Tag Archives: liquid particle counting

Cleanroom Consumables: LPC Testing for Cleanliness

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In industries requiring extremely high cleanliness such as precision manufacturing, medical consumables, and semiconductors, the presence of tiny particles can directly impact product performance and reliability. Liquid Particle Counting (LPC) testing is an efficient cleanliness evaluation method that quantifies particle shedding from tested materials’ surfaces, providing crucial data for product quality control.

1. Core Purpose of LPC Testing

The primary goal of LPC testing is to assess the number of particles released from tested materials such as cleanroom wipes, swabs, and other cleaning tools during use. Particles entering production environments or contacting sensitive products (e.g., chips, medical devices) may cause contamination, short circuits, or failures. LPC testing precisely quantifies particle release levels, enabling selection of materials that meet cleanliness standards and reduce contamination risks.

2. Testing Method and Procedure

  • Sample Preparation:
    Samples must be kept sealed to avoid environmental particle contamination. Textile samples (wipes) require neat-cut edges to ensure consistent testing areas; swabs should remain in intact packaging to maintain sample integrity.

  • Soaking and Use Simulation:
    Samples are fully immersed in ultrapure water and mechanically stirred to simulate real usage scenarios such as wiping or agitation. This promotes thorough detachment and dispersion of particles from the material surface into the water.

  • Particle Counting and Analysis:
    A high-precision liquid particle counter quantifies particles in the water across various size ranges. Results are expressed as particle density per unit area (counts/cm² or counts/m² for textiles) or total particle count per individual swab (counts/tip).

  • Testing Efficiency:
    Each sample test takes approximately 40 minutes, supporting rapid batch testing and enabling real-time quality monitoring during production.

3. Technical Points and Standardization

  • Sample Size:
    Textile wipes require 3 independent samples; swabs require 60 individual tips to ensure data representativeness.

  • Environmental Control:
    Testing is performed entirely within cleanrooms or laminar flow hoods to avoid external particle interference.

  • Particle Size Range:
    Particles sized 0.5 μm to 25 μm are typically counted, with focus on those most impactful to downstream products.

4. Application Fields

  • Electronics and Semiconductor Industry:
    Monitors particle release from cleanroom wipes and swabs used in wafer processing to prevent microscopic dust contamination impacting chip yields.

  • Medical Consumables:
    Evaluates cleanliness of surgical swabs and medical dressings to avoid particle contamination entering the body or pharmaceuticals.

  • Precision Instrument Manufacturing:
    Verifies suitability of cleaning tools such as optical lens wipes, ensuring particulate-free assembly environments.

5. Value of LPC Testing

  • Risk Prediction:
    Identifies high particle-releasing materials in advance, preventing batch quality issues caused by contamination.

  • Process Optimization:
    Guides suppliers to improve material washing, cutting, and packaging processes to reduce particle adherence.

  • Compliance Assurance:
    Ensures adherence to international cleanliness standards such as ISO 14644 and GMP.

Special Note:
Some cleanroom wipe manufacturers lack in-house testing capabilities; purchasers are advised to choose suppliers like USTER, which have professional testing laboratories and perform rigorous pre-shipment inspections.

6. Conclusion

As industrial cleanliness standards continue to rise, LPC testing has become an essential step in material selection and process control for cleanroom consumables. USTER, as a professional manufacturer with advanced testing equipment and scientific protocols, provides a reliable quality safeguard for highly sensitive industries, supporting a leap from “clean” to “ultra-clean” standards.

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In high-cleanliness environments such as semiconductor manufacturing, biopharmaceuticals, and aerospace, cleanroom wipes are critical consumables for maintaining cleanroom classification and process stability. The IEST (Institute of Environmental Sciences and Technology) released the IEST-RP-CC004.4 standard, providing a scientific and systematic testing framework for quality control of cleanroom wipes. This article analyzes the key test items and their purposes based on the standard, revealing its technical value in cleanroom applications.

1. Particle Release Characterization

  • Liquid Particle Counting (LPC, 0.5–20 μm):
    Using a liquid particle counter combined with orbital shaking to simulate mechanical friction on wet wipes, quantifying released particles between 0.5 and 20 microns to prevent contamination of precision instruments and interference with optical surfaces.

  • Fiber Analysis (>100 μm):
    Optical microscopy is used to detect large residual fibers or particles after orbital shaking, preventing clogging of microporous structures or mechanical failures caused by macroscopic particles.

  • Airborne Particle Counting (APC, 0.3–10 μm):
    Helmke drum simulates dry state wipe motion, and airborne particle counters monitor particle release between 0.3 and 10 microns to assess particulate risk during dynamic cleanroom operations.

2. Chemical Contaminant Analysis

  • Ion Content Test (IC):
    After extraction with deionized water, ion chromatography detects anions (F⁻, Cl⁻, NO₃⁻, etc.) and cations (Na⁺, K⁺, Ca²⁺, etc.) to prevent ion residues from corroding electronic components or interfering with chemical processes, especially crucial in semiconductor wafer manufacturing.

  • Non-Volatile Residue (NVR) Test:
    Short-term extraction with deionized water and isopropanol followed by evaporation and weighing quantifies transferable oils and polymers, preventing deposition on sensitive surfaces.

  • Fourier Transform Infrared Spectroscopy (FTIR):
    After hexane extraction, FTIR detects organic compounds such as silicone oils, amides, and phthalates (DOP), identifying potential contamination sources to protect optical components and ensure biocompatibility.

3. Physical Performance and Functional Evaluation

  • Liquid Absorption Capacity and Rate:
    Measures maximum liquid uptake per unit area and absorption speed, ensuring wiping efficiency and avoiding contamination from insufficient liquid absorption leading to repeated wiping.

  • Surface Static Charge Test:
    Measures surface resistivity to control static accumulation risk and prevent electrostatic discharge (ESD) damage to electronic components.

4. Biological Contamination Control

  • Bioburden Test:
    Microbial culture methods quantify aerobic bacteria and fungi counts on wipe surfaces, ensuring wipes do not introduce microbial contamination in pharmaceutical or biological lab environments.

5. Technical Significance of the Standard
IEST-RP-CC004.4 comprehensively covers physical, chemical, and biological performance indicators of cleanroom wipes through multi-dimensional testing. It offers graded particle control from submicron to macroscopic fibers, compatible with ISO Class 1 to 5 cleanrooms, tightly controls ions and organic contaminants for semiconductor and optical industries, and verifies absorption efficiency and antistatic performance to guarantee operational reliability. This standard provides a scientific basis for wipe selection, acceptance, and quality management and is a core technical specification to maintain clean environments in high-value industries.

Conclusion:
By rigorously following the IEST-RP-CC004.4 standard, users can precisely select high-quality cleanroom wipes tailored to specific cleanroom scenarios, effectively reducing contamination risks, extending equipment lifetime, improving process yield, and enhancing product reliability, thereby supporting sustained growth in high-cleanliness industries.