Electrostatic discharge is a threat that manufacturers of electronic products shouldn’t underestimate as it can damage or even kill products and should influence how your product is designed and manufactured. As we’re a contract manufacturer who often produces electronic devices for our customers, we know the risks, so here are answers to some of the common questions about ESD and its risks for you.
If you are manufacturing electronic products, this one is a must…
10 FAQs we often get about electrostatic discharge and its risks
Here are 10 FAQs about electrostatic discharge that will bring you up to speed based on a recent discussion we had about ESD and ESD testing on our group’s podcast:
1. What is Electrostatic Discharge and why is it dangerous for electronic devices?
Electrostatic Discharge (ESD) is the same as naturally occurring lightning. It can occur on a smaller scale in the factory, the office, or the home, and is an electrical charge that passes between two electrically charged objects, such as your hand and an electronic device. The discharge can cause a short which damages or ‘fries’ sensitive electronic components resulting in the product failing. If you’ve ever been ‘zapped’ when touching a metallic object or brushing past another person, that’s an electrostatic discharge.
2. How can ESD damage electronic components?
An ESD spark, for example, could be at a high enough voltage to result in a current that can break microchips, melt the silicon in circuits, and short our electronic products. Here are a few examples of ESD damage:
- Overpowering components: Many electronic components are designed to handle specific voltage levels. ESD events, which can reach thousands of volts, can be way above this limit. This surge of electricity can fry the delicate circuits within the component.
- Short circuits: ESD can create unintended electrical connections between different parts of a circuit that shouldn’t be connected. This can disrupt the normal flow of electricity and damage the components involved.
- Latent damage: Sometimes, ESD damage isn’t immediately obvious. The zap might weaken the component, making it more likely to fail prematurely down the road. This can be a nightmare for manufacturers as it can lead to field failures after the product is sold.
The unpredictable nature of a discharge could be enough to cause lasting damage to unprotected products which is why they need to be tested for resilience against it and protected accordingly. One way will be to include ESD protection circuitry (we’ll come on to that later).
3. How can products be designed to avoid ESD damage?
ESD should be in the product designer’s mind, as the final product needs to be resistant. Starting by following international ESD protection standards, such as ANSI/ESD S20.20-2021: Protection of Electrical and Electronic Parts, will set you up for success.
There are two main approaches to designing products to avoid ESD damage:
1. Grounding and Shielding
This involves creating a path for ESD current to safely flow away from sensitive components and preventing static charges from building up in the first place.
- Grounding: This involves connecting all conductive parts of the product to a common ground plane. This plane acts as a pathway for ESD current to travel directly to earth ground, bypassing sensitive components.
- Shielding: Sensitive components can be encased in conductive materials like metal enclosures or conductive coatings. This creates a barrier that weakens the electric field and prevents static charges from reaching the components. This is commonly known as a Faraday cage.
2. Component Selection and Circuit Design
Careful selection of components and circuit design practices can also help mitigate ESD risks.
- ESD-tolerant components: Look for components with high ESD voltage ratings. These components can withstand higher voltage spikes without getting damaged.
- Protection devices: Incorporate transient voltage suppressor (TVS) diodes or other ESD protection devices into the circuit. These devices act as a sacrificial element, absorbing the ESD current and protecting sensitive and sometimes critical components.
- Circuit layout: PCB layout plays a role too. Minimize loop areas in the circuit to reduce the potential for induced currents. Keeping ground planes close to signal lines also helps dissipate ESD efficiently.
4. What are the common types of ESD testing?
There are 3 common types of ESD testing to test that the product will be resilient against ESD and that measures put in place, such as implementing ESD protection circuitry, are effective:
- Human Body Model (HBM): As humans move around they generate static electricity. The HBM test simulates electrostatic discharges from human contacts, such as a finger touching the product and through to the earth. The standard HBM test’s voltage is around ±2 kV. This might happen when a consumer handles the product, for instance.
- Machine Model (MM): This simulates a machine or metal tool coming into contact with an electronic device, and the typical voltage is 100-200 V. This might happen during production when an operator works on the product with a tool, for example.
- Charged Device Model (CDM): This is meant to simulate an integrated circuit becoming electrically charged and then contacting another earthed one on a metallic surface at a voltage of 200V – 1kV. This could be during automated production when a circuit that has been held away from the earth by a machine is eventually placed onto a metallic surface.
5. What are typical voltages used in ESD testing for different devices?
Your testing laboratory will advise you on your best options for your electronic product, but in general we suggest these ranges:
- Test at around 4-8 kV for less frequently handled consumer electronics.
- For more frequently handled consumer electronics, 8-16 kV.
- Industrial, medical, automotive, and aerospace devices are tested at higher voltages, up to around 1,500V (consumer safety takes precedence here as these devices should be very resilient to failure as if vehicles fail, for instance, this could result in injury or death).
6. When should Electrostatic Discharge testing be done?
ESD testing should be done throughout the NPI process, as you need to ensure that your design, prototypes, and finished products are all resistant to ESD due to its damage risks. Basically, ESD testing needs to be a part of your general testing plan along with reliability, and more, if you manufacture electronic products. After the products are on sale, you may also do some ESD testing as a part of your Ongoing Reliability Testing procedure, too, just to be sure that future batches remain resilient to ESD damage and nothing has crept into the production process that could be causing the damage.
7. How else can ESD cause problems for a business?
As we have discussed, ESD can damage electronic products, but for the businesses selling them it is also a risk of:
- Increased warranty claims and their associated costs
- Product returns
- Negative reviews
- Lost customers
- Legal cases if consumers are harmed due to a failed product (for example, a vehicle fails during use, or a shorted-out device in the home catches fire)
8. How can a manufacturer reduce the risks of ESD damage during production?
Products can be damaged by ESD in the factory long before they get to consumers.
To safeguard electronic components from electrostatic discharge (ESD) throughout the production process, manufacturers should implement a multi-faceted approach. One crucial aspect involves properly grounding personnel. Operators wear ESD-safe smocks, gloves, and conductive wrist straps. These straps connect them to a common ground point, ensuring any static charge they accumulate is safely dissipated.
Another key element is environmental control. Production areas maintain controlled temperature and humidity levels. Lower humidity reduces the generation of static electricity, while slightly higher humidity helps dissipate existing charges.
ESD-safe tools are another line of defense. These tools are manufactured with conductive or dissipative materials, like rubberized handles. This design minimizes the transfer of static charges between the tool and the components.
Furthermore, ESD-safe packaging is used throughout production, not just for final shipment. Static-resistant bubble wrap, shielded bags, and conductive foam all play a role in protecting components during various production stages.
The work surfaces themselves are also crucial. Grounded workbenches and ESD mats further minimize static buildup around the product as it’s being assembled.
Air ionizers are another weapon in the fight against ESD. These devices neutralize static charges present in the air, significantly reducing the risk of ESD events occurring during production.
Finally, a well-trained workforce is vital. Manufacturers provide regular training to personnel on ESD risks and proper handling procedures for ESD-sensitive components. By understanding these principles and implementing the necessary precautions, employees play a vital role in ensuring the quality and functionality of the finished product.
9. Should you work with an ISO 9000-compliant manufacturer to produce your electronic devices?
Not necessarily, as ISO 9000 is rather vague and many of the auditors lack an understanding of what is important in the production and handling of electronic products. A knowledgeable auditor will raise the topic of ESD prevention with the factory, but there is no assurance that they will fail the audit because of that point.
Suppose you’re making electronic products susceptible to electrostatic discharge damage. In that case, the key is to work with a manufacturer who knows what they are doing and is experienced in manufacturing electronics.
You may also audit them before you start working with them, a best practice that many importers follow, and check that they have implemented ESD prevention and are using some of the techniques mentioned earlier (such as controlled environment, ESD-resistant tools, appropriate uniforms, etc).
10. Can Electrostatic Discharge damage occur after the sale?
Yes, as mentioned, consumers may become electrostatically charged and cause ESD damage to products in, say, the home. Aside from testing the products to ensure that they can survive, there may be certain advice for reducing the risks of ESD that you can/should provide to the customer, perhaps in the operating manual.
Next steps
If you need help with testing your products or have specific questions about ESD testing for your electronic devices, get in touch and we’ll offer you our advice based on your situation and needs.
