Development of fine line build-up organic substrate using thin film RDL technology

As a low cost solution to realize a fine line structure for high density chip interconnection, the thin film organic substrate that adopted the same concept as flip chip RDL (redistribution layers) technology has been developed in this study. The coarse line of a conventional substrate could be refined to a much finer distribution through the application of a thin film process. The thin film layers had been deposited on both sides of a 4-inch diameter BT substrate by Cu sputtering and electroplating. The dielectric material, was built-up by spin coating process. Daisy chain testing circuit has been designed to evaluate the bonding performance between the dummy die and the thin film substrate. The fine line trace with the 5μm/5μm line/space was electroplated on the top layer. A 7mm×7mm dummy die was then flip chip bonded to the thin film substrate with a unit size of 10mm×10mm. The resistance of the wiring traces was tested to make sure that the interconnection between the chip and the interposer is good. The result was similar to the theoretical value, indicating that the structure of interconnection was successful.