Frank,
Look at de-paneling as when I was consulting it was the number one source. If I had to rate your probable sources w/o knowing what equipment is used, PWA thickness, size, location of part to OPWA edge etc on a scale of 1 to 5;
1) De-paneling 3-5 depending on technique used
2) ICT 3
3) Functional Testing 3-4
4) Mechanical assembly 4-5
5) Rework 3
6) Reflow 1
Hope this helps. By the way you can hear the little buggers when they crack:-)
John
On Dec 13, 2011, at 6:13 PM, Frank Kimmey wrote:
> Eric,
> How do you depanelize these PCBs?
> 0.1uF 0603s are relatively susceptible to stress fracturing.
> Any flexing of the PCB after assembly can cause cracks.
> John Maxwell has published a number of papers on just this subject.
> Possibly checking SMTA archives may help.
> Hope it helps,
> FNK
>
> Frank N Kimmey CID+
> Manager - PCB Design
> Powerwave Technologies Inc.
> Mobile - 916-670-0645
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric Laroche
> Sent: Tuesday, December 13, 2011 5:36 PM
> To: [log in to unmask]
> Subject: [TN] cracked capacitors
>
> Hi all,
>
> We've been witnessing some field failures related to cracked capacitors. We have seen it on different PCBA's, different panel configurations, different physical locations on boards even 3 different capacitor suppliers. The only constant is that we always see it on the 0,1uF ceramic 0603. We've only had a couple of cross sections done as they are relatively expensive. All cross sections done so far show evidence of board flexing causing 45degree cracks.
>
> There must be something along our process that causes this flexing. The way I see it, pretty much every step can be the guilty one. From PnP, reflow, repair, ICT, functional testing, depanelling and final mechanical assembly...up to some extent, they could all possibly be causing flexing and damage to capacitors. I would like to make a more extensive study to isolate the source of our problems. Are there other methods, less expensive than cross sectioning, to see if a capacitor is cracked?
>
> Have any of you faced this problem in the past? What methods did you use to isolate the source of the problem? What were your results?
>
> Thanks for your help,
>
> Eric
>
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