Not unusual for the front brake to do that .
Permatex has an aerosol product called : Disc Brake Quiet .
It's a spray on blue plastic substance that acts like an adhesive, so the pads don't rattle in the caliper, they stay stuck to the piston, but it's not difficult to remove the pads when the time comes .
I think that someone mentioned that using a rattle can of automotive paint would produce the same result, I don't know for sure, as I have not tried it .
You may want to try taking the pads out, and clean everything up, check the pads for thickness as well .