Micro-cross sectioning is one of the important quality analyses of PCBs. In general, after the completion of a PCB, micro-cross sectioning is performed after sampling. Micro-cross sectioning is also implemented after an anomaly occurs to analyze the problem points with an electronic microscope after sampling to locate the causes of the anomaly.
The two most common ways of sectioning are as follows:
1.Vertical sectioning: A PCB is cut vertically to check the vertical section. Procedures of vertical sectioning: Sampling◊ Sealing◊ Grinding◊ Polishing◊ Micro-etching◊ Snapshot
From the vertical section, we can measure the thickness of each layer, the bottom copper, panel plating, pattern plating, and solder masking; or check if the contacts between different layers of copper foil and vias are normal.
2.Horizontal sectioning: A PCB is placed flat and grinded from the outermost layers into each inner layer. In general, horizontal sectioning is used to find the location of faults in a layer when broken layer/short circuit occurs.
Analysis of sectioning results:
After sectioning, the specimen is examined under an electronic microscope to judge the anomaly from the image in order to find the causes of anomaly and thereby improve quality.