Anodized McLux and heat transfer question...

I acquired some of the DIY parts from the first McLux run. I have 2 of the anodized heads, and I was wondering if I should remove the coating from the emitter mounting location. One of these will have a BB500 and a 1W. The other one that I'm actually asking for is the extended body for 3 CR123's. I want to put a BB700 and a 5W in that one. /ubbthreads/images/graemlins/grin.gif I don't know if the coating hinders the transfer of heat or not. If not, then good - less work for me. Any assistance would be appreciated.

Allen

The anodizing may impede the thermal transfer to some extent but I have not been removing it and with a 5W and 700 BB, you will feel the head heat up quickly; indication that the thermal path is quite adequate. Perhaps Doug S. or someone else in the *know* can provide a more definitive answer for you.

- Don

coating shouldn't really affect heat too much...black least of all.

smoothness is key, so you risk the chance of your sanding not being as smooth as the anodyze...this is what matters more.

and in any case, the mclx heatsink is more than adaquate /ubbthreads/images/graemlins/grin.gif

The more metallic surface contact, the better thermal conduciveness. The less anodizing surface and more bare metal, the more electrical conduciveness. In this case, like Roth said, a flat surface and some AS should hold down the heat quite well.

Whew! No grinding for me! /ubbthreads/images/graemlins/smile.gif Thanks for the info.

One other quick question. Is it worth the extra $5 for the Arctic Silver over the Arctic Alumina? Fry's carries all of the "Arctic" line, but I don't want to spend money that I don't need too...

Allen

i use the silver...

but of course...the people who know me know me as "mr. overkill" /ubbthreads/images/graemlins/grin.gif

both are great, but silver is better...and that alone should be reason enough to use it /ubbthreads/images/graemlins/grin.gif

Don't overdo it on the AS. You don't want so much AS that it actually becomes more of an insulator than a conductor. You only need AS where there's gaps in the metals contacting each other. Metal to metal's always the best way to transfer heat...

I found out the hard way with CPUs and heatsinks that more isn't always better...

When putting thermal gunk between a CPU and heatsink, I spread it out with a razor blade. This fills in the gaps, but doesn't goop so much on as to get in the way. This technique has worked well, as I've had fairly good success in overclocking. The innards of the McLux head are a little tight, but spreading the thermal adhesive on the emitter before setting it on the head worked pretty well, but CPUs have the advantage of a mounting clip pressing the heatsink down onto the CPU itself, giving better contact.

Re: RTV for McLux assembly?

Okay, here's another question specifically on McLux assembly. Does the RTV for the head assembly need to be thermally conductive? If so, where do I get some? I looked at Sears Hardware and Wal-Mart, and I'm not sure of where else to look... /ubbthreads/images/graemlins/confused.gif

Allen

Re: RTV for McLux assembly?

With heatsink coumpounds, twice as thick means half the transfer for a given thickness (and the same area). The best are no where near the theromoconductivity of metals themselves! Thinner is better! If you are using a white LS, the electrical neutrality of the slug is ok if the body of the light is neg. For other colors, the anodize will provide electrical isolation for the slug. (Try your ohmeter on an anodized part. /ubbthreads/images/graemlins/grin.gif ) (I still aint got it all figured out.)

Larry

Re: RTV for McLux assembly?

Allen,

Dat2zip feels that since the chip itself has a thermal goo under it on the PCB, the heat transfer is probably fine as is. I suspect that any RTV is better at transfering heat than air so any goop you use should provide a better path to the metal parts than no goop. I used thermally conductive RTV because I had it but to the best of my knowledge it isn't required.

- Don

Re: RTV for McLux assembly?

is there any chance of the thermally conductive stuff shorting out the electronics?

i know arctic silver has that warning, it is an unlikely chance, but present...

Re: RTV for McLux assembly?

Rothrandir,

I have ruined a few mods/ creations using Arctic Silver as a thermal path on the converter boards! I don't consider it unlikely anymore! I would count on it shorting out some of the traces and providing you with scrap! I trashed two High/Low experimental converter boards that Wayne Y. had gone to a lot of trouble to make and I had gone to the trouble of making modded E2e heads with a magnet ring collar that would trigger the high low via a Hall switch on the board. One of the mods bound up and went doggo about half way through its assembly but the other one was essentially completed! I had this light in my hand with a 5W LED that would shift from 100 mA to 700 mA at the twist of a collar! I cycled the light a few times and then it stuck in the Low mode. /ubbthreads/images/graemlins/frown.gif Days wasted and we never revisited that idea. All because I was dumb enough to use AS as the ultimate material to bleed off heat from the IC.

I use AS now to bond the LED's to the heat sink (use extreme caution on red and orange; anodized sink or two thin coats) as well as a permenant thermal path between metal parts but never let it get close to the circuitry.

- Don

Re: RTV for McLux assembly?

[ QUOTE ]
AllenInHouston said:
Does the RTV for the head assembly need to be thermally conductive? If so, where do I get some?

[/ QUOTE ]
Don just likes to show off with his thermal RTV. /ubbthreads/images/graemlins/smile.gif I've built McLuxs with thermal RTV, regular RTV and NO goop at all. They all work equally well, and don't think there is anything to worry about in the PCB cavity. Use what you've got - or even nothing at all.

The big question that I've never been able to answer is: What does RTV mean?

Re: RTV for McLux assembly?

That's a question that I actually have an answer to. RTV: Room Temperature Vulcanizing

Re: RTV for McLux assembly?

[ QUOTE ]
AllenInHouston said:
That's a question that I actually have an answer to. RTV: Room Temperature Vulcanizing

[/ QUOTE ]
COOL! I *knew* somebody here would know. Don... did you hear that? We have an answer! I searched and searched for this answer, and came up empty. Thought for sure Don would know, and all I got there was the same shrug I'd been getting from everybody else.

I'll say it again- cool. I love information.

Re: RTV for McLux assembly?

/ubbthreads/images/graemlins/smile.gif

Re: RTV for McLux assembly?

I'm glad that I could help. /ubbthreads/images/graemlins/smile.gif

I'll let you in on a secret (just don't tell anyone). I used to know what it meant, but I had forgotten, so I searched google for "RTV acronym"... /ubbthreads/images/graemlins/smirk.gif

Re: RTV for McLux assembly?

Room Temp. Vulcanizing

Re: RTV for McLux assembly?

[ QUOTE ]
AllenInHouston said:
I searched google for "RTV acronym"... /ubbthreads/images/graemlins/smirk.gif

[/ QUOTE ]Doh! I googled the HELL out of those three letters. Adding "acronym" was brilliant.