DESCO WEST
- 3651 Walnut Avenue, Chino, CA 91710 • (909) 627-8178
DESCO EAST
- One Colgate Way, Canton, MA 02021-1407 • (781) 821-8370 • Website:
Desco.com
TB-3062
Page 5 of 8
© 2013 DESCO INDUSTRIES, INC.
Employee Owned
Frequency of Compliance Verification Testing
NOTE: “The frequency of periodic testing is normally
specified in corporate operating procedures. …The frequency
of testing is driven by the amount of risk exposure that can
occur between tests. For, example, what is the quantity of
product handled between test periods?” (See ESD Handbook
ESD TR20.20)
Per ANNEX A of Compliance Verification ESD TR53 “Test
Frequency, The objective of the periodic test procedures
listed in this document is to identify if significant changes in
ESD equipment and materials performance have occurred
over time. Test frequency limits are not listed in this
document, as each user will need to develop their own set
of test frequencies based on the critical nature of those ESD
sensitive items handled and the risk of failure for the ESD
protective equipment and materials.”
Addition information includes:
• Worksurface
- at least quarterly (see ESD TR20.20
section 5.3.1.13 Periodic Tests)
• Footwear
- “Incoming inspection on a lot sampling basis
should be performed for all static control footwear.” (see
ESD TR20.20 section 5.3.3.4 Testing)
• Floor
- “The types of monitoring and type of equipment
are considerations. In some cases, a simple electrical
resistance test with a megohmmeter may suffice. In
others, a static charge generation test may be required.”
(see ESD TR20.20 section 5.3.4.13 Performance
Monitoring)
• Seating
- “The recommended electrical resistance
range for seating is less than 1 x 10
9
ohms as tested in
accordance with ANSI/ESD STM 12.1. This value should
be during acceptance testing, installation and periodically
thereafter.” (see ESD TR20.20 section 5.3.5.3 Testing)
• Garments
- “To maintain process control, it is imperative
that the garment be tested per ANSI/ESD STM 2.1. The
point-to-point and sleeve-to-sleeve resistance test should
be made.” (see ESD TR20.20 section 5.3.13.3.1.8
Periodic Testing)
Surface Resistivity
Theoretically, Resistivity is 10 times greater than Resistance.
For example, a material that measures 10
7
ohms in surface
resistance should measure 10
8
ohms/square in surface
resistivity.*
Ref: ANSI/ESD STM11.11 section 12.0 Conversion to
Resistivity states, “When it is appropriate to convert a
resistance obtained by this test method to an equivalent
resistivity in ohms per square, multiply the resistance
measurements obtained by this method by 10. The
conversion factor of 10 is derived from the geometry of the
electrode assembly.”
*Note: Although STM11.11 uses ohms/square, per ESD
TR20.20, the correct unit of measure for resistivity is just
ohms.
Product Qualification Test Lab Test Procedure Guideline
For test lab use of ESD Worksurfaces, Floor Materials,
Footwear, Garments or Seating, the best advice is to follow
the test methods in applicable ESD Association documents
which include details such as:
• Cleaning (For example per S4.1, “The test specimens
and electrodes shall be cleaned twice with a minimum
70% isopropanol-water solution using a clean, low-linting
cloth each time). Allow to the material to dry.
• Environmental chamber (For example per S4.1, control
relative humidity to 12 ±3% relative humidity and 50 ±5%
relative humidity and temperature to 23 ±1°C)
• Specimen support surface (For example per S4.1,
greater than 1 x 10
12
ohms such as PMMA, PTFE or
polycarbonate)
• Specimen Pre-Conditioning (For example per S4.1, at 23
±1°C; 3 specimens at 12 ±3% relative humidity for up to
72 hours minimum, and 3 specimens at 50 ±5% relative
humidity for up to 72 hours minimum)
• Reporting Test Results: For example per S4.1 Reporting
Test Results, report:
• Minimum, median and maximum readings for both
resistance-to-groundable point and point-to-point
resistance in ohms at low relative humidity
• Minimum, median and maximum readings for both
resistance-to-groundable point and point-to-point
resistance in ohms at moderate relative humidity
• Temperature
• Relative humidity
• Actual duration of conditioning
• Test equipment used and latest calibration date
