Moisture and Reflow Sensitivity Evaluations of SMT Packages as a Function of Reflow Profile at Eutectic and Lead Free Temperatures

摘要

Epoxy molding compounds are used extensively in the electronics industry to encapsulate surface mount Integrated Circuits (ICs). The primary purpose of encapsulating the SMT package using these molding compounds is to protect them from adverse conditions. Though the mechanical and electrical properties of epoxy make it suitable for electrical and electronic applications, epoxy is not a hermetic encapsulant and will allow moisture to diffuse into the components. The absorbed moisture affects the properties of the material especially when the components are reflowed and can lead to failures like pop corning and package cracking. Moisture induced reflow failures due to pop corning and delamination in plastic encapsulated SMT packages has been a significant issue in the assembly of PCB's. The impending transition to Printed Circuit Board (PCB) assembly involving more rigorous reflow conditions, accentuates the need for study on the integrity of such packages during and after assembly. This research involves the study of moisture and reflow sensitive behavior of an array of plastic encapsulated packages to assess their performance at both eutectic and lead free reflow conditions.