How are you putting the spacer on a SSC LED?

I have a couple of SSC LEDs that I'd like to put into some older lights. I was wondering how you guys are affixing the small copper spacer that is recommended to bring the die height up to that of a Luxeon.

It would seem best to put the spacer on the LED then let it dry before putting it into what ever gets the transplant but is there a way to make certain before the final installation to make certain that you didn't accidentally make contact with the SSC's slug? Could you touch the LED -- and the spacer/slug with a multimeter and check to see if it shorts or is there a better way?

TIA,
-LT

If you epoxy the spacer to the led, just use your multimeter to check for continuity between the spacer and the positive lead. If there is none, you're good to go.

I thought it was the negative terminal since I thought the slug was negative. (confused)

-LT

It is the negative LED terminal. Edit: Correction - the pad is connected to the positive terminal.

On a star, there's no problem, because -- at least, on every star I've seen -- the mounting pad is electrically isolated. On other mounting surfaces, I use Arctic Silver epoxy, with a thick enough layer to insulate the pad. I very gently check it with a DVM before putting it aside to cure. This is a bit tricky, since the very act of testing can cause it to make contact due to putting pressure on the spacer. But it works reasonably well. Only a couple of times have I found it to be shorted after curing. It's not hard to pry the LED back off if you do it within a couple of hours or so of when you applied the epoxy. Arctic Alumina epoxy is also ok, but it has about twice the thermal resistance of Arctic Silver, so you don't have as much leeway in how thick you make it without significantly reducing the heat transfer ability.

I smash the spacer in a flat-jawed vice, then sand it with very fine emery paper to make it very flat before I use it. This helps it "float" on the epoxy and removes any uneven edges that might poke through.

I've experimented with cutting a tiny donut of 2 mil Kapton tape, sticking it onto the LED as an insulator, then epoxying it down. Kapton has very poor thermal conductivity compared to decent epoxy or compound, so it's necessary to keep the donut ring very narrow so compound or epoxy can directly contact most of the LED pad area. I've pretty much abandoned that approach as being more trouble than it's worth, but you can give it a try if you want.

The plain epoxy method is pretty easy once you get the hang of it -- I've put Seoul LEDs into around a dozen lights so far using that method. Have fun!

c_c

Thanks c_c

That emery paper idea should help and I'll look into getting a vise since the spacers I have are slightly domed (I guess from the punch process).

-LT

On a Seoul SSC LED the slug is positive. That's why it needs to be kept from shorting to ground. If you epoxy the led to the spacer first, you can check to see if the spacer had shorted to positive before you install it in your light.
I'm talking about a bare emitter, not a star.

Walt175 said:

On a Seoul SSC LED the slug is positive. That's why it needs to be kept from shorting to ground. If you epoxy the led to the spacer first, you can check to see if the spacer had shorted to positive before you install it in your light.
I'm talking about a bare emitter, not a star.

Click to expand...

I'm sorry, you're absolutely right. The pad is connected to the positive LED terminal, not negative as I said. I apologize for the error in my earlier posting -- I've edited it.

c_c

I just ran the 11 I have of these through my digital calipers and came up with 0.97mm-1.02mm (0.03819"-0.04016") so flattening and sanding would definitely be recommended if you really want it to be 0.030" (0.762mm). Maybe the sheet from which these are punched is 0.030" but the final product isn't.

-LT

I've apparently missed the memo on these spacers. Are they recommended for all reflectors?

Luni, would you please posting a pic or a link to where I can learn more about them? I have a SSC emitter waiting for a mod.

You only need a spacer if the reflector will remain the same height. If you are able to screw the head down further- then no spacer is needed. If you are custom making a light- no spacer needed.

Lighthouse one said:

You only need a spacer if the reflector will remain the same height. If you are able to screw the head down further- then no spacer is needed. If you are custom making a light- no spacer needed.

Click to expand...

A side note -- sometimes a spacer and/or screwing down the reflector aren't sufficient to get the LED die to the focal point. The problem you can run into is that the SSC die is about 0.030" lower with respect to the upper surface of the LED body compared to a Lux. So in some cases the hole in the reflector has to be enlarged enough to allow the body of the LED to protrude into the reflector some, or the back side of the reflector has to be made thinner by sanding or filing. In modding a ProPoly lux light, I used a Dremel tool to cut some rectangular enlargements to the reflector hole to allow the reflector to be positioned below the level of the LED leads. You can dispense with a lot of this if you're happy to end up with a considerably floodier, less focused light after the mod.

c_c

Curious_character said:

The problem you can run into is that the SSC die is about 0.030" lower with respect to the upper surface of the LED body compared to a Lux.

Click to expand...

Duh! I see what you guys mean. Dedicated SSC reflectors for me.

greenLED here is a not great picture of the spacers. If I have a chance to revisit this I'll see if I can do better.


Note that they are concave on one side and convex on the other. The ones on the piece of tape have been sanded down on both sides hence the sharper looking edges.

Here's a link to them at The Sandwich Shoppe.

Unfortunately for me I have a number of older Aleph lights that I'd like to upgrade, particularly 38mm reflectored ones so the height adjustments are needed to get the maximum throw out of the lights.

Hope this helps.
-LT

I cut the reflectors on a L1T and a Q3 by .03 and moved the emitter up by .03. I never noticed a difference. I don't think it is worth the trouble.
Maybe my two lights are just an anomoly.
Mike

I replaced my Gladius with a Seoul star... the entire thing swapped in, using the original IMS27mm... focus seems good to me, and throw is good too... of course, if I did an emitter mod with the spacer, it might get a tad better theoretically, but it doesn't look worth to me either.

The SSC has a creamy beam by itself even with the non-textured, fully reflective IMS27 and it's all good.

I think someone did some comparative beam shots with and without the spacer but I can't find them now. Anyone else with exceptional Google-fu talents know where they are?

-LT

LEDcandle said:

I replaced my Gladius with a Seoul star... the entire thing swapped in, using the original IMS27mm... focus seems good to me, and throw is good too... of course, if I did an emitter mod with the spacer, it might get a tad better theoretically, but it doesn't look worth to me either.

The SSC has a creamy beam by itself even with the non-textured, fully reflective IMS27 and it's all good.

Click to expand...

I've measured both the main beam brightness (lux) and the total light output (approximate lumens, via a Quickbeam type box) before and after most of my Seoul mods. The total light output nearly always just about doubles, as you'd expect because of the doubled efficiency. The lux value typically increases around 50%, some a bit less and others approaching 100%. When the fractional increase in lux is less than the fractional increase in total light output, it means that the focus isn't as tight as before. That's been the case for most of the lights I've modded, even when I get the reflector moved to the optimum point. Either the beam shape isn't quite the same for the two LEDs or the radiating part of the Seoul die is a little bigger than the Lux. But the overall improvement has been worthwhile in all the lights, in my opinion.

c_c

That pic is most appreciated, Luni! For some reason I was thinking they were kinda like washers to add between the SSC and the reflector.

Curious_character said:

I've measured both the main beam brightness (lux) and the total light output (approximate lumens, via a Quickbeam type box) before and after most of my Seoul mods. The total light output nearly always just about doubles, as you'd expect because of the doubled efficiency. The lux value typically increases around 50%, some a bit less and others approaching 100%. When the fractional increase in lux is less than the fractional increase in total light output, it means that the focus isn't as tight as before. That's been the case for most of the lights I've modded, even when I get the reflector moved to the optimum point. Either the beam shape isn't quite the same for the two LEDs or the radiating part of the Seoul die is a little bigger than the Lux. But the overall improvement has been worthwhile in all the lights, in my opinion.

c_c

Click to expand...

The Seoul's beam is 'creamier' (sorry for the non-technical explanation) than the Luxeon or Cree, I'm not sure why this is the case. Is it because of the slightly murky dome?

Using a Luxeon or Cree in a non-textured reflector always produces artifacts in the beam or some dark ring or another.

Using the Seoul in a non-textured reflector, however, still gives a damn nice beam. I'm not surprised the throw is affected!