Engineering topics

Gallagher, B. D.

Publications and source records attributed to Gallagher, B. D..

13 records

NASA NTRS1986

Thermally-Activated Metal-to-Glass Bonding

Hermetic seals formed easily by use of metallo-organic film. Metallo-organic film thermally bonded to glass and soldered or welded to form hermetic seal. Film applied as ink consisting of silver neodecanoate in xylene. Relative amounts of ingredients selected to obtain desired viscosity. Material applied by printing or even by scribing with pen. Sealing technique useful in making solar-cell modules, microelectronic packages, and other hermetic silicon devices.

Gallagher, B. D.↗

NASA NTRS1986

Metalization Patterns by Thermal Decomposition

Metal interconnection pattern deposited on integrated circuit or solar cell economically by thermal decomposition of metallo-organic compound. In proposed process beam from laser or quartz lamp swept over substrate in required metalization pattern; wherever beam impinges on substrate, radiant heat decomposes compound, depositing metal. Process requires less costly equipment and less time than conventional metalization. Process readily adaptable to very-large-scale integrated (VLSI) circuits.

Gallagher, B. D.↗

NASA NTRS1986

Low-pressure, chemical vapor deposition polysilicon

The low-pressure chemical vapor deposition (LPCVD) of polycrystalline silicon was investigted. The physical system was described, as was the controlling process parameters and requirements for producing films for use as an integral portion of the solar cell contact system.

Gallagher, B. D.↗

NASA NTRS1985

Increased voltage photovoltaic cell

A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

Ross, B.↗

NASA NTRS1985

Metallo-organic decomposition films

A summary of metallo-organic deposition (MOD) films for solar cells was presented. The MOD materials are metal ions compounded with organic radicals. The technology is evolving quickly for solar cell metallization. Silver compounds, especially silver neodecanoate, were developed which can be applied by thick-film screening, ink-jet printing, spin-on, spray, or dip methods. Some of the advantages of MOD are: high uniform metal content, lower firing temperatures, decomposition without leaving a carbon deposit or toxic materials, and a film that is stable under ambient conditions. Molecular design criteria were explained along with compounds formulated to date, and the accompanying reactions for these compounds. Phase stability and the other experimental and analytic results of MOD films were presented.

Gallagher, B. D.↗

NASA NTRS1985

Real-time SEM studies in controlled reactive atmospheres

A unique scanning electron accessory has been developed that allows the observation of specimens under partial pressures of any gas. The sample is placed in a metal support boat inside a special sample holder. The sample in the boat is imaged on a CRT and is simultaneously recorded on a videotape, allowing the reaction between the sample and the gas to be observed in real time. Sample changes can be seen continuously as the sample is being heated or cooled. This process allows the observation of material transformations such as phase changes as they happen. Temperatures as high as 1000 C have been used and are continuously monitored using a thermocouple with a digital display on the CRT and videotape. X-ray analyses can also be run before and after any reactions. In the study described here, thick-film screen-printing inks using molybdenum/tin compositions as a replacement for silver were developed to be used on terrestrial photovoltaic cells. Pieces were placed on the sample stage and heated in both O2 and H2 atmospheres. The results were used to determine the most effective frits to be used in the thick-film inks.

Gallagher, B. D.↗

NASA NTRS1983

Module degradation catalyzed by metal-encapsulation reactions

Four major properties are considered to be relevant in determining service life of a photovoltaic module: (1) Mechanical: creep resistance, modulus, tensile strength; (2) Optical: integrated transmission at 0.4 to 1.1 m wavelength; (3) Chemical: inertness with respect to metals and other components, retention of stabilizers, etc. and (4) Electrical; maintaining effective isolation of conductive components. These properties were measured after exposing polymer specimens to three types of accelerated stress: thermal, ultraviolet radiation and metal catalysts. These conditions give rise to a large number of complex interrelated free-radical reactions that result in the deterioration of polymeric materials.

Gallagher, B. D.↗

NASA NTRS1982

Status of SEMI's solar-grade substrate standards

A proposal for a standard specifications listing covering requirements for silicon wafers used in solar cell manufacturing is outlined. The specific contents of the general requirements specifications include: ordering information; dimensions and permissible variations; material and manufacture; physical parameters; sampling; test methods; certification; and packaging and marking.

Gallagher, B. D.↗

NASA NTRS1981

Technology transfer - LSA project to industry

Program goals, procedural steps, and examples of different situations encountered in the Low-cost Solar Array (LSA) project managed at the Jet Propulsion Laboratory in conjunction with industrial contractors are outlined. The project is intended to result in the production-ready status of photovoltaic panels which produce power at $.70/peak W by 1986. The first phase of the program identified materials and processes which were promising for further development. Phase II served to correct steps and materials which did not work and were important to the array processing. The third phase will bring the processes to technical readiness by demonstration of successful fabrication of modules at a scale which can be increased to commercial production. An information exchange is ongoing between manufacturers and the JPL to alter specific steps which yield results which vary from those found in the laboratory when transferred to the factory.

Gallagher, B. D.↗

NASA NTRS1980

Low-cost production of solar-cell panels

Large-scale production model combines most modern manufacturing techniques to produce silicon-solar-cell panels of low costs by 1982. Model proposes facility capable of operating around the clock with annual production capacity of 20 W of solar cell panels.

Bickler, D. B.↗

NASA NTRS1980

Solar cells and modules from dentritic web silicon

Some of the noteworthy features of the processes developed in the fabrication of solar cell modules are the handling of long lengths of web, the use of cost effective dip coating of photoresist and antireflection coatings, selective electroplating of the grid pattern and ultrasonic bonding of the cell interconnect. Data on the cells is obtained by means of dark I-V analysis and deep level transient spectroscopy. A histogram of over 100 dentritic web solar cells fabricated in a number of runs using different web crystals shows an average efficiency of over 13%, with some efficiencies running above 15%. Lower cell efficiency is generally associated with low minority carrier time due to recombination centers sometimes present in the bulk silicon. A cost analysis of the process sequence using a 25 MW production line indicates a selling price of $0.75/peak watt in 1986. It is concluded that the efficiency of dentritic web cells approaches that of float zone silicon cells, reduced somewhat by the lower bulk lifetime of the former.

Campbell, R. B.↗

NASA NTRS1978

Vacuum soldering a metalized ceramic to a metal carrier

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.

Gallagher, B. D.↗

NASA NTRS1978

A candidate low-cost processing sequence for terrestrial silicon solar cell panel

Manufacturing sequence for silicon solar cells using Czochralsky crystal growing techniques in order to produce at a rate of 20 MW per year on a 24-hour per day basis is discussed. Cost analysis of the manufacturing is presented and consideration is given to the following processing decision categories of the manufacturing of an unencapsulated solar cell from a silicon wafer: (1) treatment of the optical surface; (2) formation of the junction(s); and (3) metallization of electrical collectors. The manufacturing of encapsulated solar modules from solar cells, using two glass plates, a low iron front surface, and a standard float glass back plate, is described. Totaling the three major activities of wafer making, cell manufacturing, and module fabrication, the resulting contribution to module price will be 1.945 $/watt.

Bickler, D. B.↗