In infrared led packaging, the copper wire process has been researched and developed by led lamp manufacturers because of its cost reduction, and has been adopted by many manufacturers, but in practical applications, compared with gold wire welding, the copper wire process has many problems. Here are some common questions that I hope will enlighten you.
1) Copper wire oxidation, resulting in gold ball deformation, affecting the product pass rate.
2) The aluminum layer of the first solder joint is damaged, for < The thickness of the 1um aluminum layer is especially serious;
3) Defects of the second solder joint, mainly due to the copper wire is not easy to combine with the support, resulting in crescent crack or damage, resulting in poor welding of the second welding, and reliability risks in the process of customer use;
4) For many supports, the power of the second solder joint, USG(ultrasonic) friction and pressure parameters need to be optimized, and the good and good rate is not easy to be high;
5) It is difficult to unpack when doing failure analysis;
6) The MTBA(hourly yield) of the equipment will be lower than that of the gold wire process, affecting the production capacity;
7) The training cycle of operators and technicians is relatively long, and the skill quality requirements of employees are higher than that of gold wire welding, which will definitely affect the production capacity at the beginning;
8) It is easy to confuse materials. If the production process of gold wire and copper wire is used at the same time, the production control must pay attention to the storage life and distinguish the material list. If the wire is incorrectly printed or oxidized, it can only be scrapped.
9) The cost of consumables increases, and the split life of copper wire is usually reduced by half or more than that of gold wire. At the same time, the complexity of production control and the cost of porcelain nozzle consumption are increased.
10) Compared with gold wire welding, in addition to the lighter rod (EFO), there are forming gas(synthetic gas) protective gas conveying pipes, and the positions of the two must be aligned. This directly affects the yield. Precise control of protective gas flow, more cost, less defect rate;
11) Aluminum Splash. It is usually easy to appear in wafers with thick aluminum layers. It is not easy to identify the impact, but be careful not to short-circuit the circuit. Easy to crush PAD or weld slider. Cause poor test or customer complaints;
12) Oxidation occurs after finishing the line, and there is no standard judgment risk, which is easy to cause poor contact and increase the defective rate;
13) Wire Pull, ball shear test standards and SPC control lines need to be re-optimized. The current gold wire standards may not be fully applicable to copper wire processes;
14) There will be some restrictions on the underlying structure of the first solder Pad, such as Low-K die electric, with holes through the layer, and the underlying circuit, which need to carefully evaluate the risk. The existing wafer bonding Pad design rule should be deeply optimized for the copper wire process. But now the use of copper wire packaging plants, it seems not enough to affect the development of chips;
15) Resistance from customers, copper wire process for some customers with high reliability requirements is still more difficult to accept, even lose customer trust;
16) The copper wire process may have reliability problems with the use of non-green plastic sealant (containing halogen elements)
17) The presence of fluorine or other impurities on the pad will also reduce the reliability of the copper wire.
18) The evaluation of Die to Die bonding and Reverse bonding is not complete.