A few days ago, our first N73 test unit finally died because this unit was
already TP Unlocked more than 80 times since December 2007.

The "temporary" death of this phone is 90% same with "temporary" death on
all N73 phones that experienced TP Unlocking. The reason is very simple, BGA
Balls "short-circuit" to the neighboring BGA Balls or Copper Traces.

To further illustrate this phenomenon, I removed the stacked RAP+NOR chip
from our N73 and took some crappy pictures.


"Under the stacked RAP+NOR"



*** Note that the CLK BGA Ball has no internal connections on the PCB.
*** This means that you can even disconnect the CLK BGA Ball from the
*** PCB and the phone will still work perfectly!!!


So if the CLK BGA Ball is not needed on the PCB, where does the actual
"short-circuit" take place in the PCB???


"Short Circuits"

RED AREA = more than 70% of the time, the CLK BGA BALL is shorted to
the RED AREA illustrated on the picture above. The reason for this is the
TP Pins can easily scrape off the protective green solder mask of the
copper trace in between BGA BALL 9 and BGA BALL 10 (CLK). Once the
protective solder mask is removed like what you can see at the picture:
"Under the stacked RAP+NOR" above, your BGA BALL 10 (CLK) can easily
short-circuit itself to the exposed copper trace.

Most people fail to see the short-circuit caused by the RED AREA because
it is very very hard to see even under a 40x ????og microscope.


BLACK AREA = Only a small percentage
of phones will suffer from short circuits caused by the BLACK AREA. The
main reason is that it would require a greater amount of FORCE to push
the BGA BALL 10 (CLK) and have it "short-circuit" itself to the neighboring
BGA BALLS. This type of short-circuit is very easy to see under the
microscope and most people are successful fixing this kind of short-circuit.



So what is the best way to fix these two kind of short-circuits?

First of all, stay away from Rework Stations, Soldering Irons and anything
that puts HEAT into the equation.

Secondly, having a good quality microscope is crucial. Don't settle for
cheap magnifying glass or any other contraption that may save you a few
buck$, but kill a $$$ phone in the process.

Third, use the thinnest / sharpest needle you can get your hands on. You
may sharpen the needle with a sandpaper or a grinder. Never use the
TP Pins from the TP Cable unless of course if you want to damage the phone
even more ;-)...


Fixing your phone is simple and fast if you have the patience and the right
tools.

Set microscope to 20x or 40x and gently scrape off the excess LEAD from
on the sides of the BGA BALL 10.

"BGA BALL 10"

Take note of the RED and BLACK Areas of possible short-circuit
when you are removing the excess LEAD from the BGA BALLS. Those are
the problematic areas and you should inspect them thoroughly especially
the RED AREA.

You should also inspect BGA BALL 9 as it is also possible that this BALL is
shorted to the RED AREA.

If you accidentally disconnect the BGA BALL 10 from the PCB because of
too much scraping of excess LEAD, you DO NOT need to reball it because it
is not internally connected to the PCB in the first place. The 66Mhz on the
CLK is generated by the RAP and it is only used by the NOR Flash chip which
is already on top of the RAP. No other component on the phone's PCB uses
the 66Mhz F-CLK.



To completely avoid short-circuits, I would strongly suggest that the next
time you will try to TP Unlock a N73 you would use "EASY-TP" instead as
illustrated below: