Selective Chemical Stripping for Thin Metallic Finish Isolation
Selective finish stripping isolates thin gold or tin layers using ligand-accelerated redox baths while protecting nickel barriers through passivating inhibitors.
SEM EDS Microsection
Material Characterization
High resolution imaging coupled with elemental spectroscopy allows a structural cross section of a multilayer circuit board to reveal the exact composition of metallic and organic layers under failure conditions. A sem eds microsection relies on an electron beam focused on a polished sample to generate secondary electron maps and characteristic X rays. Data from this procedure pinpoints the specific atomic signature of a contaminant or an intermetallic compound located at the interface between copper plating and solder.
Analysts detect deviations from acceptable alloy ratios by measuring the specific counts of emitted photons. Calibration of the detectors maintains the accuracy of the weight percentages reported across the field of view. Precise polishing techniques eliminate smear during sample preparation to ensure that internal voids or fractures remain visible.
Proper sample orientation guarantees that the beam perpendicular to the board surface provides the correct geometric view for thickness measurements. The physical cross section represents the final arbiter for confirming the integrity of plated through holes or buried vias.
Spectroscopy Integration
Quantitative elemental analysis identifies the concentration of elements within a specific area or along a linear path of the specimen. An sem eds microsection provides visual proof of ionic contamination or oxidation products by assigning color codes to different chemical species detected. Software translates the X ray energy spectra into atomic percentage values for every point scanned on the surface.
These readings distinguish between gold, nickel, tin and various common plating impurities that migrate into the solder matrix. Engineers observe how variations in thermal history influence the growth rate of brittle layers like Cu6Sn5 or Cu3Sn. Precise energy resolution allows the system to separate overlapping peaks of different elements in the periodic table.
Failure Logic
Microstructural examination defines the boundary between chemical contamination and physical mechanical stress in printed circuit board assembly. A sem eds microsection determines if a fracture occurred in a brittle state or through ductile deformation based on the morphology of the exposed grain boundaries. Discoloration found on fracture faces undergoes immediate identification to separate surface oxidation from manufacturing residues.
The analytical method confirms the presence of corrosive elements like chlorine or sulfur in the vicinity of a short circuit. Detection of these species verifies the root cause of dendritic growth. Observations within the vacuum chamber prove the presence of subsurface voids which act as nucleation points for long term fatigue failure.
The technique remains the standard method for validating the chemistry of intermetallic bonds in high reliability environments.