Patent ID: 7285321

Claim:
A multi-layer substrate, comprising: a. a low glass transition temperature polyimide layer comprising a polyimide base polymer synthesized by contacting an aromatic dianhydride with a diamine component in a molar ratio of dianhydride to diamine from 0.9 to 1.1, the diamine component comprising about 50 to about 90 mole % aliphatic diamine and about 10 to about 50 mole % aromatic diamine, said polyimide base polymer having a glass transition temperature from about 150 to about 200° C.; b. a high glass transition temperature polyimide layer having a glass transition temperature above the low glass transition temperature polyimide layer, wherein the difference in lamination temperature between the high glass transition temperature layer and the low glass transition temperature layer is in a range between and including 10 and 200° C.; and c. a conductive layer, wherein the low glass transition temperature polyimide layer has a z-axis coefficient of thermal expansion of less than 150 ppm/° C. according to ASTM Method IPC-650 2.4.41, and wherein the high glass transition temperature polyimide layer is between the conductive layer and the low glass transition polyimide layer.