AVR-Chat

Steve,
I've attached a print of the corner of a board we did this way.  Note that the holes are really big, 0.062".   I did this to allow for air flow but have no idea what difference it makes.  Maybe smaller holes are better?  Someday I should try and model this in our 3D CAD.


Tim Gilbert
JEM Innovation Inc.
www.jeminnovation.com
www.pdksolutions.com

  ----- Original Message ----- 
  From: Steve Hodge 
  To: AVR-Chat@yahoogroups.com 
  Sent: Tuesday, February 01, 2011 7:27 PM
  Subject: RE: [AVR-Chat] d2pak heat sink


    
  Thanks, Tim. Since the tab is ground, I assume you just connect the upper
  one to a regular ground plane on the bottom?

  I came across an App Note (#994) on the International Rectifier website that
  made measurements of the thermal resistance of various SMD packages, using 3
  different "pcb heat sink" techniques. Although the bottom of their test
  board was "fully metalized" there is no mention of explicitly connecting it
  to the test patterns on the top with vias. I suppose some heat conducts
  through the fiberglass but your technique should give significantly lower
  thermal resistances than they measured because the thermal conductivity of
  copper is 10000 times that of fiberglass.

  Steve

  From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
  Of tim gilbert
  Sent: Tuesday, February 01, 2011 4:33 PM
  To: AVR-Chat@yahoogroups.com
  Subject: Re: [AVR-Chat] d2pak heat sink

  Steve,
  For such packages, I usually just expand the copper area around the device
  on both the top and bottom layers. I then interconnect them with lots of
  large vias. Effectively building a heat sink into the board.

  Tim Gilbert
  JEM Innovation Inc.
  www.jeminnovation.com
  www.pdksolutions.com

  ----- Original Message ----- 
  From: Steve Hodge 
  To: AVR-Chat@yahoogroups.com <mailto:AVR-Chat%40yahoogroups.com> 
  Sent: Tuesday, February 01, 2011 2:45 PM
  Subject: [AVR-Chat] d2pak heat sink

  I've been checking out the various heat sinks for D2PAK devices and confess
  to being confused as to how they are mounted. I'd also like some
  recommendations, if anybody has any, for ones that are the easiest to use.
  I need to be able to hand solder things.

  Thanks, Steve

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