OrCAD X Resources

Smart Placement Using Design for Assembly Tools Design For Assembly is a good place to start since our boards go through placement before there is any actual routing activity. Meanwhile, the real world turns this around starting with the fabricated printed circuit board and adding value from there. This Design For Assembly feature goes back about 12 years. Let's go over the routine for setting up the PCB footprints for dynamic spacing. Start with the premise that each component footprint has an assembly outline as well as what's defined as the Package_Geometry Place_Bound-Top layer. That is usually expanded beyond the edges of the component outline. The original idea was that the Place_Bound layer was used to define the courtyard which is the minimum amount of personal space around a part. For minimum spacing, you would line up one part's shape right next to the others. If you wanted to know where any remaining space was left on the board, you turn on the Place_Bound layer. Open space was wherever the shapes were not covering the screen. I mention that because a lot of the old timer Designers were quite attached to the Place_Bound layers as a means of deter- mining where there was room to move into so that the congested area could be improved in some way. The issue with that approach is that the 3D imagery and the mechanical export of the data didn't show the actual size of the part as it included the keep-out area around each part. I could put six caps together in a 2x3 grid and you would see a monolithic shape from all six parts that looked like one big part. I'm triggered by that because it sends ambiguous messages to the mechanical design team. I'd like it if all of the components had a step model so that the 3D images were closer to a render of the actual board. Sometimes, you just can't find the step model. Like when your company builds its own part, who is going to create a step model? 2 www.cadence.com Smart Placement Using Design for Assembly Tools

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