Squealing brakes on my 1998 Chevy Prism

If anyone might be able to help me with this annoying problem, it would be appreciated. Basically, I have driven with noisy brakes for some time now. Originally, I replaced my front (disk brake) brake pads in hopes of fixing the noise. That didn’t do the trick. Next, about 2 months later, I replaced the rear (drum brake) brake shoes which were very badly worn. This helped the stopping ability of my car, but didn’t help the squealing. Finally, I replaced my front rotors (which were a few points below the discard spec) and that greatly helped the loud squealing. I thought it was problem solved, but the day after replacing them, I still occasionally hear a mild squeal when braking. Does anybody have any ideas as to where the noise might be coming from and how I can fix it? Thanks!

When you replaced the front brake pads, did you put anti-squeal compound on the backs of the pads and the shims?

Thanks for the reply. To my knowledge, I didn’t put an anti-squeal compound on the pads. I did put some sort of gel on the back of the pads, though I don’t think it was specifically for squealing. It may have been. If that’s the case, then I put it on my pads, but not my shims. Where are the shims in relation to the pads? Where do I apply the anti-squealing gel on those? I really appreciate the help.