In recent years, with the rapid development of electronic components and widely used of digital circuits, electronic machines process towards to direction of lightweight, small, multi-function, high-speed, high reliability quickly. 近年来,电子元器件飞速发展,数字电路被广泛应用,电子整机向轻量化、小型化、多功能、高速度、高可靠方向迅速发展。