Novel solder-on-pad (SoP) technology for fine-pitch flip chip bonding

Solder-on-pad (SoP) technology gives the fine-pitch flip chip bonding manufacturability and reliability. For the SoP technology with pitch equal to or less than 150 μm pitch, there are many candidates. The cost-effectiveness will be one of the major criteria determining the industry preference. A novel bumping material, which is composed of a resin and Sn3Ag0.5Cu (SAC305) solder power, has been developed for the maskless solder-on-pad technology (SoP) of the fine pitch flip chip bonding. With this material, the solder bump array was successfully formed with pitch of 150 μm in one direction.