Development of the accelerated stress testing process at Otis elevator company

Abstract

Otis Elevator Company, a subsidiary of United Technologies Corporation (UTC), recognized the need for transition from a ‘test-to-requirements’ to a ‘test-to-failure’ philosophy for electronic and electromechanical products in the late 1980s and early 1990s. Products ‘passing’ relatively benign environmental tests (although similar to actual field conditions) exhibited unacceptable field reliability performance. New test methods, defined as accelerated stress testing (AST), were investigated and implemented. The performance of AST requires a two-step approach with Step 1 performed in product development and Step 2 in manufacturing. Step 1. Highly accelerated life test (HALT)—multiple stress step-stress and combined stress application on at least five or six samples using temperature and vibration stresses. All relevant failures or those defects deemed likely to occur in deployment are driven to root cause and corrective action is developed, implemented and verified. Step 2. Highly accelerated stress screening (HASS)—appropriate combined stress application during production using temperature, vibration and electrical stresses. In addition, a stress auditing process, highly accelerated stress audit (HASA), exists. Copyright © 1998 John Wiley & Sons, Ltd.