Method for manufacturing high-precision circuit board with through-hole single-face hole ring

Abstract

The invention discloses a method for manufacturing a high-precision circuit board with a through hole single-surface hole ring, which comprises the following steps of: designing a hole ring pattern on one surface of the circuit board, drilling a through hole on a to-be-drilled circuit board of which the upper surface and the lower surface are light copper surfaces through a previous process, then carrying out flash plating to form a flash plating plate, manufacturing a dry film pattern on the first surface of the flash plating plate corresponding to the hole ring pattern, and forming a dry film pattern on the second surface of the flash plating plate; manufacturing a first through hole corresponding to the through hole in the second surface, and forming a pattern board, wherein the single side of the first through hole is smaller than the through hole; sequentially electroplating a copper layer and a tin layer on the pattern plate to form an electroplated plate; a dry film and a protective film of an electroplating plate are removed, etching is carried out, then a tin layer is removed, a circuit board is formed, a dry film pattern is adopted in the whole process, machining of an electroplating copper layer and an electroplating tin layer is matched, electroplating tin is used for protecting the electroplating copper layer, an ideal single-face hole ring structure is formed, front-back matching is tight, an efficient and reliable production chain is formed, polishing machining is avoided, and the production efficiency is improved. And the processing precision and the quality of the final circuit board are greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of circuit board manufacturing, and particularly to a method for manufacturing a high-precision circuit board with a through-hole single-sided pad ring. Background Art

[0002] For some high-precision circuit board products with a high wiring density, unnecessary pad rings are usually removed during design to increase more wiring space. This type of design is usually applied to high-precision circuit boards with single-sided pad ring through-holes.

[0003] Regarding the manufacturing method for such high-precision circuit boards with single-sided pad ring through-holes, generally, when manufacturing the circuit on the side without the designed pad ring, a dry film is used to protect the through-holes, and then the pad rings are etched away to form a pad-ring-free pattern, and then subsequent processes such as electroplating are carried out.

[0004] However, this method has the following defects: on the one hand, there are errors in the exposure alignment process during the pattern manufacturing process, which affects the etching accuracy of the pad ring and easily leads to problems such as etching deviation. On the other hand, the dry film in the through-hole is prone to falling off during etching, and it is difficult to effectively protect the copper layer on the inner wall of the through-hole, resulting in problems such as the copper in the hole being etched away.

[0005] Therefore, to solve the above-mentioned problems, a method for manufacturing a high-precision circuit board with a through-hole single-sided pad ring is provided. Summary of the Invention

[0006] The present invention aims to solve the comprehensive problems in the prior art when manufacturing a circuit board with a through-hole single-sided pad ring, such as etching deviation due to exposure errors and low processing accuracy caused by the easy etching and falling off of the dry film in the through-hole. A method for manufacturing a high-precision circuit board with a through-hole single-sided pad ring is proposed. One surface of the circuit board is designed with a pad ring pattern. The manufacturing method includes the following steps: S10: Take a copper clad laminate, perform pre-process machining to form a circuit board to be drilled with light copper surfaces on both the upper and lower sides, drill through-holes, and then flash electroplate to form a flash electroplated board; S20: Stick a dry film on the first surface of the flash electroplated board, and make a dry film pattern corresponding to the pad ring pattern. Stick a protective film on the second surface, and make a first through-hole corresponding to the through-hole. The single side of the first through-hole is smaller than the through-hole to form a pattern board; S30: Electroplate a copper layer and an electroplated tin layer on the pattern board in sequence to form an electroplated board; S40: Remove the dry film and the protective film of the electroplated board, then etch, and then strip the tin layer to form the circuit board.

[0007] Further, the flash electroplating is to electroplate with a current density of 3 ASF to 8 ASF for 20 min to 30 min to form a copper thickness of 3 μm to 8 μm.

[0008] Furthermore, the graphic board is fabricated by attaching dry film to both the first surface and the second surface of the flash plating board, fabricating a dry film pattern at the position corresponding to the pad ring pattern on the first surface, fabricating a first through hole at the position corresponding to the via hole on the second surface, with the single side of the first through hole being smaller than that of the via hole, thereby forming the graphic board.

[0009] Furthermore, the dry film is removed by means of stripping.

[0010] Furthermore, the graphic board is fabricated by attaching dry film to the first surface of the flash plating board, fabricating a dry film pattern at the position corresponding to the pad ring pattern on the first surface, then attaching a PET adhesive film, a PP adhesive film, an acrylic adhesive film, a polyimide adhesive film, an epoxy resin adhesive film or a blue tape to the second surface, and fabricating a first through hole corresponding to the via hole, with the single side of the first through hole being smaller than that of the via hole, thereby forming the graphic board.

[0011] Furthermore, the protective film is removed by means of tearing or alkali washing.

[0012] Furthermore, the first through hole and the via hole share the same hole center, and the diameter of the first through hole is 1 / 3 to 1 / 2 smaller than that of the via hole.

[0013] Furthermore, the first through hole is fabricated by means of laser ablation.

[0014] Furthermore, the copper plating layer is electroplated with a copper thickness 3 μm to 8 μm more than the designed completed copper thickness for the graphic board; forming the circuit board further includes, after stripping the tin layer, performing micro-etching.

[0015] Furthermore, the micro-etching is to etch away a copper thickness of 3 μm to 8 μm.

[0016] The technical solution of the present invention compensates for the exposure error by pasting a protective film on the second side without a hole ring design, making a first through-hole corresponding to the through-hole, and the diameter of the first through-hole is smaller than that of the through-hole, ensuring that the edge of the hole wall is completely covered. It can also effectively prevent the copper layer from depositing on the edge of the dry film or even higher than the board surface during the electroplating process. This not only simplifies the post-treatment and planarization operations but also reduces the occurrence probability of quality problems such as short circuits. It solves the problems in the prior art that during the graphic production, there are errors in the exposure alignment process, affecting the etching accuracy of the hole ring and easily causing etching deviation. By plating a tin layer on the electroplated copper layer to form a protection for the copper layer, it solves the problems in the prior art that the dry film is easy to fall off during etching, resulting in the copper in the hole being etched away. The overall process uses a dry film pattern, combined with the processing of the electroplated copper layer and the electroplated tin layer, and uses electroplated tin to protect the electroplated copper layer. This can ensure that the electroplating process only occurs on the hole ring pattern and the inner wall of the through-hole, thus forming an ideal single-sided hole ring structure and achieving the effect of high-precision processing. The front and back cooperate closely to form an efficient and reliable production chain, avoiding the large impact of grinding processing on the expansion and contraction of the board, and greatly improving the processing accuracy, first-pass qualification rate, and the quality of the final circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0018] Figure 1 It is a schematic process flow diagram of the implementation manner of the present invention; Figure 2 It is a cross-sectional view of the flash plating board of the implementation manner of the present invention; Figure 3 It is a cross-sectional view of the graphic board of the implementation manner of the present invention; Figure 4 For Figure 3 the plan view; Figure 5 It is a cross-sectional view of the electroplated board of the implementation manner of the present invention; Figure 6 It is a cross-sectional view of the stripping board of the implementation manner of the present invention; Figure 7 It is a cross-sectional view of the high-precision circuit board with a through-hole single-sided hole ring of the present implementation manner.

[0019] Explanation of the reference numerals in the drawings:

[0020] The realization, functional features and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] It should be noted that all directional indications (such as up, down, left, right, front, back, inside, outside, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0023] In addition, the descriptions such as "first" and "second" in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0024] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0025] Please refer to Figure 1 , Figure 1 which is a schematic process flow diagram of the implementation manner of the present invention.

[0026] One surface of the circuit board in the implementation manner of the present invention is designed with a hole ring pattern, and the manufacturing method includes using Figure 1 each step process in Figure 1 to achieve, and the following will further explain each step process in

[0027] Please refer to Figure 2 , Figure 2 which is a cross-sectional schematic diagram of the flash plating board in the implementation manner of the present invention.

[0028] Step S10: Take a copper clad laminate, process it through the front processes to form a circuit board to be drilled with shiny copper surfaces on both the upper and lower sides, drill through holes 1010, and then flash plate to form a flash plated board 10; The flash plating process after drilling through holes is to form a very thin and uniform conductive metal layer 1020 on the inner wall of the through holes, providing a conductive path for the subsequent electroplating process, enabling current to pass through the interior of the through holes, thereby allowing copper layers to deposit on the hole walls.

[0029] Furthermore, the flash plating is carried out by electroplating at a current density of 3 ASF to 8 ASF for 20 min to 30 min to form a copper thickness of 3 μm to 8 μm, controlling the thickness of the conductive metal layer 1020 between 3 μm and 8 μm. This can not only ensure good conductivity but also avoid unnecessary costs and processing complexities due to excessive copper thickness.

[0030] Since the current density directly affects the quality of the conductive metal layer 1020, a lower current density (such as 3 ASF) usually produces a finer, more uniform and less stressed coating, while a higher current density (such as 8 ASF) may lead to a faster deposition rate but also increases defects such as roughness, resulting in a decrease in the quality of the conductive metal layer 1020. Therefore, in this embodiment, a current density of 3 ASF to 8 ASF is selected and further controlled within a time of 20 min to 30 min, which can effectively ensure the rapid and efficient formation of a uniform and thin conductive metal layer 1020, ensuring good conductivity and the feasibility of subsequent processing, providing a processing basis for the subsequent processes.

[0031] Please refer to Figure 3 and Figure 4 , Figure 3 which is a cross-sectional schematic diagram of the graphic board according to the embodiment of the present invention; Figure 4 is Figure 3 a planar schematic diagram of

[0032] Step S20: Apply a dry film 2030 to the first side of the flash plated board, and make a dry film pattern 2010 corresponding to the hole ring pattern. Apply a protective film 2040 to the second side and make a first through hole 2020 corresponding to the through hole. The single side of the first through hole 2020 is smaller than the through hole 1010 to form a graphic board 20.

[0033] Making the dry film pattern 2010 is a process of applying a dry film, exposing and developing.

[0034] As an alternative implementation, the dry film 2030 is closely attached to the first surface of the flash plating board 10, and then using laser direct imaging (LDI) technology, the hole ring pattern to be retained is exposed onto the dry film 2030. After that, the unexposed part of the dry film 2030 is removed through the developing process, leaving the corresponding hole ring pattern. This step ensures that only the hole rings and their hole walls of the through holes 1010 will be plated with a metal layer during subsequent electroplating processing.

[0035] As an alternative implementation, it is also possible to cover the dry film 2030 that has been attached well with a film and put it into an exposure machine for exposure. After that, the unexposed part of the dry film 2030 is removed through the developing process, leaving the corresponding hole ring pattern.

[0036] Then, a protective film 2040 is covered on the second surface of the flash plating board 10. In order to maintain the chemical balance in the electroplating tank and ensure the electroplating quality, the electroplating solution needs to be replaced or supplemented regularly, and a first through hole 2020 is made corresponding to the through hole 1010 to form a flow channel for the electroplating solution, ensuring that the electroplating solution can smoothly enter and exit the through hole to achieve smooth exchange of the solution, which is beneficial to forming a good coating on the inner wall of the through hole 1010.

[0037] The key to this step is that the first through hole 2020 and the through hole 1010 have the same hole center. The diameter of the first through hole 2020 is 1 / 3 to 1 / 2 smaller than the diameter of the through hole 1010, or it can also be 10 μm to 35 μm smaller on one side. On the one hand, it is to compensate for the exposure error. Due to a certain error in the exposure accuracy, the dry film 2030 or the protective film 2040 covering the surface forms a structure that extends into the hole by a part, making up for the possible position error during the exposure process and ensuring that the edge of the hole wall is fully covered. On the other hand, when electroplating copper, if the dry film 2030 or the protective film 2040 is designed exactly according to the actual size of the through hole 1010, then during the electroplating process, copper may deposit on the edge of the dry film 2030 or even higher than the board surface. The deposited excess copper will be difficult to remove in subsequent processing. Therefore, making the diameter of the first through hole 2020 smaller than the diameter of the through hole 1010 can limit the height of the electroplated copper layer and reduce the amount of copper above the board surface, facilitating the processing and planarization operations in the subsequent processes.

[0038] In one implementation, the protective film 2040 is also a dry film. When manufacturing the pattern board 20, dry films 2030 are attached to both the first surface and the second surface of the flash plating board 10, and a dry film pattern 2010 is made at the position corresponding to the hole ring pattern on the first surface, and a first through hole 2020 is made at the position corresponding to the through hole 1010 on the second surface. The first through hole 2020 is smaller than the through hole 1010 on one side to form the pattern board 20.

[0039] Further, when removing the dry film 2030 in the post-process by stripping, it is gentler than mechanical peeling and is not likely to cause microcracks or other forms of physical damage, which can avoid damaging the already formed circuit pattern and is conducive to maintaining the overall quality and reliability of the circuit board.

[0040] In one embodiment, the protective film 2040 is an insulating and corrosion-resistant protective film layer such as blue tape. When manufacturing the pattern board 20, the dry film 2030 is pasted on the first side of the flash plating board 10, and a dry film pattern 2010 is made at the position corresponding to the hole ring pattern on the first side. Then, a PET film, PP film, acrylic film, polyimide film, epoxy resin film or blue tape is pasted on the second side, and a first through hole 2020 is made corresponding to the through hole. The unilateral dimension of the first through hole 2020 is smaller than that of the through hole 1010 to form the pattern board 20. The thickness of the protective film 2040 is optionally 10 μm to 100 μm.

[0041] Further, when manufacturing the first through hole 2020 by laser ablation, when the protective film is a PET film, PP film, acrylic film, polyimide film, epoxy resin film or blue tape, it is impossible to make the protective film pattern by exposure and development. Therefore, it is preferably processed by laser ablation. Using a laser beam with a high energy density, the material is locally heated to the evaporation temperature within a short time to form ablation, thereby forming the first through hole 2020, which is suitable for manufacturing the first through hole 2020 with high precision and small size. Optionally, when the protective film 2040 is a dry film, it can also be processed by laser ablation.

[0042] Further, when removing the protective film 2040 in the post-process, it is processed by tearing or alkali washing.

[0043] Please refer to Figure 5 , Figure 5 which is a cross-sectional schematic diagram of the electroplated board according to the embodiment of the present invention.

[0044] Step S30: The pattern board 20 is electroplated with a copper layer 3010 and a tin layer 3020 in sequence to form an electroplated board 30.

[0045] The function of the tin layer 3020 is to protect the copper layer from being etched in the subsequent etching step. The thickness of the tin layer 3020 in this embodiment is 2 μm to 10 μm, preferably 5 μm.

[0046] Furthermore, the electroplated copper layer 3010 is electroplated with 3 μm to 8 μm more copper than the designed copper thickness of the pattern board 20, providing sufficient copper layer margin for subsequent processes, compensating for the inevitable copper layer loss during the micro-etching process of the subsequent processes, and ensuring that the copper thickness provided by the final circuit board meets the design requirements. Generally, the copper thickness of the hole wall formed by electroplating is 15 μm to 35 μm. In this embodiment, the copper thickness of the hole wall formed by electroplating copper reaches 18 μm to 43 μm.

[0047] Please refer to Figure 6 and Figure 7 , Figure 6 which is a cross-sectional schematic diagram of the stripping board of the embodiment of the present invention; Figure 7 which is a cross-sectional schematic diagram of the high-precision circuit board with a through-hole single-sided pad ring of this embodiment.

[0048] Step S40: Remove the dry film 2030 and the protective film 2040 of the electroplated board 30 to form a stripping board 40, then etch, and then strip the tin layer 3020 to perform micro-etching processing to form a high-precision circuit board 50 with a through-hole single-sided pad ring.

[0049] Furthermore, the micro-etching is to etch off 3 μm to 8 μm of copper thickness, that is, after stripping the tin layer 3020, use the method of chemical etching to remove 3 μm to 8 μm of copper thickness, which forms a cooperation with the electroplated copper thickness of 3 μm to 8 μm more in the previous process. This not only helps to adjust to the required final copper layer 3010 thickness, but also can trim the pad ring pattern, remove defective copper layers such as burrs and flash on the hole edge, remove oxides and other impurities, and enhance the welding performance and reliability of the circuit board.

[0050] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing a high-precision circuit board with a through-hole single-side hole ring, wherein one surface of the circuit board is designed with a hole ring pattern, characterized in that: The production method comprises the following steps: S10: taking a copper-clad board, and processing it through the previous process to form a circuit board to be drilled with the upper and lower surfaces being bare copper surfaces, drilling through holes, and then flash plating to form a flash-plated board; S20: applying a dry film to the first surface of the flash plate, and making a dry film pattern corresponding to the hole ring pattern, A protective film is attached to the second surface, and a first through hole is made corresponding to the through hole, wherein one side of the first through hole is smaller than the through hole, so as to form a graphic board; S30: electroplating a copper layer and a tin layer on the graphic board in sequence to form an electroplated board; S40: removing the dry film and the protective film of the electroplating board, etching, and then removing the tin layer to form the circuit board.

2. The method for manufacturing a high-precision circuit board with a through-hole single-sided ring as claimed in claim 1, characterized in that: The flash plating is to use a current density of 3ASF to 8ASF for electroplating for 20 minutes to 30 minutes to form a copper thickness of 3μm to 8μm.

3. The method for manufacturing a high-precision circuit board of a through-hole single-sided ring according to claim 1, characterized in that: The graphic board is manufactured by affixing dry film to both the first surface and the second surface of the flash plated board, and manufacturing the dry film pattern at the position of the hole ring pattern corresponding to the first surface, and manufacturing the first through hole at the position of the through hole corresponding to the second surface, wherein one side of the first through hole is smaller than the through hole, thereby forming the graphic board.

4. The method for manufacturing a high-precision circuit board of a through-hole single-sided ring according to claim 3, characterized in that: The dry film is removed by using a film stripping method.

5. The method for manufacturing a high-precision circuit board of a through-hole single-sided ring according to claim 1, characterized in that: The graphic board is manufactured by affixing the dry film to the first surface of the flash-plated board, and manufacturing the dry film pattern at the position of the first surface corresponding to the hole ring pattern, and then affixing PET film, PP film, acrylic film, polyimide film, epoxy resin film or blue tape to the second surface, and manufacturing the first through hole corresponding to the through hole, wherein one side of the first through hole is smaller than the through hole, to form the graphic board.

6. A method for manufacturing a high-precision circuit board according to claim 1 or 5, characterized in that: The protective film is removed by tearing off or alkali washing.

7. A method for manufacturing a high-precision circuit board according to claim 1 or 3, characterized in that: The first through hole and the through hole have the same hole center, and the diameter of the first through hole is 1 / 3 to 1 / 2 smaller than the diameter of the through hole.

8. A method for manufacturing a high-precision circuit board with a through-hole single-sided ring as claimed in claim 1 or 5, characterized in that: The first through hole is made by laser ablation.

9. A method for manufacturing a high-precision circuit board according to claim 1 or 3, characterized in that: The electroplated copper layer is electroplated with a thickness of 3 μm to 8 μm thick on the graphic board according to the design; Forming the circuit board also includes, after removing the tin layer, performing micro-etching.

10. The method for manufacturing a high-precision circuit board of a through-hole single-sided ring according to claim 9, characterized in that: The micro-etching is to etch away copper with a thickness of 3 μm to 8 μm.

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