Hybrid Microcircuits Research Articles

Component Verification System

Typical hybrid microcircuits (HMC's) manufactured at the Bendix Corporation, Kansas City, MO, contain 100 beam lead devices and gold ribbon crossovers. Verification for the presence of these applique components historically has been done manually by comparing a visual aid to the HMC. All HMC's were verified visually, a process requiring 4-5 min/HMC. Approximately 12 percent of the defects were missed. A system has been developed for automatically verifying the presence of beam lead devices and ribbon crossovers. The component verification system (CVS) includes a minicomputercontrolled X-Y stage which indexes the HMC below a vidicon camera. The camera is interfaced to the computer through a video digitizer. Bendix-developed software uses the equipment capabilities to magnify and project a 5.l-mm2 area onto a 177.8-mm2screen with the image data points addressable in a 512 by 480 line matrix. The image analysis software determines component presence based on data point brightness. The CVS can verify beam lead device and crossover presences on a typical. HMC in fewer than 30 s. The part identification of any missing part is printed as an aid to rework. The CVS has reduced the time needed for component verification and has improved verification accuracy.

Computerized Thick-Film Printer

The computerized thick-film printer has been developed as a manufacturing tool for the efficient and economical production of small quantities of thick-film hybrid microcircuits. Its capability for fine-line definition onto ceramic substrates is based on the use of a high-speed orifice printing process. The printer reduces the time and cost of developing and producing thick-film hybrid microcircuits. Timesavings result because the printer can eliminate some of the steps involved in progressing from the design to screen printing of the circuits. Costsavings result because the printer can eliminate certain key labor-intensive thick-film manufacturing processes. Specifically, savings should be realized by the elimination of 1) critical artwork generation procedures, 2) photolithographic preparation of stencil screens for microcircuit fabrication, 3) intermediate production tooling as represented by the stencil screens, and 4) lengthy prototypeand-redesign cycles. The computerized thick-film printer provides the user with a pattern-design and printing capability suitable for producing prototypes and small-quantity production runs of hybrid.

Radiotelemetry of avian electrocardiogram

A radiotelemetry system has been developed which is capable of transmitting electrocardiogram signals from domestic fowl. The transmitter circuit consists of a frequency-modulated Colpitts oscillator operating at 104·5 MHz, followed by a single-ended amplifier. The devices are fabricated as thin-film hybrid microcircuits. Transmitters were encapsulated in silicone rubber and implanted subcutaneously over the pectoral muscles in domestic fowl. Several sites for electrode placement were tried. The most successful yielded a large distinct QRS complex, which could be used as a trigger in measuring heart rate, and a good ratio of usable to unusable trace. These results were obtained when the electrodes were sutured 60 mm apart to the connective tissue covering the keel bone. Implantation of the devices did not affect the behaviour of the birds and there were no pathological lesions associated with them up to four weeks later.

Evaluation of adhesives for hybrid microcircuit package sealing: K. L. Perkins, J. J. Licari and S. V. Caruso IEEE Trans. Components, Hybrids, Mfg Technol. Chmt-1, (4) 412 (December 1978)

Evaluation of adhesives for hybrid microcircuit package sealing: K. L. Perkins, J. J. Licari and S. V. Caruso IEEE Trans. Components, Hybrids, Mfg Technol. Chmt-1, (4) 412 (December 1978)

Contamination Control in Lead Bonding to Thick and Thin Films

Degraded wax residues from processing steps have been found to be a major source of contamination on beam lead devices for hybrid microcircuits. Two avenues of approach were used to solve bonding problems traced to this contamination: 1) a search was initiated for a more thermoxidatively stable and more easily removed wax, and 2) an effort was made to determine the level of cleanliness necessary for successful bonding and the most efficient method of attaining this level. A series of halocarbon waxes (polytrifluorochlorocthylenes) was found to be stable both chemically and thermally. The carbon contamination levels were decreased after improved solvent cleaning techniques and measured ~2 rim. This level compares with values as high as 9 nm after typical solvent cleaning. Plasma and ultraviolet cleaning both reduced carbon residues to 0.2-0.8 nm. Ball bonds made with weld forces of 1.0-1.5 N were successful on ultraviolet (UV) and plasma cleaned surfaces near 200°C and near 327°C for surfaces cleaned by improved solvent techniques. The beeswaxes presently used had adequate and better bondability than the more stable halocarbon waxes when only solvent cleaning was used and temperatures did not exceed 125°C to avoid charring.

Thick-film Technology: An Introduction to the Materials

The use of thick-film technology to manufacture electronic circuits and discrete passive components continues to grow at a rapid rate worldwide. When applied to hybrid microcircuits, it can be viewed as a means of packaging active devices, spanning the gap between monolithic integrated circuit chips and printed circuit boards with attached active and passive components. The strength of the thick-film approach is a consequence of function, size, and unit cost trade-offs; advances in materials have played a major role relative to each of these factors. Thick-film materials are developed to meet needs defined by electronic circuit design and process engineers. A general understanding of thick films is provided from a materials standpoint, particularly for the new engineer. Background is developed for a basic, yet simple, understanding of the components that make up resistor, conductor, and dielectric compositions, of processing, and of the properties of the final thick-film composite structures.

Detection of conductive condensates resulting from adhesive outgassing in hybrid microcircuits: B. L. Weigand, J. J. Licari and I. H. Pratt Proc. IEEE 28th Electron. Components Conf., Anaheim, 24–26 April 1978, p.217

Detection of conductive condensates resulting from adhesive outgassing in hybrid microcircuits: B. L. Weigand, J. J. Licari and I. H. Pratt Proc. IEEE 28th Electron. Components Conf., Anaheim, 24–26 April 1978, p.217

Some problems and possible solutions for hybrid microcircuit reliability

Thick film hybrid microcircuits developed for various telecommunications applications and made by various technologies have been examined by overstress testing and by failure analyses, which have yielded a number of promising results and revealed a number of deficiencies. Examples are presented of the poor reliability obtainable not only from low-cost plastic-coated hybrids but also from supposedly superior hermetically-sealed hybrids—degradation occurring because of moisture permeation or desorption, the evolution of deleterious vapours, bond failure due to inter-metallic reactions, and so on. Reliability problems of this sort are often encountered when the technologies or manufacturing standards are not directed towards high reliability applications, despite conformity to accepted quality standards, so demonstrating that approval of manufacturing capability does not necessarily provide reliability assurance. Nevertheless, the reliability prospects for hybrids are quite bright, because problems can and have been overcome — for example, that some circuits even in low-cost encapsulations can approach the highest reliability standards, that the long term stability of thick-film resistors can be better than 1%, that bonding problems can be obviated by using the right interconnection materials and that less hazardous adhesives are available for use in hermetic encapsulations. The observations show that while it cannot be claimed that hybrid technologies are inherently reliable, neither does it appear that the opposite is true — potentially high reliabilities being achievable by exercising intelligent choice.

Some problems and possible solutions for hybrid microcircuit reliability: F. N. Sinnadurai, K. J. Wilson and D. W. J. Brace. Microelectron J., 11, (1) 26 (1980)

Some problems and possible solutions for hybrid microcircuit reliability: F. N. Sinnadurai, K. J. Wilson and D. W. J. Brace. Microelectron J., 11, (1) 26 (1980)

A Technique for the Measurement of Hot Spots and Isotherm Profiles at the Surfaces of the Elements of Hybrid Microcircuits

A simple technique for measuring surface temperatures with high sensitivity and spatial resolution, which is particularly useful for examining temperature distributions of microcircuits, is described. The invention exploits the well-defined “Isotropic-point” transitions of nematic liquid crystals from optical birefringence to anisotropy, using a polarising microscope to detect temperatures in microscopic areas. Thus hot spots appear black against a bright background. The temperature sensitivity is better than 0.5℃ and the spatial resolution better than 5 microns. The technique has distinct advantages over alternative methods of measuring microcircuit temperatures. Examples of applications in support of design evaluation and fault diagnosis of monolithic circuits illustrate the benefits of visual information obtained. The ready application of the technique to the large planar areas of thick film resistors has enabled the location of hot spots – confirming their occurrence at the end of laser cuts – and the measurement of thermal resistances of resistors either singly or in arrays – showing that substantial heat conduction through the substrate can outweigh local non-uniformities in dissipation. Applications extend beyond the supportive role to reliability evaluation illustrated in this paper.

Some problems and possible solutions for hybrid microcircuit reliability: F. N. Sinnadurai, K. J. Wilson and D. W. J. Brace. Proc. Internepcon UK '79. p. 239, Brighton (16–18 October 1979)

Simplified methods for the analysis of socketed pile groups subject to negative skin friction are reported. In these methods, the piles are modelled using discrete elements with an axial mode of deformation. The soil behaviour is modelled using a hybrid approach in which the soil response at the individual piles is modelled using the subgrade reaction method while pile-soil-pile interaction is determined using elastic theory. The main difference between the methods lies in the manner in which pile-soil-pile interaction is determined. The accuracy of the methods is assessed by comprehensive comparisons with more rigorous theoretical solutions available. The study shows that: (a) the solutions obtained by the continuum model using Chan et al.'s solution are in close agreement with the rigorous solutions, (b) for practical pile groups, the layer model can give reasonable solutions provided the socketing is not too deep and (c) the continuum model using Mindlin's solution predicts reasonable downdrag forces but seriously under predict the pile head settlements.

Large Scale Digital Hybrid Microcircuits for New Military Systems

The packaging density of digital circuits can be significantly increased by assembling multiple MSI, LSI, and VLSI semiconductor chips in large hybrid microcircuits. The design, manufacturing, and productbility factors for these large multilayered thick film hybrid microcircuits are described. These factors include: manual and computer aided design, materials, substrate processing, assembly, testing, and environmental screening. Recent production experiences in manufacturing three unique microcircuits containing TTL, C-MOS, and ECL devices are discussed.

Bumped Tape Automated Bonding (BTAB) Practical Application Guidelines

A number of mass bonding techniques have been used to replace wire bonding in hybrid microcircuit (HM) fabrication, but none has approached universal acceptance. In recent years tape carrier technology, typically called tape automated bonding (TAB) has received considerable attention. A more recent development, bumped tape automated bonding (BTAB), maintains the advantages of conventional TAB, offers some unique features of its own, and can be quite compatible with conventional aluminum-metallized integrated circuit (lC) chips. The present status of BTAB technology from the standpoint of practical HM fabrication and performance is presented.

Screening procedure for adhesion degradation due to solder leaching in thick-film hybrid microcircuits: S. S. Leven Solid State Technology, p.39 (March 1977)

Screening procedure for adhesion degradation due to solder leaching in thick-film hybrid microcircuits: S. S. Leven Solid State Technology, p.39 (March 1977)

Application of tape automated bonding technology to hybrid microcircuits: Dr Rudolph, G. Oswald and W. R. de Miranda Solid State Technology, p.33 (March 1977)

Application of tape automated bonding technology to hybrid microcircuits: Dr Rudolph, G. Oswald and W. R. de Miranda Solid State Technology, p.33 (March 1977)

Evaluation of adhesives for hybrid microcircuit package sealing : K. L. Perkins, J. J. Licari and S.V. Caruso. IEEE Trans. Components, Hybrids, Mfg Technol. Chmt-1, (4) 412 (December 1978)

Evaluation of adhesives for hybrid microcircuit package sealing : K. L. Perkins, J. J. Licari and S.V. Caruso. IEEE Trans. Components, Hybrids, Mfg Technol. Chmt-1, (4) 412 (December 1978)

A closer look at hybrid microcircuit screening : W. K. Garrett. Proc. IEEE Reliab. Symp., Washington, D.C., 23–25 January 1979, p. 110

A closer look at hybrid microcircuit screening : W. K. Garrett. Proc. IEEE Reliab. Symp., Washington, D.C., 23–25 January 1979, p. 110

Internal Conformal Coatings for Microcircuits

Inadvertent inclusion of conductive particulate contaminants in sealed hybrid microcircuit packages often results in electrical failure of the device. Particles that escape detection by postsealing radiographic (X-ray) or particle impact noise analysis can be effectively immobilized by conformally coating the circuit with a thin resilient film of silicone, epoxy, or polyxylylene (parylene). The advantages and disadvantages of using each of these materials as a microcircuit coating are discussed, and a recommendation for the use of silicones is made, based on the objectives involved. Two silicone materials have been deposited on test structures. The methods for application of the materials are presented, including those aspects of the application process which are critical to the performance of the materials as coatings. An investigation of the two silicone materials has been conducted with respect to chemical and mechanical comparibility with hybrid circuit components and materials, chemical purity, outgassing characteristics, thermal expansion effects on wire bonds, and hybrid circuit rework and repair. The results of the initial portion of the coating evaluation phase are presented and polyxylylene (parylene) is included.

Aluminum Wire to Thick-Film Connections for High-Temperature Operation

Hybrid microcircuits in geothermal instrumentation must operate from room temperature to 300°C. Bond failure occurred during operation of initial geothermal circuits due to intermetallic growth at the aluminum wire-to-gold conductor interface. To remedy this problem, two wire bonding techniques have been qualified in high-temperature aging tests: 1) ultrasonic bonding of aluminum wire directly to modified fritless gold conductor inks (DuPont 9910, AVX 3520, and TFS A328) and 2) insertion of a I mil diffusion barrier pad between the thick film and the aluminum wire. Both systems allow 100-1000 h operation at 300°C. Three alloys of wire were tested: pure aluminum, aluminum with I percent silicon, and aluminum with 1 percent magnesium. The degradation rates differed greatly with pure aluminum being the least tolerant to temperature aging and wire with 1 percent silicon faring best. Because thick-film surfaces tend to be harder than thin-film surfaces, hardened aluminum wire (elongation 0.5 percent) formed bonds with less pad deformation and, consequently, with higher pull strengths than standard bonding wire (elongation 1-3 percent). Comparison of wire bonds aged at three temperatures (250, 300, and 350°C) demonstrated several orders of magnitude spread in degradation rates; for 1000-h bond lifetime, 300°C was found to be about the highest allowed operational temperature for direct bonding to gold. Disks of kovar and nickel of l-mil thickness and 30 mils diam were used as diffusion barriers between the gold and aluminum. Evaporated on one side of each disk was a 1 µm gold thin film for thermocompression bonding to the thick film; the other side received an evaporated aluminum film for wire bonding. Aging for 1000 h up to 350°C produced no increase in bond resistance for any of the three wire alloys tested. Some decrease in pull strength with time was noticed but was attributed to annealing of the wire.

Semiconductor memories packaged in hybrid microcircuits : L. Sutton. Proc. Electron. Components Conf. Arlington, Va., (May 16–18 1977). p. 10

Semiconductor memories packaged in hybrid microcircuits : L. Sutton. Proc. Electron. Components Conf. Arlington, Va., (May 16–18 1977). p. 10