IEEE Electronic Components and Technology Conference, San Diego, CA, pp. 663-667, May 2009.

Detection of Solder Joint Failure Precursors on Tin-Lead and Lead-Free Assemblies
using RF Impedance Analysis

Daeil Kwon, Michael H. Azarian, and Michael Pecht
Center for Advanced Life Cycle Engineering (CALCE)
University of Maryland
College Park, MD 20742
Abstract:

During the lifetime of electronic products, interconnects are susceptible to failures by mechanisms such as fatigue, creep, corrosion, and mechanical over-stress. Regardless of the failure mechanisms, interconnect degradation often starts from the surface and propagates inward. DC resistance, which has been used by the electronics industry to monitor the reliability of board level interconnects, does not offer an adequate means to predict an impending failure. However, RF impedance does respond to the early stages of interconnect degradation due to the skin effect, and thus can provide a failure precursor for an interconnect.

In this study, we compared early changes in RF impedance to changes in DC resistance to identify solder joint failure precursors under creep testing conditions. We report the effect of different solder alloys on RF impedance. The test vehicle consisted of an impedance-controlled circuit board, a surface-mount low-pass filter, and two solder joints providing both mechanical and electrical connection between them. The solder alloys under investigation were eutectic tin-lead (Sn-37Pb) and SAC305 (Sn-3.0Ag-0.5Cu). Constant mechanical load was directly applied to the filter at an elevated temperature in order to generate creep failures of the solder joints. During solder joint degradation, RF impedance and DC resistance were simultaneously monitored in order to allow a direct comparison between their respective sensitivities in detecting failure precursors before the solder joint showed a DC open circuit.

The test results showed that regardless of solder alloy RF impedance failure precursors were detectable prior to changes in DC resistance during solder joint degradation. This demonstrates that RF impedance can serve as a nondestructive and real-time degradation indicator of interconnects and can predict impending failures.

Complete article is available to CALCE Consortium Members.

IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.



[Home Page] [Articles Page]
Copyright 2008 by CALCE and the University of Maryland, All Rights Reserved