Time accelerated ultrasonic testing for disk drive suspension assemblies

This paper explains the proper application of one accelerated test design and identifies misuse so the ultrasonic cleaning technique can be used to its fullest advantage. Reliability through ultrasonic cleaning has been estimated at 0.9997 for one failure mode. To demonstrate non-parametrically with 90% confidence that reliability is greater than 0.9997 requires a sample size of 7675 parts, assuming zero defects and a binomial distribution. Using accelerated testing techniques under proper conditions, a sample size as small as 40 pieces may be used to verify this reliability. The procedure has successfully demonstrated the ability to identify part or process design weaknesses early enough for preventive action to be taken prior to production.