COB light problem. Loose chips sink ships

coreywebster

coreywebster

Well-Known Member
Alright fine fellows.

I have just been to tend to my ladies and noticed one part of my light was out. Its a 9x clu058 1825 jobby.
3 drivers running 3 cobs each at 1400mA. So on closer inspection I noticed a wire hanging down, they are soldered as the BJB holders were very slightly out of voltage range, ended up soldering them and using thermal adhesive to attach to heat sinks. Its been running fine maybe 7-8 weeks. All heat sinks were the same 34degrees C when I used my laser thermometer previously.
So I figured sheet I'm going to have to solder it back in situ. On even closer inspection I notice the COB is literally peeling off the heat sink! So I'm assuming for whatever reason the thermal adhesive has not held and the COB has desoldered itself due to the heat not been transferred
Does that sound likely?
Or when I raised my light slightly a couple of days ago and dropped it a bit, its one heavy SOB. Maybe I caught it on something which detached the wire and cob.

Is the COB likely to be ruined?
How would I remove the adhesive (which is now brittle) from the COB?

All other COBs are solid to the sinks so I just hope I can use some more adhesive and re-solder.
Luckily I have the day off work tomorrow so I can try and find some thermal adhesive from a computer shop.

Appreciate any feedback.
Cheers
C.W
 
RandomHero8913

RandomHero8913

Well-Known Member
Are the solder pads ripped off? That would point more to damaged in the fall. How far did they get dropped by the way?

Someone else will have to help with your thermal adhesive question, I've never used any so i'll be talking out my ass.
 
G

Goerilla

Member
I think that your glue has slipped and the cob´s therefor got so warm that the solder melted.
It will certainly ruin the cob´s if it happens again.

Rilla.
 
coreywebster

coreywebster

Well-Known Member
RandomHero8913 said:
Are the solder pads ripped off? That would point more to damaged in the fall. How far did they get dropped by the way?

Someone else will have to help with your thermal adhesive question, I've never used any so i'll be talking out my ass.
Click to expand...
The solder pads are fine. I have it chained on all four corners and one corner got away from me, its damn cramped in the tent so difficult to get to the back corner. It didn't land on the floor, just swang down a foot. I suspect the positive lead may have caught on something( its longer than needed) and yanked the cob off slightly. I'm hoping that's the case, I would think there would be less chance of the chip been burned out if that's what happened.

I know only time will tell! I shall go and find some thermal adhesive today. Fingers crossed. I will try and tidy the wiring while I'm at it!!
 
alesh

alesh

Well-Known Member
Seems like the thermal adhesive wasn't that adhesive after all. I use Arctic Alumina (2 part) and the only way to remove LEDs from heatsink would be a chisel I guess.
If the COB got so hot that the solder melted I'd guess it's damaged - at least partially. You can check your solder's data sheet to know what temperature the COB must have gone through.

Anyway, a lesson I learned is NOT to build light engines too big and heavy. Go with multiple smaller if possible.
 
coreywebster

coreywebster

Well-Known Member
alesh said:
Seems like the thermal adhesive wasn't that adhesive after all. I use Arctic Alumina (2 part) and the only way to remove LEDs from heatsink would be a chisel I guess.
If the COB got so hot that the solder melted I'd guess it's damaged - at least partially. You can check your solder's data sheet to know what temperature the COB must have gone through.

Anyway, a lesson I learned is NOT to build light engines too big and heavy. Go with multiple smaller if possible.
Click to expand...
I think that's a safe assumption, Don't cheap out on thermal adhesive would be another lesson I have learned. The stuff I used was some no brand stuff. Maybe I applied to much or too little. I have ordered some Arctic Alumina just now. I think I will resolder before I attempt to use the adhesive, pop the power on for a second and see if she fires up. If she does I will use the Arctic Alumina, I'm glad you posted because I knew it was good stuff but if it sticks as you describe it would be a ball ache to remove the cob should it be dead.

Yeah I went a bit overboard with the heat sinks, they only had 7 of the 150mm sinks when I was ordering so not wanting to mix different sizes I talked them into a free upgrade to 163mm. I had a smug look on my face until I tried to hang the light... :dunce:

If the cob is ruined I will have to have a word with @robincnn and see if he can ship one cob all the way over to the UK.
 
Moflow

Moflow

Well-Known Member
coreywebster said:
Alright fine fellows.

I have just been to tend to my ladies and noticed one part of my light was out. Its a 9x clu058 1825 jobby.
3 drivers running 3 cobs each at 1400mA. So on closer inspection I noticed a wire hanging down, they are soldered as the BJB holders were very slightly out of voltage range, ended up soldering them and using thermal adhesive to attach to heat sinks. Its been running fine maybe 7-8 weeks. All heat sinks were the same 34degrees C when I used my laser thermometer previously.
So I figured sheet I'm going to have to solder it back in situ. On even closer inspection I notice the COB is literally peeling off the heat sink! So I'm assuming for whatever reason the thermal adhesive has not held and the COB has desoldered itself due to the heat not been transferred
Does that sound likely?
Or when I raised my light slightly a couple of days ago and dropped it a bit, its one heavy SOB. Maybe I caught it on something which detached the wire and cob.

Is the COB likely to be ruined?
How would I remove the adhesive (which is now brittle) from the COB?

All other COBs are solid to the sinks so I just hope I can use some more adhesive and re-solder.
Luckily I have the day off work tomorrow so I can try and find some thermal adhesive from a computer shop.

Appreciate any feedback.
Cheers
C.W
Click to expand...
Sorry to hear of your cob problem.
I didn't fancy the Thermal glue and went for Paste and Kapton tape.
Doesn't seem too many use this Kapton but it's great.
Easy enough to remove and re use the cobs.
I'm always tinkering with different heatsinks so it's real easy to stick them .
:cool:
 
CobKits

CobKits

Well-Known Member
coreywebster said:
Yeah I went a bit overboard with the heat sinks, they only had 7 of the 150mm sinks when I was ordering so not wanting to mix different sizes I talked them into a free upgrade to 163mm. I had a smug look on my face until I tried to hang the light... :dunce:
Click to expand...
yeah some of those are massive like the mechatronics coolbay etc. at least it didnt knock you on the head!
 
coreywebster

coreywebster

Well-Known Member
Moflow said:
Sorry to hear of your cob problem.
I didn't fancy the Thermal glue and went for Paste and Kapton tape.
Doesn't seem too many use this Kapton but it's great.
Easy enough to remove and re use the cobs.
I'm always tinkering with different heatsinks so it's real easy to stick them .
:cool:
Click to expand...
I remember seeing the kapton tape on some of the builds that paved the way for us to copy. I might just get myself some so its there if I ever have a problem with any others. I have arctic silver paste, just cant use it without something to hold the chip on so it would be a handy thing to have. My build was very no frills in the end so it would fit right in. :eyesmoke:
 
coreywebster

coreywebster

Well-Known Member
Happy to say the chip is not burned out. Did a test , I soldered her back with some little wire connectors as a bonus. It was hard enough soldering while they where layed flat attached to the heat sinks, I didn't fancy that struggle upside down. I would probably drip solder into my eye knowing me... So I have the arctic silver alumina and tomorrow I can stick her back on so she will be fully operational! :bigjoint:
 
MediheaLed

MediheaLed

Well-Known Member
coreywebster said:
The solder pads are fine. I have it chained on all four corners and one corner got away from me, its damn cramped in the tent so difficult to get to the back corner. It didn't land on the floor, just swang down a foot. I suspect the positive lead may have caught on something( its longer than needed) and yanked the cob off slightly. I'm hoping that's the case, I would think there would be less chance of the chip been burned out if that's what happened.

I know only time will tell! I shall go and find some thermal adhesive today. Fingers crossed. I will try and tidy the wiring while I'm at it!!
Click to expand...
When I was doing my build I dropped my 3590 from about 4-5 feet up straight onto concrete in my garage. I was so happy when it fired up and all was well. Expensive mistakes suck!
 
coreywebster

coreywebster

Well-Known Member
IMG_0123.JPG

The Cob side of the tent. 9x citizen clu058 1825 3500k 90cri @1400mA , No reflectors or lenses on 163mm heat sinks.
Wiring needs a tidy. Every heat sink is earthed because they are thermal puttied to the frame which is no electro conductive.
Under it is 4x cluster bomb from bomb seeds. Did have 7 but canopy was too dense so got the other 3 around a 315cmh hung bare in the other half of the tent.

Got a weird taco going on with one leaf, not sure about that, its not hot at all in there, I did have cobs only 8" above canopy a week ago though.
@Moflow
@theslipperbandit is this pic clean data wise?
 
coreywebster

coreywebster

Well-Known Member
CobKits said:
maybe youre using too much? in a thin layer it makes a kind of suction with the heatsink, try twisting the chip a little
Click to expand...
Cheers Cobby, I got it on fine, as you say the suction does hold it there and I did apply a little too much but twisted it a wee bit and removed excess. I'm sure Glad to see it all working again.

Edit, I was speculating I would need something to hold it there while it set due to it been already hung.
 
theslipperbandit

theslipperbandit

Well-Known Member
I randomly check ppl pics to be safe for their sake some ppl are silly,I'd pmd a guy Google map of his house lol just keep location off n get an app called exif eraser which cleans the metadata from the pic then add file path for that directory n have a reference in the file path so u know like I've exif in my path so I know I'm picking the right one
 
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