Patent ID: 6949296

Claim:
A polyimide substrate comprising: at least a base layer containing a base polymer; the base polymer being a polyimide synthesized by a multiple reaction involving one or more aromatic diamines and one or more aromatic dianhydrides, the multiple reaction comprising a polymerization reaction and an imidization reaction, at least a portion of the polymerization reaction being conducted in a high tension film processing environment and at least a portion of the imidization reaction being conducted in a low tension film processing environment, the low tension film processing environment occurring after the high tension film processing environment, the film processing environments being conducted in a manner sufficient to enable a polyimide substrate having: A. a tensile modulus (at 20° C.) greater than 350, 400, 450, 500, 550, 600, 650, 675, 700, 725, 750, 775, 800, 825, or 850 kpsi, B. a droop of less than 20,000, 18,000, 16,000, 15,000, 14,000, 13,000,12,000, 11,000, 10,000, 9,000, 8,000, 7,000, 6,000, 5000, 4,000, 3,000, 2500, 2000, 1500, 1000, 750 or 500 ppm, C. a skew less than 10,000, 9,000, 8,000, 7,000, 6,000, 5000, 4,000, 3,000, 2500, 2000, 1500, 1000, 750, 600, 500, 400, 300, or 200 ppm, D. an average linear thermal expansion coefficient of less than 500, 250, 100, 75, 50, 25, 10, 5 or 1 (ppm per ° C.) in a temperature range of 50° C. to 300° C., E. a linear expansion coefficient ratio (MD/TD) between (and including) any two of the following numbers: 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.2, 3.4, 3.5, 3.6, 3.8 and 4.0; and F. a thermal dimensional stability of less than 1, 0.75, 0.50, 0.30, 0.25, 0.20, 0.10, or 0.05, where thermal dimensional stability is hereby defined as the percent change in length of film (initially at 20° C.) after exposure to 400° C. for at least 1 hour.