1. Sampling
The first step in micro-section analysis is sample selection. Based on the analysis objectives, engineers select specific areas on the PCBA for examination-such as plated-through holes (PTH), blind/buried vias, BGA solder joints, QFN pads, press-fit connectors, or other critical structures.
Sampling is typically performed using a precision cutting machine to ensure that the cutting process does not damage the sample's microstructure through overheating or mechanical stress. The choice of sampling location is crucial for the accuracy of subsequent analysis results.
2. Mounting
After sampling, the specimen is secured in a specialized mold and encapsulated using a mounting material, such as epoxy resin, which is then cured.
For high-precision analysis, a vacuum mounting process is often employed to prevent the formation of internal air bubbles in the resin, which could otherwise compromise the quality of the observation.
3. Grinding
Once mounted, the sample undergoes a progressive grinding process. Grinding is usually carried out in stages, moving from coarse to fine abrasives. This gradually removes material to bring the target area closer to the desired cross-section while ensuring surface flatness and geometric accuracy. Strict control over pressure and duration is essential during grinding to avoid issues such as over-grinding or localized deformation.
4. Polishing
Although the cross-section is largely formed after grinding, the surface retains numerous fine scratches that hinder microscopic observation. Therefore, a fine polishing step is required. Continuous polishing effectively removes grinding marks, achieving a mirror-like finish on the sample cross-section. A high-quality polished surface significantly improves the accuracy of subsequent measurements and prevents the misidentification of micro-defects.
5. Etching (Optional)
For certain analyses, distinguishing between different material layers using only a polished mirror-finish cross-section can be difficult. In such cases, an etching process may be used. Etching involves the mild chemical treatment of the cross-section, causing different materials to exhibit distinct reflective characteristics and thereby enhancing the visibility of the microstructure. It is important to strictly control the etching duration, as excessive etching can distort the original structure.
6. Microscopic Examination and Analysis
Upon completion of the aforementioned sample preparation steps, the microscopic analysis phase begins. Samples are typically examined using a metallographic or digital microscope. Following observation, micrographs are captured and measurement data recorded to compile a comprehensive micro-section analysis report, providing a basis for quality assessment, process improvement, or failure analysis.
Hot Tags: pcba microsection preparation process, China, manufacturers, factory, customized, Doorbell PCBA Assembly, multilayer pcbs, OEM turnkey, Pcba Electronic Contract, quick turn pcb, vibration resistant pcbs
