Depends on the frequency of the squeal. Professionals have a lot of solutions for high frequency squeals like beveling the edges of the pads, lubricating the caliper mounts and pad-to-caliper contact points, and proper surface finish when machining the rotors. For a low frequency drone there is a damper that can be added that is tuned to the vibration to cancel it out. The cause is making parts lighter and lighter for better fuel mileage.