Selecting the proper Anti Static Bag &  Electronics Packaging

ESD Bags

 

Electronic Packaging Products Information - Most people are aware of the effects of static electricity in general. Dragging shoes on carpet and touching a person or something metal, makes a brief shock. Drying synthetic textiles in a cloths dryer will often produce "static cling". The static electricity behind these common occurrences can damage modern electronic devices and circuits. As electronic circuits and their connecting pathways continue to shrink in size, their vulnerability to damage from static electricity has swelled. A factor of 10 shrinkage in feature size can make gate oxides 10 times more sensitive. Protective handling and packaging techniques have been adopted by all segments of the electronics industry from the chip foundry to the production floor to the field service arena. One of the most common static anticipatory items is a bag. Use of protective bags began in the 60's with the introduction of "pink poly" bags. Static shielding bags were introduced in the late 70's. While the military has long used moisture barrier bags, the increase of Surface Mount Technology has greatly increased usage. A device needs to be protected from three primary static threats:

 

Direct Discharge (ESD): A discharge directly to a bag can subject the device inside to very high current, melting or fusing the circuit.

 

Static Fields: Fields can induce destructive currents in circuit conductors. Field differentials can break down the circuit dielectric.

 

Tribocharging: Friction between the bag and device can produce damaging static voltage and fields.

 

The Static Shielding test, applies an undeviating discharge to a bag. An oscilloscope connected to a feeler inside the bag measures the amount of voltage that goes through the bag. This test also addresses the field threat. Fields are generated by the release to the outside of the bag. Fields that penetrate the bag are represented in the voltage amount. Tribocharging tests are difficult to perform and are not very repeatable. Information from bag specs are only a yardstick, and do not tell how materials will perform in use. Bag users are left to compare these standards or perform their own tests. Surface Resistivity is a sign of a material's ability to allow static to move around (dissipate). It does not necessarily suggest low tribocharging. The bag has the capacity to dissipate a static charge to ground. This keeps static electricity from building up on the package or the mechanism. The material is also antistatic, suggesting that it will not charge up when rubbed against other materials. The resistivity is in the dissipative range of about 109 - 1011. These bags have no shielding ability. A static field or discharge happening outside the bag will penetrate the bag and harm electronics inside. Pink Poly consists of plastic that has been loaded or surface coated with a chemical antistat. The pink color is only a colorant that was added to tell the difference between static control materials from normal packaging. A small number of users are now requesting clear transparent dissipative poly bags. In the past, a reactive form of amine was used in the chemical antistat. This antistat caused oxidation of some metals and stress cracking in some plastics. The pink color is sometimes incorrectly associated with this amine type antistat. Some manufacturers converted to amide-based antistats and removed the pink color in response to customer demand. Pink Poly bags are useful for packaging items that have no static vulnerability. Their primary use is to package support or processing material that will be in close proximity to static sensitive devices. This keeps static generating packaging materials away from sensitive areas. Black Poly is very conductive, usually about 103 - 4, and will dissipate a charge very fast. Regretfully this fast dissipation also means that a charged person or object can 'spark' (ESD) to its surface. The basic idea in static control is to swap charges at a slow enough rate to avoid sparks. However, not so slow as to allow a static build up. Due to the material being conductive it does provide some minute amount of shielding. anti static bags, anti static, anti static peanut, anti static poly tubing, anti static poly bag, anti static packaging, bag anti static, anti static foam, anti static product, ESD Bags, Electro Static Bags, ESD Products Wide Selection Anti Static Bags, Anitstatic bags, Anti Static Packaging, ESD Bags, ESD Tape, static electricity bags

 

Anti Static Bags (/)

 

An antistatic bag, or conductive bag, is a shipping bag for electronic devices which can be affected by electrostatic.

These plastic bags normally have a distinctive color according to its properties:

• Silver for metalized 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 descharges 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.

 

Antistatic agent

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 vapors. 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?

“METALIZED 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!
• Metalized 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 metalized shield!
• You should not use any bags damaged with TEARS AND / OR PUNTURES, as these can DESTROY THE FUNCTION OF THE FARADAY CAGE!
• Metalized 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 Terminology

• 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. Metalized 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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