Verypixel front maintenance LED displays use high quality epistar LED chips

A. LED history: 50 years ago, people have already knew about semiconductor materials can produce light. In 1962, NickHolonyakJr. From GE company developed the first practical application of visible light emitting diodes. LED is the abbreviation of light emitting diode. It is also semi-conductor place on a wire shelves and then sealed with epoxy resin,which is called solid package. This kind of solid package is mainly use to protect the internal core, so LEDs have good seismic performance. At the beginning, LED use as a light source for instruments and then used  as all kinds of traffic signal lights. For example, The United States was using long life and low luminous efficiency 140 watt incandescent lamp as the light source. After the red filter, there were 90% loss of light and only left 200 luminous red light. However, in this new designed LEDs, Lumileds Company adopted 18 red LEDs as light source, including the loss of circuit, it will total caused power consumption for about 14 watts to generate the same light effect as before.

B.The principle of LED chip: LED(Light Emitting Diode) is a solid state semiconductor devices, which can be directly converted into electricity to light. The heart of LED is a semiconductor chip, The chip is attached to a bracket, one end is negative, and the other end is positive, the entire chip is epoxy resin encapsulated. Semiconductor chip consists of two parts, one part is P-type semiconductor, which is the core inside; the other part is N-type semiconductor which play a role of electron. When you connect the two semiconductors, among them on the formation of a " P-N knot ".When the current through the wire, electronics will be pushed to the P-block and then compound with N-block, this is how LED luminous worked. The wavelength of light that is the color of the light is determined by the materials of P- N junctions.

C. The classification of LED chip:

1.The definition and characteristics of MB chip. Definition: Metal Bonding(MB) chip belongs to UEC patent product.
a. Use high heat transfer coefficient materials: Si as substrate, cooling easily. Thermal Conductivity GaAs: 46W/m-K GaP: 77W/m-K Si:125 to 150W/m-K Cupper:300 to 400W/m-k  SiC: 490W/m-K
b. Jointed by a metal layer ( waferbonding ) epitaxial Layer and the substrate, reflecting photons At the same time, to avoid absorption of substrate.
c. Conductive Si Substrate instead of GaAs substrate, which has good capacity of heat transmission,which is better adapted to areas of higher drive current.
d. Metallic reflecting layer at the bottom, to enhance luminosity and cooling.
e. The size can be increased, should be used for High power areas, eg:42milMB.

2.The definition and characteristics of GB chip. Definition: Glue Bonding(GB) chips belonging to UEC patent product.
a. Transparent sapphire substrate replace the light absorbing GaAs substrate, the output power is twice times more than AS traditional ( Absorbable structure ) chips, PPS are similar to GaP substrates of Ts chips.
b. Four light-emitting chip, excellent Pattern in / out.
c. The overall brightness has been exceeded to TS chip level ( 8.6mil )
d. Double electrode structure, the high current connection to be slightly worse than the TS single electrode chips.

3. The definition and characteristics of TS chip. Definition: Transparent Structure(TS) chips, belonging to HP patent product.
a.  The fabrication technology of this kind of chips are more complex than SALED.
b. Much more reliable.
c. Transparent GaP substrates, does not absorb light, high brightness.
d. Widely use in LED display industry.

4.The definition and characteristics of AS chip.Definition: Absorption Substrate(AS) chips. After 40 years development, Taiwan LED optoelectronic industry step into a mature stage on this type of chip development, production and sales. The large company R & D level was basically the same standards in this regard. .Postal LED Industry starts relatively late,there is a wide gap between Taiwan and postal industry in brightness and the reliability. The AS chips we write here are refer in particular to UEC product, eg:712SOL-VR,709SOL-VR, 712SYM-VR,709SYM-VR etc.

Features:
a. AlGaInP, adopt MOVPE technology, the brightness are more higher than normal chips.
b. Reliable
c. Widely use in LED display industry.

Page address: http://www.verypixel.com/blog/LED_chips_basics_encyclopedia.html