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I received my first batch of PCB's that were designed with thermal vias of diameter 0.61mm and hole diameter 0.305mm. When I inspect them, it seams that only around 10% of the vias have been coated. Can this be confirmed from the photo below?

enter image description here

Or are all vias likely plated, but they appear not to be, because they've been covered in lacquer or something?

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    \$\begingroup\$ What do the Gerbers look like? \$\endgroup\$ Commented Apr 4, 2022 at 6:22
  • \$\begingroup\$ On your next order of boards ask your vendor for a sample with no solder mask. That way you could easily inspect all the thru-holes. If you are using a quality vender all the boards should be identical, (plated or not). \$\endgroup\$
    – Nedd
    Commented Apr 4, 2022 at 8:24
  • \$\begingroup\$ How do you determine by looking that them that only 10% have been thru-plated? Are you looking at some of them and seeing different colored rings around them? If so then you're mistaken because that's no indication of whether or not they're thru-plated. \$\endgroup\$
    – brhans
    Commented Apr 4, 2022 at 15:42

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The vias are very likely just covered with solder mask, which makes them look as they were not plated.

Depending on production quality it may happen, that some vias are not perfectly covered. If you want to be sure, you could just scratch off some soldermask and you should be able to see if its plated.

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  • \$\begingroup\$ I guess you are right. I did scratch off some soldermask, and it looks OK. But these vias are so tiny that it is difficult to see for sure. Perphaps my question should have been why some vias as not perfectly covered, as in the question you linked to. Interestingly, all the uncovered vias are not covered on both sides. Does this make any sense, if the uncovered vias happen due to some natural process? (I would think not) \$\endgroup\$
    – K0ICHI
    Commented Apr 4, 2022 at 7:04
  • \$\begingroup\$ Maybe some vias have a slightly different plating thickness (which would probably be the same on each side), which might affect soldermask in some way. \$\endgroup\$
    – Rev
    Commented Apr 4, 2022 at 17:58

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