A strong, anti-sulfurized silver bonding wire and its preparation process

Abstract

The present invention belongs to the technical field of bonding silver wires, and specifically relates to a strong and anti-sulfurization bonding silver wire and its preparation process. The bonding silver wire material is mainly made of metal silver, supplemented by metal platinum, nickel, manganese, cobalt, calcium, magnesium, cerium and bismuth, and is obtained by surface passivation treatment. In order to facilitate the surface passivation treatment of the bonding wire, the bonding wire is firstly surface cleaned and impurities are removed, and then the surface of the bonding wire is evenly sprayed with a passivation liquid. The combined treatment of surface cleaning and passivation can simultaneously solve the technical problems of easy corrosion, easy sulfidation and easy oxidation of traditional bonding silver wires. The bonding silver wire formed by the preparation process of the present invention has excellent mechanical properties and bonding properties, good balling, and good anti-oxidation and anti-sulfurization properties, so as to obtain a strong and anti-sulfurization bonding silver wire, which meets the existing product pursuit.

Description

Technical Field

[0001] The invention belongs to the technical field of bonding silver wires, and in particular relates to a strong, sulfide-resistant bonding silver wire and a preparation process thereof. Background Art

[0002] Silver wire costs less than gold wire, and its electrical and thermal conductivity are the best among metal materials. Therefore, in the industry, silver wire has become a key material to replace gold bonding wire, and many scholars are conducting research in this area. Compared with copper, gold, and aluminum, silver has the following main characteristics: the best electrical and thermal conductivity, better tensile strength than gold and aluminum; higher hardness than gold, but lower than copper and aluminum; low cost, about 1 / 5 of gold wire, higher than copper and aluminum; high chemical stability, better than copper wire and aluminum wire, and close to gold wire. It can be found that compared with other bonding wires, silver wire has greater superiority in performance, so silver wire is one of the main trends in the development of bonding wires.

[0003] However, when high-purity silver bonding wire is bonded to aluminum pads, especially in a humid environment, Ag migration occurs and Ag-Al intermediate compounds are formed, which are easily dissolved at high temperatures and cracked, affecting the bonding performance and stability of use. In addition, the hardness of silver wire is not high and the strength of silver is low, so there is a risk of wire breakage under high-speed welding of the bonding machine; at the same time, silver is also very easy to react with sulfur in the air to become black silver sulfide. In the field of optoelectronics, the blackening of silver bonding wire will directly lead to a decrease in the luminous flux of optoelectronic devices, and in more serious cases, it will directly lead to device failure. If the silver bonding wire turns black before bonding, it will not be able to be welded. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a strong, anti-sulfurization bonding silver wire and a preparation process thereof.

[0005] The technical contents of the present invention are as follows:

[0006] The present invention provides a process for preparing a strong and anti-sulfurization bonding silver wire, comprising the following steps:

[0007] 1) Raw material pretreatment: The metal materials used are ultrasonically cleaned with anhydrous ethanol and vacuum dried;

[0008] 2) Material melting and casting: In a nitrogen atmosphere, metal silver, platinum, nickel, manganese and cobalt are mixed and vacuum melted at a temperature of 1800-1900°C for 15-20 minutes, then cooled to 1000-1100°C, and metal calcium, magnesium, cerium and bismuth are added, vacuum melted for 30-40 minutes and continuously cast to obtain a silver-based busbar with a diameter of 1-3 mm;

[0009] The vacuum degree of the vacuum melting is 10 -5 ~10 -3Pa;

[0010] The continuous casting speed is ≤30 mm / min, and the cooling water temperature is ≤20°C;

[0011] In terms of mass fraction, the silver-based busbar comprises 96.5-97.5% of metallic silver, 0.5-0.9% of platinum, 0.4-0.6% of nickel, 0.4-0.6% of manganese, 0.4-0.6% of cobalt, 0.1-0.3% of calcium, 0.2-0.4% of magnesium, 0.04-0.06% of cerium and 0.04-0.06% of bismuth;

[0012] The purity of each metal component is ≥99%;

[0013] 3) Rough wire drawing: The silver-based busbar is rough-drawn at 650-700°C to obtain a bonding silver wire of 0.08-0.12 mm;

[0014] 4) Surface passivation treatment: After the bonding silver wire is cooled, cleaned and dried, the surface is evenly sprayed with passivation liquid;

[0015] The cleaning is performed by using a water solvent cleaning solution including ammonia water, hydrofluoric acid and triethanolamine, and then rinsing with deionized water and vacuum drying;

[0016] The ammonia water used can adjust the acid-base environment, the hydrofluoric acid can clean the metal material well, and the triethanolamine used as the cleaning solvent has an anti-rust effect, as well as neutralizes the acidity, improves the surface treatment and brings a stabilizing effect.

[0017] The passivation solution is an aqueous solution consisting of sodium borohydride, malic acid and palladium chloride;

[0018] The concentration of the sodium borohydride is 3-5 mg / mL;

[0019] The concentration of the malic acid is 5 to 10 mg / mL;

[0020] The concentration of palladium chloride is 20-30 mg / mL;

[0021] 5) Fine wire drawing: The passivated bonding silver wire is finely drawn at 500-550° C. to make its diameter 0.04-0.06 mm;

[0022] 6) Fine wire drawing: Fine wire drawing is performed on the bonding silver wire after fine wire drawing at 400-500° C. so that its diameter is 0.01-0.03 mm;

[0023] 7) Annealing and surface passivation treatment: After fine wire drawing, the bonding silver wire is annealed at 500-550°C for 3-5h. The above passivation liquid is evenly sprayed on the surface of the bonding silver wire after annealing, and then vacuum dried to obtain the bonding silver wire product.

[0024] The present invention also provides a strong, sulfide-resistant bonding silver wire obtained by the above-mentioned preparation process.

[0025] The beneficial effects of the present invention are as follows:

[0026] The preparation process of the tough and anti-sulfurization bonding silver wire of the present invention adopts the bonding silver wire material obtained by combining surface passivation treatment with metal silver as the main material and metal platinum, nickel, manganese, cobalt, calcium, magnesium, cerium and bismuth as the auxiliary materials. In order to facilitate the surface passivation treatment of the bonding wire, the bonding wire is firstly surface cleaned and impurities are removed, and then the surface of the bonding wire is uniformly sprayed with a passivation liquid. The combined treatment of surface cleaning and passivation can simultaneously solve the technical problems of easy corrosion, easy sulfidation and easy oxidation of the traditional bonding silver wire. The passivation liquid used is an aqueous solution composed of sodium borohydride, malic acid and palladium chloride. Sodium borohydride and malic acid are used as coordination agents to form a coordination compound with palladium chloride to form a passivation film on the surface of the bonding silver wire, wherein sodium borohydride can also be used as an antioxidant, and malic acid has a complexing effect. In the prior art, many passivation liquids using chromium as the raw material are used, and chromium is toxic and affects the environment and the health of the workers; while the use of a palladium-containing passivation agent can also achieve an anti-sulfurization effect, and the effect is significant.

[0027] The bonding silver wire formed by the preparation process of the present invention has excellent mechanical properties and bonding properties, good balling properties, and good anti-oxidation and anti-sulfurization properties, thereby obtaining a strong and anti-sulfurization bonding silver wire that meets existing product requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a SEM electron microscope image of the bonding silver wire in Example 1;

[0029] Figure 2 This is a cross-sectional view of the bonding silver wire in Example 2. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below through specific implementation cases and accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art are all within the scope of the claims attached to this application.

[0031] Unless otherwise specified, all raw materials and reagents of the present invention are raw materials and reagents from the conventional market.

[0032] Example 1

[0033] Preparation of a strong, sulfide-resistant bonding silver wire

[0034] 1) Raw material pretreatment: The metal materials used are ultrasonically cleaned with anhydrous ethanol and vacuum dried;

[0035] 2) Material melting: In a nitrogen atmosphere, 97.5% silver, 0.8% platinum, 0.4% nickel, 0.4% manganese and 0.4% cobalt were mixed and vacuum melted at a vacuum degree of 10 -4 Pa, the temperature is 1850℃ and smelted for 16min, then cooled to 1000℃, and then 0.1% of metal calcium, 0.3% of magnesium, 0.06% of cerium and 0.04% of bismuth are added, and constant temperature vacuum smelting is performed for 35min and continuous casting to obtain silver-based busbars with diameters varying from 2mm;

[0036] The continuous casting speed is ≤30 mm / min, and the cooling water temperature is ≤20°C;

[0037] The purity of each metal component is ≥99%;

[0038] 3) Rough wire drawing: The silver-based busbar is rough-drawn at 680°C to obtain a 0.1 mm bonding silver wire;

[0039] 4) Surface passivation treatment: After the bonding silver wire is cooled, cleaned and dried, the surface is evenly sprayed with passivation liquid;

[0040] The cleaning is performed by using a water solvent cleaning solution including 25% ammonia water, 40% hydrofluoric acid and 15% triethanolamine, then rinsing with deionized water and vacuum drying at 100°C;

[0041] The passivation solution is an aqueous solution consisting of 4 mg / mL sodium borohydride, 7 mg / mL malic acid and 25 mg / mL palladium chloride;

[0042] 5) Fine wire drawing: The passivated bonding silver wire is finely drawn at 520°C to make its diameters 0.04, 0.05, and 0.06 mm respectively;

[0043] 6) Fine wire drawing: The bonding silver wire after fine wire drawing is finely drawn at 450°C so that its diameter is 0.01, 0.02, and 0.03 mm respectively;

[0044] 7) Annealing and surface passivation treatment: The finely drawn bonding silver wire is annealed at 530°C for 4 hours, the surface of the annealed bonding silver wire is evenly sprayed with the passivation liquid of step 4), and then vacuum dried at 100°C to obtain the bonding silver wire product.

[0045] Example 2

[0046] Preparation of a strong, sulfide-resistant bonding silver wire

[0047] 1) Raw material pretreatment: The metal materials used are ultrasonically cleaned with anhydrous ethanol and vacuum dried;

[0048] 2) Material melting: In a nitrogen atmosphere, 97.2% silver, 0.5% platinum, 0.5% nickel, 0.5% manganese and 0.6% cobalt were mixed and vacuum melted at a vacuum degree of 10 -5 Pa, the temperature is 1900℃ and smelted for 15min, then cooled to 1100℃, and then 0.3% of metal calcium, 0.2% of magnesium, 0.05% of cerium and 0.05% of bismuth are added, and constant temperature vacuum smelting is performed for 30min and continuous casting to obtain a silver-based busbar with a diameter of 1mm;

[0049] The continuous casting speed is ≤30 mm / min, and the cooling water temperature is ≤20°C;

[0050] The purity of each metal component is ≥99%;

[0051] 3) Rough wire drawing: The silver-based busbar is rough-drawn at 700°C to obtain a 0.12 mm bonding silver wire;

[0052] 4) Surface passivation treatment: After the bonding silver wire is cooled, cleaned and dried, the surface is evenly sprayed with passivation liquid;

[0053] The cleaning is performed by using a water solvent cleaning solution including 25% ammonia water, 35% hydrofluoric acid and 20% triethanolamine, then rinsing with deionized water and vacuum drying at 90°C;

[0054] The passivation solution is an aqueous solution consisting of 3 mg / mL sodium borohydride, 5 mg / mL malic acid and 20 mg / mL palladium chloride;

[0055] 5) Fine wire drawing: The passivated bonding silver wire is finely drawn at 550°C to make its diameters 0.04, 0.05, and 0.06 mm respectively;

[0056] 6) Fine wire drawing: The bonding silver wire after fine wire drawing is finely drawn at 500° C. so that its diameter is 0.01, 0.02, and 0.03 mm respectively;

[0057] 7) Annealing and surface passivation treatment: The finely drawn bonding silver wire is annealed at 500°C for 5 hours, the surface of the annealed bonding silver wire is evenly sprayed with the passivation liquid of step 4), and then vacuum dried at 90°C to obtain the bonding silver wire product.

[0058] Example 3

[0059] Preparation of a strong, sulfide-resistant bonding silver wire

[0060] 1) Raw material pretreatment: The metal materials used are ultrasonically cleaned with anhydrous ethanol and vacuum dried;

[0061] 2) Material melting: In a nitrogen atmosphere, 97.3% silver, 0.6% platinum, 0.5% nickel, 0.6% manganese and 0.5% cobalt were mixed and vacuum melted at a vacuum degree of 10 -3 Pa, the temperature is 1800℃ and smelted for 20min, then cooled to 1000℃, and then 0.2% of metal calcium, 0.2% of magnesium, 0.06% of cerium and 0.04% of bismuth are added, and constant temperature vacuum smelting is performed for 40min and continuous casting to obtain a silver-based busbar with a diameter of 3mm;

[0062] The continuous casting speed is ≤30 mm / min, and the cooling water temperature is ≤20°C;

[0063] The purity of each metal component is ≥99%;

[0064] 3) Rough wire drawing: The silver-based busbar is rough-drawn at 650°C to obtain a 0.12 mm bonding silver wire;

[0065] 4) Surface passivation treatment: After the bonding silver wire is cooled, cleaned and dried, the surface is evenly sprayed with passivation liquid;

[0066] The cleaning is performed by using a water solvent cleaning solution including 25% ammonia water, 40% hydrofluoric acid and 15% triethanolamine, then rinsing with deionized water and vacuum drying at 90°C;

[0067] The passivation solution is an aqueous solution consisting of 5 mg / mL sodium borohydride, 10 mg / mL malic acid and 30 mg / mL palladium chloride;

[0068] 5) Fine wire drawing: The passivated bonding silver wire is finely drawn at 500°C to make its diameters 0.04, 0.05, and 0.06 mm respectively;

[0069] 6) Fine wire drawing: The bonding silver wire after fine wire drawing is finely drawn at 400° C. so that its diameter is 0.01, 0.02, and 0.03 mm respectively;

[0070] 7) Annealing and surface passivation treatment: The finely drawn bonding silver wire is annealed at 550°C for 3h, the surface of the annealed bonding silver wire is evenly sprayed with the passivation liquid of step 4), and then vacuum dried at 100°C to obtain the bonding silver wire product.

[0071] Example 4

[0072] Preparation of a strong, sulfide-resistant bonding silver wire

[0073] 1) Raw material pretreatment: The metal materials used are ultrasonically cleaned with anhydrous ethanol and vacuum dried;

[0074] 2) Material melting: In a nitrogen atmosphere, 96.6% silver, 0.9% platinum, 0.6% nickel, 0.5% manganese and 0.6% cobalt were mixed and vacuum melted at a vacuum degree of 10 -3 Pa, the temperature is 1800℃ and smelted for 15min, then cooled to 1000℃, and then 0.3% of metal calcium, 0.4% of magnesium, 0.04% of cerium and 0.06% of bismuth are added, and constant temperature vacuum smelting is performed for 40min and continuous casting to obtain a silver-based busbar with a diameter of 2mm;

[0075] The continuous casting speed is ≤30 mm / min, and the cooling water temperature is ≤20°C;

[0076] The purity of each metal component is ≥99%;

[0077] 3) Rough wire drawing: The silver-based busbar is rough drawn at 680°C to obtain a 0.08 mm bonding silver wire;

[0078] 4) Surface passivation treatment: After the bonding silver wire is cooled, cleaned and dried, the surface is evenly sprayed with passivation liquid;

[0079] The cleaning is performed by using a water solvent cleaning solution including 25% ammonia water, 35% hydrofluoric acid and 45% triethanolamine, then rinsing with deionized water and vacuum drying at 100°C;

[0080] The passivation solution is an aqueous solution consisting of 5 mg / mL sodium borohydride, 8 mg / mL malic acid and 25 mg / mL palladium chloride;

[0081] 5) Fine wire drawing: The passivated bonding silver wire is finely drawn at 550°C to make its diameters 0.04, 0.05, and 0.06 mm respectively;

[0082] 6) Fine wire drawing: The bonding silver wire after fine wire drawing is finely drawn at 450°C so that its diameter is 0.01, 0.02, and 0.03 mm respectively;

[0083] 7) Annealing and surface passivation treatment: The finely drawn bonding silver wire is annealed at 500°C for 4 hours, the surface of the annealed bonding silver wire is evenly sprayed with the passivation liquid of step 4), and then vacuum dried at 90°C to obtain the bonding silver wire product.

[0084] Comparative Example 1

[0085] As a control group of Example 1, in the preparation of the bonding silver wire in Comparative Example 1, no passivation solution was used for surface treatment.

[0086] Comparative Example 2

[0087] As a control group of Example 1, in the preparation of the bonding silver wire in Comparative Example 2, the passivation solution used was only palladium chloride solution with a concentration of 20-30 mg / mL.

[0088] The bonding silver wire products prepared in the examples and comparative examples were tested as follows. The product specifications of the selected bonding silver wires are: and

[0089] 1. Mechanical properties test

[0090] The test times of tension, elongation and bonding thrust are 10 times respectively, and the average value is taken. The data are recorded as follows:

[0091] Table 1 Mechanical properties of bonding silver wire

[0092]

[0093] The standard of the pulling force is >4gf, the standard of the elongation is 10-14%, and the standard of the bonding thrust is ≥25CN.

[0094] It can be seen from Table 1 that the bonding silver wire prepared by the present invention still has excellent mechanical properties, maintaining excellent tension, elongation and bonding thrust, and for Comparative Examples 1 and 2 with different treatments, it can be seen that their mechanical properties are not greatly affected.

[0095] Depend on Figure 1 , Figure 2 It can be seen that the SEM image and the cross-sectional image of the bonding silver wire of Example 1 show that the grains inside the prepared bonding silver wire are evenly distributed, so that the bonding silver wire maintains excellent mechanical properties; and Figure 1 , Figure 2 It can be seen that the bonding silver wire forms a passivation film, which is the effect achieved on the spraying side.

[0096] 2. Spheroidization and antioxidant tests

[0097] Table 2 Balling degree and anti-oxidation performance of bonding silver wire

[0098]

[0099] The spheroidization degree is calculated by the spheroidization rate of spheroidization;

[0100] The antioxidant test is an oxidation weight gain experiment, in which 20 g of bonding copper wire is placed in an oven at 40° C. for 7 days, taken out and weighed, and the difference before and after is compared.

[0101] As can be seen from Table 2, the bonding silver wire prepared by the present invention performs well in ball-forming property and oxidation resistance, but the bonding silver wires of Comparative Example 1 and Comparative Example 2 are slightly inferior in oxidation resistance. It can be seen that the passivation solution has a significant effect on the oxidation resistance of the bonding silver wire of the present invention.

[0102] 3. LED photoelectric test before and after vulcanization

[0103] The prepared Bonding silver wire is used to encapsulate LED lamp beads. The experimental conditions for sulfurization are: sulfur concentration lg / L, ambient temperature 85℃, test time 4h, observe the changes in the luminous flux θ(lm) and color temperature Tc(K) before and after the LED sulfurization, and the test current is 150mA. If the average luminous flux maintenance rate is ≥80% after the 4h sulfurization test, the sulfurization test is considered to have passed.

[0104] Table 3 LED photoelectric test before and after bonding silver wire sulfurization

[0105]

[0106] From the results in Table 3, it can be seen that the luminous flux maintenance rate and the color temperature before and after sulfurization of the bonding silver wires treated by Examples 1 to 4 are superior to those of Comparative Examples 1 and 2. It can be seen that the passivation treatment of the bonding silver wires of the present invention has an obvious anti-sulfurization effect.

Claims

1. A process for preparing strong, anti-sulfurized silver bonding wire, characterized in that: The steps include: 1) Raw material pretreatment: The metal materials used are ultrasonically cleaned with anhydrous ethanol and vacuum dried; 2) Material melting and casting: In a nitrogen atmosphere, metal silver, platinum, nickel, manganese and cobalt are mixed and vacuum melted at a temperature of 1800-1900°C for 15-20 minutes, then cooled to 1000-1100°C, and metal calcium, magnesium, cerium and bismuth are added, vacuum melted for 30-40 minutes and continuously cast to obtain a silver-based busbar with a diameter of 1-3 mm; In the silver-based busbar, by mass fraction, metallic silver accounts for 96.5-97.5%, platinum accounts for 0.5-0.9%, nickel accounts for 0.4-0.6%, manganese accounts for 0.4-0.6%, cobalt accounts for 0.4-0.6%, calcium accounts for 0.1-0.3%, magnesium accounts for 0.2-0.4%, cerium accounts for 0.04-0.06% and bismuth accounts for 0.04-0.06%; 3) Rough wire drawing: The silver-based busbar is rough drawn at 650-700°C to obtain bonding silver wires of 0.08-0.12 mm; 4) Surface passivation treatment: After the bonding silver wire is cooled, cleaned and dried, the surface is evenly sprayed with passivation liquid; The passivation solution is an aqueous solution consisting of sodium borohydride, malic acid and palladium chloride; The concentration of the sodium borohydride is 3-5 mg / mL; The concentration of the malic acid is 5 to 10 mg / mL; The concentration of palladium chloride is 20-30 mg / mL; 5) Fine wire drawing; 6) Fine wire drawing; 7) Annealing and surface passivation treatment: After fine wire drawing, the bonding silver wire is annealed at 500-550°C for 3-5 hours. The above passivation liquid is evenly sprayed on the surface of the bonding silver wire after annealing, and then vacuum dried to obtain the bonding silver wire product.

2. The process for preparing the strong and anti-sulfurization bonding silver wire according to claim 1, characterized in that: Step 2) The vacuum degree of the vacuum melting is 10 -5 ~10 -3 Pa.

3. According to the preparation process of the strong and anti-sulfurization bonding silver wire according to claim 1, the continuous casting speed in step 2) is ≤30mm / min and the cooling water temperature is ≤20°C.

4. According to the preparation process of the strong and anti-sulfurization bonding silver wire according to claim 1, the cleaning in step 4) is carried out by using an aqueous solvent cleaning solution including ammonia water, hydrofluoric acid and triethanolamine, and then rinsing with deionized water and vacuum drying.

5. According to the preparation process of the strong and anti-sulfurization bonding silver wire according to claim 1, the fine wire drawing in step 5) is to finely draw the passivated bonding silver wire at 500-550° C. so that its diameter is 0.04-0.06 mm.

6. According to the process for preparing strong and anti-sulfurization bonding silver wires as claimed in claim 1, the fine wire drawing in step 6) is to finely draw the subsequent bonding silver wires at 0.4-0.6 so that the diameter thereof is 0.01-0.03 mm.

7. A bonding silver wire obtained by the preparation process according to any one of claims 1 to 6.

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