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Connecting the Dots: So You Want to be a Designer?
January 2, 2013 |Estimated reading time: 2 minutes
This column originally appeared in the November 2012 issue of The PCB Design Magazine.
PCB design lesson 101: Your job as a circuit board designer is to convert ideas into reality. How’s that for an opening statement?
Maybe it sounds too philosophical for a technical tutorial, but think about it. An engineer records ideas in the form of a schematic. He does this by placing symbols (which represent electronic components) and connecting the symbols together with lines (which represent conductive wires).
Each connection point on the page corresponds to a component pin in the real world. We will look at this in detail later, but the end result is a schematic that can be shared with others; anyone who understands electronics can interpret the idea no matter what language he speaks. But a schematic is only a method of recording the idea. Someone has to convert it into something physical that we can hold in our hands--something we can test.
The end result is a circuit board assembly, and if you want to learn how to create one from a schematic, you’ve come to the right place!
Welcome to the first in a series of short tutorials on becoming a circuit board designer. If you’re new, there’s a lot to learn. We’ll explore the PCB design process one step at a time, explaining the terminology and adding more pieces to the puzzle from month to month. As we go through it, I’ll try to provide other resources where you can get more help. So, let’s get started…
What is a Circuit Board?
Most of you probably wouldn’t be reading this if you didn’t already know what a circuit board is, but my goal is to teach the basics, and assume you know nothing. Many costly mistakes in this industry can be traced back to incorrect assumptions and poor communication, and one habit you should develop early is that if you don’t know, ask! None of us was born knowing any of this, so we’ll start from the beginning.
A circuit board provides a mechanically stable substrate for mounting electronic components, and provides conductive connections between them. It is constructed with layers of conductive material (usually copper) separated by layers of insulating material (usually a flame-retardant epoxy reinforced with glass fibers). Connections between conductive layers are made through plated holes.
If I had to describe the job of a circuit board designer in a single sentence, it would look like this: Circuit board designers create a board shape that fits the physical size requirements, position the mounting and tooling features, determine the number of conductive layers (cost vs. performance), logically arrange circuits into functional areas (floor-planning), populate each area with appropriate land patterns (placement), add planes and traces to connect everything together (routing), and generate data to fabricate, assemble and test the product.Beyond that, if the design is to eventually become part of a product, it needs to be manufacturable in some quantity. Feature sizes are selected to be compatible with bare board fabrication and test processes. Decisions are made with automated assembly and soldering methods in mind. There might be cost constraints involved, and environmental factors, and the final product needs to be robust enough to survive the customer’s use and expected reliability.
Good design involves juggling many factors, and we’ll look at each of these in detail in future columns.
Jack Olson has been designing circuit boards full-time for over 20 years. He can be reached at pcbjack@gmail.com.