{"id":313889,"date":"2023-10-30T08:17:40","date_gmt":"2023-10-30T08:17:40","guid":{"rendered":"\/forum\/forums\/reply\/313889\/"},"modified":"2023-10-30T08:17:40","modified_gmt":"2023-10-30T08:17:40","slug":"313889","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/313889\/","title":{"rendered":"Reply To: Multilayer PCB modal analysis first mode natural frequency related."},"content":{"rendered":"

<p>@ Erik<\/p><p>” Also how well do you know the material properties (you certain of all the properties – often there is a variation) – sometimes we need to alter\/change them a bit to get better agreement with test data.”<\/strong><\/p><p>Sir<\/p><p>Your question is valid , I am using FR4 properties given in Ansys Mechanical while this PCB board is made from Isola 370HR (FR4) dielectric material. For this i don’t have all the 9 properties values required for an orthotropic material.<\/p><p>From datasheet of Isola 370HR , i got few properties which are as below:<\/p><p>E1 (along length direction) : 3744 ksi ( ~ 25814 MPa)<\/p><p>E2 (along cross direction ) : 3178 ksi (~ 21912 MPa)<\/p><p>https:\/\/www.isola-group.com\/wp-content\/uploads\/sites\/2\/data-sheets\/370hr.pdf<\/a><\/p><p>Poisson’s Ratio :<\/p><p>A. Length direction : 0.177<br>B. Cross direction   : 0.171<\/p><p>The other properties details are missing like E3 , Vz , G12 , G13 & G23.<\/p><p>Since , these properties are not available , i have rely on FR4 properties given in Ansys Mechanical. Here, also i observed that for shear modulus calculation formula used is valid for isotropic material.<\/p><p>like Ex : 20.4 GPa<\/p><p>vxy : 0.11 <\/p><p>if you see the Gxy value it is 9200 MPa which will come from G = E\/ (2*(1+v)).<\/p><p>I don’t have exact material properties , that may be one of the reason that modal frequency is not matching.<\/p><p>Please suggest if you came across this material or having mechanical properties.<\/p><p> <\/p><p> <\/p><p> <\/p><\/p>\n","protected":false},"template":"","class_list":["post-313889","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t