Reading time ( words)
It is great to see the venerable tradition of Clyde Coombs’ Printed Circuits Handbook continued in its recently published 7th Edition, assisted by the highly qualified effort of Co-Editor-in-Chief, Happy Holden.
The Printed Circuits Handbook has been a classic reference to the industry for many years, and the new edition will assure its place for years to come. The 7th Edition features 71 chapters, four more than the last edition, structured in 12 parts, and authored by 38 contributors—a list of accomplished authors that could double as a who’s who in the world of circuit boards.
It had also been my privilege and pleasure to write book reviews on the 5th and 6th editions of the Handbook. The ~1600 page 7th edition makes a worthy addition to the collection. There is always the challenge of adding pertinent, new information while curtailing older, less relevant information so that the publisher’s limit on page count is honored.
It seems to me that this balancing act has been accomplished by the editors as best as one could expect: The chapter on fabrication has been shortened by about 20% vs. the 6th Edition, presumably a reflection on the standardization of some of the well-established fabrication steps. The chapter on HDI is about 15% shorter than in the 6th Edition. This, at first sight, appeared to be at odds with the still growing importance of HDI boards, however, here too, a certain level of standardization in fabrication techniques has taken hold (e.g., laser drilling of microvias is now the dominating microvia formation technology, and “plating vias shut” has become a well-established process). Furthermore, it should be mentioned that Happy Holden’s The HDI Handbook has become the very detailed reference book of choice for HDI, offering more information for those with a deeper interest in the subject.
The introductory chapter in the 6th edition on “Lead-free Legislation” has disappeared in the 7th edition, a streamlining that makes sense. It seemed a bit odd, especially to the uninitiated, to see a very unique, albeit consequential issue at the time, in particular for consumer electronics, dominate a handbook on printed circuits which is typically structured to first introduce high-level issues (“Drivers”), followed by a more or less chronological discourse of printed circuit topics such as design & engineering, materials, fabrication, testing, and assembly. Nevertheless, lead-free processing has found its place in the new edition where it had an impact on issues such as base material requirements, lead-free solder paste compositions and processing, and reliability testing.
What's new is the “Supply Chain” section, acknowledging the commercial reality of an industry that has largely lost vertical integration. While the material and equipment supply base for PCB fabrication has largely gravitated to Asia, design is widely scattered throughout countries where OEMs, fabricators and end-users reside, often leaving un-met needs in design for manufacturability and reliability.
Enlarged is the “Design” section, while the “Fabrication” and “Assembly/Test” sections are basically updated, with some added material to the Quality section. Reza Gaffarian did an admirable job in a major rewrite of the “Reliability” section, expanding the bare PCB chapters with new information and explanations. There is additional, updated information in the first two flex sections (“Design & Materials”). All in all, the 7th Edition feels more like a new book rather than an update of an old version.
The “Imaging” chapter of the 7th edition has been competently updated by Gareth Parry, and is about the same size as the one of the 6th edition which I am familiar with, since I assisted my former colleague Brian Conaghan in writing it. The new version includes inkjet technology, a brief overview of AOI, and a short new section on “Direct Digital Imaging” which is kept as a separate section, following “Laser Direct Imaging.” It can be argued that direct digital imaging is possibly the most important innovation in PCB fabrication in recent years, looking back on decades of a long arduous process of evolutionary progress and set backs. The long lead time in creating a new edition will explain why the significance of this technological breakthrough in most recent years is not yet fully reflected in the 7th edition. It is now viewed that laser direct imaging is just one version of digital imaging, and that the decoupling of the “digitizing” aspect (i.e., the modulation of a laser beam, from the light source itself, opens up opportunities for the use of more powerful, cost-effective, multi-wavelength energy sources such as high pressure UV lamps and LEDs, and the digitization is accomplished e.g. by the use of DMDs™—TI’s digital micro mirror devices).
In the “trivia” department, I should mention that the new edition has actual page numbers, something we missed in the previous edition. This makes it easier to maneuver through the voluminous book and to reference specific items.
In summary, the latest edition of the Printed Circuits Handbook is a great reference book for the PCB engineer and anyone who wants to gain in-depth knowledge of PCB technology.
