System reliability as a key for managing complex requirements, such as robust design of microsystems

The development process of today's microsystem technologies for products includes stages of innovation, design, development and production. Major criteria are time, cost and quality. For quality and in particular reliability new methods must be employed to evaluate the system reliability in the early stages of the product development process to keep up with the rapid developments. Today's electrical and electronic systems form a complex collection of subsystems, which may consist of any number of further subsystems (e.g. MEMS, power semiconductors). A subsystem can be a module or component but it can also be broken down into the level of electrical interconnections, such as solder joints or material structures. On each of these system levels reliability analyses can be performed. Methods like FTA or FMEA allow determining potential flaws and their impact on the system as a result of interaction of subsystems and environmental requirements. Appropriate tests allow a qualification of the system to perform under required specifications. A major challenge represents the desire for "zero defects". Statistic coverage of reliability of all system levels is generally not possible because of constraints in cost and time. Statistical confidence can usually be done at a technological level. At higher levels qualifications in terms of functionality can be done and actions towards process stability can be taken. In the development of subsystems based on new technologies an early transfer of the subsequent requirements of the higher system levels is necessary to meet both, the required quality and cost frame. In this work theories of system analysis will be combined with typical procedures of reliability assessment and are applied to a typical product development process. Levels of product development will be contrasted with levels of a system. It will be shown how requirement definitions and process controlling impact the reliability of a system and its components. The possibilities, limitations and challenges in the field of system reliability will be demonstrated. Across all levels system characteristics in terms of reliability as in functional and safety relevance will be represented