A method for manufacturing a solder mask layer of a PCB printed circuit board

Abstract

The present invention discloses a method for manufacturing a solder mask layer of a PCB printed circuit board, wherein the specific steps are as follows: (1) grinding the board; (2) drying; (3) spreading powder; (4) spray printing; (5) removing powder; (6) curing; (7) inspecting, at which point the obtained PCB printed circuit board is a semi-finished product with a solder mask layer. The present invention has the effects of environmental protection, emission reduction and reduced production cost.

Description

Technical Field

[0001] The invention belongs to the field of production and processing of PCB printed circuit boards, and in particular relates to a method for manufacturing a solder resist layer of a PCB printed circuit board. Background Art

[0002] PCB is the abbreviation of Printed Circuit Board. It is also called printed circuit board or printed circuit board. Because it is made by electronic printing, it is called "printed" circuit board. Printed circuit board is a substrate for assembling electronic components. It is a printed board on a copper-clad substrate that forms connections between electronic component points and printed component positions according to a predetermined circuit design. The main function of this product is to enable various electronic components to form a connection of a predetermined circuit. It mainly plays the role of relay transmission and is a key electronic interconnection component of electronic products. As a substrate and key interconnection component for electronic components, PCB is a component that must be equipped in any electronic equipment or product. It is widely used in various lighting, electrical appliances, automobiles, automation equipment, communications and other industries. It is an important carrier that supports the rapid, orderly and stable development of electronic information in today's society. PCB printed circuit board consists of pads, vias, circuit layers, solder mask layers, text printing and other parts. The solder mask is a protective layer that insulates the board surface. It can protect the copper circuit, prevent parts from being soldered to the wrong place, and prevent parts that should not be soldered from being connected by solder. For example, when a wave soldering machine is used to solder plug-in electronic components, the entire surface of the board passes through the hot molten tin. The exposed parts without the solder mask will be tinned and soldered, while the parts with the solder mask will not be tinned. The solder mask can also prevent the conductive solder from bridging short circuits between various electronic components.

[0003] During the processing of PCB printed circuit boards, the production of solder mask is one of the production links. It is a processing step that mainly transfers the PCB solder mask pattern to the surface of the PCB printed circuit board and solidifies the pattern material. The production of the existing solder mask is a process after the circuit layer of the PCB printed circuit board is completed. The specific process flow is as follows (such as Figure 1 shown):

[0004] (1) Polishing

[0005] The surface of the PCB printed circuit board that has been etched and completed the optical automatic inspection is polished and washed to eliminate burrs and remove the oxide layer on the copper surface of the circuit;

[0006] (2) Wash with water and bake at low temperature

[0007] The pre-treated PCB printed circuit board after washing is baked at low temperature, and the temperature of the oven is set at 80℃ to dry the surface of the PCB printed circuit board;

[0008] (3) Low temperature baking after coating or screen printing UV ink

[0009] Apply or screen print solder mask UV ink on the PCB printed circuit board, and then perform low-temperature baking at 80°C to allow the solvent of the UV ink on the PCB printed circuit board to completely evaporate and dry;

[0010] (4) Lay the solder mask pattern film, then UV exposure to cure the ink

[0011] On the PCB printed circuit board in the coating or screen printing area, a solder mask pattern film is laid according to the positioning for UV exposure. Then, the parallel UV light generated by the exposure machine is irradiated to the UV ink layer through the transparent area of ​​the film. The photoinitiator on the UV ink decomposes to produce free radicals, thereby initiating a cross-linking polymerization reaction, so that the UV ink layer exposed to light is cross-linked and cured;

[0012] (5) Circuit development

[0013] Use sodium carbonate aqueous solution to dissolve the UV ink that is not exposed under the solder mask film image, and the remaining solder mask is the required pattern;

[0014] (6) Visual inspection

[0015] For the products with problems such as film printing, solder mask bridging and unclean developing lines generated in step (4), multiple inspections are required to prevent the problem products from flowing into the next process.

[0016] (7) High temperature baking

[0017] The PCB printed circuit boards that have passed the visual inspection are baked and cured at 150℃ to prevent the UV ink from falling off in the next process and to make the UV ink after development completely hardened;

[0018] Finally, the PCB printed circuit board completes the solder mask process.

[0019] Since the existing PCB printed circuit board produces organic solvent volatile gas and developer waste liquid during the production process of the solder mask layer, it is necessary to subsequently treat the waste gas and wastewater for environmental protection, which increases the production cost. Summary of the invention

[0020] In view of the above problems, an object of the present invention is to provide a method for manufacturing a solder mask layer of a PCB printed circuit board which is environmentally friendly, reduces emissions and reduces production costs.

[0021] To achieve the above object, the present invention provides a method for manufacturing a solder mask layer of a PCB printed circuit board, wherein the specific steps are as follows:

[0022] (1) Grinding plate

[0023] Perform optical automatic inspection on the semi-finished PCB printed circuit boards that have been etched, then polish and clean the surface of the PCB printed circuit boards that have completed the optical automatic inspection, remove the oxide layer on the surface of the copper circuit of the PCB printed circuit boards, and eliminate burrs;

[0024] (2) Drying

[0025] The PCB printed circuit board is dried with hot air to eliminate the moisture that may exist on the surface of the PCB printed circuit board in step (1), thereby increasing the dryness of the surface of the PCB printed circuit board and avoiding oxidation, so as to make the surface color of the solder mask layer consistent during subsequent processing;

[0026] (3) Spreading powder

[0027] Apply the powder coating to the surface of the PCB printed circuit board after grinding and hot air drying through a 3D metal printer;

[0028] (4) Printing

[0029] The printing uses an adhesive as a raw material, and a general PCB character printer prints on the powder coating that has been spread on the surface of the PCB printed circuit board in step (3) based on the pattern of the solder mask layer, so that the adhesive fixes the powder coating and adheres it to the surface of the PCB printed circuit board;

[0030] (5) Powder removal

[0031] Use vacuum equipment to remove the powder from the area on the PCB surface where no solder mask pattern is printed and reuse it;

[0032] (6) Curing

[0033] The PCB printed circuit board of step (5) is baked at 150° C. in an oven or a tunnel furnace to fully crosslink and harden the solder resist pattern powder coating and the binder on the surface of the PCB printed circuit board;

[0034] (7) Inspection

[0035] Use visual inspection or optical automatic detection to check the PCB printed circuit board solder mask pattern production results, and complete the entire production step after confirmation;

[0036] Finally, the obtained PCB printed circuit board is a semi-finished PCB printed circuit board with a solder mask layer.

[0037] In some embodiments, the AOI inspection equipment used in the optical automatic inspection in the above step 1 first uses a high-definition image camera to quickly take a picture of the PCB printed circuit board after the circuit is etched; then, the photographed picture is compared with the circuit layer engineering file of the original file of the PCB printed circuit board, thereby achieving optical automatic inspection.

[0038] In some embodiments, the AOI inspection equipment used in the optical automatic inspection in the above step 7 first uses a high-definition image camera to quickly take a picture of the PCB printed circuit board; then, the photographed picture is compared with the solder mask layer engineering picture to find out defective products, thereby achieving automated inspection using optical equipment.

[0039] In some embodiments, the temperature of hot air drying in step 2 is 80° C. and the time required is 2 to 5 minutes.

[0040] In some embodiments, the powder coating is a powder coating with a particle size of 15-35 microns. The powder coating includes one or a mixture of epoxy powder coating, polyester powder coating or polyurethane powder coating. The thickness of the powder coating during 3D printing is 20-45 microns.

[0041] In some embodiments, the powder coating is an epoxy powder coating having a thickness of 30 microns.

[0042] In some embodiments, the powder coating further comprises and / or a dispersant and / or a leveling agent and / or a curing agent.

[0043] In some embodiments, the dispersant includes one or more of acrylate polymer, polyethylene, fumed silica and alumina. The leveling agent includes one or more of acrylate polymer, polyethylene, fumed silica and alumina. The curing agent includes one or more of phenolic resin, amines and amides.

[0044] In some embodiments, the binder includes one or more of a phenolic resin, an acrylic resin, and a blocked isocyanate.

[0045] In some embodiments, the binder is a phenolic resin binder.

[0046] In some embodiments, the phenolic resin binder is cross-linked and cured with the powder coating after being baked at 150° C. for 30 minutes and fixed on the surface of the PCB printed circuit board.

[0047] The beneficial effects of the present invention are that it has the effects of environmental protection, emission reduction and reduced production costs. The improved manufacturing method avoids the use of film on the solder mask layer and avoids the use of UV exposure to cure ink, while eliminating the development process because the ink contains organic solvent volatile gas and developer waste liquid. By applying the powder coating on the surface of the PCB printed circuit board and the adhesive fixedly bonding the powder coating on the surface of the PCB printed circuit board, and in the powder removal and curing process, the problem of waste gas and waste water in the existing technology that increases the treatment cost is solved, and the effects of environmental protection, emission reduction and reduced production costs are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Flowchart made for existing PCB solder mask;

[0049] Figure 2 The present invention is a flow chart of making a PCB solder mask. DETAILED DESCRIPTION

[0050] The invention will be further described in detail below in conjunction with the accompanying drawings.

[0051] like Figure 2 As shown, a method for manufacturing a solder mask layer of a PCB printed circuit board, wherein the specific steps are as follows:

[0052] (1) Grinding plate

[0053] Perform optical automatic inspection on the semi-finished PCB printed circuit boards that have been etched, then polish and clean the surface of the PCB printed circuit boards that have completed the optical automatic inspection, remove the oxide layer on the surface of the copper circuit of the PCB printed circuit boards, and eliminate burrs;

[0054] The AOI inspection equipment used in the optical automatic inspection in the above step 1 first uses a high-definition image camera to quickly take a picture of the PCB printed circuit board after the circuit is etched; then, the photographed picture is compared with the circuit layer engineering file of the original PCB printed circuit board file to achieve optical automatic inspection; in this way, the hidden dangers of open circuit, short circuit, micro-open, micro-short, etc. in the etched circuit can be fundamentally solved, thus avoiding the PCB printed circuit board from entering the previous process of solder mask processing without defects.

[0055] (2) Drying

[0056] The PCB printed circuit board is dried with hot air to eliminate the moisture that may exist on the surface of the PCB printed circuit board in step (1), improve the dryness of the surface of the PCB printed circuit board, avoid oxidation, and facilitate the surface color of the solder mask layer to be consistent during subsequent processing. The temperature of the hot air drying is 80°C and the time required is 2 to 5 minutes.

[0057] (3) Spreading powder

[0058] The powder coating is applied to the surface of the PCB printed circuit board after grinding and hot air drying through a 3D metal printer; the 3D metal printer is a scientific instrument used in the basic disciplines of physics, engineering and technical sciences, and mechanical engineering. It was put into use on November 26, 2015.

[0059] In the above step 3, the powder coating process of the solder mask layer has certain requirements on the selection and thickness of the powder, wherein the thickness and color of the solder mask are related to the type of powder selected.

[0060] The powder coating is a powder coating with a particle size of 15-35 microns. The powder coating includes one or a mixture of epoxy powder coating, polyester powder coating or polyurethane powder coating. The thickness of the powder coating during 3D printing is 20-45 microns. The powder coating is an epoxy powder coating with a thickness of 30 microns. The powder coating also includes and / or dispersant and / or leveling agent and / or curing agent. The dispersant includes one or more of acrylate polymer, polyethylene, fumed silica and alumina; the powder coating has environmentally friendly green characteristics (does not contain harmful ingredients), and the price of the material is relatively low, which is of great help in reducing production costs and reducing environmental pollution. The 20-micron powder thickness is the minimum thickness of the solder mask. Any lower thickness will be detrimental to the insulation of the circuit board and the powder spreading accuracy of the powder spreader. A powder thickness greater than 45 microns will increase the material cost, and the efficiency has not been significantly improved. Therefore, the economic effect and use effect of the solder mask below 45 microns are better.

[0061] The leveling agent includes one or more of acrylic polymer, polyethylene, fumed silica and alumina; the curing agent includes one or more of phenolic resin, amines and amides.

[0062] (4) Printing

[0063] The printing uses the binder as the raw material, and the general PCB character printer uses the pattern of the solder mask as the basis to print on the powder coating that has been spread on the surface of the PCB printed circuit board in step 3, so that the binder fixes the powder coating and adheres it to the surface of the PCB printed circuit board; the binder includes one or more of phenolic resin, acrylic resin and blocked isocyanate. When the binder is a phenolic resin binder, the phenolic resin binder is cross-linked and cured with the powder coating after being baked at a high temperature of 150°C for 30 minutes, and fixed on the surface of the PCB printed circuit board.

[0064] (5) Powder removal

[0065] Use vacuum equipment to remove the powder from the area on the PCB surface where no solder mask pattern is printed and reuse it;

[0066] (6) Curing

[0067] The PCB printed circuit board of step (5) is baked at 150° C. in an oven or a tunnel furnace to fully crosslink and harden the solder resist pattern powder coating and the binder on the surface of the PCB printed circuit board;

[0068] (7) Inspection

[0069] Use visual inspection or optical automatic detection to check the PCB printed circuit board solder mask layer pattern production results, and complete the entire production step after confirmation.

[0070] Finally, the obtained PCB printed circuit board is a semi-finished PCB printed circuit board with a solder mask layer. The PCB printed circuit board with the solder mask layer processed still needs subsequent processes to be considered as a complete processing of the PCB printed circuit board, rather than the PCB printed circuit board can be directly used as a circuit board after the above steps. The process method described in the present invention is only a part of the entire PCB printed circuit board processing line process.

[0071] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all belong to the protection scope of the invention.

Claims

1. A method for manufacturing a solder mask layer of a PCB printed circuit board, wherein: The specific steps are as follows: (1) Grinding plate Perform optical automatic inspection on the semi-finished PCB printed circuit boards that have been etched, then polish and clean the surface of the PCB printed circuit boards that have completed the optical automatic inspection, remove the oxide layer on the surface of the copper circuit of the PCB printed circuit boards, and eliminate burrs; (2) Drying The PCB printed circuit board is dried with hot air to eliminate the moisture that may exist on the surface of the PCB printed circuit board in step (1), thereby increasing the dryness of the surface of the PCB printed circuit board and avoiding oxidation, so as to make the surface color of the solder mask layer consistent during subsequent processing; (3) Spreading powder Apply the powder coating to the surface of the PCB printed circuit board after grinding and hot air drying through a 3D metal printer; (4) Printing The printing uses an adhesive as a raw material, and a general PCB character printer prints the pattern of the solder mask layer on the powder coating that has been fully applied on the surface of the PCB printed circuit board in step (3), so that the adhesive fixes the powder coating and adheres it to the surface of the PCB printed circuit board; (5) Powder removal Use vacuum equipment to remove the powder from the area on the PCB surface where no solder mask pattern is printed and reuse it; (6) Curing The PCB printed circuit board of step (5) is baked at 150° C. in an oven or a tunnel furnace to fully crosslink and harden the solder resist pattern powder coating and the binder on the surface of the PCB printed circuit board; (7) Inspection Use visual inspection or optical automatic detection to check the PCB printed circuit board solder mask pattern production results, and complete the entire production step after confirmation; Finally, the obtained PCB printed circuit board is a semi-finished PCB printed circuit board with a solder mask layer.

2. The method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 1, characterized in that: The AOI inspection equipment used in the optical automatic inspection in the above step 1 first uses a high-definition image camera to quickly take a picture of the PCB printed circuit board after the circuit is etched; then, the photographed picture is compared with the circuit layer engineering file of the original file of the PCB printed circuit board, thereby achieving optical automatic inspection.

3. The method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 1, characterized in that: The AOI inspection equipment used in the optical automatic inspection in the above step 7 first uses a high-definition image camera to quickly take a picture of the PCB printed circuit board; then, the photographed picture is compared with the solder mask layer engineering picture to find out defective products, thereby achieving automatic inspection using optical equipment.

4. The method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 2, characterized in that: The temperature of hot air drying in the above step 2 is 80°C and the required time is 2 to 5 minutes.

5. The method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 1, characterized in that: The powder coating is a powder coating with a particle size of 15-35 microns; The powder coating comprises one or a mixture of epoxy powder coating, polyester powder coating or polyurethane powder coating; The thickness of the powder coating during 3D printing is 20-45 microns.

6. A method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 1 or 5, characterized in that: The powder coating is epoxy powder coating with a thickness of 30 microns.

7. The method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 6, characterized in that: The powder coating also includes and / or a dispersant and / or a leveling agent and / or a curing agent.

8. The method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 7, characterized in that: The dispersant includes one or more of acrylate polymer, polyethylene, fumed silica and alumina; The leveling agent includes one or more of acrylate polymer, polyethylene, fumed silica and alumina; The curing agent includes one or more of phenolic resin, amines and amides.

9. The method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 1, characterized in that: The binder includes one or more of phenolic resin, acrylic resin and blocked isocyanate.

10. The method for manufacturing a solder mask layer of a PCB printed circuit board according to claim 9, characterized in that: The binder is a phenolic resin binder; The phenolic resin binder is cross-linked and cured with the powder coating after being baked at 150° C. for 30 minutes, and is fixed on the surface of the PCB printed circuit board.

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