How to identify whether LED lamp beads are pure gold wire
The purity of gold wire used for packaging LED lamp beads is more than 99.99% gold. The gold wire made of this material is produced by wire drawing process. In addition to 99.99% gold, this gold also contains less than 1% of other trace elements. One of the core components of LED bead packaging is the gold wire, which is the bridge connecting the light-emitting chip and the welding point, and plays a decisive role in the service life of LED bead. So how to identify the purity of gold thread?
The purity of LED gold wire can be determined by ICP purity test, mechanical property test and EDS composition test
The purity grade of gold wire can be identified and the added alloy elements can be determined by ICP purity detection method.
1. To see the appearance of the LED bead gold wire, first of all, the surface of the gold wire should be free of nicks, pits, scratches, cracks, bulges, discounts and other defects that reduce the service life of the device. During the drawing process of gold wire, the surface defects on the wire surface will increase the current density, make the damaged part easy to be burned, and reduce the resistance to mechanical stress, resulting in the fracture of the damaged part of the inner lead. Secondly, the surface of the gold wire should be free of oil, rust, dust and other adherents, which will reduce the bonding strength between the gold wire and the LED bead chip, and between the gold wire and the bracket.
2. There is a diameter deviation between the special gold wire for LED lamp beads and the unqualified gold wire. 1 gram of gold can be drawn with a length of 26.37 m and a diameter of 50 μ M (2 mil) gold wire can also be drawn with length of 105.49m and diameter of 25 μ M (1 mil) gold wire. The length of the punched gold wire is fixed. If the diameter of the incoming gold wire is half of the original, the measured resistance of the punched gold wire is one quarter of the normal. For the gold wire supplier, the thinner the diameter of the gold wire, the lower the cost, and the higher the profit with the same price.
For LED bead customers who use gold wire, if they purchase gold wire with shoddy materials in diameter, there is a risk that the resistance of gold wire will increase and the fuse current will decrease, which will greatly reduce the life of LED bead light source. The service life of 1.0mil gold wire must be shorter than that of 1.2mil gold wire, but the simple detection of the packaging factory cannot be detected, and the diameter of the gold wire can only be detected with precision instruments.
3. The special gold wire for LED lamp beads is drawn from a material with a gold purity of 99.99% or more. Through the reasonable design of alloy components, the gold wire has the advantages of high tensile strength and bonding strength, good sphericity and low vibration fracture rate. Most of the bonded alloy wires should be high-purity alloy wires with a purity of more than 99.99%, and the total amount of trace elements (such as Ag/Cu/Si/Ca/Mg) should be kept below 0.01 to maintain the characteristics of gold.
Use mechanical property test, that is, test the breaking load loading and elongation of the wire
A good gold wire that can withstand the impact produced by resin encapsulation must have the specified breaking load and elongation. At the same time, the breaking force and elongation of gold wire play a key role in the quality of wire bonding, and the bonding wire with high breaking rate and elongation is more conducive to bonding.
Too soft gold wire will cause: ① sag of arch wire; ② Spherical instability; ③ The ball neck is easy to contract; ④ Gold thread breaks easily.
Too hard gold wire will cause: ① hole the chip electrode or extension; ② Gold ball neck fracture; ③ It is difficult to form alloy; ④ It is difficult to control the arch wire arc.
Use chemical composition test - EDS composition test method
Identification of incoming materials: gold wire, silver wire, gold-coated silver alloy wire, copper wire, aluminum wire. Gold wire has the advantages of high conductivity, good thermal conductivity, corrosion resistance, good toughness, excellent chemical stability, etc., but the price of gold wire is expensive, and the packaging cost is also too
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?