Method for manufacturing microwave circuit board with metal covered edge

Abstract

The invention relates to a method for manufacturing a microwave circuit board with a metal covered edge, which is mainly used for manufacturing a resistor with a thin film. A pattern circuit is manufactured by using an alkaline etching process, so that the manufacturing process requirement of the metal covered edge is met; for the resistive film layer, the resistive film layer is firstly subjected to oxidation activation treatment through the liquid medicine, then the unnecessary resistive film layer is removed through the liquid medicine, etching of the pattern circuit and etching of the resistive film layer are separated, the resistive film layer is easier to remove after oxidation activation, and even for a microwave circuit board with a thick-surface copper design and a dense circuit design, the etching of the pattern circuit and the etching of the resistive film layer are not influenced. The resistive film layer can also be etched clean; according to a resistive film block in the method, windowing and surface processing are carried out together in a solder resist process and a process wire position for protection, a conductor copper thin film is etched together with the process wire position after surface treatment, a resistive film layer is exposed to obtain a resistor, and finally a layer of solder resist is coated for protection. The treatment mode that the resistance plate cannot be mechanically ground in the prior art is broken, and the surface treatment surface quality and the resistance value yield are improved.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing, and in particular to a method for manufacturing a microwave circuit board with metal edging. Background Technology

[0002] Microwave circuit boards typically refer to printed circuit boards with operating frequencies ranging from 300 MHz (0.3 GHz) to 300 GHz. Planar resistors are the core components of microwave circuit boards. They are fabricated directly on the dielectric substrate using thin-film or thick-film processes, rather than soldering discrete resistors. In other words, in the stacked structure of microwave circuit boards, the resistive film layer is laid flat between the insulating dielectric layer and the copper layer.

[0003] In the current manufacturing process of microwave circuit boards, the resistor strips need to be exposed through etching. This involves etching away the unwanted resistive film layer to reveal the required resistive film layer, which serves as the resistor strip. The conventional process involves first applying a photosensitive film to the microwave circuit board, then exposing and developing it to expose the copper surface to be etched. Next, acid etching is used to remove the copper surface to be etched, forming the pattern circuit. Then, the resistive film layer beneath the copper surface is etched away. After removing the photosensitive film, a dry film is applied a second time, and after exposure and development, the resistive module area located on the pattern circuit is exposed. Then, alkaline etching is used to etch away the copper layer on the resistive module area (the resistive film layer is etched by the acid etching solution but not by the alkaline etching solution). The exposed resistive film layer is the resistor strip. After the resistor strip is manufactured, subsequent processes such as gold plating and surface treatment are performed.

[0004] The aforementioned microwave circuit board has three problems. First, because the resistive film layer is etched away together with the copper layer during acid etching—etching away the upper copper layer first and then the lower resistive film layer—the etching depth of the resistive film layer is very large, especially when there are densely patterned circuits or thick copper layers. The acid etching solution cannot completely etch away the bottom resistive film layer, resulting in incomplete etching. Second, when customers require the microwave circuit board to have metal edging, acid etching cannot be used. There is an industry consensus that metal-edged circuit boards can only be made using alkaline etching. This creates a conflict between the above process and customer requirements, making it impossible to manufacture metal-edged microwave circuit boards. Finally, the above process involves surface treatment after the resistive strips are manufactured. Before surface treatment, the copper surface to be surface treated needs to be mechanically ground to clean it and improve the adhesion of the surface treatment. However, once the resistive strips are exposed, mechanical grinding would damage them, making mechanical grinding impossible. Surface treatment must be performed directly, which reduces the quality of the surface treatment. Therefore, there is an urgent need for a manufacturing method for metal-edged microwave circuit boards to solve the above problems. Summary of the Invention

[0005] To overcome the above problems, the present invention provides a method for manufacturing a microwave circuit board with metal edging. The technical solution adopted by the present invention to solve its technical problems is as follows: A method for manufacturing a microwave circuit board with metal edging includes the following steps: Step S1, providing a microwave circuit board that has been laminated and drilled, milling edge grooves at the locations where metal edging is required on the board edge, with the inner sidewall of the edge groove corresponding to the board edge requiring metal edging; Step S2, depositing copper on the entire microwave circuit board after Step S1, forming copper films on the inner walls of the drilled holes, the copper layer, and the board edge requiring metal edging; Step S3, applying a dry film to the entire microwave circuit board after Step S2, with windows in the dry film exposing the pattern lines and the board edge requiring metal edging; Step S4, performing pattern electroplating on the microwave circuit board after Step S3, adding copper plating to the exposed pattern lines and the board edge requiring metal edging, followed by plating a tin protective layer; then removing the dry film to expose the area to be etched without the tin protective layer; Step S5, performing alkaline etching on the microwave circuit board after Step S4 to etch away the copper layer in the area to be etched on the microwave circuit board, exposing the resistive film layer under the copper layer, and then removing the... The circuit board has a tin protective layer. Step S6 involves performing an oxidation activation treatment on the exposed resistive film layer on the microwave circuit board after step S5, followed by removal of the oxidation-activated resistive film layer using a chemical solution. Step S7 involves applying solder resist ink to the microwave circuit board after step S6 for the first time, opening windows to expose the gold-plated pads, resistor module area, and gold-plated leads, and then mechanically grinding the board. Step S8 involves applying a resist coating to the microwave circuit board after step S7, covering the resistor module area and gold-plated leads with the resist coating. A surface treatment layer is then applied to the gold-plated pads using electroplating, followed by removal of the resist coating to expose the resistor module area and gold-plated leads. Step S9 involves removing the copper and gold-plated leads on the resistor module area using an alkaline etching solution, exposing the resistor strips and the resistive film layer under the gold-plated leads. The resistive film layer under the gold-plated leads is then removed. Step S10 involves applying solder resist ink to the microwave circuit board after step S9 for the second time, with the solder resist ink only covering the resistor strips. The circuit then proceeds to the next process.

[0006] Furthermore, in step S1, the microwave circuit board is contained within a large board, which contains at least one microwave circuit board, and positioning holes are provided at the four corners of the large board.

[0007] Furthermore, in step S3, the width of the window opening on the plate edge is equal to 0.2mm.

[0008] Furthermore, between steps S4 and S5, a machining process is also included: for positions where the distance between the patterned circuit and the board edge is less than or equal to 0.2 mm, the tin protective layer at the connection position between the board edge and the patterned circuit is destroyed by a milling cutter, exposing the copper at the connection position, so that the copper at the connection position between the patterned circuit and the board edge can be etched away during alkaline etching in step S5.

[0009] Furthermore, in step S6, the entire microwave circuit board after step S5 is immersed in a potassium permanganate solution to perform an oxidation activation treatment on the exposed resistive film layer, and then dried with hot air.

[0010] Furthermore, in step S6, the entire microwave circuit board after the oxidation activation treatment is placed in a copper sulfate solution to etch and remove the resistive film layer after the oxidation activation treatment.

[0011] Furthermore, in step S8, the surface treatment layer is a gold layer, a silver layer, or a tin layer.

[0012] Furthermore, in step S9, the resistive film layer under the gold-plated lead is removed by laser.

[0013] The beneficial effects of this invention are: The present invention provides a method for manufacturing a microwave circuit board with metal edging. This method uses an alkaline etching process to create the patterned circuitry, meeting the manufacturing process requirements for metal edging. For the resistive film layer, it is first activated by oxidation with a chemical solution, and then the unwanted resistive film layer is removed with the same solution. This separates the etching of the patterned circuitry from the etching of the resistive film layer. Furthermore, the activated resistive film layer is easier to remove, ensuring that even microwave circuit boards with thick copper surfaces and dense circuitry can have their resistive film layer cleanly etched. In addition, the resistive strips in this method are exposed after surface treatment, and the normal mechanical grinding performed before surface treatment does not degrade the quality of the surface treatment. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 This is a top view of the large slab; Figure 2 This is a schematic diagram of a microwave circuit board stack-up; Figure 3 This is a schematic diagram of the microwave circuit board after step S6. Figure 4 This is a schematic diagram of the resistor strips after they have been fabricated on a microwave circuit board. Figure 5 This is a schematic diagram of the traditional microwave circuit board manufacturing process.

[0015] Drawing number markings: 100, large board; 101, edge groove; 102, board edge; 103, copper layer; 104, graphic circuit; 105, resistive film layer; 106, resistor strip; 107, positioning hole. Detailed Implementation

[0016] See Figure 5In the traditional microwave circuit board manufacturing method, the first step is to apply a photosensitive film to the microwave circuit board. The second step is to expose and develop the film to be etched, revealing the copper surface to be etched. The third step is to remove the copper surface to be etched by acid etching to form the pattern circuit. The fourth step is to continue etching away the resistive film layer under the copper surface to be etched. The fifth step is to remove all the photosensitive film applied in the first step. The sixth step is to apply a dry film to the microwave circuit board a second time and expose the resistive module area located on the pattern circuit by exposure and development. The seventh step is to etch away the copper layer on the resistive module area by alkaline etching (the resistive film layer is etched by acid etching solution but not by alkaline etching solution). The exposed resistive film layer is the resistor strip. After that, all the dry film applied in the second step is removed, the resistor strip is made, and then subsequent processes such as gold plating surface treatment are performed.

[0017] Traditional methods for manufacturing microwave circuit boards have three main problems. First, because the resistive film layer is etched away along with the copper layer during acid etching—etching away the upper copper layer first and then the lower resistive film layer—the etching depth is very large, especially when there are densely packed circuit patterns or thick copper layers. The acid etching solution cannot completely etch away the bottom resistive film layer, resulting in incomplete etching. Second, when customers require metal edging for microwave circuit boards, acid etching cannot be used. There is an industry consensus that metal-edged circuit boards can only be manufactured using alkaline etching. This creates a conflict between the above-mentioned processes and customer requirements, making it impossible to manufacture metal-edged microwave circuit boards. Finally, the traditional process involves surface treatment after the resistive strips are fabricated. Before surface treatment, the copper surface needs to be mechanically ground to clean it and improve the adhesion of the surface treatment. However, once the resistive strips are exposed, mechanical grinding would damage them, making mechanical grinding impossible and forcing direct surface treatment, which reduces the quality of the surface treatment. Therefore, this invention develops a method for manufacturing microwave circuit boards with metal edging to solve these problems.

[0018] To better understand the purpose, structure, and function of this invention, the following detailed description of specific embodiments of the invention, "A method for manufacturing a microwave circuit board with metal edging," is provided in conjunction with the accompanying drawings.

[0019] In this embodiment, the method for manufacturing a microwave circuit board with metal edging includes the following steps: Step S1, provide a block as follows Figure 2 The microwave circuit board shown has undergone lamination and drilling. A milling process is used to mill edge grooves 101 into the areas of the board edge 102 where metal edging is required. Figure 1 As shown, the inner sidewall of the side groove 101 corresponds to the plate edge 102 that needs to be metal-edged, exposing the plate edge 102, so that subsequent processes such as copper plating can be applied to the plate edge 102. Step S2 involves depositing copper onto the entire microwave circuit board that has passed through step S1, forming a copper film on the inner wall of the drilled holes, the copper layer 103, and the metal-clad edge 102 of the board, providing a substrate for subsequent copper plating and preventing the inability to plating copper. Step S3: Apply dry film to the entire microwave circuit board after step S2, and expose the patterned circuit 104 and the board edge 102 that needs to be metal-clad by opening windows on the dry film through exposure and development, in preparation for subsequent pattern electroplating. Step S4: Perform pattern electroplating on the microwave circuit board after step S3. Copper is plated on the patterned lines 104 exposed by the opening of the dry film and the board edge 102 that requires metal edging, and then a tin protective layer is plated on. The copper layer 103 is plated to the thickness required by the customer. Areas covered by the dry film will not be plated with copper and tin protective layers. Afterwards, all dry film is removed by the film stripping process. The areas where the dry film is removed are exposed to the area to be etched without the tin protective layer. The area to be etched is the copper layer 103 without copper plating. Step S5: Alkaline etching is performed on the microwave circuit board after step S4. The alkaline etching solution will etch away the copper layer 103 in the area to be etched on the microwave circuit board. The alkaline etching solution will not react with the resistive film layer 105, nor will it etch away the copper on the patterned circuit 104 and the board edge 102 covered by the tin protective layer. The resistive film layer 105 under the copper layer 103 in the area to be etched is exposed, which prepares the resistive film layer 105 for subsequent processing. Then all the tin protective layers are removed. Step S6: The exposed resistive film layer 105 on the microwave circuit board after step S5 is subjected to an oxidation activation treatment. Then, the oxidation-activated resistive film layer 105 is removed using a low-acid solution to obtain the desired result. Figure 3 The microwave circuit board shown; Step S7: Apply solder resist ink to the microwave circuit board after step S6 for the first time. After exposure and development, open the window to expose the corresponding gold-plated pads, resistor module area, and gold-plated leads on the microwave circuit board. The gold-plated pads are the pads that need to be surface treated later. The resistor block area corresponds to the area on the graphic circuit 104 where the resistor strip 106 needs to be exposed. At this time, it is also covered with a copper layer 103. The gold-plated leads are the parts that were originally designed to serve as power conductors for the independent gold-plated pads. After the window is opened, the entire board is mechanically ground. Since other areas are covered with solder resist ink, the mechanical grinding is mainly aimed at the gold-plated pads to clean and roughen them, preparing them for subsequent surface treatment. The mechanical grinding has no effect on the resistor module area covered with the copper layer 103 and the gold-plated leads that are already made of copper. Step S8: Apply an anti-plating film to the microwave circuit board after step S7. The anti-plating film covers the resistor module area and gold-plated leads to prevent them from being coated with a surface treatment layer during subsequent electroplating surface treatment. The surface treatment layer is then applied to the gold-plated pads through electroplating surface treatment. After that, the anti-plating film is removed to expose the resistor module area and gold-plated leads. Step S9: Remove the copper and gold-plated leads on the resistor module area using an alkaline etching solution, exposing the resistor strip 106 and the resistive film layer under the gold-plated leads; then remove the resistive film layer under the gold-plated leads to obtain the following... Figure 4 The microwave circuit board shown (solder resist layer not shown); In step S10, the microwave circuit board that has passed step S9 is printed with solder resist ink for the second time. The solder resist ink only covers the resistor strip 106; then it proceeds to the next process.

[0020] It should be noted that the method for manufacturing a microwave circuit board with metal edging of the present invention uses an alkaline etching process to create the patterned circuits, which meets the manufacturing process requirements of metal edging. For the resistive film layer 105, it is first oxidized and activated by a chemical solution, and then the unwanted resistive film layer 105 is removed by a low-acid chemical solution. In this way, the etching of the patterned circuit 104 and the etching of the resistive film layer 105 are separated, and the resistive film layer 105 is easier to remove after oxidation and activation. Thus, even for microwave circuit boards with thick copper surfaces and dense circuit designs, the resistive film layer 105 can be etched cleanly. Furthermore, the resistor strip 106 in this method is exposed after the surface treatment is completed. Normal mechanical grinding is performed before the surface treatment, which will not reduce the quality of the surface treatment.

[0021] See further Figure 1 In this embodiment, in step S1, the microwave circuit board is contained within the large board 100, and the large board 100 contains at least one microwave circuit board panel. Positioning holes 107 are provided at the four corners of the large board 100 for positioning the microwave circuit board in each process.

[0022] More specifically, in this embodiment, the window width of the board edge 102 in step S3 is equal to 0.2mm, ensuring that the board edge 102 is fully exposed, preparing for subsequent pattern electroplating; between steps S4 and S5, a mechanical processing process is also included: at the position where the pattern line 104 is less than or equal to 0.2mm from the board edge 102, the tin protective layer at the connection position between the board edge 102 and the pattern line 104 is destroyed by a milling cutter, exposing the copper at the connection position, so that the copper at the connection position between the pattern line 104 and the board edge 102 is etched away during alkaline etching in step S5, preventing a short circuit between the pattern line 104 and the board edge 102.

[0023] Furthermore, in this embodiment, in step S6, the entire microwave circuit board after step S5 is placed in a potassium permanganate solution to perform an oxidation activation treatment on the exposed resistive film layer 105, and then dried with hot air; in step S6, the entire microwave circuit board after the oxidation activation treatment is placed in a copper sulfate solution to etch and remove the oxidized resistive film layer 105. The copper sulfate solution can react with the oxidized resistive film layer 105 after the potassium permanganate solution oxidation activation treatment, and will not affect the pattern circuit 104, making it a good etching solution for the resistive film layer 105.

[0024] It should also be noted that the surface treatment layer in step S8 is an electroplated gold, silver, or tin layer; in step S9, the resistive film layer under the gold-plated lead is removed by laser. The resistive film layer under the gold-plated lead is very thin and small in area, and laser can be used to remove it precisely at specific points and in specific quantities.

[0025] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this application, "multiple" and "several" are understood as "at least two." "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. A connected to B can represent: A and B directly connected, and A and B connected through C. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

Claims

1. A method for manufacturing a microwave circuit board with metal edging, characterized in that, Includes the following steps: Step S1: Provide a microwave circuit board that has been pressed and drilled, and mill a groove (101) at the position where the board edge (102) needs to be metal-edged. The inner sidewall of the groove (101) corresponds to the board edge (102) that needs to be metal-edged. Step S2: The entire microwave circuit board that has passed step S1 is plated with copper, and a copper film is formed on the inner wall of the drilled hole, the copper layer (103), and the metal edge of the board (102). Step S3: Apply dry film to the entire microwave circuit board after step S2, and open the dry film to expose the pattern circuit (104) and the board edge (102) that needs to be metal-edged. Step S4: Perform pattern electroplating on the microwave circuit board after step S3. Add copper plating to the exposed pattern lines (104) and the board edge (102) that needs metal edging, and then plate a tin protective layer. After that, remove the dry film to expose the area to be etched that is not covered by the tin protective layer. Step S5: Alkaline etching is performed on the microwave circuit board after step S4 to etch away the copper layer (103) in the area to be etched on the microwave circuit board, exposing the resistive film layer (105) under the copper layer (103), and then all tin protective layers are removed. Step S6: The exposed resistive film layer (105) on the microwave circuit board after step S5 is subjected to oxidation activation treatment, and then the oxidized resistive film layer (105) is removed by chemical solution. Step S7: Apply solder resist ink to the microwave circuit board after step S6 for the first time, open windows to expose the gold-plated pads, resistor module area and gold-plated leads, and perform mechanical grinding. Step S8: Apply an anti-plating film to the microwave circuit board after step S7, covering the resistor module area and gold-plated leads with the anti-plating film; apply a surface treatment layer to the gold-plated pads through electroplating surface treatment, and then remove the anti-plating film to expose the resistor module area and gold-plated leads. Step S9: Remove the copper and gold-plated leads on the resistor module area using alkaline etching solution to expose the resistor strip (106) and the resistive film layer under the gold-plated leads; then remove the resistive film layer under the gold-plated leads. Step S10: Apply solder resist ink a second time to the microwave circuit board after step S9. The solder resist ink only covers the resistor strip (106); then proceed to the next process.

2. The method for manufacturing a microwave circuit board with metal edging according to claim 1, characterized in that, In step S1, the microwave circuit board is contained within the large board (100), the large board (100) contains at least one microwave circuit board, and positioning holes (107) are provided at the four corners of the large board (100).

3. The method for manufacturing a microwave circuit board with metal edging according to claim 2, characterized in that, In step S3, the window width of the plate edge (102) is equal to 0.2mm.

4. The method for manufacturing a microwave circuit board with metal edging according to claim 3, characterized in that, Between steps S4 and S5, a machining process is also included: for the position where the distance between the pattern line (104) and the board edge (102) is less than or equal to 0.2 mm, the tin protective layer at the connection position between the board edge (102) and the pattern line (104) is destroyed by a milling cutter to expose the copper at the connection position, so that the copper at the connection position between the pattern line (104) and the board edge (102) can be etched away during alkaline etching in step S5.

5. The method for manufacturing a microwave circuit board with metal edging according to claim 1, characterized in that, In step S6, the entire microwave circuit board after step S5 is placed in a potassium permanganate solution to perform an oxidation activation treatment on the exposed resistive film layer (105), and then dried with hot air.

6. The method for manufacturing a microwave circuit board with metal edging according to claim 5, characterized in that, In step S6, the entire microwave circuit board after oxidation activation treatment is placed in a copper sulfate solution to etch and remove the resistive film layer after oxidation activation treatment (105).

7. The method for manufacturing a microwave circuit board with metal edging according to claim 1, characterized in that, In step S8, the surface treatment layer is a gold layer, a silver layer, or a tin layer.

8. The method for manufacturing a microwave circuit board with metal edging according to claim 1, characterized in that, In step S9, the resistive film layer under the gold-plated lead is removed by laser.

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