Section ESD standards #8: ESD “Process assessment PWI 101-3”

In this new document, as previously indicated, methods will be discussed to determine which ESD risk a process can still pose despite all ESD protective measures and materials that have been applied.

When assessing a process with ESDS (ESD sensitive components), a number of factors play a role. (Because here too, the chain is only as strong as its weakest link).

It will be necessary to investigate whether there are potentially harmful electrostatic events and whether significant electrostatic charges can occur in persons, systems, materials, components and fully assembled parts.

In order to be able to assess ESD risks that components and products run during the entire process to be analyzed, a first requirement is that data of the components to be processed are known. Such as the electrostatic discharge currents to which a single component or assembly is resistant.

From specifications of a design department and/or supplier, the HBM (Human body model) and CDM (Charge device model) values to which a component is resistant are known. Often expressed in VHBM and VCDM respectively. The purpose of process assessment is to determine whether ESD events that exceed the values stated here do not occur in the entire process.

The measurements required for this can be either direct or indirect measurements.

Thus, the “direct” measurement of discharge currents in large systems will be difficult to do, while checking whether conductive parts in the process are properly grounded often does not present many problems. See for simplified representation fig.1

A production process usually consists of both automatic and manual steps.

The following matters will therefore be taken into account throughout the assessment process:
-Manual steps
-Conductors in the process
-Charged ESDS items
-Risks of necessary insulating materials
-Process assessment by ESDS event detectors

More about this in the next section.

If you have input or would like to contribute to the creation of this new process assessment document, we would like to hear from you!

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Bas Grootemaat

Kingsize Consultancy