Category Archives: Question & Answers
Seeing ElectroStatic Discharge (ESD) damage is basically impossible. Damage to semiconductor device structure is NOT visible at ordinary magnifications of an optical microscope. If the microscope is capable of 1000X-1500X magnifications, you just might be able to “see” something. The method used, only occasionally as there is considerable expense, is by delayering and etch enhancement producing high magnification photographs using a scanning electron micrograph (SEM). See Images of ESD Damage, photos of Human Body Model (HBM) ESD damage provided by Hi-Rel Laboratories, Inc. at 6116 N Freya, Spokane, Washington 99217 (509-325-5800 or www.hrlabs.com). Used with their permission.
It typically takes a ESD discharge greater than 2,000 or 3,000 volts for a person to feel the “zap”.
There is no exact voltage number where a person starts to feel a discharge. The ESD Association addresses this topic three times in the ESD Handbook ESD TR20.20 using these phrases:
- “greater than 2000 volts”
- “about 3,000 volts”
- “exceed 3,000 volts”
The sensitivity of people is different and measuring the voltage is imprecise, so neither 2,000 nor 3,000 is to be an exact number.
Per ESD Handbook ESD TR20.20 Wrist Strap section 22.214.171.124 “Static electricity is a natural phenomenon that occurs in all climates and at all levels of relative humidity year round. Most people cannot feel an electrostatic discharge unless the static voltage is greater than 2000 volts.”
Per ESD Handbook ESD TR20.20 section 2.3 Nature of Static Electricity “The quantity, charge, is difficult for most people to visualize without some reference. As an example, an average person has a capacitance of about 100 picofarads (pF) and can feel a static discharge at their fingertips when the potential difference between their body and a grounded conductive object is about 3,000 volts (3 kV).”
Per ESD Handbook ESD TR20.20 ionizer section 126.96.36.199.3.3 Discharge Time and Product Sensitivity “Most personnel will not notice static discharges from the human body until they exceed 3,000 volts.”
The point, of course, is just because you cannot see or feel an ESD event, it does mean that ESD events are not occurring. Human beings are insensitive unless the ESD is several thousand volts. Many electronic components can be damaged by much smaller discharges.
Do Protektive Pak In-Plant Handlers need to have lids on while ESD sensitive items are in them? How do these Protektive Pak In-Plant Handlers work?
Outside the ESD protected area (EPA), the Protektive Pak lids need to be in place to provide the electrostatic discharge shielding ESD control property which is required by the Packaging standard ANSI/ESD S541. Per section 6.2 Outside an EPA “Transportation of sensitive products outside of an EPA shall require packaging that provides: 1. Low charge generation. 2. Dissipative or conductive materials for intimate contact. 3. A structure that provides electrostatic discharge shielding.”
Inside the EPA, it would still be a good idea to have the lid in place, but it is not a requirement. The Protektive Pak impregnated corrugated has a buried shielding layer. In shielding, we utilize the fact that electrostatic charges and discharges take the path of least resistance. The charge will be either positive or negative; otherwise the charge would balance out and be no charge.
Like charges repel and so the electrostatic charge will reside on the outer conductive surface.
A Faraday Cage effect can protect ESDS contents in a container with a shielding layer (this is what a shielding bag has). This Faraday Cage effect protects people in real life when a lightning bolt strikes an airplane or automobile with the charge residing on the outer metal fuselage or car body.
The Faraday cage effect causes charges to be conducted around the outside the surface of the conductor. Since like charges repel, charges will rest on the exterior.
To complete the enclosure, make sure to place lids on boxes or containers, and close shielding bags. Packaging with holes, tears, or gaps should not be used as the contents may be able to extend outside the enclosure and lose their shielding as well as mechanical protection.
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