This paper investigates the effect of storage time on the bond strength of plasma-activated silicon (Si) wafers. Plasma activation was carried out in a reactive ion etch chamber using O2 gas. The activated wafers were stored in a clean room environment for specific time intervals before pre-bonding them (in a high vacuum environment) using a substrate bonder. Steps involved in wet chemical activation and pre-bonding of the wafers were discussed in detail. The pre-bonded wafers were thermally annealed. The bond quality, in addition to the bond strength, of in-situ and ex-situ thermal annealed wafer pairs were evaluated. The bond quality was determined using near-infrared imagery, and tensile tests were conducted on dies diced out from the bonded pair. The chemistry involved during activation, storage, pre-bonding, and thermal annealing was investigated thoroughly. The bond quality and bond strengths of wafers for corresponding storage times were compared using the near-infrared imagery and tensile tests respectively. Finally interesting phenomenon, like the increase in bond strength after a particular storage time, was studied and explained.
This research focuses on designing, fabricating, and testing a strain sensor for different soil applications. Using finite element modeling and analysis, the initial dimensions of the diaphragm were designed, and a diaphragm diameter of 1.35 cm with a thickness of 300 μm was chosen. The fabrication process of the sensor prototype is discussed in this paper along with the design for specific test benches to test the electrical and mechanical characteristics at different stages of fabrication. Displacement tests on the sensor diaphragm were performed and the corresponding voltages produced were tabulated. A maximum displacement of 250 μm was achieved producing a maximum voltage of 7.3 mV. The voltage produced by the sensor was recorded using LabVIEW, and its values were tabulated and plotted against corresponding displacement and strain magnitudes.
This paper deals with the analyses of fluid flow distribution in a microfluidic device with in-line manifolds. The analysis was performed using commercially available microfluidic simulation software called CoventorWare™. The number of channels in the microfluidic device considered for this study was kept at ten due to limitations on the number of nodes and computational time. Channels with only square profile were analyzed for flow rates varying between 1 to 60 ml/min. The length of the channels was maintained at 1.5 cm for all simulations. The fluid flow distribution characteristics for different channel widths/depths (200, 100, and 75 μm) were investigated. It was observed that the flow rate decreased from the central channels to the outer channels. The flow per channel was symmetric about the geometric centre of the microdevice. The uniformity in flow was accessed using the root mean square value of flow per channel and it decreased with decrease in channel width/depth for a specific flow rate. The difference in the flow rate through the channels increased with increase in total flow rate. Similarly, the spacing between the channels was varied (300, 200, and 100 μm) for a microdevice with channel width/depth of 100 μm and its corresponding flow characteristics were studied for flow rate ranging between 1 ml/min and 60 ml/min. Finally, the length of each manifold was varied between 2500 μm and 1000 μm for understanding the effect of manifold length on flow distribution. The standard deviation of flow per channel did not show much variation with changes in spacing and manifold length. In addition each design of the manifolds was analyzed on the basis of pressure and flow rate as well as velocity profile in each of the channels.
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