A two-stage HDI blind hole rigid-flexible combined board inner soft board copper reduction structure

Abstract

The utility model discloses a two step HDI blind hole soft and hard combination board inner layer soft board copper reduction structure, including L1 layer hard board, the bottom surface fixed setting of L1 layer hard board has PP bonding piece no.

Description

Technical Field

[0001] This utility model relates to the technical field of FPC and copper reduction process for inner flexible circuit board of two-stage HDI rigid-flex PCB, specifically a copper reduction structure for inner flexible circuit board of two-stage HDI blind via rigid-flex PCB. Background Technology

[0002] In today's era of rapid technological advancement, electronic products are characterized by extremely fast product updates and replacements. The trend is towards ever-shrinking product sizes while the number of internal layers increases, and wiring becomes increasingly complex. This places extremely high demands on the manufacturing processes of electronic products, significantly increasing production difficulty.

[0003] In the core components of electronic products, FPC (Flexible Printed Circuit) and two-tier HDI (High-Density Interconnect) rigid-flex boards occupy a crucial position. The manufacturing process of the inner layer flexible boards is particularly critical. Current processes face a series of challenging problems when producing the inner layer flexible boards of HDI rigid-flex boards. During the etching operation after the via filling and patterning processes, residual copper plating and dry film often occur. Specifically, during the removal of the dry film after via filling and patterning plating, it cannot be completely removed. This leads to serious problems such as broken lines, short circuits, and residual copper during the etching process, resulting in a large number of defective products. Furthermore, the dry film pressed under the plating layer is difficult to detect, leading to missed inspections. Once missed, it poses a significant risk to product reliability. For example, it may cause problems such as reflow blistering, board bursting, and protective film delamination during customer use. These problems not only seriously affect production progress and product yield but also pose significant quality risks to customers, reducing customer satisfaction and trust, and adversely affecting the company's market competitiveness. Summary of the Invention

[0004] The purpose of this invention is to provide a copper reduction structure for the inner layer flexible circuit board of a two-stage HDI blind via rigid-flex PCB, addressing the crucial role of FPC flexible printed circuit boards and two-stage HDI high-density interconnect rigid-flex PCBs in core electronic products, as mentioned in the background. The manufacturing process of the inner layer flexible circuit board is particularly critical. Current processes face a series of challenging problems in producing the inner layer flexible circuit board of HDI rigid-flex PCBs. During the etching operation after via filling and patterning, residual copper plating and dry film often occur. Specifically, during the removal of the dry film after via filling and patterning plating, it cannot be completely removed. This leads to serious problems such as broken lines, short circuits, and residual copper during the etching process, resulting in a large number of defective products. Furthermore, the dry film pressed under the plating layer is difficult to detect, leading to missed detections. Missed detections pose a significant risk to product reliability. For example, it may cause issues such as reflow blistering, board bursting, and protective film delamination during customer use. These problems not only seriously affect production progress and product qualification rate, but also pose significant quality risks to customers, reduce customer satisfaction and trust in the products, and adversely affect the company's market competitiveness.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a copper reduction structure for the inner flexible board of a two-stage HDI blind via rigid-flex PCB, comprising an L1 rigid board, a PP adhesive sheet one fixedly disposed on the bottom surface of the L1 rigid board, an L2 flexible board horizontally disposed on the bottom surface of the PP adhesive sheet one, an upper protective film of the L2 flexible board horizontally disposed on the top surface of the L2 flexible board, an L3 flexible board horizontally disposed on the bottom surface of the L2 flexible board, an L4 flexible board horizontally disposed on the bottom surface of the L3 flexible board, an upper protective film of the L4 flexible board horizontally disposed on the bottom surface of the L4 flexible board, a second PP adhesive sheet fixedly disposed on the bottom surface of the upper protective film of the L4 flexible board, and L5 and L6 rigid boards fixedly disposed on the bottom surface of the second PP adhesive sheet. A copper reduction area for the L2 flexible board is horizontally disposed between the L2 flexible boards, and a copper reduction area for the L4 flexible board is horizontally disposed between the L4 flexible boards.

[0006] Preferably, the L1 layer rigid plate and the PP adhesive sheet are arranged in parallel and superimposed on each other.

[0007] Preferably, the L2 layer flexible board and the PP adhesive sheet are arranged in parallel and superimposed on each other.

[0008] Preferably, the upper protective film of the L2 layer flexible board is horizontally disposed between the top surface of the L2 layer flexible board and the bottom surface of the PP adhesive sheet, and there are two L2 layer flexible boards, which are symmetrically fixed at both ends of the top surface of the L3 layer flexible board.

[0009] Preferably, the L3 layer flexible board and the L2 layer flexible board are arranged in parallel and stacked on top of each other, and the L3 layer flexible board is horizontally positioned between the bottom surface of the L2 layer flexible board and the top surface of the L4 layer flexible board.

[0010] Preferably, there are two L4 layer flexible boards, and the two L4 layer flexible boards are symmetrically fixed at both ends of the bottom surface of the L3 layer flexible board. The upper protective film of the L4 layer flexible board is horizontally fixed at the bottom surface of the L4 layer flexible board. The PP adhesive sheet and the L5 and L6 rigid boards are stacked and arranged in parallel. The bottom surface of the copper reduction area of ​​the L2 layer flexible board is fixed at the center of the top surface of the L3 layer flexible board, and the top surface of the copper reduction area of ​​the L4 layer flexible board is fixed at the center of the bottom surface of the L3 layer flexible board.

[0011] Compared with the prior art, the beneficial effects of this utility model are: This two-stage HDI blind via rigid-flex PCB inner layer copper reduction structure significantly reduces production costs during daily use. Due to the optimized process, it reduces defects caused by incomplete film removal, lowering the scrap rate and thus significantly reducing production costs. Simultaneously, its simplified operation reduces manpower and time investment, further saving costs. Regarding product quality, this structure improves production yield. Precise copper reduction and optimized processes ensure product quality stability and reliability. It reduces product defects caused by process issues, improves customer satisfaction, and enhances the company's competitiveness in the market. In terms of production efficiency, the new process simplifies operation steps and increases production speed. Operators can complete production tasks more quickly, improving overall production efficiency and better meeting the large market demand. In terms of production technology, it effectively solves many shortcomings of existing production technologies. It changes the original production process, eliminating pattern electroplating and replacing it with full-board electroplating. After full-board electroplating, advanced copper reduction technology is used in areas where additional plating is not needed, reducing copper thickness to the required level. This improvement effectively avoids the problems of incomplete film removal caused by double-sided film lamination followed by pattern electroplating and dry film pressing during previous processes. It thus solves problems such as residual copper, broken lines, and short circuits during etching, making the operation simpler and the quality more stable. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the overall structure of the two-stage HDI rigid-flex board of this utility model; In the diagram: 1. L1 layer rigid board; 2. PP adhesive sheet one; 3. L2 layer flexible board upper protective film; 4. L2 layer flexible board; 5. L3 layer flexible board; 6. L4 layer flexible board; 7. L4 layer flexible board upper protective film; 8. PP adhesive sheet two; 9. L5 and L6 layers rigid board; 10. L2 layer flexible board copper reduction area; 11. L4 layer flexible board copper reduction area. Detailed Implementation

[0013] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0014] Example 1

[0015] like Figure 1 As shown, this utility model provides a technical solution: a copper reduction structure for the inner flexible board of a two-stage HDI blind via rigid-flex PCB, including an L1 rigid board 1, a PP adhesive sheet 2 fixedly disposed on the bottom surface of the L1 rigid board 1, the L1 rigid board 1 and the PP adhesive sheet 2 are stacked and arranged in parallel, an L2 flexible board 4 is horizontally disposed on the bottom surface of the PP adhesive sheet 2, the L2 flexible board 4 and the PP adhesive sheet 2 are stacked and arranged in parallel, an upper protective film 3 is horizontally fixedly disposed on the top surface of the L2 flexible board 4, an L3 flexible board 5 is horizontally fixedly disposed on the bottom surface of the L2 flexible board 4, the upper protective film 3 is horizontally disposed between the top surface of the L2 flexible board 4 and the bottom surface of the PP adhesive sheet 2, there are two L2 flexible boards 4, and the two L2 flexible boards 4 are symmetrically fixedly disposed at both ends of the top surface of the L3 flexible board 5.

[0016] After electroplating the entire board, an advanced copper reduction process is used to remove copper from areas where plating is not required, reducing the copper thickness to the required level.

[0017] Example 2

[0018] like Figure 1As shown, this utility model provides a technical solution: a copper reduction structure for the inner flexible board of a two-stage HDI blind via rigid-flex PCB, including an L1 rigid board 1, a PP adhesive sheet 2 fixedly disposed on the bottom surface of the L1 rigid board 1, the L1 rigid board 1 and the PP adhesive sheet 2 are stacked and arranged in parallel, an L2 flexible board 4 is horizontally disposed on the bottom surface of the PP adhesive sheet 2, the L2 flexible board 4 and the PP adhesive sheet 2 are stacked and arranged in parallel, an upper protective film 3 is horizontally fixedly disposed on the top surface of the L2 flexible board 4, an L3 flexible board 5 is horizontally fixedly disposed on the bottom surface of the L2 flexible board 4, and the upper protective film 3 is horizontally disposed... Two L2 flexible boards 4 are placed between the top surface of the L2 layer flexible board 4 and the bottom surface of the PP adhesive sheet 2. The two L2 layer flexible boards 4 are symmetrically fixed at both ends of the top surface of the L3 layer flexible board 5. The bottom surface of the L3 layer flexible board 5 is horizontally fixed with an L4 layer flexible board 6. The L3 layer flexible board 5 and the L2 layer flexible board 4 are stacked and arranged in parallel. The L3 layer flexible board 5 is horizontally placed between the bottom surface of the L2 layer flexible board 4 and the top surface of the L4 layer flexible board 6. The bottom surface of the L4 layer flexible board 6 is horizontally fixed with an upper protective film 7. The bottom surface of the upper protective film 7 is fixed with a PP adhesive sheet 2.

[0019] This effectively avoids the problems of incomplete film removal caused by double-sided film lamination followed by pattern electroplating and the subsequent dry film application. It also solves issues such as residual copper, broken lines, and short circuits during circuit etching, making the operation simpler and the quality more stable.

[0020] Example 3

[0021] like Figure 1As shown, this utility model provides a technical solution: a copper reduction structure for the inner flexible board of a two-stage HDI blind via rigid-flex PCB, including an L1 rigid board 1, a PP adhesive sheet 2 fixedly disposed on the bottom surface of the L1 rigid board 1, the L1 rigid board 1 and the PP adhesive sheet 2 being arranged in parallel and stacked with each other, an L2 flexible board 4 horizontally disposed on the bottom surface of the PP adhesive sheet 2, the L2 flexible board 4 and the PP adhesive sheet 2 being arranged in parallel and stacked with each other, and an L2 flexible board 4 horizontally fixedly disposed on the top surface of the L2 flexible board 4. A protective film 3 and an L3 flexible board 5 are horizontally fixed to the bottom surface of the L2 flexible board 4. The upper protective film 3 of the L2 flexible board is horizontally positioned between the top surface of the L2 flexible board 4 and the bottom surface of the PP adhesive sheet 2. There are two L2 flexible boards 4, which are symmetrically fixed at both ends of the top surface of the L3 flexible board 5. An L4 flexible board 6 is horizontally fixed to the bottom surface of the L3 flexible board 5. The L3 flexible board 5 and the L2 flexible board 4 are arranged in a superimposed and parallel manner. Flexible circuit board 5 is horizontally positioned between the bottom surface of flexible circuit board 4 (L2 layer) and the top surface of flexible circuit board 6 (L4 layer). An upper protective film 7 is horizontally fixedly mounted on the bottom surface of flexible circuit board 6 (L4 layer). A second PP adhesive sheet 8 is fixedly mounted on the bottom surface of the upper protective film 7 (L4 layer). Rigid circuit boards 9 (L5 and L6 layers) are fixedly mounted on the bottom surface of the second PP adhesive sheet 8 (L5 and L6 layers). A copper reduction area 10 is horizontally fixedly mounted between the L2 and L4 layers of flexible circuit boards 4. A copper reduction area 11 is horizontally fixedly mounted between the L4 and L4 layers of flexible circuit boards 6. There are two flexible boards 6, and the two L4 layer flexible boards 6 are symmetrically fixed at both ends of the bottom surface of the L3 layer flexible board 5. The upper protective film 7 of the L4 layer flexible board is horizontally fixed at the bottom surface of the L4 layer flexible board 6. The PP adhesive sheet 8 and the L5 and L6 layer rigid boards 9 are stacked and arranged in parallel. The bottom surface of the copper reduction area 10 of the L2 layer flexible board is fixed at the center of the top surface of the L3 layer flexible board 5, and the top surface of the copper reduction area 11 of the L4 layer flexible board is fixed at the center of the bottom surface of the L3 layer flexible board 5.

[0022] By optimizing the process flow, the production of defective products caused by incomplete film removal was reduced, thus lowering the scrap rate and significantly reducing production costs.

[0023] Working principle: First, the layers are stacked. The L1 rigid board 1 is placed on top, with a PP adhesive sheet 2 fixed to its bottom surface. The two are tightly bonded together in a stacked, parallel arrangement. The L2 flexible board 4 is horizontally placed on the bottom surface of the PP adhesive sheet 2, also in a stacked, parallel arrangement. An upper protective film 3 is horizontally fixed to the top surface of the L2 flexible board 4, positioned between the top surface of the L2 flexible board 4 and the bottom surface of the PP adhesive sheet 2, protecting the top surface of the L2 flexible board 4. Two L2 flexible boards 4 are used, symmetrically fixed at both ends of the top surface of the L3 flexible board 5. A flexible L4 board 6 is horizontally fixed to the bottom surface of the L3 layer flexible board 5. The L3 layer flexible board 5 and the L2 layer flexible board 4 are stacked and arranged in parallel, with the L3 layer flexible board 5 positioned horizontally between the bottom surface of the L2 layer flexible board 4 and the top surface of the L4 layer flexible board 6. An upper protective film 7 of the L4 layer flexible board is horizontally fixed to the bottom surface of the L4 layer flexible board 6. A second PP adhesive sheet 8 is fixed to the bottom surface of the upper protective film 7. Rigid boards L5 and L6 are fixed to the bottom surface of the second PP adhesive sheet 8. The second PP adhesive sheet 8 and the L5 and L6 layer rigid boards 9 are stacked and arranged in parallel. A copper reduction area 10 of the L2 layer flexible board is horizontally fixed at the end between the L2 layer flexible boards 4, with its bottom surface fixed at the center of the top surface of the L3 layer flexible board 5. A copper reduction area 11 of the L4 layer flexible board is horizontally fixed at the end between the L4 layer flexible boards 6, with its top surface fixed at the center of the bottom surface of the L3 layer flexible board 5. With this specific structural setup, in subsequent processes, copper reduction is performed on the L2 and L4 flexible circuit board window locations. Copper reduction begins in the window areas where the developed dry film has been removed, decreasing by 15-25µm to achieve the required copper thickness.

[0024] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A copper reduction structure for the inner flexible board of a two-stage HDI blind via rigid-flex PCB, comprising an L1 rigid board (1), characterized in that: A PP adhesive sheet (2) is fixedly disposed on the bottom surface of the L1 layer rigid board (1). An L2 layer flexible board (4) is horizontally disposed on the bottom surface of the PP adhesive sheet (2). An L2 layer flexible board upper protective film (3) is horizontally fixedly disposed on the top surface of the L2 layer flexible board (4). An L3 layer flexible board (5) is horizontally fixedly disposed on the bottom surface of the L2 layer flexible board (4). An L4 layer flexible board (6) is horizontally fixedly disposed on the bottom surface of the L3 layer flexible board (5). The bottom surface of the L4 layer flexible board is fixedly provided with an upper protective film (7). The bottom surface of the upper protective film (7) of the L4 layer flexible board is fixedly provided with a second PP adhesive sheet (8). The bottom surface of the second PP adhesive sheet (8) is fixedly provided with L5 and L6 layers rigid boards (9). The L2 layer flexible board (4) is fixedly provided with a copper reduction area (10) at the end between the two layers. The L4 layer flexible board (6) is fixedly provided with a copper reduction area (11) at the end between the two layers.

2. The copper reduction structure of the inner layer of a two-stage HDI blind via rigid-flex PCB according to claim 1, characterized in that: The L1 layer rigid plate (1) and the PP adhesive sheet (2) are arranged in parallel and superimposed on each other.

3. The copper reduction structure of the inner layer of a two-stage HDI blind via rigid-flex PCB according to claim 1, characterized in that: The L2 layer flexible board (4) and the PP adhesive sheet (2) are arranged in parallel and superimposed on each other.

4. The copper reduction structure of the inner layer of a two-stage HDI blind via rigid-flex PCB according to claim 1, characterized in that: The upper protective film (3) of the L2 layer soft board is horizontally positioned between the top surface of the L2 layer soft board (4) and the bottom surface of the PP adhesive sheet (2). There are two L2 layer soft boards (4), and the two L2 layer soft boards (4) are symmetrically fixed at both ends of the top surface of the L3 layer soft board (5).

5. The copper reduction structure of the inner layer of a two-stage HDI blind via rigid-flex PCB according to claim 1, characterized in that: The L3 layer flexible board (5) and the L2 layer flexible board (4) are arranged in parallel and stacked with each other, and the L3 layer flexible board (5) is horizontally positioned between the bottom surface of the L2 layer flexible board (4) and the top surface of the L4 layer flexible board (6).

6. The copper reduction structure of the inner layer of a two-stage HDI blind via rigid-flex PCB according to claim 1, characterized in that: There are two L4 layer flexible boards (6), and the two L4 layer flexible boards (6) are symmetrically fixed at both ends of the bottom surface of the L3 layer flexible board (5). The upper protective film (7) of the L4 layer flexible board is horizontally fixed at the bottom surface of the L4 layer flexible board (6). The PP adhesive sheet (8) and the L5 and L6 layer rigid boards (9) are stacked and arranged in parallel. The bottom surface of the copper reduction area (10) of the L2 layer flexible board is fixed at the center of the top surface of the L3 layer flexible board (5), and the top surface of the copper reduction area (11) of the L4 layer flexible board is fixed at the center of the bottom surface of the L3 layer flexible board (5).

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