Technical Abstracts
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High-Density Connectors

“Qualification of High-Density Connector Solutions for Military and Avionic Environments”

Authors: Kim Cho, Tim Pearson, David Hillman and Ross Wilcox; kimera.cho@collins.com.

Abstract: This paper discusses the qualification of high-density connector solutions for rugged military and avionics environments. As electronic products have become progressively smaller in size, there has been a corresponding increase in the demand for miniature, electronic components and the development of high-density connectors. The consumer electronics industry has already implemented high-density connectors, while many avionics/military products still use traditional surface-mount and plated through-hole connectors. These traditional connectors are increasingly too large and cannot meet the signal capacity requirements of modern avionics/military product designs within the limited available printed circuit board space. In this study, two major types of high-density connectors, the fine-pitch leaded style and the area-array style, were installed on test boards using automated assembly with tin-lead and lead-free soldering processes. The assemblies were subjected to -55° to +125°C thermal cycle testing in accordance with IPC-9701, Performance Tests Methods and Qualification Requirements for Surface Mount Solder Attachments. The first part of this paper discusses results and observations from the new testing of fine-pitch style and area-array style connectors. The second part of this paper compares data for the fine-pitch connectors to previously tested area-array connectors. Tradeoffs between these two types of connectors, including producibility, reliability, printed circuit board space usage, rework, ease of assembly, and defect identification, are discussed. (Collins company white paper, October 2019)

Stretchable Electronics
“Three-Dimensional Curvy Electronics Created Using Conformal Additive Stamp Printing”

Authors: Kyoseung Sim, Cunjiang Yu, Ph.D., et al.

Abstract: Electronic devices are typically manufactured in planar layouts, but many emerging applications, from optoelectronics to wearables, require three-dimensional curvy structures. However, the fabrication of such structures has proved challenging due, in particular, to the lack of an effective manufacturing technology. Here, the authors show that conformal additive stamp (CAS) printing technology can be used to reliably manufacture 3-D curvy electronics. CAS printing employs a pneumatically inflated elastomeric balloon as a conformal stamping medium to pick up prefabricated electronic devices and print them onto curvy surfaces. To illustrate the capabilities of the approach, the authors use it to create various devices with curvy shapes: silicon pellets, photodetector arrays, electrically small antennas, hemispherical solar cells and smart contact lenses. The authors also show that CAS printing can be used to print onto arbitrary 3-D surfaces. (Nature Electronics, vol. 2, 2019. https://doi.org/10.1038/s41928-019-0304-4)

“Multifunctional Two-Dimensional PtSe2-Layer Kirigami Conductors with 2000% Stretchability and Metallic-to-Semiconducting Tunability”

Authors: Emmanuel Okogbue, Sang Sub Han, et al.

Abstract: Two-dimensional transition-metal dichalcogenide (2-D TMD) layers are highly attractive for emerging stretchable and foldable electronics owing to their extremely small thickness coupled with extraordinary electrical and optical properties. Although intrinsically large strain limits are projected in them (i.e., several times greater than silicon), integrating 2-D TMDs in their pristine forms does not realize superior mechanical tolerance greatly demanded in high-end stretchable and foldable devices of unconventional form factors. The authors report a versatile and rational strategy to convert 2-D TMDs of limited mechanical tolerance to tailored 3-D structures with extremely large mechanical stretchability accompanying well-preserved electrical integrity and modulated transport properties. They employed a concept of strain engineering inspired by an ancient paper-cutting art, known as kirigami patterning, and developed 2-D TMD-based kirigami electrical conductors. Specifically, the authors directly integrated 2-D platinum diselenide (2-D PtSe2) layers of controlled carrier transport characteristics on mechanically flexible polyimide (PI) substrates by taking advantage of their low synthesis temperature. The metallic 2-D PtSe2/PI kirigami patterns of optimized dimensions exhibit an extremely large stretchability of ~2000% without compromising their intrinsic electrical conductance. They also present strain-tunable and reversible photo-responsiveness when interfaced with semiconducting carbon nanotubes (CNTs), benefiting from the formation of 2-D PtSe2/CNT Schottky junctions. Moreover, kirigami field-effect transistors (FETs) employing semiconducting 2-D PtSe2 layers exhibit tunable gate responses, coupled with mechanical stretching upon electrolyte gating. The exclusive role of the kirigami pattern parameters in the resulting mechanoelectrical responses was also verified by a finite-element modeling (FEM) simulation. These multifunctional 2-D materials in unconventional yet tailored 3-D forms are believed to offer vast opportunities for emerging electronics and optoelectronics. (Nano Letters, Jun. 6, 2019; www.ncbi.nlm.nih.gov/pubmed/31244238)

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.