DIGITAL IMAGE CORRELATION USING HIGH MAGNIFICATION OPTICAL MICROSCOPY

摘要

Strain measurement of individual structures or small regions of microelectronics packages is desired for reliability testing, failure analysis, and model validation, but is difficult to perform due to the small scale. Moire interferometry is limited in the displacement directions that can be measured, requires painstaking specimen preparation, and can be very sensitive to environmental interference. A more recent optical displacement measurement technique called digital image correlation (DIC) can measure all 2D or 3D displacements simultaneously on irregular surface topographies with less specimen preparation, but has not been successfully applied to the scale appropriate for microelectronic structures. This study presents a method for measuring DIC data over a range of temperatures using optical microscopy. The novel test apparatus and specimen preparation methods have resolved the primary technical challenges of large thermally-induced rigid body motion, optical distortions, and application of high contrast surface features. This paper presents and describes the design of the apparatus and methods of specimen preparation. Two examples are presented to demonstrate the capability of this method and potential applications. This method provides a way to use common laboratory test apparatus to produce high quality thermal strain measurements of the small features of microelectronics parts.