[iyonix-support] Re: Iyonix network card failure
- From: charles <charles@xxxxxxxxxxxxxxxxxxxxxxx>
- To: iyonix-support@xxxxxxxxxxxxx
- Date: Wed, 08 Nov 2006 16:03:48 +0000 (GMT)
In article <1163001313.4551fde16f582@xxxxxxxxxxxxxxxxx>,
<davehigton@xxxxxxxxxxxxx> wrote:
> Quoting Steve Fryatt <lists@xxxxxxxxxxxxxxxxxx>:
> > ISTR being told it was moisture related: some of the original networking
> > chips fail to start under some conditions. This only affected early
> > machines, AIUI (mine is over three and a half years old).
> This has to be as unlikely as being affected by a magic spell.
> Moisture can affect chips in the manufacturing phase, in the sense that
> plastic packages are very slightly hygroscopic, and the high temperature
> that the whole package will reach during reflow soldering causes the
> absorbed moisture to create pressures up to about 10 times normal
> atmospheric pressure. The pressure can cause the package to explode,
> either outwards or inwards (not the same as imploding!) and cause
> permanent damage to the silicon slice and/or its bond wires. The
> effect is known as "popcorning" - very accurately descriptive - and
> you can look it up on the WWW under that name.
> If a chip survives the manufacturing process, it is not affected by
> humidity afterwards.
> If a chip's package were ever to develop such a gross leak that
> moisture reached the silicon, the chip would cease functioning
> and never work again.
> There is nothing else that is affected by humidity.
There is. If the pcb isn't totally clean when the ic is inserted, there
can be something hydroscopic under it. Add moisture and you change the
inter-leg capacitance. I've met it on a TV set, in a computer it could be
disastrous.
--
From KT24 - in "Leafy Surrey"
Using a RISC OS computer running v5.11
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