Method for manufacturing long and short golden fingers through local gold plating

Abstract

The invention discloses a method for manufacturing long and short golden fingers through local gold plating, which comprises the following steps of: manufacturing an outer-layer circuit and a plurality of golden finger bodies on a production board through a negative film process, and enabling all the golden finger bodies to have the same length and extend outwards to be connected with a board edge copper layer; carrying out silk-screen printing of anti-gold plating ink on the production board, and windowing at the position, corresponding to local gold plating, of each golden finger body; pasting a film on the production board, and windowing at a position corresponding to local gold plating; the production board is sequentially subjected to nickel gold electroplating and thick gold electroplating treatment; removing the film and removing the gold plating resistant ink; a film is pasted on the production board, windowing is carried out on the position, corresponding to the non-local gold plating position, in the golden finger body, and then the copper layer at the extending length part in the golden finger body is removed through alkaline etching, so that the long and short golden fingers are formed. According to the method, the production process is reduced, the labor cost and the material cost are reduced, the product quality of the local gold plating plate can be improved, and the product yield is improved.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board manufacturing, and in particular to a method for manufacturing local electroplating long and short gold fingers. Background Art

[0002] With the development of science and technology, the scope of application of circuit boards in various industries is becoming more and more extensive. In the information age, higher requirements are placed on the upgrade and iteration of circuit boards, and higher requirements are placed on the signal transmission of products, which require fast transmission speed, stable signals, and low energy loss. The conductivity of gold, silver, copper, iron, and tin has huge differences in signal transmission. Among them, the metal properties of gold have the best effect in circuit transmission, which can better ensure the transmission speed of signals, reduce energy loss, reduce heat, reduce signal distortion, and other advantages.

[0003] Among them, electroplating design is widely used in circuit board design and accounts for a high proportion. The local gold plating process of circuit boards is widely used in high-precision circuit boards, high-frequency circuit boards, RFID circuit boards, analog circuit boards, antenna circuit boards and high-reliability circuit boards. Especially in high-demand electronic products, this process technology has become one of the necessary technologies for circuit board production.

[0004] The local gold plating process of the circuit board has the following advantages:

[0005] 1. Improve the reliability and stability of the circuit board: By gold plating on the local area of ​​the circuit board, the stability and durability of the circuit board in harsh environments such as high temperature, high humidity and chemical corrosion can be improved, thereby increasing the life and reliability of the circuit board.

[0006] 2. Optimize the signal transmission of the circuit board: In the high-frequency transmission system, the signal is optimized on the circuit board and the current is evenly distributed. The local metal plating protective metal layer will be arranged evenly, which can improve the attenuation and cross-interference tolerance, thereby optimizing the signal transmission of the circuit board.

[0007] 3. Improve the aesthetics of the circuit board: The local gold plating process of the circuit board can form a unique metallic luster on the local area of ​​the circuit board, making the circuit board more beautiful, thereby increasing the added value of the circuit board.

[0008] At present, there are three main local electroplating processes. The methods are relatively traditional and can only be produced by positive film + four-time dry film method. The production process is cumbersome and complicated, the cost is high, and the scrap rate is high. The details are as follows:

[0009] 1. There are no holes in the local electroplating position. The process is as follows: pre-process → copper plating → board electroplating → outer layer pattern transfer ① (make local electroplating patterns, ensure that there are no holes in the electroplating, use DuPont GPM-220 special electroplating thick gold dry film) → pattern nickel gold (only NI / AU electroplating, not copper electroplating, the surface metal thickness of the local electroplating position is controlled to be greater than 20UM, including 5-7UM nickel layer) → electroplating thick gold (because the solder mask will lose 0.15UM gold thickness, it is necessary to increase 0.15UM gold thickness compensation on the basis of the customer's required gold thickness) → film stripping → outer layer pattern transfer ② (positive film is used to make the outer layer circuit, and the electroplating position is protected by dry film) → pattern electroplating and etching (only etching, no tin stripping) → outer layer pattern ③ (use dry film to protect the electroplating position, and other positions are exposed) → tin stripping → film stripping → A0I inspection → solder mask, characters → silk screen anti-chemical gold ink → surface treatment → film stripping → post-process.

[0010] 2. There are holes in the local electroplating position, and the outer line width / line spacing is greater than 0.127MM, and double-sided electroplating is thick gold. The process is as follows: previous process → pressing → micro-etching to 1 / 3OZ (only for customers who require copper thickness greater than 35um) → drilling → copper sinking → electroplating → outer layer pattern transfer ① (make local electroplating position pattern, use DuPont GPM-220 special electroplating thick gold dry film) → pattern nickel gold (only NI / AU, not electroplating copper, electroplating of the inner layer of the electroplating position hole is controlled at a minimum of 18um per point, including a 5-7um nickel layer, and the surface metal thickness of the local electroplating position is controlled to be greater than 30um, including a 5-7um nickel layer) → electroplating thick gold (because the solder mask grinding plate will damage Loss of 0.15um gold thickness requires an additional 0.15um gold thickness compensation based on the customer's required gold thickness) → film stripping → ceramic plate (only grind the non-electrometallurgical surface, cancel this process for double-sided electrometallurgical) → outer layer pattern transfer (positive film is used to make the outer layer circuit, the electrometallurgical position is protected by dry film, and the outer layer circuit film is pre-enlarged: ensure the spacing is 0.07MM, the dense circuit is pre-enlarged by 0.06MM, and the independent line is pre-enlarged by 0.10MM) → pattern plating → etching (only etching, no tin stripping) → outer layer pattern ③ (use dry film to protect the electrometallurgical position, and expose other positions) → tin stripping → film stripping → A0I inspection → solder mask, characters → silk screen anti-chemical gold ink → surface treatment → film stripping → post-process.

[0011] 3. There are holes in the local electroplating position, and the outer line width / line spacing is ≤0.127MM, and double-sided electroplating is thick gold. The process is as follows: pre-process → pressing (when the line width is ≤0.1MM, micro-etching to 1 / 3OZ is required) → drilling → copper sinking → board electroplating → outer layer pattern ① (hole plating pattern, only for the holes of the local electroplating position) → board electroplating (only electroplating gold position hole copper, the minimum hole copper thickness is controlled according to the customer's requirements to complete the finished product copper thickness requirements) → film stripping → outer layer pattern transfer ② (make local electroplating gold position pattern, use DuPont GPM-220 special electroplating thick gold dry film) → pattern nickel gold (only electroplating NI / AU, not electroplating copper, the surface metal thickness of the local electroplating position is according to Greater than 20um control, containing 5-7um nickel layer) → electroplating thick gold (since the solder mask will lose 0.15um gold thickness, it is necessary to increase 0.15um gold thickness compensation based on the customer's required gold thickness) → film stripping → ceramic grinding plate (only non-electroplating gold surface, double-sided electroplating cancel this process) → outer layer pattern transfer ③ (positive film is used to make the outer layer circuit, the electroplating gold position is protected by dry film, and the circuit is normally pre-enlarged) → pattern plating → etching (only etching, no tin stripping) → outer layer pattern ④ (use dry film to protect the electroplating gold position, and other positions are exposed) → tin stripping → film stripping → A0I inspection → solder mask, characters → silk screen anti-chemical gold ink → surface treatment → film stripping → post-process.

[0012] Disadvantages of existing production technology:

[0013] 1. The process is complicated and lengthy, requiring a long production cycle. The more processes there are, the more difficult it is to control errors, and quality problems increase sharply, reducing production efficiency and quality qualification rate, and increasing production costs and labor costs;

[0014] 2. There are many engineering materials that need to be produced, a lot of graphic materials need to be produced, a lot of films and dry films are used, which increases a lot of material costs and labor costs;

[0015] 3. Only the positive film process can be used, and the cost of alkaline etching is higher than the cost of acid etching for negative films. Summary of the invention

[0016] In view of the above-mentioned existing technical defects, the present invention provides a method for manufacturing long and short gold fingers of local electroplating. By designing to extend the local electroplating position to the copper foil at the edge of the board, a local electroplating process without pulling leads can be realized. A negative film process can be designed for production, which shortens the production process, reduces labor costs and material costs, and can improve the quality of local electroplating board products and increase product yield.

[0017] In order to solve the above technical problems, the present invention provides a method for manufacturing local electroplating long and short gold fingers, comprising the following steps:

[0018] S0, drilling holes on the production board, and then metalizing the holes by copper deposition and full-board electroplating, and plating the copper layer on the board surface and the copper layer on the hole wall to the thickness required by the outer layer circuit design;

[0019] S1. When making the outer layer circuit on the production board through the negative film process, several gold finger bodies are made at the same time. All the gold finger bodies have the same length and extend outward to connect with the copper layer at the edge of the board;

[0020] S2. Screen-print anti-electrostatic gold ink on the production board, and open windows at the positions corresponding to the local electrostatic gold on each gold finger body, so as to use the anti-electrostatic gold ink to cover and protect the extended length part of the gold finger body connected to the copper layer at the edge of the board;

[0021] S3, paste the film on the production board, and open windows at the positions corresponding to the local electroplating on each gold finger body;

[0022] S4, electroplating nickel-gold and electroplating thick gold on the production board in sequence, and plating a nickel layer and a gold layer in sequence on the window opening position of the gold finger body;

[0023] S5, stripping the film and removing the anti-electrostatic gold ink;

[0024] S6. Paste the film on the production board, and open windows in the gold finger body at the positions where no local electroplating gold is applied, and then remove the copper layer at the extended length portion of the gold finger body by alkaline etching to form long and short gold fingers.

[0025] Furthermore, in step S2, before screen printing the anti-static gold ink on the production board, the production board is first sandblasted.

[0026] Furthermore, in step S2, anti-static gold ink is firstly screen-printed on the entire production board, and then the anti-static gold ink is initially solidified by pre-baking, and then the anti-static gold ink at the position other than the extended length portion connected to the copper layer at the edge of the board in the gold finger body is removed by exposure and development.

[0027] Furthermore, in step S2, the pre-baking parameters are: 75°C*10min, and the developing parameters are: 6.0m / min.

[0028] Furthermore, in step S2, the width of the screen-printed anti-static gold ink area is greater than the width of the gold finger body.

[0029] Furthermore, in step S2, the width of the screen-printed anti-static gold ink area is 0.18 mm greater than the width of the gold finger body.

[0030] Furthermore, in step S2, the vertical distance between the inner side end of the screen-printed anti-electrostatic gold ink and the local electrostatic gold area of ​​the gold finger body is 0.06 mm.

[0031] Furthermore, in step S3, after a dry film is pasted on the entire production board, the dry film at the position corresponding to the local electroplating in the gold finger body is removed by exposure and development to form a window position to be locally electroplated.

[0032] Furthermore, after step S6, the following steps are also included:

[0033] S7, after the film is removed, the production board is then subjected to solder mask making, surface treatment and molding processes in sequence to obtain a finished product; wherein, during molding, the position where the gold finger is connected to the copper layer at the edge of the board is cut off.

[0034] Furthermore, in step S7, between the preparation of the solder mask layer and the surface treatment, a step of silk-screening and curing a gold-resistant ink on the long and short gold fingers is also included.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention electroplates the entire board so that the copper layer on the board surface is plated at one time to reach the thickness required by the outer circuit. Then, a negative film process is used when manufacturing the outer circuit to obtain the outer circuit and the gold finger body at the same time. Then, according to the design process of the disconnected gold finger, the local electroplating gold position is extended to the copper foil at the edge of the board by design, the extended part and the copper foil at the edge of the board are used as the conductive layer during gold plating, and then the gold finger body is locally treated with thick gold to obtain the long and short gold fingers. Compared with the existing method of using a positive film process to manufacture the outer circuit and using an electroplated gold lead to perform a local thick gold treatment on the gold finger body, the method of the present invention reduces the production process, reduces labor costs and material costs, and can improve the product quality of the local electroplated gold plate and increase the product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the production board after the outer layer is etched in the embodiment;

[0038] Figure 2 It is a schematic diagram of the production board after silk-screen printing of anti-gold-plating ink in the embodiment;

[0039] Figure 3 This is a schematic diagram of the production board in the embodiment after alkaline etching to obtain long and short gold fingers;

[0040] Figure 4 It is a schematic diagram of the circuit board obtained after the production board in the embodiment undergoes a molding process. DETAILED DESCRIPTION

[0041] In order to more fully understand the technical content of the present invention, the technical solution of the present invention will be further introduced and illustrated in conjunction with specific embodiments below.

[0042] Example

[0043] A method for manufacturing a circuit board shown in this embodiment includes the following processing steps in sequence:

[0044] (1) Cutting: Cut several core boards according to the panel size of 520mm×620mm. The thickness of the core board is 0.5mm, and the thickness of the copper layer on both surfaces of the core board is 0.5oz.

[0045] (2) Inner layer circuit production (negative film process): Inner layer pattern transfer, use a vertical coating machine to coat the photosensitive film, the film thickness of the photosensitive film is controlled to 8μm, and a fully automatic exposure machine is used to complete the exposure of the inner layer circuit with a 5-6 grid exposure ruler (21 grid exposure ruler). After development, the inner layer circuit pattern is formed; inner layer etching, the exposed and developed core board is etched to etch the inner layer circuit, and the inner layer line width is measured to be 3mil; inner layer AOI, and then check the inner layer circuit for defects such as open short circuits, circuit gaps, and circuit pinholes. Defective products are scrapped, and non-defective products are sent to the next process.

[0046] (3) Lamination: The browning speed is based on the base copper thickness. Then, the laminated boards are laminated in a vacuum laminator under appropriate lamination conditions according to the Tg of the sheet material to form a production board.

[0047] (4) Drilling: Based on the existing drilling technology, drilling processing is performed on the production board according to the design requirements.

[0048] (5) Copper plating: A thin layer of copper is deposited on the board surface and hole wall by chemical copper plating. The backlight test is level 10, and the thickness of the copper plating in the hole is 0.5μm.

[0049] (6) Full-board electroplating: The production board is subjected to full-board electroplating treatment to thicken the copper layer on the hole and the board surface, and the copper layer on the board surface and the hole wall is plated to the thickness required by the outer layer circuit design.

[0050] (7) Production of outer circuit (negative film process): Use a vertical coating machine to coat the photosensitive film, the film thickness of the photosensitive film is controlled to 8μm, and a fully automatic exposure machine is used to complete the exposure of the outer circuit with a 5-6 grid exposure ruler (21 grid exposure ruler). After development, the outer circuit pattern is formed. The outer circuit pattern includes a number of gold finger body patterns located at the edge of each unit board. The initial length of all gold finger body patterns is the same, and the outer end of the gold finger body pattern extends outward and is connected to the copper layer of the edge of the production board; outer layer etching, the production board after exposure and development is etched to etch out the outer layer circuit and a number of gold finger bodies, and the outer layer line width is measured to be 3mil; outer layer AOI, using an automatic optical inspection system, by comparing with the CAM data, detect whether the outer layer circuit has defects such as open circuit, gap, incomplete etching, short circuit, etc.

[0051] In the above, the width of the gold finger body is pre-enlarged by 70 μm based on the design.

[0052] Among the above, Figure 1As shown, the extended portion of the gold finger body 1 connected to the board edge copper layer 2 is used as the conductive portion 3, which is not used as a local electroplating portion, and its width is the same as that of the gold finger body.

[0053] In the above, the gold finger pattern includes a first gold finger pattern that is expected to be made into a longer gold finger and a second gold finger pattern that is expected to be made into a shorter gold finger. The outer end of the first gold finger pattern is just connected to the edge copper layer of the production board. The second gold finger pattern is extended outward to make it the same as the initial length of the first gold finger pattern and connected to the edge copper layer of the production board, that is, the initial length of the gold finger pattern is kept the same when the outer layer is etched.

[0054] (8) Sandblasting: Sandblast the production board to increase the roughness of the board circuit and the gold finger body, and increase the bonding strength between the dry film and ink in the later stage.

[0055] (9) Screen printing: First, screen print the anti-static gold ink on the entire production board, and then pre-cure the anti-static gold ink by pre-baking, and then remove the anti-static gold ink 4 (such as the anti-static gold ink 4) in the gold finger body outside the extended length portion connected to the copper layer of the board edge by exposure and development. Figure 2 As shown), anti-static gold ink is used to cover the extended portion (ie, the conductive portion) extending outward from the gold finger body.

[0056] In the above, the pre-bake parameters are: 75°C*10min, and the developing parameters are: 6.0m / min.

[0057] In the above, the width of the screen-printed anti-electrostatic gold ink area is 0.18mm larger than the width of the gold finger body, that is, 0.09mm larger on one side than the gold finger body, ensuring that the extended part (that is, the conductive part) is covered and protected by the anti-electrostatic gold ink to avoid the problem of incomplete etching and removal caused by infiltration of the extended part during the electroplating process.

[0058] In the above, the vertical distance between the inner end of the silk-screened anti-gold ink and the local electroplating area of ​​the gold finger body is 0.06mm, that is, there is a distance between the anti-gold ink and the designed local electroplating area. During local electroplating, the length of the local electroplating area can be expanded, and the expanded 0.06mm is used as a compensation part for the micro-etching of the gold finger end in the subsequent process, so as to avoid the problem of the gold finger length being etched too short in the subsequent process.

[0059] (10) Film pasting: After the dry film is pasted on the entire production board, the dry film at the position corresponding to the local electroplating in each gold finger body is removed by exposure and development to form a window position to be locally electroplated.

[0060] (11) Local electroplating: The production board is subjected to nickel-gold electroplating and thick gold electroplating treatments in turn. A nickel layer and a gold layer are plated in turn on the window position of the gold finger body. The thickness of the gold layer is controlled at 20-30μm; then the film is removed and the anti-electroplating gold ink is removed.

[0061] (12) Etching: A dry film is pasted on the production board, and then the dry film in the part of the gold finger body that is not locally electroplated is removed by exposure and development, that is, a window is opened at the extended part of the corresponding gold finger body (that is, the conductive part previously covered by the anti-electroplating gold ink), and then the copper layer at the extended length part (that is, the conductive part) of the gold finger body is removed by alkaline etching (such as Figure 3 As shown), that is, the outward extending part of the short gold finger body in the long and short gold finger is removed, and the film is retreated to form the long and short gold finger 5. At this time, the short gold finger is disconnected from the copper layer at the edge of the board (as shown in FIG. Figure 3 shown).

[0062] (13) Solder mask and silk screen characters: After the solder mask ink is silk screen printed on the surface of the production board, it is sequentially subjected to pre-curing, exposure, development and heat curing treatments to solidify the solder mask ink into a solder mask layer; specifically, a "UL mark" is added to the solder mask ink on the TOP surface and the characters on the TOP surface, thereby coating a layer on the circuits and substrates that do not require soldering to prevent bridging between circuits during soldering, provide a permanent electrical environment and resist chemical corrosion, and at the same time beautify the appearance.

[0063] (14) Silk screen printing of anti-chemical gold ink: Silk screen printing of anti-chemical gold ink on the long and short gold fingers and curing to use the anti-chemical gold ink to protect the gold layer on the long and short gold fingers.

[0064] (14) Surface treatment (nickel-gold immersion): The copper surface of the pad at the solder mask opening is treated with chemical principles to uniformly deposit nickel and gold layers of a certain required thickness. The nickel layer thickness is 3-5 μm; the gold layer thickness is 0.05-0.1 μm. After immersion gold, the chemical-resistant gold ink is removed.

[0065] (15) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0066] (16) Molding: According to the prior art and the design requirements, the circuit board is manufactured with a shape tolerance of + / -0.05 mm. During molding, the longer gold finger is cut off from the position where it is connected to the copper layer at the edge of the board (e.g. Figure 4 shown).

[0067] (17) FQC: Inspect the appearance of the circuit board according to the customer's acceptance standards and our inspection standards. If there are any defects, repair them in time to ensure that we provide customers with excellent quality control.

[0068] (18) FQA: Re-test the circuit board’s appearance, hole copper thickness, dielectric layer thickness, green oil thickness, inner layer copper thickness, etc. to see if they meet customer requirements.

[0069] (19) Packaging: The circuit boards are sealed and packed according to the packaging method and quantity required by the customer, and desiccant and humidity card are placed before shipment.

[0070] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for making local electroplated long and short gold fingers, characterized in that: The following steps are involved: S0, drilling holes on the production board, and then metalizing the holes by copper deposition and full-board electroplating, and plating the copper layer on the board surface and the copper layer on the hole wall to the thickness required by the outer layer circuit design; S1. When making the outer layer circuit on the production board through the negative film process, several gold finger bodies are made at the same time. All the gold finger bodies have the same length and extend outward to connect with the copper layer at the edge of the board; S2. Screen-print anti-electrostatic gold ink on the production board, and open windows at the positions corresponding to the local electrostatic gold on each gold finger body, so as to use the anti-electrostatic gold ink to cover and protect the extended length part of the gold finger body connected to the copper layer at the edge of the board; S3, paste the film on the production board, and open windows at the positions corresponding to the local electroplating on each gold finger body; S4, electroplating nickel-gold and electroplating thick gold on the production board in sequence, and plating a nickel layer and a gold layer in sequence on the window opening position of the gold finger body; S5, stripping the film and removing the anti-electrostatic gold ink; S6. Paste the film on the production board, and open windows in the gold finger body at the positions where no local electroplating gold is applied, and then remove the copper layer at the extended length portion of the gold finger body by alkaline etching to form long and short gold fingers.

2. The method for making local electroplating long and short gold fingers according to claim 1, characterized in that: In step S2, before screen printing the anti-static gold ink on the production board, the production board is first sandblasted.

3. The method for making local electroplating long and short gold fingers according to claim 1, characterized in that: In step S2, first, the anti-static gold ink is screen-printed on the entire production board, and then the anti-static gold ink is initially cured by pre-baking, and then the anti-static gold ink in the gold finger body other than the extended length portion connected to the board edge copper layer is removed by exposure and development.

4. The method for making local electroplating long and short gold fingers according to claim 3, characterized in that: In step S2, the pre-baking parameters are: 75°C*10min, and the developing parameters are: 6.0m / min.

5. The method for making local electroplated long and short gold fingers according to claim 1, characterized in that: In step S2, the width of the screen-printed anti-static gold ink area is greater than the width of the gold finger body.

6. The method for making local electroplating long and short gold fingers according to claim 5, characterized in that: In step S2, the width of the screen-printed anti-static gold ink area is 0.18 mm greater than the width of the gold finger body.

7. The method for making local electroplating long and short gold fingers according to claim 1, characterized in that: In step S2, the vertical distance between the inner side end of the screen-printed anti-electrostatic gold ink and the local electrostatic gold area of ​​the gold finger body is 0.06 mm.

8. The method for making local electroplating long and short gold fingers according to claim 1, characterized in that: In step S3, after the dry film is pasted on the entire production board, the dry film at the position corresponding to the local electroplating in the gold finger body is removed by exposure and development to form a window position to be locally electroplated.

9. The method for making local electroplating long and short gold fingers according to claim 1, characterized in that: After step S6, the following steps are also included: S7, after the film is removed, the production board is then subjected to solder mask making, surface treatment and molding processes in sequence to obtain a finished product; wherein, during molding, the position where the gold finger is connected to the copper layer at the edge of the board is cut off.

10. The method for manufacturing local electroplating long and short gold fingers according to claim 9, characterized in that: In step S7, between the preparation of the solder mask layer and the surface treatment, a step of silk-screening and curing a gold-resistant ink on the long and short gold fingers is also included.

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