Identification of Interconnect Failure Mechanisms Using RF Impedance Analysis
Michael H. Azarian 2
Daeil Kwon2
Michael Pecht1,2
1Prognostics and Health Management Center
City University of Hong Kong
2Center for Advanced Life Cycle Engineering (CALCE)
University of Maryland
College Park, MD 20742
Kowloon, Hong Kong
Abstract:
This paper presents RF impedance analysis as a nondestructive
indicator of interconnect failure mechanisms.
Physical changes on a printed circuit board can be detected
using the TDR reflection coefficient as a measure of RF
impedance. The test circuit in this study consisted of an
impedance-controlled circuit board, a surface mount low-pass
filter, and two solder joints providing both mechanical and
electrical connections between them. A cyclic mechanical
load was applied to generate either solder pad separation
failures or cracking of the solder joints. In the case of pad
separation, the test results showed that the TDR reflection
coefficient gradually decreased as the pad lifted off the circuit
board, which was distinguishable from the TDR response due
to solder joint cracking. These results are explained using a
simple theoretical analysis of the effect of each failure
mechanism on impedance. This demonstrates that RF
impedance analysis provides for the determination of failure
mechanisms as well as early detection of both pad separation
and solder joint degradation. The detection sensitivity for
solder joint cracking using this technique is also discussed.