Interconnection process by ink jet printing method

Miniaturization trend in modern electronics needs high density interconnect technologies and new materials, like elastic foils as substrates. Packaging on both external or even internal layers of such substrates needs electrically connections between layers. It is usually done by holes filled by electrically conductive materials and named as microvias. In the paper the ink-jet printing technology is proposed for creating the conductive layers of microvias. The interconnection process made by ink-jet printing seems to be very promising because of the same technique can be used for making planar as well as vertical connections in flexible substrates. The holes with diameter from 30 to 60 μm were drilled by laser beam in the polyimide substrates with a thickness of 100 μm and then filled by ink-jet printing. Two types of inks with nanosilver were used. One of them contains silver particles with a very narrow size distribution (from 4 to 10 nm) and needs high temperature for sintering, the second - with much higher silver particles size (tens of nm), but lower temperature to be electrically conductive. The experiments shows, that it is possible to achieve acceptable resistance of microvias.