With the continuous innovations in LED packaging technology and the implementation of the energy saving policies in western countries, LED light source was increasing the market share in the lighting field. Performances LEDs in the aspect of heat dissipation, light efficiency, reliability and cost-effective are still noticeable points. If LED chips cannot have breakthroughs in these aspects, or otherwise, other new lighting technologies except for LED have breakthroughs in advance, then the life of LED will come to an end. Under such pressure, COB (Chip on Board) was promoted as a new packaging technology. Compared with traditional LED packaging technologies, COB packaging LED chips have better cooling capabilities, high-density output luminous flux.
COB packaging LED chips have the shortest thermal path, can rapidly transmit heat from chips to metal substrates, and consequently to heat sinks. The current COB metal substrates are copper, aluminum, alumina, aluminum nitride. Take comprehensive considerations of production cost, cooling capacity and anti-corrosion capacity, aluminum is the most suitable material to make COB LED chips.
Normally, when taking the simulation of LED luminance, scientists hope to create sized packaging substructures that provide sufficient output luminance within limited chip size. This is unachievable among discrete-LED packaging solutions. Even using 3535 LED chips (with small size but relatively high luminous flux) cannot reach the high luminance density that COB or MCOB provided.
Although that COB packaging LED chips have many advantages, they are still not mainstream product in the market. On one hand, we should utilize these advantages to produce more advanced products. On the other hand, we also need to notice their disadvantages and find out corresponding solutions. Firstly, the luminous efficiency of COB LEDs is still relatively low. Due to the plane luminous mode, there are no assistant light-emitting devices and compartments to reflect sidelight, like PPA to discrete-G24 LED packaging solutions. That means, although each LED chip in the COB packaging solutions can send out more light (high output luminance), there is still a certain part of light (sidelight) will be wasted. Secondly, COB has no shape standards. Currently, most of domestic manufacturers produce lighting fixtures and drivers in accordance with existing COB LEDs. Different manufacturers may have different shape and other parameters for their COB packaging LED chips.