Rigid-flex brings the best – and worst – of both worlds.

Combining all aspects of a flex circuit with a rigid board that makes full use of HDI techniques is one of the breakthroughs of our time. The stacking connectors for board-to-board or the typical flex circuits are bypassed. If you've ever tried to connect a flex circuit to a stacking connector, you know that's a bottleneck in the process – blindly positioning the flex connector over the mating connector can be fiddly to the point of destroying the connectors. Now what?

Rigid-flex projects remind me of digital/analog projects: the best of both worlds and the worst of both. Just for starters, if the team is taking this route, you know they are serious about holding things together with all possible integration. Both technologies are well understood on their own, though the rigid camp is larger and better understood.

Flex circuits on their own. Flexible printed circuits (FPCs) require more than a change of materials from their stiffer cousins. Additional tolerance must be designed into the data. Reason: The different types of material stacks used in the manufacturing process. For the most part, a flex will also have a rigid section where the connector is mounted. The stiffened area could also be extended to host the ESD protection, an LED or microphone; we're flexible.

Put the pedal to the metal in your PCB layouts.

Printed circuit board design evolves over time and the rate of the evolution is not slowing. High-speed digital design becomes a key topic as we move forward.

By the time you read this, I’ll be officially old. Early retirement age is 62 and I was born in ’62 so I’m eligible for those senior discounts. One of the things that happens as we age is time seems to go by even faster. We’ve seen so much, less is novel. We’re not plowing new furrows but rather deepening ones we’ve tracked before.

I say that to say this: Circuits keep switching faster all the time. What worked in my early days no longer gets it done. My first computer didn’t have a hard drive. It had two floppy disk drives, and they were the ones with 360KB­ rather than the smaller, stiffer 1.4MB. I had DOS on one floppy and a modem driver on the other. The baud rate was a blazing 1,200B.