Self-replicating process for micro interconnect array pattern using solder/polymer hybrid materials

In the modern packaging technologies highly condensed metal interconnects such as solder bumps, gold studs, or copper pillars are typically formed by high-cost processes. These methods inevitably require the precise controls of mutually dependant process parameters, which usually cause the difficulty of the change in the layout design for interconnects of chip to-chip, or chip-to-substrate. In order to overcome these problems, so far, the unique concept and methodology of self-assembly even in micro-meter scale were developed by the author. Self-replication for micro interconnect was firstly proposed, in which micro “twin droplets” out of continuous molten solder can form in a small parallel gap between two co-planar surfaces of chips and substrates with array copper traces (typically 100 to 300 μm pitches) using the vertical detaching movement in polymer resin. In this report the geometry and yielding ratio of vertical and lateral solder bump bridges before self-replication were compared with varying filler content, copper land pitch, and gap space. It was found that the formation of the vertically bridged bump arrays with 100 to 300 μm pitch can be achievable.