How to Ensure Your Ionizer is Working Correctly - SCS - Static Control Solutions (2024)

The best way to keep electrostaticsensitive devices (ESDs) from damage is to ground all conductive objects andremove insulators from your ESD Protected Area (EPA). This is not alwayspossible because some insulators are “process-essential” and are necessary tobuild or assemble the finished product. The only way to control charges onthese necessary non-conductive items is the use of ionization systems.

However, if an ionizer is out of balance,instead of neutralizing charges, it will produce primarily positive or negativeions. This results in placing an electrostatic charge on items that are notgrounded, potentially discharging and causing ESD damage to nearby sensitiveitems.

It is therefore essential to regularlyclean your ionizers and verify they function correctly. Below we have puttogether a list of tasks you need to perform with your ionizers on a regularbasis.

Maintenance

“Allionization devices will require periodic maintenance for proper operation.Maintenance intervals for ionizers vary widely depending on the type ofionization equipment and use environment. Critical clean room uses willgenerally require more frequent attention. It is important to set-up a routineschedule for ionizer service. Routine service is typically required to meetquality audit requirements.” (ESD Handbook TR20.20 section 5.3.6.7Maintenance / Cleaning)

EIA-625, recommends checking ionizers every6 months, but this may not be suitable for many programs particularly since anout-of-balance may exist for months before it is checked again. ANSI/ESD S20.20section 6.1.3.1 Compliance Verification Plan Requirement states: “Test equipment shall be selected to makemeasurements of appropriate properties of the technical requirements that areincorporated into the ESD program plan.”

Under normal conditions, an ionizer willattract dirt and dust (especially on the emitter points). To maintain optimumneutralization efficiency and operation, cleaning should be performed on aregular basis.

1. Case

Wipe the case with a soft cloth anddeionized water. Fully squeeze the wiping cloth or sponge to remove any excessliquid. If a stronger cleaning solution is required, dab a soft cloth withmixture of isopropyl alcohol and deionized water (70% IPA and 30% DI water).

2. Emitter Points

The emitter points should be cleaned usingspecific emitter point cleaners or a swab dampened with Isopropyl alcohol.Below are general instructions on how to clean emitter points. However, eachunit is slightly different so always refer to the ionizer’s manual.

1. Turn the unit OFF and unplug the power cord.
2. Open the top screen by loosening the screw and swinging the grill to one side.
3. Clean the emitter points using the an emitter point cleaner or a swab dampened with Isopropyl alcohol.
4. Re-attach the top screen.
5. Plug in the power cord and turn the unit ON.
6. Verify the performance of the ionizer by using a charged plate monitor or ionization test kit (see below).
   

With normal handling, the emitter points should not require replacement during the life of the unit.

Check out how to clean an Ionizer in A Minute with Miranda:

Verification

Per ESD TR53 section 5.3.6.7.1 “The best practice is to measure the offsetvoltage and discharge times, clean the unit, including emitter points and airfilters if present, offset voltage to zero (if adjustable), and then repeatoffset voltage and discharge time testing. If the unit does not meet offsetvoltage specifications or minimum established discharge time limits, furtherservice is indicated. Manufacturers should provide details on serviceprocedures and typical service intervals.”

Most companies will assign a number orotherwise identify each ionizer and setup a Compliance Verification /Maintenance / Calibration schedule. If the ionizers all test good, the data canjustify lengthening the calibration period. If ionizers require adjustment, thecalibration period should be shortened. Although ESD TR53 does not advise atest frequency, JESDD625-A (Revision of EIA-625) recommends ionizers be tested semi-annually,noting to use “S3.1 except the number ofmeasurement points and locations may be selected based on the application.”

Verification should be performed inaccordance with the ESD Association ionization standard ANSI/ESD STM3.1.

Below are general instructions on how toverify your ionizer’s offset voltage and discharge time. Always refer to theUser Guide accompanying your Charge Plate Monitor or Ionization Test Kit forproper operation and setup.

1. Testing Ionizer Offset Voltage:

The required limit per ANSI/ ESD S20.20 isless than ± 35 volts. Check your ionizer’s operating manual or consult with theionizer manufacturer to determine what the offset voltage should be for yourionizer.

Charge Plate Monitor (CPM)

1. Position the ionizer and charge plate monitor as shown below.
2. Set the CPM to Decay/Offset mode.
3. Set the CPM to decay and offset voltage mode with a starting charge at either + or – 1 KV and a stopping charge at either + or -100 Volts.
4. Start the decay/offset test sequence on the CPM. This will take a few seconds.
5. Record the decay time, and offset voltage as displayed on the CPM.

Positioningyour Charge Plate Monitor for Overhead and Benchtop Ionizers

Ionization Test Kit

1. Zero the charge plate by touching it with a grounded object. Thiscan either be the finger of a grounded person or some other item which isconnected to electrical ground. In either case, zeroing the charge plate shouldmake the display on the field meter read zero.
2. Hold the meter approximately one foot (30.5 cm) in front of theionizer.
3. Monitor the display. The value displayed is the offset balance ofthe ionizer, which is the difference between the number of positive andnegative ions being emitted.

Portable Charge Plate Monitor

1. Turn the meter on.
2. Zero point adjust the meter. Bring the plate into contact with a grounded body, and press the 0ADJ button.
3. Set the desired mode. Press the SELECT button, and the meter will scroll through the modes. To measure balance (offset voltage), use I.B mode.
4. Point the plate at the measurement location, the meter will measure the balance.

Watch how to test the balance using the SCS Portable Charge Plate Monitor:

2. Testing Ionizer Discharge Time:

The required limit per ANSI/ESD S20.20 is“user defined”. Please refer to the ionizer’s operating manual or consult withthe ionizer manufacturer to determine what this discharge time should be.

Charge Plate Monitor (CPM)

1. Set the CPM to Decay/Offset mode.
2. Set the CPM to decay and offset voltage mode with a starting chargeat either + or – 1 KV and a stopping charge at either + or -100 Volts.
3. Start the decay/offset test sequence on the CPM. This will take afew seconds.
4. Record the decay time, and offset voltage as displayed on the CPM.

Ionization Test Kit

1. After charging the plate of the ionization test kit, hold the fieldmeter approximately one foot (30.5 cm) away from the ionizer.
2. Monitor the display of the meter to see how quickly the 1.1 kVcharge is dissipated to 0.1 kV.
3. The speed at which this occurs (the discharge time) indicates howwell the ionizer is operating.
4. Repeat this procedure for both a positively and a negatively chargedplate.

Portable Charge Plate Monitor

1. If you haven’t already, turn the meter on and zero it.
2. Set the desired decay range, select +Decay to measure positive discharge time. Select -Decay to measure negative discharge time.
3. Point the plate in the airflow of the ionizer to be measured and press the START button.
4. The meter will chirp and display the neutralization time when the measurement is completed.

Watch how to test the decay time using the SCS Portable Charge Plate Monitor:

Some ionizers offer adjustment options (e.g. trim pots) which allow modification of the offset voltage.

However, if your ionizer is out of balance(and cannot be adjusted) or if the discharge time is out of specification, theionizer will require service/repair by an authorized company.

Conclusion

Ionization is one of the best methods ofremoving charges from insulators and as a result plays an important role incontrolling ESD.

Remember though: ionizers require periodiccleaning of emitter pins and verifying of the offset voltage and dischargetime. Otherwise, instead of neutralizing charges, the ionizer will primarily producepositive or negative ions. The ionizer will therefore place an electrostaticcharge on items that are not grounded, potentially discharging and causing ESDdamage to nearby sensitive items.