When asked by Beth Keser and Steffen Krönert to review their new book, Advances in Embedded and Fan-out Wafer Level Packaging Technology, I was a little apprehensive. I reminded them that I was NOT an engineer, so would only be able to review it from the layperson’s perspective. They assured me that was precisely what they were looking for, so I agreed.

Written by Experts

When the book arrived and I started flipping through its pages, it was like sitting down with an old friend. It turns out that many of the chapters were written by people who have contributed to 3D InCites in one way or another over the years: People like Andreas Ostmann, Tanja Braun and Klaus-Dieter Lang, of Fraunhofer IZM; Jan Vardaman, TechSearch International; Ron Huemoeller and Curtis Zwenger, Amkor; Tim Olson and Chris Scanlan, Deca Technologies; Hugo Pristauz, BESI; Thomas Uhrmann, EV Group; Ravi Mahajan, Intel; and Habib Hrichi, SUSS MicroTec.

Additionally, there were equally as many of whom I wasn’t familiar, providing the opportunity to learn something new. Keser and Krönert clearly did their homework when lining up contributors who are experts in their field.

A Comprehensive Guide

From beginning to end, this book truly tells the story of embedded and fan-out wafer level package (FOWLP) technology. The forward is an easy-to-read summary of what’s to come. The introduction provides a history of these technologies in great detail, going all the way back to the 1980s and the motivation for multi-chip modules MCMs, through each significant R&D breakthrough in process developments, noting the key players for each.

If you’re not interested in the details, skip right to Vardaman’s chapter on market drivers, it echoes some of the history lessons before fast-forwarding to today’s varied embedded and FOWLP playing field and thus tying history to today’s technologies.

The next chapters (3-12) dive more deeply into different FOWLP types and embedded technologies —eWLB and its numerous variations, RCP, M-Series™, SWIFT™m eSiFO™, embedded interposers, panel-level packaging, etc. —with each story told by the original technology developers. There are even a couple of chapters devoted to embedded and FO for power packages, an increasingly important application given the exploding automotive electronics market.

Chapters 13-21 focus on the embedded and FOWLP supply chain, discussing materials, tools and process innovations. You’ll find entire chapters devoted to the breakthrough materials, equipment and processes that make embedded and FO possible. For example, the roles of liquid molding compounds and advanced dielectric materials are discussed at length. Metallization, die placement, temporary bonding, and molding processes — all critical to the successful implementation of FOWLP— are also closely examined with dedicated chapters, and, in some cases, multiple chapters.

Chapters 22 and 23 step outside the conventional FOWLP types to examine close cousins that leverage some of the same processes, but don’t strictly qualify as FOWLP – encapsulated wafer-level CSP (eWLCSP) and embedded multi-die interconnect bridge (EMIB).

The final chapter, on 2.5D integrated electronic systems, steps beyond FOWLP to offer a foreshadowing of things to come, or perhaps competitive technologies. The story is told in two parts: one focused on through silicon via (TSV) based 2.5D, and the other heterogeneous interconnect stitch technology (HIST) as a TSV-less approach.

Because of its thorough coverage and readability, I foresee this book becoming a valuable resource for not only engineering students but also for technical journalists and writers who may not have an engineering degree. However, this is not the type of book you’ll enjoy reading cover to cover. (I didn’t, and the next section explains why). It’s the one you keep on your desk for both quick references and deep explanations for anything related to embedded die and FOWLP. It’s likely the only book you’ll need on the subject. 

Let’s Call it Constructive Criticism

If you DO decide to read this book cover to cover, you might notice that some information is repeated, sometimes within the same chapter. For example, in the market research chapter, Deca’s adaptive patterning is described in two sections, almost verbatim.

Additionally, variations on the history of FOWLP, as well as technology and market drivers are repeated in subsequent chapter intros. It reminded me of attending a conference where all but the first few presenters skip their intro slides because they realized those who came before him already talked about those things.

Lastly, don’t expect to experience a consistent tone of voice. Each chapter could easily stand alone as a white paper, complete with references.

A Few Things I Learned

As previously mentioned, I did not read this book all the way through. If I did, I probably would have learned lots more than a few things. But as a final note, I thought I’d share some tidbits.

The first new thing I learned was that there are different ways to write out the acronym, eWLB.  I’ve always assumed it was embedded wafer-level BGA. But in the preface and the history chapter, it’s referred to as extended wafer-level BGA. So which one is right, or are both acceptable?  

I also learned that many of the processes used today for embedded and FOWLP have origins in MCMs. For example, a method for correcting chip-to-wafer misalignment using a computer-generated file for mask making was used by Wayne Johnson, Auburn University, and Ray Fillion, GE Research in their MCM pioneering research (p2-3). Could this be the inspiration behind Deca Technologies’ Adaptive Patterning process?

Lastly, it became clear once again that heterogeneous integration is not a new concept. It’s just a new phrase. In reality, it’s as old as MCM development using embedded and FO approaches (40 years). Even the early days of MCM development involved integrating MEMS, power modules, ASICs, etc.

Learn More

If you want to learn as much as you can about embedded and fan-out technologies, I recommend you buy the book. And if you’re at ECTC next month, stop by the 3D InCites table to peruse my advanced copy and perhaps pick up a 20% off coupon.

Francoise von Trapp

They call me the “Queen of 3D” because I have been following the course of…

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