ESD知识和控制课件.ppt

1、An extensive course onE L E C T R O S T A T I C D I S C H A R G E A n e xExamples:LightningZappingE x a mp l e s :An atom is made up of chargesnAn atom is made up of charges.nIn its stable state,the size of the positive charge at the centre(nucleus)of an atom is balanced by the size of all the negat

2、ive charges of the electrons,making it neutral overall.nThe electrons whirl around the centre like planets.A n a t o m i s ma d e u p o f c h a r g e s ACreating a charge imbalancenWhen an atom loses an electron,it has a charge imbalance.nSince this atom has lost an electron,which is a negative char

3、ge,the atom is now a positive charge.nWhen it gains an extra electron,an atom becomes a negative charge.Electron“lost”C r e a t i n g a c h a r g e i mb a l a n c e Wh eA dischargenThis movement of charges is called a discharge.This powerful,rapid movement of charges can damage electronic components

4、.Lets see it again!A d i s c h a r g e T h i s mo v e me n t o f c hELECTRO STATIC DISCHARGE IS DEFINED AS THE TRANSFER OF ELECTRO STATIC CHARGES BETWEEN BODIES AT DIFFERENT POTENTIAL CAUSED BY DIRECT CONTACTOR INDUCED ELECTRO STATIC FIELDIT IS AN UNPLANNED OCCURANCE OF ELECTRO-STATIC DISCHARGEWH A

5、T I S E S D?I T I S A N U N P L A N N E DWh a t i s E S D E l e c t r o s t a t i c D i s cMoving peopleImproper groundingUnshielded cablesPoor connectionsMoving machinesLow humidity(hot and dry conditions)The most common causes of ESD are:Mo v i n g p e o p l e T h e mo s t c o mmo n cFigure 13-14:

6、Power Transmission SystemF i g u r e 1 3-1 4:P o w e r T r a n s mi s s iFigure 13-15:Grounds on IC ChipsF i g u r e 1 3-1 5:G r o u n d s o n I C C hSome 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 de

7、vice in question is referred to as a solder-sucker,and is available in antistatic versions for use with MOS devices.To avoid damaging static-sensitive devices,the following procedures will help to minimize the chances of destructive static discharges:S o me d e v i c e s u s e d t o r e mo v e s oTr

8、iboelectric generationBasic Principles(2)T r i b o e l e c t r i c g e n e r a t i o n B a s i c When two materials are in intimate contact,they share electrons which are at their surfaces.When materials are in contactWh e n t w o ma t e r i a l s a r e i n i n t iThe triboelectric charge of two mat

9、erials in contact.T h e t r i b o e l e c t r i c c h a r g e o f t wWhen two materials are in intimate contact,they share electrons which are at their surfaces.When materials are in contactIt is possible for electrons to be“stolen”from one material by nuclei in the other material,because they have

10、a stronger forceWh e n t w o ma t e r i a l s a r e i n i n t iWhen these materials are separated,electrons are removed from one material and are transferred to the other material.When the materials are separatedElectrons“lost”Electrons“gained”Wh e n t h e s e ma t e r i a l s a r e s e p a rE S D 知

11、识和控制课件When the materials are separatedElectrons“lost”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 insulators,the charges remain at the points of contact.A

12、 charge spreads all over an ungrounded conductor.Wh e n t h e ma t e r i a l s a r e s e p a r a tThe triboelectric charge when two materials placed in contact are then separated.T h e t r i b o e l e c t r i c c h a r g e w h e n This action takes place with all types of materials.With insulators,t

13、he charges remain at the points of contact.A charge spreads all over an ungrounded conductor.When the materials are separatedElectrons“lost”Electrons“gained”The loss and gain of these electrons creates an imbalance of negative and positive charges on the surface of each material.T h i s a c t i o n

14、t a k e s p l a c e w i t h aWhen the materials are separatedElectrons“lost”Electrons“gained”When the surfaces are rough,this intimacy and separation is assisted by rubbing the materials together.Wh e n t h e ma t e r i a l s a r e s e p a r a tWhen the materials are separatedElectrons“lost”Electron

15、s“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 materialsWh e n t h e ma t e r i a l s a r e s e p a r a tWhen the materials are separatedElectrons“lost”Electrons“gained”The drier the air(lower relative humid

16、ity,RH)the higher the generated chargeWh e n t h e ma t e r i a l s a r e s e p a r a tThe creation of a charge when materials are separated is termed“triboelectric charging”T h e c r e a t i o n o f a c h a r g e w h e n Charging by InductionBasic Principles C h a r g i n g b y I n d u c t i o n B

17、a s i c P r iCharging by inductionC h a r g i n g b y i n d u c t i o n T h e p r e s eCharging by inductionC h a r g i n g b y i n d u c t i o n I f t h e c oCharging by inductionC h a r g i n g b y i n d u c t i o nWalking on carpetThoughts and theories Wa l k i n g o n c a r p e t T h o u g h t s

18、 a n d Walking across carpetnWalking across a carpet creates a charge imbalance on the lower surface of shoes.Wa l k i n g a c r o s s c a r p e t Wa l k i n g aA strong electric fieldnThis charge imbalance creates a strong electric field that emanates in all directions.nThe material in the sole of

19、shoe enables a strong field to influence charges within foot.A s t r o n g e l e c t r i c f i e l d T h i s c hAn induced chargenSince 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.nBut the body still

20、 has a balanced charge overall(it has not lost or gained any charges).A n i n d u c e d c h a r g e S i n c e t h e b o dContacting a source of chargesnWhile 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

21、,door knob,metal stapler,etc.)nThis enables charges to be provided by the metallic object.C o n t a c t i n g a s o u r c e o f c h a r g e sCharging through the airnThis movement of charges is thus producing an overall charge imbalance in my body,since I was previously neutral overall.C h a r g i n

22、 g t h r o u g h t h e a i r T h i s mAn overall charge imbalancenTherefore,after that brief encounter with the metallic object,my body now has an overall charge imbalance.A n o v e r a l l c h a r g e i mb a l a n c e T h eRemoving that chargenThe only way to remove the possibility of damaging an E

23、SD-sensitive device or assembly is to remove the overall charge imbalance on my body.nThis 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.R e mo v i n g t h a t c h a r g e T h e o n

24、l y w1.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 t

25、hrough the capacitance between the object and ground.E L E C T R O S T A T I C D I S C H A R G E P R O C E 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 F

26、RICTION SEPERATION INDUCTIONS T A T I C G E N E R A T I O N T H E S T A T I C CF WALKING ON SYNTHETIC SURFACEF RELATIVE MOVEMENT ON CHAIRF TABLE,COMPUTER,PLASTIC PARTS NYLON OR SYNTHETIC CLOTHESF CLEANING WITH COMPRESSED AIRF CLEANING WITH SOLVENTC A U S E S F O R E S D G E N E R A T I O N WA L TYPE

27、 OF MATERIAL RELATIVE HUMIDITY TYPE OF CLOTHING SPEED AND MANNER OF WALKING BODY RESISTANCEF A C T O R S:L In 1937,The German flying boat Hinderburg arriving in Lakehurst,New Jersey,caught fire while anchoring at its landing mast.L In 1970s,in USA,a space craft launching rocket exploded during the f

28、ueling operation,killing 3 engineers.L 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.L 3 to 3

29、0%of Integrated Circuits manufactured every year die in“infancy”due to ESD.R E C O R D E D E S D A C C I D E N T S I n 1 9 3 7Device sensitivity to Electrostatic DischargeAt higher magnification the pit in the area between the base and emitter becomes more obviousD e v i c e s e n s i t i v i t y t

30、o E l e c t r o sDevice sensitivity to Electrostatic DischargeAt this magnification see the 1/2 ofthe width of the material has been destroyed.D e v i c e s e n s i t i v i t y t o E l e c t r o sE S D 知识和控制课件E S D 知识和控制课件Statistics4 0 5 0%E Q U I P ME N T S H A V E F A I L ESENSITIVE CONSTITUENTSFA

31、ILURE MODESMOS STRUCTURESSHORTBIPOLAR JUNCTIONSLEAKAGEFILM RESISTORSVALUE SHIFTMETALIZATION STRIPESOPENFIELD PERFECT STRUCTURESOPERATIONALPIEZOELECTRIC CRYSTALSDEGRADEDCLOSELY SPACED CONDUCTORSDEGRADEDS E N S I T I V E C O N S T I T U E N T SF A I L U R E PLASTICS CONDUCTORS FURNITURES VINYL FLOOR C

32、OOLING FANS WITH PLASTIC BLADES PRINTERS/COPIERS PAPER NYLON&WOOLLEN GARMENTS COMPRESSED AIR GUN P L A S T I C S E S D S O U R C E S MA N MA D E:HUMAN BODY MOVEMENT OF CLOUDS H U MA N B O D Y PACKING HANDLING MATERIALS:COMMON POLYTHENE BAGS,WRAPS,ENVELOPESCOMMON BUBBLE PACK FOAMCOMMON PLASTIC TRAYS,

33、PLASTIC TOTE BOXES,VIALSASSEMBLY,CLEANING,TEST&REPAIR AREA ITEMS:SPRAY CLEANERSCOMMON SOLDER SUCKERSCOMMON SOLDER IRONSSOLVENT BRUSHING(SYNTHETIC BRISTLES)CLEANING,DRYINGTEPARATURE CHAMBERS P A C K I N G H A N D L I N G MA T E R I A L S:ESD VOLTAGE MEASUREMENTELECTROSTATIC VOLTAGE MEANS OF STATIC GE

34、NERATION 10%RW 40%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

35、700 40011500 4000 200025000 20000 700021000 11000 5500E S D V O L T A G E ME A S U R E ME N T E L E C T R OREASONS 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 GE

36、NERAL COMPONENT FAILURE;FAILURE MAY NOT BE INSTANT.(LATENT FAILURE)R E A S O N S F O R D I S B E L I E F E S D D A MA GSURFACE RESISTIVITY-OHMS PER SQUAREINSULATORMATERIALS IN THIS RANGE ARE NOT EFFECTIVE FOR STATIC CONTROL1012 To 10 15 G U I D E T O S T A T I C C O N T R O L M1010 To 10 12ANTISTATI

37、CTHESE MATERIALS DO NOT GENERATE AND SUPPORT HIGH STATIC CHARGES.BUT DISCHARGE RATES ARE TOO SLOW FOR MOST INDUSTRIAL APPLICATIONS.SURFACE RESISTIVITY-OHMS PER SQUARE1 0 1 0 T o 1 0 1 2 A N T I S T A T I CT H ESURFACE RESISTIVITY-OHMS PER SQUARESTATIC DISSIPATORS(PARTIALLY CONDUCTIVE)MATERIALS MOST

38、SUITABLE FOR STATIC CONTROL WORK SURFACES,FLOORING AND FLOOR MATS,SEALING,OVERALLS106 To 10 9 G U I D E T O S T A T I C C O N T R O L MSURFACE RESISTIVITY-OHMS PER SQUARECONDUCTIVEMATERIALS FOR CONTAINERS AND HANDLING EQUIPMENT.BELOW 104 OHMS PER SQUARE E F F E C T I V E S T A T I C S H I E L D I N

39、G I S 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 4G U I D E T O S T A T I C C O N T R O L MA T E R I|PREVENTING STATIC CHARGE GENERATION|DISSIPATING THE DEVELOPED CHARG

40、E|NEUTRALISING DEVELOPED CHARGE FOR A CHARGE FREE ZONEWORK SURFACEAIRHUMAN BODYFLOORO B J E C T I V E S O F E S D C O N T R O L P R E V MINIMISE HANDLING.KEEP PARTS IN ORIGINAL PACKING UNTILL READY FOR USE.USE ESD PROTECTIVE CONTAINERS AND BAGS.DISCHARGE STATIC BEFORE HANDLING DEVICE BY TOUCHING NEA

41、RBY GROUNDED SURFACE.HANDLE DEVICES BY THE BODY.TOUCH THE ESD PROTECTIVE PACKAGE BEFORE TOUCHING INSIDE OF DEVICE.KEEP A DUST FREE WORK AREA.D O S TOUCH THE LEADS OF DEVICE.SLIDE ES DEVICES OVER ANY SURFACE.PUT MASKING TAPE ON PROGRAMMABLE ICS.STORE OR CARRY SENSITIVE COMPONENTS OR ASSEMBLIES IN PLA

42、STIC BAGS.S T O R E S E N S I T I V E C O M P O N E N T S I N THERMOCOLE/PLASTIC FOAM.HANDLE ES DEVICES IN“NON ESD CONTROLLED”ENVIRONMENT.D O N T S T O U C H T H E L E A D S O F D E VESD MODELSESD MODELS HAVE BEEN DEFINED TO DESCRIBE THE EFFECTS ON ESD SENSITIVE DEVICES:HUMAN BODY MODEL CHARGED DEVI

43、CE MODEL MACHINE MODELE S D MO D E L S E S D MO D E L S H A V E B E E N 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 t

44、o 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 KVH u ma n B o d y Mo d e l (H B M)1015 1014MA T E R I A L S C L A S S I F I C A T I O N MA T PERSONNEL TRAINING FOR ESD PREVENTIVE AWARENESS TRAININ

45、G CERTIFICATION TRAINING CONTROL PROGRAM AUDITE S D A U D I T P E R S O N N E L T R A I N I N G E S D 知识和控制课件F STATIC CHARGE METERFWRIST STRAP AND GROUND TESTERFFOOTWEAR TESTERFSURFACE RESISTIVITY METERFSTATIC SENSORFCONTINUOUS WRIST STRAP MONITORFCONTINUOUS WORK STATION MONITORFTEMPARATURE AND HUMI

46、DITY INDICATORE S D T E S T&ME A S U R I N G I N S T R U ME NThe test evaluation report consists of the following test areas for each ESD item/s:vPOINT TO POINT SURFACE RESISTIVITY TOP/BOTTOMvPOINT TO POINT SURFACE RESISTIVITY IN/OUTvSURFACE TO GROUND RESISTANCEvPERSON TO GROUND RESISTANCEvSTATIC CH

47、ARGE MEASURING TESTvSTATIC SHIELDING TEST T E S T I N G E V A L U A T I O N T h e t e s t e v aW Antistatic P.E BagsW Static Shield BagsW Conductive BagsW Conductive Grid BagsW Antistatic ApronsW Conductive BrushW Foot WearW WESD Mat conductive MatW Work SurfaceW ESD LaminateW Wrist StrapW Heel Stra

48、pW ESD ChairThe tests are generally conducted for the following item/s:T E S T I N G E V A L U A T I O N T h e t e s t s PERSONAL GROUNDINGTwo types of Personal Grounding:Wrist StrapsFootwearP E R S O N A L G R O U N D I N G T w o t y p e s o fWRIST STRAPS Daily Check with Wrist Strap Worn Test with

49、 a Wrist Strap testerWR I S T S T R A P S D a i l y C h e c k w i t hFloor Point to PointF l o o r P o i n t t o P o i n tFloor Resistance to GroundF l o o r R e s i s t a n c e t o G r o u n dGarments Point to PointG a r me n t s P o i n t t o P o i n tGarments Point to Ground May need person weari

50、ng garmentNeeds to be connected to ground as wor nG a r me n t s P o i n t t o G r o u n d N e e d s Chair Check all parts of Chairs to Ground Seat,Backrest,Armrest,Foot RestC h a i r C h e c k a l l p a r t s o f C h a i rE S D 知识和控制课件E S D 知识和控制课件TYPES OF ESD DAMAGECATASTROPHIC FAILUREUPSET FAILUR