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How to identify whether LED lamp beads are pure gold



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?


The purity of LED gold wire can be determined by ICP purity detection method, mechanical property detection method and EDS composition detection method
The purity grade of gold wire can be identified by ICP purity detection method to determine the added alloy elements.
1. Look at the appearance of the LED lamp bead gold wire. First, the gold wire surface 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 parts easy to be burned, and reduce the resistance to mechanical stress, resulting in the breakage of the damaged inner lead. Secondly, the gold wire surface should be free of oil stain, rust, dust and other adhesions, which will reduce the bonding strength between the gold wire and LED lamp bead chips, 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. One gram of gold can be drawn with a length of 26.37m and a diameter of 50 μ M (2 mil) gold wire can also be drawn with a length of 105.49m and a diameter of 25 μ M (1 mil) of gold wire. The length of the gold wire is fixed. If the diameter of the incoming gold wire is half of the original, the measured resistance of the gold wire is one fourth of the normal value. For gold wire suppliers, the thinner the diameter of gold wire is, the lower the cost is, and the higher the profit will be when the selling price remains unchanged.
For LED lamp bead customers who use gold wire, purchasing gold wire with jerry built diameter will lead to the risk that the resistance of the gold wire will increase and the fuse current will decrease, which will greatly reduce the life of the LED lamp bead light source. The service life of 1.0mil gold wire is necessarily shorter than that of 1.2mil gold wire, but the simple detection of the packaging factory cannot be tested, 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 the material with a gold purity of 99.99% or more. Through the design of reasonable alloy components, the gold wire has the advantages of high tension and bonding strength, good balling performance and low vibration fracture rate. The majority of bond alloy wires shall be high-purity alloy wires with purity of 99.99% or more, and the total amount of trace elements (Ag/Cu/Si/Ca/Mg and other trace elements) shall be kept below 0.01 to maintain the characteristics of gold.
Mechanical property testing, that is, tensile load loading and elongation testing of gold wire
The good gold wire that can withstand the impact generated during 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 arch wire sagging; ② Spherical instability; ③ The ball neck is easy to contract; ④ Gold thread breaks easily.
Too hard gold wire will lead to: ① making holes in the chip electrode or epitaxy; ② The neck of the golden ball is broken; ③ Difficulty in forming alloy; ④ The arch wire arc is difficult to control.
Use chemical composition test - EDS composition test method
Identify the types of incoming materials: gold wire, silver wire, gold clad 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 high.

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