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November 2006

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Subject:
From:
"Dehoyos, Ramon" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Dehoyos, Ramon
Date:
Thu, 30 Nov 2006 15:23:09 -0500
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        Susan:
              Wouldn't you say that some of the thermal caused
delamination is repairable?  One repair that comes to mind is drilling
holes on both sides of the blister and injecting epoxy, pressing down
and bake. 
        In this case the blisters are too big and span under some
geometries. There were some serious errors in building these boards such
as poor cleaning, skipping steps,...
        Regards,
        Ramon 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Susan Mansilla
Sent: Thursday, November 30, 2006 10:28 AM
To: [log in to unmask]
Subject: Re: [TN] More delam

  1. Are any of these fixable?
No, they are not fixable.  The one thing that you could do is determine
if the delam after the hand soldering is a function of the lot of boards
or the hand soldering process.  The ground planes in the board present a
problem when pre-baking, but you can pre-bake to remove the moisture
between the ground plane layers.

  2. Would you try, or would you just let them go, or would you scrap
them?
The boards have to be scrapped, in my opinion, since you now know the
extent of the delamination within the board.

  3. Can someone interpret what IPC-A-600 means by:
  -The blister or delamination does not span more than 25% of the
distance between adjacent conductive patterns.
  (adj patterns on the same layer as the delam, or adj patterns on any
layer in the board or ...?)  For instance, dctest2.jpg spans the
conductive patterns on the top layer, but the delam is on an internal
layer (of course).
IPC-A-600 addresses a bare board.  The requirements in it are for bare
boards PRIOR to any thermal stressing for blisters and delamination.
Since the condition was propagated by the thermal stressing of the
soldering process, that alone makes it non-compliant.

Susan Hott
Robisan Lab

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