Beyond Design: High-speed PCB Design Constraints


Reading time ( words)

Digital design has entered a new realm. Modern high-speed design (HSD) not only requires the designer to continuously break new ground on a technical level but also requires the designer to account for significantly more variables associated with higher frequencies, faster transition times, and higher bandwidths. Ignoring signal and power integrity and electromagnetic compatibility invites schedule delays and increases development costs and the possibility of never succeeding to build a functional product, which is a career-limiting strategy.

The key methodology is to understand the underlying high-speed design issues and then translate these into corresponding design constraints that will be adhered to during the entire design process. It is best to develop these high-speed design constraints based on pre-layout simulation.

We had a few critical nets to manage in the past, but now, it seems that a significant number of interconnects are critical. Also, each design requires a specific set of constraints based on the technologies used. Sure, we can port basic design rules for trace width, clearance, etc., from a previous design to the next, but individual constraints still need to be established. Constraint reuse is also limited by net and group naming conventions. If you are consistent, then porting is much easier.

To begin with, every designer needs a set of well-established design rules to base the constraints on. IPC has provided the electronics industry with guidelines for designing and manufacturing PCBs compiled over the years with the support of both committee and industry members.

The IPC-2220-FAM: Design Standard for Printed Boards series is the bible for PCB designers. The series is built around IPC-2221B—the base document that covers all generic requirements for PCB regardless of materials. From here, the designer chooses the appropriate sectional standard for a specific technology.

The IPC-2220-FAM series includes:

  • IPC-2221B: Generic Standard on Printed Board Design
  • IPC-2222A: Sectional Design Standard for Rigid Organic Printed Boards
  • IPC-2223C: Sectional Design Standard for Flexible Printed Boards
  • IPC-2224: Sectional Standard for Design of PWBs for PC Cards
  • IPC-2225: Sectional Design Standard for Organic Multichip Modules (MCM-L) and MCM-L Assemblies
  • IPC-2226A: Sectional Design Standard for High-density Interconnect (HDI) Printed Boards

This series provides coverage on material and final finish selection, current-carrying capacity and minimum electrical clearances, test-specimen design, guidelines for V-groove scoring, dimensioning requirements, and conductor thickness requirements.

To read this entire column, which appeared in the May 2019 issue of Design007 Magazine, click here.

Share

Print


Suggested Items

Book Review: The Printed Circuit Designer’s Guide to…Executing Complex PCBs

11/19/2019 | Dan Beaulieu, D.B. Management Group
If you are serious about designing complex PCBs (most designs today are far from elementary) and even more serious about doing it right the first time, then this is the book for you. Loaded with guidelines for designing cutting-edge PCBs, this book is filled with real-world examples and tips, tricks, and techniques by some of Freedom CAD’s most experienced designers.

Words of Advice: The OEM Systems Designer

11/07/2019 | Andy Shaughnessy, Design007 Magazine
In a recent survey, we asked the following question: What advice would you give an OEM systems designer? Here are a few of the answers, edited slightly for clarity.

Dugan Karnazes Discusses His New Startup

11/07/2019 | Andy Shaughnessy, Design007 Magazine
I caught up with Dugan Karnazes again this year and discussed his new startup, Velocity Research, which is a one-stop shop for design made up of technical creatives. The Grand Rapids company is already doing design work for a variety of customers, from individuals to multinational companies.



Copyright © 2019 I-Connect007. All rights reserved.