Symposium Conference Proceedings

Development Of A Risk Profile From Flux Residues Trapped Under Leadless Components

Authors: Mike Bixenman, DBA, T.C. Loy and Bruno Tolla, Ph.D., Denis Jean, Jennifer Allen, Kyle Loomis
Company: Kyzen Corporation and Kester Corporation
Date Published: 3/28/2017   Conference: Symposium

Abstract: Electronic assemblies are more complex due to the use of miniaturized components and the increased density of circuitry placed in tighter geometries. Leadless components have extremely low standoff clearances. Flux residues can fill the underside of the component. If not properly outgassed, the residue can be wet, pliable and active. The residue, even when using a No-Clean solder paste, can cause leakage currents, causing intermittent and hard failures.

This research study will use a non-standard test board with sensors placed within the body of the component. The boards will be built with halide free and halogen bearing soldering pastes. The boards will be reflowed using a ramp-to-spike and soak profile. A subset of the boards will not be cleaned, a subset cleaned but with some residue remaining under the component and a subset totally cleaned. Surface Insulation Resistance testing of the boards will be used to develop a risk profile for residues remaining under the body of the components.

Key Words: 

Bottom Terminated Components, QFNs, No-Clean Solder Paste, Flux Outgassing, Cleaning

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