Transistor Insulating Bushes and Shoulder Washers are well suited for isolating the fixing screw from the device and the heatsink.
Insulating Bushes are made using Glass-Filled Nylon 66, with the option on some popular parts of high-spec PPS material suitable for aerospace and military applications.
Visit the MECI Ltd website for more information on Transistor Insulating Top-Hat & Shoulder Washers