Multilayer circuit board and manufacturing method thereof

Abstract

The invention relates to the technical field of circuit board manufacturing, and discloses a multilayer circuit board and a manufacturing method thereof.The circuit board comprises a single-face circuit board and a double-face circuit board which are bent towards the same side, and the double-face circuit board and the single-face circuit board are sequentially arranged in the direction away from the inner side of a curved surface. The problem that in the prior art, a large-curvature curved-surface circuit board is difficult to manufacture is solved.

Description

Technical Field

[0001] The invention relates to the technical field of circuit board manufacturing, in particular to a multi-layer circuit board and a manufacturing method thereof. Background Art

[0002] Compared with traditional antennas, microstrip antennas have the advantages of low thickness profile, light weight, stable size, and good mass production. They are the mainstream form currently used in phased array antennas.

[0003] Compared with the traditional planar microstrip phased array antenna, the conformal microstrip phased array antenna can obtain the maximum aperture utilization area and improve the radiation angle. At the same time, it can also avoid the need for the traditional planar antenna to be equipped with a conformal radome to achieve a conformal design, thereby avoiding the sacrifice of a series of indicators such as gain, stealth, weight, and cost caused by the radome. Therefore, the conformal microstrip antenna array is an important development trend of phased array antennas.

[0004] For airborne antennas, in order to meet the installation requirements at any position of the aircraft, the curvature radius of the antenna ranges from several thousand to tens or even more than ten millimeters. For locations such as wings, the curvature radius is only in the range of tens to more than ten millimeters. Microstrip circuit boards are the structural form of phased array antennas, and their manufacturing process is a technology that manufactures single-layer or multi-layer microstrip circuit boards on non-planar surfaces. Compared with traditional planar circuits, it involves special curved shape molding, circuit pattern precision control, reliable component installation, etc., in order to adapt to the integrated manufacturing of complex three-dimensional structures such as conformal phased array antennas.

[0005] The manufacturing technology used for circuit boards has long been the PCB process. However, as we all know, the PCB process is limited by production equipment, processes, and materials, and is mainly applicable to planar structures. For curved microstrip circuits, the main methods disclosed include PCB process, curved surface etching process, and direct writing printing process.

[0006] PCB technology is mainly applicable to planar structures. The Chinese patent publication number CN116156789A discloses "a method for manufacturing a curved multilayer radio frequency circuit board and a pressing mold", which solves the problem that traditional PCB cannot manufacture curved circuit boards, but it is mainly applicable to situations where the curvature is not large.

[0007] In the relevant patent literature, Chinese patent application number CN97110945.4 discloses "a method for manufacturing a curved microstrip antenna", which is to directly use laser surface etching under computer control on a dielectric substrate and then use an electroplating process to manufacture a spiral antenna pattern. This process can only be used to make curved surface patterns on existing dielectrics. On the one hand, it cannot solve the most core basic problem of dielectric board manufacturing for curved printed circuit boards, and on the other hand, it cannot achieve vertical interconnection. Summary of the invention

[0008] In order to overcome the deficiencies of the prior art, the present invention provides a multi-layer circuit board and a method for manufacturing the same, which solve the problems existing in the prior art such as difficulty in manufacturing a curved circuit board with a large curvature.

[0009] The technical solution adopted by the present invention to solve the above problems is:

[0010] A multi-layer circuit board comprises a single-sided circuit board and a double-sided circuit board which are bent towards the same side, wherein the double-sided circuit board and the single-sided circuit board are arranged in sequence in a direction away from the inner side of the curved surface.

[0011] As a preferred technical solution, it includes a filling layer arranged between the single-sided circuit board and the double-sided circuit board.

[0012] As a preferred technical solution, it includes a plurality of stress release grooves arranged on the inner surface of the double-sided circuit board and arranged along the top line of the curved surface.

[0013] As a preferred technical solution, the width of the stress release groove is less than 1 mm.

[0014] As a preferred technical solution, the ratio of the length of the stress relief groove to the spacing between adjacent stress relief grooves is in the range of 1 to 2.

[0015] As a preferred technical solution, the stress relief groove is a blind groove.

[0016] As a preferred technical solution, the distance between the bottom of the stress release groove and the outer surface of the double-sided circuit board is 50% to 70% of the thickness of the double-sided circuit board.

[0017] As a preferred technical solution, the second circuit and the third circuit are vertically interconnected.

[0018] As a preferred technical solution, the material of the single-sided circuit board and the double-sided circuit board are both PTFE microwave substrates without glass fiber support, and the material of the filling layer is prepreg.

[0019] The method for manufacturing a multi-layer circuit board comprises the following steps:

[0020] S1, positioning and stacking the single-sided circuit board and the double-sided circuit board on the tooling base to form a PCB product, and laying a filling layer between the single-sided circuit board and the double-sided circuit board;

[0021] S2, turn over the stacked PCB product and the tooling base so that the concave surface of the PCB product faces upward, and then put the PCB product into the PCB press for pressing, so as to realize the curved surface pressing of single-sided circuit boards and double-sided circuit boards and form a curved multi-layer printed circuit board.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] ((1) The PTFE microwave substrate without glass fiber support is used, which has better toughness than traditional glass fiber materials and reduces the risk of fracture under large curvature bending conditions;

[0024] (2) The low flowability of the low-flow prepreg is used to achieve a curved gap between two layers of curved circuits, which can realize the manufacture of curved multi-layer circuit boards with large curvature (R15 and above). At the same time, the rebound stress caused by the forced curved surface pressing process of the flat multi-layer PCB is greatly reduced, as well as the risk of inter-layer delamination and even substrate fracture caused by excessive stress, thereby improving the long-term reliability of the curved multi-layer PCB;

[0025] (3) The traditional PCB material system is retained, which does not affect the electrical performance and the environmental adaptability of the product such as vibration and temperature;

[0026] (4) The manufacturing process is compatible with traditional PCB technology and does not require additional processing equipment. The process technology is mature and feasible, which solves the problem that traditional printed circuit board technology cannot realize the manufacturing of large curvature multi-layer PCBs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the circuit board after forming;

[0028] Figure 2 It is a schematic diagram of the stress relief groove structure on the PCB;

[0029] Figure 3 It is a schematic diagram of the curved surface stacking of the circuit board;

[0030] Figure 4 It is a schematic diagram of the curved surface pressing of the circuit board;

[0031] Figure 5 This is the arrangement direction diagram of the stress relief groove.

[0032] Marks and their corresponding names in the accompanying drawings: 1. single-sided circuit board, 2. double-sided circuit board, 3. first circuit, 4. second circuit, 5. third circuit, 6. filling layer, 7. stress relief groove, 8. tooling base, 9. tooling pressure plate, 10. positioning pin, 11. PCB positioning hole, 12. PCB press. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0034] Example 1

[0035] like Figures 1 to 5As shown, the present invention is based on traditional PCB process technology and provides a method for laminating and manufacturing a large curvature microstrip circuit board by using a flexible PCB material and a prepreg as a substrate, using intermittent blind grooves as a molding stress release structure, and using a curved surface molding tool. Preferably, the material of the single-sided circuit board 1 and the double-sided circuit board 2 are both PTFE microwave substrates without glass fiber support, which are more suitable for manufacturing large curvature curved surface multilayer circuit boards compared to the material with glass fiber commonly used in the prior art.

[0036] The overall process of the present invention is a PCB process system. By changing the lamination process of the PCB process, the previous processes such as graphic manufacturing are not affected, so the graphic accuracy can remain unchanged. The overall process has good feasibility, high product reliability, and high engineering application feasibility.

[0037] The solution is as follows:

[0038] 1. When designing the feeding holes on the inner surface of the PCB, avoid the vertex of the curvature radius. The outer contour of the PCB is divided according to the expandable area of ​​the profile. After the division, each circuit board is in an expandable state;

[0039] 2. A low-loss PTFE microwave substrate without glass fiber support is used to prepare a single-sided circuit board 1 with a first circuit 3 and a double-sided circuit board 2 with a vertical interconnection circuit (the two-sided circuits are the first circuit 3 and the second circuit 4, respectively) according to the PCB process. The circuit sizes and graphic positions of the first circuit 3, the second circuit 4, and the third circuit 5 are designed according to the size after the curved surface is unfolded to ensure that the normals of the circuits of each layer are aligned after bending;

[0040] 3. Such as Figure 5 As shown, intermittent stress release grooves 7 (blind grooves) are processed on the inner surface of the double-sided circuit board 2 along the top line of the curved surface. The width of the stress release grooves 7 is less than 1 mm, and the ratio of the groove length to the spacing is about 1 to 2. During processing, the depth is controlled to leave about 0.2 mm of material at the bottom (the purpose is to ensure that the stress release grooves 7 do not penetrate. If penetrated, it will affect the overall strength and the filling material in the subsequent process will penetrate from this gap, affecting the filling effect). The stress release grooves 7 do not penetrate the overall PCB size in the length direction when not processed, and the width is less than the overall rigidity of the PCB ( Figure 2 ); The length cannot be completely pulled through, and the distance from the edge of the hole to the edge of the part is 5 to 10 mm, otherwise it is easy to delaminate on the edge; in addition, the depth cannot be penetrated, otherwise the glue of the semi-cured sheet will penetrate from the stress release groove 7 when the two layers are pressed together, thereby affecting the thickness and causing deterioration of the electrical performance.

[0041] 4.Press the single-sided circuit board 1 and double-sided circuit board 2 Figure 3The schematic diagram shows that the positioning and stacking of boards are performed directly on the tooling base 8 by means of positioning pins 10 (stacking and positioning are performed simultaneously, and positioning pins 10 are required for positioning when stacking boards, that is, when placing circuit boards), and a low-flow adhesive prepreg (filling layer 6) with a carrier of the same outer dimensions is laid between the single-sided circuit board 1 and the double-sided circuit board 2. The thickness and number of layers of the prepreg are determined according to the design requirements;

[0042] 5. Turn over the stacked product and the tooling base 8 so that the concave surface of the PCB faces upward, and then place them in the PCB press 12, and press them according to the standard pressing parameters of the semi-cured sheet to achieve curved pressing of the single-sided circuit board 1 and the double-sided circuit board 2 to form a complete curved multi-layer printed circuit board. When stacking the boards, operate on the tooling base (this is easier to operate), place the single-sided circuit board 1 and the double-sided circuit board 2 on the tooling base, buckle the tooling pressure plate 9, and then tighten it with screws; then turn the whole thing over and put it into the press. The prior art is to crimp directly without turning the tooling over, and the filling material will be lost due to gravity after it comes out, so it needs to be turned over. There are two PCB positioning holes 11 on the tooling pressure plate 9, the tooling base 8, the PCB product, and the semi-cured sheet, and the positioning pins 10 are placed in the PCB positioning holes 11.

[0043] The present invention has the following technical effects:

[0044] (1) The PTFE microwave substrate without glass fiber support is used, which has better toughness than traditional glass fiber materials and reduces the risk of fracture under large curvature bending conditions;

[0045] (2) The low flowability of the low-flow prepreg is used to achieve a curved gap between two layers of curved circuits, which can realize the manufacture of curved multi-layer circuit boards with large curvature (R15 and above). At the same time, the rebound stress caused by the forced curved surface pressing process of the flat multi-layer PCB is greatly reduced, as well as the risk of inter-layer delamination and even substrate fracture caused by excessive stress, thereby improving the long-term reliability of the curved multi-layer PCB;

[0046] (3) The traditional PCB material system is retained, which does not affect the electrical performance and the environmental adaptability of the product such as vibration and temperature;

[0047] (4) The manufacturing process is compatible with traditional PCB technology and does not require additional processing equipment. The process technology is mature and feasible, which solves the problem that traditional printed circuit board technology cannot realize the manufacturing of large curvature multi-layer PCBs.

[0048] As described above, the present invention can be preferably implemented.

[0049] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or expanded or replaced in any manner.

[0050] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. According to the technical essence of the present invention, within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A multi-layer circuit board, characterized in that: It comprises a single-sided circuit board (1) and a double-sided circuit board (2) which are bent towards the same side, wherein the double-sided circuit board (2) and the single-sided circuit board (1) are arranged in sequence in a direction away from the inner side of the curved surface.

2. A multi-layer circuit board according to claim 1, characterized in that: It comprises a filling layer (6) arranged between a single-sided circuit board (1) and a double-sided circuit board (2).

3. A multi-layer circuit board according to claim 2, characterized in that: It comprises a plurality of stress release grooves (7) arranged on the inner surface of a double-sided circuit board (2) and arranged along the top line of the curved surface.

4. A multi-layer circuit board according to claim 3, characterized in that: The width including the stress release groove (7) is less than 1 mm.

5. A multi-layer circuit board according to claim 3, characterized in that: The ratio of the length of the stress release groove (7) to the spacing between adjacent stress release grooves (7) is in the range of 1 to 2.

6. A multi-layer circuit board according to claim 3, characterized in that: The stress release groove (7) is a blind groove.

7. A multi-layer circuit board according to claim 6, characterized in that: The distance between the bottom of the stress release groove (7) and the outer surface of the double-sided circuit board (2) is 50% to 70% of the thickness of the double-sided circuit board (2).

8. A multi-layer circuit board according to claim 2, characterized in that: The second circuit (4) and the third circuit (5) are vertically interconnected.

9. A multi-layer circuit board according to any one of claims 2 to 8, characterized in that: The material of the single-sided circuit board (1) and the double-sided circuit board (2) is a PTFE microwave substrate without glass fiber support, and the material of the filling layer (6) is a prepreg.

10. A method for manufacturing a multi-layer circuit board according to any one of claims 2 to 9, characterized in that: The following steps are involved: S1, positioning and stacking the single-sided circuit board (1) and the double-sided circuit board (2) on a tooling base to form a PCB product, and laying a filling layer (6) between the single-sided circuit board (1) and the double-sided circuit board (2); S2, turning over the stacked PCB product and the tooling base so that the concave surface of the PCB product faces upward, and then placing the PCB product into a PCB press for pressing, thereby achieving curved surface pressing of the single-sided circuit board (1) and the double-sided circuit board (2) to form a curved multilayer printed circuit board.

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