3.3 Flooring & Grounding Architecture

The floor is the primary electrical foundation of the EPA. It serves as the sole ground path for mobile operators, carts, and Autonomous Guided Vehicles (AGVs). If the flooring system fails (becomes insulative), every step a technician takes generates triboelectric voltage that cannot drain to Earth. Without a functional floor-ground system, personnel are walking capacitors capable of carrying >3000V directly to the product.

The Resistance "Sweet Spot"

Flooring physics requires balancing two opposing risks: static dissipation vs. electrical safety.

Decision Logic: Resistance Zones

1. IF Resistance (R) < 1.0 x 10^5 Ω → THEN Fail (Conductive).
   • Risk: Lethal shock hazard. If an operator touches live voltage (110/220V), the floor provides a low-resistance path to ground, increasing current flow through the body.
2. IF 1.0 x 10^5 Ω ≤ R ≤ 1.0 x 10^9 Ω → THEN Pass (Dissipative).
   • Target: This is the safe operating window. Charge drains within milliseconds, but resistance is high enough to limit current to safe levels (< 5mA).
3. IF R > 1.0 x 10^9 Ω → THEN Fail (Insulative).
   • Risk: Charge accumulates faster than it decays. The floor is effectively an insulator.

Pro-Tip: Never wax an ESD floor with standard commercial polish. Standard wax is a dielectric insulator and will instantly destroy the floor's conductivity. Use only approved ESD-dissipative floor finish.

System Verification (The "Walking Test")

A conductive floor alone provides zero protection if the operator wears standard rubber-soled sneakers. We measure the System Resistance (Floor + Footwear + Person).

Performance Mandate

• Static Decay: The system must drain a 1000V charge to < 100V in less than 2 seconds.
• Body Voltage Generation (BVG):
  • IF peak voltage on walking operator > 100 Volts → THEN Process Fail.
  • Action: Verify heel strap contact or replace footwear.

Grounding Topology

The electrical connection to Earth (Earth Bonding Point) must be robust and distinct from the standard electrical neutral.

• Hard Ground (Chassis): Connect equipment chassis and machine frames directly to Earth (0 Ω impedance). This ensures breaker trips during short circuits.
• Soft Ground (Personnel): Connect wrist straps and table mats to Earth through a 1 Megohm (1 MΩ) current-limiting resistor.
  • Why: This resistor prevents the strap from becoming a lightning rod or a lethal path to ground if the operator touches a live wire.

Final Checklist