Optimisation of the Digital Image Correlation Technique and Measurement of Strain in First Level C4 Interconnect

The measurement of thermo-mechanical deformation in C4 interconnect and chip scale packages is a critical metrology problem for IC packaging. The ability to directly measure the deformation of the actual package, without applying special structures for metrology, is a major advantage of optical digital image correlation technology. Cutting edge automated digital image correlation technology allows in-plane deformation and strain to be measured directly at multiple locations on the bare cross-section or exterior surface of an IC package. In this paper the authors have shown the advantages of using digital image correlation based techniques for the measurement of advanced electronic packaging materials and components. The technique has moved on with the increasing power of computers which enable the required high intensity numerical calculations to be computed. The technique has been applied to the measurement of C4 based components. Highly accurate deformation measurements are possible with accuracy of 20 nm deformation resolution being possible. Minimal sample preparation was required with samples only requiring a minimal amount of roughening with silicon carbide paper. This compares favourably with comparable techniques such as moire interferometry which require a large amount of time-consuming sample conditioning and grating replication before any measurement can be made