How Can PCB Solder Resist Be Improved?

We have noticed that the trend in development of printed circuit board technology (PCB), is towards high precision, density and reliability. The appearance
standards for PCBs have also been increasing. Solder resist coatings, for example, must not only pass
solvent resistance tests and have a specified thickness, but they also need to be uniform in color,
gloss and have no excess traces or impurities.

The appearance of solder resists is a reflection of the technical and managerial level of an enterprise,
and it has a direct effect on its production order. PCB production plants are under pressure to improve
the appearance of solder resists.

Solder Resists Can Be Affected by a Variety of Factors, Including:

1. Printing process: During the screen-printing process, factors like the flatness and
cleanliness of the blades, the use barrier tapes, as well as the pressure of the ink will influence the
quality of the printed image. The first three factors play a major role in actual production. Impurities
can easily adhere to the surface of the solder resist print if the blade isn’t flat. Poor
environmental purification also makes it easy for impurities.

2. Process of exposure: If the flux layer is not fully cured during the contact
process, it is easy to create marks on the solder resist and the welding paste, which affects the
appearance of the paste. If the solder resistance is not fully cured during the development process, the
driving wheel, pressure wheel, and other parts of the developer may cause surface damage. This can
result in roller marks.

3. After-curing treatment: If the welding temperatures are unevenly distributed,
it’s easy to get uneven welding paste colors. A high temperature can even lead to local
discoloration and affect the appearance. The uneven surface of the screen can cause the scraper to
become uneven over time. This is because the screen surface is uneven.

The operator must therefore always be attentive to the surface conditions. If you find scraper marks,
clean them immediately. This will ensure that the solder resist is smooth. The screen printing room must
be kept clean to achieve printed boards of excellent quality. Roller dust must be applied to all parts
that come into contact with the printed board, including the workbench and screen frame. Blotting paper
and solder resistance tape are also required. During the process of turning over, it is important to
maintain the cleanliness of the area, wear special clothing and hats and adhere to the wind bath
regulations. Air purification measures are important around the factory, and can be achieved through
regular water spraying or dust removal.

When It Comes to Equipment, You Should Consider the Following:

Firstly the drive roller should be made from soft materials, or coated with soft
rollers. Examples are soft PVC “O” rings, or squeeze rollers that are made of soft rubber.Second ensure the stability of your entire transmission system.Finaly, clean the roller regularly and squeeze it to remove dirt and avoid roller
marks.

In order to improve the appearance of the PCB’s solder resist it is necessary to carry out a
comprehensive control from many aspects, including the process, the raw materials, the equipment and the
operators. A strict control over screen printing parameters and exposure, development and curing are
also essential. These measures will allow the appearance of the solder resistance layer on the printed
circuit boards to meet the customer’s needs.