Heat Conductive Epoxy???

[Quickbeam]

Can someone please point me to where to get it/brands/costs?

I took the LEDtronics FlashLED (6 LEDs) apart, found there was a resistor in the head that limited the current to 30mA per LED. I removed it so now it's 4.5 V (3 N cells) unrestricted. Light output is MUCH better now and is significantly brighter than the 4 LED lightwave 2000, but the LEDs become warm quite quickly.

I would like to heatsink the entire LED PCB to the aluminum head of the light, and I think the only way to do it (and to create a watertight seal) is to epoxy the whole thing in place with Heatsink epoxy.

BTW, the only way to access the LED array is to rip out the lens - I had to carefully drill a hole in the lens, insert a screw, and pull it out with pliers - much easier than it sounds. The heads in the new ones do not come apart at all.

 

[Bushman]

doug, go with nothing but the best ARtic silver makes an epoxy now. in two parts mix and pot it up... i have heard that people have put continuity testers in a big blob of the traditional artic silver and not a hint of electrical conductivity but a buttload of heat conducitivity in this product. do a search on google for artic silver epoxy

regards

 

[lambda]

Goto Be Cooling

and order the Artic Silver epoxy or Artic Silver II paste. The AS expoxy is very thick, almost like a paste. If you need a pourable or thinner mixture, get the AS II paste and mix 50/50 with 20 min, or longer, curing epoxy.

Becooling filled my order on a Saturday! when I ordered. You will get an email reciept of order, one when it's filled, and another when it actually ships along with tracking number. I ordered Saturday and got it on Tues with no special shipping. I recommend them highly, they haul _ss when filling orders.

 

[Chris M.]

the only way to access the LED array is to rip out the lens - I had to carefully drill a hole in the lens, insert a screw, and pull it out with pliers - much easier than it sounds

Ouch! Poor FlashLED. It`s Craig who`s supposed to torture these things, isn`t it? You`re not trying to take his job away now are you....

Anyway. You sure it won`t just unscrew? Mine does.

It`s not easy as I think it`s been threadlocked- but try it. Take off the rubber switch cover and grip that middle bit with pliers. Give the head a good normal-unscrew-direction turn, maybe for extra grip, clamp it in a vise or hold with more pliers and some sort of cushioning so as not to scratch it.

I found out the hard way after dropping it, busted the switch and knocked the LEDs all out of whack. Finally after wrenching at it for ages (heck, it was already scratched and dented by then), could get the head off to straighten them out- but the switch is still broke. Too bad, it was quite nice. Not excessively bright, but certainly OK.

Any chance you could put me in touch with your contact at LEDtoronics who sent you the samples? I`ve oft wondered about their other products but somehow, they seem hard to get hold of for me over here, or just too durn expensive.

 

[Mike]

Try www.epoxies.com and order a free sample!

 

[ElektroLumens]

Quickbeam,

I've been using some ordinary epoxy mix I get from Home Depot, (the 10 minute setup, two part kind), and mix it with some silicon heat sink compound. Works great, and is not very expensive. I doubt it works as good as Artic Silver, but it does work good. I use it in all my mods, no problems at all with heat conductance not being good enough.

I have also used aluminum powder (Alumiseal radiator stop leak), mixing it with the epoxy. This works okay too.

Wayne www.elektrolumens.com

 

[hotfoot]

Elektrolumens, that sounds like a great solution - but how's the electrical insulation on your aluminum powder/epoxy mix? I'm thinking of 'carbonizing' (encasing) an entire PCB in a thermal epoxy like that - do you think it will work with your compound?

 

[Quickbeam]

Thanks all! I'll be looking into all the suggestions.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Anyway. You sure it won`t just unscrew? Mine does.<HR></BLOCKQUOTE>

Thanks Chris, I'm VERY sure. The first thing I tried was taking it apart. The new threadlocking they use is practically bulletproof. I took the entire switch assembly/body apart just like you did, but pliers, rubber grippie stuff and all the torque my arms can put out won't move the head. Made some nice gouges in the aluminum with the pliers, and that's about it. I wouldn't have gone through the lens except as a last resort, and unfortunately I reached that point....

BTW: www.epoxies.com has this product - looks pretty good It's white (reflective to some degree) and flexible - won't crack or separate from the housing. Thanks for the suggestion.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>50-1225 THERMALLY CONDUCTIVE
SILICONE RUBBER


50-1225 is a low viscosity, room temperature curing, RTV silicone potting and encapsulating compound. When cured, this material forms a soft, highly flexible, flame retardant, and thermally conductive package.

50-1225 can be used for potting or encapsulating electronic packages that have sensitive components. Due to its' low stress during and after cure, this material will not crush or damage delicate components. This silicone system will maintain its low durometer through aging and thermal cycling.

50-1225 provides high heat transfer and does not require a post cure. It may be used immediately after curing at operating temperatures of -65°C to 210°C.<HR></BLOCKQUOTE>

The Arctic Silver adhesive product at BeCooling looks pretty good as well -

@Electrolumens: the silicon heat sink compound you mix with epoxy - is that the standard stuff you get at RadioShack? (I think it's thermal grease for between CPUs and the aluminum heatsink block)

 

[TripleDouble]

Quickbeam, that looks good for potting circuits, but if you're looking for an epoxy with better thermal conductivity, you'll probably want a silver based solution. Check out this link for data; the 556 looks promising:
http://www.aremco.com/a8.html

 

[Quickbeam]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by TripleDouble:
Quickbeam, that looks good for potting circuits, but if you're looking for an epoxy with better thermal conductivity, you'll probably want a silver based solution. Check out this link for data; the 556 looks promising:
http://www.aremco.com/a8.html<HR></BLOCKQUOTE>

Good idea, but it's electrically conductive - It would cause a short circuit between the positive and negative leads of the LEDs. This one looks good, though : Aremco-Bond™ 805

Thermally Conductive, Aluminum-Filled, Two-Part Epoxy Paste.
Low Shrink Rate & Excellent Mechanical Strength to 570 ºF.

 

[TripleDouble]

I was thinking more along the lines of using the 556 for bonding the edge of your circuit/heatsink to the sides of your flashlight. I certainly wouldn't want to accidentally spill any on the circuit itself. The thermal conductivity numbers are just too good to ignore. I wish the artic silver and alumina epoxies had specifications that we could compare.

 

[Quickbeam]

Oh. OK. I'm just looking for something to dump into the head of the light that will both cover the pos and neg leads and bond to the inside of the head of the light. This way it would both conduct the heat to the light body and seal the entire head so it's waterproof.

 

[ElektroLumens]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by hotfoot:
Elektrolumens, that sounds like a great solution - but how's the electrical insulation on your aluminum powder/epoxy mix? I'm thinking of 'carbonizing' (encasing) an entire PCB in a thermal epoxy like that - do you think it will work with your compound?<HR></BLOCKQUOTE>

I wouldn't use the aluminum powder/epoxy combination where I don't wan't electrical continuity. I'd use the silicon grease/epoxy mix. With the silicon grease/epoxy 'thermal epoxy' mix, I would think you could encase something as you propose. I've thought of doing such a thing, but have not got around to it yet. If you do it, let me know. If I do it first, I'll let you know. I think it would work just fine.

I wouldn't encase a PCB board with thermal epoxy made with with the aluminum powder.

Wayne www.elektrolumens.com

 

[ElektroLumens]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Quickbeam:


@Electrolumens: the silicon heat sink compound you mix with epoxy - is that the standard stuff you get at RadioShack? (I think it's thermal grease for between CPUs and the aluminum heatsink block)<HR></BLOCKQUOTE>


It should be the same stuff. I bought a big tube of it from Digikey. I don't remember the part number right now, but just look up 'thermal grease', or silicon grease. I'll look into my records to see if I can find the part number. Seems to me Radio Shack sells a tiny little tube of it, and it is expensive.

Because of the difference in mass, you mix 2 parts of silicon grease to 1 part of the mixed epoxy. What I found is that the more thermal grease I use, the softer and more flexible the finished hardened epoxy mix is (makes sense).

Try it out. Works great! Lot's cheaper than Artic Silver, or thermal epoxy of various types you can purchase.

I was searching the Internet one day, and found a web site in which someone actually did this mixing, and did thermal tests to prove it works. That's where I got the idea from.

Wayne www.elektrolumens.com

 

[Quickbeam]

I tried it out this weekend - 2 parts thermal paste, 1 part 30 min epoxy - stuff was very thick and had to be globbed in the head with a toothpick, but it smoothed itself out. The head of the flashLED gets warm when it's in use for a while, so it seems to be conducting the heat to the body of the light. BTW, the flashLED has some serious output now - 57 lumens at 1 meter with N cells, 6 lumens at 1 meter with AA's, and it can use AAA's as well!

Thanks all for the help!

 

[ElektroLumens]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Quickbeam:
I tried it out this weekend - 2 parts thermal paste, 1 part 30 min epoxy - stuff was very thick and had to be globbed in the head with a toothpick, but it smoothed itself out. The head of the flashLED gets warm when it's in use for a while, so it seems to be conducting the heat to the body of the light. BTW, the flashLED has some serious output now - 57 lumens at 1 meter with N cells, 6 lumens at 1 meter with AA's, and it can use AAA's as well!

Thanks all for the help!<HR></BLOCKQUOTE>


You have a great idea here to heat sink the LED's. I never thought of using this heat conductive epoxy in this way, even though I knew about it.

I had done a modificaiton with a 4 'D' cell Mag Lite, and 20 LED's. I ran straight 6 volts into the LED's with no problem. The way I got away with it is I used an aluminum plate, and drilled 5mm holes, and pressed the LED's into the holes. The aluminum plate profided enough heat sink to disipate the heat. The plate was firmly pressed to the aluminum head, and the heat transfered out and away from the LED's. I have basically used this method most of the time, when I really want to overdrive the LED's. I am thinking now that a PCB board could be used, and the thermally conductive epoxy could be poured onto the PCB, covering the leads, and possibly just touching the bottom of the LED's. The heat would be transfered away from the LED's. Perhaps I'll have to try it some time?

Wayne www.elektrolumens.com

 

[JollyRoger]

Yes, but your first method (aluminum plate) provides a more serviceable mod. What if one of the led's goes bad? It'd be a pain to try to pick away at all that heat conductive epoxy...

But I'm going to try your idea, Wayne, of mixing the silicone heat sink compound and some epoxy....for one of my mods.
Thanks!

 

[dat2zip]

Great information. I have been hesitating doing any mods. I wish I had read this more thoroughly since I just bought some Artic Silver yesterday for $7.

At least now I can try both methods. I wonder if someone wants to sell me some of their pea greens so I can experiment around with some mods

 

[dat2zip]

Has anyone tried the Arctic Silver 3 as is?

Just wondering since it says it hardens some over time.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> Then the compound thickens slightly over the next 50 to 200 hours of use to its final consistency designed for long-term stability. <HR></BLOCKQUOTE>

 

[lambda]

I haven't tried the Artic Silver 3 as it's supposed to be for large surface area CPUs; something about fibers or fillers. Might even be better in that regards, but I've gotten real good results with mixing the Artic Silver II paste with Devcon 2 ton epoxy and using the AS epoxy for mounting the Luxeon to heatsinks. With the Devcon and ASII paste, it really conducts the heat in the applications I've used it for; filling small gaps upto 1/16".