PCB surface finishes

I just came to know that we need to tell PCB manufacturer about the surface finish which we don’t define or include in the PCB layout in the design tools. What are these PCB surface finishes ? There are options for example, ENIG, ENEPIG, Leadfree HASL etc. Do they have any thing to do with signal and power integrity ? Is these finishes works only or applies only at top and bottom of the PCB ?

Surface finishes do not really have anything to do with SI/PI but if you have BGAs, you should avoid HASL. If you have edge connectors, you might require hard gold. Your fab house will let you know.

We apply those on top and bottom. You can read our article about surface finishes and see here the ones we offer at Sierra.

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Note there are losses experienced with certain finishes that can effect high frequency and RF applications and need to be considered in loss budgets. For example ENIG can add significant losses, where a solution with Silver Immersion would potentially have less and meet required loss budgets.

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