JP6324085B2 - Precious metal-coated plate material for electrical contacts and method for producing the same - Google Patents

Description

The present invention for electrical contacts noble metal covering plate material and a method for producing the same. In particular, the noble metal covering plate material for electrical contacts and a method for producing the same.

The noble metal coating plate material for electrical contacts, the electric conductivity superior copper or copper alloy have been conventionally used, progress in the recent improvements of the contact properties, used as a copper or copper alloy casing is reduced Yes. Instead of such conventional materials, various surface-treated materials on copper or copper alloys are manufactured and used. As being especially utilized many as an electrical contact for the precious metal covering plate material, there is a precious metal plated plate material to the electrical contact portion. Among them, noble metals such as gold, silver, palladium, platinum, iridium, rhodium, and ruthenium are used as precious metal-coated plates for various electrical contacts because of their stability and excellent electrical conductivity.

Incidentally, when using a noble metal as the electrical contact for the precious metal cover plate is called in order to prevent the diffusion of the noble metal and the base component, for example, as in Patent Document 1, the lower layer of the noble metal layer and the underlying layer diffusion It is known to introduce a prevention layer (see the document, paragraph [0011]). It is known to use nickel, a nickel alloy, cobalt, a cobalt alloy, or the like as the underlayer.

  However, in recent years, there are many cases where electrical contact materials are used in high temperature environments. For example, a sensor contact material in an engine room of an automobile is likely to be used in a high temperature environment such as 100 ° C. to 200 ° C. For this reason, reliability such as contact characteristics at a temperature higher than the operating temperature assumed in conventional consumer devices is required. In particular, as a cause that affects the reliability of the contact characteristics, there is a problem that the contact resistance of the noble metal portion is increased due to diffusion of the base component and surface oxidation at high temperatures. For this reason, various studies have been made on diffusion suppression and oxidation prevention of the base material component.

  For example, Patent Document 2 describes that the crystal grain size of silver or a silver alloy, which is a noble metal layer formed on the surface layer, is 5 μm or more, thereby reducing the grain boundary and suppressing the diffusion of the base component. It is disclosed that the contact resistance characteristics can be stabilized (see the same document, paragraphs [0006] and [0008]).

  However, the connection reliability in the above-described high-temperature environment may be lowered by simply introducing a base layer below the noble metal layer as in Patent Document 1. In this case, the diffusion rate of the base material component is increased under a high-temperature environment, the diffusion easily proceeds to the surface layer of the noble metal layer, and the contact resistance is easily increased.

  Furthermore, as in Patent Document 2, setting the average crystal grain size of a silver or silver alloy film to 5 μm or more is a technique that can be applied to a metal that tends to recrystallize and have large crystal grains, such as silver. However, other noble metals such as rhodium (Rh) and palladium (Pd) have a high melting point and are difficult to recrystallize, so it was difficult to increase the average crystal grain size to 5 μm or more. Furthermore, when this technology is applied to a nickel layer as a substrate, diffusion of the substrate proceeds before the particle size becomes 5 μm or more, and contact characteristics may be deteriorated by forming an oxide on the surface. is there.

JP 2007-280945 A JP-A-5-002940

The present invention overcomes the above-mentioned problems of the prior art, and suppresses the diffusion of the base component and prevents the surface from reaching the noble metal layer even in a high-temperature environment, particularly after heating at 100 ° C. or higher. It is an object of the present invention to provide a precious metal-coated plate material for electrical contacts that can be reliable for a long time.

As a result of diligent investigation in view of the above problems, there is a noble metal coated plate material for an electrical contact in which a noble metal layer made of a noble metal film is formed on the outermost surface of the conductive metal substrate, and the conductive metal substrate and the noble metal layer It has at least one layer of the underlying layer in between and an average crystal grain size of the electrical contacts for the precious metal covering plate material is 0.3μm or more 4.5μm or less of the underlying layer, the high-temperature heat for a long time It has been found that even when added, the diffusion of the conductive metal base component can be sufficiently prevented and the increase in contact resistance due to oxidation of the diffused base component can be prevented. As a result, it has been found that the thickness of the noble metal layer can be made thinner than before. The present inventors have further studied based on these findings and have come to achieve the present invention.

The above-described problems of the present invention are solved by the following means.
(1) A noble metal-coated plate material for electrical contacts having a noble metal layer on the outermost surface on a conductive metal substrate,
The noble metal layer is composed of any one or more of gold, gold alloy, silver, silver alloy, platinum, platinum alloy, palladium, palladium alloy, rhodium or rhodium alloy,
The noble metal layer has a thickness of 0.001-1.10 μm;
Between the conductive metal substrate and the noble metal layer, has an underlayer consisting of one or more of nickel, nickel alloy, cobalt or cobalt alloy ,
The underlayer has a thickness of 0.010 to 1.10 μm;
The average crystal grain size of the underlayer is Ri der than 4.5μm or less 0.3 [mu] m,
The precious metal-coated plate material for electrical contacts, wherein the contact resistance after holding at 250C for 16 hours is 10 mΩ or less .
(2) The noble metal-coated plate material for electrical contacts according to (1), wherein the conductive metal substrate is made of copper or copper alloy, iron or iron alloy, or aluminum or aluminum alloy .
(3 ) A method for producing a noble metal-coated plate material for electrical contacts according to (1) or (2) , wherein a compound in an additive is used when an underlayer is formed on a conductive metal substrate by electroplating. The total concentration of sulfur, carbon, nitrogen, and chlorine is 1000 ppm or less, and the current density of electroplating when forming the base layer is less than 10 A / dm ^2. A method for producing a precious metal-coated plate material for electrical contacts, characterized by performing a heat treatment at ~ 150 ° C for 0.08 to 3 hours, or rolling at a processing rate of 10% or more.
( 4 ) The current density of electroplating when forming the underlayer is 10 A / dm ² or more,
After forming the said base layer, the heat processing for 0.08 to 3 hours are performed at 50-150 degreeC, or it rolls with a processing rate of 10% or more, Manufacture of the noble metal covering board | plate material for electrical contacts as described in ( 3 ) Method.

According to the present invention, the conductive metal substrate on the outermost surface of the noble metal layer is a noble metal coated plate material for electrical contacts which are coated, it is possible to improve the heat resistance by suppressing the diffusion of substrate components. More specifically, since the average crystal grains of the metal constituting the underlayer have a predetermined size, there are fewer crystal grain boundaries in the underlayer than before, and the diffusion of base material components to the noble metal layer is reduced. can do. Therefore, the diffusion of the base component into the noble metal is suppressed even after holding at a high temperature for a long time of 250 ° C. for 16 hours, for example. Therefore, even when used in a high temperature environment, the conductivity of the outermost layer of the precious metal-coated plate material for electrical contacts is unlikely to deteriorate, and the increase in contact resistance is small. Also, by increasing control of the crystal grain size of the underlayer, the elastic region of the underlying layer is increased, as a result, to provide an electrical contact for the noble metal coating plate material also bending workability is improved thick underlayer Can do.

It described preferred embodiment of the electrical contacts for the precious metal covering plate material and its manufacturing method of the present invention. In addition, the noble metal in this invention has shown the metal seed | species in which a standard electrode electric potential shows a positive (plus) value.

(Electric contacts noble metal coating plate member)
<Conductive metal substrate>
The conductive substrate component used in the present invention is preferably copper or copper alloy, iron or iron alloy, aluminum or aluminum alloy, etc. Among them, copper or copper alloy having good conductivity is preferable. For example, as an example of a copper alloy, “C14410 (Cu-0.15Sn, manufactured by Furukawa Electric Co., Ltd., trade name: EFTEC-3)”, which is a CDA (Copper Development Association) alloy, “C19400 (Cu-Fe series) Alloy material, Cu-2.3Fe-0.03P-0.15Zn) "and" C18045 (Cu-0.3Cr-0.25Sn-0.5Zn, manufactured by Furukawa Electric Co., Ltd., trade name: EFTEC-) 64T) "or the like. (In addition, the unit of the number before each element of the said copper alloy shows the mass% in a copper alloy.). Since these bases have different electrical conductivity and strength, they are selected and used according to the required characteristics as appropriate. From the viewpoint of improving the electrical conductivity and heat dissipation, the strip of copper alloy having an electrical conductivity of 5% IACS or more is used. It is preferable that The “base component” of the present invention when copper or a copper alloy is handled as a metal base means that it is copper as a base metal in the case of an alloy (the same applies to other alloys hereinafter). Is). As iron or iron alloy, for example, 42 alloy (Fe-42 mass% Ni), stainless steel, or the like is used. In this case, the base component indicates iron. Although there is no restriction | limiting in particular in the thickness of a base | substrate, Usually, it is 0.05-2.00 mm, Preferably, it is 0.1-1.0 mm.

<Underlayer>
The metal constituting the base layer in the present invention is not particularly limited as long as it can prevent diffusion of the base component with a predetermined thickness and impart heat resistance. However, easy nickel inexpensive coating, a nickel alloy, cobalt, that such scolded one of cobalt alloy. Underlayers made of these metals or alloys are effective for improving adhesion and preventing diffusion of substrate components. It is sufficient that one or more underlayers are formed. For example, a nickel layer may be formed after forming the copper layer, or a cobalt layer may be formed after forming the nickel layer. However, in consideration of productivity and cost, it is desirable to make it within 3 layers. In addition, when employ | adopting copper as a base layer, it is preferable to form another layer between the copper base layer and the outermost layer which consists of noble metals. This is because it is necessary to prevent copper from coming into direct contact with the noble metal layer because the purpose is to prevent diffusion of the copper component when the substrate is copper or a copper alloy.

In the present invention, the average crystal grain size of the metal in the underlayer is 0.3 μm or more and 4.5 μm or less . The grain size is measured by observing the cross section perpendicular to the plane of the electric contacts noble metal coating plate material. The heat resistance effect is effective when the average crystal grain size of the underlayer is 0.3 μm or more and 4.5 μm or less , more preferably 0.5 μm or more and 4.5 μm or less , and more preferably 0.8 μm or more and 4. Most preferably 5 μm or less . There is no limit on the upper limit, and a single crystal state in which no crystal grain boundary is seen across the plane is the most ideal form. In such an average grain electrical contacts for the precious metal covering plate material that base layer is provided with a diameter, it is possible to suppress the diffusion of the components of the conductive metal substrate, which contributes to preventing deterioration of the noble metal layer.

  Furthermore, in the present invention, the thickness of the underlayer is not particularly limited, but for example, the underlayer is formed with a thickness of 0.001 to 5.000 μm, whereby adhesion and heat resistance can be more effectively improved. Since the bendability tends to deteriorate as the thickness of the underlayer increases, the total thickness of one or more underlayers is at most 5.000 μm, preferably 3.000 μm or less, more preferably 1. It is preferable to form it with 000 micrometers or less. Compared with the conventional product (when the average crystal grain size of the underlayer is smaller than 0.3 μm), the product of the present invention has an improved elastic range for each crystal of the underlayer, so that the bending workability is improved. Therefore, when the coating thickness is the same as the conventional product, bending workability is excellent. The lower limit of the thickness is set to 0.001 μm or more in consideration of the heat resistance improvement effect. Although the conventional underlayer thickness needs to be about 0.200 to 2.000 μm, in the present invention, since the average crystal grain size of the underlayer is coarsened, there are fewer crystal grain boundaries in the underlayer than in the past. The diffusion of the base material component into the noble metal layer can be reduced. Therefore, the thickness of the underlayer can be further reduced. The thickness of the underlayer is preferably from 0.010 to 1.000 μm. Even with this thickness, the diffusion of the base component can be prevented to the same level or higher than that of the conventional product. The underlayer can be formed by a conventional method such as sputtering, vapor deposition, or wet plating. However, in consideration of ease of control of the average crystal grain size and thickness and productivity, the wet plating method is particularly preferable. Is preferably used, and more preferably an electroplating method.

<Precious metal layer>
Further, the noble metal layer to be the outermost layer of the electrical contacts for the precious metal cover plate of the present invention include gold, gold alloy, silver, silver alloy, platinum, platinum alloys, palladium, palladium alloys, rhodium, among rhodium alloy, or A metal layer selected from is used. Since this noble metal layer has a low contact resistance, the connection reliability is good and the outermost layer with good productivity can be obtained. In particular, gold, gold alloy, silver, silver alloy, platinum, platinum alloy, palladium, palladium alloy, rhodium, rhodium alloy are preferable from the viewpoint of stable connection reliability. Gold, gold alloy, silver, silver alloy, palladium, palladium alloy Is even more preferable. Further, two or more noble metal layers may be provided. The noble metal layer can be formed by a normal method such as sputtering, vapor deposition, or wet plating. However, in consideration of controllability of the coating thickness and productivity, it is particularly preferable to use the wet plating method. More preferably, it is a method.

In the present invention, as an effect of introducing a base layer having excellent heat resistance, it acts to suppress the diffusion of the base component to the surface layer at a high temperature even if it is coated thinner than the conventionally coated noble metal layer thickness. Therefore, long-term reliability is excellent. As a result, not only the conventional coating thickness but also the precious metal layer thickness of 0.001 to 0.500 μm, for example, about 2/3 or less of the conventional coating thickness, the reliability equal to or higher than that of the conventional product is obtained, and the cost is low. in can be obtained precious metal covering plate material for electrical contacts environmentally friendly. The thickness of the noble metal layer is appropriately selected depending on the type of noble metal. For example, in gold, gold alloy, platinum, platinum alloy, palladium, palladium alloy, rhodium, rhodium alloy, preferably 0.05 to 1.0 μm. More preferably, the thickness is 0.1 to 0.5 μm. In silver and a silver alloy, it is preferably 0.2 to 1.0 μm, and more preferably 0.5 to 1.0 μm. Note that the precious metal layer for electrical contacts noble metal covering plate material, for example, all the layers of the above noble metal species used in the surface layer side than the base layer is defined as the noble metal layer. For example, when a nickel layer is formed on the underlayer, a palladium layer is formed on the upper layer, and a gold layer that forms the outermost surface is formed on the upper layer, the gold layer that forms the outermost surface is disposed between the gold layer and the underlayer. In this case, the noble metal layer is constituted by two layers of gold and palladium. In the present invention, the thickness of the noble metal layer refers to the total thickness of the noble metal layers when plural noble metal layers are formed unless otherwise specified.

Incidentally, the crystal grains large diameter of the previously underlying layer, room temperature is of course suppressed diffusion at a high temperature, since the heat resistance is improved, compared to conventional electric contacts for the precious metal covering plate material, the same coating thickness or Although the effect of diffusion of the substrate components into the surface layer even less can be suppressed for a long period is obtained, in order to obtain a more long-term reliability effects, the mean crystal grain of the noble metal layer for electrical contacts noble metal coated plate material The diameter is also preferably controlled to a predetermined size. For example, the average crystal grain size of at least one noble metal layer is preferably 0.3 μm or more, and more preferably 1.0 μm or more. . The upper limit of the average crystal grain size is not particularly limited, but is preferably 10 μm or less. In particular, silver or a silver alloy is particularly preferable because recrystallization is relatively easy to proceed.

One method for controlling the average crystal grain size of the noble metal layer can be achieved, for example, by performing a heat treatment after the noble metal layer is formed, but it is necessary to limit the heat treatment to a level that does not promote diffusion of the substrate. For this purpose, for example, it is preferable to perform heat treatment at a temperature of 50 to 150 ° C. for 0.08 to 3 hours. If the temperature of this heat treatment is too high or the time is too long, the thermal history becomes excessive, and diffusion of the base component may proceed, resulting in a decrease in connection reliability. Under the above heat treatment conditions, the precious metal layer and the underlayer can be sufficiently recrystallized.

(Method for electrical contacts noble metal coating plate member)
<Granularity control 1 of underlayer>
The present inventors have found that the average crystal grain size of the underlayer is easily influenced by the concentration of a compound containing any one or more of sulfur, carbon, nitrogen, and chlorine components in the additive. In the plating solution containing the additive, since the precipitation becomes fine, it is important to eliminate these components as much as possible (the element concentration of sulfur, carbon, nitrogen, and chlorine of the compound in the additive is 1000 ppm or less). Therefore, by using a plating solution in which the total element concentration of sulfur, carbon, nitrogen, and chlorine in the compound in the additive is 1000 ppm or less, the average crystal grain size of the underlayer is 0.3 μm at the time of formation of the underlayer. I succeeded in doing this. Thus, by setting the elemental concentration of sulfur, carbon, nitrogen, and chlorine to 1000 ppm or less, the average crystal grain size of the underlayer can be controlled to 0.3 μm or more and 4.5 μm or less, and it has excellent anti-diffusion ability without heat treatment. Can be obtained.

  The sulfur, carbon, nitrogen, and chlorine components refer only to those added as additives, and do not apply to the constituent elements of compounds for liberating the metal that forms the underlayer. For example, in the case of a nickel bath using nickel sulfamate or nickel chloride, S (sulfur) contained in sulfamic acid or chlorine contained in nickel chloride is excluded. Therefore, the additive concentration that can be detected by titration, infrared absorption analysis, or the like for managing ordinary additives is shown. The additive concentration is preferably 500 ppm or less, more preferably 100 ppm or less as the elemental concentration of sulfur, carbon, nitrogen, and chlorine of the compound in the additive. And 0-10 ppm of the inevitable impurity content grade which does not use an additive is the most preferable.

In addition, when the current density at the time of electroplating the underlayer is reduced to less than 10 A / dm ² , it is easy to obtain a desired average crystal grain size of the underlayer. When the sulfur, carbon, nitrogen, and chlorine element concentration of the compound in the additive is 1000 ppm or less, the particle size tends to increase from the initial precipitation without using recrystallization. The current density is preferably less than 10 A / dm ^{2 in} order to increase the average crystal grain size from the initial precipitation, but is further 8 A / dm ² or less, more preferably 5 A / dm ² or less.

On the other hand, when the electroplating current density of the underlayer is formed at 10 A / dm ² or more, a desired average grain size of the underlayer can be obtained by performing a rolling process or a heat treatment described later. 10A / dm ² or more in the case of using the precipitated recrystallized current density can be easily achieved by 10A / dm ² or more, more preferably 12A / dm ² or more, more preferably 15A / dm More preferably, it is ² or more. On the other hand, the upper limit value of the current density must be such that surface unevenness after plating does not appear remarkably, and is preferably 30 A / dm ² or less.

  According to the present invention, as a means for controlling the average crystal grain size of the underlayer, the following two steps may be further performed in addition to the above-described concentration control of the additive in the undercoat.

<Particle size control of underlayer 2>
According to the present invention, by performing surface-reducing processing immediately after forming the underlayer or after forming the underlayer and the noble metal layer, recrystallization driving force can be introduced into the underlayer to facilitate recrystallization. The surface reduction in this case is preferably performed by plastic working such as cold rolling or pressing. (Here, the cold rolling process and the pressing process are abbreviated as rolling process etc.) In this case, the processing rate (or area reduction rate) during plastic processing such as rolling processing is 10% or more, preferably 30. % Or more, more preferably 35% or more. The higher the processing rate, the more plastic processing is performed on the underlayer, so that the defect energy due to plastic deformation is stored, so that recrystallization is promoted by releasing this energy. Note that since recrystallization may proceed even at room temperature, heat treatment is not necessarily required after press working. However, if the processing rate is too high, a large crack develops in the underlayer, and the substrate and the outermost layer come into contact with each other, and conversely, diffusion easily proceeds. Note that if the processing rate of rolling or the like exceeds 80%, cracks or cracks during processing are likely to occur, and energy load (electric power necessary for rolling or pressing) increases, so 80% or less, preferably Is preferably 70% or less, more preferably 60% or less.

  The “processing rate” (or area reduction rate) defined in the present invention is a ratio represented by “(plate thickness before processing−plate thickness after processing completion) × 100 / (plate thickness before processing)” ( %).

  In the case of surface reduction, for example, in the case of rolling, the rolling process may be performed any number of times. However, as the number of rolling increases, the productivity deteriorates. In addition, regarding a rolling mill, it carries out with a cold rolling mill, for example. The rolling machine usually has 2 rolls, 4 rolls, 6 rolls, 12 rolls, 20 rolls, etc., but any rolling machine can be used.

Rolling rolls used in the rolling process, in electrical contact for the precious metal covering plate material surface formed by the transfer roll eyes, uneven wear resistance when used as a bending workability and sliding contact with a large deteriorate In view of this, the arithmetic average (Ra) of the surface roughness is preferably less than 0.10 μm, preferably less than 0.08 μm. Here, the cold rolling process has been described as a representative example of the plastic working. However, in the case of press working (for example, coining), the plastic working can be performed in the same manner as in the cold rolling process. In the case of the press working method, it can be achieved by plastic deformation by adjusting the working rate by adjusting the pressure at a press pressure of 0.1 N / mm ² or more.

  In addition, the heat treatment process after the surface-reducing process is not essential. Although depending on the processing rate, recrystallization of the underlayer metal usually starts immediately after rolling. At this time, since the heat treatment is only one means for exceeding the activation energy of recrystallization, further heat treatment may or may not be performed.

<Particle size control of underlayer 3>
According to the present invention, heat treatment may be performed after plating the underlayer in order to promote the coarsening of the average crystal grain size of the underlayer. By performing heat treatment (also referred to as tempering or low-temperature annealing) by a technique such as a batch type or a running type, the tempering and the underlayer can be recrystallized. However, it is necessary to limit the heat treatment to such an extent that the diffusion of the substrate cannot proceed. The conditions for such a heat treatment are determined so that the average crystal grain size of the underlayer is 0.3 μm or more and 4.5 μm or less . The temperature of heat processing becomes like this. Preferably it is 50-150 degreeC, More preferably, it is 50-100 degreeC. The heat treatment time is preferably 0.08 to 3 hours, more preferably 0.25 to 1 hour. If the temperature of this heat treatment is too high or the time is too long, the thermal history becomes excessive, and the diffusion of the substrate proceeds to increase the contact resistance. The recrystallization of the target underlayer can be promoted by the above heat treatment conditions.

As described above, according to the manufacturing method of the grain size control 1 to 3 of the base layer, the average crystal grain size of the base layer after plating can be controlled to 0.3 μm or more and 4.5 μm or less . As a result, it is possible to form a base layer with excellent heat resistance, even if the coating thickness is thin or no expensive precious metal is used for the base layer, and the precious metal coated plate material for electrical contacts with high connection reliability over a long period of time. it is those that can offer.

<Method for forming noble metal layer>
The noble metal layer in the present invention is a part that requires at least the characteristics of the noble metal film on the conductive base material or the base layer (for example, to ensure low contact resistance, solder wettability, wear resistance, wire bonding property, etc.) It only has to be formed on the surface of the part used). In other parts that do not require the characteristics of the precious metal film, it is not necessary to provide a precious metal layer. For example, in the case of electroplating, it is formed by partial plating such as single-sided plating, stripe plating, spot plating, etc. Also good. The noble metal layer to produce a precious metal covering plate material for electrical contacts which are partially formed, it is possible to reduce the use of precious metals of the portion expensive noble metal layer is not required, which contributes to economical cost. Furthermore it is possible to obtain a noble metal-coated plate material for electrical contacts in low environmental impact methods.

  The noble metal layer can be provided by a known method. The average crystal grain size of the noble metal layer is not particularly limited, but it is preferably formed to be 0.3 μm or more, more preferably 1.0 μm or more from the viewpoint of improving heat resistance. preferable. The noble metal layer can be formed by sputtering, vapor deposition, wet plating, etc. However, in consideration of ease of control of the average crystal grain size and thickness and productivity, the wet plating method is particularly used. Is more preferable, and electroplating is more preferable.

(Measuring method of average particle size)
In addition, the measurement of the average crystal grain diameter in this invention is determined by cross-sectional observation. Oite electrical contacts for the precious metal cover plate of interest, the parallel to the rolling section by cutting in FIB, after exposing the cross section, the cross-sectional magnification as 8,000 to 15,000 times to SIM observation. Next, in the obtained image, a length of 5 μm is drawn in the base plane direction from the center portion in the thickness direction of the formed underlayer portion, and how many crystal grain boundaries of the underlayer intersect the line. Is defined as the crystal grain size by dividing 5 μm by the number. This is measured three times at an arbitrary position per field of view, and the number is averaged over 3 fields and 9 positions in total. Further, when there are a plurality of underlayers, the measurement is performed for each layer, and it is only necessary that one of the layers satisfies the average crystal grain size. This is because the diffusion of the base component is effective in preventing diffusion when the crystal grain boundary is small. Therefore, it is necessary that at least one layer having a coarse average crystal grain size is formed as an underlayer.

(Application of electrical contacts for the precious metal covering plate material)
Since the precious metal-coated plate material for electrical contacts obtained in the present invention is particularly excellent in heat resistance, as a result, there is little surface layer contamination after the thermal history has elapsed in each manufacturing process, and excellent long-term reliability. For this reason, it can be used as an electrical contact material with excellent long-term reliability by applying it to electrical contacts that require electrical connection such as connectors, sliding contacts, tact switches, sheet switches, and sliding contacts. . In addition, since diffusion of the surface base component is suppressed, for example, lead frames for semiconductor devices such as IC lead frames and QFN lead frames, LED, photocoupler / photointerrupter lead frames, etc. It can also be suitably used for lead frames for optical semiconductor devices where wettability and further prevention of luminance degradation are desired.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to this.

Examples (Invention Examples 1 to 3, 5 to 23, 27 to 29)
The following pretreatment (electrolytic degreasing / pickling step) was performed on the conductive metal substrate shown in Table 1 having a thickness of 0.2 mm and a width of 50 mm. Thereafter, the underlayer and the noble metal layer shown in Table 1 were applied under the conditions shown below to obtain Invention Examples and Reference Examples shown in Table 1. However, silver strike plating was performed for those subjected to silver plating. The crystal grain size of the underlayer was controlled by setting the total element concentrations of sulfur, carbon, nitrogen, and chlorine of the compound in the additive to 1000 ppm or less in the plating solution used when the underlayer was provided. In addition, some samples were subjected to rolling treatment and heat treatment.

  In the example in which the rolling process was performed, after the underlayer was formed, a cold rolling process (using a six-high rolling mill manufactured by Hitachi, Ltd., arithmetic average roughness Ra of the work roll Ra≈0.03 μm) was produced at a processing rate described in Table 1. . The number of rolling was one, and the initial plate thickness was prepared and applied so that the plate thickness after rolling was 0.2 mm. In addition, the coating thickness of the underlayer was prepared by forming the initial coating thickness thick in consideration of the processing rate. For this reason, the coating thickness described in Table 1 represents the coating thickness after rolling (shown in μm). In addition, those subjected to heat treatment were treated at a heat treatment temperature and time shown in Table 1 using a tubular furnace in a nitrogen reducing atmosphere.

Comparative Example 1 and Conventional Examples 1 and 2
In Comparative Example 1, the following pretreatment (electrolytic degreasing / pickling step) was performed on the conductive metal substrate shown in Table 1 having a thickness of 0.2 mm and a width of 50 mm. Thereafter, the underlayer and the noble metal layer shown in Table 1 were applied under the conditions shown below to obtain comparative examples shown in Table 1. At this time, the crystal grain size of the underlayer was controlled by setting the total element concentration of sulfur, carbon, nitrogen, and chlorine in the additive in the plating solution for providing the underlayer to 1000 ppm or more. . PC nickel manufactured by Uemura Kogyo Co., Ltd. was used as the additive. Further, Conventional Example 1 was formed by simulating Example 11 of Patent Document 1, and Conventional Example 2 was prepared by gold plating in the form of Example 3 described in Japanese Patent Application Laid-Open No. 2011-214066. .

In each of the invention examples , reference examples , comparative examples, and conventional examples, each coating thickness can be arbitrarily determined using a fluorescent X-ray film thickness measuring device (SFT-9400: manufactured by SII) and a collimator diameter of 0.5 mm. Ten points were measured, and the average value was calculated as the coating thickness. Further, in order to determine the average crystal grain size of the underlayer, three views of the rolling direction parallel cross section sample were prepared by FIB, and then the SIM image was observed, and the number of grain boundaries crossing the length of 5 μm in the plane direction of the underlayer was set to 1. The number of particles per field of view was counted, and the particle diameters at a total of 9 locations were calculated based on the counted values, and the average value was shown.

(Pretreatment conditions)
[Cathode electrolytic degreasing]
Degreasing solution: NaOH 60 g / liter Degreasing conditions: 2.5 A / dm ² , temperature 60 ° C., degreasing time 60 seconds [pickling]
Pickling solution: 10% sulfuric acid pickling condition: 30 seconds immersion, room temperature [Ag strike plating]
Plating solution: KAg (CN) ₂ 4.45 g / liter, KCN 60 g / liter Plating condition: current density 5 A / dm ² , temperature 25 ° C.

(Underlayer plating conditions)
[Ni plating]
Plating _{solution: Ni (SO 3 NH 2)} 2 · 4H 2 O 500g / l, NiCl ₂ 30 g / _l, H ₃ BO ₃ 30g / l Plating Conditions: Temperature 50 ° C.
[Co plating]
Plating _{solution: Co (SO 3 NH 2)} 2 · 4H 2 O 500g / l, CoCl ₂ 30 g / _l, H ₃ BO ₃ 30g / l Plating Conditions: Temperature 50 ° C.

(Outermost layer plating conditions)
[Au plating]
Plating solution: KAu (CN) ₂ 14.6 g / liter, C ₆ H ₈ O ₇ 150 g / liter, K ₂ C ₆ H ₄ O ₇ 180 g / liter Plating condition: temperature 40 ° C.
[Pd plating]
Plating solution: Pd (NH ₃ ) ₂ Cl ₂ 45 g / liter, NH ₄ OH 90 ml / liter, (NH ₄ ) ₂ SO ₄ 50 g / liter Plating condition: temperature 30 ° C.
[Pt plating]
Plating solution: Pt (NO ₂ ) (NH ₃ ) ₂ 10 g / liter, NaNO ₂ 10 g / liter, NH ₄ NO ₃ 100 g / liter, NH ₃ 50 ml / liter Plating condition: temperature 80 ° C.
[Rh plating]
Plating solution: RHODEX (trade name, manufactured by Nippon Electroplating Engineers Co., Ltd.)
Plating conditions: temperature 50 ° C
[Ag plating] Matte plating bath Plating solution: AgCN 50 g / liter, KCN 100 g / liter, K ₂ CO ₃ 30 g / liter Plating condition: temperature 30 ° C.

Each characteristic test was performed as follows for the noble metal-coated plate materials for electrical contacts of the invention examples , reference examples , comparative examples, and conventional examples thus obtained.
(1A) Contact resistance measurement: Contact resistance measurement after forming the outermost layer was carried out by a four-terminal method. The measurement was performed immediately after the formation of the outermost layer and at 250 ° C. for 16 hours. The heat treatment was performed at two levels after treatment in a high-temperature bath in an air atmosphere, and the contact characteristics before and after the heat treatment were evaluated. For the evaluation, an Ag probe having a radius of 2 mm was used, and an average value of 10 measurement points was calculated with 10 mA energization and a load of 10 gf to measure contact resistance.
(1B) AES (Auger) analysis: About the test piece after the said heating test, the analysis of the outermost layer was measured using the Auger spectroscopic analyzer (made by ULVAC). In the measurement, the qualitative analysis of the outermost layer was performed, and the amount of the substrate component detected by diffusing to the outer layer was displayed in atomic%. In the case of copper or copper alloy, the concentration of copper is measured, and in the case of iron or iron alloy, the concentration of iron is measured.
(1C) Bending workability: For each sample, a V-bending test was performed at a bending radius of 0.4 mm in a direction perpendicular to the rolling rebar, and the top of the specimen was observed with a microscope (VHX200; manufactured by Keyence Corporation). Observed at a magnification of 200 times, those with no cracks were marked as “Excellent” with “O”, those with minor cracks were marked with “Good” with “△”, and relatively large cracks were observed The result was shown as “impossible” as “x” in Table 1.

From the results in Table 1, the following is clear.
In Comparative Example 1, since the average crystal grain size of the underlayer is less than 0.3 μm, the contact resistance at a high temperature greatly increases with the passage of time, and the amount of diffusion of the base component into the outermost layer is extremely large. Also in Conventional Example 1, the average crystal grain size of the underlayer does not reach 0.3 μm, the contact resistance greatly increases with the passage of time at a high temperature, and the diffusion amount of the base component into the outermost layer is large. In Conventional Example 2, as in Conventional Example 1, the contact resistance greatly increased over time at high temperatures. Further, the diffusion amount of the base component into the outermost layer is remarkably large, and in addition, cracking occurs in the bending workability test, which is not practical.

On the other hand, in the inventive examples 1 to 3 , 5 to 23 , and 27 to 29, the contact resistance before the first heating does not increase greatly with the passage of time under high temperature heating. Moreover, the diffusion amount of the base component into the outermost layer was small, and the bending performance was excellent or showed an excellent performance that was not a problem in practical use. Further, in Example 15 of the present invention, the contact resistance does not increase greatly with time under high-temperature heating even though the gold coating thickness of the outermost layer is remarkably reduced. The amount of diffusion is small and bending workability is excellent.

Claims (4)

A precious metal-coated plate material for electrical contacts having a precious metal layer on the outermost surface on a conductive metal substrate,
The noble metal layer is composed of any one or more of gold, gold alloy, silver, silver alloy, platinum, platinum alloy, palladium, palladium alloy, rhodium or rhodium alloy,
The noble metal layer has a thickness of 0.001-1.10 μm;
Between the conductive metal substrate and the noble metal layer, has an underlayer consisting of one or more of nickel, nickel alloy, cobalt or cobalt alloy ,
The underlayer has a thickness of 0.010 to 1.10 μm;
The average crystal grain size of the underlayer is Ri der than 4.5μm or less 0.3 [mu] m,
The precious metal-coated plate material for electrical contacts, wherein the contact resistance after holding at 250C for 16 hours is 10 mΩ or less . The noble metal covering plate material for electrical contacts according to claim 1, wherein the conductive metal substrate is made of copper or a copper alloy, iron or an iron alloy, or aluminum or an aluminum alloy . A method for producing a precious metal-coated plate material for electrical contacts according to claim 1 or 2 ,
When forming an underlayer on a conductive metal substrate by electroplating, the total element concentration of sulfur, carbon, nitrogen, and chlorine in the compound in the additive is 1000 ppm or less, and the underlayer is formed. The current density of electroplating is less than 10 A / dm ² and, after forming the base layer, heat treatment is performed at 50 to 150 ° C. for 0.08 to 3 hours, or rolling is performed at a processing rate of 10% or more. A method for producing a precious metal-coated plate material for electrical contacts. The current density of electroplating when forming the underlayer is 10 A / dm ² or more,
After the said base layer is formed, manufacture of the noble metal coating | cover board | plate material for electrical contacts of Claim 3 which heat-processes at 50-150 degreeC for 0.08-3 hours, or is rolled with a process rate of 10% or more. Method.