PCB solder mask watermark solving method

Abstract

The invention discloses a PCB solder mask watermark solving method. The method comprises the following steps: S1, confirming the influence on the gold-melting watermark after enhancing the photopolymerization reaction rate and the thermal polymerization reaction rate; s2, after solder mask exposure and development, UV light is added to make up for insufficient light reaction for testing; s3, UV illumination energy is increased according to the condition of insufficient light supplement in the step S2, the energy generated by the solder resist ink under irradiation of different UV light energy, the intensity of a cross-linking reaction generated by photocuring molecules in the photosensitive ink and the hardening strength of the ink surface are analyzed through testing, the purpose is to avoid the watermark defect in the manufacturing process of the PCB, the quality is guaranteed, and the production efficiency is improved. The production is rapid.

Description

Technical Field

[0001] The present invention relates to the field of PCB watermark removal, and in particular to a solution for removing watermarks from PCB solder mask layers. Background Art

[0002] The rapid development of modern PCB technology has led to a diversification of surface treatments, placing increasing demands on solderability, such as pad flatness, adhesion, solderability, and extremely low contact resistance. Consequently, circuit boards may undergo surface treatments after solder mask application using processes such as chemical gold (CGM), chemical silver (CGM), and OSP (Open Screen Printing). This article examines the "watermark" defect caused by CGM surface treatment. Under certain temperature conditions, CGM solutions can easily penetrate and attack the solder mask, creating "watermarks." Therefore, identifying solutions to address these issues is crucial.

[0003] The existing solder mask watermark is alleviated and eliminated by baking the board and increasing the exposure energy. After the solder mask is pre-baked, it is necessary to expose it for a photo-crosslinking reaction. If the first inspection is done during exposure and a matte gloss is found on the ink surface, it means that the exposure energy needs to be adjusted and increased until the matte color is no longer present and the ink can withstand a 3H hardness test. However, this still cannot completely solve the watermark defect after surface treatment. Summary of the Invention

[0004] To solve the above problems, this technical solution provides a solution for PCB solder mask watermark.

[0005] To achieve the above purpose, the technical solution is as follows:

[0006] Solutions to PCB solder mask watermarks include:

[0007] S1, confirm the effect of enhancing the photopolymerization reaction rate and thermal polymerization reaction rate on the gold watermark;

[0008] S2, after solder mask exposure and development, add UV light to compensate for insufficient light reaction test;

[0009] S3, according to the insufficient fill light situation in step S2, increasing the UV light energy.

[0010] In some embodiments, in step S1, exposure is performed by increasing exposure energy and different baking plate temperatures are used.

[0011] In some embodiments, the exposure energy is 8-9, 9.5-10.5, and 11-12.5, respectively, at 150 degrees for 60 minutes, 150 degrees for 60 minutes, and 150 degrees for 120 minutes, to test the light curing reaction rate and the heat curing reaction rate, and finally observe the watermark points on the substrate.

[0012] In some embodiments, in step S2, a semi-automatic exposure machine is used for light curing exposure, a tunnel oven is used for thermal curing and baking, and the UV light irradiation condition is that UV is applied after development, and UV irradiation is performed on both the upper and lower surfaces.

[0013] In some embodiments, the UV irradiation is 200-300 mj / cm2.

[0014] In some embodiments, in step S3, when manufacturing a PCB gold plate, after the solder mask exposure process, a UV machine is added at the board outlet through the developing line process.

[0015] The beneficial effects of this application are:

[0016] This application tests and analyzes the energy generated by solder mask ink under different UV light energies, promotes the strength of the cross-linking reaction of photocurable molecules in the photosensitive ink, and the intensity of the ink surface hardening. The purpose is to avoid "watermark defects" in the PCB production process, ensure quality, and accelerate production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0018] Figure 1 4 is a diagram of the device structure used in step S3 of the embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] Please refer to Figure 1 As shown, the PCB solder mask watermark solution includes:

[0021] S1, confirm the effect of enhancing the photopolymerization reaction rate and thermal polymerization reaction rate on the gold watermark;

[0022] S2, after solder mask exposure and development, add UV light to compensate for insufficient light reaction test;

[0023] S3, according to the insufficient fill light situation in step S2, increasing the UV light energy.

[0024] In some embodiments, in step S1, exposure is performed by increasing exposure energy and different baking plate temperatures are used.

[0025] In some embodiments, the exposure energy is 8-9, 9.5-10.5, and 11-12.5, respectively, at 150 degrees for 60 minutes, 150 degrees for 60 minutes, and 150 degrees for 120 minutes, to test the light curing reaction rate and the heat curing reaction rate, and finally observe the watermark points on the substrate.

[0026] After the above steps, the following data is obtained:

[0027]

[0028] It can be found that the higher the exposure UV light energy and the longer the thermal curing furnace baking time, the higher the photopolymerization rate and thermal polymerization rate. After the gold treatment, the watermark improvement effect of the substrate ink layer is more obvious. After heat curing at 150℃ / 120min, the thermal polymerization reaction rate reaches 90%. However, if a small amount of watermark still exists after the gold treatment, the subsequent steps should be started.

[0029] In some embodiments, in step S2, a semi-automatic exposure machine is used for light curing exposure, a tunnel oven is used for thermal curing and baking, and the UV light irradiation condition is that UV is applied after development, and UV irradiation is performed on both the upper and lower surfaces.

[0030] In some embodiments, the UV irradiation is 200-300 mj / cm2.

[0031] After the above steps, the following data is obtained:

[0032]

[0033] Increasing the solder mask exposure energy can improve the watermark defect, but it can not be completely eliminated. After development, UV light is used to make up for the insufficient photopolymerization reaction of the ink surface. The photocuring reaction rate reaches more than 85%. No watermark defect appears on the ink layer after gold treatment, which can effectively solve the watermark defect.

[0034] In some embodiments, in step S3, when manufacturing a PCB gold plate, after the solder mask exposure process, a UV machine is added at the board outlet through the developing line process.

[0035] When making PCB gold plate, after the solder mask exposure process, a UV machine is added to the board outlet of the developing line process, such as Figure 1 As shown, there is a UV lamp on the top and bottom, and the energy is controlled to 250±150mj / cm2, which has a significant improvement effect on the "watermark" defect of the gold plate; the FQC inspection yield is improved, which is helpful for the shipment quality and is conducive to eliminating the potential hidden dangers of ink adhesion.

[0036] The industry usually adopts the baking method after the PCB is completed and the "watermark" defect is found. This method easily carbonizes the ink on the board, causing yellowing and accelerating aging of the PCB, so it is not the best technical solution. The present invention is a solution adopted in advance during the PCB solder mask process before the defect occurs, saving manpower, effort and time. Not only will the "watermark" defect no longer appear, but there is no unnecessary rework after the process is completed.

[0037] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application. Other embodiments whose principles and basic structures are the same or similar to those of the present application are within the scope of protection of the present application.

Claims

1. The solution to PCB solder mask watermark is characterized by: include; S1, confirm the effect of enhancing the photopolymerization reaction rate and thermal polymerization reaction rate on the gold watermark; S2, after solder mask exposure and development, add UV light to compensate for insufficient light reaction test; S3: According to the insufficient fill light situation in step S2, increase the UV light energy.

2. The PCB solder mask watermark solution according to claim 1, characterized in that: In step S1, exposure is performed in a stepwise manner using exposure energy increments and different baking plate temperatures are used.

3. The PCB solder mask watermark solution according to claim 2, characterized in that: The exposure energy is 8-9, 9.5-10.5 and 11-12.5, respectively at 150 degrees for 60 minutes, 150 degrees for 60 minutes and 150 degrees for 120 minutes, to test the light curing reaction rate and the heat curing reaction rate, and finally observe the watermark points on the substrate.

4. The PCB solder mask watermark solution according to claim 3, characterized in that: In step S2, a semi-automatic exposure machine is used for light curing exposure, a tunnel oven is used for heat curing and baking, and the UV light irradiation condition is that UV is applied after development, and UV irradiation is performed on both the upper and lower surfaces.

5. The PCB solder mask watermark solution according to claim 4, characterized in that: UV irradiation is 200-300mj / cm2.

6. The PCB solder mask watermark solution according to claim 5, characterized in that: In step S3, when manufacturing the PCB gold plate, after the solder mask exposure process, a UV machine is added at the board outlet through the developing line process.

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