Placement for reliability based on physics of failure concepts

Placement of microelectronic components on a printed wiring board (PWB) is addressed based on physics of failure characteristics. The problem of component placement for reliability, based on a failure model which incorporates component temperature, a base operating temperature, a threshold temperature, and change in temperature of an individual component, is examined. Placement procedures are developed so as to minimize the time-to-failure or the total hazard rate of the components on a PWB based on a forced convection cooling technology. From the examination of failure mechanisms, it is determined that the hazard rate of a component is generally a monotonically increasing function of temperature, a specified temperature difference, and/or a cyclic temperature difference. Based on these observations, placement procedures for temperature-dependent hazard rates are established. In addition to the hazard rate placement, the problem of placement based on maximizing the minimum number of cycles to failure is examined. Placement is discussed under both probabilistic and deterministic approaches