Continuous polishing method for gold-based brittle ultrathin strip

Abstract

The invention provides a continuous polishing method for a gold-based brittle ultrathin strip, and provides the continuous polishing method for the gold-based brittle ultrathin strip by combining a traditional mechanical polishing method with an electrochemical polishing method and introducing a micro-tension control system aiming at the brittle strip with the thickness of 0.008-0.05 mm. According to different thermoplastic transformation temperatures of different gold-based alloys, different nanoscale abrasive particle polishing solutions are used for physical polishing at different temperatures, then an electrolyte is heated and stirred, and continuous polishing of the gold-based brittle ultrathin strip is achieved under a micro-tension control system. By means of the method, the gold-based strip with the smooth and clean surface and without oxide is obtained.

Description

Technical Field

[0001] The invention relates to the field of gold-based alloy material processing, and in particular to a continuous polishing method for a gold-based brittle ultra-thin strip. Background Art

[0002] Gold-based alloys such as gold-tin, gold-silicon, and gold-germanium have excellent creep and fatigue resistance, good electrical and thermal conductivity, high-temperature stability, and easy welding. They can meet the requirements of special use environments and are widely used in hybrid integrated circuits, semiconductor integrated circuits, filter devices, microwave devices, IGBT high-power devices, connectors, sensors, optoelectronic devices, and other special electronic components. Reliable packaging and connection, metal shell or ceramic shell hermetic packaging and other fields.

[0003] After adding tin, silicon, germanium and other elements to the gold matrix to adjust the melting point of the alloy, the alloy becomes highly brittle. After the gold-based alloy is processed into ultra-thin strips by special heat treatment, oxides are formed on the surface, which need to be polished to remove the oxides. Brittle strips, especially those processed into ultra-thin strips with a thickness of 0.05 mm or less, are prone to break during polishing and cannot meet the continuous processing requirements of the strips. Strips often break due to uneven tension during polishing, resulting in low production efficiency.

[0004] No patent has yet proposed a polishing method for brittle ultra-thin strips. Electrochemical mechanical polishing uses electrochemical polishing of the workpiece at the same time as mechanical polishing. This method is only for ordinary metal workpieces, which are usually thicker and larger in size. It is not suitable for precision polishing of brittle strips, and the polishing quality does not meet the surface requirements of chip packaging solder. Although the surface treatment process of metal base strips proposes physical and chemical rough polishing plus electron beam fine polishing for strip surface treatment, the rough polishing speed of this method is not less than 40 meters / hour, and the precision polishing of brittle strips cannot be achieved.

[0005] Gold-based brittle strips undergo thermoplastic transformation after heating. In view of the different thermoplastic transformation temperatures of different gold-based alloys, water-based thermal spray polishing is used for gold-tin alloys, and oil-based thermal spray polishing is used for gold-germanium and gold-silicon alloys to reduce the problem of strip breakage during polishing. At the same time, in view of the problem of oxide residue after physical polishing, the electrochemical polishing method is used to perform a second fine polishing on the strip, heating the electrolyte and applying stirring, and increasing the electrolysis speed to completely remove the surface oxide residue of the strip.

[0006] Based on the above, the polishing liquid is heated to improve the plasticity of the brittle strip, and the electrochemical polishing method is added after the physical polishing to achieve continuous polishing of the brittle ultra-thin strip. Summary of the invention

[0007] The invention aims to provide a continuous polishing method for a gold-based brittle ultra-thin strip material, which is used for continuous polishing of the brittle strip material and improves the polishing cleanliness.

[0008] A continuous polishing method for a gold-based brittle ultra-thin strip material adopts a physical polishing device combined with an electrochemical polishing device to perform a continuous polishing process combining physical mechanical thermal polishing and electrochemical polishing on the strip material to be polished, thereby obtaining a polished strip material.

[0009] In some preferred embodiments, the physical polishing device and the electrochemical polishing device are connected via a servo motor micro-tension control system to pull the strip to be polished so that it passes through the physical polishing device and the electrochemical polishing device in sequence.

[0010] In some preferred embodiments, the gold-based brittle strip is prepared by the following method: a gold-based alloy is melted by vacuum induction, the alloy type is one of gold-tin, gold-silicon, and gold-germanium alloys, and the gold-based alloy ingot obtained by casting is subjected to special hot rolling to finally obtain an ultra-thin strip with a thickness of 0.008-0.05 mm, that is, a strip to be polished.

[0011] In some preferred embodiments, a method for continuous polishing of a gold-based brittle ultra-thin strip comprises the following steps:

[0012] 1) Spraying the polishing liquid onto the surface of the strip for physical and mechanical polishing;

[0013] In the step 1), the polishing liquid is extracted by a circulation pump;

[0014] In the step 1), the polishing liquid is sprayed by hot spraying; the spraying temperature is 60-200° C.; preferably 60-90° C. or 120-200° C.;

[0015] 2) electrochemically polishing the strip after physical polishing in step 1) in an electrochemical polishing device in an electrolyte;

[0016] During the electrochemical polishing process of step 2), magnetic stirring is applied.

[0017] In some preferred embodiments, a servo motor micro-tension control system is used to stabilize the strip tension so that the strip tension is controlled at 1-2 / N m.

[0018] In some preferred embodiments, the strip to be polished comprises a gold-based alloy strip; preferably a gold-based brittle ultra-thin strip;

[0019] The brittle hardness of the strip to be polished is 80-140 HV;

[0020] The thickness of the strip to be polished is 0.008-0.05 mm.

[0021] In some preferred embodiments, the strip to be polished is selected from any one or a combination of at least two of the following groups: a gold-tin alloy strip, a gold-germanium alloy strip, and a gold-silicon alloy strip.

[0022] In some preferred embodiments, the polishing liquid in step 1) comprises a water-based polishing liquid and / or a silicone oil-based polishing liquid;

[0023] The water-based polishing liquid is prepared with deionized water, the abrasive particles are amorphous silicon dioxide suspension, the particle size is 0.02-0.05 μm, and the pH is 9.5;

[0024] The silicone oil-based polishing liquid is prepared using polydimethylsiloxane, and the abrasive particles are diamond particles with a particle size of 0.02-0.05 μm.

[0025] In some preferred embodiments, the step 1) uses a water-based polishing liquid, and the polishing liquid is heated by a heating device, and the heating temperature ranges from 60 to 90° C.;

[0026] In the step 1), an oil-based polishing liquid is used, and the polishing liquid is heated by a heating device, and the heating temperature ranges from 120 to 200°C.

[0027] In some preferred embodiments, the step 1) sets the polishing wheel speed to 30-50 Hz, the polishing wheel downward pressure to -1 to -2 mm, the polishing speed to 0.3-0.5 m / min, and during polishing, the polishing liquid carries the precious metal polishing product and flows into the precious metal precipitation tank below.

[0028] In some preferred embodiments, the electrolyte in step 2) is prepared with deionized water, and the components and concentrations thereof are 80 mL / L HCl, 80 g / L thiourea, and 60 mL / L glycerol.

[0029] In some preferred embodiments, the current density of the electrochemical polishing in step 2) is 7 mA / cm 2 -610mA / cm 2 .

[0030] In some preferred embodiments, the step 2) uses an electrolyte for electrochemical polishing, and the electrolyte is heated by a heating device, and the heating temperature ranges from 60 to 90° C.;

[0031] Preferably, during the electrochemical polishing process in step 2), magnetic stirring is applied at a stirring speed of 200-500 r / min.

[0032] The beneficial effects of the present invention are at least:

[0033] The present invention proposes to use a method combining physical mechanical polishing and electrochemical polishing to polish the strip. For the gold-based brittle ultra-thin strip with a thickness of 0.008-0.05 mm, a servo motor micro-tension control system is used to accurately control the tension of the brittle strip. According to the thermoplastic transition temperature of the material, different physical polishing liquids are selected, and the hot spray mechanical polishing is performed by heating to different temperatures. The abrasive particles are selected with a particle size of nanometers to improve the mirror polishing effect. At the same time, the precious metal particles are precipitated and filtered in the sedimentation tank below to achieve efficient recovery of precious metals. The electrolytic polishing liquid is also heated to a suitable temperature and stirred to increase the electrolytic polishing speed. This method can meet the continuous polishing requirements of brittle ultra-thin strips, and the polishing effect meets the cleanliness requirements of precious metal solder for packaging, thereby improving the polishing efficiency and polishing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the polishing device. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with some embodiments, but the present disclosure is not limited thereto.

[0036] The present invention is described in more detail by comparative examples and examples, but the present invention is not limited to the following examples.

[0037] Comparative Example 1

[0038] Use gold tin 20 strip with a thickness of 0.008mm. Pass the strip through the guide wheels of the physical mechanical polishing device and the electrochemical polishing device in turn, and finally fix it on the reel of the servo motor micro-tension control system, and the tension is set to 1 / N m. Select a water-based polishing liquid, which is composed of ordinary alumina suspension with a particle size of 0.02-0.05μm. The polishing liquid is not heated, and the supernatant in the sedimentation tank is extracted using a spray device and sprayed evenly onto the surface of the polished strip. Set the polishing wheel speed to 30-50Hz, the polishing wheel pressure to -1mm, and the polishing speed to 0.3-0.5m / min. During polishing, the polishing liquid carries the precious metal polishing products into the precious metal sedimentation tank below. Use deionized water to prepare the electrolyte, and the components and concentrations are HCL80mL / L, thiourea 80g / L, and glycerol 60mL / L. The strip after physical polishing is immersed in the electrolytic polishing liquid through the guide wheel. The fixed anode roller is the positive electrode and the fixed plate below is the negative electrode. The electrolyte is preheated to 60-90℃ and magnetic stirring is applied at the same time. The stirring speed is 200r / min and the current density is 200mA / cm 2 The equipment is started and automatic polishing is performed, and the strip breaks after polishing a certain distance.

[0039] Comparative Example 2

[0040] Use AuGe12 strip with a thickness of 0.05mm. Pass the strip through the guide wheels of the physical mechanical polishing device and the electrochemical polishing device in turn, and finally fix it on the reel of the servo motor micro-tension control system, and the tension is set to 2 / N m. Select silicone oil-based polishing liquid, and the abrasive particles are diamond particles with a particle size of 0.02-0.05μm. The polishing liquid is not heated, and the supernatant in the sedimentation tank is extracted using a spray device and evenly sprayed onto the surface of the polished strip. Set the polishing wheel speed to 40Hz, the polishing wheel pressure to -2mm, and the polishing speed to 0.4m / min. During polishing, the polishing liquid carries the precious metal polishing products and flows into the precious metal sedimentation tank below. Use deionized water to prepare the electrolyte, and the components and concentrations are HCL80mL / L, thiourea 80g / L, and glycerol 60mL / L. The strip after physical polishing is immersed in the electrolytic polishing liquid through the guide wheel. The fixed anode roller is the positive electrode and the fixed plate below is the negative electrode. The electrolyte is preheated to 80°C and magnetic stirring is applied at the same time. The stirring speed is 200r / min and the current density is 500mA / cm 2 The equipment was started and automatic polishing was performed. After polishing, the mirror effect of the strip was not obvious and there was some black dirt residue.

[0041] Comparative Example 3

[0042] AuSi3.2 strip with a thickness of 0.03mm was used. The strip was passed through the guide wheels of the physical mechanical polishing device and the electrochemical polishing device in turn, and finally fixed on the reel of the servo motor micro-tension control system, and the tension was set to 2 / N m. Silicone oil-based polishing liquid was selected, and the abrasive particles were diamond particles with a particle size of 0.02-0.05μm. The polishing liquid was heated to 180℃, and the supernatant in the sedimentation tank was extracted using a spray device and sprayed evenly onto the surface of the polished strip. The polishing wheel speed was set to 40Hz, the polishing wheel pressure was -1.5mm, and the polishing speed was 0.3m / min. During polishing, the polishing liquid entrained the precious metal polishing products and flowed into the precious metal sedimentation tank below. Deionized water was used to prepare the electrolyte, and the components and concentrations were HCL80mL / L, thiourea 80g / L, and glycerol 60mL / L. The strip after physical polishing is immersed in the electrolytic polishing liquid through the guide wheel. The fixed anode roller is the positive electrode and the fixed plate below is the negative electrode. The electrolyte is preheated to 70°C and magnetic stirring is applied at the same time. The stirring speed is 200r / min and the current density is 200mA / cm 2 The equipment was started and automatic polishing was performed. After polishing, the surface of the strip was obviously scratched.

[0043] Example 1

[0044] Polishing of gold-based brittle ultra-thin strips is carried out in the following steps:

[0045] Use gold-tin 20 strip with a thickness of 0.008mm. Pass the strip through the guide wheels of the physical mechanical polishing device and the electrochemical polishing device in turn, and finally fix it on the reel of the servo motor micro-tension control system, and the tension is set to 1 / N m. The hardness of the gold-tin strip is relatively low, about 80HV, so the gold-tin polishing chooses a water-based polishing liquid, which is composed of amorphous silica suspension, with a particle size of 0.02-0.05μm and a pH of 9.5. The weakly alkaline polishing liquid can chemically corrode the surface of the strip during the polishing process, and can achieve a better polishing effect. At the same time, it plays an air-isolating role under the spraying of the polishing liquid, which can prevent the oxidation of the strip after polishing. Heat the polishing liquid to 80℃, use a spray device to extract the supernatant from the sedimentation tank and spray it evenly onto the surface of the polished strip. Set the polishing wheel speed to 30-50Hz, the polishing wheel pressure to -1mm, and the polishing speed to 0.3-0.5m / min. During polishing, the polishing liquid carries the precious metal polishing products into the precious metal sedimentation tank below. Deionized water was used to prepare the electrolyte, and the components and concentrations were 80 mL / L HCL, 80 g / L thiourea, and 60 mL / L glycerol. The strip after physical polishing was immersed in the electrolytic polishing solution through the guide wheel, with the fixed anode roller as the positive electrode and the fixed plate below as the negative electrode. The electrolyte was preheated to 60-90°C, and magnetic stirring was applied at the same time. The stirring speed was 200 r / min and the current density was 200 mA / cm 2 Start the equipment and perform automatic polishing. After polishing, the strip has a mirror polishing effect with no scratches on the surface. Compared with ordinary paraffin polishing, there is no paraffin residue on the surface.

[0046] Example 2

[0047] Polishing of gold-based brittle ultra-thin strips is carried out in the following steps:

[0048] AuGe12 strip with a thickness of 0.05mm was used. The strip was passed through the guide wheels of the physical mechanical polishing device and the electrochemical polishing device in turn, and finally fixed on the reel of the servo motor micro-tension control system, and the tension was set to 2 / N m. The hardness of the gold germanium strip is slightly higher, about 100HV, so the gold germanium polishing selects silicone oil-based polishing liquid heated to a higher temperature, and the abrasive particles are diamond particles with a particle size of 0.02-0.05μm. At the same time, under the action of the polishing liquid spray, it plays an air isolation role, which can prevent the strip from oxidizing after polishing. The polishing liquid was heated to 120℃, and the supernatant liquid in the sedimentation tank was extracted by the spray device and sprayed evenly onto the surface of the polished strip. The polishing wheel speed was set to 40Hz, the polishing wheel pressure was -2mm, and the polishing speed was 0.4m / min. During polishing, the polishing liquid entrained the precious metal polishing products and flowed into the precious metal sedimentation tank below. Deionized water was used to prepare the electrolyte, and the components and concentrations were HCL80mL / L, thiourea 80g / L, and glycerol 60mL / L. The strip after physical polishing is immersed in the electrolytic polishing liquid through the guide wheel. The fixed anode roller is the positive electrode and the fixed plate below is the negative electrode. The electrolyte is preheated to 80°C and magnetic stirring is applied at the same time. The stirring speed is 200r / min and the current density is 500mA / cm 2 Start the equipment and perform automatic polishing. After polishing, the strip has a mirror polishing effect with no scratches on the surface. Compared with ordinary paraffin polishing, there is no paraffin residue on the surface.

[0049] Example 3

[0050] Polishing of gold-based brittle ultra-thin strips is carried out in the following steps:

[0051] AuSi3.2 strip with a thickness of 0.03mm was used. The strip was passed through the guide wheels of the physical mechanical polishing device and the electrochemical polishing device in turn, and finally fixed on the reel of the servo motor micro-tension control system, and the tension was set to 2 / N m. The gold silicon strip has the highest hardness, about 130HV. The silicone oil-based polishing liquid was also selected to be heated to a higher temperature. The abrasive particles were diamond particles with a particle size of 0.02-0.05μm. At the same time, the polishing liquid sprayed to isolate the air, which can prevent the strip from oxidizing after polishing. The polishing liquid was heated to 180℃, and the supernatant in the sedimentation tank was extracted by the spray device and sprayed evenly onto the surface of the polished strip. The polishing wheel speed was set to 40Hz, the polishing wheel pressure was -1.5mm, and the polishing speed was 0.3m / min. During polishing, the polishing liquid carried the precious metal polishing products into the precious metal sedimentation tank below. Deionized water was used to prepare the electrolyte, and the components and concentrations were HCL80mL / L, thiourea 80g / L, and glycerol 60mL / L. The strip after physical polishing is immersed in the electrolytic polishing liquid through the guide wheel. The fixed anode roller is the positive electrode and the fixed plate below is the negative electrode. The electrolyte is preheated to 70°C and magnetic stirring is applied at the same time. The stirring speed is 200r / min and the current density is 600mA / cm 2Start the equipment and perform automatic polishing. After polishing, the strip has a mirror polishing effect with no scratches on the surface. Compared with ordinary paraffin polishing, there is no paraffin residue on the surface.

[0052] The strip was polished using the comparative example and the embodiment, and the surface smoothness and mirror effect of the strip were tested. The results are shown in Table 1.

[0053] Table 1

[0054]

[0055]

[0056] It can be seen from the table that the gold-based ultra-thin strip obtained by the preparation method of the present application has a high surface finish and a mirror polishing effect. By comparison, the surface finish of the silica suspension is higher than that of the ordinary polishing liquid, and the heating of the polishing liquid can improve the polishing stability of the ultra-thin strip. The appropriate current density improves the secondary fine polishing effect, so an ultra-thin gold-based strip with a smooth surface and no damage can be obtained.

[0057] In summary, the present application provides a method for continuous polishing of gold-based ultra-thin strips. The present application adopts a combination of a physical polishing device and an electrochemical polishing device to continuously polish gold-based brittle ultra-thin strips, avoiding the problem of difficult cleaning and easy breakage of strips caused by ordinary paraffin polishing. This method not only avoids the problem of strip breakage, but also improves the smoothness of the strip surface, which is more conducive to subsequent cleaning. In addition, the continuous long strip is more conducive to improving the processing efficiency of subsequent slitting or stamping, which is conducive to industrial production.

Claims

1. A continuous polishing method for a gold-based brittle ultra-thin strip, characterized in that: A physical polishing device and an electrochemical polishing device are combined to perform a continuous polishing process combining physical mechanical thermal polishing and electrochemical polishing on the strip to be polished to obtain a polished strip; The physical polishing device and the electrochemical polishing device are connected via a servo motor micro-tension control system to pull the strip to be polished so that it passes through the physical polishing device and the electrochemical polishing device in sequence; The steps include: 1) Spraying the polishing liquid onto the surface of the strip for physical and mechanical polishing; In the step 1), the polishing liquid is extracted by a circulation pump; In the step 1), the polishing liquid is sprayed by hot spraying; the spraying temperature is 60-200° C.; preferably 60-90° C. or 120-200° C.; 2) electrochemically polishing the strip after physical polishing in step 1) in an electrochemical polishing device in an electrolyte; During the electrochemical polishing process of step 2), magnetic stirring is applied.

2. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1, characterized in that: Use servo motor micro-tension control system to stabilize the strip tension and control the strip tension at 1-2 / Nm.

3. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1, characterized in that: The strip to be polished comprises a gold-based alloy strip; preferably a gold-based brittle ultra-thin strip; The brittle hardness of the strip to be polished is 80-140 HV; The thickness of the strip to be polished is 0.008-0.05 mm.

4. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1, characterized in that: The strip to be polished is selected from any one or a combination of at least two of the following groups: a gold-tin alloy strip, a gold-germanium alloy strip, and a gold-silicon alloy strip.

5. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1, characterized in that: The polishing liquid in step 1) comprises a water-based polishing liquid and / or a silicone oil-based polishing liquid; The water-based polishing liquid is prepared with deionized water, the abrasive particles are amorphous silicon dioxide suspension, the particle size is 0.02-0.05 μm, and the pH is 9.5; The silicone oil-based polishing liquid is prepared using polydimethylsiloxane, and the abrasive particles are diamond particles with a particle size of 0.02-0.05 μm.

6. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1 or 5, characterized in that: In step 1), a water-based polishing liquid is used, and the polishing liquid is heated by a heating device, and the heating temperature range is 60-90° C.; or In the step 1), an oil-based polishing liquid is used, and the polishing liquid is heated by a heating device, and the heating temperature ranges from 120 to 200°C.

7. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1, characterized in that: In the step 1), the polishing wheel speed is set to 30-50 Hz, the polishing wheel downward pressure is -1 to -2 mm, and the polishing speed is 0.3-0.5 m / min. During polishing, the polishing liquid carries the precious metal polishing product and flows into the precious metal precipitation tank below.

8. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1, characterized in that: The electrolyte in step 2) is prepared with deionized water, and the components and concentrations thereof are 80 mL / L HCl, 80 g / L thiourea, and 60 mL / L glycerol.

9. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1 or 8, characterized in that: The current density of the electrochemical polishing in step 2) is 7 mA / cm 2 -610mA / cm 2 .

10. A continuous polishing method for a gold-based brittle ultra-thin strip as claimed in claim 1, characterized in that: In the step 2), electrochemical polishing is performed using an electrolyte, and the electrolyte is heated by a heating device, and the heating temperature range is 60-90° C.; Preferably, during the electrochemical polishing process in step 2), magnetic stirring is applied at a stirring speed of 200-500 r / min.

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