In electrostatic-sensitive environments such as electronics manufacturing and precision instrument maintenance, cleanroom wiping consumables (e.g., cleanroom wipes, cleanroom paper, and swabs) must offer reliable electrostatic discharge (ESD) protection. Effective dissipation of static electricity is essential to prevent damage to sensitive components. This article systematically outlines the commonly used test methods for evaluating anti-static properties of these materials, based on industry standards and real-world requirements.
1. Surface Resistance Method – Basic Conductivity Assessment
Principle:
Surface resistance is the ratio of direct current voltage to current between two points on the surface of a material (unit: ohms, Ω). Lower resistance indicates better conductivity and stronger ESD dissipation capability.
Testing Procedure:
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Sample Preparation: Select 5 samples and pre-condition them in a controlled environment (23±2°C, 50±5% RH) for at least 4 hours.
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Measurement: Place the electrodes (or weighted probes) of the surface resistance tester on the sample, press the test button, and record the reading.
Evaluation Criteria:
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Anti-static material: Resistance < 10¹¹ Ω
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High-quality anti-static material: 10⁵ Ω – 10⁹ Ω (balanced ESD dissipation and insulation)
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Insulating material: Resistance > 10¹² Ω (prone to static buildup)
Advantages:
Quick and simple; suitable for on-site screening in production environments.
2. Decay Time & Half-Life Method – Charge Dissipation Efficiency
Principle:
After charging the sample using a high-voltage source, its voltage decay to 50% of the initial level (half-life) or complete decay is measured using a non-contact electrostatic voltmeter. This evaluates how quickly the material dissipates static charges.
Testing Procedure:
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Sample Preparation: Pre-treat 10 samples for at least 4 hours in a controlled environment.
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Charge & Measure: Charge using corona discharge or friction method and monitor the decay curve of voltage over time.
Key Indicator:
Shorter decay time = better ESD performance. Semiconductor industries typically require decay time < 0.1 seconds.
Application:
Ideal for high-ESD-sensitive applications like chip fabrication.
3. Triboelectric Voltage Method – Real-World Friction Simulation
Principle:
The sample is rubbed against a standard fabric (e.g., nylon cloth) under a specified tension until it reaches electrostatic stability. The peak and average voltages generated simulate ESD risk from actual wiping motions.
Testing Procedure:
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Equipment: A friction apparatus and electrostatic voltmeter compliant with GB/T 24249-2009 standard.
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Sample Details: Pre-treat 10 samples for ≥4 hours; each test lasts 30 minutes.
Evaluation Criteria:
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Grade 1 anti-static material: Friction voltage ≤ 200V
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Grade 2 material: 200V–500V
Advantages:
Highly practical; mimics real-use conditions and supports cleanroom material classification.
4. Testing Conditions & Key Guidelines
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Environmental Control: All tests must be conducted at 20–25°C and 40%–60% RH.
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Pre-treatment Importance: Eliminates moisture-related influence on resistance values to ensure data reliability.
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Sample Quantity: Surface resistance test requires 5 samples; other methods require 10 to account for material variability.
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Data Recording: Must document max, min, and average values for comprehensive performance evaluation.
5. Conclusion & Selection Recommendations
Multiple tests are essential to comprehensively evaluate the anti-static performance of cleanroom wiping materials:
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Surface Resistance Method assesses base-level conductivity.
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Decay Time Method evaluates charge dissipation speed.
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Triboelectric Method simulates practical static generation risks.
For real-world application, users should align with industry standards (e.g., GB/T 24249-2009) and operational scenarios (e.g., Class 100 cleanrooms, high-precision electronics assembly). It is recommended to select products with resistance between 10⁵–10⁹ Ω and triboelectric voltage ≤200V to ensure effective ESD control while maintaining operational efficiency.