It is conventional wisdom in defence systems that electronic brains are where much of the present and future weapons system capability is developed. Electronic hardware advances, particularly in microprocessor, allow highly complex and sophisticated software to provide high degree of system autonomy and customisation to mission at hand. Since modern military systems are so much dependent on the proper functioning of electronics, the quality and reliability of electronic hardware and software have a profound impact on defensive capability and readiness. At the hardware level, due to the advances in microelectronics, functional capabilities of today's systems have increased. The advances in the hardware field have an impact on software also. Now a days, it is possible to incorporate more and more system functions through software, rather than going for a pure hardware solution. On the other hand complexities the systems are increasing, working energy levels of the systems are decreasing and the areas of reliability and quality assurance are becoming more and more wide. This paper covers major failure modes in microelectronic devices. The various techniques used to improve component and system reliability are described. The recent trends in expanding the scope of traditional quality assurance techniques are also discussed, considering both hardware and software.