As MonzaIain says,
I too always use Coppaslip grease on the backs of all pads I have ever changed on all of my many vehicles, even if they had anti squeal shims or coatings on them and I have never, ever had any brake squeal or noise at all.
The grease applied to the backs of the pads do not interfere with the pad warnings either so it is quite safe to use.
All you need is a small tube, not the exhorbitantly priced tin from Haflords, which you can get next day off ebay. DO not be tempted to use just any grease, it must be Coppaslip or a clone of it!!!!!!!!!!!!!
Quiet times ahead I hope.

Here we go

i would be more convinced, re copper slip anti squeel, if you said you had brakes that sqeeled, THEN applied copper slip which fixed the problem and it never returned.
Sounds like pads fitted simply dont squeel?
ime ad ing copper slip may quieten a squeel, but almost always toreturn as before, and in serious cases makes no odds what so ever. Ask Kai on here, rear brakes sqeeling so loud they could be heard in the next street, so much copper slip applied it was dripping off the caliper to the point we thought it must be a brake fluid leak, made not one jot of differance to the sqeel.
ime most common cause of sqeel is cheep pads with no shims on the back, you need a shim material to take out any osilation if the pads dont sit perfectly flat in the caliper, if they rock they ossilate, and do so at such a frequency as to squeel. The more they rock, the louder the squeel. Shims, preferably ferous, ime.