For the ultimate heatsinking...

Why solder? TO-220s are designed to mount on heat sink with a screw.

y.

Hear sink compound (white stuff?).

For 150W, you might want to try a copper heat sink with fan. They are much better and smaller than aluminium, at leasr for CPUs.

IR keeps publishing specs that are unbelievable, like TO220s at 350 amps. Sometimes they add some stars ** that point to tiny text footnotes like "package limited"

Be very careful here. I'd prefer to use more/bigger parts and spread the heat out.

IR shows the powirtab parts as "divested."

John

"Tim Williams" wrote in news:FeZlm.187558$ snipped-for-privacy@newsfe05.iad:

I've seen TO-220's soldered to PCBs.Commercial products.

Arctic Silver.

if you can stay within the soldering profile I guess you could, is there really much difference between a to220 and a d2pak other than the missing tap and pin?

I guess you could use some lowtemperature solder, something the melts at the upper end of the allowed operating range

y.

-Lasse

Indeed. And if it's not quite flat on that heatsink, thermal resistance goes way up. So you put heatsink goo inbetween, maybe with a pad of some sort (not sil-pads, but maybe mica for this). Now you depend on the screw for electrical connection, and thermal resistance is higher than polished, greased surfaces should be.

If you haven't looked at what a powIRtab is, this might be confusing.

I'm not concerned about moving the heat. Ten of these things, along with ten IGBTs, will be mounted on water cooled heat spreaders. I'm concerned with removing the heat from the die as efficiently as possible

Tim

I understand that metal-to-metal contact is better..grease, etc makes for lower thermal conductivity. But...if you want the ultimate, the die should be directly soldered to a diamond heatsink / radiator.

You mean...that...IR wears TWO vests?

-=*GACK*=- !!!

Yeah, but these are neither package or current limited. I just wonder about over 100W from that size device, and how best to deal with it. Since I need a mechanical and electrical connection to the tab, I'm thinking soldering is a good idea.

Well, I'm already intent on using 7 in parallel to handle the reaction of a big stinking buck converter: 120V supply, 1kA max. output (it's a constant current feedback loop). Figure 1kA and 40V as a worst-case scenario. If that's 1kA at up to 66% duty cycle for the diodes, it's 667A / 7 per diode, or a bit under 100A average, and about as many watts per diode (Vf ~= 1V).

They show up as "cheap" at Mouser. About a quarter the price of a comparable module-style device (e.g. HFA135NH40).

Seriously, what idiots make, and buy, those things? Parallel is way cheaper. I haven't seen, say, a 600V 100A dual IGBT module that's less than four times the price of 4 x TO-247 IGBTs, either. Is all the silicone goo they fill them with really worth that much?

But anyway, if they'll dissipate the power, that's good enough for me.

Tim

Even better, the powIRtab thing has a *solid* leadframe. So, like, you could bend the lead end down in a zig-zag so it's level with the backside and tack it to a board. It would look like a D2PAK with a whole ribbon lead (and extra tab..).

I don't think they make anything like that? Bismuth solder (pricey!) melts at some really low temperature, like 120C. Ordinary 60-40 isn't too bad. Just don't use lead free s*it, eh?

Tim

me

rew

Why? Only if you need to insulate the leads from the PCB.

You can still use standard TO-220 heatsink in one end and a secondary heatsink on the lead tab.

th

ed

I remember building 100W audio amp with standard TO-220 and heat sink. Copper heat sink is better than solders in spreading heat.

Silver filled chip die epoxy. No, not a suggestion for die attachment, a suggestion for attaching each device you place on that spreader.

If isolation is an issue, you need a thin, electrically insulative film or "layer". Hopefully one that has good thermal characteristics as well.

The epoxy takes up all the gaps, just like the old cream (paste) used to do.

Still, that is what the industry uses for die-to-carrier and die-to-heatsink attachment, so it has a lot of research behind it.

Have to bake at 180° F for four hours to cure. Very good numbers after that.

Not the answer you want, but is there any way to use a few more devices and run them at reduced ratings? If the cost of the individual devices is not high, this might be the most pragmatic answer - and it might give you a good reputation for bomb-proof designs.

(I presume that proving you can use devices right on their limits is not the real object of the project)

the surface mount version of TO220 seems to handle it OK.

Robert Baer wrote in news:__2dnR3yPvV- GgXXnZ2dnUVZ snipped-for-privacy@posted.localnet:

to which Arctic product are you referring? the epxoy adhesives or the thermal compound(s)?

And why?

I note neither is meant to be electrically conductive.(I was referring to the "grease" comment.)

The gak comment is retarded.

Both the silver filled thermal compound, used widely by the PC builder folks (AND SUCCESSFULLY), and the silver filled epoxy, used universally by the chip fab industry, are the best on the market. One does not see "copper filled" pastes. So let the science boys come up with it and then USE it. If you are a skeptic, you are likely too stupid to be working in this industry, because you are a STUPID skeptic, whereas a smart engineer is an intelligent skeptic.

Tim Williams writes

Not sure whether 'heat spreader' refers to something specific? I'd consider mounting them on a heat pipe, those are ridiculously cheap these days:

Yes I've been noticing amperage ratings in the 100's when searching Newark,Digikey.

Here is there testing procedure from an-1140

"IR defines what can be called the "ultimate current" for power packages on discrete products. This ultimate current represents the largest current any given package can withstand under the most FORGIVEING of setups for heat management.

The BENCH SETUP used in measuring the ultimate current at International Rectifier is full immersion of parts in a nucleated-boiling inert fluid."

The approach adopted here is more than adequate to SHOWCASE the ability of new Silicon platforms. The key word in this approach is SHOWCASE.

To actually utilize our parts in an application that targeted currents at the level of the ultimate current would likely be costly and impractical." Gee no s*it!

Full pdf - Continuous dc Current Ratings of International Rectifier's Large Semiconductor Packages

IDIOT! The heat gets from the generation point to the pipe *through* the SPREADER! A "pipe" only has a single, thin line of tangency otherwise.