Computer-aided Fringe Analysis for Deformation Studies Zhaoyang Wang Department of Mechanical Engineering, The Catholic University of America, Washington, DC 20064 Bongtae Han Department of Mechanical Engineering, University of Maryland, College Park, MD 20742 ABSTRACT Photomechanics methods have matured and emerged as important engineering tools. Although numerous image-processing algorithms have been developed to complement interferometric measurement techniques, these algorithms have been implemented originally for classical interferometry and the extensions to the general photomechanics fringe analysis have been limited. In this research, the existing computer-aided digital fringe image analysis and processing techniques are investigated; the most appropriate fringe image processing schemes and their limitations are identified. To make the computer-aided fringe analyses practical to the real engineering problems, the existing schemes have been improved and a series of new fringe analysis techniques have been developed. Selected but original applications to out-of-plane shape and warpage measurement, in-plane displacement and strain measurements of electronic packaging components are presented. INTRODUCTION Photomechanics methods have matured and emerged as important engineering tools for the in-plane and out-of-plane deformation analyses of electronic packaging components. Some of these typical methods include Twyman-Green interferometry, Fizeau interferometry, shadow moiré, moiré interferometry, microscopic moiré interferometry, and so on. These methods produce fringe patterns that represent the contours of equal displacements, and thus can provide the full field information of displacements. The deformation fields encountered in microelectronics components are usually complicated because of the existing of material and geometrical discontinuities, thus computer-aided fringe analysis is in high demand. However, although numerous image-processing algorithms have been developed to complement interferometric measurement techniques, these algorithms have been implemented originally for classical interferometry and the extensions to the general photomechanics fringe analysis in microelectronics have been limited. In this research, the existing computer-aided digital fringe image analysis and processing techniques are investigated; the most appropriate fringe image processing schemes and their limitations are identified. To make the computer-aided fringe analysis practical to the real microelectronic packaging problems, the existing schemes have been improved and a series of new fringe analysis techniques have been developed. Among these new techniques, the enhanced random phase shifting algorithm can detect the phase shift amounts and the full-field phase distributions automatically and simultaneously; the hybrid semi-automatic O/DFM fringe centering technique combines the advantages of existing techniques and can be employed to obtain full-field fractional fringe orders and their gradients accurately. These fringe analysis techniques provide a practical and automatic way for the deformation studies in complicated microelectronic components. This paper will demonstrate some typical interferogram fringe analyses and their applications to electronic packaging. FRINGE ANALYSIS TECHNIQUES AND APPLICATIONS 1. Automatic analysis: Fourier transform technique 1-3 The most important advantage of the Fourier transform method (or carrier Fourier transform method) is that only one interferogram is required for the analysis. It is ideal for the automatic calculation of full-field displacements. Figure 1 illustrates an example of interferogram analysis using carrier Fourier transform technique.