A manufacturing method of a rigid-flex combined board of a heavy-current circuit of a thin plate body thick copper

Abstract

The application discloses a manufacturing method of a thin-plate thick-copper high-load current line rigid-flexible combination board, which comprises a flexible area and a rigid area. A thick copper layer is taken twice for half-etching to form a first rigid core plate and a second rigid core plate, and the two half-etching patterns correspond to form a complete line. A double-sided thick-copper flexible copper-clad plate is taken to manufacture a flexible plate line pattern, a first cover film is pasted to the corresponding flexible area, and resin ink is screen-printed to the corresponding rigid area and dried to form a flexible core plate. A semi-cured sheet and a low-flow adhesive semi-cured sheet are taken to be stacked and pressed with the above core plate to form a pressing plate. Surface line patterns, a solder mask layer and a cover are sequentially manufactured on the pressing plate to form a rigid-flexible combination board. Through the above manufacturing, line gaps are filled, the semi-cured sheet only plays a bonding role, the semi-cured sheet arranged between layers can effectively reduce the thickness, and the problems of poor pressing and poor glue filling caused by the fact that thick-copper circuit boards need to fill more glue in line gaps are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rigid-flex circuit board manufacturing, in particular to a manufacturing method of a thin plate thick copper strong current circuit rigid-flex board. BACKGROUND

[0002] The thick copper strong current rigid-flex board is widely used in power module, vehicle-mounted system and other fields due to its strong current characteristics and the ability to meet the needs of complex circuit design.

[0003] The thick copper circuit board requires more glue filling amount for the gap between the circuit patterns, so a thicker prepreg is used as an interlayer bonding layer during the pressing process to meet the glue filling demand, but it will cause the board thickness of the thick copper circuit board to increase, which is not easy to install in a small space.

[0004] In addition, using prepreg to fill glue also has the following problems:

[0005] (1) Using a prepreg with a high glue content requires a large pressing force, and excessive pressing force can easily cause glue overflow. If the pressing force is reduced, it can easily cause insufficient glue filling and interlayer voids;

[0006] (2) Using a low-flow prepreg with a small glue content requires a larger pressing force to meet the glue filling demand, but it can easily cause the board to be deformed and the circuit to be deformed;

[0007] (3) Using a thicker prepreg, the thickness of the prepreg layer after pressing is added to the thickness of the circuit pattern, resulting in an excessively thick board, which is not conducive to the application requirements in a small space.

[0008] Therefore, in order to solve the problems raised in the above background art, a manufacturing method of a thin plate thick copper strong current circuit rigid-flex board is needed. SUMMARY

[0009] The present application aims to solve the problem of the thick copper strong current rigid-flex board in the prior art, which requires a thin board and strong current comprehensive performance. A manufacturing method of a thin plate thick copper strong current circuit rigid-flex board is proposed, which includes a flexible area and a rigid area. The manufacturing method includes the following steps:

[0010] S10: Take a thick copper layer and make a blue glue layer on the first side, a circuit pattern on the second side, form a first half-etching pattern, and press a first glue filling prepreg, then tear off the blue glue layer to form a first rigid core board;

[0011] S20: making a circuit pattern on the first surface, forming a second half-etching pattern, laminating a second glue-filled prepreg on the first surface, and polishing to form a second rigid core board; the first half-etching pattern corresponds to the second half-etching pattern, and the two form a complete circuit together;

[0012] S30: taking a double-sided thick copper flexible CCL, making a flexible board circuit pattern on the surface thereof, laminating a first cover film on the corresponding flexible area, and screen printing resin ink on the corresponding rigid area and drying to form a flexible core board;

[0013] S40: taking a general flow glue prepreg, a low flow glue prepreg, the first rigid core board, the second rigid core board, and the flexible core board to form a stacking structure, and then laminating to form a laminated board; a second cover film is laminated on the surface of the low flow glue prepreg opposite to the flexible area of the flexible core board; the stacking structure is that the flexible core board is arranged between two first rigid core boards, and a plurality of second rigid core boards are arranged between the first rigid core board and the flexible core board; the first rigid core board and the second rigid core board and the adjacent two second rigid core boards are provided with a general flow glue prepreg, and the second rigid core board and the flexible core board are provided with a low flow glue prepreg; the first surface is located on the surface of the stacking structure;

[0014] S50: sequentially making a surface circuit pattern and a solder mask layer on the surface of the laminated board, and then performing uncovering processing to form the rigid-flexible combined board; the surface circuit pattern corresponds to the first half-etching pattern.

[0015] Further, the first half-etching pattern is 2 / 3 to 4 / 5 of the thickness of the thick copper layer.

[0016] Further, the number of the second rigid core boards on both sides of the flexible core board in the stacking structure is equal.

[0017] Further, the polishing is to polish the second glue-filled prepreg until the copper layer of the first surface is exposed.

[0018] Further, after laminating the second cover film, a control deep hole is drilled on the edge of the second cover film.

[0019] Further, the uncovering processing is that a control deep milling plate is milled from the edge of the corresponding flexible area on the surface of the solder mask layer to the control deep hole position, and then the rigid board layer on the upper part of the corresponding flexible area is uncovered.

[0020] Further, the resin ink fills the circuit gap of the flexible board circuit pattern and covers the flexible board circuit pattern.

[0021] Furthermore, the ordinary flow prepreg has an adhesive content of 55% to 65%, and the low flow prepreg has an adhesive content of 45% to 52%.

[0022] Furthermore, the copper thickness of both the thick copper layer and the double-sided thick copper flexible clad laminate is greater than or equal to 70 μm.

[0023] Furthermore, the first surface of the second rigid core plate corresponds to the first rigid core plate.

[0024] This invention employs a manufacturing method that involves etching a thick copper layer twice, then laminating it, and finally connecting the etched patterns to form a complete circuit. This method "pre-fills" the gaps in the thick copper circuit patterns of the formed rigid core board with adhesive, improving the flatness of the rigid core board and reducing its thickness. Furthermore, the thickness of the prepreg used in the two etching processes can be selectively reduced according to the thickness of the etched circuit, further reducing the thickness of the circuit board. By combining two types of prepreg, the invention solves the problem of insufficient compaction caused by the large adhesive filling area when laminating thick copper boards with low-flow prepreg, while also avoiding the need to use multiple low-flow prepreg sheets. The problem of excess adhesive after lamination of the prepreg is addressed. Based on the above manufacturing process, the gaps between circuits have been filled, and the prepreg is only used for bonding and no longer for filling adhesive. Therefore, the thickness of the prepreg placed between layers can be effectively reduced during lamination. This solves the problems of weak lamination, poor filling, and interlayer voids caused by the large amount of adhesive required to fill the gaps between circuits in thick copper circuit boards. The overall manufacturing method results in a thinner rigid-flex board, which effectively improves the applicability of rigid-flex boards in confined installation spaces and enables the manufacturing and application of thick copper high-current-carrying circuit boards on thinner circuit boards. Attached Figure Description

[0025] 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.

[0026] Figure 1 This is a schematic diagram of the process flow of the rigid-flex circuit board according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the structure for creating a first half-etched pattern on a thick copper layer according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure of the first rigid core plate according to an embodiment of the present invention;

[0029] Figure 4This is a schematic diagram of the structure for creating a second half-etched pattern on a thick copper layer according to an embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram of the structure of the second rigid core plate according to an embodiment of the present invention;

[0031] Figure 6 This is a schematic diagram of the structure of the flexible core board according to an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram of the stacked structure according to an embodiment of the present invention;

[0033] Figure 8 This is a schematic diagram of the structure of the pressing plate according to an embodiment of the present invention;

[0034] Figure 9 This is a schematic diagram of the rigid-flexible plate according to an embodiment of the present invention.

[0035] Explanation of icon numbers:

[0036]

[0037] 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

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Please see Figure 1 , Figure 1 This is a schematic diagram of the process flow according to an embodiment of the present invention.

[0043] 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.

[0044] Please see Figure 2 and Figure 3 , Figure 2 This is a schematic diagram of the structure for creating a first half-etched pattern on a thick copper layer according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the structure of the first rigid core plate according to an embodiment of the present invention.

[0045] Step S10:

[0046] Take a thick copper layer 1010 and make a blue adhesive layer 1020 on its first side and a circuit pattern on its second side to form a first semi-etched pattern 1030. Then press a first adhesive-filled semi-cured sheet 1040 on it and then peel off the blue adhesive layer 1020 to form a first rigid core board 10.

[0047] In this embodiment, a blue adhesive layer 1020 is first fabricated on the first side of the thick copper layer 1010. The blue adhesive layer 1020 serves as a support layer to provide support for the subsequent fabrication of the first half-etched pattern 1030 on the thick copper layer 1010. Since the blue adhesive layer 1020 is peelable, it can be peeled off after processing without affecting the original copper surface effect.

[0048] It is worth noting that in this embodiment, the circuit pattern is divided into two half-etchings and then connected to form a complete circuit. This is because half of the copper is etched first. The first half-etched pattern 1030 is 2 / 3 to 4 / 5 of the thickness of the thick copper layer. This can provide a certain filling depth for the subsequent process of laminating the first filler prepreg 1040. The unetched copper layer plays a role in ensuring the integrity of the copper layer. It also helps the first filler prepreg 1040 and the first half-etched pattern 1030 to fill and bond better. This prevents complete etching at one time, which would cause the circuit to scatter and the gap between the circuits to be too deep. This would lead to problems such as insufficient filling of the prepreg or the circuit being pressed off when laminating the filler prepreg.

[0049] Please see Figure 4 and Figure 5 ;Figure 4 This is a schematic diagram of the structure for creating a second half-etched pattern on a thick copper layer according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the second rigid core plate according to an embodiment of the present invention.

[0050] Step S20:

[0051] The circuit pattern is made on the first side to form the second semi-etched pattern 2010. Then, the second adhesive-filled semi-cured sheet 2020 is pressed onto the first side and polished to form the second rigid core board 20.

[0052] In this embodiment, the first half-etched pattern 1030 corresponds to the second half-etched pattern 2010 and is connected to form a complete circuit. The formed full etched pattern is completely filled by the first filler semi-cured sheet 1040 and the second filler semi-cured sheet 2020, forming a state in which the circuit pattern is "embedded in the semi-cured sheet layer". The first filler semi-cured sheet 1040 and the second filler semi-cured sheet 2020 "pre-fill" the circuit gaps, which is beneficial to make the semi-cured sheets between the layers thinner during subsequent lamination, thereby reducing the overall thickness of the circuit board.

[0053] It is worth noting that the thickness of the prepreg used for the two fillings is different. Since the first half-etched pattern 1030 is 2 / 3 to 4 / 5 of the thickness of the thick copper layer 1010, and the remaining copper thickness of the second half-etched pattern 2010 is 1 / 5 to 1 / 3, the deeper the etching of the circuit pattern, the greater the demand for prepreg. Therefore, the thickness of the first prepreg 1040 used for the first half-etched pattern 1030 is greater than that of the second prepreg 2020 used for the second half-etched pattern 2010.

[0054] Furthermore, the depth of the first half-etched pattern 1030 is greater than the depth of the second half-etched pattern 2010 because the first side needs to be polished in subsequent processing. Polishing is to polish the second filler semi-cured sheet 2020 until the copper layer of the first side is exposed, providing a core board base for subsequent lamination processing. Therefore, the etching depth of the second half-etched pattern 2010 is shallower, and the thickness of the second filler semi-cured sheet 2020 that needs to be laminated is also relatively thinner. At the same time, it also makes subsequent polishing more convenient and improves the polishing processing efficiency.

[0055] Please see Figure 6 , Figure 6 This is a schematic diagram of the structure of the flexible core board according to an embodiment of the present invention.

[0056] Step S30:

[0057] Take a double-sided thick copper flexible copper-clad laminate, make a flexible board circuit pattern 3010 on its surface, and apply a first cover film 3020 to the corresponding flexible area 3040. Then, screen print resin ink 3030 on the corresponding rigid area 3050 and dry it to form a flexible core board 30.

[0058] In this embodiment, resin ink 3030 is used to fill the gaps in the circuit pattern 3010 of the flexible board and cover the circuit pattern 3010 of the flexible board, so that the surface of the flexible core board 30 is flat. Furthermore, since the material properties of resin ink 3030 are similar to those of the low-flow prepreg 4020 used for subsequent lamination, the resin ink 3030 is used to form a cured layer. During the subsequent lamination process, it can effectively form an interlayer bonding effect by bonding with the low-flow prepreg 4020.

[0059] It is worth noting that the copper thickness of both the thick copper layer 1010 and the double-sided thick copper flexible copper clad laminate is greater than or equal to 70μm.

[0060] Please see Figure 7 and Figure 8 , Figure 7 This is a schematic diagram of the stacked structure according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the structure of the pressing plate according to an embodiment of the present invention.

[0061] Step S40:

[0062] Take ordinary flow prepreg 4010, low flow prepreg 4020, first rigid core board 10, second rigid core board 20 and flexible core board 30 and stack them to form a stacked structure 40, and then press them together to form a press plate 50.

[0063] A second cover film 4030 is attached to the flexible area 3040 opposite to the flexible core board 30 on the surface of the low-flow prepreg 4020. This is because the rigid plate layer above the flexible area 3040 needs to be peeled off later. The second cover film 4030 and the first cover film 3020 are set to form a film-to-film structure. The inertness of the cover film (usually polyimide material) is stronger than that of the prepreg (usually epoxy resin material). During pressing, the film-to-film structure cannot form a mutual adhesion, which facilitates subsequent release and peeling. After attaching the second cover film 4030, deep holes are drilled on the surface of the low-flow prepreg 4020 at the edge of the second cover film 4030 to effectively cooperate with the subsequent peeling process and improve the efficiency of peeling.

[0064] The stacked structure 40 is as follows: a flexible core plate 30 is disposed between two first rigid core plates 10, and several second rigid core plates 20 are stacked between the first rigid core plates 10 and the flexible core plate 30.

[0065] In this embodiment, the number of second rigid core plates 20 on both sides of the flexible core plate 30 in the stacked structure 40 is equal. Therefore, when pressing, since the stacked structure 40 is a structure symmetrical about the flexible core plate 30, the auxiliary mechanisms on both sides are the same, and the two sides of the entire stacked structure 40 are subjected to uniform force, resulting in a better pressing effect.

[0066] In this embodiment, the prepregs that serve as adhesives in the stacked structure 40 are of two types with different adhesive contents. Specifically, a prepreg, 4010, is provided between the first rigid core plate 10, the second rigid core plate 20, and two adjacent second rigid core plates 20. This prepreg is a common flow prepreg 4010 with a relatively high adhesive content, resulting in good adhesion and filling performance. A low flow prepreg 4020 is provided between the second rigid core plate 20 and the flexible core plate 30. This prepreg has a relatively low adhesive content, preventing excessive flow that could cause excessive adhesive overflow at the rigid-flexible bonding position, leading to difficulties in subsequent capping. It also avoids unevenness or excessive expansion and contraction of the plate caused by excessive filling during the pressing of the second rigid core plate 20 and the flexible core plate 30.

[0067] It is worth noting that the glue content of the ordinary flow prepreg 4010 is 55% to 65%, while the glue content of the low flow prepreg 4020 is 45% to 52%.

[0068] The first surface is located on the surface of the stacked structure 40; that is, the first surface exposed after polishing is a complete copper layer, which needs to be used as the outer surface of the stacked structure 40 to ensure that the two surface copper layers of the entire stacked structure 40 are subjected to uniform force and the interlayer bonding is tighter.

[0069] In this embodiment, the first copper layer of the second rigid core board 20 corresponds to the first rigid core board 10, which can form a more uniform circuit layer distribution effect and improve the bonding force between layers.

[0070] Please see Figure 9 , Figure 9 This is a schematic diagram of the rigid-flexible plate according to an embodiment of the present invention.

[0071] Step S50:

[0072] A surface circuit pattern 6010 and a solder resist layer 6020 are sequentially fabricated on the surface of the press plate 50, and then a cover-up process is performed to form a rigid-flex plate 60. The surface circuit pattern 6010 corresponds to the first half-etched pattern 1030. That is, the final surface circuit pattern 6010 corresponds to and is connected to the first half-etched pattern 1030 to form a complete circuit pattern.

[0073] In this embodiment, the peeling process is as follows: the edge of the flexible area 3040 corresponding to the surface of the solder resist layer is milled to the position of the depth control hole, and then the rigid plate layer above the flexible area 3040 is peeled off to form the peeling area 6030, thus forming a rigid-flexible bonded plate.

[0074] 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 thin-plate, thick-copper, high-current-carrying rigid-flex circuit board, wherein the rigid-flex circuit board comprises a flexible region and a rigid region, characterized in that, The manufacturing method includes the following steps: S10: Take a thick copper layer and make a blue glue layer on its first side, make a circuit pattern on the second side to form a first semi-etched pattern, and press a first glue-filled semi-cured sheet, then peel off the blue glue layer to form a first rigid core board. S20: Create a circuit pattern on the first surface to form a second semi-etched pattern, then press a second filler semi-cured sheet onto the first surface and polish it to form a second rigid core board. The first half-etched pattern corresponds to the second half-etched pattern and is connected to form a complete circuit; S30: Take a double-sided thick copper flexible copper-clad board, make a flexible board circuit pattern on its surface, and apply a first cover film to the corresponding flexible area. Then, screen print resin ink on the corresponding rigid area and dry it to form a flexible core board. S40: Take ordinary flow prepreg, low flow prepreg, the first rigid core board, the second rigid core board and the flexible core board, stack them to form a stacked structure, and then press them together to form a press plate. A second cover film is attached to the flexible area on the surface of the low-flow prepreg opposite to the flexible core board; The stacked structure is as follows: the flexible core board is disposed between two first rigid core boards, and several second rigid core boards are stacked between the first rigid core board and the flexible core board; A standard flow prepreg is provided between the first rigid core board, the second rigid core board, and two adjacent second rigid core boards, and a low flow prepreg is provided between the second rigid core board and the flexible core board. The first surface is located on the surface of the stacked structure; S50: The surface circuit pattern and solder mask layer are sequentially formed on the surface of the press plate, and then the cover is removed to form the rigid-flex plate. The surface circuit pattern corresponds to the first half-etched pattern.

2. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 1, characterized in that, The first half-etched pattern is 2 / 3 to 4 / 5 of the thickness of the thick copper layer.

3. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 1, characterized in that, The number of second rigid core plates on both sides of the flexible core plate in the stacked structure is equal.

4. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 1, characterized in that, The polishing process involves polishing the second prepreg-filled sheet until the copper layer on the first surface is exposed.

5. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 1, characterized in that, After the second cover film is applied, deep holes are drilled along the edge of the second cover film.

6. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 5, characterized in that, The peeling process involves: milling the plate from the edge of the flexible area corresponding to the surface of the solder resist layer to the position of the depth control hole, and then peeling off the rigid plate layer corresponding to the upper part of the flexible area.

7. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 1, characterized in that, The resin ink fills the gaps in the circuit pattern of the flexible board and covers the circuit pattern of the flexible board.

8. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 1, characterized in that, The ordinary flow prepreg has an adhesive content of 55% to 65%, while the low flow prepreg has an adhesive content of 45% to 52%.

9. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 1, characterized in that, The copper thickness of both the thick copper layer and the double-sided thick copper flexible copper clad laminate is greater than or equal to 70 μm.

10. The method for manufacturing a thin-plate, thick-copper, high-current-carrying rigid-flex circuit board as described in claim 1, characterized in that, The first surface of the second rigid core plate corresponds to the first rigid core plate.

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