Heatsink usage

For use with a TO220 package device, the LA6/150 12V heatsink would be an overkill and expensive too. From what I have seen, this type heatsinks are used on SMD ICs like processors or FPGAs. Basically on devices that can get quite hot. If you have multiple TO220 packages for example incase of inverter circuits or any other power electronics circuits, then I think it's feasible to use and yes drilling and hole and screwing the TO220 in the LA6/150 is fine. I have used simple aluminum from the waste material of frames for french windows in my house. They work fine as a heat sink.

I'm no thermodynamic expert, but agree with your advice. Unless a device is being driven to its max limits, the important thing is to get a thermally conductive piece of metal on a TO220 into a puff of fresh airflow, in an enclosure that an air intake path and an exhaust path (to minimize the enclosure ambient temperature) .   

I Was more interested in sussing out how that series worked and whether the design intrinsically required the IC to be attached to the bottom 1.2mm plate or not.  Have you used one or, like me, looked at it and thought that devices could be attached to the side: it certainly looks feasible.

That beast looks like it will dissipate a lot of heat. Might be good for an electronic load.

Definitely want a low thermal impedance to the middle of the thick side of the aluminum.

If you can't get the flat side of your TO220 bolted to the heatsink, you may need a copper block, and some heatsink compound.

If the fan is oriented to suck air through the fins, then the 3 Watts of fan power doesn't add to the temperature.

If you tap the mounting hole, you could use a brass screw (3X better than steel for heat conduction)

That seems to be a sort of "channel" or "tunnel" heatsink as I like to call them. They're quite popular in test equipment that need to dissipate quite a bit of heat while remaining compact.

You can see a similar unit inside my Rohde & Schwarz NGM202 where it uses one channel heatsink with semiconductors and a temperature sensor mounted on both sides of the channel. They just tap the holes in and bolt/clip them in.

I'm not sure you would mount anything on the flat metal plate on the bottom in the picture - it looks quite thin and not well thermally coupled. Instead, if you had a flat package which was board mounted, perhaps turning the heatsink upside down and using the thick metal surface (top in the picture) is a better idea.

I suspect the removable metal plate may just be to modify the airflow - in the case the plate is in, air must flow all the way through the heatsink to the rear, otherwise the air may "leak" out and contribute to cooling of surrounding components. But perhaps the main reason would be that the removable plate should be mounted oriented upwards so you can remove it to clean the fins during maintenance!

- Gough

Hi Andrew,

I remember a little from my thermodynamics classes that there are special materials/coatings that will have high thermal conductivity/capacity. I'm not sure if these heat sinks have that or work uniformly from all side (device attached to any of the four side) but the inner fin structure seems to be an important parameter to decide on which side the device should be mounted.

Good pointers Doug, thanks.  Looks like bolting to the side is the way it should work.  My thermal calculation gives a requirement for 0.7C/W max with the simplest solution I have.  The trade off I’m making is against a more complex approach, size, layout and costs.  A smaller version of the above would suit and the price from CPC.Farnell is about 50% of the uk.farnell price which works out quite well in terms of a separate alu block and fan.

That’s really useful Gough, thanks.  I never thought about the plate being for cleaning but that makes sense.  The pictures look like the fan vents out of the side of the enclosure?  Does it have a fan or clearance at the opposite end?

The unit is designed such that the fan blows through the channel towards the rear of the unit out the back - you will see a "cover" for the channel that has dabs of glue to prevent the panel from vibrating while in use due to the fan.

(images from https://goughlui.com/2019/08/20/rs-ngm202-in-depth-ch6-teardown/ )

(image from https://goughlui.com/2019/08/20/rs-ngm202-in-depth-ch2-unboxing/ )

Ah, I see, thanks.