Title:

Effects of Mold Compound Properties on Lead-on-Chip (LOC) Package Reliability During IR Reflow

Author(s):

Yang Ji-Cheng, Leong Chew Weng, Goh Jing Sua, Yew Chee Kiang, Texas Instruments Singapore Pte. Ltd.

Gist:

This paper deals with the effects of mold compound properties on the package cracking resistance of the Lead-on-Chip (LOC) package. The study was conducted using a DRAM LOC package as vehicle, four mold compounds and two reflow conditions (220 C and 260 C). Predicting package cracking requires a thorough understanding of the packaging materials' properties as well as the effects of environmental factors such as temperature and moisture. Mold compound mechanical properties such as elastic modulus, ultimate tensile strength, and fracture toughness greatly depend on the temperature. At high temperatures, these mechanical properties decrease significantly making the package susceptible to cracking. Moisture in the mold compound results in a reduction in its ultimate tensile strength, elastic modulus, and fracture toughness, etc, with the reduction being more serious at higher temperatures. Mold compounds exhibit creep/stress relaxation behavior in a large scale at high temperatures. The study concluded that with fracture mechanics criterion, materials characterization and finite element simulation can help predict package reliability and allow proper selection of packaging materials.

Published in :

46th Electronic Components and Technology Conference Proceedings, 1996