flattened obelisk has an aspect ratio (length to width) of at least 5: 1.

  The inventors have determined that spheroids grow at about twice the rate of flattened dentrites.

  Obviously, according to the present invention, there is provided a barrier layer interposed between a copper-based substrate and a tin-based coating layer, which completely satisfies the above-mentioned objects, means and advantages. is there. While the invention has been described in terms of its embodiments, it will be apparent to those skilled in the art that numerous alternatives, modifications, and variations will be apparent in light of the above description. All such alternatives, modifications and variations are intended to fall within the spirit and general scope of the appended claims.

1 is a cross-sectional view illustrating an electrical connector according to the present invention. 6 is a graph showing the relationship between nickel content and intermetallic compound formation rate for a system having a copper / nickel binary barrier layer. It is sectional drawing which illustrates the multilayer adhesion process for forming a barrier layer. It is sectional drawing which illustrates the intermetallic compound layer combined with the barrier layer. FIG. 6 is a graph showing contact resistance as a function of aging time and aging temperature. FIG. Figure 5 is a graph showing free tin thickness as a function of aging time and aging temperature. FIG. 5 is a graph showing the effect of the barrier layer on intermetallic compound thickness as a function of aging time. FIG. It is the microscope picture of the copper / tin intermetallic compound produced | generated on the non-wrought substrate. It is a microscope picture of the copper / tin intermetallic compound produced | generated on the training substrate.

Claims (8)

Copper or copper-based alloy substrate (12);
A coating layer (14) made of tin or a tin-based alloy covering a portion of the substrate (12); and a barrier (16) interposed between the substrate and the coating layer, at least a first and a different second metal Or the barrier is an alloy formed from metal alloy component layers (26, 28), wherein the first metal or alloy component layer is selected from the group consisting of nickel, cobalt, nickel base alloy and cobalt base alloy, And having a desired thickness of less than 1.25 microns, wherein the second alloy component layer (28) is predominantly copper and is in direct contact with the coating layer (14), so that 0.2 to 5 microns Said barrier having a thickness of 16;
A composite material (10) characterized by   The composite material (10) of claim 1, wherein the first alloy component layer (26) is adjacent to the substrate (12). Copper or copper-based alloy substrate (12);
A coating layer (14) made of tin or a tin-based alloy covering a portion of the substrate (12); and a barrier (16) interposed between the substrate and the coating layer, at least first, third and different The barrier (16) which is an alloy formed from two metal or metal alloy component layers (26, 28, 30), wherein the second alloy component layer (28) is mainly copper and the coating layer Said barrier (16) in direct contact with (14), and thus having a thickness of 0.2-5 [mu];
A composite material (10) characterized by   The third alloy component layer (30), which is nickel or a nickel alloy, is adjacent to the second alloy component layer (28), and the second alloy component layer (28) and the first alloy layer (26). And a fourth alloy component layer (32) made of copper or a copper alloy is disposed adjacent to the third alloy component layer (30) and the third alloy component layer (30). The composite material (10) according to claim 3, characterized in that it is arranged between the first alloy layers (26).   Another alloy component layer (32) selected from the group consisting of silver, silicon, aluminum, zinc, iron, chromium, manganese, cobalt, vanadium, indium and alloys thereof is adjacent to the third alloy component layer (30). The composite material of claim 4, wherein the composite material is disposed between the third alloy component layer (30) and the coating layer (16).   The first metal or alloy component layer (26) is in direct contact with the substrate, and the second metal or alloy component layer (28) is the first metal or alloy component layer (26) and the 2. Composite material according to claim 1, characterized in that it is in direct contact with both coatings (16).   The first metal or alloy component layer (26) is in direct contact with the substrate (12), and the second alloy component layer (28) is the first alloy component layer (26) and the third alloy component. The fourth alloy component layer (32) is in direct contact with both the third metal or alloy component layer (30) and the coating layer (16). The composite material according to claim 3, wherein:   The composite material of claim 1 or 2, wherein the second alloy component layer (28) is bonded to the coating layer (14) to form a saturated copper / tin intermetallic compound.