Technical Abstracts
In Case You Missed It
Heat Shielding Materials

“Ultra-High Thermal Isolation across Heterogeneously Layered Two-Dimensional Materials”

Authors: Sam Vaziri, et al.

Abstract: Heterogeneous integration of nanomaterials has enabled advanced electronics and photonics applications. However, similar progress has been challenging for thermal applications, in part due to shorter wavelengths of heat carriers (phonons) compared to electrons and photons. Here, the authors demonstrate unusually high thermal isolation across ultrathin heterostructures, achieved by layering atomically thin two-dimensional (2-D) materials. The authors realize artificial stacks of monolayer graphene, MoS2, and WSe2 with thermal resistance greater than 100 times thicker than SiO2 and effective thermal conductivity lower than air at room temperature. Using Raman thermometry, we simultaneously identify the thermal resistance between any 2-D monolayers in the stack. Ultra-high thermal isolation is achieved through the mismatch in mass density and phonon density of states between the 2-D layers. These thermal metamaterials are an example in the emerging field of phononics and could find applications where ultrathin thermal insulation is desired in thermal energy harvesting or for routing heat in ultracompact geometries. (Science Advances, Aug. 16, 2019, advances.sciencemag.org/content/5/8/eaax1325)

PCB Design

“EMC & EMI on High-Speed PCB Design”

Authors: Zhiwei Tang and Xiaoqing Chen; 99chaoyang@163.com.

Abstract: In higher complexity electronics systems, PCB clock frequencies and densities increase as well. Signal integrity is a top priority in high-speed PCB design. Many factors such as electromagnetic compatibility (EMC), PCB electrical parameters, component layout and high-speed signal line cabling affect the performance of the final system. How to reasonably avoid the impact of these factors and issues of note are the key to successful design of high-speed PCBs. (International Conference on Applications and Techniques in Cyber Security and Intelligence, Jul. 31, 2019)

PCB Processing

“Advanced Manufacturing Technology of Microwave Multilayer Printed Circuit Board”

Authors: Zhaohang Zhang, et al; zzh_william@126china.com.

Abstract: The requirements for new-type antenna electronics equipment are high performance, high reliability and large capacity, but small size and lightweight. This paper discusses the processing of rigid antenna microwave multilayer PCBs, which presents some key developing fields and solutions, specifically in registration control and any-layer interconnect. With performance requirements increasing for rigid antennas, a PTFE-based composite lays a foundation for the development of microwave multilayer PCBs. From the advanced mechanical manufacturing point of view, the future technology development of microwave multilayer PCBs includes control of the deformation and expansion/contraction of the PCB substrate, large data software systems, any-layer interconnect design requirements, and performance indicators. (Proceedings of the Seventh Asia International Symposium on Mechatronics, Aug. 31, 2019)

Reliability

“Solder Joint Reliability of a 0.65mm Pitch Molded Array Package for Automotive Applications”

Authors: Burton Carpenter, Mollie Benson and Andrew Mawer; andrew.mawer@nxp.com.

Abstract: BGA components used in high-reliability automotive microprocessor applications have historically been 0.8mm pitch or larger. Recently, emerging market requirements have pushed BGA pitches down to 0.65mm. However, industry expectations of solder-joint reliability remain constant; customers expect cyclical thermal fatigue lifetimes to be the same as or, in some cases, more robust than prior generations of packages. In addition, automotive Tier 1 electronics manufacturers often include drop test and other board-mounted testing criteria to mitigate the risk of module-level failure during SMT, module or final vehicle assembly. The paper reports the board-level reliability of a 0.65mm pitch, 10 x 10mm MAPBGA (molded array plastic BGA) package used as an automotive radar microprocessor. Thermal fatigue life was assessed per IPC-9701A using AATS (air-to-air thermal shock) between -40°C and +125°C, while drop testing followed Jedec JESD22-B111A at 1500G. (SMTA International, October 2018)

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.