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His current teaching and research interests include design, characterization, and rapid prototyping of information processing systems, embedded cyber-physical systems, and engineering education. He is the lead author of the textbook Introduction to Embedded Systems: Using Microcontrollers and the MSP430 (Springer 2014). From 2013 to 2018 served as Associate Dean of engineering at UPRM. He currently directs the Engineering PEARLS program at UPRM, a College-wide NSF funded initiative, and coordinates the Rapid Systems Prototyping and the Electronic Testing and Characterization Laboratories at UPRM. He is a member of ASEE and IEEE.

There is a need for electromechanical devices capable of operating in high-temperature environments (> 200°C) for a wide variety of applications. Today's wide-bandgap semiconductor-based power electronics have demonstrated a potential of operating above 400°C, however, they are still limited by packaging. Among the most promising alternatives is the Au-Sn eutectic solder, which has been widely used due to its excellent mechanical and thermal properties. However, the operating temperature of this metallurgical system is still limited to ∼250°C owing to its melting temperature of 280°C. Therefore, a high-temperature-resistant system is much needed, but without affecting the current processing temperature of ∼325°C, typically exhibited in most high-temperature Pb-free solders. In this paper, we present the development and characterization of a fluxless die-attach soldering process based on goldenriched solid-liquid interdiffusion (SLID). A low-melting-point material (eutectic Au-Sn) is deposited in the face of a substrate, whereas a high-melting-point material, gold in this instance, is deposited in its mating substrate. Deposition of all materials was performed using a jet vapor deposition (JVD) equipment where thicknesses are controlled to achieve specific compositions in the mixture. Sandwiched coupons are isothermally processed in a vacuum reflow furnace for different reflow times. Postprocessed samples confirm the interdiffusion mechanism as evidenced by the formation of sound joints that prove to be thermally stable up to ∼490°C after the completion of the SLID process. Differential scanning calorimetry demonstrate the progression of the SLID process by quantifying the remaining low-meltingpoint constituent as a function of time and temperature, this serving as an indicator of the completion of the soldering process. Mechanical testing reveals a joint with shear strength varying from 39 to 45.5 MPa, demonstrating to be stable even after 500 h of isothermal aging. Moreover, these investigations successfully demonstrate the use of the Au-Sn SLID system and the JVD technology as potential manufacturing processes and as a leadfree die-attach technology.Index Terms-Fluxless, hermetic packages, isothermal solidification, jet vapor deposition (JVD), lead-free, shear strength, SLID, solder, transient liquid phase (TLP) bonding.

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