Thermal stress evaluation of printed circuit board and connector due to current flow by using holography

Due to recent trends toward miniaturization and high level current flow in printed circuit boards (PCBs) and connectors, thermal deformation became an important factor to be evaluated from the reliability viewpoint in electronic systems. The authors have developed a new measuring system, the holographic pattern measuring system (HPMS), which was applied to evaluate the thermal stress of the PCB and connector due to current flow. In order to examine the applicability of the HPMS to testing PCB deformation due to current flow which causes thermal stress, a simple circuit pattern was fabricated as a test PCB and was examined. Firstly, we observed the surface temperature distribution and the contact resistance variation with respect to the current flow time elapsed, and we found some irregularities in the contact resistance of the mounted contact on the PCB. We also applied the HPMS to measure PCB deformation due to current flow, and we found that the HPMS could be used effectively as a tool for PCB deformation analysis, i.e. the distribution of microscopical displacement of the PCB surface and the connector due to thermal stress could be visualized as a 3D graphic image.