Meaning
Destructive sample preparation and analysis technique used to evaluate the internal quality and structural integrity of printed circuit boards and electronic packages. Micro-sectioning involves mounting a specimen in a polymer resin, cutting it along a specific plane, and polishing it to a mirror finish. This process allows detailed measurements of internal copper plating thickness, solder joint quality, and laminate layer registration.
Quality Control
Manufacturing standards require this inspection method to verify the quality of multi-layer circuit boards. The use of micro-sectioning exposes hidden defects like resin recession, inner-layer separation, or micro-voids in the copper plating of via holes. These structural flaws cannot be detected by non-destructive optical or electrical testing methods.
Failure Inspection
Analysis of field returns and qualification test failures relies on this technique to pinpoint the root cause of electrical opens or shorts. The cross-sectional view created by micro-sectioning reveals whether solder joints failed due to thermal fatigue or poor intermetallic compound formation. This feedback is utilized by assembly engineers to optimize the reflow oven temperature profiles.
Detailed images from this step are included in the final engineering report provided to the customer.
Process Step
Precision grinding machines remove material incrementally while the operator monitors progress under a microscope. Acid etching is then applied to the polished metal surface to highlight the grain structure and the boundaries between different copper plating layers.
