Solder Mask Thickness

This Gold Phoenix PCB Knowledge Center article explains solder mask thickness requirements and key guidelines for printed circuit board fabrication.

While the solder mask should be thick enough to protect the circuits, it is important to measure the solder mask to ensure that it is not too thick. On the side edges and top of the conductor, the thickness should be greater than 7 micrometers. The maximum thickness for solder masks on finished copper parts up to 35 micrometers thick is 40 micrometers. If the copper is thicker, the solder mask can be as thick as 80 micrometers.

Other good rules when it comes to solder mask include:

• Meet minimum annular ring requirements if the solder resist encroaches on lands.

• Do not allow exposed isolated pads.

• Permit solder resist only when plated through holes are not intended for solder fill.

• Do not allow solder resist on test points or connector fingers.

Applying solder mask with the appropriate thickness can be a delicate task and is one of many challenges faced by fabricators of quality printed circuit boards.