JP2010215979A - Sn-COATED COPPER OR COPPER ALLOY, AND MANUFACTURING METHOD THEREFOR - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Sn-coated copper or copper alloy which is superior in such heat resistance as to be useful for suppressing the increase of a contact resistance value and suppressing a color change after having been left in a high-temperature environment, and has the surface with a small friction coefficient, and to provide a method for efficiently manufacturing the Sn-coated copper or copper alloy, which can make use of a normally-used surface treatment facility as in the state prior to reflow treatment, and does not newly need to invest in a facility, purchase a reagent and expense a cost for a liquid control because of using water usually used in a plant and needing no process of liquid draining and drying. <P>SOLUTION: The Sn-coated copper or copper alloy has the outermost surface which contains such oxygen atoms (O) that when the existing form of the oxygen atoms (O) is analyzed with ESCA (X-ray electron spectroscopy for chemical analysis), the top of the peak of the binding energy of the 1s orbit is 531-532 eV, and has an Sn layer thereon of which the thickness is 0.05 μm or more but less than 0.4 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a Sn-coated copper excellent in heat resistance and low insertion force suitable as a control board, connector, lead frame, relay, terminal used for a consumer device such as a car, a mobile phone, a personal computer, or a switch, or a bus bar material. The present invention relates to a method for producing a copper alloy and Sn-coated copper or copper alloy.

  Conventionally, copper or copper alloys used for automobile terminals, consumer terminals, bus bar materials, and the like have been coated with Sn from the viewpoints of contact reliability, corrosion resistance, solderability, and economy. As such a Sn coating method, electroplating is the mainstream, and immediately after electroplating, a reflow process (Sn melting process) effective in removing internal stress and suppressing whisker generation is generally performed. Is.

  When the reflow treatment is performed after Sn plating, a material, a base component, and a diffusion layer are partially formed, and a Sn layer having a soft melt-solidified structure is formed thereon, and an Sn oxide layer is formed on the outermost surface. It is formed. When the Sn layer is thick, when it is actually used as a terminal or the like including a fitting portion, the soft Sn layer is scraped, the insertion force is increased, and a problem is imposed on the operator. In order to solve this problem, a method of increasing the amount of heat of reflow to grow a diffusion layer with a material and a base component and reducing the thickness of the Sn layer can be considered. The layer grows and defects such as increased contact resistance and yellowing occur.

  For example, (1) strict atmosphere control in the reflow furnace, (2) materials washed with water after Sn plating, phosphoric acid compound, carboxylic acid, sulfuric acid. , Surface modification by immersion or spraying in a solution containing hydrochloric acid, acid-based Sn plating solution (sulfuric acid-based, sulfamic acid-based, etc.), zinc sulfate, etc. at a predetermined concentration, followed by reflow treatment Techniques have been proposed (see Patent Documents 1 to 6). The means (1) is disadvantageous in terms of initial cost and management, and the means (2) basically reduces Sn oxide and hydroxide after Sn plating before reflow treatment, A thin Sn oxide film or another oxide (such as zinc oxide) film is formed after the reflow treatment.

  In addition, the reflow pretreatment increases the cost because it requires chemicals and the concentration range is limited, increasing the load on the management surface. Also, if the concentration adjustment fails, the appearance is not obvious immediately after the reflow treatment, but it is used as a terminal due to changes over time due to surface residue (such as residual sulfur when using sulfuric acid chemicals). There may be problems such as partial discoloration / corrosion and increased contact resistance. Furthermore, many of the above-mentioned prior art documents require a water washing step and a drying step after the solution adheres, and there is a problem that the step becomes long and the management side is increased.

JP-A-63-250491 JP 2005-139503 A JP 2008-248332 A JP 2007-56286 A JP-A-5-9785 JP-A-6-10184

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention is Sn-coated copper or copper alloy having excellent heat resistance such as suppression of increase in contact resistance and suppression of discoloration after being left in a high temperature environment, and a small surface friction coefficient, and a reflow treatment that is normally used. The previous surface treatment equipment can be used as it is, and the cost of new equipment investment, reagent purchase, and liquid management is eliminated because it does not require liquid draining and drying processes using water normally used in the factory. It aims at providing the manufacturing method of efficient Sn covering copper or copper alloy which does not start.

Means for solving the problems are as follows. That is,
<1> When the presence state of oxygen atoms (O) existing on the outermost surface is analyzed by ESCA (X-ray photoelectron spectrometer), the top of the binding energy peak of the 1s orbital of oxygen atoms (O) is 531 eV or more and 532 eV. The Sn-coated copper or copper alloy is characterized in that the Sn layer has a thickness of 0.05 μm or more and less than 0.4 μm.
<2> The Sn-coated copper or copper alloy according to <1>, wherein oxygen atoms are present in a range of 15 nm or less from the outermost surface in the depth direction.
<3> The Sn-coated copper or copper alloy according to any one of <1> to <2>, wherein the presence form of oxygen atoms (O) present on the outermost surface is a form of Sn hydroxide.
<4> The Sn-coated copper or copper alloy according to any one of <1> to <3>, wherein the Sn layer has a thickness of 0.05 μm to 0.3 μm.
<5> The Sn-coated copper or copper alloy according to any one of <1> to <4>, wherein a Cu—Sn diffusion layer having a thickness of 0.3 μm to 1.5 μm is provided inside the Sn layer.
<6> The Sn-coated copper or copper alloy according to any one of <1> to <4>, wherein a Ni—Sn diffusion layer having a thickness of 0.1 μm to 1.0 μm is provided inside the Sn layer.
<7> The Sn-coated copper or copper alloy according to any one of <1> to <6>, wherein the structure of the Sn layer is a melt-solidified structure.
<8> The Sn-coated copper or copper alloy according to any one of <1> to <7>, wherein the surface friction coefficient is 0.3 or less.
<9> After coating an Sn layer having a thickness of 0.1 μm to 1.2 μm on copper or a copper alloy by electroplating, the Sn layer surface has an electric conductivity of 600 μS / cm or less and a pH of 4.5 to 9.5. This is a method for producing Sn-coated copper or a copper alloy, characterized in that a reflow treatment is performed without drying the applied water.
<10> The Sn-coated copper or copper alloy according to <9>, wherein a Ni and / or Cu underlayer having a thickness of 0.1 μm to 1.0 μm is coated before the Sn layer is coated on copper or a copper alloy. It is a manufacturing method.
<11> The method for producing an Sn-coated copper or copper alloy according to any one of <9> to <10>, wherein an applied amount of water is 1 mg / dm ² or more.
<12> The method for producing Sn-coated copper or copper alloy according to any one of <9> to <11>, wherein the temperature increase rate of the material to be reflowed during the reflow treatment is 10 ° C./s or more.
<13> An electrical / electronic component using the Sn-coated copper or copper alloy according to any one of <1> to <8>.

  According to the present invention, various problems in the prior art can be solved, excellent in heat resistance such as contact resistance value increase suppression and discoloration suppression after being left in a high temperature environment, and Sn-coated copper or copper alloy having a small surface friction coefficient, and The surface treatment equipment that is normally used before reflow treatment can be used as it is, and water that is usually used in the factory is not required, so there is no need for liquid draining and drying. It is possible to provide an efficient method for producing Sn-coated copper or copper alloy that does not require the cost of purchase and liquid management.

(Sn coated copper or copper alloy)
The Sn-coated copper or copper alloy of the present invention is obtained by coating copper or a copper alloy with an Sn layer, and further having other layers as necessary.

In the present invention, when the presence state of the oxygen atom (O) existing on the outermost surface is analyzed by ESCA (X-ray photoelectron spectrometer), the peak of the binding energy of the 1s orbit of the oxygen atom (O) is 531 eV or more and 532 eV. It is below. Thereby, it turns out that it exists in the form of Sn hydroxide on the outermost surface.
The existence form of oxygen atoms on the outermost surface can be examined using ESCA analysis (X-ray photoelectron spectroscopy). For example, using an X-ray photoelectron spectrometer (ESCA5800 manufactured by ULVAC-PHI Co., Ltd.), qualitative analysis (analysis from the surface to a depth of tens of nm), state analysis (analysis from the surface to a depth of tens of nm) From the result of analysis in the depth direction (depth is converted to SiO ₂ ), it can be determined whether it is an oxide or a hydroxide.
That is, the depth direction analysis is used to measure how far oxygen atoms are present in the depth direction from the outermost layer. Since oxygen atoms cannot be determined to be either oxides or hydroxides as they are, surface state analysis is also performed, and the peak of the bond energy of the 1s orbital of oxygen atoms (O) is 531 eV or more and 532 eV or less It can be determined that hydroxide exists. Similarly, when the top of the 1s orbital bond energy peak of the oxygen atom (O) is less than 531 eV, it can be determined as an oxide. Since the metal element present on the surface is Sn, Sn hydroxide is determined to be a hydroxide at the top of the above peak of the binding energy of oxygen, and Sn oxide is determined to be an oxide. It is determined that it exists.
When the peak of the bond energy of the oxygen atom (O) in the 1s orbital exists at 531 eV or more and 532 eV or less (hydroxide), an increase in the contact resistance value can be suppressed. Furthermore, it seems to be effective in avoiding surface discoloration.
The oxygen atoms are preferably present within a range of 15 nm or less in the depth direction from the outermost surface, and more preferably within 10 nm. If the oxygen atoms are present in a depth direction exceeding 15 nm from the outermost surface, the contact resistance value may increase, and the energization function of the used product may be impaired.

The presence form of oxygen atoms (O) present on the outermost surface is preferably a Sn hydroxide form from the viewpoint of suppressing the growth of oxide films when used as a product such as a terminal. The form of the hydroxide of said Sn, for example, _Sn (OH) 2, etc. Sn _{(OH) 4} can be mentioned.

It is preferable from the viewpoint of whisker suppression that the structure of the Sn layer is a melt-solidified structure formed by a reflow process after Sn coating.
Here, the Sn layer means a layer that is substantially composed only of Sn and does not include Sn oxide, Sn hydroxide and Cu—Sn, Ni—Sn compound layer. It can be distinguished by a formula film thickness meter, SIM (scanning ion microscope) or the like.
That the structure of the Sn layer is a melt-solidified structure can be determined from the fact that crystal grain boundaries are hardly observed by cross-sectional SEM observation (magnification: 5,000 to 10,000 times). In other words, when the structure of the Sn layer is a melt-solidified structure, the average crystal grain size according to the cross-sectional SEM observation is 5 μm or more. On the other hand, the average crystal grain size of the Sn layer of the electrodeposited structure by electroplating or the like (not subjected to reflow treatment) is 0.1 μm to 3 μm and can be clearly distinguished. The crystal grain size was measured by a cutting method.

Examples of the Sn-coated copper or copper alloy include a strip material and a wire material subjected to Sn plating on the outermost layer; a strip material after pressing, and a terminal material subjected to Sn plating on the outermost layer after press punching and the like. .
There is no restriction | limiting in particular as said copper or copper alloy, According to the objective, it can select suitably, For example, Cu type | system | groups, such as pure copper (C1020, C1100) and phosphorus deoxidized copper (C1220); C2600, C2680, etc.), Cu-Zn series such as brass containing Sn (C44250, etc.); Phosphor bronze series (C5110, C5191, C5210, C5240, etc.), Cu-Ni-Sn-P series (C19020, C19020, C19025, etc.) Cu-Ni-Si (C7025, C64745, etc.), Cu-Fe (C194, C19220, C19010, C19720, etc.), and the like. Note that the present invention can also be applied to a copper alloy of other composition system, Fe—Ni system, pure Ni system, stainless steel, and Al system, when the outermost layer is subjected to reflow treatment after Sn plating.

The film to be coated with copper or a copper alloy may be finished with Sn at the outermost surface, and the base is simply Sn from the viewpoints of strengthening adhesion, suppressing whisker by suppressing diffusion of material components, and improving heat resistance. In addition to layer coating, a Cu underlayer or a Ni underlayer can be provided. As a means for further improving the heat resistance, it is preferable to coat Ni, Cu, and Sn in this order.
Examples of the method for coating the Sn layer include electroplating, electroless plating, melt dipping, vapor deposition, and sputtering. Among these, electroplating is particularly preferable because of excellent thickness control and cost advantages. Moreover, the same effect is acquired even if it contains Ag, Pb, etc. in 0-10 mass% in Sn plating.

  The thickness of the Sn layer is 0.05 μm or more and less than 0.4 μm, preferably 0.05 μm to 0.3 μm. If the thickness of the Sn layer is less than 0.05 μm, desired characteristics such as a friction coefficient, appearance, and contact resistance may not be obtained. If the thickness is 0.4 μm or more, the terminal insertion force increases, Plating productivity may be reduced.

It is preferable to have a Cu—Sn diffusion layer having a thickness of 0.3 μm to 1.5 μm inside the Sn layer, and more preferably 0.4 μm to 1.5 μm. If the thickness is less than 0.3 μm, it is not sufficient to suppress the diffusion of the base and material components inside the diffusion layer. If the thickness exceeds 1.5 μm, the diffusion layer is hard, and thus to the terminals. It may become a starting point of cracking during molding. If the thickness is 1.5 μm or less, bending workability is improved, which is preferable for applications requiring bending work such as electrical / electronic parts such as connector terminals.
Examples of the Cu—Sn diffusion layer include a layer made of Cu ₆ Sn ₅ .

It is preferable to have a Ni—Sn diffusion layer having a thickness of 0.1 μm to 1.0 μm inside the Sn layer, and more preferably 0.2 μm to 1.0 μm. If the thickness is less than 0.1 μm, it is not sufficient to suppress the diffusion of the base or material components inside the diffusion layer. If the thickness exceeds 1.0 μm, the diffusion layer is hard, and thus to the terminal or the like. It may become a starting point of cracking during molding. If the thickness is 1.0 μm or less, bending workability is improved, which is preferable for applications requiring bending work such as electrical / electronic parts such as connector terminals.
Examples of the Ni—Sn diffusion layer include a layer made of Ni ₃ Sn ₄ .

  It is preferable to have a Ni layer having a thickness of 0.1 μm to 1.0 μm inside the Sn layer, and more preferably 0.2 μm to 0.7 μm. If the thickness is less than 0.1 μm, it is not sufficient to suppress the diffusion of the foundation and material components inside the Ni layer, and if it exceeds 1.0 μm, the Ni layer is hard, so that the terminals and the like It may become a starting point of cracking during molding. In addition, if the said thickness is 0.7 micrometer or less, since a bending workability will improve, it is preferable for the use which requires a bending process like electrical / electronic components, such as a connector terminal.

The thicknesses of the Sn layer, the Cu—Sn diffusion layer, and the Cu layer can be measured using, for example, an electrolytic film thickness meter (manufactured by Chuo Seisakusho, THICKNESS TESTER TH11).
The thickness of the Ni layer and the Ni—Sn layer is determined by exposing the cross section of the plating using, for example, FIB (focused ion beam), and observing the cross section with a SIM (scanning ion microscope). The thickness can be measured.
(1) From the surface to the Sn layer, the Cu—Sn layer, and the material (copper or copper alloy), (2) From the surface to the Sn layer, the Cu—Sn layer, the Ni layer, and the material, or (3 ) It is preferable that the structure is in the order of Sn layer, Ni-Sn layer, Ni layer, and material from the surface.
In the case of (2), the Sn layer is 0.2 μm or more and less than 0.4 μm, the Cu—Sn layer is 0.4 to 0.7 μm, and the Ni layer is 0.1 to 0.6 μm. From the viewpoint of cost.

The Sn-coated copper or copper alloy of the present invention preferably has a surface friction coefficient of 0.3 or less. When the coefficient of friction exceeds 0.3, the insertion force of the terminal increases, the burden on the connector mounting operator increases, and an auxiliary lever may need to be attached to the connector. May be a problem.
The friction coefficient is a substitute evaluation of the insertion force by measuring the friction coefficient because the insertion force when fitting the female terminal and the male terminal is correlated with the friction coefficient of the surface when the terminal contact pressure is constant. be able to. The terminal side is assumed to be the terminal side where the indent of R = 3 mm is formed using a desktop press machine, and the flat plate is the terminal side. In measuring the friction coefficient, a device combining an electrical contact simulator, stage controller, load cell, and load cell amplifier manufactured by Yamazaki Seiki Laboratories Co., Ltd. is used. The load is 300 gf on the flat plate fixed to the stage, and the sliding speed is 60 mm / Friction coefficient is calculated by scanning the indent forming plate for 5 mm at min and dividing the average value of the sliding force data detected by the load cell amplifier in the 3 mm section from the sliding distance of 2 mm to 5 mm by the load. be able to.

(Method for producing Sn-coated copper or copper alloy)
In the method for producing a Sn-coated copper or copper alloy of the present invention, a Sn layer having a thickness of 0.1 μm to 1.2 μm is coated on the copper or copper alloy by electroplating, and then the electric conductivity of the Sn layer is 600 μS / cm or less. The reflow treatment is performed without drying the applied water. If the thickness of the Sn layer is less than 0.1 μm, characteristics such as desired appearance and contact resistance may not be obtained after the reflow treatment. If the thickness exceeds 1.2 μm, the Sn coating of the present invention after the reflow treatment may not be obtained. When copper or copper alloy is processed into, for example, a connector terminal, the insertion / removal property of the terminal is lowered, the productivity of plating is reduced, the raw material cost is increased, and the cost may be increased. The thickness of the Sn plating layer is more preferably 0.2 μm to 1.0 μm, and still more preferably 0.3 μm to 1.0 μm.

First, before the Sn layer is coated on the surface of copper or copper alloy, a base layer of Ni and / or Cu (that is, at least one of Ni and Cu) having a thickness of 0.1 μm to 1.0 μm may be coated. Preferably, if the thickness is 0.1 μm or more, it is possible to suppress diffusion of components such as Cu, Zn, etc. in the material to the surface layer when heated such as reflow treatment, that is, in terms of improving heat resistance. preferable. The Ni and / or Cu underlayer is more preferably 0.2 μm to 1.0 μm in thickness, and more preferably 0.2 μm to 0.6 μm.
The underlayer of Ni and / or Cu is not particularly limited and can be appropriately selected according to the purpose. However, coating by electroplating has sufficient characteristics even after reflow treatment, and is inexpensive. Since it can form, it is preferable. When both Ni and Cu are used as a base layer, it is preferable to coat Ni, Cu, and Sn in this order from the material side.
The Ni plating is performed, for example, as a double salt bath, a normal bath, a rotating bath, a high sulfate bath, a watt bath, a total chloride bath, a sulfate-chloride bath, a total sulfate bath, a high quality bath, a strike nickel bath, or a sulfamine. It is preferably carried out in a bath such as a nickel acid bath or a nickel borofluoride bath.
The Cu plating is preferably performed in a bath such as a copper sulfate bath, a copper borofluoride bath, a copper cyanide bath, or a copper pyrophosphate bath.
In addition, although it is not necessary to add a brightener to each plating bath, it is preferable from the point of suppression of discoloration that a brightener is not added.
The thickness of each plating can be adjusted by the electrodeposition time.

Next, an Sn layer having a thickness of 0.1 μm to 1.2 μm (preferably 0.2 μm to 1.0 μm) is coated by electroplating.
The Sn plating is preferably performed in a bath such as an alkaline bath, a sulfuric acid bath, a hydrochloric acid bath, a sulfonic acid bath, a cyanic bath, a pyrophosphoric acid bath, or a fluorinated bath.
As described above, the plating of Ni and Cu may be omitted depending on the target characteristics.

Next, water having an electric conductivity of 600 μS / cm or less is applied to the surface of the Sn plating layer, and the applied water is put into a reflow furnace without drying and reflow treatment (melting and solidification treatment of the Sn coating layer or the like by heating). I do.
Preferably the applied amount of water applied before reflow treatment Sn layer surface is 1 mg / dm ² or ^more, more preferably ^{3mg / dm 2 ~300mg / dm 2} , 3mg / dm 2 ~100mg / dm more preferably ^2, and particularly preferably ^{3mg / dm 2 ~50mg / dm 2} . When the applied amount of water is less than 1 mg / dm ^2, it is likely to be overheated as in the case of dried and reflow-treated, and there is no hydroxide on the surface of Sn, and only the surface of the oxide Thus, desired characteristics cannot be obtained. However, if it exceeds 300 mg / dm ² , a hydroxide is produced, but the heat required for melting by the heat of vaporization is lost and the productivity is lowered.
As described above, the Sn plating layer changes from an electrodeposition (electrodeposition) structure to a melt-solidified structure by the reflow process.

The water is preferably water having an electric conductivity of 600 μS / cm or less in order to prevent impurities from remaining on the surface after reflow treatment and causing discoloration or corrosion. Water having a high electric conductivity exceeding 600 μS / cm has a large amount of impurities such as metal elements and may cause discoloration. The electrical conductivity is more preferably 300 μS / cm or less.
The pH of the water is preferably 4.5 to 9.5 in order to suppress corrosion of Sn on the acidic side and the alkaline side, since Sn is an amphoteric metal. If the pH is less than 4.5 (acidic) or exceeds 9.5 (alkaline), corrosion of the surface of the Sn layer, which is an amphoteric metal, occurs when water adheres, and unevenness occurs in the appearance of the Sn layer after reflow treatment. . From the above, city water (tap water, industrial water, etc.) as well as pure water can be applied to the present invention.

The water application method is not particularly limited and may be appropriately selected depending on the purpose. For example, immersion in a water tank, spraying with a spray, contact with a roll containing water, contact with a material such as a roll surface, etc. For example, contact with a sheet of water-absorbing cloth or paper wound around the portion, and the thickness of the water film may be controlled according to the amount of each. The formation of this water film does not require electrodeposition or chemical reaction of reagents, so that the time required for the treatment is not burdened.
After forming the water film, a squeeze roll and a dry blower may be used as necessary. However, it is important to shift to a reflow process while a predetermined water film is formed on the surface of the Sn plating layer. The mechanism that suppresses yellowing of the surface by the water film is presumed to be that when the surface of the Sn plating layer is heated, it becomes a hydroxide film and the surface oxidation can be suppressed.

There is no restriction | limiting in particular as the heating method of the said reflow process, According to the objective, it can select suitably, For example, a hot-air circulation system, infrared rays, an electric heater, a burner direct flame, etc. are mentioned.
More preferably, the temperature of the material to be reflowed during the reflow treatment is 10 ° C./s or more at a temperature increase rate from room temperature to a melting point of Sn exceeding 232 ° C. When the heating rate is less than 10 ° C./s, the surface water film is dried before the effect is exerted, and after the reflow treatment, no hydroxide remains on the surface of the Sn plating layer. Covered with yellow and causes yellowing. In addition, the effect of the present invention can be exerted even in the reflow treatment in the atmosphere, and the effect of the present invention can be exhibited regardless of the atmosphere. This is also effective in reducing the atmospheric gas and the management cost. .

  Reflow treatment sets the maximum temperature (material temperature) to a predetermined temperature (240 to 300 ° C), and after the Sn layer melts, cools it to 100 ° C or less within 10 seconds to suppress generation of surface cooling flaws. It is preferable to do. There is no restriction | limiting in particular as said cooling method, According to the objective, it can select suitably, For example, spraying of atmospheric gas or air | atmosphere, the immersion to a 10 degreeC-90 degreeC water tank etc. are mentioned.

  The Sn-coated copper or copper alloy of the present invention is suitable as an electrical / electronic component such as a terminal used for a control board, a connector, a lead frame, a relay, a switch or the like of a car, a mobile phone, a personal computer, or a bus bar material.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
As a material, copper alloy C19025 (Cu-1.0Ni-0.9Sn-0.05P (mass%)) widely used as a connector terminal or bus bar material, having a Vickers hardness of 170 (Mitutoyo Co., Ltd.) , Measured with a load of 200 gf) and a surface roughness (Ra) in the range of 0.13 μm (manufactured by Kosaka Laboratories Ltd., contact surface roughness meter), and a plate-like member having a thickness of 0.2 mm is used. did.

The plate-like member is electrolytically degreased and then Sn-plated as follows. The surface of the obtained Sn layer is sprayed using a quick fogger manufactured by Spraying Systems Japan Co., Ltd., and sprayed to form a 10 mg / dm ² water film. After forming, the reflow process was performed as follows. As described above, the Sn-coated copper or copper alloy product of Example 1 was produced.
The amount of water film formed on the surface of the Sn layer was determined by weighing the mass of the plate member with an electronic balance before and after spraying and dividing the difference by the surface area of the plate member (Sn layer).

-Sn plating-
The Sn plating uses a bath to which 55 g / L of sulfuric acid, 80 g / L of sulfuric acid, 40 g / L of cresol sulfonic acid, and 1 g / L of β-naphthol are added, and the bath temperature is 20 ° C. and the cathode current density is 3 A / dm ^2. An electroplating layer of Sn having a thickness of 0.3 μm was formed on the entire surface of the plate member.

-Reflow processing-
The reflow treatment was performed in an air atmosphere using a near-infrared heater (manufactured by Highbeck). The temperature increase rate was adjusted by conducting a preliminary test with a Sn-plated test piece (without surface water application) to which a thermocouple was attached, and controlling a near infrared output controller. The rate of temperature increase was 60 ° C./s, and the maximum temperature reached was controlled such that the temperature of the test piece was 280 ° C. to melt Sn. For the cooling after the reflow treatment, a method of immersing in a water bath at 40 ° C. within 5 seconds after melting of Sn was adopted. After cooling to 100 ° C. or less within 10 seconds after melting, blower drying was performed.

(Examples 2 to 10 and Comparative Examples 1 to 5)
In Example 1, as shown in Table 1, the thickness of the Sn layer, the type and thickness of the underlayer, the amount of water applied, the electrical conductivity and pH, the rate of temperature increase during the reflow treatment, and the maximum reflow treatment Products of Examples 2 to 10 and Comparative Examples 1 to 5 were produced in the same manner as Example 1 except that the temperature reached was changed.
Cu undercoat before Sn plating, Ni undercoat, or Cu undercoat over Ni undercoat was formed as follows.
-Cu plating-
For Cu plating, a bath to which 200 g / L of copper sulfate and 50 g / L of sulfuric acid were added was used, the bath temperature was 30 ° C., the cathode current density was 3 A / dm ^2, and a Cu electroplating layer with a predetermined thickness was formed into a plate shape It was formed on the entire surface of the member.
-Ni plating-
Ni plating uses a bath to which 450 g / L of nickel sulfamate, a slight amount of nickel chloride, and 30 g / L of boric acid are added, pH 4.0, bath temperature 50 ° C., cathode current density 5 A / dm ² , and a predetermined thickness. A nickel electroplating layer was formed on the entire surface of the plate-like member. The thickness of each plating was adjusted by the electrodeposition time.

  Next, about each obtained product, the measurement of the thickness of each layer and various evaluation tests were done as follows. The results are shown in Table 1.

<Thickness of each layer after reflow treatment>
The thickness of each layer after the reflow treatment was measured as follows.
-The thickness of Sn layer, Cu-Sn diffused layer, and Cu layer was measured using the electrolytic film thickness meter (Chuo Seisakusho make, THICKNESS TESTER TH11).
The thickness of the Ni layer and the Ni—Sn diffusion layer was measured by exposing the cross section of the plating using FIB (focused ion beam) and observing the cross section with a SIM (scanning ion microscope).

<Determination of presence or absence of Sn oxide layer or Sn hydroxide layer (presence or absence of hydroxide), measurement of thickness of Sn oxide layer or Sn hydroxide layer>
Determination of the presence or absence of Sn oxide layer or Sn hydroxide layer (presence or absence of hydroxide) and the thickness of Sn oxide layer or Sn hydroxide layer were performed using ESCA5800 manufactured by ULVAC-PHI Co., Ltd. .
For the presence or absence of Sn oxide layer or Sn hydroxide layer (presence or absence of hydroxide), after confirming the presence of oxygen atoms by qualitative analysis, state analysis of binding energy of 1s orbital of oxygen atoms (O) is performed. Determined by doing. Conditions for analyzing the state of the bond energy of the 1s orbital of the oxygen atom (O) are as follows.
-X-ray source: Al anode source (Al monochrome X-ray), 150 W
・ Analysis area: Diameter 800μm
・ Sample preparation: Set on the sample holder ・ Photoelectron extraction angle: 45 °
・ Pass energy: 58.70eV
・ Measurement time: 6.75 min
The surface of the Sn layer (sample) was measured under these conditions, and the top of the peak of the binding energy of the 1s orbital of O is shown from the graph in which the horizontal axis represents the binding energy and the vertical axis represents the photoelectron count number c / s (count second). It was determined whether or not (the portion where the photoelectron count c / s is maximum, the maximum value of the peak) is 531 eV or more and 532 eV or less. It was determined that a hydroxide was present when the top of the bond energy peak of the 1s orbital of the oxygen atom (O) was 531 eV or more and 532 eV or less. Similarly, when the top of the peak of the binding energy was less than 531 eV, it was determined as an oxide. In addition, it can be more reliably determined that it is 531.2 eV to 532 eV.
The thicknesses of the Sn oxide layer and Sn hydroxide layer are as follows: X-ray source is Al anode source, 150 W, analysis area diameter is 800 μm, sample is set on sample holder, photoelectron extraction angle is 45 °, Ar sputter etching The speed was 10 nm / min (SiO ₂ conversion). The depth was measured by the depth direction analysis to determine how many oxygen atoms exist in the depth direction from the outermost layer.

<Accelerated discoloration test>
The sample was left in a thermostatic chamber (atmosphere) maintained at 180 ° C. for 1 hour to determine whether yellowing occurred. When the thickness of the Sn oxide layer increases, yellowing occurs. Even if there is no discoloration in the initial state, if yellow discoloration occurs in this test, the discoloration occurs during long-term storage such as 6 months at room temperature.
〔Evaluation criteria〕
○: Yellow discoloration did not occur in the accelerated discoloration test ×: Yellow discoloration occurred

<Measurement of contact resistance value after standing at high temperature>
After holding for 0 hours (no high temperature), 500 hours, and 1000 hours in a constant temperature bath (atmosphere) held at 120 ° C., remove from the constant temperature bath and measure the contact resistance value of the surface in a measurement chamber controlled at 20 ° C. It was measured. The contact resistance value is a micro ohmmeter YMR-3 manufactured by Yamazaki Seiki Laboratory Co., Ltd., open voltage 20 mV, current 10 mA, U-shaped wire probe with a diameter of 0.5 mm, maximum load 100 gf, no sliding condition The number of tests (N = 5) was measured and the average value was obtained.
The contact resistance value (mΩ) after holding for 1000 hours is preferably 40 mΩ or less, more preferably 30 mΩ or less.

<180 ° adhesion bending test>
A test piece having a width of 10 mm and a length of 40 mm is cut out from the product after the reflow treatment, bent at the center, applied with a load of 10 kN using a compression tester and held for 5 seconds. Was observed at a magnification of 100, and the presence or absence of cracks was observed and evaluated according to the following criteria.
〔Evaluation criteria〕
○: No crack ×: Crack occurred

<Friction coefficient>
Since the insertion force when the female terminal and the male terminal are fitted has a correlation with the surface friction coefficient when the terminal contact pressure is constant, the friction coefficient was measured and used as a substitute evaluation of the insertion force. Assuming that the terminal side is the one on which a plate on which an indent of R = 3 mm is formed using a desktop press machine, the terminal side is a flat plate. For measuring the friction coefficient, use a device that combines an electrical contact simulator, stage controller, load cell, and load cell amplifier manufactured by Yamazaki Seiki Research Co., Ltd., and the indent of the indent forming plate on the flat plate fixed to the stage is 300 gf. The friction coefficient is obtained by dividing the average value of the sliding force data detected by the load cell amplifier in the 3 mm section from the sliding distance of 2 mm to 5 mm by the load load by scanning 5 mm at a sliding speed of 60 mm / min. Calculated.

<Melt solidification structure>
SEM observation of the cross section of the Sn layer (magnification of 5,000 times) hardly observed the crystal grain boundaries, and when the average crystal grain size was 5 μm or more, it was judged as a melt-solidified structure. The average grain size of the Sn layer before reflow treatment (after electroplating) was 0.1 to 3 μm. The crystal grain size was measured by the cutting method of JIS H0501.
〔Evaluation criteria〕
○: After the reflow treatment, it is a melt-solidified structure. ×: After the reflow treatment, it is not a melt-solidified structure.

From the results of Table 1, in Examples 1 to 10, the electroplated Sn layer has a thickness of 0.1 to 1.1 μm, and Ni and / or Cu underplating is the thickness. Is in the range of 0.1 μm to 0.5 μm. When the thickness of each layer was measured after the reflow treatment, the Sn layer was in the range of 0.1 μm to 0.3 μm, the Cu—Sn layer was in the range of 0.4 μm to 1.4 μm, and the Ni—Sn layer was 0.00. It was confirmed that the Ni layer was 2 to 0.9 μm, the Ni layer was 0.1 to 0.2 μm, and the Sn layer was a melt-solidified structure.
Moreover, all the temperature increase rates of the reflow process were 10 degrees C / s or more.
When the surface of the Sn layer after the reflow treatment is analyzed by ESCA, the peak top exists between 531.2 eV and 532 eV in the state analysis of the binding energy of the 1s orbital of the oxygen atom (O), and the presence of hydroxide exists. As a result, the appearance was not yellow discolored and the increase in the contact resistance was small. The result of the 180 ° bending test was good, and the friction coefficient was 0.3 or less.

In Comparative Example 1, the thickness of the electroplated Sn layer was 1.6 μm, and after reflow treatment, the Sn layer had a thickness of 0.9 μm and the Cu—Sn layer had a thickness of 0.9 μm. In other words, the Sn layer was confirmed to be a melt-solidified structure. Moreover, the temperature increase rate of the reflow process was 20 ° C./s. The coefficient of friction was 0.45.
In Comparative Example 2, the thickness of the electroplated Sn layer was 0.7 μm, and after reflow treatment, the Sn layer had a thickness of 0.55 μm and the Cu—Sn layer had a thickness of 0.45 μm. In other words, the Sn layer was confirmed to be a melt-solidified structure. Moreover, the temperature increase rate of the reflow process was 5 ° C./s. The coefficient of friction was 0.35.
In Comparative Examples 1 and 2, when the surface of the Sn layer after the reflow treatment was analyzed, the presence of hydroxide was not observed, and an increase in the contact resistance value after 1,000 hours was observed.
In Comparative Example 1, the amount of water applied to the Sn layer surface before the reflow treatment was 0 mg / dm ² , and no hydroxide was generated on the Sn layer surface after the reflow treatment.
In Comparative Example 2, the temperature increase rate was less than 10 ° C./s, the water applied to the surface during temperature increase was dry, and no hydroxide was formed on the Sn layer surface after the reflow treatment. It is thought that occurred.
In Comparative Examples 3 to 5, when the surface of the Sn layer after the reflow treatment was analyzed, the presence of hydroxide was not recognized, and the contact resistance value after holding at 120 ° C. for 1000 hours exceeded 40 mΩ, The appearance was yellow.
In Comparative Example 3, since water was not applied to the surface before reflowing, it was considered that no hydroxide was formed, the contact resistance value deteriorated, and the appearance became yellow.
In Comparative Example 4, it was considered that the pH of the applied water was 13, and the alkali was so strong that no hydroxide was generated, the contact resistance value was deteriorated, and the appearance became yellow.
In Comparative Example 5, the electrical conductivity of the applied water was 1000 μS / cm, and because the electrical conductivity was very high, no hydroxide was generated, the contact resistance value was deteriorated, and the appearance turned yellow. Conceivable.

  The Sn-coated copper or copper alloy of the present invention is suitably used for a control board, a connector, a lead frame, a relay, a terminal used for a switch, a bus bar material, etc., for example, for automobiles, mobile phones, personal computers and the like.

Claims (13)

  When the presence form of oxygen atoms (O) existing on the outermost surface is analyzed by ESCA (X-ray photoelectron spectrometer), the top of the peak of the binding energy of the 1s orbit of oxygen atoms (O) is 531 eV or more and 532 eV or less. The Sn-coated copper or copper alloy, wherein the Sn layer has a thickness of 0.05 μm or more and less than 0.4 μm.   The Sn-coated copper or copper alloy according to claim 1, wherein oxygen atoms are present in a range of 15 nm or less in the depth direction from the outermost surface.   The Sn-coated copper or copper alloy according to claim 1, wherein the presence form of oxygen atoms (O) existing on the outermost surface is a form of Sn hydroxide.   The Sn-coated copper or copper alloy according to claim 1, wherein the Sn layer has a thickness of 0.05 μm to 0.3 μm.   5. The Sn-coated copper or copper alloy according to claim 1, further comprising a Cu—Sn diffusion layer having a thickness of 0.3 μm to 1.5 μm inside the Sn layer.   5. The Sn-coated copper or copper alloy according to claim 1, further comprising a Ni—Sn diffusion layer having a thickness of 0.1 μm to 1.0 μm inside the Sn layer.   The Sn-coated copper or copper alloy according to any one of claims 1 to 6, wherein the structure of the Sn layer is a melt-solidified structure.   The Sn-coated copper or copper alloy according to any one of claims 1 to 7, wherein a surface friction coefficient is 0.3 or less.   After a Sn layer having a thickness of 0.1 μm to 1.2 μm is coated on copper or a copper alloy by electroplating, water having an electric conductivity of 600 μS / cm or less and a pH of 4.5 to 9.5 is applied to the surface of the Sn layer. A method for producing Sn-coated copper or a copper alloy, which comprises applying and performing a reflow treatment without drying the applied water.   The method for producing a Sn-coated copper or copper alloy according to claim 9, wherein a Ni and / or Cu underlayer having a thickness of 0.1 to 1.0 µm is coated before the Sn layer is coated on copper or a copper alloy. Application amount of water, a manufacturing method of the Sn-coated copper or a copper alloy according to any of claims 9 10, is 1 mg / dm ² or more.   The method for producing an Sn-coated copper or copper alloy according to any one of claims 9 to 11, wherein the temperature increase rate of the material to be reflowed during the reflow treatment is 10 ° C / s or more.   An electrical / electronic component using the Sn-coated copper or copper alloy according to any one of claims 1 to 8.