Organosoluble thermoplastic polyimide with improved thermal stability and UV absorption for temporary bonding and debonding in ultra-thin chip package

Thermoplastic polyimide (TPI) has been extensively applied in electronic industry due to improved processibility, superior mechanical and dielectric properties. However, TPI is still restricted by the limited thermal stability and insufficient UV absorption for the application of temporary bonding and debonding (TBDB) in ultra-thin chip package. In this work, the rigid biphenyl group, twisted non-coplanar structure, rigid bulky side group and flexible ether bond are introduced to obtain a series of novel quaternary copolymerized TPIs with superior comprehensive performance. The results show that the as-prepared TPI possesses excellent solubility in NMP, DMF, DMAc and DMSO, and thermoplasticity (E’ drop > 103 MPa). Besides, the temperature of 5% weight loss and glass transition temperature could achieve as high as 548.1 °C and 335.4 °C, respectively. Furthermore, the tensile strength of TPI-4 is 128.7 MPa and elongation at break is about 14.2%. Moreover, the TPI-4 also exhibits superior adhesion on silicon wafer (adhesion strength >5 B by hundred grid test) and wonderful absorption at 355 nm UV laser (99.7%). At last, the application in TBDB process has also been proved with a laser energy of 400 mJ/cm2 within 60 s, showing superior efficiency and low-cost. All these results prove their application in TBDB of ultra-thin chip package for 5G era and so forth.