A mesa-type structure (52) is formed from polyimide (or a similar polymer material) to achieve a supporting structure for mounting a focal plane array (30 and 130) on an integrated circuit substrate (70 and 170). In an exemplary thermal imaging system (20 and 120), a thermal isolation structure (50 and 150) is disposed on an integrated circuit substrate (70 and 170) for electrically connecting and mechanically bonding a corresponding focal plane array (30 and 130) of thermal sensors (40 and 140). Each mesa-type structure (52 and 152) initially includes a polyimide mesa (54) over which is formed a reinforcing layer (56 and 156) and a metal conductor (58, 158 and 168) that extends from the top of the mesa-type structure (52 and 152) to an adjacent contact pad (72, 172 and 174). After the focal plane array (30 and 130) is bonded to the corresponding array of mesa-type structures (52 and 152), the polyimide mesas (54) are removed to create void spaces (60 and 160). The resulting mesa-type structures (52 and 152) provide a thermally isolated, but electrically conductive path between the sensor signal electrode (44 and 144) of each thermal sensor (40 and 140) and the corresponding contact pad (72 and 172) on the integrated circuit substrate (70 and 170).