Designer’s Notebook

Leave more metal behind.

Being cool used to be easy. Modern times call for a more comprehensive approach to keeping the lights on when it comes to our PCB layouts. The early days of electronics saw through-hole components bearing a single transistor that sat well above the board much like a water tower commands the skyline in a pastoral setting.

The device was free to blow off as much steam as required without scorching the stuff we call FR-4. Fun fact: Did you know that the FR in FR-4 stands for “fire retardant” and that 4 is the number of iterations that lead to the resin/glass combo that undergirds our industry’s history to this day? The material is rated by its ability to withstand high temperatures without breaking down.

One of the most important characteristics of FR-4 is the glass transition temperature, or Tg, where the material simply melts down and fails. It is measured in centigrade, and a working number is between 140° and 170°. That will not be sufficient for extreme environments and hard-working chips. There may be exceptions but you’re nominally looking at exotic dielectric materials that are meant to cater primarily to data centers and broadcast scenarios. The ancient art of ceramics plays a part in withstanding higher temperatures for devices and PCB laminates.

Read more: Thermal Considerations for Printed Circuit Board Designers

To land the job you want, it pays to be grounded and groomable.

Starting a new job is a big deal even if you're not leaving your current company. It's a commitment to learn the ropes while being humble and deferring to those in the know. In the field of PCB layout, a lateral move is often as good as moving up if the move expands your skill set in a way that helps your long-term goals.

Long-term goals should be about more than money. What is your dream company? What is the role that would keep you engaged or become a step toward the top rung of your personal career ladder? My niche is in wireless. Once that die was cast, the industry kept pulling me back into its orbit. It is nearly always that the employer initiates the contact for a new opportunity.

Read more: PCB Design in a Chip Company: Some Significant Particulars

Proper planning can protect a board's victims from noisy aggressors.

Good fences make good neighbors, or so they say. That said, some folks can get along just fine without a fence or wall to provide peace of mind. The signals that run around on a printed circuit board are similar in that regard. Aside from the presumably inert ground domain, all the energized copper contributes to the overall noise factor.

Just as there is an audible difference between a major city and a wide-open prairie, location matters. A high-density layout is more likely to run into locations where a so-called victim finds itself in proximity to an aggressor. So, what is an aggressor and why does it bother the victim? Defining the aggressors is easy. They're everywhere.

Read more: Isolating Noise on a Printed Circuit Board

Tips for better communication and preparation.

The PCB designer is often the recipient of a file or series of files that provide the working parameters of the board. These documents will come from a physical designer who does the mechanical engineering for the project. In some cases, the PCB designer wears that hat themselves.

When the PCB outline is straightforward, do it yourself. One-off test jigs come to mind. We’re probably working with a rectangle that provides ample real estate for the intended circuit. There will be room to grow and iterate, but also space for plenty of text to ease setup and debugging. Put a hole in each corner so standoffs can be installed to raise the board above the test bench.

Read more: PCB Outline Transfer

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