Laminate for transfer

Abstract

Provided is a laminate for transfer which is used when forming a circuit board, has a small change in peelability before and after a heat load, and has good peelability after the heat load. The laminate for transfer has a base material, a conductive layer, a peeling layer, and a conductive auxiliary layer in this order. The conductive layer contains Cu. The peeling layer contains an alloy of Ni and Cr. The conductive auxiliary layer contains Cu.

Description

Transfer laminate

[0001] The present invention relates to a transfer laminate. More specifically, the present invention relates to a transfer laminate used in forming a circuit board, which exhibits little change in peelability before and after thermal loading, and good peelability after thermal loading.

[0002] Conventionally, transfer laminates have been developed for use in processing steps to form circuits using methods such as build-up (for example, Patent Document 1). Patent Document 1 discloses a carrier-equipped copper foil consisting of a carrier, an intermediate layer, and an ultrathin copper layer. The carrier-equipped copper foil is used after the surface of the ultrathin copper layer is bonded to an insulating substrate and thermocompressed (heat press), and then the carrier is peeled off.

[0003] Japanese Patent Publication No. 2017-88970

[0004] In the processing steps for forming circuits using a transfer laminate, there are cases where significant heat is applied, as well as cases where no significant heat is applied. The carrier-equipped copper foil described in Patent Document 1 warrants further investigation regarding its peelability when no significant heat is applied, and the change in peelability before and after heat application.

[0005] The present invention has been made in view of the above-mentioned conventional inventions, and aims to provide a transfer laminate that can be used when forming a circuit board, has little change in peelability before and after thermal loading, and has good peelability after thermal loading.

[0006] As a result of diligent research, the inventors discovered that the above problems could be solved by selecting the raw materials that constitute each layer, and thus completed the present invention.

[0007] A transfer laminate according to one aspect of the present invention, which solves the above problems, comprises a substrate, a conductive layer, a release layer, and a conductive auxiliary layer in this order, wherein the conductive layer contains Cu, the release layer contains an alloy of Ni and Cr, and the conductive auxiliary layer contains Cu.

[0008] Figure 1 is a graph showing the results of the XPS depth-direction composition analysis of the transfer laminate before heat treatment in Example 1. Figure 2 is a graph showing the results of the XPS depth-direction composition analysis of the transfer laminate after heat treatment in Example 1. Figure 3 is a graph showing the results of the XPS depth-direction composition analysis of the transfer laminate before heat treatment in Comparative Example 1. Figure 4 is a graph showing the results of the XPS depth-direction composition analysis of the transfer laminate after heat treatment in Comparative Example 1.

[0009] <Transfer Laminate> The transfer laminate of one embodiment of the present invention comprises a substrate, a conductive layer, a release layer, and a conductive auxiliary layer in this order. The conductive layer contains Cu. The release layer contains an alloy of Ni and Cr. The conductive auxiliary layer contains Cu. The respective components will be described below.

[0010] (Substrate) The substrate is not particularly limited. For example, the substrate may be a resin film, a metal, or a composite film of a metal and a resin film. Resin films may be polyester films such as polyethylene terephthalate or polyethylene naphthalate, polyethylene films, polypropylene films, polystyrene films, or polyimide films. Metals may be copper foil, aluminum foil, nickel foil, iron foil, or alloy foil. A composite film of a metal and a resin film may be made by laminating the above-mentioned resin film with a metal.

[0011] The thickness of the substrate is not particularly limited. For example, the thickness of the substrate is preferably 6 μm or more, more preferably 9 μm or more, and even more preferably 12 μm or more. Also, the thickness of the substrate is preferably 200 μm or less, and more preferably 125 μm or less. By having the substrate thickness within the above range, the resulting transfer laminate can exhibit appropriate rigidity and strength.

[0012] (Conductive layer) The conductive layer is formed on the substrate. The conductive layer contains Cu. The Cu content in the conductive layer is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably 99% by mass or more. In this embodiment, the conductive layer may contain impurities that are unavoidably present.

[0013] The transfer laminate of this embodiment, due to the presence of a conductive layer, exhibits minimal change in peelability before and after heat loading, regardless of the type of substrate, and also exhibits good peelability after heat loading. For example, when the substrate is copper foil, the presence of the conductive layer allows for peeling at a favorable location. Furthermore, when the substrate is polyimide, the presence of the conductive layer ensures that peeling occurs at a favorable location even when heat treatment is performed, resulting in minimal change in peelability before and after heat loading and good peelability after heat loading. In addition, the transfer laminate has excellent conductivity due to the presence of the conductive layer, making it easy to form a copper layer by electroplating on the conductive auxiliary layer described later.

[0014] The surface resistance of the conductive layer formed on the substrate is preferably 4.0 Ω / □ or less, and more preferably 2.0 Ω / □ or less. The surface resistance can be measured, for example, using a low-resistivity resistivity meter (Rolestar AX MCP-T370, manufactured by Mitsubishi Chemical Analytec Co., Ltd.) with a four-terminal, four-probe method.

[0015] The thickness of the conductive layer is not particularly limited. For example, the thickness of the conductive layer is preferably 40 nm or more, and more preferably 60 nm or more. Furthermore, the thickness of the conductive layer is preferably 200 nm or less, and more preferably 150 nm or less. By having the thickness of the conductive layer within the above range, the transfer laminate exhibits excellent conductivity and peelability. In this embodiment, the thickness of the conductive layer can be measured, for example, by quantitative analysis using a calibration curve method with an X-ray fluorescence analyzer (e.g., a scanning X-ray fluorescence analyzer, ZSX Primus IV, manufactured by Rigaku Corporation). The same applies to the peel layer, peel auxiliary layer, and conductive auxiliary layer described later.

[0016] The method for forming the conductive layer is not particularly limited. For example, the conductive layer can be formed on a substrate using a composition constituting the conductive layer by a dry coating method such as vacuum deposition, sputtering, or ion plating. Among these, the conductive layer is preferably formed by sputtering because it allows for easy formation of a thin film and enables the formation of a release layer with good productivity.

[0017] (Release Layer) The release layer is formed on the conductive layer. The release layer contains an alloy of Ni and Cr. In this embodiment, the transfer laminate has a release layer made of an alloy of Ni and Cr, so even when heat treatment is performed in each step of forming the circuit board, Cu is less likely to diffuse from the conductive layer and the conductive auxiliary layer described later to the release layer. As a result, the transfer laminate exhibits excellent release properties, with little change in release properties before and after heat loading, and good release properties after heat loading.

[0018] In Ni and Cr alloys, the proportion of Cr to the total amount of Ni and Cr is preferably 7% by mass or more, and more preferably 20% by mass or more. Furthermore, the proportion of Cr to the total amount of Ni and Cr is preferably 35% by mass or less, and more preferably 30% by mass or less. When the proportion of Cr is within the above range, a strong and continuous Cr oxide film is easily formed on the release layer by opening it to the atmosphere after the release layer is formed. As a result, the release properties (release strength and release position) of the transfer laminate are stable.

[0019] The Ni and Cr alloy content in the release layer is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably 99% by mass or more. In this embodiment, the release layer may contain impurities that are unavoidably present.

[0020] The transfer laminate of this embodiment exhibits little change in peelability before and after heat loading, and good peelability after heat loading. This can be explained by measuring and comparing the minimum value of the copper element concentration in the release layer before and after heat treatment. Specifically, when the transfer laminate of this embodiment is subjected to heat treatment at 180°C for 2 hours, it is preferable that the minimum value of the copper element concentration (atomic %) measured by depth composition analysis by X-ray photoelectron spectroscopy in the thickness direction of the release layer satisfies the following formula (1): C2 - C1 ≤ 10.0 atomic % (1) (In formula (1), C1 is the minimum value of the copper element concentration (atomic %) in the transfer laminate before heat treatment, and C2 is the minimum value of the copper element concentration (atomic %) in the transfer laminate after heat treatment.)

[0021] The above formula (1) indicates that even when a heat treatment of 180°C for 2 hours is performed, the minimum value of the copper element concentration in the release layer does not change significantly before and after the heat treatment, and the difference is 10.0 atomic percent or less. In other words, in the transfer laminate of this embodiment, the release layer is sandwiched between a conductive layer containing Cu and a conductive auxiliary layer containing Cu. However, because the transfer laminate of this embodiment has a release layer made of an alloy of Ni and Cr, the diffusion of copper elements from the conductive layer and conductive auxiliary layer to the release layer is less likely to occur due to the heat treatment. As a result, the minimum value of the copper element concentration (atomic percent) in the release layer does not change significantly before and after the heat treatment, and the difference (C2-C1) may be 10.0 atomic percent or less. As a result, the adhesion between the conductive auxiliary layer and the release layer, and between the conductive layer and the release layer, is prevented from becoming too high due to the diffused copper elements. Therefore, the transfer laminate of this embodiment exhibits better release properties, the change in release properties before and after heat loading is small, and the release properties after heat loading are good.

[0022] In this embodiment, the minimum value of the copper element concentration can be confirmed by measuring and evaluating the elemental concentration of each element and the sputtering time (minutes) by depth composition analysis using X-ray photoelectron spectroscopy in the thickness direction of the peeled layer. Figure 1 is a graph showing the results of XPS depth composition analysis of the transfer laminate before heat treatment in Example 1, which will be described later. Figure 2 is a graph showing the results of XPS depth composition analysis of the transfer laminate after heat treatment in Example 1, which will be described later. Figure 3 is a graph showing the results of XPS depth composition analysis of the transfer laminate before heat treatment in Comparative Example 1, which will be described later. Figure 4 is a graph showing the results of XPS depth composition analysis of the transfer laminate after heat treatment in Comparative Example 1, which will be described later.

[0023] As shown in Figure 1, in the transfer laminate of Example 1 before heating, the minimum value of copper element concentration C1, shown by the solid line in the thickness direction of the release layer, was detected at approximately 10 minutes of sputtering time, and its value was 37.6 atomic%. On the other hand, as shown in Figure 2, in the transfer laminate of Example 1 after heating, the minimum value of copper element concentration C2, shown by the solid line in the thickness direction of the release layer, was detected at approximately 12 minutes of sputtering time, and its value was 40.5 atomic%. As a result, the difference (C2-C1) was 2.9 atomic%. Furthermore, as will be described later, the transfer laminate of Example 1 showed little change in release properties before and after heat loading, and good release properties after heat loading. On the other hand, as shown in Figure 3, in the transfer laminate of Comparative Example 1 before heating, the minimum value of copper element concentration C1, shown by the solid line in the thickness direction of the release layer, was detected at approximately 12 minutes of sputtering time, and its value was 57.5 atomic%. On the other hand, as shown in Figure 4, in the transfer laminate of Comparative Example 1 after heating, the minimum value of the copper element concentration C2, shown by the solid line in the thickness direction of the release layer, was detected at approximately 11 minutes of sputtering time, and its value was 74.0 atomic percent. As a result, the difference (C2 - C1) was 16.5 atomic percent. Furthermore, as will be described later, the transfer laminate of Comparative Example 1 showed increased adhesion between the release layer and the conductive auxiliary layer due to the application of heat load, resulting in poor release properties. Consequently, the transfer laminate of Comparative Example 1 showed a large change in release properties before and after heat load. Thus, the transfer laminate of this embodiment is also characterized by its focus on the change in the minimum value of the copper element concentration (atomic percent) before and after the heating process, and the discovery of a good correlation between this and release properties.

[0024] In this embodiment, the measurement of copper element concentration by XPS can be performed, for example, using an X-ray photoelectron spectroscopy analyzer (PHI5000 VersaProbe2, manufactured by ULVAC-PHI) under the following conditions.

[0025] (Measurement conditions for depth-direction composition analysis by X-ray photoelectron spectroscopy (XPS)) ・Sputtering conditions Ion species: Ar + Acceleration voltage: 3kV; Sputtering area: 2mm x 2mm; Interval: 0.5 min; Sputtering speed: 6.9nm / min (SiO2 equivalent)

[0026] The difference (C2-C1) is preferably 10.0 atomic% or less, more preferably 9.5 atomic% or less, and even more preferably 8.8 atomic% or less. When the difference (C2-C1) is within the above range, the transfer laminate exhibits little change in peelability before and after heat loading, and has good peelability after heat loading.

[0027] The thickness of the release layer is not particularly limited. For example, the thickness of the release layer is preferably 2 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. Furthermore, the thickness of the release layer is preferably 50 nm or less, and more preferably 30 nm or less. When the thickness of the release layer is within the above range, the transfer laminate exhibits excellent release properties.

[0028] The method for forming the release layer is not particularly limited. For example, the release layer can be formed on the conductive layer using a composition that constitutes the release layer by a dry coating method such as vacuum deposition, sputtering, or ion plating. Among these, the release layer is preferably formed by sputtering because it is easy to form a thin film, easy to control the alloy ratio in continuous processing, and easy to control the thickness.

[0029] (Release Aid Layer) In this embodiment, the transfer laminate may have a release aid layer formed on top of the release layer. The release aid layer is an adjustment layer for slightly adjusting the release force.

[0030] The raw materials constituting the peel-off auxiliary layer are not particularly limited. For example, the raw materials constituting the peel-off auxiliary layer may consist of one or more of the oxides of copper, aluminum, nickel, chromium, silicon, or titanium. Among these, copper oxide (CuOx) is preferred as the raw material constituting the peel-off auxiliary layer because it has good adhesion to the conductive auxiliary layer, which is Cu. In this embodiment, the peel-off auxiliary layer may contain impurities that are unavoidably present.

[0031] The thickness of the release aid layer is not particularly limited. For example, the thickness of the release aid layer is preferably 1 nm or more, and more preferably 2 nm or more. Furthermore, the thickness of the release aid layer is preferably 8 nm or less, and more preferably 5 nm or less. When the thickness of the release aid layer is within the above range, the transfer laminate is more likely to exhibit good release properties in the release process.

[0032] The method for forming the peel-off auxiliary layer is not particularly limited. For example, the peel-off auxiliary layer can be formed on the peel-off layer using a composition constituting the peel-off auxiliary layer by a dry coating method such as vacuum deposition, sputtering, or ion plating. Among these, the peel-off auxiliary layer is preferably formed by sputtering because it allows for easy formation of a thin film, easy control of the oxidation state of the oxide, and fine thickness adjustment.

[0033] (Conductive auxiliary layer) The conductive auxiliary layer is formed on the release layer (or the release auxiliary layer if one is formed). The conductive auxiliary layer contains Cu. The Cu content in the conductive auxiliary layer is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably 99% by mass or more. In this embodiment, the conductive auxiliary layer may contain impurities that are unavoidably present.

[0034] The transfer laminate of this embodiment has excellent conductivity due to the presence of a conductive auxiliary layer, and facilitates the formation of a copper layer by electroplating on the conductive auxiliary layer.

[0035] When a conductive layer, a release layer, (a release auxiliary layer if one is formed) and a conductive auxiliary layer are formed on the substrate, the surface resistance of the conductive auxiliary layer is preferably 2.0 Ω / □ or less, more preferably 1.0 Ω / □ or less, and even more preferably 0.5 Ω / □ or less. The surface resistance can be measured, for example, using a low-resistivity resistivity meter (Rolestar AX MCP-T370, manufactured by Mitsubishi Chemical Analytec Co., Ltd.) using a four-terminal four-probe method.

[0036] The thickness of the conductive auxiliary layer is not particularly limited. For example, the thickness of the conductive auxiliary layer is preferably 20 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. Further, the thickness of the conductive auxiliary layer is preferably 400 nm or less, and more preferably 200 nm or less. When the thickness of the conductive auxiliary layer falls within the above range, the transfer laminate exhibits excellent conductivity.

[0037] The method for forming the conductive auxiliary layer is not particularly limited. For example, the conductive auxiliary layer can be formed on a release layer (or a release auxiliary layer if a release auxiliary layer is provided) by dry coating methods such as vacuum deposition, sputtering, and ion plating using a composition constituting the conductive auxiliary layer. Among these, the conductive auxiliary layer is preferably formed by sputtering, because this method facilitates thin film formation and provides good adhesion between the conductive auxiliary layer and the release layer or release auxiliary layer.

[0038] Returning to the overall description of the transfer laminate, the transfer laminate of the present embodiment can be used when forming a circuit board by, for example, forming a copper plating layer on the conductive auxiliary layer through electrolytic copper plating.

[0039] More specifically, in the step of forming a circuit board using the transfer laminate of the present embodiment, a copper plating layer can be formed on the surface of the conductive auxiliary layer opposite to the surface on which the release layer is provided. After performing a heat treatment at 180°C for 2 hours and then peeling off the copper plating layer, peeling can occur at the interface between the conductive auxiliary layer and the release layer. The maximum Ni element concentration measured by depth-direction composition analysis via X-ray photoelectron spectroscopy in the thickness direction of the conductive auxiliary layer in the peeled surface surface layer region of the peeled conductive auxiliary layer can be 10.0 atomic% or less.

[0040] That is, after heat treatment, the transfer laminate of the present embodiment can be peeled cleanly at the interface between the conductive auxiliary layer and the release layer. As a result, Ni derived from the Ni-Cr alloy of the release layer is unlikely to be detected on the peeled surface on the conductive auxiliary layer side.

[0041] The maximum value of the Ni element concentration is preferably 10.0 atomic% or less, more preferably 5.0 atomic% or less, even more preferably 2.0 atomic% or less, and particularly preferably 1.5 atomic% or less. By having the maximum value of the Ni element concentration within the above range, the transfer laminate exhibits better peelability. That is, the Ni contained in the alloy contained in the peeling layer is a magnetic material, and when a high-frequency current is passed through a magnetic material, it generates a magnetic field, and this magnetic field is the cause of the skin effect. Here, the skin effect is a phenomenon in which, as the frequency of the current passed through a conductor increases, it becomes more difficult for the current to flow in the center of the conductor (preventing the current from flowing throughout the entire conductor), and the current flows only on the surface of the conductor. If the skin effect becomes large and the signal only flows near the surface of the conductor, it will affect the wiring resistance and transmission loss. For this reason, it is preferable that the peeling is clean at the interface between the peeling layer and the conductive auxiliary layer, and that there is little Ni element contained in the peeling layer on the peeled surface on the conductive auxiliary layer side (copper plating layer side).

[0042] In this embodiment, the measurement of the concentration of each element by XPS can be performed, for example, using an X-ray photoelectron spectroscopy analyzer (PHI5000 VersaProbe2, manufactured by ULVAC-PHI) under the following conditions.

[0043] (Measurement conditions for depth-direction composition analysis by X-ray photoelectron spectroscopy (XPS)) ・Sputtering conditions Ion species: Ar + Acceleration voltage: 1 kV Sputtering area: 2 mm x 2 mm Interval: 1 minute Sputtering speed: 1.6 nm / min (SiO2 equivalent) The elemental concentration analysis result of the unsputtered delamination surface is defined as cycle 0. Sputtering at a sputtering speed of 1.6 nm / min (SiO2 equivalent) for 1 minute followed by elemental concentration analysis is defined as one cycle, and this is repeated up to cycle 10. The depth sputtered from cycle 0 to cycle 10 is defined as the surface region of the delamination surface (16 nm in terms of SiO2 film thickness), and the maximum value of the elemental concentration (atomic %) of each element (Cu, Ni, Cr, O) in the surface region of the delamination surface is determined.

[0044] The transfer laminate of this embodiment can be peeled between the release layer and the conductive auxiliary layer. The peel strength between the release layer and the conductive auxiliary layer is preferably 5 N / m or more, and more preferably 10 N / m or more. Furthermore, the peel strength between the release layer and the conductive auxiliary layer is preferably 120 N / m or less, and more preferably 100 N / m or less. By having the peel strength within the above range, the transfer laminate can exhibit good peelability between the release layer and the conductive auxiliary layer. In this embodiment, the peel strength can be evaluated, for example, by preparing a sample in which a copper plating layer with a thickness of 5 μm is formed on the conductive auxiliary layer by electrolytic copper plating, and a polyester adhesive tape is attached to the copper plating layer, fixing the sample horizontally, and pulling the end of the attached polyester adhesive tape using an Autograph (AGS-100G, manufactured by Shimadzu Corporation) under the conditions of a tensile direction of 90° and a tensile speed of 300 mm / min.

[0045] <Method for Manufacturing a Transfer Laminate> The method for manufacturing the transfer laminate of one embodiment of the present invention is not particularly limited. For example, the method for manufacturing the transfer laminate of this embodiment includes a first step of preparing a substrate, a second step of forming a conductive layer on the substrate under a vacuum atmosphere, a third step of forming a release layer on the conductive layer under a vacuum atmosphere, a fourth step of exposing the release layer to the atmosphere under an atmospheric atmosphere, and a fifth step of forming a conductive auxiliary layer on the release layer under a vacuum atmosphere. The second and third steps are preferably carried out continuously under a vacuum atmosphere. The conductive layer contains Cu. The release layer contains an alloy of Ni and Cr. The conductive auxiliary layer contains Cu. The respective components will be described below.

[0046] (First Step) The first step is the step of preparing the substrate. The substrate is not particularly limited. For example, the substrate is the same as that described above in relation to the embodiment of the transfer laminate.

[0047] (Second and Third Steps) The second step is to form a conductive layer on the substrate under a vacuum atmosphere. The third step is to form a release layer on the conductive layer under a vacuum atmosphere.

[0048] The conductive layer contains Cu. The conductive layer is the same as that described above in relation to the embodiment of the transfer laminate.

[0049] The second step is performed under a vacuum atmosphere (for example, 1 to 10 -5 It will be implemented in Pa.

[0050] The release layer comprises an alloy of Ni and Cr. The release layer is the same as that described above in relation to embodiments of the transfer laminate.

[0051] The third step is performed under a vacuum atmosphere (for example, 1 to 10 -5 It will be implemented in Pa.

[0052] The second and third steps are preferably carried out by sputtering. This allows the manufacturing method of the transfer laminate according to this embodiment to efficiently form the conductive layer and the release layer, even when the substrate is a non-conductive resin substrate (such as polyimide or PET).

[0053] The sputtering conditions are not particularly limited. For example, in the second step, copper is used as the target for sputtering, and the pressure in the deposition chamber is adjusted to 1.0 Pa or less using argon gas, with a sputtering power density of approximately 5 W / cm². 2 This can be carried out under the following conditions. Furthermore, the sputtering conditions in the third step involve targeting an alloy of Ni and Cr, adjusting the pressure in the deposition chamber to 1.0 Pa or less using argon gas, and sputtering power density of approximately 5 W / cm². 2 This can be carried out by transporting the substrate into the film deposition chamber under these conditions. According to the above method, the composition of the deposited film can be in a ratio similar to that of the target material.

[0054] In the manufacturing method of the transfer laminate of this embodiment, it is preferable that the second and third steps are carried out continuously under a vacuum atmosphere. Specifically, the second and third steps can be carried out continuously, for example, by connecting the vacuum deposition chambers in which each process is performed with a vacuum transfer chamber. This suppresses the formation of a native oxide film on the surface of the conductive layer before the third step, resulting in good adhesion between the conductive layer and the release layer, and making it possible to obtain a transfer laminate with good release properties.

[0055] (Fourth Step) The fourth step is to expose the release layer to the atmosphere under an atmospheric environment. The method of exposing the release layer to the atmosphere is not particularly limited. For example, in the fourth step, after forming the release layer in the third step, the release layer can be exposed to the atmosphere by opening it to the atmosphere. The method for manufacturing the transfer laminate of this embodiment can expose the release layer to the atmosphere by such a simple method and oxidize the surface layer of the release layer. As a result, the method for manufacturing the transfer laminate of this embodiment can form an oxide film with high uniformity in the width direction while adjusting the amount of oxygen present on the surface layer of the release layer. As a result, the release force of the obtained transfer laminate can be appropriately adjusted.

[0056] The conditions for exposure to the atmosphere are not particularly limited. For example, the exposure time (oxidation environment exposure time) is preferably 1 second or more, more preferably 3 seconds or more, and even more preferably 6 seconds or more. Furthermore, the exposure time is preferably 60 seconds or less, and more preferably 30 seconds or less. By having the exposure time within the above range, the release layer can form an oxide film with higher uniformity in the width direction. As a result, the release force of the resulting transfer laminate can be adjusted more appropriately. Note that the oxidation environment exposure time refers to the time that the surface of the release layer is separated from the substrate (the surface on which the conductive layer is not formed) and exposed to the atmosphere in a long roll-shaped substrate. For example, when a long roll-shaped substrate is rewound in an atmospheric environment after the release layer has been formed, and the transport path from the unwinding side to the winding side of the rewinding machine is 10 m, and the rewinding speed is 10 m / min, the oxidation environment exposure time will be 60 seconds.

[0057] Furthermore, after the fourth step and before the conductive auxiliary layer is formed, a peel-off auxiliary layer may be provided as needed. The peel-off auxiliary layer is the same as that described above in relation to the embodiment of the transfer laminate.

[0058] The peeling aid layer can be provided, for example, by sputtering. The sputtering conditions can be appropriately selected from conventionally known conditions based on the desired thickness of the peeling aid layer.

[0059] (Fifth step) The fifth step is to form a conductive auxiliary layer on the peeling layer (or the peeling auxiliary layer if one has been formed) under a vacuum atmosphere.

[0060] The conductive auxiliary layer contains Cu. The conductive auxiliary layer is the same as that described above in relation to the embodiment of the transfer laminate.

[0061] The fifth step is performed under a vacuum atmosphere (for example, 1 to 10 -5 It will be implemented in Pa.

[0062] The fifth step is preferably carried out by sputtering. The sputtering conditions are not particularly limited. For example, in the sputtering of the fifth step, copper is used as the target, and the pressure in the deposition chamber is adjusted to 1.0 Pa or less using argon gas, with a sputtering power density of approximately 5 W / cm². 2 This can be carried out by transporting the substrate into the film deposition chamber under these conditions.

[0063] According to the above process, a transfer laminate having a substrate, a conductive layer, a release layer, and a conductive auxiliary layer in that order is produced. The obtained transfer laminate is used when forming a circuit board and exhibits superior release properties, with little change in release properties before and after heat loading, and good release properties after heat loading.

[0064] One embodiment of the present invention has been described above. The present invention is not particularly limited to the above embodiment. The above embodiment mainly describes an invention having the following configuration.

[0065] (1) A transfer laminate comprising a base material, a conductive layer, a release layer, and a conductive auxiliary layer in this order, wherein the conductive layer contains Cu, the release layer contains an alloy of Ni and Cr, and the conductive auxiliary layer contains Cu.

[0066] With this configuration, the transfer laminate exhibits minimal change in peelability before and after heat loading, and maintains good peelability after heat loading.

[0067] (2) The laminate for transfer according to (1), wherein when heat treatment is performed at 180° C. for 2 hours, the minimum value of copper element concentration (atomic %) measured by performing depth-direction composition analysis in the thickness direction of the release layer by X-ray photoelectron spectroscopy satisfies the following formula (1): C2−C1≦10.0 atomic % (1), wherein in formula (1), C1 is the minimum value of copper element concentration (atomic %) in the laminate for transfer before the heat treatment, and C2 is the minimum value of copper element concentration (atomic %) in the laminate for transfer after the heat treatment.

[0068] According to such a configuration, the laminate for transfer has a smaller change in releasability before and after thermal load, and has good releasability after thermal load.

[0069] (3) The laminate for transfer according to (1) or (2), wherein a copper plating layer is formed on a surface of the conductive auxiliary layer opposite to the surface on which the release layer is formed, after heat treatment at 180° C. for 2 hours is performed, when the copper plating layer is peeled off, peeling occurs at an interface between the conductive auxiliary layer and the release layer, and the maximum value of Ni element concentration measured by performing depth-direction composition analysis in the thickness direction of the conductive auxiliary layer by X-ray photoelectron spectroscopy on a peeled surface surface layer region of the peeled conductive auxiliary layer is 10.0 atomic % or less.

[0070] According to such a configuration, the laminate for transfer has a small change in releasability before and after thermal load, and has better releasability after thermal load.

[0071] Hereinafter, the present invention will be described more specifically by way of examples. The present invention is not limited to these examples in any way.

[0072] (Example 1) A long roll-shaped base material (a 25 μm-thick polyimide (PI) film (Kapton EN, manufactured by Du Pont-Toray Co., Ltd.)) was prepared (first step). The base material was conveyed in the longitudinal direction, a conductive layer was formed to a thickness of 120 nm on the base material by a sputtering method (second step), and a release layer was formed to a thickness of 10 nm on the conductive layer by a sputtering method (third step). The second step and the third step are performed under a vacuum atmosphere (ultimate pressure in the film forming chamber: 10 -3The process was carried out continuously at a pressure of 0.2 Pa. A Cu target material was used to form the conductive layer, and the deposition pressure with Ar gas introduced was 0.2 Pa. A Ni-Cr alloy target material (Ni: 80 mass%, Cr: 20 mass%) was used to form the release layer, and the deposition pressure with Ar gas introduced was 0.4 Pa. Subsequently, the long roll-shaped substrate with the release layer formed was transported in the longitudinal direction and rewound under an atmospheric environment, thereby exposing the release layer to the air (fourth step). The exposure time of the release layer to the air (oxidation environment exposure time) was 6 seconds. After exposure of the release layer to the air, a 50 nm conductive auxiliary layer was formed on the release layer by sputtering (fifth step) to create a transfer laminate. The fifth step was carried out under a vacuum atmosphere (deposition chamber pressure: 10 -3 The process was carried out at Pa. A Cu target material was used to form the conductive auxiliary layer, and the deposition pressure with Ar gas introduced was 0.2 Pa.

[0073] (Examples 2 and 4) Transfer laminates were prepared in the same manner as in Example 1, except that the thickness of the release layer was changed as shown in Tables 1 and 2.

[0074] (Example 3) A transfer laminate was prepared in the same manner as in Example 1, except that a release aid layer was formed on the release layer with the thicknesses described in Tables 1 and 2. The release aid layer was formed as follows: After the release layer was exposed to air, a release aid layer was formed on the release layer by sputtering to a thickness of 2.5 nm, and a conductive aid layer was formed on the release aid layer to a thickness of 50 nm. The release aid layer and the conductive aid layer were formed by sputtering under a vacuum atmosphere (maximum pressure in the deposition chamber: 10 -3 The film was formed continuously at a pressure of 0.2 Pa. A Cu target was used to form the peeling auxiliary layer, and the deposition pressure with Ar gas and O2 gas introduced was 0.2 Pa. The Ar gas and O2 gas were introduced in a ratio of 7:3 (flow rate).

[0075] (Example 5) A transfer laminate was prepared in the same manner as in Example 1, except that the target material for forming the release layer was changed to a Ni-Cr alloy (Ni: 93% by mass, Cr: 7% by mass).

[0076] (Example 6) A transfer laminate was prepared in the same manner as in Example 1, except that the base material was changed to copper foil 1 with a thickness of 12 μm (Fukuda Metal Foil & Powder Industry Co., Ltd., CF-T4X-SV-12), and the thickness of the release layer and the thickness of the conductive auxiliary layer were changed as shown in Tables 1 and 2.

[0077] (Example 7) A transfer laminate was prepared in the same manner as in Example 1, except that the substrate was changed to copper foil 2 (CF-SPS9-18, manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.) with a thickness of 18 μm, the thickness of the release layer was changed as shown in Tables 1 and 2, and a release auxiliary layer was formed on the release layer. The release auxiliary layer was formed as follows: After the release layer was exposed to the atmosphere, a release auxiliary layer was formed on the release layer by sputtering to a thickness of 2.5 nm, and a conductive auxiliary layer was formed on the release auxiliary layer to a thickness of 50 nm. The release auxiliary layer and the conductive auxiliary layer were formed by sputtering under a vacuum atmosphere (maximum pressure in the deposition chamber: 10 -3 The film was formed continuously at a pressure of 0.2 Pa. A Cu target material was used to form the peeling auxiliary layer, and the deposition pressure with Ar gas and O2 gas introduced was 0.2 Pa. The Ar gas and O2 gas were introduced in a ratio of 7:3 (flow rate).

[0078] (Example 8) A long roll-shaped substrate (25 μm thick polyimide (PI) film (manufactured by Toray DuPont, Kapton EN)) was prepared (Step 1). The substrate was transported in the longitudinal direction, and a conductive layer with a thickness of 120 nm was formed on the substrate by sputtering (Step 2), and a release layer with a thickness of 10 nm was formed on the conductive layer by sputtering (Step 3). Steps 2 and 3 were carried out under a vacuum atmosphere (maximum pressure in the deposition chamber: 10 -3The process was carried out continuously at a pressure of 0.2 Pa. A Cu target material was used to form the conductive layer, and the deposition pressure with Ar gas introduced was 0.2 Pa. A Ni-Cr alloy target material (Ni: 80 mass%, Cr: 20 mass%) was used to form the delamination layer, and the deposition pressure with Ar gas introduced was 0.5 Pa. Subsequently, the long roll-shaped substrate with the delamination layer formed was transported in the longitudinal direction and rewound under an atmospheric environment, thereby exposing the delamination layer to the atmosphere (fourth step). The exposure time of the delamination layer to the atmosphere (oxidation environment exposure time) was 6 seconds. After exposure of the delamination layer to the atmosphere, a 50 nm conductive auxiliary layer was formed on the delamination layer by sputtering (fifth step). The fifth step was carried out under a vacuum atmosphere (deposition chamber pressure: 10 -3 The procedure was carried out at a pressure of 0.2 Pa. A Cu target material was used to form the conductive auxiliary layer, and the film deposition pressure with Ar gas introduced was 0.2 Pa. Subsequently, a copper plating layer with a thickness of 5 μm was formed on the conductive auxiliary layer by electrolytic copper plating to create a transfer laminate.

[0079] (Example 9) A transfer laminate was prepared in the same manner as in Example 8, except that the base material was changed to copper foil 3 with a thickness of 18 μm (Fukuda Metal Foil & Powder Industry Co., Ltd., CF-T4X-SV-18) and the thickness of the release layer was changed as shown in Tables 3 and 4.

[0080] (Comparative Example 1) A transfer laminate was prepared in the same manner as in Example 1, except that a Ni-Cu alloy target material (Ni: 65% by mass, Cu: 35% by mass) was used to form the release layer.

[0081] (Comparative Example 2) A transfer laminate was prepared in the same manner as in Example 2, except that the base material was changed to a copper foil 2 with a thickness of 18 μm and no conductive layer was formed.

[0082] (Comparative Example 3) A transfer laminate was prepared in the same manner as in Example 2, except that a conductive layer was not formed.

[0083] For Examples 1 to 7 and Comparative Examples 1 to 3, the minimum value of copper element concentration (atomic %), peelability (peel strength (N / m) and peel position) in the XPS depth profile composition analysis of the peeled layer, and the peelability were measured and evaluated before and after heat treatment at 180°C for 2 hours, using the following evaluation method. The results are shown in Tables 1 and 2.

[0084] <Minimum copper concentration (atomic %) in XPS depth profiling analysis of the delamination layer> For each transfer laminate, an evaluation Ni alloy layer was formed on the conductive auxiliary layer under the following formation conditions. (Formation conditions for the Ni alloy layer) ・Formation method: Sputtering method ・Target material: Ni alloy target (Ni: 80 mass%, Cr: 20 mass%) ・Introduced gas: Ar gas ・Pressure during film formation: 0.4 Pa ・Thickness of the Ni alloy layer: 10 nm A pre-heating sample was prepared, in which no heating was performed after the formation of the Ni alloy layer, and a post-heating sample was prepared, in which the Ni alloy layer was heated at 180°C for 2 hours after formation. The minimum copper concentration (atomic %) of the delamination layer was measured by performing depth profiling analysis of the obtained samples from the Ni alloy layer side toward the substrate side using XPS. The measurement was performed using a multi-functional scanning X-ray photoelectron spectrometer (PHI5000 VersaProbe2, ULVAC-PHI) under the following conditions. (Conditions for depth profiling analysis by XPS) ・Sputtering conditions Ion species: Ar + Acceleration voltage: 3kV Sputtering area: 2mm x 2mm Interval: 0.5 min Sputtering speed: 6.9nm / min (in SiO2 equivalent) For Comparative Example 1, three elements Cu, Ni, and O were selected for analysis, while for the others, four elements Cu, Ni, Cr, and O were selected for analysis. In depth composition analysis by XPS, the delamination layer was defined as the region sandwiched between areas with a copper element concentration of 94 atomic% or less (see Figure 1). The minimum copper element concentration C1 of the delamination layer before heating and the minimum copper element concentration C2 of the delamination layer after heating were determined, and the difference (C2 - C1) was calculated.

[0085] <Removability> (Preparation of evaluation samples) Each transfer laminate was prepared in a 10 cm square, and a copper plating layer with a thickness of 5 μm was formed on the conductive auxiliary layer by electrolytic copper plating. Samples were prepared in three ways: a pre-heating sample (no heating after copper plating layer formation), a post-heating sample (heated at 180°C for 2 hours after copper plating layer formation), and a post-heating sample (heated at 180°C for 4 hours after copper plating layer formation). (Evaluation method) Polyester adhesive tape (manufactured by Nitto Denko Corporation, No. 31B, 15 mm wide) was attached to the copper plating layer. The obtained sample was fixed horizontally, and a peelability test was performed by pulling the end of the attached polyester adhesive tape using an Autograph (manufactured by Shimadzu Corporation, AGS-100G) under the conditions of a tensile direction of 90° and a tensile speed of 300 mm / min. The preferred peeling position is between the peeling layer and the conductive auxiliary layer, and it is preferable that the peeling layer does not adhere to the peeled surface on the copper plating layer side after peeling. The delamination locations were confirmed by visually inspecting the metallic color of the surface of each delamination and by performing a compositional analysis of the surface of each delamination using XPS.

[0086]

[0087]

[0088] As shown in Tables 1 and 2, the transfer laminate of the present invention exhibited good peelability, with delamination occurring between the release layer and the conductive auxiliary layer, minimal change in peelability before and after heat loading, and good peelability after heat loading.

[0089] Furthermore, regarding the minimum copper element concentration C1 of the release layer before heating, the minimum copper element concentration C2 of the release layer after heating, and the difference (C2-C1), as shown in Figure 1, in the transfer laminate of Example 1 before heating, the minimum copper element concentration C1, shown by the solid line, was detected at approximately 10 minutes of sputtering time, and its value was 37.6 atomic%. On the other hand, as shown in Figure 2, in the transfer laminate of Example 1 after heating, the minimum copper element concentration C2, shown by the solid line, was detected at approximately 12 minutes of sputtering time, and its value was 40.5 atomic%. As a result, the difference (C2-C1) was 2.9 atomic%. Thus, as described above, the transfer laminate of Example 1 showed better release properties, with a small change in release properties before and after heat loading, and good release properties after heat loading. On the other hand, as shown in Figure 3, in the transfer laminate of Comparative Example 1 before heating, the minimum value of copper element concentration C1, shown by the solid line, was detected at approximately 12 minutes of sputtering time, and its value was 57.5 atomic percent. On the other hand, as shown in Figure 4, in the transfer laminate of Comparative Example 1 after heating, the minimum value of copper element concentration C2, shown by the solid line, was detected at approximately 11 minutes of sputtering time, and its value was 74.0 atomic percent. As a result, the difference (C2 - C1) was 16.5 atomic percent. Furthermore, as described above, in the transfer laminate of Comparative Example 1, the adhesion between the release layer and the conductive auxiliary layer became stronger when a thermal load was applied, resulting in poorer release properties.

[0090] For Examples 8 and 9, the maximum values ​​(atomic percent) of elemental concentrations, peelability (peel strength (N / m) and peel location) in the surface region of the peeled surface were measured and evaluated after heating at 180°C for 2 hours using the following evaluation method. The results are shown in Tables 3 and 4.

[0091] <Maximum concentration of each element (atomic %) in the surface region of the peeled surface after peeling of the copper plating layer following heating at 180°C for 2 hours> For each transfer laminate, a post-heating sample was prepared after heat treatment at 180°C for 2 hours. The copper plating layer was peeled off using the same method as the evaluation method for the peelability test described above. After peeling, depth profiling analysis was performed on the peeled surface on the conductive auxiliary layer side (copper plating layer side) and the peeled surface on the peeled layer side (substrate side) by XPS. The measurements were performed using a multi-functional scanning X-ray photoelectron spectrometer (PHI5000 VersaProbe2, ULVAC-PHI) under the following conditions. (Conditions for depth profiling analysis by XPS) ・Sputtering conditions Ion species: Ar + Acceleration voltage: 1 kV Sputtering area: 2 mm x 2 mm Interval: 1 minute Sputtering speed: 1.6 nm / min (SiO2 equivalent) The elemental concentration analysis results of the unsputtered delamination surface were defined as cycle 0. One cycle consisted of sputtering at a sputtering speed of 1.6 nm / min (SiO2 equivalent) for 1 minute, followed by elemental concentration analysis. This was repeated up to cycle 10. The depth sputtered from cycle 0 to cycle 10 was defined as the surface region of the delamination surface (16 nm in terms of SiO2 film thickness), and the maximum value of the elemental concentration (atomic %) of each element (Cu, Ni, Cr, O) in the surface region of the delamination surface was determined.

[0092] <Removability> (Preparation of evaluation samples) Each transfer laminate was prepared in a 10 cm square. A pre-heating sample (without heating), a post-heating sample (heated at 180°C for 2 hours), and a post-heating sample (heated at 180°C for 4 hours) were prepared. (Evaluation method) Polyester adhesive tape (manufactured by Nitto Denko Corporation, No. 31B, 15 mm wide) was attached to the copper plating layer. The obtained sample was fixed horizontally, and a peelability test was performed by pulling the end of the attached polyester adhesive tape using an Autograph (manufactured by Shimadzu Corporation, AGS-100G) under the conditions of a tensile direction of 90° and a tensile speed of 300 mm / min. The preferred peeling position is between the peeling layer and the conductive auxiliary layer, and it is preferable that the peeling layer does not adhere to the peeled surface on the copper plating layer side after peeling. The peeling position was confirmed by visually checking the metallic color of the surface of each peeled surface and by compositional analysis of the surface of each peeled surface by XPS.

[0093]

[0094]

[0095] As shown in Tables 3 and 4, the transfer laminate of the present invention exhibited good peelability, with delamination occurring between the release layer and the conductive auxiliary layer, minimal change in peelability before and after heat loading, and good peelability after heat loading. Furthermore, the maximum value of Ni element concentration on the release surface on the conductive auxiliary layer side was smaller than the maximum value of Ni element concentration on the release surface on the release layer side.

Claims

1. A transfer laminate comprising a base material, a conductive layer, a release layer, and a conductive auxiliary layer in this order, wherein the conductive layer contains Cu, the release layer contains an alloy of Ni and Cr, and the conductive auxiliary layer contains Cu.

2. When heat treatment is performed at 180°C for 2 hours, the minimum value of the copper element concentration (atomic %) measured by depth direction composition analysis by X-ray photoelectron spectroscopy in the thickness direction of the peeled layer satisfies the following formula (1) for the transfer laminate according to claim 1: C2 - C1 ≤ 10.0 atomic % (1) (In formula (1), C1 is the minimum value of the copper element concentration (atomic %) in the transfer laminate before heat treatment, and C2 is the minimum value of the copper element concentration (atomic %) in the transfer laminate after heat treatment.) 3. The transfer laminate according to claim 1 or 2, wherein a copper plating layer is formed on the surface of the conductive auxiliary layer opposite to the surface on which the release layer is formed, and after heat treatment at 180°C for 2 hours, the copper plating layer is peeled off, causing peeling at the interface between the conductive auxiliary layer and the release layer, and the maximum value of the Ni element concentration measured by depth direction composition analysis in the thickness direction of the conductive auxiliary layer by X-ray photoelectron spectroscopy in the surface layer region of the peeled surface of the conductive auxiliary layer is 10.0 atomic% or less.

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