The metal in the holes helps transfer the heat from the components to
the other side of the PC board.  The goal would be to have the holes
filled all the way so there would be no trapped flux and maximum heat
transfer.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Charlie Pitarys
Sent: Tuesday, March 13, 2012 12:43 PM
To: [log in to unmask]
Subject: [TN] Purpose of these plated vias?

I have these PCB's (mixed technology) in house, used for an automotive
under hood application. In several spots on the board are these array of
holes. On the A-side a smt component like a thyristor will cover up the
array.
What are these there for? 
The wave flux residue is proving tenacious to effectively clean out of
every via. Especially with the old school cleaning tool at this account.

Some of the vias are clear but some have solder filling or partially
filling them. These are now also filled with wave flux.
Below is a link to a picture of the array.
http://i123.photobucket.com/albums/o319/dartfrogmts/Kyzen/A-Side00140xFC
R145
F20min-1.jpg

I'll get them clean but curious as to why these are on the board.
Thanks in advance

Charlie




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