KR101243454B1 - Tinned copper alloy bar with excellent abrasion resistance, insertion properties, and heat resistance - Google Patents

Abstract

Rsm/(y＋Rz)

4.0 이고, 표면부터 모재에 걸쳐, 두께가 0.5 ∼ 1.5 ㎛ 인 Sn 층, 두께가 0.6 ∼ 2.0 ㎛ 인 Cu-Sn 합금층, 두께가 0 ∼ 0.8 ㎛ 인 Cu 층의 각 층으로 도금 피막이 구성되어 있거나, 또는 두께가 0.5 ∼ 1.5 ㎛ 인 Sn 층, 두께가 0.4 ∼ 2.0 ㎛ 인 Cu-Sn 층, 두께가 0.1 ∼ 0.8 ㎛ 인 Ni 층의 각 층으로 도금 피막이 구성되어 있는 주석 도금조.Tin plating bath which is excellent as abrasion resistance, insertability, and heat resistance as a conductive spring material. Electroplating is performed on the surface of the copper alloy bath in order of base plating and Sn plating, and thereafter, as a plating bath subjected to a reflow process, the difference in altitude between the outermost surface of the Sn plating and the outermost point on the Cu-Sn alloy is 0.1 to 0.5. It is a copper alloy tin plating bath whose maximum height of the roughness curve of a Cu-Sn alloy phase is 0.6-1.2 micrometer, and the average length of the roughness curve of a Cu-Sn alloy phase is 2.0-5.0 micrometers, Preferably it is 2.0

Rsm / (y + Rz)

The coating film is comprised from each layer of the Sn layer whose thickness is 0.5-1.5 micrometers, the Cu-Sn alloy layer whose thickness is 0.6-2.0 micrometers, and the Cu layer whose thickness is 0-0.8 micrometer from the surface to a base material, or Or the tin plating tank in which the plating film is comprised by each layer of the Sn layer whose thickness is 0.5-1.5 micrometers, the Cu-Sn layer whose thickness is 0.4-2.0 micrometers, and the Ni layer whose thickness is 0.1-0.8 micrometer.

Description

Copper alloy tin plating bath with excellent wear resistance, insertability and heat resistance {TINNED COPPER ALLOY BAR WITH EXCELLENT ABRASION RESISTANCE, INSERTION PROPERTIES, AND HEAT RESISTANCE}

The present invention relates to a tin plating bath excellent in wear resistance, insertability, and heat resistance, which is preferable as conductive spring materials such as connectors, terminals, relays, and switches.

Copper or copper alloy baths with Sn plating are used for conductive spring materials for electronic parts such as automotive and consumer connectors, terminals, relays, and switches, taking advantage of Sn's excellent corrosion resistance, solder wettability, and electrical connectivity. . In general, the Sn plating bath of the copper alloy forms a Cu base plated phase by electroplating, after degreasing and pickling in a continuous plating line, and then forms a Sn plated phase by electroplating, and finally reflows. It is manufactured by the process of performing a process and melting a Sn plating phase.

In the Sn plated material, over time, components of the base material and the base plating diffuse into the Sn layer to form an alloy phase, so that the Sn layer is lost, and the base material or the base plating component is formed as an oxide thickly on the entire surface. Various properties such as contact resistance and solderability deteriorate. For Cu to Sn plating of the copper alloy, the alloy phase is mainly an intermetallic compound such as _{Cu 3 Sn, Cu 6 Sn 5} . The temporal deterioration of characteristics is accelerated at higher temperatures, and is particularly remarkable in the engine rotation of an automobile.

On the other hand, in recent years, as the number of circuits of electronic and electrical components increases, the polarization of the connector which supplies an electric signal to a circuit is progressing. Since the Sn plating material adopts the gas tight structure which adhere | attaches male and female at the contact point of a connector from the flexibility, the insertion force of a connector is high compared with the connector comprised with gold plating etc. For this reason, the increase of the connector insertion force by the multipolarization of a connector becomes a problem.

For example, in the assembly line of an automobile, the work which fits a connector is currently made with almost manpower. When the insertion force of a connector becomes large, a burden is put on an operator in an assembly line, and it leads directly to the fall of work efficiency. In addition, the possibility of harming the health of the worker is pointed out. For this reason, the reduction of the insertion force of Sn plating material is strongly desired.

In addition, the contact of the spring member slides due to vibration of the engine, vibration caused by vehicle running, thermal expansion and contraction of the terminal material, and the like. When Sn plating wears out by sliding, the characteristics of the solder wettability, corrosion resistance, and electrical connection characteristic which are characteristic of Sn deteriorate. For example, when the male and female terminals are fitted and the reciprocating movement is repeated in the contact portion, an oxide of Sn-plated material generated by abrasion is deposited, and this oxide is close to insulation, resulting in poor contact (increase in contact resistance). ) Occurs.

As mentioned above, in Sn plating material, reduction of insertion force, improvement of heat resistance, and abrasion resistance have become a recent subject. Effective methods for reducing the insertion force of the connector are known documents such as Japanese Patent Application Laid-Open No. Hei 10-265992, Japanese Patent Application Laid-Open No. Hei 10-302864, Japanese Patent Application Laid-Open No. 2000-164279, and Japanese Patent Application Laid-Open No. 2007-258156. As disclosed in, the Sn-plated phase is thinned.

However, when the Sn-plated phase is made thin, the deterioration of characteristics due to the disappearance of the Sn phase proceeds early. That is, simply by thinning Sn plating reduces the insertion force, while deteriorating heat resistance. Therefore, when thinning Sn phase, it is necessary to apply the technique which improves the heat resistance of Sn plating.

As a technique for improving the heat resistance of Sn plating, a technique of preventing diffusion of Cu and the like into Sn by underlying plating has been studied. For example, Japanese Patent Laid-Open No. 6-196349, Japanese Patent Laid-Open No. 11-135226, Japanese Patent Laid-Open No. 2002-226982, Japanese Patent Laid-Open No. 2003-293187, Japanese Patent Laid-Open No. 2004-68026, Japanese Patent Laid-Open No. In 2007-258156, a technique for performing two-phase base plating of Cu / Ni is disclosed. When this Sn plating is reflowed, it becomes a structure of Sn / Cu-Sn alloy / Ni / copper alloy base material. Since the base Ni phase prevents diffusion of the base metal Cu into the Sn phase and further suppresses diffusion of Ni in the Sn phase by the presence of the Cu—Sn phase, the loss of the Sn phase is delayed. In Japanese Unexamined Patent Publication No. 2007-258156 (Patent Document 1), in order to maintain electrical reliability (low contact resistance) and maintain good solderability even under high temperature, long time, corrosive atmosphere or vibration environment, the surface of Sn coating layer is maintained. The illuminance and thickness of the is controlled. In JP 2007-63624 A (Patent Document 2), the average roughness of a Cu-Sn alloy phase after a reflow treatment of a Sn-plated copper alloy bath is controlled to balance insertion extraction and heat resistance.

Japanese Unexamined Patent Publication No. 2007-258156 Japanese Unexamined Patent Publication No. 2007-63624

In the said patent document 1, in order to control the roughness of the Sn coating layer surface, the base material which has a specific surface roughness is used, and it is necessary to roughen a base material surface by ion etching, electrolytic polishing, rolling, polishing, shot blasting, etc. There was a problem that the equipment cost was high and the manufacturing cost became expensive (Patent Document 2 “0032” to “0033”).

Moreover, in the said patent document 2, since insertion insertion property is so favorable that the average roughness of Cu-Sn alloy phase is large, and heat resistance is so good that the average roughness is small, in order to adjust these opposing effects, average roughness of Cu-Sn alloy phase is adjusted. It is necessary to make delicate adjustment of the size, and to control the size of the Cu electrodeposited particles which are precipitated at the time of Cu plating, special care and operation were necessary for this purpose (Patent Document 1 “0018”).

As mentioned above, it is a subject of the art to manufacture Sn plating bath which maintains excellent corrosion resistance and low contact resistance after high temperature and / or long time, and is also excellent in abrasion resistance with low insertion force by industrially easy operation. It was.

As a result of intensive studies, the inventors found that excellent abrasion resistance, insertability and heat resistance are obtained when the unevenness of the interface with the pure Sn phase of the Cu—Sn alloy phase of the copper alloy tin plating bath is dense and large. This invention is made | formed based on this discovery, and has the following structure.

(1) A plating bath subjected to electroplating in the order of base plating and Sn plating on the surface of the copper alloy bath, and then subjected to reflow treatment; in the vertical cross section with respect to the plating surface, the Sn plating outermost surface and Cu Altitude difference (y) of outermost point of -Sn alloy phase is 0.1-0.5 micrometer; Maximum height of the roughness curve (Rz) of this Cu-Sn alloy phase when dissolving and removing a Sn phase and making a Cu-Sn alloy phase appear on the surface. ) Is 0.6 to 1.2 µm, and the average length Rsm of the roughness curve of the Cu-Sn alloy phase is 2.0 to 5.0 µm.

(2) The copper alloy tin plating bath of (1), wherein Rsm, y, and Rz have the following relationship.

Rsm/(y＋Rz)

4.02.0

Rsm / (y + Rz)

4.0

(3) The plating film is comprised by each layer of a Sn layer, a Cu-Sn alloy layer, and a Cu layer from the surface to a base material, The thickness of a Sn layer is 0.5-1.5 micrometers and the thickness of a Cu-Sn alloy layer is 0.6-2.0. The thickness of the micrometer and Cu layer is 0-0.8 micrometer, The copper alloy tin plating tank of said (1) or (2) characterized by the above-mentioned.

(4) The plating film is comprised by each layer of Sn layer, Cu-Sn layer, and Ni layer from the surface to a base material, and the thickness of Sn layer is 0.5-1.5 micrometers and the thickness of a Cu-Sn alloy layer is 0.6-2.0 micrometers. The thickness of the Ni layer is 0.1-0.8 micrometer, The copper alloy tin plating tank of said (1) or (2) characterized by the above-mentioned.

The tin plating bath of this invention is preferable as conductive spring materials, such as a connector, a terminal, a relay, and a switch, and is excellent in abrasion resistance, insertability, and heat resistance.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of Cu base Sn plating tank after the reflow process of this invention.
2 is an uneven SEM image in which a Cu—Sn alloy phase appears on a surface thereof.
3 is a roughness curve of the Cu—Sn alloy phase measured along the measurement line of FIG. 2.
4 is a schematic view showing the cross section of Sn plating materials of the conventional example (a) and the inventive example (b).
5 is a schematic view showing a method of measuring dynamic friction coefficient.
6 is a schematic view showing a machining method of a contact tip.

Best Mode for Carrying Out the Invention

The structural requirements of the present invention and a description thereof will be described below.

Structure between Sn phase and Cu-Sn alloy phase

The copper alloy tin plating tank of this invention is obtained by electroplating on the surface of a copper alloy tank in order of base plating and Sn plating, and then performing a reflow process. Rz and Rsm are parameters of an illuminance curve defined in JIS B 0601: 2001.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of Cu base Sn plating tank after the reflow process of this invention, The height difference "y" of the outermost surface of Sn plating and the outermost point of a Cu-Sn alloy phase, and the maximum height "Rz" of the roughness curve of a Cu-Sn alloy phase. The average length "Rsm" of the said illuminance curve is typically shown.

The determination method of the roughness curve of the said Cu-Sn alloy phase, the maximum height "Rz" of a roughness curve, and an average length "Rsm" is shown below.

2, the SEM image obtained by the commercially available uneven SEM (scanning electron microscope) (ERA-8000) apparatus after dissolving and removing the Sn phase on the surface of the tin plating bath to make the Cu-Sn alloy phase appear on the surface. 3000 times) and any measurement line. Each 100 line (1 line 40 micrometers) is measured in a rolling parallel direction and a perpendicular direction.

The roughness curve of the Cu-Sn alloy phase measured along the measuring line of FIG. 2 is shown in FIG. The highest height of each peak shown on the roughness curve is averaged, and let it be the maximum height "Rz" of the roughness curve of a Cu-Sn alloy phase. Similarly, the interval of the peak shown on the roughness curve is averaged, and it is set as average length "Rsm" of the roughness curve of a Cu-Sn alloy phase.

In FIG. 4, (a) is a cross-sectional schematic diagram of the conventional Cu base Sn plating tank, where peak maximum height "Rz" is small and peak average length "Rsm" is large. (b) is a cross-sectional schematic diagram of Cu base Sn plating bath of this invention which has the average Sn phase thickness (i) and average Cu-Sn alloy phase thickness (ii) similar to a prior art example, and Rz is large and Rsm is small. In addition, the maximum Cu-Sn alloy phase thickness (iii) is larger than the peak maximum height "Rz".

The altitude difference y between the outermost surface of Sn plating of a prior art example and the outermost point of a Cu-Sn alloy phase is larger than the thing of this invention. However, since the pure Sn phase is easily deformed and removed by inserting a connector once, the state in which the Cu-Sn alloy phase appears on the surface is important for the examination of wear resistance. In addition, in the present invention, since the interval between the peaks of the hard Cu-Sn alloy phase is short and the valley portion is deep in comparison with the conventional example, the pure Sn phase of the valley portion is not easily lost and wear resistance is excellent.

The maximum height Rz of the roughness curve of the Cu-Sn alloy phase of the tin plating bath of this invention is 0.6-1.2 micrometers. If it is in this range, the pure Sn phase which exists in the valley part of a Cu-Sn alloy phase interface will show a lubrication effect, and abrasion resistance improves. When Rz is less than 0.6 µm, the pure Sn phase present in the valley portion of the Cu-Sn alloy phase interface is abrasion-dissipated, and the Cu-Sn alloy phase is also brittle and the wear resistance is bad. When Rz exceeds 1.2 micrometers, it is difficult to achieve the range of the following Rsm.

The average length Rsm of the roughness curve of the Cu-Sn alloy phase of the tin plating bath of this invention is 2.0-5.0 micrometers. If it is in this range, the valley part of suitable depth exists in a Cu-Sn alloy phase interface, and the pure Sn phase which exhibits a lubrication action is ensured. When Rsm exceeds 5.0 micrometers, the space | interval of the acid of the hard Cu-Sn alloy phase which bears weight at the time of insertion extraction becomes large, and the pure Sn phase of a valley part tends to wear-out, and it is inferior to abrasion resistance. If Rsm is less than 2.0, it is difficult to attain the range of Rz.

In the tin plating tank of this invention, in the vertical cross section with respect to a plating surface, the altitude difference y between the outermost surface of Sn plating and the outermost point of a Cu-Sn alloy phase is 0.1-0.5 micrometer. If y is less than 0.1 micrometer, heat resistance is inferior. Specifically, when the heat resistance test is performed at 175 ° C. for 1000 hours, the Cu—Sn alloy phase is exposed on the surface to increase the contact resistance. When y exceeds 0.5 µm, the deformation resistance due to the excavation of Sn plating at the time of terminal insertion or the shear resistance for shearing adhesion are increased, resulting in a large insertion force.

y cut | disconnects the sample after reflow in the rolling parallel direction, and can measure and calculate | require by measuring the cross section by 10000 times the magnification.

In the tin plating bath of the present invention, since the unevenness of the Sn phase / Cu-Sn alloy phase interface is high, that is, Rsm is small and Rz is large, since the average net Sn thickness is smaller than the conventional case, since the value of y is small, friction The resistance is lowered, and at the time of abrasion, the peak of the acid at the Cu-Sn alloy phase interface acts as a support, so that the required insertion power is lowered.

It is preferable that Rsm, y, and Rz of this invention have the following relationship.

Rsm/(y＋Rz)

4.02.0

Rsm / (y + Rz)

4.0

(y + Rz) is the sum of the `` altitude difference (y) between the outermost point of the Sn-plated surface and the Cu-Sn alloy phase '' and the `` maximum height of the roughness curve of the Cu-Sn alloy phase '', and the Cu-Sn alloy phase and the Cu base material or base The space | interval of the interface of a plating phase and the outermost surface of Sn plating is shown. Therefore, the average length Rsm of the roughness curve of a Cu-Sn alloy phase becomes like this. Preferably it is 2 to 5 times the space | interval from the lowermost part of a Cu-Sn alloy phase to Sn plating outermost surface. When it exceeds 4.0, since the space | interval of the acid of the hard Cu-Sn alloy phase which bears the weight at the time of insertion extraction becomes large, and there are few pure Sn phases of a valley part, the pure Sn phase of a valley part is easy to lose | wear, and it is inferior to abrasion resistance. In addition, the heat resistance is also inferior. It is usually technically difficult to set it to less than 2.0, and the increase in wear resistance cannot be expected very much.

Type of plating

The following are mentioned as a specification of the base plating and Sn plating to which this invention is applicable.

(1) Cu not reflow Sn plating

The plating film is comprised by the Sn phase, Cu-Sn alloy phase, and each phase of Cu phase from the surface to a base material. This plating film structure is obtained by electroplating in order of Cu base plating and Sn plating, and performing a reflow process.

As for the average thickness of Sn phase after reflow, 0.5-1.5 micrometers is preferable. If the Sn phase is less than 0.5 µm, the solder wettability is lowered. If the Sn phase is more than 1.5 µm, the required insertion force is increased.

As for the thickness of the Cu-Sn alloy phase after reflow, 0.6-2.0 micrometers is preferable. Since the Cu-Sn alloy phase is hard, when the interface with the Sn phase exists in the thickness of 0.6 micrometer or more, when it exists in thickness of 0.6 micrometer or more, it contributes to reducing insertion force and is excellent in abrasion resistance and heat resistance. On the other hand, when the thickness of a Cu-Sn alloy phase exceeds 2.0 micrometers, mechanical characteristics, such as bendability, will deteriorate.

Since the average thickness of the Cu-Sn alloy phase (diffusion layer) of this invention has an unevenness | corrugation in the interface of a Sn phase and a Cu-Sn alloy phase, it can be made thicker than before. Therefore, the plating bath of this invention which can thicken the Cu-Sn alloy phase harder than a pure Sn layer and a base material has the outstanding wear resistance. Moreover, since the plating bath of this invention has a thick Cu-Sn alloy phase, heat resistance is also improved. Although the present invention is not limited by theory, it is believed that the reason lies in the inhibition of Cu diffusion. That is, when the Cu supplied from the base material reaches the interface between the Cu-Sn alloy phase and the Sn phase, and the Cu-Sn alloy phase grows by bonding with Sn in the Sn phase, the Cu base material interface is thick when the average thickness of the Cu-Sn alloy phase is thick. The distance between the Cu-Sn alloy phase / Sn phase interface becomes longer, and the time required for diffusion of Cu to the Cu-Sn alloy phase / Sn phase interface becomes longer. In particular, since the thickness of the Cu-Sn alloy phase between the Cu base material to the outermost point of the Cu-Sn alloy phase is the largest, Cu reaches from the base material to the outermost point of the alloy phase, and as a result, the Cu-Sn alloy phase grows and the Sn phase disappears. It is difficult even in high temperature long time severe conditions. Therefore, the plating bath of this invention has very excellent heat resistance.

The Cu base plating formed by electroplating may be consumed for Cu-Sn alloy (phase) formation at the time of reflow, and the thickness may be zero. On the other hand, in the plating material whose thickness of the Cu phase after reflow exceeds 0.8 micrometers, Rz and Rsm of the Cu-Sn alloy phase after reflow are out of the scope of this invention. This is considered to be because, as the Cu base plating becomes thicker, the electrodeposited particles of Cu coarsen locally and adversely affect the growth of the Cu—Sn alloy phase.

The plating structure of this invention is obtained by adjusting the thickness of each plating at the time of electroplating suitably in the range of 0.6-2.0 micrometers, and Cu plating in the range of 0.1-1.5 micrometers, and subsequently performing a reflow process. Lose.

Although the reflow process of this invention is performed in 230-600 degreeC and the range for 3 to 30 second, it heats rapidly at the temperature increase rate of 20-100 degreeC / sec, Preferably it is 30-70 degreeC / sec, and cooling rate 100- The heating is performed at 300 ° C / sec, for example, using a heat transfer means such as a suitable conduction, convection, and radiation such as a circulation fan and a radiation plate, and the cooling is uniformly heated regardless of both ends and the center of the plating bath, for example, by water cooling. Cool.

Although the present invention is not limited by theory, the nucleus of the Sn-Cu phase, which is relatively small initially generated between the Sn-plated phase and the Cu phase by the reflow process, is faster and faster than a new nucleus is generated. It is thought that the Sn-Cu phase / Sn phase interface structure of the present invention is formed by growing in the Sn phase and rapidly cooling at a predetermined time point.

In the conventional reflow treatment, rapid heating for the purpose of the present invention is not necessary, and even if the heating is performed quickly by simply increasing the line speed, uniform heating is not possible. Therefore, in the material width direction and the longitudinal direction after reflow, It was difficult to obtain a uniform plating thickness.

(2) Cu / Ni not reflow Sn plating

A plating film is comprised by the Sn phase, Cu-Sn alloy phase, and Ni phase each phase from a surface to a base material. This plating film structure is obtained by electroplating in order of Ni base plating, Cu base plating, and Sn plating, and performing a reflow process.

As for the average thickness of Sn phase after reflow, 0.5-1.5 micrometers is preferable. If the Sn phase is less than 0.5 µm, the solder wettability is lowered. If the Sn phase is more than 1.5 µm, the insertion force is increased.

As for the thickness of the Cu-Sn alloy phase after reflow, 0.4-2.0 micrometers is preferable. Since the Cu-Sn alloy phase is hard, when it exists in thickness of 0.4 micrometer or more, it contributes to reduction of insertion force. On the other hand, when the thickness of a Cu-Sn alloy phase exceeds 2.0 micrometers, mechanical characteristics, such as bendability, will deteriorate.

As for the thickness of Ni phase after reflow, 0.1-0.8 micrometer is preferable. If the thickness of Ni is less than 0.1 µm, the corrosion resistance and heat resistance of the plating decrease. On the other hand, in the plating material in which the thickness of Ni after reflow exceeds 0.8 micrometers, the thermal stress which generate | occur | produces inside a plating layer when it heats becomes high, and plating peeling is accelerated | stimulated.

The thickness of each plating at the time of electroplating is suitably adjusted in the range of 0.6-2.0 micrometers of Sn plating, 0.1-1.5 micrometers of Cu plating, and 0.1-0.8 micrometer of Ni plating, and then ripple similarly to the above. By performing a row process, the plating structure of this invention is obtained. The Cu plated phase may be completely converted to a Cu-Sn alloy phase after reflow, and may remain at a thickness of 0.4 µm or less.

The thickness of each phase of the Sn phase, Cu—Sn alloy phase, Cu phase, and Ni phase after the reflow is mainly determined by using an electrolytic film thickness meter, a fluorescent X-ray film thickness meter, SEM observation from the cross section, and GDS from the surface ( Glow discharge luminescence spectroscopy) analysis and the like were also used as necessary. Details are described in Examples.

Types of Copper Alloy Base Materials

Although the following is mentioned as a copper alloy base material to which this invention is applicable, It is not limited to these.

(1) Cu-Ni-Si-based alloy (Colson alloy)

By performing the aging treatment, compound particles of Ni and Si are precipitated in Cu, and high strength and electrical conductivity are obtained. Examples of the practical alloys include C70250, C64725, and C64760 (CDA numbers, the same below). In order to improve characteristics such as strength and heat resistance, one or more selected from the group of Zn, Sn, Mg, Co, Ag, Cr, and Mn may be further added as necessary.

(2) phosphor bronze

Examples of the practical alloys include C52400, C52100, C51910, and C51020. In order to improve characteristics, such as strength and heat resistance, 1 or more types chosen from the group of Zn, Ni, Co, Fe, Ag, and Mn can be further added as needed.

(3) brass

Examples of the practical alloys include C26000 and C26800. In order to improve characteristics, such as strength and heat resistance, 1 or more types chosen from the group of Ni, Cr, Co, Sn, Fe, Ag, and Mn can be further added as needed.

(4) single acting

Examples of the practical alloys include C23000, C22000, and C21000. In order to improve characteristics, such as strength and heat resistance, 1 or more types chosen from the group of Ni, Cr, Co, Sn, Fe, Ag, and Mn can be further added as needed.

(5) titanium copper

Examples of the practical alloys include C19900. By performing the aging treatment, a compound of Ti and Cu is precipitated in Cu, and very high strength is obtained. In order to improve characteristics such as strength and heat resistance, one or more selected from the group of Zn, Ni, Co, P, Cr, Fe, Ag, and Mn may be further added as necessary.

The tin plating bath of this invention is excellent in abrasion resistance, insertability, and heat resistance, and is suitable as conductive spring materials, such as a connector, a terminal, a relay, and a switch. Here, being excellent in abrasion resistance means the case where the maximum depth of the sliding trace obtained by the following abrasion resistance test is 3 micrometers or less. The excellent insertion property means that the insertion force required in the case of using as a connector is low, and the kinetic friction coefficient mu is 0.50 or less. The excellent heat resistance means that the contact resistance after heating at 145 degreeC for Cu base plating and 1000 h at 175 degreeC for Cu / Ni underlying plating is 8 mPa or less.

Example

Although the manufacture example of the copper alloy tin plating tank which concerns on this invention below, and the result of the characteristic test are shown, these are provided in order to understand this invention and its advantage better, and it does not intend that this invention is limited.

(a) base material

Ni plating and copper in the following order in the copper alloy of composition Cu-35% Zn (thickness: 0.32 mm, tensile strength 540 MPa, 0.2% yield strength 510 MPa, Young's modulus 103 GPa, electrical conductivity 26% IACS, Vickers hardness 171 Hv) Base plating, Sn plating was performed, and the reflow process was performed. In addition, the said Vickers hardness is the value measured based on JISZ2244 about the rolling direction right angle cross section of a base material.

(b) plating treatment

(Electrolytic degreasing order)

In an aqueous alkali solution, the sample is subjected to electrolytic degreasing as a cathode.

It is pickled using 10 mass% sulfuric acid aqueous solution.

(Ni not plating condition)

Plating bath composition: nickel sulfate 250 g / l, nickel chloride 45 g / l, boric acid 30 g / l

Plating bath temperature: 50 degrees Celsius

Current density: 5 A / dm 2

Ni plating thickness is adjusted according to electrodeposition time

(Cu not plating condition)

Plating bath composition: copper sulfate 200 g / l, sulfuric acid 60 g / l

Plating bath temperature: 25 degrees Celsius

Current density: 5 A / dm 2

Stirring speed: 5 m / min

Cu plating thickness is adjusted according to electrodeposition time

(Sn plating condition)

Plating bath composition: 41 g / l of 1st tin oxide, 268 g / l of phenolsulfonic acid, 5 g / l of surfactant.

Plating bath temperature: 50 degreeC.

Current density: 9 A / dm 2.

Sn plating thickness is adjusted according to electrodeposition time.

(c) reflow processing

In the heating furnace which adjusted atmospheric gas to nitrogen (oxygen 1 vol% or less) at the temperature shown in a table | surface, the sample was inserted in the time described in the table | surface, it heated at the temperature increase rate shown in a table | surface, and it puts in 60 degreeC water, It cooled by the cooling rate 200 degreeC / sec.

The following evaluation was performed about the sample manufactured above.

(d) Plating thickness measurement by electrolytic film thickness meter

Ni-plated layer in the case of Sn plating layer, Cu-Sn alloy layer, Cu / Ni base plating layer according to JIS H 8501 for the sample after reflow using CT-1 type electrolytic film thickness meter (manufactured by Densoku Co., Ltd.). The thickness of was measured. The measurement conditions are as follows.

Electrolyte

(1) Sn plating layer and Cu-Sn alloy layer: Electrolytic solution R-50 by Cockle Corporation

(2) Ni plating layer: Electrolytic solution R-54 by Cockle Corporation

In the case of Cu base Sn plating, when electrolysis is performed with electrolyte solution R-50, electrolysis stops immediately in front of a Cu-Sn alloy layer by electrolyzing Sn plating layer for the first time, and the display value of the apparatus here becomes a Sn plating layer thickness. Subsequently, electrolysis is started again, and the Cu-Sn alloy layer is electrolyzed until the apparatus stops next, and the display value at the end time corresponds to the thickness of the Cu-Sn alloy layer.

In the case of the Cu / Ni base plating layer, the thickness of the Ni plating layer was first measured by the thickness of the Sn plating layer and the Cu-Sn alloy layer as described above using the electrolyte solution R-50, and then sucked into the electrolyte solution R-50 with a dropper. It is sent out, washed with pure water thoroughly, exchanged with electrolyte R-54, and the thickness of the Ni plating layer is measured.

(e) Measurement of Cu Plating Layer Thickness by Plating Layer Observation

Since the Cu plating thickness of a copper alloy phase cannot be measured in the said electrolytic film thickness meter, the thickness of the Cu plating layer was calculated | required by observing the cross section of the plating layer by SEM.

Samples were made of resin so that the cross section in the direction parallel to the rolling direction could be observed, and the observation surface was finished on the mirror surface by mechanical polishing, and then the characteristics of the reflected electron image, the base material component and the plating component were magnified at 2000 times by SEM. Take a line image. In the reflection electron image, in the case of each plating layer, for example, Cu under Sn plating, color contrast is generated in order of a Sn plating layer, a Cu-Sn alloy layer, a Cu plating layer, and a base material from a plating surface layer. In addition, in the characteristic X-ray image, since the Sn plating layer detects only Sn, the Cu-Sn alloy layer Sn and Cu, and the base material detects the components thereof, it is understood that the layer where only Cu is detected is the Cu plating layer. Therefore, the thickness of a Cu plating layer can be calculated | required by measuring by the reflection electron image the thickness of the layer which only Cu was detected in the characteristic X-ray image, and whose contrast of a hue differs from another. The thickness measures the thickness of 5 points arbitrarily on a reflection electronic image, and makes the average value into Cu plating layer thickness.

In this method, however, only a very narrow range of thickness can be obtained compared to the electrolytic film thickness method. Therefore, this observation was carried out in ten cross sections, and the average value was made into the Cu plating thickness.

(f) Rsm, Rz and y on Cu-Sn alloy

The sample after reflow was immersed for 1 minute in 25 degreeC in Meltex Inc. strip TL-105 liquid, the Sn phase was dissolved and removed, and the Cu-Sn alloy phase appeared on the surface. The average roughness curve of the Cu-Sn alloy phase was calculated | required by the uneven | corrugated SEM (ERA-8000) by ELIONIX company. At a magnification of 3000 times, each of the ten lines (one line of 40 µm) was measured in the rolling parallel direction and the perpendicular direction, and Rsm and Rz were determined from the average value. The surface roughness profile of the Cu-Sn alloy phase which measured the SEM image of 3000 times magnification along the straight line in FIG. 2 image is shown in FIG. Rsm and Rz were calculated from this profile.

y cut | disconnected the sample after reflow in the rolling parallel direction, and measured and averaged the cross section by measuring 4 points | pieces of 5 viewing angles by 10000 times magnification using the unevenness | corrugation SEM (ERA-8000) made by ELIONIX.

(g) Heat resistance (contact resistance after heating)

As evaluation of heat resistance, the contact resistance after 1000 h heating was measured. In addition, Cu base plating was heated at 145 degreeC, and Cu / Ni base plating was heated at 175 degreeC. Contact resistance, using the Yamazaki Periodical Institute manufactured electrical contact Schmitter CRS-113-Au type, by a four-terminal method, voltage 200 mV, current 10 mA, sliding load 0.49 N, sliding speed 1 mm / min, sliding distance 1 Measured in mm. If the contact resistance after heating is 8 mPa or less, it can use suitably as a normal connector terminal.

(h) Insertion force (kinetic friction coefficient)

As shown in FIG. 5, the plate sample of the Sn plating material was fixed on the sample stage, and the contactor was pressurized by the load W to the Sn plating surface. Next, the movable table was moved in the horizontal direction, and the resistive load F acting on the contactor at this time was measured by a load cell. And the dynamic friction coefficient ((mu)) was computed from (micro | micron | mu) = F / W.

W was 4.9 N and the sliding speed of the contactor (moving speed of the sample stand) was 50 mm / min. Sliding was performed in a direction parallel to the rolling direction of the plate sample. The sliding distance was 100 mm, and the average value of F between these was calculated | required.

The contactor was manufactured as in FIG. 6 using the same Sn plating material as the plate sample. That is, the stainless steel sphere of diameter 7mm was pressed to the sample, and the part which contacts a plate sample was shape | molded in hemispherical shape.

(i) wear resistance

A brass-Sn plating material having a plate thickness of 0.2 mm was prepared. Sn plating is a reflow Sn plating material whose thickness at the time of electrodeposition is Sn = 1.2 micrometer and Cu = 0.6 micrometer, respectively. About this brass-Sn plating material, the elongation (embossing) process of height 0.2mm and radius 0.6mm is performed, and the terminal which provided the hemispherical protrusion was produced. This terminal and Sn plating material of this invention are arrange | positioned as shown in FIG. 5, and the Sn plating material of this invention is reciprocated 150 times at the speed of 5 mm / sec, loading a 300g load on a terminal. While observing the external appearance of the Sn plating material of the present invention after sliding, the maximum depth (μm) of the sliding part was measured using a surface roughness meter (manufactured by Kosaka Research Institute, Surfcoder SE1600). It was judged that good wear resistance was obtained when the maximum depth of the sliding trace was 3 μm or less.

Example:

Cu base plating shown in Table 1 and Ni / Cu base plating shown in Table 2 were implemented.

In Inventive Examples 1-6 of Table 1 and Comparative Examples 9-13, electrodeposition plating thickness was adjusted so that a pure Sn layer might be set to about 0.8 micrometer. Since the reflow heating rate was slow, Comparative Examples 9-13 with the smooth interface of a diffusion layer (Cu-Sn phase) were inferior to abrasion resistance, heat resistance, and insertability with respect to invention examples 1-6. Although Inventive Example 7 and Comparative Example 14 had the same Sn layer thickness, Comparative Example 14 was inferior in heat resistance with respect to contact resistance because the thickness of the diffusion layer (Cu-Sn phase) was thin. Inventive Example 8 and Comparative Example 15 were the same conditions except for the difference in height (y), but Comparative Example 15 was inferior in heat resistance with respect to contact resistance because y was small.

In Inventive Examples 16-21 and Comparative Examples 24-27 of Table 2, electrodeposition plating thickness was adjusted so that a pure Sn layer might be set to about 0.8 micrometer. Since the reflow heating rate was slow, Comparative Examples 24 to 27 having a smooth interface of the diffusion layer (Cu-Sn phase) were inferior in wear resistance, heat resistance, and insertability to Inventive Examples 16 to 21. Although Inventive Example 22 and Comparative Example 28 had the same Sn layer thickness, Comparative Example 28 was slightly inferior in heat resistance with respect to contact resistance because the thickness of the diffusion layer (Cu-Sn phase) was thin. Inventive Example 23 and Comparative Example 29 had the same conditions except for the difference in height (y), but Comparative Example 29 had inferior heat resistance with respect to contact resistance because y was small.

Claims (5)

Electroplating is performed on the surface of the copper alloy bath in the order of base plating and Sn plating, and thereafter, as a plating bath subjected to reflow treatment; in the vertical cross section with respect to the plating surface, the Sn plating outermost surface and the Cu-Sn alloy The altitude difference (y) of the outermost point of the phase is 0.1 to 0.5 µm;
When dissolving and removing a Sn phase and making a Cu-Sn alloy phase appear on the surface, the maximum height Rz of the roughness curve of this Cu-Sn alloy phase is 0.6-1.2 micrometer, and averages the roughness curve of a Cu-Sn alloy phase The length Rsm is 2.0-5.0 micrometers, The copper alloy tin plating tank characterized by the above-mentioned. The method of claim 1,
A copper alloy tin plating bath, wherein Rsm, y, and Rz have the following relationship.
2.0

Rsm / (y + Rz)

4.0 3. The method according to claim 1 or 2,
From the surface to a base material, a plating film is comprised by each layer of a Sn layer, a Cu-Sn alloy layer, and a Cu layer, The thickness of a Sn layer is 0.5-1.5 micrometers, and the thickness of a Cu-Sn alloy layer is 0.6-2.0 micrometers, Cu The thickness of a layer is more than 0 and 0.8 micrometer or less, The copper alloy tin plating tank characterized by the above-mentioned. 3. The method according to claim 1 or 2,
From the surface to a base material, a plating film is comprised by each layer of a Sn layer, a Cu-Sn layer, and a Ni layer, the thickness of a Sn layer is 0.5-1.5 micrometers, and the thickness of a Cu-Sn alloy layer is 0.6-2.0 micrometers, Ni layer The copper alloy tin plating bath characterized by the thickness of 0.1-0.8 micrometer. 3. The method according to claim 1 or 2,
The plating film is comprised by each layer of a Sn layer and a Cu-Sn alloy layer from the surface to a base material, The thickness of a Sn layer is 0.5-1.5 micrometers and the thickness of a Cu-Sn alloy layer is 0.6-2.0 micrometers, It is characterized by the above-mentioned. Copper alloy tin plating bath.

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