Volume 9, Number 3 • May/June 2001

Technology Opportunity Showcase highlights some unique technologies that NASA has developed and which we believe have strong potential for commercial application. While the descriptions provided here are brief, they should provide enough information to communicate the potential applications of the technology.or more detailed information, contact the person listed. Please mention that you read about it in Innovation

Packaging Technology Operable to 500 Degrees Celsius for High-Temperature Microsystems

Researchers in the Instrumentation and Controls Division of NASA Glenn Research Center (GRC) have developed in-house a high-temperature, electronic packaging technology for operation up to 500 degrees Celsius. The Sensors and Electronic Technology Branch of GRC is seeking potential industry partners for cooperative application, development and commercialization of this technology for high-temperature electronics, sensors and MEMS. This advanced packaging technology extends the maximum operation temperature of packaging systems to 500 degrees Celsius, which, though significantly higher than the high-temperature limit of the packaging technology currently available on the market, is necessary for packaging for high-temperature electronics and devices such as silicon carbide-based (SiC) electronics for signal processing and communication; high-temperature electronic sensors for gas, chemical and emission sensing, as well as for fire and leak detection; and harsh environment-operable microsystems for control and actuation.

Commercialization of this packaging technology will expedite the infusion of high-temperature electronic sensors and devices into space, aeronautic and civil applications. Various high-temperature SiC electronic devices and sensors have recently been demonstrated to be operable at high temperatures, but only in the probe station environment, because the essential packaging technology suitable for high-temperature operation (500 degrees Celsius and above) has not been commercially available. Therefore, high-temperature packaging technology is an immediate need for in situ characterization and testing and commercialization of SiC-based high-temperature sensors, electronics and microsystems.

All the materials and processes for basic packaging components are innovative for high-temperature and harsh environment operation.

The prototype electronic package survived a soak test at 500 degrees Celsius in air. Packaging components tested include internal wire and wire bonds, external lead bonds and SiC (diode) chip die-attach. One of the test loops was composed of printed wire, wire bonds and lead bonds subjected to a DC current load at 500 degrees Celsius. As desired, the electrical resistances of the test loops (of thick-film printed wires, wire bond and lead bonds) soaked at 500 degrees Celsius with or without current load were low and very stable. Also as expected, the electrical isolation impedance between printed wires that were not electrically jointed by a wire bond remained high during and after the 500 degree Celsius soak test. The characterization of the attached SiC die (diode) showed low resistance of backside electrical contact through die-attach at both room temperature and 500 degrees Celsius. This packaging research effort is currently supported by GRC’s Glennan Microsystems Initiative (GMI) and the NASA Electronic Parts and Packaging (NEPP) Program.

For more information, contact Dr. Jih-Fen Lei, 216/433-6328, Jih–Fen.Lei@grc.nasa.gov. Please mention you read about it in Innovation.

Low-Cost Brushless DC Motor Rate Sensor

NASA Marshall Space Flight Center is seeking commercial partners to license or jointly develop new brushless DC motor rate sensor technology that offers a promising alternative to brush tachometers, resolvers, encoders and other rotation sensors. This direction-sensitive, reliable, low-cost device is ideal for numerous commercial applications. The device is long-lasting, extremely reliable and inexpensive, with a simple design and quiet operation. Potential commercial applications include use in antilock brake systems, industrial robotics, medical and other scanning devices, power generators and navigation systems.

The sensor addresses the drawbacks associated with other rotation sensor technologies. The mechanical brushes on brush-type tachometers produce electrical arcing and wear out relatively quickly, requiring that the devices be replaced. Although prior technology using brushless DC motors/tachometers addresses this issue, most alternatives must be used in conjunction with position sensors and require that wires be added to excite the position sensor. Resolver-developed rate sensors also require wires for an excitation signal. Additionally, they usually require differentiation, which is quite noisy, to produce rate information. Finally, encoder-developed rate sensors’ accuracy degrades at low rates because of the discrete nature of encoder outputs.

NASA’s technology is a brushless, direction-sensitive, motor-based rate sensor that produces a DC output that is proportional to the rotation rate of a shaft. This new device is inherently linear and produces accurate rotation rate signals. The instrument is a stand-alone sensor, requiring neither electrical excitation nor an additional position sensor. Furthermore, this direction-sensitive device has a simple design that requires no mechanical brushes.

A patent application has been filed for this technology, and development and testing are continuing. NASA invites commercial companies to consider licensing or jointly developing this technology. Opportunities exist for nonexclusive and exclusive field-of-use licensing.

For more information, contact Rhonda Thompson of NASA Marshall Space Flight Center’s Technology Transfer Office, 256/544-4329, rhonda.c.thompson@msfc.nasa.gov. Please mention you read about it in Innovation.