Antistatic Bags & Conductive Bags
An antistatic bag, or conductive bag, is a shipping bag for electronic devices which can be affected by electrostatic.
These plastic bags normally and have a distinctive colour according to its properties:
- Silver for metallised PET film and other similar plastics
- Pink or black for polyethylene
* The polyethylene model can also be made as foam or bubble wrap, either as sheets or bags.
To create the anti-static effect, the black bags or silver bags are slightly conductive, forming what is known as a Faraday Cage around the item to be protected avoiding any discharges from being deposited onto the protected devices as the bags are handled.
What is static electricity?
All items are made of small atoms. These atoms are made up of even smaller items called protons, neutrons and electrons. The protons are charged positive; the neutrons have no charge and the electrons are charged negative. Under normal conditions there are the same amount of protons and electrons giving atoms no charge.
However, these electrons can move. When separating or rubbing together of materials, electrons can move from atom to atom or from one material to another (triboelectric charges). This can mean that atoms can hold a positive or negative charge. (Dependant on movement and direction of electrons). If the material in question is an insulator, this charge can be held and not move. This is called static electricity.
The rapid movement or decay of these charges can cause expensive problems, whether it is huge and dangerous charges such as lightening or simply an annoying (and sometimes painful) "Electric shock" when touching a filing cabinet or when getting out of a car. (These charges are normally on you!).
These charges can be a huge problem for small sensitive electronic devices. Some devices can be damaged or destroyed by as little as 30 volts. Charges on your body simply by walking or even sitting at your chair can be in excess of 5000 volts (Human body model). This is because of items of clothing rubbing together or as simple as shoes separating from the ground. When items are insulators such as carpets, charges are much higher.
Imagine the damage this could cause. This is why it is important that insulators should be avoided and all possible static electricity generators (Such as you) should/must be grounded to eliminate any build up of charges.
An antistatic agent is a compound used for treatment of materials or their surfaces in order to reduce or eliminate build up of static electricity generally caused by the triboelectric effect. Its role is to make the surface or the material itself slightly conductive, either by being conductive itself, or by absorbing moisture from the air, so some humectants can be used. The molecules of an antistatic agent often have both hydrophilic and hydrophobic areas, similar to those of a surfactant; the hydrophobic side interacts with the surface of the material, while the hydrophilic side interacts with the air moisture and binds the water molecules.
Internal antistatic agents are designed to be mixed directly into the material, external antistatic agents are applied to the surface.
Common antistatic agents are based on long-chain aliphatic amines (optionally ethoxylated) and amides, quaternary ammonium salts (e.g., behentrimonium chloride or cocamidopropyl betaine), esters of phosphoric acid, polyethylene glycol esters, or polyols. Indium tin oxide can be used as transparent antistatic coating of windows.
Conductive polymers are another option. PEDOT:PSS is used by H.C. Starck (a former Bayer company) as an antistatic coating under name "BAYTRON P" in several applications, eg. in some Agfa photographic films.
Antistatic agents are also added to some military jet fuels, to impart electrical conductivity to them and avoid buildup of static charge that could lead to sparking igniting the fuel vapours. Stadis 450, with dinonylnaphthylsulfonic acid (DINNSA) as the active ingredient, is the agent added to some distillate fuels, solvents, commercial jet fuels, and to the military JP-8 fuel. Stadis 425 is a similar compound, for use in distillate fuels and solvents.
Antistatic bags - Which one and when?
"METALISED SHIELDING" BAGS (Silver in colour).
- If bags, holding STATIC SENSITIVE COMPONENTS, are to be handled OUTSIDE OF AN "EPA", they should be METALISED SHIELDING BAGS, a FARADAY CAGE!
- Metallised Shielding bags can be an effective FARADAY CAGE, subject to the quality of material and physical condition.
- DO NOT CREASE the bag, as this can breakdown the integrity of the metallised shield!
- You should not use any bags damaged with TEARS AND / OR PUNTURES, as these can DESTROY THE FUNCTION OF THE FARADAY CAGE!
- Metallised Shielding bags CAN DETERIORATE with use, MONITORING them for effectiveness is VERY IMPORTANT!
BLACK CONDUCTIVE BAGS
- It is POSSIBLE TO DAMAGE a static sensitive component inside a Black Conductive bag with a contact ESD!
- Black Conductive bags, holding static sensitive components, should only be handled in an EPA and while the person is grounded in order to ensure that no potential difference occurs.
- Black Conductive bags allow for a good path to Earth when used with other.
ANTISTATIC BAGS (Pink, clear etc.)
- These are the only acceptable "plastic" bags in an EPA!
- Antistatic bags offer NO effective protection against a contact ESD!
- They should only be used for NON STATIC SENSITIVE components, e.g. nuts, bolts, paper etc.
- ORDINARY PLASTIC BAGS can generate and hold static charges in excess of 10,000v! Antistatic bags deteriorate with time and wear, MONITORING them is VERY IMPORTANT.
- ESD: Electrostatic Discharge. An uncontrolled surge of "static" between objects with different voltage potentials.
- STATIC: An electrical charge/field that isn't moving.
- EPA: Electrostatic Protected Area. A static safe handling area which could be a bench, a room or any other designed area, which should not have any "static field" greater than 100v maximum.
- ANTISTATIC: Minimal generation or retention of a "static" charge.
- CONDUCTIVE: Low resistance i.e. less than 1Meg-ohm (106) - the closer to 1Meg-ohm, the slower the discharge.
- STATIC DISSIPATIVE: Increased resistance, which protects better against an ESD i.e. between 1Meg-Ohm (106) and 1000 Meg-Ohm (109).
- INSULATIVE: Does not allow the free flow of electrons, therefore, it will more than likely cause problems e.g. prevent a path to earth, hold a "static" field, etc.
- FARADAY CAGE: A conductive barrier against ESD e.g. Metallised Shielding Bag, Conductive Box etc.
- TRIBOCHARGE: To generate "static" by the rubbing or separating of surfaces.
For detailed explanations of the above, Please see IEC61340-5.
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