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From: williams@kirk.DEC (John Williams 223-3402)
Newsgroups: net.analog
Subject: Heat and Solid State
Message-ID: <2722@decwrl.UUCP>
Date: Mon, 17-Jun-85 11:26:56 EDT
Article-I.D.: decwrl.2722
Posted: Mon Jun 17 11:26:56 1985
Date-Received: Wed, 19-Jun-85 02:34:56 EDT
Sender: daemon@decwrl.UUCP
Organization: DEC Engineering Network
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Two important effects that contribute to Solid State wearing out:

1) Diffusion

If the device is extremely hot, the features will lose their clarity
due to diffusion which will tend to make the crystal impurities
homogenous.

2) Thermal Cycle

When the device is powered up and down, The device expands and contracts
causing micro fractures in the structure.

	The silicon will tend to anneal itself, and diffuse causing greater
leakage currents, and the metal structure will tend to develop cracks,
which will increase the series resistance.

	The major failure mechanism to date in Computers is that of
the device slowing down due to these effects. If the timing requirements
for this device are critical, then this effect constitutes a failure.

						John.