The common problems and solutions of PCB soldermask
The solder mask for printed circuit board printing is mixed with solder mask ink and curing agent according to some percentage. The two materials should be fully mixed and then stand for 30min-45min. The solder mask cannot be used until it is cured. The mixed ink viscosity is about 150 + 20PS (25℃). The viscosity of the mixture decreases with the increase of temperature.
This article will refer to the common problems and trouble shooting of faults for usage of solder resist, so as to guarantee the PCB Board manufacture.
Common PCB Soldermask Problems & Solutions
Problems:
Solder resist ink is not even attached to the plate surface
Mixing time for soldermask ink is not enough
Ink mixing faults
There is residual grease or water stains on plate surface (incomplete pre-treatment)
Ink impurities (grease dropped in and destroy the surface tension)
Bad scraping film material
Dirty Screen
Use expired ink
Solutions:
Guarantee a complete pre-treatment
Check water breaking, grinding marks, etc meet the standards
Make sure the ink mixing parameters
Clean the screen, replace squeegee blade and other tools
Problems:
Ink and copper surface are separated
Inadequate pre-treatment
Impurities attach on plate surface
Copper surface depression
Adverse ink mixing
Uneven thickness of the ink on copper surface
Damage on ink surface
Uneven oven temperature and baking inadequate or over-baking
Multiple HAL or HAL temperature is too high
Solutions:
Guarantee a complete pre-treatment
Make sure the oven baking temperature and the heating curve distribution
Make sure the ink mixing parameters
Check the production process to reduce the external impact
Confirm HAL operating parameters and status
Problems:
Ink overflow after exposure
Bad exposure
Orientation film not in the hole
Vacuum pressure instability
Debris attached to the negatives film
Solutions:
While exposure attach the film to the board
Use thinner strips than plates
Location PIN needs to insert into the positioning hole
Check the negatives film
Problems:
Ink overflow after baking
No section of the warming
The temperature is too high for the low-temperature section
The time is too short for the low-temperature section
The low-temperature section is not continuously baked
Oven temperature is uneven
Solutions:
