[clug] sec: unclassified - re: OT: Life-span of motherboards

[Ellis, LCDR Peter]

A few weeks ago I heard an interesting tale of how the alternate cycling of
a (power) transistor can, eventually, cause a physical breakdown of solder
joints. In some cases, if proper care is not taken, the slight expansions of
the leads with heating *can* cause the lead to create a 'track' through the
solder: The edges lose their conductivity and actually either (a) form a
series of point-contacts, or (b) allow in air and so form oxide layer, (c)
etc... and thus become resistive. This has several effects, the most benign
of which is to slightly bias the transistor into another part of its
operating range. Or, that part of the circuit just stops working. 

Add vibration (ever felt a computer case?) and computers are a great proving
ground for odd life-cycles. 

Anyway, there are many explanations for why a motherboard may stop working.

Peter

		-----Original Message-----
		From:	Steve Jenkin [mailto:sjenkin at canb.auug.org.au]
		Sent:	Monday, 17 November 2003 19:40
		To:	Phil and Marlene Carter
		Cc:	Linux list
		Subject:	Re: [clug] OT: Life-span of motherboards

		This is an electronic engineering question :-)
		It is also manufacturing/production quality question.