Manufacturing method of high-shielding large-copper-surface thin flexible circuit board

Abstract

The invention discloses a manufacturing method of a high-shielding large-copper-surface thin flexible circuit board, and the method comprises the steps: manufacturing a first core board with a via hole and an exhaust through hole, and manufacturing a circuit pattern for a first surface, and manufacturing a second core board with a corresponding exhaust through hole; the first core plate and the second core plate are stacked, the circuit pattern is located between the two core plates, and pre-pressing is carried out to form a pre-pressed plate; sequentially arranging a first covering film, a pre-pressing plate and a second covering film between the two mutually symmetrical auxiliary pressing structures, pressing, and then forming to form the circuit board; by designing an auxiliary vent hole and an auxiliary pressing structure of an arched curved surface, the problems that gas is easy to hide between layers during pressing, so that a plate body is blistered, even the plate is exploded and the like are effectively avoided; by controlling the heating rate and the cooling rate during pressing, the problems that a large copper surface is high in heat conduction speed in the pressing process, interlayer colloid is prone to being impacted, colloid flows and is not condensed uniformly, and pressing adhesion is not firm and not uniform are effectively solved.

Description

Technical Field

[0001] The invention relates to the field of flexible board manufacturing, and in particular to a method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board. Background Art

[0002] In some areas of smart connected cars and low-altitude aircraft, flexible circuit boards with large copper surfaces or covered with circuit graphic layers are usually used to achieve electrostatic shielding or electromagnetic shielding functions.

[0003] The current processing method for this type of circuit board is to heat-press the multi-layer core board together to form a whole board, and then press the cover film, but this processing method has the following disadvantages: During the lamination process of flexible circuit boards with large copper surfaces, it is easy for gas to be hidden between layers. Especially when the board has holes, it is easier for gas to be hidden in the holes. During the hot lamination or subsequent welding process, the hidden gas is easy to expand and push up the layers, causing blistering or even explosion of the board. Flexible circuit boards with large copper surfaces conduct heat faster during the lamination process, and are more likely to impact the colloid between layers, causing problems such as uneven colloid flow and condensation, resulting in problems such as loose and uneven lamination adhesion.

[0004] Therefore, in order to solve the above-mentioned background problems, it is necessary to provide a method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board. Summary of the invention

[0005] The present invention aims to solve the problems of blistering and board explosion caused by gas hiding during the processing of the flexible circuit board in the prior art, as well as the uneven colloid flow and condensation caused by excessive heat conduction, and proposes a method for manufacturing a high-shielding, large-copper-surface, thin flexible circuit board: S10: Take a double-sided flexible copper-clad laminate, make a via hole and a first exhaust via hole, and then make a circuit pattern on the first copper layer to form a first core board; S20: Take a single-sided flexible copper-clad laminate and make a second exhaust through hole corresponding to the first exhaust through hole to form a second core board; S30: stacking 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 pre-pressing to form a pre-pressed board; S40: stacking the first release layer, the coating layer, the buffer layer, and the second release layer in sequence to form an auxiliary lamination structure; then taking the first covering film and the second covering film, sequentially arranging the first covering film, the pre-pressing plate, and the second covering film between two mutually symmetrical auxiliary lamination structures to form a layout structure, and then laminating to form a pressing plate; S50: molding the laminate to form the high-shielding, large-copper-surface, thin-type flexible circuit board.

[0006] Furthermore, the buffer layer is a single arched surface, and the arch height of the single arched surface is 2.0 mm to 5.0 mm; the arch surface of the single arched surface in the auxiliary pressing structure faces the second release layer; and the arch surface of the single arched surface in the layout structure faces the pre-pressing plate.

[0007] Furthermore, the material of the buffer layer is PP, PET or epoxy resin.

[0008] Furthermore, the production of the pre-pressed plate includes browning the circuit pattern, performing the pre-pressing process, browning the entire plate, and then fading the browning to form the pre-pressed plate.

[0009] Furthermore, the pre-pressing process is to cover the upper and lower surfaces of the stacked structure with film, and then use a double-roller laminating machine to press from one end to the other end, and finally remove the film and bake to form the pre-pressed plate.

[0010] Furthermore, the working pressure of the double-roll laminating machine is 0.15MPa to 0.30MPa, and the working temperature is 50°C to 80°C.

[0011] Furthermore, the baking is low-temperature baking, the baking temperature is 80° C. to 100° C., and the baking time is 20 min to 30 min.

[0012] Furthermore, the coating layer is manufactured by: taking a single-sided copper clad board, manufacturing a pad pattern corresponding to the via hole, and forming the coating layer; the pad pattern faces the first release layer.

[0013] Furthermore, a heat insulation film is attached to the edge of the coating layer.

[0014] Furthermore, the pressing is performed by slowly heating at a heating rate of 1.0°C / min to 1.8°C / min and slowly cooling at a cooling rate of 4.0°C / min to 7.5°C / min.

[0015] The technical solution of the present invention designs exhaust holes in the core board to assist in exhausting the gas between layers, and sets an arched curved buffer layer and a pad pattern corresponding to the through hole for the auxiliary pressing structure, so as to guide the gas flow from the middle of the board to the edge area at both ends, which helps to discharge the gas from the center to the outside, thereby reducing the voids or bubbles in the circuit board, and solves the problem that the gas is easily hidden between layers in the processing process of the prior art, causing blistering or even bursting of the board. By controlling the heating rate and cooling rate during pressing, the pressing process is effectively avoided. Due to the fast thermal conductivity of the large copper surface, the colloid of the insulating medium layer between layers is easily impacted, resulting in uneven colloid flow and condensation, resulting in loose and uneven pressing adhesion, etc. The front and rear processes are effectively coordinated to achieve high-precision processing and increase the service life of the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 the structures shown in these drawings without paying creative work.

[0017] Figure 1 Schematic diagram of the process flow of an embodiment of the present invention; Figure 2 is a schematic cross-sectional view of a stacked structure according to an embodiment of the present invention; Figure 3 It is a cross-sectional schematic diagram of a pre-pressing process according to an embodiment of the present invention; Figure 4 A schematic cross-sectional view of a layout structure according to an embodiment of the present invention; Figure 5 is a schematic diagram of the cross-sectional structure of a pressed plate according to an embodiment of the present invention; Figure 6 It is a schematic diagram of the cross-sectional structure of a high-shielding, large-copper-surface, thin-type flexible circuit board according to an embodiment of the present invention.

[0018] Description of Figure Numbers:

[0019] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, inside, outside...) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0022] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0023] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] See also Figure 1 , Figure 1 Schematic diagram of the process flow of an embodiment of the present invention.

[0025] The manufacturing process of the embodiment of the present invention includes using Figure 1 The following will implement the various steps in the process Figure 1 Each step in the process is further explained step by step.

[0026] See also Figure 2 , Figure 2 Schematic cross-sectional view of a stacked structure according to an embodiment of the present invention.

[0027] Step S10: Take a double-sided flexible copper clad laminate, make a via 1010 and a first exhaust via 1020, then make a circuit pattern 1030 on the first copper layer, and the second copper layer is a first shielding layer 1040, forming a first core board 10; the via 1010 connects the circuit pattern 1030 with the first shielding layer 1040, forming the electrostatic shielding effect and electromagnetic shielding effect of the first shielding layer 1040 on the circuit pattern 1030, and also provides a core board foundation for subsequent processing.

[0028] Step S20: Take a single-sided flexible copper clad laminate and make a second exhaust hole 2010 corresponding to the first exhaust hole 1020, providing a longitudinal channel for exhausting gas between the first core board 10 and the second core board 20 during pre-pressing in the subsequent process. The copper surface is the second shielding layer 2020, and the second shielding layer 2020 provides electromagnetic shielding for the circuit pattern 1030 to form the second core board 20.

[0029] Please continue reading Figure 2 , and see Figure 3 , Figure 3 It is a cross-sectional schematic diagram of the pre-pressing process according to the embodiment of the present invention.

[0030] Step S30: 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 board 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 top and bottom.

[0031] In this embodiment, the preparation of the pre-pressed plate 40 includes browning the circuit pattern 1030 so that the surface of the circuit pattern 1030 forms a uniform rough surface, effectively improving the interlayer bonding force between the first core plate 10 and the second core plate 20, and then performing a pre-pressing process, that is, the first core plate 10 and the second core plate 20 are initially pressed together to form a semi-finished product, which helps to remove air bubbles between the first core plate 10 and the second core plate 20, ensure the flatness of the pressing of the first core plate 10 and the second core plate 20, and prepare for the final lamination. Furthermore, the whole plate is browned and then browned to form a pre-pressed plate 40, that is, an oxide film of a uniform browning layer is formed on the upper and lower surfaces of the pre-pressed plate 40, and then the oxide film is faded to provide a rougher and more uniform board surface to be pressed for the final lamination.

[0032] In the present embodiment, the pre-pressing process is to cover the upper and lower surfaces of the stacked structure 30 with film 3010, and then use a double-roll laminator 3020 to press from one end to the other end, and finally remove the film 3010 and bake it to form a pre-pressing plate 40. The film 3010 itself has a certain flexibility and thickness, and can play a buffering role under the pressure applied by the double-roll laminator 3020, helping the pressure to be more evenly distributed on the stacked structure 30, effectively avoiding problems such as lamination defects caused by uneven pressure, and then pre-pressing is performed to drive out the water vapor and gas inside the stacked structure 30, so that the layers of the stacked structure 30 form a micro-pressing state, providing a processing basis for the final lamination; in particular, the film can use scrapped film, which plays a role in recycling and reducing processing costs.

[0033] Furthermore, the working pressure of the double-roll laminator 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 relatively soft, and there may be problems of arching and gas storage when stacked. Therefore, they are pressed within the pressure range of 0.15MPa to 0.30MPa to ensure 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 to make the first core board 10 and the second core board 20 fit closely to form a preliminary bond and prevent rebound, which helps to quickly complete the pre-pressing process while maintaining good surface quality and internal structural integrity.

[0034] Furthermore, baking is performed after removing the film 3010 to further solidify the pressing effect between the first core board 10 and the second core board 20. The baking is low-temperature baking with a baking temperature of 80°C to 100°C and a baking time of 20min to 30min, which helps to reduce the risk of excessive shrinkage or expansion of the material due to excessive temperature. Low-temperature and long-time baking helps to remove some internal stresses in the first core board insulating dielectric layer 1050 and the second core board insulating dielectric layer 2030, and there is enough time to complete the curing reaction, thereby enhancing the interlayer bonding strength, reducing the occurrence of problems such as bubbles and cracks, and forming a smooth surface pre-compression plate 40.

[0035] It is worth mentioning that after baking, it is necessary to check whether the water vapor and gas between the layers are fully expelled. If problems such as stratification and white spots occur during baking, it means that the gas is not fully expelled, and the above pre-pressing process should be repeated.

[0036] See also Figure 4 and Figure 5 , Figure 4 A schematic cross-sectional view of a layout structure according to an embodiment of the present invention; Figure 5 It is a schematic diagram of the cross-sectional structure of a pressed plate according to an embodiment of the present invention.

[0037] Step S40: The first release layer 5010, the coating layer 5020, the buffer layer 5030, and the second release layer 5040 are stacked in sequence to form an auxiliary lamination structure 50; the first covering film 6010 and the second covering film 6020 are then placed in sequence between two mutually symmetrical auxiliary lamination structures 50 to form a layout structure 60, which are then pressed together to form a pressing plate 70; In this embodiment, the coating layer 5020 is prepared by taking a single-sided copper clad laminate, and preparing a pad pattern 5020A corresponding to the via hole 1010 to form the coating 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, and by increasing the coating ability of the via hole 1010 during pressing, the flowing second core board insulating dielectric layer 2030 and the second covering film 6020 are fully filled into the via hole 1010, forming an effect of filling the via hole 1010.

[0038] In order to prevent local overheating during lamination, resulting in a differentiated state where heat conduction is weak at the edge and strong at the center, and to promote more complete colloid flow in the center and weak colloid flow in the edge, in this embodiment, a thermal insulation film 5020B is attached to the edge of the coating layer 5020 to effectively isolate the influence of external heat on the circuit board and improve the colloid adhesion between layers during lamination.

[0039] In this embodiment, the buffer layer 5030 is a single arched curved surface 5030A, and the arch height of the single arched curved surface 5030A is 2.0 mm to 5.0 mm; the arch of the single arched curved surface 5030A in the auxiliary pressing structure 50 is toward the second release layer, and the arch of the single arched curved surface 5030A in the layout structure 60 is toward the pre-pressing plate. During the pressing process, the effect of first pressing the middle of the first covering film 6010 and the second covering film 6020, and then pressing the two ends of the first covering film 6010 and the second covering film 6020 is formed, preventing 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 is easy to hide gas and other problems. That is, the arched structure of the single arched curved surface 5030A is used to drive away the interlayer gas from the middle to the edge.

[0040] On the one hand, the single-arch curved surface 5030A can more effectively disperse the applied pressure during the pressing process. When external pressure acts on the buffer layer 5030, due to its unique arch structure, the force can be evenly transferred to the entire contact surface, avoiding damage or deformation of the pre-pressing plate 40 caused by excessive local pressure. On the other hand, during the pressing process, the arch top of the single-arch curved surface 5030A is formed to guide the flow from the middle to the two ends to the edge area, which can promote the discharge of gas from the center to the outside, thereby reducing the voids or bubbles in the final plate.

[0041] In this embodiment, the material of the buffer layer 5030 is PP, PET or epoxy resin.

[0042] Since the large copper surface conducts heat quickly, in order to avoid large internal stress caused by rapid heating or rapid cooling, which may lead to problems such as delamination and cracks between layers, in this embodiment, the pressing is first performed by slowly heating the temperature at a heating rate of 1.0℃ / min to 1.8℃ / min, which effectively avoids the problems of uneven flow and coagulation of the colloid between layers, and then slowly cooling the temperature at a cooling rate of 4.0℃ / min to 7.5℃ / min, which effectively avoids the problem of too rapid coagulation of the colloid, which may lead to excessive expansion and contraction of the plate.

[0043] The above-mentioned method of using slow heating and slow cooling during the pressing process is conducive to forming a good fit and flatness between the first covering film 6010, the pre-pressing plate 40 and the second covering film 6020, thereby ensuring the integrity and continuity of the first shielding layer 1040 and the second shielding layer 2020, and providing a better electromagnetic shielding capability for the high-shielding large copper surface thin flexible circuit board 80.

[0044] See also Figure 6 , Figure 6 It is a schematic diagram of the cross-sectional structure of a high-shielding, large-copper-surface, thin-type flexible circuit board according to an embodiment of the present invention.

[0045] Step S50: The laminated plate 70 is molded along the molding line 100 to form a high-shielding, large-copper-surface, thin-type flexible circuit board 80 .

[0046] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board, characterized in that: The production method comprises the following steps: S10: Take a double-sided flexible copper-clad laminate, make a via hole and a first exhaust via hole, and then make a circuit pattern on the first copper layer to form a first core board; S20: Take a single-sided flexible copper-clad laminate, and make a second exhaust through hole corresponding to the first exhaust through hole to form a second core board; S30: stacking 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 pre-pressing to form a pre-pressed board; S40: taking a first release layer, a coating layer, a buffer layer, and a second release layer and stacking them in sequence to form an auxiliary lamination structure; Then take the first covering film and the second covering film, and stack the first covering film, the pre-pressing plate and the second covering 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; S50: molding the laminate to form the high-shielding, large-copper-surface, thin-type flexible circuit board.

2. The method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board according to claim 1, characterized in that: The buffer layer is a single arched curved surface, and the arch height of the single arched curved surface is 2.0 mm to 5.0 mm; The arch surface of the single arched curved surface in the auxiliary pressing structure faces the second release layer; The arch surface of the single arched curved surface in the layout structure faces the pre-pressing plate.

3. A method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board as claimed in claim 1 or 2, characterized in that: The material of the buffer layer is PP, PET or epoxy resin.

4. The method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board according to claim 1, characterized in that: The manufacturing of the pre-pressed plate includes browning the circuit pattern, performing the pre-pressing process, browning the entire plate, and then fading the browning to form the pre-pressed plate.

5. The method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board according to claim 1, characterized in that: The pre-pressing process is to cover the upper and lower surfaces of the stacked structure with films, and then use a double-roller laminating machine to press from one end to the other end, and finally remove the films and bake to form the pre-pressed plate.

6. The method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board according to claim 4, characterized in that: The double-roll laminating machine has an operating pressure of 0.15 MPa to 0.30 MPa and an operating temperature of 50° C. to 80° C.

7. The method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board according to claim 4, characterized in that: The baking is low-temperature baking, the baking temperature is 80° C. to 100° C., and the baking time is 20 min to 30 min.

8. The method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board according to claim 1, characterized in that: The coating layer is manufactured by: taking a single-sided copper-clad board, manufacturing a pad pattern corresponding to the via hole, and forming the coating layer; the pad pattern faces the first release layer.

9. The method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board according to claim 1 or 8, characterized in that: A heat insulation film is attached to the edge of the coating layer.

10. The method for manufacturing a high-shielding, large-copper-surface, thin-type flexible circuit board according to claim 1, characterized in that: The pressing is performed by slowly heating at a heating rate of 1.0°C / min to 1.8°C / min and slowly cooling at a cooling rate of 4.0°C / min to 7.5°C / min.

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