Harsh Environment Reliability of Micro-Leadframe (QFN) Components and Conformal Coating Effects
Authors: Jim Wilcox, Michael Meilunas, and Martin Anselm Company: Universal Instruments Corporation and Rochester Institute of Technology Date Published: 9/27/2015
Abstract: Conformal coatings are used to promote the survival of electronic assemblies in harsh environments as encountered by military / aerospace applications. Such coatings are intended to protect against corrosive environmental agents and more recently to constrain the growth of Sn whiskers and prevent their shorting to adjacent conductors. These coatings are designed to be deposited as uniform thin layers covering all board surfaces and components. The impact of such coatings on the reliability of the solder interconnects in the system are often overlooked. This study examines the consequences of several common conformal coating materials on the reliability of SAC305 solder joints as tested in a thermal shock stress cycle (-40 to 125°C). Of specific interest will be the impact of conformal coatings on the solder joint reliability of micro-leadframe (MLF), a.k.a. QFN, components such as MLF100 and DR-MLF124. Common polyurethane and acrylic coating materials will be evaluated.