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Static Awareness Seminar

3. Static Awareness Seminar. Types of ESD Failures to Electronic Devices. Catastrophic Failure Device no longer operates Represents 10% of ESD failures Intermittent / Walking Wounded Device is operational, but erratic and will cause additional service calls

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Static Awareness Seminar

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  1. 3 Static Awareness Seminar

  2. Types of ESD Failures to Electronic Devices • Catastrophic Failure • Device no longer operates • Represents10%of ESD failures • Intermittent / Walking Wounded • Device is operational, but erratic and will cause additional service calls • Represents90%of ESD failures

  3. Static Damaged Mos Transistor OXIDE LAYER GATE DRAIN SOURCE

  4. Cost of ESD damage increases by ten (10) fold at every process level Field Service Level System Level Board Level $5000 Component Level $500 $50 $5

  5. Where do you need static protection ? • Incoming inspection and test • Stores and storage • Transfer carts • Kitting • Manual and automated insertion • Wave soldering • Equipment assembly and test • Packaging and shipping • Repair stations • Field service

  6. DEFINITION OF STATIC ELECTRICITY • The electrification of materials through physical contact and separation, and the various effects that result from the positive and negative charges so formed. + + + + + + + _ _ _ _ _ _ _

  7. MAJOR PROBLEMS CAUSED BY STATIC • Dust and Lint Attraction • Material Handling Problems • Damage to Products • Product Malfunction • Fire and Explosion Hazards • Shock to Personnel

  8. Ranking of Semiconductor Failure Causes EOS/ESD is the #1 Cause of Semiconductor Failure EOS/ESD 59% Electrical testing 3% Oxide/passivation failure 3% Conductor failure 3% Die fracture 4% Lead short/open 7% Wire bonds 15% Others 6% Source : Semiconductor Reliability News, March 1993

  9. Device Type MOSFET VMOS NMOS GaAsFET EPROM CMOS GaAsFET JFET SAW Op-AMP Schottky Diodes Film Resistors Bipolar Resistors ECL SCR SChottky TTL Threshold Susceptivity (Volts) 10 - 100 30 - 1800 60 - 100 60 - 2000 100+ 200 - 3000 25 - 50 140-7000 150-500 190-2500 300-2500 300-3000 300-7000 500+ 500-1000 500-2500 SEMICONDUCTOR DEVICE SENSITIVITIES

  10. HUMAN PERCEPTIONS OF ESD • At 3000 volts, you can ESD • At 5000 volts, you can ESD • At 10000 volts, you can ESD

  11. Typical Electrostatic Voltages ELECTROSTATIC VOLTAGES MEANS OF STATIC GENERATION 10 TO 20 PERCENT RELATIVE HUMIDITY 65 TO 90 PERCENT RELATIVE HUMIDITY WALKING ACROSS CARPET WALKING OVER VINYL FLOOR WORKER AT BENCH VINYL ENVELOPES FOR WORK INSTRUCTIONS COMMON POLY BAG PICKED UP FROM BENCH WORK CHAIR PADDED WITH POLYURETHANE FOAM 35,000 12,000 6,000 7,000 20,000 18,000 1,500 250 100 600 1,200 1,500 OWEN J. McATEER MILITARY ELECTRONICS/COUNTERMEASURES

  12. ELECTROSTATIC DISCHARGE (ESD) • Billions of Dollars $$$ are wasted each year because of ESD damage. • Millions of dollars in PC Board float is the result of ESD damage.

  13. DAMAGE MODES Catastrophic Failure • Device no longer operates • Are mostly caught in-house • Represents 10% of ESD failures Intermittent / Walking Wounded • Device is operational, but erratic and will cause additional service calls • Most expensive static problem • Represents 90% of ESD failures

  14. DAMAGES CAUSED BY ESD

  15. PROPERTIES OF STATIC ELECTRICITY • A charged surface has electrical potential energy (voltage) • A charged surface emanates an electric field • A charged surface can produce kinetic energy (current)

  16. STATIC CHARGE GENERATORS • Work surfaces • Floors • Chairs • Clothing • Papers and work order holders • Packaging materials • PERSONNEL

  17. DEVICE FAILURE CAN HAPPEN AT ANY LEVEL • Single device • Circuit board • Product assembly • Field service

  18. STATIC GENERATION • Triboelectric charging • Induction • Changes in capacitance

  19. TRIBOELECTRIFICATION • Static Charge can be generated by contact and separation of dissimilar surfaces. • Static Charge on contacting surfaces can be increased with addition of friction or rubbing.

  20. INDUCTION • Process of separating charges on a material through space at a distance by the influence of an electric field. • A conductor in the presence of an electric field can acquire a charge and hold it. • Non-conductors are polarizedand able to be attracted to charged surfaces (like dust to a TV screen).

  21. CHANGES IN CAPACITANCE • Voltage on an object is greatly affected by the capacitance of the object. • Capacitance can change in the environment due to position of the object relative to other objects in the area. • Increase capacitance, reduces voltage. • Decrease capacitance, increases voltage.

  22. MATERIALS CHARACTERISTICS • Conductors • Allow the flow of electrons • Non-conductors or Insulators • Resist the flow of electrons

  23. FACTORS AFFECTING STATIC CHARGE GENERATION • Intimacy of contact • Speed of separation • Conductivity of materials • Position on Triboelectric series

  24. Air Asbestos Glass Mica Human Hair Nylon Wool Fur Lead Silk Aluminum Paper Cotton Steel Wood Amber Hard Rubber Brass Silver Sulfur Polyester Polyurethane Polyethylene Polypropylene PVC Teflon MATERIALS Increasing Positive Increasing Negative

  25. HOW STATIC IS GENERATED + + + + + + + _ _ _ _ _ _ _ Contact and Separation of Materials

  26. STATIC FIELD EMANATES FROM CHARGED OBJECT 5,000 Volts 2,000V 3,000V 4,000V

  27. Fundamentals of Static • VOLTAGES associated with static charges can be created by : • 1. Triboelectric charging • 2. Induction • 3. Changes in capacitance • SCIENTIFIC BASIS : • 1. Coulomb’s Law • like charges repel • opposite charges attract • 2. V = Q/C • V = voltage in volts • Q = charge in coulomb • C = capacitance in farads

  28. Typical Voltage Variations Monitored on a Person with No Wrist Strap Feet Raised Operator Sat Down 1550 v(max) Operator Stands Up Operator Sat Down Operator Walking Feet Lowered 1400 v(max) 1500 Voltage Pulse Height 850 v(max) 1000 3200 v/sec 5000 v/sec 3800 v/sec 500 0 Time

  29. SOLUTIONS TO STATIC PROBLEMS • Prevention of Charge Generation • Neutralization of Charge • Dissipation of Charge • Shielding

  30. PREVENTION • Static cannot be totally prevented .......... • Only Limited !!!!!

  31. PREVENTION • The property of Antistaticity is related to Prevention of static charge generation - • Providing surface lubricity and slightly conducting properties usually results in low charging properties.

  32. DISSIPATION • Removal of Charge from Conductors • Rate of dissipation controlled by resistance to ground • Slow rate of dissipation preferred by most

  33. DISSIPATION • Device damage models have helped determine the need for dissipative worksurfaces. • Human Body Model • Charged Device Model • Machine Model

  34. Human Body Model oxide layer _ _ _ _ _ _ static discharge _ _ _ _ _ _ _ _ _ _ _ _ _ _

  35. Charged Device Model _ _ _ _ _ _ _ _ _ _ _ tweezers _ _ _ _ _ _ _ discharge _ _ _ _ _ _

  36. DISSIPATION • Dissipation is the most important control property in electrostatics. • Dissipation includes grounding of people, worksurfaces and flooring. • Electrical system ground preferred over a separate system or building ground.

  37. IONIZATION • Creation of free charge in gases (usually air). • Coulombs Law dictates that opposite charges attract. • Ionization cancels out static charges, one for one on surfaces. • Ionization must be balanced, otherwise a charge can be added to a surface.

  38. SHIELDING • Shielding is used to protect electrostatic susceptible items when they are being transported between Static Protected Areas. • Shielding is a requirement for most classes of components in Military and commercial specifications.

  39. 4 RULES OF STATIC CONTROL • Handle all static sensitive items at a static safeguarded work station. • Transport all static sensitive items in static protective containers. • Test and monitor the static control process. • Make sure every party in the supply chain follows then above 3 rules.

  40. RULE 1 - STATIC SAFEGUARDED WORK AREA • Provides bonding and grounding for all conductors used in the area, including people. • Provides neutralization of charge on the necessary non-conductors used in the area.

  41. RULE 1 - SOLUTIONS • Worksurface Materials • Flooring Materials • Wrist Straps • Shoe Grounding • Ionization

  42. OHM’S LAW VOLTS = AMPS OHMS EXAMPLE: 120 VOLTS = 120 MICROAMPS 1,000,000 OHMS

  43. RULE 2 - TRANSPORTATION • Products must be protected when they are moved from the static safeguarded work station.

  44. RULE 2 - SOLUTIONS • Flexible packaging - shielding bags • Rigid containers - tote boxes, trays, card carriers

  45. RULE 3 - TEST EQUIPMENT • Tester for Wrist/Shoe Strap. • “Megger” (high voltage meter) for worksurfaces and flooring. • “Charge Plate” for Ionization.

  46. RULE 4 • Make sure everyone that is in the supply and distribution system follows the first 3 Rules. • Conduct audits on suppliers for conformance to Operating Procedures if necessary.

  47. STANDARDIZATION IN STATIC CONTROL • Standards setting organization exist in the US, Europe, and Internationally. • The most active organizations are : ESD Association, EIA, JEDEC. • The US Military also has many standards related to Static Electricity.

  48. ESD ASSOCIATION TEST METHODS • Individual Products Wrist straps, flooring, table mats etc. • Measurement Techniques Resistance, Shielding, Charge Generation • Advisories Guidelines, Practices, Procedures, Definitions

  49. EIA - Electronic Industry Association • Packaging of Electronic Products for Shipment - EIA 541 Specifications for materials used in packaging materials • ESD Standard 625

  50. PREREQUISITES FOR A SUCCESSFUL STATIC CONTROL PROGRAM • A full commitment on the part of top management • ESD control compliance on all suppliers • A comprehensive in-house ESD control program • Advise your customers on proper handling • Select a professional and knowledgeable static control vendor

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