Lead frame identification code and silver plating process thereof

Abstract

This invention discloses an identification code for leadframes and its silver plating process, belonging to the field of leadframe surface treatment technology. The identification code includes a silver plating layer; silver is selectively plated at the edges of the leadframe, utilizing the color difference between silver and copper to form the identification code, which can be better recognized by machines. During the semiconductor leadframe fabrication process, selective silver plating forms the identification code, and a database is established based on different process flows and material batches. The identification code contains information such as the work order number and the row / column coordinates of the leadframe on the entire copper strip. The work order number is associated with the part number, batch, production time, and leadframe model of the copper alloy raw material. This allows for accurate location and traceability of the entire production process from raw materials to the chip, including production process information and quality information. This facilitates information sharing between leadframe manufacturers and chip packaging companies, improves production efficiency, increases chip yield, allows for chip information traceability, and enables timely adjustments or improvements to the process.

Description

Technical Field

[0001] This invention belongs to the field of frame surface treatment technology, specifically relating to an identification code for a lead frame and its silver plating process. Background Technology

[0002] As a chip carrier for integrated circuits, the lead frame is a key structural component that uses bonding materials (gold wire, aluminum wire, copper wire) to achieve electrical connection between the internal circuit leads of the chip and the external leads, forming an electrical circuit. It acts as a bridge connecting to external wires. Most semiconductor integrated circuits require the use of lead frames, which are an important basic material in the electronics and information industry.

[0003] During the formation and testing of integrated circuit materials, chips need to be marked for testing. Under high-frequency operation, testing and marking alone cannot meet production needs, and manual marking cannot meet current production needs. Summary of the Invention

[0004] The purpose of this invention is to provide an identification code for lead frames and its silver plating process, so as to solve the problem that individual testing and marking cannot meet production requirements under high-frequency operation.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] An identification code for a lead frame includes a silver plating layer; the identification code is formed by selectively plating silver on the edge of the lead frame, and a photosensitive dry film is used to mask it, exposing the silver-plated portion; the identification code includes the following information: work order number and row / column coordinate data of the frame on the entire copper strip, the work order number being associated with the part number, batch, production time of the copper alloy raw material, and the model of the frame.

[0007] Furthermore, the shape of the identification code is one of the following: circular, linear, or dot matrix.

[0008] A silver plating process for identification codes on lead frames involves chemical degreasing, water washing, acid pickling activation, water washing, drying, applying photosensitive dry film, exposure, development, water washing, followed by silver plating using a silver plating solution, and finally removing the photosensitive dry film from the non-silver plating areas.

[0009] Furthermore, the silver plating solution includes silver nitrate, surfactant, pH adjuster, 5,5-dimethylhydantoin and brightener;

[0010] The brightening agent is prepared by the following steps:

[0011] 5-Carboxybenzotriazole and benzene were mixed, and thionyl chloride was added under ice-water bath conditions. The temperature was controlled not to exceed 30°C, and the reaction was carried out for 30 min. The temperature was then raised to 60°C and the reaction was continued for 2 h. The mixture was cooled to room temperature, and the solvent and thionyl chloride were removed by vacuum distillation to obtain the acyl chloride monomer.

[0012] 5-hydroxy-2,2'-bipyridine and pyridine were mixed, and then an acyl chloride monomer was added and stirred for 30 min. The mixture was then heated to reflux for 3 h, cooled, and neutralized with water and sodium bicarbonate. The solvent and water were removed by vacuum distillation, and then ethanol was added and stirred under reflux. The mixture was filtered, and the filtrate was rotary evaporated to obtain a brightener.

[0013] Furthermore, the ratio of 5-carboxybenzotriazole, thionyl chloride, and benzene is 3g:5mL:20mL; the ratio of 5-hydroxy-2,2'-bipyridine, acyl chloride monomer, and pyridine is 2g:1.2g:30mL.

[0014] Furthermore, the surfactant is one of nonylphenol polyoxyethylene ether (NP-10), linear fatty alcohol polyoxyethylene ether (AE05-80), and polyethylene glycol (PEG-200). This enhances the dispersion of each component in the plating bath, thereby improving the bath's dispersion capability and allowing silver to be uniformly distributed and deposited on the cathode substrate surface, resulting in a fine and uniform electrodeposited coating.

[0015] Furthermore, the concentrations of each raw material in the silver plating solution are as follows: silver nitrate 30-40 g / L, surfactant 0.2-0.3 g / L, 5,5-dimethylhydantoin 50-60 g / L, brightener 1.5-1.8 g / L, pH adjuster to maintain the pH value of the system at 8-10; the remainder is water.

[0016] Furthermore, the current density for the electroplating of silver is 0.5-0.7 A / dm². 2 The temperature of the electroplating solution is 40-60℃.

[0017] The beneficial effects of this invention are:

[0018] This invention selectively silver-plats the edges of the lead frame, utilizing the color difference between silver and copper to form an identification code. The resulting plating layer is silvery-white, exhibiting good resistance to discoloration and providing a color contrast with the lead frame for better machine identification. During the semiconductor frame fabrication process, a database can be established based on different process flows and material batches. The selective silver plating at the lead frame edges creates an identification code. This code contains information such as the work order number and the row / column coordinates of the frame across the copper strip. The work order number is associated with the copper alloy raw material's part number, batch, production time, and the frame's model. This allows for accurate tracking of the entire production process from raw materials to the chip, including manufacturing process information and quality information. This facilitates information sharing between lead frame manufacturers and chip packaging companies, improving production efficiency, chip yield, chip information traceability, and timely process adjustments or improvements.

[0019] In order to improve the silver plating effect of the cyanide-free silver plating solution in the silver plating process of this invention, the composition of the plating solution is adjusted to improve the plating effect. The silver plating solution of this invention does not contain sulfur, thus avoiding the inclusion of sulfur in the plating layer and improving the anti-discoloration ability of the plating layer.

[0020] The brightener in this invention contains benzotriazole and pyridine structures, providing a conjugated system of π electrons, a highly electronegative N atom, and a carbonyl structure. This gives the brightener multiple adsorption centers, enabling it to provide active electrons for chemical adsorption onto the metal surface. Combined with a surfactant, this allows silver in the plating solution to be uniformly deposited on the copper substrate surface, thereby improving the bonding strength between the silver plating layer and the copper substrate and enhancing the performance of the cyanide-free silver plating solution. Attached Figure Description

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of the sample prepared in Example 2 of the present invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment provides a brightening agent, which is prepared through the following steps:

[0026] 5-Carboxybenzotriazole and benzene were mixed, and thionyl chloride was added under ice-water bath conditions. The temperature was controlled not to exceed 30°C, and the reaction was carried out for 30 min. The temperature was then raised to 60°C, and the reaction was continued for 2 h. The mixture was cooled to room temperature, and the solvent and thionyl chloride were removed by vacuum distillation to obtain the acyl chloride monomer. The ratio of 5-carboxybenzotriazole, thionyl chloride, and benzene was 3 g: 5 mL: 20 mL.

[0027] 5-Hydroxy-2,2'-bipyridine and pyridine were mixed, and then an acyl chloride monomer was added and stirred for 30 min. The mixture was then refluxed for 3 h, cooled, and neutralized with water and sodium bicarbonate. The solvent and water were removed by vacuum distillation, and then ethanol was added and stirred under reflux. The mixture was filtered, and the filtrate was rotary evaporated to obtain a brightening agent. The ratio of 5-hydroxy-2,2'-bipyridine, acyl chloride monomer, and pyridine was 2 g: 1.2 g: 30 mL.

[0028] Example 2

[0029] This embodiment provides a silver plating process for identification codes on lead frames, which selectively plating silver on the edges of the lead frame to form the identification code, including the following steps:

[0030] Step 1) After removing the oil stains on the surface of the copper substrate with a water-based degreaser, rinse with water. After rinsing, acid pickle with a 50% hydrochloric acid aqueous solution for about 20 seconds. After acid pickling, rinse with water, dry, apply photosensitive dry film, expose, develop, and rinse with water.

[0031] Step 2) Electroplating silver is performed using a silver plating solution with a current density of 0.5 A / dm³. 2 The electroplating solution temperature was 60℃, the silver plating time was 10s, and finally, the non-silver-plated areas underwent photosensitive dry film removal treatment to obtain an identification code for lead frames. See the image for the identification code effect. Figure 1 As shown. The concentrations of each raw material in the silver plating solution are: silver nitrate 40 g / L, polyethylene glycol 0.3 g / L, 5,5-dimethylhydantoin 60 g / L, brightener prepared in Example 1 1.8 g / L, pH adjuster: to keep the pH of the system at 10; the balance is water.

[0032] Example 3

[0033] This embodiment provides a silver plating process for identification codes on lead frames, which selectively plating silver on the edges of the lead frame to form the identification code, including the following steps:

[0034] Step 1) After removing the oil stains on the surface of the copper substrate with a water-based degreaser, rinse with water. After rinsing, acid pickle with a 50% hydrochloric acid aqueous solution for about 20 seconds. After acid pickling, rinse with water, dry, apply photosensitive dry film, expose, develop, and rinse with water.

[0035] Step 2) Electroplating silver is performed using a silver plating solution with a current density of 0.6 A / dm³. 2 The electroplating solution temperature was 50℃, the silver plating time was 10s, and finally, the non-silver-plated areas were treated to remove the photosensitive dry film to obtain an identification code for a lead frame. The concentrations of each raw material in the silver plating solution were: silver nitrate 35g / L, polyethylene glycol 0.3g / L, 5,5-dimethylhydantoin 55g / L, brightener prepared in Example 1 1.7g / L, pH adjuster: to keep the pH of the system at 9; the balance was water.

[0036] Example 4

[0037] This embodiment provides a silver plating process for identification codes on lead frames, which selectively plating silver on the edges of the lead frame to form the identification code, including the following steps:

[0038] Step 1) After removing the oil stains on the surface of the copper substrate with a water-based degreaser, rinse with water. After rinsing, acid pickle with a 50% hydrochloric acid aqueous solution for about 20 seconds. After acid pickling, rinse with water, dry, apply photosensitive dry film, expose, develop, and rinse with water.

[0039] Step 2) Electroplating silver is performed using a silver plating solution with a current density of 0.7 A / dm³. 2 The electroplating solution temperature was 40℃, the silver plating time was 10s, and finally, the non-silver-plated areas were subjected to photosensitive dry film removal treatment to obtain an identification code for a lead frame. The concentrations of each raw material in the silver plating solution were: silver nitrate 30g / L, polyethylene glycol 0.2g / L, 5,5-dimethylhydantoin 50g / L, brightener prepared in Example 1 1.5g / L, pH adjuster: to keep the pH value of the system at 8; the balance was water.

[0040] Comparative Example 1

[0041] Compared with Example 2, the brightener in this comparative example was replaced with benzotriazole.

[0042] Comparative Example 2

[0043] In this comparative example and Example 2, the brightener was replaced with benzotriazole, and the amount of benzotriazole was adjusted to 0.2 g / L.

[0044] Performance tests were conducted on Examples 2-4 and Comparative Example 1, and the appearance of the coating was inspected visually.

[0045] Adhesion test: After silver plating, bend the plate twice at 90° and observe whether the plating layer peels off or falls off; or place the plated sample in an oven, heat it to 200°C, keep it at that temperature for 1 hour, and then quickly remove it and place it in cold water to observe whether the plating layer peels or bubbles.

[0046] Test the anti-discoloration performance of the coating: Drop 0.1 mol / L K2S solution onto the silver plating layer, remove it after 15 minutes and blow it dry, then observe the changes in the coating; or place it in the air for 6 months and observe the changes in the coating.

[0047] The results are shown in Table 1:

[0048] Table 1

[0049]

[0050] As can be seen from Table 1, the silver plating layer prepared by the silver plating process provided by the present invention has strong adhesion to the lead frame and good color-changing performance. The plating layer and the lead frame form a color difference contrast, which can be better recognized by the machine.

[0051] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A silver plating process for an identification code on a lead frame, characterized in that, The process includes the following steps: chemical degreasing, water washing, acid pickling activation, water washing, drying, applying photosensitive dry film, exposure, development, water washing, followed by silver electroplating using a silver plating solution, and finally, removal of the photosensitive dry film from the non-silver-plated areas. The concentrations of each raw material in the silver plating solution are: silver nitrate 30-40 g / L, surfactant 0.2-0.3 g / L, 5,5-dimethylhydantoin 50-60 g / L, brightener 1.5-1.8 g / L, pH adjuster to maintain the pH value of the system at 8-10; the remainder is water. The brightening agent is prepared by the following steps: 5-Carboxybenzotriazole and benzene were mixed, and thionyl chloride was added under ice-water bath conditions. The temperature was controlled not to exceed 30°C, and the reaction was carried out for 30 min. The temperature was then raised to 60°C, and the reaction was continued for 2 h. After cooling to room temperature, the solvent and thionyl chloride were removed by vacuum distillation to obtain the acyl chloride monomer. The ratio of 5-carboxybenzotriazole, thionyl chloride, and benzene was 3 g: 5 mL: 20 mL; the ratio of 5-hydroxy-2,2'-bipyridine, acyl chloride monomer, and pyridine was 2 g: 1.2 g: 30 mL. 5-hydroxy-2,2'-bipyridine and pyridine were mixed, and then an acyl chloride monomer was added and stirred for 30 min. The mixture was then heated to reflux for 3 h, cooled, and neutralized with water and sodium bicarbonate. The solvent and water were removed by vacuum distillation, and then ethanol was added and stirred under reflux. The mixture was filtered, and the filtrate was rotary evaporated to obtain a brightener.

2. The silver plating process for an identification code for a lead frame according to claim 1, characterized in that, The surfactant is one of nonylphenol polyoxyethylene ether, linear fatty alcohol polyoxyethylene ether, and polyethylene glycol.

3. The silver plating process for an identification code for a lead frame according to claim 1, characterized in that, The current density for the electroplating of silver is 0.5-0.7 A / dm³. 2 The temperature of the electroplating solution is 40-60℃.

4. An identification code for a lead frame, characterized in that, Includes a silver plating layer; selectively silver plating is performed on the edge of the lead frame using the silver plating process described in any one of claims 1-3 to form an identification code; the identification code includes the following information: work order number and row / column coordinate data of the frame on the entire copper strip, the work order number being associated with the part number, batch, production time of the copper alloy raw material, and the model of the frame.

5. The identification code for a lead frame according to claim 4, characterized in that, The shape of the identification code is one of the following: circular, linear, or dot matrix.

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