Elementary, Mr. Watson: Rules of Thumb—Guidelines vs. Principles for PCB Design
Beyond Design: High-speed Rules of Thumb
Global PCB Connections: A Technical Overview of Long-flex Printed Circuit Boards
Accelerating the PCB Design Cycle
November 4, 2015 | Scott Miller, FreedomCAD ServicesEstimated reading time: 2 minutes
Mylar. Black tape. X-acto knives. Drafting tables. Ring lights.
These were the tools of the trade for the pioneers of printed circuit board design. Manually creating the large artwork that would then be photo-reduced to make the filmwork to image double-sided boards was truly an art form. The best designers were both neat and efficient. Somehow they avoided going home at night with their shirts or skirts covered with bits of tape stuck to them.
For those of you experienced designers, it’s incredible to see how far the art of PCB design has come over these 40+ years of evolution. CAD software has replaced Mylar, and computer screens have replaced lighted drafting tables. And now, it’s more science than art. PCB design now requires puzzle-solving skills on many levels to handle ever-increasing density and speed challenges.
The Need for Speed
By the mid-’90s, technologists were predicting that the use of conductive copper interconnections would need to be replaced with optics in order to address the increasing signal speeds. Year after year, the industry has found ways to increase the capabilities of copper interconnect to meet the escalating challenges. Some of these solutions were materials’ improvements such as high-speed laminates, smooth copper foil, and high-speed connectors. But many were based on PCB design strategies, including the use of back-drilling, reference planes, differential pairs, length matching, hole, pad and anti-pad shapes and sizes. Engineers and designers use many other strategies to maximize performance while minimizing cost.
One thing is clear: Designing printed circuit boards today is much more complicated and challenging than ever. Designing today’s leading-edge circuit boards requires that the designer:
- Has a strong knowledge of the capabilities of the CAD software.
- Understands PCB fabrication processes.
- Has a general knowledge of electronics and component functionality.
- Has a general knowledge of signal and power integrity.
- Understands PCB assembly processes.
- Understands industry specs.
In addition to all of these challenges, designers have to be efficient three-dimensional puzzles solvers because time-to-market is still a vitally important objective. After all, time is money.
So how do today’s designers balance the technical and timing demands? There isn’t one answer. It requires efficient use of the CAD tools, floor planning and effective communication with all parties involved.
Fortunately, Cadence Design Systems, Mentor Graphics, Altium and other PCB CAD software developers continue to make great strides at improving the capabilities of PCB layout tools. This has made it much faster to route differential pairs, create shapes or replicate circuits. And while they strive to make user interfaces logical and easy to use, many capabilities aren’t as obvious.
To read this entire article, which appeared in the October 2015 issue of The PCB Design Magazine, click here.
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