A rigid-flex printed circuit board with blind vias across a layer step

Abstract

This utility model discloses a rigid-flex PCB with stepped blind vias across layers, including a base copper plate L1. A flexible PCB layer (PI layer) is horizontally fixed on the bottom surface of the base copper plate L1. Regarding product reliability, the stepped blind vias connecting the rigid and flexible PCBs increase the connection area between the third layer and the first and fourth layers, making the connections between layers more robust and improving the electrical performance and mechanical stability of the product. This better meets the requirements for long-term stable operation of electronic products in complex environments. In terms of production cycle, this process shortens the original "two-stage blind via" process for rigid-flex PCBs, which involved two laser processes, two copper plating processes, and two copper plating processes to one laser process, one copper plating process, and one copper plating process. This significantly reduces the number of laser processes, copper plating processes, and copper plating processes, effectively shortening the production process and reducing production time. This allows for faster product launches, meeting the market demand for rapid delivery of electronic products.

Description

Technical Field

[0001] This utility model relates to the field of manufacturing technology of blind hole type circuit boards with multilayer rigid-flex boards, specifically a rigid-flex board with cross-layer stepped blind holes. Background Technology

[0002] Currently, the electronics industry is undergoing a comprehensive upgrade towards digitalization, intelligentization, high performance, and lightweighting. In this process, high-density circuit board technology has become a key driver of this upgrade. Its basic principle is to optimize circuit board design so that various components can be arranged as closely as possible on the board, thereby increasing the number and density of components on the board and meeting the ever-growing demands of electronic products for high performance and miniaturization.

[0003] To achieve high-density circuit boards, the number of layers needs to be increased, wiring density increased, and the number of vias or blind vias increased. In the manufacturing process of HDI (High-Density Interconnect) boards, the industry commonly uses a "two-stage blind via" process. The specific process is as follows: first, laser-cut blind vias are performed on the inner double-sided rigid board; then, copper plating is applied to fill the vias. The inner double-sided rigid board with the filled blind vias and the next outer double-sided flexible board are used to fabricate the inner layer circuitry. Next, the prepared PP prepreg and the inner double-sided rigid board, next outer double-sided flexible board, and next outer rigid board with the circuitry are stacked and laminated. Then, based on the copper filling of the inner double-sided rigid board from the first laser-cut process, the blind vias on the outer double-sided flexible board are laser-cut, and copper plating is applied again to fill the vias. Finally, the remaining processes are completed. However, the "two-stage blind via" process has some significant problems. Firstly, the production cycle is relatively long. Because the process requires two laser blind via operations, two copper plating operations, and two copper plating operations to fill the vias, each step takes time, resulting in a lengthy production process that cannot meet the market's demand for rapid delivery of electronic products. Furthermore, the costs are high. Multiple laser, copper plating, and copper plating operations not only increase equipment operating time and energy consumption but also increase raw material consumption, significantly raising production costs and reducing the product's competitiveness in the market. Utility Model Content

[0004] The purpose of this invention is to provide a rigid-flex PCB with cross-layer stepped blind vias, to solve the problem mentioned in the background art where the industry commonly uses the "second-order blind via" process in the manufacturing of HDI high-density interconnect boards. The specific process is as follows: first, laser-cut blind vias are performed on the inner double-sided rigid board; then, copper plating is performed to fill the vias; the inner double-sided rigid board with the filled blind vias and the next outer double-sided flexible board are used to fabricate inner layer circuitry; then, the prepared PP prepreg and the inner double-sided rigid board, next outer double-sided flexible board, and next outer rigid board with the circuitry are stacked and pressed together; then, based on the copper filling of the inner double-sided rigid board from the first laser-cut process, the blind vias of the outer double-sided flexible board are laser-cut, and copper plating is performed again to fill the vias; finally, the remaining processes are completed. However, the "second-order blind via" process has some obvious problems. On the one hand, the production cycle is relatively long. Because the process requires two laser blind via operations, two copper plating operations, and two copper plating operations to fill the vias, each step takes time, resulting in a lengthy production process that cannot meet the market's demand for rapid delivery of electronic products. Furthermore, the costs are high. Multiple laser, copper plating, and copper plating operations not only increase equipment operating time and energy consumption but also increase raw material consumption, significantly raising production costs and reducing the product's competitiveness in the market.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a rigid-flex PCB with cross-layer stepped blind holes, comprising a base copper plate L1, a flexible PI layer horizontally fixedly disposed on the bottom surface of the base copper plate L1, a base copper layer L2 horizontally fixedly disposed on the bottom surface of the flexible PI layer, a PP sheet layer horizontally fixedly disposed on the bottom surface of the base copper layer L2, a base copper layer L3 horizontally fixedly disposed on the bottom surface of the PP sheet layer, a rigid FR4 layer horizontally fixedly disposed on the bottom surface of the base copper layer L3, a base copper layer L4 horizontally fixedly disposed on the bottom surface of the rigid FR4 layer, and a first PP sheet layer horizontally fixedly disposed on the bottom surface of the base copper layer L4. A base copper layer L5 is fixedly provided. A rigid board FR4 layer is horizontally fixedly provided on the bottom surface of the base copper layer L5. A base copper layer L5 is horizontally fixedly provided on the bottom surface of the rigid board FR4 layer. A flexible board area with a rigid-flex bonding region is formed on the bottom surface of the base copper layer L5. An outer layer hole of a cross-layer stepped blind hole is formed on the top surface of the base copper plate L1. An inner layer hole of a cross-layer stepped blind hole is formed at the bottom end of the outer layer hole of the cross-layer stepped blind hole. A step is provided at the bottom end of the outer layer hole of the cross-layer stepped blind hole and the top end of the inner layer hole of the cross-layer stepped blind hole. A through hole of a rigid-flex bonding plate is formed on the top surface of the base copper plate L1. The interior of the outer layer hole of the cross-layer stepped blind hole and the inner layer hole of the cross-layer stepped blind hole is filled with filler copper.

[0006] Preferably, the base copper plate L1, the flexible board PI layer and the base copper layer L2 form an outer double-sided flexible board, the base copper layer L3, the rigid board FR4 layer and the base copper layer L4 form an inner double-sided rigid board, and the base copper layer L5, the rigid board FR4 layer one and the base copper layer L5 one form an outer double-sided rigid board.

[0007] Preferably, the outer double-sided flexible board and the inner double-sided rigid board are fixedly connected to each other by a PP sheet layer, and the inner double-sided rigid board and the outer double-sided rigid board are fixedly connected to each other by a PP sheet layer.

[0008] Preferably, the flexible board area of ​​the rigid-flex bonding region is sequentially formed by the following layers: the bottom base copper layer L5, the rigid board FR4 layer, the base copper layer L5, the PP sheet layer, the base copper layer L4, the rigid board FR4 layer, the base copper layer L3, the PP sheet layer, and the base copper layer L2.

[0009] Preferably, the outer hole of the cross-layer step blind hole is sequentially formed by the top base copper plate L1, the flexible board PI layer, the base copper layer L2 and the PP sheet layer, and the inner hole of the cross-layer step blind hole is sequentially formed by the base copper layer L3 and the rigid board FR4 layer.

[0010] Preferably, the through holes of the rigid-flex PCB are provided in a continuous manner, extending from the top base copper plate L1 to the bottom base copper layer L5 through a mechanical drilling structure.

[0011] Compared with the prior art, the beneficial effects of this utility model are: This rigid-flex PCB with stepped blind vias significantly reduces production costs in daily use. It decreases the number of laser, copper plating, and through-hole copper plating operations, reducing equipment uptime and energy consumption, as well as raw material consumption, thus enhancing the product's market competitiveness. In terms of process adaptability, this method is applicable not only to the production of multilayer rigid-flex HDI boards but also to the production of ordinary rigid-flex boards, demonstrating strong versatility and adaptability, providing efficient manufacturing solutions for different types of products. Regarding product reliability, the stepped blind vias connecting the rigid and flexible boards increase the connection area between the third layer and the first and fourth layers, resulting in stronger connections between layers and improved electrical performance and mechanical stability, better meeting the requirements for long-term stable operation of electronic products in complex environments. In terms of production cycle, this process shortens the original "two-stage blind via" process for rigid-flex boards, which involved two laser processes, two copper plating operations, and two through-hole copper plating operations, to a single laser process, one copper plating operation, and one through-hole copper plating operation. This significantly reduces the number of laser treatments, copper plating, and through-hole copper plating processes, effectively shortening the production process and reducing production time. This allows products to be brought to market more quickly, meeting the market's demand for rapid delivery of electronic products. Attached Figure Description

[0012] Figure 1 Prepare circuit diagrams for the outer double-sided flexible board, the inner double-sided rigid board, and the outer double-sided rigid board of this utility model; Figure 2 This is a schematic diagram of the six-layer rigid-flex PVC board substrate of this utility model after pressing. Figure 3 This is a schematic diagram of the "orifice" of the outer flexible plate of the laser-finished rigid-flex plate of this utility model, which is a "blind hole across a step". Figure 4 This invention provides a schematic diagram of the inner hard plate "hard plate blind hole" of the laser-finished rigid-flex plate and the through hole of the mechanically drilled rigid-flex plate. Figure 5 This is a schematic diagram of the copper filling for the "cross-layer step blind hole" in the flexible board and rigid board of the complete flexible-rigid bonding board of this utility model.

[0013] In the diagram: 1. Base copper plate L1; 2. Flexible board PI layer; 3. Base copper layer L2; 4. PP sheet layer; 5. Base copper layer L3; 6. Rigid board FR4 layer; 7. Base copper layer L4; 8. PP sheet layer one; 9. Base copper layer L5; 10. Rigid board FR4 layer one; 11. Base copper layer L5 layer one; 12. Flexible board area in the rigid-flex zone; 13. Outer hole of the cross-layer step blind hole; 14. Inner hole of the cross-layer step blind hole; 15. Step; 16. Through hole of the rigid-flex board; 17. Filler copper; 21. Outer double-sided flexible board; 22. Inner double-sided rigid board; 23. Outer double-sided rigid board. Detailed Implementation

[0014] 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.

[0015] Example 1:

[0016] like Figure 1-5As shown, this utility model provides a technical solution: a rigid-flex PCB with cross-layer stepped blind holes, including a base copper plate L11, a flexible PI layer 2 horizontally fixed on the bottom surface of the base copper plate L11, a base copper layer L23 horizontally fixed on the bottom surface of the flexible PI layer 2, a PP sheet layer 4 horizontally fixed on the bottom surface of the base copper layer L23, an outer double-sided flexible PCB 21 and an inner double-sided rigid PCB 22 fixedly connected to each other by the PP sheet layer 4, an inner double-sided rigid PCB 22 and an outer double-sided rigid PCB 23 fixedly connected to each other by the PP sheet layer 8, and a base copper layer L35 horizontally fixed on the bottom surface of the PP sheet layer 4.

[0017] This process reduces the original "second-order blind via" process for rigid-flex PCBs, which involved two laser processes, two copper plating processes, and two copper plating steps, to a single laser process, a single copper plating process, and a single copper plating step. This significantly reduces the number of laser processes, copper plating steps, and copper plating steps, effectively shortening the production process.

[0018] Example 2:

[0019] like Figure 1-5 As shown, this utility model provides a technical solution: a rigid-flex PCB with cross-layer stepped blind holes, including a base copper plate L11, a flexible PI layer 2 horizontally fixed on the bottom surface of the base copper plate L11, a base copper layer L23 horizontally fixed on the bottom surface of the flexible PI layer 2, a PP sheet layer 4 horizontally fixed on the bottom surface of the base copper layer L23, an outer double-sided flexible PCB 21 and an inner double-sided rigid PCB 22 fixedly connected to each other by the PP sheet layer 4, an inner double-sided rigid PCB 22 and an outer double-sided rigid PCB 23 fixedly connected to each other by the PP sheet layer 8, a base copper layer L35 horizontally fixed on the bottom surface of the PP sheet layer 4, a rigid FR4 layer 6 horizontally fixed on the bottom surface of the base copper layer L35, a base copper layer L47 horizontally fixed on the bottom surface of the rigid FR4 layer 6, a PP sheet layer 8 horizontally fixed on the bottom surface of the base copper layer L47, and a base copper layer L59 horizontally fixed on the bottom surface of the PP sheet layer 8.

[0020] By creating a stepped shape through blind holes connecting the rigid and flexible boards, the connection area between the third layer and the first and fourth layers is increased, making the connection between each layer more robust and improving the electrical performance and mechanical stability of the product.

[0021] Example 3:

[0022] like Figure 1-5As shown, this utility model provides a technical solution: a rigid-flex PCB with cross-layer stepped blind holes, comprising a base copper plate L11, a flexible PI layer 2 horizontally fixedly disposed on the bottom surface of the base copper plate L11, a base copper layer L23 horizontally fixedly disposed on the bottom surface of the flexible PI layer 2, a PP sheet layer 4 horizontally fixedly disposed on the bottom surface of the base copper layer L23, an outer double-sided flexible PCB 21 and an inner double-sided rigid PCB 22 fixedly connected to each other by the PP sheet layer 4, an inner double-sided rigid PCB 22 and an outer double-sided rigid PCB 23 fixedly connected to each other by the PP sheet layer 8, and a base copper layer L35 horizontally fixedly disposed on the bottom surface of the PP sheet layer 4. A rigid FR4 layer 6 is fixedly installed. A base copper layer L47 is horizontally fixedly installed on the bottom surface of the rigid FR4 layer 6. A PP sheet layer 8 is horizontally fixedly installed on the bottom surface of the base copper layer L47. A base copper layer L59 is horizontally fixedly installed on the bottom surface of the PP sheet layer 8. A rigid FR4 layer 10 is horizontally fixedly installed on the bottom surface of the base copper layer L59. A base copper layer L5-11 is horizontally fixedly installed on the bottom surface of the rigid FR4 layer 10. A flexible board area 12 with a rigid-flex bonding region is formed on the bottom surface of the base copper layer L5-11, the rigid FR4 layer 10, the base copper layer L59, the PP sheet layer 8, and the base copper layer L47. A bottom copper layer L47, a rigid FR4 layer 6, a base copper layer L35, a PP sheet layer 4, and a base copper layer L23 are connected through the bottom copper plate L11. A cross-layer stepped blind hole outer aperture 13 is formed on the top surface of the base copper plate L11. The cross-layer stepped blind hole outer aperture 13 is connected through the top base copper plate L11, the flexible PI layer 2, the base copper layer L23, and the PP sheet layer 4. A cross-layer stepped blind hole inner aperture 14 is connected through the base copper layer L35 and the rigid FR4 layer 6. A cross-layer stepped blind hole inner aperture 14 is formed at the bottom of the cross-layer stepped blind hole outer aperture 13. A step 1 is formed at the bottom of the cross-layer stepped blind hole outer aperture 13 and the top of the cross-layer stepped blind hole inner aperture 14. 5. A through hole 16 for a rigid-flex PCB is provided on the top surface of the base copper plate L11. The through hole 16 is provided through the base copper plate L11 at the top and the base copper layer L5-11 at the bottom through the mechanical drilling structure. The outer hole 13 of the cross-layer step blind hole and the inner hole 14 of the cross-layer step blind hole are filled with filler copper 17. The base copper plate L11, the flexible board PI layer 2 and the base copper layer L23 form the outer double-sided flexible board 21. The base copper layer L35, the rigid board FR4 layer 6 and the base copper layer L47 form the inner double-sided rigid board 22. The base copper layer L59, the rigid board FR4 layer 10 and the base copper layer L5-11 form the outer double-sided rigid board 23.

[0023] By reducing the number of laser, copper plating, and through-hole copper plating operations, the equipment's operating time and energy consumption are reduced, while raw material consumption is also reduced, thereby significantly lowering production costs and improving the product's competitiveness in the market.

[0024] Working Principle: When using this rigid-flex PCB, the circuitry of the outermost flexible board (outer double-sided flexible board 21), the innermost rigid board (inner double-sided rigid board 22), and the outermost rigid board (outer double-sided rigid board 23) is first fabricated. Then, the prepared adhesive is layered and pressed onto each layer according to the structural sequence, ensuring a tight bond between the layers to form a complete six-layer rigid-flex PCB substrate. Next, following the laser program, blind vias are drilled from the outer flexible board's base copper plate L11 towards the inner rigid board. A single laser strike can cross one layer of circuitry, penetrate another, and reach the fourth layer, creating a stepped effect and forming a rigid-flex PCB cross-layer stepped blind via. At this point, a cross-layer stepped blind hole outer layer opening 13 is formed on the top surface of the base copper plate L11. This outer layer opening is sequentially formed by the top base copper plate L11, the flexible board PI layer 2, the base copper layer L23, and the PP sheet layer 4. The cross-layer stepped blind hole inner layer opening 14 is sequentially formed by the base copper layer L35 and the rigid board FR4 layer 6. Steps 15 are provided at the bottom of the cross-layer stepped blind hole outer layer opening 13 and the top of the cross-layer stepped blind hole inner layer opening 14. Next, an outer layer through hole 16 is drilled. This through hole 16 of the rigid-flex board is formed by mechanical drilling, extending from the top base copper plate L11 to the bottom base copper layer L5-11. Finally, a copper plating and a filling copper plating operation are performed to fill the interior of the cross-layer stepped blind hole outer layer opening 13 and the cross-layer stepped blind hole inner layer opening 14 with filling copper 17, completing the remaining process and obtaining the final rigid-flex board product.

[0025] 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 rigid-flex PCB with cross-layer stepped blind holes, comprising a base copper plate L1 (1), characterized in that: A flexible PI layer (2) is horizontally fixed on the bottom surface of the base copper plate L1 (1). A base copper layer L2 (3) is horizontally fixed on the bottom surface of the flexible PI layer (2). A PP sheet layer (4) is horizontally fixed on the bottom surface of the base copper layer L2 (3). A base copper layer L3 (5) is horizontally fixed on the bottom surface of the PP sheet layer (4). A rigid FR4 layer (6) is horizontally fixed on the bottom surface of the base copper layer L3 (5). A base copper layer L4 (7) is horizontally fixed on the bottom surface of the rigid FR4 layer (6). A PP sheet layer (8) is horizontally fixed on the bottom surface of the base copper layer L4 (7). A base copper layer L5 (9) is horizontally fixed on the bottom surface of the PP sheet layer (8). A rigid board is horizontally fixed on the bottom surface of the base copper layer L5 (9). FR4 layer 1 (10), the bottom surface of the rigid FR4 layer 1 (10) is horizontally fixed with a base copper layer L5- (11), the bottom surface of the base copper layer L5- (11) is provided with a soft board area (12) for hard and soft bonding, the top surface of the base copper plate L1 (1) is provided with an outer layer hole (13) for cross-layer step blind hole, the bottom end of the outer layer hole (13) for cross-layer step blind hole is provided with an inner layer hole (14) for cross-layer step blind hole, the bottom end of the outer layer hole (13) for cross-layer step blind hole and the top end of the inner layer hole (14) for cross-layer step blind hole are provided with a step (15), the top surface of the base copper plate L1 (1) is provided with a through hole (16) for hard and soft bonding plate, and the interior of the outer layer hole (13) for cross-layer step blind hole and the inner layer hole (14) for cross-layer step blind hole is filled with filler copper (17).

2. A rigid-flexible bonded plate with cross-layer stepped blind holes according to claim 1, characterized in that: The base copper plate L1 (1), the flexible board PI layer (2) and the base copper layer L2 (3) form the outer double-sided flexible board (21), the base copper layer L3 (5), the rigid board FR4 layer (6) and the base copper layer L4 (7) form the inner double-sided rigid board (22), and the base copper layer L5 (9), the rigid board FR4 layer (10) and the base copper layer L5 (11) form the outer double-sided rigid board (23).

3. A rigid-flexible bonded plate with cross-layer stepped blind holes according to claim 2, characterized in that: The outer double-sided flexible board (21) and the inner double-sided rigid board (22) are fixedly connected to each other by a PP sheet layer (4), and the inner double-sided rigid board (22) and the outer double-sided rigid board (23) are fixedly connected to each other by a PP sheet layer (8).

4. A rigid-flexible bonded plate with cross-layer stepped blind holes according to claim 1, characterized in that: The flexible board area (12) of the soft and hard bonding area is sequentially formed by the bottom base copper layer L5-(11), the hard board FR4 layer-(10), the base copper layer L5 (9), the PP sheet layer-(8), the base copper layer L4 (7), the hard board FR4 layer (6), the base copper layer L3 (5), the PP sheet layer (4) and the base copper layer L2 (3).

5. A rigid-flex plate with cross-layer stepped blind holes according to claim 1, characterized in that: The outer hole (13) of the cross-layer step blind hole is sequentially formed by the top base copper plate L1 (1), the flexible board PI layer (2), the base copper layer L2 (3) and the PP sheet layer (4), and the inner hole (14) of the cross-layer step blind hole is sequentially formed by the base copper layer L3 (5) and the rigid board FR4 layer (6).

6. A rigid-flex plate with cross-layer stepped blind holes according to claim 1, characterized in that: The through hole (16) of the rigid-flexible plate is set through the mechanical drilling structure, extending from the top base copper plate L1 (1) to the bottom base copper layer L5 (11).

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