In this series of 8 Bitesize ESD Basics Training videos, Vaughan Callan demonstrates and explains the basic concepts of electrostatic discharge (ESD) and how in the hi-tech manufacturing environment we can overcome the harmful effects of ESD and learn to control it. Today, we will start with part 1 on…
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The first thing to note is that all materials will tribocharge. Electrostatic charge generation occurs when two surfaces contact and then separate. Some atom electrons transfer causing an imbalance; one surface has positive charge, and the other surface has negative charge. Both polarity charges need to be controlled in your ESD control program, since both positive and negative charges can discharge and damage electronic components. A static field meter can be used to measure the charge of a field and after contact and separation will show that one item will be negatively charged having an excess of electrons the other item will be positively charged having lost some electrons.
For most people static electricity is represented by the noise or crackle heard on a radio that interferes with good reception or the shock experienced when touching a metal object after walking across a carpeted room or sliding across a car seat. Static electricity is also observed as static cling when clothes are stuck together after coming out of a clothes dryer. Most of the time people have observed static electricity when the weather is cold and dry. While many people tend to think of static electricity as being at rest or not moving, static electricity causes the most concern when it ceases to be stationary. Electrostatic charge is most commonly formed by the contact and separation of two materials. The materials may be similar or dissimilar, although dissimilar materials tend to liberate higher levels of static charge. An example is a person walking across the floor, static electricity is produced when the person’s shoe sole makes contact then separates from the floor surface. Another example is an electronic device sliding in or out of a bag, a magazine or a tube.
ESD or ElectroStatic Discharge is the rapid, spontaneous transfer of electrostatic charge induced by a high electrostatic field. Usually, the charge flows through a spark between two bodies at different electrostatic potentials as they approach one another. If two items are at different electrostatic charge levels, as they approach one another a spark or electrostatic discharge can occur. This rapid, spontaneous transfer of electrostatic charge can generate heat and melt circuitry in electronic components.
In a normal environment like your home there are innumerable ESD events occurring, most of which you do not see or feel. It takes a discharge greater than 2,000 volts for a person to feel the discharge. ESD is the hidden enemy in a hi-tech manufacturing environment; just because you cannot see or feel an ESD event it does not mean that ESD events are not occurring. Human beings are insensitive unless the ESD event is around 2,000 volts or more, whereas many electronic components can be damaged by much smaller discharges. ESD control is necessary to prevent innumerable little lightning bolts or ESD events from occurring. It’s estimated that around 25% of unidentified electronic failures are typically a result of ESD.
Here we have a photo of ESD arcing from a person’s finger to a component. This is not a computer simulation, although the technician was connected to a small magneto to enable us to take the photograph of the ESD arcing from his finger to the component. As you can see here, manifesting itself in that small lightning bolt.
This is that same component we saw in the previous image, although we’ve taken a photograph on a scanning electron micrograph. The image is of the ESD damage after the removal of the capacitor metallization. Note the characteristic eruption through the oxide. To get this photograph it was magnified 10,500 times.
Watch the whole episode below: