Mounting TO-220 device on heatsink

[mike_mike]

Hello, I have got the following problem: I designed a new layout and I built it. After soldering the components, I found that I need a new heat sink, the old one which was supposed to be used with this design is not good anymore. Is there any possibility to mount the device on the heat sink without using the device's mounting hole and excluding the mounting clips ?

For example, I have 3 TO-220 components: 2 single gauge (the 2 ones on the right, with thin tab) and 1 double gauge (the one on the left, with normal tab), please have a look at the screenshot attached.
I think about drilling 2 holes into the heat sink, one hole between Q3 and U3 and one hole between U3 and U2. Then I will tighten the devices on the heat sink using a piece of metal - but I don't know what kind of metal I should use. I don't want to use the mounting holes of the single gauge TO-220 because it is very thin and it bends when I am tightening it using the M3 screw. I also have some clips that can be used, but I can't install them for each device because on the other side of the heat sink are the heat sink fins, and I cannot drill through them.

Please have a look at the images and give me some ideas, if you can. Thank you.

[Ian.M]

Its quite usual to see that in commercial equipment, and they usually use some sort of flat bottomed shallow U section steel channel, as the clamp must be stiff.  You'll also need elastomer pads between the clamp and the TO220 packages to get reasonably uniform clamping pressure across the width of each package and to compensate for slight dfferences in package thickness

[rsjsouza]

You can search for to220 heatsink with clips. This can yield parts like the one in the link below.

https://www.westfloridacomponents.com/G339APF03/TO220+Heat+Sink+with+Clip+Thermalloy+7022B-TC1-MT.html

[mike_mike]

I found some clips(TRK-2 is their name) and I want to use them. But I don't know if it should be a good idea to use them at angle (please find attached the image).

[Ian.M]

I wouldn't do that if I had any alternative.  If you get clip Fix&Fasten TRK-1, its got a plain hole, so you can use machine screws in tapped holes in the back of the heatsink (or self-tappers or thread forming screws in plain holes) and can position the clips in line with the transistors without having to worry about the fin positions on the other side.

[JustMeHere]

Can you make an adapter out some scrap metal or a beer can?

[exe]

Can you replaces those to-220 devices with a similar part, but with a thicker tab? What are those to-220?

[wraper]

https://sa.rsdelivers.com/product/rs-pro/tsc607-zp/heatsink-transistor-spring-clip-for-use-with-to/1311216
https://sa.rsdelivers.com/product/fischer-elektronik/thfm10/heatsink-retaining-spring-for-use-with-to-218-to/5040615

[SmokedComponent]

Can you replaces those to-220 devices with a similar part, but with a thicker tab? What are those to-220?

Those would probably be ST "TO-220"s. ST has to be the worst offender with those crappy, paper-thin tabs. I just received a bunch of ST LM1117 regs with those obnoxious tabs  , while I still have bunch of same devices with *normal*, thick tabs from TI/NatSemi. Those tabs do not bend.

[wraper]

Those would probably be ST "TO-220"s. ST has to be the worst offender with those crappy, paper-thin tabs. I just received a bunch of ST LM1117 regs with those obnoxious tabs  , while I still have bunch of same devices with *normal*, thick tabs from TI/NatSemi. Those tabs do not bend.

Nothing to do with ST. Many manufacturers make them, including your vaunted TI.

[SmokedComponent]

Nothing to do with ST. Many manufacturers make them, including your vaunted TI.

Well, thanks. I guess this is what you get for not checking datasheets and exact part numbers before ordering... And I don't care for TI...

[T3sl4co1l]

Yes, the bar is fine.  Use relatively thick material, say, almost 1mm steel, or maybe 1.6mm aluminum.

Preferably, the strip should be somewhat springy so it can deliver some preload force, and should be dimpled or embossed over the center of the device body, so it provides centered clamping force (whereas a flat plate will press exclusively towards the screwed side).  In lieu of that, the thick material has more stiffness, so you don't get much springiness but the force is more evenly distributed -- which is the higher priority.

Regarding TO-220, did you know the leads can be round wires, too?  Yep, the thin gauge tab, terrifically loose dimensions, and other oddities, have been in this very old standard since the beginning (which was introduced in what, mid 60s?).  The thin tab feels unnatural and scammy, but it's absolutely compliant for TO-220!  Shop for TO-220AB or the like, if you want better guaranteed dimensions (including a usefully substantial tab).

Tim