Double-sided mixed electroplating method for lead frame

Abstract

The invention discloses a double-sided mixed electroplating method for a lead frame, which comprises the steps of etching, first-time film feeding, exposure and development, silver electroplating, second-time film feeding, exposure and development, nickel-palladium-gold electroplating and the like. By arranging the frame and arranging the hanging holes and the plate body positioning holes on the two sides of the frame respectively, single electroplating of a traditional single lead frame base band is upgraded to full-page hanging hole multiple electroplating design, and the problem of large positioning deviation can be solved by adopting the independent frame and the positioning pins, so that the problem that films cannot be applied twice in the prior art is solved; therefore, a qualitative span from one-time single electroplating to multiple-time mixed electroplating can be realized, so that the production requirements of various different front and back mixed electroplating can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of lead frames, and more particularly to a double-sided mixed electroplating method for a lead frame. Background Art

[0002] Leadframes, as the chip carrier for integrated circuits, are key structural components that utilize bonding materials to achieve electrical connections between the chip's internal circuit terminals and external leads, forming the electrical circuit. They serve as a bridge connecting to external wiring and are required in most semiconductor integrated circuits. They are a crucial foundational material in the electronics and information industry. However, existing leadframe plating products typically only allow for single-sided full NIPDAU or AG plating, or double-sided plating of the same material, with no ability to achieve mixed plating of different materials. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and provide a double-sided mixed electroplating method for a lead frame. The method adopts a new lead frame electroplating layout design, and sets a separate frame + positioning pin to solve the problem of large positioning deviation, and solves the technical difficulties of two film layers, exposure and development. It can realize mixed electroplating of different metals on the front and back sides of the same lead frame product.

[0004] To achieve the above object, the present invention provides a lead frame double-sided hybrid electroplating method, comprising the following steps:

[0005] Etching: Etching at least two lead frame strips and a frame around all the lead frame strips on the copper substrate through an etching process; wherein the outer edge of each lead frame strip is provided with a connection portion connected to the inner edge of the frame, and the two sides of the frame are provided with a hanging hole and a plate positioning hole;

[0006] First film loading and exposure and development: The etched substrate is placed between two first dry films, and a positioning needle is used to pass through the film body positioning holes of the first dry film and the plate body positioning holes of the substrate to position the plate and film combination. Then, the first wet film loading, first exposure and first development operations are carried out in sequence;

[0007] Silver electroplating: After the first development process, the substrate is hung on the hanger and placed in the corresponding electroplating tank. The electroplating area on the first surface of each lead frame base strip is first electroplated with copper and then electroplated with silver.

[0008] Second film application and exposure and development: The silver-plated substrate is placed between two sheets of the second dry film, and a positioning needle is used to pass through the film body positioning holes of the second dry film and the plate body positioning holes of the substrate to position the plate and film. Then, the second wet film application, second exposure and second development operations are carried out in sequence;

[0009] Electroplating of nickel, palladium and gold: The hanging holes of the substrate after the second development treatment are hung on the hanger and placed in the corresponding electroplating tank. Nickel, palladium and gold are electroplated in sequence on the electroplating area of ​​the second surface of each lead frame base tape, thus completing the entire front and back mixed electroplating process.

[0010] Preferably, the etching step further includes a pre-etching pretreatment.

[0011] Preferably, the first wet film application specifically comprises the following steps:

[0012] The substrate is preliminarily treated with mixed alkaline washing, acid washing and water washing in sequence, and then covered with film using film solution. After the film is applied, it is washed with water and baked again.

[0013] Preferably, the film solution mainly includes water, electronic grade propylene glycol 107-98-2 monomethyl ether, dye and ethyl acrylate.

[0014] Preferably, the first exposure and development specifically include the following steps:

[0015] The substrate is exposed using an exposure machine and then developed. After the exposure is completed, the substrate undergoes a chemical reaction between the lactic acid solution and the film in the developing tank, exposing the first surface of each lead frame base tape where copper plating is required. The substrate is then washed and cured.

[0016] Preferably, the silver electroplating specifically comprises the following steps:

[0017] The substrate is pickled and washed in turn to treat its surface, then electroplated with copper, then electroplated with silver and washed with water. After the silver plating is completed, the film on the surface of the substrate is removed with lactic acid solution, and finally the substrate is cleaned and baked.

[0018] Preferably, the second wet film application specifically includes the following steps:

[0019] The substrate is preliminarily treated with mixed alkaline washing, acid washing and water washing in sequence, and then covered with film using film solution. After the film is applied, it is washed with water and baked again.

[0020] Preferably, the film solution mainly includes water, electronic grade propylene glycol 107-98-2 monomethyl ether, dye and ethyl acrylate.

[0021] Preferably, the second exposure and development specifically include the following steps:

[0022] The substrate is exposed using an exposure machine and then developed. After the exposure is completed, the substrate undergoes a chemical reaction between lactic acid solution and film in the developing tank, exposing the second surface of each lead frame base tape where copper plating is required. The substrate is then washed and cured.

[0023] Preferably, the nickel-palladium-gold electroplating method specifically comprises the following steps:

[0024] The substrate is pickled and washed with water in sequence to treat its surface, then electroplated with nickel and washed with water, then electroplated with palladium and washed with water, and then electroplated with gold and washed with water. After the gold plating is completed, the film on the surface of the substrate is removed with lactic acid solution, and finally the substrate is cleaned and baked.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention can etch at least two lead frame base strips and a frame on a copper substrate through an etching process, and respectively set hanging holes and plate positioning holes on both sides of the frame, upgrading from the traditional single-time electroplating of a single lead frame base strip to the multiple electroplating design of the entire hanging hole. A separate frame + positioning pin can be used to solve the problem of large positioning deviation, thereby solving the problem that the existing technology cannot put on the film twice. In this way, a qualitative leap can be achieved from single electroplating once to mixed electroplating multiple times, thereby adapting to various production requirements of mixed electroplating on the front and back sides.

[0027] 2. The present invention etches at least two lead frame base strips on a copper substrate. Compared with the traditional single electroplating of a single lead frame base strip, it can increase the number of electroplated products and greatly improve production efficiency.

[0028] 3. The lead frame produced by the hybrid electroplating method of the present invention combines the respective advantages of NIPDAU and AG, so that the product can achieve more stable conductive performance and can adapt to more complex packaging, testing and conductive requirements.

[0029] 4. The frame of the present invention needs to be separated from the lead frame base during the subsequent processing of the lead frame. Damage caused during the positioning and electroplating of the substrate will only occur on the frame and will not affect the lead frame base, thereby improving the production quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a flow chart of a double-sided mixed electroplating method for a lead frame provided by an embodiment of the present invention;

[0032] Figure 2 is a schematic structural diagram of a substrate after etching provided by an embodiment of the present invention;

[0033] Figure 3 yes Figure 2 A magnified view of the area at center A; Figure 4 It is a structural schematic diagram of the plate-membrane combination positioning provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] like Figure 1 As shown, an embodiment of the present invention provides a lead frame double-sided hybrid electroplating method, comprising the following steps:

[0036] (1) Pre-etching treatment: Degreasing and other pre-treatment of the copper substrate;

[0037] (2) Etching: etching at least two lead frame base strips and a frame on the copper substrate by an etching process;

[0038] like Figure 2 and Figure 3 As shown, a frame 2 is positioned around all horizontally arranged lead frame strips 1. The left and right edges of each lead frame strip 1 are connected to the inner edge of the frame 2 via connectors 5. A gap is provided between each lead frame strip 1. Both sides of the frame 2 are provided with hanging holes 3 for attaching to a hanger and plate positioning holes 4 for aligning the positioning holes of the dry film. The etching of the frame and the steps of etching the positioning and hanging holes are specifically designed for the second electroplating step.

[0039] (3) First film loading and exposure and development: The etched substrate is placed between two first dry films, and a positioning needle is used to pass through the film body positioning hole of the first dry film and the plate body positioning hole of the substrate to position the plate film combination, and then the first wet film loading, first exposure and first development operations are carried out in sequence;

[0040] like Figure 4 As shown, the substrate can be placed between two dry films 10 , and the plate positioning holes 4 on the frame 2 can be aligned and positioned with the film positioning holes on the dry films 10 by the positioning pins 11 .

[0041] In this embodiment, the first wet film application specifically includes the following steps:

[0042] The substrate is preliminarily treated with mixed alkaline washing, acid washing and water washing in sequence, and then covered with film using film solution. After the film is applied, it is washed with water and baked again.

[0043] Preferably, the film solution may include water, electronic grade propylene glycol 107-98-2 monomethyl ether, dye and ethyl acrylate.

[0044] In this embodiment, the first exposure and development specifically include the following steps:

[0045] Use a professional exposure machine to expose the substrate, and then develop it after the exposure is completed. After the substrate undergoes a chemical reaction between lactic acid solution and film in the developing tank, the first surface of each lead frame base tape is exposed to the area that needs to be exposed copper electroplating, and then it is washed and cured (dried and cured).

[0046] (4) Silver electroplating: The substrate after the first development process is hung on a hanger and placed in a corresponding electroplating tank. The electroplating area of ​​the first surface of each lead frame base strip is first electroplated with copper and then electroplated with silver;

[0047] In this embodiment, the silver electroplating specifically includes the following steps:

[0048] The substrate is pickled and washed in turn to treat its surface, then electroplated with copper, then electroplated with silver and washed with water. After the silver plating is completed, the film on the surface of the substrate is removed with lactic acid solution, and finally the substrate is cleaned and baked.

[0049] Before silver plating, pre-plating copper will make the silver layer and substrate bond more closely.

[0050] (5) Second film application and exposure and development: The substrate obtained by electroplating silver is placed between two second dry films, and a positioning needle is used to pass through the film body positioning hole of the second dry film and the plate body positioning hole of the substrate to position the plate film combination, and then the second wet film application, second exposure and second development operations are carried out in sequence;

[0051] In this embodiment, the second wet film application specifically includes the following steps:

[0052] The substrate is initially treated with mixed alkaline washing, acid washing and water washing in sequence, and then covered with film using film solution. After the film is applied, it is washed and baked again;

[0053] The film solution can mainly include water, electronic grade propylene glycol 107-98-2 monomethyl ether, dye and ethyl acrylate.

[0054] In this embodiment, the second exposure and development specifically includes the following steps:

[0055] Use a professional exposure machine to expose the substrate, and then develop it after the exposure is completed. After the substrate undergoes a chemical reaction between lactic acid solution and film in the developing tank, the second surface of each lead frame base tape is exposed to the area that needs to be exposed copper electroplating, and then it is washed and cured (dried and cured).

[0056] (6) Electroplating of nickel, palladium and gold: The hanging holes of the substrate after the second development treatment are hung on the hanger and placed in the corresponding electroplating tank. Nickel, palladium and gold are electroplated in sequence on the electroplating area of ​​the second surface of each lead frame base tape, thereby completing the entire front and back mixed electroplating process.

[0057] In this embodiment, the nickel-palladium-gold electroplating specifically includes the following steps:

[0058] The substrate is pickled and washed with water in sequence to treat its surface, then electroplated with nickel and washed with water, then electroplated with palladium and washed with water, and then electroplated with gold and washed with water. After the gold plating is completed, the film on the surface of the substrate is removed with lactic acid solution, and finally the substrate is cleaned and baked.

[0059] In summary, the present invention adopts a new lead frame electroplating layout design, and sets a separate frame + positioning pin to solve the problem of large positioning deviation, and solves the technical difficulties of two film, exposure and development. It can realize mixed electroplating of different metals on the front and back sides of the same lead frame product, and meet the electroplating and wire bonding conductivity requirements of special products.

[0060] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A double-sided mixed electroplating method for a lead frame, characterized in that: The following steps are involved: Etching: Etching at least two lead frame strips and a frame around all the lead frame strips on the copper substrate through an etching process; wherein the outer edge of each lead frame strip is provided with a connection portion connected to the inner edge of the frame, and the two sides of the frame are provided with a hanging hole and a plate positioning hole; First film loading and exposure and development: The etched substrate is placed between two first dry films, and a positioning needle is used to pass through the film body positioning holes of the first dry film and the plate body positioning holes of the substrate to position the plate and film combination. Then, the first wet film loading, first exposure and first development operations are carried out in sequence; Silver electroplating: After the first development process, the substrate is hung on the hanger and placed in the corresponding electroplating tank. The electroplating area on the first surface of each lead frame base strip is first electroplated with copper and then electroplated with silver. Second film application and exposure and development: The silver-plated substrate is placed between two sheets of the second dry film, and a positioning needle is used to pass through the film body positioning holes of the second dry film and the plate body positioning holes of the substrate to position the plate and film. Then, the second wet film application, second exposure and second development operations are carried out in sequence; Electroplating of nickel, palladium and gold: The hanging holes of the substrate after the second development treatment are hung on the hanger and placed in the corresponding electroplating tank. Nickel, palladium and gold are electroplated in sequence on the electroplating area of ​​the second surface of each lead frame base tape, thus completing the entire front and back mixed electroplating process.

2. A lead frame double-sided mixed electroplating method according to claim 1, characterized in that: Before the etching step, a pre-etching pretreatment is also included.

3. The double-sided mixed electroplating method for a lead frame according to claim 1, characterized in that: The first wet film application specifically comprises the following steps: The substrate is preliminarily treated with mixed alkaline washing, acid washing and water washing in sequence, and then covered with film using film solution. After the film is applied, it is washed with water and baked again.

4. A lead frame double-sided mixed electroplating method according to claim 3, characterized in that: The film solution mainly includes water, electronic grade propylene glycol 107-98-2 monomethyl ether, dye and ethyl acrylate.

5. The double-sided mixed electroplating method for a lead frame according to claim 1, characterized in that: The first exposure and development specifically include the following steps: The substrate is exposed using an exposure machine and then developed. After the exposure is completed, the substrate undergoes a chemical reaction between the lactic acid solution and the film in the developing tank, exposing the first surface of each lead frame base tape where copper plating is required. The substrate is then washed and cured.

6. The double-sided mixed electroplating method for a lead frame according to claim 1, characterized in that: The silver electroplating specifically comprises the following steps: The substrate is pickled and washed in turn to treat its surface, then electroplated with copper, then electroplated with silver and washed with water. After the silver plating is completed, the film on the surface of the substrate is removed with lactic acid solution, and finally the substrate is cleaned and baked.

7. The double-sided mixed electroplating method for a lead frame according to claim 1, characterized in that: The second wet film application specifically comprises the following steps: The substrate is preliminarily treated with mixed alkaline washing, acid washing and water washing in sequence, and then covered with film using film solution. After the film is applied, it is washed with water and baked again.

8. The double-sided mixed electroplating method for a lead frame according to claim 7, characterized in that: The film solution mainly includes water, electronic grade propylene glycol 107-98-2 monomethyl ether, dye and ethyl acrylate.

9. The double-sided mixed electroplating method for a lead frame according to claim 1, characterized in that: The second exposure and development specifically include the following steps: The substrate is exposed using an exposure machine and then developed. After the exposure is completed, the substrate undergoes a chemical reaction between lactic acid solution and film in the developing tank, exposing the second surface of each lead frame base tape where copper plating is required. The substrate is then washed and cured.

10. The double-sided mixed electroplating method for a lead frame according to claim 1, characterized in that: The nickel-palladium-gold electroplating specifically comprises the following steps: The substrate is pickled and washed with water in sequence to treat its surface, then electroplated with nickel and washed with water, then electroplated with palladium and washed with water, and then electroplated with gold and washed with water. After the gold plating is completed, the film on the surface of the substrate is removed with lactic acid solution, and finally the substrate is cleaned and baked.

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