Gauging Interest - Should I Sell Aluminum SinkPADs?

Hello All,

So my name’s Rob, and I worked with DJozz to help him acquire SinkPAD’s for testing the differences between traditional MPCB’s with a dielectric layer and those with a direct thermal path. The results were very good—his graphs show the Aluminum SinkPads being neck-and-neck with their Copper counterparts through 4A, and at 7A, the difference in Lux numbers is only about 4% or so.

Not only are the Aluminum SinkPads cheaper (since Aluminum is cheaper than Copper), the LEDs offered are significantly more varied. Want to run a Osram Olson Square IR LED for…whatever you need tons of IR for? A deep red hunting light that most animals will be unable to see? Or how about a DrJones based Cree XM-L Color light running at higher than 700mA per die (since we know it can) Same story here. There are a lot of LEDs out there that could make for very cool custom projects—particularly if we’re talking about color, IR, or UV light. That’s where these would come in.

If you’re interested in a direct thermal path MPCB offering great performance that’s also cheaper than a copper SinkPad/Noctigon, please fill out this form

I’ll answer questions below, and try to wrap things in to a FAQ so responders don’t have to read through the entire thread.

Thanks,
Rob


FAQ

Can these be soldered to a brass or copper pill?
No, unfortunately they cannot. In that regard, copper is king.

“What sort of price savings would we be looking at? It doesn’t seem worth it to lose the ability to solder the emitter to the pill over a few pennies in price difference”
The price difference is actually fairly significant.
table(table#posts).
|Quantity|Aluminum Star|Copper Star|
|1-300 units|$1|$2.50|
|301-600 units|$0.75|$1.50|
|601-1000 units|$0.60|$1.25|
|1000+ units|$0.50|$1.00|

“How would the SinkPad for the Luxeon Rebel LEDs perform compared to the CoolBase system offered by Luxeon Star LEDs?”

In my opinion, no comparison. The CoolBase system is a FR4 (fiberglass) printed circuit board that uses vias that presumably get filled with solder to transfer the heat. So the amount of surface area that is transferring heat to the heatsink (the pinpricks in those vias) is no match for solid aluminum. You also cannot purchase bare CoolBase boards, and Luxeon Star seems to sell mid-tier binned LEDs at top-bin prices, which isn’t exactly thrilling to see. :frowning:

“How does the direct bond work on the Al version? How does the solder under the center pad of the LED stick to the Al base?”

Good question! I thought it best to leave this up to the diagrams to answer this question for you. The SinkPad Generation 1 has the punched up thermal pad, with Generation two has a flat bottom, utilizing solder to fill a 3 mil gap. Their research and DJozz’s research seem to indicate that performance is identical or better in Generation II.

Generation 1 vs. Generation 2 (click to enlarge):

To me the slight cost savings of Al vs Cu isn’t worth it to loose the ability to solder the base to a Cu/brass pill so I wouldn’t be interested in Al sinkpads but I do have a question…

How does the direct bond work on the Al version? How does the solder under the center pad of the LED stick to the Al base? There must still be a Cu layer or something?

Personally, I have no interest in alu sinkpads.

When I mod a light, I want to put in the best… and that means direct copper. The slight cost savings of going with alu v. copper sinkpads isn’t worth it to me.

What level of cost savings might be possible?

I think many will opt for the Copper stars. The price difference is not an issue, since you can buy leds already on copper stars for about the same price as aluminum. For me, it's a no brainer for any led running more than the recommended stock amperage. Copper is all I use any more, since it's what most everyone wants, just like XM-L2 over XM-L. It's the thing now.

I’d like to see a comparison that includes the Luxeon “CoolBase” 20mm star and 10mm square mounts

Maybe interesting for manufacturers, but hardly for flashlight enthusiasts because the price difference is negligible.
On the other hand, it’s cool to not get caught up in the copper-hype. :wink:

Forget the small price difference, the main advantage is the greater selection of LED's. No?

We’re all caught up in the copper hype, so saving a few pennies on aluminium SinkPads doesn’t sound too promising. :~

Just switch all your aluminum bases over to copper bases, and we will all be happy!

Hi Rob, I would certainly be interested in aluminium Sinkpads (not truckloads of them, just a few now and then), they offer boards for some special leds that I sometimes want to use. The copper ones are a bit more versatile (solderable), but the variety offered in aluminium boards is really nice.

I appreciate your effort in offering them, I think it is valuable for the flashlight community to have source for these special boards, but I hope that you do not do expect huge sales, most people are stuck to the Cree leds (mostly for good reason) and there's obviously not much interest from them.

I’m interested just due to the huge selection of available die patterns…I don’t think the savings of a few pennies a star (unless you buy hundreds or thousands at a time) is worth it, nice thing is with direct heat path stars there is negligible difference in the material…copper or aluminum, as long as there is NO PCB material between the heat slug under the emitter die and the physical star the heat WILL soak thru to the star faster than stock ones that have the PCB heat insulator between.

I wonder if you could make them out of brass like the pills in most of the Convoy S series or P60 dropins, still have direct path for heat AND retain the ability to solder (aluminum is soooooo hard to solder [well at temps safe for emitters])

+1 for copper :wink:

I will say that for the same reason as WarHawk I would be interested in some. I’m not going to stop using copper for XM’s/XP’s to save a few ¢ but I have a tape of rebels I bought a long time ago and only one non-direct board so I’ve never been able to use them. If they were easily available I would pick some up and find a project to start putting HCIR Rebels in.

Is the Luxeon deep read linked above on a star with a dielectric layer under the led? Is there a direct copper replacement available for it? Does the Al direct replacement already exist?

I would also be interested in these and thanks for posting this. The oddball sizes are important and really if the savings is enough I would use them on some of the multi-emitters that I build. 9x and 12x’s aren’t going to blow without the sinkpads anyway, but the drop from thermal sag is a lot. So if the price was 50% less I would go for it for these mods. Not for mods where I am really pushing the limit for for ones that could benefit from these but don’t really need the full blown copper star treatment.

The Luxeon Deep Red LED in the Convoy M1 is on an Aluminum SinkPAD, Generation 1. So it’s a direct thermal path solution, which is why I’ve pushed it to 2A (and beyond)

Has anyone tried building a temperature sensor into a pill, so it could be connected to read the temperature directly?

rollinstone157 didn’t seem to address this question in his FAQ, but I’d assume that they simply tin the aluminum. I’ve read that the only reason you can’t solder to aluminum is the oxide layer that (quickly!) forms when aluminum comes into contact with the atmosphere. The Sinkpad folks are no doubt simply cleaning this oxide layer away and then soldering to the regular aluminum - or using a special solder that allows them to tin the oxide layer.

Mine is from RapidLed.com, and I am only pushing it at about an amp. so far.