Physics of failure as an integrated part of design for reliability

As part of a UK DTI collaborative funded project developing a holistic methodology and assessment model for the enhancement of electronics reliability, a study into the use of physics of failure (PoF) methods was undertaken. It was conducted by reviewing the use made of PoF techniques by the partners and specifically by undertaking a of a number of case studies. It is concluded that PoF methods, and particularly life modelling, are an essential tool in design for reliability. PoF analysis can also be used in establishing reliability enhancement testing (RET) and environmental stress screening (ESS) conditions. A guide for the effective use and inclusion of the PoF methods into product design and development process has been developed and described. The techniques offer benefits in getting a design right first time, thereby avoiding redesign and retest cycles, with consequent cost savings and reduced product development times. The PoF method has limitations associated with the fact that it is essentially a bottom up approach assessing time to failure due to known failure mechanisms. It is consequently difficult to apply to full systems, has limitations in assessing failure rate prior to the onset of life limiting wear out, and is dependent on identifying, and having a validated model, for all potential failure mechanisms.