A manufacturing method of a single-sided POFV process of a printed circuit board

Abstract

The present application relates to the technical field of printed circuit, and particularly relates to a manufacturing method of a single-sided POFV process of a printed circuit board, which comprises the following steps: drilling; first copper deposition, copper layer thickness 0.3-0.8 um; first electroplating, plating layer thickness 25-30 um; resin ink filling; first polishing; second copper deposition, copper layer thickness 0.3-0.8 um; second electroplating, flash plating, plating layer thickness 3-5 um; outer layer film covering; outer layer exposure, one side of which does not need third electroplating is pasted with transparent film, one side of which needs third electroplating is pasted with black film and exposed; outer layer development, after development, the photosensitive dry film of one side which needs third electroplating is removed; third electroplating, single-sided electroplating thickening, plating layer thickness >=15 um; film removing; second polishing, the flash plating layer and the second deposition copper layer of one side which does not need third electroplating are polished away. The method provided by the present application improves polishing efficiency, reduces the scrappage rate of the single-sided POFV product of the printed circuit board, and eliminates problems such as soldering pollution and short circuit.

Description

Technical Field

[0001] This invention relates to the field of printed circuit technology, and in particular to a method for manufacturing a single-sided POFV process for printed circuit boards. Background Technology

[0002] Printed circuit boards typically incorporate multiple vias for conductivity and heat dissipation. To shorten the distance between the pads and vias, the pads are often designed directly above the vias, creating a via-pad structure. The vias in this via-pad structure require resin plugging to create a cover via, followed by copper plating. This process makes the vias invisible on both sides of the pads; this is the double-sided POFV process. In contrast, the single-sided POFV process involves plating the vias on only one side, leaving the other side unplated. This latter process is currently rare and lacks a mature manufacturing method.

[0003] Currently, there are two main manufacturing processes:

[0004] Method 1: After using the two-sided POFV process, remove the copper coating on one side by single-sided grinding;

[0005] Method 2: After using the two-sided POFV process, the copper coating on one side is removed by single-sided etching.

[0006] For Method 1, after the via is filled with resin to form a cover hole, copper plating is performed on both sides and then electroplated to cover it. The copper plating at the cover hole is thicker, and after multiple electroplatings, the board surface is uneven. It is difficult to polish the copper plating layer on the cover hole 100% clean by single-sided grinding; the defect rate reaches 40%.

[0007] For method two, after using the two-sided POFV process, the copper cover on one side is removed by single-sided etching. There is a significant height difference at the etching position of the cover hole, which makes it impossible to achieve a smooth surface, which is difficult for customers to accept. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for manufacturing a single-sided POFV process for printed circuit boards. By optimizing the process flow, the grinding thickness of the printed circuit board is greatly reduced, the grinding efficiency is improved, and the scrap rate of single-sided POFV products of printed circuit boards is reduced. It also eliminates the problems of soldering contamination and short circuits caused by residual solder in the hole recesses covered by etching process.

[0009] This invention is achieved through the following technical solution:

[0010] A method for manufacturing a single-sided POFV printed circuit board includes the following steps:

[0011] S1: Drilling: Drilling through holes in a printed circuit board;

[0012] S2: First copper plating: Chemical copper plating is performed on the printed circuit board after drilling, with a copper layer thickness of 0.3-0.8um;

[0013] S3: First electroplating: The printed circuit board after the first copper plating is thickened by the first electroplating, with a plating thickness of 25-30um;

[0014] S4: Resin ink filling: Fill the through holes of the printed circuit board after the first electroplating with resin ink to make the through holes become covered holes;

[0015] S5: First polishing: Polish the resin ink covering the protruding openings clean and smooth.

[0016] S6: Second copper plating: The printed circuit board after the via plugging is subjected to a second copper plating, with a copper layer thickness of 0.3-0.8um;

[0017] S7: Second electroplating: Flash plating is performed on the printed circuit board after the second copper plating, with a plating thickness of 3-5um;

[0018] S8: Outer layer coating: Applying a photosensitive dry film to the outer layer of the flash-plated printed circuit board;

[0019] S9: Outer layer exposure: Apply a transparent film to the side of the printed circuit board that does not require a third electroplating after the outer layer coating, and apply a black film to the side that requires a third electroplating, and then perform exposure treatment;

[0020] S10: Outer layer development: After developing the printed circuit board after the outer layer exposure, the photosensitive dry film on the side that needs to be electroplated for the third time is removed to form a single-sided coated printed circuit board.

[0021] S11: Third electroplating: The side of the printed circuit board that needs a third electroplating after the outer layer development and single-sided film coating is thickened by single-sided electroplating, with a coating thickness ≥15um.

[0022] S12: Film Removal: Remove the photosensitive dry film from the side of the printed circuit board that does not require a third electroplating after the third electroplating.

[0023] S13: Second polishing: Polish one side of the printed circuit board after the film is removed to remove the flash plating layer and the second copper plating layer on the side that does not require a third electroplating.

[0024] The optimized printed circuit board is a double-sided or multi-layer board, which includes a surface layer and inner layers.

[0025] Furthermore, in step S9, the transparent film has black light-blocking dots on the through-holes of the printed circuit board where no cover hole is formed, and the diameter of the light-blocking dots is 0.1 mm smaller than the diameter of the through-holes where no cover hole is formed.

[0026] In the optimized step S4, a vacuum via-filling machine is used to fill the through holes of the printed circuit board with resin ink.

[0027] In the optimized version, the printed circuit board is polished using a belt abrasive grinding equipment in both steps S5 and S13.

[0028] Beneficial effects of the invention:

[0029] 1. The process flow has been optimized, reducing the final polishing copper thickness required for printed circuit boards from ≥18um to 3-5um, which greatly reduces the number of final polishing operations from the original 9-10 times to 2-3 times, thereby improving the polishing efficiency of printed circuit boards.

[0030] 2. The optimized process flow reduced the scrap rate of single-sided POFV products from 40% to 5%.

[0031] 3. The optimized process flow eliminates the issue of via depressions caused by etching, greatly improving customer satisfaction from an aesthetic perspective; from the customer's assembly and use perspective, it eliminates problems such as solder contamination and short circuits caused by residual solder at the via depression locations. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the printed circuit board structure after step S1 of the present invention.

[0033] Figure 2 This is a schematic diagram of the printed circuit board structure after step S2 of the present invention.

[0034] Figure 3 This is a schematic diagram of the printed circuit board structure after step S3 of the present invention.

[0035] Figure 4 This is a schematic diagram of the printed circuit board structure after step S4 of the present invention.

[0036] Figure 5 This is a schematic diagram of the printed circuit board structure after step S5 of the present invention.

[0037] Figure 6 This is a schematic diagram of the printed circuit board structure after step S6 of the present invention.

[0038] Figure 7 This is a schematic diagram of the printed circuit board structure after step S7 of the present invention.

[0039] Figure 8 This is a schematic diagram of the printed circuit board structure after step S8 of the present invention.

[0040] Figure 9This is a schematic diagram of the printed circuit board structure after step S9 of the present invention.

[0041] Figure 10 This is a schematic diagram of the printed circuit board structure after step S10 of the present invention.

[0042] Figure 11 This is a schematic diagram of the printed circuit board structure after the processing in step S11 of the present invention.

[0043] Figure 12 This is a schematic diagram of the printed circuit board structure after step S12 of the present invention.

[0044] Figure 13 This is a schematic diagram of the printed circuit board structure after processing in step S13 of the present invention.

[0045] In the diagram: 1. Printed circuit board, 2. Top layer, 3. Inner layer, 4. Through hole, 5. First copper plating layer, 6. First electroplating layer, 7. Resin ink, 8. Second copper plating layer, 9. Flash plating layer, 10. Photosensitive dry film, 11. Transparent film, 12. Black film, 13. Third electroplating layer. Detailed Implementation

[0046] A method for manufacturing a single-sided POFV printed circuit board includes the following steps:

[0047] S1: Drilling: Drill through holes 4 on printed circuit board 1. The schematic diagram of the printed circuit board structure after this step is attached. Figure 1 As shown;

[0048] S2: First Copper Plating: The drilled printed circuit board undergoes its first copper plating process. The first copper plating layer is 0.3-0.8µm thick. A schematic diagram of the printed circuit board structure after this step is attached. Figure 2 As shown;

[0049] S3: First Electroplating: The printed circuit board after the first copper plating is thickened by a first electroplating layer, with a thickness of 25-30µm, to achieve conductivity between the inner and outer layers. A schematic diagram of the printed circuit board structure after this step is attached. Figure 3 As shown;

[0050] S4: Resin Ink Filling. The through-holes of the printed circuit board after the first electroplating are filled with resin ink 7, making the through-holes become covered holes. A vacuum filling machine can be used to fill the through-holes of the printed circuit board with resin ink. A schematic diagram of the printed circuit board structure after this step is attached. Figure 4 As shown;

[0051] S5: First Polishing: Polish the resin ink covering the protruding holes cleanly and evenly. A belt abrasive can be used to polish the printed circuit board. The resulting printed circuit board structure diagram is shown in the attached diagram. Figure 5 As shown;

[0052] S6: Second Copper Plating: The printed circuit board after via plugging undergoes a second copper plating process. The second copper plating layer is 0.3-0.8µm thick. The schematic diagram of the printed circuit board structure after this step is attached. Figure 6 As shown;

[0053] S7: Second Electroplating: The printed circuit board after the second copper plating is flash plated, with a flash plating layer thickness of 3-5µm. A schematic diagram of the printed circuit board structure after this step is attached. Figure 7 As shown;

[0054] S8: Outer Layer Coating: A photosensitive dry film 10 is applied to the outer layer of the flash-plated printed circuit board. A schematic diagram of the printed circuit board structure after this step is attached. Figure 8 As shown;

[0055] S9: Outer Layer Exposure: A transparent film 11 is applied to the side of the printed circuit board that does not require a third electroplating after the outer layer coating, and a black film 12 is applied to the side that requires a third electroplating. Then, exposure processing is performed. A schematic diagram of the printed circuit board structure after this step is attached. Figure 9 As shown;

[0056] S10: Outer Layer Development: After developing the outer layer of the printed circuit board, the photosensitive dry film on the side requiring a third electroplating is removed to form a single-sided coated printed circuit board. A schematic diagram of the printed circuit board structure after this step is attached. Figure 10 As shown;

[0057] S11: Third Electroplating: After the outer layer development, the side of the printed circuit board that requires a third electroplating layer is thickened by single-sided electroplating. The thickness of the third electroplating layer 13 is ≥15um. The schematic diagram of the printed circuit board structure after this step is attached. Figure 11 As shown;

[0058] S12: Film Removal: Remove the photosensitive dry film from the side of the printed circuit board that does not require a third electroplating after the third electroplating. A schematic diagram of the printed circuit board structure after this step is attached. Figure 12 As shown;

[0059] S13: Second Polishing: Polish one side of the printed circuit board after the film is removed. Remove the flash plating layer and the second copper plating layer from the side that does not require a third electroplating. A belt abrasive can also be used for polishing. The resulting printed circuit board structure diagram is shown in the attached diagram. Figure 13 As shown.

[0060] The optimized printed circuit board is a double-sided or multi-layer board, which includes a surface layer 2 and an inner layer 3.

[0061] The single-sided POFV process for printed circuit boards provided by this invention involves a first copper plating and a first electroplating followed by resin plugging to form covered vias. At this stage, there are no copper or plating layers on either side of the covered vias, thus eliminating the need for polishing the first copper plating and electroplating layers. During the second copper plating, the copper layer thickness is only 0.3-0.8 μm. During the second electroplating, flash plating is performed, resulting in a plating thickness of only 3-5 μm. After double-sided photosensitive dry film coating and exposure and development, the photosensitive dry film on the side requiring a third electroplating is removed, while the photosensitive dry film on the other side is retained, forming a single-sided coated printed circuit board. Then, single-sided electroplating is performed to thicken the coating, while the other side is coated with a different coating. After single-sided electroplating is completed with a photosensitive dry film, no third electroplating layer will adhere after the photosensitive dry film is removed. Therefore, the final copper layer thickness requiring polishing is only 3-5 μm (the thickness of the flash plating layer) and 0.3-0.8 μm (the thickness of the second copper plating layer). Compared to existing two-sided POFV processes that require single-sided grinding to remove one side of the copper coating, or two-sided POFV processes that require single-sided etching to remove one side of the copper coating, the method provided by this invention significantly reduces the polishing thickness. This is because the existing two-sided POFV process requires polishing away the second electroplating layer, and the second electroplating layer in the two existing methods is at least 18 μm thick. The thickness that needs to be ground away in this invention is only about 3-5µm, thus reducing the number of final grinding operations from 9-10 to 2-3, thereby improving the grinding efficiency of printed circuit boards. Furthermore, it avoids the problems of existing methods where double-sided copper plating and subsequent electroplating result in thicker copper plating at the cover holes, leading to uneven board surfaces after multiple electroplating operations, and making it difficult to completely remove the copper plating layer on the cover holes with single-sided grinding. It also avoids the problem of significant height differences at the etched cover hole positions in existing methods where a smooth surface cannot be achieved. This reduces the scrap rate of single-sided POFV process products from 40% to 5%. Simultaneously, it eliminates the through-hole depression problem caused by the etching process, greatly improving customer satisfaction from an aesthetic perspective. From the customer's assembly and use perspective, it eliminates problems such as solder contamination and short circuits caused by residual solder at the through-hole depression positions.

[0062] Furthermore, in step S9, the transparent film has black light-blocking dots on the areas of the printed circuit board where there are other unfilled vias, and the diameter of the light-blocking dots is 0.1mm smaller than the diameter of the unfilled vias. This allows the other unfilled vias to be transparent, avoiding the problem of insufficient washing of the electroplating solution or water after electroplating and contamination of the board surface due to the photosensitive dry film covering only one side.

[0063] In summary, the method for manufacturing a single-sided POFV printed circuit board proposed in this invention greatly reduces the grinding thickness of the printed circuit board and improves the grinding efficiency by optimizing the process flow. It also reduces the scrap rate of single-sided POFV printed circuit board products and eliminates problems such as soldering contamination and short circuits caused by residual solder in the hole recesses covered by etching processes.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing a single-sided POFV printed circuit board, characterized in that: Includes the following steps: S1: Drilling: Drilling through holes in a printed circuit board; S2: First copper plating: Chemical copper plating is performed on the printed circuit board after drilling, with a copper layer thickness of 0.3-0.8um; S3: First electroplating: The printed circuit board after the first copper plating is thickened by the first electroplating, with a plating thickness of 25-30um; S4: Resin ink filling: Fill the through holes of the printed circuit board after the first electroplating with resin ink to make the through holes become covered holes; S5: First polishing: Polish the resin ink covering the protruding openings clean and smooth. S6: Second copper plating: The printed circuit board after the via plugging is subjected to a second chemical copper plating, with a copper layer thickness of 0.3-0.8um; S7: Second electroplating: Flash plating is performed on the printed circuit board after the second copper plating, with a plating thickness of 3-5um; S8: Outer layer coating: Applying a photosensitive dry film to the outer layer of the flash-plated printed circuit board; S9: Outer layer exposure: Apply a transparent film to the side of the printed circuit board that does not require a third electroplating after the outer layer coating, and apply a black film to the side that requires a third electroplating, and then perform exposure treatment; S10: Outer layer development: After developing the printed circuit board after the outer layer exposure, the photosensitive dry film on the side that needs to be electroplated for the third time is removed to form a single-sided coated printed circuit board. S11: Third electroplating: The side of the printed circuit board that needs a third electroplating after the outer layer development and single-sided film coating is thickened by single-sided electroplating, with a coating thickness ≥15um. S12: Film Removal: Remove the photosensitive dry film from the side of the printed circuit board that does not require a third electroplating after the third electroplating. S13: Second polishing: Polish one side of the printed circuit board after the film is removed to remove the flash plating layer and the second copper plating layer on the side that does not require a third electroplating.

2. The method for manufacturing a single-sided POFV printed circuit board according to claim 1, characterized in that: The printed circuit board is a double-sided or multi-layer board, and the printed circuit board includes a surface layer and an inner layer.

3. The method for manufacturing a single-sided POFV printed circuit board according to claim 1, characterized in that: In step S9, the transparent film has black light-blocking dots on the areas of the printed circuit board where there are other unfilled through holes, and the diameter of the light-blocking dots is 0.1 mm smaller than the diameter of the unfilled through holes.

4. The method for manufacturing a single-sided POFV printed circuit board according to claim 1, characterized in that: In step S4, a vacuum hole-filling machine is used to fill the through holes of the printed circuit board with resin ink.

5. The method for manufacturing a single-sided POFV printed circuit board according to claim 1, characterized in that: In both steps S5 and S13, the printed circuit board is polished using a belt abrasive grinding equipment.

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