Patent ID: 8794502
Filing Date: 2014-08-05
Classification: H01L

Abstract:
1. A method of forming a solder on pad on a fine pitch PCB, the method comprising: forming a metal pad and a solder mask on a PCB, wherein: applying a solder bump maker (SBM) paste with a predetermined thickness over an entire surface of the PCB including the metal pad and the solder mask, wherein the SBM paste applied over the PCB forms a first region covering the upper surface of the metal pad and a second region covering the entire upper surface of the solder mask, and the SBM paste of the first region has a bottom surface facing the metal pad and a top surface opposite to the bottom surface, the top surface being disposed at a level higher than a level at which the upper surface of the solder mask is disposed; while the SBM paste is above the solder mask, at a temperature higher than a melting point of solder contained in the SBM paste and then cooling the SBM paste to form a solder on pad; and washing a residual polymer resin and residual solder particles of the SBM paste by using a solvent.