Connectors are used in nearly every electrical or electronic system to connect two devices through voltage or electrical signals. Geometry and physical characteristics vary according to the project, the required application and the environment of use, but - in any case - the resin plays a leading role.
Atra S.r.l. is a Pordenone (Italy) based company with over thirty years of experience in resin dosing technologies and corollary processes such as plasma treatment, polymerization furnaces and automation. These processes are a crucial part of electro-mechanical manufacturing in many sectors, as the encapsulation of electronic components in liquid resin (in atmosphere or vacuum) protects them from harsh environmental conditions, avoids corrosion, prevents possible damage caused by vibrations and mechanical stresses.
Below we illustrate some examples of applications in which Atra has solved interesting challenges in the field of connections through resins.
Connectors in the automotive industry are designed as custom shells that feature multiple pins. Often only a part of the seats is needed to position the pins: the rest must be sealed through a precision resin coating of the back of the shell. In the hypothesis of a shell in which, for example, only 8 harnesses are required and the other housings remain free, at the time of the resin coating, the resin would leak out of the housings without pins.
To solve this problem, Atra has worked in collaboration with some resin manufacturers and with the main components companies for the automotive sector. In this way, special polyurethane resins have been created which increase in viscosity according to an extremely precise temporal progression. In this way, the resin gels exactly at the desired time during the process, avoiding any leakage and without passing through the gaps without pins (generally diameters between 0.2 and 0.4 mm). In particular, the most performing resins have a peak of viscosity so precise that it is possible to resin the rear part of the connector and fill the entire platform of the pins, while the free holes are only partially filled: the resin gels inside the holes, sealing the system with extreme precision. This occurs thanks to additives, proportioned according to the processing temperature, which are added to the resin.
The connectors obtained are perfect for operation in all external parts of the vehicle, wherever they can be hit by a jet of water: for example, doors, headlights, license plate lights, reversing light, etc.
Other interesting applications are gel muffles, special resin-coated joints that protect electrical fittings so effectively to allow them to be buried or even to lay submarine wiring. In the automotive sector this is sometimes used in the long connections required for trucks and commercial vehicles. These are junction boxes, equipped with quick couplings, which incorporate the connections between different cable sections in gel resin (silicone or polyurethane) and keep them completely embedded in the container. This resin maintains the consistency of the gel over time: this guarantees all the protection of the resin but at the same time it is soft enough so that the box can be reopened in case of intervention. After the cables have been repaired, the two halves of the box can be reassembled and the two surfaces of the gel adhere perfectly to each other again, closing hermetically.
In the automotive sector, but also in portable tools and for other products such as capacitors, switches and more, connectors or other components often protrude significantly from the PCB on which they are applied. They are thus exposed to great vibration stresses during their normal operating life, with a considerable increase in the possibility of breakage. Consider that automotive sector requires acceleration stress tests up to 5G.
For these cases, polyurethane resins with special properties have been developed, which are applied to the edges and contact points between connectors and PCBs, acting as reinforcement of the component locking on the connection. Even after polymerization, these substances maintain considerable elastic and adhesive properties, reducing the stress on the connection and elastically recomposing the vibration: the resin acts as an elastic reinforcing element.
Another interesting field of work for Atra is the development of Atex applications in the Oil & Gas sector, where resin applications have been developed in explosion-proof field, to build and seal insulator or feedthrough components.
In the last century, the electrical systems designed for environments with danger of explosion were mainly made with pipes featuring simple joints at the inlet and outlet terminations of the containers. This technique had the disadvantage that, in case of repairs, it was necessary to cut the cable previously sealed in the joint. The advent of the cable gland has radically changed the method of plant engineering, facilitating installation and giving the possibility to recover the cable in the event of restoration work.
The modern Atex connecting elements are sealed using a two-component resin with high technical and mechanical characteristics which is applied to each conductor. The elements thus treated must conduct energy even at high potentials, up to 1,000 A, allowing electrical contact between bodies inside or outside the protected system. This is essential in extreme environments, with a high presence of flammable or explosive dusts, liquids and vapours, such as in the distribution of electrical cables in the oil, chemical and pharmaceutical fields. The protective piping that leads electrical cables through hazardous environments inevitably has junctions, T or Y junctions, elbows: within all these fittings, usually in aluminium, Atra intervenes with polyurethane resins with appropriate technical and mechanical characteristics. This prevents any infiltration of flammable and explosive gases from continuing along the entire pipeline. Atra systems thus sealed in the field pass tests with pressures up to 30 bar and 130 °C.
This technique can be applied to all the main components of an electrical system with Atex characteristics: fittings, adapters, closing caps, 90° bends, opening bends, sleeves, locking fittings, rigid and flexible pipes, explosion-proof junction boxes, watertight enclosures and cable glands.
In the field of power connections, an interesting example of the application of epoxy resins in the field of heavy industry is found in stirrers, for example magnetic stirrers for crucibles at melting temperatures of metal alloys and special steels.
In the crucible of steel mills, it is necessary to keep the special components in suspension until the moment of casting. If this were not done, any charges of chromium, vanadium, manganese or other, which have different specific weights, would settle in the crucible, stratifying at different heights: at the time of casting, different metal mixtures would be obtained with different physical and chemical properties depending on the different depths of the fluid.
The casing that protects the magnets of the stirrers must be powered with large amperages to produce powerful magnetic fields. Arranged in sequence and activated in rotation, they keep the melted metal bath in agitation. They work in an extreme environment, because they are immersed in a recirculation of refrigerant water under pressure, at 80 °C. For one of its customers with these specific needs, Atra has created systems of perfect insulated feedthroughs that withstand up to 30 bar of pressure. This is possible thanks to the precise mechanics, the perfect hydraulic seal and suitable resins and surface treatments. Between the mechanical bushing and the internal guide, the interposition of particular epoxy resins ensures low water absorption and excellent mechanical strength torque.
In conclusion, over the years Atra has developed a growing vocation as a consultant to support each customer and solve specific production needs. The company searches the market for the materials, technologies and experiences closest to the customer's needs, customizing them and building the most suitable solution for each specific production process. Often it is a question of inserting into a new field a solution already tested in a different sector. For example, Atra has come to use in the automotive sector some technologies matured thanks to the initial experiences in the optical field. This transversal vision is one of the characteristics that distinguishes the company on the market.