Metal-laminated polyimide substrate, and method for production thereof

1. A method for producing a laminated polyimide substrate, comprising:

subjecting a surface of a polyimide layer to alkali treatment to form an alkali-treated layer containing an anionic functional group derived from the polyimide layer;

subjecting the alkali-treated layer to a palladium catalyst-imparting treatment to introduce a complex of the palladium catalyst;

subjecting the alkali-treated layer containing the complex of the palladium catalyst to a reducing treatment to form a laminated structure having a layer containing the palladium catalyst on a surface side of the alkali-treated layer and a layer containing the complex of the palladium catalyst on a polyimide layer side of the alkali-treated layer; and

forming a metal layer on the surface of the polyimide layer, wherein the metal layer is a laminated structure having a layer formed by electroless nickel phosphorous plating and a layer formed by electrolytic plating, and wherein a peel strength between the metal layer and the polyimide layer is at least 0.35 N/mm before and after 168 hours of exposure in a 150° C. environment when a total thickness of the metal layer is greater than or equal to 8 μm and less than 18 μm,

wherein the alkali-treated layer has a thickness of 40 nm or less,

wherein during said subjecting of the alkali-treated layer to the reducing treatment, the layer containing the palladium catalyst and the layer containing the complex of the palladium catalyst are adjusted to a film thickness ratio of 1:7 to 7:1,

wherein the layer containing the palladium catalyst and the layer containing the complex of the palladium catalyst each have a thickness of 1 to 15 nm,

wherein the layer formed by electroless nickel phosphorous plating has a phosphorus-rich layer on the alkali-treated layer side and a non-phosphorus-rich layer on the surface side, and

wherein the layer formed by electroless nickel phosphorous plating has ratio of phosphorus concentrations between the phosphorus-rich layer and the non-phosphorus-rich layer of 10:5 to 10:8, as determined by Auger electron microscopy, and wherein the layer formed by electroless nickel phosphorous plating has ratio of thickness between the phosphorus-rich layer and the non-phosphorus-rich layer of 1:9 to 9:1.

2. The method according to claim 1 , wherein the reducing treatment is carried out using at least one kind of reducing agent selected from the group consisting of NaBH 4 , KBH 4 hydrazine, dimethylamine borane, and trimethylamine borane.

3. The method according to claim 1 , wherein during said subjecting of the alkali-treated layer to the reducing treatment, the layer containing the palladium catalyst and the layer containing the complex of the palladium catalyst are adjusted to a film thickness ratio of 1:4 to 4:1.

4. The method according to claim 1 , wherein the alkali-treated layer has a thickness of 5 to 40 nm.

5. The method according to claim 1 , wherein the peel strength between the metal layer and the polyimide layer is at least 0.40 N/mm before and after 168 hours of exposure in a 150° C. environment when a total thickness of the metal layer is greater than or equal to 8 μm and less than 18 μm.

6. The method according to claim 1 , wherein the alkali-treated layer is present in a thickness of no more than 10% of a thickness of the polyimide layer.

7. The method according to claim 1 , wherein the anionic functional group is a carboxyl group.

8. The method according to claim 1 , wherein the polyimide layer has a thickness of about 1 μm to 100 μm.

9. The method according to claim 1 , wherein the polyimide layer has a 10-point mean roughness of 100 nm or less measured in accordance with JIS B0601 (1994).

10. The method according to claim 1 , wherein the alkali treatment comprises immersing the polyimide layer for about 10 seconds to 50 minutes in an alkali solution having a concentration of about 0.01 to 10 mol/L at a temperature ranging from about 20 to 100° C., thereby opening the imide rings of the polyimide layer by means of hydrolysis, and resulting in polyamic acid ions and carboxyl groups.

11. The method according to claim 1 , wherein the complex of the palladium catalyst is Formula (I)

wherein L is an alkylene group,

wherein R is an amino group or guanidyl group, and

wherein the complex of the palladium catalyst is a trans isomer, which is shown in Formula (I), or a cis isomer of Formula (I), or mixtures thereof.

12. The method according to claim 11 , wherein the alkylene group in Formula (I) has 1 to 20 carbon atoms.

13. The method according to claim 1 , wherein the palladium catalyst-imparting treatment is carried out at a temperature in the range of about 20 to 100° C. for about 1 second to 10 hours, and allows cationic groups in the complex of the palladium catalyst to interact with anionic functional groups in the alkali-treated layer of the polyimide layer so that the complex of the palladium catalyst is introduced into the alkali-treated layer.

14. The method according to claim 1 , wherein the reducing treatment is carried out by immersing the alkali-treated layer in a solution containing a reducing agent, or by spraying or applying the solution.

15. The method according to claim 1 , further comprising at least one treatment selected from the group consisting of physical roughening treatment, surface degreasing treatment, solvent washing or water washing, corrosion resistance treatment, drying, and combinations thereof.