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1 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.

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Presentation on theme: "1 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."— Presentation transcript:

1 1 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 ELECTROSTATIC DISCHARGE (ESD) AWARENESS TRAINING Credits

2 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 3 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

4 4 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

5 5 Photo taken on a Microscope of ESD damage Photo taken on a Microscope of ESD damage Micro Wire ESD Damage, 1 st of 7 Extent of ESD Damage

6 6 A DEMO on a MOSFET A 3N157 MOSFET is lying on a circuit board to illustrate the relative size of the all metal package.

7 7 An ESD Shock is applied

8 8 Microscopic Postmortem There is no visible damage at 150 power !

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

10 10 Susceptibility Device Type Range of ESD Susceptibility (Volts) MOSFET JFET CMOS Schottky Diodes, TTL Bipolar Transistors SCR , , , , ,000 “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

11 11 Telephone Systems Cost in Millions Year = Range of ESD Damage 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

12 12 “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 1983AT&T HIC Shop ESD Losses 39% 1984USAF Missile Guidance Video Board $492,000 ESD Failures (250 Failed) 1984USAF Depot ESD failures $788, Early IBM Printer Module ESD Failures 62% Extent of ESD Damage

13 13 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 % of the Failures could be ESD. Extent of ESD Damage Estimate of Failures Due to ESD

14 14 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

15 15 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 Level where Fault was Discovered Device Board System Field Hewlett Packard Packard Commercial Commercial Product Product $1 $5 $50 $500 GouldMilitarySystem $5 $50 $1,500 $10,000

16 16 Directives, 1 st of 6  Air Force Policy Directive 21-1 and 21-3 “Compliance with AF T.O.s is mandatory”  T.O , 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

17 17 The following Air Force documents authorize AF time and money for ESD Control as indicated Section 7 of T.O )?  AF Policy Directive 21-3  AF Policy Directive 21-1  AFI  AFI Directives Authorize Time & Money

18 18 Mandatory Compliance Directives AIR FORCE POLICY DIRECTIVE 21-3, “Technical Orders” Says… “Compliance with Air Force T.O.s is mandatory” – Includes TO 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”

19 19 Directives AIR FORCE INSTRUCTION “Maintenance and Management of Communication Electronics” Para , under responsibilities of the Maintenance Support Representative (MSR) requires: “Compliance with Electrostatic Discharge practices, where applicable. (TO )” TECHNICAL ORDER , “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

20 20 Directives AIR FORCE INSTRUCTION “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 , 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

21 21 Directives AIR FORCE INSTRUCTION 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.” 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 Identify ESD items by Type Cargo Code 3 on DD Form A, and by special interior and exterior sensitive-electronic-device caution label. Supply & AFI

22 22 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

23 23 Classification Sheet Resistivity Ohms 10 6 to 10 9 Ohms Not Defined Section 7 of AF T.O Conductive Static Dissipative Insulative Conductive Static Dissipative Insulative Ohms/Square 10 5 to Ohms/Square Greater than 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

24 24 Tribocharging 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 ESD Physics, 1 st of ESD Physics

25 25 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

26 26 At the Molecular Level Both Molecules are Electrically Neutral Both Molecules are Electrically Charged ESD Physics

27 27 Like Charges Repel Opposite Charges Attract Charge, Attract & Repel ESD Physics Charges

28 28 Electric Field Demonstrations Around insulators  Styrofoam + * Teflon - Around human body standing on an insulator * With wrist strap * Without wrist strap Absent around grounded conductors ESD Physics

29 29 Charge Distribution ESD Physics NONCONDUCTOR CONDUCTOR BeforeandAftergrounding Can have Random Charge Distribution (Mixed Shown) Will have Uniform Charge Distribution (Positive Shown) Does not DischargeComplete Discharge “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.27

30 30 Retention of Charges GROUNDED CONDUCTOR no charge no charge GROUNDED CONDUCTOR INSULATOR no charge charged INSULATED CONDUCTOR INSULATOR charged charged 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

31 31 Nickel, Copper Brass, Silver Gold, Platinum Polyester Celluloid Saran Polyurethane Polyethylene Polypropylene PVC Silicon Teflon Glass Human Hair Nylon Wool Lead Aluminum Paper Cotton Steel Wood Sealing Wax Hard Rubber - + “Basic ESD Seminar” prepared by Burt Unger for the ESD Association, Rome, NY, P.32 Tribocharging Tribocharging Triboelectric Series

32 32 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

33 33 Effects of Humidity Winter, Low Humidity, High Static Winter, Low Humidity, High Static – Extra caution is necessary – The colder it gets, the more electrostatic discharge Summer, High Humidity, Low Static Summer, High Humidity, Low Static – Exception is Lightening – Difficult to demonstrate static events Desert Areas and at High Atmospheres Desert Areas and at High Atmospheres – These places have low humidity – Static is a problem year around Varies with Season Location and and Time

34 34 Voltage & Humidity Means of Static Generation Electrostatic Voltages Refer to Table 7-2 in T.O % 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, 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

35 35 ESD Control Work Areas T.O , 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.

36 36 ESD Control Work Areas T.O , Section VII Requires: ESD Control Work Area Certification: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.

37 37 Controlling Body Voltage Wrist Straps Purpose: An ESD control wrist strap is used to prevent body voltage from damaging ESD sensitive items. Use: Use: Typically, an ESD control wrist strap should be worn anytime you are handling an ESD sensitive item. Testing Requirement: Testing Requirement: Single conductor wrist straps shall be tested prior to first use each day per person.

38 38 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 Controlling Body Voltage

39 39 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

40 40 Controlling Body Voltage Wrist Straps T.O requires that all wrist straps have adjustable diameter cuffs. Metal wrist strap cuffs have not been approved. Adjustable Cuffs

41 41 WARNING The personnel wrist strap shall not be on worn when working on energized parts, assemblies and equipment. Controlling Body Voltage Wrist Strap Warning

42 42 Current, Physiologic Effects Current Values (Milliamperes) Effect AC 25 TO 400 HZ DC Over Over 300 Perception Surprise Reflex Action Muscular inhibition Respiratory block Usually fatal (Ref. MIL-STD-454) Also in Table 7-4 of TO Effect of Electrical Current on Humans Controlling Body Voltage

43 43 Controlling Body Voltage Wrist Strap Testers, Electrical Aspects Don’t use an Ohmmeter to test wrist straps. Table 7-3 ITEM Passing Range Output Ohms Volts Ohms Volts 61 8x10 5 to 1x Wrist Strap Testing

44 44 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 MOISTURE DEPENDENT. LOTIONS SOMETIMES REQUIRED Controlling Body Voltage

45 45 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

46 46 Wrist Strap Continuous Monitors Both types require dual wire cords and special wrist strap cuffs. and special wrist strap cuffs. Dual Wire Cords Controlling Body Voltage

47 47 Footwear Testing Footwear Testing – Refer to ESD STM Demonstrate Footwear Test with: – Demonstrate Footwear Test with:  Integrated wrist strap / footwear tester  Portable Flooring Megger Demonstrate the Footwear Test Demonstrate the Footwear Test – Combat Boots – ESD Shoes – Stocking Feet Controlling Body Voltage Footwear Testing

48 48 Lab Data on Max Body Voltage Without Wrist Strap Actual Lab Data On Nylon Carpet At 10 % RH With Combat Boots 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! complete system approach! Controlling Body Voltage Footwear/Floor System

49 49 SUMMARY OF ESD CONTROL. STRATEGIES. STRATEGIES. RULE 1. – RULE 1. Handle all ESD Sensitive items at an ESD. Workstation. Workstation. RULE 2. – RULE 2. Transport and store all ESDS items ( both. reparable and serviceable) in static. shielding and non-charge generating. packages or containers. Packaging, 1 st of 8 TO Chapter 7, 7-5.b Packaging

50 50 ESD Packaging Objectives ESD Packaging Objectives Provides Shielding – Provides Shielding – Immune to Tribocharging – Allow charge transfer from package exterior to an ESD protective worksurface Packaging Objectives

51 51 Mil-Prf-81705D for ESD Protective, Heat-Sealable, Barrier Materials 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 Packaging Types 1, 2, & 3

52 52 EMI/Static Shield Bag (Type I) EMI/Static Shield Bag (Type I) Top of the Line, heavy duty outer wrap. – Top of the Line, heavy duty outer wrap. Required for long – Required for long term storage. term storage. Protects from – Protects from water vapor & water vapor & Electromagnetic ElectromagneticFields. ESD Protective. – ESD Protective. Packaging Type 1, details

53 53 Pink Poly Bags (Type II). Pink Poly Bags (Type II). Pink Polyethylene reduces tribocharging. – Pink Polyethylene reduces tribocharging. – Does not provide. good ESD protection. good ESD protection. – Is used to protect. from physical damage. Shown: Zip Lock Bubble. Wrap. Type 2, details Packaging

54 54 Static Shielding Bag (Type III) Static Shielding Bag (Type III) Transparent, Local use, Shielding bag – Transparent, Local use, Shielding bag  Reduces need to open bags – Water proof (not vapor proof) (not vapor proof) – Protects from Electrostatic fields Electrostatic fields (not magnetic fields) (not magnetic fields) – Dissipates a Charge Packaging Type 3, Details

55 55 Avoid Unnecessary Charge Generators Avoid Unnecessary Charge Generators Styrofoam materials – Styrofoam materials – Clear Polyethylene and Polypropylene films Polypropylene films and bags and bags Packaging Materials to Avoid

56 56 Demonstrate the Properties of the three types of bags: Demonstrate the Properties of the three types of bags: Transparency – Transparency – Tribocharging – ESD Shielding – EMI Shielding – Puncture Resistance – Vapor and water Resistance This is not a Faraday Cage ! Packaging, Demos Packaging

57 57 Packaging When does ESD susceptibility stop? 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

58 58 Cabinets, Shelves, & Work Surfaces Cabinets, Shelves, & Work Surfaces Requirements: 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.

59 59 Connector Caps, NASM5501/31 & 32 Formerly Mil-C-5501/31A & 32A Connector Caps, NASM5501/31 & 32 Formerly Mil-C-5501/31A & 32A They complete the Faraday Cage – 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. – 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 – They can be tested with a DMM There is a supply problem – There is a supply problem  Some are not labeled correctly. ESD Connector Caps

60 60 Marking & Signs, 1 st of 4 Marking, Labeling, & Signs Equipment Label Equipment Label TO , Fig 7-8 – TO , Fig 7-8 – Attach on a readily visible exterior surface, if space is available and does not hinder operation of the item.

61 61 Unit Pack Label The Unit Pack Label The Unit Pack Label TO , Fig 7-11 – TO , Fig 7-11 – Attach to both sides of outermost bag. ATTENTION HANDLE ONLY AT STATIC SAFE WORK STATIONS STATIC SENSITIVE DEVICES Marking, Labeling, & Signs

62 62 Shipping Container Label Shipping Container Label Shipping Container Label TO , Fig 7-12 – TO , Fig 7-12 – Attach to Fast-Pack, Intermediate Pack, Exterior Pack, or Shipping Container which contain the unit packs. The preferred color – The preferred color scheme is shown. scheme is shown. Marking, Labeling, & Signs

63 63 ESD Work Area Sign ESD Work Area Sign ESD Work Area Sign TO , Fig 7-16 – TO , Fig 7-16 – Placed at or near the entrance to ESD Work Area. Work Area. ATTENTION STATIC SAFEGUARDED WORK AREA Marking, Labeling, & Signs

64 64 ESD Worksurfaces, 1 st of 4 TYPES OF ESD WORKSURFACES TYPES OF ESD WORKSURFACES – RIGID  None approved at this time » They have smooth hard surfaces, but do not dissipate charge at low humidity. – CUSHIONED  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 – FOLDABLE  These are portable and have CPG & W/S ESD Worksurfaces

65 65 Permanent Type Permanent ESD Workstation Surface. 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 in Table 7-3 ESD Worksurfaces

66 66 ESD Worksurfaces What to do with a non ESD Workstation? 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

67 67 Cleaning them CLEANING WORKSURFACES. CLEANING WORKSURFACES. Best to use 70 / 30 IPA / water. – 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. – 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

68 68 Scrim Layer Functions 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 Test the electrical contact from Snap to Scrim – Use a DMM or Megger across the Snaps Cardboard Layer #2 for strength and thickness Insulative, Protective, Transparent Paper Layer Humectants, Metal particles, Salts, Ionic Materials The Colored Decorative Paper Layer The Conductive Scrim layer, usually carbon doped paper Cardboard Layer #1 for strength and thickness ESD Worksurfaces

69 69 Air Ionizers, what they do IONIZED AIR REMOVES CHARGES IONIZED AIR REMOVES CHARGES FROM JOB ESSENTIAL NON CONDUCTORS – FROM JOB ESSENTIAL NON CONDUCTORS PACKAGING MATERIALS  PACKAGING MATERIALS  LAMINATED SCHEMATICS & DRAWINGS AND FROM ISOLATED CONDUCTORS – AND FROM ISOLATED CONDUCTORS NEED TO MAINTAIN A BALANCE OF – NEED TO MAINTAIN A BALANCE OF POSITIVE & NEGATIVE IONS POSITIVE & NEGATIVE IONS AIR IONIZATION

70 70 When to use Ionizers AIR IONIZATION Use When: – The Work Area Survey requires it. Demonstrate Value of Ionization: Ionizers require periodic testing. Refer to d.6.a

71 71 View of Open Outlet Box Showing Equipment Grounding Conductors. Equipment Grounding Conductors Third Wire “Ground”

72 72 Wiring Verification Test Utility Wiring Verification Test is done first. Par. 7-5.e(3)(b) of T.O photo

73 73 Utility Ground Wiring Verification Check, Par. 7-5.e(3)(c) Utility Ground Check Item 66 of Table 7-3

74 74 Resistance Check from Bench’s Groundable point to third wire ground. Par. 7-5.e(3)(d) Bench Ground Check

75 75 USE AN OHMMETER TO CHECK CONTINUITY FROM THE CPG TO: USE AN OHMMETER TO CHECK CONTINUITY FROM THE CPG TO: WRIST STRAP WRIST STRAP PLUG-INS, PLUG-INS, BENCH BENCH DRAWERS, DRAWERS, BENCH MATS, BENCH MATS, SHELF MATS SHELF MATS

76 76 A KEY PLAYER IN ESD CAPACITANCE The Role of Capacitance

77 77 Capacitance Equations Q = CVC = Q / VV = Q / C Q = CV C = Q / V V = Q / C Q Q - charge in coulombs C C - Capacitance in farads V V - potential in volts Nanocoulomb (nc) = C Picofarad (pF) = F CAPACITANCE EQUATIONS The Role of Capacitance

78 78 C C = Farads A A = meters 2 d d = meters  0 = 8.85 x f/m K K = dielectric constant Capacitance becomes larger as the distance becomes less. as the distance becomes less. Let Q (coulombs) remain Let Q (coulombs) remain constant. constant. The Voltage goes down The Voltage goes down as the capacitance goes up. as the capacitance goes up. Parallel Plate Capacitance A C K C = ---  0 K d A d VQCV = Q / CVQCV = Q / C Parallel Plate Example The Role of Capacitance

79 79 Your Capacitance A PRACTICAL EXAMPLE OF CAPACITANCE AT WORK If you have insulative shoes, your soles become the dielectric in a capacitor between you and the grounded floor. With a charge on your body lift your leg high. What happens in terms of the equations ?  What happens in terms of the equations ? What happens to the voltage on your body ?  What happens to the voltage on your body ? The Role of Capacitance

80 80 Reference, 1 st of 4 Measuring Charge, Coulombs Measuring Charge, Coulombs Reference Electrometer Faraday Cup

81 81 Energy Equations E = 1/2 C V 2 E = 1/2 Q V E = 1/2 Q 2 / C E = energy in Joules C = Capacitance in Farads V = Volts DC Reference

82 82 Numerical Prefixes Reference Examples:1 nanocoulomb = 1 x coulombs 10 picofarad = 10 x farads

83 83 Useful Derived Units Reference

84 84 ANY Questions??? Rome Site ESD Contacts  See Next slide

85 85 ESD Contacts Rome Site1Lt Christopher Lowex2276 RIBRon Ziminskix4450 RIEBob Maciorx2480 RIF1Lt Christopher Lowex2276 RIGSteve Tylerx3618 RIK Charlene Boothx2203 RIOLinda Dittmarx2684 RISJulie Brichacekx4995 RITJohn Rooksx2618 RYBill Lipex4878


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