KR102482321B1 - Palladium plating solution and palladium coating obtained using same - Google Patents

Abstract

Soluble palladium as a palladium source, with the goal of providing a palladium plating solution capable of reducing the occurrence of defective parts such as pinholes occurring in palladium coatings and obtaining heat resistance performance equivalent to that of the conventional ones even when the gold plating coating formed on the palladium coatings is thinned. In salts, an alkyl group is bonded to the nitrogen atom at position 1, and 1 to 5 at positions 2 to 6 are an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a sulfo group, an alkoxysulfonyl group, an amino group, an alkylamino group, and a dialkyl group. A palladium plating solution containing a specific pyridinium compound substituted with one or two or more specific substituents selected from the group consisting of an amino group and a cyano group, and a film phase of nickel, nickel alloy, copper or copper alloy using the palladium plating solution The subject was solved by the palladium film obtained by giving palladium plating to this.

Description

Palladium plating solution and palladium coating obtained using the same {PALLADIUM PLATING SOLUTION AND PALLADIUM COATING OBTAINED USING SAME}

The present invention relates to a palladium plating solution having a specific composition, a palladium coating obtained using the palladium plating solution, and particularly a palladium coating on a coating of nickel, nickel alloy, copper or copper alloy.

Precious metal plating, especially gold plating, is widely used because it has excellent corrosion resistance, mechanical properties, and electrical properties. In particular, gold plating applied on a nickel film is widely used in fields such as electronic and electric parts because gold has excellent corrosion resistance, mechanical properties, electrical properties, etc., and nickel has excellent heat resistance as a base metal.

In recent years, in order to reduce production costs, gold coatings are thinned to reduce costs, and film properties such as heat resistance, which are lacking due to thinning of gold coatings, are supplemented by forming a coating of palladium cheaper than gold between nickel and gold. A method has been proposed and put into practical use.

However, there was a problem that defective parts such as pinholes were generated in the formed palladium film, and the expected physical properties of the film, such as heat resistance, could not be obtained.

In order to solve this problem, in Patent Document 1, the pH of the bath is adjusted to 5 to 10, an amine compound and ammonia are used in combination as a complexing agent, and an organic compound containing divalent sulfur is blended with a palladium plating solution This is disclosed, and it is disclosed that when the thickness of a plated film is increased using the palladium plating solution of Patent Document 1, the plated film has a particularly good appearance and a plated film with few cracks is obtained.

Further, in Patent Document 2, an electroless palladium plating solution in which a polymeric polyethyleneimine having a molecular weight of 300 to 100,000 and an unsaturated alkylamine are used in combination is excellent in bath stability, and furthermore, while reducing or preventing internal stress generated in the obtained palladium plating layer, It is disclosed that a uniform and dense film can be formed.

Further, in Patent Document 3, a palladium compound and a reducing agent selected from hypophosphorous acid and its salts, or a reducing agent selected from formic acid and formate salts are used in combination, a complexing agent selected from amines, and a bath selected from inorganic sulfur compounds The plating solution composed of the stabilizer improves plating injection time, improves plating unevenness, which is a concern of electroless palladium-phosphorus plating solutions, and suppresses the amount of nickel elution during palladium plating. It is disclosed that heat diffusion between gold and palladium after high-melting point solder mounting, which is a subject of pure palladium coating, is improved.

However, in these conventional techniques, it cannot be said that it is sufficient to maintain the properties of a film having stable heat resistance performance while seeking cost reduction by suppressing the amount of expensive gold used by further thinning gold, and further improvement this was needed

Japanese Unexamined Patent Publication No. 62-124280 Japanese Unexamined Patent Publication No. 5-039580 Japanese Unexamined Patent Publication No. 2010-261082

The present invention has been made in view of the above background art, and its object is to reduce the occurrence of defective parts such as pinholes occurring in palladium films, and even if the gold plating film formed on the palladium film is thinned, it is equivalent to that formed with a conventional gold plating film thickness. It is to provide a palladium plating solution capable of obtaining heat resistance performance.

As a result of repeated intensive studies in order to solve the above problems, the present inventors have found that when a palladium coating film is formed using a palladium plating solution containing a specific pyridinium compound as an essential component, the above problems are solved, the above problems are solved, and palladium /The present invention has been completed by finding that it is possible to significantly reduce the production cost by realizing a significant reduction in the thickness of the gold plating film while maintaining the heat resistance required for the gold plating film.

That is, the present invention is a soluble palladium salt, and an alkyl group is bonded to the nitrogen atom at position 1, and 1 to 5 at positions 2 to 6 are an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a sulfo group, an alkoxysulfonyl group To provide a palladium plating solution characterized by containing a specific pyridinium compound substituted with one or two or more specific substituents selected from the group consisting of an amino group, an alkylamino group, a dialkylamino group and a cyano group.

Moreover, this invention provides the palladium film characterized by being obtained by performing palladium plating on the film of nickel, a nickel alloy, copper, or copper alloy using the said palladium plating solution.

Moreover, this invention provides the contact member of the electronic component characterized by having the said palladium film.

Further, the present invention provides an electroless palladium plating solution and an electrolytic palladium plating solution characterized by comprising the palladium plating solution described above.

ADVANTAGE OF THE INVENTION According to the palladium plating solution of this invention, it is possible to remarkably reduce plating defect parts, such as a pinhole, which generate|occur|produce in a palladium film, and to improve heat resistance performance dramatically.

When a palladium film is formed using the palladium plating solution of the present invention, the film thickness of the palladium film is excellent in heat resistance even if the film thickness of the palladium film is reduced from that of a conventional palladium film formed for the same purpose of reducing the film thickness of a gold plating film. etc., the film performance can be maintained.

In addition, when a palladium film is formed using the palladium plating solution of the present invention, it becomes possible to significantly reduce the film thickness of the gold plating film formed on the palladium film without causing a decrease in performance such as heat resistance. Significant cost reduction can be realized.

That is, the film thickness of the palladium coating film can be reduced, and the film thickness of the gold coating film can be significantly reduced while maintaining the heat resistance required of the "palladium plating film/gold plating film". Therefore, it becomes possible to drastically reduce cost.

Hereinafter, the present invention will be described, but the present invention is not limited to the specific embodiments described below, and can be arbitrarily modified and implemented within the scope of the technical idea.

<Specific pyridinium compound>

The palladium plating solution of the present invention contains at least a soluble palladium salt as a palladium source, and it is essential to contain a "specific pyridinium compound" shown below.

"Specific pyridinium compound" means that an alkyl group is bonded to the nitrogen atom at position 1, and 1 to 5 at positions 2 to 6 are an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a sulfo group, an alkoxysulfonyl group, an amino group, It refers to a pyridinium compound substituted with one or two or more specific substituents selected from the group consisting of an alkylamino group, a dialkylamino group and a cyano group.

In the "specific pyridinium compound", when an alkyl group (-R ¹ ) is bonded to a nitrogen atom, the nitrogen atom has a positive electric charge and becomes a pyridinium compound. In the present invention, a hydrogen atom is excluded from "a bond atom bonded to a nitrogen atom to form a pyridinium compound". In the case where the bonding atom bonded to the nitrogen atom is a hydrogen atom, it is difficult to obtain the above effects of the present invention.

The alkyl group (-R ¹ ) bonded to the nitrogen atom may be either a linear alkyl group or a branched alkyl group, and the number of carbon atoms is not particularly limited. In terms of, an alkyl group having 1 to 5 carbon atoms is preferable, an alkyl group having 1 to 4 carbon atoms is more preferable, 1 to 3 carbon atoms is particularly preferable, and 1 or 2 carbon atoms is still more preferable.

If an alkyl group having too many carbon atoms is bonded, the number of pinholes in the palladium film may increase, the rate of precipitation of palladium may decrease, the appearance of palladium may be poor, or it may be difficult to obtain.

In addition, when the group bonded to the nitrogen atom is not an alkyl group (-R ¹ ) but a hydrogen atom, the effect of the present invention described above is not exhibited. In some cases, appearance defects may occur.

It is essential that the "specific pyridinium compound" in the present invention has the above chemical structure in a palladium plating solution, and may be changed to one having the above chemical structure in a palladium plating solution. Although there is no particular limitation on the chemical structure of the substance to be added at the time of liquid preparation of the palladium plating solution, it is preferable to add (liquid using) a substance having the above chemical structure.

The anion of the "specific pyridinium compound" contained in the palladium plating solution of the present invention is not particularly limited, but specific examples include sulfate ion, nitrate ion, chloride ion, bromine ion, iodine ion, etc. there is. Anion exchange (salt exchange) may occur in the palladium plating solution, and therefore salt exchange with anions such as (added) soluble palladium salt, reducing agent, conduction salt, and buffer salt formulated during preparation of the solution may be mentioned. As the composition in the palladium plating solution, those described above are included in the scope of the present invention.

However, it is preferable to add (to prepare a liquid using this) one having the above anion (sulfate ion, nitrate ion, chloride ion, bromine ion, iodine ion, etc.).

The "specific pyridinium compound" in the present invention is an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a sulfo group, an alkoxysulfonyl group, an amino group, an alkyl It is essential that it is substituted with one or two or more substituents selected from the group consisting of an amino group, a dialkylamino group and a cyano group. In the present invention, these substituents are referred to as "specific substituents".

That is, the "specific pyridinium compound" in the present invention is a 6-membered pyridine ring (pyridinium ring), since the nitrogen atom is at the 1st position, bonded to 5 carbon atoms constituting the ring other than the nitrogen atom Among the 5 hydrogens, some of 1 to 5 are substituted with the above-mentioned specific substituents that may be different.

The alkyl group as a specific substituent may be either a linear alkyl group or a branched alkyl group, and may have substituents other than the alkyl group, and the number of carbon atoms is not particularly limited. An alkyl group is preferable, an alkyl group having 1 to 5 carbon atoms is more preferable, and an alkyl group having 1 to 4 carbon atoms, ie, a methyl group, an ethyl group, a propyl group or a butyl group is particularly preferable.

When an alkyl group having too many carbon atoms is bonded, a decrease in the palladium precipitation rate or poor appearance of the palladium film may occur.

The aryl group as a specific substituent may have a substituent such as an alkyl group, and is not particularly limited. Specific examples thereof include a phenyl group, a naphthyl group, a tolyl group, and a xylyl group.

A carboxyl group as a specific substituent is a group represented by "-COOH", and an "alkoxycarbonyl group" is a group represented by "-COOR ¹¹ ", which is a residue of a carboxylic acid ester. In the above formula, R ¹¹ represents an alkyl group or an aryl group, preferably the same as the alkyl group or aryl group as the above specific substituent, and particularly preferably a methyl group.

A sulfo group as a specific substituent is a group represented by "-SO ₃ H" and is also called a sulfonic acid group.

The alkoxysulfonyl group as a specific substituent is a group represented by the following general formula (a), and is a sulfonic acid ester residue.

[Formula 1]

[In Formula (a), R ¹² represents an alkyl group or an aryl group.]

In the general formula (a), R ¹² represents an alkyl group or an aryl group, and is preferably the same as the specific substituent, such as an alkyl group or an aryl group, and more preferably a methyl group.

The amino group as a specific substituent is a group represented by "-NH ₂ ", the alkylamino group is a group represented by "-NHR ¹³ ", and the dialkylamino group is a group represented by "-NR ¹⁴ R ¹⁵ ".

In the above formula, R ¹³ , R ¹⁴ , and R ¹⁵ each represent an alkyl group or an aryl group which may be different, preferably the same as the alkyl group or aryl group as the specific substituent, and particularly preferably a methyl group.

A cyano group as a specific substituent is a group represented by "-CN".

The specific substituent may have a substituent in addition to the specific substituent within a range not impairing the effect of the present invention, but from the viewpoints of easy to exhibit the effect of the present invention described above, good plating performance, easy availability, etc. Although not limited, it is particularly preferred that the above specific substituent has no further substituent.

Although the 2nd to 6th positions of the 6-membered pyridine ring (pyridinium ring) may have substituents other than the above-mentioned specific substituents within a range not impairing the effects of the present invention, the effects of the present invention described above are easily exhibited. , From the viewpoint of good plating performance, ease of acquisition, etc., "substituents other than the above specific substituents" are not limited, but it is particularly preferable not to have them.

Among the above specific substituents, those in which one or two or more substituents selected from the group consisting of an alkyl group, a carboxy group, an alkoxysulfonyl group, and an amino group are substituted are likely to exhibit the above-described effects of the present invention, good plating performance, and easy availability It is particularly preferable in terms of the like.

Furthermore, the palladium plating solution of the present invention contains a pyridinium compound in which one or three of the 2- to 4-positions of the pyridinium ring are substituted with one or two or more of the above specific substituents, and the above effect is more preferable. It is desirable in terms of exerting it appropriately.

In other words, it is preferable to contain a pyridinium compound in which one or two or more of the above specific substituents are substituted at one to three positions in the 2nd, 3rd or 4th positions of the pyridinium ring. .

More preferably, one or two (particularly preferably one) of positions 2 to 4 of the pyridinium ring is substituted with one or two (especially preferably one) substituents specified above. It contains a dinium compound.

Although the pyridinium ring may have a substituent other than a specific substituent, it is preferable not to have it.

A particularly preferable pyridinium compound is represented by the following general formula (1).

[Formula 2]

[In Formula (1), R ¹ represents an alkyl group, and R ² , R ³ and R ⁴ may be different from each other, a hydrogen atom, an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a sulfo group, an alkoxysulfonyl group, an amino group , An alkylamino group, a dialkylamino group, or a cyano group, except when all of R ² , R ³ and R ⁴ are hydrogen atoms.]

The alkyl group (R ¹ ) bonded to the nitrogen atom may be a linear alkyl group or a branched alkyl group, and the number of carbon atoms is not particularly limited. An alkyl group having 1 to 6 carbon atoms is preferable, and an alkyl group having 1 to 5 carbon atoms is more preferable. , an alkyl group having 1 to 4 carbon atoms, that is, a methyl group, an ethyl group, a propyl group or a butyl group is particularly preferred.

If an alkyl group having too many carbon atoms is bonded, the effect of the present invention described above is not exhibited, the number of pinholes in the palladium film increases, the rate of precipitation of palladium decreases, the appearance of palladium deteriorates, or the availability of palladium becomes difficult. There are times when

In addition, when the group bonded to the nitrogen atom is not an alkyl group but a hydrogen atom, the effect of the present invention described above is not exhibited, and in particular, when the palladium concentration in the palladium plating solution is high, or when plating at a high temperature, the appearance is poor. may occur.

R ² , R ³ and R ⁴ represent a hydrogen atom, an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a sulfo group, an alkoxysulfonyl group, an amino group, an alkylamino group, a dialkylamino group or a cyano group, which may be different from each other; , R ² , R ³ and R ⁴ are all hydrogen atoms.

As R ² , R ³ and R ⁴ , “specific substituents” described above as “more preferred”, “particularly preferred”, etc. are more (especially) preferred from the point of exhibiting the above-mentioned effect more preferably.

Although there is no particular limitation on the anion (counter ion) of the general formula (1), specific examples thereof include those described above, such as sulfate ion, nitrate ion, chloride ion, bromine ion, and iodine ion, as preferred examples. .

The anion of the general formula (1) specifies the form present in the palladium plating solution of the present invention, and is salt-exchanged with anions such as (added) soluble palladium salt, reducing agent, conductive salt, buffer salt, etc. is also desirable

However, sulfate ions, nitrate ions, chloride ions, bromide ions, iodine ions and the like are preferable as anions (counter ions) of raw materials to be dissolved (mixed, added) during preparation of the palladium plating solution of the present invention.

The description of the specific pyridinium compound described above specifies the form present in the palladium plating solution of the present invention. However, it is preferable to use the specific pyridinium compound described above as a raw material to be dissolved at the time of liquid preparation of the palladium plating solution of the present invention.

By containing a specific pyridinium compound, a pinhole-free palladium film is realizable. In addition, by containing a specific pyridinium compound, the film thickness of the conventional palladium film can be significantly reduced in that it has high heat resistance that is dramatically superior to that of the conventional palladium film, and the gold plating film formed on the palladium film can be significantly reduced. Thinning is possible, and significant cost reduction is realized.

In the "pinhole test", if the palladium plating solution of the present invention capable of realizing a pinhole-free palladium coating film with a "palladium coating film with a film thickness of 0.03 μm" is used, relatively few pinholes are obtained even in a palladium coating film thinner than that, If it is a palladium film thicker than that, a thing without a further pinhole is obtained and reliability further increases.

In addition, a gold film generally does not easily form pinholes, and a palladium film generally tends to form pinholes. Therefore, when the palladium plating solution of the present invention, which does not easily cause pinholes, is used, there is no need to cover pinholes in the palladium film with a gold film, and the film thickness of the gold film can be reduced, thereby reducing costs.

In the present invention, the "pinhole test" will be described later, and a palladium plating solution that provides a palladium film with a small conduction current is excellent during all from "the start of the test" to "5 minutes after the start of the test", and during that time, An excellent palladium plating solution is a palladium plating solution that always provides film properties such that the conduction current is 100 μA or less.

In the present invention, "heat resistance" is defined as evaluated by the method described in Examples and evaluated as such.

"Heat resistance" is an essential performance for a contact member of an electronic component. Contact members of electronic components need to be joined to other members by solder bonding or wire bonding, and the bonding process necessarily includes a heating process at 100°C to 300°C, and this heating process is also performed not once but multiple times. often exist

In this heating process, metals such as copper, copper alloy, nickel, and nickel alloy are oxidized, causing defects such as solder bonding failure, increase in contact resistance, and wire bonding failure. Therefore, for the purpose of preventing the oxidation of copper, nickel, etc., it is important to form a surface protective layer by performing noble metal plating such as gold plating or palladium plating.

However, even if a noble metal plating film such as a gold plating film or a palladium plating film is formed, if a pinhole is present in the noble metal plating film, copper, nickel, etc., which are the base of the noble metal plating film, is removed from the pinhole by the above heating step. It is diffused and oxidized, and the effect of applying the noble metal plating film may be lost.

Therefore, the presence of pinholes in the noble metal plating film is an index of whether or not the contact member of the electronic component has heat resistance. The fact that there are few pinholes in a noble metal plating film such as a gold plating film or a palladium plating film indicates that it has excellent "heat resistance".

Preferred specific examples of the specific pyridinium compound described above include, for example,

1-methyl-2-methylpyridinium, 1-methyl-2-ethylpyridinium, 1-methyl-2-butylpyridinium, 1-methyl-2-sulfopyridinium, 1-methyl-2-methoxysulfonyl Pyridinium, 1-methyl-2-aminopyridinium, 1-methyl-2-carboxypyridinium, 1-methyl-2-methoxycarbonylpyridinium, 1-methyl-2-phenylpyridinium, 1-methyl- 2-position substituted methylpyridinium such as 2-cyanopyridinium;

1-ethyl-2-methylpyridinium, 1-ethyl-2-ethylpyridinium, 1-ethyl-2-butylpyridinium, 1-ethyl-2-sulfopyridinium, 1-ethyl-2-methoxysulfonyl Pyridinium, 1-ethyl-2-aminopyridinium, 1-ethyl-2-carboxypyridinium, 1-ethyl-2-methoxycarbonylpyridinium, 1-ethyl-2-phenylpyridinium, 1-ethyl- Ethylpyridinium of 2-position substitution, such as 2-cyanopyridinium;

1-propyl-2-methylpyridinium, 1-propyl-2-ethylpyridinium, 1-propyl-2-butylpyridinium, 1-propyl-2-sulfopyridinium, 1-propyl-2-methoxysulfonyl Pyridinium, 1-propyl-2-aminopyridinium, 1-propyl-2-carboxypyridinium, 1-propyl-2-methoxycarbonylpyridinium, 1-propyl-2-phenylpyridinium, 1-propyl- 2-position substituted propylpyridinium such as 2-cyanopyridinium;

1-butyl-2-methylpyridinium, 1-butyl-2-ethylpyridinium, 1-butyl-2-butylpyridinium, 1-butyl-2-sulfopyridinium, 1-butyl-2-methoxysulfonyl Pyridinium, 1-butyl-2-aminopyridinium, 1-butyl-2-carboxypyridinium, 1-butyl-2-methoxycarbonylpyridinium, 1-butyl-2-phenylpyridinium, 1-butyl- 2-position substituted butylpyridinium such as 2-cyanopyridinium;

1-methyl-3-methylpyridinium, 1-methyl-3-ethylpyridinium, 1-methyl-3-butylpyridinium, 1-methyl-3-sulfopyridinium, 1-methyl-3-methoxysulfonyl Pyridinium, 1-methyl-3-aminopyridinium, 1-methyl-3-carboxypyridinium, 1-methyl-3-methoxycarbonylpyridinium, 1-methyl-3-phenylpyridinium, 1-methyl- 3-position substituted methylpyridinium such as 3-cyanopyridinium;

1-ethyl-3-methylpyridinium, 1-ethyl-3-ethylpyridinium, 1-ethyl-3-butylpyridinium, 1-ethyl-3-sulfopyridinium, 1-ethyl-3-methoxysulfonyl Pyridinium, 1-ethyl-3-aminopyridinium, 1-ethyl-3-carboxypyridinium, 1-ethyl-3-methoxycarbonylpyridinium, 1-ethyl-3-phenylpyridinium, 1-ethyl- Ethylpyridinium of 3-position substitution, such as 3-cyanopyridinium;

1-propyl-3-methylpyridinium, 1-propyl-3-ethylpyridinium, 1-propyl-3-butylpyridinium, 1-propyl-3-sulfopyridinium, 1-propyl-3-methoxysulfonyl Pyridinium, 1-propyl-3-aminopyridinium, 1-propyl-3-carboxypyridinium, 1-propyl-3-methoxycarbonylpyridinium, 1-propyl-3-phenylpyridinium, 1-propyl- 3-position substituted propylpyridinium such as 3-cyanopyridinium;

1-butyl-3-methylpyridinium, 1-butyl-3-ethylpyridinium, 1-butyl-3-butylpyridinium, 1-butyl-3-sulfopyridinium, 1-butyl-3-methoxysulfonyl Pyridinium, 1-butyl-3-aminopyridinium, 1-butyl-3-carboxypyridinium, 1-butyl-3-methoxycarbonylpyridinium, 1-butyl-3-phenylpyridinium, 1-butyl- 3-position substituted butylpyridinium such as 3-cyanopyridinium;

1-methyl-4-methylpyridinium, 1-methyl-4-ethylpyridinium, 1-methyl-4-butylpyridinium, 1-methyl-4-sulfopyridinium, 1-methyl-4-methoxysulfonyl Pyridinium, 1-methyl-4-aminopyridinium, 1-methyl-4-carboxypyridinium, 1-methyl-4-methoxycarbonylpyridinium, 1-methyl-4-phenylpyridinium, 1-methyl- 4-position substituted methylpyridinium such as 4-cyanopyridinium;

1-ethyl-4-methylpyridinium, 1-ethyl-4-ethylpyridinium, 1-ethyl-4-butylpyridinium, 1-ethyl-4-sulfopyridinium, 1-ethyl-4-methoxysulfonyl Pyridinium, 1-ethyl-4-aminopyridinium, 1-ethyl-4-carboxypyridinium, 1-ethyl-4-methoxycarbonylpyridinium, 1-ethyl-4-phenylpyridinium, 1-ethyl- Ethylpyridinium of 4-position substitution, such as 4-cyanopyridinium;

1-propyl-4-methylpyridinium, 1-propyl-4-ethylpyridinium, 1-propyl-4-butylpyridinium, 1-propyl-4-sulfopyridinium, 1-propyl-4-methoxysulfonyl Pyridinium, 1-propyl-4-aminopyridinium, 1-propyl-4-carboxypyridinium, 1-propyl-4-methoxycarbonylpyridinium, 1-propyl-4-phenylpyridinium, 1-propyl- 4-position substituted propylpyridinium such as 4-cyanopyridinium;

1-butyl-4-methylpyridinium, 1-butyl-4-ethylpyridinium, 1-butyl-4-butylpyridinium, 1-butyl-4-sulfopyridinium, 1-butyl-4-methoxysulfonyl Pyridinium, 1-butyl-4-aminopyridinium, 1-butyl-4-carboxypyridinium, 1-butyl-4-methoxycarbonylpyridinium, 1-butyl-4-phenylpyridinium, 1-butyl- 4-position substituted butylpyridinium such as 4-cyanopyridinium;

etc. can be mentioned.

These specific pyridinium compounds are preferable also from the viewpoints of easy to exhibit the above-described effects of the present invention, good palladium plating performance, ease of dissolution in water, easy availability, and low cost.

Among them, specific examples particularly preferred in the above points and the like include:

1-methyl-2-methylpyridinium, 1-methyl-2-ethylpyridinium, 1-methyl-2-butylpyridinium, 1-methyl-2-sulfopyridinium, 1-methyl-2-methoxysulfonyl 2-position substituted methylpyridinium such as pyridinium, 1-methyl-2-aminopyridinium, and 1-methyl-2-carboxypyridinium;

1-ethyl-2-methylpyridinium, 1-ethyl-2-ethylpyridinium, 1-ethyl-2-butylpyridinium, 1-ethyl-2-sulfopyridinium, 1-ethyl-2-methoxysulfonyl 2-position substituted ethylpyridiniums such as pyridinium, 1-ethyl-2-aminopyridinium, and 1-ethyl-2-carboxypyridinium;

1-methyl-3-methylpyridinium, 1-methyl-3-ethylpyridinium, 1-methyl-3-butylpyridinium, 1-methyl-3-sulfopyridinium, 1-methyl-3-methoxysulfonyl 3-position substituted methylpyridinium such as pyridinium, 1-methyl-3-aminopyridinium, and 1-methyl-3-carboxypyridinium;

1-ethyl-3-methylpyridinium, 1-ethyl-3-ethylpyridinium, 1-ethyl-3-butylpyridinium, 1-ethyl-3-sulfopyridinium, 1-ethyl-3-methoxysulfonyl 3-position substituted ethylpyridinium such as pyridinium, 1-ethyl-3-aminopyridinium, and 1-ethyl-3-carboxypyridinium;

1-methyl-4-methylpyridinium, 1-methyl-4-ethylpyridinium, 1-methyl-4-butylpyridinium, 1-methyl-4-sulfopyridinium, 1-methyl-4-methoxysulfonyl 4-position substituted methylpyridinium such as pyridinium, 1-methyl-4-aminopyridinium, and 1-methyl-4-carboxypyridinium;

1-ethyl-4-methylpyridinium, 1-ethyl-4-ethylpyridinium, 1-ethyl-4-butylpyridinium, 1-ethyl-4-sulfopyridinium, 1-ethyl-4-methoxysulfonyl 4-position substituted ethylpyridinium such as pyridinium, 1-ethyl-4-aminopyridinium, and 1-ethyl-4-carboxypyridinium;

etc. can be mentioned.

These specific pyridinium compounds are particularly preferable from the viewpoints of more easily exhibiting the effects of the present invention described above, and good palladium plating performance, ease of dissolution in water, easy availability, and low cost.

In the present invention, the content of the specific pyridinium compound is not particularly limited, but is preferably 1 ppm to 50000 ppm, more preferably 10 ppm to 30000 ppm, particularly preferably by mass with respect to the entire palladium plating solution 20 ppm to 10000 ppm, more preferably 50 ppm to 5000 ppm, most preferably 100 ppm to 3000 ppm. In addition, when two or more types of said specific pyridinium compounds are contained, the said numerical value shows their total content.

If the content of the specific pyridinium compound in the palladium plating solution is too small, it becomes difficult to exert the effect of the present invention described above, increasing the number (density) of pinholes formed in the palladium coating, or causing poor appearance of the palladium coating. there is On the other hand, if the content is too large, further increase in the above effects of the present invention may become uneconomical in some cases.

Although the description of the specific pyridinium compound above specifies the form present in the palladium plating solution of the present invention, it is preferable to use the specific pyridinium compound described above as a raw material to be dissolved during preparation of the palladium plating solution of the present invention. .

<Soluble palladium salt>

It is essential that the palladium plating solution of the present invention contains a soluble palladium salt. The soluble palladium salt is used as a palladium source for the palladium plating solution of the present invention. A soluble palladium salt is not limited to 1 type of use, It can use 2 or more types together. The meaning of "soluble" is the meaning of being soluble in water.

The soluble palladium salt is not particularly limited, and a known one can be used. Specifically, for example, palladium chloride, palladium sulfate, palladium acetate, palladium nitrate, palladium oxide, dichlorotetraammine palladium, dinitrodiammine Palladium, dichlorodiethylenediaminepalladium, tetrakis(triphenylphosphine)palladium, dichlorobis(triphenylphosphine)palladium and/or bis(acetylacetonato)palladium are preferred in terms of solubility in water, availability and the like. can be heard

Among them, dichlorotetraammine palladium or dinitrodiammine palladium is more preferable in view of the fact that there is no need for labor when replenishing the palladium salt by being supplied as an aqueous solution. Also, from the same viewpoint, dichlorotetraammine palladium is particularly preferred.

The content of the palladium salt in the palladium plating solution of the present invention is not particularly limited, but is usually 0.001 g/L to 50 g/L, preferably 0.005 g/L to 30 g/L as metal palladium with respect to the entire palladium plating solution, Especially preferably, they are 0.01 g/L - 20 g/L.

When content of the soluble palladium salt in a palladium plating solution is too small, formation of the palladium film of a normal uniform color tone may become difficult. That is, when the color and throwing power of the palladium film are observed with the naked eye, palladium precipitation abnormality may be observed.

On the other hand, when the content of the palladium salt in the palladium plating solution is too large, there is no particular problem with the performance of the palladium plating solution, but the palladium salt is very expensive, and it is uneconomical to store it in a state contained in the palladium plating solution.

The description of the palladium salt described above specifies the form present in the palladium plating solution of the present invention, but it is preferable to use the palladium salt described above as a raw material to be dissolved in the preparation of the palladium plating solution of the present invention.

<Reducing agent>

The palladium plating solution of the present invention preferably contains a reducing agent in addition to a soluble palladium salt and a specific pyridinium compound. As the reducing agent, hypophosphorous acid, hypophosphite, phosphorous acid, phosphite, formic acid, formate, formaldehyde and the like are particularly preferred.

The said reducing agent is not limited to use of 1 type, Two or more types can be used together.

Specifically, as the reducing agent, for example, hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, phosphorous acid, sodium phosphite, potassium phosphite, ammonium phosphite, formic acid, sodium formate, potassium formate, ammonium formate, formate Aldehydes and the like are preferable from the viewpoints of good palladium plating performance, ease of dissolution in water, ease of handling as a chemical, easy availability, and low cost.

The content of the reducing agent in the palladium plating solution of the present invention is not particularly limited, but is preferably 1 ppm to 100,000 ppm, more preferably 10 ppm to 60,000 ppm, and particularly preferably 50 ppm to 30,000 ppm with respect to the entire palladium plating solution. ppm, more preferably 100 ppm to 10000 ppm. In addition, when using 2 or more types of reducing agents, the said numerical value shows their total content.

When content is too small, formation of the palladium film of a normal uniform color tone may become difficult. In other words, when the color and throwing power of the palladium film are visually observed, palladium precipitation abnormality may be observed. On the other hand, if the content is too large, the palladium plating bath becomes unstable, expensive palladium is abnormally deposited in the storage container, and unnecessary costs are required for palladium recovery, or the color tone of the palladium film may be poor.

<Other additives>

In the palladium plating solution of the present invention, in addition to the above components, if necessary, a buffer to keep the pH of the palladium plating solution constant, a conductive salt to ensure the conductivity of the palladium plating solution, and an impurity metal in the palladium plating solution to remove the effect when they are mixed. A metal ion sequestering agent for the above, a surfactant for improving the disappearance of bubbles in the palladium plating solution, a brightening agent for smoothing the palladium film, and the like can be appropriately contained and used.

The buffering agent contained as necessary in the palladium plating solution of the present invention is not particularly limited as long as it is a well-known buffering agent, but inorganic acids such as boric acid and phosphoric acid are preferable; Oxycarboxylic acids, such as citric acid, tartaric acid, and malic acid; etc. can be mentioned. These can be used 1 type or in mixture of 2 or more types.

The content of the buffering agent in the palladium plating solution of the present invention is not particularly limited, but is usually 1 g/L to 500 g/L, preferably 10 g/L to 100 g/L with respect to the entire palladium plating solution.

When the content of the buffering agent in the palladium plating solution is too small, the buffering effect may not be exhibited in some cases. On the other hand, when the content of the buffering agent in the palladium plating solution is too large, the increase in the buffering effect is not observed and may be uneconomical.

The conductive salt contained as necessary in the palladium plating solution of the present invention is not particularly limited as long as it is a well-known conductive salt, but inorganic acid salts such as sulfates, nitrates, and phosphates are preferable; carboxylic acids such as oxalic acid, succinic acid, glutaric acid, malonic acid, citric acid, tartaric acid, and malic acid; etc. can be mentioned. These can be used 1 type or in mixture of 2 or more types.

The content of the conductive salt in the palladium plating solution of the present invention is not particularly limited, but is usually 1 g/L to 500 g/L, preferably 10 g/L to 100 g/L, based on the entire palladium plating solution.

If the content of the conductive salt in the palladium plating solution is too small, the conductive effect may not be exhibited in some cases. On the other hand, if the content of the conductive salt in the palladium plating solution is too large, the increase in the conductive effect may not be observed and may be uneconomical.

In addition, the same components as the buffering agent may be used in common.

The metal ion sequestering agent contained as necessary in the palladium plating solution of the present invention is not particularly limited as long as it is a well-known metal ion sequestering agent, but preferred examples include aminocarboxyls such as iminodiacetic acid, nitrilotriacetic acid, and ethylenediaminetetraacetic acid. acidic chelating agents; phosphonic acid-based chelating agents such as hydroxyethylidenediphosphonic acid, nitrilomethylenephosphonic acid, and ethylenediamine tetramethylenephosphonic acid; etc. can be mentioned. These can be used 1 type or in mixture of 2 or more types.

The content of the metal ion sequestering agent in the palladium plating solution of the present invention is not particularly limited, but is usually 0.1 g/L to 100 g/L, preferably 0.5 g/L to 50 g/L, based on the entire palladium plating solution.

When the content of the metal ion sequestering agent in the palladium plating solution is too small, the effect of removing the influence of the impurity metal may not be exhibited in some cases. There are negative cases.

The surfactant contained as necessary in the palladium plating solution of the present invention is not particularly limited as long as it is a known surfactant, and a nonionic surfactant, anionic surfactant, amphoteric surfactant or cationic surfactant is used. These can be used 1 type or in mixture of 2 or more types.

As the nonionic surfactant, preferred are ether type nonionics such as noniphenol polyalkoxylate, α-naphthol polyalkoxylate, dibutyl-β-naphthol polyalkoxylate, and styrenated phenol polyalkoxylate. system surfactant; amine type nonionic surfactants such as octylamine polyalkoxylate, hexynylamine polyalkoxylate, and linoleylamine polyalkoxylate; etc. can be mentioned.

Preferable examples of the anionic surfactant include alkyl sulfates such as sodium lauryl sulfate; polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene nonyl ether sulfate; polyoxyethylene alkyl phenyl ether sulfate; Alkylbenzene sulfonic acid salt etc. are mentioned.

As the amphoteric surfactant, preferably, 2-undecyl-1-carboxymethyl-1-hydroxyethylimidazolium, N-stearyl-N,N-dimethyl-N-carboxymethyl betaine, lauryldimethyl An amine oxide etc. are mentioned.

Preferred cationic surfactants include lauryltrimethylammonium salt, lauryldimethylammonium betaine, laurylpyridinium salt, oleylimidazolium salt, and stearylamine acetate.

These surfactants can be used alone or in combination of two or more. Preferably, it is a nonionic surfactant or an amphoteric surfactant.

The content of the surfactant in the palladium plating solution of the present invention is preferably 0.01 g/L to 20 g/L with respect to the entire palladium plating solution, but the desired performance may be exhibited, and the content is not particularly limited.

The brightening agent contained as necessary in the palladium plating solution of the present invention is not particularly limited as long as it is a well-known brightening agent, but "amine compounds having a pyridine skeleton" that cannot become the specific pyridinium compound in the present invention among palladium plating. can be heard These can be used 1 type or in mixture of 2 or more types.

Examples of the amine compound having a pyridine skeleton include 2-aminopyridine, 3-aminopyridine and 4-aminopyridine.

The content of the brightener in the palladium plating solution of the present invention is preferably 0.01 g/L to 20 g/L with respect to the entire palladium plating solution, but the desired performance may be exhibited, and the content is not particularly limited.

<Physical properties of palladium plating solution>

The palladium plating solution of the present invention uses a palladium plating solution as a physical property of the palladium plating solution. A base material plated so that the film thickness of the palladium film is 0.03 μm is immersed in a 5% by mass sulfuric acid aqueous solution, and a pinhole is applied at a constant voltage of 300 mV. In the case of testing, it is a palladium plating solution that provides film properties such that the conduction current is 100 μA or less between the start of the test and all of 5 minutes after the start of the test.

A palladium plating solution having such physical properties is a new palladium plating solution first realized as a palladium plating solution having the above composition.

In the palladium plating solution of the present invention, as physical properties of the palladium plating solution, a copper plate base material plated on a copper plate so that the electroless nickel plating film is 5 µm and the palladium film thickness is 0.03 µm, immersed in a 5% by mass sulfuric acid solution, When a pinhole test is performed at a voltage of 300 mV, it is preferable that the current does not flow more than 100 μA between the start of the test and 5 minutes.

The "pinhole test" of the present invention is a copper plate material subjected to electroless nickel plating and then palladium plating by a conventional method by removing copper in a circular shape with a diameter of 10 mm to open an anode, and It refers to a test in which a material is used as a cathode and immersed in a 5% by mass sulfuric acid solution, and a voltage of 300 mV is continuously applied to observe the current value passed.

If a defective part such as a pinhole is formed in the palladium film, nickel ions or copper ions are dissolved from the pinhole in the palladium film, which is the anode, and the flowing current value shows a large value. Moreover, compared with the sample for evaluation in which a defective part, such as a pinhole, was not produced|generated in the palladium film|membrane, a current started to flow relatively quickly.

The limitation of the physical properties is to limit the physical properties of the palladium plating solution, but does not limit the method of using the palladium plating solution. The palladium film actually formed with this palladium plating solution does not have to be 0.03 μm. Using the palladium plating solution of the present invention, for example, a palladium film having a film thickness of less than 0.03 μm may be formed, or a palladium film thicker than 0.03 μm may be formed. can form

In the case of carrying out the pinhole test of the present invention, in the palladium film thickness of 0.05 μm or less (therefore, in the palladium film thickness of 0.03 μm or less), from the start of the test to “5 minutes after the start of the test”, the current A palladium plating solution having a physical property of not flowing more than 100 μA has not existed in the past.

<Method for producing palladium plating solution>

The manufacturing method of the palladium plating solution of this invention is not specifically limited, A well-known method including the mixing|blending order of each component etc. is used.

<Palladium coating>

The palladium film obtained by performing palladium plating using the palladium plating solution of the present invention exhibits the above effect.

The palladium concentration (palladium purity) in the palladium coating of the present invention is not particularly limited, but is preferably 90% by mass or more, and particularly preferably 95.0% by mass to 99.9% by mass with respect to the entire “palladium coating”.

<Conditions of palladium plating>

Plating conditions of the palladium plating solution of the present invention described above are not particularly limited, but the temperature condition is preferably from 20°C to 90°C, particularly preferably from 30°C to 70°C. In addition, the pH of the plating solution is preferably from pH 2.0 to 9.0, and particularly preferably from pH 3.0 to 8.0.

The film thickness of the palladium film obtained by performing palladium plating using the palladium plating solution of the present invention is not particularly limited, but is preferably 0.0001 μm to 5 μm, more preferably 0.001 μm to 1 μm, and particularly preferably 0.005 μm. to 0.5 μm, more preferably 0.01 μm to 0.3 μm.

Although the film thickness of the palladium plating film produced using the conventional palladium plating solution differs depending on a use, in the case of a connector, it was normally 0.01 micrometer - 0.5 micrometer. The palladium-plated film produced using the palladium plating solution of the present invention gives substantially equivalent pinhole test and heat resistance results even when the film thickness is reduced to the conventional range of 30% to 60%.

A palladium film obtained by performing palladium plating on a film of nickel, nickel alloy, copper or copper alloy using the palladium plating solution of the present invention exhibits the above-mentioned effects, and is therefore preferable. Among them, a coating phase of nickel or a nickel alloy is more preferable in terms of heat resistance and there is no possibility of mixing in palladium plating to adversely affect the coating, etc., and a nickel coating phase is particularly preferred.

<Usage of palladium plating solution and all laminated plating films>

Although the palladium plating solution of this invention is not specifically limited, The case where it is used for manufacture of the contact member of an electronic component is more preferable.

Therefore, when palladium plating is performed using the palladium plating solution of the present invention, it is more preferable to form a nickel plating film as a base plating treatment.

The nickel plating solution at this time is not particularly limited, but a generally practical electroless nickel solution is preferable, and an electroless nickel-phosphorus solution is particularly preferable. The method of using the nickel plating solution is not particularly limited and is used according to a conventional method.

The film thickness of the nickel plating film is not particularly limited, but is preferably 0.01 μm to 20 μm, particularly preferably 0.05 μm to 5 μm.

The palladium plating solution of the present invention is preferably used for forming a palladium film as a base for forming a gold film by performing gold plating on a palladium film.

The film thickness of the gold plating film is not particularly limited, but is preferably 0.0001 μm to 5 μm, more preferably 0.001 μm to 1 μm, and particularly preferably 0.01 μm to 0.5 μm.

A preferred embodiment of the coating of the present invention is an embodiment in which a gold coating is formed on a palladium coating, and a particularly preferred embodiment is an embodiment in which a palladium coating is formed on a nickel coating and a gold coating is formed thereon.

The film thickness of the gold coating film formed on the palladium plating film produced using a conventional palladium plating solution varies depending on the application, but in the case of a connector, it was usually 0.05 μm to 0.2 μm. Even when the film thickness of the gold film formed on the palladium-plated film produced using the palladium plating solution of the present invention was reduced to the conventional range of 20% to 60%, almost equivalent pinhole test and heat resistance results were obtained. lose

The palladium plating solution of the present invention is used as either an electroless palladium plating solution or an electrolytic palladium plating solution. That is, the present invention is an electroless palladium plating solution composed of the palladium plating solution, and is also an electrolytic palladium plating solution composed of the palladium plating solution.

Even if the "specific pyridinium compound" described above is contained in an electroless palladium plating solution or an electrolytic palladium plating solution, the above effect is exhibited.

Among the above-described soluble palladium salts, specific pyridinium compounds, buffers, conductive salts, metal ion sequestering agents, surfactants, reducing agents and brighteners, the electroless palladium plating solution contains soluble palladium salts, specific pyridinium compounds and reducing agents as essential components. and a buffer, a metal ion sequestering agent, a surfactant and/or a brightening agent as suitable components.

In addition, the electrolytic palladium plating solution contains a soluble palladium salt, a specific pyridinium compound and a conductive salt as essential components, and contains a buffer, a metal ion sequestering agent, a surfactant and/or a brightening agent as suitable components.

The content of each component in both the electroless palladium plating solution and the electrolytic palladium plating solution is preferably within the above range (more preferably, particularly preferably).

In the case of electroless palladium plating, it may be carried out according to a conventional method and is not particularly limited, but the solution temperature is preferably 30°C to 90°C, and particularly preferably 40°C to 80°C. In addition, time is suitably adjusted so that it may become the said palladium film thickness.

In the case of electrolytic palladium plating, what is necessary is just to carry out according to a conventional method, and although it is not specifically limited, 30 degreeC - 90 degreeC of solution temperature is preferable, and 40 degreeC - 80 degreeC is especially preferable. Moreover, a current density of 0.1 A/dm ² to 100 A/dm ² is preferable, and 0.5 A/dm ² to 50 A/dm ² is particularly preferable. Moreover, time is suitably adjusted so that it may become the said palladium film thickness.

＜Action/principle＞

The action and principle by which the palladium plating solution of the present invention can form a palladium coating film with significantly less defective parts such as pinholes is not clear, but the following can be considered. However, the present invention is not limited to the range in which the following actions and principles are established.

The specific pyridinium compound which is an essential component of the palladium plating solution of the present invention is considered to have an effect as a kind of crystal regulator. When the palladium film is to be formed by the plating reaction, it is considered that if the palladium film grows without any control, a very rough film grows. A rough film is a film with irregularities.

It is considered that the "specific pyridinium compound" is selectively adsorbed to this convex portion and inhibits the growth. It is thought that by inhibiting the plating growth on the convex portion where the plating growth was rapid, the plating reaction on the concave portion was promoted, the concave portion was filled, and as a result, a plated film without irregularities could be formed. The plated film without concave portions is a palladium film that uniformly covers the underlying metal with a palladium film and has remarkably few pinholes.

Example

The present invention will be described in more detail by way of Examples and Comparative Examples below, but the present invention is not limited to these Examples unless the gist thereof is exceeded.

In addition, the numerical value of the concentration in the composition of the palladium plating solution is the numerical value of the concentration obtained from the mass without including the water of crystallization when the component contains water of crystallization.

"%" regarding content represents "mass %" unless otherwise specified, and "ppm" represents "mass ppm". In the heat resistance evaluation method, "%" of nickel and copper indicates "atm% (atomic standard concentration)".

Examples 1 to 8, Comparative Examples 1 to 7

<Evaluation of electroless palladium plating solution>

With respect to the entire palladium plating solution, the dichlorotetraammine palladium solution was 1 g/L in terms of palladium, the specific pyridinium compound described in each Example and each comparative example shown in Table 1 or its comparative compound was 1000 ppm, respectively, and formic acid was used as a reducing agent. 1000 ppm, and citric acid as a component serving as both a conductive salt and a buffer were dissolved so as to be 100 g/L, and the pH was adjusted to 6.5 to obtain an electroless palladium plating solution. However, Comparative Example 7 contained neither a specific pyridinium compound nor a comparative compound.

As the "comparative compound", pyridine, pyridine-3-sulfonic acid, picoline, quinolinesulfonic acid, 2,3-diaminopyridine, and 3-(3-pyridyl)acrylic acid were used.

In addition, as Comparative Example 7, a palladium plating solution similarly prepared without containing either the "specific pyridinium compound" or the "comparative compound" was also evaluated.

The pH of the electroless palladium plating solution was adjusted with a 20% by mass potassium hydroxide aqueous solution and citric acid, the bath temperature of the palladium plating solution was set to 70°C, and evaluation described below was performed.

<Formation method of palladium coating for testing (for evaluation)>

Using the palladium plating solutions prepared in each Example and each Comparative Example, a palladium coating was applied on a 5.0 μm electroless nickel plating coating on a 10 mm × 10 mm copper plate at the steps shown in Table 2 so that the film thickness was 0.03 μm. , The time of the electroless palladium plating treatment was adjusted within the range of 30 seconds to 3 minutes.

In addition, the electroless nickel plating film was formed into a film thickness of 5.0 μm by plating according to a conventional method using “electroless nickel plating solution ICP Nicoron GM” (trade name) (manufactured by Okuno Pharmaceutical Industry Co., Ltd.).

<Method of pinhole test>

As described above, a palladium coating having a film thickness of 0.03 μm formed on a nickel-plated coating on a copper plate was immersed in a 5% by mass aqueous sulfuric acid solution, and a constant voltage of 300 mV was always applied using POTENTIONSTAT/GALVANOSTAT (manufactured by Hokuto Electric Co., Ltd.). Authorized.

Current values (μA) at 1 minute, 3 minutes, and 5 minutes from the start of the test were measured.

If there is a pinhole, the current value increases, so it is judged to be an excellent palladium plating solution when the conduction current is always 100 μA or less between the start of the test and “5 minutes from the start of the test”, and it is judged to be an excellent palladium plating solution when the conduction current is smaller. It was judged to be

<Evaluation method of appearance (color tone uniformity) of palladium coating>

As described above, the palladium film having a film thickness of 0.03 μm formed on the nickel plating film on the copper plate was visually observed from a position 30 cm directly above the palladium film, and the color tone of the surface of the palladium film was observed. .

Since the base metal is nickel, the color tone is similar and the determination is difficult. However, when a uniform palladium film is not formed, unevenness (unevenness) of about 0.5 mm to 3 mm in size is observed, so the unevenness (unevenness) A palladium plating solution which was not observed at all was judged to be an excellent palladium plating solution, and a case where only less unevenness (unevenness) was observed was judged to be a more excellent palladium plating solution.

<Method for measuring film thickness of palladium film>

The film thickness of the palladium film was measured in the vicinity of the center of the palladium film subjected to palladium plating using a fluorescence X-ray analyzer (SFT9255 manufactured by Seiko Instruments Co., Ltd.) according to a conventional method.

<Evaluation method of heat resistance>

In the same process as the evaluation sample prepared for the pinhole test, a palladium film was formed on the nickel-plated film on the copper plate to a film thickness of 0.03 μm to prepare an evaluation sample.

In the case where a gold coating was applied on the palladium coating, after forming the palladium coating, a gold coating was formed to a predetermined film thickness according to a conventional method to prepare samples for evaluation.

The evaluation sample was heated in an oven adjusted to 200°C for 15 hours.

The surface of the sample for evaluation after heating is surface Auger; Measurement was performed at an accelerating voltage of 5 kV using SAM-4300 (manufactured by Albac Pi Co., Ltd.).

A sample for evaluation and a palladium plating solution satisfying that the content of nickel is less than 10% and the content of copper is less than 0.5% are judged to be "defective products", and samples for evaluation and palladium plating solutions in which either nickel or copper are above the specified value are judged to be "defective products". judged.

As can be seen from Table 3, when the electroless palladium plating solution of the present invention is used, in the pinhole test, a current larger than 100 μA does not always flow from the start of the test to “5 minutes after the start of the test”, and furthermore, the palladium coating No unevenness or unevenness was observed in the visual appearance, the color tone uniformity was good, and palladium precipitation abnormality was not observed.

In addition, in the heat resistance test, nickel was less than 10% and copper was less than 0.5%, and all were judged as “good products”.

On the other hand, in the electrolytic palladium plating solution containing no specific pyridinium compound, either or both of the pinhole test results and the external appearance (color tone uniformity) of the palladium coating were inferior.

Moreover, in the heat resistance test, nickel was 10% or more in all, and all were judged as "defective goods".

Examples 11 to 18

Samples for evaluation similar to those used in Examples 1 to 8 were prepared, and gold films of 0.01 μm, 0.05 μm, and 0.1 μm were respectively formed thereon.

As a result of the heat resistance test, all of Examples 11 to 18 were judged to be good products because nickel was less than 10% and copper was less than 0.5% even in the case of gold coatings of any film thickness.

Comparative Examples 11 to 17

The same samples for evaluation were prepared corresponding to those used in Comparative Examples 1 to 7, and gold coatings of 0.01 μm, 0.05 μm, and 0.1 μm were respectively formed thereon.

As a result of the heat resistance test, all of Comparative Examples 11 to 17 were judged to be excellent products with less than 10% of nickel and less than 0.5% of copper in the case of 0.1 μm gold coating, but in the case of 0.01 μm and 0.05 μm gold coating In all, 10% or more of nickel or 0.5% or more of copper was detected, and all were judged as defective products.

In Comparative Examples 11 to 17, it was found that the gold coating on the palladium coating could not be sufficiently thin because the heat resistance of the palladium coating was inferior.

Example 21

<Evaluation of electrolytic palladium plating solution>

For the entire palladium plating solution, the dichlorotetraammine palladium solution was 1 g/L in terms of palladium, the same specific pyridinium compound (1-methyl-3-carboxypyridinium hydrochloride) as in Example 1 was 1000 ppm, and a conductive salt and buffer As a component combining citric acid was dissolved so as to be 100 g/L, the pH was adjusted to 6.5, and an electrolytic palladium plating solution was obtained.

Comparative Example 21

In Example 21, an electrolytic palladium plating solution was prepared in the same manner as in Example 21, except that the comparative compound (pyridine) of Comparative Example 1 was used instead of using a specific pyridinium compound.

<Formation method of palladium coating for testing (for evaluation)>

In the case of using the electroless palladium plating solution, the part of "the time of the electroless palladium plating treatment was adjusted in the range of 30 seconds to 3 minutes so that the film thickness was 0.03 μm." The current density of the electrolytic palladium plating treatment was adjusted to 0.5 A/dm ² for about 5 seconds so that . ), samples for evaluation were prepared in the same manner as in the method for forming a palladium film.

As can be seen from Table 4, when the electrolytic palladium plating solution of the present invention (Example 21) is used, in the pinhole test, a current larger than 100 μA does not always flow from the start of the test to “5 minutes after the start of the test”, In addition, no unevenness or non-uniformity was observed in the visual appearance of the palladium film, the color tone uniformity was good, and palladium precipitation abnormality was not recognized.

In addition, in the heat resistance test, nickel was less than 10% and copper was less than 0.5%, and it was judged as a “good product”.

On the other hand, in the electrolytic palladium plating solution containing no specific pyridinium compound (Comparative Example 21), the pinhole test result was inferior.

Moreover, in the heat resistance test, nickel was 10% or more and copper was 0.5% or more, and it was judged as a "defective product".

Examples 22 to 28, Comparative Examples 22 to 27

<Evaluation of electrolytic palladium plating solution>

Examples 22 to 28 and Comparative Examples 22 to 27, except that 1000 ppm of each of the specific pyridinium compound described in Examples 2 to 8 and Comparative Examples 2 to 7 shown in Table 1 or its comparative compound was used, respectively. In the same way as in 21, an electrolytic palladium plating solution was prepared and evaluated in the same way. However, Comparative Example 27 contained neither a specific pyridinium compound nor a comparative compound.

When the electrolytic palladium plating solution of the present invention (Examples 22 to 28) is used, in the pinhole test, a current larger than 100 μA does not always flow from the start of the test to “up to 5 minutes after the start of the test”, and furthermore, the palladium coating No unevenness or unevenness was observed in the visual appearance, the color tone uniformity was good, and palladium precipitation abnormality was not observed.

In addition, in the heat resistance test, nickel was less than 10% and copper was less than 0.5%, and all were judged as “good products”.

On the other hand, in the electrolytic palladium plating solution containing no specific pyridinium compound, either or both of the pinhole test results and the external appearance (color tone uniformity) of the palladium coating were inferior.

In addition, in the heat resistance test, all were judged as "defective products" when nickel was 10% or more or copper was 0.5% or more.

The palladium coating film obtained using the palladium plating solution of the present invention has excellent heat resistance, and because of its excellent heat resistance, the film thickness of the gold plating film formed on the palladium coating film can be reduced, and a significant cost reduction can be realized. In particular, It is widely used for palladium/gold plating, and is optimal for a process having a layer configuration of electroless nickel/palladium/gold, and is particularly preferably used in the field of plating electronic device members.

Claims (12)

A soluble palladium salt as a source of palladium, and
1-methyl-2-sulfopyridinium, 1-methyl-2-methoxysulfonylpyridinium, 1-methyl-2-aminopyridinium, 1-methyl-2-carboxypyridinium, 1-methyl-2-methoxypyridinium Toxycarbonylpyridinium, 1-methyl-2-cyanopyridinium;
1-ethyl-2-sulfopyridinium, 1-ethyl-2-methoxysulfonylpyridinium, 1-ethyl-2-aminopyridinium, 1-ethyl-2-carboxypyridinium, 1-ethyl-2-methoxypyridinium Toxycarbonylpyridinium, 1-ethyl-2-cyanopyridinium;
1-propyl-2-sulfopyridinium, 1-propyl-2-methoxysulfonylpyridinium, 1-propyl-2-aminopyridinium, 1-propyl-2-carboxypyridinium, 1-propyl-2-methyl Toxycarbonylpyridinium, 1-propyl-2-cyanopyridinium;
1-butyl-2-sulfopyridinium, 1-butyl-2-methoxysulfonylpyridinium, 1-butyl-2-aminopyridinium, 1-butyl-2-carboxypyridinium, 1-butyl-2-methyl Toxycarbonylpyridinium, 1-butyl-2-cyanopyridinium;
1-methyl-3-sulfopyridinium, 1-methyl-3-methoxysulfonylpyridinium, 1-methyl-3-aminopyridinium, 1-methyl-3-carboxypyridinium, 1-methyl-3-methoxypyridinium Toxycarbonylpyridinium, 1-methyl-3-cyanopyridinium;
1-ethyl-3-sulfopyridinium, 1-ethyl-3-methoxysulfonylpyridinium, 1-ethyl-3-aminopyridinium, 1-ethyl-3-carboxypyridinium, 1-ethyl-3-methyl Toxycarbonylpyridinium, 1-ethyl-3-cyanopyridinium;
1-propyl-3-sulfopyridinium, 1-propyl-3-methoxysulfonylpyridinium, 1-propyl-3-aminopyridinium, 1-propyl-3-carboxypyridinium, 1-propyl-3-methyl Toxycarbonylpyridinium, 1-propyl-3-cyanopyridinium;
1-butyl-3-sulfopyridinium, 1-butyl-3-methoxysulfonylpyridinium, 1-butyl-3-aminopyridinium, 1-butyl-3-carboxypyridinium, 1-butyl-3-methoxypyridinium Toxycarbonylpyridinium, 1-butyl-3-cyanopyridinium;
1-methyl-4-sulfopyridinium, 1-methyl-4-methoxysulfonylpyridinium, 1-methyl-4-aminopyridinium, 1-methyl-4-carboxypyridinium, 1-methyl-4-methoxypyridinium Toxycarbonylpyridinium, 1-methyl-4-cyanopyridinium;
1-ethyl-4-sulfopyridinium, 1-ethyl-4-methoxysulfonylpyridinium, 1-ethyl-4-aminopyridinium, 1-ethyl-4-carboxypyridinium, 1-ethyl-4-methyl Toxycarbonylpyridinium, 1-ethyl-4-cyanopyridinium;
1-propyl-4-sulfopyridinium, 1-propyl-4-methoxysulfonylpyridinium, 1-propyl-4-aminopyridinium, 1-propyl-4-carboxypyridinium, 1-propyl-4-methyl Toxycarbonylpyridinium, 1-propyl-4-cyanopyridinium;
1-butyl-4-sulfopyridinium, 1-butyl-4-methoxysulfonylpyridinium, 1-butyl-4-aminopyridinium, 1-butyl-4-carboxypyridinium, 1-butyl-4-methyl Toxycarbonylpyridinium, 1-butyl-4-cyanopyridinium;
An electroless palladium plating solution characterized by containing any one or two or more specific pyridinium compounds. According to claim 1,
The soluble palladium salt is palladium chloride, palladium sulfate, palladium acetate, palladium nitrate, dichlorotetraammine palladium, dinitrodiammine palladium, dichlorodiethylenediamine palladium, tetrakis (triphenylphosphine) palladium, dichlorobis (triphenyl An electroless palladium plating solution that is phosphine)palladium and/or bis(acetylacetonato)palladium. According to claim 1,
Additionally, an electroless palladium plating solution containing hypophosphorous acid, hypophosphite, phosphorous acid, phosphite, formic acid, formate and/or formaldehyde as a reducing agent. According to claim 3,
An electroless palladium plating solution wherein the reducing agent is hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, phosphorous acid, sodium phosphite, potassium phosphite, ammonium phosphite, formic acid, sodium formate, potassium formate, ammonium formate and/or formaldehyde. . An electroless palladium coating obtained by performing palladium plating on a coating of nickel, nickel alloy, copper or copper alloy using the electroless palladium plating solution according to any one of claims 1 to 4. An electronic component contact member characterized by having the electroless palladium coating according to claim 5. delete delete delete delete delete delete