I want copper copper copper! (well... maybe not)

Well okay Mr. Materials Scientist! Tonight I'll try to knock out some of the calc based on a standard C6 heatsink (that's a good average for heatsink sizes... some are a lot larger, some are a lot smaller).

Wolfman29 said:

Well okay Mr. Materials Scientist! Tonight I'll try to knock out some of the calc based on a standard C6 heatsink (that's a good average for heatsink sizes... some are a lot larger, some are a lot smaller).

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Don't forget to include another factor...time.

How much of a difference in final operating temperature is your time worth? If I told you that you could lower your diode's operating temperature by 10C if you spend several hours doing all of this analysis, is that worth it to you?

It's not to me. To me, I'm already pushing it with the amount of time I've spent typing 2 posts if the only value I was getting was lowering the temperature a few degrees. If I were heatsink shopping for a portable handheld laser right now, I'd likely just pick the color I thought would work better, because it's not an application where I care that much about getting ultimate performance.

Luckily for me, there are other values associated with discussion on internet forums, so I'm still here.

pullbangdead said:

:: puts on materials scientist hat ::

Everybody is talking WAY too generally here. In general, for a heatsink you want high thermal conductivity and high heat capacity. You want both. Like anything else in the world though, you can't have both, so you have to make an engineering decision: higher heat capacity, or higher thermal conductivity.

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No, you are making it harder than it is - there are only a few metals that we really have the option of using. All we have to do is look at the options and determine the best of those metals and then decide if the cost is worth the performance.

It almost certainly boils down to aluminum or copper, but there are a few other materials worth looking into. RHD brought up some good points and asked some thought provoking questions that were worth looking in to for those of us building lasers and trying to get the maximum duty cycles that we can out of them.

When you are toasting $45-$55 (or more) diodes it makes sense to invest some time and perhaps even money into making sure your design is good. Especially if you plan on selling your builds.

And that decision will change in every application. Heat load, geometry, environment, it all changes the calculus, and you'll have to calculate it or measure it for YOUR application to find the best one. You can wave your hands around and say "heat capacity is more important" all you want, but until you either calculate it or measure it, then you're just blowing hot air.

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Well, that is the goal. But no, we aren't blowing hot air. We are talking it out, putting lots of eyes and brains on the problem and making sure that we have the right answers.

By defining the problem, then finding materials that can solve the problem, we are able to improve the design.

You say the situation changes with every application but that is the whole point of this discussion, to determine the needs of our application.

But as of now, this is a thread full of hand-waving arguments with no real data, because every application is different.

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I strongly disagree. First of all, a lot of this work has been done before. It is out there and researchable. There is a good reason that most sinks are made from Aluminum and Copper.

By looking at their properties and determining why they make good sink material we can look at other materials with similar specs and try to see if they might be better.

Your attitude seems to be that it is too tough to solve so we are wasting our time talking about it.

pullbangdead said:

Don't forget to include another factor...time.

How much of a difference in final operating temperature is your time worth? If I told you that you could lower your diode's operating temperature by 10C if you spend several hours doing all of this analysis, is that worth it to you?

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I think most of us participating in this thread find the mental exercise stimulating. It's fun. If it isn't fun to you, that's fine.

Stop using modules seems like the obvious solution, but you folks can keep doing your maths if you want... You could make aizix modules out of pure diamond, but it ain't gonna fit in your heatsink any better...

BShanahan14rulz said:

Stop using modules seems like the obvious solution, but you folks can keep doing your maths if you want... You could make aizix modules out of pure diamond, but it ain't gonna fit in your heatsink any better...

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That is only one facet of this equation. Not using modules is a great idea if you can machine your own stuff. But if you need more standardization then using aluminum or copper modules should help evacuate the heat into the sink better.

And it still leaves the original question posed by RHD which is, "are there better heat sink materials for handheld lasers than copper and aluminum?"

tsteele93 said:

That is only one facet of this equation. Not using modules is a great idea if you can machine your own stuff. But if you need more standardization then using aluminum or copper modules should help evacuate the heat into the sink better.

And it still leaves the original question posed by RHD which is, "are there better heat sink materials for handheld lasers than copper and aluminum?"

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Facet...:crackup::crackup::crackup:
Good one...


Jerry

tsteele93 said:

Not using modules is a great idea if you can machine your own stuff.

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And if you can't, you buy from someone who can. That's the way it works anyway.

tsteele93 said:

shooting for lower diode temps (and the accompanying increase in diode life)

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Lets not kid ourselves. If builders were worried about diode life, they would run them at a lower current. Keeping the diode 0.7C cooler will do virtually nothing.

tsteele93 said:

There is nothing wrong with...trying to increase duty cycles or eliminate them altogether.

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Perhaps, but if you want to go 60mph, it's easier and probably cheaper to buy an appropriate vehicle than to buy and modify an electric scooter. Either way, the copper "go faster stripes" won't help much. If you absolutely need a high duty cycle, use large fins or forced air. And here's a goddamn bat-shit-crazy idea... build a lab unit. :shhh:

There are many ready-made interference fit heatsinks. As far as the module materials helping to get the heat to the heatsink faster, maybe you should just use better heatsink designs.

Stop using modules; use brains instead!

BShanahan14rulz said:

There are many ready-made interference fit heatsinks. As far as the module materials helping to get the heat to the heatsink faster, maybe you should just use better heatsink designs.

Stop using modules; use brains instead!

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Please point me to the heatsinks you are talking about! :thanks:

For small size heat sources (like a laser diode chip) a high thermal conductivity is more important than a specific heat - the heat must be carried away as fast as possible to a larger (external) surface area where it is dissipated to air [switch off your lasers to reduce global warming :thanks:

Though all kind factors decide what is appropriate for an application. What good for a 5-mW red laser might kill a 100-Mw blue one. :na:

radiant electronics stocks ones for the common C6 host as well as the wf-501b drop-in host.

Alright - there's one way to solve this all. Is there anyone willing to make me identical heatsinks in each of the following:

1) Aluminum
2) Copper
3) Steel
4) Nickel (this one will be pricey)

Quote me a price, lets get them made to fit a SAIK (I've got a bunch of them on hand), and we'll do some testing

rhd said:

Alright - there's one way to solve this all. Is there anyone willing to make me identical heatsinks in each of the following:

1) Aluminum
2) Copper
3) Steel
4) Nickel (this one will be pricey)

Quote me a price, lets get them made to fit a SAIK (I've got a bunch of them on hand), and we'll do some testing

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Even if you are being serious, what is that going to solve? You need multiple heatsink geometries, different diodes with different heat generation conditions, account for different outside conditions (ambient temperature, air movement, etc.). If you settle on a single standard, then does that prove anything as well?

All this stuff can be done mathematically. What will be more important is to determine what material and geometry is needed for specific heat generation, for expected durations, in typical or assumed ambient conditions. Maybe you really do want to simply "store" heat in the heatsink rather than facilitate its removal at the outside surface. Or maybe the opposite. Experimenting with one single condition is not helpful to anyone unless that condition is replicated.

Bionic-Badger said:

Even if you are being serious, what is that going to solve? You need multiple heatsink geometries, different diodes with different heat generation conditions, account for different outside conditions (ambient temperature, air movement, etc.). If you settle on a single standard, then does that prove anything as well?

All this stuff can be done mathematically. What will be more important is to determine what material and geometry is needed for specific heat generation, for expected durations, in typical or assumed ambient conditions. Maybe you really do want to simply "store" heat in the heatsink rather than facilitate its removal at the outside surface. Or maybe the opposite. Experimenting with one single condition is not helpful to anyone unless that condition is replicated.

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That's all fine and dandy - but I presented my best efforts at the theoretical stuff in the OP. I'd like to take a stab at some practical data now.

Yes, we need lots of empirical data, and a single comparison won't put the issue to rest. However, that's not a reason not to do some initial testing.

I have some efficiency binned diodes, and the ability to fairly decently control the other non-metal variables. I can tackle some experimentation. I can't afford to commission 4 heatsinks per design for ten different host geometries (especially considering the cost of copper and nickel). But I probably CAN swing getting it done for one host design. Maybe two. So, I'd like to give it a shot. Yes, I am "being serious". I'm surprised you found my inquiry so shocking ?!? It's experimentation. We do that all the time. No drama required

Cyparagon said:

And here's a goddamn bat-shit-crazy idea... build a lab unit. :shhh:

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I pissed my pants I started laughing so hard when I read that..



How many people have had a diode die on them yet from old age? Anyone?

My LPC died of 15minute duty cycle ~350mA !! True Story!!