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3D Modeling for PCB Systems: The Quest for Security Despite Complexity

Edge connector on a blue PCB


When I was younger I used to take apart old CD-ROM drives just to see how they worked. Simply looking at a moving CD tray and laser head wasn’t very informative, but I always wondered what the flexible ribbons in these drives were used for. As a PCB designer, the necessity of flexible ribbons for providing electronic connections seems obvious.

From clamshell phones to DVD drives and laptops, mechanical functionality is an important part of modern consumer and industrial electronics. Verifying the functionality of these systems and ensuring they meet important mechanical requirements is much easier when your PCB design package allows 3D modeling for PCB systems and includes ECAD functions. Form factor is important, but the right design software will give you more than just a pretty 3D image of your PCB.

3D Modeling for PCB Systems and Collaboration Across Design Teams

Historically, mechanical design teams have operated separately from electrical design teams due to a lack of common design software options. Mechanical design software was great for creating beautiful 3D models of electronic devices and even models that looked like circuit boards with realistic components. However, the design functions in these mechanical modeling programs were not adaptable to designing electronic functionality beyond simply arranging 3D models for components.

While MCAD software is excellent for verifying mechanical clearances and designing the form factor of a new product, electrical designers would inevitably have to remake the design in their electronics design software. Electronics designers would inevitably make changes to the design to ensure proper functionality, and these changes would need to be applied in the mechanical model. The time required to work in this environment is prohibitive.

3D modeling capabilities in PCB design software help you design and verify the mechanical aspects of your board right alongside the electrical aspects. Some examples include connector placement, sizing and placing bulky parts like heat sinks, transformers, or capacitors, and designing ground/power planes with complex shapes in the interior layers of your board. This type of ECAD/MCAD collaboration allows you to implement immediate layout changes if your packaging cannot accommodate your component arrangement, or vice versa.


 PCB with bulky components

The bulky components will require specific clearances that can be verified with 3D modeling tools

Flex and Rigid-flex Design

Rigid flex and flexible PCBs are two areas that necessitate 3D modeling tools. Designing a rigid-flex board in 2D is fine in that you can still layout your components, route electrical connections over your flex ribbon, and design your layer stack to integrate a flex ribbon. However, there are other important aspects of flex and rigid-flex boards that cannot be addressed when designing in 2D.

Rigid-flex and flex boards tend to have unique shapes and often require folding at specific angles in order to fit inside their packaging. Rigid-flex boards tend to require specific bends along a defined line across the flex ribbon, or they may need to wrap around a corner in order to fit in their packaging. This is where 3D modeling tools present in your PCB design software help you examine these bends and ensure that components will not collide and clearances are met.

With fully flex boards, the situation can be a bit more complicated. You may need to design multiple bends in order to fit the device into a complex package. One example can be found in some digital cameras, where flex ribbons need to fit into a compact space with odd shape. 3D modeling tools can help visualize the rearrangement of your components should you need to accommodate packaging with an odd shape.


Flexible circuit

Utilizing proper flexibility in printed circuit boards allows for more interactive devices


Multi-board Systems and Beyond

Multi-board systems can be arranged with multiple boards placed at odd angles using slot connectors or cables. Examples include laptop motherboards, televisions, and a variety of other consumer electronics. If you are designing connectivity in your multi-board system using short cables or by making direct connections between boards (e.g., with edge connectors), you can verify mechanical clearances in the same way you would with flex and rigid-flex boards.

Keeping all areas of your flex, rigid-flex, or multi-board system organized is easiest when your PCB design software allows you to build hierarchical schematics. This helps you separate functionality on different boards and within individual boards into their own electronic schematics, and you can define parent-child relationships between each schematic.These schematics can then be captured as a group into an initial layout, and you can then arrange components throughout your boards.

Using 3D mechanical design tools in all these applications helps you prevent problems that may not become obvious until fabrication begins. The last thing a company needs is to produce a portion of a manufacturing run, only to be told that there is some mechanical problem that was not obvious during the PCB design phase. Working with MCAD tools directly in your ECAD software helps you identify and fix these potential problems before disaster strikes, as well as reducing the number of interactions between PCB design and mechanical design teams, saving time and money.

With 3D modeling for PCB systems becoming more important in a number of areas, designers need the right PCB design and analysis software with a full suite of layout and simulation tools that integrate with MCAD features. The OrCAD PCB Designer from Cadence includes ECAD MCAD co-design tools that engineers need to collaborate across design teams on multi-board systems, rigid-flex boards, and other boards with odd form factor.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.