Ag-COATED MATERIAL AND ELECTRICAL / ELECTRONIC COMPONENT

Abstract

The present invention provides an Ag-coated material and an electrical / electronic component which are capable of suppressing a decrease in adhesion against fatigue and are also capable of suppressing an increase in contact resistance after heating. This Ag-coated material is obtained by superposing, on one surface or both surfaces of a conductive base material that is formed of an Fe-based alloy and has a Vickers hardness (HV) of 300 or more, an Ni-containing layer, a Cu-containing layer, and an Ag-containing layer in this order. The thickness of the Ni-containing layer is 0.05 μm or more and 2.00 μm or less, and the thickness of the Cu-containing layer is 0.05 μm or more and 1.00 μm or less. When a cross-section including the thickness direction of the Ag-coated material is observed, the average crystal grain size of a plurality of Ni crystal grains which are cut by a straight line that is perpendicular to the thickness direction of the Ag-coated material in the Ni-containing layer is 0.80 μm or less, and the average crystal grain size of a plurality of Cu crystal grains which are cut by the straight line in the Cu-containing layer is 0.80 μm or less.

Description

Ag-coated materials and electrical and electronic components

[0001] The present disclosure relates to an Ag-coated material and an electric / electronic component.

[0002] Conventionally, plated materials have been used as materials for contacts and terminal parts in connectors, switches, etc. Plated materials are made by plating a substrate, such as stainless steel or a copper-based material like copper or a copper alloy, which is relatively inexpensive and has excellent corrosion resistance and mechanical properties, with tin, silver, gold, or other plating material depending on the desired properties, such as electrical properties and solderability.

[0003] For example, Patent Document 1 describes a silver-plated product in which a base layer made of Ni is formed on the surface of a material made of stainless steel, an intermediate layer made of Cu is formed thereon, and a surface layer made of Ag is formed thereon, and the crystallite diameter in the direction perpendicular to the (111) plane of the surface layer is 300 angstroms or more.

[0004] In recent years, the miniaturization and increased lifespan of electronic devices has led to increased loads on surface layers, which are formed on the surface of a substrate and consist of a single layer or multiple laminated layers. In particular, for components that operate repeatedly, such as switches, fatigue characteristics become an issue as lifespans increase. However, with the silver-plated material disclosed in Patent Document 1, it is difficult to maintain adhesion between the substrate and the surface layer even after a fatigue test that involves a long thermal history, which is required when incorporating the plated material into products such as connectors.

[0005] JP 2012-119308 A

[0006] An object of the present disclosure is to provide an Ag coating material and an electric / electronic component that can suppress a decrease in adhesion due to fatigue and can suppress an increase in contact resistance after heating.

[0007] [1] An Ag-coated material comprising a conductive substrate made of an Fe-based alloy and having a Vickers hardness (HV) of 300 or more, and a Ni-containing layer, a Cu-containing layer, and an Ag-containing layer laminated in this order on one or both sides of the conductive substrate, the Ni-containing layer having a thickness of 0.05 μm to 2.00 μm, the Cu-containing layer having a thickness of 0.05 μm to 1.00 μm, and a cross section including the thickness direction of the Ag-coated material, in the Ni-containing layer, taken along a line perpendicular to the thickness direction of the Ag-coated material, has an average crystal grain size of 0.80 μm or less, and a cross section including the thickness direction of the Ag-coated material, in the Cu-containing layer, taken along the line, has an average crystal grain size of 0.80 μm or less. [2] The Ag-coated material according to [1] above, wherein the conductive substrate is made of an Fe—Ni—Cr-based alloy or an Fe—Ni-based alloy. [3] The Ag-coated material according to [1] or [2] above, wherein, when viewing the lamination interface between the Ni-containing layer and the Cu-containing layer in the cross section, the ratio (l / L) of the sum of the lengths (l) of one or more interface portions at the lamination interface, where a Ni crystal grain and a Cu crystal grain adjacent to the Ni crystal grain have the same crystal orientation, to the total length (L) of the lamination interface in the measurement region is 0.2 or more. [4] The Ag-coated material according to any one of [1] to [3] above, wherein the Ag-containing layer has a thickness of 0.05 μm or more and 5.00 μm or less. [5] An electric / electronic component comprising the Ag-coated material according to any one of [1] to [4] above.

[0008] According to the present disclosure, it is possible to provide an Ag coating material and an electric / electronic component that can suppress a decrease in adhesion due to fatigue and can suppress an increase in contact resistance after heating.

[0009] Fig. 1 is a perspective view showing an example of an Ag-coated material according to an embodiment. Fig. 2 is a cross-sectional view showing an example of a cross-section including the thickness direction of the Ag-coated material shown in Fig. 1. Fig. 3 is an enlarged cross-sectional view showing region A in Fig. 2. Fig. 4 is a SIM image obtained by observing a cross-section including the thickness direction of the Ag-coated material of Example 9 using SIM.

[0010] The embodiments will be described in detail below.

[0011] As a result of extensive research, the present inventors have found that an Ag coating material having a Ni-containing layer having a predetermined thickness and including Ni crystal grains with a predetermined average crystal grain size, a Cu-containing layer having a predetermined thickness and including Cu crystal grains with a predetermined average crystal grain size, and an Ag-containing layer laminated in this order on the surface of a conductive substrate made of an Fe-based alloy having a predetermined Vickers hardness can suppress a decrease in adhesion due to fatigue and can also suppress an increase in contact resistance after heating, and have completed the present disclosure based on this finding.

[0012] The Ag-coated material of the embodiment comprises a conductive substrate made of an Fe-based alloy and having a Vickers hardness (HV) of 300 or more, on one or both sides of which a Ni-containing layer, a Cu-containing layer, and an Ag-containing layer are laminated in this order. The Ni-containing layer has a thickness of 0.05 μm or more and 2.00 μm or less, and the Cu-containing layer has a thickness of 0.05 μm or more and 1.00 μm or less. When viewed in a cross section including the thickness direction of the Ag-coated material, the Ni-containing layer has a plurality of Ni crystal grains cut by a line perpendicular to the thickness direction of the Ag-coated material, and the Cu-containing layer has a plurality of Cu crystal grains cut by the line, which have an average crystal grain size of 0.80 μm or less.

[0013] Fig. 1 is a perspective view showing an example of an Ag-coated material according to an embodiment. Fig. 2 is a cross-sectional view showing an example of a cross-section including the thickness direction of the Ag-coated material shown in Fig. 1. Fig. 3 is an enlarged cross-sectional view showing region A in Fig. 2. Note that Figs. 1 to 3 show an example in which Ni-containing layers 3a and 3b are provided on both sides of a conductive substrate 2.

[0014] 1 to 3, an Ag-coated material 1 according to an embodiment includes a conductive substrate 2, Ni-containing layers 3a and 3b, Cu-containing layers 4a and 4b, and Ag-containing layers 5a and 5b. In the Ag-coated material 1, the Ni-containing layers 3a and 3b, the Cu-containing layers 4a and 4b, and the Ag-containing layers 5a and 5b are laminated in this order on one or both surfaces of the conductive substrate 2.

[0015] 1 to 3, Ni-containing layers 3a, 3b, Cu-containing layers 4a, 4b, and Ag-containing layers 5a, 5b are laminated in this order on both sides of the conductive substrate 2. That is, the Ni-containing layer 3a, Cu-containing layer 4a, and Ag-containing layer 5a are laminated in this order on the front surface 2a of the conductive substrate 2, and the Ni-containing layer 3b, Cu-containing layer 4b, and Ag-containing layer 5b are laminated in this order on the back surface 2b of the conductive substrate 2. However, in the Ag-coated material 1, the Ni-containing layer 3a, Cu-containing layer 4a, and Ag-containing layer 5a are laminated in this order only on the front surface 2a of the conductive substrate 2, and the Ni-containing layer 3b does not necessarily have to be provided on the back surface 2b of the conductive substrate 2. In addition, the Ni-containing layer 3b, the Cu-containing layer 4b, and the Ag-containing layer 5b may be laminated in this order only on the back surface 2b of the conductive substrate 2, and the Ni-containing layer 3a may not be provided on the front surface 2a of the conductive substrate 2.

[0016] The conductive substrate 2 constituting the Ag coating material 1 is made of an Fe-based alloy and has a Vickers hardness (HV) of 300 or more. The conductive substrate 2 is plate-shaped and has two opposing main surfaces, a front surface 2a and a back surface 2b. Here, the upper surface of the conductive substrate 2 is the front surface 2a, and the lower surface is the back surface 2b.

[0017] An Fe-based alloy has strength that is difficult to achieve with a Cu-based alloy, and the conductive substrate 2 has excellent fatigue properties, so the conductive substrate 2 is made of an Fe-based alloy rather than a Cu-based alloy. The Fe-based alloy that constitutes the conductive substrate 2 is preferably an alloy containing at least one element of nickel (Ni) and chromium (Cr). In particular, from the viewpoint of increasing the mechanical strength of the conductive substrate 2, the conductive substrate 2 is preferably an Fe—Ni—Cr-based alloy or an Fe—Ni-based alloy.

[0018] The Fe—Ni—Cr alloy is preferably stainless steel, more preferably SUS 301, SUS 304, or SUS 630. The Fe—Ni alloy is preferably 42 alloy (Fe-42 mass % Ni).

[0019] The Fe—Ni—Cr alloy and the Fe—Ni alloy may be produced by melting and casting, or the Fe—Ni alloy may be produced by electroplating.

[0020] From the viewpoint of improving the fatigue life of the conductive substrate 2, the Vickers hardness (HV) of the conductive substrate 2 is 300 or more, and preferably 330 or more. From the viewpoint of processability, the Vickers hardness (HV) of the conductive substrate 2 is preferably 650 or less.

[0021] The Vickers hardness (HV) of the conductive substrate 2 is measured in accordance with the Vickers hardness testing method described in JIS Z2244 (2009) at a cross section including the thickness direction Y of the conductive substrate 2. The Vickers hardness (HV) of the conductive substrate 2 is determined by measuring the Vickers hardness (HV) at a cross section including the thickness direction Y of the conductive substrate 2 with a load (test force) of 0.049 N when pressing the diamond indenter into the cross section including the thickness direction Y of the conductive substrate 2 and setting the pressing time of the indenter to 15 seconds.

[0022] The thickness t2 of the conductive substrate 2 is not particularly limited, and is, for example, 10 μm or more and 100 μm or less from the viewpoint of reducing the height and size of the electric / electronic component provided with the Ag coating material 1.

[0023] Ni-containing layers 3a, 3b are provided on both surfaces (front surface 2a and back surface 2b) of the conductive substrate 2. The Ni-containing layer 3a only needs to be provided on at least a portion of the front surface 2a of the conductive substrate 2, and may be provided, for example, on the entire surface of the front surface 2a as shown in the figure, or on a portion of the front surface 2a. The Ni-containing layer 3b only needs to be provided on at least a portion of the back surface 2b of the conductive substrate 2, and may be provided, for example, on the entire surface of the back surface 2b as shown in the figure, or on a portion of the back surface 2b.

[0024] In the Ag coating material 1, by providing the Ni-containing layers 3a and 3b between the conductive substrate 2 and the Cu-containing layers 4a and 4b, respectively, it is possible to improve the adhesion between the conductive substrate 2 and the Cu-containing layers 4a and 4b. On the other hand, if the Cu-containing layers 4a and 4b are provided directly on the surfaces (front surface 2a and back surface 2b) of the conductive substrate 2 without providing the Ni-containing layers 3a and 3b, the Cu-containing layers 4a and 4b are likely to peel off from the surface of the conductive substrate 2.

[0025] The Ni-containing layers 3 a, 3 b are preferably made of nickel (Ni) or a Ni-based alloy. From the viewpoint of further improving the adhesion between the conductive substrate 2 and the Cu-containing layers 4 a, 4 b, the Ni-containing layers 3 a, 3 b are preferably made of Ni or a Ni-based alloy containing 99.0 mass % or more of Ni, with the remainder being unavoidable impurities.

[0026] If the thicknesses t3a and t3b of the Ni-containing layers 3a and 3b are less than 0.05 μm, the Ni-containing layers 3a and 3b cannot exhibit the effect of improving the adhesion between the conductive substrate 2 and the Cu-containing layers 4a and 4b. If the thicknesses t3a and t3b of the Ni-containing layers 3a and 3b are 2.00 μm or less, cracking and peeling of the Ni-containing layers 3a and 3b can be suppressed when the Ag-coated material 1 is bent. Therefore, the lower limit of the thicknesses t3a and t3b of the Ni-containing layers 3a and 3b is 0.05 μm or more, and the upper limit is 2.00 μm or less, preferably 1.50 μm or less.

[0027] The Cu-containing layers 4a and 4b are provided on the surfaces of the Ni-containing layers 3a and 3b (the surfaces not in contact with the conductive substrate 2). The Cu-containing layers 4a and 4b are provided between the Ni-containing layers 3a and 3b and the Ag-containing layers 5a and 5b.

[0028] The Cu-containing layers 4a, 4b improve the adhesion between the Ni-containing layers 3a, 3b and the Ag-containing layers 5a, 5b, and also contribute to improving the overall adhesion of the surface layer composed of the Ni-containing layers 3a, 3b, the Cu-containing layers 4a, 4b, and the Ag-containing layers 5a, 5b laminated on the surfaces (front surface 2a and back surface 2b) of the conductive substrate 2.

[0029] The Cu-containing layers 4 a, 4 b are preferably made of copper (Cu) or a Cu-based alloy. From the viewpoint of improving the tensile strength and electrical conductivity of the Ag-coated material 1, the Cu-containing layers 4 a, 4 b are preferably made of Cu or a Cu-based alloy containing 99.0 mass % or more of Cu with the remainder being unavoidable impurities.

[0030] If the thicknesses t4a and t4b of the Cu-containing layers 4a and 4b are less than 0.05 μm, the Cu-containing layers 4a and 4b cannot exhibit the effect of improving the adhesion between the Ni-containing layers 3a and 3b and the Ag-containing layers 5a and 5b. Furthermore, if the thicknesses t4a and t4b of the Cu-containing layers 4a and 4b are 1.00 μm or less, an increase in the contact resistance of the Ag-coated material 1 can be suppressed even when the Ag-coated material 1 is exposed to high temperatures. Therefore, the lower limit of the thicknesses t4a and t4b of the Cu-containing layers 4a and 4b is 0.05 μm or more, and the upper limit is 1.00 μm or less, preferably 0.80 μm or less.

[0031] 3 , when viewed in a cross section including the thickness direction Y of the Ag coating material 1, the average crystal grain size of the plurality of Ni crystal grains 30a, 30b in the Ni-containing layers 3a, 3b (hereinafter simply referred to as the average crystal grain size of the Ni-containing layers) is 0.80 μm or less, and the average crystal grain size of the plurality of Cu crystal grains 40a, 40b in the Cu-containing layers 4a, 4b (hereinafter simply referred to as the average crystal grain size of the Cu-containing layers) is 0.80 μm or less. The average crystal grain size of the Ni-containing layers 3a, 3b is the average outer dimension of the plurality of Ni crystal grains 30a, 30b cut by a line perpendicular to the thickness direction Y of the Ag coating material 1. The average crystal grain size of the Cu-containing layers 4a, 4b is the average outer dimension of the plurality of Cu crystal grains 40a, 40b cut by a line perpendicular to the thickness direction Y of the Ag coating material 1.

[0032] Setting the average crystal grain size of the Ni-containing layers 3a, 3b to 0.80 μm or less can suppress non-uniform deformation of the Ag-coated material 1 and disperse bending strain during use of the Ag-coated material 1, thereby improving the adhesion between the conductive substrate 2 and the Cu-containing layers 4a, 4b after bending the Ag-coated material 1. The lower limit of the average crystal grain size of the Ni-containing layers 3a, 3b is not particularly limited, but is, for example, 0.05 μm or more.

[0033] Furthermore, by setting the average crystal grain size of the Cu-containing layers 4a, 4b to 0.80 μm or less, it is possible to suppress non-uniform deformation of the Ag-coated material 1 and to distribute bending strain during use of the Ag-coated material 1. Furthermore, since the Cu-containing layers 4a, 4b are softer and more susceptible to local deformation than the Ni-containing layers 3a, 3b, setting the average crystal grain size of the Cu-containing layers 4a, 4b to 0.80 μm or less can efficiently improve the adhesion between the Ni-containing layers 3a, 3b and the Ag-containing layers 5a, 5b after bending the Ag-coated material 1. The lower limit of the average crystal grain size of the Cu-containing layers 4a, 4b is not particularly limited, but is, for example, 0.05 μm or more.

[0034] The average crystal grain size of the Ni-containing layers 3a, 3b and the average crystal grain size of the Cu-containing layers 4a, 4b are measured as follows. First, a cross section including the thickness direction Y of the Ag-coated material 1 is formed using a focused ion beam (FIB) device (Hitachi, Ltd., FB2000A). Next, the cross section of the Ag-coated material 1 is observed using a scanning ion microscope (Seiko Instruments Inc., SMI3050TB). From the channeling contrast (crystal orientation information) appearing in the obtained scanning ion microscope (SIM) image, the number of points where each crystal grain (Ni crystal grain, Cu crystal grain) intersects with a line perpendicular to the thickness direction Y of the Ag-coated material 1 can be counted, and the average length of the line segments defined by each crystal grain can be calculated using a cutting method to determine the average crystal grain size of the multiple crystal grains (Ni crystal grains, Cu crystal grains).

[0035] In order to further improve the adhesion between the Ni-containing layers 3 a, 3 b and the Cu-containing layers 4 a, 4 b, it is preferable that the crystal orientations of the Ni crystal grains 30 a, 30 b and the Cu crystal grains 40 a, 40 b adjacent to each other via the stacking interfaces 6 a, 6 b are highly identical. More specifically, as shown in Fig. 3, when the stacking interfaces 6 a, 6 b between the Ni-containing layers 3 a, 3 b and the Cu-containing layers 4 a, 4 b are viewed in a cross section including the thickness direction Y of the Ag coating material 1, the ratio (l) of the sum (l) of the lengths (l1 to l10) of one or more interface portions at the stacking interfaces 6 a, 6 b, where the Ni crystal grains 30 a, 30 b and the Cu crystal grains 40 a, 40 b adjacent to the Ni crystal grains 30 a, 30 b have the same crystal orientation, to the total length (L) of the stacking interfaces 6 a, 6 b in the measurement region 10 is preferably 0.2 or more.

[0036] Here, when the Ni-containing layers 3a, 3b, the Cu-containing layers 4a, 4b, and the Ag-containing layers 5a, 5b are provided on both sides of the conductive substrate 2, the total length (L) is the sum of the total length La of the lamination interface 6a and the total length Lb of the lamination interface 6b. When the Ni-containing layer 3a, the Cu-containing layer 4a, and the Ag-containing layer 5a are provided on the front surface 2a of the conductive substrate 2, and the Ni-containing layer 3b, the Cu-containing layer 4b, and the Ag-containing layer 5b are not provided on the back surface 2b of the conductive substrate 2, the total length (L) is the total length La of the lamination interface 6a. When the Ni-containing layer 3b, the Cu-containing layer 4b, and the Ag-containing layer 5b are provided on the back surface 2b of the conductive substrate 2, and the Ni-containing layer 3a, the Cu-containing layer 4a, and the Ag-containing layer 5a are not provided on the front surface 2a of the conductive substrate 2, the total length (L) is the total length Lb of the lamination interface 6b.

[0037] When the ratio (l / L) of the sum of the lengths (l=l1 to l10 in FIG. 3 ) of the interface portions where the Ni crystal grains 30a, 30b of the Ni-containing layers 3a, 3b and the Cu crystal grains 40a, 40b of the Cu-containing layers 4a, 4b adjacent to the Ni crystal grains 30a, 30b via the stacking interfaces 6a, 6b have the same crystal orientation, relative to the total length (L) of the stacking interfaces 6a, 6b, is 0.2 or more, the Ni-containing layers 3a, 3b and the Cu-containing layers 4a, 4b undergo deformation similarly, thereby further improving the adhesion between the Ni-containing layers 3a, 3b and the Cu-containing layers 4a, 4b. The upper limit of the ratio (l / L) is not particularly limited, but may be, for example, 1.0 or less.

[0038] The crystal orientations of the Ni crystal grains 30a, 30b and the Cu crystal grains 40a, 40b, which are located on either side of the stacking interfaces 6a, 6b, are confirmed as follows: First, a cross section of the Ag coating material 1, including the thickness direction Y, is formed using a focused ion beam device (Hitachi, FB2000A). Next, the cross section of the Ag coating material 1 is observed using a scanning ion microscope (Seiko Instruments Inc., SMI3050TB), and the channeling contrast that appears in the resulting SIM image is used. In the SIM image, the interface portions 6a and 6b at which the dark Ni crystal grains 30a and 30b in the Ni-containing layers 3a and 3b are adjacent to the dark Cu crystal grains 40a and 40b in the Cu-containing layers 4a and 4b, and the interface portions 6a and 6b at which the light Ni crystal grains 30a and 30b in the Ni-containing layers 3a and 3b are adjacent to the light Cu crystal grains 40a and 40b in the Cu-containing layers 4a and 4b, are referred to as interface portions at which the Ni crystal grains 30a and 30b and the Cu crystal grains 40a and 40b have the same crystal orientation. In Fig. 3, the Ni crystal grains 30a and 30b and the Cu crystal grains 40a and 40b among the plurality of Ni crystal grains 30a and 30b and the plurality of Cu crystal grains 40a and 40b that have the same crystal orientation and are adjacent to each other through the interface portions are hatched for convenience.

[0039] The Ag-containing layers 5a and 5b are provided on the surfaces of the Cu-containing layers 4a and 4b (the surfaces not in contact with the Ni-containing layers 3a and 3b). The Ag-containing layers 5a and 5b are the outermost layers on both sides of the Ag-coated material 1 and can reduce the contact resistance of the Ag-coated material 1.

[0040] The Ag-containing layers 5 a, 5 b are preferably made of Ag (silver) or an Ag-based alloy. From the viewpoint of efficiently reducing the contact resistance of the Ag coating material 1, the Ag-containing layers 5 a, 5 b are preferably made of Ag or an Ag-based alloy containing 99.0 mass % or more of Ag and the remainder being unavoidable impurities.

[0041] Furthermore, when the thicknesses t5a and t5b of the Ag-containing layers 5a and 5b are 0.05 μm or more, the contact resistance of the Ag coating material 1 can be further reduced. From the viewpoint of cost, the thicknesses t5a and t5b of the Ag-containing layers 5a and 5b are preferably 5.00 μm or less. Therefore, the thicknesses t5a and t5b of the Ag-containing layers 5a and 5b are preferably 0.05 μm or more and 5.00 μm or less.

[0042] Such an Ag coating material is suitable for use in electrical and electronic components that require suppression of a decrease in adhesion due to fatigue and suppression of an increase in contact resistance after heating. Such electrical and electronic components include connectors, switches, relays, shield cases, and flexible flat cables.

[0043] Next, a method for producing the Ag-coated material of the above embodiment will be described. The method for producing the Ag-coated material includes a degreasing step, an activation step, a Ni-containing layer formation step, a Cu-containing layer formation pretreatment step, a Cu-containing layer formation step, and an Ag-containing layer formation step. After each step, the sample may be washed with water.

[0044] In the degreasing step, the conductive substrate is degreased before the Ni-containing layer is formed in order to improve the adhesion between the conductive substrate and the Ni-containing layer. For example, cathodic electrolytic degreasing can be performed as the degreasing step. An example of the conditions for cathodic electrolytic degreasing is shown below.

[0045] Treatment solution: 100 g / L aqueous sodium orthosilicate solution Temperature of treatment solution: 60°C Cathode current density: 2.5 A / dm ２ Processing time: 10 seconds

[0046] In the activation step carried out after the degreasing step, the conductive substrate that has been subjected to the degreasing step is activated to improve the adhesion between the conductive substrate and the Ni-containing layer. An example of the conditions for the activation step is shown below.

[0047] Treatment solution: 10% hydrochloric acid Treatment solution temperature: 30°C Immersion treatment time: 10 seconds

[0048] In the Ni-containing layer forming process carried out after the activation process, the conductive substrate that has been subjected to the activation process is electroplated to form a Ni-containing layer on one or both sides of the conductive substrate. The Ni-containing layer is an electroplated layer. In the Ni-containing layer forming process, Ni crystal grains can be refined by increasing the stirring of the plating solution during electroplating and by increasing the current density. An example of conditions for the Ni-containing layer forming process is shown below.

[0049] Plating solution: nickel chloride 250 g / L, free hydrochloric acid 50 g / L Plating solution temperature: 60 ° C Current density: 6 A / dm ２ 9A / dm or more ２ Stirring: Strong Plating thickness: 0.05 μm to 2.00 μm Treatment time: Adjust for each plating thickness

[0050] The Cu-containing layer formation pretreatment step, which is performed after the Ni-containing layer formation step, is a treatment to enhance the identity between the crystal orientation of Ni crystal grains in the Ni-containing layer and the crystal orientation of Cu crystal grains in the Cu-containing layer formed in the Cu-containing layer formation step performed immediately thereafter. In the Cu-containing layer formation pretreatment step, the sample obtained in the Ni-containing layer formation step is used as an anode, and the Ni-containing layer is slightly dissolved in a treatment solution containing Cu ions. An example of the conditions for the Cu-containing layer formation pretreatment step is shown below.

[0051] Treatment liquid: 250g / L copper sulfate, 55g / L sulfuric acid Treatment liquid temperature: 40°C Current density: 0.05A / dm ２ Stirring: Strong Processing time: 0.5 seconds

[0052] In the Cu-containing layer formation process, which is performed after the Cu-containing layer formation pretreatment process, electroplating is performed on the sample that has undergone the Cu-containing layer formation pretreatment process, thereby forming a Cu-containing layer on the surface of the Ni-containing layer. The Cu-containing layer is an electroplated layer. In the Cu-containing layer formation process, by weakening the stirring of the plating solution during electroplating and reducing the current density, precipitation nuclei of the Cu-containing layer can be controlled, thereby improving adhesion between the Cu-containing layer and the Ni-containing layer and improving the uniformity of the crystal orientation between adjacent Cu crystal grains and Ni crystal grains across the laminate interface. Furthermore, by changing the current density, the characteristics of the interface between the Cu-containing layer and the Ni-containing layer can be changed. Furthermore, by changing the copper ion concentration in the plating solution, the crystal grain size of the Cu crystal grains can be adjusted. An example of conditions for the Cu-containing layer formation process is shown below.

[0053] Plating solution: Copper cyanide 60 g / L or more and 85 g / L or less, sodium cyanide 105 g / L, free sodium cyanide 25 g / L Plating solution temperature: 50°C Current density: 1.0 A / dm ２ 1.8A / dm or more ２ Stirring: Weak Plating thickness: 0.05 μm to 1.00 μm Treatment time: Adjust for each plating thickness

[0054] In the Ag-containing layer forming step performed after the Cu-containing layer forming step, the sample that has been subjected to the Cu-containing layer forming step is subjected to two-stage electroplating to form an Ag-containing layer on the surface of the Cu-containing layer. The Ag-containing layer is an electroplated layer.

[0055] An example of the conditions for the first stage of the Ag-containing layer formation process is shown below: Plating solution: silver cyanide 10 g / L, potassium carbonate 30 g / L, free potassium cyanide 70 g / L Plating solution temperature: 30°C Current density: 2 A / dm ２ Stirring: Strong Plating thickness: Predetermined thickness Processing time: Adjust for each plating thickness

[0056] An example of the conditions for the second stage of the Ag-containing layer formation process is shown below: Plating solution: silver cyanide 80 g / L, potassium carbonate 50 g / L, free potassium cyanide 100 g / L Plating solution temperature: 40°C Current density: 1 A / dm ２Stirring: Weak Plating thickness: Predetermined thickness Processing time: Adjust for each plating thickness

[0057] According to the embodiment described above, by laminating a Ni-containing layer having a predetermined thickness and including Ni crystal grains with a predetermined average crystal grain size, a Cu-containing layer having a predetermined thickness and including Cu crystal grains with a predetermined average crystal grain size, and an Ag-containing layer in this order on the surface of a conductive substrate made of an Fe-based alloy having a predetermined Vickers hardness, the Ag coating material can suppress a decrease in adhesion due to fatigue and can also suppress an increase in contact resistance after heating.

[0058] Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept and scope of the claims of the present disclosure, and can be modified in various ways within the scope of the present disclosure.

[0059] Next, examples and comparative examples will be described, but the present disclosure is not limited to these examples.

[0060] (Examples 1 to 13 and Comparative Examples 1 to 6) In Examples 1 to 11 and Comparative Examples 1 to 4 and 6, a substrate having a thickness of 0.03 mm, made of an alloy shown in Table 1, and having a Vickers hardness shown in Table 1 was pressed to obtain a conductive substrate having a length of 200 mm, a width of 60 mm, and a thickness of 0.03 mm.

[0061] In Examples 12 and 13 and Comparative Example 5, a 42 alloy (Fe-42% by mass Ni) substrate formed by electroplating under the conditions shown below was used as the conductive substrate. Specifically, an aqueous solution containing nickel chloride with a metal concentration of 40 g / L as nickel (Ni), iron (II) sulfate with a metal concentration of 83 g / L as iron (Fe), 30 g / L of boric acid, 2 g / L of sodium saccharin dihydrate, and 5 g / L of malonic acid was prepared as an electroplating solution. Next, a stainless steel plate (SUS304) measuring 200 mm in length and 60 mm in width was placed as a cathode electrode in the plating electrolytic cell, and a pure Ni plate and a pure Fe plate, each measuring 200 mm in length and 60 mm in width, were placed in an anode bag so as to face both sides of the cathode electrode. Next, 1 L of electroplating solution was placed in the tank, and the temperature was 50°C. The stirring was performed with the stirrer rotation speed set to 100 rpm, while the flow rate was 4 A / dm ２ A 42 alloy substrate having a thickness of 0.03 mm and a Vickers hardness shown in Table 1 was deposited on the surface of the cathode electrode by electroplating by passing a current through the cathode electrode at a current density of 0.03 mm. The obtained 42 alloy substrate was then peeled off from the cathode electrode to obtain a conductive substrate.

[0062] Next, as a pretreatment, the conductive substrate was subjected to cathodic electrolytic degreasing and activation treatment.

[0063] In cathodic electrolytic degreasing, a sodium orthosilicate aqueous solution with a concentration of 100 g / L was placed in an electrolytic cell as a degreasing solution and heated. The conductive substrate was immersed in the degreasing solution heated to 60°C and connected to the anode of the electrolytic cell. ２ The current was passed for 10 seconds at a current density of 1000 kJ / s.

[0064] In the activation treatment, the conductive substrate after cathodic electrolytic degreasing was immersed in 10 mass % hydrochloric acid at 30° C. for 10 seconds.

[0065] Thereafter, for Examples 1 to 2, 5 to 13 and Comparative Examples 2, 4 to 6, Ni-containing layers 3 a, 3 b were formed on the front surface 2 a and back surface 2 b of the conductive substrate 2 by electroplating under the conditions shown below. For Examples 3 and 4, the back surface 2 b of the conductive substrate 2, the characteristics of which will not be evaluated later, was masked with tape so that the Ni-containing layer 3 a was formed on the front surface 2 a of the conductive substrate 2 and the Ni-containing layer 3 b was not formed on the back surface 2 b of the conductive substrate 2.

[0066] Here, when forming the Ni-containing layers 3a and 3b by electroplating, an aqueous solution containing 250 g / L of nickel chloride and 50 g / L of free hydrochloric acid was prepared as the electroplating solution in Examples 1 to 13 and Comparative Examples 2 and 4. Next, the conductive substrate after activation treatment, which served as the cathode electrode, was placed in a plating electrolytic bath, and pure Ni plates, which served as the anode electrodes and were 20 cm long and 6 cm wide, were placed facing both plate surfaces of the cathode electrode. 1 L of the electroplating solution was poured into the bath, and the electroplating solution was stirred at a temperature of 60°C with a stirrer rotation speed set to 350 rpm to 550 rpm, at a current of 8 A / dm ２ The Ni-containing layers 3a and 3b having the thickness and average crystal grain size shown in Table 1 were formed by electroplating by passing a current at a current density of 1 A / dm ２ The Ni-containing layers 3a and 3b were formed by electroplating with the thickness and average crystal grain size shown in Table 1 by passing a current at a current density of 2.5 A / dm. ２ By passing a current at a current density of 1000 kJ / cm2, Ni-containing layers 3a and 3b having the thickness and average crystal grain size shown in Table 1 were formed by electroplating.

[0067] Next, in the step of slightly dissolving the surface of the Ni-containing layer for Examples 1 to 13, a conductive substrate having the Ni-containing layer obtained by electroplating described above was used as the anode electrode, a stainless steel plate was placed as the cathode electrode, and 1 L of the treatment solution was placed in a tank, and the treatment solution was stirred at a temperature of 40°C with a stirrer rotation speed set to 350 rpm to 550 rpm, at a current of 0.05 A / dm ２ In Comparative Examples 1 to 6, this treatment was not carried out.

[0068] Next, in Examples 1 to 2, 5 to 13 and Comparative Examples 3 to 6, Cu-containing layers 4 a, 4 b were formed on the front surface 2 a side and the back surface 2 b side of the conductive substrate 2 by electroplating under the conditions shown below. In Examples 3 and 4, the back surface 2 b of the conductive substrate 2 was masked with tape so that the Cu-containing layer 4 a was formed on the front surface 2 a side of the conductive substrate 2 and the Cu-containing layer 4 b was not formed on the back surface 2 b side of the conductive substrate 2.

[0069] Here, when forming the Cu-containing layers 4a and 4b by electroplating, an aqueous solution containing 60 g / L of copper cyanide, 105 g / L of sodium cyanide, and 25 g / L of free sodium cyanide was prepared. Next, the pretreated conductive substrate, which served as a cathode electrode, was placed in a plating electrolytic bath, and phosphorus-deoxidized copper plates, each measuring 20 cm in length and 6 cm in width, were placed as anode electrodes facing the plate surfaces of both sides of the cathode electrode. 1 L of electroplating solution was poured into the bath, and the plating was carried out at a temperature of 50°C with a stirrer rotation speed set to 100 rpm to 400 rpm, while stirring at 1 A / dm ２ By passing a current at a current density of 1000 kJ / cm2, Cu-containing layers 4a and 4b having the thickness and average crystal grain size shown in Table 1 were formed by electroplating.

[0070] Next, two-stage electroplating was performed to form Ag-containing layers 5a, 5b on the front surface 2a side and the back surface 2b side of the conductive substrate 2 in Examples 1 to 2, 5 to 13 and Comparative Examples 1 to 6, and in Examples 3 and 4, the back surface 2b of the conductive substrate 2 was masked with tape to form the Ag-containing layer 5a on the front surface 2a side of the conductive substrate 2 and to prevent the Ag-containing layer 5b from being formed on the back surface 2b side of the conductive substrate 2.

[0071] In the first stage, silver cyanide was 10 g / L, potassium carbonate was 30 g / L, and free potassium cyanide was 70 g / L. A conductive substrate (after electroplating) was placed as a cathode electrode in a plating electrolytic tank, and a silver plate (20 cm long x 6 cm wide) as an anode electrode was placed opposite the plate surface of both sides of the cathode electrode. 1 L of electroplating solution was poured into the tank, and the plating solution was stirred at a temperature of 30°C with a stirrer speed set to 100 rpm to 400 rpm at 2 A / dm ２ Electroplating was carried out by passing a current at a current density of 1000 kJ / min.

[0072] In the second stage, silver cyanide was added at 80 g / L, potassium carbonate at 50 g / L, and free potassium cyanide at 100 g / L. The conductive substrate after electroplating in the first stage, which served as a cathode electrode, was placed in the plating electrolytic tank, and silver plates measuring 20 cm in length and 6 cm in width, which served as anode electrodes, were placed opposite the plate surfaces of both sides of the cathode electrode. 1 L of electroplating solution was poured into the tank, and the plating solution was stirred at a temperature of 40°C with a stirrer speed set at 400 rpm to 600 rpm, at a current of 1 A / dm ２ In this way, Ag-containing layers 5a and 5b having thicknesses shown in Table 1 were formed by two-stage electroplating.

[0073] [Measurements and Evaluations] The conductive substrates used in the above Examples and Comparative Examples and the Ag-coated materials obtained in the above Examples and Comparative Examples were subjected to the following measurements and evaluations. The results are shown in Tables 1 and 2.

[0074] [1] Vickers hardness (HV) of conductive substrate The Vickers hardness (HV) measurement method of conductive substrate is in accordance with the Vickers hardness test method described in JIS Z2244 (2009).First, conductive substrate is embedded in resin, and the cross section including the thickness direction of conductive substrate is produced by mechanical polishing, to prepare the cross section sample of conductive substrate.Subsequently, when the load (test force) when pressing diamond indenter into this cross section sample is 0.049N, and the pressing time of indenter is 15 seconds, the Vickers hardness (HV) of conductive substrate is measured.

[0075] [2] Average Crystal Grain Size of Ni-Containing Layer and Cu-Containing Layer in Ag-Coated Material The average crystal grain size of the Ni-Containing Layer and the average crystal grain size of the Cu-Containing Layer were measured as follows. First, a cross section including the thickness direction of the Ag-coated material was formed using a focused ion beam device (Hitachi, FB2000A). Next, the cross section was observed using a scanning ion microscope (Seiko Instruments Inc., SMI3050TB). From the channeling contrast appearing in the obtained SIM image, the number of intersections between each crystal grain (Ni crystal grains, Cu crystal grains) and a line perpendicular to the thickness direction of the Ag-coated material was counted, and the average crystal grain size of the multiple crystal grains (Ni crystal grains, Cu crystal grains) was determined using a cutting method to determine the average length of the line segments defined by each crystal grain. In the cross-sectional observation by SIM, a range of 3 μm in width was defined as one field of view, and three fields of view were randomly selected from each of the Ni-containing layer and the Cu-containing layer. The average values ​​of the average crystal grain sizes determined for each of the three fields of view were used as the average crystal grain size of the Ni-containing layer and the average crystal grain size of the Cu-containing layer.

[0076] [3] Ratio (l / L) in Ag Coating Material The ratio (l / L) of the total length (L = La) of the interface portion where Ni crystal grains and Cu crystal grains adjacent to the Ni crystal grains have the same crystal orientation to the total length of the interface in the measurement area was measured as follows. Using SIM, the interface between the Ni-containing layer and the Cu-containing layer in the cross section obtained in [2] above was observed. For the SIM cross-sectional observation, three fields of view were randomly selected at the interface, with each field being a 3 μm horizontal range. From the channeling contrast of the obtained three fields of view, the total length of the interface in the measurement area was calculated for each field of view, and the total length of the interface portion where Ni crystal grains and Cu crystal grains have the same crystal orientation was calculated via the interface, and the ratio of these was calculated. The average of the ratios obtained from the three fields of view was taken as the ratio (l / L).

[0077] Here, the length of the interface portion where Ni crystal grains and Cu crystal grains have the same crystal orientation across the stacking interface was defined as the sum of the length of the interface portion of the stacking interface where, in the above channeling contrast, a dark-colored Ni crystal grain in the Ni-containing layer is adjacent to a dark-colored Cu crystal grain in the Cu-containing layer, and the length of the interface portion of the stacking interface where a light-colored Ni crystal grain in the Ni-containing layer is adjacent to a light-colored Cu crystal grain in the Cu-containing layer.

[0078] [4] Adhesion after fatigue test A fatigue test was performed on the Ag-coated material using an MIT testing machine. In the fatigue test, the Ag-coated material was bent 10,000 times under the following conditions: a load of 9.8 N, a bending angle of 135° (left and right), a bending speed of 175 rpm, and a bending radius of 3.6 mm. Using the Ag-coated material after the fatigue test, the presence or absence of peeling of at least one of the Ni-containing layer, Cu-containing layer, and Ag-containing layer (at least one layer constituting the surface layer) from the Ag-coated material was observed in accordance with the tape test specified in JIS H 8504, and adhesion was evaluated.

[0079] In the initial tape test, tape was applied to the surface of the Ag-coated material, and then the tape was peeled off to evaluate adhesion. Furthermore, for Ag-coated materials for which no peeling of the surface layer occurred in the initial tape test, a scratch (a square with a side length of 2 mm) was formed with a sharp blade that reached the conductive substrate, and then the tape test was conducted again. The evaluation of adhesion was ranked according to the following criteria.

[0080] ⊚: No peeling occurred even when the tape test was performed again. ○: Minor peeling occurred near the scratch when the tape test was performed again. ×: Peeling occurred when the tape test was performed for the first time.

[0081] [5] Contact Resistance After Heating The contact resistance of the Ag-coated material before heating and after heating at 155°C for 16 hours were measured, and the increase in contact resistance after heating was calculated. The measurement was performed using an electrical contact simulator with a contact load of 0.5 N. The increase in contact resistance after heating was evaluated as follows: ⊚, ∘, more than 2 mΩ but less than 3 mΩ, and ×, respectively.

[0082] [6] Overall evaluation The overall evaluation was ranked according to the following criteria: When both adhesion and contact resistance after heating were ranked as ◎, the overall evaluation was also ◎; when only one of them was ◎ or both were ○, the overall evaluation was ○; and when at least one was ×, the overall evaluation was ×.

[0083]

[0084]

[0085] 4 is a SIM image obtained by observing a cross section of the Ag-coated material of Example 9 in the thickness direction using SIM. As shown in Tables 1 and 2, in Examples 1 to 13, a Ni-containing layer having a predetermined thickness and containing Ni crystal grains with a predetermined average crystal grain size, a Cu-containing layer having a predetermined thickness and containing Cu crystal grains with a predetermined average crystal grain size, and an Ag-containing layer were laminated in this order on the surface of a conductive substrate made of an Fe-based alloy having a predetermined Vickers hardness. Therefore, the Ag-coated material had good adhesion after fatigue testing and a small increase in contact resistance after heating. As a result, the overall evaluation was Good. On the other hand, in Comparative Examples 1 to 6, a Ni-containing layer having a predetermined thickness and containing Ni crystal grains with a predetermined average crystal grain size, a Cu-containing layer having a predetermined thickness and containing Cu crystal grains with a predetermined average crystal grain size, and an Ag-containing layer were not laminated in this order on the surface of a conductive substrate made of an Fe-based alloy having a predetermined Vickers hardness. Therefore, the overall evaluation was Poor.

[0086] 1 Ag-coated material 10 Measurement area of ​​Ag-coated material 2 Conductive substrate 2a Surface of conductive substrate 2b Back surface of conductive substrate 3a, 3b Ni-containing layer 30a, 30b Ni crystal grains 4a, 4b Cu-containing layer 40a, 40b Cu crystal grains 5a, 5b Ag-containing layer 6a, 6b Lamination interface t2 Thickness of conductive substrate t3a, t3b Thickness of Ni-containing layer t4a, t4b Thickness of Cu-containing layer t5a, t5b Thickness of Ag-containing layer L Total length of lamination interface in measurement area La Total length of lamination interface 6a in measurement area Lb Total length of lamination interface 6b in measurement area l1 to l10 Length of interface portion where Ni crystal grains and Cu crystal grains have the same crystal orientation

Claims

1. An Ag-coated material comprising a conductive substrate made of an Fe-based alloy and having a Vickers hardness (HV) of 300 or more, on one or both sides of which a Ni-containing layer, a Cu-containing layer, and an Ag-containing layer are laminated in this order, wherein the Ni-containing layer has a thickness of 0.05 μm or more and 2.00 μm or less, and the Cu-containing layer has a thickness of 0.05 μm or more and 1.00 μm or less, and when viewed in a cross section including the thickness direction of the Ag-coated material, the average crystal grain size of a plurality of Ni crystal grains in the Ni-containing layer, cut by a straight line perpendicular to the thickness direction of the Ag-coated material, is 0.80 μm or less, and the average crystal grain size of a plurality of Cu crystal grains in the Cu-containing layer, cut by the straight line, is 0.80 μm or less.

2. The Ag coating material according to claim 1, wherein the conductive substrate is made of an Fe-Ni-Cr alloy or an Fe-Ni alloy.

3. The Ag coating material according to claim 1, wherein, when the lamination interface between the Ni-containing layer and the Cu-containing layer is viewed in the cross section, the ratio (l / L) of the total length (l) of one or more interface portions at the lamination interface, where Ni crystal grains and Cu crystal grains adjacent to the Ni crystal grains have the same crystal orientation, to the total length (L) of the lamination interface in the measurement region is 0.2 or more.

4. The Ag-coated material according to claim 1, wherein the thickness of the Ag-containing layer is 0.05 μm or more and 5.00 μm or less.

5. An electric / electronic component comprising the Ag coating material according to any one of claims 1 to 4.

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