JP2873751B2 - Electroless tin or tin-lead alloy plating solution and electroless tin or tin-lead alloy plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acidic electroless tin which is suitably used for forming a tin or tin-lead alloy layer on a copper circuit or the like of an electronic component for the purpose of improving an etching resist or solderability. Also, the present invention relates to an electroless tin / lead alloy plating solution and a plating method using the plating solution.

[0002]

2. Description of the Related Art Conventionally, electroless tin or tin-lead alloy plating has been performed on a copper or copper alloy portion forming a circuit of an electronic component such as a printed wiring board in order to improve solderability. However, with the miniaturization of electronic devices, parts and circuits are also miniaturized or complicated, and some parts cannot be plated by electroplating. Therefore, an electroless tin or tin-lead alloy plating method capable of plating on these portions has been studied. For example, Japanese Unexamined Patent Publication (Kokai) No. 1-184279 discloses an electroless tin containing organic sulfonic acid, tin and lead salts of organic sulfonic acid, sodium hypophosphite (reducing agent) and thiourea (complexing agent) as main components. -A method using a lead alloy plating bath has been proposed.

[0003]

On the other hand, recently, the mounting technology of electronic components such as an integrated circuit package has been changed from a DIP type package insertion mounting system (VMT) to a flat package surface mounting system (SMT). As a result, a printed wiring board having a smooth contact surface with a mounted product such as an integrated circuit package, that is, a printed wiring board having a highly uniform tin or tin-lead alloy plating film formed thereon is desired. It is becoming.

[0004] However, the plating film formed by the conventional electroless tin or tin-lead alloy plating solution has coarse deposited particles and is inferior in uniformity of the film. Therefore, the plating film is inferior in reflowability and solderability and solder supply property. It was difficult to perform plating on a fine pitch SMT-compatible printed wiring board.

The present invention has been made in view of the above circumstances, and provides a uniform plating film in which precipitated particles are fine,
An object of the present invention is to provide an acid-type electroless tin or tin-lead alloy plating solution and an electroless tin or tin-lead alloy plating method that can well cope with plating on a fine pitch printed wiring board compatible with SMT. .

[0006]

In order to achieve the above object, the present inventor has set forth the composition of an electroless tin or tin-lead alloy plating solution capable of providing a fine and uniform plating film of precipitated particles. As a result of intensive studies, electroless tin or tin / lead containing a soluble stannous salt or a metal salt component comprising a mixture of a stannous salt and a lead salt, an acid, thiourea, and a reducing agent. One or more heterocyclic compounds having a nitrogen atom (but excluding a quaternary ammonium salt type nitrogen atom) in the ring together with one or more nonionic surfactants in the alloy plating solution or one of its derivatives Alternatively, by adding two or more kinds in combination, it is possible to obtain a fine and uniform precipitated particle, a plating film having good reflow properties, and sufficiently cope with plating on a fine pitch SMT compatible printed wiring board. Heading, complete the invention One in which the.

Accordingly, the present invention provides an electroless tin or tin containing a metal salt component comprising a soluble stannous salt or a mixture of a stannous salt and a lead salt, an acid, thiourea and a reducing agent. A heterocyclic compound or a derivative thereof having a nitrogen atom (excluding a quaternary ammonium salt type nitrogen atom) in the ring together with one or more nonionic surfactants in the lead alloy plating solution. An electroless tin or tin-lead alloy plating solution characterized by adding one or more kinds, and a plating object is immersed in the plating solution, and tin or tin. Provided is an electroless tin or tin / lead alloy plating method characterized by forming a lead alloy plating film.

Hereinafter, the present invention will be described in more detail. The electroless tin-lead alloy plating solution of the present invention contains a soluble stannous salt or a stannous salt and a lead salt as described above. In this case, the tin source for providing stannous ions (divalent tin ions) in the plating solution is not particularly limited and may be variously selected. For example, tin oxide, tin chloride, tin sulfate, organic tin sulfonate, organic tin sulfonate, Tin carboxylate, tin borofluoride, and the like can be given. The amount of stannous ions in the plating solution is 1 to 50.
g / L, particularly preferably 5 to 25 g / L.

Further, as a lead ion source when a tin / lead alloy plating solution is used, lead chloride, lead sulfate, organic lead sulfonate, lead borofluoride, lead oxide and the like can be used. The amount of these lead ions is appropriately selected according to the alloy ratio and the like, but is usually 0.1 to 50 g / L, particularly 0.5 to 10 g.
/ L.

As an acid component for dissolving these metal salts,
Organic sulfonic acid, perchloric acid, borofluoric acid, phosphoric acid, condensed phosphoric acid such as pyrophosphoric acid, polyphosphoric acid, hydrochloric acid, and the like, and one or more of these can be used. Among these, organic sulfonic acids include alkanesulfonic acid, hydroxyalkanesulfonic acid, benzenesulfonic acid, and naphthalenesulfonic acid, and some of these hydrogen atoms are hydroxyl, halogen, alkyl, carboxyl, nitro, and mercapto groups. , An amino group, those substituted with a sulfonic acid group or the like are used, and more specifically,
Examples of the organic sulfonic acids that can be suitably used in the present invention include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, 2-propanesulfonic acid, butanesulfonic acid, and 2-sulfonic acid.
Butanesulfonic acid, pentanesulfonic acid, chloropropanesulfonic acid, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentanesulfonic acid, Allylsulfonic acid, 2-sulfoacetic acid,
2- or 3-sulfopropionic acid, sulfosuccinic acid, sulfomaleic acid, sulfofumaric acid, benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, sulfosalicylic acid, benzaldehydesulfonic acid, p-phenol sulfone Acids and the like can be mentioned. The use amount of these acids is not particularly limited, but is preferably 10 to 300 g / L, particularly preferably 50 to 200 g / L, and the ratio between the acid and the metal ion is 1: 1 to 1:20, particularly 1: 3 ~
Preferably, the ratio is 1:10.

The plating solution of the present invention contains thiourea, and the presence of thiourea makes it possible to deposit tin or a tin-lead alloy. Although the amount of the thiourea is not particularly limited, it is usually 10 to 200 per liter of the plating solution.
g, especially about 50 to 150 g. Furthermore, tartaric acid, malic acid, citric acid,
EDTA or the like can be used in combination as a complexing agent.

The plating solution of the present invention contains a reducing agent. Examples of the reducing agent include hypophosphorous acid and hypophosphites such as sodium hypophosphite and potassium hypophosphite. It is preferably used. The compounding amount of this reducing agent can be a usual amount, and specifically, is preferably about 10 to 200 g / L, particularly preferably about 50 to 150 g / L.

The tin or tin-lead alloy plating solution comprising the above components is made acidic, and preferably has a pH of 2 or less.

[0014] The plating solution of the present invention is obtained by adding one or more nonionic surfactants to a plating solution prepared by appropriately mixing the above components. By the addition of the activator, the deposition plating film was made uniform. Examples of the nonionic surfactant include a polyoxyalkyl ether surfactant such as polyoxynonylphenyl ether and polyoxylauryl phenyl ether, a pooxyalkylamide ether surfactant such as polyoxystearyl amide ether, Polyoxyalkylamine ether surfactants such as oxyoleylamine ether;
Propylene block polymer surfactants and the like are mentioned, and the amount of addition is not particularly limited, but can be usually 0.01 to 50 g / L, particularly 1 to 10 g / L.

Further, the plating solution of the present invention contains a heterocyclic compound having a nitrogen atom (excluding a quaternary ammonium salt type nitrogen atom) in the ring or a derivative thereof together with the above-mentioned nonionic surfactant. One or two or more kinds of additives are used in combination, whereby a more uniform deposited film can be achieved. In this case, examples of the heterocyclic compound having a nitrogen atom in the ring include an alkylpyridine compound, an alkylimidazole compound, an alkylquinoline compound, an alkylpurine compound and the like.
-Oxypyridine, 2-oxyimidazole and the like are preferably used.

The amount of these additives is not particularly limited, but is usually 0.01 to 50 g / L, particularly about 1 to 10 g / L, of the heterocyclic compound or its derivative.

Using the plating solution of the present invention, electroless tin or tin
When performing lead alloy plating, the plating is performed by immersing a plating object such as copper or a copper alloy in the plating solution of the present invention, and the temperature at that time is preferably 50 to 90 ° C, particularly preferably 60 to 80 ° C. . In addition, stirring can be performed if necessary. The plating solution and the plating method of the present invention are preferably used for plating electronic components such as printed wiring boards, but can also be suitably used for electroless plating of other copper and copper alloys. Things.

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples and Comparative Examples] The plating solutions of the following compositions (1) to (3)
Add the additives (A) to (C) to make four plating solutions
Prepared. Pre-printed copper circuit formed on these plating solutions
Immerse the printed wiring test board at 70 ° C. for 6 minutes.
5μm thick tin or tin-lead alloy plating layer on copper circuit
After the plating is completed, the solderability of the plating film is evaluated.
Was. Further, this substrate was charged into a reflow apparatus, and 235 ° C.
Treatment for 15 seconds and observe the appearance of the plating film
The reflow property was evaluated more. Table 1 shows the results. In addition,
For comparison, the plating solutions (1) to (3) were applied to (A) to (C)
Print as well, without adding any additives
Form a plating layer on the wiring test board,
Field supply and reflow were evaluated. The results are shown in Table 1.
I do. The evaluation criteria for solderability and reflowability are as follows:
It is as described.Plating solution composition Plating solution (1) Methanesulfonic acid 50 g / L Stannous methanesulfonate 20 g / L Lead methanesulfonate 13 g / L Thiourea 75 g / L Sodium hypophosphite 80 g / L Citric acid 15 g / L EDTA 3 g / L pH 2.0 Plating solution (2) Stannous borofluoride 20 g / L Lead borofluoride 10 g / L borofluoric acid 200 g / L thiourea 50 g / L Sodium hypophosphite 30 g / L pH 0.8 Plating solution (3) Methane Sulfonic acid 90 g / L Stannous methanesulfonate 20 g / L Thiourea 120 g / L Sodium hypophosphite 80 g / L pH 2.0Additive Additive (A) Polyoxynonyl phenyl ether 5 g / L (EO 8 mol) 2-oxypyridine 1 g / L Additive (B) Polyoxynonyl phenyl ether 5 g / L (EO 8 mol) Polyoxystearyl amide ether 5 g / L (EO 15 mol) 2-methyl-8-hydroxyquinoline 3 g / L Additive (C) Polyoxyethylene polypropylene 8 g / L Block polymer^*  Alkyl propylene diamine acetate 3 g / L (EO 20 mol) 2-oxyimidazole 1 g / L * EO 300%, PO MW. 1300

[0020]

[Table 1]

As is clear from the results in Table 1, according to the electroless tin or tin-lead alloy plating solution of the present invention, a uniform plating film having fine precipitated particles can be formed. It was confirmed that the plated printed wiring board was excellent in reflow properties and the like, and could sufficiently cope with fine pitch SMT.

[0022]

As described above, according to the electroless tin or tin-lead alloy plating solution and the plating method of the present invention, the plating film is fine and uniform, and has excellent solder supply properties and reflow properties. Can be obtained, and it is possible to satisfactorily cope with plating on a fine pitch printed wiring board compatible with SMT.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Masayuki Kiso, Inventor 1-5-1, Hirakata-shi, Osaka Prefecture Uemura Industries, Ltd. Central Research Laboratory (72) Inventor Teruyuki Hotta 1-1-5-1, Hirakata-shi, Osaka Uemura Kogyo Co., Ltd. Central Research Laboratory (72) Inventor Tohru Uetama 1-5-1, Hirakata Exit, Osaka Prefecture Uemura Kogyo Co., Ltd. Central Research Laboratory (56) References JP-A-1-184279 (JP, A) Kaihei 2-197580 (JP, A)

Claims (2)

(57) [Claims] 1. An electroless tin or tin-lead alloy plating containing a soluble metal salt component comprising a stannous salt or a mixture of a stannous salt and a lead salt, an acid, thiourea, and a reducing agent. One or two or more heterocyclic compounds having a nitrogen atom (however, excluding a quaternary ammonium salt type nitrogen atom) in a ring or a derivative thereof together with one or more nonionic surfactants in the solution. Electroless tin or tin
Lead alloy plating solution. 2. An electroless tin or tin comprising immersing an object to be plated in the electroless plating solution according to claim 1 to form a tin or tin-lead alloy plating film on the object to be plated.・ Lead alloy plating method.