chapter  14
34 Pages


Producers of oscilloscopes are in a highly competitive market that does not tolerate high purchase or maintenance costs. One company decided to develop a family of oscilloscopes with increased capability and reliability three times greater than existing models (Wheeler, 1986). To accomplish this goal, reliability and quality engineers were involved at the start of the design decisionmaking efforts. The initial task of the development group was to perform analyses of past equipment failures. The result of this effort provided information that identified that many failures were caused by temperature stress. The design process obviously focused on reducing stress To realize their company goal of improving reliability by 300%, it was determined that the new design would have to limit the oscilloscope's internal temperature increase to 10° C or less. As reported by Wheeler (1981), the stress analysis revealed the following as design goals:

1. Hold stress levels to 50% of a component's rated stress to decrease failure rates. Examples: A bipolar integrated circuit (IC) at 70% has twice the probability of failure than one at 50%. A dielectric capacitor operating at 70% of its rated voltage fails five times more frequently than one at 50%.