On the Mechanical Properties of a Poly(oxazolidone) Polymer for Encapsulant Applications

ABSTRACTEpoxy based resins have been widely used as encapsulation materials in microelectronics components due to their good mechanical, thermal and electrical properties, outstanding adhesion to various substrates and the ability to be processed under a variety of conditions. These epoxy resins have a high glass transition temperature but low toughness and damage tolerance. As electronic devices continue to be miniaturized and the scale of integration increases, the encapsulation of these chips leads to mechanical and thermal stress related failures. Mechanical stresses could result from the mismatch in thermal expansion rates between the polymeric encapsulant, the silicon chip and the metal leadframe. The accommodation of these stresses may lead to cracking of the encapsulant or delamination. In this study, poly(oxazolidone) polymer was prepared by reacting 4,4′-Diphenyl-methanediisocyanate (MDI) with diglycidyl ether of bisphenol A (DGEBA) at elevated temperature. The mechanical properties of this polymer were investigated both as a stand-alone material as well as a bi-material sandwich with a brittle substrate. The degree of cracking in the substrate is shown to be a function of the thickness of the polymer layer. This result is analyzed based on the variation in the position of the neutral axis in this composite.