SURFACE-TREATED COPPER FOIL AND METHOD FOR MANUFACTURING SAME

Abstract

Provided is a surface-treated copper foil in which in order to avoid failures of electronic parts by corrosion, a high bond strength between an electrolytic copper foil and a resin base material can be maintained even when the surface-treated copper foil is exposed to corrosive gases and microparticles, and a method for manufacturing the same. The surface-treated copper foil of the present invention comprises an electrolytic copper foil, a roughened layer covering at least one surface side of the electrolytic copper foil, and a rust preventive layer further covering the roughened layer, wherein the rust preventive layer is at least one surface of the surface-treated copper foil; the rust preventive layer comprises at least a nickel layer; and the thickness of the nickel layer is 0.8 to 4.4 g/m.sup.2 in terms of mass per unit area of nickel; and the noncontact roughness Spd of the rust preventive layer is 1.4 to 2.6 peaks/μm.sup.2 and the surface roughness RzJIS of the rust preventive layer is 1.0 to 2.5 μm. The method for manufacturing the surface-treated copper foil forms the roughened layer having higher roughnesses than the noncontact roughness Spd and surface roughness RzJIS on one surface of the electrolytic copper foil, and thereafter forming the rust preventive layer meeting the predetermined condition.

Claims

1. A surface-treated copper foil comprising: an electrolytic copper foil; a roughened layer covering at least one surface side of the electrolytic copper foil; and a rust preventive layer further covering the roughened layer, wherein the rust preventive layer is at least one surface of the surface-treated copper foil; the rust preventive layer comprises at least a nickel layer; and a thickness of the nickel layer is 0.8 to 4.4 g/m.sup.2 in terms of mass per unit area of nickel; and a noncontact roughness Spd of the rust preventive layer is 1.4 to 2.6 peaks/μm.sup.2 and a surface roughness RzJIS of the rust preventive layer is 1.0 to 2.5 μm.

2. The surface-treated copper foil according to claim 1, wherein the rust preventive layer further comprises a chromate-treated layer and/or a silane coupling agent-treated layer.

3. The surface-treated copper foil according to claim 1, wherein the surface-treated copper foil further comprises a composite metal layer of copper with at least one or more metals selected from molybdenum, zinc, tungsten, nickel, cobalt and iron, between the electrolytic copper foil and the roughened layer.

4. A method for manufacturing a surface-treated copper foil, comprising: a roughening treatment step of forming a roughened layer on at least one surface of an electrolytic copper foil wherein a noncontact roughness Spd of the roughened layer is made to be more than 2.6 peaks/μm.sup.2 and a surface roughness RzJIS of the rust preventive layer is made to be greater than 2.5 μm; and a rust preventive treatment step of forming at least a nickel layer as a rust preventive layer on the roughened layer wherein a thickness of the nickel layer is made to be 0.8 to 4.4 g/m.sup.2 in terms of mass per unit area of nickel; and a noncontact roughness Spd of the rust preventive layer is made to be 1.4 to 2.6 peaks/μm.sup.2 and a surface roughness RzJIS of the rust preventive layer is made to be 1.0 to 2.5 μm.

5. The method for manufacturing a surface-treated copper foil according to claim 4, wherein the rust preventive treatment step further comprises, in addition to the formation of the nickel layer, a chromate treatment and/or a silane coupling agent treatment.

6. The method for manufacturing a surface-treated copper foil according to claim 4, wherein the method further comprises, before the roughening treatment step, a step of forming a composite metal layer on a surface of the electrolytic copper foil on which the roughened layer is to be formed, by a plating bath containing copper and one or more metals selected from molybdenum, zinc, tungsten, nickel, cobalt and iron.

Description

EXAMPLES

[0039] Hereinafter, the present invention will be described in more detail by way of Examples of the present invention and Comparative Examples. The present invention, however, is not limited to the following Examples.

Example 1

[0040] (1) Production of a surface-treated copper foil

[0041] First, an electrolytic copper foil (Nippon Denkai, Ltd., item number: SEED Foil) of 12 μm in thickness was subjected to acid cleaning treatment with a 10% sulfuric acid for 20 s. Then, the electrolytic copper foil was water washed; and both surfaces of the electrolytic copper foil were plated by using a plating bath containing copper sulfate pentahydrate at 50 g/L, sodium molybdate dihydrate at 2 g/L and zinc sulfate heptahydrate at 50 g/L, where a pH thereof is regulated to 2.5 and a bath temperature thereof is regulated to 30° C. to thereby form composite metal layers containing copper, molybdenum and zinc.

[0042] Then, the resultant copper foil was water washed; and both surfaces of the resultant copper foil were plated by using a plating solution containing copper sulfate pentahydrate at 130 g/L and sulfuric acid at 100 g/L, where a bath temperature thereof is regulated to 30° C. at a current density of 2 A/dm' for a treatment time of 20 s to thereby form roughened layers composed of copper on the composite metal layers.

[0043] Furthermore, the resultant copper foil was water washed; and both surfaces of the resultant copper foil were plated by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm.sup.2 for a treatment time of 4 s to form rust preventive layers composed of nickel to thereby obtain a surface-treated copper foil (Example 1).

(2) Tests for properties of the surface-treated copper foil

[0044] For the surface-treated copper foil thus obtained, the amount of nickel per unit area of the rust preventive layer was measured based on X-ray fluorescence analysis using a wave-length dispersive X-ray fluorescence spectrometric analyzer (Rigaku Corp., ZSX Primus II). The results are shown in Table 1.

[0045] Then, in order to measure the bond strength of the surface-treated copper foil, an FR-5-equivalent glass epoxy resin-impregnated base material was laminated on one surface of the surface-treated copper foil to make a copper clad laminate to thereby fabricate a test piece. The bond strength between the surface-treated copper foil and the resin base material of the test piece was measured (copper foil width: 1 mm) at room temperature according to JIS C6481. Here, the bond strength was measured for the test piece in the state before treatment (normal state) of being immersed in a hydrochloric acid solution (concentration: 18%), and for the test piece in the state after the treatment (after the hydrochloric acid immersion). The measurement of the bond strength was carried out by a tensile tester (Toyo Seiki Seisaku-sho Ltd., Strograph E3-L). The results are shown in Table 1.

[0046] Furthermore, the noncontact roughness Spd of the surface-treated copper foil was measured according to ISO 25178; and the surface roughness RzJIS of the surface-treated copper foil was measured according to JIS B0601:1994. Here, the measurements of the noncontact roughness Spd and the surface roughness RzJIS were carried out by a laser microscope device (Keyence Corp., VK-X150). The results are shown in Table 1.

Example 2

[0047] A surface-treated copper foil was manufactured and subjected to the respective property tests as in Example 1, except for forming rust preventive layers composed of nickel by plating the resultant copper foil by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm' for a treatment time of 8 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

Example 3

[0048] A surface-treated copper foil was manufactured and subjected to each property test as in Example 1, except for forming rust preventive layers composed of nickel by plating the resultant copper foil by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm' for a treatment time of 12 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

Example 4

[0049] A surface-treated copper foil was produced and subjected to each property test as in Example 1, except for forming rust preventive layers composed of nickel by plating the resultant copper foil by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm' for a treatment time of 17 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

Comparative Example 1

[0050] A surface-treated copper foil was manufactured and subjected to each property test as in Example 1, except for forming rust preventive layers by immersing the resultant copper foil in an aqueous solution containing sodium dichromate dihydrate at 3.5 g/L, where a pH thereof is regulated to 5.3 and a bath temperature thereof is regulated to 28° C. for 10 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

Comparative Example 2

[0051] A surface-treated copper foil was manufactured and subjected to each property test as in Example 1, except for forming rust preventive layers composed of nickel by plating the resultant copper foil by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm' for a treatment time of 1 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

Comparative Example 3

[0052] A surface-treated copper foil was produced and subjected to each property test as in Example 1, except for forming rust preventive layers composed of nickel by plating the resultant copper foil by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm' for a treatment time of 2 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

Comparative Example 4

[0053] A surface-treated copper foil was manufactured and subjected to each property test as in Example 1, except for forming rust preventive layers composed of nickel by plating the resultant copper foil by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm' for a treatment time of 20 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

Comparative Example 5

[0054] A surface-treated copper foil was manufactured and subjected to each property test as in Example 1, except for forming rust preventive layers composed of nickel by plating the resultant copper foil by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm' for a treatment time of 40 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

Comparative Example 6

[0055] A surface-treated copper foil was manufactured and subjected to each property test as in Example 1, except for forming rust preventive layers composed of nickel by plating the resultant copper foil by using a plating solution containing nickel sulfate hexahydrate at 400 g/L and boric acid at 40 g/L, where a bath temperature thereof is regulated to 50° C. at a current density of 10 A/dm' for a treatment time of 2 s, and further laminating rust preventive layers by immersing the resultant copper foil in an aqueous solution containing sodium dichromate dihydrate of 3.5 g/L, where a pH thereof is regulated to 5.3 and a bath temperature thereof is regulated to 28° C. for 10 s, in manufacture of the surface-treated copper foil. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Bond strength Bond strength (after hydrochloric Noncontact Surface Ni (normal state) acid immersion) roughness roughness amount (FR-5) (FR-5) Spd RzJIS No. [g/m.sup.2] [kN/m] [kN/m] [peaks/μm.sup.2] [μm] Example 1 1 0.77 0.76 1.98 1.80 Example 2 2 0.81 0.80 1.84 1.72 Example 3 3 0.76 0.75 1.75 1.69 Example 4 4.3 0.75 0.74 1.71 1.85 Comparative 0 0.67 0.61 2.10 2.09 Example 1 Comparative 0.25 0.66 0.53 2.09 2.11 Example 2 Comparative 0.5 0.69 0.52 2.07 2.05 Example 3 Comparative 5 0.23 0.22 1.68 1.28 Example 4 Comparative 10 0.06 0.06 1.65 1.23 Example 5 Comparative 0.25 0.69 0.61 1.82 1.73 Example 6

[0056] As shown in Table 1, the surface-treated copper foils of Examples 1 to 4, in which the amount of nickel of the rust preventive layer was 0.8 to 4.4 g/m.sup.2, and the surface noncontact roughness Spd of the rust preventive layer was 1.7 to 2.0 peaks/μm.sup.2 and the surface roughness RzJIS of the rust preventive layer was 1.3 to 1.9 μm, had a bond strength with the resin base material of 0.70 kN/m or higher for both in the normal state and after the hydrochloric acid immersion, so that it was confirmed that the bond strength was excellent in resisting corrosive gases was able to be retained.

[0057] In contrast, in Comparative Example 1, which had the rust preventive layer formed only of chromate treatment, the bond strength near to those in Examples was exhibited in the normal state, but after the hydrochloric acid immersion, the bond strength decreased to about 0.6 kN/m, so that it was confirmed that the influence by corrosion was large. Then, the surface-treated copper foils of Comparative Examples 2 and 3, in which the amount of nickel of the rust preventive layer was less than 0.8, and the surface noncontact roughness Spd of the rust preventive layer was more than 2.0 peaks/μm.sup.2, and the surface roughness RzJIS of the rust preventive layer was higher than 1.9 μm, had a bond strength near to those in Examples exhibited in the normal state, but after the hydrochloric acid immersion, the bond strength decreased even by 0.1 kN/m or higher, so that it was confirmed that the effects of corrosion were very large.

[0058] The surface-treated copper foils of Comparative Examples 4 and 5, in which the amount of nickel of the rust preventive layer was greater than 4.4 g, the surface noncontact roughness Spd of the rust preventive layer was less than 1.7 peaks/μm.sup.2 and the surface roughness RzJIS of the rust preventive layer was less than 1.3 μm, could not exhibit a sufficient bond strength, since the bond strength with the resin base material became a remarkably low value for both in the normal state and after the hydrochloric acid immersion. The surface-treated copper foil of Comparative Example 6 having the rust preventive layer formed of two layers of the nickel layer and the chromate-treated layer had a surface noncontact roughness Spd of the rust preventive layer of 1.7 to 2.0 peaks/μm and a surface roughness RzJIS of the rust preventive layer of 1.3 to 1.9 μm; however, the nickel amount was less than 0.8, thus the bond strength with the resin base material exhibited a bond strength near those in Examples in the normal state, but after the hydrochloric acid immersion, the bond strength decreased to about 0.6 kN/m, so that it was confirmed that the effects of corrosion were large.