How to improve the quality of the appearance of solder resist

An Introduction

People talk about the development trend of PCB, the PCB is often thought of moving high-precision, high density and reliability direction, which is the development trend. On the other hand, the appearance of the user requirements of the PCB more strict. PCB solder mask is like a "coat", in addition to requiring a certain degree of thickness and hardness, solvent resistance test and adhesion test standard, but also requires the surface color of uniform, shiny (general requirements for domestic rooms the brighter the better), the surface no garbage, no extra marks. We can say that the appearance of solder resist is not only a good or bad quality of enterprise technology and management level of expression, but also directly affect the "order." Therefore, how to improve the appearance of printed circuit board solder quality has become the PCB plant need to be addressed for each subject. According to my practical experience following from the solder resist printing, exposure, developing and post-cured in four areas to talk about how to improve their appearance.

Affect the quality of the appearance of two factors solder resist

1, screen:

Photosensitive solder mask of the screen printing process, the flatness of the blade, clean the environment between the degree of screen printing, screen printing, when used close up tape and ink formulation, printing pressure, pre-screen appearance of the brush plate and so will the quality of impact. According to the actual situation of production, the most influential factor is the first three. Scraper is not easy to solder flat surface scraper marks; screen cleaning is not enough room in the solder surface is easy to waste; close up tape improper use, easy to make plastic dissolved in solvent ink resulting surface compounds.

2 Exposure:

Solder mask exposure process, because solder has not completely cured, solder and solder resist film prone to stick together when the imprint, which is affecting the quality of the main reasons for the appearance of solder resist.

3, developing:

The current level of solder mask imaging commonly used transmission-type imaging, the solder has not completely cured, imaging machine drive wheel, roller and so easy to damage its surface, resulting in roll mark, thus affecting the appearance quality of solder resist. In addition, incorrect exposure will also affect the energy of the solder resist gloss, but this can be controlled through the wedge table.

4, after the curing
basket cable trays, flexible cable tray, electrical cable tray
After the curing temperature of the solder resist non-uniform color likely to cause uneven solder resist, even when the temperature is too high, resulting in local yellow, black, affecting the appearance of solder resist.

Conclusion

To improve the appearance of printed circuit board solder quality is required from the process methods, materials, equipment, operator of integrated process control and other aspects of discipline, in particular, be on the screen, exposure, developing, after the curing process of the parameters strict monitoring.
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