Study of high UPH TCB process with slow cure NCP

Abstract

The recent development trend of smaller flip chip packages requires narrower gaps and smaller pitches. The capillary type underfill is still mainly used for the flip chip mass-production process. The Non-Conductive Paste (NCP), which is applied before chip attachment, has been introduced for fine pitch applications. These pre-applied type underfills have some advantages, such as no need for dispensing area and no flux cleaning process. However, the NCP has issues for connectivity, void control and low productivity. In this study, Thermal Compression Bonding (TCB) process which ensures high-throughput is presented. The use of constant heating during the TCB process results in shorter die mounting time, achieving high-throughput via the use of mass reflow (MR), which implies a possible high UPH. Optimization of the mounting process eliminated die-shift. We have successfully developed a new Slow Cure Non Conductive Paste (Slow Cure NCP) suitable for the high-throughput process.