Chip on Board LEDs (COB LEDs) offer a more efficient LED manufacturing process by removing the LED packaging steps and mounting bare LED chips directly onto a PCB and then wire bonding to achieve the electrical connections. Along with reduced costs are the benefits of better binning, design flexibility and better light distribution. COB LEDs are wide-area light emitters – making them ideal for applications such as street lighting but unsuitable for point light sources such as automotive headlights. As the finished product is a modular unit it can be sold ready for install by any electrical installer – removing the requirement for complex arrays.
Chip on Board LED manufacture’s also gain from better colour mixing, better lighting effect and low thermal resistance. This makes it feasible to increase the density of LEDs on a smaller board space, perfect for general lighting applications.
All sounds great, right?
One of the challenges of COB LEDs has been to manage the junction temperature of the LEDs, also known by the friendly name of Tj! While getting the heat out of densely packed LEDs is challenging, this is a strength of the Chip on Board – thermal management becomes the responsibility of the COB manufacturer, not of the luminaire designer. This moves the management of LED operating temperature closer to the manufacturer of the LED – the people who are best placed to understand and manage the thermal issues.
Managing Tj is critical to improving the reliability of the light source. Ultimately temperature defines how hard the LEDs can be driven. In turn, this dictates how many LEDs are required to deliver a given brightness.
In an ideal world a ceramic substrate would be used but this has been prohibitively expensive for general LED applications. Instead aluminium MCPCBs are generally used, which whilst cost effective significantly reduces reliability due to its greater thermal resistance.
This is where Nanotherm’s patented Nanoceramic aluminium substrates come into play. Our patented ECO process converts the surface of aluminium into a Nanoceramic dielectric with excellent thermal conductivity. The copper layer is then attached to the Nanoceramic using an ultra-thin thermally conductive adhesive. This stack of Nanoceramic, adhesive and copper makes up Nanotherm LC – the industry’s best performing MCPCB. LEDs can be mounted directly onto the Nanoceramic board offering exceptional thermal properties at a price point that makes economic sense for the mass market, and without any of the complex manufacturing steps often seen in the management of high power LED arrays.