Bill,
	I used to specify in my manufacturing notes 'vias must be plugged
using LPI solder resist' I was told more then one once and from different
suppliers that they could not guarantee the vias would be 100% 'plugged'
using LPI. They would however guarantee that there would be LPI in the via
hole or that the LPI would tent over the via, leaving a void in the center.
If I required 100% via fill I would have to require that they fill the holes
with some type of conductive filler.

Thank you,

Ted T

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brooks,Bill
Sent: Tuesday, October 02, 2007 3:44 PM
To: [log in to unmask]
Subject: [TN] Via plugging with LPI soldermask...

Just a quick question... 

When specifying 'plugged' vias using LPI soldermask... what is the actual
process used to accomplish this procedure? How do you make sure the vias are
plugged and what is the proper acceptance criteria used to verify and
inspect the finished results? What is an acceptable plugged via vs. a
reject? Is there a spec or standard that spells this out process and
inspection criteria and method for reference?

Thanks in advance... 


Bill



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