Study Of Warpage Measurement System For Packaging Substrate Based On Shadow Moire Method

In recent years, as the trend of microelectronic devices towards light, small, highintegration, Thermal-Mechanical Reliability in microelectronic devices has become more andmore important. Coefficient of thermal expansion mismatch in microelectronic devicesinduces deformation when these devices are subjected to thermal loading duringmanufacturing or everyday operation. During the packaging process, the warpage of PCB,ceramic substrates, silicon substrates, metal substrates is one of the main factors that affect thequality, performance, and reliability of microelectronic devices. Therefore, quantitativewarpage measurement is critical in manufacture process to improve product reliability andprocess yield, and determining overall thermal performance characteristics.As a high resolution, non-contact and whole field measurement, shadow moiré hasevolved as the method most widely chosen for out-of-plane displacement measurements in thefield of solid mechanics.In this thesis, a warpage measurement system for large scale packaging substrate basedon noncontact shadow Moiré technology was developed, warpage of various substrates suchas QFN metal substrates, BGA substrates and back flower surface of the coin are measured.Phase-shifting technology is applied to the analysis of fringe pattern images of varioussubstrates obtained by shadow moiré. Sensitivity of the fringe pattern analysis isdemonstrated to be significantly increased. The traditional shadow moiré Measurement isgreatly influenced by the ambient light. The main error of the system comes from the ambientlight deviating from the primary illumination light, which come into the reference grating.Several shadow superimposed over the surface of the sample, resulting in moiré fringe noise;In this shadow moiré Measurement, a collimating lens is placed between the light source andthe reference grating. Light rays from the white light source pass through the collimating lensand then come into the reference grating. So that most of the energy of light rays do notdeviate from the direction of the main light, reducing the ambient light error. In conductingwarpage measuring, the position of CCD camera of the warpage measurement system isadjustable, which can fit to evaluate warpage of different area of microelectronic packaging substrates; and the incoming angle is adjustable, which can change the sensitivity of thiswarpage measurement system in the face of different applications.In this thesis, two types of samples, QFN metal substrate and BGA substrate aremeasured by the warpage measurement system, the accuracy of this warpage measurementsystem can reach1μm and the repeatability error is under2%. The system will meet thedemand of warpage of microelectronic packaging substrates from industry and academia.