NAVIGATING THE PITFALLS OF

MULTILAYER HIGH PERFORMANCE DESIGN AND FABRICATION

RF / MW / HIGH SPEED DIGITAL

Who are We?

Michael InghamMichael Ingham specializes in the design and development of multilayer PCBs for RF and ultra High-Speed Digital applications.  He has held engineering positions with Vitesse Semiconductor and Intel and is currently a Principle Design Engineer with Spectrum Integrity, Inc. where he primarily focuses on 10GHz to 50GHz applications.  He has completed hundreds of successful designs and is often consulted with to identify and solve signal integrity issues.   Michael holds BSEE from California Polytechnic University, San Luis Obispo, and a Sr. Member of IEEE.

Judy WarnerJudy Warner has nearly two decades of experience in the Printed Circuit Board Manufacturing Industry. She is the director of Sales and Marketing for Transline Technology, whose focus is on RF/MW and High Performance PCBs. She is an author of a current blog that is hosted by Printed Circuit Design and Fabrication and Microwave Journal websites. The blog focuses on RF/MW and High Performance PCB manufacturing.

The ProblemThe are gaps of knowledge and understanding

that exist between Engineering, Design, and Manufacturing

This is Particularly true in the area of High Performance Multilayer PCBs

Most of us are not aware that these gaps exist and therefore fall into “pitfalls” that cause

much needless frustration and failure!

What creates these Gaps?

Many CAD Programs allow for any design to be created without regard to the “real world” viability for a PCB to be manufactured. As the software manufacturers have removed the stop-gaps, to allow for more flexibility and innovation, they have taken out the some safeguards that would prevent design engineers from unwittingly creating designs that are unfit or impractical for manufacturing.

Integrative courses have been removed at Academic levels

Fundamental understanding of Design and Mfg not being taught to engineers and increased demands for specialization leads to lack of exposure to design and manufacturing principles

RF techniques are very different than digital design, yet digital

designers are being increasingly called upon for High-speed digital

and RF designs

It Starts with the Design and High Performance Expertise

High Performance designs are not straight forward builds that rely only on the fabricator and material suppliers

High Performance Expertise is needed at the design, layout and fabrication levels

Synergy between disciplines is key to success

The Conundrum of the Non- Homogenous design The last decade’s evolution and

emergence of high speed digital.

Mixing Dielectrics(Unlike Materials)

Materials

Common Pitfalls:Specifying an overrated material.

The lowest loss tangent is not always the best choice!

Looking at the Big Picture when selecting materials

Addressing Conductive Loss

Low dielectric materials are more costly, and typically more difficult to use in manufacturing

Common Pitfalls:Stack-ups that are not fit for

manufacturing

Knowing your pre-pregs, bond plies and cores.

Variances of final product

Reading the fine print on the data sheets

Partnering with you Advanced Material Division Representatives and your design and fabrication suppliers

Common Pitfalls:

Unbalanced Stack-ups

Temperature Issues

Warping

Latent Problems

Common Pitfalls

Unrealistic Tolerances

Lack of knowledge of process capabilities and limitations, set up unrealistic expectations

The benefits of partnering with your board supplier and/or layout engineers

Common Pitfalls

Very thin transmission lines

Impedance issues

Very “lossy”

Manufacturing challenges

Common Pitfalls

Hole to Metal Clearances (Spacing)

Over crowding vias too tightly together

Running lines between vias with insufficient clearance

Vulnerability for shorts/signal issues

Common Pitfalls

Poor Documentation and Data Problems

Fab drawings should NOT be optional!!!

Accurate drawings are imperative to success

Careful DRC before releasing gerber data

Keys to Success

Identifying Expertise

Avoid the Pitfalls!

Communication

Partnerships(Self-directed continuing education!)

Creating Win-wins