Design Of FPGA-based Electronic Flame-Off System For Gold Wire Ball Bonder

Gold ball wire bonding machine is used to realize the chip packages of internal lead before welding, which includes image recognition technology, motion control technology, power electronic technology, and IC bonding technology, playing an more and more important role in the semiconductor industry. In the Gold wire ball bonder, it is the first step of the entire bonding process to melt the gold wire into a ball. The main effect is to increase the contact area between the gold wire and frame, being helpful for the improvement of the quality of welding. Therefore, as a part of the gold wire ball bonder, the quality of forming a ball is rather critical to the effect of the wire bonding.According to the working characteristics and technical requirements of the gold wire ball boner, the thesis makes an analysis on the theory of EFO system and makes sure the key parameters. An under-controlled constant-current source is the theory model of the EFO system, with fire current and time as input parameter, the under-controlled constant-current source as under-controlled object, the diameter of the gold ball as output parameter. According to the drawback of the existing EFO systems, a FPGA-based EFO system is proposed, which method is elaborated, object is made, and experiments are analyzed. The FPGA-based EFO system mainly includes two parts:the hardware circuit and the software control, in order to realize the closed-loop control on fire current. The hardware circuit mainly includes push-pull power convert circuit, current sample circuit, signal adjust circuit, A/D converter circuit, switching transistor driving circuit, serial communication and FPGA controller circuit. Software control mainly includes digital filter module, digital PID module, serial communication module and main control module.etc. Through a precise resistance, the fire current is controlled by a close loop. Incremental PID is used, which PID parameters are made sure by a relay tuning method. The experiment includes PWM waveform generation and forming balls.Through the fabrication and experiments on the FPGA-based EFO system, it can be concluded that the system works steady; operation is simple, the size of ball is adjusted; the system reaches to the demand of the design, have promotion value to some extent.