Are the vias selectively tented under parts? If so maybe you could
selectively plugged the vias in question (only 1 side of each via).

www.quickturnflex.com
Thank you, 
Jim Mahoney 
Quick Turn Flex Circuits, LLC 
Applications Project Manager 
P# 603-821-7071
M# 603-305-6250 
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vargas, Stephen M
Sent: Wednesday, June 17, 2009 12:22 PM
To: [log in to unmask]
Subject: [TN] SolderMask Question

All:

 

We have a Class III PCB, that we are building using leaded technology
(non-RoHS), HASL finish, where my customer is specifying double masking
over vias for "via protection". Dry film is initially being placed over
the vias only, then the board is covered by LPI. Our problem is that it
creates problems with the solder stencil not properly gasketing to the
PCB during screen-printing resulting in solder defects. We are seeing
raised solder mask as high as .003". Is this (double masking)
commonplace? Are there more "manufacturing friendly" options for optimum
via protection? I've asked about possibly using dry film mask only (no
LPI on top), but was told that the mask feature sizes are too small for
dry film. Any insight would be appreciated. 

 

Regards,

Steve Vargas

 

Polaris Contract Mfg Inc


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