# LED reflow soldering at home



## kuksul08 (Oct 31, 2012)

I made this video documenting how I have done reflow soldering in the past. I find it to be a little simpler and somewhat more controlled than a toaster oven, stove-top, or heat gun, since you can adjust the amount of thermal "inertia" and capacity by the size of the plate you are heating up. Despite being so simple, it's actually not too far off from the preferred reflow profile in the Cree datasheets. With a temperature controlled soldering iron, you could actually get pretty close.

Any comments?

http://www.youtube.com/watch?v=0ZcOqYFtzo4


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## jmpaul320 (Oct 31, 2012)

cool - up until now i had no idea how to do this... thanks for sharing!


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## pinetree89 (Nov 13, 2012)

Excellent video, thanks for sharing. :twothumbs:


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## hoffmyster86 (Nov 15, 2012)

i've just started on this stuff, so far i've gone through routine from thick wire solder and a hot iron to clipping small bits of solder wire and placeing it just there an heating with a gas solder iron with a heatshrink tip on..

seems theres two parts, use solder and use heat lol. (too much makes the diodes go a funny colour inside but they change back again after for the animal way).

any good links to the flow solders? 25 quid for piddley little syringes is taking the ppee in my book.


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## kuksul08 (Dec 8, 2012)

You can get "Mechanics solder paste" at DX for cheap. I also have some industrial tubs of solder paste, you can try contacting a local semiconductor manufacturer for expired material.


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## langham (Dec 8, 2012)

I just take a soldering iron and hold it to the back of the led's heatsink and hold lead core solder to the pad until it melts and then I place the LED in place and let it cool, this has worked great for me. I know quite a bit about metallurgy and a few things that you could do to make it better would be to perform the whole process in a vacuum, use an inert gas to remove any impurities from the area, and the one that you can't do is slowly cool the solder to ambient temperature due to the damage that it would cause the led. That being said I do what is listed at the top in my guest bathroom on the rare occasion that I actually have to re-flow solder something.


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## kuksul08 (Dec 8, 2012)

langham said:


> I just take a soldering iron and hold it to the back of the led's heatsink and hold lead core solder to the pad until it melts and then I place the LED in place and let it cool, this has worked great for me. I know quite a bit about metallurgy and a few things that you could do to make it better would be to perform the whole process in a vacuum, use an inert gas to remove any impurities from the area, and the one that you can't do is slowly cool the solder to ambient temperature due to the damage that it would cause the led. That being said I do what is listed at the top in my guest bathroom on the rare occasion that I actually have to re-flow solder something.



That first part would be a bad idea since you will thermally shock the LED which could damage it. Cree specifies a very specific ramp rate assuming the parts are dry to allow for the chip to warm up gradually and evenly, and for the flux to work properly.


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## CTS (Dec 8, 2012)

All you have between the LED and the board to conduct heat is solder. There is a vast difference between different solders and their ability to conduct heat away from the diode. Higher heat = lower lumens. Really high heat = no more LED.







Notice how bad the old standard 50/50 solder conducts.

SRA-solder.com stocks SnAg 96.5/3.5 paste in syringes


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## MUSTARD (Dec 19, 2012)

for reflowing an led onto a pcb would you use a free flowing paste or a restictive flow one??

should a different paste be used when reflowing a led onto a copper pcb?


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## SteveoMiami (Mar 12, 2013)

Is this SnAg 96.5/3.5 solder good for sodering on circuit drivers as well? Is there a case where we shouldnt use this soldier? I already have another soldering paste on order but it doesnt give andy details of its contents and it was really cheap so im assuming its 50/50. If this solder makes any kind of difference Id rather use it. I'm new to solder pastes but good with regular solder


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## xevious (Mar 12, 2013)

Interesting approach, but I'd worry about the heat becoming too much and possibly damaging the LED... since you're heating the entire piece of aluminum plating. A guy going by the name "Old Lumens" on YouTube has an LED reflow video that looks very good. He actually heats the back of the board, right below where the LED sits, which acts reasonably fast on the solder without heating up the whole board.


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## degarb (Nov 6, 2016)

CTS said:


> All you have between the LED and the board to conduct heat is solder. There is a vast difference between different solders and their ability to conduct heat away from the diode. Higher heat = lower lumens. Really high heat = no more LED.
> 
> 
> 
> ...



I did my first reflow, yesterday, xpl hi onto copper pcb. . I used 66 tin 33 lead paste. Used heat gun, tweezers, vise, reading glasses. . Very scary, but really quick and easy with that formula. . Other swore by that paste after other formulations were like hitting head on Wall. . I can give up a few c/w for success. . Which formula strikes best balance between success and c/w?


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## vestureofblood (Nov 11, 2016)

Here is my 2 cents on the subject.
https://www.youtube.com/watch?v=B3F68ubfBkk


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## oly999 (Mar 9, 2018)

im also doing some reflowing with sink pads but im having an issue with the leds not lighting up after reflow.
leds all are fine i think its the stencil ive been using isnt getting enough paste under the leds . im thinking of taking all the leds off and putting more paste on an re doing them . 

do i need to do this or can i just put blobs of solder paste net to each led would this get sucked under each led ??? and fix my issue ??


any advice ?? thanks


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## rayman (Mar 10, 2018)

I had that too in my first tries. I think one problem could also be that there is to much solder and you have a short circuit under the emitter. What I do is get barely enough solder on the pad and the place the emitter on it and heat up the pad.

In you case I would take of the LEDs which are not working and start over again with an adequat amount of solder.


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