An Organic Package Designer’s Guide to Transitioning to FOWLP and 2.5D Design

Abstract

Many package designers have many years of hands-on experience designing organic FR4/HDI build-up BGA/LGA substrates. We’ve memorized the design guidelines and the substrate fabrication is well understood. We know how to wield our design tools like precision scalpels to get the design completed on-time, on-specification and on budget. Whether it’s flipchip attach, wire bond or a stacked die combo the design methodology is well understood. Then management mentions that the next generation of designs are going to be “heterogeneously integrated”, utilizing new integration platforms such as RDL-based fan-out wafer level and/or interposers. Suddenly, people start mentioning things like “Assembly Design Kits”, “Stream-out”, “sign-off using PDK’s”, multi-pass degassing, seal rings, assembly LVS and HBM stack routing. The suggestion is made that new design tools might be needed – semiconductor P&R tools that only work on Linux and are all TCL/TK script driven. We start doing some research online and attend a conference or two and listen to some of the EDA tool vendors and you could easily arrive at a point where you start to think, “Am I obsolete? Do I really need to learn to use silicon P&R tools? What is “assembly LVS”, multiple-pass degassing and why do my metal planes need to be hatched and offset?” For many of us, the shift in technology can be overwhelming. Do not despair; yes, there is new terminology to understand and many new design techniques to be understood and mastered, as well as a completely new design process and flow. The good news is that this can all be overcome without having to learn silicon P&R design tools. This paper will discuss real-world experiences of organic package substrate designers who have transitioned and mastered RDL-based FOWLP and 2.5D silicon and organic interposer design, while still using (and preserving) the majority of their existing packaged design tools and skills.