Konrad Kielbasinski

Noise properties of Pb/Cd-free thick film resistors

Low-frequency noise spectroscopy has been used to examine noise properties of Pb/Cd-free RuO2- and CaRuO3-based thick films screen printed on alumina substrates. Experiments were performed in the temperature range 77–300 K and the frequency range 0.5–5000 Hz with multiterminal devices. The measured noise has been recognized as resistance noise that consists of background 1/f noise and components generated by several thermally activated noise sources (TANSs) of different activation energies. The total noise has been composed of the contributions generated in the resistive layer and in the resistive/conductive layers interface. These noise sources are non-uniformly distributed in the resistor volume. Noise intensity of new-resistive layers has been described by the noise parameter Cbulk. Pb/Cd-free layers turned out to be noisier than their Pb-containing counterparts; however, the removal of Pb and Cd from resistive composition is hardly responsible for the increase in the noise. In the case of RuO2 layers noise increases most likely due to larger grain size of RuO2 powder used to prepare resistive pastes. Information on the quality of the resistive-to-conductive layers interface occurred to be stored in the values of noise parameter Cint. Pb/Cd-free RuO2-based resistive pastes form well-behaved interfaces with various Ag-based conductive pastes. In contrast, CaRuO3-based paste forms bad contacts with AgPd terminations because the density of TANSs increases in the interface area.

Graphene platelets as morphology tailoring additive in carbon nanotube transparent and flexible electrodes for heating applications

Flexible and transparent electrodes were fabricated with spray coating technique from paints based on multiwalled carbon nanotubes with the addition of graphene platelets. The work presents the influence of graphene platelets on the paints rheology and layers morphology, which has a strong connection to the electrooptical parameters of the electrodes. The paints rheology affects the atomization during spray coating and later the leveling of the coating on the substrate. Both technological aspects shape the morphology of the electrode and the distribution of nanoparticles in the coating. All these factors influence the sheet resistance and roughness, which is linked to the optical transmission and absorbance. In our research the electrode was applied as a transparent and elastic heating element with 68% optical transmission at 550 nm wavelength and 8.4 kΩ/• sheet resistance. The elastic heating element was tested with a thermal camera at the 3 diverse supply voltages -20, 30, and 60 VDC. The test successfully confirmed and supported our proposed uses of elaborated electrodes.

Inkjet printed microwave circuits on flexible substrates using heterophase graphene based inks

Purpose – The purpose of this paper is to present the result of research on a new fabrication technology of printed circuits board and electronics modules. The new method is based on inkjet printing technique on flexible substrates using new generations of heterophase inks. New fabrications method was used to print microwave waveguides and signal splitters as new technology demonstrators. Design/methodology/approach – A fully Inkjet printed filter was printed on a flexible, transparent Kapton foil using heterophase inks developed in Instytut Technologii Materialow Elektronicznych (ITME) for the purpose of this research based on graphene and silver nanoparticles. Findings – A microwave module was printed using two types of Inkjet printers – PixDro LP50 with KonicaMinolta 512 printhead – and developed in an Instytut Tele- i Radiotechniczny (ITR) laboratory printer using MicroDrop a 100-μm glass nozzle printhead. Fully printed microwave circuits were evaluated by their print quality and electrical properties...

New technology of silvering aluminium busbar joints with the use of printable paste containing nano-size Ag particles

Aluminium silvering is widely used for creating high current joints between two busbar connectors to transfer electrical power. Silver properties improved joints quality and long term conductivity. The most commonly used technique is the laborious electroplating, which produces a lot of toxic sludges. As an alternative, the authors elaborated new technology of silvering busbar connectors. The new method of aluminium silvering consists of well-known screen printing process of properly prepared paste with silver nanoparticles. Use of nanoparticles gives an opportunity to print and sinter the silver layer on aluminium base. Another advantage of this technology is that the layer can be deposited and sintered in outdoor conditions, using acetylene torch or hot air gun. In this paper, several technological parameters, as well as obtained results, are discussed. Different paste compositions, grain size of silver nanoparticles and sintering method were measured. The adhesion between silver layer and aluminium base was measured. The contact resistivity of joints between silvered electrodes were tested and compared to electroplated joints or pure aluminium contacts. The measurements results are shown and discuss. The screen printed layer was less dependent on joint pressure than those from pure or electroplated aluminium.

Carbon nanomaterials dedicated to heating systems

Purpose – The paper aims to present the research results related to transparent heating elements made from carbon nanomaterials. Heating elements were fabricated only with cost-effective techniques with the aim to be easily implemented in large area applications. Presented materials and methods are an interesting alternative to vacuum deposition of transparent resistive layers and etching of low-resistive patterns. Fabricated heating elements were designed to be used as de-icing structures in roof-top windows. Design/methodology/approach – The paper presents the research results related to transparent heating elements made from carbon nanomaterials. Heating elements were fabricated only with cost-effective techniques with the aim to be easily implemented in large area applications. Presented materials and methods are an interesting alternative to vacuum deposition of transparent resistive layers and etching of low-resistive patterns. Fabricated heating elements were designed to be used as de-icing structu...

Efficient Inkjet Printing of Graphene-Based Elements: Influence of Dispersing Agent on Ink Viscosity

Inkjet printing is an excellent printing technique and an attractive alternative to conventional technologies for the production of flexible, low-cost microelectronic devices. Among many parameters that have a significant impact on the correctness of the printing process, the most important is ink viscosity. During the printing process, the ink is influenced by different strains and forces, which significantly change the printing results. The authors present a model and calculations referring to the shear rate of ink in an inkjet printer nozzle. Supporting experiments were conducted, proving the model assumptions for two different ink formulations: initial ink and with the addition of a dispersing agent. The most important findings are summarized by the process window regime of parameters, which is much broader for the inks with a dispersing agent. Such inks exhibit preferable viscosity, better print-ability, and higher path quality with lower resistivity. Presented results allow stating that proper, stable graphene inks adjusted for inkjet technique rheology must contain modifiers such as dispersing agents to be effectively printed.

Thermal properties of modified carbon films

Purpose – The purpose of this paper is to present thermal properties of palladium-carbon films prepared by physical vapour deposition (PVD)/chemical vapour deposition (CVD) methods. Design/methodology/approach – Thin palladium-carbon films were prepared at Tele- and Radioresearch Institute. Test structures containing palladium-carbon films and titanium electrodes were made. Temperature-resistance characteristics were measured. Findings – The results show strong temperature dependence of modified carbon film resistance. The dependence is stable, and so modified carbon films can be applied for various electronic applications. Originality/value – The paper presents thermal properties of thin palladium-carbon prepared by original PVD/CVD method at Tele- and Radioresearch Institute.

Nanosilver sintered joints on elastic substrates

In Institute of Electronic Materials Technology in Warsaw novel silver pastes were elaborated, that contains silver nanoparticles and are able to sinter at temperatures below 300°C resulting in low resistance layers (2 mQ/□). No other thick film paste is capable of achieving this resistance in such a low curing temperature. Low exposure to heat allows depositing and curing on wide variety of elastic substrates including elastic Kapton foil or paper. In present work the authors proved that this paste is suitable for low temperature joining technique (LTJT) which is an alternative to soldering and adhesive joining. The temperature 300°C was suitable to obtain joints, which can withstand over 30000 cycles in bend test.

Aluminium silvering of high current connectors using printing techniques and nanopowders

Aluminium busbar connectors provide high current connections between metal connectors and are widely used in electrical power industry. They are formed by clamping two or more plates of flat aluminium with the use of bolts and nuts. Plain aluminium tends to form oxide, which is known of its very high resistivity To avoid that effect, a surface of aluminium can be electroplated with silver. The main drawback of this method is a toxic waste production. Another problem is the possibility to repair it in outdoor conditions Due to high surface energy of nano-particles, sintering of layers occurs in temperatures much below silver melting point (961°C), and which is more important below melting point of aluminium (660°C). Pastes containing nanosize silver powders were prepared. They were screen printed on etched aluminium plates and cured in several temperatures varying from 300 to 500°C. The plates were pressed towards, forming contact joint that simulates the bolted connection. The contact resistivity versus pressure was tested.

Low temperature joining technique (LTJT) as an alternative to lead-free soldering for die-attach applications

A group of silver, thick-film, screen printable and lead-free pastes varying in composition, with different grain size distribution of used Ag powders, has been elaborated and tested. They are designed to be sintered between 300 and 400°C. The technology of preparing these pastes is discussed. The application of the elaborated materials in die-attachment is demonstrated. Shear strengths ∼20 N/mm2 were achieved.