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Thick-film thermistor and its applications
World Abstracts on Microelectronics and Reliability following high-temperature storage, and focus is placed on the first Pd/Ag system which overcame these problems. Extension of this technology and subsequent improvements in both binders and vehicles to fulfil adhesion requirements to A120 3 substrates of varying chemistries and to meet demands for high-speed printing are described also. In the second segment an overview of the present understanding of thick-film conductor composites from a mechanistic point of view is given. The various types of binder systems commonly employed in conductors are discussed in terms of how they effect a bond between the sintered metal and the substrate, and the advantages and disadvantages.
Thick-film thermistor and its applications. AKIRA IKEGAMI, HIDEO ARIMA, HIROMI TOSAKI, YOSHITAKA MATSUOKA, MITSURO AI, HITOSHI MINORIKAWA and YOSHIO ASAHINO. IEEE Trans. Components, Hybrids, Manuf. Technol. CHMT-3 (4) 541 (December 1980). The electrical properties, reliability, and several successful applications of a thick-film thermistor are described. The thick-film thermistor is composed of a semiconducting oxide, precious metal (RuO2), and glass. The resistivity and thermistor constant are affected to a great extent by the electrical properties of the semiconducting oxide, the particle size of RuO2, and the characteristics of the glass. The thermal expansion coefficient of the semiconducting oxide is required to be less than 105 × 10 -7 K -1 in order to prevent the cracks in as-fired film. A resistivity ranging from lf2.cm to 10Mf~.cm together with a thermistor constant from 100 to 4500 K can be obtained by controlling these factors. These glass coated thick-film thermistors exhibit extremely high stability. An accelerated life test shows the drift rate as less than 0.02 percent/year in the resistance of a thick-film thermistor with a crystallized glass coating. A thick-film thermistor can be used widely as an accurate and stable temperature sensor and as an exact temperature compensating element in a thick-film hybrid circuit. Plasma deposition of silicon dioxide and silicon nitride films. EVERT P. G. T. VAN DE VEN. Solid-St. Technol. 167 (April 1981). Plasma deposition processes for silicon dioxide and silicon nitride are compared and the various applications discussed. The optimization of both processes requires a different approach which is determined primarily by the nature of the reaction gases used. For plasma oxide, control of the gas phase reactions has to be maintained to prevent particles, pinholes and other localized structural defects, whereas for plasma nitride the surface reactions are critical. The applications for which the films are used are determined by their effect on the device electrical parameters. Both plasma oxide and nitride are successfully used for device passivation and interlayer insulation; in addition, plasma oxide can also be used as an insulating layer in high voltage ICs and devices with critical dopant profiles. Ni-P as a new material for thick film technology. I. BARYCKA, B. HOLODN1Kand A. MISlUK. Electrocomponent Sci. Technol. 7, 221 (1981). The product of nickel ions reduction in buffered solution by hypophosphite, known as Ni-P, was examined as a potentially useful material for thick film technology. This material, when mixed with glass oxidizes if heated above 450°C in an air atmosphere. For this reason we investigated the possibility of using an additive to stabilize the Ni-P against oxidation. We found that B20 3 as an additive showed itself to be most satisfactory. A detailed investigation of the phase relations in heated Ni-P, Ni-Pglass and Ni-P-glass-B20 3 compositions was performed. The inks prepared so far from the mixture of Ni-P-glassB20 3 can only be used in thick film technology for conductor layer production (R [] ~ 0.1D). The most satisfying and practically useful characteristics were obtained for inks produced from solid components containing 45 to 80 wt % Ni-P and about 10 wt To B2 03.
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Strain sensitivity of thick-film resistors. JAYANT S. SHAH. IEEE Trans. Components, Hybrids, Manuf. Technol. CHMT-3 (4) 554 (December 1980). The strain sensitivity measurements of Dupont 1400-Birox ® thick-film resistor materials in untrimmed and laser trimmed conditions are described. This was studied to better understand the postlaser trim drift phenomenon and evaluate the effect of packaging/assembly induced stresses on the resistors. The strain coefficient of resistance or the strain sensitivity of the untrimmed 102-106-f~/[] resistor materials is small, reversible, and independent of resistor geometry or fired thickness (tf). This strain sensitivity (7i) is an intrinsic material property which is determined by the conduction mechanism in the material. The strain sensitivity of the laser trimmed resistors is a sum of the intrinsic sensitivity (Yi) and an additional term called the extrinsic strain sensitivity (~cx). The additional extrinsic contribution can be large and irreversible and depends strongly on the fired thickness (tf) of the resistor. A mechanism is proposed to explain these observations. The mismatch of the thermal expansion coefficients of the resistor material and the substrate leads to high internal stresses in the thick resistor. Hence crack formation and propagation is easier which leads to increased strain sensitivity (extrinsic) and post-trim drift. It was experimentally determined that A120 a from the substrate dissolved 6-8 #m into the thick-film resistor during resistor firing. For thin resistors the relatively higher amount of dissolved A120 3 from the substrate in the resistor glass reduces the thermal expansion mismatch between the fired resistor and substrate. Thus its strain sensitivity and drift are much smaller than a thicker fired resistor. Origins and minimization of defects in sputtered thin films. RONALD S. NOWICKI. Solid-St. Technol. 83 (December 1980). Owing to time limitations and the improbability of investigating the large matrix of deposition parameters available, sputtered thin films tend to exhibit a wide variety of potential defects typical of non-optimization. For example, the thickness-limiting high intrinsic stress found in sputtered refractory metal films is a frequently encountered problem. Another problem often seen is the premature failure of passivating, or abrasive resistant films, e.g., aluminum oxide. Additionally, so-called thin film "barrier" metallizations are sometimes seen to fail for no apparent reason after performing well previously. This study discusses specific examples of the above problems and presents workable solutions. The use of thin film analytical techniques, e.g., Auger and ESCA microanalysis, to achieve these solutions is stressed. New approach to thick film resistor design. Electron. Prod. 29 (April 1981). A novel resistor design has been developed by EMCA, Mamaroneck, New York, which utilises recent advances in thick film multilayer technology to produce trim factors in excess of 1000 with excellent stability, and offers a unique method to reduce a discrete component or components to planar form.
Membrane touch switches: thick-film materials systems and processing options. W. T. HICKS, TREVOR R. ALLINGTONand VAN JOHNSON. IEEE Trans. Components, Hybrids, Manuf. Technol. CHMT-3 (4) 518 (December 1980). Thick-film materials and processing parameters critical to the production of membrane touch switches are reviewed. The primary emphasis is on polymer-bonded silver conductor systems; electrical conductivity versus silver content, conduction mechanisms, techniques to determine adhesion, materials for screen printing, choice of Mylar ® polyester film, and appropriate drying conditions are discussed. Also described is the performance of a new series of polymeric resistors on various substrates (including Mylar ® polyester), under different curing and storage conditions. Future trends in the development of materials systems for membrane switches and associated circuitry are also briefly reviewed.
Thick-film thermistor and its applications. AKIRA IKEGAMI, HIDEO ARIMA, HIROMI TOSAKI, YOSHITAKA MATSUOKA, MITSURO AI, HITOSHI MINORIKAWA and YOSHIO ASAHINO. IEEE Trans. Components, Hybrids, Manuf. Technol. CHMT-3 (4) 541 (December 1980). The electrical properties, reliability, and several successful applications of a thick-film thermistor are described. The thick-film thermistor is composed of a semiconducting oxide, precious metal (RuO2), and glass. The resistivity and thermistor constant are affected to a great extent by the electrical properties of the semiconducting oxide, the particle size of RuO2, and the characteristics of the glass. The thermal expansion coefficient of the semiconducting oxide is required to be less than 105 × 10 -7 K -1 in order to prevent the cracks in as-fired film. A resistivity ranging from lf2.cm to 10Mf~.cm together with a thermistor constant from 100 to 4500 K can be obtained by controlling these factors. These glass coated thick-film thermistors exhibit extremely high stability. An accelerated life test shows the drift rate as less than 0.02 percent/year in the resistance of a thick-film thermistor with a crystallized glass coating. A thick-film thermistor can be used widely as an accurate and stable temperature sensor and as an exact temperature compensating element in a thick-film hybrid circuit. Plasma deposition of silicon dioxide and silicon nitride films. EVERT P. G. T. VAN DE VEN. Solid-St. Technol. 167 (April 1981). Plasma deposition processes for silicon dioxide and silicon nitride are compared and the various applications discussed. The optimization of both processes requires a different approach which is determined primarily by the nature of the reaction gases used. For plasma oxide, control of the gas phase reactions has to be maintained to prevent particles, pinholes and other localized structural defects, whereas for plasma nitride the surface reactions are critical. The applications for which the films are used are determined by their effect on the device electrical parameters. Both plasma oxide and nitride are successfully used for device passivation and interlayer insulation; in addition, plasma oxide can also be used as an insulating layer in high voltage ICs and devices with critical dopant profiles. Ni-P as a new material for thick film technology. I. BARYCKA, B. HOLODN1Kand A. MISlUK. Electrocomponent Sci. Technol. 7, 221 (1981). The product of nickel ions reduction in buffered solution by hypophosphite, known as Ni-P, was examined as a potentially useful material for thick film technology. This material, when mixed with glass oxidizes if heated above 450°C in an air atmosphere. For this reason we investigated the possibility of using an additive to stabilize the Ni-P against oxidation. We found that B20 3 as an additive showed itself to be most satisfactory. A detailed investigation of the phase relations in heated Ni-P, Ni-Pglass and Ni-P-glass-B20 3 compositions was performed. The inks prepared so far from the mixture of Ni-P-glassB20 3 can only be used in thick film technology for conductor layer production (R [] ~ 0.1D). The most satisfying and practically useful characteristics were obtained for inks produced from solid components containing 45 to 80 wt % Ni-P and about 10 wt To B2 03.
763
Strain sensitivity of thick-film resistors. JAYANT S. SHAH. IEEE Trans. Components, Hybrids, Manuf. Technol. CHMT-3 (4) 554 (December 1980). The strain sensitivity measurements of Dupont 1400-Birox ® thick-film resistor materials in untrimmed and laser trimmed conditions are described. This was studied to better understand the postlaser trim drift phenomenon and evaluate the effect of packaging/assembly induced stresses on the resistors. The strain coefficient of resistance or the strain sensitivity of the untrimmed 102-106-f~/[] resistor materials is small, reversible, and independent of resistor geometry or fired thickness (tf). This strain sensitivity (7i) is an intrinsic material property which is determined by the conduction mechanism in the material. The strain sensitivity of the laser trimmed resistors is a sum of the intrinsic sensitivity (Yi) and an additional term called the extrinsic strain sensitivity (~cx). The additional extrinsic contribution can be large and irreversible and depends strongly on the fired thickness (tf) of the resistor. A mechanism is proposed to explain these observations. The mismatch of the thermal expansion coefficients of the resistor material and the substrate leads to high internal stresses in the thick resistor. Hence crack formation and propagation is easier which leads to increased strain sensitivity (extrinsic) and post-trim drift. It was experimentally determined that A120 a from the substrate dissolved 6-8 #m into the thick-film resistor during resistor firing. For thin resistors the relatively higher amount of dissolved A120 3 from the substrate in the resistor glass reduces the thermal expansion mismatch between the fired resistor and substrate. Thus its strain sensitivity and drift are much smaller than a thicker fired resistor. Origins and minimization of defects in sputtered thin films. RONALD S. NOWICKI. Solid-St. Technol. 83 (December 1980). Owing to time limitations and the improbability of investigating the large matrix of deposition parameters available, sputtered thin films tend to exhibit a wide variety of potential defects typical of non-optimization. For example, the thickness-limiting high intrinsic stress found in sputtered refractory metal films is a frequently encountered problem. Another problem often seen is the premature failure of passivating, or abrasive resistant films, e.g., aluminum oxide. Additionally, so-called thin film "barrier" metallizations are sometimes seen to fail for no apparent reason after performing well previously. This study discusses specific examples of the above problems and presents workable solutions. The use of thin film analytical techniques, e.g., Auger and ESCA microanalysis, to achieve these solutions is stressed. New approach to thick film resistor design. Electron. Prod. 29 (April 1981). A novel resistor design has been developed by EMCA, Mamaroneck, New York, which utilises recent advances in thick film multilayer technology to produce trim factors in excess of 1000 with excellent stability, and offers a unique method to reduce a discrete component or components to planar form.
Membrane touch switches: thick-film materials systems and processing options. W. T. HICKS, TREVOR R. ALLINGTONand VAN JOHNSON. IEEE Trans. Components, Hybrids, Manuf. Technol. CHMT-3 (4) 518 (December 1980). Thick-film materials and processing parameters critical to the production of membrane touch switches are reviewed. The primary emphasis is on polymer-bonded silver conductor systems; electrical conductivity versus silver content, conduction mechanisms, techniques to determine adhesion, materials for screen printing, choice of Mylar ® polyester film, and appropriate drying conditions are discussed. Also described is the performance of a new series of polymeric resistors on various substrates (including Mylar ® polyester), under different curing and storage conditions. Future trends in the development of materials systems for membrane switches and associated circuitry are also briefly reviewed.