The advantage of Slow Cure NCP in filp chip package

Smaller flip chip packages have been developing and narrow gap and small pitch are required. The capillary type underfill still mainly applies for the flip chip mass-production process. The Non-Conductive Past (NCP), which is applied before chip attachment, has been introduced for fine pitch applications. These pre-applied type underfill have some advantages, such as no free space for dispensing and no flux cleaning process. However, the NCP has issue for connectivity and void control. We develop the new NCP, which is named Slow Cure NCP (SCNCP), to improve the connectivity and void control. SCNCP has slow cure ability to be void free after a pressure oven cure. It leads to an easier void controlling. In addition, slow cure property makes solder wettability higher and achieves better joint shape.