NEW BUILD-UP PRINTED WIRING BOARD FOR FLIP CHIP ATTACH BASED ON UNIQUE HIGH Tg EPOXY RESIN

摘要

We have developed a new technology for making the build-up "Printed Wiring Board (PWB)" which has brought the best solution to "Flip Chip Attachment (FCA) ". The Build-up layers consist of a thin coating of high Tg Thermosetting epoxy resin, developed for the heat-resistant PWB. The use of this material could make the thin layers maintain high heat-resistance (Tg=180 鳦, corresponding to FR-5 grade) and high insulation reliability. It is currently too difficult to maintain these characteristics if a photo-sensitive resin process is used for the PWB, because such resins typically use the general epoxy acrylate resin, including hydrophilic functions. The build-up PWB has very small "Interstitial Blind Via Holes (IVH) " with 80um Min. diameter, produced by a pulse oscillated CO_2 laser. This IVH can condense the signal traces and provide the circuit design with more flexibility. Moreover, it can achieve finer patterns (e.g. L/S=20/20um) than the previous subtractive process. The tighter tolerance of pattern alignment (+-25um or less), is also practical with the combination of the semi-additive process and the high-performance exposure unit. These processes and techniques can be useful for making a Build-up PWB IC Package which performs as an interposer between the semiconductor and the mother board. Today the IC tends to be more integrated and requires the higher density interconnect solution. This new Build-up PWB, we believe, is a better solution for the advanced assembly technology; FCA, BGA (Ball Grid Array), CSP (Chip Scale Packages), etc. In this paper we will focus on the unique high Tg epoxy resin system with the detail data of materials and reliability.