(ECS Meeting PRiME 2020) High TEC copper to connect copper bond pads for low temperature wafer bonding

Copper to copper wafer hybrid bonding is the most promising technology for three-dimensional (3D) integration. In the hybrid bonding process, two silicon wafers are aligned and contacted. At room temperature, these aligned copper pads contain radial-shaped nanometer-sized hollows due to the dishing effect induced by chemical-mechanical polishing (CMP). These wafers are annealed for copper to expand and connect upper and lower pads. This copper expansion is key to eliminate the radial-shaped hollows and make copper pads contacted. Therefore, in this research, we investigated the new high thermal expansion coefficient (TEC) electrodeposited copper to eliminate dishing hollows at lower temperature than that with conventional copper using the combination of new additive A and three other additives. The TEC of new electrodeposited copper is 25.2 x 10-6 oC-1, 46% higher than conventional copper and the calculated contact area of copper surface at 250oC with 5 nm dishing depth is 100%.

Influence of Sm2O3 Additive on BaO-Al2O3-B2O3-SiO2 Glass-Ceramics for CBGA Package

Sm2O3 additive significantly influenced the microstructure, mechanical, and electrical properties of BaO-Al2O3-B2O3-SiO2 glass-ceramics. The calculation by the whole pattern fitting method based on XRD patterns revealed that Sm2O3 additive improved the crystallization process of this tetra-system and promoted the formation of major phase quartz. The sintering kinetics showed that Sm2O3 addition markedly reduced the sintering activation energy from 406.86 kJ/mol to 391.38 kJ/mol, which benefited the sintering densification and the grain growth, and thus enhanced mechanical properties. Doping 2% Sm2O3 reinforced the flexure strength from 136.3 to 171.6 MPa and the Young’s modulus from 49.4 to 79.7 GPa. It also exhibited low dielectric constant of 5.31, low dielectric loss of 5.30 × 10-4, and high thermal expansion coefficient of 11.76 × 10-6/°C.

Cryogenic expansion joint for LNG service

Pipelines transporting cryogenic liquids, such as liquefied natural gas (LNG), are typically constructed with metal components with a relatively high thermal expansion coefficient. Pipelines contract in length due to the large temperature differential that occurs. To accommodate this thermal contraction, LNG plants, offloading jetties, and other facilities typically utilise expansion loops and/or conventional in-line expansion joints (e.g. bellows). However, expansion loops require a large amount of space and support platforms, which can be costly and/or disruptive to an LNG facility construction. Additionally, conventional bellows-type expansion joints offer very little torsional strength, which may lead to catastrophic failure in the joint. Engineers at Clough Limited have patented two unique embodiments of a cryogenic expansion joint: a sliding concentric pipe-in-pipe cryogenic expansion joint; and a torsional cryogenic expansion joint. Both designs utilise inherent material properties to seal sequential pipeline segments together at cryogenic conditions. The pipe-in-pipe expansion joint provides large axial and unlimited torsional movement. The torsional expansion joint provides unlimited radial and some axial movement. These embodiments eliminate the large conventional expansion loops and reduce project capital expenditure.

Advanced Coating Systems for Future Shroudless Turbines

Shroudless turbine designs offer the advantages of weight reduction and lower mechanical loads on the one hand but bear challenges as high gap sensitivity and high temperatures of the static parts on the other hand. In the last years, a lot of work was carried out in order to develop a sealing system for a shroudless design consisting of an abrasive blade tip coating and an abradable segment coating addressing all the requirements defined. Aside from being abradable, the segment coatings have to be mechanically stable, withstand high thermo-mechanical loadings and have to work for thicknesses larger than 1 mm. Due to the limited temperature capability of the currently used segment coating material yttria-stabilised zirconia, which combines advantageously a suitable thermal conductivity with a high thermal expansion coefficient, new ceramic materials for the segment coating had to be developed. A very promising sealing system combines an abrasive blade tip coating with an yttria-stabilised zirconia / magnesia alumina spinel double-layer abradable coating system with a 3D interface structure between the bond coat and the ceramic coatings. The present work gives an overview of the development and the performance of this sealing system.

Influence of Polymer Material on the Sensitivity of Packaged Fiber Bragg Grating

Numerical calculation method is adopted to analyze to the influence of the polymer material on the sensitivity of coated FBG. The calculation results show that, the polymer material with high Young's modulus and high thermal expansion coefficient helps to improve the temperature sensitivity of the coated FBG; and the material with low Young's modulus and low Poisson's ratio helps to improve the pressure sensitivity. The polymer-coated FBG experiment is explored, in which the pressure and temperature sensitivities are enhanced 12-fold and 7-fold respectively.