LU101147A1

LU101147A1 - Copper foil with carrier, copper-clad laminate and printed wiring board

Info

Publication number: LU101147A1
Application number: LU101147A
Authority: LU
Inventors: Makoto Hosokawa; Akitoshi Takanashi; Takuma Nishida
Original assignee: Mitsui Mining & Smelting Co
Priority date: 2018-03-23
Filing date: 2019-03-04
Publication date: 2019-10-02
Also published as: JP6462940B1; KR102213585B1; LU101147B1; KR20190111803A; CN110293712A; JP2019166821A; TWI697573B; TW201940709A; CN110293712B

Abstract

There is provided a copper foil with a carrier capable of significantly reducing the generation of blisters caused by hot pressing for stacking to a resin substrate. The copper foil with a carrier includes, in sequence, a carrier, a release layer and an extremely thin copper foil. The release layer comprises a carboxyl group-containing compound and a derivative thereof. The number of H₂O molecules per unit area in the copper foil with a carrier is 3.44*10¹⁶/cm² or less, and the number of CO₂ molecules per unit area in the copper foil with a carrier is 1.39x10¹⁶/cm² or less.

Description

COPPER FOIL WITH CARRIER, COPPER-CLAD LAMINATE AND PRINTED WIRING BOARD

TECHNICAL FIELD [0001]

The present invention relates to a copper foil with a carrier, a copper-clad laminate and a printed wiring board.

BACKGROUND ART [0002]

A copper foil with a carrier has been widely used as a material for manufacturing a printed wiring board. The copper foil with a carrier is bonded to an insulating resin substrate, such as a glass-epoxy substrate, a phenol substrate, a polyimide substrate by hot pressing into a copper-clad laminate, which is used for manufacturing a printed wiring board.

[0003]

A copper foil with a carrier typically has, in sequence, a carrier, a release layer, and an extremely thin copper foil, and the use of an organic release layer containing an organic compound has been proposed for the release layer. For example, PTL 1 (JP2003-328178A) discloses a method of manufacturing a copper foil with a carrier. The method comprises pickling and dissolving a surface of the carrier with a pickling acid solution containing an organic agent of 50 ppm to 2000 ppm, and simultaneously forming an organic film, as an organic release layer, containing the adsorbed organic agent after the pickling, and discloses the use of carboxybenzotriazole (CBTA) as the organic agent. In addition, PTL 2 (JP5842077B) also discloses a copper foil with a carrier through the use of carboxybenzotriazole (CBTA) as an organic release layer.

[0004]

Meanwhile, when a copper foil with a carrier is bonded to a resin substrate by hot pressing, blisters (air bubbles) may be generated between the extremely thin copper foil and the carrier. Since the blisters adversely affects the formation of circuits, the product yield decreases. Techniques for reducing the amount of moisture in a release layer have been proposed in order to address such a problem. For example, PTL 3 (JP2015-199355A) LU101147 discloses a copper foil with a carrier having a moisture content of 160 ppm in weight or less generated when being heated at 30 °C/min up to 500 °C, and indicates that the copper foil with a carrier in which the production of moisture is reduced can effectively restrain the generation of the blisters.

CITATION LIST

PATENT LITERATURES [0005]

PTL 1: JP2003-328178A

PTL 2: JP5842077B

PTL 3: JP2015-199355A

SUMMARY OF INVENTION [0006]

However, a further improvement is desired since the prior art as disclosed in PTL 3 is not still a satisfactory solution to a problem in a yield reduction due to the generation of blisters. [0007]

The present inventors have now found that a copper foil with a carrier provided with a release layer including a carboxyl group-containing compound and a derivative thereof can remarkably decrease the generation of blisters caused by hot pressing for stacking to a resin substrate by lowering the number densities of H₂O molecules and CO₂ molecules to predetermined values or less.

[0008]

Accordingly, an object of the present invention is to provide a copper foil with a carrier capable of significantly reducing the generation of blisters caused by hot pressing for stacking to a resin substrate.

[0009]

One embodiment of the present invention provides a copper foil with a carrier including, in sequence, a carrier, a release layer, and an extremely thin copper foil, wherein the release layer comprises a carboxyl group-containing compound and a derivative thereof, and the number of H₂O molecules per unit area in the copper foil with a carrier 3.44*10¹⁶/cm² or less, and the number of CO₂ molecules per unit area in the copper foil with a carrier is 1.39*10¹⁶/cm² or less.

[0010]

Another embodiment of the present invention provides a copper-clad laminate including a copper foil with a carrier.

[0011]

Another embodiment of the present invention provides a printed wiring board including a copper foil with a carrier.

[0012]

Another embodiment of the present invention provides a method of manufacturing a printed wiring board using a copper foil with a carrier.

BRIEF DESCRIPTION OF DRAWINGS [0013]

FIG. 1 is a graph illustrating the numbers of H₂O molecules and CO₂ molecules per unit area in a copper foil with a carrier of Examples 1 to 9.

FIG. 2 is a diagram illustrating a thermal desorption profile of linoleic acid.

DESCRIPTION OF EMBODIMENTS [0014]

Copper foil with carrier

A copper foil with a carrier of the present invention comprises, in sequence, a carrier, a release layer, and an extremely thin copper foil. The release layer comprises a carboxyl group-containing compound (typically, an organic compound having a carboxyl group) and a derivative thereof. The number of H₂O molecules per unit area in the copper foil with a carrier is 3.44*10¹⁶/cm² or less. In addition, the number of CO₂ molecules per unit area in the copper foil with a carrier is 1.39*10¹⁶/cm² or less. Accordingly, a copper foil with a carrier provided with a release layer comprising a carboxyl group-containing compound and a derivative thereof can remarkably decrease the generation of blisters caused by hot pressing for bonding to a resin substrate by lowering the number densities of the H₂O molecules and the CO₂ molecules to predetermined values or less. The reduction in the blisters contributes to an increase in production yield because the blisters adversely affects the formation of circuits.

[0015]

Although the mechanism by which blisters generate is not clear, the following hypothesis is made: FIG. 2 shows a thermal desorption profile of linoleic acid that is a typical carboxyl group-containing compound. The thermal desorption profile shown in FIG. 2 illustrates the numbers, as a function of the temperature, of H₂O molecules and CO₂ molecules desorbed from the surface of a sample (linoleic acid) heated at a predetermined rate. As shown in FIG. 2, three major peaks corresponding to the desorption of water are observed, which include, in sequence from a low temperature side, i) a peak resulting from the desorption of water adsorbed on the sample surface (desorption of adsorbed water) , ii) a peak resulting from the desorption of water resonated with the carboxyl group (desorption of resonated water), and iii) desorption of water caused by a dehydration condensation reaction between adjacent linoleic acids (an esterification reaction). Meanwhile, one major peak corresponding to the desorption of carbon dioxide is observed at around 180 °C. This peak is caused by a decarboxylation reaction involving dissociation of carbon dioxide from the carboxyl group of the linoleic acid. The decarboxylation reaction generally occurs at 150 °C or higher, although the temperature of the reaction varies depending on the type of the organic compound. In this manner, large amounts of water and carbon dioxide are generated from an organic compound containing the carboxyl group even at a temperature (for example, 110 to 200 °C) higher than that at which adsorbed water is desorbed (for example, around 90 °C). Accordingly, when a copper foil with a carrier provided with a release layer including a carboxyl group-containing compound is bonded to a resin substrate by hot pressing, the above-described reaction occurs in the release layer heated, and water and carbon dioxide are abundantly generated. As a result, it is believed that blisters due to the water and carbon dioxide gas generates between the extremely thin copper foil and the carrier. In contrast, the present invention can reduce the number densities of the H₂O molecules and the CO₂ molecules in the copper foil with a carrier to predetermined values or less in advance, prevent the LU101147 production of large amounts of water and carbon dioxide from the release layer during hot pressing for bonding to a resin substrate, and thus significantly reduce the generation of the blisters.

[0016]

Accordingly, the number of H2O molecules per unit area in the copper foil with a carrier is 3.44x10¹⁶/cm² or less, preferably 3.38x10¹⁶/cm² or less, more preferably 3.30x10¹⁶/cm² or less. The minimum number of H2O molecules per unit area may be any value, and is typically 1.00x10¹⁵/cm², more typically 1.50x10¹⁵/cm², further more typically 1.04x10¹⁶/cm². The number of CO2 molecules per unit area in the copper foil with a carrier is 1,39x10¹⁶/cm² or less, preferably 1.34x10¹⁶/cm² or less, more preferably 1.32x10¹⁶/cm² or less. The minimum number of CO2 molecules per unit area may be any value, and is typically 1.00x10¹⁵/cm², more typically 1.50x10¹⁵/cm², further more typically 9.17x10¹⁵/cm². Each number of H2O molecules and CO₂ molecules in the copper foil with a carrier can be preferably measured by thermal desorption spectrometry (TDS), as mentioned in the examples described later.

[0017]

The release layer has a function to decrease a release strength between the carrier and the extremely thin copper foil, to ensure the stability of the strength, and further restrain the interdiffusion which may occur between the carrier and the copper foil during hot pressing. The release layer is generally formed on one side of the carrier, or may be formed on two sides. The release layer contains a carboxyl group-containing compound and/or a derivative thereof. Accordingly, the release layer is typically an organic release layer, or may be a composite release layer of an organic release sublayer and an inorganic release sublayer, or a mixed release layer containing an organic release agent and an inorganic release agent. The derivative of the carboxyl group-containing compound includes a compound in which a portion in the molecule of the carboxyl group-containing compound is modified by, for example, a dissociation reaction or a substitution reaction, or a compound in which an atomic group is added to a portion in the molecule of the carboxyl group-containing compound by, for example, an additive reaction. Examples of such derivatives include a compound in which a carboxyl group-containing compound is converted into an acid anhydride (typically dimer) by a dehydration condensation reaction; a compound in which a CO₂ molecule is eliminated from a carboxyl group by a decarboxylation reaction; or a compound in which a substituent such as a methyl group is added to a carboxyl group-containing compound. Accordingly, the release layer may contain a carboxyl group-containing compound and a derivative thereof from an initial stage in forming a layer, or a portion of the carboxyl group-containing compound may be preferably converted into a derivative afterwards or unavoidably by heat treatment described later. That is, the release layer initially contains a carboxyl group-containing compound without a derivative thereof, and may be thereafter subjected to the heat treatment described later to react a portion of the carboxyl group-containing compound (for example, a dehydration condensation reaction, or a decarboxylation reaction) so as to contain a carboxyl group-containing compound and a derivative thereof.

[0018]

The carboxyl group-containing compound is preferably carboxybenzotriazole (CBTA). Alternatively, the carboxyl group-containing compound may be monocarboxylic acid and/or dicarboxylic acid. Preferred examples of the monocarboxylic acid include linoleic acid, oleic acid, linolenic acid, thioglycolic acid, and 3-mercapto-2-pyridinecarboxylic acid. Preferred examples of the dicarboxylic acid include thiomalic acid, diisopropyl azodicarboxylate, and diethyl azodicarboxylate. The release layer can further retain a state ready for separation of a carrier even when the release layer is subjected to hot pressing (for example, 250 °C or more) or long baking treatment (for example, at 200 °C for eight hours), because the release layer contains the carboxyl group-containing compound as described above.

[0019]

The carrier is a support for improving the support and handling of an extremely thin copper foil, and a typical carrier is a metal layer. Examples of such carriers include aluminum foil, copper foil, stainless steel (SUS) foil, and resin films and glass surface-coated with metal, such as copper. Preferred is copper foil. The copper foil may be either a rolled copper foil or an electrodeposited copper foil. The carrier typically has a thickness of 250 μm or less, preferably 9 to 200 μm. LU101147 [0020]

The extremely thin copper foil may be any foil, and have a known structure employed in the extremely thin copper foil with a carrier. For example, the extremely thin copper foil may be produced by a wet process of film formation such as copper electroless plating and copper electroplating, a dry process of film formation such as sputtering and chemical vapor deposition, or a combination thereof. The extremely thin copper foil has a thickness of preferably 0.1 to 7.0 μm, more preferably 0.5 to 5.0 μm, further more preferably 1.0 to 3.0 μm.

[0021]

The outermost surface of the extremely thin copper foil (that is, the surface remote from the release layer) is preferably a roughened surface. One surface of the extremely thin copper foil is preferably roughened. Such roughening can improve the adhesiveness to a resin layer in a manufacturing process of a copper-clad laminate or a printed wiring board. This roughening treatment is preferably performed by a known plating procedure through at least two plating processes, i.e., a burning plating process for depositing and fixing fine copper particles on the extremely thin copper foil and a covering plating process for preventing dropping-off of the fine copper particles.

[0022]

Another functional layer may be provided between the release layer and the carrier and/or the extremely thin copper foil. An example of such a functional layer is an auxiliary metal layer. The auxiliary metal layer is preferably composed of nickel and/or cobalt. Interdiffusion which may occur between the carrier and the extremely thin copper foil during hot pressing at high temperature or for long time can be further restrained and the release strength stability of the carrier can be ensured by stacking such an auxiliary metal layer on the surface side of the carrier and/or the surface side of the extremely thin copper foil. The auxiliary metal layer has a thickness of preferably 0.001 to 3 μm.

[0023]

The extremely thin copper foil may be optionally subjected to rust proofing treatment. The rust proofing treatment preferably includes a plating process with zinc. The plating process with zinc may be either a zinc plating process or zinc alloy plating process, and the LU101147 alloy particularly preferred in the zinc alloy plating process is a zinc-nickel alloy. The zinc-nickel alloy contains at least Ni and Zn, and may further contain other elements, such as Sn, Cr, and Co. The deposited Ni/Zn mass ratio in the zinc-nickel alloy plating is preferably 1.2 to 10, more preferably 2 to 7, further more preferably 2.7 to 4. Preferably, the rust proofing treatment further includes a chromate process. More preferably, the chromate process is performed on the surface of a plated layer containing zinc after plating process with zinc. Such a process further improves rust proofing characteristics. A particularly preferred rust proofing treatment is a combination of zinc-nickel alloy plating and subsequent chromate process.

[0024]

The surface of the extremely thin copper foil may be subjected to a treatment with a silane coupling agent, as desired, to form a layer of a silane coupling agent, which improves the moisture resistance, chemical resistance, and adhesion to, for example, an adhesive. The silane coupling agent may be appropriately diluted, applied and then dried to form a layer of the silane coupling agent. Examples of the silane coupling agent include epoxy-functional silane coupling agents, such as 4-glycidylbutyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane; amino-functional silane coupling agents, such as 3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane,

N-3-(4-(3-amino-propoxy)butoxy)propyl-3-aminopropyltrimethoxysilane, and

N-phenyl-3-aminopropyltrimethoxysilane; mercapto-functional silane coupling agents, such as 3-mercaptopropyltrimethoxysilane; olefin-functional silane coupling agents, such as vinyl trimethoxysilane and vinyl phenyl trimethoxysilane; acryl-functional silane coupling agents, such as 3-methacryloxypropyl trimethoxysilane; imidazole-functional silane coupling agents, such as imidazole silane; and triazine-functional silane coupling agents, such as triazine silane.

[0025]

Method of manufacturing copper foil with carrier

A copper foil with a carrier in the present invention can be preferably manufactured by the steps of: producing the copper foil with a carrier that, in sequence, a release layer, an extremely thin copper foil and other layers are bonded on the carrier in accordance with known techniques; and then facilitating the generation and discharge of water and carbon dioxide from the release layer through heat treatment in two stages as described below. [0026]

The first stage in the heat treatment involves proceeding the above-mentioned reaction that generates water and carbon dioxide by high temperature treatment. Preferred heat treatment conditions may vary depending on, for example, the size and shape of the copper foil with a carrier, and the type of oven furnace used. Accordingly, the heat treatment conditions may be appropriately determined depending on these variable factors. Such conditions can promote the generation of enough water and carbon dioxide, i.e., not only the desorption of adsorbed water but also the desorption of resonated water from the carboxyl group-containing compound contained in the release layer and the desorption of water and carbon dioxide caused by a dehydration condensation reaction and a decarboxylation reaction. A heat treatment temperature in the first stage is typically higher than 180 °C, preferably 200 to 280 °C, more preferably 220 to 250 °C. A heat treatment time in the first stage is typically 0.5 to 40 hours, preferably 1 to 30 hours, more preferably 2 to 24 hours. Through this treatment, water and carbon dioxide can be adequately generated from a copper foil with carrier (typically, a release layer) while effectively preventing the deterioration of the copper foil and the separation of the optional layer of silane coupling agent. In particular, the heat treatment in the first stage at a temperature close to hot pressing for bonding to the resin substrate contributes to effectively restrain the generation of blisters caused by hot pressing. Typically, a portion of the carboxyl group-containing compound contained in the release layer transforms into derivatives thereof (for example, a dimer or a compound from which CO₂ molecules are eliminated) during the high temperature treatment in the first stage.

[0027]

The second stage in the heat treatment involves discharging water and carbon dioxide generated in the first stage of the heat treatment from the copper foil with a carrier by heat treatment at a relatively low temperature for a long time. That is, since water and carbon dioxide generated from the copper foil with a carrier in the first stage of the heat treatment are typically derived from the release layer comprising the carboxyl group-containing LU101147 compound, water and carbon dioxide remain within the copper foil with a carrier (for example, between the carrier and the extremely thin copper foil), and cause the generation of the blisters. The second stage in the heat treatment may desirably discharge water and carbon dioxide remained within the copper foil with a carrier to the outside of the system. As a result, this heat treatment can modify into the copper foil with a carrier (in particular, the release layer) such that the number of H₂O molecules per unit area is 3.44x10¹⁶/cm² or less and the number of CO₂ molecules per unit area is 1.39x10¹⁶/cm² or less. At this time, a heating temperature in the second stage is preferably lower than that in the first stage from the viewpoint of preventing further generation of water and carbon dioxide from the release layer. The heating temperature in the second stage is typically 180 °C or less, preferably 90 to 180 °C, more preferably 100 to 180 °C. In addition, the heating treatment time in the second stage is typically 3 to 40 hours, preferably 5 to 35 hours, more preferably 5 to 30 hours. Through the heat treatment in the second stage within such ranges of temperature and time, water and carbon dioxide generated in the first stage can be effectively discharged from the copper foil with a carrier. Similar to the heat treatment conditions in the first stage, preferred conditions in the second stage may also vary depending on, for example, the size and shape of the copper foil with a carrier, and the type of oven furnace used.

[0028]

Copper-clad laminate

The copper foil with a carrier in the present invention is preferably used for manufacturing a copper-clad laminate for printed wiring boards. That is, a preferred embodiment of the present invention provides a copper-clad laminate comprising the copper foil with a carrier as described above. This copper-clad laminate comprises the copper foil with a carrier of the present invention and a resin layer provided in close contact with the extremely thin copper foil of the copper foil with a carrier. The copper foil with a carrier may be provided on one side or on two sides of the resin layer. The resin layer contains a resin, preferably an insulating resin. The resin layer is preferably a prepreg and/or a resin sheet. The prepreg is a generic term for a composite material prepared by impregnating a substrate, such as a synthetic resin plate, a glass plate, a glass woven fabric, a glass nonwoven LU101147 fabric, or paper, with a synthetic resin. Preferred examples of the insulating resin include epoxy resins, cyanate resins, bismaleimide triazine resins (BT resins), polyphenylene ether resins, and phenol resins. Examples of the insulating resin constituting the resin sheet include epoxy resins, polyimide resins, and polyester resins. The resin layer may contain filler particles or other additives composed of various inorganic particles, such as silica and alumina from the viewpoint of, for example, improving the insulating property. The resin layer may have any thickness, but a thickness of preferably 1 to 1000 μm, more preferably 2 to 400 μm, further more preferably 3 to 200 μm. The resin layer may be composed of a plurality of sublayers. The resin layer composed of, for example, the prepreg and/or the resin sheet may be provided on a primer resin layer preliminarily applied onto the surface of the extremely thin copper foil with a carrier.

[0029]

Printed Wiring Board

The copper foil with a carrier of the present invention is preferably used for manufacturing a printed wiring board. A preferred embodiment of the present invention provides a printed wiring board comprising the copper foil with a carrier, or a method of manufacturing the printed wiring board. The printed wiring board according to the embodiment includes a stack of a resin layer and a copper layer. The resin layer is as described above in the explanation of the copper-clad laminate. In any case, any known layer structure can be employed in the printed wiring board. Specific examples of the printed wiring board include a single- or double-sided printed wiring board in which circuits are formed by bonding the extremely thin copper foil of the present invention on one side or two sides of a prepreg to form a cured laminate, and a multilayered printed wiring board in which these single- or double-sided printed wiring board are stacked. Other specific examples include flexible printed wiring boards, COF tapes, and TAB tapes which include the extremely thin copper foil of the present invention formed on a resin film and circuits formed thereon. Further specific examples include a build-up wiring board in which circuits are formed by, for example, a modified semi-additive process (MSAP) or a subtractive process using the extremely thin layer as all or part of the wiring layer after forming a resin-coated copper foil (RCC) coated with the above resin layer on the extremely thin copper foil of the present invention and stacking the resin layer as an insulating adhesive layer on the printed wiring board; a build-up wiring board in which circuits are formed by a semi additive process (SAP) after removing the extremely thin copper foil; and a direct build-up-on-wafer wiring board in which the stacking of a resin-coated copper foil and the formation of circuits are alternately repeated on a semiconductor integrated circuit. The copper foil with a carrier of the present invention can also be preferably employed in a manufacturing method including a coreless buildup process in which insulating resin layers and conducting layers are alternately stacked without use of a so-called core substrate.

EXAMPLES [0030]

The present invention will be described more specifically with reference to the following examples.

[0031]

Examples 1, 2 and 4 to 8

Each copper foil with a carrier was produced and evaluated as follows.

[0032] (1) Provision of a career

An electrodeposited copper foil having a thickness of 18 μm, classified as Grade 3 in accordance with the IPC standard, was provided as a carrier. The electrodeposited copper foil as the carrier was a copper foil produced electrolytically as it is (a so-called plain foil), and was not subjected to the surface treatment such as rust proofing treatment or roughening treatment. The surface of the carrier was pickled to remove grease components and surface oxide film.

[0033] (2) Formation of release layer

The electrode surface of the pickled carrier was immersed in an aqueous CBTA solution composed of 1 g/L CBTA (carboxybenzotriazole), 150 g/L sulfuric acid and 10 g/L copper at 30 °C for 30 seconds, and the components of CBTA were adsorbed on the electrode surface of the carrier. A CBTA layer, as a release layer, was formed on the electrode LU101147 surface of the carrier.

[0034] (3) Formation of auxiliary metal layer

The carrier provided with the release layer was immersed in the solution which was prepared using nickel sulfate and composed of 20 g/L nickel to deposit nickel having a thickness of 0.001 μm on the release layer of the carrier under the conditions of a liquid temperature of 45 °C, pH of 3 and a current density of 5 A/dm². A nickel layer, as an auxiliary metal layer, was formed on the release layer.

[0035] (4) Formation of extremely thin copper foil

The carrier on which the auxiliary metal layer was formed was immersed in a copper sulfate solution having 60 g/L copper and 200 g/L sulfuric acid, and electrolyzed under the conditions of a liquid temperature of 50 °C and a current density of 5 to 30 A/dm² to form an extremely thin copper foil having a thickness of 1.5 μm on the auxiliary metal layer.

[0036] (5) Roughening treatment

The surface of the extremely thin copper foil was roughened. This roughening treatment was performed in the following two plating stages: In the first plating stage, the surface was electroplated under the plating conditions of a liquid temperature of 40 °C and a current density of 30 A/dm² with an acidic copper sulfate solution containing 10 g/L copper and 120 g/L sulfuric acid. In the second plating stage, the surface was electroplated under the plating conditions of a liquid temperature of 40 °C and a current density of 30 A/dm² with an acidic copper sulfate solution containing 70 g/L copper and 120 g/L sulfuric acid.

[0037] (6) Rust proofing treatment

Rust proofing treatment consisting of inorganic rust proofing treatment and chromate treatment was performed on the two surfaces of the copper foil with a carrier after the roughening treatment. The inorganic rust proofing treatment was carried out with a zinc-nickel alloy in a pyrophosphoric acid bath containing 80 g/L potassium pyrophosphate, LU101147 0.2 g/L zinc and 2 g/L nickel under the conditions of a liquid temperature of 40 °C and a current density of 0.5 A/dm². A chromate layer was further deposited on the zinc-nickel alloy (the chromate treatment). This chromate treatment was carried out under the conditions of 1 g/L chromic acid, a pH of 11, a liquid temperature of 25 °C and a current density of 1 A/dm².

[0038] (7) Silane coupling agent treatment

The copper foil subjected to the rust proofing treatment was washed with water and immediately treated with a silane coupling agent, and the silane coupling agent was adsorbed on the roughened surface of the rust proofing layer. In this silane coupling agent treatment, the adsorption treatment was carried out by showering a solution that contains pure water as a solvent and 3 g/L 3-aminopropyltrimethoxysilane onto the roughened surface. After the adsorption of the silane coupling agent, water was finally evaporated with an electric heater to give a roughened copper foil with a carrier having a total thickness of 1.5 μm.

[0039] (8) Heat treatment

The resultant copper foil with carrier was subjected to one or two stages of heat treatment under the conditions shown in Table 1 in an air oven. At this time, various samples with different contents of moisture and carbon dioxide in the release layer were prepared by appropriate changes of the heating conditions in Examples 1, 2 and 4 to 8 as shown in Table 1. It should be appreciated that the conditions of the heat treatment vary depending on, for example, the size of the sample and the type of the oven, and the present invention should not be limited at all by these conditions.

[0040] (9) Evaluations of copper foil with carrier

The resultant copper foils with a carrier were evaluated as follows.

[0041] <Evaluation 1 : Measurement of moisture and carbon dioxide>

The amounts of moisture and carbon dioxide contained in the resultant copper foils with carriers (in particular, the release layer) were measured by thermal desorption spectrometry (TDS) as follows. In order to remove moisture adsorbed on the surface of the copper foil with a carrier subjected to the heat treatment in the above item (8), the copper foil with a carrier was dried in a vacuum thermostatic oven at 50 °C and at -0.1 MPa against the atmospheric pressure for seven days. The copper foil with a carrier dried in vacuum was then stamped out with a puncher to produce a test piece with a size of 1 cm in diameter, and this test piece was quickly weighed. The test piece was placed in a chamber of a thermal desorption spectrometer (TDS 120011, manufactured by Electronic Science Co., Ltd.) in a state where the carrier and the extremely thin copper foil were separated (that is, a state where the release layer was exposed), and the chamber is purged with nitrogen gas for 3 minutes and then evacuated for 5 minutes. After that, the test piece was irradiated with lamp light, and the temperature of the test piece was raised up to 400 °C at a heating rate of 30 °C/min by light absorption. During this step, the gas generated from the test piece was measured qualitatively and quantitatively by mass spectrometer. In this measurement, the H₂O gas and CO₂ gas were analyzed, respectively, at m/z = 18 and at m/z = 44, and the numbers of H₂O molecules and CO₂molecules were calculated in a circle with 1 cm diameter of the copper foil with a carrier. The resultant numbers were divided by the area of a circle having a diameter of 1 cm (0.785 cm²) into the numbers of H₂O molecules and CO₂ molecules per unit area. The results are as shown in Table 1 and FIG. 1. For reference, Table 1 illustrates the weight ratios (ppm) of H₂O and CO₂ of the copper foil with a carrier, which are calculated by dividing each weight of H₂O and CO₂ (converted from each number of molecules) by the weight of the test piece.

[0042]

Evaluation 2: Measurement of blisters>

A prepreg with a thickness of 100 μm (GHPL-830 NSF, manufactured by Mitsubishi Gas Chemical Company, Inc.) was provided as a resin substrate. The copper foil with a carrier subjected to the heat treatment in the above item (8) was stacked onto the resin substrate such that the copper foil with a carrier was in contact with the resin substrate at the side of the extremely thin copper foil, and hot-pressed at a pressure of 2.4 MPa and at 250 °C for 90 minutes, followed by the baking treatment in an oven at 200 °C for eight hours to give a sample of copper-clad laminate. After the carrier was released from the sample of copper-clad laminate, the surface of the extremely thin copper foil was observed under the conditions of a magnification of 20 folds and a visual measured field of 18 mmx13.5 mm with an optical microscope (VHX-5000, manufactured by Keyence Corporation), and the number of dimples was counted to give a mean value of three different visual fields as the number of blisters. In other words, since the dimples are formed on the surface of the sample of copper-clad laminate after releasing of the carrier (that is, the surface of the extremely thin copper foil) as the traces caused by the blisters generated between the carrier and the extremely thin copper foil, the number of dimples was regarded as the number of blisters generated. The results are shown in Table 1.

[0043]

Example 3 (comparative)

A copper foil with a carrier was prepared and evaluated in the same process as in Example except that the copper foil with a carrier was not subjected to heat treatment. The result is as shown in Table 1 and FIG. 1.

[0044]

Example 9 (comparative)

A copper foil with a carrier was prepared and evaluated in the same process as in Example except that an aqueous linoleic acid solution containing 1000 ppm by weight linoleic acid was used instead of the CBTA aqueous solution in the step of forming the release layer. The result is as shown in Table 1 and FIG. 1.

ΙΟ ο ο

Tablel

Evaluations

Measurement of blisters

Number of blisters

[Number] I-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

LO

CM

—

O in X~

CO X“

CM CO X“

00

0)

CO

Measurement of water and carbon dioxide

: ratios id CO₂on >ample

CM Έ o O â

CO 10

LO

σ> co

co

CD

O CO

00 m

0> m

0) 10

Weight of H₂O an <p1cm i

o e CM Q_ T S

co in

O m

00 co

CO co

00 in

o CO

00 'M^-

Numbers of H₂O molecules and CO₂molecules per unit area______

CM CM~ Ο E O £

CD o X co X^-

CD o X o CM X“

m O X X“ CM CD

co O X CM O X^-

CD o X co X” X“

co O X X“

CD b X 0) CO X“

co O X ? X^-

CO O X O M; χ—

oÇ CM C X

CD o X co co co

CD o X co σ> CM

CD b X CD co

CD b X

co b X CM OO CO

CD O X 00 CO CO

CO o X 00 CO

CD O X CM 10 CO

CD O X X“·' 00 CM

Heat treatment

Heat treatment in the second stage

Φ

co

CO m

ro

ro c

ro

CM

ra

CL r—. EO

o CM X“

o co X^-

o 00 X^-

O CO CM

Heat treatment in the first stage

Φ r— E

CM

ra

co co CM

co in

CM

CO in

Φ c

CL,—

o co CM

O CO CM

O CM x—

o co X“

O CO CM

o CO CM

o CO X^-

0) c ω φ ΞΕ

<D σ π OT CM

Φ ) σ φ *5 CM

c o Z

Φ σ ro X“

Φ ) σ σ ω χ-

Φ ) σ J5 7Z X“

0) σ ro cxi

Φ ) σ 2 ω CM

c o Z

Component of release laver

Carboxyl groupcontaining compound

m o

Linoleic acid

X LU

C\ X LL

* co X LU

♦ X LU

+ LC X LL

* cc X LL

« b*. X U-

* 00 X LU

* 0) X LUI

Claims

EXPECTATIONS

1. copper foil with a carrier, which successively comprises a carrier, a release layer and an extremely thin copper foil, the release layer comprising a carboxyl group-containing compound and a derivative thereof and the number of H ₂ O molecules per unit area in the copper foil with a carrier 3.44 × 10 ¹⁶ / cm ² or less and the number of CCb molecules per unit area in the copper foil with a support is 1.39x10 ¹⁶ / cm ² or less.

2. Copper foil with a support according to claim 1, wherein the carboxyl group-containing compound is carboxybenzotriazole (CBTA).

3. copper foil with a carrier according to claim 1, wherein the carboxyl group-containing compound is monocarboxylic acid and / or dicarboxylic acid.

4. copper foil with a carrier according to any one of claims 1 to 3, wherein the carrier includes a metal layer.

5. Copper foil with a carrier according to one of claims 1 to 4, further comprising an auxiliary metal layer between the release layer and the carrier and / or the extremely thin copper foil.

6. A copper-coated laminate comprising the copper foil with a carrier according to one of claims 1 to 5.

7. Printed circuit board comprising the copper foil with a carrier according to one of claims 1 to 5.

8. A method for producing a printed circuit board, wherein the printed circuit board is produced with the copper foil with a carrier according to one of claims 1 to 5.