Effects of oxide additive on thermoelectricity of FeSi2
Thermoelectricity has been hot issue in these days, because of environmental problems and energy sources deficit. Moreover, material development for thermoelectricity is now busy in oxide and metal or alloy, basically. However, conclusive materials with good performance have not yet been found in application basis. We have studied oxide-added beta-FeSi2 for these years. Iron disilicide is well known and utilized in relatively higher temperature. In this report, we indicated our successful improvement of performance of beta-FeSi2 added with Ta2O5 showing the figure of merit almost 0.3 times 10-3/K This was obtained by reducing thermal conductivity and electrical resistivity (a half of standard FeSi2)
Effect of Electronic Structure on Seebeck Coefficient of Oxide Thermoelectric Semiconductor and Role of the Oxide
An oxide is functionally classified into two categories when regarding oxide as thermoelectricity: 1) an oxide itself has thermoelectric properties such as CaMnO3, homologous series of (ZnO)m and NaCo2O4, and they have been researched since around 1995. 2) there are researches on oxide as an additive to conventional thermoelectric material. We have investigated to approach thermoelectric property from the electronic structures by ab initio calculation. We propose to estimate Seebeck coefficient of oxide by regarding movement of electron between energy levels in the electronic structures. Thereby, it will lead to a new thermoelectric material of oxide. Furthermore, we can improve figure of merit by adding oxide to FeSi2 due to reducing thermal conductivity in the present study.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.