One-shot double, triple, and quadruple borylation reactions of triarylamines were developed through a judicious choice of boron source and Brønsted base. With the aid of borylation reactions, a variety of BN-doped nanographenes were synthesized in two steps from commercially available starting materials. An organic light-emitting diode device employing BN-doped nanographene as an emitter exhibited deep pure-blue emission at 460 nm, with CIE coordinates of (0.13, 0.11), and an external quantum efficiency of 18.3%.

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Some instability problems were found on natural or engineered slopes mostly lying on Subang claystones. The instability problems included excessive erosion, slumps and rock falls. The field performance surveys of the problems suggested that the claystones physically weather rapidly so that the rock properties they exhibit during excavation often change to properties with a more characteristic of soil. Such a phenomenon is generally known as a slaking process. In order to gain better understanding about the slaking of Subang claystones, a series of experimental laboratory studies were carried out involving a modified slaking index test. Claystone samples used in this study were obtained from their exposures along the Northern West Java area of Indonesia. Petrographic analysis was correspondingly performed to identify mineral and texture/fabric, and in turn, to determine the inherent factors of the rocks which might affect the slaking process. The study results indicated that the claystones were characterized by high to very high slaking properties having a maximum slaking index (I s ) of 57.4% and a mean I s of 43.8%. Major dispersion slaking on sample surfaces and high cracking in response to excessive swelling were recognized as main slaking modes within the claystones. All samples lose progressively less material through the five wet-dry cycles of a slaking index test, indicating a decelerated slaking rate. It was evident that the main inherent factors controlling the slaking process were expandable clay mineral smectite, non-clay mineral pyrite and soluble mineral calcite. Moreover, a quite important of inherent bonding material and stress release energy in the slaking characteristics of the claystones was revealed by a closure phase of an initial hairline crack during unloading.

Advanced power module technology capable of taking advantage of the superior features of next-generation power devices, such as those fabricated with SiC and GaN, must be developed to create much more compact and costeffective power conversion systems. New power modules based on such technology are especially required to allow fast switching of power devices in the extended junction temperature range. This paper describes the major technical challenges involved in sufficiently improving the thermal stress reliability of the critical package systems in SiC power modules and in markedly reducing internal parasitic inductance. Thermal stress reliabilities of the die attachment system, wire bonding system, and encapsulant system are successfully improved, all of which are shown to be able to achieve common life targets: 1) 3000 h for a storage test at 250°C and 2) 3000 cycles for thermal cycling between −40°C and 250°C. A novel phase-leg power module capable of substantially reducing the loop inductance along the principal current tracks is proposed and fabricated by applying SiC-JFETs, SiC-Schottky barrier diodes, and the abovementioned reliable thermal stress package systems. Double pulse switching testing of the module reveals smaller drain-source voltage spikes and ringing even in turn-ON and turn-OFF transients at very high slew rates of current and voltage. Finally, a 0.34 L forced-air-cooled dc 600 V input ac 50 Hz 400 V 25 kW output three-phase SiC inverter is fabricated using three-phase leg modules and its operation is demonstrated at high-power levels.

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A eutectic Au-Ge (12 wt%) die attach system has traditionally been used in electrical characterization of SiC devices in a temperature range up to 300°C. However, only fragmentary results have been reported concerning the applicability of the system. In this paper, a eutectic Au-Ge die attach system composed of 0.3-mm-thick, 2×2 mm2 SiC dies soldered on ceramic (SiN) substrates with Ni/Au-plated Cu foil is systematically discussed on the basis of the results of storage tests at 300°C and thermal cycle tests ranging from −40°C to 300°C. Die attachments were performed at ~400°C by using a vacuum reflow soldering system. Shear testing of the samples indicated that the initial dies had very strong shear strength of more than 100 MPa. After 300°C storage for 3000 hours in air, it was found that their shear strength markedly dropped, but still maintained an average value two times larger than the JAITA standard of 6.2 MPa specified in IEC 749 for die shear strength. The test results for a thermal cycle from −40°C to 300°C showed that although the shear strength of the samples gradually declined with an increasing number of cycles, it was still 10 MPa on average even after 2000 cycles.

Abstract.A new SiC power module package structure is proposed that is capable of withstanding greater ∆Tj cycle stress. Its most notable feature is the use of a SiN substrate having Cu/Invar/Cu foils (C/I/C thickness ratio of 1/8/1) brazed on both sides as conductor plates. The CIC foils show a very low coefficient of thermal expansion (CTE) of 5.1 ppm/°C and therefore can significantly reduce package degradation resulting from the larger CTE mismatch of the conductor to SiC and SiN. A thermal cycle test (TCT) was conducted between -40°C and 250°C (∆Tj = 290°C). It was found that the SiC/Au-Ge/CIC-SiN die attachment maintained joint strength of 78 MPa even after 3000 cycles.