Development and reliability of wire bonding used in optoelectronics

The wire bonding industry is a process widely used in the manufacturing and assembly of electronic and optoelectronic devices. This industry covers many application areas such as semiconductor manufacturing, microelectronics assembly, automotive electronics, consumer electronics, telecommunications, healthcare, defense and space technologies. Many devices that fall within this scope, such as laser diode, LED, solar cell and lidar, can be given as examples. Reliability is important in wire bonding in optoelectronics, as in every field. At this point, the importance of the reliability of the wires connected provides an advantage in terms of both prestige and preventing future errors. The studies carried out in this thesis are on the development of the wire bonding method and optimization of its reliability. In the study, connections on wires with diameters of 25 and 33 µm were carried out in a fully automatic wire bonding device with the thermosonic ball bonding method, using Au wire and Au bonding surface, that is, Au-Au metallurgy. By keeping the 170 °C table temperature and 22 ms binding time constant, the binding force and the diameter of the binding wire were changed, the effect on the bonding strength was applied to all connected wires one by one, and the results were evaluated, taking the MIL-STD-883K method 2011.9 standard as reference. Detailed optical microscope and SEM images were taken. Analyzes and comparisons of error mechanisms were made. It was observed that the best bonding for gold wire with a diameter of 25 µm was at 30 and 40 g bonding strength. In the study where the bond strength was applied as 30 g, the average tensile test result was found to be 11.36 gf. At an applied bond strength of 40, a tensile test result of 11.53 gf was obtained. The causes of failure resulting from tensile tests were examined using various imaging techniques. In the analyzes and comparisons made, it was observed that the best bonding was achieved at a binding strength of 30-40 g. Bonding errors were encountered at very low and very high applied forces. It has been found that irregularities occur after 80 g for 25 µm gold wire and after 50 g for 33 µm wire diameter, especially at very high bonding strengths.