JP2942157B2 - Post-treatment method of Zn plated steel sheet for solder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to Cr ⁶⁺ or Cr ³⁺
The present invention relates to a post-treatment method for a Zn-plated steel sheet, a Zn-alloy-plated steel sheet, or a multi-layer plated steel sheet for soldering using a bath containing Cu.

[0002]

2. Description of the Related Art Conventionally, in the case of Zn or alloy-plated or multi-layer plated steel sheets containing Zn as a main component, in order to improve corrosion resistance, a post-treatment such as a chromate treatment, a phosphate treatment or the like; However, these treatments significantly reduce solderability. Therefore, unless a highly corrosive flux containing chlorine is used at the time of soldering, there is a practical problem. However, the use of this flux causes environmental deterioration during the soldering operation. In addition, the residue of the flux significantly reduces the corrosion resistance of the soldered portion, and therefore, after the soldering, it must be washed with an organic solvent such as chlorofluorocarbon and trichloroethane. Since these organic solvents destroy the ozone layer, their future use is problematic. For this reason, there is a method that uses a non-chlorine flux that is weakly corrosive and does not use an organic solvent for cleaning. However, the non-chlorine flux has the ability to remove Cr that deteriorates solder wettability attached to the plating surface. Is small.

[0003]

In an industrial production line, chromate treatment is often used as a post-treatment such as Zn plating. However, the tank for the chromate treatment in this case is often used for other purposes, and may be used after being changed to a tank for post-treatment after plating. When used as a post-treatment tank, the chromate treatment tank is washed in advance with an inorganic acid or alkali, but it is impossible to completely remove the Cr ⁶⁺ or Cr ³⁺ ions used in the chromate treatment bath. It is not possible and usually 2 to 100 ppm remains in the post-treatment tank. Therefore, when passing through this post-treatment tank as a post-treatment such as Zn plating, C
As described above, it is difficult to exhibit the effect even if r is attached or precipitated and a process for improving solderability is performed thereafter. In view of these problems, the present invention provides a soldering Z using a bath containing Cr ⁶⁺ or Cr ^3+.
An object of the present invention is to provide a post-treatment method that does not precipitate Cr as much as possible in a post-treatment method of an n-plated steel sheet, a Zn alloy-plated steel sheet, or a multi-layer plated steel sheet.

[0004]

The post-processing method of the present invention comprises:
In a post-treatment method for a Zn-plated steel sheet for soldering using a bath containing Cr ⁶⁺ or Cr ³⁺ , electrolytic plating or immersion treatment is performed using an acidic post-treatment solution having a pH of 0.5 to 4 after Zn plating. And then washed with water. In these post-treatment methods, it is desirable to carry out electrolysis or immersion treatment using an alkaline post-treatment liquid having a pH of 8 to 13 and to wash with water. Alternatively, it is also preferable to perform immersion treatment using a water-soluble or water-dispersible post-treatment liquid having a pH of 0.5 to 13 to which an organic compound of 0.01 to 20 g / l is added, and to perform water washing. These post-treatments are suitably applied to a Zn alloy plated steel sheet and a multi-layer plated steel sheet.

[0005]

When a treatment using an inorganic acidic or alkaline post-treatment liquid is performed after Zn plating, Zn alloy plating or multi-layer plating, the inside of the tank of the post-treatment liquid is replaced with a solution containing an excessive amount of inorganic acid or alkali. ^Therefore , the adsorption or precipitation of Cr by Cr ⁶⁺ or Cr ³⁺ ions contained as impurities in the post-treatment tank is 0.1 mg / m ^2.
It is suppressed as follows. In addition, when a treatment is performed with a post-treatment solution containing an organic compound, the organic compound surrounds the Cr ⁶⁺ or Cr ³⁺ ions, thereby suppressing the adsorption or precipitation of Cr on the plating surface. When these post-treatments are performed, the adsorption or precipitation of Cr on the plating surface is suppressed. Therefore, by performing a known solderability improving treatment in the next step, the ability to clean the surface during soldering is performed. The solder wettability is significantly improved even if a non-chlorine flux having a very low flux density is used.

[0006]

Embodiments of the present invention will be described below in more detail. As the plated steel sheet, Zn plating or Sn, Co, Ni, Fe, P
Alloy plating containing at least one of b and Cu, or multi-layer plating is employed. Plating amount is 2-50g
/ M ² is appropriate. If it is less than 2 g / m ² , the corrosion resistance is poor. If it exceeds 50 g / m ² , the economic efficiency is inferior and it is not preferable.

After plating, the substrate is treated with an inorganic acidic post-treatment solution having a pH of 0.5 to 4, an inorganic alkaline post-treatment solution having a pH of 8 to 13, or a post-treatment solution containing an organic compound having a pH of 0.5 to 13. Thereby, precipitation of Cr on the plating surface is suppressed to 0.1 mg / m ² . In the case of using an inorganic acidic post-treatment solution, if the pH is less than 0.5, Zn
It is not preferable because the plating is severely dissolved and the corrosion resistance is reduced. On the other hand, when the pH exceeds 4, Cr is easily adsorbed or precipitated, and solder wettability is reduced. When an inorganic alkaline post-treatment liquid is used, if the pH is less than 8, Cr is easily adsorbed or precipitated, and solder wettability is reduced. On the other hand, when the pH exceeds 13, the corrosion resistance decreases. When the above-mentioned post-treatment liquid is used, the inorganic acid solution for pH adjustment is not particularly limited, but it is easy to use sulfuric acid and hydrochloric acid alone or as a mixture. As the inorganic alkali solution for adjusting the pH, sodium hydroxide or potassium hydroxide is preferable. As a treatment method, there is electrolysis or immersion, but immersion treatment is easy.

When a post-treatment solution containing an organic compound is used, the following solution is used. That is, water-soluble or water-dispersible phosphate ester salts, fluorine-based organic compounds, organic phosphates, organic amine soaps, water-soluble or water-dispersible abietic acid,
Benzoic acid, glycerin, C _{12 to} C ₂₄ saturated fatty acids, C ₁₈
Unsaturated fatty acids, diols, polyethylene glycols,
Fatty acid glycerin esters, benzotriazole derivatives, paraffin-based waxes and the above metal salts, ammonium salts, amine salts, aliphatic higher alcohols, alkylphenols, and fatty acid salts obtained by condensing ethylene oxide, polyethylene glycol alkylamines, At least one of sorbitan and fatty acid ester condensed, polypropylene glycol group as hydrophobic group, polyethylene glycol as hydrophilic group, fatty acid and sucrose ester bond, lanolin alcohol, lanolin fatty acid and saponified They may be used alone or in combination. These solutions are prepared at 0.01 to 20 g / l.
It is treated with the added post-treatment solution of pH 0.5 to 13. p
If H is less than 0.5 or more than 13, the corrosion resistance of the plated surface is inferior, which is not preferable. Although the temperature of the post-treatment liquid is not particularly limited, it may gel at 80 ° C. or more and degrade the stability of the treatment liquid, and usually 20 to 40 ° C. is economically suitable.

The water-soluble or water-dispersible phosphate ester salts include the soaps with mono- or dibasic acids with one or two alkyl groups or with organic amines. Those having a large alkyl group and being insoluble in water can be used after increasing the hydrophilicity by converting them to alkali salts or adding ethylene oxide.

The water-soluble or water-dispersible fluorine-containing organic compound contains a perfluoroalkyl group and has a general formula of C _n F
_{Assuming that 2n + 1} R ₁ R ₂ , R ₁ contains a methylene group and an ethylene group and may be used in other resin systems. R ₂ is one that facilitates water solubility or water dispersibility, and includes acrylates, methacrylates, phosphates,
Carboxylic acid esters and ethylene oxide adducts are included. Emulsifiers, surfactants and organic solvents can be added for the same purpose. Further, even if there is a part of H in place of F in the perfluoroalkyl group, no problem may occur.

The organic phosphates include sodium, potassium, calcium and ammonium salts of alkyl phosphates. Organic amine soaps include dodecylamine, oleoylimidazoline, aminopropyl tallowamine, and rosinamine, and amines can be used after forming a salt with a carboxylic acid or the like.

[0012] Stearic acid is an unsaturated fatty acid C _18, lauric acid, palmitic acid, such as oleic acid.

The benzotriazole derivatives include benzotriazole, azimidol, 1-Nbenzoylbenzotriazole and the like. 20 carbons as wax
Molecular weight of 300 to 36 as a main component
~ 500 paraffinic waxes.

As additives, for example, water-soluble or water-dispersible abietic acid, benzoic acid, glycerin,
Saturated fatty acids C ₁₂ -C _24, as the organic alcohol or fatty acid esters, glycerol, diols, polyethylene glycol, fatty acid glycerol ester. In addition, water-soluble or water-dispersible aliphatic higher alcohols, alkylphenols and fatty acid salts condensed with ethylene oxide, polyethylene glycol / alkylamines, sorbitan and fatty acid ester condensed, and polypropylene glycol Group, those with polyethylene glycol as a hydrophilic group, those with an amide bond between a fatty acid and diethanolamine,
It may contain one or more of fatty acid and sucrose ester-bonded, lanolin alcohol, and lanolin fatty acid saponified. In addition, a known water-soluble or water-dispersible preservative may be added.

After the post-treatment of the present invention, the surface of the plating is
Rinsing is performed, and a process for imparting solderability and corrosion resistance is performed.

The treatment for imparting solderability and corrosion resistance includes:
Known ones may be used, for example, JP-A-63-8805,
JP-A-63-115670, JP-A-63-22476
No. 9 or JP-A-1-290778.

(Embodiment) A cold-rolled steel sheet having a thickness of 0.5 mm was degreased, pickled, washed with water, and immediately subjected to electro-Zn plating on both sides using a sulfuric acid bath so that the plating amount was 20 g / m ² . . After washing with water, a post-treatment of immersing in a sulfuric acid solution having a pH of 0.5 containing Cr ²⁺ ions at a concentration of 0.02 g / l for 1 second was performed. After that, in order to improve the solderability, after washing with water, a monobasic phosphate ester 20 g / l,
A treatment liquid was prepared in 10 g / l of tetrafluoropropyl methacrylate, 15 g / l of rosin amine, and 0.5 g / l of sodium alkyl phosphate, so that CrO ₃ became 0.01 g / l as Cr ⁶⁺ ion. ,
Roll squeezing so that the thickness after drying is 0.1 μm,
It dried at 60 degreeC and the test piece for evaluation was created. Next, several samples were prepared by changing the bath composition of the post-treatment liquid of the present invention (Examples 1 to 30). Tables 1 to 5 show the type of plating, the amount of plating, the type of liquid used in the post-treatment, and the treatment method in that case. Of these tables, Table 1 shows the case where an acidic post-treatment liquid was used in the post-treatment (the method according to claim 1), and Table 2 shows the case where an alkaline post-treatment liquid was used in the post-treatment (Claim 1). 2), and Tables 3 to 5 show the case where a post-treatment liquid to which an organic compound was added in post-treatment was used (the method according to claim 3).

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

COMPARATIVE EXAMPLE Plating was performed in the same manner as in the example, and immersed for 1 second in an aqueous solution containing 0.02 g / l of Cr ⁶⁺ ions. Next,
A sample of a comparative example was prepared by performing the same solderability improving treatment as in the example. The bath composition is shown at the end of Table 5. The properties of the samples obtained in Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Tables 6 and 7.

[0024]

[Table 6]

[0025]

[Table 7] In the post-treatment liquid of the present invention, those obtained by removing acids, alkalis, and organic compounds (Comparative Example), the adsorption of Cr on a plated steel sheet or the precipitation amount of Cr exceeding 0.1 mg / m ² , When a chlorine-free flux was used, solder wettability was poor. When the pH of the post-treatment liquid was less than 0.5 or more than 13, the corrosion resistance was poor. Further, in a post-treatment method using an aqueous solution containing an organic compound other than the present invention, or a post-treatment solution using an inorganic acid or an alkaline solution having a pH outside the range of the numerical limitation of the present invention, the adsorption of Cr is performed. Alternatively, the deposition amount exceeded 0.1 mg / m ^2, and when a chlorine-free flux was used during soldering, the solder wettability was poor.

(Evaluation Method of Characteristics) The characteristic evaluations shown in Tables 6 and 7 were carried out as follows. 1. Solder wettability The solder wettability of the plated steel sheet is measured using a solder checker (RH
ESCA CO. And SAT-2000 manufactured by LTD. The condition of the solder checker is immersion depth 2
mm, the immersion speed was 2 mm / sec, and the immersion time was 10 seconds.
Solder is H60A (JIS Z 3282) at a temperature of 250
° C. A sample having a width of 10 mm and a length of 50 mm was subjected to a chlorine-free flux (RMN manufactured by Nihon Handa Kogyo Co., Ltd.).
A) After immersion for 2 seconds, attach to solder checker,
Zero cross time was measured. In Tables 6 and 7 that summarize the characteristic results, those having excellent zero-cross times of less than 5 seconds are represented by ○, and those having inferior zero-cross times of 9 seconds or more are represented by x.

2. Corrosion resistance JIS Z 23 is used to evaluate the corrosion resistance of plated steel sheets.
A salt spray test was performed for 8 hours using No. 71, and evaluated by the degree of occurrence of red rust. In Tables 6 and 7, which summarize the characteristic results, the absence of red rust is indicated by ○ (evaluation of excellent).

[0028]

As shown in Tables 6 and 7, in the plated steel sheet subjected to the post-treatment of the present invention, the adsorption or precipitation of Cr, which reduces the solder wettability, on the plating surface is suppressed. Then, by performing a process of improving solderability, it is possible to obtain Zn or Zn-based alloy-plated or multi-layer plated steel having excellent solder wettability and excellent corrosion resistance even when using a chlorine-free flux during soldering. it can.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-115670 (JP, A) JP-A-62-224769 (JP, A) JP-A-1-290778 (JP, A) JP-A 57-57 110692 (JP, A) JP-A-2-205687 (JP, A) JP-A-53-100139 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C25D 5/48 C25D 5 / 26

Claims (5)

(57) [Claims] 1. A post-treatment method for a Zn-plated steel sheet for soldering using a bath containing Cr ⁶⁺ or Cr ³⁺ , wherein after Zn plating, an acid post-treatment liquid having a pH of 0.5 to 4 is used. A post-treatment method for a Zn-plated steel sheet for soldering, which comprises subjecting to electrolytic or immersion treatment and washing with water. 2. A post-treatment method for a Zn-plated steel sheet for soldering using a bath containing Cr ⁶⁺ or Cr ³⁺ , wherein after Zn plating, an alkaline post-treatment solution having a pH of 8 to 13 is used. Alternatively, a post-treatment method for a Zn-plated steel sheet for soldering, which comprises immersing and washing with water. 3. A post-treatment method for a Zn-plated steel sheet for soldering using a bath containing Cr ⁶⁺ or Cr ³⁺ , wherein 0.01 to 20 g / l of an organic compound is added after Zn plating. A post-treatment method for a Zn-plated steel sheet for soldering, which comprises immersing using a water-soluble or water-dispersible post-treatment liquid having a pH of 0.5 to 13 and rinsing with water. 4. The post-treatment method according to claim 1, wherein the Zn-plated steel sheet is a Zn alloy-plated steel sheet. 5. The post-processing method according to claim 1, wherein the Zn-plated steel sheet is a multi-layer plated steel sheet.