KR102356407B1 - Copper foil for laser processing, carrier-foil-supported copper foil for laser processing, copper-clad laminate, and process for producing printed wiring board - Google Patents

Abstract

It aims at providing the manufacturing method of the copper foil for laser processing, copper foil for laser processing with carrier foil, copper clad laminated body, and a printed wiring board which is excellent in laser processability and can form a wiring pattern favorably. In order to achieve this objective, the copper foil for laser processing which concerns on this invention has etching property with respect to a copper etching liquid, the etching rate is slower than copper foil, and a scarcely soluble laser absorption layer which absorbs infrared laser beam is copper It is formed on the surface of the foil.

Description

Copper foil for laser processing, copper foil for laser processing with carrier foil, copper clad laminate and manufacturing method of a printed wiring board TECHNICAL FIELD PRINTED WIRING BOARD}

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

Conventionally, multilayering of a printed wiring board is advancing with high functionalization and compactization of an electronic device and an electric device. A multilayer printed wiring board laminates|stacks three or more wiring layers via an insulating layer, and electrically connects each wiring layer by interlayer connection means, such as a via hole and a through hole. As a manufacturing method of a printed wiring board, the build-up method is known. The build-up method refers to a manufacturing method in which wiring layers are laminated on an inner circuit with an insulating layer interposed therebetween and multilayered while performing interlayer connection. For example, when an ultra-high-definition wiring pattern is formed by a modified semi-additive method (MSAP method) or the like, a build-up printed wiring board is manufactured in the following procedure. First, copper foil is laminated on a core substrate or the like having an inner layer circuit with an insulating layer interposed therebetween, via holes or the like are formed by laser processing or the like, and interlayer connection is performed by electroless plating. Next, a plating resist is formed on the seed layer (copper foil + electroless plating layer) according to a wiring pattern, and after electrolytic plating, the seed layer under the plating resist together with the plating resist is removed by etching. By repeating the above process a necessary number of times, the buildup multilayer printed wiring board which has the desired number of wiring layers can be obtained.

In recent years, with the miniaturization of wiring patterns, interlayer connection has been made by means of microvia holes having a top diameter of 100 µm or less. These microvia holes are generally drilled by laser processing using a carbon dioxide laser or the like. At this time, the Cu direct method in which a carbon dioxide laser or the like is directly irradiated from the copper foil onto the copper foil and simultaneously punctures the copper foil and the insulating layer is employed in many cases. However, since copper has an extremely low absorption rate of laser light in the wavelength region of far-infrared to infrared rays such as a carbon dioxide laser, when forming microvia holes by the Cu direct method, a laser on the surface of copper foil such as blackening treatment in advance It was necessary to perform pretreatment for increasing the light absorptivity.

However, when the blackening process is performed with respect to the surface of copper foil, since the surface of copper foil is etched, while the thickness of copper foil decreases, a dispersion|variation generate|occur|produces in thickness. For this reason, when removing the seed layer, it is necessary to set the etching time according to the thickest part of the seed layer, and it becomes difficult to form a wiring pattern having a good line width with high linearity.

On the other hand, in patent document 1, the copper foil which formed the alloy layer which has Sn and Cu as a main body on the copper foil surface is described as a technique unnecessary at the time of the pre-processing at the time of laser processing. According to Patent Document 1, in the case of the same room temperature and the same surface roughness, Sn has a laser absorptivity twice or more higher than that of Cu. It is said that a via hole having a diameter of 100 µm can be formed by irradiating a laser beam directly on the surface of the copper foil without performing a pretreatment such as treatment.

Japanese Patent Laid-Open No. 2001-226796

However, the copper foil for laser drilling described in Patent Document 1 forms a metal Sn layer by vapor deposition or plating on the surface of the copper foil, and then, by diffusion treatment with heat, Sn and Cu on the surface of the copper foil A method of forming an alloyed alloy layer is employed. For this reason, in the said alloy layer, distribution generate|occur|produces in content of Sn in the thickness direction, and it is thought that dispersion|variation generate|occur|produces in the etching rate in the thickness direction of the said copper foil. Moreover, content of Sn is extremely high in the outermost surface of the said copper foil, and it is thought that the copper foil of patent document 1 has three-layer structure of a Sn layer, the alloy layer of Sn and Cu, and a copper layer in order from the surface layer. Since metallic Sn layer does not have the solubility with respect to the etching liquid with respect to common copper foil, when the copper foil of this patent document 1 is used, it is difficult to dissolve and remove an outermost surface by etching. Therefore, when the copper foil of patent document 1 is used, after removing the outermost surface of copper foil with the etching liquid of the metal Sn layer which can melt|dissolve Sn in advance at the time of an etching process, it is necessary to etch the lower layer, , the etching process becomes complicated. In addition, since the alloy layer of Sn and Cu described in Patent Document 1 is a layer alloyed by thermal diffusion, the metal composition in the thickness direction is considered to be non-uniform, and variations may occur in the etching rate in the thickness direction. have. For this reason, at the time of etching, copper foil cannot be etched with uniform thickness, but there exists a possibility that dispersion|variation may arise in the thickness of copper foil. Moreover, when content of Sn is high, it is thought that the etching rate becomes slower than the wiring pattern part formed by electrolytic copper plating on the surface of the said alloy layer. For this reason, when the seed layer is removed, the wiring pattern part is etched quickly, and the line width becomes narrow, making it difficult to obtain a good wiring pattern.

Therefore, the present invention is excellent in laser processability and the purpose of providing a method for manufacturing a copper foil for laser processing, a copper foil for laser processing with a carrier foil, a copper clad laminate, and a printed wiring board capable of forming a wiring pattern satisfactorily do.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching, the present inventors came to achieve the said objective by employ|adopting the following copper foils for laser processing.

The copper foil for laser processing according to the present invention has an etching property with respect to a copper etching solution, the etching rate is slower than that of copper foil, and a scarcely soluble laser absorption layer absorbing infrared laser light is provided on the surface of the copper foil characterized.

Copper foil for laser processing according to the present invention WHEREIN: It is preferable that the said sparingly soluble laser absorption layer is an electrolytic copper-tin alloy layer formed by the electrolytic plating method whose tin content is 25 mass % or more and 50 mass % or less.

The copper foil for laser processing which concerns on this invention WHEREIN: It is preferable that the thickness of the said sparingly soluble laser absorption layer is 3 micrometers or less.

Copper foil for laser processing which concerns on this invention WHEREIN: It is preferable that the thickness of the said copper foil is 7 micrometers or less.

Copper foil for laser processing which concerns on this invention WHEREIN: It is preferable to provide at least any one of a roughening process layer and a primer resin layer on the other surface of the said copper foil.

The copper foil for laser processing with carrier foil which concerns on this invention is equipped with carrier foil so that peeling is possible on the said sparingly soluble laser absorption layer, It is characterized by the above-mentioned.

The copper clad laminate according to the present invention is characterized in that the copper foil for laser processing and the insulating layer constituent material are laminated so that the sparingly soluble laser absorption layer is disposed on the side to which the infrared laser beam is irradiated.

The manufacturing method of the printed wiring board which concerns on this invention has etching property with respect to copper etching liquid, the etching rate is slower than copper foil, and the laser which equipped the laser absorption layer which absorbs infrared laser beam on the surface of copper foil. With respect to a laminate in which a copper foil for processing and another conductor layer are laminated through an insulating layer, an infrared laser beam is directly irradiated to the poorly soluble laser absorption layer to form a via hole for interlayer connection, and the smear in the via hole is removed. The micro-etching process as a pretreatment of a desmear process and/or an electroless-plating process WHEREIN: The said poorly soluble laser absorption layer is removed from the surface of the said copper foil, It is characterized by the above-mentioned.

The copper foil for laser processing which concerns on this invention is excellent in laser workability, and the etching process after that WHEREIN: An etching rate uniform in the thickness direction is obtained. In addition, direct drilling of the copper foil for laser processing of a copper clad laminate using a carbon dioxide laser becomes possible, and pretreatment such as blackening treatment for increasing laser light absorption efficiency becomes unnecessary, and the total manufacturing cost is reduced by reducing the process can do. In addition, since the poorly soluble laser absorption layer can function as an etching resist, the surface of the copper foil (layer) is dissolved in various etching steps before the wiring pattern is formed, thereby preventing the occurrence of variation in the thickness of the copper foil (layer) can do. For this reason, a wiring pattern can be formed with a favorable etching factor.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the relationship between the tin content of the electrolytic metal foil which concerns on this invention, and an etching rate.
It is a figure for demonstrating an example of the manufacturing method of the printed wiring board which concerns on this invention.
It is a figure for evaluating the etching property of the electrolytic copper foil in the copper clad laminated board produced by the Example and the comparative example 1. FIG.

Hereinafter, embodiment of the manufacturing method of the copper foil for laser processing which concerns on this invention, the copper foil for laser processing with carrier foil, a copper clad laminated board, and a printed wiring board is demonstrated in order.

1. Copper foil for laser processing

The copper foil for laser processing according to the present invention has an etching property with respect to a copper etching solution, the etching rate is slower than that of copper foil, and a scarcely soluble laser absorption layer absorbing infrared laser light is provided on the surface of the copper foil characterized. In the copper foil for laser processing according to the present invention, the copper foil for laser processing according to the present invention is directly irradiated with a laser beam to the surface of the copper foil for laser processing by the Cu direct method without pretreatment such as blackening treatment by the Cu direct method, It is made possible to form micropores, such as a hole, by laser processing.

Here, the sparingly soluble laser absorbing layer is, for example, a copper layer containing an infrared laser absorbing metal material having absorptivity to infrared laser light, and by containing the infrared absorbing material in the copper layer, the etching rate with respect to the copper etching solution is increased. It is preferable to set it as the copper layer containing the infrared laser absorbing metal material which can be made slower than the etching rate of copper foil. As a specific example of this poorly soluble laser absorption layer, the electrolytic copper-tin alloy layer containing 25 mass % or more and 50 mass % or less of the tin formed by the electrolytic plating method is mentioned, for example. In this embodiment, mainly as a poorly soluble laser absorption layer, this electrolytic copper-tin alloy layer is used, and it demonstrates below.

1-1. Electrolytic copper-tin alloy layer

First, an electrolytic copper-tin alloy layer is demonstrated. Compared with copper, tin has a high absorption rate of laser light (carbon dioxide laser light, etc.) having a wavelength in the far-infrared to infrared wavelength range. That is, the said electrolytic copper-tin alloy layer can be made to function as a laser beam absorption layer, and as mentioned above, the pretreatment at the time of drilling by Cu direct method can be made unnecessary. In addition, in the present invention, the electrolytic copper-tin alloy layer prevents the surface of the copper foil from being etched in the various etching processes performed in the desmear process or the micro-etching process performed before the wiring pattern formation after the drilling process. It can also function as an etching resist layer for The said electrolytic copper-tin alloy layer is etched in the various etching processes performed before these wiring pattern formation. However, the timing at which the said electrolytic-copper-tin alloy layer is melt|dissolved and removed is controllable according to the tin content and thickness. For this reason, it becomes possible to dissolve and remove only the electrolytic copper-tin alloy layer without dissolving the surface of the copper foil until the previous stage of the electroless plating process for interlayer connection. Therefore, for example, when forming a wiring pattern by the MSAP method, an electroless plating film can be formed on the copper foil of the state which maintained the original thickness, and the seed layer of uniform thickness can be obtained.

(1) Tin content

In the present invention, when an electrolytic copper-tin alloy layer is used as the sparingly soluble laser absorption layer, the tin content in the electrolytic copper-tin alloy layer is 25% by mass or more, in order to exhibit the function as the etching resist described above. to be. As shown in FIG. 1, when the tin content in an electrolytic-copper-tin alloy layer is less than 25 mass %, the etching rate of an electrolytic-copper-tin alloy layer becomes quick compared with the electrolytic copper foil of 0 mass % of tin content. On the other hand, when the tin content in the electrolytic copper-tin alloy layer becomes 25 mass % or more, the etching rate becomes slow compared with the normal electrolytic copper foil which does not contain a tin. Therefore, by setting the tin content in the electrolytic copper-tin alloy layer to be 25 mass% or more, as described above, the electrolytic copper-tin alloy layer can function as an etching resist, and various etching treatments performed before forming the wiring pattern. When the copper foil is melted, it is possible to prevent the occurrence of variation in the thickness of the copper foil. In addition, this specification is describing about invention regarding the specific tin mass % when the sum total content of copper and tin in a copper- tin alloy layer is 100 mass %.

In addition, since the electrolytic copper-tin alloy layer is composed of a copper-tin alloy obtained by precipitating on the surface of copper foil by an electrolytic plating method, the metal composition in the thickness direction becomes uniform, and the electrolytic copper-tin alloy layer is etched The speed can be made uniform in the thickness direction. Therefore, in the various etching treatments 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 etching rate becomes slow, so that content of tin increases. For this reason, as mentioned above, by adjusting the tin content and thickness in the said electrolytic-copper-tin alloy layer, an electrolytic-copper-tin alloy layer can be melt|dissolved and removed at an appropriate timing. Therefore, for example, if only the electrolytic copper-tin alloy layer is dissolved before the electroless plating process for interlayer connection, an electroless plating film can be formed on the copper foil surface in a state in which the original thickness is maintained. For this reason, for example, when a wiring pattern is formed by the MSAP method, a seed layer with a uniform thickness can be formed. Since it has a uniform composition, it is possible to dissolve and remove the seed layer at a uniform etching rate. From the above, it becomes possible to form a wiring pattern favorable to the etching factor. In addition, the same thing can be said also when forming a wiring pattern by the method including etching processes, such as a subtractive method, not limited to the MSAP method. That is, in the desmear process after laser drilling, etc., the electrolytic copper-tin alloy layer is removed and the copper foil (layer) in a state of maintaining the initial thickness can be exposed, so that a conductor layer with a uniform thickness can be obtained. Therefore, it is possible to form a good wiring pattern of the etching factor.

Here, when the etching rate of the electrolytic copper foil which does not contain a tin is 100, the etching rate of the electrolytic-copper-tin alloy foil in which a tin content exceeds 50 mass % becomes less than 3. Therefore, when the tin content in the electrolytic copper-tin alloy layer exceeds 50% by mass, the etching rate with respect to the copper etching solution becomes too slow, so at the time of various etching treatments performed before the formation of the wiring pattern, the electrolytic copper-tin alloy It becomes difficult to dissolve and remove the 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 with respect to the copper etching solution becomes 0 µm, so the general copper The etchant cannot remove the electrolytic copper-tin alloy layer from the surface of the copper foil. In these cases, it is necessary to separately provide an etching process for removing the electrolytic copper-tin alloy layer, which is not preferable. It is preferable that it is 45 mass % or less, as for the tin content in the said viewpoint to an electrolytic-copper-tin alloy layer, It is more preferable that it is 40 mass % or less, It is more preferable that it is 35 mass % or less. At this time, when the etching rate of the electrolytic copper foil with respect to copper etching liquid is 100, the etching rate of electrolytic copper- tin alloy foil is 4 (tin content: 45 mass %), respectively 13 (tin content: 40 mass %), 25 (tin content: 35 mass %). For this reason, by making tin content in an electrolytic-copper-tin alloy layer into said preferable range, it becomes easy to remove an electrolytic-copper-tin alloy layer in various etching processes performed before the said wiring pattern formation.

On the other hand, when the tin content is less than 25% by mass, the etching rate of the electrolytic copper-tin alloy foil with respect to the copper etching solution becomes faster than the etching rate of the copper foil containing no tin. Since it is necessary to increase the thickness of the copper-tin alloy layer and the amount of copper removed by etching increases, it is not economically preferable. However, the etching rate shown in FIG. 1 produces another electrolytic copper-tin alloy foil (thickness: 3 µm) having a tin content (mass%), and each electrolytic copper-tin alloy foil is dissolved in a sulfuric acid-hydrogen peroxide-based etchant for 30 It is a value calculated|required as the amount of etching per unit time (micrometer) calculated|required based on the thickness which was immersed for a second, washed with water, and dried, the thickness was measured by cross-sectional observation, and was calculated|required based on the thickness reduced by etching. In addition, tin content here can be measured by the following method. In the case of a copper foil for laser processing having a layer structure of "copper foil / electrolytic copper-tin alloy layer", a solution in which the entire copper foil for laser processing as a sample is dissolved, ICP analysis method, fluorescence X-ray apparatus, titration method, etc. "The amount of copper contained in the electrolytic copper-tin alloy layer" and "tin content in the total solution" calculated by measuring total copper content and subtracting "the amount of copper converted from the cross-sectional thickness of copper foil" from this total copper content ', the tin content (mass %) can be calculated. In addition, when the thickness of copper foil is known beforehand by cross-sectional observation etc., composition analysis of the foil defined as two-layer foil is performed using a fluorescent X-ray film thickness meter, and tin content (mass) in an electrolytic copper-tin alloy layer %) can be calculated.

(3) the thickness of the electrolytic copper-tin alloy layer

The thickness of an electrolytic-copper-tin alloy layer is suitable according to the thickness and use of the said copper foil for laser processing, and can be made into an appropriate value. However, considering that the electrolytic copper-tin alloy layer is dissolved and removed by etching at an appropriate stage before wiring pattern formation, it is preferably 3 µm or less, and 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 becomes difficult to achieve the objective of improving the absorption rate of laser light, and in the various etching treatments performed before wiring pattern formation, the electrolytic copper- It may become impossible to make a tin alloy layer fully function as an etching resist of copper foil. Therefore, from the said viewpoint, it is preferable that it is 0.3 micrometer or more, and, as for the thickness of an electrolytic-copper-tin alloy layer, it is more preferable that it is 0.5 micrometer or more. In addition, as described above, since the etching rate with respect to the copper etching solution changes with the tin content in the electrolytic copper-tin alloy layer, the thickness of the electrolytic copper-tin alloy layer is appropriate depending on the tin content, and It is preferable to set it as a value.

(4) copper etchant

In this invention, if it is an etching liquid generally used as an etching liquid with respect to copper as a copper etching liquid, it can use without specifically limiting. For example, various copper etching liquids, such as a copper chloride type etching liquid, an iron chloride type etching liquid, a sulfuric acid-hydrogen peroxide type etching liquid, a sodium persulfate type etching liquid, an ammonium persulfate type etching liquid, a potassium persulfate type etching liquid, can be used.

1-2. copper foil

Next, copper foil is demonstrated. In this invention, copper foil means the metal foil whose copper content is 99 mass % or more, removes an unavoidable impurity, and points out the tin non-containing copper foil which does not contain a tin. Any of an electrolytic copper foil and a rolled copper foil may be sufficient as the said copper foil. However, when economical efficiency and production efficiency are considered, it is more preferable that it is an electrolytic copper foil.

The said copper foil is a layer which adhere|attaches to an insulating layer constituent material, and comprises a part of a seed layer, etc., when manufacturing a multilayer printed wiring board. The thickness of the said copper foil can be made into the same thickness as the copper foil marketed as a general printed wiring board material. However, for example, when forming a wiring pattern by a method including an etching process such as the MSAP method or the subtractive method, from the viewpoint of obtaining a better etching factor, the copper foil is preferably thinner and 7 µm It is preferable that it is below. In particular, when forming a wiring pattern by the MSAP method using the said copper foil for laser processing, from a viewpoint of forming a finer wiring pattern with a favorable etching factor, the thickness of the said copper foil is 3 micrometers or less ultra-thin electrolytic copper It is more preferable that it is foil, and it is still more preferable that it is 2 micrometers or less. However, when the thickness of the said copper foil is 7 micrometers or less, it is preferable to use in the form of the copper foil for laser processing with carrier foil mentioned later so as not to cause problems, such as wrinkles and cracks, at the time of handling.

In addition, from the viewpoint of improving the etching factor, the surface on the side to be adhered to the interlayer insulating layer of the copper foil, that is, the surface on the opposite side to the surface on which the electrolytic copper-tin alloy layer is formed (hereinafter referred to as the adhesive surface) is smooth it is preferable to do Specifically, it is preferable that it is 3 micrometers or less, and, as for the surface roughness (Rzjis) of the said bonding surface, it is more preferable that it is 2 micrometers or less. However, when the roughening process layer demonstrated next is formed in the adhesive surface of the said copper foil, the surface roughness of the said adhesive surface points out the surface roughness of the adhesive surface after forming a roughening process layer.

1-3. harmonic treatment layer

The copper foil for laser processing which concerns on this invention WHEREIN: The roughening process layer may be formed in the surface on the opposite side to the adhesive surface of copper foil, ie, the surface in which the said electrolytic-copper-tin alloy layer is formed. By providing a roughening process layer in the adhesive surface of copper foil, the adhesiveness of copper foil and an insulating layer can be improved. A roughening process layer can be formed by the method of making a fine metal particle adhere to the surface (adhesion surface) of copper foil, the method of forming a roughening surface by an etching method, etc. As long as the adhesiveness of copper foil and an insulating layer can be physically improved, the method for forming a roughening process layer may be performed by any method, and various methods regarding a conventionally well-known roughening process can be employ|adopted.

1-4. Primer resin layer

The copper foil for laser processing which concerns on this invention WHEREIN: The primer resin layer may be formed in the said adhesive surface of copper foil. In this invention, a primer resin layer is an adhesive bond layer which has favorable adhesiveness with respect to both copper foil and an insulating layer constituent material. For example, as a primer resin layer, it can be set as the layer which consists of a resin composition containing an epoxy resin and an aromatic polyamide resin. By forming the said primer resin layer on the adhesive surface of copper foil, copper foil can be made to closely_contact|adhere to an insulating layer constituent material favorably.

The thickness of the primer resin layer is not particularly limited as long as the adhesiveness between the copper foil and the insulating layer constituent material can be improved, but for example, it can be in the range of 0.5 µm or more and 10 µm or less. Moreover, the roughening process layer and the primer resin layer may be formed simultaneously in the adhesive surface of copper foil.

1-5. Manufacturing method of copper foil for laser processing

In the copper foil for laser processing according to the present invention, when the sparingly soluble laser absorption layer is the above-mentioned electrolytic copper-tin alloy layer, for example, an electrolytic solution containing copper ions and tin ions is used, and the electrolytic plating method on the copper foil The manufacturing method will not be specifically limited if tin content can obtain the copper foil for laser processing which laminated|stacked the electrolytic-copper-tin alloy layer whose tin content is 25 mass % or more and 50 mass % or less. In addition, it goes without saying that you may provide various surface treatment layers as needed, such as a rust prevention process layer and a silane coupling process layer, in the adhesive surface of copper foil other than the roughening process layer and primer resin layer mentioned above.

2. Copper foil for laser processing with carrier foil

Next, the copper foil for laser processing with carrier foil (henceforth copper foil for laser processing with carrier foil) which concerns on this invention is demonstrated. The copper foil for laser processing with carrier foil is provided so that carrier foil is peelable on the sparingly-soluble laser absorption layer of the copper foil for laser processing, carrier foil / peeling layer / copper foil for laser processing (slightly soluble laser absorption layer / copper foil) Each layer is stacked as shown. The said copper foil for laser processing with carrier foil WHEREIN: Since the structure similar to the copper foil for laser processing mentioned above except the structure regarding carrier foil is employable, only the structure regarding carrier foil is demonstrated here.

2-1. carrier foil

Carrier foil is a metal foil provided so as to be peelable on the copper foil for laser processing, and when the copper foil for laser processing is an ultra-thin copper foil with a thickness of 7 µm or less as described above, by supporting the copper foil for laser processing with a carrier foil, wrinkles and cracks, etc. By preventing it, its handling property can be improved. The material constituting the carrier foil is not particularly limited, but in order to enable the formation of the electrolytic copper-tin alloy layer and the copper foil by electrodeposition on the carrier foil with a release layer interposed therebetween, it is a metallic material having conductivity it is preferable For example, copper foil, copper alloy foil, aluminum foil, composite foil in which a metal plating layer such as copper or zinc is formed on the surface of the aluminum foil, stainless foil, a resin film having a metal coating on the surface, etc. can be used. Among these materials, copper foil can be suitably used as carrier foil. After peeling carrier foil from the copper foil for laser processing by using copper foil as carrier foil, since this can be reused as a copper raw material, it is preferable from a viewpoint of resource conservation.

Although the thickness of carrier foil is not specifically limited, For example, it can be 5 micrometers or more and 100 micrometers or less. When the thickness of carrier foil is less than 5 micrometers, the thickness of carrier foil is thin, and the original objective of carrier foil of improving the handling property of the copper foil for ultra-thin laser processing of 7 micrometers or less cannot be achieved, and it is not preferable. In addition, from a viewpoint of resource conservation etc., it is preferable that the thickness of carrier foil is 100 micrometers or less, and it is applicable also in the thickness of 35 micrometers or less.

2-2. release layer

The said copper foil for laser processing with carrier foil is a so-called peelable type copper foil for laser processing with carrier foil. In the peeling layer, while enabling the carrier foil to be easily peeled by hand with respect to the copper foil for laser processing, it is required to adhere to the carrier foil and the copper foil for laser processing with an appropriate adhesion strength until the carrier foil is peeled off. . As such a peeling layer, the inorganic peeling layer comprised from an inorganic material, and the organic peeling layer comprised from an organic agent are mentioned, for example.

(1) inorganic release layer

As the inorganic agent constituting the inorganic release layer, for example, one or two or more selected from chromium, nickel, molybdenum, tantalum, vanadium, tungsten, cobalt, and oxides thereof can be used.

(2) organic release layer

As the organic agent constituting the organic release layer, for example, one selected from a nitrogen-containing organic compound, a sulfur-containing organic compound, and a carboxylic acid, or two or more of them can be used in combination. Although any of an inorganic peeling layer and an organic peeling layer may be sufficient as a peeling layer, it is preferable that it is an organic peeling layer from a viewpoint that the peeling characteristic of carrier foil is stable.

More specifically, the following compounds are preferably employed as the nitrogen-containing organic compound, the sulfur-containing organic compound, and the carboxylic acid. Examples of the nitrogen-containing compound include orthotriazoles, aminotriazoles, imidazoles, salts thereof, or derivatives thereof. In particular, carboxybenzotriazole as orthotriazoles, 3-amino-1H-1, 2,4-triazole as aminotriazoles, and N' and N'-bis(benzotriazolylmethyl)urea as triazole derivatives are mentioned. can Any one or more of these can be used to form an organic release layer composed of a nitrogen-containing compound.

As the sulfur-containing compound, for example, thiazole, mercaptobenzothiazole, dibenzoazyldisulfide, cyclohexylamine salt of mercaptobenzothiazole, dicyclohexylamine salt of mercaptobenzothiazole, thiocyanur acid and 2-benzimidazolethiol; and the like. When forming an organic peeling layer using a sulfur-containing compound, it is especially preferable to use mercaptobenzothiazole and thiocyanuric acid among these.

As carboxylic acids, high molecular weight carboxylic acid is mentioned, for example. It is especially preferable to use the fatty acid which is a monocarboxylic acid of a long-chain hydrocarbon among high molecular weight carboxylic acids. Although the fatty acid may be a saturated fatty acid, it is especially preferable to use unsaturated fatty acids, such as an oleic acid and a linolenic acid.

(3) thickness of release layer

It is preferable that it is 100 nm or less, and, as for the thickness of a peeling layer, it is more preferable that it is 50 nm or less. In a so-called peelable type copper foil with carrier foil, in general, a release layer is formed on the surface of the carrier foil, and copper is deposited on the carrier foil through the release layer by an electrolysis or the like method to form an electrolytic copper foil. to form At this time, when the thickness of a peeling layer exceeds 100 nm, in the case of an organic type peeling layer, it will become difficult to form an electrolytic copper foil on the said peeling layer. Moreover, simultaneously with this, the adhesive strength of carrier foil and electrolytic-copper foil falls. Therefore, the thickness of the release layer is preferably 100 nm or less. The lower limit of the thickness of the release layer is not particularly limited as long as a release layer having a uniform thickness can be formed. However, when the thickness is less than 1 nm, it becomes difficult to form a peeling layer with a uniform thickness, and a deviation occurs in the thickness. For this reason, it is preferable that it is 1 nm or more, and, as for the thickness of a peeling layer, it is more preferable that it is 2 nm or more.

2-3. heat-resistant metal layer

The copper foil for laser processing with carrier foil forms a heat-resistant metal layer between the carrier foil and the peeling layer, or between the peeling layer and the electrolytic copper-tin alloy layer of the copper foil for laser processing, carrier foil / heat-resistant metal layer / peeling layer / laser It is also preferable to set it as the laminated constitution of the copper foil for a process or the laminated constitution of carrier foil / peeling layer / heat-resistant metal layer / copper foil for a laser process.

2-4. Manufacturing method of copper foil for laser processing with carrier foil

The manufacturing method of the copper foil for laser processing with carrier foil is not specifically limited. For example, after forming a peeling layer on the surface of carrier foil, the said electrolytic copper-tin alloy layer and copper foil are electrolytically deposited on the carrier foil through a peeling layer, copper for laser processing with carrier foil of the said structure, etc. As long as foil can be obtained, you may manufacture it by any method.

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

In the case of the copper foil for laser processing with carrier foil, the laminated constitution of "carrier foil / peeling layer / electrolytic copper- tin alloy layer / copper foil" is provided. Therefore, in order to measure the tin content of an electrolytic-copper-tin alloy layer, it is preferable to employ|adopt the following methods. In the case of the copper foil for laser processing with carrier foil which concerns on this application, when carrier foil is peeled, it will become the laminated constitution of "a peeling layer/electrolytic copper-tin alloy layer/copper foil." In addition, since the peeling layer at this time is comprised from the component mentioned above, it does not affect the measurement of the tin content of an electrolytic-copper-tin alloy layer. Therefore, the total copper content is measured using the ICP analysis method, the fluorescence X-ray apparatus, the titration method, etc. for the solution in which all the samples of the layer constitution of "exfoliation layer / electrolytic copper-tin alloy layer / copper foil" are dissolved, and this whole Tin content (mass %) is computed from "the amount of copper contained in the electrolytic copper-tin alloy layer" and "tin content in solution" computed by subtracting "the amount of copper converted from the cross-sectional thickness of copper foil" from copper content can do. In addition, when the thickness of copper foil is known beforehand by cross-sectional observation etc., composition analysis of the foil defined as two-layer foil is performed using a fluorescent X-ray film thickness meter, and tin content (mass) in an electrolytic copper-tin alloy layer %) can be calculated.

3. Copper clad laminate

Next, the copper clad laminated body which concerns on this invention is demonstrated. The copper clad laminate according to the present invention is characterized in that the copper foil for laser processing and the insulating layer constituent material are laminated so that the sparingly soluble laser absorbing layer is disposed on the side to which the infrared laser beam is irradiated. That is, in the copper clad laminate according to the present invention, an insulating layer constituent material and the above-mentioned copper foil for laser processing are laminated, and the insulating layer constituent material/copper foil/slightly soluble laser absorption layer (electrolytic copper-tin alloy layer) are laminated in this order. Any laminate may be used as long as it has a laminated structure. In addition, as long as the said copper clad laminated body can be obtained, there will be no limitation in particular in the manufacturing method. For example, by laminating the copper foil side of the copper foil for laser processing or copper foil with carrier foil on the so-called B-stage insulating resin substrate or insulating resin layer, and heating and pressing, the copper foil for laser processing is formed on the insulating resin substrate or insulating resin layer. A laminated copper clad laminate can be obtained. In addition, when the copper foil for laser processing with carrier foil is used, what is necessary is just to remove carrier foil at an appropriate stage.

4. Manufacturing method of printed wiring board

Next, the manufacturing method of the printed wiring board which concerns on this invention is demonstrated. Here, referring to FIG. 2, using the copper foil 10 for laser processing which concerns on this invention, the case where a wiring pattern is formed by the MSAP method is mentioned as an example and demonstrated. In addition, the copper foil 10 for laser processing used here is a layer of primer resin layer 11/copper foil (electrolytic copper thin layer) 12/electrolytic copper-tin alloy layer 13 (slightly soluble laser absorption layer) It shall be provided with a structure, and the roughening process layer shall not be formed in the adhesive surface of the copper foil 12. In addition, below, the method of manufacturing the multilayer printed wiring board in which the wiring layer laminated|stacked 3 or more layers through the insulating layer is demonstrated. However, the manufacturing method of the printed wiring board which concerns on this invention is not limited to the manufacturing method of a multilayer printed wiring board, It is applicable also when manufacturing a double-sided printed wiring board.

First, the so-called B-stage insulating layer constituent material 20 is interposed on the inner circuit 30 (another conductor layer), and the adhesive surface side of the copper foil 10 for laser processing with carrier foil is laminated on the adhesive surface. And the laminated body shown to Fig.2 (a) is obtained by making the insulating layer constituent material 20, the inner-layer circuit 30, and the copper foil 10 for laser processing each closely_contact|adhere by heating and pressurizing, respectively.

Then, the surface of the electrolytic copper-tin alloy layer 13 serving as the outermost layer is directly irradiated with infrared laser light by a carbon dioxide laser or the like, and a microvia hole having the conductor pattern portion 30a of the inner circuit 30 as the bottom portion. (40) is formed (see Fig. 2 (b)).

After forming the microvia hole 40, a desmear process of removing the smear remaining in the bottom of the microvia hole 40 using a desmear liquid is performed (refer FIG.2(c)). In the desmear step, after immersing the layered product 100 in the swelling liquid, immersed in a so-called desmear liquid (eg, alkaline permanganic acid aqueous solution, etc.) to remove the smear, and then immersed in a neutralizing liquid (reducing agent), A neutralization treatment for reducing and removing potassium permanganate is performed.

Then, the micro-etching process as a pre-processing of an electroless-plating process is performed. In the micro-etching step, splashes adhering to the periphery of the micro-via hole 40 are removed using a micro-etching solution (eg, sulfuric acid-hydrogen peroxide etching solution, ammonium persulfate-based aqueous solution, etc.). In addition, when smear remains at the bottom of the micro-via hole 40, it is removed (refer to FIG. 2(d)).

In these desmear processes and micro-etching processes, the surface of the said laminated body 100 comes into contact with the processing liquid which has etching property with respect to copper, such as a neutralization liquid and a micro-etching liquid. Since the said electrolytic copper-tin alloy layer 13 has etching property with respect to a copper etching liquid, the surface is etched in these processes. Since the etching rate with respect to copper etching liquid changes with the thickness and tin content of the said electrolytic-copper-tin alloy layer 13, the timing of dissolving the said electrolytic-copper-tin alloy layer 13 can be controlled by adjusting these. have. For example, in the micro-etching process, when it is necessary to clean the surface of the copper foil 12, by adjusting the thickness, material, etc. of the said electrolytic copper-tin alloy layer 13, to a desmear process Therefore, it is preferable to completely dissolve and remove the said electrolytic copper-tin alloy layer 13. On the other hand, when it is necessary to maintain the thickness of the copper foil 12 at the initial thickness, in the desmear process, the electrolytic copper-tin alloy layer 13 is left without completely dissolving, and in the subsequent micro-etching process In this case, what is necessary is just to completely melt|dissolve and remove the said electrolytic-copper-tin alloy layer 13. The timing at which the electrolytic copper-tin alloy layer 13 is dissolved and removed is appropriate and appropriate according to the characteristics required for the printed wiring board, and the like.

Then, an electroless plating film is formed on the inside of the microvia hole 40 and on the copper thin layer 12 by an electroless plating process to perform interlayer connection (not shown). Thereafter, a plating resist is provided on the seed layer (copper foil + electroless plating film), a wiring pattern is formed by the electrolytic plating method, and the inside of the via hole is filled and plated. And the seed layer under the plating resist is removed together with a plating resist by a flash etching process. In addition, in FIG. 2, illustration is abbreviate|omitted about the process after an electroless-plating process. In addition, below, the code|symbol for each component is abbreviate|omitted.

As mentioned above, according to the copper foil for laser processing which concerns on this invention, a laser beam is irradiated directly, and a drilling process can be performed, without performing pre-processing for increasing the absorption rate of laser beams, such as a blackening process. For this reason, the number of times of the etching process before wiring pattern formation can be reduced. Further, according to the present invention, since the surface of the copper foil is provided with a poorly soluble laser absorption layer such as an electrolytic copper-tin alloy layer, various etching treatments performed after laser drilling and before wiring pattern formation WHEREIN: The surface of the copper foil This can be prevented from being etched. In addition, as mentioned above, when employ|adopting an electrolytic copper-tin alloy layer as a sparingly soluble laser absorption layer, by adjusting the tin content and the thickness of the said electrolytic copper-tin alloy layer suitably, an electrolytic copper-tin alloy layer The timing of dissolving and removing can be controlled. In the example shown in FIG. 2, there was comparatively much tin content in an electrolytic-copper-tin alloy layer, and the case where an electrolytic-copper-tin layer did not melt|dissolve in the desmear process was shown. However, it is not limited to the example of illustration, According to the characteristic etc. requested|required of the said printed wiring board, you may dissolve and remove the electrolytic copper- tin alloy layer in a desmear process by adjusting the amount and thickness of the tin in an electrolytic-copper-tin alloy layer. .

Hereinafter, an Example is shown and this invention is demonstrated further more concretely. In addition, the present invention is not limited to the following examples.

Example

In this Example, the copper foil for carrier foil laser processing is produced by the method demonstrated below, the copper clad laminated body is produced after that, and laser drilling processability evaluation by a carbon dioxide laser is performed, and the manufacturing process of a printed wiring board WHEREIN: Variation evaluation of the thickness of copper foil (electrolytic copper foil layer) at the time of using to the etching process performed before wiring pattern formation was performed. Hereinafter, they are sequentially described. In addition, the method of evaluation, etc. are mentioned later.

[Production of copper foil for laser processing with carrier foil]

In this Example, the copper foil for laser processing with carrier foil was produced by the following processes A - E.

Step A: An electrolytic copper foil having a thickness of 18 µm with a surface roughness (Rzjis) of 0.6 µm on one side was used as the carrier foil, and a release layer was formed on the surface of the carrier foil as follows. In addition, the surface roughness Rzjis is the value measured with the stylus type surface roughness meter using a diamond stylus with a tip curvature radius of 2 micrometers based on JISB0601.

Free sulfuric acid concentration of 150 g/l, copper concentration of this carrier foil was immersed for 30 second with respect to carboxybenzotriazole containing dilute sulfuric acid aqueous solution of 800 ppm and 30 degreeC liquid temperature of 150 g/l, copper concentration, and carboxybenzotriazole density|concentration. Then, by pulling up carrier foil, while acid washing removes the contaminant component adhering to the surface of carrier foil, carboxybenzotriazole is made to adsorb|suck to the surface, a peeling layer is formed on the surface of carrier foil, and a peeling layer It was set as carrier foil provided with.

Step B: Next, in the metal component-containing electrolyte solution, the carrier foil provided with the release layer was cathode-polarized, and a heat-resistant metal layer was formed on the surface of the release layer to obtain a carrier foil provided with the heat-resistant metal layer and the release layer. Here, as the nickel electrolyte solution, nickel sulfate containing (NiSO ₄ · 6H ₂ O) to 330g / l, nickel chloride _{(NiCl 2 · 6H 2 O)} 45g / l, boric acid 30g / l, the bath pH 3 the Using a Watt bath, electrolysis was carried out at a liquid temperature of 45 ° C. and a cathode current density of 2.5 A/dm ² , a nickel layer having a thickness of 0.01 μm was formed on the surface of the release layer, and a carrier foil having a heat-resistant metal layer and a release layer was produced. .

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

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

CuSO ₄ 5H ₂ O: 157 g/l (Cu conversion 40 g/l)

SnSO ₄ :127g/l (Sn equivalent 70g/l)

C ₆ H ₁₁ O ₇ Na:70 g/l

Free H ₂ SO ₄ :70 g/l

Liquid temperature: 35 degrees Celsius

Cathode current density: 30A/dm ²

Step D: Next, a carrier foil having an electrolytic copper-tin alloy layer or the like is cathode polarized under the following conditions in a copper plating bath of the following composition, and an electrolytic copper foil having a thickness of 2 μm is applied to the surface of the electrolytic copper-tin metal layer. It formed and obtained the copper foil for laser processing with carrier foil which concerns on this invention.

(Composition of copper plating bath and electrolytic conditions)

CuSO ₄ 5H ₂ O: 255 g/l (Cu conversion 65 g/l)

Free H ₂ SO ₄ :150 g/l

Liquid temperature: 45 degrees Celsius

Cathode current density: 15A/dm ²

Step E: In this embodiment, a zinc-nickel alloy rust prevention layer is further formed on the surface of the electrolytic copper foil side of the copper foil for laser processing with carrier foil, and electrolytic chromate treatment and amino-based silane coupling agent treatment are performed, the carrier foil Copper foil for a surface treatment laser processing with a provision was obtained.

This copper foil for laser processing with carrier foil WHEREIN: Tin content in an electrolytic-copper-tin alloy layer was 27.5 mass %. The tin content of the Example was measured as follows. What is the step of forming a release layer on the surface of the carrier foil, forming a heat-resistant metal layer on the surface of the release layer, and forming an electrolytic copper-tin alloy layer on the surface of the heat-resistant metal layer, the tin content in the electrolytic copper-tin alloy layer It was set as the measurement sample. Thereafter, the electrolytic copper-tin alloy layer of the sample was peeled off from the carrier foil, and composition analysis of the foil was performed using a fluorescent X-ray film thickness meter XDAL-FD (manufactured by Fischer Instruments), and the electrolytic copper-tin alloy layer was Tin content (mass %) was computed. In addition, also about the following comparative example, the tin content is measured by the same method.

[Production of copper clad laminate]

Using the above-mentioned copper foil for laser processing with carrier foil, a prepreg of FR-4 having a thickness of 100 µm was bonded to the adhesive surface of the electrolytic copper foil by hot pressing as an insulating resin layer constituent material. And the carrier foil of the copper foil for laser processing with carrier foil was peeled off through the peeling layer, the carrier foil was removed and the copper clad laminated board was obtained.

comparative example

[Comparative Example 1]

In Comparative Example 1, an electrolytic copper foil with carrier foil of a peelable type was produced in the same manner as in Examples except that the electrolytic copper-tin alloy layer was not provided. And using this electrolytic copper foil with carrier foil, it carried out similarly to an Example, and produced the copper-clad laminated board.

[Comparative Example 2]

In Comparative Example 2, in step C, in a copper-tin plating bath of the following composition, the carrier foil was cathode polarized under the following electrolysis conditions, and a peeling layer and a heat-resistant metal layer were interposed on the carrier foil, and the electrolysis having a thickness of 0.7 μm Except having formed the copper- tin alloy layer, it carried out similarly to the Example, and produced the electrolytic copper foil with carrier foil. And using this electrolytic copper foil with carrier foil, it carried out similarly to an Example, and produced the copper-clad laminated board.

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

CuSO ₄ 5H ₂ O: 79 g/l (Cu equivalent 20 g/l)

SnSO ₄ :72 g/l (Sn equivalent: 40 g/l)

H ₂ SO ₄ :70 g/l

Liquid temperature: 45 degrees Celsius

Cathode current density: 15A/dm ²

This electrolytic copper foil with carrier foil WHEREIN: Tin content in an electrolytic-copper-tin alloy layer was 12.9 mass %.

[Comparative Example 3]

In Comparative Example 3, using the electrolytic copper foil with carrier foil of Comparative Example 1, a copper clad laminate was produced in the same manner as in Examples. Then, on the surface of the copper foil of this copper clad laminate, a metal tin layer having a thickness of 0.4 µm was formed using a commercially available electroless tin plating solution. Then, the copper clad laminate on which the metal tin layer is formed is heat-treated under the condition of 200° C. × 30 minutes to cause mutual diffusion between the copper component of the electrolytic copper foil and the tin component of the metal tin layer, and A copper-clad laminate having a surface layer of a diffusion alloy layer mainly composed of tin-copper was obtained.

[evaluation]

1. Evaluation method

(1) Evaluation of laser drilling workability

Carbon dioxide gas laser was used for evaluation of laser drilling processing performance using each copper clad laminated board produced by the said Example and the comparative example. The drilling|boring processing conditions by the carbon dioxide laser at this time were performed on the conditions of a processing energy of 6.9 mJ, a pulse width of 16 microseconds, and a beam diameter of 120 micrometers.

(2) Evaluation of variation in thickness of copper foil

Using each of the copper clad laminates produced in the Examples and Comparative Examples, the same processing as the desmear process and micro-etching process generally performed in the manufacturing process of the printed wiring board is performed, and the thickness of the copper foil before and after each process change was evaluated.

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

Micro-etching step: Next, in the micro-etching step, each copper clad laminate after the desmear step is 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, followed by washing with water. After drying, the thickness was measured by cross-sectional observation. In addition, VE-9800 manufactured by Keyence Corporation was used for cross-sectional observation.

2. Evaluation results

(1) Evaluation of laser drilling workability

Table 1 shows the top diameter of each copper clad laminate when via holes are formed under the above processing conditions. Here, the top diameter refers to the opening diameter of the via hole as shown in FIG. 2B . As shown in Table 1, in the copper clad laminates produced in Examples and 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 added to the electrolytic copper-tin alloy layer. In order to irradiate a laser beam, it was confirmed that a perforation was possible by laser processing, without performing pre-processing for increasing the absorption rate of laser beam, such as a blackening process. In addition, in the copper clad laminate produced in Comparative Example 1, it cannot be directly drilled by laser processing, and microvia holes are formed by laser processing unless pretreatment for increasing the absorption rate of laser light such as blackening is performed. It was confirmed that it could not be done.

On the other hand, in the case of the electrolytic copper foil of Comparative Example 3, the top diameter of the microvia hole is 99.5 μm, and when only the top diameter is considered, the electrolytic copper foil of Comparative Example 3 has laser drilling properties equivalent to those of Examples and Comparative Example 2 . However, the electrolytic copper foil of Comparative Example 3 is provided with a diffusion alloy layer obtained by mutually diffusing copper and tin by thermal diffusion of a metal tin layer formed on the surface by an electroless plating method. In the said diffusion alloy layer, distribution of the tin in the thickness direction is non-uniform|heterogenous, and distribution of tin increases so that the surface is near. Therefore, when the said diffusion alloy layer is irradiated with a laser beam, tin with a low melting|fusing point melts, it becomes easy to generate|occur|produce splash, and the amount of splash adhering to the periphery of a via hole increases. For this reason, depending on the micro-etching process or the like, the splash around the hole cannot be sufficiently removed, and it is considered that the splash remains around the hole as a protrusion even after the micro-etching process. In this case, when interlayer connection is achieved by the electroless plating process, abnormal precipitation may be caused in the said projection part, and it is unpreferable.

[Table 1]

(2) Evaluation of variation in thickness of copper foil

Next, the FIB-SIM image which shows the cross section of the copper clad laminated board of Example and Comparative Example 1 is shown in FIG. As shown in FIG. 3, the copper clad laminated board produced in the Example is equipped with the electrolytic copper-tin alloy layer of 0.7 micrometer on the electrolytic copper thin layer of thickness 2 micrometer. As for the copper clad laminate, when the desmear process was performed as described above, the surface of the electrolytic copper-tin alloy layer was dissolved, and the thickness of the electrolytic copper-tin alloy layer decreased by 0.21 µm. Next, when the micro-etching process was performed on the copper clad laminate as described above, the surface of the electrolytic copper-tin alloy layer was dissolved, and the thickness of the electrolytic copper-tin alloy layer decreased by 0.38 µm. In this way, although the electrolytic copper-tin alloy layer is dissolved during the desmear process and the micro-etching process, there is no change in the thickness of the copper foil due to the presence of the electrolytic copper-tin alloy layer, and the initial thickness (2 µm) is can keep In contrast, in the copper clad laminate prepared in Comparative Example 1, since the electrolytic copper-tin alloy layer was not provided on the electrolytic copper thin layer, the thickness decreased by 0.10 µm during the desmear process and 1.03 µm during the micro-etching process. do. In addition, in an Example, the tin content in an electrolytic copper-tin alloy layer is 27.5 mass %, and as shown in FIG. 1, compared with the electrolytic copper foil which does not contain a tin, an etching rate is slow. For this reason, in the copper clad laminated board of the comparative example 1, compared with the copper clad laminated board of an Example, the etching amount also becomes large, and the possibility that a dispersion|variation arises in the thickness of copper foil increases.

On the other hand, although not illustrated, the copper clad laminate of Comparative Example 2 includes an electrolytic copper-tin alloy layer having a tin content of 12.9% by mass, and as shown in FIG. 1 , the electrolytic copper-tin alloy layer is etched. The rate is higher than the etching rate of the electrolytic copper foil containing no tin. For this reason, although the copper clad laminate of Comparative Example 2 has an electrolytic copper-tin alloy layer on the surface of the electrolytic copper thin layer, the etching amount in the desmear process is 0.20 µm and the etching amount in the micro-etching process is 1.25 µm, which is large. , also in this case, the surface of the thin electrolytic copper layer is melted, and a deviation may occur in the thickness of the electrolytic copper thin layer.

In addition, in the copper clad laminate produced in Comparative Example 3, since the diffusion alloy layer mainly composed of tin-copper has a two-layer configuration of a tin layer and a tin-copper diffusion alloy layer, as described above, a metal tin layer And, in a tin-copper diffusion alloy layer, the etching rate with respect to each etching liquid differs, respectively. In particular, it is difficult to melt|dissolve the metal tin layer used as the outermost layer in the general etching process liquid with respect to copper foil (refer FIG. 1). For this reason, the etching amount after the desmear process and the micro-etching process is as small as 0.05 µm in total, and functions as an etching resist layer, but in the subsequent flash etching process after wiring pattern formation, it becomes difficult to remove the seed layer by etching. . Moreover, in the said copper foil, in each layer of a metal tin layer, a tin copper diffusion alloy layer, and an electrolytic copper foil layer, it is thought that an etching rate differs, and it becomes difficult to etch uniformly in the thickness direction. Moreover, when the general etching process liquid with respect to copper foil is used, the direction of the wiring pattern part formed by electrolytic copper plating becomes faster than the metal tin layer used as outermost layer. Accordingly, the etching factor is lowered, and it becomes difficult to form a wiring pattern with a satisfactory line width.

On the other hand, according to the copper clad laminate of the example, since the electrolytic copper-tin alloy layer can be dissolved and removed in the desmear process and the micro-etching process, when removing the seed layer, the electrolytic copper thin layer and this electrolytic copper thin layer What is necessary is just to remove the electroless copper plating film formed on it. Since these are all copper layers, a large difference in etching rate is not seen. Moreover, a large difference with the etching rate of the wiring pattern part formed by electrolytic copper plating is not revealed either. Therefore, according to the copper foil for laser processing which concerns on this invention, it becomes possible to form a wiring pattern with a favorable etching factor.

As mentioned above, it is excellent in laser workability by using the copper foil for laser processing which concerns on this invention, and the etching process after that WHEREIN: An etching rate uniform in the thickness direction is obtained. In addition, direct drilling of copper foil for laser processing of a copper clad laminate using a carbon dioxide laser becomes possible, and pretreatment such as blackening treatment for increasing laser light absorption efficiency becomes unnecessary, and the total manufacturing cost is reduced by reducing the process can do. In addition, since the electrolytic copper-tin alloy layer can function as an etching resist, it is possible to prevent the surface of the copper foil from dissolving in various etching steps before formation of the wiring pattern and occurrence of variation in the thickness of the copper foil. In addition, when removing the seed layer, since only the copper foil portion needs to be dissolved and removed, a wiring pattern can be formed with a good etching factor.

Claims (8)

It has etching property with respect to copper etching liquid, the etching rate is slower than copper foil, and is equipped with the sparingly soluble laser absorption layer which absorbs infrared laser beam on the surface of copper foil,
The sparingly soluble laser absorption layer is an electrolytic copper-tin alloy layer having a tin content of 25 mass% or more and 50 mass% or less, formed by an electrolytic plating method and having a uniform metal composition in the thickness direction, for laser processing copper foil. delete The copper foil for laser processing according to claim 1, wherein the thickness of the sparingly soluble laser absorption layer is 3 µm or less. The copper foil for laser processing of Claim 1 or 3 whose thickness of the said copper foil is 7 micrometers or less. The copper foil for laser processing of Claim 1 or 3 provided with at least any one of a roughening process layer and a primer resin layer on the other surface of the said copper foil. The copper foil for laser processing with carrier foil was provided so that peeling was possible on the said hardly soluble laser absorption layer of the copper foil for laser processing of Claim 1 or 3 characterized by the above-mentioned. A copper clad laminate, wherein the copper foil for laser processing according to claim 1 or 3 and an insulating layer constituent material are laminated so that the sparingly soluble laser absorption layer is disposed on the side to which the infrared laser beam is irradiated. The tin content is 25 mass % or more and 50 mass % or less, it is an electrolytic copper-tin alloy layer formed by the electrolytic plating method and having a uniform metal composition in the thickness direction, and while having etching property to a copper etchant, the etching The speed is slower than that of copper foil, and the copper foil for laser processing in which a sparingly soluble laser absorption layer for absorbing infrared laser light is provided on the surface of the copper foil, and another conductor layer laminated through an insulating layer, infrared rays In the microetching process as a pretreatment of the desmear process and/or the electroless plating process of forming a via hole for interlayer connection by irradiating a laser beam directly to a sparingly soluble laser absorption layer, and removing smear in a via hole, the said poorly soluble A method for manufacturing a printed wiring board, wherein the laser absorption layer is removed from the surface of the copper foil.

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