Design007 Magazine

18 DESIGN007 MAGAZINE I NOVEMBER 2024 Feature Article by Scott Miller FREEDOM CAD SERVICES The dictionar y defines a "rule of thumb" as "a broadly accurate guide or principle, based on experience or practice rather than theory." Rules of thumb are oen the foundation of a PCB designer's thought process when tackling a layout. Ultimately, a product spec or design guideline will provide the detailed design guid- ance, but rules of thumb can help to provide the general guidance that will help to stream- line the layout process and avoid design or manufacturing issues. Here are some rules of thumb that the design team at Freedom CAD Services has established over the years. Fabrication • Aspect ratios should ideally be less than 10:1 for board thickness/smallest plated holes. is is typically within the standard capabilities of most PCB fabricators. • If controlled impedance is required, get your stackup from your target fabricator and do this as early as possible. • Avoid placing copper closer than 10 mils to board edge. e PCB fabrication rout- ers have a tolerance of ±10 mils from true position; placing copper inside 10 mils could result in exposed copper. is can cause warpage, creepage, and delamina- tion over time.

• Design007 Magazine — November 2024
• Feature Contents — Rules of Thumb
• Additional Contents
• Column — A Handy Look at Rules of Thumb
• Short — Fresh PCB Concepts: The Critical Nature of Copper Thickness on PCBs
• Feature Interview — Rules of Thumb: A Primer
• Short — Merging Atomic Clocks with Quantum Computers
• Feature Article — Rules of Thumb for PCB Layout
• Feature Column — High-speed Rules of Thumb
• Feature Article — PCB Layout Rules of Thumb for Consideration
• Article — UHDI Bleeding-edge Manufacturing Applications, Part 2
• Feature Column — Rules of Thumb: A Word to the Wise
• MilAero007 Highlights
• Column — Designing for Reality: Strip-Etch-Strip
• Feature Column — Rules of Thumb: Guidelines vs. Principles for PCB Design
• Feature Q&A — If You Can Define It Right, You Can Design It Right
• Interview — From Construction Work to PCB Design in Under a Year
• Top Ten Editor's Picks
• Career Opportunities
• Educational Resources
• Advertiser Index and Masthead
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