Desoldering The Atmega Chip Using Chip Quik

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by mbanzi » Mon Jan 14, 2013 4:50 pm

Showmaster, I used the syringe applicator that came with the eBay kit. Flux supplied worked well, just don't apply too much. If I'd known Fry's had the kit, I probably would have gotten that.

João, I used a 0.8mm chisel tip to solder the chip, each pin individually, as shown in the video on the ChipQuik website. I don't have a tip to try drag soldering, but it looked like it would take some practice.

http://www.youtube.com/watch?v=3NN7UGWYmBY#t=240s

As apprehensive as I was to do this mod, the whole process was surprisingly easy! I replaced the ATmega64s on both my 9x transmitters in a couple of hours. Hardest thing about the whole process was soldering those mod wires back onto the chip afterwards.

Things to note:
- It's a lot easier to do this with the main PCB removed from the transmitter.
- Use a broad tip to desolder. Believe I used a 1.2 or 1.6mm chisel tip.
- After removing the chip, use a little more flux, heat the pads with your soldering iron then use a cotton swab to wipe off any remaining soler/ChipQuick. Be careful about applying too much heat, one of the pads started lifting off the PCB! Afterwards clean off all the flux, there will be a lot, using alcohol.
- I have USBASP programmers built into my transmitters. Both had the SCK error, so I had to update the firmware to be able to slow it down to set the fuses.
- I used Companion9x to set the fuses the first time, just added -B 100 to the "Extra Arguments" in the Configuration dialog.

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Mon Jan 14, 2013 5:36 pm

oh, also my atmegas came on a pice of styrofoam.. :o
I hope they are not damaged..
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by Flaps 30 » Mon Jan 14, 2013 5:49 pm

jhsa wrote:I've been watching a few videos about drag soldering.. It looks quite easy if we're generous on the flux. on most of the videos they are using an iron with a flat tip. Is that mandatory or can it be made safely with my normal pointy tip?
Drag soldering isn't easy to get right first time round. I wouldn't suggest doing it if this is your first time. The tip that I used to solder the m128 was a 1mm chisel tip, that allowed a small pool of solder to be held on it. The iron temperature was set at 350°C (662°F ). The solder used here was LMP solder 60(tin), 38(lead), 2(silver) only because I had it in a small diameter of 0.5mm as against the super thick 60/40 0.71mm diameter solder that is used for general work.

The most important part IMO is insuring that there is enough flux allow the join to happen properly.

Go for it João. Plug up that drippy nose of yours and get stuck in.. :)

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by mbanzi » Mon Jan 14, 2013 6:37 pm

jhsa wrote:oh, also my atmegas came on a pice of styrofoam.. :o
I hope they are not damaged..
So did mine, taped to a piece of styrofoam. Don't worry both of mine worked fine :D

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Mon Jan 14, 2013 7:12 pm

So, I guess I don't have any more excuses then ;) :D

Thank you guys..
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Mon Jan 14, 2013 7:52 pm

Flaps 30 wrote: Drag soldering isn't easy to get right first time round. I wouldn't suggest doing it if this is your first time. The tip that I used to solder the m128 was a 1mm chisel tip, that allowed a small pool of solder to be held on it. The iron temperature was set at 350°C (662°F ).
I have a chisel tip for my iron but I guess it is too big. Maybe good to use it with the chip quik.
for soldering I have my normal tip, quite thin(ish).
Ok, drag soldering not recommended. then what technique do you guys recommend? Solder the pins one by one? that sounds more difficult than the drag soldering :)
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by mbanzi » Mon Jan 14, 2013 8:05 pm

jhsa wrote: Ok, drag soldering not recommended. then what technique do you guys recommend? Solder the pins one by one? that sounds more difficult than the drag soldering :)
I soldered the pins one by one, it actually goes pretty fast. I followed the technique in the video I linked in an earlier post: blob of solder on the tip, touch the end of the pin & drag away. You can actually do 2-3 pins with one blob I found. Important to use thin solder, I used 0.5mm. Using 4.0x reading glasses helped a lot, then inspected with a 10x loupe afterwards.

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by Flaps 30 » Mon Jan 14, 2013 9:39 pm

Doing it as mbanzi has mentioned works well. :)

If you haven't got any thin solder (0.5mm) don't let that put you off. As long as you have added a bit of flux to the pins, it will work fine with standard gauge (0.71mm) solder.

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Mon Jan 14, 2013 10:10 pm

I have 0.5mm solder. My concern is the iron tip..
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by Flaps 30 » Mon Jan 14, 2013 10:42 pm

What's wrong with your iron tip?

Okay.... If it is too big. You could just give this a go, or try some variation on that technique -----> Drag Soldering

If you haven't got any additional flux. I would suggest doing the job this way. The person who did the demo used extra flux on some of the work, which is why no extra solder was added at times. It does work without any extra flux being added, as long as you use a fresh bit of solder for each pin which brings out the flux from the core of the solder. Make sure that you wipe the tip of the iron before each join. I used this technique on my second TX ----> Soldering a TQFP 64-pin SMT (m128) package

Hope that makes sense. Trust me when I say that it is easier doing it than watching it being done. Having some form of magnification and a good strong light source will go a long way to making it all work.

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Mon Jan 14, 2013 11:00 pm

Thanks for your help guys..
I have a pointy iron tip. On the videos I watched, they always advice other type of tips. I used my tip to solder the wires for the mods on the m64's legs, and it was ok. Sometimes it took 2 or 3 times till I got it done.. I normally use the iron at a higher temperature (about 400ºC) because I then take less time with it on the spot, and the risk of damaging the component and pads is smaller, I suppose

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by Flaps 30 » Mon Jan 14, 2013 11:39 pm

Hmm... It looks like you are suffering from a huge bout of procrastination.. You have already demonstrated on a number of tasks that has involved a lot of fine soldering that you are up to the task. What is the worst case scenario... Lifted pads? .. Nahh.. Not with Chip Quik and a low temperature setting.... Blown M128? .. Possibly.. You do have a spare haven't you? Along with the old M64 that you know works.

I would go for it, but if it was me. I would lower your iron down to say 360ºC... But you are not me are you? ;)

Edit - I am rather concerned that you are going to go into this operation with your iron temperature set at 400ºC for all the work on this. I would strongly suggest that you resist yourself from doing this, as the dangers of lifting the fine tracks/pads is great at tempertures that high.. When using the Chip Quik I would suggest keeping the iron at no more than 300ºC. For the soldering operation I would use what I said earlier if you are using tin/lead solder which I personally prefer. Wiping the iron tip to remove old solder after each pin or series of pins if you are dragging the bit, will help to produce good quality joints.
Last edited by Flaps 30 on Tue Jan 15, 2013 12:14 am, edited 1 time in total.

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Tue Jan 15, 2013 12:08 am

loooool. It will be done after tomorrow. ;)
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by ShowMaster » Tue Jan 15, 2013 12:49 am

Ok, bought the chip quick today locally for $15 no waiting for the mailman.
Now I need a m128.
SM


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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 3:25 pm

Guys, I'm having problems. I did as on the videos and described here. put flux on all pins, then apply the alloy. temperature set at 270ºC.
The propblem is that the chip quik is not mixing with the solder. even when I melt all the sides it tends to make a big blob and the chip doesn't cdome out.. don't know what to do.. increase the temperature??
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 3:52 pm

I managed to do it, but not before I put chip quik all over the place as you can see :D
easy enough to remove it with a bit wick..
I think the problem was the m64 was glued to the PCB.. when I hold it im my hand it sticks.. Also does the PCB.. or maybe it is the flux??
Anyway I had to set the temp of the iron at over 300ºC.
It was difficult to keep the alloy on all the pins but at the end, it is out.. now to clean the board with solder wick and some alcohol..

I'm sure the next one will be easier. I didn't have any other PCB to train before. Shaking like hell didn't help also :D :D
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by Flaps 30 » Wed Jan 16, 2013 3:55 pm

That sure is a heck of a lot of Chip Quik you have there. :o With that amount. I would use the biggest tip you have and increase the temperature to something like 350ºC. Have something ready in your other hand to push the chip clear.

Edit - Glad you sorted it out. :) Yes the second chip you do one isn't so traumatic. Now the fun bit is putting the new chip in place. Take your time over it.. No shaky hands whilst you are doing it.

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 4:04 pm

as soon as it started moving, I just turned the board around and shaked it.. the m64 just fell defeated on the table..
There is an huge amount of alloy because it just went into a ball and didn't want to spread to all the pins. the alternative was to put more I thought.
I guess another problem might be the lead free solder that they used on the boards..

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by Flaps 30 » Wed Jan 16, 2013 4:14 pm

From what you have described, it seems that the temperature on the tip of the iron was too low. On the removal operation I was using 220ºC with a big tip. Of course the iron calibration might be off which would be enough to throw things out.

When you apply the Chip Quik it does tend to ball up. I found when it did that, just keeping the iron in the same place for a short time sorted that out.

On the picture you posted. Do I see some Chip Quik on a few SMD components at the lower left of the chip?

So how many transmitters are you looking to convert?

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 4:35 pm

yes you do see some of it spread around the board. :D I will convert this one and if all goes well, will do the same with my other radio.
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jbeebo » Wed Jan 16, 2013 5:03 pm

yes, increase the soldering iron temp a bit. Chip Quick is Tin-Bismuth solder with liquidus temp about 140degC. SAC Pb-free solder has liquidus temp ~270degC. You need the iron hot enough to melt the SAC, then the Sn-Bi solder will readily fuse with SAC and reduce the solidus temp to between 100degC and 150degC. This is what allows removal of the component. After Sn-Bi solder has mixed with SAC, you can lower the iron temp again if so desired, but not necessary.

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 7:39 pm

Yeah, the problem is that I was using a thin tip.. that was mistake number one.. when I increased the temp to 300ºC the chip came out after a few seconds..
lesson learnt I think.. ;)
I hope the board is ok..
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 9:33 pm

ok, ready for the next step.. :) I hope :D
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jbeebo » Wed Jan 16, 2013 9:39 pm

Well isn't that interesting. All the unused pins have a thru-hole to the backside of the board. I wonder are they plated thru-hole? If so, it's sure a lot easier to push a wire into the thru-hole and solder than trying to attach hair-thin wires to the micro legs.

@jhsa, would you mind doing continuity check from one side of a thru hole to other side of board? One of the thru holes hidden under the micro... Thanks!

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 9:43 pm

I would, but I don't really want to remove the foam that is glued on the back.. I don't have any replacement :(
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Re: Desoldering The Atmega Chip Using Chip Quik

Post by MikeB » Wed Jan 16, 2013 9:46 pm

The board is rotated 180 degrees, the pins for the telemetry mod don't have any through holes beside them.

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 9:52 pm

Yes, the board is upside down.. :D sorry..

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by Flaps 30 » Wed Jan 16, 2013 10:25 pm

I had to rotate my head to check it out.. Nice clean up job. :)

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jbeebo » Wed Jan 16, 2013 10:41 pm

@MikeB - I noticed that shortly after submitting my question - hence the retraction. The good stuff, pins 42, 43, 44 do not have thruholes. So much for easier haptic and telemetry mods!

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Re: Desoldering The Atmega Chip Using Chip Quik

Post by jhsa » Wed Jan 16, 2013 10:50 pm

Flaps 30 wrote:I had to rotate my head to check it out.. Nice clean up job. :)

Ha Ha, you could have just turned the screen upside down :mrgreen:

Guys, remind me to kick myself in the a** later for getting myself in such situations like this one..
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