Evaluation of Digital Image Correlation Techniques for the Determination of Coefficients of Thermal Expansion for Thin Reinforced Polymers

Considering the application specific temperature loads microelectronic packages have to endure, thermal management plays a major role for reliability evaluations. A key aspect of thermal management is the assessment of mechanical stresses arising from the thermal mismatch of polymeric and metallic regimes within a given package. Generally, these material classes exhibit an entirely different thermal expansion behavior. In order to validate new designs of microelectronic packages and assess their reliability, a precise determination of the coefficients of thermal expansion (CTE) is necessary. However, modern polymeric materials in power electronics are extremely thin and may also exhibit an anisotropic material behavior, yet Digital Image Correlation (DIC) systems enable the contactless and precise measurement of thermally induced strains of these materials. Within the scope of this research work two DIC systems are employed and compared, a multi-use DIC system and a specialized DIC system, which is specifically designed for CTE measurement. To this end, an anisotropic FR4-prepreg material and the corresponding pure epoxy resin (isotropic) are examined using both DIC systems. Furthermore, Thermo-Mechanical-Analysis (TMA) is used as reference measurement for the isotropic epoxy material. The collected results are evaluated and compared against each other.