Does anyone know if that stuff is good heat conductor? I have some P4 leds that I would like to 'glue' with the stuff into bicycle lamp, but I'm not sure if that stuff would work as heat conductor so that heat from led is transferred to casing?

Hi Jani.
A few years ago one of my core plugs popped out in extremly cold weather
{ my fault for not having enough antifreeze in it } I managed to squeeze in a
replacement and with the help of liquid metel there has been no futher leeks.
Hope this helps.
Cheers Mark.

Chemical metal should be fine, a friend of mine has his oil cooler plugged up with it.

Also, I love reading the classic adverts for this stuff in hot rod magazines:

Its basically plastic resin with a powder filler, so its not a great thermal conductor. If the LED spec is suggesting you need a good heat sink you probably need something better. How many watts of heat do you need to dissipate?

Normally you would buy them on a PCB which should be well enough designed.

Ride_on wrote:Its basically plastic resin with a powder filler, so its not a great thermal conductor. If the LED spec is suggesting you need a good heat sink you probably need something better. How many watts of heat do you need to dissipate?

Normally you would buy them on a PCB which should be well enough designed.

Ah, so it is not metal after all, EU will probably soon ban that marketing as a metal as they did with meat of moose, it is not natural product in eyes of EU

LED is Cree P4 XRE (WE), runs at 3.7V and 1A at max, I guess, I'm not sure what I have bought
http://dx.com/p/cree-xr-e-p4-wd-with-13mm-base-3393

I guess it is this:
http://www.cree.com/~/media/Files/Cree/ ... 090XRE.pdf

I think that this is the same, but it is confusing that there are difference in mA ratings.
http://www.cree.com/~/media/Files/Cree/ ... 0XREBL.pdf

I'm not sure about amount of heat, but I think with this it should work, oddly they shipped me one that is not such two boards in one, but just one board. :
http://dx.com/p/3v-8-4v-5w-cree-3-mode- ... -6mm-25517

I don't understand too much about this stuff, just want to improve old bicycle lamp without paying insane amounts of money.

I was thinking that I would get heat to go into bulb holder and then to metal reflector of the lamp, from there metal casing of the lamp as it is old lamp, it is all metal construction.

Here is pic of what I had in mind, led is on top of bulb holder there, in bulb holder there is hole at the middle of course, but I was hoping to put some thermal conductor material there that would hold LED on place and also transfer heat to bulb holder.



I guess I'm bit over my head here, also I have read 240lm to 80lm ratings for led's illumination ability, maybe lower is for low power of 350mA and other is for max power of 1A if those numbers do mean such that there are in those documents?

Inside the lamp itself there is lot of space, but bulb holder area has of course bit limitations in space. It is one of those egg shaped Solifer brand old lamps, not sure if anyone here knows about them, it would hold two leds, low and high beam kind of setup possible, but I wanted to first test with just one led. Maybe I need to invest to some heatpaste that acts as a glue and fill bulb holder with such to get effect I'm after, or maybe I would be better of with different approach, I'm not too sure at the moment.

I too have Cree bike lights and torches. You cannot beat them for the money!

Don't use plastic padding... there are "proper" thermal epoxies on the market.

However, if this is a "Make it so it's cheaper than buying one" then use a very thin layer, or, CPU compound behind the LED die itself and epoxy around the edges.

There is a huge amount of heat to get out of the die.

Chris_C wrote:Don't use plastic padding... there are "proper" thermal epoxies on the market.

However, if this is a "Make it so it's cheaper than buying one" then use a very thin layer, or, CPU compound behind the LED die itself and epoxy around the edges.

There is a huge amount of heat to get out of the die.

Solder is expensive, but you know that similar stuff we use at new year to melt the metal and drop it into bucket of water, then telling next years fortune from weird looking metal cast? I know only word tin for it, we use same word for solder and that stuff, also there is tinfoil, which is actually aluminum.

Anyway, I was thinking of getting those new year tin horse shoes and melt them, then cast nice solid surface to bulb holder, fill interior of it with molten metal and use thermal adhesive compound to attach the led to that new flat surface.

I plan to make cooling like some Apple laptops have, whole laptop is metal and whole laptop is heatsink, so I plan to use whole metal lamp as a heatsink.

Should be ton more cooling than AAA flashlights have which this led has been used.

I think that that lower under 400mA current is enough for normal operation, that would be 80 lumens, which is already lot better than market lights we have here. 1A would be around 250 lumens which might be tad too much and it would blind areas outside of beam to pitch black which is not nice. Especially at full moon it is nice to see into forest too.

Using thermal compound as a filler might be indeed bit bad for wallet.

I'm not that much up with LEDs, but the simple solution is to measure the temp of the die if you can. The data sheet is the for the component not the PCB mounted unit. My P14 LEDlenser is thermally coupled to the Al casing.

As Chris says the main issue is to get the heat away from the Die, the PCB might be fine but the heat still has to get out of the casing. If its a plastic case it might not be suitable, or you may need to arrange some external sinking.
I actually have some guys in my office doing some development on a much larger sealed product (home coffee machine sized) and having trouble getting rid of 25w. Running thermal simulations etc. you could do that if you have £30K to spare

If you are going to make your own products you need to engage in Engineering testing, or just suck it and see and modify it when it fails.

Ride_on wrote:I'm not that much up with LEDs, but the simple solution is to measure the temp of the die if you can. The data sheet is the for the component not the PCB mounted unit. My P14 LEDlenser is thermally coupled to the Al casing.

As Chris says the main issue is to get the heat away from the Die, the PCB might be fine but the heat still has to get out of the casing. If its a plastic case it might not be suitable, or you may need to arrange some external sinking.
I actually have some guys in my office doing some development on a much larger sealed product (home coffee machine sized) and having trouble getting rid of 25w. Running thermal simulations etc. you could do that if you have £30K to spare

If you are going to make your own products you need to engage in Engineering testing, or just suck it and see and modify it when it fails.

I guess that I can buy quite many ~2£$€ leds with 30K, for research and development

There is only one plastic part in whole bicycle lamp, it is knob of switch that selects which bulb is lit oh and wire insulation is plastic too, but rest is metal and glass, yes, it has no plastic lens, it is glass, this is proper old school lamp from 60's when they made things properly and not some silly plastics. Also it is made so that it can be disassembled, serviced, even individual parts can be replaced, some properly made lamp and it even looks nice.

Lamp is similar to this, different brand though:


Backside of that led pcb is aluminum, it is meant that heat is removed with something placed against that surface I believe. From there I conduct heat to lamp casing, it should be around 3 palm size of area that is dissipating heat, which, imo, should be plenty.

use heatsink paste wherever the bulb contacts the holder, everywhere else use filler. Allow a little air flow somehow.