Composite structure for manufacturing FPC circuit board and preparation method and application thereof

Abstract

The invention belongs to the technical field of FPC circuit board manufacturing. The composite structure for manufacturing the FPC circuit board sequentially comprises a wiring base material layer, a thermal viscosity reduction adhesive film layer, a circuit diagram layer, a substrate adhesive film layer and a substrate base material layer from top to bottom, and the thermal viscosity reduction adhesive film layer and the substrate adhesive film layer are opposite in viscosity change along with temperature change. The composite structure used for manufacturing the FPC circuit board is subjected to transfer hot pressing, the circuit diagram layer is bonded with the substrate base material layer and is stripped from the wiring base material layer, and transfer of the circuit is completed; and covering the surface of the circuit pattern layer with a layer of covering film, and sealing the circuit through sealing and hot pressing to obtain the FPC circuit board. According to the technical scheme, circuit printing is carried out in a printing mode, no three wastes are discharged in the printing process, compared with the original industry, power consumption is greatly reduced, the usage amount of production materials, especially copper, is greatly reduced, and the raw material cost is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of FPC circuit board manufacturing, and in particular relates to a composite structure for manufacturing an FPC circuit board and an FPC circuit manufacturing method. Background Art

[0002] FPC circuit board (flexible circuit board) is a highly reliable and extremely flexible printed circuit board made of polyimide or polyester film as the base material. By embedding the circuit design on the bendable thin plastic sheet, a large number of precision components can be stacked in a narrow and limited space, thus forming a bendable flexible circuit.

[0003] In the prior art, the preparation process of FPC circuit boards is as follows: electroplating copper foil on the substrate, attaching a layer of photosensitive dry film of a specified thickness on the copper surface, then using an ultraviolet exposure machine and a specified pattern film to irradiate the dry film, so that the dry film undergoes a photopolymerization reaction to form an anti-corrosion layer; finally, the exposed board is developed, etched, and film stripped to obtain the circuit pattern. Simply put, the copper foil is chemically etched to remove the unwanted parts and produce the desired circuit. This process requires the copper material in the non-circuit area on the plane to be removed. The circuit forming process alone involves a lot of pollution, such as: harmful gases: the etching solution used in the etching process (such as copper etching solution) may volatilize harmful gases, such as ammonia, nitrogen oxides, etc. When these gases accumulate to a certain concentration in the air, they will cause harm to human health, and may also form secondary pollution such as acid rain or photochemical smog. Organic waste gas: organic waste gas may be generated in certain stages of FPC circuit etching, such as the coating and curing process of photoresist. These waste gases are also harmful to human health and the environment. Heavy metal ions: Etching liquid contains heavy metal ions, such as copper ions. During the etching process, these heavy metal ions may be discharged into the environment with wastewater, causing water pollution. Heavy metal ions are toxic, difficult to be biodegraded, and easily enriched in organisms, causing long-term harm to the ecosystem. Acid-base wastewater: During the etching process, acid-base solutions may be required for cleaning and neutralization. If these wastewaters are discharged directly without proper treatment, they will cause acid-base pollution to the water body, affecting the pH value and ecological balance of the water body. Organic wastewater: Organic matter such as photoresist and washing liquid may be discharged with wastewater during the etching process. These organic matter are difficult to degrade in the environment and will cause water pollution.

[0004] There are other pollution sources in other processes, such as: electroplating wastewater: electroplating is an important process in FPC production, but the electroplating process will produce wastewater containing heavy metal ions (such as copper, nickel, gold, etc.) and other harmful substances. If it is discharged directly without proper treatment, it will cause serious pollution to the water body. Cleaning wastewater: In the production process of FPC, the circuit board needs to be cleaned many times to remove impurities such as oil and dust on the surface. The wastewater generated in these cleaning processes also contains harmful substances. If it is discharged directly, it will also pollute the environment.

[0005] In addition, the traditional FPC production process uses a subtractive method to remove useless parts, which will result in a large amount of raw material waste and high production material costs. Summary of the invention

[0006] The invention provides a composite structure for manufacturing an FPC circuit board, a preparation method and an application thereof, so as to solve the problems of serious pollution and waste of raw materials in the current production process of the FPC circuit board.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a composite structure for manufacturing an FPC circuit board, which includes, from top to bottom, a wiring substrate layer, a heat-reducing adhesive film layer, a circuit layer, a substrate adhesive film layer and a substrate substrate layer, and the viscosity of the heat-reducing adhesive film layer and the substrate adhesive film layer changes oppositely with temperature.

[0008] It should be pointed out that if the viscosity of the heat-reducing adhesive film layer and the substrate adhesive film layer changes oppositely with changes in pressure, light, etc., it is also an inventive concept of the present invention and can achieve similar technical effects.

[0009] Optionally, the wiring substrate layer is a PET (polyethylene terephthalate) film or a PI (polyimide) film.

[0010] Optionally, the thermal viscosity-reducing adhesive film layer is a thermal viscosity-reducing adhesive, and the thermal viscosity-reducing adhesive is an acrylic thermal viscosity-reducing adhesive.

[0011] Optionally, the heat-reducing adhesive has an adhesion of 500-1500gf / 25mm at room temperature, a shrinkage rate of ≤3, a tensile strength of ≥20kg / 25mm, an elongation at break of ≥70kg / 25mm, debonding conditions: 2-4min at 90-120°C, and an initial adhesion of 800-1200N / cm 2 .

[0012] Normal temperature refers to room temperature, which is generally around 25℃.

[0013] Optionally, the substrate base material is a PI film or a polyester film.

[0014] Optionally, the substrate adhesive film is AD adhesive (acrylic hot melt adhesive).

[0015] The present invention also provides an FPC circuit board, which is obtained by the composite structure for manufacturing the FPC circuit board.

[0016] Optionally, the manufacturing method of the FPC circuit board includes the following steps: the composite structure for manufacturing the FPC circuit board is subjected to transfer hot pressing, the circuit layer is bonded to the substrate base material layer and peeled off from the wiring base material layer to complete the transfer of the circuit; a layer of coating is covered on the surface of the circuit layer, and the circuit is sealed by sealing hot pressing.

[0017] Optionally, the coating includes a PI film and an AD glue coated on the surface of the PI film, and the AD glue surface covers the surface of the circuit layer.

[0018] Optionally, the transfer heat pressing specifically includes: heat pressing for 2-5 minutes by a 70-80° C. heat press machine, and then further heat pressing by a heating roller, the temperature of the heating roller is 120-130° C., and finally recycling the stripped wiring substrate layer by a winder.

[0019] Optionally, the traction force of the winder is 4.5±0.5kgf.

[0020] The present invention also provides a method for preparing the composite structure for manufacturing an FPC circuit board, which comprises the following steps: using a printing device to print the wire on the surface of a wiring composite film to form a circuit layer, wherein the wiring composite film comprises a wiring substrate layer and a heat-reducing adhesive film layer coated on the surface of the wiring substrate; covering the surface of the circuit layer with a substrate composite film, wherein the substrate composite film comprises a substrate substrate layer and a substrate adhesive film layer coated on the surface of the substrate substrate layer.

[0021] Optionally, a travel path of the printer's filament outlet head is planned according to the designed circuit diagram.

[0022] Optionally, the filament outlet head of the printer is a rotating filament outlet head.

[0023] Optionally, the conductive wire is a bare copper wire, an enameled copper wire or a self-adhesive copper wire.

[0024] The technical solution provided by the present invention prints circuits by printing, and no three wastes are discharged during the printing process. Compared with the original industry, the power consumption is greatly reduced, the use of production materials, especially copper, is greatly reduced, and the cost of raw materials is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of a specific embodiment of the composite structure for manufacturing an FPC circuit board according to the present invention;

[0026] Figure 2It is a schematic diagram of a specific processing process of the composite structure for manufacturing an FPC circuit board according to the present invention;

[0027] Figure 3 It is a schematic diagram of a specific implementation process of circuit transfer in manufacturing an FPC circuit board according to the present invention.

[0028] As shown in the figure:

[0029] 10-wiring composite film, 11-wiring base material layer, 12-heat-reducing adhesive film layer, 20-circuit layer layer, 30-substrate composite film, 31-substrate adhesive film layer, 32-substrate base material layer;

[0030] 40-printer, 50-conductor wire, 60-heat press, 70-heat roller, 80-winder. DETAILED DESCRIPTION

[0031] For ease of understanding, the composite structure for manufacturing an FPC circuit board, its preparation method and application are described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0032] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation and positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Example 1 Composite structure for manufacturing FPC circuit board

[0035] like Figure 1As shown, the composite structure for manufacturing an FPC circuit board includes, from top to bottom, a wiring substrate layer 11, a heat-reducing adhesive film layer 12, a circuit layer 20, a substrate adhesive film layer 31, and a substrate substrate layer 32. The wiring substrate layer is a PET film, and the heat-reducing adhesive film layer is an acrylic heat-reducing adhesive; the substrate substrate layer is a PI film, and the substrate adhesive film layer is an AD adhesive.

[0036] It should be pointed out that the product model of the acrylic thermal de-viscosity adhesive used in this embodiment is: YS10008B-50, the adhesive has a thermal decomposition surface adhesion of 1000±200gf / 25mm at room temperature; shrinkage rate ≤3; tensile strength ≥20kg / 25mm; elongation at break ≥70kg / 25mm; de-bonding test condition 100℃ / 3min. Under room temperature, the copper wire led out of the wire outlet is adhered to the adhesive film by the viscosity of the colloid. The selection of thermal de-viscosity adhesive must meet the requirements of 1000N / cm 2 The initial adhesion is above 100°C, and the adhesive layer will quickly debond or even completely lose its adhesiveness after being heated above 100°C.

[0037] In this embodiment, the PI film used is a covering film produced by Huizhou Hongtian Electronic Materials Co., Ltd., product specification: HCJB1. This film is a commonly used surface film material for flexible circuit boards FPC for electronics. This film material has the characteristics of high temperature resistance (soldering heat resistance 288 degrees Celsius / 10sec) and high peeling strength.

[0038] In addition, in addition to the specific selections given in this embodiment, the corresponding substrate materials in the prior art FPC for the substrate base material layer and the substrate adhesive film layer, such as polyester film and the adhesive film used, are applicable. The substrate adhesive film has almost no viscosity at room temperature and is in a solid state. It has a certain viscosity and fluidity under high temperature conditions, and solidifies rapidly after cooling. This property makes the film material widely used in electronic flexible circuits that need to be further processed by reflow soldering.

[0039] The composite structure for manufacturing the FPC circuit board can be obtained by the following steps: Figure 2 As shown, a printing device such as a 3D printer 40 is used to print a conductor 50 on the surface of a wiring composite film 10 to form a circuit layer 20, wherein the wiring composite film 10 includes a wiring substrate layer 11 and a heat-reducing adhesive film layer 12 coated on the surface of the wiring substrate; and then a substrate composite film 30 is covered on the surface of the circuit layer 20, wherein the substrate composite film 30 includes a substrate substrate layer 32 and a substrate adhesive film layer 31 coated on the surface of the substrate substrate layer 32, to obtain a circuit layer 20 as shown in FIG. Figure 1 composite structure.

[0040] The printing equipment uses a high-precision motor as the motion control source, and controls the precise movement of the wire head in the plane X and Y axis directions through programming. The high-precision positioning capability of the motor ensures that the wire head can be routed strictly according to the drawing path input in advance, and the highest accuracy is controlled within 0.01mm.

[0041] The wire head is designed as a rotatable structure, which is used to lead out bare copper wire, lacquered copper wire or copper core wire with self-adhesive layer and other wires 50. During the wiring process, the wire head rotates according to the preset rotation parameters, driving the wire to rotate synchronously to release the torsional stress of the wire caused by the change of the path direction.

[0042] Example 2: Manufacturing of FPC Circuit Board

[0043] The composite structure 01 used to manufacture the FPC circuit board is transferred and hot pressed, the circuit layer 20 is bonded to the substrate composite film 30 and peeled off from the wiring composite film 10, and the circuit transfer is completed. Figure 3 As shown, the composite structure 01 used to manufacture the FPC circuit board is firstly hot-pressed for 3 minutes by a 70-80°C hot press machine 60, so that the substrate adhesive film layer 31 on the surface of the substrate substrate layer 32 can have a certain viscosity and adhere to the other side of the wiring layer 20; then a pair of heating rollers 70 are used for further hot pressing, and the heating temperature of the heating rollers 70 is 120-130°C, so that the heat-reducing adhesive of the heat-reducing adhesive film layer 12 can quickly reduce the viscosity, and the wiring composite film 10 is automatically separated from the substrate composite film 30 by the gravity of the wiring composite film 10 and the pulling force of the winder 80. The traction force of the winder 80 is 4.5±0.5kgf. After completion, the circuit can be completely transferred to the substrate composite film 30.

[0044] After the circuit transfer is completed, a layer of coating is attached to the circuit layer. The coating includes PI film and AD glue coated on the surface of PI film. The AD glue surface covers the surface of the circuit layer. The film is tightly attached to the substrate through a hot pressing process to achieve overall sealing and reinforcement of the circuit, completing the manufacture of the FPC circuit board.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite structure for manufacturing an FPC circuit board, characterized in that: From top to bottom, it includes a wiring base material layer, a heat-reducing adhesive film layer, a circuit layer, a substrate adhesive film layer and a substrate base material layer. The viscosity of the heat-reducing adhesive film layer and the substrate adhesive film layer changes oppositely with temperature.

2. The composite structure for manufacturing an FPC circuit board according to claim 1, characterized in that: The wiring substrate layer is a PET film or a PI film.

3. The composite structure for manufacturing an FPC circuit board according to claim 1, characterized in that: The thermal viscosity-reducing adhesive film layer is a thermal viscosity-reducing adhesive, and the thermal viscosity-reducing adhesive is an acrylic thermal viscosity-reducing adhesive.

4. The composite structure for manufacturing an FPC circuit board according to claim 1, characterized in that: The substrate base material is a PI film or a polyester film, and the substrate adhesive film is an AD adhesive.

5. An FPC circuit board, characterized in that: The method is obtained by using the composite structure for manufacturing an FPC circuit board as claimed in any one of claims 1 to 4.

6. The FPC circuit board according to claim 5, characterized in that: The manufacturing method of the FPC circuit board comprises the following steps: the composite structure for manufacturing the FPC circuit board is transferred and hot pressed, the circuit layer is bonded to the substrate base material layer and peeled off from the wiring base material layer, and the circuit is transferred; A layer of film is covered on the surface of the circuit layer, and the circuit is sealed by sealing heat pressing.

7. The FPC circuit board according to claim 6, characterized in that: The transfer hot pressing specifically includes: hot pressing for 2-5 minutes by a 70-80° C. hot press, further hot pressing by a heating roller, the temperature of the heating roller is 120-130° C., and finally recycling the stripped wiring substrate layer by a winder.

8. The FPC circuit board according to claim 7, characterized in that: The traction force of the winder is 4.5±0.5kgf.

9. The method for preparing a composite structure for manufacturing an FPC circuit board according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: using a printing device to print a conductor on the surface of a wiring composite film to form a circuit layer, wherein the wiring composite film comprises a wiring substrate layer and a heat-reducing adhesive film layer coated on the surface of the wiring substrate; A substrate composite film is covered on the surface of the circuit layer, wherein the substrate composite film comprises a substrate base material layer and a base material adhesive film layer coated on the surface of the substrate base material layer.

10. The preparation method according to claim 9, characterized in that: The conductor is a bare copper wire, an enameled copper wire or a self-adhesive copper wire.

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