Intermittent Brake Squeek

I have a 2000 740iL, I bought it used with 60K miles on it. It has new front rotors (Rears were perfect), and new pads all the way around. A foreign car shop did the brakes not a stealer...For some reason I am getting an intermittant break squeek from the rear right brake, when driving lets say on the highway no brakes applied. If I turn slightly to change lanes etc it stops or under braking no squeek. Any idea WTF is causing that.

I guess they fortgot to grease metal part of the brake pads. when you braking they vibrate at very high frequence, so you get squeak. another thing is brake disk shield, maybe it is touching disk. U need to bent it.