Slide 77 -
CAPT JESSE D. S. MORGAN, III
Additional Slides by
Technical Assistance by
Steve Gerken and Mike Manders
AF ESD Control Center
Materials Integrity Branch
Materials and Manufacturing Directorate
Air Force Research Laboratories
AFMC ELECTROSTATIC DISCHARGE (ESD) AWARENESS TRAINING Credits What is ESD?
Electrostatic Discharge (ESD) is the discharge of stored static electricity.
Some circuits today are sensitive to as little as 25 volts. Typically humans begin to feel a static discharge at 3500 volts.
You can damage a circuit without feeling it! Notes Included ELECTROSTATIC DISCHARGE (ESD)
CONTROL TRAINING For those viewing this on their
computer, most of the slides
have their ‘Notes’ pages filled
in which amplify the information
provided on the slides.
Version 3a 9/5/03 Overview Extent of ESD Damage
Summary of ESD Principles
Effects of Humidity
Controlling Body Voltage
Marking, Labeling, and signs
The Role of Capacitance
Reference Photo taken on a Microscope of ESD damage ESD Damage, 1st of 7 Extent of ESD Damage A DEMO on a MOSFET A 3N157 MOSFET is lying on a circuit board to
illustrate the relative size of the all metal package. An ESD Shock is applied Microscopic Postmortem There is no visible damage at 150 power ! 2500 Magnification At 2500 power, damage to a via is seen. Susceptibility “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.39 Susceptibility of Various Devices Exposed to ESD Extent of ESD Damage Telephone Systems 78 79 80 81 Cost in Millions 0 94 129 150 160 43 43 20 40 60 80 100 120 140 160 Year = Range of ESD Damage 25 35 Extent of ESD Damage “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.17 Estimate of Telephone System ESD Costs “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.19 Published ESD Losses 1980 Delco Electronics study on Auto $22M
Electronics Product ESD Failures
1983 AT&T HIC Shop ESD Losses 39%
1984 USAF Missile Guidance Video Board $492,000
ESD Failures (250 Failed)
1984 USAF Depot ESD failures $788,000
1985 Early IBM Printer Module ESD Failures 62% Extent of ESD Damage Air Force’s ESD Estimate 1988 USAF, A Review of EOS/ESD Field Failures
in Military Equipment. Capt Thomas Green
1988 EOS / ESD
Symposium Proceedings Up to 12 %
ESD. Extent of ESD Damage Estimate of Failures Due to ESD Damage in Manufacturing Extent of ESD Damage EOS/ESD Damage During Manufacturing.
Data from 23 designs from High Reliability Facility.
Out of 1193 Processing Failures.
There were 414 EOS/ESD Failures.
At Another Plant 1607 Devices Were Analyzed.
The Conclusion in 1993 was.
“25.8 % of the product rejected by this.
facility was damaged by the cumulative.
effects of EOS and ESD, all of which.
“Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.20 Repair Cost vs Discovery REPAIR COSTS
Extent of ESD Damage “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.16 Directives, 1st of 6 Air Force Policy Directive 21-1 and 21-3
“Compliance with AF T.O.s is mandatory”
T.O. 00-25-234, General Shop Practice Requirement for the Repair, Maintenance, and Test of Electrical Equipment.
ANSI/ESD S20.20, Development of an ESD Control Program is replacing Mil-Std-1686
MIL-HDBK-263B, Electrostatic Discharge
Local Operating Instructions Directives The following Air Force documents authorize
AF time and money for ESD Control as indicated
Section 7 of T.O. 00-25-234)?
AF Policy Directive 21-3
AF Policy Directive 21-1
AFI 24-202 Directives Authorize Time & Money Mandatory Compliance Directives AIR FORCE POLICY DIRECTIVE 21-3, “Technical Orders”
Says… “Compliance with Air Force T.O.s is mandatory”
Includes TO 00-25-234
AIR FORCE POLICY DIRECTIVE 21-1 “Managing Aerospace Equipment Maintenance”
Defines Aerospace Equipment as “Equipment used and maintained to meet the Air Force mission. It includes aircraft, missiles, space equipment, communications, electronic equipment, avionics, engines, training equipment, support equipment, aerospace ground equipment, sound suppresser systems, test, measurement and diagnostic equipment and major-end-items of all equipment” Directives AIR FORCE INSTRUCTION 21-116 “Maintenance and Management of Communication Electronics”
Para 18.104.22.168.7.9, under responsibilities of the Maintenance Support Representative (MSR) requires:
“Compliance with Electrostatic Discharge practices, where applicable. (TO 00-25-234)”
TECHNICAL ORDER 00-25-234, “General Shop Practice Requirements for the Repair, Maintenance, and Test of Electrical Equipment”
Says… “The provisions contained herein are applicable to Air Force and contractual personnel engaged in repair, maintenance, or test of Aerospace Electronic Equipment” AFI 21-116 Directives AIR FORCE INSTRUCTION 24-202 “Preservation and Packaging” Chapter 2 (Packaging Operations), paragraph 2.4:
Packaging Line Layout should include: “At least one electrostatic discharge (ESD) protective workstation where trained personnel can package sensitive (ESDS) items. This must include a conductive work surface and personnel grounding devices. TO 00-25-234, Section VII, contains detailed information about ESD protective workstations. Post signs prohibiting entry of unauthorized personnel and static-producing materials in areas designated for packaging ESDS items” Supply is to Comply ESD Control in Supply Directives AIR FORCE INSTRUCTION 24-202 Chapter 3, “Preserving Supply and Equipment Items”, para 3.2, “Electrostatic Discharge Sensitive Items” says:
3.2 “Never handle ESD-sensitive items, regardless of condition, without their protective packaging except at a grounded ESD workstation.”
3.2.1. Use care in opening ESD items. ESD bags are usually constructed with enough extra material to allow for at least one additional heat seal, thereby facilitating reuse in the maintenance activity.
3.2.2. Identify ESD items by Type Cargo Code 3 on DD Form 1348-1A, and by special interior and exterior sensitive-electronic-device caution label . Supply & AFI 24-202 Electrical Definitions Conductors - Materials that permit the free
movement of electrons.
Electrons - Small negatively charged particles
Electric Current - Movement of free electrons
Insulators - Materials that impede the free
movement of electrons.
Negative Charge - A surplus of electrons
Positive Charge - A deficiency of electrons
A Proton - A positively charged particle Ms. Kim Wagner, Hill AFG, OO-ALC / TIUBA Definitions Classification Sheet Resistivity 100-106 Ohms
106 to 109 Ohms
Not Defined Section 7 of AF T.O. 00-25-234 Conductive
Insulative 100-105 Ohms/Square
105 to 1012 Ohms/Square
Greater than 1012 Ohms/Square Ohms / Square is done with special electrodes and converted
to a number that is about 10 X more than is obtained by 7.8 a
Work Surface Test Procedure. Resistance Classification Definitions Tribocharging
Separation of surfaces
Rubbing of surfaces together
Footwear against the floor
Clothing against anything it touches
Flow of fluids
Fuel, oil and water ESD Physics, 1st of 6 ESD Physics Ben Franklin was surely protected by the Angels during his foolish kite stunt, or should we say shunt? Ms. Kim Wagner, Hill AFG, OO-ALC / TIUBA Ben Franklin Painting At the Molecular Level Both Molecules are
Electrically Neutral Both Molecules are
Electrically Charged ESD Physics Like Charges Repel Opposite Charges Attract Charge, Attract & Repel ESD Physics Charges Electric Field Demonstrations Around insulators
Around human body standing on an insulator
With wrist strap
Without wrist strap
Absent around grounded conductors ESD Physics Charge Distribution ESD Physics Retention of Charges GROUNDED CONDUCTOR GROUNDED CONDUCTOR
no charge no charge GROUNDED CONDUCTOR INSULATOR
no charge charged INSULATED CONDUCTOR INSULATOR
charged charged INSULATOR INSULATOR
charged charged “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.28 ESD Physics Retention of Charges After Separation of Surfaces
“Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.32 Tribocharging Tribocharging Triboelectric Series Amount & Rate of Charge Tribocharging Amount of Charge Generated
- Relative position in triboelectric series
- Intimacy of contact
- Rate of separation
- Coefficient of friction
Rate of Discharge
- Conductivity of materials
- Relative humidity
Moisture on surface
“Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.37 Effects of Humidity Winter, Low Humidity, High Static
Extra caution is necessary
The colder it gets, the more electrostatic discharge
Summer, High Humidity, Low Static
Exception is Lightening
Difficult to demonstrate static events
Desert Areas and at High Atmospheres
These places have low humidity
Static is a problem year around Varies with Season Location and and Time Voltage & Humidity Means of Static Generation Electrostatic Voltages
Refer to Table 7-2 in T.O. 00-25-234 10% 40% 55%
R.H. R.H. R.H. Person Walking Across Carpet 35,000 15,000 7,500
Person Walking Across Vinyl Floor 12,000 5,000 3,000
Worker at a Bench (No wrist Strap!) 6,000 500 400
White Styrofoam packing 120,000 50,000 15,000
Common plastic bag picked up from bench 60,000 25,000 10,000 Effects of Humidity Notice that with higher humidity, the charging potentials
decrease significantly but are still at damaging levels. “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.38
Voltages at Various Humidities ESD Control Work Areas T.O. 00-25-234, Section VII Requires: ESD Control Work Area Survey:
The Work Area Survey (performed by the ESD POC) defines the ESD work area and identifies the necessary ESD control items required for that work area.
Keep Two Basic Rules in Mind:
Handle all ESD Sensitive items at an approved static control workstation.
Transport and store all static sensitive components, circuit boards, assemblies and systems in static shielding (Faraday Cage) packages or containers.
ESD Control Work Areas T.O. 00-25-234, Section VII Requires: ESD Control Work Area Certification:
The Work Area Certification is an evaluation by the ESD POC to ensure an ESD work area meets the requirements of the Work Area Survey.
The appropriate certification document (letter signed by ESD POC) shall be posted at the entrance to the ESD work area or in a readily accessible file.
Controlling Body Voltage Wrist Straps Purpose:
An ESD control wrist strap is used to prevent body
voltage from damaging ESD sensitive items.
Typically, an ESD control wrist strap should be worn anytime you are handling an ESD sensitive item.
Single conductor wrist straps shall be tested prior to first use each day per person. Wrist Straps Advantages:
Drains body voltage to ground
An economical ESD solution
Can be used almost anywhere
Prevents body voltage buildup
Adjustable size and cord length
Ease of use Controlling Body Voltage Disadvantages:
You have to remember to use them.
Requires testing !
You don’t know when they are working !
You have to test them periodically
Reasons for test failures:
They frequently do not make good
body contact because:
Body hair, Dry skin, Loose fit
Worn Cuff, Broken cord, etc. Controlling Body Voltage Wrist Straps Wrist Straps Controlling Body Voltage Wrist Straps T.O. 00-25-234 requires that
all wrist straps have adjustable
Metal wrist strap cuffs have
not been approved. Adjustable Cuffs WARNING The personnel wrist strap shall not be
worn when working on energized
parts, assemblies and equipment. Controlling Body Voltage Wrist Strap Warning Current, Physiologic Effects (Ref. MIL-STD-454) Also in Table 7-4 of TO 00-25-234 Effect of Electrical Current on Humans Controlling Body Voltage Controlling Body Voltage Wrist Strap Testers, Electrical Aspects Don’t use an Ohmmeter to test wrist straps. Wrist Strap Testing Non-Linear Resistance Skin Resistance is Non-Linear A DMM puts out less than a volt when measuring
ohms; therefore, a good cuff will test as defective. VERY
REQUIRED Controlling Body Voltage Wrist Strap Continuous Monitors Resistance Measurement Type:
The system resistance is continuously
monitored during use.
Resistance Range: 0.8 to 10 Meg ohms Voltage Sensing Type:
Body Voltage is monitored continuously.
Acceptable Voltage Range: 0 to +/-10V Controlling Body Voltage Continuous Monitors Wrist Strap Continuous Monitors
Both types require dual wire cords
and special wrist strap cuffs. Dual Wire Cords Controlling Body Voltage Footwear Testing
Refer to ESD STM97.1-1999
Demonstrate Footwear Test with:
Integrated wrist strap / footwear tester
Portable Flooring Megger
Demonstrate the Footwear Test
Stocking Feet Controlling Body Voltage Footwear Testing Lab Data on Max Body Voltage
Without Wrist Strap Actual Lab Data
On Nylon Carpet At 10 % RH
With Combat Boots - 840 V
With ESD Shoes 215 V
On ESD Carpet
With Combat Boots 558 V
With ESD Shoes 41 V
Good ESD control requires a
complete system approach! Controlling Body Voltage Footwear/Floor System SUMMARY OF ESD CONTROL.
Handle all ESD Sensitive items at an ESD.
Transport and store all ESDS items ( both.
reparable and serviceable) in static.
shielding and non-charge generating.
packages or containers. Packaging, 1st of 8 TO 00-25-234 Chapter 7, 7-5.b Packaging ESD Packaging Objectives
Immune to Tribocharging
Allow charge transfer from package exterior to an ESD protective worksurface Packaging Objectives Mil-Prf-81705D for ESD Protective, Heat-Sealable, Barrier Materials
A Navy Spec 3 Sep 98
Type I Not transparent, Water-vapor proof, ESD
protective, EMI and ESD shielding. Heavy duty.
Type II Transparent, Waterproof, ESD protective and
dissipative. Pink Poly fits here.
Type III Transparent, Waterproof, ESD protective and
static shielding Packaging Types 1, 2, & 3 EMI/Static Shield Bag (Type I)
Top of the Line, heavy duty outer wrap.
Required for long
water vapor &
ESD Protective. Packaging Type 1, details Pink Poly Bags (Type II).
Pink Polyethylene reduces tribocharging.
Does not provide.
good ESD protection.
Is used to protect.
from physical damage.
Shown: Zip Lock Bubble.
Wrap. Type 2, details Packaging Static Shielding Bag (Type III)
Transparent, Local use, Shielding bag
Reduces need to open bags
(not vapor proof)
(not magnetic fields)
Dissipates a Charge Packaging Type 3, Details Avoid Unnecessary Charge Generators
Styrofoam materials Clear Polyethylene and
and bags Packaging Materials to Avoid Demonstrate the Properties of the three types of bags:
Vapor and water Resistance
This is not a
Faraday Cage ! Packaging, Demos Packaging Packaging When does ESD susceptibility stop?
When ESD sensitive items are properly packaged in ESD control packaging materials.
When the level of assembly or packaging is such that a complete electrostatic shield (Faraday Cage) exists around the item.
Faraday Cage Examples:
ESD Shielding Bag/Pouch, Conductive Tote Box (with lid), Conductive Case/Enclosure
Cabinets, Shelves, & Work Surfaces Cabinets, Shelves, & Work Surfaces Requirements:
Ground cabinets, shelves, and work surfaces used during handling or storage of ESD sensitive items.
All ESD control work surfaces, storage cabinets, and shelves shall be tested annually.
Non ESD designed shelves and storage cabinets may require fitted ESD work surface material to meet this requirement.
Cabinets and shelves used exclusively for storage of non ESD Sensitive items (or ESD Sensitive items protected by a complete Faraday Cage) do not require a ground connection or periodic testing.
Connector Caps, NASM5501/31 & 32 Formerly Mil-C-5501/31A & 32A
They complete the Faraday Cage
They protect against discharge to the pins.
They keep moisture and dust out.
They need to be conductive to work.
Pink Poly will not work
None of the colored ones will protect electronics
They can be tested with a DMM
There is a supply problem
Some are not labeled correctly. ESD Connector Caps Marking & Signs, 1st of 4 Marking, Labeling, & Signs Equipment Label
TO 00-25-234, Fig 7-8
Attach on a readily visible exterior surface,
if space is available and does not hinder
operation of the item. Unit Pack Label The Unit Pack Label
TO 00-25-234, Fig 7-11
Attach to both sides of outermost bag. Marking, Labeling, & Signs Shipping Container Label Shipping Container Label
TO 00-25-234, Fig 7-12
Attach to Fast-Pack, Intermediate Pack, Exterior Pack, or Shipping Container which contain the unit packs. The preferred color
scheme is shown. Marking, Labeling, & Signs ESD Work Area Sign ESD Work Area Sign
TO 00-25-234, Fig 7-16
Placed at or near the entrance to ESD
Work Area. Marking, Labeling, & Signs ESD Worksurfaces, 1st of 4 TYPES OF ESD WORKSURFACES
None approved at this time
They have smooth hard surfaces, but do not dissipate charge at low humidity.
These are most commonly used.
Available in standard 2 x 4’ size (Table 7-3 item 16)
The 40’ Roll, Item 19 in Table 7-3, does about 10 work benches
These are portable and have CPG & W/S ESD Worksurfaces Permanent Type Permanent ESD Workstation Surface.
Glued to the wood subsurface.
Prevents sliding and buckling of the surface.
Durable hard rubber increases service life.
Surface hardness is between Rigid and Cushioned.
Passes AF’s static dissipation, and resistance.
tests. Refer to items 1 - 12
in Table 7-3 ESD Worksurfaces ESD Worksurfaces What to do with a non ESD Workstation?
Add a 2 x 4’ ESD control work surface.
Sits on top of existing surface.
Reduces cost of replacing entire workstation
Reference Table 7-3, item 13 in T.O. 00-25-234.
Cleaning them CLEANING WORKSURFACES.
Best to use 70 / 30 IPA / water.
Do not use any silicones !
Do not use oils or waxes !
Demonstrate Testing the Work Surface.
Test Annually or sooner if desired.
The Work Surface Test Procedure is in 7-8 a.
A Megohmmeter and a 5 LB electrode is used.
Test points from the surface to the CPG. ESD Worksurfaces Scrim Layer Functions Scrim Layer Functions
Provides a uniform top to top resistance
It is part of the grounding system
Test the electrical contact from Snap to Scrim
Use a DMM or Megger across the Snaps
ESD Worksurfaces Air Ionizers, what they do IONIZED AIR REMOVES CHARGES
FROM JOB ESSENTIAL NON CONDUCTORS
LAMINATED SCHEMATICS & DRAWINGS
AND FROM ISOLATED CONDUCTORS
NEED TO MAINTAIN A BALANCE OF
POSITIVE & NEGATIVE IONS AIR IONIZATION When to use Ionizers AIR IONIZATION Use When:
The Work Area Survey requires it. Demonstrate Value of Ionization: Ionizers require
periodic testing. Refer to 00-25-234
7-7.d.6.a View of Open Outlet Box Showing Equipment Grounding Conductors. Grounding, 1st of 5 Grounding Wiring Verification Test Utility Wiring Verification Test is done first.
Par. 7-5.e(3)(b) of T.O. 00-25-234. photo Grounding Utility Ground Wiring Verification Check,
Par. 7-5.e(3)(c) Utility Ground Check Item 66 of
Table 7-3 Grounding Grounding Resistance Check from Bench’s Groundable point to
Par. 7-5.e(3)(d) Bench Ground Check Common Point Ground USE AN OHMMETER TO CHECK CONTINUITY FROM THE CPG TO:
SHELF MATS Grounding A KEY PLAYER IN ESD CAPACITANCE The Role of Capacitance Capacitance Equations Q = CV C = Q / V V = Q / C Q - charge in coulombs
C - Capacitance in farads
V - potential in volts Nanocoulomb (nc) = 10-9 C
Picofarad (pF) = 10-12 F CAPACITANCE EQUATIONS The Role of Capacitance