resurrected XO-1.5, died again

[John Watlington]

I'm tired of revisiting an issue that thankfully only affected less
than a thousand production units (repaired under a catastrophic
failure clause).  Unfortunately, the effect on our developer
community was disastrous, as they only received affected units.

I'm willing to send an XO-4 to replace a broken XO-1.5
if you tell me what you are using it for.

The root cause was the alloy used in the solder balls between the
CPU interposer board and the CPU silicon.   These balls are under
significant stress due to the difference in coefficient of thermal expansion
between FR4 and silicon.   This problem only showed up after the
solder balls had had time for the alloy to separate.
VIA switched the RoHS alloy used in these balls as we were entering
production.

So while mechanical stress on the motherboard might accelerate the
problem, simple thermal stress from powering the device on (or moving
in/out of suspend) is a more likely culprit.

wad


On Jul 2, 2013, at 3:26 PM, Ian MacArthur wrote:

> On 2 Jul 2013, at 08:58, Yioryos Asprobounitis wrote:
> 
>> Back to the original question. Should I conclude at this point that there is no information/experience  on the effect of repetition on the effectiveness of the soldering reflow process? (ie try and see what happens ;)
> 
> No OLPC information. However, a little time with google looking for the PS3 "yellow light of death" of the Xbox-360 "red ring of death" will produce more opinions than could ever be wanted, all based on no substantial evidence whatsoever...
> 
> 
> 
> 
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