JPH0853796A - Production of copper foil for printed circuit - Google Patents

Abstract

PURPOSE:To establish a technique for producing copper coil for printed circuits capable of easily and cost effectively controlling the surface roughness of a copper foil matte surface. CONSTITUTION:A DC current having ripples of a pulsation rate of >=5%, more preferably >=20% is used as an electrolytic current in production of the electrolytic copper foil by filling an electrolyte contg. copper ions between a horizontally rotating cathode cylinder and an anode arranged to face this cathode cylinder and effecting electrolysis to electrodeposit copper on the cathode cylinder, then peeling the electrodeposited copper to a foil form. The waveform of the ripple currents is regulated by the pulsation rate, i.e., the ratio (i1/i2) of the ripple current value to the average current value and period (T). Control of the pulsation rate is executed by changing the secondary voltage of a transformer of a DC power source by a thyristor phase control system or changing to make the ratio of the current rectification output small in the pulsation rate and the current rectification output large in the pulsation rate and mixing both outputs. The nucleus generation in the initial period of copper electrodeposition is accelerated and uniform crystal growth is effected if the pulsation rate is made larger. The surface roughness of the matte surface is thus controlled small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a copper foil for a printed circuit, and in particular, it is possible to easily control the surface roughness of a rough surface, and particularly to reduce the surface roughness. Manufacturing method.

[0002]

2. Description of the Related Art Copper and copper alloy foils (hereinafter referred to as copper foils)
Contributes greatly to the development of the electrical and electronic related industries,
In particular, it is indispensable as a printed circuit material. There are electrolytic copper foil and rolled copper foil in the copper foil, the copper foil used for the printed wiring board, from the viewpoint of its adhesive strength,
Most are electrolytic copper foil. The electrolytic copper foil is prepared by preparing an electrolytic solution containing copper ions from electric wire scrap having the same purity as electrolytic copper or a raw material, and a horizontally rotating cathode cylinder as a cathode that is immersed in the electrolytic solution, and the cathode cylinder. Between the anode disposed opposite to the cylindrical surface of, the electrolytic solution containing copper ions is filled to perform electrolysis, and copper is continuously electrodeposited on the cylindrical surface of the cathode cylinder. Basically, a raw foil is manufactured by peeling a thick electrodeposit from a rotary drum in a foil shape. Then, depending on the quality requirements for the printed circuit board copper foil, many surface treatments are performed on the matte surface (adhesive surface) and the glossy surface (non-adhesive surface) that are adhered to the resin base material. In the case of ordinary electrolytic copper foil, for example, on the matte surface, roughening treatment is performed to perform galvanic deposition of copper, thin copper plating treatment is performed to form a covering layer to prevent electrodeposited particles from falling off, and if necessary, metal is used. Further, a treat treatment for forming an alloy layer and a rust preventive treatment are performed.

The obtained copper foil for printed circuits is generally laminated and adhered to a resin substrate under high temperature and high pressure, and then subjected to etching treatment or the like to form a desired circuit. After that, various electric elements are assembled to finally form a printed circuit board.

With the recent trend toward miniaturization and high performance of electric devices, the density of printed circuit boards has increased, and it has been required to reduce the width of circuits to be formed. For that purpose, it is necessary to uniformly perform the etching treatment, and the surface roughness of the copper foil matte surface is greatly related to this. The matte surface is the surface of the copper foil that is adhered to the resin substrate. By controlling the surface roughness of the matte surface and suppressing it to a small value, uniform etching can be performed.

Conventionally, in the copper foil for printed circuits produced by the electrolytic method, the surface roughness of the matte surface is controlled mainly by an additive added to the electrolytic solution.

On the other hand, in the field of electroplating, it is known that the surface roughness of the plated surface is reduced by using a pulse current as the electrolytic current. In connection with the use of pulse current, there is an example of a technique using pulse current in the field of copper foil for printed circuits for the purpose of preventing the generation of pinholes, microporosity, etc. of the copper foil (Japanese Patent Publication Sho 63). -28228
No. 8), there is no application example for controlling the surface roughness of the copper foil. Also, as part of the roughening treatment after the production of green foil, an attempt to improve the adhesive strength by using a pulsed current has been made in JP-A-61-6297 and JP-B-2-6024.
Although described in No. 0, it is not directly related to the production of green foil.

[0007]

However, even if a pulse current is used as the electrolytic current for the purpose of controlling the surface roughness of the copper foil mat surface, the pulse power source is more expensive and consumes more power than the DC power source, which is economical. Is disadvantageous to Moreover, a pulsed power supply for supplying a large current, which is used for manufacturing an electrolytic copper foil, is difficult to obtain and is not practical. Therefore, in general, the method of controlling the surface roughness of the copper foil matt surface by using the additive has been adopted as described above. In this case, it is always necessary to control and manage the concentration and amount of the additive in the electrolytic solution at the time of manufacturing. However, when a conventional roughened foil and a foil with a reduced roughness are separately produced, the method of adding the additive differs depending on the electrolytic cell, which makes control difficult. If one tries to make these foils with one electrolysis cell, it is necessary to switch the control method, and the foils are wastefully made before the steady state is reached.

An object of the present invention is to provide a printed circuit copper foil which can solve the above-mentioned drawbacks of the prior art and can easily and economically control the surface roughness of the copper foil matte surface, particularly, reduce the surface roughness. Establishing manufacturing technology.

[0009]

The inventors of the present invention have found that the surface roughness of the matte surface can be controlled by using a rippled direct current having a pulsation rate of 5% or more as the electrolytic current. For example, it has been found that the average surface roughness can be changed from 0.95 μm to 0.80 μm level by changing the pulsation rate from 5% to 100%. The ripple means a pulsating current component of a voltage or current included in the output of the DC power supply obtained by rectifying the AC power supply, which is synchronized with the power supply AC. The pulsation rate is defined as the ratio (= i ₁ / i ₂ ) of the ripple current value (i ₁ ) to the average current value (i ₂ ) in the ripple current waveform. Based on this finding, the present invention performs electrolysis by filling an electrolytic solution containing copper ions between a horizontally rotating cathode cylinder and an anode arranged opposite to the cylindrical surface of the cathode cylinder, In the method for producing an electrolytic copper foil in which copper is electrodeposited on the cylindrical surface of the cylinder, and then the electrodeposit is peeled off from the cylindrical surface of the cathode cylinder in a foil shape, the electrolytic current has a pulsation rate of 5% or more, preferably Two
Provided is a method for manufacturing a copper foil for a printed circuit, which uses a direct current having a ripple of 0% or more. The pulsation rate is controlled by (A) changing the secondary voltage of the transformer in the DC power supply by the thyristor phase control method, or (B) rectifying the pulsation rate by reducing the pulsation rate and increasing the pulsation rate. This can be done by changing the ratio with the output and mixing.

[0010]

[Function] Although the mechanism by which a rippled direct current influences the surface roughness of the matte surface is not clear, increasing the pulsation rate promotes nucleation in the early stage of copper electrodeposition, resulting in uniform crystal growth. Due to the formation of the copper thin film,
It is presumed that the surface roughness of the matte surface is controlled to be small.
As a waveform of a direct current having a ripple used in the present invention, for example, a waveform shown in FIG. 1 can be mentioned. In FIG. 1, T represents the ripple period, i
₁ and i ₂ represent a ripple current value and an average current value, respectively. Usually, the ripple current waveform has a pulsation rate, that is, a ratio of the ripple current value to the average current value (i ₁ / i ₂ ) and a period (T ). The copper foil matte surface can be adjusted by adjusting the pulsation rate of the direct current used according to the surface roughness required for the copper foil by obtaining the relationship between the pulsation rate and the surface roughness of the raw foil in the specified equipment. The surface roughness can be controlled easily and economically. The pulsation rate is controlled by (A) changing the secondary voltage of the transformer in the DC power supply by the thyristor phase control method, or (B) rectifying the pulsation rate by reducing the pulsation rate and increasing the pulsation rate. This is done by changing the ratio with the output and mixing.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An electrolytic copper foil raw foil is prepared by preparing an electrolytic solution containing copper ions from electrolytic copper or electric wire scrap having a purity equivalent to that of electrolytic copper, and horizontally laying it as a cathode to be immersed in the electrolytic solution. Between the rotating cathode cylinder and the anode arranged opposite to the cylindrical surface of the cathode cylinder, an electrolytic solution containing copper ions is filled for electrolysis, and copper is continuously electrodeposited on the cathode cylinder. After that, the electrodeposit having a predetermined thickness is peeled from the cathode cylinder in a foil shape to manufacture. Figure 2
Shows a conventional cathode cylinder 11 and an anode 12 arranged to face the cylindrical surface. The cathode cylinder 11 is installed so as to be horizontally rotatable in a normal state of being partially immersed in an electrolytic cell (not shown) that stores an electrolytic solution. For example, two anodes 12 are arranged so as to cover approximately the lower half of the cathode cylinder 11 and to be spaced apart from the cathode cylinder 11 by a predetermined distance. The electrolytic solution is supplied from between the two anodes, flows through the gap between the cathode cylinder and the anode, overflows from the upper edge of the anode, and is circulated in the electrolytic cell. The rectifier 13 maintains a predetermined direct current between the cathode cylinder and the anode.

Raw foils are generally produced using the following electrolysis conditions: CuSO ₄ .5H ₂ O: 130-500 g / l H ₂ SO ₄ : 80-150 g / l Liquid temperature: 50-70 ° C. Average current density: 100 to 150 A / dm ²

According to the present invention, a DC current having a ripple with a pulsation rate of 5% or more, preferably 20% or more is used as the electrolytic current. An example of the waveform of the DC current having a ripple is the one shown in FIG. Usually, the ripple current waveform is defined by the pulsation rate, that is, the ratio (i ₁ / i ₂ ) of the ripple current value to the average current value and the period (T). By making the ripples large and dense, the pulsation rate increases. As a method of controlling the pulsation rate, a method of controlling the pulsation rate by changing the secondary voltage of the transformer in the DC power supply according to the conventional thyristor phase control method shown in FIGS. 3 and 4 is mentioned. be able to. As shown in FIG. 3, the current from the single-phase or three-phase AC power supply 2 is supplied to the electrolytic cell 8 from a current controller 3 such as a thyristor, a transformer 4, a rectifier 5 such as a diode, and an ammeter 6. Phase controller 7
Is connected from the ammeter 6 to the current controller 3 for phase control. Alternatively, as shown in FIG. 4, the current from the single-phase or three-phase AC power supply 2 is passed through the transformer 4,
It is also possible to change the next voltage so that it flows from the thyristor 9 to the electrolytic cell 8 through the ammeter 6. The phase control controller 7 is connected from the ammeter 6 to the thyristor 9 to control the phase. The pulsation rate is controlled by switching the secondary voltage of the transformer 4, and the pulsation rate is increased by increasing the secondary voltage of the transformer 4. However, in this method, load fluctuations are easily affected by power supply fluctuations.

For stable operation, therefore, in the DC power supply shown in FIGS. 5 and 6, for example, the three-phase rectified output with a small pulsation rate and the single-phase rectified output with a large pulsation rate are changed. A method of controlling the pulsation rate can be used by mixing them. Ripple control by mixing currents controlled by a current controller 3, a transformer 4, a rectifier 5, an ammeter 6, and a phase controller 7 using a three-phase AC power supply 1 and a single-phase or three-phase AC power supply 2. I do. As shown in FIG. 6, the circuit can be simplified by using the thyristor 9.

The pulsation cycle (T) is determined by the frequency and phase (single phase, three phase, etc.) of the AC power supply.

As described above, in the present invention, the method of controlling the pulsation rate is used as the means for controlling the surface roughness of the matte surface of the electrolytic copper foil. As described above, when the ripple current value increases, that is, when the pulsation rate increases, the surface roughness of the rough surface of the electrolytic copper foil decreases. However, when the pulsation rate takes a value smaller than 5% like ordinary direct current, almost no effect is recognized, and when a larger effect is desired, 20% or more is preferable.

[0017]

EXAMPLES Examples and comparative examples will be shown below. The surface roughness was measured according to JIS BO 60 in both the examples and the comparative examples.
1 based on 1.

(Example) Table 1 shows the surface roughness of the rough surface of the electrolytic copper foil produced under the following conditions. (Electrolysis conditions): CuSO ₄ .5H ₂ O: 300 g / l H ₂ SO ₄ : 120 g / l Liquid temperature: 55 ° C. Average current density: 100 A / dm ² Copper foil thickness: 30 μm Pulsation rate: 5%, 10%, 20%, 30%, 50%, 10
0%

[0019]

[Table 1]

The obtained copper foil was laminated and adhered to a resin substrate under high temperature and high pressure, and then a circuit was formed by etching treatment. The etching accuracy was good at a pulsation rate of 5 to 50%, and particularly good at 100%.

(Comparative Example) Table 2 shows the surface roughness of the rough surface of the electrolytic copper foil produced under the same conditions as in Example except that a direct current having a pulsation rate of 0 was used as the electrolytic current.

[0022]

[Table 2]

[0023]

According to the present invention, the surface roughness of the copper foil matte surface can be easily controlled without changing the method of adding the additive. In particular, when foils having different surface roughness are produced by one electrolysis cell, there is no need to produce wasteful foils until the steady state is achieved after changing the addition method as in the conventional case. Further, in applying the method of the present invention, it is not necessary to remodel the conventional electrolysis device, and it can be carried out only by changing the DC power supply device, which has a large economical burden.

[Brief description of drawings]

FIG. 1 shows an example of a waveform of a DC current having a ripple used in the present invention.

FIG. 2 is a simplified diagram of a raw foil manufacturing facility.

FIG. 3 is a schematic diagram showing an example of a rectifier that generates a direct current having a ripple by a thyristor phase control method.

FIG. 4 is a schematic view showing another example of a rectifier that generates a direct current having a ripple by a thyristor phase control method.

FIG. 5 is a schematic diagram showing an example of a rectifier that generates a direct current having a ripple that mixes by changing two types of rectification output ratios.

FIG. 6 is a schematic diagram showing another example of a rectifier that generates a direct current having a ripple that mixes by changing two types of rectification output ratios.

[Explanation of symbols]

 1 3 Phase AC Power Supply 2 1 Phase or 3 Phase AC Power Supply 3 Current Controller (Thyristor etc.) 4 Transformer 5 Rectifier (Diode etc.) 6 Ammeter 7 Phase Control Controller 8 Electrolysis Cell 9 Thyristor 11 Cathode Cylinder 12 Anode 13 Rectifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Sugihara 3-3-1, Shiragincho, Hitachi-shi, Ibaraki Nikko Gold Foil Co., Ltd. Hitachi factory

Claims (4)

[Claims] 1. On the cylindrical surface of the cathode cylinder, an electrolytic solution containing copper ions is filled between a horizontally rotating cathode cylinder and an anode arranged opposite to the cylindrical surface of the cathode cylinder to perform electrolysis. In the method for producing an electro-deposited copper foil in which copper is electrodeposited on, and then the electro-deposit is peeled from the cylindrical surface of the cathode cylinder in a foil shape, a direct current having a ripple with a pulsation rate of 5% or more is used as the electrolysis current. A method for producing a copper foil for a printed circuit, which is used. 2. The method for producing a copper foil for a printed circuit according to claim 1, wherein the pulsation rate is 20% or more. 3. The method for manufacturing a copper foil for a printed circuit according to claim 1, wherein the pulsation rate is controlled by changing the secondary voltage of the transformer in a DC power supply of the thyristor phase control system. 4. The production of a copper foil for a printed circuit according to claim 1, wherein the pulsation rate is controlled by changing the ratio of the rectified output with a small pulsation rate and the rectified output with a large pulsation rate and mixing them. Method.