Issue link: https://te.mouser.com/i/1410845
these devices and then affix them to heatsinks in the lighting fixtures. The traditional method was to hand-solder the wires to the pads on the substrate [Fig. 8] and then secure these assemblies with screws to the heatsink- a process that was time consuming and subject to variability. As with the earlier discrete devices, this presented an ideal opportunity for socket solutions. TE and other connector companies addressed this emergence of initial COB devices the same way earlier discrete LED packages were addressed: custom sockets. As other COBs started to enter the market, connector manufacturers realized the status quo method of developing a socket for each would be prohibitively expensive and time consuming resulting in never-ending efforts forever chasing the next new COB to enter the market. With well over 50 different COB products commercially available around the world from multiple manufacturers, finding a single solution to address each would be a challenge to say the least. Aside from the fact that all were rectangular, all had two electrical contact pads and most had circular light emitting areas, there were few other dimensional similarities. This presents a challenge to connector companies…How do we address these varied but similar COB LEDs with a minimum of engineering and tooling expenditure while providing a future-proof & flexible platform based product? One such solution is a flexible, scalable, platform-based socket solution. An analysis of available COBs yielded a crack in the shell of these "fried egg" LEDs . While not exactly identical, there are similarities between contact pad locations that, when combined with the rectangular nature of the devices and diagonal contact pad placement form the basis for the platform solution. As a result, a holder product, referenced off the corners of the COB, could yield a virtually limitless array of use scenarios with the varied COBs available on the market as well as those to come in the future. The substrate differences among LEDs is yet another issue that needs to be tackled by socket/holder suppliers. While most of the early COBs incorporated aluminum substrates, further investigation of the commercially available COBs indicated a number of COBs that are based on ceramic substrates (typically aluminum nitride). While not a significant differentiator, these two substrate variants have physical features that differ enough to require special handling due to their different material properties. The aluminum substrate COBs are rather robust and in some instances are mounted using machine screws. On the other hand, ceramic-based COBs create some frustration for fixture manufacturers since unlike aluminum-based substrates where they could simply secure the COBs with a screw to a heatsink, these ceramic substrates were far too brittle to secure with screws and thereby mandated some sort of secondary attachment to ensure suitable thermal performance. This attachment needs to be accomplished using thermal adhesives or by a mechanical holder that provides thermal normal force, mechanical attachment, and electrical interconnection. Holder devices that accommodates the COB nuances mentioned in the previous paragraphs are appearing on the market. An example of one such platform solution is the TE Scalable LED Socket connector utilizes the corners of the COB as a reference. In this manner, the two datums formed by the sides of the COB can be used to positively locate the electrical contact on each of the COBs electrical pads. The commonly diagonally opposed contact pads on the COB takes advantage of the symmetry inherent in most COB designs and thereby allows use of the same socket assembly on both corners of the COB [Fig 10 & 11]. By doing this, SKU numbers are drastically reduced by eliminating the need for a right and left version of the socket. Fig. 8 Fig. 10 Fig. 11 Copyright 2018 TE Connectivity Ltd. Family of Companies TE Connectivity, TE connectivity (logo) and TE (logo) are trademarks. Other logos, product and/or company names might be trademarks of their respective owners.