Electrostatic Discharge: How to test & Monitor on Production Floor


Electrostatic Discharge is a very old phenomenon in the industry but it was becoming more important after the use of solid-state electronics and complected integrated circuits.

Devices used for protection against ESD are exposed to wear and contamination. To ensure cleaning and maintenance measures are sufficiently rigorous for maintaining their protective function, regular routine inspections must be conducted in accordance with this document.

What is an ESD

What is esd? Electrostatic discharge (ESD) is is the release of static electricity between two electrically charged objects when they come into contact. The ESD occurs when two different objects rub together build-up of an electrostatic charge.

A simple example of the build-up of an electrostatic discharge when we walking on the floor. ESD can cause harmful effects and can cause even latent or permanent damage to low voltage electronic devices.

Protection and monitoring of Electrostatic Discharge during manufacturing when dealing with electro-sensitive devices. Here in this article, we are going to discuss the test and protection methods from Electrostatic Discharge

1Test of Workbench and wrist Strap Sockets

Requirements:- The discharge resistance of installed (loose-lying or glued) coverings should be 0.75 – 100 MΩ measured from the surface of the covering to the equipment or EPA earth. All wrist strap sockets must be grounded.


Test method to measure

The covering should be brushed off with a soft brush before measuring. The discharge resistance should be measured in at least 3 points per m2 of covering, evenly distributed over the surface. Measure the resistance for all wrist strap sockets to the ground.

1. ESD Testing with insulation meter

Connect the instrument’s rounding terminal to EPA ground and measuring socket to the measuring electrode, 2.27 Kg, which is placed on the surface to be measured.

Measure with the insulation tester. Measuring voltage 100 volts.

2. ESD Testing with Multimeter (ohmmeter)

Connect the instrument’s Grounding terminal to EPA ground & measure socket to the Measuring electrode, 2.27 Kg, which is placed on the surface to be measured.

For an approved result, the value should be < 2 MΩ.

Actions to be taken in case of fault

If the measurement results for the first batch of measurements are not approved, the following procedure should be adopted

Actions Needs to taken

(1) If the measured value is ≤109 Ω (≤ 1000 MΩ)
Clean the table covering
Let the covering air-dry for at least 12 hours in a normal working environment
Perform a new control measurement
NB– The table covering may be used during that time.

(2) If the measured value is > 109 Ω (> 1000 MΩ)
Clean the table covering !!
Let the covering air-dry for at least 12 hours in a normal working environment
Perform a new control measurement.

Check Points :- If any of the wrist strap sockets is not in contact with earth ground, examine the cabling, cable shoes and jointing, and repair or replace any defective materials.

Check that the table’s grounding cable is connected and in good condition. Measure again with a measuring voltage of 100 volts. Use an insulation tester.

2.Testing Production Floor Surfaces

The discharge resistance must not exceed 100 MΩ when measured from the surface of the floor to the facility ground or EPA ground.

  • General Test Method:- The floor covering should be brushed off at the measuring points with a soft brush before measuring. Reading should be taken 15 seconds after applying voltage. One measuring point per 10 m2, but a minimum of five (5) points per test surface must be measured.
  • Testing with floor measuring stick:- Connect the instrument’s grounding cable to EPA ground. Press on the instrument so that it touches the bottom against the surface to be measured. The green light-emitting diode “OK” lights up when the control result is approved
  • Testing with insulation tester:- Connect the instrument’s grounding terminal to EPA ground and measuring socket to the measuring electrode, 2,27 Kg, which is placed on the surface to be measured. Measure with the insulation tester. Measuring voltage 100 volts.

Accepted level

The following criteria must be met for a test surface to be approved.

• Discharge resistance must be ≤ 100 MΩ for a minimum of 95% of all measuring
points. The extra measuring points must not be included.
• The discharge resistance for all extra measuring points must be ≤ 100 MΩ.

3.Electrostatic Discharge Testing chairs

Discharge resistance must not exceed 100 MΩ measured from the seat of the chair, backrest, and armrest, if applicable, to the floor.

  • General Test Method:- The chair should be placed on an insulating base with one of the wheels on a metal sheet. The discharge resistance should then be measured from the sheet to a measuring electrode that is pressed against the chair seat.

    The measurement is then repeated with the sheet under each one of the wheels. Then the discharge resistance should be measured from the backrest (both sides) and the armrests, if fitted, to the sheet with one wheel remaining on it.
  • Testing with insulation tester:- Connect the instrument’s grounding terminal to the metal sheet and measuring socket to the measuring electrode, which is placed on the surface to be measured.

    NB – Measure with the insulation tester. Measuring voltage 100 volts.

Actions to be taken in case of test Failure

In the case of a non-approved measurement result, the wheels should be cleaned and the measurement taken again after they have been air-dried for at least 12 hours in a normal working environment.

A non-approved measurement result may be due to the connection cable inside the chair’s column having snapped. If non-conformance remains after measures have been taken, a non-conformance report must be written and the chair sent away for repair.

Tips :- If the chair is fitted with anti static plastic wheels, a measure for improvement
may be to replace these with metal wheels.

Move the grounding cable to the chair chassis and check the wheels, chair
seat, backrest and armrests, if fitted, separately with the instrument.

4.Testing Shoes / Shoe Straps

Electrostatic Discharge to ground maximum 100 MΩ per shoe. System resistance with shoe/floor combination must be lower than 35 MΩ or lower than 1GΩ and where potentials higher than 100 volts must not be built up in the body in a “walking test”

The shoes are checked by measuring the discharge resistance of the shoes plus the user. The method in accordance with IEC 61340-4-5 First edition, 2004

Testing with shoe resistance tester
For the measurement to be taken, the user stands with one shoe on each of two insulated metal plates between which the discharge resistance is measured.

If the green light-emitting diode “OK” lights up or the red light-emitting diode “LOW” lights up, the control result has been approved.

Actions to be taken in case of test Failure

In the case of a non-approved measurement result, when checking shoes, they should be cleaned and the measurement taken again.

If cleaned with water, the shoes must be air-dried for at least 12 hours in a normal working environment before a new measurement is taken.

In the case of a non-approved measurement result, when checking shoe grounders, check that the shoe grounders are turned the right way round and that the strap is in contact with the skin and tucked properly into the socks or shoes.

Tips :- Use shoe grounders until you get some new shoes.

5.Testing Methods Wrist Straps

For Electrostatic Discharge the wrist strap is checked by measuring the discharge resistance of the fitted wrist strap plus user. The discharge resistance must be 750 kΩ to 10 MΩ measured from the cable’s ground connection to the hand.

Requirements :- Complete strap: lower than 107 Ω ,Strap only: lower than 105 Ω, Cable: lower than 106 Ω.

Testing Method
Step 1 :-The following limits apply when measuring with this equipment: 0.9 – 10 MΩ. Put on the strap and connect the cable to the instrument’s grounding terminal.

Step 2 :- Press down on the instrument’s metal plate with your hand.The green light-emitting diode “OK” lights up when the control result is approved..

Actions to be taken in case of test Failure

If the red light-emitting diode “LOW” lights up, the wrist strap has failed and must be replaced immediately. If the red light-emitting diode “HIGH” lights up, the wrist strap has failed.Check that the wrist strap fits close to the wrist.

If Electrostatic Discharge non-conformance is still evident after measures have been taken, a non-conformance report must be documented and published.

Tips :- To achieve better contact, we recommend that you use hand lotion (NB must not contain silicone).

6.Testing Methods of Soldering Irons

After a period of use, an oxide coating can form between the soldering iron element and tip which increases resistance between the tip and earth.However, this is of no great significance from the ESD standpoint.

Requirements :- The resistance between tip and ground must be less than 5 Ω.

Testing Method
The resistance of a soldering iron can be checked with an ohmmeter with a measuring voltage of at least 10 volts DC.

Step 1 :- Connect one of the ohmmeter’s probes to the soldering iron tip and the other to EPA ground or grounding terminal on the soldering equipment.

Step 2 :- Press down on the instrument’s metal plate with your hand.The green light-emitting diode “OK” lights up when the control result is approved..

Actions to be taken in case of test Failure

With a Electrostatic Discharge failed result, the soldering equipment should be sent off for repair and avoid to use such equipments without certification and repairing.

7.Testing Methods ESD clothes

After friction charging an article of clothing, the voltage should fall to below 100 volts within 2 seconds. This applies to the whole of the article of clothing

Thus it is not sufficient for only parts of a coat, e.g. an arm, to meet the requirement. Protective clothing should primarily be tested in accordance with SP methods or an equivalent institute.

General test Method :- To ensure the whole garment has the capacity to discharge static electricity,charging and measuring must be done on surfaces that compel charges to pass through seams on the way to ground.

Method 1 :- The coat/overall should be hung up by both cuffs. As the cuffs are normally the only route by which charges from the garment can be discharged to the person and then to ground, only the cuff should be tucked into the clip.

Method 2 :- Measure the garment worn by a person.

Testing with a field indicator :- Switch on the field indicator and set it to zero. Check how quickly the voltage falls.

Actions to be taken in case of test Failure

Measures to be taken in case of fault If the garment fails to meet the above requirement, the following troubleshooting for Electrostatic Discharge failure.

Check that the article of clothing has contact with ground. Test the “defective” garment by charging up and measuring an arm instead of the front or back of the garment.

If it turns out that the contact is broken via the seams and the coat only conducts from arm to cuff, the garment should be scrapped.

7.Testing Methods of packaging materials

Components, products and materials that are packaged and delivered to EPA must be packaged in specially-designed ESD-adapted packs.

Materials used within an EPA area must primarily be electrostatic conductive or electrostatic dissipative No material should be charged up to more than 100 volts.

  • General test Method :-Stroke the upper side of the hand smartly, several times over the surface of the material to be checked. Check with the field indicator that the material is not charged up. The indication in the most sensitive area should not exceed a maximum of 100 volts.
  • Testing with field indicator :- Switch on the field indicator and set it to zero. Conduct inspection according to instructions.
  • If the field indicator gives a reading in excess of 100 volts, the electrostatics discharge sensitive material must be removed from EPA and be reported in accordance with the local routine for ESD-faulty packaging or treated in accordance with 14.2 Exceptions.

Exception

Where a risk assessment shows that electrostatics discharge faulty packaging materials are not at risk of damaging electrostatics discharge ( e.g. where the distance between the charged material and Electrostatic Discharge is sufficiently great) chargeable material can be handled on an EPA surface.

Tips :- Chargeable Electrostatic Discharge sensitive material can be removed to ensure there is no risk of ESD damage. See also 155 03-FCH 102 02.

Terminology/definitions

ESD :- ElectroStatic Discharge
EPA :- ESD protected area
ESDS :- ElectroStatic Discharge Sensitive device

Final Thoughts

In this article “Electrostatic Discharge: How to test and monitor on Production Floor” now it is clear that what is esds and why to electrostatics discharge needs to test and monitor on shop floor.

Electrostatic Discharge can cause the permanent failure of any electronic device so precautions must be implemented.

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Hello, this is Manoj, A Soldering and DIY Tool expert. Writing is one of my hobbies. With more than 20 years of broad experience. I love researching, discovering, and sharing new products with others, I hope you’ll enjoy the greatest featured products to make life easier, more fun, and more productive.

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