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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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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 & Characterization Laboratories at UPRM. He is a member of ASEE and IEEE.

The demand for electronics capable of operating at temperatures above the traditional 125°C limit continues to increase. Devices based on wide band gap semiconductors have been demonstrated to operate at temperatures up to 500°C, but packaging remains a major hurdle to product development. Recent regulations, such as RoHS and WEEE, increase the complexity of the packaging task as they prohibit the use of certain materials in electronic products such as lead (Pb), which has traditionally been used in high temperature solder die attach. In this investigation, an Ag-In solder paste is presented as a die attach alternative for high temperature applications. The proposed material has been processed by a transient liquid phase sintering method resulting in an in situ alloying of its main constituents. A shift of the melting point of the system, confirmed by differential scanning calorimetry, provided the basis for a breakthrough in the typical processing temperature rule. The mechanical integrity and reliability of this novel attachment material is discussed.

The demand for electronics capable of operating at temperatures above the traditional 125°C limit continues to increase. Devices based on wide band gap semiconductors have been demonstrated to operate at temperatures up to 500°C, but packaging them remains major hurdle to product development. Recent regulations, such as RoHS and WEEE, increase the complexity of the packaging task as they prohibit the use of certain materials in electronic products such as lead, which has traditionally been widely used in high temperature solder attach. In this investigation, a series of Pb-free die attach technologies have been identified as possible alternatives to Pb-based ones for high temperature applications. This paper describes the fabrication sequence for each system and assesses their long term reliability using accelerated thermal cycling and physics-of-failure modeling. The reliability of the lead rich alloy was confirmed during this investigation while early failures of the silver filled epoxy demonstrated their inability to survive high temperatures. An empirical damage model was developed for the silver nanoparticle paste based on fatigue induced failures. Encouraging reliability data has been presented for the goldtin SLID system where bond quality was demonstrated to be a critical factor on its failure mode and mechanism. IntroductionThe development of electronics and microsystems that can operate at temperatures in excess of the traditional maximum [1] of 125°C is a critical enabling technology for the creation of next generation electronic systems for a wide range of military and commercial applications; including avionics, hybrid-electric automotive electronics, deep well drilling, chemical processing systems, and space/earth explorations. Critical elements of these systems are the sub-assemblies for power control, distribution, and management. The last several years have seen the advent of silicon carbide (SiC) power devices operating at temperatures well above 125°C [2]. These devices provide higher switching speed and lower on-state losses with higher thermal conductivity. Developing reliable technologies for packaging is now the main hurdle to successful operation of SiC based power electronics at high temperature.This work focuses on the first-level interconnection process known as die attach, the primary function of which is to mechanically secure the semiconductor chip to a lead frame or substrate, and to ensure it does not detach or fracture over an operational lifetime that may include power and temperature excursions. One of the most common approaches for packaging SiC devices is to mount the back of the chip on a ceramic substrate with a suitable die attach and route the