Jul 24th, 2018
What do you do if you have an interference problem? Rick Hartley is an industry leader in the correct design of circuits and PC boards to prevent and solve noise, signal integrity and EMI problems. He consults and teaches internationally and he has taught seminars at numerous conferences, including the IEEE EMC Symposium, PCB West, IPC Apex/Expo and others. He is a past member of the Editorial Review Board of Printed Circuit Design Magazine and has written numerous technical papers and articles on methods to control noise, EMI and signal integrity.
Listen to this episode where Rick shares the worst ideas for a 4-layer and 6-layer stackups. He also offers a sneak peek of what to expect at his AltiumLive 2018 Keynote Presentation: The Extreme Importance of PC Board Stack-up.
- Contest - can you guess how many countries the OnTrack podcast has reached? You can win a Summit pass to be Judy’s personal guest at AltiumLive 2018! Just tag #OnTrackPodcast on Twitter with your best guess!
- Mid-80s - in digital domain things started to not work right and no one had answers. There was research to do (120 books later), learned what causes function vs. not function
- In the 90s, began to realize the problem wasn’t clock frequency, the problem is the frequency associated with the rising and falling edges of signals.
- Person who helped me the most - Ralph Morrison
- I didn’t learn what I needed in college, it had to come from experience.
- Energy and Fields and how they move - the energy is in the fields, not in the Voltage and current.
- Field dielectric / routing
- AltiumLive Keynote talk: The Extreme Importance of PC Board Stack-up
- If I’m contacted with an Interference problem, the question I ask is: “What is your printed circuit board stackup?”
- The most critical item is the board stackup, and it’s what people most often get wrong.
- Two or three voltage planes in a stackup with no grounds anywhere - a very serious problem e.g. high layer count board, 20 ground planes in board + signal routed on layer 1 and ground plane on layer 2 - return - 100% of signal on layer 1 would be in ground plane on layer 2. No current from that trace would be in any other ground layers, because energy is in the dielectric between layers 1 and 2
- With 2 or 3 signal layers, and then a plane - all signals try to reference one plane, all fields intermingling in the dielectric space, all coupling energy into one another and that’s one of the places where EMI comes from.
- It’s a matter of keeping fields isolated from one another for proper functioning.
- 4-Layer worst stack-up
- 6-Layer worst stack-up
- What to expect at AltiumLive (Early bird pricing - 10% off through end of July.)
- Setting the record straight: 15 years ago, Rick wrote a paper called ‘Board Stackup to Control EMI’ and “some ideas that I suggested in that paper, I have since learned are not good ideas.” Ignore this paper because the physics have changed. The speeds have become too fast.
Links and Resources:
High Speed PCB Designer’s Guide, Martyn Gaudion