Using the cover slide technique, cross sectioning allows for
in-depth analysis of the inner layers of chips, and will catch
weaknesses that are almost impossible to pinpoint. A cross sectioned
chip is effective for viewing and studying stack-up structures, PCB
plating thickness, solder coverage, and wetting conditions. Cross
sectioning is often applied in failure analysis to study comparisons
of materials through changes in structural forms. Such changes can
indicate damage through thermal cycling, embrittlement, or fatigue.
Foresite has the capability to look at cross sections with up to
1000x magnification.
With the electronics manufacturing environment becoming RoHS
compliant, it is critically important to study such factors as
intermetallic formation, solder thickness, solder morphology and
solder grain structure.
Applications of Cross Sectioning
To
study assembly process quality and product reliability
• Component fractures
• Adhesion
• Intermetallic formation
• Solder thickness
• Bond line thickness
• Package architecture
• Plating thickness
• Solder morphology (voids)
• Solder grain structure
• Solder coverage
• Wetting conditions
Photos of Various Issues Seen Through Cross Sectional Analysis
Au/Al intermetallic phase
Copper
adhesion to FR4
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Plated
thru-hole (PTH)
Epoxy
filler formation / distribution
Die
attach thickness
Through-hole plating into fiberglass bundles
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