There are numerous amount of electrostatic discharge (ESD) related standards and many variations on the most common IEC 61000-4-2 setup. However, given the common usage of this standard by the Electrotechnical Commission, we will base the majority of our discussion on it. This standard is currently in its second edition(1) and is available for purchase, you will find a link in the reference and additional resources at the bottom of this page. Part of this standards popularity is based upon its applicability to (an) basic reference for this type of immunity testing. Below is a breakout of the common components of the setup:
- Ground Coupling Plane (GCP)
- Vertical Coupling Plane (VCP) & Stand
- Horizontal Coupling Plane (HCP)
- Table - All Wood & Sizing per Standard
- Grounding/Bleed off Cables & Resistors (2)
- Insulating Foil/Paper
Given the industrial nature of the test setup/equipment it is ideal to only built components that would be required for an individual testing requirement. IEC 61000-4-2 places preference on contact discharge either through vertical (VCP) or horizontal coupling planes (HCP). This standard can be purchased through the International Electrotechnical Commission website, by clicking here. Should another standard be used as a reference for manufacturing, please reference accordingly. The below video is an overview on how the setup comes together with the most common complete components.
ESD Table (Table, HCP, Insulating Paper) For our purposes we put all three of the components together. The table being one of the largest and most time consuming components requires significant planning. There are many considerations to planning these components to include, wood type, bracing, portability, and weight bearing capabilities.
1. Order the Metal (HCP, VCP, GCP)
There are a few metal components in this setup, the vertical coupling plane (VCP), horizontal coupling plane (HCP), and ground coupling plane (GCP). All three of these components are referenced directly by the standard which specifies the types and sizes of allowed metals.
How you plan to use the setup, will determine which metal option is best. If the setup is to be shipped often and assembled, a lighter metal, such as aluminum, would be ideal. Another consideration is how metal components are assembled either as individual sheets, or combining multiple sheets of metal. Having a single sheet of metal for the ground coupling plane can make it difficult to transport and have delivered.
The most cost effective option for aluminum is to use multiple sheets as this metal plane needs to be roughly 180cm(~70.8in) by 260cm(~102.4in). Taking a look below, you will find smaller connecting sheets for connecting to the larger sheets providing a single metal plane.
Do some comparison shopping to find these metal sheets at the lowest price. While researching different companies to both provide and cut the metal, we received quotes from upwards of $2,500. This portion of the setup can take a considerable amount of time, and depending on turn around of the metal and quotes, could be the most time consuming.
It is also the most costly component of the setup. Companies that can provide these capabilities can be easily found with a quick google search for metal, or aluminum fabricators. You can find a link below for the company that we went with for our metal sheets.
As a general guideline, spending more then $1000 on these metal components using aluminum is on the higher side. We went through Metal Supermarket they offered a competitive price and have several locations, not only locally in Chicago, but throughout the United States. Their website can be accessed by clicking here.
2. Design the ESD Table & Vertical Coupling Plane (VCP)
When designing the table 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. For our table we opted to use pine 2x4s to build the table. 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.
Another consideration is how large the frame needs to be to support the table top. We allowed a few inches of the edge of the table top.
The final component of the design is the vertical coupling plan. We used the same method to build the VCP as we did the table. To cut the slot in the wood to allow the metal plane to sit in, all that is needed is a wood saw and a straight line (table saw is the ideal solution).
In the picture below you will find the framing and how we designed the legs to slide in with plastic rods to secure them. Should you not need the legs to be removed, you could simple secure them into the frame.
You can purchase the plastic threaded rod & nuts to secure wood legs to the frame from Grainger. The threaded rods come in a variety of sizes and can easily be cut to different lengths. Another great resource of insulating foil/paper is Pyramid Wire & Insulation. The provide delivery throughout the United States and data sheets for products.
3. Assemble Table and IEC 61000-4-2 Setup
The challenge of working entirely with wood is the need for wood glue and pins. This requires time to let the wood glue dry, and to mark and drill the holes for the pins. Below you will find a picture demonstrating how you would accomplish this. In the picture below, you will find the markers to show where to drill the holes that came with the pins. You will also notice a pin is inserted in the hole to give you an idea how this would all come together.
This same method will be done to secure all corners involved with the table and vertical coupling plane. If you have designed the table to come apart, holes will also need to be drilled through the legs and respective frame(s) to provide a hole for the plastic bolts.
As a general rule of thumb, we let all of our joints dry for at least 24 hours to give the wood glue time to dry. To expedite this process you could use multiple clamps to have several joints drying simultaneously. This could bring assembly time of the table and VCP to a matter of days, as opposed to weeks. As always, when dealing and working with power tools, it is crucial to consider safety.
The final step in assembling is purchasing the wire and four 470kΩ resistors. You can reference the standard for specifications on the resistors and wire. The best resource that we have found for these high voltage metal oxide resistors is Caddock. There are a variety of sources for HV wire able to handle an ESD discharge that meets testing requirements. We chose to go with Allied Wire & Cable company.
While designing and building the setup for IEC 61000-4-2 you have referenced the standard, but before you begin ESD testing, it would be useful to be sure all the pieces came together correctly.
We used a third party EMC consultant to review our setup and table to ensure that we did not miss any detail. This can also be done by having a colleague not involved in the project review the standard and your setup. This will remove small mistakes that could lead to larger issues during the testing process.
Wikipedia - IEC 61000-4-2
1. IEC 61000-4-2:2008 - International Electrotechnical Commission Purchase/Preview standard.