ESD Setup Overview
What is the ESD Test Setup?
Electrostatic discharge testing requirements, commonly IEC 61000-4-2 for commercial products, includes criteria for the ESD test setup. This post will focus on the setup designed for table top equipment under test (EUT) and best practices for manufacturing the associated environment used for testing. When designing the setup IEC 61000-4-2 should be used a reference following the dimensions and measurements provided.
The video overview for designing an ESD setup table top setup includes:
- Horizonal & Vertical Coupling Planes
- Metal information and sizing
- All wood table design
- Setting up components
- Accessories & stand
Test Setup Considerations - Pre-Compliance
When considering building or manufacturing an ESD setup, it is important to know what type of testing will be conducted. For many situations where EMI pre-compliance or troubleshooting is the focus, certain components may be removed completely if deemed unnecessary. For example, if indirect discharges will not be applied, no vertical coupling plane is needed. Additional information on ESD testing can be found on the ESD testing overview and methods article.
Types of ESD Setups
ESD Table Top Setup
The most commonly used setup is the ESD table top setup. The image on the left is a generic diagram of the setup provided in the Teseq NSG 435 user manual. While the diagram does not providing exact information, it does provide an overview of the setup and the major components. This setup is designed for EUT that can be placed on the insulating material to conduct testing. Common components of an ESD Table top Setup Include:
- Horizontal Coupling Plane (HCP)
- Insulation placed under EUT
- All wood table
- Bleed off Cabling including resistors
- Ground Reference Plane
What is the ESD Table top test setup?
Floor standing EUT Setup
Equipment under test that is designed, or is too large to be placed on a table is tested using the floor standing EUT test setup. This setup while less common this setup does provide a solution for larger EUT.
- Ground reference plane
- Insulating support/pallet
- Earth wire connection
- Mains connection for EUT
- Earth connection to GRP
Automotive & Military ESD Setups
The requirements for ESD setups designed for testing EUT to military or automotive standards will typically be different from those for commercial applications. EMI standards attempt to replicate the EMI stress from anticipated environment where the EUT will operate, also reflecting in the associated setups.
The setup on the left is the ISO 10605 FCP designed for power on testing where discharge are applied to copper island while the impact on the DUT is evaluated. Common requirements include: ISO 10605 MIL-STD-461 MIL-STD-883/HBM
Design Guide & Build Instructions
As mentioned previously, understanding how the equipment will be tested will impact the what parts of the setup are necessary to have. We will focus on the complete table top setup referencing IEC 61000-4-2 splitting the setup components into three main sections:
- Metal Components
- Wood Table
Metal Components - Coupling Planes
The vertical coupling plane (VCP), horizontal coupling plane (HCP), and ground coupling/reference plane (GCP) will be the metal components used within the ESD test setup. While the standard does allow for a variety of different metals we would recommend either brass, copper, or aluminum. These three metals are fairly light, malleable, and are readily available at metal machine shops.
The exact specifications for width and sizing of the metal can be referenced in the standard, however we used 1/8th in aluminum throughout our setup. While it far exceeds the minimum width requirements, it was readily available and cheaper than purchasing thinner metal width aluminum.
Given the large size of the GCP, it is difficult to ship or transport in a single piece. The easiest is to split the plane into a few different sections with connecting sheets across the sections. It is ideal to use a pallet sizing (or something comparable) as a guideline for each section making the metal easy to move and transport.
The image on the left indicates how to line up the three larger sheets with the two connecting sheets ensuring a single ground reference plane. Splitting up the ground reference plane also allows for easier transport and fabricating helping to lower costs for completing the setup.
The best way to find local companies that are able to acquire and fabricate metals is through a quick Google search. We went with Metal Supermarkets who have locations trough out North America. The metal is the most costly component of the setup, getting quotes from a different vendors is recommended.
ESD Wood Test Table
The all wood table can either be made on site, or purchased through a carpenter. Should the table be manufactured internally it is important to consider the weight of your equipment under test, metal on the table, and if you wish to have the legs be removable. The table top must be at least 160x80cm per IEC 61000-4-2 and all wood. We secured our joints using dowel rods (3/8" by 1.5") and wood glue. This can be a lengthy process depending on the amount of clamps accessible.
The bleed off cables as well as the insulation matt or paper are the final components required by the setup. The bleed off cables with the associated 470 kOhm resistors can either be purchase, as with the EM Test EAS 30, or made. The best place to purchase high voltage resistors capable of handling the voltage would be Caddock. High voltage wire and casings are fairly common and can be purchased independently and assembled to desired lengths.
Wikipedia - IEC 61000-4-2
1. IEC 61000-4-2:2008 - International Electrotechnical Commission Purchase/Preview standard.