These heat spread arrays are common in automotive boards. Somethimes they are called "via farms".  



-----Original Message-----
From: Charlie Pitarys <[log in to unmask]>
To: TechNet <[log in to unmask]>
Sent: Tue, Mar 13, 2012 3:45 pm
Subject: [TN] Purpose of these plated vias?


I have these PCB's (mixed technology) in house, used for an automotive under
ood application. In several spots on the board are these array of holes. On
he A-side a smt component like a thyristor will cover up the array.
hat are these there for? 
he wave flux residue is proving tenacious to effectively clean out of every
ia. Especially with the old school cleaning tool at this account.
Some of the vias are clear but some have solder filling or partially filling
hem. These are now also filled with wave flux.
elow is a link to a picture of the array.
ttp://i123.photobucket.com/albums/o319/dartfrogmts/Kyzen/A-Side00140xFCR145
20min-1.jpg
I'll get them clean but curious as to why these are on the board.
hanks in advance
Charlie


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