A double-sided PCB board and its preparation method

Abstract

This invention discloses a method for preparing a double-sided PCB board, comprising the following key steps: (1) drilling holes in the double-sided copper-clad laminate to form trapezoidal conical holes, with the side corresponding to the larger hole diameter being the A side of the double-sided copper-clad laminate and the side corresponding to the smaller hole diameter being the B side; (2) metallizing the trapezoidal conical holes; (3) inkjet printing anti-etching mask ink on the A side, with the printing area being the circuit area and the inner wall area of ​​the trapezoidal conical hole, ensuring that the edge of the A side hole and the inner wall area of ​​the trapezoidal conical hole are completely covered by the anti-etching mask ink; (4) inkjet printing anti-etching mask ink on the B side, with the printing area being the circuit area, ensuring that the edge of the B side hole and the inner wall of the trapezoidal conical hole form a continuous coverage; (5) performing chemical etching; and (6) removing the mask. The technical solution of this invention can combine the circuit protection and hole protection processes into one, reducing the process flow, compressing the hole protection construction time, and significantly improving the production efficiency of double-sided boards.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, specifically to a technology for preparing double-sided PCBs based on inkjet printing of anti-etch mask ink. Background Technology

[0002] A double-sided PCB is a printed circuit board with copper plating on both sides, including the top and bottom layers. Both sides can be used for wiring and soldering, with an insulating layer in between. It is a commonly used type of printed circuit board in the electronics industry. Because traces can be routed on both sides, the area of ​​a double-sided board is twice that of a single-sided board. Furthermore, double-sided boards solve the problem of cross-wiring in single-sided boards (through holes to the other side), making them more suitable for more complex circuits.

[0003] Double-sided PCBs have wiring on both sides. To utilize the conductors on both sides, there must be a circuit connection between the two sides. This "bridge" connecting the top and bottom circuits of a double-sided PCB is called a via or via. The via metallization process involves forming a layer of metal on the inner wall of the via to connect the printed conductors on the top and bottom layers.

[0004] Currently, via metallization mainly employs chemical copper plating or electroplating processes. After the double-sided copper-clad laminate has undergone via metallization, the vias need to be protected before etching can proceed on both sides. If the vias are not protected, the copper layer formed on the via walls will be etched away during the etching process.

[0005] There are various methods for via protection. A common method is to fill the via with a via filler to protect the copper layer formed on the inner wall of the via. Dry film masking is another method, using a dry film to seal both ends of the via, preventing etching solutions from entering the via. Currently, via protection is a separate process step requiring specialized equipment.

[0006] In the process of researching and practicing this method, the inventors of this invention developed a method for preparing double-sided PCB boards using inkjet printing of anti-etch mask ink and via protection. Summary of the Invention

[0007] This invention provides a method for manufacturing double-sided PCBs that combines circuit protection and via protection into one process, reducing process steps, improving production efficiency, and lowering production costs.

[0008] A method for preparing a double-sided PCB board according to the present invention includes the following steps: (1) drilling holes in the double-sided copper-clad board to drill trapezoidal conical holes, with the side corresponding to the larger hole diameter being the A side of the double-sided copper-clad board and the side corresponding to the smaller hole diameter being the B side of the double-sided copper-clad board; (2) metallizing the trapezoidal conical holes; (3) inkjet printing anti-etching mask ink on the A side, with the printing area being the circuit area and the inner wall area of ​​the trapezoidal conical hole, and ensuring that the edge of the A side hole and the inner wall area of ​​the trapezoidal conical hole are completely covered by the anti-etching mask ink; (4) inkjet printing anti-etching mask ink on the B side, with the printing area being the circuit area, and ensuring that the edge of the B side hole and the inner wall of the trapezoidal conical hole form a continuous coverage; (5) chemical etching using etching solution; (6) removing the film.

[0009] The double-sided PCB board described in step (1) above has a three-layer structure: copper foil conductive layer - insulating layer - copper foil conductive layer. The double-sided PCB board is a rigid board with a thickness ≥ 0.5 mm.

[0010] The trapezoidal conical hole described in step (1) above is different from the traditional cylindrical hole. It forms a circular hole with different diameters on both sides. The radius of hole A is R1 and the radius of hole B is R2, and R1≥1.2 ×R2, preferably R1≥2×R2.

[0011] The metallization described in step (2) above includes pretreatment processes such as deburring and cleaning of the trapezoidal conical hole according to traditional processes, followed by metallization of the hole through electrochemical deposition, and electroplating can be performed as needed to thicken the hole.

[0012] The anti-etching mask ink described in steps (3) and (4) above forms a protective layer after being inkjet printed on the surface of the copper-clad laminate and cured. The area covered by the cured ink can protect the copper foil from the effects of the etching solution. The copper foil in the uncovered area reacts chemically with the etching solution, and then the copper is transformed from a metallic element into copper ions and dissolved in the etching solution.

[0013] The circuit area mentioned in steps (3) and (4) above is the circuit wiring area of ​​the circuit board. The circuit parts that need to be retained on both sides of the copper-clad board are covered and protected by printing anti-etching mask ink.

[0014] The trapezoidal conical hole inner wall region described in steps (3) and (4) above is fully covered by inkjet-printed anti-etch mask ink. The inkjet-printed inner wall portion forms a continuous, defect-free coverage connection with the inkjet-printed hole edge portion in the circuit area. The inkjet printing preferably uses a piezoelectric printhead. The piezoelectric printhead includes a piezoelectric crystal; the piezoelectric crystal receives pulse signals, deforms to generate instantaneous pressure, thereby squeezing the inner ink cartridge to eject a drop of anti-etch mask ink, forming an ink dot on the copper-clad laminate.

[0015] The chemical etching described in step (5) above involves a chemical reaction between the etching solution and the copper foil, which converts the elemental copper into copper ions that dissolve in the etching solution.

[0016] The removal of the film in step (6) above refers to the removal of the cured resist mask ink by chemical or physical methods, including the removal of the cured resist mask ink covering the circuit area and the cured resist mask ink covering the inner wall of the trapezoidal conical hole.

[0017] A double-sided PCB board prepared according to any of the above methods.

[0018] The technical solution of this invention combines inkjet printing of resist mask ink to form circuit patterns and via protection into one process. The inkjet-printed pattern covers both the circuit pattern area and the inner wall area of ​​the via. However, due to the vertical spraying of ink droplets, traditional cylindrical vias (with the same inner diameter at both ends of the via) cannot retain ink and are difficult to print onto the inner wall surface. Therefore, the inventors of this invention prepare the vias as trapezoidal conical vias, allowing ink droplets to adhere to the inclined inner wall as they fall vertically. This technical solution of the invention completes via protection simultaneously during the process of patterning the resist mask, combining circuit protection and via protection into one process. This reduces the process flow, shortens the via protection construction time, significantly improves the production efficiency of double-sided boards, and reduces the production cost of double-sided PCBs.

[0019] The beneficial effects of this invention are as follows: Since this invention combines circuit protection and hole protection processes into one, it reduces the process flow, shortens the hole protection construction time, significantly improves the production efficiency of double-sided boards, and reduces the production cost of double-sided PCB boards. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 It is the double-sided copper-clad laminate used in Example 1;

[0022] Figure 2 A trapezoidal conical hole is drilled on the double-sided copper-clad board of Example 1;

[0023] Figure 3 The trapezoidal conical hole in Example 1 is metallized;

[0024] Figure 4 The etching-resistant mask ink is printed on the A side of the double-sided copper-clad laminate in Example 1;

[0025] Figure 5 The etching-resistant mask ink is printed on the B side of the double-sided copper-clad laminate in Example 1.

[0026] Figure 6 This is the pattern etched on side A of the double-sided copper-clad laminate in Example 1;

[0027] Figure 7 This is the pattern etched on side B of the double-sided copper-clad laminate in Example 1;

[0028] Figure 8 This is the removal of the film from side A of the double-sided copper-clad laminate in Example 1;

[0029] Figure 9 This is the B-side film removal of the double-sided copper-clad laminate in Example 1. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention provides a method for manufacturing double-sided PCBs, which can reduce the process flow, shorten the construction time for hole protection, significantly improve the production efficiency of double-sided PCBs, and reduce the production cost of double-sided PCBs. Detailed descriptions follow.

[0032] Example 1

[0033] A method for preparing a double-sided PCB board includes the following steps: (1) Drilling holes in the double-sided copper-clad board to drill trapezoidal conical holes, with the side corresponding to the larger hole diameter being the A side of the double-sided copper-clad board and the side corresponding to the smaller hole diameter being the B side of the double-sided copper-clad board. Figure 1 This is the double-sided copper-clad laminate used in Example 1. The double-sided PCB has a three-layer structure: copper foil conductive layer - insulating layer - copper foil conductive layer. The double-sided PCB is a rigid board with a thickness of 0.5mm. Figure 2 A trapezoidal conical hole is drilled on the double-sided copper-clad board of Example 1. Unlike traditional cylindrical holes, the trapezoidal conical hole has different diameters on both sides. The radius of hole A is R1, and the radius of hole B is R2, where R1 = 1.2 × R2.

[0034] (2) Metallize the trapezoidal conical hole. Figure 3 The trapezoidal conical hole in Example 1 is metallized. The trapezoidal conical hole is pretreated by traditional processes such as deburring and cleaning, and then metallized by electrochemical deposition, followed by electroplating for thickening.

[0035] (3) Print anti-etch mask ink on surface A. The printing area is the line area and the inner wall area of ​​the trapezoidal conical hole. Ensure that the edge of surface A and the inner wall area of ​​the trapezoidal conical hole are completely covered with anti-etch mask ink. Figure 4 The etching mask ink is printed on the A side of the double-sided copper-clad board in Example 1.

[0036] (4) Print anti-etch mask ink on side B, the printing area is the line area, and ensure that the edge of the B-face is continuously covered with the inner wall of the trapezoidal conical hole; Figure 5 The etching mask ink is printed on the B side of the double-sided copper-clad laminate in Example 1.

[0037] After the anti-etching mask ink from steps (3) and (4) is inkjet printed on the surface of the copper-clad laminate and cured, it forms a protective layer. The area covered by the cured layer can protect the copper foil from the effects of the etching solution. The copper foil in the uncovered area reacts chemically with the etching solution, and then the copper changes from a metallic element to copper ions and dissolves in the etching solution.

[0038] The circuit area mentioned in steps (3) and (4) is the circuit wiring area of ​​the circuit board. The circuit parts that need to be retained on both sides of the copper-clad board are covered and protected by printing anti-etching mask ink.

[0039] In steps (3) and (4), the inner wall area of ​​the trapezoidal conical hole is fully covered by inkjet-printed anti-etch mask ink. The inkjet-printed inner wall area forms a continuous, defect-free coverage connection with the inkjet-printed hole edge area in the circuit area. The anti-etch mask ink is used to create circuit patterns on the surface of the double-sided copper-clad laminate by inkjet printing. The printing is performed on the surface of the double-sided copper-clad laminate using an inkjet printer, followed by UV curing. Inkjet printing conditions: film thickness: 0.3um; piezoelectric printhead, printhead temperature 25℃; UV curing conditions: UV exposure energy: 800mj / cm 2 .

[0040] (5) Chemical etching is performed using an etching solution. The etching solution is an aqueous solution of ferric chloride and hydrochloric acid. The etching solution reacts chemically with the copper foil, converting the elemental copper into copper ions that dissolve into the etching solution. Figure 6 This is the pattern etched on side A of the double-sided copper-clad laminate in Example 1. Figure 7 This is the pattern after etching on side B of the double-sided copper-clad laminate in Example 1. The copper on both sides of the double-sided copper-clad laminate that was not covered by the anti-etching ink was removed by the etching solution.

[0041] (6) Demolding. Figure 8 This is the removal of the film from side A of the double-sided copper-clad laminate in Example 1. Figure 9This is the B-side stripping of the double-sided copper-clad laminate in Example 1. The cured resist mask ink is removed by immersion in an alkaline solution, including removing the cured resist mask ink covering the circuit areas and the cured resist mask ink covering the inner wall of the trapezoidal conical hole, to obtain a double-sided copper circuit board.

[0042] Example 2

[0043] A method for preparing a double-sided PCB board includes the following steps: (1) Drilling holes in the double-sided copper-clad laminate to form trapezoidal conical holes. The side with the larger hole diameter is the A side of the double-sided copper-clad laminate, and the side with the smaller hole diameter is the B side of the double-sided copper-clad laminate. The double-sided PCB board has a three-layer structure: copper foil conductive layer - insulating layer - copper foil conductive layer. The double-sided PCB board is a rigid board with a thickness of 1.2 mm. The trapezoidal conical holes are different from traditional cylindrical holes, forming circular holes with different diameters on both sides. The radius of the hole on the A side is R1, and the radius of the hole on the B side is R2, and R1 = 1.65 × R2.

[0044] (2) Metallize the trapezoidal conical hole, including pretreatment processes such as deburring and cleaning of the trapezoidal conical hole according to traditional processes, and then metallize the hole by electrochemical deposition.

[0045] (3) Print anti-etch mask ink on surface A, the printing area is the line area and the inner wall area of ​​the trapezoidal conical hole, and ensure that the edge of the surface A and the inner wall area of ​​the trapezoidal conical hole are completely covered by anti-etch mask ink; (4) Print anti-etch mask ink on surface B, the printing area is the line area, and ensure that the edge of the surface B and the inner wall of the trapezoidal conical hole form a continuous coverage.

[0046] After the anti-etching mask ink from steps (3) and (4) is inkjet printed on the surface of the copper-clad laminate and cured, it forms a protective layer. The area covered by the cured layer can protect the copper foil from the effects of the etching solution. The copper foil in the uncovered area reacts chemically with the etching solution, and then the copper changes from a metallic element to copper ions and dissolves in the etching solution.

[0047] The circuit area mentioned in steps (3) and (4) is the circuit wiring area of ​​the circuit board. The circuit parts that need to be retained on both sides of the copper-clad board are covered and protected by printing anti-etching mask ink.

[0048] In steps (3) and (4), the inner wall area of ​​the trapezoidal conical hole is fully covered by inkjet-printed anti-etch mask ink. The inkjet-printed inner wall area forms a continuous, defect-free coverage connection with the inkjet-printed hole edge area in the circuit area. The anti-etch mask ink is used to create circuit patterns on the surface of the double-sided copper-clad laminate by inkjet printing. The printing is performed on the surface of the double-sided copper-clad laminate using an inkjet printer, followed by UV curing. Inkjet printing conditions: film thickness: 0.5um; piezoelectric printhead, printhead temperature 35℃; UV curing conditions: UV exposure energy: 1100mj / cm 2 .

[0049] (5) Chemical etching is performed using an etching solution; the etching solution is an aqueous solution of ferric chloride and hydrochloric acid. The etching solution reacts chemically with the copper foil to convert elemental copper into copper ions which dissolve into the etching solution.

[0050] (6) Removal of the film: The cured resist mask ink is removed by immersion in an alkaline solution, including removing the cured resist mask ink covering the circuit area and the cured resist mask ink covering the inner wall of the trapezoidal conical hole, to obtain a double-sided copper circuit board.

[0051] Example 3

[0052] A method for preparing a double-sided PCB board includes the following steps: (1) Drilling holes in the double-sided copper-clad laminate to form trapezoidal conical holes. The side with the larger hole diameter is the A side of the double-sided copper-clad laminate, and the side with the smaller hole diameter is the B side of the double-sided copper-clad laminate. The double-sided PCB board has a three-layer structure: copper foil conductive layer - insulating layer - copper foil conductive layer. The double-sided PCB board is a rigid board with a thickness of 2.4 mm. The trapezoidal conical holes are different from traditional cylindrical holes, forming circular holes with different diameters on both sides. The radius of the hole on the A side is R1, and the radius of the hole on the B side is R2, and R1 = 2.2 × R2.

[0053] (2) Metallize the trapezoidal conical hole, including pretreatment processes such as deburring and cleaning of the trapezoidal conical hole according to traditional processes, then metallize the hole by electrochemical deposition, and then perform electroplating to thicken it;

[0054] (3) Print anti-etch mask ink on surface A, the printing area is the line area and the inner wall area of ​​the trapezoidal conical hole, and ensure that the edge of the surface A and the inner wall area of ​​the trapezoidal conical hole are completely covered by anti-etch mask ink; (4) Print anti-etch mask ink on surface B, the printing area is the line area, and ensure that the edge of the surface B and the inner wall of the trapezoidal conical hole form a continuous coverage.

[0055] After the anti-etching mask ink from steps (3) and (4) is inkjet printed on the surface of the copper-clad laminate and cured, it forms a protective layer. The area covered by the cured layer can protect the copper foil from the effects of the etching solution. The copper foil in the uncovered area reacts chemically with the etching solution, and then the copper changes from a metallic element to copper ions and dissolves in the etching solution.

[0056] The circuit area mentioned in steps (3) and (4) is the circuit wiring area of ​​the circuit board. The circuit parts that need to be retained on both sides of the copper-clad board are covered and protected by printing anti-etching mask ink.

[0057] The trapezoidal conical hole inner wall area described in steps (3) and (4) is fully covered by inkjet-printed anti-etch mask ink. The inkjet-printed inner wall portion forms a continuous, defect-free coverage connection with the inkjet-printed hole edge portion of the circuit area.

[0058] (5) Chemical etching is performed using an etching solution; the etching solution is an aqueous solution of ferric chloride and hydrochloric acid. The etching solution reacts chemically with the copper foil to convert elemental copper into copper ions which dissolve into the etching solution.

[0059] (6) Removal of the film: The cured resist mask ink is removed by immersion in sodium hydroxide solution, including the removal of the cured resist mask ink covering the circuit area and the cured resist mask ink covering the inner wall of the trapezoidal conical hole, to obtain a double-sided copper circuit board.

[0060] The above provides a detailed description of a method for preparing a double-sided PCB board according to embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this embodiment should not be construed as a limitation of the present invention.

Claims

1. A method of manufacturing a double-sided PCB board, characterized by, It comprises the following steps: (1) drilling a double-sided copper-clad plate to form a trapezoidal conical hole, the larger hole diameter corresponding to one side of the double-sided copper-clad plate A surface, and the smaller hole diameter corresponding to one side of the double-sided copper-clad plate B surface; (2) metalizing the trapezoidal conical hole; (3) inkjet printing an etching-resistant mask ink on the A surface, the printing area being a circuit area and a trapezoidal conical hole inner wall area, and ensuring that the A surface hole edge and the trapezoidal conical hole inner wall area are entirely printed with the etching-resistant mask ink; (4) inkjet printing an etching-resistant mask ink on the B surface, the printing area being a circuit area, and ensuring that the B surface hole edge and the trapezoidal conical hole inner wall form a continuous coverage; (5) chemical etching using etching chemicals; and (6) removing the film. The trapezoidal conical hole of step (1) is different from a traditional cylindrical hole, and is a circular hole with different hole diameters on two surfaces, the A surface hole radius being R1, and the B surface hole radius being R2, and R1≥1.2×R2; The inkjet printing uses a piezoelectric nozzle. The double-sided PCB board of step (1) has a three-layer structure: a copper foil conductive layer-insulating layer-copper foil conductive layer, and the double-sided PCB board is a hard board with a thickness≥0.5mm. The trapezoidal conical hole inner wall area of steps (3) and (4) is entirely covered by the inkjet printing of the etching-resistant mask ink, and the inkjet printed inner wall portion and the inkjet printed hole edge portion of the circuit area form a continuous defect-free coverage connection. The metalization of step (2) comprises a traditional process of deburring and cleaning for the trapezoidal conical hole, and then the hole is metalized by electrochemical deposition, and can be electroplated to increase the thickness as needed. The etching-resistant mask ink of steps (3) and (4) forms a protective layer after being inkjet printed and solidified on the surface of the copper-clad plate, and the solidified and covered area can protect the copper foil from the etching chemicals, and the uncovered area of the copper foil reacts with the etching chemicals, and then the copper is converted from a metal element into copper ions dissolved in the etching chemicals.

2. The method of claim 1, wherein, The circuit area of steps (3) and (4) is a circuit layout area of the circuit board, and the circuit parts on both surfaces of the copper-clad plate that need to be reserved are covered and protected by printing the etching-resistant mask ink.

3. The method of claim 1, wherein the method further comprises: The chemical etching of step (5) is a chemical reaction between the etching chemicals and the copper foil, which converts the metal copper element into copper ions dissolved in the etching chemicals.

4. The method of claim 1, wherein the method further comprises: The film removing of step (6) is to remove the solidified etching-resistant mask ink by chemical or physical methods, including removing the solidified etching-resistant mask ink covered in the circuit area and the solidified etching-resistant mask ink covered in the trapezoidal conical hole inner wall.

5. A double-sided PCB board, characterized by Prepared according to the method of any one of claims 1-4.

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