Abstract: Processes for forming an electric heater comprise providing a heater element and a power supply, applying a layer of a diffusion solder paste onto the heater element and/or the power supply and drying the applied diffusion solder paste, arranging the heater element and the power supply such that the heater element and the power supply contact each other via the dried diffusion solder paste, and diffusion soldering the arrangement to form a connection between the heater element and the power supply. The diffusion solder paste comprises or consists of 10-30 wt.-% of at least one type of particles selected from the group consisting of copper particles, copper-rich copper/zinc alloy particles, and copper-rich copper/tin alloy particles, 60-80 wt.-% of at least one type of particles selected from tin particles, tin-rich tin/copper alloy particles, tin-rich tin/silver alloy particles, and tin-rich tin/copper/silver alloy particles, and 3-30 wt.-% of a solder flux.