A New Approach of Flip Chip on Board Technology Using SMT Compatible Processes

摘要

A flip chip on board technology fully compatible with current PCB facilities is reported in this paper. It uses reflow soldering for chip attachment. It requires electroless nickel/immersion gold finishing on the board pads as well as on the chip pads. A no-clean solder paste is printed on the boards. There is no requirement for solder deposition on the chip side. Assembly tests with various chip formats have shown the feasibility of this technology. Preliminary thermal cycling has revealed the promising reliability of underfilled assemblies. Cross-sections and X-ray inspections have proved the good shape and alignment of the solder joints.