Flexible circuit board, rigid-flexible circuit board and preparation method thereof

Abstract

The invention discloses a flexible circuit board, a rigid-flexible circuit board and a preparation method thereof. The preparation method comprises the following steps: providing a metal layer; a first circuit pattern is formed on the upper surface of the metal layer, a second circuit pattern is formed on the lower surface of the metal layer, and the metal layer with the first circuit pattern and the second circuit pattern is obtained; a first covering film is formed on one circuit pattern of the metal layer, a second covering film is formed on the other circuit pattern of the metal layer, the space between the first covering film and the second covering film is filled with an adhesive layer, and the circuit board with the covering films and the adhesive layer is obtained; and forming a welding part on the surface of the circuit board to obtain the flexible single-layer circuit board. The circuit pattern in the metal layer is protected from being influenced by environmental factors and mechanical stress, the electrical performance of the circuit board is optimized, and the reliability of the circuit board is improved.

Description

Technical Field

[0001] The present invention relates to the field of circuit boards, and in particular to a flexible circuit board, a rigid-flex circuit board and a preparation method thereof. Background Art

[0002] With the rapid development of electronic technology, electronic devices are becoming increasingly miniaturized, high-power, and multifunctional, placing higher demands on the performance of circuit boards. In particular, in high-frequency, high-power scenarios, the thick copper layers of existing circuit boards struggle to meet the high current carrying capacity and efficient thermal conductivity requirements. Furthermore, long-term bending can easily lead to metal fatigue fractures, resulting in low circuit board reliability. Summary of the Invention

[0003] Embodiments of the present invention provide a flexible circuit board, a rigid-flex circuit board, and a method for manufacturing the same, to solve the problem of low reliability of existing circuit boards.

[0004] Based on the above purpose, in one embodiment, a method for preparing a flexible circuit board is provided, the method comprising: providing a metal layer; forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer to obtain a metal layer having the first circuit pattern and the second circuit pattern; forming a first covering film on one of the circuit patterns of the metal layer, and forming a second covering film on another circuit pattern of the metal layer, with a glue layer filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer; A soldering portion is formed on the surface of the circuit board to obtain a flexible circuit board.

[0005] The above-mentioned method for preparing a flexible single-layer circuit board comprises processing a metal layer and forming a first cover film, a glue layer, and a second cover film to form a flexible circuit board having the cover films and glue layers. Furthermore, solder joints are formed on the flexible circuit board to obtain the flexible circuit board. This method protects the circuit patterns in the metal layer from environmental factors and mechanical stress, optimizes the electrical performance of the circuit board, and improves the reliability of the flexible single-layer circuit board.

[0006] In one embodiment, forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer, and obtaining the metal layer having the first circuit pattern and the second circuit pattern includes: A first circuit pattern having a first groove is formed on the upper surface of the metal layer, and a second circuit pattern having a second groove is formed on the lower surface of the metal layer, wherein a spacing structure is provided between the bottom of the first groove and the bottom of the second groove; A first covering film is formed on one of the circuit patterns of the metal layer, and a second covering film is formed on another circuit pattern of the metal layer, wherein a glue layer is filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer, comprising: A first covering film is formed on one of the circuit patterns of the metal layer, the spacing structure is etched away, a glue layer is filled on the first covering film and the other circuit pattern, and a second covering film is formed on the glue layer to obtain a circuit board having a covering film and a glue layer.

[0007] In one embodiment, before forming the soldering portion on the surface of the circuit board, the preparation method further includes: forming at least two circuit boards with cover films and glue layers, Performing a lamination process on the circuit board having the cover film and the adhesive layer to obtain a laminated multilayer circuit board; The laminated multilayer circuit board is subjected to drilling and electroplating treatments to obtain a circuit board after drilling and electroplating treatments.

[0008] This embodiment describes a method for preparing a flexible multilayer circuit board. Two flexible boards with cover films and adhesive layers are laminated, drilled, and laminated to form a flexible multilayer circuit board. This multilayer structure allows for more circuit functions within a limited space, improving the circuit board's integration. Customization is possible based on actual needs, expanding user options. Furthermore, the flexible multilayer circuit board exhibits increased mechanical strength, enabling stable operation in more complex environments and enhancing the circuit board's reliability.

[0009] In one embodiment, drilling and electroplating are performed on the laminated multilayer circuit board to obtain a circuit board after drilling and electroplating, including: Drilling the laminated multilayer circuit board to obtain a multilayer circuit board with through holes; The multilayer circuit board with through holes is electroplated to obtain a multilayer circuit board with metal columns, and the metal columns are used to connect at least two circuit boards in the multilayer circuit board to form a circuit board after drilling and electroplating.

[0010] In one embodiment, a method for preparing a rigid-flexible circuit board is provided, the method comprising: Providing a substrate having a circuit layer; Providing at least one circuit board having a cover film and a glue layer, forming the circuit board having the cover film and the glue layer includes: providing a metal layer; forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer to obtain a metal layer having the first circuit pattern and the second circuit pattern; forming a first covering film on one of the circuit patterns of the metal layer, and forming a second covering film on another circuit pattern of the metal layer, with a glue layer filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer; Laminating the substrate and the circuit board having the cover film and the adhesive layer to obtain a laminated multilayer circuit board; The multilayer circuit board is subjected to drilling and electroplating treatments to obtain a rigid-flexible circuit board.

[0011] The above-mentioned method for preparing a rigid-flexible circuit board obtains a rigid-flexible circuit board by laminating, drilling and electroplating at least one flexible board with a covering film and an adhesive layer and a hard board with a conventional circuit layer. The rigid-flexible circuit board combines the strength of the hard board and the flexibility of the soft board, and can play an advantage in application scenarios that require high-strength support and flexible connection. At the same time, it improves the integration of the circuit board and optimizes the electrical performance of the circuit board, so that the rigid-flexible circuit board can work stably in complex environments and has high reliability.

[0012] In one embodiment, forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer, and obtaining the metal layer having the first circuit pattern and the second circuit pattern includes: A first circuit pattern having a first groove is formed on the upper surface of the metal layer, and a second circuit pattern having a second groove is formed on the lower surface of the metal layer, wherein a spacing structure is provided between the bottom of the first groove and the bottom of the second groove; A first covering film is formed on one of the circuit patterns of the metal layer, and a second covering film is formed on another circuit pattern of the metal layer, wherein a glue layer is filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer, comprising: A first covering film is formed on one of the circuit patterns of the metal layer, the spacing structure is etched away, a glue layer is filled on the first covering film and the other circuit pattern, and a second covering film is formed on the glue layer to obtain a circuit board having a covering film and a glue layer.

[0013] In one embodiment, drilling and electroplating the multilayer circuit board to obtain a rigid-flex circuit board includes: Drilling the laminated multilayer circuit board to obtain a multilayer circuit board with through holes; The multilayer circuit board with through holes is electroplated to obtain a multilayer circuit board with metal columns, and the metal columns are used to connect the substrate and the circuit board with the cover film and the adhesive layer to form a rigid-flexible circuit board.

[0014] In one embodiment, a flexible circuit board is provided, comprising: A metal layer, wherein a first circuit pattern is provided on the upper surface of the metal layer, a second circuit pattern is provided on the lower surface of the metal layer, a first covering film is provided on one of the circuit patterns of the metal layer, a second covering film is provided on another circuit pattern of the metal layer, and an adhesive layer is provided between the first covering film and the second covering film to obtain a circuit board having a covering film and an adhesive layer; a welding portion is provided on the surface of the circuit board.

[0015] This embodiment is directed to a flexible single-layer circuit board. By providing a first covering film, an adhesive layer, a second covering film and a welding portion on the circuit pattern, the circuit pattern in the metal layer is protected from environmental factors and mechanical stress, thereby optimizing the electrical performance of the circuit board and improving the reliability of the flexible single-layer circuit board.

[0016] In one embodiment, the flexible circuit board further includes: At least two circuit boards are provided with a cover film and an adhesive layer, and adjacent circuit boards are connected via metal pillars.

[0017] This embodiment features a flexible multilayer circuit board. Adjacent circuit boards are connected by metal posts, forming a multilayer structure. This allows for more circuit functionality within a limited space, improving circuit board integration. Customization is possible based on actual needs, expanding user options. Furthermore, the flexible multilayer circuit board boasts greater mechanical strength, enabling stable operation in more complex environments and enhancing circuit board reliability.

[0018] In one embodiment, a rigid-flexible circuit board is provided, the rigid-flexible circuit board comprising: A substrate having a circuit layer and at least one circuit board having a cover film and an adhesive layer, wherein the substrate and the circuit board are connected via metal pillars, and the circuit board comprises: A metal layer, wherein a first circuit pattern is provided on the upper surface of the metal layer, a second circuit pattern is provided on the lower surface of the metal layer, a first covering film is provided on one of the circuit patterns of the metal layer, a second covering film is provided on another circuit pattern of the metal layer, and an adhesive layer is provided between the first covering film and the second covering film.

[0019] The above-mentioned rigid-flexible circuit board combines the strength of a hard board and the flexibility of a soft board by connecting the substrate and the circuit board through metal columns. It can play its advantages in application scenarios that require high-strength support and flexible connection. At the same time, it improves the integration of the circuit board, optimizes the electrical performance of the circuit board, and can work stably in complex environments with high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0021] Figure 1 is a schematic diagram of a method for preparing a flexible single-layer circuit board in one embodiment of the present invention; Figure 2 is a schematic diagram of a metal layer in one embodiment of the present invention; Figure 3 is a schematic diagram of a metal layer after forming a first circuit pattern and a second circuit pattern in one embodiment of the present invention; Figure 4 is a schematic diagram of a circuit board with a cover film and an adhesive layer in one embodiment of the present invention; Figure 5 is a schematic diagram of forming a first covering film in one embodiment of the present invention; Figure 6 is a schematic diagram of an embodiment of the present invention after the spacer structure is etched away; Figure 7 is a schematic diagram of a method for preparing a flexible multilayer circuit board according to one embodiment of the present invention; Figure 8 is a schematic diagram of forming any of the circuit boards having a cover film and an adhesive layer in one embodiment of the present invention; Figure 9 is a schematic diagram of a multi-layer circuit board after lamination in one embodiment of the present invention; Figure 10 is a schematic diagram of a flexible circuit board in one embodiment of the present invention; Figure 11 is a schematic diagram of a multilayer circuit board with through holes in one embodiment of the present invention; Figure 12 1 is a schematic diagram of a method for preparing a rigid-flex circuit board according to an embodiment of the present invention; Figure 13 is a schematic diagram of forming a circuit board having a cover film and an adhesive layer in one embodiment of the present invention; Figure 14is a schematic diagram of a substrate having a circuit layer in one embodiment of the present invention; Figure 15 is a schematic diagram of a multi-layer circuit board after lamination processing in one embodiment of the present invention; Figure 16 FIG. 1 is a schematic diagram of a rigid-flex circuit board according to an embodiment of the present invention.

[0022] Figure numerals: 1. Metal layer, 2. Spacer structure, 3. First covering film, 31. First epoxy resin adhesive layer, 32. First polyimide layer, 5. Second covering film, 51. Epoxy resin adhesive, 52. Polyimide, 7. Adhesive layer, 9. Prepreg, 11. Substrate with circuit layer. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] It should be understood that the present invention can be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the invention to those skilled in the art. In the drawings, the dimensions and relative dimensions of layers and regions may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0025] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, a first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part without departing from the teachings of the present invention.

[0026] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the device in use and operation in addition to the orientations shown in the figures. For example, if the device in the drawings is flipped, then the elements or features described as "under" or "beneath" or "beneath" the other elements will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both the upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0027] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0028] In order to fully understand the present invention, detailed structures and steps will be provided in the following description to illustrate the technical solutions proposed by the present invention. Preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementations.

[0029] In one embodiment, if Figure 1 As shown, a method for preparing a flexible circuit board is provided, the preparation method comprising: S101, providing a metal layer; Among them, such as Figure 2 As shown, the metal layer 1 can be copper foil, and the thickness of the metal layer 1 is greater than or equal to 6OZ, and 1OZ is 35 m.

[0030] S102, forming a first circuit pattern on the upper surface of the metal layer, and forming a second circuit pattern on the lower surface of the metal layer, to obtain a metal layer having the first circuit pattern and the second circuit pattern; Among them, such as Figure 3As shown, LDI laser exposure is used on the upper surface of metal layer 1 to etch out the customer-specified circuits, forming a first circuit pattern. LDI laser exposure is also used on the lower surface of metal layer 1 to etch out the customer-specified circuits, forming a second circuit pattern. When the thickness of metal layer 1 is 6 oz, the thickness of both the first and second circuit patterns is 1.5 oz.

[0031] S103, forming a first covering film on one of the circuit patterns of the metal layer, and forming a second covering film on another circuit pattern of the metal layer, with a glue layer filled between the first covering film and the second covering film, to obtain a circuit board having the covering films and the glue layer; Among them, such as Figure 4 As shown, a first cover film 3 is formed on one circuit pattern of metal layer 1 and laminated to ensure close contact between the first cover film 3 and the circuit pattern. The first cover film 3 includes a first epoxy resin adhesive layer 31 and a first polyimide layer 32 (PI layer). A second cover film 5 is formed on another circuit pattern of metal layer 1. The second cover film includes a second epoxy resin adhesive layer 51 and a second polyimide layer 52 (PI layer). An adhesive layer 7 is filled between the first cover film 3 and the second cover film 5.

[0032] S104, forming a soldering portion on the surface of the circuit board to obtain a flexible circuit board.

[0033] Wherein, a welding portion is formed on the surface of the circuit board with the cover film and the adhesive layer, so that the circuit board with the cover film and the adhesive layer is connected to electronic devices such as resistors and capacitors.

[0034] In this embodiment, a flexible single-layer circuit board is obtained by processing a metal layer and forming a first cover film, an adhesive layer, and a second cover film to form a flexible circuit board with a cover film and an adhesive layer. Furthermore, solder joints are formed on the flexible circuit board to obtain a flexible single-layer circuit board. This protects the circuit patterns in the metal layer from environmental factors and mechanical stress, optimizes the electrical performance of the circuit board, and improves the reliability of the flexible single-layer circuit board.

[0035] In one embodiment, forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer, and obtaining the metal layer having the first circuit pattern and the second circuit pattern includes: A first circuit pattern having a first groove is formed on the upper surface of the metal layer, and a second circuit pattern having a second groove is formed on the lower surface of the metal layer, wherein a spacing structure is provided between the bottom of the first groove and the bottom of the second groove; Among them, such as Figure 3As shown, when LDI laser exposure is performed to etch out the circuit required by the customer, a first groove is formed on the upper surface of the metal layer 1, and a second groove is formed on the lower surface of the metal layer 1. A spacing structure 2 is provided at the bottom of the first groove and the bottom of the second groove.

[0036] A first covering film is formed on one of the circuit patterns of the metal layer, and a second covering film is formed on another circuit pattern of the metal layer, wherein a glue layer is filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer, comprising: A first covering film is formed on one of the circuit patterns of the metal layer, the spacing structure is etched away, a glue layer is filled on the first covering film and the other circuit pattern, and a second covering film is formed on the glue layer to obtain a circuit board having a covering film and a glue layer.

[0037] Here, first, a first covering film 3 is formed on a circuit pattern of the metal layer 1, such as Figure 5 As shown, in this embodiment, the first covering film 3 is formed on the second circuit pattern of the metal layer 1, and the covering film can also be formed on the first circuit pattern of the metal layer 1. Any circuit pattern can be selected; Secondly, if Figure 6 As shown, the spacer structure 2 is etched away by LDI laser exposure; Next, fill the first cover film 3 and another circuit pattern with a glue layer 7, as shown in FIG. Figure 4 As shown, in this embodiment, the first cover film 3 is formed on the second circuit pattern, and the other circuit pattern is referred to as the first circuit pattern. That is, a glue layer 7 is filled on the first cover film 3 and the first circuit pattern. The material of the glue layer 7 is epoxy resin glue. When filling the glue layer 7, the epoxy resin glue can be filled to a position flush with the metal layer 1, or it can be filled to cover the metal layer 1, and the adjustment is adjusted according to needs. Finally, if Figure 4 As shown, the second cover film 5 is placed on the adhesive layer 7 and pressed together to tightly connect the second cover film 5 to the adhesive layer 7, thereby obtaining a circuit board having the cover film and the adhesive layer.

[0038] In this embodiment, the spacing structure between the two circuit patterns is completely etched away, and epoxy resin glue is used to fill it to obtain a glue layer. A second covering film is provided on the glue layer, so that the circuit patterns of the metal layer 1 are completely filled with soft material. This can protect the circuit patterns in the metal layer from environmental factors and mechanical stress, optimize the electrical performance of the circuit board, and improve the reliability of the flexible single-layer circuit board.

[0039] In one embodiment, if Figure 7 As shown, a method for preparing a flexible circuit board is provided, the preparation method comprising: S31, forming at least two circuit boards with cover films and adhesive layers, such as Figure 8 As shown, forming any of the circuit boards having a cover film and a glue layer includes: S3101, providing a metal layer; Among them, such as Figure 2 As shown, the metal layer 1 can be copper foil, and the thickness of the metal layer 1 is greater than or equal to 6OZ, and 1OZ is 35 m.

[0040] S3102, forming a first circuit pattern on the upper surface of the metal layer, and forming a second circuit pattern on the lower surface of the metal layer, to obtain a metal layer having the first circuit pattern and the second circuit pattern; Among them, such as Figure 3 As shown, LDI laser exposure is used on the upper surface of metal layer 1 to etch out the customer-specified circuits, forming a first circuit pattern. LDI laser exposure is also used on the lower surface of metal layer 1 to etch out the customer-specified circuits, forming a second circuit pattern. When the thickness of metal layer 1 is 6 oz, the thickness of both the first and second circuit patterns is 1.5 oz.

[0041] S3103, forming a first covering film on one of the circuit patterns of the metal layer, and forming a second covering film on another circuit pattern of the metal layer, with a glue layer being filled between the first covering film and the second covering film, to obtain a circuit board having the covering films and the glue layer; Among them, such as Figure 4 As shown, a first cover film 3 is formed on one circuit pattern of metal layer 1 and laminated to ensure close contact between the two patterns. The first cover film 3 comprises a first epoxy resin adhesive layer 31 and a first polyimide layer 32 (PI layer). A second cover film 5 is formed on another circuit pattern of metal layer 1. The second cover film 5 comprises a second epoxy resin adhesive layer 51 and a second polyimide layer 52 (PI layer). An adhesive layer 7 is placed between the first cover film 3 and the second cover film 5.

[0042] S32, laminating the at least two circuit boards having the cover films and the adhesive layer to obtain a laminated multilayer circuit board; Among them, such as Figure 9 As shown, this example provides two circuit boards with cover films and adhesive layers, and a prepreg 9 is arranged between the two circuit boards with cover films and adhesive layers for pressing, so that the two circuit boards with cover films and adhesive layers are tightly fitted.

[0043] S33, performing drilling and electroplating on the laminated multilayer circuit board to obtain a flexible circuit board.

[0044] Among them, such as Figure 10As shown, after drilling and electroplating, a flexible circuit board is obtained.

[0045] In this embodiment, two flexible boards with cover films and adhesive layers are laminated, drilled, and laminated to form a flexible multilayer circuit board. This multilayer structure allows for more circuit functionality within a limited space, improving the circuit board's integration. Customization is possible based on actual needs, expanding user options. Furthermore, the flexible multilayer circuit board boasts greater mechanical strength, enabling stable operation in complex environments and enhancing its reliability.

[0046] In one embodiment, forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer, and obtaining the metal layer having the first circuit pattern and the second circuit pattern includes: A first circuit pattern having a first groove is formed on the upper surface of the metal layer, and a second circuit pattern having a second groove is formed on the lower surface of the metal layer, wherein a spacing structure is provided between the bottom of the first groove and the bottom of the second groove; Among them, such as Figure 3 As shown, when LDI laser exposure is performed to etch out the circuit required by the customer, a first groove is formed on the upper surface of the metal layer 1, and a second groove is formed on the lower surface of the metal layer 1. A spacing structure 2 is provided at the bottom of the first groove and the bottom of the second groove.

[0047] A first covering film is formed on one of the circuit patterns of the metal layer, and a second covering film is formed on another circuit pattern of the metal layer, wherein a glue layer is filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer, comprising: A first covering film is formed on one of the circuit patterns of the metal layer, the spacing structure is etched away, a glue layer is filled on the first covering film and the other circuit pattern, and a second covering film is formed on the glue layer to obtain a circuit board having a covering film and a glue layer.

[0048] Here, first, a first covering film 3 is formed on a circuit pattern of the metal layer 1, such as Figure 5 As shown, in this embodiment, the first covering film 3 is formed on the second circuit pattern of the metal layer 1, and the covering film can also be formed on the first circuit pattern of the metal layer 1. Any circuit pattern can be selected; Secondly, if Figure 6 As shown, the spacer structure 2 is etched away by LDI laser exposure; Next, fill the first cover film 3 and another circuit pattern with a glue layer 7, as shown in FIG. Figure 4As shown, in this embodiment, the first cover film 3 is formed on the second circuit pattern, and the other circuit pattern is referred to as the first circuit pattern. That is, a glue layer 7 is filled on the first cover film 3 and the first circuit pattern. The material of the glue layer 7 is epoxy resin glue. When filling the glue layer 7, the epoxy resin glue can be filled to a position flush with the metal layer 1, or it can be filled to cover the metal layer 1, and the adjustment is adjusted according to needs. Finally, if Figure 4 As shown, the second cover film 5 is placed on the adhesive layer 7 and pressed together to tightly connect the second cover film 5 to the adhesive layer 7, thereby obtaining a circuit board having the cover film and the adhesive layer.

[0049] In this embodiment, the spacing structure between the two circuit patterns is completely etched away, and epoxy resin glue is used to fill it to obtain a glue layer. A second covering film is provided on the glue layer, so that the circuit patterns of the metal layer 1 are completely filled with soft material. This can protect the circuit patterns in the metal layer from environmental factors and mechanical stress, optimize the electrical performance of the circuit board, and improve the reliability of the flexible multilayer circuit board.

[0050] In one embodiment, drilling and electroplating are performed on the laminated multilayer circuit board to obtain a circuit board after drilling and electroplating, including: S201, drilling the laminated multilayer circuit board to obtain a multilayer circuit board with through holes; Among them, such as Figure 11 As shown, the multi-layer circuit board after pressing is drilled. In this example, two circuit boards with cover films and adhesive layers are pressed together to form a double-layer circuit board. If there are multiple circuit boards with cover films and adhesive layers, holes can be drilled only between two circuit boards with cover films and adhesive layers, or between multiple circuit boards with cover films and adhesive layers. Adjustments can be made as needed.

[0051] S202, electroplating the multilayer circuit board with through holes to obtain a multilayer circuit board with metal pillars, wherein the metal pillars are used to connect at least two circuit boards in the multilayer circuit board to form a circuit board after drilling and electroplating.

[0052] Among them, such as Figure 10 As shown, during the electroplating process, the through-holes obtained by drilling connect the metal layers 1 of the two circuit boards through metal pillars. In this example, the metal pillars connect the two circuit boards. If holes are drilled between multiple circuit boards with cover films and adhesive layers, the metal pillars can be connected to the metal layers of two of the circuit boards, or to the metal layers of multiple circuit boards. This can be adjusted according to needs.

[0053] In this embodiment, through-holes are drilled into the laminated multilayer circuit board, followed by electroplating. At least two circuit boards within the multilayer circuit board are connected with metal posts to form a multilayer structure. This allows for more circuit functions within a limited space, improving the circuit board's integration. Customization is possible based on actual needs, expanding user options. Furthermore, the flexible multilayer circuit board has greater mechanical strength, enabling stable operation in more complex environments, thus enhancing its reliability.

[0054] In one embodiment, if Figure 12 As shown, a method for preparing a rigid-flexible circuit board is provided, the preparation method comprising: S61, providing a substrate having a circuit layer; Among them, such as Figure 14 As shown, the substrate 11 having the circuit layer is a conventional FR4 hard board.

[0055] S62, providing at least one circuit board having a cover film and a glue layer, forming the circuit board having the cover film and the glue layer as Figure 13 Shown, including: S6201, providing a metal layer; Among them, such as Figure 2 As shown, the metal layer 1 can be copper foil, and the thickness of the metal layer 1 is greater than or equal to 6OZ, and 1OZ is 35 m.

[0056] S6202, forming a first circuit pattern on the upper surface of the metal layer, and forming a second circuit pattern on the lower surface of the metal layer, to obtain a metal layer having the first circuit pattern and the second circuit pattern; Among them, such as Figure 3 As shown, LDI laser exposure is used on the upper surface of metal layer 1 to etch out the customer-specified circuits, forming a first circuit pattern. LDI laser exposure is also used on the lower surface of metal layer 1 to etch out the customer-specified circuits, forming a second circuit pattern. When the thickness of metal layer 1 is 6 oz, the thickness of both the first and second circuit patterns is 1.5 oz.

[0057] S6203, forming a first covering film on one of the circuit patterns of the metal layer, and forming a second covering film on another circuit pattern of the metal layer, with a glue layer being filled between the first covering film and the second covering film, to obtain a circuit board having the covering films and the glue layer; Among them, such as Figure 4As shown, a first cover film 3 is formed on one circuit pattern of metal layer 1 and laminated to ensure close contact between the two patterns. The first cover film 3 comprises a first epoxy resin adhesive layer 31 and a first polyimide layer 32 (PI layer). A second cover film 5 is formed on another circuit pattern of metal layer 1. The second cover film 5 comprises a second epoxy resin adhesive layer 51 and a second polyimide layer 52 (PI layer). An adhesive layer 7 is placed between the first cover film 3 and the second cover film 5.

[0058] S63, laminating the substrate and the circuit board having the cover film and the adhesive layer to obtain a laminated multilayer circuit board; Among them, such as Figure 15 As shown, this example provides a circuit board with a cover film and an adhesive layer, and a prepreg 9 is set between the substrate with the circuit layer and the circuit board with the cover film and the adhesive layer for pressing, so that the two circuit boards with the cover film and the adhesive layer are tightly fitted.

[0059] S64, performing drilling and electroplating on the multilayer circuit board to obtain a rigid-flex circuit board.

[0060] Among them, such as Figure 16 As shown, after drilling and electroplating, a rigid-flexible circuit board is obtained.

[0061] In this embodiment, a rigid-flexible circuit board is obtained by laminating, drilling, and electroplating at least one flexible board with a covering film and an adhesive layer and a hard board with a conventional circuit layer. It combines the strength of a hard board with the flexibility of a soft board, and can play an advantage in application scenarios that require high-strength support and flexible connection. At the same time, it improves the integration of the circuit board and optimizes the electrical performance of the circuit board, so that the rigid-flexible circuit board can work stably in complex environments and has high reliability.

[0062] In one embodiment, a first circuit pattern is formed on the upper surface of the metal layer, and a second circuit pattern is formed on the lower surface of the metal layer. The metal layer having the first circuit pattern and the second circuit pattern includes: A first circuit pattern having a first groove is formed on the upper surface of the metal layer, and a second circuit pattern having a second groove is formed on the lower surface of the metal layer, wherein a spacing structure is provided between the bottom of the first groove and the bottom of the second groove; Among them, such as Figure 3 As shown, when LDI laser exposure is performed to etch out the circuit required by the customer, a first groove is formed on the upper surface of the metal layer 1, and a second groove is formed on the lower surface of the metal layer 1. A spacing structure 2 is provided at the bottom of the first groove and the bottom of the second groove.

[0063] A first covering film is formed on one of the circuit patterns of the metal layer, and a second covering film is formed on another circuit pattern of the metal layer, wherein a glue layer is filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer, comprising: A first covering film is formed on one of the circuit patterns of the metal layer, the spacing structure is etched away, a glue layer is filled on the first covering film and the other circuit pattern, and a second covering film is formed on the glue layer to obtain a circuit board having a covering film and a glue layer.

[0064] Here, first, a first covering film 3 is formed on a circuit pattern of the metal layer 1, such as Figure 5 As shown, in this embodiment, the first covering film 3 is formed on the second circuit pattern of the metal layer 1, and the covering film can also be formed on the first circuit pattern of the metal layer 1. Any circuit pattern can be selected; Secondly, if Figure 6 As shown, the spacer structure 2 is etched away using LDI laser exposure; Next, fill the first cover film 3 and another circuit pattern with a glue layer 7, as shown in FIG. Figure 4 As shown, in this embodiment, the first cover film 3 is formed on the second circuit pattern, and the other circuit pattern is referred to as the first circuit pattern. That is, a glue layer 7 is filled on the first cover film 3 and the first circuit pattern. The material of the glue layer 7 is epoxy resin glue. When filling the glue layer 7, the epoxy resin glue can be filled to a position flush with the metal layer 1, or it can be filled to cover the metal layer 1, and the adjustment is adjusted according to needs. Finally, if Figure 4 As shown, the second cover film 5 is placed on the adhesive layer 7 and pressed together to tightly connect the second cover film 5 to the adhesive layer 7, thereby obtaining a circuit board having the cover film and the adhesive layer.

[0065] In this embodiment, the spacing structure between the two circuit patterns is completely etched away, and epoxy resin glue is used to fill it to obtain a glue layer. A second covering film is provided on the glue layer, so that the circuit patterns of the metal layer 1 are completely filled with soft material, which can protect the circuit patterns in the metal layer from environmental factors and mechanical stress, optimize the electrical performance of the circuit board, and improve the reliability of the rigid-flexible circuit board.

[0066] In one embodiment, drilling and electroplating the multilayer circuit board to obtain a rigid-flex circuit board includes: Drilling the laminated multilayer circuit board to obtain a multilayer circuit board with through holes; The multilayer circuit board with through holes is electroplated to obtain a multilayer circuit board with metal columns, and the metal columns are used to connect the substrate and the circuit board with the cover film and the adhesive layer to form a rigid-flexible circuit board.

[0067] In one embodiment, if Figure 4 As shown, a flexible circuit board is provided, the flexible circuit board comprising: A metal layer 1 is provided with a first circuit pattern on the upper surface of the metal layer 1, a second circuit pattern is provided on the lower surface of the metal layer 1, a first covering film 3 is provided on one of the circuit patterns of the metal layer 1, a second covering film 5 is provided on another circuit pattern of the metal layer 1, and an adhesive layer 7 is provided between the first covering film 3 and the second covering film 5; a welding portion is provided on the surface of the circuit board.

[0068] Among them, the first covering film 3 includes a first epoxy resin adhesive layer 31 and a first polyimide layer 32 (PI layer), the second covering film 5 includes a second epoxy resin adhesive layer 51 and a second polyimide layer 52 (PI layer), and there is an adhesive layer 7 between the first covering film 3 and the second covering film 5. The material of the adhesive layer 7 is epoxy resin adhesive. The adhesive layer 7 can be flush with the metal layer 1, or it can cover the metal layer 1, and can be adjusted according to needs.

[0069] In this embodiment, by providing a first covering film, an adhesive layer, a second covering film and a welding portion on the circuit pattern, the circuit pattern in the metal layer is protected from environmental factors and mechanical stress, thereby optimizing the electrical performance of the circuit board and improving the reliability of the flexible single-layer circuit board.

[0070] In one embodiment, if Figure 10 As shown, a flexible circuit board is provided, the flexible circuit board comprising: At least two circuit boards having a cover film and an adhesive layer, adjacent circuit boards being connected by metal posts, any of the circuit boards comprising: A metal layer 1, wherein a first circuit pattern is provided on the upper surface of the metal layer 1, a second circuit pattern is provided on the lower surface of the metal layer 1, a first covering film 3 is provided on one of the circuit patterns of the metal layer 1, a second covering film 5 is provided on another circuit pattern of the metal layer 1, and an adhesive layer 7 is provided between the first covering film 3 and the second covering film 5.

[0071] Among them, the flexible multilayer circuit board includes a semi-cured sheet 9 between each circuit board, the first cover film 3 includes a first epoxy resin adhesive layer 31 and a first polyimide layer 32 (PI layer), the second cover film 5 includes a second epoxy resin adhesive layer 51 and a second polyimide layer (52PI layer), and there is an adhesive layer 7 between the first cover film 3 and the second cover film 5. The material of the adhesive layer 7 is epoxy resin adhesive. The adhesive layer 7 can be flush with the metal layer 1, or it can cover the metal layer 1, and can be adjusted according to needs.

[0072] In this example, a flexible double-layer circuit board is formed by two circuit boards with cover films and adhesive layers. The two circuit boards are connected by metal pillars. If there are multiple circuit boards with cover films and adhesive layers, the metal pillars can be connected to the metal layers of two of the circuit boards, or to the metal layers of multiple circuit boards. This can be adjusted according to needs.

[0073] In this embodiment, adjacent circuit boards are connected by metal pillars, forming a multi-layer structure. This allows for more circuit functionality within a limited space, improving circuit board integration. Customization is possible based on actual needs, expanding user options. Furthermore, flexible multi-layer circuit boards offer greater mechanical strength, enabling stable operation in more complex environments and enhancing circuit board reliability.

[0074] In one embodiment, if Figure 16 As shown, a rigid-flexible circuit board is provided, the rigid-flexible circuit board comprising: A substrate 11 having a circuit layer and at least one circuit board having a cover film and an adhesive layer, wherein the substrate 11 having a circuit layer and the circuit board are connected via metal pillars, and the circuit board comprises: A metal layer 1, wherein a first circuit pattern is provided on the upper surface of the metal layer 1, a second circuit pattern is provided on the lower surface of the metal layer 1, a first covering film 3 is provided on one of the circuit patterns of the metal layer 1, a second covering film 5 is provided on another circuit pattern of the metal layer 1, and an adhesive layer 7 is provided between the first covering film 3 and the second covering film 5.

[0075] Among them, the flexible multilayer circuit board includes a semi-cured sheet 9 between each circuit board, the first cover film 3 includes a first epoxy resin adhesive layer 31 and a first polyimide layer 32 (PI layer), the second cover film 5 includes a second epoxy resin adhesive layer 51 and a second polyimide layer 52 (PI layer), and there is an adhesive layer 7 between the first cover film 3 and the second cover film 5. The material of the adhesive layer 7 is epoxy resin adhesive. The adhesive layer 7 can be flush with the metal layer 1, or it can cover the metal layer 1, and can be adjusted according to needs.

[0076] In this example, a rigid-flex double-layer circuit board is formed by a substrate and a circuit board with a cover film and an adhesive layer. The substrate and the circuit board with the cover film and the adhesive layer are connected by metal pillars. If there are multiple circuit boards with cover films and adhesive layers, the metal pillars can be connected to the metal layers of the substrate and one circuit board, or to the metal layers of multiple circuit boards. This can be adjusted according to needs.

[0077] In this embodiment, by connecting the substrate and the circuit board through metal columns, the rigid-flexible circuit board combines the strength of a hard board and the flexibility of a soft board, and can play its advantages in application scenarios that require high-strength support and flexible connection. At the same time, it improves the integration of the circuit board, optimizes the electrical performance of the circuit board, and can also work stably in complex environments with high reliability.

[0078] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A method for preparing a flexible circuit board, characterized in that: The preparation method comprises: providing a metal layer; forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer to obtain a metal layer having the first circuit pattern and the second circuit pattern; forming a first covering film on one of the circuit patterns of the metal layer, and forming a second covering film on another circuit pattern of the metal layer, with a glue layer filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer; A soldering portion is formed on the surface of the circuit board to obtain a flexible circuit board.

2. The preparation method according to claim 1, characterized in that Forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer to obtain a metal layer having the first circuit pattern and the second circuit pattern includes: A first circuit pattern having a first groove is formed on the upper surface of the metal layer, and a second circuit pattern having a second groove is formed on the lower surface of the metal layer, wherein a spacing structure is provided between the bottom of the first groove and the bottom of the second groove; A first covering film is formed on one of the circuit patterns of the metal layer, and a second covering film is formed on another circuit pattern of the metal layer, wherein a glue layer is filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer, comprising: A first covering film is formed on one of the circuit patterns of the metal layer, the spacing structure is etched away, a glue layer is filled on the first covering film and the other circuit pattern, and a second covering film is formed on the glue layer to obtain a circuit board having a covering film and a glue layer.

3. The preparation method according to claim 1, characterized in that Before forming the soldering portion on the surface of the circuit board, the preparation method further includes: forming at least two circuit boards having a cover film and a glue layer, Performing a lamination process on the circuit board having the cover film and the adhesive layer to obtain a laminated multilayer circuit board; The laminated multilayer circuit board is subjected to drilling and electroplating treatments to obtain a circuit board after drilling and electroplating treatments.

4. The preparation method according to claim 3, characterized in that The laminated multilayer circuit board is subjected to drilling and electroplating to obtain a circuit board after drilling and electroplating, comprising: Drilling the laminated multilayer circuit board to obtain a multilayer circuit board with through holes; The multilayer circuit board with through holes is electroplated to obtain a multilayer circuit board with metal columns, and the metal columns are used to connect at least two circuit boards in the multilayer circuit board to form a circuit board after drilling and electroplating.

5. A method for preparing a rigid-flex circuit board, characterized in that: The preparation method comprises: Providing a substrate having a circuit layer; Providing at least one circuit board having a cover film and a glue layer, forming the circuit board having the cover film and the glue layer includes: providing a metal layer; forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer to obtain a metal layer having the first circuit pattern and the second circuit pattern; forming a first covering film on one of the circuit patterns of the metal layer, and forming a second covering film on another circuit pattern of the metal layer, with a glue layer filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer; Laminating the substrate and the circuit board having the cover film and the adhesive layer to obtain a laminated multilayer circuit board; The multilayer circuit board is subjected to drilling and electroplating treatments to obtain a rigid-flexible circuit board.

6. The preparation method according to claim 5, characterized in that Forming a first circuit pattern on the upper surface of the metal layer and forming a second circuit pattern on the lower surface of the metal layer to obtain a metal layer having the first circuit pattern and the second circuit pattern includes: A first circuit pattern having a first groove is formed on the upper surface of the metal layer, and a second circuit pattern having a second groove is formed on the lower surface of the metal layer, wherein a spacing structure is provided between the bottom of the first groove and the bottom of the second groove; A first covering film is formed on one of the circuit patterns of the metal layer, and a second covering film is formed on another circuit pattern of the metal layer, wherein a glue layer is filled between the first covering film and the second covering film, to obtain a circuit board having the covering film and the glue layer, comprising: A first covering film is formed on one of the circuit patterns of the metal layer, the spacing structure is etched away, a glue layer is filled on the first covering film and the other circuit pattern, and a second covering film is formed on the glue layer to obtain a circuit board having a covering film and a glue layer.

7. The preparation method according to claim 6, characterized in that The multilayer circuit board is subjected to drilling and electroplating to obtain a rigid-flex circuit board, comprising: Drilling the laminated multilayer circuit board to obtain a multilayer circuit board with through holes; The multilayer circuit board with through holes is electroplated to obtain a multilayer circuit board with metal columns, and the metal columns are used to connect the substrate and the circuit board with the cover film and the adhesive layer to form a rigid-flexible circuit board.

8. A flexible circuit board, characterized in that: The flexible circuit board comprises: A metal layer, wherein a first circuit pattern is provided on the upper surface of the metal layer, a second circuit pattern is provided on the lower surface of the metal layer, a first covering film is provided on one of the circuit patterns of the metal layer, a second covering film is provided on another circuit pattern of the metal layer, and an adhesive layer is provided between the first covering film and the second covering film to obtain a circuit board having a covering film and an adhesive layer; a welding portion is provided on the surface of the circuit board.

9. The flexible circuit board according to claim 8, wherein: The flexible circuit board also includes: At least two circuit boards are provided with a cover film and an adhesive layer, and adjacent circuit boards are connected via metal pillars.

10. A rigid-flex circuit board, characterized in that: The rigid-flex circuit board comprises: A substrate having a circuit layer and at least one circuit board having a cover film and an adhesive layer, wherein the substrate and the circuit board are connected via metal pillars, and the circuit board comprises: A metal layer, wherein a first circuit pattern is provided on the upper surface of the metal layer, a second circuit pattern is provided on the lower surface of the metal layer, a first covering film is provided on one of the circuit patterns of the metal layer, a second covering film is provided on another circuit pattern of the metal layer, and an adhesive layer is provided between the first covering film and the second covering film.

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