Preparation method of tin whisker and fretting wear-resistant pin conductor and pin conductor

Abstract

The present invention provides a pin conductor that is resistant to tin whiskers and fretting wear. The pin conductor comprises a core material composed of copper or a copper alloy, and a nickel layer and a tin-silver-copper alloy layer sequentially coated on the outside of the core material. The weight percentages of the components in the tin-silver-copper alloy are 2% to 4% silver, 0.2% to 1.0% copper, and the balance is tin. The present invention also provides a method for manufacturing a pin conductor that is resistant to tin whiskers and fretting wear. The method comprises sequentially deforming a high-strength and high-conductivity copper or copper alloy conductor material, electroplating an intermediate nickel layer, and hot-dip plating a tin-silver-copper alloy layer, and then performing a cold deformation process to draw the conductor material as a whole. This further enhances the bonding strength between the core material and the plating layer, improves the hardness and wear resistance of the pin conductor, and effectively prevents the generation of tin whiskers and reduces fretting wear during use of the pin conductor.

Description

Technical Field

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

[0002] In the field of precision electronics, tin solder is often used to connect electronic components. However, stress on the surface of electroplated or soldered components can produce tin whiskers, which can cause serious faults such as short circuits. In applications such as sensors, this growth is accompanied by fretting wear, which can have disastrous consequences for the operation of precision components like sensors. Particularly on the pins and plugs of electronic components, which are often subject to mechanical stresses such as vibration, these areas are particularly susceptible to the damage caused by tin whiskers and fretting 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

[0004] One of the objectives of the present invention is to provide a method for manufacturing a pin conductor that is resistant to tin whiskers and fretting wear. The method involves sequentially deforming a high-strength, high-conductivity copper or copper alloy conductor material, electroplating an intermediate nickel layer, and hot-dip-plating a tin-silver-copper alloy layer. The conductor material is then cold-formed to draw the entire conductor material. This further enhances the bonding strength between the core material and the plating, and improves the hardness and surface finish of the pin conductor, thereby reducing fretting wear and providing the pin conductor with improved wear resistance and corrosion resistance.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for manufacturing a pin conductor that is resistant to tin whiskers and fretting wear, specifically comprising the following steps:

[0007] (1) Deforming copper or copper alloy conductor materials into core materials of the desired shape;

[0008] (2) Electroplating nickel on the surface of the core material after deformation;

[0009] (3) hot-dip plating the nickel-plated conductor material in step (2) with a tin-silver-copper alloy;

[0010] (4) The conductor material obtained in step (3) is subjected to cold deformation processing to obtain a pin conductor.

[0011] Preferably, the step (1) is a drawing process, wherein 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%.

[0012] Preferably, the temperature of the hot-dip plating in step (3) is 250-300° C., and the tensile strength of the tin-silver-copper alloy coating is 10-20 MPa.

[0013] 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.

[0014] A second object of the present invention is to provide a pin conductor that is resistant to tin whiskers and fretting wear. The pin conductor is made of a high-conductivity copper or copper alloy material with a certain strength as the conductor substrate, nickel is electroplated as a transition base layer, and then a tin-silver-copper alloy is plated on the nickel plating layer. This effectively prevents the generation of tin whiskers and reduces fretting wear during use of the pin conductor.

[0015] To achieve the above object, the present invention provides the following technical solutions:

[0016] A pin conductor that is resistant to tin whiskers and fretting wear comprises 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. The weight percentages of the components in the tin-silver-copper alloy are 2% to 4% silver, 0.2% to 1.0% copper, and the balance tin.

[0017] Preferably, 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. The use of highly conductive copper or copper alloy material can significantly reduce contact resistance.

[0018] 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.

[0019] 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.

[0020] Preferably, the melting point of the tin-silver-copper alloy layer is in the range of 230-250° C. to meet the soldering requirements of component pins.

[0021] Beneficial effects of the present invention:

[0022] The pin conductor of the present invention is coated with a nickel layer to effectively isolate the chemical reaction between tin and copper, reduce the stress between the plating layers, and thus reduce the possibility of tin whiskers generated in the tin plating layer from the inside. When the pin generates micro-wear in a vibration environment, the bottom nickel layer can provide additional anti-wear and anti-oxidation protection, avoiding the core material from being exposed and oxidized, thereby increasing the contact resistance of the pin; (2) by using a 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, reducing micro-wear; and the hardness of the coating is about 3 times that of pure tin coating, and its wear resistance is greater than that of pure tin coating.

[0023] (3) By cold-drawing the plated conductor material to form the 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-wear and also makes the pin conductor have better wear resistance and corrosion resistance.

[0024] In summary, the present invention is particularly suitable for components on precision devices that are susceptible to vibration 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 fretting wear. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of a pin conductor according to some embodiments of this specification;

[0026] Figure 2 The following are photos of the pin conductor shown in Example 1 before and after cold drawing under an optical microscope at a magnification of 50 times;

[0027] FIG3( a ) and FIG3 ( b ) are cross-sectional views of the pin conductor before and after cold drawing in Example 1 under an optical microscope at a magnification of 50 times.

[0028] Figure 4 is an exemplary flow chart of a method for manufacturing a pin conductor according to some embodiments of this specification. DETAILED DESCRIPTION

[0029] To more clearly illustrate the technical solutions of the embodiments of this specification, the following briefly describes the drawings required for describing the embodiments. Obviously, the drawings described below are merely examples or embodiments of this specification. Those skilled in the art can apply this specification to other similar scenarios based on these drawings without inventive effort. Unless otherwise apparent from the context or otherwise noted, the same reference numerals in the figures represent the same structure or operation.

[0030] It should be understood that the terms "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 terms can achieve the same purpose, the terms may be replaced by other expressions.

[0031] Unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not refer to the singular but include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list. A method or apparatus may also include other steps or elements.

[0032] Flowcharts are used throughout this specification to illustrate the operations performed by systems according to embodiments of this specification. It should be understood that preceding or following operations do not necessarily need to be performed in exact order. Instead, the steps may be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0033] Example 1

[0034] Figure 1 is a schematic structural diagram of a pin conductor according to some embodiments of this specification;

[0035] 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. The weight percentages of the components in the tin-silver-copper alloy are 2% to 4% silver, 0.2% to 1.0% copper, and the balance tin;

[0036] The method for preparing the above-mentioned pin conductor specifically comprises the following steps:

[0037] (1) Drawing the copper-magnesium alloy rod into a wire of the required size, with a tensile strength greater than 500 MPa and a conductivity greater than 60%;

[0038] (2) electroplating a nickel layer on the surface of the drawn wire, wherein the nickel plating layer has a thickness of 1 μm;

[0039] (3) hot-dip plating the nickel-plated wire in step (2) with a tin-silver-copper alloy, wherein the alloy bath temperature is 250-300°C, the tin-silver-copper alloy coating thickness is 3 μm, and the coating tensile strength is 13-18 MPa;

[0040] (4) The wire material obtained in step (3) is cold-drawn to obtain a pin conductor with a deformation rate not exceeding 80%.

[0041] The core material tensile strength 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.

[0042] Example 2

[0043] This embodiment provides a pin conductor that is resistant to tin whiskers and fretting wear, comprising a core material 1 made of H65 brass, 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. The weight percentages of the components in the tin-silver-copper alloy are 2% to 4% silver, 0.2% to 1.0% copper, and the balance tin.

[0044] The method for preparing the above-mentioned pin conductor specifically comprises the following steps:

[0045] (1) Drawing H65 brass rod into wire of required size, with tensile strength greater than 500 MPa and conductivity greater than 60%;

[0046] (2) Electroplating a nickel layer on the surface of the drawn brass wire with a nickel plating thickness of 0.5 μm;

[0047] (3) hot-dip plating the nickel-plated wire in step (2) with a tin-silver-copper alloy, wherein the alloy bath temperature is 250-300°C, the tin-silver-copper alloy coating thickness is 0.8 μm, and the tensile strength is 12-16 MPa;

[0048] (4) The wire material obtained in step (3) is cold-drawn to obtain a pin conductor with a deformation rate not exceeding 40%.

[0049] The core material tensile strength 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 its melting point ranges from 230 to 250°C.

[0050] Comparative Example 1

[0051] 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 covering the core material. The weight percentages of the components in the tin-silver-copper alloy are 2% to 4% silver, 0.2% to 1.0% copper, and the balance tin.

[0052] The method for preparing the above-mentioned pin conductor specifically comprises the following steps:

[0053] (1) Drawing the copper-magnesium alloy rod into a wire of the required size, with a tensile strength greater than 500 MPa and a conductivity greater than 60%;

[0054] (2) hot-dip coating the wire obtained in step (1) with a tin-silver-copper alloy, wherein the alloy bath temperature is 250-300°C, the tin-silver-copper alloy coating thickness is 3 μm, and the tensile strength is 13-18 MPa;

[0055] (3) The wire material obtained in step (2) is cold-drawn to obtain a pin conductor with a deformation rate not exceeding 40%.

[0056] The pin conductor obtained above was found to not produce tin whiskers during actual use. However, after the tin-silver-copper alloy coating was worn, the core material was exposed and oxidized, 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 Examples 1 and 2.

[0057] Comparative Example 2

[0058] 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;

[0059] The method for preparing the above-mentioned pin conductor specifically comprises the following steps:

[0060] (1) Drawing the copper-magnesium alloy rod into a wire of the required size, with a tensile strength greater than 500 MPa and a conductivity greater than 60%;

[0061] (2) electroplating a nickel layer on the surface of the drawn wire, wherein the nickel plating layer has a thickness of 0.5 μm;

[0062] (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.

[0063] The pin conductor obtained above cannot prevent tin whiskers generated 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 compared to the pin conductors of Examples 1 and 2.

[0064] In summary, the comprehensive performance parameters of Example 1 are optimal compared to 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 conductors is relatively high, which can effectively reduce fretting wear and extend the effective service life of the pin conductors, meeting the requirements of the operating conditions.

[0065] 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 scope of protection of the present invention.

Claims

1. A method for manufacturing a pin conductor that is resistant to tin whiskers and fretting wear, characterized in that: The following steps are involved: (1) Deforming copper or copper alloy conductor materials into core materials 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 nickel-plated conductor material in step (2); (4) performing cold deformation processing on the conductor material obtained in step (3) to obtain a pin conductor; In 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.

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, wherein 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. A pin conductor that is resistant to tin whiskers and fretting wear, characterized in that: The invention comprises 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% to 4% silver, 0.2% to 1.0% copper, and the balance is tin.

5. The pin conductor according to claim 4, 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.

6. The pin conductor according to claim 4 or 5, 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.

7. The pin conductor according to claim 6, 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.

8. The pin conductor according to claim 6, characterized in that The melting point of the tin-silver-copper alloy layer is in the range of 230-250°C.

Images