Preparation method of pin conductor capable of preventing tin whisker and fretting wear and pin conductor

Abstract

The invention provides a pin conductor capable of preventing tin whisker and fretting wear, which is provided with a core material made of copper or copper alloy, and a nickel layer and a tin-silver-copper alloy layer which are sequentially coated outside the core material, and the tin-silver-copper alloy comprises the following components in percentage by weight: 2-4% of silver, 0.2-1.0% of copper and the balance of tin; the invention also provides a manufacturing method of the pin conductor capable of preventing tin whisker and fretting wear, which comprises the following steps: sequentially carrying out deformation processing, electroplating of the middle nickel layer and hot dipping of the tin-silver-copper alloy layer on the high-strength and high-conductivity copper or copper alloy conductor material, and then carrying out cold deformation processing to draw the whole conductor material. The binding force between the core material and the plating layer is further improved, the hardness and wear resistance of the pin conductor are improved, tin whiskers are effectively prevented from being generated in the use process of the pin conductor, and meanwhile fretting wear is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of copper or copper alloy wire material processing, and in particular to a tin whisker and fretting wear resistant plug conductor and a preparation method thereof. Background Art

[0002] In the field of precision electronics, most electronic components are connected by tin solder. However, the surface of electroplated tin or soldered devices will produce tin whiskers due to stress. The growth of tin whiskers will cause serious faults such as short circuits. Especially in applications such as sensors, the growth of tin whiskers is accompanied by micro-motion wear, which will have disastrous consequences for the operation of precision devices such as sensors. Especially in the pins and plugs of electronic components, which are often also affected by mechanical influences such as vibration, these parts are more seriously affected by the above-mentioned tin whiskers and micro-motion wear.

[0003] Therefore, there is a need to design a high-conductivity conductor material that can be used in precision electronic devices and has the advantages of preventing tin whisker growth and fretting wear. Summary of the invention One of the purposes of the present invention is to provide a method for manufacturing a pin conductor that is resistant to tin whiskers and fretting wear, by sequentially deforming a high-strength and high-conductivity copper or copper alloy conductor material, electroplating an intermediate nickel layer, and hot-dip tin-silver-copper alloy layer, and then performing a cold deformation process to draw the conductor material as a whole, thereby further improving the bonding strength between the core material and the plating layer, further improving the hardness and surface finish of the pin conductor, and being more conducive to reducing fretting wear, while also making the pin conductor have better wear resistance and corrosion resistance.

[0004] To achieve the above object, the present invention provides the following technical solutions: A method for manufacturing a tin whisker and fretting wear-resistant pin conductor comprises the following steps: (1) Deform copper or copper alloy conductor material into a core material of the desired shape; (2) Electroplating nickel on the surface of the core material after deformation; (3) hot-dip plating the conductor material after nickel plating in step (2) with tin-silver-copper alloy; (4) The conductor material obtained in step (3) is subjected to cold deformation processing to obtain a pin conductor.

[0005] Preferably, the step (1) is a drawing process, in which the copper or copper alloy conductor material is drawn into a wire of a desired shape and size, with a tensile strength greater than 500 MPa and a conductivity greater than 60%.

[0006] Preferably, the hot-dip plating temperature in step (3) is 250-300° C., and the tensile strength of the tin-silver-copper alloy coating is 10-20 MPa.

[0007] Preferably, the cold deformation processing method in step (4) is cold drawing, the deformation rate does not exceed 80%, and the tensile strength of the obtained tin-silver-copper alloy layer of the pin conductor is 40-50 MPa.

[0008] The second object of the present invention is to provide a pin conductor that is resistant to tin whiskers and fretting wear. The pin conductor uses a high-conductivity copper or copper alloy material with a certain strength as a conductor substrate, electroplated nickel is used as a transition base layer, and then a tin-silver-copper alloy is plated on the nickel plating layer, so as to effectively prevent the generation of tin whiskers and reduce fretting wear during use of the pin conductor.

[0009] To achieve the above object, the present invention provides the following technical solutions: A pin conductor that prevents tin whiskers and fretting wear, comprising a core material composed of copper or a copper alloy, and an electroplated nickel layer and a hot-dip tin-silver-copper alloy layer sequentially coated on the outside of the core material, wherein the weight percentage of each component in the tin-silver-copper alloy is 2% to 4% silver, 0.2% to 1.0% copper, and the balance is tin.

[0010] Preferably, the core material is a high-strength and high-conductivity copper alloy material, whose conductivity is greater than 60% and whose tensile strength is not less than 600 MPa. The use of highly conductive copper or copper alloy material can significantly reduce the contact resistance.

[0011] Preferably, the thickness of the nickel layer is not less than 0.1 μm, the thickness of the tin-silver-copper alloy layer is not less than 0.3 μm, and the tensile strength of the tin-silver-copper alloy layer is not less than 40 MPa.

[0012] Preferably, the nickel layer has a thickness of 0.1 μm to 10 μm, the tin-silver-copper alloy layer has a thickness of 0.3 μm to 10 μm, and the tensile strength of the tin-silver-copper alloy layer is 40 to 50 MPa.

[0013] Preferably, the melting point of the tin-silver-copper alloy layer is in the range of 230-250° C. to meet the welding requirements of component pins.

[0014] Beneficial effects of the present invention: The pin conductor of the present invention uses a nickel layer as the base layer, which can effectively isolate the chemical reaction between tin and copper and reduce the stress between the plating layers, thereby reducing the possibility of tin whiskers generated in the tin plating layer from the inside. When the pin generates micro-motion wear in a vibration environment, the base nickel layer can provide additional anti-wear and anti-oxidation protection to prevent the core material from being exposed and oxidized, thereby increasing the contact resistance of the pin; (2) by hot-dip tin-silver-copper alloy on the surface of the conductor nickel plating layer, the whisker phenomenon on the outside of the tin plating layer can be further avoided, and the surface hardness of the conductor can be further improved to reduce micro-motion wear; and the hardness of the plating layer is about 3 times that of the pure tin plating layer, and its wear resistance is greater than that of the pure tin plating layer.

[0015] (3) By cold-drawing the plated conductor material to form a pin conductor, the hardness and density of the core material and its coating material are further enhanced, and the hardness and surface finish of the pin conductor are further improved, which is more conducive to reducing micro-motion wear. At the same time, the pin conductor also has better wear resistance and corrosion resistance.

[0016] In summary, the present invention is particularly suitable for components on precision devices that are prone to vibration and wear, such as pins and plugs. It has the advantages of reducing the possibility of tin whisker generation and having high surface hardness, thereby reducing micro-motion wear. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the structure of a pin conductor according to some embodiments of this specification; Figure 2 This is a photo of the pin conductor shown in Example 1 before and after cold drawing under an optical microscope at a magnification of 50 times; FIG. 3( a ) and FIG. 3( b ) are cross-sectional views of the pin conductor before and after cold drawing of Example 1 under an optical microscope at a magnification of 50 times.

[0018] Figure 4 is an exemplary flow chart of a method for manufacturing a pin conductor according to some embodiments of the present specification. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of this specification. For ordinary technicians in this field, this specification can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0020] It should be understood that the "system", "device", "unit" and / or "module" used herein are a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the words can be replaced by other expressions.

[0021] Unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0022] Flowcharts are used in this specification to illustrate the operations performed by the system according to the embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed precisely in order. Instead, the steps may be processed in reverse order or simultaneously. At the same time, other operations may also be added to these processes, or one or more operations may be removed from these processes.

[0023] Example 1 Figure 1 is a schematic diagram of the structure of a pin conductor according to some embodiments of this specification; like Figure 1-Figure 2 , Figure 3(a), Figure 3(b) and Figure 4 As shown, a pin conductor for preventing tin whisker and fretting wear of the present invention comprises a core material 1 composed of a copper-magnesium alloy, and an electroplated nickel layer 2 and a hot-dip tin-silver-copper alloy layer 3 sequentially coated on the outside of the core material 1, wherein the weight percentage of each component in the tin-silver-copper alloy is 2% to 4% silver, 0.2% to 1.0% copper, and the balance is tin; The method for preparing the above-mentioned pin conductor specifically comprises the following steps: (1) Drawing the copper-magnesium alloy rod into a wire of required size, with a tensile strength greater than 500 MPa and a conductivity greater than 60%; (2) electroplating a nickel layer on the surface of the drawn wire, wherein the nickel plating layer has a thickness of 1 μm; (3) hot-dip plating the nickel-plated wire in step (2) with a tin-silver-copper alloy, wherein the alloy pool temperature is 250-300° C., the tin-silver-copper alloy coating thickness is 3 μm, and the coating tensile strength is 13-18 MPa; (4) The wire obtained in step (3) is cold-drawn to obtain a pin conductor with a deformation rate not exceeding 80%.

[0024] The tensile strength of the core material of the formed pin conductor is not less than 600MPa, the conductivity is not less than 70%, the tensile strength of the tin-silver-copper plating material is 48MPa, and its melting point ranges from 230 to 250°C.

[0025] Example 2 This embodiment provides a pin conductor that is resistant to tin whiskers and fretting wear, comprising a core material 1 composed of H65 brass, and an electroplated nickel layer 2 and a hot-dip tin-silver-copper alloy layer 3 sequentially coated on the outside of the core material 1, wherein the weight percentage of each component in the tin-silver-copper alloy is 2% to 4% silver, 0.2% to 1.0% copper, and the balance is tin; The method for preparing the above-mentioned pin conductor specifically comprises the following steps: (1) Drawing H65 brass rod into wire of required size, with tensile strength greater than 500MPa and conductivity greater than 60%; (2) electroplating a nickel layer on the surface of the drawn brass wire, with the thickness of the nickel plating layer being 0.5 μm; (3) hot-dip plating the nickel-plated wire in step (2) with a tin-silver-copper alloy, wherein the alloy pool temperature is 250-300° C., the tin-silver-copper alloy coating thickness is 0.8 μm, and the tensile strength is 12-16 MPa; (4) The wire obtained in step (3) is cold-drawn to obtain a pin conductor with a deformation rate not exceeding 40%.

[0026] The tensile strength of the core material of the formed pin conductor is not less than 600MPa, the conductivity is not less than 30%, the tensile strength of the tin-silver-copper plating material is 45MPa, and the melting point ranges from 230 to 250°C.

[0027] Comparative Example 1 As shown in FIG3 , a pin conductor comprises a core material 1 composed of a copper-magnesium alloy and a tin-silver-copper alloy layer 3 coated on the outside of the core material, wherein the weight percentage of each component in the tin-silver-copper alloy is 2% to 4% silver, 0.2% to 1.0% copper, and the balance is tin; The method for preparing the above-mentioned pin conductor specifically comprises the following steps: (1) Drawing the copper-magnesium alloy rod into a wire of required size, with a tensile strength greater than 500 MPa and a conductivity greater than 60%; (2) hot-dip tin-silver-copper alloy plating is performed on the wire material of step (1), the alloy pool temperature is 250-300° C., the tin-silver-copper alloy plating thickness is 3 μm, and the tensile strength is 13-18 MPa; (3) The wire obtained in step (2) is cold-drawn to obtain a pin conductor with a deformation rate not exceeding 40%.

[0028] The pin conductor obtained above was found to not produce tin whiskers in actual use conditions. However, after the tin-silver-copper alloy coating was worn, the core material was exposed to oxidation, which increased the contact resistance of the pin and affected the use of precision devices. This effectively shortened the life of the pin conductor compared to that of the pin conductors of Examples 1 and 2.

[0029] Comparative Example 2 A pin conductor comprises a core material composed of a copper-magnesium alloy and a nickel layer and a tin layer sequentially coated on the outside of the core material; The method for preparing the above-mentioned pin conductor specifically comprises the following steps: (1) Drawing the copper-magnesium alloy rod into a wire of required size, with a tensile strength greater than 500 MPa and a conductivity greater than 60%; (2) electroplating a nickel layer on the surface of the drawn wire, wherein the nickel plating layer has a thickness of 0.5 μm; (3) The wire material after nickel plating in step (2) is electroplated with a tin layer with a thickness of 0.8 μm to obtain a pin conductor, and the tensile strength of the tin plating layer is 7 to 10 MPa.

[0030] The pin conductor obtained above cannot prevent tin whiskers caused by external environmental influences during actual use, and the pure tin plating has a low hardness. It is easily worn when used in a vibrating environment, which effectively shortens its service life significantly compared with the pin conductors of Examples 1 and 2.

[0031] In summary, the comprehensive performance parameters of Example 1 are optimal compared with those of Example 2, and the pin conductors obtained in Examples 1 and 2 will not generate tin whiskers in actual use, and the surface hardness of the conductor is relatively high, which can effectively reduce micro-motion wear and extend the effective service life of the pin conductor, meeting the requirements of the use conditions.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a pin conductor that prevents tin whiskers and fretting wear, characterized in that: The following steps are involved: (1) Deform copper or copper alloy conductor material into a core material of the desired shape; (2) Electroplating a nickel layer on the surface of the core material after deformation processing; (3) hot-dip plating a tin-silver-copper alloy layer on the conductor material after nickel plating in step (2); (4) The conductor material obtained in step (3) is subjected to cold deformation processing to obtain a pin conductor.

2. The manufacturing method according to claim 1, characterized in that The step (1) is a drawing process, in which the copper or copper alloy conductor material is drawn into a wire of a desired shape and size, with a tensile strength greater than 500 MPa and a conductivity greater than 60%.

3. The manufacturing method according to claim 1, characterized in that The hot-dip plating temperature in step (3) is 250-300° C., and the tensile strength of the tin-silver-copper alloy coating is 10-20 MPa.

4. The manufacturing method according to claim 1, characterized in that In the step (4), the cold deformation processing method is cold drawing, and the deformation rate does not exceed 80%. The tensile strength of the obtained tin-silver-copper alloy layer of the pin conductor is 40-50 MPa.

5. A pin conductor that prevents tin whiskers and fretting wear, characterized in that: It has a core material composed of copper or copper alloy and an electroplated nickel layer and a hot-dip tin-silver-copper alloy layer sequentially coated on the outside of the core material. The weight percentage of each component in the tin-silver-copper alloy is 2%-4% silver, 0.2%-1.0% copper, and the balance is tin.

6. The pin conductor according to claim 5, characterized in that The core material is a high-strength and high-conductivity copper alloy material, with a conductivity greater than 60% and a tensile strength of not less than 600 MPa.

7. The pin conductor according to claim 5 or 6, characterized in that The thickness of the nickel layer is not less than 0.1 μm, the thickness of the tin-silver-copper alloy layer is not less than 0.3 μm, and the tensile strength of the tin-silver-copper alloy layer is not less than 40 MPa.

8. The pin conductor according to claim 7, characterized in that The thickness of the nickel layer is 0.1 μm to 10 μm, the thickness of the tin-silver-copper alloy layer is 0.3 μm to 10 μm, and the tensile strength of the tin-silver-copper alloy layer is 40 to 50 MPa.

9. The pin conductor according to claim 7, characterized in that The melting point of the tin-silver-copper alloy layer is in the range of 230-250°C.

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