Comparison of Warpage Measurement Capabilities and Results Obtained by Using Laser and Digital Fringe Projection Methods

Electronic packaged devices are becoming increasingly smaller in size and higher in density while requiring higher performance and superior reliability. Warpage is one of the crucial factors for the thermo-mechanical reliability of electronic packages and warpage control becomes a more crucial process during the printed wiring board (PWB) fabrication and package assembly processes. This requirement necessitates more accurate methods of measuring warpage. The fringe projection methods are recent trends for measuring the warpage of chip packages, PWBs, and PWB assemblies because of their noncontact, full-field, and high-resolution measurement capabilities. This paper presents a comparison of two fringe projection methods: laser fringe projection (projection moiré) and digital fringe projection. Experimental results show that digital fringe projection has higher practical resolution, and better accuracy and precision than laser fringe projection.