Hello-
I'd like to ask how some of you are handling vias under a QFN package. 
What I'd like to do is plug them completely from the bottom with epoxy. 
Many high volume manufacturers will only use solder mask for plugging 
vias, or charge a 10% increase in cost.  The vias are required for thermal 
relief under the part, so solder mask must be left open on the top.  These 
vias need to be filled or tented from the bottom to prevent solder from 
wicking up during the solder wave process, after reflow.  So far, using 
only solder mask for plugging isn't working out very well.  I haven't been 
able to find a simple solution, everything I've read basically said yes, 
this is a problem.  But haven't found any solutions.  One company has 
offered a LGA pattern for an identical part, but this land pattern has 
even more vias exposed under the LGA package, also for thermal refief. Any 
suggestions? 
Thank You So Much,
Kitty

Kitty Hines
The Chamberlain Group, Inc.
(630)516-6655
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