How much Kapton is too much?

[cityworker415]

Well just like it says I'm curious how much Kapton tape people are using to hold down their LEDs. Just started messing around and have built four single 60 watt 3070 on artic 11 sinks.

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[Castaman]

I think its enough.
Can capton reduce cob thermal condition?
I heard some of CXA2***'s UNDER LENS with holder had evaporated phospor or some kind of condensate on lens.

 

[coolbreez1]

I would think that as long as you are not covering the array of LEDs you should be fine. I am currently building some lights and using the Kapton tape for mounting, I figure its mostly for stability from bumps and vibrations. I am mounting them on the 4.6" heat sinks from heat sink USA, I tested attempting to pull off the LEDs after I mounted them with the thermal paste and it was nearly impossible to do by hand without prying them some how. If you have overhang on those heat sinks it might be a bit different, but over all there is a lot suction holding them down.

 

[FranJan]

About a pound....or in the OP's case would be 2

Supra was the first person to do this around here and as he, and coolbreez1, pointed out the Kapton is not holding on the COB, it is the vacuum from the paste holding the COB down and the Kapton just helps preserve that vacuum. I use like 2 small strips on each of the COBs in my veg cab. My guess is you're probably increasing j temps with all that Kapton covering up the COB when some airflow could really help. Hell some of the fake Kapton tape I use has peeled off. 2mil was too thick IMO.

 

[SupraSPL]

With decent quality kapton it doesnt take much to do the job. Just make sure to remove any oil from the heatsink surface with alcohol or it may not grip, especially with copper.

Ideally I should have taped 2 corners before soldering the wires on, but this Z2 was mounted with PK2 and taped in early 2014, has been hanging in my workshop and gets used often at ~38W. I am glad my soldering has gotten a bit prettier since then.


That said, better safe than sorry, this is how I mount them now, one long piece holding 2 corners. The rest of the tape is to hold magnets for the lens

 

[stardustsailor]

Never will be enough.....
No matter how much you'll put ...
That is why CREE does NOT suggest any Kapton tape ,or any "Vaccum properties of TIM " as
securing and installing COB arrays in place ....

But hey ....WTF do I know ?

Use the damn tape ....
Just make sure to replace it every couple of hunderd hours or so ...
It's hot and humid ,inside there ,ain't so ?

" However, Kapton insulation ages poorly: an FAA study shows degradation in under 100 hours in a hot, humid environment. "

https://en.wikipedia.org/wiki/Kapton
http://www.tc.faa.gov/its/worldpac/techrpt/ar082.pdf


Have you ever heard some weird things ,called "COB holders " ?
I just wonder why they 've made such things?
What's the purpose ,the reason of their existence ,whatsoever ?
Who needs such a thing as a"COB holder " and why the hell ,somebody will ever use such thing ?
Since ,all we need is a roll of o kapton tape and some extra thick ,gummy 'n' sticky thermal paste ...

anyway ....
Nothin' beats a good screw ...
Or I'm just screwing around ,where I shouldn't 've been ,firstplace ....

Kapton vs holder ...
Make your decision ...
" Wisdom " will arrive ,sooner or later ,no matter what ...

Right or wrong ...

At the end ,wisdom always comes ,to put several things "back in the right place "...

The slight detail between a wrong and a right decision ,
is actually the difference in price (money & time ) paid ,for the acquired "wisdom " ...

With a grain of salt
It may be correct ,it maybe a fault ...
Don't mind whether I 'm friend or foe..
Yet ...
WTF do I know ?


Cheers.


P.S.

I've a much better idea / advice to give you ...
In case you're living in New York you're lucky ....
Just take the lift ,to the rooftop of a (tall ? ) building and start screaming
"HELP ME -HELP-PLEASE, PLEASE SOMEONE HELP ME FOR GOD'S SHAKE !!! ".
Wait until Spiderman shows up ...
Then ask him politely ,for some of his spider-web ...
Nothing beats good ol' Spidy's web ,for securing COB arrays in place ...
He knows better than anyone else ......

 

[SupraSPL]

I agree COB holders are the technically correct way to install COBs and I would not expect CREE to say otherwise. However, paste + kapton works well and it may appeal to some DIYers. If I had used holder for my 3070s, all my heatsinks would have holes drilled in the wrong spots and I would have had to replace all the holders because I have been switching to the 3590s. In 2009 I used kapton to secure hundreds of 20mm stars with no drill holes on those very same heatsinks.

I have never seen the grip of the tape degrade over the years. If applied to a clean surface, it stays put. I recently disassembled one of my earliest lamps (2009, 52000 hours ago) which depended heavily on kapton to isolate the traces. It peeled off like it was brand new, good grip, still sticky and left no residue behind.


The kapton+paste method allows us to press a thorough, even, thin layer of paste quickly and easily, without printing or stenciling. Recent test for CXB3590 mounted with kapton, 2.5% temp droop at 100W dissipation using only .5W of fan fan power. Amazing thermal performance, no pressure from screws required. Anyway, nothing wrong with keeping it simple and saving a few $.

 

[SupraSPL]

The FAA test cited above subjected kapton wrapped wires to dynamic and static stress while being cooked in ovens at several hundred degrees celsius. The study states:

"The time-to-failure at very high temperature is not indicative of most aircraft conditions. Correlation to more typical aircraft operating conditions (temperature = 71°C and RH = 33%) shows the estimated hours to be approximately 240,000 hours to the median failure when a 10- times dynamic bend is present. For wire that is not mechanically disturbed, the time increases dramatically to 4,000,000 hours, provided no nonaging unpredictable event takes place to severely damage the wire."

 

[SupraSPL]

I have ordered here a few times. No complaints about the adhesive, although I have never come across a roll of kapton that was problematic.

http://stores.ebay.com/dorladream2011/_i.html?_nkw=kapton&submit=Search&_sid=1067199962

 

[coolbreez1]

I ordered mine on amazon prime, I assume most anything on there is not crap, everything is reviewed, free 2 day shipping... I think it cost $13 for 36 yards of one inch tape, rated at 25 lbs per square inch. I used it to mount the heat sinks in the aluminum channels even. I applied the thermal paste to the Vero 29s and then placed a 1/8 inch pad on it and applied even pressure with a short bit of wood, jiggled and rocked it lightly to remove any air bubbles, and then taped them down. No reason to mess up a $9 chunk of aluminum I can use indefinitely, and if Supra had his last 6 years I am feeling good about it right now.

 

[Tazbud]

I'd say some of that will peel back C/w It's good stuff if completely stuck down. In the end I added reflector bases (without the lenses) to the few cobs I have on bar style heatsinks, they put 4 points on the cob and the two screw holes are wide enough for future changes. these things (just another thought for the bubble):

 

[cityworker415]

Thanks for everything guy's and others! So helpful vs. Radishack what's molex! Moving on to cob holders next

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[Michael Lehfrau]

Great thread

I love non-invasive solutions. There is also thin double-sided sticky tape one can use as TIM without Kapton. Still, I guess the heat transfer with thermal paste is probably the best. Any recommendations which thermal paste to use?

There is a huge price range when it comes to Kapton tape. Some chinese sellers give it away at 1/10th of the price you pay in other places. I wonder if it is the same. Anybody orders Kapton directly from China with good results?

 

[frica]

Nothin' beats a good screw ...
Or I'm just screwing around ,where I shouldn't 've been ,firstplace ....

Thermal adhesive/epoxy is just as strong I think.
Also depends a little on how much the holder/screw head can take.

But screws are better because if you want to upgrade cobs that are attached with thermal epoxy you will have to scrape them off the heatsink.

 

[frica]

Great thread

I love non-invasive solutions. There is also thin double-sided sticky tape one can use as TIM without Kapton. Still, I guess the heat transfer with thermal paste is probably the best. Any recommendations which thermal paste to use?

There is a huge price range when it comes to Kapton tape. Some chinese sellers give it away at 1/10th of the price you pay in other places. I wonder if it is the same. Anybody orders Kapton directly from China with good results?

Artic silver 5 or any other good CPU thermal paste.

(Don't get thermal epoxy/adhesive unless you're 100% too lazy for screws, epoxy is forever)

 

[Michael Lehfrau]

Is there a thermal paste you recommend? Any maybe a tutorial on how to apply the paste on the COBs and how to put the COB on the heat sink without damaging it?
How many square-mm2 or sq-inch will a small tube get me covered?