Manufacturing method of wireless charging FPC

Abstract

The invention discloses a manufacturing method of a wireless charging FPC (Flexible Printed Circuit), which comprises the steps of blanking, drilling, black hole, copper plating, dry film pasting, exposure, etching, lead electroplating, secondary copper plating, copper laying, blue film pasting, protective film pressing, appearance inspection and electrical performance test. Before lamination, the protective film is subjected to vacuum false pressing, four-opening lamination is used during lamination, and sectional control is adopted in the lamination process, so that a uniform and stable high-temperature and high-pressure environment can be provided within a short time, and glue between the protective film and the FPC is rapidly cured; in the laminating process, the pressure is uniformly distributed on the surface of the FPC, so that the protective film and the FPC can be tightly attached, the defects of bubbles, wrinkles and the like are avoided, the flatness of the surface of the FPC is ensured, the quality and the reliability of the product are improved, and the generation of the bubbles and the wrinkles can be effectively avoided by adopting sectional pressure control.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible circuit boards, and in particular to a method for manufacturing a wireless charging FPC. Background Art

[0002] As the wireless charging function of electronic devices becomes more and more popular, the quality and performance of wireless charging FPC has received widespread attention. In the production process of wireless charging FPC, etching, electroplating, lamination and protective film lamination processes may affect the electrical performance of wireless charging FPC, thereby reducing the quality of wireless charging FPC products, especially the lamination of protective film. When using thin protective film, its filling property is poor, and bubbles are easily generated between the protective film and FPC during the lamination process. These bubbles will affect the electrical performance and stability of FPC, and may even cause problems such as local short circuits. In addition, when the protective film is matched with a thicker copper layer, because the copper is thicker and the covering film is thinner, the thickness of the glue cannot be avoided, so the thin protective film will have poor filling property and bubbles are prone to appear in the protective film lamination; the thin protective film PI is thin, and the thick copper is easy to cause the protective film to crack; the protective film lamination wrinkles the board.

[0003] In view of this, the present invention is directed to the problems existing in the manufacturing process of the existing wireless charging FPC that affect the electrical performance of the wireless charging FPC, and proposes a method for manufacturing the wireless charging FPC, aiming to improve the service life and stability of the wireless charging FPC. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art, provide a method for manufacturing a wireless charging FPC that can significantly improve the quality of wireless charging FPC products, improve the service life and stability of the wireless charging FPC, and meet the demand for high-quality FPC in the wireless charging market.

[0005] In order to achieve the above object, the solution of the present invention is: A method for manufacturing a wireless charging FPC, comprising the following steps: Step S1, cutting materials, selecting PI as the base material of FPC; Step S2, drilling, drilling holes into the PI substrate; Step S3, black hole treatment, performing black hole treatment on the drilled FPC to form a conductive layer on the hole wall of the FPC; Step S4: copper plating, coating both sides of the FPC with a uniform layer of copper foil; Step S5, applying a dry film, pressing a layer of dry film on the copper surfaces on both sides of the FPC; Step S6: Exposure, transferring the pattern on the film to the dry film through exposure plate making; Step S7, etching, etching the coils on both sides of the FPC through an etching process, and making the coils on both sides conduct through the conducting holes; in addition to etching the coils, it is also necessary to etch out the circuits pre-designed by the FPC; Step S8, electroplating leads, reserving or making electroplating leads on the edge of the prepared circuit pattern, and designing a test PAD on the electroplating leads; Step S9, secondary copper plating, performing secondary copper plating on the coils and circuits on both sides to make the copper thickness reach a specified thickness; Step S10, copper plating, copper plating at positions without copper; Step S11, applying blue film to the parts with circuits and solder joints; Step S12, laminating the protective film. Before laminating, the protective film is subjected to vacuum false lamination. During lamination, four-opening lamination is used, and segmented control is adopted. Low-pressure lamination is adopted in the initial lamination stage, and after a period of time, a slow pressurization stage is entered. In the final stage of lamination, a stable pressure is maintained for a period of time; Step S13: Appearance inspection: After the protective film is pressed, an appearance inspection is performed to ensure that the protective film is well attached and has no bubbles, wrinkles or damage; Step S14: Electrical performance test: testing the electrical performance of the FPC to ensure that the wireless charging function is normal, mainly including checking the conductivity and insulation of the circuit and whether there is a short circuit.

[0006] Furthermore, in step S2, before drilling, the PI substrate is cleaned and then fixed to ensure that the substrate does not shift during the drilling process.

[0007] Furthermore, after the second copper plating in step S9, line width compensation is performed, and the line width compensation is consistent with the copper thickness and the minimum line spacing is ≥0.055mm.

[0008] Furthermore, in step S11, the blue film completely covers the circuit part of the flexible circuit board and the area that has a significant impact on the performance of the circuit board, including the area around the installation position of sensitive components such as chips and sensors.

[0009] Further, in step S12, before laminating the protective film, the protective film is firstly micro-etched to increase the roughness of the surface of the protective film, and the FPC to be laminated is cleaned; Furthermore, the micro-etching treatment of the protective film adopts plasma treatment, and the protective film is placed in a plasma treatment device. The surface of the treated protective film presents nanometer-scale roughness, and active functional groups are simultaneously introduced in the plasma treatment device to enhance the adhesion between the protective film and the FPC surface; the surface of the FPC to be laminated is coated with a layer of composite nanomaterial, and the main components of the composite nanomaterial include nano-silicon dioxide, silicone resin and coupling agent. The composite nanomaterial coating fills the tiny pores on the surface of the FPC and chemically bonds with the active functional groups on the surface of the protective film during the lamination process.

[0010] Furthermore, the pressure head of the four-opening laminator adopts an elastic buffer pressure head, which automatically adjusts the pressure distribution according to the actual conditions of the protective film and the surface to be pressed.

[0011] Further, in step S12, the specific steps of four-opening lamination are: in the initial lamination stage, the pressure setting value is 20kg / cm 2 , set the pressing time to 5 minutes, then enter the slow pressurization stage, the pressure of the stage is increased to 60kg / cm 2 The entire pressurization stage lasts for 5 minutes; in the final stage of pressing, the pressure value is set to 100 kg / cm 2 , maintain this pressure for 70 minutes.

[0012] Further, in step S12, after the protective film is pressed, the FPC is immediately cooled, the cold pressing pressure is set to 100 kg, the vacuum release time is set to 2 minutes, the cold pressing time is set to 45 minutes, the pre-vacuuming is 3 minutes, and the initial pressure is 20 kg. This further stabilizes the bonding between the protective film and the FPC surface and reduces the wrinkle problem caused by temperature changes.

[0013] After adopting the above scheme, the manufacturing method of the wireless charging FPC of the present invention has the following advantages compared with the prior art: the present invention improves the lamination process of the protective film, and before lamination, the protective film is vacuum-pressed, so that the protective film can be better attached to the surface of the FPC, the air is removed, and defects such as bubbles and delamination are avoided in the subsequent processing. During lamination, four-opening lamination is used, and the lamination process adopts segmented control, which can provide a uniform and stable high-temperature and high-pressure environment in a short time, so that the glue between the protective film and the FPC can be quickly solidified; during the lamination process, the pressure is evenly distributed on the surface of the FPC, which helps to make the protective film and the FPC fit closely, avoid defects such as bubbles and wrinkles, and ensure the flatness of the FPC surface, thereby improving the quality and reliability of the product. The use of segmented pressure control can effectively avoid the generation of bubbles and wrinkles. If high pressure is used at the beginning, it is easy to trap air between the protective film and the FPC to form bubbles, or cause wrinkles on the protective film. By gradually increasing the pressure, the air can have enough time to escape, and the protective film can be evenly attached to the FPC. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0015] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0016] like Figure 1 As shown, the present invention discloses a method for manufacturing a wireless charging FPC, which includes the following steps: Step S1, cutting materials, selecting a PI substrate that is resistant to high temperatures, has good insulation, is antistatic and flat.

[0017] Step S2, drilling, drilling the PI substrate; before drilling, cleaning the PI substrate, and then fixing the substrate to ensure that the substrate will not shift during the drilling process.

[0018] Step S3, black hole, black hole treatment is performed on the drilled FPC to form a conductive layer on the hole wall of the FPC, so that a conductive layer can be formed after drilling, which facilitates the subsequent conduction of the upper and lower copper layers.

[0019] Step S4, copper plating, a uniform layer of copper foil is respectively coated on both sides of the FPC, and the electroplating can be performed multiple times according to the actual situation.

[0020] Step S5, applying a dry film, pressing a layer of dry film on the copper surfaces on both sides of the FPC respectively, so as to form a circuit after exposure.

[0021] Step S6: Exposure, transferring the pattern on the film to the dry film through exposure platemaking technology.

[0022] Step S7, etching, etching the coils on both sides of the FPC through an etching process, and make the coils on both sides conduct through the conductive holes. The shape and parameters of the coils can be adjusted according to actual needs. In addition to etching the coils, it is also necessary to etch out the pre-designed circuits of the FPC, including power circuits, communication circuits, and ground circuits.

[0023] Step S8, after etching the coil and circuit, electroplating leads are performed to implement subsequent electroplating copper thickening and other processes. By reserving or making electroplating leads on the edge of the prepared circuit pattern, the current can be evenly distributed on the surface of the copper layer to be electroplated, ensuring the uniformity of the electroplating effect. A test PAD is designed on the electroplating lead. In addition to facilitating circuit performance testing, the test PAD can also be used as a contact point for monitoring the electroplating effect. When the wireless charging FPC fails, the test PAD provides a convenient test point for fault diagnosis. Maintenance personnel can quickly locate the fault position by applying test signals or measuring related parameters on the test PAD, and determine whether it is a problem with the electroplating lead itself or a fault in other components or circuits connected to it, which is convenient for maintenance; the design of the test PAD can also help evaluate the impact of the electroplating lead on signal transmission.

[0024] Step S9, secondary copper plating, secondary copper plating is performed on the coils and circuits on both sides, and it can be performed multiple times according to actual conditions to make the copper thickness reach the specified thickness.

[0025] After the secondary copper plating, line width compensation is performed. The line width compensation is consistent with the copper thickness and the minimum line spacing is ≥0.055mm.

[0026] Step S10, copper plating. Large areas without copper will cause uneven products. Therefore, the present invention appropriately lays copper in the copper-free position. In addition to making the FPC surface smoother, copper is laid in the copper-free position and connected to the ground plane to form a complete shielding layer, thereby reducing electromagnetic radiation and improving anti-interference ability, so that the wireless charging device can better resist external interference when working, and also avoid interference with other electronic devices.

[0027] Step S11, apply blue film to the areas with circuits and solder joints. The blue film should completely cover the circuit part of the flexible circuit board to ensure that the circuit is protected to prevent scratches or short circuits during subsequent processing or use. In addition to copper circuits and solder joints, it is also necessary to cover areas that have a significant impact on the performance of the circuit board, including areas around the installation locations of sensitive components such as chips and sensors. Although there is no copper in these areas, they may be affected by static electricity, moisture or physical collisions, and the blue film can provide additional protection.

[0028] Step S12, laminating the protective film. In order to overcome the problems existing in laminating the protective film, the protective film is first micro-etched to increase the roughness of the protective film surface, improve the filling property of the protective film, and reduce the possibility of bubbles generated during laminating. The micro-etching treatment can be plasma treatment. The protective film is placed in a plasma treatment device. The surface of the treated protective film presents nano-scale roughness and microscopic rough structure. The active functional groups introduced in the plasma treatment device at the same time can enhance the adhesion between the protective film and the FPC surface. After cleaning the FPC to be laminated, remove impurities such as oil, dust, etc. on the surface. Then, a layer of composite nanomaterial is coated on the surface of the FPC. Its main components include nano-silicon dioxide, silicone resin and a small amount of coupling agent. The composite nanomaterial coating can fill the tiny pores on the surface of the FPC and chemically bond with the active functional groups on the surface of the protective film during the lamination process, further improving the bonding force between the two and reducing the generation of bubbles.

[0029] Before lamination, the protective film is vacuum pressed to make it fit better on the surface of the FPC, remove air, and avoid defects such as bubbles and delamination in the subsequent processing. During lamination, four-opening lamination is used, which can provide a uniform and stable high-temperature and high-pressure environment in a short time, so that the glue between the protective film and the FPC can be quickly cured; during the lamination process, the pressure is evenly distributed on the FPC surface, which helps to make the protective film and FPC fit tightly, avoid defects such as bubbles and wrinkles, and ensure the flatness of the FPC surface, thereby improving the quality and reliability of the product.

[0030] When laminating with four openings, segmented control is used. In the initial lamination stage, low pressure lamination is used and the pressure setting value is 20kg / cm 2 , set the lamination time to 5 minutes. This pressure is enough to make the protective film lay flat on the FPC, but it will not cause deformation of the protective film or FPC due to excessive pressure. After 5 minutes, it enters the slow pressurization stage. Properly increasing the pressure can make the protective film and FPC fit more closely. The pressure in this stage is increased to 60kg / cm 2 The entire pressurization stage lasts for 5 minutes. This pressure range helps to squeeze out the tiny bubbles between the protective film and the FPC, ensuring that there is no gap between the two, thereby improving the bonding accuracy; in the final stage of lamination, the pressure value is set to 100 kg / cm 2 , maintaining this pressure for 70 minutes can allow the glue between the protective film and the FPC to fully solidify and bond smoothly.

[0031] The pressure head of the four-opening laminator adopts an elastic buffer pressure head to avoid fracturing the protective film. The elastic buffer pressure head can automatically adjust the pressure distribution according to the actual conditions of the protective film and the surface to be pressed, further reducing the generation of bubbles and the risk of fracturing the protective film.

[0032] The present invention adopts segmented pressure control to effectively avoid the generation of bubbles and wrinkles. If high pressure is used at the beginning, it is easy to trap air between the protective film and the FPC to form bubbles, or cause wrinkles on the protective film. By gradually increasing the pressure, the air can have enough time to escape, and the protective film can be evenly attached to the FPC.

[0033] After the pressing is completed, the FPC is immediately cooled, the cold pressing pressure is set to 100kg, the vacuum release time is set to 2min, the cold pressing time is set to 45min, the pre-vacuuming is 3min, and the initial pressure is 20kg. Cold pressing further stabilizes the bond between the protective film and the FPC surface and reduces the wrinkle problem caused by temperature changes.

[0034] Step S13, appearance inspection: after laminating the protective film, firstly, an appearance inspection is performed to ensure that the protective film is well attached and has no problems such as bubbles, wrinkles or damage.

[0035] Step S14: Electrical performance test, testing the electrical performance of the circuit board to ensure the normal function of the wireless charging, mainly including checking the conductivity and insulation of the circuit and whether there is a short circuit.

[0036] The above embodiments do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. A method for manufacturing a wireless charging FPC, characterized in that: The following steps are involved: Step S1, cutting materials, selecting PI as the base material of FPC; Step S2, drilling, drilling holes into the PI substrate; Step S3, black hole treatment, performing black hole treatment on the drilled FPC to form a conductive layer on the hole wall of the FPC; Step S4: copper plating, coating both sides of the FPC with a uniform layer of copper foil; Step S5, applying a dry film, pressing a layer of dry film on the copper surfaces on both sides of the FPC; Step S6: Exposure, transferring the pattern on the film to the dry film through exposure plate making; Step S7, etching, etching coils on the front and back sides of the FPC through an etching process, and making the coils on the front and back sides conduct through the conducting holes; In addition to etching the coil, you also need to etch out the pre-designed circuit of the FPC; Step S8, electroplating leads, reserving or making electroplating leads on the edge of the prepared circuit pattern, and designing a test PAD on the electroplating leads; Step S9, secondary copper plating, performing secondary copper plating on the coils and circuits on both sides to make the copper thickness reach a specified thickness; Step S10, copper plating, copper plating at positions without copper; Step S11, applying blue film to the parts with circuits and solder joints; Step S12, laminating the protective film. Before laminating, the protective film is subjected to vacuum false lamination. During lamination, four-opening lamination is used, and segmented control is adopted. Low-pressure lamination is adopted in the initial lamination stage, and after a period of time, a slow pressurization stage is entered. In the final stage of lamination, a stable pressure is maintained for a period of time; Step S13: Appearance inspection: After the protective film is pressed, an appearance inspection is performed to ensure that the protective film is well attached and has no bubbles, wrinkles or damage; Step S14: electrical performance test, testing the electrical performance of the FPC to ensure that the wireless charging function is normal.

2. A method for manufacturing a wireless charging FPC as claimed in claim 1, characterized in that: Step S2, before drilling, clean the PI substrate, and then fix the substrate to ensure that the substrate will not shift during the drilling process.

3. The method for manufacturing a wireless charging FPC as claimed in claim 1, characterized in that: After the second copper plating in step S9, line width compensation is performed. The line width compensation is consistent with the copper thickness and the minimum line spacing is ≥0.055mm.

4. The method for manufacturing a wireless charging FPC as claimed in claim 1, characterized in that: Step S11, the blue film completely covers the circuit part of the flexible circuit board and the area that has a significant impact on the performance of the circuit board, including the area around the installation position of sensitive components such as chips and sensors.

5. The method for manufacturing a wireless charging FPC as claimed in claim 1, characterized in that: Step S12, before laminating the protective film, the protective film is firstly micro-etched to increase the roughness of the surface of the protective film, and the FPC to be laminated is cleaned.

6. A method for manufacturing a wireless charging FPC as claimed in claim 5, characterized in that: The micro-etching treatment of the protective film adopts plasma treatment. The protective film is placed in a plasma treatment device. The surface of the protective film after treatment presents nano-scale roughness. Active functional groups are simultaneously introduced in the plasma treatment device to enhance the adhesion between the protective film and the FPC surface. The surface of the FPC to be laminated is coated with a layer of composite nanomaterials. The main components of the composite nanomaterials include nano-silicon dioxide, silicone resin and coupling agent. The composite nanomaterial coating fills the tiny pores on the surface of the FPC and chemically bonds with the active functional groups on the surface of the protective film during the lamination process.

7. The method for manufacturing a wireless charging FPC as claimed in claim 1, characterized in that: The pressure head of the four-opening laminator adopts an elastic buffer pressure head, which automatically adjusts the pressure distribution according to the actual conditions of the protective film and the surface to be pressed.

8. The method for manufacturing a wireless charging FPC as claimed in claim 1, characterized in that: In step S12, the specific steps of four-opening lamination are: in the initial lamination stage, the pressure setting value is 20kg / cm2, and the lamination time is set to 5 minutes, then entering the slow pressurization stage, the stage pressure is increased to 60kg / cm2, and the entire pressurization stage lasts for 5 minutes; in the final stage of lamination, the pressure value is set to 100 kg / cm2, and the pressure is maintained for 70 minutes.

9. The method for manufacturing a wireless charging FPC as claimed in claim 1, characterized in that: After the protective film is pressed, the FPC is immediately cooled, the cold pressing pressure is set to 100kg, the vacuum release time is set to 2min, the cold pressing time is set to 45min, the pre-vacuum is 3min, and the initial pressure is 20kg.

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