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High frequency design and characterization of SU-8 based conductor backed coplanar waveguide transmission lines
Mid Sweden University, Campus Östersund, Department of Information Technology and Media (ITM), Östersund.
Mid Sweden University, Campus Östersund, Department of Information Technology and Media (ITM), Östersund.
2005 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The epoxy-based negative photoresist SU8 is widely used within the MEMS (Micro-Electro-Mechanical Systems) community, and is well known for its ability to form thick layers with high aspect ratios and for its chemical resistance. However, only a few papers have investigated the electrical properties of this material and mostly within the MEMS area or at lower frequency ranges.

This paper presents the design and characterization of conductor-backed coplanar waveguide (CBCPW) transmission lines using SU-8 dielectric material. The coplanar transmission lines are carefully designed using EDA tools, and fabricated on a metallized glass substrate coated with SU-8 material. S-parameter measurements are performed from 45 MHz to 50 GHz using a vector network analyzer and a probe station. From these measurements, transmission line parameters such as characteristic impedance, attenuation constant, effective dielectric constant, loss tangent, etc, are determined. The design procedure, fabrication process and measurement results are described in this paper.

To our knowledge, this is the first time the SU-8 material is characterized in Microelectronics using CBCPW transmission lines.

Place, publisher, year, edition, pages
2005. no 1432083, 243-248 p.
Keyword [en]
Conductor-backed coplanar waveguides (CBCPW) transmission lines; Coplanar waveguides (CPW); Dielectric measurement; High frequency electrical characterization; Microwave measurements; Chemical resistance; Microelectromechanical devices; Natural frequencies; Photoresistors; Conductor-backed coplanar waveguides (CBCPW) transmission lines; Coplanar waveguides (CPW); Dielectric measurement; High frequency electrical characterization; Microwave measurements; Waveguides
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6943DOI: 10.1109/ISAPM.2005.1432083ISI: 000230430400050OAI: oai:DiVA.org:kth-6943DiVA: diva2:11799
Note

QC 20100809. Konferens: 10th International Symposium on Advanced Packaging Materials: Processes, Properties and Interfaces, Irvine, CA, MAR 16-18, 2005.

Available from: 2007-04-10 Created: 2007-04-10 Last updated: 2017-04-04Bibliographically approved
In thesis
1. Some Aspects of Advanced Technologies and Signal Integrity Issues in High Frequency PCBs, with Emphasis on Planar Transmission Lines and RF/Microwave Filters
Open this publication in new window or tab >>Some Aspects of Advanced Technologies and Signal Integrity Issues in High Frequency PCBs, with Emphasis on Planar Transmission Lines and RF/Microwave Filters
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The main focus of this thesis is placed on high frequency PCB signal Integrity Is-sues and RF/Microwave filters using EBG structures.

From the signal Integrity aspect, two topics were mainly discussed. On one hand, the effect of increasing frequency on classical design rules for crosstalk reduction in PCBs was investigated experimentally and by full-wave simulations. An emphasis was placed on the 3×W spacing rule and the use of guard traces. Single-ended and differential transmission lines were considered. S-parameter measurements and simu-lations were carried out at high-frequency (up to 20 GHz). The results emphasize the necessity to reevaluate traditional design rules for their suitability in high frequency applications. Also, the impacts of using guard traces for high frequency crosstalk re-duction were clearly pointed out. On the other hand, the effect of high loss PCB ma-terials on the signal transmission characteristics of microstrip lines at high frequency (up to 20 GHz) was treated. Comparative studies were carried out on different micro-strip configurations using standard FR4 substrate and a high frequency dielectric ma-terial from Rogers, Corporation. The experimental results highlight the dramatic im-pact of high dielectric loss materials (FR4 and solder mask) and magnetic plating metal (nickel) on the high frequency signal attenuation and loss of microstrip trans-mission lines.

Besides, the epoxy-based SU8 photoresist was characterized at high frequency (up to 50 GHz) using on-wafer conductor-backed coplanar waveguide transmission lines. A relative dielectric constant of 3.2 was obtained at 30 GHz. Some issues related to the processing of this material, such as cracks, hard-skin, etc, were also discussed.

Regarding RF/Microwave filters, the concept of Electromagnetic Band Gap (EBG) was used to design and fabricate novel microstrip bandstop filters using periodically modified substrate. The proposed EBG structures, which don’t suffer conductor backing issues, exhibit interesting frequency response characteristics.

The limitations of modeling and simulation tools in terms of speed and accuracy are also examined in this thesis. Experiments and simulations were carried out show-ing the inadequacies of the Spice diode model for the simulations in power electronics. Also, an Artificial Neural Network (ANN) model was proposed as an alternative and a complement to full-wave solvers, for a quick and sufficiently accurate simulation of interconnects. A software implementation of this model using Matlab’s ANN toolbox was shown to considerably reduce (by over 800 times) the simulation time of microstrip lines using full-wave solvers such as Ansoft’s HFSS and CST’s MWS.

Finally, a novel cooling structure using a double heatsink for high performance electronics was presented. Methods for optimizing this structure were also discussed.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. xvii, 77 p.
Series
Trita-ICT/MAP, 2007:03
Keyword
Signal integrity, crosstalk, guard trace, PCB, transmission line loss, high frequency measurement, dielectric, SU-8, electromagnetic bandgap, microwave filter
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4324 (URN)978-91-7178-605-0 (ISBN)
Public defence
2007-04-17, Rum 5435, KTH-Electrum, Isafjordsg. 22, Kista, 10:00
Opponent
Supervisors
Note
QC 20100809Available from: 2007-04-10 Created: 2007-04-10 Last updated: 2011-09-30Bibliographically approved

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