Understanding the impact of hatched ground planes on PCB impedance 

By Stephen V. Chavez

 

Controlling the energy within a printed circuit board is key to achieving success. At times, how we control and contain this energy is no easy task. Utilization of ground planes is how this can be successfully achieved.

 

Ground, typically referred to as a reference, plays a crucial role in signal integrity, electromagnetic interference, and electromagnetic performance. While solid ground planes are commonly used and are an industry best practice, especially when it comes to strip line and micro-strip routing techniques, hatched (or crosshatched) ground planes can be employed and present an interesting alternative with specific implications for impedance control.

 

Why would someone utilize a crosshatched ground plane over a solid ground plane? Personally, I am a “solid ground plane” kinda guy, and after speaking with many in my professional network, both PCB engineers and PCB fabricators, the common theme that continues to resonate to the top is that the industry best practice for PCB design is to implement solid ground planes, especially when impedance requirements need to be employed. One thing is for sure, no matter the spectrum you’re designing your PCB in: digital, analog, mixed signal, RF, or microwave, the performance of your PCB is one of the three perspectives that must be addressed, along with solvability and manufacturing.

 

Typically, crosshatched ground planes are found in flex and rigid-flex PCB designs, more specifically in the flex portion of the design, for easier static or dynamic bending in a particular section of the design. Yet, there are those engineers who choose to employ the crosshatch approach into their ground plans instead of a solid ground plane.

 

Look, I know some experts, especially RF folks, get nervous when they see crosshatched ground planes being used for high-frequency signals. I’ve been there myself during design reviews. And yes, they’ve got a valid point about those longer return paths not being ideal. But here’s the real deal: when you’re working with flex and flex-rigid PCBs, crosshatched planes are actually a pretty clever solution, especially with today’s advanced materials and processes. From my experience in industry discussions and hands-on work, I’ve seen how they help maintain controlled impedance while keeping traces at manufacturable sizes, plus you get that crucial flexibility your board needs. The key is knowing how to properly implement these crosshatch ground planes when you need to maintain specific impedance requirements across the flex section. Sure, it might not be theoretically perfect from an RF purist’s perspective, but real-world applications have consistently shown that the practical benefits outweigh those theoretical drawbacks. It’s all about finding that sweet spot between perfect RF performance and what actually works in manufacturing. At the end of the day, it’s a solution that gets the job done, and gets it done well. So, let’s dive into how these patterns affect your circuit’s performance.

 

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