Hyundai Repair: brake noise, hyundai elantra gls, wheel bearing grease


Question
i just recently (week or so ago) changed out the old/worn front brake pads on my 2000 hyundai elantra gls with a set of semi-metallic duralast brake pads i picked up at the local autozone.
not having much knowlodge or experince on changing out my own brake pads, i enlisted an experinced mechanic friend of mine to help me out. with the help, everything went smoothly. i knew without someone with experince i'd screw up my brakes rather that achieve what i set out to do.
now there is a occasional screeching that occurs when i apply the brakes at about 20-30 mph but almost always when i apply them at slow speed 5-20 mph. no vibrations occur or pulling when i apply the brakes, just the screeching.
i would also like to say that before changing the brake pads there was no screeching at anytime.
please let me know what the cause of the screeching is or might be and what can be done to fix this problem if possible. thank you

Answer
Most likely, this noise is a byproduct of the aftermarket friction material.  

You can try to reduce it by taking the caliper back loose and coating the backing plates of the pads with some brake grease.  This should also be available at your local parts supplier.  It'll need to be able to withstand significantly higher temps than the standard wheel bearing grease.  And make absolutely certain you don't get any grease on the rotors or friction material.  But again, this may or may not reduce the noise.  You'll probably be putting up with at least some noise until you change the pads again.