Popatim: Yup... Backside, just like the H7 which (from my experience with the H7) can be a little awkward when the so-called "X-bar" doesn't line up perfectly. When it doesn't line up perfectly, it can be very difficult getting all four holes to do so on motherboards with large VRM heatsinks.
Neither is anything like Cryorig's original R1 or its H5 mounting design, each of which are screwed through the top to arms/bars that are securely affixed to the backplate.
Mounting instructions for the C7 were not available on Cryorig's website.
I would have preferred the fan use standard mounting holes in case it ever died and required replacement or if someone wanted to use a more powerful fan for greater airflow. With registration, Cryorig offers up to a 6-year warranty on its products, so consumers may not ever need to use a standard fan as a replacement.
I have an ITX system that could use this sink. Right now it has a AMD Phenom II copper heatsink without a fan + 120mm fan sitting on top. With the cases panel installed the fan fits perfectly sandwiched between the two.
With the C7, you actually have the screw pillars already attached to the heatsink. So basically you first push the heatsink and the pillars through the mainboard. Then you snap on the backplate (it snaps into place now) and screw the nuts on the back.
We tried to improve on the H7 design and made some adjustments to the backplate so that it snaps onto the screw pillars.