Received: |
by ipc.org (Smail3.1.28.1 #2)
id m0u3jw1-00008RC; Mon, 1 Apr 96 07:46 CST |
Old-Return-Path: |
|
Date: |
Mon, 1 Apr 1996 08:50:56 -0500 |
Precedence: |
list |
Resent-From: |
|
Resent-Sender: |
|
X-Status: |
|
Status: |
O |
X-Mailing-List: |
|
TO: |
|
Return-Path: |
<TechNet-request> |
Resent-Message-ID: |
<"yNMSC2.0.hm7.euzNn"@ipc> |
From [log in to unmask] Wed Apr 3 16: |
46:18 1996 |
From: |
|
Subject: |
|
X-Loop: |
|
Message-ID: |
<960401085056_366903440@mail04> |
Parts/Attachments: |
|
|
ed
My comment addresses the PINK RING issue
of your problem
Although the various specifications state that
pink ring is a process indicator and not a failure
mechanism - remember that it indicates that
there is a problem or there would not be any
pink ring.
That problem is: At some point in time the
bond between the prepreg and inner layer was
breached and chemical solutions were allowed
to invade this breach.
Whether or not this becomes a failure mechanism
depends upon several things such as: did the
subsequent electrolytic plating "heal" this breach
and completely prevent any voids at this location.
Ionic contamination within a board, if hydrolized by
moisture, will migrate if under a bias.
My controversial opinion is that all boards with pink
ring are suspect for wedge voiding and contamination
within the board. Some boards will not degrade due
to their use and others will. I am not certain if this is
related to the laminate system (polyimide is more
hydroscopic than epoxy), but it sounds reasonable.
The problem is you cannot microsection every hole
when you see pink ring conditions. If "pink ring" extends
down associated conductors of affected pads, I think
you have more than pink ring,
Susan Mansilla
Robisan Laboratory
317-353-6249
|
|
|