MC-E questions (optics, drive current, etc)

[kuksul08]

Alright, so here's what I'm working with

It has two XR-E Q5's right now, and yes I already want more light :laughing:

I think I will buy an MC-E to use on one side for now, with a ledil CMC (RS/SS/D) square lense. I just have a few questions about setting it up.

1. Parallel is going to be my only option since my power source is 4.8V. What will be a good drive current so that it doesnt get too hot? Is 2 amps too much? (500mA per die).

2. DX only sells the WG tint MC-E on a star board, but they sell the WC tint MC-E as a bare emitter (I like the WC tint), If I were to get something like this http://www.dealextreme.com/details.dx/sku.16545 , how would I go about attaching the emitter? I am guessing some thermal grease on the pad, then just solder the legs one by one....

edit: If I use the solder paste, do I just spread it out, heat up the star so it melts, then place the emitter onto the molten metal?

3. removed

4. Any general suggestions for me? I'm still relatively new to all of this, especially the MC-E.

Thank you!

 

[kuksul08]

bump I need to know #2 kind of soon...

 

[Techjunkie]

To attach the bare emitter to the star board, you're supposed to use solder paste, like this: http://www.dealextreme.com/details.dx/sku.4711

I don't know how good that particular paste is, and I think all solder paste expires and is supposed to be refrigerated when not in use, and I'm sure DX is not sending to you by way of HK Post on dry ice, but putting all that aside... I think that it's basically mirco solder balls suspended in flux, and one of the reviewers raves about it.

You're supposed to apply a small amount between the emitter and the board and then heat up the board, either with a soldering iron (which I imagine is where the extended thermal pad on the star comes in handy) or a hot plate.

I'm a little more daring. I apply a little ordinary solder to the thermal pad of the star with my iron, then move it to the hot plate (old copper-core, steel frying pan on my range on medium heat) and wait until the solder liquifies, usually just a few seconds. Then I quickly place the emitter onto the star with forceps, and very quickly move the entire star to a cold frying pan using heavy pliers to cool it quickly. I press down on the corners of the emitter with the forceps I used before and then check it to ensure that the emitter is seated properly. If it isn't, then it's back to the heat to melt the solder and reposition the emitter. I usually get it right on the first or second try. Remaining calm is important to avoid burning yourself and/or destroying the emitter.

After the emitter is snugly soldered to the star, I then solder the contacts (feet) to the solder pads on the star.

In any case, using solder or solder paste is recommended over thermally conductive epoxy, which isn't nearly as thermally conductive. I do use the thermal epoxy to mount the stars though, being that their surface area is so much greater than that of just the emitter.

Good luck.

P.S. I've used the WC tint emitters and the WG tint boards from DX and there's so much variation and overlap in the tint of each that I recommend you just get the WG tint boards and save yourself the trouble.

 

[kuksul08]

To attach the bare emitter to the star board, you're supposed to use solder paste, like this: http://www.dealextreme.com/details.dx/sku.4711

I don't know how good that particular paste is, and I think all solder paste expires and is supposed to be refrigerated when not in use, and I'm sure DX is not sending to you by way of HK Post on dry ice, but putting all that aside... I think that it's basically mirco solder balls suspended in flux, and one of the reviewers raves about it.

You're supposed to apply a small amount between the emitter and the board and then heat up the board, either with a soldering iron (which I imagine is where the extended thermal pad on the star comes in handy) or a hot plate.

I'm a little more daring. I apply a little ordinary solder to the thermal pad of the star with my iron, then move it to the hot plate (old copper-core, steel frying pan on my range on medium heat) and wait until the solder liquifies, usually just a few seconds. Then I quickly place the emitter onto the star with forceps, and very quickly move the entire star to a cold frying pan using heavy pliers to cool it quickly. I press down on the corners of the emitter with the forceps I used before and then check it to ensure that the emitter is seated properly. If it isn't, then it's back to the heat to melt the solder and reposition the emitter. I usually get it right on the first or second try. Remaining calm is important to avoid burning yourself and/or destroying the emitter.

After the emitter is snugly soldered to the star, I then solder the contacts (feet) to the solder pads on the star.

In any case, using solder or solder paste is recommended over thermally conductive epoxy, which isn't nearly as thermally conductive. I do use the thermal epoxy to mount the stars though, being that their surface area is so much greater than that of just the emitter.

Good luck.

P.S. I've used the WC tint emitters and the WG tint boards from DX and there's so much variation and overlap in the tint of each that I recommend you just get the WG tint boards and save yourself the trouble.

I really don't want to order from DX, but they wouldn't give me a refund from my last order which never shipped... so I'm forced to.

I have seen multiple of the WG ones that came with the solder all messed up. Don't know if I can really trust it, also I see continual claims that they are too yellow or green.


thanks

 

[kuksul08]

bump.

original post edited.

 

[bshanahan14rulz]

try techjunkie's "daring" approach. I did that with a cree XP-E, and that's probably a little harder than an MC-e due to size. Not to mention first time reflowing anything. Just tin the pads, use an iron or hotplate, and reflow.

 

[kuksul08]

So I can just use regular solder?

Can anyone else verify this?

 

[HarryN]

I use "solder it" paste from fry's electronics for my soldering. So much easier for a beginner like me.

 

[Th232]

Either regular solder or solder paste will work.

Personally, for SMDs and other small fiddly bits, I use a little solder paste to stick two legs down to start with (not much choice there with an LED ehh?). The point of that is just to get it to stick, not for any conductivity or mechanical strength.

Then I cut about 1 mm or less of solder wire, pick it up with the soldering iron, and before all the flux goes away I put the iron on the pad and let it flow from there.