Defects & Troubleshooting
Resistance Drift Over Time
Why ESD surfaces change resistance after installation and how to diagnose the root cause.
Resistance drift refers to a gradual change in the electrical resistance of an ESD surface after installation. A surface that initially meets specification may slowly move outside the acceptable range, creating unpredictable ESD behaviour and audit failures.
How resistance drift typically appears
- Resistance increases over weeks or months
- Measurements vary widely between test locations
- Performance changes after cleaning or handling
- Results differ significantly with humidity
Drift may be subtle at first and only become obvious during routine verification testing or customer audits.
Common root causes
- Surface wear: abrasion removes conductive or dissipative surface layers.
- Contamination: oils, dust, or cleaning residues form insulating films.
- Humidity dependence: some systems rely on moisture to conduct.
- Material migration: additives or fillers migrate or deplete over time.
- Inadequate grounding: poor connections exaggerate apparent resistance.
How to diagnose resistance drift
Effective diagnosis focuses on separating environmental effects from material degradation.
- Compare measurements at different humidity levels
- Test cleaned vs uncleaned areas
- Inspect high-wear zones separately
- Verify grounding continuity
- Review historical test records for trends
Corrective actions
Corrective actions depend on the root cause rather than the measured value alone.
- Replace or recoat worn surfaces
- Adopt compatible cleaning procedures
- Improve grounding and continuity
- Select materials with stable, intrinsic conductivity
- Increase verification frequency in high-wear areas
- Resistance drift is a gradual, real-world failure mode.
- Initial compliance does not guarantee long-term performance.
- Environmental and surface factors must be evaluated together.
- Corrective action should target the root cause, not just the reading.