The details of layer structure are revealed by PCB cross-section analysis.
Special treatment is applied to the cross-section specimen in order to delineate metal layers, through holes (TH) and plating layers. The TH plating thickness then can be measured and the corresponding plating time can be estimated.
The following example show an image representing an advanced Cu electroplating technology.
(Cu thickness is trending upwards in order to to improve the heat dissipation and to reduce the parasitic resistance.)
●Cross section of PCB
●L1 plate expansion
Magnified image of a TH.
The Cu whisker depths are shown along the vertical TH plating in PCB A and PCB B. The whisker heights are significantly larger in PCB ; therefore, this board is likely to have higher risk of shorts or possibly electrical leakage. This may cause electrical short, or electro-migration in finer layout patterns.
Cross-section analysis is effective to evaluate product workmanship.
●Cross section comparison of PCB