Technical Abstracts
In Case You Missed It

Embedded Cooling

“Orientation Effects in Two-Phase Microgap Flow”

Authors: Franklin L. Robinson and Avram Bar-Cohen; franklin.l.robinson@nasa.gov.

Abstract: The high power density of emerging electronic devices is driving the transition from remote cooling, which relies on conduction and spreading, to embedded cooling, which extracts dissipated heat on site. Two-phase microgap coolers employ the forced flow of dielectric fluids undergoing phase change in a heated channel within or between devices. Such coolers must work reliably in all orientations for a variety of applications (e.g., vehicle-based equipment), as well as in microgravity and high-g for aerospace applications, but the lack of acceptable models and correlations for orientation- and gravity-independent operation has limited their use. Reliable criteria for achieving orientation- and gravity-independent flow boiling would enable emerging systems to exploit this thermal management technique and streamline the technology development process. As a first step toward understanding the effect of gravity in two-phase microgap flow and transport, the authors have studied the effect of evaporator orientation, mass flux, and heat flux on flow boiling of HFE7100 in a 1.01mm tall × 13.0mm wide × 12.7mm long microgap channel. Orientation-independence, defined as achieving similar critical heat fluxes (CHFs), heat transfer coefficients (HTCs), and flow regimes across orientations, was achieved for mass fluxes of 400 kg/m2 s and greater (corresponding to a Froude number of about 0.8). The present results are compared to published criteria for achieving orientation- and gravity-independence. (Journal of Electronic Packaging, vol. 141, no. 3, September 2019)

Molecular Electronics

“Single Molecule-Based Electronic Devices: A Review”

Authors: Bingrun Chen and Ke Xu

Abstract: As development of traditional silicon-based electronic devices is increasingly limited, a single-molecule electronic device is considered one of the most hopeful candidates to realize the miniaturization of conventional electronic devices. This paper provides an overview of single-molecule electronic devices, including molecular electronic devices and electrode types. First, several molecular electronic devices are presented, including molecular diodes, molecular memories, molecular wires, molecular field effect transistors (FET) and molecular switches. Then the influence of different electrode types of the transport characteristics is introduced, showing graphene is a promising electrode material for single-molecule electronic devices. Moreover, other excellent characteristics of molecular devices are briefly introduced, such as potential thermoelectric effects, new thermally induced spin transport phenomena and negative differential resistance (NDR) behavior. Finally, the future challenges to the development of electronic devices based on single molecules are described. (Nano, vol. 14, no. 11, November 2019)

Roadmaps

“Comparing Past Board Assembly iNEMI Roadmaps to Technology Outcomes”

Authors: Annaka Rose Balch; annaka.r.balch.19@dartmouth.edu.

Abstract: This project compares past board assembly roadmaps with actual technological outcomes, examining the progression of predictions across seven significant aspects of board assembly covered in the 1994, 2002, 2007, 2013 and 2017 roadmaps: 1) conversion costs, 2) NPI cycle time, 3) component trends, 4) solder paste, 5) bar solder, 6) wave solder flux and 7) die attach adhesives. It should be noted there are discrepancies between these roadmaps – from general outline to the many aspects of board assembly that are investigated. This project aims to bridge these discrepancies in a comprehensive fashion to better inform iNEMI and identify possible areas for improvement. (Pan Pac Symposium, February 2020)

Wearables

“Mechanically Transformative Electronics, Sensors and Implantable Devices”

Authors: Sang-Hyuk Byun, et al.

Abstract: Traditionally, electronics have been designed with static form factors to serve designated purposes. This approach has been an optimal direction for maintaining the overall device performance and reliability for targeted applications. However, electronics capable of changing their shape, flexibility, and stretchability will enable versatile and accommodating systems for more diverse applications. Here, the authors report design concepts, materials, physics, and manufacturing strategies that enable these reconfigurable electronic systems based on temperature-triggered tuning of mechanical characteristics of device platforms. They applied this technology to create personal electronics with variable stiffness and stretchability, a pressure sensor with tunable bandwidth and sensitivity, and a neural probe that softens upon integration with brain tissue. Together, these types of transformative electronics will substantially broaden the use of electronics for wearable and implantable applications. (Science Advances, Nov. 1, 2019, https://advances.sciencemag.org/content/5/11/eaay0418)

This column provides abstracts from recent industry conferences and company white papers. Our goal is to provide an added opportunity for readers to keep abreast of technology and business trends.