Detection of shape error through solder bump edge extraction of flip-chip by using exponential approximation function

Abstract

As the technology of semi-conductor chip progresses to pursue high density and high speed, flip-chip technology recently has played a successful role to overcome technological limit of the existent gold wire bonding technology made a connection with outside terminal. Flip-chip is systemically different to the existent chip that transfers electrical signal by connecting wires to the chip externally. Because the interior connecting part of flip-chip is hidden into an invisible region between a die and a PCB, it is indispensable for preparing cut or sliced chips to observe inner joint parts. Therefore, this work embodied nondestructive inspection system that can examine the bonding part of flip-chip without damage of chip using an X-ray system. Using an attenuation characteristic of X-ray (the intensity after transmitting an X-ray), it could do monitoring the shape of solder bumps without damaging the chip. The suggested inspection method can effectively extract the edge of solder bumps from an X-ray image by using the exponential approximation for the intensity of transmitting an X-ray and detect inside bad bonding parts utilizing information about shape. The embodied inspection system is applied to evaluate actual bonded flip-chip.