Wafer level batch packaging (WLBP): incorporation of air pores/foams in a polyimide matrix using a low modulus sacrificial commercial polymer

This research focuses on using polycaprolactone (PCL-sacrificial polymer) as the thermally labile component that decomposes and diffuses our of the polyimide (PI) matrix at elevated temperatures forming pores (pores are in the micrometer nearing the nanometer range) in the PI matrix. This diffusion evolves pores/foams, which lowers the dielectric constant (via air-filled pores) and minimizes crosstalk and the transmission delay between metal interconnects. Research focuses on how the chemical compositions of the PI-PCL film effect the distribution and size of the pores. The effect of variation of the molecular weight and functionality of the PCL moiety is studied to better optimize the pore size. Controlling the pore size is the focal point since an enlarged pore can cause contaminants to diffuse into the PI passivation layer, which has an adverse effect on the material's mechanical property. Optimizing the rheological properties during polymer cure are studied. Characterization of the porous polyimide film is evaluated via Thermogravimetric Analysis (TGA) to follow the degradation of the sacrificial polymer. The use of Scanning Electron Microscopy (SEM) is used to give information about the pore size front a quantitative standpoint. The premise of the research is based on adhering to the specifications of Wafer Level Batch Packaging (WLBP).