ESD知識和控制課件

1、ELECTRO STATIC DISCHARGE AWARENESS AND CONTROLAn extensive course onELECTRO STATIC DISCHARGE An exExamples :LightningZappingExamples :An atom is made up of chargesAn 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

2、size of all the negative charges of the electrons, making it neutral overall.The electrons whirl around the centre like planets.An atom is made up of chargesACreating a charge imbalanceWhen an atom loses an electron, it has a charge imbalance.Since this atom has lost an electron, which is a negative

3、 charge, the atom is now a positive charge.When it gains an extra electron, an atom becomes a negative charge.Electron “l(fā)ost”Creating a charge imbalanceWheA dischargeThis movement of charges is called a discharge.When something which has a charge imbalance is brought close to or touches something el

4、se, 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.Lets see it again!A dischargeThis movement of chWHAT IS ESD? ELECTRO STATIC DISCHARGE IS DEFINED AS THE TRANSFER OF ELECTRO

5、STATIC CHARGES BETWEEN BODIES AT DIFFERENT POTENTIAL CAUSED BY DIRECT CONTACTOR INDUCED ELECTRO STATIC FIELD. ESD EVENTIT IS AN UNPLANNED OCCURANCE OF ELECTRO- STATIC DISCHARGEWHAT IS ESD?IT IS AN UNPLANNEDWhat is ESDElectrostatic Discharges (ESD) are the most severe form of Electromagnet Interferen

6、ce (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.What is ESDElectrostatic DiscMoving peo

7、pleImproper groundingUnshielded cablesPoor connectionsMoving machinesLow humidity (hot and dry conditions)The most common causes of ESD are:Moving peopleThe most common cFigure 13-14: Power Transmission SystemFigure 13-14: Power TransmissiFigure 13-15: Grounds on IC ChipsFigure 13-15: Grounds on IC

8、ChSome 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.To avoid damaging static-sensi

9、tive devices, the following procedures will help to minimize the chances of destructive static discharges:Some devices used to remove soTriboelectric generationBasic Principles (2)Triboelectric generationBasic When two materials are in intimate contact, they share electrons which are at their surfac

10、es.When materials are in contactWhen two materials are in intiThe triboelectric charge of two materials in contact. The triboelectric charge of twWhen two materials are in intimate contact, they share electrons which are at their surfaces.When materials are in contactIt is possible for electrons to

11、be “stolen” from one material by nuclei in the other material, because they have a stronger forceWhen two materials are in intiWhen these materials are separated, electrons are removed from one material and are transferred to the other material.When the materials are separatedElectrons “l(fā)ost”Electro

12、ns “gained”When these materials are separESD知識和控制課件When the materials are separatedElectrons “l(fā)ost”Electrons “gained”When these materials are separated, electrons are removed from one material and are transferred to the other material.This action takes place with all types of materials. With insulat

13、ors, the charges remain at the points of contact. A charge spreads all over an ungrounded conductor.When the materials are separatThe triboelectric charge when two materials placed in contact are then separated.The triboelectric charge when This action takes place with all types of materials. With i

14、nsulators, the charges remain at the points of contact. A charge spreads all over an ungrounded conductor.When the materials are separatedElectrons “l(fā)ost”Electrons “gained”The loss and gain of these electrons creates an imbalance of negative and positive charges on the surface of each material.This

15、action takes place with aWhen the materials are separatedElectrons “l(fā)ost”Electrons “gained”When the surfaces are rough, this intimacy and separation is assisted by rubbing the materials together.When the materials are separatWhen the materials are separatedElectrons “l(fā)ost”Electrons “gained”The size

16、of the charge (imbalance) depends on the intimacy of the contact, how fast they were separated, the humidity and the kinds of materialsWhen the materials are separatWhen the materials are separatedElectrons “l(fā)ost”Electrons “gained”The drier the air (lower relative humidity, RH) the higher the genera

17、ted chargeWhen the materials are separatThe creation of a charge when materials are separated is termed “triboelectric charging”The creation of a charge when Charging by InductionBasic Principles Charging by InductionBasic PriCharging by inductionThe presence of this very strong force causes similar

18、 charges on the surfaces of nearby conductors to be repelled.The charge imbalance on a surface produces an electric field. Charging by inductionThe preseCharging by inductionIf the conductor is grounded while it is still influenced by the electric field, these repelled charges go to earth, thus main

19、taining a charge balance in the areas of the conductor that are not affected by the electric field.Charging by inductionIf the coCharging by inductionCharging by inductionWalking on carpetThoughts and theories Walking on carpetThoughts and Walking across carpetWalking across a carpet creates a charg

20、e imbalance on the lower surface of shoes.Walking across carpetWalking aA strong electric fieldThis 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.A strong electric fieldThis ch

21、An induced chargeSince 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).An induced chargeSince the bodContacting a

22、 source of chargesWhile 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.Contacting a source of chargesCharging

23、through the airThis movement of charges is thus producing an overall charge imbalance in my body, since I was previously neutral overall.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.Charging

24、through the airThis mAn overall charge imbalanceTherefore, after that brief encounter with the metallic object, my body now has an overall charge imbalance.An overall charge imbalanceTheRemoving that chargeThe only way to remove the possibility of damaging an ESD-sensitive device or assembly is to r

25、emove 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.Removing that chargeThe only wELECTROSTATIC DISCHARGE PROCESS1. Charge is generated

26、 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 capacitan

27、ce between the object and ground. ELECTROSTATIC DISCHARGE PROCESTATIC GENERATION 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 FR

28、ICTION SEPERATION INDUCTIONSTATIC GENERATION THE STATIC CCAUSES 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 SOLVENTESDCAUSES FOR ESD GENERATION WALFACTORS: TYPE OF MATE

29、RIAL RELATIVE HUMIDITY TYPE OF CLOTHING SPEED AND MANNER OF WALKING BODY RESISTANCEFACTORS:RECORDED ESD ACCIDENTS In 1937, The German flying boat Hinderburg arriving in Lakehurst, New Jersey, caught fire while anchoring at its landing mast. In 1970s, in USA, a space craft launching rocket exploded d

30、uring 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

31、3 people. 3 to 30% of Integrated Circuits manufactured every year die in “infancy” due to ESD. RECORDED ESD ACCIDENTS In 1937Device sensitivity to Electrostatic DischargeAt higher magnification the pit in the area between the base and emitter becomes more obviousDevice sensitivity to ElectrosDevice

32、sensitivity to Electrostatic DischargeAt this magnification see the 1/2 ofthe width of the material has been destroyed.Device sensitivity to ElectrosESD知識和控制課件ESD知識和控制課件40 50% EQUIPMENTS HAVE FAILED IN THE FIELD DUE TO ESDStatistics40 50% EQUIPMENTS HAVE FAILESENSITIVE CONSTITUENTSFAILURE MODESMOS S

33、TRUCTURESSHORTBIPOLAR JUNCTIONSLEAKAGEFILM RESISTORSVALUE SHIFTMETALIZATION STRIPESOPENFIELD PERFECT STRUCTURESOPERATIONALPIEZOELECTRIC CRYSTALSDEGRADEDCLOSELY SPACED CONDUCTORSDEGRADEDSENSITIVE CONSTITUENTSFAILURE PLASTICS CONDUCTORS FURNITURES VINYL FLOOR COOLING FANS WITH PLASTIC BLADES PRINTERS/

34、COPIERS PAPER NYLON & WOOLLEN GARMENTS COMPRESSED AIR GUNESD SOURCESMAN MADE: PLASTICSESD SOURCESMAN MADE:NATURAL: HUMAN BODY MOVEMENT OF CLOUDS HUMAN BODY PACKING HANDLING MATERIALS: COMMON POLYTHENE BAGS, WRAPS,ENVELOPESCOMMON BUBBLE PACK FOAMCOMMON PLASTIC TRAYS, PLASTIC TOTE BOXES, VIALSTYPICAL

35、CHARGE GENERATORSASSEMBLY, CLEANING, TEST & REPAIR AREA ITEMS: SPRAY CLEANERSCOMMON SOLDER SUCKERSCOMMON SOLDER IRONSSOLVENT BRUSHING ( SYNTHETIC BRISTLES)CLEANING, DRYINGTEPARATURE CHAMBERS PACKING HANDLING MATERIALS:ESD VOLTAGE MEASUREMENTELECTROSTATIC VOLTAGE MEANS OF STATIC GENERATION 10% RW 40%

36、 RW 55% RWPERSON WALKING ACROSS CARPETPERSON WALKING ACROSS VINYLFLOOR WORKER AT A BENCHCERAMIC DIPS IN PLASTIC TUBE CERAMIC DIPS IN VINYL SET UP TRAYS CIRCUIT AS BUBBLE PLASTIC COVER REMOVED CIRCUIT AS PACKED IN FOAM LINED SHIPPING BOX35000 15000 750012000 5000 30006000 800 4002000 700 40011500 400

37、0 200025000 20000 700021000 11000 5500ESD VOLTAGE MEASUREMENTELECTROREASONS FOR DISBELIEFESD 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

38、NOT BE INSTANT. (LATENT FAILURE) REASONS FOR DISBELIEFESD DAMAG GUIDE TO STATIC CONTROL MATERIALSSURFACE RESISTIVITY-OHMS PER SQUAREINSULATORMATERIALS IN THIS RANGE ARE NOT EFFECTIVE FOR STATIC CONTROL1012 To 10 15 GUIDE TO STATIC CONTROL M1010 To 10 12ANTISTATICTHESE MATERIALS DO NOT GENERATE AND S

39、UPPORT HIGH STATIC CHARGES. BUT DISCHARGE RATES ARE TOO SLOW FOR MOST INDUSTRIAL APPLICATIONS.SURFACE RESISTIVITY-OHMS PER SQUARE GUIDE TO STATIC CONTROL MATERIALS1010 To 10 12ANTISTATICTHE GUIDE TO STATIC CONTROL MATERIALSSURFACE RESISTIVITY-OHMS PER SQUARESTATIC DISSIPATORS ( PARTIALLY CONDUCTIVE)

40、MATERIALS MOST SUITABLE FOR STATIC CONTROL WORK SURFACES, FLOORING AND FLOOR MATS, SEALING, OVERALLS106 To 10 9 GUIDE TO STATIC CONTROL MGUIDE TO STATIC CONTROL MATERIALSSURFACE RESISTIVITY-OHMS PER SQUARECONDUCTIVEMATERIALS FOR CONTAINERS AND HANDLING EQUIPMENT.BELOW 104 OHMS PER SQUARE EFFECTIVE S

41、TATIC 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 EQUIPMENTS IN USE.101 To 10 4GUIDE TO STATIC CONTROL MATERIOBJECTIVES OF ESD CONTROL PREVENTING STATIC CHARGE GENERATIONDISSIPATING T

42、HE DEVELOPED CHARGENEUTRALISING DEVELOPED CHARGE FOR A CHARGE FREE ZONECONTROLLING OF ESDWORK SURFACEAIRHUMAN BODYFLOOROBJECTIVES OF ESD CONTROL PREVDOS MINIMISE HANDLING. KEEP PARTS IN ORIGINAL PACKING UNTILL READY FOR USE. USE ESD PROTECTIVE CONTAINERS AND BAGS. DISCHARGE STATIC BEFORE HANDLING DE

43、VICE 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.DOSDONTS TOUCH THE LEADS OF DEVICE. SLIDE ES DEVICES OVER ANY SURFACE. PUT MASKING TAPE ON PROGRAMMABLE ICS. STORE OR CARRY SENSITIVE CO

44、MPONENTS OR ASSEMBLIES IN PLASTIC BAGS. STORE SENSITIVE COMPONENTS IN THERMOCOLE/PLASTIC FOAM. HANDLE ES DEVICES IN “NON ESD CONTROLLED” ENVIRONMENT. DONTS TOUCH THE LEADS OF DEVESD MODELSESD MODELS HAVE BEEN DEFINED TO DESCRIBE THE EFFECTS ON ESD SENSITIVE DEVICES: HUMAN BODY MODEL CHARGED DEVICE M

45、ODEL MACHINE MODELESD MODELSESD MODELS HAVE BEENHuman 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

46、to an ESD sensitive part, the part may be damaged by direct discharge or by an electro static field.0.1mHRbVbCbCb : 50 to 350pFRb : 150 to 10KOhmsVb : 3 to 20 KVHuman Body Model (HBM)1015 1014MATERIALS CLASSIFICATION MATESD AUDIT PERSONNEL TRAINING FOR ESD PREVENTIVE AWARENESS TRAINING CERTIFICATION

47、 TRAINING CONTROL PROGRAM AUDITESD AUDIT PERSONNEL TRAINING ESD知識和控制課件ESD TEST & MEASURING INSTRUMENTS STATIC CHARGE METERWRIST STRAP AND GROUND TESTERFOOTWEAR TESTERSURFACE RESISTIVITY METERSTATIC SENSORCONTINUOUS WRIST STRAP MONITORCONTINUOUS WORK STATION MONITORTEMPARATURE AND HUMIDITY INDICATORE

48、SD TEST & MEASURING INSTRUMENTESTING EVALUATIONThe test evaluation report consists of the following test areas for each ESD item/s:POINT TO POINT SURFACE RESISTIVITY TOP/BOTTOMPOINT TO POINT SURFACE RESISTIVITY IN/OUTSURFACE TO GROUND RESISTANCEPERSON TO GROUND RESISTANCESTATIC CHARGE MEASURING TEST

49、STATIC SHIELDING TEST TESTING EVALUATIONThe test evaTESTING EVALUATION 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 ChairThe tests are generally conducted for the following item/s:TESTING EVALUATION The tests PERSONAL GROUNDINGTwo types of Personal Grounding:Wrist StrapsFoo