Metal-clad laminate and method for manufacturing the same

Abstract

The problem to be solved by the present invention is to provide a metal-clad laminate and a method for manufacturing the same, which can suppress the decrease in the bonding strength of the metal layer to the insulating layer having a thermosetting polyimide layer under long-term use with temperature changes. The metal-clad laminate (11) includes an insulating layer (12) and a metal layer (13) deposited on one or both sides of the insulating layer (12). The insulating layer (12) includes a thermosetting polyimide layer (21) and a heat-fused resin layer (31) disposed between the thermosetting polyimide layer (21) and the metal layer (13). The water absorption rate of the heat-fused resin layer (31) is lower than that of the thermosetting polyimide layer (21).

Description

[Technical Field]

[0001] This invention relates to a metal-clad laminate and its manufacturing method. [Previous Technology]

[0002] In recent years, with the application of the Internet of Things (IoT), there has been a trend of using electronic devices such as sensors in various environments. For example, the extremely high frequency (UHF) used in sensors, due to its high stability to light, weather, and environment, is assumed to be used in harsher environments in addition to its application in automotive UHF radar. Therefore, electronic devices are sometimes used in harsher environments, and there is a current pursuit to improve the environmental resistance of electronic devices. In this regard, the printed circuit boards equipped with electronic devices use, for example, the metal-clad laminate disclosed in Patent Document 1. The metal-clad laminate has a laminated structure, for example, a polyimide layer as an insulating layer and a copper layer as a metal layer. From the viewpoint of improving the environmental resistance of electronic devices, the environmental resistance currently sought in such metal-clad laminates lies in the bonding strength between the insulating layer and the metal layer.

[0003] Prior Art Documents Patent Document 1: Japanese Patent Application Publication No. 2016-187913 [Summary of the Invention]

[0004] The problem that the invention aims to solve is as described above. In metal-clad laminates, when a thermosetting polyimide layer is used as the insulating layer, although the dimensional stability of the metal-clad laminate can be easily ensured, there is a concern that the bonding between the thermosetting polyimide layer and the metal layer may decrease under long-term use with temperature changes.

[0005] Means for Solving the Problems One aspect of the present invention for solving the above-mentioned problems provides a metal-clad laminate comprising an insulating layer and a metal layer deposited on one or both sides of the insulating layer. The insulating layer comprises a thermosetting polyimide layer and a heat-fused resin layer disposed between the thermosetting polyimide layer and the metal layer, wherein the water absorption rate of the heat-fused resin layer is lower than the water absorption rate of the thermosetting polyimide layer.

[0006] Based on this configuration, it is conjectured that by suppressing the absorption or dehydration of water by the thermosetting resin layer bonded to the metal layer, the state change of the interface between the metal layer and the thermosetting resin layer can be suppressed. In this way, the decrease in the adhesion of the metal layer to the insulating layer with the thermosetting polyimide layer under long-term use accompanied by temperature changes can be suppressed.

[0007] In the above-described metal-clad laminate, it is preferable that the thermosetting resin layer has a water absorption rate of 0.1% or less. According to this configuration, it is possible to suppress the decrease in the adhesion of the metal layer to the insulating layer having a thermosetting polyimide layer under long-term use accompanied by temperature changes.

[0008] In the above-described metal-clad laminate, it is preferable that the hot-melt resin layer has a melting point of 280°C or higher. According to this configuration, the heat resistance of the solder in the metal-clad laminate can be easily improved.

[0009] In the above-described metal-clad laminate, it is preferable that the metal layer is composed of a metal foil whose ten-point average roughness (Rzjis) of the main surface bonded to the above-described hot-melt resin layer is 2.0 or less. According to this configuration, since the smoothness of the main surface of the metal foil is improved, the skin effect of high-frequency band current concentration on the surface of the metal layer can be suppressed, thus fully utilizing the electronic characteristics of the high-frequency band in the metal layer.

[0010] In the above-described metal-clad laminate, it is preferable that the coefficient of linear expansion of the thermosetting polyimide layer is in the range of 10 ppm / K or more and 26 ppm / K or less. According to this configuration, the dimensional stability of, for example, the metal-clad laminate can be improved.

[0011] In the above-mentioned metal-clad laminate, it is preferable that the hot-melt resin layer is composed of a fluorine-based resin. According to this configuration, since the permittivity of the insulating layer can be reduced, electronic characteristics, such as those in the high-frequency band, can be fully utilized.

[0012] In the above-mentioned metal-clad laminate, it is preferable that when the peel strength of the metal layer before the thermal cycling test is set to 100%, the peel strength of the metal layer after the thermal cycling test is 80% or more, and the conditions of the thermal cycling test are a temperature range of -50°C to 150°C, a holding time of 0 minutes, and 3000 cycles of heating and cooling.

[0013] Another aspect of the present invention provides a method for manufacturing a metal-clad laminate, which includes an insulating layer and a metal layer deposited on one or both sides of the insulating layer. The insulating layer includes a thermosetting polyimide layer and a heat-melting resin layer disposed between the thermosetting polyimide layer and the metal layer, wherein the water absorption rate of the heat-melting resin layer is lower than that of the thermosetting polyimide layer. Preferably, the method for manufacturing the metal-clad laminate includes the following step: hot-pressing a laminate in which a thermosetting polyimide film serving as the thermosetting polyimide layer and a thermoplastic resin film serving as the heat-melting resin layer are disposed between a metal foil serving as the metal layer.

[0014] Effects of the invention According to the present invention, it is possible to suppress the decrease in the bonding between the metal layer and the insulating layer having a thermosetting polyimide layer under long-term use accompanied by temperature changes.

Implementation Method

[0016] Hereinafter, an embodiment of a metal-clad laminate and its manufacturing method will be described. Note that the thickness of each layer constituting the metal-clad laminate may sometimes be exaggerated in the illustrations.

[0017] As shown in FIG1, the metal-clad laminate 11 includes an insulating layer 12 and a metal layer 13 deposited on the insulating layer 12. In this embodiment, the metal layer 13 is composed of a first metal layer 13a deposited on one side of the insulating layer 12 and a second metal layer 13b deposited on the other side of the insulating layer 12.

[0018] The insulating layer 12 comprises a thermosetting polyimide layer 21 and a thermosetting resin layer 31. The thermosetting resin layer 31 is composed of a first thermosetting resin layer 31a disposed between the thermosetting polyimide layer 21 and the first metal layer 13a, and a second thermosetting resin layer 31b disposed between the thermosetting polyimide layer 21 and the second metal layer 13b. Therefore, the metal-clad laminate 11 of this embodiment is a double-sided metal-clad laminate with a 5-layer structure, which has an insulating layer 12 with a 3-layer structure composed of a thermosetting polyimide layer 21, a first thermosetting resin layer 31a, and a second thermosetting resin layer 31b, and metal layers 13 are respectively deposited on both sides of the insulating layer 12.

[0019] <Thermosetting Polyimide Layer 21> Thermosetting polyimide layer 21 can be composed of a thermosetting polyimide film. The thermosetting polyimide film is obtained by combining an acid component and a diamine component. Examples of acid components include 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA), pyromellitic acid, etc. Examples of diamine components include p-phenylenediamine (PPD), 4,4-diaminodiphenyl ether, m-toluidine, 4,4'-diaminobenzylaniline, etc. Commercially available thermosetting polyimide films include, for example, UPILEX-S (trade name) and UPILEX-SGA (trade name) manufactured by Ube Industries, Ltd.

[0020] From the viewpoint of excellent low dielectric properties such as low permittivity and low dielectric tangent, the thermosetting polyimide layer 21 preferably contains 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and p-phenylenediamine as copolymerizing components. When the total acid content is set to 100 mol%, the content of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride in the thermosetting polyimide layer 21 is preferably 50 mol% or more, more preferably 70 mol% or more. When the total diamine content is set to 100 mol%, the content of p-phenylenediamine in the thermosetting polyimide layer 21 is preferably 50 mol% or more, more preferably 70 mol% or more. Among them, commercially available thermosetting polyimide films containing 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and p-phenylenediamine as copolymerizing components include, for example, UPILEX-SGA (trade name) manufactured by Ube Industries, Ltd.

[0021] In thermosetting polyimide films, from the viewpoint of improving the adhesion between the thermosetting polyimide layer 21 and the heat-fused resin layer 31, the main surface bonded to the heat-fused resin layer 31 is preferably subjected to a discharge treatment. Examples of discharge treatments include corona discharge treatment, atmospheric pressure plasma discharge treatment, and vacuum plasma discharge treatment. The discharge treatment preferably results in a water contact angle of 20° or less, more preferably 17° or less, and most preferably 14° or less on the main surface of the thermosetting polyimide film bonded to the heat-fused resin layer 31. From a production point of view, the water contact angle of the thermosetting polyimide film is preferably, for example, 5° or more, and more preferably 6° or more. The water contact angle can be measured using a droplet method with a contact angle meter.

[0022] The thickness of the thermosetting polyimide layer 21 is preferably, for example, 125 μm or less. The water absorption rate of the thermosetting polyimide layer 21 is preferably, for example, in the range of 1.0% or more and 2.0% or less.

[0023] <Thermofused Resin Layer 31> The water absorption rate of the thermofused resin layer 31 is lower than that of the thermosetting polyimide layer 21. The water absorption rate of the thermofused resin layer 31 is preferably 0.1% or less, more preferably 0.07% or less, and most preferably 0.05% or less.

[0024] From the viewpoint of easily improving the heat resistance of the solder, the heat-fusion resin layer 31 preferably has a melting point of, for example, 280°C or higher. From the viewpoint of ease of heat fusion, the melting point of the heat-fusion resin layer 31 is preferably 320°C or lower.

[0025] The thickness of the first hot-melt resin layer 31a and the thickness of the second hot-melt resin layer 31b are preferably 5 μm or more, more preferably 10 μm or more, and most preferably 12.5 μm or more. The thickness of the first hot-melt resin layer 31a and the thickness of the second hot-melt resin layer 31b are preferably 150 μm or less, more preferably 120 μm or less, and most preferably 100 μm or less. The thickness of the first hot-melt resin layer 31a and the thickness of the second hot-melt resin layer 31b may be the same or different. From the viewpoint of suppressing the twisting or warping of the metal-clad laminate 11, the difference between the thickness of the first hot-melt resin layer 31a and the thickness of the second hot-melt resin layer 31b is preferably 3 μm or less, more preferably 2 μm or less, and most preferably 1 μm or less.

[0026] The thickness of the insulating layer 12 in this embodiment is preferably 10 μm or more, more preferably 20 μm or more, and most preferably 25 μm or more. From the viewpoint of further improving flexibility, the thickness of the insulating layer 12 in this embodiment is preferably, for example, 400 μm or less, and more preferably 300 μm or less.

[0027] From the viewpoint of reducing capacitance, the heat-fused resin layer 31 is preferably made of, for example, a fluorinated resin. From the viewpoint of having good low dielectric properties or good bonding properties, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) are preferred among fluorinated resins.

[0028] <Metal Layer 13> Examples of metals used in metal layer 13 include gold, silver, copper, copper alloys, aluminum, and aluminum alloys. The first metal layer 13a and the second metal layer 13b may be made of the same metal or different metals. Metal layer 13 may be formed using, for example, copper foil. Examples of copper foil include electrolytic copper foil and rolled copper foil. The metal foil forming the first metal layer 13a and the metal foil forming the second metal layer 13b may be obtained by the same manufacturing method or by different manufacturing methods.

[0029] The thickness of the first metal layer 13a and the thickness of the second metal layer 13b are preferably in the range of 2 μm to 105 μm, and more preferably in the range of 2 μm to 35 μm. The thickness of the first metal layer 13a and the thickness of the second metal layer 13b may be the same or different.

[0030] Here, the coarser the surface roughness of the main surface of the metal foil bonded to the thermosetting resin layer 31, the higher the bonding strength between the metal layer 13 and the thermosetting resin layer 31 tends to be. On the other hand, if the main surface of the metal foil is relatively smooth, the skin effect of current concentration in the high-frequency band on the surface of the metal layer 13 can be suppressed, thereby fully utilizing the electronic characteristics of the high-frequency band. In recent years, with the increasing frequency of electronic devices such as 5G smartphones, the demand for printed circuit boards with lower transmission loss has gradually increased. Therefore, when the metal-clad laminate 11 is used as a printed circuit board corresponding to the high-frequency band, the metal layer 13 is preferably composed of a metal foil with a ten-point average roughness (Rzjis) of 2.0 or less on the main surface bonded to the thermosetting resin layer 31. The ten-point average roughness (Rzjis) is specified in JIS B0601 (2001). JIS B0601 corresponds to ISO 4287. The ten-point average roughness (Rzjis) of the main surface of the metal foil is preferably below 1.5, and most preferably below 1.0.

[0031] <Coefficient of Linear Expansion> By making the coefficient of linear expansion of the insulating layer 12 close to that of the metal layer 13, the dimensional stability of the metal-clad laminate 11 can be improved. For example, the coefficient of linear expansion of copper is 18 ppm / K. When the metal layer 13 is a copper layer, the coefficient of linear expansion of the insulating layer 12 is preferably in the range of, for example, 10 ppm / K or more and 40 ppm / K or less. The coefficient of linear expansion of the thermosetting polyimide layer 21 constituting the insulating layer 12 is preferably in the range of 10 ppm / K or more and 26 ppm / K or less. For example, even if the coefficient of linear expansion of the heat-fused resin layer 31 is greater than that of the thermosetting polyimide layer 21, by setting the coefficient of linear expansion of the thermosetting polyimide layer 21 within the above range, the dimensional stability of the metal-clad laminate 11 can be improved.

[0032] <Peel strength of metal layer> In the metal-clad laminate 11 of this embodiment, it is preferable that when the peel strength of the metal layer 13 before the following thermal cycling test is set to 100%, the peel strength of the metal layer 13 measured after the thermal cycling test is 80% or more.

[0033] (Conditions for thermal cycling test) Temperature range: -50℃~150℃ Holding time: 0 minutes Heating time: 2 hours Cooling time: 2 hours Number of heating and cooling cycles: 3000

[0034] <Manufacturing method of metal-clad laminate 11> Next, the manufacturing method of metal-clad laminate 11 will be described.

[0035] As shown in FIG. 2, the manufacturing method of the metal-clad laminate 11 includes the following steps: hot-pressing a laminate 111 in which a thermosetting polyimide film 121 and a metal foil 113 are disposed between them with a thermoplastic resin film 131. The thermosetting polyimide film 121 forms the aforementioned thermosetting polyimide layer 21. The first thermoplastic resin film 131a and the second thermoplastic resin film 131b respectively form a first hot-melt resin layer 31a and a second hot-melt resin layer 31b. The first metal foil 113a and the second metal foil 113b respectively form a first metal layer 13a and a second metal layer 13b.

[0036] In the step of hot-pressing the laminate 111, the laminate 111 is heated so that the thermoplastic resin film 131 reaches a temperature above its melting point. When the melting point of the thermoplastic resin film 131 is set to Tm℃, the highest temperature in the step of hot-pressing the laminate 111 is preferably below Tm+70℃.

[0037] The pressure in the step of hot pressing the laminate 111 is preferably in the range of, for example, 0.5 N / mm2 to 10 N / mm2, and more preferably in the range of 2 N / mm2 to 6 N / mm2.

[0038] The heating time in the step of hot pressing the laminate 111 is preferably in the range of, for example, 10 seconds to 600 seconds, and more preferably in the range of 30 seconds to 500 seconds.

[0039] In the step of hot-pressing the laminate 111, it is preferable to use a dual-pressure device 51. The dual-pressure device 51 heats and pressurizes the laminate 111 while transporting it. The dual-pressure device 51 has a first transport section 52 located on the upstream side in the transport direction of the laminate 111 and a second transport section 53 located on the downstream side.

[0040] The first conveying unit 52 is equipped with an upper first roller 52a and a lower first roller 52b. The second conveying unit 53 is equipped with an upper second roller 53a and a lower second roller 53b. An endless upper belt 54 is mounted on the upper first roller 52a and the upper second roller 53a. An endless lower belt 55 is mounted on the lower first roller 52b and the lower second roller 53b. Furthermore, each first roller 52a, 52b is configured to be driven by each second roller 53a, 53b and driven by each belt 54, 55. Each belt 54, 55 is formed of a metal such as stainless steel.

[0041] An upper temperature regulating device 56 and a lower temperature regulating device 57 are disposed between the first transport section 52 and the second transport section 53, sandwiched between the belts 54 and 55 and facing each other. The upper temperature regulating device 56 and the lower temperature regulating device 57 heat and pressurize the laminate 111 through the upper belt 54 and the lower belt 55. The upper temperature regulating device 56 and the lower temperature regulating device 57 heat and pressurize the upper belt 54 and the lower belt 55 through a heat medium such as oil.

[0042] The metal-clad laminate 11 can be continuously obtained by using the dual-pressure device 51. The long strip of metal-clad laminate 11 is wound up as a cylindrical object for storage or transportation. The metal-clad laminate 11 can be used for printed circuit boards, such as flexible printed circuit boards.

[0043] Next, the function and effect of this embodiment will be explained.

[0044] (1) The insulating layer 12 of the metal-clad laminate 11 has a thermosetting polyimide layer 21 and a heat-fused resin layer 31 disposed between the thermosetting polyimide layer 21 and the metal layer 13. The water absorption rate of the heat-fused resin layer 31 is lower than that of the thermosetting polyimide layer 21.

[0045] Based on this configuration, it is speculated that by suppressing the absorption or dehydration of water by the thermosetting resin layer 31 bonded to the metal layer 13, the state change of the interface between the metal layer 13 and the thermosetting resin layer 31 can be suppressed. In this way, the decrease in the adhesion of the metal layer 13 to the insulating layer 12 having the thermosetting polyimide layer 21 under long-term use with temperature changes can be suppressed. Furthermore, since the insulating layer 12 has the thermosetting polyimide layer 21, the dimensional stability of the metal-clad laminate 11 can also be easily ensured.

[0046] (2) The heat-fusion resin layer 31 preferably has a water absorption rate of less than 0.1%. In this case, the decrease in the adhesion of the metal layer 13 to the insulating layer 12 with the thermosetting polyimide layer 21 under long-term use with temperature changes can be suppressed.

[0047] (3) The hot-melt resin layer 31 preferably has a melting point of 280°C or higher. In this case, the heat resistance of the solder of the metal-clad laminate 11 can be easily improved.

[0048] (4) The metal layer 13 is preferably composed of a metal foil whose ten-point average roughness (Rzjis) of the main surface bonded to the hot-melt resin layer 31 is 2.0 or less. In this case, the skin effect of high-frequency band current concentration on the surface of the metal layer 13 can be suppressed by improving the smoothness of the main surface of the metal foil, so that the electronic characteristics of the high-frequency band in the metal layer 13 can be fully utilized.

[0049] (5) The coefficient of linear expansion of the thermosetting polyimide layer 21 is preferably in the range of 10 ppm / K or higher and 26 ppm / K or lower. In this case, the dimensional stability of the metal-clad laminate 11 can be improved.

[0050] (6) The heat-fused resin layer 31 is preferably made of a fluorine-based resin. In this case, since the permittivity of the insulating layer 12 can be reduced, the electronic characteristics, such as those in the high-frequency band, can be fully utilized.

[0051] (7) When the peel strength of the metal layer 13 before the thermal cycling test is set to 100%, the peel strength of the metal layer 13 after the thermal cycling test is preferably 80% or more. Therefore, a metal-clad laminate 11 in which the decrease in the adhesion of the metal layer 13 to the heat-fused resin layer 31 is suppressed can be provided.

[0052] (8) A method for manufacturing a metal-clad laminate 11 includes the following steps: hot-pressing a laminate 111, in which a thermosetting polyimide film 121 serving as a thermosetting polyimide layer 21 and a metal foil 113 serving as a metal layer 13 are disposed between them, with a thermoplastic resin film 131 serving as a hot-melt resin layer 31 disposed between them. At this time, the metal-clad laminate 11 can be manufactured efficiently. Furthermore, in the step of hot-pressing the laminate 111, since the metal-clad laminate 11 can be manufactured continuously by using a dual-pressure device 51, the manufacturing efficiency of the metal-clad laminate 11 can be easily improved.

[0053] (Modification Example) The above embodiments can also be modified in the following ways. The above embodiments and the following modifications can be combined and implemented with each other within the scope of technical non-contradiction.

[0054] The metal-clad laminate 11 can also be manufactured using a lamination device other than the dual-pressure device 51. In addition, the above embodiment continuously manufactures the long strip-shaped metal-clad laminate 11, but metal-clad laminates of a predetermined size can also be manufactured piece by piece.

[0055] ・The above embodiment manufactures the metal-clad laminate 11 by a one-stage hot pressing process, but it can also be manufactured by a multi-stage hot pressing process. For example, the metal-clad laminate 11 can be manufactured by a step of hot pressing a thermosetting polyimide film 121 and a thermoplastic resin film 131 to obtain a laminated film, and a step of hot pressing the laminated film to a metal foil 113.

[0056] ・In the above-described metal-clad laminate 11, the laminate structure consisting of the first thermosetting resin layer 31a and the first metal layer 13a, and the laminate structure consisting of the second thermosetting resin layer 31b and the second metal layer 13b, may be omitted. That is, the metal-clad laminate may also be a single-sided metal-clad laminate, that is, an insulating layer having a two-layer structure of a thermosetting polyimide layer and a thermosetting resin layer, and having a metal layer deposited on one side of the insulating layer. When it is a single-sided metal-clad laminate, the thickness of the insulating layer is preferably 5 μm or more, more preferably 10 μm or more, and most preferably 12.5 μm or more. When it is a single-sided metal-clad laminate, from the viewpoint of further improving flexibility, the thickness of the insulating layer is preferably, for example, 200 μm or less, and more preferably 150 μm or less.

[0057] Example

[0058] Next, the embodiments and comparative examples will be described.

[0059] (Example 1) Example 1 describes a metal-clad laminate with a metal layer on a double-sided insulating layer. The thermosetting polyimide layer of the insulating layer is formed by corona discharge treatment of both sides of a thermosetting polyimide film (manufactured by Ube Industries, Ltd., trade name: UPILEX-SGA) at a discharge rate of 155 W·min / m2. The first and second thermosetting resin layers of the insulating layer are both formed using a fluorinated resin film (manufactured by AGC Corporation, trade name: EA-2000, melting point: 298°C). The metal layer is formed using copper foil (manufactured by Mitsui Mining & Metals Corporation, trade name: TQ-M4-VSP). The hot-pressing process of the film and copper foil is performed using a double-pressure device. The physical properties of each layer and the hot-pressing conditions are shown in Table 1.

[0060] The water absorption rates of the thermosetting polyimide layer and the hot-melt resin layer shown in Table 1 are values ​​obtained from the determination of the rate of weight change of the film forming each layer after immersion in water at 23°C for 24 hours, in accordance with JIS K7209:2000 (ASTM D570). JIS K7209:2000 corresponds to ISO 62:1999.

[0061] (Example 2) Example 2 is a metal-clad laminate with a metal layer on a double-sided insulating layer manufactured in the same manner as in Example 1. The thermosetting polyimide layer of Example 2 is formed by vacuum plasma discharge treatment on both sides of a thermosetting polyimide film (manufactured by Ube Industries, Inc., trade name: UPILEX-S) different from that of Example 1, under a discharge rate of 520 W·min / m2. The first and second thermosetting resin layers of Example 2 are formed using a fluorinated resin film (manufactured by AGC Corporation, trade name: EA-2000, melting point: 298°C) with a thickness different from that of Example 1. The metal layer of Example 2 is formed using the same copper foil as in Example 1. The hot-pressing step of the film and copper foil is performed using the same double-pressure device as in Example 1. The physical properties of each layer and the hot-pressing conditions are shown in Table 1.

[0062] (Example 3) Example 3 is a metal-clad laminate with a metal layer on a double-sided insulating layer manufactured in the same manner as in Example 1. The thermosetting polyimide layer of Example 3 is formed by vacuum plasma discharge treatment on both sides of a thermosetting polyimide film (manufactured by Ube Industries, Inc., trade name: UPILEX-S) different from that of Example 1, under a discharge rate of 520 W·min / m2. The first and second thermosetting resin layers of Example 3 are formed using a fluorinated resin film (manufactured by AGC Corporation, trade name: EA-2000, melting point: 298°C) with a thickness different from that of Example 1. The metal layer in Example 3 is formed using a copper foil with a different ten-point average roughness (Rzjis) than that of the copper foil in Example 1. The hot-pressing step of the film and copper foil is performed using the same double-pressure device as in Example 1. The physical properties of each layer and the hot-pressing conditions are shown in Table 1.

[0063] (Comparative Example 1) In Comparative Example 1, the heat-fusion resin layer is omitted, and a metal-clad laminate with a metal layer is manufactured on a double-sided surface layer of thermosetting polyimide. The thermosetting polyimide layer of Comparative Example 1 is formed using a thermosetting polyimide film (manufactured by Ube Industries, Ltd., trade name: UPILEX-VT) with a different water absorption rate than the thermosetting polyimide film of Example 1. The metal layer of Comparative Example 1 is formed using the same copper foil as in Example 1. The step of heat-pressing the film and copper foil is performed using the same double-pressure device as in Example 1. The physical properties of each layer and the heat-pressing conditions are shown in Table 1.

[0064] (Comparative Example 2) In Comparative Example 2, the thermosetting polyimide film is omitted, and a metal-clad laminate with a metal layer is manufactured on the double-sided surface layer of the heat-fusion resin layer. The heat-fusion resin layer of Comparative Example 2 is formed using a fluorinated resin film (manufactured by AGC Corporation, trade name: EA-2000, melting point: 298°C) with a different thickness than the fluorinated resin film of Example 1. The metal layer of Comparative Example 2 is formed using the same copper foil as in Example 1. The heat-bonding step of the film and copper foil is performed using the same double-pressure device as in Example 1. The physical properties of each layer and the heat-bonding conditions are shown in Table 1.

[0065] <Peel Strength> The metal-clad laminates prepared in each example were cut into 3mm wide samples and the peel strength of the metal layer was determined using "Method A" (90° direction peeling method) specified in JIS C6471. JIS C6471-1995 corresponds to IEC249-1 (1982). A peel strength of 0.6 N / mm or higher was considered good (○), and a peel strength of less than 0.6 N / mm was considered poor (×). The results are shown in the "Peel Strength of Metal Layer (Initial)" column of Table 1.

[0066] In addition, the metal-clad laminates prepared in each example were cut into samples with a width of 3 mm, and then the samples were subjected to thermal cycling tests under the above conditions.

[0067] The peel strength of the specimen after the thermal cycling test was measured, and the peel strength retention rate when the initial peel strength was set to 100% was calculated. A peel strength retention rate of 80% or more was judged as good (○), and a peel strength retention rate of less than 80% was judged as poor (×). The results are shown in the "Peel Strength of Metal Layer (After Thermal Cycling Test)" column of Table 1.

[0068] <Dimensional Change Rate> Prepare the test specimens by dividing each example of the metal-clad laminate into three segments: the center segment and the two ends segment in the width direction. Cut each segment to dimensions of MD (machine direction): 200 mm and TD (transverse direction): 160 mm. Use an electric drill or punch press to create multiple 1 mm φ holes (markings) at equal intervals on each test specimen. A total of 16 markings are made, with a distance of MD5 points and TD5 points between the markings.

[0069] According to JIS C6471, the distances between 5 punctuation points in the MD direction and 5 punctuation points in the TD direction are measured to determine the dimensional change rate.

[0070] The dimensional change rate was measured after etching the metal layer, after heat treatment at 150°C, and after heat treatment at 250°C, and was determined by the following criteria.

[0071] The dimensional change rate after etching is judged as good (○) if it is within ±0.10%, and as bad (×) if it is outside the range of ±0.10%. The results are shown in the "Dimensional Change Rate (After Etching)" column in Table 1.

[0072] The dimensional change rate after heating at 150°C is judged as good (○) if it is within ±0.10%, and as bad (×) if it is outside the range of ±0.10%. The results are shown in the "Dimensional Change Rate (after heating at 150°C)" column in Table 1.

[0073] The dimensional change rate after heating at 250°C is judged as good (○) if it is within ±0.15%, and as bad (×) if it is outside the range of ±0.15%. The results are shown in the "Dimensional Change Rate (after heating at 250°C)" column in Table 1.

[0074] <Solder Heat Resistance Test> For each example of metal-clad laminate, two samples at different positions in the TD direction were prepared, and the solder heat resistance test was performed according to JIS C6471. Specifically, each sample was first dried at 105°C for at least 60 minutes, and then directly immersed in a solder bath at 300°C for 60 seconds. Next, the samples were placed in standard condition for 1 hour, and then both sides of the samples were observed to check for abnormalities such as foaming and discoloration. Samples without abnormalities were judged as good (○), and samples with abnormalities were judged as poor (×). The results are shown in the "Solder Heat Resistance Test" column of Table 1.

[0075] <High-frequency transmission characteristics> Samples were prepared by etching the metal layers in the metal-clad laminates of each example to form microstrip lines with a circuit length of 100 mm and an impedance of 50 Ω. The insertion loss (S21) at 40 GHz was measured for this sample using a network analyzer (manufactured by Keysight Technologies, trade name: E8363B).

[0076] When the absolute value of the insertion loss (S21) is less than 0.4 dB / cm, it is judged as having good high-frequency transmission characteristics (○); when it is above 0.4 dB / cm but less than 0.5 dB / cm, it is judged as having slightly poor high-frequency transmission characteristics (△); and when it is above 0.5 dB / cm, it is judged as having poor high-frequency transmission characteristics (×). The results are shown in the "High-Frequency Transmission Characteristics" column of Table 1.

[0077] Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Insulation layer Thermosetting polyimide layer Thickness [μm] 25 50 25 25 - Water absorption rate [%) 1.2 1.4 1.4 1.1 - Coefficient of linear expansion [ppm / K] 13 16 16 20 - Hot melt resin layer Thickness [μm] 12.5 25 25 - 25 Water absorption rate [%) 0.01 0.01 0.01 - 0.01 Metal layer Thickness [μm] 12 12 12 12 12 Rzjis[μm] 0.5 0.5 2.5 0.5 0.5 Conditions for hot pressing Maximum temperature [°C] 360 330 330 330 330 Pressure [N / mm] 2 ] 4.0 4.0 4.0 4.0 4.0 Heating time (seconds) 175 140 140 140 140 Peel strength of the metal layer (initial stage) ○ ○ ○ ○ Unable evaluate Peel strength of the metal layer (after thermal cycling test) ○ ○ ○ × Dimensional change rate (after etching) ○ ○ ○ ○ Dimensional change rate (after heating at 150℃) ○ ○ ○ ○ Dimensional change rate (after heating at 250℃) ○ ○ ○ ○ Solder heat resistance test ○ ○ ○ ○ High-frequency transmission characteristics ○ ○ × ×

[0078] As shown in Table 1, the peel strength of the metal layer after the thermal cycling test in Examples 1-3 obtained good evaluation results. In addition, the dimensional change rate in Examples 1-3 also obtained good evaluation results.

[0079] In Examples 1 and 2, since a metal foil with a smooth main surface is used to form the metal layer, good evaluation results were obtained regarding the high-frequency transmission characteristics.

[0080] On the other hand, as shown in Comparative Example 1, when the heat-fusion resin layer is omitted, a good evaluation result cannot be obtained regarding the peel strength after the thermal cycling test. Furthermore, as shown in Comparative Example 2, when the thermosetting polyimide layer is omitted, the resulting metal-clad laminate exhibits large warping, making it impossible to evaluate the peel strength, etc. [Simplified Explanation of the Diagram]

[0015] FIG1 is a cross-sectional view showing the metal-clad laminate of this embodiment. FIG2 is a schematic diagram illustrating the manufacturing method of the metal-clad laminate.

Claims

1. A method for manufacturing a metal-clad laminate, comprising manufacturing a metal-clad laminate having an insulating layer and a metal layer deposited on one or both sides of the insulating layer, wherein the insulating layer has a thermosetting polyimide layer and a hot-melt resin layer disposed between the thermosetting polyimide layer and the metal layer, the water absorption rate of the hot-melt resin layer being lower than the water absorption rate of the thermosetting polyimide layer, the method for manufacturing the metal-clad laminate comprising a preparation step, a step of forming a processed surface, and a step of hot-pressing: the preparation step: preparing a thermosetting polyimide film as the thermosetting polyimide layer, a metal foil as the metal layer, and a hot-melt resin as the hot-melt resin. The step of forming a treated surface of a thermoplastic resin film: Among the main surface of the prepared thermosetting polyimide film and the main surface of the thermoplastic resin film, only the main surface of the thermosetting polyimide film is subjected to discharge treatment to reduce the water contact angle to form a treated surface, while the main surface of the thermoplastic resin film is not subjected to treatment to reduce the water contact angle. The step of hot pressing: The main surface of the thermoplastic resin film and the treated surface of the thermosetting polyimide film are overlapped and the thermoplastic resin film is placed between the thermosetting polyimide film with the treated surface formed and the metal foil to obtain a laminate, and the laminate is hot pressed.

2. The method for manufacturing a metal-clad laminate as claimed in claim 1, wherein the aforementioned hot-melt resin layer has a water absorption rate of 0.1% or less.

3. A method for manufacturing a metal-clad laminate as described in claim 1 or claim 2, wherein the aforementioned hot-melt resin layer has a melting point of 280°C or higher.

4. A method for manufacturing a metal-clad laminate as described in claim 1 or claim 2, wherein the metal foil is composed of a metal foil whose ten-point average roughness (Rzjis) of the main surface bonded to the hot-melt resin layer is 2.0 or less.

5. A method for manufacturing a metal-clad laminate as described in claim 1 or claim 2, wherein the coefficient of linear expansion of the thermosetting polyimide layer is in the range of 10 ppm / K or more and 26 ppm / K or less.

6. A method for manufacturing a metal-clad laminate as described in claim 1 or claim 2, wherein the aforementioned hot-melt resin layer is composed of a fluorinated resin.

7. A method for manufacturing a metal-clad laminate as described in claim 1 or claim 2, wherein when the peel strength of the metal layer before the thermal cycling test is set to 100%, the peel strength of the metal layer after the thermal cycling test is 80% or more, and the conditions of the thermal cycling test are a temperature range of -50°C to 150°C, a holding time of 0 minutes, and 3000 cycles of heating and cooling.

8. A method for manufacturing a metal-clad laminate as claimed in claim 1 or claim 2, wherein the discharge treatment is selected from at least one of corona discharge treatment, atmospheric pressure plasma discharge treatment, and vacuum plasma discharge treatment.

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