KR20110022576A - Electrolytic gold plating solution and gold film obtained using same - Google Patents

Abstract

As for the physical properties of the gold plated film, to provide an electrolytic gold plating solution suitable for nickel barrier plating while maintaining excellent mechanical properties, abrasion resistance, and electrical properties, that is, a part that does not require gold plating (a nickel barrier that mechanically presses the member) To prevent electrolytic gold from occurring and to provide an electrolytic gold plating solution capable of producing a stable product without abnormal deposition of gold. And a heterocyclic compound having at least one nitrogen atom in the ring, wherein at least one nitro group is substituted for the carbon atom in the ring, and the electrolytic gold plating solution described above. By the electrolytic gold plating on the nickel coating, It solved the task group.

Description

ELECTROLYTIC GOLD PLATING SOLUTION AND GOLD FILM OBTAINED USING SAME

The present invention relates to an electrolytic gold plating solution having a specific composition and a gold coating on a nickel film obtained by using the electrolytic gold plating solution.

Gold plating on a nickel film has been widely used in the field of electronic and electrical parts, because gold has excellent corrosion resistance, mechanical properties, electrical properties, and the like, and nickel has excellent heat resistance as a base metal. Among them, hard gold plating alloyed with metals such as cobalt and nickel has been widely used as gold plating of contact joints such as fitting members such as connectors and contact members such as switches, utilizing its high hardness and excellent wear resistance.

In recent years, due to the miniaturization of electronic equipment, contact members such as connectors and contacts such as switches are also downsized and complicated in shape, and the spacing between the points requiring solder bonding and the positions that should function as contacts are significantly narrowed. The phenomenon that solder gets wet even to this part which is not needed becomes a problem. Therefore, this problem is solved by forming a portion which is not subjected to gold plating between the contact portion and the solder joint portion, so that only the necessary portions of the solder are wetted.

This method is an electrolytic gold plating technique commonly referred to as nickel barrier plating, and mechanically pressurizes a member such as silicon rubber to a portion where the gold plating is not required (nickel barrier portion) in order to make a gold plating portion and an unnecessary portion in one part. In this way, the gold plating solution and the plated part cannot be brought into contact with each other, thereby forming a part where the gold plating is applied and a part where the gold plating is not applied (nickel barrier part) in one part.

However, since the part to be gold-plated and the part not to be made within one part must be made, even if the part which is not required to be gold-plated mechanically by a member such as silicone rubber is completely prevented from leaking the gold-plating solution to the part. There was a problem in that it was very difficult in the plating apparatus.

In order to solve this problem, Patent Document 1 discloses a gold plating bath in which the gold cobalt plating solution is kept slightly weak, and hexamethylenetetramine is added to suppress the deposition of the gold plating film on unnecessary portions. However, this technique cannot be said to have sufficient performance in the selectivity of gold precipitation, and since reductive hexamethylenetetramine is added to the gold plating bath, gold precipitates abnormally in the gold plating bath, Gold adhered to the shaft portion of the pump for circulation, and the pump stopped, or gold was consumed in addition to the plating reaction, which was not very economically practical.

In recent years, due to the miniaturization of electronic devices, the portions to which gold plating has been applied and the portions not to be implemented have to be clearly distinguished. However, the conventional techniques do not achieve this, and further improvement is required.

Japanese Unexamined Patent Publication No. 2008-045194

This invention is made | formed in view of the said background art, and the subject is maintaining the mechanical property, abrasion resistance, electrical property, etc. equivalent to what was obtained using the conventional electrolytic gold plating solution about the physical property of a gold-plated coating, It is to provide a suitable electrolytic gold plating solution. In other words, gold precipitation in the `` gold plating unnecessary portion (nickel barrier portion) '' that mechanically pressurized the member is suppressed, and good gold precipitation occurs in the portion where gold plating is required, and there is no abnormal precipitation of gold, thus making stable product manufacturing. It is to provide a possible electrolytic gold plating solution.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, as for the part which a gold plating liquid contacts a to-be-plated part, plating reaction advances by high current density (setting current density), and a gold plating liquid does not reach a plating part, The part looked at the progress of plating reaction at a low current density, and discovered that the electrolytic gold plating solution should be developed using the difference.

1 is a measurement using a general purpose electrolytic gold plating solution and the electrolytic gold plating solution of the composition described in Example 1 of the present invention, after the current plating (A / dm 2) on the horizontal axis and the gold plating treatment on the vertical axis for 10 seconds. It is a graph which took the film thickness (micrometer) of a gold film. That is, the gold concentration of the general-purpose electrolytic gold plating solution was adjusted to the gold conversion concentration (9 g / L) of the electrolytic gold plating solution of Example 1, the bath temperature was raised to 50 ° C., and in the step described in Table 2, Gold plating was performed on 2.0 micrometers of primary glossy nickel plating films on a copper plate of 10 mm x 10 mm. Gold plating is a current density of 1 A / dm 2, 5 A / dm 2, 10 A / dm 2, while dividing and stirring the gold plating solution with a pump at a flow rate of 18 L per minute from a circular flow outlet having a diameter of 8 mm. Change to 20 A / dm 2, 30 A / dm 2, 40 A / dm 2, 50 A / dm 2, 60 A / dm 2, and gold plating for 10 seconds. It is a graph which measured the film thickness of a gold film by the conventional method using the X-ray analyzer (SFT9255 by Seiko Instruments Co., Ltd.), and plotted the measurement result.

0 A / dm 2 to 5 A / dm 2 (hereinafter abbreviated as “low current density range”) in FIG. 1 correspond to a portion which is not subjected to gold plating in the nickel barrier plating technique, and has a low current. It was judged that the thinner the film thickness of the gold film in the density region, the better the nickel barrier property. In addition, 20 A / dm <2> -60 A / dm <2> (it abbreviates as "high current density area" hereafter) in FIG. 1 corresponds to the part which carries out gold plating in a nickel barrier plating technique, and has high current density. It was judged that the thicker the film thickness of the gold film in the reverse region, the better the nickel barrier property. See the plot graph of the electrolytic gold plating solution of the composition described in Example 1.

In the nickel barrier plating technique, as described above, even if a portion where gold plating is unnecessary is mechanically pressurized with a member such as silicone rubber, it is very difficult to completely prevent the gold plating solution from leaking into the portion. In the characteristic of the electrolytic gold plating solution required for the nickel barrier plating technique, the gold deposition film thickness in the low current density region is very thin, and the gold deposition amount in the low current density region and the gold deposition amount in the high current density region are as follows. The difference was large, and it was found that the amount of gold deposited in the high current density region forming the gold-plated film on the product was the maximum possible property. The electrolytic gold plating solution having such characteristics was considered to be an electrolytic gold plating solution suitable for the nickel barrier plating technique because of its selectivity with respect to gold deposition.

Therefore, the present inventors earnestly studied to solve the above problems from the viewpoint of the composition of the electrolytic gold plating solution, and as a result, the gold cyanide salt and the "cyclic cyclic compound having one or more nitrogen atoms in the ring, the carbon in the ring When the gold film is formed using an electrolytic gold plating solution containing a heterocyclic compound in which one or more nitro groups are substituted with atoms as an essential component, the above problems are solved and the problem is solved. The precipitation of gold in the density region was suppressed, and it was found that no abnormal precipitation of gold was able to produce a stable product, and thus the present invention was completed.

That is, the present invention contains an electrolytic gold plating solution comprising a gold cyanide salt as a gold source and a heterocyclic compound having at least one nitrogen atom in the ring and in which at least one nitro group is substituted for the carbon atom in the ring. To provide.

Moreover, this invention provides the said electrolytic gold plating solution containing cobalt salt, nickel salt, and / or iron salt further.

In addition, the present invention, when the plating treatment for 10 seconds by setting the current density to 5 A / dm 2 and 40 A / dm 2 using a jet jet plating apparatus, respectively, at a current density of 5 A / dm 2 The film thickness of the gold film is 0.1 µm or less, and the film thickness of the gold film at 40 A / dm 2 is 5 times or more the film thickness of the gold film at 5 A / dm 2, which provides the above-mentioned electrolytic gold plating solution. will be.

Moreover, this invention provides the gold film | membrane obtained by performing electrolytic gold plating on a nickel film using said electrolytic gold plating solution.

According to the electrolytic gold plating solution of the present invention, the gold deposition rate in a low current density region of a gold film obtained by using a conventional electrolytic gold plating solution while maintaining mechanical properties such as excellent wear resistance, corrosion resistance, electrical properties, and the like Very slowly, the gold deposition rate in the high current density region can be made very fast (hereinafter, this performance is referred to as the "gold selective precipitation performance"), so that the gold deposition film thickness in the low current density region and the high current density region The difference in the thickness of the gold precipitation film can be increased.

As a result, the precipitation of gold in the "gold plating unnecessary part (nickel barrier part)" mechanically pressurized by a member such as silicone rubber can be suppressed, and good gold precipitation can be realized in the unpressurized part (gold plating part). In addition, it is possible to provide an electrolytic gold plating solution capable of producing a stable product without abnormal precipitation of gold, and can be preferably adapted to the nickel barrier plating technology required for contact members such as connectors of electronic devices.

1 is a diagram showing a relationship between the "current density of electrolytic gold plating" and the "film thickness of a gold film obtained by electrolytic gold plating for 10 seconds".
2 is a view for explaining a nickel barrier plating technique, which is an example of a form of a connector to which electrolytic gold plating is performed in the nickel barrier plating technique.
It is a figure which shows the distribution of the gold film thickness at the time of giving the connector of FIG. 2 the electrolytic gold plating of this invention.

Carrying out the invention  Best form for

EMBODIMENT OF THE INVENTION Hereafter, although this invention is demonstrated, this invention is not limited to the specific form of the following implementation, It can be arbitrarily modified and implemented within the range of technical idea.

The present invention contains at least a gold cyanide salt as a gold source, and further includes "a heterocyclic compound having at least one nitrogen atom in a ring, in which at least one nitro group is substituted with a carbon atom in the ring ''. It is an electrolytic gold plating solution containing as an essential component. The "electrolyte gold plating solution" of the present invention also includes the "electrolyte gold plating solution". Moreover, "gold alloy film" is also contained in the "gold film" of this invention. That is, you may contain metal other than gold.

When using the electrolytic gold plating liquid of this invention for hard gold plating, it contains a cobalt salt, nickel salt, and / or iron salt further. That is, in addition to the gold cyanide salt as a gold source, it contains any 1 type, or 2 or more types of a cobalt salt, a nickel salt, and an iron salt.

<Gold cyanide salt>

It is essential that the electrolytic gold plating solution of the present invention contains a gold cyanide salt. The gold cyanide salt is used as a gold source of the electrolytic gold plating solution of the present invention. Gold cyanide salt is not limited to 1 type of use, It can use 2 or more types together.

As this gold cyanide salt, a gold cyanide alkali metal or gold ammonium cyanide is preferable. Moreover, as a valence (oxidized water) of the gold of the cyanide gold salt, either monovalent or trivalent can be used, but monovalent is preferable from the viewpoint of the precipitation efficiency of gold. That is, the first cyanide gold salt is preferable.

As a specific example of the gold cyanide salt, there may be mentioned, for example, sodium cyanide, potassium cyanide, potassium cyanide, ammonium cyanide, potassium cyanide, potassium cyanide, ammonium cyanide, and the like. have. Among them, from the viewpoints of plating performance such as deposition efficiency of gold, cost, and availability, the first gold sodium cyanide, the first gold potassium cyanide, and the first gold ammonium cyanide are preferable, and from the same viewpoint, the first cyanide Gold potassium is particularly preferred.

The content of the gold cyanide salt in the electrolytic gold plating solution of the present invention is not particularly limited, and is generally 0.05 g / L to 50 g / L, preferably 0.5 g / L to 30 g /, with respect to the entire electrolytic gold plating solution. L, particularly preferably 1 g / L to 20 g / L. If the content of gold cyanide salt in the electrolytic gold plating solution is too small, golden gold plating may be difficult. On the other hand, when the metal gold content in the electrolytic gold plating solution is too large, there is no particular problem as to the performance of the electrolytic gold plating solution, but the gold cyanide salt is a very expensive metal, and it is uneconomical to store it in the state contained in the electrolytic gold plating solution. It may become.

The description of the above-mentioned gold cyanide salt specifies a form present in the electrolytic gold plating solution of the present invention, and the above-mentioned gold cyanide salt is used as a raw material to be dissolved in the crude liquid of the electrolytic gold plating solution of the present invention. It is preferable.

<Compound Cyclic Compound>

In the electrolytic gold plating solution of the present invention, "a heterocyclic compound having at least one nitrogen atom in a ring and at least one nitro group is substituted with a carbon atom in the ring" (hereinafter, the parentheses include "a specific heterocyclic compound. May be abbreviated as “) as an essential ingredient. By containing a specific heterocyclic compound, the gold precipitation film thickness in the low current density range can be made small while maintaining the excellent high corrosion resistance, mechanical properties, electrical properties, etc. of the conventional electrolytic gold plated film, and low current density. The difference between the gold precipitation film thickness in the region and the gold precipitation film thickness in the high current density region can be made very large. That is, by containing a specific heterocyclic compound, an electrolytic gold plating solution excellent in gold selective precipitation performance can be obtained, and an electrolytic gold plating solution optimal for nickel barrier plating is realized.

The heterocyclic ring in the specific heterocyclic compound is not particularly limited and may or may not have aromaticity, but the aromatic ring preferably has the above-mentioned effects in terms of good plating performance and availability. It is preferable at the point which shows. There are no particular limitations on these atoms other than the carbon atoms constituting the heterocycle, and examples include nitrogen, oxygen, and sulfur, and at least one of the binary atoms must be a nitrogen atom. Moreover, it is preferable at the point of favorable plating performance, availability, etc. that the binary atom which comprises a heterocyclic ring becomes only a nitrogen atom.

Arbitrary substituents may be substituted by the carbon atom in a heterocyclic ring in the range which does not impair the effect of this invention. It is essential that at least one of the substituents for the carbon atoms in the hetero ring is a nitro group. As substituents other than a nitro group, an alkyl group, a hydroxyl group, a phenyl group, etc. are mentioned. Although the number of nitro groups substituted by the carbon atom in a hetero ring will not be specifically limited if it is one or more, 1-3 are preferable and 1-2 are especially preferable.

Specific examples of the specific heterocyclic compound include pyrrole, imidazole, pyrazole, triazole, tetrazole, oxazole, isoxazole, indole, pyridine, pyridazine, pyrimidine, pyrazine, uracil, Preferred are those in which at least one nitro group is substituted on a carbon atom constituting a ring of cytosine, thymine, adenine, guanine, quinoline, isoquinoline, quillin, isoquisaline, acridine, cinosolin or morpholine. have.

More specifically, nitropyrrole, dinitropyrrole, nitroimidazole, dinitroimidazole, nitropyrazole, dinitropyazole, nitrotriazole, dinitrotriazole, nitroteazole, nitrooxazole, dinitro Oxazole, nitroisoxazole, dinitroisoxazole, nitroindole, nitropyridine, dinitropyridine, nitropyridazine, dinitropyridazine, nitropyrimidine, dinitropyrimidine, nitropyrazine, dinitropyrazine, nitroiracil , Nitrocytosine, nitrothymine, nitroadenine, nitroguanine, nitroquinoline, dinitroquinoline, nitroisoquinoline, dinitroisoquinoline, nitroquisaline, dinitroisoquisaline, nitroacridine, nitrocinnosolin, dinitro Shinnosolin, nitromorpholine, dinitromorpholine and the like are plated in a good plating performance, easy dissolution in water, low current density range To inhibit the performance of the gold deposition, it can be obtained from the point of view of ease, low cost, etc., and particularly preferable examples.

In this invention, although there is no restriction | limiting in particular about content of a specific heterocyclic compound, Preferably it is 10 ppm-50000 ppm, More preferably, 50 ppm-30000 ppm with respect to the whole electrolytic gold plating liquid, Especially preferably, 100 ppm to 10000 ppm. In addition, when containing 2 or more types of said specific heterocyclic compounds, the said numerical value shows those total content. If the content of the specific heterocyclic compound in the electrolytic gold plating solution is too small, gold precipitation in the case of plating in a low current density region may not be suppressed, or the appearance of the gold film may be poor. On the other hand, when there is too much content, the further increase of the said effect of this invention cannot be anticipated, and may become uneconomical.

The description of the specific heterocyclic compound described above specifies a form present in the electrolytic gold plating solution of the present invention. The above-mentioned specific heterocyclic compound is used as a raw material to be dissolved during the preparation of the electrolytic gold alloy plating solution of the present invention. Preference is given to using.

<Cobalt salt, nickel salt, iron salt>

In the electrolytic gold alloy plating solution of the present invention, in addition to the gold cyanide salt and the specific heterocyclic compound described above, cobalt salt, nickel salt and / or iron salt may be used together to form a hard gold film that is optimal for nickel barrier plating. It is preferable because an electrolytic gold plating solution can be obtained.

The cobalt salt, nickel salt or iron salt is precipitated together with gold in the gold plated film on the nickel plated film to form a hard gold film, which is required for contact members such as connectors of electronic components. High hardness, high wear resistance, and the like can be realized.

It is preferable that said cobalt salt, nickel salt, and iron salt are water-soluble. Said cobalt salt, nickel salt, and / or iron salt is not limited to 1 type of use in each metal salt, It can use 2 or more types together. Moreover, among cobalt salt, nickel salt, and iron salt, 2 or more types can be used together without restricting the metal salt of a different metal to 1 type.

There is no restriction | limiting in particular as said cobalt salt, For example, cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt carbonate, phthalocyanine cobalt, cobalt stearate, ethylenediamine tetrasodium acetate cobalt, naphthenic acid cobalt, cobalt borate, thiocyanate Cobalt, cobalt sulfamate, cobalt acetate, cobalt citrate, cobalt hydroxide, cobalt oxalate, cobalt phosphate, etc., have good plating performance, ease of dissolution in water, ease of vacancies in gold film, availability, low cost, and the like. It is mentioned as a preferable thing in these.

Although there is no limitation in particular as said nickel salt, For example, nickel sulfate, nickel acetate, nickel chloride, nickel borate, nickel benzoate, nickel oxalate, nickel naphthenate, nickel oxide, nickel phosphate, nickel stearate, nickel tartarate, thiocyanate Nickel acrylate, nickel amide sulfate, nickel carbonate, nickel citrate, nickel formate, nickel cyanide, nickel hydroxide, nickel nitrate, nickel octanate, etc., good plating performance, ease of dissolution in water, ease of vacancies in gold film, It is mentioned as a preferable thing from a viewpoint of ease of acquisition, low cost, etc.

Although there is no limitation in particular as said iron salt, For example, ferrous sulfate, ferric sulfate, ferric chloride, ferric chloride, ferric citrate, ferric citrate, ferric formate, hypophosphite Ferric iron, ferric naphthenate, ferric stearate, ferric pyrolate, ferrous tartarate, ferric tartarate, ferric thiocyanate, ferric thiocyanate, ferric fumarate, Ferrous gluconate, ethylenediamine ferric acetate, ferrous nitrate, ferric nitrate, etc., with good plating performance, ease of dissolution in water, ease of vacancies in gold coating, ease of availability, low cost, etc. It is mentioned as a preferable point from a viewpoint.

The content of the cobalt salt, nickel salt and iron salt in the electrolytic gold plating solution of the present invention is not particularly limited, but is preferably 1 ppm to 50000 ppm, more preferably, as a metal (in terms of metal) to the entire electrolytic gold plating solution. Preferably it is 10 ppm-30000 ppm, Especially preferably, it is 50 ppm-10000 ppm. In addition, when using 2 or more types of said cobalt salt, nickel salt, and iron salt, the said numerical value shows those total content. If the content is too small, the amount of vacancies in the gold film may be too small and sufficient hardness may not be obtained. On the other hand, when there is too much content, the amount of vacancies with respect to a gold film will become too large, the color tone defect of a gold film, increase of a contact resistance may arise, or the increase of hardness may not be expected.

<Other additives>

In the electrolytic gold plating solution of the present invention, in addition to the above components, a buffer for maintaining a constant pH of the electrolytic gold plating solution, a conducting salt for securing the conductivity of the electrolytic gold plating solution, and an impurity metal are mixed in the electrolytic gold plating solution, if necessary. In this case, a metal ion blocking agent for removing the influence, a pinhole for removing the gold film, or a surfactant for improving bubble escape of the electrolytic gold plating solution, a polishing agent for smoothing the gold film, and the like can be used.

As a buffer contained as needed in the electrolytic gold plating liquid of this invention, if it is a well-known buffer, there will be no limitation in particular, but inorganic acids, such as boric acid and phosphoric acid; And oxycarboxylic acids such as citric acid, tartaric acid and malic acid. These can be used 1 type or in mixture of 2 or more types.

Although content of the buffer in the electrolytic gold plating solution of this invention is not specifically limited, Usually, it is 1 g / L-500 g / L, Preferably it is 10 g / L-100 g / L with respect to the whole electrolytic gold plating solution. When the content of the buffer in the electrolytic gold plating solution is too small, the buffering effect may be difficult to be exhibited. On the other hand, when the content of the buffering agent is too large, the increase in the buffering effect may not be exhibited, which may be uneconomical.

The conductive salt contained in the electrolytic gold plating solution of the present invention as needed is not particularly limited as long as it is a well-known conductive salt, but may include inorganic acids such as sulfate, nitrate and phosphate; Carboxylic acids, such as oxalic acid, succinic acid, glutaric acid, malonic acid, citric acid, tartaric acid, and malic acid, etc. are mentioned. These can be used 1 type or in mixture of 2 or more types.

Although content of the conducting salt in the electrolytic gold plating liquid of this invention is not specifically limited, Usually, it is 1 g / L-500 g / L, Preferably it is 10 g / L-100 g / L with respect to the whole electrolytic gold plating liquid. When the content of the conductive salt in the electrolytic gold plating solution is too small, the conductive effect may be difficult to be exhibited, while when too large, the increase in the buffering effect may not be exhibited, which may be uneconomical. Moreover, it can also share common component with a buffer.

The metal ion blocking agent contained in the electrolytic gold plating solution of the present invention as needed is not particularly limited as long as it is a well-known metal ion blocking agent, but aminocarboxylic acid chelating agents such as iminodiacetic acid, nitrilotriacetic acid and ethylenediaminetetraacetic acid. ; Phosphonic acid chelating agents such as hydroxyethylidenediphosphonic acid, nitrilo methylenephosphonic acid, ethylenediamine tetramethylenephosphonic acid, and the like. These can be used 1 type or in mixture of 2 or more types.

The content of the metal ion blocking agent in the electrolytic gold plating solution of the present invention is not particularly limited, but is usually 0.1 g / L to 100 g / L, and preferably 0.5 g / L to 50 g / L with respect to the whole electrolytic gold plating solution. . If the content of the metal ion blocking agent in the electrolytic gold plating solution is too small, the effect of removing the influence of the impurity metal may be difficult to be exerted. On the other hand, the effect of removing the influence of the impurity metal cannot be increased. It is uneconomical.

If it is a well-known surfactant, there is no restriction | limiting in particular as surfactant contained in an electrolytic gold plating solution of this invention as needed, A nonionic surfactant, an anionic surfactant, an amphoteric surfactant, or a cationic surfactant is used. These can be used 1 type or in mixture of 2 or more types.

-나프톨폴리알콕실레이트, 디부틸-β-나프톨폴리알콕실레이트, 스티렌화 페놀폴리알콕실레이트 등의 에테르형 노니온계 계면 활성제 ; 옥틸아민폴리알콕실레이트, 헥시닐아민폴리알콕실레이트, 리놀레일아민폴리알콕실레이트 등의 아민형 노니온계 계면 활성제 등을 들 수 있다.As nonionic surfactant, noniphenol polyalkoxylate,

Ether type nonionic surfactants such as naphthol polyalkoxylate, dibutyl-β-naphthol polyalkoxylate and styrenated phenol polyalkoxylate; Amine type nonionic surfactants such as octylamine polyalkoxylate, hexynylamine polyalkoxylate, linoleylamine polyalkoxylate, and the like.

As an anionic surfactant, Alkyl sulfates, such as sodium lauryl sulfate; Polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene nonyl ether sulfate; Polyoxyethylene alkyl phenyl ether sulfate; Alkylbenzene sulfonate etc. are mentioned.

As the amphoteric surfactant, 2-undecyl-1-carboxymethyl-1-hydroxyethylimidazolium betaine, N-stearyl-N, N-dimethyl-N-carboxymethyl betaine, lauryldimethylamine oxide and the like Can be mentioned.

Examples of the cationic surfactant include lauryltrimethylammonium salt, lauryldimethylammonium betaine, laurylpyridinium salt, oleyl imidazolium salt, stearylamine acetate, and the like.

These can be used 1 type or in mixture of 2 or more types, Preferably they are nonionic surfactant or amphoteric surfactant.

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

If it is a well-known polisher, there will be no limitation in particular as a polisher contained as needed in the electrolytic gold plating liquid of this invention, An amine compound etc. which have a pyridine skeleton are mentioned. These can be used 1 type or in mixture of 2 or more types.

As an amine compound which has a pyridine skeleton, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, etc. are mentioned.

The content of the gloss agent in the electrolytic gold plating solution of the present invention is preferably 0.01 g / L to 20 g / L with respect to the whole electrolytic gold plating solution, but the desired performance may be exhibited, and the content is not particularly limited.

<The property of electrolytic gold plating amount>

When the electrolytic gold plating solution of the present invention is used, the current density is set to 5 A / dm 2 and 40 A / dm 2 using the jet jet plating apparatus, and the current density is 5 A / The film thickness of the gold film at dm 2 can be 0.1 μm or less, and the film thickness of the gold film at 40 A / dm 2 is at least 5 times the film thickness of the gold film at 5 A / dm 2. can do. Furthermore, the film thickness of the gold film at a current density of 5 A / dm 2 can also be 0.08 μm or less, and the film thickness of the gold film at 40 A / dm 2 is the gold film at 5 A / dm 2. Can be more than 7 times the film thickness of.

Therefore, the electrolytic gold plating solution of the present invention has the above composition, and when the plating treatment is performed for 10 seconds by setting the current density to 5 A / dm 2 and 40 A / dm 2 using the jet jet plating apparatus, respectively. The film thickness of the gold film at a current density of 5 A / dm 2 was 0.1 μm or less, and the film thickness of the gold film at 40 A / dm 2 was 5 of the film thickness of the gold film at 5 A / dm 2. It is preferable that it is an electrolytic gold plating liquid more than twice. Furthermore, under the above conditions, the film thickness of the gold film at a current density of 5 A / dm 2 is 0.08 μm or less, and the film thickness of the gold film at 40 A / dm 2 is gold at 5 A / dm 2. It is especially preferable that it is an electrolytic gold plating liquid which is 7 times or more of the film thickness of a film.

Thereby, the electrolytic gold plating solution of the present invention can be particularly preferably used for the nickel barrier plating technique described above.

<Gold film>

As described above, the "electrolyte gold plating solution" of the present invention also includes the "electrolyte gold plating solution". Moreover, "gold alloy film" is also contained in the "gold film" of this invention. That is, you may contain metals other than gold, such as cobalt, nickel, and iron. Metals other than gold are vaccinated with gold in the gold plated film on the nickel plated film to form a hard gold film that is optimal for nickel barrier plating, thereby realizing high hardness and high wear resistance required for contact members such as connectors of electronic components. You can.

Although the concentration (gold purity) of gold in the "gold film" is not particularly limited, it is preferable that gold is 95 mass% or more with respect to the entire "gold film", and in order to obtain a hard gold film for the use, it is 97 mass. %-99.99 mass% are more preferable, and 99 mass%-99.9 mass% are especially preferable.

<Condition of electrolytic gold plating>

Although the plating conditions of the above-mentioned electrolytic gold plating solution of this invention are not specifically limited, As temperature conditions, it is preferable that they are 20 degreeC-90 degreeC, Especially preferably, they are 30 degreeC-70 degreeC. Moreover, it is preferable that pH of a plating liquid is pH 2.0-pH 9.0, Especially preferably, it is pH 3.0-pH 8.0.

Although there is no restriction | limiting in particular in the film thickness of the gold film obtained by electrolytic plating using the electrolytic gold plating liquid of this invention, Preferably it is 0.01 micrometer-20 micrometers, Especially preferably, it is 0.05 micrometer-5 micrometers.

In addition, when the electrolytic gold plating solution is used, a thin gold plating treatment having a thickness of about 0.01 µm to 0.05 µm is performed on the gold coating, called flash gold plating, for the purpose of improving the adhesion between the gold coating and the base metal. It is common to apply gold plating thickly to thickness. Although the electrolytic gold plating liquid of this invention can be used suitably for the gold plating process at this time, even if it carries out gold plating process with the electrolytic gold plating liquid of this invention, it is possible to perform flash gold plating, and flash gold plating For example, a commercially available flash gold plating solution or the electrolytic gold plating solution of the present invention can be suitably used.

It is preferable that the electrolytic gold plating liquid of this invention is used for said nickel barrier plating technique. Therefore, when electrolytic gold plating is performed using the electrolytic gold plating solution of the present invention, it is preferable to form a nickel plating film as the base plating treatment. Although the nickel plating liquid at this time is not specifically limited, The watt bath, the sulfamine bath, the nickel bromide bath etc. which are generally utilized are preferable. Moreover, an anti-pitcher, a primary varnish, and a secondary varnish can be added and used as needed to the nickel plating liquid to be used. The method of using the nickel plating solution is not particularly limited and is used in accordance with a conventional method.

Although the film thickness of a nickel plating film is not specifically limited, either, It is preferable that they are 0.1 micrometer-20 micrometers, Especially preferably, they are 0.5 micrometer-5 micrometers.

<Action, principle>

The action and principle of the electrolytic gold plating solution of the present invention exhibiting excellent gold selective precipitation performance required for nickel barrier plating technology are not clear, and the present invention is not limited to the scope of the following action and principle. have. In particular, in the low current density region, rather than reducing the gold in the gold cyanide salt to become metal gold, the nitro group of the specific heterocyclic compound as a substituent is reduced to become a nitroso group, so that the gold in the low current density region is dominant. Precipitation is suppressed, and as a result, it is thought that the outstanding gold selective precipitation performance was shown.

Example

Although an Example and a comparative example are given to the following and this invention is demonstrated to it further more concretely, this invention is not limited to these Examples, unless the summary is exceeded. In addition, the density | concentration value in the composition of an electrolytic gold plating liquid is a numerical value of the density | concentration calculated | required from the mass which does not contain crystal water, when the component contains crystal water.

<Preparation of electrolytic gold plating amount>

Examples 1-10, Comparative Examples 1-12

For the entire electrolytic gold plating solution, 200 ppm of a metal-based cobalt salt, nickel salt or iron salt described in each of Examples and Comparative Examples shown in 9 g / L of gold potassium cyanide in gold, Table 1 and a specific heterocyclic ring The compound or the comparative compound was dissolved in a content of 1000 ppm, a conductive salt, and a buffer so that citric acid became 100 g / L, and the pH was adjusted to 4.3 to obtain an electrolytic gold plating solution.

As the "comparative compound", hexamethylenetetramine, a benzene ring compound in which one or more nitro groups were substituted with a carbon atom in the ring, and a heterocyclic compound in which the nitro group was not substituted were used. In addition, pH was adjusted with 20 mass% potassium hydroxide aqueous solution and citric acid, the bath temperature of the electrolytic gold plating liquid was set to 50 degreeC, and the following evaluation was performed.

Example 11

Except not containing metal salts other than gold salts such as cobalt salt, nickel salt and iron salt, an electrolytic gold plating solution was prepared in the same manner as in Example 1, and electrolytic gold plating was carried out in the same manner as in Example 1, The described evaluation was performed.

<Method of electrolytic gold plating>

Using the electrolytic gold plating solution prepared in each Example and each comparative example, electrolytic gold plating was performed on the primary glossy nickel plating film 2.0 micrometers on the copper plate which is 10 mm x 10 mm by the process shown in Table 2. Electrolytic gold plating is performed by dividing and stirring the electrolytic gold plating solution by a pump at a flow rate of 18 L per minute from a circular flow outlet having a diameter of 8 mm (hereinafter referred to as the "jet jet type gold plating method"). Electrolytic gold plating was carried out at 2 levels of d 2 and 40 A / dm 2 for 10 seconds each.

In addition, the primary gloss nickel plating film was plated by the film thickness of 2.0 micrometer using the following electrolytic nickel plating solution A. Namely, commercially available nickel sulfamate plating solution (manufactured by Murata Co., Ltd.) 500 mL / L, commercially available nickel chloride 10 g / L, commercially available boric acid 30 g / L, and anti-pitcher (manufactured by Ebara Yujilite Co., Ltd.) , Antipiter # 82 (brand name)) was prepared at a concentration of 2 mL / L to obtain "Electrolytic Nickel Plating Solution A".

<Measuring method of film thickness of gold film and evaluation method of gold selective precipitation performance>

The film thickness of the gold film was measured using the fluorescent X-ray analyzer (SFT9255, Seiko Instruments Co., Ltd. product) in the vicinity of the center electrolytic gold-plated by circular shape. The results are shown in Table 3.

When the electrolytic gold plating process was carried out at a current density of 5 A / dm 2, the film thickness of the gold film was determined to be 0.1 μm or less as the optimum electrolytic gold plating solution for the nickel barrier plating technique having excellent gold selective precipitation performance. 0.1 micrometer or less is made into "good | favorableness", the thing thicker than 0.1 micrometer is made into "defect", and a result is shown in Table 3.

In addition, when the electrolytic gold plating treatment was carried out at a current density of 40 A / dm 2, the film thickness of the gold coating was 5 times or more that the electrolytic gold plating treatment was performed at a current density of 5 A / dm 2. It determined with the electrolytic gold plating solution optimal for this excellent nickel barrier plating technique. 5 times or more is made into "good", less than 5 times is made into "bad", and a result is shown in Table 3.

<Measuring method of gold purity of gold film>

Cathode current density of 40 A / dm 2 on the primary glossy nickel plated coating on a copper plate of 10 mm × 10 mm in a step shown in Table 2 using the electrolytic gold plating solution prepared in each example and each comparative example. The 50-micrometer electrolytic gold plating film was produced by the jet jet gold plating method, and a copper material and a nickel plating film were dissolved with nitric acid to produce a gold foil. After measuring the weight of the produced gold leaf, it was dissolved in 20 mL of aqua regia and quantitatively analyzed Cu, Ni, Co, Fe as an impurity element with an ICP emission spectrophotometer (SPS3000, manufactured by Seiko Instruments Inc.). Gold purity was calculated from the mass of precipitated gold and the mass of impurities. The results are shown in Table 3. In Table 3, "%" represents "mass%."

<Relationship between current density and film thickness of gold film>

Using the general-purpose electrolytic gold plating solution containing no specific heterocyclic compound and electrolytic gold plating solution of Example 1 of the present invention, any electrolytic gold plating solution was set to 9 g / L in terms of gold. And bath temperature were heated up at 50 degreeC, and the gold plating was performed on 2.0 micrometers of primary glossy nickel plating films on the copper plate which is 10 mm x 10 mm by the process of Table 2 mentioned above. As for gold plating, the current density was 1 A / dm 2, 5 A / dm 2, 10 A / dm 2, 15 A / dm 2 (only in the electrolytic gold plating solution of Example 1) by the jet jet gold plating method described above. Electrolytic gold plating was carried out for 10 seconds by changing to A / dm 2, 30 A / dm 2, 40 A / dm 2, 50 A / dm 2, 60 A / dm 2, and the vicinity of the center of the gold-plated circle was described. The film thickness of the gold film was measured by the method. The graph which plotted the measurement result is shown in FIG.

In 0 A / dm 2 to 5 A / dm 2 (low current density range), in the electrolytic gold plating solution of Example 1, the film thickness of the gold film was very thin, but in the general-purpose electrolytic gold plating solution, a thick gold film was formed. It has become. Moreover, in 20 A / dm <2> -60 A / dm <2> (high current density range), the electrolytic gold plating liquid of Example 1 was able to form the gold film of film thickness more than the general-purpose electrolytic gold plating liquid.

As found in the present invention, in the nickel barrier plating technique, the low current density range corresponds to the portion not to be plated with gold, and the high current density range is considered to correspond to the portion to be gold-plated. The thinner and thinner the film thickness of the gold film, the thicker the film thickness in the high current density region, the better the nickel barrier property. Therefore, the electrolytic gold plating solution of Example 1 containing a specific heterocyclic compound has "excellent performance adapted to nickel barrier plating technology" from the properties and the reason shown in FIG.

<Apply for High Precision Connector>

In the process shown in Table 2, using the electrolytic gold plating solution prepared in Example 1 and Comparative Example 1, 2.0 µm of a primary glossy nickel plating film was applied on copper of the high precision connector. Next, as shown in FIG. 2, the silicone rubber member is pressurized only to the part (nickel barrier part) which does not intend to carry out electrolytic gold plating, and the average cathode current density 40A / at 50 degreeC. An electrolytic gold plated film was produced by the jet jet gold plating method for 10 seconds at d m 2. The form of the connector in the nickel barrier plating technique used above is shown in FIG. 2, and the film thickness distribution of the position corresponding to FIG. 2 when the electrolytic gold plating solution prepared in Example 1 is used is shown in FIG.

In the case of using the electrolytic gold plating solution of Example 1, only the gold film having a thickness of 0.05 μm or less was always formed in the portion (nickel barrier portion) (the portion where the silicon rubber member was pressed) where the electrolytic gold plating was not to be performed. As for the part which is going to electrolytic gold plating (part which did not pressurize a silicone rubber member), the gold film of average 0.67 micrometer was formed over the whole. Moreover, only the gold film of 0.03 micrometer or less was always formed also in the side surface of the part which pressurized the silicone rubber member. Since almost no gold film was formed at the edges of the nickel barrier portion, no smudges of solder were observed.

On the other hand, in the case where the electrolytic gold plating solution of Comparative Example 1 was used, even in a portion where the silicon rubber member was pressed, there was a portion in which a gold film having a thickness of 0.2 µm was formed. Moreover, the part in which the 0.2 micrometer gold film was formed also in the side surface of the part which pressed the silicone rubber member. Therefore, even in a portion where electrolytic gold plating is not to be performed, since a thin gold film was formed, a barrier effect of nickel was not sufficient, and a solder smudge was observed.

<Arrangement of Examples and Comparative Examples>

In Examples 1 to 11 using the electrolytic gold plating solution of the present invention, the gold film thickness at the current density of 5 A / dm 2 was 0.1 μm or less, and the film of the gold film at the current density of 5 A / dm 2. It can be seen that the ratio of the film thickness of the gold film at the thickness and the current density of 40 A / dm 2 is 1: 5 or more, and the gold selective precipitation performance is both “good” and thus the gold plating solution is optimal for nickel barrier plating.

Moreover, the gold film obtained using the electrolytic gold plating liquid of this invention of Example 1-Example 11 had mechanical characteristics, such as excellent abrasion resistance, corrosion resistance, and electrical characteristics. In particular, the gold alloy film obtained by using the electrolytic gold alloy plating solution of Examples 1 to 10 had mechanical characteristics such as excellent wear resistance.

On the other hand, in Comparative Examples 1 to 12, the film thickness of the gold film at the current density of 5 A / dm 2 was greatly larger than 0.1 μm, and the film thickness of the gold film at the current density of 5 A / dm 2 was The ratio of the gold film thickness at the current density of 40 A / dm 2 is less than 1: 5, and the difference between the gold deposition film thickness at the low current density region and the gold deposition film thickness at the high current density region is small, and both are gold selective precipitation. It is found that the performance is not suitable for nickel barrier plating.

As a result of application to the actual connector, if the difference between the gold deposition film thickness in the low current density region and the gold precipitation film thickness in the high current density region is large, it can be confirmed that the electrolytic gold plating solution is suitable for nickel barrier plating. Examples 1 to 11 It can be seen that the electrolytic gold plating solution of is suitable for nickel barrier plating.

Industrial availability

Since the gold film obtained by using the electrolytic gold plating solution of the present invention has excellent mechanical properties, corrosion resistance and electrical properties, and is excellent in gold selective precipitation performance, a nickel barrier is currently used in contact members of electronic devices. Optimum for plating, nickel barrier plating can be applied to a connector or micronized connector of a complicated shape which has been considered very difficult so far, and is widely used in this field.

This application is based on the JP Patent application 2008-153188 of the Japanese patent application for which it applied on June 11, 2008, and all the content of that application is integrated here as an indication of the specification of this invention.

Claims (15)

An electrolytic gold plating solution comprising a gold cyanide salt as a gold source, and a heterocyclic compound having at least one nitrogen atom in a ring and in which at least one nitro group is substituted for a carbon atom in the ring. The method of claim 1,
Furthermore, the electrolytic gold plating solution containing cobalt salt, nickel salt, and / or iron salt. The method of claim 1,
The electrolytic gold plating solution wherein said gold cyanide salt is cuprous cyanide, cuprous cyanide potassium, cuprous cyanide ammonium, cuprous cyanide sodium, cupric cyanide potassium or cupric ammonium cyanide. The method of claim 1,
The heterocyclic compounds include pyrrole, imidazole, pyrazole, triazole, tetrazole, oxazole, isoxazole, indole, pyridine, pyridazine, pyrimidine, pyrazine, uracil, cytosine, thymine, adenine, guanine, An electrolytic gold plating solution in which at least one nitro group is substituted with a carbon atom of quinoline, isoquinoline, quillin, isoquisaline, acridine, cinosolin or morpholine. The method of claim 2,
The heterocyclic compounds include pyrrole, imidazole, pyrazole, triazole, tetrazole, oxazole, isoxazole, indole, pyridine, pyridazine, pyrimidine, pyrazine, uracil, cytosine, thymine, adenine, guanine, An electrolytic gold plating solution in which at least one nitro group is substituted with a carbon atom of quinoline, isoquinoline, quillin, isoquisaline, acridine, cinosolin or morpholine. The method of claim 1,
The heterocyclic compound includes nitropyrrole, dinitropyrrole, nitroimidazole, dinitroimidazole, nitropyrazole, dinitropyrazole, nitrotriazole, dinitrotriazole, nitrotetazole, nitrooxazole, Dinitrooxazole, nitroisoxazole, dinitroisoxazole, nitroindole, nitropyridine, dinitropyridine, nitropyridazine, dinitropyridazine, nitropyrimidine, dinitropyrimidine, nitropyrazine, dinitropyrazine, Nitrouracil, nitrocytosine, nitrothymine, nitroadenine, nitroguanine, nitroquinoline, dinitroquinoline, nitroisoquinoline, dinitroisoquinoline, nitroquisaline, dinitroisoquisaline, nitroacridine, nitrocinnoline, An electrolytic gold plating solution that is dinitrocin nosolin, nitromorpholine or dinitromorpholine. The method of claim 2,
The heterocyclic compound includes nitropyrrole, dinitropyrrole, nitroimidazole, dinitroimidazole, nitropyrazole, dinitropyrazole, nitrotriazole, dinitrotriazole, nitrotetazole, nitrooxazole, Dinitrooxazole, nitroisoxazole, dinitroisoxazole, nitroindole, nitropyridine, dinitropyridine, nitropyridazine, dinitropyridazine, nitropyrimidine, dinitropyrimidine, nitropyrazine, dinitropyrazine, Nitrouracil, nitrocytosine, nitrothymine, nitroadenine, nitroguanine, nitroquinoline, dinitroquinoline, nitroisoquinoline, dinitroisoquinoline, nitroquisaline, dinitroisoquisaline, nitroacridine, nitrocinnoline, An electrolytic gold plating solution that is dinitrocin nosolin, nitromorpholine or dinitromorpholine. The method of claim 2,
The cobalt salt is cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt carbonate, phthalocyanine cobalt, cobalt stearate, ethylenediamine tetraacetic acid cobalt, naphthenic acid cobalt, cobalt borate, cobalt thiocyanate, cobalt sulfamate, cobalt acetate , Electrolytic gold plating solution which is cobalt citrate, cobalt hydroxide, cobalt oxalate or cobalt phosphate. The method of claim 2,
The nickel salt is nickel sulfate, nickel acetate, nickel chloride, nickel borate, nickel benzoate, nickel oxalate, nickel naphthenate, nickel oxide, nickel phosphate, nickel stearate, nickel tartarate, nickel thiocyanate, nickel amide sulfate, carbonic acid An electrolytic gold plating solution which is nickel, nickel citrate, nickel formate, nickel cyanide, nickel hydroxide, nickel nitrate or nickel octanoate. The method of claim 2,
The iron salt is ferrous sulfate, ferric sulfate, ferrous chloride, ferric chloride, ferrous citrate, ferric citrate, ferric formate, ferric hypophosphite, ferric naphthenate Ferric stearate, ferric pyrolate, ferrous tartarate, ferric tartarate, ferric thiocyanate, ferric thiocyanate, ferrous fumarate, ferrous gluconate, ethylenediamine 4 An electrolytic gold plating solution which is iron acetate, ferrous nitrate or ferric nitrate. The method according to any one of claims 1 to 10,
When the current density was set to 5 A / dm 2 and 40 A / dm 2 for 10 seconds using the jet jet plating apparatus, the film thickness of the gold film at the current density of 5 A / dm 2 was The electrolytic gold plating solution which is 0.1 micrometer or less and whose film thickness of the gold film at 40 A / dm <2> is 5 times or more of the film thickness of the gold film at 5 A / dm <2>. The gold film obtained by performing electrolytic gold plating on a nickel film using the electrolytic gold plating liquid as described in any one of Claims 1-10. The gold film obtained by performing electrolytic gold plating on a nickel film using the electrolytic gold plating liquid of Claim 11. The method of claim 12,
The gold film of which gold purity of the said gold film is 95 mass% or more. The method of claim 13,
The gold film of which gold purity of the said gold film is 95 mass% or more.

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