ESD Class Zero
What should you do when your customer tells you that their new product contains “Class Zero” parts? The wrong thing to do is panic. The right thing to do is ask a series of questions that will help to clarify the issue and assist in developing a course of action – if one is even needed. However, before we start asking questions let’s discuss the meaning of “Class Zero”.
The term Class Zero has its origins in component and microcircuit test standards that deal with Human Body Model (HBM) testing. Documents such as ANSI/ESDA/JEDEC JS-001-2011 classify a device’s ESD sensitivity based on its withstand voltage. The lowest classification (the most ESD sensitive device classification) is a category called Class 0A /0B or simply Class 0. As defined in the ANSI standard a Class 0 device has a withstand voltage of less than 250 volts.
The HBM device test standard is the ONLY standard that utilizes “Class Zero”. Unfortunately, individuals, consultants and organizations misapply the term Class Zero to devices regardless of which model they are tested to. It has unofficially become a term that is applied to devices that are considered to be very ESD sensitive. It is the incorrect use of the term “Class Zero” that is causing so much confusion in the electronics industry today. People do not know what to do when dealing with so-called “Class Zero” parts.
So, back to the original question, what do you do when confronted with devices that are described as “Class Zero”? First, there is absolutely nothing that you can do with this information – except to possibly worry! It is not possible to design an ESD process when your only information is that the part has a “Class Zero” ESD sensitivity.
Even if “Class Zero” applies to a device’s HBM sensitivity it still does not provide enough information to develop an ESD program for personnel. In order to develop an ESD control program for the grounding of personnel one needs to know the exact sensitivity of the parts being handled.
So, ask the following questions:
- Which ESD model are you referring to?
- Can you get specific failure voltage levels for the part in question?
- Can you obtain the withstand voltage for the main ESD models such as HBM, Machine Model (MM) and Charged Device Model (CDM)?
If you can get this information it is possible to evaluate your existing ESD process and make an informed decision on what needs to be done to safely handle this part. Without detailed ESD sensitivity information you may be spending money on ESD controls that are not necessary.