Interfacial Intermetallic Compound Kinetics in Lead Free Solder Joints
Control reflow peak dwell and solid-state thermal exposure to limit interfacial intermetallic growth below four micrometers, preventing brittle joint fracture.
SEM EDS Cross Sectioning
Meaning
Analytical microscopy techniques in microelectronics failure analysis combine mechanical sample preparation with electron beam imaging and elemental X-ray spectroscopy to inspect internal material interfaces. Scanning electron microscopy energy dispersive X-ray spectroscopy cross sectioning cuts and analyzes solder joints, plating stacks, and component leads at high magnification. IPC-TM-650 Method 2.1.1 outlines metallurgical sample preparation procedures required to expose pristine microstructural planes without smearing soft metals.
This analytical process identifies interfacial intermetallic compounds, micro-voids, contamination layers, and plating layer thickness values with sub-micron resolution.
Analytical Sequence
Sample preparation begins with mounting electronic assemblies in epoxy resin followed by precision grinding and diamond polishing. In sem eds cross sectioning, high-energy electron beams raster across the polished cross-section to capture high-contrast backscattered electron images of grain structures. Energy dispersive X-ray detectors capture characteristic X-ray spectra emitted by target elements to identify chemical composition across intermetallic boundaries.
Line scans and elemental mapping quantify diffusion profiles and detect trace contaminants like phosphorus or zinc.
Defect Detection
Interfacial failures in electronic packages present clear spectroscopic signatures under elemental mapping. When sem eds cross sectioning reveals nickel hyper-corrosion or gold phase embrittlement, spatial maps pin point exact atomic concentrations along fracture paths. Quantitative spectral data verify compliance with IPC plating thickness specifications across manufacturing batches.
Verification Standard
Quality assurance laboratories use calibrated spectra to resolve contract disputes regarding microstructural solder defects.