Full analysis of LED lamp bead structure
The LED lamp beads are mainly composed of five materials: bracket, silver glue, chip, gold wire and epoxy resin.
LED lamp bead bracket
1. Functions of support: conducting and supporting
2. Composition of the support: The support is formed by electroplating the support material, which is composed of five layers of material, copper, nickel, copper and silver from the inside to the outside.
3. Type of bracket: the bracket with cup is of spotlight type, and the flat head bracket is of large angle astigmatism type.
LED lamp bead silver glue
1. The function of silver glue is to fix the chip and conduct electricity.
2. Main ingredients of silver glue: silver powder accounts for 75-80%, EPOXY (epoxy resin) accounts for 10-15%, and additives account for 5-10%.
3. Use of silver glue: refrigerate, defrost and fully stir the silver glue before use. As silver glue will precipitate after being placed for a long time, if it is not stirred evenly, the use performance of silver glue will be affected.
LED lamp bead chip
1. The function of the chip: The chip is the main component of the LED lamp, and it is a light-emitting semiconductor material.
2. Composition of the chip: The chip is made of gallium phosphide (GaP), gallium aluminum arsenic (GaAlAs) or gallium arsenide (GaAs), gallium nitride (GaN) and other materials, and its internal structure has single conductivity.
3. Chip structure: welded single wire positive polarity (P/N structure) chip, double wire chip. The dimension unit of the wafer is mil. The welding pad of the wafer is generally gold pad or aluminum pad. The welding pads are circular, square and cross shaped.
4. Luminous color of the chip: The luminous color of the chip depends on the wavelength. Common visible light is roughly classified as dark red (700nm), dark red (640-660nm), red (615-635nm), amber (600-610nm), yellow (580-595nm), yellow green (565-575nm), pure green (500-540nm), blue (450-480nm), and purple (380-430nm).
White light and pink light are a mixture of light. The most common is a mixture of blue light+yellow phosphor and blue light+red phosphor.
5. Main technical parameters of the chip:
a. Volt ampere characteristic diagram of the chip;
b. Forward voltage (VF): the voltage applied to both ends of the chip to make the chip conduct forward. This voltage is related to the chip itself and the test current. If the VF is too large, the chip will be broken down.
c. Forward current (IF): The forward conduction current generated by the chip after a certain voltage is applied. The value of IF is related to the value of forward voltage. The working current of the chip is about 10-20mA.
d. Reverse voltage (VR): the reverse voltage applied to the chip.
e. Reverse current (IR): refers to a leakage current generated by the wafer after the reverse voltage is applied. The lower the current, the better. Because the current is high, it is easy to cause reverse breakdown of the chip.
f. Luminance (IV): refers to the brightness of the light source. Unit conversion: 1cd=1000mcd
g. Wavelength: reflects the luminous color of the chip. Different wavelength chips have different luminous colors. Unit: nm
LED lamp bead gold wire
1. Function of gold wire: connect chip PAD (welding pad) and bracket, and make them conductive.
The purity of gold wire is 99.99% Au; Elongation is 2-6%, and the dimensions of gold wire are 0.9mil, 1.0mil, 1.1mil, etc.
LED lamp bead epoxy resin
1. Function of epoxy resin: protect the internal structure of the lamp, and slightly change the luminous color, brightness and angle of the lamp; Shape the lamp.
2. Packaging resin includes four parts: adhesive A (main agent), adhesive B (hardener), DP (diffusion agent) and CP (colorant). Its main components are epoxy resin, anhydride (anhydrous acid), light diffusion and thermal stable dye.
There are many welding methods for LED lamp beads on the chip, and the following is one of the commonly used methods for reference. First, use an electric soldering iron to heat some soldering tin on the positive and negative electrode pads of the lamp bead (the soldering tin must not be too much, otherwise, the positive and negative electrode pads will be connected once heated with a hot-air gun), then use a hot-air gun to heat the positive and negative electrode pads at the same time, after the tin melts, use tweezers to place the positive and negative electrodes of the lamp bead on the corresponding pad.
LED is the light emitting diode, which is a semiconductor solid light emitting device that converts electric energy into light energy. Its core is the PN junction. In addition to the forward conduction, reverse cut-off and breakdown characteristics of the general PN junction, it also has the light emitting characteristics under certain conditions. Its structure mainly includes the following parts: lead, bracket, encapsulation glue, bonding wire, LED chip, solid crystal glue and phosphor. The discoloration failure of LED lamp bead is closely related to its material, structure, packaging process and service conditions. The following will analyze the causes of its discoloration through specific cases.
LED lamp beads are also called light emitting diodes. It has a wide range of applications. Its luminous colors include red light, emerald green light, yellow green light, yellow light, purple light, blue light, white light and orange light. The above is monochromatic light. It can also be made into two or three colors.
The gold wire used to package LED lamp beads contains more than 99.99% gold. It is produced by drawing gold from this material. In addition to 99.99% gold, this gold also contains less than 1% other trace elements. One of the core components of LED lamp bead packaging is gold wire, which is the bridge connecting the luminous chip and the welding point, and plays a decisive role in the service life of LED lamp bead. So how to identify the purity of gold thread?