Low-cost high-efficiency fine printed circuit board processing method

Abstract

The invention discloses a low-cost high-efficiency fine printed circuit board processing method, and belongs to the technical field of printed circuit board manufacturing. According to the method, a double-sided bearing film structure is adopted, two pure copper foils are pasted on the two sides of a bearing film to form a symmetrical composite base material, then a thickened circuit is formed through photosensitive dry film pasting, exposure developing and pattern electroplating, and then the working procedures of pressing an insulating auxiliary material, then tearing off the bearing film and finally etching base copper are executed. According to the method, synchronous manufacturing of two same plates is achieved through a unique double-face structure, the production efficiency is greatly improved, and the veneer cost is reduced; and meanwhile, the fine circuit is pre-fixed by using a pressing process, so that the circuit damage in the subsequent process is effectively prevented, the product yield and reliability are remarkably improved, and the method is particularly suitable for large-scale production of fine circuit boards of which the line width / line distance is less than or equal to 20 / 20 microns.

Description

Technical Field

[0001] This application belongs to the field of printed circuit board manufacturing technology, and in particular relates to a low-cost, high-efficiency, and precision printed circuit board processing method. Background Technology

[0002] As electronic products become smaller and faster, the width and spacing of printed circuit board lines are constantly decreasing, placing higher demands on manufacturing processes. Semi-additive methods have become one of the mainstream processes due to their ability to create fine lines.

[0003] Traditional or modified semi-additive processes typically employ a single-sided processing mode, meaning only one printed circuit board can be produced per process. While these processes offer improved circuit precision, their production efficiency is limited, and unit costs are high, making it difficult to meet the large-scale demand in the consumer electronics market for high-performance, cost-effective circuit boards. Furthermore, both traditional and modified semi-additive processes involve a "copper plating followed by flash etching" process for fine circuit manufacturing. As the plating layer thickness increases, the crystal size also increases. Since the semi-additive or modified semi-additive processes flash-etch the top of the plating layer, the large crystals at the top and the potential for abnormal crystallization easily lead to pinhole defects.

[0004] Furthermore, in traditional or modified semi-additive processing, the lamination of insulating auxiliary materials is usually performed after the final circuit pattern is formed. For ultra-fine circuits, individual circuit patterns are easily damaged or deformed by physical stress during subsequent transportation and processing, affecting product yield and reliability.

[0005] Therefore, there is an urgent need for a new processing method that can significantly improve production efficiency and reduce costs while ensuring the precision of the circuit. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a low-cost, high-efficiency, and precision printed circuit board manufacturing method. This method, through an innovative double-sided synchronous processing structure and optimized process flow, achieves the simultaneous manufacturing of two identical boards and improves the mechanical stability of the circuitry.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a low-cost, high-efficiency, and precision printed circuit board processing method, comprising the following steps:

[0009] S100, Applying carrier film: Two pure copper foils are respectively applied to both sides of a double-sided carrier film to form a symmetrical composite structure;

[0010] The step specifically comprises: providing a double-sided carrier film, both sides of the double-sided carrier film having adhesion, and pasting two pure copper foils on both sides of the double-sided carrier film respectively to form a symmetrical composite structure of "copper foil-carrier film-copper foil", wherein the thickness of the pure copper foil is 5-17 μm, and the pasting is performed by a winding machine with the pasting tension controlled between 50 N and 200 N to ensure that there is no bubble after pasting. The structure provides a physical basis for the synchronous manufacturing of two printed circuit boards, and the use of ultra-thin pure copper foil is conducive to subsequent fine line etching, and the winding process realizes continuous and large-scale production, laying a foundation for high efficiency and low cost.

[0011] S200, pasting a photosensitive dry film: pasting a photosensitive dry film on the exposed copper surface of the symmetrical composite structure on both sides respectively;

[0012] The step specifically comprises: after cleaning and roughening the exposed copper surface of the symmetrical composite structure on both sides, pasting a photosensitive dry film on both sides respectively by a film pressing machine, wherein the roller temperature of the film pressing machine is controlled to be 110±10℃, the pressure is 0.3-0.6 MPa, and the linear speed is 1.0-2.0 m / min. By synchronously pasting the film on both sides, the efficiency is greatly improved, and by controlling the film pressing parameters, the good pasting between the photosensitive dry film and the ultra-thin pure copper foil without gaps and wrinkles is ensured, which provides a guarantee for obtaining high-precision pattern transfer subsequently.

[0013] S300, exposure and development: transferring a preset line pattern to the photosensitive dry film on both sides and developing to expose the copper surface for pattern electroplating;

[0014] The step specifically comprises: first, using a double-sided alignment exposure machine, simultaneously or sequentially exposing the two sides of the processing plate to the preset line pattern through a mask, wherein the exposure energy is 80-150 mJ / cm 2 ; then, using a sodium carbonate solution with a mass concentration of 0.8-1.2% as a developing solution, performing spray development under the conditions of a temperature of 30±2℃ and a pressure of 2-3 bar to remove the photosensitive dry film in the unexposed area and expose the copper surface. By synchronously patterning on both sides, the efficiency is improved again, and by controlling the exposure and development parameters, the edge of the preset line pattern is steep and the resolution is high, and fine lines with a line width / line spacing of ≤20 / 20 μm can be realized.

[0015] S400, pattern electroplating: electroplating a thick copper layer on the exposed copper surface area;

[0016] The step specifically comprises: sending the developed plate into an electroplating line, and performing pattern electroplating on the exposed copper surface area of the plate, wherein the electroplating solution is a copper sulfate system, the copper ion concentration is 40-90 g / L, the sulfuric acid concentration is 180-220 g / L, the current density is 2.0-3.0 ASD, the electroplating time is 15-40 min, and the thickness of the electroplated copper layer is 5-20 μm. This step only deposits copper on the circuit pattern that needs to be thickened, thereby saving metal material, and the thickened circuit formed by electroplating has excellent electrical conductivity and mechanical strength, thereby meeting the current-carrying and reliability requirements of the circuit.

[0017] S500, film removal: removing the photosensitive dry film on both sides of the plate;

[0018] The step specifically comprises: using a sodium hydroxide solution with a mass concentration of 3-5% as the film removal solution, completely removing the photosensitive dry film between the protective circuit gaps by spraying at a temperature of 50±5 ℃, and exposing the underlying initial pure copper foil (base copper). The photosensitive dry film is completely removed, thereby providing a clean interface for the subsequent lamination process, and ensuring good bonding between the insulating auxiliary material and the substrate.

[0019] S600, lamination of auxiliary material: laminating insulating auxiliary material on both sides of the plate after film removal and curing;

[0020] The step specifically comprises: laminating insulating auxiliary material on both sides of the plate after film removal, and then performing lamination, wherein the insulating auxiliary material is a prepreg or a cover film, the lamination process uses a vacuum press, the lamination pressure is 20-30 kg / cm 2 , the lamination temperature is 180-220 ℃, and the holding pressure time is 60-90 min, so that the insulating auxiliary material is completely cured and tightly combined with the preset circuit pattern. By performing lamination before final etching, the thickened circuit formed is embedded and fixed in the cured insulating auxiliary material, which greatly enhances the mechanical stability of the fine circuit, effectively prevents the circuit from deforming or breaking due to stress in the subsequent film tearing and transportation process, and thereby significantly improves the product yield.

[0021] S700, tear the carrier film: peeling and removing the double-sided carrier film to obtain two independent processed plates;

[0022] The step specifically comprises: peeling and removing the double-sided carrier film from both sides of the laminated and cured plate manually or by a mechanical device. After removing the temporary double-sided carrier film, the originally integrated symmetrical composite structure is separated into two independent, mirror-symmetrical plates, thereby achieving the production effect of "one effort, two results".

[0023] S800, etch the base copper: etching and removing the initial pure copper foil on the two independent processed plates that is not covered by the pattern electroplated copper layer to obtain two printed circuit boards with circuits.

[0024] The step specifically comprises: etching the two independent processed plate parts obtained in the step S700 by using acidic copper chloride etching solution or ammonia alkaline etching solution, and then completely removing the initial pure copper foil which is not protected by the patterned copper plating layer, so that two printed circuit boards with preset circuit patterns are obtained. Since the pure copper foil is thin, the etching time is short, and the side etching amount is small, the circuit precision is further ensured. Through etching of the base copper, the area protected by the patterned copper is retained, and the thin base copper which is not protected is quickly etched away, so that a fine circuit with steep side wall and high precision is formed, and a clear circuit pattern is finally defined.

[0025] The application further provides a printed circuit board prepared by the processing method, and the line width / line spacing of the printed circuit board is ≤30 / 30 μm.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] (1) The application synchronously manufactures two identical printed circuit boards in one production process through the innovative double-sided carrier film structure, so that the production efficiency is theoretically increased by nearly one time, and the production cost of a single board is greatly reduced.

[0028] (2) The application adopts the process of "electroplating a pattern first, pressing and protecting second, and etching and shaping third", and the fine circuit is pre-fixed by the insulating layer after pressing, so that the damage of the thin circuit in the subsequent process is effectively avoided, and the mechanical strength and product yield are improved.

[0029] (3) The application etches the bottom end of the crystal uniform and dense plating layer, and needle holes are not easy to form, so that the technical problem of easy formation of needle hole defects after flash etching in the traditional semi-additive method or improved semi-additive method is solved.

[0030] (4) The application can use 5-17 μm pure copper foil as base copper, so that the production cost can be effectively reduced. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0032] Figure 1 It is a flow chart of a low-cost and high-efficiency fine printed circuit board processing method of the application;

[0033] Figure 2 It is a structural schematic view of the application in which two pure copper foils are attached to the two surfaces of the double-sided carrier film;

[0034] Figure 3 is a structural schematic diagram after the photosensitive dry film is pasted in the application;

[0035] Figure 4 is a structural schematic diagram after exposure and development in the application;

[0036] Figure 5 is a structural schematic diagram after pattern plating in the application;

[0037] Figure 6 is a structural schematic diagram after the photosensitive dry film is removed in the application;

[0038] Figure 7 is a structural schematic diagram after the auxiliary material is pressed in the application;

[0039] Figure 8 is a structural schematic diagram after the double-sided carrier film is peeled off in the application;

[0040] Figure 9 is a structural schematic diagram after the base copper is etched in the application. DETAILED DESCRIPTION

[0041] The application will be described in detail below with specific examples. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form.

[0042] Example 1:

[0043] A fine printed circuit board with a line width / line spacing of 20 / 20 μm is made, and the preparation process is as shown in Figure 1 .

[0044] S100, two pure copper foils with a thickness of 12 μm are selected, and they are pasted with a PET double-sided adhesive film (as a double-sided carrier film) with a thickness of 50 μm through a winding machine to form a symmetrical composite structure, wherein the winding tension of the winding machine is controlled at 50 N;

[0045] S200, a photosensitive dry film with a model of RD-1215 is selected, and the photosensitive dry film is pasted on the two exposed copper surfaces of the symmetrical composite structure by using a film pressing machine, wherein the roller temperature of the film pressing machine is set to 110°C, and the pressure is 0.5 MPa;

[0046] S300, an LDI (laser direct imaging) exposure machine is used for exposure to transfer the preset circuit pattern to the two photosensitive dry films, wherein the exposure energy is set to 110 mJ / cm 2 ; then a developing solution of 1.0% sodium carbonate solution is selected to develop the exposed board, and the developing temperature is set to 30°C;

[0047] S400, electroplating the exposed copper surface area to form a thickened copper layer, wherein the electroplating solution has a copper ion concentration of 75 g / L, a sulfuric acid concentration of 200 g / L, a current density of 2.0 ASD, and an electroplating time of 30 min, to obtain a thickened copper layer with a thickness of 10 μm;

[0048] S500, using a 4% sodium hydroxide solution as a film stripping solution, and spraying the board with the film stripping solution at a film stripping temperature of 55°C to remove the photosensitive dry film;

[0049] S600, using a 1080 type prepreg as an insulating auxiliary material, and pressing the prepreg onto both sides of the board after film stripping in a vacuum press at a temperature of 200°C, a pressure of 20 kg / cm 2 for 75 min to solidify the prepreg on both sides of the board after film stripping;

[0050] S700, manually tearing off the double-sided carrier film from both sides to obtain two independent processed boards;

[0051] S800, etching the two independent processed boards using an ammonia alkaline etching solution to etch away the exposed 12 μm base copper, and finally obtaining two pieces of printed circuit boards that meet the requirements.

[0052] Example 2:

[0053] A fine printed circuit board with a line width / line spacing of 20 / 20 μm is made, and the preparation process is as shown in Figure 1 .

[0054] S100, two pieces of pure copper foil with a thickness of 17 μm are selected, and a piece of PET double-sided adhesive film with a thickness of 50 μm is attached to the copper foil by a winding machine to form a symmetrical composite structure, wherein the winding tension of the winding machine is controlled at 50 N;

[0055] S200, a photosensitive dry film with a model number of RD-1215 is selected, and the photosensitive dry film is attached to the exposed copper surfaces of the symmetrical composite structure using a film press, wherein the roller temperature of the film press is set to 100°C, and the pressure is 0.3 MPa;

[0056] S300, an LDI (laser direct imaging) exposure machine is used for exposure to transfer the pre-set circuit pattern to the two photosensitive dry films, wherein the exposure energy is set to 80 mJ / cm 2 ; then a 0.8% sodium carbonate solution is selected as the developing solution to develop the exposed board, and the developing temperature is set to 28°C;

[0057] S400, electroplating the exposed copper surface area to form a thickened copper layer, wherein the electroplating solution has a copper ion concentration of 75 g / L, a sulfuric acid concentration of 200 g / L, a current density of 1.5 ASD, and an electroplating time of 15 min, to obtain a thickened copper layer with a thickness of 5 μm;

[0058] S500, using a 4% sodium hydroxide solution as a film stripping solution, and spraying the board with the film stripping solution at a film stripping temperature of 45°C to remove the photosensitive dry film;

[0059] S600, using a 1080 type prepreg as an insulating auxiliary material, and pressing the prepreg onto both sides of the board after film stripping in a vacuum press at a temperature of 180°C and a pressure of 25 kg / cm 2 for 90 min to solidify the prepreg;

[0060] S700, manually tearing off the double-sided carrier film from both sides to obtain two independent processed boards;

[0061] S800, etching the two independent processed boards using an ammonia alkaline etching solution to etch away the exposed 17 μm base copper, and finally obtaining two pieces of printed circuit boards that meet the requirements.

[0062] Example 3

[0063] A fine printed circuit board with a line width / line spacing of 20 / 20 μm is made, and the preparation process is as shown in Figure 1 .

[0064] S100, two pieces of pure copper foil with a thickness of 5 μm are selected, and a piece of PET double-sided adhesive film with a thickness of 50 μm is attached to the copper foil by a winding machine to form a symmetrical composite structure, wherein the winding tension of the winding machine is controlled at 100 N;

[0065] S200, a photosensitive dry film with a model number of RD-1215 is selected, and the photosensitive dry film is attached to the exposed copper surfaces of the symmetrical composite structure using a film pressing machine, wherein the roller temperature of the film pressing machine is set to 120°C, and the pressure is 0.6 MPa;

[0066] S300, an LDI (laser direct imaging) exposure machine is used for exposure to transfer the pre-set circuit pattern to the photosensitive dry film on both sides, wherein the exposure energy is set to 150 mJ / cm 2 ; then a 1.2% sodium carbonate solution is selected as the developing solution to develop the exposed board, and the developing temperature is set to 32°C;

[0067] S400, electroplating the exposed copper surface area to form a thickened copper layer, wherein the electroplating solution has a copper ion concentration of 75 g / L, a sulfuric acid concentration of 200 g / L, a current density of 3.0 ASD, and an electroplating time of 40 min, to obtain a thickened copper layer with a thickness of 20 μm;

[0068] S500, spraying the board with a 4% sodium hydroxide solution as a film removal solution at a film removal temperature of 50°C to remove the photosensitive dry film;

[0069] S600, using a 1080 type prepreg as an insulating auxiliary material, and pressing and curing the prepreg on both sides of the board after film removal in a vacuum press at a temperature of 220°C and a pressure of 30 kg / cm 2 for 60 min;

[0070] S700, manually and smoothly tearing off the double-sided carrier film from both sides to obtain two independent processed boards;

[0071] S800, etching the two independent processed boards using an ammonia alkaline etching solution to etch away the exposed 2 μm base copper, and finally obtaining two pieces of printed circuit boards meeting the requirements.

[0072] The printed circuit boards obtained in Examples 1-3 are subjected to performance tests including scanning electron microscope (SEM) detection and flying probe testing, and the results are shown in Table 1.

[0073] Table 1 Performance test results of the printed circuit boards obtained in Examples 1-3

[0074] Scanning electron microscopy Flying probe testing Example 1 Clear line edges, no pinholes No short / open defects Example 2 Clear line edges, no pinholes No short / open defects Example 3 Clear line edges, no pinholes No short / open defects

[0075] As can be seen from Table 1, the printed circuit boards obtained in Examples 1-3 have clear line edges, no pinholes, and no short circuit / open circuit defects, and compared with the traditional semi-additive method or the improved semi-additive method, two pieces of printed circuit boards can be produced at one time in Examples 1-3. Therefore, the processing method provided by the present application improves the production efficiency by nearly one time under the premise of ensuring the line fineness, and greatly reduces the production cost.

[0076] The above describes in detail a low-cost and high-efficiency fine printed circuit board processing method provided by the present application. The principles and implementation modes of the present application are described by applying specific examples, and the above description of examples is only used to help understand the core idea of the present application. It should be pointed out that those skilled in the art can make some improvements and modifications to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A low-cost, high-efficiency, and precision printed circuit board processing method, characterized in that, Includes the following steps: S100, Applying carrier film: Two pure copper foils are respectively applied to both sides of a double-sided carrier film to form a symmetrical composite structure; S200, Applying photosensitive dry film: Applying photosensitive dry film to the exposed copper surfaces on both sides of the symmetrical composite structure; S300, Exposure and Development: Transfer the preset circuit pattern to the photosensitive dry film on both sides, and develop to expose the copper surface that needs to be plated. S400, Pattern Plating: A thicker copper layer is plated on the copper surface area exposed during development; S500, Film Removal: Removes the photosensitive dry film from both sides of the board; S600, Pressing Auxiliary Material: Pressing insulating auxiliary material onto both sides of the board after the film is removed and then curing it; S700, Peel off the carrier film: Peel off and remove the double-sided carrier film to obtain two independent processed plates; S800, Etching Base Copper: Etching removes the initial pure copper foil not covered by the patterned electroplated copper layer from two independently processed boards, resulting in two printed circuit boards with lines.

2. The low-cost, high-efficiency, and precision printed circuit board processing method as described in claim 1, characterized in that, In step S100, the thickness of the pure copper foil is 5-17 μm.

3. The low-cost, high-efficiency, and precision printed circuit board processing method as described in claim 1, characterized in that, In step S100, two pure copper foils are applied to both sides of the double-sided carrier film using a winding machine, and the winding tension of the winding machine is controlled between 50N and 200N.

4. The low-cost, high-efficiency, and precision printed circuit board processing method as described in claim 1, characterized in that, In step S200, a photosensitive dry film is applied to both sides of the symmetrical composite structure using a laminating machine. The temperature of the laminating machine roller is 110±10℃, and the pressure is 0.3MPa-0.6MPa.

5. The low-cost, high-efficiency, and precision printed circuit board processing method as described in claim 1, characterized in that, In step S300, the exposure energy is 80-150 mJ / cm². 2 The developer is a sodium carbonate solution with a mass concentration of 0.8-1.2%, and the developing temperature is 30±2℃.

6. The low-cost, high-efficiency, and precision printed circuit board processing method as described in claim 1, characterized in that, In step S400, the pattern electroplating uses copper sulfate electroplating solution, the current density is 1.5-3.0 ASD, the electroplating time is 15-40 min, and the thickness of the thickened copper layer is 5-20 μm.

7. The low-cost, high-efficiency, and precision printed circuit board processing method as described in claim 1, characterized in that, In step S500, a sodium hydroxide solution with a mass concentration of 3%-5% is used as the film removal solution, and the film removal temperature is 50±5℃.

8. The low-cost, high-efficiency, and precision printed circuit board processing method as described in claim 1, characterized in that, In step S600, the insulating auxiliary material is a prepreg or a cover film; the pressing process is vacuum pressing, with a pressure of 20-30 kg / cm². 2 The temperature is 180-220℃, and the heat preservation and pressure holding time is 60-90min.

9. The low-cost, high-efficiency, and precision printed circuit board processing method as described in claim 1, characterized in that, In step S800, etching is performed using an acidic copper chloride etching solution or an ammonia-based etching solution.

10. The printed circuit board manufactured by the processing method according to any one of claims 1-9, characterized in that, The line width / line spacing of the printed circuit board is ≤20 / 20μm.

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