Failure Analysis of Interconnection Fault in a PoP Module Applied for Mobile Phone

Abstract

Abstract A typical early fault case of some mobile phones was studied in this paper. The failure phenomenon was manifested as that the mobile phones could not be powered on after one year in their service, with the malfunction rate having reached about 2% of the whole yield in the same manufacturing lot as the fault machines returned from client side continuously. The results of fault location showed that there was interconnection failure in the main chip module, which used package on package (PoP) packaging. A series of experimental technique was used for the failure analysis, such as 3D X-ray inspection, shadow moiré test, microsectioning, scanning electron microscope (SEM), electron backscattered diffraction (EBSD) analysis, etc. The results showed that some solder joints' through cracking in the PoP module was the immediate cause of the mobile phones' malfunction, and the main reason for the cracking was thermal-mechanical fatigue with recrystallization microstructure degradation. It is important to further study on the technological method for controlling grain orientations in electronic interconnections.