A process for applying an oxidation- and corrosion-resistant plating coating to the surface of a semiconductor lead frame.

Abstract

This application relates to the field of semiconductor leadframe surface treatment technology, specifically disclosing a process for treating the surface of semiconductor leadframes with an oxidation- and corrosion-resistant plating layer. The process includes: S1, electrolytic degreasing and water washing; S2, primary activation, water washing, ammonium fluoride solution washing, water washing, nickel electroplating, and water washing; S3, secondary activation, water washing, ammonium fluoride solution washing, water washing, copper electroplating, and water washing; S4, partial masking, tertiary activation, water washing, ammonium fluoride solution washing, water washing, silver electroplating, and water washing; S5, removing the masking layer and annealing; S6, passivation, water washing, and drying to constant weight. The passivation solution is mainly composed of the following raw materials in parts by weight: 1000 parts water, 5-8 parts 2-ethylbenzimidazole, 0.5-1.5 parts branched amide, and 1-3 parts glacial acetic acid. The semiconductor leadframe obtained by this treatment method has excellent oxidation and corrosion resistance, meeting market demands.

Description

Technical Field

[0001] This application relates to the field of semiconductor leadframe surface treatment technology, and more specifically, it relates to a process for applying an oxidation-resistant and corrosion-resistant plating coating to the surface of a semiconductor leadframe. Background Technology

[0002] Semiconductor lead frames are one of the three basic materials for semiconductor packaging. They not only support the packaged devices but also enable the chips to be connected to the substrate. They also provide electrical and thermal paths from the chips to the circuit boards, making them an important basic material in the electronics and information industry.

[0003] Semiconductor leadframes are typically produced by stamping copper alloys. After stamping, further surface treatment is required. Related surface treatment methods for semiconductor leadframes generally include degreasing, copper plating, silver plating, copper layer protection, and silver layer protection. Copper protection involves attaching a copper protective film to the copper layer surface using Rohm and Haas copper protectant. Silver protection involves attaching a bipolar chemical film to the silver layer surface via chemical adsorption using a solution containing SJ-2 non-porous honeycomb organic solvent, diaminoethane, and alkylbenzodiazole. While the copper protective film and bipolar chemical film can increase the oxidation and corrosion resistance of semiconductor leadframes, the neutral salt spray resistance time of the copper metal layer in semiconductor leadframes is generally only 30 hours. Further improvements in the oxidation and corrosion resistance of the copper metal layer are needed to meet higher requirements. Summary of the Invention

[0004] To improve the oxidation and corrosion resistance of the copper metal layer on the surface of semiconductor leadframes, this application provides a process for applying an oxidation and corrosion resistant plating layer to the surface of semiconductor leadframes, employing the following technical solution:

[0005] A process for applying an oxidation- and corrosion-resistant plating coating to the surface of a semiconductor leadframe includes the following steps:

[0006] S1. Electrolytically degrease the semiconductor lead frame and wash it with water;

[0007] S2. The semiconductor lead frame is immersed in an acid activation solution for initial activation, washed with water, washed with ammonium fluoride solution, washed with water, and then immersed in a nickel plating solution for electroplating to form a nickel metal layer, and then washed with water.

[0008] S3. The semiconductor lead frame is immersed in an acid activation solution for secondary activation, washed with water, washed with ammonium fluoride solution, washed with water, and then immersed in a copper electroplating solution for electroplating to form a copper metal layer, and then washed with water.

[0009] S4. The part of the semiconductor lead frame outside the silver plating area is masked, then it is immersed in acid activation solution for three activations, washed with water, washed with ammonium fluoride solution, washed with water, and then the semiconductor lead frame is immersed in silver plating solution for electroplating to form a silver metal layer, and then washed with water.

[0010] S5. Remove the masking from the surface of the semiconductor lead frame and then perform annealing;

[0011] S6. Immerse the semiconductor lead frame in the passivation solution and passivate it for 20-40 minutes at a temperature of 40-50℃. Wash it with water and dry it to constant weight to complete the surface treatment of the semiconductor lead frame.

[0012] The passivation solution is mainly made of the following raw materials in parts by weight: 1000 parts deionized water, 5-8 parts 2-ethylbenzimidazole, 0.5-1.5 parts branched amide, and 1-3 parts glacial acetic acid.

[0013] By adopting the above technical solution, the semiconductor lead frame is first activated by nickel electroplating, then activated a second time by copper electroplating, followed by partial masking and a third activation by silver electroplating. At this point, a portion of the semiconductor lead frame surface has a nickel metal layer, a copper metal layer, and a silver metal layer sequentially, with this copper metal layer designated as the inner metal layer. Another portion of the surface has a nickel metal layer and a copper metal layer sequentially, with this copper metal layer designated as the outer metal layer. In other words, the copper metal layer comprises both an inner and an outer metal layer.

[0014] Furthermore, the semiconductor lead frame is passivated by immersing it in a passivation solution. At this time, a protective film can be formed on the surface of the outer metal layer and the silver metal layer, so that the copper metal layer of the surface-treated semiconductor lead frame has a neutral salt spray resistance of ≥42h and an alternating damp heat resistance of >720h, exhibiting excellent oxidation and corrosion resistance, which meets market demand.

[0015] 2-Ethylbenzimidazole and branched amide were added simultaneously to the passivation solution. 2-Ethylbenzimidazole adsorbed onto the surfaces of the silver and outer copper metal layers to form a protective film. The branched amide, containing nine alkyl groups, four imide groups, four amino groups, and four tertiary amine groups, also formed a protective film on the surfaces of the silver and outer copper metal layers. Through the synergistic effect between 2-ethylbenzimidazole and branched amide, the bonding strength between the protective film and the silver and outer copper metal layers was increased, as was the density of the protective film, thus improving oxidation and corrosion resistance and extending service life.

[0016] Optionally, the branched amide is prepared by the following method: adding methyl 3-butenoate and a portion of ethylenediamine to anhydrous ethanol, stirring for 9-11 hours, then adding the remaining ethylenediamine, stirring for 9-11 hours, and distilling under reduced pressure to obtain the branched amide.

[0017] By employing the above technical solution, methyl 3-butenoate and a portion of ethylenediamine undergo an addition reaction at a molar ratio of 4:1 to obtain the product. Then, the remaining ethylenediamine is added, and at this point, the remaining ethylenediamine and the product undergo an amidation reaction at a molar ratio of 4:1 to obtain a mixture containing branched amides. Simultaneously, methanol is obtained as a byproduct. After vacuum distillation to remove ethanol and methanol, the branched amides are obtained. The branched amide preparation method of this application, by adding ethylenediamine in steps, facilitates the control of the reaction between ethylenediamine and methyl 3-butenoate, making the preparation of branched amides simple and stable.

[0018] Optionally, the amount of ethylenediamine added is 0.13-0.17 times the total weight of ethyl isonicotinic acid ester; the amount of the remaining ethylenediamine added is 0.55-0.65 times the total weight of ethyl isonicotinic acid ester.

[0019] By adopting the above technical solution, the ratio of raw materials methyl 3-butenoate, part of ethylenediamine, and the remainder ethylenediamine is optimized, which facilitates the preparation of branched amides.

[0020] Furthermore, the amount of anhydrous ethanol added is 40-60 times the total weight of isonicotinic acid ethyl ester.

[0021] Optionally, the copper electroplating solution is mainly made of the following raw materials in parts by weight: 1000 parts deionized water, 40-50 parts copper sulfate pentahydrate, 70-90 parts potassium sulfate, 5-15 parts sodium citrate, 10-20 parts pyridine complex, and 0.1-0.3 parts sodium dodecyl sulfate.

[0022] The silver electroplating solution is mainly made of the following raw materials in parts by weight: 1000 parts deionized water, 15-25 parts silver nitrate, 45-65 parts potassium sulfate, 2-8 parts sodium citrate, 5-15 parts pyridine complex, 0.1-0.3 parts sodium dodecyl sulfate, and 0.1-0.3 parts disodium 3,3'-dithiobis(1-propanesulfonic acid).

[0023] By adopting the above technical solution, the raw materials and raw material ratios of copper electroplating solution and silver electroplating solution are optimized, which facilitates the electroplating of copper metal layer and silver metal layer.

[0024] Optionally, the pyridine complex is prepared using the following method:

[0025] The acetonitrile was heated to 70-80℃, and 4,4'-dibromomethylbiphenyl and ethyl isonicotinate were added. The mixture was stirred for 22-26 hours, cooled to 20-30℃, and filtered to obtain the intermediate product.

[0026] The sulfuric acid solution was heated to 70-80℃, the intermediate product was added, and the mixture was stirred for 7-9 hours. The mixture was then cooled to 20-30℃, filtered, washed with water, and dried to constant weight to obtain the pyridine complex.

[0027] Optionally, the amount of 4,4'-dibromomethylbiphenyl added is 0.9-1.3 times the total weight of isonicotinic acid ethyl ester; the amount of sulfuric acid solution added is 9-11 times the total weight of isonicotinic acid ethyl ester, and the mass concentration of the sulfuric acid solution is 10-20%.

[0028] By adopting the above technical solution, 4,4'-dibromomethylbiphenyl and ethyl isonicotinate undergo a substitution reaction during stirring to obtain an intermediate product. The intermediate product is then treated with sulfuric acid solution, and the intermediate product undergoes ester hydrolysis to obtain a pyridine complex, which facilitates the preparation of pyridine salt complexes.

[0029] The copper electroplating solution of this application simultaneously incorporates a pyridine complex and sodium citrate. Sodium citrate can form a coordination complex with metal ions. The pyridine complex, containing two pyridine sulfates, two benzene rings, and two carboxyl groups, can also form a coordination complex with metal ions. Through the synergistic effect between the pyridine complex and sodium citrate, the grain size of the copper metal layer is reduced, the density is increased, and the hardness is improved. Simultaneously, the number of active sites on the surface of the copper metal layer is increased. Furthermore, combined with the passivation treatment of the passivation solution, the oxidation and corrosion resistance of the copper metal layer is improved.

[0030] The silver plating solution of this application also contains pyridine complex and sodium citrate, which can reduce the crystal grain size of the silver metal layer and increase its density. Combined with the passivation treatment of the passivation solution, it can also enhance the oxidation and corrosion resistance of the silver metal layer.

[0031] Furthermore, the amount of acetonitrile added is 5-15 times the total weight of isonicotinic acid ethyl ester.

[0032] Optionally, the acid activation solution is mainly made from the following raw materials in parts by weight: 1000 parts deionized water, 1-3 parts dioctadecyl dimethyl ammonium chloride, 1-3 parts glacial acetic acid, and 5-8 parts concentrated sulfuric acid.

[0033] By adopting the above technical solution, adding bis(octadecyl)dimethylammonium chloride to the acid activation solution can reduce the surface tension of the acid activation solution, increase the interfacial tension between the acid activation solution and the substrate, promote the use effect of the acid activation solution, enhance the interfacial bonding strength and stability between the semiconductor lead frame, nickel metal layer, copper metal layer and silver metal layer, and extend the service life.

[0034] Optionally, the nickel plating solution is mainly made of the following raw materials in parts by weight: 1000 parts deionized water, 10-20 parts nickel sulfate hexahydrate, 30-50 parts potassium sulfate, 2-8 parts sodium citrate, 10-20 parts ethylenediaminetetraacetic acid, and 0.1-0.3 parts sodium dodecyl sulfate.

[0035] By adopting the above technical solution, the raw materials and raw material ratio of the nickel electroplating solution are optimized, which facilitates the electroplating of nickel metal layers.

[0036] Optionally, in step S2, the electroplating current density is 3-8 A / dm². 2 The electroplating time is 10-20 seconds, and the temperature is 45-55℃; in step S3, the electroplating current density is 5-10 A / dm³. 2 The time is 5-15 seconds, and the temperature is 45-55℃.

[0037] In step S4, the electroplating current density is 1-5 A / dm². 2 The time is 20-30 seconds and the temperature is 45-55℃.

[0038] By adopting the above technical solution, the current density, time, and temperature of the nickel metal layer, as well as the copper metal layer and the silver metal layer, are optimized. This facilitates the control of the deposition rate and thickness of the nickel, copper, and silver metal layers, and also facilitates the surface treatment of the semiconductor lead frame. Preferably, in step S2, the electroplating current density is 5 A / dm³. 2 The time is 15 seconds and the temperature is 45°C; in step S3, the electroplating current density is 8 A / dm³. 2 The time is 10 seconds and the temperature is 45°C; in step S4, the electroplating current density is 2 A / dm³. 2 The time is 25 seconds and the temperature is 45℃.

[0039] Optionally, in step S5, the annealing temperature is 140-160℃ and the time is 2-3h.

[0040] By adopting the above technical solution, annealing at a temperature of 140-160℃ can reduce the influence of hydrogen on the nickel, copper, and silver metal layers during electroplating, enhance the hardness and interfacial bonding strength of the nickel, copper, and silver metal layers, and improve the stability and quality of the nickel, copper, and silver metal layers.

[0041] In summary, this application has at least the following beneficial effects:

[0042] 1. The oxidation and corrosion resistant coating process for the semiconductor lead frame surface of this application, by adding branched amide to the passivation solution, wherein the branched amide contains nine alkyl groups, four imide groups, four amino groups, and four tertiary amine groups, and is combined with 2-ethylbenzimidazole, enables it to withstand neutral salt spray for ≥42h and alternating damp heat for >720h, exhibiting excellent oxidation and corrosion resistance, and meeting market demands.

[0043] 2. The copper electroplating solution of this application contains a pyridine complex containing two pyridine sulfates, two benzene rings, and two carboxyl groups. Combined with sodium citrate, it reduces the grain size, increases density and hardness, and increases the surface active sites of the copper metal layer. Further combined with the passivation solution, it improves the resistance to neutral salt spray and alternating damp heat, so that the surface-treated semiconductor lead frame exhibits better performance and quality. Detailed Implementation

[0044] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0045] Preparation Example

[0046] Preparation Example 1

[0047] An acid-activated solution is prepared by the following method: 2g of glacial acetic acid is added to 1000g of deionized water and stirred for 10min. Then, 7g of concentrated sulfuric acid and 2g of dioctadecyldimethylammonium chloride are added and stirred for 10min to obtain the acid-activated solution.

[0048] Preparation Example 2

[0049] A nickel plating solution is prepared by the following method: 40g of potassium sulfate is added to 1000g of deionized water and stirred for 10min. Then, 15g of nickel sulfate hexahydrate, 5g of sodium citrate, 15g of ethylenediaminetetraacetic acid, and 0.2g of sodium dodecyl sulfate are added and stirred for 10min to obtain the nickel plating solution.

[0050] Preparation Example 3

[0051] A copper electroplating solution is prepared by the following method: 80g of potassium sulfate is added to 1000g of deionized water and stirred for 10min. Then, 45g of copper sulfate pentahydrate, 10g of sodium citrate, 15g of pyridine complex, and 0.2g of sodium dodecyl sulfate are added and stirred for 10min to obtain the copper electroplating solution.

[0052] The pyridine complex was prepared using the following method:

[0053] 100g of acetonitrile was heated to 75℃, and 11.2g of 4,4'-dibromomethylbiphenyl and 10g of ethyl isonicotinate were added. The mixture was stirred for 24h, cooled to 25℃, and filtered to obtain the intermediate product.

[0054] 100g of sulfuric acid solution was heated to 75℃, the mass concentration of the sulfuric acid solution was 15%, the intermediate product was added, the mixture was stirred for 8 hours, cooled to 25℃, filtered, washed with water, and dried to constant weight to obtain the pyridine complex.

[0055] Preparation Example 4

[0056] A silver electroplating solution is prepared by the following method: 55g of potassium sulfate is added to 1000g of deionized water and stirred for 10min. Then, 20g of silver nitrate, 5g of sodium citrate, 10g of pyridine complex, 0.2g of sodium dodecyl sulfate, and 0.2g of disodium 3,3'-dithiobis(1-propanesulfonic acid) are added and stirred for 10min to obtain the silver electroplating solution.

[0057] The pyridine complex was prepared using the following method:

[0058] 100g of acetonitrile was heated to 75℃, and 11.2g of 4,4'-dibromomethylbiphenyl and 10g of ethyl isonicotinate were added. The mixture was stirred for 24h, cooled to 25℃, and filtered to obtain the intermediate product.

[0059] 100g of sulfuric acid solution was heated to 75℃, the mass concentration of the sulfuric acid solution was 15%, the intermediate product was added, the mixture was stirred for 8 hours, cooled to 25℃, filtered, washed with water, and dried to constant weight to obtain the pyridine complex.

[0060] Preparation Example 5

[0061] A passivation solution is prepared by the following method: 2g of glacial acetic acid is added to 1000g of deionized water and stirred for 10min, then 7g of 2-ethylbenzimidazole and 1g of branched amide are added.

[0062] The branched amide was prepared by the following method: 1 g of methyl 3-butenoate and 0.15 g of partial ethylenediamine were added to 50 g of anhydrous ethanol, and the mixture was stirred for 10 h. Then, 0.6 g of the remaining ethylenediamine was added, and the mixture was stirred for another 10 h. The ethanol and methanol obtained from the reaction were removed by vacuum distillation to obtain the branched amide.

[0063] Preparation Example 6

[0064] A passivation solution, which differs from the preparation example 5 in that the amount of glacial acetic acid added is 1g, the amount of 2-ethylbenzimidazole added is 5g, and the amount of branched amide added is 1.5g.

[0065] Preparation Example 7

[0066] A passivation solution, which differs from the preparation example 5 in that the amount of glacial acetic acid added is 3g, the amount of 2-ethylbenzimidazole added is 8g, and the amount of branched amide added is 0.5g.

[0067] Example

[0068] Example 1

[0069] A process for applying an oxidation- and corrosion-resistant plating coating to the surface of a semiconductor leadframe includes the following steps:

[0070] S1. Immerse the semiconductor lead frame in degreasing solution and electrolyze it for 20 seconds at a temperature of 45°C and a current density of 25A, then rinse with water.

[0071] The semiconductor lead frame is a copper-nickel-silicon alloy lead frame. The degreasing solution is mainly made from the following raw materials in parts by weight: 1000g deionized water and 100g degreasing agent. The degreasing agent is selected from Bolaiful Chemical's copper cleaning agent PC-106.

[0072] S2. The semiconductor lead frame was immersed in the acid activation solution obtained in Preparation Example 1 and activated for 20 seconds at 45°C. It was then washed with water, followed by washing with an ammonium fluoride solution (5% by mass concentration), and then washed with water again. The semiconductor lead frame was then immersed in the nickel plating solution obtained in Preparation Example 2 and electroplated for 15 seconds at 45°C and a current density of 5A, at which point a nickel metal layer was formed. It was then washed with water.

[0073] S3. The semiconductor lead frame is immersed in the acid activation solution obtained in Preparation Example 1 and subjected to a secondary activation treatment at a temperature of 45°C for 10 seconds. It is then washed with water, followed by washing with an ammonium fluoride solution (5% by mass concentration), and then washed with water again. The semiconductor lead frame is then immersed in the copper plating solution obtained in Preparation Example 3 and subjected to electroplating treatment at a temperature of 45°C and a current density of 8A for 10 seconds, at which point a copper metal layer is formed. It is then washed with water.

[0074] S4. The portion of the semiconductor lead frame outside the silver plating area is masked, and then immersed in the acid activation solution obtained in Preparation Example 1 for activation treatment at 45°C for 10 seconds. Afterwards, it is washed with water, then washed with an ammonium fluoride solution (5% by mass concentration), and then washed with water again. Next, the semiconductor lead frame is immersed in the silver plating solution obtained in Preparation Example 4 for electroplating treatment at 45°C and a current density of 2A for 25 seconds, at which point a silver metal layer is formed, and then washed with water.

[0075] S5. Remove the shielding from the surface of the semiconductor lead frame, and then anneal the semiconductor lead frame for 2.5 hours under nitrogen protection at a temperature of 150°C, and then cool it down to 25°C.

[0076] S6. Immerse the semiconductor lead frame in the passivation solution obtained in Preparation Example 5, passivate at 45°C for 30 min, then wash with water and dry to constant weight to complete the surface treatment of the semiconductor lead frame.

[0077] Example 2

[0078] A process for treating the surface of a semiconductor lead frame with an oxidation-resistant and corrosion-resistant coating is disclosed, which differs from Example 1 in that, in step S5, the passivation solution is prepared using Preparation Example 6.

[0079] Example 3

[0080] A process for treating the surface of a semiconductor lead frame with an oxidation-resistant and corrosion-resistant coating is disclosed, which differs from Example 1 in that, in step S5, the passivation solution is prepared using Preparation Example 7.

[0081] Comparative Example

[0082] Comparative Example 1

[0083] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that, in step S5, 2-ethylbenzimidazole and branched amide are not added to the raw materials of the passivation solution.

[0084] Comparative Example 2

[0085] A method for improving the stability of semiconductor leadframe plating is different from that in Example 1, in step S5, the branched amide is replaced with an equal amount of 2-ethylbenzimidazole in the raw materials of the passivation solution.

[0086] Comparative Example 3

[0087] A method for improving the stability of semiconductor leadframe plating differs from Example 1 in that, in step S5, an equal amount of branched amide is used to replace 2-ethylbenzimidazole in the raw materials of the passivation solution.

[0088] Comparative Example 4

[0089] A method for improving the stability of semiconductor leadframe plating is different from that in Example 1, in step S3, sodium citrate and pyridine complex are not added to the raw materials of the copper electroplating solution.

[0090] Comparative Example 5

[0091] A method for improving the stability of semiconductor leadframe plating is different from that in Example 1, in step S3, an equal amount of sodium citrate is used to replace the pyridine complex in the raw materials of the copper electroplating solution.

[0092] Comparative Example 6

[0093] A method for improving the stability of semiconductor leadframe plating is different from that in Example 1, in step S3, an equal amount of pyridine complex is used to replace sodium citrate in the raw materials of the copper electroplating solution.

[0094] Performance testing

[0095] The semiconductor lead frames obtained in Examples 1-3 and Comparative Examples 1-6 were used as samples, and the following performance tests were performed on the samples. The test results are shown in Table 1.

[0096] In accordance with GB / T10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test", a neutral salt spray test was conducted on the copper metal layer of the sample, and the time of corrosion occurrence was recorded.

[0097] According to QJ481-90 "Metallic Coatings Resistance to Alternating Damp Heat Test Method", the copper metal layer of the sample was subjected to alternating damp heat test, and the time of corrosion was recorded.

[0098] According to GB5934-1986 "Methods for testing the hardness of metal coatings on light industrial products - Microhardness method", the hardness of the copper metal layer of the sample was tested.

[0099] The pass rate is determined by the following method: process 100 products separately and observe whether there are any omissions in the semiconductor lead frame plating. If there are no omissions, the product is considered passable; if there are omissions, the product is considered failable. The pass rate is then calculated.

[0100] Table 1 Test Results

[0101]

[0102] As shown in Table 1, the semiconductor leadframes obtained by the oxidation- and corrosion-resistant plating process of this application exhibit excellent oxidation and corrosion resistance, with a neutral salt spray resistance of ≥42h and an alternating damp heat resistance of >720h. Furthermore, the copper metal layer has a hardness of ≥242HV, demonstrating even higher hardness. Simultaneously, the yield rate is ≥99%, showcasing the advantage of a stable processing technology and meeting market demands.

[0103] Example 1 was compared with Comparative Examples 1-3, with Comparative Example 1 as the basis. In Comparative Example 2, 2-ethylbenzimidazole was added to the raw materials of the passivation solution compared to Comparative Example 1; in Comparative Example 3, branched amide was added to the raw materials of the passivation solution compared to Comparative Example 1; and in Example 1, both 2-ethylbenzimidazole and branched amide were added to the raw materials of the passivation solution compared to Comparative Example 1. This demonstrates that the simultaneous addition of 2-ethylbenzimidazole and branched amide to the passivation solution, and the synergistic effect between them, significantly increases the resistance of the copper metal layer to neutral salt spray and alternating damp heat, thereby improving the surface treatment quality of the semiconductor lead frame.

[0104] Example 1 was compared with Comparative Examples 4-6, with Comparative Example 4 as the basis. In Comparative Example 5, sodium citrate was added to the raw materials of the copper plating solution compared to Comparative Example 4; in Comparative Example 6, pyridine complex was added to the raw materials of the copper plating solution compared to Comparative Example 4; and in Example 1, sodium citrate and pyridine complex were added to the raw materials of the copper plating solution compared to Comparative Example 4. It can be seen that the simultaneous addition of sodium citrate and pyridine complex to the copper plating solution not only increases resistance to neutral salt spray and alternating damp heat, but also increases the hardness of the copper metal layer. This is likely due to the synergistic effect of the two, reducing grain size and increasing density, thereby improving the quality of the copper metal layer, as well as increasing oxidation and corrosion resistance and extending the lifespan of the semiconductor leadframe.

[0105] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. A process for surface oxidation and corrosion resistant plating of a semiconductor lead frame, characterized by: It comprises the following steps: S1, electrolytic degreasing of the semiconductor lead frame, water washing; S2, the semiconductor lead frame is soaked in acid activation solution for primary activation, water washing, ammonium fluoride solution washing, water washing, then the semiconductor lead frame is soaked in nickel electroplating solution for electroplating, forming a nickel metal layer, water washing; S3, the semiconductor lead frame is soaked in acid activation solution for secondary activation, water washing, ammonium fluoride solution washing, water washing, then the semiconductor lead frame is soaked in copper electroplating solution for electroplating, forming a copper metal layer, water washing; S4, the semiconductor lead frame is shielded outside the silver plating area, then soaked in acid activation solution for tertiary activation, water washing, ammonium fluoride solution washing, water washing, then the semiconductor lead frame is soaked in silver electroplating solution for electroplating, forming a silver metal layer, water washing; S5, removing the shielding on the surface of the semiconductor lead frame, then annealing; S6, the semiconductor lead frame is soaked in passivation solution, passivation treatment is carried out at a temperature of 40-50℃ for 20-40min, water washing, drying to constant weight, completing the surface treatment of the semiconductor lead frame; The passivation solution is mainly made of the following raw materials by weight: deionized water 1000 parts, 2-ethyl benzimidazole 5-8 parts, branched amide 0.5-1.5 parts, glacial acetic acid 1-3 parts; The branched amide is prepared by the following method: adding 3-butenoic acid methyl ester and part of ethylenediamine in anhydrous ethanol, stirring for 9-11h, then adding the remaining ethylenediamine, stirring for 9-11h, and reducing pressure distillation to obtain the branched amide; The addition amount of part of ethylenediamine is 0.13-0.17 times the total weight of ethyl isonicotinate; the addition amount of the remaining ethylenediamine is 0.55-0.65 times the total weight of ethyl isonicotinate; The copper electroplating solution is mainly made of the following raw materials by weight: deionized water 1000 parts, copper sulfate pentahydrate 40-50 parts, potassium sulfate 70-90 parts, sodium citrate 5-15 parts, pyridine complex 10-20 parts, sodium dodecyl sulfate 0.1-0.3 parts; The silver electroplating solution is mainly made of the following raw materials by weight: deionized water 1000 parts, silver nitrate 15-25 parts, potassium sulfate 45-65 parts, sodium citrate 2-8 parts, pyridine complex 5-15 parts, sodium dodecyl sulfate 0.1-0.3 parts, 3,3'-dithiobis(1-propanesulfonic acid) disodium 0.1-0.3 parts; The pyridine complex is prepared by the following method: Acetonitrile is heated to 70-80℃, 4,4'-dibromomethyl biphenyl and ethyl isonicotinate are added, stirring for 22-26h, cooling to 20-30℃, filtering to obtain an intermediate product; Sulfuric acid solution is heated to 70-80℃, the intermediate product is added, stirring for 7-9h, cooling to 20-30℃, filtering, water washing, drying to constant weight to obtain the pyridine complex; The addition amount of 4,4'-dibromomethyl biphenyl is 0.9-1.3 times the total weight of ethyl isonicotinate; the addition amount of sulfuric acid solution is 9-11 times the total weight of ethyl isonicotinate, and the mass concentration of the sulfuric acid solution is 10-20%.

2. The process for surface oxidation and corrosion resistant plating of a semiconductor lead frame according to claim 1, wherein: The acid activation solution is mainly made of the following raw materials by weight: deionized water 1000 parts, dioctadecyl dimethyl ammonium chloride 1-3 parts, glacial acetic acid 1-3 parts, concentrated sulfuric acid 5-8 parts.

3. The process for surface oxidation and corrosion resistant plating of a semiconductor lead frame according to claim 1, wherein: The nickel electroplating solution is mainly made of the following raw materials by weight: deionized water 1000 parts, nickel sulfate hexahydrate 10-20 parts, potassium sulfate 30-50 parts, sodium citrate 2-8 parts, ethylenediaminetetraacetic acid 10-20 parts, sodium dodecyl sulfate 0.1-0.3 parts.

4. The process for surface oxidation and corrosion resistant plating of a semiconductor lead frame according to claim 1, wherein: In step S2, the current density of electroplating is 3-8 A / dm 2 , the time is 10-20 s, and the temperature is 45-55℃. In step S3, the current density of electroplating is 5-10 A / dm 2 , the time is 5-15 s, and the temperature is 45-55℃. In step S4, the current density of electroplating is 1-5 A / dm 2 for 20-30 s at 45-55 °C.

5. The process for surface oxidation and corrosion resistant plating of a semiconductor lead frame according to claim 1, wherein: In step S5, the temperature of annealing is 140-160℃, and the time is 2-3h.

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