NASA personnel from JPL, GSFC, GRC, HQ, LaRC, and JPL interacted with the the following speakers through VITS. Abstracts and videos of the talks follow.

• Electronic Packaging Technology for SiC based High Temperature Micro-systems
  Liangyu Chen, PhD
  NASA Glenn Research Center (GRC)   
• Known Problems with the Use of Pure Tin Coatings
  Henning Leidecker, PhD
  NASA Goddard Space Flight Center (GSFC)   
• Packaging and Reliability of Electronic Noses for Space Applications
  Rajeshuni Ramesham, PhD
  NASA Jet Propulsion Laboratory (JPL)   
• Kilowatt Diode Laser Array Performance
  Carl Magee, PhD
  NASA Langley Research Center (LaRC)

Electronic Packaging Technology for SiC based High Temperature Micro-systems
Liangyu Chen
NASA Glenn Research Center

Gary W. Hunter, Philip G. Neudeck
AYT

Gold thick-film metallization based electronic packaging components, which include electrical interconnection (thick film printed wires and thick film metallization based wire-bond) system and a conductive SiC die-attach scheme, have been validated for high temperature (up to 500 oC) chip level packaging. During a 1500-hour test in atmospheric oxygen with and without DC bias, the basic interconnection elements demonstrated low and relatively stable resistance in a temperature range from room temperature to 500oC. The die-attach scheme was successfully validated by testing a SiC high temperature diode, which was attached to a ceramic substrate using gold thick-film material as conductive bonding layer. The attached SiC diode was tested at 500 oC in oxidizing air for 1000 hours setting records of both high temperature electronic packaging and high temperature device testing. A brief discussion of the scope of high temperature electronic packaging program at NASA Glenn Research Center will also be covered.

Known Problems with the Use of Pure Tin Coatings
Henning Leidecker, PhD
NASA Goddard Space Flight Center

Pure tin coatings grow whiskers, sometimes promptly, sometimes after a delay of several years. These have shorted electrical circuits, introducing anomalies and even failures. The risk of anomalies and failures is increasing as the typical bus voltages and available currents decreases. Also, spacecraft are subject to the occurance of a whisker-induced vacuum metal arc which sustains hundreds of amperes, until there is fatal damage. Finally, operation at temperatures below about 20 °C allows the transformation of tin from its metallic phase into a semiconducting phase that is both brittle and relatively non-conducting.

Video

Successful development of an electronic nose requires a development of an array of sensors that are specific to the compounds of interest. Our main objective is to assess the reliability of packaged JPL developed and commercially available electronic noses to determine their utility as an air quality monitor in crew habitat on a spacecraft, International Space Station (ISS) like missions. This presentation covers on overview of the current status of e-nose packaging technology and reliability issues from commercial-off-the-shelf (COTS) e-noses to specific application and provides lessons learned in the past missions.

Video

Kilowatt Diode Laser Array Performance
Carl Magee, PhD
NASA Langley Research Center

In late 1962, the first demonstration of stimulated emission from GaAs homojunction (diffused) diode lasers (DLs) was reported by several laboratories in the scientific literature. These early DLs required operation at cryogenic temperatures since they exhibited threshold current densities (Jth) of >10,000 A/cm2---. Development of liquid epitaxy (LPE) growth technology permitted the introduction of AlGaAs alloys to be employed for improvement of DL designs. The first such design was the "single-heterojunction" (SH) structure. The SH design used resulted in the reduction of Jth to < 4KA/cm2--. The heterojunction design concept was further extended and resulted in a "double-heterojunction" (DH) structure. These DH AlGaAs lasers were capable of continuous wave (CW) operation at room temperature and could also be modulated at rates in the gigahertz range. These early DLs had outputs in the tens of milliwatt range and were used in initial fiber optic telecommunication experiments.

Many advances have occurred since these mid-1970's achievements. Improvements in understanding of device physics, materials quality requirements, growth technologies, processing, packaging, et cetera have yielded great gains in performance. These advances have led to the current production of linear diode arrays that emit quasi-continuous wave (QCW) powers in excess of 100 watts for a bar of ~ 1 centimeter width. Two-dimensional (2D) arrays fabricated from these linear arrays are capable of peak output powers of multiple kilowatts.

The impact of device design, materials growth, processing, and packaging upon performance of 2D kilowatt, diode laser will be presented. Also, proper application and operation of these high power devices will be discussed.

Video