The fast-changing world of LED technology has spurred some new developments in LED light housings. Thermoplastics are now outperforming their metal counterparts in LED housing applications due to their enhanced properties, which were once thought to be unique to metals alone.
By Shruti Mishra
Ask any LED lighting designer or manufacturer, and you will discover what a key role the housing plays in any LED lighting system. The housing not only protects the LED modules, optical lenses, reflectors and drivers, but also prevents external damage from heat, moisture, etc. Beyond operating as a protective layer, housings also play a vital role in the thermal management of LED lights. They are considered the last level from which heat is finally transferred to the ambient environment through heat convection and thermal radiation.
Conventional types of LED housings
Earlier, aluminium was widely used for making LED housings because metals are considered the most reliable material when designing a part that needs to withstand the test of time. Also, its abundant availability and low cost made it a preferred choice for LED manufacturers. Despite such benefits, the demand for aluminium-based housing is gradually dropping because of its bulkiness and stiffness. With the LED lighting industry gravitating towards miniaturisation, it has become difficult to design sleek and attractive lights using aluminium.
The miniaturisation of LED lighting systems has also made thermal management a major challenge. Along with LEDs, housing technology has also had to continuously miniaturise, due to which the heat generated is now dissipated from smaller and smaller spaces. Therefore, LED lighting fixture manufacturers have started looking for new options to house the LED lights, which not only reduce costs but also offer better electrical insulation and design freedom, compared to the traditional aluminium housing.
Over the last few decades, there have been rapid advances in the field of plastic engineering, which have paved the way for new engineering-grade heat dissipative plastics known as thermoplatics. These offer a perfect combination of thermal conductivity, electrical insulation and design freedom. Certainly, there will always be a need for aluminium-based housings, but for LED housing applications, plastic is becoming the material of choice for many compelling reasons.
Key benefits of thermally conductive plastics
- Better heat dissipation
- Low manufacturing costs
- Enhanced productivity
- Low weight
- Flexibility in design
- Less expensive
- Good chemical and corrosion resistance for long term use
Advantages of thermoplastic-based LED housings
Like any other lighting system, LED lighting systems also face problems in managing the extreme heat generated during operation. LED lights are very compact in nature and are built using semiconductors, which makes temperature a very critical parameter for light output and the life of the device. To dissipate heat naturally, modern LED designers are using new types of housings made of thermally conductive plastics that direct heat away naturally, without any forced cooling. Such materials have a tensile strength similar to that of metal and that too, with increased flexibility. In addition, thermoplastic-based housings have a better resistance to climatic conditions like heat and moisture as compared to the metal ones.
The other reason that thermoplastics are being used is the cost reduction. The thermoplastic-based LED housings are extremely lightweight, due to which they dramatically slash shipping, packaging and installation costs. Additionally, the production process of thermoplastics is faster and cheaper compared to metal housings. Also, working with plastics is enabling LED designers to incorporate multiple components into a single mould, thereby reducing the assembling cost and increasing the overall durability of the final product. Therefore, today we see many manufacturers of LED luminaires converting their metal housings into single injection-moulded parts using modern engineering-grade polymers that have properties similar to aluminium.
At the design level, these thermoplastic compounds provide more freedom due to their high degree of flexibility. Therefore, manufacturers can now easily shape their LED lights into any complex shape that is in high demand, thereby satisfying the needs of the consumers.
Technological innovations
Many chemicals and adhesive companies like Lanxess and Covestro have done a lot of innovations in thermally conductive plastics in recent years, and these new materials could provide a potential replacement for metal LED housings. In spite of there being a big difference in thermal conductivity between metals and plastics, these improved thermoplastics are capable of meeting the performance requirements of many thermal management applications. Similarly, many other companies are making use of different types of plastic compounds to design LED chip housings with slim dimensions and enhanced features.
Lanxess, a German chemical company, has developed four new compounds for LED housings that are based on polycyclohexylenedimethylene terephthalate (PCT), namely, Pocan TP 555-911, -991, -912 and -992. PCT is a type of polyester that helps in achieving very high reflection levels of nearly 93 per cent to 96 per cent. When this compound is used as an LED housing, it reflects the light of the LEDs almost completely, with almost zero loss of brightness.
In addition to this, these four innovative products also have very high heat deflection temperatures. Under test conditions, they can easily withstand high temperatures of 240°C to 280°C. The high temperature tolerance property of these compounds are making them popular for outdoor LED applications.
Additional advantages: These Pocan TP variants also offer design flexibility and have good mechanical properties.
Similarly, Covestro (another German firm that was earlier a part of Bayer) is offering three new types of polycarbonate blends for LED housings—Makrolon, Bayblend and Makroblend. The technical advantages of these compounds are listed below.
Makrolon polycarbonate blend: This high-performance thermoplastic is extremely robust and lightweight. This compound ensures the long life of the LED lights and reduces breakage during distribution and use.
Additional advantages: High mechanical strength, heat and flame resistance.
Bayblend polycarbonate blend: This product is a mixture of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS). This unique combination offers an excellent balance of properties, most notably, high toughness, dimensional stability, low moisture absorption and good heat resistance.
Additional advantage: Good indoor light stability.
Makroblend polycarbonate blend: Covestro places this compound in the family of ultra-tough materials. This compound is known for its rigidity and hence reduces the chances of cracking due to stress.
Additional advantage: Improved chemical resistance.
Some of the many advantages of transitioning to thermoplastics are that the overall part weight is reduced, and the manufacturing process becomes more efficient and shorter since there are minimal secondary operations needed.
