Hi All,
I saw two videos on a TO-220 footprint which is horizontally laying on the PCB.
I assume the trick is to use the PCB as heatsink. please correct me if I am wrong.
is there any footprint library that I can use on Kicad or I have to create my own one?
assume that no enough heat is generated from the transistor, is there any pros or cons for such layout ?
TO-220-3_Horizontal_TabDown from the library Package_TO_SOT_THT? But do not over estimate a piece of copper or even a complete plane as a heatsink. It may take peaks or moderate power dissipation but it can not replace halve a pound of aluminium.
That’s what the D2PAK (TO-263) was made for.
Don’t expect too much, but a couple of watts dissipation is possible.
There are calculators for how much heat a PCB can handle. Using 70um copper helps too.
You can dissipate a few watts by using the copper of a PCB as a heatsink, but you will never get anywhere near to the 75 or so Watts that is the maximum for a TO-220 package. (TO-263 is the “SMT variant” of the TO-220, it basically has the tab cut off and it’s pins bent).
Another common trick is to add a bunch of via’s under the tab, and also add a copper area on the other side of the PCB. More surface area is more power dissipation. These methods are mostly useful when power dissipation is very moderate, and automated assembly is a significant cost saver. But it’s no substitute for a beefy chunk of aluminimum and maybe even a fan.
Cooling with the pcb is very common in newer designs. It is much more mechanically rugged than standing up components and heatsinks with their added mass. Laying down the TO-220 on a small heatsink of that type might be a good compromise.
I think there is significant thermal resistance in the mechanical-only thermal connection to the pcb. Many heatsink assemblies use thermal grease or something else to reduce the thermal resistance. Whatever semiconductor device is in the TO-220: Is it available in a D2Pak? That is the surface mount thermal package which is “equivalent” to the TO220. That is, I think it can fit the same semiconductor die and has similar lead spacing, and is designed for surface mounting. The solder will make a much better thermal connection than mechanical-only mounting of a TO220. I am not saying that it can dissipate as much heat as a TO220 which is nicely thermally bonded to a large heatsink. But if you are planning to heatsink with the pcb only, I think that a D2pak is likely to be better.
FWIW: I think that TO220 thermal tabs are generally not solderable but there may be exceptions.
Lay it face down and put the heat sync on back? Mass in the air, not on the board?
The first question that must be answered is: How much heat do you need to dissapate?
Until you know that, all answers are just speculation.
I’ve done this for LM7808, & 7810’s in addition for SN754410 of Stepper-Motor drivers… I have a photo somewhere of Thermal Camera showing the Temperature but, can’ty fond it just now…
It does get Hot but, No PCB/other damage and I still use this approach. But, as noted, it depends on how much Power/Watt (Heat)…
I guess I had not been specific there. I was thinking of the TO-220 being on its back, disoriented like this:
how would that SMT heatsink work ?
I see few contacts with PCB board.
The larger pad of the TRT (collector or drain) transfers heat to the PCB. The SMT heatsink is also soldered to the PCB. Therefore it helps in dissipation by ‘removing’ heat from the PCB.
In this case there are 2 contacts. The advantage is that it is not necessary to have such a large space on the PCB for dissipation.
I’ve used them.
They aren’t great, but can reduce theta-j-a by 10-20%, which is sometimes all you need.
Ridiculous.
Just the thermal transfer route to the “heatsink” (35 um copper) is questionable at best.
Stay away from snake oil, even if it looks cool.
And the OP has still not stated how much power needs to be dissipated, which makes this thread futile.
Not really related to KiCad.
