I want to design a two layer PCB as heating surface that is screwed against a heat exchanger. I plan to use lots of distributed SMD resistors with one pad on the ground plane (no thermals) and the other one connected through a via to Vcc. For technical reasons, I want to place the resistors on the side against the heat exchanger featuring a trench in which they are placed.
To make the heat transfer uniform and efficient, I do not want to have a soldermask except a small frame around the pad of the resistor. This way, the thick copper layer is pressed directly against the heatsink.
The ideal thing would be to be able to inverse the definition of the tstop layer: Directly draw the solder stop shapes, instead of defining all the zones where no solderstop is allowed (as its typically done).
Is this possible? Or are there any good work arounds a PCB manufacturer can work with?