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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Werner Engelmaier <[log in to unmask]>
Date:
Tue, 19 Jan 2010 14:10:30 -0500
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 Hi Chris,
The only way to accelerate the process is in a temp/humidity chamber doing T/H-cycling—it still will take some 500 hours,
Werner

 


 

 

-----Original Message-----
From: Chris Mahanna <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Jan 19, 2010 1:49 pm
Subject: Re: [TN] TI MSP Early Life Failure?


Werner, Vlad, Paul-
Thanks for reassuring me that we are playing the probabilities correctly.  We've 
used sectioning/lapping, polarizer/analyzer, and SEM/EDS (to find the Cu, Br) 
successfully many times.  Our problem this time is that we need to grow one.  We 
used four of the actual boards, with 12 opportunities each = 48 total.  A good 
CAF test vehicle would have 100s.  We used 2 cycles of 2.6.27 260C profile for 
precondition.   Customer wanted 2 cycles and actual product bias voltage (3.3V), 
which doesn't help us accelerate.  Oh well.  I was just wondering if anyone 
would reply "hey those MSPs will short if they were damaged..."

Chris

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of vladimir Igoshev
Sent: Tuesday, January 19, 2010 11:43 AM
To: [log in to unmask]
Subject: Re: [TN] TI MSP Early Life Failure?

Chris,

Werner is right, it's difficult, yet doable to prove you are dealing with CAF. 
You'd need to have sectionning, as well as lapping done to find Cu between 
fibers and resin in the board.

Regards,

Vladimir
SENTEC
SENTEC
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca

-----Original Message-----
From: Werner Engelmaier <[log in to unmask]>
Date:         Tue, 19 Jan 2010 11:25:37 
To: <[log in to unmask]>
Subject: Re: [TN] TI MSP Early Life Failure?

 Hi Chris,
Your scenario sure points towards CAF given the reflows, the via spacing, the 
timing of the failures, the high resistance of the shorts.
And yes, 'proving' CAF is difficult at best. What are you trying to do to 
'prove' CAF?
IMHO, the best you can do is finding circumstantial evidence--the best is rough 
drilled hole walls on other vias with Cu-plating along separations of 
glassfibers and resin.
Werner

 


 

 

-----Original Message-----
From: Chris Mahanna <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Jan 19, 2010 11:13 am
Subject: [TN] TI MSP Early Life Failure?


Hello Technet,
We are working on a failure analysis of a battery operated remote sensing 
device.  Failure is linked to 500ohm short power/ground.  The assembly 
experiences at least (2) 255C reflow thermal excursions.  Failure manifests at
~6 months.
Slicing/dicing isolation yielded: breakdown between two vias (17 mil spacing) 
and/or MSP input impedance.  Beyond that, original evidence is lost.
We are working the CAF theory, however reproduction of the problem is proving 
difficult, possibly due to the low number of opportunities on the actual board.
For those of you who know that I'm pushing for placement of (the new) CAF 
coupons on panels, yes this is our most recent example of the problem.

I would like to get feedback on the possibility that it was the microcontroller 
instead...

TI MSP430F1612
Level-3-260C-168 HR


Thanks!

Chris Mahanna
Robisan Laboratory Inc.

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