Low cost flip chip bumping

A driving force to achieve increased speed and performance along with higher I/O count is the Flip Chip (FC) Technology which has therefore an high level of importance for a variety of applications. A breakthrough, however, will be the use of flip chip due to cost reduction. For this aim it is essential to use low cost bumping techniques. However, to provide FC technologies also for devices with high I/O count and high pin density applications like Microcontrollers, RAMBUS devices, etc.... it is necessary to redistribute the historically peripheral bond pads with ultra fine pad pitch into a wafer level CSP. This paper describes a low cost electroless Ni/Au Under Bump Metallization (UBM), a wafer level redistribution process based on electroless copper circuitization and different methods of single and multiple solder ball placement.