Symposium Conference Proceedings

Bottom Termination Component Design Considerations to Improve Cleaning

Authors: Dr. Mike Bixenman, Dale Lee, Bill Vuono, and Steve Stach
Company: Kyzen Corporation, Plexus Corporation, Raytheon, and Austin American Technology
Date Published: 4/8/2014   Conference: Symposium

Abstract: Bottom Termination Components (BTC’s) are the fastest growing package types in the electronics industry. BTCs acceptance in long-life devices exposed to harsh environments is currently limited due to reliability concerns. The large area heat sink associated with the BTC design, floods the perimeter of BTC in the soldering process with flux residue making the BTC one of today’s toughest cleaning challenges. Un-cleaned flux residues trapped under the BTC have the potential to be hydroscopic and conductive. Concentrated ionic levels lower dielectric strength and can result in dendrite growth.

From a cleaning perspective, many designers have poor insight into factors that assure a cleanable design. Variables such as solder paste, reflow conditions, component placement, component clearance (standoff), cleaning agent and cleaning equipment are important factors. Collaboration between process engineers, assembly designers, solder materials, cleaning agent and cleaning equipment experts can improve integration of the BTC design and assembly. Circuit board design plays an important role when cleaning is required. The purpose of this research is to study design considerations of BTC components in an effort to reduce flux residue under the bottom termination and improve cleaning effects.

Key Words: 

QFN, MLF, LPCC, QLP, HVQFN, LCC, Electronic Assembly Cleaning, Flux Residue, Electrochemical Migration

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