Design in design


The PCB Designer’s Guide to…Stacks: Design in Design

If you have ever considered crosstalk, eye closure, power loss, or a list of other issues defined in this manual, you also need to understand what, why, and how stacking can and will impact the performance of your circuit. After all, stacking is one of the few things that directly affects every part of your design; therefore, you should prepare for the greatest probability of success by establishing a solid foundation through a well-designed stackup.

There are many amazing resources for those working in the high-speed design industry: Eric Bogatin’s Simplified Power and Signal IntegrityLee Ritchey’s Right the first time, and a host of other books and websites. However, there is an apparent void in the area of ​​stacking design. How has the industry spent so long avoiding such an important topic as the one that influences everything on the board? The PCB Designer‘s Guide to…Stacks: Design in Design begins to fill the industry-wide void in an easy-to-understand overview that helps define what you as an engineer need to think about when building a stackup.

With 25 years of experience in PCB manufacturing and signal integrity, author Bill Hargin is an expert in the field of stack design and it shows here. In Chapter 3, Bill shows how the dielectric of your choice will directly impact your “eye”. It explains how each variable contributes to the overall loss budget, then defines how it recommends planning for hardware before any routing begins. This book helps the reader establish the variables of interest and the impact of those variables, and makes a recommendation on what to do about it so you can improve your future designs.

Boards are getting thinner, power requirements are increasing, and routing densities are getting thinner. You will have to compromise in your stacking, so understand that trade space is vital. This book breaks down concepts like map loss, material selection, impedance planning, and more. to help you understand how each will influence your design once made. This book will help you learn to make informed trade-offs earlier in the design cycle.

If you’re a hardware or electrical engineer who isn’t already deeply into stack design, this book is definitely for you. It’s packed with practical information, doesn’t get bogged down in technical jargon, has easy-to-understand and helpful images, and gets you to the races quickly. Even the seasoned veteran will find this book a valuable reference to understand when one needs to know things like the percentage contribution of each variable to impedance. No matter where you are in your knowledge, I recommend that you download the book and read it! It will be well worth your time and may save you future headaches.

Skyler Sopp is a signal integrity engineer for Mercury Systems.

This article originally appeared in the April 2022 issue of Design007 magazine.


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