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Old 8th June 2008, 02:31 PM   #11
luka is offline luka  Slovenia
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Hi

Thermal pad in under the chip, I have had same with Amp2
you can check that thread

http://www.youtube.com/watch?v=cHnl5...C9427&index=14
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Old 8th June 2008, 03:16 PM   #12
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Thanks guys. I have a small toaster oven and contemplated doing the thermal pad that way, but I don't have any solder paste and it isn't something available locally. I'm too cheap and impatient to order it by mail. I think it should be fine with the combination of thermal compound and the pins connected to the ground plane.
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Old 8th June 2008, 03:24 PM   #13
luka is offline luka  Slovenia
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Hi

Solder paste? nah didn't you read my thread? I used normal solder, which melted nicely between board and IC, making great termal conduction
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Old 8th June 2008, 04:36 PM   #14
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Quote:
Originally posted by luka
Hi

Solder paste? nah didn't you read my thread? I used normal solder, which melted nicely between board and IC, making great termal conduction
I read the thread, but I'm not sure exactly how you did it. Did you melt some solder to the PCB first, or did you put some of the un-melted solder wire between the board and the IC?
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Old 8th June 2008, 07:28 PM   #15
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I managed to scavenge enough parts to complete a board. I like this one even better than the TPA3122D2N. I also love when a project powers on and works the very first time.

Click the image to open in full size.

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Old 8th June 2008, 07:52 PM   #16
luka is offline luka  Slovenia
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Hi

Damn that looks nice

Ok let me gide you for any later project you would need this
You will be able to see first pic, I used that as test, some broken fet and unused PCB and do this:

1. Make sure your solder material has a melting point that is not higher than 190C. Most 60%Zn 40%Pb will melt at around 180C. (My was one of them)
2. Heat an oven to about 230-240C (I think I had 230, and was enough, or did I had only 220, it is stil more then enough)
3. Scrape of the solder mask in the rectangle in the middle of the chip position on the PCB with a sharp knife. Make sure you remove all solder mask varnish in this area. (That is if you have factory made PCB, for home you don't have to do anything)
4. Place about 20 mm (3/4”) long bit of solder with a diameter of 0.6 mm or the equivalent amount, bent into a circle, on the cleaned PCB area. Place the PCB in the oven and measure the time it takes before the solder has melted and flowed out on the solder area. (This was for TK2350, so you can use diffrent wire lenght and it doesn't have to be 0.6mm, but my was 0.7mm) It may take about 2-3 minutes.(it was in that time somewhere)
5. Remove the PCB from the oven and let the PCB cool down.
6. Spread some “no-clean” non aggressive solder flux on the solder area. A solder flux pen is handy for this. (I used normal whatever I use normaly, no problems with it, just very small amount)
7. Place the chip perfectly in place on the PCB. Make sure all chip leads are aligned to the solder pads of the PCB.
8. Place the PCB in the oven and allow as much time as before, but add 20 seconds for the chip to heat up. After this time shut of the oven power, open the oven door and gently fan cool air into the oven. (I have waited about 30s, and then slowly and easy took whole board leveled out and put it down to cool)
9. Let the PCB cool down and inspect it.
10. If everything is OK, solder the chip legs to the PCB pads.
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Old 8th June 2008, 11:36 PM   #17
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Quote:
Originally posted by luka
Hi

Damn that looks nice

Ok let me gide you for any later project you would need this
You will be able to see first pic, I used that as test, some broken fet and unused PCB and do this:

1. Make sure your solder material has a melting point that is not higher than 190C. Most 60%Zn 40%Pb will melt at around 180C. (My was one of them)
2. Heat an oven to about 230-240C (I think I had 230, and was enough, or did I had only 220, it is stil more then enough)
3. Scrape of the solder mask in the rectangle in the middle of the chip position on the PCB with a sharp knife. Make sure you remove all solder mask varnish in this area. (That is if you have factory made PCB, for home you don't have to do anything)
4. Place about 20 mm (3/4”) long bit of solder with a diameter of 0.6 mm or the equivalent amount, bent into a circle, on the cleaned PCB area. Place the PCB in the oven and measure the time it takes before the solder has melted and flowed out on the solder area. (This was for TK2350, so you can use diffrent wire lenght and it doesn't have to be 0.6mm, but my was 0.7mm) It may take about 2-3 minutes.(it was in that time somewhere)
5. Remove the PCB from the oven and let the PCB cool down.
6. Spread some “no-clean” non aggressive solder flux on the solder area. A solder flux pen is handy for this. (I used normal whatever I use normaly, no problems with it, just very small amount)
7. Place the chip perfectly in place on the PCB. Make sure all chip leads are aligned to the solder pads of the PCB.
8. Place the PCB in the oven and allow as much time as before, but add 20 seconds for the chip to heat up. After this time shut of the oven power, open the oven door and gently fan cool air into the oven. (I have waited about 30s, and then slowly and easy took whole board leveled out and put it down to cool)
9. Let the PCB cool down and inspect it.
10. If everything is OK, solder the chip legs to the PCB pads.
Thanks Luka.

I'm kind of glad I didn't solder the thermal pad to the PCB now. I made the stupid decision to try and ground the negative input while the board was powered up. It didn't like that and decided to throw the rail voltage at my test speaker.

Oh well, 15 minutes and a fresh IC later it is back singing again. I think this amp might work better with a differential input, even though is doesn't need it to work BTL. I will give it a try and report back.
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Old 10th June 2008, 02:17 PM   #18
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It seems I have a small inductor heating problem with the TPA3106D1 board. I didn't notice it at first , but they are definitely heating more than the ones on the TPA3122D2N (which don't heat at all really).

I know a multimeter isn't exactly the correct tool to trouble shoot a problem like this, but I did measure some differences between the two boards with it.

AC voltage across output inductors:

TPA3122D2N = 1.938Vac
TPA3106D1 = 2.664Vac

AC voltage from output to ground:

TPA3122D2N = 0.003Vac
TPA3106D1 = 0.078Vac

You can see both reading were higher with the TPA3106D1. Both boards were being powered from the same 12v battery.

The only thing I did differently with the TPA3106D1 board is put one inductor on each side of the board and I used 1uF WIMA MKS capacitors for the output filter instead of 1uF X7R ceramics. Could either of those things cause this problem, or could it just be a layout issue?
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Old 10th June 2008, 02:50 PM   #19
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A small dab of lead free solder paste is what we use for the pad,
but if you are doing this at home I would definitely use LEAD....

The machine can do lead free just fine, but when it come to the
manual rework. I dread the lead free on the heatsinkless PCB,
where the board itself conducts the heat... The difference from
just enough heat, and burning up the board is a very fine line.
You need something (like hot air) to warm the board from the
back side, and the iron (or slightly hotter air jet from the top)
to do the fine local melting....

I don't recommend thermal compound, cause you will still need
to clean the flux from between the pins, and this will wash out
any grease you may have tried to substitute.

The DIP is so much easier package for the do-it-yourselfer...
But I even the DIP needs to be soldered too, I wouldn't risk
a socket to conduct the heat...
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Old 10th June 2008, 03:40 PM   #20
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Quote:
Originally posted by kenpeter
I don't recommend thermal compound, cause you will still need
to clean the flux from between the pins, and this will wash out
any grease you may have tried to substitute.
Surprisingly it didn't. After I finished soldering the IC I had submerged the board in alcohol forgetting that the thermal compound was there. When I killed the IC and had to replace it all of the thermal compound was still there. I didn't submerge it again after the replacement; I just used cotton swabs to clean the flux.

I wouldn't touch lead free solder if I was given a truck load of it for free.
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