Sebastian J. Tesarski

Properties of conductive microstructures containing nano sized silver particles

The properties of the structures made by ink-jet printing with the use of the ink containing nano silver sized particles are presented. After structures printing on substrate, to obtain good electrical conductivity, sintering process is necessary. It is shown, that thermal process influences strongly the resistance, and after the process the resistivity of printed structures can be only a little bit higher than the value of the bulk material. Also different electrical test proved similarity between printed and bulk silver. It was stated that the adding some polymer materials for mechanical parameters improving of printed materials up to 1.5% of total mass of the ink do not influence significantly electrical parameters of the printed layers.

An approach to measurement and evaluation of the thermal conductivity of the thermal adhesives in electronic packaging

In the following paper the measurement method of thermal conductivity is described. This method was especially designed for measuring the thermal conductivity of the thermal adhesives. The principal informations about heat transfer are given, and the experimental setup, mathematical model of experiment and its uncertainty with 95% of probability are shown. The thermal conductivity of polymer based material filled in 0.5% with carbon nanotubes is measured.

Assessment of thermo mechanical properties of crosslinked epoxy mesoscale approach — Preliminary results

Usage of polymers materials in microelectronics and especially in packing is nowadays common. Polymer materials are used for example in case of encapsulation, underfills for flip chip, moulding compound, electrically or thermally conductive adhesive, flexible electronics, materials for Printed Circuits Board (PCB), etc.

A multi-scale approach to the thermo-mechanical behaviour of silica-filled epoxies for electronic packaging

Delamination of mating interfaces can cause serious reliability problems in different application areas. The causes of delamination are multiple. In the case of leadframe-based chip packages, a critical interface is that between the leadframe and the moulding compound. Delamination can magnify stress levels at the interface and can lead to fatigue of interconnects.

Influence of meso–scale analysis parameters of cross–linked polymers on final simulation results

Molecular modeling is one of the fastest developing branch of material science. There are a couple of reasons of such a state: on one hand molecular modeling tools are nowadays quite easy to implement to selected problems and on the other hand experimental research and analysis might be impossible to made or too expensive in comparison to numerical modeling as an alternative. Anyway there is a question of accuracy but in some cases we are not so much interested in precise numbers but an estimation of a proper trend would be sufficient. Literature study shows that results achieved by application of advanced numerical modeling tools fulfills convergence criteria and fits quite well to experimental data. Recently some researchers concentrate on molecular mesoscale modeling of crosslink polymers. Preliminary study shows need for an investigation of dependency of simulation parameters (time length, time step, force field type, size of a bead ect.) for final results. It is a key for good estimation of Tg and CTE of polymers. Results of simulation help to optimize the performance of polymers materials in electronics technology Mesoscale results were compared with molecular modeling simulations. The results are promising.

Numerical approach to multiscale evaluation and analysis of Tg of crosslinked polymers

Molecular modeling is one of the fastest developing tools in material science. There are a couple of reasons of such a state: on one hand molecular modeling seems to be nowadays much more user friendly and on the other hand is much more efficient in comparison to research based on traditional experiments, which are quite expensive and long lasting. Though the basic problem of numerical analysis is accuracy, in certain cases we can agree with it as long as the predicted tendency or trends are assessed properly. Due to the current state of the art it is justified to formulate the assumption that that results of advanced numerical modeling fulfills expected convergence criteria and correlates well with the experimental data.

A multi-scale approach of the thermo-mechanical properties of silica-filled epoxies used in electronic packaging

Abstract Delamination of mating interfaces can cause serious reliability problems in different application areas. The causes of delamination are multiple. In the case of leadframe-based chip packages, a critical interface is that between the leadframe and the moulding compound. Delamination can magnify stress levels at the interface and can lead to fatigue of interconnects. The objective of this study is to evaluate the influence of different causes of delamination on degradation of the leadframe–compound interface by means of simulation, supported by targeted experiments. Up to now two models have been devised, which show good convergence. However the simulations are not yet compatible and need to be validated.

Analysis of an Influence of a Conversion Level on Simulation Results of the Crosslinked Polymers

In the modern world, there is a tendency to miniaturize electronic devices. To do so, new materials with dedicated physical properties are needed. It seems like that nowadays a vast number of materials used in microelectronics are polymers. One of the problems is there is a large variety of them and mixing them could change their physical properties significantly. On the other hand new products require shorter time-to-market. This induces a need for shortened research and development (R&D) processes. Experimental research is time and money consuming. Using Advanced Computer Techniques it is possible to shorten the R&D time, for example, by running parallel simulations. It is obvious that in a selected group of materials with the best properties, it is necessary to conduct experimental validation of them. As the computer simulation only gives a tendency or trend rather than exact numerous values, which nevertheless in most of the cases is sufficient for optimization procedures. One such numerical tool is molecular modeling, which provides a possibility of extracting properties of different materials in micro and nanoscale as e.g. polymers. Polymers are used especially as moulding compounds in electronic packaging. The knowledge on thermomechanical properties of moulding compounds is essential in order to provide reliability prediction of the microelectronic devices on satisfactory level. The above said research describes analysis of commonly used polymers as moulding compound in reference to their conversion level. Full conversion level is never achieved and thus such an analysis can give some insight into the so-called real life problem. Although the molecular simulation in nanoscale is more accurate, it needs significantly more CPU power, for this reason an alternative method was suggested, which introduces modeling in mesoscale.

Glass Transition Analysis of Cross-Linked Polymers: Numerical and Mesoscale Approach

Molecular modeling is one of the fastest developing tools in material science. There are a couple of reasons of such a state: on the one hand molecular modeling today seems to be much more user friendly, and on the other hand it is much more efficient in comparison to research based on traditional experiments, which are quite expensive and long lasting. Although the basic problem of numerical analysis is accuracy, in certain cases we can accept even high inaccuracy as long as the predicted tendency or trends is assessed properly. In recent years there has been a noticeable tendency and need for numerical material science using multiscale analysis especially in case of polymer materials. Thus, recently a number of researchers have concentrated on molecular mesoscale modeling of cross-link polymers. Cross-linked polymers seem to be very important in microelectronic and nanoelectronic packaging and assembly. One of the basic benefits of mesoscale analysis is the possibility of extending the time and length scale and reduce the usage of CPU power needed for analysis. In this paper we describe the preliminary research on cross-linked polymers and results of numerical modeling, which was done in Accelerys Material Studio and facilitated by its scripting capabilities through user defined subroutines. The developed subroutine allows one to differentiate statistically the process of polymer model creation and saves time needed for preparing the simulation. The main goal of the analysis was to estimate the glass transition temperature of the selected polymer through the density versus temperature dependence.

An analysis of VOC-free fluxes and lead-free solders application in a manual SMD soldering

The overview of electronic assembly publications shows that almost all authors concentrate on mass-scale (industrial) lead-free soldering. On the contrary there are almost no publications concerning possibility of manual soldering using lead-free solders and VOC-free fluxes. Manual soldering of SMD is widely used during PCB prototyping, especially at home or academic laboratories. European Union directive RoHS forbids to use in electrical and electronic equipment hazardous materials such as lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (Cr6+), PBBs (polybrominated biphenyls) and PBDEs (polybrominated diphenys ethers). The practice shows that in manual soldering SnPb solder and rosin is commonly used, damaging health of people who use it. The aim of this study is to check possibility of ldquodomestic userdquo of lead-free solders and VOC-free fluxes. The test will be held using different lead-free solders, VOC-free fluxes and various soldering conditions. SMD passive elements will be used for the tests due to its susceptibility for overheating (usage of lead-free solders enforces higher temperatures). The test will evaluate visual assessment of joint quality, analysis of PCB damage and degradation of passive elements parameters after manual soldering.