ArraynHere is the way I used to add non structural mass to a structure.nCreate a copy of the material called pcb and call it populated pcb. Where the density was 2.364 g/cm^3, type in a new value of 3.873 g/cm^3.nIf you have three boards, you will need a unique material for each board, assuming they have different populated masses.nThis is the old school way of adding distributed mass. Now they have a the distributed mass in the Workbench interface, it probably isn't necessary anymore.n=== Modal Results===nHere is mode 7, the first bending mode. Are those panels supposed to be free to bend like that or is a contact missing in the model? Try fastening this panel and rerunning Modal.nModes 1-6 are all rigid body modes as you can see from the deformation animation.nI don't know why the frequency ratio between mode 6 and 7 is not larger. The ratio should be greater than 100. It is only 4. Maybe someone else has a comment.n