Filimon Zacharatos - Academia.edu (original) (raw)

Papers by Filimon Zacharatos

HAL (Le Centre pour la Communication Scientifique Directe), May 26, 2013

International audienc

Laser 3D Manufacturing IV, 2017

During the last decade there is an ever-increasing interest for the study of laser processes dyna... more During the last decade there is an ever-increasing interest for the study of laser processes dynamics and specifically of the Laser Induced Forward Transfer (LIFT) technique, since the evolution of the phenomena under investigation may provide real time metrology in terms of jet velocity, adjacent jet interaction and impact pressure. The study of such effects leads to a more thorough understanding of the deposition process, hence to an improved printing outcome and in these frames, this work presents a study on the dynamics of LIFT for conductive nanoparticles inks using high-speed imaging approaches. Moreover, in this study, we investigated the printing regimes and the printing quality during the transfer of copper (Cu) nanoink, which is a metallic nanoink usually employed in interconnect formation as well as the printing of silver nanowires, which provide transparency and may be used in applications where transparent electrodes are needed as in photovoltaics, batteries, etc. Furthermore, we demonstrate the fabrication of an all laser printed resistive chemical sensor device that combines Ag nanoparticles ink and graphene oxide, for the detection of humidity fabricated on a flexible polyimide substrate. The sensor device architecture was able to host multiple pairs of electrodes, where Ag nanoink or nanopaste were laser printed, to form the electrodes as well as the electrical interconnections between the operating device and the printed circuit board. Performance evaluation was conducted upon flow of different concentrations of humidity vapors to the sensor, and good response (500 ppm limit of detection) with reproducible operation was observed.

Materials Science And Engineering: B, Dec 1, 2009

We report on the fabrication and the photoluminescence (PL) study of hybrid nanocomposites formed... more We report on the fabrication and the photoluminescence (PL) study of hybrid nanocomposites formed by embedding fluorene dye molecules in the vertical cylindrical nanopores of a nanoporous silicon layer. The pores had a diameter of ∼20nm and were homogeneously filled with the fluorene molecules as evidenced by scanning electron microscopy images. Efficient PL in the blue spectral region, attributed to

Organic Electronics and Photonics: Fundamentals and Devices III

Nanoscale and Quantum Materials: From Synthesis and Laser Processing to Applications 2023

Materials Today: Proceedings

Virtual and Physical Prototyping

Optics & Laser Technology, 2016

Flexible electronics have emerged as a very promising alternative of CMOS compatible electronics ... more Flexible electronics have emerged as a very promising alternative of CMOS compatible electronics for a plethora of applications. Laser microfabrication techniques, such as selective laser patterning and sintering are compatible with flexible substrates and have demonstrated impressive results in the field of flexible electronic circuits and sensors. However, laser based manufacturing of radio frequency (RF) passive components or devices is still at an early stage. In this work we report on the all-laser fabrication of Silver Co-Planar Waveguides (CPWs) on polyethylene-naphthalate (PEN) substrates employing flat-top optics to achieve uniform laser fluence and thus high fabrication precision and reproducibility but also to mitigate the thermal effects of nanosecond laser pulses. The CPWs have been fabricated to match the impedance of 50 Ω ports of an Anritsu vector network analyzer operating from 40 MHz to 40 GHz. The all laser fabrication process consisted in the selective laser sintering of square dies on a Silver Nano Particle layer spin-coated on a PEN substrate followed by the selective laser patterning of the CPWs with a ns pulsed Nd:YAG laser source operating at 532 nm, according to the optimized parameters extracted from a previous studies of the authors. The CPWs have been characterized electrically at the 0.04-40 GHz regime and found to be excellent transmission lines with a 40 GHz 3 dB bandwidth, owing to the high electrical conductivity of Ag and the excellent dielectric properties of PEN. This novel process is a milestone towards the RF technology transfer to flexible electronics with low cost and specs comparable to the CMOS compatible equivalents.

Applied Surface Science, 2016

To date, Laser Direct Write (LDW) techniques, such as Laser Induced Forward Transfer (LIFT), sele... more To date, Laser Direct Write (LDW) techniques, such as Laser Induced Forward Transfer (LIFT), selective laser ablation and selective laser sintering of metal nanoparticle (NP) ink layers are receiving growing attention for the printing of uniform and well-defined conductive patterns with resolution down to 10 mu m. For flexible substrates in particular, selective laser sintering of such NP patterns has been widely applied, as a low temperature and high resolution process compatible with large area electronics. In this work, LDW of silver NP inks has been carried out on polyethylene-terephthalate (PET), polyethylenenaphthalate (PEN) and polyimide (PI) substrates to achieve low electrical resistivity electrodes. In more detail, high speed short pulsed (picosecond and nanosecond) lasers with repetition rates up to 1 MHz were used to print (LIFT) metal NP inks. We thus achieved uniform and continuous patterns with a minimum feature size of 1 mu m and a total footprint larger than 1 cm(2). Next, the printed patterns were laser sintered with ns pulses at 532 nm over a wide laser fluence window, resulting in an electrical resistivity of 10 mu Omega cm. We carried out spatial beam shaping experiments to achieve a top-hat laser intensity profile and employed selective laser ablation of thin films (thickness on the order of 100 nm) to produce silver micro-electrodes with a resolution on the order of 10 pin and a low line edge roughness. Laser sintering was combined with laser ablation to constitute a fully autonomous micro-patterning technique of metallic micro-features, with a 10 pin resolution and geometrical characteristics tuned for interdigitated electrodes for sensor applications. (C) 2015 Elsevier B.V. All rights reserved.

Nevertheless, data communication and power consumption are still daunting issues in Data Centers ... more Nevertheless, data communication and power consumption are still daunting issues in Data Centers and HPCs. According to recent predictions made in [4], the barrier of 10PFlops Plasmonics-Principles and Applications 524 computing performance should have been overcome in 2012 by a supercomputer that consumes 5MW of power [5]. In addition, [4] predicted that exascale supercomputing machines would consume 20MW having a power efficiency of 1mW/Gb/s [5]. Nonetheless, power consumption in such environments has been proven to be even higher than expected: Today's top-ranked supercomputer, the "K computer", has already reached the 10PFlops performance benchmark but at the expense of excessive consumed power that is more than twice [6] the value that was predicted in 2008. All the above imply that the use of optics at inter-rack communication level is not enough for delivering the necessary performance enhancements. Therefore, the optical technology should now be exploited at shrinked networking environments: The penetration of low-energy photonic solutions at board-toboard, chip-to-chip and eventually intra-chip interconnects would yield remarkable savings in energy consumption [7]. The current mainstream photonic route with high integration and low-cost perspectives relies on the Silicon-on-Insulator (SOI) photonics platform, whose growing maturity is soon expected to release Tb/s-scale data transmission and switching capabilities in datacom and computercom units ensuring low latency, low power consumption and chip-scale integration credentials [8].

IEEE Journal of Selected Topics in Quantum Electronics

Current trends in microelectronics chip bonding and assembly encompass ultra-fine pitch component... more Current trends in microelectronics chip bonding and assembly encompass ultra-fine pitch components with flexible form factors and advanced die-attach materials, which can sustain conformal strain without compromise in adhesion and reliability. These trends have highlighted the need for advanced microfrabrication technologies, which allow the on-demand digital fabrication of interconnections and die-attach bumps on chip carriers and interposers with challenging topographies. Laser printing, based on the laser induced forward transfer (LIFT) technique, has addressed such micromanufacturing challenges over the past decade. Several previous demonstrations of highly resolved and conformal interconnections for the bonding and packaging of micro and opto-electronic components are summarized in this paper. Latest advances in the laser printing and laser sintering of highly viscous nanopastes for achieving planar or three-dimensional (3D) structures consisting of Ag paste are demonstrated. The latter is achieved by stacking of arrays or bumps in a digital manner. The reported results verify that LIFT offers control over both the lateral and vertical dimensions. This control can facilitate the soldering process of heterogeneous components, whose pads have significant height and pitch dissimilarities. The applicability of LIFT in the fields of packaging and assembly of flexible and heterogeneous integration schemes, is further validated.

Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXVI, 2021

Currently the most widely used technique for solder paste deposition is Surface Mount Technology ... more Currently the most widely used technique for solder paste deposition is Surface Mount Technology (SMT), which involves the printing of solder paste using a stencil, onto printed circuit board (PCB) interconnection pads. However, this process accounts for 50-70% of post-assembly defects. Here, we report the use of Laser Induced Forward Transfer (LIFT), for the reliable printing of commercially available solder pastes. LIFT is an environmentally friendly, mask-less technique and offers high resolution (down to 60 μm) control over the printed volume with high throughput. LIFT has been previously employed for the reproducible and high throughput (speed up to 2 m/s) printing of metal nanoparticle inks, but the achievement of reproducible deposition of bumps comprising micro-particles (such as in type-5 or 6 solder pastes) stills poses severe challenges. By investigating the whole spectrum of LIFT process parameters – the donor film thickness, the donor – receiver gap, the effect of a sacrificial layer, the laser spot size and shape and the laser fluence - this paper reports on the digital and reproducible transfer of solder paste bumps at the designated pads of ultra-fine pitch PCBs. The process optimization is enabled by employing a side view set-up, consisting of a high-speed camera (up to 540 kfps) coupled with a lens system for 3x optical magnification of the ejection. The reported results highlight the advantages of a digital and high-resolution solder paste deposition method and validate the compatibility of LIFT with PCB assembly.

Publisher’s Note: This conference presentation, originally published on 5 March 2021, was withdra... more Publisher’s Note: This conference presentation, originally published on 5 March 2021, was withdrawn on 20 May 2021 per author request.

Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXV, 2020

The recent developments in the field of large area, flexible and printed electronics have fueled ... more The recent developments in the field of large area, flexible and printed electronics have fueled substantial advancements in Laser Printing and Laser Sintering, which have been attracting interest over the past decade. Resulting applications, ranging from flexible displays and sensors, to biometric devices and healthcare, have already showcased transformational advantages in terms of form factor, weight and durability. In HiperLAM project, Laser-Induced Forward Transfer (LIFT), combined with high speed laser micro-sintering are employed, as digital microfabrication tools for the demonstration of fully functional RFID antennas and fingerprint sensors based on highly viscous Ag and Cu nanoparticle inks. Having previously successfully demonstrated complex structures, this work’s focus is on increasing the process throughput and yield by increasing the laser repetition rate (up to 40 kHz) and scanning speed (up to 2 m/s), without compromising reliability and resolution. In order to gain insight into the effects of the incremented repetition rate on the printing procedure, the latter was monitored in real time via a high-speed camera, able to acquire up to 540.000 fps, coupled to the setup. Examples of resulting structures comprise well-defined interdigitated and spiral micro-electrodes with post-sintering electrical resistivity lower than 5 x bulk Ag and 3 x bulk Cu. The aforementioned results validate the compatibility of laser based processing with the field of flexible RFID tags and OTFT based fingerprint sensors and foster the wider adoption of LIFT and laser micro-sintering technology for laboratory and industrial use.

Graphene and related 2D semiconductors, owing to their exquisite optoelectronic and mechanical pr... more Graphene and related 2D semiconductors, owing to their exquisite optoelectronic and mechanical properties, hold great promise as active materials in flexible electronics applications and devices. In this work, we report the use of Laser Induced Forward Transfer (LIFT) for the precise and micro-scale printing of graphene pixels on conventional and flexible substrates in a single step process. Complementary to the experimental studies, Density Functional Theory (DFT) is also employed to investigate the interactions between graphene and metallic substrates (Cu, Ni) as well as to shed light on the energy that is required to detach and deposit intact graphene pixels.

Materials, 2021

Current challenges in printed circuit board (PCB) assembly require high-resolution deposition of ... more Current challenges in printed circuit board (PCB) assembly require high-resolution deposition of ultra-fine pitch components (<0.3 mm and <60 μm respectively), high throughput and compatibility with flexible substrates, which are poorly met by the conventional deposition techniques (e.g., stencil printing). Laser-Induced Forward Transfer (LIFT) constitutes an excellent alternative for assembly of electronic components: it is fully compatible with lead-free soldering materials and offers high-resolution printing of solder paste bumps (<60 μm) and throughput (up to 10,000 pads/s). In this work, the laser-process conditions which allow control over the transfer of solder paste bumps and arrays, with form factors in line with the features of fine pitch PCBs, are investigated. The study of solder paste as a function of donor/receiver gap confirmed that controllable printing of bumps containing many microparticles is feasible for a gap < 100 μm from a donor layer thickness set...

Optics & Laser Technology, 2021