Experimental assessment of electronic package deformation using optical full-field deformation measurement system.

摘要

Over the past several decades, experimental solid mechanics has played an important role in the highly interdisciplinary field of electronic packaging. Optical full-field deformation measurement techniques including moire systems and digital image correlation (DIC) have been mostly adopted and applied to the experimental mechanics of electronic packages. Especially, DIC technique combined with other imaging systems was selected in this research due to its practical advantages. By using this technique, in this research, there are three major experimental mechanics developed to assess various deformation behaviors of electronic packages.;For the experimental assessment, thermo-mechanical behavior of solder joints, 2-D microscopic DIC technique was utilized to quantify the deformation behavior and strains of a solder bump of flip-chip package subjected to thermal loading. The computed full-field displacement fields clearly depicted both normal and shear deformation of the solder bump under the thermal loading. In addition, the strain trends of solder bumps were effectively analyzed with respect to the distance to neutral point (DNP). Subsequently, FEA model was performed to optimize underfill material properties in order to improve the reliability of solder bump under thermal cycling.;Plastic encapsulated electronic packages absorb moisture when they are subjected to humid ambient conditions. Then, the absorbed moisture in the material influences the mechanical properties. In this study, hygroscopic material properties of the mold compound used in the MEMS package were characterized. From the desorption measurement after preconditioning at 85ºC/85%RH, the saturated moisture content and diffusivity were obtained. In addition, a new experimental setup was devised using DIC system together with a precision weight scale in order to obtain the coefficient of hygroscopic swelling at different temperatures. Using the obtained hygroscopic material properties, FEA model was performed to understand conjugated hygro and thermo-mechanical behavior of a MEMS package during a reflow process after moisture preconditioned.;Cellular phones and other handheld electronic devices are often exposed to severe shock/drop impact loading. These transient and dynamic deformations of electronic assemblies have been measured by using DIC with stereo-high-speed camera. In order to protect electronic components of electronic devices on a Printed Circuit Board (PCB) against electromagnetic radiation, a conductive shield-can or box is normally attached on the PCB covering the electronic components. In this regard, the effect of shield-can to the dynamic behavior of PCB was investigated.