A method for improving the stability of semiconductor leadframe plating

Abstract

This application relates to the field of semiconductor leadframe manufacturing technology, specifically disclosing a method for improving the stability of semiconductor leadframe plating. The method includes: S1, electrolytically degreasing the semiconductor leadframe and washing it with water; S2, immersing the semiconductor leadframe in an acid activation solution, washing it with water, then washing it with ammonium fluoride solution, and finally washing it with water; S3, electroplating the semiconductor leadframe in a copper plating solution and washing it with water; S4, allowing the semiconductor leadframe to stand for 2-3 hours under inert gas protection and at a temperature of 140-160℃; S5, immersing the semiconductor leadframe in a passivation solution, washing it with water, and drying it. The acid activation solution includes the following solutes: concentrated sulfuric acid 5-8 g / L, glacial acetic acid 1-3 g / L, and dioctadecyl dimethyl ammonium chloride 1-3 g / L. The semiconductor leadframe obtained by this method has a plating with excellent stability and thermal stability, as well as high hardness, meeting market demands.

Description

Technical Field

[0001] This application relates to the field of semiconductor leadframe manufacturing technology, and more specifically, it relates to a method for improving the stability of semiconductor leadframe plating. Background Technology

[0002] Leadframes serve as the chip carrier for integrated circuits, using bonding materials to achieve electrical connections between the internal circuit leads and external leads. They act as a bridge connecting to external wires and are an important basic material in the electronics and information industry, widely used in integrated circuits, lighting, photovoltaic power generation, and other fields.

[0003] Common semiconductor leadframes are mostly made of copper alloys, obtained through a die-stamping process. Copper alloys commonly used include copper-iron, copper-nickel-silicon, copper-chromium, and copper-nickel-tin alloys. After die-stamping, the semiconductor leadframe undergoes surface treatment. Current surface treatments generally involve degreasing, sulfuric acid activation, copper electroplating, and plating protection, which offer advantages such as increased oxidation resistance, wear resistance, and solderability. However, the plating on currently available semiconductor leadframes generally suffers from poor stability, especially after being left to stand at 300℃ for 10 minutes, resulting in a peeling rate exceeding 10% after being removed with scribe-on tape. Therefore, there is an urgent need to research a treatment method to improve the stability of semiconductor leadframe plating to meet market demands. Summary of the Invention

[0004] To improve the stability of semiconductor leadframe plating, this application provides a method for enhancing the stability of semiconductor leadframe plating, employing the following technical solution:

[0005] A method for improving the stability of semiconductor leadframe plating includes the following steps:

[0006] S1. Pretreatment: Electrolytic degreasing of the semiconductor lead frame followed by water washing;

[0007] S2. Activation: Immerse the semiconductor lead frame in the acid activation solution for 15-25 seconds, wash with water, wash with ammonium fluoride solution, and wash with water again.

[0008] S3, Copper plating: The semiconductor lead frame is immersed in a copper plating solution for electroplating, and a copper layer is electroplated on the surface of the semiconductor lead frame, followed by water washing.

[0009] S4. Annealing: Under inert gas protection and at a temperature of 140-160℃, the semiconductor lead frame is left to stand for 2-3 hours and then cooled down.

[0010] S5. Passivation: Immerse the semiconductor lead frame in passivation solution, apply a protective film to the surface, wash with water, and dry to complete the surface treatment of the semiconductor lead frame.

[0011] The acid activation solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: concentrated sulfuric acid 5-8 g / L, glacial acetic acid 1-3 g / L, and dioctadecyl dimethyl ammonium chloride 1-3 g / L.

[0012] By adopting the above technical solution, the semiconductor lead frame is first electrolytically degreased to remove surface grease. Then, the semiconductor lead frame is activated in an acid activation solution to increase its surface roughness. Following this, copper is electroplated to form a copper layer. Since hydrogen may permeate into the semiconductor lead frame or copper layer during the copper plating process, annealing at 140-160℃ effectively reduces the impact of hydrogen during electroplating and improves the surface treatment quality of the semiconductor lead frame.

[0013] Adding sulfuric acid and acetic acid to the acid activation solution, and their synergistic effect, effectively increases surface roughness. Furthermore, the addition of dioctadecyldimethylammonium chloride not only provides acid resistance and stability within the solution, but also reduces the surface tension of the acid activation solution, lowering the interfacial tension between the solution and the semiconductor lead frame. This promotes the interaction of sulfuric acid and acetic acid with the semiconductor lead frame, enhancing the activation effect and improving the stability of the copper layer.

[0014] Furthermore, since dioctadecyl dimethyl ammonium chloride is added to the acid activation solution, when the semiconductor lead frame is immersed in the acid activation solution, some dioctadecyl dimethyl ammonium chloride may remain on the surface of the semiconductor lead frame. At this time, washing with ammonium fluoride solution can continuously provide hydroxide ions, effectively removing the residual dioctadecyl dimethyl ammonium chloride on the surface of the semiconductor lead frame and reducing the impact of the residual dioctadecyl dimethyl ammonium chloride on electroplating.

[0015] The method for improving the stability of semiconductor lead frame plating in this application involves adding dioctadecyl dimethyl ammonium chloride to an acid activation solution and washing with ammonium fluoride solution. This effectively increases the stability of the semiconductor lead frame plating, and after standing at 300°C for 10 minutes, there is no peeling or detachment after being peeled off with scribe tape.

[0016] Optionally, the copper electroplating solution uses deionized water as a solvent, and by mass concentration, the copper electroplating solution includes the following solutes: copper sulfate pentahydrate 40-50 g / L, conductive salt 70-90 g / L, organic salt complex 10-20 g / L, sodium citrate 5-15 g / L, and anionic surfactant 0.1-0.3 g / L;

[0017] The organic salt complex was obtained by sequentially substituting isonicotinic acid ethyl ester and 4,4'-dibromomethylbiphenyl through a substitution reaction and an ester hydrolysis reaction.

[0018] Copper ions in deionized water mainly exist as [Cu(H₂O)₄]. 2+ It exists in the form of a substance with a relatively large heat of hydration and a relatively stable bond. At this point, adding an organic salt complex and sodium citrate to the raw materials of the copper electroplating solution will affect the [Cu(H₂O)₄]₂. 2+ The water molecules in the solution are replaced to form a complex, reducing the bonding stability and improving the stability of the copper electroplating solution. Simultaneously, in the organic salt complex, the hydrogen atom bonded to the nitrogen atom in ethyl isonicotinate is replaced, causing a substitution reaction between ethyl isonicotinate and 4,4'-dibromomethylbiphenyl. Then, the ester group in ethyl isonicotinate undergoes ester hydrolysis to obtain the organic salt complex. Because 4,4'-dibromomethylbiphenyl has a symmetrical structure and contains two bromine atoms, it can substitute with two ethyl isonicotinates, resulting in an organic salt complex containing two carboxyl groups, two benzene rings, and two pyridine sulfates. Combined with sodium citrate, the synergistic effect between the two increases the electrodeposition rate, improves the stability of the copper layer, reduces the copper layer crystal grain size, increases the copper layer density, and achieves a semiconductor leadframe hardness >220 HV, exhibiting the advantage of high hardness.

[0019] Optionally, the organic salt complex is prepared using the following method:

[0020] SA, under constant stirring, isonicotinic acid ethyl ester and 4,4'-dibromomethylbiphenyl are added to acetonitrile and mixed. The mixture is heated to 70-80℃ and kept at that temperature for 22-26 hours. After cooling, the mixture is filtered to obtain solid A.

[0021] SB. Under constant stirring, solid A is added to sulfuric acid solution and mixed. The mixture is heated to 70-80℃ and kept at that temperature for 7-9 hours. After cooling, it is filtered, washed, and dried to obtain an organic salt complex.

[0022] Optionally, the weight ratio of ethyl isonicotinate, 4,4'-dibromomethylbiphenyl, and sulfuric acid solution is 10:(9-13):(90-110), and the mass concentration of sulfuric acid solution is 10-20%.

[0023] By adopting the above technical solution, the raw materials react in steps, first with a substitution reaction and then with an ester hydrolysis reaction, making the preparation of organic salt complexes simple, stable and easy to control.

[0024] Furthermore, the weight ratio of ethyl isonicotinic acid to acetonitrile is 1:(9-11). Preferably, the weight ratio of ethyl isonicotinic acid to acetonitrile is 1:10.

[0025] Optionally, the conductive salt is one or more of sodium sulfate, potassium sulfate, sodium nitrate, and potassium nitrate. Sodium sulfate, potassium sulfate, sodium nitrate, and potassium nitrate are all inorganic salts that can increase the ion migration rate in the copper electrolyte, increase the conductivity of the copper plating solution, reduce the copper ion concentration difference between the positive and negative electrodes, enhance the copper layer coverage, and improve the quality of the copper layer.

[0026] Optionally, the anionic surfactant is sodium dodecyl sulfate. Sodium dodecyl sulfate not only increases the stability of the copper plating solution, but also reduces the surface tension of the copper plating solution, thereby improving the coverage and quality of the copper layer.

[0027] Optionally, in step S3, the electroplating current density is 5-10 A / dm2, the time is 5-15 s, and the temperature is 45-55℃.

[0028] By adopting the above technical solution, the current density, plating time, and plating temperature in the copper electroplating process are optimized, facilitating the plating of the copper layer. Preferably, the current density for copper plating is 8 A / dm³. 2 The time is 10 seconds and the temperature is 50℃.

[0029] Optionally, the mass concentration of the ammonium fluoride solution is 3-8%.

[0030] By adopting the above technical solution, the mass concentration of ammonium fluoride solution is optimized, which facilitates the removal of residual dioctadecyl dimethyl ammonium chloride from the surface of the semiconductor lead frame and reduces the impact of residual dioctadecyl dimethyl ammonium chloride on the stability of the coating.

[0031] Furthermore, the electrolytic degreasing process specifically involves immersing the semiconductor lead frame in an electrolytic degreasing solution for electrolytic degreasing. The current density for electrolytic degreasing is 20-30 A / dm³. 2 The time is 15-25 seconds, and the temperature is 45-55℃. Furthermore, the electrolytic degreasing solution uses deionized water as a solvent, and by mass concentration, the electrolytic degreasing solution includes the following solutes: degreasing agent 90-110 g / L.

[0032] By adopting the above technical solution, the degreasing agent can remove grease from the surface of the semiconductor lead frame. In addition, hydrogen gas is continuously released during the electrolytic degreasing process. The hydrogen gas can not only remove the grease from the surface of the semiconductor lead frame, but also enhance the degreasing effect of the degreasing agent. Through the synergy between electrolysis and the degreasing agent, the grease on the surface of the semiconductor lead frame is completely removed.

[0033] Optionally, the passivation solution uses deionized water as a solvent, and by mass concentration, the passivation solution includes the following solutes: 2-ethylbenzimidazole 5-8 g / L and glacial acetic acid 1-3 g / L.

[0034] By adopting the above technical solution, 2-ethylbenzimidazole can form a protective film on the surface of the copper layer. The protective film has the advantages of hydrophobicity, heat resistance and corrosion resistance, which facilitates the storage of semiconductor lead frames. Moreover, the protective film is also solderable and does not affect the subsequent soldering process.

[0035] Furthermore, in step S5, the soaking treatment lasts for 20-40 minutes. Preferably, the soaking treatment lasts for 30 minutes.

[0036] Optionally, the semiconductor lead frame is one of a copper-iron alloy lead frame, a copper-nickel-silicon alloy lead frame, a copper-chromium alloy lead frame, or a copper-nickel-tin alloy lead frame.

[0037] By adopting the above technical solutions, it is convenient to select semiconductor lead frames. Moreover, when semiconductor lead frames are selected within the above range, the processing method of this application can enhance the stability of the coating and achieve the expected technical effect.

[0038] In summary, this application has at least the following beneficial effects:

[0039] 1. This application provides a method for improving the stability of semiconductor leadframe plating. By adding dioctadecyldimethylammonium chloride to the acid activation solution, the interfacial tension between the acid activation solution and the semiconductor leadframe is reduced, thus promoting the acid activation effect. Furthermore, washing with ammonium fluoride solution reduces the impact of residual dioctadecyldimethylammonium chloride on electroplating. Through the synergistic effect of these steps, the plating stability is effectively increased. After standing at 300°C for 10 minutes, and then peeling off with scribe-on tape, there is no peeling or detachment, meeting market demands.

[0040] 2. An organic salt complex containing two carboxyl groups, two benzene rings, and two pyridine sulfates is added to the copper electroplating solution. Sodium citrate is also added, and through the synergistic effect between the two, the hardness of the semiconductor lead frame is increased to >220HV, significantly increasing the hardness of the plating layer. Detailed Implementation

[0041] 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.

[0042] Preparation Example

[0043] Preparation Example 1

[0044] An organic salt complex is prepared by the following method:

[0045] SA, at a rotation speed of 400 r / min, 10 g of ethyl isonicotinate and 11.2 g of 4,4'-dibromomethylbiphenyl were added to 100 g of acetonitrile and stirred for 30 min. Then the mixture was heated to 75 °C and kept at that temperature for 24 h. After that, the mixture was cooled to 25 °C and filtered to obtain solid A.

[0046] SB. Solid A was added to 100g of sulfuric acid solution at a rotation speed of 400r / min and stirred for 30min. The solution was then heated to 75℃ and held at that temperature for 8h. Afterward, the temperature was lowered to 25℃ and filtered. The solution was then washed three times with 30g of water each time. Finally, it was dried at 75℃ to constant weight to obtain an organic salt complex.

[0047] The sulfuric acid solution has a mass concentration of 15%.

[0048] Preparation Example 2

[0049] An organic salt complex, which differs from Preparation Example 1 in that the amount of 4,4'-dibromomethylbiphenyl added is different, and the amount of 4,4'-dibromomethylbiphenyl added is 9g.

[0050] Preparation Example 3

[0051] An organic salt complex, which differs from Preparation Example 1 in that the amount of 4,4'-dibromomethylbiphenyl added is different, and the amount of 4,4'-dibromomethylbiphenyl added is 13g.

[0052] Example

[0053] Example 1

[0054] A method for improving the stability of semiconductor leadframe plating includes the following steps:

[0055] S1. Pretreatment: Electrolytic degreasing of the semiconductor lead frame, followed by water washing.

[0056] The semiconductor lead frame is a copper-nickel-silicon alloy lead frame. Electrolytic degreasing specifically involves immersing the semiconductor lead frame in an electrolytic degreasing solution for electrolytic degreasing, with a current density of 25 A / dm³. 2 The time is 20 seconds and the temperature is 50℃.

[0057] The electrolytic degreasing solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: degreasing agent 100 g / L. The degreasing agent is selected from Bolaiful Chemical's copper cleaning agent PC-106.

[0058] S2. Activation: Immerse the semiconductor lead frame in the acid activation solution for 20 seconds, then wash with water, followed by washing with a 5% ammonium fluoride solution, and then washing with water.

[0059] The acid activation solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: concentrated sulfuric acid 7 g / L, glacial acetic acid 2 g / L, and dioctadecyl dimethyl ammonium chloride 2 g / L.

[0060] S3. Copper plating: The semiconductor lead frame is immersed in a copper plating solution for electroplating, and the current density of the electroplating is 8A / dm³. 2 The process takes 10 seconds and takes 50°C. At this time, a copper layer is electroplated on the surface of the semiconductor lead frame, and then the surface is washed with water.

[0061] The copper electroplating solution uses deionized water as a solvent and, by mass concentration, comprises the following solutes: copper sulfate pentahydrate 45 g / L, conductive salt 80 g / L, organic salt complex 15 g / L, sodium citrate 10 g / L, and anionic surfactant 0.2 g / L. The conductive salt is potassium sulfate; the anionic surfactant is sodium dodecyl sulfate; and the organic salt complex was prepared using Preparation Example 1.

[0062] S4. Annealing: Under nitrogen protection and at a temperature of 150°C, the semiconductor lead frame is left to stand for 2.5 hours, and then cooled to 25°C.

[0063] S5. Passivation: Immerse the semiconductor lead frame in the passivation solution for 30 minutes, apply a protective film to the surface, wash with water, and then dry at 70°C to constant weight to complete the surface treatment of the semiconductor lead frame.

[0064] The passivation solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: 2-ethylbenzimidazole 7 g / L and glacial acetic acid 2 g / L.

[0065] Example 2

[0066] A method for improving the stability of semiconductor leadframe plating includes the following steps:

[0067] S1. Pretreatment: Electrolytic degreasing of the semiconductor lead frame, followed by water washing.

[0068] The semiconductor lead frame is a copper-nickel-silicon alloy lead frame. Electrolytic degreasing specifically involves immersing the semiconductor lead frame in an electrolytic degreasing solution for electrolytic degreasing, with a current density of 20 A / dm³. 2 The time is 25 seconds and the temperature is 55℃.

[0069] The electrolytic degreasing solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: degreasing agent 90 g / L. The degreasing agent is selected from Bolaiful Chemical's copper cleaning agent PC-106.

[0070] S2. Activation: Immerse the semiconductor lead frame in the acid activation solution for 25 seconds, then wash with water, followed by washing with an 8% ammonium fluoride solution, and then washing with water.

[0071] The acid activation solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: concentrated sulfuric acid 5 g / L, glacial acetic acid 3 g / L, and dioctadecyl dimethyl ammonium chloride 1 g / L.

[0072] S3. Copper plating: The semiconductor lead frame is immersed in a copper plating solution for electroplating, and the current density of the electroplating is 5A / dm³. 2 The process takes 15 seconds and takes 55°C. At this time, a copper layer is electroplated on the surface of the semiconductor lead frame, and then the surface is washed with water.

[0073] The copper electroplating solution uses deionized water as a solvent and, by mass concentration, comprises the following solutes: copper sulfate pentahydrate 40 g / L, conductive salt 90 g / L, organic salt complex 10 g / L, sodium citrate 15 g / L, and anionic surfactant 0.3 g / L. The conductive salt is potassium sulfate; the anionic surfactant is sodium dodecyl sulfate; and the organic salt complex was prepared using Preparation Example 1.

[0074] S4. Annealing: Under nitrogen protection and at a temperature of 140°C, the semiconductor lead frame is left to stand for 3 hours, and then cooled to 25°C.

[0075] S5. Passivation: Immerse the semiconductor lead frame in the passivation solution for 40 minutes, apply a protective film to the surface, wash with water, and then dry at 70°C to constant weight to complete the surface treatment of the semiconductor lead frame.

[0076] The passivation solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: 2-ethylbenzimidazole 5g / L and glacial acetic acid 3g / L.

[0077] Example 3

[0078] A method for improving the stability of semiconductor leadframe plating includes the following steps:

[0079] S1. Pretreatment: Electrolytic degreasing of the semiconductor lead frame, followed by water washing.

[0080] The semiconductor lead frame is a copper-nickel-silicon alloy lead frame. Electrolytic degreasing specifically involves immersing the semiconductor lead frame in an electrolytic degreasing solution for electrolytic degreasing, with a current density of 30 A / dm³. 2 The time is 15 seconds and the temperature is 45℃.

[0081] The electrolytic degreasing solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: degreasing agent 110 g / L. The degreasing agent is selected from Bolaiful Chemical's copper cleaning agent PC-106.

[0082] S2. Activation: Immerse the semiconductor lead frame in the acid activation solution for 15 seconds, then wash with water, followed by washing with a 3% ammonium fluoride solution, and then washing with water.

[0083] The acid activation solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: concentrated sulfuric acid 8 g / L, glacial acetic acid 1 g / L, and dioctadecyl dimethyl ammonium chloride 3 g / L.

[0084] S3. Copper plating: The semiconductor lead frame is immersed in a copper plating solution for electroplating, and the current density of the electroplating is 10A / dm³. 2 The process takes 5 seconds and takes 45°C. At this time, a copper layer is electroplated on the surface of the semiconductor lead frame, and then the surface is washed with water.

[0085] The copper electroplating solution uses deionized water as a solvent and, by mass concentration, comprises the following solutes: copper sulfate pentahydrate 50 g / L, conductive salt 70 g / L, organic salt complex 20 g / L, sodium citrate 5 g / L, and anionic surfactant 0.1 g / L. Specifically, the conductive salt is potassium sulfate; the anionic surfactant is sodium dodecyl sulfate; and the organic salt complex was prepared using Preparation Example 1.

[0086] S4. Annealing: Under nitrogen protection and at a temperature of 160°C, the semiconductor lead frame is left to stand for 2 hours, and then cooled to 25°C.

[0087] S5. Passivation: Immerse the semiconductor lead frame in the passivation solution for 20 minutes, apply a protective film to the surface, wash with water, and then dry at 70°C to constant weight to complete the surface treatment of the semiconductor lead frame.

[0088] The passivation solution uses deionized water as a solvent and, by mass concentration, includes the following solutes: 2-ethylbenzimidazole 8 g / L and glacial acetic acid 1 g / L.

[0089] Example 4

[0090] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that the organic salt complex in the raw materials of the copper electroplating solution is prepared using Example 2.

[0091] Example 5

[0092] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that the organic salt complex in the raw materials of the copper electroplating solution is prepared using Example 3.

[0093] Comparative Example

[0094] Comparative Example 1

[0095] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that the raw materials of the acid activation solution do not contain dioctadecyldimethylammonium chloride.

[0096] Comparative Example 2

[0097] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that the raw materials of the copper electroplating solution do not contain organic salt complexes or sodium citrate.

[0098] Comparative Example 3

[0099] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that an equal amount of organic salt complex is used to replace sodium citrate in the raw materials of the copper electroplating solution.

[0100] Comparative Example 4

[0101] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that an equal amount of sodium citrate is used to replace the organic salt complex in the raw materials of the copper electroplating solution.

[0102] Comparative Example 5

[0103] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that an equal amount of ethylenediaminetetraacetic acid is used to replace the organic salt complex in the raw materials of the copper electroplating solution.

[0104] Comparative Example 6

[0105] A method for improving the stability of semiconductor leadframe plating is different from Example 1 in that an equal amount of 3-(1-pyridyl)propanesulfonic acid is used to replace the organic salt complex in the raw materials of the copper electroplating solution.

[0106] Performance testing

[0107] The semiconductor lead frames obtained in Examples 1-5 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.

[0108] The coating stability was determined using the following method: At 25℃, a 1mm × 1mm × 1mm square grid was drawn on the sample surface using a 30-degree acute-angle hard steel scribing tool. The grid consisted of 100 squares, with the scribing lines cutting through the coating to the surface of the semiconductor lead frame. Adhesive tape was then adhered to the square grid, and a rubber roller was used to roll it over the grid to remove air bubbles. After standing for 10 seconds, the tape was peeled off using a force perpendicular to the coating. The presence of peeling was observed, and if peeling was observed, the peeling rate was calculated.

[0109] The thermal stability of the coating was determined using the following method: the sample was left to stand at 300℃ for 10 minutes, then removed and cooled to 25℃. The coating stability method was then used to observe whether there was any peeling. If peeling was observed, the peeling rate was calculated.

[0110] The hardness of the coating of the sample was tested according to GB5934-1986 "Method for testing the hardness of metal coatings on light industrial products - microhardness method".

[0111] Table 1 Test Results

[0112]

[0113] As shown in Table 1, the semiconductor leadframe obtained by the method for improving the stability of the semiconductor leadframe plating in this application exhibits no peeling or detachment at room temperature. After being left to stand at 300°C for 10 minutes and then peeled off with scribe-on tape, no peeling or detachment is observed, demonstrating excellent plating stability and thermal stability. Furthermore, the plating hardness is 221-244 HV, exhibiting the advantage of high hardness and meeting market demands.

[0114] Comparing Example 1 and Comparative Example 1, it can be seen that adding dioctadecyl dimethyl ammonium chloride to the raw materials of the acid activation solution can improve the stability of the coating.

[0115] Example 1 was compared with Comparative Examples 2-4, with Comparative Example 2 as the basis. In Comparative Example 3, an organic salt complex was added to the raw materials of the copper plating solution compared to Comparative Example 2; in Comparative Example 4, sodium citrate was added to the raw materials of the copper plating solution compared to Comparative Example 2; and in Example 1, both an organic salt complex and sodium citrate were added to the raw materials of the copper plating solution compared to Comparative Example 2. This demonstrates that the simultaneous addition of an organic salt complex and sodium citrate to the copper plating solution, and the synergistic effect between them, significantly increases the thermal stability and hardness of the coating, thereby improving the stability and quality of the coating.

[0116] Example 1 and Comparative Examples 5-6 were compared. Comparative Example 5's copper plating solution contained ethylenediaminetetraacetic acid; Comparative Example 6's copper plating solution contained 3-(1-pyridyl)propanesulfonic acid; and Example 1's copper plating solution contained an organic salt complex. This demonstrates that the organic salt complex obtained by sequentially substituting and hydrolyzing isonicotinic acid and 4,4'-dibromomethylbiphenyl can achieve a better synergistic effect with sodium citrate, thus improving coating stability, thermal stability, hardness, and overall coating quality.

[0117] 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 improving the stability of plating on a semiconductor lead frame, characterized by: It comprises the following steps: S1, pretreatment: electrolytic degreasing of the semiconductor lead frame, water washing; S2, activation: the semiconductor lead frame is put into an acid activation solution, soaked for 15-25s, water washing, ammonium fluoride solution washing, water washing; S3, copper plating: the semiconductor lead frame is put into a copper plating solution for electroplating, and a copper layer is plated on the surface of the semiconductor lead frame, water washing; S4, annealing: under the protection of inert gas and at a temperature of 140-160℃, the semiconductor lead frame is treated for 2-3h, and then cooled; S5, passivation: the semiconductor lead frame is put into a passivation solution for soaking, and a protective film is attached to the surface, water washing, drying, and the surface treatment of the semiconductor lead frame is completed. The acid activation solution uses deionized water as the solvent, and according to the mass concentration, the acid activation solution comprises the following solutes: concentrated sulfuric acid 5-8g / L, glacial acetic acid 1-3g / L, and dioctadecyldimethylammonium chloride 1-3g / L; The copper plating solution uses deionized water as the solvent, and according to the mass concentration, the copper plating solution comprises the following solutes: copper sulfate pentahydrate 40-50g / L, conductive salt 70-90g / L, organic salt complex 10-20g / L, sodium citrate 5-15g / L, and anionic surfactant 0.1-0.3g / L; The organic salt complex is prepared by the following method: SA, under constant stirring, ethyl isonicotinate and 4,4'-dibromomethyl biphenyl are mixed in acetonitrile, heated to 70-80℃, treated for 22-26h, cooled, filtered, and solid A is obtained; SB, under constant stirring, solid A is mixed in sulfuric acid solution, heated to 70-80℃, treated for 7-9h, cooled, filtered, washed, and dried to obtain the organic salt complex; The weight ratio of ethyl isonicotinate, 4,4'-dibromomethyl biphenyl, and sulfuric acid solution is 10:(9-13):(90-110), and the mass concentration of the sulfuric acid solution is 10-20%.

2. The process for improving the stability of the plating layer of a semiconductor lead frame according to claim 1, wherein: The conductive salt is one or more of sodium sulfate, potassium sulfate, sodium nitrate, and potassium nitrate.

3. The process of claim 1, wherein the process is characterized by: The anionic surfactant is sodium dodecyl sulfate.

4. The process of claim 1, wherein the process is characterized by: In step S3, the current density of electroplating is 5-10A / dm2, the time is 5-15s, and the temperature is 45-55℃.

5. The process of claim 1, wherein the process is characterized by: The mass concentration of the ammonium fluoride solution is 3-8%.

6. The process of claim 1, wherein the process is characterized by: The passivation solution uses deionized water as the solvent, and according to the mass concentration, the passivation solution comprises the following solutes: 2-ethylbenzimidazole 5-8g / L and glacial acetic acid 1-3g / L.

7. The process of claim 1, wherein the process is characterized by: The semiconductor lead frame is one of copper-iron alloy lead frame, copper-nickel-silicon alloy lead frame, copper-chromium alloy lead frame, and copper-nickel-tin alloy lead frame.

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