lewong
Newly Enlightened
On this Youtube video, Steve Dahl at DigiKey demonstrates a method of soldering high-brightness LEDs to a thermal pad using a heat gun.
Soldering High-Brightness LEDs
- Thread starter lewong
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spc
Enlightened
wow looks so easy!
tebore
Flashlight Enthusiast
That's not just any old heat gun or the ones you get at home depot to scrap paint. That's a very very expensive heat gun that's used in electronics.
Techjunkie
Enlightened
Ha! Funny this should appear now. I just soldered an MC-E directly to a brass pill. I didn't have heat gun though...
AlexGT
Flashlight Enthusiast
Doesn't the die fry when exposed to 600 F? How does he control how hot the die gets?
tebore
Flashlight Enthusiast
It's ok if it's for a short period of time. That's why there's a soldering profile in the spec sheets. That's why it's important to have good hot air gun one where you can control the heat.
You want to set the gun to just melt the paste but not super hot so it exceeds the max temp in the profile in the sheets. I think the XR-E can take 500F for like 1 minute(I'm going from memory).
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:thumbsup::thanks:
Techjunkie
Enlightened
This stuff is super cheap and does the job. If you need to use a syringe, you'll have to mix it with flux to thin it according to some of the reviewers. Refrigerate after opening to keep fresh:
http://www.dealextreme.com/details.dx/sku.4711
spc
Enlightened
is this the same stuff jewelers use? Ive seen some thats looks similar but it comes in soft med and hard...
Well a problem is that heatsinks with large thermal masses, or very weak, slow heat sources may heat it up so slowly that the die experiences prolonged periods at these temps. Even after the heat is removed, a large thermal mass sink can have excessive temps for an additional minute or two.
Be aware MOST "solder paste" sold at KD/DX is only a flux, and bears no solder. The sku.4711 mentioned IS the right stuff though, the only actual lead solder paste they have AFAIK. Refrigerate even if it HASN'T been opened. However, cold paste may not spread as easily, ideally you wanna pull it out an hour or two before using it.
lewong
Newly Enlightened
I'm reviving this post because I finally tried soldering some LEDs using the method in the video I linked to in the first post.
I recently bought a Veleno Designs SureFire E-Series XP-G Tower Module with a cool LED. With an E2E reflector, the beam was very green. I thought I'd try a neutral XP-G so I ordered some from Digikey. I also had some of the KD boards for XP-Gs and the DX LodeStar solder paste.
I don't have an expensive heat gun - just one for removing paint. I thought if I used my infrared thermometer, I could measure the tip temperature and when the gun was maintaining the correct temperature, I would hold the board/LED in the heat.
The Cree specs say 215 degrees C (~419 degrees F) for Peak/Classification temperature. When my thermometer read that, I put the board in the heat. In the video, they use 600 degrees, which seems way out of spec.
I put a dab of paste on one of the contact pads so I could see when the solder liquefied. In a few seconds the paste melted and the LED centered itself, just like in the video. I immediately turned the heat off and kept the fan running to cool the board.
In the photo below, the bottom board has been soldered. The upper left board shows the amount of paste I used. The upper right board has the LED on it before soldering.
I recently bought a Veleno Designs SureFire E-Series XP-G Tower Module with a cool LED. With an E2E reflector, the beam was very green. I thought I'd try a neutral XP-G so I ordered some from Digikey. I also had some of the KD boards for XP-Gs and the DX LodeStar solder paste.
I don't have an expensive heat gun - just one for removing paint. I thought if I used my infrared thermometer, I could measure the tip temperature and when the gun was maintaining the correct temperature, I would hold the board/LED in the heat.
The Cree specs say 215 degrees C (~419 degrees F) for Peak/Classification temperature. When my thermometer read that, I put the board in the heat. In the video, they use 600 degrees, which seems way out of spec.
I put a dab of paste on one of the contact pads so I could see when the solder liquefied. In a few seconds the paste melted and the LED centered itself, just like in the video. I immediately turned the heat off and kept the fan running to cool the board.
In the photo below, the bottom board has been soldered. The upper left board shows the amount of paste I used. The upper right board has the LED on it before soldering.
Aircraft800
Flashlight Enthusiast
Very nice job for your first time reflow soldering! This comes in handy for emitter swaps!
I solder led's (luxeon rebels) without solder paste and a heatgun!
I first wipe flux on the led contacts and mcpcb, then using a lighter I heat the board up and tin it with a little solder and let it cool. Then I put the led on the board and heat it again with a lighter untill the solder melts and centers the led, I turn off the lighter and press down on to the led with a pin to squeeze any extra solder out (while it is still molten) to increase heat transfer I have found insted of a lighter you can use a soldering iron but it is slower.
I have found this method works very well and after soldering 38 rebels to mcpcbs all of them have worked except 2 because the solder had bridged the electrical contacts, so I just re heated them and they worked
.
I first wipe flux on the led contacts and mcpcb, then using a lighter I heat the board up and tin it with a little solder and let it cool. Then I put the led on the board and heat it again with a lighter untill the solder melts and centers the led, I turn off the lighter and press down on to the led with a pin to squeeze any extra solder out (while it is still molten) to increase heat transfer I have found insted of a lighter you can use a soldering iron but it is slower.
I have found this method works very well and after soldering 38 rebels to mcpcbs all of them have worked except 2 because the solder had bridged the electrical contacts, so I just re heated them and they worked
.
KevinL
Flashlight Enthusiast
Another CPF wow. lovecpf
Frying pans, toaster ovens, lighters, home reflow soldering....wow. And who says lights aren't educational?!
Dealextreme link bookmarked. Now I know where to find the paste.....never thought it would be useful to me
Frying pans, toaster ovens, lighters, home reflow soldering....wow. And who says lights aren't educational?!
Dealextreme link bookmarked. Now I know where to find the paste.....never thought it would be useful to me
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Fichtenelch
Enlightened
After i saw that video, i also reflow-soldered some sst-90's on cree stars with a cheap hot air gun. worked out pretty good
I have also used a heat gun to desolder LEDs from their stars when I'm salvaging parts. Heat guns aren't the best tool to use, but if you're only going to be using them for stuff like this and not precision SMT electronics, it works great.
Keep in mind the temperature the gun is outputting isn't the temperature the LED will get, since the transmission of heat isn't perfect; in the video he turned the gun off right after the solder paste became molten, so I doubt it got over 300 degrees.
The one thing I'd caution against is completely blocking the exhaust of the heat gun with the board, like he did, although I don't think that's a problem with the smaller boards most people use.
Keep in mind the temperature the gun is outputting isn't the temperature the LED will get, since the transmission of heat isn't perfect; in the video he turned the gun off right after the solder paste became molten, so I doubt it got over 300 degrees.
The one thing I'd caution against is completely blocking the exhaust of the heat gun with the board, like he did, although I don't think that's a problem with the smaller boards most people use.
