Thermally conductive adhesive

I explained it in another post. Basically we wish to take advantage of the fact that the published derating curve is a "worst-case", based on mounting the led up on its legs. So it assumes a bigger case temperature rise at maximum current than would obtain with some heatsinking. At maximum temperature it means we can put twice the current through the LED, which directly affects the performance of our product.

Yes, but I think it is designed to be soldered via its leads. Soldering the can directly could melt the insides. There is quite a thick baseplate on the device, so to solder it would raise the whole thing to soldering temperature.

Unfortunately it's by far the best one we found for our application (it's not actually the one I linked to, but the case and temperature specs are the same).

Thanks,

While you could certainly glue it down, and may want to for vibration, I suspect you'd get better bang on the heat removal aspect by putting an annular ring heat sink on it - and depending how you did that, you could also get your solid, vibration-free mounting. Make use of that metal can.

ie, for glue down - glue it down, but add one of these (brim up):

For an alternate mount method, press fit, clamp, or glue the case into a block of aluminum with fins milled into it, and screw (with loctite, since you mention vibration) that down to your board - going nowhere.

Thanks for the link, I had not seen those before. Another useful option.

We do actually have an aluminium block too, but it is mainly coupled to the groundplane rather than the LED itself (because of manufacturing tolerances). Fixed pitch font:

. | LED . V . . _ . [XXXXXXX]| |[XXXXXXX]

And if you have room, you could even put a flat heat sink (with grease, rather than epoxy) on the backside as part of the "clamp" (with a couple of holes for the anode connection). Some small heat-shrink on the anode lead makes things simpler in terms of not shorting it. A short pin/post soldered into the board might make for a less-labor intensive (faster/easier for production) connection to the anode lead.

The "super glues" are all way to brittle.

Using a thin layer of epoxy to hold it down to a metal layer is about the best you can do without adding an extra part.

Adding a via or two to take the heat all the way to the far side of the PCB can help to get the heat away. Arranging things so that it isn't very far through the PCB to get to the mounting hardware can help to keep the temperature rise on the PCB low.

No room unfortunately - just getting the lead bend in may be a problem, will have to check exactly how much room there is.

Actually the anode lead seems to naturally bend around 180 degrees with quite a nice smooth curve. I think it will only take a few seconds in production.

Thanks,

OK, thanks for that advice.

Yes, we have done all that. Lots of thermal vias and one side of the board is all groundplance.

Thoughts:

The Hamamatsu part looks expensive.

The datasheet directivity curves are beautifully centered on 0 degrees; they always are. Verify that. Small variation in chip position or lens tilt can shoot that beam all over the place from part to part.

Even if the parts themselves are perfectly aligned, your epoxy/solder operation will need to be precise. That's a narrow beam.

Epoxy+solder will be messy.

A T1-3/4 type package heatsinks pretty well through its leads. You may not need heatsinking at all, at this sort of power level.

The last time I did something like this, the best solution was to use a flat-face (no lens) T1-3/4 package. No alignment problems, nice sharp point source, cheap, easy. It put more light in the sensor than a typically-misaligned lensed part.

There are probably nice surface-mount parts that would work.

John

Whose rule is that? What army is going to enforce it?

ftp://jjlarkin.lmi.net/Heatsink.JPG

Do I have to give the money back?

John

For arbitrary values of "truly."

And excluding diamond.

John

It doesn't have to go *too* far; our testing so far indicates they are OK for our purposes.

I am coming to that conclusion...

We need the intense spot with a fairly well collimated beam (anything else would need an external lens). They are not too expensive for our application, so we are happy with the part itself for now.

Thanks,

It is an IR transmitter, yes? Would TWO LEDs side by side yield the same energy and end up with the same transmission range?

Ever see those radial finned 'hats' for that package size from thermalloy?

This one is the simple variety:

They even have many with radial fins.

No. They are made to withstand a normal ramp up, and wave solder session, generally. If yours is that sensitive, hand soldering is required, and that by a VERY qualified person with some common sense.

If this device is really that sensitive to heat, I would question the maker as to why. If hand soldering is required and that at the leads only, you also then need to elevate it and put sinking clips on the leads while soldering. This is because simply touching a lead with the high temp solder iron feeds that heat right up the lead frame and into the package, no ifs ands or buts.

You could bend the leads surface mount style, and use the silver epoxy for the electrical attachment as well.

Alas, without an active sink that actually has air moving over it, you can temps are not going to be that much better no matter what you do after the soaking takes place.

Funny, that is the same link I posted a few minutes ago, before I read this post.

A nice, large annular ring plated thru hole IS a very nice way to mount it. If that is your choice, you should also surround that hole with some cladding and add some smaller plated thru holes as they increase the thermal mass of the PCB and make it conduct heat better Then you could place little heat radiators 'posts' into the other holes on the underside of the board and air currents can carry a lot of the heat away from the PCB.

So does Teflon tubing, which does NOT require a HEAT GUN!

THINK!

Want colored tubing? Strip a small length from a TFE SPC wire you might have nearby of the color you desire.

No, they are not. There is a VERY WIDE range of properties available.

I used to use a tube applied gel that I attached a heat sensor to the top of a transformer with. Ten second cure... no, it ain't coming back off.

The Store bought CRAP is likely what you have experience with.

Without moving air, it will ALL come up to a settled in temp when he subjects it to the power level he desires. Time period and frequency of use can be an issue.

Show me where I declared that it was a rule, dipshit.

You're an idiot.

If you attach that with straight epoxy, you are an idiot.

Every think of using an IR laser diode? Definite spot, and lower power needs. Maybe a couple more components.