Tomas Podprocky

A comparative study of via drilling and scribing on PEN and PET substrates for flexible electronic applications using excimer and Nd:YAG laser sources

A study on via drilling and channel scribing on PEN and PET substrates for flexible electronic application is discussed in this paper. For the experiments, both KrF excimer laser (248 nm) and frequency tripled Nd:YAG (355 nm) laser are used. Different measurement techniques like optical microscopy, Dektak profilometer, Confocal microscopy and scanning electron microscopy (SEM) were employed to characterize the quality of the channels and vias. The patterned structures were filled by three different methods using a conductive paste or ink that is cured in an oven at an elevated temperature. The cross-sectional measurements of channels and vias were carried out using SEM to study the uniformity of filling.

Flipchip Bonding of Si Chip on Flexible PEN Foil using Novel Electronic 100 μm Pitch Fan-out Circuitry

A novel, cost effective technology to manufacture high density embedded electronic circuitry is demonstrated. The process consists of laser photoablation of the circuitry into a substrate through a mask and subsequent filling using a polymer thick film paste. Because the volume of the substrate is used it is possible to make thick and thereby highly conductive lines using low cost materials and processes. The process is demonstrated for a fan out circuitry in 100 µm thick polyethylene naphthalate (PEN). The fan out circuitry has linewidths of 50 µm and line spacings of 100 µm. The usability of the circuitry is demonstrated by the successful flipchip bonding of a thinned Si daisy chain dummy chip with 176 IOs.

Miniaturized pumps and valves, based on conductive polimer actuators, for lab-on-chip application

We developed a new type of conductive polymer (CP) actuator, specifically designed for miniaturized pumps and valves for lab-on-a-chip (LoC) applications. CP films soaked in an electrolyte solution reversibly change their thickness upon bias application. A large stroke actuator was fabricated by stacking several CP layers, bonded together by means of epoxy dots. The CP deposition process was optimized for obtaining the low surface roughness required for stacking. The maximum strain of stacked actuators and of individual layers was identical (13%), indicating that the dot gluing process eliminates strain losses previously observed in multi-layers actuators. Pumps and valves were fabricated and mounted on a microfluidic chip.

SiGe micromirrors for optical applications

Micromirrors are a typical example of Micro-Electromechanical Systems (MEMS) with many applications including optical scanners, optical switching, projection displays, etc. We have succeeded in producing MEMS micromirrors in a SiGe structural layer, which can be used to realize CMOS-integrated MEMS structures. Several pixel designs were simulated using COMSOL multiphysics and subsequently verified in hardware. They differ in mirror size, hinge length and number of attracting electrodes (two or four). One particular mirror design enables variable Pulse Width Modulation (PWM) addressing. In this design, the mirror switches between two extreme states with a variable duty cycle determined by two generic high voltage signals and two CMOS-compatible pixel-specific DC voltages applied to the four attracting electrodes. The processed arrays were subjected to Laser Doppler Vibrometer (LDV) measurements in order to verify the simulation results. The simulated and measured pull-in voltages are compared for 8, 10 and 15μm mirrors. The agreement between simulation and measurement lies within the expectations, which is an encouraging result for future designs.

Integration of thick film resistors in a multilayer structure

Today, demands for electronic components are getting higher, with requirements containing smaller size, better reliability, higher integration and cheaper production. This paper presents some results of the work on voltage-controlled oscillators (VCO), especially on the problem of integration of resistors. The benefits coming from using thick film materials are low cost production, reliability and rigidity. The paper describes the behavior of thick film cermet resistors integrated in a multilayer structure based on Fodel dielectric material. Trimming in such multilayer structures is not always possible. Our goal was to asses this behavior with regard to resistor design and their resulting value. The effect of the refiring process and the interaction between resistor material and dielectrics was investigated.

A 4k projection display for D-cinema, medical imaging and simulation

Liquid crystal on silicon (LCOS) combines two very well-known technologies, namely the IC/CMOS and the liquid crystal (LC) technologies. As both of these are very mature, it is obvious that LCOS has a huge potential for very high-end applications, more than any other (projection) technology. The aim of the FORK project is the development of a LCOS microdisplay device for very diverse applications in simulation, medical imaging, control rooms and digital cinema. These applications require or benefit from very high pixel counts, high contrast ratios, very high light fluxes and very good colour and brightness uniformity, analog pixel addressing and high response times. A few microdisplay devices have recently been marketed for the applications mentioned above although none of these devices which meet all of these criteria.