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The real improvement occurred in version I.4 when the firingtemperature of the electrolyte was increased up to 1600°C. Theopen circuit voltage and short circuit current reached 990 mVand 2600 mA, respectively. SEM photo of the electrolyte fired at1600°C proves that the layer is dense and well sintered (Fig. 6).Figures 8 shows the plots of the fuel cell output voltage andoutput power versus output current for version I.4 of the cell operatingat 800°C. Active area of the operating fuel cell was 4 cm 2 .This sample provided power density greater than 400 mW/cm 2 .In the proposed SOFC design, technological processes relatedto the performance of the tight electrolyte layer seems to playthe decisive role in the cell operation. The firing temperature ofelectrolyte equal to 1600°C was established as optimal for thisdesign.ConclusionsCeramic model of a planar high temperature solid oxide fuel cellSOFC different from the reported in the literature and convenientfor assembly into stacks was performed.The proposed base anode structure with embedded fuel channelssimplifies construction of fuel cells.The advantage of this proposed structure of SOFC can be easilyexamined with a simple test fixture prior assembly into stack.Research on the electrolyte density and the cathode conductivityare crucial in order to improve the fuel cell model operation.The authors believe that further works on the proposed planarSOFC design will enable to build a compact, efficient batteryof fuel cells.This project has been supported in the years 2010–2012 by thegovernment funds for science. No. of project 18.120.946.References[1] SINGHAL S. and KENDALL K.: High Temperature Solid Oxide FuelCells: Fundamentals, Design and Applications, Elsevier 2003.[2] GASIK M.: Materials for fuel cells, RCR Press 2008.[3] ISHIHARA T., Perovskite Oxide for Solid Oxide Fuel Cells, Springer2009.[4] SUN Ch., HUI R., ROLLER J.: J Solid State Electrochem, 14 (2010),1125-1144.[5] LINDEROTH S.: Solid oxide cell R&D at Riso National Laboratoryandits transfer to technology, J Electroceram, 22 (2009) 61–66.[6] MALZBENDER J., STEINBRECH R., SINGHEISER L.: A review ofadvanced techniques for characterizing SOFC behaviour, Fuel Cells,6 (2009), 785–793.[7] YOON K., ZINK P., GOPALAN S., PAL U.: Polarization measurementson single-step co-fired solid oxide fuel cells (SOFCs), Journalof Power Sources 172 (2007) 39–49.Miniaturized arms for three-dimensional thick-filmthermoelectric microgenerator(Miniaturowe ramiona dla trówymiarowych grubowarstwowychmikrogeneratorów termoelektrycznych)dr inż. Piotr MarkowskiWrocław University of Technology, Faculty of Microsystem Electronics and PhotonicsWhen two different metals are connected by their ends and thereis a temperature difference between the junctions the electric currentflows into the circuit. This kind of structure is called thermocoupleand it can be used to electrical power generation. Outputvoltage and power can be multiplied if a number of thermocouplesare 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 shouldbe thermally connected in parallel). Such a structure is calledthermopile.Thermopiles produce “green” energy and can be used as analternative power sources for microsystems and low-power electronicmicro-circuits [1, 2]. Their dimensions should be small –comparable with dimensions of powered systems. It is the reasonwhy miniaturization of such generators is important.Fabrication processTwo ways of fabrication of thermopiles are presented. First onebases on precise screen-printing only. Ag and Ni or PdAg pasteswere used. They were printed using AUREL VS1520 Fine LineScreen Stencil Printer. In the second method precise screen-printingand photoimageable inks technique were combined. Ag-basedphotosensitive paste was used to fabricate first thermocouples’arms. Second arms were precisely screen printed betweenAg paths.As a substrate DP951 unfired ceramic foil was used in bothcases. LTCC (Low Temperature Cofired Ceramic) technique allowsfabrication of microelectronic multilayer structures [3]. It canbe exploited to construct stack of thermopiles – a number of thermopilesfabricated on single foils are connected in one, multilayer18stack (“sandwich” structure). In the result the output parameters(like generated voltage or electrical power) are multiplied. DuPontceramic was chosen because of its good compatibility with usedthick-film pastes.Precise printing – the „A” type structureThermocouples’ arms fabricated using that method had 200 μmin width. In the first step Ag-based arms were screen-printed (DP6145 paste). Patterns shown in Fig. 1a and 1b were fabricated.(a)(c)Fig. 1. Precise printed thermocouples: a, b) masks for screen-printing;c) achieved Ag/Ni junctions; d) Ag/Ni thermopile (25 thermocouples)on DP 951 tapeRys. 1. Termopary naniesione metodą sitodruku precyzyjnego:a, b) maski dla sitodruku; c) wykonane złącza Ag/Ni; d) termostosAg/Ni (25 termopar) na folii DP 951(b)(d)Elektronika 4/2012
They were used alternately when „sandwich” structure was assembled.Second arms were PdAg- (DP 6146 paste) or Ni-based(ESL 2554-N1 paste). They were precisely printed betweenAg arms. The same patterns were used. Owing to high-qualityof screen printer vision system high-accuracy of thermocouples’junctions were achieved – Fig. 1c. Onto the 25 × 30 mm 2 , 165 μmthick substrate 25 thermocouples (each 25 millimeters long) werefabricated (Fig. 1d). Distances between single thermocouple’sarms were 200 μm.Photoimageable inks – the „B” type structureIn this method two different techniques were used. The secondarms, PdAg or Ni-based, were precisely screen-printed– process described in point 2.1 (the same pastes). But beforeit, the first arms were fabricated using photoimageable inkstechnique. The process flow of photoimageable pattern formingis shown in Fig. 2.(a) (b) (c) (d)Fig. 3. Test paterns: a) pads – 60 μm; b) electrodes – 60 μm; c) circles– 60 μm; d) meander – 30 μmRys. 3. Wzory testowe: a) pady – 60 μm; b) elektrody – 60 μm; c) okręgi– 60 μm; d) meander – 30 μmScreen-printinglayersubstrate(a)UV lightphotomask(b)(a)(b)UV exposuredeveloper(c)(c)(d)DevelopingFiringFig. 2. The process flow of photoimageable inks technique: a) screen-printingof the pad; b) UV-exposure; c) developing; d) firing [4]Rys. 2. Proces wykonywania warstw fotodefiniowalnych: a) sitodrukpadu; b) naświetlanie UV; c) wywoływanie; d) wypalanie [4]Photosensitive ink was deposited onto the substrate in a screen-printingprocess (Fig. 2a). Then it was dried and exposed toUV radiation through a photomask with a proper pattern (Fig. 2b).UV light causes polymerization of the photosensitive ink. Notexposed areas are not polymerized and it is possible to removethem in the next technological step – spraying (as a developerethanolamine solution was used) – Fig. 2c. Ag-based paste preparedby Institute of Electronic Materials Technology (ITME, Warszawa)were used (marked Ag-71).Some compatibility tests between used photosensitive pasteand DP951 substrate were performed. The tests patterns like circles,squares, strait and broken lines were fabricated. The width ofthese details was in the 30 to 100 μm range. Details were preciselyimaged on the substrates after developing procedure. Differencesbetween designed and achieved paths width were smallerthan 10%. The test shows also that distances between every singleelement should be not smaller than 50 μm. Otherwise pathscould be short circuited one to another. Details had sharp, perpendicularedges what is characteristic for the photoimageableinks technique [5–7]. Some results are shown in Fig. 3.Process parameters like thickness of printed paste, drying timeand temperature, exposure time, developing time are crucial toachieve proper patterns with designed shapes and dimensions.There were series of tests performed before fabrication of finalstructures and all mentioned parameters were experimentally determined.(d)Fig. 4. Photoimageable thermocouples: a, b) masks for UV exposure;c) achieved Ag/Ni junctions; d) Ag/Ni thermopile (36 thermocouples)on DP 951 tapeRys. 4. Termopary fotodefiniowalne: a, b) maski dla naświetlania UV;c) wykonane złącza Ag/Ni; d) termostos Ag/Ni (36 termopar) na foliiDP 951The next step was the final structures fabrication. Thermocouples’arms like shown in Fig. 4a and 4b were made. Thepaths width was 60 μm, distances between them – 400 μm.Second arms were precisely screen-printed between Ag arms(Fig. 4c). Their width was 200 μm. PdAg or Ni pastes wereused. In the result the 165 μm thick substrate 36 thermocouples(each 20 millimeters long) were fabricated onto the 20 × 25 mm 2(Fig. 4d ). The distances between single thermocouple’s armswere 100 μm.„Sandwich” type microgeneratorAg/Ni combination is more suitable than Ag/PdAg one, due to it’shigher Seebeck coefficient (about 21 μV/K in comparison to about6 μV/K for Ag/PdAg). Test showed that printing order have noinfluence on results (Ag/Ni and Ni/Ag thermocouples gives thesame results). Sheet resistance of Ni and PdAg pastes was 45and 170 mΩ/□ respectively, Ag paste – 3,5 mΩ/□. Single thermocoupleresistance (result of Ag paste resistivity, PdAg or Ni pasteresistivity and junctions resistance) for „A” type structures wasabout 6,5 Ω for Ag/Ni and 22 Ω for Ag/PdAg. For “B” type structures– 6 Ω and 19 Ω, respectively.Ag/Ni structures had better output parameters (output voltage,power). It is suitable composition for planar thermopiles construction.To increase output parameters of micro-thermoelectricgenerators the stack consisted of single thermopiles can be constructed(„sandwich” structure as mentioned in section 2). A numberof substrates are put together and the electrical connectionbetween the layers are realized [4] – Fig. 5. Pads placed on thethermopile’s sides were used to connect adjacent layers (Fig. 1dand 4b). The last step of „sandwich” type micro-generator constructionis whole structure cofiring in the proper temperature profile(Fig. 2d).Elektronika 4/2012 19
Page 4 and 5: Analiza efektywności czasowej meto
Page 7 and 8: Streszczenia artykułów ● Summar
Page 9 and 10: Kwantowy efekt Hall’a w epitaksja
Page 11: Bonding technologies for 3D-packagi
Page 16 and 17: lable pore geometries, a high degre
Page 18 and 19: Processing of the Fuel CellOnce the
Page 22 and 23: Fig. 5. „Sandwich” type microge
Page 24 and 25: Tabl. 2. Percentage content of lead
Page 26 and 27: BGA676CSP132CSP84Profile P1 Profile
Page 28 and 29: ExperimentalThe developed capacitor
Page 30 and 31: Termoelektryczne, konduktometryczne
Page 32 and 33: References[1] Zhang M., Yuan Z., So
Page 34 and 35: detektora MEMS, bezwładność ukł
Page 36 and 37: óżnych wilgotności. Jeżeli zał
Page 38 and 39: elektronicznych, szczególnie ukła
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Page 42 and 43: HTML5 versus Flash - możliwości t
Page 44 and 45: Rys. 2. Interaktywne wideo na iPhon
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