Flexible circuit board with exhaust channel and manufacturing method thereof

Abstract

The present invention discloses a method for manufacturing a flexible circuit board with an exhaust channel. The method comprises: providing multiple flexible circuit boards to be laminated, the multiple flexible circuit boards including copper layer graphic areas and non-copper layer graphic areas; subjecting the multiple flexible circuit boards to an inner layer rapid lamination process, and providing air guide strips in the non-copper layer graphic areas to obtain a laminated multilayer flexible circuit board; subjecting the non-copper layer graphic areas of the multilayer flexible circuit board to a drilling process, wherein the drilling process includes through holes located on the air guide strips; and subjecting the drilled multilayer flexible circuit board to a solder mask process to obtain a multilayer flexible circuit board with an exhaust channel. The present invention provides an exhaust path for gas within the flexible circuit board by providing air guide strips; and drilling through holes in the air guide strips to provide an exhaust outlet for gas within the flexible circuit board, thereby forming an exhaust channel. This effectively solves the problem of blistering during the manufacture of flexible circuit boards, improves productivity, and saves production costs.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible circuit board manufacturing, and in particular to a manufacturing method of a flexible circuit board with an exhaust channel and the flexible circuit board with an exhaust channel. Background Art

[0002] Flexible Printed Circuit (FPC) is a highly reliable material made of polyimide or polyester film. It has the characteristics of good flexibility, high wiring density, light weight, thin thickness and good bendability.

[0003] Generally speaking, after the internal structure of a flexible circuit board is made, a solder mask layer needs to be made on the surface. That is, the ink is silk-screened on the bare surface of the flexible circuit board using silk-screen ink, and then pre-baking, exposure, development, post-baking and other processes are performed to form a cured solder mask layer.

[0004] However, in order to meet the mutual bonding between the internal structures of the flexible circuit board and prevent excessive lamination from causing the expansion and contraction of the middle dielectric layer of the flexible circuit board to exceed the standard, rapid lamination is adopted. Among them, the parameters of rapid lamination are lamination temperature of 150℃~180℃ and lamination time of 5min~20min. After the rapid lamination is completed, the interlayer bonding force requirements of the flexible circuit board can be met, but the interlayer bonding force is relatively weaker than that of the rigid circuit board. In addition, during the processing of the flexible circuit board, there is adhesive bonding between the layers, etc. During the baking process, the internal structure of the flexible circuit board will produce water vapor, flatulence and other problems. Since the post-solder mask baking process adopts pressure-free high-temperature baking, the baking parameters are baking temperature of 150℃ and baking time of 30min~60min. Therefore, the post-baking process is very likely to cause blistering, flatulence, delamination, and bursting of the board.

[0005] Currently, enhanced pressing is usually used to improve the above problems. However, enhanced pressing can easily lead to additional problems such as deformation of the flexible circuit board and excessive expansion and contraction, and cannot completely prevent problems such as blistering during post-baking.

[0006] Based on the above problems, it is necessary to explore a method for manufacturing a flexible circuit board with an internal exhaust channel to solve the blistering problem of the flexible circuit board during the solder mask baking process. Summary of the Invention

[0007] The main purpose of the present invention is to provide a method for manufacturing a flexible circuit board with an exhaust channel and a flexible circuit board with an exhaust channel, aiming to solve the technical problem in the prior art that flexible circuit boards are prone to blistering during the solder resist baking process.

[0008] To achieve the above-mentioned objectives, an embodiment of the present invention proposes a method for manufacturing a flexible circuit board with an exhaust channel, the manufacturing method comprising: providing a plurality of flexible circuit boards to be pressed together, wherein the plurality of flexible circuit boards include a copper layer graphic area and a non-copper layer graphic area; subjecting the plurality of flexible circuit boards to an inner layer rapid pressing process, and providing an air guide strip in the non-copper layer graphic area to obtain a pressed multi-layer flexible circuit board; subjecting the non-copper layer graphic area of ​​the multi-layer flexible circuit board to a drilling process, wherein the drilling process position includes a through hole located on the air guide strip; subjecting the drilled multi-layer flexible circuit board to a solder mask process to obtain a multi-layer flexible circuit board with an exhaust channel.

[0009] Among them, after the step of subjecting the drilled multilayer flexible circuit board to a solder mask process to obtain a multilayer flexible circuit board with an exhaust channel, the step includes: pasting a gasket at the through hole, and subjecting the multilayer flexible circuit board with the gasket to a surface treatment process to complete the production of the flexible circuit board.

[0010] Wherein, the diameter of the gasket is larger than the diameter of the through hole by 0.6 to 1.4 mm.

[0011] Among them, the step of subjecting the drilled multilayer flexible circuit board to a solder mask process to obtain a multilayer flexible circuit board with an exhaust channel includes: subjecting the drilled multilayer flexible circuit board to a silk screen ink process so that the copper layer graphic area of ​​the multilayer flexible circuit board is covered with ink; subjecting the multilayer flexible circuit board covered with ink to a pre-baking process, an exposure process, and a development process to obtain a multilayer flexible circuit board to be baked; subjecting the multilayer flexible circuit board to be baked to a hot pressing and post-baking process so that the gas in the multilayer flexible circuit board is discharged from the exhaust channel to obtain the multilayer flexible circuit board with an exhaust channel.

[0012] Wherein, the width of the air guide strip ranges from 1 to 4 mm.

[0013] Wherein, the thickness of the gas guide strip ranges from 20 to 30 μm.

[0014] The aperture of the through hole is smaller than or equal to the width of the air guide strip, and the aperture range of the through hole is 0.5-4 mm.

[0015] Wherein, a plurality of through holes are provided on the air guide strip, and the spacing between the through holes is greater than or equal to 5 mm.

[0016] Wherein, the material of the gas guide strip is polytetrafluoroethylene.

[0017] To achieve the above objectives, an embodiment of the present invention further proposes a flexible circuit board with an exhaust channel, which is manufactured by the manufacturing method described above. The flexible circuit board includes: a first flexible circuit board and a second flexible circuit board; an intermediate dielectric layer located between the first flexible circuit board and the second flexible circuit board; wherein the first flexible circuit board, the intermediate dielectric layer, and the second flexible circuit board all include a copper layer graphic area and a non-copper layer graphic area, and an exhaust channel is provided in the non-copper layer graphic area.

[0018] Compared with the existing technology, the technical solution proposed in the present invention provides an exhaust path for the gas in the flexible circuit board by setting a gas guide strip in the non-copper layer graphic area; and drilling through holes on the gas guide strip to provide an exhaust outlet for the gas in the flexible circuit board, thereby forming an exhaust channel, which effectively solves the problem of easy blistering during the production of flexible circuit boards, improves the productivity of flexible circuit boards, and saves production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0020] Figure 1 This is a flow chart of an embodiment of a method for manufacturing a flexible circuit board with an exhaust channel according to the present invention;

[0021] Figure 2 for Figure 1 Specific process diagram of some steps in the figure;

[0022] Figure 3 This is a flow chart of another embodiment of a method for manufacturing a flexible circuit board with an exhaust channel according to the present invention;

[0023] Figure 4 This is a schematic plan view of the structure of a flexible circuit board with an exhaust channel according to an embodiment of the present invention;

[0024] Figure 5 for Figure 4 Schematic diagram of the cross-sectional structure of the middle copper layer graphic area DD;

[0025] Figure 6 for Figure 4 Schematic diagram of the cross-sectional structure of the non-copper layer graphic area EE.

[0026] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0027] 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 the embodiments. 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 embodiments of the present invention.

[0028] In order to better understand the above technical solution, the above technical solution is described in detail below with reference to the accompanying drawings.

[0029] Please also refer to Figure 1 and Figure 2 , Figure 1 This is a flow chart of an embodiment of a method for manufacturing a flexible circuit board with an exhaust channel according to the present invention; Figure 2 for Figure 1 Specific flow chart of some steps in the figure.

[0030] like Figure 1 As shown, the steps of a method for manufacturing a flexible circuit board with an exhaust channel are as follows:

[0031] Step S110: providing a plurality of flexible circuit boards to be laminated, wherein the plurality of flexible circuit boards include copper layer pattern areas and non-copper layer pattern areas.

[0032] In this embodiment, using a three-layer flexible circuit board as an example, the multiple flexible circuit boards to be laminated may include a single-layer flexible circuit board and a double-layer flexible circuit board, or three single-layer flexible circuit boards. An intermediate dielectric layer is placed between the multiple flexible circuit boards for electrical isolation. Typically, the intermediate dielectric layer is made of polyimide, meaning a polyimide dielectric layer is added between the multiple flexible circuit boards for lamination. Each flexible circuit board has a copper layer pattern area and a non-copper layer pattern area. The copper layer pattern area is the active circuit area. Multiple small panels SET can be placed on a single large panel PNL. For example, a single large panel PNL can include six small panel SETs. Areas outside the copper layer pattern area are non-copper layer pattern areas, or inactive areas, which can be used to process other auxiliary patterns and are also referred to as auxiliary processing areas.

[0033] Step S120: performing an inner layer rapid lamination process on the plurality of flexible circuit boards, and setting air guide strips in the non-copper layer pattern area to obtain a laminated multi-layer flexible circuit board.

[0034] Specifically, a single-layer flexible circuit board and a double-layer flexible circuit board are subjected to an inner layer rapid pressing process, and air guide strips are set in the non-copper layer graphic area. When the flexible circuit boards are pressed, the air guide strips are pressed into the inner layer of the flexible circuit boards by a rapid pressing method.

[0035] The gas strips in this embodiment are made of polytetrafluoroethylene (PTFE), with a width ranging from 1 to 4 mm and a thickness ranging from 20 to 30 μm. PTFE is a high molecular weight polymer made from tetrafluoroethylene (PTFE) as a monomer. It is white, waxy, translucent, and has excellent heat and cold resistance, capable of long-term use at temperatures between -180°C and 260°C. Its resistance to acids, alkalis, various organic solvents, high temperatures, and an extremely low coefficient of friction make it an ideal material for gas strips. The thickness of the gas strips must be less than the thickness of the copper layer in the copper pattern area. Specifically, the thickness of the polytetrafluoroethylene film used for the gas strips is generally 20 to 30 μm, with the copper layer thickness in the copper pattern area being ≥30 μm. The width of the gas strips is generally less than the gap between the two copper pattern areas (to allow for subsequent solder mask fabrication, the width of the gas strips is generally 1 to 4 mm). In addition, it is worth mentioning that the air guide strip is set in the non-copper layer pattern area between two adjacent copper layer pattern areas, while the non-copper layer pattern area at the edge of the multi-layer flexible circuit board is not provided with an air guide strip.

[0036] Multi-layer flexible circuit boards are typically manufactured using rapid lamination, with the parameters for rapid lamination of the inner panels being a lamination temperature of 150°C to 180°C and a lamination time of 5 to 20 minutes. After rapid lamination, the interlayer bonding strength requirements of the flexible circuit board can be met. Specifically, the dielectric layer of both single-layer and double-layer flexible circuit boards is generally made of polyimide. The polytetrafluoroethylene (PTFE) of the gas strips in this embodiment cannot effectively bond with polyimide under rapid lamination conditions. Therefore, the PTFE gas strips are in a semi-bonded state after rapid lamination, providing a path for the exhaust of gases within the board during subsequent post-baking.

[0037] Therefore, multiple flexible circuit boards are subjected to an inner layer rapid lamination process, and air guide strips are arranged in the non-copper layer pattern area between two adjacent copper layer pattern areas to obtain a laminated multi-layer flexible circuit board.

[0038] The air guide strip is placed between the single flexible circuit board and the intermediate dielectric layer, and can be arranged on one side of the intermediate dielectric layer or on both sides of the intermediate dielectric layer.

[0039] Step S130: performing a drilling process on the non-copper layer pattern area of ​​the multi-layer flexible circuit board, where the drilling process processing positions include the through holes located on the gas guide strips.

[0040] In this step, the non-copper patterned area of ​​the multilayer flexible circuit board is drilled. This drilling process includes drilling vent holes. These vent holes are drilled in the non-copper patterned area of ​​the multilayer flexible circuit board, specifically, at the locations of the gas guide strips on the non-copper patterned area. In this embodiment, multiple holes can be drilled in the same gas guide strip. The diameter of the holes is less than or equal to the width of the gas guide strip, and the diameter ranges from 0.5 to 4 mm. If multiple holes are provided on the gas guide strip, the spacing between the holes is greater than or equal to 5 mm.

[0041] Step S140: performing a solder resist process on the drilled multi-layer flexible circuit board to obtain a multi-layer flexible circuit board with an exhaust channel.

[0042] See also Figure 2 Step S140 specifically includes the following steps:

[0043] Step S141: performing a silk screen printing ink process on the drilled multi-layer flexible circuit board so that the copper layer pattern area of ​​the multi-layer flexible circuit board is covered with ink.

[0044] Step S142: performing a pre-baking process, an exposure process, and a development process on the multi-layer flexible circuit board covered with ink to obtain a multi-layer flexible circuit board to be baked.

[0045] Step S143: performing a post-heat pressing baking process on the multi-layer flexible circuit board to be baked, so that the gas in the multi-layer flexible circuit board is discharged from the exhaust channel, thereby obtaining a multi-layer flexible circuit board with an exhaust channel.

[0046] Specifically, a solder mask layer is produced on the surface of a multi-layer flexible circuit board. In actual application, the production process of the solder mask layer is: screen printing ink → pre-baking → exposure → development → hot pressing and then baking.

[0047] Because the gas strips are made of PTFE and are semi-pressed before the solder mask process, gas within the board can seep into the gas strips through the gaps between the PTFE strips and the polyimide layer of the dielectric layer. Finally, the solder mask process includes a post-hot pressing and baking sub-process. This allows gas within the multi-layer flexible circuit board to be smoothly discharged through the vent holes of the gas strips. Specifically, the post-hot pressing and baking process involves applying a certain amount of pressure to the surface of the multi-layer flexible circuit board using a flat steel plate (or other flat surface made of thermally conductive material) during baking to promote gas discharge.

[0048] The method for manufacturing a flexible circuit board with an exhaust channel provided by the present invention is to provide an exhaust path for the gas in the flexible circuit board by arranging an air guide strip in the non-copper layer graphic area; and drilling through holes in the air guide strip to provide an exhaust outlet for the gas in the flexible circuit board, thereby forming an exhaust channel, effectively solving the problem of easy blistering of the flexible circuit board during production, improving the productivity of the flexible circuit board, and saving production costs.

[0049] See also Figure 3 , Figure 3 This is a flow chart of another embodiment of a method for manufacturing a flexible printed circuit board with an exhaust channel according to the present invention. Part of the method flow of this embodiment is substantially the same as that of the above embodiment and will not be described in detail again.

[0050] like Figure 3 As shown, the steps of a method for manufacturing a flexible circuit board with an exhaust channel in this embodiment are as follows:

[0051] Step S110: providing a plurality of flexible circuit boards to be laminated, wherein the plurality of flexible circuit boards include copper layer pattern areas and non-copper layer pattern areas.

[0052] Step S120: performing an inner layer rapid lamination process on the plurality of flexible circuit boards, and setting air guide strips in the non-copper layer pattern area to obtain a laminated multi-layer flexible circuit board.

[0053] Step S130: performing a drilling process on the non-copper layer pattern area of ​​the multi-layer flexible circuit board, where the drilling process processing positions include the through holes located on the gas guide strips.

[0054] Step S140: performing a solder resist process on the drilled multi-layer flexible circuit board to obtain a multi-layer flexible circuit board with an exhaust channel.

[0055] Step S150: pasting gaskets at the through holes and performing a surface treatment process on the multi-layer flexible circuit board with the gaskets pasted thereon to complete the production of the flexible circuit board.

[0056] In this embodiment, after the solder mask layer (the multi-layer flexible circuit board after the solder mask treatment) is completed, the flexible circuit board still needs to undergo the next process, namely, surface treatment. This surface treatment process requires the multi-layer flexible circuit board to be completed within the liquid medicine tank. To prevent the liquid medicine from entering the vent channel and causing delamination or circuit board cracking, the vent holes need to be sealed.

[0057] In specific applications, after the post-heat pressing and baking process, gaskets are attached to both sides of the vent (i.e., through-hole) location. The gaskets are made of a polyimide film with an adhesive layer, with the adhesive layer facing the flexible circuit board. The gasket's diameter is 0.6mm to 1.4mm larger than the vent's diameter, meaning it's 0.6mm to 1.4mm larger than the through-hole's diameter.

[0058] In this embodiment, the gasket is produced using a punching and laminating machine. The gasket is circular in shape. In practical applications, the gasket attachment process involves punching and laminating, followed by rapid lamination (at 75°C to 150°C for 2 to 5 minutes). This rapid lamination process strengthens the gasket's bond to the flexible circuit board. The gasket is then attached to both sides of the through-hole, completely covering the vent. Finally, conventional surface treatment steps are performed to complete the flexible circuit board.

[0059] The manufacturing method of the flexible circuit board with exhaust channels provided by the present invention is not only to set gas guide strips in the non-copper layer graphic area, but also to drill through holes on the gas guide strips to provide exhaust channels for the gas in the flexible circuit board, which effectively solves the problem of easy bubbling during the production of the flexible circuit board. Then, after the gas in the board is discharged, the through holes are sealed to prevent the medicine from entering the medicine tank into the exhaust channel, thereby causing problems such as delamination and board explosion, thereby improving the performance of the flexible circuit board and improving the production quality of the flexible circuit board.

[0060] Please also refer to Figures 4 to 6 , Figure 4 This is a schematic plan view of the structure of a flexible circuit board with an exhaust channel according to an embodiment of the present invention; Figure 5 for Figure 4 Schematic diagram of the side structure of the middle copper layer graphic area; Figure 6 for Figure 4 Schematic diagram of the side structure of the non-copper layer graphic area.

[0061] like Figure 4 and Figure 5 As shown, flexible circuit board 100 with venting channels includes a first flexible circuit board 110, a second flexible circuit board 120, and an intermediate dielectric layer 130. Intermediate dielectric layer 130 is located between first and second flexible circuit boards 110, 120. First flexible circuit board 110, intermediate dielectric layer 130, and second flexible circuit board 120 each include a copper layer pattern area A and a non-copper layer pattern area B. Venting channels C are provided in non-copper layer pattern area B. The method for fabricating venting channels C is described above and will not be repeated here.

[0062] The copper layer in the copper layer pattern area A of the first flexible circuit board 110 and the second flexible circuit board 120 is covered with a welding layer 140. A gasket 150 is also provided at the through hole of the exhaust channel C. The manufacturing process of the welding layer 140 and the gasket 150 is as described above and will not be repeated here.

[0063] In this embodiment, first flexible circuit board 110 can be a single-layer flexible circuit board, and second flexible circuit board 120 can be a double-layer flexible circuit board. An intermediate dielectric layer 130 is added between first flexible circuit board 110 and second flexible circuit board 120 for electrical isolation, and an exhaust channel C is provided on intermediate dielectric layer 130. In other embodiments, first flexible circuit board 110 and second flexible circuit board 120 can both be single-layer flexible circuit boards. Air guide strips are simply added between the non-copper patterned areas B of the single-layer flexible circuit boards for lamination. Exhaust channels C can also be formed between the dielectric layers and air guide strips of the flexible circuit boards themselves, thus forming a double-layer flexible circuit board with exhaust channels. Exhaust channels C for other circuit boards with higher numbers of layers are described above and will not be further described here.

[0064] In summary, those skilled in the art will readily understand that the present invention provides a method for manufacturing a flexible circuit board with an exhaust channel. By providing an exhaust path for the gas within the flexible circuit board by disposing a gas guide strip in the non-copper layer pattern area, and drilling a through hole in the gas guide strip to provide an exhaust outlet for the gas within the flexible circuit board, thereby forming an exhaust channel, the method effectively solves the problem of blistering during the manufacture of flexible circuit boards, improves the productivity of flexible circuit boards, and saves production costs. The above description is merely a preferred embodiment of the present invention and does not limit the scope of the patent of the present invention. Any equivalent structural transformation made using the contents of the present invention's description and drawings, or any direct or indirect application in other related technical fields, within the scope of the present invention, is included in the scope of patent protection of the present invention.

Claims

1. A method for manufacturing a flexible circuit board with an exhaust channel, characterized in that: The production method comprises: Providing a plurality of flexible circuit boards to be laminated, wherein the plurality of flexible circuit boards include copper layer pattern areas and non-copper layer pattern areas; The plurality of flexible circuit boards are subjected to an inner layer rapid lamination process, and an air guide strip is provided in the non-copper layer pattern area to obtain a laminated multi-layer flexible circuit board; the material of the air guide strip is polytetrafluoroethylene; Performing a drilling process on the non-copper layer pattern area of ​​the multi-layer flexible circuit board, wherein the drilling process processing position includes the through hole located on the gas guide strip; The multi-layer flexible circuit board after drilling is subjected to a solder resist process to obtain a multi-layer flexible circuit board with an exhaust channel.

2. The production method according to claim 1, characterized in that The step of subjecting the drilled multilayer flexible circuit board to a solder resist process to obtain a multilayer flexible circuit board with an exhaust channel includes: A gasket is pasted on the through hole, and the multi-layer flexible circuit board with the gasket pasted thereon is subjected to a surface treatment process to complete the production of the flexible circuit board.

3. The production method according to claim 2, characterized in that: The diameter of the gasket is 0.6 to 1.4 mm larger than the diameter of the through hole.

4. The production method according to claim 1, characterized in that The step of subjecting the drilled multilayer flexible circuit board to a solder resist process to obtain a multilayer flexible circuit board with an exhaust channel includes: Performing a silk screen printing ink treatment on the drilled multilayer flexible circuit board so that the copper layer pattern area of ​​the multilayer flexible circuit board is covered with ink; The multilayer flexible circuit board covered with ink is subjected to a pre-baking process, an exposure process, and a development process to obtain a multilayer flexible circuit board to be baked; The multilayer flexible circuit board to be baked is subjected to a hot pressing and then baking process, so that the gas in the multilayer flexible circuit board is discharged from the exhaust channel, thereby obtaining the multilayer flexible circuit board with the exhaust channel.

5. The production method according to claim 1, characterized in that: The width of the air guide strip is in the range of 1 to 4 mm.

6. The manufacturing method according to claim 5, characterized in that: The thickness of the gas guide strip is in the range of 20 to 30 μm.

7. The production method according to claim 5, characterized in that: The aperture of the through hole is smaller than or equal to the width of the air guide strip, and the aperture range of the through hole is 0.5 to 4 mm.

8. The production method according to claim 1, characterized in that: The air guide strip is provided with a plurality of through holes, and the spacing between the through holes is greater than or equal to 5 mm.

9. A flexible circuit board with an exhaust channel, characterized in that: The flexible circuit board is manufactured by the manufacturing method according to any one of claims 1 to 8, and the flexible circuit board comprises: a first flexible circuit board and a second flexible circuit board; An intermediate dielectric layer is located between the first flexible circuit board and the second flexible circuit board; wherein the first flexible circuit board, the intermediate dielectric layer, and the second flexible circuit board all include a copper layer graphic area and a non-copper layer graphic area, and an exhaust channel is provided in the non-copper layer graphic area.

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