The study of μ-BGA(Ball Grid Array) singulation with a pulsed Nd:YAG laser

초록

In a microelectronics industry, the -BGA singulation system has been studied by mechanical type. However this has burr and device damage by mechanical stress. So we need to research other system to solve many problems. There are only a few types of lasers excimer, CO2, Nd:YAG, copper vapor lasers in use for microelectronics application. The Nd:YAG laser can be used for processing such materials as polymers and metals. In this paper, we have studied minimization of the line-width and surface burning which are occurred after the singulation process with a pulsed Nd:YAG( = 532 nm, repetition rate = 10 Hz) laser. The thermal energy of a pulsed Nd:YAG laser is used to cut the copper layer. Especially, the sacrifice layer and N2 blowing are effective to minimize of the surface burning. The N2 blowing reduces a laser energy loss by debris and suppresses a surface oxidation. The SEM(scanning electron microscopes), non-contact 3D inspector and high-resolution microscope are used to measure cutting line-width and surface state. The μ-BGA singulation threshold energy is 234.1 kJ/cm2 at 50 ㎛/s scan speed.