The gold wire is one of the core components in the LED lamp bead packaging process. It is a bridge connecting the light-emitting chip and the solder joint, and plays a decisive factor in the service life of the LED lamp bead. However, due to the high cost and high price of the gold wire, some manufacturers have tried their best to develop some alloy materials that can replace the LED gold wire to rush into the expensive LED gold wire. In order not to let the majority of LED packaging chain companies be deceived again, how to identify the purity of gold wire?
The gold wire used for encapsulating the LED lamp bead has a gold content of 99.99% or more. It is produced by the gold-drawing process of this material. In addition to containing 99.99% gold, the gold contains less than 1%. Trace elements such as Ag/Cu/Si/Ca/Mg. A silver wire is sometimes used for soldering, and the silver wire is composed of a trace element having a purity of 99.99% or more and a silver element plus 1% or less.
This kind of high purity gold wire (or silver wire) is used in the LED packaging process, but due to its high cost and high price, some merchants have developed many copper alloy gold wires and silver alloys in order to reduce costs. Alloy materials such as gold wire and gold-clad silver alloy gold wire are used instead of expensive gold wire.
In the identification of LED gold wire, Zhang Manager usually uses the following effective methods to determine the purity of LED gold wire: ICP purity detection method, mechanical property test method, EDS component detection method.
The purity level of the gold wire can be identified using the ICP purity test to determine the added alloying elements.
1. The LED special gold wire is made of material with a purity of 99.99% or more. Through reasonable design of the alloy composition, the gold wire has high tensile strength and bonding strength, good sphericity and low vibration fracture rate. advantage. Most of the bond alloy wire should be a high-purity alloy wire with a purity of 99.99% or more, 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 LED special gold wire 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). It can also draw a length of 105.49m and a diameter. 25μm (1 mil) gold wire. If the length of the gold wire is fixed, if the diameter of the incoming gold wire is half of the original, the resistance measured by the gold wire is one quarter of the normal. For gold wire suppliers, the finer the diameter of the gold wire, the lower the cost, and the higher the profit, the higher the profit.
For LED customers using gold wire, the purchase of gold wire for cutting corners on the diameter will increase the risk of gold wire resistance and the reduction of the fuse current, which will greatly reduce the life of the LED light source. The 1.0 mil gold wire life is necessarily shorter than the 1.2 mil gold wire, but the simple test of the packaging factory is not tested, and the diameter of the gold wire must be detected with a precision instrument.
3, look at the appearance of the LED gold wire, first look at the surface of the gold wire should not exceed the wire diameter of 5% of the nicks, pits, scratches, cracks, bumps, discounts and other defects that reduce the service life of the device. During the drawing process, the surface defects appearing on the surface of the wire lead to an increase in current density, which makes the damaged part easy to be burned, and the ability to resist mechanical stress is reduced, causing breakage of the inner lead damage. 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.
Use mechanical property testing, that is, pull-off load loading and elongation detection of gold wire
A good gold wire that can withstand the impact generated by 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 the wire bonding, and the bonding wire having a high breaking rate and elongation is more advantageous for bonding. Too soft gold wire will lead to the following defects: 1 arch sag; 2 spherical instability; 3 ball neck easy to shrink; 4 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 pit; 2 the gold ball neck is broken; 3 is difficult to form the alloy; 4 the arch wire arc is difficult to control.
Use chemical composition test - EDS component detection method to identify the type of incoming materials: gold wire, silver wire, gold-clad silver alloy wire, copper wire, aluminum wire. Gold wire has the advantages of large electrical conductivity, good thermal conductivity, corrosion resistance, good toughness and excellent chemical stability. It is very popular among the majority of packaging manufacturers, but the price of gold wire is expensive, resulting in high packaging cost. In the periodic table, the metal elements of gold, silver, copper and aluminum in the transition group metal elements have high electrical conductivity. Many LED manufacturers are trying to develop copper alloys, gold-clad silver alloy wires, and silver alloy wires to replace expensive gold wires.
Although these alternatives are superior to gold wires in some properties, they are much less chemically stable. For example, silver wire and gold-coated silver alloy wires are susceptible to sulfur/chlorine/bromination corrosion, and copper wires are easily oxidized. In encapsulated silica gels similar to water-absorbing and breathable sponges, these alternatives make the bonding wires susceptible to chemical corrosion, the reliability of the light source is reduced, and the LED lamp beads are easily broken and dead.
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