Intermetallic Compound Kinetics in Lead Free Solder Reliability Warranties
Excessive intermetallic layer growth and Kirkendall voiding cause brittle solder joint field failures that require precise contractual latent defect rules.
Cross-Section Polishing
Meaning
Destructive analytical technique used to expose the internal structure of a material sample for microscopic examination. Laboratory technicians use cross-section polishing to prepare electronic components for the inspection of solder joints and plating layers. The process removes material in a controlled plane to reveal defects that are hidden from external view.
Sample Preparation
Encapsulating the component in a rigid epoxy resin prevents the delicate internal structures from collapsing during the cutting phase. After the resin cures, cross-section polishing proceeds through various grades of abrasive media to achieve a mirror finish. This smooth surface is necessary for high resolution imaging.
Interface Examination
Microscopic viewing reveals the thickness and uniformity of the intermetallic compound layers. In cases of field failure, cross-section polishing allows the investigator to see the exact path of a crack through the metal. It also shows the presence of internal voids or contamination within the joint.
Analytical Procedure
Etching the polished surface with a mild acid highlights different grain structures and alloy phases. While x-ray inspection provides a top down view, cross-section polishing provides the vertical detail needed to measure layer thickness at the micron level. Results from this method provide the evidence needed to confirm or rule out manufacturing defects.