A method for manufacturing a large-current thick copper circuit board

Abstract

The application discloses a manufacturing method of a large-current thick copper circuit board, and comprises the following steps: manufacturing a copper core plate with a pad pattern, manufacturing a dry film pattern corresponding to the pad pattern, taking a high-flow prepreg sheet to manufacture a windowed prepreg sheet, taking two layers of copper-clad plates to manufacture auxiliary lines, 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 windowed prepreg sheet, the thick copper core plate and the second auxiliary layer from top to bottom, and pressing to form a pressed plate, and milling to form a circuit board, wherein the prepreg sheet is used to replace the solder mask layer to form a protection layer with higher reliability, the upper and lower combination of the low-flow prepreg sheet and the high-flow prepreg sheet solves the problems of window deformation caused by the flow of the prepreg sheet, and the auxiliary lines are arranged to solve the problems of edge whitening and the clogging of the milling cutter caused by the flow of the prepreg sheet.

Description

TECHNICAL FIELD

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

[0002] The circuit board is usually made of ink to make the surface solder resist layer to form the protection of the circuit pattern, but for the large-current thick copper circuit board with thick copper, the ink is difficult to cover the thick copper, and the problem of insufficient thickness of the solder resist layer or exposure of the circuit is easily caused, and for some circuit boards with high reliability requirements, the solder resist layer is difficult to meet the mechanical and electrical performance requirements.

[0003] Therefore, a manufacturing method using prepreg to replace the solder resist layer appears, that is, the prepreg is used to cover the surface of the thick copper circuit to form a protective layer on the surface, and the existing method is to directly make a window on the prepreg and then press the prepreg to make the surface layer of the prepreg.

[0004] However, the above method has the following defects:

[0005] (1) Since the prepreg is different from the solder resist ink which can be made by silk printing and then exposed and developed, the prepreg has a flow glue process during the pressing process, and the method of pressing after windowing is used, which is easy to cause the prepreg to flow and deform the window, thereby deforming the exposed pad pattern;

[0006] (2) When the plate is formed and milled, the prepreg as the surface layer is easily milled to cause the edge to be white, the milling cutter to be filled with glue, and other problems.

[0007] Therefore, in order to solve the above problems, a manufacturing method of large-current thick copper circuit board is needed. SUMMARY

[0008] The present application aims to solve the problems of the prior art that the solder resist layer of the thick copper plate is made of prepreg, which is easy to cause the prepreg to flow and deform the window, resulting in deformation of the pad pattern, and when the plate is formed and milled, the prepreg as the surface layer is easily milled to cause the edge to be white, the milling cutter to be filled with glue, and other problems, and a manufacturing method of large-current thick copper circuit board is provided, the circuit board is designed with a forming line, the area outside the forming line is an invalid area, and the manufacturing method comprises the following steps:

[0009] S10: taking a single-sided thick copper clad plate, making a pad pattern, and corresponding to the pad pattern, making a dry film pattern to form a thick copper core plate;

[0010] S20: taking a high-flow prepreg, corresponding to the dry film pattern, making a first window pattern to form a windowed prepreg;

[0011] S30: taking a first single-sided copper-clad plate, making a first circuit pattern from the forming line to the invalid area to form a first auxiliary circuit, and then making a second windowing pattern corresponding to the dry film pattern to form a first auxiliary layer;

[0012] taking a second single-sided copper-clad plate, making a second circuit pattern from the forming line to the invalid area to form a second auxiliary circuit, and then forming a second auxiliary layer as a whole;

[0013] S50: sequentially stacking the first auxiliary layer, the windowing prepreg, the thick copper core plate, and the second auxiliary layer from top to bottom to form a stacking structure, and then pressing to form a pressed plate;

[0014] The pad pattern faces the windowing prepreg, and the first auxiliary circuit and the second auxiliary circuit both face away from the thick copper core plate.

[0015] S60: removing the dry film pattern from the pressed plate, and then milling and forming to form the circuit board;

[0016] The milling cutter head radius of the milling is smaller than the width of the auxiliary circuit.

[0017] Further, the glue content of the high-flow prepreg is 56% to 68%.

[0018] Further, the model of the high-flow prepreg is 1080 or 2116.

[0019] Further, the insulating medium layer of the first single-sided copper-clad plate is a low-flow prepreg with a glue content of 43% to 50%.

[0020] Further, the model of the low-flow prepreg is 7628, 7628M, or 7628H.

[0021] Further, the dry film pattern is smaller than the first windowing pattern or smaller than the second windowing pattern.

[0022] Further, the dry film pattern is smaller than the second windowing pattern, and the second windowing pattern is smaller than the first windowing pattern.

[0023] Further, after removing the dry film pattern, laser ablation is performed on the edge of the second windowing pattern.

[0024] Further, the pressed plate is formed by taking a release layer and an aluminum sheet layer, sequentially stacking the release layer and the aluminum sheet layer from near to far on the upper and lower surfaces of the stacking structure, and then pressing to form a pressed plate.

[0025] Further, the thickness of the aluminum sheet layer is 25 μm to 105 μm, preferably 35 μm.

[0026] The technical solution of the present invention is to combine a low-flow adhesive prepreg and a high-flow adhesive prepreg together. The low-flow adhesive prepreg plays the role of surface coating, and the high-flow adhesive prepreg serves as an adhesive layer, using the fluidity of the adhesive to fill the thick copper circuit pattern. This 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. By arranging the first auxiliary circuit and the second auxiliary circuit at the milling edge, the two 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. The front and back form an effective coordination, effectively improving the processing accuracy of large current-carrying thick copper circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0028] Figure 1 Schematic diagram of the process flow of an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of a thick copper core board according to an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of a typesetting and pressing structure according to an embodiment of the present invention;

[0031] Figure 4 Schematic diagram of the cross-sectional structure of a pressed plate according to an embodiment of the present invention;

[0032] Figure 5 Schematic diagram of the cross-sectional structure of a film stripping plate according to an embodiment of the present invention;

[0033] Figure 6 A schematic plan view of a high current carrying thick copper circuit board according to an embodiment of the present invention;

[0034] Figure 7 for Figure 6 Schematic diagram of the AA cross-section structure.

[0035] Description of Figure Numbers:

[0036]

[0037] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0039] It should be noted that all directionality indications (such as up, down, left, right, front, back, inside, outside, etc.) in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directionality indications also change accordingly.

[0040] In addition, the description such as "first", "second" and the like in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0041] In addition, the technical solutions of each embodiment of the present application can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist and is not within the protection scope claimed by the present application.

[0042] The manufacturing method of the thick copper circuit board with a large current-carrying capacity and a copper thickness of ≥105 μm shown in the embodiment includes the following processes in sequence:

[0043] Please refer to Figure 1 and Figure 2 , Figure 1 is a process flow diagram of the embodiment of the present application; please refer to Figure 2 , Figure 2 is a plan view of the thick copper core plate of the embodiment of the present application.

[0044] (1) Cutting: cut the core plate according to the panel size of the design data, and the thickness of the copper layer on both surfaces of the core plate is ≥105 μm.

[0045] (2) Inner layer circuit manufacturing S10: take a single thick copper clad plate, manufacture inner layer thick copper circuit pattern and pad pattern 1010, then check the inner layer thick copper circuit pattern for open / short circuit, circuit gap, circuit pinhole and other defects, scrap the defective products, and manufacture dry film pattern 1020 on the corresponding pad pattern 1010 of the non-defective product to form thick copper core plate 100.

[0046] It is worth noting that, since the first auxiliary layer 300 and the second auxiliary layer 400 are needed to participate in the pressing process of the thick copper core plate 100 in the subsequent process, which is equivalent to increasing the thickness of a part of the insulating medium layer, the thickness of the design data of the thick copper core plate insulating medium layer 1030 is reduced, and the sum of the thickness of the prepreg forming the first auxiliary layer 300 and the second auxiliary layer 400 and the reduced thick copper core plate insulating medium layer 1030 is equal to the original design data of the insulating medium layer thickness.

[0047] Please refer to Figure 3 , Figure 3 is a schematic diagram of the layout structure of an embodiment of the present application.

[0048] (3) Manufacturing windowed prepreg S20: taking high-flow prepreg, manufacturing first windowed pattern 2010 corresponding to dry film pattern 1020 to form windowed prepreg 200, and the thickness of windowed prepreg 200 is 10-50 microns, 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.

[0049] Optionally, the adhesive content of the windowed prepreg 200 is 56-68%, which can ensure that the flowability of the high-flow prepreg after heat pressing is within a controllable range, and can form coverage on the inner layer thick copper circuit pattern, but not to the extent of excessive flow, resulting in poor coverage of the inner layer thick copper circuit pattern and other problems.

[0050] Optionally, the model of the windowed prepreg 200 can be 1080 or 2116.

[0051] Optionally, the material of the windowed prepreg 200 is an acrylic adhesive layer or a polyolefin adhesive layer.

[0052] (4) Manufacturing auxiliary layer S30: taking a first single-sided copper clad plate, manufacturing a first circuit pattern from forming line 10A to invalid area 10B to form first auxiliary circuit 3010, and then manufacturing second windowed pattern 3020 corresponding to dry film pattern 1020 to form first auxiliary layer 300; taking a second single-sided copper clad plate, manufacturing a second circuit pattern from forming line 10A to invalid area 10B to form a second auxiliary circuit, and forming a second auxiliary layer 400 as a whole.

[0053] In the embodiment, the insulating medium layer of the first single-sided copper-clad plate is a low-flow prepreg 3030, and the resin content is 43% to 50%. Although the resin content is relatively low compared with the high-flow prepreg, it is still sufficient to provide sufficient adhesion during hot pressing, form a good adhesive bonding with the windowed prepreg 200, and form a firm bond, effectively avoiding problems such as cavities, white spots, and bubbles during pressing.

[0054] Further, since the low-flow prepreg 3030 mainly plays a role of replacing the solder mask covering surface, the low-flow prepreg 3030 can prevent the first windowed pattern 2010 from flowing too much and causing deformation problems, and can improve the surface flatness, effectively avoiding the flow deformation problem in the traditional pressing process and the delamination problem caused by excessive resin flow.

[0055] Preferably, the model of the low-flow prepreg 3030 is 7628, 7628M, or 7628H, and the resin content is in the range of 43% to 50%.

[0056] Preferably, the thickness of the low-flow prepreg 3030 is ≥75 μm, which can effectively cover the thick copper circuit.

[0057] Optionally, the first auxiliary circuit 3010 and the second auxiliary circuit 4010 can mainly play the role of an effective “spacer layer” during milling forming, preventing the milling cutter from directly milling and causing edge whitening and other problems.

[0058] 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 it will affect the flatness of the pressed plate.

[0059] In an embodiment, the dry film pattern 1020 is smaller than the first windowed pattern 2010 or smaller than the second windowed pattern 3020, and the single-side distance is 20 μm to 50 μm, effectively avoiding the problem that the dry film pattern 1020 forms a structure that penetrates into the inside of the pressed plate 20 after pressing, causing difficulties in film stripping or incomplete film stripping in the later process.

[0060] In the embodiment, the dry film pattern 1020 is smaller than the second windowed pattern 3020, and the second windowed pattern 3020 is smaller than the first windowed pattern 2010 (i.e., the dry film pattern 1020 < the second windowed pattern 3020 < the first windowed pattern 2010), and the single-side distance is 20 μm to 50 μm. The flow amount of the windowed prepreg 200 during pressing is relatively large, and the flow amount of the low-flow prepreg 3030 during pressing is relatively small. The first windowed pattern 2010 being smaller than or equal to the second windowed pattern 3020 can provide a large space for the flow of the windowed prepreg 200.

[0061] 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 prepreg or a low-flow prepreg.

[0062] Optionally, the thickness of the insulating dielectric layer 4020 of the second single-sided copper clad laminate is 10 μm to 50 μm.

[0063] (5) Stacking S40: The first auxiliary layer 300, the windowed 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 windowed prepreg 200; the first auxiliary circuit 3010 and the second auxiliary circuit 4010 both face away from the thick copper core board 100.

[0064] 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 Schematic diagram of the cross-sectional structure of a pressed plate according to an embodiment of the present invention.

[0065] (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.

[0066] 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 in sequence from near to far on the upper and lower surfaces of the stacked structure 10, 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 the 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.

[0067] 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, preventing large bumps on the board surface after pressing, and having an auxiliary covering 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.

[0068] (7) Electrical test: test the electrical conduction performance of the press plate 30, and the test method is flying probe test.

[0069] Please refer to Figure 5 , Figure 6 and Figure 7 , Figure 5 , which are cross-sectional structural diagrams of the film stripping plate according to the embodiments of the present application. Figure 6 is a plan view of the thick copper circuit board with large current carrying capacity according to the embodiments of the present application; Figure 7 is Figure 6 a cross-sectional structural diagram of A-A.

[0070] Molding: S50: the dry film pattern 1020 is stripped off from the press plate 30, and then milling and molding are performed according to the designed molding line 10A, the cutter head of the milling cutter 410 travels along the milling cutter trace 420, the radius of the cutter head of the milling cutter 410 is smaller than the width of the first auxiliary line 3010 and the second auxiliary line 4010, and the thick copper circuit board with large current carrying capacity is prepared.

[0071] As shown in Figure 7 , the windowed prepreg 200 is formed to bond with the first auxiliary layer 300 instead of the original solder resist layer, and the thickness of the sum of the two is equal to the thickness of the original solder resist layer.

[0072] In the present embodiment, if the windowed prepreg 200 has more glue overflow during pressing, the glue overflow of the first windowed pattern 2010 is easy to enter the range of the second windowed pattern 3020, so after the dry film pattern 1020 is stripped off, laser ablation is required to be performed on the edge of the first windowed pattern 2010 to trim the glue overflow at the edge of the first windowed pattern 2010.

[0073] (9) FQC: according to the customer acceptance standard and the inspection standard of the company, the appearance of the thick copper circuit board with large current carrying capacity 50 is checked, and if there is a defect, it is repaired in time to ensure that excellent quality control is provided for the customer.

[0074] (10) FQA: the appearance, dielectric layer thickness, inner layer copper thickness, etc. of the thick copper circuit board with large current carrying capacity 50 are re-tested to see whether they meet the requirements of the customer.

[0075] (11) Packaging: according to the packaging method and packaging quantity required by the customer, the thick copper circuit board with large current carrying capacity 50 is sealed and packaged, and then dry agent and humidity card are put in, and then the product is shipped.

[0076] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made according to the inventive concept of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A method for manufacturing a high current carrying thick copper circuit board, characterized in that: The circuit board is designed with a forming line, and an area outside the forming line is an invalid area, and the manufacturing method comprises the following steps: S10: taking a single-sided thick copper clad plate, manufacturing a pad pattern, and manufacturing a dry film pattern corresponding to the pad pattern to form a thick copper core plate; S20: taking a high-flow adhesive prepreg, manufacturing a first windowing pattern corresponding to the dry film pattern to form a windowing prepreg; S30: taking a first single-sided copper clad plate, manufacturing a first circuit pattern from the forming line to the invalid area to form a first auxiliary circuit, and manufacturing a second windowing pattern corresponding to the dry film pattern to form a first auxiliary layer; The insulating medium layer of the first single-sided copper clad plate is a low-flow adhesive prepreg with a glue content of 43% to 50%, which plays a covering surface role instead of solder mask; Taking a second single-sided copper clad plate, manufacturing a second circuit pattern from the forming line to the invalid area to form a second auxiliary circuit, and forming a second auxiliary layer as a whole; S40: sequentially stacking the first auxiliary layer, the windowing prepreg, the thick copper core plate, and the second auxiliary layer from top to bottom to form a stacking structure, and then pressing to form a pressed plate; The pad pattern faces the windowing prepreg, and the first auxiliary circuit and the second auxiliary circuit both face away from the thick copper core plate; S50: removing the dry film pattern from the pressed plate, and then milling and forming to form the circuit board; The milling cutter head radius of the milling is smaller than the width of the auxiliary circuit.

2. The method of manufacturing a thick copper circuit board with high current carrying capacity as claimed in claim 1, wherein, The high-flow adhesive prepreg has a glue content of 56% to 68%.

3. The method of manufacturing a thick copper circuit board with high current carrying capacity as claimed in claim 1 or 2, wherein, The model of the high-flow adhesive prepreg is 1080 or 2116.

4. The method of manufacturing a thick copper circuit board with high current carrying capacity as recited in claim 1, wherein, The model of the low-flow adhesive prepreg is 7628, 7628M, or 7628H.

5. The method of manufacturing a thick copper circuit board with high current carrying capacity as recited in claim 1, wherein, The dry film pattern is smaller than the first windowing pattern or smaller than the second windowing pattern.

6. The method of manufacturing a thick copper circuit board with high current carrying capacity as claimed in claim 1 or 5 wherein, The dry film pattern is smaller than the second windowing pattern, and the second windowing pattern is smaller than the first windowing pattern.

7. The method of manufacturing a thick copper circuit board with high current carrying capacity as recited in claim 1, wherein, After removing the dry film pattern, laser ablation is performed on the edge of the second windowing pattern.

8. The method of manufacturing a thick copper circuit board with high current carrying capacity as recited in Claim 1, wherein, The pressed plate is formed by taking a release layer and an aluminum sheet layer, and sequentially stacking the release layer and the aluminum sheet layer from near to far on the upper and lower surfaces of the stacking structure, and then pressing to form a pressed plate.

9. The method of manufacturing a thick copper circuit board with high current carrying capacity as recited in claim 8, wherein, The thickness of the aluminum sheet layer is 25μm to 105μm.

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