Impact of wafer surface profile on IC packaging

In this paper, delamination occurring in a plastic quad flat package (PQFP) had been found after the molding process. From preliminary observation, the wafer surface profile is found to be different from the others by atomic force microscopy (AFM) analysis, e.g. the pitch and trench of the local die surface. A stress simulation was performed to characterize the interaction between the molding compound formula design, molding process and wafer surface topography. The results show that the wafer topography does have a significant impact on the in-situ molding process. Aside from simulation, Fourier transform infrared spectrometry (FTIR) was used to characterize the uniformity of top layer passivation. The result showed that the uniformity of deposited passivation was not quite homogeneous as compared to a well-adhered area, which might cause insufficient adhesion which is contributed to by low density chemical bonding in the interface. Therefore, wafer surface topography and its chemistry do have a significant impact on IC packaging.