Method for manufacturing copper foil with rough surface in plating tank and its product

Abstract

A method for manufacturing a copper foil with a rough surface in a plating tank includes causing an electrolyte solution to flow between an anode and a cathode with a current density of 5 ASF-40 ASF. The copper foil with a rough surface including dense nodules of single copper crystals is deposited on the cathode. The electrolyte solution includes chloride ions (20 ppm-80 ppm), polyethylene glycol (PEG) with a molecular weight of 400-8000 (100 ppm-700 ppm), sulfuric acid (20 g/L-200 g/L), copper sulfate pentahydrate (70 g/L-320 g/L) and a sulfur compound (1 ppm-60 ppm).

Claims

1. A copper foil, being an electro-deposited copper foil with a rough surface; wherein the rough surface comprises dense nodules of single copper crystals and has an arithmetic mean roughness (Ra) of 0.20 μm-1.5 μm and a ten-point mean roughness (Rz) of 0.5 μm-8.0 μm, wherein the nodules of single copper crystals are integrally formed with the copper foil and in the form of specific shapes.

2. The copper foil of claim 1, wherein the copper foil excluding the nodules of single copper crystals has a thickness of 2.5 μm-5.0 μm.

3. The copper foil of claim 1, wherein the nodules of single copper crystals are in the form of stepped cones, eggs or grains.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a plating tank for manufacturing the electro-deposited copper foil.

(2) FIG. 2A shows the SEM image (2000×) of the rough surface on the matte side of the raw copper foil; FIG. 2B shows the SEM image (5000×) of the stepped-cone-like copper nodules; and FIG. 2C shows the FIB image (5000×) of the stepped-cone-like copper nodules of Example 1.

(3) FIG. 3 shows the TEM & electron diffraction analysis of the stepped-cone-like copper nodules of Example 1.

(4) FIG. 4A shows the SEM image (2000×) of the rough surface on the matte side of the raw copper foil; FIG. 4B shows the SEM image (5000×) of the rough surface on the matte side of the raw copper foil; and FIG. 4C shows the FIB image (5000×) of the egg-like copper nodules of Example 2.

(5) FIG. 5A shows the SEM image (1000×) of the rough surface on the matte side of the raw copper foil; FIG. 5B shows the SEM image (2000×) of the rough surface on the matte side of the raw copper foil; and FIG. 5C shows the FIB image (2500×) of the grain-like copper nodules of Example 3.

(6) FIG. 6A shows the SEM image of top view of the rough surface on the matte side of the raw copper foil and FIG. 6B shows the SEM image of FIG. 6A after FIB process; FIG. 6C and FIG. 6D show the TEM image and electron diffraction analysis, respectively, of the mansion-like copper nodules of Example 4.

(7) FIG. 7A shows the SEM image of top view of the rough surface on the matte side of the raw copper foil and FIG. 7B shows the SEM image of FIG. 7A after FIB process; FIG. 7C and FIG. 7D show the TEM image and electron diffraction analysis, respectively, of the Eiffel Tower-like copper nodules of Example 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) FIG. 1 illustrates a plating tank for manufacturing the electro-depositing copper foil of the present invention, which includes a rotatable cylindrical cathode 20, an anode 10 and an electrolyte solution 30. The cathode 20 is made of titanium, or a polyimide film with a layer of nickel or cobalt film. The anode 10 can be soluble, usually being phosphorus-doped copper or insoluble, usually being platinum, IrO.sub.2/Ti or Ta.sub.2O.sub.5/IrO.sub.2/Ti. The electrolyte solution 30 flows between the cathode 20 and the anode 10, and a current passes through the anode 10 and the cathode 20. Metal copper is then deposited on the cathode 20 and then separated from the rotating cathode 20 to form a copper foil 100.

(9) Operating conditions and components of the electrolyte solution 30 are as follows:

(10) current density: 5 ASF-40 ASF;

(11) temperature: 20° C.-25° C.;

(12) chloride ions: 20 ppm-80 ppm;

(13) polyethylene glycol (PEG, the preferred wetting agent, having a molecular weight of 400-8000): 100 ppm-700 ppm;

(14) sulfuric acid: 20 g/L-200 g/L;

(15) copper sulfate pentahydrate: 70 g/L-320 g/L; and a sulfur compound having the formula (1): 1 ppm-60 ppm,
R.sub.1—S—C.sub.nH.sub.2n—R.sub.2  (1),

(16) wherein R.sub.1 is —H, —C.sub.7H.sub.4NS, —CH.sub.4N.sub.2, —S—C.sub.nH.sub.2n—R.sub.2 or —C.sub.nH.sub.2n—R.sub.2, R.sub.2 is —SO.sub.3.sup.−, —PO.sub.4.sup.− or —COO.sup.−.Math., and n is an integer of 2-10.

(17) According to the formula (1), the preferred sulfur compound is selected from the group consisting of 3-mercaptopropanesulfonate (MPS), bis-(3-sulfopropyl)-disulfide (SPS), 3-(2-benzthiazolylthio)-1-propanesulfonate (ZPS), 3-(N,N-dimethylthiocarbamoyl)-thiopropanesulfonate (DPS), (o-ethyldithiocarbonato)-s-(3-sulfopropyl)-ester (OPX), 3-[(amino-iminomethyl)thio]-1-propanesulfonate (UPS) and 3,3-thiobis(1-propanesulfonate) (TBPS).

(18) Through the process with the above plating tank, conditions and the electrolyte solution, a raw copper foil having a thickness of 3 μm-5 μm is formed on the cathode. As shown in FIG. 1, the foil includes a shiny side 101 close to the rotary cathode and a matte side 102 on the reverse side. The matte side is roughed and includes dense nodules of single copper crystals. The matte side has an arithmetic mean roughness (Ra) of 0.20 μm-1.5 μm and a ten-point mean roughness (Rz) of 0.5 μm-8.0 μm, which can be controlled by changing the electrolyte solution.

Example 1

(19) The electrolyte solution includes chloride ions (30 ppm-60 ppm), polyethylene glycol (PEG) having a molecular weight of 400-5000 (100 ppm-700 ppm), sulfuric acid (20 g/L-200 g/L), copper sulfate pentahydrate (70 g/L-250 g/L) and a sulfur compound (1 ppm-15 ppm).

(20) FIG. 2A and FIG. 2B show the scanning electron microscope (SEM) images (respectively at 2000× and 5000×) of the rough surface on the matte side of the raw copper foil. The copper nodules in the form of stepped cones are densely distributed on the surface. A ten-point mean roughness (Rz) of 3.0 μm-7.0 μm is measured.

(21) FIG. 2C shows the focused ions beam (FIB) image (5000×) of the stepped-cone-like copper nodules.

(22) FIG. 3 shows the SEM images (upper) and the transmission electron microscope (TEM) & electron diffraction analysis (lower) of the stepped-cone-like copper nodules, which can verify that these nodules have the structure of single crystals.

Example 2

(23) The electrolyte solution includes chloride ions (50 ppm-80 ppm), polyethylene glycol (PEG) having a molecular weight of 4000-8000 (100 ppm-700 ppm), sulfuric acid (20 g/L-200 g/L), copper sulfate pentahydrate (70 g/L-250 g/L) and a sulfur compound (15 ppm-60 ppm).

(24) FIG. 4A and FIG. 4B show the SEM images (respectively at 2000× and 5000×) of the rough surface on the matte side of the raw copper foil. The copper nodules in the form of eggs are densely distributed on the surface. A ten-point mean roughness (Rz) of 1.0 μm-3.0 μm is measured.

(25) FIG. 4C shows the FIB image (5000×) of the egg-like copper nodules, which can verify that these nodules have the structure of single crystals.

Example 3

(26) The electrolyte solution includes chloride ions (60 ppm-80 ppm), polyethylene glycol (PEG) having a molecular weight of 4000-8000 (100 ppm-700 ppm), sulfuric acid (20 g/L-200 g/L), copper sulfate pentahydrate (70 g/L-250 g/L) and a sulfur compound (40 ppm-60 ppm).

(27) FIG. 5A and FIG. 5B show the SEM images (respectively at 1000× and 2000×) of the rough surface on the matte side of the raw copper foil. The copper nodules in the form of grains are densely distributed on the surface. A ten-point mean roughness (Rz) of 0.6 μm-4.0 μm is measured.

(28) FIG. 5C shows the FIB image (2500×) of the grain-like copper nodules, which can verify that these nodules have the structure of single crystals.

Example 4

(29) The electrolyte solution includes chloride ions (40 ppm-80 ppm), polyethylene glycol (PEG) having a molecular weight of 1000-2500 (50 ppm-300 ppm), sulfuric acid (100 g/L-200 g/L), copper sulfate pentahydrate (120 g/L-220 g/L) and a sulfur compound (40 ppm-60 ppm).

(30) FIG. 6A shows the SEM image of top view of the rough surface on the matte side of the raw copper foil and FIG. 6B shows the SEM image of FIG. 6A after FIB process. It is observable that the shape of the copper nodule is vertical toward the substrate and has an interesting cubic stacking geometrics. The copper nodules in the form of grains are densely distributed on the surface. A ten-point mean roughness (Rz) of 7.0 μm-10.0 μm is measured.

(31) FIG. 6C and FIG. 6D show the TEM image and electron diffraction analysis, respectively, of the mansion-like copper nodules, which can verify that these nodules have the structure of single crystals.

Example 5

(32) The electrolyte solution includes chloride ions (40 ppm-80 ppm), polyethylene glycol (PEG) having a molecular weight of 1000-3000 (100 ppm-300 ppm), sulfuric acid (200 g/L-300 g/L), copper sulfate pentahydrate (100 g/L-200 g/L) and a sulfur compound (5 ppm-30 ppm).

(33) FIG. 7A shows the SEM image of top view of the rough surface on the matte side of the raw copper foil and FIG. 7B shows the SEM image of FIG. 7A after FIB process. FIG. 7A and FIG. 7B show the SEM images of the rough surface on the matte side of the raw copper foil. It is observable that the shape of the copper nodule is vertical toward the substrate and has an interesting tower geometrics. The copper nodules in the form of grains are densely distributed on the surface. A ten-point mean roughness (Rz) of 10.0 μm-20.0 μm is measured.

(34) FIG. 7C and FIG. 7D show the TEM image and electron diffraction analysis, respectively, of the Eiffel Tower-like copper nodules, which can verify that these nodules have the structure of single crystals.

(35) Summarily, the electro-deposition process is improved as the rough surface of the copper foil can be achieved simultaneously in one plating tank. The rough surface includes uniform and dense nodules of single copper crystals having specific outlooks. Compared with the traditional methods, this invention is more efficient and therefore saves a lot of cost. The single copper crystals with the rough surface have lower electric resistance than the roughed matte sides formed by the traditional methods and can be controlled in shapes and sizes by changing the components of the electrolyte solution.