Traditionally, placement techniques have focused on improving rotability based on minimizing the total wire length between interconnected components. However, electronic card assembly (ECA) reliability, which is measured in terms of time to failure, cycles to failure, or the hazard rates of the individual components, the interconnections, and the PWB, is also affected by component placement. This paper discusses component placement for reliability based on a failure model which incorporates component temperature, a base operating temperature, a threshold temperature, and change in temperature. Placement procedures are developed so as to minimize the time to failure or the total hazard rate of the components on a PWB utilizing a forced convection cooling.

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