Rothrandir
Flashaholic
Circuit Works CW2400 is a great conductive epoxy
Thermal Adhesives
- Thread starter NightShift
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Minjin
Flashlight Enthusiast
<font size="2" face="Verdana, Arial">Are you saying that there are more than one PN junction in the luxeon? I guess I've always assumed that the luxeon was just a super led, and therefore just a larger PN junction. Does anyone have a schematic of the insides of a luxeon?
As for needing to know what conductivity I require, I'm just looking for some general recommendations. I'm not building rocket ships here, just wondering what solder alternatives are available that don't cost an arm and a leg.
Mark
Doug S
Flashlight Enthusiast
<font size="2" face="Verdana, Arial">I'm saying that it is a plausible possibility. In fabricating semiconductors, for process reasons the device sometimes will have a junction that is not required for the device proper but exists as a consequence of the fabrication sequence.
R.e., my comment on epoxy bulk conductivity, be aware that conductivity of the epoxies is *much* less than solders. In general they are not a good choice unless there is a really compelling reason to not use solder.
Has anyone tried using Thermagic as a thermal transfer material? It is non conductive, and they claim to deliver performance 15% better than any other product on the market. I have seen a few reviews that say it will beat Arctic Silver. You can get it at www.tigerdirect.com
monanza
Flashlight Enthusiast
What epoxy would I add to Thermagic to provide adhesion?
Doug S,
Circuit Works CW2400 works just like solder; very conductive, with no measureable resistance. Hard to believe, but I've run amps thru small junctions with no measureable voltage drop.
Brody,
Remember the 'glue' part is important also, as it can degrade over time with heat. I'd stick with AS for long term reliability.
In general, if doing multi Luxeon project, then use Artic Alumina for its insulative properties.
Circuit Works CW2400 works just like solder; very conductive, with no measureable resistance. Hard to believe, but I've run amps thru small junctions with no measureable voltage drop.
Brody,
Remember the 'glue' part is important also, as it can degrade over time with heat. I'd stick with AS for long term reliability.
In general, if doing multi Luxeon project, then use Artic Alumina for its insulative properties.
Doug S
Flashlight Enthusiast
<font size="2" face="Verdana, Arial">Neat! It sounds like conductive epoxies have come a long way from the earlier versions.
EDIT: Here is a link to a datasheet for the CW2400 product:
http://www.chemtronics.com/tds2/CW2400.pdf
The resistivity limit is about 600 times that of copper but this is actually amazingly good for a conductive epoxy.
MicroE
Enlightened
I know that this goes against the wisdom in this thread but I use JB Weld. It's a steel-filled epoxy meant for mechanical repairs. It can be machined and sanded. It is also the strongest epoxy I have ever come across that is available commercially.
You can buy it at Ace Hardware stores in the US.---Marc
You can buy it at Ace Hardware stores in the US.---Marc
Doug S
Flashlight Enthusiast
<font size="2" face="Verdana, Arial">Actually Marc, I think quite a few use it. I know that I have. I seem to remember reading a review on one of those overclocker sites where they actually tested the thermal performance and found it to be quite respectable. For any thermal coupling compound, the thermal resistance is directly proportional to the thickness of the joint. The thinner the joint the better. JB Weld is a bit viscous. The trick to getting a thin joint is to heat the two pieces to be joined so that when the JB Weld is applied it heats up and thins so that it will squish out better when pressure is applied.
hotfoot
Flashlight Enthusiast
<font size="2" face="Verdana, Arial">Neither have I. That's why I've carefully mentioned multi-emitter arrangments. And to answer your question, they were wired up in series (for up to 3 emitters) and in a series-parallel arrangement (for up to 6 emitters).
In all cases, emitters were mounted on an aluminum bulkhead(heatsink) with AS.
But there are a lot of mods possible out there and some may involve the use of integral switching mechanisms or electronics that share the same ground path. It never hurts to be safe. Or, at least, be absolutely sure of what you're doing.
I'm merely stating a fact.
hotfoot
Flashlight Enthusiast
<font size="2" face="Verdana, Arial">Ouch!
But I have to salute ya for innovatively using that slug!
PsycoBob[Q2]
Enlightened
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My 5w Cyan has a a lower voltage drop from the slug to the other electrode, than from one electrode to the other. Not much, .3v at max, but... Enough to make me wonder if those little gold whiskers need to be upgraded to handle the 1.2A I put thru the LS.
<font size="2" face="Verdana, Arial">Thanks Hotfoot, I'm thinking that single and MAYBE parallel would be OK on the same ground plane.
But it makes perfect sense to me that wiring them in series would be a problem on the same ground plane. I guess I should "breadboard it" to test the theory. I'm sure glad I breadboarded the Red/Orange BEFORE
Doug S
Flashlight Enthusiast
<font size="2" face="Verdana, Arial">Bob, you have piqued my curiosity here. I interpret what you are saying to imply that in the case of the 5W cyan, the slug is common to one of the two power input leads. If correct, which one? Has someone here specifically checked a 1W cyan? I ask because somewhere I got the impression that in the case of the 1W cyan the slug is not a direct connection to either power lead. I am wondering if I got the wrong impression or if the 1W and 5W actually do differ in this regard.
<font size="2" face="Verdana, Arial">Bob, you have piqued my curiosity here. I interpret what you are saying to imply that in the case of the 5W cyan, the slug is common to one of the two power input leads. If correct, which one? Has someone here specifically checked a 1W cyan? I ask because somewhere I got the impression that in the case of the 1W cyan the slug is not a direct connection to either power lead. I am wondering if I got the wrong impression or if the 1W and 5W actually do differ in this regard.</font><hr /></blockquote><font size="2" face="Verdana, Arial">DOUG - If the slug on a 5W Cyan were to be common to one of the leads, it would have to be negative, because I just built a mod using one of these emitters and the slug is sitting directly on the negative ground plane.
However, it's my feeling that it's pretty much isloated as I have noted infinite resistant when checking for any continuety between the negative lead and the die slug.
PsycoBob[Q2]
Enlightened
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Doug, you convinced me to yank my 5w light apart to test this. I had to pull it completely out of the light to get a good reading. It is bonded to the negative side. When in the metal-bodied light the voltage into the LED goes up slightly, due to the ground-current (and the fact that it's wired with a 22AWG negative ground).
Interestingly, to safely get a reading, I put a small blue wire-nut over the LS. Removing it almost 10 seconds later, I almost burned myself on it. The plate the LED was mounted to was still cool, as was the area around the LS emmitter. That certainly helped remind me about the amount of light it puts out.
Interestingly, to safely get a reading, I put a small blue wire-nut over the LS. Removing it almost 10 seconds later, I almost burned myself on it. The plate the LED was mounted to was still cool, as was the area around the LS emmitter. That certainly helped remind me about the amount of light it puts out.
Doug S
Flashlight Enthusiast
<font size="2" face="Verdana, Arial">Gee, Bob, I didn't know that I was such an influential guy
PsycoBob[Q2]
Enlightened
- Joined
- Apr 9, 2002
- Messages
- 518
I MIGHT be willing to unwrap my second 5w Cyan emitter tomorrow, uh, 'Today' and check it. I might have gooped something up when I mounted the first one. It's currently on a 1w LS/o PCB that had the PCB material scraped off under the emmiter, to allow direct-mounting to the aluminum with AS epoxy.
Amazingly enough, my spare emitter is still in the original Future-Active reel-wrap.
Amazingly enough, my spare emitter is still in the original Future-Active reel-wrap.
NightShift
Enlightened
I found Arctic Alumina Adhesive for $8.50 USD, Priority Mail 2-3 Day Shipping for $1.65(!) at www.1coolpc.com located in Edmonds WA. I was trying to decide whether the silver would be bad in conducting some electricity so I just went with the Alumina.
tvodrd
*Flashaholic* ,
Something for the scratch-builders to consider- Plain old type II sulphuric anodize is damn thin and not electrically conductive. Where you need conductivity, machine it after anodizing. AS II's electrical conductivity shouldn't be an issue.
Larry
Larry
