Insulating transistor from heatsink question

[Stvrob63]

Do the transistors without any metal on the back require electrical isolation from its heatsink? I am looking specifically at H669A and H649A with TO-126 package. There is not a metal plate, or any exposed metal on the surface or the screw hole.

 

[Mooly]

If there is no metal then no, you do not need insulators although insulation washers correctly applied could still help with thermal coupling.

I'm not familiar with the 'H' suffix for the 669 and 648 and I know those as 2SD669 and 2SB648 which definitely did need insulating as they were metal backed.

 

[Stvrob63]

If there is no metal then no, you do not need insulators although insulation washers correctly applied could still help with thermal coupling.

I'm not familiar with the 'H' suffix for the 669 and 648 and I know those as 2SD669 and 2SB648 which definitely did need insulating as they were metal backed.

Thank you. I will simply seat it with a thin layer of silicone heat sink compound and screw pressure.