Micro-soldering tool

A tool for micro-soldering connecting tags of an integrated circuit chip to corresponding terminals of conductors on a substrate by Joule heating comprising a high electrical conductivity bit having a bottom planar face adapted to contact the tags and press them against the terminals while applying sufficient heat to the tags to solder them to the terminals, said face having a centrally apertured portion adapted to receive and accomodate an integrated circuit chip, said apertured portion forming a geometrical loop on said planar face, said loop having first and second opposite sides spaced from each other and adapted to contact the connecting tags of the integrated circuit chip, first and second high electrical conductivity strips extending from first and second intersections with first and second opposite sides of the bit, said first and second strips respectively applying and removing current from the opposite sides of the face so that a pair of symmetrical current half loops extend about the geometrical loop between said opposite sides, each of said strips having a reduced cross-sectional area in proximity with its intersection with the bit, said bit having a continuous upstanding peripheral flange to provide rigidity to the bit, the reduced cross-sectional area of said first and second strips being respectively symmetrical with respect to said first and second sides and being removed from the intersection of the strip with the bit so that cross-sectional area of the reduced area is less than the strip at its intersection with the bit