A robust digital image correlation technique for high-resolution characterisation of microelectronic packaging materials

In this study, we demonstrate a robust Digital Image Correlation (DIC) technique and describe the methods implemented in the DIC code for characterising microelectronic packaging materials. We show how sample preparation may be entirely eliminated by using the natural speckle inherent in specular (rough) surfaces with the help of a robust correlation measure implemented in the code. We use DIC to characterise both time-independent and time-dependent material properties at high spatial and displacement resolution. We measure the Coefficient of Thermal Expansion (CTE) of common metals such as copper and aluminium followed by characterisation of 19 Printed Circuit Board (PCB) coupons. We characterise the CTE of microscale Alumina (Al2O3) specimen using its natural speckle. We calculate the strain and therefore the modulus during mechanical testing of copper, epoxies as well as fibre-reinforced composite materials. Finally, we characterise the time dependent behaviour of a microfibre-reinforced composite (RT/Duroid) at high temperature.