Help with Heatsinks!

[6 Cuicos]

Hello all, I have 4 30cm x 35cm aluminium PCBs. I bought some aluminium channel to use as structure and heatsink, here's a couple pics:
https://imgur.com/Wpxr4jh
https://imgur.com/cZ8ewT3

I got 12 of them, they're 122cm long, 3cm wide, and 4mm thick. I want to make two fixtures, sets of 2 boards attached to 6 bars spread evenly on the 30cm the boards have of width. The boards have 9 holes each so I'm thinking of screwing 3 bars and then attaching the other 3 with thermal adhesive (not sure if paste or tape, any help? Brands?), someone told me on reddit that thermal paste would work to attach the non screwed in bars too but I'm not sure I believe that.
Anyway do you guys think there's a better way? I want the most heat dissipation as possible and I'm open to any suggestions apart from "get an actual heatsink" or something like that.


Next question is about spacing and coverage. They're in a 150x150cm tent, if I attach the (30x35cm)boards to the (122cm long) channels edges, the board's inner edges would be separated by about 52cm, and the outers would be 14cm away from tent walls, at full coverage the 2 sets would be equidistant too.
Is this arrangement ok? Is there a better way? I know I could take PAR readings myself for this but there's no practical way for me to do that without drilling a ton of holes on the channel. I know they're not QBs but consider them as if they were QB304s.

Thanks very much in advance!

[Jolly Green Giant]

welcome to the forum first off

I'm not sure if I would fully trust "just" thermal paste or tape to hold together forever... but I would use it, and then use a screw on top of that...

i run a 150cm x 150cm tent also... I have the 120cm x 120cm RapidLED substrate and rails as framework viewtopic.php?f=11&t=56. in my build..( just a visual reference) I had the boards so from front to back where roughly 30cm from the edge of frame to the center of the board( my frame rails can be adjusted ) and side to side where only about 7 cm in from the edge.( planning on sticking 4 more boards here soon) that base spread in my tent was pretty dang awesome!!

your on the right path... I would use screws on top of paste.. and your pattern should be pretty close to a even spread..

again welcome

[LEDG]

Trying to visualize this. So you're using 6 pieces of U-channel for each fixture, and each fixture holds 2 boards?

[6 Cuicos]

welcome to the forum first off

Thanks and thanks for the visual, it helped. Only thing is I can just screw 3 onto the 2 boards, I can't make more holes in the boards so the other 3 need to be attached by paste or adhesive, or I can make more holes on the "fins" of my channels and secure then somehow on top of thermal paste.

Trying to visualize this. So you're using 6 pieces of U-channel for each fixture, and each fixture holds 2 boards?

Exactly. But only 3 can be secured with screws since the boards have 9 holes each.

You just made me realize I will end up with and odd fit, 5 per board would be better I think, I still need to physically see how 6 would be spaced evenly and if the central holes of the boards holes don't end up right below a "fin" or vertical wall of the channel. How sticky is thermal paste(silicon and zinc)? Would attaching the 3 boards with screws then the other 2 with paste and finally putting a driver on top of that in between boards work fine? Can you think of a better way?

[LEDG]

I think it finally just clicked in my head how you intend to use it. And I agree that 5 would probably be a better fit. Depending on how hard you run the board though, you may not benefit a whole lot from the 2 or 3 other chunks of u-channel. What will you be powering them with?

[6 Cuicos]

I think it finally just clicked in my head how you intend to use it. And I agree that 5 would probably be a better fit.

I want to run them at 2.369a(or that's the max my 320 c2100a driver does according to your datasheets I think) its 24s 14p, it gets up to 55°c running at max by themselves if I recall correctly, maybe more.
Here's a pic https://imgur.com/a/tbGTP with 6 and 5 bars, I felt them a bit cooler with 6 just resting them on top without screws or nothing. I may ditch screwing on 3 and using paste in 2 and just screw 2 on them and using the paste for the 4 others instead. Would that hold? I don't know, what would you do? Another option is getting thermal Adhesive paste for using the 6 bars instead of the normal paste I have but I want to flip to 12/12 and full power asap, and this would take like a week for it to get to me.

I really don't know what to do, what do you guys think? I'm little high so sorry if I'm not fully coherent.

[DC-10]

I worry about adhesives, especially if you will put any force on the aluminum rails (like using them for hanging the lights). Also, when the LEDs turn on and off each day, the aluminum will expand and contract. Could crack your adhesive. So, my recommendation is use the screws for as many rails as you can. For the others, I recommend rigging some additional aluminum to the ones you bolted down and holding the remaining ones in place. Don't drill the PCBs, as you might hit a copper trace and destroy the whole thing.

[6 Cuicos]

Don't drill the PCBs, as you might hit a copper trace and destroy the whole thing.

Cool, I was going to ask about that.

Wouldn't the thermal adhesive paste work with expanding and that? It is for attaching heatsinks after all, and the hanging would be on the outermost rails that I used paste on. I think I'll be using 5 rails all with paste, and use the driver to keep the 2 without screws in place or like you said another rail but it's going to be hard, I don't know how I would use a rail on top to keep them in place...

Here's what I got so far https://imgur.com/mIonODJ, any ideas on how to do it. I can only think of glue for it.

Thermal paste is a bitch to work with btw.

[DC-10]

Took a look at the picture; looks great! I see that you have bolts through the 3 rails already, so you are probably right, you should be fine to glue the others. As far as thermal expansion and contraction goes, I guess as long as the adhesive is flexible enough when cured, it shouldn't be a problem.

Good luck, and please post a picture of the final product!

[LEDG]

Took a look at the picture; looks great! I see that you have bolts through the 3 rails already, so you are probably right, you should be fine to glue the others. As far as thermal expansion and contraction goes, I guess as long as the adhesive is flexible enough when cured, it shouldn't be a problem.

Good luck, and please post a picture of the final product!

Agreed. they should be pretty rigid with the bolts through three of the channels and a thermal adhesive should hold fine for the floaters.