Obtaining High Reliability Performance from Commercial Quality Opto-Isolators

Techniques are presented for effectively screening plastic DIP opto-isolators for latent dark current leakage and premature current transfer end of life, with resultant low laboratory field failure rates. Investigations are described which included long life tests conducted at TRW Components Laboratories and vendor test laboratories, and field experience with TRW/Data Systems and TRW/VIDAR/Digital Products equipment. Resultant from these investigations were discovery of environmental stress conditions for predictable rates of dark current leakage acceleration and annealing, and for criteria and test conditions to identify latent premature end-of life current transfer characteristics. These findings were instrumental in the development of customized burn-in and screening techniques to effectively surface parts with latent infant mortality characteristics. Field failure rates were improved to less than eleven failures per billion hours. Laboratory test experience projects to failure rates of less than 13 failures in 10⁹device-operating h at 25°C for these specially screened devices. This is approximately 100 times improvement over prior life experience of similar commercial and "high rel" devices, thus resulting in significant maintenance cost savings.