Product Maturity 1

4Components with Limited Service Life

As already noted, a product is considered mature provided no aging mechanisms are observed when it is put into operation. However, all components have several potential aging mechanisms. Let us take the example of complex integrated circuits; there are failure mechanisms that may be generated at three different locations:

• – the chip:
  • - hot carrier injection (HCI),
  • - negative bias thermal instabilities (NBTI),
  • - positive bias thermal instabilities (PBTI),
  • - electromigration (EM);
• – the interface between chip and package:
  • - bonding lift-off,
  • - bonding breakage,
  • - degradation of the braze between chip and substrate;
• – the component interface between the printed circuit and the pins of the component:
  • - breakage of the brazed joints.

However, experience shows that if the component is correctly designed, these aging mechanisms are never observed, except for certain categories of components which have limited service life under certain conditions.

Hence, using the bill of materials of the product under consideration, it is absolutely essential to check whether or not these mechanisms will be observed under the operational conditions to which the component will be subjected.

Figure 4.1. Overview diagram of an integrated circuit. For a color version of this figure, see www.iste.co.uk/bayle/maturity1.zip

Certain predictive reliability ...