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Desoldering from a heatsink pcb?

18358414
By 18358414
in Hobby Electronics
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I live about 300km from the nearest electronics recycler and I got some LED light bulbs to save on electricity.  Unfortunately, the 50'000 hour reported lifetime is a complete lie and the company refuses to honour their warranty so I'm stuck with some "dead" LED light bulbs. 

 

With some testing, I've found that the only real problem is the voltage regulator on the board and the SMD LEDs are all fully operational.  I'd like to desolder them from the heatsink pcb so that I can continue to use them on other projects.  What is the appropriate way to desolder LEDs that are applied with some kind of adhesive to an aluminium plate?

 

I've tried with a thin soldering pencil, but that just wrecked the LED.  I didn't really expect it would work, I'm thinking I'll have to use a hot air gun but I don't know what temp to dial in or what procedure to use with this heatsink.

LED1.JPG

LED2.JPG

If I have to explain every detail, I won't talk to you.  If you answer a question with what can be found through 10 seconds of googling, you've contributed nothing, as I assure you I've already considered it.

 

What a world we would be living in if I had to post several paragraphs every time I ask a question.

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I don't think you'd melt Solder with a heat gun, and if you could you'd basically melt that entire thing since you couldn't control the airflow. I'm not one to mess with soldering a lot but don't most solder guns have a dial to control the temps. And if yours doesn't have one couldnt you just pop out your tip on it and just pop something else finer in like a thick sewing needle?

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1 minute ago, Randolf said:

I don't think you'd melt Solder with a heat gun, and if you could you'd basically melt that entire thing since you couldn't control the airflow. I'm not one to mess with soldering a lot but don't most solder guns have a dial to control the temps. And if yours doesn't have one couldnt you just pop out your tip on it and just pop something else finer in like a thick sewing needle?

I have a weller solder station that controls the temp pretty well, but you can see from the first picture that it just destroyed LED #2.  Unfortunately the solder station isn't too kind to allowing 3rd-party soldering tips (can't even figure how I'd fashion something like that up).  The problem with soldering on this is that the heat doesn't stay at the solder joint.  The heatsink carries the heat away making it very difficult to both heat up and control.

If I have to explain every detail, I won't talk to you.  If you answer a question with what can be found through 10 seconds of googling, you've contributed nothing, as I assure you I've already considered it.

 

What a world we would be living in if I had to post several paragraphs every time I ask a question.

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Well I re read what your trying to do. Thought you wanted to fix that thing not take all the leds off. You might try clamping it down and cranking a heat gun underneath it aimed at the aluminum side. And taking something like a Xacto knife underneath the led to lift it free. 

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what I've always done to remove regulators like that is clip the little legs, turn your iron up to 400c and heat up the big bit of the regulator to get it off.

ASU

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1 hour ago, Hackentosher said:

what I've always done to remove regulators like that is clip the little legs, turn your iron up to 400c and heat up the big bit of the regulator to get it off.

The regulator's dead.  I'm trying to get the LEDs off

If I have to explain every detail, I won't talk to you.  If you answer a question with what can be found through 10 seconds of googling, you've contributed nothing, as I assure you I've already considered it.

 

What a world we would be living in if I had to post several paragraphs every time I ask a question.

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7 minutes ago, 7he404guy said:

The regulator's dead.  I'm trying to get the LEDs off

Why not replace the regulator and use the LEDs on that board? If not, you'll almost certainly need a rework station to remove those LEDs.

ASU

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1 hour ago, Hackentosher said:

Why not replace the regulator and use the LEDs on that board?

The board is configured in a format that I can't effectively use.  My plan is to desolder them and solder them to a ribbon cable to make an LED strip which I can then install in my lightbox.  Right now they're concentrated, I need them to be disperse.

If I have to explain every detail, I won't talk to you.  If you answer a question with what can be found through 10 seconds of googling, you've contributed nothing, as I assure you I've already considered it.

 

What a world we would be living in if I had to post several paragraphs every time I ask a question.

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6 minutes ago, 7he404guy said:

The board is configured in a format that I can't effectively use.  My plan is to desolder them and solder them to a ribbon cable to make an LED strip which I can then install in my lightbox.  Right now they're concentrated, I need them to be disperse.

Okay so you need a rework station. Also wouldn't it be easier to buy a roll of 5050 LED strips for a few bucks? Or some larger LED COBs?

 

ASU

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1 minute ago, Hackentosher said:

wouldn't it be easier to buy a roll of 5050 LED strips for a few bucks?

Not where I live -- Shipping anything here is at least $10 and with that I still have to drive into town to pick it up.  Aside from that, I hesitate to throw anything away if it can be re-used within a month or two.

 

Any suggestions for a good rework station?

If I have to explain every detail, I won't talk to you.  If you answer a question with what can be found through 10 seconds of googling, you've contributed nothing, as I assure you I've already considered it.

 

What a world we would be living in if I had to post several paragraphs every time I ask a question.

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That sucks, you sure you can't find free shipping on a certain ebay sellers?

 

Good rework stations are around $500, but you can find knock offs on ebay for maybe $50. They're a good investment if you want to do a lot of SMD work like this. https://www.ebay.com/itm/8786D-2in1-Soldering-Rework-Station-ESD-Iron-Welder-Gun-Hot-Air-Gun-Desolder-SMD/331386085832?hash=item4d282661c8%3Ag%3AGJ8AAOSw~RVaF7j6&_sacat=0&_nkw=rework+station&_from=R40&rt=nc&_trksid=p2380057.m570.l1311.R1.TR12.TRC2.A0.H0.Xrework+.TRS0

 

Just be careful, some of them are a little sketchy on the inside. It may be worth it to open it up and make sure there aren't any loose wires anywhere, bad solder joints, and make sure the grounding is proper.

ASU

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One can try cutting (or sawing) the circuit board around each individual LED. Then it requires heating only a tiny surface to desolder a LED.

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Get a hair dryer or ideally a paint stripping gun and heat the whole board from the bottom to heat the whole aluminum board.  Put the pcb between two planks of wood or something so you can have the heat source under the board and have the heat gun (whatever you use) at 10-20cm from the circuit board blowing hot air on it.

You want to get the aluminum pcb to maybe 70-90c ,, any higher and you risk the plastic case of the leds melting and the small wires connecting the led diode inside the package to desolder from the actual terminals on the packaging.

Then once the whole aluminum sheet is warm, ADD solder to the leads of that regulator and the big tab of the chip and once all three ends flow you can lift the regulator off the board.

If you don't need the regulator chip anymore, use some wire cutters to cut the two leads first, for less thermal mass...

 

It's a pain to do anything with cheap soldering irons... a soldering station is not that expensive (less than 100$) and it's an investment that will last you 10+ years if you take care of it... it's a few dollars per year practically.

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