Thermomechanical properties of 1C molding compounds

✍ Scribed by H. E. Bair; D. J. Boyle; J. T. Ryan; C. R. Taylor; S. C. Tighe; D. L. Crouthamel

• Book ID: 104522713
• Publisher: Society for Plastic Engineers
• Year: 1990
• Tongue: English
• Weight: 855 KB
• Volume: 30
• Category: Article
• ISSN: 0032-3888
• DOI: 10.1002/pen.760301008

✦ Synopsis

Abstract

Eight commercial semiconductor grade epoxy compounds that are used to encapsulate 1C (integrated circuit) devices have been evaluated for their ability to minimize the development of thermal stresses which can cause failure during device temperature cycling. Thermal expansion, dynamic modulus and adhesion studies are used to describe the mechanical interaction between the plastic package and the silicon device it surrounds. A “figure of merit” is defined for the development of stress on the 1C device as it is cooled after the packaging process. The stress is shown to be proportional to the product of three terms: (α~p~‐α~s~) E~p~ (T~anch~‐T) where α~p~ and α~s~ are the expansion coefficients for the plastic and silicon, respectively, E~p~ is the modulus of the epoxy and T~anch~ is the temperature at which the epoxy becomes anchored to the silicon device during transfer molding. In addition, the importance of good adhesion between the epoxy encapsulant and the silicon device to prevent package cracking has been demonstrated by finite element analysis and a novel adhesion test.