Four-layer flexible circuit board applied to VCM and circuit manufacturing method thereof

Abstract

The invention discloses a four-layer flexible circuit board applied to a VCM (voice coil motor) and a circuit manufacturing method of the four-layer flexible circuit board. According to circuit manufacturing, grooves are formed in a PI base material, filling metal is electroplated to form the circuit, a traditional copper foil etching process is not needed, copper-clad plate etching is not needed, a high-precision fine circuit can be manufactured, the physical limit of traditional etching can be broken through, and the circuit manufacturing cost is reduced. Therefore, the use requirements of small and fine VCM are met. According to the four-layer flexible circuit board, circuits of all layers are manufactured independently, so that the precision and quality of the circuits of all layers can be better controlled, and detection and maintenance of the circuits are facilitated; after each layer of circuit is manufactured, lamination is carried out in sequence from the inner layer to the outer layer, so that the alignment precision between the layers can be improved, the problem of circuit offset between the layers is reduced, and the electrical performance and the reliability of the flexible circuit board are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible circuit board manufacturing, and particularly to a four-layer flexible circuit board applied to VCM and a method for manufacturing its circuit. Background Art

[0002] In electronic products, the AF (auto focus) function and OIS (optical image stabilization) function of cameras both rely on the VCM voice coil motor to achieve the movement of the lens or the photosensitive chip. The voice coil motors that control this movement are mainly divided into open-loop motors and closed-loop motors. The closed-loop motor can achieve higher precision and faster response speed by means of a position feedback mechanism. For this reason, closed-loop motors are generally used in the camera modules of mid- to high-end mobile phones.

[0003] The flexible circuit board applied to VCM is mainly used to connect VCM with other electronic components to achieve electrical signal transmission and mechanical connection, so as to precisely control functions such as the focusing and anti-shake of the camera. Because it is necessary to meet the high-precision requirements of VCM for position control, its circuit layout and parameter design need to be more precise to ensure the stability and accuracy of signal transmission, so as to achieve functions such as fast and precise focusing of the camera.

[0004] In order to match the structure of VCM, the shape and size of the flexible circuit board applied to VCM are not only small and special, but also need to be designed according to the specific VCM model and installation position to ensure close cooperation with VCM and other related components. Since the circuit requirements of the flexible circuit board applied to VCM are relatively high in precision, multi-layer boards are generally used. The traditional etching circuit method cannot meet the precision requirements of VCM and the requirements for line width and line spacing. The circuits made by the etching method have insufficient copper thickness after copper reduction, subsequent damage caused by degumming and micro-etching, and abnormal copper thickness caused by excessive copper damage during the laser process. Therefore, the flexible circuit boards produced according to the conventional production process cannot meet the usage requirements of VCM.

[0005] In view of this, the present invention proposes a method for manufacturing a flexible circuit board applied to VCM to meet the usage requirements of VCM for the flexible circuit board. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for manufacturing a flexible circuit board applied to VCM to meet the usage requirements of VCM circuits.

[0007] To achieve the above purpose, the solution of the present invention is as follows: A method for manufacturing a flexible circuit board applied to VCM, which includes the following steps: Step S1, design the circuit according to the functional requirements of VCM; Step S2: Layout the designed circuit components on the FPC board, perform wiring design, and convert the design file after layout and wiring into a Gerber file; Step S3: Select a single-sided PI substrate with a copper layer; Step S4: PI groove cutting: According to the Gerber file, use laser drilling to drill grooves corresponding to the circuit pattern on the PI substrate; Step S5: Plasma and micro-etching: Treat the grooved PI substrate with plasma; Step S6: Black shadowing, immerse the plasma-treated PI substrate in the black shadow agent to form a conductive layer on the wall of the groove; Step S7: Electroplating to fill the grooves: Place the pre-treated PI substrate into an electroplating tank equipped with electroplating solution, so that the electroplating solution completely covers the grooves; during electroplating, keep the electroplating solution stirred evenly to make the copper ions deposit evenly in the grooves, and complete the production of the single-layer flexible circuit board lines.

[0008] Furthermore, in step S7, an ultrasonic device is provided in the electroplating tank, and the vibration of the ultrasonic wave is used to break and disperse the bubbles. At the same time, the ultrasonic device is also used to enhance the mass transfer process of the electroplating solution.

[0009] Furthermore, in step S7, the copper electroplating adopts a multi-fill method, allowing the gas to have a chance to escape after each fill, and then performing the next fill until the coating in the groove reaches the preset thickness.

[0010] Furthermore, in step S2, when laying out the circuit, stress relief grooves or notches are designed at the parts where stress is likely to occur.

[0011] Another object of the present invention is to overcome the deficiencies of the prior art and provide a manufacturing method for a four-layer flexible circuit board applied to a VCM to meet the usage requirements of VCM circuits.

[0012] To achieve the above object, the solution of the present invention is: A manufacturing method for a four-layer flexible circuit board applied to a VCM, which includes the following steps: Step A: Manufacture four single-sided boards with circuits L1, L2, L3, and L4 according to the above steps S1 - S7; Step B: Select the single-sided boards of L2 and L3 for pure glue pressing. The pure glue is located on the PI surfaces of the two single-sided boards, and the two single-sided boards are pressed into a double-sided board; Step C: Etch the outer layer copper at both ends of the double-sided board; Step D: Select the single-sided board of lines L1 and L4 and lines L2 and L3 for pure glue pressing, line L1 is pressed on the top surface of line L2 by pure glue, and line L4 is pressed on the bottom surface of line L3 by pure glue, so as to form a four-layer flexible circuit board; Step E, drilling a through hole; Step F, electroplating, copper plating the through holes, and plating a layer of copper on the top and bottom surfaces of the four-layer flexible circuit board; Step G, etching away the surface copper to form a four-layer flexible circuit board with conductive lines; Step H: Post-processing: Process according to the conventional flexible circuit board process.

[0013] Furthermore, in step S2, a circuit mold with a positioning structure is manufactured according to the Gerber file, and during the lamination of L2 and L3, the lamination of L2 and L1, and the lamination of L4 and L3, the position of each layer is positioned by the positioning structure on the circuit mold.

[0014] After adopting the above scheme, the circuit manufacturing method of the flexible circuit board applied to VCM of the present invention directly constructs the circuits of each layer of the flexible circuit board through the process of cutting single-sided copper-clad board → PI slotting → plasma → black shadow → copper plating, without relying on copper-clad board etching, and can produce high-precision fine circuits, which can break through the physical limits of traditional etching, so as to meet the small and precise use requirements of VCM. Compared with the circuits made by traditional etching process, the circuits made by the present invention by filling the wire groove can reduce electromagnetic radiation and electromagnetic interference to a certain extent. This is because the conductive material in the wire groove is relatively closed, which reduces the leakage of the electromagnetic field and helps to improve the electromagnetic compatibility of the product; in addition, the wire groove filling method does not need to etch a large amount of copper foil, reducing waste and pollution; the copper filled in the wire groove has a stronger bonding force with the PI substrate, and the anti-bending performance is better than the etched circuit.

[0015] The four-layer flexible circuit board applied to VCM of the present invention is to first manufacture the circuits of each layer separately, so that the accuracy and quality of the circuits of each layer can be better controlled, and the detection and maintenance of the circuits are convenient; after the circuits of each layer are manufactured, they are laminated in the order of the inner layer first and the outer layer later, which can improve the alignment accuracy between the layers, reduce the problem of inter-layer circuit deviation, and is beneficial to improving the electrical performance and reliability of the flexible circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figure is a flow chart of manufacturing the four-layer flexible circuit board of the present invention. DETAILED DESCRIPTION

[0017] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0018] A method for manufacturing a flexible circuit board line applied to a VCM, comprising the following steps: Step S1: Design a circuit according to the functional requirements of the VCM; Step S2: Layout the designed circuit components on the FPC board, perform wiring design, and convert the design file after layout and wiring into a Gerber file. The Gerber file contains the graphic information of four layers of the FPC (including the shape and position information of the circuit, pads, and holes). During layout, stress relief grooves or notches are designed at positions prone to stress, including the edges and interfaces of the circuit board, etc., so that when the flexible circuit board is subjected to external forces, the stress can be dispersed and released, protecting the circuit from damage; Step S3: Select a PI substrate with a copper layer, where the copper layer mainly plays a supporting role and provides support for subsequent grooving; Step S4: PI grooving: According to the Gerber file, use laser drilling to drill grooves corresponding to the circuit pattern on the PI substrate; In this embodiment, the depth of the PI groove is 50um; Step S5: Plasma: Use plasma equipment to process the grooved PI substrate to remove contaminants such as resin residues and oil stains in the PI grooves after grooving; Step S6: Black shadow, immerse the PI substrate after plasma treatment in the black shadow agent to form a graphene conductive layer on the wall of the groove; deposit graphene on the surface of the groove through physical adsorption to form a dense conductive layer of 0.5 - 1μm as the base for subsequent copper electroplating; Step S7: Electroplating to fill the grooves: Place the pre-treated PI substrate into an electroplating tank equipped with electroplating solution so that the electroplating solution completely covers the grooves; adjust electroplating parameters according to factors such as the size, depth of the grooves, and the material of the PI substrate, including current density, electroplating time, temperature, etc. During electroplating, keep the electroplating solution stirred evenly so that copper ions can be deposited evenly in the grooves. Stirring can also promote the floating and discharging of bubbles, and at the same time make copper ions evenly distributed, improving the uniformity of the coating. In order to further avoid the coating in the grooves getting stuck with bubbles, the present invention also sets an ultrasonic device in the electroplating tank. Through the vibration of ultrasonic waves, the bubbles are effectively broken and dispersed, preventing the bubbles from adhering to the surface or inside of the grooves. At the same time, ultrasonic waves can also enhance the mass transfer process of the electroplating solution, improving the electroplating efficiency and coating quality. In addition, during electroplating, a multiple-filling method is adopted, allowing the gas to have the opportunity to escape after each filling, and then proceeding with the next filling until the coating in the grooves reaches the preset thickness. In this embodiment, the coating thickness is 35um, leaving a certain adhesive space in the grooves of the PI substrate to improve the bonding strength of subsequent lamination.

[0019] Complete the manufacturing of the flexible circuit board line.

[0020] Another object of the present invention is to overcome the deficiencies of the prior art and provide a method for manufacturing a four-layer flexible circuit board applied to a VCM to meet the usage requirements of VCM circuits.

[0021] To achieve the above object, the solution of the present invention is as follows: A method for manufacturing a flexible circuit board line applied to a VCM, which includes the following steps: Step A: Manufacture four single-sided boards with lines L1, L2, L3, and L4 according to the above steps S1 - S7; Step B: Select the single-sided boards of L2 and L3 for pure glue pressing. In this embodiment, the pure glue is located on the PI surfaces of the two single-sided boards, and the thickness of the pure glue is 25 mm, so as to press the two single-sided boards into a double-sided board; Step C: Etch the outer layer copper at both ends of the double-sided board; Step D: Select the single-sided boards of lines L1 and L4 and press them with the lines L2 and L3. Line L1 is pressed onto the top surface of line L2 through pure glue, and line L4 is pressed onto the bottom surface of line L3 through pure glue, so as to form a four-layer flexible circuit board; Step E: Drill through holes. In this embodiment, the diameter of the through holes is 0.2 mm; Step F: Electroplate. Copper is plated on the through holes and a layer of copper is plated on the top and bottom surfaces of the four-layer flexible circuit board. In this embodiment, the thickness of the electroplated copper > 10 μm; Step G: Etch the surface copper to form a four-layer flexible circuit board with conductive lines; Step H: Post-treatment, which is processed according to the conventional flexible circuit board process.

[0022] To further improve the alignment accuracy during lamination, the present invention can, after completing the layout of the FPC in step S2, manufacture a circuit mold with a positioning structure. During the lamination process, the positions of each layer can be accurately positioned through the positioning pins or positioning grooves provided on the circuit mold, ensuring the alignment accuracy between layers, preventing misalignment during the pressing process, and making the accuracy of the pressed circuit board higher.

[0023] After adopting the above solution, the method for manufacturing the circuit of the flexible circuit board applied to VCM in the present invention directly constructs the circuits of each layer of the four-layer flexible circuit board through the process of cutting single-sided board → PI slotting → plasma → black shadow → copper plating, without relying on copper clad laminate etching, and can manufacture fine circuits with high precision, breaking through the physical limit of traditional etching, so as to meet the small and precise usage requirements of VCM. Compared with the circuits manufactured by the traditional etching process, the method of manufacturing circuits by filling the slots in the present invention can reduce electromagnetic radiation and electromagnetic interference to a certain extent because the conductive material in the filled slots is relatively enclosed, reducing the leakage of electromagnetic fields and helping to improve the electromagnetic compatibility of the product; in addition, the method of filling the slots does not require etching a large amount of copper foil, reducing waste and pollution; the bonding force between the copper filled in the slots and the PI substrate is stronger, and the anti-bending performance is better than that of the etched circuits.

[0024] The four-layer flexible circuit board applied to VCM in the present invention manufactures the circuits of each layer separately first, so as to better control the precision and quality of the circuits of each layer, facilitating the detection and repair of the circuits; after the circuits of each layer are manufactured, lamination is carried out in the order of inner layer first and then outer layer, which can improve the alignment precision between layers and reduce the problem of circuit offset between layers, being beneficial to improving the electrical performance and reliability of the flexible circuit board.

[0025] The above embodiments and drawings do not limit the product form and style of the present invention. Any appropriate changes or modifications made by those of ordinary skill in the art shall be regarded as not departing from the patent scope of the present invention.

Claims

1. A method for manufacturing a flexible circuit board line applied to a VCM, characterized in that, It includes the following steps: Step S1: Design a circuit according to the functional requirements of the VCM. Step S2: Layout the designed circuit components on the FPC board, conduct wiring design, and convert the design file after layout and wiring into a Gerber file. Step S3: Select a single-sided PI substrate with a copper layer. Step S4: PI slotting: According to the Gerber file, use laser drilling to drill slots corresponding to the circuit pattern on the PI substrate. Step S5: Plasma treatment: Treat the PI substrate after slotting with plasma. Step S6: Black shadowing: Immerse the PI substrate after plasma treatment in the black shadow agent to form a conductive layer on the wall of the slot. Step S7: Electroplating to fill the slots: Place the pre-treated PI substrate into an electroplating bath configured with electroplating solution to make the electroplating solution completely cover the slots. During the electroplating process, keep the electroplating solution stirred evenly to make copper ions deposit evenly in the slots, and complete the production of the single-layer flexible circuit board lines.

2. The method for manufacturing a flexible circuit board line applied to a VCM according to claim 1, wherein: In Step S7, an ultrasonic device is arranged in the electroplating bath to break and disperse bubbles through the vibration of ultrasonic waves, and at the same time, the ultrasonic device is also used to enhance the mass transfer process of the electroplating solution.

3. The method for manufacturing a flexible circuit board line applied to a VCM according to claim 1, characterized in that: In Step S7, electroplating copper is carried out in a multiple-filling manner, allowing gas to have a chance to escape after each filling, and then proceeding with the next filling until the coating thickness of the slot reaches the preset thickness, and the copper thickness of each filling ≤ 10um.

4. The method for manufacturing a flexible circuit board line applied to VCM according to claim 1, wherein: In Step S2, when arranging the circuit, stress relief slots or notches are designed at the parts where stress is likely to occur.

5. A manufacturing method of a four-layer flexible circuit board applied to a VCM, characterized in that, It includes the following steps: Step A: Manufacture four single-sided boards with circuits L1, L2, L3, and L4 according to the above Steps S1 - S7. Step B: Select the single-sided boards of L2 and L3 for pure glue pressing. The pure glue is located on the PI surface of the two single-sided boards, and the two single-sided boards are pressed into a double-sided board. Step C: Etch the outer copper at both ends of the double-sided board. Step D: Select the single-sided boards of circuits L1 and L4 and press them with circuits L2 and L3 with pure glue. Circuit L1 is pressed on the top surface of circuit L2 with pure glue, and circuit L4 is pressed on the bottom surface of circuit L3 with pure glue, thereby forming a four-layer flexible circuit board. Step E: Drill through holes. Step F: Electroplating: Electroplate copper on the through holes and coat a layer of copper on the top and bottom surfaces of the four-layer flexible circuit board. Step G: Etch the surface copper to form a four-layer flexible circuit board with circuit conduction. Step H: Post-treatment: Process according to the conventional flexible circuit board process.

6. The manufacturing method of the four-layer flexible circuit board applied to VCM according to claim 5, wherein: In Step S2, make a circuit mold with a positioning structure according to the Gerber file, and during the lamination of L2 and L3, L2 and L1, and L4 and L3, position the positions of each layer through the positioning structure on the circuit mold.

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