To answer the question from Chris.  

With a curtain coat solder mask process no solder mask enters the small 
via holes.  The coating speed is fast and the momentary tent that forms 
is not sustained due to the low viscosity of the LPI at this stage. 

As I see it these solder filled vias would therefore be appropriate to 
use as test points.  Our experience is with wave soldered product.  Can 
anyone give some input on the possibility of using this with reflow 
techniques.

Richard Wood-Roe
Artetch Circuits 
Littlehampton UK
   ********** ORIGINAL MESSAGE FOLLOWS ********** 
This sounds like a good solution.  One question though.  Can these vias 
also be used as test points or does the soldermask come down the hole and 

interfere with the probe making contact?
Thanks,


--- Chris Stack
--- Ext. 231                       
--- [log in to unmask]                    
--- CD Electronics, Inc.                   
--- Printed Circuit Board Designer and Purchasing Agent 

             ********** ORIGINAL MESSAGE FOLLOWS **********


When vacuum fixture testing is required we encourage our customers to use 
the following fix.

Soldermask phototools are created that leave an open pad area on the 
solder side but tent the component side of the pcb.  Our curtain coat LPI 
process of course does not tent or plug the vias.  However the subsequent 
wave solder process will!

This has the advantage that we have no risk of chemical residues from 
HASL being trapped in the via holes.  We can also mass produce plugged 
vias effectively without the use of dry film solder mask etc.

Our customers really like this cost effective fix and have not seen 
problems with solder balls on the top side.


Richard Wood-Roe
Artetch Circuits Ltd.
Littlehampton - UK