What impact, if any, does the solder mask color have on the electrical and mechanical properties of a PCB

by crasic   Last Updated July 31, 2018 22:25 PM

At my place of work, we use soldermask colors as a sort of poke-yoke for manufacturing purposes E.g. Technicians know that green pcb goes with green, blue pcb with blue, etc. This has lead to some ... esoteric color choices including matte white, hot pink, blue/red sunburst, etc. for our soldermask. Our board fabs are usually happy to oblige, and we have had no reason thus far to question the dye choices.

However, during a discussion with a manufacturer about quality defects, their production engineer claimed that dye's used to make the soldermask color have a subtle impact on reflow, creepage, solderability, electrical conformance and dielectric effect. Specifically citing increased risk of soldermask voids and solder spreading under the soldermask layer for blue dye solder masks.

Is there any validity to this, or research to support this claim?. Moreover, are there any differences that could conceivable have an effect. For example, reflow temperature considerations when using very different solder mask colors (e.g. gloss white vs matte black) but nearly identical PCB and components.

I assume any material differences are up to the PCB material supplier, and while I am sure in that domain there are different materials and dye's used, I have always assumed it to be equivalent if it is offered as an option by the fab.

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