Patent ID: 7579134

Claim:
A multi-layer composite coverlay substrate, comprising: A. an adhesive layer having a thickness in a range between and including 1-20 microns, comprising: i. an adhesive polyamic acid precursor curable to an adhesive polyimide base polymer wherein said adhesive base polymer exhibits a glass transition temperature (“Tg”) between and including 170° C. and 250° C.; ii. an ethylenically unsaturated photo-monomer wherein at least 2 percent by weight of the photo-monomer is an amine acrylate, a methacrylate having amine functionality, or a combination of the two; B. a cover layer adjacent to the adhesive layer having a thickness between 10 and 75 microns, comprising: i. 60 to 83.9 percent by weight (on a dry solids basis) cover layer polyamic acid precursor curable to a cover layer polyimide base polymer having a glass transition temperature (Tg) from 10° C. to 100° C. greater than the glass transition temperature of the adhesive polyimide base polymer, the cover layer polyamic acid precursor comprising: a. 95 to 100 mole % diamine component, b. 85 to 99 mole % dianhydride component, c. 1 to 15 mol % tetra carboxylic acid wherein the amount of tetracarboxylic acid is based on the amount of corresponding dianhydride needed to react with the unreacted diamine ends, and wherein the cover layer polyamic acid precursor has a weight-average molecular weight equal to or below 50,000, and ii. 15 to 35 percent by weight (on a dry solids basis) an ethylenically unsaturated photo-monomer where at least 2 percent by weight of the photo-monomer is an amine acrylate, a methacrylate having amine functionality, or a combination of the two; iii. 1 to 10 percent by weight, on a dry solids basis, of a photo-initiator; and iv. 0.1 to 1.0 percent by weight (on a dry solids basis) a visible light sensitizer; wherein the overall in-plane coefficient of thermal expansion (“CTE”), of the coverlay is between 10 and 40 ppm/° C. measured at 30° C.