JPS63161183A - Production of reflow-treated tinned material - Google Patents

Abstract

PURPOSE:To make the thickness of a film uniform and to improve the corrosion resistance by using an electrolytic tinning bath obtd. by adding a surfactant selected among compds. each represented by a prescribed molecular formula to a soln. contg. a free acid component and a bivalent Sn salt when tinning followed by reflow treatment is carried out. CONSTITUTION:A soln. contg. a free acid component (alkanesulfonic acid and/or alkanolsulfonic acid) and a bivalent Sn salt is prepd. One or more kinds of surfactants selected among compds. represented by formulae I-IV (where n=5-15, m=5-30, x=5-30, y=1-10, X=1-10 and Y=5-30) are added to the soln. to obtain an electrolytic tinning bath. A layer formed by electrolytic tinning in the bath is heated to the m.p. of the layer or above to carry out reflow treatment.

Description

[Detailed Description of the Invention] Emperor Presentation 2 ■ 亙圀! The present invention performs a surface treatment consisting of electroplating tin on a metal strip and then subjecting the plating layer to a reflow treatment,
The present invention relates to a method for producing a high-quality reflow-treated tin-plated material that has a good appearance and uniform plating film thickness.

l Yoneni Ibaragai Conventionally, as one of the surface treatment methods for applying tin plating to metal materials, after electroplating tin on various metal materials, the plating layer is melted, which is the so-called reflow treatment.
It is known to improve quality such as appearance and corrosion resistance.

As electroplating baths used to produce reflow-treated tin-plated materials by the above method, alkaline baths, halogen baths, ferrostane baths, sulfuric acid baths, and the like are known.

Among these electroplating baths, the alkaline bath is an alkaline bath containing potassium stannate or sodium stannate as a main component, and is one of the ones that have been used for the longest time. Although this alkaline bath has the advantage of being able to form a tin plating layer by electrodeposition without adding any organic additives and also has good film quality after reflow treatment, it does not contain tetravalent tin ions. Alkaline baths have rarely been used in recent years because they require reduction to form a film and also have low current efficiency (and extremely low productivity).

Next, a halogen bath is an acidic bath containing stannous chloride as a main component, and is often used along with a ferrostane bath in tinplate manufacturing lines for steel. This halogen bath allows for high current density (cathode current density of 5OA/d tyf
It has the advantage of high productivity because it can be operated continuously (at low temperatures), but on the other hand, it is highly corrosive, which increases equipment costs.
Another drawback is that it is not very economical due to the low degree of effective use of tin.Therefore, halogen baths are rarely used in newly constructed tin plating lines in recent years.

Further, ferrostane baths have fewer drawbacks seen in the above-mentioned alkaline baths and halogen baths, and are used in the majority of tinplate lines. However, since phenolsulfonic acid, which is a free acid component of this bath, contains phenol, which is a pollution control substance, treatment such as activated sludge treatment is required, which poses a cost problem. Furthermore, the Ferroskun bath cannot be used in low-speed, low-volume production lines or rack-type or barrel-type lines because the quality is not stable at relatively low current density areas of 10 A/d rrf or less.

Furthermore, sulfuric acid baths (mainly composed of stannous sulfate and sulfuric acid) and borofluoride baths (mainly composed of stannous borofluoride and borofluoric acid) are mainly used as tin plating baths for non-ferrous metals. However, these baths were not developed with consideration to the flow properties of the electrodeposited film obtained by the baths, and therefore, for example, amine aldehyde compounds, that is, Schiff bases, are used as brighteners. When a tin plating film electroplated in a sulfuric acid bath or a borofluoride bath is subjected to reflow treatment, the molten tin partially collects and forms small droplets, resulting in a rough surface. This surface roughness is called “wetting failure” or “
This is called dewetting 1, and if this becomes significant, the plating thickness will become uneven, degrading not only the appearance but also the quality of the plating film, such as corrosion resistance.

However, the present invention was developed in view of the above-mentioned problems in tin plating, which is subjected to reflow treatment after electroplating. An object of the present invention is to provide a method for manufacturing a high-quality reflow-treated tin-plated material with excellent corrosion resistance.

The present invention will be explained in detail below.

A feature of the present invention is that, in a method for producing a reflow-treated tin-plated material, which comprises subjecting a tin plating layer formed by electroplating to a reflow treatment, free tin plating material consisting of alkanesulfonic acid or alkanolsulfonic acid or a mixture of both is used. Using an electroplating bath consisting of a solution containing an acid component and a divalent tin salt, to which one or more surfactants consisting of compounds represented by the following formulas (I) to (rV) are added. There is a particular thing.

(In the formula, represents 5 to 15) (In the formula, represents 5 to 30) (In the formula, represents 5 to 301. respectively) (In the formula, represents 1 to 10.7) 5 to 30 respectively)
In the present invention, the alkanesulfonic acid and alkanolsulfonic acid used in the electroplating bath have the following formula (V
) and (VI).

R-3O3H(V) HO-R-3OsH(Vl) (wherein, R is an alkyl group having 1 to 12 carbon atoms,
(The hydroxyl group may be bonded to any position of the alkyl group) The alkanesulfonic acids mentioned above include methanesulfonic acid,
Examples include ethanesulfonic acid, propanesulfonic acid, 2-propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, etc., and these can be used alone or in a mixture of two or more.

In addition, examples of alkanolsulfonic acids include 2-hydroxyethane-1-sulfonic acid and 2-hydroxypropane-1-sulfonic acid.
Examples include 1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, and 2-hydroxypent-1-sulfonic acid, which can be used alone or in a mixture of two or more.

The divalent tin salt that is also used in the electroplating bath can be used in the form of the above-mentioned tin alkanesulfonate, tin alkanolsulfonate, or a mixture thereof, but it may also be added and used as stannous sulfate. The concentration of tin ions in the plating bath is 5 to 100 g/j2,
In reality, if the current density is lower than Log/l, there is a problem of burnt formation in high current density areas, while if the current density is higher than 50g/l, there is no particular improvement in the electrodeposition speed or the quality of the resulting plating, and This is not preferable because it causes high costs due to pumping out the plating solution. Therefore, the concentration of tin ions is preferably 10 to 50 g/β.

In the present invention, the surfactants represented by formulas (1) to (IV) added to the electroplating bath include ethoxylate (α- or β-)naphtholsulfonic acid having formula (I);
Ethoxylates having the formula (n) (α- or β-)naphthol and ethoxylates having the formula (III) (α- or β-)
- or β-) propylene oxide adduct of naphthol, and a propylene oxide/ethylene oxide adduct of naphthol (α- or β-) having formula (IV).

By adding 0.3 to 30 g/It of each of these surfactants to the above tin plating solution, the electrodeposited tin obtained using the plating solution has a uniform matte to semi-glossy appearance. The quality of the plating material after reflow treatment is also stable.

In this case, if the amount of surfactant added to the tin plating solution is less than 0.3 g/41, the leveling effect of the plating obtained using that plating bath will be low, and the electrodeposited particles will become rough, resulting in poor flow of the plating layer. This is not preferable because it makes processing difficult. On the other hand, if the amount exceeds 30 g/II, the effect of adding the surfactant becomes saturated, which is not economically advantageous.

These surfactants can be used alone, but when used in combination, they exhibit even better leveling effects. In particular, ethoxylates (α- or β-) of formula (I)
Naphtholsulfonic acid 0.5-15g/l and formula (n)
ethoxylate (α- or β-)naphthol 0.5 to 15 g/II, or the above ethoxylate (α- or β-) naphthol sulfonic acid 0.5 to 15 g/ N and the ethoxylate represented by formula (III) (α- or β-) A propylene oxide adduct of naphthol (0.5 to 15 g/l) is added in combination to a soaking bath, or the above ethoxylate (α- or β-) Naphtholsulfonic acid 0.5~
15 g/β and the (α- or β-) propylene oxide/ethylene oxide adduct represented by formula (TV) 0.
5-15g/7! The tin plating layer electrodeposited from a matting bath containing a combination of the above forms a uniform semi-glossy surface, and is particularly excellent in gloss, film thickness uniformity, and corrosion resistance after reflow treatment. .

In the present invention, in order to make the electrodeposited surface more dense and improve the quality of plating after reflow treatment, 0.1 to 20+1 formalin is added to the tin plating bath in addition to the above surfactant.
/ You may add about 1. In this case, the amount of formalin added is 0.1 mj! If it is less than /J, there is no effect of making the electrodeposited particles finer, and if it is more than 2 J/J, the effect will be saturated, which is uneconomical.

According to the present invention, tin is electroplated from the tin plating bath as described above by using the metal strip as a cathode. Next, in the present invention, the plated layer after electroplating is subjected to a reflow treatment, but the reflow treatment tin plating material is used for so-called tin plate, which is applied to steel to be processed into food cans, etc. Examples include light electrical parts such as terminals and connectors formed by press working or the like on copper or copper alloys.

The results of applying the reflow tin plating method of the present invention to various metal strips show that it is superior in corrosion resistance and solderability compared to conventional methods, especially when copper or copper alloy is used as the base material. I understand. The copper alloys mentioned here include copper-zinc alloys such as brass and red bronze, copper-tin alloys such as phosphor bronze, copper-nickel-zinc alloys such as nickel silver, and copper-titanium alloys such as titanium copper. mentioned,
Among these alloys, the above effect is observed when the copper content is 30 wt% or more.

Note that even if the base material is not copper-based, the same effect as described above can be obtained if copper or copper alloy is included in the base of tin plating as base plating or cladding. Incidentally, in this case, the thickness and uniformity of the intermetallic compound layer (consisting of Cu*Sn and Cu4Snl) formed by tin and underlying copper is stable without being affected by the reflow processing conditions. It is thought that the same effects of improving corrosion resistance and solderability as described above can be obtained.

Regarding the reflow treatment performed in the present invention, a method is conventionally known in which the material is electroplated and electrodeposited, then immersed in an aqueous solution containing various free acids, bases, or surfactants, and further reflowed. This method is usually processed in a drag-out tank after tin plating, but this process is called flux treatment, and in the process of heating the tin plating layer to just above the melting point and reflowing, SnO and 5nO1 It has the function of suppressing the generation of tin particles and causing them to flow quickly to form a smooth surface after the tin particles are melted.

In the present invention, the above-mentioned flux treatment was also studied, and the following results were obtained.

0.5 to 100 g/l of alkanesulfonic acid or alkanolsulfonic acid or a mixture of both used as the free acid component of the electroplating bath, and one or more surfactants used by adding to the electroplating bath. 0 mixture of
．． Using an aqueous solution containing 01 to Log/J as a flux,
When applied to the tin plating layer after electroplating and subjected to reflow treatment, the appearance and gloss are even better, and the quality is also improved. Note that, according to the present invention, effective treatment can be performed even under a wide range of current density, temperature, and stirring conditions.

EXAMPLES The present invention and its effects will be specifically explained below with reference to Examples. It should be noted that the plating composition and plating work conditions shown in the following examples are merely exemplary, and it is understood that the present invention is not limited thereto and can be arbitrarily changed according to the purpose of the ridge. Should.

Examples Various gold YA plates of 0.2 m thickness shown in Table 1 below were subjected to alkaline degreasing, electrolytic degreasing, and pickling/neutralization treatment.
For each plating composition and plating condition shown in Table 1, 1.5
μ-white tin plating is applied.

However, for SUS 304, in order to improve the adhesion, a wood bath (IViC1z・6Hz0240g
, Hydrochloric acid 10 (1 wj!mu0) was used to perform strike plating at 5 A/d resistance for 1 minute. Also, for copper plating as the base plating for tin, after performing the above treatments, sulfuric acid bath (C
uSO4'5)1zo 250g/l, HtSO41
A mist thickness of 1 μm was applied using 00 g/j.

The tin plating layer glue flow treatment is performed in an electric furnace (in the atmosphere) at 7
The temperature was maintained at 00°C for 5 to 10 seconds.

Next, the obtained reflow-treated tin-plated material was evaluated as good if it had a uniform gloss and good appearance, and if the tin plating did not cause wetting. In addition, solderability was determined by aging the plated test piece for 1 hour (MILSTD).
-202E208 C), then applied rosin methanol flux and maintained at 230 ± 5 °C.
It was evaluated by crushing it in a solder bath of 0Sn/40Pb and measuring the time t2 until it became wet using the meniscograph method.

The salt spray test was conducted in accordance with JIS Z 2371.
Those in which white rust did not occur after 12 hours of spraying were judged to be good.

The results of the evaluation as described above are also shown in Table 1. For the comparative examples, the plating bath composition, plating conditions, and evaluation results are also shown in Table 2.

As seen in Tables 1 and 2, Sou 1 according to the present invention
In samples 1 to 9, tin-plated materials with better quality than Comparative Examples 1 to 3 can be obtained.

In addition, the base is copper or copper alloy (l1m1 in the example, Na3
and! The quality was good in comparison with lh4, N1)5, and Ih8), and furthermore, the effect of quality improvement by flux treatment and addition of formalin to the plating solution was observed.

Claims (8)

[Claims] (1) In a method for manufacturing reflow-treated tin-plated materials, which consists of electroplating tin on a metal strip and then performing a reflow treatment in which the plating layer is heated above its melting point and melted, the method is used as an electroplating bath. , the following formulas (I) to (
A method for producing a reflow-treated tin-plated material, characterized by using a solution containing one or more surfactants consisting of the compound shown in IV). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, n represents 5 to 15) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, m represents 5 to 30) ▲Mathematical formula , chemical formulas, tables, etc. ▼ (III) (In the formula, x represents 5 to 30, and y represents 1 to 10, respectively) ▲ There are numerical formulas, chemical formulas, tables, etc. ▼ (IV) (In the formula, x represents 1 to 10 , y represents 5 to 30, respectively) (2) The electroplating bath contains ethoxylate (α- or β-)naphtholsulfonic acid represented by the above formula (I).
Claim (1) consisting of a liquid to which 5 to 10 g/l and 0.5 to 10 g/l of ethoxylate (α- or β-) naphthol represented by the above formula (II) are added as a surfactant component. Manufacturing method described in section. (3) The electroplating bath contains ethoxylate (α- or β-)naphtholsulfonic acid represented by the above formula (I).
5 to 15 g/l and 0.5 to 15 g/l of a propylene oxide adduct of ethoxylate (α- or β-) naphthol represented by the above formula (III) is added as a surfactant component. The manufacturing method described in scope item (1). (4) The electroplating bath is an ethoxylate (α- or β-)naphtholsulfonic acid represented by the above formula (I) with 0.5
~10 g/l and the above formula (IV) (α- or β-
2.) The manufacturing method according to claim 1, wherein 0.5 to 10 g/l of a propylene oxide/ethylene oxide adduct of naphthol is added as a surfactant component. (5) The electroplating bath comprises a liquid containing a tin salt that produces 10 to 50 g/l of stannous ions. manufacturing method. (6) The manufacturing method according to any one of claims (1) to (5), wherein the electroplating bath comprises a liquid to which 0.1 to 20 ml/l of formalin has been added. (7) The manufacturing method according to claim (1), wherein the metal strip is made of copper or a copper alloy. (8) The tin-plated layer obtained by electroplating tin was mixed with alkanesulfonic acid or alkanolsulfonic acid or a mixture of both, which was used as a free acid component in the electroplating bath.
5 to 100 g/l and the above formula (
An aqueous solution containing 0.01 to 10 g/l of one or a mixture of two or more of the surfactant components shown in I) to (IV) is applied as a flux to the tinned layer and subjected to reflow treatment. A manufacturing method according to claim (1).