Adhesive film and flexible metal laminate
To provide an adhesive film comprising a polyimide film and a fluorinated resin layer directly laminated, in which blisters (foaming) in an atmosphere corresponding to reflow soldering at high temperature are suppressed, and a flexible metal laminate. An adhesive film having a fluorinated resin layer containing a fluorinated copolymer (A) directly laminated on one side or both sides of a polyimide film, wherein the fluorinated copolymer (A) has a melting point of at least 280° C. and at most 320° C., is melt-moldable, and has at least one type of functional groups selected from the group consisting of a carbonyl group-containing group, a hydroxy group, an epoxy group and an isocyanate group, and the fluorinated resin layer has a thickness of from 1 to 20 μm.
1. An adhesive film comprising a fluorinated resin layer comprising a fluorinated copolymer (A) directly laminated on both sides of a polyimide film, wherein
the fluorinated copolymer (A) has a melting point of at least 280° C. and at most 320° C., is melt-moldable, and comprises structural units (a1) derived from tetrafluoroethylene, structural units (a2) derived from a cyclic hydrocarbon monomer having an acid anhydride residue and a polymerizable unsaturated bond and structural units (a3) derived from a fluorinated monomer, excluding tetrafluoroethylene, and
the fluorinated resin layer has a thickness of from 1 to 20 μm.
2. The adhesive film according to claim 1 , wherein a content of the functional groups is from 10 to 60,000 groups per 1×10 6 carbon atoms in the main chain of the fluorinated copolymer (A).
3. The adhesive film according to claim 1 , wherein the fluorinated resin layer has a thickness of from 3 to 15 μm.
4. The adhesive film according to claim 1 , wherein the polyimide film has a thickness of from 3 to 50 μm.
5. The adhesive film according to claim 1 , wherein the melt flow rate of the fluorinated copolymer (A) at 372° C. under a load of 49 N is from 0.5 to 15 g/10 min, and the melt flow rate of the fluorinated copolymer (A) subjected to heat treatment at 370° C. or higher is lower than the melt flow rate of the fluorinated copolymer (A) before the heat treatment.
6. The adhesive film according to claim 1 , which has an entire thickness of at most 150 μm.
7. A flexible metal laminate comprising the adhesive film according to claim 1 , and a metal film directly laminated on the fluorinated resin layer of the adhesive film.
8. A flexible printed circuit board, having a pattern circuit formed by etching the metal film of the flexible metal laminate according to claim 7 .
9. A flexible printed circuit board, comprising a microstrip line comprising a microstrip transmission line formed by etching the metal foil of the flexible metal laminate according to claim 7 , wherein
in the microstrip line, the transmission loss [a] after the following conditioning [a] and the transmission loss [b] after the following conditioning [b], measured at a temperature of from 20 to 25° C. under a humidity of from 40 to 60% RH after the conditioning [a] or [b], satisfy ([b]−[a])<0.004 dB/mm:
[a]: firing at a temperature of 105° C. for 48 hours;
[b]: firing at a temperature of 105° C. for 24 hours and storing at a temperature of 60° C. under a humidity of 90% RH for 24 hours.
10. A method for producing a flexible printed circuit board, which comprises:
forming a pattern circuit by etching the metal film of the flexible metal laminate according to claim 7 ; and
soldering on the pattern circuit with a soldering iron,
to form a flexible printed circuit board.
11. The adhesive film according to claim 1 , wherein
the fluorinated resin layer has a thickness of from 3 to 15 μm,
the polyimide film has a thickness of from 5 to 25 μm.
12. The adhesive film according to claim 1 , wherein the fluorinated resin layer has a thickness of from 6 to 15 μm, the polyimide film has a thickness of from 12.5 to 25 μm.
13. The flexible metal laminate according to claim 7 , wherein the flexible metal laminate has a solder iron heat resistance of at least 330° C.
14. The flexible metal laminate according to claim 7 , wherein the flexible metal laminate has a solder iron heat resistance of 330° C. to 340° C.
15. A method for producing an adhesive film, which comprises subjecting an adhesive film comprising
a fluorinated resin layer comprising a fluorinated copolymer (A) directly laminated on one side or both sides of a polyimide film, wherein the fluorinated copolymer (A) has a melting point of at least 280° C. and at most 320° C., is melt-moldable, and comprises structural units (a1) derived from tetrafluoroethylene, structural units (a2) derived from a cyclic hydrocarbon monomer having an acid anhydride residue and a polymerizable unsaturated bond and structural units (a3) derived from a fluorinated monomer, excluding tetrafluoroethylene, and the fluorinated resin layer has a thickness of from 1 to 20 μm,
to heat treatment at 370° C. or higher.
16. A method for producing a flexible metal laminate, which comprises subjecting a flexible metal laminate comprising an adhesive film and a metal film directly laminated on the fluorinated resin layer of the adhesive film, to heat treatment at 370° C. or higher,
wherein the adhesive film comprises a fluorinated resin layer comprising a fluorinated copolymer (A) directly laminated on one side or both sides of a polyimide film, wherein the fluorinated copolymer (A) has a melting point of at least 280° C. and at most 320° C., is melt-moldable, and comprises structural units (a1) derived from tetrafluoroethylene, structural units (a2) derived from a cyclic hydrocarbon monomer having an acid anhydride residue and a polymerizable unsaturated bond and structural units (a3) derived from a fluorinated monomer, excluding tetrafluoroethylene, and the fluorinated resin layer has a thickness of from 1 to 20 μm.