An apparatus for filling patterned mold cavities formed on a surface of a mold structure with solder comprising: an injector head assembly comprising a solder reservoir having a bottom surface with an elongated slot for injecting solder into said mold cavities; a carriage assembly configured to carry and scan said mold structure under said injector head assembly, characterized in that said carriage assembly comprises first and second parallel rails, a plate assembly movable upon said first and second parallel rails, a start parking space and a finish parking space and in that said mold structure is placed upon said movable plate assembly for performing said scanning under said injector head assembly and in that each of said parking spaces (152, 162) comprises a parking plate having a V-groove (155v, 162v) on its bottom surface, a heated base supporting said parking plate, an insulator plate (154, 164) supporting said heated base, a back plate supporting said insulator plate and first and second leveling plates (156, 166) configured to level said back plate; and wherein, in use, said mold structure is brought into contact with said solder reservoir bottom surface and a seal is formed between an area of said solder reservoir bottom surface surrounding said elongated slot and said mold structure surface and then said mold cavities are filled with solder by scanning said mold structure under said injector head in a first direction from a starting position to a finish position while solder is injected into them and then said mold structure with the filled mold cavities is returned back to said starting position by scanning it in a second direction opposite to said first direction without any further solder injection. an injector head assembly comprising a solder reservoir having a bottom surface with an elongated slot for injecting solder into said mold cavities; a carriage assembly configured to carry and scan said mold structure under said injector head assembly, characterized in that said carriage assembly comprises first and second parallel rails, a plate assembly movable upon said first and second parallel rails, a start parking space and a finish parking space and in that said mold structure is placed upon said movable plate assembly for performing said scanning under said injector head assembly and in that each of said parking spaces (152, 162) comprises a parking plate having a V-groove (155v, 162v) on its bottom surface, a heated base supporting said parking plate, an insulator plate (154, 164) supporting said heated base, a back plate supporting said insulator plate and first and second leveling plates (156, 166) configured to level said back plate; and wherein, in use, said mold structure is brought into contact with said solder reservoir bottom surface and a seal is formed between an area of said solder reservoir bottom surface surrounding said elongated slot and said mold structure surface and then said mold cavities are filled with solder by scanning said mold structure under said injector head in a first direction from a starting position to a finish position while solder is injected into them and then said mold structure with the filled mold cavities is returned back to said starting position by scanning it in a second direction opposite to said first direction without any further solder injection.