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This paper focuses on significant advances in flip-chip underfill materials via a thorough characterization of the uncured and cured material properties. These characteristics are then translated into what amounts to substantial gains in productivity and reliability. A unique method for determining material flow rates is presented. The data demonstrate the critical relationship between viscosity and flow rate as a function of time and temperature. Material cure rates as a function of time and temperature are also presented using results derived from differential scanning calorimetry or DSC. In addition, the dielectric constant and dissipation factor during the cure process are also measured as an added, more sensitive gauge of the degree of cure. The data from both measurement tools demonstrates what the optimum cure time and temperature parameters are, so as to achieve the optimum glass transition temperature (Tg, generated using DSC). Another critical thermal mechanical property of the underfill material, the linear coefficient of thermal expansion, is characterized with results generated using thermomechanical analysis or TMA. The data is then summarized and translated in terms of its actual impact on manufacturing productivity and component reliability. |
