Diode Housing Heat Dissipation

[pupper42]

Hi everyone,
I've got these diode housings and I'm not sure what kind of metal they're made of (the description just says metal). I'm guessing it might be iron or steel though I'm not sure. Does anyone have any ideas?

Anyway I was wondering if there was a rule of thumb of choosing a housing material to go with a certain powered diode. For example what powers can be safely used in a housing made of iron/steel, and at what point would I need a copper housing to safely dissipate the heat? Like if I had a 445nm 1.6W Sharp GH04C01A2G diode would that burn up in an iron/steel housing?
Thanks

 

[Alaskan]

I believe those are nickel plated brass, when I first got into this hobby I bought them, but I now use copper diode mounts, wouldn't consider putting a laser diode into one of those unless fairly low power. I'm sure they are fine for 1 watt diodes, but for the most part these laser diode devices aren't cheap, I'd rather spend more for the best mount I can reasonably afford. That said, you can probably use that diode in them without too much worry except for a plastic lens, if that is what they give you, will eventually melt and fail. If they give you a glass lens, expect greater loss than you might want, they usually won't pair them with a high quality lens.

These are what I buy: https://www.ebay.com/itm/12mm-Coppe...les-3-8mm-5-6mm-9mm-DTR-CLMV5-12/173497977232

 

[pupper42]

I believe those are nickel plated brass, when I first got into this hobby I bought them, but I now use copper diode mounts, wouldn't consider putting a laser diode into one of those unless fairly low power. I'm sure they are fine for 1 watt diodes, but for the most part these laser diode devices aren't cheap, I'd rather spend more for the best mount I can reasonably afford. That said, you can probably use that diode in them without too much worry except for a plastic lens, if that is what they give you, will eventually melt and fail. If they give you a glass lens, expect greater loss than you might want, they usually won't pair them with a high quality lens.

These are what I buy:

I see thanks for that
What do you think the power limit is for brass housings though? Also I live in Australia so the shipping is a bit pricey for me

 

[FireMyLaser]

Copper or brass housing don't matter much by themselves as both have too little mass and surface area to make meaningful heat dissipation with high power diodes. You need to attach it to a heatsink, maybe even a fan for continuous use, and if that heatsink is good, then it don't matter much if the housing is brass or copper. Copper is still better of course. Think of the housing as an adapter between your diode and your heatsink, and its job is to conduct the heat to the heatsink.

 

[Alaskan]

Good catch, hope you were intending on inserting that diode mount into a heat sink! Regarding the brass mount, assuming the diode has a tight enough fit it's OK. What you need to make sure of is the diode is tightly mounted inside so it can transfer heat to it and again for the module to the heat sink it goes in. I suppose the quality isn't the same from manufacturer to manufacturer, so may depend on some variables I cannot know about.

Anyone else here use those? I like to use heat sink compound between the diode mounting module and the heat sink it goes into, as well as a tight mechanical coupling through some means.

 

[pupper42]

Ooh I see. Yeah I'll be sure to put it in a heatsink, thanks for the help
Sorry about all the noob questions haha I just got started into lasers

 

[FireMyLaser]

No problem, the only real noobs get the beam in their eye so just don't do that.

 

[pupper42]

No problem, the only real noobs get the beam in their eye so just don't do that.

I'll be sure not to do that haha

 

[Buffo]

Anyone else here use those?

Are you talking about the ubiquitous 12 mm nickel-plated-brass modules from Aixis? I've done a few builds with them back in the day (mostly the early A140 445 nm diodes that were harvested from Ca$io projectors).

I would stick the assembled module in one of the Z-bolt heat sinks with a little Arctic Thermal Paste to ensure the thermal connection was solid, then bolt the Z-bolt down to the optical plate. Never had any thermal issues.

I like to use heat sink compound between the diode mounting module and the heat sink it goes into

Yep. Not a bad idea to use some between the heat sink and the baseplate either, to be honest.

Adam

 

[FireMyLaser]

I press in my diodes without any compound. The pressure and fit feel to me to not need any paste, as it would just get pushed out of the way.

 

[RA_pierce]

My rule of thumb is that the chrome plated brass 12 mm modules are only effective at dissipating heat for a diode that produces no more than 0.75 W of heat, under comfortable ambient temperatures.
For example, a 660 nm diode producing 250 mW of light with 2.5 V, 0.4 A input will work because:
(2.5 V x 0.4 A) - 0.25 W = 0.75 W

In my experience, these modules used with 660 nm diodes do allow for a stable output for several minutes with no additional heat sink although the case temperature does rise with use but some diodes are more sensitive to heat than others.
You can get away with more power if you use the copper and aluminum modules.
Below is a link to a laser I sold a long time ago using the copper and aluminum module in a brass pen host. There is a video that demonstrates the stability with minimal heat-sink mass - the laser produces over 300 mW for 2 minutes continuously.

SOLD 300mW 660nm Super Pen

So I wanted to rebuild my personal collection but I am really just not that into lasers anymore. I am offering a nice laser here for what it cost me to make it. 300mW+ LPC-815 diode ~660nm 650-G-1 Lens Flex V5 Custom Stainless Steel Flaminpyro focus ring Fixed/Focusable DTR Cu + Al module...

laserpointerforums.com

Estimate the amount of heat your diode will be producing in the same way to get an idea of what kind of heat management your project requires.
Remember that heat dissipation depends on more than just mass and material. If you want to get technical about it, do a little reading on heat transfer by radiation and conduction.

 

[Cyparagon]

My rule of thumb is that the chrome plated brass 12 mm modules are only effective at dissipating heat for a diode that produces no more than 0.75 W of heat, under comfortable ambient temperatures.

With or without the threaded back half? What's the temperature rise above ambient at 3/4W?

 

[RA_pierce]

With or without the threaded back half? What's the temperature rise above ambient at 3/4W?

I just tested a module with the approximate configuration described: 660 nm diode producing about 250 mW light. I don't recall the exact current and voltage at the diode but it's likely in the ballpark of 0.4 A, 2.5 V.
Ambient temp is 83 F. After 3 minutes, the case temperature I measured is 101 F, for an increase of 18 F or about 10 C. After another minute, the temperature rose to 108 F (another +4 C).
Sample size is 1 and temp was measured with a cheap household thermometer (I've got nothing better on hand), with no fans or anything to move air around. Take it for what it's worth. It may also be worth noting that some of the heat generated is from inefficiency in the driver which is soldered directly to the diode inside the back half of the module (Groove V2 linear driver).

While this won't be adequate for every project, the housing (if it accurately reflects diode case temperature) remains within specified operating temperatures for several minutes. The upper bound on the data sheets I've seen is 75 C (167 F) for similar diodes.
For general pointer use that doesn't include long continuous operation, I consider this "good enough."

 

[pupper42]

Thanks for your findings pierce

I wonder at what power acrylic lens would melt and you would need AR coated glass lens?

 

[Alaskan]

I have had them melt at 1 watt, also depends if any dust or contaminate on the lens, they fail much quicker if there is. AR coating just helps with reducing loss. For myself, even a half watt is pushing it with plastic due to how fast heat can destroy them, if a contaminate gets on it, glass is more forgiving when something is on the lens.