2.3 ESD Mitigation During Manufacturing

The two primary ways to reduce ESD events during the manufacturing flow and handling are charge mitigation and discharge prevention. Charge build-up is commonly controlled through the use of ionizers and static dissipative work surfaces at key points in the manufacturing flow. Unwanted discharge events can be controlled by using ESD safe tools and gloves.

The Contact package allows the simple attachment of an electronic device to a disposable in an environment that is not otherwise concerned about ESD precautions. It may feel like a daunting task to adapt a manufacturing environment previously unconcerned with ESD controls to one that must support them, but when you weigh the additional manufacturing costs against protecting the ecosystem from counterfeiting and cloning, the value of the additional measures can readily be determined.

Tools and Techniques for Removing or Minimizing Charge

Grounding of Equipment
Any manufacturing equipment that the devices may come in close proximity or contact with must have their surfaces appropriately and properly grounded through static dissipative means.
Grounding of Personnel
Workers that handle the equipment or the devices must be connected to ground through an ESD grounding strap. Furthermore, the workers must make sure they are grounded and discharged before touching the disposable unit. Straps are typically worn on the wrist.
Humidity Controls
It is recommended that the humidity level be kept between 40% and 60%. Charge build-up is more prone to happen when the air is very dry and the humidity is low. Low humidity levels provide a scenario where you can have a strong ESD discharge, which may damage the device. If the humidity level is high, you may have to worry about condensation issues in the manufacturing environment.
Ionizers

Ionizers are the only way to remove charge build-up from insulating surfaces. The ionizer will force ionized air containing both positive and negative ions over the surface, thus causing any charge build-up to be neutralized. It is very important that ionizers be monitored, calibrated and maintained on a regular basis.

Care must be taken to ensure the proper placement of ionizers to make sure they provide a verified benefit.

Tools for Measuring

As with any manufacturing environment, the appropriate tools must be utilized to measure the effectiveness of the measures taken to ensure ESD controls. It is recommended that these tools be deployed initially to measure the existing manufacturing environment characteristics. These tools can, then, be used to monitor and help mitigate issues within the environment after the appropriate ESD controls are implemented.

ESD Event Detectors

ESD event detectors are used to quantify and locate ESD events in a manufacturing environment. ESD event detectors are actually radio receivers that are sensitive to the characteristic RF energy transmitted when an ESD event occurs.

Tip: If you listen to the radio during a thunderstorm or sometimes when passing under high-voltage power lines, you may hear static on your radio. This is an example of the RF energy interfering with the primary signal. The ESD event detector essentially detects the same type of phenomenon.
ESD Voltage Meters

ESD voltage meters and electric field meters are used to measure the static voltage or electric field strength from charge build-up on surfaces.

Surface Resistivity and Resistance Checker
This measures the resistance of a surface and the resistance between a surface and ground. These meters can be used to verify the resistance of a surface to ensure that they remain in a static dissipative range. They can also be used to verify that grounding straps are working appropriately.
Humidity Meters
A given humidity level must be maintained; therefore, it is important that this be monitored across the manufacturing floor. One or more humidity meters may need to be deployed in a manufacturing environment.