Method for producing metal-clad laminate and metal-clad laminate

Abstract

The present disclosure provides a method for manufacturing a metal-clad laminate, which makes it easy to increase the thickness of the insulating layer and difficult to reduce the peel strength of the metal foil relative to the insulating layer. In the manufacturing method, a first metal foil (31), a plurality of insulating films, and a second metal foil (32) are sequentially stacked between an endless belt and subjected to hot press molding, thereby manufacturing an insulating layer (2) from the plurality of insulating films. Each of the plurality of insulating films has a first surface and a second surface, and the ten-point average roughness (Rzjis) of the second surface is greater than the ten-point average roughness (Rzjis) of the first surface. The absolute value of the difference between the ten-point average roughness (Rzjis) of the surface (401) of the insulating layer (2) in contact with the first metal foil (31) and the ten-point average roughness (Rzjis) of the surface (402) of the insulating layer (2) in contact with the second metal foil (32) is 0.35 μm or less.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a metal-clad laminate and the metal-clad laminate. Background Art

[0002] Metal-clad laminates comprise an insulating layer containing a thermoplastic resin and a metal foil sheet superposed on the insulating layer, and have long been used as materials for printed wiring boards, such as flexible printed wiring boards. Liquid crystal polymers are one of the various materials used for the insulating layer (see Patent Document 1). Liquid crystal polymers have the advantage of imparting excellent radio frequency characteristics to printed wiring boards formed from metal-clad laminates.

[0003] Reference List

[0004] Patent Literature

[0005] Patent Document 1: JP 2010-221694 A Summary of the Invention

[0006] The problem solved by the present disclosure is to provide a method for manufacturing a metal-clad laminate and a metal-clad laminate, both of which make it easier to increase the thickness of the insulating layer and reduce the possibility of causing a decrease in the peel strength of the metal foil sheet with respect to the insulating layer.

[0007] A method for manufacturing a metal-clad laminate according to one aspect of the present disclosure includes: continuously supplying a first metal foil sheet, a plurality of insulating films, and a second metal foil sheet different from the first metal foil sheet between two endless belts (endless belts); and sequentially stacking the first metal foil sheet, the plurality of insulating films, and the second metal foil sheet between the endless belts, and thermoforming the first metal foil sheet, the plurality of insulating films, and the second metal foil sheet together to form an insulating layer from the plurality of insulating films. Each of the plurality of insulating films has a first surface and a second surface opposite to the first surface. The second surface has a larger ten-point average roughness (Rzjis) than the first surface. The absolute value of the difference between the ten-point average roughness (Rzjis) of the surface of the insulating layer in contact with the first metal foil sheet and the ten-point average roughness (Rzjis) of the other surface of the insulating layer in contact with the second metal foil sheet is equal to or less than 0.35 μm.

[0008] According to another aspect of the present disclosure, a metal-clad laminate includes: an insulating layer; and a metal foil sheet superimposed on the insulating layer. The insulating layer includes a plurality of resin layers. The insulating layer has a thickness of 100 μm or greater and 300 μm or less. Each of the resin layers contains a liquid crystal polymer. The metal foil sheet has a peel strength of 0.60 N / mm or greater relative to the insulating layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram illustrating a manufacturing process of a metal-clad laminate according to a first embodiment of the present disclosure;

[0010] Figure 2 is a schematic cross-sectional view of a metal-clad laminate according to a second embodiment of the present disclosure or a metal-clad laminate manufactured by the manufacturing method according to the first embodiment of the present disclosure;

[0011] Figure 3 A is a schematic cross-sectional view of a laminate during the production of a metal-clad laminate in the case where only one insulating film is used;

[0012] Figure 3 B is a schematic cross-sectional view of a metal-clad laminate and an endless belt during the production of the metal-clad laminate in the case where only one insulating film is used;

[0013] Figure 4 A is in Figure 1 a schematic cross-sectional view of the stack during the manufacturing process shown; and

[0014] Figure 4 B is in Figure 1 Schematic cross-sectional view of a metal-clad laminate and endless belt during manufacturing process shown. DETAILED DESCRIPTION

[0015] In order to improve the stability of radio frequency characteristics of a printed wiring board, the present inventors have attempted to increase the thickness of an insulating layer included in the printed wiring board.

[0016] As a result of research and development, the present inventors have discovered that insulating films, such as liquid crystal polymer films, having a thickness greater than 100 μm are not only rarely available due to the difficulty of producing such thick insulating films, but can also lead to reduced performance stability of printed wiring boards. In particular, the present inventors have discovered that such thick insulating films tend to reduce the peel strength of the metal foil sheet relative to the insulating layer.

[0017] Therefore, the present inventors conducted intensive and meticulous research and development to provide a method for manufacturing a metal-clad laminate and a metal-clad laminate, both of which make it easier to increase the thickness of the insulating layer and reduce the possibility of causing a decrease in the peel strength of the metal foil sheet relative to the insulating layer, thereby conceiving the concept of the present disclosure.

[0018] An exemplary embodiment of the present disclosure will now be described. Note that the embodiment described below is merely an exemplary embodiment of the various embodiments of the present disclosure and should not be construed as limiting. Rather, the exemplary embodiment can be readily modified in various ways according to design choices or any other factors without departing from the scope of the present disclosure.

[0019] A method for producing the metal-clad laminate 1 according to the first embodiment will be described. In the production method according to this embodiment, as Figure 1 As shown, a first metal foil sheet 31, a plurality of insulating films 6, and a second metal foil sheet 32 different from the first metal foil sheet 31 are continuously supplied between two endless belts 5. Between the endless belts 5, the first metal foil sheet 31, the plurality of insulating films 6, and the second metal foil sheet 32 are sequentially stacked and thermoformed, thereby forming an insulating layer 2 from the plurality of insulating films 6. Each of the plurality of insulating films 6 has a first surface 601 and a second surface 602 opposite the first surface 601. The second surface 602 has a greater ten-point average roughness (Rzjis) than the first surface 601. The absolute value of the difference between the ten-point average roughness (Rzjis) of the surface 401 of the insulating layer 2 in contact with the first metal foil sheet 31 and the ten-point average roughness (Rzjis) of the other surface 402 of the insulating layer 2 in contact with the second metal foil sheet 32 is equal to or less than 0.35 μm.

[0020] According to this embodiment, insulating layer 2 is formed of a plurality of insulating films 6, thereby making it easier to increase the thickness of insulating layer 2. In a printed wiring board formed of metal-clad laminate 1, thickening insulating layer 2 can reduce the possibility of transmission loss caused by electrostatic capacitance and leakage resistance between portions of the conductor line, which become increasingly significant as the transmission rate and frequency of the signal further increase.

[0021] Furthermore, even if each insulating film 6 has a first surface 601 and a second surface 602 having different ten-point average roughness (Rzjis) values, the insulating film 6 can be arranged so that the absolute value of the difference between the ten-point average roughness (Rzjis) of one surface 401 of the insulating layer 2 and the ten-point average roughness (Rzjis) of the other surface 402 of the insulating layer 2 is equal to or less than 0.35 μm. This makes it possible to increase the peel strength of the metal foil sheet 3 relative to the insulating layer 2 to 0.60 N / mm or more. This is probably because setting the ten-point average roughness (Rzjis) of the surface 401 of the insulating layer 2 in contact with the first metal foil sheet 31 to be equal to or approximately equal to the ten-point average roughness (Rzjis) of the surface 402 of the insulating layer 2 in contact with the second metal foil sheet 32 reduces the possibility of a time lag occurring between the timing of bonding the insulating layer 2 and the first metal foil sheet 31 and the timing of bonding the insulating layer 2 and the second metal foil sheet 32 during the manufacturing process of the metal-clad laminate 1. However, this theory is only a conjecture and should not be construed as limiting the scope of the present embodiments.

[0022] The absolute value of the difference between the ten-point average roughness (Rzjis) of one surface 401 of the insulating layer 2 in contact with the first metal foil sheet 31 and the ten-point average roughness (Rzjis) of the other surface 402 of the insulating layer 2 in contact with the second metal foil sheet 32 is preferably equal to or less than 0.25 μm, and more preferably equal to or less than 0.15 μm. The absolute value of this difference is particularly preferably equal to zero.

[0023] It is also preferable that the absolute value of the difference between the arithmetic mean roughness (Ra) of one surface 401 of the insulating layer 2 in contact with the first metal foil sheet 31 and the arithmetic mean roughness (Ra) of the other surface 402 of the insulating layer 2 in contact with the second metal foil sheet 32 is equal to or less than 0.025 μm. This makes it easier to further improve the peel strength of the metal foil sheet 3.

[0024] The absolute value of the difference between the arithmetic mean roughness (Ra) of one surface 401 of the insulating layer 2 in contact with the first metal foil sheet 31 and the arithmetic mean roughness (Ra) of the other surface 402 of the insulating layer 2 in contact with the second metal foil sheet 32 is more preferably equal to or less than 0.015 μm, and even more preferably equal to or less than 0.005 μm. The absolute value of this difference is particularly preferably equal to zero.

[0025] Note that the values of the ten-point average roughness (Rzjis) and the arithmetic average roughness (Ra) are obtained based on the results of surface profile measurement of the insulating layer 2 by, for example, a confocal laser scanning microscope.

[0026] The plurality of insulating films 6 preferably include at least: a first insulating film 61; and a second insulating film 62 having a greater thickness than the first insulating film 61. Furthermore, in this embodiment, the insulating film 6 having the smaller thickness (e.g., the first insulating film 61) among the plurality of insulating films 6 forming the insulating layer 2 preferably has a smaller dimension measured in the width direction. This allows stress that could cause deformation at the end edges of the insulating layer 2 to be absorbed by bending the thicker insulating film 6 in the portion where it does not overlap with the thinner insulating film 6. Consequently, the degree of deformation in the portion where the thicker insulating film 6 (e.g., the second insulating film 62) overlaps with the thinner insulating film 6 (e.g., the first insulating film 61). This increases the likelihood of a more gradual change in thickness at the end edges of the metal-clad laminate 1 in the width direction, thereby making it easier to further increase the dimension W2 measured in the width direction of the portion of the metal-clad laminate 1 that can be used as a product (i.e., further increase its effective width). Note that the dimension of the first insulating film 61 measured in the width direction is measured perpendicularly to both the direction in which the first insulating film 61 is conveyed and the thickness direction of the first insulating film 61. Likewise, the size of the second insulating film 62 (measured in the width direction) is measured perpendicularly to both the direction in which the second insulating film 62 is transported and the thickness direction of the second insulating film 62 .

[0027] According to this embodiment, Figure 2 As shown, the insulating layer 2 is formed of a plurality of insulating films 6, and the metal foil sheet 3 is stacked and bonded onto the insulating layer 2, thereby producing a metal-clad laminate 1 including the insulating layer 2 and the metal foil sheet 3 stacked on the insulating layer 2. The insulating layer 2 includes a plurality of resin layers 4 derived from the plurality of insulating films 6. In the insulating layer 2, the plurality of resin layers 4 are stacked on top of each other. In other words, the insulating layer 2 includes a plurality of resin layers 4 stacked on top of each other. If each of the insulating films 6 contains a liquid crystal polymer (i.e., if the insulating films 6 are liquid crystal polymer films), each of the resin layers 4 contains a liquid crystal polymer. The manufacturing method according to this embodiment is applicable to the manufacture of the metal-clad laminate 1 according to the first embodiment.

[0028] In the first embodiment, the insulating film 6 does not necessarily need to be a liquid crystal polymer film. It is preferable that each insulating film 6 is made of a flexible thermoplastic resin. For example, each insulating film 6 may contain at least one resin selected from the group consisting of a liquid crystal polymer, a polyimide resin, a polyethylene terephthalate resin, and a polyethylene naphthalate resin.

[0029] In this embodiment, the width dimension of the first insulating film 61 is smaller than the width dimension of the second insulating film 62. This increases the possibility of a more gradual change in thickness at the end edges of the metal-clad laminate 1 and increases the effective width of the metal-clad laminate 1. This makes it easier for the metal-clad laminate 1 to achieve a thickness accuracy of less than ±10% or equal to or less than ±7%. These points will be described in more detail later.

[0030] A method for manufacturing the metal-clad laminate 1 will be described in detail below.

[0031] In this embodiment, two metal foil sheets 3 are used. One of the two metal foil sheets 3 will be referred to below as "first metal foil sheet 31," and the other metal foil sheet 3 will be referred to below as "second metal foil sheet 32." In this embodiment, not only the first metal foil sheet 31 and the plurality of insulating films 6, but also the second metal foil sheet 32 are continuously supplied between two endless belts 5. The metal-clad laminate 1 is manufactured by sequentially stacking the first metal foil sheet 31, the plurality of insulating films 6, and the second metal foil sheet 32 between the two endless belts 5 and heat-pressing these sheets and films together.

[0032] Will refer to Figure 1 A manufacturing system for manufacturing a metal-clad laminate 1 is described. The manufacturing system includes a double-belt press 7. The double-belt press 7 includes: two endless belts 5 arranged to face each other; and two hot pressing devices 10, each for a corresponding one of the two endless belts 5. The endless belts 5 can be made of, for example, stainless steel. Each of these endless belts 5 is wound around two rotating drums 9 and runs around the circumference of the rotating drums 9 as the two rotating drums 9 rotate. A laminate 11, in which a first metal foil sheet 31, a plurality of insulating films 6, and a second metal foil sheet 32 are sequentially stacked on one another, is passed through the gap between the two endless belts 5. While the laminate 11 passes through the gap between the two endless belts 5, the endless belts 5 can press the laminate 11 while being in planar contact with one surface of the laminate 11 and its opposite surface. The hot pressing device 10 is disposed inside each of these endless belts 5 and can heat the laminate 11 while being pressed by the endless belts 5. For example, the hot press device 10 may be a hydraulic plate configured to heat-form the laminate 11 via the endless belt 5, for example, using the hydraulic pressure of a heated liquid medium. Alternatively, a plurality of press rollers may be arranged between two rotating drums 9, such that the hot press device 10 is formed by the two rotating drums 9 and the press rollers. This enables heating of the laminate 11 by, for example, inductively heating the press rollers and the rotating drums 9, thereby applying heat to the endless belt 5. Furthermore, this also enables pressing of the laminate 11 via the endless belt 5 by the press rollers.

[0033] The manufacturing system includes a plurality of feeders 12, each of which holds an insulating film 6 thereon by winding the long insulating film 6 into a roll. In this embodiment, only two insulating films 6 are provided, namely, a first insulating film 61 and a second insulating film 62. Therefore, the feeders 12 include a first feeder 121 for holding the first insulating film 61 and a second feeder 122 for holding the second insulating film 62. In addition, the manufacturing system also includes two additional feeders 13 for holding the first and second long metal foil sheets 31, 32, respectively, by winding each of the first and second long metal foil sheets 31, 32 into a roll.

[0034] Feeders 12 and 13 can continuously supply insulating film 6 and metal foil sheet 3 (i.e., first metal foil sheet 31 and second metal foil sheet 32), respectively. The manufacturing system also includes a coiler 8 for winding the long metal-clad laminate 1 into a coil. A double-belt press 7 is provided between feeders 12, 13, and coiler 8.

[0035] When manufacturing the metal-clad laminate 1, first, the insulating film 6 discharged from the feeder 12 and the metal foil sheet 3 discharged from the feeder 13 are fed to the double-belt press 7. At this time, the first metal foil sheet 31, the plurality of insulating films 6, and the second metal foil sheet 32 are sequentially stacked on one another to form the laminate 11. Alternatively, when manufacturing a metal-clad laminate 1 including only one metal foil sheet 3, the laminate 11 can be formed by discharging the metal foil sheet 3 from only one of the two feeders 13 and sequentially stacking this metal foil sheet 3 and the plurality of insulating films 6 on one another. The laminate 11 is fed into the gap between the two endless belts 5 of the double-belt press 7.

[0036] In the double-belt press 7, the laminate 11 passes through the gap between the two endless belts 5 while being sandwiched between them. The endless belts 5 run around the circumference of the rotating drum 9 at a speed as high as the conveying speed of the insulating film 6 and the metal foil sheet 3. While moving through the gap between the two endless belts 5, the laminate 11 is not only pressed but also heated by the endless belts 5 by the heat press device 10. This causes the softened or melted insulating film 6 to bond together to form the insulating layer 2, and also causes the insulating layer 2 and the metal foil sheet 3 to bond together. In this way, the metal-clad laminate 1 is produced and removed from the double-belt press 7. The thus produced metal-clad laminate 1 is then wound into a roll by a coiler 8.

[0037] The maximum heating temperature during hot press molding of the laminate 11 can be, for example, equal to or higher than a temperature 5°C below the melting point of the insulating film 6 and equal to or lower than a temperature 20°C above the melting point. Setting the maximum heating temperature equal to or higher than a temperature 5°C below the melting point allows the insulating film 6 to fully soften during hot press molding, thereby improving the adhesion between the insulating layer 2 and the metal foil sheet 3 and, consequently, improving the peel strength. Setting the maximum heating temperature equal to or lower than a temperature 20°C above the melting point reduces the likelihood of excessive deformation of the insulating film 6 during hot press molding, thereby further improving dimensional accuracy. Alternatively, the maximum heating temperature can be equal to or higher than the melting point and equal to or lower than a temperature 15°C above the melting point.

[0038] The pressing pressure applied during hot press forming can be, for example, equal to or higher than 0.49 MPa, and can also be equal to or higher than 2 MPa. This will further improve peel strength. The pressing pressure can be equal to or lower than 5.9 MPa, and can also be equal to or lower than 5 MPa. This will further improve dimensional accuracy.

[0039] The heating and pressing time during hot press molding can be, for example, equal to or greater than 90 seconds, and can also be equal to or greater than 120 seconds. This will further improve peel strength. The heating and pressing time during hot press molding can be equal to or less than 360 seconds, and can also be equal to or less than 240 seconds. This will further improve dimensional accuracy.

[0040] Manufacturing the metal-clad laminate 1 using a method involving double belt pressing allows the endless belt 5 to press the laminate 11 while maintaining planar contact with it for a certain period of time. This also facilitates heating the entire laminate 11 under uniform conditions. This reduces the likelihood of variations in heating temperature and pressing pressure, thereby achieving higher peel strength and dimensional accuracy compared to hot plate pressing and roller pressing. Furthermore, this makes it easier to improve the dimensional stability of the metal-clad laminate 1 during, for example, etching or heat treatment of the metal-clad laminate 1.

[0041] In addition, when the laminated body 11 is hot-pressed, it is assumed that Figure 3 A shows the case where only a single thick insulating film 6 is used. In this case, when the laminate 11 is thermoformed, as shown in FIG. Figure 3 As shown in FIG. 2B , the endless belt 5 may be significantly deformed into a curved shape at its end edge portions in the width direction. This increases the possibility of causing significant thickness variations at the end edge portions of the metal-clad laminate 1 formed from the stack 11. Consequently, the metal-clad laminate 1 becomes reduced in effective width. The same statement applies even when multiple insulating films 6 are used, all of which have the same widthwise dimensions.

[0042] On the other hand, according to the present embodiment, as described above, the insulating film 6 preferably includes the first insulating film 61 and the second insulating film 62, the thickness of the first insulating film 61 is preferably smaller than the thickness of the second insulating film 62, and the dimension of the first insulating film 61 measured in the width direction is preferably smaller than the dimension of the second insulating film 62 measured in the width direction. In this case, in the laminated body 11, as Figure 4 As shown in A, the second insulating film 62 can be arranged so that both end edges of the second insulating film 62 in the width direction protrude outward relative to the end edges of the first insulating film 61. In this case, when the stack 11 is hot-pressed, the amount of resin at the two end edges of the metal-clad laminate 1 in the width direction is reduced, and these end edges tend to be formed so that their thickness decreases toward the outer edges in the width direction. Because the thickness of the first insulating film 61 is less than the thickness of the second insulating film 62, the thickness changes smoothly. This increases the possibility that the end edges of the annular belt 5 in the width direction of the stack will deform smoothly along the stack. Therefore, as Figure 4 As shown in B, the thickness of the metal laminate 1 is only slightly reduced at the end edge portions in the width direction, and thus generally comes to have an increased effective width.

[0043] Furthermore, according to this embodiment, even when the laminate 11 is hot-pressed, the endless belt 5 is unlikely to deform significantly. Therefore, even when the pressing pressure is increased to improve the peel strength of the metal foil sheet 3 relative to the insulating layer 2 in the metal-clad laminate 1, the metal-clad laminate 1 can still maintain sufficiently high thickness accuracy. Therefore, this embodiment makes it easier to achieve both high thickness accuracy and high peel strength. Thus, this embodiment can simultaneously achieve a thickness accuracy of less than ±10% or equal to or less than ±7% and a peel strength of 0.60 N / mm or greater.

[0044] The thickness of each of the plurality of insulating films 6 is preferably equal to or greater than 45 μm and equal to or less than 120 μm. In this case, a resin layer 40 having a thickness of equal to or greater than 45 μm and equal to or less than 120 μm can be formed from each insulating film 6. Such insulating films 6 having a thickness of equal to or greater than 45 μm and equal to or less than 120 μm can be easily manufactured and thus readily available, and generally have high uniformity. This increases the likelihood that the insulating layer 2 formed by the insulating films 6 will have high uniformity.

[0045] The dimension of each of the plurality of insulating films 6 measured in the width direction is preferably equal to or greater than 500 mm and equal to or less than 570 mm. As used herein, the "width direction" is perpendicular to both the thickness direction of the insulating film 6 and the direction in which the insulating film 6 and the metal-clad laminate 1 are conveyed during the manufacturing process of the metal-clad laminate 1. In this case, the insulating layer 2 having a dimension equal to or greater than 500 mm and equal to or less than 570 mm measured in the width direction can be formed from the insulating film 6.

[0046] The difference in dimension measured in the width direction between the first insulating film 61 and the second insulating film 62 is preferably equal to or greater than 10 mm and equal to or less than 70 mm. This increases the likelihood that the thickness of the two end edge portions of the laminate 11 in the width direction will change smoothly, thereby significantly reducing the likelihood of deformation of the endless belt 5 and significantly increasing the likelihood that the metal-clad laminate 1 will have an increased effective width. The difference in dimension measured in the width direction is more preferably equal to or greater than 10 mm and equal to or less than 50 mm, and even more preferably equal to or greater than 10 mm and equal to or less than 30 mm.

[0047] The difference in thickness between the first insulating film 61 and the second insulating film 62 is preferably equal to or greater than 25 μm and equal to or less than 200 μm. This significantly increases the likelihood that the thickness of the two end edge portions of the laminate 11 in the width direction will change smoothly, thereby reducing the likelihood that the endless belt 5 will significantly deform (e.g., become curved) and significantly increasing the likelihood that the metal-clad laminate 1 will have an increased effective width. The thickness difference is more preferably equal to or greater than 25 μm and equal to or less than 150 μm, and even more preferably equal to or greater than 50 μm and equal to or less than 100 μm.

[0048] The number of insulating films 6 provided is determined according to the thickness of the insulating layer 2 and the thickness of each of the insulating films 6 , and may be, for example, equal to or greater than two and equal to or less than four.

[0049] As described above, each of the plurality of insulating films 6 has a first surface 601 and a second surface 602 having a larger ten-point average roughness (Rzjis) than the first surface 601. In this case, the ten-point average roughness (Rzjis) of the first surface 601 can be, for example, equal to or greater than 1.5 μm and equal to or less than 3.0 μm, preferably equal to or greater than 1.8 μm and equal to or less than 2.7 μm, and more preferably equal to or greater than 2.0 μm and equal to or less than 2.5 μm. On the other hand, the ten-point average roughness (Rzjis) of the second surface 602 can be, for example, equal to or greater than 2.4 μm and equal to or less than 3.3 μm, preferably equal to or greater than 2.5 μm and equal to or less than 3.1 μm, and more preferably equal to or greater than 2.6 μm and equal to or less than 3.0 μm. In addition, the difference in ten-point average roughness (Rzjis) between the second surface 602 and the first surface 601 can be, for example, equal to or greater than 0.01μm and equal to or less than 1.0μm, preferably equal to or greater than 0.03μm and equal to or less than 0.8μm, and more preferably equal to or greater than 0.05μm and equal to or less than 0.6μm.

[0050] The second surface 602 may have a greater arithmetic mean roughness (Ra) than the first surface 601. In this case, the arithmetic mean roughness (Ra) of the first surface 601 may be, for example, equal to or greater than 0.25 μm and equal to or less than 0.45 μm, preferably equal to or greater than 0.27 μm and equal to or less than 0.40 μm, and even more preferably equal to or greater than 0.28 μm and equal to or less than 0.35 μm. The arithmetic mean roughness (Ra) of the second surface 602 may be, for example, equal to or greater than 0.27 μm and equal to or less than 0.50 μm, preferably equal to or greater than 0.28 μm and equal to or less than 0.45 μm, and even more preferably equal to or greater than 0.30 μm and equal to or less than 0.42 μm. In addition, the difference in arithmetic mean roughness (Ra) between the second surface 602 and the first surface 601 can be, for example, greater than 0 μm and equal to or less than 1.0 μm, preferably equal to or greater than 0.01 μm and equal to or less than 0.8 μm, and more preferably equal to or greater than 0.05 μm and equal to or less than 0.6 μm.

[0051] If each of the plurality of insulating films 6 has a first surface 601 and a second surface 602, then the surface of the insulating film 6 stacked on the first metal foil sheet 31 in contact with the first metal foil sheet 31, and the surface of another insulating film 6 stacked on the second metal foil sheet 32 in contact with the second metal foil sheet 32, among the plurality of insulating films 6, are preferably both the first surface 601 or the second surface 602. This significantly reduces the likelihood of a gradual weakening of the performance stability of the metal-clad laminate 1. The reason is presumably as follows. Specifically, when the metal-clad laminate 1 is manufactured, for example, by hot press molding, making the surface properties of the surface in contact with the first metal foil sheet 31 and the surface in contact with the second metal foil sheet 32 similar to each other makes it easier to achieve, for example, substantially equal degrees of misalignment between the first metal foil sheet 31 and the insulating layer 2, and between the second metal foil sheet 32 and the insulating layer 2. Furthermore, this makes it easier to apply substantially equal pressure to the surface in contact with the first metal foil sheet 31 and the second surface in contact with the second metal foil sheet 32. This will make it easier to achieve both sufficient thickness accuracy and high adhesion.

[0052] As described above, the absolute value of the difference between the ten-point average roughness (Rzjis) of one surface 401 of the insulating layer 2 in contact with the first metal foil sheet 31 and the ten-point average roughness (Rzjis) of the other surface 402 of the insulating layer 2 in contact with the second metal foil sheet 32 is equal to or less than 0.35 μm. Therefore, the absolute value of the difference between the ten-point average roughness (Rzjis) of the surface of the insulating film 6 in contact with the first metal foil sheet 31 and the ten-point average roughness (Rzjis) of the surface of the insulating film 6 in contact with the second metal foil sheet 32 is preferably equal to or less than 0.35 μm. The absolute value of this difference is more preferably equal to or less than 0.25 μm, and even more preferably equal to or less than 0.15 μm. The surface of the insulating film 6 in contact with the first metal foil sheet 31 and the surface of the insulating film 6 in contact with the second metal foil sheet 32 preferably have the same ten-point average roughness (Rzjis). This makes it easier to achieve the advantages described above.

[0053] The absolute value of the difference in arithmetic mean roughness (Ra) between the surface of the insulating film 6 in contact with the first metal foil sheet 31 and the surface of the insulating film 6 in contact with the second metal foil sheet 32 is preferably equal to or less than 0.025 μm. The absolute value of this difference is more preferably equal to or less than 0.015 μm, and even more preferably equal to or less than 0.005 μm. The surface of the insulating film 6 in contact with the first metal foil sheet 31 and the surface of the insulating film 6 in contact with the second metal foil sheet 32 preferably have the same arithmetic mean roughness (Ra).

[0054] Note that the values of the ten-point average roughness (Rzjis) and the arithmetic average roughness (Ra) are obtained based on the results of measuring the surface shape of the insulating film 6 by, for example, a confocal laser scanning microscope.

[0055] The surface of the insulating film 6 stacked on the first metal foil sheet 31 among the plurality of insulating films 6 in contact with the first metal foil sheet 31 and the surface of another insulating film 6 stacked on the second metal foil sheet 32 among the plurality of insulating films 6 in contact with the second metal foil sheet 32 are preferably both the first surface 601 or the second surface 602. This makes it easier to reduce the absolute value of the difference between the roughness of the surface 401 of the insulating layer 2 in contact with the first metal foil sheet 31 and the roughness of the surface 402 of the insulating layer 2 in contact with the second metal foil sheet 32.

[0056] In the metal-clad laminate 1 manufactured according to the first embodiment, the peel strength of the metal foil sheet 3 with respect to the insulating layer 2 is preferably equal to or greater than 0.60 N / mm. The metal foil sheet 3 more preferably has a peel strength equal to or greater than 0.8 N / mm, even more preferably has a peel strength equal to or greater than 0.9 N / mm, and particularly preferably has a peel strength equal to or greater than 1.0 N / mm.

[0057] Next, a metal-clad laminate 1 according to a second embodiment will be described. Figure 2 As shown, the metal-clad laminate 1 includes an insulating layer 2 and at least one metal foil sheet 3 stacked on the insulating layer 2. The metal-clad laminate 1 may include two metal foil sheets 3. In this case, Figure 2 As shown, two metal foil sheets 3 are stacked on one surface 401 and the opposite surface 402 of the insulating layer 2, respectively. In the following description, one of the two metal foil sheets 3 will be referred to as "first metal foil sheet 31," and the other metal foil sheet 3 will be referred to as "second metal foil sheet 32." That is, the first metal foil sheet 31, the insulating layer 2, and the second metal foil sheet 32 are stacked one on top of another in this order.

[0058] The insulating layer 2 includes a plurality of resin layers 4 stacked on top of each other. In other words, the insulating layer 2 is formed by stacking a plurality of resin layers 40 on top of each other. Each resin layer 4 can be made of, for example, a flexible thermoplastic resin. For example, each resin layer 4 can contain at least one resin selected from the group consisting of a liquid crystal polymer, a polyimide resin, a polyethylene terephthalate resin, and a polyethylene naphthalate resin. Each resin layer 40 preferably contains a liquid crystal polymer. The thickness of the insulating layer 2 is equal to or greater than 100 μm and equal to or less than 300 μm. In addition, the peel strength of the metal foil sheet 3 relative to the insulating layer 2 is equal to or greater than 0.60 N / mm.

[0059] According to this embodiment, insulating layer 2 is composed of multiple resin layers 4, making it easier to increase the thickness of insulating layer 2. In a printed wiring board formed from metal-clad laminate 1, thickening insulating layer 2 can reduce the possibility of transmission loss caused by electrostatic capacitance and leakage resistance between various portions of the conductor line. These electrostatic capacitance and leakage resistance become increasingly significant as the signal transmission rate and frequency increase. Furthermore, as described above, composing insulating layer 2 from multiple resin layers 4 and setting the peel strength of metal foil sheet 3 to 0.60 N / mm or greater also reduces the possibility of performance degradation of metal-clad laminate 1.

[0060] The metal-clad laminate 1 can be used to transmit radio frequency signals. For example, the metal-clad laminate 1 can be used to manufacture printed circuit boards. In addition, the metal-clad laminate 1 can also be used to manufacture flat cables.

[0061] The configuration of the insulating layer 2 in the metal-clad laminate 1 will be described in more detail below.

[0062] As described above, the thickness of the insulating layer 2 is equal to or greater than 100 μm and equal to or less than 300 μm. Making the thickness of the insulating layer 2 equal to or greater than 100 μm increases the likelihood that the metal-clad laminate 1 will exhibit good radio frequency characteristics. Furthermore, making the thickness of the insulating layer 2 equal to or less than 300 μm makes it easier to manufacture the metal-clad laminate 1 with good stability through hot press molding, and enables the metal-clad laminate 1 to exhibit stable characteristics. The insulating layer 2 more preferably has a thickness equal to or greater than 100 μm and equal to or less than 250 μm, and even more preferably has a thickness equal to or greater than 100 μm and equal to or less than 200 μm.

[0063] As described above, the insulating layer 2 includes a plurality of resin layers 4 stacked one on top of the other. As described above, each resin layer 4 preferably contains a liquid crystal polymer. Examples of liquid crystal polymers include polycondensates of ethylene terephthalate and p-hydroxybenzoic acid, polycondensates of phenol, phthalic acid, and p-hydroxybenzoic acid, and polycondensates of 2,6-hydroxynaphthoic acid and p-hydroxybenzoic acid. The liquid crystal polymer can be selected from commercially available products. Specific examples of liquid crystal polymers include Vecstar CTQ and Vecstar CTZ manufactured by Kuraray Co., Ltd.

[0064] The thickness of each of the plurality of resin layers 4 is preferably equal to or greater than 45 μm and equal to or less than 120 μm. In this case, each resin layer 4 can be formed from an insulating film 6 having a thickness equal to or greater than 45 μm and equal to or less than 120 μm. An insulating film 6 having such a thickness can be easily manufactured and therefore readily available, and generally has high uniformity. This increases the likelihood that the insulating layer 2 will have high uniformity. The thickness is more preferably equal to or greater than 50 μm and equal to or less than 100 μm.

[0065] The number of resin layers 4 included in the insulating layer 2 is determined according to the thickness of the insulating layer 2 and the thickness of each of the resin layers 4 , and may be, for example, equal to or greater than two and equal to or less than four.

[0066] The plurality of resin layers 4 forming the insulating layer 2 preferably include at least two resin layers 4 having thicknesses different from each other. Figure 2 In the embodiment, the resin layer 4 includes a first resin layer 41 and a second resin layer 42 which is directly laminated in contact with the first resin layer 41 and has a greater thickness than the first resin layer 41. The metal-clad laminate 1 generally tends to have a thickness variation at the end edge portions in the width direction. Therefore, generally, as Figure 2 As shown, the metal-clad laminate 1 tends to have a gradually decreasing thickness at its end edge portions. Nevertheless, compared to an insulating layer 2 formed by using only resin layers 4 each having the same thickness, an insulating layer 2 comprising at least two resin layers 4 of different thicknesses is less likely to have a thickness variation at its end edge portions. Comparing an insulating layer 2 comprising multiple resin layers 4 of different thicknesses with an insulating layer 2 comprising multiple resin layers 4 of the same thickness, assuming that the two insulating layers 2 have the same thickness, the former insulating layer 2 is less likely to have a thickness variation. This is because at each end edge portion of an insulating layer 2 comprising multiple (e.g., two) resin layers 4 of different thicknesses, the other thicker resin layer in the resin layer 4 is less likely to deform compared to the thinner resin layer in the resin layer 4. This reduces the possibility of thickness deviation at the end edge portions in the width direction of the metal-clad laminate 1, thereby making it easier for the metal-clad laminate 1 to have an increased dimension W2 (i.e., effective width) in the portion that can be used as a product. In addition, this can also reduce the possibility of inconvenience caused by deformation of the metal-clad laminate 1 (such as uneven and curved waveforms formed at its end edge portions). As used herein, the “width direction” with respect to the metal-clad laminate 1 and the “width direction” with respect to the insulating layer 2 are both perpendicular to the thickness direction and the longitudinal direction with respect to the insulating layer 2. In addition, if the metal-clad laminate 1 is manufactured by a continuous process, the “width direction” is both perpendicular to the thickness direction with respect to the insulating layer 2 and the direction in which the metal-clad laminate 1 is conveyed during the manufacturing process of the metal-clad laminate 1.

[0067] The plurality of resin layers 4 particularly preferably include at least two resin layers 4 having a thickness difference of 25 μm or more and 100 μm or less. Figure 2 In the example shown, the thickness of the second resin layer 42 is preferably greater than the thickness of the first resin layer 41 by a difference of 25 μm or more and 100 μm or less. This thickness difference is more preferably 25 μm or more and 75 μm or less, and even more preferably 25 μm or more and 50 μm or less.

[0068] The dimension W1 of the insulating layer 2, measured in the width direction, is preferably equal to or greater than 500 mm and equal to or less than 570 mm. In particular, when the metal-clad laminate 1 is manufactured by hot press molding at a temperature near the melting point of the resin layer 4, a dimension W1 measured in the width direction of 500 mm or greater and equal to or less than 570 mm makes it easier to shift any end edge portions of the insulating layer 2 where the thickness in the width direction has changed toward the outer edges. This makes it easier to locate such thickness-varying portions outside the portion of the metal-clad laminate 1 that is actually used as a product. Furthermore, this makes it easier to manufacture products conforming to the standard width of 250 mm by cutting the metal-clad laminate 1.

[0069] The metal-clad laminate 1 can be wound into a roll. This enables the metal-clad laminate 1 to be used, for example, to manufacture a printed wiring board by unwinding the roll of the metal-clad laminate 1.

[0070] The thickness accuracy of the metal-clad laminate 1 is preferably less than ±10%. That is, the absolute value of the difference between the average thickness and the maximum thickness of the metal-clad laminate 1 is preferably less than 10% of the average thickness, and the absolute value of the difference between the average thickness and the minimum thickness of the metal-clad laminate 1 is also preferably less than 10% of the average thickness. The average thickness, maximum thickness and minimum thickness of the metal-clad laminate 1 are determined in the following manner. Specifically, the thickness of each of the six parts of the metal-clad laminate 1 arranged at equal intervals in the width direction is measured with a micrometer. The six parts consist of two end edge parts of the metal-clad laminate 1 and four parts located between the two end edge parts. The average value of the six measurement values thus obtained can be regarded as the average thickness. The maximum value of the six measurement values is defined as the maximum thickness, and the minimum value therein is defined as the minimum thickness. The thickness accuracy is more preferably equal to or less than ±7%.

[0071] If the thickness of the metal-clad laminate 1 at both end edge portions in the width direction varies, the above-mentioned thickness accuracy can be achieved by cutting off the end edge portions. As described above, the present embodiment makes it easier to move any end edge portion of the metal-clad laminate 1 where the thickness of the insulating layer 2 in the width direction has varied toward the outer edge. This makes it easier to increase the dimension measured in the width direction (i.e., the effective width) of this portion of the metal-clad laminate 1 that can be used as a product. In other words, this makes it easier to reduce the width of the end edge portion of the metal-clad laminate 1 where the thickness varies. Therefore, the above-mentioned thickness accuracy is achieved by cutting off the portion with the reduced width from the metal-clad laminate 1.

[0072] Furthermore, as described above, the peel strength of the metal foil sheet 3 relative to the insulating layer 2 in the metal-clad laminate 1 is equal to or greater than 0.60 N / mm. This enables the metal-clad laminate 1 to exhibit stable performance. The peel strength of the metal foil sheet 3 is more preferably equal to or greater than 0.8 N / mm, even more preferably equal to or greater than 0.9 N / mm, and particularly preferably equal to or greater than 1.0 N / mm. Note that the peel strength of the metal foil sheet 3 is the average value of the peel strengths of the metal foil sheet 3 measured at eight points on the metal-clad laminate 1 using a 90-degree peeling method and an autograph.

[0073] The metal-clad laminate 1 according to the second embodiment can be manufactured by the manufacturing method according to the first embodiment. Alternatively, the metal-clad laminate 1 according to the second embodiment can also be manufactured by any method other than the manufacturing method according to the first embodiment.

[0074] A printed wiring board such as a flexible printed wiring board can be formed by each of the metal-clad laminate 1 manufactured by the manufacturing method according to the first embodiment and the metal-clad laminate 1 according to the second embodiment. For example, a printed wiring board can be manufactured by patterning the metal foil sheet 3 of the metal-clad laminate 1 into the shape of a conductor circuit by photolithography or any other suitable method. In addition, a multilayer printed wiring board can also be manufactured by stacking a plurality of such printed wiring boards on each other by a known method. Alternatively, a rigid-flexible (flex-rigid) multilayer printed wiring board can also be manufactured by partially stacking a plurality of printed wiring boards on each other by a known method. In addition, a flat cable can also be formed by each of the metal-clad laminate 1 manufactured by the manufacturing method according to the first embodiment and the metal-clad laminate 1 according to the second embodiment.

[0075] Example

[0076] Next, more specific examples of the first embodiment and the second embodiment will be described. Note that the following are merely examples of the first embodiment and the second embodiment and should not be construed as limitative.

[0077] 1. Production of Metal-Clad Laminates

[0078] Materials for metal-clad laminates are provided as shown in Tables 1 and 2 below. Note that CTQ in the "Material Type" column for the first, second, third, and fourth insulating films refers to Vecstar CTQ manufactured by Kuraray Co., Ltd. The first surface of each of the first, second, third, and fourth insulating films has a ten-point average roughness (Rzjis) of 2.3 μm and an arithmetic average roughness (Ra) of 0.30 μm. Its second surface has a ten-point average roughness (Rzjis) of 2.7 μm and an arithmetic average roughness (Ra) of 0.33 μm. In addition, TP4-S in the "Material Type" column for the first and second metal foil sheets refers to a copper foil sheet (product number TP4-S) manufactured by Fukuda Metal Foil & Powder Co., Ltd. The difference in size measured in the width direction between the first and second insulating films is shown in Tables 1 and 2.

[0079] In the first to ninth embodiments and the first to eighth comparative examples, the hot press forming process is performed by hot press forming a laminated body in which a first metal foil sheet, a first insulating film, a second insulating film, and a second metal foil sheet are sequentially stacked on each other. In the tenth embodiment, the hot press forming process is performed by hot press forming a laminated body in which a first metal foil sheet, a first insulating film, a second insulating film, and a third insulating film are sequentially stacked on each other. In the eleventh embodiment, the hot press forming process is performed by hot press forming a laminated body in which a first metal foil sheet, a fourth insulating film, a first insulating film, a second insulating film, and a third insulating film are sequentially stacked on each other. The hot press forming method, maximum heating temperature, pressing pressure, and heating and pressing time in each embodiment and comparative example are also shown in Tables 1 and 2 below. In addition, Tables 1 and 2 below also show whether the surface of the first insulating film in contact with the first metal foil sheet is the first surface or the second surface, and whether the surface of the second insulating film in contact with the second metal foil sheet is the first surface or the second surface.

[0080] 2. Evaluation test

[0081] The metal-clad laminate was subjected to the following evaluation tests. The results are summarized in Tables 1 and 2 below.

[0082] 2.1. Effective width

[0083] The thickness of the metal-clad laminate is measured with a micrometer while the measuring section is moved in the width direction, thereby examining the thickness variation of the metal-clad laminate in the width direction. The effective width is defined as the dimension of the portion of the metal-clad laminate that has a thickness variation within ±10% and includes the center portion. As used herein, "thickness variation" refers to the ratio of the thickness measured at non-center portions to the thickness measured at the center portion. The thickness variation is calculated as the average of the thicknesses measured at the six non-center portions.

[0084] 2.2. Thickness accuracy

[0085] In a metal-clad laminate, the thickness of each of six locations, each with a thickness variation within ±10%, is measured using a micrometer. These six locations, including the center of the metal-clad laminate and spaced evenly across the width of the laminate, include both end edges and four locations located between them. The average of the six measured values is defined as the average thickness, the maximum value of the six measured values is defined as the maximum thickness, and the minimum value of the six measured values is defined as the minimum thickness. Thickness accuracy is calculated based on these measurement results.

[0086] 2.3. Peel strength

[0087] A metal foil sheet of a metal-clad laminate was etched to form a linear wiring pattern measuring 1 mm x 200 mm. The peel strength of this wiring pattern relative to the insulating layer was measured using the 90-degree peel method. This measurement was repeated eight times in the same manner, and the arithmetic mean of the results was calculated. Regarding Example 6, the measured values varied significantly, with the majority being approximately 0.9 N / mm and 1.9 N / mm, resulting in an evaluation of "0.9-1.9."

[0088] Membrane interface

[0089] The metal-clad laminate was cut and the cross section of the insulating layer was observed using an optical microscope to determine whether any interface was identified between two adjacent resin layers in the insulating layer. If any interface was identified, the answer was "yes." If no interface was identified, the answer was "no."

[0090] 2.5. Dimensional stability during the etching process

[0091] The dimensional stability of the metal-clad laminate during the etching process was evaluated in the following manner according to IPC-TM650 2.2.4. Specifically, a test sample having a size of 250 mm × 250 mm in a plan view was formed by cutting the metal-clad laminate. For dimensional measurement, four holes were opened through this test sample. The spacing between these holes of the test sample in the width direction and in the conveying direction was measured. Subsequently, the metal foil sheet of the test sample was completely removed by an etching process to obtain an unclad plate. The spacing between the holes of the unclad plate in the width direction and in the conveying direction was measured. Based on these results, the rate of change of the dimensions measured in the width direction and the dimensions measured in the conveying direction was calculated.

[0092] 2.6. Dimensional stability during heat treatment

[0093] A test sample was formed as described in "2.5. Dimensional Stability During Etching Process." The spacing between the holes of this test sample in the width direction and in the transport direction was measured. Subsequently, the test sample was heated under conditions including a heating temperature of 150°C and a heating time of 30 minutes. Next, the spacing between the test sample in the width direction and in the transport direction was measured. Based on these results, the rate of change of the dimension measured in the width direction and the dimension measured in the transport direction was calculated.

[0094]

[0095]

[0096]

[0097]

Claims

1. A method for manufacturing a metal-clad laminate, the method comprising: continuously supplying a first metal foil sheet, a plurality of insulating films, and a second metal foil sheet different from the first metal foil sheet between two endless belts; as well as The first metal foil sheet, the plurality of insulating films, and the second metal foil sheet are sequentially stacked on one another between the endless belts, and the first metal foil sheet, the plurality of insulating films, and the second metal foil sheet are heat-pressed together to form an insulating layer from the plurality of insulating films. Each of the plurality of insulating films has a first surface and a second surface opposite to the first surface, the second surface having a larger ten-point average roughness Rzjis than the first surface, The absolute value of the difference between the ten-point average roughness Rzjis of the surface of the insulating layer in contact with the first metal foil sheet and the ten-point average roughness Rzjis of the other surface of the insulating layer in contact with the second metal foil sheet is equal to or less than 0.35 μm, The surface of the insulating film stacked on the first metal foil sheet among the plurality of insulating films in contact with the first metal foil sheet and the surface of another insulating film stacked on the second metal foil sheet among the plurality of insulating films in contact with the second metal foil sheet are both the first surface or the second surface. a sum of respective thicknesses of the plurality of insulating films is equal to or greater than 100 μm and equal to or less than 300 μm, The insulating films each contain a liquid crystal polymer, and The liquid crystal polymer is selected from the group consisting of a condensation polymer of ethylene terephthalate and p-hydroxybenzoic acid, a condensation polymer of phenol, phthalic acid and p-hydroxybenzoic acid, and a condensation polymer of 2,6-hydroxynaphthoic acid and p-hydroxybenzoic acid.

2. The method of claim 1, wherein An absolute value of a difference between an arithmetic mean roughness Ra of a surface of the insulating layer in contact with the first metal foil sheet and an arithmetic mean roughness Ra of another surface of the insulating layer in contact with the second metal foil sheet is equal to or smaller than 0.025 μm.

3. The method of claim 1 or 2, wherein The plurality of insulating films include: at least a first insulating film; and a second insulating film having a larger thickness than that of the first insulating film, A dimension of the first insulating film measured in the width direction is smaller than a dimension of the second insulating film measured in the width direction, The width direction with respect to the first insulating film is perpendicular to both a direction in which the first insulating film is transported and a thickness direction with respect to the first insulating film, and The width direction with respect to the second insulating film is perpendicular to both a direction in which the second insulating film is transported and a thickness direction with respect to the second insulating film.

4. The method of claim 3, wherein A difference between a dimension of the first insulating film measured in the width direction and a dimension of the second insulating film measured in the width direction is equal to or greater than 10 mm and equal to or less than 30 mm.

5. A metal-clad laminate manufactured according to the method of claim 1, comprising: Insulation layer; and a first metal foil sheet and a second metal foil sheet stacked on the insulating layer, The insulating layer includes a plurality of resin layers, The peel strength of the first metal foil sheet or the second metal foil sheet relative to the insulating layer is equal to or greater than 0.60 N / mm.

6. The metal-clad laminate according to claim 5, wherein The thickness accuracy of the metal-clad laminate is less than ±10%.

7. The metal-clad laminate according to claim 5 or 6, wherein The thickness of each of the plurality of resin layers is equal to or greater than 45 μm and equal to or less than 120 μm.

8. The metal-clad laminate according to claim 5 or 6, wherein The plurality of resin layers include at least two resin layers having thicknesses different from each other.

9. The metal-clad laminate according to claim 5 or 6, wherein The dimension of the insulating layer measured in the width direction is equal to or greater than 500 mm and equal to or less than 570 mm, and The width direction with respect to the insulating layer is perpendicular to both a thickness direction and a longitudinal direction with respect to the insulating layer.

10. The metal-clad laminate according to claim 5 or 6, wherein The metal-clad laminate is wound into a roll.

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