Mine have squealed from new, only at slow speeds though. Will get it checked at first service, can't be bothered going to the dealer just for the brakes. Copper slip on the back of the pad when assembling usually does the trick though.
Copper grease will help but the main problem is asbestos, or rather, the lack of it. Modern pads have substituted metal particles for it. Most of the sqeal comes from contact between the pad and the disk causing high-frequency vibrations in the same way as rubbing a wet finger around the rim of a large thin glass.
A low speed squeal is of little concern. It's very difficult ro remove. Abrading the pads may provide temporary relief but it will probably return. It's made worse if your car stands unmoved outside for days. The thin film of rust that forms contaminates the pads and adds to the problem.