JP5419737B2 - Tin-plated copper alloy sheet for mating type terminal and method for manufacturing the same - Google Patents

Description

  The present invention relates to a tin-plated copper alloy sheet suitable for fitting type connection terminals with a low friction coefficient, and a method for producing the same.

Conventionally, as a fitting type terminal for in-vehicle use or the like that obtains electrical contact by fitting a male terminal and a female terminal, a copper alloy plate material with tin plating is punched and formed into a terminal, which is generally used. Yes.
When fitting male and female terminals with a mating terminal formed from a tin-plated copper alloy plate, tin adheres to each other and the resistance to shearing is very high. Insertion force increases. Moreover, when the fitted contact portion is displaced due to thermal expansion and vibration, tin on the surface is scraped, oxidized wear powder accumulates on the contact portion, and a fine sliding wear phenomenon occurs in which the contact resistance value increases. In recent years, there has been a strong demand for reducing the insertion force and the fine sliding wear phenomenon, particularly for in-vehicle fitting type terminals.

In Patent Document 1, after Cu plating and Sn plating are performed on the surface of a copper alloy plate material, a reflow treatment is performed to form a Cu-Sn alloy layer from Cu plating and Sn plating, and a Cu-Sn alloy coating layer and It describes that a surface plating layer comprising a Sn coating layer is formed.
In Patent Documents 2 to 4, Ni plating, Cu plating, and Sn plating are performed on the surface of a copper alloy sheet, and then reflow treatment is performed to form a Cu-Sn alloy layer from Cu plating and Sn plating. Forming a surface plating layer comprising a layer, a Cu—Sn alloy coating layer, and a Sn coating layer, among which, Patent Documents 3 and 4 describe a Cu coating between a Ni coating layer and a Cu—Sn alloy coating layer. It is also described that a surface plating layer consisting of four layers is formed by leaving the layer.
However, in order to further reduce the insertion force of the mating type terminal in these technologies, it is necessary to make the outermost Sn coating layer thin so as to reduce the adhesion between tins as much as possible. It is difficult to achieve both reductions. In Patent Documents 1 to 4, an increase in contact resistance due to the fine sliding wear phenomenon is not considered.

In Patent Documents 5 to 7, as in Patent Documents 1 to 4, after performing Cu plating and Sn plating on the surface of the copper alloy plate material, or after performing Ni plating, Cu plating and Sn plating, reflow treatment is performed. Then, a surface plating layer composed of a Cu-Sn alloy coating layer and a Sn coating layer or a surface plating layer composed of a Ni coating layer, a Cu-Sn alloy coating layer and a Sn coating layer is formed. Using a roughened copper alloy sheet, the Cu-Sn alloy coating layer is partially exposed (at the peak of the roughness curve) on the surface, or the thickness of the Sn coating layer is made extremely thin. A tin-plated copper alloy sheet material capable of reducing the insertion force of the fitting type terminal has been proposed. In Patent Documents 5 to 7, in the case of a surface plating layer comprising a Cu—Sn alloy coating layer and a Sn coating layer, a Ni coating layer and a Cu—Sn alloy coating are provided between the copper alloy plate material and the Cu—Sn alloy layer. In the case of a surface plating layer comprising a layer and a Sn coating layer, it is described that the Cu coating layer may be left between the Ni coating layer and the Cu—Sn alloy coating layer. Patent Documents 5 and 6 also describe that a low contact resistance can be maintained by suppressing the fine sliding wear phenomenon.
According to the techniques of Patent Documents 5 to 7, it is possible to achieve both reduction of the insertion force of the fitting type terminal and reduction of the temporal change of the contact resistance, but the low insertion force effect is small for a terminal having a large contact pressure. Become.

  On the other hand, a tin-plated copper alloy sheet that can reduce the insertion force of the mating type terminal and change the contact resistance with time by forming an Sn plating layer in which carbon particles are dispersed on the surface of the copper alloy sheet is proposed. (See Patent Document 8). However, in order to produce this plate material, a special Sn plating bath in which graphite particles are dispersed is necessary, and it is difficult to manage the bath to form a Sn plating layer in which graphite particles are uniformly dispersed in a predetermined amount. This leads to cost increase. In addition, the carbon particles are present in the Sn plating layer, and only a part of the carbon particles exposed on the surface is insufficient as an effect of reducing the insertion force.

  Also, tin or tin for multipolar terminals with a reduced friction coefficient by adjusting the brightener concentration in the tin plating bath and forming a Sn or Sn alloy plating layer containing C on the surface of the copper alloy sheet. An alloy-plated copper alloy sheet has been proposed (see Patent Document 9). However, even with this plate material, the effect of reducing the insertion force is insufficient, and there is a concern that a short circuit due to whiskers occurs because no reflow treatment is performed.

Japanese Patent Laid-Open No. 10-60666 JP 2004-68026 A JP 2002-226882 A JP-A-11-135226 JP 2007-258156 A JP 2006-183068 A JP 2006-77307 A JP 2006-97062 A Japanese Patent No. 2971035

  The present invention not only reduces the friction coefficient and insertion force when fitting the terminals used in the connector regardless of the contact pressure, but also has high electrical reliability (less change in contact resistance over time) It aims at providing the copper alloy board | plate material with a tin plating for fitting type terminals.

The copper or copper alloy sheet with tin plating for mating type terminals according to the present invention has a surface plating layer composed of a Ni coating layer, a Cu-Sn alloy coating layer and a Sn coating layer in this order on the surface of the copper or copper alloy sheet. The Ni coating layer is formed with an average thickness of 0.1 to 1.0 μm, the Cu—Sn alloy coating layer has a surface exposed area ratio of 10 to 75%, and an average thickness of 0.1 to 1.0 μm. The Sn coating layer has been reflowed and has an average thickness of 0.2 to 1.5 μm. The graphite particles are dispersed and adhered to the surface of the surface plating layer, and the graphite particles are attached to the surface plating layer. covered the surface with an area ratio of 30% or less, and the average particle size of the inner diameter 2μm or more of the graphite particles of the graphite particles in 3 to 30 .mu.m, it covered the surface plating layer surface area ratio of 3% or more, grain split of the number of out particle size 10μm or more particles of diameter 2μm or more graphite particles Wherein the but 3% or more. The region where the surface plating layer is formed may extend over one side or both sides of the plate material, or may occupy only part of one side or both sides.

In the tin-plated copper or copper alloy sheet, a Cu coating layer having an average thickness of 0.5 μm or less may be further formed between the Ni coating layer and the Cu—Sn alloy coating layer.
Moreover, it is desirable that the surface of the copper or copper alloy sheet (plating base material) has an arithmetic average roughness Ra in a direction in which the surface roughness appears to be the largest, in a range of 0.15 to 1.0 μm.
In the present invention, the Ni coating layer, the Cu coating layer, and the Sn coating layer include Ni alloy, Cu alloy, and Sn alloy in addition to Ni, Cu, and Sn metal, respectively.

The tin-plated copper or copper alloy plate material for fitting type terminals is formed by forming a Ni plating layer, a Cu plating layer, and a Sn plating layer in this order on the surface of the copper or copper alloy plate material, and graphite particles on the surface of the Sn plating layer. And then reflow treatment. The Cu—Sn alloy coating layer is formed by mutual diffusion of Cu and Sn in the Cu plating layer and the Sn plating layer by reflow treatment. In this case, all of the initial Cu plating layer disappears. May remain (in this case, the Cu coating layer is formed).
In the present invention, the Ni plating layer, the Cu plating layer, and the Sn plating layer include Ni alloy, Cu alloy, and Sn alloy in addition to Ni, Cu, and Sn metal, respectively.
In the present specification, each layer constituting the surface plating layer after the reflow treatment is expressed as “coating layer”, and each layer constituting the surface plating layer before the reflow treatment is expressed as “plating layer”.

The tin-plated copper or copper alloy sheet material according to the present invention is a general tin-plated copper or copper with which the Sn layer covers the entire surface by exposing the Cu-Sn alloy coating layer to the surface at a predetermined ratio. Compared to an alloy plate material, the friction coefficient can be reduced, the insertion force can be reduced, and a decrease in electrical reliability due to a fine sliding wear phenomenon can be prevented mainly at a low contact pressure (Patent Documents 5 to 7). reference).
According to the present invention, the coefficient of friction of such tin-plated copper or copper alloy sheet is further greatly reduced, and the insertion force of the mating type terminal, which becomes a problem particularly when the contact pressure is increased, is greatly reduced. be able to. More specifically, in small terminals with many poles, even if the contact pressure is increased to improve the electrical reliability of the contacts, the friction coefficient can be reduced and the insertion force can be reduced. Even in a terminal having a small number of poles, the insertion force can be reduced even if the contact pressure is high. Moreover, it can be realized by a simple and inexpensive means of attaching graphite particles to the surface plating layer.
In addition, in the copper or copper alloy sheet with tin plating according to the present invention, the electrical reliability of the copper alloy sheet with tin plating is not lowered by the graphite particles attached to the surface of the Sn coating layer.

It is a stereomicroscope structure | tissue photograph of the surface of the copper alloy sheet | seat with a tin plating which made the reflow process after making a graphite particle adhere. It is the structure photograph which compares the surface of the tin-plated copper alloy sheet material (top) to which graphite particles were adhered after reflow treatment and the surface of the tin-plated copper alloy sheet material (bottom) to which graphite particles were adhered and reflow-treated is there. A stereomicrograph showing a comparison of the surface of a tin-plated copper alloy sheet (upper) with graphite particles adhered after reflow treatment and a tin-plated copper alloy sheet (lower) with graphite particles deposited and reflowed is there.

Hereinafter, the tin-plated copper alloy sheet according to the present invention and the manufacturing method thereof will be described more specifically. In addition, about copper or a copper alloy board | plate material (plating base material) and a surface plating layer (Ni coating layer, Cu-Sn alloy coating layer, Sn coating layer, Cu coating layer), itself is a well-known technique (especially patent document 5). To 7).
(Copper or copper alloy sheet)
The copper or copper alloy plate material (plating base material) may have any composition and characteristics as long as it can be used after being molded into a terminal. For example, brass, phosphor bronze, Cu—Ni—Si alloy, Cu—Fe—P alloy, Cu—Ni—Sn—P alloy, or the like can be used. The plate thickness may be determined in accordance with the use of the terminal, the conductivity of the plate material, the mechanical properties, etc., but about 0.1 to 2.0 mm is generally appropriate.

(Ni coating layer)
Of the surface plating layers, the Ni coating layer is formed as an intermediate layer between the copper or copper alloy plate material that is the plating base and the Cu-Sn alloy coating layer, and is applied to the Cu-Sn alloy coating layer and the Sn coating layer. It is applied to prevent the diffusion of Cu from the copper or copper alloy sheet. Further, the Ni coating layer also has an effect of suppressing solder wettability deterioration due to diffusion of alloy elements in the copper alloy sheet. Regarding the difference in the diffusion prevention effect between the Cu—Sn alloy coating layer and the Ni coating layer, the Ni coating layer exhibits the diffusion prevention effect even when a higher temperature environment is assumed compared to the Cu—Sn alloy coating layer. When the average thickness of the Ni coating layer is less than 0.1 μm, the diffusion preventing effect is insufficient, Cu diffuses to the surface of the Sn coating layer to form an oxide, and the contact resistance increases with discoloration. The reliability of the machine is reduced. On the other hand, if it exceeds 1.0 μm, the formability to the terminal is deteriorated, for example, cracking occurs in bending. Therefore, the average thickness of the Ni coating layer is 0.1 to 1.0 μm. Preferably it is 0.1-0.5 micrometer. The Ni coating layer contains not only pure Ni but also a Ni alloy containing about 1 to 10% by mass of one or more elements selected from the group of Cu, Ag, Sn, Co, P, B and the like.

(Cu-Sn alloy coating layer)
Of the surface plating layer, the Cu—Sn alloy coating layer prevents the diffusion of Ni into the Sn coating layer. When the average thickness of the Cu—Sn alloy coating layer is less than 0.1 μm, the diffusion preventing effect is insufficient, Cu diffuses to the surface layer of the Sn coating layer to form an oxide, and the contact resistance increases with discoloration. Reliability decreases. On the other hand, when the average thickness exceeds 1.0 μm, the formability to the terminal is deteriorated, for example, cracking occurs in bending. Therefore, the average thickness of the Cu—Sn alloy coating layer is 0.1 to 1.0 μm. Preferably it is 0.1-0.5 micrometer.

The Cu—Sn alloy coating layer is made of an intermetallic compound mainly composed of a Cu ₆ Sn ₅ phase having a Cu content of 20 to 70 at%. Preferably it is 45-65 at%. The Cu ₆ Sn ₅ phase is very hard compared to Sn or Sn alloy, and if it is formed on the surface of the material, it can reduce the shear resistance due to the adhesion that occurs between the Sn coating layers during terminal fitting. The coefficient of friction can be lowered. On the other hand, the Cu ₃ Sn phase is harder than the Cu ₆ Sn ₅ phase, but due to the high Cu content, if it is formed on the material surface, the Cu on the material surface diffuses to the Sn coating layer surface due to heat aging or corrosion. In addition, the amount of Cu oxide on the surface increases, increasing the contact resistance and making it difficult to maintain electrical reliability. However, a part of Cu ₃ Sn phase may be included in the Cu—Sn alloy coating layer. Moreover, the component element in Sn coating layer may be contained.
This Cu—Sn alloy coating layer is generally formed by interdiffusion of Cu and Sn in the Cu plating layer and the Sn plating layer by a reflow process.

  The Cu—Sn alloy coating layer is partially exposed on the outermost surface of the surface plating layer. The surface exposed area ratio is calculated as a value obtained by multiplying the surface area of the Cu—Sn alloy coating layer exposed per unit surface area of the material by 100. When the surface exposed area ratio of the Cu—Sn alloy coating layer is less than 10%, the rate of contact of the counterpart tin plating material with the Cu—Sn alloy coating layer is small, and there is much contact between Sn, so that Sn adhesion There is almost no effect of reducing, and a low friction coefficient cannot be obtained. Further, when the material surface exposure rate of the Cu—Sn alloy coating layer exceeds 75%, the proportion of Sn exhibiting the anticorrosion effect in the corrosive environment is small and deterioration due to corrosion occurs early, so that the contact resistance value is increased. For example, it is difficult to maintain electrical reliability. Therefore, the material surface exposed area ratio of the Cu—Sn alloy coating layer is set to 10 to 75%. Desirably, it is 20 to 50%.

(Sn coating layer)
Of the surface plating layer, the Sn coating layer is applied to ensure corrosion resistance and reliability as an electrical contact. When the average thickness of the Sn coating layer is less than 0.2 μm, the corrosion resistance and the reliability as an electrical contact are insufficient. On the other hand, when the thickness exceeds 1.5 μm, the Cu—Sn alloy coating layer is hardly exposed on the surface, and the effect of reducing the insertion force cannot be expected. Therefore, the average thickness of the Sn coating layer is set to 0.2 to 1.5 μm. Preferably it is 0.4-1.2 micrometers. The Sn coating layer includes not only pure Sn but also an Sn alloy containing about 1 to 10% by mass of one or more elements selected from the group of Cu, Ag, Ni, Co, Bi, P, Zn and the like. This Sn coating layer is surface plated even after the formation of the Cu-Sn alloy coating layer when the Cu-Sn alloy coating layer is formed by mutual diffusion of Cu and Sn in the Cu plating layer and the Sn plating layer by reflow treatment. It is the layer that remains as the top layer of the layer.

(Cu coating layer)
When the Cu-Sn alloy is formed from Cu of the Cu plating layer and Sn of the Sn plating layer by the reflow process, the Cu coating layer is formed when the Cu plating layer does not completely disappear and a part remains. . The remaining Cu coating layer has a role of an anti-diffusion layer of alloy elements in the copper alloy plate which is the plating base and Ni in the Ni coating layer due to the presence of an average thickness of 0.1 μm or more. The average thickness is limited to 0.5 μm or less because there is a possibility that the corrosion resistance is reduced and the plating is peeled off due to diffusion. Preferably it is 0.1-0.3 micrometer. The Cu coating layer may contain not only pure Cu but also other elements such as Sn and Zn. In the case of Sn, it is desirable that it is 50 mass% or less, and about 5 mass% or less about another element. Moreover, the component contained in a copper alloy board | plate material may be contained in a small amount.

(Graphite particles)
Graphite particles adhering to and dispersing on the surface of the Sn coating layer have a very low shearing force and lubricity, so that the friction coefficient at the sliding part of the mating type terminal is reduced, thereby inserting the graphite particles. The power can be greatly reduced. In addition to reducing the insertion force due to the Cu—Sn alloy coating layer being exposed on the surface, it is possible to further reduce the insertion force.
Graphite particles having a small diameter (particle diameter of less than 2 μm) are less effective for reducing the friction coefficient. For graphite particles having a particle size of 2 μm or more with a large lubricating effect, if the average particle size is less than 3 μm, there is a high probability that the particles will not be caught in the contact surface during sliding, and even if they are caught, the graphite particles are small. Therefore, even if cleavage occurs, the lubricating effect is small. On the other hand, when the average particle size exceeds 30 μm, large graphite is bitten and cleaved during sliding, so that a sufficient lubricating effect is obtained, but conversely, it is difficult to secure a contact area at the contact point between tins, Electrical reliability may be impaired.

The area ratio of the graphite particles covering the surface plating layer surface means the area ratio of the graphite particles occupying the surface plating layer surface. If this exceeds 30%, it becomes difficult to ensure the contact area at the contact point between the tins. Reliability may be compromised. On the other hand, if the area ratio of graphite particles having a large particle size of 2 μm or more among the graphite particles is less than 3%, a sufficient lubricating effect cannot be obtained at the sliding portion of the fitting type terminal.
Further, if the ratio of the number of particles having a particle size of 10 μm or more among the graphite particles having a particle size of 2 μm or more is less than 3%, the graphite particles necessary for reducing the insertion force do not bite into the sliding portion of the fitting type terminal, A sufficient lubricating effect cannot be obtained.

Therefore, in the present invention, the graphite particles cover the surface plating layer surface with an area ratio of 30% or less, and among the graphite particles, the average particle size of graphite particles having a particle size of 2 μm or more is 3 to 30 μm, and the surface plating layer surface Is covered with an area ratio of 3% or more (30% or less), of which the ratio of the number of particles having a particle diameter of 10 μm or more is 3% or more. Preferably, for graphite particles having a particle size of 2 μm or more, the average particle size is 5 to 25 μm, the area ratio is 5 to 28%, the ratio of the number of particles having a particle size of 10 μm or more is 5 to 60%, more preferably the average particle size Is 10 to 15 μm, the area ratio is 10 to 20%, and the ratio of the number of particles having a particle diameter of 10 μm or more is 20 to 40%. FIG. 1 shows a stereoscopic microscope photograph of the surface plating layer surface to which the graphite particles are attached.
Regarding the shape and properties of the graphite particles to be used, the shape is preferably a flake shape, a flake shape, a soil shape, or a lump shape, and preferably has a high purity and few impurities.

(Characteristic)
In the present invention, the Cu—Sn alloy coating layer is exposed at a predetermined ratio on the outermost surface of the surface plating layer, thereby reducing the amount of Sn adhesion during terminal fitting, and simultaneously exposing the surface Sn coating layer and the surface plating layer. By dispersing and adhering the graphite particles on the Cu—Sn alloy coating layer, the amount of adhesion between Sn at the time of terminal fitting can be further reduced, and the friction coefficient can be greatly reduced. Further, in the contact portion, connection reliability can be ensured in the mixed contact with the graphite particles and Sn having conductivity.
Thereby, as shown in the Examples, the copper or copper alloy sheet for fitting type terminals according to the present invention has a dynamic friction coefficient of less than 0.27 (load: 5 N), a contact resistance value of 1.0 mΩ or less, and excellent bendability. Can be realized. Even if the contact pressure is set high, there is no significant increase in insertion force.

(Production method)
The copper or copper alloy plate material for fitting type terminals is formed with a Ni plating layer, a Cu plating layer, and a Sn plating layer in this order on a copper or copper alloy plate which is a plating base, and on the surface of the Sn plating layer. It can be manufactured by attaching flake graphite and then performing a reflow treatment.

To attach graphite particles to the surface of a tin-plated copper or copper alloy sheet (before reflow treatment), after Sn plating, the graphite particles are blown onto the surface (one or both sides) of the sheet by air or the like. Spraying turbid alcohol, passing a plate material through a container filled with graphite particles, or dropping graphite particles on the surface while passing the plate material, then air blowing to remove excess graphite particles, etc. A method is possible.
Even if the graphite particles adhere non-uniformly (partially in an aggregated state) to the Sn plating layer surface, the Sn plating layer can be melted by reflowing the Sn plating layer. And uniformly adhered to the surface of the Sn coating layer and the exposed Cu-Sn alloy coating layer. The graphite particles simply physically attached to the surface plating layer (Sn coating layer and exposed Cu-Sn alloy coating layer) surface are weakly bonded and easily detached by degreasing and wiping. By manufacturing with, the adhesion to the surface plating layer surface becomes strong, the desorption due to the degreasing process and wiping can be minimized, and the low friction effect can be maintained. Therefore, it is desirable to adhere the graphite particles before the reflow treatment, rather than the graphite particles after the reflow treatment.

  A tin-plated copper or copper alloy plate material with graphite particles attached to the surface of the surface plating layer after the reflow treatment, and a tin-plated copper or copper alloy plate material with graphite particles attached to the surface of the surface plating layer and then reflow treatment; Are clearly distinguishable. When visually observed, the former (the upper part of FIG. 2) covers the surface of the surface plating layer with black graphite particles, and the mirror gloss is not seen, whereas the latter (the lower part of FIG. 2) has a certain mirror surface. The appearance is almost the same as a general reflow tin plating in the state that it has a gloss and has a thin graphite film on its surface. Further, from a stereoscopic micrograph, the former (the upper part in FIG. 3) is in a state where some of the graphite particles are aggregated, while the latter (the lower part in FIG. 3) is in a substantially uniformly dispersed state. Further, for example, when acetone ultrasonic degreasing and wiping are performed, the former has many graphite particles to be detached, but the latter is small and the difference is remarkable.

In the above manufacturing method, it is desirable that the Ni plating layer, the Cu plating layer, and the Sn plating layer formed on the copper or copper alloy plate as the plating base material are all formed by electroplating. Although there is a method of performing electroless plating, the reducing agent is taken into the plating film, and voids are generated after being left at a high temperature. In addition, when the Ni plating layer, the Cu plating layer, and the Sn plating layer are respectively made of a Ni alloy, a Cu alloy, and a Sn alloy, it is possible to use the respective alloys described above regarding the Ni coating layer, the Cu coating layer, and the Sn coating layer. it can.
As a desirable condition for electroplating, a watt bath or a sulfamic acid bath is used as a plating bath for Ni plating. The plating conditions are a temperature of 45 ° C. to 60 ° C. and a current density of 3 to 20 A / dm ² . What is important in the Ni plating is the current density. If it is less than 3 A / dm ² , the throwing power is poor, and if it exceeds 20 A / dm ² , the Ni plating grains become rough.

As a plating bath for Cu plating, a cyan bath is usually used, but a sulfuric acid bath is desirable because there is a problem of liquid deterioration and wastewater treatment due to cyan mixing in the Sn plating solution. The plating conditions are a temperature of 30 ° C. to 40 ° C. and a current density of 2.5 to 10 A / dm ² . When the temperature exceeds 40 ° C., Cu plating grains are rough, and a Cu plating layer having a uniform thickness cannot be formed. On the other hand, when the temperature is less than 30 ° C., the Cu plating grains are not roughened, but the throwing power is deteriorated.
A sulfuric acid bath is used as a plating bath for Sn plating. The plating conditions are a temperature of 25 ° C. or less and a current density of ² to 10 A / dm ² .

  The reflow treatment is preferably a heat treatment in which heating is performed at a temperature of 230 ° C. to 600 ° C. for 5 to 30 seconds. By performing this reflow treatment, Cu and Sn are mutually diffused from the Cu plating layer and the Sn plating layer to form a Cu—Sn alloy coating layer, the residual stress of plating is relaxed, and whiskers are not generated. When the heating temperature is less than 230 ° C., Sn does not melt, and when it exceeds 600 ° C., the copper or copper alloy plate that is the plating base material is softened, distortion occurs, and a Cu—Sn alloy coating layer having a high Cu content is formed. As a result, the contact resistance value increases. Further, the adhered graphite particles start to oxidize, and the lubricating effect cannot be obtained. If the heating time is less than 5 seconds, heat transfer is uneven, and a Cu—Sn alloy coating layer with a required thickness cannot be formed. If it exceeds 30 seconds, oxidation of the Sn plating layer on the surface proceeds and the contact resistance value increases. To do. When the Cu plating layer is not completely disappeared by the reflow process and a part thereof remains, the average thickness of the remaining Cu plating layer is limited to 0.5 μm or less.

Although the explanation was later, in the present invention, in order to expose a part of the Cu-Sn alloy coating layer on the surface after the reflow treatment, the arithmetic average roughness Ra in the direction in which the surface roughness appears to be the largest is 0.15. It is desirable to use a copper or copper alloy sheet having a thickness of ˜1.0 μm. This surface roughness (uneven surface) can be formed by rolling or mechanical polishing. It is desirable to form the uneven surface uniformly so that there are no extremely large peaks and valleys.
The copper or copper alloy plate material that is the plating substrate has this surface roughness, so that the reflow treatment causes the molten surface convex portion Sn to flow into the surface concave portion, the surface of the Sn coating layer is smoothed, and reflow A part of the Cu—Sn alloy coating layer formed during the processing is exposed on the surface of the Sn coating layer. When the arithmetic average roughness Ra is 0.15 μm or more, the surface exposed area ratio of the Cu—Sn alloy coating layer is 10 to 75%, and at the same time, the average thickness of the Sn coating layer is 0.2 to 1. .5 μm. On the other hand, when the arithmetic average roughness Ra is 1.0 μm or less, the surface of the Sn coating layer can be smoothed by the flowing action of molten Sn. If the surface of the Sn coating layer is not smoothed, the bending workability deteriorates and the contact resistance increases.

  Up to now, regarding the method for producing a surface plating layer according to the present invention, a Ni plating layer, a Cu plating layer, and a Sn plating layer are formed in this order on a copper or copper alloy sheet, and a reflow treatment is performed. The method of forming a Cu—Sn alloy coating layer by interdiffusion of Cu and Sn from the above has been described. Alternatively, a Cu—Sn alloy plating layer is applied on the Ni plating layer, and the Sn plating layer is formed thereon. Can be obtained. Also in this case, it is desirable to adhere the flake graphite to the surface of the Sn plating layer, and subsequently to perform a reflow treatment of the Sn plating layer.

  A Cu—Ni—P-based copper alloy sheet having a thickness of 0.25 mm was subjected to a surface roughening treatment by a mechanical method (rolling or polishing) to finish a copper alloy sheet having a predetermined surface roughness. The copper alloy plate material was subjected to Ni plating (partially not performed), Cu plating, and Sn plating with a predetermined thickness to produce a copper alloy plate material with tin plating. The plating baths and plating conditions for Ni plating, Cu plating and Sn plating are shown in Tables 1 to 3, the surface roughness (arithmetic average roughness Ra) of each copper alloy sheet is shown in Table 4, and the average thickness of each plating layer is shown. Similarly, it is shown in the column of the initial surface plating layer in Table 4.

The surface roughness of the copper alloy sheet and the average thickness of each plating layer constituting the initial surface plating layer (before reflow treatment) were measured as follows.
[Surface roughness measurement]
It measured based on JISB0601-2001 using the contact-type surface roughness meter (Tokyo Seimitsu: Surfcom 1400). The measurement conditions for the surface roughness were a cutoff value of 0.8 mm, a reference length of 0.8 mm, an evaluation length of 4.0 mm, a measurement speed of 0.3 mm / s, and a stylus tip radius of 5? It was set as mR. The measurement direction of the surface roughness was a direction perpendicular to the rolling or polishing direction in which the surface roughening treatment was performed (the direction in which the surface roughness appears the largest).

[Measurement of thickness of Ni plating layer and Sn plating layer]
The average thickness was measured using a fluorescent X-ray film thickness meter (Seiko Instruments Inc .; model SFT3200). The measurement conditions were a single layer calibration curve of Sn / base material for the calibration curve, and a collimator meter of φ0.5 mm.
[Cu plating layer thickness measurement]
The cross section of the plate material processed by the microtome method was observed at a magnification of 1000 times using an SEM (scanning electron microscope), and the average thickness was calculated by image analysis processing.

  Subsequently, scaly graphite particles were adhered to the surface of the tin-plated copper alloy sheet (No. 23 to 25 were not adhered), and a reflow treatment was performed, which was used as a test material. The average thickness of each coating layer constituting the surface plating layer after the reflow treatment is shown in the column of the surface plating layer after reflowing in Table 5, the area ratio of the graphite particles adhering to the surface, the graphite particles having a particle size of 2 μm or more Table 5 shows the average particle diameter, and the ratio of the number of particles having a particle diameter of 10 μm or more. The area ratio of graphite particles having a particle diameter of less than 2 μm was 1% or less. Table 5 shows only the area ratio of graphite particles having a particle diameter of 2 μm or more.

The average thickness of each coating layer (after reflow treatment) was measured in the following manner, and the Cu content and the surface exposed area ratio in the Cu—Sn alloy coating layer were confirmed in the following manner. Further, the area ratio of the graphite particles, the average particle diameter of the graphite particles, and the ratio of the number of particles having a particle diameter of 10 μm or more were measured in the following manner.
[Sn coating layer thickness measurement]
The sum of the average thickness of the Sn coating layer and the average thickness of the Sn component contained in the Cu-Sn alloy coating layer was measured using a fluorescent X-ray film thickness meter (Seiko Instruments Inc .: SFT3200). Then, it immersed in the aqueous solution which uses p-nitrophenol and caustic soda as a component for 10 minutes, and removed Sn coating layer. Again, the average thickness of the Sn component contained in the Cu—Sn alloy coating layer was measured using a fluorescent X-ray film thickness meter (Seiko Instruments Inc .: SFT3200). The measurement conditions were a single-layer Sn / base metal calibration curve as the calibration curve, and a collimator diameter of 0.5 mm. The average thickness of the Sn component contained in the Cu-Sn alloy coating layer is subtracted from the sum of the average thickness of the obtained Sn coating layer and the average thickness of the Sn component contained in the Cu-Sn alloy coating layer. Thus, the average thickness of the Sn coating layer was calculated.

[Measurement of thickness of Cu-Sn alloy coating layer]
The thickness of the Cu—Sn alloy layer was measured using a fluorescent X-ray film thickness meter after immersing the test material in the above stripping solution and stripping the Sn layer.
[Cu coating layer thickness measurement]
The thickness of the Cu coating layer was calculated as an average thickness by SEM observation of the cross section of the plate material processed by the microtome method, and image analysis processing.
[Measurement of Ni coating layer thickness]
The thickness of the Ni coating layer was measured using a fluorescent X-ray film thickness meter.

[Measurement of Cu content (at%) in Cu-Sn alloy]
First, the outermost Sn layer is removed by immersing in a stripping solution containing p-nitrophenol and caustic soda as components for 10 minutes. Thereafter, the surface of the sample was subjected to argon etching to a depth of 300 mm in order to eliminate the influence of oxidation and contamination on the sample surface, and the Cu content in the Cu—Sn alloy layer was measured with ESCA-LAB210D (manufactured by VG). No. The Cu contents of 1 to 26 were all 55 at% (composition of Cu ₆ Sn ₅ ).

[Area ratio of graphite particles]
The surface of the test material to which the graphite particles are adhered is observed with a stereomicroscope to obtain a surface image (magnification × 500, area 500 μm × 670 μm). Based on the image, all the graphite particles having a particle size of 2 μm or more are obtained. Is calculated by image analysis software, and the sum of the areas is defined as the total area of graphite particles having a particle size of 2 μm or more in the image, and the value obtained by dividing this by the area of the entire image is calculated for the graphite particles having a particle size of 2 μm or more. The area ratio was used. An example of a stereoscopic microscope image is shown in FIG. On the other hand, the area ratio of the graphite particles having a particle diameter of less than 2 μm was obtained by obtaining a larger image (higher magnification) and using the same image analysis technique as described above. As a result, in this example, the area ratio of graphite particles having a particle diameter of less than 2 μm was extremely small, and both were calculated to be 1% or less. This result coincided with the result of visual judgment in advance using the 500 times image (determined to be 1% or less).

[Average particle size]
The particle diameter of graphite particles having a particle diameter of 2 μm or more was set to the equivalent circle diameter (the diameter of a circle having the same area as each particle). Based on the image, the particle size was obtained for all graphite particles having a particle size of 2 μm or more, and the average particle size was obtained by dividing the sum of the particle sizes by the number of all graphite particles having a particle size of 2 μm or more.
[Ratio of particle size of 10 μm or more]
Based on the image, the ratio of graphite particles having a particle size of 10 μm or more out of graphite particles having a particle size of 2 μm or more is divided by the total number of graphite particles having a particle size of 2 μm or more. Asked.

Subsequently, no. Using the test materials 1 to 26, the dynamic friction coefficient, contact resistance value, bending workability, and plating smoothness were evaluated in the following manner. The results are shown in Table 6.

[Measurement method of friction force and dynamic friction coefficient]
The maximum frictional force and the dynamic friction coefficient were used for evaluating the insertion force at the time of terminal fitting. Assuming the shape of the contact part of the mating type terminal, a female plate obtained by fixing a plate-shaped male test piece cut out from the test material to a horizontal base and processing the test material with an inner diameter of 1.5 mm thereon Place the test piece, bring the tin-plated surfaces into contact with each other, apply a load W (3.0N, 5.0N) to the female test piece to hold the male test piece, and press the horizontal load measuring machine (Model- made by Aiko Engineering Co., Ltd.). 2152), the male test piece was pulled in the horizontal direction (sliding speed 80 mm / min), and the maximum frictional force F up to a sliding distance of 5 mm was measured. The coefficient of friction μ was determined by the following formula (1). The test material was applied to a male test piece, and the female test piece was a copper alloy material with tin plating to which graphite was not attached (Cu-Sn alloy coating layer having an average thickness of 0.5 μm as a surface plating layer and an average thickness of 0). Having a Sn coating layer of 5 μm).
The maximum frictional force at each load W was taken as the frictional force at each load, and the value calculated using the following equation (1) was taken as the friction coefficient at each load.
Friction coefficient = F / W (1)
Standard tin-plated copper alloy material (conventional example) No. Based on the friction force and coefficient of friction at 23N of 3N and 5N, those having a friction force and coefficient of friction of less than 50% were evaluated as acceptable.

[Measurement of contact resistance after standing at high temperature]
As an evaluation of the reliability of the electrical contact during heating, the contact resistance value after leaving at high temperature was used. After the heat treatment of 160 ° C. × 120 hr was performed on the test material in the air, the contact resistance was measured by a four-terminal method under the conditions of an open circuit voltage of 20 mV, a current of 10 mA, a load of 3 N, and sliding.
[Bending workability]
The test piece was cut out so that the rolling direction was long, and was bent with a load of 9.8 × 103 N so as to be perpendicular to the rolling direction using a W bending test jig defined in JISH3110. Then, the cross section was cut out and observed by the microtome method. For the evaluation of bending workability, the level at which the crack generated in the bent part after the test does not propagate to the copper alloy sheet is evaluated as ◯, and the level at which the crack propagates to the copper alloy base material and the crack occurs in the copper alloy sheet is evaluated as x. evaluated.

[Plating smoothness]
Arithmetic average waviness Wa is determined based on JIS B0601-2001 using a contact surface roughness meter (Tokyo Seimitsu: Surfcom 1400). Rated bad. Even in cross-sectional SEM observation, it was confirmed that the surface of the surface plating layer was not smooth when the arithmetic average waviness Wa exceeded 0.6 μm. The measurement direction of the waviness curve was a direction perpendicular to the rolling or polishing direction in which the surface roughening treatment was performed.

As shown in Table 6, No. 1 satisfying the provisions of the present invention relating to the structure of the surface plating layer after reflow and the distribution form of the graphite particles. 1 to 8 had a dynamic friction coefficient of less than 0.25 for both 3N and 5N loads, which was significantly lower (less than 50%) compared to the standard material (No. 23). In addition, the contact resistance after standing at high temperature is small (less than 1 mΩ), and it is excellent in bending workability and plating smoothness.
On the other hand, No. which does not satisfy any of the provisions of the present invention regarding the distribution form of graphite particles. Nos. 18 to 25 have a smaller decrease in the dynamic friction coefficient mainly at a high load (5N) or higher contact resistance after being left at a high temperature as compared with the standard material (No. 23). Moreover, No. which does not satisfy any of the provisions of the present invention relating to the configuration of the surface plating layer after reflow. Nos. 9 to 17 and 26 are inferior in any one or more characteristics of a dynamic friction coefficient, contact resistance after leaving at high temperature, bending workability and plating smoothness.

More specifically, no. No. 18 has a small average particle diameter of graphite particles of 2 μm or more, so that the lubrication effect is insufficient, and the dynamic friction coefficient is less decreased at high contact pressure (5N). Since No. 19 has a large average particle size, the contact resistance after leaving at high temperature is large. No. No. 20 has a low number ratio of graphite particles of 10 μm or more. Since No. 21 has a low area ratio of graphite particles of 2 μm or more, the lubrication effect is insufficient, and the dynamic friction coefficient is hardly lowered. No. Since No. 22 has a high area ratio of graphite particles of 2 μm or more, the contact resistance after standing at high temperature is large. No. In Nos. 23 to 25, graphite particles were not dispersed and adhered (prior art), and the dynamic friction coefficient was not improved. In particular, the structure of the surface plating layer satisfies No. 1 of the present invention. About 25, the dynamic friction coefficient in high contact pressure (5N) is high.
No. Nos. 9 and 26 have no exposure of the Cu—Sn alloy layer, so the dynamic friction coefficient does not decrease much at high contact pressure (5 N). No. 10 is inferior in contact resistance and bending workability after being left at high temperature due to poor surface smoothness. No. Since No. 11 has no Ni coating layer, the contact resistance after standing at high temperature is large. No. No. 12 has a thick Ni coating layer. No. 15 is inferior in bending workability because the Cu—Sn alloy coating layer is thick. No. No. 13 has a thick Cu coating layer. No. 14 has a thin Cu—Sn alloy coating layer. Since No. 16 has a high exposed area ratio of the Cu—Sn alloy coating layer, all have high contact resistance after being left at high temperature. No. In No. 17, the exposed area ratio of the Cu—Sn alloy coating layer is low, and the Sn coating layer is thick, so that there is little decrease in the dynamic friction coefficient at high contact pressure (5N).

Claims (6)

On the surface of the copper or copper alloy plate material, a Ni plating layer, a Cu-Sn alloy coating layer, and a surface plating layer comprising a Sn coating layer are formed in this order, and the Ni coating layer has an average thickness of 0.1 to 1.0 μm. The Cu—Sn alloy coating layer has a surface exposed area ratio of 10 to 75% and an average thickness of 0.1 to 1.0 μm. The Sn coating layer is reflow-treated and has an average thickness of 0.2. ˜1.5 μm, the graphite particles are dispersed and attached to the surface of the surface plating layer, the graphite particles cover the surface plating layer surface with an area ratio of 30% or less, and the particle size of the graphite particles The average particle diameter of graphite particles having a particle diameter of 2 μm or more is 3 to 30 μm , the surface plating layer surface is covered with an area ratio of 3% or more, and the ratio of the number of particles having a particle diameter of 10 μm or more among graphite particles having a particle diameter of 2 μm or more is 3% or more with tin plating for mating type terminals Copper or copper alloy sheet. The tin coating for fitting type terminals according to claim 1, wherein a Cu coating layer having an average thickness of 0.5 µm or less is further formed between the Ni coating layer and the Cu-Sn alloy coating layer. Copper or copper alloy sheet. 3. The fitting according to claim 1, wherein the surface of the copper or copper alloy sheet has an arithmetic average roughness Ra of 0.15 to 1.0 μm in a direction in which the surface roughness is maximized. Copper or copper alloy sheet with tin plating for mold terminals. Of the graphite particles, graphite particles having a particle diameter of 2 μm or more have an average particle diameter of 10 to 15 μm, the surface plating layer surface is covered with an area ratio of 10 to 20%, and among the graphite particles having a particle diameter of 2 μm or more, the particle diameter is 10 μm. The ratio of the number of the above-mentioned particle | grains is 20 to 40%, The copper or copper alloy board | plate material with a tin plating for fitting type terminals described in any one of Claims 1-3 characterized by the above-mentioned. The said Sn coating layer is a reflow-processed after graphite particle adhesion, The copper or copper alloy board | plate material with tin plating for fitting type terminals described in any one of Claims 1-4 characterized by the above-mentioned. After forming the Ni plating layer, the Cu plating layer, and the Sn plating layer in this order on the surface of the copper or copper alloy plate material, the graphite particles are adhered to the surface of the Sn plating layer, and then the reflow treatment of the Sn plating layer is performed. The manufacturing method of the copper or copper alloy board | plate material with a tin plating for fitting type terminals described in any one of Claims 1-4 characterized by the above-mentioned.