Fatigue Analysis and Optimization of Flexible Printed Circuits

Flexible printed circuits (FPC) are widely used in various electronic packages to interconnect high-performance devices. In case of dynamic applications mechanical reliability of FPCs is becoming a serious issue as complexity of the devices grows and miniaturization trend continues. For many of such applications, failures of FPCs can lead to serious consequences. Fatigue data on FPCs are not commonly available in published literature. One way to obtain such data is to combine fatigue test results from standard or proprietary FPC dynamic testers with Finite Element Analysis (FEA) based simulations. This paper describes first results of a research project on development of an automated procedure of fatigue life assessment of FPCs by FEA combined with fatigue and optimization analysis. Two goals have been pursued with development of the methodology: to enable quick modeling and FEA of FPCs by electrical or mechanical designers who are not familiar with FEA technology and ABAQUS software; to develop a fully parameterized model for subsequent sensitivity and optimization studies. The automated modeling of FPCs has been implemented as a vertical application or plug-in in Abaqus/CAE. Fatigue analysis based on the strain-life method has been programmed in Excel since location of the most dangerous area from fatique point of view could be predicted in advance. In general cases one should use specialized fatigue analysis software for this purpose. FEA and fatigue analysis have been combined using OPTIMUS software to find out an optimum design of the FPC from the fatigue point of view. First results of the sensitivity and optimization studies have shown that the method can be used provided more detailed test results are available both on a material and FPC level.