Quartz crystal unit modeling at cryogenic temperatures

The aim of this paper was to develop the new quartz crystal electrical model including its temperature properties in the temperature range from 83.15 K (−190 °C) to 303.15 K (+30 °C) through experimental set-up and simulation analysis. Both the methodology of the quartz resonator measurements, the instrument setup, and the measurement methods needed to collect the necessary data as well as polynomial approximation of temperature dependence were described. The electrical model of AT-cut type quartz crystal for cryogenic temperatures was developed, in which its elements were expressed as functions of temperature. Using these polynomials, the behavioral model for PSPICE computer program has been worked out.     

Electrical properties of dielectric foil for embedded PCB capacitors

One of the methods of achieving high packaging density of passive elements on the PCB is using the capacitors embedded in multilayer PCB. Test structures consisting of embedded capacitors were fabricated using the FaradFlex? capacitive internal layers. Impedance spectroscopy and equivalent circuit modelling was used to determine their electrical properties such as the capacitance, parasitic resistance and inductance. The use of several stages of accelerated ageing allowed us to test the durability of the structures. The results showed good quality stability of the embedded elements. The spatial distribution of the capacitance of the test structures on the surface of the PCB form was tested. The influence of the process parameters during lamination on the values of embedded capacitors was revealed.     

Analysis of electromigration phenomenon in thick-film and LTCC structures at elevated temperature

Studies on electromigration phenomenon in thick-film structures on alumina and LTCC substrates are presented in this paper. The effects of storage of Au and Ag electrode patterns in temperature range up to 300 °C under voltage bias were examined. The leakage characteristics of electrodes with 100 μm spacing at 50 V dc bias as a function of time and temperature are presented and analyzed. Scanning electron microscope (SEM) equipped with the energy-dispersive X-ray spectroscopy (EDX) detector was applied for determination of metal ions transport. Test structures with Au-based conductive material are much more resistant to electromigration than Ag-based layers.     

Properties of laser cut LTCC heaters

This article describes fabrication and properties of buried microheaters made inside low temperature co-fired ceramics (LTCC) structures. Laser cutting is used for meander pattern generation in dried Pt, PtAu or PdAg conductive pads. The electrical characterisation of microheaters is based on measurement and analysis of R(T) dependence in the range from 20°C to 850°C, measurement and analysis of thermal dynamic properties, long-term high-temperature passive or active ageing and behaviour of the heater in a pulse operation mode. The presented results are very promising for application of LTCC microheaters in various microsystem devices.     

如何选用正确的干燥设备,以适应工艺需求

<正>在干燥工序中,选用哪种干燥设备?如何正确使用干燥设备来取得最佳的干燥效果?这是干燥设备选型过程中最常见的问题。1去湿干燥     

Phenolic acids and related compounds as antioxidants for edible oils

A series of hydroxy aromatic acids, esters and lactones have been evaluated as antioxidants for lard at 120°C at 0·025%, 0·05% and 0·1% concentrations. Most of the compounds studied are direct biochemical precursors of chalcones and these, in turn, of various flavonoids commonly occurring in plant material.Antioxidant efficiency has been shown to be very dependent on the number of phenolic hydroxyl groups in the molecule and also to be promoted by steric hindrance. Cinnamic acids are more effective than corresponding benzoic acids, and phenylacetic and phenylpropionic acids are even more effective. 3,4-Dihydroxy chalcone is more effective than the analogous caffeic acid. In general, the presence of a carbonyl group in the molecule appears to be necessary in this series for a high level of antioxidant activity.     

Hyperbaric oxygen inhibits the growth of cultured rabbit lens epithelial cells without affecting glutathione level

The influence of electron beam irradiation on migrational behaviour of additives present in food packaging material was studied. The migration experiments were carried out on irradiated and non-irradiated polypropylene pouches containing aqueous food simulating liquids (FSL) for 10 days at 40 degrees C. The controls were irradiated and non-irradiated pouches without FSL contact. After the contact period, the polypropylene and the FSL were analysed. A comparison between the results obtained by the two analyses showed the migration of three products of antioxidant degradation from the polypropylene into the FSL, and a partial decomposition of these migrants in the FSL.     

Phosphatidyl ethanolamine as a synergist for primary antioxidants in edible oils

Dipalmitoyl phosphatidyl ethanolamine (DPE) is a potent synergist for a wide range of primary antioxidants in edible oils at elevated temperature, i.e., above 80 C. At lower temperatures it has very little synergistic action. At 120 C the synergistic effect increases progressively as the concentration of synergist increases from 0.025% to 0.25%. At a given level of synergist, its effect is proportionately greater at low rather than high levels of primary antioxidant.