thermal gurus: a question about cob mounting>>>

BOBBY_G

BOBBY_G

Well-Known Member
im about to mount and test the 135 and 275W cutter cobs from @welight , and since there arent any holders for these i was going to use thermal epoxy. i want it to be removable and was wondering if i permanently epoxied the cob to a 3x3 square of 1/4" aluminum and used arctic silver between this 3x3x1/4" square mounting plate and an existing heatsink if that would essentailly be as good as straight mounting it to the heatsink itself. I would be using 4 bolts in the corners of the mounting plate. the plate would be cut from barstock so i can alternatively make it 3x4 or 3x5 (up to 3x8 ) if that would help

the cob itself is 2.5 x 2.5" and assuming this would have decent heat transfer id build a similar plate and epoxy the 135W to it.

im using an 8" length of an 8" profile from Heatsink USA, which is only $34, but i already have it drilled and tapped for (5) 3590s so id like to retain that for future use as opposed to permanently mounting the cutter cob

thanks
 
JorgeGonzales

JorgeGonzales

Well-Known Member
I'm no guru, but that would definitely not be as good as mounting straight to the heatsink. Thermal epoxy is poor at it's job, and two layers of TIM is much worse than one. I wouldn't mess around with those monsters.

Thermal paste and kapton tape should hold just fine, if you'd like to try that first. I was afraid I was going to destroy one of my cobs trying to overcome the suction from regular old thermal paste when I tried removing one two days later.
 
JorgeGonzales

JorgeGonzales

Well-Known Member
Airwalker16

Airwalker16

Well-Known Member
BOBBY_G said:
im about to mount and test the 135 and 275W cutter cobs from @welight , and since there arent any holders for these i was going to use thermal epoxy. i want it to be removable and was wondering if i permanently epoxied the cob to a 3x3 square of 1/4" aluminum and used arctic silver between this 3x3x1/4" square mounting plate and an existing heatsink if that would essentailly be as good as straight mounting it to the heatsink itself. I would be using 4 bolts in the corners of the mounting plate. the plate would be cut from barstock so i can alternatively make it 3x4 or 3x5 (up to 3x8 ) if that would help

the cob itself is 2.5 x 2.5" and assuming this would have decent heat transfer id build a similar plate and epoxy the 135W to it.

im using an 8" length of an 8" profile from Heatsink USA, which is only $34, but i already have it drilled and tapped for (5) 3590s so id like to retain that for future use as opposed to permanently mounting the cutter cob

thanks
Click to expand...
Stevesleds has one part thermal glue that you just twist to release if you ever need to. I'd try that?
 
Airwalker16

Airwalker16

Well-Known Member
By the way @BOBBY_G I used that 1 part glue on my far reds. Holds them VERY well. And like you attested to, the heat transfer was phenomenal. I couldn't even get the soldering pad hot enough once it was mounted to solder correctly.
 
Growmau5

Growmau5

Well-Known Member
By bar stock do you mean 3" extruded bar or plate aluminum? If so, check for "cupping" by setting a straight edge across it and try to slip a piece of paper under the gap(if there is one)

Also, check TE connectivity. They may have an adaptable solution.
 

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PurpleBuz

Well-Known Member
You could use a piece of copper as a heat spreader. with the right sized plate it would more than make up for the extra layer of thermal epoxy.
I would be careful about which thermal epoxy you use, I looked around for something similar I'm designing and found a LOT of variability in thermal conductivity of thermal epoxies.
 
Growmau5

Growmau5

Well-Known Member
PurpleBuz said:
You could use a piece of copper as a heat spreader. with the right sized plate it would more than make up for the extra layer of thermal epoxy.
I would be careful about which thermal epoxy you use, I looked around for something similar I'm designing and found a LOT of variability in thermal conductivity of thermal epoxies.
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I like the copper plate idea. I am not well informed on the grades of copper. but here is a $4.32 solution from ebay.

http://www.ebay.com/itm/like/181659269378?lpid=82&chn=ps&ul_noapp=true
 
B

benbud89

Well-Known Member
JorgeGonzales said:
I'm no guru, but that would definitely not be as good as mounting straight to the heatsink. Thermal epoxy is poor at it's job, and two layers of TIM is much worse than one. I wouldn't mess around with those monsters.

Thermal paste and kapton tape should hold just fine, if you'd like to try that first. I was afraid I was going to destroy one of my cobs trying to overcome the suction from regular old thermal paste when I tried removing one two days later.
Click to expand...
Do you apply the thermal paste in the form of a pea, cross, lines, pencil, or what method's working for you? Ive been reading a lot about this, since it seems to be a very important part of the assembly. Thank you, Jorge! I do not want to mess this up, Ive been waiting about six months to have everything imported x.x
 
JorgeGonzales

JorgeGonzales

Well-Known Member
benbud89 said:
Do you apply the thermal paste in the form of a pea, cross, lines, pencil, or what method's working for you? Ive been reading a lot about this, since it seems to be a very important part of the assembly. Thank you, Jorge! I do not want to mess this up, Ive been waiting about six months to have everything imported x.x
Click to expand...
Pea for me :) My thought process was: it's a cob, it's round. I also like to "tint" first, spread a thin layer out with a plastic card or baggie covered finger, and then wipe it all off with some thing lint free, like a coffee filter or well-washed cotton (I use disposable lens cloths) That fills in all the microscopic bits and bumps first before the main event.
 
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Sativied

Sativied

Well-Known Member
Tape will do but depending on cob size you may be able to use these too


That is a socket 775 mounting backplate, center window varies slightly, but there are plenty of options, and you can obviously modify one.



And/or use something like the clamps on the left in the pic below.


Obviously fits perfectly with alpine coolers and many others too, eliminating the need to drill in those, easily removable yet solid and reliable. Incorporate the spring screws, cut to size if needed...

Cutter or someone else could easily make a universal cob holder borrowing ideas from cpu heatsink mounting. Retention bracket with spring mounting screws and sort of lever-clamp mechanism. Ideally with a few adapter pieces for different cob size and possibly even solderless connections.
 
nickmad94

nickmad94

Active Member
Hey guys, first post here im a major noob, and this is just a shot in the dark but just wanted to know if you guys think electrothermal cooling plates could work for mounting cobs to further cool them before the heatsink? I was looking for cooling mates for hydro then found the cooling plates. I think they are for refrigerators or wine coolers but could something like this be made before cobs are rendered useless? Would its not even be nessesary? Saw some pics of them attached to heatsink which just look like they begging for a mounting.
 
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