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» Miniaturized arms for three-dimensional thick-film thermoelectric microgenerator

When two different metals are connected by their ends and there is a temperature difference between the junctions the electric current flows into the circuit. This kind of structure is called thermocouple and it can be used to electrical power generation. Output voltage and power can be multiplied if a number of thermocouples are electrically connected in series. At the same time all “cold" junction should have approximately the same temperature - lower than the temperature of "hot" joints (thermocouples should be thermally connected in parallel). Such a structure is called thermopile. Thermopiles produce “green" energy and can be used as an alternative power sources for microsystems and low-power electronic micro-circuits [1, 2]. Their dimensions should be small - comparable with dimensions of powered systems. It is the reason why miniaturization of such generators is important. Fabrication process Two ways of fabrication of thermopiles are presented. First one bases on precise screen-printing only. Ag and Ni or PdAg pastes were used. They were printed using AUREL VS1520 Fine Line Screen Stencil Printer. In the second method precise screen-printing and photoimageable inks technique were combined. Ag-based photosensitive paste was used to fabricate first thermocouples’ arms. Second arms were precisely screen printed between Ag paths. As a substrate DP951 unfired ceramic foil was used in both cases. LTCC (Low Temperature Cofired Ceramic) technique allows fabrication of microelectronic multilayer structures [3]. It can be exploited to construct stack of thermopiles - a number of thermopiles fabricated on single foils are connected in one, multilayer stack (“sandwich" structure). In the result the output parameters (like generated voltage or electrical power) are multiplied. DuPont ceramic was chosen because of its good compatibility with used thick-film pastes. Precise printing - the "A" type structure[...] więcej»
w zeszycie ELEKTRONIKA - KONSTRUKCJE, TECHNOLOGIE, ZASTOSOWANIA 2012/4

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» Modelowanie i analiza grubowarstwowych mikrogeneratorów termoelektrycznych

PIOTR MARKOWSKI

ANDRZEJ DZIEDZIC

Współczesna mikroelektronika potrzebuje nowych źródeł energii elektrycznej do zasilania mikroukładów. Wśród różnych rozwiązań pojawiają się również elementy termoelektryczne, wykorzystujące do wytwarzania energii elektrycznej zjawisko Seebecka. Jeżeli dwa różne materiały A i B (ramiona termopary) zostaną złączone końcówkami i utworzą taki zamknięty obwód elektryczny, że powstałe złącza będą [...] więcej»
w zeszycie ELEKTRONIKA - KONSTRUKCJE, TECHNOLOGIE, ZASTOSOWANIA 2007/3

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» Properties of thick-film photoimageable inks for LTCC substrates

PIOTR MARKOWSKI

MAŁGORZATA JAKUBOWSKA

Miniaturization of electronic circuits is strongly associated with miniaturization of conductive paths and pads. It also refers to thick-film technology. Fabrication of details narrower than 150 μm by using of standard screen-printing is very difficult task. There are few more precise techniques - for example photoimageable inks method [1, 2]. It enables to create even several-micrometers wide paths. The inks prepared at Institute of Electronic Materials Technology (ITME) were tested. The compatibility between such inks and LTCC (Low Temperature Cofired Ceramics) substrates was especially an object of interest. The investigations were performed at Wrocław University of Technology, Warsaw University of Technology or Dresden Technical University. The path’s resolution, inks shrinkage as well as chosen electrical and mechanical properties (electrical resistivity, solderability, adhesion, shear resistance) were determined. Fabrication The photoimageable films were made using standard screen-printing combined with photolithography [3]. A special ink was screen- printed onto the substrate (Fig. 1a). The investigated pastes had good UV-resistance and using of UV-filters was unnecessary [4]. However, they need large amount of radiation during exposing. A proper photomask caused that only selected areas of ink were polymerized by UV light (Fig. 1b). The Hibridas Exposure Unit MA-4K were used. Remaining areas stayed unpolymerized and it was possible to remove them in the next technological step - spraying with proper developing solution (Fig. 1c). The Hibridas Developer Unit SC-4K and ethanolamine solution were used. As a result pattern from the photomask was transferred onto the substrate. The last technological step was firing of achieved layer in t[...] więcej»
w zeszycie ELEKTRONIKA - KONSTRUKCJE, TECHNOLOGIE, ZASTOSOWANIA 2011/3

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» Influence of Selected Constructional and Technological Factors on Tolerance and Stability of Thin-Film Resistors Embedded in PCBs

WOJCIECH STĘPLEWSKI

In the study the OhmegaPly? material was selected to forming resistors. The commercial available material is produced by deposition the resistive layer (Ni-P) on copper foil and lamination onto FR4 material. Resistivity of Ni-P layer depends on thickness of this layer and can be in range from 10 Ω/□ to 250 Ω/□. In the investigation it was used material with sheet resistance of 25 Ω/□ (thickness - 0.4 μm) and 100 Ω/□ (thickness - 0.1 μm). Thin-film character of the resistor cause that it can be embedded inside of PCB without increasing its thickness. The other advantage is that embedded resistor is not assembled in the contrast to conventional element so the number of component solder joints will decrease and this can improve reliability of final product. However, the resistive layer is very thin and simultaneously it has very rough surface (Fig. 1). It can be the reason that the thin-film resistive layer is sensitive to mechanical factors (scratch, stress during lamination) and also on chemicals that are used in PCB manufacturing process. Influence of crucial constructional factors such as size, shape and resistors orientation as well as technological parameters of resistor forming process and PCB manufacturing process on the tolerance and stability of embedded resistor parameters was assessed. The experiments were carried out both in the laboratory and on technological line at Tele and Radio Research Institute. The Sequential Build Up technology was applied to manufacture PCBs with thin-film embedded resistors. The results revealed that some factors can accumulate or neutralize each other influence on the final value of resistance also in dependence on the existing manufacturing processes and production facilities. The knowledge on changes in resistors properties introduced by individual parameters of the design and technological processes is a crucial issue before intr[...] więcej»
w zeszycie ELEKTRONIKA - KONSTRUKCJE, TECHNOLOGIE, ZASTOSOWANIA 2011/3

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