Creep and fatigue as main degradation phenomena in reliability of solder joints

Observed from many years a rapid growth of electronic devices production, induced by introducing new functionalities for customers and moving towards environmentally friendly packaging caused that life prediction of solder joints is more prominent issue in electronic assembly. Thanks to their properties solder alloys are a part of fundamental components of each printed circuit boards. They are responsible for mechanical (structural support, heat transportation) and electrical (signals transmission) connections. Therefore it is very important to estimate behavior of solder joint in various work conditions. One of the problems is failure due to the combined loading of creep and fatigue phenomena which initiate degradation process. In daily engineer practice creep and fatigue phenomena are taken into account only in an independent way. As a result reliability prototyping is not very precise, long lasting and very costly. The usual tests are based only on one dominating failure mode, which can last for a number of months. Moreover all failure analysis are done under the simplified conditions, which means that obtained results are not so reliable. To accelerate that kind of tests simultaneously acting of creep and fatigue is needed. That combination can include analytical, experimental and numerical approach for understanding the combined multi-loading and multi-failure problem. Therefore, an appropriate understanding and development of analytical methods and experimental tools for multifailure criteria analysis could be very helpful. In this work new method, which allows for combined failure of solder joints, in order to examine simultaneously creep and fatigue phenomena is presented. Using this or similar method with numerical modeling and simulation technique can help establish the failure time, at which specimen is damaged due to accelerated tests and behaviour of the sample based on obtained material model describing shape and parameters of tested solder joints [1].