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Laser diode thermal regulation / potting

RDTech

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I have always been under the impression that most of the heat comes off the laser diode comes off the back of the diode and the case lead. If this is true, using my thermal, electrically isolated epoxy from Arctic Silver (not the conductive type) should help remove the heat from the Aixiz lens holder/heatsink. Anyone test this theory yet, with some sort of thermal epoxy? I always heat shrink the pos/neg leads on the laser diode anyway, use 28g Teflon wire, so there is plenty of room for a good area of compound... I will try it since I have a build this week to finish. Ideas?
 



CrazyMonkey

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I've thought about that too. I think it would help..
No way to know for sure, not without decanning it and maybe
using your thermal Imager?(if it shows temp)

Can't hurt anyway, with the exception of replacing the diode :yh:
 

Eudaimonium

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What you are talking about is very hard to produce. The laser die produces heat, which is spreaded over it's entire brass mass.

Now, if you want to exchange the heat of the diode with it's surroundings, you need a large surface. The surface in contact with aixiz while pressfited is much larger than only one pin.

I don't know how to properly explain you, but there is a wiki article :
Heat sink - Wikipedia, the free encyclopedia

It might help you explain how heat is transfered and exchanged (sinked).
 

wicked1

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how hot can these diodes get? How hot do they run in the projectors?

I know 1watt+ LED's run HOT in many of their applications. (under counter and store display lighting, etc) (I'd compare the heat to an incandescent lightbulb.. The heat sink will sizzle a wet finger in many cases) (obviously the LED is giving more light per heat..watt, but thats not my point)

Basically, as soon as I feel my laser pointer getting warm, it gets turned off for a while. (with this new 445, that's about 30 seconds) Can it take longer run times and more heat than that?
 

LazyBeam

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I think he's talking about the back face of the diode that the pins stick out of.
That's alot of direct diode area for sure. I think Arctic Alumina Adhesive would be great back there.
 

BShanahan14rulz

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Can't hurt. That back face of the diode with the pins sticking out is usually insulated by air anyways. It's possible that arctic ceramic or arctic silver has better thermal properties than air, but I don't know if anybody's ever tested that.... You'd be better off adding metal to the backside, if anything, to help transfer the heat from the back of the diode to the walls of the module. If you already insulated the entire power pin and connecting wires with heatshrink, thermally epoxying a metal slug with holes in it for the pins/wires onto the back of the diode would probably work better than a glob of insulating glue. No easy task, though.

I think a press-fit is sufficient for the average hobbyist's needs.
 

charliebruce

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how hot can these diodes get? How hot do they run in the projectors?

I know 1watt+ LED's run HOT in many of their applications. (under counter and store display lighting, etc) (I'd compare the heat to an incandescent lightbulb.. The heat sink will sizzle a wet finger in many cases) (obviously the LED is giving more light per heat..watt, but thats not my point)

Basically, as soon as I feel my laser pointer getting warm, it gets turned off for a while. (with this new 445, that's about 30 seconds) Can it take longer run times and more heat than that?
In the projector they have a thermal cutoff, but that's comfortably above "too hot to touch" (85 degrees at the heatsink rings a bell but I'm not certain).
 

RDTech

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NO, i'm not saying it is released through 1 pin, it is released throughout the entire metal form the die sits on. But the Aixiz heatsink only touches the outside diameter of the LD, not the bottom. That is my point.

My thermal camera is not a color calibrated one, so it will show heat and temperature differentials but in shades of B&W..I'll try and get some images.
 

CrazyMonkey

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I wonder if your thermal camera is at least consistent. If it is,
just use photoshop or some other software, where you can just
see the color values. You can calibrate it against knows temps..

Or at least see if its brighter or darker, lol..

If its optimizes to see temp differences then its no good.
Auto contrast/brightness would make it not work of course.
 

RDTech

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If you look at this companies products (5.6mm laser diode mount) you will see the rear of the diode is mostly touching the rear surface. They are from Arroyo Instruments -

Micro 5.6 5.6mm TO-Can LaserMount
 
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RDTech

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As far as the thermal camera photos. I will give it a shot. I have access at the business I consult for where I can use calibrated (color) imagers.
 

RDTech

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5.6mm LD (TO-56 in Aixiz housing) Question - I asked Aixiz staff about a year ago if they could make and send lots of their heatsink / module housings WITHOUT chrome coating. I was under the impression that a chrome coating raises the thermal resistance, thereby reducing heat transfer. I realize these small items like potting and coatings may not matter in short duty cycle units, but long term, not so sure...IMHO, anyone think the chrome is an issue?
 

psi seeker 34

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Depends on how the chrome is attached if it's the kind that could peel off it may be a problem or become one over time. On the other hand considering that chrome is a type of metal alloy if it's the real thing that was electroplated onto the module you shouldn't have any problems with it.
 

blrock

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I drilled a hole in a pentium III heatsink. Applied Artic Thermal Adhesive to the diode (messy job) and ran the diode @ 1.3 amps continuously for 3 days. No thermal issues
 




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