We've recently gotten into a debate over our via plugging process.

When I came here 13 months ago, the standard process was to screen 
print SR-1000 into the via holes, then apply LPI with the DP-1000
over the plugs, then HASL.  I didn't like that process because the 
vias plugged on one side are little pockets that trap liquids going 
into HASL causing poor solder coverage.  In worst case they can entrap 
microetch and cause etched out holes after component assembly.  I have 
pictures of microsections on returned modules where the entire hole is 
eaten away except where the plug ink is.

Anyway, I switched some parts and then later, all our plug work over to
plug after HASL.  We used LPI artwork with a dot pattern .006" larger 
than the drill size, then HASL, then via plug with a dot pattern .010"
larger than the the drill size.  

Recently, management has mandated we change back to the old 
process because they feel it's more in tune with what the customer wants.
They seem to be overlooking the fact that we used to get dozens of boards 
back that had failed due to opens in the vias after component assembly as 
well as the fact that first pass yields at HASL have risen 20% since the 
via process changed.

My question is this, how do big board shops plug vias?  Or do they 
plug vias at all?  

---------------------------------------------
While cruising the Internet, be sure to visit
our home page at  http://www.automata.com
---------------------------------------------