PCB with nickel-gold immersion and anti-oxidation surface treatments and its manufacturing method

Abstract

The present invention discloses a PCB with two surface treatments, namely, electroplating nickel and gold, and anti-oxidation, and a manufacturing method thereof. The manufacturing method comprises the following steps: making a solder mask layer on a production board, and making a first pad on the production board to be electroplated nickel and a second pad to be anti-oxidation exposed by opening windows; printing characters on the production board; applying a dry film to the production board, and then opening windows at the corresponding first pad and characters through exposure and development in sequence; subjecting the production board to chemical electroplating nickel and gold, and then stripping the film; and subjecting the second pad on the production board to anti-oxidation. In the method of the present invention, the dry film at the corresponding characters is not exposed, and the dry film here will not undergo a cross-linking reaction with the characters, so that the dry film at the characters can be stripped cleanly during later development, thereby solving the problem of incomplete film stripping and unclear characters on characters in the prior art of producing electroplating nickel and OSP selective printing boards.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board manufacturing, and in particular to a PCB with two surface treatments: nickel-gold immersion and anti-oxidation, and a manufacturing method thereof. Background Art

[0002] In recent years, due to the presence of nickel corrosion on nickel-immersion gold (IGM) boards, small BGA points (diameter ≤ 0.3mm) have more severe nickel corrosion than PADs, resulting in frequent solder joint cracking during soldering. With the rapid development of electronic technology, a single surface treatment process on the same PCB board can no longer meet customer needs. The development of a combination of multiple surface treatment processes has become increasingly important. However, when performing multiple surface treatments on the same PCB board at the same time, mutual interference will occur, increasing the technical difficulty.

[0003] To address this solder joint cracking issue, the PCB industry has developed a nickel-plated gold (Immersion Nickel Gold) + OSP selective process. The BGA area is protected with OSP film to prevent nickel corrosion, while other areas are treated with nickel-plated gold. The main process is: cutting → inner layer → lamination → drilling → copper plating → board layout → outer layer circuitry → negative etching → solder mask → marking → secondary dry film (covering the BGA area to prevent nickel-plated gold) → nickel-plated gold → film stripping → molding → testing → OSP (OSP film applied to the BGA area) → FQC → FQA → packaging.

[0004] At present, in order to improve production efficiency, PCB factories generally use printed characters in their character process. Because the printing character ink is UV curable ink, not thermosetting ink, the UV light curing + post-baking method after printing the characters cannot make it completely cured. Generally, the curing degree of the character ink can only be about 80%. There are still many components in the printed characters that cannot be completely cured. Ordinary nickel-immersion gold boards are not affected. However, in various surface treatment processes, when the secondary dry film is made later, the character ink and the dry film produce a cross-linking reaction when the outer layer of the pattern is exposed and become one. The subsequent film stripping process cannot completely remove the dry film on the characters, resulting in blurred characters and scrapped. Summary of the Invention

[0005] In view of the above-mentioned technical defects, the present invention provides a PCB manufacturing method with two surface treatments of nickel-plated gold and anti-oxidation, which solves the problem of unclean film removal and unclear characters on the characters of nickel-plated gold + OSP selective boards produced by the prior art.

[0006] In order to solve the above technical problems, the present invention provides a method for manufacturing a PCB with two surface treatments: nickel-plated gold and anti-oxidation, comprising the following steps:

[0007] S1. Prepare a solder mask layer on the production board, and make windows to expose the first pads that need to be etched with nickel and gold and the second pads that need to be treated with anti-oxidation;

[0008] S2, print out characters on the production board;

[0009] S3, applying a dry film on the production board, and then sequentially performing exposure and development to open windows at the corresponding first pads and characters;

[0010] S4, perform chemical nickel-gold treatment on the production board, and then remove the film;

[0011] S5. Perform anti-oxidation treatment on the second solder pad on the production board.

[0012] Furthermore, in step S1, solder mask ink is first screen-printed on the production board, and then pre-curing, exposure and development are performed in sequence to open windows to expose the first pad and the second pad on the production board. Finally, the solder mask ink is cured by baking to complete the production of the solder mask layer.

[0013] Furthermore, in step S2, a character printer is used to print out characters at the designed positions of the characters on the production board.

[0014] Furthermore, in step S2, after printing the characters, the character printer uses UV light to pre-cure the characters.

[0015] Furthermore, in step S2, the characters are pre-cured using UV light, and then the production board is baked.

[0016] Furthermore, in step S3, the exposure scale during exposure is controlled at 8-10 grids.

[0017] Furthermore, in step S4, the pre-treatment in the electroless nickel-gold treatment does not include the grinding and sandblasting processes.

[0018] Furthermore, the following steps are included between steps S4 and S5:

[0019] S41, forming the production board;

[0020] S42. Perform electrical testing on the production board.

[0021] Furthermore, the production board is a multi-layer board in which the inner core board and the outer copper foil are pressed together by a semi-cured sheet, and the multi-layer board has undergone the processes of drilling, copper deposition, full-board electroplating and outer layer circuit production in sequence.

[0022] In a second aspect, the present invention further provides another method for manufacturing a PCB having two surface treatments, nickel-gold immersion and anti-oxidation, comprising the following steps:

[0023] S1. Prepare a solder mask layer on the production board, and make windows to expose the first pads that need to be etched with nickel and gold and the second pads that need to be treated with anti-oxidation;

[0024] S2, applying a dry film on the production board, and then sequentially performing exposure and development to open a window at the corresponding first pad;

[0025] S3, perform chemical nickel-gold treatment on the production board, and then remove the film;

[0026] S4, print out characters on the production board;

[0027] S5. Perform anti-oxidation treatment on the second solder pad on the production board.

[0028] In a third aspect, the present invention further provides a PCB having two surface treatments: nickel-gold immersion and anti-oxidation, which is manufactured using the PCB manufacturing method described in either the first aspect or the second aspect.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] In the first method of the present invention, in the secondary film lamination after printing characters, the dry film at the corresponding characters is opened and exposed during exposure and development, that is, the dry film at the corresponding characters is not exposed, and the dry film here will not undergo cross-linking reaction with the characters, so that the dry film at the characters can be cleanly removed during the subsequent development, solving the problem of unclean film removal and unclear characters on the characters of the existing technology for producing nickel-plated gold + OSP selective board.

[0031] In the second method, characters are not made after the solder mask is made. Secondly, characters are made after nickel-plated gold. In this way, the character ink made later also avoids cross-linking reaction with the dry film of the secondary paste, ensuring its clarity and solving the problem of unclean film removal and unclear characters on the characters of nickel-plated gold + OSP selective board made by the existing technology. DETAILED DESCRIPTION

[0032] 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.

[0033] Example 1

[0034] The present embodiment shows a method for manufacturing a PCB with two surface treatments, namely, nickel-plated gold and anti-oxidation, which includes the following processing steps in sequence:

[0035] (1) Cutting: Cut the core board 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.

[0036] (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 at 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), and the inner layer circuit pattern is formed after development; 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 and short circuits, circuit gaps, and circuit pinholes. Defective products will be scrapped, and products without defects will be sent to the next process.

[0037] (3) Lamination: The browning speed is based on the browning thickness of the bottom copper. The core board, prepreg, and outer copper foil are laminated in sequence as required. Then, appropriate lamination conditions are selected according to the Tg of the sheet material to press the laminated board to form a production board.

[0038] (4) Drilling: Based on existing drilling technology, drilling is performed on the production board according to design requirements.

[0039] (5) Copper plating: A thin layer of copper is deposited on the board surface and the hole wall using the chemical copper plating method. The backlight test is level 10, and the thickness of the copper plating in the hole is 0.5μm.

[0040] (6) Full-board electroplating: Full-board electroplating is performed at a current density of 18ASF for 120 minutes, and the thickness of the hole copper and the board surface copper layer is thickened to the required thickness. The hole copper thickness is ≥30μm.

[0041] (7) Production of outer layer circuits (negative film process): Transfer of outer layer pattern, coating of photosensitive film with a vertical coating machine, the thickness of the photosensitive film is controlled at 8μm, and a fully automatic exposure machine is used to complete the exposure of the outer layer circuit with a 5-6 grid exposure ruler (21 grid exposure ruler), and the outer layer circuit pattern is formed after development; outer layer etching, etching the production board after exposure and development to produce the outer layer circuit, the outer layer line width is measured to be 3mil, and a number of first pads that need to be treated with nickel-gold and second pads that do not need to be treated with nickel-gold are made on the outer layer circuit; 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.

[0042] (8) Solder mask: After the solder mask ink is screen-printed on the surface of the production board, it is sequentially processed through pre-curing, exposure, development and heat curing to solidify the solder mask ink into a solder mask layer. The first pad on the production board that needs to be nickel-gold plated and the second pad that needs to be treated with anti-oxidation are exposed through windows. Thus, a layer of protection is applied on the circuits and substrates that do not need to be soldered to prevent bridging between circuits during soldering, provide a permanent electrical environment and resist chemical corrosion, and beautify the appearance.

[0043] (9) Printing characters: Use a character printer to print characters at the designed position of the characters on the production board; after printing the characters, use UV light to pre-cure the characters, and then bake the production board.

[0044] (10) Film pasting: A gold-resistant dry film is pressed on the entire production board, and then windows are opened at the first pads and characters corresponding to the nickel-gold treatment through exposure and development in sequence, so that the first pads and characters are exposed; that is, the dry film at the corresponding characters is not exposed, and the dry film here will not undergo a cross-linking reaction with the characters, so that the dry film at the characters can be removed cleanly during the subsequent development, solving the problem of unclean film removal and unclear characters on the characters of the existing technology for producing nickel-gold + OSP selective printing boards.

[0045] In the above, the exposure scale is controlled at 8-10 grids during exposure to increase the exposure energy and prevent the dry film from cracking under the attack of nickel-gold immersion solution, resulting in nickel-gold immersion on the second pad in the BGA area.

[0046] In the above, it is preferred to use an LDI exposure machine for exposure to improve exposure accuracy.

[0047] (11) Surface treatment (immersion nickel and gold): The copper surface of the first pad on the production board is chemically deposited with a nickel layer and a gold layer of a certain required thickness. The thickness of the nickel layer is: 3-6μm; the thickness of the gold layer is: 0.05-0.07μm.

[0048] In the above, the pre-treatment of the chemical nickel-gold treatment does not include the grinding and sandblasting process, so as to prevent the dry film of the secondary bonding from falling off and causing nickel-gold to be deposited on the second pad of the BGA area.

[0049] (12) Film removal: remove the dry film.

[0050] (13) Molding: According to existing technology and design requirements, the shape of the gong shall be made with a shape tolerance of + / -0.05mm.

[0051] (14) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0052] (15) Anti-oxidation treatment: Anti-oxidation treatment is performed on the second pad of the production board to form an anti-oxidation protective film on the surface of the second pad. The thickness of the protective film is 0.2-0.5 μm, and a PCB is produced. The anti-oxidation treatment is preferably an OSP surface treatment.

[0053] (16) 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.

[0054] (17) FQA: Re-test the PCB appearance, hole copper thickness, dielectric layer thickness, green oil thickness, inner layer copper thickness, etc. to see if they meet customer requirements.

[0055] (18) Packaging: According to the packaging method and packaging quantity required by the customer, the circuit board is sealed and packed, and desiccant and humidity card are placed before shipment.

[0056] Example 2

[0057] The present embodiment shows a method for manufacturing a PCB with two surface treatments, namely, nickel-plated gold and anti-oxidation, which includes the following processing steps in sequence:

[0058] (1) Cutting: Cut the core board 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.

[0059] (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 at 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), and the inner layer circuit pattern is formed after development; 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 and short circuits, circuit gaps, and circuit pinholes. Defective products will be scrapped, and products without defects will be sent to the next process.

[0060] (3) Lamination: The browning speed is based on the browning thickness of the bottom copper. The core board, prepreg, and outer copper foil are laminated in sequence as required. Then, appropriate lamination conditions are selected according to the Tg of the sheet material to press the laminated board to form a production board.

[0061] (4) Drilling: Based on existing drilling technology, drilling is performed on the production board according to design requirements.

[0062] (5) Copper plating: A thin layer of copper is deposited on the board surface and the hole wall using the chemical copper plating method. The backlight test is level 10, and the thickness of the copper plating in the hole is 0.5μm.

[0063] (6) Full-board electroplating: Full-board electroplating is performed at a current density of 18ASF for 120 minutes, and the thickness of the hole copper and the board surface copper layer is thickened to the required thickness. The hole copper thickness is ≥30μm.

[0064] (7) Production of outer layer circuits (negative film process): Transfer of outer layer pattern, coating of photosensitive film with a vertical coating machine, the thickness of the photosensitive film is controlled at 8μm, and a fully automatic exposure machine is used to complete the exposure of the outer layer circuit with a 5-6 grid exposure ruler (21 grid exposure ruler), and the outer layer circuit pattern is formed after development; outer layer etching, etching the production board after exposure and development to produce the outer layer circuit, the outer layer line width is measured to be 3mil, and a number of first pads that need to be treated with nickel-gold and second pads that do not need to be treated with nickel-gold are made on the outer layer circuit; 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.

[0065] (8) Solder mask: After the solder mask ink is screen-printed on the surface of the production board, it is sequentially processed through pre-curing, exposure, development and heat curing to solidify the solder mask ink into a solder mask layer. The first pad on the production board that needs to be nickel-gold plated and the second pad that needs to be treated with anti-oxidation are exposed through windows. Thus, a layer of protection is applied on the circuits and substrates that do not need to be soldered to prevent bridging between circuits during soldering, provide a permanent electrical environment and resist chemical corrosion, and beautify the appearance.

[0066] (9) Film pasting: A gold-resistant dry film is pressed on the entire production board, and then a window is opened at the first pad that needs to be treated with nickel-gold through exposure and development in sequence to expose the first pad.

[0067] In the above, the exposure scale is controlled at 8-10 grids during exposure to increase the exposure energy and prevent the dry film from cracking under the attack of nickel-gold immersion solution, resulting in nickel-gold immersion on the second pad in the BGA area.

[0068] In the above, it is preferred to use an LDI exposure machine for exposure to improve exposure accuracy.

[0069] (10) Surface treatment (nickel-gold immersion): The copper surface of the first pad on the production board is chemically deposited with a nickel layer and a gold layer of a certain required thickness. The thickness of the nickel layer is 3-6 μm; the thickness of the gold layer is 0.05-0.07 μm.

[0070] In the above, the pre-treatment of the chemical nickel-gold treatment does not include the grinding and sandblasting process, so as to prevent the dry film of the secondary bonding from falling off and causing nickel-gold to be deposited on the second pad of the BGA area.

[0071] (11) Film removal: remove the dry film.

[0072] (12) Printing characters: Use a character printer to print characters at the designed position of the characters on the production board; after printing the characters, use UV light to pre-cure the characters, and then bake the production board.

[0073] (13) Molding: According to existing technology and design requirements, the shape of the gong shall be made with a shape tolerance of + / -0.05mm.

[0074] (14) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0075] (15) Anti-oxidation treatment: Anti-oxidation treatment is performed on the second pad of the production board to form an anti-oxidation protective film on the surface of the second pad. The thickness of the protective film is 0.2-0.5 μm, and a PCB is produced. The anti-oxidation treatment is preferably an OSP surface treatment.

[0076] (16) 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.

[0077] (17) FQA: Re-test the PCB appearance, hole copper thickness, dielectric layer thickness, green oil thickness, inner layer copper thickness, etc. to see if they meet customer requirements.

[0078] (18) Packaging: According to the packaging method and packaging quantity required by the customer, the circuit board is sealed and packed, and desiccant and humidity card are placed before shipment.

[0079] 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 may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for manufacturing a PCB with two surface treatments: nickel-gold immersion and anti-oxidation, characterized in that: The following steps are involved: S1. A solder mask layer is formed on a production board, and windows are opened to expose the first pad on the production board that needs nickel-gold plating and the second pad on the production board that needs anti-oxidation treatment; solder mask ink is first screen-printed on the production board, and then pre-curing, exposure, and development are performed in sequence to expose the first pad and the second pad on the production board through windows, and finally the solder mask ink is cured by baking to complete the production of the solder mask layer; the production board is a multi-layer board in which an inner core board and an outer copper foil are pressed together by a prepreg, and the multi-layer board has undergone drilling, copper plating, full-board electroplating, and outer layer circuit production processes in sequence; S2, print out characters on the production board; S3, applying a dry film on the production board, and then sequentially performing exposure and development to open windows at the corresponding first pads and characters; S4, perform chemical nickel-gold treatment on the production board, and then remove the film; S41, forming the production board; S42, perform electrical testing on the production board; S5. Perform anti-oxidation treatment on the second solder pad on the production board.

2. The method for manufacturing a PCB with both nickel-gold immersion and anti-oxidation surface treatments according to claim 1, characterized in that: In step S2, a character printer is used to print characters at the designed positions of the characters on the production board.

3. The method for manufacturing a PCB with both nickel-gold immersion and anti-oxidation surface treatments according to claim 2, characterized in that: In step S2, after the character printer prints the characters, it uses UV light to pre-cure the characters and then bakes the production board.

4. The method for manufacturing a PCB with both nickel-gold immersion and anti-oxidation surface treatments according to claim 1, characterized in that: In step S3, the exposure scale is controlled at 8-10 grids during exposure.

5. The method for manufacturing a PCB with both nickel-gold immersion and anti-oxidation surface treatments according to claim 1, characterized in that: In step S4, the pre-treatment in the electroless nickel-gold process does not include the grinding and sandblasting processes.