Method for manufacturing thick copper high current carrying flexible circuit board

Abstract

The invention discloses a method for manufacturing a thick copper high-current-carrying flexible circuit board, comprising the steps of: forming a first dry film pattern on both sides of a copper layer, then etching a portion of the thickness, stripping the film, preparing a first ink, baking and curing, printing water glue, pre-baking, attaching a first covering film layer and pressing, forming a second dry film pattern on both sides, etching for a second time, stripping the film, preparing a second ink, baking and curing, attaching a second covering film layer and pressing, electroplating gold, and forming to form a thick copper high-current-carrying flexible circuit board; by adopting a method of manufacturing circuit patterns from both sides, the side etching phenomenon generated during etching is effectively reduced, the first ink pattern and the second ink pattern are manufactured, the gaps between the thick copper circuit patterns are effectively filled, the overall circuit gaps are fully filled, the covering film layer has strong bonding strength, and the overall manufacturing method forms a complete processing process with front-to-back coordination and mutual complementation, thereby providing an effective manufacturing method for the manufacturing of such products.

Description

Technical Field

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

[0002] For application areas such as intelligent connected vehicles, smart charging piles, and low-altitude aircraft, there is a technology that uses thick copper, high-current-carrying flexible circuit boards that can carry large currents and high voltages to replace traditional wiring harness products.

[0003] For thick copper, high-current-carrying flexible circuit boards, since they need to provide a function similar to that of wires in a wiring harness and the copper thickness is relatively thick, they are generally designed as circuit patterns of independent thick copper layers, that is, the circuits are independent hollow thick copper circuits. During processing, one side of the thick copper hollow independent circuit needs to be supported, and the circuit pattern is made on the other side.

[0004] Due to the thick copper thickness, one-time etching is prone to excessive side etching or incomplete etching, resulting in large errors in the circuit pattern or even short circuit problems. In addition, when the surface cover film layer is subsequently pressed, the thickness of the thick copper circuit pattern is relatively thick, and the cover film layer is not easy to effectively fill the circuit gap, which is prone to problems such as voids and delamination in the pressed cover film layer.

[0005] Therefore, in view of the above background and problems, it is necessary to provide a method for manufacturing a thick copper, high current-carrying flexible circuit board. Summary of the Invention

[0006] The present invention aims to address the problems of excessive or incomplete etching during the etching process of the circuit pattern in a flexible circuit board with a thick copper hollow independent circuit design, as well as the problems of voids and delamination that easily occur during the lamination of the cover film layer. A method for manufacturing a thick copper, high-current-carrying flexible circuit board is provided. The manufacturing method comprises the following steps:

[0007] S10: taking a copper layer, the copper layer including a circuit area, a gold finger area, and a support area adjacent to each other in sequence, attaching a first dry film to both sides of the copper layer, and forming a first dry film pattern, then etching away a portion of the thickness of the copper layer, etching the circuit area and the gold finger area to form a half-circuit pattern, and stripping the film, and processing the entirety to form a half-etched board;

[0008] S20: preparing a first ink on the half-etched plate, baking and curing the ink to form a first ink pattern, and processing the whole plate to form a first ink pattern plate;

[0009] S30: printing water-based glue on the first ink graphic plate, pre-baking it to form a water-based glue layer, and then attaching a first cover film layer to the water-based glue layer and pressing it to form a first cover film plate as a whole;

[0010] S40: attaching a second dry film to both sides of the first cover film plate, forming a second dry film pattern, performing a second etching to etch away the remaining thickness of the copper layer, forming a copper layer circuit pattern from the semi-circuit pattern, and performing film stripping to form a circuit pattern board as a whole;

[0011] S50: preparing the second ink, baking and curing it to form a second ink pattern, and processing the whole to form a second ink pattern plate;

[0012] S60: attaching a second covering film layer to the second ink graphic plate and pressing them together to form a double-sided covering film plate;

[0013] S70: performing electroplating gold processing on the gold finger area of ​​the double-sided cover film board, and then performing whole board forming processing, removing the support area, to form the thick copper high current carrying flexible circuit board.

[0014] Furthermore, the copper layer has a thickness of 105 microns to 420 microns.

[0015] Furthermore, the thickness of the portion of the copper layer etched away is 1 / 3 to 2 / 3 of the thickness of the copper layer.

[0016] Furthermore, the first step of preparing the ink is to screen print the first step of the ink into the gaps of the half-circuit pattern in the circuit area.

[0017] Furthermore, the printing water glue is to print the water glue on the circuit area on one side of the first ink pattern of the first ink pattern plate.

[0018] Furthermore, the water-based adhesive is acrylic liquid composite adhesive, epoxy resin liquid composite adhesive, or polyimide liquid composite adhesive.

[0019] Furthermore, the pre-baking is performed at a temperature of 75° C. to 100° C. for 20 minutes to 40 minutes.

[0020] Furthermore, the second dry film pattern and the first dry film pattern are identical and correspond to each other on opposite sides.

[0021] Furthermore, the second ink preparation is to screen print the second ink in the gaps between the copper layer circuit patterns in the circuit area on one side of the copper layer circuit pattern of the circuit pattern board.

[0022] Furthermore, the attaching of the second covering film layer is to attach the second covering film layer to the circuit area on one side of the second ink pattern of the second ink pattern plate.

[0023] The technical solution of the present invention adopts the method of first making a half-circuit pattern to form the support of the remaining copper thickness for the subsequent process, ensuring the support during the subsequent process, making a first ink pattern to fill the half-circuit pattern, and providing a basis for making the first covering film layer. Making a water-gel layer can effectively improve the filling effect and improve the adhesion effect of the first covering film layer. Then, after making the remaining pattern on the back side, the circuit pattern is made from two sides, which effectively reduces the side etching phenomenon caused by etching and improves the processing accuracy of the circuit. The second ink pattern is made to form an effective filling of the gap between the thick copper circuit patterns, and at the same time provides a board surface basis for the pressing of the second covering film layer. After the subsequent process, a thick copper and large current-carrying flexible circuit board is formed. The overall circuit gap is fully filled and the covering film layer has strong adhesion. The overall production method forms a complete processing process that cooperates and complements each other, providing an effective production method for the production of such products. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 1 This is a key process flow chart for an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of a front pattern for producing a first dry film pattern according to an embodiment of the present invention;

[0027] Figure 3 Implementation of the present invention Figure 2 AA cross-sectional diagram of ;

[0028] Figure 4 A schematic diagram of a front pattern of a half-etched plate produced according to an embodiment of the present invention;

[0029] Figure 5 Implementation of the present invention Figure 4 BB cross-section diagram;

[0030] Figure 6 A schematic diagram of a front pattern of a first ink pattern plate formed in accordance with an embodiment of the present invention;

[0031] Figure 7 Implementation of the present invention Figure 6 Schematic diagram of CC cross section;

[0032] Figure 8 A schematic diagram of the front surface of a first covering film plate formed in accordance with an embodiment of the present invention;

[0033] Figure 9 Implementation of the present invention Figure 8 DD cross-sectional diagram;

[0034] Figure 10 A schematic diagram of a backside pattern for producing a second dry film pattern according to an embodiment of the present invention;

[0035] Figure 11 Implementation of the present invention Figure 9 EE cross-sectional diagram;

[0036] Figure 12 A schematic diagram of the back surface pattern of a circuit pattern board produced in accordance with an embodiment of the present invention;

[0037] Figure 13 Implementation of the present invention Figure 12 FF cross-sectional diagram;

[0038] Figure 14 A schematic diagram of the back surface pattern of the second ink pattern plate produced in accordance with an embodiment of the present invention;

[0039] Figure 15 Implementation of the present invention Figure 14 Schematic diagram of HH cross section;

[0040] Figure 16 A schematic diagram of the back surface pattern of a double-sided covering film plate produced in accordance with an embodiment of the present invention;

[0041] Figure 17 Implementation of the present invention Figure 16 Schematic diagram of section II;

[0042] Figure 18 This is a schematic diagram of the front surface of a thick copper, high current-carrying flexible circuit board manufactured according to an embodiment of the present invention;

[0043] Figure 19 Implementation of the present invention Figure 18 Schematic diagram of the JJ cross section.

[0044] Description of Figure Numbers:

[0045]

[0046]

[0047] 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

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0049] 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, etc.) are only used to explain the relative position relationship and movement status between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0050] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0051] 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 this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0052] See also Figure 1 , Figure 1 This is a key process flow chart for an embodiment of the present invention;

[0053] The method for manufacturing a thick copper high current carrying flexible circuit board according to an embodiment of the present invention comprises: Figure 1 The key production process is described in detail step by step below.

[0054] See also Figures 2 to 5 ; Figure 2 A schematic diagram of a front pattern for producing a first dry film pattern according to an embodiment of the present invention; Figure 3 Implementation of the present invention Figure 2 AA cross-sectional diagram of ; Figure 4 A schematic diagram of a front pattern of a half-etched plate produced according to an embodiment of the present invention; Figure 5 Implementation of the present invention Figure 4 BB cross-section diagram.

[0055] Since the present embodiment manufactures the copper layer on different sides, the side manufactured first is called the front side, and the other side is called the back side.

[0056] Step S10:

[0057] Take a copper layer 100, which includes a circuit area 110, a gold finger area 120 and a support area 130 adjacent to each other in sequence, and attach a first dry film to both sides of the copper layer 100, and make a first dry film pattern 140 (such as Figure 2 and Figure 3 As shown), part of the thickness of the copper layer 100 is then etched away, and the circuit area 110 and the gold finger area 120 are etched to form a half-circuit pattern 150. The unetched thickness is half the copper layer 160, and the film is stripped to form a half-etched board 10 as a whole.

[0058] The thick copper, high-current-carrying flexible circuit board of this embodiment has a thick copper hollow independent circuit pattern and thick copper gold fingers. Therefore, during processing, the board surface is divided into a circuit area 110, a gold finger area 120 and a support area 130, which is convenient for distinguishing between the various areas during production. Since the hollow gold fingers are individually suspended circuits, the support area 130 is provided to support the hollow gold fingers in the planar direction. First, a first dry film pattern 140 is produced (the front side is the front first dry film pattern 1410, and the back side is the back first dry film pattern 1420). Then, the area uncovered by the first dry film pattern 140 is half-etched, that is, part of the thickness of the copper layer is etched away, so that the unetched half copper layer 160 of the copper layer plays an effective supporting role, providing a panel surface support foundation for the subsequent production of ink and covering film.

[0059] The thick copper, high-current-carrying flexible circuit board of this embodiment has a relatively thick copper thickness, and thus can withstand relatively large currents and voltages. Generally, a good and reliable processing process can be formed for flexible circuit boards with a copper layer 100 thickness of 105 microns to 420 microns; and generally, a portion of the copper layer 100 is etched away with a thickness of 1 / 3 to 2 / 3, which can effectively ensure that the remaining thickness of the half copper layer 160 forms a supporting effect.

[0060] See also Figures 6 and 7 ; Figure 6 A schematic diagram of a front pattern of a first ink pattern plate formed in accordance with an embodiment of the present invention; Figure 7 Implementation of the present invention Figure 6 Schematic diagram of CC cross section.

[0061] Step S20:

[0062] The first ink is made on the half-etched plate 10. In this embodiment, the first ink is screen-printed on the gaps of the half-circuit pattern 150 of the circuit area 110, and baked and cured to form a first ink pattern 210. The entire process is processed to form a first ink pattern plate 20.

[0063] Since the overall copper thickness of the circuit is relatively thick, the circuit gap formed is relatively deep. Directly attaching a press-fit cover film is likely to cause problems such as loose cover film pressing and voids. This embodiment adopts a method of preparing ink for the circuit gap and combining ink filling with attaching a press-fit cover film filling (later process). This can effectively improve the filling effect of the thick copper circuit gap and prevent problems such as looseness and voids between layers.

[0064] Since the gold finger of this embodiment is a hollow gold finger, there is no need to prepare ink in the gold finger area, and since the half-etched plate only etches away part of the thickness of the copper layer, there is a half copper layer 160 for support, so the ink can be effectively prevented from flowing disorderly when it is prepared. The first ink can be prepared by preparing a silk screen, silk screen ink, and baking and curing. The silk screen is used to control the thickness of the silk screen ink area to improve the accuracy of ink processing. The ink can be an ordinary solder mask ink (optionally a transparent ink) or a resin ink.

[0065] See also Figures 8 and 9 ; Figure 8 A schematic diagram of the front surface of a first covering film plate formed in accordance with an embodiment of the present invention; Figure 9 Implementation of the present invention Figure 8 DD cross-section diagram.

[0066] Step S30:

[0067] Water glue is printed on the first ink graphic plate 20. In this embodiment, the water glue is printed on the circuit area on one side of the first ink graphic plate, pre-baked to form a water glue layer 320, and then the first covering film layer 310 is attached to the water glue layer 320 and pressed to form the first covering film plate 30 as a whole.

[0068] In this embodiment, the water-based adhesive is acrylic liquid composite adhesive, epoxy resin liquid composite adhesive, or polyimide liquid composite adhesive.

[0069] In this embodiment, the pre-baking is performed at a temperature of 75° C. to 100° C. for 20 minutes to 40 minutes.

[0070] If the copper thickness is relatively thick, the first ink (silk-screen ink) produced above should not be too thick, otherwise the disordered flow of ink may occur, causing the ink to contaminate the board surface. Therefore, after the first ink pattern 210 is produced, the thick copper layer may still have a large gap in the circuit gap. In this embodiment, a screen-printed water-gel layer 320 is used to produce a glue layer for attaching the cover film (instead of directly attaching and laminating the cover film layer with a solid glue layer), that is, a liquid colloid is screen-printed and then baked and cured to form a water-gel layer. The screen-printed water-gel can effectively ensure that the colloid can flow to areas such as the circuit gap (where the solid glue layer cannot fill and adhere), and the screen-printed water-gel can effectively ensure that the corners of the circuit can be covered with the glue layer, providing a glue layer foundation for the subsequent attachment and lamination of the cover film layer.

[0071] The water glue can use acrylic liquid composite glue, epoxy resin liquid composite glue, or polyimide liquid composite glue, so that it can be effectively cured and have a good adhesive bonding effect with the first ink pattern, copper layer, and polyimide layer of the cover film; a pre-baking method is adopted to dry the water glue layer 320 to a preliminary cured state rather than completely cured, retaining greater adhesive properties and forming a stronger adhesive state with the first cover film layer 310. When the first cover film layer 310 is pressed, the water glue layer 320 is baked again at the same time to form a curing process.

[0072] See also Figures 10 to 13 ; Figure 10 A schematic diagram of a backside pattern for producing a second dry film pattern according to an embodiment of the present invention; Figure 11 Implementation of the present invention Figure 9 EE cross-sectional diagram; Figure 12 A schematic diagram of the back surface pattern of a circuit pattern board produced in accordance with an embodiment of the present invention; Figure 13 Implementation of the present invention Figure 12 FF cross-sectional diagram.

[0073] Step S40:

[0074] A second dry film is attached to both sides of the first cover film plate 30 to form a second dry film pattern 330. A second etching is performed to etch away the remaining thickness of the copper layer 100. The semi-circuit pattern 150 forms a copper layer circuit pattern 410. The film is then stripped and the entire process is completed to form a circuit pattern plate 40.

[0075] In this embodiment, the second dry film pattern 330 (the front side is the front second dry film pattern 3310 , and the back side is the back second dry film pattern 3320 ) and the first dry film pattern 140 are the same but correspond to opposite sides.

[0076] Since the first cover film layer 310 and the first ink pattern 210 have a good supporting effect on the entire circuit, the second dry film pattern 330 and the copper layer circuit pattern 410 are manufactured according to the method of manufacturing the first dry film pattern 140 and the manufacturing method of the half circuit pattern 150. The second etching and the first etching form an overall etching, that is, a complete circuit pattern is formed.

[0077] See also Figures 14 and 15 ; Figure 14 A schematic diagram of the back surface pattern of the second ink pattern plate produced in accordance with an embodiment of the present invention; Figure 15 Implementation of the present invention Figure 14 Schematic diagram of the HH cross section.

[0078] Step S50:

[0079] To prepare the second ink, in this embodiment, the second ink is screen-printed on one side of the copper layer circuit pattern 410 of the circuit pattern board 40 toward the gaps between the copper layer circuit pattern 410 in the circuit area 110, and baked and cured to form a second ink pattern 510, and the entire process is processed to form a second ink pattern board 50.

[0080] Similar to the production of the first ink pattern 210, a second ink pattern 510 is produced on the back side to further form ink filling in the gaps between the thick copper lines, facilitating the attachment and lamination of the second covering film layer 610 and making the front and back surfaces of the board form a relatively flat surface state.

[0081] See also Figures 16 and 17 ; Figure 16 A schematic diagram of the back surface pattern of a double-sided covering film plate produced in accordance with an embodiment of the present invention; Figure 17 Implementation of the present invention Figure 16 Schematic diagram of the II cross section.

[0082] Step S60:

[0083] The second covering film layer 610 is attached to the second ink graphic plate 50 and pressed. In this embodiment, the second covering film layer 610 is attached to the circuit area 110 on one side of the second ink graphic 510 of the second ink graphic plate 50; a double-sided covering film plate 60 is formed as a whole.

[0084] Since the copper layer circuit pattern 410 is formed by processing, and the circuit gaps of the copper layer circuit pattern 410 are effectively filled with the first ink pattern 210 and the second ink pattern 510, when making the second covering film layer 610, there is no need to screen print the water-based adhesive layer. The adhesive layer of the second covering film layer 610 can be directly used to adhere to the board surface to form a flat surface.

[0085] See also Figures 18 and 19 ; Figure 18 This is a schematic diagram of the front surface of a thick copper, high current-carrying flexible circuit board manufactured according to an embodiment of the present invention; Figure 19 Implementation of the present invention Figure 18 Schematic diagram of the JJ cross section.

[0086] Step S70:

[0087] The gold finger area of ​​the double-sided cover film plate 60 is subjected to electroplating gold processing to form an electroplated gold layer 710, and then the entire board is formed to remove the support area 130 to form the thick copper high current carrying flexible circuit board 70.

[0088] In summary, it can be seen that the method first forms a half-circuit pattern 150, and the remaining copper-thick half-copper layer 160 forms support for subsequent processes and forms a circuit thickness buffer and support function for the production of the first ink pattern 210 and the first cover film layer 310. The first cover film layer is attached using the printed water glue layer 320 to form a firm attachment of the first cover film layer 310 without damaging the circuit pattern. Then, by producing the remaining pattern on the back side, a complete copper layer circuit pattern 410 is formed. By producing the second ink pattern 510, the gap between the thick copper circuit pattern 510 is effectively filled, and at the same time, a board surface foundation is provided for the lamination of the second cover film layer 610. After the lamination of the second cover film layer 610 and subsequent process processing, the thick copper high-current-carrying flexible circuit board 70 with good circuit gap filling and firm cover film attachment effect is formed as a whole. The overall production method forms a complete processing process with front and back coordination and mutual complementation, providing an effective production method for the production of such products.

[0089] It is worth noting that due to the actual design and processing of circuit boards, which are relatively precise, the actual structural diagrams and the thickness of each layer, line width and other dimensions are all at the micron level. For example, the thickness of each layer is generally between 5μm and 50μm. If the drawings in the specification are made according to the actual proportions, there will be a problem of unclear drawings. Therefore, in order to more clearly show the implementation process of the manufacturing method, the drawings of this embodiment are all schematic diagrams that enlarge the technical features, and do not represent the size of the actual structural diagram, nor do they represent enlarged drawings of the actual structural diagram in proportion.

[0090] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's description and drawings, or direct / indirect applications in other related technical fields, within the scope of the present invention are included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing a thick copper high current carrying flexible circuit board, characterized in that: The production method comprises the following steps: S10: taking a copper layer, the copper layer including a circuit area, a gold finger area, and a support area adjacent to each other in sequence, attaching a first dry film to both sides of the copper layer, and forming a first dry film pattern, then etching away a portion of the thickness of the copper layer, etching the circuit area and the gold finger area to form a half-circuit pattern, and stripping the film, and processing the entirety to form a half-etched board; S20: Screen printing a first ink into the gaps of the half-circuit pattern in the circuit area, and baking and curing the screen printing to form a first ink pattern, and then forming a first ink pattern plate through overall processing; S30: printing water-based glue on the first ink graphic plate, pre-baking it to form a water-based glue layer, and then attaching a first cover film layer to the water-based glue layer and pressing it to form a first cover film plate as a whole; S40: attaching a second dry film to both sides of the first cover film plate, forming a second dry film pattern, performing a second etching to etch away the remaining thickness of the copper layer, forming a copper layer circuit pattern from the semi-circuit pattern, and performing film stripping to form a circuit pattern board as a whole; S50: On one side of the copper layer circuit pattern of the circuit pattern board, screen-printing ink for a second time in the gaps between the copper layer circuit pattern in the circuit area, and baking and curing the ink to form a second ink pattern, and then processing the whole board into a second ink pattern board; S60: attaching a second covering film layer to the second ink graphic plate and pressing them together to form a double-sided covering film plate; S70: performing electroplating gold processing on the gold finger area of ​​the double-sided cover film board, and then performing whole board forming processing, removing the support area, to form the thick copper high current carrying flexible circuit board.

2. The method for manufacturing a thick copper high current carrying flexible circuit board according to claim 1, characterized in that: The copper layer has a thickness of 105 micrometers to 420 micrometers.

3. The method for manufacturing a thick copper high current carrying flexible circuit board according to claim 1, characterized in that: The thickness of the portion of the copper layer etched away is 1 / 3 to 2 / 3 of the thickness of the copper layer.

4. The method for manufacturing a thick copper high current carrying flexible circuit board according to claim 1, characterized in that: The printing water glue is to print the water glue on the circuit area on one side of the first ink pattern of the first ink pattern plate.

5. The method for manufacturing a thick copper high current carrying flexible circuit board according to claim 1 or 4, characterized in that: The water-based adhesive is acrylic acid liquid composite adhesive, epoxy resin liquid composite adhesive, or polyimide liquid composite adhesive.

6. The method for manufacturing a thick copper high current carrying flexible circuit board according to claim 1, characterized in that: The pre-baking is performed at a temperature of 75° C. to 100° C. for 20 to 40 minutes.

7. The method for manufacturing a thick copper high current carrying flexible circuit board according to claim 1, characterized in that: The second dry film pattern and the first dry film pattern are identical and correspond to each other on opposite sides.

8. The method for manufacturing a thick copper high current carrying flexible circuit board according to claim 1, characterized in that: The attaching of the second covering film layer is to attach the second covering film layer to the circuit area on one side of the second ink pattern of the second ink pattern plate.

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