JP2023150441A - Connector terminal material - Google Patents

Abstract

To provide a connector terminal material in which the heat-resistant peel property of a connector terminal material having a copper-tin alloy layer and a tin layer is further improved.SOLUTION: Provided is a connector terminal material 1 in which a copper-tin alloy layer 3 and a tin layer 4 made of tin or a tin alloy are laminated in this order on a substrate 2 made of copper or a copper alloy, and in which, in EBSD measurement using the surface of the tin layer 4 as an observation surface, the length of a final solidification line per unit area is 50 mm/mm2 or less, the tin layer has an average thickness of 0.2 μm or more and 1.7 μm or less, and the average thickness of the copper-tin alloy layer may be 0.1 μm or more and 1.5 μm or less.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a connector terminal material provided with a useful film used for connecting electrical wiring in automobiles, consumer electronics, etc.

2. Description of the Related Art Conventionally, connectors used for connecting electrical wiring in automobiles and the like have been known. In this automotive connector (vehicle terminal), the contact part provided on the female terminal contacts the male terminal inserted into the female terminal with a predetermined contact pressure, so that an electrical connection is established. A device with a pair of terminals designed to For such connectors (terminals), copper (Cu) plating and tin (Sn) plating are performed on a base material made of copper or copper alloy, followed by reflow treatment, so that copper-tin is added to the lower layer of the surface tin layer. Terminal materials on which a (Cu--Sn) alloy layer is formed are widely used.

In recent years, for example, automobiles have been rapidly electrified and equipped with electric equipment, and with the increase in current and the high integration of electrical equipment, the terminal temperature has increased due to the heat generated by electricity and the lack of heat dissipation capacity when heat is generated, causing harsher conditions. There are concerns about the electrical connection reliability of plating films when used in high-temperature environments. Therefore, there is a method in which a nickel or nickel alloy layer is formed on a base material and a copper-tin alloy layer of Cu ₆ Sn ₅ is formed thereon, but there is a need for further improvement in heat resistance.

For example, in Patent Document 1, a Ni layer, an intermediate layer consisting of a Cu-Sn alloy layer (Cu-Sn intermetallic compound layer), and a surface layer consisting of Sn or Sn alloy are formed on the surface of a base material made of Cu or Cu alloy. A terminal material formed in this order is disclosed. In this case, the Ni layer is epitaxially grown on the base material, the average crystal grain size of the Ni layer is 1 μm or more, the thickness of the Ni layer is 0.1 to 1.0 μm, and the thickness of the intermediate layer is 0.2 μm. By setting the thickness of the surface layer to ~1.0 μm and 0.5 to 2.0 μm, it increases the barrier properties against the base material made of Cu or Cu alloy, more reliably prevents Cu diffusion, and improves heat resistance. Sn-plated materials have been obtained that can improve contact resistance and maintain stable contact resistance even in high-temperature environments. However, since the existence of the Ni layer is assumed, if the Ni layer cannot be introduced due to cost considerations, the heat resistance cannot be improved. Furthermore, since pretreatment of the base material is required for epitaxial growth of the Ni layer, there is a problem that the base material whose heat resistance can be improved is limited.

Patent Document 2 discloses that the surface of a Cu-based base material has a plurality of plating layers, and the surface layer of the Sn-based plating layer made of Sn or Sn alloy has an average thickness of 0.05 to 1.5 μm. discloses a terminal material in which a Sn-Ag coating layer is formed with a hardness of 10 to 20 Hv and an average thickness of 0.05 to 0.5 μm. Further, it is described that the Sn-Ag coating layer includes Sn particles and Ag ₃ Sn particles, and the average particle size of the Sn particles is 1 to 10 μm, and the average particle size of the Ag ₃ Sn particles is 10 to 100 nm. There is. However, since an additional Sn--Ag coating layer is required, the cost increases.

Japanese Patent Application Publication No. 2014-122403 JP2010-280946A

The present invention has been made in view of the above circumstances, and an object of the present invention is to further improve the heat-resistant peelability of a terminal material for a connector having a copper-tin alloy layer and a tin layer.

The terminal material for a connector of the present invention is a terminal material for a connector in which a copper-tin alloy layer and a tin layer made of tin or a tin alloy are laminated in this order on a base material made of copper or a copper alloy, and wherein the tin layer is laminated in this order. In EBSD measurement using the surface of the layer as an observation surface, the length of the final coagulation line per unit area is 50 mm/mm ² or less.

Since the surface of this connector terminal material is made of a tin layer, it has good electrical properties inherent to the tin layer. By setting the final solidification line length per unit area of the tin layer surface to 50 mm/ ^mm2 or less, peeling and cracking of the film at high temperatures can be prevented and heat-resistant peelability can be improved. .
The reason why the length of the final solidification line per unit area was set to 50 mm/ ^mm2 or less is because if the length per unit area exceeds 50 mm/ ^mm2 , the number of final solidification lines that can become the starting point of cracks increases. This is because peeling of the film cannot be suppressed. The length of the final coagulation line per unit area is preferably 25 mm/mm ² or less, more preferably 10 mm/mm ² or less, and even more preferably 5 mm/mm ² or less.
Even when the terminal material does not have a nickel layer as the base layer, it is possible to obtain a terminal material having excellent heat resistance.

In the connector terminal material of the present invention, the tin layer preferably has an average thickness of 0.2 μm or more and 1.7 μm or less.

The reason why the average thickness of the tin layer is set to 0.2 μm or more and 1.7 μm or less is because if it is less than 0.2 μm, the electrical connection reliability may deteriorate, and if it exceeds 1.7 μm, the contact resistance will not decrease. This is because there is a risk that the plating cost will increase and the coefficient of dynamic friction will increase. The upper limit thickness of the tin layer is preferably 1.6 μm or less, more preferably 1.5 μm or less.

In the connector terminal material of the present invention, it is preferable that the average thickness of the copper-tin alloy layer is 0.1 μm or more and 1.5 μm or less.

The reason why the average thickness of the copper-tin alloy layer is set to 0.1 μm or more and 1.5 μm or less is that if it is less than 0.1 μm, the heat resistance tends to decrease, and if it exceeds 1.5 μm, there is a risk that the heat peeling resistance will decrease. This is because there is.

In the connector terminal material of the present invention, a part of the copper-tin alloy layer is exposed on the surface of the tin layer, and the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer is 50% or less. Good.

When a part of the copper-tin alloy layer is exposed on the surface of the tin layer, the interface between the copper-tin alloy layer and the tin layer is formed into a steep uneven shape, and the tin of the tin layer and the copper-tin alloy near the surface layer are exposed. It has a composite structure, and the soft tin between the hard copper-tin alloy layers acts as a lubricant, lowering the coefficient of dynamic friction and improving wear resistance.
In this case, if the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer exceeds 50%, there is a risk that the reliability of the electrical connection characteristics will decrease. The lower limit of the exposed area ratio is 1%, preferably 1.5% or more. Furthermore, in order to reliably suppress deterioration in electrical connection reliability, it is more desirable that the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer is 40% or less.

In the connector terminal material of the present invention, it is preferable that a nickel layer made of nickel or a nickel alloy having an average thickness of 0.05 μm or more and 3.0 μm or less be provided between the base material and the copper-tin alloy layer. The nickel layer can prevent copper from diffusing from the base material and further improve heat resistance.

According to the present invention, there is provided a terminal material for a connector that can prevent peeling and cracking of the film when used in a high-temperature environment, improve heat-resistance peelability, increase glossiness, and have an excellent appearance. Obtainable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view schematically showing a first embodiment of a coated copper terminal material of the present invention. This is an EBSD image showing the crystal structure of the surface of a tin layer. This is an enlarged image of the final coagulation line in FIG. 2. This is an EBSD image of a different site from that in FIG. 2. It is a sectional view showing typically a 2nd embodiment of the copper terminal material with a film of the present invention.

Embodiments of the terminal material for connectors of the present invention will be described.

(First embodiment)
As shown in FIG. 1, the connector terminal material 1 of the first embodiment has a copper-tin alloy layer 3 made of an alloy of copper and tin as a film on a base material 2 made of copper or a copper alloy, and a tin alloy layer 3 made of an alloy of copper and tin. Alternatively, a tin layer 4 made of a tin alloy is formed in this order.

The base material 2 is a strip material formed in the shape of a strip, and its composition is not particularly limited as long as it is made of copper or a copper alloy.

The copper-tin alloy layer 3 and the tin layer 4 are formed by sequentially forming a copper plating layer and a tin plating layer on the base material 2 and performing a reflow process, as will be described later.
Among them _{, the copper-tin alloy layer 3 includes a Cu 3 Sn layer 3a partially formed on the base material 2 and this Cu 3 Sn} layer, as shown in an enlarged view of the circled area in FIG. 3a and the base material 2 where the Cu ₃ Sn layer 3a does not exist, or a Cu ₆ Sn ₅ layer 3b formed so as to straddle these. The average thickness of this copper-tin alloy layer 3 is 0.1 μm or more and 1.5 μm or less. This is because if the average thickness of the copper-tin alloy layer 3 is less than 0.1 μm, the heat resistance may be reduced, and if it exceeds 1.5 μm, the heat-resistant peelability may be reduced.
Heat resistance and heat peel resistance are both terms that refer to performance when exposed to a high temperature environment. This property prevents the film from peeling or cracking during such operations.

The average thickness of the tin layer 4 is 0.2 μm or more and 1.7 μm or less. The reason why the average thickness of the tin layer 4 is set to 0.2 μm or more and 1.7 μm or less is because if it is less than 0.2 μm, there is a risk of a decrease in electrical connection reliability, and if it exceeds 1.7 μm, the contact resistance will not decrease. This is because there is a risk that the cost of plating will increase and the coefficient of dynamic friction will increase. The average thickness of the tin layer 4 is preferably 1.6 μm or less, more preferably 1.5 μm or less.

In EBSD measurement using the surface of the tin layer 4 as an observation surface, the length of the final solidification line per unit area is 50 mm/mm ² or less.
The final solidification line is a line in which solidification progresses in different directions on the surface of the tin layer 4 when the tin liquid phase formed by heating in the reflow process solidifies, so that they meet at the final point where solidification ends. It is a boundary line formed by Specifically, when the surface of the tin layer 4 was measured by azimuthal diffraction using EBSD (Electron Backscatter Diffraction) method, the case where the angle difference between the mutual solidification directions was 10° or more was defined as the final solidification line. Figure 2 shows an EBSD image in which this final solidification line appears. In the case of Figure 2, the crystal solidification line progresses vertically in approximately the upper half of the figure, and the crystal solidification line progresses slightly diagonally in the lower half. By abutting the solidification lines of the crystals, a final solidification line is formed at the abutting position along the left and right direction of the figure, as shown by the arrows.
This final solidification line refers to the line that is formed at the point where adjacent solidification lines meet when there is a difference of 10° or more in the intersection angle of adjacent solidification lines in the direction of growth (solidification direction) of the solidification lines of the crystal. . FIG. 3 shows an enlarged view of a part of the final coagulation lines in FIG. 2, and in this case, the coagulation lines intersect at 19°.
Further, in FIG. 4, the left side is an image obtained by EBSD, and the right side is an image in which the final coagulation line is shown in black.

By setting the final coagulation line length per unit area to 50mm/ ^mm2 or less, peeling and cracking of the terminal material film when used in high-temperature environments is prevented, and the surface gloss is improved. Moreover, the appearance is also excellent. The lower limit of the length of the final coagulation line per unit area is not necessarily limited, but is preferably 0.01 mm/mm ² .
The presence of this final solidification line tends to be a problem in welding and casting, and when a heat-resistant peel test is performed, the final solidification line, which has low strength, cannot withstand stress and cracks tend to occur. When the length of the final solidification line per unit area exceeds 50mm/ ^mm2 , the presence of many final solidification lines increases the number of places that are likely to start cracks, making it easier for the film to crack or peel. . By reducing the number of final solidification lines, the surface condition also improves in gloss. The length of the final coagulation line per unit area is preferably 25 mm/mm ² or less, more preferably 10 mm/mm ² or less, and still more preferably 5 mm/mm ² or less.

A method of manufacturing the connector terminal material 1 configured as described above will be described.
A plate made of copper or a copper alloy is prepared as the base material 2, and the surface of the plate is cleaned by degreasing, pickling, or other treatments.
This base material 2 is continuously run through a rolling process or the like, or is wound into a coil, and is continuously run while unwinding the coil, and the surface of the base material 2 that is continuously running is , copper plating, and tin plating are applied in this order to form a copper plating layer and a tin plating layer in this order.

For copper plating, a general copper plating bath may be used, such as a copper sulfate bath containing copper sulfate (CuSO ₄ ) and sulfuric acid (H ₂ SO ₄ ) as main components. The temperature of the plating bath is 20 to 50° C., and the current density is 1 A/dm ² or more and 50 A/dm ² or less.

As a plating bath for forming a tin plating layer, a general tin plating bath may be used, for example, a sulfuric acid bath containing sulfuric acid (H ₂ SO ₄ ) and stannous sulfate (SnSO ₄ ) as main components may be used. I can do it. The temperature of the plating bath is 15 to 35° C., and the current density is 1 A/dm ² or more and 30 A/dm ² or less.

In the reflow treatment, the base material 2 that has been subjected to various plating treatments is heated while being continuously moved, and the plating layer is once melted and then rapidly cooled.
Specifically, primary heating involves heating a plating material obtained by applying various platings to the base material 2 to 240°C at a heating rate of 20°C/second to 75°C/second in a heating furnace with a CO reducing atmosphere. After that, a heating step is performed in which secondary heating is performed at a temperature of 240° C. or more and 350° C. or less for a period of 1 second or more and 15 seconds or less, and after the heating step, a primary cooling step and a secondary cooling step are sequentially performed.
Regarding the temperature setting during secondary heating, for example, it may be held at the temperature reached during primary heating (240°C), or it may be heated to 240°C during primary heating and then gradually raised to the target temperature. Alternatively, the temperature may be changed as appropriate within the temperature range of 240° C. or higher and 350° C. or lower.

In the primary cooling process, the temperature gradient per unit length in the length direction (travel direction) of the continuously running base material 2 is G°C/m, and the cooling rate is R°C/sec. is cooled so that it becomes 0.5 or more. When this G/R is large, the final coagulation line length per unit area can be reduced. From the viewpoint of increasing the temperature gradient G°C/m, it is desirable that the cooling rate in the primary cooling step is 40°C/second or more.If the cooling rate in the primary cooling step is less than 40°C/second, the temperature gradient G°C/m cannot be increased, and G/R is less than 0.5. Therefore, it is not possible to reduce the final solidification line, and it is not possible to improve heat-resistant peelability.
Next, in the secondary cooling step, after the primary cooling step, cooling is performed at a cooling rate of 150° C./second or more and 300° C./second or less.
From the viewpoint of reducing the final solidification line length through this reflow treatment, it is preferable to use a process in which the material is cooled to below the melting point of tin (Sn) in the primary cooling step, and rapidly cooled in the subsequent secondary cooling step.

By performing such a reflow process, the temperature reached by secondary heating is adjusted, and the primary cooling conditions are adjusted as described above to heat tin (Sn) above its melting point, and the primary cooling conditions are adjusted as described above. Adjustments as described above can be made to reduce the length of the final coagulation line per unit area.
Furthermore, by performing this reflow treatment in a reducing atmosphere, it is possible to prevent the formation of a tin oxide film with a high melting temperature on the surface of the tin layer 4, and to perform the reflow treatment at a lower temperature and in a shorter time. .

The connector terminal material 1 manufactured in this manner has good electrical properties due to the tin layer 4 on the surface, and the length of the final solidified line per unit area of the surface of the tin layer 4 is 50 mm/ By setting it to mm ² or less, peeling and cracking of the film at high temperatures can be prevented, and heat-resistant peelability can be improved.

(Second embodiment)
In contrast to the first embodiment described above, the connector terminal material 11 of the second embodiment has a nickel layer made of nickel or a nickel alloy between the base material 2 and the copper-tin alloy layer 12, as shown in FIG. 13 is formed, and on the nickel layer 13, a copper-tin alloy layer 12 and a tin layer 14 are formed.

The nickel layer 13 is formed by electrolytically plating nickel or a nickel alloy on the surface of the base material 2, and has a thickness of 0.05 μm or more and 3.0 μm or less. By providing this nickel layer 13, it is possible to prevent copper (Cu) from the base material 2 from diffusing into the film. If the thickness of this nickel layer 13 is less than 0.05 μm, the effect of preventing the diffusion of copper (Cu) from the base material 2 is poor, and the effect of improving heat resistance by preventing copper diffusion cannot be expected. If it exceeds this, the followability of bending etc. may deteriorate and cracks may occur.

The copper-tin alloy layer 12 is formed by sequentially forming a nickel plating layer, a copper plating layer, and a tin plating layer on the base material 2 and performing a reflow treatment. Although not shown, in the case of FIG. Similarly, a partially formed Cu ₃ Sn layer, either on this Cu ₃ Sn layer or on the nickel layer 13 where the Cu ₃ Sn layer does not exist, or formed so as to straddle these. It is composed of _five layers of Cu ₆ Sn. The average thickness of this copper-tin alloy layer 12 is 0.1 μm or more and 1.5 μm or less. Further, the volume ratio of the Cu ₃ Sn alloy layer 12a to the Cu ₆ Sn ₅ alloy layer 12b is preferably 20% or less. Note that the Cu ₆ Sn ₅ layer may be a compound alloy layer in which part of the copper (Cu) is replaced with nickel (Ni).

The average thickness of the tin layer 14 is the same as in the first embodiment, but a portion of the copper-tin alloy layer 12 is exposed on the surface of the tin layer 14. In this embodiment, the interface between the copper-tin alloy layer 12 and the tin layer 14 is formed into a steep uneven shape, and the vicinity of the interface has a composite structure of the copper-tin alloy layer 12 and the tin layer 14. A portion of the tin alloy layer 12 is exposed on the surface of the tin layer 14. Therefore, since the soft tin layer 14 is supported by the hard copper-tin alloy layer 12, the coefficient of friction is lowered and the ease of insertion and removal as a connector is improved.
The exposure rate of this copper-tin alloy layer 12 to the surface of the tin layer 14 is 50% or less. If the exposed area ratio of the copper-tin alloy layer 12 exceeds 50%, there is a risk that electrical connection reliability will decrease. The lower limit of the exposed area ratio is 1%, preferably 1.5% or more, and the upper limit is 40% or less.
Further, in the EBSD measurement using the surface of the tin layer 14 as the observation surface, the configuration in which the length of the final solidification line per unit area is 50 mm/mm ² or less is the same as in the first embodiment. It is.

In order to manufacture the connector terminal material 11 of the second embodiment, nickel plating, copper plating, and tin plating may be sequentially applied to the base material 2, followed by reflow treatment.
As a plating bath for nickel plating, a general nickel plating bath may be used, such as a Watt bath containing nickel sulfate (NiSO ₄ ), nickel chloride (NiCl ₂ ), and boric acid (H ₃ BO ₃ ) as main components. can be used. The temperature of the plating bath is 20° C. or more and 60° C. or less, and the current density is 5 A/dm ² or more and 60 A/dm ² or less.
Copper plating, tin plating, and reflow treatment are performed under the same conditions as in the first embodiment.

In the connector terminal material 11 of the second embodiment, the interface between the copper-tin alloy layer 12 and the tin layer 14 is formed into a steep uneven shape, so that near the interface between the tin layer 14 and the copper-tin alloy layer 12 However, a composite structure is formed in which the hard copper-tin alloy layer 12 supports the tin layer 14 directly below the soft tin layer 14, and the coefficient of dynamic friction can be reduced. Of course, since the outermost surface is mainly composed of the tin layer 14, the electrical connection reliability is excellent.
Note that such a composite structure of a tin layer and a copper-tin alloy layer can also be formed by using a copper alloy containing nickel as a base material without forming a nickel layer.

A copper alloy plate with a thickness of 0.25 mm was used as a base material, and various platings were applied under the following plating bath conditions. The thicknesses of these plating layers were as shown in Table 1.

(copper plating)
Copper sulfate: 250g/L
Sulfuric acid: 50g/L
Liquid temperature: 25℃
Current density: 5ASD (abbreviation of A/ ^dm2 ; same below)

(Tin plating)
Tin sulfate: 75g/L
Sulfuric acid: 85g/L
Additive: 10g/L
Liquid temperature: 25℃
Current density: 2ASD

Next, the base material with the plating layer was subjected to a reflow treatment under the conditions shown in Table 1.
After the reflow treatment, the thicknesses of the copper-tin alloy layer and the tin layer were measured, as well as the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer and the final solidification line length per unit area on the surface of the tin layer.
In addition, the glossiness and contact resistance of the tin layer surface were measured, and the heat-resistant peelability of the film was evaluated.

(Method for measuring average thickness of copper-tin alloy layer and tin layer)
The thickness of the tin layer and the copper-tin alloy layer was measured using a fluorescent X-ray film thickness meter (SEA5120A) manufactured by SII Nano Technology Co., Ltd. To measure the thickness of the tin layer and the copper-tin alloy layer, first measure the thickness of the entire tin-containing film (copper-tin alloy layer and tin layer) on the sample after reflow, and then measure the thickness of the copper-tin alloy layer. The tin layer is removed by immersion in an etching solution for plating film removal made of non-corrosive ingredients for 5 minutes, the copper-tin alloy layer underneath is exposed, and the thickness of the copper-tin alloy layer is measured to determine the thickness of the copper-tin alloy layer. After calculating the average thickness, (thickness of the entire film including the tin layer−average thickness of the copper-tin alloy layer) was defined as the average thickness of the tin layer. Each thickness shown in Table 1 is the average value of the measured values at five locations.

(Method for measuring exposed area ratio of copper-tin alloy layer)
The exposed area ratio of the copper-tin alloy layer was determined by observing a 100×100 μm area using a scanning ion microscope after removing the surface oxide film. According to the measurement principle, if Cu ₆ Sn ₅ alloy exists in a depth region of about 20 nm from the outermost surface, it will be imaged white, so image processing software is used to calculate the ratio of the area of the white region to the area of the measurement region. It was regarded as the exposed area ratio of the tin alloy layer.

(Method of measuring final coagulation line length per unit area)
The length of the final coagulation line per unit area was measured by the EBSD method (Electron Backscatter Diffraction) using a scanning electron microscope (SU7000) manufactured by Hitachi High-Tech Corporation. The measurement conditions were a set voltage of 15 kV, a probe current value of Hi80, an objective aperture diameter of 70 μm, a measurement area of 1000 μm×1000 μm including 100 or more crystal grains, and a scan step of 2 μm. This was measured in 20 visual fields. To analyze the crystal grains after the measurement, the length of the final coagulation line was measured from an IPF (Inverse Pole Figure) map and an IQ (Image Quality) map using analysis software OIM Analysis manufactured by TSL. This final solidification line is defined as the line formed by butting these solidification lines when the intersecting angle of the propagation direction (solidification direction) of the solidification lines of adjacent crystals is 10° or more. The length was measured.
Then, the length per unit area was calculated by dividing the total length of the final coagulation line obtained by measuring the 20 visual fields by the total area of the 20 visual fields.

(Measurement method of glossiness)
Glossiness was measured using a gloss meter (model number: VG-2PD) manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS Z 8741 at an incident angle of 60 degrees.

(contact resistance)
The contact resistance was measured by holding the sample at high temperature in the atmosphere. The holding conditions were 120°C for up to 1000 hours. The measurement method was to measure the contact resistance using a 4-terminal contact resistance tester (manufactured by Yamazaki Seiki Laboratory: CRS-113-AU) with a sliding type (1 mm) and varying the load from 0 to 100 g, and the load was 100 g. It was evaluated based on the contact resistance value at that time. If the contact resistance was 5mΩ or less even after 1000 hours had passed, it would be labeled "A", if it exceeded 5mΩ but not more than 10mΩ, it would be labeled "B", and if it exceeded 10mΩ after 1000 hours, it would be labeled "C". did.

(Evaluation of film heat-resistant peelability)
A test piece with a width of 10 mm and a length of 80 mm (long axis direction perpendicular to the rolling direction) was cut out from the sample material, and the prepared test piece was bent 180 degrees with a radius of curvature R = 3 mm and heated at 170 ° C for 250 hours. A holding heating test was conducted in air. Furthermore, the test pieces after heating were bent back at room temperature. Visually observe the bent part, and if there are no cracks, peeling, or wrinkles in the film, it is ``A'', and if there are wrinkles on the surface of the film, it is ``B''. Those with exposed parts were rated "C".

These results are shown in Table 1.

As can be seen from Table 1, the examples in which the final solidification line length per unit area on the tin layer surface was 50 mm/ ^mm2 or less were evaluated to be good, with only wrinkles being observed in the evaluation of the heat-resistant peelability of the film. Ta. The glossiness also showed a higher value than the comparative example.
Further, the contact resistance is also low and good, at 10 mΩ or less after heating.
On the other hand, in all of the comparative examples, the final coagulation line length exceeded 50 mm/mm ² , and in the evaluation of heat-resistant peelability, exposure of the base material was observed due to cracking or peeling of the film.

Next, a sample was also prepared in which a nickel layer was formed between the base material and the copper-tin alloy layer. The conditions for the base material, copper plating, and tin plating are the same as in the previous example.
(Nickel plating)
Nickel sulfate: 300g/L
Sulfuric acid: 2g/L
Liquid temperature: 45℃
Current density: 20ASD
The reflow treatment was performed under the conditions shown in Table 2.
Regarding the obtained sample, in the same manner as described above, after the reflow treatment, the thickness of the copper-tin alloy layer and the tin layer was measured, and the exposed area ratio of the copper-tin alloy layer on the surface of the tin layer and the unit area on the surface of the tin layer were measured. The final coagulation line length was measured.
Further, the thickness of the nickel layer was also measured using a fluorescent X-ray film thickness meter (SEA5120A) manufactured by SII Nano Technology Co., Ltd. The average thickness of the nickel layer is the average of the measured values at five locations.
In addition, the glossiness and contact resistance of the tin layer surface were measured, and the heat-resistant peelability of the film was evaluated.
The evaluation was conducted under the same conditions as in the example shown in Table 1, except that the heating conditions for evaluating the heat-resistant peelability of the film were 180° C. for 200 hours.
The results are shown in Table 2.

As can be seen from Table 2, in the examples in which the final solidification line length per unit area on the tin layer surface was 50 mm/ ^mm2 or less, no cracking or peeling of the film was observed, and the results were even better than those in Table 1. there were. The surface gloss is high and the contact resistance after being held at high temperatures is low, indicating that forming a nickel layer can make an even more excellent terminal material. Note that Table 2 shows the thickness of the nickel plating layer, and the average thickness of the nickel layer as a terminal material was also 0.05 μm or more and 3.0 μm or less.
In the comparative example, the final coagulation line length per unit area on the surface of the tin layer exceeded 50 mm/mm ² , so the heat-resistant peelability was poor.

1 Terminal material for connector 2 Base material 3 Copper-tin alloy layer 3a Cu ₃ Sn layer 3b Cu ₆ Sn ₅ layer 4 Tin layer 11 Terminal material for connector 12 Copper-tin alloy layer 13 Nickel layer 14 Tin layer

Claims (5)

EBSD is a terminal material for a connector in which a copper-tin alloy layer, a tin layer made of tin or a tin alloy are laminated in this order on a base material made of copper or a copper alloy, and the surface of the tin layer is an observation surface. A terminal material for a connector, characterized in that the length of the final coagulated line per unit area is 50 mm/mm ² or less when measured. 2. The connector terminal material according to claim 1, wherein the tin layer has an average thickness of 0.2 μm or more and 1.7 μm or less. The terminal material for a connector according to claim 1 or 2, wherein the average thickness of the copper-tin alloy layer is 0.1 μm or more and 1.5 μm or less. A portion of the copper-tin alloy layer is exposed on the surface of the tin layer, and an exposed area ratio of the copper-tin alloy layer on the surface of the tin layer is 50% or less. 3. The terminal material for a connector according to any one of 3. Any one of claims 1 to 4, further comprising a nickel layer made of nickel or a nickel alloy having an average thickness of 0.05 μm or more and 3.0 μm or less between the base material and the copper-tin alloy layer. Terminal material for connectors described in .

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