Flip chip on board connection technology: process characterization and reliability

The authors discuss a ultrafine pitch attachment method called Flip Chip on Board (FCOB). This technique is capable of connecting unpackaged integrated circuits directly to organic printed circuit boards (PCBs), accomplishing the ultimate in assembly miniaturization. The process utilizes solder bumped I/O pads on the chips that are bonded to mating solder bumped sites on the board. In order to produce high quality electronic products in volume with FCOB, characterization of the assembly process is essential. Thorough characterization reveals the critical process variables that must be controlled in production, allowing cost-efficient manufacturing to occur. The authors describe the process characterization of FCOB, and demonstrate the compatibility of the technology with conventional surface mount processes. Key failure mechanisms are identified and discussed with respect to the degree of process control required to eliminate them