Learning Forum

[yeti_tsau]

Hello Team,

To better reconcile the gap between our simulation predictions and experimental measurements in PCB thermal warpage validation, I would like to step back to the fundamental theory behind the equivalent (homogenized) material property generation used in Trace Mapping within Ansys Mechanical.

From the Ansys documentation and blog description, Trace Mapping/Trace Import first calculates a local metal fraction on the target mesh and then assigns equivalent element-wise material properties based on the fractions of metal and dielectric (i.e., a rule-of-mixtures-type approach). 

With that in mind, could you please help clarify the CTE homogenization method used specifically for trace mapping? In particular:

1. What is the exact formulation used to homogenize CTE for each element (e.g., linear rule of mixtures based on metal fraction, or another model)? 
2. Is the CTE homogenization purely fraction-based, or does it incorporate stiffness weighting / constraint effects of constituents (as in commonly cited approaches such as the Turner model)?
3. What are the assumptions, applicability range, and known limitations of the current homogenization approach for PCB thermal warpage analysis (e.g., when copper dominates stiffness locally, or when anisotropy/orthotropy is significant)?
4. Are there any references (publications, application notes, internal technical notes, or benchmark studies) that compare different homogenization theories (e.g., rule of mixtures vs. Turner-type stiffness-weighted models) in the context of trace modeling / PCB warpage simulations?

Any guidance on the theoretical rationale and recommended practice would be greatly appreciated, as it will help us identify the potential contributors to the simulation–test discrepancy and apply the method correctly.

Thank you very much for your support.

Best regards,
Yeti Tsau