What are the ESD Classifications? A Look at the Human Body Model

by Andy on October 31, 2011

When working with ESD sensitive products you need to know exactly what protection is needed. To help let workers know how sensitive certain devices are there are several classifications that are used. The three ESD classifications are the human body model (HBM), charge device model (CDM) and the machine model (MM). Each has its own standards for different situations in ESD-safe rooms and products. In this article we will be looking at the human body model classification.

Human Body Model Classifications

The human body model is the most common classification system for ESD-safe products. When preparing a room with HBM concerns you are trying to stop static buildup on humans from discharging to a conductor. The various classifications for this model tell the user what level of voltage will damage the parts being made.

To the right is a chart of the various classifications for the human body model. The lowest class is Class 0 which requires very stringent regulation. In order to meet this classification you need to make sure that you have the best systems in place possible for dissipating charge on human operators.

HBM classification deals with direct, short bursts of current, so products are typically put into various classes through a rather simple process. The tester will normally hook up the device to a positive and negative lead and given a pulse of a specific voltage level. The voltage of the pulse is increased until the product is damaged and that level designates the class of the project.

If you want to make sure your work area is ESD-safe there are a number of products that you can use. Surface resistivity meters allow you to test any ESD-safe mats or flooring that you have to make sure they are as conductive as they should be. Having conductive, dissipative, or anti-static mats and flooring can help reduce the amount of charge generated from the operator moving around. To directly check the operator you can use workstation monitors. These can check that the workstation, worker, and wrist strap are properly grounded to protect your products.

If you have any further questions about the human body model classification leave a comment below or check out Electrostatic Discharge Association’s website.

Make sure to check back in next Monday, November 7 for another blog post on the charge device model ESD classification system!

Read Part 3 of “What are the ESD Classifications? Machine Model”

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