Development of VCI (Vertical Circuit Interconnection) technology for stacked die package

Wire bonding technology has been the mainstream for stacked die packages for over five years. Yet, based on current design rule, the package body size increases with respect to the number of dice stacked in the package. Furthermore, the electrical performance is greatly dependant to the wire length. By applying Vertical Circuit Interconnection technology, VCI, the package footprint can be reduced to offer relatively smaller package size. As such, the electrical performance is enhanced due to shorter signal transmitting length. The concept of VCI technology is to replace wire bond by conductive glue, which vertically connects electric pads from strum to strum inside the die stack. Besides the standard assembly process flow, such as die attach, molding, singulation, three new process stages ─ parylene coating, laser ablation and conductive glue dispensing, are introduced to replace wire bonding after die attach process. Two test vehicles, tier stack and pyramid stack structure, were discussed in the report. Open / short test and reliability performance were examined post assembly. The packages delivered by VCI technology can be an alternative choice in small package as it offers competitive cost and performance to those by WB technology.