Printed Circuit Design & Fab Online Magazine

Designer’s Notebook

Four important lessons gleaned over a three-decade design career.

There’s an old saying among test pilots: “Any landing that you can walk away from is a good landing.” They also know that there are old pilots, there are bold pilots, but no old, bold pilots – or so the saying goes. If you want to hang around as a PCB designer, you can only hope to walk away from your mistakes with your career intact. So, this is a chance to learn from my mistakes from 35 years of design work.

Going all the way back to the ’90s finds me in my first PCB design role. I had just taken an internal transfer to the commercial side of the business after a couple of years of feeding from the government trough. My manager on the mil-spec side, Merrill, was a father of a dozen children and was an all-around nice guy, perhaps a bit of a pushover.

Before applying for the transfer, I wanted to talk with Merrill, so I came up behind him and asked if he wanted to go to Armadillo Willy’s, a local barbecue place, for lunch. I didn’t see that he had a sandwich in his hand and was about to take the first bite. Instead, the sandwich hit the desk with a thunk, and we were off to the restaurant. Such was his dedication to his people.

Read more: Living on the Edge

Whether in wire or trace form, keep copper thickness in mind for your design.

Once upon a time, about eight decades back, we didn’t have printed circuit boards. We had copper wires that came in various diameters. Carrying a larger amount of current requires conductors of a larger diameter. These various diameters were identified by the American Wire Gauge (AWG) where smaller numbers indicated thicker wires. There is a metric equivalent where the opposite is true – a higher number for a thicker conductor. Set that aside for this discussion.

Heavy gauge wire for power. A 12- to 14-gauge wire is about the diameter of a cooked spaghetti noodle (~2mm) and is commonly found in power cords for smaller electronics such as a table lamp or a fan. An electric dryer running on 220V will require something between 10- and 6-gauge wire depending on the amperage of the appliance. Again, smaller numbers refer to larger cross-sections.

For the sake of flexibility, these thicker wires are typically constructed of several smaller wires twisted like a candy cane prior to adding the insulation coating. The coating itself is not part of the gauge, only the conductor matters in that regard.

Read more: Metal Health: Know Your Copper Thicknesses