Re: hardware texturing broken on Octane HELP

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Date: Thu, 26 Feb 2004 18:38:46 GMT

In article <103r0o4a87iqr2d@corp.supernews.com>,
 Greg Douglas <gdouglas@reputable.com> wrote:

: Andreas Backhaus wrote:
:
:
: > the pins of the RAMs desolder because of the heat - you just have to
: > check the four TRAMs on each module for those desoldered pins. That's
: > about it ;)
:
: I seriously doubt that the TRAMs get to around 400 degrees F. (204.4
: degrees C), which is the temperature that 60/40 tin/lead solder
: melts. I've never seen any semiconductor device boil spit
: (100 deg. C) and survive more than a few minutes.
:
: More likely they weren't IR reflowed properly during production. When
: fresh, the resin in the solder paste allows the solder paste to make a
: connection. But as the resin dries out over time (and high temps),
: it loses the electrical connection.
:
: BTW, I have seen this (loose pins) on TRAMs, I use a stereo microscope,
: and press down on each pin of the RAM ICs with the tip of an Xacto
: knife. If the IC lead moves at all, it's not soldered. It IS a
: bit of an art (and requires much practice), but it can be soldered.
: Use a very fine tip soldering iron, at around 600-650 deg. F, and
: very fine solder, or solder paste if you can find it.

Self-desoldering pins aren't actually all that uncommon in electronics, even
when the original solder joint is good. The Alpha CPU in particular was
notorious for this, and it's a very common failure mode for TVs and Monitors to
have some pins in the flyback circutry desolder themselves.

There's no actual melting of solder involved, of course. The process is one of
both mechanical stresses during thermal cycles and I believe in the case of high
voltage components the solder itself can tend to migrate, forming pits and gaps
that make the joint look a lot like a moonscape. Both of these conditions can be
worsened if the board was not properly cleaned of flux residue after soldering.

The Flux or Resin does not provide any function in the joint after the joint has
been properly soldered.

Cheers - Tony 'Nicoya' Mantler :)

-- 
Tony 'Nicoya' Mantler -- Master of Code-fu -- nicoya@ubb.ca
--  http://nicoya.feline.pp.se/  --  http://www.ubb.ca/  --

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