Thermal Test Wrap Materials and Resulting Junction Temperature

Wow, you are clearly still in the middle of the write-up, no graph yet, but it sounds like a very thorough en informative set of tests. Eagerly awaiting the results :-)

Edit: now with the graphs: awesome results, thanks for doing this and posting! I would not have expected that wrapping would help a lot because of the many material/air transitions with those layers, that the heat has to go through, but you have proved different, in a very convincing set-up!

Oh, and welcome to BLF! :-)

Welcome to BLF. A lot of good stuff here, looking forward to reading more.

I did a simple experiment awhile back, where I supplied a constant voltage to a P60 light and measured the current. It rose as the temperature of the pill rose. What would be interesting to me is what was happening, lumens wise, as that current rose. Supplying a constant 3V DD initially pushed 1.6A thru, but as the temperature increased, it rose to 2.7. That is when I shut it down. What would be interesting is seeing a graph of lumens vs current under those conditions.

You’re right about having thermal loss each time the heat must travel from one layer to the next…I have tested 10 layers of .002 copper foil vs solid .02 copper sheet. I haven’t compiled the info to make it presentable yet, but the solid sheet performs much better. Copper is so good, even with the wrap layers, with good pressure, it still seems to be the best for heat transfer.

Welcome to BLF pflexpro ! :party:

You’ve proved something I already assumed, the widely available 3M copper adhesive foil (which is also quite expensive) performs not as good as al-foil everyone got in his/her household.

Thank you for your test and presentation !

I read that the surfaces of objects can’t touch each other because of all the negative electrons repelling them apart. The closer the surfaces are, the more they repel. A test was done with annealed copper and it was found that the rate of improvement in thermal transfer diminished with increased pressure beyond a certain point.

Welcome to BLF! :party: Are you selling these PflexPro MCPCBs/drop-ins? Thanks for the tests!

Welcome to the forum! Its great to have you here.

Somewhere online can be found a graph that shows thermal conductance ratings of Cu alloys. Pure copper is obviously the best, whereas any common CU alloy becomes far less efficient as the alloy percentages increase. It was enough to make me scrap the use of copper pipe fittings in building high powered LED flashlights. Im still looking for the graph. If anyone finds it, please feel free to post it here.

Before getting rid of my entire P60 collection, I used a heavy gauge specialty roof flashing (with low alloy content) that I cut into precise strips, then wound so tightly around the pill that I had to turn the head with a large strap wrench to fully seat the coils inside. I even cut a thin coil to contact only the pill and then a larger coil to fill the gap so there was no air space inside. All Al to Cu contact had a very thin layer of AA, mostly to prevent galling while turning the assembly. That is when I discovered that the P60 concept should have been discontinued the moment they made the jump from incan to LED. Sure, the design can be improved with copper wrap, but it completely circumvents its only attraction, which was to quickly swap dropins from one to another.

Probably any cheap similarly sized LED host will greatly outperform the best copper wrapped P60.

Gosh I hope not, but it is starting to smell like the makings of a sales thread (complete with seller derived performance evaluations). IMO, completely avoid the P60 design for builds in access of 2 amp. There are far better options available for the price.

Probably would, but that wouldn't be as much fun. They were probably fine till LEDs capable of being driven past 2A became available. At least as long as you don't use a stainless steel host.

But these days there is no point to the P60 as you say.

I have made some of the PflexPro drop ins to sell -it has other thermal enhancements that puts it lowest on the temp chart. The wrap testing was a necessary final step in developing the pflexpro.

Very nice chart. 110C vs about 72C at 7.5minutes it's a huge difference.

How can the pflexpro run so much cooler?

Ah, thank you! Can you share any of the differences in the MCPCB compared to Noctigon? Is it thicker? Nevermind, there is this list from the auction:

Wrapping the threads isn’t specifically mentioned above but it is in the ad. All the other mods will have minimum effect without bridging the gap between the threads since that’s the main path from the pill to the outside world!

This is all great information! I'm glad you joined up and posted this very thorough write-up on the testing method and results. Sure, there are some negatives with the P60 design but it's still very popular and one of the rare true form-factor standards in the LED flashlight industry. Every few days, it seems like, there is someone asking about availability of higher end P60 drop-ins.

Your published test results, along with the details is all too rare to find on our forum. Please just ignore the negative posts -- most of us will appreciate the insight, and it really doesn't matter you sell a P60 drop-in. This has never been a factor before and personally, I wish more sellers would post as much detail technical info on their products as you do.

I myself, have read a lot about wrapping and other P60 techniques, but without the data, was never sure what was a truly better method. Of course I've heard about the copper vs. aluminum wraps, but never actually 'knew' copper was any better. I don't have that much practical experience with P60 lights, though I've built up a few P60 pills.

Great information. Always love threads about p60 lights. If you search around there are a few good threads about heatsinking. I think what was concluded was that after added a copper star, the next junction to take care of is the star—>pill—> reflector. Someone bypassed the pill portion with copper on top of the star mated to the reflector so the heat flows directly into the reflector. This is really good because wrapping a drop-in pulls heat away from the reflector. In a typical set up the heat has to first get to the pill and then the reflector through the threads which is quite inefficient.

Found the thread by lilkevin. Great information in there too.

I think the ultimate set up for heat would be:

- copper board

- copper mod in linked thread

- replace spring with copper ring (also mentioned in aboved thread + a link to lilkevin’s thread on CPF with data)

- copper foil wrap drop in

- thermal grease on threads

- lapping/filing flat the brass pill as the surface is usually quite uneven

  • copper rounds on underside of pill that touches the walls of the pill (more thermal mass + improve the heat transfer of the original thin brass shelf)

Also try thermal paste on the copper wrap… thermal conductivity sucks, but it is a LOT better than any air trapped between the layers of wrap.

That is definitely not right, as you sate it. The layers are electrically connected, so all the net charge goes to the outside. Also, the voltages are too small to cause measurable electrostatic forces. Clean similar metals can be welded together, by pressure only, at room temperature, because attractive forces dominate at very small distance. Of course there is repulsion between the atoms that keeps the material from being compressed to much more than its normal density.

The title would be more specific if it had “P60” in it.