Tin-silver anode and preparation method thereof

Abstract

The invention relates to the technical field of metal material processing and microelectronic material manufacturing, in particular to a tin-silver anode and a preparation method thereof. The method comprises the following steps: proportioning: proportioning high-purity tin and high-purity silver serving as raw materials to obtain a material; the mass ratio of the high-purity tin to the high-purity silver is 98: 2-92: 8; smelting: smelting the materials to obtain a tin-silver anode cast ingot; and cold deformation: carrying out cold deformation on the tin-silver anode cast ingot. According to the invention, a short-process processing technology is adopted, and more excellent performance and economic benefits are taken into account. The tin-silver anode with uniform components is designed and prepared, has conductivity and ductility, is more excellent in performance, gives consideration to economic benefits, and can be widely applied to the industries of electronic components, communication, solar photovoltaic photoelectricity and the like.

Description

Technical Field

[0001] This invention relates to the fields of metal material processing and microelectronic material manufacturing technology, and in particular to a tin-silver anode and its preparation method. Background Technology

[0002] The application of tin anodes in the semiconductor integrated circuit field is mainly reflected in the packaging process. The main function of electroplated tin anodes is to provide tin ions during the electroplating process, which are then reduced and deposited onto the surface of the object being processed, forming a tin film. This tin film can improve the corrosion resistance, electrical conductivity, and appearance quality of the processed object, playing an important role in semiconductor integrated circuit manufacturing. Electroplated tin anodes are usually made of high-purity tin material, which is prone to abnormal dissolution during the electroplating process. Pure tin tends to dissolve rapidly along specific grain boundaries, leading to the formation of dendritic crystals (tin dendrites) or loose tin powder (pulverization) on the anode surface. These tin powders or dendrites can fall into the plating bath, forming suspended particles, resulting in a rough coating, pitting, or nodules, severely contaminating the plating bath and reducing current efficiency. Silver atoms dissolve into the tin lattice, refining the grains and strengthening the grain boundaries. This makes the anode dissolution process more uniform, suppressing the tendency for rapid dissolution along specific grain boundaries, thus effectively preventing the formation of tin dendrites and pulverization, and ensuring stable and uniform anode dissolution. Silver is much harder than tin. Co-depositing silver into tin plating significantly improves the microhardness and mechanical strength of the tin plating, thus improving plating quality. Simultaneously, the addition of silver greatly improves the solderability (anti-oxidation, low melting point, high-strength solder joints) and low-temperature stability (inhibiting tin blast). Silver-containing tin-silver anodes are less prone to electrochemical passivation, while possessing both the ductility of tin and the conductivity of silver. They are easily soluble and have better performance suitable for higher process requirements. For example, in integrated circuit electroplating, tin-silver plating can reduce signal transmission loss and prevent substrate oxidation. CN116005214A discloses a method for ultrasonic electroplating Sn-Ag bumps at high current density. The preparation of the tin-silver anode plate involves pressing a silver plate onto a tin plate and connecting copper wires to the silver plate with insulating tape, thus establishing a physical connection between the copper wires and the tin-silver anode plate. Currently, there is no complete process in the industry for preparing tin-silver anodes with uniform and fine microstructure. There is an urgent need to design a tin-silver anode preparation process to meet customer and market requirements. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for preparing a tin-silver anode. This invention employs a short-process manufacturing procedure, achieving both superior performance and economic benefits. This invention designs and prepares a tin-silver anode with uniform composition, exhibiting both conductivity and ductility, resulting in superior performance while maintaining economic efficiency. It can be widely applied in industries such as electronic components, communications, and solar photovoltaics.

[0004] In a first aspect, the present invention provides a method for preparing a tin-silver anode, comprising: 1) Ingredients: High-purity tin and high-purity silver are used as raw materials to obtain the material; the mass ratio of high-purity tin to high-purity silver is 98:2-92:8.

[0005] 2) Smelting: The material is smelted to obtain tin-silver anode ingots.

[0006] 3) Cold deformation: The tin-silver anode ingot is cold deformed.

[0007] This invention employs a short-process manufacturing technique, achieving both superior performance and economic benefits. The resulting tin-silver anode contains 2-8% Ag, with a purity exceeding 99.99%. It combines the ductility of tin with the conductivity of silver, while maintaining economic viability. The tin-silver anode exhibits a dense, non-porous crystal structure with fine, uniform grains (≤100μm). It boasts high coating efficiency and can be widely applied in industries such as electronic components, communications, and solar photovoltaics.

[0008] Preferably, in step 1), the purity of the high-purity tin and high-purity silver is ≥4N.

[0009] Further optimization is achieved by using a mass ratio of high-purity tin to high-purity silver of 95:5-92:8 in step 1), such as 95:5, 94:6, 93:7, 92:8, etc. This preferred ratio results in superior overall performance of the tin-silver anode.

[0010] Preferably, in step 2), the melting method is vacuum induction melting, suspension melting, or electron beam melting.

[0011] Preferably, in step 2), the purity of the tin-silver anode ingot is 99.99-99.999%.

[0012] Preferably, in step 3), the cold deformation method includes upsetting and rolling.

[0013] Further optimization is made in step 3), where the deformation per rolling pass is 10±2% and the total cold deformation is over 85%.

[0014] In this invention, by optimizing the material composition and cold deformation applied to the ingot, the tin-silver anode can achieve a high purity of 99.99-99.999%, resulting in higher coating purity and excellent ductility and conductivity. This significantly improves the microhardness and mechanical strength of the tin coating while also being economically efficient. Furthermore, only large cold deformation is required, resulting in a fine and uniform grain structure with a diameter ≤60μm. The anode dissolution process becomes more uniform, leading to better coating thickness uniformity, improved coating quality, and superior overall performance.

[0015] Further preferably, the cold deformation process also includes 4) machining and 5) cleaning and packaging.

[0016] Further preferred, in step 4), the machining includes conventional turning, CNC machining and surface polishing.

[0017] Further preferred, in step 5), the cleaning and packaging includes process cleaning, finished product cleaning, vacuum drying, vacuum packaging, and outer packaging.

[0018] Secondly, the present invention provides a tin-silver anode, obtained by the preparation method of the tin-silver anode; the mass content of Ag is 2%-8%, and the grain size of the tin-silver anode is ≤100μm, with fine and uniformly distributed grains.

[0019] The beneficial effects of this invention are at least as follows: By combining component content control with processes such as cold deformation, this invention efficiently prepares high-performance tin-silver anodes with fine and uniform grains in a short process, achieving both excellent performance and economic benefits. The tin-silver anode of this invention has high purity (above 99.99%), possessing both the ductility of tin and the conductivity of silver, while also being economically viable; its microstructure is dense and free of pores, with fine and uniform grains (≤100μm); it exhibits high coating efficiency and excellent quality, and can be widely used in industries such as electronic components, communications, and solar photovoltaics. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a microstructure diagram of the tin-silver anode blank in Example 1 of the present invention.

[0022] Figure 2 This is a microstructure diagram of the tin-silver anode blank in Example 2 of the present invention.

[0023] Figure 3 This is a flowchart illustrating the preparation of the tin-silver anode in an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0026] Unless otherwise specified, the techniques or conditions described in the embodiments of this invention shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Devices, instruments, reagents, etc., without specified manufacturers, are all conventional products that can be purchased through legitimate channels. All experimental reagents and raw materials involved are commercially available products, and all reagents are analytical grade products.

[0027] Example 1 This embodiment provides a tin-silver anode and its preparation method, see [link to documentation]. Figure 3 Prepare tin-silver anodes according to the following steps: Step 1) The raw materials used for the tin-silver anode preparation are high-purity tin plates and high-purity silver with a purity ≥ 99.99% (4N). The high-purity tin plates and high-purity silver are weighed according to the Ag content of 5% (the mass ratio of high-purity tin to high-purity silver is 95:5) in the preparation step.

[0028] Step 2) The high-purity tin plate and silver from Step 1) are melted and cast into an ingot using a vacuum induction process. After melting, the composition of the tin-silver anode ingot is tested, wherein the content of Ag is 5±0.5% and the purity of the tin-silver anode ingot is 99.99-99.999%.

[0029] Step 3) The billet from Step 2) is cold rolled. The deformation per rolling pass is 10±2%, and the total cold deformation is 90%.

[0030] Samples were taken from the billet and its microstructure was analyzed. The grain structure was uniform and fine, with an average grain size of 58 μm. See [link to sample analysis]. Figure 1 .

[0031] Step 4) Machin the blank from Step 3). The machining process consists of conventional turning, CNC machining, and surface polishing. The dimensions must meet the drawing requirements, and the surface roughness must be ≤0.8μm.

[0032] Step 5) Clean and package the blanks from Step 4). The cleaning and packaging process includes in-process cleaning, finished product cleaning, vacuum drying, vacuum packaging, and outer packaging.

[0033] Example 2 This embodiment provides a tin-silver anode and its preparation method, wherein the tin-silver anode is prepared according to the following steps: Step 1) The raw materials used for the tin-silver anode preparation are high-purity tin plates and high-purity silver with a purity ≥ 99.99% (4N). The high-purity tin plates and high-purity silver are weighed and prepared according to the Ag content of 8%.

[0034] Step 2) The high-purity tin plate and silver from Step 1) are smelted and cast into ingots using a suspension method. After smelting, the composition of the tin-silver anode ingot is tested, wherein the content of Ag is 8±0.8% and the purity of the tin-silver anode ingot is 99.99-99.999%.

[0035] Step 3) The billet from Step 2) is subjected to cold heading deformation, with a total cold deformation amount of 85%.

[0036] Samples were taken from the billet and its microstructure was analyzed. The grain structure was uniform and fine, with an average grain size of 56 μm. See Figure 2 .

[0037] Step 4) Machin the blank from Step 3). The machining process consists of conventional turning, CNC machining, and surface polishing. The dimensions must meet the drawing requirements, and the surface roughness must be ≤0.8μm.

[0038] Step 5) Clean and package the blanks from Step 4). The cleaning and packaging process includes in-process cleaning, finished product cleaning, vacuum drying, vacuum packaging, and outer packaging.

[0039] Example 3 This embodiment provides a method for preparing a tin-silver anode, which is prepared according to the following steps: Step 1) The raw materials used for the tin-silver anode preparation are high-purity tin plates with a purity ≥ 99.99% (4N) and high-purity silver. The high-purity tin plates and silver are weighed and prepared according to the Ag content of 2%.

[0040] Step 2) The high-purity tin plate and high-purity silver from Step 1) are smelted and cast into ingots using a suspension method. After smelting, the composition of the tin-silver anode ingot is tested, wherein the content of Ag is 2±0.2% and the purity of the tin-silver anode ingot is 99.99-99.999%.

[0041] Step 3) The billet from Step 2) is subjected to cold heading deformation, with a total cold deformation amount of 85%.

[0042] Samples were taken from the billet and its microstructure was analyzed. The grain structure was uniform and fine, with an average grain size of 75 μm.

[0043] Step 4) Machin the blank from Step 3). The machining process consists of conventional turning, CNC machining, and surface polishing. The dimensions must meet the drawing requirements, and the surface roughness must be ≤0.8μm.

[0044] Step 5) Clean and package the blanks from Step 4). The cleaning and packaging process includes in-process cleaning, finished product cleaning, vacuum drying, vacuum packaging, and outer packaging.

[0045] Example 4 This embodiment provides a method for preparing a tin-silver anode, which is prepared according to the following steps: Step 1) The raw materials used for the tin-silver anode preparation are high-purity tin plates and high-purity silver with a purity ≥99.99% (4N). The high-purity tin plates and high-purity silver are weighed and prepared according to the Ag content of 6%.

[0046] Step 2) The high-purity tin plate and silver from Step 1) are smelted and cast into ingots using a suspension method. After smelting, the composition of the tin-silver anode ingot is tested, wherein the content of Ag is 6±0.6% and the purity of the tin-silver anode ingot is 99.99-99.999%.

[0047] Step 3) The billet from Step 2) is subjected to cold heading deformation, with a total cold deformation amount of 85%.

[0048] Samples were taken from the billet and its microstructure was analyzed. The grain structure was uniform and fine, with an average grain size of 59 μm.

[0049] Step 4) Machin the blank from Step 3). The machining process consists of conventional turning, CNC machining, and surface polishing. The dimensions must meet the drawing requirements, and the surface roughness must be ≤0.8μm.

[0050] Step 5) Clean and package the blanks from Step 4). The cleaning and packaging process includes in-process cleaning, finished product cleaning, vacuum drying, vacuum packaging, and outer packaging.

[0051] Comparative Example 1 Prepare tin-silver anodes according to the following steps: Step 1) The raw materials used for tin-silver anode preparation are tin plates and silver with a purity of 99.95% (3N5). The high-purity tin plates and silver are weighed and prepared according to the Ag content of 5%.

[0052] Step 2) The high-purity tin plate and silver from Step 1) are melted and cast into an ingot using vacuum induction melting. After melting, the composition of the ingot is tested, and the content of Ag is 5±0.5%. The purity of the tin-silver ingot is 99.9-99.95%.

[0053] If the purity of the ingot does not meet the requirements and the impurity elements are too high, it will affect the coating quality, and the ingot will be scrapped.

[0054] Comparative Example 2 Step 1) The raw material used for tin-silver anode preparation is a high-purity tin plate with a purity of ≥99.99% (4N).

[0055] Step 2) The high-purity tin plate from Step 1) is melted and cast into an ingot using a vacuum induction process. After melting, the composition of the ingot is tested, and the content of Ag is 0 ppm. The purity of the tin ingot is 99.99-99.999%.

[0056] If the ingot composition does not meet the requirements, abnormal dissolution can easily occur during electroplating without Ag. Pure tin tends to dissolve rapidly along specific grain boundaries, leading to the formation of dendritic crystals (tin dendrites) or loose tin powder (pulverization) on the anode surface. These tin powders or dendrites can detach and enter the plating bath, forming suspended particles that result in a rough plating layer, pitting, or nodules. This severely contaminates the plating bath and reduces current efficiency, affecting the quality and efficiency of the plating film. It also leads to excessive signal transmission loss in the product, rendering it unusable.

[0057] Comparative Example 3 Step 1) The raw materials used for the tin-silver anode preparation are high-purity tin plates with a purity ≥ 99.99 (4N) and high-purity silver. The high-purity tin plates and silver are weighed and prepared according to the Ag content of 30%.

[0058] Step 2) The high-purity tin plate and silver from Step 1) are melted and cast into an ingot using vacuum induction melting. After melting, the composition of the ingot is tested, and the content of Ag is 30±1%. The purity of the tin-silver ingot is 99.99-99.999%.

[0059] If the composition of the ingot does not meet the requirements, the high Ag content may embrittle the coating and affect the coating quality. Moreover, based on the unit price of tin of 375 yuan / kg and the unit price of Ag of 8000 yuan / kg, the product cost increases by more than 250%, and the ingot is scrapped.

[0060] Comparative Example 4 Prepare tin-silver anodes according to the following steps: Step 1) The raw materials used for the tin-silver anode preparation are high-purity tin plates with a purity ≥ 99.99% (4N) and high-purity silver. The high-purity tin plates and silver are weighed and prepared according to the Ag content of 5%.

[0061] Step 2) The high-purity tin plate and silver from Step 1) are melted and cast into an ingot using a vacuum induction process. After melting, the composition of the ingot is tested, and the content of Ag is 5±0.5%. The purity of the tin-silver ingot is 99.99-99.999%.

[0062] Step 3) The billet from Step 2) is cold rolled. The deformation per rolling pass is 10±2%, and the total cold deformation is 90%.

[0063] Step 4) Machining the blank from Step 3). Machining includes conventional turning and CNC machining. Dimensions meet the drawing requirements, and surface roughness is ≤0.8μm. Although the surface roughness of the machined tin-silver anode meets the requirements, the surface texture is inconsistent from the center to the outer diameter and has scratches affecting the appearance, resulting in substandard surface quality. Surface polishing is required for rework. After rework, the surface texture is consistent, and the surface quality is acceptable.

[0064] Step 5) Clean and package the blanks from Step 4). The cleaning and packaging process includes in-process cleaning, finished product cleaning, vacuum drying, vacuum packaging, and outer packaging.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a tin-silver anode, characterized in that, include: 1) Ingredients: High-purity tin and high-purity silver are used as raw materials to obtain the material; the mass ratio of high-purity tin to high-purity silver is 98:2-92:8; 2) Smelting: The material is smelted to obtain tin-silver anode ingots; 3) Cold deformation: The tin-silver anode ingot is cold deformed.

2. The method for preparing the tin-silver anode according to claim 1, characterized in that, In step 1), the purity of the high-purity tin and high-purity silver is ≥4N.

3. The method for preparing the tin-silver anode according to claim 1 or 2, characterized in that, In step 2), the melting method is vacuum induction melting, suspension melting, or electron beam melting.

4. The method for preparing the tin-silver anode according to claim 3, characterized in that, In step 2), the purity of the tin-silver anode ingot is 99.99-99.999%.

5. The method for preparing a tin-silver anode according to any one of claims 1-4, characterized in that, In step 3), the cold deformation method includes upsetting and / or rolling.

6. The method for preparing a tin-silver anode according to claim 5, characterized in that, In step 3), the deformation amount of each rolling pass is 10±2%, and the total cold deformation amount is more than 85%.

7. The method for preparing a tin-silver anode according to any one of claims 1-6, characterized in that, The process after cold deformation also includes 4) machining and 5) cleaning and packaging.

8. The method for preparing the tin-silver anode according to claim 7, characterized in that, In step 4), the machining includes conventional turning, CNC machining, and surface polishing; and / or, in step 5), the cleaning and packaging includes process cleaning, finished product cleaning, vacuum drying, vacuum packaging, and outer packaging.

9. A tin-silver anode, characterized in that, It is obtained by the method for preparing the tin-silver anode according to any one of claims 1-8.

10. The tin-silver anode according to claim 9, characterized in that, The tin-silver anode contains 2%-8% Ag by mass, and has a grain size ≤100μm, with fine and uniformly distributed grains.

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