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May 2005

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From:
Joyce Koo <[log in to unmask]>
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Date:
Fri, 13 May 2005 17:09:54 -0400
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thermal shock 10 times and electrical test as part of screening or burn-in.
                                        jk

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bev Christian
Sent: Friday, May 13, 2005 3:17 PM
To: [log in to unmask]
Subject: Re: [TN] NDT Question


Werner,

I used the hokey expression of "intermittent micro-cracks" to waylay
people suggesting I use x-ray of one sort or another.  And, yes, I was
talking about a full crack across the entire SJ.  The problem with this
part is that it is so complex I am not sure that 100% functional testing
is possible.

Bev

RIM



  _____

From: [log in to unmask] [mailto:[log in to unmask]]
Sent: May 13, 2005 3:14 PM
To: [log in to unmask]; Bev Christian
Subject: Re: [TN] NDT Question



Hi Bev,
It sort of dependents. First there is no such thing as intermittent
micro-cracks in SJs. If they are micro-cracks, they can be present
starting about 40% into the life of the SJs, but they do not impact
electrical signals, intermittent or otherwise. If you have a full solder
joint fracture, electrical signal interruption will be intermittent,
because the fracture surfaces are in at least some slight compression
and make very good 'connector surfaces.'
If you have fully fractures SJs, they will only show intermittent opens
if they are disturbed by either temperature changes or mechanical
shock/vibration. The best way to find them is to do functional tests
during vibration loading.

Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com







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