Metal laminate and method for manufacturing same

Abstract

The present disclosure provides a metal laminate comprising a base metal layer and a thin metal film formed on the base metal layer, wherein the thin metal film includes a high-density region and a low-density region, and wherein the thin metal film has the high-density region on at least the surface side of the thin metal film.

Description

Metal laminate and method for manufacturing same

[0001] The present disclosure relates to a metal laminate and a method for manufacturing the same.

[0002] 2. Description of the Related Art Electronic components such as inductors are provided with metal thin films as external electrodes.

[0003] JP 2012-253292 A

[0004] Whiskers may develop on metal thin films provided as external electrodes of electronic components.

[0005] Conventionally, in order to suppress the growth of whiskers, multiple gaps are sometimes provided on the surface of the metal thin film (Patent Document 1). However, the multiple gaps may impair the smoothness of the surface of the metal thin film and adversely affect solder wettability.

[0006] An object of the present disclosure is to provide a metal laminate that suppresses whisker growth and has excellent solder wettability.

[0007] The present disclosure provides a metal laminate comprising a base metal layer and a metal thin film formed on the base metal layer, wherein the metal thin film includes a high density region and a low density region, and the metal thin film has a high density region at least on the surface side of the metal thin film.

[0008] The present disclosure also provides a method for manufacturing a metal laminate, including: preparing a base metal layer; forming a metal thin film on the base metal layer; placing the base metal layer with the metal thin film formed on it into a barrel; and rotating the barrel without applying current.

[0009] The metal laminate of the present disclosure provides a metal laminate that inhibits whisker growth and has excellent solder wettability.

[0010] The method for manufacturing a metal laminate according to the present disclosure can produce a metal laminate that suppresses whisker growth and has excellent solder wettability.

[0011] Fig. 1 is a schematic cross-sectional view of a metal laminate according to an embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view of an enlarged portion of the metal laminate according to an embodiment of the present disclosure. Fig. 3 is a schematic perspective view of an electronic component according to an embodiment of the present disclosure. Fig. 4 is a schematic cross-sectional view obtained when the electronic component according to an embodiment of the present disclosure shown in Fig. 3 is cut along line II. Fig. 5 is an exploded perspective view of the electronic component according to an embodiment of the present disclosure shown in Fig. 3. Fig. 6 is a schematic cross-sectional view of a metal laminate according to an embodiment of the present disclosure.

[0012] The metal laminate of the present disclosure will be described in more detail below. While the description will be made with reference to drawings as necessary, various elements in the drawings are merely shown schematically and exemplarily to facilitate understanding of the metal laminate of the present disclosure, and the appearance and / or dimensional ratios may differ from those of the actual objects.

[0013] The various numerical ranges mentioned in this specification are intended to include the lower and upper limits themselves. That is, for example, a numerical range of 1 to 10 can be interpreted as including the lower limit of "1" and the upper limit of "10."

[0014] <Metal Laminate> FIG. 1 shows a metal laminate 1 according to one embodiment of the present disclosure.

[0015] The metal laminate 1 of the present disclosure includes a base metal layer 10 and a metal thin film 20 formed on the base metal layer 10. The metal thin film 20 includes a high-density region 30 and a low-density region 40, and the metal thin film 20 has the high-density region 30 on at least a surface side 21 of the metal thin film.

[0016] The highly dense region refers to a portion of the metal thin film formed by densely packing the metal material and having few voids. For example, as shown in FIG. 1 , the highly dense region 30 has relatively fewer voids 50 than the less dense region 40. In other words, the surface side 21 of the metal thin film has relatively fewer voids than other portions of the metal thin film (e.g., the portion of the metal thin film on the undercoat metal layer side). Note that the above "voids" can be expressed in other ways, such as gaps, pores, holes, or gaps.

[0017] The surface side of the metal thin film refers to the surface side of the metal thin film that is exposed to the outside. As shown in Figure 1, the part of the metal thin film 20 located on the surface side 21 of the metal thin film is a part close to the surface side 21 of the metal thin film, such as the surface 21a of the metal thin film or a part including the surface 21a of the metal thin film.

[0018] The low-density region is a portion of the metal thin film formed by sparsely gathering metal material, and refers to a region with many voids. For example, as shown in FIG. 1 , the low-density region 40 is a region with more voids 50 than the high-density region 30. Since the high-density region 30 exists on the surface side 21 of the metal thin film, the low-density region 40 exists in some region of the metal thin film 20 other than the surface side 21 of the metal thin film. For example, the metal thin film on the side of the base metal layer has relatively fewer voids than the metal thin film on the surface side.

[0019] The metal laminate of the present disclosure has the above-described characteristics and can therefore exhibit the following effects.

[0020] (Whisker Growth Prevention) Whiskers, or beard-like or needle-like metal protrusions, can sometimes appear on metal surfaces. Whiskers can grow naturally over time. For example, if whiskers grow on the surface of a metal used in the electrical connection of an electronic circuit or electronic component, the whiskers may come into contact with other electronic circuits or electrical connection parts, causing a short circuit and potentially resulting in failure of the electrical product or electronic component.

[0021] When stress, especially compressive stress, is applied to metal, whiskers may grow on the metal surface in order to release the stress. From the viewpoint of suppressing whisker growth, one possible countermeasure is to release and disperse the stress applied to the metal.

[0022] Conventionally, in order to suppress whisker growth, a metal thin film formed by sparsely packed metal materials may be used. Such a metal thin film may have a low density. Stress applied to the metal thin film can be dispersed in the low density metal thin film, thereby suppressing whisker growth. However, a low density metal thin film has many voids, which can impair the smoothness of the surface of the metal thin film and potentially deteriorate solder wettability. In particular, when the surface of a metal thin film has many voids, the metal on the surface is more likely to oxidize, forming an oxide film, which can deteriorate solder wettability.

[0023] 1, the metal thin film 20 of the metal laminate of the present disclosure includes a high-density region 30 and a low-density region 40, with the high-density region 30 being present at least on the surface side 21 of the metal thin film. The low-density region 40 of the metal thin film 20 is an area with many voids 50, and therefore stress applied to the metal thin film 20 can first act toward the voids (in the direction indicated by the arrow in FIG. 1) before whiskers are generated from the metal thin film surface 21a.

[0024] Stress acting toward the voids may, for example, reduce the size of the voids. Alternatively, the structure of the metal thin film itself may change so as to relieve the stress through the voids. In other words, the stress applied to the metal thin film may escape and be dispersed in less dense regions. Therefore, whiskers may be less likely to develop in the metal thin film due to stress applied to the metal thin film, and whisker growth may be suppressed.

[0025] (Improvement of solder wettability) On the other hand, the metal thin film of the metal laminate of the present disclosure has a highly dense region 30 at least on the surface side 21 of the metal thin film, as shown in Fig. 1. The highly dense region 30 has few voids 50, making it a dense metal thin film, which makes it easier to improve the smoothness of the surface 21a of the metal thin film, and can improve solder wettability.

[0026] In addition, the term "whisker" in the present disclosure includes whiskers that are generated by stress mechanisms, such as high-temperature (constant-temperature) whiskers, thermal shock whiskers, and humidity whiskers. The metal laminate of the present disclosure can suppress any of the above whiskers.

[0027] As a result, the metal laminate of the present disclosure can be a metal laminate that suppresses whisker growth and has excellent solder wettability.

[0028] The metal laminate of the present disclosure will be described in detail below.

[0029] [Base Metal Layer] The base metal layer is a layer that serves as a base for forming the metal thin film of the metal laminate of the present disclosure. The base metal layer may be formed on another metal layer, for example, on an electronic component such as an inductor. The base metal layer may be in a state of being the base metal layer alone. The form of the base metal layer is not particularly limited, and may be, for example, a sintered body of a conductive paste, a plated film, a metal plate, a vapor deposition film, a sputtered film, or the like.

[0030] The metal underlayer may be an alloy containing at least one selected from the group consisting of Ag, Ni, Cu, Ti, Al, Zn, Mg, Fe, and Cr, preferably an alloy containing at least one selected from the group consisting of Ag, Ni, C, and Cu, and more preferably an alloy containing Ag and / or Ni. The metal underlayer may be a single layer or may consist of multiple layers. When the metal underlayer consists of multiple layers, for example, the metal underlayer may include a first metal underlayer containing Cu and a second metal underlayer containing Ni. The metal thin film is preferably formed on the second metal underlayer.

[0031] [Metal Thin Film] The metal thin film is a thin metal film formed on a base metal layer. The metal thin film may be an alloy containing Sn and / or Zn, preferably an alloy containing Sn. The metal thin film may be a plated film.

[0032] The metal thin film of the metal laminate of the present disclosure has a high-density region on the surface side of the metal thin film and a low-density region on the base metal layer side of the metal thin film. In the metal thin film, the high-density region may be adjacent to the low-density region.

[0033] The "underlying metal layer side" of the metal thin film refers to the surface of the metal thin film that is in contact with the underlying metal layer. As shown in Figure 1, the part of the metal thin film located on the underlying metal layer side 22 of the metal thin film is a part of the metal thin film that is close to the underlying metal layer side 22, such as the interface 22a between the metal thin film and the underlying metal layer, or a part including the interface 22a.

[0034] The thickness of the metal thin film is not particularly limited as long as it is 2 μm or more, and may be, for example, 3 μm or more, 4 μm or more, 5 μm or more, or 10 μm or less, 9 μm or less, or 8 μm or less.

[0035] [Low-density region] The low-density region is a part of the metal thin film formed by sparsely gathering metal material, and refers to a region with many voids.

[0036] In one embodiment, the low-density region may be a region that is more than 50% thick from the interface between the metal thin film and the underlying metal layer. For example, the low-density region may be a region that is 40% to 100% thick of the metal thin film from the surface of the metal thin film. In one embodiment, the low-density region may be a region that is up to 50% thick from the interface between the metal thin film and the underlying metal layer.

[0037] From the viewpoint of further suppressing whisker growth, the low-density region may be a region that is more than 60% of the thickness from the interface between the metal thin film and the underlying metal layer, preferably more than 70%, more preferably more than 80%, even more preferably more than 90%, and particularly preferably more than 95%. By setting the low-density region within the above range, whisker growth can be more easily suppressed.

[0038] From the viewpoint of further suppressing whisker growth, the low-density region may be a region up to 60% of the thickness from the interface between the metal thin film and the underlying metal layer, preferably up to 70%, more preferably up to 80%, even more preferably up to 90%, and particularly preferably up to 95%. By setting the low-density region within the above range, whisker growth can be more easily suppressed.

[0039] In one embodiment, the low-density region may have a thickness of 1.0 μm or more. From the viewpoint of further suppressing whisker growth, the low-density region may have a thickness of 1.5 μm or more, preferably 2.0 μm or more, more preferably 3.0 μm or more, even more preferably 4.0 μm or more, and particularly preferably 5.0 μm or more.

[0040] In one embodiment, the low-density region may be continuously present in the thickness direction from the interface between the underlying metal layer and the metal thin film toward the surface of the metal thin film. This configuration allows the voids in the low-density region and the interface to be positioned closer to each other. The proximity of the voids to the interface makes it easier to disperse stresses originating from the underlying metal layer, among the stresses applied to the metal thin film, into the voids. Examples of stresses originating from the underlying metal layer on the metal thin film include compressive stresses applied to the metal thin film by the metal diffused from the underlying metal layer into the metal thin film.

[0041] [Porosity] The metal laminate of the present disclosure has a low-density region, and the low-density region may have voids. The density of the low-density region can be evaluated by the porosity. The porosity can be measured by observing the metal laminate of the present disclosure with an FIB-SEM. Specifically, in FIB-SEM observation, the metal laminate is subjected to FIB processing to expose a cross section of the metal laminate, and the porosity of the metal laminate can be measured by observing the cross section with an SEM.

[0042] The cross section of the metal laminate to be observed may be a cross section obtained by cutting the metal laminate along the short direction of the main surface of the metal laminate (or perpendicular to the long direction). In the case of a cross section of an electronic component described below, such as a multilayer chip inductor, the cross section may be a cross section near the center of the end face of the multilayer chip inductor. Specifically, the cross section obtained by cutting along line II as shown in Figure 3 may be a cross section of region A shown in Figure 4.

[0043] In SEM observation, the cross section of the metal laminate is observed at a magnification of a field of view that allows at least measurement of the thickness of the metal thin film, and an SEM image is obtained. When the vertical direction of the region of interest in the SEM image for calculating the porosity is the thickness direction of the metal thin film and the horizontal direction is the surface extension direction of the metal thin film, the region of interest in the SEM image for calculating the porosity is a rectangular region with a length (μm) equal to the thickness of the metal thin film in the vertical direction and a width of 10 μm in the horizontal direction. In this rectangular region, the area of ​​the metal thin film and the area of ​​voids in the metal thin film are calculated, and the ratio of the area of ​​the voids to the total area of ​​the metal thin film and the area of ​​the voids is defined as the porosity.

[0044] In one embodiment, the porosity of the less dense region may be 1% or more. From the viewpoint of further suppressing whisker growth, the porosity of the less dense region may be 2% or more, preferably 3% or more, more preferably 4% or more, and even more preferably 5% or more. The porosity of the less dense region may be 10% or less, preferably 9% or less, more preferably 8% or less, and even more preferably 7% or less. Such a porosity can suppress whisker growth and / or improve solder wettability.

[0045] [Volume porosity] By subjecting a metal laminate to FIB processing and SEM observation at successive and equal intervals, and reconstructing the obtained SEM images as a three-dimensional structure, the porosity of the metal thin film can be evaluated three-dimensionally, i.e., the volume porosity can be evaluated.

[0046] In the evaluation of the volume porosity, the three-dimensional structure of the metal thin film is first obtained by FIB-SEM observation of the metal thin film. The three-dimensional structure is a reconstructed SEM image obtained by observing the cross section of the metal laminate at a magnification that allows at least the thickness of the metal thin film to be measured.

[0047] In the three-dimensional structure of the metal thin film, the vertical direction of the region to be targeted for calculating the volume porosity is the film thickness direction of the metal thin film, the depth direction is the SEM observation direction of the metal thin film, and the horizontal direction is the surface extension direction of the metal thin film perpendicular to the SEM observation direction of the metal thin film. In the three-dimensional structure of the metal thin film, the region to be targeted for calculating the volume porosity is a cubic region with a length (μm) of the film thickness of the metal thin film in the vertical direction, a depth direction of 10 μm, and a horizontal direction of 10 μm. In this cubic region, the volume of the metal thin film and the volume of voids in the metal thin film are calculated, and the ratio of the volume of voids to the total volume of the metal thin film and the volume of voids is taken as the void volume ratio. Regarding the change in the volume porosity in the thickness direction, the film thickness of the metal thin film is divided into 20 equal parts, and the density is evaluated for each area.

[0048] The SEM image used to calculate the porosity and volume porosity may be used as is, or a binarized SEM image may be used. Specifically, the obtained SEM image may be binarized using image analysis software, and the porosity and volume porosity may be calculated by calculating the black-white ratio through image analysis using the image analysis software. For example, commercially available ImageJ can be used as the image analysis software.

[0049] In one embodiment, the volume porosity of the less dense region may be 1% or more. From the viewpoint of further suppressing whisker growth, the volume porosity of the less dense region may be 2% or more, preferably 3% or more, more preferably 4% or more, and even more preferably 5% or more. The volume porosity of the less dense region may be 10% or less, preferably 9% or less, more preferably 8% or less, and even more preferably 7% or less. Such a volume porosity can suppress whisker growth and / or improve solder wettability.

[0050] [Highly dense region] The highly dense region is a portion of the metal thin film formed by densely packing the metal material, and refers to a region with few voids. In one embodiment, the highly dense region is present in a portion close to the surface side of the metal thin film. In one embodiment, the highly dense region is a region including the surface of the metal thin film.

[0051] Regarding the formation of a highly dense region on the surface side of the metal thin film, the highly dense region may be formed on the surface side of the metal thin film during deposition of the metal thin film, or may be formed on the surface side of the metal thin film after deposition. For example, the highly dense region may be formed on the surface side of the metal thin film by adjusting the type and / or amount of additives added to the raw materials of the metal thin film, or by applying an external force to the surface of the metal thin film after deposition. For example, the surface of the metal thin film can be compressed by hitting it, thereby giving the surface side of the metal thin film a dense structure.

[0052] In one embodiment, the highly dense region may be a region from the surface of the metal thin film to 50% of the thickness of the metal thin film. In other words, the thickness of the highly dense region may be a region from the surface of the metal thin film to 50% of the thickness of the metal thin film.

[0053] From the viewpoint of ensuring the thickness of the above-mentioned low-density region, the high-density region may be a region up to 40% of the thickness from the surface of the metal thin film, preferably up to 30%, more preferably up to 20%, even more preferably up to 10%, and particularly preferably up to 5%. By setting the thickness of the high-density region within the above range, it becomes easier to increase the thickness of the low-density region, and it becomes easier to suppress the growth of whiskers.

[0054] Here, the surface of the metal thin film may not necessarily be a uniform, smooth plane. In this case, the reference "from the surface of the metal thin film" refers to the surface of the metal thin film that is closest to the interface between the metal thin film and the underlying metal layer. Specifically, as shown in Figure 2, when the metal laminate 1 according to one embodiment is cut and the cross section is observed, the surface 21a of the metal thin film where the line segment connecting the interface 22a between the metal thin film 20 and the underlying metal layer 10 and the surface 21a of the metal thin film has the shortest length is defined as "from the surface of the metal thin film" when calculating the range of the highly dense region.

[0055] As shown in Figure 2, "the region from the surface of the metal thin film to 50% of the thickness" means the region of the metal thin film from the surface of the metal thin film to 50% of the length between the surface 21a and interface 22a of the metal thin film, as indicated by the double arrow.

[0056] In one embodiment, the highly dense region may be a region up to 0.5 μm from the surface of the metal thin film. From the viewpoint of ensuring the thickness of the less dense region described below, the highly dense region may be a region up to 0.4 μm from the surface of the metal thin film, preferably up to 0.3 μm, more preferably up to 0.2 μm, and even more preferably up to 0.1 μm. By setting the thickness of the highly dense region within the above range, it becomes easier to increase the thickness of the less dense region, and it becomes easier to suppress whisker growth.

[0057] [Porosity] A metal thin film has a highly dense region. The denseness of the highly dense region can be evaluated by the porosity. The denser the region, the smaller the porosity.

[0058] The porosity of the highly dense region may be less than 1%, preferably 0.7% or less, more preferably 0.5% or less, and even more preferably 0.3% or less. Such a porosity can further improve solder wettability. In one embodiment, the highly dense region may be substantially free of voids, and the porosity may be 0%.

[0059] [Volume porosity] The volume porosity of the highly dense region may be less than 1%, preferably 0.7% or less, more preferably 0.5% or less, and even more preferably 0.3% or less. Such a volume porosity can further improve solder wettability. In one embodiment, the highly dense region may be substantially free of voids, and the volume porosity may be 0%.

[0060] [Surface Roughness] In one embodiment, a highly dense region exists on the surface side of the metal thin film, and the surface of the metal thin film can be a dense surface, resulting in a smooth surface. The smoothness of the surface of the metal thin film can be evaluated by measuring the surface roughness of the metal thin film. Specifically, the surface smoothness can be measured by observing the surface using a laser microscope, a scanning probe microscope (SPM), or the like. In the case of a laser microscope or SPM, the surface of the first metal layer is observed within a 10 μm square area to calculate Sa, and a surface with Sa of 1 μm or less is considered smooth. From the viewpoint of further improving solder wettability, Sa may be 0.5 μm or less, 0.3 μm or less, or 0.1 μm or less.

[0061] (Aspect in which a low-density region is present between high-density regions) In one embodiment, the metal thin film further has a high-density region on the underlayer metal layer side, and the low-density region is located between the high-density region on the surface side and the high-density region on the underlayer metal layer side. By adopting such a configuration, the following effects can be achieved.

[0062] If an oxide film exists on the base metal layer at the interface between the metal laminate and the base metal layer, the oxide film may repel the solder during solder mounting, which may result in poor soldering. The oxide film on the base metal layer may be formed when the base metal layer comes into contact with air. For example, if a gap exists at the interface between the metal laminate and the base metal layer, the air in the gap may oxidize the base metal layer.

[0063] 1, when a highly dense region exists continuously from the interface between the metal laminate and the base metal layer toward the metal laminate, the dense region has few voids, so voids are unlikely to exist at the interface. Therefore, an oxide film is unlikely to form at the interface, making it easier to suppress soldering defects.

[0064] In one embodiment of the above configuration, the highly dense region may be a region from the surface of the metal thin film to 25% of the thickness of the underlying metal layer and a region from the interface between the metal thin film and the underlying metal layer to 25% of the thickness, and the less dense region may be a region of the metal thin film from the surface of the metal thin film to more than 25% but less than 75% of the thickness of the underlying metal layer.

[0065] In one embodiment of the above configuration, the highly dense region may be a region from the surface of the metal thin film up to 20% of the thickness of the underlying metal layer, preferably up to 15%, more preferably up to 10%, and even more preferably up to 5%.

[0066] In one embodiment of the above configuration, the highly dense region may be a region up to 20% of the thickness from the interface between the metal thin film and the underlying metal layer, preferably up to 15%, more preferably up to 10%, and even more preferably up to 5%.

[0067] In one embodiment of the above configuration, the low density region may be a region of the metal thin film that is more than 20% but less than 80% of the thickness of the underlying metal layer from the surface of the metal thin film, preferably more than 15% but less than 85%, more preferably more than 10% but less than 90%, and even more preferably more than 5% but less than 95%.

[0068] In one embodiment, the metal thin film of the metal laminate of the present disclosure may be composed of a high-density region and a low-density region. That is, the metal thin film may be composed of only two regions, a high-density region and a low-density region. In other words, the region of the metal thin film other than the high-density region may be a low-density region.

[0069] In one embodiment, the region from the surface of the metal thin film to 50% of the thickness of the metal thin film may be a highly dense region, and the remaining region (i.e., the region from more than 50% to 100% of the thickness) may be a less dense region; the region from the surface of the metal thin film to 40% of the thickness may be a highly dense region, and the remaining region (i.e., the region from more than 40% to 100% of the thickness) may be a less dense region; the region from the surface of the metal thin film to 30% of the thickness may be a highly dense region, and the remaining region (i.e., the region from more than 30% to 100% of the thickness) may be a less dense region; the region from the surface of the metal thin film to 20% of the thickness may be a highly dense region, and the remaining region (i.e., the region from more than 20% to 100% of the thickness) may be a less dense region; the region from the surface of the metal thin film to 10% of the thickness may be a highly dense region, and the remaining region (i.e., the region from more than 10% to 100% of the thickness) may be a less dense region; or the region from the surface of the metal thin film to 5% of the thickness may be a highly dense region, and the remaining region (i.e., the region from more than 5% to 100% of the thickness) may be a less dense region.

[0070] <Electronic Components> The metal laminate of the present disclosure can be applied to electronic components. The electronic components may be components that can be mounted on a substrate, such as capacitors, resistors, batteries, inductors, coils, thermistors, light-emitting elements, sensors, connectors, and other chip-shaped components. In particular, the metal laminate of the present disclosure can be applied to electronic components as external electrodes. The external electrodes are electrically connected to internal electrodes inside the element body of the electronic component.

[0071] [Inductor] A multilayer chip inductor will be described as an example of an electronic component including a metal laminate according to the present disclosure, but the present invention is not limited to this. Figures 3 and 4 show a multilayer chip inductor 100 according to one embodiment of the present invention.

[0072] The multilayer chip inductor 100 includes a ceramic laminate element 110 and a pair of external electrodes 120. Here, the external electrodes 120 may correspond to the metal laminate of the present disclosure.

[0073] The ceramic laminate element 110 includes a structure in which a plurality of internal electrodes (also called coil electrodes) 111 and a plurality of magnetic ceramic layers 112 are laminated.

[0074] As shown in Figures 4 and 5, internal electrodes 111 constituting a coil are formed on each main surface of the magnetic ceramic layer 112. The internal electrodes 111 on each main surface are electrically connected between via holes 113 and have a U-shape. That is, the internal electrodes 111 on each main surface have a length of 3 / 4 turn. The internal electrodes formed on the bottom and top in the stacking direction are each connected to an external electrode 120. Note that the coil electrodes are not limited to 3 / 4 turn.

[0075] The material constituting the internal electrodes 111 may be, for example, Ni, Cu, Ag, Pd, Ag, Pd, Au, or an alloy thereof (for example, Ag-Pd, etc.). The material constituting the magnetic ceramic layers 112 may be, for example, ferric oxide (Fe ２ O ３ The ceramic material may be a fired ceramic material containing zinc oxide (ZnO), nickel oxide (NiO), or copper oxide (CuO) as its main components.

[0076] 4 , the external electrodes 120 may include the metal laminate of the present disclosure, and are provided on the end surfaces of the ceramic laminate element 110 so as to be electrically connected to the internal electrodes 111. The external electrodes 120 include a first external electrode 121, a second external electrode 122, and a third external electrode 123.

[0077] The first external electrode 121 is a conductive layer containing Cu or Ag, and covers the end faces of the ceramic laminate element 110. The second external electrode 122 may be a conductive layer containing Ni, and covers the first external electrode 121. The second external electrode 122 may be a plated coating. The second external electrode 122 contributes to preventing solder erosion. The third external electrode 123 is a conductive layer containing Sn, and covers the second external electrode 122. The third external electrode 123 is the outermost layer. The third external electrode 123 may be a plated coating.

[0078] The first to third external electrodes may be made of a metal other than the above metals. For example, the first to third external electrodes may be made of at least one metal selected from the group consisting of Cu, Ni, Sn, Ag, and Au.

[0079] 1 and 4, the first external electrode 121 and the second external electrode 122 may correspond to the underlying metal layer 10 constituting the metal laminate of the present disclosure. The third external electrode 123 may correspond to the metal thin film 20 constituting the metal laminate of the present disclosure.

[0080] The inductor of the present disclosure uses the metal laminate of the present disclosure as its external electrodes. The external electrodes of the inductor of the present disclosure can suppress whisker growth, making it less likely to short-circuit between the inductor and electronic circuits, etc. Furthermore, the external electrodes of the inductor can have excellent solder wettability, making it less likely to cause soldering defects when the inductor is mounted on a substrate.

[0081] <Manufacturing method>

[0082] [Method for Manufacturing Metal Laminate] Hereinafter, a method for manufacturing a metal laminate according to one embodiment of the present disclosure will be described.

[0083] A method for manufacturing a metal laminate according to an embodiment of the present disclosure includes carrying out a base metal layer preparation step, a metal thin film formation step, and a densification step in this order.

[0084] Specifically, the method includes preparing a base metal layer, forming a metal thin film on the base metal layer, placing the base metal layer with the metal thin film formed on it into a barrel, and rotating the barrel without applying current.

[0085] [Metallic Base Layer Preparation Step] In the metallic base layer preparation step, a metallic base layer is prepared. The means for preparing the metallic base layer is not particularly limited, and a metal product such as a metal plate may be used as the metallic base layer itself, or a metal film may be formed on another article or material by a film formation method such as plating, vapor deposition, or sputtering. Alternatively, a sintered conductive paste may be used as the metallic base layer. The material for forming the metallic base layer may be any of the metals listed above in the <Metal Laminate> that can form the metallic base layer.

[0086] [Metal Thin Film Forming Step] In the metal thin film forming step, a metal thin film is formed on the base metal layer. The metal thin film may be formed by plating. The plating may be formed by conventional means. The plating is preferably wet plating. Any method such as a barrel method or a hook method can be used as the wet plating, but the barrel method is preferred in view of the densification step described below. In other words, the metal thin film may be formed by barrel plating. The material for forming the metal thin film may be a metal capable of forming the metal thin film listed above in <Metal Laminate> or a plating solution capable of forming the metal thin film.

[0087] The metal thin film formed in the metal thin film formation step may have voids. As described above, such voids can contribute to suppressing whisker growth. The voids in the metal thin film can be controlled by adjusting the conditions for forming the metal thin film. For example, the voids can be controlled by adjusting the degree of adsorption of the metal thin film to the underlying metal layer, the concentration of raw materials for the metal thin film, etc.

[0088] When the metal thin film is a plated film, the voids in the metal thin film can be controlled by the following method. The voids in the metal thin film can be controlled, for example, by adjusting the type, amount, and / or concentration of additives in the plating solution. For example, additives that are usually added to the plating solution to reduce voids in the formed plated film can be intentionally not added.

[0089] The porosity of the metal thin film can be controlled by adjusting the temperature and pH of the plating solution above or below 6. The current used for plating may be a pulse current or a constant current. A pulse current facilitates the production of a metal thin film with fewer porosity (i.e., a dense metal thin film). A constant current facilitates the production of a metal thin film with many porosity.

[0090] [Densification Step] In the densification step, the base metal layer on which the metal thin film is formed is placed in a barrel, and the barrel is rotated without passing current. The barrel may be a barrel that is normally used in barrel plating. In barrel plating, a plating process is performed by passing current through the barrel while the barrel containing the plated article is rotated. However, in the method for producing a metal laminate of the present disclosure, the barrel is rotated without passing current, so no plating process occurs.

[0091] In addition, if the metal thin film is formed by barrel plating and the base metal layer on which the metal thin film is formed is already in the barrel, the step of "putting the base metal layer on which the metal thin film is formed into the barrel" can be omitted, and the barrel can be rotated without current flow.

[0092] When the barrel is rotated without current flow, the base metal layer on which the metal thin film is formed is stirred within the barrel. Due to the stirring, the base metal layer within the barrel may come into contact with the inner wall of the barrel and / or other base metal layers contained within the barrel, and an external force is applied to the surface side of the metal thin film on the base metal layer during this contact. In other words, the surface of the metal thin film on the base metal layer may be struck by the external force resulting from the contact while the barrel is rotating. In this way, the surface side of the metal thin film on the base metal layer may have voids crushed and removed and / or the metal thin film may be compressed, resulting in a dense structure in which the metal material is densely packed.

[0093] In one embodiment, the densification process may be performed by storing media in the barrel together with the base metal layer on which the metal thin film is formed. By using media, the media come into contact with the metal thin film while the barrel is rotating, making it easier to strike the surface side of the metal thin film more efficiently.

[0094] The barrel may be rotated for 30 minutes or more up to 3 hours, for example 1 hour.

[0095] The method for manufacturing a metal laminate according to one embodiment of the present disclosure may further include, after the base metal layer preparation step and before the metal thin film formation step, the following additional metal thin film formation step and additional densification step: forming an additional metal thin film on the base metal layer; and placing the base metal layer with the additional metal thin film formed thereon into a barrel and rotating the barrel without applying current.

[0096] This manufacturing method can form a metal laminate having a structure as shown in Fig. 6. That is, the metal laminate can have a structure in which low-density regions are located between high-density regions. In this structure, high-density regions can be continuously present from the interface between the metal laminate and the base metal layer toward the metal laminate.

[0097] [Additional Metal Thin Film Forming Step] The additional metal thin film forming step can be carried out in the same manner as in the above-mentioned [Metal Thin Film Formation]. When barrel plating is used in both the [Additional Metal Thin Film Forming Step] and the [Metal Thin Film Forming Step], the metal thin film can be formed in a single process using barrel plating from the [Additional Metal Thin Film Forming Step] to the [Densification Step].

[0098] The thickness of the additional metal thin film may be thinner than the metal thin film produced in the subsequent process [Metal Thin Film Formation]. For example, the thickness of the additional metal thin film is not particularly limited as long as it is 0.5 μm or more, and may be, for example, 1.0 μm or more, 1.5 μm or more. The thickness of the additional metal thin film may be 3.0 μm or less, 2.5 μm or less, or 2.0 μm or less.

[0099] [Additional Densification Step] The additional densification step can be carried out in the same manner as in the above-mentioned [Densification Step].

[0100] The metal laminate of the present disclosure can be manufactured by the above steps.

[0101] [Method for Manufacturing Electronic Component] A method for manufacturing an electronic component according to an embodiment of the present disclosure will be described below.

[0102] A method for manufacturing an electronic component according to an embodiment of the present disclosure includes carrying out an electronic component element preparation step, a base metal layer formation step, a metal thin film formation step, and a densification step in this order.

[0103] Specifically, the method includes forming a base metal layer on the surface of an electronic component body, forming a metal thin film on the base metal layer, placing the electronic component body with the base metal layer and metal thin film formed thereon into a barrel, and rotating the barrel without applying current.

[0104] [Electronic Component Base Preparation Process] In the electronic component base preparation process, an electronic component base is prepared. An electronic component base is an electronic component in a pre-finished stage or in the middle of manufacturing. For example, it is an electronic component before a specific metal member is provided, and more specifically, it is an electronic component before an external electrode is provided. In the electronic component base, the member that performs the function of the electronic component and / or the internal electrode may be exposed to the outside.

[0105] Examples of the electronic component element include capacitors, resistors, batteries, inductors, coils, thermistors, light-emitting elements, sensors, connectors, and other chip-shaped component elements.

[0106] In one embodiment, the electronic component may be a multilayer chip inductor in which a base metal layer and a thin metal film are formed as external electrodes on the surface of an electronic component body having a structure in which internal electrodes and magnetic layers are alternately stacked. An example of a method for manufacturing a multilayer chip inductor body is described below.

[0107] First, ceramic green sheets, conductive paste for internal electrodes, and conductive paste for external electrodes are prepared. The ceramic green sheets and various conductive pastes contain binders and solvents, and known organic binders and organic solvents can be used.

[0108] The ceramic green sheets may be prepared as follows.

[0109] Ferric oxide (Fe ２ O ３ The raw materials were weighed out in the following ratios: 45 mol% zinc oxide (ZnO), 5 mol% nickel oxide (NiO), and 10 mol% copper oxide (CuO), and these materials were placed in a ball mill and wet-mixed. The resulting mixture was dried and pulverized, and the resulting powder was calcined at 800°C for 1 hour. The calcined powder was wet-pulverized in a ball mill, dried, and then crushed to obtain a ferrite ceramic powder with a particle size of 0.5 μm.

[0110] A binder (such as vinyl acetate or water-soluble acrylic), a plasticizer, a wetting agent, and a dispersant are added to the ferrite ceramic powder and mixed in a ball mill. The mixture is then degassed under reduced pressure. The resulting ceramic slurry is formed into a sheet using a doctor blade method and dried to obtain a ceramic green sheet. This ceramic green sheet can be used as a magnetic layer.

[0111] Via-hole conductors are formed in each of the prepared ceramic green sheets to connect the ceramic green sheets when the ceramic green sheets are stacked. Specifically, via holes are formed by irradiating each ceramic green sheet with a laser beam. Next, the via holes are filled with a conductive paste such as Ag, Pd, Cu, Au, or an alloy thereof by printing or other methods.

[0112] Next, an internal electrode pattern is formed by printing a conductive paste for internal electrodes on each ceramic green sheet in a predetermined pattern as shown in Fig. 5 by, for example, screen printing. The step of forming the internal electrode pattern and the step of filling the via holes with the conductive paste may be performed in the same step.

[0113] Then, a predetermined number of ceramic green sheets for outer layers that are not printed with an internal electrode pattern are stacked, and ceramic green sheets that are printed with an internal electrode pattern are stacked on top of these in order, and a predetermined number of ceramic green sheets for outer layers are stacked on top of these in the order of a pattern such as that shown in Figure 5, for example, to produce a mother laminate.

[0114] Then, the mother laminate is pressed in the lamination direction by means of a hydrostatic press or the like.

[0115] The pressed mother laminate is then cut to a predetermined size to obtain a green ceramic laminate. At this time, the corners and edges of the green ceramic laminate may be rounded by barrel polishing or the like.

[0116] The green ceramic laminate is then fired. In this case, the firing temperature is preferably 700°C to 1300°C, although this depends on the materials of the ceramic layers 112 and the internal electrodes 111. The fired ceramic laminate becomes the ceramic laminate element 110 including the ceramic layers 112 and the internal electrodes 111 of the multilayer chip inductor 100.

[0117] [Metallic Base Layer Formation Process] In the metallic base layer formation, a metallic base layer is formed on the body of the electronic component. The method for forming the metallic base layer on the body of the electronic component is not particularly limited, and for example, the metallic base layer may be formed on the body of the electronic component by applying a conductive paste and sintering it. As another method, the metallic base layer may be formed on the body of the electronic component by a film formation means such as plating, vapor deposition, or sputtering.

[0118] When a multilayer chip inductor element is used as the element of the electronic component, a base metal layer can be formed by applying a conductive paste to both end faces of the element and baking it. The conductive paste may be a paste whose main component is silver. The base metal layer forming process can be used as a process for providing external electrodes on the electronic component element.

[0119] [Metal thin film formation process] In the metal thin film formation process, a metal thin film is formed on a base metal layer. In the [metal thin film formation process] in the method for manufacturing an electronic component according to the present disclosure, the metal thin film can be formed by the same method as described in the [metal thin film formation process] for the metal laminate.

[0120] In the densification step, the electronic component element having the metal base layer and the metal thin film formed thereon is placed in a barrel, and the barrel is rotated without current flow. In the densification step in the method for manufacturing an electronic component according to the present disclosure, the metal thin film can be formed in the same manner as described in the densification step for the metal laminate described above.

[0121] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0122] In the examples, multilayer chip inductors according to Example 1, Comparative Example 1, and Comparative Example 2 shown below were manufactured, and whiskers in the coating of these multilayer chip inductors were evaluated.

[0123] Example 1 In Example 1, the multilayer chip inductor 100 shown in Figures 3 and 4 was manufactured using the method described above. In this case, the outer dimensions of the multilayer chip inductor 100 were 2.0 mm in length, 1.25 mm in width, and 1.25 mm in height. Furthermore, an Fe-Ni magnetic ceramic was used for the ceramic layer 112 (magnetic ceramic). Furthermore, Ag was used as the material for the internal electrode 111. Furthermore, Ag was used as the material for the first external electrode 121.

[0124] In Example 1, the second external electrode 122 was a Ni-plated film, and the third external electrode 123 was a Sn-plated film. The respective films were formed under the following conditions: (1) Plating Bath: The plating bath composition for forming the Ni-plated film was 300 g / L nickel sulfate, 45 g / L nickel chloride, 40 mg / L boric acid, pH: 4.0, and bath temperature: 55°C. The plating bath composition for forming the Sn-plated film was a Sn sulfate bath (50 g / L stannous sulfate, 100 g / L diammonium hydrogen citrate, and 150 g / L ammonium sulfate), with a bath temperature of 30°C and pH: 4.5. (2) Current Conditions: The Ni-plated film was formed at a current of 10 A for 75 minutes, with a thickness of 3 μm. - Sn plating film with many voids: A current of 6 A was applied for 30 minutes, resulting in a first plating layer with a thickness of 3 μm. Then, barrel processing was performed without applying current for 1 hour to form a highly dense film. (3) Plating Equipment - Plating equipment for forming the plating layer: The plating method was performed using a rotating barrel with a volume of 300 ml and a diameter of 70 mm. 40 ml of balls made of Sn with a diameter of 0.7 mm were used as the media. A nylon-coated iron ball with a diameter of 8.0 mm and a capacity of 50 cc was used as the stirring ball. The chip charge amount was 20 ml. The barrel rotation speed was 20 rpm.

[0125] After the Ni plating film and the Sn plating film were formed as described above, they were dried in air for 15 minutes at 80° C. After each Ni plating film and each Sn plating film was formed, the film was washed with pure water.

[0126] [Comparative Example 1] - Composition of plating bath for forming Sn plating film: NB-RZS manufactured by Ishihara Pharmaceutical Co., Ltd., bath temperature 30°C, pH: 4.5. This Ni plating layer forms only a highly dense plating layer. (No current barrel processing is required.)

[0127] Comparative Example 2 A multilayer ceramic capacitor was produced in the same manner as in Example 1, except that no current-free barrel processing was performed.

[0128] Next, the growth of whiskers occurring in the plating film was evaluated for each of the multilayer chip inductors of Example 1, Comparative Example 1, and Comparative Example 2 in accordance with the JEDEC standard shown below. The evaluation of whisker growth was performed using the thermal shock test and humidity storage test described below. The thermal shock test was performed mainly to evaluate the growth of whiskers occurring due to differences in thermal expansion coefficients, and the humidity storage test was performed mainly to evaluate the growth of whiskers occurring due to galvanic corrosion.

[0129] (Thermal Shock Test) Number of samples (number of electrodes): 6 Test conditions: Minimum temperature -55°C (+0 / -10), maximum temperature 85°C (+10 / -0), held at each temperature for 10 minutes, and subjected to 1500 thermal shocks in a gas phase. Observation method: Observed using a scanning electron microscope (SEM) at 1000x magnification. Evaluation criteria: Class 2 (communications infrastructure equipment, automotive equipment) was applied, and for each sample of Example 1, Comparative Example 1, and Comparative Example 2, a whisker maximum length (linear length) of less than 45 μm was evaluated as good, and a whisker maximum length of 45 μm or more was evaluated as not good.

[0130] (Wet storage test) Number of tests (number of electrodes): 6 Test conditions: Ambient temperature 55°C (+0 / -10), humidity 85% RH, and storage for 4000 hours. Observation method: Observation was performed using a scanning electron microscope (SEM) and electron micrographs at 1000x magnification. Evaluation criteria: Class 2 (communications infrastructure equipment, automotive equipment) was applied, and for the samples of Example 1, Comparative Example 1, and Comparative Example 2, a maximum whisker length (linear length) of less than 45 μm was evaluated as good, and a maximum whisker length of 45 μm or more was evaluated as not good.

[0131] Furthermore, the solder wettability was evaluated for each of the multilayer chip inductors of Example 1, Comparative Example 1, and Comparative Example 2. The evaluation was performed by the wettability evaluation test described below.

[0132] (Wettability Evaluation Test) In the wettability evaluation test, the multilayer chip inductors obtained in Example 1, Comparative Example 1, and Comparative Example 2 were immersed in a solder bath (245°C) containing lead-free solder M705 (Sn-3Ag-0.5Cu) using flux C (rosin-ethanol). The solderability in Example 1, Comparative Example 1, and Comparative Example 2 was evaluated based on the zero-cross time measured by the solder sphere equilibrium method using a solderability tester (RHESCA SAT-5000). The evaluation criteria for the zero-cross time were an average of 2 seconds or less, which was deemed to be good (corresponding standards: International Standard IEC 60068-2-69, Japanese Industrial Standard JIS C 60068-2-69).

[0133] Table 1 shows the test results and the evaluation results for each of Example 1, Comparative Example 1, and Comparative Example 2. In Table 1, evaluation results that met the evaluation criteria are indicated by "G," and results that did not meet the evaluation criteria are indicated by "NG."

[0134]

[0135] First, looking at the results of the thermal shock test, in Example 1, the maximum whisker length was 20 μm, which satisfied the evaluation criteria. On the other hand, in Comparative Example 1, the maximum whisker length was 60 μm, which did not satisfy the evaluation criteria. In Comparative Example 2, the maximum whisker length was 30 μm, which satisfied the evaluation criteria.

[0136] Next, looking at the results of the humidity storage test, the maximum whisker length was 0 μm in Example 1, which met the evaluation criteria. On the other hand, the maximum whisker length was 0 μm in Comparative Example 1, which met the evaluation criteria. The maximum whisker length was 60 μm in Comparative Example 2, which did not meet the evaluation criteria.

[0137] To summarise the results of the thermal shock test and the wet storage test, Example 1 was judged to have whiskers as "G" because the evaluation results of both tests met the criteria, while Comparative Examples 1 and 2 were judged to have whiskers as "NG" because one of the evaluation results did not meet the criteria.

[0138] One of the reasons for the formation of whiskers is thought to be that stress concentration occurring inside the Sn-plated film causes Sn crystal grains in the Sn-plated film to be pushed out of the film.

[0139] The reason that Example 1 and Comparative Example 2 satisfied the criteria in the thermal shock test is believed to be because the Sn-plated film has a low-density region. More specifically, it is believed that Example 1 has a low-density region in the Sn-plated film closer to the Ni-plated film. It is believed that Comparative Example 2 has a low-density region throughout the Sn film. A relatively large number of voids exist in the low-density region. Stress generated in the Sn film can escape and disperse into the voids, so the stress generated in the Sn film can be reduced. It is believed that this is the reason why whisker growth was suppressed in Example 1 and Comparative Example 2.

[0140] Looking at the results of the solderability evaluation test, the solderability test results for Example 1 met the criteria. On the other hand, the solderability test results for Comparative Example 1 met the criteria. On the other hand, the solderability test results for Comparative Example 2 did not meet the criteria.

[0141] The reason why Example 1 and Comparative Example 1 obtained good results in the solderability evaluation test is thought to be because the Sn plated film has a highly dense region. More specifically, Example 1 is thought to have a highly dense region on the surface side of the Sn plated film. In Comparative Example 1, the entire Sn film is thought to have a highly dense region. The highly dense region is thought to have few voids, resulting in a dense Sn film, which can result in improved smoothness of the Sn film surface. For these reasons, it is thought that Example 1 and Comparative Example 1 had improved solder wettability.

[0142] The metal laminate and the manufacturing method thereof according to the present disclosure have been described above, but they are merely typical examples. Therefore, those skilled in the art will easily understand that the coil component and the manufacturing method thereof according to the present disclosure are not limited to these, and that various embodiments are possible.

[0143] The present disclosure provides a metal laminate and a method for manufacturing the same, including: <1> a metal laminate comprising a metal base layer and a metal thin film formed on the metal base layer, wherein the metal thin film includes a high-density region and a low-density region, and the high-density region is at least on the surface side of the metal thin film. <2> The metal laminate according to <1>, wherein the high-density region is adjacent to the low-density region. <3> The metal laminate according to <1> or <2>, wherein the metal thin film comprises a high-density region and a low-density region. <4> The metal laminate according to any one of <1> to <3>, wherein the high-density region is a region extending up to 50% of the thickness from the surface of the metal thin film, and the low-density region is a region extending more than 50% of the thickness from the interface between the metal thin film and the metal base layer. <5> The metal laminate according to any one of <1> to <4>, wherein the high-density region is a region extending up to 0.5 μm from the surface of the metal thin film. <6> The metal laminate according to any one of <1> to <5>, wherein the low-density region has a thickness of 1.0 μm or more. <7> The metal laminate according to any one of <1> to <6>, wherein the low-density region exists continuously in the thickness direction from the interface between the base metal layer and the metal thin film to the surface of the metal thin film. <8> The metal laminate according to any one of <1> to <7>, wherein the metal thin film further includes a high-density region on the base metal layer side, and the low-density region is located between the high-density region on the surface side and the high-density region on the base metal layer side. <9> The metal laminate according to <8>, wherein the high-density region is a region from the surface of the metal thin film to 25% of the thickness of the base metal layer and a region from the interface between the metal thin film and the base metal layer to 25% of the thickness, and the low-density region is a region of the metal thin film from the surface of the metal thin film to more than 25% but less than 75% of the thickness of the base metal layer. <10> The metal laminate according to any one of <1> to <9>, wherein the low-density region has voids, and the porosity of the low-density region is 1% or more. <11> The metal laminate according to <10>, wherein the low-density region has voids, and the porosity of the low-density region is 10% or less.<12> The metal laminate according to any one of <1> to <11>, wherein the surface roughness Sa of the surface of the metal thin film is 1 μm or less. <13> The metal laminate according to <1>, wherein the metal thin film comprises a high-density region and a low-density region, the high-density region being a region extending from the surface of the metal thin film to 50% of the thickness, the low-density region being a region extending from the interface between the metal thin film and the base metal layer to more than 50% of the thickness, the low-density region having voids, and the porosity of the low-density region being 1% or more. <14> The metal laminate according to any one of <1> to <13>, wherein the metal thin film is a plated film. <15> The metal laminate according to any one of <1> to <14>, wherein the metal thin film contains Sn. <16> An electronic component having the metal laminate according to any one of <1> to <15>. <17> The electronic component according to <16>, which is a multilayer chip inductor having a structure in which internal electrodes and magnetic layers are alternately stacked. <18> A method for manufacturing a metal laminate, comprising: preparing a base metal layer; forming a metal thin film on the base metal layer; placing the base metal layer with the metal thin film formed on it in a barrel and rotating the barrel without passing current through it. <19> A method for manufacturing an electronic component, comprising: forming a base metal layer on the surface of an electronic component base body; forming a metal thin film on the base metal layer; placing the electronic component base body with the base metal layer and the metal thin film formed on it in a barrel and rotating the barrel without passing current through it. <20> The method for manufacturing an electronic component according to <19>, wherein the electronic component is a multilayer chip inductor in which the base metal layer and the metal thin film are formed as external electrodes on the surface of the electronic component base body having a structure in which internal electrodes and magnetic layers are alternately stacked.

[0144] The metal laminate of the present disclosure is applicable to various electronic components, such as multilayer chip inductors that are mounted at high density.

[0145] REFERENCE SIGNS LIST 1 Metal laminate 10 Undercoating metal layer 20 Metal thin film 21 Surface side of metal thin film 21a Surface of metal thin film 22 Undercoating metal layer side of metal thin film 22a Interface between metal thin film and undercoating metal layer 30 Highly dense region 40 Less dense region 50 Void 100 Multilayer chip inductor 110 Ceramic laminate element 111 Internal electrode 112 Magnetic ceramic layer 113 Via hole 120 External electrode 121 First external electrode 122 Second external electrode 123 Third external electrode

Claims

1. A metal laminate comprising a base metal layer and a thin metal film formed on the base metal layer, the thin metal film including a highly dense region and a less dense region, and the thin metal film having a highly dense region at least on the surface side of the thin metal film.

2. The metal laminate according to claim 1, wherein the high density region is adjacent to the low density region.

3. The metal laminate according to claim 1, wherein the metal thin film comprises a highly dense region and a less dense region.

4. A metal laminate according to any one of claims 1 to 3, wherein the highly dense region is a region extending from the surface of the metal thin film to 50% of the thickness, and the less dense region is a region extending from the interface between the metal thin film and the base metal layer to more than 50% of the thickness.

5. A metal laminate according to any one of claims 1 to 4, wherein the highly dense region is a region extending from the surface of the metal thin film to a depth of 0.5 μm.

6. The metal laminate according to any one of claims 1 to 5, wherein the region with low density has a thickness of 1.0 μm or more.

7. A metal laminate according to any one of claims 1 to 6, wherein the region of low density exists continuously in the thickness direction from the interface between the base metal layer and the metal thin film toward the surface of the metal thin film.

8. A metal laminate according to any one of claims 1 to 7, further comprising a highly dense region on the base metal layer side of the metal thin film, the less dense region being located between the highly dense region on the surface side and the highly dense region on the base metal layer side.

9. The metal laminate described in claim 8, wherein the highly dense region is a region from the surface of the metal thin film to 25% of the thickness of the base metal layer and a region from the interface between the metal thin film and the base metal layer to 25% of the thickness, and the less dense region is a region of the metal thin film from the surface of the metal thin film to more than 25% but less than 75% of the thickness of the base metal layer.

10. A metal laminate according to any one of claims 1 to 9, wherein the less dense region has voids, and the porosity of the less dense region is 1% or more.

11. The metal laminate according to claim 10, wherein the less dense region has voids, and the porosity of the less dense region is 10% or less.

12. The metal laminate according to any one of claims 1 to 11, wherein the surface roughness Sa of the surface of the metal thin film is 1 μm or less.

13. The metal laminate of claim 1, wherein the metal thin film is composed of a highly dense region and a less dense region, the highly dense region being a region extending up to 50% of the thickness from the surface of the metal thin film, the less dense region being a region extending more than 50% of the thickness from the interface between the metal thin film and the underlying metal layer, the less dense region having voids, and the porosity of the less dense region being 1% or more.

14. The metal laminate according to any one of claims 1 to 13, wherein the thin metal film is a plated film.

15. The metal laminate according to any one of claims 1 to 14, wherein the metal thin film contains Sn.

16. An electronic component having the metal laminate according to any one of claims 1 to 15.

17. The electronic component according to claim 16, which is a multilayer chip inductor having a structure in which internal electrodes and magnetic layers are alternately laminated.

18. A method for manufacturing a metal laminate, comprising: preparing a base metal layer; forming a metal thin film on the base metal layer; placing the base metal layer with the metal thin film formed thereon into a barrel; and rotating the barrel without passing electric current through it.

19. A method for manufacturing an electronic component, comprising: forming a base metal layer on a surface of an electronic component body; forming a thin metal film on the base metal layer; placing the electronic component body with the base metal layer and thin metal film formed thereon into a barrel; and rotating the barrel without passing current through it.

20. A method for manufacturing an electronic component as described in claim 19, wherein the electronic component is a multilayer chip inductor in which the base metal layer and the metal thin film are formed as external electrodes on the surface of the electronic component base body having a structure in which internal electrodes and magnetic layers are alternately laminated.

Images