Part 1 of an overview on Electrostatic Discharge (ESD) management in chip and electronics manufacturing environments. Effective ESD management in these settings requires a control system built upon three pillars: an equipotential grounding foundation, personnel protection, and a closed-loop process of periodic verification.

 

System Grounding: A dedicated ESD grounding system is typically required, with an internal control standard often set at a resistance of ≤4Ω.

Equipment and Tooling Grounding: The resistance to ground for soldering iron tips must be ≤2Ω, and for test fixtures, it must be ≤1Ω.

Worksurface Mat Grounding: ESD-safe mats and personnel wrist straps must be connected to ground through a 1MΩ resistor to prevent excessive discharge currents that could damage sensitive components.

Equipotential Bonding: All conductive elements—including equipment enclosures, workstations, shelving, and personnel—must be connected to a common grounding reference point. This ensures there is no potential difference between them, thereby preventing electrostatic discharge between objects.

 

1) Insulators, such as plastics or PCB substrates, cannot dissipate charge through grounding; instead, they must be neutralized using an ionizer (ion fan). Ionizers should be installed at ESD-sensitive workstations and throughout the Electrostatic Protected Area (EPA). Requirements include: Ion balance within ±50V (measured at a distance of 30cm); neutralization time of ≤10 seconds (decaying from ±1000V to ±100V); and an airflow velocity of 1.5–3.0 m/s (directed toward the work surface). Maintenance involves cleaning the ion-emitting needles and performing monthly ion-balance testing (documented in an "Ionizer Test Record").

 

2) For operations such as fastening copper busbars to power modules (e.g., IGBTs or SiC devices):

Eliminate the use of standard household-style (two-prong or three-prong) plugs for grounding. In high-risk ESD workstations, these must be replaced with dedicated ESD-compliant grounding systems that feature continuous ground monitoring.

Electric screwdrivers and automated screw-fastening machines must be equipped with real-time ground-monitoring alarm modules.

If a grounding fault is detected, the system must trigger an immediate audible and visual alarm and halt equipment operation, ensuring that work cannot continue under compromised ESD-protection conditions. 3) Requirements for Automated Soldering and Manual Soldering (with Soldering Iron)

Leakage Voltage: Less than 20 mVAC at the soldering iron tip.

Grounding Resistance: Less than 2 Ω from the soldering iron tip to the ground.

 

4) ESD Management for Equipment and Tools

4.1 Grounding System

Main Grounding Electrode: The ESD grounding system for the workshop must be independent, with a grounding resistance of ≤4 Ω (separate from the electrical grounding system). It must be located at least 20 meters away from any lightning protection grounding system. This must be tested monthly and documented in the "Grounding Resistance Test Record."

Workstation Grounding: ESD-safe work surfaces must be connected to the main grounding electrode via a 1 MΩ resistor, with a surface resistance of 10⁶–10⁹ Ω. This must be tested weekly and documented in the "Workstation Surface Resistance Test Record."

Equipment Grounding: Equipment such as SMT placement machines, reflow ovens, wave soldering machines, and test fixtures must be independently grounded with a grounding resistance of ≤4 Ω, tested monthly. For soldering irons, the grounding resistance must be ≤2 Ω and tested daily before the start of a shift (performed by the operator).

 

4.2 Equipment Maintenance

An "Equipment Inventory/Log" must be maintained for all ESD-related equipment (ionizers, grounding systems, test instruments), recording the model, serial number, installation location, maintenance schedule, and test records.

After any equipment repair, ESD parameters must be re-tested; the equipment may only be put back into use once it passes these tests.

The use of unverified alternative tools (e.g., standard screwdrivers, non-ESD-safe tweezers) is prohibited.

 

5) Component Storage and Handling

Storage Requirements: ESD-sensitive components (ICs, MOSFETs, crystal oscillators, etc.) must be stored in ESD-safe trays, metal shielding bags, or on ESD-safe shelving (with a surface resistance of 10⁶–10⁹ Ω). These must be labeled with ESD warning signs (a yellow lightning bolt symbol accompanied by the text "ESD Sensitive"). Storage areas must meet specific temperature and humidity requirements; storing these components alongside flammable or corrosive materials is strictly prohibited. Unpacking Requirements: Unpacking must be performed at an ESD-protected workstation within an Electrostatic Protected Area (EPA). Personnel performing the unpacking must wear wrist straps and gloves. Any components remaining after unpacking must be immediately returned to their shielding bags and sealed (leaving them exposed is strictly prohibited).

Handling and Transport Requirements: PCBs, semi-finished products, and finished goods must be transported using ESD-safe carts (with a surface resistance of 10⁶–10⁹ Ω and grounded wheels) and ESD-safe containers (equipped with lids and clear labeling). The use of standard cardboard boxes, plastic bags, or foam for handling ESD-sensitive materials is prohibited.

 

6) Incoming and Outgoing Inspection

IQC (Incoming Quality Control): Before ESD-sensitive components are placed into storage, the integrity of their packaging must be verified (ensuring shielding bags are undamaged and blister packs are not deformed). The surface resistance of packaging materials must be spot-checked and recorded in the "ESD Incoming Inspection Record." Non-conforming batches must be returned to the supplier, with a requirement for corrective action.

OQC (Outgoing Quality Control): Before finished goods are shipped, the outer packaging must be verified for ESD compliance (ensuring the presence of internal shielding bags and external ESD warning labels). The "ESD Outgoing Inspection Report" must be reviewed and verified. Shipping finished goods without appropriate ESD protection is strictly prohibited.

 

7) ESD System Audits and Management Reviews

An internal audit of the ESD system must be conducted at least once a year (in accordance with the ANSI/ESD S20.20 standard) to identify non-conformities and develop corrective action plans.

An ESD management review must be held at least annually (led by the ESD management team) to evaluate the achievement of ESD policies and objectives, assess the effectiveness of the system, and propose areas for improvement (such as implementing real-time monitoring systems or updating protection standards).

Employees are encouraged to submit suggestions for ESD improvements (e.g., optimizing the design of transport carts or improving packaging materials); effective suggestions shall be rewarded.