From an interconnect standpoint, there are a wide and sometimes dizzying array of options available to the designer. Options are always good and there are a number of unique, SSL-targeted connector products that are optimized for different applications within a lighting system. This month, we will discuss interconnection of the Chip On Board (COB) LED to facilitate easy integration of the light source into the lighting fixture or luminaire.
Chip-on-board devices began to enter the market a few years ago as manufacturers sought ways to increase light output beyond what was possible with single die devices. By tightly arraying die on a single, thermally conductive substrate and flooding the area with a phosphor pool, light output could be concentrated in a much smaller area than possible with discrete devices. This was not without issues since these substrates and their inherent thermal conductivity created challenges in how to effectively and repeatably solder a wire to pads located on a device that by its design was made to pull heat away from devices. Further complicating the COB is the wide variety of package sizes, solder pad locations, and plating types offered by manufacturers. Given TE Connectivity’s (TE) long history and expertise in providing separable solutions to replace soldered connections, this clearly was a termination challenge and after some consideration, we decided there was an opportunity to offer a more effective solution to customers.
TE Connectivity sought to develop a highly adaptable, scalable holder to meet the interconnection needs for a majority of the COB products being introduced. The first step of the design process involved a rather lengthy identification and analysis of common commercially available COB LEDs. The simplified results of this analysis yielded three common COB LED attributes.
- Rectangular geometry
2. Centralized light emitting area
3. Diagonally opposed (+) & (-) contact
The TE solderless scalable holder that was developed as a result provides a stable, repeatable interconnect to the aforementioned COB devices while providing poke-in wire termination technology, allowing ample clearance around the light source for lensing, achieving a low profile and facilitating heat dissipation from the device. The scalable design allows a lighting manufacturer to choose from a wide array of COB devices for adoption into the final fixture. As an added benefit, the scalable nature makes it easy for TE to offer a reference pad layout to COB manufacturers for future COB designs which, when utilized, ensures an available off-the-shelf solderless interconnect solution for the new COB when released.
As with many adoptions of new technologies, standards soon follow in an effort to accelerate mass adoption. One standard being followed today is Zhaga. The international Zhaga consortium is creating specifications that enable interchangeability of LED light sources made by different manufacturers thus simplifying LED implementation in general lighting applications. TE developed an interconnect solution focused on providing a quick path to develop compliant products. The solderless Z50 LED holder, aligned to the Zhaga book 3 specifications, incorporates a number of unique attributes providing snap-in LED retention, poke-in wire connection, and compatibility with leading optics to support the integration of LED lighting components within the LED ecosystem. This 50 mm diameter holder is available at a standard height and a 3.4 mm low profile version. A smaller solderless Z32 LED holder, built off the same design principle, but in smaller form factor at 32 mm in diameter is also offered for smaller COB LEDs.
Next month we shall discuss in greater detail the options around interconnect of the LED lighting fixture itself and system configurations.