How to mount Vero 29s without screws?

coolbreez1

coolbreez1

Well-Known Member
I saw something around here about Kapton tape being used? Not using screws would make the whole process way faster and simpler. The main concern is getting enough compression on the COB to evenly spread out the thermal paste for good conductivity.

Thoughts?
 
AquariusPanta

AquariusPanta

Well-Known Member
Adhesive paste or pads perhaps?

Drilling and tapping took me a few hours with 6x Arctic Alpines (by hand) but I can rest assured that the COBs don't take flight. Plus I'm using Pico EZ mates, which require a little tug and pull action.
 
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Abiqua

Abiqua

Well-Known Member
You can, but I don't recommend it, especially with a 29 and long term. They have built in holder's, all you have to do is drill two holes :)

Thermal impedance is usually much lower when the mounting psi is above 20 at least. Tape won't get you there.....I use tape too on Vero 10's and it works by itself with just thermal paste.....
 
coolbreez1

coolbreez1

Well-Known Member
I have already mounted 9 of the Vero 29s, I can do it, its just the most shitty time consuming part of the process. Simple fact is I will just have to suck it up and use screws again this time around again. I was deluding my self into thinking there might be a different easy solution.
 
AquariusPanta

AquariusPanta

Well-Known Member
coolbreez1 said:
I have already mounted 9 of the Vero 29s, I can do it, its just the most shitty time consuming part of the process. Simple fact is I will just have to suck it up and use screws again this time around again. I was deluding my self into thinking there might be a different easy solution.
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LOL! And here I thought I had it bad with 6x Vero 18s to mount.

My solution will be a drill press, on sale or not; I will not put up with the hand drill again gahhh.

Thank god for Pandora...
 
bicit

bicit

Well-Known Member
coolbreez1 said:
I have already mounted 9 of the Vero 29s, I can do it, its just the most shitty time consuming part of the process. Simple fact is I will just have to suck it up and use screws again this time around again. I was deluding my self into thinking there might be a different easy solution.
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Oh but there is.
A cheap drill press+A drill bit+A tapping tool+ A thread forming tap = easy holes for about $100.

Takes me less than 5-15 min to drill and tap a heatsink for a vero 29 with that setup.
 
Observe & Report

Observe & Report

Well-Known Member
You have to smear the paste evenly and thinly over the heat spreader anyway. Don't rely on the pressure to spread it out. Maybe some TIMs are thinner than others, but the Arctic Silver I've used is too thick. Any uncoated portions will not be in contact with the sink and will basically not conduct any heat at all. It may not look like much area is wasted when just the edges are uncoated with TIM but looks are deceiving! Having uncoated portions of the spreader is going to make a way bigger difference than the difference between PK3 and toothpaste.
 
SupraSPL

SupraSPL

Well-Known Member
You can mount them thermal paste and kapton tape, I have done it hundreds of times with 16mm star sizes and up, without a single failure. It would be regrettable if any DIYers were discouraged by the additional complexity of drilling and tapping. Thermal adhesives and pads would work, although their thermal performance is low compared to thermal paste and the pads may be thicker as well. Thermal epoxy would work, although I do not recommend it.

The PSI will not affect thermal performance if thermal paste is used. I have tested that theory by pressing (with a thermally insulated tool) on a hard running COB while monitoring the Vf, absolutely no change detected by my Fluke115, therefore no decrease in Tj. Even if there were a tiny decrease in Tj, it would have an even tinier decrease in photon output.

The kapton tape is not there to press the COB against the heatsink with any force, it is there to keep the COB from sliding sideways and to eliminate the possibility of air creeping under the COB over time. The only thing that will allow the COB to come off the heatsink is if air gets underneath, breaking the vacuum created by the paste. There is no vacuum pressure until you pull on the COB, but there is no way gravity can break the vacuum. The harder you pull, the more the vacuum resists. Imagine trying to pull 2 wet CDs apart, it is physically impossible without destroying them, you have to bend or slide them sideways to allow air to break the vacuum.

Recently someone had an expensive COB fall off while operating while using the paste + Kapton tape method. I suspect the kapton let go because of an antioxidant lube that was used to coat the copper heatsink. So that has to be cleaned off with alcohol or the tape will not stick. Also we have to make sure to use enough paste to coat the entire base of the COB, as O&R just pointed out.

I agree that drilling and tapping is a PITA, especially for large numbers of small COB/LEDs and especially if it is for a large build. It makes holes in expensive heatsinks which may be a problem when upgrading or changing the design down the road. But I also recognize the professional look that it gives and in the case of CXA, the COB holders are nonsoldering and can add the ability to attach reflectors. So both methods have their ups and downs.
DSC07269a.jpg
 
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coolbreez1

coolbreez1

Well-Known Member
Thank you so much Supra!

You said exactly what I was thinking:

"The only thing that will allow the COB to come off the heatsink is if air gets underneath, breaking the vacuum created by the paste"

I was concerned that when it got hot the thermal paste might become thinner, but as you say it is a vacuum force, the viscosity of the liquid has very little to do with the suction.

Drilling, tapping, is a significant part of the project time wise and it is more technically demanding then most of the other parts, I think removing it would reduce the over all build time by 10-25%, and reduce over all costs, while increasing re-usability. The idea that it would be more aesthetically pleasing to use screws means very little to me, the shiny unblemished heat sink seems like it would be more aesthetically pleasing in the long run.

You just saved me hours of work, and reduced my materials cost on my next build.
 
SupraSPL

SupraSPL

Well-Known Member
Glad to hear it. I just mounted a few CXA3590s with PK3 and I paid close attention to the method so I could describe it. I used a good amount of paste and then I press it onto the heatsink until I am satisfied the layer is very thin and evenly covered. Then I tape 2 of the corners so it cannot move in any direction. The kapton has a strong grip and the COB cannot move even slightly. To solder it I use flux gel and tin the the solder pads with 63/57 lead solder and tins the wire ends the same way. It is important to make sure there is no strain on the wire while soldering because there is a risk that the wire can pull the solder pad away from the COB. So I do my best to relieve any strain, blow on the joint as soon as it is soldered, then kapton tape the wire and zip tie it to the heatsink for additional strain relief.

Also worth mentioning, I had to remove a pair of CXA3590s to switch to a different heatsink. The only way to remove them without damage is to twist them. They were stuck fast, I had to use quite a bit of force to get it to let go but it was easy and quick. The not so quick part was cleaning the thermal paste off of them.
 
Hot Diggity Sog

Hot Diggity Sog

Well-Known Member
SupraSPL said:
You can mount them thermal paste and kapton tape, I have done it hundreds of times with 16mm star sizes and up, without a single failure. It would be regrettable if any DIYers were discouraged by the additional complexity of drilling and tapping. Thermal adhesives and pads would work, although their thermal performance is low compared to thermal paste and the pads may be thicker as well. Thermal epoxy would work, although I do not recommend it.

The PSI will not affect thermal performance if thermal paste is used. I have tested that theory by pressing (with a thermally insulated tool) on a hard running COB while monitoring the Vf, absolutely no change detected by my Fluke115, therefore no decrease in Tj. Even if there were a tiny decrease in Tj, it would have an even tinier decrease in photon output.

The kapton tape is not there to press the COB against the heatsink with any force, it is there to keep the COB from sliding sideways and to eliminate the possibility of air creeping under the COB over time. The only thing that will allow the COB to come off the heatsink is if air gets underneath, breaking the vacuum created by the paste. There is no vacuum pressure until you pull on the COB, but there is no way gravity can break the vacuum. The harder you pull, the more the vacuum resists. Imagine trying to pull 2 wet CDs apart, it is physically impossible without destroying them, you have to bend or slide them sideways to allow air to break the vacuum.

Recently someone had an expensive COB fall off while operating while using the paste + Kapton tape method. I suspect the kapton let go because of an antioxidant lube that was used to coat the copper heatsink. So that has to be cleaned off with alcohol or the tape will not stick. Also we have to make sure to use enough paste to coat the entire base of the COB, as O&R just pointed out.

I agree that drilling and tapping is a PITA, especially for large numbers of small COB/LEDs and especially if it is for a large build. It makes holes in expensive heatsinks which may be a problem when upgrading or changing the design down the road. But I also recognize the professional look that it gives and in the case of CXA, the COB holders are nonsoldering and can add the ability to attach reflectors. So both methods have their ups and downs.
View attachment 3330933
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I'm preparing to do my 1st build and since I have no metal working skills yet I've been looking at other options as well. I'll probably just go with tape initially. One product that I've used in the past is high temp silicone. Have you seen anyone use this around the perimeter or perhaps on 2 corners? It's rated at 500F or 260C and seems like it would work yet be removable with a razor. Just thinking out loud...
 
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