Steve,
 I have seen cases where epoxy was used to support larger devices on
the bottomside. This could also mean the devices may not be easily
repaired. So I would only recommend this approach if you had extremely
good process controls and the component it's self was very robust will
low failure rates.
 Only a suggestion.

>>> [log in to unmask] 06/30/03 03:38PM >>>
Hi Steve

We don't double reflow this part. We wouldn't consider it without a
fixture or some other support.

You know that sound, the almost involuntary sound that patrons in a
restaurant make when a waiter drops a glass or a tray? It's kind of an
"oooooo" sound. Well if you run these parts, the sound that the troops
at your plant will make will be so loud as those pups start Peter
Panning to the floor that the people in the front will stop playing
games on the computer and walk out back to find-out what's going on.

Do the numbers:
* Part weight: 15.1 gm
* Lead toe to heel: 0.46/0.66 mm
* Lead width: 0.17/0.27 mm

Lead wetting area = 240* [0.46*0.17] mm^2 = 18.7 mm^2 [0.03inch^2]
Weight of component to total pad mating area ratio: 15.1 gm / 18.7 mm^2
= 804.6 mgm per mm^2 [519.1 gm per inch^2]

A commonly acceptable ratio is: 50 mgm per mm^2 [30 gm per inch^2]
Pushing the boundary ratio is: 44 gm per inch^2

Dave Fish

  ----- Original Message -----
  From: Steve Gregory
  To: [log in to unmask]
  Sent: Monday, June 30, 2003 8:42 AM
  Subject: [TN] Double-sided reflow with Altera RQFP...


  Mornin' All!

  Just a quick question, has anybody ever done a double-sided reflow
with a 240-pin Altera RQFP on the bottom that has a metal heatsink in
the top?

  Thanks!

  -Steve Gregory- ---------------------------------------------------
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