Guest
 Posted: Thu Sep 11, 2026 10:47 pm Post subject: Is 50X TC a Good Screen for Die Cracking? |
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| We have a die crack issue and the MRB decided to screen the lot with 50X temp cycle. Is this a good screen?
Assy Engr 2 |
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Joined: 16 Jun 2026
Posts: 107
Location: Paranaque City, Phils.
| Posted: Mon Sep 15, 2026 11:14 am Post subject: |
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| Hi Assy Engr 2,
I’m not a big fan of subjecting a lot to 50X TC to weed out its mechanically weak parts. For all we know, the weakest parts of the lot are robust enough to survive 51X, so all the units in the lot will still pass e-test after 50X. The parts can then fail generously once in the field. In effect, all that 50X TC does is to ‘weaken’ the lot prior to shipment. What I would recommend for reliability assessment is for you to get a sample population from the lot, and to subject the samples to 500X TC. All the weak parts in this sample set (sample size = SS) will certainly fail after 500X TC, so you’ll end up with a good estimate of the field failure rate (Rej/SS x 100%). You can then decide on whether or not the lot is shippable based on the field failure rate you’re seeing. Be sure to select the SS based on the LTPD level that you want to reject. Thanks, EE |
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