Solder mask on pad with thermal vias in it?

[treez]

Just noting the page 3 of the below article on thermal vias on pads of SMD devices says "do not cover the vias with solder mask which causes excessive voiding"

...dont they mean "solder resist"?...they are talking about vias in pads of QFN.s
..Surely you want solder mask over a QFN pad....even when it has thermal vias in it?

Thermal vias article:
https://www.ti.com/lit/an/sloa122/sloa122.pdf

This closed thread is similar but not quite same
https://www.edaboard.com/showthread.php?t=275722

 

[SLK001]

Solder mask and solder resist are the same. The thermal pads in a QFN are usually where a bottom pad will be soldered to the board, so you definitely don't want mask over this pad.

 

[treez]

Thanks, i appreciate that its only terminology, but isnt " solder mask" , the abscence of solder resist?...ie , the mask is where the solder resist does not go

 

[FvM]

but isn't " solder mask" , the absence of solder resist?

Don't think so, I believe Wikipedia describes the commonly understood meaning of the term well https://en.wikipedia.org/wiki/Solder_mask

You are probably confused by the negative solder mask artwork in CAD layout.

 

[SLK001]

You're "masking" the solder, or you're "resisting" the solder, both mean "no solder here"!