Introduction

Countermeasures against ESD (Electrostatic Discharge) are an unavoidable and important topic for engineers involved in the design of semiconductor devices and electronic equipment. In particular, many designers ask, "Is HBM ±2kV sufficient ESD protection for electronic equipment?"

This article answers this question by comparing two ESD test models used in manufacturing and real-world environments—the Human Body Model (HBM) and IEC 61000-4-2—to determine the level of protection required.

What is Electrostatic Discharge (ESD)?

ESD occurs when a statically charged object approaches or comes into contact with another object, causing a transfer of charge and a large current to flow in a short period of time. This fast, high-energy transient phenomenon can cause serious damage to ICs. ESD occurs not only during the manufacturing process (processing, assembly, testing, and packaging), but also when users actually use the equipment.

Component-level ESD testing: HBM (Human Body Model)

HBM is the most widely used component-level test, simulating ESD caused by a charged human body touching an IC, and is tested to the JEDEC JESD22-A114E standard.

■HBM test conditions
- Uses a 100pF capacitor
- Discharge through a 1,500Ω resistor
・Test voltage: ±1kV to ±8kV
Rise time: 5 to 10 ns
・Decay time: approx. 150ns
・HBM is a test that targets "ESD environments in controlled manufacturing processes" and checks whether ICs can withstand ESD on the manufacturing line.

System-level ESD testing: IEC 61000-4-2

IEC 61000-4-2 is a system-level test designed to simulate the ESD that equipment would experience in a real user environment.

■IEC 61000-4-2 test conditions
・150pF capacitor
- Discharge through a 330Ω resistor
・Rise time: 0.7 to 1 ns
- Waveform with a second peak around 30 ns
・Test positive and negative at least 10 times
・It has a much higher peak current and faster rise time than HBM

■Test level (contact discharge)

Is HBM ±2kV enough? Peak current comparison

HBM and IEC 61000-4-2 have very different peak currents at the same voltage.
■Peak current comparison between ±2kV and ±8kV

The peak current for the IEC is over 5.6 times that of the HBM. Additionally, it can be seen that the peak current for the ±2kV IEC test (7.5A) is greater than the peak current for the ±8kV HBM test (5.33A).
This means that an IC that passes ±8kV HBM may be destroyed by ±2kV IEC.

The figure on the left shows a side-by-side comparison of the current waveforms obtained using IEC 61000-4-2 and HBM under ±8kV conditions. As can be seen from this figure, the IEC 61000-4-2 pulse has a very sharp rise time, with the first current peak reaching its peak in less than 1ns. In contrast, the HBM pulse takes 5-10ns to reach its peak, and the initial current is also relatively modest.

Furthermore, the second current peak in the IEC waveform reaches around 18 A, which is significantly higher than the peak value seen in HBM. Overall, the IEC 61000-4-2 pulse has a faster rise time, a higher current value, and a larger amount of released energy than HBM, placing a much greater load on ICs. Therefore, to protect the entire system from ESD, it is essential to incorporate ESD protection components that can receive high-energy, steep pulses with low impedance.

Why system-level protection?

・HBM is primarily designed for ESD environments within factories.
・IEC 61000-4-2 reproduces the actual environment in which users operate
・All products, including smartphones, home appliances, and industrial machinery, are exposed to the threat of ESD.
・Due to the miniaturization of semiconductors, ICs are becoming more vulnerable to ESD
Therefore, ESD countermeasures at the system level are essential when bringing a product to market.

The Solution: TVS Protection Elements for System-Level ESD Absorption

Semtech is a leading manufacturer of high performance and reliable TVS (Transient Voltage Suppressor) products. TVS absorbs large amounts of energy at high speeds, protecting ICs from ESD and EOS.

We have a lineup that covers a wide range of applications, including "TVS for automotive, industrial equipment, and consumer use."​

Summary

・HBM ±2kV is intended for manufacturing processes and is not sufficient as a protection level for real-world environments.
・System-level IEC 61000-4-2 is a more stringent test than HBM and is essential for the actual use of electronic devices.
・System-level ESD protection such as TVS is required to ensure reliability in the market

In future product designs, it will be important to design products that not only consider HBM values but also assume protection at the IEC level. For more information about Semtech's protective product lineup, please contact Macnica.