WO2023109051A1

WO2023109051A1 - Method for preparing pcb, and pcb

Info

Publication number: WO2023109051A1
Application number: PCT/CN2022/099434
Authority: WO
Inventors: 焦其正; 纪成光; 王洪府; 王小平; 张志远
Original assignee: 生益电子股份有限公司
Priority date: 2021-12-14
Filing date: 2022-06-17
Publication date: 2023-06-22
Also published as: CN114302578A

Abstract

Disclosed in the present application are a method for preparing a PCB, and a PCB. The method for preparing a PCB comprises: providing a first hole ring in a preset hole region of a specified core plate; providing a water absorbent resin on a side of the first hole ring facing away from the specified core plate; stacking and pressing the specified core plate and a first core plate to form a multi-layer plate; drilling a hole in a corresponding preset hole area of the multi-layer plate, to form a through hole in the multi-layer plate; chemically depositing copper on the multi-layer plate, such that the water absorbent resin absorbs water, and depositing a conductive layer on a hole wall of the through hole; drying the multi-layer plate to make the water absorbent resin generate water vapor, with the water absorbent resin expanding in size and protruding from a hole wall surface of the through hole; and disconnecting a conductive layer at the specified core plate from a conductive layer at the first core plate.

Description

Preparation method of PCB and PCB

This application claims the priority of a Chinese patent application with a filing date of December 14, 2021 and application number 202111528186.4, the entire contents of which are incorporated herein by reference.

technical field

The present application relates to the technical field of printed circuit boards, for example, to a method for preparing a PCB and the PCB.

Background technique

The invalid hole copper length of signal vias on PCB (Printed Circuit Boards, printed circuit boards) (commonly referred to as via stubs, via stubs) has a great influence on the signal integrity of signal vias. Related technologies In this method, the length of the stub is reduced by back drilling. If the stub can be completely eliminated (no stub or zero stub), the influence of the stub on signal transmission can be completely eliminated.

In the related art, in order to realize no stub at all, a special lamination and multiple lamination process is adopted, or a material with special properties (a plate of anti-plating material) is used to realize it. However, the properties of materials used in the preparation method are generally special, and there are characteristics such as poor compatibility with materials in related technologies and poor compatibility with PCB manufacturing processes in related technologies, which affects the preparation of PCBs.

Contents of the invention

The present application proposes a method for preparing a PCB and the PCB, which can completely eliminate the influence of stumps on signal transmission.

The PCB preparation method proposed by an embodiment of the present application includes: setting a first grommet in the predetermined opening area of the designated core board; setting a water-absorbing resin on the side of the first grommet facing away from the designated core board; The designated core board and the first core board are stacked and pressed together to form a multi-layer board; wherein, the water-absorbing resin is located between the designated core board and the first core board; corresponding to the multi-layer board Drill holes in the preset opening area to form a through hole in the multi-layer board; wherein, the through hole passes through the first annular ring, and the water-absorbing resin is exposed on the hole wall of the through hole; for the The multi-layer board is subjected to electroless copper deposition, so that the water-absorbing resin absorbs water, and a conductive layer is deposited on the hole wall of the through hole; the multi-layer board is baked to make the water-absorbing resin generate water vapor, and the water-absorbing resin The volume of the resin expands and protrudes from the wall surface of the through hole; and the conductive layer on the specified core board is disconnected from the conductive layer on the first core board.

In one embodiment, after the step of disconnecting the conductive layer located on the specified core board from the conductive layer located on the first core board, further includes: removing the conductive layer located on the first core board.

In one embodiment, the multi-layer board further includes a first copper layer disposed outside the first core board and a second copper layer disposed outside the designated core board, and the removal is located at the first The conductive layer of the core board includes: an isolated copper ring formed on the first copper layer corresponding to the periphery of the through hole.

In one embodiment, the forming of the isolated copper ring includes: preparing a surface dry film pattern on the first copper layer, where the dry film pattern includes a copper ring area at a predetermined position of the copper ring and an unpredetermined copper ring area. A reserved area at the position of the copper ring is provided, wherein there is a gap between the copper ring area and the reserved area; and the multilayer board is etched to remove the hole copper corresponding to the gap in the first copper layer, An isolated copper ring is formed on the first copper layer.

In one embodiment, after the step of forming an isolated copper ring, it further includes: tin-plating the multi-layer board, so that the surface of the first copper layer, the surface of the second copper layer, and the forming a tin layer on the surface of the conductive layer of the specified core board; and etching the multi-layer board to remove the isolated copper ring and the conductive layer on the first core board.

In one embodiment, after the step of etching the multilayer board, the preparation method further includes: removing the tin layer.

In an embodiment, the etching the multi-layer board to remove the hole copper in the first copper layer corresponding to the gap, so as to form an isolated copper ring on the first copper layer, includes: removing all described dry film graphics.

In one embodiment, the disconnecting the conductive layer located on the specified core board from the conductive layer located on the first core board includes at least one of the following steps:

Laser ablation of at least one of the conductive layer located on the water-absorbing resin and the water-absorbing resin protruding from the wall of the through hole, so as to disconnect the conductive layer located on the specified core board from the conductive layer located on the first core board. layer; and cleaning the through hole with an alkaline solution to remove the water-absorbing resin and disconnect the conductive layer located on the specified core board from the conductive layer located on the first core board.

In one embodiment, the water-absorbing resin includes hydrogel, and the hydrogel includes one or both of sodium polyacrylate and polyacrylamide.

An embodiment of the present application also proposes a PCB, which is prepared by the above PCB preparation method; the PCB preparation method includes: setting a first annular ring in the preset opening area of the designated core board; Water-absorbing resin is provided on the side of the first grommet facing away from the designated core board; the designated core board is stacked with the first core board and pressed together to form a multi-layer board; wherein the water-absorbing resin is located on the designated core board Between the first core board; drilling holes corresponding to the preset opening area of the multi-layer board, forming through holes in the multi-layer board; wherein, the through holes pass through the first hole ring, The water-absorbing resin is exposed on the hole wall of the through hole; electroless copper deposition is performed on the multi-layer board to make the water-absorbing resin absorb water, and a conductive layer is deposited on the hole wall of the through hole; The laminate is baked to make the water-absorbing resin generate water vapor, and the water-absorbing resin expands in volume and protrudes from the hole wall of the through hole; and the conductive layer located on the designated core board and the conductive layer located on the first core board The conductive layer is disconnected.

Description of drawings

Fig. 1 is a structural schematic diagram of an embodiment of a method for preparing a PCB of the present application;

Figure 2 is a schematic structural view of an embodiment of the specified core plate, the first annular ring and the water-absorbing resin in the present application;

Fig. 3 is a schematic structural view of an embodiment of the multilayer board of the present application;

Fig. 4 is a structural schematic diagram of an embodiment after multilayer board drilling of the present application;

Fig. 5 is a structural schematic diagram of an embodiment of the electroless copper deposition of the multilayer board of the present application;

Fig. 6 is a schematic structural view of an embodiment of the multi-layer board baking plate of the present application;

Figure 7 is a schematic structural view of an embodiment of the present application after removing the water-absorbing resin protruding from the hole wall;

Figure 8 is a schematic structural view of an embodiment of the present application after washing away the water-absorbing resin in the multi-layer board;

Fig. 9 is a schematic structural view of an embodiment of a dry film pattern provided on a multilayer board of the present application;

FIG. 10 is a schematic structural view of an embodiment of an isolated copper ring formed by a multilayer board of the present application;

Fig. 11 is a structural schematic diagram of an embodiment after removing the dry film pattern of the multilayer board of the present application;

Fig. 12 is a structural schematic diagram of an embodiment of the multilayer board of the present application after tinning;

Fig. 13 is a schematic structural diagram of an embodiment of the present application after removing invalid hole copper;

FIG. 14 is a schematic structural diagram of an embodiment of the present application after removing the tin layer of the multilayer board.

Detailed ways

If there is a directional indication (such as up, down, left, right, front, back...) in the embodiment of the present application, the directional indication is only used to explain the If the relative positional relationship, movement conditions, etc. among the components change, the directional indication will also change accordingly.

In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes, and cannot be interpreted as indications or hints Its relative importance or implicitly indicates the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In addition, if the meaning of "and/or" appearing in the whole text includes three parallel schemes, taking "A and/or B" as an example, it includes scheme A, scheme B, or schemes in which both A and B are satisfied . In addition, the technical solutions of the various embodiments can be combined with each other, but it must be based on the realization of those skilled in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist , nor within the scope of protection required by the present application.

The present application proposes a method for preparing a PCB.

Fig. 1 is a flowchart of the PCB preparation method of the present application, and Fig. 2 to Fig. 14 are sequential structural schematic diagrams of the PCB preparation process of the present application.

In the embodiment of this application, please refer to Figure 1, the preparation method of the PCB includes:

In S100, a first grommet 310 is set in the predetermined opening area of the designated core plate 100;

In S200, a water-absorbent resin 400 is provided on the side of the first annular ring 310 away from the specified core plate 100;

In S300, the designated core board 100 and the first core board 210 are stacked and pressed together to form a multi-layer board 10; between;

In S400, the multilayer board 10 is drilled corresponding to the predetermined opening area, and a through hole 10a is formed in the multilayer board 10; wherein, the through hole 10a passes through the first annular ring 310, and the The water-absorbing resin 400 is exposed on the wall of the through-hole 10a;

In S500, electroless copper deposition is performed on the multi-layer board 10, so that the water-absorbent resin 400 absorbs water, and a conductive layer 500 is deposited on the hole wall of the through hole 10a;

S600, drying the multi-layer board 10, so that the water-absorbent resin 400 generates water vapor, and the water-absorbent resin 400 expands in volume and protrudes from the wall surface of the through hole 10a;

S700. Disconnect the conductive layer 500 located on the specified core board 100 from the conductive layer 500 located on the first core board 210 .

In one embodiment, please refer to FIG. 2 , the manufacturing method of the specified core board 100 may include: inner layer manufacturing, drilling, desmearing, copper sinking, electroplating, plugging, micro-etching and other process steps, and may also use The method for preparing a PCB in the prior art prepares a specified core board 100 . That is, a circuit may also be formed inside a given core board 100 . The designated core board 100 is used for signal transmission, and the structure of the first core board 210 can be set with reference to the structure of the designated core board 100 , or the structures of the first core board 210 and the designated core board 100 can be different from each other.

Please continue to refer to FIG. 2 , the first annular ring 310 can be disposed on the designated core board 100 by a method in the related art. The first annular ring 310 is made of metal, and in an embodiment, it can be made of copper foil. The quantity, size and position of the first annular ring 310 can be set according to specific conditions. Before preparing the first annular ring 310, a core plate pattern can be prepared on the specified core plate 100, and then the first annular ring 310 can be set on the core plate pattern, or the first annular ring 310 and the core plate pattern can be produced at the same time. limit. In order to obtain a high-quality PCB, the first annular ring 310 may be 0.1 mm to 0.2 mm larger than the diameter of the through hole 10 a on one side.

Please refer to Fig. 2, in S200, the present application attaches the water-absorbent resin 400 on the first annular ring 310 first, and sets the attachment position and size of the water-absorbent resin 400 according to the position of the preset hole and the size of the aperture. The size of the resin 400 is larger than the diameter of the opening, so that after the through-hole 10a is formed, the water-absorbent resin 400 is exposed on the wall of the through-hole 10a. There are many ways to attach the water-absorbing resin 400 to the specified core board 100 . In one embodiment, the water-absorbing resin 400 is screen-printed on the first annular ring 310 .

Please refer to FIG. 3 , put the first core board 210 on the designated core board 100 , with the water-absorbent resin 400 facing the first core board 210 , stack and press them together to form the multi-layer board 10 . One or both of the first core board 210 and the designated core board 100 may be a multilayer board 10, and the multilayer board 10 formed by pressing may only include the first core board 210 and the designated core board 100, please continue to refer to Fig. 3 may also include other core boards, such as a second core board 220, a third core board, etc., the second core board 220 may be located between the first core board 210 and the specified core board 100, or be located The board 210 faces away from the designated core board 100 . In an embodiment, the multi-layer board 10 may further include a second annular ring 320, and the second annular ring 320 may be disposed on the first core board 210, or clamped between the first core board 210 and the second Between the core plates 220 ; wherein, the second annular ring 320 is opposite to the first annular ring 310 .

Then, please refer to Fig. 4, carry out drilling operation to multi-layer board 10, carry out drilling in multi-layer board 10 corresponding pre-opening area according to the position and the size of perforation, form through hole 10a, this through hole 10a passes through the first An annular ring 310. The through-hole 10a passes through the water-absorbent resin 400, so that the water-absorbent resin 400 is exposed on the wall of the through-hole 10a, so that the water-absorbent resin 400 can be in contact with liquid, so that the water-absorbent resin 400 can absorb liquid.

Please refer to Fig. 5. After the drilling operation is completed, the chemical copper deposition operation is performed on the multi-layer board 10, and the multi-layer board 10 is soaked in the copper sinking potion. absorb water. At the same time, a conductive layer 500 is deposited and formed on the wall surface of the through hole 10a, and the thickness of the conductive layer 500 is relatively small, which may be 0.3 micron to 0.5 micron.

In S600, please refer to FIG. 6 , the multi-layer board 10 is heated at a high temperature by a baking plate, and the moisture absorbed by the water-absorbent resin 400 is heated and evaporated, so that the water-absorbent resin 400 is fluffy, expands and protrudes toward the inner wall of the through hole 10a, and the conductive layer 500 is cracked. It is convenient for the subsequent disconnection operation of the conductive layer 500 . The conductive layer 500 of the chapped part is an incomplete copper layer, and cracks exist, and part of the water-absorbent resin 400 is exposed.

The temperature of the baking plate only needs to be higher than the evaporation temperature of water, which can be 100°C to 125°C, and the drying time of the plate is 10 minutes to 20 minutes. In one embodiment, the baking temperature of the multilayer board 10 is 110° C., and the baking time is 15 minutes, so as to achieve volume expansion of the water-absorbing resin 400 , reduce energy consumption, and lower production costs.

There are many kinds of materials for the water-absorbing resin 400 . In one embodiment, the water-absorbing resin 400 includes hydrogel, which can quickly absorb water, expand in volume after being heated, and protrude from the wall surface of the through hole 10 a. There are many types of the hydrogel, and in one embodiment, the hydrogel may include one or both of sodium polyacrylate and polyacrylamide. In one embodiment, the water-absorbing resin 400 can also be other water-absorbing polymer resins, as long as the volume expands after absorbing water and being heated.

In order to realize that the designated core board 100 is not connected to the first core board 210 (the two are not conductive after being energized and are independent of each other), please refer to FIG. The conductive layer 500 of a core board 210 is an invalid hole copper 520, and the effective hole copper 510 is disconnected from the invalid hole copper 520, so that the conductive layer 500 is incoherent, so as to prevent the effective hole copper 510 and the invalid hole copper 520 from conducting, and realize PCB Zero stubs.

The technical solution of this application first sets the first grommet 310 on the designated core board 100, attaches the water-absorbing resin 400 to the first grommet 310, and then clamps the water-absorbing resin 400 between the designated core board 100 and the first core board 210 Composite multi-layer board 10 by intermediate pressure; Drill holes in the corresponding preset opening area of multi-layer board 10 to form a through hole 10a, the through hole 10a passes through the first hole ring 310 and the water-absorbent resin 400, and the water-absorbent resin 400 is exposed on the through hole. The hole wall of the hole 10a; after the electroless copper plating of the multi-layer board 10, the plate is baked so that the water-absorbent resin 400 generates water vapor, and the water-absorbent resin 400 expands in volume and protrudes on the hole wall surface of the through hole 10a, so that it is deposited on the hole wall of the through hole 10a. The conductive layer 500 is chapped; finally, the effective hole copper 510 is disconnected from the invalid hole copper 520, so that the effective hole copper 510 and the invalid hole copper 520 are separated and non-conductive, thereby eliminating the failure of the invalid hole copper 520 (that is, via stubs) to the specified signal transmission of the core board 100 .

In this application, the water-absorbing resin 400 is installed between the specified core board 100 and the first core board 210, and the water-absorbing resin 400 is used for electroless copper deposition, and the volume expansion is prominent after the water is absorbed and the plate is baked, and then the effective hole copper 510 and the invalid hole copper 520 are disconnected. , so as to completely eliminate the influence of the invalid hole copper 520 on signal transmission. The PCB preparation method does not use materials with special properties, and has good compatibility with existing materials and PCB preparation processes. Moreover, the PCB preparation method is simple, the process is short, and only one pressing is required, and no multiple times are required. Pressing, thereby improving the production efficiency of PCB.

In order to ensure the reliability of disconnection and avoid the invalid hole copper 520 from affecting the transmission of signals, please refer to FIG. After the step of disconnecting the conductive layer 500 of the board 210 , the following step is further included: removing the copper 520 in the invalid hole of the multi-layer board 10 .

After the effective hole copper 510 is disconnected from the invalid hole copper 520, by removing the invalid hole copper 520 of the multilayer board 10, the multilayer board 10 has no residual piles, further avoiding the influence of the invalid hole copper 520 on signal transmission, and improving signal transmission reliability and guaranteed product performance.

Please refer to FIG. 3 to FIG. 5 , in one embodiment, the multilayer board 10 further includes a first copper layer 610 and a second copper layer 620, and the step of forming the multilayer board 10 includes: stacking the The first copper layer 610, the first core board 210, the designated core board 100 and the second copper layer 620 are pressed.

Please refer to FIG. 3. The first copper layer 610 is located on the side of the first core board 210 away from the designated core board 100, and the second copper layer 620 is located on the side of the designated core board 100 away from the first core board 210. After lamination, the first The copper layer 610 and the second copper layer 620 are respectively located on the upper and lower surfaces of the multilayer board 10 . In one embodiment, the first copper layer 610 can be copper foil, which can be stacked on the first core board 210 during lamination, or can be prepared on the first core board 210 when the first core board 210 is manufactured. 210; similarly, the second copper layer 620 can be stacked on the designated core board 100 during lamination, or can be prepared on the surface of the designated core board 100 when the designated core board 100 is manufactured.

Since the multilayer board 10 includes a first copper layer 610 and a second copper layer 620, please refer to FIG. 5 , in the operation of electroless copper deposition, the deposited conductive layer 500 is connected to the first copper layer 610 and the second copper layer 620 respectively. , That is to say, the first copper layer 610 is connected to the second copper layer 620 through the conductive layer 500 .

The part of the first copper layer 610 located at the periphery of the through hole 10a and the copper 520 of the invalid hole can be removed, please refer to FIG. 11 , in one embodiment, the removal of the conductive layer 500 located on the first core board 210 includes the following Step: forming an isolated copper ring 630 on the first copper layer 610 corresponding to the periphery of the through hole 10a.

Please refer to FIG. 11 , the copper ring 630 is separated from the first copper layer 610 away from the portion of the through hole 10a. By forming an isolated copper ring 630 on the first copper layer 610, the first copper layer 610 and the copper ring 630 are not electrically conductive. It is connected, and then it is not connected with the copper 520 of the invalid hole. On the one hand, it facilitates the subsequent removal of the copper in the invalid hole 520;

There are many ways to form the isolated copper ring 630, please refer to FIG. 9 to FIG. 10. In one embodiment, the formation of the isolated copper ring 630 includes the following steps:

Prepare the surface dry film pattern 700 on the multi-layer board 10, and the dry film pattern 700 includes the copper ring area 710 covering the preset copper ring 630 position and the surface pattern area 720 of the non-preset copper ring 630 position, wherein , there is a gap 700a between the copper ring region 710 and the reserved region 720; and the multilayer board 10 is etched to remove the hole copper in the first copper layer 610 corresponding to the gap 700a, so that The first copper layer 610 forms an isolated copper ring 630 .

Please refer to FIG. 10 , the dry film pattern 700 is arranged on the surface of the first copper layer 610 and the second copper layer 620. Since an isolated copper ring 630 needs to be formed on the first copper layer 610, the dry film pattern 700 includes a preset The copper ring area 710 at the position of the copper ring 630 and the reserved area 720 at the position of the non-preset copper ring 630, the gap 700a between the copper ring area 710 and the reserved area 720 forms a closed ring, so that subsequent etching can be carried out along the annular gap 700a , remove the hole copper of the first copper layer 610 corresponding to the gap 700a, so that the first copper layer 610 forms an isolated copper ring 630 at the periphery of the through hole 10a.

That is, please refer to FIG. 9 to FIG. 10 , the first copper layer 610 that does not need to be etched is protected by the dry film pattern 700, and the first copper layer 610 that is not covered by the dry film pattern 700 is etched, so that in the first An isolated copper ring 630 is formed on the copper layer 610 . It can be understood that the dry film pattern 700 can be produced by conventional dry film methods.

In order to facilitate the subsequent processing operations, please refer to FIG. 10 to FIG. 11 , in one embodiment, the multilayer board 10 is etched to remove the copper hole corresponding to the gap 700a in the first copper layer 610, Forming the isolated copper ring 630 on the first copper layer 610 further includes the following step: removing the dry film pattern 700 . Specifically, an alkaline solution or an organic solvent can be used to completely dissolve and remove the dry film pattern 700 on the surface of the multilayer board 10 , thereby exposing the first copper layer 610 , the second copper layer 620 and the isolated copper ring 630 .

Please refer to Fig. 12 to Fig. 13, in one embodiment, after the step of forming the isolated copper ring 630, the manufacturing method further includes the following steps: tinning the multi-layer board 10, so that the first copper forming a tin layer 800 on the surface of the layer 610, the surface of the second copper layer 620, and the surface of the conductive layer 500 located on the designated core board 100; and etching the multilayer board 10 to remove the isolated copper ring 630 and Inactive hole copper 520.

Please refer to FIG. 11 to FIG. 13 , since the isolated copper ring 630 is not connected to the first copper layer 610, the invalid hole copper 520 and the effective hole copper 510, and no current passes through, the isolated copper ring 630 and the invalid hole copper 520 cannot be connected. Tin plating, thereby forming a tin layer 800 on the surface of the first copper layer 610 , the surface of the second copper layer 620 and the surface of the effective hole copper 510 . The etching protective layer is formed by tin plating to protect the first copper layer 610 , the second copper layer 620 and the effective hole copper 510 so as not to be removed by etching. In this way, by means of etching, the isolated copper ring 630 and the ineffective hole copper 520 are removed to meet different needs of the product and also realize the product without stubs. In one embodiment, in addition to tin plating, copper plating may also be performed on the multilayer board 10 to form copper layers on the surface of the first copper layer 610 , the surface of the second copper layer 620 and the surface of the effective hole copper 510 .

After the copper 520 in the invalid hole and the copper ring 630 are removed, the tin layer 800 may be removed, or the tin layer 800 may not be removed. Please refer to FIG. 13 and FIG. 14 , in one embodiment, after the etching of the multilayer board 10 , the following steps are further included: removing the tin layer 800 of the multilayer board 10 . By peeling off the protective tin layer 800 , the effective hole copper 510 , the first copper layer 610 and the second copper layer 620 on the inner wall of the through hole 10 a are exposed, so as to facilitate subsequent normal process fabrication.

Please refer to FIG. 6 to FIG. 8 , in one embodiment, the disconnecting the copper via holes 520 from the copper via holes 510 includes at least one of the following steps: laser ablation of the conductive layer located in the water-absorbent resin 400 500 and/or the water-absorbing resin 400 protruding from the wall of the through-hole 10a to disconnect the copper in the invalid hole 520 and the copper in the effective hole 510; and use an alkaline solution to clean the through-hole 10a to remove the water-absorbing The resin 400 disconnects the invalid copper hole 520 from the valid hole copper 510 .

Referring to FIGS. 6 to 7 , the conductive layer 500 located on the water-absorbing resin 400 is removed by laser ablation, so that the copper holes 520 in invalid holes are disconnected from the copper copper holes 510 in effective holes. Alternatively, the water-absorbing resin 400 protruding from the inner wall of the through hole 10 a is removed, thereby removing the conductive layer 500 located on the water-absorbing resin 400 , and realizing the disconnection of the copper in the invalid hole 520 and the copper in the effective hole 510 .

Please refer to FIG. 8 , since the water-absorbent resin 400 expands in volume after being heated, and protrudes into the through hole 10a, the conductive layer 500 is cracked, and the conductive layer 500 in the cracked part is an incomplete copper layer, exposing part of the water-absorbent resin 400 . Thus, the water-absorbing resin 400 located on the multi-layer board 10 is washed away by immersion and cleaning in an alkaline solution, so that the conductive layer 500 located on the water-absorbing resin 400 loses its attached body and falls off, thereby realizing the effective hole copper 520 and the effective hole copper 510. disconnection.

Alternatively, laser ablation may be performed first to remove at least one of the conductive layer 500 located on the water-absorbing resin 400 and the water-absorbing resin 400 protruding from the inner wall of the through hole 10a, and then the water-absorbing resin 400 is washed away, thereby completely removing the water-absorbing resin 400. removed, so that the invalid hole copper 520 is completely disconnected from the effective hole copper 510 .

The present application also proposes a PCB, which is prepared by the above PCB preparation method. For the specific method of the PCB, refer to the above-mentioned embodiments. Since this PCB adopts all the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, and will not repeat them here. Wherein, the PCB is a circuit board without stubs, and the stub-free here may mean that there are no stubs, or it may be free from the influence of stubs.

Claims

A method for preparing a PCB, comprising:

setting a first grommet (310) in the predetermined opening area of the designated core plate (100);

setting water-absorbent resin (400) on the side of the first annular ring (310) away from the specified core plate (100);

The designated core board (100) and the first core board (210) are stacked and pressed together to form a multi-layer board (10); wherein the water-absorbing resin (400) is located between the designated core board (100) and between the first core boards (210);

Drilling holes in the multilayer board (10) corresponding to the predetermined opening area, forming a through hole (10a) in the multilayer board (10); wherein, the through hole (10a) passes through the first hole a ring (310), the water-absorbing resin (400) is exposed on the hole wall of the through hole (10a);

performing electroless copper deposition on the multi-layer board (10), so that the water-absorbing resin (400) absorbs water, and depositing a conductive layer (500) on the hole wall of the through-hole (10a);

Baking the multi-layer board (10) so that the water-absorbing resin (400) generates water vapor, and the water-absorbing resin (400) expands in volume and protrudes from the wall surface of the through hole (10a); and

Disconnecting the conductive layer (500) on the designated core board (100) from the conductive layer (500) on the first core board (210).
The method for preparing PCB according to claim 1, said disconnecting the conductive layer (500) located on said specified core board (100) from the conductive layer (500) located on said first core board (210) After the step, it also includes: removing the conductive layer (500) located on the first core board (210).
The preparation method of PCB according to claim 2, wherein, the multi-layer board (10) further comprises a first copper layer (610) arranged on the outside of the first core board (210) and the first copper layer (610) arranged on the specified The second copper layer (620) outside the core board (100), the removal of the conductive layer (500) located on the first core board (210) includes: corresponding to the first copper layer (610) An isolated copper ring (630) is formed around the through hole (10a).
The method for preparing PCB according to claim 3, wherein said forming an isolated copper ring (630) comprises: preparing a surface dry film pattern (700) on said first copper layer (610), said dry The film pattern (700) includes a copper ring area (710) at a preset copper ring (630) position and a reserved area (720) at a non-preset copper ring (630) position, wherein the copper ring area (710) and There is a gap (700a) between the reserved regions (720); and etching the multi-layer board (10) to remove the hole copper corresponding to the gap (700a) in the first copper layer (610), so as to Isolated copper rings (630) are formed on the first copper layer (610).
The preparation method of PCB according to claim 4, after the step of forming the isolated copper ring (630), further comprising: tinning the multi-layer board (10), so as to coat the first copper layer ( 610), the surface of the second copper layer (620) and the surface of the conductive layer (500) located on the designated core board (100) to form a tin layer (800); and etching the multilayer board (10) , removing the isolated copper ring (630) and the conductive layer (500) located on the first core board (210).
The method for preparing a PCB according to claim 5, after the step of etching the multilayer board (10), further comprises: removing the tin layer (800).
The method for preparing PCB according to claim 5, wherein said etching the multilayer board (10) removes the hole copper corresponding to the gap (700a) of the first copper layer (610), so as to Forming an isolated copper ring (630) on the first copper layer (610) includes: removing the dry film pattern (700).
The method for preparing PCB according to any one of claims 1 to 7, wherein the conductive layer (500) to be located on the specified core board (100) and the conductive layer (500) located on the first core board (210) Disconnecting the conductive layer (500) includes at least one of the following steps:

Laser ablation of at least one of the conductive layer (500) located on the water-absorbing resin (400) and the water-absorbing resin (400) protruding from the wall of the through hole (10a), so as to disconnect the conductive layer (500) located on the designated core board The conductive layer (500) of (100) and the conductive layer (500) located on the first core board (210); and

The through hole (10a) is cleaned with an alkaline solution to remove the water-absorbing resin (400), so that the conductive layer (500) located on the specified core board (100) and the conductive layer (500) located on the first core board ( 210) of the conductive layer (500) is disconnected.
The method for preparing PCB according to any one of claims 1 to 7, wherein the water-absorbing resin (400) comprises a hydrogel, and the hydrogel comprises one or more of sodium polyacrylate and polyacrylamide two kinds.
A PCB, which is prepared by the PCB preparation method according to any one of claims 1 to 9.