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Annex 1 (BE01) — Lesson BE.01.02 • TLO: 28XX-MAIN-1001 • ELOs: 28XX-MAIN-1001a, 1001b, 1001c • Reference: TM 9999-15/2

ESD & Electrical Safety

Personal safety and Electrostatic Discharge (ESD) prevention govern every maintenance action at the electronics bench. While electrical shock presents an immediate life-safety hazard to the technician, undetected electrostatic discharge degrades or destroys sensitive solid-state components and deadlines tactical equipment.

1. Physiological Effects of Electrical Shock

Electrical shock is the sensation and involuntary muscular spasm caused by electrical current ($I$) passing through the human body when two parts of the body complete an energized electrical path.

Core Principle: It is current—not voltage—that causes physiological injury. Any voltage source capable of driving current through the body’s resistance along a conductive path presents a shock hazard.

Three Factors Determining Shock Severity

1. Body Resistance ($R$): By Ohm’s Law ($I = \frac{E}{R}$), lower body resistance permits higher current flow. Dry intact skin offers significantly higher resistance than wet, perspiring, or broken skin, or skin in contact with metal jewelry.
2. Current Path: The entry and exit points dictate which vital organs lie in the circuit. A hand-to-hand or hand-to-foot path crosses the chest cavity, heart, and diaphragm, creating maximum lethality.
3. Duration (Time): The longer current flows through the body, the greater the thermal tissue damage, respiratory arrest risk, and probability of fatal cardiac disruption.

Physiological Thresholds of 60 Hz Current

2. Shock Avoidance & Emergency Rescue Protocol

The Shock Avoidance Triad: Isolate, Insulate, Ground

1. Isolate: Remove power (de-energize and unplug) before servicing equipment. Keep protective covers, doors, and interlock enclosures installed whenever active troubleshooting is not underway. If circuitry must remain exposed, post clear warnings to nearby personnel.
2. Insulate: Use only approved, insulated hand tools and test leads. Inspect power cords, extension cords, and probe insulation before every use for cracks, fraying, or exposed conductors.
3. Ground: Electric current follows the path of least resistance. Properly grounded equipment chassis direct stray fault currents and voltage spikes safely to earth ground rather than through the technician’s body.

Safe Probing & Measurement Habits

• Barrier Test Probes: Always use multimeter test probes equipped with finger safety guards/barriers to prevent fingers from slipping onto bare metal tips.
• Insulated Clips: Always use fully insulated alligator clips when anchoring reference leads.
• Clearance from Metal Chassis: Keep your body, forearms, and knees clear of grounded metal racks, benches, and equipment frames.
• The One-Hand Rule: When probing an energized circuit, keep one hand in your pocket or behind your back. This eliminates the possibility of forming a lethal hand-to-hand current path directly across the heart.

Emergency Response: Electrical Shock First Aid

If a fellow Marine or technician is being shocked:

1. Shut Off Power Immediately: Throw the circuit breaker, main power switch, or emergency power-off (EPO) button at once.
2. Separate Victim Without Direct Contact: If power cannot be cut immediately, use a dry, non-conducting material (dry wooden board, leather belt, dry rope, or heavy dry clothing) to pull or push the victim free of the live conductor. NEVER touch the victim with your bare hands while they are in contact with an energized source, or you will become part of the circuit.
3. Check Breathing & Initiate CPR: If the victim is not breathing, begin CPR immediately. Loosen restrictive clothing around the neck, chest, and waist, and keep the victim warm with a cover.
4. Prevent Physical Exertion: Keep the victim from moving or standing up. After a severe electrical shock, the heart is weakened and irritable; sudden movement or exertion can trigger fatal cardiac arrest.
5. Summon Medical Aid: Send for a Corpsman or medical emergency personnel immediately while remaining with the victim. Never administer stimulants.

3. Electrostatic Discharge (ESD) Fundamentals

Electrostatic Discharge (ESD) is the rapid, spontaneous transfer of electrostatic charge (electrons) between two bodies at different electrical potentials. Although human perception of a static spark typically requires roughly $2{,}000\text{–}3{,}000,\text{V}$, microelectronic junctions and MOSFET gates can be permanently punctured by discharges well below $100,\text{V}$.

Common Static-Producing Activities & Voltages

Three Physical Causes of Electrostatic Charge

1. Friction (Triboelectric Charging): Rubbing or sliding contact between two materials causes electrons to transfer from one surface to the other.
2. Separation: Pulling two contacting surfaces apart (such as unrolling tape, opening a plastic bag, or lifting a shoe off flooring) leaves an imbalance of charge on each surface.
3. Induction: Bringing an already-charged object into the proximity of an isolated conductor redistributes charges within that conductor without direct physical contact, statically charging it via the electrostatic field.

4. Controlling ESD (TM 9999-15/2)

Three Primary Principles of ESD Control

1. Assume All Assemblies Are ESD-Sensitive (ESDS): Treat every circuit card assembly (CCA), integrated circuit, and discrete component as susceptible to static damage.
2. Handle ESDS Items Only When Grounded: The human body readily accumulates charge on skin, hair, and clothing. Always ground yourself at a certified static-safe workstation before touching components.
3. Store and Transport in Static-Shielding Containers: Never transport bare boards or place components in standard plastic bags or styrofoam.

Technical Mechanisms of Static Neutralization

12 Mandatory ESD-Sensitive (ESDS) Device Precautions

1. ALWAYS ground workbenches where ESDS devices are handled.
2. ALWAYS verify that your person is properly grounded (blue ESD wrist strap snug against bare skin) before starting work.
3. ALWAYS inspect component packaging and technical manuals for MIL-STD-129 / JEDEC ESDS warning symbols and handling directives.
4. ALWAYS ground the exterior of an ESDS unit package on the grounded mat before opening it.
5. ALWAYS minimize physical handling of ESDS assemblies (hold circuit cards by their non-conductive edges, never by gold edge-connector fingers).
6. ALWAYS avoid unnecessary movement, scuffing, or clothing friction while working at the bench.
7. ALWAYS hold an ESDS device through its antistatic/electrostatic-free wrap when removing or installing it, if practical.
8. ALWAYS touch the resting surface of an ESDS device with bare skin for at least $1,\text{second}$ before picking up the device.
9. ALWAYS avoid component-level soldering directly inside higher-level equipment assemblies whenever possible.
10. ALWAYS ground the test leads of measurement equipment (multimeters, oscilloscopes) before energizing the instrument and before probing ESDS items.
11. NEVER allow ESDS components or assemblies to contact ungrounded materials (paper, common plastic, styrofoam, clothing).
12. NEVER touch static-generating materials while servicing ESDS equipment without immediately repeating your grounding action.

5. Bench & Troubleshooting Application

Pre-Lab Workstation Verification Checklist

Before building or troubleshooting any circuit on the solderless breadboard:

• Step 1 — Personal Prep: Remove watches, rings, bracelets, and metal dog tags/chains. Ensure no food or beverages are on the bench.
• Step 2 — ESD Grounding (ELO 28XX-MAIN-1001d/e): Verify the ESD field mat is connected to the workstation common ground point. Don the blue ESD wrist strap snugly against bare skin and snap its cord (which contains an internal current-limiting safety resistor) to the grounded mat/bench jack.
• Step 3 — Cord & Equipment Inspection: Inspect power supply leads and multimeter test probes for intact insulation. Confirm the breadboard power supply is disconnected (de-energized) before inserting resistors, switches, or jumper wires.
• Step 4 — Safe De-Energization Upon Completion: At the end of every lab evolution, disconnect the power source from the breadboard, turn the Fluke 77/BN selector switch to OFF, power down bench monitors/test gear as directed, and account for all tools and test leads.

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