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Ion Migration Tests for Printboards
Ion migration occurs in highly humid environment as voltage is applied to an installed printboard and interelectrode ionized metal migrates in a conductor ultimately leading to short-circuits due to the momentum transfer between conducting electrons and diffusing metal atoms.
Recently, the reliability of electric insulation has become an ever important issue as device contact pitches and print patterns shrink. OKI Engineering performs ion migration tests which examines a printboard's insulation reliability by constantly monitoring electrical potential and conversion of so recorded data to resistance values.
Cause of Ion Migration
- Environmental Condition:
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- Electric field （superimposed voltage）
- Temperature
- Humidity
- Causes of increasing ion migration:
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- Probability of ionization in metal material
- Type of board insulation material
- Additive elements （Br, etc.） or presence of impurity （Na+, Cl-, NH4+）
Migration Test Method
Ion migration tests employ the "fall-of-potential" method by once applying current to a shunted location in order to raise a recovery phenomena of the burn-out enabling continuous monitoring and measuring within range of 1.0E7~8Ω, thus easy evaluation of the degradation condition.
Wiring Diagram for Migration Tests
Measurement Result of Continous Monitoring
Migration Test and EPMA Analysis Images
Optical microscope image enlarged in the migration test and EPMA analysis in the SEM image.
Optical microscope image
SEM image （2D electron image）
Analysis image of Cu and Sn EPMA analysd from the SEM image.
EPMA analysis image of Cu formation
EPMA analysis image of Sn formation
