Burned up a cob.Heatsink still good?

nevergoodenuf said:

Were you using paste or pads? I have tested pads and found them to perform horribly. A few times they worked OK, but I will only use paste now. Both thermal imaging and Tc testing showed me that the paste (arctic silver) out performed the pads. I had a CLU058 averaged Tj 245*c @ 320 watts with the pad and Tj 107*c with paste . The COB is domed but still works.

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Pads, I agree they suck. Crazy part is, I have a brand new tube of Arctic silver 3 years old. Lazily and out of fear of fucking up an investment,I used the TIM pads when I built these over 3 years ago. I wasn't confident in my abilities to apply the paste correctly.

Ironic, I think the pad was my downfall. It appear to shrink and wasn't covering the whole chip in spots.

Renfro said:

I agree. IMO the pads are only good for low wattage uses, so if you are gonna drive your cob hard at all you will want the paste.

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What is considered low wattage for cobs?(Cree) These were ran about 50watta per.
I have some 3590's on a 320-2100 driver also.

When I do redesign my lights, paste will be used on all no doubt. Lol it seems everyone was on the pads back then except the people that really new better. Robin,Supra,GreenGene,Abiqua,and a lot of other "techies" suggested paste over pads.
My sinks from HLG came with the aforementioned Arctic silver paste heh, I had to order the pads! Smh.

GBAUTO said:

This is just my laymen, grease monkey insight...
I think that the original TIM had a hard time making a thermal bridge around its perimeter. Clean the surface well and try again.

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Hi GBAUTO, thank you. I speak laymen greasy monkey well! More-so than techie talk. I agree, the PAD sucked! The cob is no more. It's replacement was wiped clean,heatsink also and replaced.

Dougnsalem said:

I know very little about COBs. However, I have worked a ton with heatsinks. Great info from these guys. Just IMHO, but I'd hit the area with some 320 or 400 wet sandpaper, using a perfectly flat block and doing it in a X pattern. Try to get rid of all of the discoloration. Then like mentioned above- Use Arctic Silver paste. It's the best. Shoot, if you have the time, I'd do all the others too while it's down....

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I'm going to do this after this run,when the space is down. Especially the sandpaper. Those char marks fuck with my self diagnosed OCD. Just needed to get'em back up and running ASAP. I needed the photons in the space she was covering.

ALL the cobs x12 will have their pads replaced.

Airwalker16 said:

You'll be just fine hiatuses Thermal Grease this time not a pad. You'd be advised to do all your cobs while you have the grease out anyways, as well.

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Hey thanks for replying to my other thread that day. I ordered from digikey as you suggested.Shipped quickly. They have a new customer.
Much appreciated.

When you apply the paste, preheat the heatsink with a heatgun to help spread the paste. I use an old credit to spread.

Renfro said:

I would just give it the polish with some steel wool and call it good.

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This is the way. Or maybe some scotbrite pads. Sorry for spelling

Second thought, put a square up to it, make sure the heatsink is still true(flat). If so, rock it. If not, you run the risk of getting heat spots where its not flush.