Method for manufacturing high-density circuit board with BGA copper layer and high-out solder mask layer

Abstract

The invention discloses a manufacturing method of a high-density circuit board with a BGA copper layer and a high-out solder mask layer. The manufacturing method comprises the following steps of a pre-process, drilling, copper deposition, negative electroplating, external light imaging, acid etching, solder mask / character, external light imaging 2, copper plating, film stripping, external light imaging 3, acid etching 2, solder mask / character 2 and a post-process. Whole plate electroplating is carried out in the negative plate electroplating process, so that the copper layer thickness of hole copper and the copper-clad plate is increased, and customer requirements are met; in the copper plating process, current is not set on one surface of the BGA, and low current is set on the other surface for normal electroplating to enhance the thickness of the BGA copper layer. According to the manufacturing method of the high-density circuit board with the BGA copper layer and the high-density solder mask layer, a chemical deposition method is adopted to carry out metallization processing on the hole wall, the conductivity of the copper layer in the hole is ensured, whole board electroplating is carried out to increase the thickness of hole copper and the copper layer of a copper-clad plate, the corrosion resistance and the mechanical strength of the circuit are enhanced, and the high requirement of clients for signal transmission is met; the problem of poor contact of welding spots caused by the fact that the solder mask layer is higher than the line layer is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board manufacturing, in particular to a method for manufacturing a high-density circuit board in which a BGA copper layer is higher than a solder resist layer. Background Art

[0002] With the continuous development of the electronic information industry, new electronic devices will inevitably be launched continuously. This series of new application fields have put forward new requirements for PCB products. Circuit boards are important electronic components, but the existing high-density circuit board production methods still have certain defects when used, such as; In the process of use, the production of high-density circuit boards is to complete the blind hole stacking first, and then use the photosensitive solder mask to protect the step area. However, this operation is not only extremely difficult, which reduces the overall processing efficiency, but also difficult to protect in place, and the product qualification rate cannot be guaranteed; In order to overcome the above defects, prior art 1 (Chinese patent with application number 202311066431.3 and application date 2023-08-23) is a multilayer circuit board and a method for manufacturing the same. The method for manufacturing the multilayer circuit board comprises: providing a sub-board, wherein a via hole is provided in the sub-board and a conductive pattern electrically connected to the via hole is provided on the first surface of the sub-board; a photosensitive film is formed on the first surface so that the photosensitive film covers at least part of the conductive pattern; the photosensitive film is exposed and developed to form a protective pattern at the conductive pattern; an insulating layer is formed on the first surface so that the insulating layer covers the first surface where the protective pattern is not retained; the protective pattern is removed so that the insulating layer forms a conductive channel at the conductive pattern; a conductive material is filled into the conductive channel to form a conductive column electrically connected to the conductive pattern; a build-up circuit is formed on the sub-board, which solves the technical problems of low processing efficiency and poor product quality of multilayer circuit boards in the related art; There is also prior art 2 (Chinese patent with application number 202010053611.8 and application date 2020-01-17), a method for manufacturing a high-density, micro-pitch, high-thermal-conductivity ultra-thin copper-based circuit board, which relates to the technical field of ultra-thin circuit board manufacturing methods, the method comprising: S1, opening a window on an RCC with a protective film; S2, making a boss on a copper-based separation carrier, and browning the boss, the boss position corresponds to the window position, the copper-based separation carrier comprises a copper substrate and a carrier, the boss is arranged on the copper substrate; S3, remove the protective film from the RCC with the window opened, and press it with the copper substrate, wherein the RCC window opening position cannot intersect with the boss; S4, separate the copper-based separation carrier obtained in S3 to obtain a carrier and a copper substrate with RCC attached; S5, reduce the copper thickness of the circuit surface of the copper substrate obtained in S4 to 5-8um, and make circuits, so that the total thickness of the finished product can be less than 0.4mm; the circuit layer has a high-density micro-pitch high-thermal conductivity ultra-thin copper-based circuit board with a line width of less than 50um and a line spacing of less than 30um, which can carry more electronic components and realize more functions; And prior art 3 (Chinese patent with application number 201911116861.5 and application date 2019-11-15) A method for manufacturing a flexible circuit board, which relates to the technical field of circuit board manufacturing. The method for manufacturing a flexible circuit board comprises the following steps: S1, coating a layer of adhesive material on the surface of an insulating film substrate; S2, punching and pressing the insulating film substrate with a mold, forming sprocket holes on both sides of the insulating film substrate, and forming a component hole in the central part; S3, then pasting a conductive layer on the adhesive material; S4, uniformly coating the surface of the conductive layer with photoresist, and after the photoresist is hardened, exposing the surface of the insulating film substrate. When the flexible circuit board is installed on a liquid crystal panel, the spacer contacts the liquid crystal panel. Since a certain distance is maintained with the liquid crystal panel, even if there are burrs on the panel frame of the liquid crystal panel, the flexible circuit board will not contact the burrs, so that the circuit formed in the conductive layer of the flexible circuit board can be prevented from being damaged by contact with the burrs; Although the existing technology can improve the overall processing efficiency, during the working process, the conductive layer is pasted after the circuit board is punched, and the solder mask is printed after the outer layer circuit is made as a whole. Therefore, the solder mask layer will be higher than the circuit layer, which is easy to cause poor contact of the solder joints as a whole, thereby affecting the connection quality of the electronic components. After long-term use, the solder mask layer is easily damaged, thereby affecting the overall reliability of the circuit board. Since the overall line width spacing is very small, the overall maintenance is difficult, which increases the overall maintenance cost.

[0003] In view of the above problems, it is urgent to carry out innovative design based on the original high-density circuit board manufacturing method in which the BGA copper layer is higher than the solder mask layer. Therefore, we propose a high-density circuit board manufacturing method in which the BGA copper layer is higher than the solder mask layer, which can solve the above problems well. Summary of the invention

[0004] The purpose of the present invention is to provide a method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder mask layer, so as to solve the problem raised in the above-mentioned background technology that the circuit board is currently punched and then a conductive layer is pasted, and the outer layer circuit is manufactured as a whole and then the solder mask is printed. Therefore, the solder mask layer will be higher than the circuit layer, which is easy to cause poor contact of the solder joints as a whole, thereby affecting the connection quality of the electronic components, and after long-term use, the solder mask layer is easily damaged, thereby affecting the overall reliability of the circuit board. Since the overall line width spacing is very small, the overall maintenance is difficult, which increases the overall maintenance cost.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: A method for manufacturing a high-density circuit board in which a BGA copper layer is higher than a solder mask layer, comprising the following steps: pre-process - drilling - copper deposition - negative film electroplating - external light imaging - acid etching - solder mask / character - external light imaging 2 - copper plating - film stripping - external light imaging 3 - acid etching 2 - solder mask / character 2 - post-process; The negative electroplating process is used to electroplate the entire board to increase the copper thickness of the copper holes and copper clad boards to meet customer requirements, enhance the corrosion resistance and mechanical strength of the circuit, meet customers' high requirements for signal transmission, reduce the problem of poor contact of solder joints caused by the solder mask layer being higher than the circuit layer, and improve overall reliability; In the external light imaging process, a photosensitive dry film is pasted on the electroplated board, and the required pattern is formed by exposure. The circuit pattern is formed on one side with BGA and the other side is covered with dry film. The solder mask / character process is to print solder mask ink, pre-bake and cure it, then expose and develop it to expose the pad. In this process, only the pad is exposed normally on the side with BGA, and the other side is not solder masked. Characters are printed on the board and cured at high temperature. The copper plating process does not set current on one side of the BGA, and sets a small current on the other side for normal electroplating, which enhances the thickness of the BGA copper layer, improves thermal conductivity and electrical connection quality, ensures component reliability, and uses alkaline chemical solutions to remove the dry film, exposing the copper layer and solder mask, providing a good base for subsequent processes and ensuring good electrical connections.

[0006] Preferably, the drilling process uses a drilling machine to drill through holes of different diameters according to design data, and through precise diameter control to ensure smooth progress of subsequent processes and meet different design requirements.

[0007] Preferably, the copper plating process uses a chemical deposition method to metallize the hole wall to ensure the conductivity of the copper layer in the hole. Chemical deposition is used to ensure the uniformity and conductivity of the copper layer in the hole, thereby improving the overall electrical performance of the PCB.

[0008] Preferably, the acid etching process uses chemical solutions to etch the exposed copper layer to form a circuit pattern. This process only processes one side of the BGA, and the other side remains as a copper layer. Acid etching can efficiently remove excess copper layers, form clear circuit patterns, and improve the conductivity and reliability of the circuit.

[0009] Preferably, the external light imaging 2 process is to stick a dry film on the processed board, expose it to form the required pattern, reveal the BGA area through development, and cover other pads with dry film, which can accurately replicate the designed pattern, ensure the accuracy of the circuit, and lay the foundation for subsequent etching.

[0010] Preferably, the film stripping process uses alkaline chemical solution to remove the dry film to expose the copper layer and the solder resist layer.

[0011] Preferably, the external light imaging process is to stick a dry film on the board again, expose it to form a desired pattern, and complete it through development, so that the BGA area is fully covered with the dry film and a circuit pattern is formed on the other side.

[0012] Preferably, the acid etching step 2 uses chemical solutions to etch the exposed copper layer to form a circuit pattern. This step forms a circuit on the side without BGA, and the side with BGA is not etched due to dry film coverage. Through precise etching, the circuit pattern is clarified to ensure that the side without BGA is optimized.

[0013] Preferably, the solder mask / character 2 process performs solder mask treatment on the other side, prints solder mask ink, exposes and develops after pre-baking and curing, exposes the pads, prints characters on the board and performs high-temperature curing, thereby improving the overall protection capability and increasing the readability of the PCB, ensuring the efficiency and accuracy of production.

[0014] Compared with the prior art, the invention has the following beneficial effects: the method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder mask layer adopts a chemical deposition method to metallize the hole wall to ensure the conductivity of the copper layer in the hole, and performs electroplating on the entire board to increase the copper layer thickness of the hole copper and the copper clad board, thereby enhancing the corrosion resistance and mechanical strength of the circuit, meeting the high requirements of customers for signal transmission, and reducing the problem of poor contact of solder joints caused by the solder mask layer being higher than the circuit layer. The specific contents are as follows: (1) The whole board is electroplated to increase the copper layer thickness of the hole copper and the copper clad board, enhance the corrosion resistance and mechanical strength of the circuit, meet the customer's high requirements for signal transmission, reduce the problem of poor contact of solder joints caused by the solder mask layer being higher than the circuit layer, and improve the overall reliability; (2) Use chemical solutions to etch the exposed copper layer to form a circuit pattern. Acid etching can efficiently remove the excess copper layer to form a clear circuit pattern, improve the conductivity and reliability of the circuit, and reduce the problem of increased maintenance costs due to greater maintenance difficulty; (3) No current is set on one side of the BGA, and a small current is set on the other side for normal electroplating to enhance the thickness of the BGA copper layer, improve thermal conductivity and electrical connection quality, ensure component reliability, and use alkaline chemical solution to remove the dry film, expose the copper layer and solder mask layer, and ensure good electrical connection; (4) Through precise etching, the circuit pattern is made clear, ensuring that the surface without BGA is optimized, solder mask treatment is performed on the other side, solder mask ink is printed, pre-baked and cured, then exposed and developed to expose the pad, characters are printed on the board and high-temperature cured to improve the overall protection capability; (5) BGA and copper foil are a whole, forming a current loop, so that the copper thickness of BGA meets customer needs, which reduces the difficulty of overall processing and greatly improves the overall processing efficiency, avoiding the problem of being unable to set the current due to design limitations. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall process of the present invention; Figure 2It is a schematic diagram of the drilling structure of the present invention; Figure 3 This is a schematic diagram of the copper deposition structure of the present invention; Figure 4 It is a schematic diagram of the negative film electroplating structure of the present invention; Figure 5 It is a schematic diagram of the external light imaging structure of the present invention; Figure 6 It is a schematic diagram of the acid etching structure of the present invention; Figure 7 It is a schematic diagram of the solder mask / character structure of the present invention; Figure 8 This is a schematic diagram of the structure of the external light imaging 2 of the present invention; Fig. 9 This is a schematic diagram of the copper plating structure of the present invention; Fig.10 It is a schematic diagram of the film stripping structure of the present invention; Fig.11 This is a schematic diagram of the structure of the external light imaging 3 of the present invention; Fig.12 It is a schematic diagram of the structure of the acid etching 2 of the present invention; Fig.13 It is a schematic diagram of the solder mask / character 2 structure of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Embodiment 1:

[0018] In this embodiment, the copper plating process does not set current on one side of the BGA, and sets a small current on the other side for normal electroplating to enhance the thickness of the BGA copper layer. Figure 1-Figure 7The technical solution shown in the figure is as follows: the front process - drilling - copper deposition - negative electroplating - external light imaging - acid etching - solder mask / character - external light imaging 2 - copper plating - film stripping - external light imaging 3 - acid etching 2 - solder mask / character 2 - the back process. The negative electroplating process is to electroplate the whole board to increase the copper thickness of the hole copper and the copper clad board to meet customer requirements. The external light imaging process is to stick a photosensitive dry film on the electroplated board, expose it to form the required pattern, and develop it with weak alkaline solution to form a circuit pattern on the side with BGA and cover the other side with dry film. The solder mask / character process is to print solder mask ink, pre-bake and cure it, and then expose and develop it to expose the pad. This process only exposes the pad normally on the side with BGA, and the other side is covered with dry film. No solder mask is applied on one side, and characters are printed on the board and cured at high temperature. In the copper plating process, no current is set on one side of the BGA, and a small current is set on the other side for normal electroplating to enhance the thickness of the BGA copper layer. In the drilling process, a drilling machine is used according to the design data to drill through holes of different apertures. In the copper deposition process, chemical deposition is used to metallize the hole wall to ensure the conductivity of the copper layer in the hole. In the acid etching process, chemical solutions are used to etch the exposed copper layer to form a circuit pattern. This process only processes one side with the BGA, and the other side remains as a copper layer. A drilling machine is used according to the design data to drill through holes of different apertures. Through precise aperture control, the smooth progress of subsequent processes is ensured to meet different design requirements. In order to meet the requirements of customers, chemical deposition method is used to metallize the hole wall to ensure the conductivity of the copper layer in the hole. Chemical deposition is used to ensure the uniformity and conductivity of the copper layer in the hole, improve the overall electrical performance of the PCB, and perform electroplating on the whole board to increase the copper layer thickness of the hole copper and copper clad board, enhance the corrosion resistance and mechanical strength of the circuit, meet the high requirements of customers for signal transmission, reduce the problem of poor contact of solder joints caused by the solder mask layer being higher than the circuit layer, and improve the overall reliability. A photosensitive dry film is attached to the electroplated board, and the required pattern is formed by exposure. Through weak alkaline solution development, the circuit pattern is formed on one side with BGA and the other side is covered with dry film, which can accurately replicate the design pattern and ensure the circuit Accuracy, and lay the foundation for subsequent etching, use chemical solutions to etch the exposed copper layer to form a circuit pattern. This step only processes the side with BGA, and the other side remains as a copper layer. Acid etching can efficiently remove the excess copper layer to form a clear circuit pattern, improve the conductivity and reliability of the circuit, print solder mask ink, pre-bake and cure, then expose and develop to expose the pad. The pad is normally exposed on one side with BGA, and no solder mask is applied on the other side. This can effectively prevent short circuits during welding and protect the circuit from damage. Print characters on the board and perform high-temperature curing, which enhances the readability and recognition of the PCB, makes it easier to maintain as a whole, and reduces the problem of increased maintenance costs due to greater maintenance difficulties.

[0019] Embodiment 2:

[0020] In this embodiment, the acid etching 2 process uses chemical solution to etch the exposed copper layer to form a circuit pattern. This process forms a circuit on the side without BGA, and the side with BGA is not etched due to the dry film covering. Figure 1 , Figure 8-Figure 13 In the technical solution shown, the external light imaging process 2 is to stick a dry film on the treated board again, and the required pattern is formed by exposure. The BGA area is revealed by development, and other pads are covered with dry film. The film stripping process uses alkaline chemical solution to remove the dry film to expose the copper layer and the solder mask layer. The external light imaging process is to stick a dry film on the board again, and the required pattern is formed by exposure. After development, the BGA area is fully covered with dry film, and a circuit pattern is formed on the other side. The acid etching process 2 uses chemical solution to etch the exposed copper layer to form a circuit pattern. This process forms a circuit on the side without BGA, and the side with BGA is not etched due to the coverage of dry film. The solder mask / character process 2 is to perform solder mask treatment on the other side, print solder mask ink, expose and develop after pre-baking and curing, expose the pads, print characters on the board and perform high-temperature curing, stick a dry film on the treated board again, and the required pattern is formed by exposure. The BGA area is revealed by development, and other pads are covered with dry film, which ensures accurate coverage of the BGA area again, providing reliable support for subsequent copper plating processes. The foundation is that no current is set on one side of the BGA, and a small current is set on the other side for normal electroplating to enhance the thickness of the BGA copper layer, improve thermal conductivity and electrical connection quality, and ensure component reliability. Alkaline chemical solutions are used to remove the dry film to expose the copper layer and solder mask layer, providing a good base for subsequent processes and ensuring good electrical connection. The dry film is pasted on the board again and exposed to form the required pattern. After development, the BGA area is fully covered with dry film, and a circuit pattern is formed on the other side to improve the accuracy and functionality of the circuit design. Chemical solutions are used to etch the exposed copper layer to form a circuit pattern. The circuit is formed on the side without BGA, and the side with BGA is not etched due to the dry film coverage. Through precise etching, the circuit pattern is clarified to ensure that the side without BGA is optimized. Solder mask treatment is performed on the other side, solder mask ink is printed, and exposure and development are performed after pre-baking and curing to expose the pad. Characters are printed on the board and high-temperature cured to improve the overall protection capability and increase the readability of the PCB to ensure the efficiency and accuracy of production.

[0021] Embodiment three:

[0022] In this embodiment, after the dry film is removed, solder mask and characters are applied to the other copper surface. By setting the current, the copper layer thickness in the BGA area is ensured to meet customer requirements, thereby avoiding the problem of being unable to set the current due to design limitations. Figure 1-Figure 13The technical solution shown in the figure makes the outer layer circuit on one side with BGA, and the whole board on the other side is copper layer, so that BGA and the other side are still connected without designing leads, solder mask / characters are made on the side with BGA, and then covered with dry film, the BGA window is leaked out, the other pads are covered with dry film, and the board is electroplated with copper, so that the copper layer of BGA will be higher than the solder mask layer, and no current is set on the side with BGA, and a small current is set on the copper side, because BGA and copper skin are a whole, although there is no designed current, a current loop can still be formed, so that the copper thickness of BGA meets customer needs. This can avoid the problem of being unable to set the current, reduce the difficulty of the overall processing, and greatly improve the overall processing efficiency. Then, the film is applied to etch out the circuit on the other side of the copper. After removing the dry film, the solder mask and characters are made on the other copper side. By setting the current, the copper layer thickness in the BGA area is ensured to meet customer requirements, avoiding the problem of being unable to set the current due to design limitations. In addition, by covering different areas with dry film, the etching process can be effectively controlled to ensure the accuracy of the circuit graphics. By printing solder mask ink and characters, the readability and functionality of the PCB can be enhanced to prevent short circuits during the welding process.

[0023] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a high-density circuit board in which a BGA copper layer is higher than a solder mask layer, comprising the following steps: pre-process - drilling - copper deposition - negative film electroplating - external light imaging - acid etching - solder mask / character - external light imaging 2 - copper plating - film stripping - external light imaging 3 - acid etching 2 - solder mask / character 2 - post-process; It is characterized in that Also includes: The negative electroplating process is used to electroplate the entire board to increase the copper thickness of the hole copper and the copper clad laminate; In the external light imaging process, a photosensitive dry film is pasted on the electroplated board, and the required pattern is formed by exposure. The circuit pattern is formed on one side with BGA and the other side is covered with dry film. The solder mask / character process is to print solder mask ink, pre-bake and cure it, then expose and develop it to expose the pad. In this process, only the pad is exposed normally on the side with BGA, and the other side is not solder masked. Characters are printed on the board and cured at high temperature. The copper plating process does not set current on one side of the BGA, and sets a small current on the other side for normal electroplating to enhance the thickness of the BGA copper layer.

2. The method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder mask layer according to claim 1, characterized in that: The drilling process uses a drilling machine to drill through holes of different diameters according to design data.

3. The method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder resist layer according to claim 1, characterized in that: The copper deposition process uses a chemical deposition method to metallize the hole wall to ensure the conductivity of the copper layer in the hole.

4. The method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder resist layer according to claim 1, characterized in that: The acid etching process uses chemical solutions to etch the exposed copper layer to form a circuit pattern. This process only processes one side of the BGA, and the other side remains as a copper layer.

5. The method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder resist layer according to claim 1, characterized in that: In the external light imaging step 2, a dry film is pasted on the processed board, exposed to form a desired pattern, the BGA area is revealed by development, and other pads are covered with the dry film.

6. The method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder resist layer according to claim 1, characterized in that: The film stripping process uses alkaline chemical solution to remove the dry film to expose the copper layer and the solder mask layer.

7. The method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder resist layer according to claim 1, characterized in that: The external light imaging process again sticks the dry film on the board, exposes it to form the required pattern, and completes it through development. The BGA area is fully covered with the dry film, and the circuit pattern is formed on the other side.

8. The method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder resist layer according to claim 1, characterized in that: The acid etching step 2 uses chemical solution to etch the exposed copper layer to form a circuit pattern. This step forms a circuit on the side without BGA, and the side with BGA is not etched due to the dry film covering.

9. The method for manufacturing a high-density circuit board in which the BGA copper layer is higher than the solder resist layer according to claim 1, characterized in that: The solder resist / character 2 process performs solder resist treatment on the other side, prints solder resist ink, pre-bakes and cures, then exposes and develops to expose the pads, prints characters on the board, and performs high-temperature curing.

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