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Using vacuum-soldering method, attachments that are 85 to 95 percent void free can be made. Method is useful for various large scale substrate attachment processes in microelectronic industry.
This paper presents data that has been generated within NASA, especially the Marshall Space Flight Center, concerning several failure mechanisms that have occurred with microelectronic packages. The types of packages that will be discussed are primarily flat packs with 14-24 exit leads that are composed of Kovar electro-deposited nickel and finally gold plated.
The trend toward smaller and lighter electronic packages was examined. It is suggested that electronic packaging engineers and microelectronic designers closely associate and give full attention to optimization of both disciplines on all product lines. Extensive research and development work underway to explore innovative ideas and make new inroads into the technology base, is expected to satisfy the demands of the 1980's.
A rotor mounted flight instrumentation system developed for helicopter rotor blade research is described. The system utilizes high speed digital techniques to acquire research data from miniature pressure transducers on advanced rotor airfoils which are flight tested on an AH-1G helicopter. The system employs microelectronic pulse code modulation (PCM) multiplexer digitizer stations located remotely on the blade and in a hub mounted metal canister. As many as 25 sensors can be remotely digitized by a 2.5 mm thick electronics package mounted on the blade near the tip to reduce blade wiring. The electronics contained in the canister digitizes up to 16 sensors, formats these data with serial PCM data from the remote stations, and transmits the data from the canister which is above the plane of the rotor. Data are transmitted over an RF link to the ground for real time monitoring and to the helicopter fuselage for tape recording. The complete system is powered by batteries located in the canister and requires no slip rings on the rotor shaft.
A unique miniature pressure sensor system consisting of an array of fifty integrated sensor pressure transducers with integral electronic logic and switching is described. Solid state processing of the piezoresistive array is combined with hybrid microelectronics to produce a very small, dense (80 cc displacement), high reliability pressure measuring system. Application to high speed data acquisition, energy conservation in wind tunnels and flight test is discussed. Test data are presented typifying system performance.
The appearance of nonmetallic structural materials and microelectronics in aircraft design has resulted in a need for better knowledge of hazardous environments such as lightning and the effects these environments have on the aircraft. This feasibility study was performed to determine the lightning parameters in the greatest need of clarification and the performance requirements of equipment necessary to sense and record these parameters on an instrumented flight research aircraft. It was found that electric field rate of change, lightning currents, and induced voltages in aircraft wiring are the parameters of greatest importance. Flat-plate electric field sensors and resistive current shunts are proposed for electric field and current sensors, to provide direct measurements of these parameters. Six bit analog-to-digital signal conversion at a 5 nanosecond sampling rate, short-term storage of 85000 bits and long term storage of 5 x 10 to the 7th power bits of electric field, current and induced voltage data on the airplane are proposed, with readout and further analysis to be accomplished on the ground. A NASA F-106B was found to be suitable for use as the research aircraft because it has a minimum number of possible lightning attachment points, space for the necessary instrumentation, and appears to meet operational requirements. Safety considerations are also presented.
A rotor-blade-mounted telemetry instrumentation system developed and used in flight tests by the NASA/Langley Research Center is described. The system uses high-speed digital techniques to acquire research data from miniature pressure transducers on advanced rotor airfoils which are flight tested using an AH-1G helicopter. The system employs microelectronic PCM multiplexer-digitizer stations located remotely on the blade and in a hub-mounted metal canister. The electronics contained in the canister digitizes up to 16 sensors, formats this data with serial PCM data from the remote stations, and transmits the data from the canister which is above the plane of the rotor. Data is transmitted over an RF link to the ground for real-time monitoring and to the helicopter fuselage for tape recording.
The design and performance of ambient temperature secondary cells based on the titanium disulfide cathode are discussed. These limited performance products were developed for microelectronic applications such as solar rechargeable watches and clocks which require low drain rate and do not require many deep cycles.
The research facilities of the Mississippi State University devoted to microelectronics are described. The fabrication and processing capabilities, computer aided design, and experimental evaluation capabilities are discussed.
The influence of chemical and particulate contamination upon the reliability and service life of hybrid microelectronic systems is documented. Several coating systems used include the parylene and Dow Corning silicone (DC90-711). These passivating coatings have potential for decreasing the degradation caused by particulate contaminants in hybrid systems as well as the possible deleterious effect of trapping chemical contaminants which have long term degrading influences upon the performance of the system. The reliability of a representative hybrid microcircuit is enhanced by the coating process.
NASA is examining the merits of a significant expansion of its avionics, controls, and human factors technology program for the 1980's. The rationale for an expanded program is related to two factors. One factor is related to a utilization of recent and anticipated significant advances in microelectronics. The second factor is the need to develop new concepts in avionics and control systems for more efficient aircraft operation and better utilization of extremely limited airport capacity. Substantial benefits could be realized in three major categories, including improved aircraft efficiency, improved flight operations, and improved/extended operational capability. The NASA Avionics, Controls, and Human Factors Technology Plan is the report of a task force of agency personnel working in close cooperation with industry, DOD, and FAA. Attention is given to the NASA role, aircraft controls, crew station technology, flight management, integration and interfacing, commercial transports, general aviation, rotorcraft, V/STOL, and high performance aircraft.
The processing of wafer devices to form multilevel interconnects for microelectronic circuits is described. The method is directed to performing the sequential steps of etching the via, removing the photo resist pattern, back sputtering the entire wafer surface and depositing the next layer of interconnect material under common vacuum conditions without exposure to atmospheric conditions. Apparatus for performing the method includes a vacuum system having a vacuum chamber in which wafers are processed on rotating turntables. The vacuum chamber is provided with an RF sputtering system and a DC magnetron sputtering system. A gas inlet is provided in the chamber for the introduction of various gases to the vacuum chamber and the creation of various gas plasma during the sputtering steps.
Recently two independent applications have emerged for highly radiation-sensitive polymers: as resists for production of microelectronic circuitry and as materials to record the tracks of energetic nuclear particles. The relief images used for masking in resist materials are generated by radiation-induced differential dissolution rates, whereas the techniques used in recording nuclear particle tracks employ differential etching processes, that is, development by a chemical etchant that actually degrades the polymer. It is found that the sensitivity of materials to these very different processes is related to their gamma-ray scission efficiency. This correlation provides a predictive capability.
In order to achieve the full sensitivity required for future space astronomy applications, IR detector systems will have to be cooled to 0.1 K or less. The feasibility of such cryocooling has been demonstrated for the established laboratory technique of adiabatic demagnetization, and it has been shown that bolometers made from compensated silicon, with ion-implanted contacts, come close to calculated ultimate performance limits. Unlike bolometers, silicon and germanium photoconductors are highly wavelength-dependent. Useful wavelengths are presented for the most promising photodetectors based on these materials. It is noted that, as the relevant microelectronic technology advances, array detectors in the near-IR may be expected to approach the size and performance of large, intrinsic silicon CCD arrays now available for optical wavelengths.
Microelectronic test chips contain a number of test structures that are used for a variety of purposes in fabricating integrated circuits. For convenience, their use is divided into six groups: layout-rule evaluating, process-parameter extraction, device-parameter extraction, circuit-parameter extraction, initial-fabrication failure analysis, and reliability failure analysis. A given test structure can be used to gather information in a number of these groups. Examples are given here of the kinds of parameters that can be obtained in each of these groups. A table is included summarizing various device failures common to bulk CMOS and indicating failure mechanisms appearing after wafer fabrication and after stress.
The strength of the interface between metals and aluminum oxide is an important factor in the successful operation of devices found throughout modern technology. One finds the interface in machine tools, jet engines, and microelectronic integrated circuits. The strength of the interface, however, should be strong or weak depending on the application. The diverse technological demands have led to some general ideas concerning the origin of the interfacial strength, and have stimulated fundamental research on the problem. Present status of our understanding of the source of the strength of the metal - aluminum oxide interface in terms of interatomic bonds are reviewed. Some future directions for research are suggested.
Improved qualification standards and test procedures for adhesives used in microelectronic packaging are developed. The test methods in specification for the Selection and Use of Organic Adhesives in Hybrid Microcircuits are reevaluated versus industry and government requirements. Four electrically insulative and four electrically conductive adhesives used in the assembly of hybrid microcircuits are selected to evaluate the proposed revised test methods. An estimate of the cost to perform qualification testing of an adhesive to the requirements of the revised specification is also prepared.
An assessment is made of the development possibilities of aerospace vehicle materials and structures, propulsion, avionics, configurations, computerized simulation, and operational capabilities. The supersonic transports envisioned for the 21st century would incorporate advanced, high temperature material structural design techniques, and a variable-cycle engine technology capable of a 40 percent increase in cruise efficiency over current systems, combined with low takeoff noise and efficient subsonic operation. This technology, as well as that of tilt-rotor VTOL aircraft which will be able to cruise at speeds comparable to those of present fixed-wing aircraft, are directly applicable to military systems. The impact of microelectronics and computer technologies on both avionics and the computational simulation of three-dimensional aerodynamic characteristics are also noted as important prospective developments.