Bonding make PAD and PCB of NTC chip with aluminum or gold wire by bonding machine to connect with corresponding gold finger and complete the electrical connection. Bonding is one of the most important in COB technology process. In this procedure of using bonding mechanical model, parameter setting, Even the wire, wire diameter and wire hardness etc. It will be very important to influence the final product quality and reliability. The main process also will produce the bad products. Examine about the wire selection as below.
NTC chip of the wire selection: 1. According to the size is divided into thick and thin wire. The thick wire diameter is 1.25MIL, and the thin wire diameter is 1.0MIL. This is often according to the NTC chip PAD size to choose the diameter. 2. According to the wire hardness is divided into hard and cords wire. Because the hardness wire requirements of bearing the pulling force solder joint line is difference. And the tension and wire diameter are limited by NTC chip PAD . 3. In addition, according to the different wire materials can be divided into aluminium and gold wire. In COB production are usually using aluminum, and gold is usually used CMOS devices. Such as the internal NTC chip is connected with the CMOS tube connecting wire. At the same time also pay attention to NTC chip surface coating, such as if the surface coating is silver then using gold wire, If the coating is gold then using aluminum wire.