A strategy to prepare low-temperature curable photosensitive polyimide with good comprehensive performance

Low-temperature curable photosensitive polyimide (PSPI) materials have attracted widespread attention in advanced packaging, serving as key insulating dielectric materials in redistribution layer (RDL) to avoid wafer warpage. Considering PSPI and copper together formed the core RDL part, the adhesion between PI and copper need to be concerned to realize high reliability. However, the exploration of novel diamines with desirable characteristics such as low temperature curing ability, improved adhesion and excellent lithography properties was limited. We designed a new diamine with fluorine-containing pyridine side group named PyFNH2, which facilitated preparation of low-temperature curable polyimide (at 200 °C) with remarkable degree of imidization (≥95.9 %). Secondly, the coordination interaction between pyridine side group and copper enhanced adhesion strength. Thirdly, the PI films cured at 200 °C exhibited favorable dielectric properties compared to control films without PyFNH2, because of the introduction of electronegative fluorine atoms and rigid side groups. Apart of these, the PI films possessed fairly good thermal and mechanical properties. Significantly, negative-tone PSPI employing the precursor poly (amic ester) with PyFNH2 was successfully prepared and cured at 200 °C, enabling precise lithography patterns with line resolutions down to 3 µm. Our findings highlight promising application potential of PyFNH2 in photolithography technology, offering a feasible strategy for structure designs of low-temperature curable diamine.