JP6304829B2 - Copper foil for laser processing, copper foil for laser processing with carrier foil, copper-clad laminate, and method for producing printed wiring board - Google Patents

Description

  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 for a printed wiring board, a copper foil for laser processing with a carrier foil, a copper clad laminate, and a method for manufacturing a printed wiring board.

  2. Description of the Related Art Conventionally, with the increase in functionality and compactness of electronic devices and electrical devices, multilayered printed wiring boards have been developed. A multilayer printed wiring board is obtained by laminating three or more wiring layers via an insulating layer, and electrically connecting each wiring layer by an interlayer connection means such as a via hole or a through hole. A build-up method is known as a method for manufacturing a printed wiring board. The build-up method is a manufacturing method in which a wiring layer is laminated on an inner layer circuit via an insulating layer, and multilayered while performing interlayer connection. For example, when an ultrahigh-definition wiring pattern is formed by the modified-semiadditive method (MSAP method) or the like, a build-up printed wiring board is manufactured by the following procedure. First, a copper foil is laminated via an insulating layer on a core substrate or the like provided with an inner layer circuit, via holes are formed by laser processing or the like, and interlayer connection is performed by an electroless plating method. Next, after forming a plating resist on the seed layer (copper foil + electroless plating layer) according to the wiring pattern and performing electrolytic plating, the seed layer under the plating resist is removed by etching together with the plating resist. By repeating the above steps as many times as necessary, a build-up multilayer printed wiring board having a desired number of wiring layers can be obtained.

  In recent years, with the miniaturization of wiring patterns, interlayer connection has been performed by micro via holes having a top diameter of 100 μm or less. Such micro via holes are generally drilled by laser processing using a carbon dioxide laser or the like. In this case, a Cu direct method is often employed in which a carbon dioxide laser or the like is directly irradiated from above the copper foil to simultaneously perforate the copper foil and the insulating layer. However, since copper has an extremely low absorption rate of laser light in the far-infrared to infrared wavelength region such as a carbon dioxide laser, when forming a micro via hole by the Cu direct method, copper such as blackening treatment is used in advance. It was necessary to perform a pretreatment to increase the absorption rate of the laser beam on the foil surface.

  However, when the blackening process is performed on the surface of the copper foil, the surface of the copper foil is etched, so that the thickness of the copper foil decreases and the thickness varies. For this reason, when removing the seed layer, it is necessary to set an etching time in accordance with the thickest portion of the seed layer, and it becomes difficult to form a wiring pattern with high linearity and good line width.

  On the other hand, Patent Literature 1 describes a copper foil in which an alloy layer mainly composed of Sn and Cu is provided on the surface of the copper foil as a technique that eliminates the need for pretreatment during laser processing. According to Patent Document 1, in the case of the same surface roughness at the same room temperature, Sn has a laser absorption rate that is twice or more higher than that of Cu, so an alloy layer mainly composed of Sn and Cu is provided on the copper foil surface. Thus, a via hole having a diameter of 100 μm can be formed by directly irradiating the surface of the copper foil with laser light without performing a pretreatment such as a blackening treatment.

JP 2001-226996 A

  However, the copper foil for laser drilling described in Patent Document 1 is provided with a metal Sn layer by vapor deposition or plating on the surface of the copper foil, and then Sn and Cu on the surface of the copper foil by heat diffusion treatment. Is used as an alloy layer. For this reason, in the said alloy layer, distribution will arise in Sn content in the thickness direction, and it will be thought that the etching rate in the thickness direction of the said copper foil varies. Further, the outermost surface of the copper foil has a very high Sn content, and the copper foil described in Patent Document 1 is considered to have a three-layer structure of an Sn layer, an alloy layer of Sn and Cu, and a copper layer in order from the surface layer. It is done. Since the metal Sn layer is not soluble in an etching solution for a general copper foil, when the copper foil described in Patent Document 1 is used, it is difficult to dissolve and remove the outermost surface by etching. Therefore, when the copper foil described in Patent Document 1 is used, in the etching process, after removing the outermost surface of the copper foil with a metal Sn layer etching solution capable of dissolving Sn in advance, The lower layer needs to be etched, and the etching process becomes complicated. Further, since the alloy layer of Sn and Cu described in Patent Document 1 is an alloyed layer by thermal diffusion, it is considered that the metal composition in the thickness direction is not uniform, and the etching rate in the thickness direction varies. Can occur. For this reason, during etching, the copper foil cannot be etched with a uniform thickness, and the thickness of the copper foil may vary. Furthermore, it is considered that the etching rate of the surface of the alloy layer is slower than that of the wiring pattern portion formed by electrolytic copper plating when the Sn content is high. For this reason, when the seed layer is removed, the wiring pattern portion is etched faster, the line width becomes narrower, and it is difficult to obtain a good wiring pattern.

  Therefore, the present invention provides a copper foil for laser processing, a copper foil for laser processing with a carrier foil, a copper-clad laminate, and a method for producing a printed wiring board that is excellent in laser processability and capable of forming a wiring pattern satisfactorily. The purpose is to provide.

  As a result of intensive studies, the present inventors have achieved the above object by employing the following 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, has an etching rate slower than that of the copper foil, and a hardly soluble laser absorbing layer that absorbs infrared laser light on the surface of the copper foil. And the hardly soluble laser absorption layer is an electrolytic copper-tin alloy layer formed by an electrolytic plating method with a tin content of 25 mass% or more and 50 mass% or less .

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

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

  In the copper foil for laser processing according to the present invention, the other surface of the copper foil preferably includes at least one of a roughening treatment layer and a primer resin layer.

  The copper foil for laser processing with a carrier foil according to the present invention is provided with a carrier foil so as to be peelable on the hardly soluble laser absorbing layer.

  In the copper clad laminate according to the present invention, the copper foil for laser processing and the insulating layer constituting material are laminated so that the hardly soluble laser absorption layer is disposed on the side irradiated with the infrared laser light. It is characterized by that.

The method for producing a printed wiring board according to the present invention is an electrolytic copper-tin alloy layer formed by an electrolytic plating method with a tin content of 25% by mass or more and 50% by mass or less, and has an etching property with respect to a copper etching solution. together with, the etching rate is slower than the copper foil, further, a laser processing copper foil with a surface of the copper foil sparingly soluble laser absorbing layer which absorbs infrared laser light, and the other conductor layer insulating layer the laminated body are laminated via the infrared laser beam is irradiated directly on the poorly soluble laser-absorbing layer to form a via hole for interlayer connection, desmear process and / or electroless removing smear in the via hole In the microetching process as a pretreatment of the plating process, the hardly soluble laser absorbing layer is removed from the surface of the copper foil.

  The copper foil for laser processing according to the present invention is excellent in laser processability, and a uniform etching rate in the thickness direction can be obtained in the subsequent etching process. In addition, it is possible to directly drill a copper foil for laser processing of a copper clad laminate using a carbon dioxide laser, eliminating the need for pre-treatment such as blackening to increase laser light absorption efficiency, and reducing the number of processes. The total manufacturing cost can be reduced. Furthermore, since the hardly soluble laser absorbing layer can function as an etching resist, the surface of the copper foil (layer) is dissolved in various etching steps before the formation of the wiring pattern, resulting in variations in the thickness of the copper foil (layer). Can be prevented. For this reason, a wiring pattern can be formed with a favorable etching factor.

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, the embodiment of the manufacturing method of the copper foil for laser processing which concerns on this invention, the copper foil for laser processing with a carrier foil, a copper clad laminated board, and a printed wiring board is described 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, an etching rate that is slower than that of the copper foil, and a hardly soluble laser absorbing layer that absorbs infrared laser light. It is provided on the surface of the copper foil. The copper foil for laser processing according to the present invention provides laser light to the surface of the copper foil for laser processing without performing pretreatment such as blackening treatment by the Cu direct method in the manufacturing process of the printed wiring board. By direct irradiation, micro holes such as micro via holes can be formed by laser processing.

  Here, the hardly soluble laser absorbing layer is, for example, a copper layer containing an infrared laser absorbing metal material having absorbability with respect to infrared laser light, and by containing the infrared absorbing material in the copper layer, It is preferable to use a copper layer containing an infrared laser-absorbing metal material capable of making the etching rate with respect to the copper etching solution slower than the etching rate of the copper foil. Specific examples of the hardly soluble laser absorbing layer include an electrolytic copper-tin alloy layer containing 25% by mass or more and 50% by mass or less of tin formed by an electrolytic plating method. In the present embodiment, the following description will be made mainly assuming that this electrolytic copper-tin alloy layer is used as the hardly soluble laser absorbing layer.

1-1. Electrolytic copper-tin alloy layer First, the electrolytic copper-tin alloy layer will be described. Compared with copper, tin has a higher absorption rate of laser light (carbon dioxide laser light, etc.) having a wavelength in the far infrared to infrared wavelength region. That is, the electrolytic copper-tin alloy layer can be made to function as a laser light absorption layer, and as described above, the pretreatment at the time of drilling by the Cu direct method can be made unnecessary. Further, in the present invention, the electrolytic copper-tin alloy layer is etched on the surface of the copper foil in various etching processes performed in the desmear process, the microetching process, etc. performed after the drilling process and before forming the wiring pattern. It can also function as an etching resist layer for preventing the above. The electrolytic copper-tin alloy layer is etched in various etching processes performed before forming these wiring patterns. However, the timing at which the electrolytic copper-tin alloy layer is dissolved and removed can be controlled by its tin content and thickness. For this reason, it is also possible to dissolve and remove only the electrolytic copper-tin alloy layer without dissolving the surface of the copper foil before the electroless plating process for interlayer connection. Therefore, for example, when a wiring pattern is formed by the MSAP method, an electroless plating film can be formed on a copper foil in which the original thickness is maintained, and a seed layer having a uniform thickness can be obtained. .

(1) Tin content In this invention, when using an electrolytic copper-tin alloy layer as a sparingly soluble laser absorption layer, it is mentioned above that the tin content in the said electrolytic copper-tin alloy layer shall be 25 mass% or more. This is because the function as an etching resist is 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 compared with the electrolytic copper foil having a tin content of 0% by mass. Then it will be faster. On the other hand, when the tin content in the electrolytic copper-tin alloy layer is 25% by mass or more, the etching rate is slow compared to a normal electrolytic copper foil containing no 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 before the wiring pattern is formed, It is possible to prevent the copper foil from being melted and causing variations in the thickness of the copper foil during various etching processes to be performed. This specification describes an invention relating to a specific tin mass% when the total content of copper and tin in the copper-tin alloy layer is 100 mass%.

  Further, since the electrolytic copper-tin alloy layer is composed of the obtained copper-tin alloy deposited on the surface of the copper foil by the electrolytic plating method, the metal composition in the thickness direction becomes uniform, and the electrolytic copper-tin alloy The etching rate of the layer can be made uniform in the thickness direction. Therefore, in various etching processes performed before the wiring pattern is formed, 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 decreases as the tin content increases. For this reason, as described above, the electrolytic copper-tin alloy layer can be dissolved and removed at an appropriate timing by adjusting the tin content and thickness in the electrolytic copper-tin alloy layer. Therefore, for example, if only the electrolytic copper-tin alloy layer is dissolved before the electroless plating step for interlayer connection, an electroless plating film is formed on the surface of the copper foil in the state where the original thickness is maintained. Can do. Therefore, for example, when a wiring pattern is formed by the MSAP method, a seed layer having a uniform thickness can be formed. Therefore, when the seed layer is removed in a flash etching process after the wiring pattern is formed, Since it has a uniform composition in the thickness direction, the seed layer can be dissolved and removed at a uniform etching rate. As described above, it is possible to form a wiring pattern having a good etching factor. The same applies to the case where the wiring pattern is formed not only by the MSAP method but also by a method including an etching process such as a subtractive method. That is, in the desmear process after laser drilling, etc., the electrolytic copper-tin alloy layer can be removed to expose the copper foil (layer) in a state in which the initial thickness is maintained. A layer can be obtained, and a wiring pattern having a good etching factor can be formed.

  Here, when the etching rate of the electrolytic copper foil not containing tin is 100, the etching rate of the electrolytic copper-tin alloy foil having a tin content exceeding 50% by mass is less than 3. Accordingly, if 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, and thus during various etching processes performed before the wiring pattern is formed. It becomes 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 with respect to the copper etching solution is 0 μm. With a copper etchant, the electrolytic copper-tin alloy layer cannot be removed from the surface of the copper foil. In these cases, it is necessary to separately 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 further preferably 35% by mass or less. At this time, when the etching rate of the electrolytic copper foil with respect to the copper etching solution is 100, the etching rates of the electrolytic copper-tin alloy foil are 4 (tin content: 45 mass%) and 13 (tin content: 40 mass), respectively. %), 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 is faster than the etching rate of the copper foil not containing tin, so that it functions as an etching resist. Is not economically preferable because it is necessary to increase the thickness of the electrolytic copper-tin alloy layer and the amount of copper removed by etching increases. However, the etching rate shown in FIG. 1 is to prepare electrolytic copper-tin alloy foils (thickness: 3 μm) having different tin contents (mass%), and to treat each electrolytic copper-tin alloy foil with a sulfuric acid-hydrogen peroxide etching solution. This is a value obtained as an etching amount (μm) per unit time obtained by immersing in 30 seconds, washing with water and drying, then measuring the thickness by cross-sectional observation, and obtaining the thickness reduced by etching. The tin content here can be measured by the following method. In the case of a copper foil for laser processing having a layer configuration of “copper foil / electrolytic copper-tin alloy layer”, a solution in which the copper foil for laser processing as a sample is completely dissolved is subjected to ICP analysis, fluorescent X-ray apparatus, titration determination The amount of copper contained in the electrolytic copper-tin alloy layer was calculated by measuring the total copper content using a method, etc., and subtracting the “copper amount converted from the cross-sectional thickness of the copper foil” from the total copper content. ”And“ tin content in the total solution ”, the tin content (% by mass) can be calculated. In addition, when the thickness of the copper foil is known in advance by cross-sectional observation, etc., a composition analysis of the foil defined as a two-layer foil is performed using a fluorescent X-ray film thickness measuring instrument, and the electrolytic copper-tin alloy layer The tin content (% by mass) 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 value depending on the thickness and application of the laser processing copper foil. However, in consideration of dissolving and removing the electrolytic copper-tin alloy layer by etching at an appropriate stage before forming the wiring pattern, 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 purpose of improving the absorption rate of the laser beam, and in various etching processes performed before forming the wiring pattern. In some cases, the electrolytic copper-tin alloy layer cannot function sufficiently 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, and more preferably 0.5 μm or more. Moreover, since the etching rate with respect to the copper etching solution varies depending on the tin content in the electrolytic copper-tin alloy layer as described above, the thickness of the electrolytic copper-tin alloy layer is appropriately determined according to the tin content. An appropriate value is preferable.

(4) Copper etchant In the present invention, any copper etchant can be used without particular limitation as long as it is an etchant generally used as an etchant for copper. For example, various copper etching solutions such as copper chloride etching solution, iron chloride etching solution, sulfuric acid-hydrogen peroxide etching solution, sodium persulfate etching solution, ammonium persulfate etching solution, potassium persulfate etching solution, etc. Can be used.

1-2. Copper foil Next, copper foil is demonstrated. In the present invention, the copper foil refers to a metal foil having a copper content of 99% by mass or more, and refers to a tin-free copper foil that does not contain tin except for inevitable impurities. The copper foil may be either an electrolytic copper foil or a rolled copper foil. However, in view of economy and production efficiency, an electrolytic copper foil is more preferable.

  The copper foil is a layer that is bonded to an insulating layer constituting material and constitutes a part of a seed layer or the like when a multilayer printed wiring board is manufactured. The thickness of the copper foil can be the same as that of a commercially available copper foil as a general printed wiring board material. However, for example, when a wiring pattern is formed by a method including an etching process such as an MSAP method or a subtractive method, the copper foil is preferably thin from the viewpoint of obtaining a better etching factor, and is 7 μm or less. Is preferred. In particular, when a wiring pattern is formed by the MSAP method using the copper foil for laser processing, the thickness of the copper foil is 3 μm or less from the viewpoint of forming a finer wiring pattern with a good etching factor. It is more preferably a thin electrolytic copper foil, and further preferably 2 μm or less. However, when the copper foil has a thickness of 7 μm or less, it is preferably used in the form of a copper foil for laser processing with a carrier foil, which will be described later, so as not to cause problems such as wrinkles and tearing during handling.

  From the viewpoint of improving the etching factor, the surface of the copper foil that is bonded to the interlayer insulating layer, that is, the surface opposite to the surface on which the electrolytic copper-tin alloy layer is provided (hereinafter referred to as the bonding surface) is It is preferably smooth. Specifically, the surface roughness (Rzjis) of the adhesion surface is preferably 3 μm or less, and more preferably 2 μm or less. However, when the roughening process layer demonstrated below is provided in the adhesion surface of the said copper foil, the surface roughness of the said adhesion surface points out the surface roughness of the adhesion surface after forming a roughening process layer.

1-3. Roughening treatment layer In the copper foil for laser processing according to the present invention, a roughening treatment layer is provided on the adhesive surface of the copper foil, that is, the surface opposite to the surface on which the electrolytic copper-tin alloy layer is provided. Also good. By providing the roughening treatment layer on the bonding 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 depositing and forming fine metal particles on the surface (adhesion surface) of the copper foil, a method of forming a roughened surface by an etching method, or the like. The method for forming the roughened layer may be any method as long as the adhesion between the copper foil and the insulating layer can be physically improved. Can be adopted.

1-4. Primer resin layer In the copper foil for laser processing according to the present invention, a primer resin layer may be provided on the adhesive surface of the copper foil. In the present invention, the primer resin layer is an adhesive layer having good adhesion to both the copper foil and the insulating layer constituting material. For example, the primer resin layer can be a layer made of a resin composition containing an epoxy resin or an aromatic polyamide resin. By providing the primer resin layer on the adhesive surface of the copper foil, the copper foil can be satisfactorily adhered to the insulating layer constituting material.

  The thickness of the primer resin layer is not particularly limited as long as the adhesion between the copper foil and the insulating layer constituting material can be improved. For example, the thickness of the primer resin layer can be in the range of 0.5 μm to 10 μm. . In addition, the roughening process layer and the primer resin layer may be simultaneously provided 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 hardly soluble laser absorption layer is the above-described electrolytic copper-tin alloy layer, for example, an electrolytic solution containing copper ions and tin ions is used. If 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 on the said copper foil by the electroplating method can be obtained, the manufacturing method will be specifically limited. It is not something. In addition to the roughening treatment layer and primer resin layer described above, various surface treatment layers such as a rust prevention treatment layer and a silane coupling treatment layer may be provided on the adhesive surface of the copper foil as required. It is.

2. Next, the copper foil for laser processing with carrier foil according to the present invention (hereinafter, copper foil for laser processing with carrier foil) according to the present invention will be described. The copper foil for laser processing with carrier foil is provided with the carrier foil peelable on the hardly soluble laser absorbing layer of the copper foil for laser processing, and the carrier foil / peeling layer / copper foil for laser processing (difficulty Each layer is laminated like a soluble laser absorption layer / copper foil). In the copper foil for laser processing with carrier foil, since the same configuration as the above-described copper foil for laser processing can be adopted except for the configuration related to the carrier foil, only the configuration related to the carrier foil will be described here.

2-1. Carrier foil Carrier foil is a metal foil that is detachably provided on a copper foil for laser processing. When the copper foil for laser processing is an ultrathin copper foil having a thickness of 7 μm or less as described above, By supporting the processing copper foil, it is possible to prevent wrinkles and tears and to improve the handling properties. The material constituting the carrier foil is not particularly limited. However, in order to allow the electrolytic copper-tin alloy layer and the copper foil to be formed on the carrier foil by electrodeposition through a release layer, the conductivity is improved. It is preferable that it is the metal material which has. 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 provided on the surface of the aluminum foil, a stainless steel foil, a resin film whose surface is metal-coated, or the like can be used. Among these materials, a copper foil can be suitably used as a carrier foil. By using the copper foil as the carrier foil, the carrier foil can be reused as a copper raw material after being peeled from the laser processing copper foil, and therefore, it is preferable from the viewpoint of resource conservation.

  Although the thickness of carrier foil is not specifically limited, For example, it is 5 micrometers or more and 100 micrometers or less. 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 to improve the handling property of the copper foil for ultrathin laser processing having a thickness of 7 μm or less cannot be achieved, It is not preferable. From the viewpoint of resource conservation and the like, the thickness of the carrier foil is preferably 100 μm or less, and a thickness of 35 μm or less is also applicable.

2-2. Release Layer The copper foil for laser processing with carrier foil is a so-called peelable type copper foil for laser processing with carrier foil. The release layer allows the carrier foil to be easily peeled from the copper foil for laser processing by hand, and the adhesive strength between the carrier foil and the copper foil for laser processing is appropriate until the carrier foil is peeled off. It is required to be in close contact. As such a peeling layer, the inorganic peeling layer comprised from an inorganic agent and the organic peeling layer comprised from an organic agent are mentioned, for example.

(1) Inorganic release layer As an inorganic agent constituting the inorganic release layer, for example, one or more selected from chromium, nickel, molybdenum, tantalum, vanadium, tungsten, cobalt, and oxides thereof are mixed and used. be able to.

(2) Organic release layer As an organic agent constituting the organic release layer, for example, one or more selected from nitrogen-containing organic compounds, sulfur-containing organic compounds, and carboxylic acids can be mixed and used. . 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 that the peeling properties of the carrier foil are stabilized.

  More specifically, it is preferable to employ the following compounds 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, and derivatives thereof. In particular, carboxybenzotriazole, which is an orthotriazole, 3-amino-1H-1,2,4-triazole, which is an aminotriazole, and N ′, N′-bis (benzotriazolylmethyl) urea, which is a triazole derivative. Can be mentioned. Any one or more of these can be used to form an organic release layer composed of a nitrogen-containing compound.

  Examples of the sulfur-containing compound include thiazole, mercaptobenzothiazole, dibenzoazyl disulfide, mercaptobenzothiazole cyclohexylamine salt, mercaptobenzothiazole dicyclohexylamine salt, thiocyanuric acid, and 2-benzimidazolethiol. When forming an organic peeling layer using a sulfur-containing compound, it is particularly preferable to use mercaptobenzothiazole and thiocyanuric acid among these.

  Examples of carboxylic acids include high molecular weight carboxylic acids. Among the high molecular weight carboxylic acids, it is particularly preferable to use a fatty acid that is a long-chain hydrocarbon monocarboxylic acid. The fatty acid may be a saturated fatty acid, but it is particularly preferable to use an unsaturated fatty acid such as oleic acid or linolenic acid.

(3) Thickness of release layer The thickness of the release layer is preferably 100 nm or less, and more preferably 50 nm or less. In the so-called peelable copper foil with carrier foil, generally, a release layer is provided on the surface of the carrier foil, and copper is deposited on the carrier foil via the release layer by a method such as electrolysis to form an electrolytic copper foil. . At this time, when the thickness of the release layer exceeds 100 nm, particularly in the case of an organic release layer, it becomes 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. Accordingly, the thickness of the release layer is preferably 100 nm or less. If the release layer having a uniform thickness can be formed, the lower limit value of the thickness of the release layer is not particularly limited. However, when the thickness is less than 1 nm, it becomes difficult to form a release layer with a uniform thickness, and the thickness varies. For this reason, it is preferable that the thickness of a peeling layer is 1 nm or more, and 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 release layer, or between the release layer and the electrolytic copper-tin alloy layer of the copper foil for laser processing, It is also preferable to have a layer configuration of carrier foil / heat-resistant metal layer / release layer / copper foil for laser processing or a layer configuration of carrier foil / release layer / heat-resistant metal layer / copper foil for laser processing.

2-4. The manufacturing method of the copper foil for laser processing with a carrier foil The manufacturing method of the copper foil for laser processing with a carrier foil is not specifically limited. For example, after forming a peeling layer on the surface of the carrier foil, the electrolytic copper-tin alloy layer and the copper foil for laser processing with the carrier foil having the above-described configuration, such as electrolytically depositing the electrolytic copper-tin alloy layer and the copper foil on the carrier foil through the peeling layer, etc. Any method may be used as long as the foil can be obtained.

2-5. Measuring method of tin content of electrolytic copper-tin alloy layer of copper foil for laser processing with carrier foil For copper foil for laser processing with carrier foil, "carrier foil / peeling layer / electrolytic copper-tin alloy layer / copper foil" The layer structure is provided. Therefore, in order to measure the tin content of the electrolytic copper-tin alloy layer, it is preferable to employ the following method. In the case of the copper foil for laser processing with a carrier foil according to the present application, when the carrier foil is peeled off, the layer configuration is “peeling layer / electrolytic copper-tin alloy layer / copper foil”. And since the peeling layer at this time is comprised with the above-mentioned component, it does not affect the measurement of the tin content of an electrolytic copper-tin alloy layer. Therefore, measure the total copper content of a solution in which the sample with the layer configuration of “peeling layer / electrolytic copper-tin alloy layer / copper foil” is completely dissolved using ICP analysis, X-ray fluorescence apparatus, titration method, etc. And "the amount of copper contained in the electrolytic copper-tin alloy layer" calculated by subtracting "the amount of copper converted from the cross-sectional thickness of the copper foil" from this total copper content and "the tin content in the solution" From this, the tin content (% by mass) can be calculated. In addition, if the thickness of the copper foil is known in advance by cross-sectional observation, etc., using a fluorescent X-ray film thickness measuring instrument, perform a composition analysis of the foil defined as a two-layer foil, and in the electrolytic copper-tin alloy layer The tin content (% by mass) can be calculated.

3. Next, the copper clad laminate according to the present invention will be described. In the copper clad laminate according to the present invention, the copper foil for laser processing and the insulating layer constituting material are laminated so that the hardly soluble laser absorption layer is disposed on the side irradiated with the infrared laser light. It is characterized by that. That is, the copper-clad laminate according to the present invention is formed by laminating the insulating layer constituent material and the copper foil for laser processing, and the insulating layer constituent material / copper foil / slightly soluble laser absorbing layer (electrolytic copper-tin alloy layer). Any structure may be used as long as it has a layer structure stacked in the order of). Moreover, if the said copper clad laminated body can be obtained, there will be no limitation in the manufacturing method in particular. For example, the copper foil side of the copper foil for laser processing or the copper foil with carrier foil is laminated on the insulating resin base material or insulating resin layer of the so-called B stage, and heated and pressed on the insulating resin base material or insulating resin layer. A copper clad laminate in which a copper foil for laser processing is laminated can be obtained. When the copper foil for laser processing with carrier foil is used, the carrier foil may be removed at an appropriate stage.

4). Next, a method for manufacturing a printed wiring board according to the present invention will be described. Here, a case where a wiring pattern is formed by the MSAP method using the copper foil 10 for laser processing according to the present invention will be described as an example with reference to FIG. In addition, the copper foil 10 for laser processing used here shall be equipped with the layer structure of primer resin layer 11 / copper foil (electrolytic copper foil layer) 12 / electrolytic copper-tin alloy layer 13 (hardly soluble laser absorption layer), It is assumed that no roughening treatment layer is provided on the bonding surface of the copper foil 12. In the following, a method for manufacturing a multilayer printed wiring board in which three or more wiring layers are laminated via an insulating layer will be described. However, the method for producing a printed wiring board according to the present invention is not limited to the method for producing a multilayer printed wiring board, and can also be applied when producing a double-sided printed wiring board.

  First, the bonding surface side of the copper foil 10 for laser processing with a carrier foil is laminated on the bonding surface via a so-called B-stage insulating layer constituting material 20 on the inner layer circuit 30 (other conductor layer). And the laminated body shown to Fig.2 (a) is obtained by closely_contact | adhering the insulating layer constituent material 20, the inner layer circuit 30, and the copper foil 10 for laser processing by heat-pressing.

  Next, the surface of the electrolytic copper-tin alloy layer 13 which is the outermost layer is directly irradiated with infrared laser light by a carbon dioxide laser or the like to form the micro via hole 40 having the conductor pattern portion 30a of the inner layer circuit 30 as the bottom (FIG. 2 (b)).

  After the micro via hole 40 is formed, a desmear process is performed to remove smear remaining at the bottom of the micro via hole 40 using a desmear liquid (see FIG. 2C). In the desmear process, after immersing the laminate 100 in a swelling solution, the laminate 100 is immersed in a so-called desmear solution (for example, an alkaline permanganate aqueous solution) to remove smear, and then immersed in a neutralization solution (reducing agent). A neutralization treatment is performed to reduce and remove potassium permanganate.

  Subsequently, a microetching process is performed as a pretreatment for the electroless plating process. In the microetching step, the splash and the like attached around the micro via hole 40 is removed using a microetching solution (for example, a sulfuric acid-hydrogen peroxide etchant or an ammonium persulfate aqueous solution). If smear remains at the bottom of the micro via hole 40, it is removed (see FIG. 2D).

  In these desmear process and microetching process, the surface of the laminate 100 is in contact with a processing solution having etching properties with respect to copper such as a neutralizing solution and a microetching solution. Since the electrolytic copper-tin alloy layer 13 has an etching property with respect to a copper etchant, the surface thereof is etched in these steps. Since the etching rate with respect to the copper etching solution varies depending on the thickness and tin content of the electrolytic copper-tin alloy layer 13, it is possible to control the timing of dissolving the electrolytic copper-tin alloy layer 13 by adjusting these. it can. For example, when it is necessary to clean the surface of the copper foil 12 in the microetching process, the electrolytic copper-tin in the desmear process is adjusted by adjusting the thickness and material of the electrolytic copper-tin alloy layer 13. It is preferable to completely dissolve and remove the alloy layer 13. On the other hand, when it is necessary to maintain the thickness of the copper foil 12 at the initial thickness, the electrolytic copper-tin alloy layer 13 is left without being completely dissolved in the desmear process, and in the subsequent microetching process. The electrolytic copper-tin alloy layer 13 may be completely dissolved and removed. The timing for dissolving and removing the electrolytic copper-tin alloy layer 13 may be set appropriately according to the characteristics required for the printed wiring board.

  Then, an electroless plating film is formed on the inside of the micro via hole 40 and on the copper foil layer 12 by an electroless plating process, and interlayer connection is made (not shown). Thereafter, a plating resist is provided on the seed layer (copper foil + electroless plating film), a wiring pattern is formed by an electrolytic plating method, and the via hole is filled and plated. Then, the seed layer under the plating resist is removed together with the plating resist by flash etching. In FIG. 2, the steps after the electroless plating step are not shown. In the following, the reference numerals for the respective constituent elements are omitted.

  As described above, according to the copper foil for laser processing according to the present invention, it is possible to directly irradiate the laser beam without performing pretreatment for increasing the absorption rate of the laser beam such as blackening treatment. Processing can be performed. For this reason, the frequency | count of the etching process before wiring pattern formation can be reduced. In addition, according to the present invention, since the surface of the copper foil is provided with a hardly soluble laser absorbing layer such as an electrolytic copper-tin alloy layer, the copper foil is subjected to various etching processes performed after laser drilling and before wiring pattern formation. It is possible to prevent the surface of the substrate from being etched. In addition, as above-mentioned, when employ | adopting an electrolytic copper-tin alloy layer as a hardly soluble laser absorption layer, by adjusting the tin content and the thickness of the said electrolytic copper-tin alloy layer suitably, electrolytic copper- The timing for dissolving and removing the tin alloy layer can be controlled. In the example shown in FIG. 2, the case where the tin content in the electrolytic copper-tin alloy layer is relatively large and the electrolytic copper-tin layer is not dissolved in the desmear process is shown. However, the present invention is not limited to the illustrated example, and the electrolytic copper-tin alloy is adjusted in the desmear process by adjusting the amount and thickness of tin in the electrolytic copper-tin alloy layer according to the characteristics required for the printed wiring board. The layer may be removed by dissolution.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.

  In this example, a copper foil for carrier foil laser processing is prepared by the method described below, and then a copper-clad laminate is manufactured, and laser hole drilling processability evaluation using a carbon dioxide gas laser is performed, and a printed wiring board manufacturing process is performed. The evaluation of the variation in the thickness of the copper foil (electrolytic copper foil layer) when subjected to the etching treatment performed before forming the wiring pattern was performed. Hereinafter, it will be described in order. The evaluation method will be described later.

[Preparation of copper foil for laser processing with carrier foil]
In this example, a copper foil for laser processing with a carrier foil was produced by the following steps A to E.

Step A: An electrolytic copper foil having a surface roughness (Rzjis) on one side of 0.6 μm and a thickness of 18 μm was used as a carrier foil, and a release layer was formed on the surface of the carrier foil as follows. The surface roughness (Rzjis) is a value measured by a stylus type surface roughness meter using a diamond stylus having a tip curvature radius of 2 μm in accordance with JIS B 0601.

  This carrier foil was immersed in a dilute sulfuric acid aqueous solution containing carboxybenzotriazole having a free sulfuric acid concentration of 150 g / l, a copper concentration of 10 g / l, a carboxybenzotriazole concentration of 800 ppm, and a liquid temperature of 30 ° C. for 30 seconds. Then, by picking up the carrier foil, the contaminated components adhering to the surface of the carrier foil are pickled and removed, and carboxybenzotriazole is adsorbed on the surface to form a release layer on the surface of the carrier foil. The carrier foil provided.

Step B: Next, in the metal component-containing electrolyte, the carrier foil provided with the release layer is cathode-polarized to form a heat-resistant metal layer on the surface of the release layer, and the carrier foil provided with the heat-resistant metal layer and the release layer; did. Here, as nickel electrolyte, nickel sulfate _(NiSO 4 · _6H 2 O) and 330 g / l, nickel chloride _(NiCl 2 · _6H 2 O) and 45 g / l, containing boric acid 30 g / l, the bath pH is 3 A watt bath, electrolysis 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 is formed on the surface of the release layer, and a carrier having a heat-resistant metal layer and a release layer A foil was prepared.

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

(Composition of copper-tin plating bath and electrolysis conditions)
_{CuSO 4 · 5H 2 O: 157g} / l (Cu terms 40 g / l)
SnSO ₄ : 127 g / l (Sn equivalent 70 g / l)
C ₆ H ₁₁ O ₇ Na: 70 g / l
Free H ₂ SO ₄ : 70 g / l
Liquid temperature: 35 ° C
Cathode current density: 30 A / dm ²

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

(Composition of copper plating bath and electrolysis conditions)
_{CuSO 4 · 5H 2 O: 255g} / l (Cu terms 65 g / l)
Free H ₂ SO ₄ : 150 g / l
Liquid temperature: 45 ° C
Cathode current density: 15 A / dm ²

Step E: In this example, a zinc-nickel alloy rust preventive layer is further formed on the surface of the copper foil for laser processing with a carrier foil on the side of the electrolytic copper foil, followed by electrolytic chromate treatment and amino silane coupling agent treatment. The copper foil for surface treatment laser processing with a carrier foil was obtained.

  In the copper foil for laser processing with a carrier foil, the tin content in the electrolytic copper-tin alloy layer was 27.5% by mass. The tin content in the examples was measured as follows. Form a release layer on the surface of the carrier foil, form a heat-resistant metal layer on the surface of the release layer, and form an electrolytic copper-tin alloy layer on the surface of the heat-resistant metal layer. A tin content measurement sample was used. Thereafter, the electrolytic copper-tin alloy layer of the sample is peeled from the carrier foil, and the composition analysis of the foil is performed using a fluorescent X-ray film thickness measuring device XDAL-FD (manufactured by Fisher Instruments), and the electrolytic copper-tin alloy layer The tin content (% by mass) was calculated. In the following comparative examples, the tin content is measured by the same method.

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

Comparative example

[Comparative Example 1]
In Comparative Example 1, a peelable type electrolytic copper foil with a carrier foil was prepared in the same manner as in Example except that the electrolytic copper-tin alloy layer was not provided. And using this electrolytic copper foil with carrier foil, the copper clad laminated board was produced like the Example.

[Comparative Example 2]
In Comparative Example 2, in Step C, the carrier foil was cathode-polarized under the following electrolysis conditions in a copper-tin plating bath having the following composition, and the thickness of 0.7 μm was interposed on the carrier foil via a release layer and a heat-resistant metal layer. An electrolytic copper foil with a carrier foil was prepared in the same manner as in the example except that the electrolytic copper-tin alloy layer was formed. And using this electrolytic copper foil with carrier foil, the copper clad laminated board was produced like the Example.

(Composition of copper-tin plating bath and electrolysis conditions)
_{CuSO 4 · 5H 2 O: 79g} / l (Cu terms 20 g / l)
SnSO ₄ : 72 g / l (Sn equivalent 40 g / l)
H ₂ SO ₄ : 70 g / l
Liquid temperature: 45 ° C
Cathode current density: 15 A / dm ²

  In this electrolytic copper foil with 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, using the electrolytic copper foil with carrier foil of Comparative Example 1, a copper clad laminate was produced in the same manner as in the example. Then, a metal tin layer having a thickness of 0.4 μm was formed on the surface of the copper foil of the copper clad laminate using a commercially available electroless tin plating solution. Then, the copper clad laminate on which the metal tin layer is formed is heat-treated 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 metal tin layer, A copper-clad laminate having a diffusion alloy layer mainly composed of tin-copper on the surface layer of the copper foil was obtained.

[Evaluation]
1. Evaluation Method (1) Evaluation of Laser Drilling Workability A carbon dioxide laser was used for evaluation of laser drilling performance using each copper-clad laminate produced in the above examples and comparative examples. The conditions for drilling with a carbon dioxide laser at this time were as follows: machining energy 6.9 mJ, pulse width 16 μsec. The beam diameter was 120 μm.

(2) Evaluation of variation in thickness of copper foil Using each copper-clad laminate produced in the above examples and comparative examples, the same treatment as the desmear process and microetching process generally performed in the manufacturing process of printed wiring boards And the change in the thickness of the copper foil before and after each step was evaluated.

Desmear process: First, in the desmear process, 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: RHM & Haas MLB-213, liquid temperature: 80 ° C., treatment time: 15 minutes, neutralization treatment (neutralization treatment liquid: Rohm & Haas MLB-216, liquid temperature: 40 ° C., treatment time 15 minutes) After that, after washing and drying, the thickness was measured by cross-sectional observation.

Micro-etching process: Next, in the micro-etching process, each copper clad laminate after the desmear process is immersed in a sulfuric acid-hydrogen peroxide etching solution (CPE800 manufactured by Mitsubishi Gas Chemical Co., Ltd.) at a liquid temperature of 30 ° C. for 60 seconds. After washing with water and drying, the thickness was measured by cross-sectional observation. Note that 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 when via holes are formed under the above processing conditions for each copper-clad laminate. Here, the top diameter refers to the opening diameter of the via hole as shown in FIG. 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 is the outermost layer, and this electrolytic copper-tin alloy layer In order to irradiate laser light, it was confirmed that drilling was possible by laser processing without performing pretreatment for increasing the absorption rate of laser light such as blackening treatment. In addition, the copper-clad laminate produced in Comparative Example 1 cannot be directly drilled by laser processing, and if no pretreatment for increasing the laser light absorption rate, such as blackening treatment, is performed, the laser It was confirmed that micro via holes cannot be formed by processing.

  On the other hand, in the case of the electrolytic copper foil of Comparative Example 3, the top diameter of the micro via hole is 99.5 μm, and considering only the top diameter, the electrolytic copper foil of Comparative Example 3 is the same laser as in Example and Comparative Example 2. Has drilling workability. However, the electrolytic copper foil of Comparative Example 3 includes a diffusion alloy layer obtained by interdiffusing copper and tin with a metal tin layer formed by electroless plating on the surface thereof by thermal diffusion. In the diffusion alloy layer, the distribution of tin in the thickness direction is nonuniform, and the closer to the surface, the greater the distribution of tin. Therefore, when the diffusion alloy layer is irradiated with laser light, tin having a low melting point melts and splash is likely to occur, and the amount of splash adhering to the periphery of the via hole increases. For this reason, it is considered that the splash around the hole cannot be sufficiently removed depending on the microetching process or the like, and the splash remains as a protrusion around the hole even after the microetching process. In this case, when interlayer connection is attempted by an electroless plating process, abnormal projection may be caused in the protrusion, which is not preferable.

(2) Evaluation of variation in thickness of copper foil Next, FIG. 3 shows a FIB-SIM image showing a cross section of the copper clad laminate of Example and Comparative Example 1. As shown in FIG. 3, the copper clad laminate produced in the example includes a 0.7 μm electrolytic copper-tin alloy layer on an electrolytic copper foil layer having a thickness of 2 μm. As described above, when the desmear process was performed on the copper-clad laminate, the surface of the electrolytic copper-tin alloy layer was dissolved, and the thickness of the electrolytic copper-tin alloy layer was reduced by 0.21 μm. Next, as described above, when the microetching process was performed on the copper-clad laminate, the surface of the electrolytic copper-tin alloy layer was dissolved, and the thickness of the electrolytic copper-tin alloy layer was reduced by 0.38 μm. . Thus, although the electrolytic copper-tin alloy layer is dissolved during the desmear process and the microetching process, the thickness of the copper foil is not changed due to the presence of the electrolytic copper-tin alloy layer. The 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 layer, so that it is 0.10 μm in the desmear process, and in the microetching process. The thickness is reduced to 1.03 μm. Moreover, in an Example, tin content in an electrolytic copper-tin alloy layer is 27.5 mass%, and as shown in FIG. 1, an etching rate is slow compared with the electrolytic copper foil which does not contain tin. 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 amount of etchings also becomes large and there exists a possibility that variation may arise in the thickness of copper foil.

  On the other hand, although not shown, the copper clad laminate of Comparative Example 2 includes an electrolytic copper-tin alloy layer having a tin content of 12.9% by mass. As shown in FIG. The etching rate of the layer is faster than that of the electrolytic copper foil containing no tin. For this reason, 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 in the desmear process is 0.20 μm, and the etching amount in the microetching process is 1.25 μm. Also in this case, the surface of the electrolytic copper foil layer is dissolved, and the thickness of the electrolytic copper foil layer may vary.

  Moreover, in the copper clad laminated board produced by the comparative example 3, since the diffusion alloy layer which has tin-copper as a main part has a two-layer structure of a tin layer and a tin copper diffusion alloy layer as above-mentioned, metal tin layer And the etching rate with respect to each etching liquid differs in a tin copper diffusion alloy layer. In particular, it is difficult to dissolve the metal tin layer as the outermost layer with a general etching treatment liquid for copper foil (see FIG. 1). For this reason, the total amount of etching after the desmear process and the micro-etching process is as small as 0.05 μm and functions as an etching resist layer, but the seed layer is removed by etching in the subsequent flash etching process after the wiring pattern is formed. Becomes difficult. Moreover, in the said copper foil, it thinks that an etching rate differs in each layer of a metal tin layer, a tin copper diffusion alloy layer, and an electrolytic copper foil layer, and it becomes difficult to etch uniformly in the thickness direction. Further, when a general etching solution for copper foil is used, the etching rate of the wiring pattern portion formed by electrolytic copper plating is higher than that of the metal tin layer that is the outermost layer. Therefore, the etching factor is reduced, and it becomes difficult to form a wiring pattern with a good line width.

  On the other hand, according to the copper clad laminate of the embodiment, the electrolytic copper-tin alloy layer can be dissolved and removed in the desmear process and the microetching process, and therefore, when removing the seed layer, the electrolytic copper foil What is necessary is just to remove the layer and the electroless copper plating film formed on this electrolytic copper foil layer. Since these are all copper layers, there is no significant difference in the etching rate. Further, no great difference appears with the etching rate of the wiring pattern portion formed by electrolytic copper plating. Therefore, according to the copper foil for laser processing according to the present invention, it is possible to form a wiring pattern with a good etching factor.

  As described above, by using the laser processing copper foil according to the present invention, the laser processing property is excellent, and a uniform etching rate in the thickness direction can be obtained in the subsequent etching process. In addition, it is possible to directly drill a copper foil for laser processing of a copper clad laminate using a carbon dioxide laser, eliminating the need for pre-treatment such as blackening to increase laser light absorption efficiency, and reducing the number of processes. The total manufacturing cost can be reduced. Furthermore, 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 being melted in various etching steps before forming the wiring pattern and causing variations in the thickness of the copper foil. it can. Further, when removing the seed layer, only the copper foil portion needs to be dissolved and removed, so that a wiring pattern can be formed with a good etching factor.

Claims (7)

While having etchability with respect to the copper etchant, the etching rate is slower than the copper foil, and the surface of the copper foil is provided with a hardly soluble laser absorbing layer that absorbs infrared laser light ,
The copper foil for laser processing, wherein the hardly soluble laser absorption layer is an electrolytic copper-tin alloy layer formed by an electrolytic plating method 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 a thickness of the hardly soluble laser absorbing layer is 3 μm or less. The thickness of the copper foil, for laser processing a copper foil according to claim 1 or claim 2 is 7μm or less. The copper foil for laser processing as described in any one of Claims 1-3 provided with at least any one among a roughening process layer and a primer resin layer in the other surface of the said copper foil. A copper foil for laser processing with a carrier foil, wherein the copper foil for laser processing according to any one of claims 1 to 4 is provided with a carrier foil so as to be peelable on the hardly soluble laser absorbing layer. . The copper foil for laser processing according to any one of claims 1 to 4 and an insulating layer constituting material, such that the hardly soluble laser absorption layer is disposed on the side irradiated with the infrared laser light. A copper-clad laminate characterized in that is laminated. It is an electrolytic copper-tin alloy layer formed by an electrolytic plating method having a tin content of 25% by mass or more and 50% by mass or less, and has an etching property with respect to a copper etching solution , and its etching rate is slower than that of a copper foil. Furthermore, for a laminate in which a copper foil for laser processing provided with a hardly soluble laser absorbing layer that absorbs infrared laser light on the surface of the copper foil and other conductor layers are laminated via an insulating layer, the infrared laser beam is irradiated directly on the poorly soluble laser-absorbing layer to form a via hole for interlayer connection, the micro-etching step as a pretreatment for desmear process and / or electroless plating process for removing smear in the via hole, A method for producing a printed wiring board, comprising removing the hardly soluble laser absorbing layer from the surface of the copper foil.

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