Molded Underfill (MUF) Technology for Flip Chip Packages in Mobile Applications Joshi M., Pendse R., Pandey V., Lee T.K., Yoon I.S., Yun J.S., Kim Y.C., Lee H.R., STATS ChipPAC Inc. Abstract Increased functionality requirements coupled with progressively reducing package size have necessitated the integration of flip chip packages into various baseband and application processor products in mobile platforms. Such products use flip chip technology using traditional capillary underfill (CUF) process on a strip based package which is subsequently over molded to finish the end-product assembly. The growing pricing pressures and competitive landscape in mobile-packaging has made it imperative for assembly subcontractors to drive the flip chip assembly cost down. To achieve this without compromising product reliability requires a fundamental shift in the way these packages are assembled. Molded underfill (MUF) approach offers such unique solution with promising advantages over CUF; such as lower material cost, higher through put and excellent reliability to meet the overall product needs of today’s evolving mobile market; and is discussed in this paper. Capillary Underfill (CUF) has been the cornerstone of today’s flip chip technology in both flip chip BGA and flip chip CSP format. Several advancements in CUF materials and dispense technologies made over years has made CUF the underfill technology of choice for various flip chip applications. However as the need for reducing package assembly cost has grown simultaneously; CUF material and underfill process comes under scrutiny due to higher material cost and slow through put process in the flip chip assembly flow. MUF was explored and found to be a viable lower c...
