How to arrange LED packaging chips and its influence on the performance of the whole light source module

1. In terms of LED structure, GaN-based LEDs can be divided into forward structure, flip-chip structure and vertical structure. The light emitted from the active region of the forward structure is emitted through the P-type GaN region and the transparent electrode. Simple structure and relatively mature manufacturing technology. However, the front structure LED has two obvious disadvantages. First, the front structure LEDp and the N electrode are on the same side of the LED, and the current must flow transversely through the N-GaN layer, resulting in current congestion and high local heating, which limits the driving current; Secondly, due to the poor thermal conductivity of sapphire substrate (35w/(m? K)), which seriously hinders the loss of heat.

2. In order to solve the heat dissipation problem, Mi Lu led Lighting Company invented flip chip technology. In this method, firstly, a large-size LED chip suitable for crystal bonding is prepared, and at the same time, a silicon backplane with corresponding size is prepared, on which a gold conductive layer and an extraction conductive layer (ultrasonic gold ball solder joint) of the crystal bonding electrode are made. Then use * * * crystal welding equipment to weld the large-size LED chip with the silicon backplane. The mounting structure greatly improves the heat dissipation effect, but the usual mounting structure of GaN-based LED is still horizontal, and the current crowding phenomenon still exists, which still limits the further improvement of driving current.

3. Vertical structure can effectively solve two problems of vertical structure LED. GaN-based LED with vertical structure adopts high thermal conductivity substrates (5 1, Ge and Cu substrates) instead of sapphire substrates, which greatly improves the heat dissipation efficiency. The two electrodes of the vertical LED chip are located on both sides of the LED epitaxial layer. Through the patterned N electrode, almost all the current flows vertically through the LED epitaxial layer, and little current flows horizontally, which can avoid the current congestion problem of the front structure, improve the luminous efficiency, solve the shading problem of the P electrode, and improve the luminous area of the LED.