ESDBasics (1)

1、ESD BASICS Basic Concepts inElectroStatic Discharge (ESD)基本的概念关于静电基本的概念关于静电Copyright 2005 DESCO INDUSTRIES INC.7/05ESD Control Training（ESD控制培训）控制培训）IntroductionDPer ANSI/ESD S20.20 Training Plan Requirement, Initial and recurrent ESD awareness and prevention training shall be provided to all person

2、nel”Use PowerPoint with Desco 06821 ESD Awareness GuideAnsi/ESD s20.20培训计划要求，最初和现在的ESD，每一个人都应知道和如何预防？Safety First - Concern WHEN Working Around High Voltage As important as ESD control is, it is of secondary importance compared to employee safety When working with voltages over 250 VAC, ESD personne

3、l grounding should not be used including Wrist Straps, ESD Footwear & GarmentsGround fault circuit interrupters (GFCI) and other safety protection should be considered wherever personnel might come into contact with electrical sources.安全第一：关系到人身安全问题，当你工作时，你身边有高电压包围你。当工作带电压超过250V，带静电人员接地将不能使用接地，包

4、括静电带，静电鞋，静电衣。人体任何可能接触电源的地方，可以考虑使用接地电路断流器，和其它的安全保护。SafetyDThe written ESD Control Plan should be in accordance with ANSI/ESD S20.20 100 volt Human Body Model limit as a large majority of the ESD products greater than 100 volt sensitivity ESD Association wrote commercial version of MIL-STD- 1686 for U

5、S Department of Defense which has adopted itESD training should be repeated as specified in the companys written ESD Control PlanQuizzes in Awareness Guide could be “objective evaluation technique to ensure trainee comprehension and training adequacy.”ESD控制计划将要与ANSI/ESD S20.20一致。100V人体限制电压，静电ESD将会产生

6、电压将会远远大于100V。ESD协会写了一 本商业版本“MIL-STD-1686 “将会采用。ESD培训将重复再三被列入公司ESD控制计划测试将指导将评估技术和保证新人的理解和适当的培训。IntroductionDStatic Electricity OR Electrostatic ChargeWhen 2 surfaces contact then separate.Some Electrons move or are given up to the other surface, causing an imbalance.Electrons are Negative.Protons are

7、 Positive. Defined as Electric charge at restAll Materials TribochargeElectroStatic ChargeGeneration or TribochargingD定义为静电静止不动的所有物料都会摩擦起电当二个表面接触，然后分开。一些电荷移动到到其它的表面，出现电荷不平衡。电子是正极负离子是负极All Materials Tribocharge Opening plastic bag, combing hair, unrolling tape, etc. Build up charge walking on carpet,

8、 sliding across car seat. Charge greater when weather is cold and dry. ESD is when the charge moves.ElectroStatic Charge Generation:静电的产生静电的产生D打开塑料袋，梳头发，解开带子等等行走在地毯上会增加电荷，滑行车座位当天气很冷和很干，静电将远远增大ESD就是电荷移动Charge Generation or TribochargingWhen two materials make contact and are then separated, a transfe

9、r of electrons from one material to the other may take place. The amount of static electricity generated depends upon the materials subjected to contact or separation, friction, the area of contact or separation, and the relative humidity of the environment. At lower relative humidity, as the enviro

10、nment is drier, charge generation will increase significantly. Common plastics generally will create the greatest static charges.D当2个物料接触或分开，电荷转移从一个物料到其它的地方静电的数量产生依靠物料接触，分开，摩擦，接触和分开的空间，及相关的湿度和环境。很低湿度环境，如同很干燥的环境，静电将会增加，同一塑料通常来说是会产生最大的静电。ESD or ElectroStatic Discharge Charges Seek Balance Discharge is

11、 Rapid Creating Heat静电寻找平衡迅速放电产生热量If two items are at different electrostatic charge levels, as they approach one another, a spark or Electrostatic Discharge (ESD) can occur. This rapid, spontaneous transfer of electrostatic charge can generate heat and melt circuitry in electronic components.D假如两块不

12、同的静电电压，它们相接时，静电会产生火花，并且迅速的转移电荷，并且能产生热量和烧毁电子电路。Examples Of Electrostatic Discharge or ESDESD的例子 Lightning闪电闪电 Zap from a door门窗旁补电击到门窗旁补电击到 There are innumerable ESD events occurring which you do not see or feel. ESD is the hidden enemy in a high tech manufacturing environment. 这里有无数件事件静电发生，哪里你没有看见或感

13、觉到，ESD是一个高隐藏的，高技术的制造环境。DPhoto of ESD arcing from finger to component 图片是ESD从手机到元器件喇叭This is not a computer simulation. 这不是计算机模拟。这不是计算机模拟。 Technician was connected to a small magneto.技术上是连一个小的磁铁。技术上是连一个小的磁铁。 Photos courtesy of Hi-Rel Laboratories, Inc., Spokane, WA 图片是高能量消耗实验室。DScanning electron micr

14、ograph (SEM) image of the ESD damage after removal of the capacitor metallization. Note the characteristic eruption thru the oxide. Magnification is 10,500 times.现扫描现扫描ESD损坏损坏显微图片，注意这图片特性爆发通过氧化物。放大倍数显微图片，注意这图片特性爆发通过氧化物。放大倍数10500倍。倍。 Photos courtesy of of Hi-Rel Laboratories, Inc., Spokane, WA 图片是高能量

15、消耗实验室。DTwo Types of Materials Conductors Electrical Current Flows Easily So Can be Grounded Examples: metals, carbon and people (due to impurities the human bodys sweat layer) 电子电流所以要接地比如：铁，碳墨，和人（由于人体的汗水杂质）Materials that are called dissipative are conductors, able to remove electrostatic charges to

16、ground. The resistance of dissipative materials is the higher portion of the conductive range.物体消耗又称传导，能将静电传导地。物体消耗阻值是一个高传导的一部份。D Electrical Current Does Not Flow Easily So Cannot be GroundedExample: Plastics, glass, and dry airTwo Types of Materials Insulators Insulators or Non-Conductors Insulator

17、s like this plastic cup will hold the charge and cannot be grounded and conduct the charge away.DTypical ElectroStatic Voltages Walking across a carpet: 1,500 - 35,000 volts Walking over untreated vinyl floor: 250 - 12,000 volts Vinyl envelope used for work instructions: 600 - 7,000 volts Worker at

18、a bench: 700 - 6,000 volts Unwinding regular tape: 9,000 - 15,000 volts Higher number is generated at low humidityDBut to Feel a Discharge it must be about 2,000 voltsCostly Effects Of ESDPeople Discharge FrequentlyDESD That a Person Cant Feel Can Easily Damage Electronic Components Even less than10

19、0 volts might damage a component!DESD is The Hidden Enemy Consider all electronic components ESD sensitive Program may identify classification of sensitivity to ESD damage Newer electronic components can have reduced width of circuits and microscopic spacing of insulators within them, increasing the

20、ir sensitivity to ESD ESD damage cannot be seen by the naked eyeDOptical photo of a large Integrated Circuit which has experienced ESD damage to the pin noted by the arrow.D Photos courtesy of of Hi-Rel Laboratories, Inc., Spokane, WAHigher magnification photo of pin noted by the arrow in the prior

21、slide This taken at 400 times magnification on a 4 X 5 photo. The damage is noted as the fuzz at the end of the arrow. Photos courtesy of of Hi-Rel Laboratories, Inc., Spokane, WADNow you see it! Overlying glassivation has been removed and the surface decorated to show the ESD damage at 5,000 times

22、magnification in this scanning electron micrograph.D Photos courtesy of of Hi-Rel Laboratories, Inc., Spokane, WATypes Of ESDDevice Damage Latent DefectComponent woundedbut Inspection passes as good Catastrophic FailuresInspection is able to detect failureDLatent DefectsMore Costly Sub Assembly pass

23、es inspection Assembly passes inspection Product passes inspection Works a while for customer Then Upsets & Mysterious Problems More Returns More Warranty Costs Lower Customer Satisfaction DRepair Costs Increase if Failure Detected LaterOne study indicated the repair cost to be:$10 Device$10 Dev

24、ice in board - $100$10 Device in board and in system - $1,000$10 Device and system fails - $10,000Catastrophic failures are detected during inspection but components with latent defects pass as goodDLatent DefectsMost Frustrating Pass inspection as good May fail later Cause equipment down time Costl

25、y field repair work Adversely impacting customer satisfactionHidden EnemyESD damage may occur Cannot be felt Cannot be seen Not detected through normal inspection proceduresDLike Germs, ESD Is The Hidden EnemyControl Germs Sterilization in medicine You would never consider having surgery in a contam

26、inated operating room, you should never handle electronic assemblies without taking adequate protective measures against ESDControl ESDDThe Prerequisitesof ESD Control Identify ESD Protected Area Identify ESD sensitive items Provide ESD control trainingDThe Basics Of ESD Control Ground Conductors Sh

27、ield ESDS when Stored or Transported outside EPA Remove or Neutralize Insulators with IonizersD Wrist Straps Snug on skin Clean Cord connected to groundGround ConductorsIncluding People Foot Grounders Grounding tab under foot Worn on both feet Contact to ESD floor Personnel Grounding DevicesD Wrist

28、StrapsDaily Test Personnel Grounding Devices Must work, so test wrist strap daily (or use continuous monitors) Foot Grounders Must work, so test foot grounder dailyDWorkstation Grounding Devices Dissipative Worksurfaces Ground ESD worksurface via ground cord to common point ground to equipment groun

29、d Conductive Floor Mats Ground ESD floor mats via ground cord to equipment groundDClean Using Only ESD Cleaners Dissipative WorkSurfacesYou should be aware of the type of work surfaces and flooring materials used by your companyBe sure to keep your work surface clean, and follow the maintenance proc

30、edures recommended by the manufacturerRegular cleaners contain silicone, an insulatorDNeutralize Insulators Via Ionization Ionizer air flow floods area with Ions - Neutralizing Charge Insulators cannot be groundedDDirect Ionizer Air Flow to ESD Sensitive Items Ionizers produce positively and negativ

31、ely charged ions Fans airflow to cover the work area Ionization can reduce static charges on an insulator or isolated conductorsDTypes of Ionizers Bench Top Ionizers Neutralizing Air Nozzles / Hand Gun Overhead Ionizers Neutralize charges on insulators and isolated conductors Ionizers require period

32、ic cleaning of emitter pins If out of balance (or voltage offset) they can charge itemsDShield ESD Sensitive Items Outside Protected AreaFaraday Cage effect charges to be conducted on surface of the conductor. Closed Metallized Shielding BagSince like charges repel, charges will rest on the exterior

33、. Charges Kept on Outside of Package: Covered Conductive Tote BoxDESD Packaging Electrostatic discharge shield A barrier or enclosure that limits the passage of current and attenuates an electromagnetic field resulting from an electrostatic discharge. ESD bags should be closed and containers have li

34、ds in place ESD packaging only be opened at an ESD protective workstation by properly grounded personnel.DESD Protected Workstations An ESD protective workstation is an area that has been established to effectively control electrostatic charges. Grounding all conductors (including people) Removing all insulators Or neutralizing process