Mounting a heat sink on a S202S02 SSR

I'd like to mount a heat sink on a Sharp S202S02 SSR. Here's a drawing the indicates that the back surface of the device might be connected to AC:

In the "Design Guide" section of the datasheet it is recommended to add insulation between the device and the heat sink. That's quite clear. However, I still don't know if a metal screw used to mount the heat sink could still lead to a short between the back surface and the heat sink.

Does mounting a heat sink with a metal screw cause a short between AC and the heat sink, even if I add sheet insulation between the device and the heat sink?

I can of course use a nylon (or other plastic) screw, but it will get as warm as the SSR and degrade over time. Another option is to use a smaller screw and add a nylon sleeve, although the SSR's mounting hole is made for an M3 screw.

Here are photos of the real device. The first one shows the front, including the small area that is common to pin 1:

And here's the heat sink side. No metal to be seen:

It's all plastic, except those small rectangles at the front.

• @Christoph There are insulating shoulder washers for TO-220 which are used to insulate screws. If the hole fits M3 screw, perhaps one such washer could be used to insulate the screw as well. Search for TO-220 insulation kit and you'll probably find numerous examples. Feb 19, 2013 at 22:03