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Author Topic: Fixing the Axon - replacing mega640  (Read 1799 times)

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Offline Razor ConceptsTopic starter

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Fixing the Axon - replacing mega640
« on: February 15, 2010, 01:30:45 PM »
A few months ago I fried my axon by static discharge; I was trying to use a 16x2 LCD. So now it is time to start the repair process!

Axon to be desoldered, washer for heat transfer:



Washer must be thicker than the header pin solder:



Washer on stove, heating up:



Testing temperature with leaded solder (I have leaded axon).
Solder melts, time to put axon on washer.



Hypersonic-suction IC remover device successfully extracts mega640, the 16mhz crystal felt like coming, too



Melted soldermask due to the heat:




Next up is to determine the damage to the underside and see if it is still worth it to fix. Luckily there only appears to be two small traces that might be affected, the majority of the burns are on the power/ground planes.

Offline SmAsH

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Re: Fixing the Axon - replacing mega640
« Reply #1 on: February 15, 2010, 01:53:01 PM »
Nice job, does this mean you aren't selling the board?
Howdy

Offline Razor ConceptsTopic starter

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Re: Fixing the Axon - replacing mega640
« Reply #2 on: February 15, 2010, 02:07:05 PM »
Yup, I figured I could spend the $10 on a new mega640 in order to revive my $140 investment  :D

Anyways, the two traces in the burn area just happen to be the crystal traces... they are still intact, however dunno how the bare exposed copper will affect it. Oh well, I could always just use the internal clock.

So thankfully all traces are intact!!! No repairs ahead of me, just have to get a new mega640, some solder paste and off I go.

Offline madsci1016

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Re: Fixing the Axon - replacing mega640
« Reply #3 on: February 15, 2010, 03:01:23 PM »
inb4 Admin.

The internal clock is crap. something like 10% error if i remember correctly, so high speed Uarts and time sensitive stuff all won't work well. There's a reason most uC designers still have an external crystal.

Offline dunk

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Re: Fixing the Axon - replacing mega640
« Reply #4 on: February 15, 2010, 06:47:33 PM »
hey Razor,
my method for this (without the cataclysmic scorching) is lots of extra solder and a hot soldering iron.
add solder until there are ugly solder bridges completely joining all the pins then keep heating all sides, alternating from one side to the next.
as soon as you manage to get all 4 sides molten at the same time, turn the board upside down and tap it. the chip should drop right off.
then tidy up with solder wick.

you don't get the cool scorched battle scars my way though...

The internal clock is crap. something like 10% error if i remember correctly, so high speed Uarts and time sensitive stuff all won't work well. There's a reason most uC designers still have an external crystal.
i *think* the ATmega640 has an offset register so you can tune the clock speed of the internal resonator.
it's a pain to do but only needs done once per MCU.
make a loop that should take exactly 1 second and time out some minutes to get a multiplier.


dunk.

Offline galannthegreat

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Re: Fixing the Axon - replacing mega640
« Reply #5 on: February 15, 2010, 06:56:29 PM »
Kurt

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Re: Fixing the Axon - replacing mega640
« Reply #6 on: February 16, 2010, 12:37:08 AM »
Quote
my method for this (without the cataclysmic scorching) is lots of extra solder and a hot soldering iron.
add solder until there are ugly solder bridges completely joining all the pins then keep heating all sides, alternating from one side to the next.
as soon as you manage to get all 4 sides molten at the same time, turn the board upside down and tap it. the chip should drop right off.
then tidy up with solder wick.

Dunk, for the Axon, this won't work. I specifically designed it to suck away huge amounts of heat - which is why it can safely handle up to 13A of current at 6V. Having 100 pins, and unleaded solder, makes it all the much harder.

A method I've found to remove the 640, for anyone else that has to do this, is to use tiny snips and bend the pins away from the PCB individually with a hot soldering iron. Just be careful to not damage the pin pads when doing this.

You can also coat the pins with this stuff:
http://curiousinventor.com/store/product/102
Then heat and mix it around . . . it cools very slowly, then use Dunks method.


Razor, test to see if your USB still works. You might have caused it to shift with all that heat . . .

Offline Ro-Bot-X

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Re: Fixing the Axon - replacing mega640
« Reply #7 on: February 16, 2010, 06:04:29 AM »
I would have used a Dremel to cut the pins as close to the chip as possible and after the chip would have been removed, a tweezer and a regular soldering iron would have cleaned the board without much hassle. And some soldering wick too, as Dunk pointed out already.

Anyway, to repair the damage, try to clean the board with some light abrasive pad and acethone on a rag or something like that and after you have it cleaned, cover the unaffected area with tape and spray paint the exposed copper. On the top, you may use some thin paint brush and magnifying glass to apply paint as close to the pads as possible. You can still (apply tape to protect them) spray and clean the pads with a razor if they get any paint by mistake.
« Last Edit: February 16, 2010, 06:11:24 AM by Ro-Bot-X »
Check out the uBotino robot controller!

Offline TrickyNekro

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Re: Fixing the Axon - replacing mega640
« Reply #8 on: February 19, 2010, 10:36:54 AM »
Have you ever seen how they reflow Xboxs
Just an aluminum cap and some acetylene...

Add some solder to the IC then turn the Axon upside down...
put the cap above the IC area then light it up...
what destroys boards is direct heat from flames... not the heat won't damage it...
But not so quickly...
Then remove the IC with a needle with upside down... and done...
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

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Re: Fixing the Axon - replacing mega640
« Reply #9 on: February 19, 2010, 09:40:13 PM »
what destroys boards is direct heat from flames... not the heat won't damage it...
Oh believe me, I've burnt a few Axons black using just hot air guns . . .

Offline Razor ConceptsTopic starter

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Re: Fixing the Axon - replacing mega640
« Reply #10 on: March 29, 2010, 04:58:10 PM »
And it is fixed  ;D

http://i40.tinypic.com/jie3oj.jpg

Nothing like some solder and about 3 feet of solder wick.


Offline SmAsH

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Re: Fixing the Axon - replacing mega640
« Reply #11 on: March 29, 2010, 11:30:03 PM »
It uh... works right?
Howdy

 


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