Organo-Soluble Low CTE Polyimides and their Applications to Photosensitive Cover Layer Materials in Flexible Printed Circuit Boards

Abstract

A novel cover layer material for flexible printed circuit (FPC) applications was developed in this work. A high molecular weight of polyimide composed of four monomers, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BisApAf) was prepared by the one-pot polycondensation in N-methyl-2-pyrrolidone (NMP) without precipitation and gelation. The polyimide (PI) was highly soluble in various common organic solvents. Interestingly, the PI film formed by simple solution-casting of the PI solution had a low CTE value close to that of copper foil, therefore almost no curling of the PI/copper laminate was observed when the PI film was directly formed on a copper foil. The PI film also exhibited other combined properties, including a low CTE, a high T _g, high thermal stability, low water absorption, comparatively good transparency, the highest levels of non-flammability, good insulation properties and sufficient film flexibility. In addition, fine positive-tone patterns could be obtained from DNQ-containing PI with a sensitivity of 238 mJ cm^-2. The results revealed that the present PI system is a promising candidate as a novel cover layer material.

Keywords

organo-soluble polyimides low CTE positive-tone photosensitive polyimides flexible printed circuit (FPC)cover layer

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References

Furukawa, N. , Yuasa, M. , Omori, F. and Yamada, Y. (1996). Adhesive Properties of Siloxane Modified Polyimides and Application for Multi-Layer Printed Circuit Boards. J. Adhesion, 59: 281-294.

Jou, J.-H. and Chen, L.-J. (1991). Relaxation modulus and thermal expansion coefficient of polyimide films coated on substrates . Appl. Phys. Lett., 59(1): 46-47.

Furukawa, N. , Yamada, Y. and Kimura, Y. (1996). Preparation and stress relaxation properties of thermoplastic polysiloxane-block-polyimides. High Perform. Polym., 8: 617-630.

Mochizuki, A. and Ueda, M. (2001). Recent Development in Photosensitive Polyimide (PSPI). J. Photopolym. Sci. Technol. , 14(5): 677-687.

Numata, S. , Fujisaki, K. and Kinjo, N. (1987). Re-examination of the relationship between packing coefficient and thermal expansion coefficient for aromatic polyimides. Polymer, 28: 2282-2288.

Hasegawa, M. , Koyama, J. , Horii, S. and Fujii, M. (2007). Low-K and Low-CTE Polyimides (15). Low CTE Induced by Solution-casting from Polyimide Varnishes. Polym. Prepr. Jpn., 56: 1560.

Pryde, C.A. (1989). IR Studies of Polyimides. 1. Effects of Chemical and Physical Changes During Cure. J. Polym. Sci. Part A: polymer Chemistry, 27: 711-724.

Hasegawa, M. and Horii, S. (2007). Low-CTE Polyimides Derived from 2,3,6,7-Naphthalenetetracarboxylic Dianhydride. Polym. J., 39: 610-621.

Arnold, F.E. Jr. , Cheng, S.Z.D. , Hsu, S.L.-C. , Lee, C.J. and Harris, F.W. (1992). Organo-soluble, segmented rigid-rod polyimide films: 2. Properties for microelectronic applications. Polymer, 33: 5179- 5185.

10.

Hasegawa, M. , Matano, T. , Shindo, Y. and Sugimura, T. (1996). Spontaneous molecular orientation of polyimides induced by thermal imidization (2): In-plane Orientation. Macromolecules, 29: 7897-7909.

11.

Hasegawa, M. and Horie, K. (2001). Photophysics, Photochemistry, and Optical Properties of Polyimides. Progress in Polymer Science, 26: 259-335.

12.

Miyagawa, K. , Naruse, K. , Ohnishi, S. , Yamaguchi, K. , Seko, K. , Numa, N. , and Iwasawa, N. (2000). Study on Thermal Reactions of o-Naphthoquinone Diazides and Its Application to Electrodeposition Positive Photoresist. KANSAI Paint Co. ltd. technical report, 135: 2-9.

13.

Reiser, A. , Huang, J.P. , He, X. , Yeh, T.F. and Jha, S. (2002). The molecular mechanism of novolakdiazonaphthoquinone resist. European Polymer Journal , 38: 619-629.

14.

Nakayama, T. , Mochizuki, A. and Ueda, M. (1996). New positive-type photosensitive polyimide: poly (hydroxyimide) with diazonaphthoquinone. Reactive & Functional Polymers, 30: 109-115.