1. Look at the appearance of the gold wire of the LED lamp beads. First of all, the surface of the gold wire should be free of nicks, pits, scratches, cracks, bumps, discounts and other defects that reduce the service life of the device that exceed 5% of the wire diameter. During the drawing process of the gold wire, the surface defects on the wire surface will increase the current density and make the damaged part easily burned. At the same time, the resistance to mechanical stress is reduced and the damaged part of the inner lead is broken. 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 chip, and between the gold wire and the bracket.
2. There is a difference in diameter between the special gold wire for LED lamp beads and the unqualified gold wire. 1 gram of gold can draw a gold wire with a length of 26.37m and a diameter of 50μm (2 mil) or a length of 105.49m , Gold wire with a diameter of 25μm (1 mil). The length of the gold wire is fixed. If the diameter of the incoming gold wire is half of the original diameter, the resistance measured on the gold wire is one-fourth of the normal. For gold wire suppliers, the thinner the wire diameter, the lower the cost, and the higher the profit will be if the price remains unchanged.
For LED lamp beads customers who use gold wires, purchasing gold wires that cut corners on the diameter will increase the resistance of the gold wires and reduce the risk of fusing current, which will greatly reduce the life of the LED lamp bead light source. The life of the 1.0mil gold wire must be shorter than the 1.2mil gold wire, but the simple inspection of the packaging factory cannot be tested, and the diameter of the gold wire must be detected with precision instruments.
3. The special gold wire for LED lamp beads is made of wire drawing with a gold purity of 99.99% or more. By designing a reasonable alloy composition, the gold wire has high tensile and bonding strength, good ball formation, and vibration fracture rate. Low advantage. Most of the bonding alloy wires should be high-purity alloy wires with a purity of 99.99% or more, and the total amount of trace elements (Ag/Cu/Si/Ca/Mg and other trace elements) should be kept below 0.01 to maintain the characteristics of gold.
Use mechanical performance testing, that is, testing the breaking load 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 the gold wire play a key 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 will cause: ①The arch wire sags; ②The ball is unstable; ③The neck of the ball is easy to shrink; ④The gold wire is easy to break.
Too hard gold wire will cause: ① to punch the chip electrode or epitaxial hole; ② the neck of the gold ball is broken; ③ difficult to form alloy; ④ difficult to control the arch wire arc.
Use chemical composition inspection-EDS composition detection method
Identify the types of incoming materials: gold wire, silver wire, gold-coated silver alloy wire, copper wire, aluminum wire. Gold wire has the advantages of high electrical 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 too high.
