Gold wire is one of the core components in the LED lamp bead packaging process. It is the bridge connecting the light-emitting chip and the solder joint, and it also plays a decisive factor in the service life of the LED lamp bead. However, due to the high cost and high price of gold wire, some manufacturers will try their best to develop some alloy materials that can replace the LED gold wire to replace the expensive LED gold wire. In order to prevent the majority of LED packaging chain companies from being deceived again, how to identify the purity of the gold wire?

The gold wire used for packaging LED lamp beads has a gold content of more than 99.99%. The gold of this material is produced by a wire drawing process. In addition to 99.99% gold, this gold also contains 1% or less of other elements. Trace elements, such as Ag/Cu/Si/Ca/Mg, etc. Silver wire is sometimes used in welding. The silver wire is composed of silver with a purity of more than 99.99% and other trace elements with a purity of less than 1%.

It is this kind of high-purity gold wire (or silver wire) that is used in the LED packaging process. However, due to its high cost and high price, some businesses have now developed many copper alloy gold wires and silver alloys in order to reduce costs. Gold wire, gold clad silver alloy gold wire and other alloy materials replace expensive gold wire.

When identifying LED gold wires, Manager Zhang usually uses the following effective methods to determine the purity of LED gold wires: ICP purity testing method, mechanical property testing method, and EDS component testing method.

Gold wire purity grades can be identified using ICP purity testing to determine added alloying elements.

      1. The special gold wire for LED is drawn from a material with a gold purity of more than 99.99%. By designing a reasonable alloy composition, the gold wire has high enough tensile force and bonding strength, good sphericity and low vibration fracture rate. advantage. Most of the bonding 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.

2. There is a diameter deviation between the special gold wire for LED 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 and a diameter of 105.49m. 25µm (1 mil) gold wire. If the length of the gold wire is fixed, and if the diameter of the incoming gold wire is half of the original diameter, then the measured resistance of the gold wire to be beaten is a quarter of the normal value. For gold wire suppliers, the thinner the diameter of the gold wire, the lower the cost, and the higher the profit when the selling price remains the same.

For LED customers who use gold wires, purchasing gold wires that cut corners in diameter will increase the resistance of the gold wires and reduce the fuse current, which will greatly reduce the life of the LED light source. The life of 1.0 mil gold wire is necessarily shorter than that of 1.2 mil 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. Looking at the appearance of the LED gold wire, 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 surface of the wire will lead to an increase in the current density, making the damaged part easy to be burned, and at the same time, the ability to resist mechanical stress is reduced, causing the inner lead to break at the damaged part. Secondly, the surface of the gold wire should be free of oil, rust, dust and other adhesions, which will reduce the bonding strength between the gold wire and the LED chip, and between the gold wire and the bracket.

Using mechanical property testing, that is, testing the breaking load and elongation of the gold wire

A good gold wire that can withstand the shock of 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 the bonding wire with high breaking rate and elongation is more conducive to bonding. Gold wire that is too soft will cause the following defects: ① the arch wire sags; ② the spherical shape is unstable; ③ the ball neck is easy to shrink; ④ the gold wire is easy to break. Too hard gold wire will lead to the following defects: ① The chip electrode or epitaxy is punched out of the hole; ② The neck of the gold ball is broken; ③ It is difficult to form an alloy; ④ It is difficult to control the arc of the arch wire.

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 electrical conductivity, good thermal conductivity, corrosion resistance, good toughness, and excellent chemical stability, which are deeply loved by packaging manufacturers. However, the price of gold wire is expensive, which leads to high packaging costs. In the periodic table of elements, gold, silver, copper and aluminum in the transition group metal elements have high electrical conductivity. Many LED manufacturers try to develop such as copper alloy, gold clad silver alloy wire, silver alloy wire to replace the expensive gold wire.