Methods of measurement of LTCC metallization thickness
Metallization provides electrical routing and serves as thermal via in LTCC (Low Temperature Cofired Ceramic) technology. High electrical and thermal conductivity is desirable. It is often achieved with the use of low electrical resistance materials, such as gold, silver and copper. The conductive paste made of these materials is expensive. Hence, the fabrication of LTCC has to be performance-wise and cost effective. The width, length and thickness of metallization are associated with the amount of conductor paste used. The thickness of metallization governs the functionality and performance of some components, such as resistor. In this paper, the physical attributes of LTCC substrate and its metallization was studied. Due to the constraint brought by the physical attributes of LTCC samples, various methods had been carried out. This paper also summarized the pros and cons of each method. The methods are limited to the equipment available.
Curvature evolution in LTCC tapes and laminates
Low temperature cofired ceramic (LTCC) substrates provide a low-cost packaging approach for radio frequency (RF) integrated circuits. Thermally-driven curvature development in these LTCC tapes and laminates, which can introduce property-limiting defects into a device, was examined quantitatively using an optical profilometer. Contrary to the standard perception of tape cast products, these specimens consistently experienced the largest increases in curvature during burnout rather than during sintering. Sintering actually leads to dramatic decreases in curvature. Slight anisotropic changes in curvature were observed when comparing those directions parallel and perpendicular to the tape casting direction. In the laminates, individual layer orientations had strong effects on overall curvature. Springback after the application of lamination pressure strongly contributes to curvature. "Microslumping" at the ends of the tapes/laminates occurred during sintering and could be accounted for via discrete element models of sintering. The latter phenomenon can be eliminated by controlling relative tape orientation.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.