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Connect the Dots: Exploding PCBs: Don’t Lose Track of Voltage in Your Design

Managing split planes? Your CAM tool will not do it for you. We see this almost every day—not exploding PCBs, which pretty rare—but rather problems created by having more than one voltage on a power plane layer. From where we sit, this is one of the more insidious and costly challenges facing PCB designers.

Losing an entire lot of boards to spontaneous combustion offers an immediate, measurable cost, but the less noticeable anomalies can eventually cost even more once you add up production delays and resources directed at solving the problem. Worse yet, malfunctioning boards can make it into the field and create even bigger headaches.

The severity of the PCB failure seems to have an inverse relationship to the amount of effort required to fix it. When there’s smoke coming out of your PCB, it’s relatively easy to find out why. Digital glitches and signal anomalies are more subtle issues that can take many hours of tedious detective work to solve. We’ll explain why managing split planes can be so challenging and take a look at some best practices for avoiding this common issue.

Why Does This Happen?

PCB design tools offer the ability to assign voltage amounts to the entire plane, but that can lead to problems if your design assigns multiple voltages to the same plane. You can divide the plane into separate, electrically isolated areas using a split plane—an enclosed region on an internal plane layer. But when you have more than one voltage assigned to a power plane layer, your CAM tool does not check whether you have a 12-V via going into a 3-V section of the board. In this situation, the board will fail.

To read this entire column, which appeared in the February 2019 issue of Design007 Magazine, click here.