Tin or zinc based, halide free, surface mount technology processing solder paste: -with metal contents of 87,5 % or more, but not more than 90,1 % by weight, -with an alloy solidus temperature of 210°C or more, -with a viscosity of 178 Pa·s or more, but not more than 235 Pa·s, -with a particle size of 40 µm or less, -with a silver content either of 3,15 % or more, but not more than 3,5 % by weight for tin based paste or of 0,25 % or more, but not more than 0,28 % by weight for zinc based paste, -with or without bismuth content of 2,55 % or more, but not more than 2,71 % by weight, -with or without copper content of 0,6 % or more, but not more than 0,7 % by weight