Synthesis and properties study of a thermoplastic polyimide with high glass transition temperature for wafer level package

Polyimides (PIs) have been used in a wide spectrum of high-tech fields for their excellent thermal property, excellent mechanical property, extremely low dielectric constant, excellent low temperature resistance, low CTE and good chemical resistance. However, the rigid molecular structure combined with strong intermolecular interaction results in insolubility and low meltability. In this work, the non-coplanar and isomeric diamine of 5(6)-amino-l-(4-aminophenyl)-1,3,3-trimethylindane (DAPI) and ether-contained flexible dianhydride of 4,4-oxydiphthalic anhydride (s-ODP A) are selected for the preparation of the soluble thermoplastic polyimide (TPI) with high glass transition temperature. Fourier transform infrared spectrometer indicates that polyimide resin has been successfully synthesized. And thanks to the noncoplanar and flexible ether group, the as-synthesized polyimide exhibits good solubility in high boiler point polar solvents such as m-Cresol, N-methylpyrrolidone (NMP). Then, differential scanning calorimeter shows that glass transition temperature (Tg) is about 300 °C. In addition, an elongation-at-break of 4–5 % and high tensile modulus above 1500 MPa is also proved. Moreover, the thermal gravity analysis test shows that its 5% thermal weight loss temperature (T5%) is about above 460 °C. So, the as-prepared TPI shows excellent comprehensive property with superior solubility, thermal, mechanical performance which is suitable for the application in wafer level package.