Electroless plating solution

Abstract

Precious metal such as a silver-plated film or a tin-plated film, or a single-metal plating film, has high conductivity, and thus can be widely used in contacts and terminal members such as connectors, switches, relays, and the like of electronic devices. However, a single metal terminal using such a noble metal has a problem in durability. This problem is solved by an electroless plating solution containing a metal ion source in which intermetallic compound crystals containing Sn, Cu, Cr and Al are dispersed in a parent phase containing Sn and an Sn-Cu alloy.

Description

Technical Field

[0001] This invention relates to non-electrolytic plating solutions. Background Technology

[0002] Silver-plated or tin-plated coatings, made of precious metals or single metals, have high conductivity and are therefore widely used in electronic devices such as connectors, switches, relays, semiconductor bumps, and substrate wiring coatings for contacts, terminals, and components. However, terminals using such precious metals or single metals have issues with durability over time.

[0003] It should be noted that Patent Document 1 disclosed a tin-copper intermetallic compound dispersed tin contact terminal, characterized in that a tin-plated layer with a tin-copper intermetallic compound dispersed on the surface of a substrate formed of copper or copper alloy is formed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-82499 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The purpose of this invention is to provide an electrolytic plating solution that can produce a coating film with improved durability over time.

[0009] Methods for solving problems

[0010] The present invention provides a non-electrolytic plating solution containing a metal ion source in which intermetallic compound crystals comprising Sn, Cu, Cr and Al are dispersed in a matrix phase comprising Sn and Sn-Cu alloy.

[0011] In addition, the present invention provides a non-electrolytic plating solution containing a metal ion source in which intermetallic compound crystals comprising Sn, Cu, Cr, Al and Ni are dispersed in a matrix phase comprising Sn and Sn-Cu alloy.

[0012] Invention Effects

[0013] According to the present invention, it is possible to provide an electrolytic plating solution that yields a coating film with improved durability over time. Attached Figure Description

[0014] Figure 1 This is a cross-sectional SEM image of block 1 in Example 1.

[0015] Figure 2 This is a graph showing the results of elemental mapping analysis of one cross section of block 1 using EDS.

[0016] Figure 3 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 1.

[0017] Figure 4 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 1.

[0018] Figure 5 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 1.

[0019] Figure 6 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 1.

[0020] Figure 7 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 1.

[0021] Figure 8 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 1.

[0022] Figure 9 This is a cross-sectional SEM image of block 2 in Example 2.

[0023] Figure 10 This is a graph showing the results of elemental distribution analysis using EDS for one cross-section of block 2.

[0024] Figure 11 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 2.

[0025] Figure 12 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 2.

[0026] Figure 13 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 2.

[0027] Figure 14 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 2.

[0028] Figure 15 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 2.

[0029] Figure 16 This is a graph showing the results of elemental distribution analysis using EDS for a specific part of a cross-section of block 2.

[0030] Figure 17 This is a diagram illustrating an example of a manufacturing apparatus suitable for producing the metal particles of the present invention.

[0031] Figure 18 This is a graph showing the results of the durability of the articles in Examples 1 and 2.

[0032] Explanation of reference numerals in the attached figures

[0033] 1 Granulation chamber

[0034] 2 lids

[0035] 3 nozzles

[0036] 4. Disc-shaped rotating plate

[0037] 5. Rotary disk support mechanism

[0038] 6 Particle discharge tube

[0039] 7 Electric Furnace

[0040] 8 Mixed Gas Tanks

[0041] 9 piping

[0042] 10 piping

[0043] 11 valves

[0044] 12 Exhaust device

[0045] 13 valves

[0046] 14 Exhaust device

[0047] 15 Automatic Filters

[0048] 16. Particulate matter recovery device Detailed Implementation

[0049] The embodiments of the present invention will be further described in detail below.

[0050] First, the terminology used in this manual is based on the following, unless otherwise specified.

[0051] (1) When it is called a metal, it includes not only elemental metals, but also alloys and intermetallic compound crystals containing multiple metals.

[0052] (2) When referring to a certain elemental metal, it does not simply mean a substance composed entirely of that metal element, but also includes trace amounts of other substances. That is, it does not mean excluding substances containing trace amounts of impurities that have almost no effect on the properties of that metal element. For example, in the case of what is called the parent phase, it does not mean excluding substances in which some atoms in a Sn crystal have been replaced by other elements (e.g., Cu). For example, these other substances or elements sometimes contain 0 to 0.1% by mass in the electrodes described below.

[0053] The non-electrolytic plating solution of the present invention exists in the following two forms.

[0054] (1) A metal ion source containing intermetallic compound crystals containing Sn, Cu, Cr and Al dispersed in a parent phase containing Sn and Sn-Cu alloys.

[0055] (2) A metal ion source containing intermetallic compound crystals containing Sn, Cu, Cr, Al and Ni dispersed in a parent phase containing Sn and Sn-Cu alloys.

[0056] The metal ion source described above in this invention can be manufactured as follows.

[0057] First, the metal particles described below are manufactured (hereinafter, sometimes referred to as the metal particles of the present invention).

[0058] Next, the metal particles obtained in this invention are melted under vacuum by high-frequency induction heating, and then cast in a mold under nitrogen atmosphere and atmospheric pressure. After cooling and solidification, they are made into rolled sheets, which are then stacked into multiple sheets (hereinafter sometimes referred to as bulk) as needed, and then crushed to obtain the final product.

[0059] The metal particles of the present invention, in the form described in (1) above, can be manufactured, for example, from raw materials consisting of Cu 8% by mass, Cr 0.5% by mass, Al 0.2% by mass, and the remainder being Sn.

[0060] In addition, in the above-mentioned (2) form, for example, it can be manufactured from raw materials composed of Cu 8% by mass, Cr 0.5% by mass, Al 0.5% by mass, Ni 0.5% by mass and the remainder being Sn.

[0061] For example, the raw material is melted and fed onto a disc that rotates at high speed in a nitrogen atmosphere. Centrifugal force is used to disperse the molten metal into droplets, and the metal particles of the present invention are cooled and solidified under reduced pressure.

[0062] Reference Figure 17An example of a preferred manufacturing apparatus for producing the metal particles of the present invention will be described. The granulation chamber 1 has a cylindrical upper portion and a conical lower portion, with a cover 2 at the upper portion. A nozzle 3 is vertically inserted into the center of the cover 2, and a disc-shaped rotating disk 4 is positioned directly below the nozzle 3. Reference numeral 5 indicates a mechanism that supports the disc-shaped rotating disk 4 in a manner that allows it to move up and down. Furthermore, a discharge pipe 6 for the generated particles is connected to the lower end of the conical portion of the granulation chamber 1. The upper part of the nozzle 3 is connected to an electric furnace (high-frequency furnace: conventionally ceramic crucibles are used, but a carbon crucible is used in this invention) 7 for melting the granulated metal. An atmosphere gas adjusted to a predetermined composition in a mixed gas tank 8 is supplied to the interior of the granulation chamber 1 and the upper part of the electric furnace 7 via pipes 9 and 10, respectively. The pressure inside the granulation chamber 1 is controlled by a valve 11 and an exhaust device 12, and the pressure inside the electric furnace 7 is controlled by a valve 13 and an exhaust device 14. The molten metal supplied from nozzle 3 to the disc-shaped rotating disk 4 is condensed into fine droplets by the centrifugal force generated by the disk 4 and dispersed. Under reduced pressure, these droplets are cooled and become solid particles. The generated solid particles are supplied from discharge pipe 6 to an automatic filter 15 for separation. Symbol 16 indicates a particulate recovery device.

[0063] The process of cooling and solidifying molten metal from a high temperature is important for the formation of the metal particles of this invention.

[0064] For example, the following conditions can be cited.

[0065] The melting temperature of the metal in the melting furnace 7 is set to 800℃~1000℃. While maintaining this temperature, molten metal is supplied from the nozzle 3 to the disc-shaped rotating disk 4.

[0066] As the disc-shaped rotating disk 4, a disc-shaped disk with an inner diameter of 35mm and a rotating body thickness of 5mm is used, and the rotation speed is set to 80,000 to 100,000 revolutions per minute.

[0067] As granulation chamber 1, a chamber with a pressure reduction of 9 × 10⁻⁶ is used. -2 After reducing the pressure in the vacuum chamber with a performance of approximately Pa, nitrogen gas at 15–50°C is supplied while exhaust is performed simultaneously, setting the gas pressure in the granulation chamber 1 to 1 × 10⁻⁶. -1 Below Pa.

[0068] As described above, the metal particles of the present invention with the above-described forms (1) and (2) are obtained. The particle size of the metal particles of the present invention is about 5 μm, but the particle size of the metal particles of the present invention is preferably in the range of 1 μm to 50 μm, for example.

[0069] Next, the metal particles obtained in this invention are melted by high-frequency induction heating under vacuum, and then cast in a mold under atmospheric pressure in a nitrogen atmosphere to cool and solidify, forming a rolled sheet. Multiple sheets are then stacked as needed to obtain a block.

[0070] Examples of the high-frequency induction heating and cooling curing conditions include the following.

[0071] High-frequency induction heating: capable of reducing pressure to 9×10 -2 A high-frequency melting crucible is placed in a vacuum chamber with a performance of about Pa. The metal particles of the present invention are introduced into the crucible. The metal particles of the present invention are subjected to high-frequency induction heating under a decompression of about Pa to the aforementioned decompression degree, so that the heating temperature is 800°C to 1000°C to melt the metal particles of the present invention, and the temperature is maintained for 5 minutes to 15 minutes.

[0072] Cooling and solidification: Next, while nitrogen gas at 15-50°C is flowing into the tank, the heating temperature is set to about 400°C or higher under atmospheric pressure for casting, and then cooled and solidified at 30°C or lower.

[0073] The block in this invention, for example in the above-described form (1), is composed of:

[0074] Cu 0.7–15% by mass

[0075] Cr 2~0.02% by mass

[0076] Al 3~0.02% by mass

[0077] The remainder is Sn (wherein unavoidable impurities may be present in less than 0.1% by mass).

[0078] Furthermore, the block in the present invention, for example in the above-described form (2), has the following composition:

[0079] Cu 0.7–15% by mass

[0080] Cr 2~0.02% by mass

[0081] Al 3~0.02% by mass

[0082] Ni 1~0.02% by mass

[0083] The remainder is Sn (wherein unavoidable impurities may be present in less than 0.1% by mass).

[0084] The above composition is the same as that of the metal particles of the present invention.

[0085] Furthermore, the composition of the parent phase of the block in the form (1) of the present invention can be:

[0086] Cu 5~0.02% by mass

[0087] Cr 0.001~18% by mass

[0088] Al 3~0.02% by mass

[0089] The remaining part is Sn.

[0090] The composition of the parent phase described above is the same as that of the metal particles of the present invention.

[0091] Furthermore, the composition of the parent phase of the block in the form (2) of the present invention can be:

[0092] Cu 5~0.02% by mass

[0093] Cr 0.001~18% by mass

[0094] Al 3~0.02% by mass

[0095] Ni 1~0.02% by mass

[0096] The remaining part is Sn.

[0097] The composition of the parent phase described above is the same as that of the metal particles of the present invention.

[0098] Furthermore, the composition of the intermetallic compound crystal of the bulk body in the present invention (1) can be:

[0099] Cu 5-50% by mass

[0100] Cr 0.001~10% by mass

[0101] Al 0.1~20% by mass

[0102] The remaining part is Sn.

[0103] Furthermore, the composition of the intermetallic compound crystal of the bulk body in the form (2) of the present invention can be:

[0104] Cu 5-50% by mass

[0105] Cr 0.001~18% by mass

[0106] Al 0.1~20% by mass

[0107] Ni 0.1~6.5% by mass

[0108] The remaining part is Sn.

[0109] Furthermore, in the bulk bodies of the forms (1) and (2), the proportion of intermetallic compound crystals is, for example, 20 to 60% by mass, preferably 30 to 40% by mass.

[0110] The intermetallic compound crystal is contained within the parent phase.

[0111] The composition and proportion of the parent phase and intermetallic compound crystals described above in this invention can be satisfied by following the manufacturing conditions of the aforementioned bulk material. It should be noted that the inventors have confirmed that the structure of the aforementioned bulk material is identical to that of the metal particles of this invention.

[0112] Furthermore, in the plating method using the non-electrolytic plating solution of the present invention, the intermetallic compound crystals and the parent phase contained in the pulverized bulk material are dissolved as a metal ion source in the plating bath, and they are plated onto the surface of the substrate to form a coating. The formed coating is composed of a Sn-Cu alloy. The formed coating has a structure in which intermetallic compound crystals containing Sn, Cu, Cr, and Al or containing Sn, Cu, Cr, Al, and Ni are dispersed in the parent phase composed of the Sn-Cu alloy.

[0113] The non-electrolytic plating solution of the present invention may, for example, contain various additives known in the past as a reduction plating solution.

[0114] Examples of reducing agents include hypophosphite, formaldehyde, paraformaldehyde, ammonium borohydride, and dimethylamine borane.

[0115] Examples of complexing agents include acetic acid, lactic acid, glycine, citric acid, malonic acid, malic acid, oxalic acid, succinic acid, tartaric acid, thioglycolic acid, ammonia, alanine, glutamic acid, and ethylenediamine.

[0116] As a pH adjuster and as a base, solutions of hydroxides of alkali metals and alkaline earth metals, such as sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia, can be used. As an acid, hydrochloric acid, sulfuric acid, and nitric acid can be used.

[0117] Examples of stabilizers include nitrates of lead, bismuth, thallium, etc.

[0118] In the non-electrolytic plating solution of the present invention, the metal ion source concentration is preferably 10-200 g / L, and the plating temperature is preferably 25-65°C.

[0119] The composition of the intermetallic compound crystals in the resulting coating is the same as that of the bulk material used.

[0120] In addition, the amount of intermetallic compound crystals contained in the above-mentioned coating is, for example, 20 to 60% by mass. The composition of the parent phase is also the same as that of the bulk material used.

[0121] The composition and structure of the overall coating, the parent phase, and the intermetallic compound can be formed by the coating conditions.

[0122] The plated substrate is then subjected to heat treatment as needed. For example, the heat treatment conditions may be a temperature of 100–300°C and a heating time of approximately 5–300 seconds.

[0123] Through the above operations, a coating is formed on the surface of the substrate. The thickness of the coating is, for example, 2 μm to 10 μm.

[0124] It should be noted that, as a base material, examples include metals such as aluminum, aluminum alloys, copper, copper alloys, or stainless steel, as well as resins such as glass epoxy. These can be selected from well-known materials without particular restrictions. For example, as a copper alloy, examples include brass and phosphor bronze.

[0125] It should be noted that a titanium, nickel, or nickel alloy layer can also be formed on the substrate of the coating, which can further improve the heat resistance. As the nickel alloy, an alloy containing one or two of the following can be used: iron, tin, zinc, copper, cobalt, phosphorus, silver, and boron. The thickness of the substrate layer is preferably, for example, about 0.1 μm to 1.5 μm.

[0126] Articles having a coating formed by an electroless plating solution of the above-described form (1) are particularly useful, for example, as bumps or millimeter-wave radar antennas. By forming a film that does not contain the magnetic metal Ni that causes transmission loss, it has the effect of suppressing transmission loss.

[0127] In addition, the surface roughness of the substrate coating on the substrate is usually about 5 micrometers, but by forming the coating film in this invention, it has been confirmed that the surface roughness can be improved to about 100 nanometers without causing significant transmission loss, and high-performance transmission can be expected, which is useful.

[0128] In addition, the article with a coating film formed by non-electrolytic plating solution in the above-described form (2) is particularly useful as a terminal, for example.

[0129] Example

[0130] The present invention will be further illustrated below by way of examples and comparative examples, but the present invention is not limited to the examples described below.

[0131] Example 1

[0132] Example 1 is an example of a non-electrolytic plating solution containing a metal ion source in which intermetallic compound crystals comprising Sn, Cu, Cr and Al are dispersed in a parent phase comprising Sn and Sn-Cu alloys.

[0133] As raw materials, a composition consisting of 8% Cu by mass, 0.5% Cr by mass, 0.2% Al by mass, and the remainder being Sn is used. Figure 17 The manufacturing apparatus shown manufactures metal particles 1 with a diameter of approximately 3 to 50 μm.

[0134] At this point, the following conditions shall apply.

[0135] A melting crucible is placed in the melting furnace 7, and the above-mentioned raw materials are placed in it and melted at 900°C. While maintaining this temperature, molten metal is supplied from the nozzle 3 to the disc-shaped rotating disk 4.

[0136] As the disc-shaped rotating disk 4, a disc-shaped disk with a diameter of 35mm and a thickness of 3-5mm is used, and the rotation speed is set to 80,000-100,000 revolutions per minute.

[0137] As granulation chamber 1, a chamber with a pressure reduction of 9 × 10⁻⁶ is used. -2 After reducing the pressure in the vacuum chamber with a pressure of approximately Pa, nitrogen gas at 15–50°C is supplied while exhaust is performed simultaneously, so that the gas pressure in the granulation chamber 1 is 1 × 10⁻⁶. -1 Below Pa.

[0138] Use the obtained metal powder 1 to make a block.

[0139] At this point, the following conditions shall apply.

[0140] High-frequency induction heating: capable of reducing pressure to 9×10 -2 A high-frequency melting crucible is placed in a vacuum chamber with a performance of about Pa. The metal particles of the present invention are introduced into the crucible. The metal particles of the present invention are subjected to high-frequency induction heating under a depressurization state of about Pa to a heating temperature of 900°C to melt the metal particles of the present invention. The temperature is maintained for 5 minutes.

[0141] Cooling and curing: Next, nitrogen gas at 15-50°C is circulated in the tank for 10 minutes, while the heating temperature of the raw material is set to about 400°C under atmospheric pressure. The material is then cast in a mold and allowed to cool and solidify at room temperature.

[0142] Using the obtained material, the sheet is calendered and multiple sheets are stacked to form a block 1. Next, the block 1 is heated to 150°C and crushed into small pieces, and the resulting crushed material is placed in the plating bath described below.

[0143] The cross-sectional SEM image of block 1 of Example 1 is shown below. Figure 1 .according to Figure 1 It was confirmed that the intermetallic compound crystals (dark-colored) were contained within the parent phase (light-colored).

[0144] In addition, when performing an EDS-based elemental distribution analysis of one cross-section of the aforementioned block 1 (refer to...) Figure 2 The composition was determined to be Cu 6.9% by mass, Cr 0.59% by mass, Al 0.15% by mass, with the remainder being Sn.

[0145] It should be noted that, to conduct Figures 7-8In the EDS-based elemental distribution analysis of points 005-006, the composition of the parent phase is as follows:

[0146] Sn 86–90.9% by mass

[0147] Cu 2.06–4.14% by mass

[0148] The presence of Sn-Cu alloys was confirmed when Al content was below 1.1% by mass.

[0149] In addition, regarding the composition of intermetallic compound crystals, Figures 3-6 The element distribution analysis based on EDS for points 001-004 in the data shows that:

[0150] Sn 62.69~74.72% by mass

[0151] Cu 5.35–33.17% by mass

[0152] Cr ≤ 7.8% by mass

[0153] Al ≤ 3.29% by mass.

[0154] In addition, the intermetallic compound crystals in the above-mentioned block 1 account for 30-35% by mass.

[0155] As the substrate, a substrate with copper wiring, copper antennas, and copper bumps formed on a ceramic substrate is used, and electroless plating is performed on the copper plating layer. Details of the electroless plating bath are as follows: Electroless plating bath composition (concentration relative to 1 liter of water):

[0156] Metal ion source: intermetallic compound crystals and parent phase contained in the bulk 1

[0157] Sn concentration = 10 g / L

[0158] Cu concentration = 1 g / L

[0159] Cr concentration = 0.1 g / L

[0160] Al concentration = 0.1 g / L

[0161] The non-electrolytic plating conditions are as follows.

[0162] Plating temperature: 50℃

[0163] Plating time: 120 minutes

[0164] Heat treatment temperature of the plated substrate: 200℃

[0165] Heat treatment time for the coated substrate: 300 seconds (under nitrogen atmosphere)

[0166] The composition of the coating on the obtained item is the same as that of block 1 described above. Furthermore, the thickness of the coating is 5 μm.

[0167] The article obtained in Example 1 above was immersed in a 5% NaCl aqueous solution for 120 hours, and its condition was observed. The results are shown below. Figure 18 middle. Figure 18 (a) is the result of this Example 1, where no corrosion was observed on the surface. Figure 18 (b) Corrosion was observed on the surface of an article with a previous Sn-Cu coating.

[0168] Example 2

[0169] Example 2 is an example of a non-electrolytic plating solution containing a metal ion source in which intermetallic compound crystals comprising Sn, Cu, Cr, Al and Ni are dispersed in a matrix phase comprising Sn and Sn-Cu alloys.

[0170] As raw materials, a composition consisting of 8% Cu by mass, 0.5% Cr by mass, 0.5% Al by mass, 0.5% Ni by mass, and the remainder being Sn is used. Figure 17 The manufacturing apparatus shown produced metal particles 2 with a diameter of approximately 3 to 50 μm.

[0171] At this point, the following conditions shall apply.

[0172] A melting crucible is placed in the melting furnace 7, and the above-mentioned raw materials are placed in it and melted at 900°C. While maintaining this temperature, molten metal is supplied from the nozzle 3 to the disc-shaped rotating disk 4.

[0173] As the disc-shaped rotating disk 4, a disc-shaped disk with a diameter of 35mm and a thickness of 3-5mm is used, and the rotation speed is set to 80,000-100,000 revolutions per minute.

[0174] As granulation chamber 1, a chamber with a pressure reduction of 9 × 10⁻⁶ is used. -2 After reducing the pressure in the vacuum chamber with a pressure of approximately Pa, nitrogen gas at 15–50°C is supplied while exhaust is performed simultaneously, so that the gas pressure in the granulation chamber 1 is 1 × 10⁻⁶. -1 Below Pa.

[0175] Use the obtained metal powder 1 to make a block.

[0176] At this point, the following conditions shall apply.

[0177] High-frequency induction heating: capable of reducing pressure to 9×10 -2A high-frequency melting crucible is placed in a vacuum chamber with a performance of about Pa. The metal particles of the present invention are introduced into the crucible. The metal particles of the present invention are subjected to high-frequency induction heating under a depressurization state of about Pa to a heating temperature of 900°C to melt the metal particles of the present invention. The temperature is maintained for 5 minutes.

[0178] Cooling and curing: Next, nitrogen gas at 15-50°C is circulated in the tank for 10 minutes, while the heating temperature of the raw material is set to about 400°C under atmospheric pressure. The material is then cast in a mold and allowed to cool and solidify at room temperature.

[0179] Using the obtained material, the sheet is calendered and multiple sheets are stacked to produce block 2. Next, block 2 is placed in a cutting machine heated to 150°C and crushed into sizes of 1cm to 3cm × 1mm to 5mm. The resulting crushed material is then placed in the plating bath described below.

[0180] The cross-sectional SEM image of block 2 of Example 2 is shown below. Figure 9 According to Figure 9 It was confirmed that the intermetallic compound crystals (dark-colored) were contained within the parent phase (light-colored).

[0181] In addition, when performing an EDS-based elemental distribution analysis of one cross-section of the aforementioned block 2 (refer to...) Figure 10 The composition was determined to be Cu 7.22 wt%, Cr 0.54 wt%, Al 0.28 wt%, Ni 0.24 wt%, with the remainder being Sn.

[0182] It should be noted that, to conduct Figures 15-16 In the EDS-based elemental distribution analysis of points 005-006, the composition of the parent phase is as follows:

[0183] Sn 74.38%–85.74% by mass

[0184] Cu 4.11%–4.49% by mass

[0185] Al 0.78%–1.77% by mass

[0186] Ni 0.61%–0.86% by mass, the presence of Sn and Sn-Cu alloy was confirmed.

[0187] In addition, the composition of intermetallic compound crystals was investigated. Figures 11-14 The element distribution analysis based on EDS for points 001-004 in the data shows that:

[0188] Sn 30.61% by mass to 68.66% by mass

[0189] Cu 7.48% by mass to 27.37% by mass

[0190] Cr ≤ 15.67% by mass

[0191] Al 7.38% by mass or less

[0192] Ni is less than 10.74% by mass.

[0193] In addition, the intermetallic compound crystals in the above-mentioned block 2 account for 30-35% by mass.

[0194] A copper spring was used as the substrate for electroless plating. Details of the electroless plating bath are described below.

[0195] Non-electrolytic plating bath composition (concentration relative to 1 liter of water):

[0196] Metal ion source: intermetallic compound crystals and parent phase contained in the above-mentioned block 2

[0197] Sn concentration in plating solution = 10 g / L

[0198] Cu concentration in the plating solution = 1 g / L

[0199] The Cr concentration in the plating solution is 0.1 g / L.

[0200] The Ni concentration in the plating solution is 0.1 g / L.

[0201] The Al concentration in the plating solution is 0.1 g / L.

[0202] The non-electrolytic plating conditions are as follows.

[0203] Plating temperature: 50℃

[0204] Plating time: 120 minutes

[0205] Heat treatment temperature of the plated substrate: 200℃

[0206] Heat treatment time for the coated substrate: 300 seconds (under nitrogen atmosphere)

[0207] The composition of the coating on the obtained item is the same as that of block 2 described above. Furthermore, the thickness of the coating is 5 μm.

[0208] The article obtained in Example 2 was immersed in a 5% NaCl aqueous solution for 120 hours, and its condition was observed. The result was the same as in Example 1 (refer to...). Figure 18 (a)).

[0209] The present invention has been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Those skilled in the art can certainly conceive of various modifications based on its basic technical ideas and teachings.

Claims

1. A non-electrolytic plating solution containing a metal ion source having intermetallic compound crystals containing Sn, Cu, Cr and Al dispersed in a matrix phase containing Sn and Sn-Cu alloy, wherein the composition of the matrix phase in the metal ion source, the composition of the intermetallic compound crystals and the proportion of the intermetallic compound crystals are as follows, the composition of the matrix phase is: Cu 5 to 0.02 mass%, Cr 0.001 to 18 mass%, Al 3 to 0.02 mass%, the remainder being Sn, the composition of the intermetallic compound crystals is: Cu 5 to 50 mass%, Cr 0.001 to 10 mass%, Al 0.1 to 20 mass%, the remainder being Sn, the proportion of the intermetallic compound crystals is 20 to 60 mass%.

2. A non-electrolytic plating solution containing a metal ion source having intermetallic compound crystals containing Sn, Cu, Cr, Al and Ni dispersed in a matrix phase containing Sn and Sn-Cu alloy, wherein the composition of the matrix phase in the metal ion source, the composition of the intermetallic compound crystals and the proportion of the intermetallic compound crystals are as follows, the composition of the matrix phase is: Cu 5 to 0.02 mass%, Cr 0.001 to 18 mass%, Al 3 to 0.02 mass%, Ni 1 to 0.02 mass%, the remainder being Sn, the composition of the intermetallic compound crystals is: Cu 5 to 50 mass%, Cr 0.001 to 18 mass%, Al 0.1 to 20 mass%, Ni 0.1 to 6.5 mass%, the remainder being Sn, the proportion of the intermetallic compound crystals is 20 to 60 mass%. ​ ​

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