WIRE BONDING ||MODULE 6 || EC 465 || KTU MEMS || LECTURE 43

Hi all, today we are discussing about wire bounding. Wire bounding provides electrical connection to or from the core elements such as the silicon diaphragm in pressure sensor or actuating members in the micro accelerometer. Common wire materials are gold and aluminum. Other wire materials include copper, silver, and palladium. Common wire materials are Gold and Aluminium. Other wire materials include Copper, Silver and Palladium. Common materials used for wire bonding are Gold and Aluminium. We also use Copper, Silver and Palladium. Wire size is 20 to 80 micrometer in diameter. Three main wire bonding techniques are used in the industry. Thermocompression, Wedge-Wedge Ultrasonic Wire Bonding and Thermosonic Wire Bonding. Wire bonding is used to provide electrical connection to the core elements. Let's see these three techniques one by one. First one is Thermocompression. Thermocompression is the process of heating a material with heat. The principle of thermocompression wire bonding is to press heated metal bales onto metal bars. The metal wire is fed through a capillary bonding tool with the tip of the wire above the metal pad. A torch is used to heat the tip of the wire up to 400 degrees Celsius. The tip of the wire is formed into a ball shape with the help of a torch. The metal wire is fed through the metal pad. The pressing process takes about 40 milliseconds. The metal wire is bonded to the metal pad. The bonding process is done through two physical actions. Next one is Wedge-Wedge Ultrasonic Wire Bonding. The diagram of the bonding process is shown here. A wedge bonding tool is used for the bonding process. The bonding tool is in the shape of a wedge through which the wire is fed. The energy supplied for the bonding is an ultrasonic wave that is generated by a transducer that vibrates the tool at a frequency from 20 to 60 kHz. Here the bonding tool travels in parallel to the bonding pad. After moving over the desired bonding pad, the wedge tool is lowered to the pad surface. A compressive force is applied and a burst of ultrasonic energy is released to break down the contact surfaces and achieve desired surface bonding. The time required for this is 20 ms. The next bonding technique is thermosonic bonding. The thermosonic bonding is done by combining the two wire bonding techniques we discussed earlier. Here ultrasonic energy is used with thermocompression at moderate temperatures of 100 to 150 degrees Celsius. A capillary tool is used to provide ball joints. So this lecture was about wire bonding techniques. There are mainly three types of wire bonding. These are thermocompression, wedge-wedge wire bonding and thermosonic bonding. I hope everyone understood this topic. See you in the next class.