CN107849721B

CN107849721B - Plating material having excellent heat resistance and method for producing same

Info

Publication number: CN107849721B
Application number: CN201680045594.5A
Authority: CN
Inventors: 藤井惠人; 奥野良和; 川田绅悟; 橘昭赖; 中津川达也; 北河秀一
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 2015-09-01
Filing date: 2016-08-30
Publication date: 2020-11-17
Anticipated expiration: 2036-08-30
Also published as: JPWO2017038825A1; KR20180044886A; JP6219553B2; WO2017038825A1; KR102503365B1; CN107849721A

Abstract

Provided are an Sn plating material which can maintain desired heat resistance even at a high temperature of 175 ℃, and which does not cause cracking when a contact portion is formed, and a method for manufacturing the Sn plating material. [ MEANS FOR solving PROBLEMS ] an Sn plating material (10) comprising, on a conductive base material (1) made of Cu or a Cu alloy, a first foundation layer (2) made of Ni or a Ni alloy, an intermediate layer (4) made of a CuSn compound, and a surface layer (5) made of Sn or a Sn alloy in this order, wherein, when a cross section composed of a rolling direction and a plate thickness direction is observed, a processing-modified layer (6) is left on the surface of the conductive base material at a length of 0.5 to 10 [ mu ] m with respect to the length of 20 [ mu ] m of the interface between the first foundation layer and the conductive base material; or two or more processing-modified layers (6) having a total length of 0.5 to 10 [ mu ] m with respect to the interface length of 20 [ mu ] m.

Description

Plating material having excellent heat resistance and method for producing same

Technical Field

The present invention relates to a tin (Sn) plating material suitable for vehicle-mounted components, electrical and electronic components, lead frames, relays, switches, sockets, and the like, and a method for producing the same and use thereof.

Background

Conventionally, an electrical contact material has been used of copper (Cu) or a copper alloy having excellent electrical conductivity. In recent years, contact characteristics have been improved, and cases of using copper or a copper alloy as it is have been reduced. Such conventional materials are replaced with materials obtained by performing various surface treatments on copper or copper alloys. In particular, as an electrical contact material, a member in which tin or a tin alloy is plated on copper or a copper alloy is commonly used for an electrical contact portion.

The plating material is known to be widely used for various terminals, connectors, and the like used in electric/electronic devices as a high-performance electrical conductor having excellent conductivity and strength of a conductive base material and excellent electrical connectivity, corrosion resistance, and weldability of a plating layer. In this plating material, in general, an undercoat plating of nickel (Ni), cobalt (Co), or the like having a barrier function is performed on the base material in order to prevent the alloy component of the conductive base material such as copper from diffusing into the plating layer.

When the plating material is used as a terminal, for example, in a high-temperature environment such as an engine room of an automobile, tin in the tin plating layer on the surface of the terminal is easily oxidized to form an oxide film on the surface of the tin plating layer. The oxide film is brittle and thus cracks at the time of terminal connection, and the underlying non-tin oxide plating layer is exposed, whereby good electrical connectivity is obtained.

However, in recent years, as an environment in which an electrical contact material is used, there are an increasing number of cases in which the electrical contact material is used in a high-temperature environment. For example, contact materials for sensors in the engine room of automobiles are highly likely to be used in high temperature environments such as 100 ℃ to 200 ℃. Therefore, reliability of contact characteristics and the like at a higher temperature than the use temperature assumed in conventional consumer devices is required. In particular, as a cause of affecting the reliability of the contact characteristics, there is a problem that the contact resistance at the outermost layer is increased by diffusion of the conductive base material component and surface oxidation at high temperature. Therefore, various studies have been made on the suppression of the diffusion of the conductive base material component and the oxidation resistance.

In patent document 1, a Ni or Ni alloy layer is formed on the surface of a Cu or Cu alloy substrate, an Sn or Sn alloy layer having a thickness of 0.25 to 1.5 μm is formed on the outermost surface side, and one or more intermediate layers containing Cu and Sn are formed between the Ni or Ni alloy layer and the Sn or Sn alloy layer, and among these intermediate layers, the intermediate layer in contact with the Sn or Sn alloy layer has a Cu content of 50 mass% or less, an Ni content of 20 mass% or less, and an average crystal grain size of 0.5 to 3.0 μm, whereby a plating material having excellent characteristics such as solderability, whisker resistance, and heat resistance reliability, and further excellent press workability is obtained.

In patent document 2, a surface plating layer composed of a Ni layer, a Cu — Sn alloy layer, and a Sn layer is formed in this order on the surface of a base material composed of Cu or a Cu alloy, and the Ni layer is made to have a thickness of 0.1 to 1.0 μm, the Cu — Sn alloy layer is made to have a thickness of 0.1 to 1.0 μm, the Cu concentration of the Cu — Sn alloy layer is 35 to 75 at%, and the Sn layer is made to have a thickness of 0.5 μm or less, whereby electrical reliability (low contact resistance) can be maintained even after a long period of time in a high-temperature atmosphere, and a plating material excellent in corrosion resistance to sulfur dioxide and free from cracks even in severe working can be obtained.

In patent document 3, a Ni layer, an intermediate layer made of a Cu — Sn alloy layer, and a surface layer made of Sn or an Sn alloy are formed in this order on the surface of a base material made of Cu or a Cu alloy in which no work modifying layer is present. The Ni layer is epitaxially grown on the base material, and the average crystal grain size of the Ni layer is 1 [ mu ] m or more, the thickness of the Ni layer is 0.1 to 1.0 [ mu ] m, the thickness of the intermediate layer is 0.2 to 1.0 [ mu ] m, and the thickness of the surface layer is 0.5 to 2.0 [ mu ] m, whereby the barrier property against the base material made of Cu or a Cu alloy can be improved, diffusion of Cu can be more reliably prevented, the heat resistance can be improved, and an Sn plating material capable of maintaining stable contact resistance even in a high-temperature environment can be obtained.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2003-293187

Patent document 2: japanese laid-open patent publication No. 2004-068026

Patent document 3: japanese patent laid-open No. 2014-

Disclosure of Invention

Problems to be solved by the invention

In recent years, for example, in vehicle-mounted parts, materials are required to have good electrical connectivity at high temperatures (hereinafter, simply referred to as heat resistance) compared to conventional materials due to an increase in the amount of current caused by an increase in the ambient temperature or the spread of electric vehicles. In other applications, an increase in circuit current density has been observed with an increase in ambient temperature, a reduction in size of components, and an increase in output power, and improvement in heat resistance has been still required. Further, along with the miniaturization of parts, further good bending workability is required.

In

patent documents

1 and 2, a test at 160 ℃ was performed as an index of heat resistance. However, only this level is achieved, and the heat resistance required in recent years cannot be sufficiently satisfied. For example, in a test at 175 ℃, it can be seen that: cu diffused from the conductive base material reacts with Sn on the surface to form a compound, and Sn on the surface disappears, thereby deteriorating electrical connectivity.

The Sn-plated material of patent document 3 has good electrical connectivity even after heating at 175 ℃ for 1000 hours, and has excellent heat resistance. However, since the Ni plating layer has a larger crystal grain size than conventional Ni plating layers, cracks are likely to occur when forming a contact portion by bulging or bending. When a member having cracks is used in a hot environment, corrosion of the base material progresses in the plating crack portion, and there is a possibility that electrical connectivity is impaired.

In view of the above, an object of the present invention is to provide an Sn plating material that can maintain desired heat resistance even at a high temperature of 175 ℃, and that does not cause cracking when forming a contact portion, and a method for manufacturing the Sn plating material.

Means for solving the problems

The present inventors have conducted various studies to solve the above problems. As a result, the present inventors have conducted intensive studies on an Sn plating material suitable for vehicle-mounted components, electric and electronic components, lead frames, relays, switches, sockets, and the like, and found that an Sn plating material in which each of a first base layer made of Ni or an Ni alloy, an intermediate layer made of a CuSn compound, and a surface layer made of Sn or an Sn alloy is formed in this order on a conductive base material made of Cu or a Cu alloy, wherein a working modification layer is left on the surface of the conductive base material at a length of 0.5 to 10 μm with respect to an interface length 20 μm between the first base layer and the conductive base material when a cross section made of a rolling direction and a plate thickness direction is observed; or two or more processing-modified layers having a total length of 0.5 to 10 μm with respect to an interface length of 20 μm, thereby achieving both heat resistance and processability.

According to the present invention, the following means can be provided.

(1) An Sn plating material comprising, on a conductive base material made of Cu or a Cu alloy, a first base layer made of Ni or a Ni alloy, an intermediate layer made of a CuSn compound, and a surface layer made of Sn or a Sn alloy in this order, characterized in that, when a cross section in a rolling direction and a plate thickness direction is observed, a processing-modified layer is left on the surface of the conductive base material at a length of 0.5 to 10 μm relative to the length of 20 μm of the interface between the first base layer and the conductive base material; or two or more processing-modified layers having a total length of 0.5 to 10 μm with respect to the interface length of 20 μm.

(2) An Sn plating material comprising, on a conductive base material composed of Cu or a Cu alloy, a first base layer composed of Ni or a Ni alloy, a second base layer composed of Cu or a Cu alloy, an intermediate layer composed of a CuSn compound, and a surface layer composed of Sn or a Sn alloy in this order, characterized in that, when a cross section composed of a rolling direction and a plate thickness direction is observed, a processing-modified layer is left on the surface of the conductive base material at a length of 0.5 to 10 μm with respect to the interface length 20 μm between the first base layer and the conductive base material; or two or more processing-modified layers having a total length of 0.5 to 10 μm with respect to the interface length of 20 μm.

(3) The Sn plating material according to (1) or (2), wherein the first underlayer contains a portion having a crystal grain size of 1 μm or more and a portion having a crystal grain size of less than 1 μm.

(4) The Sn plating material according to any one of (1) to (3), wherein the surface layer has a thickness of 0.2 to 5 μm.

(5) The Sn plating material according to any one of (1) to (4), wherein the thickness of the intermediate layer is 0.1 to 1 μm.

(6) The Sn plating material according to any one of (1) to (5), wherein the first underlayer has a thickness of 0.1 to 2 μm.

(7) The Sn plating material according to any one of (2) to (6), wherein the second underlayer has a thickness of 0 to 0.1. mu.m.

(8) The Sn plating material according to any one of (1) to (7), wherein the intermediate layer is exposed to the surface of the material at an area ratio of 0.1 to 60% when heat-treated at 175 ℃ for 240 hours.

(9) An in-vehicle component using the Sn plating material according to any one of (1) to (8).

(10) An electric/electronic component using the Sn plating material according to any one of (1) to (8).

(11) A method for producing an Sn plating material, comprising sequentially forming a first base layer made of Ni or an Ni alloy, an intermediate layer made of a CuSn compound, and a surface layer made of Sn or an Sn alloy on a conductive base material made of Cu or a Cu alloy,

forming the first base layer, the second base layer made of Cu or a Cu alloy, and the surface layer on the conductive substrate in this order, reacting the second base layer with the surface layer by reflow treatment until the second base layer disappears to form the intermediate layer,

adjusting polishing and pickling conditions of the conductive base material to a polishing particle size of #1000 to 5000, and adjusting the immersion time in the pickling solution to 0 to 60 seconds, and adjusting the processing rate of the refining conditions to 0 to 70%, and further adjusting refining heat treatment conditions to 250 to 650 ℃ for 5 seconds to 5 hours as the case may be, to control the remaining amount of the processing-modified layer on the surface of the conductive base material, whereby when the Sn-plated material is observed in a cross section composed of a rolling direction and a plate thickness direction, the processing-modified layer remains on the surface of the conductive base material at a length of 0.5 to 10 μm relative to 20 μm, which is the interface length between the first base layer and the conductive base material; or two or more processing-modified layers having a total length of 0.5 to 10 μm with respect to the interface length of 20 μm.

(12) A method for producing an Sn plating material, comprising sequentially forming, on a conductive base material composed of Cu or a Cu alloy, a first base layer composed of Ni or a Ni alloy, a second base layer composed of Cu or a Cu alloy, an intermediate layer composed of a CuSn compound, and a surface layer composed of Sn or a Sn alloy, wherein the first base layer, the second base layer, the intermediate layer, and the surface layer are formed of a metal or a metal alloy,

forming the first foundation layer, the second foundation layer, and the surface layer in this order on the conductive base material, and then forming the intermediate layer by reacting the second foundation layer with the surface layer by reflow treatment so that the second foundation layer partially remains,

ADVANTAGEOUS EFFECTS OF INVENTION

According to the Sn plating material of the present invention, since a part of the processing-modified layer remains on the surface of the conductive base material, diffusion of the base material component Cu from the conductive base material to the surface layer can be suppressed, and excellent heat resistance can be obtained. Further, cracks in the contact portion formed in the bending process or the bulging forming can be suppressed.

The above and other features and advantages of the present invention will be further apparent from the following description and the accompanying drawings.

Drawings

Fig. 1 is a cross-sectional view of an embodiment of the Sn plating material of the present invention.

Fig. 2 is a cross-sectional view of another embodiment of the Sn plating material of the present invention.

FIG. 3 is a sectional view of a bulging forming method performed in the example.

Fig. 4 is a sectional view of the bump-formed Sn plating material performed in the example.

Fig. 5 is a schematic diagram schematically showing the state of chronological deterioration.

Detailed Description

A preferred embodiment of the Sn plating material of the present invention will be described in detail. As shown in fig. 1, the Sn plating material (10) of the present embodiment is formed by sequentially forming a first base layer (2) made of Ni or a Ni alloy, an intermediate layer (4) made of a CuSn compound, and a surface layer (5) made of Sn or a Sn alloy on a conductive base material (1) made of Cu or a Cu alloy. In some cases, as shown in fig. 2, a second base layer (3) made of Cu or a Cu alloy may be formed between the first base layer (2) and the intermediate layer (4). In either case, the processing-modified layer (6) remains between the first base layer (2) and the conductive base material (1) in the specific length.

By leaving a part of the processing-modified layer on the surface of the conductive base material, a first foundation layer having a small crystal grain size is formed on the part of the conductive base material, and a first foundation layer having a large crystal grain size is formed on the part from which the processing-modified layer is removed. The small crystal grain size portion contributes to improvement in workability, and the large crystal grain size portion contributes to improvement in heat resistance by suppressing diffusion of Cu as a base material component from the conductive base material to the surface layer. The surface layer disappears or decreases just above the portion of the first base layer where the crystal grain size is small due to diffusion of the base component Cu from the conductive base material, but good heat resistance is obtained as a whole due to the surface layer remaining just above the portion where the crystal grain size is large. In addition, when maintenance is performed after use in a high-temperature environment such as a vehicle-mounted terminal, the insertion force at the time of insertion and extraction is reduced from the initial stage due to the effect of the intermediate layer growing directly above the portion of the first foundation layer where the crystal grain size is small.

The shape of the conductive substrate (1) is not particularly limited, and examples thereof include a plate, a strip, a foil, and a wire. In the following, a plate material and a strip material will be described as an embodiment, but the shape thereof is not limited to these. Cu or a Cu alloy is used as the conductive base material (1). The kind of Cu or Cu alloy is not particularly limited, and may be appropriately selected according to the requirements of strength, electrical conductivity, and the like of the application to be used.

As an example of a Copper alloy that can be used for the conductive base material (1), "C14410 (Cu-0.15Sn, product name: EFTEC3, manufactured by Cuhewa Electrical industries, Ltd.)", "C19400 (Cu-Fe alloy material, Cu-2.3Fe-0.03P-0.15Zn)," C18045(Cu-0.3Cr-0.25Sn-0.5Zn, manufactured by Cuhewa Electrical industries, Ltd., "EFTEC 64, 64T)," C64770(Cu-Ni-Si alloy material, manufactured by Cuhewa Electrical industries, Ltd., "EFTEC-97, C64775(Cu-Ni-Si alloy material, manufactured by Cuhewa Electrical industries, Ltd.," EFTEC-820) "and the like, which are published alloys of CDA (Copper Development Association), can be used. (the unit of the number before each element of the copper alloy indicates% by mass in the copper alloy.) TPC (tough pitch copper), OFC (oxygen free copper), phosphor bronze, brass (for example, 70% by mass Cu to 30% by mass Zn., abbreviated as 7/3 brass) and the like can also be used. From the viewpoint of improving electrical conductivity and heat dissipation, it is preferable to produce a copper alloy strip having an electrical conductivity of 5% IACS or more. The "base material component" of the present invention when a copper alloy is treated as the conductive base material (1) means copper as a base metal. The thickness of the conductive substrate (1) is not particularly limited, but is usually 0.05 to 2.00mm, preferably 0.1 to 1.2 mm.

The first base layer (2) uses, for example, Ni, and functions as a diffusion barrier layer that suppresses diffusion of the base component Cu from the conductive base material (1) to the surface layer (5). The thickness of the first base layer (2) is preferably 0.1 to 2 μm, more preferably 0.2 to 1 μm. When the first base layer (2) is too thin, the diffusion suppressing effect of the base material component Cu is reduced, and the heat resistance of the Sn plating material (10) is lowered. Further, when the first base layer (2) is too thick, workability may be deteriorated and cracks may be generated. The first underlayer (2) may be made of Ni alloy, and for example, Ni-P, Ni-Cu, Ni-Cr, Ni-Sn, Ni-Zn, Ni-Fe, etc. may be used.

For example, in the first base layer (2) formed on the conductive base material (1) by plating, the orientation and Ni grain growth occur in the conductive base material (1) at the portion where the processing-modified layer (6) is removed, and the crystal grain size is obtained to the same extent as that of the conductive base material (1). Since the crystal grain size of Cu or Cu alloy is usually about 1 to 30 μm, the crystal grain size of the first base layer (2) (Ni) formed in the portion excluding the processing-modified layer (6) is substantially 1 μm or more. On the other hand, in the portion where the processing-modified layer (6) remains, the crystal grain size of the first foundation layer (2) in the vicinity of the surface of the conductive base material (6) is very small compared to the original crystal grain size of the base material, and the first foundation layer (2) (Ni) obtained thereon has a small crystal grain size of 0.01 μm or more and less than 1 μm.

The intermediate layer (4) is obtained by forming a second base layer (3) and a surface layer (5) in this order on the first base layer (2), and then subjecting the second base layer (3) and the surface layer (5) to a reflow treatment, and is mainly composed of Cu₃Sn and Cu₆Sn₅And (4) forming. Mainly composed of Cu₃Sn and Cu₆Sn₅The composition is Cu₃Sn and Cu₆Sn₅Is constituted by 50% by mass or more. The intermediate layer (4) functions as a diffusion barrier layer that prevents a reaction between the surface layer (5) and the first base layer (2). The thickness of the intermediate layer (4) is preferably 0.1 to 1 μm, more preferably 0.2 to 0.8. mu.m. If the intermediate layer (4) is too thin, thenThe effect as a diffusion barrier layer is reduced, and the reaction between the surface layer (5) and the first base layer (2) proceeds, and the heat resistance of the Sn plating material (10) is reduced. If the intermediate layer (4) is too thick, workability may be reduced and cracks may occur.

A surface layer (5) is required to ensure the electrical connectivity of the contact. The thickness of the surface layer (5) is preferably 0.2 to 5 μm, more preferably 0.3 to 2 μm. When the surface layer (5) is too thin, Sn reacts with Cu diffused from the conductive base material (1) at high temperature and disappears, and the electrical connectivity is impaired. When the surface layer (5) is too thick, the influence of the hard intermediate layer (4) near the surface is reduced, and the influence of the surface layer (5) made of soft Sn or Sn alloy is increased, so that the insertion/extraction force is increased when the fitting type terminal or the like is inserted/extracted, and the work load is increased. In particular, the insertion force can be significantly reduced by a thickness of 2 μm or less. The surface layer (5) may be formed of Sn alloy, and Sn-Cu, Sn-Bi, Sn-Pb, Sn-Ag, Sn-Sb, Sn-In, etc., may be used, for example.

A second substrate layer (3) can be formed between the first substrate layer (2) and the intermediate layer (4). In the second base layer (3), when the second base layer (3), the intermediate layer (4), and the surface layer (5) are formed in this order on the first base layer (2) and then reflow-processed, the second base layer (3) may be entirely used for forming the intermediate layer (4) and disappear as shown in fig. 1, or a part of the second base layer (3) may be left unused and the second base layer (3) not used for forming the intermediate layer (4) may be left as shown in fig. 2. The thickness of the remaining second base layer (3) is preferably 0 to 0.1 μm, more preferably 0 to 0.05. mu.m. The second base layer (3) functions as a diffusion barrier layer for preventing a reaction between the surface layer (5) and the first base layer (2) in the same manner as the intermediate layer (4). However, when the second base layer (3) is too thick, it reacts with the surface layer (5) at high temperature, and the heat resistance is lowered. Examples of the Cu alloy used as the second base layer (3) include Cu-Ni and Cu-Sn.

In the present embodiment, a part of the processing-modified layer (6) remains on the surface of the conductive substrate (1). The process-modified layer (6) is known per se. The processing-modified layer (6) is a layer formed under the influence of heat or force generated in the polishing step or rolling (machining), the surrounding atmosphere, the properties of the metal fresh surface, and the like, and has a finer structure than the crystal structure in the metal matrix. The processing-modified layer (6) contains fine crystalline and amorphous portions, and the size of crystal grains present in the processing-modified layer (6) is 1 μm or less. The processing-modified layer is composed of a Bohr's ratio layer (upper layer) and a plastic deformation layer (lower layer). Here, the berl ratio layer is composed of an extremely fine crystal texture or an amorphous texture. On the other hand, the plastic deformation layer has a nonuniform crystal texture with a large strain, and the size of the crystal grains is substantially intermediate between the crystal grains of the berl ratio layer and the crystal grains inside the metal base.

Since the processing-modified layer has a thermally unstable structure, the atomic arrangement is changed to a thermally stable atomic arrangement by atomic diffusion due to heat in the heating treatment, and is reduced. The processing-modified layer can be partially or completely removed by dissolving the surface of the conductive substrate. In the Sn plating material (10) of the present embodiment, when a cross section composed of a rolling direction and a plate thickness direction is observed, a processing modification layer (6) is preferably left on the surface of the conductive base material (1) at a length of 0.5 to 10 [ mu ] m relative to the 20 [ mu ] m interface length of the first base layer (2) and the conductive base material (1); or two or more process-modified layers (6) having a total length of 0.5 to 10 μm with respect to an interface length of 20 μm, and more preferably one or two or more process-modified layers (6) having a total length of 1 to 5 μm. If the length of the working-modified layer (6) is too short, most of the crystal grains of the first base layer (2) (Ni) become large, and the workability is lowered, whereby cracks are generated in the contact portions, and the electrical connectivity may be impaired. Conversely, if the length of the processing-modified layer (6) is too long, most of the crystal grains of the first base layer (2) (Ni) are small, and the base component Cu diffuses from the conductive base material (1) to the surface layer (5), possibly resulting in a decrease in heat resistance.

In the present embodiment, the crystal grain size of Ni of the first base layer (2) is small directly above the portion where the processing-modified layer (6) remains, and therefore diffusion of the base component Cu from the conductive base material (1) to the surface layer (5) proceeds, and the intermediate layer (4) easily grows. On the other hand, in the portion excluding the processing-modified layer (6), the crystal grain size of Ni in the first base layer (2) is large, diffusion of the base component Cu from the conductive base material (1) to the surface layer (5) is suppressed, and the intermediate layer (4) is difficult to grow. Therefore, when this embodiment is used at a high temperature, a difference occurs in the growth of the intermediate layer (4) in the material, and the intermediate layer (4) is partially exposed on the surface of the Sn plating material (10) (see fig. 5). When the intermediate layer (4) is partially exposed after use at high temperatures, for example, when the terminal is inserted and removed during maintenance of the in-vehicle terminal, the insertion force is reduced compared to the initial state, and the workload is reduced. When 0.1 to 60% of the intermediate layer (4) is exposed on the surface of the Sn plating material (10) after heating at 175 ℃ for 240 hours, both a lower insertion force than the initial insertion force and good electrical connectivity can be obtained. In order to obtain both a lower insertion force than the initial insertion force and good electrical connectivity, the area ratio of the exposed intermediate layer (4) is preferably 0.1 to 60%, more preferably 0.5 to 40%, and still more preferably 1 to 30%. When the exposed area ratio of the intermediate layer (4) is too small, a low insertion force cannot be obtained; when the area ratio is too large, good electrical connectivity cannot be obtained.

Next, a method for producing the Sn plating material (10) of the present embodiment will be described. The Sn-plated material (10) of the present embodiment is generally produced by sequentially performing Ni or Ni alloy plating → Cu or Cu alloy plating → Sn or Sn alloy plating on a conductive base material (1) made of Cu or Cu alloy, and then performing reflow treatment. Before and after each step, degreasing, acid washing, water washing and drying treatment may be appropriately performed. In the production method of the present embodiment, it is important to leave a part of the processing-modified layer (6) on the surface of the conductive base material (1) before Ni or Ni alloy plating. In the manufacturing method of the present embodiment, the polishing and pickling conditions of the conductive base material are adjusted, the processing rate of the refining conditions is adjusted to 0 to 70%, and the remaining amount of the processing-modified layer (6) is controlled. The purification heat treatment may be carried out under conditions of 250 to 650 ℃ for 5 seconds to 5 hours, if necessary. The production method of the present embodiment has the same number of steps as the conventional method, but improves material properties by appropriately adjusting the conditions of the respective steps.

< conductive substrate >

The conductive substrate (1) is not particularly limited as long as it is Cu or a Cu alloy, and may be appropriately selected according to requirements such as strength and conductivity of the application to be used. The processing-modified layer (6) on the surface of the conductive substrate (1) can be controlled by adjusting the polishing amount in the polishing and pickling steps after the heat treatment, the surface dissolution amount by the pickling solution, the processing rate of the refining process, and further, if necessary, the refining annealing conditions. The amount of polishing or surface dissolution by the acid washing solution can be controlled by the size of polishing particles, the composition of the acid washing solution, the immersion time in the acid washing solution, and the like. Specifically, the size of the polishing particles is set to #1000 to 5000, and the time for immersion in the acid washing solution is set to 0 to 60 seconds. When the size of the polishing particles is less than #1000, the surface of the ground conductive base material (1) is rough, and the defects such as pinholes and the like are easily generated in the coating; in addition, in the case where the size of the polishing particles is larger than #5000, it is difficult to obtain the polishing effect. When the immersion time in the acid washing solution is longer than 60 seconds, acid burn may occur on the surface of the conductive base material (1), and a normal plating film may not be obtained. The immersion time of 0 second means that pickling was not performed. As the acid cleaning solution, a sulfuric acid-based aqueous solution, a hydrofluoric acid-based aqueous solution, a nitric acid-based aqueous solution, a phosphoric acid-based aqueous solution, or the like can be used. The purification process can be carried out at a processing rate of, for example, 0 to 70%. Here, 0% of the purification treatment means that the purification treatment is not performed. When the refining ratio exceeds 70%, the bending workability of the obtained Sn-plated material (10) is significantly reduced. In addition, when the purification annealing is performed, the annealing can be performed at 250 to 650 ℃ for 5 seconds to 5 hours, for example. If the temperature is lower or the time is shorter than this condition, the effect of the purification annealing is difficult to obtain, and the remaining amount of the processing-modified layer may be more than a predetermined range. When the temperature is high or the time is long, the remaining amount of the process-modified layer is less than a predetermined range, and the material strength of the Sn plating material (10) may be significantly reduced.

< Ni or Ni alloy plating for Forming first base layer (2) >

Ni or Ni alloy may be plated by a conventional method. As the plating bath, for example, a sulfonamide bath, a watt bath, a sulfuric acid bath, or the like can be used. Make the plating stripThe bath temperature is 20-60 ℃, and the current density is 1-30A/dm²Thus, plating may be performed.

< Cu or Cu alloy plating for Forming second base layer (3) >

Cu or Cu alloy may be plated using a conventional method. As the plating bath, for example, a sulfuric acid bath or a cyanide bath can be used. The plating conditions are such that the bath temperature is 20 to 60 ℃ and the current density is 1 to 30A/dm²Thus, plating may be performed.

< Sn or Sn alloy plating for forming surface layer (5) >

Sn or Sn alloy may be plated using a conventional method. As the plating bath, for example, a sulfuric acid bath or the like can be used. The plating conditions are such that the bath temperature is 10 to 40 ℃ and the current density is 1 to 30A/dm²Thus, plating may be performed.

< reflow treatment >

The reflow process until the surface layer (5) is formed can be performed by a conventional method. The material is passed through a furnace set at 400 to 800 ℃, for example, heated for 5 to 20 seconds and then cooled. The second base layer (3) is reacted with the surface layer (5) by reflow treatment to form the intermediate layer (4).

Therefore, when the intermediate layer (4) is formed by reacting the second base layer (3) and the surface layer (5) by reflow treatment until the second base layer (3) disappears, the second base layer does not exist between the first base layer (2) and the intermediate layer (4), as shown in fig. 1.

When the intermediate layer (4) is formed by reacting the second base layer (3) and the surface layer (5) so that the second base layer (3) partially remains by reflow processing, the second base layer (3) is formed between the first base layer (2) and the intermediate layer (4), as shown in fig. 2.

In the Sn plating material (10) of the present embodiment, the processing-modified layer (6) is partially left on the surface of the conductive base material (1), whereby diffusion of the base material component Cu from the conductive base material (1) to the surface layer (5) can be suppressed, and good heat resistance can be obtained. Further, cracks in the contact portion formed in the bending process or the bulging forming can be suppressed.

(use of Sn plating Material (10))

The Sn plating material (10) of the present embodiment is particularly excellent in heat resistance (electrical connectivity) at high temperatures. Therefore, the Sn plating material (10) of the present embodiment is suitable for vehicle-mounted components such as small-sized terminals and high-voltage and high-current terminals, and electrical and electronic components such as terminals, connectors, and lead frames.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

A copper alloy substrate (trade name: EFTEC-97, manufactured by Kogaku electric industries Co., Ltd.) having a plate thickness of 0.25mm was polished and acid-washed, refined and annealed, then subjected to electrolytic degreasing and acid-washing, Ni plating, Cu plating and Sn plating in this order, and passed through a furnace maintained at 700 ℃ for 5 to 10 seconds to perform reflow treatment. The respective plating conditions are shown in table 1. The remaining amount of the work-modified layer in the cross section of the substrate after reflow treatment is controlled to be within a predetermined range in the polishing, pickling, refining, and refining annealing. The polishing amount is adjusted by making the size of the polishing particles in the range of #1000 to 5000. The surface dissolution amount is adjusted by setting the immersion time in a mixed aqueous solution of sulfuric acid and hydrogen peroxide as an acid washing solution to a range of 0 to 60 seconds. The conditions are adjusted so that the working ratio of the refining is in the range of 0 to 70% and the refining annealing is at 250 to 650 ℃ for 5 seconds to 5 hours. The remaining amount of the processing-modified layer was measured by the method described below.

Under such conditions, as shown in table 2 below, Sn plating materials (10) of invention examples 1 to 7 having different layer thickness configurations were produced as examples within the scope of the present invention.

In addition, as comparative examples, Sn plating materials (comparative examples 1, 2, 3, and 4) were also produced in which the remaining amount of the processing-modified layer deviated from the predetermined amount of the present invention.

Here, comparative example 1 corresponds to the case of the absence of the processing-modified layer in patent document 3 (examples 1 to 6 in patent document 3), and was produced by immersing the wafer in an acid washing solution for 60 seconds after polishing in the polishing and acid washing steps, without performing the refining process and the refining annealing. Comparative example 4 corresponds to the case where the processing-modified layer remained on the entire surface of the conductive base material (1) (comparative example 1 of patent document 3), and was prepared by performing a purification process 70% after polishing and pickling, and not performing a purification annealing. Comparative examples 2 and 3 are examples in which a processing-modified layer partially remains on a conductive base material and the amount of remaining is adjusted to be out of the range specified in the present invention. Comparative example 2 the polishing and acid washing were performed, and the polishing annealing was performed at 675 ℃ higher than the temperature specified in the present invention for 2 hours, so that the remaining amount of the processing-modified layer was less than the range specified in the present invention. Comparative example 3 the polishing and acid washing were performed, and then the polishing annealing was performed at 225 ℃ which is lower than the temperature specified in the present invention for 2 hours, so that the remaining amount of the processing-modified layer was more than the range specified in the present invention.

[ TABLE 1 ]

[ cathodic electrolytic degreasing ]

Degreasing fluid: NaOH 60 g/l

Degreasing conditions: 2.5A/dm²At 60 ℃ for 60 seconds

[ acid washing ]

Acid washing solution: 10% sulfuric acid

Acid washing conditions are as follows: 30 seconds immersion, room temperature

The sample material thus produced was subjected to the following evaluation.

(measurement of layer thickness of Sn plating Material)

The thickness of each layer of the Sn-plated material prepared above was measured by a constant current dissolution method described in JIS H8501, 10.

(tissue observation-amount of remaining modified layer)

The cross section of the Sn plating material (10) thus produced, which was composed of the rolling direction and the thickness direction, was observed using a FIB-SIM (focused ion beam-scanning ion microscope), and the length (remaining amount) of the modified layer (6) remaining on the surface of the conductive base material (1) was measured. The observation is performed at 10000-50000 times of magnification. In the measurement, the interface between the first base layer (2) and the conductive base material (1) is measured by taking a range including an interface length of 20 μm as 1 visual field, measuring the interface length of the portion of the processing-modified layer (6) remaining in the 3 visual fields so that the visual field ranges do not overlap, and then using the average value thereof as the measurement result. Alternatively, it was confirmed that: two or more process-modifying layers (6) are present in a total length of 0.5 to 10 [ mu ] m with respect to the interface length of 20 [ mu ] m. The position of the interface between the first base layer (2) and the conductive base material (1) is determined by using elemental mapping using the auger electron spectroscopy analysis attached to the FIB. The first base layer (2) immediately above is oriented in the conductive base material (1), and the portion where the grain boundary of Ni matches the grain boundary of Cu can be determined as having removed the processing-modified layer (6). On the other hand, the portion of the first base layer (2) where the crystal grain size of Ni is smaller than the grain boundary of Cu of the conductive base material (1) is determined to be the processing-modified layer (6) remaining.

(Heat resistance at high temperature)

The Sn remaining amount after heating at 160 ℃ for 1000 hours (160 ℃ heat resistance) and the Sn remaining amount after heating at 175 ℃ for 240 hours (175 ℃ heat resistance) were measured by the constant current test method described in 10 of JIS H8501, and if Sn were left in small amounts, the evaluation was regarded as A (good); if no residue remained, the evaluation was regarded as D (difference).

Fig. 5 schematically shows a state of aged deterioration at the above-described high temperature (for example, a state of being left at 150 ℃ for 1000 hours). In fig. 5, the intermediate layer (4) and the surface layer (5) thereon remain in the portion where the processing-modified layer (6) is not present, but the intermediate layer (4) becomes thick directly above the processing-modified layer (6) and the surface layer (5) substantially disappears.

(bulge formability)

The Sn plating material (10) thus produced was subjected to bulging molding, and the case where no plating crack occurred after the processing was denoted as a (good), and the case where a plating crack occurred was denoted as D (bad). The determination of the plating crack is made by observing the surface of the machined bulging portion at 50 to 500 times with an optical microscope, and determining that the substrate is exposed as a crack. Fig. 3 is a schematic cross-sectional view of the bump forming method and the bump-formed Sn plating material (10). In the bulging forming, a jig having a hemisphere with a tip of 0.5mmR is pressed, and the fixed Sn plating material (10) thus produced is deformed and worked. In the drawing, O denotes the center of a hemisphere located at the tip of a jig used in the bulging forming. Fig. 4 is a schematic cross-sectional view of the Sn plating material (10) after the bump forming. In the figure, O denotes the center of the hemisphere of the bulging portion.

(exposed area ratio of intermediate layer (CuSn compound layer) on surface of Sn plating material after high-temperature heating)

The surface of the Sn-plated material (10) produced above after heating at 175 ℃ for 240 hours was observed by SEM at 1000 magnifications, and the area ratio of the exposed portion of the intermediate layer (4) was determined by image analysis. The presence or absence of the exposure of the intermediate layer (4) is judged by jointly using secondary electron image observation, reflected electron image observation, and EDX element mapping attached to SEM. The case where the exposed area ratio is 1 to 30% is referred to as a (good), the case where the exposed area ratio is 0.5% or more and less than 1%, or more than 30% and 40% or less is referred to as B (good), the case where the exposed area ratio is 0.1% or more and less than 0.5%, or more than 40% and 60% or less is referred to as C (good), and the case where the exposed area ratio is less than 0.1% or more and more than 60% is referred to as D (bad).

[ TABLE 2 ]

Table 2 summarizes the plating layer thickness (layer thickness), remaining amount (length) of the processing-modified layer, and characteristics of each layer of the Sn plating material (10) produced as described above.

In table 2, the column denoted by "Ni" in the column denoted by "layer thickness (μm)" shows the thickness of the first base layer (2), the column denoted by "Cu" shows the thickness of the second base layer (3), the column denoted by "CuSn" shows the thickness of the intermediate layer (4), and the column denoted by "Sn" shows the thickness of the surface layer (5). In these invention examples, the embodiment shown in FIG. 1 is shown when the "Cu" layer, that is, the second base layer (3) is 0 μm; when the "Cu" layer, that is, the second base layer (3) is not 0 μm, it is the embodiment shown in fig. 2.

In table 2, inventive examples 1 to 7 satisfying the conditions of the present invention are all excellent in all of heat resistance and bulge formability.

In contrast, comparative examples 1 to 4 were inferior in any evaluation of heat resistance and bulge formability. In comparative examples 1 and 2 in which the remaining amount of the processing-modified layer is less than the predetermined range of the present invention, the bulging formability is poor, and the exposed area ratio of the intermediate layer (4) after heating at 175 ℃ for 240 hours in comparative example 1 is extremely small. In comparative examples 3 and 4 in which the remaining amount of the processing-modified layer is larger than the predetermined range of the present invention, the heat resistance is poor at 175 ℃ during 240 hours of heating, the exposed area ratio of the intermediate layer (4) after heating becomes extremely large, and the surface layer (5) hardly remains.

As described above, it was confirmed that the Sn plating material satisfying the conditions of the present invention exhibits excellent characteristics.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

This application claims priority based on Japanese patent application 2015-172147, filed in Japan on 9/1/2015, which is hereby incorporated by reference and the contents of which are incorporated as part of the disclosure of this specification.

Description of the symbols

1 conductive base material

2 first substrate layer

3 second substrate layer

4 intermediate layer

5 surface layer

6 processing modified layer

10 Sn plating material

Claims

1. An Sn plating material comprising, on a conductive base material made of Cu or a Cu alloy, a first base layer made of Ni or a Ni alloy, an intermediate layer made of a CuSn compound, and a surface layer made of Sn or a Sn alloy in this order, characterized in that, when a cross section in a rolling direction and a plate thickness direction is observed, a processing-modified layer is left on the surface of the conductive base material at a length of 0.5 to 10 μm relative to the length of 20 μm of the interface between the first base layer and the conductive base material; or two or more processing-modified layers having a total length of 0.5 to 10 μm with respect to the interface length of 20 μm,

the crystal grains of the first base layer are smaller in the portion directly above the portion where the processing-modified layer remains than in the portion where the processing-modified layer does not remain.

2. An Sn plating material comprising, on a conductive base material composed of Cu or a Cu alloy, a first base layer composed of Ni or a Ni alloy, a second base layer composed of Cu or a Cu alloy, an intermediate layer composed of a CuSn compound, and a surface layer composed of Sn or a Sn alloy in this order, characterized in that, when a cross section composed of a rolling direction and a plate thickness direction is observed, a processing-modified layer is left on the surface of the conductive base material at a length of 0.5 to 10 μm with respect to the interface length 20 μm between the first base layer and the conductive base material; or two or more processing-modified layers having a total length of 0.5 to 10 μm with respect to the interface length of 20 μm,

3. The Sn plating material of claim 1 or claim 2, wherein the first base layer is intermixed with a fraction having a crystal grain size of 1 μm or more and a fraction smaller than 1 μm.

4. The Sn plating material of claim 1 or 2, wherein a thickness of the surface layer is 0.2 to 5 μm.

5. The Sn plating material of claim 1 or 2, wherein the intermediate layer has a thickness of 0.1 to 1 μm.

6. The Sn plating material of claim 1 or 2, wherein the first base layer has a thickness of 0.1 to 2 μm.

7. The Sn plating material of claim 2, wherein the second base layer has a thickness of 0 to 0.1 μm.

8. The Sn plating material according to claim 1 or 2, wherein the intermediate layer is exposed to the surface of the material at an area ratio of 0.1 to 60% when heat-treated at 175 ℃ for 240 hours.

9. An in-vehicle component using the Sn-plated material according to any one of claims 1 to 8.

10. An electrical/electronic component using the Sn plating material according to any one of claims 1 to 8.

11. A method for producing an Sn plating material, comprising sequentially forming a first base layer made of Ni or an Ni alloy, an intermediate layer made of a CuSn compound, and a surface layer made of Sn or an Sn alloy on a conductive base material made of Cu or a Cu alloy,

forming the first base layer, a second base layer made of Cu or a Cu alloy, and the surface layer in this order on the conductive base material, and then reacting the second base layer and the surface layer by reflow treatment until the second base layer disappears to form the intermediate layer,

adjusting polishing and pickling conditions of the conductive base material to a polishing particle size of #1000 to 5000, and adjusting immersion time in a pickling solution to 0 to 60 seconds, and adjusting a processing rate of a refining condition to 0 to 70%, and further adjusting refining heat treatment conditions to 250 to 650 ℃ for 5 seconds to 5 hours as the case may be, to control a remaining amount of the processing-modified layer on the surface of the conductive base material, whereby the processing-modified layer remains on the surface of the conductive base material at a length of 0.5 to 10 μm with respect to an interface length of 20 μm between the first base layer and the conductive base material when a cross section composed of a rolling direction and a plate thickness direction is observed in the Sn plating material; or two or more processing-modified layers having a total length of 0.5 to 10 μm with respect to the interface length of 20 μm.

12. A method for producing an Sn plating material, comprising sequentially forming, on a conductive base material composed of Cu or a Cu alloy, a first base layer composed of Ni or a Ni alloy, a second base layer composed of Cu or a Cu alloy, an intermediate layer composed of a CuSn compound, and a surface layer composed of Sn or a Sn alloy, wherein the first base layer, the second base layer, the intermediate layer, and the surface layer are formed of a metal or a metal alloy,

forming the first foundation layer, the second foundation layer, and the surface layer in this order on the conductive base material, and then forming the intermediate layer by reacting the second foundation layer with the surface layer through reflow processing so that the second foundation layer partially remains,