Components drive circuit layout, but PCB designers are here to stay.

Like almost everything these days, the art of PCB design has its underpinnings in data. We're data driven – and swamped in a sea of information. Some of my favorite info is found on the literature offered up by the printed circuit fabricators. We get what's called a technology roadmap. While maps usually refer to geography, these roadmaps show the way into the future.

Open one up and it looks like a spreadsheet with physical attributes on the y-axis and calendar years filling up the rows. The numbers are sorted into columns with the values decreasing over time. The left column of data provides today's mainstream values for important characteristics of the circuit board.

We focus on minimum air gaps and line widths for inner and outer layers. Machining tolerances, dielectric thickness numbers, and so on are at their highest in the first column. Mass production boards should have technology that is aligned with standard processes.

When Google launched the first Chromecast dongle, Flextronics was the ODM. It owned Multek back then, which had five fabrication plants. Each site had different equipment and cost structures. To use its bottom-tier factory, we couldn't stack microvias, so I had to spin the board to stair step the 1-2 and 2-3 vias. The more price-conscious you are, the more you go for older factories.

TECs can be a countermeasure to high current density.

Thermoelectric cooling, or TEC, is seen as a breakthrough in small refrigerators that do not consume a lot of power. Sporting goods stores carry micro-fridges that plug into a car's weird circular power plug. Some of us – not me, of course – can remember when those plugs were used to create a glowing hot element to light cigarettes. Getting cold out of the same socket took a little more technology than creating a short circuit.

Where would you use a TEC device? Aside from keeping a six-pack (or a transplant organ) on ice, electronics can be kept at a reasonable operating temperature with the addition of a component or a cold plate like the one in FIGURE 1. It is 40mm square and 3.2mm thick. The basic function is that it gets cold on one side while getting warm on the other. Put it in the other way to warm up the contents. This can be placed below the board or above the high load component if it has a flat top. More remote placement is possible by incorporating a heat spreader. We'll circle back to that shortly.

Figure 1. A TEC device. (Amazon)