ESD trays and packaging: “lightning protection” for electronics
An article by Klaus Vollrath
Electronic assemblies are conquering more and more products, from children’s toys, sports equipment and keys to machines and cars. However, they are sensitive to sudden discharges of static electricity and can be damaged or even destroyed as a result. Transportation and packaging should therefore only be carried out using underlays or wrapping made of conductive plastics. Their manufacture is an art that requires a great deal of expertise. What to look out for? A discussion with a manufacturer with extensive experience in this field.
“In order to offer optimum protection and be economical at the same time, antistatic trays and packaging should be custom-designed,” says Reto Grütter, Managing Director of Grütter Kunststoff und Formen AG in Hombrechtikon (Switzerland). Static electrical voltages between plastic surfaces and earthed components can quickly reach several 100 to 1,000 volts. Flashover (ESD, electrostatic discharge) can cause damage to electronic components or assemblies. Conductive underlays or packaging offer protection. However, the parts in question should not be treated as bulk goods. In automated processes in particular, which require feeding in the correct position, such parts are usually transported in suitably shaped trays during production. Customized packaging is also available for shipping.
The decisive prerequisite for their production is the conductivity of the plastics used. This is usually achieved by adding fine graphite powder to non-conductive plastic base materials during production. The raw material is usually supplied in the form of semi-finished products (foils or sheets), which are then thermoformed or embossed. Rotational molding can also be used for thick-walled, hollow parts. In this process, conductive plastic granulate is filled into a metal mold. It is first melted in the mold and then cooled under constant tumbling motion. This creates a hollow body with the desired geometry in the mold. ESD plastics can also be used here.
Materials
“Due to certain properties of ESD plastics, there are only a handful of companies that offer ESD packaging at all,” adds Jannis Petros, Head of Sales and Technical Consulting at Grütter. The company has been dealing with this topic for many years and, thanks to its broad expertise, generates around 20% of its turnover with it. The usual materials are PS and PET, copolymers and, in the case of foams, polyethylene. The latter is mainly used in closed-pore form for form-fitting inserts that are used to pad the inside of trays or packaging. In order to be able to serve customers quickly, the company keeps a whole range of thermoforming materials with different properties in a variety of wall thicknesses in stock. Customized multilayer films or sheets with two or even three layers are also available on request. For procurement, Grütter can rely on an extensive and
efficient network of proven suppliers, so that even larger quantities of material can often be provided at short notice.
Due to the graphite content, these materials are usually black, with the exception of thin PET films, for example, which appear transparent and smoky. Depending on requirements, the material is obtained in the form of foils or sheets and formed by deep drawing or embossing. From an ESG point of view, the high proportion of regenerated material, which in many cases is 80%, is attractive. Any leftover material produced in-house is collected by type and sent directly to specialized recyclers.
Advice is the be-all and end-all
“Such packaging often has to fulfill a wide variety of purposes at the same time. Determining the optimum solution in terms of both technology and cost therefore requires a great deal of experience and expertise,” reveals R. Grütter. This starts with defining the requirements and selecting the most suitable material for the application. This involves material knowledge as well as how the costs for individual adaptations can be kept within reasonable limits, especially for small and medium quantities. The best results are usually achieved when the customer meets with Grütters’ specialists as early as possible in the development process of new products. All issues relating to production and shipping logistics are then clarified together as a team. First of all, the required stability and load-bearing capacity as well as protection against impact loads are considered. Other questions relate to stability when stacking when full in production or minimizing transport costs by saving space when returning empty containers. Additional aspects include safety against mix-ups and clear orientation. In the case of automated processes, the permissible position tolerances must also be clarified. All this influences the choice of material and the required wall thickness. To ensure the suitability of the designs, Grütter can produce prototypes in advance for trials using 3D printing, even before expensive tools are produced. The material then used for 3D printing is conductive and therefore suitable for ESD applications.
Variability as a cost brake
“Once these points have been clarified, cost issues come to the fore. Deep-drawing or embossing tools are made of metal and are correspondingly expensive,” says J. Petros. For example, we recommend using a base frame with customized inserts for different products. One of the advantages of this is that the footprint and stacking properties of all trays in the company are consistent with the conditions at the production facilities. For different products, for example, standardized trays can be used, which are adapted to the respective product with appropriately shaped foam inserts. Sometimes inserts can also be designed in such a way that they can be used for different components. In other cases, it makes sense to produce customized trays by inserting appropriate inserts into the mould frame. Depending on the circumstances, it is also possible to use cheaper ceramic molded components produced using the 3D printing process instead of costly metal inserts. Thanks to many years of experience, the Grütter team has a lot of know-how when it comes to such tricks for cost-effective solutions.
Development partner with a proximity advantage
“We can offer our customers a decisive advantage in both development and production: Bundled expertise in their vicinity,” affirms R. Grütter. The company has a well-coordinated team of experts with many years of experience in all areas. This includes the design department, the in-house mold making department and the production specialists. These employees have access to modern IT tools and various 3D printing systems for the production of prototypes or devices. The customer therefore finds highly qualified contacts at all levels who are well networked with each other and pull together. As everything comes from a single source, there are no interfaces to other companies. The employees also speak the same language, come from the same cultural background and have the same working hours. The whole thing is rounded off by an efficient management system certified to ISO 9001: 2015.
Klaus Vollrath b2dcomm.ch
