Transcript ANSI/ESD S20.20, EIA 625, or Industry Standard

Compliance
Verification Testing
of Installed ESD
Protective Products
9/05
©Copyright 2011 DESCO INDUSTRIES INC.
ESD TR53
Compliance Verification
Use ESD Association Technical Report
ESD TR53-2006 Compliance Verification of
ESD Protective Equipment and Materials.
Can be purchased from www.ESDA.org
TR53 includes equipment, test procedures
and troubleshooting tips to periodically
verify the performance of ESD protective
equipment and materials.
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ESD Protected Area
Clearly Identified
“Caution signs indicating the existence of
the Protected Area shall be posted and
clearly visible to personnel prior to entry to
the EPA [ESD Protected Area].
NOTE: An EPA can consist of a single
workstation, entire room or building.”
Ref: ANSI/ESD S20.20 section 8.3.
Report Visual Observations
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ESD Protected Area
Clearly Identified
Attention Sign
Aisle Tape
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Access to ESD Protected
Area Controlled
“Access to the EPA shall be limited to
personnel who have completed
appropriate ESD training
Untrained individuals shall be escorted by
trained personnel while in an EPA.”
Ref: ANSI/ESD S20.20 section 8.3.
Report Visual Observations
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Wrist Strap & Footwear
Tester
SmartLogX3
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Check Ground
“The AC equipment ground is the
preferred ground connection because all
electrical equipment (e.g., soldering irons,'
scopes, etc.) at the workstation is already
connected to this ground.”
Ref: ESD Handbook ESD TR20.20
section 5.1.3
Check AC outlet properly wired with AC
Outlet Analyzer
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Check Ground
AC Outlet Analyzer and
Wrist Strap Tester
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Check Ground Points
< 1 Ohm
• Can use ohmmeter or (as an indicator)
Megohmmeter (note: if has resistor expected
measurement 1 megohm +/- 20%)
• Suggest extension cord with AC Outlet Analyzer
to connect to AC equipment ground and use
Surface Resistance Megohmmeter without 5#
Electrodes.
• Plug one lead into wrist strap ground jack and
sensing lead into electrical ground
• At 10 volts, look for lowest reading if no resistor
or about 1 x 10^6 ohms if there is a resistor.
• Report Rtg
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Check Ground Points
< 1 Ohm
Ohmmeter
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No Resistor in Mat
Ground Cord
“a direct connection from the ESD technical element
to the common point ground or common connection
point is acceptable and recommended.
Note: Manufacturers may add resistance to the
grounding conductors for purposes other than ESD
(e.g. current limiting).
… The typical added resistance in grounding
conductors is 1 megohm”
Ref: Grounding ANSI/ESD S6.1 section 5.3.3
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Rtg and Rtt
Resistance
• The most important resistance measurement is resistance to
ground or Rtg. How well the material conducts charges to
ground; whether material is or can be grounded
• Rtg or Resistance to ground
The resistance in ohms measured between a single electrode
placed on a surface and ground.
• Rtt or Point-to-point resistance (or top to top)
The resistance in ohms measured between two electrodes
placed on any surface.
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Worksurfaces 10^6 – 10^8 Ohms
Use Megohmmeter Test Kit
Worksurfaces, Shelves, and Cart storage surfaces in EPA
S20.20 specifies no lower limit, however, ANSI/ESD S4.1
recommends in the manufacturing environment a resistance
range of over or equal to 1 x 10^6 to less than 1 x 10^9 ohms.
Report Rtg resistance mat to equipment ground
If fails or if measures close to 1 x10^6 ohms (perhaps
measuring resistor in ground cord) measure Rtt with two 5#
electrodes about 10” apart measuring mat resistance itself.
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Worksurfaces 10^6 – 10^8 Ohms
Use Megohmmeter Test Kit
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Use Megohmmeter Test Kit
• For Rtg use Surface Resistance
Megohmmeter with one 5#
electrode
• For Rtt use Surface Resistance
Megohmmeter with two 5#
electrodes
• Measure at 10 volts; if over 10^5
then at 100 volts
• Desco 19780 will change test
voltage automatically, and has a
switch to set only at 10 volts
• Some other equipment use a manual
switch
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Worksurfaces 106 – 108 Ohms
Use Megohmmeter Test Kit
• For Rtg use Surface Resistance Megohmmeter with one 5#
Electrode
• Suggest using a extension cord with AC Outlet Analyzer to
connect sensing lead to AC equipment ground
• Place the one 5# electrode on mat’s center or most worn
area; measure Rtg at 10 volts; if over 10^5 at 100 volts
• Measure at least one of each type or color mat and laminate.
• If fail high, measure Rtt with two 5# electrodes about 10”
apart before and after cleaning (first allow to dry).
• Report Rtg (& Rtt if fail)
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Worksurfaces Troubleshooting
ESD Mat Cleaner
• Static dissipative solution cleans & restores ESD
properties
• Does not contain silicone which will leave a
insulative film
• Report observations and Rtg or Rtt before and
after cleaning allowing time to dry
– Cleaners will have some alcohol as a carrier. As the
alcohol evaporates, it cools the surface and thus
condenses moisture on the surface. Recommended
"dry time" is ~20 minutes from cleaning to retest
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Worksurface Troubleshooting
Check if Properly Grounded
“Grounding / Equipotential Bonding Systems
shall be used to ensure that ESDS items,
personnel and any other conductors (e.g.,
mobile equipment) are at the same electrical
potential.”
Ref: ANSI/ESD S20.20-2007 section 8.1
Use ohmmeter to ensure electrical continuity
between components in path to ground
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ESD Seating < 10^9 Ohms
Use Megohmmeter Test Kit
• Use Surface Resistance Megohmmeter with one 5# Electrode
• Suggest extension cord with AC Outlet Analyzer to connect
sensing lead to equipment ground
• Place the one 5# electrode on various seating surfaces
• Measure Rtg at 10 volts; if over 10^5 at 100 volts
• Can measure with two 5# Electrodes; one on seating
and one to known good ESD Floor
• Report resistance measurements.
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ESD Seating
Troubleshooting
• If high Rtg, measure ESD Floor Rtg to
determine if floor is high
• If high, check if conductive casters are dirty
• If high, use ohmmeter to ensure electrical
continuity between components in path to ground
Note: if measuring Seating back surface ensure that you are
holding insulative surface of 5# Electrode (or wear insulative
gloves) otherwise could create a secondary path to ground
through the person performing the test
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Storage Shelves & Cart Shelves
Electrically Connected & Grounded
• Less than 10^9 ohms Rtg; 10^6-10^8 if unprotected
ESD sensitive items (ESDS)
• Mats and Shelves worksurfaces to be grounded
• Use Surface Resistance Megohmmeter with one 5#
electrode same test as worksurface
• Can measure with two 5# Electrodes to a known good
ESD Floor
• If shelf material is unknown, measure Rtt with two 5#
electrodes about 10” apart
• Report resistance measured
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ESD Flooring
Less Than 10^9 Ohms Rtg
Per Floor standard ANSI/ESD S7.1 section
5.3.1.6 “Perform a minimum of five tests per
contiguous floor surface material or a minimum
of five tests per 5,000 square feet (464.5 m2) of
floor material, whichever is greater. A minimum
of three of the five tests should be conducted in
those areas that are subject to wear or that have
chemical or water spillage or that are visibly
dirty.”
Report Rtg and Rtt if measured
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ESD Floor <10^9 Ohms
Use Megohmmeter Test Kit
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ESD Floor
Less Than 10^9 Ohms Rtg
• Use Surface Resistance Megohmmeter with one 5# Electrode
• Suggest extension cord with AC Outlet Analyzer to connect
sensing lead to equipment ground
• For 3 of 5 tests, place the one 5# electrode on areas that are
subject to wear or that have chemical or water spillage or that
are visibly dirty. Measure Rtg at 10 VDC; if over 10^5 at 100
VDC
• If fail high, measure Rtt with two 5# electrodes about 3 feet
apart before and after cleaning (first allow to dry). If tiles, place
electrodes on different tiles.
• Report Rtg and Rtt if measured
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Flooring-Footwear System
Less Than 35 megohms Rtg
• Use Surface Resistance Megohmmeter with one 5#
Electrode
• Suggest extension cord with AC Outlet Analyzer to
connect sensing lead to equipment ground
• Place the one 5# electrode on bare palm of person
wearing ESD footwear standing on ESD Floor;
• Measure Rtg at 10 VDC; should be < 3.5 10^7
ohms (35 megohms) resistance in series thru person – ESD
Footwear – ESD Floor to ground.
• Report Rtg
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Personnel Grounding Guideline
ESD TR20.20 Figure 14 Relationship Body Voltage and Resistance to Ground
120
Body Voltage
100
80
60
40
20
0
1
10
20
40
Resistance (megohms)
Data used to set Resistance Limit in Combination with a Person < 35 megohms
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Flooring-Footwear System Charge
Generation Less Than 100V
• Use Charged Plate Monitor to measure
electrostatic charge on a person wearing ESD
Footwear on ESD Floor.
• With person connected to isolated
conductive plate via a wrist strap and bulldog
clip, and moving feet, report highest peak
voltage
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Charged Plate Analyzer
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Flooring-Footwear System
Demonstration
• Need both ESD flooring and footwear
•To demonstrate can use Human Body Model
Fixture & Ionization Test Kit
• Try regular athletic shoes on ESD floor and
then with ESD Footwear
• Ground equipment and hold Fixture portion
• Have person moving feet or walking.
• Note peak voltage
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Human Body Model Fixture
& Ionization Test Kit
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Flooring-Footwear System Charge
Generation Less Than 100V
Charged Plate Monitor for more accurate
reading
Human Body Model Fixture & Ionization Test
Kit for indication or demonstration purposes
Dance 6-step recommended in ANSI/ESD
97.2, or as people normally walk in the facility
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ESD Protected Area
Clear of Insulators
• All nonessential insulators, such as those made of
plastics and paper must be removed from the ESD
workstation. Less than 2,000 volts or kept 12” from
ESDS
• Visual – Are non-essential insulators present?
• Measure what charge can be generated on item
• Use Static Field Meter to measure ability to charge
after rubbing item with hand or on your clothing.
• Report voltage; report observations of closest
distance to ESD Sensitive component or assembly
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Digital Field Meter
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Measuring ElectroStatic
Field Tips
• Static Field Meter may have oscillating light
beam to position 1” away from surface.
• Typically display ElectroStatic field in
kilovolts (so 1.20 would be 1,200 volts)
• Static Field Meter to be grounded
• Technician to be grounded
• Measured charge on items smaller than 3"
x 3“ only an indication
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ESD Protected Area
Clear of Insulators - Resistance
• Can measure Rtg with item between 5# electrode and
ESD mat
• Use Surface Resistance Test Kit sensing lead to AC
equipment ground & one 5# electrode on item on ESD
mat. Note: paper absorbs moisture so may not
interfere with path-to-ground, but measure with &
without
• Report resistance Rtg
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ESD Garments
Compliance Verification
• ESD Garment should be grounded via cord or ESD
flooring/footwear. Can be tested while worn using a
Wrist Strap or Footwear Tester < 3.5 x 10^7 ohms
• Observe that Garment is properly worn covering all
clothing with cuffs or wristband in snug contact with
skin.
• Can use Surface Resistance Megohmmeter with two
5# Electrodes sleeve to sleeve Rtt
• Place Garment on insulative surface; place one 5#
electrode on each sleeve or cuff. Measure Rtt at 10
volts; if over 10^5 ohms at 100 volts
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Testing ESD Garments Rtt
Sleeve to Sleeve
Garment on
Insulative
Surface
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Essential Insulators
Neutralized with Ionizers
• “Necessary non-conductors in the environment cannot
lose their electrostatic charge by attachment to ground.
Ionization systems provide neutralization of charges on
these necessary non-conductive items (circuit board
materials and some device packages are examples of
necessary non-conductors).” [ANSI/ESD S20.20-2007
Foreword]
• Test Ionizers, use Charged Plate Monitor or Ionization
Test Kit
• Report Offset Voltage (Balance)
& Discharge Times (both polarities)
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Ionizer being Tested
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Ionizers < +/-50 Offset Voltage
User Defined Discharge Times
• Test ionizer as being used; do not clean.
• Remove from the surface only those items that might block airflow.
• Technician and Ionization Test Kit to be grounded.
• If adjustable, zero reading, and then locate test fixture on
worksurface furthest away from the ionizer where ESD sensitive
products are handled.
• Using Charging Unit, hold acorn nut & simultaneously press button
to charge Conductive Plate.
• With Ionizer operating at normal speed, use a stop watch or count
time in seconds it takes to go from 1,000 volt reading to 100 volts.
• Change polarity and repeat discharge time test -1,000 volts to -100
volts
• Measure Offset Voltage or Balance reading after allowing sufficient
time for reading to stabilize.
• Record Discharge Times and Offset Voltage
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Ionizer Troubleshooting
• If poor performance, remove filter & repeat
test without filter in place (passing then
suggests maintenance is the problem). If still
fails, remove electrical power, and clean
wiping emitter pins with alcohol & re-test.
• Calibrate: adjust improving offset voltage
[balance] to near zero
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Continuous Monitors Checked
•Continuous monitoring devices should be
functionally checked prior to use and
periodically to ensure that they are operating
as designed.
•Use Manufacturer’s Calibration or Verification
Device
•Follow manufacturer’s instructions
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Continuous Monitor
Calibration Unit
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Packaging / Material Handling
Dissipative Preferred 10^4 –
10^10 ohms
• Can use Static Field Meter to measure ability to
charge after rubbing surface. Report voltage;
report observations of closest distance to ESDS
• Use Surface Resistance Megohmmeter with two
5# Electrodes
• Place Packaging on insulative surface; place 5#
electrodes 10” apart if possible. Measure Rtt at 10
VDC; if over 10^5 ohms, measure Rtt at 100 VDC
• Report Voltage and/or Rtt
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Use Shielding Bags / Containers
Outside ESD Protected Area
When not specified by [contract]… the
organization shall define ESD protective
packaging requirements, both inside and outside
the EPA per ANSI/ESD S541.”
Ref: ANSI/ESD S20.20-2007 section 8.4
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In-Plant Handler
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Are Re-used Bags / Containers
in Good Condition?
Users should be aware that some
packaging materials may be humidity
dependent and may have limited shelf life.
They may also lose static shielding
properties by crumpling, puncturing and
folding.
Report: Observations
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ESD Packaging Properly
Marked
ESD protective packaging should be marked
in accordance with ESD Protective Symbol
[ANSI/ESD S541]
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Test Per What Reference?
• Compliance Verification of ESD
Protective Equipment and Materials ESD
TR53-2006
• Recommend buying a copy from
www.ESDA.org at
http://ESDA.org/Documents.html
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Compliance Verification
Testing of Installed ESD
Products
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