5.1 ESD Control Program (ANSI/ESD S20.20)

Electrostatic Discharge (ESD) is the invisible assassin of electronics. A human can only feel a shock at 3,000V, but a MOSFET gate can be destroyed by less than 100V. The danger is not the "dead on arrival" component; it is the Latent Failure—a component that is wounded but passes functional test, only to fail in the field weeks later. This chapter defines the non-negotiable architecture for the Electrostatic Protected Area (EPA) in compliance with ANSI/ESD S20.20.

The EPA Boundary (The Kill Zone)

The EPA is a hard electrical fortress. It is not a suggestion; it is a discipline.

Requirement: Clearly mark all EPA entrances with yellow/black caution tape and official ESD signage.
Logic:
- If you are inside the yellow tape -> Then you must be grounded.
- If you are a visitor -> Then you must wear heel straps and be escorted by a trained operator.
- If material enters the EPA -> Then it must be removed from cardboard/plastic transport packaging outside the boundary.

Pro-Tip: "Pink" plastic (Dissipative) is not a magic shield. It only prevents charge generation; it does not block external fields. Never use pink bags for shipping outside the EPA.

Personal Grounding Strategy

Gravity holds you to the floor; grounding holds you to zero volts. The method of grounding depends on the operator's posture.

1. Seated Operations (Bench Work)

Primary Ground: Wrist Strap connected to a Common Point Ground (CPG).
Constraint: Heel straps alone are insufficient for seated operators because lifting feet breaks the connection to the floor.
Test: Daily verify wrist strap resistance (Range: 800 kΩ – 35 MΩ).

2. Standing/Mobile Operations (Logistics/SMT)

Primary Ground: ESD Footwear (Heel Straps or ESD Shoes) + ESD Flooring.
Constraint: Both feet must be grounded. One strap is zero straps.
Test: Verify conductivity upon entry using a combo-tester gate.

Managing Insulators (The 12-Inch Rule)

Insulators (standard plastic, styrofoam, scotch tape, acrylic) cannot be grounded. They hold charge until it arcs to your PCBA. You have three tactical options to neutralize them:

Remove: Keep all non-essential plastics (coffee cups, wrappers, personal binders) > 30 cm (12 inches) away from open electronics.
Replace: Substitute standard tools with ESD-safe versions (e.g., ESD mats, conductive bins).
Ionize: If the insulator is essential (e.g., connector housing, label liner), use an Air Ionizer to flood the area with positive/negative ions to neutralize the charge.

If Ionizer is used -> Then verify offset voltage < ±35V monthly.

Packaging Logic (The Shield)

Material movement is the highest risk event for triboelectric charging (friction). Use the correct armor for the environment.

Inside EPA (Work in Progress):
- Use Static Dissipative (Pink) bags or totes.
- Function: Prevents charge buildup during handling.
Outside EPA (Storage/Shipping):
- Use Static Shielding (Metallized/Silver) bags or Conductive Black Totes.
- Function: Creates a Faraday Cage to block external static fields.
- Rule: A pink bag outside the EPA is a failure.

Compliance Verification (Audit or Fail)

A grounding system that isn't measured is a hallucination.

Daily: Operator tests wrist/heel straps. Log results (Pass/Fail).
Weekly: Visual inspection of ground cords (check for fraying/disconnection).
Monthly: Measure Work Surface Resistance (Rtg) and Floor Resistance (Rtg).
- Limit: < 1 x 10^9 Ω.
Quarterly: Ionizer balance and decay time verification.

Final Checklist

Control Point	Requirement / Threshold	Non-Negotiable Rule
EPA Entry	Visual Boundary	No ungrounded personnel past the yellow tape.
Seated Ground	Wrist Strap	Heel straps do not ground seated operators.
Insulators	30 cm (12 inch) Separation	Keep standard plastics away from open PCBA.
Shielding	Silver Bag (Faraday Cage)	PCBs leaving the EPA must be in Shielding Bags, not Pink Bags.
Humidity	> 30% RH	Low humidity increases charge generation risk. Monitor continuously.
Testing	Daily Log	If the tester doesn't print a pass, the operator cannot touch hardware.