SuZhou Tonkida Electromechanical Technology Co., Ltd Professional SMT whole line supplier

Semiconductor LED chip, also known as LED light chip, is the core component of LED lamp, its main material is monocrystalline silicon, that is, monocrystalline silicon is cut into a chip attached to a bracket and packaged. The chip is composed of two parts, one is a P-type semiconductor, in which holes dominate, the other end is an N-type semiconductor, on this side is mainly electrons, the two semiconductors are connected together to form a P-N junction. When the current is applied to the chip through the wire, the electrons are pushed to the P region, where the electrons are combined with the holes, and then the energy is emitted in the form of photons, which is the principle of LED light.

It is understood that the current LED chip structure mainly has: formal, flip, vertical three schools, of which formal structure because of low price advantage and occupy the main market. However, with the continuous improvement of output power, problems such as large light decay restricting the development of high-power LED have emerged.

Due to the p and n electrodes on the same side of the LED, the formal structure is prone to current crowding, and due to the poor thermal conductivity of the sapphire substrate, the heat loss is seriously hindered. In the process of long-term use, the high temperature caused by poor heat dissipation affects the performance and transmittance of silica gel, resulting in a large optical output power attenuation.

Compared with the formal LED, the vertical chip structure uses a substrate with high thermal conductivity (Si, Ge, Cu and other substrates) to replace the sapphire substrate, which greatly improves the heat dissipation efficiency; The two electrodes of the vertically structured LED chip are respectively on both sides of the LED epitaxial layer, through the n electrode, so that the current almost all vertically flows through the LED epitaxial layer, and the transverse flow of the current is very small, which can avoid local high temperature. However, in the current vertical structure preparation process, the sapphire stripping process is difficult, which restricts the industrialization development process.

Inversion technology can be subdivided into two categories, one is on the basis of sapphire chip inversion, sapphire substrate retention, conducive to heat dissipation, but the current density increase is not obvious; The other is inverted structure and stripped of the substrate material, which can greatly improve the current density.

Inversion technology first appeared in 2007, by the packaging company first product application, and more first used in the field of lighting. The reason why the flip chip is called "flip" is relative to the traditional metal Wire Bonding connection method (Wire Bonding) and the process after planting the ball. The electrical side of the traditional chip connected to the substrate through metal wire bonding is facing up, and the electrical side of the flip chip is facing down, which is equivalent to turning the former over, so it is called "flip chip".

Due to the poor conductivity of P-type GaN, it is necessary to form a Ni-Au metal electrode layer on the surface of P-region by evaporation technology in order to obtain a good current expansion. The P-zone leads are drawn through the metal film. In order to obtain good current expansion, the Ni-Au metal electrode layer cannot be too thin. For this reason, the luminous efficiency of the device will be greatly affected, and two factors of current expansion and luminous efficiency are usually taken into account at the same time. But no matter in what case, the existence of metal film will always make the light transmission performance worse. In addition, the existence of lead solder joints also affects the optical efficiency of the device. The use of GaNLED flip chip structure can fundamentally eliminate the above problems.

For LED chip companies, the expansion of production can seize the scale advantage, the use of large-scale manufacturing to reduce production costs, so in 2017, major LED chip manufacturers have purchased equipment to expand the scale of production. However, this has also LED to increased competition in the LED chip industry. However, the manufacturing technology of LED chips and the corresponding packaging technology jointly determine the future application prospects of LED chips, therefore, the development of inverted LED chips will become the trend of The Times.