Explore some of the knowledge you need to safeguard your electronic products against ESD (electrostatic discharge). Learn about its potential damage, and understand the preventive measures for ESD in the product design process, during manufacturing and transport, and the types of ESD testing that you can do.
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What is ESD?
ESD is basically static electricity or lightning from thunderstorms in its natural form. For electronic devices with ICs and sensitive components or without protection, high-voltage from ESD can burn or melt their electronics or, at the very least, cause minor damage. This is why today’s electronic products really need to pass reliability testing for ESD resistance to assure you that they will be unaffected by this naturally occurring phenomenon. In the old days, for example, TVs had to have a separate unit plugged into the wall that would burn out or blow if ESD of a high voltage hit it to protect the TV itself from blowing up as the arial acting as a lightning conductor or poorly grounded wiring in the house might allow this to occur. (02:24)
3 ESD testing models.
There are a few different types of ESD tests that electronic products commonly undergo in testing labs, including RSQ-Labs, our product testing laboratory:
- HBM (Human Body Model) testing – this simulates the ESD that can be generated from the body (such as when you brush against someone and feel a slight zap) and ensures that the product can withstand this charge. It is both useful and cheap to do, especially for consumer electronics.
- MM (Machine Model) testing – this simulates the scenario where one machine touches another by accident and discharges ESD, perhaps at a higher voltage than the human body. Machines are usually designed to avoid this these days, but as a product designer, it is good to know that your product will be able to avoid damage in this situation. MM testing has a faster discharge time than HBM testing and will identify vulnerabilities in an automated process, so it’s good for manufacturing and industrial devices.
- CDM (Charged Device Model) testing – simulates when a charged device comes into contact with a grounded object. To illustrate the danger of this, consider what happens to people who are struck by lightning…they are the grounded objects! It gives a fast and efficient way to know if ESD will damage equipment and is relevant to automated handling and packaging processes because they use plastics and paper and sometimes in humid environments which can tend to cause ESD. (06:59)
Common tests and voltages.
Regardless of the location, most test labs can conduct ESD testing fairly easily these days and only need an investment of around 10 to 20 thousand dollars to perform them.
A common test is the touch test where you take an ESD gun and touch the product at different points where it might come into contact with a changed human being. Different devices require different voltages and will also be different voltages for air touch where there’s a gap and then a lower voltage for actual physical touching. The more people who might touch a device, the higher the voltage you might test to, and this would go up to very high voltages for, say, airplanes that are likely to be hit by lightning.
For consumer electronics that aren’t handled too much by humans voltages of about 4-8 kV are fine, then for more handled ones 8-16kV.
For industrial equipment, medical devices, automotive vehicles, aerospace vehicles, and so on, the levels of voltage increase. For example, for automotive, you may test up to around 1,500V which is very high. (13:41)
The harm or damage that can be caused by ESD.
ESD testing can identify design issues quickly. But if you skip it, the products are in danger of being DOA as the ESD damages them during transit, or an ESD-charged customer touches the device and damages it, the knock-on effect of these situations being an increase of product returns, warranty costs, angry customers, and bad online reviews. There is even a risk of customer injury or property damage as in the worst cases electronic products might catch fire after an ESD shock, and the lawsuits for this could be very damaging. So ESD testing is as important as reliability testing for avoiding problems once the products hit the market as you know there are sources of static electricity that you can’t control, whereas you can control if the product can withstand them. (18:53)
How to prevent the effects of ESD?
Product design to protect the product from ESD in the field when being used by consumers is one way to protect the products, but on the manufacturing side, we must also be careful.
In a manufacturing facility, many efforts are made to prevent ESD, from ESD-conductive clothing, hats, sandals, wristbands, etc, to the mats at entrances, blue or green floors, desks, ESD-safe tools, and more. During transport plastic-wrapped pallets cause an ESD charge to build up during transportation, so products inside need to be grounded and protected, perhaps with antistatic bags or packaging inside the cartons.
Humidity control is also important, as ESD can be caused by drier air and environments, so the environment should be controlled and kept at normal humidity and temperature.
A continuous improvement goal for the manufacturing facility is helpful, as during the continual audits and assessments of the manufacturing floor, processes, and workers, one goal can be to monitor if ESD prevention is being kept up and followed correctly.
When sourcing your manufacturer you can keep in mind their facility and the environment, paying particular attention to whether they’re using antistatic materials and measures in the factory and if the operators are properly trained in ESD-preventive measures. (25:42)
Product design to prevent ESD.
You will naturally design your product to be suitable for its environment, and there are certain standards for different countries’ ESD requirements that you will bear in mind and test later on.
During the early stages of design, it is worth doing a very quick ESD test on the first prototype as this helps to assure you that your components are resistant to ESD. (35:53)
ESD testing is affordable and effective, so for anyone bringing new electronic devices to market it’s a must. During the design and development phases for your product be sure that your workstations and testing labs are ESD-resistant and design the product’s circuitry to protect your IC and other sensitive components from ESD. Then when you test the product prototypes for reliability you can do compliance screening tests and ESD tests to uncover other issues that you can fix. Typically if you’re testing for reliability, ESDm, and compliance you will give your product the best chance of reaching consumers and working correctly, reducing the chances of poor feedback, warranty claims, returns, and even disasters like fires and so on.
Then, when selecting your manufacturer, be sure that they’re ISO 9000 compliant as this includes having ESD prevention in the correct areas which reduces your risks of ESD damage to products during manufacturing even if you have already designed the product well.
Finally, once the product has started mass production it’s worth running all of the tests on some of the first products coming off the line to assure yourself that production hasn’t caused any ESD or reliability issues. (38:34)