A highly accelerated life test method for computer keyboards

Abstract

A new method of Highly Accelerated Stress Screen/Life Testing (HASS/HALT) for computer keyboards is introduced and compared with User Information Investigation (UII) from manufacturer, Accelerated Life Testing (ALT), and Normal Stress Reliability Testing (NSRT). The results of the above three lab testing processes all showed good accordance trends with the data from the UII. The failure mechanism shows that a silicone cushion component acts as the spring and the shock absorber when keys are pressed, and acts as a key role to the key function, also decides the life of the key. When the dynamic load of “knocks” (mechanically simulated key presses) increases, the key life decreases, with degradation or failure especially apparent of the silicone cushion. Once a cushion fails, the dynamic shocking forces greatly increase, and the key cap soon breaks. The cushion failure was not a exclusive failure mode observed in the UII, NSRT, ALT and HALT tests, but a crucial one in the Complete Failure Mode Set. The HASS/HALT tests were able to show some quality control features of keyboards within a very short period. The trends corresponded well with real-world failure rate reported by users, ALT and NSRT. This study aids the design of rapid reliability/life testing which is important for product development and efficient quality control. With the help of this method, long-term reliability certification testing can be reduced from months to days.