Dear Technetters,

We see some failures in one of our products due to resistance drop across a
1206 resistor on a PWB assembly. The products failed after hours of
operation in the burn-in environment and is suspected to be the effects of
SIR drop or electromigration. There's 135Vdc across the resistor during
operation. The designer thought it's ok because the resistor itself has a
max. operating voltage of 200Vdc. The land pattern is of the IPC-SM-782
standard (1.2mm gap in between). The solderpaste is also claimed to be
compliant with IPC-SF-818 and Bellcore TR-78 in terms of SIR and EM.

My understand is that SIR and EM are tested with bias voltage of 50Vdc and
10Vdc respectively. Are these standard tests really applicable to this high
voltage case?

Thanks!

KK Chin
Artesyn Technologies
47173 Benicia Street,
Fremont, CA 94538

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