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  1. Credits ELECTROSTATIC DISCHARGE (ESD) AWARENESS TRAINING Prepared by CAPT JESSE D. S. MORGAN, III Additional Slides by JULIUS BRODBECK Technical Assistance by Steve Gerken and Mike Manders AF ESD Control Center Materials Integrity Branch Materials and Manufacturing Directorate Air Force Research Laboratories AFMC

  2. 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!

  3. Overview • Extent of ESD Damage • Directives • Definitions • Summary of ESD Principles • Tribocharging • Effects of Humidity • Controlling Body Voltage • Packaging • Marking, Labeling, and signs • ESD Worksurfaces • Air Ionization • Grounding • The Role of Capacitance • Reference

  4. ESD Damage, 1st of 7 Micro Wire Extent of ESD Damage Photo taken on a Microscope of ESD damage

  5. A DEMO on a MOSFET A 3N157 MOSFET is lying on a circuit board to illustrate the relative size of the all metal package.

  6. An ESD Shock is applied

  7. Microscopic Postmortem There is no visible damage at 150 power !

  8. 2500 Magnification At 2500 power, damage to a via is seen.

  9. Device TypeRange of ESD Susceptibility (Volts) MOSFET JFET CMOS Schottky Diodes, TTL Bipolar Transistors SCR 100 - 200 140 - 1,000 250 - 2,000 300 - 2,500 300 - 7,000 600 - 1,000 Susceptibility Extent of ESD Damage Susceptibility of Various Devices Exposed to ESD “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.39

  10. Telephone Systems Extent of ESD Damage Estimate of Telephone System ESD Costs 160 150 160 129 140 120 94 100 Cost in Millions 80 60 40 43 43 20 35 25 0 78 Year 79 80 81 = Range of ESD Damage “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.17

  11. Published ESD Losses Extent of ESD Damage 1980 Delco Electronicsstudy 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% “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.19

  12. Air Force’s ESD Estimate Extent of ESD Damage Estimate of Failures Due to ESD 1988 USAF, A Review of EOS/ESD Field Failures in Military Equipment. Up to 12 % of the Failures could be ESD. Capt Thomas Green 1988 EOS / ESD Symposium Proceedings

  13. 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. were avoidable.” “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.20

  14. Hewlett Packard Commercial Product $1 $5 $50 $500 Level where Fault was Discovered Device Board System Field Gould Military System $5 $50 $1,500 $10,000 Repair Cost vs Discovery Extent of ESD Damage REPAIR COSTS “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.16

  15. Directives, 1st of 6 Directives • 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

  16. Authorize Time & Money 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 21-116 • AFI 24-202

  17. Mandatory Compliance Directives AIR FORCE POLICY DIRECTIVE 21-3, “Technical Orders” Says… “Compliance with Air Force T.O.s ismandatory” • Includes TO 00-25-234 AIR FORCE POLICY DIRECTIVE 21-1 “Managing Aerospace Equipment Maintenance” Defines Aerospace Equipmentas “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”

  18. AFI 21-116 Directives AIR FORCE INSTRUCTION 21-116 “Maintenance and Management of Communication Electronics” Para 5.17.4.3.7.9, 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 ofAerospace Electronic Equipment”

  19. Supply is to Comply Directives ESD Control in Supply 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”

  20. Supply & AFI 24-202 Directives AIR FORCE INSTRUCTION24-202Chapter 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 .

  21. Electrical Definitions 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

  22. Conductive • Static Dissipative • Insulative 100-105 Ohms/Square 105 to 1012 Ohms/Square Greater than 1012 Ohms/Square Section 7 of AF T.O. 00-25-234 • Conductive • Static Dissipative • Insulative 100-106 Ohms 106 to 109 Ohms Not Defined Resistance Classification Definitions ClassificationSheet Resistivity 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.

  23. + + + + ESD Physics ESD Physics, 1st of 6 • Tribocharging • Separation of surfaces • Tape • Binder Pages • Rubbing of surfaces together • Footwear against the floor • Clothing against anything it touches • Flow of fluids • Fuel, oil and water

  24. Ben Franklin Painting 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

  25. At the Molecular Level ESD Physics Both Molecules are Electrically Neutral Both Molecules are Electrically Charged

  26. Charge, Attract & Repel + - + + ESD Physics Opposite Charges Attract Charges Like Charges Repel

  27. ESD Physics Electric Field Demonstrations • Around insulators • Styrofoam + • Teflon - • Around human body standing on an insulator • With wrist strap • Without wrist strap • Absent around grounded conductors

  28. CONDUCTOR NONCONDUCTOR + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + - - + + - - + + + + + + + -+ + - - - + + - - - - + + + + - - - - Before and After grounding Will have Uniform Charge Distribution (Positive Shown) Can have Random Charge Distribution (Mixed Shown) + + - - + + - - + + + + + + + -+ + - - - + + - - - - + + + + - - - - Does not Discharge Complete Discharge “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.27 ESD Physics Charge Distribution

  29. ESD Physics Retention of Charges Retention of Charges After Separation of Surfaces 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

  30. Tribocharging + Glass Human Hair Nylon Wool Lead Aluminum Paper Cotton Steel Wood Sealing Wax Hard Rubber - Tribocharging Triboelectric Series Nickel, Copper Brass, Silver Gold, Platinum Polyester Celluloid Saran Polyurethane Polyethylene Polypropylene PVC Silicon Teflon “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.32

  31. 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

  32. Effects of Humidity Varies with Season Location and and Time • 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

  33. Voltage & Humidity Effects of Humidity Voltages at Various Humidities 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 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

  34. 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.

  35. 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.

  36. Controlling Body Voltage Wrist Straps • Purpose: An ESD control wrist strap is used to prevent body voltage from damaging ESD sensitive items. • Use: Typically, an ESD control wrist strap should be worn anytime you are handling an ESD sensitive item. • Testing Requirement: Single conductor wrist straps shall be tested prior to first use each day per person.

  37. Controlling Body Voltage 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 • Light weight • Ease of use

  38. Wrist Straps Controlling Body Voltage Wrist Straps • 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.

  39. Adjustable Cuffs Controlling Body Voltage Wrist Straps T.O. 00-25-234 requires that all wrist straps have adjustable diameter cuffs. Metal wrist strap cuffs have not been approved.

  40. Wrist Strap Warning Controlling Body Voltage WARNING The personnel wrist strap shall not be worn when working on energized parts, assemblies and equipment.

  41. Current Values (Milliamperes) Effect AC DC 25 TO 400 HZ 0-1 1-4 4-21 21-40 40-100 Over 100 0-4 4-15 15-80 80-160 160-300 Over 300 Perception Surprise Reflex Action Muscular inhibition Respiratory block Usually fatal Current, Physiologic Effects Controlling Body Voltage Effect of Electrical Current on Humans (Ref. MIL-STD-454) Also in Table 7-4 of TO 00-25-234

  42. Wrist Strap Testing Table 7-3ITEMPassing Range Output Ohms Volts 61 8x105 to 1x107 8 - 13 Controlling Body Voltage Wrist Strap Testers, Electrical Aspects Don’t use an Ohmmeter to test wrist straps.

  43. Non-Linear Resistance Controlling Body Voltage Skin Resistance is Non-Linear VERY MOISTURE DEPENDENT. LOTIONS SOMETIMES REQUIRED A DMM puts out less than a volt when measuring ohms; therefore, a good cuff will test as defective.

  44. Continuous Monitors 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

  45. Dual Wire Cords Controlling Body Voltage Wrist Strap Continuous Monitors • Both types require dual wire cords and special wrist strap cuffs.

  46. Footwear Testing 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 • Combat Boots • ESD Shoes • Stocking Feet

  47. Footwear/Floor System Controlling Body Voltage 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!

  48. Packaging Packaging, 1st of 8 SUMMARY OF ESD CONTROL. • STRATEGIES. • RULE 1. Handle all ESD Sensitive items at an ESD. Workstation. • RULE 2. Transport and store all ESDS items ( both. reparable and serviceable) in static. shielding and non-charge generating. packages or containers. TO 00-25-234 Chapter 7, 7-5.b

  49. Objectives Packaging ESD Packaging Objectives • Provides Shielding • Immune to Tribocharging • Allow charge transfer from package exterior to an ESD protective worksurface

  50. Types 1, 2, & 3 Packaging Mil-Prf-81705D for ESD Protective, Heat-Sealable, Barrier Materials • A Navy Spec 3 Sep 98 Three Types: • 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