Citation
(2014), "IMAPS Poland 37th International Microelectronics and Packaging ConferenceCPMT Conference, Kraków 23-25 September 2013", Soldering & Surface Mount Technology, Vol. 26 No. 1. https://doi.org/10.1108/SSMT.21926aaa.010
Publisher
:Emerald Group Publishing Limited
IMAPS Poland 37th International Microelectronics and Packaging ConferenceCPMT Conference, Kraków 23-25 September 2013
Article Type: Conferences and exhibitions From: Soldering & Surface Mount Technology, Volume 26, Issue 1
Monday 23 September 2013
The conference was held in the Hotel Swing, located on the ul.Dobrego Pasterza in the historic city of Kraków and 100+ delegates came from all over Europe to benefit from a very full programme. The opening address was given by the IMAPS Poland President Professor Jan Felba, from the Technical University of Wroclaw. He reflected that such events are necessary as they reflect the work being done in the various centres in the country, and brings it all together in one place. There were 79 presenters, and 65 poster displays, and the whole affair was organised by the Institute of Electron Technology.
It therefore was appropriate for Professor Jerzy Katcki from the Institute to give the first paper, which was on the research potential in nanotechnology. Nanotechnology is everywhere now; it is in our homes, our offices, our cars, the mobile phone, GPS, and in all advanced medical instruments. The institute was established in 1966, and is now very much involved in photonics and semiconductor electronics. They also have a new division working in the field of optoelectronics, employing 320 people, with 50 PhDs and 15 professors, involved with circuit design and hybrid microelectronics amongst others, with their main site in Warsaw, one in Krakow, and one in Piaseczno.
They have four divisions; EMC certification, nano-characterisation, photonic and nanotechnology, and microsystems. Their ITE centres focus on nano photonics, multilayer and ceramic technologies, and electronic microsystems. An €11 million investment in development and design of micro and nano technology under the MINTYE label, with an emphasis on industrial applications. Under the MNS-DIAG banner, they have an experimental LTCC line, and development of biomedical devices and diagnostics; there are 11 partners, working on lab on chip, MEMS for medical diagnostic equipment, and arrays for chemical sensors. Under FP7 they have a project called NANOHEAT which is developing sensors for heat measurement; Professor Katcki showed an excellent illustration of a typical modern car with sensors, proximity sensors, heat sensors, tyre pressure sensors, and the now expected electronic car systems; there is a glaucoma sensor, a cochlear implant, in which micro sensors are embedded in polymer, and detectors for finding radon, used in the radiation industry.
Quantum Cascade Lasers have been developed by gas detection systems, for gases and pollutants in the atmosphere. NANOBIOM is about quantum semiconductor nanostructures, quantum dot structures. Under his supervision, there is a lot going on.
The next speaker was Dr Reiner Dudeck of the Fraunhofer Institute ENAS. His topic was on reliability issues for high temperature interconnections based on transient liquid phase (TLP) soldering. ENAS started in 2008, and covers the main micro material activities such as visual prototyping, testing, diagnostic and failure analysis, and deformation and stress management.
In the field of soldering, there are issues with high temperature solders and reliability, and there are alternative soft solders based on TLP soldering, and silver sintering.
In testing reliability, voltage, temperature and mechanical loading all have a role to play, and failure can be fracturing or fatigue, where vibration and noise and thermal cycling contribute. Dr Dudeck illustrated power modules subjected to temperature loading, and how ultrasonic scanning microscopy revealed cracking after 200 cycles, where the damage starts at the corners. The banning of lead has had a drastic impact on interconnection reliability, and SAC solders have their own limitations. He spoke about Innolot alloy (Sn-Ag-Cu-Bi-Sb-Ni) having good creep resistance, and some new soft solder materials, such as HT1 with a different alloy composition which is better on ceramics and will withstand temperatures up to 170°C. There are bismuth based alloys, and zinc based alloys, but they, too, have weak points (wetting, and ductility), so the development of TLP methodologies is vital; they use a melting interlayer which diffuses into the adjacent materials, causing isothermal solidification. The principle of TLP soldering is the creation of a composite solder paste, with embedded metal powder to increase the reaction surface area. But there are reliability issues due to stiffness, which can cause delamination. Analysis of the copper-tin material shows that the Youngs modulus drops when heated, but goes up again once cooled. The elasticity is insufficient, so working with IMC interlinking with various particle sizes, they have shown that the stress-strain curve of the IMC is much better than SAC, as is creep strain, and the maximum die stress for pure IMC is two to three times higher than SAC. The delamination risk of IMC against SAC is much higher but a sloped edge design of die metallisation can significantly reduce brittle delamination risk.
Silver sintering is a technique that is suitable for planar applications only, so good for die attach. Silver sintering has low shear deformation, and provides a more rigid multi-material assembly for power electronics. Higher joint stiffness makes them prone to brittle failure, but the characteristic of low cycle fatigue solder failures become less likely.
The third paper was given by Professor Josef Šanders from Brno University of Technology who heads up their Department of Microelectronics. He expounded on the benefits of modularity, which saves PCB surface area, makes for easier product diagnostic, maintenance repair and disposal, and it is possible to route printed tracks under assembly modules saving the need for a multilayer board.
Examples of modules produced at Tesla, in the Czech Republic, were shown, both chip level, either standard or 3D and PCB level construction, also standard or 3D. Connection to a PCB is done with lead-free solders, isotropic and anisotropic electrically conductive adhesive, and solders balls, amongst others. Multichip modules offering a level between chip and board, and consist of an interconnected substrate, onto which are mounted one or two semiconductor devices, active or passive. Substrates can be ceramic, silicon, a co-fired ceramic substrate, with screen-printed thick film or plated thin film.
Stacked silicon chip production techniques were illustrated; the Harris technique; the Motorola technology, which is BGA based; the Tessera one is based on a specially designed folding substrate used for ASIC and memory chips. There is a 3D system for integrated power electronic modules, and Honeywell use a stacked multichip system, and AT&S use a stacked MCM/3D technology called "Ultra Dense"; Grumman Aerospace has connection through stacking alumina substrates with connect of the vertical faces of the stacked dies. GE in the USA has planer top and bottom surfaces with their HDI MCM process which can be interconnected.
Stacked board assembly – Thomson-CSF have a 3D process for memory modules, with connection on the edge. Solder ball connection can be done on the component side, and how to repair such assemblies was described. Thermo-mechanical reliability was covered; here stress can be caused by temperature, and where the CTEs of the materials varied. Professor Sander described the characteristics of failures in solder joints caused by thermo mechanical loading, and how failures with modules can be in simple or daisy chain connection.
Professor Robert Bogdanowicz heads up the Faculty of Electronics at Gdansk University of Technology, where he teaches materials sciences. He came to explain hybrid boron doped diamond structures for chemical and optical sensing.
Diamond MEMS are used in sensing, there are diamond SGFETS, diamond microelectrodes, diamond-like carbon coated optical fibre sensors, and bio-hybrid systems for solar energy harvesting. Robert works mostly with diamonds, which have better parameters than almost all substrates; diamonds will need doping to provide conductivity, but there is no really good way of doing this. High levels of boron are needed to provide conductivity, which has a good interface with diamond. Boron-doped diamond doping control is by means of Raman spectroscopy, which shows a better morphology of surface with boron-doping applied by plasma application of hydrogenated films.
Diamond films are robust and inert, have high thermal conductivity and a high refractive index, so make excellent optical fibre sensors. Robert went on to explain how ultrasonics was used in seeding diamond grains, down to 5 nm using solvent (DMSO), and 50 nm with water, either at 36 W or 72 W.
He touched upon biosensing microarrays. Here, diamond on glass was illustrated, and as for the future? How about a 4″ wafer coated with diamonds. There are pluses and minuses, of course, you have to weigh biocompatibility, against high cost and a wide range transmittance against complications with integration. Diamonds may be a girls best friend, but the relationship with microelectronics need further nurturing.
For further information, please contact: mailto:r.bogdanovicz@eti.pg.gda.pl
Mirjana Videnović-Mišić is the Assistant Professor in the Department of Electronics at the Faculty of Technical Sciences, University of Novi Sad, Republic of Serbia.
She introduced us to the Senseiver Project, which is on low cost and energy efficient LTCC sensors and IR/ultra-wide band (UWB) transceiver solutions for a sustainable and healthy environment.
There are seven partners in this project, in Portugal (INESC Porto), Austria (Technical University of Vienna), Serbia (University of Novi Sad, North Point), Romania (Technical University Iasi), Poland (ITE Krakow), and Germany (TES, Stuttgart). This is a €3 million project which started two years ago, and they have two more years to run. There are nine work packages, and at Novi Sad they have three researchers doing their PhDs in the project, 19 in total within the whole network.
The project concept is to develop a system through training and research which uses developed cost-effective LTCC sensors and the IR/UWB transceivers compatible with these sensors, in order to monitor air, soil and water quality. The sensors currently being developed are gas, pH and fluid sensors, based on either chemical or electrical principle. This is all taking place in Krakow, Vienna, and Novi Sad. Sensor fabrication using metal oxides continues, with gold and silver resinate paste being tested for fluidic sensors. As for the communication part of the environment monitoring system, several circuits have been designed: UWB LNA operating at 3-11 GHz, digitally controlled attenuator, power detector and filter with automatic process compensation in Novi Sad, Porto and Stuttgart.
The main goals of the project are to improve career prospects of the involved PhD students, to contribute to the structuring of the initial research training at the European level, to spread skills and knowledge in the field of innovative sensors, materials, transceivers and data acquisition systems, and to improve collaboration between the public-private sector.
For further information, please contact: mailto:mirjam@uns.ac.rs
In the afternoon there were two poster sessions. Here the delegates were given the opportunity of being able to study no less than 65 poster displays covering a whole range of activity in research in the microelectronic and nanoelectronics fields. Standing by each poster were mostly two people from the project concerned who were able to talk to the delegates about their work, and its application. This started at 2.00 p.m., and when it was supposed to close at 5.30 p.m., there were still a great number of people in discussion around the poster displays; this is a most effective means of disseminating knowledge and sharing experiences, it makes networking less abstract and more realistic, and the organising committee should be congratulated on this concept.
Tuesday 24 September 2013
Dr Goran Radosavljević from the Technical University of Novi Sad, Serbia was the first speaker on Day 2 of the conference, and spoke on the work they are doing on sensor design and fabrication, for medical and automotive applications. They started on passive components, and their current research hinges around conductors and inductors. Inductors are needed for low-noise amplifiers, voltage control oscillators, power amplifiers and chokes, EMI suppressors, and NMR. Inductors, he stressed, should have a good quality factor, inductance, self-resonance frequency and an occupied chip size. They think that LTCC technology helps as it offers good control of dielectric thickness, tapes of different materials, it is good for mechanical structuring, and a complex shape of substrate is possible, with an unlimited number of signal layers. It permits double sided substrates, buried passives, and has a high resistance against ambient working temperatures, as well as a low CTE.
They use the standard LTCC process with laser micromachining, fine line printing of conductive pastes and via filling, lamination, firing and dicing to single elements. They also use standard high frequency measurement methods, and they have much improved the performance by changing the printing surface and changing the air gap between the inductor and backside metallisation gave dramatic improvement in performance. 3D LTCC inductors with air cores have a self-resonance frequency above 800 MHz, a conductor width of 300 μm, and an inductance of 100 nH. They reduced the parasitic capacitance by adjusting their printing techniques, coils were attached to an FR4 board with SMA connector using 100 μm copper wire, and connected to a network analyser, and they found SRF of 2.84. Ferrite LTCC were also produced, they measured the influence of sintering temperature on the permeability, and found that silver was better than platinum. Co-firing takes place at 818°C. The design of LTCC transformers was illustrated, dielectric and ferrite, and the values were almost the same, and they proved that one can embed within the material.
Professor Goran Stojanović is also from the Technical University of Novi Sad and looked at new trends in flexible electronics. In Serbia, IT is well-developed, but electronics less so. Professors get paid according to the number of students they teach, and whilst he had 70 five years ago, it is now down to 23, they have all gone to write software!
They have a project running under FP7 on flexible electronics and have been funded €1 million to buy equipment. He gave some examples on how flexible electronics can be employed, such as in food packaging where sensors are embedded to act as freshness indicators, by colour changes on the label. A flexible scanner was another application, which showed how the problem to scan non-planar matter was resolved. They also produce RFID tags for wine bottles. Solar cells are flexible, too.
They have a Dimatix printer for printing onto foils, paper, with curing at room temperature and they have produced antennae, sensors, resonators. He showed a very good film clip all about the project entitled "Apostille" in the field of organic nanotechnology. Both active and passive components are now all produced in Novi Sad, and they are synthesising inks for ink-jet printing. They are in their third and final year, and we were shown some of the results of all their efforts, such as "Active Shelf" in which products have a built-in shelf-life sensor; they have produced both inductive and capacitive sensors; sensors for liquids, movement sensors, memristors, tag and find sensors, as well as humidity sensors, all of which was demonstrated at the German printed electronics show LOPE-C.
Dr Marco Luniak from the Technical University in Dresden had polymer thick film (PTF) technology as his topic, and the materials and their applications.
What is PTF technology? It is used to manufacture low-cost hybrid circuits, by means of an additive layer applied by screen printing; it is a low temperature process, and can be applied to a wide range of substrates. There is potential for multilayer construction and the integration of passive components. There are standard pastes used for conductors, isolators and resistors, and special pastes for solar cells, batteries sensors, etc.
A comparison was made between CERMET technology and PTF screen printing with the latter being better for "soft" substrates, such as paper, foil, film, and the former for "hard substrates" such as ceramics, glass, etc. Pastes can contain solder, copper, carbon, gold and platinum. Conductivity depends on the particle concentration and size and shape. Flakes have bigger contact areas, and can be used for simple circuits, multi-layer circuits, antenna for RFID, electronic games, heaters, tickets, medical electrodes, and the grid of solar cells. Pastes can be used for isolating, and as resistor pastes as well as for electro-luminescent layers, and you can form small batteries by additive technology.
Using silver nano-paste, he described how they formed a sensor on polyimide film, then curing for 200°C for 60 minutes, after which a polyimide precursor spin-coating for the sensor shows good sensitivity and repeatable results. The post-cure effect on silver nano-paste was illustrated, such as 200°C curing then 5 hours at 320°C, with no further effect. The acrylic binder seems to have an effect here. Silver nano pastes can be soldered, and to improve wetting, plasma treatment is to be tested.
Dr Piotr Majchrzak from the University of Koszalin spoke about a model of the integral thermal conductivity of granular structures. Conductivity can be affected in two ways, by the effect of heat over time or the effect of flux over time. The integrated thermal conductivity of granular structures is where the glue which holds the grains together has bad thermal conductivity but the grains have good thermal conductivity. The grains are 73 per cent of the volume of the structure. The depth of the thermal wave diffusion had been measured, it is better at low frequency, shown by 2D modelling of heat propagation. Using samples of 50/50 grain and adhesive, they carried out a series of tests, which showed that, in a deeply technical paper, poor thermal conductivity of the adhesive reduces the thermal conductivity of the grain.
From the Gydinia Maritime University Department of Marine Electronics came Dr Krystof Górecki to tell the conference about the measurement of thermal resistance of power LEDs. Some 20-30 per cent of electrical energy is used up on lighting, which explains the switch to power LEDs which is being made, as one can obtain high values of luminous efficiency with considerable electrical energy saving.
LEDs have many good points: they can have a spectrum of emitted light similar to the solar spectrum; there is an easy selection of the colour temperature of emitted light; there is high resistant to mechanical shock, combined with high watt/hour efficiency and a long life time.
There is, however, an influence of temperature on the characteristics of LEDs, and it has been found that a decrease of LED temperature by 20°C gives a six-fold increase in lifetime. The cooling of LEDs is therefore important, but as there are no ideal cooling solutions, he has done some work on the influence of self-heating of LEDs, measuring the internal device temperature using the Stephen-Boltzmann equation. In a very detailed presentation he explained how he had obtained the thermal resistance figures, and how the classical measurement of the diode for power of emitted light is adrift by about 15 per cent. LED cooling would make an interesting follow-on paper.
Wednesday 25 September 2013
“Inorganic oxides for transparent electronics: past, present and future prospects was the title of the first paper of the day, given by Professor Jaroslaw Domaradski of the Wroclaw University of Technology Faculty of Microsystem Electronics and Photonics.
Transparent electronics (TE) is in effect a merger of electronics and photonics, which relies upon the union of two opposite properties – conductivity and radiation. High transparency relies upon visible photons with high electrical conduction which can flow with virtually no loss. Here there is a compromise to be struck, and this is where amorphous metal oxides come into play. Oxides are abundant, compatible with the environment, have high heat stability, can be deposited thinly over large areas, and they are low in cost. Typical transparent oxides can be traced back to 1907, but indium oxide (In203-x) was about the best for some time. Later work was on indium tin oxide (ITO) thin film and cadmium, too, then came ZnO, and ZnO: Al and now along comes graphene. The main application area is in displays. But it is now moving into the area of touch panels, photovoltaics, transparent electrodes for smart windows, and gas sensors.
ITO on glass gives 80 per cent transparency. Flurorine doped tin oxide (FTO) and alumium doped zinc oxide (AZO) are very much cheaper than ITO, and titanium dioxide is the cheapest of the lot, but it is not known as a conductor. It has a large dielectric constant, but has an average transparency of some 80 per cent. So, how to make this insulating material conductive? By changing the dopant (TiO2:Nb), and with extra annealing at 300°C.
Materials for TE are transparent conducting oxide (TCO), with a resistivity of less than 10−4 Ω/cm, and transparent oxide semiconductor (TSO). TE can be traced back to 1997, and now TCOs are used in transparent diodes, solar cells, transistors, UV emitters and UV sensors. In Wroclaw they have produced over 100 scientific works on TiO2, which includes modification of the electrical properties to cover a deposition process, and material composition. This includes modification with palladium as a dopant, but whilst this decreases resistivity, it also decreases the level of transparency. By including other metals, including vanadium, this problem was resolved.
The impact of transparency on electronics was discussed, and it seems that within five years we will have transparent CMOS, solar cells and wall lighting. The selection criteria for materials includes transparency, resistivity (TCO or TOS see above), a figure of merit, and others including thermal expansion, mechanical properties, deposition technology, availability and cost.
Oxide semiconductors under development include titanium dioxide, carbon nanotubes and graphene.
Professor Piotr Slobodzian is from the same stable; he is involved with chip LTCC antennae in Wroclaw and so was in a good position to tell us about their benefits and their challenges. Chip antennae and conventional antennae vary in cost and ease of application to an enormous degree, but performance is sadly not the same. Chip antennae require PCB customisation, but given that they are so small (0.75 mm2) their application is undoubted. This includes use in VHF, UHF, microwave and millimetre wave areas, and here LTCC technology has some advantages – effective miniaturisation, 3D structuring, excellent RF and microwave performance, housing capability and SMD assembly compatibility.
Chip antenna consist of wire or strip embedded in a ceramic material, in an eight-layer structure usually, and measuring some 7.5×2.0 1.2 mm typically. For ISM 2.4 GHz (Bluetooth) applications, the strips are thicker, and printed on a ceramic structure; for ISM 2.4-5.2 GHz, again the strips are printed on a ceramic structure, but this would be a 19-layer structures (78 μm/layer). Chip antennae for GPS are helical with circular polarisation, eight to ten layers, densely packed turns; one for the Galileo system is a patch antenna, again multilayer, 60×60×5 mm, with ground plane and 90° ring hybrid in the substrate. UWB antennae are small with a single layer substrate, microwave antennae work at higher frequency and operate above 10 GHz, consist of a two stacked patches with an air cavity (4×6 mm) operating between 25 and 32 GHz. Millimetre wave antenna operate in the 60 GHz range, are eight-layer structures (96.5 μm/layer) and measure 2.0×2.0×0.7 mm.
Challenges for LTCC antennae include miniaturisation, layer count, interconnects, but antenna are thinner than PCBs, have better dielectric constants, but LTCC will be higher in cost than a PCB, and there are more manufacturers of circuit boards than there are of LTCC antennae.
LTCC is the undeniable leader in the high frequency world, but microwave and PCB antenna are strong competitors in the field of chip antenna.
The next speaker was Professor Katazyna Zakrzewska from the AGH University of Science and Technology Faculty of Computer Science, Electronics and Telecommunications in Krakow. Within her jurisdiction there are 2,000 students and 34 professors, operating in new facilities. The topic of her paper was functional nano materials for electronic applications. Here, microstructure, form and composition make up the three composites for applications, and her specialisation is in metal oxides, for self-sealing sensors, for example. TiO2, SnO2 and ZnO come in different forms – powder, ceramics and thin films, all of which can be functionalised by light.
The breakthrough came with the invention of nanomaterials. In 2001 Zhong Lin Wang introduced nano belts, but it was left to European academics to take it stage further into nanomaterials, nano tubes, nanowires, and the advantages are that the surface to volume ratio increases, and they are studying anatase, rutile and non-stoichiometry for undoped TiO2, and surface and bulk incorporation of metals (Cr, Sn, Ag and Au) and nitrogen doped TiO2.
Reactive magnetron sputtering is one of their technologies working in the laboratory, and they are able to complete all their investigations with the right equipment, which makes results meaningful. Gas sensors being one result, a metal oxide semiconductor (MOS) with detection by oxygen absorbtion is another, and also the detection of hydrogen. Sensors are "electronic noses" and can be traced back to 1987, with the first commercial products coming to market in 1993.
For gas sensors, the application of TiO2 was in both rutile, working at very high temperatures (800°C), and then, because such high temperatures were not suitable, anatase was found to work just as well, chromium doping and decreasing grain size acted to decrease the operating temperature, the lower the better. One of her students has built an "electronic nose" using nanomaterials, and this works extremely well as a gas sensor.
Hydrogen reactors form another part of her work; here they are splitting hydrogen atoms to provide electricity via photo anodes. Photoanodes have to have high stability and resistivity to corrosion and photo-corrosion, as well as low cost and availability. Solar energy conversion still waiting for the breakthrough, however.
Dr Piotr Dumania from the Institute of Electron Technology in Warsaw was the final speaker, and as their Manager for International Cooperation was well-placed to talk about their smart framework for SMEs focused on modern industrial technologies. Buying technologies from the Western world really does not work; what is needed is to be the leader in technologies, and so far the track record in Poland for research/industry co-operation has not been, shall we say, very rosy. But there is some work going on, one project is NANOHEAT, and PROFACTOR in which Heraeus and Steyr are some of the partners, and the Smart Frame is now in existence between partners in Hungary, the Czech Republic, Germany, Poland and Austria, with research results spinning-off into commercial reality. They are focussing on modern technologies, sensors, materials, processes and a combination and research institutes and companies.
The new President of IMAPS Poland, Professor Malgorzata Jukubowska closed the conference, and thanked all the presenters for their invaluable contributions, and paid an especial thanks to the organisers, the Institute of Electron Technology, for an excellent programme and generous hospitality.
The 38th IMAPS Poland will be held on 21-24 September 2014 in Arłamów, near Rzeszow, and will be organised by the Rzeszow University of Technology under the Chairman Professor Jerzy Potencki.
In 2017 IMAPS Poland will be organising the next European Microelectronics Packaging Convention in Warsaw, dates yet to be advised.
John Ling
Associate Editor