Infant-mortality period: bathtub curve

Figure 6.17 Weibull plots and the bathtub curve (a) infant-mortality period, (b) infant mortality and useful life period and (c) useful life and end-of-life period.

The lifetime of a population of units at the component, board, box, or system level can be divided into three distinct periods. This is most often defined by the so-called reliability bathtub curve (Fig. 6.16). The bathtub curve describes the cradle-to-grave failure rates or frequency of failures as a function of time. The curve is divided into three distinct areas early failure rate (also known as infant mortality), the useful life period, and the wearout failure period. The infant-mortality portion of the curve, also known as the early life period, is the initial steep slope from the start to... 

The lifetime of an entire population of products often is graphically represented by a set of curves collectively called the bathtub curve. Bathtub curve has been depicted in Fig. VII/1.2.2-1. The bathtub curve consists of three periods. First is an infant mortality or burnt-in period with a decreasing failure rate showing early-life failure. These... 

A plot of the failure rate of a product as a function of time typically takes the shape of a bathtub curve (see Fig. 57.2). This curve illustrates the three phases that occur during the lifespan of a product from a reliability perspective. In the first, infant mortahty phase, there is an initially high but rapidly declining failure rate caused by infant mortahty. Infant mortality is typically caused by manufacturing defects that went undetected during inspection and testing and lead to rapid failure in service. Burn-in can be used to remove these units before shipment. The second phase, the normal operating life of the product, is characterized by a period of stable, relatively low failure rates. 

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