JP3363519B2 - Surface treatment method for copper foil for printed wiring boards - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface roughening treatment method for a printed wiring board, particularly a copper foil used for an inner layer circuit of a multilayer printed wiring board.

[0002]

2. Description of the Related Art Printed wiring board copper foil laminates have recently been rapidly multi-layered, finely patterned and highly densified, and along with this, the adhesion performance of the copper foil laminate to the laminate is required to be better than before. Has been. In particular, as the copper foil for the inner layer circuit, it is necessary to use a double-sided roughened copper foil having a high adhesion strength, especially a large peel strength, without performing a chemical surface roughening treatment after lamination.

However, the adhesion performance of this double-sided roughened copper foil is not sufficient for use as a copper foil for inner layer circuits. In the case of electro-deposited copper foil, the surface shape of the foil-making machine is transferred to the glossy surface, so if the conventional roughening treatment is applied, the roughened particles will not adhere uniformly or will adhere to the resin. However, there is a problem in forming a fine pattern in the circuit network.
Also, in the case of rolled copper foil, since the surface shape of the rolling roll is transferred, there is the same problem as in the case of electrolytic copper foil.

[0004]

An object of the present invention is to provide a high adhesion strength with a prepreg, which can be used for a copper foil for a printed wiring board, especially for a copper foil for an inner layer circuit, and to uniformly attach roughening particles. A surface roughening treatment method is provided.

The present invention relates to a surface roughening treatment method for a copper foil for a printed wiring board, which comprises (1) subjecting at least one surface of the copper foil for a printed wiring board to an AC electrolytic treatment in an electrolytic solution containing sulfuric acid and copper sulfate. And (2) then depositing roughened copper particles on the treated surface.

In the present invention, in order to deposit the roughened copper particles on the surface smoothed by the first step, the copper foil is subjected to cathodic electrolysis in an electrolytic solution containing sulfuric acid and copper sulfate. Treatment or cathodic pulse electrolytic treatment. By this second step treatment, it goes without saying that fine copper particles are evenly attached to the glossy surface of the copper foil, but also on the matte side of the copper foil, the fine copper particles are uneven in the base shape of the copper foil. It does not concentrate only on the peaks, but also adheres evenly on the valleys, and does not concentrate in dendritic form.

The copper foil used in the present invention is not particularly limited, but examples thereof include rolled copper foil or electrolytic copper foil manufactured by a known method.

The AC electrolytic treatment in the first step of the present invention can be carried out in a known electrolytic solution by a known method. This AC electrolysis treatment is preferably sulfuric acid 50-150.
In an electrolyte consisting of g / l and 80-300 g / l of copper sulfate,
The temperature range of the liquid bath is 20 to 80 ° C., and the alternating current density is 10
It is carried out at -40 A / dm ² and a processing time of 2-10 seconds. 40
At current densities above A / dm ² , their cost performance becomes significantly worse. In the AC electrolytic treatment, the material of the counter electrode of the treated copper foil is not particularly limited, but carbon graphite is preferable.

In the second step of the present invention, the electrolytically treated liquid is preferably 75 to 150 g / l of sulfuric acid and 60 to 1 of copper sulfate.
It is a liquid consisting of 60 g / l, and the temperature range of the liquid bath is preferably 15 to 40 ° C. The current density at the time of cathodic electrolysis treatment varies depending on the concentration and temperature of the liquid bath used and is not limited, but it is usually a value not exceeding the limiting current density, and preferably 25 to 35 A / dm. ^{Is 2} . The electrolytic treatment time is preferably 5 to 15 seconds. The current density during the cathode pulse treatment is 15 to 25 A / dm ² as the average current density. The processing time is 10 ms (milliseconds), off-time: 30-90 ms pulse waveform, preferably 5
~ 20 seconds.

[0010]

EXAMPLES The present invention will be described more concretely with reference to the following examples.

Example 1 First Step A carbon graphite plate was placed as a counter electrode on the glossy surface and matte surface of an electrolytic copper foil (thickness: 35 μm), and surface treatment was carried out under the following liquid bath composition and AC electrolysis conditions. Liquid bath _{composition: H 2 SO 4 ... 100g /} l, CuSO 4 · 5H
₂ O ... 100 g / l; Electrolysis conditions (the same conditions were applied for glossy surface treatment and matte surface treatment): Bath temperature ... 25 ° C .; Commercial AC electrolytic current density ...
32 A / dm ² , processing time ... 6 seconds.

Second step Next, after the treated surface is thoroughly washed with water, iridium oxide-coated titanium plates are arranged as counter electrodes on the glossy surface and the matte surface, respectively, and fine copper particles are prepared according to the following bath composition and cathodic electrolysis conditions. Adhered and formed. Bath _{composition: H 2 SO 4 ... 115g /} l, CuSO 4 · 5H 2
O ... 95 g / l; electrolysis conditions: bath temperature ... respectively 27 ℃, 35A / dm ² at 30A / dm ² and matte processed in cathodic average current density ... glossy surface treatment, the treatment time ... each 6 seconds. Further, in order to firmly fix the fine copper particles, treatment was carried out with the following liquid bath composition and cathodic electrolysis conditions. Liquid bath _{composition: H 2 SO 4 ... 115g /} l, CuSO 4 · 5H
₂ O ... 250g / l; electrolysis conditions: bath temperature ... respectively 50 ℃, 24A / dm ² at the cathode average current density for electrolysis ... 30A / dm ² and matte processed in glossy surface treatment, the treatment time ... 15 seconds, respectively. The obtained double-sided roughened copper foil was evaluated for the following items, and the results are shown in Table 1.

Uniformity of Cobb Shape The adhered shape of fine copper particles on the roughened surface was observed with a scanning electron microscope. On the glossy side and matte side, if the size of the individual bumps is uniform and adheres well, it is ○, when it is almost uniform, it is □, when it is slightly non-uniform, it is completely non-uniform. The case was designated as x.

Peeling strength after being laminated on a glass epoxy prepreg Roughened surface is laminated on four glass epoxy prepregs (thickness 180 μm), sandwiched between press plates and heated at 170 ° C. for 120 minutes. It was pressure molded. With respect to the obtained copper-clad laminate, the peel strength of the copper foil was measured by the method specified in JIS C-6481.

Residual copper particles on the laminate (transfer)
The surface of the glass substrate after the copper foil was peeled off as described above was observed with an optical microscope. Unit area (0.5mm × 0.5mm)
The number of residual copper particles per measurement is measured, and when the number of residual copper particles is large, it is ×, when there is some residual copper, Δ, when almost no residual copper is □, when there is no residual copper, ○. did.

Measurement of surface roughness JIS B-06 is used as a measure of the surface roughness of the roughened surface.
The Rz value was measured by the method specified in 01.

Example 2 A surface treatment was performed in the same manner as in Example 1 except that one surface of the rolled copper foil (thickness: 35 μm) was surface-treated. The obtained single-sided roughened copper foil was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 First Step The electrolytic copper foil (thickness: 35 μm) having a glossy surface and a matte surface was subjected to AC electrolytic treatment under the same conditions as in Example 1.

Second Step Next, cathodic pulse electrolysis treatment was carried out under the same liquid bath composition as in Example 1 and the following electrolysis conditions. Electrolysis conditions (the same conditions were applied for glossy surface and matte surface treatment): bath temperature ... 25 ° C., average current density ... 20 A / dm ² ; on-time ... 10 ms, off-time ... 60 ms; treatment time ... 5 seconds. Further, a cathodic electrolysis treatment for firmly fixing the fine copper particles was performed on the glossy surface and the matte surface under the same conditions as in Example 1. The obtained double-sided roughened copper foil was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 A surface treatment was carried out in the same manner as in Example 3 except that one surface of the rolled copper foil (thickness: 35 μm) was surface-treated. The obtained single-sided roughened copper foil was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 Cathodic electrolysis was performed in the same manner as in Example 1 except that the glossy surface of the electrolytic copper foil (thickness: 35 μm) was not subjected to AC electrolysis. The obtained double-sided roughened copper foil was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 Cathodic electrolysis was performed in the same manner as in Example 1 except that one side of the rolled copper foil (thickness 35 μm) was not subjected to AC electrolysis. The obtained single-sided roughened copper foil was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 3 The same treatment as in Example 3 was performed except that the glossy surface of the electrolytic copper foil (thickness: 35 μm) was not subjected to AC electrolytic treatment. The obtained double-sided roughened copper foil was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 4 Cathodic electrolysis was performed in the same manner as in Example 3 except that one side of the rolled copper foil (thickness 35 μm) was not subjected to AC electrolysis. The obtained single-sided roughened copper foil was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0025]

[Table 1]

[0026]

The surface-roughened copper foil for a printed wiring board obtained by the method of the present invention is a copper foil in which fine copper particles are evenly attached to the copper foil and which has irregularities in the base shape. In addition, since the fine copper particles do not concentrate only on the peaks but also uniformly adhere to the valleys, the adhesion to the prepreg is large, and it is particularly excellent as a copper foil for inner layer circuits.

Front page continuation (56) Reference JP-A-3-202500 (JP, A) JP-A-3-276739 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05K 3 / 38 H05K 3/46

Claims (2)

(57) [Claims] 1. A method for roughening a surface of a copper foil for a printed wiring board, comprising: (1) at least one surface of the copper foil for a printed wiring board from 50 to 150 g / l of sulfuric acid and 80 to 300 g / l of copper sulfate. In an electrolytic solution containing AC electrolysis current density of 10 to 40 A / dm ² , and (2) then depositing roughened copper particles on the treated surface. . 2. The method according to claim 1, wherein the step of depositing the roughened copper particles comprises cathodic electrolysis or cathodic pulse electrolysis in an electrolytic solution containing sulfuric acid and copper sulfate.