Imidization and Interdiffusion of Poly (amic ethyl ester) Precursors of PMDA/3,4 -ODA NANCY C. STOFFEL, 1 EDWARD J. KRAMER, 1 WILLI VOLKSEN, 2 THOMAS P. RUSSELL 2 1 Department of Materials Science and Engineering, Bard Hall, Cornell University, Ithaca, New York 14853 2 IBM Almaden Research Center, 650 Harry Rd., San Jose, California 95120 Received 3 May 1996; revised 17 June 1997; accepted 19 June 1997 ABSTRACT: Para-, meta-, and mixed isomeric poly(amic ethyl ester) precursors of the polyimide based on pyromellitic dianhydride ( PMDA ) and 3,4 -oxydianiline ( 3,4 -ODA ) were synthesized. The intrinsic viscosity of each of the isomers was measured in an NMP solution and found to be less than corresponding isomers derived from PMDA and 4,4 -oxydianiline ( 4,4 -ODA ) precursors with comparable molecular weight. The imidization and solvent retention were measured as a function of imidization tempera- tures, T i using forward recoil spectrometry (FRES). For samples cast from a single solvent, either N-methyl pyrrolidone (NMP) or dimethyl sulfoxide (DMSO), no differ- ence was observed in the temperature-dependent imidization behavior between the isomers. In all cases the imide fraction f increased as T i increased, and reached a value of unity, i.e., full conversion at 400°C. At the same T i , samples cast from DMSO showed a slightly higher f than samples cast from NMP. FRES and time of flight FRES (TOF- FRES ) were used to measure the interdiffusion distance, w , of deuterium-labeled trac- ers into nondeuterated base layers of the polyimide of PMDA / 3,4 -ODA treated at various T i . The primary determinant of w for all isomers was T i , and the particular isomer used as either the base or the tracer molecule did not seem to affect w .  1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2247–2258, 1998 Keywords: polyimide; imidization; interdiffusion; PMDA / 3,4 -ODA INTRODUCTION polyimide may be increased by a factor of two by cold drawing precursor poly(amic acid) (PAA) films and imidizing the film while it is stretched. The most common polyimide utilized in electron- ics is the polyimide synthesized from pyromellitic This increase in the in-plane modulus arises from an increase in the in-plane orientation of the mol- dianhydride (PMDA) and 4,4 -oxydianiline ( 4,4  ODA ) . This polyimide has good thermo-oxidative ecules. 3 Although PMDA / 4,4 -ODA is a very useful ma- stability, mechanical properties, solvent resis- tance, and a high broad glass transition tempera- terial for electronics applications, it is far from ideal. One problem is that the in-plane coefficient ture ( T g Å 380°C), 1 and good resistance to sol- of thermal expansion (CTE) is 30 1 10 06 / °C at vents. The PMDA / 4,4 -ODA is highly deformable 100°C. 4 If the material is used as an interlayer with a measured strain to break of 70% at 25°C. 2 dielectric, or as a carrier film for tape automated The modulus is 3 GPa, and the tensile strength bonding ( TAB ) structures, the CTE mismatch to is 0.2 GPa, 2 which while high for a polymer, are silicon and/or copper is rather large which pro- far less than the theoretically achievable values. 2 duces undesirable stresses during processing or The in-plane modulus of the PMDA/4,4 -ODA operation. The processing of the polyimide precur- sor solutions is made more difficult in certain ap- Correspondence to: N. C. Stoffel plications because of the rather high intrinsic vis- Journal of Polymer Science: Part B: Polymer Physics, Vol. 36, 2247–2258 (1998)  1998 John Wiley & Sons, Inc. CCC 0887-6266/98 / 132247-12 cosities of poly(amic acid) precursors of PMDA/ 2247 9605001 / 8q42$$5001 07-20-98 16:44:19 polpal W: Poly Physics