WO2016035645A1

WO2016035645A1 - Palladium plating solution and palladium coating obtained using same

Info

Publication number: WO2016035645A1
Application number: PCT/JP2015/074073
Authority: WO
Inventors: 歓三清原; 和也柴田; 隆太大須賀; 中川　裕介; 祐弥大久保
Original assignee: 日本高純度化学株式会社
Priority date: 2014-09-04
Filing date: 2015-08-26
Publication date: 2016-03-10
Also published as: CN106661735B; CN106661735A; KR102482321B1; TW201614103A; KR20170045211A; JP6620103B2; JPWO2016035645A1

Abstract

　The present invention addresses the problem of providing a palladium plating solution in which occurrence of defective parts such as pin holes on a palladium coating is reduced, and in which heat resistance performance equivalent to that obtained conventionally can be obtained even when a gold plating coating formed on the palladium coating is made thinner. The problem was overcome by: a palladium plating solution containing a soluble palladium salt as a palladium source, and a specific pyridinium compound in which an alkyl group is bonded to a nitrogen atom at the 1-position and one to five of the 2- to 6-positions are substituted with one or more specific substituents selected from the group consisting of an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a sulfo group, an alkoxy sulfonyl group, an amino group, an alkylamino group, a dialkylamino group, and a cyano group; and a palladium coating obtained by performing palladium plating on a nickel, nickel alloy, copper, or copper alloy coating using the palladium plating solution.

Description

Palladium plating solution and palladium film obtained using the same

The present invention relates to a palladium plating solution having a specific composition, a palladium film obtained by using the palladium plating solution, and in particular, a palladium film on a nickel, nickel alloy, copper or copper alloy film.

Precious metal plating, particularly gold plating, is widely used because it has excellent corrosion resistance, mechanical characteristics, electrical characteristics, and the like. In particular, the gold plating applied on the nickel coating is widely used in the field of electronic and electrical parts because gold has excellent corrosion resistance, mechanical characteristics, electrical characteristics, etc., and nickel has excellent heat resistance as a base metal. It is used.

In recent years, in order to reduce production costs, the gold film has been thinned to reduce the cost, and the film physical properties such as heat resistance, which are insufficient due to the thinning of the gold film, can be reduced between the nickel and gold. A method of compensating by forming a film has been proposed and put into practical use.
However, there is a problem that defective parts such as pinholes are generated in the formed palladium film, and the film properties such as heat resistance as expected may 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. A palladium plating solution is disclosed, and when the plating film is thickened using the palladium plating solution of Patent Document 1, the plating film has a particularly good appearance and a plating film with few cracks can be obtained. The effect is disclosed.

Patent Document 2 discloses that an electroless palladium plating solution using a high molecular weight polyethyleneimine having a molecular weight of 300 to 100,000 and an unsaturated alkylamine is excellent in bath stability and is generated in the resulting palladium plating layer. It is disclosed that a uniform and dense film can be formed while reducing or preventing internal stress.

Patent Document 3 discloses a complexing agent selected from amines in combination with a palladium compound and a reducing agent selected from hypophosphorous acid and salts thereof, or a reducing agent selected from formic acid and formate. In addition, the plating solution composed of a bath stabilizer selected from inorganic sulfur compounds improves the plating injection time, improves the plating unevenness that is a concern of the electroless palladium-phosphorus plating solution, and elutes nickel during palladium plating. It is disclosed that the amount of the deposited palladium film is suppressed and the thermal diffusion between gold and palladium after the high melting point solder mounting, which is a problem of the electroless pure palladium film, is improved.

However, in these conventional technologies, it is not sufficient to maintain film physical properties having stable heat resistance performance while reducing the cost by reducing the amount of gold used by further thinning the gold and reducing the cost. Further improvements were needed.

Japanese Patent Laid-Open No. 62-124280 Japanese Patent Laid-Open No. 5-039580 JP 2010-261082 A

The present invention has been made in view of the above-described background art, and its problem is to reduce the occurrence of defective parts such as pinholes generated in the palladium film, and to reduce the thickness of the gold plating film formed on the palladium film. However, it is providing the palladium plating solution which can obtain the heat resistance equivalent to what was formed by the conventional gold plating film thickness.

As a result of intensive studies to solve the above-mentioned problems, the present inventor solved the above problems by forming a palladium film using a palladium plating solution containing a specific pyridinium compound as an essential component. , And found that it is possible to significantly reduce the production cost while maintaining the heat resistance required for palladium \ gold plating film while significantly reducing the gold film thickness. The invention has been completed.

That is, the present invention relates to a soluble palladium salt, as well as an alkyl group bonded to the 1st nitrogen atom, and 1 to 5 of the 2nd to 6th positions are an alkyl group, aryl group, carboxy group, alkoxycarbonyl group, Containing a specific pyridinium compound substituted with one or more specific substituents selected from the group consisting of a sulfo group, an alkoxysulfonyl group, an amino group, an alkylamino group, a dialkylamino group and a cyano group A palladium plating solution is provided.

The present invention also provides a palladium film obtained by performing palladium plating on a nickel, nickel alloy, copper or copper alloy film using the palladium plating solution. Is.

The present invention also provides a contact member for an electronic component characterized by having the palladium film.

The present invention also provides an electroless palladium plating solution and an electrolytic palladium plating solution characterized by comprising the above palladium plating solution.

According to the palladium plating solution of the present invention, it is possible to remarkably reduce defective plating portions such as pinholes generated in the palladium film, and greatly improve the heat resistance.
If a palladium film is formed using the palladium plating solution of the present invention, the film thickness of the palladium film is reduced from the film thickness of the conventional palladium film formed for the same purpose of reducing the film thickness of the gold plating film. Even if it is reduced, film performance such as excellent heat resistance can be maintained.

In addition, if a palladium film is formed using the palladium plating solution of the present invention, the thickness of the gold plating film formed on the palladium film can be significantly reduced without causing performance degradation such as heat resistance. As a result, further significant cost reduction can be realized.
That is, the film thickness of the palladium film can be reduced while maintaining the heat resistance required for “palladium plating film \ gold plating film”, and the film thickness of the gold film can be significantly reduced. Therefore, the cost can be greatly reduced.

Hereinafter, the present invention will be described, but the present invention is not limited to the following specific embodiments, and can be carried out by being arbitrarily modified within the scope of the technical idea.

<Specific pyridinium compounds>
The palladium plating solution of the present invention contains at least a soluble palladium salt as a palladium source, and further contains the “specific pyridinium compound” shown below.
The “specific pyridinium compound” means that an alkyl group is bonded to the 1st nitrogen atom, and 1 to 5 of the 2nd to 6th positions are an alkyl group, aryl group, carboxy group, alkoxycarbonyl group, sulfo group, alkoxy group. A pyridinium compound substituted with one or more specific substituents selected from the group consisting of a sulfonyl group, an amino group, an alkylamino group, a dialkylamino group and a cyano group.

In the “specific pyridinium compound”, an alkyl group (—R ¹ ) is bonded to a nitrogen atom, so that the nitrogen atom has a positive charge and is a pyridinium compound. In the present invention, hydrogen atoms are excluded from “bonding atoms that are bonded to nitrogen atoms to form pyridinium compounds”. When the bonding atom bonded to the nitrogen atom is a hydrogen atom, it is difficult to obtain the effect of the present invention described above.

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. From the viewpoints of performance and availability, 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 carbon atom is preferable. Or two is more preferable.
When alkyl groups with too many carbon atoms are bonded, the pinhole of palladium film increases, the deposition rate of palladium decreases, the appearance of palladium deteriorates, or it is difficult to obtain There is.

In addition, when the group bonded to the nitrogen atom is not an alkyl group (—R ¹ ) but a hydrogen atom, the above-described effects of the present invention are not exhibited, and in particular, the palladium concentration in the palladium plating solution is When the concentration is high, appearance defects may occur when plating is performed at a high temperature.

The “specific pyridinium compound” in the present invention is essential to have the above chemical structure in the palladium plating solution, and may be changed to one having the above chemical structure in the palladium plating solution. There is no particular limitation on the chemical structure of the substance to be added at the time of preparing the palladium plating solution, but it is preferable to add (prepare using) one 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. Specifically, for example, sulfate ion, nitrate ion, chlorine ion, bromine ion, iodine ion, etc. Can be mentioned. Anion exchange (salt exchange) may occur in the palladium plating solution. Therefore, anions such as soluble palladium salt, reducing agent, conductive salt, buffer salt, etc. added (added) at the time of preparation are used. Examples include those obtained by salt exchange with ions. The above-mentioned compositions in the palladium plating solution are included in the scope of the present invention.
However, it is preferable to add (prepare using) an anion having the above anions (sulfate ion, nitrate ion, chlorine ion, bromine ion, iodine ion, etc.).

In the “specific pyridinium compound” in the present invention, any one of 1 to 5 positions out of the 2nd to 6th positions is an alkyl group, aryl group, carboxy group, alkoxycarbonyl group, sulfo group, alkoxysulfonyl group. It is essential that it is substituted with one or more substituents selected from the group consisting of a group, an amino group, an alkylamino group, a dialkylamino group and a cyano group. In the present invention, such a substituent is referred to as a “specific substituent”.
That is, the “specific pyridinium compound” in the present invention is a 6-membered pyridine ring (pyridinium ring), and since the nitrogen atom is at position 1, it is bonded to 5 carbon atoms constituting the ring other than the nitrogen atom. Any one of 1 to 5 hydrogen atoms is substituted with the above-mentioned specific substituent which may be different.

The alkyl group as the specific substituent may be either a linear alkyl group or a branched alkyl group, and may further have a substituent other than an alkyl group, and the number of carbon atoms is not particularly limited, In order to further exert the effect, an alkyl group having 1 to 6 carbon atoms is preferable, an alkyl group having 1 to 5 carbon atoms is more preferable, and an alkyl group having 1 to 4 carbon atoms, that is, a methyl group or 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 palladium deposition rate may be reduced or the appearance of the palladium film may be deteriorated.

The aryl group as the 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. It is done.

The carboxy group as the specific substituent is a group represented by “—COOH”, and the “alkoxycarbonyl group” is a group represented by “—COOR ¹¹ ” and is a residue of a carboxylic acid ester. In the above formula, R ¹¹ represents an alkyl group or an aryl group, and preferable one is the same as the alkyl group or aryl group as the specific substituent, and particularly preferably a methyl group.

The sulfo group as the specific substituent is a group represented by “—SO ₃ H” and is also referred to as a sulfonic acid group.
The alkoxysulfonyl group as the specific substituent is a group represented by the following general formula (a) and is a sulfonate residue.

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

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

The amino group as the specific substituent is a group represented by “—NH ₂ ”, the alkylamino group is a group represented by “—NHR ¹³ ”, and the dialkylamino group is 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 that may be different from each other, and preferable ones are the same as the alkyl group and aryl group as the specific substituent, A methyl group is preferred.

The cyano group as the specific substituent is a group represented by “—CN”.

The specific substituent may have a substituent in the specific substituent as long as the effects of the invention of the present invention are not impaired. Although it is not necessarily limited from the viewpoints of easiness and the like, it is particularly preferable that the specific substituent does not further have a substituent.

The 6-membered pyridine ring (pyridinium ring) may have a substituent other than the specific substituent at the 2-position to the 6-position, as long as the effects of the present invention are not impaired. From the viewpoints of easily exerting the effects of the invention, good plating performance, availability, etc., the “substituents other than the specific substituents” are not particularly limited, but are particularly preferably not included.

Among the specific substituents, the 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. It is particularly preferable from the viewpoints of easy performance, good plating performance, availability, and the like.

Furthermore, the palladium plating solution of the present invention contains a pyridinium compound in which one to three of the 2-position to 4-position of the pyridinium ring are substituted with one or more of the above-mentioned specific substituents. It is preferable in that the effect is more suitably exhibited.
That is, in other words, a pyridinium compound in which any one of the 2-position, 3-position, or 4-position of the pyridinium ring is substituted with one or more specific substituents. It is preferable to contain.
More preferably, one or two (particularly preferably one) of the 2-position to the 4-position of the pyridinium ring is substituted with one or two (particularly preferably one) of the specific substituents. It contains a pyridinium compound.
The pyridinium ring may have a substituent other than the specific substituent, but preferably has no substituent.

Particularly preferred pyridinium compounds are those represented by the following general formula (1).

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

The alkyl group (R ¹ ) bonded to the nitrogen atom may be either a linear alkyl group or a branched alkyl group, and the carbon number is not particularly limited, but an alkyl group having 1 to 6 carbon atoms is preferable, and the carbon number is 1 More preferred are ˜5 alkyl groups, and particularly preferred are alkyl groups having 1 to 4 carbon atoms, ie, methyl group, ethyl group, propyl group or butyl group.
If an alkyl group having too many carbon atoms is bonded, the effect of the present invention described above will not be exhibited, the pinhole of the palladium film will increase, the deposition rate of palladium will decrease, and the appearance of palladium will be poor. Or it may be difficult to obtain.
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, particularly when the palladium concentration in the palladium plating solution is high, An appearance defect may occur when plating is performed at a high temperature.

R ² , R ³ and R ⁴ may be different from each other, hydrogen atom, alkyl group, aryl group, carboxy group, alkoxycarbonyl group, sulfo group, alkoxysulfonyl group, amino group, alkylamino group, dialkylamino group Or a cyano group, except that R ² , R ³ and R ⁴ are all hydrogen atoms.
As R ² , R ³ and R ⁴ , the “specific substituent” described above as “more preferable”, “particularly preferable” and the like is more (particularly) more preferable in that the above-described effects are more suitably exhibited.

The anion (counter ion) of the general formula (1) is not particularly limited, but specifically, for example, preferable examples include those described above such as sulfate ion, nitrate ion, chlorine ion, bromine ion, iodine ion and the like. Is mentioned.
The anion of the general formula (1) specifies the form present in the palladium plating solution of the present invention, and is added (added) to the soluble palladium salt, reducing agent, conductive salt, buffer, which is blended at the time of preparation. Those obtained by salt exchange with anions such as agent salts are also preferred.
However, sulfate ions, nitrate ions, chlorine ions, bromine ions, iodine ions and the like are preferable as the anions (counter ions) of the raw material to be dissolved (formulated and added) in the preparation of the palladium plating solution of the present invention.
The above description of the specific pyridinium compound specifies the form present in the palladium plating solution of the present invention. However, when preparing the palladium plating solution of the present invention, it is preferable to use the specific pyridinium compound as a raw material to be dissolved.

By including a specific pyridinium compound, a palladium film without a pinhole can be realized. In addition, by containing a specific pyridinium compound, it has high heat resistance that is dramatically superior to that of the conventional palladium film, so that the film thickness of the conventional palladium film can be greatly reduced. The gold plating film to be formed can be greatly reduced in thickness, and the cost can be greatly reduced.

In the “pinhole test”, when the palladium plating solution of the present invention capable of realizing a palladium film having no pinhole with “a 0.03 μm-thickness palladium film” is used, even if the palladium film is thinner than that, If the palladium film is thicker than that, a pinhole-free film is obtained and the reliability is further increased.
In addition, gold films are generally difficult to make pinholes, and palladium films are generally easy to make pinholes. Therefore, when the palladium plating solution of the present invention which is difficult to form pinholes is used, it is not necessary to cover the pinholes of the palladium film with a gold film, the film thickness of the gold film can be reduced, and the cost can be reduced.

In the present invention, the “pinhole test” will be described later, but during the period from “test start” to “5 minutes after the start of test”, a palladium plating solution that gives a palladium film with a small energization current is considered to be excellent. An excellent palladium plating solution is a palladium plating solution that always provides film properties such that the energization current is 100 μA or less.

In the present invention, "heat resistance" is defined as the value evaluated by the method described in the examples and evaluated as such.
“Heat resistance” is a performance essential for a contact member of an electronic component. The contact member of an electronic component must be joined to another member by soldering or wire bonding, and the joining process always includes a heating process of 100 ° C. to 300 ° C. This heating process is also performed once. It often exists multiple times.
This heating process oxidizes metals such as copper, copper alloy, nickel, nickel alloy, etc., causing defects such as poor solder joints, increased contact resistance, and poor wire bonding joints. Therefore, it is important to form a surface protective layer by performing noble metal plating such as gold plating or palladium plating for the purpose of preventing the oxidation of copper, nickel and the like.

However, even if a noble metal plating film such as a gold plating film or a palladium plating film is formed, if there is a pinhole in the noble metal plating film, copper, nickel, etc., which are the base of the noble metal plating film, are not treated by the heating process. The effect of diffusing from the pinhole to the outermost surface and being oxidized and precious metal plating film may be lost.
Therefore, the presence of pinholes in the noble metal plating film is an indicator of whether or not the contact member of the electronic component has heat resistance. A small number of 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”.

As preferable specific examples of the specific pyridinium compound, for example,
1-methyl-2-methylpyridinium, 1-methyl-2-ethylpyridinium, 1-methyl-2-butylpyridinium, 1-methyl-2-sulfopyridinium, 1-methyl-2-methoxysulfonylpyridinium, 1-methyl- 2-position-substituted methylpyridinium such as 2-aminopyridinium, 1-methyl-2-carboxypyridinium, 1-methyl-2-methoxycarbonylpyridinium, 1-methyl-2-phenylpyridinium, 1-methyl-2-cyanopyridinium;
1-ethyl-2-methylpyridinium, 1-ethyl-2-ethylpyridinium, 1-ethyl-2-butylpyridinium, 1-ethyl-2-sulfopyridinium, 1-ethyl-2-methoxysulfonylpyridinium, 1-ethyl- 2-substituted pyridinium such as 2-aminopyridinium, 1-ethyl-2-carboxypyridinium, 1-ethyl-2-methoxycarbonylpyridinium, 1-ethyl-2-phenylpyridinium, 1-ethyl-2-cyanopyridinium;
1-propyl-2-methylpyridinium, 1-propyl-2-ethylpyridinium, 1-propyl-2-butylpyridinium, 1-propyl-2-sulfopyridinium, 1-propyl-2-methoxysulfonylpyridinium, 1-propyl- 2-substituted propylpyridinium such as 2-aminopyridinium, 1-propyl-2-carboxypyridinium, 1-propyl-2-methoxycarbonylpyridinium, 1-propyl-2-phenylpyridinium, 1-propyl-2-cyanopyridinium;
1-butyl-2-methylpyridinium, 1-butyl-2-ethylpyridinium, 1-butyl-2-butylpyridinium, 1-butyl-2-sulfopyridinium, 1-butyl-2-methoxysulfonylpyridinium, 1-butyl- 2-position-substituted butylpyridinium such as 2-aminopyridinium, 1-butyl-2-carboxypyridinium, 1-butyl-2-methoxycarbonylpyridinium, 1-butyl-2-phenylpyridinium, 1-butyl-2-cyanopyridinium;
1-methyl-3-methylpyridinium, 1-methyl-3-ethylpyridinium, 1-methyl-3-butylpyridinium, 1-methyl-3-sulfopyridinium, 1-methyl-3-methoxysulfonylpyridinium, 1-methyl- 3-substituted pyridinium such as 3-aminopyridinium, 1-methyl-3-carboxypyridinium, 1-methyl-3-methoxycarbonylpyridinium, 1-methyl-3-phenylpyridinium, 1-methyl-3-cyanopyridinium;
1-ethyl-3-methylpyridinium, 1-ethyl-3-ethylpyridinium, 1-ethyl-3-butylpyridinium, 1-ethyl-3-sulfopyridinium, 1-ethyl-3-methoxysulfonylpyridinium, 1-ethyl- 3-position-substituted ethylpyridinium such as 3-aminopyridinium, 1-ethyl-3-carboxypyridinium, 1-ethyl-3-methoxycarbonylpyridinium, 1-ethyl-3-phenylpyridinium, 1-ethyl-3-cyanopyridinium;
1-propyl-3-methylpyridinium, 1-propyl-3-ethylpyridinium, 1-propyl-3-butylpyridinium, 1-propyl-3-sulfopyridinium, 1-propyl-3-methoxysulfonylpyridinium, 1-propyl- 3-substituted propylpyridinium such as 3-aminopyridinium, 1-propyl-3-carboxypyridinium, 1-propyl-3-methoxycarbonylpyridinium, 1-propyl-3-phenylpyridinium, 1-propyl-3-cyanopyridinium;
1-butyl-3-methylpyridinium, 1-butyl-3-ethylpyridinium, 1-butyl-3-butylpyridinium, 1-butyl-3-sulfopyridinium, 1-butyl-3-methoxysulfonylpyridinium, 1-butyl- 3-substituted butylpyridinium such as 3-aminopyridinium, 1-butyl-3-carboxypyridinium, 1-butyl-3-methoxycarbonylpyridinium, 1-butyl-3-phenylpyridinium, 1-butyl-3-cyanopyridinium;
1-methyl-4-methylpyridinium, 1-methyl-4-ethylpyridinium, 1-methyl-4-butylpyridinium, 1-methyl-4-sulfopyridinium, 1-methyl-4-methoxysulfonylpyridinium, 1-methyl- 4-methylpyridinium substituted in 4-position such as 4-aminopyridinium, 1-methyl-4-carboxypyridinium, 1-methyl-4-methoxycarbonylpyridinium, 1-methyl-4-phenylpyridinium, 1-methyl-4-cyanopyridinium;
1-ethyl-4-methylpyridinium, 1-ethyl-4-ethylpyridinium, 1-ethyl-4-butylpyridinium, 1-ethyl-4-sulfopyridinium, 1-ethyl-4-methoxysulfonylpyridinium, 1-ethyl- 4-substituted pyridinium such as 4-aminopyridinium, 1-ethyl-4-carboxypyridinium, 1-ethyl-4-methoxycarbonylpyridinium, 1-ethyl-4-phenylpyridinium, 1-ethyl-4-cyanopyridinium;
1-propyl-4-methylpyridinium, 1-propyl-4-ethylpyridinium, 1-propyl-4-butylpyridinium, 1-propyl-4-sulfopyridinium, 1-propyl-4-methoxysulfonylpyridinium, 1-propyl- 4-position-substituted propylpyridinium such as 4-aminopyridinium, 1-propyl-4-carboxypyridinium, 1-propyl-4-methoxycarbonylpyridinium, 1-propyl-4-phenylpyridinium, 1-propyl-4-cyanopyridinium;
1-butyl-4-methylpyridinium, 1-butyl-4-ethylpyridinium, 1-butyl-4-butylpyridinium, 1-butyl-4-sulfopyridinium, 1-butyl-4-methoxysulfonylpyridinium, 1-butyl- 4-position-substituted butylpyridinium such as 4-aminopyridinium, 1-butyl-4-carboxypyridinium, 1-butyl-4-methoxycarbonylpyridinium, 1-butyl-4-phenylpyridinium, 1-butyl-4-cyanopyridinium;
Etc.

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

Among these, from the above points, as a particularly preferred specific example,
1-methyl-2-methylpyridinium, 1-methyl-2-ethylpyridinium, 1-methyl-2-butylpyridinium, 1-methyl-2-sulfopyridinium, 1-methyl-2-methoxysulfonylpyridinium, 1-methyl- 2-methylpyridinium substituted at 2-position such as 2-aminopyridinium, 1-methyl-2-carboxypyridinium;
1-ethyl-2-methylpyridinium, 1-ethyl-2-ethylpyridinium, 1-ethyl-2-butylpyridinium, 1-ethyl-2-sulfopyridinium, 1-ethyl-2-methoxysulfonylpyridinium, 1-ethyl- 2-position-substituted ethylpyridinium such as 2-aminopyridinium, 1-ethyl-2-carboxylpyridinium;
1-methyl-3-methylpyridinium, 1-methyl-3-ethylpyridinium, 1-methyl-3-butylpyridinium, 1-methyl-3-sulfopyridinium, 1-methyl-3-methoxysulfonylpyridinium, 1-methyl- 3-positioned methylpyridinium such as 3-aminopyridinium, 1-methyl-3-carboxylpyridinium;
1-ethyl-3-methylpyridinium, 1-ethyl-3-ethylpyridinium, 1-ethyl-3-butylpyridinium, 1-ethyl-3-sulfopyridinium, 1-ethyl-3-methoxysulfonylpyridinium, 1-ethyl- 3-substituted pyridinium such as 3-aminopyridinium, 1-ethyl-3-carboxylpyridinium;
1-methyl-4-methylpyridinium, 1-methyl-4-ethylpyridinium, 1-methyl-4-butylpyridinium, 1-methyl-4-sulfopyridinium, 1-methyl-4-methoxysulfonylpyridinium, 1-methyl- 4-methylpyridinium substituted at the 4-position, such as 4-aminopyridinium, 1-methyl-4-carboxylpyridinium;
1-ethyl-4-methylpyridinium, 1-ethyl-4-ethylpyridinium, 1-ethyl-4-butylpyridinium, 1-ethyl-4-sulfopyridinium, 1-ethyl-4-methoxysulfonylpyridinium, 1-ethyl- 4-substituted pyridinium such as 4-aminopyridinium and 1-ethyl-4-carboxylpyridinium;
Etc.

These specific pyridinium compounds are particularly preferable from the viewpoints of easily exhibiting the effects of the present invention described above, and further, from the viewpoint of good palladium plating performance, ease of dissolution in water, availability, low cost, and the like. It is mentioned as a thing.

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, and particularly preferably 20 ppm to 10000 ppm by mass with respect to the total palladium plating solution. Preferably, it is 50 ppm to 5000 ppm, and most preferably 100 ppm to 3000 ppm. In addition, when 2 or more types of said specific pyridinium compounds are contained, the said numerical value shows those 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, the number of pinholes (density) generated in the palladium film increases, and the appearance of the palladium film is poor. May occur. On the other hand, when there is too much content, the further increase of the said effect of this invention cannot be anticipated, and it may become uneconomical.

The above description about the specific pyridinium compound specifies the form existing in the palladium plating solution of the present invention, but the above-mentioned specific as a raw material to be dissolved in the preparation of the palladium plating solution of the present invention. It is preferable to use a pyridinium compound.

<Soluble palladium salt>
It is essential for the palladium plating solution of the present invention to contain a soluble palladium salt. The soluble palladium salt is used as a palladium source for the palladium plating solution of the present invention. The soluble palladium salt is not limited to one type of use, and two or more types can be used in combination. The meaning of “soluble” means soluble in water.

The soluble palladium salt is not particularly limited and known ones can be used. Specific examples include palladium chloride, palladium sulfate, palladium acetate, palladium nitrate, palladium oxide, dichlorotetraammine palladium, dinitrodiammine palladium, dichloromethane. Diethylenediamine palladium, tetrakis (triphenylphosphine) palladium, dichlorobis (triphenylphosphine) palladium and / or bis (acetylacetonato) palladium are preferable because of their solubility in water and availability.

Among them, dichlorotetraamminepalladium or dinitrodiamminepalladium is more preferable from the viewpoint that it is not time-consuming to replenish the palladium salt by being supplied as an aqueous solution. Further, from the same viewpoint, dichlorotetraammine palladium is particularly preferable.

The content of the palladium salt in the palladium plating solution of the present invention is not particularly limited, and is generally 0.001 g / L to 50 g / L, preferably 0.005 g / L as metal palladium with respect to the whole palladium plating solution. -30 g / L, particularly preferably 0.01 g / L to 20 g / L.
If the content of the soluble palladium salt in the palladium plating solution is too small, it may be difficult to form a palladium film having a normal and uniform color tone. That is, there is a case where an abnormal precipitation of palladium is observed when the color and attached color of the palladium film are visually observed.
On the other hand, if the palladium salt content in the palladium plating solution is too high, there is no particular problem with the performance of the palladium plating solution, but the palladium salt is very expensive and is stored in the palladium plating solution. Doing so can be uneconomical.

The above description about the palladium salt specifies the form present in the palladium plating solution of the present invention. As a raw material to be dissolved in the preparation of the palladium plating solution of the present invention, the above palladium salt is used. It is preferable to use it.

<Reducing agent>
The palladium plating solution of the present invention preferably further contains a reducing agent in addition to the soluble palladium salt and the specific pyridinium compound. As the reducing agent, hypophosphorous acid, hypophosphite, phosphorous acid, phosphite, formic acid, formate, formaldehyde and the like are particularly preferable.
Said reducing agent is not limited to 1 type of use, It can use 2 or more types together.

Specific examples of the reducing agent include hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, phosphorous acid, sodium phosphite, potassium phosphite, Ammonium phosphite, formic acid, sodium formate, potassium formate, ammonium formate, formaldehyde, etc. have good palladium plating performance, ease of dissolution in water, easy handling as chemicals, easy availability, low cost From the viewpoint of the above, it is preferable.

The content of the reducing agent in the palladium plating solution of the present invention is not particularly limited, but is preferably from 1 ppm to 100,000 ppm, more preferably from 10 ppm to 60000 ppm, particularly preferably from 50 ppm to 30000 ppm, based on the whole palladium plating solution. More preferably, it is 100 ppm to 10,000 ppm. In addition, when using 2 or more types of reducing agents, the said numerical value shows those total content.
If the content is too small, it may be difficult to form a palladium film having a normal and uniform color tone. That is, there is a case where an abnormal precipitation of palladium is observed when the color and attached color of the palladium film are visually observed. On the other hand, if the content is too high, the palladium plating bath becomes unstable, and expensive palladium is abnormally deposited in the storage container, which requires extra costs for palladium recovery, or the color tone of the palladium film is poor. It may cause.

<Other additives>
In addition to the above components, the palladium plating solution of the present invention includes, as necessary, a buffer for keeping the pH of the palladium plating solution constant, a conductive salt for ensuring the conductivity of the palladium plating solution, and a palladium plating solution. Appropriate metal sequestering agent to remove the effects of impurities contained in impurities, surfactants to improve the foaming of the palladium plating solution, brighteners to smooth the palladium film, etc. It can be used by declaring it.

The buffer contained in the palladium plating solution of the present invention as needed is not particularly limited as long as it is a known buffer, but preferred are inorganic acids such as boric acid and phosphoric acid; citric acid and tartaric acid. And oxycarboxylic acids such as malic acid; These can be used alone or in combination of two or more.

The content of the buffer 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 whole palladium plating solution.
If the content of the buffering agent in the palladium plating solution is too small, the buffering effect may be difficult to be exhibited. On the other hand, if the content is too large, the buffering effect may not be increased and it may be uneconomical.

The conductive salt contained as needed in the palladium plating solution of the present invention is not particularly limited as long as it is a known conductive salt, but preferred are inorganic acid salts such as sulfates, nitrates and phosphates; And carboxylic acids such as oxalic acid, succinic acid, glutaric acid, malonic acid, citric acid, tartaric acid and malic acid. These may be used alone or in combination of two or more.

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 whole palladium plating solution.
If the content of the conductive salt in the palladium plating solution is too small, the conductive effect may be difficult to be exhibited. On the other hand, if the content is too high, the conductive effect may not be increased, which may be uneconomical.
It is also possible to share the same component as the buffer.

The sequestering agent contained as needed in the palladium plating solution of the present invention is not particularly limited as long as it is a well-known sequestering agent, but as preferred, iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, etc. Aminocarboxylic acid-based chelating agents; phosphonic acid-based chelating agents such as hydroxyethylidenediphosphonic acid, nitrilomethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid; and the like. These may be used alone or in combination of two or more.

The content of the 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 based on the whole palladium plating solution. / L.
If the content of the sequestering agent in the palladium plating solution is too small, the effect of removing the influence of the impurity metal may be difficult to be exhibited, while if too much, the effect of removing the influence of the impurity metal may be increased. It may not be seen and it may be uneconomical.

The surfactant contained as needed in the palladium plating solution of the present invention is not particularly limited as long as it is a known surfactant, and is a nonionic surfactant, an anionic surfactant, an amphoteric surfactant or Cationic surfactants are used. These may be used alone or in combination of two or more.

Preferred nonionic surfactants include ether type nonionic surfactants such as noniphenol polyalkoxylate, α-naphthol polyalkoxylate, dibutyl-β-naphthol polyalkoxylate, and styrenated phenol polyalkoxylate; And amine type nonionic surfactants such as octylamine polyalkoxylate, hexynylamine polyalkoxylate, and linoleylamine polyalkoxylate.
Preferred 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 alkylphenyl ether sulfates; Salt; and the like.

Preferred examples of the amphoteric surfactant include 2-undecyl-1-carboxymethyl-1-hydroxyethylimidazolium, N-stearyl-N, N-carboxymethylbetaine, lauryldimethylamine oxide, and the like.
Preferred examples of the cationic surfactant 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. Nonionic surfactants or amphoteric surfactants are preferred.

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 whole palladium plating solution. The amount is not limited.

The brightener contained as needed in the palladium plating solution of the present invention is not particularly limited as long as it is a well-known brightener. However, it cannot be a specific pyridinium compound in the present invention during palladium plating. And the like ". These may be used alone or in combination of two or more.
Examples of the amine compound having a pyridine skeleton include 2-aminopyridine, 3-aminopyridine, 4-aminopyridine and the like.

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 whole palladium plating solution, but it is sufficient that the desired performance is exhibited, and particularly the content. It is not intended to limit.

<Physical properties of palladium plating solution>
In the palladium plating solution of the present invention, as a physical property of the palladium plating solution, a substrate plated by using a palladium plating solution so that the film thickness of the palladium film is 0.03 μm is immersed in a 5% by mass sulfuric acid aqueous solution. When the pinhole test is performed at a constant voltage of 300 mV, it is a palladium plating solution that gives film properties such that the energization current is 100 μA or less during the entire period from the start of the test to 5 minutes after the start of the test.
The palladium plating solution having such physical properties is a novel palladium plating solution realized for the first time with the palladium plating solution having the above-described composition.

The palladium plating solution of the present invention is a 5% by mass sulfuric acid copper substrate plated on a copper plate to have an electroless nickel plating film thickness of 5 μm and a palladium film thickness of 0.03 μm. When immersed in a solution and subjected to a pinhole test at a voltage of 300 mV, it preferably has a physical property such that a current does not flow more than 100 μA for 5 minutes from the start of the test.

The “pinhole test” of the present invention is a copper plate material that has been electrolessly nickel-plated and then palladium-plated by a conventional method, removing copper in a circular shape with a diameter of 10 mm to form an anode, and copper A test in which a material is immersed in a 5% by mass sulfuric acid solution as a cathode, a voltage of 300 mV is continuously applied, and a current value to be energized is observed.
When a defective part such as a pinhole is generated in the palladium film, nickel ions and copper ions are dissolved from the pinhole of the palladium film as the anode, and the flowing current value shows a large value. In addition, the current starts to flow relatively quickly as compared with an evaluation sample in which a defective portion such as a pinhole is not formed on the palladium film.

The limitation of the physical properties described above limits the physical properties of the palladium plating solution, and does not limit the method of using the palladium plating solution. The palladium film actually formed with such a palladium plating solution does not need to be 0.03 μm. For example, a palladium film having a thickness of less than 0.03 μm may be formed using the palladium plating solution of the present invention. However, a palladium film thicker than 0.03 μm may be formed.

When the pinhole test of the present invention is carried out, when the palladium plating film thickness is 0.05 μm or less (thus, when the palladium film thickness is 0.03 μm or less), from the start of the test to “5 minutes after the start of the test” In the past, there was no palladium plating solution having such a physical property that current does not flow more than 100 μA.

<Method for producing palladium plating solution>
The method for producing the palladium plating solution of the present invention is not particularly limited, and known methods including the blending order of each component and the like are used.

<Palladium film>
The palladium film obtained by performing palladium plating using the palladium plating solution of the present invention exhibits the effects described above.
The concentration of palladium in the palladium film of the present invention (palladium purity) is not particularly limited, but is preferably 90% by mass or more, and 95.0% to 99.99% by mass with respect to the entire “palladium film”. 9% by mass is particularly preferred.

<Palladium plating conditions>
The plating conditions of the palladium plating solution of the present invention described above are not particularly limited, but the temperature conditions are preferably 20 ° C. to 90 ° C., particularly preferably 30 ° C. to 70 ° C. The pH of the plating solution is preferably pH 2.0 to 9.0, particularly preferably 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. 0.005 μm to 0.5 μm, more preferably 0.01 μm to 0.3 μm.

The film thickness of a palladium plating film produced using a conventional palladium plating solution is usually 0.01 μm to 0.5 μm in the case of a connector, although it depends on the application. The palladium plating film produced using the palladium plating solution of the present invention can obtain almost the same 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 nickel, nickel alloy, copper, or copper alloy film using the palladium plating solution of the present invention is preferable in order to achieve the above-described effects. Among these, a nickel or nickel alloy film is more preferable from the viewpoints of heat resistance and the possibility that it may be adversely affected when mixed with palladium plating, and a nickel film is particularly preferable.

<Use of palladium plating solution and overall plating film laminated>
The palladium plating solution of the present invention is not particularly limited, but is more preferably used for manufacturing a contact member for an electronic component.
Therefore, when performing palladium plating using the palladium plating solution of the present invention, it is more preferable to form a nickel plating film as the base plating treatment.
The nickel plating solution at this time is not particularly limited, but an electroless nickel solution generally used in practice is preferred, and an electroless nickel-phosphorus solution is particularly preferred. The method of using the nickel plating solution is not particularly limited and is used according to a conventional method.

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

The palladium plating solution of the present invention is preferably used for forming a base palladium film for forming a gold film by performing gold plating on the palladium film.
The 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 coating mode of the present invention is a mode in which a gold coating is applied on a palladium coating, and a particularly preferable mode is a mode in which a palladium coating is applied on a nickel coating and a gold coating is applied thereon. It is.

The film thickness of a gold film formed on a palladium plating film produced using a conventional palladium plating solution is usually 0.05 μm to 0.2 μm in the case of a connector, although it depends on the application. The film thickness of the gold film formed on the palladium plating film produced using the palladium plating solution of the present invention is almost equal to the pinhole even when the film thickness is reduced to the conventional range of 20% to 60%. Test and heat resistance results are obtained.

The palladium plating solution of the present invention can be used as an electroless palladium plating solution or an electrolytic palladium plating solution. That is, the present invention is an electroless palladium plating solution made of the palladium plating solution and an electrolytic palladium plating solution made of the palladium plating solution.
The above-mentioned “specific pyridinium compound” exerts the above-described effect regardless of whether it is contained in the electroless palladium plating solution or in the electrolytic palladium plating solution.

Among the above-mentioned soluble palladium salts, specific pyridinium compounds, buffers, conductive salts, sequestering agents, surfactants, reducing agents and brighteners, electroless palladium plating solutions are soluble palladium salts, specific pyridinium compounds and reducing agents. An agent is an essential component, and a buffering agent, a sequestering agent, a surfactant and / or a brightener are included as preferred components.
Further, the electrolytic palladium plating solution contains a soluble palladium salt, a specific pyridinium compound and a conductive salt as essential components, and a buffer, a metal ion sequestering agent, a surfactant and / or a brightening agent as preferred components.
The content of each component of the electroless palladium plating solution and the electrolytic palladium plating solution is preferably in the above range (more preferably, particularly preferable).

In the case of electroless palladium plating, there is no particular limitation as long as it is carried out according to a conventional method, but the liquid temperature is preferably 30 ° C to 90 ° C, particularly preferably 40 ° C to 80 ° C. The time is appropriately adjusted so that the palladium film thickness is obtained.

In the case of electrolytic palladium plating, it may be carried out in accordance with a conventional method, but there is no particular limitation, but the liquid temperature is preferably 30 ° C. to 90 ° C., particularly preferably 40 ° C. to 80 ° C. Also, preferably the current density of ^{0.1A / dm 2 ~ 100A / dm} 2, 0.5A / dm 2 ~ 50A / dm 2 are particularly preferred. The time is appropriately adjusted so that the palladium film thickness is obtained.

<Action and principle>
Although the action / principle that the palladium plating solution of the present invention can form a palladium film with extremely few defective parts such as pinholes is not clear, the following can be considered. However, the present invention is not limited to the range where the following actions and principles are established.

The specific pyridinium compound that is an essential component of the palladium plating solution of the present invention is considered to have an effect as a kind of crystal modifier. When a palladium film is about to be formed by a plating reaction, it is considered that a very rough film grows when the palladium film grows without any control. A rough film means a film having irregularities.
It is considered that the “specific pyridinium compound” is selectively adsorbed on the convex portions and inhibits the growth. By inhibiting plating growth at the convex part where plating growth was fast, the plating reaction to the concave part was promoted and the concave part was filled, and as a result, a plating film without unevenness could be formed. Conceivable. The plating film having no concave portion is a palladium film in which the base metal is uniformly coated with a palladium film and pinholes are extremely small.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples unless it exceeds the gist.
Moreover, the numerical value of the density | concentration in the composition of a palladium plating solution is a numerical value of the density | concentration calculated | required from the mass which does not put crystallization water, when the component contains crystallization water.
“%” Regarding the content indicates “mass%” unless otherwise specified, and “ppm” indicates “mass ppm”. In the heat resistance evaluation method, “%” of nickel and copper indicates “atm% (atomic reference concentration)”.

Examples 1-8, Comparative Examples 1-7
<Evaluation of electroless palladium plating solution>
Dichlorotetraammine palladium solution is 1 g / L in terms of palladium with respect to the entire palladium plating solution, each specific pyridinium compound or its comparative compound shown in Table 1 is 1000 ppm, and formic acid is used as a reducing agent. Was dissolved at 1000 ppm, and citric acid as a component serving as both a conductive salt and a buffer was adjusted to 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 “comparative compounds”, 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 prepared in the same manner was evaluated without containing the “specific pyridinium compound” and the “comparative compound”.

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 the following evaluation was performed.

<Method for Forming Palladium Film for Testing (Evaluation)>
Using the palladium plating solution prepared in each example and each comparative example, a palladium film was formed on the electroless nickel plating film 5.0 μm on a 10 mm × 10 mm copper plate in the step shown in Table 2, and the film thickness thereof Was adjusted so that the electroless palladium plating time was 30 seconds to 3 minutes.

In addition, the electroless nickel plating film was plated according to an ordinary method using “electroless nickel plating solution ICP Nicolon GM” (trade name) (manufactured by Okuno Pharmaceutical Co., Ltd.) to form a film thickness of 5.0 μm. .

<Pinhole test method>
As described above, a palladium film having a thickness of 0.03 μm formed on a nickel plating film on a copper plate is immersed in a 5% by mass sulfuric acid aqueous solution, and POTENTIONSTAT / GALVANOSTAT (manufactured by Hokuto Denko Co., Ltd.) is always used. A constant voltage of 300 mV was applied.
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 will increase, so from the start of the test until “5 minutes after the start of the test”, it is always judged that the current is 100 μA or less and that the plating solution is excellent, and the current is smaller. It was determined that the palladium plating solution was more excellent in the case of current.

<Evaluation method of appearance (color tone uniformity) of palladium film>
As described above, about the palladium film with a film thickness of 0.03 μm formed on the nickel plating film on the copper plate, the color tone of the surface of the palladium film is visually observed from 30 cm directly above the palladium film. Observed.

Since the underlying metal is nickel, the color tone is similar and difficult to judge, but when a uniform palladium film is not formed, a mottled pattern (unevenness) with a size of about 0.5 mm to 3 mm is observed. Therefore, the palladium plating solution in which the mottled pattern (unevenness) was not observed at all was determined to be an excellent palladium plating solution, and when only a less mottled pattern (unevenness) was observed, it was determined to be an excellent palladium plating solution.

<Measurement method of film thickness of palladium film>
The thickness of the palladium film was measured in the vicinity of the center of the palladium film on which the palladium plating was performed using a fluorescent X-ray analyzer (SFT 9255, manufactured by Seiko Instruments Inc.) according to a conventional method.

<Method for evaluating heat resistance>
In the same process as the evaluation sample prepared for the pinhole test, an evaluation sample was prepared by forming a palladium film with a film thickness of 0.03 μm on the nickel plating film on the copper plate.
In the case of applying a gold film on the palladium film, after forming the palladium film, a gold film was formed with a predetermined film thickness according to a conventional method to prepare an evaluation sample.
The sample for evaluation was heated for 15 hours in an oven whose inside was adjusted to 200 ° C.
The surface of the sample for evaluation after heating was measured at an acceleration voltage of 5 kV using a surface Auger; SAM-4300 (manufactured by ULVAC-PHI Co., Ltd.).

Evaluation samples satisfying nickel content of less than 10% and copper content of less than 0.5% and palladium plating solutions are judged as “non-defective”, and either nickel or copper is above the specified value. The sample and the palladium plating solution were determined as “defective products”.

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 greater than 100 μA does not always flow during the time from the start of the test to “5 minutes after the start of the test”, and the palladium In the visual appearance of the film, no mottled pattern or unevenness was observed, the color tone uniformity was good, and no abnormal precipitation of palladium was observed.
In the heat resistance test, nickel was less than 10% and copper was less than 0.5%, and all were judged as “good”.
On the other hand, in the electrolytic palladium plating solution not containing the specific pyridinium compound, either or both of the pinhole test result and the appearance (color tone uniformity) of the palladium film were inferior.
In the heat resistance test, nickel was 10% or more, and all were judged as “defective products”.

Examples 11-18
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 formed thereon, respectively.

When a heat resistance test was conducted, all of Examples 11 to 18 were less than 10% nickel and less than 0.5% copper in all cases of the gold film. It was determined to be good.

Comparative Examples 11-17
Corresponding samples for evaluation were prepared corresponding to those used in Comparative Examples 1 to 7, and gold films of 0.01 μm, 0.05 μm, and 0.1 μm were formed thereon, respectively.

When a heat resistance test was conducted, all of Comparative Examples 11 to 17 had a nickel film of 0.1 μm, which was less than 10% nickel and less than 0.5% copper. In the case of 0.01 μm and 0.05 μm gold films, either nickel was 10% or more, or copper was detected 0.5% or more, and both were judged to be defective.
In Comparative Examples 11 to 17, it was found that the gold film on the palladium film could not be made sufficiently thin because the heat resistance performance of the palladium film was inferior.

Example 21
<Evaluation of electrolytic palladium plating solution>
With respect to the whole palladium plating solution, the dichlorotetraammine palladium solution is 1 g / L in terms of palladium, the specific pyridinium compound similar to Example 1 (1-methyl-3-carboxypyridinium hydrochloride) is 1000 ppm, and the conductive salt Citric acid was dissolved as a component also serving as a buffer so as to be 100 g / L, and the pH was adjusted to 6.5 to obtain an electrolytic palladium plating solution.

Comparative Example 21
In Example 21, instead of using the specific pyridinium compound, 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.

<Method for Forming Palladium Film for Testing (Evaluation)>
When the electroless palladium plating solution is used, “the electroless palladium plating treatment time is adjusted in the range of 30 seconds to 3 minutes so that the film thickness is 0.03 μm”. Except that the current density of the electrolytic palladium plating treatment was adjusted to 0.5 A / dm ² before and after 5 seconds so that the film thickness was 0.03 μm. An evaluation sample was prepared in the same manner as in “Method for forming a test (evaluation) palladium film” in the case of using an electroless palladium plating solution.

As can be seen from Table 4, when the electrolytic palladium plating solution of the present invention (Example 21) was used, a current greater than 100 μA did not always flow in the pinhole test from the start of the test to “5 minutes after the start of the test”. In addition, no speckled pattern or unevenness was observed in the visual appearance of the palladium film, the color tone uniformity was good, and no abnormal precipitation of palladium was observed.
Further, in the heat resistance test, nickel was less than 10% and copper was less than 0.5%, which was judged as “good”.
On the other hand, the electrolytic palladium plating solution not containing the specific pyridinium compound (Comparative Example 21) was inferior in the pinhole test result.
Further, in the heat resistance test, nickel was 10% or more and copper was 0.5% or more, which was judged as “defective product”.

Examples 22 to 28, Comparative Examples 22 to 27
<Evaluation of electrolytic palladium plating solution>
Corresponding to Examples 22 to 28 and Comparative Examples 22 to 27, except that 1000 ppm 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 manner as in Example 21, an electrolytic palladium plating solution was prepared and evaluated in the same manner. 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, a current exceeding 100 μA does not always flow in the pinhole test from the start of the test to “5 minutes after the start of the test”, and the palladium film In the visual appearance, no mottled pattern or unevenness was observed, the color tone uniformity was good, and no abnormal precipitation of palladium was observed.
In the heat resistance test, nickel was less than 10% and copper was less than 0.5%, and all were judged as “good”.
On the other hand, in the electrolytic palladium plating solution not containing the specific pyridinium compound, either or both of the pinhole test result and the appearance (color tone uniformity) of the palladium film were inferior.
In the heat resistance test, nickel was 10% or more, or copper was 0.5% or more, and it was determined as “defective”.

The palladium film obtained using the palladium plating solution of the present invention has excellent heat resistance characteristics, and can reduce the film thickness of the gold plating film formed on the palladium film due to its excellent heat resistance. Cost reduction can be realized, and it is especially widely used for palladium / gold plating, and it is most suitable for processes having a layer structure of electroless nickel / palladium / gold. Is particularly preferably used.

Claims

Soluble palladium salt as a palladium source, and an alkyl group is bonded to the nitrogen atom at the 1-position, and 1 to 5 at the 2-position to the 6-position are an alkyl group, aryl group, carboxy group, alkoxycarbonyl group, sulfo group A specific pyridinium compound substituted with one or more specific substituents selected from the group consisting of an alkoxysulfonyl group, an amino group, an alkylamino group, a dialkylamino group and a cyano group. Palladium plating solution.
The palladium plating solution according to claim 1, comprising one or three of the 2-position to 4-position of the pyridinium ring containing a specific pyridinium compound substituted with one or more of the specific substituents.
The palladium plating solution according to claim 1 or 2, which contains the specific pyridinium compound in which a methyl group, an ethyl group, a propyl group, or a butyl group is bonded to a nitrogen atom at the 1-position.
The soluble palladium salt is palladium chloride, palladium sulfate, palladium acetate, palladium nitrate, palladium oxide, dichlorotetraammine palladium, dinitrodiammine palladium, dichlorodiethylenediamine palladium, tetrakis (triphenylphosphine) palladium, dichlorobis (triphenylphosphine) palladium and The palladium plating solution according to any one of claims 1 to 3, which is / or bis (acetylacetonato) palladium.
Furthermore, hypophosphorous acid, hypophosphite, phosphorous acid, phosphite, formic acid, formate and / or formaldehyde as a reducing agent is claimed in any one of claims 1 to 4. 2. Palladium plating solution described in 1.
The specific pyridinium compound is
1-methyl-2-methylpyridinium, 1-methyl-2-ethylpyridinium, 1-methyl-2-butylpyridinium, 1-methyl-2-sulfopyridinium, 1-methyl-2-methoxysulfonylpyridinium, 1-methyl- 2-aminopyridinium, 1-methyl-2-carboxypyridinium, 1-methyl-2-methoxycarbonylpyridinium, 1-methyl-2-phenylpyridinium, 1-methyl-2-cyanopyridinium;
1-ethyl-2-methylpyridinium, 1-ethyl-2-ethylpyridinium, 1-ethyl-2-butylpyridinium, 1-ethyl-2-sulfopyridinium, 1-ethyl-2-methoxysulfonylpyridinium, 1-ethyl- 2-aminopyridinium, 1-ethyl-2-carboxypyridinium, 1-ethyl-2-methoxycarbonylpyridinium, 1-ethyl-2-phenylpyridinium, 1-ethyl-2-cyanopyridinium;
1-propyl-2-methylpyridinium, 1-propyl-2-ethylpyridinium, 1-propyl-2-butylpyridinium, 1-propyl-2-sulfopyridinium, 1-propyl-2-methoxysulfonylpyridinium, 1-propyl- 2-aminopyridinium, 1-propyl-2-carboxypyridinium, 1-propyl-2-methoxycarbonylpyridinium, 1-propyl-2-phenylpyridinium, 1-propyl-2-cyanopyridinium;
1-butyl-2-methylpyridinium, 1-butyl-2-ethylpyridinium, 1-butyl-2-butylpyridinium, 1-butyl-2-sulfopyridinium, 1-butyl-2-methoxysulfonylpyridinium, 1-butyl- 2-aminopyridinium, 1-butyl-2-carboxypyridinium, 1-butyl-2-methoxycarbonylpyridinium, 1-butyl-2-phenylpyridinium, 1-butyl-2-cyanopyridinium;
1-methyl-3-methylpyridinium, 1-methyl-3-ethylpyridinium, 1-methyl-3-butylpyridinium, 1-methyl-3-sulfopyridinium, 1-methyl-3-methoxysulfonylpyridinium, 1-methyl- 3-aminopyridinium, 1-methyl-3-carboxypyridinium, 1-methyl-3-methoxycarbonylpyridinium, 1-methyl-3-phenylpyridinium, 1-methyl-3-cyanopyridinium;
1-ethyl-3-methylpyridinium, 1-ethyl-3-ethylpyridinium, 1-ethyl-3-butylpyridinium, 1-ethyl-3-sulfopyridinium, 1-ethyl-3-methoxysulfonylpyridinium, 1-ethyl- 3-aminopyridinium, 1-ethyl-3-carboxypyridinium, 1-ethyl-3-methoxycarbonylpyridinium, 1-ethyl-3-phenylpyridinium, 1-ethyl-3-cyanopyridinium;
1-propyl-3-methylpyridinium, 1-propyl-3-ethylpyridinium, 1-propyl-3-butylpyridinium, 1-propyl-3-sulfopyridinium, 1-propyl-3-methoxysulfonylpyridinium, 1-propyl- 3-aminopyridinium, 1-propyl-3-carboxypyridinium, 1-propyl-3-methoxycarbonylpyridinium, 1-propyl-3-phenylpyridinium, 1-propyl-3-cyanopyridinium;
1-butyl-3-methylpyridinium, 1-butyl-3-ethylpyridinium, 1-butyl-3-butylpyridinium, 1-butyl-3-sulfopyridinium, 1-butyl-3-methoxysulfonylpyridinium, 1-butyl- 3-aminopyridinium, 1-butyl-3-carboxypyridinium, 1-butyl-3-methoxycarbonylpyridinium, 1-butyl-3-phenylpyridinium, 1-butyl-3-cyanopyridinium;
1-methyl-4-methylpyridinium, 1-methyl-4-ethylpyridinium, 1-methyl-4-butylpyridinium, 1-methyl-4-sulfopyridinium, 1-methyl-4-methoxysulfonylpyridinium, 1-methyl- 4-aminopyridinium, 1-methyl-4-carboxypyridinium, 1-methyl-4-methoxycarbonylpyridinium, 1-methyl-4-phenylpyridinium, 1-methyl-4-cyanopyridinium;
1-ethyl-4-methylpyridinium, 1-ethyl-4-ethylpyridinium, 1-ethyl-4-butylpyridinium, 1-ethyl-4-sulfopyridinium, 1-ethyl-4-methoxysulfonylpyridinium, 1-ethyl- 4-aminopyridinium, 1-ethyl-4-carboxypyridinium, 1-ethyl-4-methoxycarbonylpyridinium, 1-ethyl-4-phenylpyridinium, 1-ethyl-4-cyanopyridinium;
1-propyl-4-methylpyridinium, 1-propyl-4-ethylpyridinium, 1-propyl-4-butylpyridinium, 1-propyl-4-sulfopyridinium, 1-propyl-4-methoxysulfonylpyridinium, 1-propyl- 4-aminopyridinium, 1-propyl-4-carboxypyridinium, 1-propyl-4-methoxycarbonylpyridinium, 1-propyl-4-phenylpyridinium, 1-propyl-4-cyanopyridinium;
1-butyl-4-methylpyridinium, 1-butyl-4-ethylpyridinium, 1-butyl-4-butylpyridinium, 1-butyl-4-sulfopyridinium, 1-butyl-4-methoxysulfonylpyridinium, 1-butyl- 4-aminopyridinium, 1-butyl-4-carboxypyridinium, 1-butyl-4-methoxycarbonylpyridinium, 1-butyl-4-phenylpyridinium, 1-butyl-4-cyanopyridinium;
The palladium plating solution according to any one of claims 1 to 5, wherein the palladium plating solution is any one or two or more specific pyridinium compounds.
The reducing agent is hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, phosphorous acid, sodium phosphite, potassium phosphite, ammonium phosphite, formic acid, formic acid The palladium plating solution according to claim 5 or 6, which is sodium, potassium formate, ammonium formate and / or formaldehyde.
The test was started when a substrate plated with a palladium plating solution so that the film thickness of the palladium film was 0.03 μm was immersed in a 5 mass% sulfuric acid aqueous solution and a pinhole test was performed at a constant voltage of 300 mV. The palladium plating solution according to any one of claims 1 to 7, wherein the plating physical property is such that an energization current is 100 µA or less for all of from 5 to 5 minutes after the start of the test.
It is obtained by performing palladium plating on the nickel, nickel alloy, copper or copper alloy film using the palladium plating solution according to any one of claims 1 to 8. Characteristic palladium film.
A contact member for electronic parts, comprising the palladium film according to claim 9.
An electroless palladium plating solution comprising the palladium plating solution according to any one of claims 1 to 8.
An electrolytic palladium plating solution comprising the palladium plating solution according to any one of claims 1 to 8.