METHOD FOR FORMING SOLDER BUMP

PURPOSE: A method for forming a solder bump is provided to numerically control a ratio of tin ions and lead ions and solve the problem of an electroplating method by performing a printing method using solder paste in which the ratio of the tin ions and the lead ions is uniformly controlled. CONSTITUTION: Solder bumps are formed on a wafer(200) having a plurality of input/output pads(202) and a passivation layer(204). An isolating metal layer(205) is formed on the input/output pads and the passivation layer. An under bump metal(UBM) layer(206) is formed on the isolating metal layer. The UBM layer in a portion except the region that a bump is to be positioned is eliminated to perform an exposure process on the isolating metal layer. A photoresist layer(208) having a plurality of openings is formed wherein each opening of the photoresist layer corresponds to the position of the bump. The solder paste(210) is filled in the openings of the photoresist layer through a printing method. The solder paste is reflowed. The photoresist layer is eliminated. An exposure process is performed on the isolating metal layer.