Ashok Sridhar

PhD Project:


Start / End:

January 2006 to May 2010


This PhD project falls under the framework of PACMAN, a collaborative research project between Thales, Astron, University of Twente and Technical University of Eindhoven.

Links to the participating organizations:


PROCESS: Inkjet printing is a widely deployed process for printing texts, pictures etc., on paper. But of late, this process is being promoted as a potential fabrication technique for printed electronics or, more specifically, for organic electronics. The term ‘printed electronics’ encompasses thin film silicon, organic or printed inorganic semiconductors that can be used to form Thin Film Transistor Circuits (TFTCs), thereby replacing the functionality of simple silicon chips (source: ‘Polymer electronics’ is more specific, and concerns only with the polymer-based circuits/circuit elements.

APPLICATION: PACMAN’s goal is to research and develop an integrated technology for the design and manufacture of mass-market, low-cost phased array antennae that can be applied in various domains, such as telecom, wireless internet, satellite communication, radars, large area astronomic antennae, automotive and security. If successful, mass-markets with high volumes and relatively high added value can then be developed, based on these new technologies.

SUMMARY OF THE THESIS: A process chain to fabricate conductive structures on printed circuit board materials is presented in this thesis. This process chain comprises four main steps: plasma treatment, inkjet printing, electroless plating and functional characterisation. It represents a drastic reduction in the number of process steps when compared to the conventional lithography-based method, widely used in the printed circuit board industry.

The proposed process chain is validated by fabricating radio frequency circuit structures in the form of an S-band filter and a transmission line, and comparing their performance with that of conventionally fabricated S-band filter and transmission line. The comparison shows that the inkjet printing-electroless plating combination can be used even for the GHz frequency range, marking an improvement from the oft-discussed RFID applications in the context of inkjet printing.

APPLICATION EXAMPLE: S-band filter and transmission line on a high-frequency substrate material (Rogers 4003):

About me in a nutshell:

­From Chennai (Madras), India; DoB: 02-05-1980

­Bachelors in Mechanical Engineering, from University of Madras, India (1997-2001)

­Masters in Production Engineering from RWTH, Aachen, Germany (2002-05)

­Worked for one year as a Design Engineer at Caterpillar, India (2001-02)

­Worked for one year as an Intern/Graduand at DaimlerChrysler, Germany (2004-05)

­Interests: History, Geography, General Knowledge, Astronomy, Languages & their evolution

­Private email id: Ashok.Sridhar[a]


1. Inkjet-printing- and electroless-plating-based fabrication of RF circuit structures on high-frequency substrates, Journal of Micromechanics and Microengineering, 2009

2. Inkjet printing and adhesion characterisation of conductive tracks on a commercial printed circuit board material, Thin Solid Films, 2009

3. Fabrication of RF circuit structures on a PCB material by inkjet printing-electroless plating and the substrate preparation therefor, Transactions on the Japanese Institute of Electronics Packaging, 2009

4. Application and modelling of hybrid stereolithography injection mould tooling, Virtual and Physical Prototyping, 2006

Conference presentations/papers

1. Advances in Printing and Media Technology, IARIGAI, Montreal, Canada, 2010

2. International Conference on Competitive Manufacturing, Stellenbosch, South Africa, 2010

3. Printing Future Days, Chemnitz, Germany, 2009 (Best Author Award)

4. Large-area, Organic and Printed Electronic Convention, Frankfurt, Germany, 2009

5. International Conference on Electronic Packaging, Kyoto, Japan, 2009

6. European Institute of Printed Circuits - Winter Conference, Rome, Italy, 2008

7. Printing Future Days, Chemnitz, Germany, 2007 (Best Poster Award)

Other publications

1. Trends and expertise exchange within rapid manufacturing in Europe, RT e-journal, 2010

A. Sridhar, An inkjet printing-based process chain for conductive structures on printed circuit board materials, PhD thesis University of Twente, 2010, ISBN 978-90‑365‑3027‑9.

Life after PhD

Ashok is now Post-Doc at the Fraunhofer Research Institution

for Electronic Nano Systems ENAS, Department Printed Functionalities, Chemnitz, Germany