[Amps] Transistor Lifetime

[Alex]

...forget it!
The transistors, and for that matter all semiconductors, manufactured over
the last 20 years incorporate a passivation layer of glass or silicon
nitride on the chip. None rely on the cases for environmental protection. I
still install transistors from CTC, a company defunct for over 20 years now,
without any trouble. Just think of all these cheap transistor radios made 30
years ago and still going strong. Most were thrown out because they were
obsolete by new standards, not because they broke down. I still use them as
a source of scavenged parts, especially Germanium transistors and diodes.
What goes bang are usually the electrolytic caps which dry out, not
semiconductors!
73 and all the best:
Alex	4Z5KS

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Dan Hearn
Sent: Friday, July 04, 2008 9:25 PM
To: amps
Subject: [Amps] Transistor Lifetime

I have  several  NPN RF power transistors which were acquired about 10-12
years ago. They were new at the time and are still in the factory sealed
packages. Some are matched pairs. Included are MRF454, MRF421, MRF422MP . Do
these deteriorate in storage? These are all in ceramic cases. Would you
expect to see any deterioration in PA output with use over a number of years
? How about epoxy cased transistors?
73, Dan, N5AR
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