# Stop Relating Trace Temperature to Current Density

Many design engineers and even many software suppliers make the significant mistake of equating changes in trace or via temperature with current density. This is incorrect at best and dangerous at worst. There is little if any correlation between temperature and current density. Current and trace dimensions (among other things) are the relevant variables, but current density is not. I hope by the end of this article you will see why. Here are four illustrations that will help you understand this.

1. Current Density Is Not an Independent Measure

We can understand that the change in trace (and via) temperatures are a function of other variables. Thus, we can formulate the following as two possible relationships (all other things equal). Let:

C = current
J = current density
w = trace width
th = trace thickness
ΔT = change in trace temperature

Then, we can suggest the following:
Equation 1: ΔT = fn(C, w, th)
Equation 2: ΔT = fn(J, w, th)

Now, the question is, “Are both of these relationships true, or, if not, is either one true?” We know from the extensive experimental evaluations reported in IPC-2152 that Equation 1 is true, so is Equation 2 also true? From Equations 1 and 2, it follows that:

Equation 1a: C = fn(ΔT, w, th)
Equation 2a: J = fn(ΔT, w, th)

To read this entire article, which appeared in the September 2020 issue of Design007 Magazine, click here.

## Just Ask Heidi: Attracting New Designers and Engineers

12/31/2020 | I-Connect007 Editorial Team
First, we asked you to send in your questions for Happy Holden, Joe Fjelstad, Eric Camden, John Mitchell, and Tara Dunn in our “Just Ask” series. Now, it’s Heidi Barnes’s turn! Today's question: How can we attract more young designers and design engineers to this industry?

## So Many Standards Committees, So Little Time

10/28/2019 | Andy Shaughnessy, Design007 Magazine
During the IPC Summer Meetings and Panelpalooza in Raleigh, North Carolina, I met with Leo Lambert, vice president and director of technology at EPTAC. We discussed IPC’s recent efforts to revamp the way standards are developed and interpreted as well as changes to training and education committees and a variety of methods for eliminating errors and duplicated comments when revising standards.

## XNC Format: Gerber Takes Data Into the Future

05/20/2019 | Denis Morin, Karel Tavernier, Jean-Pierre Charras, and Marius Matioc
The problem is that so many NC files are of deplorable quality because the NC format was never designed as a data transfer format. It has always been a machine driver and contains all sorts of information that a drilling machine needs, but that is irrelevant and confusing for data exchange.