Effects of thickness on the residual stress behavior of high temperature polyimide films

The effects of thickness on the residual stress behavior of the hinged structure poly(4,4-oxydiphenylene pyromellitimide) (PMDA-ODA) and rigid planar structure poly (p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide were studied. Depending on the polyimide chemistry, residual stress behavior of polyimide film with thickness variation was significantly different. For fully cured BPDA-PDA polyimide at 400 degrees C, residual stress of polyimide film increased from 5.4 MPa to 45 MPa. For fully cured PMDA-ODA polyimide at 400 degrees C, residual stress of polyimide film with thickness variation changed from 29.1 MPa to 40.2 MPa. The effect of thickness on the residual stress for the rigid structure BPDA-PDA was significant, but relatively not for the semiflexible structure PMDA-ODA. Residual stress behavior was quite related to the morphology of fully cured polyimide as shown WAXD analysis. Higher molecular anisotropy leads to lower residual stress of polyimide film. Residual stress behavior of polyimide films with thickness variation is thus closely related to chain rigidity and chain anisotropy associated with polyimide chemistry and morphological structure.