Bimodal failure behaviour of metal film resistors

Abstract

The ageing behaviour of metal film resistors was studied using high-resolution in-situ resistance measurements. A temperature storage experiment was performed at five different temperature levels. At each condition, the ageing behaviour of 128 resistors was monitored. It turned out that the failure behaviour of the samples is rather complicated. One remarkable fact is that measurements coming from two different production lots led to completely different results. One production lot displayed monomodal failure behaviour, while for the other lot bimodality was observed. Serious errors in the calculation of the FTTF (first time to failure) can be expected when this fact is not properly taken into consideration. This paper also discusses some important aspects of the analysis of failure time data, such as (i) the choice of the underlying failure distribution, (ii) the number of samples to be tested and (iii) the failure criterion to be used. (C) 1998 John Wiley & Sons, Ltd.