Power Transistor Reliability Investigation.
Final technical rept. 8 Jan 73-28 Feb 75,
RCA MISSILE AND SURFACE RADAR DIV MOORESTOWN N J
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The objectives of the investigation were to evaluate the reliability of an existing L-band power transistor, the RCA TA 8694 overlay transistor, introduce the indicated design changes to enhance the reliability, and subsequently evaluate the improved device. The evaluation included RF operation in normal circuits with pulsed waveforms at high temperatures to accelerate failures. The TA 8694 was found to fail predominantly due to metal restructuring due to the thermal cycling caused by the pulsed operation. The principal redesign measure was to change the metal system from aluminum to gold, although internal matching elements were also introduced. The new design, the TA 8777 exhibited no evidence of metal or other pellet failures. The predominant failure mode deduced from evaluation of 4 groups of 12 devices each, was degradation of the series collector bonds. However, an MTF of 1650 hours was achieved at a function temperature of 280C, indicating a satisfactory level of reliability for the intended operational usage.
- Electrical and Electronic Equipment