ESD Knowledge Hub
What is Electrostatic Discharge (ESD)?
A practical guide to ESD and EOS — what they are, why they destroy electronic components, and how ANSI/ESD S20.20 and IEC 61340-5-1 compliant control programs prevent the damage. Written and maintained by a certified ESD Control Program Auditor.
What is ESD (Electrostatic Discharge)?
Additional Information
Electrostatic discharge (ESD) is the sudden flow of static electricity between two objects at different electrical potentials — for example, from a charged human body to a semiconductor device. A discharge you can barely feel (around 3,000 volts) is already hundreds of times higher than the level that damages many modern components, which can fail from events below 100 volts.
ESD is generated constantly in normal work: walking across a floor, sliding off a chair, removing plastic packaging, or handling a PCB without a grounded wrist strap. Because most ESD events are invisible and silent, damage often goes undetected until the product fails — sometimes at the customer's site.
Minutes of Learning vs. Months of Failures
The time it takes to understand ESD is small — the time lost to it is not. A single undetected discharge can trigger weeks of failure analysis, scrapped batches, warranty claims, and difficult customer conversations. Ten minutes spent learning how ESD works, and a trained team behind it, costs a fraction of a single field failure. Awareness is the cheapest ESD control measure there is — and the one every standard puts first.
What are the ESD models: HBM, CDM, MM and FIM?
How sensitive are components really? Devices are classified using standard ESD models.
ESD models (also called ESD failure models or discharge models) are standardized ways of simulating the different real-world discharge events that damage components. Each model reproduces a different source of ESD, and devices are classified by the voltage level they survive under each test.
HBM — Human Body Model (ANSI/ESDA/JEDEC JS-001). Simulates a charged person touching a device with a fingertip: a 100 pF capacitor discharging through 1,500 ohms. This is the oldest and most widely quoted model — a "Class 1A" HBM device withstands only 500 to 1,000 volts, and modern high-speed ICs are often rated below 250 volts. HBM failures typically appear as junction or oxide damage from the relatively slow, energy-carrying pulse.
CDM — Charged Device Model (ANSI/ESDA/JEDEC JS-002). Simulates a device that has itself become charged — for example by sliding along a track, tray, or tube — and then discharges rapidly when a pin touches a grounded metal surface. CDM events last under a nanosecond with very high peak currents, making CDM the dominant failure model in today's automated assembly lines, where machines, not people, handle the parts. Many advanced components are sensitive below 200 volts CDM.
MM — Machine Model (ANSI/ESD S5.2, now withdrawn). Simulated a discharge from a charged conductive machine element: 200 pF with essentially no series resistance, producing a harsher, oscillating pulse. Because MM failures correlate strongly with HBM and it added little new information, the ESD Association and JEDEC formally discontinued MM testing — but the term still appears on older datasheets, so it is worth recognizing.
FIM — Field-Induced Model. Describes charging by electrostatic induction: a device becomes charged without contact, simply by sitting in the electric field of a nearby charged object (such as a regular plastic tray or an operator's clothing), then discharges on touching ground. Field-induced charging is the mechanism behind the modern field-induced CDM (FICDM) test method — and it is why insulators that cannot be grounded must be kept away from ESD-sensitive devices, and why ionizers are required where they cannot be removed.
The practical takeaway: a factory ESD control program must protect against all of these events at once. Personnel grounding addresses HBM, equipment grounding and process design address CDM and machine-type discharges, and field control (keeping insulators out of the EPA, plus ionization) addresses induction charging. This is exactly what ANSI/ESD S20.20 and IEC 61340-5-1 compliance verification measures.
You Can't See ESD — But an Audit Can Measure It
Every ESD control item degrades quietly — flooring loses conductivity, wrist strap cords fatigue, ionizers drift out of balance — and nothing looks different until failures start. An independent audit replaces assumption with measurement: every ground path, every workstation, every EPA boundary verified against ANSI/ESD S20.20 and IEC 61340-5-1, with findings graded and a clear corrective roadmap. It is the difference between believing your program works and proving it — to yourself, and to your customers.
What is the difference between ESD and EOS?
ESD (electrostatic discharge) is a very fast, high-voltage, low-energy event lasting nanoseconds, caused by static charge. EOS (electrical overstress) is a longer-duration event — microseconds to seconds — caused by excessive voltage or current from sources such as unstable power supplies, poor grounding of soldering irons and test equipment, hot plugging, or transient spikes.
They leave different failure signatures: ESD typically causes microscopic gate-oxide or junction damage visible only under failure analysis, while EOS often causes visible burn marks, melted metallization, or charred packages. Controlling them requires different measures — ESD needs a static control program (grounding, ionization, protective packaging), while EOS needs power quality management, equipment grounding verification, and process electrical audits. A complete factory assessment covers both.