I remember that years ago there was a process called printed through holes that 
essentially printed conductive material through a hole to make a double sided 
board. This technology may not be used anymore, being replaced by plated through
holes. This did nearly fill holes.

______________________________ Reply Separator _________________________________
Subject: Fab/Assy:  Thermal Vias
Author:  [log in to unmask] at INTERNET
Date:    7/31/97 8:24 AM


Hello Technetters,

        Has anyone found a method to completely fill a via?  I don't think 
that the standard plating process will guarantee 100 % fill.  We're also 
looking at the option of screen printing conductive epoxy and trying to force 
it through the hole.  But, I don't have a lot of confidence in this process 
either.  The last option we're considering would be to plug the vias with LPI 
soldermask.  This seems like the best guarantee of fill.  Thermal conductivity 
is not so great, but it is better than air.
        I'd sure appreciate any comments.

Glenn Pelkey
Quality/Reliability Engineer
Maxtek Components Corp.

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