Ceramic devices

Radiation in the infrared region of the spectrum is obtained from heated ceramic devices such as the Nemst glower or Globar. The Globar is made of silicon carbide and is heated to approximately 800-1500°C to emit black-body radiation in the infrared region of the spectrum. Coils of nichrome wire also emit infrared radiation when electrically heated. 

Figure 13. Example of image storage quality in memory PLZT 7065 (left) stored image and (right) original positive ceramic device under development at Sandia...

CD Cu-S(e) films have been proposed for a number of different potential applications. Solar control coatings, where the visible and IR transmission and reflectivity can be varied, is probably the most studied, e.g.. Refs. 44 and 45. The relatively high conductivity and the partial transmittance in the visible spectrum are useful for transparent conductors [46]. Other possible applications are for Cu sensor electrodes and electrical contacts for ceramic devices [46]. 

A. Peterson, T. Lopez, E. Ortiz Islas, R.D. Gonzalez, Pore structures in an implantable sol-gel titania ceramic device used in controlled drug release applications A modeling study . Applied Surface Science, 253, 5767-5771,... 

W R. Cannon, J. R. Morris and K. R. Mikeska, Dispersants for Nonaqueous Tape Casting pp. 161-74 in Advances in Ceramics, Vol. 19, Multilayer Ceramic Devices. Edited by J. B. Blum and W R. Cannon. The American Ceramic Society, Westerville, OH, 1986. 

The discussion of lead properties of course does not apply to leadless devices such as leadless ceramic chip carriers (LCCCs). Design teams using these and similar packages must understand the better heat transfer properties of the alumina used in ceramic packages and must match coefficients of thermal expansion (CTEs or TCEs) between the LCCC and the substrate since there are no leads to bend and absorb mismatches of expansion. Use of ceramic devices may lead the design team to consider the use of Low Temperature Co-fired Ceramic (LTCC) substrates and assembly technologies XXX. 

The sintered microstructure of thick film ceramic devices can be quite complex. This is caused by two factors (1) the ceramic itself may be multiphase, such as low-firing glass—ceramic packaging material and (2) dissimilar materials, such as ceramics and metals, are in contact during the high-temperature sintering process. Therefore, a variety of characterization techniques must be used in concert to determine adequately the phase and composition distributions in these materials. The following examples illustrate this point. 

Up to now piezoelectric composite transducers (e. g. AFC, MFC and PFC) are not widespread in adaptive structures. There exist many publications about the application of piezoelectric ceramic plates or wafers in structures but there is rarely something said about realistic application conditions or the load capacity of such devices. With regard to that piezo composite transducers promise to be robust alternatives to bulk ceramic devices. 

Cannon, W.R., Morris, J.R., and Mikeska, K.R., Dispersants for nonaqueous tape casting, in Blum, J.B. and Cannon, W.R., Eds., Advances in Ceramics Multilayer Ceramic Devices, Vol. 19, Westerville American Ceramic Society, 1986. 

Figures 27.17 to 27.19 show a comparison of the HDI build-ups for Types I, II, and III. In each case, complexity is added by building add-on layers sequentially.The build-up layers are typically for signal routing and contain low copper weight. Dielectric-coated (nonreinforced) microfoils (as thin as 9 to 12 pm) are employed to provide a low-profile thickness after copper plating.This is needed to facilitate the image of fine-hne widths typically associated with HDI.These styles of circuits offer some economy through use of a variety of dielectrics. The use and style of construction type must be matched with the product s expected application environment and operating life. Often the need for CTE match of area array components compels the application of a non-woven aramid layer at the surface. The resin system selection should be based on the expected CTE mismatch concerns, such as when a ceramic device is surface-mounted to the assembly. Thermal cycling of power on and off can cause earlier failure when a large mismatch is present.

The all-ceramic devices have material advantages for higher-temperature applications. However, many of the benefits of hot gas cleanup can be realized at the relatively mild temperatures of only 400-500°F. At these conditions, no need exists to condense water vapor out of the gas or to wet the fly ash. Chlorides and other trace components can also be removed in a dry form with the fly ash. Dry fly ash recovery significantly reduces the buildup of fixed salts in recycle process water and the cost of waste water cleanup. 

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