DVD-76C ESD Control for Non-Manufacturing Personnel

DVD-76C ScriptDVD-76CESD Control for Non-ManufacturingPersonnelBelow is a copy of the narration for DVD-76C. The contents forthis script were developed by a review group of industry experts andwere based on the best available knowledge at the time ofdevelopment. The narration may be helpful for translation andtechnical reference.Copyright © IPC – Association Connecting Electronics Industries. All Rights Reserved.Although the scene you’ve just witnessed has been exaggerated, the effects of ESD damage arequite real. Many companies do a good job of ensuring that their manufacturing employees areproperly trained and knowledgeable about the effects of ESD. However there are many othernon-manufacturing personnel that may require access to ESD safe areas.This video is about controlling ESD in the facility. You’ll be introduced to ESD and see how itaffects the world of electronics and electronics assembly. Then we’ll show how ESD controlapplies to non-manufacturing personnel. We’re talking about managers; the purchasing, sales andmarketing folks; customers; and maintenance personnel. We’re also including the president of thecompany and the janitorial staff.ESD is the sudden transfer, or discharge of electricity from one object to another. 2000 volts isthe lowest level of ESD that most people feel. But static zaps under twenty volts are capable ofdamaging, or destroying sensitive electronic components.Let’s begin by looking at how electrostatic charges are generated. Every object has the ability totake on an electrostatic charge. The charge may be positive, negative or neutral. A positive chargemeans some atoms or molecules on the surface of a material are missing electrons. A negative netcharge means that some atoms or molecules on the surface of a material have acquired extraelectrons. A charge is neutral on the surface of a material when the atoms and molecules have abalanced number of protons and electrons.Positive or negative charges are usually developed when two objects are placed into contact, thenmoved against each other and separated. One material attracts electrons from the other material.Therefore one material has a positively charged surface. The other material is negative in netcharge. When an item has a charge, this charge is called static electricity. The word “static”means “at rest” so we can say that the charge is just sitting on the item – waiting for anopportunity to move.When two conductive objects with different levels or polarity of charge come close together, or incontact with each other, the charge rapidly moves from one object to the other. This rapid

DVD-76C Scriptmovement of the electrical charge changes it from static electricity to ESD. It is important tounderstand how certain materials behave with these electrostatic charges. We’ll separate theminto three categories.The first material we’ll talk about is a conductor. Conductors are typically some type of metal,like a piece of wire. The term conductor means that this material will conduct electricity. It willfreely allow the movement of electrons through it. This will enable us to use groundingtechniques to eliminate charges. Grounding means providing a path for the extra charges to flowinto the earth, leaving the material with a neutral charge.The second material is called an insulator. Insulators prevent the flow of electricity. As withconductors, these materials can also become charged, but grounding techniques will have little tono effect of charge neutralization.The third material is called dissipative. These are materials that are partially conductive, and theirresistive properties fall somewhere in between conductors and insulators. They are conductors ofelectricity – just not very fast conductors. The human body, most electronic components andstatic control materials are classed as dissipative. They will allow grounding techniques to beused, but electrical charges are drained slowly. This is actually a desired feature in many casessince draining charges slowly minimizes the chance of damaging electronic components.People are the biggest cause of ESD. That’s because our bodies easily pick up static electricity. Infact, our skin can store relatively large amounts of this electric charge. Door knobs probably don’tmind the spark. But when ESD passes through an electronic device such as an integrated circuit,it can cause serious internal damage to that component – resulting in a scrapped component.The tiny circuit paths in these sensitive devices can be burned up, or severed by an ESD voltageso small that our senses can’t even detect it. Remember, we can only feel discharges above about2,000 volts, but some ESD sensitive components can be damaged by voltages less than twentyvolts. And you won’t even know the damage has occurred – but the destruction will exist insidethe component.Even when the device is soldered onto a printed circuit board, it’s still not safe. It can be damagedby a discharge that passes through the board’s conductive pattern to the ESD sensitivecomponent. The amount of voltage needed to damage or destroy varies from component tocomponent, but as these devices become smaller and more complex, their sensitivity to ESDgenerally increases.Sometimes the damage caused by ESD doesn’t mean the component will immediately fail.Instead, the assembly passes inspection, gets shipped to a customer – and then fails later on,creating a very unhappy customer.ESD is one of the most serious problems facing the electronics industry today. If it isn’tcontrolled, the results are higher costs, lower product quality and angry customers – especially ifa product fails at a critical time.On the other hand, controlling ESD means product quality can be improved and costs can be keptdown. This usually leads to increased customer satisfaction and sales – which is a win-winsituation for everyone. Let’s stop for a moment to review the information we just covered.Now that you know what ESD is and what it can do to electronic devices, let’s see how ESDcontrol applies to non-manufacturing personnel – the people who don’t touch the product. In this

DVD-76C Scriptsection we’ll be discussing personal grounding, product handling, static fields and how torecognize and report unsafe ESD practices.The most important thing to learn about controlling ESD is that we are the most important part ofESD control. In order to reduce the risk of ESD damage to the devices, it’s necessary to wearpersonal grounding equipment. The idea is to drain off charges in a controlled manner before theyreach the devices. To do that, all conductive surfaces and our bodies need to be connected to acommon grounding point.If a static charge comes into contact with any partially conductive surface, this contact safelychannels the charge away from ESD sensitive devices and neutralizes them into the earth, or“ground.” People who don’t work directly with product need to be properly grounded whenentering ESD safe areas. Since they are walking, heel straps, also known as shoe grounders, mustbe worn. These shoe grounders will drain off charges that may be carried into the area.Shoe grounders are designed to connect your body through your sock to a special conductivefloor or mat. It is ideal for shoe grounders to be worn on both feet. That’s because when you arestanding or walking, one foot will always be on the floor – unless you have the ability to levitate.These charts show why most companies require people to wear two shoe grounders.Now, let’s take a look at how a typical shoe grounder is worn. The strap is adjusted so that oneend is in contact with your sock or skin, and the other end is in contact with the floor. There isenough moisture in your sock to provide a complete electrical connection from your body toground. Shoe grounders come in a variety of styles to accommodate different types of footwear.Visitors to ESD safe areas also need to wear company provided equipment. In many cases, thiswill consist of disposable shoe grounders – which are worn once, then discarded.Shoe grounders should be tested at regular intervals to make sure they are working properly. Yourcompany will let you know where and how often you should do this. When testing shoegrounders, place one foot on the metal plate and press the test button. The pass light indicatesthat the device is functioning properly. Remove that foot and test the other foot. Each foot mustbe tested individually. Testing both feet at the same time will not indicate a failure unless bothstraps fail.If you experience any problem with shoe grounders, make sure they have been put on properly.Always test a new set before entering the ESD safe area.Your company may also require you to wear a conductive smock. Conductive smocks are used tocover static generating clothing and drain any charges to ground. It’s important to completelybutton the smock so no part of your clothing is exposed. The sleeves should never be rolled up tothe point where underlying clothing is exposed.At this point, let’s talk about the rules regarding product handling. There’s really only one ruleand it’s pretty simple to remember. Do not touch any electronic components or assemblies. Itdoesn’t matter if they’re on the production floor, in receiving or in shipping. The rule is: don’ttouch.What if the CEO of your company gives you a direct order to bring him an electronic assembly?In this type of situation, make sure you’re adequately supervised and have received training inproper handling. Customers and other visitors should also be cautioned against touching anythingout on the production floor.

DVD-76C ScriptOur next topic is static fields. Static generating material can affect ESD sensitive devices. Whatwe’re talking about are common plastics such as hair brushes, plastic safety glasses, pens andtape dispensers; paper products; and styrofoam cups. These types of non-conductive materialstend to generate and hold static charges – thereby creating electric fields.The way this works is that when a charged object such as these plastic safety glasses is broughtclose to an ESD sensitive device, the electric field causes charge separation in the ESD sensitivedevice. If the ESD sensitive device then comes in contact with a conductive item while exposedto the field, the device can be damaged. Therefore, don’t bring these types of materials into ESDsafe areas, or if you must have them in the area, keep them away from electronic assemblies.Even your clothing can generate and hold static charges. It’s important that you don’t stand tooclose to a workstation containing ESD sensitive devices. Your company will have an assigneddistance – usually one to three feet.How do you know that a component or an assembly is ESD sensitive? You don’t really.Therefore, it’s a good practice to assume all electronic components and assemblies are ESDsensitive. That way, there won’t be unexpected problems.Our last topic has to do with becoming a member of the ESD police. Our motto: to protect andserve. When you’re out on the production floor, you can practice your powers of observation. Beon the lookout for unsafe ESD practices.Does everyone have on his or her personal grounding equipment? Aside from shoe grounders,operators seated at workstations should be wearing wrist straps. Your company may requireconductive smocks. Is everyone wearing one? Are they worn properly? Are workstations free ofstatic generating materials? Are visitors properly supervised and wearing shoe grounders? Do yousee another activity that could produce an ESD event?Let’s take a look at these scenes from the production floor. Can you recognize the unsafe ESDpractices? This person isn’t wearing any personal grounding equipment. In this case, the ESDsensitive items being transported aren't protected.Here, an operator is passing an unprotected assembly too close to an unprotected video monitor.At this workstation, there are non-conductive items near to the ESD sensitive components. Byrecognizing and reporting unsafe ESD practices, you directly affect the quality of the productsyour company produces.This program has presented the details of ESD control for non-manufacturing personnel. First, wediscussed static electricity and took as look at how poor ESD practices can affect electroniccomponents. Then we discussed personal grounding; the rule about touching product; staticfields; and concluded with an offer to join the ESD police.ESD control is everyone’s responsibility – even when you don’t work in production. You need towear the appropriate equipment and observe the rules for safe ESD practices. In this way, you canmake a difference.