Technical Abstracts
In Case You Missed It
Computer Memory
“Ultralow-Switching Current Density Multilevel Phase-Change Memory on a Flexible Substrate”

Authors: Asir Intisar Khan, et al.

Abstract: Phase-change memory (PCM) is a promising candidate for data storage in flexible electronics, but its high switching current and power are often drawbacks. In this study, the authors demonstrate a switching current density of ~0.1MA per sq. cm. in flexible superlattice PCM, a value that is one to two orders of magnitude lower than in conventional PCM on flexible or silicon substrates. This reduced switching current density is enabled by heat confinement in the superlattice material, assisted by current confinement in a pore-type device and the thermally insulating flexible substrate. The authors’ devices also show multilevel operation with low-resistance drift. The low switching current and good resistance on/off ratio are retained before, during, and after repeated bending and cycling. These results pave the way to low-power memory for flexible electronics and provide key insights for PCM optimization on conventional silicon substrates. (Science, Sept. 10, 2021, https://www.science.org/doi/10.1126/science.abj1261)

Counterfeit Detection
“Deterministic Tagging Technology for Device Authentication”

Authors: Jungjoon Ahn, Joseph Kopanski, Yaw S. Obeng and Jihong Kim

Abstract: This paper discusses the development of a rapid, large-scale integration of deterministic dopant placement technique for encoding information in physical structures at the nanoscale. The doped structures inherit identical and customizable RF electronic signature, which could be leveraged into an identification feature unique to the tag item. This will permit any manufactured item (e.g., an IC) to be uniquely identifiable and authenticatable. Applications of this technology include enabling a secure IoT and eliminating counterfeit products. (International Conference on IC Design and Technology, September 2021, https://www.nist.gov/publications/deterministic-tagging-technology-device-authentication)

Soldering Reliability
“Effects of Ag Flake Addition in Sn-3.0Ag-0.5Cu on Microstructure and Mechanical Properties with High-Temperature Storage Test”

Authors: Jun-Ho Jang, et al.

Abstract: In the 3-D IC package industry, remelting of solder joints during repeated stacking processes can cause electrical failure and low bonding strength. Transient liquid phase sintering (TLPS) bonding based on forming full intermetallic compounds (IMCs) in the solder joint to increase the remelting point has emerged as a potential solution to this issue. Here, pressureless TLPS Cu-Cu bonding was conducted with Sn-3.0Ag-0.5Cu solder powders and various Ag flake powder content (15 wt.%, 30 wt.%, 45 wt.%, and 60 wt.%). The TLPS paste was screen-printed, and the bonding process was conducted at 255°C for 2 hr. in an air atmosphere without bonding pressure. Additionally, this study investigated the microstructural evolution and fracture modes of the TLPS joints after the shear tests were investigated. High-temperature storage tests were conducted at 300°C for 24 hr., 48 hr., and 96 hr., and a shear test was then performed to evaluate bonding strength. A differential scanning calorimetry (DSC) analysis of the TLPS paste was conducted to investigate the thermal behavior of the paste during the bonding process. No residual solder was found in TLPS joints with an Ag flake content above 45 wt.% The highest bonding strength in a TLPS joint with full IMC layers was 27.3 MPa, representing an approximate 9% decrease after 96 hr. of high-temperature storage test. TLPS bonding with an optimal composition was resistant to the remelting of solder joints due to the full IMC layers; i.e., it represents a reliable interconnection method for 3-D stacking. (Journal of Electronic Materials, July 2021, https://link.springer.com/article/10.1007/s11664-021-09102-4)

Others of Note
What if your smartphone or laptop started charging as soon as you walked in the door? Researchers have developed a specially built room that can transmit energy to a variety of electronic devices within it, charging phones and powering home appliances without plugs or batteries. (www.scientificamerican.com/article/this-room-could-wirelessly-charge-all-your-devices)

Michigan Technological University researchers have created a way to make a 3-D-printable nanocomposite polymeric ink that uses carbon nanotubes (CNTs), a method that could supplant epoxies. (www.eurekalert.org/news-releases/929545)

UCLA researchers observed that a soft magnetoelastic composite can be used for stretchable and water-resistant magnetoelastic generators, adhering conformably to human skin. Such devices can be used as wearable or implantable power generators and biomedical sensors, opening alternative avenues for human-body-centered applications. (www.nature.com/articles/s41563-021-01093-1)

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.