Bill of material and geometry on FCBGA packaging warpage impacts

This paper investigates the warpage behavior of FCBGA (flip chip ball grid array) packaging with an assumed condition of an underfill filling process. Chip and substrate core thickness were investigated in this study for geometry optimization. Bump, underfill and core material were also discussed for material impact. Beside, the bump numbers and chip/substrate area ratio were considered in this research. The warpage will be focus on the difference of substrate center and corner to deliberate the warp situation of FCBGA packaging. The appearance and cross-section of FCBGA packaging are shown in Figure 1 and Figure 2. The chip size is 21 mm × 21 mm with 775 um thickness and the packaging size is 42.5 mm × 42.5 mm. This chip is mounted on the six-layered (2/2/2) organic substrate with 1.058 mm thickness, and filling the gap with underfill. Shadow moiré will be used to measure the packaging warpage and the resolution of experiment measurement is 14.6 um. This quarter simulation model included chip, underfill, bumps and substrate. The substrate used for this investigation has three Cu layers isolated by ABF on double sides, and solder mask is covered on the outside surface. In this simulation study SnAg bumps and copper bumps will be discussed, furthermore two types of underfill (Underfill A, Underfill B) and substrate core (Core A, Core B) materials were investigated. The varied thickness of substrate core (200 um, 400 um, 600 um, 800 um), and chip (193 um, 387 um, 581 um, 775 um) are also consider in the investigation.