On-Line Measurement of Thermally Induced Warpage of BGAs with High Sensitivity Shadow Moiré

Abstract

The thermally induced warpage of electronic substrates is a significant concern in manufacturing processes. The ability to eva luate substrate behavior with respect to temperature is particularly important to manufacturing engineers. Previous measurement of ther mally induced warpage on Printed Circuit Boards (PCBs) 1 using general Shadow Moire cannot provide enough sensitivity for modern electronic substrates and packages. Today’s chip-carrier substrates and packages have tighter flatness requirements than the older throug h-hole connection designs. A successful application of the phase-stepping technique to general Shadow Moire is reported in this paper . This application has made fringe pattern analysis fully automated and significantly increased the effective sensitivity of the analy sis.