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June 2006

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Subject:
From:
John Maxwell <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Maxwell <[log in to unmask]>
Date:
Mon, 5 Jun 2006 11:12:12 -0700
Content-Type:
text/plain
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Dale,
Man oh man I can only say I wish I was still consulting as this is not a
very good idea. Thermal shock with soldering irons was always a such a
good source of revenue for me in the old days.

John Maxwell

>Quite a lot has been done in regard to this in the design of electronic
>assemblies. There are some pretty good white papers out on part placement
>changes during board design that minimize this risk, especially during
>depanelization. I used to have one saved aside after an incident with a
>customer of ours. I'll see if I can find it and post same.
>
>The only solid way we were ever successful in finding these was with a quick
>touch with a hot soldering iron. The cracked terminus usually pops off the
>pad if it has cracked away from the body of the part. Yes, it does expose
>the cap to another shot of high temp, but it does ensure that you detect all
>cracked caps and get them replaced. Since caps with cracked terminus
>typically don't fail consistently during ICT or functional testing (as they
>can be in parallel or be making partial contact to pogo pins which still see
>a device), the soldering iron method was our only recourse. But, this is
>only practical if you have a consistent problematic area of the board. In a
>case where the caps may be located in many areas, trying the soldering iron
>technique on an entire board is probably not very timely or cost effective.
>
>Good luck with this. It's a tough one...
>Dale Ritzen
>Quality Manager
>Austin Manufacturing Services
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of John Maxwell
>Sent: Monday, June 05, 2006 10:46 AM
>To: [log in to unmask]
>Subject: Re: [TN] Finding cracked capacitors
>
>
>Daniel,
>Most flex cracks are hidden under the termination at the capacitor
>termination/PWA interrface making it very difficult to detect using SLAM
>or C-SAM. A quick way to uncover cracks is exposure to humidity & bias
>accelerating failure. A few temp cycles ahead of humidity testing will
>open the cracks a bit easing humidity entering the capacitor body
>accelerating failure.
>
>John Maxwell
>
>

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