Make sure the caliper is tight. If you used the original rotors, there might be a higher ridge along the edge of the rotor. The brake pads could shift enough in reverse ( or during regular braking) to hit the ridge. Should wear down in time. If you used new rotors, i'd go back in and have a look.
13 elantra 67k 5w30 QSUD
03 chevy avalanche76k synpwr 5w30
01 saturnsc1 185k synpwr rebuilt
17 mazda cx-5 2200 miles m1 0w20/0w40 mix