Each component has a life curve in the form of a bathtub, also called Weibull distribution. In the first phase are early failures caused by material weaknesses, quality variations in manufacturing, operator errors and spurious, unconfirmed failures. In the second phase, the permissible failures are defined, which are usually constant in time. In this second phase, the decisive failure rates for electronic components are calculated and determined. Phase 3, wear phase, hardly ever occurs for electronic components.