Learning Forum

[peteroznewman]

PCBs and enclosures are thin-walled parts. The best practice for modeling those are to reduce the parts to midsurface models that are meshed with shell elements. You can imprint the outline of the larger, heavier components onto the PCB and create a remote point on each outline to attach a Point Mass to represent each of those components. You can use a Distributed Mass on the remaining area of the PCB to smear the mass of the smaller, lighter components over the PCB to get that up to the correct total mass.

The enclosure should also be a midsurface and meshed with shell elements. Is the enclosure a box shape? Are the seams welded or screwed together. If welded, then those surfaces should meet at a clean corner. If screwed, then you need to use a Fixed Joint to hold the edges of the two holes. You could use Remote Points to define one side of the Fixed Joint and add a Point Mass to represent the mass of the screw.

One component that is convienient to leave as solid are the stand-offs that hold the PCB above one face of the enclosure. It is best if some features of the stand-offs, such as holes and chamfers are deleted from the geometry so that the part becomes a sweepable body. The cleaner geometry will allow better solid element shapes to fill the volume. I doubt you need to impose a Patch Conforming mesh control, you will get better element shapes if you don’t impose that and probably don’t need to maintain the details of each and every face on the solid body. Bonded Contact can be made between each end of the stand-off and the enclosure or PCB, even though there is a 1/2 wall thickness gap at each end, by turning on the Thickness Effect in the contact. Set the behavior to MPC so you can see the spider of elements holding the parts together after the model is solved.

Once you have done all this geometry clean-up, you will get much better element qualities and by replacing solid meshed components with shell elements and Point or Distributed Masses, you will have a much smaller model.

Solid elements must be Quadratic and not Linear unless you have a pure Hex mesh. Linear Tet or Pyramid elements are overly stiff and do not give accurate modal results, especially if there is only one or two elements through the thickness of a thin walled part.

I can’t imagine the geometry of a PCB and its enclosure to be an issue for confidentiality, but that is entirely up to you.