JPH0826470B2 - Copper plating solution and method for producing electrolytic copper foil using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a copper plating solution and a method for producing an electrolytic copper foil using the same, and more specifically, the surface roughness and the roughness on the rough surface side of the copper foil. And a copper plating solution containing a specific additive capable of improving the continuous unevenness form which constitutes a small and uniform improvement, and a method for producing an electrolytic copper foil capable of suitably producing an electrolytic copper foil using the same Regarding

[Conventional technology]

Electrolytic copper foil is widely used mainly as a copper foil for printed circuits. The printed circuit copper foil is laminated with a resin base material by heat and pressure to form a copper clad laminate, and after a desired circuit network is formed by etching means, an electric element is mounted and printed on a television, a computer or the like. It becomes a circuit.

There is a marked tendency for high density and narrow conductor width of this circuit,
The quality requirements of the electro-deposited copper foil used for this are becoming more stringent than ever before. Among the physical properties of the electrolytic copper foil are tensile strength, elongation, surface roughness, hardness and the like. In particular, the copper foil rough surface side, that is, the surface state of the side having continuous unevenness when copper is electrodeposited on the drum surface of the cathode to reach a desired thickness in the method for producing an electrolytic copper foil described later. Is deeply related to the physical properties of the electrolytic copper foil such as peel strength from a resin base material, etching accuracy, and interlayer insulation with a resin substrate. Especially when used in high-frequency circuits, if the surface roughness or unevenness of the rough surface of the copper foil is large or uneven, the phase shift of the signal will occur and the waveform will eventually be deformed, resulting in electrolytic copper foil. The impedance as the circuit conductor of may deteriorate. Therefore, especially in the formation of a fine circuit, it is required to reduce the surface roughness on the rough surface side of the copper foil and to make uniform the respective irregularities constituting the roughness in order to obtain the reliability of the circuit quality.

Now, as a method for producing an electrolytic copper foil, mainly, an acidic copper plating solution containing copper ions is used, a rotating drum is used as a cathode, and an anode is disposed in close proximity to the lower half of the drum so as to face each other, and a gap between both electrodes is provided. A method of continuous electrolytic treatment in which a plating solution is injected into the electrode, electrolytic treatment is performed with a current in a range not exceeding the limiting current density to deposit copper on the drum surface of the cathode, and the deposited copper thin film is peeled off and continuously wound. Has been adopted. The thickness of the copper foil at this time can be adjusted to an arbitrary thickness by increasing or decreasing the number of rotations of the drum or the current density. Therefore, the above-mentioned characteristics of the thin film, that is, the copper foil itself are mainly due to the concentration (copper concentration,
Acid concentration), liquid temperature, liquid flow rate, type of additive and its concentration, and current density, etc., and it is important to establish these individual conditions and control them in continuous production of electrolytic copper foil. It's important. In particular, the additive added to the plating solution affects the characteristics of the rough surface of the copper foil.

Conventionally, in order to give preferable characteristics to the rough surface side of the copper foil,
It is practiced to add some specific additive to the plating solution. Examples of the additive include gelatin,
Organic substances such as glue, thiourea, polyethylene glycol, polyvinyl alcohol, starch and saccharides, as well as anions and metal salts are known. Since the characteristics of the copper foil described above slightly change when one kind of these additives is added to the plating solution or two or more kinds of them are added in combination, these additives are controlled individually like other manufacturing conditions. Has been done.

Conventionally, it is possible to reduce the surface roughness of the copper foil rough surface side by adding a small amount of the above-mentioned additive, but the unevenness morphology lacks uniformity, or copper deposition becomes dendritic or copper granular. In case of abnormal precipitation or long-term continuous operation,
There is a problem in that stable quality is not maintained and the quality such as peel strength from the resin base material and electrical characteristics is impaired.

[Problems to be Solved by the Invention]

Therefore, the present invention is an electrolytic copper foil having a quality suitable for forming a fine circuit when used for a printed wiring board, that is, a surface roughness on the rough surface side of the copper foil and a continuous unevenness form which constitutes roughness are small and An object of the present invention is to provide a copper plating solution capable of producing an electrolytic copper foil having an improved quality.

Another object of the present invention is to provide a method for producing an electro-deposited copper foil, which can suitably produce an electro-deposited copper foil having the above-mentioned characteristics using this copper plating solution.

[Means for solving the problem]

The present invention provides a copper plating solution obtained by adding 5 to 50 ppm of enzyme-decomposed gelatin to an acidic copper plating solution containing copper sulfate and sulfuric acid as main components.

 Hereinafter, the present invention will be described in detail.

The copper plating solution of the present invention is a copper plating solution containing copper sulfate and sulfuric acid as main components. First, the main component will be described. It is preferable that the concentration of copper sulfate (CuSO ₄ .5H ₂ O) is in the range of 100 to 400 g / l. If the concentration is less than 100 g / l, so-called burn plating accompanied by hydrogen gas when increasing the productivity of the copper foil at high current density, the characteristics of the copper foil itself is not improved, for example, the surface roughness of the rough surface side Roughness that forms the roughness without becoming small may be rough, and tensile strength,
Properties such as elongation may also be impaired. Also, the concentration is 40
If it exceeds 0 g / l, copper sulfate is likely to be recrystallized in electrolytic devices and equipment such as tanks and pipes, which is not preferable in terms of work.

On the other hand, the concentration of sulfuric acid (H ₂ SO ₄ ) is preferably in the range of 30 to 150 g / l. If the concentration is less than 30 g / l, the manufacturing cost of the copper foil increases as the bath voltage increases. On the other hand, if the concentration exceeds 150 g / l, the wear of the anode and the cathode tends to be remarkable, which is inconvenient.

In the copper plating solution of the present invention, 5 to 50 ppm of enzyme-decomposed gelatin is added to the above main components.

Explaining this enzyme-decomposed gelatin, enzyme-decomposed gelatin is obtained by purifying cowhide, cow bone, etc. with acid or alkali,
It is a peptide obtained by extracting collagen or gelatin from this and further hydrolyzing it with an enzyme such as pepsin or trypsin. Conventional gelatin has an average molecular weight of 60,000 to 70,000, whereas enzyme-degraded gelatin has a low average molecular weight of 1,000 to 20,000. In addition, the component has an amino acid composition, glycine, proline, alanine, hydroxyproline,
Consists of arginine and glutamic acid. Such enzyme-decomposed gelatin may be further decolorized, deodorized and refined, and adjusted in pH and concentration. Usually, commercially available liquid products, paste products, spray-dried powder products and the like can all be suitably used. The enzyme-decomposed gelatin added to the copper plating solution of the present invention has a molecular weight of 5,000 to 20,00.
Those of 0 are particularly suitable.

The concentration of enzyme-degraded gelatin in the copper plating solution is 5 to 50 ppm
And When the concentration is less than 5 ppm, the unevenness of the copper foil rough surface side can be obtained uniformly, but the surface roughness tends to increase, and when it exceeds 50 ppm, the unevenness of the uneven shape becomes irregular and abnormal precipitation occurs. Is liable to occur, which increases the accuracy of copper foil thickness and electrical characteristics, for example, increases transmission loss, and in any case deteriorates the quality of the copper foil. A particularly preferred range is 5 to 30 ppm.

By electrolytically treating the copper plating solution containing the enzyme-decomposed gelatin under appropriate conditions, the electrolytic copper foil of the present invention, that is, the surface roughness on the rough side of the copper foil is small and It is possible to manufacture an electro-deposited copper foil having a uniform ruggedness that constitutes the ridge.

The enzyme-decomposed gelatin is likely to change into a different chemical component with time due to copper ions, sulfate ions in the plating solution and the solution temperature or electrolytic treatment. The component due to this alteration may act as a variable factor that deteriorates the surface roughness on the rough surface side of the copper foil and the irregular shape of the copper foil. Therefore, when using the copper plating solution of the present invention, it is preferable to remove harmful components due to this alteration.

There is no particular limitation on the method of removing the harmful component due to the alteration, but for example, a method of adsorbing and removing the harmful component using activated carbon is suitable.

Specifically, when producing an electrolytic copper foil by an electrolytic treatment method using the copper plating solution, it is preferable to filter the copper plating solution during the electrolytic treatment with 0.1 to 2.0 g / l of activated carbon per hour. .

The effect of filtration with activated carbon is to remove impurities in the plating solution, and in particular to sufficiently exert the effect of the enzyme-decomposed gelatin. In particular, the purpose is to adsorb and remove harmful components caused by the alteration of the enzymatically-degraded gelatin, so that it is possible to stably maintain the surface roughness on the rough surface side of the copper foil and the uneven shape that constitutes the roughness.

The preferred usage range of activated carbon is 0.1 to 2.0 per hour.
g / l. If the amount is less than 0.1 g / l, not only the above-mentioned effects cannot be obtained, but also the characteristics of the copper plating solution change with time, and a stable quality copper foil may not be obtained. Also 2.0g / l
If it exceeds, the surface roughness on the rough surface side tends to be large, and in addition, the unevenness of the roughness is not uniform, and it is disadvantageous from the economical point of view. A particularly preferably used range is 0.3 to 1.5 g / l per hour.

The type of activated carbon used may be any activated carbon such as granular or powder. When powdered activated carbon is used, the amount of activated carbon used is 1/3 of that when granular activated carbon is used.
A similar effect can be obtained with a small amount. In addition, when using any activated carbon, it is preferable that chlorine contained in the activated carbon is removed as much as possible. In other words, the fact that the plating solution does not contain chlorine ions is effective in reducing the surface roughness of the copper foil rough surface side, and specifically,
In the case of a copper foil having a thickness of 70 μm or less, it is effective in keeping the roughness of the center line average roughness Ra at 0.5 μm or less.

As a method of filtering the plating solution with activated carbon, for example, a plurality of filtration devices are filled with a predetermined amount of activated carbon, and the plating solution is passed through the activated carbon for a certain period of time by one filtration device to be filtered, and then a new activated carbon is sequentially added. A method of performing continuous filtration by performing a switching operation with a filtration device can be mentioned. It is preferable to continuously filter the plating solution in this manner while supplying the filtered plating solution to the electrolysis device for continuous electrolysis.

In order to achieve the object of the present invention, there is a close relationship between the concentration of the additive and the filtration amount of activated carbon, and it is usually necessary to increase the filtration amount of activated carbon when the concentration of the additive is increased.
However, there are cases where the proportional relationship between the addition concentration and the activated carbon filtration amount is not always established by appropriately setting the electrolytic treatment conditions such as the liquid temperature and the liquid flow rate.

Next, to describe the electrolytic treatment conditions of the method of the present invention,
A suitable current density is a current density less than or equal to the limiting current density, and shows a numerical value that fluctuates depending on other conditions, for example, the concentration of copper sulfate in the plating solution, the concentration of sulfuric acid, the solution temperature, the solution flow rate, or the production rate. Can not be decided, but usually 10 ~ 300A
It is preferable to be appropriately selected from the range of / dm ² .

It is preferable that the liquid temperature is usually selected from the range of 35 to 80 ° C., and the liquid flow rate is usually selected from the range of 0.1 to 2 m / sec.

A copper foil film having a required thickness is electrodeposited on the surface of the cathode rotating drum by continuous electrolytic treatment under such electrolytic treatment conditions, and if this is peeled off, an electrolytic copper foil is produced by the method of the present invention. You can

The obtained electrolytic copper foil can be used as a copper foil for a printed wiring board having a quality suitable for forming a fine circuit by subjecting it to a surface roughening treatment and an anticorrosion treatment, if necessary.

〔Example〕

 Hereinafter, the present invention will be described in detail based on examples.

Example 1 A copper plating solution prepared by adding 30 ppm of enzyme-decomposed gelatin (trade name: Nippi Peptide PBH, molecular weight 10,000, manufactured by Nippi Corporation) to an acidic copper plating solution containing 300 g / l of copper sulfate and 50 g / l of sulfuric acid. 10000 liters were prepared. This plating solution is maintained at a liquid temperature of 45 ° C, and a foil-making device for testing (diameter 1,000 mm, length
A rotating drum made of titanium of 1,400 mm is used as a cathode, and a semicircular lead anode is arranged to face the lower half of the drum,
The gap between the two electrodes, that is, the distance between the electrodes was set to 5 mm. ), The plating solution is circulated between both electrodes at a liquid flow rate of 0.5 m / sec, and the plating solution is used per hour by using a filtration device.
It was filtered through 1.0 g / l activated carbon.

Next, while continuously rotating the cathode rotating drum made of titanium so that the thickness of the copper foil is 30 μm, a continuous electrolytic treatment is performed at a current density of 30 A / dm ² to electrolytically deposit copper on the cathode, and peel it off.
An electrolytic copper foil was manufactured.

The following characteristics were measured using this copper foil as a sample. The results are collectively shown in Table 1.

(1) Copper foil rough surface side surface roughness [Ra (μm), Rmax (μ
m)] The center line average roughness Ra (μm) and the maximum height Rmax (μm) were measured according to JIS B 0651 (a stylus type surface roughness measuring instrument).

(2) Tensile strength (kg / mm ² ) and elongation (%) A JIS Z 2201 (tensile test piece for metallic material) No. 5 test piece was prepared and measured according to JIS Z 2241 (tensile test method for metallic material). did.

(3) Morphology and uniformity of irregularities on the rough surface of the copper foil The electrodeposited morphology on the rough surface of the copper foil was observed with a scanning electron microscope at a magnification of 1000 times. The concavo-convex shape and the irregular shape of the surface were observed. Among them, the conical one has excellent peeling strength from the resin substrate. Regarding the evaluation of uniformity in the table, ◯ means that the shape of the unevenness is conical and the diameter of the bottom surface is 2 to 5 μm occupies 60% or more of the unevenness in the visual field. However, x means that the above-mentioned unevenness is less than 40%.

Examples 2 to 7, Comparative Examples 1 to 7 Using the same manufacturing apparatus as in Example 1 except that the additive concentration and the activated carbon filtration amount were changed as shown in Example 1,
Various copper foils were manufactured under the same conditions as above. However, in Example 7 and Comparative Example 6, the thickness of the copper foil was 70 μm. The characteristics of these copper foils were measured with the same specifications as in Example 1. The results are collectively shown in Table 1.

When the electrolytic copper foil of the example produced by the method of the present invention using the copper plating solution of the present invention to which the enzyme-decomposed gelatin is added is compared with the electrolytic copper foil of the comparative example, the following results are shown in Table 1. It became clear.

In the electrolytic copper foil of the present invention, the center line average roughness Ra is 0.5 μm in the surface roughness on the rough surface side of the copper foil and the unevenness form of the roughness.
Hereinafter, the maximum height Rmax showed a small value of 5 μm or less.
Moreover, the concavo-convex shape was also conical and maintained uniformity. From this, it is considered that the enzyme-decomposed gelatin added to the copper plating solution of the present invention is effectively acting, and a specific amount of this additive is contained and electrolysis is performed while performing a filtering operation with a specific amount of activated carbon. It was clarified that a remarkably excellent electrolytic copper foil was obtained by the treatment.

On the other hand, Comparative Examples 1 and 2 are examples in which the molecular weight and addition concentration of the enzyme-decomposed gelatin in the copper plating solution were the same as those in Example 1 or 2, and the activated carbon filtration amount was deviated from the preferable range of the method of the present invention. At this time, the surface roughness, morphology and uniformity were all inferior to those of the electrolytic copper foil produced by the method of the present invention.

When conventional high molecular weight gelatin was used in place of the enzyme-decomposed gelatin, as shown in Comparative Examples 4 and 5, the morphology and the uniformity of the unevenness constituting the roughness were good. On the other hand, it was clear that there is a difficulty in improving the surface roughness to be small.

Furthermore, the properties such as tensile strength and elongation of the copper foils of the present invention obtained in Examples 1 to 7 all sufficiently satisfied the requirements as a copper foil for printed circuits.

[Effects of the Invention] According to the copper plating solution of the present invention, the surface roughness on the rough surface side is small, and the irregularities forming the roughness and the uniformity thereof are also excellent, and this is a printed wiring board for forming a fine circuit. It is possible to produce an electro-deposited copper foil which can sufficiently exhibit suitable qualities of etching accuracy and electric characteristics when it is used for, or when it is used for a high frequency circuit.

Further, according to the method for producing an electrolytic copper foil of the present invention, an electrolytic copper foil having the above characteristics can be favorably produced using this copper plating solution.

Claims (2)

[Claims] 1. A copper plating solution obtained by adding 5 to 50 ppm of enzyme-decomposed gelatin to an acidic copper plating solution containing copper sulfate and sulfuric acid as main components. 2. When producing an electrolytic copper foil by an electrolytic treatment method using the copper plating solution according to claim 1, the copper plating solution during the electrolytic treatment is filtered with 0.1 to 2.0 g / l of activated carbon per hour. A method for producing an electrolytic copper foil, comprising: