2Types of ESD Failures to Electronic Devices Catastrophic FailureDevice no longer operatesRepresents 10% of ESD failuresIntermittent / Walking WoundedDevice is operational, but erratic and will cause additional service callsRepresents 90% of ESD failures
3Static Damaged Mos Transistor OXIDE LAYERGATEDRAINSOURCE
4Cost of ESD damage increases by ten (10) fold at every process level Field Service LevelSystem LevelBoard Level$5000Component Level$500$50$5
5Where do you need static protection ? Incoming inspection and testStores and storageTransfer cartsKittingManual and automated insertionWave solderingEquipment assembly and testPackaging and shippingRepair stationsField service
6DEFINITION 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.+++++++_______
7MAJOR PROBLEMS CAUSED BY STATIC Dust and Lint AttractionMaterial Handling ProblemsDamage to ProductsProduct MalfunctionFire and Explosion HazardsShock to Personnel
8Ranking of Semiconductor Failure Causes EOS/ESD is the #1 Cause ofSemiconductor FailureEOS/ESD 59%Electrical testing 3%Oxide/passivationfailure 3%Conductor failure 3%Die fracture 4%Lead short/open 7%Wire bonds 15%Others 6%Source : Semiconductor Reliability News, March 1993
10HUMAN PERCEPTIONS OF ESD At 3000 volts, you can ESDAt 5000 volts, you can ESDAt volts, you can ESD
11ELECTROSTATIC VOLTAGES Typical Electrostatic VoltagesELECTROSTATIC VOLTAGESMEANS OFSTATIC GENERATION10 TO 20 PERCENTRELATIVE HUMIDITY65 TO 90 PERCENTRELATIVE HUMIDITYWALKING ACROSS CARPETWALKING OVER VINYL FLOORWORKER AT BENCHVINYL ENVELOPES FOR WORKINSTRUCTIONSCOMMON POLY BAG PICKED UPFROM BENCHWORK CHAIR PADDED WITHPOLYURETHANE FOAM35,00012,0006,0007,00020,00018,0001,5002501006001,200OWEN J. McATEERMILITARY ELECTRONICS/COUNTERMEASURES
12ELECTROSTATIC 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.
13DAMAGE MODES Catastrophic Failure Device no longer operates Are mostly caught in-houseRepresents 10% of ESD failuresIntermittent / Walking WoundedDevice is operational, but erratic and will cause additional service callsMost expensive static problemRepresents 90% of ESD failures
15PROPERTIES OF STATIC ELECTRICITY A charged surface has electrical potential energy (voltage)A charged surface emanates an electric fieldA charged surface can produce kinetic energy (current)
16STATIC CHARGE GENERATORS Work surfacesFloorsChairsClothingPapers and work order holdersPackaging materialsPERSONNEL
17DEVICE FAILURE CAN HAPPEN AT ANY LEVEL Single deviceCircuit boardProduct assemblyField service
18STATIC GENERATION Triboelectric charging Induction Changes in capacitance
19TRIBOELECTRIFICATION 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.
20INDUCTIONProcess 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 polarized and able to be attracted to charged surfaces (like dust to a TV screen).
21CHANGES 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.
22MATERIALS CHARACTERISTICS ConductorsAllow the flow of electronsNon-conductors or InsulatorsResist the flow of electrons
23FACTORS AFFECTING STATIC CHARGE GENERATION Intimacy of contactSpeed of separationConductivity of materialsPosition on Triboelectric series
25HOW STATIC IS GENERATED +++++++_______Contact and Separation of Materials
26STATIC FIELD EMANATES FROM CHARGED OBJECT 5,000 Volts2,000V3,000V4,000V
27Fundamentals of Static VOLTAGES associated with static charges can be created by :1. Triboelectric charging2. Induction3. Changes in capacitanceSCIENTIFIC BASIS :1. Coulomb’s Lawlike charges repelopposite charges attract2. V = Q/CV = voltage in voltsQ = charge in coulombC = capacitance in farads
28Typical Voltage Variations Monitored on a Person with No Wrist Strap FeetRaised1550v(max)OperatorSat DownOperatorStands UpOperatorSat DownOperatorWalkingFeetLowered1400 v(max)1500VoltagePulseHeight850 v(max)10003200 v/sec5000v/sec5003800 v/secTime
29SOLUTIONS TO STATIC PROBLEMS Prevention of Charge GenerationNeutralization of ChargeDissipation of ChargeShielding
30PREVENTION Static cannot be totally prevented .......... Only Limited !!!!!
31PREVENTIONThe property of Antistaticity is related to Prevention of static charge generation -Providing surface lubricity and slightly conducting properties usually results in low charging properties.
32DISSIPATION Removal of Charge from Conductors Rate of dissipation controlled by resistance to groundSlow rate of dissipation preferred by most
33DISSIPATIONDevice damage models have helped determine the need for dissipative worksurfaces.Human Body ModelCharged Device ModelMachine Model
36DISSIPATIONDissipation 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.
37IONIZATION 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.
38SHIELDINGShielding 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.
394 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.
40RULE 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.
45RULE 3 - TEST EQUIPMENT Tester for Wrist/Shoe Strap. “Megger” (high voltage meter) for worksurfaces and flooring.“Charge Plate” for Ionization.
46RULE 4Make 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.
47STANDARDIZATION 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.
48ESD ASSOCIATION TEST METHODS Individual ProductsWrist straps, flooring, table mats etc.Measurement TechniquesResistance, Shielding, Charge GenerationAdvisoriesGuidelines, Practices, Procedures, Definitions
49EIA - Electronic Industry Association Packaging of Electronic Products for Shipment - EIA 541Specifications for materials used in packaging materialsESD Standard 625
50PREREQUISITES FOR A SUCCESSFUL STATIC CONTROL PROGRAM A full commitment on the part of top managementESD control compliance on all suppliersA comprehensive in-house ESD control programAdvise your customers on proper handlingSelect a professional and knowledgeable static control vendor
51Benefits of a total static control program Reduced IC and PC board rejectsReduced field service callsMore competitive service contract due to lower warranty costsReduced circuit board float resulting from increased IC and PC board reliability$$ Savings proportion example:5 PC boards in inventory per 1 PC board in the field can be reduced to:3 PC boards in inventory per 1 PC board in the fieldReduced physical space requirements for PCSavings = return on investment capital investedImproved customer satisfaction (goodwill) and assure customer re-orders.Increase share of marketplace with high quality and reliable productsImprove profits