I have ATE discs and ATE pads. All is well on my car.
Do you have the shims behind the pads? If not, that might help.
Also I assume the pads are completely coated on the backs right?
I always coat mine fully, and use the shims that are there.
I do not have any squeaking problem.
What pads are you using now?
Do your discs have a lip on the outer edge?
If so, I would think about replacing the rotors and pads with new ones. I had a lip on my old discs, and my pads were earing quickly, and I had a bit of a squeal. Changing both seemed to aleviate that.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.