关键词: 高密度组装, 激光软钎焊, 钎料桥连, 数值模拟, 低碳钢板, 激光超声, 能量衰减法, 平均晶粒尺寸

Abstract: In order to develop a no solder bridging assembly method for high density electronic devices, temperature distribution of joints of fine pitch QFP device is simulated under heating condition of laser single point and laser scanning. Then experiments of QFP256 device assembly are performed under heating condition of infrared furnace and laser scanning. Simulation results shows that temperature distribution in fine pitch joints is controlled by laser local heating characteristics, and then melting range of solder on the joint is controlled for defense solder bridging on adjacent leads. Experimental results show that suitable laser heating can carry out no bridging assembly for fine pitch devices.

Key words: Bridge, High density assembly, Laser soldering, Simulation, Grain size, Laser ultrasonics, Low carbon steel sheets, Time domain energy attenuation