Wiring circuit board

Abstract

To provide a wiring circuit board in which a first metal thin film can be easily formed and the resistance between a conductor layer and a metal support substrate can be lowered.SOLUTION: A wiring circuit board 1 includes a metal support substrate 2, a first metal thin film 3, an insulating layer 4, a second metal thin film 5, and a conductor layer 6. The first metal thin film 3 is arranged on one side of the metal support substrate 2 in the thickness direction. The insulating layer 4 is arranged on one side of the first metal thin film 3 in the thickness direction and has a through hole 41 penetrating in the thickness direction. The second metal thin film 5 is arranged on one side of the insulating layer 4 in the thickness direction. The conductor layer 6 is arranged on one side of the second metal thin film 5. Inside the through hole 41, the first metal thin film 3 and the second metal thin film 5 are arranged between the metal support substrate 2 and the conductor layer 6, the other surface of the first metal thin film 3 is in contact with one surface of the metal support substrate 2, and the other surface of the second metal thin film 5 is in contact with one surface of the first metal thin film 3. The other surface of the conductor layer 6 is in contact with one surface of the second metal thin film 5. At least the first metal thin film 3 is an alloy containing chromium.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a wiring circuit board. 【Background Art】 【0002】 A wiring circuit board including a metal support substrate, a first metal thin film, an insulating layer, a second metal thin film, and a ground layer is known (for example, see Patent Document 1 below). 【0003】 In the wiring circuit board described in Patent Document 1, the first metal thin film is disposed on the upper surface of the metal support substrate. The insulating layer is disposed on the upper surface of the first metal thin film. The first metal thin film and the insulating layer commonly have an opening penetrating in the thickness direction. Note that the opening of the first metal thin film is formed by removing the first metal thin film exposed from the opening of the insulating layer. 【0004】 The second metal thin film and the ground layer are disposed in the above-described opening, and in the opening, they are electrically connected to the metal support substrate via the second metal thin film. 【Prior Art Documents】 【Patent Documents】 【0005】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2022-30666 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0006】 In forming the first metal thin film of the wiring circuit board described in Patent Document 1, it is necessary to remove the portion exposed from the opening of the insulating layer. Therefore, forming the first metal thin film is laborious. 【0007】 【0008】 Therefore, in order to simply form the first metal thin film, attempts are made to leave the above-described portion in the opening without removing it.In the above attempt, when the insulating layer is formed by photolithography after the first metal thin film has been formed, the first metal thin film is heated together with the insulating layer after exposure. As a result, the first metal thin film exposed through the openings in the insulating layer is exposed to the atmosphere and oxidized. If the first metal thin film is pure chromium, the oxidation described above significantly increases the resistance of the first metal thin film. This results in the problem that the resistance between the ground layer and the metal support substrate cannot be reduced. 【0009】 The present invention provides a wiring circuit board that allows for the easy formation of a first metal thin film while maintaining low resistance between the conductor layer and the metal support substrate, even when the first and second metal thin films are interposed between the conductor layer and the metal support substrate. [Means for solving the problem] 【0010】 The present invention [1] includes a wiring circuit board comprising: a metal support substrate; a first metal thin film disposed on one side of the metal support substrate in the thickness direction; an insulating layer disposed on one side of the first metal thin film in the thickness direction, the insulating layer having through holes penetrating in the thickness direction; a second metal thin film disposed on one side of the insulating layer; and a conductor layer disposed on one side of the second metal thin film, wherein within the through holes, the first metal thin film and the second metal thin film are disposed between the metal support substrate and the conductor layer, the other side of the first metal thin film is in contact with one side of the metal support substrate, the other side of the second metal thin film is in contact with one side of the first metal thin film, and the other side of the conductor layer is in contact with one side of the second metal thin film, and at least the material of the first metal thin film is a chromium-containing alloy. 【0011】 According to this wiring circuit board, the first and second metal thin films are positioned between the metal support substrate and the conductor layer within the through-hole, thus eliminating the need to remove the first metal thin film and allowing for easy formation of the first metal thin film. 【0012】 Furthermore, in this wiring circuit board, since the material of the first metal thin film is a chromium-containing alloy, the resistance between the conductor layer and the metal support substrate can be kept low even when the first and second metal thin films are interposed between the conductor layer and the metal support substrate. 【0013】 The present invention [2] includes the wiring circuit board described in [1], wherein the chromium content in the alloy is 50% by mass or less. 【0014】 The present invention [3] includes a wiring circuit board according to [1] or [2], wherein the alloy further contains at least one metal selected from the group consisting of nickel, titanium, tungsten, and molybdenum. 【0015】 The present invention [4] includes a wiring circuit board according to [1] or [2], wherein the material of the second metal thin film is a second alloy containing chromium. 【0016】 In this wiring circuit board, the material of the second metal thin film is a second alloy containing chromium, which further reduces the resistance between the conductor layer and the metal support substrate. 【0017】 The present invention [5] includes the wiring circuit board described in [4], wherein the chromium content in the second alloy is 50% by mass or less. 【0018】 The present invention [6] includes the wiring circuit board described in [4], wherein the alloy further comprises at least one metal selected from the group consisting of nickel, titanium, tungsten, and molybdenum. 【0019】 The present invention [7] includes the wiring circuit board described in [4], wherein the alloy and the second alloy have the same composition. 【0020】 In this wiring circuit board, since the alloy of the first metal thin film and the second alloy of the second metal thin film have the same composition, the first metal thin film and the second metal thin film can be efficiently formed by a common device. Further, the first metal thin film and the second metal thin film can be efficiently patterned using the same type of etching solution. 【0021】 The present invention [8] includes the wiring circuit board according to [1] or [2], wherein the first metal thin film includes a first metal layer and a first oxide layer disposed on one surface of the first metal layer in the thickness direction. 【0022】 Since the first metal thin film includes a first oxide layer, the resistance of the first metal thin film tends to increase. 【0023】 However, in this wiring circuit board, since the material of the first metal thin film is an alloy containing chromium, the resistance between the conductor layer and the metal support substrate can be reduced. 【0024】 The present invention [9] includes the wiring circuit board according to [1] or [2], wherein the metal support substrate includes a metal support layer and a surface metal layer disposed on one surface of the metal support layer in the thickness direction, and the surface metal layer has a higher conductivity than the metal support layer. 【0025】 In this wiring circuit board, since the metal support substrate includes a surface metal layer having a higher conductivity than the metal support layer, the resistance between the conductor layer and the metal support layer can be further reduced. 【Advantages of the Invention】 【0026】 The wiring circuit board of the present invention can easily form the first metal thin film, and even if the first metal thin film and the second metal thin film are interposed between the conductor layer and the metal support substrate, the resistance between the conductor layer and the metal support substrate can be reduced. 【Brief Description of the Drawings】 【0027】 [Figure 1] It is a cross-sectional view of an embodiment of the wiring circuit board of the present invention. [Figure 2]Figure 1 is a process diagram for the wiring circuit board shown. Figure 2A shows the process of forming the first metal thin film. Figure 2B shows the process of forming the insulating layer. Figure 2C shows the process of forming the second metal thin film. Figure 2D shows the process of forming the conductor layer. Figure 2E shows the process of forming the cover insulating layer. [Figure 3] This is a cross-sectional view of the wiring circuit board of the first modified example. [Modes for carrying out the invention] 【0028】 1. One embodiment of the wiring circuit board of the present invention An embodiment of the wiring circuit board of the present invention will be described with reference to Figure 1. 【0029】 As shown in Figure 1, the wiring circuit board 1 has thickness. The wiring circuit board 1 has a sheet shape. The wiring circuit board 1 extends in the planar direction. The planar direction is perpendicular to the thickness direction. The wiring circuit board 1 comprises a metal support substrate 2, a first metal thin film 3, an insulating layer 4, a second metal thin film 5, and a conductor layer 6. The wiring circuit board 1 also comprises a cover insulating layer 7. 【0030】 2. Metal support substrate 2 The metal support substrate 2 is positioned at the other end of the wiring circuit board 1 in the thickness direction. The metal support substrate 2 extends in the plane direction. In this embodiment, the metal support substrate 2 comprises only the metal support layer 21. The metal support layer 21 forms the other surface of the wiring circuit board 1 in the thickness direction. Examples of materials for the metal support layer 21 include iron, stainless steel, copper, and copper alloys, with stainless steel and copper alloys being preferred. The thickness of the metal support layer 21 is, for example, 1 μm or more, preferably 10 μm or more, and also, for example, 1000 μm or less, preferably 500 μm or less. 【0031】 3. First metal thin film 3 The first metal thin film 3 is positioned on one side of the metal support substrate 2 in the thickness direction. The other side of the first metal thin film 3 in the thickness direction is in contact with the other side of the metal support substrate 2 in the thickness direction. Specifically, the other side of the first metal thin film 3 in the thickness direction is in contact with one side of the metal support layer 21 in the thickness direction. Preferably, the first metal thin film 3 is in contact with the entire surface of one side of the metal support layer 21 in the thickness direction. The first metal thin film 3 extends in the plane direction. The material of the first metal thin film 3 is an alloy. The alloy contains chromium. In addition to chromium, the alloy contains at least one metal selected from the group consisting of, for example, nickel, titanium, tungsten, and molybdenum. By the alloy containing the above-mentioned at least one metal, the first metal thin film 3 can suppress increased resistance even when oxidized. Preferably, the metals are nickel and titanium. Preferably, the alloys are CrTi alloys and NiCr alloys. 【0032】 The chromium content in the alloy is, for example, 90% by mass or less, preferably 50% by mass or less, more preferably 30% by mass or less, and also, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more. 【0033】 If the chromium content in the alloy is below the upper limit mentioned above, the resistance of the first metal thin film 3 can be reduced, and more specifically, the increase in the resistance of the first metal thin film 3 due to the presence of the first oxide layer 32 can be suppressed. As a result, the resistance between the conductor layer 6 and the metal support substrate 2, which will be described later, can be further reduced. 【0034】 Adhesion to the insulating layer 4 can be ensured if the chromium content in the alloy is above the lower limit mentioned above. The chromium content in the alloy can be determined by TEM-EDX (energy-dispersive X-ray spectroscopy). 【0035】 The metal content in an alloy, excluding chromium, is the remainder of the chromium content as described above. The metal content in an alloy is determined by TEM-EDX. 【0036】 3.1 First metal layer 31 The first metal thin film 3 comprises a first metal layer 31 and a first oxide layer 32. The first metal layer 31 is located at the other end of the first metal thin film 3 in the thickness direction. The first metal layer 31 extends in the plane direction. The first metal layer 31 is in contact with the entire surface of one side of the metal support substrate 2 in the thickness direction. The material of the first metal thin film 3 is the alloy described above. The thickness of the first metal layer 31 is, for example, 1 nm or more, preferably 10 nm or more, and also, for example, 500 nm or less, preferably 250 nm or less. 【0037】 3.2 First Oxide Layer 32 The first oxide layer 32 is positioned at one end of the first metal thin film 3 in the thickness direction. The first oxide layer 32 is positioned on one side of the first metal layer 31 in the thickness direction. In other words, the first oxide layer 32 is in contact with the entire surface of one side of the first metal layer 31 in the thickness direction. The first oxide layer 32 is formed by heating (post-exposure heating) in the manufacturing of the insulating layer 4, which will be described later. The material of the first oxide layer 32 is a composite oxide of the alloy described above. The thickness of the first oxide layer 32 is, for example, 0.5 nm or more, preferably 1 nm or more, and also, for example, 20 nm or less, preferably 10 nm or less. The ratio of the thickness of the first oxide layer 32 to the thickness of the first metal layer 31 is, for example, 0.001 or more, preferably 0.002 or more, and also, for example, 1 or less, preferably 0.5 or less. The boundary between the first metal layer 31 and the first oxide layer 32 is shown by a dashed line, as shown in the enlarged view of Figure 1, but it is acceptable if the boundary is not clearly visible. The presence of the first oxide layer 32 is determined by TEM-EDX. 【0038】 The thickness of the first metal thin film 3 is, for example, 1 nm or more, preferably 10 nm or more, and also, for example, 500 nm or less, preferably 250 nm or less. 【0039】 4. Insulating layer 4 The insulating layer 4 is located on one side of the first metal thin film 3 in the thickness direction. The insulating layer 4 is in contact with one side of the first metal thin film 3 in the thickness direction. The insulating layer 4 is located on one side of the first oxide layer 32 in the thickness direction and is in contact with one side of the first oxide layer 32. The insulating layer 4 extends in the plane direction. The insulating layer 4 is a base insulating layer. 【0040】 The insulating layer 4 has through holes 41. The through holes 41 penetrate the insulating layer 4 in the thickness direction. In this embodiment, the through holes 41 have a substantially tapered cross-sectional shape, with the opening cross-sectional area increasing toward one side in the thickness direction. The through holes 41 are demarcated by the inner circumferential surface 42 of the insulating layer 4. Examples of materials for the insulating layer 4 include insulating resins. Examples of insulating resins include polyimide. The thickness of the insulating layer 4 is, for example, 1 μm or more, preferably 5 μm or more, and also, for example, 100 μm or less, preferably 50 μm or less. 【0041】 5. Second metal thin film 5 The second metal thin film 5 is positioned on one side of the insulating layer 4. Specifically, the second metal thin film 5 is in contact with one side of the insulating layer 4 in the thickness direction and with the inner circumferential surface 42 of the insulating layer 4. Furthermore, within the through hole 41, the second metal thin film 5 is positioned on one side of the first metal thin film 3 in the thickness direction. Specifically, the other side of the second metal thin film 5 in the thickness direction is in contact with one side of the first metal thin film 3 in the thickness direction within the through hole 41. The second metal thin film 5 in contact with the insulating layer 4 and the second metal thin film 5 in contact with the first metal thin film 3 are continuous. 【0042】 The material of the second metal thin film 5 is, for example, a second alloy. The second alloy contains chromium. In addition to chromium, the second alloy contains at least one metal selected from the group consisting of, for example, nickel, titanium, tungsten, and molybdenum. By containing at least one of the above-mentioned metals in the second alloy, the increase in resistance of the second metal thin film 5 can be suppressed even if the second metal thin film 5 oxidizes. Preferably, the metals are nickel and titanium. Preferably, the second alloy of the second metal thin film 5 and the alloy of the first metal thin film 3 have the same composition. 【0043】 If the second alloy of the second metal thin film 5 and the alloy of the first metal thin film 3 have the same composition, then the first metal thin film 3 and the second metal thin film 5 can be efficiently formed using the same equipment. Furthermore, the first metal thin film 3 and the second metal thin film 5 can be efficiently patterned using the same type of etching solution. 【0044】 The chromium content in the second alloy is, for example, 90% by mass or less, preferably 50% by mass or less, more preferably 30% by mass or less, and also, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more. 【0045】 If the chromium content in the second alloy is below the upper limit mentioned above, the resistance of the second metal thin film 5 can be reduced, and more specifically, the increase in the resistance of the second metal thin film 5 caused by oxidation can be suppressed. As a result, the resistance between the conductor layer 6 and the metal support substrate 2, which will be described later, can be further reduced. 【0046】 Adhesion to the insulating layer 4 can be ensured if the chromium content in the second alloy is above the lower limit mentioned above. The chromium content in the second alloy is determined by TEM-EDX. 【0047】 If the second alloy of the second metal thin film 5 and the alloy of the first metal thin film 3 have the same composition, then the chromium content in the second alloy and the chromium content in the alloy are the same. 【0048】 The metal content in the second alloy, excluding chromium, is the remainder of the chromium content as described above. The metal content in the second alloy is determined by TEM-EDX. 【0049】 The thickness of the second metal thin film 5 is, for example, 1 nm or more, preferably 10 nm or more, and also, for example, 500 nm or less, preferably 250 nm or less. 【0050】 6. Conductor layer 6 The conductive layer 6 is positioned on one side of the second metal thin film 5. The other side of the conductive layer 6 in the thickness direction is in contact with the one side of the second metal thin film 5 in the thickness direction. As a result, the first metal thin film 3 and the second metal thin film 5 are positioned between the metal support substrate 2 and the conductive layer 6 so as to be in contact with the metal support substrate 2 and the conductive layer 6, respectively, within the through hole 41. In this embodiment, the conductive layer 6 is a ground layer. The conductive layer 6 is grounded to the metal support substrate 2 via the first metal thin film 3 and the second metal thin film 5 within the through hole 41. Examples of materials for the conductive layer 6 include copper, silver, gold, iron, aluminum, chromium, and alloys thereof. Copper is preferred as the material for the conductive layer 6. The thickness of the conductive layer 6 is, for example, 1 μm or more, preferably 3 μm or more, and also, for example, 50 μm or less, preferably 30 μm or less. 【0051】 7. Cover insulation layer 7 The cover insulating layer 7, shown by the dashed line, is positioned at one end of the wiring circuit board 1 in the thickness direction. The cover insulating layer 7 forms one side of the wiring circuit board 1 in the thickness direction. Although not shown, the cover insulating layer 7 is positioned on one side of the insulating layer 4 in the thickness direction. The cover insulating layer 7 covers the conductor layer 6. Examples of materials for the cover insulating layer 7 include insulating resin. Examples of insulating resins include polyimide. The thickness of the cover insulating layer 7 is, for example, 1 μm or more, and for example, 100 μm or less. 【0052】 8. Manufacturing method of the wiring circuit board 1 The manufacturing method of the wiring circuit board 1 will be explained with reference to Figures 2A-2E. 【0053】 As shown in Figure 2A, first, the first metal thin film 3 is placed on one side of the metal support substrate 2 in the thickness direction. For example, the first metal thin film 3 is formed on one side of the metal support substrate 2 by a thin film formation method, preferably a dry process, and more preferably by sputtering. In sputtering, a target made of the alloy described above is used, or chromium and a metal other than chromium (Ti if the alloy is a CrTi alloy, or Ni if the alloy is a NiCr alloy) are used as targets. In this step, the first metal thin film 3 does not yet have a first oxide layer 32 (see Figure 2B), and only has a first metal layer 31. 【0054】 As shown in Figure 2B, the insulating layer 4 is then placed on one side of the first metal thin film 3 in the thickness direction. For example, a varnish containing a photosensitive insulating resin is applied to the entire surface of one side of the first metal thin film 3, and then the insulating layer 4 having through holes 41 is formed by photolithography. When forming the insulating layer 4 by photolithography, the insulating layer 4 is heated after exposure (post-exposure heating). The insulating layer 4 is heated in an atmospheric environment to, for example, 100°C or higher, preferably 150°C or higher, and for example, 500°C or lower. The above heating forms the first oxide layer 32 on one side of the first metal layer 31. 【0055】 As shown in Figure 2C, the second metal thin film 5 is then placed on one side of the insulating layer 4 in the thickness direction, on the inner circumferential surface of the insulating layer 4, and on one side of the first metal thin film 3 within the through hole 41. For example, the second metal thin film 5 is formed on one side of the insulating layer 4 and on one side of the first metal thin film 3 within the through hole 41 by a thin film formation method, preferably a dry process, and more preferably by sputtering. In sputtering, a target made of the second alloy described above is used, or chromium and a metal other than chromium (Ti if the second alloy is a CrTi alloy, or Ni if the second alloy is a NiCr alloy) are used as targets. In this process, the surface of the second metal thin film 5 is not oxidized. 【0056】 As shown in Figure 2D, the conductive layer 6 is then placed on one side of the second metal thin film 5 in the thickness direction. For example, the conductive layer 6 is formed on one side of the second metal thin film 5 in the thickness direction by a conductive pattern formation method, preferably a wet process, more preferably plating, and even more preferably electroplating. In electroplating, for example, current is passed from the metal support substrate 2 through the first metal thin film 3 to the second metal thin film 5. 【0057】 As shown in Figure 2E, the cover insulating layer 7 is then placed on one side of the insulating layer 4 so as to cover the conductive layer 6. For example, a varnish containing a photosensitive insulating resin is applied to the entire surface of one side of both the insulating layer 4 and the conductive layer 6, and then the cover insulating layer 7 is formed by photolithography. When forming the cover insulating layer 7 by photolithography, the cover insulating layer 7 is heated after exposure (post-exposure heating). The cover insulating layer 7 is heated in an atmospheric environment to, for example, 100°C or higher, preferably 150°C or higher, and for example, 500°C or lower. 【0058】 This is how the wiring circuit board 1 is manufactured. 【0059】 9. Effects of one embodiment According to this wiring circuit board 1, the first metal thin film 3 is in contact with the metal support substrate 2 within the through hole 41, so it is not necessary to remove the first metal thin film 3 as described in Patent Document 1, and the first metal thin film 3 can be easily formed. 【0060】 Furthermore, in this wiring circuit board 1, since the material of the first metal thin film 3 is a chromium-containing alloy, even if the first metal thin film 3 and the second metal thin film 5 are interposed between the conductor layer 6 and the metal support substrate 2, the resistance between the conductor layer 6 and the metal support substrate 2 can be kept low. 【0061】 On the other hand, since the first metal thin film 3 includes the first oxide layer 32, the resistance of the first metal thin film 3 tends to increase. 【0062】 However, in this wiring circuit board 1, since the material of the first metal thin film 3 is a chromium-containing alloy, the resistance between the conductor layer 6 and the metal support substrate 2 can be reduced. 【0063】 If the second alloy of the second metal thin film 5 and the alloy of the first metal thin film 3 have the same composition, the first metal thin film 3 and the second metal thin film 5 can be easily formed using the same equipment. Furthermore, the first metal thin film 3 and the second metal thin film 5 can be patterned using the same type of etching solution. 【0064】 10. Variations In the following modifications, the same reference numerals are used for components and processes as in the above-described embodiment, and their detailed descriptions are omitted. Furthermore, the modifications can achieve the same effects and advantages as the first embodiment, unless otherwise specified. Moreover, the first embodiment and its modifications can be combined as appropriate. 【0065】 10.1 First Variation As shown in Figure 3, in the first modified example, the metal support substrate 2 comprises a metal support layer 21 and a surface metal layer 22. 【0066】 The thickness of the metal support layer 21 is, for example, 1 μm or more, preferably 10 μm or more, and also, for example, 1000 μm or less, preferably 500 μm or less. 【0067】 The surface metal layer 22 is positioned at one end of the metal support substrate 2 in the thickness direction. The surface metal layer 22 is positioned on one side of the metal support layer 21 in the thickness direction. The surface metal layer 22 is in contact with one side of the metal support layer 21 in the thickness direction. The surface metal layer 22 is also in contact with the other side of the first metal thin film 3 (first metal layer 31) in the thickness direction. 【0068】 The conductivity of the surface metal layer 22 is higher than that of the metal support layer 21. Examples of materials for the surface metal layer 22 include copper, silver, and gold. These can be used alone or in combination. Copper is preferably used as the material for the surface metal layer 22. 【0069】 The thickness of the surface metal layer 22 is, for example, 0.5 μm or more, preferably 3 μm or more, and also, for example, 10 μm or less. 【0070】 In the first modified wiring circuit board 1, the metal support substrate 2 has a surface metal layer 22 with higher conductivity than the metal support layer 21, so the resistance between the conductor layer 6 and the metal support layer 21 can be further reduced. 【0071】 10.2 Second Variation Although not shown in the diagram, in the second modified example, the material of the second metal thin film 5 is not a second alloy containing chromium, but rather, for example, chromium, nickel, titanium, tungsten, and molybdenum. Specifically, the material of the second metal thin film 5 may be, for example, elemental chromium, elemental nickel, elemental titanium, elemental tungsten, and elemental molybdenum. Alternatively, it may be an alloy containing at least two metals selected from the group consisting of nickel, titanium, tungsten, and molybdenum. 【0072】 10.3 Third Variation Although not shown in the figures, the second metal thin film 5 may have a second metal layer and a second oxide layer disposed on one side of the second metal layer in the thickness direction. [Examples] 【0073】 The present invention will be further described below with reference to test examples. However, the present invention is not limited to these test examples. Furthermore, specific numerical values ​​such as blending ratios (content percentages), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than or equal to") of the blending ratios (content percentages), physical properties, and parameters described in the "Modes for Carrying Out the Invention" section above. 【0074】 Test Example 1 [Manufacturing of a first test circuit board having a first metal thin film 3 that has not undergone oxidation treatment, and DCR measurement] 【0075】 A metal support substrate 2 made of copper, a first metal thin film 3 made of a CrTi alloy with the composition described in Table 1, and a conductive layer 6 made of copper were sequentially formed on one side of a glass plate in the thickness direction. This produced the first test circuit board. The first metal thin film 3 in this first test circuit board has not yet undergone oxidation treatment (described later). In other words, the first metal thin film 3 does not yet have a first oxide layer 32 and only has a first metal layer 31. 【0076】 Subsequently, the DC resistance (DCR) between the metal support substrate 2 and the conductor layer 6 was measured using a digital multimeter. 【0077】 [Manufacturing of a second test circuit board comprising a first metal thin film 3 that has undergone oxidation treatment] A metal support substrate 2 made of copper and a first metal thin film 3 made of a CrTi alloy with the composition described in Table 1 were sequentially formed on one side of a glass plate in the thickness direction. Subsequently, one side of the first metal thin film 3 was oxidized. This formed a first oxide layer 32 on the first metal thin film 3. During oxidation, one side of the first metal thin film 3 was exposed to oxygen plasma. 【0078】 Subsequently, a conductive layer 6 made of copper was formed on one side of the first metal thin film 3. 【0079】 This allowed us to manufacture a second test circuit board. 【0080】 Subsequently, the DC resistance (DCR) between the metal support substrate 2 and the conductor layer 6 was measured using a digital multimeter. 【0081】 Then, the difference in DCR was calculated by subtracting the DCR of the first test circuit board from the DCR of the second test circuit board. The difference in DCR is shown in Table 1. 【0082】 Test Examples 2-5 The first and second test circuit boards were manufactured in the same manner as in Test Example 1, and the difference in DCR was determined. However, the composition of the first metal thin film 3 was changed as shown in Table 1. The difference in DCR is shown in Table 1. 【0083】 Comparative Test Example 1 (First Metal Thin Film 3 consisting of elemental Cr) In the same manner as in Test Example 1, the first and second test circuit boards were manufactured, and the difference in DCR was determined. However, as shown in Table 1, the material of the first metal thin film 3 was changed to pure Cr. The difference in DCR is shown in Table 1. 【0084】 Comparative Test Example 2 (First Metal Thin Film 3 made of pure Ti) The first and second test circuit boards were manufactured in the same manner as in Test Example 1, and the difference in DCR was determined. However, as shown in Table 1, the material of the first metal thin film 3 was changed to pure Ti. The difference in DCR is shown in Table 1. 【0085】 Comparative Test Example 3 (First Metal Thin Film 3 made of elemental Ni) The first and second test circuit boards were manufactured in the same manner as in Test Example 1, and the difference in DCR was determined. However, as shown in Table 1, the material of the first metal thin film 3 was changed to pure Ni. The difference in DCR is shown in Table 1. 【0086】 [Consideration] As can be seen from Table 1, in Test Examples 1 and 2, where the material of the first metal thin film 3 is a CrTi alloy, the difference in DCR is lower compared to Comparative Test Example 1, where the material of the first metal thin film 3 is pure Cr. In other words, even when the first metal thin film 3 has a first oxide layer 32, the increase in the resistance of the first metal thin film 3 can be suppressed. 【0087】 In comparative test example 2, the material of the first metal thin film 3 is pure Ti (Cr content is 0% by mass), while the Ti content is 100% by mass, and the adhesion between the insulating layer 4 and the first metal thin film 3 is evaluated as low. 【0088】 As can be seen from Table 1, in each of the test examples 3-5, where the material of the first metal thin film 3 is a NiCr alloy, the difference in DCR is lower compared to comparative test example 1, where the material of the first metal thin film 3 is pure Cr. In other words, even when the first metal thin film 3 has a first oxide layer 32, the increase in the resistance of the first metal thin film 3 can be suppressed. 【0089】 In comparative test example 3, the material of the first metal thin film 3 is pure Ni (with a Cr content of 0% by mass), and since Ni is magnetic, it is evaluated as unsuitable due to the large high-frequency transmission loss. 【0090】 [Table 1] [Explanation of symbols] 【0091】 1 Wiring circuit board 2. Metal support substrate 3 First metal thin film 4. Insulating layer 5 Second metal thin film 6 Conductor layers 21 Metal support layer 22 Surface metal layer 31 1st metal layer 32 First Oxide Layer 41 Through hole

Claims

[Claim 1] Metal support substrate and A first metal thin film is disposed on one side of the metal support substrate in the thickness direction, An insulating layer disposed on one side of the first metal thin film in the thickness direction, the insulating layer having through holes penetrating in the thickness direction, A second metal thin film is disposed on one side of the insulating layer, The second metal thin film comprises a conductive layer disposed on one side thereof, Within the through-hole, the first metal thin film and the second metal thin film are arranged between the metal support substrate and the conductor layer, with the other side of the first metal thin film in contact with one surface of the metal support substrate, the other side of the second metal thin film in contact with one surface of the first metal thin film, and the other side of the conductor layer in contact with one surface of the second metal thin film. At least the material of the first metal thin film is a chromium-containing alloy, A wiring circuit board in which the chromium content in the alloy is 50% by mass or less. [Claim 2] The wiring circuit board according to claim 1, wherein the alloy further contains at least one metal selected from the group consisting of nickel, titanium, tungsten, and molybdenum. [Claim 3] The wiring circuit board according to claim 1, wherein the material of the second metal thin film is a second alloy containing chromium. [Claim 4] The wiring circuit board according to claim 3, wherein the chromium content in the second alloy is 50% by mass or less. [Claim 5] The wiring circuit board according to claim 3, wherein the second alloy further contains at least one metal selected from the group consisting of nickel, titanium, tungsten, and molybdenum. [Claim 6] The wiring circuit board according to claim 3, wherein the alloy and the second alloy have the same composition. [Claim 7] The first metal thin film is The first metal layer and A first oxide layer disposed on one side of the first metal layer in the thickness direction and A wiring circuit board according to claim 1, comprising: [Claim 8] The aforementioned metal support substrate is Metal support layer, A surface metal layer disposed on one side of the metal support layer in the thickness direction, wherein the surface metal layer has a higher conductivity than the metal support layer. A wiring circuit board according to claim 1, comprising:

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