Circuit board acid etching ring-hole-free manufacturing method

Abstract

The invention relates to the field of circuit board production, in particular to a circuit board acid etching ring-hole-free manufacturing method. According to the method, copper on the hole wall of a via hole is thickened to meet the copper thickness design requirement, then a circuit and a hole ring of the via hole are etched through acid etching, then a tin protection layer is plated on the hole wall of the via hole, then the hole ring is independently etched away, tin is removed, and the PCB without the ring hole after acid etching is obtained. According to the method, a required circuit and an attached hole ring are etched through acid etching, hole wall copper is protected by a tin protection layer, the hole ring is etched off, and a ring-free hole is obtained; and the circuit requirement of acid etching can be met, and the design requirement of no ring hole can also be met.

Description

Technical Field

[0001] The invention relates to the field of circuit board production, and in particular to a method for manufacturing a circuit board acid-etched ring-free hole. Background Art

[0002] At present, there are two production methods for etching circuits in the production of circuit boards, namely acid etching and alkaline etching. Among them, acid etching is to cover the drilled and electroplated circuit board with dry film. After wrapping and development, the dry film covers the circuits and vias that need to retain copper for conductivity. Since the via holes are hollow, in order to support and cover the via holes, the diameter of the dry film covering the via holes must be larger than the diameter of the via holes to prevent the dry film from sinking. In this way, when the etching is completed and the film is withdrawn, a circle of hole rings will be formed at the opening of the via hole, also called a solder ring, that is, the existing acid etching method will inevitably form a hole ring at the opening of the via hole.

[0003] However, in some customers' designs, some vias do not require annular rings, such as single solder ring holes, and due to special circuit designs (special line width, line spacing, and copper thickness), such PCB boards without annular rings can only be produced by etching the circuits using acid etching, and cannot be etched using alkaline etching. This results in the existing acid etching method being unable to meet the production requirements of such PCB boards without annular rings, and a method for producing PCB boards without annular rings using acid etching is required. Summary of the invention

[0004] In order to overcome the above problems, the present invention provides a method for manufacturing a circuit board acid-etched ring-free hole. The technical solution adopted by the present invention to solve the technical problem is:

[0005] A method for manufacturing a circuit board acid-etched ring-free hole comprises the following steps:

[0006] Step S1: providing a PCB board after drilling, and forming a copper layer on the hole wall of the via hole of the PCB board by copper deposition;

[0007] Step S2: performing film lamination, exposure and development processing on the PCB board after copper deposition, covering the PCB board with dry film, opening a window of dry film just above the via hole, and covering other positions with dry film;

[0008] Step S3: electroplating the PCB after step S2 to increase the copper thickness of the via hole wall; then removing the dry film on the PCB through a film stripping process;

[0009] Step S4: The PCB board after step S3 is subjected to film lamination, exposure and development again, the via holes and circuits are covered with dry film, and windows are opened in other locations of the dry film;

[0010] Step S5: Acid etching is performed on the PCB board after step S4 to form circuits and prefabricated hole rings for via holes; then the dry film on the PCB board is removed by a film stripping process;

[0011] Step S6: The PCB board after step S5 is subjected to film lamination, exposure and development again, a window is opened on the dry film directly above the via hole, and other positions are covered with dry film;

[0012] Step S7: tinning the PCB after step S6, so that the via hole wall is covered with a tin protective layer; then, the dry film on the PCB is removed through a film stripping process;

[0013] Step S8: The PCB board after step S7 is subjected to film lamination, exposure and development again, and windows are opened in the dry film just above the via hole and the prefabricated hole ring of the via hole, and other positions are covered with dry film;

[0014] Step S9: etching the PCB after step S8 to remove the prefabricated hole ring of the via hole, and then removing the dry film and the tin protective layer on the hole wall through film stripping and tin stripping processes to obtain a ring-free hole.

[0015] Furthermore, the step S2 also includes a ceramic grinding process, in which the via holes are subjected to ceramic grinding after the film is removed to grind off the convex points at the openings of the via holes.

[0016] Furthermore, the step S5 also includes a first outer layer etching inspection process, in which the PCB board after film stripping is optically inspected to detect whether there are open or short circuits in the circuit.

[0017] Furthermore, the step S9 also includes a second outer layer etching inspection process, in which the PCB board after film and tin stripping is optically inspected to detect whether the prefabricated hole ring is completely etched away.

[0018] Furthermore, in step S2, the diameter of the dry film window is less than or equal to the diameter of the via hole.

[0019] Furthermore, in step S6, the diameter of the dry film window is less than or equal to the diameter of the via hole.

[0020] Furthermore, in step S9, the etching process uses an etching solution that can etch the hole ring without damaging the tin protective layer on the wall of the via hole.

[0021] Furthermore, the diameter of the prefabricated hole ring is 10mil-20mil larger than the diameter of the conducting hole.

[0022] The beneficial effects of the present invention are:

[0023] This method first thickens the copper of the via hole wall to meet the copper thickness design requirement, then etches out the circuit and the via hole ring by acid etching, then plates a tin protective layer on the via hole wall, then etches out the via ring separately, and strips the tin to obtain a PCB board with an acid-etched ringless hole; This method first etches out the required circuit and the accompanying via ring by acid etching, then protects the hole wall copper with a tin protective layer, and then etches out the via ring to obtain a ringless hole; It can meet both the circuit requirements of acid etching and the design requirements of the ringless hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, wherein:

[0025] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0026] In order to better understand the purpose, structure and function of the present invention, the specific embodiment of the present invention "a method for making a circuit board acid etching ring-free hole" is further described in detail below in conjunction with the accompanying drawings.

[0027] See also Figure 1 In this embodiment, the manufacturing method of the present invention comprises the following steps:

[0028] Step S1: providing a PCB board after drilling, and forming a copper layer on the surface of the PCB board and the hole wall of the through hole by copper deposition, so that copper ions can be attached by subsequent electroplating.

[0029] Step S2: the PCB board after copper deposition is subjected to film lamination, exposure and development treatment. The film lamination is for the whole board. The exposure is to irradiate the part that needs to be covered by the dry film with X-rays, so that the dry film in this area undergoes a photochemical reaction. The reacted dry film will not be washed off in the development stage. The dry film in the area not irradiated by light will be removed in the development stage, thereby forming a dry film window. In this step, the dry film directly on the conductive hole of the PCB board undergoes a photochemical reaction without being exposed to light, and a dry film window is formed after development. The dry film at other positions of the PCB board undergoes a photochemical reaction when exposed to light. The dry film after the photochemical reaction cannot be removed by development, and these positions are covered by the dry film to play a role of isolation and protection.

[0030] Step S3: Electroplating the PCB after step S2. Since other positions are covered by dry film, copper will not be plated. In this process, only the via hole wall with dry film opening is plated with copper, and the copper thickness of the via hole wall is thickened to reach the copper thickness required by the design. After that, the whole board is removed by the film stripping process to remove the remaining photochemically reacted dry film on the PCB for subsequent operations.

[0031] Step S4: The PCB board after step S3 is subjected to film lamination, exposure and development again. The principle is the same as that in step S2: the film lamination is for the whole board, and the exposure is to use X-rays to irradiate the part that needs to be covered by the dry film so that the dry film in this area undergoes a photochemical reaction. The reacted dry film will not be washed off in the development stage. The dry film in the area not irradiated by light will be removed in the development stage to form a dry film window. In this step, the dry film after the photochemical reaction will be covered on the via hole and the required circuit to protect these areas. The dry film in other positions does not undergo a photochemical reaction, and the dry film in these areas is removed by development to form a dry film window so that the copper in these areas can be etched away later.

[0032] Step S5: Acid etching is performed on the PCB board after step S4 to etch away the copper in the area not covered and protected by the dry film, and then etching forms the circuit and the prefabricated hole ring surrounding the via hole; then the whole board is subjected to the film stripping process to remove the remaining dry film on the PCB board that has undergone photochemical reaction, so as to facilitate subsequent operations.

[0033] Step S6: the PCB board after step S5 is subjected to film lamination, exposure and development again, and the principle is the same as that in step S2: the film lamination is for the whole board, and the exposure is to use X-rays to irradiate the part that needs to be covered by the dry film so that the dry film in this area undergoes a photochemical reaction, and the reacted dry film will not be washed off in the development stage. The dry film in the area not irradiated by light will be removed in the development stage, thereby forming a dry film window; in this step, the dry film directly above the via hole of the PCB board is not photochemically reacted and is removed by development to form a dry film window to expose the via hole, and the dry film at other positions of the PCB board undergoes a photochemical reaction, and the development cannot remove this part of the dry film, so the dry film is kept covered to form a protective layer.

[0034] Step S7: Tin-plating the PCB after step S6 so that the via hole walls are covered with a tin protective layer; then, a film stripping process is performed to remove the remaining dry film on the PCB that has undergone photochemical reaction.

[0035] Step S8: The PCB board after step S7 is subjected to film lamination, exposure and development again, and the principle is the same as that in step S2; in this step, the dry film directly above the via hole of the PCB board and the prefabricated hole ring of the via hole is not photochemically reacted and is removed by development to form a dry film opening, and the dry film at other positions of the PCB board undergoes photochemical reaction, and the development cannot remove this part of the dry film, so the dry film is kept covered to form a protective layer.

[0036] Step S9: etching the PCB board after step S8. The etching solution used here is different from the acid etching solution. It will etch away copper without reacting with the tin protective layer, so as to achieve the purpose of etching away only the prefabricated hole ring of the via hole. Preferably, the etching process in this step is carried out in an alkaline etching process, and the alkaline etching solution is used to etch away the prefabricated hole ring; then the remaining dry film on the PCB board that has undergone photochemical reaction and the tin protective layer on the wall of the via hole are removed respectively through the film stripping and tin stripping processes, so as to obtain a PCB board with acid-etched circuits and ring-free holes.

[0037] Furthermore, in this embodiment, step S2 also includes a ceramic grinding process, in which the conductive holes are subjected to ceramic grinding after the film is removed to grind off the protrusions at the openings of the conductive holes so as to ensure the smoothness of the subsequent film application.

[0038] Furthermore, in the present embodiment, the step S5 also includes a first outer layer etching inspection process, in which the PCB board after film stripping is optically inspected to detect whether the circuit has an open short circuit; in step S9, a second outer layer etching inspection process is also included, in which the PCB board after film stripping and tin stripping is optically inspected to detect whether the prefabricated hole ring is completely etched away to meet the requirement of ring-free hole.

[0039] Furthermore, in this embodiment, the diameter of the dry film window in step S2 is less than or equal to the diameter of the via hole, so as to ensure that only the copper thickness of the hole wall of the via hole increases, and copper will not be plated around the hole opening of the via hole; the diameter of the dry film window in step S6 is less than or equal to the diameter of the via hole, so as to ensure that the tin protective layer is only plated on the hole wall of the via hole, and the tin protective layer is not plated around the hole opening of the via hole.

[0040] It should be noted that, in the present embodiment, the diameter of the prefabricated hole ring is 10mil-20mil larger than the diameter of the conductive hole, and is greater than or equal to 10mil. This makes it convenient to design the exposure film of the prefabricated hole ring and ensures that the gripping force is large enough when the dry film covers the conductive hole. It is less than or equal to 20mil, so that the prefabricated hole ring will not be too large to occupy the wiring space.

[0041] The method of the invention first etches out the required circuit and the accompanying hole ring by acid etching, then protects the hole wall copper with a tin protective layer, and then etches out the hole ring to obtain the ring-free hole; the method can meet both the circuit requirements of acid etching and the design requirements of the ring-free hole; and solves the problem that some circuit boards with ring-free holes of special circuit designs cannot be produced.

[0042] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

[0043] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

Claims

1. A method for producing a circuit board acid-etched ring-free hole, characterized in that: The steps include: Step S1: providing a PCB board after drilling, and forming a copper layer on the hole wall of the via hole of the PCB board by copper deposition; Step S2: performing film lamination, exposure and development processing on the PCB board after copper deposition, covering the PCB board with dry film, opening a window of dry film just above the via hole, and covering other positions with dry film; Step S3: electroplating the PCB after step S2 to increase the copper thickness of the via hole wall; then removing the dry film on the PCB through a film stripping process; Step S4: The PCB board after step S3 is subjected to film lamination, exposure and development again, the via holes and circuits are covered with dry film, and windows are opened in other locations of the dry film; Step S5: Acid etching is performed on the PCB board after step S4 to form circuits and prefabricated hole rings for via holes; then the dry film on the PCB board is removed by a film stripping process; Step S6: The PCB board after step S5 is subjected to film lamination, exposure and development again, a window is opened on the dry film directly above the via hole, and other positions are covered with dry film; Step S7: tinning the PCB after step S6, so that the via hole wall is covered with a tin protective layer; then, the dry film on the PCB is removed through a film stripping process; Step S8: The PCB board after step S7 is subjected to film lamination, exposure and development again, and windows are opened in the dry film just above the via hole and the prefabricated hole ring of the via hole, and other positions are covered with dry film; Step S9: etching the PCB after step S8 to remove the prefabricated hole ring of the via hole, and then removing the dry film and the tin protective layer on the hole wall through film stripping and tin stripping processes to obtain a ring-free hole.

2. A method for producing a circuit board acid-etched ring-free hole according to claim 1, characterized in that: The step S2 also includes a ceramic grinding process, in which the via holes are subjected to ceramic grinding after the film is removed to grind off the convex points at the openings of the via holes.

3. A method for producing a circuit board acid-etched ring-free hole according to claim 2, characterized in that: The step S5 also includes a first outer layer etching inspection process, in which the PCB board after film stripping is optically inspected to detect whether there are open or short circuits in the circuit.

4. A method for producing a circuit board acid-etched ring-free hole according to claim 3, characterized in that: The step S9 also includes a second outer layer etching inspection process, in which the PCB board after film and tin stripping is optically inspected to detect whether the prefabricated hole ring is completely etched away.

5. The method for producing a circuit board acid-etched ring-free hole according to claim 1, characterized in that: In the step S2, the diameter of the dry film window is less than or equal to the diameter of the via hole.

6. A method for producing a circuit board acid-etched ring-free hole according to claim 5, characterized in that: In the step S6, the diameter of the dry film window is smaller than or equal to the diameter of the via hole.

7. The method for producing a circuit board acid-etched ring-free hole according to claim 1, characterized in that: In the step S9, the etching process uses an etching solution that can etch the hole ring without damaging the tin protective layer on the wall of the conductive hole.

8. A method for producing a circuit board acid-etched ring-free hole according to any one of claims 1 to 7, characterized in that: The diameter of the prefabricated hole ring is 10 mil-20 mil larger than the diameter of the through hole.

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