Application of Thermal Analysis to Evaluation of Semiconductor Encapsulation

Abstract

Encapsulation of semiconductors in plastic has introduced many problems. Economical manufacture of reliable plastic-encapsulated semiconductors requires evaluation and control of (i) the uniformity of parts from different mold cavities, (ii) the coefficient of thermal expansion of the package, and (iii) the moldability of the plastic. The usefulness of the thermal analyzer for evaluation of these properties will be demonstrated. Thermomechanical analysis (TMA) has been used to sense cavitytocavity variations in properties of parts molded in the same shot. TMA has also been used to determine the coefficient of thermal expansion of the plastic in the very important region near the semiconductor die surface. The microscopic uniformity of the molding compound is an important variable which affects the encapsulation of small delicate devices. Semi-quantitative evaluation of differences in moldability have been made by combining radio-frequency dielectric heating with differential scanning calorimetry.