JPH1161426A - Electroless tin and tin alloy plating bath, electroless plating and electronic part coated with tin or tin alloy film in the electroless plating bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the growing activity of a dendrite in a plating film to be formed, to increase film forming property and joining strength and to improve reliability of a high-density product such as a fine pitch printed circuit board by adding a phosphorus compd. to a plating bath. SOLUTION: The plating bath consists of a soluble salt of either a stannous salt or a mixture of stannous salt and a specified metal such as bismuth, zinc and copper, and one of org. acids such as org. sulfonic acid and carboxylic acid and inorg. acids such as hydrochloric acid and sulfuric acid, and a complexing agent, and a dendrite inhibitor comprising a phosphorus compd. The phosphorus compd. is selected from inorg. phorphorus compds. such as orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, hypophosphorous acid, phosphorus acid, and their salts and org. phosphorus compds. such as methylene phosphonic acid, alkylphosphate and their salts. The phosphorus compd. may be used in a single state or a mixture and is added by 0.01 to 100 g/l, preferably 0.1 to 5 g/l in the plating bath.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless tin and tin alloy plating bath, a plating method, and an electronic component such as a TAB film carrier having a tin or tin alloy film formed in the electroless plating bath. That can effectively prevent the growth of a (state-like material) and provide a tin or tin alloy plating film having excellent film-regulating properties.

[0002]

BACKGROUND OF THE INVENTION In recent years, a tin plating bath or a tin alloy plating bath such as a tin-lead alloy has been used as a film for improving solderability, and for surface treatment of electronic components such as semiconductor devices, connectors and chip components. It is widely used. On the other hand, these electronic components are becoming smaller, more complex, and multi-pinned year by year, and the area to be joined by soldering is becoming finer. Strongly required.

However, in general, in an electroless tin or tin alloy plating bath, a film to be obtained is abnormally deposited in a needle-like or sponge-like form, and so-called dendrite is often observed over the entire surface. Usually, an excellent plating film has a microscopically uniform and dense particle shape.
Although properties such as possessing white or silvery luster (macroscopically) (so-called film-regulating properties; specifically, see FIG. 2) are observed, the precipitates in which dendrites are formed are powdery and brittle. It has almost no film-regulating properties, is no longer a practical plating film, and is out of the evaluation target such as bonding strength. Even if the generation of dendrites in the deposited film remains in a spot-like (partial) state, the film-forming property of the entire plating film is reduced, and the deterioration of the bonding strength is inevitable. Moreover, since the film is dark and has poor gloss, its commercial value is low.

Accordingly, in order to maintain high reliability of high-density mounting products such as TAB and SMT-compatible fine pitch printed circuit boards, it is necessary to reliably prevent the above-mentioned dendrite from being generated in the plating film and to reduce the bonding strength. It is particularly necessary to hold it properly.

[0005]

2. Description of the Related Art For example, an electroless tin plating bath disclosed in JP-A-63-230883 (hereinafter referred to as prior art 1), or an electroless tin-lead alloy plating bath disclosed in JP-A-1-184279 (hereinafter referred to as "prior art 1"). , Referred to as prior art 2) describes adding various surfactants to smooth the surface of the plating film.

[0006]

However, even if a surfactant is added as a leveling agent to the electroless plating bath as in the above-mentioned prior art 1 or 2, the precipitate actually grows into dendrite. It is difficult to control. Even if dendrite can be prevented from being generated on the entire surface of the precipitate, it is not easy to prevent spot-like generation, and it is necessary to obtain a practical plating film having film-forming properties and bonding strength. Still have many inadequate points.

An object of the present invention is to develop an electroless bath capable of imparting a tin or tin alloy plating film having excellent film-regulating properties by reliably suppressing dendrite growth.

[0008]

In the above prior arts 1 and 2, an electroless tin or tin-lead alloy plating bath containing sodium hypophosphite is described, wherein hypophosphite is used as a reducing agent. Techniques for use in electroless baths are well known in the art. In addition, Japanese Patent Application Laid-Open No. 4-72071 (hereinafter referred to as
Prior art 3), hypophosphorous acid or a salt thereof as an antioxidant in an electroless tin or tin-lead alloy plating bath,
It is described that phosphoric acid or condensed phosphoric acid is contained in order to stably dissolve tin and thiourea.

As described above, the present inventors have hypophosphorous acid or a salt thereof used as a reducing agent (or an antioxidant) in an electroless plating bath, or phosphoric acid used for stable dissolution. Alternatively, focusing on condensed phosphoric acid, first, hypophosphorous acid, condensed phosphoric acid, and the like are further expanded to organic phosphorus compounds such as aminotri (methylenephosphonic acid) and alkyl phosphate, whereby these compounds are phosphorylated. From the compound aspect
We grasped (as a general concept) and studied intensively what the phosphorus compound does to the deposited film when it is contained in an electroless tin or tin alloy plating bath. As a result, the phosphorus compound has a strong effect not only on the action of the plating bath such as the reducing action or the stable dissolving action, but also on the properties of the resulting plating film (particularly, the film-forming property of the film). I found it. That is, when the above-mentioned phosphorus compound was blended in the electroless tin or tin alloy bath, it was found that the generation of dendrites was surely suppressed, and the film-forming property was improved, and the present invention was completed.

The present invention relates to (A) a stannous salt and a salt of a stannous salt and a metal selected from the group consisting of bismuth, indium, antimony, zinc, cobalt, nickel, silver, copper and lead. (B) organic acids such as organic sulfonic acids and carboxylic acids, or at least one acid selected from inorganic acids such as hydrochloric acid, sulfuric acid and borofluoric acid; An electroless tin and tin alloy plating bath containing a complexing agent and a dendrite inhibitor comprising a phosphorus compound (D).

The present invention 2 is the invention according to the above-mentioned invention 1, wherein (D)
Phosphoric acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, polyphosphoric acid, hypophosphorous acid, phosphorous acid, and their sodium salt, potassium salt, calcium salt, magnesium salt, ammonium salt, barium salt, iron salt, Inorganic phosphorus compounds such as salts such as zinc salts, aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), alkyl phosphate (e.g., ethylphosphoric acid, diethylphosphoric acid, etc.) And at least one of organic phosphorus compounds such as salts such as sodium salt, potassium salt, calcium salt, magnesium salt, ammonium salt, barium salt, iron salt and zinc salt.

The present invention 3 is characterized in that, in the above-mentioned present invention 1 or 2, the acid (B) is an organic acid.

The present invention 4 is characterized in that a reducing agent is further added to the electroless plating bath of any of the above-mentioned present inventions 1 to 3.

A fifth aspect of the present invention is characterized in that a surfactant is further added to the electroless plating bath according to any one of the first to fourth aspects of the present invention.

According to a sixth aspect of the present invention, there is provided an electronic component having a tin or tin alloy film formed by immersing the electronic component in the electroless plating bath according to any one of the first to fifth aspects.

According to a seventh aspect of the present invention, in the sixth aspect, the electronic component is a TAB film carrier.

The present invention relates to (A) a stannous salt and a salt of a stannous salt and a metal selected from the group consisting of bismuth, indium, antimony, zinc, cobalt, nickel, silver, copper and lead. (B) organic acids such as organic sulfonic acids and carboxylic acids, or at least one acid selected from inorganic acids such as hydrochloric acid, sulfuric acid and borofluoric acid; Complexing agent, by applying plating using an electroless tin or tin alloy plating bath containing a (D) phosphorus compound, to obtain a tin or tin alloy film with suppressed dendrites, This is a tin alloy plating method.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The above phosphorus compound as a dendrite inhibitor is as follows (1) and (2). (1) orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, polyphosphoric acid, hypophosphorous acid, phosphorous acid, and their sodium, potassium, calcium, magnesium, ammonium, barium, iron, and zinc salts And inorganic phosphorus compounds such as salts. However, for example, the sodium salt of orthophosphoric acid includes hydrogen phosphate such as sodium hydrogen phosphate. (2) aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), alkyl phosphate (e.g., ethylphosphoric acid, diethylphosphoric acid, etc.), and their sodium salts, potassium Organic phosphorus compounds such as salts such as salts, calcium salts, magnesium salts, ammonium salts, barium salts, iron salts and zinc salts. The phosphorus compound can be used alone or in combination. The amount of the phosphorus compound is generally 0.01 to 100 g / L, preferably 0.05 to 10 g / L, more preferably 0.1 to 100 g / L based on the entire plating bath.
It is 5 g / L.

The present invention is directed to a tin plating bath and a tin alloy plating bath.
It refers to an alloy of tin and at least one specific metal selected from bismuth, indium, antimony, zinc, cobalt, nickel, silver, copper, and lead. Specifically, tin-bismuth, tin-indium, tin-antimony, tin-
Binary tin alloys such as zinc, tin-cobalt, tin-nickel, tin-silver, tin-copper, tin-lead, and ternary tin alloys such as tin-nickel-zinc and tin-copper-zinc Alloys are also included.

As the stannous salt, any soluble salts can be used, and the following acids (particularly, organic sulfonic acids)
And a complex salt (water-soluble) obtained by dissolving a metal or metal oxide in the acid can also be used. On the other hand, the salt of the specific metal that forms an alloy with tin is mixed with various metal ions (Bi ³⁺ , In ³⁺ , Sb ³⁺ , Zn) in a plating bath.
²⁺ , Co2 ⁺ , Co3 ⁺ , Ni2 ⁺ , Ag ⁺ , Cu ⁺ , Cu2 ⁺ ,
Pb ²⁺ ) or any soluble salt that produces
Among them, salts with the below-mentioned acids (particularly, organic sulfonic acids) are preferable.

Specific examples of the soluble salt of the above-mentioned specific metal are as follows. (1) Oxide: Bi ₂ O ₃ , In ₂ O ₃ , ZnO, PbO, Ag
₂ O, Cu ₂ O, CuO, CoO, NiO and the like. (2) halides: BiCl ₃ , InCl ₃ , PbCl ₂ ,
BiI ₃ , InI ₃ , ZnCl ₂ , ZnBr ₂ , ZnI ₂ ,
PbI ₂ , BiBr ₃ , InBr ₃ , PbBr ₂ , AgC
1, AgBr, CuCl, CuBr, CuI, SbCl
₃ , CoCl ₂ , NiCl _{2 and the} like. (3) Salts with inorganic and organic acids, and others: bismuth nitrate, bismuth sulfate, lead acetate, indium sulfate, zinc sulfate, indium methanesulfonate, indium ethanesulfonate, lead methanesulfonate, lead ethanesulfonate,
Lead 2-propanesulfonate, lead phenolsulfonate,
Bismuth methanesulfonate, bismuth 2-propanolsulfonate, bismuth p-phenolsulfonate, zinc methanesulfonate, zinc p-phenolsulfonate, antimony tartrate, silver nitrate, silver methanesulfonate, silver citrate, p-phenolsulfonate Cupric, Cu ₃ P, C
uSCN, CuBr (S (CH ₃ ) ₂ ), antimony methanesulfonate, antimony borofluoride, cobalt sulfate, cobalt acetate, nickel sulfate, nickel methanesulfonate and the like.

The above-mentioned soluble salt of the specific metal can be used alone or in combination. The total concentration of tin in the tin bath (converted addition amount as a metal) or the total concentration of tin and other specific metals in the tin alloy bath is generally 5 to 100 g / L.

As the above-mentioned acid, alkanesulfonic acid, which has a relatively mild reaction in a plating bath and is easy to treat waste water,
Organic sulfonic acids such as alkanolsulfonic acids or organic acids such as carboxylic acids are preferred, but inorganic acids such as hydrochloric acid, hydrofluoric acid, sulfuric acid, hydrofluoric acid and perchloric acid can also be selected. The above acids are used alone or in combination, and the amount of the acid is generally 0.1 to 200 g / L, preferably 10 to 150 g / L.

As the alkanesulfonic acid, those represented by the chemical formula C _n H _{2n + 1} SO ₃ H (for example, n = 1 to 11) can be used. Specifically, methanesulfonic acid, ethanesulfonic acid, Examples thereof include 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid, and dodecanesulfonic acid.

[0025] Examples of the alkanol sulfonic acid, the formula _{C m H 2m + 1 -CH (} OH) -C p H 2p -SO 3 H ( e.g., m
= 0 to 2, p = 1 to 10), specifically, 2-hydroxyethane-1-sulfonic acid,
Hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1
-In addition to sulfonic acid, 1-hydroxypropane-2-
Sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, 2-hydroxydodecane-1- Sulfonic acid and the like.

Specific examples of the carboxylic acid include acetic acid,
Propionic acid, butyric acid, citric acid, tartaric acid, gluconic acid,
Sulfosuccinic acid, lactic acid, oxalic acid, malonic acid, thioglycolic acid, salicylic acid, malic acid and the like.

The receiving base metal plated with tin is:
For example, copper, copper alloy, iron, nickel, iron-42% nickel alloy, which forms a circuit pattern on the TAB method,
Zinc, aluminum, etc. The receiving side may be a non-metal surface such as plastic or ceramic to which a catalyst such as palladium is applied.

The complexing agent coordinates with the base metal such as copper or copper alloy to form a complex ion.
It is preferable to use the chelating agents (1) to (3) alone or in combination. (1) Thiourea and derivatives thereof As a derivative of thiourea, 1,3-dimethylthiourea, trimethylthiourea, diethylthiourea (for example,
1,3-diethyl-2-thiourea), N, N'-diisopropylthiourea, allylthiourea, acetylthiourea,
Ethylenethiourea, 1,3-diphenylthiourea, thiourea dioxide, thiosemicarbazide and the like can be mentioned. (2) Ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid disodium salt (EDTA2Na), hydroxyethylethylenediaminetriacetic acid (HEDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), ethylenediaminetetrapropion Acid, ethylenediaminetetramethylenephosphoric acid, diethylenetriaminepentamethylenephosphoric acid and the like. (3) nitrilotriacetic acid (NTA), iminodiacetic acid (IDA),
Iminodipropionic acid (IDP), aminotrimethylene phosphate, aminotrimethylene phosphate pentasodium salt, benzylamine, 2-naphthylamine, isobutylamine,
Isoamylamine, methylenediamine, ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine,
Tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, cinnamylamine, p
-Methoxycinnamylamine and the like. The amount of the complexing agent is generally 0.1 to 300 g / L,
Preferably it is 5-200 g / L.

The reducing agent of the present invention 4 is added for the purpose of reducing the metal salt and adjusting the deposition rate thereof, and it is preferable to use an amine borane, a borohydride compound, a hydrazine derivative or the like singly or in combination. preferable. Further, among the phosphorus compounds of the present invention, hypophosphorous acid, phosphorous acid, or a salt thereof can also be used as a reducing agent. Examples of the amine borane include dimethylamine borane, diethylamine borane, trimethylamine borane, isopropylamine borane, and morpholine borane. Examples of the borohydride compound include sodium borohydride, potassium borohydride, and the like. As the hydrazine derivative, hydrazine hydrate, hydrazine hydrochloride,
Phenylhydrazine and the like. When hypophosphorous acid or its hypophosphorous acid compound such as ammonium, lithium, sodium, potassium or calcium salt is selected as the phosphorus compound contained in the electroless bath as the dendrite inhibitor of the present invention, The dendrite inhibitor can also serve as the reducing agent. The amount of the reducing agent is generally 0.01 to 200 g / L, preferably 1 to 150 g / L.
L.

The surfactant of the present invention 5 is added in order to improve the denseness, adhesion, smoothness, etc. of the plating film, and includes a nonionic surfactant, an amphoteric surfactant, a cationic surfactant, Anionic surfactants can be used alone or in combination, and among them, nonionic or amphoteric surfactants are preferred. In general, the amount of the surfactant added is 0.1.
The amount is from 01 to 50 g / L, preferably from 1 to 20 g / L.

Examples of the nonionic surfactant include nonylphenol polyalkoxylate, α- (or β-) naphthol polyalkoxylate, dibutyl-β-naphthol polyalkoxylate, styrenated phenol polyalkoxylate, cumylphenol polyalkoxylate. Nonionic surfactants such as polyacrylates and bisphenol A polyalkoxylates, or amine nonionics such as laurylamine polyalkoxylate, octylamine polyalkoxylate, hexynylamine polyalkoxylate, and linoleylamine polyalkoxylate Surfactants and the like.

Examples of the amphoteric surfactant include 2-undecyl-1-carboxymethyl-1-hydroxyethylimidazolium betaine, N-stearyl-N, N-dimethyl-N-carboxymethylbetaine and lauryl dimethylamine oxide. No.

The cationic surfactant includes, in the form of salts, lauryltrimethylammonium salt, lauryldimethylammonium betaine, laurylpyridinium salt, oleylimidazolium salt, stearylamine acetate and the like.

Examples of the anionic surfactant include alkyl sulfates such as sodium lauryl sulfate, polyoxyalkylene alkyl ether sulfates such as sodium polyoxyethylene (EO12) nonyl ether sulfate, and polyoxyethylene (EO20) octyl phenyl ether. Examples include polyoxyalkylene alkyl phenyl ether sulfates such as potassium sulfate, and alkylbenzene sulfonates such as ammonium laurylbenzenesulfonate.

As the conditions of the plating bath of the present invention, the bath temperature is about 45 to 90 ° C., but from the viewpoint of increasing the deposition rate, it is preferably about 50 to 70 ° C. In addition, the plating bath of the present invention, in addition to various additives such as the above brightener, semi-brightener,
Needless to say, an antioxidant such as hydroquinone, catechol, resorcin, pyrogallol, or a pH adjuster, a buffer, a wetting agent, and the like used in a normal plating bath can be added.

The electronic component of the present invention 6 includes a TAB film carrier, a resistor, a capacitor, a connector, an inductor, a semiconductor printed board, and the like. For example,
Invention 7 is a TAB film carrier in which the electroless tin or tin alloy plating bath of Inventions 1 to 5 is applied to TAB, and an electroless plating film is formed on an inner lead or the like.

[0037]

In general, in the electroless plating process of tin or a tin alloy, the precipitate during the formation continues crystal growth with a specific direction at many active points on its surface (that is, at each active point). Since the crystal tends to grow only in a specific direction), it tends to grow into dendrites via fine needle-like crystals. However, when a phosphorus compound is present in the electroless plating bath, the phosphorus compound is adsorbed at the active points on the surface of the film, thereby reducing the activity of crystal growth and inhibiting crystal growth in a specific direction. In order to promote uniform crystal growth throughout (ie, to grow crystals in all directions), it can be estimated that the tin or tin alloy plating film is effectively suppressed from growing in a dendrite shape.

On the other hand, when an electroless tin or tin alloy plating bath is used for a long time, even when an antioxidant or the like is added,
Stannous ions in the bath undergo air oxidation and change to stannic ions, which are further hydrolyzed to easily generate colloidal particles of stannic oxide. Since the fine particles of stannic oxide are finer than the pore size of the filter of the filter provided in the plating apparatus, it is difficult to capture and remove the fine particles with the filter. In addition, many water molecules are adsorbed on stannic oxide, and it is presumed that these water molecules are a major factor inhibiting aggregation of stannic oxide or crystal growth. However, when the phosphorus compound of the present invention is added to the electroless plating bath, the phosphorus compound acts on this water molecule, and agglomeration (or crystal growth) of stannic oxide occurs.
Can be promoted. For this reason, when the electroless tin and tin alloy plating baths are used for a long time, if the phosphorus compound of the present invention is blended, even if fine particles of stannic oxide are generated,
Since the particle diameter of stannic oxide can be increased by the coagulation action of the phosphorus compound and the stannic oxide can be quickly removed from the plating bath, the transparency of the bath is stabilized over time, and the bath can be easily managed.

When electroless plating is performed in the presence of the above-mentioned stannic oxide fine particles, many water molecules are adsorbed on the surface of the fine particles as described above. The adsorbed stannic oxide is eutectoid with the plating film. Therefore, the TA with the electroless plating film formed
When soldering is applied to a member such as B, the water vaporizes and expands due to the heat, and voids (bubbles) are generated in the solder joint, and there is a possibility that the joint strength is reduced. However, when the phosphorus compound of the present invention is added to the plating bath, as described above, the harmful effect of voids can be eliminated by removing stannic oxide in advance, so that the reliability of the bonding strength of the plating film also increases from this side. Can hold.

In the aggregating action of the above-mentioned phosphorus compound on the plating bath, pyrophosphoric acid or a salt thereof has a greater aggregating ability than other phosphorus compounds, and hypophosphorous acid, phosphorous acid or a salt thereof is particularly oxidized. In addition to the action of aggregating the stannic fine particles, it also has the ability to reduce the amount of stannic oxide generated itself.

[0041]

【The invention's effect】

(1) As in the present invention 1 or 8, when a phosphorus compound is present in the electroless plating bath, the activity of crystal growth of the plating film is reduced, and the generation of dendrites in the tin or tin alloy plating film is reduced. Can be effectively suppressed. That is, not only can the entire precipitate be prevented from becoming dendrite-like, but also the occurrence of spots of dendrite can be surely prevented, so that the film uniformity of the tin or tin alloy film can be improved. For this reason, the plating film has a dense crystal particle shape suitable for bonding, and the bonding strength of the film can be improved satisfactorily (see FIG. 2).

In addition, when electroless plating is performed using the tin or tin alloy bath of the present invention, it is possible to sufficiently cope with a high-density mounting product such as the TAB method of the present invention 6, and the T
The reliability and production yield of products (such as liquid crystal) using AB can be improved satisfactorily. In addition, the obtained plating film is rich in film-regulating properties and dense, so that it has high gloss of metallic color (silver color), good appearance, and can enhance the value of electroless plated products.

According to the above-mentioned prior art 3, stannous ions or stannous ions and lead ions are dissolved in phosphoric acid or condensed phosphoric acid, thiourea is added, and hypophosphorous acid is used as a reducing agent. Or use of a salt thereof, the deposition rate is high, the thickness is easy, and the plating film obtained is also good (the lower right column of the upper right column to the lower left column, line 6 of page 2 of the publication). reference). Therefore, when the description of the goodness of the plating film is examined from the entire description of the prior art 3, the relationship between the plating time and the deposition film thickness is emphasized in the examples and drawings, and the deposition rate of the plating bath is reduced. Although the improvement is considered to be the main purpose of this technology, the properties of the plating film
There is no specific reference to (especially the appearance of the film).
In other words, there is no description that directly describes what aspect of the film properties is improved and to what extent, and there is no expression that suggests it.

(2) As shown in a test example described later, the present invention 3 wherein a phosphorus compound was added to an organic acid bath such as an organic sulfonic acid.
As compared with the case of adding to an inorganic acid bath, a synergistic effect of an organic acid and a phosphorus compound can be expected, so that the ability to suppress dendrite increases, and the film uniformity of a plating film is further improved,
The reliability of the bonding strength of the plating film increases.

(3) As in the present invention 4, when a reducing agent is additionally mixed into the electroless plating bath, the deposition rate of tin can be increased, and the productivity of plating can be increased.

(4) As in the present invention 5, when a surfactant is additionally mixed into the electroless plating bath, the smoothness, adhesion, and denseness of the plating film can be further improved.

<< Examples >> Examples of electroless plating baths of tin and tin alloy will be sequentially described below, and dendrite generation will be observed by visual observation and observation using an electron microscope with respect to the plating films obtained in the respective examples. An example of a film appearance test in which the presence or absence and the state thereof were examined will be described. It should be noted that the present invention is not limited to the following embodiments, and it is needless to say that many modifications can be made within the technical idea of the present invention.

In the following Examples 1 to 16 and Comparative Examples 1 to 3, Examples 1 to 11 and Comparative Examples 1 to 3 are electroless plating baths based on organic acids (specifically, organic sulfonic acids). And the remaining Examples 12 to 16 are electroless baths based on inorganic acids. Comparative Examples 1 to 3 are tin-lead alloy plating baths each having a basic composition of a soluble metal salt, an organic sulfonic acid, and a complexing agent, and Comparative Example 1 is a bath containing no phosphorus compound.
Comparative Example 2 was a bath in which a nonionic surfactant was added as a so-called smoothing agent instead of a phosphorus compound, and Comparative Example 3 was a hydrazine derivative instead of a phosphorus compound added as a so-called reducing agent in the presence of a nonionic surfactant. It is a bath.

Example 1 An electroless tin plating bath was constructed with the following composition. Stannous methanesulfonate (as Sn ²⁺ ): 34 g / L Methanesulfonic acid: 70 g / L Acetylthiourea: 100 g / L Sodium hypophosphite: 5 g / L This tin plating bath is kept at 65 ° C. Then, a test piece of a TAB film carrier patterned with VLP (a type of electrolytic copper foil) was immersed for 5 minutes, and subjected to electroless plating. The resulting tin-plated film had a thickness of 0.45 μm.

Example 2 An electroless tin-lead alloy plating bath having the following composition was prepared. Stannous ethanesulfonate (as Sn ²⁺ ): 18 g / L Lead ethanesulfonate (as Pb ²⁺ ): 8 g / L Ethanesulfonic acid: 150 g / L Thiourea: 80 g / L Metaphosphoric acid : 85g / L ・ Nonylphenol polyethoxylate (EO15): 5g / L This tin-lead alloy plating bath was maintained at 65 ° C and VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film has a thickness of 0.48 μm and a thickness of 5 μm.
% Lead content.

Example 3 An electroless tin-lead alloy plating bath having the following composition was prepared. • Stannous p-phenolsulfonate (as Sn ²⁺ ): 22 g / L • Lead p-phenolsulfonate (as Pb ²⁺ ): 17 g / L • p-phenolsulfonate: 80 g / L • 1,3 -Dimethylthiourea: 125 g / L Pyrophosphoric acid: 40 g / L This tin-lead alloy plating bath was maintained at 65 ° C. and VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film has a thickness of 0.65 μm and a thickness of 1 μm.
It had a lead content of 8%.

Example 4 An electroless tin-lead alloy plating bath was constructed with the following composition. Stannous p-phenolsulfonate (as Sn2 ⁺ ): 15 g / L 2-Hydroxypropane-1-leadsulfonate (as Pb2 ⁺ ): 15 g / L 1-butanesulfonic acid: 85 g / L・ Diethylthiourea: 110 g / L ・ Potassium phosphite: 20 g / L ・ N-lauryl-N, N-dimethyl-N-carboxymethylbetaine: 10 g / L This tin-lead alloy plating bath was kept at 65 ° C. , VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film has a thickness of 0.51 μm and a thickness of 2 μm.
It had a lead content of 5%.

Example 5 An electroless tin-lead alloy plating bath having the following composition was prepared. Stannous ethanesulfonate (as Sn ²⁺ ): 30 g / L Lead p-phenolsulfonate (as Pb ²⁺ ): 20 g / L Methanesulfonic acid: 55 g / L Trimethylthiourea: 160 g / L・ Methyl phosphate: 8 g / L This tin-lead alloy plating bath is maintained at 65 ° C. and VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film had a thickness of 0.70 μm and a thickness of 3 μm.
It had a lead content of 1%.

Example 6 An electroless tin-lead alloy plating bath having the following composition was prepared. Stannous ethanesulfonate (as Sn ²⁺ ): 18 g / L Lead ethanesulfonate (as Pb ²⁺ ): 8 g / L Ethanesulfonic acid: 150 g / L Thiourea: 80 g / L Phosphoric acid: 20 g / L Hydrazine hydrochloride: 55 g / L Nonylphenol polyethoxylate (EO15): 5 g / L This tin-lead alloy plating bath is maintained at 65 ° C., and VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film had a thickness of 0.71 μm and a film thickness of 5.
It had a lead content of 0%.

Example 7 An electroless tin-lead alloy plating bath having the following composition was prepared. Stannous ethanesulfonate (as Sn ²⁺ ): 18 g / L Lead ethanesulfonate (as Pb ²⁺ ): 8 g / L Ethanesulfonic acid: 150 g / L EDTA: 80 g / L Ethylenediaminetetramethylene Phosphonic acid: 85 g / L Nonylphenol polyethoxylate (EO15): 5 g / L This tin-lead alloy plating bath is maintained at 65 ° C. and VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film had a thickness of 0.42 μm and a thickness of 4.
It had a lead content of 0%.

Example 8 An electroless tin-bismuth alloy plating bath having the following composition was prepared. Stannous methanesulfonate (as Sn ²⁺ ): 20 g / L bismuth methanesulfonate (as Bi ³⁺ ): 5 g / L 2-butanesulfonic acid: 80 g / L 1,3-dimethylthiourea: 120 g / L ・ Calcium hypophosphite: 20 g / L ・ Linoleylamine polyethoxylate (EO12) -polypropoxylate (PO3): 12 g / L This plating bath is kept at 65 ° C., and TAB patterned by VLP is formed. The test piece of the film carrier was immersed for 5 minutes and subjected to electroless plating. The resulting tin-bismuth alloy plating film had a thickness of 1.2 μm and a bismuth content of 20%.

Example 9 An electroless tin-indium alloy plating bath having the following composition was prepared. Stannous ethanesulfonate (as Sn2 ⁺ ): 30 g / L Indium methanesulfonate (as In3 ⁺ ): 10 g / L Ethanesulfonic acid: 70 g / L Allylthiourea: 150 g / L Orthophosphoric acid : 65 g / L Lauryl dimethylamine oxide: 15 g / L While holding this plating bath at 65 ° C, a test piece of a TAB film carrier patterned by VLP was immersed for 5 minutes, and subjected to electroless plating. The resulting tin-indium alloy plating film had a thickness of 0.7 μm and an indium content of 3.3%.

Example 10 Electroless tin having the following composition
A zinc alloy plating bath was built. Stannous methanesulfonate (as Sn ²⁺ ): 35 g / L Zinc methanesulfonate (as Zn ²⁺ ): 6 g / L Citric acid: 120 g / L Thiourea: 180 g / L Polyphosphoric acid: 100 g / L hexynylamine polyethoxylate (EO10): 3 g / L While holding this plating bath at 65 ° C., a test piece of a TAB film carrier patterned by VLP is immersed for 5 minutes to perform electroless plating. Was given. The resulting tin-zinc alloy plated coating had a thickness of 0.6 μm and a zinc content of 1.5%.

Example 11 Electroless tin having the following composition
A silver alloy plating bath was built. Stannous p-phenolsulfonate (as Sn ²⁺ ): 40 g / L Silver p-phenolsulfonate (as Ag ⁺ ): 3 g / L Pyrophosphoric acid: 50 g / L Potassium iodide: 100 g / L • Thiourea: 120 g / L • Ammonium hypophosphite: 10 g / L • Styrenated phenol polyethoxylate (EO18): 7 g / L • Adjusted to pH 8 with KOH This plating bath was maintained at 65 ° C and VLP A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The resulting tin-silver alloy plated coating had a thickness of 1.0 μm and a silver content of 3.5%.

Example 12 An electroless tin plating bath was constructed with the following composition. Stannous sulfate (as Sn ²⁺ ): 20 g / L Sulfuric acid: 90 g / L Thiourea: 100 g / L Sodium hypophosphite: 15 g / L This tin plating bath is maintained at 65 ° C. and VLP The test piece of the TAB film carrier patterned by
Then, it was immersed for a minute and subjected to electroless plating. The resulting tin-plated film had a thickness of 0.42 μm.

Example 13 Electroless tin having the following composition
A lead alloy plating bath was built. Stannous chloride (as Sn ²⁺ ): 15 g / L Lead chloride (as Pb ²⁺ ): 15 g / L Hydrochloric acid: 50 g / L Ethylene thiourea: 80 g / L Metaphosphoric acid: 50 g / L Octyl Amine polyethoxylate (EO8): 8 g / L This tin-lead alloy plating bath is maintained at 65 ° C., and VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film had a thickness of 0.61 μm and a thickness of 2 μm.
It had a lead content of 5%.

Example 14 Electroless tin having the following composition
A lead alloy plating bath was built. Stannous borofluoride (as Sn ²⁺ ): 24 g / L Lead borofluoride (as Pb ²⁺ ): 12 g / L Hydrofluoric acid: 75 g / L Allylthiourea: 100 g / L Pyrophosphate: 35 g / L This tin-lead alloy plating bath was maintained at 65 ° C.
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The resulting tin-lead alloy plating film had a thickness of 0.57 μm and a thickness of 1 μm.
It had a lead content of 0%.

Example 15 An electroless tin having the following composition was used.
A lead alloy plating bath was built. -Stannous fluorosilicate (as Sn2 +): 20 g / L-Lead fluorosilicate (as Pb2 +): 15 g / L-Hydrofluoric acid: 50 g / L-Thiourea: 130 g / L-Potassium phosphite: 45 g / L L This tin-lead alloy plating bath is maintained at 65 ° C.
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film had a thickness of 0.50 μm and a thickness of 1 μm.
It had a lead content of 5%.

Example 16 An electroless tin having the following composition:
A lead alloy plating bath was built. Stannous chloride (as Sn ²⁺ ): 25 g / L Lead borofluoride (as Pb ²⁺ ): 20 g / L Hydrochloric acid: 60 g / L 1,3-diphenylthiourea: 90 g / L Phosphoric acid Methyl: 12 g / L ・ α-naphthol polyethoxylate (EO15): 12 g / L This tin-lead alloy plating bath is maintained at 65 ° C. and VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film had a thickness of 0.55 μm and a thickness of 3 μm.
It had a lead content of 8%.

Comparative Example 1 An electroless tin-lead alloy plating bath having the following composition was prepared. Stannous methanesulfonate (as Sn2 ⁺ ): 20 g / L Lead ethanesulfonate (as Pb2 ⁺ ): 10 g / L p-phenolsulfonic acid: 40 g / L Thiourea: 75 g / L While maintaining the tin-lead alloy plating bath at 65 ° C, VLP
A test piece of a TAB film carrier patterned by the above method was immersed for 5 minutes and subjected to electroless plating. The obtained tin-lead alloy plating film had a thickness of 0.43 μm and a thickness of 1 μm.
It had a lead content of 3%.

Comparative Example 2 An electroless tin-lead alloy plating bath having the following composition was prepared. Stannous ethanesulfonate (as Sn ²⁺ ): 18 g / L Lead ethanesulfonate (as Pb ²⁺ ): 8 g / L Ethanesulfonic acid: 150 g / L Thiourea: 80 g / L Nonylphenol poly Ethoxylate (EO15): 5 g / L The plating bath was kept at 65 ° C., and a test piece of a TAB film carrier patterned by VLP was immersed for 5 minutes to perform electroless plating. The resulting tin-lead alloy plating film had a thickness of 0.35 μm and a lead content of 4%.

Comparative Example 3 An electroless tin-lead alloy plating bath having the following composition was prepared. Stannous ethanesulfonate (as Sn ²⁺ ): 18 g / L Lead ethanesulfonate (as Pb ²⁺ ): 8 g / L Ethanesulfonic acid: 150 g / L Thiourea: 80 g / L Hydrazine hydrochloride : 55 g / L ・ Nonylphenol polyethoxylate (EO15): 5 g / L While holding this plating bath at 65 ° C., a test piece of a TAB film carrier patterned by VLP was immersed for 5 minutes to perform electroless plating. gave. The resulting tin-lead alloy plating film had a thickness of 0.25 μm and a lead content of 2%.

<< Evaluation Test Examples of Dendrite >> Each of the tin plating baths or tin alloy plating baths of Examples 1 to 16 and Comparative Examples 1 to 3 was used to obtain TA at 65 ° C. for 5 minutes.
The result of applying the electroless plating on the film carrier of B is as described above.
Observation was made using an electron microscope (S-2460N, manufactured by Hitachi, Ltd.), and the presence or absence of dendrite or the state thereof was examined. That is, when dendrite is generated in the deposit of the electroless plating, in general, at a visual level, a black-brown or similar dark appearance is observed, and a rough surface similar to a shark skin is observed. At a microscope observation level, needle-like crystals, fine particles, or sponge-like crystals in which pine needles are closely stacked are observed. For this reason, the situation of dendrite generation was evaluated based on these trends.

The details of the evaluation criteria for dendrite are as follows. (1) Visual evaluation criteria of dendrite A: Uniform white semi-gloss or silver appearance, and excellent film appearance. ：: A slightly uneven gray appearance was observed, but no blackening or the like was observed. ×: Uneven black or brownish brown appearance peculiar to dendrite was present, and the powder was fragile. (2) Evaluation criteria for dendrite by observation with an electron microscope A: Uniform and dense particle shape was observed. ；: An uneven particle shape was observed, but the particle shape was at a practical level as a whole. X: Needle-like, fine-particle-like, or sponge-like crystals unique to dendrite are generally observed, and no uniform particle shape is observed at all.

<< Results of Dendrite Evaluation Test >> FIG. 1 shows evaluation results of the dendrite test. Visually, according to observation with an electron microscope, generation of dendrites was not observed in Examples 1 to 16, but generation of dendrites was observed over the entire surface of the electrodeposit in Comparative Examples 1 to 3 containing no phosphorus compound, Practicality as a plating film was poor.

That is, first, when comparing the example with the comparative example mainly by observation with an electron microscope in which the fine morphology of the electrodeposit can be well understood, for example, in FIG. Comparative Example 1 while a unique particle shape was observed.
3, needle-like and pine needle-like crystals peculiar to dendrite were entirely observed, and did not have a uniform particle shape at all, which was clearly different from Example 2. Regarding the microscopic observation, in Examples 1 and 3 to 11 based on the organic sulfonic acid bath, the same uniform and dense particle shape as in Example 2 was observed, and the evaluation was ◎. In Examples 12 to 16 based on the inorganic acid bath, the result was one step away from the examples based on the organic acid bath in terms of uniformity of the particle shape, etc., but the particle shape at a practical level is retained, The evaluation was ○. On the other hand, in Comparative Example 1, as described above, needle-like crystals unique to dendrite were confirmed (evaluation of ×), and a comparison was made in which a nonionic surfactant was added as a smoothing agent instead of the phosphorus compound of the present invention. Example 2 also showed needle-like crystals unique to dendrite. Further, the hydrazine derivative is commonly used as a reducing agent in an electroless plating bath such as hypophosphite, but also with respect to Comparative Example 3 in which the phosphorus compound of the present invention was replaced with this hydrazine derivative.
The result was similar to that of Comparative Example 1. Incidentally, in Example 6 in which this hydrazine derivative (reducing agent) was used in combination with hypophosphorous acid (dendritic inhibitor), unlike Comparative Example 3, the film-forming property of the electroless plating film was improved. Evaluation was obtained.

On the other hand, the visual observation is mainly for evaluating the film appearance and glossiness. Examples 1 to 11 based on the sulfonic acid bath have a uniform white semi-gloss or silver appearance. The evaluation was ◎. Examples 12 to 16 based on the inorganic acid bath exhibited a slightly uneven gray appearance, but no blackening characteristic of dendrite was observed at all.
Met. On the other hand, in Comparative Examples 1 to 3, an uneven black or brownish appearance unique to dendrite was observed, and the powders were all fragile as a whole.

[Brief description of the drawings]

FIG. 1 is a chart showing the results of a dendrite evaluation test based on visual observation and observation using an electron microscope in Examples 1 to 16 and Comparative Examples 1 to 3.

FIG. 2 is an electron micrograph (magnification: 2000) showing a tin-lead alloy plating film of Example 2.

FIG. 3 is an electron micrograph (magnification: 2000) showing a tin-lead alloy plating film of Comparative Example 1.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 11, 1997

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Title of the invention Electroless tin and tin alloy plating bath,
The electroless plating method, and an electronic component having a tin or tin alloy film formed in the electroless plating bath

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0055

[Correction method] Change

[Correction contents]

Example 11 Electroless tin having the following composition
A silver alloy plating bath was built. • Stannous p-phenolsulfonate (as Sn ²⁺ ): 40 g / L • Silver p-phenolsulfonate (as Ag ⁺ ): 3 g / L. Pyrophosphoric acid: 50 g / L Potassium iodide: 100 g / L Thiourea: 120 g / L Ammonium hypophosphite: 10 g / L Styrenated phenol polyethoxylate (E018): 7 g / L While maintaining the temperature at ° C., a test piece of a TAB film carrier patterned by VLP was immersed for 5 minutes and subjected to electroless plating. The resulting tin-silver alloy plated coating had a thickness of 1.0 μm and a silver content of 3.5%.

Claims (8)

[Claims] (A) A stannous salt and a mixture of a stannous salt and a salt of a metal selected from the group consisting of bismuth, indium, antimony, zinc, cobalt, nickel, silver, copper and lead. (B) at least one acid selected from organic acids such as organic sulfonic acid and carboxylic acid, or at least one acid selected from inorganic acids such as hydrochloric acid, sulfuric acid, and borofluoric acid; (D) An electroless tin and tin alloy plating bath comprising a dendrite inhibitor comprising a phosphorus compound. 2. The phosphorus compound (D) is orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, polyphosphoric acid, hypophosphorous acid, phosphorous acid, and sodium, potassium, calcium, magnesium and ammonium salts thereof. Salts, barium salts, iron salts, inorganic phosphorus compounds such as salts such as zinc salts, aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), alkyl phosphate (e.g., Ethyl phosphate, diethyl phosphate, etc.), and their sodium salts,
The electroless tin and tin alloy according to claim 1, wherein the electroless tin is at least one kind of an organic phosphorus compound such as a salt such as a potassium salt, a calcium salt, a magnesium salt, an ammonium salt, a barium salt, an iron salt, and a zinc salt. Gold plating bath. 3. The electroless tin and tin alloy plating bath according to claim 1, wherein the acid (B) is an organic acid. 4. An electroless tin and tin alloy plating bath, further comprising a reducing agent added to the electroless plating bath according to claim 1. 5. An electroless tin and tin alloy plating bath, wherein a surfactant is further added to the electroless plating bath according to any one of claims 1 to 4. 6. An electronic component having a tin or tin alloy film formed by immersing the electronic component in the electroless plating bath according to any one of claims 1 to 5. 7. The method according to claim 6, wherein the electronic component is a TAB film carrier. 8. A mixture of a stannous salt and a salt of a stannous salt and a salt of a metal selected from the group consisting of bismuth, indium, antimony, zinc, cobalt, nickel, silver, copper and lead. (B) at least one acid selected from organic acids such as organic sulfonic acid and carboxylic acid, or at least one acid selected from inorganic acids such as hydrochloric acid, sulfuric acid, and borofluoric acid; (D) electroless tin or tin alloy plating characterized by obtaining a tin or tin alloy film with suppressed dendrite by plating using an electroless tin or tin alloy plating bath containing a phosphorus compound. Method.