Good afternoon,

OK, here is this afternoon's question.  Solder mask thickness, what is the "industry standard"?  We currently specify 0.001" thickness and this may be fine on a large area when tested via IP TM-650, 2.5.6.1.  Now use 2 ounce copper traces in a normal board configuration.  Our board vendors are stating that they cannot hold the 0.001" thickness at the edges of the etch, it is more like 0.0003".  And if we spec 4 ounce or 6 ounce I'm sure it doesn't get any better.

How are you specifying solder mask thickness on your heavy copper weight circuit boards?

Do your board vendors use two coats of mask to obtain the thickness needed to comply?

IPC-SM-840 section 3.4 says it must meet the requirements of section 3.8.1, thickness of 0.001" at 500 Vdc.

Your guidance is requested.

Thanks,

Phil Nutting

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