A method for manufacturing a blind via circuit board

Abstract

The application relates to a manufacturing method of a blind slot circuit board, wherein after a pattern on a top layer of a second sub-board is manufactured, a reserved copper sheet exists in a blind slot pattern area besides a circuit, the reserved copper sheet can reduce the area of a non-copper area, so that a half-cured sheet cannot flow into the non-copper area in large quantity during pressing, the thickness of the cured sheet between the two sub-boards after pressing can be improved, the board can be prevented from being exploded, the reserved copper sheet is etched off after the blind slot is milled, the total board is uniformly stressed during pressing and subsequent processes after pressing, the board surface is not prone to warping, and the yield of products is improved; and in the method, the first sub-board bottom layer and the second sub-board top layer are covered with PI films, the circuit in the blind slot pattern area can be effectively protected during milling, and the circuit is prevented from being scratched due to an uncontrolled milling depth.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of circuit board, in particular to a manufacturing method of blind slot circuit board. BACKGROUND

[0002] The blind slot circuit board (Blind Slot PCB) generally refers to a circuit board with a blind slot (Blind Slot) structure in the design and processing of printed circuit board (PCB). Its characteristics are to use a partially through slot hole for realizing specific assembly, insulation or structural requirements; the blind slot is not a full-through slot of the PCB, but only a slot from one side or a specific layer, and the slot bottom stops at a certain layer of copper or board material, the blind slot is only opened to a specified depth for specific functions, such as local wiring isolation, shape positioning, etc.

[0003] Taking a four-layer board composed of two core boards as an example, the blind slot penetrates L1 and L2 layers and exposes L3 layer, the existing blind slot manufacturing method is to first complete the inner layer pattern of the two core boards, and only keep the circuit in the area below the blind slot of L3 layer, etch off all copper skins, then hollow out the semi-cured sheet corresponding to the blind slot area, the semi-cured sheet is clamped between the two core boards, then the pressing is performed, and then the other subsequent processes are normally completed, and then the blind slot is milled from L1 layer from top to bottom by numerical control milling or laser processing, and the circuit in the area below the blind slot of L3 layer is exposed.

[0004] However, the current method has two disadvantages, first, when it is a large-area blind slot, the area below the blind slot of L3 layer only keeps the circuit, and the copper skin is etched off, which will have a large area of copper-free area, so that the semi-cured sheet melts and flows into the copper-free area during the subsequent pressing, which reduces the thickness of the cured sheet for the bonding between the two core boards, and the board is easily separated in the subsequent process, and the large area of copper-free area will cause uneven stress during pressing, and the board surface of the pressed circuit board is easily bent. Secondly, directly controlling the depth of milling / laser washing blind slot is easy to damage the circuit in the area below the blind slot of L3 layer, which causes scratches. SUMMARY

[0005] In order to overcome the above problems, the present application provides a manufacturing method of blind slot circuit board, and the technical scheme adopted by the present application to solve the technical problems is:

[0006] A manufacturing method of blind slot circuit board, comprising the following steps:

[0007] Step S1: providing a circuit board sub-board, completing the bottom layer pattern of the sub-board to obtain a first sub-board; the first sub-board has a blind slot milling area, and a PI film is covered on the blind slot milling area of the bottom layer of the first sub-board;

[0008] Step S2: providing a circuit board sub-board, the sub-board being provided with a top layer pattern, the top layer pattern having a blind slot pattern area, the blind slot pattern area including a circuit and a reserved copper skin, to obtain a second sub-board;

[0009] Step S3: plating gold on the circuit of the blind slot pattern area of the second sub-board;

[0010] Step S4: obtaining the second sub-board after step S3, and covering the blind slot pattern area of the top layer of the second sub-board with a PI film;

[0011] Step S5: providing a prepreg, the prepreg having a blind slot hollow area;

[0012] Step S6: stacking the first sub-board, the prepreg and the second sub-board from top to bottom, and waiting for the blind slot area, the blind slot hollow area and the blind slot pattern area to be aligned; pressing the stacked circuit board to obtain a pressed total board;

[0013] Step S7: drilling, electroplating and manufacturing an outer layer pattern for the pressed total board; pasting a dry film on the entire surface of the pressed total board, and exposing the to-be-milled blind slot area of the top layer of the first sub-board; milling the blind slot from top to bottom in the to-be-milled blind slot area of the top layer of the first sub-board, the depth of the blind slot reaching the PI film of the bottom layer of the first sub-board; and then removing the PI film covering the to-be-milled blind slot area of the bottom layer of the first sub-board and the PI film covering the blind slot pattern area of the top layer of the second sub-board from the blind slot;

[0014] Step S8: etching away the reserved copper skin of the blind slot pattern area, and removing the dry film to obtain a blind slot circuit board.

[0015] Further, in step S1, the PI film is first covered on the entire surface of the bottom layer of the first sub-board, and then the PI film in the non-to-be-milled blind slot area is removed by laser cutting.

[0016] Further, in step S2, the distance from the reserved copper skin to the circuit is greater than or equal to 2 mm.

[0017] Further, in step S3, the dry film is first pasted on the entire surface of the second sub-board, then the dry film in all areas except the circuit of the blind slot pattern area is solidified by light, then the dry film on the circuit of the blind slot pattern area is removed by a chemical method to expose the circuit of the blind slot pattern area, then the second sub-board is plated with gold to plate gold on the circuit of the blind slot pattern area, and then the dry film on the second sub-board is removed.

[0018] Further, in step S4, the PI film is first covered on the entire surface of the top layer of the second sub-board, and then the PI film in the non-blind slot pattern area is removed by laser cutting.

[0019] Further, the number of layers of the first sub-board is greater than or equal to two, and the first sub-board is a circuit board with an inner layer pattern.

[0020] Further, the second sub-board has more than or equal to two layers of sub-boards, and the second sub-board is a circuit board with inner layer patterns.

[0021] Further, the step S8 further includes conventional outer layer pattern detection, solder mask, surface treatment, molding and electrical testing processes.

[0022] The present application has the following advantages:

[0023] The manufacturing method of the blind slot circuit board, after the top layer pattern of the second sub-board is manufactured, the blind slot pattern area has a reserved copper skin in addition to the circuit, the reserved copper skin can reduce the area of the copper-free area, so that the semi-cured sheet will not flow into the copper-free area during pressing, the thickness of the cured sheet between the two sub-boards after pressing can be improved, and the board can be prevented from exploding; and the reserved copper skin is etched off after the blind slot is milled, so that the total board is uniformly stressed during pressing and subsequent processes after pressing, and the board surface is not easy to warp, improving the yield of the product; and in the method, the first sub-board bottom layer to be milled blind slot area and the second sub-board top layer blind slot pattern area are covered with PI film, which can effectively protect the circuit of the blind slot pattern area during milling, preventing the circuit from being scratched due to improper milling depth. BRIEF DESCRIPTION OF DRAWINGS

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

[0025] Figure 1 is the explosion view of the total board after pressing Figure One ;

[0026] Figure 2 is the explosion view of the total board after pressing Figure Two .

[0027] Figure number mark:

[0028] 100, first sub-board; 101, to-be-milled blind slot area;

[0029] 200, second sub-board; 201, blind slot pattern area; 202, circuit; 203, reserved copper skin;

[0030] 300, semi-cured sheet; 301, blind slot hollow area. DETAILED DESCRIPTION

[0031] In order to better understand the purpose, structure and function of the present application, the specific embodiments of the present application "a manufacturing method of a blind slot circuit board" will be further described in detail below in conjunction with the drawings.

[0032] Referring to Figure 1 and Figure 2 , in the present embodiment, the manufacturing method of the blind slot circuit board comprises the following steps:

[0033] Step S1: providing a circuit board sub-board, which is a double-layer core board or a multi-layer circuit board after pressing and with inner layer patterns, making bottom layer patterns of the sub-board through a conventional pattern transfer process to obtain a first sub-board 100 as shown in Figure 1 and Figure 2 The first sub-board 100 has a to-be-milled blind slot area 101 penetrating the top layer and the bottom layer of the first sub-board 100 from top to bottom, and the PI film is covered on the to-be-milled blind slot area 101 of the bottom layer of the first sub-board 100 to provide a buffer for subsequent milling and protect the circuit at the bottom of the slot;

[0034] Step S2: providing a circuit board sub-board, which is a double-layer core board or a multi-layer circuit board after pressing and with inner layer patterns, making top layer patterns of the sub-board through a conventional pattern transfer process, and the top layer patterns have a blind slot pattern area 201 at the bottom of the blind slot after the blind slot is finally milled, the blind slot pattern area 201 includes a circuit 202 and a reserved copper skin 203, to obtain a second sub-board 200 as shown in Figure 1 and Figure 2 ;

[0035] Step S3: plating gold on the circuit 202 of the blind slot pattern area 201 of the second sub-board 200, which can effectively protect the circuit 202 from damage in subsequent processes;

[0036] Step S4: obtaining the second sub-board 200 after step S3, covering the blind slot pattern area 201 of the top layer of the second sub-board 200 with a PI film to provide a buffer for subsequent milling, and the circuit 202 of the blind slot pattern area 201 to prevent damage to the circuit 202 during milling of the blind slot;

[0037] Step S5: providing a prepreg 300 corresponding in size to the first sub-board 100 and the second sub-board 200, and cutting a blind slot hollow area 301 on the prepreg 300, the size of the blind slot hollow area 301 corresponding to the size of the blind slot;

[0038] Step S6: stacking the first sub-board 100, the prepreg 300 and the second sub-board 200 in order from top to bottom, and aligning and overlapping the to-be-milled blind slot area 101, the blind slot hollow area 301 and the blind slot pattern area 201 after stacking; pressing the stacked circuit board to obtain a pressed total board;

[0039] Step S7: After the total board is pressed, the outer layer pattern is made by the outer layer pattern transfer process after the conventional drilling and electroplating; then the dry film is pasted on the whole surface (two outer layers) of the total board to protect the outer layer pattern; then the dry film on the first sub-board 100 top layer blind-milling groove area 101 is completely light-cured, and then the dry film on the first sub-board 100 top layer blind-milling groove area 101 is removed by a chemical method to expose the first sub-board 100 top layer blind-milling groove area 101, and then the blind groove is milled from top to bottom in the first sub-board 100 top layer blind-milling groove area 101 by numerical control milling or laser processing, and the milling is stopped until the PI film of the first sub-board 100 bottom layer; then the PI film covering the first sub-board 100 bottom layer blind-milling groove area 101 and the PI film covering the second sub-board 200 top layer blind groove pattern area 201 are taken out from the milled blind groove, and the blind groove pattern area 201 is exposed;

[0040] Step S8: The reserved copper skin 203 of the blind groove pattern area 201 is etched away by an alkaline etching or an acid etching process, and since the circuit 202 has been plated with gold, it will not be etched away; after the etching of the reserved copper skin 203 is completed, the dry film on the total board is removed by a chemical method, and then the blind groove circuit board is obtained after the subsequent conventional outer layer pattern detection, solder mask, surface treatment, forming and electrical measurement processes.

[0041] In summary, the manufacturing method of the blind groove circuit board of the present application, before pressing, the blind groove pattern area 201 on the top surface of the second sub-board 200 is provided with a reserved copper skin 203, so that there is no large area of copper-free area, and after the semi-cured sheet melts during pressing, it will not flow into the copper-free area in large quantities, the thickness of the cured sheet between the first sub-board 100 and the second sub-board 200 is normal after pressing, and the total board is not easy to burst during the subsequent processes; and the presence of the reserved copper skin 203 can ensure that the total board is evenly stressed during pressing, and the board surface will not be bent. In the present method, the blind-milling groove area 101 of the first sub-board 100 bottom layer and the blind groove pattern area 201 of the second sub-board (200) top layer are both covered with PI film, which can effectively protect the circuit of the blind groove pattern area 201 from being damaged during blind groove milling, and effectively improve the yield of the blind groove circuit board.

[0042] Further, in the embodiment, the PI film is first covered on the whole surface of the first sub-board 100 bottom layer in step S1, and then the PI film of the non-blind-milling groove area 101 is removed by laser cutting; similarly, the PI film is first covered on the whole surface of the second sub-board 200 top layer in step S4, and then the PI film of the non-blind groove pattern area 201 is removed by laser cutting; which facilitates the mechanical automation of the PI film.

[0043] Further, in the embodiment, the dry film is first attached to the entire surface (both upper and lower surfaces) of the second sub-board 200, then the dry film in all areas except the blind groove pattern area 201 is cured by light, and then the dry film on the circuit 202 in the blind groove pattern area 201 is removed by a conventional chemical method to expose the circuit 202 in the blind groove pattern area 201, and then the second sub-board 200 is gold-plated to plate gold on the circuit 202 in the blind groove pattern area 201, and then the dry film on the second sub-board 200 is removed by a conventional chemical method.

[0044] More specifically, in the embodiment, the distance between the copper skin 203 and the circuit 202 is greater than or equal to 2 mm, ensuring that the copper skin 203 has enough dry film covering space, so that the copper skin 203 will not be plated with gold when gold plating.

[0045] It can be understood that the present application is described by some embodiments, and those skilled in the art know that various changes or equivalent replacements can be made to these features and embodiments without departing from the spirit and scope of the present application. In addition, under the guidance of the present application, modifications can be made to these features and embodiments to adapt to specific conditions and materials without departing from the spirit and scope of the present application. Therefore, the present application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the scope of the present application.

[0046] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In the description of the present application, "a plurality of", "several" is understood as "at least two". The association relationship between the associated objects is described, which means that there can be three relationships, for example, A and / or B can represent three cases: A exists alone, A and B exist together, and B exists alone. A and B are connected, which can represent two cases: A and B are directly connected and A and B are connected through C. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

Claims

1. A method of manufacturing a blind-matrix circuit board, characterized by, The method comprises the following steps: Step S1: providing a circuit board sub-board, the sub-board is provided with a bottom layer pattern to obtain a first sub-board (100); the first sub-board (100) has a to-be-milled blind groove area (101), and the to-be-milled blind groove area (101) on the bottom layer of the first sub-board (100) is covered with a PI film; Step S2: providing a circuit board sub-board, the sub-board is provided with a top layer pattern, and the top layer pattern has a blind groove pattern area (201), the blind groove pattern area (201) comprises a circuit (202) and a reserved copper skin (203), and a second sub-board (200) is obtained; Step S3: the circuit (202) of the blind groove pattern area (201) of the second sub-board (200) is plated with gold; Step S4: obtaining the second sub-board (200) after step S3, and covering the blind groove pattern area (201) on the top layer of the second sub-board (200) with a PI film; Step S5: providing a prepreg (300), and the prepreg (300) has a blind groove hollow area (301); Step S6: stacking the first sub-board (100), the prepreg (300) and the second sub-board (200) from top to bottom, the to-be-milled blind groove area (101), the blind groove hollow area (301) and the blind groove pattern area (201) are overlapped from top to bottom; the stacked circuit board is laminated to obtain a laminated total board; Step S7: the laminated total board is drilled, electroplated and provided with an outer layer pattern; the laminated total board is entirely provided with a dry film, and the to-be-milled blind groove area (101) on the top layer of the first sub-board (100) is exposed; the blind groove is milled from top to bottom in the to-be-milled blind groove area (101) on the top layer of the first sub-board (100), the depth of the blind groove reaches the PI film on the bottom layer of the first sub-board (100), and then the PI film covering the to-be-milled blind groove area (101) on the bottom layer of the first sub-board (100) and the PI film covering the blind groove pattern area (201) on the top layer of the second sub-board (200) are removed from the blind groove; Step S8: etching away the reserved copper skin (203) of the blind groove pattern area (201), and removing the dry film to obtain a blind groove circuit board.

2. The method of claim 1, wherein In step S1, the PI film is entirely covered on the bottom layer of the first sub-board (100), and then the PI film in the non-to-be-milled blind groove area (101) is removed by laser cutting.

3. The method of claim 1, wherein In step S2, the distance between the reserved copper skin (203) and the circuit (202) is greater than or equal to 2 mm.

4. The method of claim 3, wherein the step of forming the blind via comprises the steps of: forming a first via in the substrate; and forming a second via in the substrate, the second via being formed in a direction opposite to the first via. In step S3, the dry film is entirely attached to the second sub-board (200), then the dry film in all areas except the circuit (202) of the blind groove pattern area (201) is solidified by light irradiation, then the dry film on the circuit (202) of the blind groove pattern area (201) is removed by a chemical method to expose the circuit (202) of the blind groove pattern area (201), then the second sub-board (200) is plated with gold to plate the circuit (202) of the blind groove pattern area (201) with gold, and then the dry film on the second sub-board (200) is removed.

5. The method for manufacturing a blind slot circuit board according to claim 1, characterized in that, In step S4, the PI film is entirely covered on the top layer of the second sub-board (200), and then the PI film in the non-blind groove pattern area (201) is removed by laser cutting.

6. The method of claim 1, wherein The first sub-board (100) has a number of layers greater than or equal to two, and the first sub-board (100) is a circuit board with inner layer patterns completed.

7. The method for manufacturing a blind slot circuit board according to claim 1, characterized in that, The second sub-board (200) has a number of layers greater than or equal to two, and the second sub-board (200) is a circuit board with inner layer patterns completed.

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