Back in the days when Roger Moore was James Bond, there were various criticisms of his acting style (or lack of it): I am so surprised, I shall raise my left eyebrow. I am so amused, I shall raise my right eyebrow. And now...both eyebrows together! Printed circuit board design is a bit like that. The speeds are such that I need to do signal integrity analysis. The enclosure is so small that I need to do thermal analysis. And now....both analyses together! At CDNLive Israel, the opening presentation of two of the tracks (PCB design and PCB analysis) was a presentation by Cadence's An-Yu Kuo on Bridging the Gap between Electrical, Mechanical, and More . Today this involves a lot more than two eyebrows, requiring multi-physics analysis of electro-magnetics, signal integrity analysis, heat transfer analysis, fluid dynamics (for cooling air currents etc), and the actual mechanical design of boards and enclosures. The basic reason that complicates all this analysis is that they all interact. For example, making holes in an enclosure can improve thermal issues (more ventilation) but make EM emissions worse (more gaps for the RF signals to escape through). Resulting changes in temperature affect signal integrity. Almost everything depends on everything else. Since this is beyond the scope of the designer to handle manually, the solution is more and more automation. Mechanical and Electrical The biggest change that we are in the middle of is in just this area: mechanical design has been largely independent of electrical design, but now these two domains are getting more and more intertwined. The shape of the connector affects signal integrity in ways that are no longer small enough to ignore. This connector can be modeled using finite element methods (FEM), where the mechanical structure is broken down into tiny elements that together make up the whole structure, but are small enough that everything is, to a first approximation, fixed across the element. Using adaptive meshing, where the level of detail varies depending on the accuracy required there, can speed up the run time a lot by not wasting time doing very detailed analysis of unimportant parts of the structure. The above images show the meshing, and then an analysis of the current, further broken down into electrical and magnetic fields. And that is just a single connector. Complete Thermal and EMI Optimization Flow A complete flow involving both thermal and EMI starts from both the mechanical design and the PCB and package designs. This is fed into the 3D simulation model. Multi-physics optimization then performs both the EMI analysis, and the thermal and stress analysis, resulting in an optimized system design. In keeping with the secret agent theme, here is the analysis of a camera module. This is actually intended for automotive applications, but maybe it goes in a suitable Aston-Martin for James Bond to drive. The camera is actually about the size of a quarter, so smaller than the impression these images give. Here's the camera, on the right a picture of the real thing, and on the left as modeled. Inside the camera are two PCBs, one primarily the image sensor, one primarily the interface to get the images out of the camera. Remember this camera is the size of a quarter—these are really small PCBs. Now we can take each board in turn and do thermal and then electrical analysis. Finally, we arrive at the temperature of the main IC and the transient power profile that results. Summary An-Yu went into a lot more detail of how all the solvers interact to create an integrated solution. The solution is built up from innovative solvers at the bottom for mechanical, thermal, EM, and signal analysis. These are tightly integrated together so that you can do, for example, a board design with a complex connector, and bring the connector analysis into Allegro to use within the board layout. All the solvers are grouped into one canvas, with a workflow that the user can configure, and a TCL interface for automating batch runs. Sign up for Sunday Brunch, the weekly Breakfast Bytes email
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