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Computerized thermal analysis of hybrid circuits
World Abstracts on Microelectronics and Reliability
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8. THICK- AND THIN-FILM COMPONENTS, HYBRID CIRCUITS AND MATERIALS Development and production of hybrid circuits for microwave radio links. PER CHR, MALMIN. Electrocomp. Sci. Technol. 4, 79 (1977). During the last few years, the use of hybrid integrated circuits in microwave radio links has increased significantly. This paper reports on a range of microwave hybrid circuits now in production at our plant. These include transistor high power amplifiers, low noise mixers and various other circuits. The hybrid technology has proven to be cost competitive with the more conventional waveguide and coaxial technologies, and gives quite a few other advantages as well. Among these, the standardization of packages and modules is discussed in some detail. The trend is now to use the hybrid technology in VHF circuits as well. This opens up the possibility of integrating related functions in one package. The production cost in this case must be related to printed circuit boards, and it remains to be seen if there is anything to gain in this respect. However the reduction of the size of modules and the time for circuit alignment will certainly given an improvement in the overall system cost. In order to reduce the cost of microwave hybrid circuits, thick film technology is currently being investigated for use up to 15 GHz. There is probably no specific upper frequency for thick film circuits, but the possibility of using conventional thick film technology depends on the actual circuits under consideration. Preliminary results of this work are reported, together with a cost comparison between thick film and thin film microwave hybrid circuits. Conduction processes in high value thick film resistors. J. ROBERTSON. Electrocomp. Sei. Technol. 4, 105 (1977). This paper describes conduction processes in thick film resistors made from 1 Mf~/square and 10 MD/square pastes. Conductivity as a function of temperature indicates activation energies in the order of 1 meV. At high fields, conductivity is increased. These results are interpreted on the basis of a model where the main resistor characteristics are determined by hopping conduction in a narrow impurity band in the glass phase of the resistor. Pulsed photovoltaic effect in thin film MIS devices. F. MORIN. Vacuum 27, (4) 241. A MIS structure, illuminated by pulsed light, can generate a pulsed photocurrent. We have observed this effect in various kinds of MIS structures (Si3N4/Si; Polymer/Si). We have shown that the detected photovoltage pulse across a high impedance load is directly related to surface potential ~,(qcb~/KT; band bending at insulator/semiconductor interface). Indeed, the photo-voltage versus external bias V curves are found in good agreement with the q~(V) curves obtained by capacitance-voltage measurements. For instance, photovoltage is found to reverse polarity, like es, at flatband voltage (V = VFB). This pulsed photovoltaic effect is then studied on thin film sandwiches: Metal/Polymer/CdSe/Metal. The CdSe film, evaporated on to a chromium contact, is coated by a polyparaxylene film (2000 A-rf plasma polymerized) and a semi-transparent counter-electrode. A pulse of light creates a 0.2 V voltage pulse across a 1 Mf~ load resistor. Furthermore, after a + 5 V short time bias, photo response vanishes, and reappears by reversing the bias. Hysteresis investigations of the capacitance-voltage curves is used to explain this memory effect. A short time bias is sufficient to fill or empty polymer traps near the interface. The respective semiconductor surface is then accumulated (low/q~s) or depleted (high/~s). Photoresponse is in good agreement with these results. Pulsed photovoltaic effect may be used to investigate MIS structures, and also to make up a new thin film memory device.
Resistor geometry comparison with respect to current noise and trim sensitivity. W. ULBRICH. Electrocomp. Sci. Technol. 4, 63 (1977). The paper deals with laser trimming of film resistors. The finite-difference solution of the electric field calculated by a digital computer gives the total resistance and the inhomogeneous current distribution within the resistor area. The current noise voltage was found to be proportional to the sum of reciprocal subareas wherein the current density is approximately constant. Resistor trimming is modelled by finite increments of cut length to obtain the resistancee trim rate and the trim sensitivity. Known and new resistor geometries and cut configurations are compared (based on the same resistor area and the same initial tolerance of ___20~o) to find the optimal geometry depending on the ratio of the nominal resistance value to the sheet resistivity. Diagrams are given leading to practical design rules not only for resistance trimming but also for deterministic and functional tuning. Computerized thermal analysis of hybrid circuits. DR RICHARD F. DAVID. Proc. Electron. Components Conf. Arlington, Va., (May 16-18 1977) p. 324. A computer program was written to perform steady state analysis for hybrid circuits. The output of the program gives the temperature of each power dissipating element in the hybrid. The program is based upon solution of Laplace's equation in three dimensions using Fourier techniques. The assumptions made are: no convection or radiation, constant and isotropic thermal conductivity for any single material, and constant temperature at the bottom of the hybrid package. Bessel's inequality allows one to input the desired accuracy and to determine where the infinite series should be truncated. Theoretically the program will attain any desired accuracy less than 100 per cent, but practical considerations of computer run times limit accuracies to the 90 per cent to 95 per cent region. The program has been tested by comparing computer results to known theoretical exact solutions and to actual measurements on sample hybrids. When compared to known theoretical exact solutions, the computer result accuracy is between 95 per cent and 100 per cent. When compared to actual measurements on sample hybrids, the computer result accuracy is between 90 per cent and 95 per cent. This program has been used successfully on over twenty circuit designs. It has also been used to evaluate simpler types of thermal analyses. Thermal characterization of epoxy and alloy attachment of hybrid components. THO~tAS W. ELSBY, Proc. Electron. Components Conf. Arlington, Va., (May 16-18 1977) p. 320. Thermal characterization of thick film multilayer hybrid circuits can lead to improved performance and reliability by providing a better understanding of the materials and processes used in circuit fabrication. Although many materials and combinations of materials are available to the hybrid manufacturer, this paper will be limited to an evaluation and comparison of several epoxy materials and one all metal alloy bonding system. Data for thermal measurements, made using infrared radiometry, are presented for each of the organic bonding materials and for the metal alloy bonding system. Predict contact performance with film measurements. ROBERT H. GOSCIORA. Prec. Electron. Components Conf. Arlington, Va., (May 16-18 1977). p. 269. An electrical test method which monitors contact cleanliness and manufacturer's process consistency is described. The test method was developed as a quality control technique for relays and switches, but it is applicable to other contact devices
261
8. THICK- AND THIN-FILM COMPONENTS, HYBRID CIRCUITS AND MATERIALS Development and production of hybrid circuits for microwave radio links. PER CHR, MALMIN. Electrocomp. Sci. Technol. 4, 79 (1977). During the last few years, the use of hybrid integrated circuits in microwave radio links has increased significantly. This paper reports on a range of microwave hybrid circuits now in production at our plant. These include transistor high power amplifiers, low noise mixers and various other circuits. The hybrid technology has proven to be cost competitive with the more conventional waveguide and coaxial technologies, and gives quite a few other advantages as well. Among these, the standardization of packages and modules is discussed in some detail. The trend is now to use the hybrid technology in VHF circuits as well. This opens up the possibility of integrating related functions in one package. The production cost in this case must be related to printed circuit boards, and it remains to be seen if there is anything to gain in this respect. However the reduction of the size of modules and the time for circuit alignment will certainly given an improvement in the overall system cost. In order to reduce the cost of microwave hybrid circuits, thick film technology is currently being investigated for use up to 15 GHz. There is probably no specific upper frequency for thick film circuits, but the possibility of using conventional thick film technology depends on the actual circuits under consideration. Preliminary results of this work are reported, together with a cost comparison between thick film and thin film microwave hybrid circuits. Conduction processes in high value thick film resistors. J. ROBERTSON. Electrocomp. Sei. Technol. 4, 105 (1977). This paper describes conduction processes in thick film resistors made from 1 Mf~/square and 10 MD/square pastes. Conductivity as a function of temperature indicates activation energies in the order of 1 meV. At high fields, conductivity is increased. These results are interpreted on the basis of a model where the main resistor characteristics are determined by hopping conduction in a narrow impurity band in the glass phase of the resistor. Pulsed photovoltaic effect in thin film MIS devices. F. MORIN. Vacuum 27, (4) 241. A MIS structure, illuminated by pulsed light, can generate a pulsed photocurrent. We have observed this effect in various kinds of MIS structures (Si3N4/Si; Polymer/Si). We have shown that the detected photovoltage pulse across a high impedance load is directly related to surface potential ~,(qcb~/KT; band bending at insulator/semiconductor interface). Indeed, the photo-voltage versus external bias V curves are found in good agreement with the q~(V) curves obtained by capacitance-voltage measurements. For instance, photovoltage is found to reverse polarity, like es, at flatband voltage (V = VFB). This pulsed photovoltaic effect is then studied on thin film sandwiches: Metal/Polymer/CdSe/Metal. The CdSe film, evaporated on to a chromium contact, is coated by a polyparaxylene film (2000 A-rf plasma polymerized) and a semi-transparent counter-electrode. A pulse of light creates a 0.2 V voltage pulse across a 1 Mf~ load resistor. Furthermore, after a + 5 V short time bias, photo response vanishes, and reappears by reversing the bias. Hysteresis investigations of the capacitance-voltage curves is used to explain this memory effect. A short time bias is sufficient to fill or empty polymer traps near the interface. The respective semiconductor surface is then accumulated (low/q~s) or depleted (high/~s). Photoresponse is in good agreement with these results. Pulsed photovoltaic effect may be used to investigate MIS structures, and also to make up a new thin film memory device.
Resistor geometry comparison with respect to current noise and trim sensitivity. W. ULBRICH. Electrocomp. Sci. Technol. 4, 63 (1977). The paper deals with laser trimming of film resistors. The finite-difference solution of the electric field calculated by a digital computer gives the total resistance and the inhomogeneous current distribution within the resistor area. The current noise voltage was found to be proportional to the sum of reciprocal subareas wherein the current density is approximately constant. Resistor trimming is modelled by finite increments of cut length to obtain the resistancee trim rate and the trim sensitivity. Known and new resistor geometries and cut configurations are compared (based on the same resistor area and the same initial tolerance of ___20~o) to find the optimal geometry depending on the ratio of the nominal resistance value to the sheet resistivity. Diagrams are given leading to practical design rules not only for resistance trimming but also for deterministic and functional tuning. Computerized thermal analysis of hybrid circuits. DR RICHARD F. DAVID. Proc. Electron. Components Conf. Arlington, Va., (May 16-18 1977) p. 324. A computer program was written to perform steady state analysis for hybrid circuits. The output of the program gives the temperature of each power dissipating element in the hybrid. The program is based upon solution of Laplace's equation in three dimensions using Fourier techniques. The assumptions made are: no convection or radiation, constant and isotropic thermal conductivity for any single material, and constant temperature at the bottom of the hybrid package. Bessel's inequality allows one to input the desired accuracy and to determine where the infinite series should be truncated. Theoretically the program will attain any desired accuracy less than 100 per cent, but practical considerations of computer run times limit accuracies to the 90 per cent to 95 per cent region. The program has been tested by comparing computer results to known theoretical exact solutions and to actual measurements on sample hybrids. When compared to known theoretical exact solutions, the computer result accuracy is between 95 per cent and 100 per cent. When compared to actual measurements on sample hybrids, the computer result accuracy is between 90 per cent and 95 per cent. This program has been used successfully on over twenty circuit designs. It has also been used to evaluate simpler types of thermal analyses. Thermal characterization of epoxy and alloy attachment of hybrid components. THO~tAS W. ELSBY, Proc. Electron. Components Conf. Arlington, Va., (May 16-18 1977) p. 320. Thermal characterization of thick film multilayer hybrid circuits can lead to improved performance and reliability by providing a better understanding of the materials and processes used in circuit fabrication. Although many materials and combinations of materials are available to the hybrid manufacturer, this paper will be limited to an evaluation and comparison of several epoxy materials and one all metal alloy bonding system. Data for thermal measurements, made using infrared radiometry, are presented for each of the organic bonding materials and for the metal alloy bonding system. Predict contact performance with film measurements. ROBERT H. GOSCIORA. Prec. Electron. Components Conf. Arlington, Va., (May 16-18 1977). p. 269. An electrical test method which monitors contact cleanliness and manufacturer's process consistency is described. The test method was developed as a quality control technique for relays and switches, but it is applicable to other contact devices