Table of Contents
Electrostatic Discharge (ESD) occurs when two static-charged objects unintentionally release electrostatic energy between them. It can occur due to direct contact between two objects, an electrical short, or a breakdown in a dielectric medium.
For printed circuit boards, ESD can damage delicate components, disrupt signal flow, and cause permanent damage. Understanding how ESD affects PCBs is important for preserving their dependability and guaranteeing their function without issues.
This article is a complete guide to electrostatic discharge, covering its definition, damages, standards and how to protect circuit boards from electrostatic discharge damage.
What is Electrostatic Discharge (ESD)?
Electrostatic discharge (ESD) is a brief and instantaneous flow of electrical current surging between two objects that possess different voltage potentials. Usually, this is the result of a charged object coming into contact with, or approaching, a grounded object. This interaction yields an instantaneous discharge.
Main Causes of Electrostatic Discharge
| ESD Source | Key Characteristics & Risks |
| Human Touch | • Discharge from human contact to components • Light touch can transfer ≥2,000V • Primary risk during handling/assembly |
| Charged Devices | • PCB/components accumulate charge during manufacturing/shipping • Sudden discharge when shorted to ground • Affects IC pins/leads |
| Environmental Factors | • Generated by material friction + low humidity (<40% RH) • Dry environments increase charge retention • Causes unpredictable discharges on sensitive surfaces |
| Cable Connections | • Plugging/unplugging connectors creates surges • Direct path to I/O ports (USB, Ethernet, HDMI) • Common in hot-swap scenarios |
How ESD Impacts PCBs
Knowing how ESD can damage electronic components makes it easier to design shielding for PCBs and increases the reliability of the product.
Physical Damage Mechanisms of ESD on PCBs
Although static electricity is relatively common, static charges can reach voltages of several thousand volts, which can be harmful to the dielectric layers and destroy tiny electrical pathways, leading to the complete failure of transistors, gates, and capacitors.
During the assembly or handling processes, even microcontrollers, analog sensors, or high-speed logic units undergo internal damage due to microdischarges of considerably low levels.
When the voltage difference is large enough, a conduction path is created for the current, resulting in a huge current pulse. As this pulse develops, the resulting heat dissipates within the PCB’s components and conductors. At extreme field strengths and currents, the PCB and components may be damaged or destroyed.
Hidden Latent Damage Risks
Electrostatic discharges can cause damage that is difficult to detect on the surface or that does not manifest itself as obvious damage straight away. However, these deep-seated problems can still damage components and cause further issues. In the case of precision-reliant frameworks like medical equipment, vehicle systems, and aeronautical technology, the precision-reliant frameworks can cause system partial failures, unanticipated restarts, or complete circuit damage.
Uncontrolled Static Accumulation in Manufacturing
When producing, examining, or moving a device, the control of goods dealt with static electricity can dangerously accumulate charges that, when shed, remain invisible until the device is powered on. This also emphasizes circuit-level protective measures, as well as grounding and shielding, covering the item, and ESD-safe workstations.
Real Cases of Electrostatic Discharge Failure
Example1: A technician touches an unprotected I/O pin, or when a charged cable is plugged in, sending an ESD pulse straight to the circuit.Example 2: Internal damage occurs to integrated circuit (IC) due to ESD during the assembly or handling processes. Analysis of failure usually indicates to us burnt silicon, fractured passivation layers, and sometimes even carbonized traces inside the IC. These damages are a result of high surges of voltage that either bypass or excessively overpower the protective mechanisms put in place.
Electrostatic Discharge Protection Strategies
Electrostatic protection in PCB design and manufacturing is particularly important because ESD can cause serious consequences. Firstly, protection should focus on key areas such as integrated circuits and connectors.
- ESD pulses can cause current to flow through the cores of integrated circuits, generating high temperatures that can damage components.
- While connectors themselves are not a source of ESD, any static charge that builds up on them can cause it. ESD events frequently occur in metal shrouds and floating pins on connectors in some consumer and industrial products. Inserting a chip, unplugging a cable or pressing a button can put a device at risk of static electricity.
ESD Protection for the Whole Product
- The products with high ESD requirements should avoid the use of metal, plating materials, and other materials that easily attract and gather static electricity to be used in shell or decorative parts. The distance from the device and the alignment must be greater than 2.2 mm.
- If conductor material must be used, the structure should be designed in advance for effective grounding and uniform layout.
- It is not possible to apply grounding to the plated sides of the keys, so you need to focus on the main board and carry out special processing to eliminate a certain amount of static electricity.
Using ESD Diodes and TVS Components
With regard to electrostatic discharge protection on the PCB, surge protection devices and ESD protection devices are critical to the operation of the system as a whole. Damage from electrostatic discharge will be sustained by voltage-limited circuitry without protective devices that reroute voltage discharge. TVS diode protection circuits are among the most common types of circuits found in low-voltage, non-industrial setups.
TVS surge diode protectors offer greater voltage rejection than other electrostatic discharge (ESD) protection components found in power management integrated circuits (ICs) or microcontrollers.
The varistor is another typical electrical part used for ESD protection. Below is a comparison between varisotors and TVS diodes:
TVS Diodes vs. Varistors
| Parameter | TVS Diodes | Varistors (MOVs) | Selection Criteria |
| Response Time | 0.5-5 ns | 5-50 ns | • TVS for >1GHz high-speed interfaces • MOVs acceptable for power lines |
| Clamping Voltage | Tight control (e.g., 12V → 22V clamp) | Wider tolerance (±20%) | • TVS for voltage-sensitive ICs (MCUs, FPGAs) • MOVs for non-critical power rails |
| Lifetime | >10⁹ surge cycles | Degrades after 10³-10⁵ surges | • TVS for frequent ESD environments • MOVs for occasional surges |
| Leakage Current | Low (µA range) | Higher (mA range) | • TVS for battery-powered devices • MOVs for mains-powered systems |
| Capacitance | Low (0.5-50 pF) | High (100pF-10µF) | • TVS for high-speed data lines (USB/HDMI) • MOVs for AC/DC inputs |
| Cost | $0.05-$2.00 | $0.02-$0.50 | • MOVs for cost-sensitive bulk protection • TVS for critical signal paths |
| Failure Mode | Fails short-circuit (safer) | Fails open-circuit (fire risk) | • TVS in medical/safety-critical apps • MOVs require |
Considerations for PCB Layout
- Traces should be minimized in length where diodes are mounted next to the buttons or ports.
- Optimal protection requires that the trace length from a USB port to a TVS diode be less than 5mm to reduce inductance and provide rapid clamping during ESD events.
- Short, wide traces also help reduce resistive barriers to the flow of ESD energy.
- Ground signal layer improves the ability of the system to absorb discharges and also improves the current return path.
Optimizing Grounding and Shielding
- Attaching the PCB ground to a metallic box or chassis provides additional protection against Electrostatic Discharge (ESD). This method diverts dangerous energy flow from components towards the ground system.
- Connect the TVS ground pin directly to a ground plane at the same level and use multiple ground planes where possible.
- Well-placed grounding vias near critical locations also help to control the discharge pathways. Ensure that the ground plane has nearby vias connected to adjacent internal ground planes.
Applying Coatings and Handling
Conformal coatings isolate exposed surfaces from direct discharge while simultaneously protecting them. While an item is being produced or transported, the use of grounding, antistatic bags, ESD-safe practices such as grounded workstations is also important in eliminating static electricity build-up as well as preventing unintended discharges.
Diagnostic & Testing Standards
Checking how sensitive a printed circuit board (PCB) is to electrostatic discharge ESD is important to guarantee product reliability.
Testing Standard: IEC 61000-4-2
The most renowned level of reference for electrostatic discharge testing is the IEC 61000-4-2 standard. It demonstrates the complete ESD event simulation process in practical scenarios. It includes both contact discharge, where an ESD gun touches the test point directly, and air discharge, which simulates an ESD arc through the air.
Testing is usually done at voltages of ±2 kV to ±8 kV for specific product classes.
- Medical Devices:
- Contact Discharge: ±8 kV (ensures patient safety).
- Air Discharge: ±15 kV (ensures patient safety).
- Automotive ECUs (Electronic Control Units):
- Test Voltage: ±15 kV and higher (high ESD exposure in vehicle environments).
IEC 61000-4-2 standard seeks to assess the performance of the PCB and its components under instantaneous electrostatic stress. Results have been classified into four performance categories:
- Class A: No performance degradation or functional loss.
- Class B/C: Malfunction or deviation from the expected performance that is automatically recoverable.
- Class D: Irreparable damage or failure that requires manual intervention for repair or replacement.
As with any diagnosis, the identify-issues phase can employ skilled personnel using oscilloscopes, current probes, and high-speed cameras to track the discharge path and pinpoint design vulnerabilities. Discharge compliance requirements of IEC 61000-4-2 are pivotal not only for attaining worldwide compliance on the safety of electronic devices, but also for safeguarding electronics in environments susceptible to electrostatic discharges over time.
Conclusion
Protecting PCBs from ESD requires a multi-layered defense strategy. Designing for ESD protection in PCBs requires TVS and Zener diodes to be placed spatially to provide protective covering as well as implementing low impedance grounds, having a well-designed protective case, applying serviceable coatings, and controlling handling and storage to very rigid standards.
By integrating these approaches, designers can build PCBs that survive real-world electrostatic threats. For enduring protection against evolving ESD challenges, partner with experts like ELE PCB to future-proof your electronics.
Contact us today to reduce electrostatic discharge risk and get reliable PCB products!
FAQs
A1: While ESD damage most often goes unnoticed, it can lead to very small internal component failures within the integrated circuits or leave faint burn marks alongside cracked packages or open traces. The device can have functional issues like partial resets or total failure. Identifying issues usually requires the use of thermal imaging or scanning electron microscopes.
A2: The problem is likely a result of latent ESD damage—small electrostatic discharges caused during production or handling may not lead to complete failure immediately, but they can compromise the internal architecture of the component. Electrical stress, when combined with the device’s environmental conditions, will eventually exceed the weakened device’s threshold and lead to failure.
A3: ESD barriers are commonly found at the I/O ports, USB ports, antennas, exposed pads, and test points. These regions of a PCB are the most vulnerable to ESD threats and therefore require ESD protection measures.
A4: Conformal coatings offer some dielectric isolation but, by themselves, do not fully mitigate ESD damage. They help minimize the intrusion of physical contacts, but voltage peaks remain unmitigated. Protection against ESD must integrate appropriate grounding, relevant circuitry (“grounding scheme”), and physical layout components.
CONTACT US
English 
Italian 
Hungarian