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Working with STEP Enclosure Models in PCB Design

Screenshot of 3D layout with enclosure includedI am the kind of person who has to see something in order to work with it. Where some can build a tool shed from scratch, I need to work from a set of blueprints. Others may be able to create a tasty dish off the top of their head, but I need a recipe. I suppose that you could say that “seeing is believing” is my personal motto. In reality, though I think that “seeing is producing” would be the better phrase, especially when it comes to PCB design.

From the first tape up jobs to the current range of CAD tools, PCB designers have always relied on what they could see in order to complete their work. Historically this has been restricted to 2D views only, and PCB designers had to rely on help from their mechanical designer counterparts to let them know how the board looks in 3D. The recent generation of CAD tools has made 3D workspaces available for the PCB designer, and with STEP enclosure models you now have a much clearer picture of the entire design. 

STEP Enclosure Models, More than PCB Footprints

As we have said, PCB layout for years has relied on 2D environments for design. Although the component footprints stored height values as an attribute within them, the design displays would portray them as flat 2D models only. Eventually, PCB design CAD tools progressed to the point where they began to offer the ability to view the stored height values in 3D. This would render the parts as a generic, rectangular shape, giving designers a taste for the full feature 3D views that would eventually be coming. Those days have finally arrived, and now most CAD systems offer designers the ability to work with their component footprints in 3D landscapes within their PCB layouts. This gives the components realistic depth, contours, and shapes.

The magic that brings this to life is the STEP file, or the Standard for the Exchange of Product Data file. This file contains the three-dimensional data that CAD systems need to display the component footprint in 3D. The file, or model, has both header and data information in it organized into different sub-groups. STEP files are created in a format that multiple systems can recognize making them an excellent way to pass shape information between different systems.

STEP files can be used for more than just PCB component footprint models, however, and here is where they can help bridge the gap between electrical design and mechanical design. By modeling system enclosures or other mechanical features, PCB designers can now see in real time how their components will interact with the entire system.


Screenshot of 3D layout with and without the system enclosure

3D PCB CAD tools showing the relationship of components to the enclosure with STEP models


PCB Layout That is No Longer in the Dark

In the picture above, you can see on the left how the mechanical cover obscures the components of the board. By moving the shield out of the way within the CAD system as you can see on the right, the designer can view the components underneath it. This gives the PCB designer the ability to visually check the layout for conflicts with the system enclosure or other mechanical objects. In addition to visually checking your design, these systems will also give you the ability to run automated checks to alert you to conflicts and collision between components and mechanical objects.

As layouts continue to increase in density while at the same time decrease in size, functionality like this is becoming more important all the time. Even on boards that aren’t as dense or complex, it is still useful to check your parts placement to the other mechanical features of the board. I have seen tall components like electrolytic capacitors placed where they would have stuck out of the system enclosure, because the design wasn’t first checked in 3D. And as designs become even more complex, as with the flex design shown in the picture below, you can see how the design will fit within its enclosure after it is all folded up.


Screenshot of cut-away view of 3D flex circuit and enclosure layout

3D STEP models enable cut-away views making fitting this flex circuit to its enclosure easier


Collaborative ECAD MCAD Co-Design

The ability for PCB designers to pull mechanical features into their design through STEP files, has helped make the successful collaborative co-design process a reality. No longer do the electrical and mechanical design teams have to work their portions of the design, and then “throw it over the wall” to the other team. Each team can have immediate access to the other team’s work in progress for real-time co-design, thanks to the easily exchangeable STEP model format.

This solves the problems of the past where PCB placement errors occurred because the mechanical design was changed without the electrical team being aware of the changes. Now with both design teams working together with real-time information, there is less opportunity for errors to creep into the final product. In addition, with a smoothly running co-design process in place, design teams are able to spend less time and expense on multiple prototypes to iron out the bugs. This helps to get the product to market ahead of schedule and under budget.

To leverage the benefits of working with STEP enclosure models in your PCB design, you need to work with an advanced PCB design system that has the 3D capabilities that we’ve described. OrCAD PCB Designer has the 3D functionality that will allow you to manipulate the mechanical features, display cut-away views, and run automated checking. This will give you the advantage by verifying your PCB to the mechanical design before sending it out for manufacturing. In addition to that, OrCAD also provides you with a powerful set of schematic capture and SPICE tools, online library access, and a host of PCB layout and analysis features to further help you.

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