Flip chip molding - highly reliable flip chip encapsulation

Abstract

Flip chip technology has the shortest interconnect length for minimum signal disturbance and simultaneous interconnection leading to reduced process times especially for high I/O counts and for RF applications. Flip chip technology allows for reliabilities required for automotive applications, but to achieve this goal, a plastic encapsulant, the so called underfiller, has to be used. New material developments for transfer molding allow underfilling and overmolding in one single transfer molding step. Existing standard equipment for encapsulation can be used and no additional process step for underfill dispensing is required. Molded flip chips have the potential of high reliability as the low CTE of the flip chip molding compound reduces the thermal mismatch. State of the art in FC molding is the encapsulation of single chip packages as BGA or CSP. Trends of the market drive towards SIPs with an integration of different devices as e.g. SMD and FC. Therefore the highly reliable encapsulation of these hybrid packages with inhomogeneous topography is the future goal. For the qualification of flip chip molding a test vehicle has been designed at Fraunhofer IZM. This test vehicle for process evaluation allows the encapsulation and underfilling of a single flip chip.