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

colourdielectricpcbsolder-mask

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.

Best Answer

I'm certainly no expert, but the other day I came across this article from a PCB manufacturer that I would like to bring to your attention. It states:

  1. Green solder mask is physically superior

Due to the traditional aspect of using green pigments, R&D into making better solder mask oils focused on the standard green color. The actual chemical pigments used influence the performance of the resin during application and in the field. When demand is pushing form factors to their limits, no one cares about having pink boards. As a result, green solder mask now has superior properties compared to other aesthetically orientated colors.

Most prominently, commercial green solder mask is the only available color that can reliably produce solder mask dams of 0.1mm (4mil). Next up is red, yellow and blue that can produce 0.12mm dams and then black and white which can only achieve 0.15mm. Solder mask dams are vital for ICs and fine pitch components since they are valuable in preventing solder bridges from forming.

enter image description here

So yes, based upon this information I would say that there are differences in quality, as the factory itself states. Green would be the way to go for best quality.

Hope this helps.

Edit: Added picture of solder mask dam, from here

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