Delivered by Ingenta to: Main CID is 80004805 (JPP) IP: 5.189.207.152 On: Mon, 20 Jun 2016 09:32:08 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2011 American Scientiﬁc Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 11, 1468–1471, 2011 Electrical Characteristics of Printed Ag Nanopaste on Polyimide Substrate Young-Chul Lee 1 , Kwang-Seok Kim 1 , Jong-Woong Kim 2 , Jong-Min Kim 3 , Wansoo Nah 3 , Seong-Hee Lee 4 , and Seung-Boo Jung 1 ∗ 1 School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, 440-746, Gyeonggi-do, South Korea 2 Display Center, Korea Electronics Technology Institute, 68 Yatap-dong, Bundang-gu, Seongnam, Gyeonggi-do, 463-816, South Korea 3 School of Electrical and Computer Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, 440-746, Gyeonggi-do, South Korea 4 Department of Advanced Materials Science and Engineering, Mokpo National University, Muan-gun 534-729, Chonnam, Korea We investigated the effects of sintering temperature on the microstructural evolution and electrical characteristics of screen-printed Ag patterns. A conducting paste containing 20 nm Ag nanoparticles (73 wt%) was screen printed onto a polyimide (PI) substrate and sintered at a temperature of 150, 200, 250 and 300  C for 30 min. The microstructures of the sintered patterns were examined using ﬁeld emission scanning electron microscopy (FESEM). The resistivity under the application of a DC signal decreased with increasing temperature. In the frequency range from 10 MHz to 20 GHz, the S-parameters of the sintered Ag conducting patterns were measured. The S-parameters indicated that the insertion losses at high frequency decreased with increasing sintering temperature due to the formation of interparticle necking after sintering. Keywords: Direct Printing, Ag Nanopaste, Screen Printing, Electrical Characteristics, S-Parameter. 1. INTRODUCTION Until recently, the ﬁeld of electronics was more focused on high density integration and miniaturization. However, light and thin ﬁlm electronics such as ﬂexible displays have now attracted growing interest in the development of electronics industries, as the ﬁeld of ﬂexible electron- ics has gradually matured. The various methods for fab- ricating ﬂexible electronics have included applied printing methods such as gravure, ink-jet and screen printing. Such printed electronics offer the following advantages over the expensive processes such as photo-lithography, etching and vacuum deposition: the ability to rapidly change circuit designs in real time in a highly cost effective fashion, envi- ronmentally friendly process, reduction in material loss, high productivity, and mass customization. 1–3 One of the most prominent applications of printed cir- cuits is the ﬂexible radiofrequency identiﬁcation (RFID) tag, which uses a signal frequency of only several tens or hundreds mega hertz, because sufﬁcient information has ∗ Author to whom correspondence should be addressed. not yet been elucidated for the high frequency performance of the conductive circuits that are formed by the printing methods. In order to expand the application areas of the direct printing methods, we need to focus on the radio fre- quency (RF) and rather higher frequency signal transmis- sion properties of the printed circuits. Although a variety of research has recently been conducted on the electri- cal properties of the conductive circuits fabricated by the printing techniques, most was focused on direct current (DC) resistance and the resulting circuit conductivity. 4–5 To expand our understanding of the electrical transmis- sion properties, it is important to clarify and conﬁrm the phenomenological facts by RF signal transmission mea- surements on the basis of proper design techniques. Only then can we diversify the applicable areas of the printing technology into various RF devices utilizing higher fre- quencies such as cellular phones, Bluetooth modules, and various mobile internet devices. We report the electrical characteristics of the screen- printed Ag patterns on the PI substrate sintered at vari- ous temperatures. PI is beginning to be applied in ﬂexible ﬁelds due to its good mechanical strength, a higher glass 1468 J. Nanosci. Nanotechnol. 2011, Vol. 11, No. 2 1533-4880/2011/11/1468/004 doi:10.1166/jnn.2011.3354