[sdiy] modern AD/DA chips?

Eric Brombaugh ebrombaugh1 at cox.net
Fri May 8 00:34:47 CEST 2009


Dave Manley wrote:
> Beware the leadless QFN.  In my job we had a prototype board with 
> leadless QFN, assembled by a very large, well-known manufacturer.  We 
> had many board defects due to solder issues on QFN packages.  A real 
> pain in the...

Over on some other electronic DIY lists I'm on I've seen some additional 
complaints about problems with QFNs, even in non-DIY contexts. One of 
the most interesting (to me) was that it's difficult to clean flux from 
underneath these parts which often results in high impedance leakage 
issues. Apparently QFNs have even less clearance than BGAs after 
assembly and if you can't wash under them the flux can conduct. Don't be 
trying to build any long-duration sample-holds with QFN parts...

Whose idea was this anyway?

That said, I've had reasonable luck with QFN parts and other blind 
soldered parts (TSSOP24 with bottom heat slug) using a hot-plate reflow 
process.

Eric



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