Infrared Curing of Polyimide Precursors
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Disclosed is a process for fully curing polyimide and photosensitive polyimide precursors using short wavelength infrared (IR) radiation. Total process time is reduced from a couple of hours to minutes. A very uniform etchable polyimide is formed. During the curing of polyamic acid (I), water is split out and polyimide (II) is formed (Fig. 1). This process is known as imidization. In the convection oven curing process, 2-3 hours, the polyamic acid is cured from top to bottom resulting in a tough skin forming on top of the polyimide. Penetration by hydroxide is extremely difficult and etching of the polyimide requires very concentrated base, hydrazine hydrate or other exotic chemicals. The rate determining step of imidization is the loss of hydrogen from the amide linkage, which occurs at a wavelength of 2-3 microns.