Reliability of microsystems from the material point of view

The determination of the reliability of microsystems is very important from the customer satisfaction perspective. The reliability of electromechanical components is determined by using mechanical tests, metallographic investigations, nondestructive testing and corrosion tests. All tests are accelerated tests which determine the behaviour of a component or a system during hours, days or weeks with regard to their lifetime and are well known. The behaviour of these components under working conditions confirm the test results if the chosen tests characterise the real loads. In addition to the accelerated reliability tests, more and more simulation tools are used to optimise the design of a given component in order to reduce the costs and the time of development and testing and to increase the lifetime and reliability. To determine the thermo mechanical reliability, i.e. to reduce the mechanical stresses, which are mainly responsible for cracks under working conditions, stress-strain diagrams depending on temperature and strain velocity are urgently needed. The paper describes the necessity of material parameters which characterise the material under working conditions to obtain simulation results with high accuracy. However in microsystems the materials parameters as described are not known exactly at present.