Surface Modification Studies of Polyimide Films Using Rutherford Backscattering and Forward Recoil Spectrometry

Abstract

We followed the surface imide ring hydrolysis of fully imidized polyimide films by aqueous base solutions using Rutherford backscattering spectrometry. The hydrolysis reaction was studied using several different polyimide films including spuncast and thermally imidized PMDA-ODA, Kapton-H, and Upilex-S films. The boundary between the modified layer at the surface and the underlying film is a sharp front behind which the conversion of the polyimide into poly(amic acid) is complete and ahead of which there is almost no hydrolysis. The modified layer grows linearly with the time it is exposed to the basic solution. The growth velocity increased strongly with increases in the temperature of the basic solution. Under the reasonable hypothesis that the growth of the modified layer is controlled by the kinetics of the hydrolysis of the imide ring at the interface, we extract an activation energy for this process in Kapton-H films of 60 kJ/mol as compared to 68 kJ/mol for Upilex-S. Using forward recoil spectrometry, we studied the amount of interpenetration when a second layer of deuterium-labeled poly(amic acid) was spun-cast onto the surface-modified PMDA/ODA film. We determined that the interface between the spun-cast layer and the base layer is broader when the modification depth is greater. The fracture energy of such an interface, as measured with a T-peel test, rises rapidly as a function of modification depth and saturates at a value ∼20 times the value for an interface formed from PMDA/ODA polyimide with an unmodified surface.

Low-resistance films of polyimides with impregnated copper sulfide

“…This explanation accounts for the differences that we observed concerning a larger experimental content of carbon and oxygen in relation to nitrogen when comparing the theoretical and Fig. 2(b) show agreement with the results published by Stoffel et al 9 and Lee et al, 7 who observed the conversion of surface polyimide film to poly(amide acid).…”

“…Characteristics absorption bands of the polyamide layer 18,19 occurred at 1667 and 1540 cm −1 , and the appearance of a N-H stretching absorption mode at about 3250 cm −1 was observed, giving further evidence that the imide ring had been hydrolyzed. As pointed out by Stoffel et al, 9 the modified layer should be penetrated by a subsequently deposited layer. This molecular interdiffusion should allow strong bonding to occur between layers, which is thus not susceptible to environmental degradation.…”

“…This molecular interdiffusion should allow strong bonding to occur between layers, which is thus not susceptible to environmental degradation. 9 The depth of the hydrolyzed surface layer grows roughly with base exposure. This is consistent with the idea that the layer growth kinetics is controlled by the chemical reaction at the interface which is situated between the basemodified layer and the underlying polyimide.…”

“…This is consistent with the idea that the layer growth kinetics is controlled by the chemical reaction at the interface which is situated between the basemodified layer and the underlying polyimide. Stoffel et al 9 have calculated the modification rate of Kapton, in nm/min, as a function of temperature for a 1 M KOH treatment. Using their relation, we may estimate that the depth of hydrolysis in our treatment reached about 1500 nm.…”

“…The modification of a) a polyimide surface with a solution of moderate basicity has also been shown to improve the adhesion between polyimide and metal. [7][8][9] The deposition of metal sulfide as fine particles onto the surface of an organic polymer film is a promising approach to obtain electrically conductive films. Although this method has the advantage of giving largesize electrically conductive films, there have been only a few reports 10,11 on the subject, probably due to difficulty in obtaining a good adhesion between sulfide layer and polymer film surface.…”