Metal film and electronic component

Abstract

This metal film comprises a metal foil, and a plurality of silica particles in which the average particle diameter is 100 (nm) or less. The plurality of silica particles are in contact the surface of the metal foil.

Description

Metallic Films and Electronic Components

[0001] Disclosed embodiments relate to metal films and electronic components.

[0002] Conventionally, metal foils such as copper foils have been used as conductor layers of wiring boards. For example, a technique for forming a wiring board by attaching copper foil to the surface of an insulating substrate via an adhesive containing rigid particles has been disclosed (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 59-194487

[0004] The metal film of the present disclosure includes a metal foil and a plurality of silica particles having an average particle size of 100 nm or less, the silica particles being in contact with the surface of the metal foil.

[0005] 1 is a cross-sectional view showing an example of the configuration of a metal film according to an embodiment, and FIG. 2 is a cross-sectional view showing an example of the configuration of a wiring board according to an embodiment.

[0006] Hereinafter, embodiments of the metal film and electronic components disclosed herein will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments described below. Furthermore, each embodiment can be appropriately combined within the scope of not causing any contradiction in the processing content. Furthermore, the same components in each of the following embodiments will be assigned the same reference numerals, and duplicated explanations will be omitted.

[0007] Conventionally, metal foils such as copper foils have been used as conductor layers of wiring boards. For example, a technique for forming a wiring board by attaching copper foil to the surface of an insulating substrate via an adhesive containing rigid particles has been disclosed.

[0008] However, the conventional techniques have room for further improvement in terms of improving the adhesion between the insulating layer and the metal foil, and therefore, there is a need for a technique that can solve the above problems and achieve good adhesive strength to the insulating layer.

[0009] <Metal Film> Fig. 1 is a cross-sectional view showing an example of a metal film 1 according to an embodiment. Fig. 1(a) is a cross-sectional view showing the entire metal film 1, and Fig. 1(b) is a cross-sectional view showing an enlarged view of the surface of the metal film 1.

[0010] As shown in FIG. 1 , a metal film 1 according to the embodiment includes a metal foil 10 and a plurality of silica particles 11 .

[0011] The metal foil 10 is a thin film (foil-like) containing a metal as a main component. The metal foil 10 has a main surface 10a. The main surface 10a is an example of a surface. The metal foil 10 is not particularly limited, and examples thereof include copper foils such as electrolytic copper foils and rolled copper foils, nickel foils, and composite foils made by layering these metal foils.

[0012] The thickness of the metal foil 10 is not particularly limited and is, for example, about 5 μm or more and 105 μm or less. The surface roughness of the metal foil 10 is not particularly limited and may be, for example, 0.5 μm or less, or 0.3 μm or less. The surface roughness of the metal foil 10 may also be 0.001 μm or more.

[0013] The silica particles 11 are spherical and made of silica (SiO ２ The average particle size of the plurality of silica particles 11 may be 100 (nm) or less, or may be 20 (nm) or less.

[0014] Furthermore, the particle size range of the multiple silica particles 11 may be, for example, a range of D10 (10% cumulative) to D90 (90% cumulative) when measuring the particle size distribution, which may be 5 (nm) or more and 50 (nm) or less, or 10 (nm) or more and 30 (nm) or less.

[0015] 1B, in the metal film 1 according to the embodiment, a plurality of nano-sized silica particles 11 may be in contact with the main surface 10a of the metal foil 10. This improves the adhesive strength between the metal foil 10 and the insulating layer 12 when the insulating layer 12 (see FIG. 2) is positioned so as to be in contact with the main surface 10a of the metal foil 10.

[0016] This is because the metal film 1 of the embodiment is composed of a metal foil 10 and a plurality of silica particles 11, and therefore there are almost no components that volatilize during the firing process, so the adhesive strength between the metal foil 10 and the insulating layer 12 is unlikely to be compromised even after the firing process is performed to form the wiring substrate 2 (see Figure 2).

[0017] Furthermore, the metal film 1 of the embodiment is configured such that a large number of nano-sized silica particles 11 are attached to the main surface 10a of the metal foil 10, and these nano-sized silica particles 11 exhibit high adhesive strength with the glass ceramic that is the insulating layer 12.

[0018] Therefore, according to the embodiment, it is possible to realize a metal film 1 having good adhesive strength to the insulating layer 12. In the metal film 1 according to the embodiment, the silica particles 11 may be adhered only to a part of the surface of the metal foil 10, or the silica particles 11 may be adhered to the entire surface of the metal foil 10.

[0019] In addition, in the embodiment, since the silica particles 11 contained in the metal film 1 are nano-sized, even if the silica particles 11 diffuse into the glass ceramic insulating layer 12, the deterioration of the dielectric properties of the insulating layer 12 can be reduced. Therefore, according to the embodiment, an electronic component with good high-frequency characteristics can be realized. The nano-sized silica particles 11 are present at the interface between the glass ceramic insulating layer 12 and the metal foil 10.

[0020] In addition, in an embodiment, electrostatic attraction may be present between the metal foil 10 and the silica particles 11. This allows a strong bond to be achieved between the metal foil 10 and the silica particles 11 without the intervention of a different material such as an adhesive. In this case, the electrostatic attraction between the metal foil 10 and the silica particles 11 is evaluated using an electrostatic scanner. The electrostatic scanner can visualize the generation of static electricity between the metal foil 10 and the silica particles 11.

[0021] Therefore, according to the embodiment, the falling off of the silica particles 11 during handling of the metal film 1 can be reduced, and therefore the metal film 1 can be easily handled in the manufacturing process of electronic components.

[0022] In addition, in an embodiment, as shown in FIG. 1, the spherical silica particles 11 may be in point contact with the metal foil 10, and the portions of the metal foil 10 that are not in contact with the silica particles 11 may be bare.

[0023] Here, the point contact of the spherical silica particles 11 with the metal foil 10 does not simply refer to the length of the outline that can be interpreted as a point, as in the case of two perfect spheres coming into contact. In fact, although the silica particles 11 are spherical, they do not have a theoretically perfect spherical shape, but rather have a shape that is close to a perfect sphere.

[0024] For this reason, there are parts within the surface of silica particle 11 that have a curvature larger than that estimated from the average radius of silica particle 11, and the region where such a part with a large curvature comes into contact with metal foil 10 has a contact area that is not a point but a surface having a predetermined area. The ratio of the area of ​​contact between metal foil 10 and silica particle 11, when the length of the outline of silica particle 11 is taken as 100, may be 1 to 20 or 5 to 10.

[0025] The relative dielectric constant of the silica particles 11 is approximately 2.0 to 2.4. Because the metal foil 10 is in contact with the silica particles 11, which have such a low dielectric constant, a conductive layer with high interfacial conductivity can be obtained due to the effect of the portions in contact with the silica particles 11, even if the insulating layer 12 made of glass ceramic has a higher relative dielectric constant than the silica particles 11. The silica particles 11 are dispersed in a planar pattern at the interface between the insulating layer 12 and the metal foil 10.

[0026] In the embodiment, the silica particles 11 may have a neck-shaped neck portion (not shown) at a portion in contact with the metal foil 10. That is, some of the silica particles 11 may have a neck portion between them and the metal foil 10.

[0027] This allows for a stronger bond between the metal foil 10 and the silica particles 11 without the need for a different material such as an adhesive, and therefore, according to the embodiment, the metal film 1 can be handled more easily in the manufacturing process of electronic components.

[0028] In addition, in the embodiment, the area ratio of the plurality of silica particles 11 may be 1% or more and 60% or less when the unit area of ​​the metal foil 10 in a plan view is 1. This allows the electronic component to achieve both good adhesion between the metal foil 10 and the insulating layer 12 and good electrical properties (such as interfacial conductivity).

[0029] For example, when the area ratio of the plurality of silica particles 11 is 1 (%), the area is 10 (μm) × 10 (μm) (i.e., the area is 100 (μm) ２ )) on the metal foil 10, a plurality of silica particles 11 are 1 (μm ２ ) will be occupied by an area of

[0030] In addition, if the diameter of the silica particle 11 is 20 (nm), the area of ​​the silica particle 11 when viewed in plan is 3.14 × 10 －４ (μm ２ )

[0031] Therefore, when the area ratio of the plurality of silica particles 11 is 1 (%), the silica particles 11 are distributed on the metal foil 10 of 10 (μm) × 10 (μm) by 1 / (3.14 × 10 －４ ) = 3184 pieces.

[0032] In this manner, in the embodiment, since a large number of silica particles 11 are present on the main surface 10 a of the metal foil 10 , a high adhesive strength can be achieved between the metal foil 10 and the insulating layer 12 .

[0033] Furthermore, by setting the area ratio of the plurality of silica particles 11 to 60(%) or less, all of the silica particles 11 can be arranged in a dispersed state without overlapping on the main surface 10a of the metal foil 10. The plurality of silica particles 11 are dispersed in the thickness direction of the metal foil 10 without overlapping.

[0034] In the embodiment, the metal foil 10 may contain copper or nickel as a main component. When the metal foil 10 contains copper as a main component, the conductor layer of the wiring board 2 can have high interfacial conductivity and low DC electrical resistance.

[0035] Furthermore, when the metal foil 10 is primarily composed of nickel, it can be used as an electrode material for a fuel cell, for example, as a conductor with low resistance and high temperature resistance, and is also useful as an internal electrode layer for a capacitor.

[0036] In an embodiment, the silica particles 11 may be aggregates of a plurality of primary particles having an average particle size of 1 nm or more and 5 nm or less. When the silica particles 11 are formed of fine primary particles, the silica particles 11 have a higher surface energy.

[0037] This allows for a stronger bond between the metal foil 10 and the silica particles 11 without the need for a different material such as an adhesive, and therefore, according to the embodiment, the metal film 1 can be handled more easily in the manufacturing process of electronic components.

[0038] <Wiring Board> Fig. 2 is a cross-sectional view showing an example of the configuration of a wiring board 2 according to an embodiment. Fig. 2(a) is a cross-sectional view showing the entire wiring board 2, and Fig. 2(b) is an enlarged cross-sectional view of the interface between the metal foil 10 and the insulating layer 12 in the wiring board 2. The wiring board 2 is an example of an electronic component.

[0039] 2 , the wiring board 2 according to the embodiment includes a metal film 1 and an insulating layer 12. That is, the wiring board 2 according to the embodiment includes a metal foil 10, a plurality of silica particles 11, and the insulating layer 12.

[0040] The insulating layer 12 is a thin plate-like layer containing an insulator as a main component. The material of the insulating layer 12 is not particularly limited, and examples thereof include various ceramic materials such as glass ceramics and zirconia-based ceramics, and organic resins.

[0041] Furthermore, in the wiring board 2 according to the embodiment, the metal foil 10 functions as a wiring layer. In this way, in the wiring board 2 according to the embodiment, the wiring layer is formed of the metal foil 10 rather than a metallized layer, so that it is possible to obtain a wiring board 2 having a conductive layer that exhibits high conductivity. In this case, it is preferable that the metal foil 10 contains copper as a main component.

[0042] Furthermore, in the wiring board 2 according to the embodiment, the metal foil 10 and the insulating layer 12 are bonded together such that the main surface 10a of the metal foil 10 is in contact with the main surface 12a of the insulating layer 12. That is, in the embodiment, the metal foil 10 is bonded to the insulating layer 12 via a plurality of silica particles 11. Therefore, in the embodiment, as described above, the adhesive strength between the metal foil 10 and the insulating layer 12 can be improved.

[0043] Furthermore, in the embodiment, since the silica particles 11 contained in the metal film 1 are nano-sized, even if the silica particles 11 diffuse into the glass ceramic insulating layer 12, it is possible to reduce the degradation of the dielectric properties of the insulating layer 12. Therefore, according to the embodiment, it is possible to realize a wiring substrate 2 having good high-frequency properties.

[0044] <Electronic Component> The present disclosure can also be applied to the following electronic component, which also includes a metal foil 10 (see FIG. 2), a plurality of silica particles 11 (see FIG. 2), and an insulating layer 12 (see FIG. 2).

[0045] The electronic component may have a configuration in which the metal foil 10 is disposed on the main surface 12a of the insulating layer 12, similar to the above-described wiring board 2. Alternatively, the electronic component may have a configuration in which the metal foil 10 is disposed on both surfaces of the insulating layer 12.

[0046] In this case, the material of the metal foil 10 is preferably nickel. When the material of the metal foil 10 is nickel, the material of the insulating layer is preferably a ceramic material exhibiting dielectric properties. A ceramic material exhibiting dielectric properties may also be referred to as a dielectric ceramic.

[0047] An example of a dielectric ceramic is a ceramic material whose main component is barium titanate. Here, "main component" refers to a dielectric ceramic containing 80% or more (mol%) of barium titanate. Dielectric ceramics are used, for example, in the dielectric layers of multilayer ceramic capacitors.

[0048] <Fuel Cell> The present disclosure can also be applied to the following fuel cell: This fuel cell also has a metal foil 10 (see FIG. 2), a plurality of silica particles 11 (see FIG. 2), and an insulating layer 12 (see FIG. 2).

[0049] This fuel cell also has an anode and a support. The anode includes a solid electrolyte material and nickel. The anode material in the fuel cell is primarily made of zirconia. In this case, the metal foil 10 is preferably made of nickel. Again, the nickel conductor preferably has a plurality of silica particles 11 located on its surface.

[0050] Examples of the present disclosure will be specifically described below. Note that in the examples described below, a metal film having a copper foil will first be described, followed by a wiring board having such a metal film and an insulating layer made of glass ceramics, but the present disclosure is not limited to the following examples.

[0051] <Sample 1> First, a copper foil with a thickness of 18 μm was prepared as the metal foil material. A plurality of silica particles with an average particle size of 20 nm were also prepared. The silica particles were aggregates of primary particles with particle sizes of approximately 1 nm to 10 nm.

[0052] Next, the prepared copper foil was treated with hydrochloric acid to remove the oxide film on the surface, followed by alkaline cleaning and water rinsing.

[0053] Next, a process of adhering a plurality of silica particles to the copper foil after the water washing process was carried out. Specifically, first, silica particles were prepared in an amount that would cover about 50% of the area of ​​the main surface of the copper foil.

[0054] The copper foil was then attached to a metal substrate, a metal frame was placed around the copper foil, the above amount of silica particles was placed inside the frame, and ultrasonic waves were applied to the metal substrate to disperse the silica particles on the copper foil.

[0055] After the dispersion treatment, a stainless steel metal plate was placed on the silica particles, and the silica particles were pressed with a predetermined pressure via the metal plate. This resulted in a metal film of Sample 1 having a plurality of silica particles attached to its main surface. The ratio of the attached silica particles to the silica particles placed in the frame was approximately 10% to 20%.

[0056] Next, the metal film obtained above was used to produce a wiring board of Sample 1. First, a glass ceramic green sheet having a thickness of 0.2 mm was prepared, and six of these green sheets were stacked.

[0057] Next, metal films were attached to both main surfaces of the green sheet, with the green sheet and metal films positioned so that the silica particles of the metal films would adhere to the green sheet.

[0058] Next, the resulting laminate of the green sheet and metal film was fired in a reducing atmosphere using a hydrogen-nitrogen mixed gas at a maximum temperature of 930°C for a holding time of 2 hours.

[0059] Next, the copper foil of the fired body was etched in a conventional manner to form a predetermined shape, thereby obtaining a wiring board of Sample 1.

[0060] <Sample 2> The metal film and wiring substrate of Sample 2 were obtained using the same method and conditions as those for Sample 1, except that in the metal film production process, borosilicate glass powder with an average particle size of 1 (μm) was used instead of the nano-sized silica particles.

[0061] <Sample 3> The metal film and wiring board of Sample 3 were obtained using the same method and conditions as those for Sample 1, except that in the metal film production process, nano-sized silica particles were attached to the copper foil with an organic resin adhesive.

[0062] <Various Evaluations> Next, the metal films and wiring boards of Samples 1 to 3 obtained above were visually observed. As a result, in the metal film of Sample 1, the silica particles were firmly adhered to the copper foil, and the silica particles did not fall off from the copper foil even when the metal film was handled. In the metal film of Sample 1, the silica particles were bonded to the copper foil by electrostatic force and van der Waals force.

[0063] The metal films and wiring substrates of Samples 1 to 3 obtained above were cut, and the cut surfaces were filled with resin and mirror-polished. The cross sections were then observed with a scanning electron microscope (SEM). As a result, in the metal film of Sample 1, multiple silica particles were observed that were firmly bonded to the copper foil by neck bonding.

[0064] In addition, in the wiring board of Sample 1, the silica particles were present in particulate form between the copper foil and the glass ceramic, and the silica particles were bonded to the glass ceramic. In the wiring board of Sample 1, the periphery of the neck bond of the silica particles was filled with glass ceramic.

[0065] Thus, in the wiring board of Sample 1, by using nano-sized silica particles as a binder in the copper foil, the silica particles were firmly bonded to the copper foil while remaining in a particulate state, while preventing solid dissolution into the glass ceramic.

[0066] On the other hand, in the wiring board of Sample 2, the glass powder was dissolved in the insulating layer side, and was hardly present in the form of particles between the copper foil and the glass ceramic.

[0067] The wiring substrates of Samples 1 to 3 obtained above were evaluated for the presence or absence of conductor peeling. The samples used for evaluation were those in which copper foil was laminated on both sides of an insulating layer measuring 10 mm to 50 mm on a side.

[0068] To evaluate conductor peeling, the evaluation sample was first cut at a position approximately halfway along one direction, and both interfaces between the insulating layer and the copper foil on the cross section were observed. If peeling was observed at even one location, it was judged as "peeling present," and if peeling was not observed at any interface, it was judged as "no peeling present."

[0069] In the above evaluation, the state of "peeling" was defined as a case where the length of the region where the insulating layer and the copper foil were separated by 0.1 (mm) or more was 1 (mm) or more. As a result, the wiring board of sample 1 was evaluated as "no peeling," while the wiring boards of samples 2 and 3 were evaluated as "peeling."

[0070] The interfacial conductivity of the wiring substrates of Samples 1 to 3 obtained above was measured. The interfacial conductivity was measured using the dielectric cylindrical resonator method described below. The measurement samples used were 50 mm in diameter and had copper foil formed over almost the entire surface of both sides.

[0071] The method for measuring interfacial conductivity using the dielectric rod resonator method is a method for measuring the conductivity at the interface between the copper foil and the insulating layer, i.e., the conductor interface, by attaching an insulating layer with the above-mentioned conductor formed inside to both end faces or one end face of a dielectric rod made of a dielectric material with known relative permittivity and dielectric loss in a predetermined relationship to form a dielectric resonator.

[0072] The principle of this measurement method is that when an electromagnetic resonator is constructed by sandwiching a conductor plate (usually a conductor plate having a diameter D about three times the diameter d of the dielectric cylinder) that is large enough to ignore the edge effect, parallel to both end faces of a dielectric cylinder having a predetermined dimensional ratio (height h / diameter d), the high-frequency current flowing in the conductor plate due to the TEomn resonance mode (hereinafter referred to as the TEomn mode) is distributed only on the short-circuit surface, i.e., the opposing surface between the dielectric and the conductor.

[0073] In a dielectric resonator, the high-frequency current flowing in the conductor due to the TEomn mode (m = 1, 2, 3 ..., n = 1, 2, 3 ...) is distributed only at the interface between the conductor and the dielectric substrate in contact with the dielectric cylinder. Utilizing this, the interfacial conductivity can be calculated from the measured resonant frequency f0 of the TEomn mode (m = 1, 2, 3 ..., n = 1, 2, 3 ...) and the unloaded Q and Qu. The interfacial conductivity was measured in the frequency range of 1 (GHz) to 49 (GHz) and evaluated as a relative value when the interfacial conductivity in DC was set to 100 (%).

[0074] As a result, the wiring substrate of Sample 1 had an interface conductivity of 80% or more in the frequency range of 1 GHz to 49 GHz. On the other hand, the wiring substrates of Samples 2 and 3 had an interface conductivity of 80% in the frequency range of 1 GHz to 49 GHz.

[0075] Furthermore, a thermal shock resistance test was conducted by immersing the wiring substrates of Samples 1 to 3 obtained above in a heated solder bath for approximately 1 second. In this thermal shock resistance test, the temperature of the solder bath was set to two temperatures: 325°C (i.e., ΔT = 300°C) and 355°C (i.e., ΔT = 330°C).

[0076] The cracks occurring in the wiring board were confirmed by observing the cross-sections of the wiring boards polished under a stereomicroscope. As a result, the wiring board of sample 1 exhibited good thermal shock resistance at all temperatures, whereas the wiring boards of samples 2 and 3 did not exhibit good thermal shock resistance at any temperature.

[0077] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments and various modifications are possible without departing from the spirit of the present disclosure. For example, in the above embodiments, an example in which fine powder of silica particles is adhered to the metal foil 10 is shown, but the present disclosure is not limited to such an example.

[0078] For example, fine ceramic powder other than silica (such as fine alumina powder) may be adhered to the metal foil 10. This also provides the same effects as those of the above embodiment.

[0079] Further advantages and other aspects may readily occur to those skilled in the art. Therefore, the disclosure in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0080] The present technology can also be configured as follows. (1) A metal film comprising a metal foil and a plurality of silica particles having an average particle size of 100 nm or less, wherein the plurality of silica particles are in contact with a surface of the metal foil. (2) The metal film according to (1), wherein electrostatic attraction acts between the metal foil and the silica particles. (3) The metal film according to (1) or (2), wherein the silica particles are spherical and in point contact with the metal foil, and portions of the metal foil that are not in contact with the silica particles are bare. (4) The metal film according to any one of (1) to (3), wherein, when the unit area of ​​the metal foil is 1 in a plan view, the area ratio of the plurality of silica particles is 1% or more and 60% or less. (5) The metal film according to any one of (1) to (4), wherein the metal foil contains copper or nickel as a main component. (6) The metal film according to any one of (1) to (5), wherein the silica particles are aggregates of a plurality of primary particles having an average particle size of 1 nm or more and 5 nm or less. (7) An electronic component comprising: the metal film according to any one of (1) to (6); and an insulating layer, wherein the metal foil is bonded to the insulating layer via a plurality of the silica particles. (8) The electronic component according to (7), wherein the metal foil is made of at least one metal foil selected from the group consisting of copper foil such as electrolytic copper foil and rolled copper foil, nickel foil, and composite foil obtained by layering these metal foils. (9) The electronic component according to (7) or (8), wherein the surface roughness of the metal foil is 0.001 μm or more and 0.5 μm or less. (10) The electronic component according to any one of (7) to (9), wherein, when a particle size distribution of the silica particles is measured, the range of particle size D10 (10% cumulative) to D90 (90% cumulative) is 5 (nm) or more and 50 (nm) or less. (11) The electronic component according to any one of (7) to (10), wherein the silica particles are present at an interface between the metal foil and the insulating layer.(12) The electronic component according to any one of (7) to (11), wherein the surface of the silica particles has a portion with a curvature larger than that estimated from the average radius of the silica particles, and the region where such a portion with a large curvature is in contact with the metal foil forms a surface having a predetermined area. (13) The electronic component according to any one of (7) to (12), wherein the silica particles are dispersed planarly at the interface between the insulating layer and the metal foil. (14) The electronic component according to any one of (7) to (13), wherein the silica particles are dispersed without overlapping on the main surface of the metal foil. (15) The electronic component according to any one of (7) to (14), wherein some of the silica particles have a neck portion between them and the metal foil.

[0081] REFERENCE SIGNS LIST 1 Metal film 2 Wiring board (an example of an electronic component) 10 Metal foil 10a Main surface (an example of a surface) 11 Silica particles 12 Insulating layer 12a Main surface

Claims

1. Metal foil; A plurality of silica particles having an average particle size of 100 (nm) or less; Equipped with A plurality of the silica particles are in contact with the surface of the metal foil. Metal film.

2. An electrostatic attraction acts between the metal foil and the silica particles. The metal film of claim 1.

3. the silica particles are spherical and in point contact with the metal foil; The portions of the metal foil that are not in contact with the silica particles are exposed. The metal film according to claim 1 or 2.

4. When the unit area of ​​the metal foil is taken as 1 in a plan view, the area ratio of the plurality of silica particles is 1(%) or more and 60(%) or less. The metal film according to claim 1 or 2.

5. The metal foil contains copper or nickel as a main component. The metal film according to claim 1 or 2.

6. The silica particles are aggregates of a plurality of primary particles having an average particle size of 1 nm or more and 5 nm or less. The metal film according to claim 1 or 2.

7. The metal film according to claim 1 or 2; An insulating layer; Equipped with The metal foil is bonded to the insulating layer via a plurality of the silica particles. Electronic components.

8. The metal foil is at least one metal foil selected from the group consisting of copper foil such as electrolytic copper foil and rolled copper foil, nickel foil, and composite foil obtained by laminating these metal foils. The electronic component according to claim 7.

9. The surface roughness of the metal foil is 0.001 (μm) or more and 0.5 (μm) or less. The electronic component according to claim 7.

10. The particle size range of the silica particles, when the particle size distribution is measured, is such that the range of D10 (10% cumulative) to D90 (90% cumulative) is 5 (nm) or more and 50 (nm) or less. The electronic component according to claim 7.

11. The silica particles are present at the interface between the metal foil and the insulating layer. The electronic component according to claim 7.

12. The surface of the silica particle has a portion having a curvature larger than that estimated from the average radius of the silica particle, and the region where the portion having the large curvature is in contact with the metal foil forms a surface having a predetermined area. The electronic component according to claim 7.

13. The silica particles are planarly dispersed at the interface between the insulating layer and the metal foil. The electronic component according to claim 7.

14. The silica particles are dispersed on the main surface of the metal foil without overlapping. The electronic component according to claim 7.

15. Among the silica particles, there are particles having a neck portion between the silica particles and the metal foil. The electronic component according to claim 7.