Electrical connection components

Abstract

To provide an electric connection member material capable of suppressing adhesion in an Ag layer even without using a special metal layer, and an electric connection member.SOLUTION: An electric connection member material 1 includes: a metal material 10 having an Ag layer 13 on the surface; and a coating layer 2 for coating the surface of the metal material 10. The coating layer 2 is formed to contact an organic compound having a mercapto group and an aromatic ring to the surface of the metal material 10, where a case that the surface of the Ag layer 13 has a hardness of 90 HV or more is excluded. An electric connection member includes the electric connection member material 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a material for an electrical connection member and an electrical connection member.

Background Art

[0002] In electrical connection members such as connector terminals for high currents used in automobiles, a metal material having an Ag layer formed on its surface by plating or the like may be used. While a metal material having an Ag layer is excellent in heat resistance, corrosion resistance, and electrical conductivity, it has a property that Ag is soft and likely to cause adhesion, resulting in easy wear and peeling on the surface. If a part of the Ag layer is removed due to wear and peeling and the underlying metal such as the base material or the underlayer is exposed, the electrical connection characteristics of the surface will change. Wear and peeling of the Ag layer due to adhesion are particularly likely to occur in a high-temperature environment.

[0003] In order to suppress adhesion on the surface of the Ag layer, studies have been conducted on the materials constituting the metal material. As one direction of the material study, providing a predetermined Ag alloy layer instead of the Ag layer on the surface of the metal material, or providing an underlayer made of a predetermined metal under the Ag layer or the Ag alloy layer has been studied. Studies in such a direction are disclosed in, for example, Patent Document 1. Also, as another direction, attempts have been made to suppress adhesion of the Ag layer by providing a metal layer having a predetermined composition on the surface of the mating member that contacts the electrical connection member with the Ag layer exposed on the outermost surface. Studies in such a direction are disclosed in, for example, Patent Document 2.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In metal materials containing Ag in a surface layer, as described in Patent Documents 1 and 2, etc., it is an effective means to devise the composition and structure of the surface layer or the metal layer in contact with the surface layer to reduce Ag adhesion. However, if wear and peeling caused by Ag adhesion, and these phenomena in high-temperature environments, can be suppressed in a general metal material having an Ag layer without using a metal layer with a special composition or structure, then metal materials having an Ag layer can be used even more easily for applications as electrical connection components such as terminals. Therefore, the objective is to provide an electrical connection component material and an electrical connection component that can suppress Ag adhesion in the Ag layer without using a special metal layer. [Means for solving the problem]

[0006] The electrical connection member material of this disclosure comprises a metal material having an Ag layer on its surface with a surface hardness of 90 HV or more, and a coating layer covering the surface of the metal material, wherein the coating layer is formed by bringing an organic compound having a mercapto group into contact with the surface of the metal material.

[0007] The electrical connection member of this disclosure is comprised of the material for the electrical connection member. [Effects of the Invention]

[0008] The electrical connection material and electrical connection member according to this disclosure can suppress adhesion in the Ag layer without using a special metal layer. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing a cross-section of an electrical connection member material according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a cross-sectional view showing a connection terminal as an electrical connection member according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0010] [Description of Embodiments in this Disclosure] First, embodiments of this disclosure will be listed and described.

[0011] The electrical connection material according to this disclosure comprises a metal material having an Ag layer on its surface with a surface hardness of 90 HV or more, and a coating layer covering the surface of the metal material, wherein the coating layer is formed by bringing an organic compound having a mercapto group into contact with the surface of the metal material.

[0012] When the above-mentioned electrical connection material comes into contact with other components on its surface, the Ag layer with a surface hardness of 90 HV or higher comes into contact with the other components via the coating layer. Because the Ag layer is composed of a hard Ag layer with a hardness of 90 HV or higher, and because the surface of this hard Ag layer is covered with a coating layer formed using an organic compound having mercapto groups, when the above-mentioned electrical connection material is subjected to contact or sliding with other components, adhesion of Ag, and the resulting wear and peeling of the Ag layer, are less likely to occur. The coating layer formed from the organic compound having mercapto groups maintains a stable coating state on the surface of the Ag layer even at high temperatures, and shows a high effect in suppressing adhesion of the Ag layer even in high-temperature environments.

[0013] Here, it is preferable that the organic compound has an aromatic ring. In this case, the state in which the surface of the Ag layer is covered by the coating layer is stably maintained until high temperatures are reached, and a high effect of suppressing adhesion of the Ag layer in a high-temperature environment is obtained.

[0014] In this case, the aromatic ring is preferably a heterocycle containing at least one of a sulfur atom and a nitrogen atom in addition to a carbon atom. This further enhances the stability of the Ag layer when its surface is covered by the coating layer, and allows for a high degree of suppression of Ag layer adhesion even when exposed to high-temperature environments or when large surface pressure is applied to the surface of the electrical connection material.

[0015] The electrical connection member according to this disclosure is composed of the material for the electrical connection member. As described above, the surface of the material for the electrical connection member according to this disclosure is covered with a coating layer formed using an organic compound having mercapto groups over a hard Ag layer, so that even when subjected to contact or sliding with other members, wear and peeling due to adhesion can be easily suppressed. Furthermore, these phenomena originating from Ag adhesion can be suppressed even in high-temperature environments. By constructing an electrical connection member using a material having such properties, an electrical connection member can be made that is less susceptible to wear and peeling of the Ag layer due to adhesion, and can suppress the occurrence of these phenomena even after exposure to high-temperature environments.

[0016] Here, the electrical connection member is configured as a connection terminal having a contact portion that electrically contacts a mating conductive member, and it is preferable that the coating layer is formed on the surface of the metal material at least at the contact portion. This makes it less likely for the Ag layer to adhere to the contact portion of the connection terminal due to contact and sliding with the mating conductive member, and consequently wear and peel off the Ag layer, and allows the electrical connection characteristics and heat resistance and other properties imparted to the contact portion by the Ag layer to be well maintained. Furthermore, even after heating of the contact portion due to current flow, adhesion to the surface of the Ag layer is less likely to occur, and the properties imparted by the Ag layer can be maintained.

[0017] In this case, it is preferable that the surface pressure applied to the contact portion be 30 MPa or more. In connection terminals, the greater the surface pressure applied to the contact portion, the more likely adhesion is to occur in the metal layer on the surface of the contact portion. However, in the above-mentioned electrical connection member, a hard Ag layer is formed on the surface of the contact portion, and the surface of the hard Ag layer is covered with a coating layer. Therefore, adhesion of Ag, and the resulting wear and peeling of the Ag layer, are less likely to occur on the surface of the contact portion.

[0018] [Details of the embodiments of this disclosure] Embodiments of this disclosure will be described in detail below with reference to the drawings.

[0019] <Outline of materials and electrical connection components> First, the material for an electrical connection member and the configuration of the electrical connection member according to an embodiment of the present disclosure will be briefly described.

[0020] (Material for Electrical Connection Member) The material for an electrical connection member according to an embodiment of the present disclosure has a structure in which the surface of a metal material is coated with a coating layer. The material for an electrical connection member according to an embodiment of the present disclosure can be suitably used as a material constituting an electrical connection member such as a connection terminal.

[0021] In FIG. 1, the configuration of a material 1 for an electrical connection member (hereinafter sometimes referred to as a connection material) according to a first embodiment of the present disclosure is shown in a cross-sectional view. The connection material 1 has a metal material 10 and a coating layer 2 that coats the surface of the metal material 10. The metal material 10 has a base material 11 and an Ag layer 13. Further, an underlayer 12 is optionally provided between the base material 11 and the Ag layer 13.

[0022] The base material 11 of the metal material 10 is configured as a metal plate material. The specific metal species constituting the base material 11 is not particularly limited, but Cu or a Cu alloy that is widely used as a base material for electrical connection members such as connection terminals can be preferably used because of its excellent electrical conductivity and mechanical properties.

[0023] The Ag layer 13 is configured as a layer of hard Ag and is exposed on the outermost surface of the metal material 10. The hard Ag has a hardness on the surface of generally 90 HV or more, preferably 110 HV or more. The Ag layer 13 may contain only Ag and inevitable impurities, or may contain, in addition to Ag and inevitable impurities, an additive element for hardening the Ag layer 13. Examples of such additive elements include Se, Sb, C, N, S, etc. In particular, it is preferable to use Se, C, and S as additive elements. The addition amount of these additive elements can be exemplified in the range of 0.1 atomic% or more and 5.0 atomic% or less with respect to Ag atoms. Note that the hardness measurement in this specification indicates the value obtained when the measurement was performed by a micro-Vickers hardness test at HV0.01 (10 gf) in accordance with JIS Z 2244:2009.

[0024] The thickness of the Ag layer 13 is not particularly limited, but from the viewpoint of fully exhibiting the properties of Ag, for example, it is preferably 1 μm or more, and more preferably 3 μm or more. On the other hand, from the viewpoint of avoiding the use of an excess amount of Ag, it is preferably 100 μm or less. The Ag layer 13 may be formed by any method such as plating or vapor deposition. Using a plating method is particularly preferable from the viewpoint of simplicity and hardness control.

[0025] Between the substrate 11 and the Ag layer 13, another metal layer may be provided as an underlayer 12, as appropriate. The underlayer 12 may be a single layer or two or more metal layers may be laminated. When the substrate 11 is made of Cu or a Cu alloy, a suitable example of an underlayer 12 is a layer made of Ni or a Ni alloy. The underlayer 12 made of Ni or a Ni alloy suppresses the diffusion of Cu atoms from the substrate 11 to the Ag layer 13 and also enhances the adhesion of the Ag layer 13 to the substrate 11. In the metal material 10, at the interface of adjacent layers, some of the metal atoms constituting the layers on both sides may form an alloy.

[0026] In this embodiment, the connecting material 1 is provided with a coating layer 2 that covers the Ag layer 13 exposed on the surface of the metal material 10, while in contact with the surface of the Ag layer 13. The coating layer 2 is a layer formed by bringing an organic compound having a mercapto group (-SH group) into contact with the surface of the Ag layer 13 of the metal material 10. The details of the coating layer 2 will be explained in detail later, but the fact that the coating layer 2 covers the surface of the Ag layer 13 has the effect of suppressing the adhesion of Ag, and the resulting wear and peeling of the Ag layer 13. Furthermore, even when the metal material 10 is heated to a high temperature, wear and peeling of the Ag layer 13 due to adhesion are suppressed.

[0027] (Electrical connection components) Next, an electrical connection member according to one embodiment of the present disclosure will be described. The electrical connection member according to this embodiment is composed of the electrical connection member material 1 according to the embodiment of the present disclosure described above.

[0028] An example of an electrical connection component is a connection terminal. The connection terminal has a contact portion that electrically contacts a mating conductive member, and at least at the contact portion, the surface of the base material 11 has an Ag layer 13 made of hard Ag and a coating layer 2 that covers the surface of the Ag layer 13. On the surface of the connection terminal, as long as the Ag layer 13 and the coating layer 2 are formed at least at the contact portion, the Ag layer 13 and the coating layer 2 may cover the entire surface of the connection terminal or cover only a part of it.

[0029] The specific type and shape of the connection terminal are not particularly limited. Figure 2 shows a female connector terminal 20 as an example of a connection terminal according to one embodiment of the present disclosure. The female connector terminal 20 has a shape similar to a known mating-type female connector terminal. That is, a clamping portion 23 is formed in a cylindrical shape with an open front, and an elastic contact piece 21 is provided on the inside of the bottom surface of the clamping portion 23, which is folded inward towards the rear. When a flat tab-shaped male connector terminal 30 is inserted into the clamping portion 23 of the female connector terminal 20 as the mating conductive member, the elastic contact piece 21 of the female connector terminal 20 contacts the male connector terminal 30 at an embossed portion 21a that bulges inward from the clamping portion 23, applying an upward force to the male connector terminal 30. The surface of the ceiling portion of the clamping portion 23 that faces the elastic contact piece 21 is designated as the internal opposing contact surface 22, and the male connector terminal 30 is pressed against the internal opposing contact surface 22 by the elastic contact piece 21, thereby clamping and holding the male connector terminal 30 within the clamping portion 23.

[0030] The female connector terminal 20 is entirely composed of a metal material 10 having an Ag layer 13 on its outermost surface, as described above. Here, the surface of the metal material 10 on which the Ag layer 13 is formed is oriented inward towards the clamping portion 23 and is arranged to form mutually opposing surfaces of the elastic contact piece 21 and the internal opposing contact surface 22. A coating layer 2 is formed on the surface of the metal material 10 in the area including the embossed portion 21a of the elastic contact piece 21 and the internal opposing contact surface 22.

[0031] On the surface of the embossed portion 21a and the internal opposing contact surface 22 that contact the surface of the male connector terminal 30, the surface of the Ag layer 13 is covered with the coating layer 2, and in those areas, the coating layer 2 exerts an adhesion-suppressing effect on the Ag layer 13. As a result, even when sliding occurs when inserting the male connector terminal 30 into the clamping portion 23 of the female connector terminal 20, wear and peeling of the Ag layer 13 due to adhesion are unlikely to occur. Furthermore, even if the male connector terminal 30 and the female connector terminal 20 are left mated for a long period of time, or even if they are heated to a high temperature due to current flow while mated, wear and peeling of the Ag layer 13 due to Ag adhesion are unlikely to occur. In the female connector terminal 20, the surface pressure at the contact portion, that is, the surface pressure exerted from the top of the embossed portion 21a to the surface of the male connector terminal 30 by the elastic restoring force of the elastic contact piece 21, is preferably 30 MPa or more, and more preferably 40 MPa or more. The greater the surface pressure, the stronger the Ag layer 13 on the surface is pressed against the surface of the male connector terminal 30 at the top of the embossed portion 21a, making adhesion of the Ag layer 13 more likely. However, because the surface of the Ag layer 13 is covered by the coating layer 2, adhesion of Ag can be effectively suppressed even when a large surface pressure is applied as described above. However, if a surface pressure of about 4 to 5 times the hardness of the Ag layer 13 is applied, the deformation of the Ag layer 13 at the point of contact with the surface of the male connector terminal 30 changes from elastic deformation to plastic deformation. Therefore, it is preferable to keep the surface pressure below 5 times the hardness of the Ag layer 13.

[0032] Here, we have described a configuration in which the entire female connector terminal 20 is made of a metal material 10 having an Ag layer 13, and only the portion of the Ag layer 13 that contacts the male connector terminal 30 is covered with a coating layer 2. However, as described above, as long as the Ag layer 13 and the coating layer 2 are formed on the surface of the contact portion that contacts the mating conductive member, the range in which these layers are formed is not particularly limited. Furthermore, while the constituent material of the male connector terminal 30 is not particularly limited, it is preferable that the male connector terminal 30 is also made of a connecting material 1 according to the embodiment of this disclosure, in which at least the surface of the contact portion, i.e., the tab-shaped portion that contacts the female connector terminal 20, has an Ag layer 13 formed as a layer of hard Ag on the surface of the base material 11, similar to the female connector terminal 20, and the surface of the Ag layer 13 is further covered with a coating layer 2. In this case, at the electrical connection portion between the female connector terminal 20 and the male connector terminal 30, the Ag layers 13 made of hard Ag will be in contact with each other via two layers of coating layers 2. As a result, wear and peeling of the Ag layer 13 due to adhesion can be effectively suppressed not only at the female connector terminal 20 but also at the contact points of the male connector terminal 30, and these effects are maintained even after a long period of time or when exposed to high-temperature environments.

[0033] The connection terminals according to the embodiments of this disclosure can take various forms, including, in addition to the mating-type female connector terminal 20 or male connector terminal 30 described above, press-fit terminals that are press-fitted into through-holes formed on a printed circuit board. The various connection terminals according to the embodiments of this disclosure can be housed in a connector housing made of an insulating material and used in the form of a connector. Alternatively, they can be connected to the end of an electric wire and used in the form of a wire harness.

[0034] <Composition of the coating layer and its adhesion-inhibiting effect> As described above, in the connecting material 1 according to the embodiment of this disclosure, an Ag layer 13 made of hard Ag is formed on the surface of the metal material 10, and the surface of the Ag layer 13 is covered with a coating layer 2 made of an organic compound having a mercapto group (-SH group). Although Ag is a metal that is prone to adhesion, the occurrence of adhesion in the Ag layer 13 is suppressed by being covered with the coating layer 2.

[0035] Here, we will briefly explain the situation when the Ag layer is exposed on the outermost surface of the connecting material without being covered by other layers. Ag is a metal that is relatively resistant to oxidation, exhibits low contact resistance on its surface, and also has excellent heat resistance and corrosion resistance. By providing an Ag layer on the surface of a connecting material, such as a connector, it is easy to maintain good electrical properties even in high-temperature environments. On the other hand, Ag has a very strong tendency to adhere, and if adhesion occurs at the contact point with the mating member, the Ag on the surface will wear down or peel off when the contact point is slid or when it is left in contact with the mating member. In a connecting material having an Ag layer on its surface, if wear or peeling of Ag due to adhesion occurs, the properties of Ag, such as low contact resistance and heat resistance, cannot be fully utilized in the connecting material. Furthermore, if the base material such as Cu or Cu alloy, or the underlayer such as Ni or Ni alloy, which is present in the layer below Ag, is exposed due to wear or peeling of Ag, it may have a significant impact on the properties of the connecting material, such as electrical connection characteristics. In particular, if a layer of Ag is also formed on the surface of the mating component, the Ag particles will come into contact with each other at the surface, making adhesion and the resulting wear and peeling more likely to occur between both Ag layers. Furthermore, if the surface Ag layer is in contact with the mating component and exposed to a high-temperature environment, or if a large contact load (surface pressure) is applied, adhesion will progress even further due to creep and atomic diffusion.

[0036] However, in the connecting material 1 according to the embodiment of this disclosure, the Ag layer 13 on the surface of the metal material 10 is covered by a coating layer 2. When the connecting material 1 comes into contact with another member, the Ag layer 13 does not come into direct contact with the surface of the other member, but rather the coating layer 2 is interposed between the Ag layer 13 and the other member. As a result, the Ag layer 13 is less likely to adhere due to contact and sliding with the other member. Consequently, wear and peeling of the Ag layer 13 due to Ag adhesion are less likely to occur, and the properties of the Ag layer 13, such as low contact resistance and heat resistance, can be more easily maintained even after contact and sliding with the other member. In particular, in this embodiment, since the coating layer 2 is formed by bringing an organic compound having a mercapto group into contact with the Ag layer 13, the state in which the coating layer 2 covers the surface of the Ag layer 13 is stably maintained. This is thought to be because the Ag atoms and S atoms readily form bonds, and the coating layer 2 is firmly fixed to the surface of the Ag layer 13. Furthermore, the state in which the coating layer 2 covers the surface of the Ag layer 13 is stably maintained even at high temperatures. Therefore, even if the connecting material 1 is placed in a high-temperature environment, the Ag layer 13 is less likely to come into direct contact with the surface of the mating member, and adhesion of the Ag layer 13, and the resulting wear and peeling, are less likely to occur. In addition, even when a high load is applied to the contact area with the mating member, the presence of the coating layer 2 suppresses adhesion of the Ag layer 13.

[0037] Based on these considerations, the connecting material 1 according to this embodiment can be suitably used as a component material for connecting terminals that are prone to becoming hot due to heating from the surrounding environment or heat generation from electrical current. Examples of such connecting terminals include automotive connecting terminals. Furthermore, in the connecting material 1 according to this embodiment, a high adhesion suppression effect can be obtained simply by contacting a predetermined organic compound with the surface of the Ag layer 13, which is composed of a hard Ag layer, to form a coating layer 2. Since it does not require a special metal layer for adhesion suppression, it has high versatility. A high adhesion suppression effect can be imparted to conventional or existing connecting materials having a hard Ag layer simply by forming a coating layer 2.

[0038] In the connecting material 1 according to this embodiment, the Ag layer 13 provided on the surface of the metal material 10 is formed as a hard Ag layer. Because the Ag layer 13 is composed of hard Ag, compared to the case where it is composed of soft Ag with a surface hardness of approximately 60 HV or less, the adhesion of Ag can be highly suppressed on the surface where the Ag layer 13 is covered with the coating layer 2. One of the factors contributing to this high adhesion suppression effect is the high hardness of the hard Ag layer itself. Ag is a metal that easily adheres, but by increasing the surface hardness through the addition of small amounts of additive elements or by controlling crystal growth, adhesion can be suppressed to a certain extent. Furthermore, as another factor, as shown in later embodiments, by covering the surface of Ag with a coating layer 2 formed from an organic compound having a mercapto group, the magnitude of the adhesion suppression effect, that is, the degree of adhesion reduction compared to the case where the coating layer 2 is not formed, is greater in the case of a hard Ag layer than in the case of a soft Ag layer. This is presumed to be because, in the case of a soft Ag layer, the Ag layer deforms due to plastic deformation, and the coating layer cannot follow that deformation, causing adhesion to progress through the resulting gap in the coating layer. In contrast, with a hard Ag layer, plastic deformation is less likely to occur, and defects are less likely to occur in the coating layer 2, so the Ag layer 13 is less likely to come into direct contact with the surface of the mating conductive member.

[0039] In this embodiment, the coating layer 2 is formed by contacting an organic compound having a mercapto group with the Ag layer 13. However, the organic compound does not need to maintain its original state in the formed coating layer 2. For example, the organic compound may constitute the coating layer 2 in a thiolate state, where the SH bond of the mercapto group (-SH group) is cleaved and the H atom is removed. In this case, if we represent the organic compound used to form the coating layer 2 as R-SH, an S-Ag bond may be formed between the organic compound and the Ag layer 13, and the organic compound may be strongly bonded to the Ag layer 13 in the form of an RS-Ag structure. The formation of this structure is particularly preferable from the viewpoint of increasing the stability of the coating layer 2. Alternatively, it is also possible that the bond between the C atom constituting the organic compound and the mercapto group (-SH group) is cleaved, and the organic compound is bonded to the Ag layer 13 in the form of R-Ag.

[0040] Alternatively, an organic compound containing a mercapto group (-SH group) can be converted into a form having a sulfur-containing functional group other than the mercapto group to constitute coating layer 2. Examples of sulfur-containing functional groups other than the mercapto group include sulfide bonds (-S-), disulfide bonds (-SS-), thiocyanate groups (-SC=N), isothiocyanate groups (-N=C=S), sulfo groups (-SO3), sulfonyl groups (-SO2-), sulfinyl groups (-S(=O)-), thioester groups (-SC(=O)-), thiocarbonyl groups (>C=S), and thiocarboxyl groups (-C(=O)-SH). Furthermore, in the R-SH structure of an organic compound containing a mercapto group, bond cleavage or conversion may occur in the R portion. When the R portion contains a ring structure, ring opening of the ring structure can be exemplified as an example of bond cleavage. In cases like these, where an organic compound containing a mercapto group is converted to another form to constitute the coating layer 2, the coating layer 2 does not necessarily have to be formed by contacting the organic compound containing the mercapto group with the Ag layer 13. For example, the compound itself in the converted form may be formed by contacting it with the surface of the Ag layer 13. In either manufacturing method, if the form of the organic compound forming the coating layer 2 on the surface of the Ag layer 13 is the same, those coating layers 2 will exhibit equivalent effects in suppressing adhesion to the Ag layer 13. The organic compound constituting the coating layer 2 may be in a substantially single state, or it may be a mixture of two or more states, such as a state in which the SH bond is cleaved and a state in which it is not cleaved.

[0041] The thickness of coating layer 2 is not particularly limited. For example, from the viewpoint of enhancing the effect of coating layer 2 in suppressing adhesion of Ag layer 13, it may be 1 nm or more. On the other hand, from the viewpoint of avoiding the outflow of excess organic compounds and stickiness, it may be 10 μm or less.

[0042] When forming the coating layer 2 by contacting an organic compound having a mercapto group with the Ag layer 13, the specific form of contact is not particularly limited, and methods such as coating, immersion, dropping, flow, and spraying can be used. The state of the compound at the time of contact with the Ag layer 13 is also not particularly limited; the liquid organic compound may be contacted as is, or it may be dissolved, dispersed, or diluted using a solvent or water as appropriate before contact. When contacting a solution containing an organic compound with the Ag layer 13, the pH may be adjusted to about 5-7 to improve the stability of the organic compound before contact. It is preferable to use sulfuric acid, nitric acid, hydrochloric acid, or phosphoric acid as the pH adjusting agent in this case. Furthermore, after contact, any excess organic compound required to form a coating layer 2 of the desired thickness may be removed as appropriate by washing with a solvent or water.

[0043] The organic compound forming the coating layer 2 is not limited to any specific type, as long as it contains a mercapto group. The number of mercapto groups contained within the molecule of the organic compound is also not limited; it may be one, two (dithiol), or three or more. Furthermore, the organic compound constituting the coating layer 2 may be a single type or a mixture of two or more types.

[0044] In the R-SH structure of an organic compound, the R portion is mainly composed of C and H atoms, but may also contain heteroatoms such as N, O, S, P, and Si as appropriate. Furthermore, the R portion may consist solely of a chain structure, or it may contain at least a portion of a cyclic structure. Examples of chain structures constituting the R portion include hydrocarbon groups such as alkyl groups, alkenyl groups, and alkynyl groups, as well as those in which some of the C atoms constituting these hydrocarbon groups are substituted with heteroatoms. The chain structure may be linear or branched. The cyclic structure constituting the R portion may be either an aromatic or non-aromatic ring. Examples of non-aromatic rings include aliphatic rings such as cycloalkyl rings, and those in which some of the C atoms are substituted with heteroatoms. An example of an aromatic ring that does not contain heteroatoms is a benzene ring. Furthermore, examples of aromatic rings containing heteroatoms, i.e., heterocycles, include imidazole rings, triazine rings, isocyanuric acid skeletons, pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, pyrazole rings, triazole rings, thiazole rings, thiophene rings, and pyrrole rings. The aromatic rings may be formed by the condensation of two or more rings. In this case, the multiple aromatic rings to be condensed may be of the same type (e.g., naphthalene rings) or of different types (e.g., benzothiazole rings, benzimidazole rings). The R portion may include both a chain structure and a cyclic structure, and the chain structure and / or cyclic structure may be included in multiple parts of the R portion. Substituents may also be introduced into the chain portion and / or cyclic portion as appropriate, and it is particularly preferable that functional groups other than mercapto groups that can interact with or form bonds with the surface of the Ag layer 13 are introduced. The molecular weight of the R portion is not particularly limited, but from the viewpoint of enhancing the stability of the structure in which the coating layer 2 coats the Ag layer 13, it is preferably 50 or more, and more preferably 100 or more. On the other hand, from the viewpoint of the ease of forming the coating layer 2 by contact with the Ag layer 13, the molecular weight of the R portion is preferably 1000 or less.

[0045] The organic compound having a mercapto group that constitutes the coating layer 2 is particularly preferably one of the various compounds listed above that has an aromatic ring. This improves the stability of the structure in which the formed coating layer 2 coats the surface of the Ag layer 13, and enhances the effect of suppressing adhesion of the Ag layer 13. In particular, it is excellent in suppressing adhesion of the Ag layer 13 in high-temperature environments. This is thought to be because the conjugated π-electron system of the aromatic ring, which has a planar structure, interacts with the surface of the Ag layer 13, and together with the interaction between the S atom derived from the mercapto group and the Ag atom, the coating layer 2 is firmly fixed to the surface of the Ag layer 13. In particular, if the organic compound contains a heteroatom containing at least one of an S atom and an N atom in addition to a C atom, the formed coating layer 2 shows a particularly high effect in suppressing adhesion of the Ag layer 13 and maintaining the adhesion suppression effect at high temperatures. This is presumed to be because the interaction between the heteroatom contained in the ring structure and the surface of the Ag layer 13 enhances the bonding strength of the coating layer 2 to the Ag surface. The aromatic ring may contain one heteroatom or multiple heteroatoms, but it is preferable that it contains multiple heteroatoms. Furthermore, it is preferable that at least one sulfur atom is included in the aromatic ring. In addition, when the organic compound has an aromatic ring, it is particularly preferable that the mercapto group is bonded to a position close to the aromatic ring. For example, it is preferable that the mercapto group is directly bonded to the aromatic ring, or that the mercapto group is bonded to a carbon atom directly bonded to the aromatic ring.

[0046] Examples of organic compounds having a mercapto group and a heteroaromatic ring that can be suitably used to constitute the coating layer 2 include, but are not limited to, the following. These compounds may be used individually or in combination of two or more. (2-mercaptoethyl)pyrazine, 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 5-amino-2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 6-amino-2-mercaptobenzothiazole, 2-mercapto-5-methoxybenzothiazole, 2-mercapto-6-nitrobenzothiazole, 2-mercaptopyridine, 4-mercaptopyridine, 3-pyridylisocyanate, 3-nitropyridine-2-thiol, 2-mercapto-5-nitropyridine, thiocyanuric acid, 6 -(dibutylamino)-1,3,5-triazine-2,4-dithiol, tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate, 2-(dibutylamino)-1,3,5-triazine-4,6-dithiol, 6-diallylamino-1,3,5-triazine-2,4-dithiol, 6-(4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4-dithiol, 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol, 6-anilino-1,3,5-triazine-2,4-dithiol

[0047] Examples of organic compounds having a mercapto group and an aromatic ring other than a heteroaromatic ring that can be suitably used to constitute the coating layer 2 include, but are not limited to, the following. These compounds may be used individually or in combination of two or more. 2-phenylethanethiol, benzenethiol, benzyl mercaptan, m-toluenethiol, o-toluenethiol, p-toluenethiol, 2-aminobenzenethiol, 3-aminobenzenethiol, 4-aminobenzenethiol, 2-hydroxybenzenethiol, 3-hydroxybenzenethiol, 4-hydroxybenzenethiol, 2-phenylethanethiol, 3,4-dimethylbenzenethiol, 3,5-dimethylbenzenethiol, 4-methylbenzyl mercaptan, 2,4-dimethylbenzenethiol, 2,5-dimethylbenzenethiol, 2-methoxybenzenethiol, 3-methoxybenzenethiol, 4-Methoxybenzenethiol, 1,3-Benzenedithiol, 1,4-Benzenedithiol, 2-Isopropylbenzenethiol, 4-Isopropylbenzenethiol, 4-(Dimethylamino)benzenethiol, Thiosalicylic acid, 3-Mercaptobenzoic acid, 4-Mercaptobenzoic acid, 4-Methoxy-α-Toluenethiol, 3-Ethoxybenzenethiol, 4-Nitrobenzenethiol, 4-(Methylthio)benzenethiol, Toluene-3,4-Dithiol, 2-Naphthalenchiol, 4-Tert-Butylbenzenethiol, Methyl mercaptobenzoate, 1,3-Benzenedimethanethiol, 1,4-Benzenedimethanethiol

[0048] In addition to those having aromatic rings, the following are examples of organic compounds having mercapto groups that can be suitably used to constitute the coating layer 2, but are not limited to these. These compounds may be used individually or in combination of two or more. 1-Propanethiol, Isobutyl mercaptan, 1-Butanethiol, 2-Butanethiol, 3-Mercapto-1-Propanol, Cyclopentanethol, 3-Mercapto-2-Butanol, 2-Methyl-1-Butanethiol, 1-Pentanethiol, Isoamyl mercaptan, 3-Methyl-2-Butanethiol, 3-Mercapto-2-Butanol, α-Thioglycerol, 1,3-Propanedithiol, 1,2-Propanedithiol, Cyclohexanethiol, 2-Methyltetrahydrofuran-3-thiol, 3-Mercapto-2-Pentanone, Hexyl mercaptan, 3-Mercapto Butyrate, methyl 3-mercaptopropionate, 3-mercapto-3-methyl-1-butanol, L-cysteine, 1,2-butanedithiol, 1,4-butanedithiol, 2,3-butanedithiol, 2,3-dimercapto-1-propanol, 4-mercapto-4-methyl-2-pentanone, 1-heptanethiol, 1,5-pentanedithiol, 1-(mercaptomethyl)cyclopropaneacetic acid, 1-octanethiol, 2-ethyl-1-hexanethiol, isopropyl 3-mercaptopropionate, D-penicillamine, thiomalic acid, 1,6-hexanedithiol, dithioerythritol [Examples]

[0049] Examples are shown below. However, the present invention is not limited to these examples. Here, we confirmed the effect of forming a coating layer on the surface of the Ag layer in suppressing Ag adhesion, and investigated the differences in effect depending on the hardness of the Ag layer and the type of organic compound constituting the coating layer. Unless otherwise specified, sample preparation and evaluation were carried out in air at room temperature.

[0050] <Sample preparation> First, metal materials were prepared. Specifically, a 1 μm thick Ni layer was formed on the surface of a clean Cu alloy substrate by electroplating. Furthermore, a 5 μm thick Ag layer was formed on the surface of the Ni layer by electroplating. Two types of Ag layers were prepared: a hard Ag layer and a soft Ag layer. The hard Ag layer was hardened by including 0.01 atomic percent of Se relative to Ag, and its surface hardness was 130 HV. The soft Ag layer did not contain any additive elements for hardening, and its surface hardness was 60 HV.

[0051] Next, the metal materials having a hard Ag layer and a metal material having a soft Ag layer, prepared as described above, were processed into flat test pieces and embossed test pieces (R=3mm or R=20mm), and a coating layer was formed on the surface of the Ag layer of each test piece. Specifically, the organic compounds shown in Tables 1 and 2 were dissolved in water to a concentration of 150 ppm, and phosphoric acid was added to adjust the pH to 5 to prepare the raw material solution. Each test piece prepared as described above was immersed in this raw material solution for 30 seconds. After that, the surface of the sample was cleaned in a water washing process, and the surface was dried to obtain the test sample. Separately, test pieces of the same shape were also prepared for metal materials without a coating layer.

[0052] <Evaluation Method> The adhesion resistance of each test sample obtained above was evaluated. For the evaluation, an embossed test piece was brought into contact with the surface of a flat test piece, so that the Ag layer of the flat test piece and the Ag layer of the embossed test piece were in contact at the top of the embossing, via the coating layer covering each surface. In this state, surface pressure was applied from the embossed test piece toward the flat test piece. At this time, the test pieces were exchanged and two different surface pressures, high and low, were applied. For the high surface pressure, an emboss with R=3 mm was used and a surface pressure of 220 MPa was applied, and for the low surface pressure, an emboss with R=20 mm was used and a surface pressure of 60 MPa was applied.

[0053] Each set of test specimens was left at room temperature for 2000 hours with the surface pressure applied as described above. Subsequently, the adhesion state at the contact points between the test specimens was evaluated by energy-dispersive X-ray analysis (SEM / EDX) using a scanning electron microscope. If almost no adhesion marks were observed, it was evaluated as "A+", indicating very high adhesion resistance. If adhesion marks were observed and some Ag peeling was observed, but the underlying Ni layer was not exposed, it was evaluated as "A", indicating high adhesion resistance. On the other hand, if the underlying Ni layer was exposed, it was evaluated as "B", indicating low adhesion resistance. Samples evaluated as having low adhesion resistance (B) were considered unsuitable for practical use.

[0054] Furthermore, a newly prepared set of test specimens was subjected to the same surface pressure as described above and left at a high temperature of 140°C for 500 hours. Subsequently, the adhesion state of the contact areas between the test specimens was evaluated using the same evaluation method and criteria as described above to assess high-temperature adhesion resistance. In addition, for samples with a coating layer formed using some organic compounds, and for samples without a coating layer, the time until adhesion occurred and the underlying Ni layer was exposed under high surface pressure was measured and recorded.

[0055] <Evaluation Results> Tables 1 and 2 below show the evaluation results of adhesion resistance at room temperature and high-temperature adhesion resistance when large and small surface pressures are applied to samples A1-A16 and B1-B16, which have coating layers formed on the surfaces of hard Ag layers and soft Ag layers using various organic compounds, respectively, as well as sample B17, which has a hard Ag layer without a coating layer.

[0056] [Table 1]

[0057] [Table 2]

[0058] According to Tables 1 and 2, in sample B17, which did not have a coating layer formed on the surface of the Ag layer, exposure of the Ni underlayer was observed even at room temperature when high surface pressure was applied (adhesion resistance: B). In other words, even when the Ag layer is composed of hard Ag, if high surface pressure is applied and the Ag layers come into direct contact with each other, Ag adhesion will occur. In samples B1 to B16, which had a coating layer formed on the surface of the soft Ag layer, high adhesion resistance (A) was obtained at room temperature, or at least when low surface pressure was applied. However, in all cases where a compound was used to form the coating layer, the high-temperature adhesion resistance was low (B). In other words, by providing a coating layer composed of an organic compound having a mercapto group on the surface of the Ag layer, Ag adhesion can be suppressed at room temperature even when the Ag layer is composed of soft Ag which is relatively prone to adhesion, but Ag adhesion cannot be sufficiently suppressed at high temperatures.

[0059] On the other hand, in samples A1 to A16, where a coating layer was formed on the surface of the hard Ag layer, very high adhesion resistance was obtained at room temperature in all samples, regardless of surface pressure (A+). In other words, by providing a coating layer composed of an organic compound having a mercapto group on the surface of the hard Ag layer, Ag adhesion is less likely to occur than when a similar coating layer is provided on the surface of the soft Ag layer. Furthermore, high-temperature adhesion resistance was also high in all samples A1 to A16 (A or A+). Compared to samples B1 to B16, where the high-temperature adhesion resistance was low in all samples, where a coating layer was provided on the surface of the soft Ag layer (B), high-temperature adhesion resistance was significantly improved. In other words, by providing a coating layer on the surface of the hard Ag layer, Ag adhesion is less likely to occur compared to when a coating layer is provided on the surface of the soft Ag layer, and Ag adhesion in high-temperature environments is particularly effectively suppressed.

[0060] When comparing the high-temperature adhesion resistance of samples A1 to A16, which consist of different compound species constituting the coating layer, samples A1 to A5, which use compounds without aromatic rings, were evaluated as high (A) at all surface pressures. In contrast, samples A6 to A9, which use compounds with aromatic rings that are not heteroatoms, were evaluated as very high (A+) at low surface pressures. Furthermore, samples A10 to A16, which use compounds with heteroatoms, were evaluated as very high (A+) even at high surface pressures. From this, it can be seen that forming the coating layer using organic compounds with aromatic rings, as in samples A6 to A16, is more effective in suppressing Ag layer adhesion at high temperatures than using organic compounds without aromatic rings, as in samples A1 to A5. In particular, when using organic compounds with heteroatoms containing heteroatoms, as in samples A10 to A16, the effect of suppressing Ag layer adhesion at high temperatures is especially high.

[0061] Next, Table 3 below shows the time until exposure of the Ni underlayment occurs under high surface pressure conditions in a high-temperature environment, for cases where no coating layer is formed on the surface of the hard Ag layer and the soft Ag layer, and for cases where a coating layer formed from some organic compounds is provided. Except for sample B18, each sample listed in Table 3 corresponds to the sample with the same number listed in Tables 1 and 2.

[0062] [Table 3]

[0063] According to Table 3, regardless of whether the Ag layer is hard Ag or soft Ag, or which organic compound is used, the time until the Ni substrate is exposed is longer when a coating layer is applied compared to when no coating layer is applied. In other words, the formation of the coating layer makes it more difficult for Ag to adhere. When comparing samples with a coating layer applied to a hard Ag layer and samples with a coating layer applied to a soft Ag layer, using the same organic molecule to form the coating layer, the time until the Ni substrate is exposed is significantly longer when a coating layer is applied to a hard Ag layer, indicating that Ag adhesion is less likely to progress. This corresponds to the adhesion resistance evaluation results shown in Tables 1 and 2 above. Furthermore, the time until the Ni substrate is exposed, which is more than 1000 hours when a coating layer is applied to the surface of a hard Ag layer, is sufficiently long considering the adhesion suppression effect required at connection terminals.

[0064] Furthermore, we compared how much the time until the Ni substrate is exposed is extended by providing a coating layer, comparing the case of a hard Ag layer and a soft Ag layer. In the case of a soft Ag layer, the time until the Ni substrate is exposed is only increased by a factor of 10 due to the formation of the coating layer, whereas in the case of a hard Ag layer, the time until the Ni substrate is exposed is increased by more than 40 times due to the formation of the coating layer. In other words, whether the Ag layer is composed of soft Ag or hard Ag, providing a coating layer on the surface has the effect of suppressing Ag adhesion, but it can be seen that the adhesion suppression effect due to the formation of the coating layer is relatively greater in the case of a hard Ag layer. From this, as seen in the comparison between samples A1-A16 and samples B1-B16 in Tables 1 and 2, the phenomenon in which the adhesion resistance and high-temperature adhesion resistance of the coated samples are higher when the Ag layer is hard Ag than when the Ag layer is soft Ag can be said to be due not only to the difference in the hardness of the Ag layer itself, but also to the difference in the magnitude of the effect that the formation of the coating layer has on improving adhesion. In other words, by making the Ag layer coated by the coating layer a hard Ag layer, a very high effect in suppressing Ag adhesion can be obtained due to the high hardness of the Ag layer itself, as well as the magnitude of the effect brought about by the formation of the coating layer.

[0065] Although embodiments of the present disclosure have been described in detail above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. [Explanation of Symbols]

[0066] 1. Materials for electrical connection components (connection materials) 10 Metal materials 11 Base material 12 Base layer 13 Ag layer 2 Covering layer 20 Female connector terminals 21 Elastic contact piece 21a Embossed area 22 Internal opposing contact surfaces 23 Clamping section 30 Male connector terminals

Claims

1. An electrical connection member configured as a connection terminal having a contact portion that electrically contacts the contact portion of a mating conductive member, The electrical connection member and the mating conductive member are, A metal material having an Ag layer exposed on its outermost surface, The material for an electrical connection member comprises a coating layer that covers the surface of the metal material, The coating layer is formed by bringing an organic compound having a mercapto group and an aromatic ring into contact with the surface of the metal material. An electrical connection member wherein the coating layer is formed on the surface of the metal material at least at the contact portion of the electrical connection member and the contact portion of the mating conductive member. However, this excludes cases where the surface hardness of the Ag layer is 90 HV or higher.

2. The electrical connecting member according to claim 1, wherein the aromatic ring is a heterocycle containing at least one of a sulfur atom and a nitrogen atom in addition to a carbon atom.

3. The electrical connection member according to claim 2, wherein the aromatic ring contains at least a sulfur atom.

4. The electrical connection member according to any one of claims 1 to 3, wherein the surface hardness of the Ag layer is 60 HV or less.

5. The electrical connection member according to any one of claims 1 to 4, wherein the surface pressure applied to the contact portion of the electrical connection member is less than or equal to the surface pressure of 60 MPa applied to the surface of a flat plate-shaped test piece formed from the electrical connection member using an embossed surface with R=20 mm formed from the electrical connection member.

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