Improved Reliability of Leadfree Flip Chip Assemblies Using Direct Underfilling by Transfer Molding

Flip Chip technology has been widely accepted within microelectronics as a technology for maximum miniaturization. Transfer molding is the standard process for a highly reliable encapsulation of leaded and area array packages as BGAs or CSPs. Advanced materials and process developments now allow the use of transfer molding technology for direct underfilling and / or overmolding of Flip Chip assemblies. Existing standard equipment for encapsulation can be used and no additional process step for underfill dispensing or jetting 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. Trends of the market drive towards SIPs with an integration of different devices. Therefore the highly reliable encapsulation of these hybrid packages with inhomogeneous topography is the goal. For testing the reliability limits and the determination of failure mechanism of molded Flip Chips a test vehicle has been designed at Fraunhofer IZM.