Numbers on a data sheet are a good start, but confirm them with your own testing.
"Trust, but verify." While some readers will recall hearing this in the context of nuclear disarmament, I have it most notably drilled into my conscience by my first engineering manager while working in software quality assurance. And for good reason too! It was literally my role to verify the fixes that the engineers claimed they had implemented and to find the issues that were still open. While most of the time their fixes resolved the issue, sometimes it was only partially dispositioned.
So how do we successfully trust, but verify when it comes to information in data sheets for not just copper roughness, but other values significant for modeling signal integrity in printed circuit boards?
In a previous column, I discussed copper roughness and a partial story of the lifecycle of the copper as it moves along in the process of becoming part of a printed circuit board. In that article, I mentioned the dielectric constant/permittivity (Dk) and the dissipation factor/loss tangent (Df) of the resin/filler/glass combination. The data sheets used to be very secretive, with material suppliers concerned about corporate espionage regarding chemistries if the Dk and Df information was made publicly available. Depending on the material supplier and the materials in question, many times one can also find the construction data – glass weave style and quantity, resin content, and shelf thickness.
Read more: Models Can Be Deceiving: Trust, but Verify
System-driven part selection and routing are closer than ever.
it's rare for a motivational keynote speaker to have a lasting impact on attendees. At Zuken Innovation World's US iteration in June, however, Dan Thurmon certainly set the pace for the conference. The author of Off Balance on Purpose and a popular Ted Talk on embracing uncertainty, Thurmon's address had attendees referencing and even reenacting portions of his opening presentation in their subsequent presentations. The motivational speaker helped set an energetic and educational tone for the conference that followed.
And thanks to the coming AI revolution, uncertainty is what's ahead.
Zuken Innovation World is a series of conferences around the world dedicated to bringing customers, partners and Zuken experts together. A good portion of the eight concurrent training tracks at the June event in Scottsdale, AZ, was dedicated to sessions led by customer-users sharing design best practices and success stories. Surprisingly for a conference dedicated to a specific supplier, there was never even a hint of sales; this was a full-on conference dedicated to networking and educating, where one could learn about upcoming technologies, best practices, and novel implementations of toolsets that only a user would discover. At times, it was overwhelming to decide which of the concurrent sessions to attend, as multiple competing interesting presentations were occurring!
Read more: The AI Revolution is Coming to PCB Design
Smooth copper isn't always what it is purported to be.
I always trusted datasheets. Why shouldn't I? Every time I picked one up, I understood they were harbingers of truth about what something did and how to interact with it. From chips to components to widgets, manufacturers have a vested interest in ensuring users know what and how to use their products.
My trust in datasheets was eviscerated the very week I entered the printed circuit board industry. I was attending a weeklong training session on signal integrity taught by Eric Bogatin when he surveyed the attendees about datasheets and their accuracy. While my memory of the day and exact content isn't perfect, I do recall that as the very moment I learned the harsh reality: Datasheets are sometimes not as accurate as one would hope! (As an aside, Eric Bogatin's books on signal integrity are excellent resources because he has that special gift of teaching and explaining complex topics in approachable and understandable ways. The concept of "being the signal" and walking down a transmission line is just fantastic.)
When I first started in the PCB fabrication industry, I was fresh from college and ready to jump in and make an impact. The first hurdle I hit was likely the same as many first-time designers: units of measure for PCB design. Remember back in school, your physics professors or science teachers likely pointed out missing units in tables, graphs or homework assignments? That problem.
Figure 1.The three units of measure commonly used to describe the relative thickness of a PCB layer.
Numbers on a data sheet are a good start, but confirm them with your own testing.
