Electroless nickel plating solution, electroless nickel plating method, nickel plating film, and product

Abstract

[Problem] To provide: a nickel plating film that has suitable bath stability, pattern deposition properties, and plating deposition properties in a fine pad part, and excellent in solder connection reliability and surface smoothness; and an electroless nickel plating solution useful for forming the plating film. [Solution] A nickel plating film is formed on an object to be plated by subjecting the object to be plated to surface treatment using an electroless nickel plating solution that contains at least S2+ and a Co metal and in which the Co metal is included in the form of Co2+ and Co3+.

Description

Electroless Ni plating solution, electroless Ni plating method, Ni plating film, and product

[0001] The present invention relates to an electroless Ni plating solution, an electroless Ni plating method, a Ni plating film, and a product.

[0002] Conventionally, as a surface treatment method for parts where soldering, bonding, etc. are performed in electronic components, particularly printed wiring boards, a method of forming a Ni plating film and then performing substitution Au plating has been widely adopted. In recent years, methods of performing electroless Pd plating and electroless Pd / Au plating have been developed.

[0003] The conductor circuit of a printed wiring board is generally formed of copper. However, since copper has no catalytic action on electroless Ni plating, usually, a catalytic substance such as Pd is adhered before performing electroless Ni plating.

[0004] However, in such a method, the catalytic substance adheres not only to the conductor circuit portion but also to unnecessary portions of the plating. Therefore, the electroless Ni plating solution is required to have the property of selectively forming a plating film only on the conductor circuit pattern portion, that is, pattern deposition property. Conventionally, in order to improve the pattern deposition property of the electroless Ni plating solution and further improve the bath stability, as additives, metal salts such as water-soluble Pb salts and Bi salts, sulfur compounds such as thiodiglycolic acid (S ２＋ ) etc. have been used.

[0005] However, with the miniaturization of the pattern width of the conductor circuit, when using a conventional electroless Ni plating solution, for the narrow part of the pattern width of the conductor circuit, plating is deposited around the circuit, so-called plating spread, or so-called step plating occurs where the end face and tip part of the circuit are thinner than other parts. In addition, many reticular patterns occur by including S ２＋ etc., and problems such as deterioration of solder wettability, solder connection reliability, and surface smoothness have arisen.

[0006] On the other hand, in recent years, IC packages with minute pads of approximately Φ0.1 to 0.5 mm, such as ball grid arrays (BGAs) and chip-scale packages (CSPs), have been manufactured to mount components at high density. In this case, electroless Ni plating solutions containing the additives mentioned above are prone to problems such as insufficient plating deposition in the minute pad areas or the plating deposition reaction stopping midway.

[0007] Such cessation of the plating reaction tends to occur when a large amount of additive is added. The mechanism is not clear, but it is thought that in small-diameter pads surrounded by resist, dissolved oxygen in the solution and reaction gases from electroless Ni plating make it easier for bubbles to adhere, and the reaction is more easily suppressed compared to relatively large pad areas or fine wiring areas without resist (for example, slit-shaped areas).

[0008] Patent Document 2, described below, discloses an electroless Ni plating solution used as an undercoat for Au plating, in which two or more metal elements with valencies at pH 3 to 8 are added for the purpose of improving bath stability, solderability, corrosion resistance, etc. Specifically, sulfates and chlorides of one or more metals selected from Mn, Sn, Fe, Cr, and Co are described as such additives. However, in electroless Ni plating solutions with these sulfates and chlorides added, while bath stability is slightly improved and plating abnormalities in fine wire patterns are reduced accordingly, the deposition of plating on minute pad areas such as BGA and CSP is conversely reduced, resulting in the problem of unplated areas and reaction stoppage areas.

[0009] Patent Document 1 and Non-Patent Document 1 below describe an electroless Ni plating solution that, by adding Fe, Sn, Co, and S, exhibits good bath stability and pattern deposition properties, as well as excellent deposition properties in minute pad areas. However, the solder connection reliability and surface smoothness were insufficient, and it was still not satisfactory.

[0010] Japanese Patent Publication No. 3800213, Japanese Unexamined Patent Publication No. 2002-180261

[0011] Hiroki Seto, Yoshi Hashizume, Toshinari Murata, "Electroless Ni-P plating corresponding to fine patterns", Journal of the Institute of Electronics Packaging., Vol. 21, No. 2, 155-159, 2018

[0012] The main object of the present invention is to provide a Ni plating film having good bath stability, pattern deposition properties, and plating deposition properties in a fine pad portion, and further excellent solder connection reliability and surface smoothness, and an electroless Ni plating solution useful for forming the plating film.

[0013] The present inventors have conducted intensive studies to achieve the above object. As a result, when S ２＋ and Co ２＋ and Co ３＋ are included in the electroless Ni plating solution, the generation of a reticular pattern seen on the surface of the Ni plating film is suppressed, and thereby, when Au plating or Pd / Au plating treatment is performed as a subsequent process, the interface with the Ni plating film becomes smooth and uniform, and an improvement in solder connection reliability is expected. Also, after obtaining findings such as that the arithmetic mean roughness Ra also decreases and the transmission loss is expected to become small, further studies were repeated, and an electroless Ni plating solution containing at least S ２＋ and Co metal was found, wherein the Co metal is contained in the forms of Co ２＋ and Co ３＋ and has good bath stability, pattern deposition properties, and deposition properties in a fine pad portion, and is further excellent in solder connection reliability and surface smoothness. After further repeated studies, the present invention was completed.

[0014] That is, the present invention relates to the following inventions. (1) An electroless Ni plating solution containing at least S ２＋ and Co metal, wherein the Co metal is contained in the forms of Co ２＋ and Co ３＋ . (2) The electroless Ni plating solution according to (1) above, wherein the content of S ２＋ is 1 mg / L or more. (3) The electroless Ni plating solution according to (1) above, wherein the content of Co ２＋ is 5 mg / L or more. (4) Co ３＋The electroless Ni plating solution described in (1) above, wherein the content of is 1 mg / L or more. (5) S ２＋ and Co ２＋ and Co ３＋ The ratio of the blend is S by weight. ２＋ For 1, Co ２＋ If it is 0.5 or higher, Co ３＋ The electroless Ni plating solution described in (1) above, wherein the ratio is 0.1 or higher. (6) S ２＋ The electroless Ni plating solution described in (5) above, wherein the content of is 1 to 20 mg / L. (7) S ２＋ The content is 1 to 20 mg / L, and Co ２＋ The content is 5 to 200 mg / L, Co ３＋ (1) The electroless Ni plating solution according to (1), wherein the content of is 1 to 50 mg / L. (8) An electroless Ni plating method characterized by contacting an object to be plated with the electroless Ni plating solution according to (1). (9) A Ni plating film containing at least S and Co, characterized in that the content of S is 0.001 wt% or more and the content of Co is 0.01 wt% or more. (10) The Ni plating film according to (9), wherein the content of Co is 0.03 wt% or more. (11) The Ni plating film according to (9), wherein the arithmetic mean roughness (Ra) as defined in JIS B 0601-2001 is less than 0.1 μm. (12) A Ni plating film in which, when a horizontal 1200 nm straight line is drawn on an image obtained by observing the surface of the Ni plating film at a magnification of 100,000x using an FE-SEM with an acceleration voltage of 5 kV, and the intersection points where the straight line intersects with the mesh-like pattern formed in the crystal grains of the Ni plating film are determined, the number of intersection points obtained is less than 10. (13) The Ni plating film according to (12) further containing 0.001 wt% or more of S. (14) A product and a part thereof comprising a Ni plating film, wherein the Ni plating film is the Ni plating film according to (9) or (12).

[0015] The Ni plating film of the present invention exhibits excellent bath stability, pattern deposition properties, and deposition properties in minute pad areas, and also provides superior solder connection reliability and surface smoothness. Furthermore, the electroless Ni plating solution of the present invention can produce the Ni plating film in an industrially advantageous manner.

[0016] This figure shows the pattern properties in Example 1. This figure shows the pattern properties in Comparative Example 2. This figure shows the pattern properties in Comparative Example 1. This figure shows the solder connection reliability in Example 1. This figure shows the solder connection reliability in Comparative Example 1. This figure shows the surface smoothness in Example 1. This figure shows the surface smoothness in Comparative Example 1. This figure shows the surface smoothness in Comparative Example 2. This figure shows the solder wettability in Example 1.

[0017] The electroless Ni plating solution of the present invention is S ２＋ An electroless Ni plating solution comprising at least Co metal, wherein the Co metal is Co ２＋ and Co ３＋ It is characterized by being included in the form of S ２＋ and Co ２＋ and Co ３＋ Additives containing S can be suitably used, ２＋ Additives containing Co ３＋ Using additives containing Co in the plating solution ２＋ The form may be changed. Examples of the additives include reducing agents, complexing agents, and complex compounds and / or metal salts.

[0018] A preferred electroless Ni plating solution of the present invention contains, for example, (1) a water-soluble Ni salt, (2) a reducing agent, (3) a complexing agent, and (4) a complex compound and / or a metal salt. In particular, the electroless Ni plating solution of the present invention contains S ２＋ and Co ２＋ and Co ３＋ It is preferable to include compounds containing these in the form of complex compounds. By adding these compounds in the form of complex compounds, not only pattern deposition properties, deposition properties in the micro-pad area, and bath stability can be greatly improved, but also solder connection reliability and surface smoothness.

[0019] The ligands and other components of the complex compound are not particularly limited as long as they do not hinder the objectives of the present invention, and may be known ligands and other components.

[0020] The coordination number of the ligand described above is usually determined by the type and valency of the metal, Co２＋ , and Co ３＋ The coordination number in this case is 6.

[0021] Specific examples of complex compounds and / or metal salts that can be used in the present invention include potassium hexacyanocobalt(II)ate, hexaamminecobalt(II) chloride, cobalt(II) sulfate, dichlorodiamminecobalt(II), cis-diacotetraamminecobalt(III) sulfate, hexaamminecobalt(III) sulfate, hexaamminecobalt(III) chloride, sodium hexacyanocobalt(III)ate, and hexanitrocobalt(III) ammonium. Examples include trisethylenediaminecobalt(III) chloride, trichlorotriamminecobalt(III), chloropentaamminecobalt(III) chloride, cis-triacotriamminecobalt(III) chloride, dichloroacotriamminecobalt(III) chloride, dichlorodiacodiamminecobalt(III) nitrate, dichlorodiacodiamminecobalt(III) chloride, and ammonium trioxalatocobalt(III)ate.

[0022] The above complex compounds and / or metal salts can be used individually or in combination of two or more. ２＋ The content of is more preferably about 5 to 200 mg / L, and most preferably about 10 to 100 mg / L. Also, Co ３＋ The content of is more preferably about 1 to 50 mg / L, and most preferably about 10 to 30 mg / L. Within this preferred range, patternability, precipitation properties, and bath stability are improved.

[0023] As a water-soluble Ni salt, any salt that is soluble in the plating solution and can be prepared as an aqueous solution of a predetermined concentration can be used without particular limitations. Specific examples of water-soluble Ni salts include Ni sulfate, Ni chloride, Ni sulfamate, and Ni hypophosphorous acid. Ni sulfate is particularly preferred due to its good solubility. Water-soluble Ni salts can be used individually or in combination of two or more.

[0024] The water-soluble Ni salt content is preferably about 0.5 to 50 g / L, and more preferably about 2 to 10 g / L.

[0025] As the reducing agent, any reducing agent used in known electroless Ni plating solutions can be used. Specific examples include hypophosphorous acid, hypophosphate (sodium salt, potassium salt, ammonium salt, etc.), dimethylamine borane, hydrazine, etc. The reducing agent can be used alone or in a mixture of two or more.

[0026] The reducing agent content is preferably about 0.01 to 100 g / L, and more preferably about 0.1 to 50 g / L.

[0027] As a complexing agent, complexing agents used in known electroless Ni plating solutions can be used. Specific examples include monocarboxylic acids such as acetic acid and formic acid; dicarboxylic acids such as malonic acid, succinic acid, adipic acid, maleic acid, and fumaric acid; hydroxycarboxylic acids such as malic acid, lactic acid, glycolic acid, gluconic acid, and citric acid; amino acids such as glycine, alanine, iminodiacetic acid, arginine, aspartic acid, and glutamic acid; organic acids such as aminopolycarboxylic acids such as nitrilotriacetic acid, ethylenediaminediacetic acid, ethylenediaminetetraacetic acid, and diethylenetriaminepentaacetic acid; soluble salts of these organic acids (sodium salts, potassium salts, ammonium salts, etc.); and amines such as ethylenediamine, diethylenetriamine, and triethylenetetramine. The complexing agent can be used alone or in combination of two or more types.

[0028] The total amount of the complexing agent is preferably about 1 to 100 g / L, and more preferably about 5 to 50 g / L.

[0029] The electroless Ni plating solution of the present invention may further contain various additives that are added to conventional electroless Ni plating baths, as needed. For example, as stabilizers, Pb salts such as lead nitrate and lead acetate, Bi salts such as bismuth nitrate and bismuth acetate, and sulfur compounds such as thiodiglycolic acid (S ２＋) can be added individually or in a mixture of two or more. In the present invention, sulfur compounds such as thiodiglycolic acid (S ２＋ ) to Co ２＋ and Co ３＋ By using this method, pattern deposition properties, solder connection reliability, surface smoothness, and other properties can be improved.

[0030] Sulfur compounds that can be used in the present invention (S ２＋ Specific examples of these include thiobenzoic acid, thiolactic acid, 2,2'-thiodiacetic acid, ethylenedithiodiacetic acid, 4-mercaptobenzoic acid, 3-mercapto-1-propanesulfonic acid, 3-(benzothiazole-2-ylthio)-1-propanesulfonic acid, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonic acid, 5-hydroxythionaphthene, thiodiglycolic acid, dithiodiglycolic acid, 1-octadecanethiol, 2,2'-thiodiethanol, benzothiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-amino-4-methylthiazole, 2-aminobenzothiazole, 2-aminothiazole, thiourea, 1-phenyl-2-thiourea, tetramethylthiourea, thiouracil, thiophene, benzothiophene, 2-thiophenecarboxylic acid, L-cysteine, and the like.

[0031] The above S ２＋ It can be used as a single type or as a mixture of two or more types, S ２＋ The amount of additive is more preferably about 1 to 20 mg / L, and most preferably about 1 to 10 mg / L. Within this preferred range, patternability, precipitation properties, bath stability, solder connection reliability, and surface smoothness are improved.

[0032] In the present invention, S ２＋ It is preferable to blend the additive such that its content is 1 mg / L or more. Within this preferred range, pattern deposition properties, solder connection reliability, and surface smoothness are improved. Furthermore, in this invention, Co ２＋It is preferable to blend the additive such that its content is 5 mg / L or more. Within this preferred range, pattern deposition properties, solder connection reliability, and surface smoothness are improved. Furthermore, in this invention, Co ３＋ It is preferable to blend the additive such that the content of is 1 mg / L or more. According to this preferred range, pattern deposition properties, solder connection reliability and surface smoothness are better. In addition, in the present invention, S ２＋ and Co ２＋ and Co ３＋ The ratio of the blend is S by weight. ２＋ For 1, Co ２＋ If it is 0.5 or higher, Co ３＋ It is preferable to blend the additive such that the ratio is 0.1 or higher. According to this preferred range, pattern deposition properties, solder connection reliability, and surface smoothness are improved. In addition, in the present invention, S ２＋ It is preferable to blend the additive such that its content is 1 to 20 mg / L. Within this preferred range, pattern deposition properties, solder connection reliability, and surface smoothness are improved. In addition, in the present invention, S ２＋ The content is 1 to 20 mg / L, and Co ２＋ The content is 5 to 200 mg / L, Co ３＋ It is preferable to blend the additive such that its content is 1 to 50 mg / L. Within this preferred range, pattern deposition properties, solder connection reliability, and surface smoothness are improved.

[0033] The electroless Ni plating solution of the present invention is obtained by dissolving each of the above-mentioned components in water. The pH of the plating solution when performing electroless Ni plating is preferably around 2 to 9, and more preferably around 3 to 7. The pH of the plating solution can be adjusted according to conventional methods, for example, by using an inorganic acid such as sulfuric acid or phosphoric acid, sodium hydroxide, ammonia water, etc.

[0034] To perform plating using the electroless Ni plating solution of the present invention, the object to be plated should be immersed in the plating solution according to a conventional method. At this time, the plating solution may be stirred or the object to be plated may be agitated as needed.

[0035] Various materials that have conventionally been targeted for electroless nickel plating can be used as the material to be plated. For example, metals that are catalytic for the reduction deposition of electroless nickel plating, such as Fe, Co, Ni, Pd, and their alloys, can be used as the material to be plated. Furthermore, even metals that are not catalytic for electroless nickel plating, such as copper, as well as glass and ceramics, can be plated by attaching a metal catalyst nucleus such as a Pd nucleus according to a conventional method. In the present invention, it is preferable that the material to be plated has undergone pretreatment such as degreasing or soft etching.

[0036] In particular, the electroless Ni plating solution of the present invention exhibits excellent pattern deposition properties, superior deposition properties in minute pad areas, and also excellent solder connection reliability and surface smoothness. Therefore, it is a highly useful plating solution when plating conductor circuit areas of printed circuit boards, ball grid arrays (BGAs), chip scale packages (CSPs), and other minute pad areas.

[0037] The temperature of the plating solution during electroless Ni plating is preferably around 40 to 98°C, and more preferably around 60 to 95°C.

[0038] In the present invention, the Ni plating film can be easily obtained by bringing the above-described preferred electroless Ni plating solution into contact with the object to be plated. The Ni plating film of the present invention is a Ni plating film containing at least S and Co, preferably with an S content of 0.001 wt% or more and a Co content of 0.01 wt% or more. More preferably, the S content is 0.001 to 0.05 wt% and the Co content is 0.01 to 0.5 wt%. Such preferred ranges result in better patternability, solder connection reliability, and surface smoothness.

[0039] The Ni plating film of the present invention is preferably one in which, when a horizontal 1200 nm straight line is drawn on an image obtained by observing the surface of the Ni plating film at a magnification of 100,000x using an FE-SEM with an acceleration voltage of 5 kV, and the intersection points of the straight line and the mesh-like pattern formed within the crystal grains of the Ni plating film are determined, the number of intersection points obtained is less than 10, and these preferred Ni plating films are also included in the present invention.

[0040] Furthermore, in the present invention, by performing electroless Ni plating under the above-described preferred conditions, a Ni plated film can be obtained in which, when a horizontal 1200 nm straight line is drawn on an image obtained by observing the surface of the Ni plated film at a magnification of 100,000x using an FE-SEM with an acceleration voltage of 5 kV, and the intersection points where the straight line intersects with the mesh-like pattern are determined, the number of intersection points obtained is less than 10. The mesh-like pattern is a mesh-like pattern formed on the inner surface of the crystal grains of the Ni plated film. In the present invention, for convenience, for example, as shown in Figures 6 to 8, a horizontal 1200 nm straight line is drawn on an image obtained by observing the surface of the Ni plated film at a magnification of 100,000x using an FE-SEM with an acceleration voltage of 5 kV, and the intersection points where the straight line intersects with the mesh-like pattern are determined.

[0041] The present invention will be described in more detail below with reference to examples. Example 1 (1) Preparation of electroless Ni plating solution The following composition (S ２＋ and Co ２＋ and Co ３＋ An electroless Ni plating bath (containing S) was prepared. The prepared plating bath exhibited excellent bath stability. ２＋ and Co ２＋ and Co ３＋ The concentration ratio is S ２＋ : Co ２＋ : Co ３＋= 1:10:5. (Electroless Ni plating bath composition) Nickel(II) sulfate hexahydrate 22.5 g / L Sodium hypophosphite 25 g / L Malic acid 5-20 g / L Succinic acid 5-20 g / L Lead nitrate 0.2-1.0 mg / L Thiodiglycolic acid 20 mg / L Cobalt(II) sulfate heptahydrate 250 mg / L Hexaamminecobalt(III) chloride 125 mg / L pH 4-5 (adjusted with sulfuric acid-sodium hydroxide) (2) Formation of Ni plating film A Ni plating film was formed on a substrate using an electroless Ni plating bath of the above composition. Three types of substrates were prepared: a rolled copper plate (2.5 × 2.5 cm), a SUS304 plate (5 × 10 cm), and a BGA resin substrate having over-resist type fine wiring (L / S = 50 / 50 μm, Φ0.6 mm) on a resin base material. A Ni plating film was formed on each substrate. The formed Ni plating films all exhibited excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating films is shown in Table 3.

[0042] Example 2 (1) Preparation of electroless Ni plating solution S ２＋ : Co ２＋ : Co ３＋ An electroless Ni plating bath was prepared in the same manner as in Example 1, except that the ratio was set to 1:50:25. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All of the formed Ni plating films had excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0043] Example 3 (1) Preparation of electroless Ni plating solution S ２＋ : Co ２＋ : Co ３＋An electroless Ni plating bath was prepared in the same manner as in Example 1, except that the ratio was set to 1:4:2. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All of the formed Ni plating films had excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3.

[0044] Example 4 (1) Preparation of electroless Ni plating solution S ２＋ : Co ２＋ : Co ３＋ An electroless Ni plating bath was prepared in the same manner as in Example 1, except that the ratio was set to 1:1:5. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All of the formed Ni plating films had excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0045] Example 5 (1) Preparation of electroless Ni plating solution S ２＋ : Co ２＋ : Co ３＋ An electroless Ni plating bath was prepared in the same manner as in Example 1, except that the ratio was set to 1:40:5. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All of the formed Ni plating films had excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0046] Example 6 (1) Preparation of electroless Ni plating solution S ２＋ : Co ２＋ : Co ３＋An electroless Ni plating bath was prepared in the same manner as in Example 1, except that the ratio was set to 1:10:1. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All the formed Ni plating films were excellent in pattern deposition property, plating deposition property in the micro-pad portion, solder connection reliability, and surface smoothness. The contents of Co and S in the Ni plating film are shown in Table 3, respectively.

[0047] Example 7 (1) Preparation of electroless Ni plating solution S ２＋ : Co ２＋ : Co ３＋ An electroless Ni plating bath was prepared in the same manner as in Example 1, except that the ratio was set to 1:10:10. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All the formed Ni plating films were excellent in pattern deposition property, plating deposition property in the micro-pad portion, solder connection reliability, and surface smoothness. The contents of Co and S in the Ni plating film are shown in Table 3, respectively.

[0048] Example 8 S ２＋ : Co ２＋ : Co ３＋ An electroless Ni plating bath was prepared in the same manner as in Example 1, except that the ratio was set to 1:1:1. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All the formed Ni plating films were excellent in pattern deposition property, plating deposition property in the micro-pad portion, solder connection reliability, and surface smoothness. The contents of Co and S in the Ni plating film are shown in Table 3, respectively.

[0049] Example 9 S ２＋ : Co ２＋ : Co ３＋An electroless Ni plating bath was prepared in the same manner as in Example 1, except that the ratio was set to 1:40:10. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All of the formed Ni plating films had excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0050] Example 10 (1) Preparation of electroless Ni plating solution An electroless Ni plating bath was prepared in the same manner as in Example 1, except that thiourea was added at a concentration of 10 mg / L instead of thiodiglycolic acid. The prepared plating bath exhibited excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. The formed Ni plating films all exhibited excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0051] Example 11 (1) Preparation of electroless Ni plating solution An electroless Ni plating bath was prepared in the same manner as in Example 1, except that hexaamminecobalt(II) chloride was added at a concentration of 250 mg / L instead of cobalt(II) sulfate heptahydrate. The prepared plating bath exhibited excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. The formed Ni plating films all exhibited excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0052] Example 12 (1) Preparation of electroless Ni plating solution An electroless Ni plating bath was prepared in the same manner as in Example 1, except that 100 mg / L of trichlorotriamminecobalt(III) was added instead of hexaamminecobalt(III) chloride. The prepared plating bath had excellent bath stability. (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. The formed Ni plating films all had excellent pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0053] The present invention will be described in more detail below with reference to comparative examples. Comparative Example 1 (1) Preparation of electroless Ni plating solution An electroless Ni plating bath with the following composition was prepared. The prepared plating bath had poor bath stability. (Composition of electroless Ni plating bath) Nickel(II) sulfate hexahydrate 22.5 g / L Sodium hypophosphite 25 g / L Malic acid 5-20 g / L Succinic acid 5-20 g / L Lead nitrate 0.2-1.0 mg / L Thiodiglycolic acid 30 mg / L pH 4-5 (adjusted with sulfuric acid-sodium hydroxide) (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. The formed Ni plating films all had poor pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0054] Comparative Example 2 (1) Preparation of electroless Ni plating solution An electroless Ni plating bath with the following composition was prepared. The prepared plating bath had poor bath stability. (Composition of electroless Ni plating bath) Nickel(II) sulfate hexahydrate 22.5 g / L Sodium hypophosphite 25 g / L Malic acid 5-20 g / L Succinic acid 5-20 g / L Lead nitrate 0.2-1.0 mg / L Thiodiglycolic acid 50 mg / L pH 4-5 (adjusted with sulfuric acid-sodium hydroxide) (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. The formed Ni plating films all had poor pattern deposition, plating deposition in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3.

[0055] Comparative Example 3 (1) Preparation of Electroless Ni Plating Solution An electroless Ni plating bath with the following composition was prepared. The prepared plating bath did not have good bath stability. (Electroless Ni Plating Bath Composition) Nickel(II) sulfate hexahydrate 22.5 g / L Sodium hypophosphite 25 g / L Malic acid 5-20 g / L Succinic acid 5-20 g / L Lead nitrate 0.2-1.0 mg / L Thiodiglycolic acid 30 mg / L (S ２＋ (4.3 mg / L) Cobalt(II) sulfate heptahydrate 50 mg / L pH 4-5 (adjusted with sulfuric acid-sodium hydroxide) (2) Formation of Ni plating film A Ni plating film was formed in the same manner as in Example 1. All of the formed Ni plating films had poor pattern deposition properties, plating deposition properties in the micro-pad areas, solder connection reliability, and surface smoothness. The Co and S content in the Ni plating film is shown in Table 3, respectively.

[0056] Each physical property was evaluated for each sample in the test examples and comparative examples. The results are shown in Tables 1, 2, and 3 below. The evaluation of each physical property is as follows: (1) Patterning: After forming a Ni plating film on a BGA substrate using the above processing steps, the deposition state of the plating in the copper wiring pattern area was observed at 100x magnification using a microscope (KEYENCE VHX-7000). 1: The exposed width of the resin substrate between copper wiring patterns is 36 to 50 μm (see Figure 1) 2: The exposed width of the resin substrate between copper wiring patterns is 21 to 35 μm (see Figure 2) 3: The exposed width of the resin substrate between copper wiring patterns is 0 (short circuit) to 20 μm (see Figure 3) (2) Deposition on minute pad areas: After forming a Ni plating film on the BGA substrate using the above processing steps, the deposition state of the plating on minute copper pad areas (Φ60 to 200 μm, 80 pads) was observed at 20x magnification using a microscope (KEYENCE VHX-7000). The minute pad areas where plating was deposited normally were white, while the unreacted areas where no plating had deposited at all were reddish-black in color, and areas where the reaction stopped during plating were black to grayish-black, which was used to determine this. 1: Fewer than 10 abnormal deposition locations 2: 10 to 19 abnormal deposition locations 3: 20 or more abnormal deposition locations (3) Bath stability: Each plating solution was placed in a 1L glass beaker and left at 90°C for 2 days, after which the condition of the plating solution and the beaker was observed. 1: No reaction gas was generated at the bottom of the beaker 2: Reaction gas was generated at the bottom of the beaker 3: Ni particles were deposited at the bottom and on the walls of the beaker (4) Solder wettability: After forming an electroless Ni / Au plating film on a rolled copper plate using the above processing steps, flux (Delta Lux 523 manufactured by Senju Metal Industries) was applied, and 0.76 mmΦ Sn-3Ag-0.5Cu solder balls (manufactured by Senju Metal Industries) were joined under the conditions of pre-reflow 150°C and reflow peak 250°C. Subsequently, the length of solder wetting was observed using a microscope (KEYENCE VHX-7000) at 50x magnification. Specifically, the sum of the length and width of the solder ball was divided by 2 to calculate the wetting spread value, and the average of the wetting spread values, calculated similarly at three other locations, was used as the measurement result.(See Figure 9) 1: Average wetting spread of 2300 μm or more 2: Average wetting spread of 2000 to 2299 μm 3: Average wetting spread of less than 2000 μm (5) Solder connection reliability: After forming an electroless Ni / Au plating film on the BGA substrate using the above processing steps, flux (Deltalux 523 manufactured by Senju Metal Industries) was applied, and 0.76 mmΦ Sn-3Ag-0.5Cu solder balls (manufactured by Senju Metal Industries) were joined under the conditions of pre-reflow 150°C and reflow peak 250°C. Then, a solder shear test (PTR-10 manufactured by Resca) was performed at a shear speed of 1 mm / sec. to evaluate the solder connection reliability. Specifically, it was evaluated by measuring solder shear strength and performing a fracture mode test. Solder shear strength was measured at 25 locations, and the individual measurements were totaled to calculate the average value as the measurement result. The fracture mode test was evaluated by counting the presence or absence of interfacial delamination by observing at 50x magnification using a microscope (KEYENCE VHX-7000). When the solder connection is good, the solder breaks completely across the entire surface, so the entire fracture surface is covered with solder (see Figure 4). In contrast, when the solder connection is not good, interfacial delamination is observed between Ni and solder (see Figure 5). Solder shear strength measurement 1: Shear strength of 1800 gf or more 2: Shear strength of 1700 to 1799 gf 3: Shear strength less than 1700 gf Fracture mode test 1: No interfacial delamination occurred between Ni and solder at any of the 25 locations 2: Interfacial delamination occurred between Ni and solder at 1 to 5 locations out of 25 locations 3: Interfacial delamination occurred between Ni and solder at 6 or more locations out of 25 locations (6) Smoothness of the Ni plating film surface: After forming a Ni plating film on a rolled copper plate using the above processing steps, a horizontal 1200 nm straight line was drawn on the image obtained by observing the surface of the Ni plating film at a magnification of 100,000 times using an FE-SEM with an acceleration voltage of 5 kV, and the intersection points where the straight line and the mesh pattern intersect were found.1: The number of intersecting mesh-like patterns is less than 10 (see Figure 6) 2: The number of intersecting mesh-like patterns is 10 to 19 (see Figure 7) 3: The number of intersecting mesh-like patterns is 20 or more (see Figure 8) (7) Arithmetic mean roughness (Ra) of the Ni plating film: After forming a Ni plating film on a rolled copper sheet using the above processing steps, the arithmetic mean roughness Ra of the Ni plating film surface was measured using a laser microscope (KEYENCE VK-X3000) in accordance with JIS B 0601-2001. 1: Ra is less than 0.1 μm 2: Ra is 0.1 to 0.19 μm 3: Ra is 0.2 μm or more (8) Co content in Ni plating film: After forming a Ni plating film on a SUS304 plate using the above processing steps, the mass (g) of the Ni plating film was calculated by measuring the weight difference before and after the plating process. Next, the Ni plating film was dissolved in a nitric acid (1+1) solution, and the Co concentration (mg / L) was measured using an ICP emission spectrometer (PS3520UVDOII manufactured by Hitachi High-Tech Science). The Co content (wt%) in the Ni plating film was calculated by dividing the mass-converted value by the mass of the Ni plating film. (9) S content in Ni plating film: After forming a Ni plating film on a SUS304 plate using the above processing steps, the mass (g) of the Ni plating film was calculated by measuring the weight difference before and after the plating process. Next, the sulfur concentration in the Ni plating film was measured using a carbon-sulfur analyzer (LECO CS-844), and the sulfur content (wt%) in the Ni plating film was calculated. Some of the results from the above test examples are shown in the figure as reference examples.

[0057] Reference Example 1 Figure 1 shows the results of evaluating the patternability of the sample from Example 1. As is clear from Figure 1, the sample from Example 1 has excellent patternability. Figure 2 shows the results of evaluating the patternability of the sample from Comparative Example 2. As is clear from Figure 2, the sample from Comparative Example 2 did not have good patternability. Figure 3 shows the results of evaluating the patternability of the sample from Comparative Example 1. As is clear from Figure 3, the sample from Comparative Example 1 had poor patternability.

[0058] Reference Example 2: Figure 4 shows the fracture mode mode in which the entire fracture surface is covered with solder, as evaluated by a fracture mode test for the solder connection reliability of the sample from Example 1. The sample from Example 1, which only showed the fracture mode in Figure 4, was clearly superior in solder connection reliability. Figure 5 shows the fracture mode mode in which interfacial delamination was observed between Ni and solder, as evaluated by a fracture mode test for the sample from Comparative Example 1. The sample from Comparative Example 1, which showed the fracture mode in Figure 5, was clearly inferior in solder connection reliability.

[0059] Reference Example 3: Figure 6 shows the results of evaluating the surface smoothness of the sample from Example 1. As is clear from Figure 6, the sample from Example 1 has excellent surface smoothness. Figure 7 shows the results of evaluating the surface smoothness of the sample from Comparative Example 1. As is clear from Figure 7, the sample from Comparative Example 1 did not have good surface smoothness. Figure 8 shows the results of evaluating the surface smoothness of the sample from Comparative Example 2. As is clear from Figure 8, the sample from Comparative Example 2 had poor surface smoothness.

[0060] Reference Example 4: Figure 9 shows the results of evaluating the solder wettability of the sample from Example 1. As is clear from Figure 9, the sample from Example 1 showed a clean circular solder wetting spread, indicating good solder wettability.

[0061] The electroless Ni plating solution of the present invention is useful for surface treatment of electronic components, particularly parts of printed circuit boards that are soldered, bonded, etc. Furthermore, the Ni plating film of the present invention is also useful for soldering, bonding, etc., of electronic components, particularly printed circuit boards.

[0062] 1. Delamination at the interface between Ni and solder.

Claims

1. S ２＋ An electroless Ni plating solution comprising at least Co metal, wherein the Co metal is Co ２＋ and Co ３＋ An electroless Ni plating solution characterized by being contained in the form of [this].

2. S ２＋ The electroless Ni plating solution according to claim 1, wherein the content of is 1 mg / L or more.

3. Co ２＋ The electroless Ni plating solution according to claim 1, wherein the content of is 5 mg / L or more.

4. Co ３＋ The electroless Ni plating solution according to claim 1, wherein the content of is 1 mg / L or more.

5. S ２＋ and Co ２＋ and Co ３＋ The mixing ratio with is by weight ratio S ２＋ is 1 with respect to Co ２＋ is 0.5 or more, Co ３＋ is 0.1 or more. The electroless Ni plating solution according to claim 1.

6. S ２＋ The electroless Ni plating solution according to claim 5, wherein the content of is 1 to 20 mg / L.

7. S ２＋ The content is 1 to 20 mg / L, and Co ２＋ The content is 5 to 200 mg / L, Co ３＋ The electroless Ni plating solution according to claim 1, wherein the content of is 1 to 50 mg / L.

8. An electroless Ni plating method characterized by bringing an object to be plated into contact with the electroless Ni plating solution described in claim 1.

9. A Ni plating film containing at least S and Co, characterized in that the S content is 0.001 wt% or more and the Co content is 0.01 wt% or more.

10. The Ni plating film according to claim 9, wherein the Co content is 0.03 wt% or more.

11. The Ni plating film according to claim 9, wherein the arithmetic mean roughness (Ra) as defined in JIS B 0601-2001 is less than 0.1 μm.

12. A Ni-plated film in which, when a horizontal 1200 nm straight line is drawn on an image obtained by observing the surface of the Ni-plated film at a magnification of 100,000x using an FE-SEM with an acceleration voltage of 5 kV, and the intersection points of the straight line and the mesh-like pattern formed within the crystal grains of the Ni-plated film are determined, the number of intersection points obtained is less than 10.

13. The Ni plating film according to claim 12, further comprising 0.001 wt% or more of S.

14. A product and a component thereof comprising a Ni plating film, wherein the Ni plating film is the Ni plating film according to claim 9 or claim 12.

Images