JP2812028B2 - Fusing treatment method for tin or tin-lead alloy plating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fusing a tin or tin-lead alloy plating film capable of obtaining a highly uniform fading finish.

[0002]

2. Description of the Related Art Conventionally, as a method for imparting solderability to a circuit of a printed wiring board, a hot air leveler or a solder paste treatment is known.

However, as electronic devices have become more multifunctional and highly integrated in recent years, the number of pins and the pitch of package components such as LSIs have been increased, and printed wiring boards have become increasingly finer. For this reason, conventional hot air levelers and solder paste treatments are sometimes difficult to cope with. In such a case, the electroless plating method uses tin or tin on the copper or copper alloy circuit. -The formation of a lead alloy plating film is being studied.

In this case, in a printed wiring board,
The tin or tin-alloy (solder) plating film formed on the copper circuit is heated and melted to eliminate overhang and undercut, and the solder plating film is subjected to a fusing process for uniform alloying.

However, the conventional fading treatment is performed by applying a fading flux to the plating film and heating the plating film. In the case of an electroless tin or tin-lead alloy plating film, the deposited film is porous. However, it is difficult to obtain a uniform finish by the conventional method. For this reason, it is desired to develop a new fading treatment method capable of obtaining a good finish even on an electroless tin or tin-lead alloy plating film.

[0006]

The inventor of the present invention has conducted intensive studies to meet the above-mentioned demands, and as a result, has found that tin or tin.
The lead alloy plating film is immersed in a diluting solution of a fusing flux or a solution of an amine, hydrazine, carboxylic acid or a salt thereof, and these are immersed in the pores of the plating film, and dried to obtain water. After the removal, the plating film is preferably subjected to a flux treatment,
It has been found that a uniform fading finish can be obtained by preheating at 160 ° C. for 1 to 3 minutes and then fading, thereby completing the present invention.

Therefore, the present invention provides a method for immersing a tin or tin-lead alloy plating film in a diluting solution of a fusing flux, or in a solution of an amine, hydrazine, carboxylic acid or a salt thereof, and drying it. Preferably, the plating film is subjected to a flux treatment, and
Provided is a method for fading an electroless tin or tin-lead alloy plating film, which comprises preheating for 3 minutes and then fading.

Hereinafter, the present invention will be described in more detail. In the fading treatment method of the present invention, as described above, before the tin or tin-lead alloy plating film is heated and subjected to fading, the plating film to be treated is fused. In a diluting solution of a flux for use, or immersed in a solution of an amine, hydrazine, carboxylic acid or a salt thereof to infiltrate these chemicals into the pores of the plating film, and then dry to remove water. It is something to keep.

Here, the tin or tin / lead alloy plating film to be treated may be an electroplating film or an electroless plating film, and is particularly preferably used for an electroless tin / lead alloy plating film.

[0010] The fading treatment method of the present invention is a method for preparing a tin or tin-lead alloy plating film formed on a copper or copper alloy material, by diluting a flux for fusing or using an amine, hydrazine, carboxylic acid or a salt thereof. Immerse in the solution.

As the fading flux, any of known compositions and commercially available fluxes can be used without any problem. In the present invention, a diluting solution of such a fusing flux is used, and it is preferable that the fading flux is diluted to about 1/5 to 1/2. In this case, if a commercially available flux contains a large amount of activator and is used without being diluted, or if the concentration of the diluting solution is too high, the plating film becomes inactive at the time of drying, so that fading may not easily occur.

The amines and salts thereof include ethylenediamine, triethanolamine, aniline hydrochloride and the like, and the hydrazines and salts thereof include hydrazine hydrochloride and the like. Examples of the carboxylic acids and salts thereof include formic acid, acetic acid, oleic acid, stearic acid, lactic acid, and glutamic acid. These amines, hydrazines, carboxylic acids are usually used by being dissolved in water,
The concentration is usually 0.1 to 100 g / L, particularly 1 to 30 g.
/ L.

The diluting solution of the above-mentioned flux for fading, a solution of amine, hydrazine and carboxylic acid react with tin, lead in the plating film and an oxide of copper as a base to form a complex and serve as an antioxidant. It is thought to work.

Next, the plating film subjected to the immersion treatment is washed with water as required, and then dried. in this case,
The drying temperature is not particularly limited, but may be 80 to 90C.

After drying, the plating film is treated with a fading flux by a conventional method to perform fading.
It is preferable to perform preheating before fading. In this case, the preheat temperature is preferably 100 to 160 ° C., particularly preferably about 120 to 140 ° C., and if the preheat temperature is too high or too low, uneven treatment or voids may easily occur in the plating film. is there.

The fading processing method of the present invention comprises:
It is preferably used for an electroless tin or tin-lead alloy plating film formed on a copper or copper alloy circuit of a printed wiring board. It can also be used for lead alloy plating films, and can be used for electronic components other than printed wiring boards, and also for uses other than electronic components.

[0017]

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.

A 10 μm-thick electroless tin-lead alloy plating film was formed on a copper circuit of a printed wiring board by plating with a plating solution having the following composition. Electroless tin-lead alloy plating solution methanesulfonic acid 50 g / L tin methanesulfonate 20 g / L lead methanesulfonate 13 g / L thiourea 75 g / L sodium hypophosphite 80 g / L citric acid 15 g / L laurylpyridinium chloride 5 g / L EDTA 3g / L

Next, the printed wiring board was immersed in the treatment liquid shown in Table 1 for 1 minute, dried at 80 ° C. for 3 minutes, and then supplied with a commercially available flux for fading (manufactured by Mec Co., Ltd .;
41M), and preheated at 130 ° C. for 3 minutes, followed by fading at 230 ° C. for 10 seconds. The appearance of the plating film after the fading treatment was observed. Table 1 shows the results. As a comparison, a fading flux was directly applied to the plating film without performing the immersion treatment, and a fading treatment was performed. The results are also shown in Table 1.

[0020]

[Table 1]

From the results shown in Table 1, it is recognized that according to the fading treatment method of the present invention, a uniform fading treatment can be performed on the electroless tin-lead alloy plating film without occurrence of displacement and voids. .

[0022]

As described above, according to the method for fading tin or tin-lead alloy plating film of the present invention,
A good fading finish can be obtained without generating a shift or a void even in the electroless tin or tin-lead alloy plating film.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Teruyuki Hotta 1-5-1, Hirakata Exit, Osaka Pref. Uemura Industry Co., Ltd. Central Research Laboratory (72) Inventor Tohru Uetama 1-5-1 Exit, Hirakata City, Osaka No. Uemura Industry Co., Ltd. Central Research Laboratory (56) Reference JP-A-59-219496 (JP, A) JP-B 62-12317 (JP, B2) JP-B 60-14116 (JP, B2) (58) Survey (Int.Cl. ⁶ , DB name) C23C 18/31 C23C 18/48 H05K 3/24 C25D 5/50

Claims (2)

(57) [Claims] 1. A tin or tin-lead alloy plating film is immersed in a diluting solution of a fusing flux or in a solution of an amine, hydrazine, carboxylic acid or a salt thereof,
A fading treatment method for an electroless tin or tin-lead alloy plating film, which is dried and then fused. 2. The fusing treatment method according to claim 1, wherein the plating film subjected to flux treatment after drying and before fading is preheated at 100 to 160 ° C. for 1 to 3 minutes.