Scientific and Technical Aerospace Reports Volume 38 July 28, 2000

20000067664 Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA USA
Different Approaches for Ensuring Performance/Reliability of Plastic Encapsulated Microcircuits (PEMs) in Space
Applications
Gerke, R. David, Jet Propulsion Lab., California Inst. of Tech., USA; Sandor, Mike, Jet Propulsion Lab., California Inst. of Tech.,
USA; Agarwal, Shri, Jet Propulsion Lab., California Inst. of Tech., USA; Moor, Andrew F., Johns Hopkins Univ., USA; Cooper,
Kim A., Johns Hopkins Univ., USA; [2000]; 8p; In English; No Copyright; Avail: CASI; A02, Hardcopy; A01, Microfiche
Engineers within the commercial and aerospace industries are using trade-off and risk analysis to aid in reducing spacecraft
system cost while increasing performance and maintaining high reliability. In many cases, Commercial Off-The-Shelf (COTS)
components, which include Plastic Encapsulated Microcircuits (PEMs), are candidate packaging technologies for spacecrafts due
to their lower cost, lower weight and enhanced functionality. Establishing and implementing a parts program that effectively and
reliably makes use of these potentially less reliable, but state-of-the-art devices, has become a significant portion of the job for
the parts engineer. Assembling a reliable high performance electronic system, which includes COTS components, requires that
the end user assume a risk. to minimize the risk involved, companies have developed methodologies by which they use accelerated
stress testing to assess the product and reduce the risk involved to the total system. Currently, there are no industry standard procedures
for accomplishing this risk mitigation. This paper will present the approaches for reducing the risk of using PEMs devices
in space flight systems as developed by two independent Laboratories. The JPL procedure involves primarily a tailored screening
with accelerated stress philosophy while the APL procedure is primarily, a lot qualification procedure. Both Laboratories successfully
have reduced the risk of using the particular devices for their respective systems and mission requirements.
Author
Aerospace Industry; Encapsulated Microcircuits; Reliability; Technology Utilization; Plastics; NASA Space Programs
20000067674 Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA USA
Effects of Hydrogen on Tantalum Nitride Resistors
Weiler, James, Jet Propulsion Lab., California Inst. of Tech., USA; [2000]; 1p; In English; No Copyright; Avail: Issuing Activity;
Abstract Only
In this paper we report on observations of degradation of thin film Tantalum Nitride chip resistors in a hermetically sealed
hybrid. The observations have been attributed to the reaction of residual Palladium with desorbed Hydrogen on the surface of the
resistor film. Hydrogen gas has been observed to desorb from various sources within the sealed hybrid as a result of temperature
elevation. The hydrogen gas has been reported to undergo a reaction with elements such as Platinum and Palladium causing device
degradation in Gallium Arsenide Field Effect Transistors. The experimental procedures and data relating to this observation along
with a discussion of available risk mitigation techniques will be presented.
Author
Hydrogen; Tantalum Nitrides; Resistors; Degradation; Thin Films
34
FLUID MECHANICS AND THERMODYNAMICS
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20000062307 Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA USA
A Priori Subgrid Scale Modeling for a Droplet Laden Temporal Mixing Layer
Okongo, Nora, Jet Propulsion Lab., California Inst. of Tech., USA; Bellan, Josette, Jet Propulsion Lab., California Inst. of Tech.,
USA; [2000]; 8p; In English; No Copyright; Avail: CASI; A02, Hardcopy; A01, Microfiche
Subgrid analysis of a transitional temporal mixing layer with evaporating droplets has been performed using a direct numerical
simulation (DNS) database. The DNS is for a Reynolds number (based on initial vorticity thickness) of 600, with droplet mass
loading of 0.2. The gas phase is computed using a Eulerian formulation, with Lagrangian droplet tracking. Since Large Eddy Simulation
(LES) of this flow requires the computation of unfiltered gas-phase variables at droplet locations from filtered gas-phase
variables at the grid points, it is proposed to model these by assuming the gas-phase variables to be given by the filtered variables
plus a correction based on the filtered standard deviation, which can be computed from the sub-grid scale (SGS) standard deviation.
This model predicts unfiltered variables at droplet locations better than simply interpolating the filtered variables. Three
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