A method for manufacturing a high-shielding large-copper-area thin flexible circuit board

Abstract

The application discloses a manufacturing method of a high-shielding large-copper-surface thin flexible circuit board, which comprises the following steps: manufacturing a first core plate with a through hole and an exhaust hole, and manufacturing a circuit pattern on a first surface of the first core plate; manufacturing a second core plate with an exhaust hole corresponding to the exhaust hole of the first core plate; stacking the first core plate and the second core plate, with the circuit pattern being located between the two core plates, and pre-pressing to form a pre-pressed plate; sequentially arranging a first cover film, the pre-pressed plate and a second cover film between two mutually symmetrical auxiliary pressing structures, and then pressing and reforming to form the circuit board; and through the auxiliary exhaust hole and the auxiliary pressing structure with an arched curved surface, the problem that gas is easily hidden between layers during pressing and causes the board to bubble or even burst is effectively avoided; and through the control of the heating rate and the cooling rate during pressing, the problem that the large copper surface is easily impacted by the interlayer colloid due to fast heat conduction during pressing, and the problems of uneven colloid flow and condensation, adhesion and unevenness of the pressed plate are effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of flexible board manufacturing, and more particularly to a method for manufacturing a high-shield, large-copper-surface thin flexible circuit board. Background Technology

[0002] In some fields such as intelligent connected vehicles and low-altitude aircraft, flexible circuit boards with large copper surfaces connected to or covering the circuit pattern layer are often used to achieve electrostatic shielding or electromagnetic shielding functions.

[0003] The current processing method for this type of circuit board is to heat-press multiple layers of core boards together to form a whole board, and then press a cover film onto it. However, this processing method has the following disadvantages:

[0004] During the lamination process, flexible circuit boards with large copper surfaces are prone to trapping gas between layers, especially when the board has holes. Gas can easily get trapped in the holes, and during hot pressing or subsequent soldering, the trapped gas can easily expand, pushing up the interlayer and causing problems such as blistering or even board bursting.

[0005] Flexible circuit boards with large copper surfaces conduct heat faster during the lamination process, making them more prone to impacting the interlayer colloids. This can lead to problems such as uneven colloid flow and coagulation, resulting in weak and uneven lamination adhesion.

[0006] Therefore, in order to solve the problems mentioned above, it is necessary to provide a method for manufacturing a thin flexible circuit board with high shielding and large copper surface. Summary of the Invention

[0007] This invention aims to solve the problems of blistering and board bursting caused by gas trapping during the processing of flexible circuit boards in the prior art, as well as the uneven flow and coagulation of colloids caused by excessively rapid heat conduction. It proposes a method for manufacturing a high-shield, large-copper-surface thin flexible circuit board:

[0008] S10: Take a double-sided flexible copper-clad board, make through holes and the first exhaust through hole, and then make circuit patterns on the copper layer of the first side to form the first core board.

[0009] S20: Take a single-sided flexible copper-clad board and make a second venting through hole corresponding to the first venting through hole to form a second core board;

[0010] S30: Stack the first core board and the second core board, with the circuit pattern located between the first core board and the second core board to form a stacked structure, and then perform pre-pressing to form a pre-pressed board;

[0011] S40: Take the first release layer, the covering layer, the buffer layer, and the second release layer and stack them in sequence to form an auxiliary pressing structure; then take the first cover film and the second cover film, and place the first cover film, the pre-pressing plate, and the second cover film in sequence between the two mutually symmetrical auxiliary pressing structures to form a layout structure, and then press them together to form a pressing plate;

[0012] S50: The pressing plate is formed to create the high-shield, large-copper-surface thin flexible circuit board.

[0013] Furthermore, the buffer layer is a single-arch curved surface with an arch height of 2.0mm to 5.0mm; the arch surface of the single-arch curved surface in the auxiliary pressing structure faces the second release layer; the arch surface of the single-arch curved surface in the layout structure faces the pre-pressing plate.

[0014] Furthermore, the buffer layer is made of PP, PET, or epoxy resin.

[0015] Furthermore, the production of the pre-pressed plate includes browning the circuit pattern, performing the pre-pressing process, browning the entire plate, and then de-browning to form the pre-pressed plate.

[0016] Furthermore, the pre-pressing process involves covering the upper and lower surfaces of the stacked structure with film, then using a two-roller press to press it from one end to the other, and finally removing the film and baking it to form the pre-pressed plate.

[0017] Furthermore, the working pressure of the twin-roller press is 0.15MPa to 0.30MPa, and the working temperature is 50℃ to 80℃.

[0018] Furthermore, the baking is a low-temperature baking, with a baking temperature of 80°C to 100°C and a baking time of 20 to 30 minutes.

[0019] Furthermore, the overlay layer is fabricated by: taking a single-sided copper-clad board, fabricating pad patterns corresponding to the vias to form the overlay layer; the pad patterns face the first release layer.

[0020] Furthermore, an insulating film is attached to the edge of the coating layer.

[0021] Furthermore, the pressing process employs a slow heating rate of 1.0℃ / min to 1.8℃ / min and a slow cooling rate of 4.0℃ / min to 7.5℃ / min.

[0022] This invention addresses the issue of gas leakage from the circuit board by incorporating vent holes in the core board to facilitate gas discharge between layers. It also utilizes an arched buffer layer with corresponding pad patterns for the auxiliary pressing structure, guiding gas flow from the center to the edges. This helps gas escape from the center outwards, reducing voids or bubbles in the circuit board and solving problems such as gas trapping between layers during existing processes, leading to blistering or even board bursting. By controlling the heating and cooling rates during pressing, the invention effectively avoids the rapid thermal conductivity of the large copper surface impacting the insulating dielectric layer colloid, causing uneven colloid flow and coagulation, resulting in weak and uneven adhesion. The effective coordination between the preceding and following processes enables high-precision processing and improves the lifespan of the circuit board. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the process flow of an embodiment of the present invention;

[0025] Figure 2 This is a cross-sectional schematic diagram of the stacked structure according to an embodiment of the present invention;

[0026] Figure 3 This is a cross-sectional schematic diagram of the pre-compression process according to an embodiment of the present invention;

[0027] Figure 4 This is a cross-sectional structural diagram of the typesetting structure according to an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the cross-sectional structure of the pressing plate according to an embodiment of the present invention;

[0029] Figure 6 This is a schematic cross-sectional view of a high-shield, large-copper-surface thin flexible circuit board according to an embodiment of the present invention.

[0030] Explanation of icon numbers:

[0031]

[0032] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that all directional indications (such as up, down, left, right, front, back, inside, outside, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0035] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0036] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0037] Please see Figure 1 , Figure 1 This is a schematic diagram of the process flow according to an embodiment of the present invention.

[0038] The manufacturing process of this invention includes using Figure 1 The implementation of each step in the process will be described below. Figure 1 The process of each step will be explained step by step.

[0039] Please see Figure 2 , Figure 2 This is a cross-sectional schematic diagram of the stacked structure according to an embodiment of the present invention.

[0040] Step S10:

[0041] A double-sided flexible copper-clad laminate is used to fabricate a via 1010 and a first venting via 1020. Then, a circuit pattern 1030 is fabricated on the first copper layer, and the second copper layer is the first shielding layer 1040, forming the first core board 10. The via 1010 connects the circuit pattern 1030 and the first shielding layer 1040, forming the electrostatic shielding and electromagnetic shielding effect of the first shielding layer 1040 on the circuit pattern 1030, and also providing the core board foundation for subsequent processing.

[0042] Step S20:

[0043] A single-sided flexible copper-clad laminate is used to create a second venting through-hole 2010 corresponding to the first venting through-hole 1020. This provides a longitudinal channel for venting gas between the first core board 10 and the second core board 20 during the subsequent pre-pressing process. The copper surface serves as the second shielding layer 2020, which provides electromagnetic shielding for the circuit pattern 1030, thus forming the second core board 20.

[0044] Please continue reading. Figure 2 And see Figure 3 , Figure 3 This is a cross-sectional schematic diagram of the pre-pressing process according to an embodiment of the present invention.

[0045] Step S30:

[0046] The first core board 10 and the second core board 20 are stacked to form a stacked structure 30, and then pre-pressed to form a pre-pressed plate 40, with the circuit pattern 1030 facing the second core board 20, forming the first shielding layer 1040 and the second shielding layer 2020 to shield the circuit pattern 1030 from the top and bottom.

[0047] In this embodiment, the fabrication of the pre-pressed plate 40 includes: browning the circuit pattern 1030 to form a uniform rough surface on the surface of the circuit pattern 1030, effectively improving the interlayer bonding force between the first core board 10 and the second core board 20; then performing pre-pressing processing, that is, initially pressing the first core board 10 and the second core board 20 together to form a semi-finished product, which helps to remove air bubbles between the first core board 10 and the second core board 20, ensuring the flatness of the pressing of the first core board 10 and the second core board 20, and preparing for the final lamination; further, performing whole-board browning and then de-browning to form the pre-pressed plate 40, that is, forming a uniform browned oxide film on the upper and lower surfaces of the pre-pressed plate 40, and then de-browning the oxide film to provide a rougher and more uniform plate surface to be pressed for the final lamination.

[0048] In this embodiment, the pre-pressing process involves covering the upper and lower surfaces of the stacked structure 30 with film 3010, then using a two-roll laminator 3020 to press it from one end to the other. Finally, the film 3010 is removed and baked to form a pre-pressed plate 40. The film 3010 itself has a certain degree of flexibility and thickness, which can act as a buffer under the pressure applied by the two-roll laminator 3020, helping to distribute the pressure more evenly on the stacked structure 30 and effectively avoiding problems such as pressing defects caused by uneven pressure. The pre-pressing process then removes moisture and gas from inside the stacked structure 30, creating a micro-pressed state between the layers of the stacked structure 30, providing a processing basis for the final lamination. In particular, scrap film can be used, which can be recycled and reused, reducing processing costs.

[0049] Furthermore, the working pressure of the twin-roll press 3020 is 0.15MPa to 0.30MPa, and the working temperature is 50℃ to 80℃. On the one hand, the first core board 10, the second core board 20, and the film 3010 are all relatively soft, and there may be problems of arching and gas trapping when stacked. Therefore, pressing within a pressure range of 0.15MPa to 0.30MPa ensures sufficient pressure to expel water vapor and gas inside the stacked structure 30. On the other hand, controlling the working temperature at 50℃ to 80℃ helps the first core board 10 and the second core board 20 to fit tightly together, forming a preliminary bond, preventing rebound, and helping to quickly complete the pre-pressing process while maintaining good surface quality and internal structural integrity.

[0050] Furthermore, baking after removing film 3010 can further solidify the bonding effect between the first core board 10 and the second core board 20. The baking is a low-temperature baking, with a baking temperature of 80°C to 100°C and a baking time of 20 to 30 minutes. This helps to reduce the risk of excessive shrinkage or expansion of the material due to excessive temperature. The low-temperature and long-term baking helps to remove some of the internal stress between the insulating dielectric layer 1050 of the first core board and the insulating dielectric layer 2030 of the second core board. Sufficient time is available to complete the curing reaction, which enhances the interlayer bonding strength, reduces the occurrence of problems such as bubbles and cracks, and forms a smooth surface pre-pressed plate 40.

[0051] It is worth noting that after baking, it is necessary to check whether the moisture and gas between the layers have been fully expelled. If problems such as layering or white spots occur during baking, it indicates that the gas has not been fully expelled, and the pre-pressurization process above should be repeated.

[0052] Please see Figure 4 and Figure 5 , Figure 4 This is a cross-sectional structural diagram of the typesetting structure according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the cross-sectional structure of the pressing plate according to an embodiment of the present invention.

[0053] Step S40:

[0054] The first release layer 5010, the covering layer 5020, the buffer layer 5030, and the second release layer 5040 are stacked in sequence to form an auxiliary pressing structure 50; then the first cover film 6010 and the second cover film 6020 are taken, and the first cover film 6010, the pre-pressing plate 40, and the second cover film 6020 are arranged in sequence between the two mutually symmetrical auxiliary pressing structures 50 to form a layout structure 60, and then pressed together to form a pressing plate 70;

[0055] In this embodiment, the overlay layer 5020 is fabricated as follows: a single-sided copper-clad board is taken, and a pad pattern 5020A is fabricated corresponding to the via 1010 to form the overlay layer 5020; and the pad pattern 5020A faces the first release layer 5010, that is, the pad pattern 5020A has a certain thickness and hardness. By increasing the overlay capability at the position of the via 1010 during lamination, the fluid dynamic second core board insulating dielectric layer 2030 and the second cover film 6020 are fully filled into the via 1010, forming a filling effect of the via 1010.

[0056] To prevent localized overheating during lamination, which could result in a differential state where heat conduction is weaker at the edges and stronger in the center, thus promoting more complete flow of the adhesive in the center and weaker flow at the edges, in this embodiment, a heat insulation film 5020B is attached to the edge of the overlay layer 5020. This effectively isolates the influence of external heat on the circuit board and improves the adhesive bonding force between the layers during lamination.

[0057] In this embodiment, the buffer layer 5030 is a single-arch curved surface 5030A, and the arch height of the single-arch curved surface 5030A is 2.0mm to 5.0mm. The arch of the single-arch curved surface 5030A in the auxiliary pressing structure 50 faces the second release layer, and the arch of the single-arch curved surface 5030A in the layout structure 60 faces the pre-pressing plate. During the pressing process, the middle of the first covering film 6010 and the second covering film 6020 is pressed first, and then the two ends of the first covering film 6010 and the second covering film 6020 are pressed. This prevents the whole from contacting the first covering film 6010 and the second covering film 6020 with the pre-pressing plate 40 at the same time, which can easily trap gas. That is, the arch structure of the single-arch curved surface 5030A is used to drive away the interlayer gas from the middle to the edge.

[0058] On the one hand, the single-arch curved surface 5030A can more effectively disperse the applied pressure during the pressing process. When external pressure is applied to the buffer layer 5030, its unique arched structure can evenly transmit the force to the entire contact surface, avoiding damage or deformation of the pre-press plate 40 due to excessive local pressure. On the other hand, during the pressing process, the arch of the single-arch curved surface 5030A forms a flow that guides the gas from the middle to both ends to the edge area, which can promote the gas to be discharged from the center to the outside, thereby reducing voids or bubbles in the final plate.

[0059] In this embodiment, the buffer layer 5030 is made of PP, PET or epoxy resin.

[0060] Because the large copper surface conducts heat quickly, in order to avoid problems such as delamination and cracking caused by excessive internal stress due to rapid heating or cooling, in this embodiment, the pressing is first carried out by a slow heating method with a heating rate of 1.0℃ / min to 1.8℃ / min, which effectively avoids the problem of uneven flow and coagulation of the interlayer colloid. Then, the pressing is carried out by a slow cooling method with a cooling rate of 4.0℃ / min to 7.5℃ / min, which effectively avoids the problem of excessive expansion and contraction of the board caused by the colloid coagulating too quickly.

[0061] The above-mentioned method of using slow heating and slow cooling during the pressing process is conducive to the formation of good adhesion and flatness between the first cover film 6010, the pre-press plate 40 and the second cover film 6020, thereby ensuring the integrity and continuity of the first shielding layer 1040 and the second shielding layer 2020, and providing better electromagnetic shielding capability for the high-shield large copper surface thin flexible circuit board 80.

[0062] Please see Figure 6 , Figure 6 This is a schematic cross-sectional view of a high-shield, large-copper-surface thin flexible circuit board according to an embodiment of the present invention.

[0063] Step S50:

[0064] The press plate 70 is formed along the forming line 100 to form a high-shield, large-copper-surface, thin, flexible circuit board 80.

[0065] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing a high-shield, large-copper-surface thin flexible circuit board, characterized in that, The manufacturing method includes the following steps: S10: Take a double-sided flexible copper-clad board, make through holes and the first exhaust through hole, and then make circuit patterns on the copper layer of the first side to form the first core board. S20: Take a single-sided flexible copper-clad board and make a second venting hole corresponding to the first venting hole to form a second core board; S30: Stack the first core board and the second core board with the circuit pattern facing between the second core boards to form a stacked structure, and then perform pre-pressing to form a pre-pressed board; S40: Take the first release layer, the covering layer, the buffer layer, and the second release layer and stack them in sequence to form an auxiliary pressing structure; Then take the first cover film and the second cover film, and stack the first cover film, the pre-press plate and the second cover film in sequence between the two mutually symmetrical auxiliary pressing structures to form a layout structure, and then press them together to form a pressing plate; The buffer layer is a single-arch curved surface, and the arch surface of the single-arch curved surface in the auxiliary pressing structure faces the second release layer; the arch surface of the single-arch curved surface in the layout structure faces the pre-pressing plate; The overlay layer is fabricated as follows: a single-sided copper-clad laminate is taken, and pad patterns are fabricated corresponding to the vias to form the overlay layer; the pad patterns face the first release layer; a heat insulation film is attached to the edge of the overlay layer; S50: The pressing plate is formed to create the high-shield, large-copper-surface thin flexible circuit board.

2. The method for manufacturing a high-shield, large-copper-surface thin flexible circuit board as described in claim 1, characterized in that, The arch height of the single-arch curved surface is 2.0 mm to 5.0 mm.

3. A method for manufacturing a high-shield, large-copper-surface thin flexible circuit board as described in claim 1 or 2, characterized in that, The buffer layer is made of PP, PET or epoxy resin.

4. The method for manufacturing a high-shield, large-copper-surface thin flexible circuit board as described in claim 1, characterized in that, The process of manufacturing the pre-pressed board includes browning the circuit pattern, performing the pre-pressing process, browning the entire board, and then de-browning to form the pre-pressed board.

5. The method for manufacturing a high-shield, large-copper-surface thin flexible circuit board as described in claim 1, characterized in that, The pre-pressing process involves covering the top and bottom surfaces of the stacked structure with film, then using a two-roller press to press the film from one end to the other, and finally removing the film and baking it to form the pre-pressed plate.

6. The method for manufacturing a high-shield, large-copper-surface thin flexible circuit board as described in claim 5, characterized in that, The working pressure of the twin-roller film press is 0.15MPa to 0.30MPa, and the working temperature is 50℃ to 80℃.

7. The method for manufacturing a high-shield, large-copper-surface thin flexible circuit board as described in claim 5, characterized in that, The baking is a low-temperature baking, with a baking temperature of 80°C to 100°C and a baking time of 20 to 30 minutes.

8. The method for manufacturing a high-shield, large-copper-surface thin flexible circuit board as described in claim 1, characterized in that, The pressing process employs a slow heating rate of 1.0℃ / min to 1.8℃ / min and a slow cooling rate of 4.0℃ / min to 7.5℃ / min.

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