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Assessment of micropackaged integrated circuits in high reliability applications
170
World Abstracts on Microelectronics and Reliability
Thus we have recommended that DGR156 inlay material be substituted for the Co hardened Au finish used in the PCB family of connector codes. This will result in considerable cost savings without significant decrease in reliability.
The intermittent multi-layer board--a case history. TONY D. Cox and WILLIAM G. KINDIG. Proc. A. Reliab. Maintainab. Symp. 435 (1983). An intermittent failure is typically a failure which prevents system operation at the time of its occurrence but will clear itself within a few seconds or go away upon retest/troubleshooting. This paper discusses a case history of the troublesome intermittent condition which was experienced on multilayer boards used on several military and commercial flight control programs. The multilayer boards that are addressed are typically 10-layer boards constructed of glass-epoxy flame-retardant material (Type GF). The first and last internal layers are two-ounce copper layers. The external layers and the remaining internal layers are oneounce copper layers. Failure mechanisms and failure rates of the multilayer boards are identified based on reliability development testing, flight tests, and specially designed experiments. In addition, the tests commonly used for acceptance screening are discussed and evaluated. These evaluations should help interested parties to improve quality and increase productivity.
Semi-custom I.e.'s--reliable and productive. KEITH BEASLEY. Proc. A. Reliab. Maintainab. Syrup. 469 (1983). To reduce the time and cost of designing advanced microelectronic devices, a recent move has been to Semi-custom methods, where standard circuit elements or "cells" are combined to meet specific customer requirements. Since design and m a n u facturing methods (e.g. Computer Aided Design) are standard for a range of devices, productivity and reliability are comparable to "standard parts" rather than full custom methods. Semi-custom devices, as with other advanced Large Scale integration (LSI) devices, rely greatly on decreasing geometries of circuit elements on the silicon chip to give the greater complexity. To reduce chip size and allow the "gate array" structure to be used, two (or more) layers of metal separated by an insulating layer of polyimide have proved to be highly reliable for use in Semi-custom I.C.'s. The reliability model given in M I L H D B K 217 gives a reasonably good prediction as to trends in reliability as LSI advances, with the possible exception of the learning factor/ZL. AS computers are used more and more during design and test of I.C.'s, so the quality and reliability of devices depend heavily on the quality of the software used. Emphasis is given in particular to the procedures for controlling computer programs and libraries.
A two-level sparing approach for plug-in modules. F. J. O'NEIL. Proc. A. Reliab. Maintainab. Syrup. 388 (1983). The operational sparing environment for telephone Central Offices (COs) can be viewed as a two-level support system where one central stocking point on the upper level serves many locations on the lower level with spare plug-in units on demand. A methodology is developed to determine optimal sparing requirements for all locations, including the upperlevel location, that satisfies a "spares availability objective" at the lower-level locations. A two-level model is used to define this single item/many locations sparing problem and a novel approximate solution technique is presented. Optimality is defined as m i n i m u m spares requirements for the entire two-level support system.
Assessments of micropackaged integrated circuits in high reliability applications. N. SINNADURAI and D. ROBERTS. Microeleetron. J. 14 (2), 5 (1983). An earlier study showed that plastic coatings could provide adequate protection of microcircuits for long life applications. This promise that low
cost techniques could be used in high reliability telecomms applications encouraged further investigations of micropackaged integrated circuits. Transistor arrays and operational amplifiers typical of those required for hybrids in telecomms applications were used as the test vehicles. The micropackages included SO packages supplied as standard components and leadless ceramic and epoxy-glass chip carriers coated with the more promising plastics. These micropackaged ICs have been exposed to a range of damp heat stress in non-saturating autoclaves and thermal overstress in ovens for extended durations representing operation for more than 20yr in telecomms environments, and the failures and survivors were then analysed in detail. Very promising results have been obtained, showing that the majority of the micropackaged lCs had reliabilities that would survive 20 yr lifetimes, and some in particular Ti-PtAu metallized, silicon nitride passivated ICs in plastic-coated and lidded epoxy-glass chip carriers would comfortably exceed this lifetime. The results are very encouraging indeed for the prospects of low-cost, plastic micropackaging for high reliability applications.
A study of some factors influencing the wear resistance of lubricated gold contacts. LARS-GUNNAR LILJESTRAND. IEEE Trans. Components Hybrids nffy Technol. C H M T - 6 (1), 108 (1983). Friction, and wear tests have been performed on goldplated (2 3 gm thick) contacts lubricated with three different lubricants: polyphenyl ether, perfluorinated polyether, and microcrystalline wax. The lubricating properties were studied on gold coatings with a hardness varying between 80 and 200 Vicker's hardness number (VHN) and surface roughness between 0.05 and 0.15 gm centre line average (CLA). The lubricants were tested both in unaged and aged conditions. The wear tests were chosen to simulate the action of different types of electrical contacts. The wear was estimated from observations in scanning electron microscopy (SEM) and worn surfaces were analysed with energy dispersive X-ray analysis (EDAX) and Auger electron spectroscopy (AES). At low numbers of cycles (l 2.5N load), wear could be correlated with the viscosity of the lubricants, while for longer runs (20,000 cycles) the creep rate of the lubricants becomes important. At 100,000 cycles or more (0.25 N load) the gold coatings on a number of specimens were worn through either due to depletion of the lubricant, or when lubricant was still present in the wear track, simply due to the repeated minor wear, which occurs for each cycle during boundary lubrication conditions. Contact resistance, viscosity and creep rate were measured for the three lubricants both i n the initial condition and after prolonged exposure at elevated temperature and in an SO2 atmosphere. The results are discussed in terms of practical recommendations for use of different lubricants on various types of separable electrical contacts.
Reliability of medium-voltage vacuum power circuit-breakers. CHARLES R. HEISING. IEEE Trans. Reliab. R-32 (1), 3 (1983). A medium-voltage vacuum power circuit-breaker is used as an example of how a manufacturer can reduce the failure rate by 75 '~o and reduce the maintenance costs by at least 73 o . This required the expenditure of significant additional money and resources by the manufacturer. Questions are posed to users of circuit breakers to determine if this is what they wish to motivate a manufacturer to do; and if so, how this can be implemented in the market place.
Assuring VLSI quality and reliability with test patterns. WALTER B. ADELMAN.Proc. A. Reliab. Maintainab. Symp. 465 (1983). This paper discusses a means of employing test pattern data derived from each VLSI process lot, in conjunction with an established data base, as a condition of lot acceptance. It is proposed that these methods, when fully developed, will enable low cost and efficient control of
World Abstracts on Microelectronics and Reliability
Thus we have recommended that DGR156 inlay material be substituted for the Co hardened Au finish used in the PCB family of connector codes. This will result in considerable cost savings without significant decrease in reliability.
The intermittent multi-layer board--a case history. TONY D. Cox and WILLIAM G. KINDIG. Proc. A. Reliab. Maintainab. Symp. 435 (1983). An intermittent failure is typically a failure which prevents system operation at the time of its occurrence but will clear itself within a few seconds or go away upon retest/troubleshooting. This paper discusses a case history of the troublesome intermittent condition which was experienced on multilayer boards used on several military and commercial flight control programs. The multilayer boards that are addressed are typically 10-layer boards constructed of glass-epoxy flame-retardant material (Type GF). The first and last internal layers are two-ounce copper layers. The external layers and the remaining internal layers are oneounce copper layers. Failure mechanisms and failure rates of the multilayer boards are identified based on reliability development testing, flight tests, and specially designed experiments. In addition, the tests commonly used for acceptance screening are discussed and evaluated. These evaluations should help interested parties to improve quality and increase productivity.
Semi-custom I.e.'s--reliable and productive. KEITH BEASLEY. Proc. A. Reliab. Maintainab. Syrup. 469 (1983). To reduce the time and cost of designing advanced microelectronic devices, a recent move has been to Semi-custom methods, where standard circuit elements or "cells" are combined to meet specific customer requirements. Since design and m a n u facturing methods (e.g. Computer Aided Design) are standard for a range of devices, productivity and reliability are comparable to "standard parts" rather than full custom methods. Semi-custom devices, as with other advanced Large Scale integration (LSI) devices, rely greatly on decreasing geometries of circuit elements on the silicon chip to give the greater complexity. To reduce chip size and allow the "gate array" structure to be used, two (or more) layers of metal separated by an insulating layer of polyimide have proved to be highly reliable for use in Semi-custom I.C.'s. The reliability model given in M I L H D B K 217 gives a reasonably good prediction as to trends in reliability as LSI advances, with the possible exception of the learning factor/ZL. AS computers are used more and more during design and test of I.C.'s, so the quality and reliability of devices depend heavily on the quality of the software used. Emphasis is given in particular to the procedures for controlling computer programs and libraries.
A two-level sparing approach for plug-in modules. F. J. O'NEIL. Proc. A. Reliab. Maintainab. Syrup. 388 (1983). The operational sparing environment for telephone Central Offices (COs) can be viewed as a two-level support system where one central stocking point on the upper level serves many locations on the lower level with spare plug-in units on demand. A methodology is developed to determine optimal sparing requirements for all locations, including the upperlevel location, that satisfies a "spares availability objective" at the lower-level locations. A two-level model is used to define this single item/many locations sparing problem and a novel approximate solution technique is presented. Optimality is defined as m i n i m u m spares requirements for the entire two-level support system.
Assessments of micropackaged integrated circuits in high reliability applications. N. SINNADURAI and D. ROBERTS. Microeleetron. J. 14 (2), 5 (1983). An earlier study showed that plastic coatings could provide adequate protection of microcircuits for long life applications. This promise that low
cost techniques could be used in high reliability telecomms applications encouraged further investigations of micropackaged integrated circuits. Transistor arrays and operational amplifiers typical of those required for hybrids in telecomms applications were used as the test vehicles. The micropackages included SO packages supplied as standard components and leadless ceramic and epoxy-glass chip carriers coated with the more promising plastics. These micropackaged ICs have been exposed to a range of damp heat stress in non-saturating autoclaves and thermal overstress in ovens for extended durations representing operation for more than 20yr in telecomms environments, and the failures and survivors were then analysed in detail. Very promising results have been obtained, showing that the majority of the micropackaged lCs had reliabilities that would survive 20 yr lifetimes, and some in particular Ti-PtAu metallized, silicon nitride passivated ICs in plastic-coated and lidded epoxy-glass chip carriers would comfortably exceed this lifetime. The results are very encouraging indeed for the prospects of low-cost, plastic micropackaging for high reliability applications.
A study of some factors influencing the wear resistance of lubricated gold contacts. LARS-GUNNAR LILJESTRAND. IEEE Trans. Components Hybrids nffy Technol. C H M T - 6 (1), 108 (1983). Friction, and wear tests have been performed on goldplated (2 3 gm thick) contacts lubricated with three different lubricants: polyphenyl ether, perfluorinated polyether, and microcrystalline wax. The lubricating properties were studied on gold coatings with a hardness varying between 80 and 200 Vicker's hardness number (VHN) and surface roughness between 0.05 and 0.15 gm centre line average (CLA). The lubricants were tested both in unaged and aged conditions. The wear tests were chosen to simulate the action of different types of electrical contacts. The wear was estimated from observations in scanning electron microscopy (SEM) and worn surfaces were analysed with energy dispersive X-ray analysis (EDAX) and Auger electron spectroscopy (AES). At low numbers of cycles (l 2.5N load), wear could be correlated with the viscosity of the lubricants, while for longer runs (20,000 cycles) the creep rate of the lubricants becomes important. At 100,000 cycles or more (0.25 N load) the gold coatings on a number of specimens were worn through either due to depletion of the lubricant, or when lubricant was still present in the wear track, simply due to the repeated minor wear, which occurs for each cycle during boundary lubrication conditions. Contact resistance, viscosity and creep rate were measured for the three lubricants both i n the initial condition and after prolonged exposure at elevated temperature and in an SO2 atmosphere. The results are discussed in terms of practical recommendations for use of different lubricants on various types of separable electrical contacts.
Reliability of medium-voltage vacuum power circuit-breakers. CHARLES R. HEISING. IEEE Trans. Reliab. R-32 (1), 3 (1983). A medium-voltage vacuum power circuit-breaker is used as an example of how a manufacturer can reduce the failure rate by 75 '~o and reduce the maintenance costs by at least 73 o . This required the expenditure of significant additional money and resources by the manufacturer. Questions are posed to users of circuit breakers to determine if this is what they wish to motivate a manufacturer to do; and if so, how this can be implemented in the market place.
Assuring VLSI quality and reliability with test patterns. WALTER B. ADELMAN.Proc. A. Reliab. Maintainab. Symp. 465 (1983). This paper discusses a means of employing test pattern data derived from each VLSI process lot, in conjunction with an established data base, as a condition of lot acceptance. It is proposed that these methods, when fully developed, will enable low cost and efficient control of