I've used a few different aftermarket pads, and only briefly on one of them did I have any problem with brake noise. In all cases, I used Permatex Quiet Stop on the backs of the pads. This is not a grease like what you would use on caliper pins, but instead is a high-temp adhesive that keeps the backs of the pads in contact with the calipers or pistons. The effect is to keep the pads from being able to resonate at their own frequency. For the price of one spray can, I'd be quick to buy a can and hand it to your mechanic, insisting that he remove the pads, clean the backs of them thoroughly, and apply a coating of this stuff before reinstalling the same pads. I'd put money on it that this solves the problem.

And to Klaus, I want to warn you about an admittedly rare problem with the PBR Deluxe Pads. See http://www.jimrothe.com/volvo/pbr_brake_pads.html.

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Jim Rothe, '99 S70 T5M,
http://www.jimrothe.com/volvo/index.html