Learning Forum

[peteroznewman]

nA more accurate model would be to imprint the two large chip outlines onto the pcb surface. Then you can add a point mass of each chip. There are two choices when adding point mass. If you choose Behavior = Rigid, you will also insert an area of rigidity into the surface. This will increase the natural frequency. If you choose Behavior = Flexible, that will add no additional stiffness and decrease the natural frequency. I recommend you run this model twice and report the range on the natural frequencies.nThank you for the photo of the pcb populated with components. Find out exactly how much that populated board weighs. Subtract from the mass of the populated board the mass of the two chips that you will add as point masses, call that mass Mp. In the model, you have defined a density for the pcb material, call that Db. Mechanical shows the mass of the pcb body, call that Mb. You want the pcb body in Mechanical to show up with a mass of Mp. Therefore, multiply the density of pcb in Engineering Data by the ratio of the masses and type in a new value for the density of the pcb material. The new density for the pcb material is Db*Mp/Mb. After you do that, Mechanical will report the mass of the pcb body as Mp. When the two point masses are added in, the total mass will equal the mass of the real populated part.nDo a Google search using the exact text of the warning about conflicting conditions in the model and you will find some information. If you provide the exact text, I can help some more.n