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June 1999

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Subject:
Re: [DC] Via holes within SMD pads
From:
"Joy, Stephen C" <[log in to unmask]>
Reply To:
DesignerCouncil E-Mail Forum." <[log in to unmask]>, "Joy, Stephen C" <[log in to unmask]>
Date:
Wed, 16 Jun 1999 07:07:20 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (37 lines) 
Not sure what kind of SMT pad you are talking about, but there are some
simple solutions.
For .020 pitch QFP pads, make a lollipop design and have the solder mask
aperture .006 larger than the hole. The holes will have to be staggered on
each side of the lands and you have to have an assembly process that does
not mind holes under QFP devices.
For passives, you can do the same thing, except make the passive land equal
to standard land plus minimum diameter necessary for your annular ring
requirements. Solder mask the aditional rectangle as noted above.
The board guys can resolve a .004" solder mask line, so adjust copper via
"lands" accordingly.
Hope this helps.
Steve

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