FYI
I have reviewed the attachments to this email, and I would not be very
happy to see this in product.  Arlon says this is ok, but I would have a
concern where the spots are between closely spaced traces, and might
lead to CAF failures.  We do not use the 33N material in our production.
The material meets the IPC-4101/41, but our experience is that the /41
materials are brittle and prone to haloing around NPTH's---not good--,
so we typically use IPC-4101/42 polyimides.  There is a slight loss in
Tg properties between the (2) materials, but they still meet ROHS
criteria, and I personally would prefer a little more "plasticity" in
our laminates for processability.  Choice is yours.


Dennis J. Cantwell
R & D Liaison
Printed Circuits, Inc.
1200 West 96th Street
Minneapolis, MN 55431-2699
952-888-7900
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-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Dung Tiet
Sent: Monday, March 24, 2008 5:26 PM
To: [log in to unmask]
Subject: [IPC-600-6012] Arlon 33N polyimide laminate condition: whitish
spotty/hazy appearances

Hi all,

We recently ran across a whitish spotty/hazy laminate condition first
spotted 
after a couple of boards had gone thru assembly (see attached PWB.jpg 
picture showing condition on laminate between connector fingers on 
assembly).  The condition was brought into question and after some 
investigation, we learned that such condition is a pre-existing one at
the bare 
laminate level that normally occurs with Arlon's 33N polyimide laminates
due to 
a micro-disperse second phase of the flame retardant brominated sytem.

And apparently, this condition is seen to varying degrees within the 33N
(see 
attached pictures: 113_1335a.jpg - more so, 113_1352a.jpg - less so).
Also 
attached is Arlon's letter that explains this laminate appearance,
concluding 
that it's not a laminate defect.

How have other end-users of this 33N laminates dealt with this laminate 
appearance at the assembly level?  Has it caused any grief and how had
the 
assemblies been dispositioned?

Of course this condition, when it exists, can only be seen under
magnification, 
but even then, the whitish spotty/hazy appearance can be confused with 
other possible laminate imperfections/defects when seen by the
inexperienced, 
like we were.  I'm not even sure if we're able to automatically say this
is the 
condition we have when similar appearances are seen on future finished 
assemblies.

Any feedback you have is greatly appreciated.

Thank you,

Dung Q. Tiet
Lockheed Martin Space Systems Co.
Sunnyvale, CA
Tel: 408-756-2365
Email: [log in to unmask]