Electrical Sintering of Silver Nanoparticle Ink Studied by In-Situ TEM Probing

Metallic nanoparticle inks are used for printed electronics, but to reach acceptable conductivity the structures need to be sintered, usually using a furnace. Recently, sintering by direct resistive heating has been demonstrated. For a microscopic understanding of this Joule heating sintering method, we studied the entire process in real time inside a transmission electron microscope equipped with a movable electrical probe. We found an onset of Joule heating induced sintering and coalescence of nanoparticles at power levels of 0.1–10 mW/m3. In addition, a carbonization of the organic shells that stabilize the nanoparticles were found, with a conductivity of 4 105 Sm−1

Graphene -- Based Nanocomposites as Highly Efficient Thermal Interface Materials

We found that an optimized mixture of graphene and multilayer graphene - produced by the high-yield inexpensive liquid-phase-exfoliation technique - can lead to an extremely strong enhancement of the cross-plane thermal conductivity K of the composite. The "laser flash" measurements revealed a record-high enhancement of K by 2300 % in the graphene-based polymer at the filler loading fraction f =10 vol. %. It was determined that a relatively high concentration of single-layer and bilayer graphene flakes (~10-15%) present simultaneously with thicker multilayers of large lateral size (~ 1 micrometer) were essential for the observed unusual K enhancement. The thermal conductivity of a commercial thermal grease was increased from an initial value of ~5.8 W/mK to K=14 W/mK at the small loading f=2%, which preserved all mechanical properties of the hybrid. Our modeling results suggest that graphene - multilayer graphene nanocomposite used as the thermal interface material outperforms those with carbon nanotubes or metal nanoparticles owing to graphene's aspect ratio and lower Kapitza resistance at the graphene - matrix interface.Comment: 4 figure

Molecular modeling as a novel and promising numerical tool in microelectronics packaging

Numerical modeling is a widespread tool in microelectronics, which is used generally for support of the prototyping stage. One of the novel numerical tools that are currently emerging is technique based on molecular modeling. Molecular modeling is well known and utilized method in chemistry, biology, medicine, biotechnology, pharmacy and physics. Scientists and researchers have been using molecular modeling to simulate reactions at the molecular levels for many years. Additionally molecular modeling is used in e.g. material modeling. Scientists are interested in material modeling and simulations because of complexity of novel materials. Many novel materials include fillers or particular structure that ensures its mechanical or electrical properties. Molecular modeling and simulations enables to control structure and properties of the materials in the nano-scale. By conducting molecular modeling researchers can obtain proposals of materials that vary in properties by low costs. Molecular modeling also ensures control of processes and prediction possibility. The current paper is focused on possible areas of application of molecular modeling in microelectronic packaging. The paper describes the current state-of-the-art and benefits of molecular modeling to selected problems common in microelectronic packages. Our goal in the future is to apply molecular modeling, as a support tool, to resolve problems that occur in microelectronic packaging as e.g. problem of surface phenomena, thin films, viscoelasticity or mechanical and thermal properties of novel materials and compounds

Analiza procesu formowania mikrootworów nieprzelotowych w wielowarstwowych płytkach obwodów drukowanych

The paper is focused on application of experiment design technique, called Taguchi method, and application of multi-criteria analysis, in blind microvias forming process in multilayer Printed Circuit Boards (PCBs). In the paper the results of investigations of microvia laser drilling are presented. The use of multi-criteria analysis is a helpful tool which should lead to manufacture microvias with aspect ratio (relation of via deep to via diameter) higher than 1, and diameter of via in the range of 25 to 350 μm. Finally, it is possible to manufacture blind microvias with aspect ratio about 6.5.Artykuł jest poświecony zastosowaniu techniki planowania eksperymentu zwanej metodą Taguchi'ego oraz analizy wielokryterialnej w procesie formowania mikrootworów nieprzelotowych w wielowarstwowych płytkach obwodów drukowanych. W artykule zamieszczono wyniki doświadczeń w zakresie formowania mikrootworów techniką drążenia laserowego. Zastosowanie analizy wielokryterialnej jest pomocnym narzędziem pozwalającym na wytwarzanie mikrootworów, których współczynnik kształtu (stosunek głębokości otworu do jego średnicy) jest większy od 1, a średnica formowanych otworów zawiera się w przedziale od 25 do 350 μm. W rezultacie możliwe jest formowanie mikrootworów nieprzelotowych o współczynniku kształtu wynoszącym 6.5

Influence of nano silver filler content on properties of ink-jet printed structures for microelectronics

The influence of nano silver filler content on properties of ink-jet printed structures for microelectronics were investigated. Samples were prepared by using ink with different nano silver filler content: 44%, 41% and 38%. The electrical measurements were performed during and after heating process. It was shown, that filler content does not have a strong influence on sintering time, but it changes the final resistivity of printed and sintered structures. The enhancement of sintering process by UV exposure was also investigated. Preliminary results are promising and the further study will be conducted

Experimental method for low-temperature sintering of nano-Ag inks using electrical excitation

Conductive inks market for printable electronic grows rapidly last years. The main disadvantage of using inks filled with nano-Ag particles is sintering process, which often requires relatively high temperatures (over 180°C). This forces the use of expensive, high temperature substrates, for example polyimide foils. In some applications it is unacceptable to subject substrate to high temperature, which prevents or hinders the use of common silver inks. An experimental method for low-temperature sintering was investigated and presented in this paper. Electric field was applied to the sample and current flow induced to initiate the sintering process instead of commonly used high-temperature heating or light pulses