When I resigned from Medtronic, Accelerated Life Testing (ALT) was being performed at levels less stressful than what would be performed for a commercial high-reliability cell phone radio. Standard practice is to soak a product at hot temperatures for many hours and then alternate with a soak at cold temperatures for a period of weeks.
Highly Accelerated Life Testing (HALT) is an attempt to quickly age a product with shorter temperature cycles, faster transitions between temperatures and more extreme temperatures as compared to ALT. I've looked into using HALT when working for another employer and the determination was made that there wasn't enough evidence to support the conclusions of the proponents. Typically papers on HALT conclude that because HALT was successfully performed on a piece of angle iron, it should be universally applicable to all types of electronic circuits. Electronics can have many failure modes not exhibited by a solid piece of steel such as dendrite growths, effects caused by oxide layers, etc. HALT has not yet been proven to be a suitable replacement for ALT for a high reliability radio.
The senior radio design engineer that developed the Concerto laptop radio, and the senior radio engineer for Conexus (a technical fellow at Medtronic) agreed that ALT is the better test. The senior radio engineer for Conexus and I met with the individual in charge of addressing new quality issues and we communicated our concerns in mid-2005. Not performing ALT was something that slipped through the cracks and the test isn't very significant in terms of manpower, but we never heard from the individual in charge of new quality issues again. The concerns regarding ALT testing were later presented to senior management by yet another concerned radio engineer and again nothing happened. The day after I submitted my protest resignation, Medtronic claimed that none of my (and others) concerns had merit. Medtronic did not tell me how they arrived at this conclusion in opposition to the majority professional opinion of their radio engineers. Now Medtronic claims they adopted some of the recommendations. Medtronic refuses to say what they did to verify Concerto and it's associated laptop are safe.
