Room-temperature chip-stack interconnection using compliant bumps and wedge-incorporated electrodes

We propose room-temperature chip-stack interconnection using mechanical caulking between compliant bumps and wedge-incorporated electrodes. In this method, cone-shaped compliant bumps made of Au are pressed into wedge-incorporated electrodes made of Au at room temperature in the ambient air. Because of the edge structures of the Au wedge incorporated electrodes, the pressing load is effectively applied to the interfaces between Au cone bumps and Au wedge-incorporated electrodes. Therefore, Au wedge-incorporated electrodes are caulked with Au cone bumps at low pressing load. By using this method, high-density inter-chip connections were realized at 0.50 gf/bump and 30 °C. The number of inter-chip connections realized was 30,600 with 20 μm pitch. It is also demonstrated that this method allows lower inter-chip connection resistance than the mechanical caulking between compliant bumps and doughnut-shaped electrodes.