Technical Abstracts
In Case You Missed It
Connectors
“Impact of Thermal Cycling on Cu Press-Fit Connector Pin Interconnect Mechanical Stability”

Authors: Yeon-Jin Baek, et al.

Abstract: Compared with a BGA interconnection press-fit pin connector, interconnects are expected to have a different degradation mechanism. In this study, the impact factors affecting the reliability and degradation mechanism of press-fit connector pins were investigated. The bonding strength of inserted pins was measured before and after thermal cycling at room temperature and elevated temperature conditions. Bonding strength of the press-fit pins to the PCB copper barrel was observed to increase after thermal cycling. Development of an intermetallic compound between the copper pin and the copper barrel is observed. The microstructure of the press-fit connector pin and the barrel and localized stress and strain levels were analyzed by electron backscattered diffraction, including inverse pole figure maps, grain reference orientation deviation maps, and strain contouring maps. Along with the increase of pull strength after thermal cycling, an increase in residual stresses was observed, while strain contouring maps exhibited a decrease in localized strains at the interface between a press-fit pin and copper barrel. (Journal of Electronic Materials, June 2021)

Component Authentication
“How Nanotech Can Foil Counterfeiters”

Authors: Roozbeh Tabrizian and Swarup Bhunia

Abstract: Radio frequency (RF) nanoelectromechanical systems (NEMS) are devices that don’t have to be visible to be scanned. Consisting of two 50nm-thick conductive layers of indium tin oxide, with a 100nm-thick piezoelectric film composed of a scandium-doped aluminum nitride, they can be fabricated with lithographic techniques similar to those used to make ICs. An etched pattern includes a ring in the middle suspended by four slender arms. That design leaves the circular surface free to vibrate. When the film is mechanically deformed, the material generates an electric voltage across it: the converse piezoelectric effect. A coil on the perimeter of the tag is connected at one end to the top conductive layer and on the other end to the bottom conductive layer. Subjecting the tag to an oscillating magnetic field creates an oscillating voltage across the piezoelectric layer, as dictated by Faraday’s law of electromagnetic induction. The resulting mechanical deformation of the piezo film in turn causes the flexible parts of the tag to vibrate. A network analyzer is then used to scan for the unique resonances of an individual tag. (IEEE Spectrum, May 28, 2021, https://spectrum.ieee.org/consumer-electronics/portable-devices/how-nanotech-can-foil-counterfeiters)

Flexible Electronics
“Pioneering Chemistry Approach Could Lead to More Robust Soft Electronics”

Authors: Susil Baral, Chunming Liu, et al.

Abstract: A new approach to studying conjugated polymers made it possible to measure the individual molecules’ mechanical and kinetic properties during polymerization reaction. The insights gained could lead to more flexible and robust soft electronic materials, such as health monitors and soft robotics.

Conjugated polymers are essentially clusters of molecules strung along a backbone that can conduct electrons and absorb light. This makes them a perfect fit for creating soft optoelectronics, such as wearable electronic devices; however, as flexible as they are, these polymers are difficult to study in bulk because they aggregate and fall out from solution. Cornell University researchers employed an approach called magnetic tweezers to stretch and twist individual molecules of the conjugated polymer polyacetylene. Through use of novel single-molecule manipulation and imaging approaches, this work provided the first observations of single-chain behaviors in conjugated polymers, which lays the foundation for the rational design and processing of these materials to enable widespread application. (ScienceDaily, Jun. 16, 2021, sciencedaily.com/releases/2021/06/210616143239.htm)

“High-Performance Flexible Nanoscale Transistors Based on Transition Metal Dichalcogenides”

Authors: Alwin Daus, Sam Vaziri, et al.

Abstract: Two-dimensional semiconducting transition metal dichalcogenides could be used to build high-performance flexible electronics. However, flexible field-effect transistors (FETs) based on such materials are typically fabricated with channel lengths on the micrometer scale, not benefitting from the short-channel advantages of 2-D materials. Here, the authors report flexible nanoscale FETs based on 2-D semiconductors; these are fabricated by transferring chemical-vapor-deposited transition metal dichalcogenides from rigid growth substrates together with nano-patterned metal contacts, using a polyimide film, which becomes the flexible substrate after release. Transistors based on monolayer molybdenum disulfide (MoS2) are created with channel lengths down to 60nm and on-state currents up to 470µA µm−1 at a drain-source voltage of 1V, comparable to the performance of flexible graphene and crystalline silicon FETs. Despite the low thermal conductivity of the flexible substrate, it was found heat spreading through the metal gate and contacts is essential to reach such high current densities. (Nature Electronics, Jun. 17. 2021, nature.com/articles/s41928-021-00598-6)

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.