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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Sheila Prather (sheila_s_prather@mail.northgrum.com )
Organization:Northrop Grumman Corporation
Date posted: Wed May 17 13:49:02 US/Eastern 2000
Subject: Derating of Industrial/Commercial ICs in Plastic Packages
Message:
I reviewed the recent "Reliability Toolkit: Commercial Practices Edition" and although Table 5.1.3-1 does not specifically state that the derating information provided pertains to hermetic/ceramic packages, I assume this to be true. In light of my assumption, would like your recommendations regarding the derating levels you feel appropriate for both silicon and GaAs MMIC ICs in plastic packages. Would like both the case and junctions temperature guidelines, as appropriate (but, at a minimum the junction temperature derating level). Thanks for your response.


Reply:

Subject: Junction Temperature Derating
Reply Posted by: Bruce Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Wed May 24 10:09:22 US/Eastern 2000
Message:
The derating levels in the Reliability Toolkit Commercial Practices Edition for temperature do not differentiate between package types as there was insufficient data to support alternate approaches. However, the Navy does support this concept of different derating parameters as is shown in their publication "TE000-AB-GTP-010 Parts Requirment and Application Manual". In this publication, the recommended levels of derating are: 100 to 125 degrees C for hermetic bipolar, 85 to 90 degrees C for plastic bipolar, 90 to 150 degrees C for hermetic GaAs and 90 to 125 degrees C for plastic GaAs. In the new RAC publication on derating to be issued in July 2000, we recommend temperature derating levels of 95 to 115 degrees C for bipolar and 100 to 125 degrees C for GaAs. These values are based on conditions that apply for both hermetic an plastic packages. These values are lower than previously indicated in the reliability toolkit. The rational is many of the plastic and hermetic devices are not built to operate at higher temperature levels with consistent electrical characteristics, hence must be operated at lower levels. We do not have a set of guidelines for the case temperatures as these values are dependent on the power of the device, the thermal resistance of the package and other external conditions (cooling or heating). The old MIL-HDBK-217 "Reliability Prediction of Electronic Equipment" has default values for case temperature for a number of environmental conditions in the microcircuit section 5.11 that could be considered as a starting base level.


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