A method for solder resisting printed circuit boards and the pretreatment solution used therein; a circuit board.

Abstract

This invention provides a method for solder resist application on printed circuit boards, comprising the following steps: S1. Before digitally printing solder resist ink onto the circuit board, the circuit board substrate is fully immersed in a pretreatment solution for solder resist that prevents seepage for 1 to 30 seconds, then removed and dried for later use. The pretreatment solution for solder resist that prevents seepage contains functional substances selected from one or more of soluble resins, metal salt additives, water-based crosslinking agents, and water-based silane coupling agents; S2. UV inkjet-printed solder resist ink is applied to the printed circuit board treated in step S1, and the board is irradiated under a UV-LED lamp for initial curing; S3. The circuit board substrate treated in step S2 is heated and dried for post-curing to obtain the solder resist layer. The circuit board obtained by the above method reduces the phenomenon of solder resist ink seeping into the window area, and the current carrying capacity of the circuit board can be normally utilized.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board technology, specifically to a solder resist method for printed circuit boards and the pretreatment solution used therein, as well as a circuit board. Background Technology

[0002] Solder mask fabrication is an important step in PCB manufacturing. It involves applying a layer of solder mask ink to the PCB surface after the outer circuit pattern is completed. The solder mask ink is applied to the circuit lines and substrate that do not require soldering to prevent bridging between lines during soldering, which could cause short circuits. It also saves on solder usage. In addition, the solder mask layer provides a permanent electrical environment and chemical protection layer, preventing moisture and various electrolytes from oxidizing the circuit lines and compromising their electrical properties. Furthermore, it protects against external mechanical damage and maintains good insulation performance of the board surface.

[0003] Traditional solder resist processes are not only numerous and complex, but also face the following drawbacks: First, they consume a large amount of water and chemicals, resulting in a large amount of chemical waste; second, the solvents in solder resist materials pose additional health and safety risks; third, the processing time is long; fourth, they lack flexibility; fifth, they require a large factory area and various different process equipment; and sixth, they consume a lot of energy.

[0004] Inkjet printing technology can significantly improve the solder resist coating process on circuit boards. Its technical advantages are numerous and noteworthy. It is an additive process that allows for digital, non-contact printing, is fast, saves materials, and provides high precision. Its inks are solvent-free. Through selective printing, more solder resist ink can be applied to necessary areas such as circuitry, while less ink is applied to the substrate of the circuit board.

[0005] With the rapid development of electronic technology, the design requirements for circuit boards are becoming increasingly stringent, gradually moving towards higher precision, smaller apertures, finer pitch, and thinner designs. Therefore, during the solder resist ink application stage, it is crucial to strictly control the flow and penetration of the solder resist ink. This requires maintaining the complete pattern of the solder resist ink on the copper surface of the circuit board while preventing excessive ink penetration into the openings, which would affect the circuit board's current-carrying capacity, significantly increasing the difficulty. Summary of the Invention

[0006] The first objective of this invention is to provide a solder resist method for printed circuit boards that prevents solder penetration.

[0007] A second objective of this invention is to provide a pretreatment liquid for preventing the seepage of solder resist in circuits, used in the above-mentioned solder resist method for printed circuit boards.

[0008] A third objective of this invention is to provide a circuit board that has been treated with the solder mask method described above for printed circuit boards.

[0009] To achieve the aforementioned first objective, the present invention provides a method for solder resist application on printed circuit boards, comprising the following steps: S1. Before digitally printing solder resist ink onto the circuit board, the circuit board substrate is fully immersed in a pretreatment solution for solder resist that prevents leakage for 1 to 30 seconds, then removed and dried for later use. The pretreatment solution for solder resist that prevents leakage contains functional substances selected from one or more of soluble resins, metal salt additives, water-based crosslinking agents, and water-based silane coupling agents; S2. UV inkjet printing solder resist ink is sprayed onto the printed circuit board treated in step S1, and then irradiated under a UV-LED lamp for initial curing; S3. The circuit board substrate treated in step S2 is heated and dried for post-curing to obtain a solder resist layer.

[0010] A further solution is to use UV inkjet printing solder resist ink with a viscosity of less than 100 cps.

[0011] A further option is to place the printed circuit board in an oven, set the baking temperature to 100-180℃, and the baking time to 0.5-3 hours.

[0012] As can be seen from the above scheme, before making the solder resist ink layer, the printed circuit board is first treated with a pretreatment liquid containing functional substances. This allows the solder resist ink to be applied to the printed circuit board containing the pretreatment liquid, forming a complete solder resist layer, and the ink will not seep into the opening range of the circuit board, affecting the current carrying capacity of the circuit board.

[0013] To achieve the second objective mentioned above, the present invention provides a pretreatment solution for preventing solder mask penetration, used in the aforementioned solder mask method for printed circuit boards. The pretreatment solution for preventing solder mask penetration contains 0.1% to 5% functional substances and the balance being a carrier, calculated by mass percentage; the functional substances are selected from one or more of soluble resins, metal salt additives, aqueous crosslinking agents, and aqueous silane coupling agents; the carrier is water and / or an alcoholic organic solvent.

[0014] A further option is to use a pretreatment solution for solder resisting circuits with anti-seepage properties containing 0-50% alcoholic organic solvents by weight percentage.

[0015] As can be seen from the above solution, on the one hand, the aforementioned functional material has strong adhesion and long-term stability, can adhere well to the circuit board, and can also effectively absorb the solder resist ink printed subsequently, providing good long-term adhesion of the solder resist layer on the circuit board; on the other hand, the functional material is miscible with water in any ratio, and after the solder resist ink is printed, the pretreatment solution exposed in the non-printed areas can be easily removed in the circuit board washing or alkaline washing process, and the exposed copper surface is easy to clean, will not affect any process after coating the solder resist layer, and will not remain on the circuit board and have any impact on the performance of the circuit board, thereby obtaining a perfect solder resist ink layer; thirdly, the inventors have found through experiments that this type of functional material can effectively prevent the solder resist ink from seeping on the circuit board, thereby improving the sharpness and windowing accuracy of the solder resist layer, etc.

[0016] A further option is that the water-soluble resin is selected from one of water-soluble polyacrylate resin, water-soluble polyester resin, and water-soluble polyurethane resin.

[0017] A further approach is to use metal salt additives that are anionic surfactants containing a polyoxyethylene ether structure.

[0018] A further option is that the anionic surfactant containing a polyoxyethylene ether structure is selected from one of linear alkyl polyoxyethylene ether sulfate, linear alkyl polyoxyethylene ether carboxylate, linear alkyl polyoxyethylene ether sulfonate, and linear alkyl alcohol polyoxyethylene ether sulfate.

[0019] A further option is to select one of the following as the waterborne crosslinking agent: oxazoline crosslinking agent, polycarbodiimide crosslinking agent, silicon crosslinking agent, modified ammonium crosslinking agent, organotitanium crosslinking agent, and aziridine crosslinking agent.

[0020] A further approach is to use aqueous silane coupling agents containing acidic groups.

[0021] As can be seen from the above solution, in the full-coverage immersion treatment of circuit boards, there is no need to consider the issue of controlling the seepage of the liquid in delicate components. Even high-precision circuit boards with a large number of openings and small window diameters can be processed efficiently and easily. Therefore, before inkjet printing solder resist ink on the circuit board, a pretreatment solution is used to fully immerse the circuit board. This ensures a tight bond between the solution and the solder resist ink, achieving complete shaping and precise positioning of the solder resist ink. This solves the problem of increased circuit board defect rates and scrap rates caused by ink seepage and diffusion into the fine window diameters.

[0022] To achieve the third objective mentioned above, the present invention provides a circuit board treated with the above-described solder mask method for printed circuit boards.

[0023] As can be seen from the above solution, the circuit board reduces the phenomenon of excessive solder resist ink seeping into the opening area, and the current carrying capacity of the circuit board can be performed normally. Attached Figure Description

[0024] Figure 1 and Figure 2 This is a schematic diagram of the solder resist layer obtained by processing a PCB board according to an embodiment of the present invention.

[0025] Figure 3 and Figure 4 This is a schematic diagram of the solder resist layer obtained by processing a PCB board in a comparative example according to the present invention. Detailed Implementation

[0026] The present invention provides a method for solder mask application on printed circuit boards, comprising the following steps:

[0027] S1. Before digitally printing solder resist ink on the circuit board, the circuit board substrate is fully immersed in the anti-seepage solder resist pretreatment solution for 1s to 30s, then removed and dried for later use. The anti-seepage solder resist pretreatment solution contains functional substances, which are selected from one or more of soluble resins, metal salt additives, water-based crosslinking agents and water-based silane coupling agents.

[0028] S2. Spray UV inkjet printing solder resist ink onto the printed circuit board processed in step S1, and place it under a UV-LED lamp for initial curing.

[0029] S3. Heat and dry the circuit board substrate after step S2, and then perform post-curing to obtain a solder resist layer.

[0030] This invention discloses a pretreatment solution for solder resisting circuits that prevents leakage. By mass percentage, it contains 0.1% to 5% functional substances and the balance being a carrier. The functional substances are selected from one or more of soluble resins, metal salt additives, water-based crosslinking agents, and water-based silane coupling agents. The carrier is water and / or an alcohol-based organic solvent.

[0031] Examples of water-soluble resins that can be used as functional materials include water-soluble polyacrylate resins, water-soluble polyester resins, and water-soluble polyurethane resins.

[0032] As functional substances mentioned above, metal salt additives can include linear alkyl polyoxyethylene ether sulfates, linear alkyl polyoxyethylene ether carboxylates, linear alkyl polyoxyethylene ether sulfonates, and linear alkanol-based polyoxyethylene ether sulfates. Commercially available examples include C12-C18 alkyl polyoxyethylene ether sodium sulfate (linear alkyl polyoxyethylene ether sulfate), C12-15 alkyl polyoxyethylene ether sodium carboxylate (linear alkyl polyoxyethylene ether carboxylate), hexadecyl polyoxyethylene ether sulfonate (linear alkyl polyoxyethylene ether sulfonate), and lauryl polyoxyethylene ether sodium sulfate (linear alkanol-based polyoxyethylene ether sulfate).

[0033] As functional substances mentioned above, aqueous crosslinking agents include oxazoline crosslinking agents, polycarbodiimide crosslinking agents, silicon crosslinking agents, modified ammonium crosslinking agents, organotitanium crosslinking agents, and aziridine crosslinking agents. Commercially available examples include oxazoline crosslinking agents such as WS-700, WS-500, and WS-100X (Nippon Shokubai); aziridine crosslinking agents such as NWIIT C9 (Wanjun Chemical); polycarbodiimide crosslinking agents such as NWIIT C40 and NWIIT C42 (Wanjun Chemical); silicon crosslinking agents such as NWIIT C32 and NWIIT C61 (Wanjun Chemical); and organotitanium crosslinking agents such as Tyzor-371 (DuPont).

[0034] As functional substances mentioned above, aqueous silane coupling agents include QX-4926, QX-4776, QX-680, QX-470, KH-460, KH-450, and MP-200.

[0035] As a water-based carrier, alcoholic organic solvents can be added together with water as a carrier to accelerate the drying speed of the pretreatment solution.

[0036] The present invention will be further described below with reference to the embodiments.

[0037] I. Pretreatment solution for solder resist application to prevent seepage

[0038] Prepare the pretreatment solutions 1-14 of this invention according to the mass percentages shown in Table 1.

[0039] Table 1

[0040]

[0041]

[0042] II. A method for solder mask application on printed circuit boards

[0043] Examples 1-14

[0044] The present invention provides a method for solder mask application on printed circuit boards, comprising the following steps:

[0045] S1. Before digitally printing solder resist ink on the circuit board, immerse the entire circuit board substrate in a pretreatment solution for solder resist that prevents seepage for 15s to 30s, then remove and dry for later use.

[0046] S2. Spray UV inkjet printing solder resist ink onto the printed circuit board processed in step S1, and place it under a UV-LED lamp for initial curing.

[0047] S3. Heat and dry the circuit board substrate after step S2, and then perform post-curing to obtain a solder resist layer.

[0048] In Examples 1-14, the pretreatment solution for solder resisting the anti-seepage circuit described in step S1. is the same as the pretreatment solution 1-14 described above.

[0049] The UV inkjet printing solder resist ink mentioned in step S2 can be any solder resist ink available on the market.

[0050] Comparative Example 1

[0051] The difference between Comparative Example 1 and the Example is that the pretreatment of the printed circuit board in step S1 is omitted, and the solder resist ink is directly printed and cured on the printed circuit board.

[0052] The solder resist ink used in step S2 is the same ink as the solder resist ink in the embodiment.

[0053] III. A type of circuit board

[0054] Circuit Board 1-15

[0055] Circuit boards 1-14 are circuit boards treated with the solder mask method of one of the printed circuit boards in Examples 1-14; circuit board 15 is a circuit board treated with the solder mask method of Comparative Example 1.

[0056] IV. Circuit Board Reliability Testing Standards

[0057] Reliability testing was performed on circuit boards 1-15. The test items, methods, and standards are shown in Table 2 below.

[0058] Table 2

[0059]

[0060] V. Circuit Board Reliability Testing

[0061] The reliability test results for circuit boards 1-15 are shown in Table 3 below.

[0062] Table 3

[0063]

[0064]

[0065] It should be noted that NG in Table 3 indicates non-compliance.

[0066] See Figures 1 to 4 visible, Figure 1 and Figure 2 The circuit board obtained in the example did not undergo diffusion. Figure 3 and Figure 4The circuit board obtained for comparison underwent diffusion. Therefore, it can be seen that in Examples 1-14, the pretreatment solutions 1-14 all contain functional substances, which are selected from one or more of soluble resins, metal salt additives, water-based crosslinking agents, and water-based silane coupling agents. Before digitally printing solder resist ink on the circuit board, the circuit board substrate is first fully immersed in a diffusion-preventing solder resist pretreatment solution, which contains functional substances selected from one or more of soluble resins, metal salt additives, water-based crosslinking agents, and water-based silane coupling agents. Thus, the circuit board of the present invention, by using a pretreatment solution containing one or more functional substances selected from water-soluble resins, metal salt additives, water-based crosslinking agents, and water-based silane coupling agents for full-coverage wetting, can effectively prevent the diffusion of solder resist ink on the circuit board, and the resulting circuit board has good adhesion, insulation, solderability, and protection, meeting production requirements.

[0067] The above embodiments are merely preferred examples of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications made in accordance with the structure, features and principles of the present invention should be included within the scope of the present invention.

Claims

1. A circuit solder resist method for a printed wiring board, characterized by, It comprises the following steps: S1. Before printing solder resist ink on the circuit board, the circuit board substrate is soaked in a seepage-proof pretreatment solution for 1-30 seconds, and then dried for standby, wherein the seepage-proof pretreatment solution contains functional substances selected from one or more of soluble resin, metal salt additive, water-based crosslinking agent and water-based silane coupling agent; S2. UV inkjet printing solder resist ink is printed on the printed circuit board treated in step S1, and then subjected to initial curing under UV-LED lamp irradiation; S3. The circuit board substrate treated in step S2 is heated and dried for post-curing to obtain a solder resist layer.

2. The circuit board solder resist method according to claim 1, wherein the viscosity of the UV inkjet printing solder resist ink is less than 100 cps.

3. The circuit board solder resist method according to claim 1, wherein the post-curing condition is that the printed circuit board is placed in an oven, the baking temperature is set to 100-180℃, and the baking time is 0.5-3 hours.

4. A seepage-proof pretreatment solution for circuit board solder resist, used in step S1 of claim 1, wherein the seepage-proof pretreatment solution contains 0.1-5% functional substances and the rest is carrier, calculated by mass percentage; the functional substances are selected from one or more of soluble resin, metal salt additive, water-based crosslinking agent and water-based silane coupling agent; the carrier is water and / or alcohol organic solvent.

5. The seepage-proof pretreatment solution for circuit board solder resist according to claim 4, wherein the seepage-proof pretreatment solution contains 0-50% alcohol organic solvent, calculated by mass percentage.

6. The seepage-proof pretreatment solution for circuit board solder resist according to claim 4, wherein the soluble resin is selected from one of water-soluble resin, alkali-soluble resin or alcohol-soluble resin; the water-soluble resin is selected from one of water-soluble polyacrylate resin, water-soluble polyester resin and water-soluble polyurethane resin.

7. The seepage-proof pretreatment solution for circuit board solder resist according to claim 4, wherein the metal salt additive is an anionic surfactant containing polyoxyethylene ether structure; the anionic surfactant containing polyoxyethylene ether structure is selected from one of linear alkyl polyoxyethylene ether sulfate, linear alkyl polyoxyethylene ether carboxylate, linear alkyl polyoxyethylene ether sulfonate and linear alkanol polyoxyethylene ether sulfate.

8. The seepage-proof pretreatment solution for circuit board solder resist according to claim 4, wherein the water-based crosslinking agent is selected from one of oxazoline crosslinking agent, polycarbodiimide crosslinking agent, silicon crosslinking agent, modified ammonium crosslinking agent, organic titanium crosslinking agent and aziridine crosslinking agent.

9. The seepage-proof pretreatment solution for circuit board solder resist according to claim 4, wherein the water-based silane coupling agent contains an acidic group.

10. A circuit board, ​ ​ ​ ​ ​ ​ ​ ​ The circuit board is a circuit board treated by the circuit solder resist method of the printed circuit board according to any one of claims 1 to 3.

Images