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Capacitor Failure

Views: 1902

Darren

#41199

Capacitor Failure | 26 April, 2006

Hi

We have a new product that has a 22uF 0805 X5R 6.3V Chip Cap. It is placed on standard 0805 pads but is 1.25 mm high and although we are not getting the best fillet it appears sufficient. The trouble is we are getting a small number of returns that have failed but when we touch up the terminations the units come back to life. The oven profile is good.

Any help would be much apreciated.

Regards

Darren

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Rob

#41205

Capacitor Failure | 26 April, 2006

Hi Darren,

First thing is to check the footprint against the manufacturers:

http://search.murata.co.jp/Ceramy/image/img/A18X/C2EB3M.pdf

as this may behave differently thermally to other 0805 devices due to the exceptional number of layers inside.

Cheers,

Rob.

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#41209

Capacitor Failure | 26 April, 2006

Since the connection improves when you touch it with a soldering iron, it indicates that the reflow recipe is NOT good. Something may have changed with the termination material requiring a higher peak temperature.

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PWH

#41211

Capacitor Failure | 26 April, 2006

I've seen failures like this with multilayer parts that seem to be affected by high activity flux during SMT (water soluable in this process). High, high failure rate in our case. I'm not sure what was going on with our parts but we thought maybe the chip layers could somehow absorb the flux which affected the functionaliy of the part. We went to a lower activity, no-clean solder paste and the problem went away.

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Rob

#41224

Capacitor Failure | 26 April, 2006

I'm guessing it's part No. GRM21BR60J226ME39, which has a Matte tin finish.

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#41239

Capacitor Failure | 26 April, 2006

I find is fascinating that a lot of people blame the Pbfree finish before anything else, as if this is some new and scary thing. It MAY be a contributing factor, but I doubt it is the main or only issue. When we started evaluating our BOM's 1.5 years ago, we found that probably 90% or higher of our caps had already become Pbfree without us knowing about it. Kemet has been Pbfree on their chip caps since 1998! Rohm has supplied only Pbfree components for almost all of their parts since mid 2004, and some converted before that. Murata's standard finish has been Pbfree for several years as well. AVX standard PN is Pbfree, Panasonic changed w/o changing PN's, although they won't reveal the exact date when most components changed.

We have all been populating Pbfree parts in a SnPb process successfully for years. This has seldom been a problem.

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Rob

#41246

Capacitor Failure | 27 April, 2006

Most of Murata's parts were changed over by 1996, except high reliability/automotive as there wasn't enough data to prove or disprove this at the time.

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