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CC BY 3.0 Frank Zheng
There’s only so much you can do with a single printed circuit board (PCB). We’ve seen advances in miniaturization and the steady rise in the number of transistors you can squeeze on a single chip. Even so, factors such as EMI concerns, thermal limits, and the overall rise in circuit complexity have turned multi-board PCB design into an industry necessity.
A multi-board PCB system is any design that requires more than one PCB working together. From partitioning, to intra-board connectivity, to 3D design considerations, and tips for EMI (electromagnetic interference) reduction, let’s dive into common component placement strategies for multi-board PCB systems.
PCB partitioning (not to be confused with the digital partitioning of a hard drive for memory purposes) is about physically grouping components based on functionality. Each functional subsystem can be viewed as a set of components and their supporting circuitry.
For example, your typical motherboard can be further subdivided into a number of functional units such as your processor clock logic, bus controller, bus interface, memory, video/audio processing modules, and peripherals (in/out).
In the context of multi-board PCB design, partitioning may be followed by refactoring components onto different boards. There are many reasons one might do this, including:
Intra-board connectors serve as the cornerstone of multi-board PCB design. Here’s a quick look at the different types of intra-board connections:
Whether your design requires creating towers of PCBs stacked on top of one another, or sliding boards into racks or backplanes, it’s important to ensure you’re able to get a solid connection between the different boards that make up your product.
EMC/EMI concerns are one of the major driving forces behind multi-board PCB design. All it takes to create EMI is energy and an antenna. The demand for higher performing electronics means high-speed signal circuits are only going to become more prevalent in the years to come.
Multi-board designs give you more room to accommodate EMI/EMC best practices. Things such as keeping analog and digital signals separate, avoiding right-angle traces on cramped boards, and the cost-effective use of multilayer boards on an as-needed basis. At the same time, multi-board designs also introduce new concerns, requiring you to extend your analysis beyond single boards to the connections between boards and the entire system.
Multi-board design is like an expensive 3D puzzle. Each board that makes up your system must fit into a physical enclosure or case. There’s nothing worse than drafting up the “perfect” CAD drawing, procuring all the boards, parts, and connectors, only to find out on assembly day that you didn’t get all your 3D clearances right. Worse still, not leaving enough room for proper ventilation, subjects your product to heat-related performance degradation. And we haven’t even scratched the surface of the physical realities of EMI.
Fortunately, we now live in a time where software exists to help the designer keep track of all these “puzzle pieces.” With the July 2018 release of Cadence® Sigrity, Sigrity tools have been integrated with Cadence Allegro technology and a new 3D Workbench to bridge the gap between mechanical and electrical domains in PCB design. Designers can now take a holistic approach to multi-board PCB design, performing signal integrity analysis across all boards, connectors, cables, sockets, and other structures. Ready to streamline your next multi-board PCB project? Check out Cadence’s suite of PCB design and analysis tools today.