The only way I found to cure my front (TC) pads from squealing was to replace them with a new set. They've been squeak free now for the past 2/3000 miles. 
Iirc,as only two of the pads have shims, there was talk of adding the used shims from the old pads onto the non shimmed pads on the new set, due to an initial squeal from new...?
(the idea being having four pads with shims, the mat black pad thingy stuck on with double sided tape )
That rings a distant bell .............. :-/ but TC pads just have the soft backing on 2 pads don't they :-/ :-/ :-/
Yes, so take the backing of the old ones, apply to new ones, making four pads with shims...
Shims, being soft, take the resonance out of the pad to caliper. Usually a soft metal. Although in this case being cheap pads, are a springy tin material with a rubbery type coating of some sort....?
So you didn't stick the old shims on the new unshimmed pads...? By the sound of it..?
