Eliminate the MCPCB?

How about this. Make a heavily finned light then create a ball bearing sleeve around the handle so when you want turbo you give it a spin and go to town. You can add a latch to keep it in place for lower modes.

Practical and fun and still mostly water resistant!


OK, that’s different. Instead of having a fan, spin the heat dissipation fins for more air circulation :slight_smile: :beer: :beer: :beer:

I think you’re on the right track for high wattage applications. Interestingly, Lambda Lights used to mod and resell high amp LED maglites with the same mod. He had to heat the entire chunk of copper (around +2 pounds as I recall) in order to flow the emitter onto the gargantuan copper pill. There were technical challenges he had to overcome before they would adhere. Here are some of his creations. I owned several before reselling.

You can try another way.
Regular pcb (fr4 or alu based) with central pad hole, and copper plate with extruding pin of same shape. This way have no user benefits in comparation with dtp pcb, but making fr4 or alu core pcb of any shape and design is widely available (while dtp pcb is not).

Brilliant! I’ll make my pads out of standard double sided PCB. I can machine pockets into the copper base material for the pads, and even reflow the pads onto the copper. It’s basically making my own MCPCB, but the MCPCB is a huge piece of copper, with heat sinks machined into it. I’ll make sure to cut the pad reliefs a few thousandths deeper than needed, so the center section (the tombstone that the LED mounts to) is proud just a tiny bit. This will ensure the thinnest film of solder at this critical point.

I’ll model it up and post it in the morning.

Holy F! I remember those lights from back in the day! Like I think I even bookmarked that exact thread in my early days of lurking. LED technology sure has progressed in a decade.

Some BLF-history:

This made me think of the mods that have attached a star MCPCB to the base of a heatpipe based heatsink.
Too bad there is nothing akin to that or even a vapor chamber for the pill to move heat away, far faster than any solid metal you can think of.

This is exactly what a DTP MCPCB is…
So your idea is basically just a bigger mcpcb?
If you use liquid metal between the mcpcb and a heatsink it’s basically like having no mcpcb, the extremely high thermal transfer and large area on the bottom of the PCB make it so that heat flow restriciton is as low as possible for the LED.

Yep, the idea is to eliminate the thermal resistance of the MCPCB~~pill connection and pill~~>heat sink connection by making everything from a monolithic piece of copper. No need for liquid metal connection to the heat sink when the LED is already directly attached to the heat sink.

If you do make it, you may test the performance compared to a copper DTP-board with ordinairy Arctic silver 5 paste connection to the pill. Back in 2012 our BLF member match tested the performance of the first Sinkpads against his machined copper slugs and found to his disappointment that it was the same, all his hard work did not have unique performance anymore, any layman could by a cheap Sinkpad and get the same performance in a much easier package. It so appears that the thermal performance at the tiny solderpads of the led is way dominant over what happens further away from the led spread out over larger surface areas.

Okay, here's the latest. Two pieces of FR-4 circuit board material are set into the copper monolith. They're copper on both sides, so I can reflow them down to the monolith underneath. There's a thin tombstone right under the LED's thermal pad, just a couple thousandths above the FR-4 pads and the rest of the monolith. This ensures a thin solder connection where it counts (from the LED thermal pad to the monolith), and lets the solder be thicker for the electrical connections.from the die to the FR-4.

Section view. The only FR-4 I have is thicker than I'd like (0.056"), but I don't think it'll make a massive difference here. The chamfers on the FR-4 should keep any solder bridging from happening during reflow.

Again, this is just the LED->monolith interface. The rest of the monolith and heat sinks aren't shown.

Always good to see creativity :slight_smile:
I’m not knowledgeable enough to comment on the existing plan but is there scope/neccessity to raise the emitter up a little, away from the shelf, for better focus in a reflector?

The thing is there is no significant thermal resistance between the MCPCB and pill.
The area of contact is extremely large, hundreds of times larger than the area between the LED thermal pad and MCPCB.
The bottleneck is there, not between the PCB and pill.
If you want every bit of extra performance then use a larger 32mm pcb and liquid metal, but you can do tests and you will probably not be able to measure any difference than if you used a 20mm one, or if you used a solid copper block.

Definitely a concern. If anything, the LED sits too far forward into the reflector in this host. That’s good because I can easily machine a shim to step it away just a bit. I guess I could turn down the base of the reflector to go the other direction, though.

I’m getting convinced that this will be the case. But I like building stuff, and this will be a cool piece regardless. And I always learn more from cutting my own path (even if it’s been traveled before) than from just doing the status quo.

I milled out the thermal pad center section of a aluminum mcpcb and milled a copper heatsink with the matching rectangle of the thermal pad sandwiched together so the led soldered directly to the copper heatsink and the connections where made on the aluminum mcpcb. It worked great but a time consuming project.


All my pics are being held by photobucket for randsom in this thread :frowning: .

This thread reminds me of the old recoil throwers. Led XR-C soldered to copper slug pressed into aluminum head, wires direct to led contacts.

Cool! My first thought was “how tiny was his end mill to get such small radii on those MCPCB internal cuts?!” Then I saw you used a file to finish things up. CNC gives me tunnel vision sometimes. It’s also fun to look back and see the state of the hobby just 6 years ago.