Robust interface bonding with B-staged thermoplastic polyimide adhesive

1. A heat activated adhesive thermoplastic laminating film for joining two surfaces comprising in combination:

A. a substrate; and

B. a heat activated thermoplastic adhesive coated on said substrate, said adhesive comprising in combination:

i. a solvent; and

ii. a mixture of polyamic-acid polymer and thermoplastic polyimide polymer solids disposed in said solvent, said mixture containing no less than 10% and no greater than 50% thermoplastic polyimide of the total polymer mass and said mixture containing an amount of said solvent of between 20 and 60% of the total mass of the mixture, said adhesive forming a bondline between said surfaces; and

wherein said laminating film is configured to outgas said solvent from said adhesive along said bondline upon the application of heat and pressure over the entire area of said surfaces to be bonded during a lamination process.

2. The laminating film of claim 1 wherein said solvent is selected from the group consisting of N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAC).

3. The laminating film of claim 1 wherein said polyamic-acid polymer comprises a mixture of diamine and dianhydride monomers, said diamine monomer is selected from the group consisting of 3,5-diaminobenzoic acid (DABA), 3,3′-diaminobenzophenone (3,3′-DABP), 3,4′-diaminobenzophenone (3,4′-DABP), 1,3-Bis (4-aminophenoxy) benzene (TPER), 3,4′-Oxydianiline (3,4′-ODA), 4,4′-Oxydianiline (4,4′-ODA), 4,4′-Methylene dianiline (4,4′-MDA), an aliphatic diamine, and a silicon diamine; and said dianhydride monomer is selected from the group consisting of 3,3′,4,4′-Biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-Benzophenone tetracarboxylic dianhydride (BTDA), 4,4′-Oxydiphthalic anhydride (ODPA), Pyromellitic dianhydride (PMDA), and 2,2′-Bis-(3,4-Dicarboxyphenyl) hexafluoropropane dianhydride (6FDA).

4. A process of fabricating a heat activated thermoplastic laminating film for joining two surfaces comprising in combination the steps of:

A. providing a substrate;

B. providing a solvent;

C. providing a quantity of polyamic-acid polymer with diamine and dianhydride constituent monomers;

D. adding said monomers to said solvent to create a polyamic-acid solution coating bath;

E. providing a gravure coating roller having a surface arranged to rotate through said bath and hold a quantity of said polyamic-acid solution on said gravure coating roller surface;

F. passing said substrate in contact with said gravure coating roller surface to deposit a coating of said polyamic-acid solution on said substrate;

G. providing an oven;

H. passing said coated substrate through said oven at a temperature of between 85 and 190° C., said coating upon emerging from said oven comprising a mixture of polyamic-acid polymer and thermoplastic polyimide polymer solids disposed in said solvent, said mixture containing no less than 10% and no greater than 50% thermoplastic polyimide of the total polymer mass and said mixture containing an amount of said solvent of between 20 and 60% of the total mass of the mixture.

5. The process of claim 4 wherein said solvent is selected from the group consisting of N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAC).

6. The process of claim 4 wherein said polyamic-acid polymer comprises a mixture of diamine and dianhydride monomers, said diamine monomer is selected from the group consisting of 3,5-diaminobenzoic acid (DABA), 3,3′-diaminobenzophenone (3,3′-DABP), 3,4′-diaminobenzophenone (3,4′-DABP), 1,3-Bis (4-aminophenoxy) benzene (TPER), 3,4′-Oxydianiline (3,4′-ODA), 4,4′-Oxydianiline (4,4′-ODA), 4,4′-Methylene dianiline (4,4′-MDA), an aliphatic diamine, and a silicon-diamine; and said dianhydride monomer is selected from the group consisting of 3,3′,4,4′-Biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-Benzophenone tetracarboxylic dianhydride (BTDA), 4,4′-Oxydiphthalic anhydride (ODPA), Pyromellitic dianhydride (PMDA), and 2,2′-Bis-(3,4-Dicarboxyphenyl) hexafluoropropane dianhydride (6FDA).