Download Static electricity

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Electrical ballast wikipedia, lookup

Ohm's law wikipedia, lookup

Voltage optimisation wikipedia, lookup

Flexible electronics wikipedia, lookup

Alternating current wikipedia, lookup

Electrical engineering wikipedia, lookup

Opto-isolator wikipedia, lookup

Electromagnetic compatibility wikipedia, lookup

Electronic engineering wikipedia, lookup

History of electric power transmission wikipedia, lookup

Mains electricity wikipedia, lookup

Stray voltage wikipedia, lookup

Semiconductor device wikipedia, lookup

Electrification wikipedia, lookup

Integrated circuit wikipedia, lookup

History of electromagnetic theory wikipedia, lookup

Electricity market wikipedia, lookup

Ground (electricity) wikipedia, lookup

Electrostatic loudspeaker wikipedia, lookup

Transcript
Static Electricity and Precautions
Static electricity is an imbalance in the amount of positive and negative charges found within
the surface of an object. The sudden flow of static electricity or Electrostatic discharge (ESD)
can interfere with the operation of electronic circuits especially the circuits using CMOS and
Microprocessor devices.
Static electricity in an imbalance in the amount of positive and negative charges within the
surface of an object. There is strong e-field around these charges whether the charges are
moving or still.’ Contact induced charge separation’ causes instant static discharges in the form
of unnoticed sparks. Static electricity is most often noticed in dry climates and especially in
centrally heated buildings and near photocopy machines.
The sudden flow of static electricity or Electrostatic discharge (ESD) can interfere with the
operation of electronic circuits especially the circuits using CMOS and Microprocessor
devices. ESD produces very high current waveforms and fast magnetic (H-field) or electrostatic
field (E-field) disturbances. These can induce very high voltage or current in nearby sensitive
circuitry and corrupt data or even cause spurious breakdown. Such things happen if a flash drive
or an input device is plugged into the USB when there is high static charge in the body.
The “Tribocharging” poses a constant danger to electronic devices, especially when handling
CMOS semiconductors. This also can cause catastrophic effect when one device is plugged into
another such as the use of USB to connect peripherals to PC. Static electricity may be very high
in low humid environments such as air conditioned rooms. Usually negative charge
accumulates near the floor while positive charge accumulates 1 meter above the ground. The
static charge can be removed by grounding the body or allowing air flow in the room.
Static Electricity Precautions
1 Be cautious when working around or with electronics during the dry months of the year.
Discharge yourself often, and think before you touch a static sensitive device. Static electricity
may be free, but it can be costly.
2. When working with any electronic equipment it is best to be sure you are totally discharged
by touching something that is metal.
3. Before handling electronic components, it’s important to realize that semiconductors can be
damaged by high voltage “static electricity” carried on your body.
4. Integrated circuits and transistors have several connections. If all of these connections are at
the same voltage, there is no potential difference across them and no damage will result.
However, if just one of the connections sees a different voltage from the rest, damage may
occur. Protect them by connecting all of the pins together or wrap them in aluminium foil.
5. Increase humidity. Static effect is increased in environments of low humidity. Buildings
using air-conditioning, high levels of heating, or those with a lot of insulation can have low
humidity. Increase the airflow into the room. It will remove static electricity.
6. When working with sensitive electrical components or volatile materials (such as
papers/powders/flammable liquids) sparks and electrical discharge can cause catastrophic
failure in sensitive electrical components and ignite volatile substances. Take steps to eliminate
them:
Electrostatic discharge
ESD is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits
are made from semiconductor materials such as silicon and insulating materials such as silicon
dioxide. Either of these materials can suffer permanent damage when subjected to high
voltages, as a result there are now a number of antistatic devices that help prevent static build
up
Causes of ESD
One of the causes of ESD events is static electricity. Static electricity is often generated through
Tribocharging, the separation of electric charges that occurs when two materials are brought
into contact and then separated. Friction between two materials results in Tribocharging, thus
creating a difference of electrical potential that can lead to an ESD event.
Another cause of ESD damage is through “Electrostatic induction”. This occurs when an
electrically charged object is placed near a conductive object isolated from ground. The
presence of the charged object creates an electrostatic field that causes electrical charges on the
surface of the other object to redistribute. Even though the net electrostatic charge of the object
has not changed, it now has regions of excess positive and negative charges.
An ESD spark is triggered when the electric field strength exceeds approximately 10 – 30
kV/cm (the dielectric field strength of air). This may cause a very rapid increase in the number
of free electrons and ions in the air, temporarily causing the air to abruptly become an electrical
conductor in a process called dielectric breakdown.
ESD Damage due to charge potentials
Nonconductive objects can be damaging charge carriers even without any sparking or obvious
effect. This occurs due to the formation of very small static electricity charge potentials when
nonconductor come into contact with each other and then separate.
Lightning strike – The natural ESD
The best known example of a natural spark is a lightning strike. In this case the potential
difference between a cloud and ground, or between two clouds, is typically hundreds of millions
of volts. The resulting current that flows through the ionized air causes an explosive release of
energy. During an electrostatic discharge, the intervening atmosphere becomes electrically
overstressed. The diatomic oxygen molecules are split, and then recombine to form ozone (O3),
which is unstable, or reacts with metals and organic matter. If the electrical stress is high
enough, nitrogen oxides can form.