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December 2008

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Subject:
From:
Paul Edwards <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Paul Edwards <[log in to unmask]>
Date:
Fri, 12 Dec 2008 11:33:50 -0800
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Sounds to me like moisture is being absorbed by the no-clean flux and is causing high resistance shorts in the BGAs and fine pitch components...

Seen this on PCAs built in China and RF stuff built in the US...

Paul

Paul Edwards
Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Tremmel
Sent: Thursday, December 11, 2008 6:51 PM
To: [log in to unmask]
Subject: [TN] Xbox360s

Hello Technetters,



I have had some people contact me out of the forum regarding the Xbox360s
but there is also another failure mechanism that I find interesting and I
agree with one person who thinks that the Xbox360 is a case of over-hurried,
poor quality engineering but it goes far beyond the BGAs.



A Google search for 'xbox360 towel trick' will generate 131,000 results and
the 'towel trick' does work for a while.  The towel trick by the way is when
you wrap the Xbox with 3 towels (as I saw in the YouTube video), turn it on
and let it run for 20 minutes.  You turn off the unit, remove the towels and
let cool and just like magic it works !!  I even took an Xbox360 logic board
that had the dreaded Red Ring of Death failure and baked the board for 24
hours at 105°C and the console ran for 5 or 6 weeks before failing again.



Anywho, I believe the reason is because the Xbox360 logic boards are poorly
manufactured (just like the XB360 BGAs) or manufactured with substandard
materials or both.  If you wrap three towels around an Xbox360 and turn it
on for 20 minutes you certainly are not doing any kind of reflow.  Even if
it did the tension and weight of the heat sinks would cause a solder
sandwich with the BGAs and the logic board not to mention the electrolytic
caps exploding.  If you do the towel trick you certainly are not going to
'repair' the electrolytic caps on the board by elevating the temperature
close to their 105°C limits.  It could also be that the ceramic caps need a
baking so that they go back to their original values but that might be a
stretch to even a fanciful idea.  Even though the copper power and ground
planes do not distribute the heat generated by the BGAs symmetrically around
what is called the GPU, I fail to see how the towel trick would address any
failures asymmetrical heat distribution may cause.



I think it is either because the logic boards themselves are made with
substandard materials for their application or even better the logic boards
were not manufactured well enough; such as a problem with the resin system
or via misalignment.  Could there be latent failures with insufficiently
aligned vias that could be pushed to failure by poor thermal management or
resin system issues?





I am interested in what the gurus have to say regarding this.





Thank you,



David Tremmel

 <http://valurecovery.com/> http://ValuRecovery.com




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