TWI599279B - Copper foil for laser processing, copper foil with carrier foil for laser processing, copper clad laminate and method for manufacturing printed wiring board - Google Patents

Description

Copper foil for laser processing, copper foil for laser processing with carrier foil, copper laminated body, and printing Wiring board manufacturing method

The present invention relates to a copper foil for laser processing, and more particularly to a copper foil for laser processing suitable for a manufacturing material of a printed wiring board, a copper foil for laser processing having a carrier foil, a copper-clad laminate, and a printed wiring board. Production method.

In the past, with the high functionality and miniaturization of electronic equipment and electrical equipment, the multilayering of printed wiring boards has also progressed. The multilayer printed wiring board is formed by laminating three or more wiring layers through an insulating layer, and each of the wiring layers is electrically connected by an interlayer connection mechanism such as a via hole or a via. As for the method of manufacturing a printed wiring board, a build up method is known. The build-up method refers to a manufacturing method in which an edge layer is insulated on an inner layer circuit to laminate a wiring layer, and multilayering is performed while performing interlayer connection. For example, when an ultra-high-fine wiring pattern is formed by a modified semi-additive process (MSAP method) or the like, a build-up printed wiring board is produced in the following order. First, a copper foil is laminated on a core substrate having an inner layer circuit, and a via hole is formed by laser processing or the like, and then interlayer connection is performed by electroless plating. Next, a plating resist corresponding to the wiring pattern is formed on the seed layer (copper foil + electroless plating layer), and after electrolytic plating, the plating resist and the resist are removed together by etching. The seed layer. By repeating the above steps of the necessary number of times, it is possible to obtain the number of wiring layers required. Addition of multilayer printed wiring boards.

In recent years, with the miniaturization of the wiring pattern, it has become 100 by the tip diameter. Microvias below μm are connected by layers. These micro-through holes are generally subjected to drilling processing by laser processing using a carbon dioxide gas laser or the like. At this time, in many cases, a Cu direct laser method in which a copper foil is directly irradiated with a carbon dioxide gas laser and a copper foil and an insulating layer are simultaneously opened is used. However, since copper has a very low absorption rate of laser light in the far-infrared-infrared wavelength region such as a carbon dioxide gas laser, it is necessary to perform blackening treatment in advance when a micro-via hole is formed by a Cu direct laser method. It is used to improve the laser light absorption rate of the copper foil surface before processing.

However, when the surface of the copper foil is blackened, since the surface of the copper foil is etched, The thickness of the copper foil is reduced while causing unevenness in thickness. Therefore, when the seed layer is removed, it is necessary to set the etching time point corresponding to the thickest portion of the seed layer, so that it is difficult to form a wiring pattern having a high linearity and a good line width.

On the other hand, Patent Document 1 (Japanese Patent Application No.: JP-A-2001-226796) In the publication, it is described that an alloy layer mainly composed of Sn and Cu is provided on the surface of the copper foil as a technique before the laser processing is not required. According to Patent Document 1, when the same surface roughness is obtained at the same room temperature, the laser absorption ratio of Sn is twice or more higher than that of Cu, so that Sn and Cu are mainly used for the surface of the surface of the copper foil. The alloy layer can be directly irradiated with laser light on the surface of the copper foil without applying a blackening treatment or the like to form a through hole having a diameter of 100 μm.

However, the copper foil for laser opening processing described in Patent Document 1 is used. A method of forming a metal Sn layer on the surface of the copper foil by vapor deposition or plating, followed by diffusion treatment by heat, thereby alloying Sn and Cu into an alloy layer on the surface of the copper foil. Therefore, in the alloy layer, the Sn content is distributed in the thickness direction, and it is considered that the etching speed in the thickness direction of the copper foil varies. Moreover, the content of Sn on the outermost surface of the copper foil is extremely high, It is considered that the copper foil described in Patent Document 1 has three layers of a Sn layer, an alloy layer of Sn and Cu, and a copper layer in this order from the surface layer. Since the metal Sn layer does not have solubility in the etching liquid of the general copper foil, when the copper foil described in Patent Document 1 is used, the outermost surface is hardly dissolved and removed by etching. Therefore, when the copper foil described in Patent Document 1 is used, it is necessary to remove the outermost surface of the copper foil by etching the etching solution of the Sn-containing metal Sn layer before etching, and then etching the lower layer to form an etching step. Worry. In addition, the alloy layer of Sn and Cu described in Patent Document 1 is a layer which is alloyed by thermal diffusion, and therefore it is considered that the metal composition in the thickness direction is not uniform, and the etching rate in the thickness direction may vary. Therefore, at the time of etching, the copper foil cannot be etched with a uniform thickness, and there is a variation in the thickness of the copper foil. Further, in the case where the surface Sn content of the alloy layer is high, it is considered that the etching rate is also slower than the wiring pattern portion formed by electrolytic copper plating. Therefore, when the seed layer is removed, the wiring pattern portion is quickly etched, and it is difficult to obtain a good wiring pattern having a fine line width.

Therefore, an object of the present invention is to provide a copper foil for laser processing which is excellent in laser processability, can form a wiring pattern satisfactorily, a copper foil for laser processing having a carrier foil, a copper-clad laminate, and a printed wiring board. method.

As a result of active research by the present inventors, it has been found that the above object can be attained by using the following copper foil for laser processing.

The copper foil for laser processing according to the present invention is characterized in that a surface of the copper foil is provided with a poorly soluble laser absorbing layer capable of absorbing infrared laser light, and the poorly soluble laser absorbing layer has etching property to a copper etching liquid, and The etching speed is slower than that of copper foil.

In the copper foil for laser processing of the present invention, it is preferred that the poorly soluble laser absorbing layer is tin The electrolytic copper-tin alloy layer formed by electrolytic plating is contained in an amount of 25% by mass or more and 50% by mass or less.

In the copper foil for laser processing of the present invention, the thickness of the poorly soluble laser absorbing layer is preferably 3 μm or less.

In the copper foil for laser processing of the present invention, the thickness of the copper foil is preferably 7 μm or less.

In the copper foil for laser processing of the present invention, it is preferred that at least one of the roughened physical layer and the undercoat resin layer is provided on the other surface of the copper foil.

A copper foil for laser processing having a carrier foil according to the present invention is characterized in that the carrier foil is peelably provided on the poorly soluble laser absorption layer.

The copper-clad laminate according to the present invention is characterized in that a material for forming the copper foil for laser processing and an insulating layer is laminated on the side irradiated with the infrared laser light so as to arrange the poorly-soluble laser absorption layer.

The method for producing a printed wiring board according to the present invention is characterized in that a laser absorbing layer having a etchability to a copper etching solution and having an etching rate slower than that of a copper foil and having a laser absorbing light that absorbs infrared laser light is provided on the surface of the copper foil. a laminated body formed by laminating a copper foil for injection processing and another conductor layer through an insulating layer, and directly irradiating the poorly soluble laser absorbing layer with infrared laser light to form a via hole for interlayer connection, thereby removing the slag in the through hole. The poorly soluble laser absorbing layer is removed from the surface of the copper foil during the slag step and/or as a microetching step prior to electroless plating.

[Effect of the invention]

The copper foil for laser processing of the present invention is excellent in laser workability, and a uniform etching rate can be obtained in the thickness direction in the subsequent etching treatment. Moreover, carbon dioxide gas can be used The direct boring process of the copper foil for laser processing for depositing a copper laminated plate is performed without pre-processing such as blackening treatment for improving the laser light absorbing efficiency, and the overall manufacturing cost can be reduced by reducing the number of steps. Further, since the poorly-soluble laser absorption layer functions as an etching resist, it is possible to prevent the surface of the copper foil (layer) from being dissolved in various etching steps before the formation of the wiring pattern, and to prevent variations in the thickness of the copper foil (layer). Therefore, the wiring pattern can be formed with a good etching factor.

10‧‧‧Rolling copper foil for processing

11‧‧‧ Primer resin layer

12‧‧‧ copper foil (electrolytic copper foil layer)

13‧‧‧ Electrolytic copper-tin alloy layer (poorly soluble laser absorbing layer)

20‧‧‧Insulation layer forming materials

30‧‧‧Inner circuit (other conductor layers)

30a‧‧‧Conductor Pattern Department

40‧‧‧microvia

100‧‧‧Layer

Fig. 1 is a graph showing the relationship between the tin content of the electrolytic metal foil of the present invention and the etching rate.

Fig. 2 is a view for explaining an example of a method of manufacturing a printed wiring board of the present invention.

Fig. 3 is a view for evaluating the etching properties of the electrolytic copper foil in the copper-clad laminate produced in the examples and the comparative example 1.

Hereinafter, an embodiment of a method for producing a copper foil for laser processing, a copper foil for laser processing having a carrier foil, a copper-clad laminate, and a printed wiring board according to the present invention will be described in order.

1. Copper foil for laser processing

The copper foil for laser processing according to the present invention is characterized in that a surface of the copper foil is provided with a poorly soluble laser absorbing layer capable of absorbing infrared laser light, and the poorly soluble laser absorbing layer has etching property to a copper etching liquid, and The etching speed is slower than that of copper foil. The copper foil for laser processing according to the present invention is in the manufacturing step of the printed wiring board, and the surface of the copper foil for laser processing is directly irradiated with the laser light by the Cu direct laser method without the prior treatment such as blackening treatment. It is possible to form micropores such as microvias by laser processing.

Here, the poorly soluble laser absorbing layer is, for example, a copper layer containing an infrared laser absorbing metal material which absorbs infrared laser light, and preferably contains the infrared absorbing material in the copper layer. A copper layer comprising an infrared laser absorptive metal material that etches the copper etching solution at a slower rate than the etching rate of the copper foil. A specific example of the poorly soluble laser absorbing layer can be exemplified as an example. An electrolytic copper-tin alloy layer containing 25% by mass or more and 50% by mass or less of tin, which is formed by electrolytic plating. In the present embodiment, the use of the electrolytic copper-tin alloy layer as a poorly soluble laser absorbing layer will be mainly described below.

1-1. Electrolytic copper-tin alloy layer

First, the electrolytic copper-tin alloy layer will be described. When compared with copper, tin pairs The absorption of laser light (carbon dioxide gas laser) having a wavelength in the far-infrared to infrared wavelength region is high. That is, the electrolytic copper-tin alloy layer functions as a laser light absorbing layer, and as described above, no pretreatment is required for the hole drilling by the Cu direct laser method. Further, in the present invention, the electrolytic copper-tin alloy layer can be used to prevent copper foil in various etching treatments performed after the opening process, such as the desmear step or the micro-etching step performed before the formation of the wiring pattern. The surface is etched to etch the function of the resist layer. The electrolytic copper-tin alloy is etched in various etching processes performed before the formation of the wiring patterns. However, the point at which the electrolytic copper-tin alloy layer is dissolved and removed can be controlled by its tin content and thickness. Therefore, the electrolytic copper-tin alloy layer can be dissolved and removed only before the stage before the electroless plating step for interlayer connection, without dissolving the surface of the copper foil. Therefore, for example, when the wiring pattern is formed by the MSAP method, an electroless plating film can be formed on the copper foil which maintains the initial thickness state, and a seed layer having a uniform thickness can be obtained.

(1) tin content

In the present invention, when an electrolytic copper-tin alloy layer is used as the poorly soluble laser absorbing layer, The reason why the tin content in the electrolytic copper-tin alloy layer is 25% by mass or more is because the function as the etching resist can be exhibited. As shown in Fig. 1, when the tin content in the electrolytic copper-tin alloy layer is less than 25% by mass, the etching rate of the electrolytic copper-tin alloy layer is faster than that of the electrolytic copper foil having a tin content of 0% by mass. On the other hand, when the tin content in the electrolytic copper-tin alloy layer is 25% by mass or more, the etching rate thereof It is slower than the usual electrolytic copper foil without tin. Therefore, by setting the tin content in the electrolytic copper-tin alloy layer to 25% by mass or more, as described above, the electrolytic copper-tin alloy layer can function as an etching resist, and various types of the wiring pattern can be formed before the formation of the wiring pattern. At the time of the etching treatment, it is possible to prevent copper from being dissolved and the thickness of the copper foil is deviated.

Moreover, the electrolytic copper-tin alloy layer is deposited on the surface of the copper foil by electrolytic plating. Since the copper-tin alloy is formed, the metal composition in the thickness direction is uniform, and the etching rate of the electrolytic copper-tin alloy layer can be made uniform in the thickness direction. Therefore, in the various etching processes performed before the formation of the wiring pattern, the electrolytic copper-tin alloy layer can be dissolved at a uniform rate in the thickness direction. As shown in FIG. 1, the more the tin content, the slower the etching rate. Therefore, as described above, by adjusting the tin content and thickness in the electrolytic copper-tin alloy layer, the electrolytic copper-tin alloy layer can be dissolved and removed at an appropriate point. Therefore, for example, before only the electrolytic copper-tin alloy layer is dissolved before the electrolytic plating step for interlayer connection, an electroless plating film can be formed on the surface of the copper foil having the initial thickness state. Therefore, for example, when a wiring pattern is formed by the MSAP method, a seed layer having a uniform thickness can be formed, so that the seed layer is uniform in the thickness direction when the seed layer is removed in a rapid etching step or the like after the wiring pattern is formed. The composition is such that the seed layer can be dissolved and removed by a uniform etching rate. From the above, it can be seen that a wiring pattern having a good etching factor can be formed. Further, it is also not limited to the MSAP method, and it is also possible to form a wiring pattern by a method including an etching step such as a subtractive process. That is, in the desmear step after the laser drilling process, since the electrolytic copper-tin alloy layer can be removed, the copper foil (layer) maintaining the initial thickness state is exposed, so that a conductor layer having a uniform thickness can be obtained. A wiring pattern with a good etching factor can be formed.

Here, when the etching rate of the electroless copper foil containing no tin is set to 100, the tin content exceeds The etching rate of 50% by mass of the electrolytic copper-tin alloy foil was less than 3. Therefore, when the tin content in the electrolytic copper-tin alloy layer exceeds 50% by mass, the etching rate of the copper etching solution becomes too slow, so When various etching treatments are performed before the formation of the line pattern, it is difficult to dissolve and remove the electrolytic copper-tin alloy layer. In particular, as shown in FIG. 1, when the tin content in the electrolytic copper-tin alloy layer exceeds 70% by mass, the etching rate of the electrolytic copper-tin alloy foil to the copper etching solution becomes 0 μm, and therefore, a general copper etching solution is used. It is not possible to remove the electrolytic copper-tin alloy layer from the surface of the copper foil. In this case, it is not necessary to additionally provide an etching step for removing the electrolytic copper-tin alloy layer, which is not preferable. From this viewpoint, the tin content in the electrolytic copper-tin alloy layer is preferably 45% by mass or less, more preferably 40% by mass or less, and still more preferably 35% by mass or less. At this time, when the etching rate of the electrolytic copper foil to the copper etching solution was 100, the etching rates of the electrolytic copper-tin alloy foil were 4 (tin content: 45 mass%), 13 (tin content: 40 mass%), and 25, respectively. (tin content: 35 mass%). Therefore, by setting the tin content in the electrolytic copper-tin alloy layer to the above preferred range, the electrolytic copper-tin alloy layer can be easily removed in various etching treatments performed before the formation of the wiring pattern.

On the other hand, when the tin content is less than 25% by mass, the electrolytic copper-tin alloy foil is copper Since the etching rate of the etching liquid is faster than the etching speed of the copper foil containing no tin, in order to function as an etching resist, it is necessary to increase the thickness of the electrolytic copper-tin alloy layer and increase the amount of copper removed by etching. Therefore, it is not economically good. However, the etching rate shown in Fig. 1 is obtained by the following values: electrolytic copper-tin alloy foil (thickness: 3 μm) having different tin contents (% by mass), and each electrolytic copper-tin alloy foil in sulfuric acid - The hydrogen peroxide-based etching liquid was immersed for 30 seconds, washed with water, dried, and the thickness was measured by cross-sectional observation, and the etching amount per unit time (μm) was determined based on the thickness reduced by etching. Further, the tin content herein can be measured by the following method. In the case of a copper foil for laser processing having a layer of a "copper foil/electrolytic copper-tin alloy layer", an ICP method and a fluorescent X-ray device are used for a solution in which all of the copper foil for laser processing to be used as a sample is dissolved. The total copper content is determined by titration and the like, and the amount of copper contained in the electrolytic copper-tin alloy layer is calculated by subtracting the amount of copper converted from the thickness of the copper foil by the total copper content. The tin content (% by mass) can be calculated from the tin content in the solution. And by doing it in advance When the thickness of the copper foil is known by cross-sectional observation or the like, the composition of the foil defined as the two-layer foil is analyzed using a fluorescent X-ray film thickness measuring device, and the tin content (% by mass) in the electrolytic copper-tin alloy layer can be calculated.

(3) Thickness of electrolytic copper-tin alloy layer

The thickness of the electrolytic copper-tin alloy layer can be set to an appropriate and appropriate value corresponding to the thickness and use of the copper foil for laser processing. However, when the electrolytic copper-tin alloy layer or the like is dissolved and removed by etching at an appropriate stage before the formation of the wiring pattern, it is preferably 3 μm or less, more preferably 2 μm or less. On the other hand, when the thickness of the electrolytic copper-tin alloy layer is less than 0.1 μm, it is difficult to achieve the purpose of improving the laser light absorption rate, and the electrolytic copper-tin alloy may be present in various etching treatments performed before the formation of the wiring pattern. The layer cannot fully utilize its function as an etching resist for copper foil. Therefore, from this viewpoint, the thickness of the electrolytic copper-tin alloy layer is preferably 0.3 μm or more, more preferably 0.5 μm or more. Further, as described above, the etching rate of the copper etching solution varies depending on the tin content in the electrolytic copper-tin alloy layer, and therefore the thickness of the electrolytic copper-tin alloy layer is set to be appropriate in accordance with the tin content. The appropriate value is better.

(4) Copper etching solution

In the present invention, the copper etching solution can be used without any particular limitation as an etching solution for copper. For example, a copper chloride-based etching solution, a ferric chloride-based etching solution, a sulfuric acid-hydrogen peroxide-based etching solution, a sodium persulfate-based etching solution, an ammonium persulfate-based etching solution, a potassium persulfate-based etching solution, or the like can be used. Copper etching solution.

1-2. Copper foil

Next, the copper foil will be described. In the present invention, the term "copper foil" means a metal foil having a copper content of 99% by mass or more, and means a non-tin-containing copper foil containing no tin other than inevitable impurities. The copper foil may be either an electrolytic copper foil or a rolled copper foil. However, in terms of economy and production efficiency, it is better to electrolyze copper foil.

The copper foil is formed by a material constituting the insulating layer when manufacturing the multilayer printed wiring board. A layer constituting a part of the seed layer or the like. The copper foil may have the same thickness as a commercially available copper foil which is generally used as a printed wiring board material. However, for example, when a wiring pattern is formed by a method including an etching step such as an MSAP method or a subtractive method, the copper foil is preferably as thin as possible from the viewpoint of obtaining a better etching factor, and is preferably 7 μm or less. In particular, when the wiring pattern is formed by the MSAP method using the copper foil for laser processing, it is more preferable that the copper foil has a thickness of 3 μm or less and an extremely thin electrolytic copper foil from the viewpoint of forming a finer wiring pattern with a good etching factor. It is better to be 2 μm or less. However, when the thickness of the copper foil is 7 μm or less, it is preferably used in the form of a copper foil for carrier foil laser processing which will be described later so as not to cause defects such as wrinkles or cracks during the treatment.

Moreover, the interlayer insulation of the copper foil is preferably based on the viewpoint that the etching factor is good. The surface on the side following the layer, that is, the surface on the opposite side to the surface on which the copper-tin alloy layer is provided (hereinafter referred to as the succeeding surface) is smooth. Specifically, the surface roughness (Rzjis) of the adhesion surface is preferably 3 μm or less, more preferably 2 μm or less. However, when the rough surface of the copper foil is provided as follows, the surface roughness of the adhesion surface means the surface roughness of the adhesion surface after the roughening treatment layer is formed.

1-3. Roughening layer

In the copper foil for laser processing of the present invention, the bonding surface of the copper foil, that is, the above A roughened layer may also be provided on the opposite side of the surface of the electrolytic copper-tin alloy layer. By providing a roughened layer on the succeeding surface of the copper foil, the adhesion between the copper foil and the insulating layer can be improved. The roughening treatment layer can be formed by a method of forming fine metal particles on the surface (continuous surface) of the copper foil, a method of forming a roughened surface by etching, or the like. The method for forming the roughened layer may be carried out by any method as long as it can physically improve the adhesion between the copper foil and the insulating layer, and various methods relating to conventional roughening treatment can be employed.

1-4. Primer resin layer

In the copper foil for laser processing of the present invention, it may be provided on the above-mentioned bonding surface of the copper foil. The bottom layer is coated with a resin layer. In the present invention, the undercoat resin layer is an adhesive layer having good adhesion to both the copper foil and the insulating layer constituent material. For example, the undercoat resin layer may be a layer made of a resin composition containing an epoxy resin or an aromatic polyamide resin. By providing the undercoat resin layer on the adhesion surface of the copper foil, the copper foil and the insulating layer constituent material can be well adhered.

The thickness of the undercoat resin layer can increase the adhesion between the copper foil and the insulating layer constituent material. The nature is not particularly limited, but may be, for example, in the range of 0.5 μm or more and 10 μm or less. Further, a roughening treatment layer and a primer resin layer may be simultaneously provided on the adhesion surface of the copper foil.

1-5. Method for manufacturing copper foil for laser processing

In the copper foil for laser processing of the present invention, the poorly soluble laser absorbing layer is the above-mentioned electrolytic copper- In the case of the tin alloy layer, for example, an electrolytic solution containing copper ions and tin ions is used, and electrolytic copper plating on the copper foil can be used to obtain electrolytic copper having a tin content of 25% by mass or more and 50% by mass or less. When the copper foil for laser processing of a tin alloy layer is used, the manufacturing method is not specifically limited. Further, in addition to the roughening layer and the undercoat resin layer, the surface of the copper foil may be provided with various surface treatment layers as necessary, such as a rustproof treatment layer and a decane coupling treatment layer.

2. Copper foil for laser processing with carrier foil

Next, a copper foil for laser processing having a carrier foil according to the present invention (hereinafter referred to as a copper foil for laser processing having a carrier foil) will be described. The copper foil for laser processing having a carrier foil is a carrier foil which is peelably provided on the poorly soluble laser absorbing layer of the copper foil for laser processing, such as a carrier foil/release layer/copper for laser processing In the form of a foil (poorly soluble laser absorbing layer/copper foil), each layer is laminated. In the copper foil for laser processing having the carrier foil, the same configuration as the copper foil for laser processing described above can be employed except for the configuration of the carrier foil. Therefore, only the configuration related to the carrier foil will be described here. Bright.

2-1. Carrier foil

The carrier foil is a metal foil which is detachably provided on the copper foil for laser processing, and is laser-coated When the copper foil for processing is an ultra-thin copper foil having a thickness of 7 μm or less as described above, by supporting the copper foil for laser processing with a carrier foil, wrinkles, cracks, and the like can be prevented, and the handleability can be improved. The material constituting the carrier foil is not particularly limited. However, in order to form the above-mentioned electrolytic copper-tin alloy layer and copper foil by electrolytic deposition on the carrier foil, it is preferred to have a conductive metal material. For example, a copper foil, a copper alloy foil, an aluminum foil, a composite foil in which a metal plating layer such as copper or zinc is plated on the surface of the aluminum foil, a stainless steel foil, a resin film coated with a metal, or the like can be used. Among these materials, a copper foil can be preferably used as the carrier foil. Since the copper foil is used as the carrier foil, the carrier foil is peeled off from the copper foil for laser processing, and since it can be reused as a copper raw material, it is preferable from the viewpoint of resource conservation.

The thickness of the carrier foil is not particularly limited, but may be, for example, 5 μm or more and 100 μm. the following. When the thickness of the carrier foil is less than 5 μm, the thickness of the carrier foil is thin, and the original purpose of the carrier foil for improving the thickness of the ultra-thin laser processing foil having a thickness of 7 μm or less cannot be achieved, which is not preferable. Further, the thickness of the carrier foil is preferably 100 μm or less, and may be used in a thickness of 35 μm or less, based on the viewpoint of resource conservation.

2-2. Peeling layer

The copper foil for laser processing having a carrier foil is a so-called peelable type copper foil for laser processing having a carrier foil. In the peeling layer, it is required that the carrier foil can be easily peeled off by a manual operation for the copper foil for laser processing, and the carrier foil and the copper foil for laser processing can be adhered to each other with a moderate adhesion strength during the peeling of the carrier foil. As such a release layer, for example, an inorganic release layer composed of an inorganic agent and an organic release layer composed of an organic agent are exemplified.

(1) Inorganic release layer

As the inorganic agent constituting the inorganic release layer, for example, chromium, nickel, molybdenum, or the like can be used. One or a mixture of two or more selected from the group consisting of ruthenium, vanadium, tungsten, cobalt, and the like.

(2) Organic peeling layer

As the organic agent constituting the organic release layer, for example, organic synthesis of nitrogen-containing compounds can be used. One or a mixture of two or more selected from the group consisting of a sulfur-containing organic compound and a carboxylic acid is used in combination. The release layer may be either an inorganic release layer or an organic release layer, but is preferably an organic release layer from the viewpoint of stability of the tear-off property of the carrier foil.

More preferably, it is a nitrogen-containing organic compound, a sulfur-containing organic compound, or a carboxylic acid. The following compounds were used. The nitrogen-containing compound may, for example, be an ortho-triazole, an aminotriazole, an imidazole, or the like or a derivative thereof. In particular, it can be exemplified by a carboxybenzotriazole of an ortho-triazole, a 3-amino-1H-1,2,4-triazole which is an aminotriazole, and a N',N' which is a triazole derivative. - bis(benzotriazolylmethyl)urea. Any one or more of these may form an organic release layer composed of a nitrogen-containing compound.

As the sulfur-containing compound, for example, thiazole, mercaptobenzothiazole, dibenzosulfuric acid can be exemplified. Aminodisulfide, a cyclohexylamine salt of mercaptobenzothiazole, a dicyclohexylamine salt of mercaptobenzothiazole, thiocyanate, 2-benzimidazolethiol, and the like. When an organic release layer is formed using a sulfur-containing compound, among these, mercaptobenzothiazole and thiocyanic acid are preferably used.

The carboxylic acid may, for example, be a high molecular weight carboxylic acid. Among the high molecular weight carboxylic acids, the most It is good to use fatty acids of long-chain hydrocarbon monocarboxylic acids. The fatty acid may be a saturated fatty acid, but an unsaturated fatty acid such as oleic acid or linolenic acid is preferably used.

(3) Thickness of the peeling layer

The thickness of the peeling layer is preferably 100 nm or less, more preferably 50 nm or less. So-called peelable The copper foil having a carrier foil which is released from the carrier is generally provided with a release layer on the surface of the carrier foil, and copper is deposited on the carrier foil through a release layer by electrolysis or the like to form an electrolytic copper foil. At this time, when the thickness of the release layer exceeds 100 nm, especially in the organic release layer, it is difficult to form an electrolytic copper foil on the release layer. At the same time, the adhesion strength between the carrier foil and the electrolytic copper foil is lowered. Therefore, the thickness of the peeling layer is preferably 100 nm or less. If a peeling layer having a uniform thickness can be formed, the lower limit of the thickness of the peeling layer is not particularly limited. However, when it is less than 1 nm, it is difficult to form a peeling layer of uniform thickness, and variations occur in thickness. Therefore, the thickness of the release layer is preferably 1 nm or more, more preferably 2 nm or more.

2-3. Heat resistant metal layer

The copper foil for laser processing having a carrier foil is preferably attached to the carrier foil and the release layer. Between the peeling layer and the electrolytic copper-tin alloy layer of the copper foil for laser processing, a heat resistant metal layer is formed, and the carrier foil/heat resistant metal layer/release layer/copper foil for laser processing is formed. Or it may be a layer of a carrier foil / peeling layer / heat resistant metal layer / copper foil for laser processing.

2-4. Method for manufacturing copper foil for laser processing with carrier foil

The method for producing the copper foil for laser processing having the carrier foil is not particularly limited. For example, after the release layer is formed on the surface of the carrier foil, the electrolytic copper-tin alloy layer, copper foil, or the like is electrically analyzed on the carrier foil through the release layer, and if the copper foil for laser processing having the carrier foil having the above configuration is obtained, It can be manufactured by any method.

2-5. Method for measuring tin content of electrolytic copper-tin alloy layer of copper foil for laser processing with carrier foil

In the case of a copper foil for laser processing having a carrier foil, a layer structure of "carrier foil/release layer/electrolytic copper-tin alloy layer/copper foil" is provided. Therefore, in order to measure the tin content of the electrolytic copper-tin alloy layer, the following method is preferably employed. In the case of the copper foil for laser processing of the carrier foil of the present invention, If the carrier foil is peeled off, it becomes a layer structure of "peeling layer/electrolytic copper-tin alloy layer/copper foil". Further, since the peeling layer at this time is composed of the above components, it does not affect the measurement of the tin content of the electrolytic copper-tin alloy layer. Therefore, the solution in which the sample consisting of the layer of the "peeling layer/electrolytic copper-tin alloy layer/copper foil" is completely dissolved is measured by ICP analysis, fluorescent X-ray apparatus, titration and the like, and the total copper content is measured. The total copper content is calculated by subtracting the amount of copper contained in the electrolytic copper-tin alloy layer calculated from the amount of copper converted from the thickness of the copper foil, and the tin content in the dissolved solution. quality%). Further, when the thickness of the known copper foil such as the cross-sectional observation is used in advance, the composition of the foil defined as the two-layer foil is analyzed using a fluorescent X-ray film thickness measuring device, and the tin content in the electrolytic copper-tin alloy layer can be calculated ( quality%).

3. Paste copper laminate

Next, the copper-clad laminate of the present invention will be described. Copper clad layer of the invention The body is characterized in that the above-described poorly-soluble laser absorbing layer is disposed on the side irradiated with the infrared laser light, and the copper foil for laser processing and the insulating layer constituting material are laminated. In other words, the copper-clad laminate according to the present invention has an insulating layer constituent material laminated with the above-described copper foil for laser processing, and has an insulating layer constituent material/copper foil/poorly soluble laser absorbing layer (electrolytic copper-tin alloy) The layered body in which the layers are stacked in any order may be any one. Further, if the copper-clad laminate is obtained, the production method thereof is not limited. For example, the copper foil for laser processing or the copper foil having the carrier foil is laminated on the insulating resin substrate or the insulating resin layer of the B-stage, and is obtained by heating and pressurizing the insulating resin substrate or the insulating resin. A copper-clad laminate formed by laminating copper foil for laser processing on a layer. Further, in the case of using a copper foil for laser processing having a carrier foil, the carrier foil may be removed at an appropriate stage.

4. Manufacturing method of printed wiring board

Next, a method of manufacturing the printed wiring board of the present invention will be described. Here, side reference map 2. The case where the wiring pattern is formed by the MSAP method using the copper foil 10 for laser processing of the present invention is An example is given. Further, the copper foil 10 for laser processing used herein is a layer including a primer resin layer 11 / a copper foil (electrolytic copper foil layer) 12 / an electrolytic copper-tin alloy layer 13 (a poorly soluble laser absorbing layer). As a component, the roughening layer is not provided on the back surface of the copper foil 12. In the following, a method of manufacturing a multilayer printed wiring board by a wiring layer having three or more layers of an insulating laminate layer will be described. However, the method of manufacturing the printed wiring board of the present invention is not limited to the method of manufacturing the multilayer printed wiring board, and may be applied to the production of the double-sided printed wiring board.

First, the so-called B-stage insulating layer structure is interposed on the inner layer circuit 30 (other conductor layers). The material 20 is laminated on the succeeding surface of the copper foil 10 for laser processing having the carrier foil. Then, the insulating layer constituent material 20 is adhered to the inner layer circuit 30 and the laser foil for laser processing 10 by heating and pressing, whereby the laminated body shown in Fig. 2(a) is obtained.

Next, on the surface of the electrolytic copper-tin alloy layer 13 which becomes the outermost layer, by oxidation The infrared laser light is directly irradiated by a carbon gas laser or the like to form a microvia 40 having a bottom portion of the conductor pattern portion 30a of the inner layer circuit 30 (refer to FIG. 2(b)).

After the micro via 40 is formed, the degumming liquid is used to remain at the bottom of the micro via 40 The desmear step of removing the glue residue (refer to FIG. 2(c)). In the desmear step, the layered body 100 is immersed in the swelling liquid, and then immersed in a so-called degreasing liquid (for example, an alkaline permanganic acid aqueous solution or the like) to remove the dregs, and then immersed in the neutralizing liquid (reducing agent). In the middle, the potassium permanganate is reduced and the neutralization treatment is removed.

Next, a micro-etching step as a treatment before the electroless plating step is performed. Microetching In the engraving step, a micro-etching liquid (for example, a sulfuric acid-hydrogen peroxide etching solution or an ammonium persulfate aqueous solution or the like) is used to remove dirt or the like adhering to the pores of the micro-through holes 40. Further, when the residue remains on the bottom of the microvia 40, it is removed (refer to FIG. 2(d)).

In the desmear step and the micro-etching step, the surface of the layered body 100 is neutralized A liquid or microetching solution or the like which is in contact with copper having an etching property. Since the electrolytic copper-tin alloy layer 13 has an etching property to the copper etching liquid, the surface is etched in the steps. Since the etching rate of the copper etching solution changes depending on the thickness and the tin content of the electrolytic copper-tin alloy layer 13, the timing at which the electrolytic copper-tin alloy layer 13 is dissolved can be controlled by adjusting these. For example, in the micro-etching step, it is necessary to clean the surface of the copper foil 12, etc., and it is preferable to completely dissolve and remove the copper-tin alloy layer 13 by adjusting the thickness or material of the electrolytic copper-tin alloy layer 13 in the desmear step. Electrolytic copper-tin alloy layer 13. On the other hand, in the case where it is necessary to maintain the initial thickness of the copper foil 12, the electrolytic copper-tin alloy layer 13 may be left incompletely dissolved in the desmear step, and in the subsequent microetching step, The electrolytic copper-tin alloy layer 13 may be completely dissolved and removed. The time at which the electrolytic copper-tin alloy layer 13 is dissolved and removed may be appropriately and appropriately determined in accordance with the characteristics required for the printed wiring board.

Next, the inside of the hole of the micro via 40 and the copper foil layer 12 are performed by an electroless plating step. On the top, an electroless plating film is formed, and interlayer connection (not shown) is performed. Subsequently, a plating resist is provided on the seed layer (copper foil + electroless plating film), and a wiring pattern is formed by electrolytic plating to perform filling plating in the via hole. Next, the plating resist and the seed layer under the plating resist are removed together by a rapid etching process. In addition, in FIG. 2, the step after the electroless plating process is abbreviate|omitted. In addition, the symbols of the respective constituent elements are also omitted in the following.

As described above, the copper foil for laser processing according to the present invention can be omitted from blackening treatment or the like. It is used to improve the absorption rate of the laser light, and directly irradiates the laser light to perform the hole drilling process. Therefore, the number of etching processes before the formation of the wiring pattern can be reduced. Further, according to the present invention, the insoluble laser absorbing layer such as an electrolytic copper-tin alloy layer is provided on the surface of the copper foil, so that after the laser boring process, copper can be prevented from being formed in various etching processes before the formation of the wiring pattern. The foil surface is etched. Further, as described above, when the electrolytic copper-tin alloy layer is used as the poorly soluble laser absorbing layer, the tin content thereof is appropriately adjusted, or The thickness of the electrolytic copper-tin alloy layer controls the point at which the electrolytic copper-tin alloy layer is dissolved and removed. In the example shown in Fig. 2, it is shown that the content of tin in the electrolytic copper-tin alloy layer is large, and the electrolytic copper-tin layer is not dissolved in the desmear step. However, the present invention is not limited to the illustrated examples, and the amount and thickness of tin in the electrolytic copper-tin alloy layer may be adjusted in accordance with characteristics required for the printed wiring board, and dissolved and removed in the desmear step. Copper-tin alloy layer.

Hereinafter, the present invention will be more specifically described by showing examples. Also, the present invention is not It is limited to the following examples.

Example

In this embodiment, a copper foil for laser processing having a carrier foil is produced by the following method. Subsequently, a copper-clad laminate is produced, and the laser drilling processability evaluation by the carbon dioxide gas laser is performed, and in the manufacturing step of the printed wiring board, copper is supplied for the etching treatment before the wiring pattern formation. Thickness deviation evaluation of foil (electrolytic copper foil layer). Hereinafter, the description will be made in order. Further, the evaluation method is equal to the description.

[Production of Copper Foil for Laser Processing with Carrier Foil]

In this embodiment, the laser with the carrier foil is fabricated by the following steps A~E. Working copper foil.

Step A: Using a surface roughness (Rzjis) of one side, a thickness of 18 μm and a thickness of 18 μm The copper foil was decomposed as a carrier foil, and a release layer was formed on the surface of the carrier foil as described below. Further, the surface roughness (Rzjis) is a value measured by a stylus type surface roughness measuring instrument using a diamond probe having a tip radius of curvature of 2 μm in accordance with JIS B 0601.

The carrier film has a free sulfuric acid concentration of 150 g/l, a copper concentration of 10 g/l, and a carboxyl group. Impregnation of dilute sulfuric acid solution containing carboxybenzotriazole with a concentration of benzotriazole of 800 ppm and a liquid temperature of 30 ° C 30 seconds. Subsequently, the carrier foil was pulled up, the contaminated component adhering to the surface of the carrier foil was removed by pickling, and the carboxybenzotriazole was adsorbed on the surface, and a release layer was formed on the surface of the carrier foil to form a carrier foil having a release layer.

Step B: Next, in the electrolytic solution containing the metal component, the carrier having the peeling layer is provided The body foil is cathodically polarized, and a heat resistant metal layer is formed on the surface of the release layer to form a carrier foil having a heat resistant metal layer and a release layer. Here, as the nickel electrolyte, a Watts bath containing a nickel sulfate (NiSO4.6H2O) 330 g/l, a nickel chloride (NiCl2.6H2O) 45 g/l, and a boric acid 30 g/l bath pH of 3 is used. Electrolysis was carried out at a liquid temperature of 45 ° C and a cathode current density of 2.5 A/dm 2 , and a nickel layer having a thickness of 0.01 μm was formed on the surface of the release layer to prepare a carrier foil having a heat resistant metal layer and a release layer.

Step C: Next, in the copper-tin plating bath having the following composition, the following electrolysis Under conditions, the carrier foil having the heat resistant metal layer and the release layer was cathodically polarized, and an electrolytic copper-tin alloy layer having a thickness of 0.7 μm was formed on the surface of the heat resistant metal layer.

(Composition of copper-tin plating bath and electrolysis conditions)

CuSO4.5H2O: 157 g/l (40 g/l in terms of Cu)

SnSO4: 127g / l (Sn conversion 70g / l)

C6H11O7Na: 70g/l

Free H2SO4: 70g/l

Liquid temperature: 35 ° C

Cathode current density: 30A/dm2

Step D: Next, a carrier film containing an electrolytic copper-tin alloy layer or the like is subjected to cathode polarization in a copper plating bath having the following composition to form an electrolytic copper having a thickness of 2 μm on the surface of the electrolytic copper-tin metal layer. A foil for obtaining a laser foil for laser processing having a carrier foil of the present invention.

(Composition of copper plating bath and electrolysis conditions)

CuSO4.5H2O: 255g/l (65g/l in Cu conversion)

Free H2SO4: 150g/l

Liquid temperature: 45 ° C

Cathode current density: 15A/dm2

Step E: In the present embodiment, a zinc-nickel alloy rust preventive layer is further formed on the surface of the electrolytic copper foil side of the copper foil for laser processing having the carrier foil, and an electrolytic chromate treatment and an amine decane are performed. The coupler is treated to obtain a surface-treated copper foil for laser processing having a carrier foil.

In the copper foil for laser processing having the carrier foil, the tin content in the electrolytic copper-tin alloy layer was 27.5% by mass. The tin content of the examples was measured as follows. A peeling layer is formed on the surface of the carrier foil, and a heat resistant metal layer is formed on the surface of the peeling layer, and a stage for forming an electrolytic copper-tin alloy layer on the surface of the heat resistant metal layer is used as a tin content measuring sample in the electrolytic copper-tin alloy layer. Subsequently, the electrolytic copper-tin alloy layer of the sample was peeled off from the carrier foil, and a foil composition analysis was performed using a fluorescent X-ray film thickness measuring device XDAL-FD (manufactured by Fischer Instruments) to calculate the tin content in the electrolytic copper-tin alloy layer. (quality%). Further, regarding the following comparative examples, the tin content was measured by the same method.

[Production of copper-clad laminate]

Using the above-described copper foil for laser processing having a carrier foil, a prepreg sheet of FR-4 having a thickness of 100 μm in which the insulating resin layer was formed was bonded to the surface of the electrodeposited copper foil by thermal press working. Next, the carrier foil of the copper foil for laser processing having the carrier foil was peeled off by the release layer, and the carrier foil was removed to obtain a copper-clad laminate.

Comparative example

[Comparative Example 1]

In Comparative Example 1, the same as the example except that the electrolytic copper-tin alloy layer was not provided. Thus, a peelable type electrolytic copper foil having a carrier foil was produced. Next, a copper-clad laminate was produced in the same manner as in the Example using the electrodeposited copper foil with a carrier foil.

[Comparative Example 2]

In Comparative Example 2, in the copper-tin plating bath of the following composition in the step C, the following Electrolytic conditions were carried out except that the carrier foil was subjected to cathode polarization, and an electrolytic copper-tin alloy layer having a thickness of 0.7 μm was formed on the carrier foil via a release layer and a heat resistant metal layer. An electrolytic copper foil having a carrier foil was produced in the same manner as in the examples. Next, a copper-clad laminate was produced in the same manner as in the Example using the electrodeposited copper foil with a carrier foil.

(Composition of copper-tin plating bath and electrolysis conditions)

CuSO4.5H2O: 79 g/l (20 g/l in terms of Cu)

SnSO4: 72g/l (Sn conversion 40g/l)

H2SO4: 70g/l

Liquid temperature: 45 ° C

Cathode current density: 15A/dm2

In the electrolytic copper foil having a carrier foil, the tin content in the electrolytic copper-tin alloy layer was 12.9% by mass.

[Comparative Example 3]

In Comparative Example 3, a copper-clad laminate was produced in the same manner as in Example using the electrodeposited copper foil having a carrier foil of Comparative Example 1. Next, a commercially available electroless tin plating solution was used on the surface of the copper foil of the copper-clad laminate to form a metal tin layer having a thickness of 0.4 μm. Then, the copper-clad laminate having the metal tin layer formed thereon is subjected to heat treatment at 200 ° C for 30 minutes to cause mutual diffusion between the copper component of the electrolytic copper foil and the tin component of the metallic tin layer. The surface of the copper foil is tin-copper-based A copper-clad laminate of a diffusion alloy layer.

[Evaluation]

Evaluation method

(1) Evaluation of laser hole drilling processability

Using the copper-clad laminates prepared in the above examples and comparative examples to open the laser holes The evaluation of the processing performance was performed using a carbon dioxide gas laser. At this time, the opening processing conditions using the carbon dioxide gas laser were 6.9 mJ in processing energy and 16 microseconds in pulse width. The beam diameter was 120 μm.

(2) Evaluation of thickness deviation of copper foil

Using the copper-clad laminates produced in the above examples and comparative examples, and manufacturing The same steps were performed in the desmear step and the micro-etching step generally performed in the process of printing the wiring board, and the thickness variation of the copper foil in the front and back of each step was evaluated.

Degreasing step: First, in the desmear step, the swelling treatment (swelling liquid: MLB-211 manufactured by Rohm and Haas Company, liquid temperature: 75 ° C, treatment time: 15 minutes), oxidation treatment using an alkaline aqueous solution of potassium permanganate (oxidation treatment liquid: MLB-213 manufactured by Rohm and Haas Company) , liquid temperature: 80 ° C, treatment time: 15 minutes), neutralization treatment (neutralization treatment liquid: MLB-216 manufactured by Rohm and Haas Company, liquid temperature: 40 ° C, treatment time: 15 minutes), followed by treatment After washing with water and drying, the thickness was measured by cross-sectional observation.

Micro-etching step: next, in the micro-etching step, each after the desolding step The copper-clad laminate was immersed in a sulfuric acid-hydrogen peroxide-based etching solution (CPE800, manufactured by Mitsubishi Gas Chemical Co., Ltd.) at a liquid temperature of 30 ° C for 60 seconds, washed with water, and dried, and the thickness was measured by cross-sectional observation. . Further, the cross-sectional observation was performed using VE-9800 manufactured by KEYENCE Co., Ltd.

2. Evaluation results

(1) Evaluation of laser hole drilling processability

In Table 1, the top of each of the copper-clad laminates is formed by the above-mentioned processing conditions. diameter. Here, the tip diameter is the opening diameter of the through hole as shown in Fig. 2(b). As shown in Table 1, in the copper-clad laminate produced in the examples and the comparative examples 2 and 3, the electrolytic copper-tin alloy layer containing tin was used as the outermost layer, and the electrolytic copper-tin alloy layer was irradiated with laser light. Therefore, in the case where the blackening treatment or the like is not performed before the laser light absorption rate is increased, it is confirmed that the opening can be performed by laser processing. Further, since the copper-clad laminate produced in Comparative Example 1 was confirmed to be directly openable by laser processing, it was impossible to borrow any treatment for improving the laser light absorption rate without performing blackening treatment or the like. Microvias are formed by laser processing.

On the other hand, in the case of the electrolytic copper foil of Comparative Example 3, the diameter of the tip end of the micro-through hole was 99.5 μm, the electrolytic copper foil of Comparative Example 3 had the same laser opening workability as those of the Example and the Comparative Example 2, considering only the tip diameter. However, the electrolytic copper foil of Comparative Example 3 has a diffusion alloy layer obtained by mutually diffusing copper and tin by thermally diffusing a metal tin layer formed by electroless plating. The diffusion alloy layer has a non-uniform distribution of tin in the thickness direction, and the distribution closer to the surface tin becomes more. Therefore, when the diffused alloy layer is irradiated with the laser light, it is considered that the tin having a low melting point is easily melted to cause dirt, and the amount of the dirt adhering to the periphery of the through hole is increased. Therefore, the dirt around the hole cannot be sufficiently removed by the micro-etching step or the like, and the dirt remains in the periphery of the hole after the micro-etching step. In this case, when the interlayer connection is to be realized by the electroless plating step, the protrusion portion may be abnormally precipitated, which is not preferable.

(2) Evaluation of the deviation of copper foil thickness

Next, FIG. 3 shows the FIB of the cross section of the copper-clad laminate of the embodiment and the comparative example 1. SIM image. As shown in Fig. 3, the copper-clad laminate produced in the examples was provided with an electrolytic copper-tin alloy layer of 0.7 μm on a 2 μm-thick electrolytic copper foil layer. With respect to the copper-clad laminate, as described above, when the desmear step is performed, the surface of the electrolytic copper-tin alloy layer is dissolved, and the thickness of the electrolytic copper-tin alloy layer is reduced by 0.21 μm. Next, when the micro-etching step is performed on the copper-clad laminate, the surface of the electrolytic copper-tin alloy layer is dissolved, and the thickness of the electrolytic copper-tin alloy layer is reduced by 0.38 μm. As described above, the electrolytic copper-tin alloy layer is dissolved in the desmear step and the microetching step, but the thickness of the copper foil does not change due to the presence of the electrolytic copper-tin alloy layer, and the initial thickness (2 μm) can be maintained. On the other hand, the copper-clad laminate produced in Comparative Example 1 does not have an electrolytic copper-tin alloy layer on the electrolytic copper foil, so the thickness is reduced by 0.10 μm at the time of the desmear step, and the thickness is small at the time of the micro-etching step. Reduced by 1.03μm. Further, in the examples, the tin content in the electrolytic copper-tin alloy layer was 27.5% by mass, and as shown in Fig. 1, the etching rate was slower when compared with the electroless copper foil containing no tin. Therefore, when the copper-clad laminate of Comparative Example 1 is compared with the copper-clad laminate of the embodiment, the etching amount is also increased, and the degree of variation in the thickness of the copper foil is increased.

On the other hand, although the illustration is omitted, the copper-clad laminate of Comparative Example 2 has a tin content of 12.9 mass% of the electrolytic copper-tin alloy layer, as shown in Fig. 1, the electrolytic copper-tin alloy layer is etched faster than the electrolytic copper foil containing no tin. Therefore, the copper-clad laminate of Comparative Example 2 has an electrolytic copper-tin alloy layer on the surface of the electrolytic copper foil layer, but the etching amount is increased to 0.20 μm in the desmear step, and the etching amount in the micro-etching step is increased to 1.25 μm, in which case the surface of the electrolytic copper foil layer is also dissolved, and the thickness of the electrolytic copper foil layer may vary.

Moreover, in the copper-clad laminate produced in Comparative Example 3, the expansion was mainly made of tin-copper. Since the scattered alloy layer has two layers of a tin layer and a tin-copper diffusion alloy layer as described above, the metal tin layer and the tin-copper diffusion layer have different etching rates for the respective etching liquids. In particular, the metal tin layer which becomes the outermost layer is hardly dissolved in the general etching treatment liquid system for copper foil (refer FIG. 1). Therefore, the etching amount after the desmear step and the micro-etching step is as small as 0.05 μm, and although it can function as an etching resist layer, it is difficult to borrow in the rapid etching step after the formation of the subsequent wiring pattern. The seed layer is removed by etching. Further, in the copper foil, it is considered that the etching rates in the respective layers of the metallic tin layer, the tin-copper diffusion alloy layer, and the electrolytic copper foil layer are different, and it is difficult to uniformly etch in the thickness direction. Further, when a general etching treatment liquid for a copper foil is used, the etching speed of the wiring pattern portion formed by electrolytic copper plating is faster than that of the metal tin layer serving as the outermost layer. Therefore, the etching factor is lowered, and it is difficult to form the wiring pattern with a good line width.

In contrast, the copper-clad laminate according to the embodiment, the desmear step and the micro-etching step In the step, since the electrolytic copper-tin alloy layer is dissolved and removed, when the seed layer is removed, the electrolytic copper foil layer and the electroless plating film formed on the electrolytic copper foil layer may be removed. Therefore, all of them are copper layers, so there is not much difference in etching speed. Moreover, the etching speed of the wiring pattern portion formed by electrolytic copper plating did not show much difference. Therefore, according to the copper foil for laser processing of the present invention, the wiring pattern can be formed with a good etching factor.

Industrial availability

By using the copper foil for laser processing of the present invention as described above, the laser processing property is excellent, and in the subsequent etching treatment, a uniform etching rate in the thickness direction can be obtained. Further, by using a carbon dioxide gas laser, direct opening of the copper foil for laser processing of the copper-clad laminate can be performed, and the pre-treatment such as blackening treatment for improving the laser light absorption efficiency can be eliminated, and the steps can be reduced. Can reduce overall manufacturing costs. Further, since the electrolytic copper-tin alloy layer functions as an etching resist, it is possible to prevent the surface of the copper foil from being dissolved and to prevent variations in the thickness of the copper foil in various etching steps before the formation of the wiring pattern. Further, when the seed layer is removed, only the copper foil portion is dissolved and removed, so that the wiring pattern can be formed by a good etching factor.

Claims (8)

A copper foil for laser processing, characterized in that a surface of a copper foil is provided with a poorly soluble laser absorbing layer capable of absorbing infrared laser light, the poorly soluble laser absorbing layer having an etching property to a copper etching solution, and an etching rate thereof The hardly soluble laser absorbing layer is an electrolytic copper-tin alloy layer having a tin content of 25% by mass or more and 50% by mass or less. The copper foil for laser processing according to claim 1, wherein the poorly soluble laser absorbing layer is an electrolytic copper-tin alloy layer formed by electrolytic plating. The copper foil for laser processing according to claim 1, wherein the thickness of the poorly soluble laser absorption layer is 3 μm or less. The copper foil for laser processing according to claim 1, wherein the copper foil has a thickness of 7 μm or less. The copper foil for laser processing according to claim 1, wherein the other surface of the copper foil has at least one of a roughened physical layer and a primer resin layer. A copper foil for laser processing having a carrier foil, characterized in that the carrier foil is peelably provided on the poorly soluble laser absorbing layer of the copper foil for laser processing according to claim 1. A copper-clad laminate is characterized in that the poorly-soluble laser absorbing layer is disposed on a side irradiated with the infrared laser light, and the copper foil for laser processing of claim 1 and a material of an insulating layer are laminated. A method for producing a printed wiring board, characterized in that it is used for laser processing having a absorbing property for a copper etching solution and having an etching rate slower than that of a copper foil and having a laser absorbing layer capable of absorbing infrared laser light on a surface of a copper foil a laminate formed by laminating copper foil and other conductor layers through an insulating layer, and directly irradiating the insoluble laser absorbing layer with infrared laser light to form a through hole for interlayer connection, thereby removing the slag in the through hole. The poorly soluble laser absorbing layer is removed from the surface of the copper foil in the step of slag and/or as a micro-etching step before the electroless plating; wherein the poorly soluble laser absorbing layer has a tin content of 25% by mass or more And a copper-tin alloy layer of 50% by mass or less.