The LED bead manufacturer asked you to identify if the LED bead is pure gold wire
Publish：Shenzhen Teng Jie Optoelectronics Technology Co., Ltd. Time：2023-11-07
The gold wire used for encapsulating LED lamp beads has a purity of over 99.99% gold content. This material of gold is then produced through a 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 serves as a bridge connecting the luminescent chip and the soldering point, and plays a decisive factor in the service life of LED beads. So how exactly can we distinguish the purity of gold thread?
The purity of LED gold wires can be determined by ICP purity testing, mechanical property testing, and EDS composition testing methods
The ICP purity detection method can be used to identify the purity level of gold wire and determine the added alloy elements.
1. When looking at the appearance of LED bead gold wire, the first thing to see is that the surface of the gold wire should be free of scratches, dents, scratches, cracks, protrusions, discounts, and other defects that reduce the service life of the device, exceeding 5% of the wire diameter. During the drawing process of gold wire, surface defects appear on the surface of the wire, which can increase the current density and make the damaged area easy to burn. At the same time, the ability to resist mechanical stress is reduced, resulting in the fracture of the damaged 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, as well as between the gold wire and the bracket.
2. There is a diameter deviation between the LED bead dedicated gold wire and the unqualified gold wire. 1 gram of gold can be drawn to 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 A gold wire of m (1 mil). The length of the punched gold wire is fixed. If the diameter of the incoming gold wire is half of the original, then the measured resistance of the punched gold wire is one fourth of the normal. For gold wire suppliers, the thinner the diameter of the wire, the lower the cost, and the higher the profit when the selling price remains the same.
For LED bead customers who use gold wire, purchasing gold wire with cut corners in diameter poses a risk of increasing the resistance of the wire and reducing the melting current, which greatly reduces the lifespan of the LED bead light source. A lifespan of 1.0 mil of gold wire is necessarily shorter than that of 1.2 mil of gold wire, but simple testing by packaging factories cannot detect the diameter of the gold wire, and precision instruments must be used to detect it.
3. LED bead dedicated gold wire is drawn from a material with a gold purity of over 99.99%. By designing reasonable alloy components, the gold wire has the advantages of high tensile and bonding strength, good sphericity, and low vibration fracture rate. The majority of bond alloy wires should be high-purity alloy wires with a purity of over 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.
Using mechanical property testing, that is, testing the tensile load loading and elongation of the gold wire
A good gold wire that can withstand the impact generated during resin encapsulation must have a specified breaking load and elongation. At the same time, the breaking force and elongation of gold wire play a crucial role in the quality of wire bonding, and bonding wires with high breaking rate and elongation are more conducive to bonding.
Too soft gold wire can cause: ① sagging arch wire; ② Spherical instability; ③ The neck of the ball is prone to contraction; ④ Gold thread is prone to breakage.
Too hard gold wire can lead to: ① drilling holes in the chip electrodes or epitaxy; ② Gold ball neck fracture; ③ Difficulty in forming alloys; ④ Difficulty in controlling the arch wire arc.
Using chemical composition testing - EDS composition detection method
Identify the types of incoming materials: gold wire, silver wire, gold clad silver alloy wire, copper wire, aluminum wire. Gold wire has advantages such as high conductivity, good thermal conductivity, corrosion resistance, good toughness, and excellent chemical stability. However, the price of gold wire is expensive, and the packaging cost is also too high.
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