Defining Design Intent in PCB Design CAD Tools

March 23, 2020 Cadence PCB Solutions

Picture of Apollo command and service modules docked with the LEM

 

In the 1995 movie Apollo 13, Jim Lovell played by Tom Hanks has to bring his crew safely back to earth after their spacecraft experiences multiple system failures. While flying around the dark side of the moon, they have to make a decision about how to proceed. Lovell draws a line in the sand for the other two men by asking them; “Gentlemen, what are your intentions?” He quickly answers that question with his own intentions by telling them; “I'd like to go home.”

Having a clearly defined objective is always the key to success in any venture, and it certainly applies to PCB design as well. Your efforts will be much better focused by defining your design intent before you start instead of by simply “winging it.” But is there more to design intent than simply setting a goal? Let’s take a closer look at design intent in PCB design, and see what else it may apply to.

Defining Design Intent as What You Intend to Accomplish

The design intent definition that usually comes to mind first, is setting the objectives of what you intend to accomplish with the product being designed, as well as a plan to get there. This intent is usually outlined in the product definition and will include design specifications and performance expectations. From there design intent can spread out to include design, fabrication, and assembly details to meet or exceed any applicable regulatory requirements and standards. Overall, the main purpose of the design intent is to create a product that will operate reliably and as expected over the course of its lifecycle.

Design intent can also be more personal as well. For instance, a PCB designer will place the components on the board in a specific pattern because of the designer’s intent to route a signal path as short as possible. In this case, the design intent is the plan that the designer has created and is working towards. By faithfully executing each step of the intended design plan, the designer knows that by the end of the project that they will have accomplished their targeted goal. Alternatively, a designer may place components according to the flow of the circuit, finding where some components will need to be placed very close together like bypass capacitors.

There is another definition of design intent that we will look at next. In this case, it is one that is more closely related to the performance of the design tools.

 

OrCAD PCB Designer routing parameters menu

The route parameters menu is where you can set up shove routing for your design intent

 

Another Form of Design Intent; How Your Design Behaves when Modified

Another definition of design intent is a method used in computer-aided design that defines the relationships between intelligent design objects. When CAD models are set up so that a change in one automatically propagates to the others, that is referred to as design intent. An example of this within a CAD system would be a design that includes a piece of metal with a hole in the middle. If the hole is referenced to the edge of the metal instead of the middle, it will have missed the design intent for that hole, which was to be associated with the middle of the metal. Its position may be initially correct, but if the piece of metal ever gets changed in size, then the hole will maintain its anchor to the edge of the metal and move away from the middle.

The goal for the correct design intent of the hole, therefore, is to reference it to the middle of the piece of metal. This way, when the metal changes its size during the normal design process, the hole will remain in the middle where it was intended to be. Also, any dimensions that have been added between the edge of the metal and the hole will be automatically updated with any changes made to the size of the metal.

In PCB CAD systems we see the same design intent at work. Dimensions that are attached to tooling or mounting holes in the board outline, will update automatically when those holes are moved. Shove routing is another example where other design objects respond to the actions of the object that the designer is manipulating. In this case, shove routing will push traces, vias, and other etch objects out of the way as long as moving those objects still obeys the design rules that have been set up. Within a modern PCB design system, there are numerous intelligent objects that are all designed to interactively work together. This way when you make a change in one part of your design, the related objects will change as well.

 

Screenshot of OrCAD PCB Designer shoving vias and traces

Shoving the selected segment on the left side down, moves vias and traces on the right side

 

PCB Design Tools to Accurately Capture Your Design Intent

To best capture your design intent, you need advanced PCB design tools that are equipped with features and functions that adhere to the design intent of related CAD models. Your tools should have extensive parameters that you can set up for different routing scenarios based on the needs of your designs. In addition, your tools also need a comprehensive design rule and constraint system, so that you can govern how the different intelligent design objects will interact with each other. To do all of this requires a powerful and versatile PCB design system.

Cadence has a long history of supplying the electronic design industry with PCB design systems that have the different PCB layout features and capabilities that we’ve talked about here. OrCAD PCB Designer has the power and versatility that you need for your work, and was created to help you achieve your design intent.

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

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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