Warpage measurement of large area multitilted silicon substrates atvarious processing conditions

In order to find a low-cost solution for the future MCM-D packaging, a multitiling approach through the incorporation of several tiles on a large carrier substrate was studied. The multitiling format provides simultaneous processing of several small silicon wafers on a carrier glass with a coefficient of thermal expansion (CTE) comparable to that of silicon. The wafers (tiles) are attached to the carrier glass (pallet) using a low modulus adhesive that can be released at an elevated temperature (~450°C). The objective of this study is to develop materials and processes for a 12-in×12-in (300-mm×300-mm) large area substrate that can be scalable up to a 600-mm×600-mm format. The fabrication process begins with a carrier CTE matched Borofloat glass on which silicon wafers are attached using a low modulus adhesive. This composite structure is exposed to high temperature thin-film processes that are required for the MCM-D manufacturing. The warpage of these structures is a critical factor that determines the processability of the thin films in a manufacturing environment. Specimen warpage was obtained using the shadow moire technique. Warpage measurement was performed (i) on as-received glasses, (ii) glasses after polishing, and (iii) pallet assembly after tiling was completed. Although polishing reduced the overall warpage of the as-received pallets, the warpage of the tile and pallet assembly was increased after the adhesive was cured at 150°C. This paper discusses the warpage issues associated with various stages of processing of the proposed large area MCM-D structures     

High-pressure processing of fish and shellfish products: Safety,quality, and research prospects

Seafood products have been one of the main drivers behind the popularity of high-pressure processing (HPP) in the food industry owing to a high demand for fresh ready-to-eat seafood products and food safety. This review provides an overview of the advanced knowledge available on the use of HPP for production of wholesome and highly nutritive clean label fish and shellfish products. Out of 653 explored items, 65 articles published during 2016–2021 were used. Analysis of the literature showed that most of the earlier work evaluated the HPP effect on physicochemical and sensorial properties, and limited information is available on nutritional aspects. HPP has several applications in the seafood industry. Application of HPP (400–600 MPa) eliminates common seafood pathogens, such as Vibrio and Listeria spp., and slows the growth of spoilage microorganisms. Use of cold water as a pressure medium induces minimal changes in sensory and nutritional properties and helps in the development of clean label seafood products. This technology (200–350 MPa) is also useful to shuck oysters, lobsters, crabs, mussels, clams, and scallops to increase recovery of the edible meat. High-pressure helps to preserve organoleptic and functional properties for an extended time during refrigerated storage. Overall, HPP helps seafood manufacturers to maintain a balance between safety, quality, processing efficiency, and regulatory compliance. Further research is required to understand the mechanisms of pressure-induced modifications and clean label strategies to minimize these modifications.     

Development of automated real-time data acquisition system for robotic weld quality monitoring

The lack of reliable non-contact, non-destructive, online sensors with the ability to detect defects as they form and with the capacity to operate at high temperatures and in harsh environments is a big obstacle to fully automated robotic welding. This paper presents a non-contact automated data acquisition system for monitoring a robotic gas–metal arc welding process based on laser ultrasonic technology. While a robot welds between two 1040 steel strips, a Nd:YAG Q-switched pulse laser generates ultrasound on one side of the weld by ablation, and a non-contact electro-magnetic acoustic transducer (EMAT) placed on the opposite side of the weld detects ultrasound transmitted through the weld bead. Ablation is employed because high temperature specimens require strong signals to compensate for attenuation within the bulk of the material. The data is then analyzed to determine the time required for ultrasound to travel from the laser source to the EMAT, termed as the time of flight (ToF). When experimental ToF is compared to theoretical ToF, it is determined that surface waves are detected by this system. Therefore, this system can measure weld bead reinforcement distance. In most cases, weld bead geometry is an indication of the weld quality, and can be used as feedback to control a welding process.     

Fundamental study of laser generation of narrowband Lamb waves using superimposed line sources technique

In this paper, a laser generated ultrasound technique called superimposed line sources is presented. The technique generates narrowband Lamb waves with a dominant wavelength by superimposing signals of line sources at the pitch corresponding to the desired wavelength. The superposition is performed in software after data are collected so that it permits flexibility of selecting the desired wavelength afterwards. By selecting the dominant wavelength in signals, signal complexity is reduced and the speeds and frequencies of wave modes with the selected wavelength can be determined through dispersion curves. Wavenumber–frequency domain filtering and continuous wavelet transform are used in this research to further reduce the complexity of the signals. Finally, simulations and experiments are conducted to investigate the defect detection ability of the technique. Reflection coefficients are calculated for fundamental A0 and S0 wave modes. Good agreement is found between the simulations and experiments and the result of coefficients with respect to defect and sample dimensions will be shown.