Thermal design criteria for an optimized cryopump

Thermal design criteria for an optimized cryopump

764 World Abstracts on Microelectronics and Reliability Electric equivalent models of glass thick films. L. GOLONKA and B. W. LICZNERSKL Electron Te...

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World Abstracts on Microelectronics and Reliability

Electric equivalent models of glass thick films. L. GOLONKA and B. W. LICZNERSKL Electron Technol. 12, (1) 19. The electrical properties of thick film structures metal-glassmetal (M-G-M) may be represented in a.c. electric field by simple electric equivalent models. Introduced models describe well the behaviour of M-G-M structures in a wide frequency range. They permit to interpret the conductance and polarization phenomena and also to evaluate the contents of glass and crystalline phases, as well as the usability of glasses in thick film technology.

A method for the rheological characterization of thick-film pastes. V. S. KAROASHIAN and S. J. RAO VELLANKI. IEEE Trans. Components, Hybrids, and Manufacturino Technolog),. Chmt-2, (2) 232 (June 1979). A complete rheological profile of a thick-film ink can provide an understanding of the effects of composition on properties and enables one to predict and control the screening behavior. A complete profile includes the thixotropic and pseudoplastic properties as well as the viscosity behavior during post-shear recovery when leveling takes place. This paper presents a set of experimental techniques with which to measure shear thinning and recovery as experienced during the screening process. The basic problem in the measurement of the viscosity profile of a pseudoplastic paste during recovery is that the shearing involved in making the measurement itself causes a change in the paste viscosity. We have developed a technique which measures viscosity at essentially zero shear. The method involves the relaxation of a springdriven cone against the viscous drag of the paste repeated at short intervals during the recovery. The moment of inertia of the cone, the compliance of the viscometer spring, the cone geometry, and the shearing action are critical factors to consider in obtaining accurate and reproducible values of the viscosity. Experimental data describing the measurement of viscosity of Newtonian standards and of the theological characteristics of thick-film pastes are presented and discussed. A practical air-fireable base metal resistor system. E. K. BROWNE. Proc. Internepcon. p. 27, Brighton, UK, October 1978. An improved air-fireable base metal resistor system which is ideally suited to consumer and high volume industrial thick film applications is discussed. This system provides an attractive alternative to traditional thick film resistor series, which continue to suffer from the escalating price of precious metals. T h e novel construction of this material is briefly explained and the special characteristics of practical importance to the thick film manufacturer are described. Heat exchange optimization technique for high-power hybrid It's. W. MALY and A. P. PIOTROWSKI, IEEE Trans. Components, Hybrids, and Manufacturing Technology. Chmt-2, (2) 226 (June 1979). An algorithm for the optimization of the heat exchange conditions in high-power thick-film hybrid IC's is presented. The algorithm for the placement of elements which are temperature sensitive and/or heat sources is discussed. The Powell's multivariable unconstrained optimization technique and the penalty function shifting method in constrained static optimization are proposed as tools. Principe d'un analyseur de spectre optique utilisant les couches minces pulveris6es, H. MURRAY. Electrocomponent Sci. Technol. 6, 1 (1979) (in French). Specific properties of photovoltaic effects in thin sandwich films have been used to describe a spectral analyser for optical radiations in the range 2000 to 7000 A. In such structures, we have shown that the photovoltaic current has a polarity depending on the wavelength of incident radiation. Further studies relating to conduction and photoconduction phenomena allow

us to attribute the reversal effect to a photoexcitation of ionised traps (Poole Frenkel effect) or a photoexcitation from valence to conduction band of the photoconductor (Interband transitions). As these two photoeffects present dimensional dependence, the reversal wavelength ).o is thickness dependent. Multilayer dielectric sandwich films may be used as spectral analysers after specific calibration of the bias voltage, with an accuracy of 0.5% when the intensity of light is greater than 10/zw/cm 2. We have obtained some applications of such detectors in the U.V. region, when the dielectric is made from spluttered zinc sulphide and in the visible region with cadmium sulphide. The specific properties of sputtering processes are particularly adapted to the introduction of such analysers in microelectronics devices.

Characterization of thermal compression wire bonds to thick-film conductors on porcelain substrates. R. W. JOHNSON, L. K. WILSON and D. L. KINSER. IEEE Trans. Components, Hybrids, and Manufacturing Technology, Chmt-2, (3) 288 (September 1979). Four conductor compositions are examined for thermal compression bondability on porcelainized metal substrates. These materials, Thick Film Systems (TFS) 3045 Au, 3106 Pt-Au, 3535 Pt-Pd-Ag, and 3408 Pd-Ag, were evaluated on Alphamet ® substrates. The study includes conductors printed on the substrate enamel and on substrates previously prinked and fired with the Thick Film Systems 1129 RCB dielectric. Polished cross sections of the TFS 3045 Au conductor on both the enamel and the dielectric are examined with an optical microscope and electron microprobe. Thermal compression bonds are made to each of the four metallizations printed on both the enamel and fhe dielectric. Pull strengths are measured initially and after storage for 1000h at 150°C. The effect of storage on electrical performance is also examined. The results obtained show initial mean bond strengths between 5.66 and 6.18 g and between 5.59 and 6.22 g after storage. The change in resistance due to high-temperature storage ranges from - 2 . 4 to + 2.2 percent for the various metallization-print surface combinations. Thermal history of substrates during sputtering and sputter etching. L. T. LAMONT, JR., Solid-St. Technol p. 107 (September 1979). A typical silicon substrate has a low thermal mass and a high surface area to volume ratio. These, combined with unfavorable optical properties, make the control and measurement of substrate temperatures a difficult matter for most vacuum processes. It is shown that, for typical sputter deposition and etching situations, substrate temperature is essentially out of control. Thermal design criteria for an optimized cryopump. C. M. PETERSEN. Solid-St. Technol. p. 77 (September 1979). Cryopumps represent the latest in high vacuum pumping technology. Since condensation or crysorption is utilized to remove gas from the vacuum system, the temperatures in the pump are very important in determining the operating characteristics. These temperatures are determined by the amount of refrigeration power available and the thermal loads placed on the pumps. The resistivity of thin gold films. J. R. SAMBLES,K. C. ELSOM and D. J. JARVlS. Solid-St. Communs. 32, 997 (1979). Results are obtained on the D.C. electrical resistivity of evaporated gold films on KBr substrates as a function of thickness and temperature. These show that the conduction electrons are not specularly reflected at the sample surface but nevertheless the temperature dependent part of the resistivity is independent of sample thickness. Comparison of the results with Fuchs-Sondheimer theory for the effects of sample thickness upon the resistivity yield a maximum specularity of approximately 0.64 for ( I 0 0 ) films on KBr.