Flexible circuit boards based on photosensitive insulating materials

Abstract

This utility model discloses a flexible circuit board based on a photosensitive insulating material. The flexible circuit board based on the photosensitive insulating material includes a first conductive layer, a first photosensitive insulating layer, a second conductive layer, a second photosensitive insulating layer, and a third photosensitive insulating layer as a substrate. The first photosensitive insulating layer covers the first conductive layer, and a first through-hole is formed on the first photosensitive insulating layer by exposure and development. The second conductive layer is disposed on the side opposite to the first photosensitive insulating layer and has a first conductive portion extending to the first through-hole. The first conductive layer and the second conductive layer are connected through the first conductive portion. The second photosensitive insulating layer and the third photosensitive insulating layer respectively cover the first conductive layer and the second conductive layer, and the second photosensitive insulating layer is located on the side opposite to the first conductive layer.

Description

Technical Field

[0001] This utility model relates to the technical field of flexible circuit boards, and specifically to a flexible circuit board based on photosensitive insulating materials. Background Technology

[0002] With the development of technology, the demand for high-frequency, high-speed flexible circuit boards is increasing. This requires the circuit board insulation layer to have a low dielectric constant and dielectric loss, which traditional polyimide cannot meet, necessitating the use of modified polyimide, liquid crystal polymers, and fluoropolymers. Due to the high cost of these materials and their largely monopolistic nature, high-frequency, high-speed flexible circuit boards still have a low market share in China.

[0003] In addition, traditional processes suffer from problems such as misalignment between laser and exposure during multiple alignments and low precision in protective film punching, which are not conducive to the production of high-density circuit boards. Utility Model Content

[0004] In view of this, the present invention provides a flexible circuit board based on photosensitive insulating material to solve the problems of misalignment in laser and exposure multiple times, low precision of protective film punching, and unfavorable conditions for manufacturing high-density circuit boards in the existing traditional process.

[0005] This utility model provides a flexible circuit board based on a photosensitive insulating material, the flexible circuit board based on the photosensitive insulating material comprising:

[0006] The first conductive layer serves as the substrate;

[0007] A first photosensitive insulating layer covers the first conductive layer, and a first through hole is formed on the first photosensitive insulating layer by exposure and development.

[0008] A second conductive layer is disposed on the side opposite to the first photosensitive insulating layer and the first conductive layer. The second conductive layer has a first conductive portion extending to the first via, and the first conductive layer and the second conductive layer are connected through the first conductive portion; and

[0009] A second photosensitive insulating layer and a third photosensitive insulating layer are respectively covered on the first conductive layer and the second conductive layer. The second photosensitive insulating layer is located on the side opposite to the first conductive layer and the third photosensitive insulating layer.

[0010] Preferably, in the flexible circuit board based on photosensitive insulating material, the flexible circuit board is a double-layer circuit board, and the second photosensitive insulating layer and the third photosensitive insulating layer serve as protective films.

[0011] Preferably, in the flexible circuit board based on the photosensitive insulating material, the second photosensitive insulating layer and the third photosensitive insulating layer are respectively provided with openings for exposing the first conductive layer and the second conductive layer.

[0012] Preferably, in the flexible circuit board based on photosensitive insulating material, the flexible circuit board is a circuit board with at least three layers.

[0013] Preferably, in the flexible circuit board based on photosensitive insulating material, a plurality of second circuit stack structures are sequentially stacked on the side opposite to the first conductive layer of the second photosensitive insulating layer, wherein the second circuit stack structure includes a third conductive layer and a fourth photosensitive insulating layer.

[0014] Preferably, in the flexible circuit board based on the photosensitive insulating material, a second via is formed on the second photosensitive insulating layer by exposure and development;

[0015] The third conductive layer has a second conductive portion extending to the second conductive hole, and the third conductive layer is connected to the first conductive layer through the second conductive portion.

[0016] Preferably, in the flexible circuit board based on photosensitive insulating material, a plurality of first circuit stacked structures are sequentially stacked on the side opposite to the second conductive layer of the third photosensitive insulating layer, wherein the first circuit stacked structure includes a fourth conductive layer and a fifth photosensitive insulating layer.

[0017] Preferably, in the flexible circuit board based on the photosensitive insulating material, a third via is formed on the third photosensitive insulating layer by exposure and development;

[0018] The fourth conductive layer has a third conductive portion extending to the third through hole, and the fourth conductive layer is connected to the second conductive layer through the third conductive portion.

[0019] Preferably, in the flexible circuit board based on photosensitive insulating material, the dielectric constant of the first, second, and third photosensitive insulating layers is less than 3.5, and the dielectric loss is less than 0.005.

[0020] Preferably, in the flexible circuit board based on photosensitive insulating material, the first conductive layer and the second conductive layer are copper foil.

[0021] This utility model has at least the following beneficial effects:

[0022] The flexible circuit board based on photosensitive insulating material provided by this utility model includes a first conductive layer, a first photosensitive insulating layer, a second conductive layer, a second photosensitive insulating layer, and a third photosensitive insulating layer as a substrate. The first photosensitive insulating layer covers the first conductive layer, and a first through-hole is formed on the first photosensitive insulating layer through exposure and development. The second conductive layer is disposed on the side opposite to the first photosensitive insulating layer and has a first conductive portion extending to the first through-hole. The first conductive layer and the second conductive layer are connected through the first conductive portion. The second and third photosensitive insulating layers respectively cover the first and second conductive layers. The second photosensitive insulating layer is located on the side opposite to the first conductive layer, and the third photosensitive insulating layer is located on the side opposite to the second conductive layer. By using the photosensitive insulating layer, due to the characteristics of the photosensitive insulating layer, the through-hole can be formed by exposure and development without the need for laser, thus realizing the fabrication of a high-precision flexible circuit board.

[0023] Furthermore, conventional methods involve using lasers to create the vias, then depositing a conductive layer, and finally exposing the image. Since the laser and conductive layer depositing are done with different equipment, separate alignment is required, leading to significant differences in accuracy due to repeated focusing and alignment. This invention, however, does not use lasers; it creates the vias in a single exposure before depositing the conductive layer. This eliminates the need for multiple focusing and alignment operations, and the conductive layer and vias are formed simultaneously. Therefore, this invention significantly improves accuracy by employing a photosensitive insulating layer.

[0024] Furthermore, this invention uses photosensitive insulating layer exposure and development to form through holes and openings, gradually stacking layers from the inner layer to gradually increase the number of layers, and finally forming a circuit board with the target number of layers; the intermediate processes are all repetitive processes, reducing the manufacturing difficulty and facilitating industrial production.

[0025] Furthermore, laser engraving typically takes a long time (e.g., 10 minutes), while this invention, by employing a photosensitive insulating layer, takes much less time. Processing the same product usually takes less than half the time of laser engraving (e.g., laser engraving takes 10 minutes, while this invention takes less than 5 minutes).

[0026] Furthermore, in the prior art, laser processing is a physical method, while the present invention uses a photosensitive insulating layer, which is a chemical method. The photosensitive insulating layer has an image-forming function to form the through holes and opening positions.

[0027] Furthermore, this invention utilizes photosensitive insulating materials with graphic functionality, and achieves metallization followed by electroplating through vacuum sputtering, replacing the traditional processes of laser drilling and windowing, lamination, protective film application, and ink application, thus reducing the process route and improving efficiency.

[0028] Furthermore, the process route of this utility model after using photosensitive materials is basically a repetitive process, which is more conducive to controlling the quality of the process and realizing intelligent production. Attached Figure Description

[0029] The features and advantages of this utility model will be more clearly understood by referring to the accompanying drawings. The drawings are schematic and should not be construed as limiting the utility model in any way. In the drawings:

[0030] Figure 1 This diagram shows a schematic representation of an embodiment of a flexible circuit board based on photosensitive insulating material provided by this utility model;

[0031] Figure 2 It shows Figure 1 A schematic diagram of the middle section structure;

[0032] Figure 3 It shows Figure 2 A schematic diagram of the middle part of the structure.

[0033] The labels in the attached figures are explained as follows:

[0034] 1-First conductive layer, 2-Second conductive layer, 21-First conductive part, 3-Third conductive layer, 31-Second conductive part, 4-Fourth conductive layer, 41-Third conductive part, 5-First photosensitive insulating layer, 51-First through hole, 6-Second photosensitive insulating layer, 61-Second through hole, 7-Third photosensitive insulating layer, 71-Third through hole, 8-Fourth photosensitive insulating layer, 9-Fifth photosensitive insulating layer. Detailed Implementation

[0035] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. The present utility model will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0036] In this embodiment of the invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0038] In this embodiment of the invention, the term "multiple" refers to two or more, and other quantifiers are similar.

[0039] In this utility model, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not used to limit this utility model.

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the various embodiments of this utility model will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are provided in the various embodiments of this utility model to facilitate a better understanding of the invention. However, the technical solutions claimed by this utility model can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the various embodiments below is for ease of description and should not constitute any limitation on the specific implementation of this utility model. The various embodiments can be combined with and referenced by each other without contradiction.

[0041] Existing methods for manufacturing multilayer circuit boards typically include laser engraving, hole metallization, dry film lamination, exposure, development, inner layer pattern electroplating, film removal, inner layer circuitry, application of auxiliary films to adhesive films, adhesive film die-cutting, outer layer material die-cutting, pre-application, lamination, baking and curing, outer layer laser engraving, hole metallization, dry film lamination, exposure, development, outer layer pattern electroplating, film removal, outer layer circuitry, picosecond laser engraving, capping, protective film die-cutting, protective film pre-application, fast pressing, baking and curing, ink printing, pre-baking, exposure, development, curing, etc.

[0042] Traditional processes suffer from issues such as misalignment during laser cutting and exposure, and low precision in protective film punching, making them unsuitable for manufacturing high-density circuit boards.

[0043] To address this issue, this invention utilizes a photosensitive insulating material. Because this material has a patterning function, and metallization followed by electroplating is achieved through vacuum sputtering, this replaces the traditional processes of laser drilling and windowing, lamination, protective film application, and ink application, thus streamlining the process. Furthermore, due to the patterning function of the photosensitive insulating material, this one-step patterning process avoids the problems of multiple alignment errors between laser and exposure, and low precision in protective film cutting found in traditional processes, making it more suitable for manufacturing high-density circuit boards.

[0044] Specifically, this utility model provides a flexible circuit board based on a photosensitive insulating material. Please refer to [link / reference]. Figures 1 to 3The flexible circuit board based on photosensitive insulating material includes a first conductive layer 1 as a substrate, a first photosensitive insulating layer 5, a second conductive layer 2, a second photosensitive insulating layer 6, and a third photosensitive insulating layer 7. The first photosensitive insulating layer 5 covers the first conductive layer 1, and a first through-hole 51 is formed on the first photosensitive insulating layer 5 through exposure and development. The second conductive layer 2 is disposed on the side of the first photosensitive insulating layer 5 opposite to the first conductive layer 1, and the second conductive layer 2 has a first conductive portion 21 extending to the first through-hole 51. The first conductive layer 1 and the second conductive layer 2 are connected through the first conductive portion 21. The second photosensitive insulating layer 6 and the third photosensitive insulating layer 7 respectively cover the first conductive layer 1 and the second conductive layer 2. The second photosensitive insulating layer 6 is located on the side of the first conductive layer 1 opposite to the first photosensitive insulating layer 5, and the third photosensitive insulating layer 7 is located on the side of the second conductive layer 2 opposite to the first photosensitive insulating layer 5.

[0045] This invention achieves high-precision flexible circuit boards by setting a photosensitive insulating layer and forming through holes through exposure and development of the photosensitive insulating layer, without the need for laser.

[0046] The first conductive layer 1 may be, but is not limited to, copper foil; in some other embodiments, the first conductive layer 1 may also be made of other conductive materials. Similarly, the second conductive layer 2 may be, but is not limited to, copper foil; in some other embodiments, the second conductive layer 2 may also be made of other conductive materials.

[0047] The first photosensitive insulating layer 5 can be a liquid photosensitive material or a film material, without specific limitations. When the first photosensitive insulating layer 5 is a liquid photosensitive material, it can be coated onto the first conductive layer 1 using a coating process. When the first photosensitive insulating layer 5 is a film material, it is pressed onto the first conductive layer 1 using a lamination process. In some embodiments, the first photosensitive insulating layer 5 is photosensitive polyimide; in other embodiments, it can also be a photosensitive material of other materials, such as benzocyclobutene, epoxy resin, polybenzoxazole, or aromatic fluoropolymers.

[0048] It is worth noting that the materials and processes of other photosensitive insulating layers in this invention (such as the second photosensitive insulating layer 6, the third photosensitive insulating layer 7, ...) can also refer to the description of the first photosensitive insulating layer 5 above, and will not be detailed here. The dielectric constant of the photosensitive insulating layer is less than 3.5, and the dielectric loss is less than 0.005.

[0049] The selection of other conductive layers in this invention can also refer to the selection of the first conductive layer 1, and will not be described in detail here.

[0050] The flexible circuit board can be a double-layer circuit board or other multi-layer circuit boards, depending on the actual needs. When the flexible circuit board is a double-layer circuit board, the second photosensitive insulating layer 6 and the third photosensitive insulating layer 7 serve as protective films. In some embodiments, the second photosensitive insulating layer 6 and the third photosensitive insulating layer 7 are respectively provided with openings for exposing the first conductive layer 1 and the second conductive layer 2, thus facilitating the exposure of the first conductive layer 1 and the second conductive layer 2.

[0051] When the flexible circuit board is a three-layer circuit board, a plurality of second circuit stack structures are sequentially stacked on the side opposite to the first conductive layer 1 of the second photosensitive insulating layer 6, wherein the second circuit stack structure includes a third conductive layer 3 and a fourth photosensitive insulating layer 8. A second via 61 is formed on the second photosensitive insulating layer 6 through exposure and development; the third conductive layer 3 has a second conductive portion 31 extending to the second via 61, thus the third conductive layer 3 and the first conductive layer 1 are connected through the second conductive portion 31.

[0052] Similarly, when the flexible circuit board is a three-layer circuit board, a plurality of first circuit stack structures are sequentially stacked on the side opposite to the second conductive layer 2 of the third photosensitive insulating layer 7, wherein the first circuit stack structure includes a fourth conductive layer 4 and a fifth photosensitive insulating layer 9. A third via 71 is formed on the third photosensitive insulating layer 7 by exposure and development; the fourth conductive layer 4 has a third conductive portion 41 extending to the third via 71, so that the fourth conductive layer 4 and the second conductive layer 2 are connected through the third conductive portion 41.

[0053] In some implementations, the number of first line stack structures and second line stack structures is the same, and in specific implementations, the first line stack structure and the second line stack structure can be formed simultaneously.

[0054] The first photosensitive insulating layer 5, the second photosensitive insulating layer 6, and the third photosensitive insulating layer 7

[0055] Taking a flexible circuit board as an example of a four-layer circuit board, such as Figure 1 As shown, the four-layer circuit board includes, in sequence, a fifth photosensitive insulating layer 9, a fourth conductive layer 4, a third photosensitive insulating layer 7, a second conductive layer 2, a first photosensitive insulating layer 5, a first conductive layer 1, a second photosensitive insulating layer 6, a third conductive layer 3, and a fourth photosensitive insulating layer 8 stacked together.

[0056] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A flexible circuit board based on a photosensitive insulating material, characterized in that, include: The first conductive layer serves as the substrate; A first photosensitive insulating layer covers the first conductive layer, and a first through hole is formed on the first photosensitive insulating layer by exposure and development. The second conductive layer is disposed on the side opposite to the first photosensitive insulating layer and the first conductive layer. The second conductive layer has a first conductive portion extending to the first through hole, and the first conductive layer and the second conductive layer are connected through the first conductive portion. as well as A second photosensitive insulating layer and a third photosensitive insulating layer are respectively covered on the first conductive layer and the second conductive layer. The second photosensitive insulating layer is located on the side opposite to the first conductive layer and the third photosensitive insulating layer.

2. The flexible circuit board based on photosensitive insulating material as described in claim 1, characterized in that, The flexible circuit board is a double-layer circuit board, with the second photosensitive insulating layer and the third photosensitive insulating layer serving as protective films.

3. The flexible circuit board based on photosensitive insulating material as described in claim 2, characterized in that, The second and third photosensitive insulating layers are respectively provided with openings for exposing the first and second conductive layers.

4. The flexible circuit board based on photosensitive insulating material as described in claim 1, characterized in that, The flexible circuit board has at least three layers.

5. The flexible circuit board based on photosensitive insulating material as described in claim 4, characterized in that, On the side opposite to the first conductive layer, the second photosensitive insulating layer is further stacked with a plurality of second circuit stack structures, wherein the second circuit stack structure includes a third conductive layer and a fourth photosensitive insulating layer.

6. The flexible circuit board based on photosensitive insulating material as described in claim 5, characterized in that, A second via is formed on the second photosensitive insulating layer by exposure and development; The third conductive layer has a second conductive portion extending to the second conductive hole, and the third conductive layer is connected to the first conductive layer through the second conductive portion.

7. The flexible circuit board based on photosensitive insulating material as described in claim 4, characterized in that, On the side opposite to the second conductive layer, the third photosensitive insulating layer is further stacked with a plurality of first circuit stack structures, wherein the first circuit stack structure includes a fourth conductive layer and a fifth photosensitive insulating layer.

8. The flexible circuit board based on photosensitive insulating material as described in claim 7, characterized in that, A third via is formed on the third photosensitive insulating layer by exposure and development. The fourth conductive layer has a third conductive portion extending to the third through hole, and the fourth conductive layer is connected to the second conductive layer through the third conductive portion.

9. The flexible circuit board based on photosensitive insulating material as described in claim 1, characterized in that, The dielectric constants of the first, second, and third photosensitive insulating layers are less than 3.5, and the dielectric loss is less than 0.

005.

10. The flexible circuit board based on photosensitive insulating material as described in claim 1, characterized in that, The first conductive layer and the second conductive layer are copper foil.

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