[time-nuts] PCB design questions thread II

Tim Shoppa shoppa at trailing-edge.com
Tue Jun 3 07:01:21 EDT 2008

Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> How do you cope with SMT parts (eg high frequency ADCs) with metal 
> thermal transfer /ground connections under the package itself?

Put a plated-through hole in the board under the part, with a pad to
match the part's ground/heatsink pattern. Make the plated-through
hole big enough to stick a blunt soldering iron point through. Pretin
the board, push the part on while heating the back of the SMT through the hole,
flow solder in through the hole.

But lots of folks are using solder paste and toaster ovens
anyway today for BGA's etc. and then it's no big deal at all.

Has worked great for me in multiple AD9954 designs (400 MHz 14-bit DAC 
for DDS is the key... is 400MHz high frequency anymore? It was several 
years ago!).


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