I had just begun doing design work on an audio power amplifier for a military aircraft intercom system. A mechanical engineer had devised a chassis structure which was essentially an aluminum box with a sheet metal plate that ran horizontally from one side of the box to the other along which an array of power semiconductors would be positioned. The power chips were to be arrayed along a metal strip that ran from vertical wall to vertical wall.
Unfortunately, when I did a thermal analysis for those chips, it very quickly became obvious that there would be severe overheating issues. I presented the situation to the mechanical engineer who very quickly grasped everything I presented and acknowledged the issues, but who then resigned from the company only a few days later.
That fellow's successor was not someone for whom I can offer any words of praise or respect. This new guy said there was nothing wrong and that no mechanical design revisions were going to be made.
One chip in particular had a published power dissipation derating curve which had the usual downward corner at 25°C and which declined to zero watts at 125°C. My estimate for that chip's temperature was a rise to 125°C which is to say, a rise to a power dissipation capability of zero watts.
Yeah!! That thing was going to get cooked good and proper and 'program management' (ahem) did NOT want to hear that.
Someone of whom I otherwise held great respect made a comment that did not help matters at all: "Maybe we could do a Weibull analysis to justify a non-zero power dissipation at 125°C."
The name Weibull refers to a probability distribution function which I was later told is used by semiconductor manufacturers to determine non-zero but acceptable failure rates of their products in field service and that the chip's power derating curve is an outcome of that analysis.
Please see: https://en.wikipedia.org/wiki/Weibull_distribution
I told the program manager (again, ahem) "You can't Weibull the Weibull!!" which I guess got taken as a flippant remark even though I meant it in all earnest.
I was only a "temp" at that company and not too much later, I was let go but about a year afterward, I heard through the grapevine that "Some changes were made."
I would guess so!!
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