Target Condition: Are Autorouters Friend or Foe?
Fresh PCB Concepts: Assembly Challenges with Micro Components and Standard Solder Mask Practices
Elementary Mr. Watson: Retro Routers vs. Modern Boards—The Silent Struggle on Your Screen
Brooks' Bits: Your Traces Have Hot Spots!
August 24, 2016 | Douglas G. Brooks, PhDEstimated reading time: 1 minute
Your traces have hot spots. At least, those that carry a moderate current do. Surprised? Well, I was a little surprised, too, when I looked at this a little more closely.
One chapter in my recent book focuses on fusing current. It contains the image (Figure 1), captured on video, which shows a 20 mil wide trace that had been heated for about 15 minutes, just at the moment of fusing. There are several interesting things in this image, especially how the smoke is blown out from under the trace at certain points with considerable pressure. But note that the trace fuses at a point, not everywhere along the trace. It is clear from observation that the trace is much hotter at some points than at others.
Figure 2 appeared in a separate article published in 2010. (It has been enhanced after some collaboration with the author of that article.) The image shows a trace being heated to the melting point. At this stage, the hottest portions of the trace are over 600°C, but other areas remain in the 200°C temperature range.
The reasons for the temperature variation at high temperatures are not too hard to understand. There may be minor contamination under the trace or in the copper that accounts for it. Certainly, at higher temperatures (say above about 300°C) the board may begin to delaminate, severely disrupting its cooling characteristics. There may be small variations in trace width or thickness that help account for the delam, and these effects would be randomly distributed along the length of the trace.
But in a variety of lower-temperature studies, I personally took trace temperature measurements using a small thermocouple. I noticed that if I moved the thermocouple slightly, I would get a different temperature reading. Not by much, maybe 1.0° or 1.5°C. This is more than the resolution of the thermocouple, but not enough for me to be satisfied that the differences were real. So I began to wonder if these variations in temperature appeared at lower trace temperatures, say in the 40°C. range.
To read this entire article, which appeared in the August 2016 issue of The PCB Design Magazine, click here.
Share on:
Suggested Items
Trouble in Your Tank: Can You Drill the Perfect Hole?
07/07/2025 | Michael Carano -- Column: Trouble in Your TankIn the movie “Friday Night Lights,” the head football coach (played by Billy Bob Thornton) addresses his high school football team on a hot day in August in West Texas. He asks his players one question: “Can you be perfect?” That is an interesting question, in football and the printed circuit board fabrication world, where being perfect is somewhat elusive. When it comes to mechanical drilling and via formation, can you drill the perfect hole time after time?
The Evolution of Picosecond Laser Drilling
06/19/2025 | Marcy LaRont, PCB007 MagazineIs it hard to imagine a single laser pulse reduced not only from nanoseconds to picoseconds in its pulse duration, but even to femtoseconds? Well, buckle up because it seems we are there. In this interview, Dr. Stefan Rung, technical director of laser machines at Schmoll Maschinen GmbH, traces the technology trajectory of the laser drill from the CO2 laser to cutting-edge picosecond and hybrid laser drilling systems, highlighting the benefits and limitations of each method, and demonstrating how laser innovations are shaping the future of PCB fabrication.
Day 2: More Cutting-edge Insights at the EIPC Summer Conference
06/18/2025 | Pete Starkey, I-Connect007The European Institute for the PCB Community (EIPC) summer conference took place this year in Edinburgh, Scotland, June 3-4. This is the third of three articles on the conference. The other two cover Day 1’s sessions and the opening keynote speech. Below is a recap of the second day’s sessions.
Day 1: Cutting Edge Insights at the EIPC Summer Conference
06/17/2025 | Pete Starkey, I-Connect007The European Institute for the PCB Community (EIPC) Summer Conference took place this year in Edinburgh, Scotland, June 3-4. This is the second of three articles on the conference. The other two cover the keynote speeches and Day 2 of the technical conference. Below is a recap of the first day’s sessions.
Preventing Surface Prep Defects and Ensuring Reliability
06/10/2025 | Marcy LaRont, PCB007 MagazineIn printed circuit board (PCB) fabrication, surface preparation is a critical process that ensures strong adhesion, reliable plating, and long-term product performance. Without proper surface treatment, manufacturers may encounter defects such as delamination, poor solder mask adhesion, and plating failures. This article examines key surface preparation techniques, common defects resulting from improper processes, and real-world case studies that illustrate best practices.