Forming method of gold-tin alloy Au80Sn20 welding ring

Abstract

This invention discloses a method for forming Au80Sn20 gold-tin alloy solder rings, relating to the field of aerospace component solder processing technology. The method includes three steps: equipment preparation, solder powder loading, and forming. This method eliminates the limitations of thickness-to-width ratio in processing Au80Sn20 gold-tin alloy solder rings, resulting in complete, crack-free, and chipped finished products. It avoids the possibility of solder falling onto the customer's chip due to cracks or chipping, which is particularly important for military-grade chips. The finished product does not require conventional powder metallurgy sintering, as the customer heats the solder above its melting point during use, combining the sintering and welding processes into one step. This method can not only form circular rings but also waist-shaped rings (runway rings), and it even surpasses conventional stamping processing on solder sheets thicker than 0.5mm.

Description

Technical Field

[0001] This invention relates to the field of aerospace component solder processing technology, specifically a method for forming a gold-tin alloy Au80Sn20 solder ring. Background Technology

[0002] Au80Sn20 gold-tin solder has a long history of use in fields such as hermetic packaging and chip packaging due to its excellent tensile strength, strong corrosion resistance, low vapor pressure, and good fluidity and wettability.

[0003] In certain applications, gold-tin solder needs to be processed into circular and oblong rings for use between pins and vias on the sidewalls of the cavity, or for welding and sealing the inner shell and core of connectors. These applications generally require the solder ring to be as narrow as possible and as thick as possible. A narrower ring uses less precious metal solder, resulting in lower material costs; a thicker ring provides a better seal. However, the requirements and processing difficulty are inversely proportional. The industry typically uses the thickness-to-width ratio (thickness / width) to assess the ease of forming.

[0004] The conventional forming method is stamping. However, because gold-tin alloys are relatively brittle, the larger the thickness-to-width ratio, the more prone they are to cracking or even brittle fracture during stamping. Based on general experience, thickness-to-width ratios greater than 1.5 are extremely prone to these defects. Therefore, gold-tin alloy weld rings with a thickness-to-width ratio greater than 2 cannot be produced using conventional stamping methods. When using conventional stamping to produce weld rings with large thickness-to-width ratios, several defects arise. First, the stamping process ideally requires a fixed width of material for continuous processing. However, gold-tin alloys are relatively brittle; when the thickness exceeds 0.2mm, slitting will cause cracking or even brittle fracture, making this difficult to achieve. Second, and most importantly, stamping is essentially a shearing process... During the shearing process, the material deforms. Normally ductile materials will naturally form a rounded corner, maintaining the integrity of the weld ring. However, gold-tin alloys are brittle and lack ductility, causing tearing or even complete brittle fracture during deformation. This defect is extremely common when the thickness-to-width ratio is greater than 1.5, making it impossible to produce gold-tin alloy weld rings with a thickness-to-width ratio greater than 2 using conventional stamping methods. Thirdly, material utilization is low. Gold-tin alloys contain 80% gold, and higher material utilization is desirable during production. However, the larger the thickness-to-width ratio of the ring, the lower the ratio of the finished product weight to the raw material weight, thus increasing costs significantly.

[0005] Under this premise, we invented a new forming method to process this gold-tin alloy welding ring with a large thickness-to-width ratio. Summary of the Invention

[0006] The purpose of this invention is to provide a method for forming a gold-tin alloy Au80Sn20 welding ring, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for forming a gold-tin alloy Au80Sn20 solder ring, comprising the following steps: S1. Equipment Preparation: Step 1: Place a heat insulation pad on the platform of the press; Step 2: Place a heating plate on the pad, with 8mm diameter through holes and M6 blind holes machined on the heating plate, and place ø8mm stainless steel heating tubes and M6 K-type temperature probes respectively. The heating tubes and K-type temperature probes are connected to the temperature control instrument to form a heating system; Step 3: Place a powder metallurgy forming mold on top of the heating block, and set the temperature of the heating plate to 110 degrees Celsius. S2. Tin powder loading: Step 1: Use a high-precision electronic scale to weigh a certain weight of gold-tin powder and add it into the cavity from the mold bevel, and add it as evenly as possible around the ring; Step 2: Place the mold filled with gold-tin alloy powder on an ultrasonic vibration table, and vibrate the powder in the mold cavity to a flat and dense state through ultrasonic vibration. S3. Molding process: Step 1: Place the molding mold on the heating plate and wait for 120 seconds to heat the powder to increase its ductility. 110 degrees Celsius will not cause the gold-tin alloy powder to oxidize. The second step is to turn on the pneumatic press, and its slider will press down. The huge pressure will compact the gold-tin alloy powder in the cavity to form a ring of the required size. The third step is to remove the mold from the equipment and take out the ring. The production of this gold-tin alloy welded ring with a large thickness-to-width ratio is completed.

[0008] Preferably, the material of the heat insulation pad in S1 is 06Cr19Ni9, which is 304 stainless steel.

[0009] Preferably, the heating plate in S1 is made of SKS5 material.

[0010] Preferably, the molding die in S2 consists of a base, a core, a frame, and a pressing block. Before use, the molding die needs to be cleaned with an ultrasonic cleaning device and dried with a clean scouring pad.

[0011] Preferably, the particle size of the gold-tin alloy powder in S2 is 45-75 μm or 25-45 μm.

[0012] Preferably, the pressure in step S3 needs to be maintained for 20 seconds after the press is applied.

[0013] Preferably, the pneumatic press parameters in S1 are three plates and four columns, and the pneumatic press pressure is selected as 4 tons or above. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 This is a schematic diagram of the process equipment of the present invention.

[0015] Beneficial effects Compared with the prior art, the present invention provides a method for forming a gold-tin alloy Au80Sn20 solder ring, which has the following beneficial effects: The forming method of this gold-tin alloy Au80Sn20 solder ring eliminates the limitations of thickness-to-width ratio in processing gold-tin alloy Au80Sn20 solder rings. The finished product is complete without cracks or chipping, avoiding the possibility of solder falling onto the customer's chip and causing damage due to cracks or chipping. This is especially valued by military-grade chips. The finished product does not require conventional powder metallurgy sintering process, because the customer will heat the solder above the melting point during use. The sintering process and the welding process during customer use are combined into one step. This method can not only form round rings, but also waist-shaped rings (racetrack rings). It is even more advantageous than conventional stamping processing on solder sheets with a thickness greater than 0.5mm. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1-2 This invention provides a technical solution: a method for forming a gold-tin alloy Au80Sn20 welding ring, comprising the following steps: S1. Equipment Preparation: Step 1: Place a heat insulation pad on the platform of the press. Step 2: Place a heating plate on the pad. The heating plate has 8mm diameter through holes and M6 blind holes. Place ø8mm stainless steel heating tubes and M6 K-type temperature probes on the heating plate. Connect the heating tubes and K-type temperature probes to the temperature control instrument to form a heating system. Step 3: Place a powder metallurgy forming mold on top of the heating block and set the temperature of the heating plate to 110 degrees Celsius. The parameters of the pneumatic press in S1 are three plates and four columns to ensure verticality and flatness. The pressure of the pneumatic press should be 4 tons or more. The material of the heat insulation pad in S1 is 06Cr19Ni9, which is the common 304 stainless steel. It has a high Cr content, poor thermal conductivity and hard texture. The material of the heating plate in S1 is SKS5 material. SKS5 is heat-resistant, does not easily rust and has high hardness. S2, Tin Powder Feeding: Step 1: Use a high-precision electronic scale to weigh a certain amount of gold-tin powder and add it into the cavity from the mold bevel, spreading it as evenly as possible around the ring; Step 2: Place the mold filled with gold-tin alloy powder on an ultrasonic vibration table, and vibrate the powder in the mold cavity to a flat and dense state through ultrasonic vibration. The mold in S2 consists of a base, core, frame and pressure block. Before use, the mold needs to be cleaned with ultrasonic cleaning equipment and dried with a clean scouring pad. The particle size of the gold-tin alloy powder in S2 is 45-75μm or 25-45μm. S3. Molding process: Step 1: Place the molding mold on the heating plate and wait for 120 seconds to heat the powder to increase its ductility. 110 degrees Celsius will not cause the gold-tin alloy powder to oxidize. The second step is to turn on the pneumatic press, and its slider will press down. The huge pressure will compact the gold-tin alloy powder in the cavity to form a ring of the required size. The third step is to remove the mold from the equipment and take out the ring. This completes the production of this gold-tin alloy welded ring with a large thickness-to-width ratio. After the press in S3 is pressed down, it needs to be held for 20 seconds. Specific example 1: When making a gold-tin alloy Au80Sn20 ring with an outer diameter of ø5mm, an inner diameter of ø4.6mm, and a thickness of 0.4mm, the first step is to make the corresponding molding mold, clean it ultrasonically, and then assemble it. According to the calculation, the mass of a single ring is M1 = 0.0175g. The second step is to weigh 0.0175g on a high-precision electronic scale. The third step involves evenly pouring the powder into a molding die, placing the die on an ultrasonic vibration table, vibrating for 30 seconds, raising the heating plate to 110 degrees Celsius, placing the mold filled with powder on the heating table, placing the pressure block on top, waiting for 120 seconds, pressing the press switch, pressing down and holding pressure for 20 seconds, removing the molding die, and taking out the finished ring to obtain the desired product; Specific Example 2: Making a waist-shaped ring (racetrack ring) with a length of 20mm, a width of 5mm, a side width of 0.25mm, and a thickness of 0.5mm. The first step involves making the corresponding molding die, ultrasonically cleaning it, and then assembling it. According to calculations, the mass of a single ring, M2, is... 0.0815g; Step 2: Weigh 0.0815g of No. 3 gold-tin Au80Sn20 powder on a high-precision electronic scale; Pour it evenly into the molding die; Step 3: Place the molding die on an ultrasonic vibration table and vibrate for 30 seconds. Heat the heating plate to 110 degrees Celsius, place the molding die filled with powder on the heating table, place the pressure block on it, wait for 120 seconds, press the press switch, the press presses down and holds pressure for 20 seconds, remove the molding die, remove the made ring, and obtain the product we need.

[0018] Therefore, it is evident that the conventional forming method is stamping. However, because gold-tin alloys are relatively brittle, the larger the thickness-to-width ratio, the more prone they are to cracking or even brittle fracture during stamping. Based on general experience, thickness-to-width ratios greater than 1.5 are extremely prone to these defects, making it impossible to produce gold-tin alloy weld rings with a thickness-to-width ratio greater than 2 using conventional stamping methods. Conventional stamping methods for producing weld rings with large thickness-to-width ratios have several drawbacks. First, the stamping process ideally requires a fixed width for continuous processing. However, gold-tin alloys are relatively brittle; when the thickness exceeds 0.2mm, slitting will cause cracking or even brittle fracture, making this difficult to achieve. Second, and most importantly, stamping is essentially a shearing process. During this shearing, the material deforms. Conventional, ductile materials will naturally form a rounded corner, maintaining the integrity of the weld ring. However, gold-tin alloys are brittle and lack ductility, leading to tearing or even brittle fracture during deformation, rendering them unusable. Thickness-to-width ratios greater than 1... The aforementioned defects are extremely prone to occur after 0.5 mm, making it impossible to produce gold-tin alloy welding rings with a thickness-to-width ratio greater than 2 using conventional stamping methods. Thirdly, material utilization is low. Gold-tin alloys contain 80% gold, and higher material utilization is desirable during production. However, the larger the thickness-to-width ratio of the ring, the lower the ratio of the finished product weight to the raw material weight, thus increasing costs significantly. The forming method of this invention for processing gold-tin alloy Au80Sn20 welding rings is no longer limited by the thickness-to-width ratio. The finished product is complete, without cracks or chipping, avoiding the possibility of solder falling onto the customer's chip due to cracks or chipping. This is especially important for military chips. The finished product does not require conventional powder metallurgy sintering, as the customer heats the solder above its melting point during use. The sintering process and the welding process during customer use are combined into one step. This method can not only form round rings but also waist-shaped rings (racetrack rings), and it is even more advantageous than conventional stamping processing for welding sheets with a thickness greater than 0.5 mm.

Claims

1. A method for forming a gold-tin alloy Au80Sn20 welding ring, characterized in that: Includes the following steps: S1. Equipment Preparation: Step 1: Place a heat insulation pad on the platform of the press; Step 2: Place a heating plate on the heat insulation pad. The heating plate has 8mm diameter through holes and M6 blind holes, where ø8mm stainless steel heating tubes and M6 K-type temperature probes are placed respectively. The heating tubes and K-type temperature probes are connected to the temperature control instrument to form a heating system; Step 3: Place a powder metallurgy forming mold on top of the heating plate and set the temperature of the heating plate to 110 degrees Celsius. S2, Tin Powder Loading: Step 1: Use a high-precision electronic scale to weigh a certain weight of gold-tin powder and add it into the cavity from the mold bevel, spreading it as evenly as possible around the ring; Step 2: Place the mold filled with gold-tin alloy powder on an ultrasonic vibration table and vibrate the powder in the mold cavity to a flat and dense state through ultrasonic vibration. S3. Molding process: Step 1: Place the molding mold on the heating plate and wait for 120 seconds to heat the powder to increase its ductility. 110 degrees Celsius will not cause the gold-tin alloy powder to oxidize. The second step is to turn on the pneumatic press, and its slider will press down. The huge pressure will compact the gold-tin alloy powder in the cavity to form a ring of the required size. The third step is to remove the mold from the equipment and take out the ring. The production of this gold-tin alloy welded ring with a large thickness-to-width ratio is completed.

2. The method for forming a gold-tin alloy Au80Sn20 welding ring according to claim 1, characterized in that: The heat insulation pad in S1 is made of 304 stainless steel.

3. The method for forming a gold-tin alloy Au80Sn20 welding ring according to claim 2, characterized in that: The heating plate in S1 is made of SKS5 material.

4. The method for forming a gold-tin alloy Au80Sn20 welding ring according to claim 3, characterized in that: The molding mold in S2 consists of a base, a core, a frame, and a pressing block. Before use, the molding mold is cleaned with an ultrasonic cleaning device and then dried with a clean scouring pad.

5. The method for forming a gold-tin alloy Au80Sn20 welding ring according to claim 4, characterized in that: The gold-tin alloy powder in S2 has a particle size of 45-75 μm or 25-45 μm.

6. The method for forming a gold-tin alloy Au80Sn20 welding ring according to claim 5, characterized in that: The press in S3 presses down and then holds the pressure for 20 seconds.

7. The method for forming a gold-tin alloy Au80Sn20 welding ring according to claim 6, characterized in that: The pneumatic press in S1 has three plates and four columns, and the pressure of the pneumatic press is selected to be 4 tons or more.

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