Welding coating process of a predicted metallic terminal area on a substrate, suitable solder paste for application by the process and flexible printed circuit board or thin sheet

摘要

A method solder-coating a metallic pad (11) provided on a substrate, whereby at least the surface of the pad is provided with a deposit of solder paste, which paste comprises a suspension of metallic solder particles (13) which, when molten, have a surface energy lower than the critical surface energy of the metallic pad (11) but higher than the critical surface energy of the substrate surface outside the borders of the pad, whereby application of heat causes metallic solder particles (13) within the paste lying upon the pad to melt and fuse together into an essentially continuous metallic solder layer, whereas the metallic solder particles (13) within any paste lying upon the substrate surface outside the borders of the pad (11) do not thus fuse together into a layer but are instead deposited as mutually-isolated solder beads, which beads can be subsequently removed from the substrate surface after completion of the heating process. IMAGE