cbk14
Mechanical
- Jun 13, 2014
- 17
Hi all,
I have tasks to analyze some mechanical assemblies which include circuit cards (PCB / PCA / CCA whichever terminology you prefer) under particular load conditions. For the purposes of this discussion, let's stick with common FR-4.
What are the recommended best practices for mechanical stress analysis of circuit cards? I have done similar jobs and had success, but I have always felt my methods could be improved.
Specifically, I am struggling to understand the failure modes and strength figures for circuit cards. The literature is widely varied on strength limits (10-45 ksi) and some even exceed the top of this range (greater than 6061-T6!?). I find that pretty hard to believe. I have also spoken with some more experienced colleagues who have relayed stories of circuit card failures at levels much lower than expected (~10 ksi).
I have used FEA simulations on the actual board layer stack-ups (known thicknesses of all layers, material, etc) to determine effective modulus of elasticity, which certainly helps reduce deflections, but the material strength limits are not influenced by assembly details (or are they?).
So what are the recommended methods for mechanical stress analysis of circuit cards? Any pointers or resources would be appreciated.
I have tasks to analyze some mechanical assemblies which include circuit cards (PCB / PCA / CCA whichever terminology you prefer) under particular load conditions. For the purposes of this discussion, let's stick with common FR-4.
What are the recommended best practices for mechanical stress analysis of circuit cards? I have done similar jobs and had success, but I have always felt my methods could be improved.
Specifically, I am struggling to understand the failure modes and strength figures for circuit cards. The literature is widely varied on strength limits (10-45 ksi) and some even exceed the top of this range (greater than 6061-T6!?). I find that pretty hard to believe. I have also spoken with some more experienced colleagues who have relayed stories of circuit card failures at levels much lower than expected (~10 ksi).
I have used FEA simulations on the actual board layer stack-ups (known thicknesses of all layers, material, etc) to determine effective modulus of elasticity, which certainly helps reduce deflections, but the material strength limits are not influenced by assembly details (or are they?).
So what are the recommended methods for mechanical stress analysis of circuit cards? Any pointers or resources would be appreciated.