Aric
A couple of suggestions:
 - use an automated dispenser to put down the epoxy in a pattern that
encourages even seating (such as a plus sign).  The manually dispensed epoxy
will make subsequent alignment more of a challenge.
 - if you can, use some sort of fixture to hold the heatsink in the x-y
plane, and use a weight to push it onto the epoxy.
 - use an adhesive with some forgiveness.  An ex product of mine had two
heatsinks on QFPs, the process was to automated dispense epoxy on the
heatsink, place it on the qfp and put the weight on top, while holding the
heatsink in alignment by hand.  The heatsink could be slightly moved if the
alignment wasn't quite right after the weight was removed.  Not high tech,
but maybe medium tech...

Good luck!

Graham Collins
Process Engineer,
Litton Systems Canada, Atlantic Facility
(902) 873-2000 ext 6215

-----Original Message-----
From: Aric Anderson [mailto:[log in to unmask]]
Sent: Monday, June 21, 1999 4:54 PM
To: [log in to unmask]
Subject: [TN] Heat Sink Assembly


Hello Technetters,

I am encountering several problems with a  heat sink assembly process.
Currently, our heat sinks are hand placed onto cpus and other components
using an epoxy dispenser ( automatic ) and a steady hand.

The Problem:  The heat sinks are not seating properly, misaligned and
uneven due to operator error.  Some of our products use clips and pins
for heat sink placement, but several do not.  I know that this is an
issue of board real estate that needs to be resolved between
manufacturing and engineering, but until then I am looking for a
solution.

I want to take the human factor out of this heat sink placement so I can
achieve the proper alignment and force to attach heat sinks to
components.  They are to large and cumbersome for any high speed
placement machine.


If anyone has experienced this problem and has any suggestions, your
response would be much appreciated.