In-situ moire measurement of adhesive flip-chip bonded assembly under thermal cycling condition

The use of flip-chip technology has many advantages over other approaches for high-density electronic packaging. Adhesive flip-chip bonding using ACFs (anisotropic conductive films) or ACPs (anisotropic conductive pastes) is one of the major flip-chip technologies, which has short chip-to-substrate interconnection length, high productivity, and miniaturization of package. Therefore, many researchers and makers are interested in this adhesive flip-chip bonding scheme. In addition, the understanding of thermal deformation has been recognized as the key for a reliable design of adhesive flip-chip bonding assembly. In this study, thermal deformations of adhesive bonded flip-chip-on-board package during thermal cycling were investigated using in-situ high sensitivity moire interferometry. For temperature cycling, a small-sized thermal chamber having an optical window was used with Portable Engineering Moire Interferometer. The warpage of the silicon chip were measured during two thermal cycles between 25°C and 125°C. When the temperature of the assembly was increased to higher than the glass transition temperature (T_g), the warpage of the chip is fully diminished and the warpage was characterized by the T_g regardless of previous temperature history. From the test results, it was shown that the in-situ moire interferometry scheme is effective and powerful tool to characterize the thermal deformation of microelectronics assembly using adhesive.