Low-stress polyimide resin for IC

Low-stress polyimide resins that will relax the internal stress (thermal stress) generated in LSI chips encapsulated with mold compound have been developed to prevent passivation films from cracking and to prevent aluminium-conductor slide. The chips were coated with three kinds of polyimide resins (regular, low modulus-of-elasticity and low thermal expansion coefficient), sealed with mold compound. Thermal cycle tests and thermal shock tests were conducted. The results revealed that the low-modulus type has the best stress-relaxing effect, and that the effect decreases in the order of low-thermal-expansion-coefficient type, regular type, and no polyimide coating case, which coincides with the behavior of the thermal stress values calculated. The polyimide resin of low modulus of elasticity has a modulus about half of those of the conventional polyimide resins. As a buffer coating film it offers easy etchability and retains the original heat resistance of the polymer.<>