DVD-75C Ray's ESD Prevention Secrets - IPC Training Home Page

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DVD-75C Transcriptthe assembly on a clean surface and plug in the component. There should be no problem. Afterall, you’re wearing shoe grounders.But the shoe grounders only work with conductive flooring – and because this is a non-ESD safework area, your body probably has a static charge that can now discharge rapidly. This rapidtransfer of a charge to a conductive surface may cause damage to the ESD sensitive componentsand assemblies.Static Producing MaterialsMany common office materials might appear harmless, but they can cause an ESD event. Thesematerials can generate and hold static charges -- thereby creating charged fields. For example,when a charged object, such as these plastic safety glasses, is brought close to an ESD sensitivedevice, the electric field causes charge separation in the ESD sensitive device. If the ESDsensitive device then comes in contact with a conductive item while exposed to the field, thedevice can be damaged.The best remedy for this problem is to completely eliminate these types of non-conductivematerials from the workstation. This includes common plastics such as hairbrushes and tapedispensers; styrofoam food and beverage containers; vinyl binders; post-it notes and other paperproducts; plastic pens; bubble wrap; and equipment with plastic housings. This also includesitems you may bring in to decorate your work area – like family photos in plastic frames andballoons. Even plants and flowers.One secret is that routing sheets and other important paperwork that travels with the job maycause ESD problems. The paper itself may be a static generating source. But what’s worse isthat many plastic document protectors can generate significant static charges. Documents in theirplastic protectors may be placed directly on top of the product, creating a significant hazard. Thesolution is to substitute the normal plastic document protector with an ESD safe documentprotector. Similarly, depending on the level of protection required, it may be beneficial to replacemany frequently used items such as water bottles, flux bottles and tool boxes with ESD safeversions of the same items. Many vendors will be able to advise you on ESD safe alternatives.And when it comes to post-it notes, they are never acceptable – no matter what color you’reusing.In addition, tape and other adhesive backed materials such as labels are very common and mayput our electronics assemblies at risk. Some of these tapes create enormous static charges whenused. Another of Ray's secrets is that just because your supervisor gives you some tape doesn'tmean that it is ESD safe. Traditional cellophane tape creates large static charges when it is pulledfrom the dispenser or reel, but many people think that high temperature tape, such aspolyimide/Kapton, is ESD safe. Not at all – as you can see. There are tapes that are specificallydesigned to be used in an electronics manufacturing environment and they do not create staticcharges when used.6
DVD-75C TranscriptWhen static generating materials are necessary for your job, we have some secrets for reducingthe effect that these items might have at the workstation. For example, anti-static solution may beapplied to tools and plastic housings on equipment. Air ionizers can also help neutralize charges.This machine blows ionized air into the work area to help neutralize any positive or negativecharges that accumulate on non-conductive items, or items that are not connected to ground.Your company may also use a humidity control system in the manufacturing area. These systemswork by ensuring that the humidity does not drop to a low enough percentage to increase the riskof an ESD occurrence. As the humidity decreases and the air gets dryer, it becomes much easierto generate a static charge.But, as we mentioned earlier, the real secret to dealing with static producing materials is toeliminate as many of these materials from your work area as possible.Static Producing ActivitiesThe way we work can also have an impact on how ESD is controlled. Many of our habitualactivities can generate static charges that can damage ESD sensitive devices. For example,sometimes we get so busy that we leave clutter around our workstations. But this clutter can leadto conditions that cause an ESD event. Ray’s secret for minimizing this potential problem is todo some housekeeping every day.Another secret for controlling ESD involves being aware of how we move as we work. Raysuggests that we not rub our hands together, raise our arms, shift our feet or legs and put on ortake off smocks around ESD sensitive devices. These movements generate charges that candamage sensitive components and assemblies. Ray likes to tell a story about an inspector whosedream was to be a ballerina. She’d be listening to the Nutcracker on her i-pod and her arms andfeet would be moving all over the place.Our final secret has to do with grooming. The desire to comb your hair is a good one – but not atyour workstation. Combing hair is a generator of static electricity and should be avoided.Another story involves a test technician who was in a reggae band. He’d be constantlyexperimenting with different hairstyles while working on assemblies. Definitely not a safepractice.HandlingIt’s important to realize that improper handling of ESD sensitive items – even when you’reproperly grounded and doing your job at an ESD safe workstation – can cause damage tocomponents and assemblies. The first secret for proper handling of components and assemblies isto minimize handling as much as possible. Whenever possible, use a vacuum pick to move acomponent from one location to another.7
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