Adhesion–delamination phenomena at the interfaces of the dielectric layer

•By modifying the thickness of the PI layer and through heat treatment before reflow process, which could effectively reduce the residual stress value.•The contact angles of the samples after plasma treatment were greatly reduced.•The order of weighting factors affecting the contact angle which is: power > process time > process pressure > gas ratio.•After plasma treatment samples must be taken to the next process immediately to reduce the occurrence of delamination. Fan-out wafer-level packaging (FOWLP) has been developed as an enhancement of standard wafer-level packaging solutions and is being intensively researched nowadays. However, issues of delamination remain unsolved. This study focuses on the interfacial characteristics between polyimide (PI) and redistribution layers (RDL) of the FOWLP to decrease the concerns in delamination. The problems of delamination were addressed through simulation and experimentation. In the simulation, the FOWLP package model was established by using the finite element analysis ANSYS software. The results showed various ways to reduce the residual stress, such as by adding a pre-baking process before reflow or by changing the thickness of each PI layer. These ways can effectively reduce the maximum residual stress of the FOWLP and improve the issue of delamination. Moreover, through plasma treatment with the different levels of powers and gases, the adhesion between PI and RDL can improve the overall strengthening of the FOWLP structure. While, in the experimental process, Taguchi design of experiment was utilized to determine the optimal process parameters and key factors. The physical and chemical properties were analyzed, such as the surface roughness via Atomic Force Microscope (AFM) and the surface material compounds by X-ray Photoelectron Spectroscopy (XPS). The relationship between the roughness and delamination was examined.