5.3 ESD Control Program

Electrostatic discharge (ESD) is invisible, unpredictable, and often devastating to sensitive electronics. A robust ESD Control Program transforms this lurking threat into a managed constant. By consistently grounding everything and using shielding only where necessary, we stabilize yields and ensure products are as robust as they were designed to be.

5.3.1 Defining the Fence: The ESD Protected Area (EPA)

The ESD Control Program defines where materials can be handled without protection (outside the fence) and where protection is mandatory (inside the fence).

The Core EPA Rule

An ESD Protected Area (EPA) is any location where exposed static-sensitive devices (SSDs)—components, bare boards, or partially assembled PCBs—are handled.

• Location: Includes the Component Store, kitting benches, feeder banks, rework benches, and test/flash stations.
• Boundary: EPAs must be visibly defined by yellow/black floor tape and clear signage that states: "EPA—ESD Controls Required."
• Action: Inside the EPA, people must be grounded, surfaces must be grounded, and only approved containers can be used. Leaving the EPA requires components to be secured inside shielding packaging.

5.3.2 The Grounded System: People, Places, and Tools

ESD control is fundamentally about bonding every handler and every conductive surface to a Common Point Ground (CPG). This architecture is the quiet backbone of the program.

People Grounding Protocol

Operators are the largest source of charge, making people grounding the most critical daily check.

1. Tester Gate: All personnel must test their grounding hardware before entering the EPA. This test confirms the wrist strap, footwear, and the path to ground are within required resistance limits (typically 0.8 MΩ to 10 MΩ for the wrist strap).
2. Hardware Use: Wrist straps are mandatory when seated at a grounded bench. ESD footwear is mandatory for all handling and movement across dissipative EPA floors.
3. Visitors: Visitors must use supervised heel straps or wrist straps and handle components only under direct supervision.

Hardware and Workstation Standards

Every surface that touches an SSD must dissipate charge quickly and safely to ground.

• Grounding Architecture: Every station mat, tool ground, and continuous monitor must tie into the same Common Point Ground (CPG) lug, which is bonded to the facility's dedicated ground.
• Surfaces: Mats, tabletops, and floors must be dissipative and continuously bonded to the CPG.
• Carts and Shelves: Metal or dissipative materials must be used. All carts and racks must have visible ground straps and their continuity verified monthly. Never use bare wood or cardboard as a primary surface.
• Tools: Soldering irons, hand tools, and tweezers must be ESD-safe models.

5.3.3 Handling the Un-Groundable: Shielding and Ionization

Not everything can be grounded (e.g., plastics, paper, films). These materials must either be shielded or neutralized with air.

Packaging Rules: Shielding is Transport, Dissipative is Inner Pouch

Use Case	Accept (Required)	Reject (High Risk)
Component Transit	Shielding bags (metal-in), shielding totes with lids.	Pink bags alone, raw bubble wrap, loose paper.
Inner Protection	Pink/clear dissipative bags used only inside a shielding tote.	Plain PE bags, any non-dissipative film.
Paperwork	Dissipative document sleeves, clipboards.	Loose paper or static-cling documents on mats.

Rule of Thumb: If a component leaves the grounded EPA or sits exposed, it must be inside a shielding package.

Ionization (Neutralizing Air)

Ionizers handle localized static charges generated by essential insulators (like plastic tray transfers or label liners) that cannot be grounded.

• When to Use: Use ionizers above benches, conveyors, or in dry environments where materials exhibit nuisance static cling or zapping.
• Maintenance: Emitter pins must be cleaned monthly. Ionizer performance (balance and decay rate) must be verified quarterly (target: ±50 V balance).

5.3.4 Compliance Oversight: Audits and Traps

A program is only as good as its enforcement. Regular, lightweight audits ensure control does not degrade into background noise.

Simple Audit Schedule

Frequency	Check Focus	Outcome
Daily	Wrist-strap tester function; clean mats; current pass stickers.	Log results at the cell PC; green tile on the dashboard means "on time."
Weekly	Spot-check two carts/shelves for ground continuity; wipe ionizer pins.	Log ground resistance readings.
Monthly	Mat resistance check; cart continuity verification.	Store results in the area binder for audit.
Quarterly	Ionizer balance/decay check; solder station tip-to-ground check.	Certify tools and ionizers are in spec.

Common Traps – Smallest Reliable Fix

Trap	Symptom	First Move (The Reliable Fix)
The "Strap Nearby" Trap	Intermittent fails/latent defects at rework benches.	Implement continuous monitors at high-risk benches; enforce daily tester gate.
Pink Bag Creep	Operators use the dissipative pink bag as the primary transport tote.	Mandate the use of shielding totes/bags for any material movement between areas.
Ungrounded Fixtures	Random failures or AOI false calls due to charge build-up on equipment.	Add a ground strap to the fixture; log monthly continuity checks.
Insulator Contamination	Paper piles or vinyl stickers on the working surface.	Use dissipative sleeves/clipboards for all paperwork; ban non-approved insulators from the benchtop.