Novel solder structures for high reliability flip chip applications - Scaling to high-density applications

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The proliferation of technology on our persons (smart phones, smart watches, medical monitoring) and within our modes of living (home assistants) and transportation (aided and autonomous driving) incite the microelectronics industry to develop systems that are increasingly powerful and reliable yet ever compact with lower power consumption and competitive cost. At the heart of these systems is the network of semiconductor chips that must connect with each other and to the outside world. Flip chip technology, using short, tiny (human hair size) metallic structures, is the leading edge means to effect such connections at the highest density and performance possible. Despite such capability, flip chip technology must continue to evolve in order to keep in step with system demands. Miniaturization is a key focal point. As densities increase and the structures are even tinier, it becomes more difficult to balance counteracting issues - solutions to maintain electrical integrity (using copper instead of solder, or changing the solder composition) come at the expense of mechanical integrity. Our invention resolves this balancing act by proposing a unique structure that actually changes during the overall flip chip interconnection process. An initially heterogeneous structure is produced using reasonable adaptations to the known manufacturing methods for producing solder interconnections. This structure increases mechanical resistance at critical points in the assembly process then changes before the end of assembly to create a final, homogeneous solder structure with optimized electrical properties for operation. We have demonstrated the structure and behavior at reasonably miniature geometries (150 micrometers) but recognize the need to scale down to the size (50 micrometers) required of future generations. We propose this project to evolve both the structure and its manufacturing methods to this smaller scale. Project success will enable a Canadian innovation to extend the reach of microelectronic interconnection technology.