Fabrication of flexible interposer using printing method

In recent years, flexible electronic devices such as printed electronics are gathering attention. To make flexible connect between one circuit device and another circuit device, interposer is necessary. However, most of conventional interposers are not flexible, because there are made of silicon or glass substrate. To solve this problem, we have been developed fabrication process of flexible interposer. Master mold was fabricated by photolithography process. First, SU-8 resist was coated on silicon substrate with 5µm thickness. Then, photolithography process was carried out to SU-8 resist. After development, pillar shape master molds with diameters of 10 or 20 µm were obtained. After release coating of master molds, hole patterns for vias were transferred by UV nanoimprint lithography. The obtained hole patterns were diameter of 10 µm or 20 µm, and pitch of 21.0 µm and 40.1 µm, respectively. Next, these holes were filled with silver ink by roll press method. Then, sintering process was carried out to evaporate of solvent of silver ink. After that, flexible interposer was obtained. As a result, we have been succeeded in filling the holes array with silver ink. Obtained interposer vias, which were silver region, were 8.2 µm diameter and 3.3 µm height, or 20.3 µm diameter and 5.3 µm height for 10 mm square size.