In a disc brake design, the friction material also called a friction block or “puck” is attached to steel brake pads backing plates ;with rivets, adhesive, or a newer NRS mechanical retention system. The backing plate is made from steel and transfers force from the brake caliper piston evenly across the backing plate to apply the friction material to the brake rotor.

http://www.odonbrakepads.com/b....rake-pads-backing-pl