JP2008184633A - Method for surface-treating metal foil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a metal foil suitable for a resettable fuse material, which can easily electrolyze the metal foil by lowering a current density in nickel burning plating which is cathodic electrolyzing treatment. <P>SOLUTION: A method for surface-treating the metal foil comprises the steps of: forming a smooth nickel-plated layer at least on one side of the metal foil through nickel-plating treatment by cathodic electrolysis; and then forming a layer of fine nickel particles on the surface of the smooth nickel-plated layer through nickel roughening treatment. It is preferable to perform the nickel roughening treatment by electrolyzing the metal foil in an electrolytic bath of a sulphate bath in which a nickel compound is dissolved and a small amount of at least one metal among copper, chromium and iron is added. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a metal foil surface treatment method, and more particularly to a metal foil surface treatment method suitable as a resettable fuse material.

With the spread of small electronic devices, lithium ion secondary batteries, which are rechargeable batteries, have grown rapidly in recent years, and their installation is indispensable for notebook computers and mobile phones. A resettable fuse (hereinafter simply referred to as a fuse) is also required as a protective component for preventing overcharge of a lithium ion secondary battery, and its mounting is currently positioned as an indispensable component. This fuse is also used for circuit protection to prevent overcurrent overvoltage in electronic circuit boards, and it is used for applications that are not exaggerated even if it is dedicated to electronic circuits that are recently incorporated in the USB jack part. It is a fuse that has been.
The structure of this fuse utilizes the characteristic that when an overcurrent overvoltage is applied, the conductive resin sandwiched between the upper and lower conductive metals constituting the fuse changes to an insulating resin and shuts off the circuit. When the overcurrent overvoltage is eliminated, the circuit returns to the energized state again, so that the circuit can be semipermanently protected.

  In recent years, the use of lithium ion secondary batteries has been developed for high capacity types on the premise of being mounted on HEV vehicles, and further consideration is required for safety. Also in the field of notebook PCs and mobile phones for consumer use, it is assumed that overcurrent overvoltage may be applied to the circuit as the information processing speed and circuit width become thinner. The fuse is becoming necessary.

  Conventionally, as the conductive metal material constituting the fuse, an electrolytic copper foil of about 30 to 50 μm is used, and this electrolytic copper foil and a functional resin having both conductive and insulating properties (hereinafter simply referred to as functional resin). In order to maintain the adhesion at the time of high-temperature press molding, a copper foil that has been subjected to a nickel roughening treatment to the extent that the copper surface is not exposed is employed on the adhesion surface side of the copper foil adhered to the functional resin. The reason why nickel is selected as a roughened metal is related not only to excellent heat resistance but also to good compatibility with chemical adhesion to functional resins.

  Copper foil with nickel roughening treatment is used as a fuse member, and when designing a fuse that can handle overcurrent overvoltages assuming circuits that can increase output in recent years, the thickness of the copper foil is increased. Although it is the safest measure in terms of cost, it does not meet the requirements of design circuits for lightness, thinness, and smallness.

Proposal to use nickel foil with appropriate thickness as a material that can cope with excessive overcurrent overvoltage without increasing the thickness of copper foil as a fuse for circuit protection components with increased output in recent years, copper foil resin A proposal has already been made to replace the nickel roughening layer having a suitable thickness on the surface to be bonded to the surface by applying a healthy burnt nickel plating using a known bath composition. However, since nickel metal is expensive, not only is the material cost high, but it is pointed out that nickel foil is difficult to handle in terms of its physical properties in the continuous production process from roll to roll. ing. On the other hand, the method of plating nickel thickly on the copper foil surface is performed by a combination of nickel roughening and nickel smooth plating, but when using a known bath composition for healthy nickel burn plating, It has been pointed out that the current density for energization requires a large value, so that the current consumption is large and the plating process is expensive.
Therefore, there has been a demand for a metal material that has handling properties and economy and satisfies the required characteristics as a fuse material.

  The present invention eliminates the above-mentioned conventional problems, facilitates the manufacturing process, reduces costs, and provides a metal foil suitable as a fuse material. Or choose aluminum foil, copper foil, stainless steel foil, iron foil manufactured and produced by electrolysis, first apply nickel smooth plating so that at least one of the surfaces is sufficiently covered with the underlying metal foil, The present invention was completed by examining nickel plating bath composition conditions that enable nickel roughening treatment on the surface by an economically superior method.

  In the surface treatment method for a metal foil of the present invention, at least one surface of the metal foil is subjected to a cathodic electrolytic nickel plating treatment to provide a nickel smooth plating layer, and the nickel smooth plating layer is subjected to a nickel roughening treatment. A fine nickel particle layer is provided.

  It is preferable that the metal foil is any one of an aluminum foil, a copper foil, a stainless steel foil, and an iron foil manufactured and manufactured by rolling or electrolysis.

The nickel roughening treatment is preferably performed in an electrolytic bath in which a nickel compound is dissolved in a sulfuric acid bath and at least one kind of a small amount of copper, chromium and iron is added as an additional metal. The addition amount is preferably in the range of 1/10 to 1/20 of the amount of metallic nickel dissolved in sulfuric acid.
In order to more firmly fix the fine nickel particle layer on the surface of the metal foil, it is preferable to provide a nickel capsule plating layer by performing a cathodic electrolytic nickel plating process on the surface of the fine nickel particle layer.

    ADVANTAGE OF THE INVENTION According to this invention, a manufacturing process is easy, cost can be reduced, and the manufacturing method of metal foil suitable as a fuse material can be provided.

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

  In the present invention, the metal foil for foods is a rolled foil made aluminum foil, copper foil, stainless steel foil, iron foil or electrolytic copper foil (hereinafter referred to simply as metal foil when it is not necessary to distinguish between these foils) Can be adopted). These metal foils are subjected to nickel smooth plating, and nickel roughening treatment is applied to the surface of the nickel smooth plating layer to form a fine nickel particle layer.

Nickel roughening treatment conditions on the surface of each metal foil are performed by burnt plating. However, the current density condition that causes burn-off plating using a normal bath or a watt bath using a known nickel plating bath composition premised on mass production becomes a large value, resulting in high cost in the plating process.
Normally, the current condition for starting the burnt plating is near the limit current density. This limit current density is determined by the concentration condition of the electrolytic bath. That is, the limiting current density can be easily reduced by reducing the nickel concentration in the electrolytic bath. However, reducing the nickel concentration in the electrolytic bath not only increases the concentration control of the electrolytic bath in industrial mass production facilities, but also reduces the current range that can be used for healthy burnt plating. The problem of lacking in uniformity is also included.

In view of this, the present invention has been studied from the viewpoint of finding a method that can easily achieve sound burn plating even when the current condition of burn plating is low.
The present inventors have used a known nickel plating bath, a normal bath or a watt bath, as a method for performing smooth nickel plating on at least one surface of each metal foil having a thickness of 50 to 70 μm. The nickel smooth plating process was performed until the surface was sufficiently covered.
Since most of the surface roughness of the rolled metal foil subjected to nickel smooth plating is 1 μm or less as measured by the measuring method specified in JISB06012, the surface of the rolled metal foil is sufficiently covered with nickel. It was confirmed that the nickel smooth plating thickness applied to was about 1.5 μm.

On the other hand, in the case of electrolytic copper foil, the nickel smooth plating layer was applied on the liquid surface side during the foil production for the purpose of obtaining the adhesion strength in the next step. The surface roughness Rz of an electrolytic copper foil having a thickness of 50 to 70 μm immediately after the production of the foil is about 3.5 to 7.5 μm, and the roughness is rougher than that of the rolled copper foil. The thickness completely covered by plating was not much different from that of rolled copper foil, and it was confirmed that a thickness of 1.5 to 3.5 μm was sufficient.
In the above confirmation experiment, if the thickness of the nickel smooth plating layer on the target metal foil is 1.5 μm or more, the surface of the metal foil made by either rolling or electrolysis is sufficiently plated with nickel. It was confirmed that it was coated.

The bath composition for smooth plating is 35-50 g / l as nickel from nickel compounds, boric acid (as H ₃ BO ₃ ) is 25 g / l or more to a saturation level, and the bath temperature condition is 30-50 ° C. A bath with pH adjusted to 2.5-4.0 was used.
The nickel compound may be any of nickel sulfate, nickel chloride, and nickel sulfamate, but it is preferable to use a sulfate compound from the relationship between pH control and residual stress.

In the present invention, the nickel smooth plating layer surface is subjected to nickel roughening by burnt plating.
Conventionally, in this nickel roughening treatment step, it is suitable for industrial production and cost to use a nickel bath in which about 15 to 25 g / l is dissolved as nickel. In general, techniques such as increasing the bath temperature, controlling the pH, and adding ammonium sulfate to the additive are generally used. However, in this case, the current density at which burning plating is started generally requires about 45 to 55 A / dm ² , which requires a rectifier having a large voltage and current capacity on the manufacturing facility.

The present invention, as a result of intensive studies to reduce the current value (current density) to start burning plating without changing the bath composition conditions, as a result, copper sulfate which is a sulfate compound as an additive metal without changing the nickel concentration, By adding at least one kind of metal such as chromium sulfate and iron sulfate, or a plurality of compounds thereof, to the nickel roughening treatment bath, more preferably in the range of 1/10 to 1/20 of the nickel metal concentration. It was possible to lower the current value for starting the burnt plating in the range of 5 to 15 A / dm ² by dissolving and adding at. The roughening shape of the nickel-roughened surface in this electrolytic bath is substantially the same as in the case of the conventional processing method, and it is dendritic microcrystalline grains that are characteristic of burnt plating, and is added to the microcrystalline grains. The metal was completely covered with nickel plating without any significant precipitation, and there was no problem in practical use.

  In the present invention, a conductive metal foil, in particular, a surface of a metal foil having a thickness of 35 μm or more is subjected to a smooth plating treatment with nickel of several μm, followed by a fine grained nickel roughening treatment. A metal foil that can be suitably used.

  The present invention is a method of subjecting at least one surface of a metal foil to a cathodic electrolytic nickel plating treatment and further subjecting the nickel plating surface of the foil to a fine nickel roughening treatment, and the metal foil is manufactured by rolling or electrolysis. It is one of foiled aluminum foil, copper foil, stainless steel foil, and iron foil. The electrolytic bath used for the nickel roughening treatment of fine particles on the surface of the selected metal foil is such that a nickel compound is dissolved in a sulfuric acid acid bath, and at least one kind of a small amount of copper, chromium, iron as an additive metal. Is added, and preferably the amount of added metal is in the range of 1/10 to 1/20 of the amount of metallic nickel dissolved in sulfuric acid, whereby not only a sound nickel roughening treatment is achieved, but also It was possible to reduce the current value required for processing.

In addition, when nickel smooth plating is given to rolled metal foil, the degreasing process which removes the rolling oil which remains on the rolled metal foil surface may be needed. Moreover, in the case of an aluminum foil, it is necessary to anodize the surface after degreasing, and man-hours are required for the treatment process.
On the other hand, since the electrolytic copper foil does not use rolling oil, there is no need for degreasing treatment, and it is excellent in terms of manufacturing cost and ease of handling. I will explain. However, although it has been confirmed by experiments that the present invention can be applied to all of the study materials (metal foils) and can be suitably used as a fuse material, the details thereof are omitted.

Hereinafter, an embodiment of the present invention will be described.
As a bath composition for subjecting at least one surface of the metal foil to cathodic electrolysis nickel plating, 40 g / l of nickel sulfate compound as nickel and 25 g / l of boric acid (as H ₃ BO ₃ ) are dissolved,
The pH of the bath was adjusted to 2.5 with dilute sulfuric acid, and the bath temperature was 35 ° C. A healthy nickel smooth plating layer could be obtained by setting the current density to 10 to 15 A / dm ² and the energization time to 30 to 60 seconds under the bath conditions.

Next, as a bath composition for subjecting the nickel smooth plating layer to a nickel roughening treatment of fine crystal grains, nickel sulfate compound as nickel is 18 ± 2 g / l, ammonium sulfate is 20 g / l, and copper sulfate compound is added as an additive metal compound to copper. 1.5 ± 0.5 g / l was dissolved, and the pH of the bath was adjusted to 3.0 to 4.0 with dilute sulfuric acid, and the bath temperature was set to about 30 ° C. By setting the current density to 35 to 40 A / dm ² and the energization time to 15 to 20 seconds under the conditions of this bath, a sound nickel burnt plating treatment could be performed and a fine nickel particle layer could be formed.
In addition, when copper which is an additional metal was not added to this bath, the same healthy nickel burn plating treatment could not be performed unless the current density was increased to 45 to 55 A / dm ² .

  Since the surface of the metal foil to which the fine nickel particle layer has been applied by the nickel roughening treatment is nickel fine particles adhering in a dendritic shape, there is a risk that the fine particles will easily fall off. For this reason, it is preferable to appropriately treat the surface of the fine nickel particle layer with a fine nickel smooth plating (nickel capsule plating) with the bath composition used in the nickel smooth plating step. Further, by treating the treated surface with a commercially available silane coupling agent at an appropriate concentration, the adhesion with the conductive resin can be improved. In particular, the silane coupling treatment with amino silane and epoxy silane is remarkable.

  Hereinafter, the present invention will be specifically described with reference to Examples.

[Example 1]
On the mat surface side, which was the liquid surface side when electrolytic copper foil having a nominal thickness of 70 μm manufactured by the electrolytic manufacturing method was applied, the thickness corresponding to 2.0 μm was obtained depending on the bath composition and cathodic electrolytic plating conditions shown below. Nickel smooth plating treatment was performed.
[Nickel smooth plating bath composition]
Nickel sulfate compound 40g / l as nickel
Boric acid 25g / l
pH 2.5
Bath temperature 35 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 10A / dm ²
Processing time 50 seconds

Subsequently, a nickel burn plating treatment was performed on the treated surface plated with nickel smooth according to the bath composition and cathodic electrolytic plating conditions described below.
[Nickel burn plating bath composition]
Nickel sulfate compound 20g / l as nickel
Copper sulfate compound As copper, 1.5 g / l
Ammonium sulfate 20g / l
pH 3.5
Bath temperature 30 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 38A / dm ²
Processing time 15 seconds Since the degree of burnt plating in this case is near the limit current density, fine nickel metal particles are in a state of being easily dropped off, and then the nickel smooth plating bath composition is not easily dropped off. As described above, nickel capsule plating was performed at a current density of 10 A / dm ² for 20 seconds.
The obtained surface-treated copper foil was evaluated for improvement in current conditions and adhesion to the resin substrate. Evaluation conditions will be described later. The evaluation results are shown in Table-1.

[Example 2]
The nickel smooth plating process and the nickel capsule plating process described in Example 1 were performed in the same manner except that the electrolytic copper foil used in Example 1 was subjected to nickel burn plating treatment under the following conditions.
[Nickel burn plating bath composition]
Nickel sulfate compound 20g / l as nickel
Copper sulfate compound 1.0 g / l as copper
Iron sulfate compound 1.0 g / l as iron
Ammonium sulfate 20g / l
pH 3.5
Bath temperature 30 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 38A / dm ²
Treatment time 15 seconds The obtained surface-treated copper foil was subjected to the same evaluation as in Example 1, and the evaluation results are also shown in Table 1.

[Example 3]
The nickel smooth plating process and the nickel capsule plating process described in Example 1 were performed in the same manner except that the electrolytic copper foil used in Example 1 was subjected to nickel burn plating treatment under the following conditions.
[Nickel burn plating bath composition]
Nickel sulfate compound 20g / l as nickel
Copper sulfate compound As copper, 0.5g / l
Iron sulfate compound As iron 0.5g / l
Chromium sulfate compound 0.5 g / l as chromium
Ammonium sulfate 20g / l
pH 3.5
Bath temperature 30 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 38A / dm ²
Treatment time 15 seconds The obtained surface-treated copper foil was subjected to the same evaluation as in Example 1, and the evaluation results are also shown in Table 1.

[Example 4]
The nickel smooth plating treatment and nickel capsule plating treatment described in Example 1 were similarly performed except that the electrolytic copper foil used in Example 1 was replaced with a rolled copper foil of 25 μm and subjected to nickel burn plating under the following conditions. did.
[Nickel burn plating bath composition]
Nickel sulfate compound 20g / l as nickel
Copper sulfate compound As copper, 1.5 g / l
Ammonium sulfate 20g / l
pH 3.5
Bath temperature 30 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 35A / dm ²
Treatment time 8 seconds The obtained surface-treated copper foil was evaluated in the same manner as in Example 1, and the evaluation results are also shown in Table 1.

[Comparative Example 1]
The nickel smooth plating process and the nickel capsule plating process described in Example 1 were performed in the same manner except that the electrolytic copper foil used in Example 1 was subjected to nickel burn plating treatment under the following conditions.
[Nickel burn plating bath composition]
Nickel sulfate compound 20g / l as nickel
Ammonium sulfate 20g / l
pH 3.5
Bath temperature 30 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 38A / dm ²
Treatment time 15 seconds The obtained surface-treated copper foil was subjected to the same evaluation as in Example 1, and the evaluation results are also shown in Table 1.

[Comparative Example 2]
The nickel smooth plating process and the nickel capsule plating process described in Example 1 were similarly performed except that the electrolytic copper foil used in Example 1 was subjected to nickel burn plating under the conditions where the cathode electrolysis current density was changed to the following. did.
[Nickel burn plating bath composition]
Nickel sulfate compound 20g / l as nickel
Ammonium sulfate 20g / l
pH 3.5
Bath temperature 30 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 46A / dm ²
Treatment time 15 seconds The obtained surface-treated copper foil was subjected to the same evaluation as in Example 1, and the evaluation results are also shown in Table 1.

[Comparative Example 3]
The nickel smooth plating process and the nickel capsule plating process described in Example 1 were the same except that the electrolytic copper foil used in Example 1 was replaced with a rolled copper foil of 25 μm and nickel burn plating was performed under the following current conditions. I gave it.
[Nickel burn plating bath composition]
Nickel sulfate compound 20g / l as nickel
Ammonium sulfate 20g / l
pH 3.5
Bath temperature 30 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 35A / dm ²
Treatment time 8 seconds The obtained surface-treated copper foil was evaluated in the same manner as in Example 1, and the evaluation results are also shown in Table 1.

[Comparative Example 4]
The nickel smooth plating process and the nickel capsule plating process described in Example 1 were the same except that the electrolytic copper foil used in Example 1 was replaced with a rolled copper foil of 25 μm and nickel burn plating was performed under the following current conditions. Applied to
[Nickel burn plating bath composition]
Nickel sulfate compound 20g / l as nickel
Ammonium sulfate 20g / l
pH 3.5
Bath temperature 30 ° C
[Cathode electrolysis conditions]
Cathodic electrolysis current density 44A / dm ²
Treatment time 8 seconds The obtained surface-treated copper foil was evaluated in the same manner as in Example 1, and the evaluation results are also shown in Table 1.

[Evaluation item]
1. Current conditions for nickel burnt plating;
The increase / decrease value of the current density was converted into an index value with the current density at which nickel burn plating treatment was started in a sulfuric acid acidic nickel bath composition based on a known bath composition (Comparative Example-2) as 100.

2. Adhesion strength;
As a method for evaluating the degree of adhesion between the surface-treated copper foil obtained in Examples 1 to 4 and Comparative Examples 1 to 4 and the functional resin, the surface-treated copper foil and a commercially available epoxy resin substrate (FR-4) The substrate is pressed for 60 minutes under a heating and pressing condition of a lamination temperature of 180 ° C. and a surface pressure of 15 kg / cm ² , and then the adhesion strength between the surface-treated copper foil and the epoxy resin with a 10 mm width is measured by a peel strength measuring instrument. did.

  According to the above-described embodiment, the limiting current density is obtained by adding 1/10 to 1/20 of the nickel concentration of the nickel bath to at least one kind of metal of copper, iron, and chromium as the additive metal to the nickel burn plating bath. The current value could be reduced by 17%. Those subjected to the roughening treatment under the conditions of each Example achieved satisfactory burn-off plating, and the adhesion strength with the epoxy resin was satisfactory. Although not shown in Table 1, by selecting and depositing a silane coupling agent having an appropriate concentration on the surface after the nickel roughening treatment, preferably by surface treatment with an epoxy silane coupling agent, The adhesion strength with the FR-4 base material could be further improved by about 0.5 to 1.5 kN / m.

  As described above, according to the nickel roughening treatment method of the present invention, the nickel burn plating current value can be lowered without significantly changing the composition of the known nickel plating bath, and the cost of the cathodic electrolysis treatment can be greatly reduced. Reduction was achieved.

Claims (5)

  At least one surface of the metal foil is subjected to a cathodic electrolytic nickel plating treatment to provide a nickel smooth plating layer, and a nickel roughening treatment is applied to the surface of the nickel smooth plating layer to provide a fine nickel particle layer. Metal foil surface treatment method.   2. The surface treatment method for a metal foil according to claim 1, wherein the metal foil is any one of an aluminum foil, a copper foil, a stainless steel foil, and an iron foil manufactured and produced by rolling or electrolysis.   2. The nickel roughening treatment is characterized in that an electrolytic treatment is performed in an electrolytic bath in which a nickel compound is dissolved in a sulfuric acid bath and at least one of a trace amount of copper, chromium, and iron is added as an additional metal. The surface treatment method of metal foil as described in 2.   4. The surface treatment method for a metal foil according to claim 3, wherein the addition amount of the additive metal is in a range of 1/10 to 1/20 of the amount of metallic nickel dissolved in sulfuric acid.   The metal foil surface treatment method according to any one of claims 1 to 4, wherein the surface of the fine nickel particle layer is subjected to cathodic electrolytic nickel plating to provide a nickel capsule plating layer.