COB-LED (Chip on Board)
In principal COB-LEDs are a number of LED-chips (mostly 9 at least) , which the manufacturer directly fixes to a substrate by means of bonding creating one single module.
As the single LEDs used in COB technology, are chips and usually do not have any enclosure, these chips can be mounted in a space-saving way and reach their maximum potential.
When the COB-LED package is powered, it appears to be a luminous surface rather than single light dots – what would be the case, if you would mount several SMD LEDs close to each other.
Advantages of COB-LEDs
Thanks to the shared enclosure of several LED-chips, the light emitting surface (LES) of a COB-LED can on the same surface contain a multiple of light sources compared to standard LEDs, which leads to a considerably higher light output per square centimetre.
COB-LEDs only need one circuit with just to contacts for the power supply of the numerous diode chips.
The result: For proper oeration less components per LED-chip are needed. Moreover thanks to the reduced number of components and the elimination of separate enclosures of traditional LED-chip structures the heat generated by every single LED-chip can be decreased as well.
The ceramic-/aluminium substrate of COB-LEDs also acts as a heat transfer medium when connecting with an external heat sink, so that consequently the total operating temperature of the sub-assembly is reduced, too.
When fixing a COB module to a heat sink it is absolutely necessary to choose a heat sink that ca dissipate the generated heat in order to be able to fully exploit the COB potential . On long term the proper heat dissipation increaes the efficacy and decreases the failure rate.
Another aspect of COB-LEDs reducing failure rates is the fact that no spot soldering of the single LED-chips is needed. It is not needed, because every chip is mounted directly to the substrate. The lower number of soldering joints leads to the reduction of the failure rate.
The light loss decreases dramatically and the viewing angle is increased – both due to the fact that when using COB-LEDs there are no lenses or other parts of the conventional LED anymore.