Hi,
My company is currently experiencing a high feild failure rate on a 100nF chip ceramic that we use in various applications across our product range. One of them being de-coupling which means we use millions of this device every month.
The failures we are getting back were all built in a two month period where we had changed supplier of the part in question as part of a cost cutting exercise. No verification was done on the part as it was deemed to be a "straight replacement". Sound familiar?
All field failures are with boards being manufactured between October 02 and after Dec 02, exactly the time we used the new supplier.
I have checked profiles, de-paneling methods, z-axis force, z-axis heights, all to no avail. Incidentally, the failures are all over the product range and on different places on each board so tooling hits are not the solution either. I also sent some part off to a local university to be analised. The findings were interesting, they noticed after sectioning that the capacitors displayed high levels of porosity. This to me was a dead give-away, the porosity seen in the new capacitor against the porosity in the old "good" capacitors meant that the new devices were inherently weak, meaning that they could be damaged as they were placed, or as the boards were snapped out of their panel. I was also interseted in the pop-corning effect that is possible with chip ceramics. This would tie in with the porosity I am seeing.
The confusing thing about all this is that the failures are not seen at test. We have full ICT test and then full functional burn-in on all of our products. No failures have been seen in house. Does this mean the popcorning or the micro cracking is causing the device to breakdown over time?
The supplier insists they have not seen the problem with any other customers. We only see the problem over the two months we used this supplier. I am convinced the parts are inherently weak, baring (bearing???!!!) in mind that no other parts we use show have problem. None of them. The nozzles we use are soft rubber and the z-axis is spring loaded. There is no way we can/should be damaging these parts.
Any past experiences of this out there? Also, how do my purchasing department deal with this supplier?
Cheers, Dougie.
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