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Intricately manufactured electronic components can be very delicate and fragile; especially those that are electrostatic-sensitive. Extra precautions must be taken, particularly during transportation and shipping, to prevent physical and electrostatic damage to the component or device. Fortunately, there is an answer to this: ESD safe foam.
Static protective foams offer protection from both physical and static damage. While they help to protect static sensitive components from electrostatic discharge, they are also widely used for their exceptional cushioning protection. Combined with exterior packaging (i.e. conductive box, container, etc.), ESD safe foam can absorb any impact, abrasion, and shock caused during shipment and handling. As a result, the products will arrive at their destination undamaged, leading to fewer returns, minimising the costs of replacements and greatly reducing product rejects. ESD safe foam packaging can even boost long-term sales through reliable supply, customer satisfaction and an enhanced company reputation.
ESD safe foam comes in three various types: conductive, anti-static and static dissipative, each with their unique properties. When it comes to choosing between anti-static, static-dissipative and conductive foams, it helps to understand the differences between the three. In this article, we will guide you on the different types of ESD safe foams, their uses and benefits, as well as helping you to decide which foam is best suited to your application.
The first type of ESD safe foam we will be introducing is conductive foam. Conductive foam is a polyethylene foam filled with carbon, giving it its conductive properties and distinctive black colour. There are two types of conductive foam: low-density conductive foam and high-density conductive foam. Although similar, the two types of conductive foams offer different properties and applications from each other. Designed for repeat use, the foam offers an extremely reliable method for protecting static-sensitive components in transit.
Conductive foam can help to minimise the effects of ESD on static-sensitive electronic components by acting like a Faraday cage when an item is fully enclosed within it. Because of this, a static shielding bag is not needed as an outer container when using conductive foam. Despite it being the most expensive type of ESD foam, it serves its purpose in fully protecting your ESD sensitive component (plus, it is better value for long-term applications!)
While conductive foam is similar to standard packaging foams, there is one crucial difference – the addition of carbon to the polymer mix during the manufacturing process to provide a high level of conductivity. This allows any electric current to pass through the cell structure of the foam and away from the component. Thus, a static shielding bag is not needed as an outer container when using conductive foam.
Overall, the foam will have permanent conductive performance, meaning it is ideal for multi-trip packaging and in-plant handling applications. Its performance isn’t affected by atmospheric conditions such as humidity.
This ESD safe material will typically have a surface resistivity of fewer than 10^(4) ohms/sq. and a volume resistivity of fewer than 10^(4) ohms/cms, which offers a quicker transfer of any static charge to a grounding source or adjacent conductive material.
High-density conductive foams are semi-rigid and have no structural strength. This type of foam should be only used for inserting “legged” static sensitive components, because it “shorts out” all of the pins, ensuring no potential difference between any of them.
In contrast, low-density conductive foams are softer, lightweight, and much more flexible compared to high-density foams. This makes them a suitable choice for transit packaging and cushioning of static-sensitive components such as circuit boards or hard disk drives.
Next, we move on to anti static foam. Anti-static foam, also known as pink anti-static foam, provides excellent cushioning and exceptional mechanical and electrical protection for static-sensitive components such as computer chips, circuit boards, etc. These specialised foams help in eliminating static discharge and provide a high degree of cushioning protection from shock, impact, and vibration. Due to this, this type of foam is widely used in many forms of anti-static packaging / storage devices like conductive euro boxes, component boxes, transit packs and so forth.
Anti-static foam is a polyurethane foam that is chemically enhanced with anti-static agent (surfactant). Its distinct pink colouring makes this type of foam easy to identify. When rubbed against itself, the foam will not generate a static charge. Generally, anti-static foam is used for single trip shipping and is not reusable.
The unique properties of pink anti-static foam allow the foam to slowly dissipative electrostatic charges that are potentially created by adjacent components, the component itself or even human handlers during the transit process. To ensure the static-sensitive component is fully protected during shipping, make sure the component is placed in a static shielding bag to protect it from outside electrostatic charges.
Manufactured to include an anti-static additive, these pink anti-static foams give a surface conductivity that will decrease over time. A commonly used additive to manufacture the foams is Glycerol Monostearate (GMS). This additive is introduced during the extrusion phase of the material manufacture. It will then slowly migrate to the edges of the foam before forming lines on the surface.
One end of the microscopic anti-static molecule protrudes from the material edge and draws in moisture from the ambient air to allow a conductive path for current to pass through. This type of foam typically has a volume resistivity in the range of 10^(10) – 10^(12) ohms/cms and often has a surface resistivity that is higher still. Due to the way in which the foam works, performance can be enhanced with increased atmospheric humidity.
The last type of ESD foam we will talk about it static-dissipative foam. Static dissipative foam, often blue in colour, falls between in the middle range of electrical resistance; greater than anti-static and lower than conductive. This type of foam allows the static charge to slowly dissipate from its surface to ground, preventing sudden electrostatic discharge. Controlling the speed in which the static charges go to the ground, helps the foam protect the material enclosed inside of it.
Now you know about the three types of ESD foams, you may ask yourself “so, which type of foam do I need?“. The choice of ESD safe foam material depends on several factors, most importantly the specific requirements of the electronic components being protected. To help guide you on choosing the best foam for your application, we have listed several key points to consider.
Bondline Electronics Ltd is one of the leading UK suppliers and manufacturers of static control products – supplying the full ESD package. Besides our extensive range of ESD control consumables, we offer a wide selection of ESD safe foams and packaging solutions for your static sensitive components. With over 35 years of experience, we can offer our combined knowledge and expertise to help you with any foam and packaging requirement. All of our foams can be tailored to your specific application. Our team will ensure compatibility with your choice of outer container.
To discuss your ESD foam requirement, simply enquire by filling the form below. You can also call us on +44 (0)1793 511000 or send us an email to sales@bondline.co.uk where you can talk to one of our friendly team members.
If you need ESD safe foam packaging for your business, please get in touch with us for a free quote and impartial advice on the best foam for your application.
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