Manufacturing method of large-current-carrying thick copper circuit board

Abstract

The invention discloses a method for manufacturing a large-current-carrying thick copper circuit board, which comprises the following steps of: manufacturing a copper core board with a bonding pad pattern, and manufacturing a dry film pattern corresponding to the bonding pad pattern; taking a high-flow glue prepreg, and manufacturing to form a windowing prepreg; taking two layers of copper-clad plates, manufacturing an auxiliary circuit, respectively forming a first auxiliary layer and a second auxiliary layer, and windowing the first auxiliary layer corresponding to the dry film pattern; stacking the first auxiliary layer, the windowing prepreg, the thick copper core plate and the second auxiliary layer from top to bottom, and laminating to form a laminated plate; milling to form a circuit board; the prepreg is adopted to replace a solder mask to form a protective layer with higher reliability, and the problem that the windowing is deformed due to the fact that the low-flow prepreg and the high-flow prepreg are combined up and down is solved through the vertical combination of the low-flow prepreg and the high-flow prepreg; by arranging the auxiliary circuit, the problems that the edge of the prepreg serving as a surface layer is easily whitened, and a milling cutter is filled with colloid are solved.

Description

Technical Field

[0001] The invention relates to the field of circuit board manufacturing, and in particular to a method for manufacturing a large current-carrying thick copper circuit board. Background Art

[0002] Circuit boards usually use ink to make surface solder mask to protect the circuit patterns. However, for thick copper circuit boards with high current carrying capacity, it is difficult for ink to cover the thick copper, which can easily lead to problems such as insufficient solder mask thickness or exposed circuits. In addition, for some circuit boards with high reliability requirements, the solder mask is difficult to meet the mechanical and electrical performance requirements.

[0003] Therefore, a method of using a prepreg to replace the solder mask has emerged, that is, using a prepreg to cover the surface of the thick copper circuit to form a protective layer on the outer surface. The existing method is to directly make a window on the prepreg, and then press it to make the surface layer of the prepreg.

[0004] However, the above method has the following defects: (1) Since the prepreg is different from solder mask ink in that it can be made by screen printing first and then exposure and development, there is a glue flow process during the prepreg lamination process. If the method of opening the window first and then lamination is used, it is easy for the prepreg to flow and cause the window to deform, thereby deforming the pad pattern that needs to be exposed; (2) When forming the milling plate, the semi-cured sheet is milled as the surface layer, which is prone to whitening of the edges and clogging of the milling cutter by colloid.

[0005] Therefore, in order to solve the above-mentioned problems, it is necessary to provide a method for manufacturing a large current-carrying thick copper circuit board. Summary of the invention

[0006] The present invention aims to solve the problems in the prior art that when using a prepreg to make a solder mask layer of a thick copper plate, the window is easily deformed due to the flow of prepreg glue, resulting in deformation of the pad pattern; and when forming a milling board, the prepreg as a surface layer is easily milled to produce white edges and the milling cutter is filled with colloid. A method for manufacturing a large current-carrying thick copper circuit board is proposed, wherein the circuit board is designed with a molding line, and the area outside the molding line is an invalid area. The manufacturing method comprises the following steps: S10: taking a single-sided thick copper clad laminate, making a pad pattern, and making a dry film pattern corresponding to the pad pattern to form a thick copper core board; S20: taking a high-flow adhesive prepreg, and making a first window pattern corresponding to the dry film pattern to form a window prepreg; S30: taking a first single-sided copper clad laminate, making a first circuit pattern from the molding line to the ineffective area to form a first auxiliary circuit, and then making a second window pattern corresponding to the dry film pattern to form a first auxiliary layer; Take a second single-sided copper-clad laminate, and make a second circuit pattern from the molding line to the ineffective area to form a second auxiliary circuit, thereby forming a second auxiliary layer as a whole; S50: stacking the first auxiliary layer, the window prepreg, the thick copper core board, and the second auxiliary layer in order from top to bottom to form a stacked structure, and then pressing them together to form a pressed board; The pad pattern faces the windowed prepreg; the first auxiliary circuit and the second auxiliary circuit both face away from the thick copper core board; S60: removing the dry film pattern from the laminated plate, and then performing milling and forming to form the circuit board; The radius of the milling cutter head of the milling is smaller than the width of the auxiliary line.

[0007] Furthermore, the high-flow adhesive prepreg has an adhesive content of 56% to 68%.

[0008] Furthermore, the model of the high-flow adhesive prepreg is 1080 or 2116.

[0009] Furthermore, the insulating dielectric layer of the first single-sided copper clad laminate is a low-flow adhesive prepreg with an adhesive content of 43% to 50%.

[0010] Furthermore, the model of the low-flow prepreg is 7628, 7628M or 7628H.

[0011] Furthermore, the dry film pattern is smaller than the first window pattern or smaller than the second window pattern.

[0012] Furthermore, the dry film pattern is smaller than the second window pattern, and the second window pattern is smaller than the first window pattern.

[0013] Furthermore, after the dry film pattern is removed, the edge of the second window pattern is laser ablated.

[0014] Furthermore, the forming of the laminated plate is to take a release layer and an aluminum sheet layer, stack the release layer and the aluminum sheet layer in sequence from near to far on both upper and lower surfaces of the stacked structure, and then press them together to form the laminated plate.

[0015] Furthermore, the thickness of the aluminum sheet layer is 25 μm to 105 μm, preferably 35 μm.

[0016] The technical solution of the present invention combines a low-flow glue prepreg with a high-flow glue prepreg up and down. The low-flow glue prepreg is used for surface coating, and the high-flow glue prepreg is used as a bonding layer. The fluidity of the glue is used to fill the thick copper circuit pattern, which solves the problem that the existing technology uses a single-layer prepreg to first open a window and then press it together, which easily causes the prepreg to flow and deform the window, thereby deforming the pad pattern to be exposed. The first auxiliary circuit and the second auxiliary circuit are arranged at the edge of the milling, so that both sides of the milling cutter head are evenly in contact with the circuit pattern, which solves the problems of the existing technology that the prepreg as the surface layer is easily whitened when milled and the milling cutter is filled with colloid, and the front and back form an effective coordination, which effectively improves the processing accuracy of the large current-carrying thick copper circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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.

[0018] Figure 1 Schematic diagram of the process flow of an embodiment of the present invention; Figure 2 A schematic plan view of a thick copper core board according to an embodiment of the present invention; Figure 3 A schematic diagram of a typesetting and pressing structure according to an embodiment of the present invention; Figure 4 is a schematic diagram of the cross-sectional structure of a pressed plate according to an embodiment of the present invention; Figure 5 It is a schematic diagram of the cross-sectional structure of a film-demolding plate according to an embodiment of the present invention; Figure 6 A schematic plan view of a high current carrying thick copper circuit board according to an embodiment of the present invention; Figure 7 for Figure 6 Schematic diagram of the AA cross-section structure.

[0019] Description of Figure Numbers:

[0020] 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

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The present embodiment shows a method for manufacturing a thick copper circuit board with a large current carrying capacity and a copper thickness of ≥105 μm. The circuit board is designed with a forming line 10A, and the area outside the forming line 10A is an invalid area 10B. The method includes the following steps in sequence: See also Figure 1 and Figure 2 , Figure 1 is a schematic diagram of the process flow of an embodiment of the present invention; please refer to Figure 2 , Figure 2 It is a schematic plan view of a thick copper core board according to an embodiment of the present invention.

[0026] (1) Cutting: Cut the core board according to the panel size of the design data. The thickness of the copper layer on both surfaces of the core board is ≥105μm.

[0027] (2) Inner layer circuit production S10: Take a single-sided thick copper clad laminate, produce an inner layer thick copper circuit pattern and a pad pattern 1010, and then check the inner layer thick copper circuit pattern for defects such as open short circuits, circuit gaps, and circuit pinholes. Defective products will be scrapped, and non-defective products will be processed into a dry film pattern 1020 corresponding to the pad pattern 1010 to form a thick copper core board 100.

[0028] It is worth noting that since the post-process requires the production of the first auxiliary layer 300 and the second auxiliary layer 400 to participate in the pressing process of the thick copper core board 100, which is equivalent to increasing the thickness of a part of the insulating dielectric layer, the thickness of the design data of the thick copper core board insulating dielectric layer 1030 is reduced, and the sum of the thickness of the semi-cured sheet of the first auxiliary layer 300 and the second auxiliary layer 400 and the reduced thick copper core board insulating dielectric layer 1030 is equal to the thickness of the insulating dielectric layer of the original design data.

[0029] See also Figure 3 , Figure 3 It is a schematic diagram of a typesetting structure according to an embodiment of the present invention.

[0030] (3) Making a windowed prepreg S20: Take a high-flow adhesive prepreg and make a first windowed pattern 2010 corresponding to the dry film pattern 1020 to form a windowed prepreg 200. The thickness of the windowed prepreg 200 is 10 μm to 50 μm, which can better adapt to the inner layer thick copper circuit pattern and ensure that the impedance distribution on the circuit board is more uniform and stable to a certain extent.

[0031] Optionally, the glue content of the windowed semi-cured sheet 200 is 56% to 68%. The glue content within this range can ensure that the fluidity of the high-flow adhesive semi-cured sheet after heat pressing is within a controllable range, and can cover the inner thick copper circuit pattern, but will not flow excessively, resulting in problems such as poor coverage of the inner thick copper circuit pattern.

[0032] Optionally, the model of the windowed prepreg 200 may be 1080 or 2116.

[0033] Optionally, the material of the window prepreg 200 is an acrylic adhesive layer or a polyolefin adhesive layer.

[0034] (4) Making an auxiliary layer S30: Take a first single-sided copper clad laminate, and make a first circuit pattern from the molding line 10A to the invalid area 10B to form a first auxiliary circuit 3010, and then make a second window pattern 3020 corresponding to the dry film pattern 1020 to form a first auxiliary layer 300; take a second single-sided copper clad laminate, and make a second circuit pattern from the molding line 10A to the invalid area 10B to form a second auxiliary circuit, and the whole forms a second auxiliary layer 400.

[0035] In this embodiment, the insulating dielectric layer of the first single-sided copper clad laminate is a low-flow prepreg 3030, and the glue content is 43% to 50%. Although the glue content is lower than that of a high-flow prepreg, it is still sufficient to provide sufficient adhesion during the hot pressing process, forming a good bonding and coating effect with the window prepreg 200, forming a firm bond, and effectively avoiding problems such as voids, white spots, and bubbles during the pressing process.

[0036] Furthermore, since the low-flow glue semi-cured sheet 3030 mainly serves to replace the covering surface of the solder mask, the low-flow glue semi-cured sheet 3030 can prevent the first window pattern 2010 from excessively flowing glue and causing deformation problems, and can improve the surface flatness, effectively avoiding the glue flow and deformation problems in the traditional pressing process, as well as the delamination problems caused by excessive resin flow.

[0037] Preferably, the model of the low-flow prepreg 3030 is 7628, 7628M or 7628H, and the glue content is in the range of 43% to 50%.

[0038] Preferably, the thickness of the low-flow prepreg 3030 is ≥75 μm, which can effectively cover the thick copper circuit.

[0039] Optionally, the first auxiliary circuit 3010 and the second auxiliary circuit 4010 can mainly play the role of an effective "gasket layer" on the board surface during milling and forming, thereby preventing problems such as whitening of edges caused by direct milling by the milling cutter.

[0040] Optionally, the thickness of the first auxiliary circuit 3010 or the second auxiliary circuit 4010 is 5 μm to 35 μm, and the thickness should not be too thick, otherwise the flatness of the board surface after lamination will be affected.

[0041] In one embodiment, the dry film pattern 1020 is smaller than the first window pattern 2010 or smaller than the second window pattern 3020, and the single-side distance is 20 μm to 50 μm, which effectively prevents the dry film pattern 1020 from forming a structure that penetrates deep into the pressing plate 20 after the pressing process, resulting in problems such as difficulty in film removal or incomplete film removal in subsequent steps.

[0042] In this embodiment, the dry film pattern 1020 is smaller than the second window pattern 3020, and the second window pattern 3020 is smaller than the first window pattern 2010 (i.e., the dry film pattern 1020 < the second window pattern 3020 < the first window pattern 2010), and the single-side distance is 20 μm to 50 μm. The flow rate of the windowed semi-cured sheet 200 during lamination is relatively large, and the flow rate of the low-flow glue semi-cured sheet 3030 during lamination is relatively small. The first window pattern 2010 is less than or equal to the second window pattern 3020, which can provide a large space for glue flow for the windowed semi-cured sheet 200.

[0043] Optionally, the second single-sided copper clad laminate only serves as an adhesive layer, so there is no requirement for the glue content of the insulating dielectric layer of the second single-sided copper clad laminate, and it can be a high-flow glue prepreg or a low-flow glue prepreg.

[0044] Optionally, the thickness of the insulating dielectric layer 4020 of the second single-sided copper clad laminate is 10 μm to 50 μm.

[0045] (5) Stacking S40: The first auxiliary layer 300, the window prepreg 200, the thick copper core board 100, and the second auxiliary layer 400 are stacked in order from top to bottom to form a stacking structure 10; the pad pattern 1010 faces the window prepreg 200; the first auxiliary circuit 3010 and the second auxiliary circuit 4010 both face away from the thick copper core board 100.

[0046] See also Figure 3 and Figure 4 , Figure 3 A schematic diagram of a typesetting structure according to an embodiment of the present invention; Figure 4 It is a schematic diagram of the cross-sectional structure of a pressed plate according to an embodiment of the present invention.

[0047] (6) Lamination: Appropriate lamination conditions are then selected according to the sheet material to laminate the stacked structure 10 to form a laminated plate 30; the glue produced during lamination flows out from the edge of the plate.

[0048] In this embodiment, the pressing plate 30 is formed by taking a release layer and an aluminum sheet layer, stacking the release layer and the aluminum sheet layer on the upper and lower surfaces of the stacked structure 10 from near to far in sequence, and then pressing them together to form the pressing plate 30. That is, the first release layer 5010, the second release layer 6010, the first aluminum sheet layer 5020 and the second aluminum sheet layer 6020 are respectively added to the auxiliary pressing structure, and the first auxiliary pressing structure 500 and the second auxiliary pressing structure 600 are respectively formed on the upper and lower surfaces of the stacked structure 10 to form a layout structure 20 as a whole. The good thermal conductivity and coating ability of the first aluminum sheet layer 5020 and the second aluminum sheet layer 6020 are used to increase the pressing flatness of the pressing plate 30.

[0049] Furthermore, the thickness of the first aluminum sheet layer 5020 and the second aluminum sheet layer 6020 is 25μm to 105μm, preferably 35μm. On the one hand, the first aluminum sheet layer 5020 and the second aluminum sheet layer 6020 are guaranteed to level the stacked structure 10 during the pressing process to prevent large bumps on the board surface after pressing, and have an auxiliary molding effect. On the other hand, the good thermal conductivity of the first aluminum sheet layer 5020 and the second aluminum sheet layer 6020 is utilized. The thickness of the aluminum sheet layer is usually 25μm to 105μm, preferably 35μm, which helps to achieve a more uniform temperature distribution on the entire board surface and reduce the risk of local overheating.

[0050] (7) Electrical test: Test the electrical conductivity of the laminated board 30. The test method used for this board is: flying probe test.

[0051] See also Figure 5 , Figure 6 and Figure 7 , Figure 5 It is a schematic diagram of the cross-sectional structure of the film-demolding plate according to an embodiment of the present invention. Figure 6 A schematic plan view of a high current carrying thick copper circuit board according to an embodiment of the present invention; Figure 7 for Figure 6 Schematic diagram of the AA cross-section structure.

[0052] Molding: S50: The dry film pattern 1020 is removed from the laminated plate 30, and then milling is performed according to the designed molding line 10A. The cutter head of the milling cutter 410 moves along the milling cutter line 420. The cutter head radius of the milling cutter 410 is smaller than the width of the first auxiliary circuit 3010 and the second auxiliary circuit 4010, so as to obtain a large current-carrying thick copper circuit board.

[0053] like Figure 7 As shown, the windowed prepreg 200 is bonded to the first auxiliary layer 300 to replace the original solder resist layer, and the sum of the thickness of the two is equal to the thickness of the original solder resist layer.

[0054] In this embodiment, if a large amount of glue overflows from the window semi-cured sheet 200 during lamination, the overflow glue of the first window pattern 2010 will easily enter the range of the second window pattern 3020. Therefore, after the dry film pattern 1020 is removed, the edge of the first window pattern 2010 needs to be laser ablated to trim the overflow glue at the edge of the first window pattern 2010.

[0055] (9) FQC: According to the customer's acceptance standards and our inspection standards, the appearance of the high current thick copper circuit board 50 is inspected. If there are any defects, they will be repaired in time to ensure that we provide customers with excellent quality control.

[0056] (10) FQA: Re-test the appearance, dielectric layer thickness, inner layer copper thickness, etc. of the high current-carrying thick copper circuit board 50 to see if they meet customer requirements.

[0057] (11) Packaging: According to the packaging method and packaging quantity required by the customer, the high current-carrying thick copper circuit board 50 is sealed and packed, and desiccant and humidity card are placed before shipment.

[0058] 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 large current-carrying thick copper circuit board, characterized in that: The circuit board is designed with a forming line, and the area outside the forming line is an invalid area. The manufacturing method includes the following steps: S10: taking a single-sided thick copper clad laminate, making a pad pattern, and making a dry film pattern corresponding to the pad pattern to form a thick copper core board; S20: taking a high-flow adhesive prepreg, and making a first window pattern corresponding to the dry film pattern to form a window prepreg; S30: taking a first single-sided copper clad laminate, making a first circuit pattern from the molding line to the ineffective area to form a first auxiliary circuit, and then making a second window pattern corresponding to the dry film pattern to form a first auxiliary layer; Take a second single-sided copper-clad laminate, and make a second circuit pattern from the molding line to the ineffective area to form a second auxiliary circuit, thereby forming a second auxiliary layer as a whole; S40: stacking the first auxiliary layer, the window prepreg, the thick copper core board, and the second auxiliary layer in order from top to bottom to form a stacked structure, and then pressing them together to form a pressed board; The pad pattern faces the windowed prepreg; the first auxiliary circuit and the second auxiliary circuit both face away from the thick copper core board; S50: removing the dry film pattern from the laminated plate, and then performing milling and forming to form the circuit board; The radius of the milling cutter head of the milling is smaller than the width of the auxiliary line.

2. The method for manufacturing a high current carrying thick copper circuit board according to claim 1, characterized in that: The high-flow adhesive prepreg has an adhesive content of 56% to 68%.

3. The method for manufacturing a high current carrying thick copper circuit board according to claim 1 or 2, characterized in that: The model of the high-flow adhesive prepreg is 1080 or 2116.

4. The method for manufacturing a high current carrying thick copper circuit board according to claim 1, characterized in that: The insulating dielectric layer of the first single-sided copper clad laminate is a low-flow adhesive prepreg with an adhesive content of 43% to 50%.

5. The method for manufacturing a high current carrying thick copper circuit board according to claim 1 or 4, characterized in that: The model of the low-flow prepreg is 7628, 7628M or 7628H.

6. The method for manufacturing a high current carrying thick copper circuit board according to claim 1, characterized in that: The dry film pattern is smaller than the first window pattern or smaller than the second window pattern.

7. A method for manufacturing a high current carrying thick copper circuit board as claimed in claim 1 or 6, characterized in that: The dry film pattern is smaller than the second window pattern, and the second window pattern is smaller than the first window pattern.

8. The method for manufacturing a high current carrying thick copper circuit board according to claim 1, characterized in that: After the dry film pattern is removed, the edge of the second window pattern is laser ablated.

9. The method for manufacturing a high current carrying thick copper circuit board according to claim 1, characterized in that: The forming of the laminated plate is to take a release layer and an aluminum sheet layer, stack the release layer and the aluminum sheet layer in sequence from near to far on both upper and lower surfaces of the stacked structure, and then press them together to form the laminated plate.

10. The method for manufacturing a high current carrying thick copper circuit board according to claim 9, characterized in that: The thickness of the aluminum sheet layer is 25 μm to 105 μm, preferably 35 μm.

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