Novel Photo Imageable Film for RDL Application

Photo imageable polyimide was widely used as RDL of advanced semiconductor packages. Photo imageable polyimide was normally used as liquid form and it had two major issues. First, it was difficult to keep surface flatness by its coating and drying process, so additional process such as CMP was needed. Second, relatively large curing shrinkage and high cure temperature cause severe warpage. We have tried to develop novel photo imageable film to overcome these issues. We have succeeded to develop two kinds of novel photo imageable film suitable for RDL. One was the photo imageable film with standard Df (ca.0.015@10GHz), which could be developed by using alkaline water. Another was the photo imageable film with low Df (ca.0.005@10GHz), which could be developed by using polar organic solvent. Both films were found to be capable of forming micro vias with a photo imaging process. Both films exhibited much lower cure shrinkage and cure temperatures than photo imageable polyimides, resulting in much lower warpage. It was found that with these films, surface flatness could be easily ensured only by vacuum lamination. These would be useful for RDL film.