A new high density organic laminate for high pin-count flip chip packages

By applying 'simultaneous curing' substrates for core substrates, we developed an ultra high transmission speed build up substrate (called Super HDBU/spl reg/) which is applicable for flip chip packages with over 3,000 I/O. Most build up interconnected substrates have been using a PWB with plated through holes (PTH) as the core substrate. Considering the form density of interconnects and transmission speed, this core with PTH has become a barrier by dividing the top and bottom surface of the substrate. Also, design interconnection lines are limited to the top side of the build up substrate which mounts the LSI devices. As for the solution to these issues, we have developed a new process of simultaneous curing with a copper foil transfer method onto an uncured prepreg. The simultaneous curing substrate method makes it possible to design signal interconnection lines on build up layers on both the top and bottom surfaces of the core substrate. In addition, it provides much finer via and narrower via pitch design on the core substrate which enables full grid area design instead of peripheral design.