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The study of the effect of pressure and temperature on the structural and mechanical properties of materials is very difficult for current experimental techniques. Here, we have synthesized the γ-Nb5Si3 compound with remarkable quality by high pressure and high temperature (HPHT) technology. The effects of high pressure and sintering temperature on its microstructure, mechanical properties, and oxidation resistance are discussed. The Vickers hardness and density of the γ-Nb5Si3 sample at 5.5 GPa and 1100 °C are 8.67 GPa and 5.73 g/cm3, respectively. It is shown that the HPHT behavior not only improves sample's compactness and microstructure, but also makes γ-Nb5Si3 to have a strong response to the Vickers hardness and related density. These results effectively demonstrate the functions of the HPHT technology, which accurately express the Vickers hardness, density, and thermal stability of γ-Nb5Si3 compounds. [ABSTRACT FROM AUTHOR]

LiF-doped MgTi(1−x)ZrxO3 (0.05 ≤ x ≤ 0.20) ceramics were fabricated via a conventional solid-state reaction route. All samples displayed MgTiO3 phase accompanying with a little of ZrO2 and Mg2TiO4 as the second phase. The lattice constant increased with increasing x due to the substitution of Zr4+ for Ti4+. The densification temperatures were reduced to the range of 1100–1150 °C due to LiF-doping. The microwave dielectric property of MgTi(1−x)ZrxO3 ceramics depended on the substitution content of Zr4+. Typical, MgTi0.90Zr0.10O3 ceramic exhibited microwave dielectric properties of εr = 18.7, tanδ = 2.8 × 10−4, and Q × f = 34300 GHz. [ABSTRACT FROM AUTHOR]

Isothermal aging effects on lead-free solders have been extensively investigated in recent studies. Researches show that aging effects significantly degrade the mechanical properties of lead-free solders. However, limited work has been done on the effects of aging on the board-level dynamic performance of lead-free solder joints, especially for large flip-chip ball grid array (FCBGA) packages. Due to the sensitivity of aging effects on lead-free solders, it is crucial to investigate the aging effects on the board-level dynamic performance of lead-free solders. In this paper, dynamic performance of lead-free solder joints has been characterized and isothermal aging effects have been investigated. It was found that the dynamic shock performance of lead-free FCBGA packages significantly degrades up to 20–35% after aging at elevated temperatures. It was also observed that aging at 100^\circC shows more severe degradation than aging at 75^\circC and 150^\circC. This is an important finding because many electronic products operate in the 100^\circC range for long periods. The unique finding of aging effects is related to the growth of Cu3Sn and Cu6Sn{5} intermetallics after aging. Even though failure analysis shows mixed failure of pad cratering and intermetallic compound (IMC) failures, the IMC growth is the most sensitive factor contributing to the failure observed. [ABSTRACT FROM PUBLISHER]

Recently studies of mechanical properties of lead-free solders show that large reductions in stiffness, yield stress, ultimate strength, and strain to failure (up to 35%) were found after 2 months of aging at room temperature. It also shows that the tensile properties of both lead-free solders and Sn–Pb solders tend to become relatively stable after 10 days of aging at room temperature. In this study, in order to minimize any room temperature aging contribution in the investigation of the dependence of temperature and strain rates, all specimens tested were preconditioned after 10 days of aging at room temperature. All tests were conducted under the same conditions. Testing has been performed at three strain rates, 10−3, 10−4, and 10−5 s−1, in temperature range from −40 to 150 °C. A linear relationship was found between the temperature and the tensile properties (elastic modulus, yield stress, and ultimate stress), while a power law relationship was found between strain rate and tensile properties. Constitutive models have also been developed based on the experimental data with multiple variables of strain rate and temperature for both lead-free and lead content solders. With the obtained constitutive models, tensile properties of lead-free solders can be predicted at any testing strain rate and temperature. [ABSTRACT FROM AUTHOR]

Novel temperature-stable Mg 2 TiO 4 -based ceramics are fabricated by a solid-state reaction method for developing low-temperature co-fired ceramics (LTCC) applications. Ba 3 (VO 4) 2 and LiF was used as additive to improve the sintering ability and temperature stability. Well-dense Mg 2 TiO 4 –Ba 3 (VO 4) 2 composite ceramics were obtained at 900 °C due to LiF liquid-phase sintering. The microwave dielectric characteristics strongly depended on Ba 3 (VO 4) 2 content x. Typically, balanced microwave dielectric properties of ε r = 13.1, Q×f = 28 900 GHz (at 7.86 GHz), τ f = −5.1 ppm/°C are obtained for 0.55Mg 2 TiO 4 -0.45Ba 3 (VO 4) 2 -6 wt%LiF ceramics. The well chemical compatibility of such composition with Ag electrodes means that it is suitable as a substrate material for LTCC applications. • Temperature stable Mg 2 TiO 4 -based ceramics were prepared. • LiF-doping lowered sintering temperature of composite ceramics to 900 °C. • The temperature stability was improved by adding Ba 3 (VO 4) 2. • A near zero τ f values of −5.1 ppm/°C is obtained for samples for x = 0.45. • Ceramics with well dielectric properties are suitable for LTCC applications. [ABSTRACT FROM AUTHOR]