Breakthrough ball attach technology by introducing solder paste screen printing

Present methods of attaching solder balls to ball grid array (BGA) package is through placing flux and pre-formed solder ball to substrate followed by reflow process. In the ever-moving electronic market, low cost and faster units per hour processing provides competitive edge in the manufacturing technology. Screen ball printing (BP) to form BGA balls provides an innovative processing solution to overcome the costly conventional processing method. The key challenges to this project are to fulfill specified ball dimension and yields with a comparable quality and reliability performance to the current ball attach process. The challenge associated with a print and reflow process is the requirement to print very high amount of solder paste volume on each pad to achieve specified ball height after reflow. Yield loss due to this process are related to solder ball bridging and monster ball formation. Defects will be aggravated on tight pitch printing application. This paper will discuss some of the challenges and solution for this technology.