Sungkyunkwan University · Engineering
Professor Daeil Kwon's research lab specializes in prognostics and health management (PHM) of electronic systems, with a strong focus on condition monitoring and reliability assessment of electronic interconnects. The lab develops advanced sensing and diagnostic techniques—such as RF impedance monitoring, time-domain reflectometry (TDR), and skin-effect-based methods—to detect early-stage degradation in solder joints and other critical components under mechanical and thermal stress. Their work bridges traditional manufacturing processes like welding and additive manufacturing with modern PHM frameworks, enabling real-time health assessment and remaining useful life prediction using data-driven models like Gaussian process regression. The lab's research is highly application-driven, targeting high-frequency electronics, smart manufacturing, and infrastructure health monitoring.
Figures are computed from collected data and may differ slightly.
Prognostics and systems health management (PHM) is an enabling discipline that uses sensors to assess the health of systems, diagnoses anomalous behavior, and predicts the remaining useful performance over the life of the asset. The advent of the Internet of Things (IoT) enables PHM to be applied to all types of assets across all sectors, thereby creating a paradigm shift that is opening up significant new business opportunities. This paper introduces the concepts of PHM and discusses the opport
Traditional methods used to monitor interconnect reliability are based on measurement of dc resistance. DC resistance is well suited for characterizing electrical continuity, such as identifying an open circuit, but is not useful for detecting a partially degraded interconnect. Degradation of interconnects, such as cracking of solder joints due to fatigue or shock loading, usually initiates at an exterior surface and propagates toward the interior. At frequencies above several hundred megahertz,
Metal additive manufacturing (AM) has several similarities to conventional metal manufacturing, such as welding and cladding. During the manufacturing process, both metal AM and welding experience repeated partial melting and cooling, referred to as deposition. Owing to deposition, metal AM and welded products often share common product quality issues, such as layer misalignment, dimensional errors, and residual stress generation. This paper comprehensively reviews the similarities in quality mo
Solder joints are among the most common failure sites in electronic assemblies. This paper presents a prognostic approach that allows for the remaining useful life prediction of solder joints using an RF impedance analysis and the Gaussian process (GP) regression. While the solder joints were exposed to a mechanical stress condition to generate fatigue failures, the RF impedance of the solder joint was continuously monitored. The RF impedance provided an early indication of the impending solder-
This paper presents time-domain reflectometry (TDR) as a nondestructive sensing method for interconnect failure mechanisms. Two competing interconnect failure mechanisms of electronics were considered: solder joint cracking and solder pad cratering. A simple theoretical analysis is presented to explain the effect of each failure mechanism on the TDR reflection coefficient. Mechanical fatigue tests have been conducted to confirm the theoretical analysis. The test results consistently demonstrated
The trend for many types of electronic products is toward higher operating frequencies or digital bit rates. At high frequencies, signal propagation is concentrated at the surface of interconnects, a phenomenon known as the skin effect. Degradation of interconnects, such as cracking of solder joints due to fatigue or shock loading, also usually initiates at the surface and propagates inward. Therefore, even a small crack at the surface of a solder joint may affect the performance of high speed e
Many types of electronic products are now operating at higher frequencies or digital bit rates. At high frequencies, signal propagation is concentrated at the surface of interconnects, a phenomenon known as the skin effect. Degradation of interconnects, such as cracking of the solder joints due to fatigue or shock loading, also usually initiates at the surface and propagates inward. Therefore, even a small crack at the surface of an interconnect may change RF impedance and adversely affect the p
This study demonstrates the value of RF impedance measurements as an early indicator of physical degradation of solder joints compared to DC resistance measurements. Mechanical fatigue tests have been conducted with an impedance-controlled circuit board on which a surface mount component was soldered. Simultaneous measurements were performed of DC resistance and the time domain reflection coefficient, as a measure of RF impedance, while the solder joints were stressed. The RF impedance was obser
This paper presents RF impedance analysis as a non-destructive 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 sol
For electronic products, interconnect failures may occur due to mechanisms such as fatigue, creep, corrosion, and mechanical over-stress. Regardless of the failure mechanism, interconnect degradation often starts at a 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 interco
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