Every year, static electricity causes billions of dollars in losses due to it not being controlled adequately in areas where microelectronic parts are manufactured, assembled, stored, and shipped. Both humans and objects generate static charges, and all microelectronic parts are affected by the electrostatic discharge.
Therefore protection of electronic parts and components from electromagnetic interference or electrostatic induced fields using ESD conductive plastic bins is crucial. When you need to store static-sensitive electronic parts that are going to be used in electrostatic discharge protected work areas, ESD bins are the most reliable option. ESD storage bins and totes lessen the risk of damage from electrostatic discharge, making it easier to handle, transport, and store static-sensitive components and materials.
ESD bins are manufactured from polypropylene with conductive material that avoids the buildup of electrostatic charge. They are permanently conductive and are not affected when washed with regular cleaners. ESD storage bins are used in data centers to store and protect microchips, circuit boards, circuit cards, assemblies, motherboards, hard drives, capacitors, transistors, logic chips, SCSI drives, spare CPUs, spare DRAM drives, flash memory, SSD drives, video cards, GBIC modules, and other semiconductor components.
ESD Protective storage bins such as anti-static ESD containers and ESD safe boxes are a necessity where microelectronic parts (ESD-sensitive small components) are manufactured, assembled, stored, or shipped to secure and protect them from ESD damage.
It’s a fact that we cannot eradicate static electricity, that it is a part of nature. We can only control it in these three ways:
1. By reducing the potential for generating static discharges by removing static producing material
2. By shielding static-sensitive parts and assemblies in unrestrained environments
3. By ensuring a safe path to ground to prevent the accumulation of charge
An appropriate container must give the right combination of grounding, attenuation, and static-generation features.
Grounding is a type of connection that creates zero potential relatives to the ground. All materials can be charged to some extent, but some dissipate this charge more quickly than others. The decay rate is the time necessary for the charge to dissipate almost completely.
Insulative objectives, by contrast, can hold a charge for a longer period. On materials that have electrical features lying between those of conductors and insulators, the charge will decay according to the material’s surface resistivity, capacitance relative to the ground, and contact resistance relative to ground.
Capacitance, compared to the ground, will affect the decay rate because high capacitance can upsurge the charge a device sees, as seen in the formula: Q = CV.
Contact resistance is the resistance between the surface of a container and ground; the (grounded) surface upon which a tote or bin will rest, for example. For a fixed charge –voltage – greater contact resistance means slower decay rates and is affected by three factors:
- Roughness or (surface asperities)
- Contaminants
- Weight (or pressure)
N.B that charge on materials in the lesser dissipative range can drop very swiftly upon grounding because the surface current is nonlinear when charge avalanche happens because of high E-fields.
Contact area and invariably contact resistance between a container and a grounded surface is usually a function of a container’s shape and size, but it also varies with the quality of the container’s surface.
In practice, the relationship of these factors implies that containers with a resistivity superior to 1010 W/square would have to reduce a decay rate. If possible, surface resistivity should be between 105 W/square and 1010 W/square.
Attenuation is the level of electrostatic shielding afforded by a container. It is defined as the strength of the field allowed to enter a container. Such materials are capable of attenuating an electrostatic field so that its effects do not reach the stored or contained items and produce damage. An electrostatic shielding material to be used for an ESD bin should have a conductive layer with a surface resistivity of < 1 X 104 W/square, or a volume resistivity of < 100 W-cm.
Although the extent of the ESD protection required will differ depending on the sensitivity of the devices to be protected. If there is the slightest possibility that a container holding ESD-sensitive items could enter an environment where static is uncontrolled, use a box that incorporates electrostatic shielding.
Charge production is the result of two surfaces coming in contact and separating from each other. Since containers rub against different materials, charge generation is a significant problem.
Unfortunately, little or no work has been carried out on charge generation characteristics in bins. Ideally, a bin should have a low propensity to generate a charge.
In summary, a container’s preferred electrical features would include:
- Surface resistivity of 105 – 1010 W/square
- Inclusion of a layer with surface resistivity of less than 104 W/square for electrostatic field attenuation
- A limited tendency toward charge generation
Chemical characteristics of an effective ESD bin
Two fundamental concerns related to the chemical composition of a container: its effect on the product and its impact on the environment.
Product compatibility means that a bin should neither alter the performance or reliability of the components it houses nor harm workers or the atmosphere.
Fortunately, a requirement calling for neutral pH will remove most concerns, although individual testing is recommended to measure the full environmental impact of container material.
Mechanical characteristics of an effective ESD bin
Durability, size, and style are the major mechanical physiognomies of an ESD bin. Shaping these features is more than just a matter of selecting a container big and sturdy enough to take the devices in question.
Style and size affect the efficiency with which plant space is used, as well as compatibility with automated handling equipment and other factors. A container significantly more significant than the device(s) it must hold during transport or storage can increase labor costs and reduce the workshop. So is a container that is too small to hold a reasonable number of items.
An ESD bin should be designed for the items it will contain, taking into consideration of the handling system to be used. Style to be used is determined by the area where it would be used and the handling system. In a static-controlled setting, a cover may be optional, while in an open space, it is a necessity.
All of these are good practices in general, and they help avoid damages that might occur as a result of casual contact. In some handling situations, a removable cover might be necessary for programmed insertion and removal of parts. In other situations where assured closure is needed, an attached cover would be the better choice.
It is also essential to take into account whether a container is going to be used vertically, horizontally, or both ways.
Generally, mechanical necessities are a function of manufacturing, shipping, and storage environments, and containers should be selected to conform with them.
In conclusion, a cost-effective ESD-protective bin must:
- Possess a surface resistivity between 105 and 1010 W/square
- Give an electrostatic-field attenuation through the inclusion of a layer with surface resistivity < 104 W/square
- Have a limited tendency toward charge generation
- Be of pH about 7.0 (i.e., chemically inert)
Also, the bins structures must conform to the environments in which they will be used, as well as to the devices that will be carried and the handling gear with which they will be used. Finally, the ESD bins selected must offer an adequate ratio of price to performance. With this guidance and intelligently defined criteria, you can ensure that the ESD bin you purchase conforms to the needs of your ESD-control and prevention purposes.
The pictures below are examples of what an ESD bin might look like:
