Silver-free copper based solder and preparation method thereof

The invention relates to a silver-free copper based solder and a preparation method thereof, particularly to the silver-free copper based solder for soldering of compressor case covers and copper tubes. The silver-free copper based solder comprises, by weight, 56-68% of Cu, 29-38% of Zn, 0.5-8% of Sn, 0.5-8% of Mn, 0.1-2% of In and other microelements. The preparation method includes fully melting the Cu, the Sn, the Mn, the In and the other microelements to obtain a master alloy; adding Zn into the cooled master alloy with full stirring; taking the alloy out of a furnace; preparing an ingot through pouring; and preparing the ingot into solder wires through extrusion and drawing. The silver-free copper based solder and the preparation method thereof have the advantages that the soldering temperature is 815-865 DEG C and satisfies the process requirement, high silver based solders can be replaced, the cost is low, and the metallographic grain size after welding is low.