They are also usedin telephony Ethernet ICs, power ICs, PoE Controllers
etc often use these.  It is very important that the manufacturer's
requirements for soldering of the heat spreader to the heat sink beneath
the Component also be followed to assure correct thermal impedance on
the bottom of the device.

mark


mark
Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave |
Westminster, CO 80234  USA |
Voice (Lab): (303) 538-2166 | email: [log in to unmask] |


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dennis Fritz
Sent: Tuesday, March 13, 2012 3:13 PM
To: [log in to unmask]
Subject: Re: [TN] Purpose of these plated vias?

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-Side00140xFCR
145
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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