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Friday, 01 July 2011 18:15

Component Substrates

“Scalable Fabrication of Self-Aligned Graphene Transistors and Circuits on Glass”

Authors: Lei Liao, Jingwei Bai, Rui Cheng, Hailong Zhou, Lixin Liu, Yuan Liu, Yu Huang and Xiangfeng Duan; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
Abstract: Graphene transistors are of considerable interest for radio frequency applications. High-frequency graphene transistors with the intrinsic cutoff frequency up to 300 GHz have been demonstrated. However, the graphene transistors reported to date only exhibit a limited extrinsic cutoff frequency up to about 10 GHz, and functional graphene circuits demonstrated so far can merely operate in the tens of megahertz regime, far from the potential the graphene transistors could offer. Here the authors report a scalable approach to fabricate self-aligned graphene transistors with the extrinsic cutoff frequency exceeding 50 GHz and graphene circuits that can operate in the 1-10 GHz regime. The devices are fabricated on a glass substrate through a self-aligned process by using chemical vapor deposition (CVD) grown graphene and a dielectrophoretic assembled nanowire gate array. The self-aligned process allows the achievement of unprecedented performance in CVD graphene transistors with a highest transconductance of 0.36 mS/µm. The use of an insulating substrate minimizes the parasitic capacitance and has therefore enabled graphene transistors with a record-high extrinsic cutoff frequency (>50 GHz) achieved to date. The excellent extrinsic cutoff frequency readily permits configuring graphene transistors into frequency doubling or mixing circuits functioning in the 1-10 GHz regime, a significant advancement over previous reports (20 MHz). The studies open a pathway to scalable fabrication of high-speed graphene transistors and functional circuits, and represent a significant step forward to grapheme-based RF devices. (Nano Letters, June 7, 2011)

Embedded Components

“Development of a Design & Manufacturing Environment for Reliable and Cost-Effective PCB Embedding Technology”

Authors: M. Brizoux et al.; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
Abstract: This paper highlights several key industrialization aspects addressed by the European-funded HERMES project to build a manufacturing environment for products with embedded components. The focus of the paper is on three critical activities: 1) The development of a PCB CAD solution that supports embedding packaged components; 2) the thermo-mechanical activities performed to support the definition of design rules. (The latter has been achieved through FEA simulations supported by a comprehensive test program based on strain gage measurements under torsion, which are detailed. The work enabled characterization of the mechanical behavior of embedded PCBs taking into account the buildup, as well as the effect of soldered components, which ensures reliable and highly functional embedded PCBs and modules.); and 3) the high production yields to achieve a cost-effective technology driven by process control and using advanced tools like high-definition 3D laser scanning. (IPC Apex Expo, April 2011)

Solders

“Investigation for Use of ‘Pin in Paste’ Reflow Process with Combination of Solder Preforms to Eliminate Wave Soldering”

Authors: Guhan Subbarayan, Scott Priore, Paul Koep, Scott Lewin, Rahul Raut and Sundar Sethuraman; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
Abstract: The objective of this study was to investigate the use and limitations of machine-placed solid solder preforms during the top-side SMT reflow process for PTH components.

The experiment was conducted on a 0.130" test vehicle using both SnPb and Pb-free materials and processes. The results of this designed experiment, along with the inspection methods, are presented and discussed in detail. The outcomes provide extensive guidelines for implementing PiP technology with a combination of solder preforms. (IPC Apex Expo, April 2011)

“Evaluation of Lead Free Solder Paste Materials for PCBA”

Authors: Jennifer Nguyen, David Geiger and Dongkai Shangguan, Ph.D.; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
Abstract: This paper discusses the strategy and methodology for selecting a good Pb-free solder paste for volume manufacturing. A statistical and methodological evaluation approach is addressed in detail. It shows how to screen paste candidates for quality using printability tests, slump test, solder ball test and wetting tests, and how to select a robust solder paste material using design of experiments. Performance of Pb-free no-clean solder paste, Pb-free water-soluble solder paste, halogen-containing solder paste and halogen-free solder paste are compared. Characteristics and requirements are also outlined. (IPC Apex Expo, April 2011)

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.

Last Updated on Tuesday, 05 July 2011 10:25
 

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