Metal-clad laminate, method for producing metal-clad laminate, and voltage withstand test method

Abstract

The present disclosure addresses the problem of providing a metal-clad laminate for which the presence or absence of foreign matter in an insulating layer is accurately inspected. A metal-clad laminate (100) comprises: an insulating layer (1) having a first main surface (11), a second main surface (12), and side surfaces (13); a first metal layer (21) overlapping the first main surface (11); and a second metal layer (22) overlapping the second main surface (12). The shortest distance (H) on a surface of one of the side surfaces (13) between a first end (131) of the side surface (13) in contact with the first main surface (11) and a second end (132) of the side surface (13) in contact with the second main surface (12) is greater than the thickness of the insulating layer (1). The insulating layer (1) has a thickness of 10-300 μm.

Description

Metal-clad laminate, method for producing metal-clad laminate, and withstand voltage test method

[0001] The present disclosure generally relates to a metal-clad laminate, a method for producing a metal-clad laminate, and a withstand voltage test method, and more particularly, to a metal-clad laminate including an insulating layer, a method for producing the metal-clad laminate, and a withstand voltage test method.

[0002] Patent Document 1 discloses a printed circuit board cutting method, which is characterized in that: a stacked printed circuit board (40) formed by stacking a plurality of printed circuit boards is placed on a table (11), the stacked printed circuit board (40) is fixed to the table (11) by a clamp device (12), the cutting position of a rotary saw (25) is set to a middle position of the stacking thickness of the stacked printed circuit board (40), in this state, the rotary saw is relatively moved from one side to the other side of the stacked printed circuit board (40), then the cutting position of the rotary saw (25) is set to a position penetrating the stacking thickness of the stacked printed circuit board (40), in this state, while rotating the rotary saw (25) in the same direction, the rotary saw is relatively moved from the other side to the one side of the stacked printed circuit board (40) to cut the stacked printed circuit board (40).

[0003] Whether there is any foreign matter on a printed circuit board is sometimes checked by applying a voltage to the printed circuit board. For example, if there is no foreign matter on the printed circuit board, no conduction will occur between the printed circuit boards even when a voltage is applied to the printed circuit boards. However, when a high voltage is applied to the printed circuit board, conduction may occur even if there is no foreign matter on the printed circuit board. That is, there has been a problem that it is difficult to accurately inspect the presence or absence of foreign matter contained in the insulating layer of the metal-clad laminate.

[0004] Japanese Patent Application Laid-Open No. 2004-209584

[0005] An object of the present disclosure is to provide a metal-clad laminate, a method for producing the metal-clad laminate, and a withstand voltage test method that enable accurate inspection of the presence or absence of foreign matter contained in an insulating layer.

[0006] A metal-clad laminate according to one aspect of the present disclosure comprises an insulating layer having a first main surface, a second main surface opposite to the first main surface, and a side surface connecting the first main surface and the second main surface; a first metal layer overlapping the first main surface; and a second metal layer overlapping the second main surface. The shortest distance on the surface of the side surface from a first end of the side surface in contact with the first main surface to a second end of the side surface in contact with the second main surface is greater than the thickness of the insulating layer. The thickness of the insulating layer is 10 μm or more and 300 μm or less.

[0007] A method for manufacturing a metal-clad laminate according to one aspect of the present disclosure includes a preparation step of preparing a laminate comprising an insulating layer having a main surface and a metal layer overlapping the main surface, and a cutting step of cutting the laminate with a cutting tool. The angle between the direction perpendicular to the main surface of the insulating layer and the cutting tool is 1° or more and 60° or less.

[0008] A dielectric strength test method according to one aspect of the present disclosure is a dielectric strength test method performed on a metal-clad laminate, comprising an insulating layer having a first main surface, a second main surface opposite to the first main surface, and a side surface connecting the first main surface and the second main surface, a first metal layer overlapping the first main surface, and a second metal layer overlapping the second main surface, wherein the distance from a first end of the side surface in contact with the first main surface to a second end of the side surface in contact with the second main surface is greater than the thickness of the insulating layer, wherein one of the first metal layer and the second metal layer is brought into contact with a + terminal of a power supply unit, and the other is brought into contact with a - terminal of the power supply unit, and a voltage is applied between the first metal layer and the second metal layer.

[0009] Figure 1 is a schematic cross-sectional view showing a metal-clad laminate according to an embodiment of the present disclosure. Figure 2 is a schematic diagram showing a preparation step included in the manufacturing method of a metal-clad laminate according to an embodiment of the present disclosure. Figure 3 is a schematic diagram showing a cutting step included in the manufacturing method of a metal-clad laminate according to an embodiment of the present disclosure. Figure 4 is a schematic cross-sectional view showing a dielectric strength test of a metal-clad laminate according to a modified example of the present disclosure. Figure 5 is a schematic cross-sectional view showing a metal-clad laminate according to a modified example of the present disclosure and the cutting tool used when manufacturing the metal-clad laminate. Figure 6 is a schematic cross-sectional view showing a metal-clad laminate according to a modified example of the present disclosure and the cutting tool used when manufacturing the metal-clad laminate. Figure 7 is a schematic cross-sectional view showing a metal-clad laminate according to a modified example of the present disclosure and the cutting tool used when manufacturing the metal-clad laminate. Figure 8 is a schematic cross-sectional view showing a metal-clad laminate according to a modified example of the present disclosure and the cutting tool used when manufacturing the metal-clad laminate. Figure 9 is a schematic cross-sectional view showing a laminate according to a modified example of the present disclosure.

[0010] Embodiments of this disclosure will now be described. Note that the embodiments described below are only a selection of the various embodiments of this disclosure. Furthermore, the embodiments described below can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. The figures referenced below are schematic diagrams, and the dimensional ratios of the components in the figures do not necessarily reflect the actual dimensional ratios. The mechanisms of operation in the embodiments may be described below, but these descriptions include explanations based on speculation, and this disclosure is not bound by the explanations of the mechanisms of operation. Also, in this disclosure, a plan view means viewing the metal-clad laminate 100 or laminate 10 along the direction in which the first main surface 11 and the second main surface 12 face each other.

[0011] 1. Overview: This section explains the circumstances leading to this disclosure.

[0012] In a metal-clad laminate comprising two metal layers and an insulating layer interposed between them, it is sometimes possible to inspect whether the insulating layer contains foreign matter (e.g., metal fragments such as iron or nickel) by applying a voltage between the two metal layers. For example, if there is no foreign matter in the insulating layer, even if a voltage is applied between the two metal layers, no conductivity will occur between them because the insulating layer is interposed. In this case, the inspection result is judged to be good. On the other hand, if there is foreign matter in the insulating layer, when a voltage is applied between the two metal layers, conductivity occurs between the two metal layers through the insulating layer, resulting in what is known as leakage current. Here, leakage current refers to a current of 0.04 mA or more that flows when a voltage of any magnitude is applied. If leakage current occurs, the inspection result is judged to be poor.

[0013] In recent years, there has been an increasing demand for insulation reliability in insulating layers (the ability to maintain a state where conductivity failure does not occur). This necessitates the ability to detect even minute foreign matter present in the insulating layer and identify defects.

[0014] To detect minute foreign matter within the insulating layer, it is necessary to apply a higher voltage to the insulating layer than in conventional methods. In this case, if the insulating layer is sufficiently thick, it is possible to detect minute foreign matter by applying a high voltage.

[0015] However, in recent years, due to the demand for thinner printed circuit boards, the thickness of the insulating layer on printed circuit boards has become thinner than that of conventional printed circuit boards.

[0016] When a voltage was applied to a metal-clad laminate used in the manufacture of such thin printed circuit boards, a so-called pseudo-defect sometimes occurred, where conductivity (leakage current) would occur even if there were no foreign matter in the insulating layer of the metal-clad laminate. The inventor investigated the cause of this pseudo-defect and discovered the following facts.

[0017] When a voltage is applied between the two metal layers of a metal-clad laminate, depending on the magnitude of the applied voltage or the thickness of the insulating layer, electrical conductivity may occur between the two metal layers via the air, regardless of the presence or absence of foreign matter in the insulating layer. This can result in a false defect, making it difficult to accurately inspect for the presence or absence of foreign matter in the insulating layer of the metal-clad laminate. This false defect is particularly likely to occur as the distance between the two metal layers decreases. This is thought to be because as the distance between the two metal layers decreases, the resistance of the air interposed between them decreases, and as a result, the resistance of the air interposed between the two metal layers becomes lower than the resistance of the insulating layer, causing electrical conductivity to occur.

[0018] Therefore, the inventor diligently conducted research and development to obtain a metal-clad laminate that can accurately inspect for the presence or absence of foreign matter in the insulating layer, which led to this disclosure.

[0019] The metal-clad laminate 100 according to this embodiment includes an insulating layer 1 having a first main surface 11, a second main surface 12 opposite to the first main surface 11, and a side surface 13 connecting the first main surface 11 and the second main surface 12, a first metal layer 21 overlapping the first main surface 11, and a second metal layer 22 overlapping the second main surface 12. The shortest distance H on the surface of the side surface 13 from the first end 131 in contact with the first main surface 11 to the second end 132 in contact with the second main surface 12 is greater than the thickness of the insulating layer 1. The thickness of the insulating layer 1 is 10 μm or more and 300 μm or less. In this case, since the shortest distance H is greater than the thickness of the insulating layer 1, the distance between the first metal layer 21 and the second metal layer 22 on the side surface 13 can be increased. Consequently, the first metal layer 21 and the second metal layer 22 become less electrically conductive through air. As a result, the presence or absence of foreign matter in the insulating layer 1 can be inspected with high accuracy.

[0020] 2. The specific configuration of the metal-clad laminate 100 according to the detailed embodiment will be described.

[0021] 2.1 Embodiments (Structure) The metal-clad laminate 100 comprises an insulating layer 1. The material of the insulating layer 1 is not particularly limited, but for example, the insulating layer 1 contains a cured prepreg. The prepreg comprises at least one of a thermosetting resin composition and a semi-cured thermosetting resin composition, and a fibrous base material. The components contained in the thermosetting resin composition are not particularly limited, but for example, the thermosetting resin composition contains at least one component selected from the group consisting of thermosetting resins and curing agents. For example, the thermosetting resin includes at least one selected from the group consisting of epoxy resins; polyamide resins; polyimide resins; triazine resins; phenolic resins; polyester resins; melamine resins; polyphenylene ether resins; maleimide resins; and hydrocarbon resins such as ethylene resins, propylene resins, and styrene resins. For example, the curing agent includes at least one selected from the group consisting of phenolic curing agents, acid anhydride curing agents, and amine curing agents. Furthermore, the prepreg may be used as a single sheet or multiple sheets may be stacked on top of each other.

[0022] The insulating layer 1 has a certain thickness. The insulating layer 1 has a first main surface 11 and a second main surface 12 opposite to the first main surface 11, and the distance between the first main surface 11 and the second main surface 12 is the thickness of the insulating layer 1. The thickness of the insulating layer 1 is not particularly limited, but the effects of the embodiment are more easily achieved when the insulating layer 1 has an appropriate thickness. Specifically, the thickness of the insulating layer 1 is preferably 10 μm or more and 300 μm or less.

[0023] The insulating layer 1 has side surfaces 13 that connect the first main surface 11 and the second main surface 12. The number of side surfaces 13 that the insulating layer 1 has is not particularly limited, but the number of side surfaces 13 that the insulating layer 1 has is determined, for example, according to the shape of the first main surface 11 and the shape of the second main surface 12. Specifically, in this embodiment, the shape of the first main surface 11 and the shape of the second main surface 12 are both quadrilaterals, and one side surface 13 of the insulating layer 1 is arranged to connect one of the edges of the first main surface 11 and one of the edges of the second main surface 12. In other words, the number of side surfaces 13 is determined according to the number of pairs of edges that are paired in the vertical direction between the first main surface 11 and the second main surface 12. In this embodiment, the number of pairs of edges that are paired in the vertical direction between the first main surface 11 and the second main surface 12 is four. Therefore, the insulating layer 1 has four side surfaces 13.

[0024] Furthermore, with respect to one side surface 13 of the insulating layer 1, the first end portion 131 of the side surface 13 that is in contact with the first main surface 11 overlaps with one of the edges of the first main surface 11, and the second end portion 132 of the side surface 13 that is in contact with the second main surface 12 overlaps with one of the edges of the second main surface 12.

[0025] As already mentioned, in the embodiment, the shortest distance H on the surface of the side surface 13 from the first end 131 that contacts the first main surface 11 of the side surface 13 to the second end 132 that contacts the second main surface 12 of the side surface 13 is greater than the thickness of the insulating layer 1. The ratio of the shortest distance H to the thickness of the insulating layer 1 is preferably 1.00015 or more, more preferably 1.00137 or more, and even more preferably 1.00751 or more. In this case, the effects of the embodiment are more easily achieved. The ratio of the shortest distance H to the thickness of the insulating layer 1 is preferably 1.74345 or less, and more preferably 1.22077 or less.

[0026] The angle between the direction perpendicular to the first main surface 11 and the second main surface 12 of the insulating layer 1 and the side surface 13 is preferably 1° or more. In this case, the effects of the embodiment are more easily achieved. This angle is more preferably 3° or more, and even more preferably 7° or more. Furthermore, the angle between the direction perpendicular to the first main surface 11 and the second main surface 12 of the insulating layer 1 and the side surface 13 is preferably 55° or less. In this case, the metal-clad laminate 100 can be handled safely and easily. This angle is more preferably 35° or less.

[0027] The surface area of ​​the first main surface 11 and the surface area of ​​the second main surface 12 may be the same or different, but in this embodiment, the surface area of ​​the first main surface 11 and the surface area of ​​the second main surface 12 are the same.

[0028] Furthermore, the shape of the side surface 13 is not particularly limited and can be processed into any shape when manufacturing the metal-clad laminate 100. In this embodiment, the shape of the side surface 13 is a parallelogram (see Figure 1).

[0029] The metal-clad laminate 100 comprises a first metal layer 21 and a second metal layer 22. The materials of the first metal layer 21 and the second metal layer 22 are not particularly limited, but for example, the first metal layer 21 and the second metal layer 22 each contain at least one metal selected from the group consisting of copper, aluminum, nickel, and iron.

[0030] Furthermore, the first metal layer 21 overlaps with the first main surface 11. The thickness of the first metal layer 21 is not particularly limited, but for example, it is 1 μm or more and 140 μm or less. The method for producing the first metal layer 21 is not particularly limited, but for example, it may be produced by placing a metal foil made of the metals mentioned above on the first main surface 11. The second metal layer 22 overlaps with the second main surface 12. The thickness of the second metal layer 22 is not particularly limited, but for example, it is 1 μm or more and 140 μm or less. The method for producing the second metal layer 22 is not particularly limited, but for example, it may be produced by placing a metal foil made of the metals mentioned above on the second main surface 12.

[0031] The surface area of ​​the surface of the first metal layer 21 that is in contact with the first main surface 11 may be the same as, or it may be different from, the surface area of ​​the surface of the first metal layer 21 that is in contact with the first main surface 11. In this embodiment, the surface area of ​​the surface of the first metal layer 21 that is in contact with the first main surface 11 is the same as the surface area of ​​the surface of the first metal layer 21 that is in contact with the first main surface 11. In other words, the surface area of ​​the surface of the first metal layer 21 that is in contact with the first main surface 11 is the same as the surface area of ​​the first main surface 11.

[0032] Similarly, the surface area of ​​the second metal layer 22 in contact with the second main surface 12 may be the same as, or it may be different from, the surface area of ​​the second metal layer 22 on the opposite side of the surface in contact with the second main surface 12. In this embodiment, the surface area of ​​the second metal layer 22 in contact with the second main surface 12 is the same as the surface area of ​​the second main surface 12. In other words, the surface area of ​​the second metal layer 22 on the opposite side of the surface in contact with the second main surface 12 is the same as the surface area of ​​the second main surface 12.

[0033] (Manufacturing Method) The method for manufacturing the metal-clad laminate 100 will be described below.

[0034] The manufacturing method for the metal-clad laminate 100 of this disclosure includes a preparation step and a cutting step. In the preparation step, a laminate 10 comprising an insulating layer 1 and a metal layer 2 overlapping the main surface of the insulating layer 1 is prepared. In the cutting step, the laminate 10 is cut with a cutting tool C. In the metal-clad laminate 100 manufactured by this method, the shortest distance H on the surface of the side surface 13, from the first end 131 in contact with the first main surface 11 of the side surface 13 to the second end 132 in contact with the second main surface 12 of the side surface 13, tends to be greater than the thickness of the insulating layer 1. Therefore, electrical conductivity between the first metal layer 21 and the second metal layer 22 via air becomes less likely to occur. Furthermore, in the above manufacturing method, burrs are less likely to occur in the metal-clad laminate 100, and problems caused by burrs are less likely to occur.

[0035] A detailed explanation will be given regarding the manufacturing method of the metal-clad laminate 100 according to this embodiment.

[0036] <Preparation Step> In the preparation step according to the embodiment, a laminate 10 is prepared, comprising an insulating layer 1 having a first main surface 11 and a second main surface 12 opposite to the first main surface 11, a first metal layer 21 overlapping the first main surface 11, and a second metal layer 22 overlapping the second main surface 12 (see Figure 2). In this embodiment, the surface visible when viewing the laminate 10 from above is quadrilateral. Therefore, the laminate 10 has an upper surface visible when viewing from above, a lower surface opposite to the upper surface, and four end surfaces connecting the upper and lower surfaces. Specifically, the upper surface visible when viewing from above is the surface opposite to the surface of the first metal layer 21 that is in contact with the first main surface 11. The lower surface is the surface opposite to the surface of the second metal layer 22 that is in contact with the second main surface 12.

[0037] The insulating layer 1 of the metal-clad laminate 100 is fabricated from the insulating layer 1 of the laminate 10. The thickness of the insulating layer 1 of the prepared laminate 10 is preferably 10 μm or more and 300 μm or less, more preferably 10 μm or more and 250 μm or less, and even more preferably 10 μm or more and 200 μm or less. When the thickness of the insulating layer 1 of the obtained metal-clad laminate 100 is 10 μm or more and 300 μm or less, the effects of the embodiment are more easily exhibited.

[0038] The first metal layer 21 and the second metal layer 22 of the metal-clad laminate 100 are each produced from the first metal layer 21 and the second metal layer 22 of the laminate 10. Therefore, the thickness and material of the first metal layer 21 and the second metal layer 22 of the laminate 10 may be the same as the thickness and material of the first metal layer 21 and the second metal layer 22 of the metal-clad laminate 100.

[0039] <Cutting Process> As already mentioned, in the cutting process, the laminate 10 is cut with a cutting tool C. For example, the cutting tool C is installed on a multilayer board outer edge finishing device, and the laminate 10 is placed against the cutting tool C to cut the laminate 10. The cutting tool C is not particularly limited, but examples include rotary blades, shear blades, router blades, etc. Examples of multilayer board outer edge finishing devices include HME-650WF and MMD-650 from Sofmix Co., Ltd., NDR-254K from Takeuchi Co., Ltd., and ACS from Shoda Tectron Co., Ltd.

[0040] In this embodiment, a metal-clad laminate 100 can be manufactured from the laminate 10 by cutting each of the four end faces of the laminate 10 with a cutting tool C. Specifically, first, the cutting tool C is placed against the laminate 10 so as to be aligned with one of the four end faces of the laminate 10. Next, the cutting tool C is operated to cut the laminate 10 by cutting the surface against which the cutting tool C is applied. In this way, by cutting the end faces of the insulating layer 1 of the laminate 10 with the cutting tool C, the side surfaces 13 of the insulating layer 1 of the metal-clad laminate 100 can be formed.

[0041] At this time, by setting the angle α between the direction perpendicular to the main surfaces 11 and 12 of the insulating layer 1 and the cutting tool C to 1° or more and 60° or less (see Figure 3), the shortest distance H on the surface of the side surface 13 of the obtained metal-clad laminate 100, from the first end 131 that contacts the first main surface 11 of the side surface 13 to the second end 132 that contacts the second main surface 12 of the side surface 13, can be easily made larger than the thickness of the insulating layer 1. In this case, the obtained metal-clad laminate 100 becomes less susceptible to electrical conduction between the first metal layer 21 and the second metal layer 22 via air. The angle α between the direction perpendicular to the main surfaces 11 and 12 of the insulating layer 1 and the cutting tool C can be appropriately adjusted, for example, by changing the shape of the cutting tool C or how the cutting tool C is applied to the end surface. Furthermore, the angle α between the direction perpendicular to the main surfaces 11 and 12 of the insulating layer 1 and the cutting tool C is such that, for example, the angle α between the direction perpendicular to the main surfaces 11 and 12 of the insulating layer 1 and a part of the cutting tool C is between 1° and 60°. In this case, electrical conductivity between the first metal layer 21 and the second metal layer 22 through air becomes less likely to occur in the resulting metal-clad laminate 100.

[0042] Further, after the side surface 13 is formed by the above method, by applying the cutting tool C to the laminate 10 along the end surface on the opposite side of the end surface where the formed side surface 13 is located and cutting the laminate 10, a side surface 13 can be formed on the opposite side of the previously formed side surface 13. At this time, if the side surface 13 on the opposite side is formed so as to be parallel to the previously formed side surface 13, the shape of the side surface 13 formed in a direction orthogonal to the direction in which these two side surfaces 13 face each other can be made into a parallelogram. Then, by performing the same operation on the remaining two of the four end surfaces of the laminate 10, a metal-clad laminate 100 including the insulating layer 1, which has four side surfaces 13 and each of the side surfaces 13 is shaped as a parallelogram, can be manufactured.

[0043] (Withstand Voltage Test) As already mentioned, for a metal-clad laminate including two metal layers and an insulating layer interposed between the two metal layers, whether the insulating layer contains foreign matter is sometimes checked by applying a voltage between the two metal layers. However, when a voltage is applied to the metal-clad laminate, even if there is no foreign matter in the insulating layer, conduction (leakage current) may occur through air. This problem particularly tends to occur as the value of the applied voltage increases. Specifically, when the applied voltage is 300 V or higher, electrical conduction occurs between the two metal layers through air regardless of the presence or absence of foreign matter in the insulating layer, so the presence or absence of foreign matter cannot be checked accurately.

[0044] In contrast, even when a withstand voltage test is performed on the metal-clad laminate 100 according to the embodiment, the presence or absence of foreign matter can be determined accurately. In other words, even when a high voltage is applied to the metal-clad laminate 100 according to the embodiment, so-called poor conduction, that is, conduction between the first metal layer 21 and the second metal layer 22 through air, is less likely to occur, so small foreign matter contained in the insulating layer 1 can be detected accurately.

[0045] The high voltage herein means 300 V or higher. Even when the value of the voltage applied to the metal-clad laminate 100 is 300 V or higher, electrical conduction between the first metal layer 21 and the second metal layer 22 via air is less likely to occur, and as a result, the presence or absence of foreign matter can be confirmed with high accuracy. By changing each of the angle α and the thickness of the insulating layer 1 within the ranges described above, the metal-clad laminate 100 according to the embodiment makes it difficult for electrical conduction to occur between the first metal layer 21 and the second metal layer 22 via air even when the applied voltage value is 400 V or higher.

[0046] In the withstand voltage test method, one of the first metal layer 21 and the second metal layer 22 is brought into contact with the positive terminal of the test apparatus T, and the other is brought into contact with the negative terminal of the test apparatus T, and a voltage is applied between the first metal layer 21 and the second metal layer 22 (see FIG. 4). The withstand voltage test is performed in accordance with IPC standards. A withstand voltage tester can be used as the test apparatus T. Examples of the withstand voltage tester include TOS9301 manufactured by Kikusui Electronics Corporation, MY10 series manufactured by Yokogawa Measurement Technologies, Ltd., and the like.

[0047] 2.2 Modified Examples Modified examples will be described with reference to FIGS. 5 to 9. The modified examples are examples of variations in which the configuration of the embodiment is partially changed, added, or deleted. In addition, regarding the modified examples, configurations that are the same as those of the metal-clad laminate 100 or the laminate 10 according to the embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

[0048] (First Modified Example) In the above embodiment, the shape of the side surface 13 is a parallelogram, but the shape is not limited thereto. That is, the shape of the side surface 13 may be any shape as long as the shortest distance H on the surface of the side surface 13 from the first end 131 of the side surface 13 in contact with the first main surface 11 to the second end 132 of the side surface 13 in contact with the second main surface 12 is larger than the thickness of the insulating layer 1. The shape of the side surface 13 may be a parallelogram, a trapezoid, a convex curved surface, a hexagon, or an octagon.

[0049] The metal-clad laminate 100 is manufactured by cutting the laminate 10 with the cutting tool C, with the angle α between the direction perpendicular to the main surfaces 11 and 12 of the insulating layer 1 and the cutting tool C being between 1° and 60°. By appropriately changing the cutting method, the shape of the side surface 13 can be any of the shapes mentioned above.

[0050] For example, the shape of the side surface 13 can be made trapezoidal by forming it in the following manner (see Figure 5). First, prepare the laminate 10 described in the above embodiment. Next, form the side surface 13 along one of the four end faces of the laminate 10 according to the method described in the above embodiment, and then form the side surface 13 on the opposite side from where the previously formed side surface 13 is located. At this time, form the later side surface 13 so that it is not parallel to the previously formed side surface 13. In this way, the shape of the side surface 13 formed in a direction perpendicular to the direction in which these two side surfaces 13 face each other can be made trapezoidal.

[0051] For example, the shape of the side surface 13 can be made hexagonal by forming it in the following manner (see Figure 6). First, prepare the laminate 10 described in the above embodiment. Next, form the side surface 13 along one of the four end faces of the laminate 10 according to the method described in the above embodiment, and then form the side surface 13 on the opposite side from where the previously formed side surface 13 is located. At this time, use a cutting tool C having a triangular groove. With the triangular groove applied to the end face, cut the end face in a direction perpendicular to the direction in which these two side surfaces 13 face each other to form the side surface 13. In this way, the shape of the two opposing side surfaces 13 can be made to follow the shape of the groove of the cutting tool C. Then, the shape of the side surface 13 formed in the direction perpendicular to the direction in which these two side surfaces 13 face each other can be made hexagonal. The recess in the cutting tool C has two surfaces, and the angle α between the direction perpendicular to the main surfaces 11 and 12 of the insulating layer 1 and each of the two surfaces provided in the recess of the cutting tool C is between 1° and 60°.

[0052] Furthermore, by forming the side surface 13 using a cutting tool C having a trapezoidal recess, in the same manner as in the method used to form the hexagonal side surface 13, an octagonal side surface 13 can be formed (see Figure 7).

[0053] Furthermore, by forming the side surface 13 using a cutting tool C having a convex curved recess, in the same manner as in the method used to form the hexagonal side surface 13, the shape of the formed side surface 13 can be made to follow the recess of the cutting tool C, i.e., convex curved (see Figure 8). Note that when forming the convex curved side surface 13, the angle α between the direction perpendicular to the main surfaces 11 and 12 of the insulating layer 1 and the cutting tool C does not have to be between 1° and 60°.

[0054] (Second Modification) In the above embodiment, the shape of the first main surface 11 and the shape of the second main surface 12 were both quadrilaterals, but are not limited to this. For example, the shape of the first main surface 11 and the shape of the second main surface 12 may be a polygon other than a quadrilateral, a circle, etc. If the shape of the first main surface 11 and the shape of the second main surface 12 are both pentagons, the number of side surfaces 13 that the insulating layer 1 has is five. If the shape of the first main surface 11 and the shape of the second main surface 12 are both circular, the number of side surfaces 13 that the insulating layer 1 has is one.

[0055] (Third Modification) In the above embodiment, the method for manufacturing the metal-clad laminate 100 included a preparation step and a cutting step, but it may also include other steps. For example, in addition to the preparation step and the cutting step, the method for manufacturing the metal-clad laminate 100 may further include a lamination step between the preparation step and the cutting step. In the lamination step, multiple laminates 10 are stacked (see Figure 9). In this case, when manufacturing the metal-clad laminate 100, multiple laminates 10 are cut together with a cutting tool C. After cutting multiple laminates 10 together with a cutting tool C, if each laminate 10 is separated, multiple metal-clad laminates 100 can be obtained efficiently.

[0056] 3. Aspects As is clear from the embodiments described above, the present disclosure includes the following aspects. Hereafter, reference numerals are enclosed in parentheses solely to indicate the correspondence with the embodiments.

[0057] A metal-clad laminate (100) according to a first aspect of this disclosure comprises an insulating layer (1) having a first main surface (11), a second main surface (12) opposite to the first main surface (11), and a side surface (13) connecting the first main surface (11) and the second main surface (12); a first metal layer (21) overlapping the first main surface (11); and a second metal layer (22) overlapping the second main surface (12). The shortest distance (H) on the surface of the side surface (13) from a first end (131) in contact with the first main surface (11) to a second end (132) in contact with the second main surface (12) is greater than the thickness of the insulating layer (1). The thickness of the insulating layer (1) is 10 μm or more and 300 μm or less.

[0058] According to this embodiment, a metal-clad laminate (100) can be provided that can accurately inspect for the presence or absence of foreign matter contained in the insulating layer (1).

[0059] In the metal-clad laminate (100) according to a second aspect of the present disclosure, in the first aspect, the surface area of ​​the first main surface (11) and the surface area of ​​the second main surface (12) are the same.

[0060] In a third aspect of the present disclosure, the metal-clad laminate (100) is such that, in the first or second aspect, the surface area of ​​the surface of the first metal layer (21) opposite to the surface in contact with the first main surface (11) is the same as the surface area of ​​the first main surface (11).

[0061] In the metal-clad laminate (100) according to a fourth aspect of the present disclosure, in any one of the first to third aspects, the surface area of ​​the first main surface (11) is smaller than the surface area of ​​the second main surface (12).

[0062] In the fifth aspect of the present disclosure, the metal-clad laminate (100) is such that, in any one of the first to fourth aspects, the side surface (13) is a parallelogram, trapezoid, convex curve, hexagon, or octagon.

[0063] A metal-clad laminate (100) according to a sixth aspect of the present disclosure, in any one of the first to fifth aspects, the insulating layer (1) contains a cured prepreg. The prepreg includes at least one of a thermosetting resin composition and a semi-cured thermosetting resin composition, and a fibrous substrate.

[0064] A method for manufacturing a metal-clad laminate (100) according to a seventh aspect of this disclosure includes a preparation step of preparing a laminate (10) comprising an insulating layer (1) having main surfaces (11, 12) and metal layers (2; 21, 22) overlapping the main surfaces (11, 12), and a cutting step of cutting the laminate (10) with a cutting tool (C). The angle (α) between the direction perpendicular to the main surfaces (11, 12) of the insulating layer (1) and the cutting tool (C) is 1° or more and 60° or less.

[0065] In the eighth aspect of the present disclosure, the method for manufacturing a metal-clad laminate (100) is such that, in the seventh aspect, the thickness of the insulating layer (1) is 10 μm or more and 300 μm or less.

[0066] A method for manufacturing a metal-clad laminate (100) according to the ninth aspect of the present disclosure further includes, in the seventh or eighth aspect, a lamination step of stacking a plurality of laminates (10) between a preparation step and a cutting step.

[0067] A dielectric strength test method according to a tenth aspect of the present disclosure comprises an insulating layer (1) having a first main surface (11), a second main surface (12) opposite to the first main surface (11), and a side surface (13) connecting the first main surface (11) and the second main surface (12), a first metal layer (21) overlapping the first main surface (11), and a second metal layer (22) overlapping the second main surface (12). A dielectric strength test method to be performed on a metal-clad laminate (100) in which the shortest distance (H) on the surface of the side surface (13) from the first end (131) in contact with the first main surface (11) of the side surface (13) to the second end (132) in contact with the second main surface (12) of the side surface (13) is greater than the thickness of the insulating layer (1), wherein a voltage is applied between the first metal layer (21) and the second metal layer (22) by bringing one of the first metal layer (21) and the second metal layer (22) into contact with the + terminal of the test device (T) and bringing the other into contact with the - terminal of the test device (T).

[0068] The following are specific examples of the present disclosure. However, the present disclosure is not limited to these examples.

[0069] 1. Method for manufacturing metal-clad laminates A laminate (manufactured by Panasonic Industries, Ltd.) was prepared in which copper foil was laminated on both sides of the insulating layer.

[0070] Next, the cutting tool was applied to the end face of the laminate to process it into a metal-clad laminate having the side shape described in the table. The laminate was cut using the cutting tool so that the angle between the main surface of the prepreg on the laminate and the cutting tool was the value described in the table, thereby forming the side.

[0071] The cutting tools used in each example and comparative example are listed in the table.

[0072] The model numbers of the laminates used in each example and comparative example are listed in the table.

[0073] Furthermore, the thickness of the insulating layer for each example and comparative example is shown in the table.

[0074] 2. Withstand Voltage Test The obtained double-sided copper-clad laminates were subjected to a withstand voltage test by applying the voltages shown in the table below. The + terminal of the test device was brought into contact with one copper foil of each obtained double-sided copper-clad laminate, and the - terminal of the test device was brought into contact with the other copper foil, and a voltage of 100V was applied to check whether continuity occurred. The test result was determined by measuring the leakage current value. If the leakage current value was less than 0.04mA, the test result was judged to be good, and if the leakage current value was 0.04mA or more, the test result was judged to be poor. Subsequently, the applied voltage was increased by 50V and the same test was performed again, and this operation was continued until the applied voltage reached 500V. The results are shown in the table, with "A" indicating a good test result and "B" indicating a poor test result.

[0075]

[0076]

[0077] The metal-clad laminates of each embodiment were able to undergo a dielectric strength test by applying a high voltage of 300V or more. In contrast, when a voltage of 300V or more was applied to the metal-clad laminates of each comparative example, leakage current occurred, causing conductivity between the two copper foils through the air, making it impossible to perform a dielectric strength test by applying a high voltage of 300V or more.

[0078] 1. Insulating layer 10. Laminate 11. First main surface 12. Second main surface 13. Side surface 131. First end 132. Second end 2. Metal layer 21. First metal layer 22. Second metal layer 100. Metal-clad laminate H. Shortest distance C. Cutting tool α. Angle T. Testing device

Claims

1. A metal-clad laminate comprising: an insulating layer having a first main surface, a second main surface opposite to the first main surface, and a side surface connecting the first main surface and the second main surface; a first metal layer overlapping the first main surface; and a second metal layer overlapping the second main surface, wherein the shortest distance on the surface of the side surface from a first end of the side surface in contact with the first main surface to a second end of the side surface in contact with the second main surface is greater than the thickness of the insulating layer, and the thickness of the insulating layer is 10 μm or more and 300 μm or less.

2. The metal-clad laminate according to claim 1, wherein the surface area of ​​the first main surface and the surface area of ​​the second main surface are the same.

3. The metal-clad laminate according to claim 1, wherein the surface area of ​​the surface of the first metal layer opposite to the surface in contact with the first main surface is the same as the surface area of ​​the first main surface.

4. The metal-clad laminate according to claim 1, wherein the surface area of ​​the first main surface is smaller than the surface area of ​​the second main surface.

5. The metal-clad laminate according to claim 1, wherein the side surface is a parallelogram, trapezoid, convex curve, hexagon, or octagon.

6. The metal-clad laminate according to claim 1, wherein the insulating layer contains a cured prepreg, and the prepreg comprises at least one of a thermosetting resin composition and a semi-cured product of the thermosetting resin composition, and a fibrous substrate.

7. A method for manufacturing a metal-clad laminate, comprising: a preparation step of preparing a laminate comprising an insulating layer having a main surface and a metal layer overlapping the main surface; and a cutting step of cutting the laminate with a cutting tool, wherein the angle between the direction perpendicular to the main surface of the insulating layer and the cutting tool is 1° or more and 60° or less.

8. The method for manufacturing a metal-clad laminate according to claim 7, wherein the thickness of the insulating layer is 10 μm or more and 300 μm or less.

9. The method for manufacturing a metal-clad laminate according to claim 7, further comprising a lamination step of stacking a plurality of the laminates between the preparation step and the cutting step.

10. A method for withstanding voltage for a metal-clad laminate, comprising: an insulating layer having a first main surface, a second main surface opposite to the first main surface, and a side surface connecting the first main surface and the second main surface; a first metal layer overlapping the first main surface; and a second metal layer overlapping the second main surface, wherein the shortest distance on the surface of the side surface from a first end of the side surface in contact with the first main surface to a second end of the side surface in contact with the second main surface is greater than the thickness of the insulating layer, wherein a voltage is applied between the first metal layer and the second metal layer by bringing one of the first metal layer and the second metal layer into contact with the + terminal of the power supply unit and the other into contact with the - terminal of the power supply unit.

Images