mount transistors to heat sink without screws?

[Dmeads]

for a PCB i am making i need a heat sink with a few different transistors attatched. I dont have a drill to drill through the heat sink, but i need a big one to mount all the transistors to, not just a bunch of little ones. Is there a way to mount to220 packages to the heatsink without the screw?? like just with thermal paste?

[xani]

The classical one would be to screw whole board to the radiator, altho of course you'd have to design it so transistor are the highest element on the side bolted to radiator

Here is an example of board like that (altho with tiny plate as radiator):

https://youtu.be/rT-1gvkFj60?t=177.

That way you just need 4 screws
 
There are also radiators you can "clip on" the transistor directly altho probably way too small for your needs, and ones like this:



which have holes to put into PCBs and pre-made holes for transistor

[Dmeads]

okay i will probably screw the board to the heatsink then good idea

[Shock]

There are both heatsink clips and clip on heaksinks. There are also thermal adhesive pads and glue. I'd drill a hole, tap it with a screw and use the proper insulators as needed.

[jhpadjustable]

Just wanted to point out that one big heatsink is very likely electrically conductive, and that you should therefore think about electrical isolation between it and all the transistor tabs.

There are thermally-conductive, electrically-insulating adhesive tapes, such as 3M 8810 among many others. They might not perform as well as the standard mica sheet with thermal paste and a proper screw attachment, but you gotta do what you gotta do.