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-Side00140xFCR145
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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