Low-Temperature Curable Negative-Tone Photosensitive Polyimides: Structure and Properties

• Published in: Polymers Vol. 15; no. 4; p. 973
• Main Authors: Fan, Sheng-nan, Yuan, Li-li, Wang, Li-zhe, Jia, Bin, Ma, Jia-xin, Yang, Hai-xia, Yang, Shi-yong
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 16.02.2023; MDPI
• Subjects: Additives; Catalysts; Chemical properties; Cryochemistry; Curing; Diamines; Electronic packaging; Elongation; Engineering research; Film thickness; Glass transition temperature; Imidazole; Infrared spectroscopy; Low temperature; Mechanical properties; Modulus of elasticity; Molecular weight; Nitrogen; Photochromic materials; Photoinitiators; Photosensitivity; Polyimide resins; Polyimides; Polymer films; Polymers; Silicon wafers; Solvents; Temperature; Tensile strength; Thermodynamic properties; Ultraviolet radiation; China; United States > US; Japan; photo-patterning; photosensitive polyimide; low-temperature imidization; mechanical properties
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym15040973

Low-temperature curable negative-tone photosensitive polyimide (n-LTPI) viscous solutions were prepared by dissolving photo-crosslinkable poly (amic ester) (pc-PAE) resin, photophotocrosslinker, photoinitiator, and the heteroaromatic base as curing catalysts, and other additives in organic solvents. Among them, the pc-PAE resin was synthesized by polycondensation of aromatic diacid chloride and diester of 2-ethoxymathacrylate, aromatic diamines in aprotic solvents. After being spun-coated on a silicon wafer surface, soft-baked, exposed to UV light, and developed, the n-LTPI with 2% of imidazole (IMZ) as a curing catalyst produced high-quality photo-patterns with line via resolution of 5 μm at 5 μm film thickness. The photo-patterned polymer films thermally cured at 230 °C/2 h in nitrogen showed 100% of the imidization degree (ID) determined by in situ FT-IR spectroscopy. The thermally cured polymer films exhibited great combined mechanical and thermal properties, including mechanical properties with tensile strength of as high as 189.0 MPa, tensile modulus of 3.7 GP, and elongation at breakage of 59.2%, as well as glass transition temperature of 282.0 °C, showing great potential in advanced microelectronic packaging applications.