JP2012107263A - Plating structure and coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plating structure having a surface that is not sulfurized and damaged by passage of time or temperature rise, and to provide a method for coating an electric component, whereby a coating material for the electric component that is hardly discolored by sulfuration and has small contact resistance can be obtained.SOLUTION: The plating structure is obtained by heat-treating a silver-plated structure that is produced by forming a plated silver layer 104 on a surface of a substrate 102 to be plated and further forming a plating layer 106 of an Sn-Co alloy on a surface of the plated silver layer. The coating method comprises: forming particle deposits that are obtained by arranging sparsely deposited particles of the Sn-Co alloy, which are deposited like dots on the surface of the silver layer formed on the face of the substrate by a particle deposition process, so as to have spaces among the sparsely deposited particles without making them overlap in a direction vertical to the surface when viewed from the above; and heating the particle deposits in a non-oxidizing atmosphere, thereby melting the sparsely deposited particles to form a coating film. Here, the average diameter of the sparsely deposited particles is 20-80 nm, and the weight of the sparsely deposited particles of the tin alloy on the surface of the silver layer per unit area is from 2×10to 8×10g/cm.

Description

The present invention relates to a plating structure with improved deterioration of surface characteristics, in particular, a plating structure of a material for an electrical component that requires prevention of sulfidation, and a method for manufacturing a material for an electrical component having the plating structure. Specifically, it is suitable for use as a metal lead frame, a lead wire using a metal strip, a lead wire provided on a non-conductive substrate such as a ceramic, an electrical contact material such as a lead pin, a reflector plate, a terminal, a connector, and a switch. The present invention relates to a plated structure of a material and a method for manufacturing the material. More specifically, the present invention relates to a plating structure of a material for electrical parts having excellent resistance to sulfidation and a method for manufacturing the same. In particular, the present invention relates to a plating structure of an electrical material having excellent sulfidation resistance and low contact resistance or high surface reflectance, and a method for producing the same.

  In a light-emitting device in which a light-emitting element such as an LED is mounted, a light reflecting surface is provided to improve brightness (see, for example, Patent Documents 1 and 2). The light reflecting surface is attached to the periphery of the light emitting element so that light radiated to the side of the light emitting element is directed in the direction of the main axis of irradiation, for example. The light reflecting surface is formed by metal plating. Of these, silver plating is preferable because of high reflection.

  However, there is a problem in that the silver plating layer is sulfided with time or temperature rise under a sulfur-containing environment, and the reflectance decreases.

  For this reason, a measure for forming an organic protective film on the reflective surface is disclosed. (For example, see Patent Documents 3 and 4)

  Alternatively, a method for protecting a surface by forming self-assembled monolayers of a substance such as a compound containing sulfur semifluoride on a metal substrate is known (see, for example, Patent Document 5). .

  Although these measures are effective as they are, the protective film for preventing sulfidation of the silver plating layer scatters due to the temperature rise due to resin curing in the mounting process when resin is used in the package. The prevention effect is greatly reduced, and it can be said that a satisfactory effect is not necessarily obtained in terms of preventing sulfidation due to sulfidation of the reflection surface and heat generation of the light emitting element and sulfidation when the apparatus is used for a long time. In view of this point, a reflecting surface excellent in heat resistance is desired.

  Furthermore, although a silver plating structure is widely used as a contact point of a switch (see, for example, Patent Document 6), the silver plating surface also has a silver plating layer due to a temperature rise due to discharge over time or during switch production or on / off. In some cases, the protective film for preventing sulfidation is scattered and the effect of preventing sulfidation is greatly reduced, resulting in sulfidation and damage to the surface. In view of this point, a plated contact having excellent heat resistance is desired.

  Thus, there is a demand for a plating structure that is sulfided by aging or temperature rise and that does not damage the surface.

  In addition, the surface of various metal substrates is plated with silver or a silver alloy to improve corrosion resistance, electrical connectivity, etc., for a variety of purposes, and LEDs are reflective using the reflective properties peculiar to silver. It is used as a board.

  For example, a material in which the surface of copper or copper alloy, which has excellent electrical and thermal conductivity and excellent mechanical strength and workability, is coated with a silver layer, in addition to the excellent characteristics of copper alloy, It is known as a material having excellent corrosion resistance, electrical connectivity, and the like, and is widely used as an electrical contact material and lead material in the field of electrical equipment.

  However, there is a problem that the silver surface is easily discolored by sulfuration. For this reason, or from the viewpoint of soldering characteristics, it has been disclosed to form a tin or tin alloy layer on the silver surface (see, for example, Patent Document 7).

  In this case, when the tin or the alloy layer of tin becomes thick, there arises a problem that the contact resistance increases. In addition, the reflectance is lowered, and the original gloss and reflection performance of silver are lost.

  Alternatively, an organic thin film is formed on the silver surface to prevent sulfidation, but the organic thin film has poor heat resistance and has a problem in sulfidation resistance at high temperatures.

[Patent Document 1] JP 2008-205501 [Patent Document 2] JP 2006-041179 [Patent Document 3] JP 2008-010591 [Patent Document 4] JP 2003-188503 [Patent Document 5] Japanese Patent Laid-Open No. 2002-327283 [Patent Document 5] Japanese Patent Laid-Open No. 2002-327283 [Patent Document 6] Japanese Patent Laid-Open No. 2008-248295
[Patent Document 7] Japanese Utility Model Publication No. 61-11085

  An object of the present invention is to provide a plating structure that is sulfided due to aging or temperature rise and whose surface is not damaged. Furthermore, it aims at providing the support body for light emitting element accommodation provided with the reflective surface which has the plating structure excellent in the heat resistance with respect to sulfidation prevention for the light-emitting devices which mounted the light emitting element.

  Furthermore, an object of the present invention is to provide a coating method for electrical parts which has such a plating structure, is not easily discolored by sulfuration, has an original gloss of silver, and has a low contact resistance. That is.

  The gist of the present invention is that a silver plating layer is formed on the surface of the plating base, and further a Sn-Co alloy plating layer having a thickness of 0.001 to 0.1 μm is formed on the surface of the silver plating layer. The silver plating structure is obtained by heat treatment.

  Further, the gist of the present invention is a light emitting element mounting support that has a concave portion for accommodating a light emitting element and reflects light at the peripheral wall of the concave portion, and the light emitting element mounting support is provided on the peripheral wall of the concave portion. It is a light emitting element housing support in which the plating structure is formed using the main body of the support as the plating base.

  Furthermore, the gist of the present invention is a light emitting device including the light emitting element housing support and a light emitting element mounted on the light emitting element housing support.

  Furthermore, the gist of the present invention resides in a switch contact comprising a plated portion having the plated structure.

  Further, the gist of the present invention resides in a component terminal including a plated portion having the plated structure.

  Furthermore, the gist of the present invention resides in a component contact comprising a plated portion having the plated structure.

Further, the gist of the present invention is a coating method for obtaining the plating structure,
On the surface of the silver layer formed on the surface of the base material, the diffracted particles of the Sn—Co alloy formed by the particle deposition step have a gap in a top view without overlapping with the surface in the vertical direction. The average diameter of the diffracted particles is 20 to 80 nm, and the weight per unit area of the diffracted particles of the Sn—Co alloy on the surface of the silver layer is 2 × 10 ⁻⁶ to 8 × 10 ⁻⁶ g / It is a coating method characterized in that a particle deposit of cm ² is heated in a non-oxidizing atmosphere to melt the deposited particles to form a film.

  According to the present invention, there is provided a plating structure in which the effect of preventing sulfidation is not reduced with time and particularly with temperature rise. Furthermore, there is provided a light emitting element storage support including a reflective surface having a plated structure with excellent heat resistance, for a light emitting device on which the light emitting element is mounted.

  According to the present invention, there are provided an electrical contact material, a reflective material for electrical components, and other coating materials for electrical components that are difficult to discolor due to sulfuration, have an original gloss of silver, and have low contact resistance.

It is sectional explanatory drawing which shows an example of the aspect of the silver plating structure for obtaining the plating structure of this invention. It is sectional explanatory drawing which shows an example of the other aspect of the silver plating structure for obtaining the plating structure of this invention. It is sectional explanatory drawing which shows an example of the aspect of the lead frame which has the plating structure of this invention. It is a cross-sectional schematic diagram which shows an example of a structure of the LED lamp using the coating | covering material for electrical components manufactured by the sulfurization prevention coating method of this invention. It is a cross-sectional schematic diagram which shows the aspect of the particle deposit used for this invention. FIG. 4 is a schematic cross-sectional view showing a particle deposit in which particles deposited in a dot shape (hereinafter referred to as stipulated particles) are arranged in a planar state in a state where stipulated particles adjacent to each other are in contact with each other, that is, without a gap. It is a cross-sectional schematic diagram which shows the particle | grain deposit arrange | positioned three-dimensionally in the state which the diffracted particle | grains adjacent to each other did not have a clearance gap, and also overlapped with the surface of the silver layer. It is a cross-sectional schematic diagram of the coating | covering material for electrical components manufactured by the sulfide prevention coating method of this invention. It is a microscope picture explaining the aspect of the particle | grain deposit used for this invention. It is a microscope picture explaining the aspect of the particle deposit used in a comparative example.

  In the plating structure of the present invention, as shown in FIG. 1A, a silver plating layer 104 is formed on the surface of a plating base 102, and a protective layer having a thickness of 0.001 to 0.1 μm is formed on the surface of the silver plating layer 104. This is a plating structure obtained by heat-treating a silver plating structure 101 formed with the plating layer 106 at 150 to 600 ° C. The heat treatment time is preferably 1 second to 60 seconds.

  The base 102 is a base capable of silver plating. The substrate 102 may be made of a metal plate. Examples include, but are not limited to, copper-based metals such as brass, iron-based metals, and stainless steel plates. Usually, when a copper-based metal plate is used, copper plating (not shown) is applied as a base before silver plating is applied to the plating base 102. When a stainless steel plate is used, nickel plating (not shown) is applied as a base before the plating base 102 is silver plated.

  Alternatively, the substrate 102 may be a substrate in which a conductive film is formed on a surface of ceramic or resin by electroless plating, vapor deposition, or metallization processing by diffusion formation of a metal layer.

  The substrate 102 is not limited to a plate shape as shown in FIG. That is, in the plating structure of the present invention, as shown in FIG. 1B, the base 102 is made of a long member such as a metal wire, and a silver plating layer 104 and a protective plating layer 106 are concentrically arranged in this order on the peripheral surface. Alternatively, a plated structure obtained by heat-treating the silver-plated structure body 101a formed at 150 to 600 ° C. may be used.

  The thickness of the protective plating layer 106 is preferably 0.001 to 0.1 μm. When the thickness of the protective plating layer 106 is within this range, the silver plating layer 104 can be prevented from being accelerated by aging or heat. Further, the plated structure has surface characteristics peculiar to silver, for example, good light reflectivity, good surface electrical conductivity, and silver peculiar luster. When the thickness of the protective plating layer 106 is less than this range, this resistance to sulfidation is insufficient, and when the thickness of the protective plating layer 106 exceeds this range, surface characteristics peculiar to silver, for example, good light reflectivity. Or good surface conductivity cannot be obtained.

  The metal constituting the protective plating layer 106 is an Sn—Co alloy (hereinafter referred to as a tin alloy). The tin alloy is preferably an alloy containing 5 to 50% by weight of Co.

  In the plated structure of the present invention, the protective plating layer 106 may contain an alloy of silver by migration and the silver plating layer 104 by heating.

  The silver plating layer 104 can be obtained by silver plating on the surface of the substrate 102 by a conventional method. The silver plating layer 104 may be formed by other film forming methods such as electroless plating. The thickness of the silver plating layer 104 is preferably 0.1 to 10 μm. The base 102 to be silver-plated is preferably provided with a base plating such as nickel on the surface.

  The silver plating structure 101 is heat-treated at 150 to 600 ° C., so that the protective plating layer 106 is as thin as 0.001 to 0.1 μm, but the silver plating layer 104 has a very good antisulfurization effect. Is obtained. This is presumed to be due to the fact that an alloy structure is formed at the interface between the silver plating layer 104 and the protective plating layer 106 by this heat treatment and guards against sulfidation. The heat treatment temperature is more preferably 250 to 300 ° C. in order to obtain a good surface state such as an antisulfurization effect and high reflectance. The treatment time for the heat treatment is preferably 1 second to 60 seconds.

  If the heat treatment temperature is less than 150 ° C., the diffusion effect of the tin alloy plating layer by heating may be insufficient, and a sufficient antisulfurization effect may not be obtained. If the heat treatment temperature exceeds 600 ° C., the physical properties of the substrate change due to the annealing of the substrate, and the mechanical properties of the substrate necessary for practical use are impaired.

  The thickness of the silver plating layer 104 is preferably 1 to 10 μm.

  The silver plating layer 104 and the protective plating layer 106 can be formed by electrolytic plating or electroless plating.

  An example of the aspect of the light emitting element accommodation support body provided with the plating structure of the present invention is shown in FIG. The light emitting element storage support 202 includes a substrate 203 called a lead frame having a recess 206 for storing the light emitting element 204. The substrate 203 (lead frame) includes a land 208 and a lead 209, and a recess 206 is formed in the land 208. The light emitting element 204 is placed on the bottom surface of the recess 206, and one terminal of the light emitting element 204 is electrically connected to the land 208, and the other terminal is electrically connected to the lead 209 via the wire 212.

  A reflective surface 214 is formed on the peripheral surface of the recess 206. In the present invention, after the reflective surface 214 is silver plated on the peripheral surface of the recess 206, a thin tin alloy plated layer is formed on the surface of the silver plated layer by flash plating or the like. It is obtained by heat-treating a substrate on which a thin tin alloy plating layer is formed at 150 to 600 ° C.

  Examples of the light emitting element 204 include an LED.

A light emitting device is obtained by mounting the light emitting element 204 in the manner shown in FIG. The process of mounting the light emitting element 204, for example, heating of the case mold, wire bonding with the chip, and curing of the resin promotes sulfidation of the reflecting surface by reducing the sulfidation prevention effect due to scattering of the sulfidation prevention film. Decrease in reflectivity due to the problem was a problem.
When the light emitting element 204 emits light, heat is generated, and in the conventional reflective surface made of a silver plating layer, sulfidation proceeds with a decrease in the sulfidation preventing effect similar to that described above due to such heat generation.

  The reflective surface 214 of the light-emitting element storage support 202 of the present invention is extremely low in sulfidation due to aging or temperature rise of the reflective surface, and can maintain a high reflectance over a long period of time.

  FIG. 3 shows an example of the structure of the LED lamp 20 to which the coating material for electric parts according to the present invention is applied. In the LED lamp 20, the LED 26 is placed on the base 22 and stored in the casing 24. The casing 24 is filled with the phosphor 28 with the LED 26 embedded in the phosphor 28, and a transparent resin cover 30 is provided on the upper surface of the phosphor 28. Reference numeral 34 denotes a lead wire. A metal member such as a copper alloy or a metallized ceramic member is used as the main body of the substrate 22, and a reflective surface 32 is formed on the surface of which the silver plating and the tin alloy plating according to the present invention are applied. Since the reflecting surface 32 has reflectivity similar to that of a silver surface and there is almost no discoloration due to sulfidation over time, the LED lamp 20 has a large amount of emitted light and a small decrease in the amount of emitted light over time.

  The plating structure of the present invention can be applied to switch contacts. The switch contact having the plated structure of the present invention has a gloss unique to silver and good surface electrical conductivity, and the surface characteristics are hardly changed by sulfidation even when used for a long time. For example, an element is mounted on a lead frame, bonded / resin-molded, pressed after plating, and assembled into a switch contact or the like.

  The plating structure of the present invention can be applied to contacts and terminals of electrical equipment. The contacts and terminals having the plated structure of the present invention have a gloss unique to silver and good surface electrical conductivity, and even when used for a long time, these surface characteristics are hardly changed by sulfidation.

  The effect of the present invention is confirmed by the following experimental examples.

[Experimental example]

Basic Sample A 1 cm square piece of copper alloy strip for lead frame (manufactured by Furukawa Electric Co., Ltd .: product name EFTEC3) was used as the equivalent of the plating base 102 in FIG. After applying 1 μm copper underplating to one side of this piece, silver plating with a thickness of 2 μm was used as a basic sample, and this basic sample was subjected to tin alloy plating and heat treatment according to the following experimental levels. . An Sn-20Co alloy was used as the tin alloy.

・ Experimental sample level L-1: Blank (as basic sample)
L-2: A tin alloy layer having a thickness of 0.01 μm was formed on the silver surface of the basic sample by flash plating.
L-3: A tin alloy layer having a thickness of 0.01 μm was formed on the silver surface of the basic sample by flash plating, and then the sample was heat-treated at 300 ° C. for 10 seconds.
L-4: A 0.02 μm thick tin alloy layer was formed on the silver surface of the basic sample by flash plating.
L-5: After forming a 0.02 μm thick tin alloy layer on the silver surface of the basic sample by flash plating, the sample was heat-treated at 300 ° C. for 10 seconds.
L-6: A tin alloy layer having a thickness of 0.2 μm was formed on the silver surface of the basic sample by flash plating.
L-7: An organic film intended to prevent sulfidation was formed using a sulfidation inhibitor that forms a self-assembled monolayer on the silver surface of the basic sample.
Table 1 shows a list of experimental sample levels and their contents.

-Sulfide test A sample was immersed in an immersion solution obtained by adding 400 cc of water to 20 mL of a 6% by weight ammonium sulfide solution, and the sample was subjected to sulfurization treatment at room temperature for 5 minutes. The piece after completion of the immersion was washed with pure water and then replaced with methanol, and blown with a nitrogen flow, and then the sample was heated at each temperature (Table 1) for 1 hour to promote sulfidation. The degree of sulfuration was judged visually. This erroneous heating of sulfidation corresponds to an accelerated test of sulfidation over a long period of time. It also supports temperature rise during device assembly and use.

・ Judgment criteria are ◎ ・ ・ ・ Gloss and tone of the silver surface are maintained (before sulfidation). Alternatively, no sulfidation is observed on the surface, and the gloss and color tone of the silver surface are maintained (after sulfidation treatment).
○: The gloss and color tone of the silver surface are almost maintained (before sulfurization treatment). Alternatively, the surface is hardly sulphurized, and the gloss and color tone of the silver surface are almost maintained (after sulphurizing treatment).
Δ: The gloss and color tone of the silver surface are maintained to an acceptable level (before sulfurization treatment). Alternatively, although some sulfuration is observed on the surface, the gloss and color tone of the silver surface are maintained to an acceptable level (after sulfuration treatment).
X: The gloss and color tone of the silver surface are lost (before sulfurization treatment). Alternatively, sulfuration is observed on the surface, and the glossiness and color tone of the silver surface are lost (after sulfuration treatment).
It was.

-Reflectance The reflectance of the experimental sample before and after the sulfidation test was measured with light having a wavelength range of 380 to 780 nm with a D65 light source in accordance with JIS R3106.

Test results Table 2 shows the results of the sulfidation test.

  From Table 2, it can be seen that when the tin alloy layer has a thickness of 0.01 μm (L-2, L-3), the gloss and color tone of the silver surface are maintained before the sulfiding treatment. Further, when the tin alloy layer has a thickness of 0.02 μm (L-4, L-5), the gloss and color tone of the silver surface are substantially maintained before the sulfiding treatment. Furthermore, after forming the tin alloy layer, the sample (L-3), which was heat-treated at 300 ° C. for 10 seconds, was also heated by sulfiding after the tin alloy layer was as thin as 0.01 μm. There is almost no sulfuration on the surface, and the gloss and tone of the silver surface are almost maintained. After forming the tin alloy layer, those that are not heat-treated (L-2, L-4) are those whose tin alloy layer is as thin as 0.01 μm (L-2), which is heated at high temperature after the sulfidation treatment As a result, the surface is sulfided and the glossiness and color tone of the silver surface are lost. When the tin alloy layer has a thickness of 0.02 μm (L-4), the degree of sulfidation by the heating after the sulfiding treatment is relatively small even without the heat treatment after the tin alloy layer is formed. When the tin alloy layer has a thickness of 0.2 μm (L-6), the luster and color tone of the silver surface are lost due to the mask made of the tin alloy layer even before the sulfiding treatment. In the basic sample having an organic film formed on the silver surface (L-7), the surface is sulfided by sulfidation, and the gloss and color tone of the silver surface are lost.

  In an example of an aspect of manufacturing a coating material for electrical parts by a coating method for obtaining a plating structure of the present invention, first, a base 102 on which a silver plating layer 104 (FIG. 1) is formed is prepared, and the silver plating layer is prepared. Tin alloy particles are deposited on the surface of 104 by a particle deposition process. At this time, as shown in FIG. 4, at least a part of the splattered particles 8 deposited in the form of fine lumps by the particle deposition step is present on the surface of the silver plating layer 104, and there is a gap 10 between the stipulated particles 8 adjacent to each other. Then, the energization is performed for a short time so as to be sparsely arranged in a plane shape and arranged so as not to overlap the surface of the silver plating layer 104 in the vertical direction. The sparsely located area means that the area of the silver plating layer 104 seen from the top view of the predetermined area where the tin alloy is deposited by the particle deposition process such as plating on the surface of the silver plating layer 104 is the entire area. It means a state that is 15% or more of the area. The area of the silver plating layer 104 that can be seen from above is preferably 15 to 50% of the area of the entire region. If this value exceeds 50%, a uniform thin film 7 cannot be obtained in the present invention.

  The particle deposition step in the present invention is a step of depositing target metal particles on a substrate by means selected from chemical means, electrical means, and physical means. Examples include a process using an electrolytic plating method, a vacuum deposition method, a chemical vapor deposition method, a sputtering method, a plasma deposition method, a cluster ion beam method, and the like. Among these, the electroplating method is preferable in that the manufacturing cost can be reduced.

  For example, when an electroplating process is used as the particle deposition process, as the energization time becomes longer, as shown in FIG. 5, the splattered particles 8 are in contact with each other adjacent splattered particles 8, that is, without a gap. Arrange in a plane. Alternatively, as shown in FIG. 6, the diffracted particles 8 adjacent to each other are arranged in a three-dimensional manner in a state where there is no gap and is also overlapped in the direction perpendicular to the surface of the silver plating layer 104.

  For example, when an electroplating process is used as the particle deposition process, in order to obtain a state where gaps 10 exist between adjacent splatting particles 8 as shown in FIG. The energization time is preferably selected in the range of 1 to 120 seconds. And it is preferable to adjust the tin alloy component density | concentration of a plating solution smaller than the conditions of normal plating, for example, to 1/5-1/20 of the density | concentration of a normal plating solution.

In the present invention, the particle diameter of the diffracted particles 8 is preferably 20 to 80 nm in order to obtain a uniform film of the coating material for electric parts. A thickness of 30 to 60 nm is more preferable in optimizing the balance between good reflectivity and antisulfurization property of the coating material for electric parts. For example, by using a plating bath in which the tin alloy component concentration is adjusted to 1/5 to 1/20 for a normal tin alloy plating bath, the current density of energization is selected in the range of 0.5 to 10 A / dm ^2. The diffracted particles 8 having such a particle size are obtained. In this case, the energization time is adjusted by the concentration of the plating solution. Alternatively, for example, pulverized particles 8 having a particle diameter in a range close to 20 to 30 nm can be obtained by performing microsecond order pulse energization.

  In the present invention, as shown in FIG. 4, the diffracted particles 8 of the tin alloy formed by the particle deposition step do not substantially overlap the surface of the silver plating layer 104 in the vertical direction, and the diffracted particles 8. The particle deposits 12 in which at least some of the particles are sparsely spaced apart from each other are heated in a non-oxidizing atmosphere to melt the tin alloy diffracted particles 8 to form a film. The non-oxidizing atmosphere is an atmosphere in which the tin alloy is oxidized only to a negligible extent. Heating in this non-oxidizing atmosphere includes heating in an inert gas such as nitrogen, heating in a vacuum, heating by a reducing flame. Etc. The heating temperature is preferably 250 ° C. or higher and 600 ° C. or lower.

  As a result, as shown in FIG. 7, a silver plating layer 104 is formed on the surface of the base 102, and further, a coating material 222 for electric parts is formed by forming the tin alloy thin film 7 on the surface of the silver plating layer 104. The

The weight per unit area of the diffracted particles 8 on the surface of the silver plating layer 104 in the particle deposit 12 is preferably 2 × 10 ⁻⁶ to 8 × 10 ⁻⁶ g / cm ² . This value indicates that when the diffracted particles 8 are melted and solidified to form a thin film made of a tin alloy on the surface of the silver plating layer 104, the thickness of the thin film made of the tin alloy becomes about 3 to 11 nm. It corresponds to the weight per unit area. For example, when a tin alloy is used, it is presumed that the thin film 7 is actually composed of a tin alloy and / or an alloy with silver. For example, per unit area of diffracted particles 8 on the surface of the silver plating layer 104 in the particle deposit 12. When the weight is 3 × 10 ⁻⁶ , the thickness of the thin film 7 is estimated to be 4 nm or more including the thermal diffusion layer of silver and tin alloy, and the surface of the silver plating layer 104 in the particle deposit 12 is observed. It is estimated that the thickness of the thin film 7 when the weight per unit area of the particles 8 is 8 × 10 ⁻⁶ is 11 nm or more. In any case, the weight of the tin alloy per unit area existing in the thin film 7 is the same as the weight per unit area of the diffracted particles 8 on the surface of the silver plating layer 104 in the particle deposit 12.

The weight per unit area of the diffracted particles 8 on the surface of the silver plating layer 104 in the particle deposit 12 is 5 × 10 ^{−6 to} 7 × 10 ⁻⁶ g / cm ² , so that contact resistance, silver luster, and sulfuration resistance More preferable in terms of balance of sex.

  The amount of tin alloy per unit area existing in the thin film 7 and the weight per unit area of the diffracted particles 8 on the surface of the silver plating layer 104 in the particle deposit 12 can be measured by a fluorescent X-ray analyzer.

  The electrical component coating material obtained by the method for producing an electrical component coating material of the present invention is less susceptible to sulfidation, has a contact resistance close to silver, and has a gloss characteristic of silver.

When the weight per unit area of the diffracted particles 8 on the surface of the silver plating layer 104 in the particle deposit 12 is less than 2 × 10 ⁻⁶ g / cm ² , the sulfidation prevention performance of the obtained coating material for electrical parts is inferior. When the weight per unit area of the diffracted particles 8 on the surface of the silver plating layer 104 in the particle deposit 12 exceeds 11 × 10 ⁻⁶ g / cm ² , the contact resistance of the obtained coating material for electrical parts becomes excessive, and silver The characteristic luster is lost. In addition, a particle deposit in which tin alloy diffracted particles 8 are arranged in a state in which almost all diffracted particles 8 adjacent to each other are in contact with the surface of the silver plating layer 104 (this is referred to as a state having no gap) is used. In such a case, it is difficult to form a uniform thin film having a desired thickness by heating, the contact resistance of the obtained coating material for electrical parts is excessive, and the silver-specific gloss is lost. The state without a gap refers to a state in which at least four of the diffracted particles surrounding a certain diffracted particle in a plane are in contact with the one diffracted particle. In addition, when a predetermined area where diffracted particles are deposited on the surface of the silver plating layer 104 by the particle deposition process, the area of the silver plating layer 104 seen from the top view is less than 15% of the total area, the heating It is difficult to form a uniform thin film having a desired thickness, the contact resistance of the obtained coating material for electrical parts is excessive, and the silver specific luster is lost.

  In addition, when a particle deposit in which the diffracted particles 8 are arranged in a state where the diffracted particles 8 overlap with the surface of the silver plating layer 104 is used, it is difficult to form a uniform thin film having a desired thickness by heating. The contact resistance of the coating material becomes excessive, and the gloss peculiar to silver is lost.

  Further, when the particle deposit 12 is heated in an oxidizing atmosphere, the fluidity of the tin alloy decreases when oxidized, so that the diffracted particles 8 are not uniformly coated, and the uniform thin film 7 cannot be obtained.

[Example 1]
Silver plating and tin alloy plating were applied to the frame having the shape of the substrate 203 shown in FIG. As a material of the frame as a base, a copper alloy strip for lead frame (Furukawa Electric Co., Ltd .: EFTEC3) was used and molded by punching. The frame was degreased, acid washed with 5% sulfuric acid, and plated with a copper base in a bright copper sulfate bath (copper sulfate 200 g / L, sulfuric acid 50 g / L, commercially available brightener 2 mL / L). The film thickness of the base copper plating was 10 μm. Next, bright silver plating with a film thickness of 2 μm was performed in a bright silver cyanide bath (silver cyanide 35 g / L, potassium cyanide 90 g / L, potassium carbonate 10 g / L). Furthermore, after tin alloy plating with a film thickness of 0.01 μm was performed in a stannate bath (sodium stannate 45 g / L, cobalt chloride 10 g / L, appropriate amount of additive), heat treatment was performed at 250 ° C. for 10 seconds to obtain a lead frame. . A sulfurization test was performed, and the same result as L-3 in Table 1 was obtained.

[Example 2]
A stainless steel (SUS304) plate with a thickness of 1 mm and 1 cm square is used as a base. After degreasing, it is acid-washed with 5% sulfuric acid, and a bright copper sulfate bath (copper sulfate 200 g / L, sulfuric acid 50 g / L, commercially available brightener 2 mL / L) The base copper plating. The film thickness of the base copper plating was 10 μm. Next, bright silver plating with a film thickness of 2 μm was performed in a bright silver cyanide bath (silver cyanide 35 g / L, potassium cyanide 90 g / L, potassium carbonate 10 g / L). Furthermore, after tin alloy plating with a film thickness of 0.01 μm was applied in a stannate bath (sodium stannate 45 g / L, cobalt chloride 10 g / L, appropriate amount of additive), a glossy plate was obtained by heat treatment at 500 ° C. for 10 seconds. . A sulfurization test was performed, and the same result as L-3 in Table 1 was obtained.

[Comparative Example 1]
A lead frame was obtained in the same manner as in Example 1 except that the heat treatment temperature after the tin alloy plating was 100 ° C. A sulfurization test was performed, and the same result as L-2 in Table 1 was obtained.

[Example 3]
A substrate obtained by subjecting a brass strip with a thickness of 0.3 mm to a nickel base plating of 0.5 μm was used. The surface of the substrate was subjected to silver plating with a thickness of 2 μm to obtain a basic sample.

The basic sample was plated with a tin alloy under the following conditions to obtain a particle deposit.
Plating solution composition Sodium stannate: 45 g / L
Cobalt chloride: 10g / L
Additive: Appropriate amount Plating temperature 55 ° C
Current density 1A / dm ²
Energizing time 4 seconds

In the obtained particle deposit, as in the case shown in FIG. 8, the diffracted particles 8 of the tin alloy do not overlap the surface of the basic sample in the direction perpendicular to the surface and there is a gap 10 in a top view. It was in a state of being placed. The average diameter of the diffracted particles 8 was 50 nm. Moreover, the quantity of the tin alloy by the fluorescent X-ray-analysis apparatus (made by SSI nanotechnology company) of a particle deposit was 5 * 10 < ^-6 > g / cm < ² >.

  This particle deposit was heated in a reducing flame of LP gas using a burner for 10 seconds to obtain a coating material for electrical parts having a high reflectance. The gas combustion atmosphere temperature was 350 ° C.

[Example 4]
The same basic sample as used in Example 3 was subjected to tin alloy plating under the following conditions to obtain a particle deposit.
Plating solution composition Same as Example 3 Plating temperature Same as Example 3 Current density Average 2 A / dm ²
Energization time 10 seconds (pulse energization: period 100 μsec)

The obtained particle deposit is in a state in which the diffracted particles 8 of the tin alloy are arranged on the surface of the basic sample without being overlapped in the direction perpendicular to the surface. The average diameter of the diffracted particles 8 was 30 nm. Moreover, the quantity of the tin alloy by the fluorescent X-ray analyzer (made by SSI nanotechnology company) of a particle deposit was 3 * 10 < ^-6 > g / cm < ² >.

  This particle deposit was heated in the same manner as in Example 3 to obtain a coating material for electrical parts.

[Example 5]
The same basic sample as used in Example 3 was subjected to tin alloy plating under the following conditions to obtain a particle deposit.
Plating solution composition Same as Example 3 Plating temperature Same as Example 3 Current density 2 A / dm ²
Energization time 6 seconds The obtained particle deposit is in a state in which the diffracted particles 8 of the tin alloy are arranged on the surface of the basic sample without being overlapped in the direction perpendicular to the surface. The average diameter of the diffracted particles 8 was 50 nm. Moreover, the quantity of the tin alloy by the fluorescent X-ray analyzer (made by SSI nanotechnology company) of a particle deposit was 7.3 * 10 < ^-6 > g / cm < ² >.
This particle deposit was heated in the same manner as in Example 3 to obtain a coating material for electrical parts.

[Comparative Example 2]
The same basic sample as used in Example 3 was subjected to tin alloy plating under the following conditions to obtain a particle deposit.
Plating solution composition Same as Example 3 Plating temperature Same as Example 3 Current density 2 A / dm ²
Energization time 1.5 seconds The obtained particle deposit is in a state in which the diffracted particles 8 of the tin alloy are arranged on the surface of the basic sample without being overlapped in the direction perpendicular to the surface. The average diameter of the diffracted particles 8 was 30 nm. Moreover, the quantity of the tin alloy by the fluorescent X-ray analyzer (made by SSI nanotechnology company) of a particle deposit was 1.9 * 10 < ^-6 > g / cm < ² >.
This particle deposit was heated in the same manner as in Example 3 to obtain a coating material for electric parts.

[Comparative Example 3]
In a basic sample similar to that used in Example 3, the amount of tin alloy was 5 × 10 ⁻⁵ g / cm ² using a particle deposit X-ray fluorescence analyzer (manufactured by SSI Nanotechnology). Alloy plating was performed to obtain a particle deposit.

  The obtained particle deposit is similar to the one shown in FIG. 9 in which the diffracted particles 8 of the tin alloy partially overlap the surface of the basic sample in the direction perpendicular to the surface and are adjacent to each other without any interval. It is in a state of being placed in contact. The average diameter of the diffracted particles 8 was 100 nm.

  This particle deposit was heated in the same manner as in Example 3 to obtain a coating material for electrical parts.

  Table 3 shows the characteristics of the covering materials for electrical parts obtained in the basic sample, the examples, and the comparative examples. In the table, the resistance to sulfidation is as follows: the sample coating material for electric parts was heated at 200 ° C. for 1 hour, then immersed in an ammonium sulfide solution having a concentration of 6% by weight at room temperature for 10 minutes, washed with pure water, and replaced with methanol. Degree of discoloration when blown in a stream. ◎: Almost no discoloration is observed. ○: Slight discoloration is observed but is acceptable. ×: Significant discoloration is observed. The contact resistance (mΩ) was measured by an alternating current four-terminal method with a probe material of NS / Au, a tip shape of 10R, a measurement current of 100 μA, and a load of 30 gf. The reflectance is a reflectance at a wavelength of 450 nm measured with a U-4000 type spectrophotometer.

The present invention is suitably suitable for preventing sulfidation of the silver surface in various devices utilizing surface characteristics such as high reflection characteristics and high surface electrical conductivity characteristics of silver. In particular, it can be suitably applied to optical machines, switches, component contacts, component terminals, vacuum heat insulating materials, and the like.
The coating material for electrical parts obtained by the present invention has low contact resistance, excellent sulfidation resistance, and has the original gloss of silver. Therefore, not only electrical contact materials such as terminals, connectors and switches, but also lead wires for IC packages And lead materials such as lead pins or lead frames, reflectors for lighting fixtures such as LED lamps, conductive materials for fuel cells, and other electrical (electronic) materials.

7: Thin film 8: Dotted particles 10: Crevice 101, 101a: Silver plating structure 102: Plating substrate 104: Silver plating layer 106: Protective plating layer 222: Coating material for electric parts

Claims (7)

A silver plating structure is formed by forming a silver plating layer on the surface of the plating substrate, and further forming a 0.001 to 0.1 μm thick Sn—Co alloy plating layer on the surface of the silver plating layer. Plating structure. A light-emitting element mounting support having a recess for housing a light-emitting element and reflecting light at the peripheral wall of the recess, wherein the main body of the light-emitting element mounting support is claimed as the plating base on the peripheral wall of the recess Item 8. A light-emitting element storage support on which the plating structure according to Item 1 is formed. A light-emitting device comprising the light-emitting element storage support according to claim 2 and a light-emitting element mounted on the light-emitting element storage support. The switch contact which consists of a plating part which has the plating structure of Claim 1. The component terminal which consists of a plating part which has the plating structure of Claim 1. A component contact comprising a plated portion having the plated structure according to claim 1. A coating method for obtaining the plated structure according to claim 1,
On the surface of the silver layer formed on the surface of the base material, the diffracted particles of the Sn—Co alloy formed by the particle deposition step have a gap in a top view without overlapping with the surface in the vertical direction. The average diameter of the diffracted particles is 20 to 80 nm, and the weight per unit area of the diffracted particles of the Sn—Co alloy on the surface of the silver layer is 2 × 10 ⁻⁶ to 8 × 10 ⁻⁶ g / A coating method comprising heating a particle deposit of cm ² in a non-oxidizing atmosphere to melt the deposited particles to form a film.

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