1. ELECTRO STATIC DISCHARGE
An extensive course on
ELECTRO STATIC DISCHARGE
AWARENESS AND CONTROL

2. Examples :
Lightning
Zapping

3. An atom is made up of charges
In its stable state, the size of the positive charge at the centre (nucleus) of an atom is balanced by the size of all the negative charges of the electrons, making it neutral overall.
The electrons whirl around the centre like planets.

4. Creating a charge imbalance
Electron “lost”
When an atom loses an electron, it has a charge imbalance.
Since this atom has lost an electron, which is a negative charge, the atom is now a positive charge.
When it gains an extra electron, an atom becomes a negative charge.

5. A discharge This movement of charges is called a discharge.
When something which has a charge imbalance is brought close to or touches something else, a stream of charges might move, to try to bring the atoms back to their stable balanced condition.
This powerful, rapid movement of charges can damage electronic components.
This movement of charges is called a discharge.
Let’s see it again!

6. WHAT IS ESD? ESD EVENT OR INDUCED ELECTRO STATIC FIELD.
ELECTRO STATIC DISCHARGE IS DEFINED AS THE TRANSFER OF ELECTRO STATIC CHARGES BETWEEN BODIES AT DIFFERENT POTENTIAL CAUSED BY DIRECT CONTACT
OR INDUCED ELECTRO STATIC FIELD.
ESD EVENT
IT IS AN UNPLANNED OCCURANCE OF ELECTRO- STATIC DISCHARGE

7. What is ESD—Electrostatic Discharges (ESD) are the most severe form of Electromagnet Interference (EMI). The human body can build up static charges that range up to 25,000 volts. These build-ups can discharge very rapidly into a electrically grounded body, or device. Placing a 25,000-volt surge through any electronic device is potentially damaging to it.

8. The most common causes of ESD are:
Moving people
Improper grounding
Unshielded cables
Poor connections
Moving machines
Low humidity (hot and dry conditions)

9. Figure 13-14: Power Transmission System

10. Figure 13-15: Grounds on IC Chips

11. To avoid damaging static-sensitive devices, the following procedures will help to minimize the chances of destructive static discharges:
Some devices used to remove solder from circuit boards and chips can cause high static discharges that may damage the good devices on the board. The device in question is referred to as a solder-sucker, and is available in antistatic versions for use with MOS devices.

12. Triboelectric generation
Basic Principles (2)

13. When materials are in contact
When two materials are in intimate contact, they share electrons which are at their surfaces.

14. The triboelectric charge of two materials in contact.

15. When materials are in contact
When two materials are in intimate contact, they share electrons which are at their surfaces.
It is possible for electrons to be “stolen” from one material by nuclei in the other material, because they have a stronger force

16. When the materials are separated
Electrons “lost”
Electrons “gained”
When these materials are separated, electrons are removed from one material and are transferred to the other material.

18. When the materials are separated
Electrons “lost”
Electrons “gained”
This action takes place with all types of materials. With insulators, the charges remain at the points of contact. A charge spreads all over an ungrounded conductor.
When these materials are separated, electrons are removed from one material and are transferred to the other material.

19. The triboelectric charge when two materials placed in contact are then separated.

20. When the materials are separated
Electrons “lost”
Electrons “gained”
This action takes place with all types of materials. With insulators, the charges remain at the points of contact. A charge spreads all over an ungrounded conductor.
The loss and gain of these electrons creates an imbalance of negative and positive charges on the surface of each material.

21. When the materials are separated
Electrons “lost”
Electrons “gained”
When the surfaces are rough, this intimacy and separation is assisted by rubbing the materials together.

22. When the materials are separated
Electrons “lost”
Electrons “gained”
The size of the charge (imbalance) depends on the intimacy of the contact, how fast they were separated, the humidity and the kinds of materials

23. When the materials are separated
Electrons “lost”
Electrons “gained”
The drier the air (lower relative humidity, RH) the higher the generated charge

24. The creation of a charge when materials are separated is termed “triboelectric charging”

25. Charging by Induction
Basic Principles

26. The charge imbalance on a surface produces an electric field.
Charging by induction
The charge imbalance on a surface produces an electric field.
The presence of this very strong force causes similar charges on the surfaces of nearby conductors to be repelled.

27. Charging by induction
If the conductor is grounded while it is still influenced by the electric field, these repelled charges go to earth, thus maintaining a charge balance in the areas of the conductor that are not affected by the electric field.

28. Charging by induction

29. Walking on carpet
Thoughts and theories

30. Walking across carpet
Walking across a carpet creates a charge imbalance on the lower surface of shoes.

31. A strong electric field
This charge imbalance creates a strong electric field that emanates in all directions.
The material in the sole of shoe enables a strong field to influence charges within foot.

32. An induced charge
Since the body is relatively conductive, the charges that are repelled from the lower regions of my foot set up a charge throughout the rest of my body.
But the body still has a balanced charge overall (it has not lost or gained any charges).

33. Contacting a source of charges
While you are still on the carpet (still influenced by the electric field on the sole of your shoe),you briefly touch a metallic object (a chair, table, door knob, metal stapler, etc.)
This enables charges to be provided by the metallic object.

34. Charging through the air
If the charge imbalance on my body is large enough, I do not need to touch the object, as the imbalance could allow a movement of charges through the air.
This movement of charges is thus producing an overall charge imbalance in my body, since I was previously neutral overall.

35. An overall charge imbalance
Therefore, after that brief encounter with the metallic object, my body now has an overall charge imbalance.

36. Removing that charge
The only way to remove the possibility of damaging an ESD-sensitive device or assembly is to remove the overall charge imbalance on my body.
This is done by connecting my body to the ready source of charges that is at the same reference potential as the item I wish to handle - using a wrist strap or foot strap.

37. ELECTROSTATIC DISCHARGE PROCESS
1. Charge is generated on the surface of an insulator.
2. This charge is transfered to a conductor by contact or induction.
3. The charged conductor comes near a metal object (grounded or ungrounded) and a discharge occurs.
4. When a discharge occurs to an ungrounded object, the discharge current flows through the capacitance between the object and ground.

38. STATIC GENERATION CAUSE FOR STATIC CHARGE
THE STATIC CHARGE IS GENERATED BY IMBALANCE IN THE MOLECULAR STRUCTURE BY RUBBING; CAUSING STRIPPING OF NEGATIVELYCHARGED ELECTRONS WITH ONE MATERIAL GETTING PASITIVE CHARGE AND OTHER NEGATIVE
CAUSE FOR STATIC CHARGE
FRICTION
SEPERATION
INDUCTION

39. CAUSES FOR ESD GENERATION
WALKING ON SYNTHETIC SURFACE
RELATIVE MOVEMENT ON CHAIR
TABLE, COMPUTER, PLASTIC PARTS NYLON OR SYNTHETIC CLOTHES
CLEANING WITH COMPRESSED AIR
CLEANING WITH SOLVENT

40. FACTORS:
TYPE OF MATERIAL
RELATIVE HUMIDITY
TYPE OF CLOTHING
SPEED AND MANNER OF WALKING
BODY RESISTANCE

41. RECORDED ESD ACCIDENTS
In 1937, The German flying boat Hinderburg arriving in Lakehurst, New Jersey, caught fire while anchoring at its landing mast.
In 1970’s, in USA, a space craft launching rocket exploded during the fueling operation, killing 3 engineers.
In January, 1985, during the assembly of a missile in Germany, the motor case made of Kelvar, got rubbbed against the cushioning in its container. The ESD generated caused the highly flammable propellant to catch fire and the motor exploded, killing 3 people.
3 to 30% of Integrated Circuits manufactured every year die in “infancy” due to ESD.

42. Device sensitivity to Electrostatic Discharge
At higher magnification the pit in the area between the base and emitter becomes more obvious

43. At this magnification see the 1/2 of
Device sensitivity to Electrostatic Discharge
At this magnification see the 1/2 of
the width of the material has been destroyed.

46. 40 – 50% EQUIPMENTS HAVE FAILED IN THE FIELD
Statistics
40 – 50% EQUIPMENTS HAVE FAILED IN THE FIELD
DUE TO ESD

47. SENSITIVE CONSTITUENTS FAILURE MODES
MOS STRUCTURES SHORT
BIPOLAR JUNCTIONS LEAKAGE
FILM RESISTORS VALUE SHIFT
METALIZATION STRIPES OPEN
FIELD PERFECT STRUCTURES OPERATIONAL
PIEZOELECTRIC CRYSTALS DEGRADED
CLOSELY SPACED CONDUCTORS DEGRADED

48. ESD SOURCES MAN MADE: PLASTICS CONDUCTORS FURNITURES VINYL FLOOR
COOLING FANS WITH PLASTIC BLADES
PRINTERS/COPIERS
PAPER
NYLON & WOOLLEN GARMENTS
COMPRESSED AIR GUN

49. NATURAL:
HUMAN BODY
MOVEMENT OF CLOUDS

50. TYPICAL CHARGE GENERATORS
PACKING HANDLING MATERIALS:
COMMON POLYTHENE BAGS, WRAPS,ENVELOPES
COMMON BUBBLE PACK FOAM
COMMON PLASTIC TRAYS, PLASTIC TOTE BOXES, VIALS
ASSEMBLY, CLEANING, TEST & REPAIR AREA ITEMS:
SPRAY CLEANERS
COMMON SOLDER SUCKERS
COMMON SOLDER IRONS
SOLVENT BRUSHING ( SYNTHETIC BRISTLES)
CLEANING, DRYING
TEPARATURE CHAMBERS

51. ESD VOLTAGE MEASUREMENT
ELECTROSTATIC VOLTAGE
MEANS OF STATIC GENERATION % RW % RW 55% RW
PERSON WALKING ACROSS CARPET
PERSON WALKING ACROSS VINYL
FLOOR
WORKER AT A BENCH
CERAMIC DIPS IN PLASTIC TUBE
CERAMIC DIPS IN VINYL SET UP TRAYS
CIRCUIT AS BUBBLE PLASTIC
COVER REMOVED
CIRCUIT AS PACKED IN FOAM
LINED SHIPPING BOX

52. ESD DAMAGE : WHEN UNNOTICED?
REASONS FOR DISBELIEF
ESD DAMAGE : WHEN UNNOTICED?
HUMAN SENSE OF FEELING OF STATIC AT 4000V
MUCH MORE HIGHER THAN SENSITIVITY OF
COMPONENTS
HARDLY ANY PHYSICAL DAMAGE
ESD FAILURES CONSIDERED AS GENERAL COMPONENT FAILURE
FAILURE MAY NOT BE INSTANT. (LATENT FAILURE)

53. GUIDE TO STATIC CONTROL MATERIALS
SURFACE RESISTIVITY-OHMS PER SQUARE
INSULATOR
MATERIALS IN THIS RANGE ARE NOT EFFECTIVE FOR STATIC CONTROL
1012 To

54. GUIDE TO STATIC CONTROL MATERIALS
SURFACE RESISTIVITY-OHMS PER SQUARE
ANTISTATIC
THESE MATERIALS DO NOT GENERATE AND SUPPORT HIGH STATIC CHARGES. BUT DISCHARGE RATES ARE TOO SLOW FOR MOST INDUSTRIAL APPLICATIONS.
1010 To

55. GUIDE TO STATIC CONTROL MATERIALS
SURFACE RESISTIVITY-OHMS PER SQUARE
STATIC DISSIPATORS ( PARTIALLY CONDUCTIVE)
106 To
MATERIALS MOST SUITABLE FOR STATIC CONTROL WORK SURFACES, FLOORING AND FLOOR MATS, SEALING, OVERALLS

56. GUIDE TO STATIC CONTROL MATERIALS
SURFACE RESISTIVITY-OHMS PER SQUARE
CONDUCTIVE
MATERIALS FOR CONTAINERS AND HANDLING EQUIPMENT.BELOW 104 OHMS PER SQUARE EFFECTIVE STATIC SHIELDING IS POSSIBLE,OPERATOR SAFELY WILL BE COMPROMISED IF THE EARTH PATH THROUGH BENCH MATS, FLOOR MATS AND FLOORING LESS THAN 5 X 104 OHMS AND MAINS POWERED EQUIPMENT’S IN USE.
101 To 10 4

57. OBJECTIVES OF ESD CONTROL
PREVENTING STATIC CHARGE GENERATION
DISSIPATING THE DEVELOPED CHARGE
NEUTRALISING DEVELOPED CHARGE FOR A CHARGE
FREE ZONE
CONTROLLING OF ESD
WORK SURFACE
AIR
HUMAN BODY
FLOOR

58. KEEP PARTS IN ORIGINAL PACKING UNTILL READY FOR USE.
DO’S
MINIMISE HANDLING.
KEEP PARTS IN ORIGINAL PACKING UNTILL READY FOR USE.
USE ESD PROTECTIVE CONTAINERS AND BAGS.
DISCHARGE STATIC BEFORE HANDLING DEVICE BY TOUCHING NEARBY GROUNDED SURFACE.
HANDLE DEVICES BY THE BODY.
TOUCH THE ESD PROTECTIVE PACKAGE BEFORE TOUCHING INSIDE OF DEVICE.
KEEP A DUST FREE WORK AREA.

59. DONT’S TOUCH THE LEADS OF DEVICE. SLIDE ES DEVICES OVER ANY SURFACE.
PUT MASKING TAPE ON PROGRAMMABLE IC’S.
STORE OR CARRY SENSITIVE COMPONENTS OR ASSEMBLIES IN PLASTIC BAGS.
STORE SENSITIVE COMPONENTS IN THERMOCOLE/PLASTIC FOAM.
HANDLE ES DEVICES IN “NON ESD CONTROLLED” ENVIRONMENT.

60. ESD MODELS HUMAN BODY MODEL CHARGED DEVICE MODEL MACHINE MODEL
ESD MODELS HAVE BEEN DEFINED TO DESCRIBE THE EFFECTS ON ESD SENSITIVE DEVICES:
HUMAN BODY MODEL
CHARGED DEVICE MODEL
MACHINE MODEL

61. Human Body Model (HBM) ^
The basic human body model consists of body capacitance and resistance. The charge is stored in the body capacitance and the discharge occurs through the body resistance.
When a charged person handles or comes in close proximity to an ESD sensitive part, the part may be damaged by direct discharge or by an electro static field. ^
<0.1mH Rb
Cb : 50 to 350pF
Rb : 150 to 10KOhms
Vb : 3 to 20 KV Vb Cb

62. Human Body Model (HBM)

63. HUMAN BODY CAPACITANCE AND RESISTANCERb ^ o o ^
50-100pF
50pF
100pF
100pF

64. ^ ^ TYPICAL ESD CURRENT WAVE FORM I . . . . . . . . 40A . tr=1nSec
tf=100nSec t

65. Machine Model
A discharge similar to the HBM event also can occur from a charged conductive object, such as a metallic tool or fixture. .

66. Charged Device Model
The transfer of charge from an ESDS device is also an ESD event. A device may become charged, for example, from sliding down the feeder in an automated assembler. If it then contacts the insertion head or another conductive surface, a rapid discharge may occur from the device to the metal object. This event is known as the Charged Device Model (CDM).

67. ANTISTATIC VINYL TABLE MAT CONDUCTIVE FLOOR MAT ESD LAMINATE
ESD CONTROL DEVICES
ANTISTATIC VINYL TABLE MAT
CONDUCTIVE FLOOR MAT
ESD LAMINATE
ESD WRIST STRAP
ESD HEEL STRAP
ESD TOE STRAP
COMMON POINT GROUND
ANTISTATIC BINS/TRAYS
PCB STORAGE RACK
CONDUCTIVE FOAM

69. ESD AUDIT

70. MATERIALS CLASSIFICATION
MATERIAL SURFACE VOLUME
CLASS RESISTIVITY RESISTIVITY
SHIELDING OR LESS OR LESS
CONDUCTIVE 105 OR LESS OR LESS
DISSIPATIVE 105 TO TO 109
ANTISTATIC TO
INSULATIVE > >1014

71. ESD AUDIT PERSONNEL TRAINING FOR ESD PREVENTIVE AWARENESS TRAINING
CERTIFICATION TRAINING
CONTROL PROGRAM AUDIT

73. ESD TEST & MEASURING INSTRUMENTS
STATIC CHARGE METER
WRIST STRAP AND GROUND TESTER
FOOTWEAR TESTER
SURFACE RESISTIVITY METER
STATIC SENSOR
CONTINUOUS WRIST STRAP MONITOR
CONTINUOUS WORK STATION MONITOR
TEMPARATURE AND HUMIDITY INDICATOR

74. TESTING EVALUATION
The test evaluation report consists of the following test areas for each ESD item/s:
POINT TO POINT SURFACE RESISTIVITY TOP/BOTTOM
POINT TO POINT SURFACE RESISTIVITY IN/OUT
SURFACE TO GROUND RESISTANCE
PERSON TO GROUND RESISTANCE
STATIC CHARGE MEASURING TEST
STATIC SHIELDING TEST

75. TESTING EVALUATION
The tests are generally conducted for the following item/s:
Antistatic P.E Bags
Static Shield Bags
Conductive Bags
Conductive Grid Bags
Antistatic Aprons
Conductive Brush
Foot Wear
ESD Mat
conductive Mat
Work Surface
ESD Laminate
Wrist Strap
Heel Strap
ESD Chair

76. Wrist Straps Footwear PERSONAL GROUNDING
Two types of Personal Grounding:
Wrist Straps
Footwear

77. WRIST STRAPS
Daily Check with Wrist Strap Worn
Test with a Wrist Strap tester

78. Floor
Point to Point

79. Floor
Resistance to Ground

80. Garments
Point to Point

81. May need person wearing garment
Garments
Point to Ground
May need person wearing garment
Needs to be connected to ground as wor n

82. Chair Check all parts of Chairs to Ground
Seat, Backrest, Armrest, Foot Rest

85. TYPES OF ESD DAMAGE
CATASTROPHIC FAILURE
UPSET FAILURE

86. SHIELDING Types of Faraday Cages
Metallized & Conductive Shielding Bags
Conductive tote box with cover
FARADAY CAGE

87. A hollow conductor A Faraday Cage is a hollow conductor.
Michael Faraday

88. WORK STATION

89. Electrostatic Voltmeter (ESV)

90. Measurement of Static Electricity
Static electricity is measured in coulombs. The charge "q" on an object is determined by the product of the capacitance of the object "C" and the voltage potential on the object (V):
q=CV
Commonly, however, we speak of the electrostatic potential on an object, which is expressed as voltage.

91. ESD Damage-How Devices Fail
Electrostatic damage to electronic devices can occur at any point from manufacture to field service.
Damage results from handling the devices in uncontrolled surroundings or when poor ESD control practices are used.
Generally damage is classified as either a catastrophic failure or a latent defect.