JP2016188436A - Copper foil for printed circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper foil for a printed circuit capable of suppressing the phenomenon that coarsened grains are peeled off from the surface of a copper foil and treatment unevenness, increasing peel strength and also improving heat resistance.SOLUTION: Provided is a copper foil for a printed circuit characterized in that the primary grain layer of copper is formed on the surface of a copper foil, and thereafter, the secondary grain layer of a three-dimensional alloy made of copper, cobalt and nickel (copper-cobalt-nickel alloy), in which the average value of the rugged height of the coarsened face of the copper foil with a laser microscope is 1,500.SELECTED DRAWING: Figure 4

Description

The present invention relates to a copper foil for printed circuit, and in particular, after forming a primary particle layer of copper on the surface of the copper foil, a secondary particle layer formed by copper-cobalt-nickel alloy plating is formed thereon. The present invention relates to a copper foil for a printed circuit that can reduce the occurrence of powder falling from the copper foil, increase the peel strength, and improve the heat resistance.
The copper foil for printed circuits of the present invention is particularly suitable for fine pattern printed circuits and flexible printed circuit boards, for example.

Copper and copper alloy foils (hereinafter referred to as copper foils) have greatly contributed to the development of electrical and electronic industries, and are indispensable particularly as printed circuit materials. Copper foil for printed circuit is generally used to produce a copper-clad laminate by laminating and bonding to a base material such as a synthetic resin board or film through an adhesive or under high temperature and high pressure without using an adhesive. In order to form a circuit, a necessary circuit is printed through a resist coating and exposure process, and then an etching process for removing unnecessary portions is performed.
Finally, the required elements are soldered to form various printed circuit boards for the electronic device. Although the copper foil for printed circuit boards differs in the surface (roughening surface) adhere | attached with a resin base material, and a non-adhesion surface (glossy surface), many methods are each proposed.

For example, the requirements for the roughened surface formed on the copper foil are as follows: 1) No oxidation discoloration during storage, 2) High peel strength with substrate, high temperature heating, wet processing, soldering, chemicals It is sufficient even after treatment or the like, and 3) that there is no so-called lamination stain that occurs after lamination with the substrate and etching.
The roughening treatment of the copper foil plays a major role as determining the adhesiveness between the copper foil and the base material. As this roughening treatment, a copper roughening treatment in which copper was electrodeposited was initially employed. However, various techniques were proposed thereafter, and copper − was used for the purpose of improving the heat-resistant peel strength, hydrochloric acid resistance and oxidation resistance. Nickel roughening is established as one typical processing method.
The present applicant has proposed a copper-nickel roughening treatment (see Patent Document 1) and has achieved results.
The copper-nickel-treated surface exhibits a black color, and particularly in the rolled foil for flexible substrates, this copper-nickel-treated black color has been recognized as a symbol as a product.

However, while the copper-nickel roughening treatment is excellent in heat-resistant peel strength, oxidation resistance and hydrochloric acid resistance, it is difficult to etch with an alkaline etchant that has recently become important as a fine pattern treatment, and has a pitch of 150 μm. When forming a fine pattern having a circuit width or less, the processing layer becomes an etching residue.
Therefore, the present applicant has previously developed a Cu—Co treatment (see Patent Literature 2 and Patent Literature 3) and a Cu—Co—Ni treatment (see Patent Literature 4) as the fine pattern treatment.
These roughening treatments were good in terms of etching property, alkali etching property and hydrochloric acid resistance, but again proved that the heat-resistant peel strength was reduced when an acrylic adhesive was used, and oxidation resistance was also improved. It was not enough as expected and the color did not reach black, and it was brown to dark brown.

With the recent trend toward fine patterning and diversification of printed circuits, 1) having heat-resistant peel strength (particularly when using an acrylic adhesive) and hydrochloric acid resistance comparable to those of Cu-Ni treatment; ) Able to etch a printed circuit with a pitch of 150 μm or less with an alkaline etchant. 3) Improve oxidation resistance (oxidation resistance in an oven at 180 ° C. × 30 minutes) as in the case of Cu—Ni treatment. 4) The blackening treatment similar to that in the Cu-Ni treatment is further required.

That is, as the circuit becomes thinner, the tendency of the circuit to be easily peeled off by the hydrochloric acid etching solution becomes stronger, and the prevention thereof is necessary. When the circuit becomes thinner, the circuit is also easily peeled off due to a high temperature during processing such as soldering, and the prevention thereof is also necessary. As fine patterning progresses, for example, it is no longer necessary to be able to etch a printed circuit having a pitch of 150 μm or less with a CuCl ₂ etchant, and alkali etching is becoming a necessary requirement as resists and the like are diversified. The black surface is also important from the viewpoint of copper foil fabrication and chip mounting in terms of increasing alignment accuracy and heat absorption.

In response to such a request, the present applicant forms a cobalt plating layer or a cobalt-nickel alloy plating layer on the surface of the copper foil and then forms a cobalt plating layer or a cobalt-nickel alloy plating layer as a printed circuit copper foil. Of course, it has the above-mentioned properties comparable to those of Cu-Ni treatment, as well as many of the general properties described above, and does not reduce the heat-resistant peel strength when using an acrylic adhesive, We have succeeded in developing a copper foil treatment method that has excellent oxidation resistance and a black surface color (see Patent Document 5).
Preferably, after the cobalt plating layer or the cobalt-nickel alloy plating layer is formed, rust prevention represented by single coating treatment of chromium oxide or mixed coating treatment of chromium oxide and zinc and / or zinc oxide. Processing is performed.

Later, as the development of electronic devices progressed, the miniaturization and high integration of semiconductor devices further progressed, and the processing performed in the manufacturing process of these printed circuits became even higher and the devices were in use after becoming products. Due to heat generation, a decrease in the bonding force between the copper foil and the resin base material has become a problem.
For this reason, a copper foil for a printed circuit that forms a cobalt plating layer or a cobalt-nickel alloy plating layer after a roughening treatment by copper-cobalt-nickel alloy plating on the surface of the copper foil established in Patent Document 5 is provided. In the processing method, an invention for improving the heat-resistant peelability was performed.

This is a method for treating a copper foil for a printed circuit in which a cobalt-nickel alloy plating layer is formed on the surface of the copper foil after a roughening treatment by copper-cobalt-nickel alloy plating, and further a zinc-nickel alloy plating layer is formed. is there. It is a very effective invention and has become one of the main products of copper foil circuit materials today.

About the process of the copper foil for printed circuits which forms the cobalt-nickel alloy plating layer after the roughening process by copper-cobalt-nickel alloy plating on the surface of copper foil, and also forms a zinc-nickel alloy plating layer, this inventor Made many proposals and made some significant progress in the characteristics of copper foil for printed circuits. The initial techniques of the roughening treatment by copper-cobalt-nickel alloy plating are disclosed in Patent Literature 6, Patent Literature 7, and Patent Literature 8.

However, because the shape of the roughened particles made of copper-cobalt-nickel alloy plating formed on the surface of the copper foil is dendritic, it peels off from the upper part or the root of the dendron, A problem commonly referred to as the powdering phenomenon occurred.

This powder-off phenomenon is a troublesome problem, and the roughened layer of copper-cobalt-nickel alloy plating has excellent adhesion to the resin layer and is also excellent in heat resistance. Nevertheless, as described above, the particles easily fall off due to an external force, resulting in problems such as peeling due to “rubbing” during processing, contamination of the roll with peeling powder, and etching residue due to peeling powder.

JP-A-52-145769 Japanese Examined Patent Publication No. 63-2158 Japanese Patent Application No. 1-112227 Japanese Patent Application No. 1-112226 Japanese Patent Publication No. 6-54831 Japanese Patent No. 2849059 Japanese Patent Laid-Open No. 4-96395 JP-A-10-18075

The object of the present invention is the phenomenon that the roughening particles formed in a dendritic shape are peeled off from the surface of the copper foil in the most basic roughening treatment comprising copper-cobalt-nickel alloy plating, and are generally referred to as powdering. The present invention provides a printed circuit copper foil capable of suppressing processing unevenness, increasing peel strength, and improving heat resistance. Along with the development of electronic devices, the miniaturization and high integration of semiconductor devices have further advanced, and the processing performed in the manufacturing process of these printed circuits has become more severe. It is an object of the present invention to provide a technology that meets these requirements.

The present invention provides the following inventions.
1) A copper foil for printed circuit, in which a primary particle layer of copper is formed on the surface of the copper foil, and then a secondary particle layer of a ternary alloy composed of copper, cobalt and nickel is formed on the primary particle layer. And when the unevenness height of the roughened surface was measured using a Keyence Corporation laser microscope (model: VK8500) and the magnification was set to 1000, the average value in the effective area of 786432 μm ² was 1500. The copper foil for printed circuits characterized by the above.
2) The average particle diameter of the primary particle layer of copper is 0.25 to 0.45 μm, and the average particle diameter of the secondary particle layer made of a ternary alloy made of copper, cobalt and nickel is 0.35 μm or less. The printed circuit copper foil according to 1), which is characterized in that it is present.
3) The copper foil for printed circuit as described in 1) or 2) above, wherein the primary particle layer and the secondary particle layer are electroplating layers.
4) The above-mentioned 1) to 3), wherein the secondary particles are one or a plurality of dendritic particles grown on the primary particles or a normal plating layer grown on the primary particles. The copper foil for printed circuits as described in any one of Claims.
5) The copper foil for a printed circuit according to any one of 1) to 4) above, wherein an average height of the unevenness of the roughened surface by a laser microscope is 1500 or more and 2000 or less. .
6) The printed circuit copper foil according to any one of 1) to 5) above, wherein the peel strength of the primary particle layer and the secondary particle layer is 0.80 kg / cm or more.
7) The copper foil for a printed circuit according to any one of 1) to 6) above, wherein the peel strength of the primary particle layer and the secondary particle layer is 0.90 kg / cm or more.
8) A copper-clad laminate using the copper foil according to any one of 1) to 7) above.
9) A printed wiring board using the copper foil according to any one of 1) to 7) above.
10) A printed circuit board using the copper foil according to any one of 1) to 7) above.
11) An electronic device using the printed wiring board according to 9) above.

Further, a printing in which a cobalt-nickel alloy plating layer is formed on the secondary particle layer by the copper-cobalt-nickel alloy plating, and a zinc-nickel alloy plating layer is further formed on the cobalt-nickel alloy plating layer. A copper foil for a circuit can be provided.
The cobalt-nickel alloy plating layer may have a cobalt adhesion amount of 200 to 3000 μg / dm ² and a cobalt ratio of 60 to 66 mass%.
It said zinc - in nickel alloy plating layer, the total amount in the range of 150~500μg / dm ^2, zinc nickel amount is 50 [mu] g / dm ² or more ranges, and the nickel ratio is in the range of 0.16 to 0.40 -A nickel alloy plating layer can be formed.

Moreover, a rust prevention treatment layer can be formed on the zinc-nickel alloy plating layer.
About this antirust process, the independent film processing of chromium oxide or the mixed film processing layer of chromium oxide, zinc, and / or zinc oxide can be formed, for example. Furthermore, a silane coupling layer can be formed on the mixed film treatment layer.
The printed circuit copper foil can produce a copper-clad laminate bonded to a resin substrate by thermocompression bonding without using an adhesive.

In the present invention, the most basic roughening treatment consisting of copper-cobalt-nickel alloy plating, dendritic roughening particles are peeled off from the surface of the copper foil, and the phenomenon generally referred to as powdering is suppressed. And the copper foil for printed circuits which can raise peel strength and can improve heat resistance is provided.
In addition, the number of abnormally grown dendritic and wedge-shaped particles is reduced and the particle diameter is uniform, so that the etching property is good and it is possible to eliminate rough particle residues at the resin substrate interface after copper foil etching. It becomes.
Along with the development of electronic equipment, the miniaturization and high integration of semiconductor devices have further progressed, and the processing performed in the manufacturing process of these printed circuits has been made more severe. Has a technical effect to answer.

It is a conceptual explanatory drawing which shows the mode of the powder fall at the time of performing the roughening process which consists of copper-cobalt-nickel alloy plating on the conventional copper foil. Conceptual explanation of a copper foil treatment layer without powder falling, in which a primary particle layer is formed in advance on a copper foil and a secondary particle layer made of copper-cobalt-nickel alloy plating is formed on the primary particle layer of the present invention. FIG. It is the microscope picture of the surface at the time of performing the roughening process which consists of copper-cobalt-nickel alloy plating on the conventional copper foil. The primary particle layer is previously formed on the copper foil of the present invention, and the secondary particle layer made of copper-cobalt-nickel alloy plating is formed on the primary particle layer. It is a micrograph.

The copper foil used in the present invention may be either an electrolytic copper foil or a rolled copper foil. Usually, the surface of the copper foil that adheres to the resin base material, that is, the roughened surface, has a “fisture” on the surface of the copper foil after degreasing for the purpose of improving the peel strength of the copper foil after lamination. A roughening treatment is performed to perform electrodeposition. Although the electrolytic copper foil has irregularities at the time of manufacture, the irregularities are further increased by enhancing the convex portions of the electrolytic copper foil by roughening treatment.
The content of treatment may be somewhat different between the rolled copper foil and the electrolytic copper foil. In the present invention, including such pretreatment and finishing treatment, a known treatment related to copper foil roughening is included as necessary, and is referred to as “roughening treatment”.

This roughening treatment is performed by copper-cobalt-nickel alloy plating (in the following description, the roughening treatment of copper-cobalt-nickel alloy plating is performed to clarify the difference from the previous step. Is called “secondary particle layer”), as described above, simply forming a copper-cobalt-nickel alloy plating layer on the copper foil causes problems such as powder falling as described above. To do.

The microscope picture of the surface of the copper foil which formed the copper-cobalt-nickel alloy plating layer on copper foil is shown in FIG. As shown in FIG. 3, fine particles developed in a dendritic shape can be seen. In general, the fine particles developed in a dendritic shape shown in FIG. 3 are produced at a high current density.
When processed at such a high current density, particle nucleation during initial electrodeposition is suppressed, and new particle nuclei are formed at the tip of the particle. Will grow.
Therefore, to prevent this, when electroplating is performed at a reduced current density, there is no sharp rise, the number of particles increases, and rounded particles grow. Even under such circumstances, powder falling is slightly improved, but sufficient peel strength cannot be obtained, which is not sufficient for achieving the object of the present invention.

The state of powder falling when the copper-cobalt-nickel alloy plating layer as shown in FIG. 3 is formed is shown in the conceptual explanatory diagram of FIG. The cause of this powder fall is that fine particles are formed in a dendritic shape on the copper foil as described above. However, the dendritic particles are easily broken by an external force and fall off from the root. The fine dendritic particles cause peeling due to “rubbing” during the process, contamination of the roll with peeling powder, and etching residue due to peeling powder.

In the present invention, after forming a primary particle layer of copper in advance on the surface of the copper foil, a secondary particle layer made of a ternary alloy made of copper, cobalt and nickel is formed on the primary particle layer. To do. FIG. 4 shows a micrograph of the surface on which the primary particles and secondary particles are formed on the copper foil (details will be described later).
This eliminates peeling due to "rubbing" during processing, dirt on the roll due to peeling powder, etching residue due to peeling powder, that is, it can suppress the phenomenon called powder falling and processing unevenness, increase peel strength, and The copper foil for printed circuits which can improve heat resistance can be obtained.

The average particle size of the primary particle layer is 0.25 to 0.45 μm, and the average particle size of the secondary particle layer made of a ternary alloy made of copper, cobalt and nickel is 0.35 or less μm. As is apparent from the examples shown in (1), this is the optimum condition for preventing powder falling.
The lower limit of the average particle diameter of the primary particle layer is preferably 0.27 μm, more preferably 0.29 μm, 0.30 μm, 0.33 μm or more.
The upper limit of the average particle diameter of the primary particle layer is preferably 0.44 μm, more preferably 0.43 μm, 0.40 μm, and 0.39 μm.
The upper limit of the average particle diameter of the secondary particle layer is preferably 0.34 μm, more preferably 0.33 μm, 0.32 μm, 0.31 μm, 0.30 μm, 0.28 μm, 0.27 μm. .
Further, the lower limit of the average particle diameter of the secondary particle layer is not particularly limited. For example, 0.001 μm or more, or 0.01 μm or more, or 0.05 μm or more, or 0.09 μm or more, or 0.10 μm. Or more, or 0.12 μm or more, or 0.15 μm or more.
The primary particle layer and the secondary particle layer are formed by an electroplating layer. The secondary particles are characterized by one or more dendritic particles grown on the primary particles. Or normal plating grown on the primary particles. That is, in the present specification, when the term “secondary particle layer” is used, a normal plating layer such as overlay plating is also included. Further, the secondary particle layer may be a layer having one or more layers formed of roughened particles, or may be a layer having one or more normal plating layers, and is normal with a layer formed of roughened particles. A layer having one or more plating layers may be used.
The peel strength of the primary particle layer and the secondary particle layer thus formed can be 0.80 kg / cm or more, and further, the peel strength can be 0.90 kg / cm or more.

In the copper foil in which the primary particle layer and the secondary particle layer are formed, more importantly, the average value of the unevenness of the roughened surface by the laser microscope is 1500 or more, preferably 1600 or more, further 1700 or more, 1800 As mentioned above, it is preferable to set it as 1900 or more.
In addition, although it is not necessary to provide the upper limit of the average value of the unevenness of the roughened surface by the laser microscope, for example, 4500 or less, 3500 or less, 3100 or less, or 3000 or less, or 2900 or less, or 2800 or less. It is.
A feature of the present invention is to form a layered treatment layer in which a primary particle layer and a secondary particle layer are formed. The roughened treatment layer is formed on one large primary particle layer as shown in FIG. A state where one or two small secondary particle layers are formed is an ideal state. Actually, there are cases where the primary particles and the secondary particles are overlapped with each other in some stages, forming a complicated layer, and it is difficult to estimate the layer height from the particle diameter. As a general tendency, for example, when secondary particles that are as large as or larger than the primary particles are formed on the smaller primary particles, when smaller secondary particles are formed thicker on the larger primary particles Although not preferable, it is difficult to specifically define this combination. Therefore, in the present invention, by controlling with a macro index “average height of unevenness of roughened surface by laser microscope”, a stable peel can be obtained even if the combination of primary particles and secondary particles is not clearly understood. It is characterized by finding a roughened layer having an effect of improving strength and preventing a stable powder falling phenomenon.
The “roughened surface” in the “average height of unevenness of the roughened surface by a laser microscope” means the surface on the final product, and the surface after the heat-resistant layer and rust-proof layer are formed. Including.

When the average value of the unevenness of the roughened surface by the laser microscope is less than 1500, the secondary particle layer is stacked in the copper foil on which the primary particle layer and the secondary particle layer are formed, so that As a result, the uneven height difference is reduced, and the powder falling phenomenon is likely to occur.
About the measurement method of the average value of the unevenness of the roughened surface by a laser microscope, the magnification was set to 1000 times using a Keyence Corporation laser microscope VK8500, and the result of measuring the roughened surface was The height of the unevenness is made into a histogram by measurement analysis in an effective area of 786432 μm ² (measurement area 100%), and the setting is performed by a method for obtaining the average value.

(Copper primary particle plating conditions)
An example of the plating conditions for the primary particles of copper is as follows.
In addition, this plating condition shows a suitable example to the last, and the average particle diameter formed on copper foil plays the role of powder omission prevention in the primary particle of copper. Therefore, as long as the average particle diameter falls within the scope of the present invention, the plating conditions other than those indicated below are not disturbed. The present invention includes these.
Liquid composition: Copper 10-20 g / L, sulfuric acid 50-100 g / L
Liquid temperature: 25-50C
Current density: 1 to 58 A / dm ²
Coulomb amount: 4 to 81 As / dm ²

(Plating conditions for secondary particles)
As described above, this plating condition is merely a suitable example, the secondary particles are formed on the primary particles, and the average particle diameter plays a role in preventing powder falling. is there. Therefore, as long as the average particle diameter falls within the scope of the present invention, the plating conditions other than those indicated below are not disturbed. The present invention includes these.
Liquid composition: Copper 10-20 g / L, nickel 5-15 g / L, cobalt 5-15 g / L
pH: 2-3
Liquid temperature: 30-50C
Current density: 24 to 50 A / dm ²
Coulomb amount: 34 to 48 As / dm ²

(Plating conditions for forming the heat-resistant layer 1)
In the present invention, a heat-resistant layer can be further formed on the secondary particle layer. The plating conditions are shown below.
Liquid composition: Nickel 5-20 g / L, cobalt 1-8 g / L
pH: 2-3
Liquid temperature: 40-60C
Current density: 5 to 20 A / dm ²
Coulomb amount: 10-20 As / dm ²

(Plating conditions for forming the heat-resistant layer 2)
The present invention can further form the following heat-resistant layer on the secondary particle layer. The plating conditions are shown below.
Liquid composition: nickel 2-30 g / L, zinc 2-30 g / L
pH: 3-4
Liquid temperature: 30-50C
Current density: 1 to ^{2 A} / dm ²
Coulomb amount: 1-2 As / dm ²

(Plating conditions for forming a rust prevention layer)
The present invention can further form the following antirust layer. The plating conditions are shown below. In the following, conditions for the immersion chromate treatment are shown, but electrolytic chromate treatment may be used.
Liquid composition: potassium dichromate 1-10 g / L, zinc 0-5 g / L
pH: 3-4
Liquid temperature: 50-60C
Current density: 0 to ^{2 A} / dm ² (for immersion chromate treatment)
Coulomb amount: 0 to ^{2 As} / dm ² (for immersion chromate treatment)

(Type of weather-resistant layer)
As an example, application of a diaminosilane aqueous solution can be mentioned.

The copper-cobalt-nickel alloy plating as the secondary particles is a ternary alloy of 10-30 mg / dm ² copper-100-3000 μg / dm ² cobalt-50-500 μg / dm ² nickel by electrolytic plating. A layer can be formed.
When the Co adhesion amount is less than 100 μg / dm ² , the heat resistance is deteriorated and the etching property is also deteriorated. If the amount of Co adhesion exceeds 3000 μg / dm ² , it is not preferable when the influence of magnetism must be taken into account, etching spots occur, and deterioration of acid resistance and chemical resistance can be considered.

When the Ni adhesion amount is less than 50 μg / dm ² , the heat resistance deteriorates. On the other hand, when the Ni adhesion amount exceeds 500 μg / dm ² , the etching property is lowered. That is, although it is not at a level where etching remains and etching cannot be performed, it becomes difficult to form a fine pattern.
Preferred Co deposition amount is 500~2000μg / dm ^2, and preferably nickel coating weight is 50~300μg / dm ^2.
From the above, it can be said that the adhesion amount of the copper-cobalt-nickel alloy plating is desirably 10 to 30 mg / dm ² copper-100 to 3000 μg / dm ² cobalt-50 to 500 μg / dm ² nickel. Each adhesion amount of the ternary alloy layer is a desirable condition, and a range exceeding this amount is not denied.

Here, the etching stain means that Co remains without being dissolved when etched with copper chloride, and the etching residue means that Ni remains undissolved when alkaline etching is performed with ammonium chloride. It means to end.
In general, when a circuit is formed, an alkaline etching solution and a copper chloride based etching solution as described in the following examples are used. Although this etching solution and etching conditions are versatile, it should be understood that they are not limited to these conditions and can be arbitrarily selected.

In the present invention, as described above, after the secondary particles are formed (after the roughening treatment), a cobalt-nickel alloy plating layer can be formed on the roughened surface.
The cobalt-nickel alloy plating layer preferably has a cobalt adhesion amount of 200 to 3000 μg / dm ² and a cobalt ratio of 60 to 66 mass%. This treatment can be regarded as a kind of rust prevention treatment in a broad sense.
This cobalt-nickel alloy plating layer needs to be performed to such an extent that the peel strength between the copper foil and the substrate is not substantially lowered. A cobalt adhesion amount of less than 200 μg / dm ² is not preferable because the heat-resistant peel strength is lowered, the oxidation resistance and chemical resistance are deteriorated, and the treated surface becomes reddish.
On the other hand, when the cobalt adhesion amount exceeds 3000 μg / dm ² , it is not preferable when the influence of magnetism must be taken into consideration, etching spots occur, and deterioration of acid resistance and chemical resistance is considered. A preferable cobalt adhesion amount is 400 to 2500 μg / dm ² .

Moreover, when there is much cobalt adhesion amount, it may become a cause of generation | occurrence | production of a soft etching penetration. From this, it can be said that the ratio of cobalt is preferably 60 to 66 mass%.
As will be described later, the direct cause of soft etching soaking is a heat-resistant rust-preventing layer consisting of a zinc-nickel alloy plating layer, but cobalt may also cause stains during soft etching. The above adjustment is a more desirable condition.
On the other hand, when the nickel adhesion amount is small, the heat-resistant peel strength is lowered, and the oxidation resistance and chemical resistance are lowered. Further, when the nickel adhesion amount is too large, the alkali etching property is deteriorated, so it is desirable to determine the balance with the cobalt content.

In the present invention, a zinc-nickel alloy plating layer can be further formed on the cobalt-nickel alloy plating. The total amount of the zinc-nickel alloy plating layer is 150 to 500 μg / dm ² , and the nickel ratio is 16 to 40% by mass. This has a role of a heat-resistant rust-proof layer. This condition is also a preferable condition, and other known zinc-nickel alloy plating can be used. It will be understood that this zinc-nickel alloy plating is a preferred additional condition in the present invention.
The processing performed in the manufacturing process of the printed circuit becomes much higher, and there is heat generation during use of the device after it has become a product. For example, in a so-called two-layer material in which a copper foil is bonded to a resin by thermocompression bonding, the resin receives heat of 300 ° C. or higher. Even in such a situation, it is necessary to prevent a decrease in bonding force between the copper foil and the resin base material, and this zinc-nickel alloy plating is effective.

In addition, in the conventional technology, in a minute circuit provided with a zinc-nickel alloy plating layer in a two-layer material in which a copper foil is bonded to a resin by thermocompression bonding, discoloration due to penetration into the edge portion of the circuit is caused during soft etching. Occur. Nickel has an effect of suppressing penetration of an etching agent (etching aqueous solution of H ₂ SO ₄ : 10 wt%, H ₂ O ₂ : 2 wt%) used in soft etching.
As described above, the total amount of the zinc-nickel alloy plating layer is 150 to 500 μg / dm ² , the lower limit of the nickel ratio in the alloy layer is 16% by mass, the upper limit is 40% by mass, and nickel A content of 50 μg / dm ² or more serves as a heat-resistant rust-preventing layer and suppresses the penetration of the etchant used during soft etching to prevent weakening of the circuit joint strength due to corrosion. It has the effect that it can be done.

In addition, when the total amount of the zinc-nickel alloy plating layer is less than 150 μg / dm ² , the heat resistance and rust prevention ability is lowered and it becomes difficult to play a role as a heat resistance rust prevention layer, and when the total amount exceeds 500 μg / dm ² The hydrochloric acid resistance tends to deteriorate.
Moreover, if the lower limit of the nickel ratio in the alloy layer is less than 16% by mass, the amount of penetration at the time of soft etching exceeds 9 μm, which is not preferable. The upper limit of 40% by mass of the nickel ratio is a technical limit value at which a zinc-nickel alloy plating layer can be formed.

As described above, according to the present invention, a cobalt-nickel alloy plating layer and further a zinc-nickel alloy plating layer may be sequentially formed on the copper-cobalt-nickel alloy plating layer as the secondary particle layer as necessary. it can. The total amount of cobalt and nickel deposited in these layers can also be adjusted. It is desirable that the total deposition amount of cobalt is 300 to 4000 μg / dm ² and the total deposition amount of nickel is 150 to 1500 μg / dm ² .
When the total deposition amount of cobalt is less than 300 μg / dm ² , the heat resistance and chemical resistance are lowered, and when the total deposition amount of cobalt exceeds 4000 μg / dm ² , etching spots may occur. Moreover, if the total adhesion amount of nickel is less than 150 μg / dm ² , heat resistance and chemical resistance are lowered. When the total adhesion amount of nickel exceeds 1500 μg / dm ² , an etching residue is generated.
Preferably, the total adhesion amount of the cobalt is 1500~3500μg / dm ^2, and the total deposition amount of nickel is 500~1000μg / dm ^2. If the above conditions are satisfied, the conditions described in this paragraph need not be particularly limited.

Thereafter, a rust prevention treatment is performed as necessary. In the present invention, a preferable antirust treatment is a coating treatment of chromium oxide alone or a mixture coating treatment of chromium oxide and zinc / zinc oxide. Chromium oxide and zinc / zinc oxide mixture coating treatment is zinc or zinc comprising zinc oxide and chromium oxide by electroplating using a plating bath containing zinc salt or zinc oxide and chromate. It is the process which coat | covers the antirust layer of a chromium group mixture.
As a plating bath, typically, at least one kind of dichromate such as K ₂ Cr ₂ O ₇ and Na ₂ Cr ₂ O ₇ or CrO ₃ and a water-soluble zinc salt such as ZnO or ZnSO ₄ · 7H are used. A mixed aqueous solution of at least one kind of ₂ O and an alkali hydroxide is used. A typical plating bath composition and electrolysis conditions are as follows.

The copper foil thus obtained has excellent heat resistance peel strength, oxidation resistance and hydrochloric acid resistance. In addition, a printed circuit having a pitch of 150 μm or less can be etched with a CuCl ₂ etching solution, and alkali etching can be performed. In addition, penetration into the circuit edge portion during soft etching can be suppressed.
As the soft etching solution, an aqueous solution of H ₂ SO ₄ : 10 wt% and H ₂ O ₂ : 2 wt% can be used. Processing time and temperature can be adjusted arbitrarily.
As the alkaline etching solution, for example, NH ₄ OH: 6 mol / liter, NH ₄ Cl: 5 mol / liter, CuCl ₂ : 2 mol / liter (temperature: 50 ° C.) and the like are known.

The copper foil obtained in all the above steps has a black to gray color. Black to gray is significant in terms of alignment accuracy and high heat absorption rate. For example, printed circuit boards including rigid boards and flexible boards are mounted with components such as ICs, resistors, and capacitors in an automatic process, and chip mounting is performed while reading circuits with sensors. At this time, alignment on the copper foil treated surface may be performed through a film such as Kapton. This also applies to positioning when forming a through hole.
The closer the processing surface is to black, the better the light absorption and the higher the positioning accuracy. Furthermore, when producing a substrate, the copper foil and the film are often cured and bonded together while applying heat. At this time, when heating is performed by using long waves such as far infrared rays and infrared rays, the heating efficiency is improved when the color tone of the treated surface is black.

Finally, if necessary, silane treatment for applying a silane coupling agent to at least the roughened surface on the rust preventive layer is performed mainly for the purpose of improving the adhesive force between the copper foil and the resin substrate.
Examples of the silane coupling agent used for the silane treatment include olefin silane, epoxy silane, acrylic silane, amino silane, and mercapto silane, which can be appropriately selected and used. .
The application method may be any of spraying a silane coupling agent solution by spraying, coating with a coater, dipping, pouring and the like. For example, Japanese Examined Patent Publication No. 60-15654 describes that the adhesion between the copper foil and the resin substrate is improved by performing a chromate treatment on the rough side of the copper foil followed by a silane coupling agent treatment. . Refer to this for details. Thereafter, if necessary, an annealing treatment may be performed for the purpose of improving the ductility of the copper foil.

Hereinafter, description will be made based on Examples and Comparative Examples. In addition, a present Example is an example to the last, and is not restrict | limited only to this example. That is, other aspects or modifications included in the present invention are included. In addition, 18 μm of standard rolled copper foil TPC (tough pitch copper standardized in JIS H3100 C1100) was used for the raw foils of the following examples and comparative examples.

Example 1 to Example 6
A primary particle layer (Cu) and a secondary particle layer (copper-cobalt-nickel alloy plating) were formed on the rolled copper foil under the conditions shown below.
The bath composition and plating conditions used are as follows.
[Bath composition and plating conditions]

(A) Formation of primary particle layer (Cu plating)
Liquid composition: Copper 15g / L, sulfuric acid 75g / L
Liquid temperature: 25-30 degreeC
Current density: 1 to 70 A / dm ²
Coulomb amount: ^{2 to} 90 As / dm ²
(B) Formation of secondary particle layer (Cu—Co—Ni alloy plating)
Liquid composition: Copper 15g / L, nickel 8g / L, cobalt 8g / L
pH: 2
Liquid temperature: 40 ° C
Current density: 10 to 50 A / dm ²
Coulomb amount: 10-80 As / dm ²

By adjusting the conditions of the formation of the primary particle layer (Cu plating) and the formation of the secondary particle layer (Cu-Co-Ni alloy plating), the average value of the unevenness of the roughened surface by the laser microscope is It was made to become 1500 or more. The surface area was measured by the measurement method using the laser microscope.

(Comparative Example 1-Comparative Example 5)
In the comparative example, the bath composition and plating conditions used are as follows.
[Bath composition and plating conditions]
(A) Formation of primary particle layer (copper plating)
Liquid composition: Copper 15g / L, sulfuric acid 75g / L
Liquid temperature: 25-35 degreeC
Current density: 1 to 70 A / dm ²
Coulomb amount: ^{2 to} 90 As / dm ²
(B) Formation of secondary particle layer (Cu—Co—Ni alloy plating conditions)
Liquid composition: Copper 15g / L, nickel 8g / L, cobalt 8g / L
pH: 2
Liquid temperature: 40 ° C
Current density: 20 to 50 A / dm ²
Coulomb amount: 30-80 As / dm ²

Average particle size of primary particles, average particle size of secondary particles when primary particle layer (Cu plating) and secondary particle layer (Cu-Co-Ni alloy plating) on copper foil formed according to the above example are formed Table 1 shows the results of measuring the average value of the diameter, powder fall, peel strength, heat resistance, and the height histogram of a certain region of the roughened surface. The average particle diameters of the primary particles and secondary particles of the roughened surface were observed with a magnification of 30000 times using S4700 manufactured by Hitachi High-Technologies Corporation, and the particle diameter was measured. The powder-off characteristics are based on the appearance of the tape discoloring due to the falling roughened particles adhering to the adhesive surface of the tape when a transparent mending tape is applied on the roughened surface of the copper foil. Evaluated. That is, when there was no or slight discoloration of the tape, the powder was OK, and when the tape was gray, the powder was NG. For normal peel strength, the copper foil roughened surface and the FR4 resin substrate are bonded together by hot pressing to prepare a copper clad laminate, and a 10 mm circuit is prepared using a general copper chloride circuit etchant. The normal peel strength was measured while peeling the foil from the substrate and pulling it in the 90 ° direction.
Moreover, the same result is shown in Table 1 as a comparative example.
In addition, in the example in which the current condition and two coulomb amounts are described in the primary particle current condition column in Table 1, after performing plating under the conditions described on the left, further plating is performed under the conditions described on the right. Means that For example, in the primary particle current condition column of Example 1, “(65 A / dm ² , 80 As / dm ² ) + (20 A / dm ² , 30 As / dm ² )” is described. After plating with a current density of 65 A / dm ² and a coulomb amount of 80 As / dm ² , plating was further performed with a current density of forming primary particles of 20 A / dm ² and a coulomb amount of 30 As / dm ² . It shows that.

As is apparent from Table 1, the results of the examples of the present invention are as follows.
In Example 1, the current density for forming the primary particles is 65 A / dm ² and 20 A / dm ² , and the coulomb amounts are 80 As / dm ² and 30 As / dm ^2. This is a case where 28 A / dm ² is used and the coulomb amount is 20 As / dm ² .
In addition, although the current density and the amount of Coulomb which form primary particles are two steps, when forming primary particles normally, two steps of electroplating are required. That is, the plating conditions for the first stage core particle formation and the electroplating for the second stage core particle growth.
The first plating conditions are electroplating conditions for forming the first stage nucleating particles, and the second plating conditions are electroplating conditions for growing the second stage nucleating particles. The same applies to the following examples and comparative examples, and the description is omitted.

As a result, the average particle diameter of the primary particles was 0.45 μm, the average particle diameter of the secondary particles was 0.30 μm, and the average height of the irregularities on the roughened surface by the laser microscope was 2689. The conditions were met.
As a result, there was little powder falling and the normal peel strength was as high as 0.95 kg / cm, and the heat resistance deterioration rate (the peel strength after heating at 180 ° C. for 48 hours after the normal peel measurement was measured and the difference was taken as the deterioration rate) Was less than 30%.

In Example 2, the current density for forming the primary particles is 65 A / dm ² and 2 A / dm ² , and the coulomb amounts are 80 As / dm ² and 4 As / dm ^2. This is a case where 25 A / dm ² is used and the coulomb amount is 15 As / dm ² .
As a result, the average particle diameter of the primary particles was 0.40 μm, the average particle diameter of the secondary particles was 0.15 μm, and the average height of the irregularities on the roughened surface by the laser microscope was 1556, which is the invention of the present application. The conditions were met.
As a result, there was no powder falling and the normal peel strength was as high as 0.89 kg / cm, and the heat resistance deterioration rate (after measuring the normal peel, the peel strength after heating at 180 ° C. for 48 hours was measured and the difference was taken as the deterioration rate) Was less than 30%.

Example 3 is a case where the current density for forming primary particles is 60 A / dm ² and 10 A / dm ² , and the coulomb amounts are 80 As / dm ² and 20 As / dm ^2. This is a case where 25 A / dm ² and the coulomb amount are 30 As / dm ² .
As a result, the average particle diameter of the primary particles is 0.30 μm, the average particle diameter of the secondary particles is 0.25 μm, and the average height of the irregularities by the laser microscope on the roughened surface is 1809, which is the invention of the present application. The conditions were met.
There was no powder fall. The normal peel strength is as high as 0.92 kg / cm, and the heat resistance deterioration rate (the peel strength after heating at 180 ° C. for 48 hours after the normal peel measurement is taken as the deterioration rate) is as small as 30% or less. It had the characteristics.

In Example 4, the current density for forming the primary particles is 55 A / dm ² and 1 A / dm ² , and the coulomb amounts are 75 As / dm ² and 5 As / dm ^2. This is a case where 25 A / dm ² and the coulomb amount are 30 As / dm ² .
As a result, the average particle diameter of the primary particles was 0.35 μm, the average particle diameter of the secondary particles was 0.25 μm, and the average height of the roughened surface by the laser microscope was 1862, which is the condition of the present invention. Was met.
No powder fall off, normal peel strength is as high as 0.94 kg / cm, heat resistance deterioration rate (measured peel strength after heating at 180 ° C. for 48 hours after normal peel measurement, the difference was taken as the deterioration rate) 30% It had the following small features.

In Example 5, the current density for forming the primary particles is 50 A / dm ² and 5 A / dm ² , and the coulomb amounts are 70 As / dm ² and 10 As / dm ^2. This is a case where 25 A / dm ² and the coulomb amount are 30 As / dm ² .
As a result, the average particle diameter of the primary particles was 0.30 μm, the average particle diameter of the secondary particles was 0.25 μm, and the average value of the height of the roughened surface by the laser microscope was 1857, which is the condition of the present invention. Was met.
No powder fall off, normal peel strength is as high as 0.91 kg / cm, heat resistance deterioration rate (measured peel strength after heating at 180 ° C. for 48 hours after normal peel measurement, and the difference was taken as the deterioration rate) 30% It had the following small features.

Example 6 is a case where the current density for forming primary particles is 60 A / dm ² and 15 A / dm ² , and the coulomb amounts are 80 As / dm ² and 20 As / dm ^2. Secondary particles (secondary particle layer) After forming the current density to 20 A / dm ² and the coulomb amount to 60 As / dm ² and performing plating (normal plating), the current density is further set to 20 A / dm ² and the particles are formed with the coulomb amount 20 As / dm ^2. This is the case.

As a result, the primary particle has an average particle size of 0.35 μm, the secondary particles are covered (normal) in a plated state (particle size is less than 0.1 μm), and the average particle size is 0.15 μm. The average height of the irregularities on the roughened surface was 1752, which satisfied the conditions of the present invention.
No peeling off, normal peel strength is as high as 0.90 kg / cm, heat resistance deterioration rate (measured peel strength after heating at 180 ° C. for 48 hours after measurement of normal peel, and the difference was taken as the deterioration rate) 30% It had the following small features.

On the other hand, the comparative example has the following results.
In Comparative Example 1, the current density for forming primary particles is 63 A / dm ² and 10 A / dm ² , and the coulomb amounts are 80 As / dm ² and 30 As / dm ^2, and the secondary particles are not formed. It is. As a result, the average particle diameter of the primary particles was 0.50 μm, and the average value of the unevenness height of the roughened surface by the laser microscope was 2001, which satisfied the conditions of the present invention.
There was no powder falling off, and the normal peel strength was as high as 0.94 kg / cm, which was an example level. However, the heat resistance deterioration rate (the peel strength after heating at 180 ° C. for 48 hours after measuring the normal peel was used as the deterioration rate) was 60%, which was extremely bad. The overall evaluation as a printed circuit copper foil was poor.

Comparative Example 2 shows a conventional example in which there is no primary particle size and only a secondary particle layer. That is, the current density for forming the secondary particles is 50 A / dm ² and the coulomb amount is 30 As / dm ² .
As a result, the average particle diameter of the secondary particles was 0.30 μm, and the average value of the height of the roughened surface with a laser microscope was 294, which did not satisfy the conditions of the present invention.
A large amount of powdered coarse particles occurred. The normal peel strength is 0.90 kg / cm, which is an example level, and the heat resistance deterioration rate (the peel strength after heating at 180 ° C. for 48 hours after the normal peel measurement and the difference as the deterioration rate) is 30% or less. When it was small, it was an example level. As described above, since there is a problem that a large amount of powder falling occurs, the overall evaluation as an overall copper foil for printed circuits was poor.

In Comparative Example 3, the current density for forming the primary particles is 63 A / dm ² and 1 A / dm ² , and the coulomb amounts are 80 As / dm ² and ² As / dm ^2. This is a case where 28 A / dm ² and the coulomb amount are 73 As / dm ² .
As a result, the average particle diameter of the primary particles was 0.35 μm, the average particle diameter of the secondary particles was 0.60 μm, and the average value of the unevenness of the roughened surface by the laser microscope was 1298, and the present invention The condition of was not satisfied. A large amount of powder fall occurred. When the normal peel strength is as high as 0.93 kg / cm and the heat resistance deterioration rate (the peel strength after heating at 180 ° C. for 48 hours after the normal peel measurement is taken as the deterioration rate) is less than 30% Although it was an example level, a large amount of powder falling occurred. The overall evaluation as a printed circuit copper foil was poor.

In Comparative Example 4, the current density for forming the primary particles is 63 A / dm ² and 1 A / dm ² , and the coulomb amounts are 80 As / dm ² and ² As / dm ^2. This is a case where 31 A / dm ² and the coulomb amount are 40 As / dm ² .
As a result, the average particle diameter of the primary particles was 0.35 μm, the average particle diameter of the secondary particles was 0.40 μm, and the average value of the height of the roughened surface by the laser microscope was 1227, which is the condition of the present invention. Did not meet.
When the normal peel strength is as high as 0.91 kg / cm and the heat resistance deterioration rate (the peel strength after heating at 180 ° C. for 48 hours after the normal peel measurement is taken as the deterioration rate) is less than 30% Although it was an example level, a large amount of powder falling occurred. The overall evaluation as a printed circuit copper foil was poor.

In Comparative Example 5, the current density for forming the primary particles is 40 A / dm ² and 1 A / dm ² , and the coulomb amounts are 40 As / dm ² and ² As / dm ^2. This is a case where 20 A / dm ² is used and the coulomb amount is 20 As / dm ² .

As a result, the average particle diameter of the primary particles is 0.15 μm, the average particle diameter of the secondary particles is 0.15 μm, and the average height of the irregularities on the roughened surface by the laser microscope is 1367, which is the invention of the present application. The conditions were met.
Powder fall did not occur. The normal peel strength was 0.75 kg / cm, and the heat resistance deterioration rate (the peel strength after heating at 180 ° C. for 48 hours after the normal peel measurement was measured and the difference was taken as the deterioration rate) was 35%. .

As is clear from the comparison of the above Examples and Comparative Examples, after forming a primary particle layer of copper on the surface of the copper foil (raw foil), 3 consisting of copper, cobalt and nickel is formed on the primary particle layer. In the case of forming a secondary particle layer made of a base alloy, in the measurement analysis by a laser microscope of a certain region of the roughened surface, the average value of the unevenness of the roughened surface is 1500 or more, It has an excellent effect of being able to stably suppress the phenomenon called powder fall and processing unevenness, and can further increase the peel strength and improve the heat resistance.
The average particle diameter of the primary particle layer is 0.25 to 0.45 μm, and the average particle diameter of the secondary particle layer made of a ternary alloy made of copper, cobalt and nickel is 0.35 μm or less. It is more effective in achieving the effect.

As described above, when forming a secondary particle layer (roughening treatment) composed of copper-cobalt-nickel alloy plating, the roughened particles formed in a dendritic shape are peeled off from the surface of the copper foil, and are generally powdered off. It is an object of the present invention to provide a copper foil for a printed circuit which has an excellent effect of suppressing the phenomenon and processing unevenness, which can further enhance the peel strength and improve the heat resistance. In addition, the number of abnormally grown particles is reduced, the particle diameter is uniform, and the entire surface is covered, so that the etching property is good and the circuit can be formed with high accuracy, so that the semiconductor device can be downsized and highly integrated. It is useful as a printed circuit material for advanced electronic equipment.

Claims (1)

  The invention described herein.