Soldering Cree XM-L or XM-L2 LED ?

[MrAl]

Hi there,

These high power LED's are surface mount and should be soldered with a hot plate or oven maybe.

But anyone have any success soldering them by hand, perhaps with a home made heat sink of some type?

It's a tricky thing to try to do because the heat sink surface is on the back and so are the anode and cathode connections. Normally they surface mount solder them to a specially designed MCPCB with the right pattern on it, but i want to find another way to do it.

But also if you have done it with a hot plate i'd like to hear about that too, thanks.

 

[ronsimpson]

I have a small toaster oven. I use solder past.

It is very important that the solder job is good. That is how the heat gets out of the part.

 

[tvtech]

^^^

Hi Ron. I also solder past most components. Keep missing them
New glasses comoing fer me.

Regards,
tvtech

 

[MrAl]

I have a small toaster oven. I use solder past.

It is very important that the solder job is good. That is how the heat gets out of the part.

Hi Ron,

What kind of board did you solder them to? I probably have to rig something up myself or else i'd have to find one of those MCPCB's to use. I would rather find some way to do it without anything special purchased except maybe alum or copper block or something.

 

[tvtech]

Anyway Ron

Pulling your leg. We all know you meant paste. My new glasses are still coming though

Anyway, back to MrAl's question:
It was a toss up for me (with my project) between DurisE3 or DurisE5....

I checked Cree out, I checked (other Osram) LED's out Dragon and what they do. Everything to do with surface mounting LED's. Checked Chinese copies and all that too.

Checked out high power LED's and how they are cooled. Learned about MCPCB. Learned that the LED assembly is essentially BONDED to the heatsink..

Checked out everything I could...at the design stage it was 18 Months ago...I realized that I need many smaller ones than maybe two big ones..

The more I looked at solder needing to flow UNDER pads to conduct heat away....the more I realized I will screw up.....

Anyway, not to take anything away from MrAls' question.....I bailed from using E5 Duris...would only have needed two with special cooling to last..

Settled for ten E3's with a nice board cooling design. As reliable as ever. And same light output....

Only a 1W light.....

And I have not answered MrAls question

Sorry guys

Regards,
tvtech

 

[Joe G]

I am using these in a new project "LZ1-00CW00" . I am able to solder the "pins" with an iron w/ thermal paste on the heat sink lug.
I'm also using a two sided pcb w/ thermal paste on a aluminum base...

 

[tvtech]

And so

Long day.

 

[MrAl]

I am using these in a new project "LZ1-00CW00" . I am able to solder the "pins" with an iron w/ thermal paste on the heat sink lug.
I'm also using a two sided pcb w/ thermal paste on a aluminum base...

Hi Joe,

Thanks for the info. This is interesting because that's almost like the LED i was talking about.

When you say 'pins' i guess you mean the back of the LED where the traces are for plus and minus right ?

What do you mean you used thermal paste on the heat sink lug? Do you mean the non drying type or the thermal epoxy like Arctic Alumina or something like that?
I was thinking of using thermal epoxy on the back but the two terminals are also on the back so it would be tricky to glue a hunk of aluminum to the back without shorting out the two leads (or pins).

What is your two sided pcb made of, epoxy like a regular PCB or some other material?
And where is the aluminum base, and did you glue that on too?

Could you tell me more? Thanks. A picture would be nice if possible too.

 

[alec_t]

I haven't tried this, but to do this without a reflow oven I think I'd solder three heavy-gauge copper strips, each ~15mm long, to the back of the LED so that strip ends protrude beyond the LED then solder the strip ends to a pcb.

 

[Joe G]

The brd is a regular FR4 1/32" double sided. the thermal paste is a white color and I don't know the brand had it a while in a small container, really good stuff $$$ I do know, (was a free-bee).
the base will be 6061 aluminum (I haven't been able to turn it yet) and the pcb's will be screwed to it with 0-80 screws .
I was gonna use the leds you asked about but wasn't sure about the soldering either and these seemed very close to what I was needing plus I am too cheep to buy them on a MCPCB.

 

[alec_t]

That coin looks just about the right size for use as a heatsink .

 

[MrAl]

I haven't tried this, but to do this without a reflow oven I think I'd solder three heavy-gauge copper strips, each ~15mm long, to the back of the LED so that strip ends protrude beyond the LED then solder the strip ends to a pcb.

Hi,

Yes, that sounds like it could work. There is a slight problem though, and that is that the center strip MUST connect directly to a heat sink, while the two outer strips are the plus and minus leads for the LED. So we have something like this:

xxxxxxxxxxxxxxxxx (+)

xxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxx (-)

The upper strip of X's is the positive, the lower strip the negative. The center four strips are actually one strip and that's the part that must connect to the heat sink. So whatever that center wide strip gets connected to, it must then connect to the large heatsink. So this is a kinda three dimensional mounting problem because the metal of the large heatsink must make good contact to the center wide area, but must not make contact with the two outer thin strips or else it will short out the LED. So maybe two small strips with insulation on top or something for the plus and minus, i dont know yet.

 

[MrAl]

View attachment 87553
The brd is a regular FR4 1/32" double sided. the thermal paste is a white color and I don't know the brand had it a while in a small container, really good stuff $$$ I do know, (was a free-bee).
the base will be 6061 aluminum (I haven't been able to turn it yet) and the pcb's will be screwed to it with 0-80 screws .
I was gonna use the leds you asked about but wasn't sure about the soldering either and these seemed very close to what I was needing plus I am too cheep to buy them on a MCPCB.

Hi Joe,

Thanks for the pic and description.

It looks like you have it soldered at the four corners. I guess that holds it down?
So there is thermal paste on the back side between LED and top of the board?
Is there copper on the board there too?
So the heat conduction path looks like it comes out of the LED back, goes to the copper on the top of the board, conducts though the fiber PC board, to the lower layer of copper on the back of the board, then to the alum heat sink?
What current do you intend to run this LED at?

 

[tvtech]

Investigate Guys...

Go to Manufacturers sites...download and learn from them.

The cooling parameters are listed...what works and all that...no guessing or wondering

Now, speaking about wondering....

I am tired. Hectic night last night. No tits for me tonight They are all sleeping peacefully on that little branch above my head.

Regards,
tvtech

 

[Joe G]

MrAl.
You got it all correct, I used a double sided brd just to make sure that the thermal paste to aluminum heat sink would be the best I could get for now.
I dabbed a bit of solder on the 4 outer pads and solder wicked it off before using an iron on the 4 corners.
A dab of thermal paste on the center copper pad.
I'll be running them at 1 Amp for now for testing for a bit before continuing w/ this project

also on that data sheet towards the end there is a bit of thermals instructions for different ways

 

[MrAl]

Hi Joe,

Wow, 1 amp? That will mean heat around 3 watts or so. What would worry me is the PC board material between the two copper laminates on ether side of the board, which means the hast has to travel through the board materiial itself. I think you said it is 1/32 inch thick right? That's better than the more usual thicker stuff, but i'd still be worried because this much heat is usually dealt with with metal to metal contact, except of course for the thermal paste.
Have you done it this way before or is this the first time?

I'll have to check out the data sheet.

My situation is even more severe though, at 3 amps it will have to dissipate around 10 watts.

LATER:
Just checked the data sheet, and they seem to be recommending a MCPCB as well. Thus i would be very very careful when using a non MC PCB like a fiber type board.
One thing you can do is measure the forward voltage with a constant current and see how it changes to estimate the temperature rise of the LED. At 1 amp it will get pretty hot even with a MCPCB so maybe you should turn up the current slowly starting at 0.250 amps or something like that.
I would be interested in hearing more about how this goes.