JPH0860376A - Electroless plating method - Google Patents

Abstract

PURPOSE: To provide a stable plating bath for forming the film of a solder consisting of tin or tin-lead alloy by electroless plating. CONSTITUTION: An antioxidant such as hydroquinone is added to an electroless plating bath. contg. stannous ion or stannous ion and lead ion, a complexing agent, a reducing agent and a pH regulator, and an inert gas such as nitrogen is passed through the bath to prevent the oxidation of the bath. Consequently, the film of a solder consisting of tin or tin-lead alloy is stably formed by electroless plating, and the deterioration of the bath is prevented.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for electroless plating tin or a tin-lead alloy.

[0002]

2. Description of the Related Art Plating with solder, which is a tin or tin-lead alloy, is generally carried out industrially by electroplating. However, the electroplating method has a problem that the film thickness is not constant due to current distribution.
Substitution tin plating, which is another plating method, is limited to copper or copper alloy as the base.

In order to obtain a uniform film, there is an electroless solder plating method as disclosed by the present applicants in Japanese Patent Application No. 4-208750.

The conventional electroless solder plating method will be described below.

The electroless plating bath used in the conventional electroless plating method contains divalent ions of tin and divalent ions of lead as metal ions, a complexing agent and a reducing agent, and titanium trichloride as a reducing agent. It is characterized by including. Here, by using titanium trichloride as a reducing agent, a solder plating film is deposited autocatalytically on a metal such as copper or nickel or on an insulating substrate activated by stannic chloride and palladium chloride. Can be made.

In the conventional electroless plating reaction using the electroless solder plating bath, the electrons generated by the oxidation reaction of the reducing agent trivalent titanium ion reduce the tin ion and the lead ion in the bath, and these tin ions And lead ions are considered to be changed to a metallic state. This change is briefly shown below.

Sn ²⁺ + 2Ti ³⁺ → Sn + 2Ti ⁴⁺ (TiO ²⁺ ) Pb ²⁺ + 2Ti ³⁺ → Pb + 2Ti ⁴⁺ (TiO ²⁺ ) This plating reaction does not accompany hydrogen generation, so in a ceramic electronic component, It has the characteristic that the ceramic is not reduced. Here, the solder plating film deposited on the object to be plated can continue the reaction in an autocatalytic manner to form a plating film having an arbitrary thickness.

[0008]

However, in the conventional electroless solder plating method, the plating bath is unstable.

The present invention has been made to solve the above problems, and provides an electroless plating method for forming a film made of tin or solder in a stable plating bath.

[0010]

The electroless plating method according to claim 1 of the present invention comprises divalent tin ions or divalent tin ions and lead ions, a complexing agent, a reducing agent, and a pH adjusting agent. Add an antioxidant to the electroless plating bath,
It is characterized by venting an inert gas.

In the electroless plating method according to claim 2 of the present invention, hydroquinone, hydrazine sulfate, resorcin, sodium sorbate, L-ascorbic acid, pyrocatechol, phenol sulfonic acid and catechol are used as antioxidants.
It is characterized by using an electroless plating bath containing 0 to 0.01 mol / L of at least one selected from the group consisting of sulfonic acid, hydroquinone sulfonic acid, resorcin sulfonic acid and pyrogallol sulfonic acid.

In the electroless plating method according to claim 3 of the present invention, the inert gas is nitrogen, argon, helium, hydrogen,
At least one selected from carbon dioxide is used, and the flow rate is 10 to 500 ml / min / L.

In the electroless plating method according to claim 4 of the present invention, the complexing agent contains citric acid in an amount of 0.05 to 0.5 mol.
/ L, ethylenediaminetetraacetic acid 0.04 to 0.2mo
1 / L, nitrilotriacetic acid 0.05 to 0.3 mol / L
It is characterized by using an electroless plating bath having a concentration of.

In the electroless plating method according to claim 5 of the present invention, at least one selected from titanium trichloride, titanium sulfate, titanium oxalate, and titanium iodide, which comprises trivalent titanium ions as a reducing agent. 0.02-0.1
It is characterized by using an electroless plating bath containing mol / L.

The electroless plating method according to claim 6 of the present invention uses an electroless plating bath, which is composed of an aqueous solution of sodium carbonate, ammonia water, and hydrochloric acid as a pH adjuster, and whose pH is adjusted to 6.5 to 11. It is characterized by

[0016]

According to the electroless plating method of claim 1, an electroless plating bath containing divalent tin ions or divalent tin ions and lead ions, a complexing agent, a reducing agent, an antioxidant and a pH adjusting agent, Since it is characterized by ventilating an inert gas, deterioration of the plating bath can be prevented.

In the electroless plating method according to the second aspect, hydroquinone, hydrazine sulfate, ledrosine, sodium sorbate, L-ascorbic acid, pyrocatechol, phenol sulfonic acid, catechol sulfonic acid as an antioxidant, Since the electroless plating bath which is at least one selected from hydroquinone sulfonic acid, resorcin sulfonic acid and pyrogallol sulfonic acid is used, deterioration of the plating bath can be prevented.

The electroless plating method according to a third aspect is characterized in that at least one inert gas selected from nitrogen, argon, helium, hydrogen and carbon dioxide is passed through the plating bath. Therefore, the concentration of oxygen dissolved in the plating bath can be reduced, and at the same time, the surface of the plating bath is covered with an inert gas, which prevents oxygen in the atmosphere from dissolving in the plating bath, preventing the oxidation of metal ions in the plating bath. It prevents the deterioration of the plating bath.

In the electroless plating method according to the fourth aspect, as a complexing agent, citric acid is 0.05 to 0.5 mol / L, ethylenediaminetetraacetic acid is 0.04 to 0.2 mol / L, and nitrilotriacetic acid is 0. Since the electroless plating bath having a concentration of 0.05 to 0.3 mol / L is used, the plating bath can be stabilized.

In the electroless plating method according to claim 5, titanium trichloride comprising trivalent titanium ions as a reducing agent,
Since it is characterized by using an electroless plating bath containing at least one selected from titanium sulfate, titanium oxalate and titanium iodide, it is possible to deposit a film by electroless plating of tin or tin-lead alloy. it can.

The electroless plating method according to claim 6 is characterized in that an electroless plating bath consisting of an aqueous solution of sodium carbonate, ammonia water and hydrochloric acid is used as a pH adjuster, so that the plating bath can be stabilized. it can.

[0022]

【Example】

(Example 1) A first example according to the present invention will be described below.

An electroless solder plating bath having the following composition was prepared.

Citric acid 0.34 mol / L Ethylenediaminetetraacetic acid 0.08 mol / L Nitrilotriacetic acid 0.10 mol / L Hydroquinone 0.008 mol / L Stannous chloride 0.07 mol / L Lead chloride 0.01 mol / L titanium trichloride 0.04 mol / L The pH of the plating solution having the above composition was adjusted to 7.0 with a 20% sodium carbonate solution and 2% hydrochloric acid, and the bath temperature was set to 60 ° C. Nitrogen gas was started to be aerated at a flow rate of 200 ml / min / L at the same time when tin chloride and lead chloride were charged, and the plating solution was continued during plating. The unit of the nitrogen gas flow rate indicates the amount of gas flowing per 1 L of plating solution for 1 minute. As the test piece, an alumina substrate activated with palladium nuclei was subjected to plating by a sensitizing activation method and a catalyst accelerator method. By a plating treatment for 45 minutes, a solder plating film having a thickness of 3.3 μm was obtained.

The composition of the plating bath is not limited to this value, and the content of citric acid is 0.05 to.
0.5 mol / L, ethylenediaminetetraacetic acid (EDTA) 0.04 to 0.2 mol / L, nitrilotriacetic acid (NTA)
Is 0.05 to 0.3 mol / L, and hydroquinone is 0
0.01 mol / L, stannous chloride 0.04 to 0.1
mol / L, lead chloride 0.001-0.05 mol /
Any amount may be used as long as L and titanium trichloride are in the range of 0.02 to 0.05 mol / L. Further, since the complexing agent may be water-soluble, it may be a compound with, for example, sodium or potassium, or may be another metal salt.

More preferably, the ratio of ethylenediaminetetraacetic acid and tin ions, that is, the value of (EDTA) / (Sn ²⁺ ) is 1.0 or more.

Similarly, (NTA) / (Ti ³⁺ ) is preferably 1.0 or more, and further (Citric acid) / {(Ti ³⁺ ).
+ (Sn ²⁺ )} is preferably 0.6 or more.

(Second Embodiment) A second embodiment according to the present invention will be described below.

An electroless solder plating bath having the following composition was prepared.

Citric acid 0.34 mol / L Ethylenediaminetetraacetic acid 0.08 mol / L Nitrilotriacetic acid 0.10 mol / L Stannous chloride 0.07 mol / L Lead chloride 0.01 mol / L Titanium trichloride 0.04 mol / L The pH of the plating solution having the above composition was adjusted to 7.0 with a 20% sodium carbonate solution and 2% hydrochloric acid, and the bath temperature was set to 60 ° C. Nitrogen gas was started to be aerated at a flow rate of 200 ml / min / L at the same time when tin chloride and lead chloride were charged, and the plating solution was continued during plating. As the test piece, an alumina substrate activated with palladium nuclei was subjected to plating by a sensitizing activation method and a catalyst accelerator method. By a plating treatment for 45 minutes, a solder plating film having a thickness of 3.2 μm was obtained.

The composition of the plating bath is not limited to this value, and the content of citric acid is 0.05 to.
0.5 mol / L, ethylenediaminetetraacetic acid (EDTA) 0.04 to 0.2 mol / L, nitrilotriacetic acid (NTA)
Is 0.05 to 0.3 mol / L, and hydroquinone is 0
0.01 mol / L, stannous chloride 0.04 to 0.1
mol / L, lead chloride 0.001-0.05 mol /
Any amount may be used as long as L and titanium trichloride are in the range of 0.02 to 0.05 mol / L. Further, since the complexing agent may be water-soluble, it may be a compound with, for example, sodium or potassium, or may be another metal salt.

More preferably, the ratio of ethylenediaminetetraacetic acid and tin ions, that is, the value of (EDTA) / (Sn ²⁺ ) should be 1.0 or more.

Similarly, (NTA) / (Ti ³⁺ ) is preferably 1.0 or more, and further (Citric acid) / {(Ti ³⁺ ).
+ (Sn ²⁺ )} is preferably 0.6 or more.

Although the plating bath according to this embodiment has been described in the case where no antioxidant is added, the electroless plating can be stably performed even with such a plating bath.

(Embodiment 3) A third embodiment of the present invention will be described below.

An electroless solder plating bath having the following composition was prepared.

Citric acid 0.34 mol / L Ethylenediaminetetraacetic acid 0.08 mol / L Nitrilotriacetic acid 0.10 mol / L Hydroquinone 0.008 mol / L Stannous chloride 0.07 mol / L Lead chloride 0.01 mol / L titanium trichloride 0.04 mol / L The pH of the plating solution having the above composition was adjusted to 9.0 with aqueous ammonia, and the bath temperature was set to 60 ° C. Plating solution is tin chloride,
Aeration of nitrogen gas was started at a flow rate of 200 ml / min / L simultaneously with the introduction of lead chloride, and was continued during plating. For the test piece,
The alumina substrate activated with palladium nuclei was subjected to plating by the sensitizing activation method and the catalyst accelerator method. By a plating treatment for 45 minutes, a solder plating film having a thickness of 3.3 μm was obtained.

The composition of the plating bath is not limited to this value, and the content of citric acid is 0.05 to.
0.5 mol / L, ethylenediaminetetraacetic acid (EDTA) 0.04 to 0.2 mol / L, nitrilotriacetic acid (NTA)
Is 0.05 to 0.3 mol / L, and hydroquinone is 0
0.01 mol / L, stannous chloride 0.04 to 0.1
mol / L, lead chloride 0.001-0.05 mol /
Any amount may be used as long as L and titanium trichloride are in the range of 0.02 to 0.05 mol / L. Further, since the complexing agent may be water-soluble, it may be a compound with, for example, sodium or potassium, or may be another metal salt.

More preferably, the ratio of disodium ethylenediaminetetraacetate to tin ions, ie (EDTA) /
The value of (Sn ²⁺ ) should be 1.0 or more.

Similarly, (NTA) / (Ti ³⁺ ) is preferably 5.0 or more, and further (Citric acid) / {(Ti ³⁺ ).
+ (Sn ²⁺ )} is preferably 2.8 or more.

(Fourth Embodiment) A fourth embodiment according to the present invention will be described below.

An electroless tin plating bath having the following composition was prepared.

Citric acid 0.34 mol / L Ethylenediaminetetraacetic acid 0.08 mol / L Nitrilotriacetic acid 0.10 mol / L Hydroquinone 0.008 mol / L Stannous chloride 0.08 mol / L Titanium trichloride 04 mol / L The pH of the plating solution having the above composition was adjusted to 7.0 with a 20% sodium carbonate solution and 2% hydrochloric acid, and the bath temperature was set to 60 ° C. At the same time when tin chloride was added to the plating solution, aeration of nitrogen gas was started at a flow rate of 200 ml / min, which was continued during plating. For the test piece, by the sensitizing activation method and the catalyst accelerator method,
An alumina substrate activated with a palladium nucleus was used for plating. By plating for 45 minutes, the thickness becomes 3.
A tin plating film of 0 μm was obtained. The plating bath composition is not limited to this value, and citric acid (Citric
acid) 0.05-0.5 mol / L, ethylenediaminetetraacetic acid (EDTA) 0.04-0.2 mol / L, nitrilotriacetic acid (NTA) 0.05-0.3 mol / L, hydroquinone 0. -0.01 mol / L, stannous chloride 0.04-0.1 mol / L, lead chloride 0.001-
0.05 mol / L, titanium trichloride 0.02-0.0
Any number may be used within the range of 5 mol / L. Further, since the complexing agent may be water-soluble, it may be a compound with, for example, sodium or potassium, or may be another metal salt.

More preferably, the ratio of disodium ethylenediaminetetraacetate to tin ions, ie (EDTA) /
The value of (Sn ²⁺ ) should be 1.0 or more.

Similarly, (NTA) / (Ti ³⁺ ) is preferably 1.0 or more, and further (Citric acid) / {(Ti ³⁺ ).
+ (Sn ²⁺ )} is preferably 0.6 or more.

(Fifth Embodiment) A fifth embodiment according to the present invention will be described below.

An electroless tin plating bath having the following composition was prepared.

Citric acid 0.34 mol / L Ethylenediaminetetraacetic acid 0.08 mol / L Nitrilotriacetic acid 0.10 mol / L Hydroquinone 0.008 mol / L Stannous chloride 0.08 mol / L Titanium trichloride 04 mol / L The pH of the plating solution having the above composition was adjusted to 9.0 with aqueous ammonia, and the bath temperature was set to 60 ° C. Plating solution is tin chloride,
Aeration of nitrogen gas was started at a flow rate of 200 ml / min / L simultaneously with the introduction of lead chloride, and was continued during plating. For the test piece,
The alumina substrate activated with palladium nuclei was subjected to plating by the sensitizing activation method and the catalyst accelerator method. A tin plating film having a thickness of 3.2 μm was obtained by the plating treatment for 45 minutes.

The composition of the plating bath is not limited to this value, and the content of citric acid is from 0.05 to.
0.5 mol / L, ethylenediaminetetraacetic acid (EDTA) 0.04 to 0.2 mol / L, nitrilotriacetic acid (NTA)
Is 0.05 to 0.3 mol / L, and hydroquinone is 0
0.01 mol / L, stannous chloride 0.04 to 0.1
mol / L, lead chloride 0.001-0.05 mol /
Any amount may be used as long as L and titanium trichloride are in the range of 0.02 to 0.05 mol / L. Further, since the complexing agent may be water-soluble, it may be a compound with, for example, sodium or potassium, or may be another metal salt.

More preferably, the ratio of disodium ethylenediaminetetraacetate to tin ions, ie (EDTA) /
The value of (Sn ²⁺ ) should be 1.0 or more.

Similarly, (NTA) / (Ti ³⁺ ) is preferably 5.0 or more, and further (Citric acid) / {(Ti ³⁺ ).
+ (Sn ²⁺ )} is preferably 2.8 or more.

In the above examples, the case where hydroquinone is used as the antioxidant has been described as an example.
The following known antioxidants for electrotin plating may be used. That is, hydrazine sulfuric acid hydrochloride, sodium hypophosphite described in JP-B-47-2161, and JP-A-53-48.
P-aminoacetanilide shown in 942 and Japanese Patent Publication Sho 60
Hydroxylamine sulfate, P-cresolsulfonic acid, formalin, hydroquinone and glucose shown in -9117, and hydrazine sulfate, resorcin, sodium sorbate, L-ascorbic acid shown in JP-B-59-3555.
Pyrocatechol and pyrogallol shown in JP-A-62-196391, 8-oxyquinoline, dihydroxynaphthalene and 2-methyl-8- shown in JP-A-1-156490.
Hydroxyquinoline and 2 as shown in Tokuhirohei 5-27710
-Hydroxypropane sulfonic acid and JP-A-2-166
And the hydroxyammonium salt shown in FIG.
Naphthol sulfonic acid shown in 194192, and JP
No. 2-243788, 2-hydroxyethanesulfonic acid, 2-hydroxypropanesulfonic acid, methanesulfonic acid, 2-carboxyethanesulfonic acid, sulfosuccinic acid, the phenolsulfonic acid shown in JP-A-3-36288, and JP-A-5-36288. An antioxidant selected from catechol sulfonic acid, hydroquinone sulfonic acid, resorcin sulfonic acid, pyrogallol sulfonic acid, 1,7-dihydroxynaphthalene sulfonic acid and the like shown in 44074 can be used.

In the above embodiments, an example in which nitrogen gas is used as the inert gas has been described, but the inert gas is not limited to nitrogen gas, and argon, helium,
Any gas can be used as long as the amount of dissolved oxygen in the plating bath can be reduced by ventilating the plating bath with a gas such as hydrogen or carbon dioxide. Further, it goes without saying that the ventilation amount is not limited to the value shown in the above embodiment.

Comparative Example 1 An alumina substrate having the same composition and the same treatment as in Example 1 was subjected to a plating treatment for 45 minutes without passing through a nitrogen gas.
A μm solder plating film was obtained. This is only 80% of the plating thickness of the example.

(Comparative Example 2) Further, except that hydroquinone, which is an antioxidant, was removed from the composition of Example 1 and an alumina substrate was subjected to plating without passing through nitrogen gas, a solder plating film of 2.0 μm in 45 minutes was obtained. Got This is only 60% of the plating thickness of the example.

[0056]

[Effect of the Invention] In a method of forming a film of tin or tin-lead alloy solder by electroless plating, an antioxidant is used to prevent oxidation of the plating bath, and an inert gas is passed through the plating bath. I decided to do it. Therefore, tin ions and lead ions can exist stably in the plating bath, a plating film of sufficient quality can be obtained, and deterioration of the plating solution can be prevented.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kosei Senda No. 26-10 Tenjin Tenjin, Nagaokakyo City, Kyoto Prefecture Murata Manufacturing Co., Ltd.

Claims (6)

[Claims] 1. An antioxidant is added to an electroless plating bath containing divalent tin ions or divalent tin ions and lead ions, a complexing agent, a reducing agent, and a pH adjusting agent, and an inert gas is ventilated. An electroless plating method comprising: 2. The antioxidant according to claim 1, which is hydroquinone, hydrazine sulfate, resorcin, sodium sorbate,
At least one selected from L-ascorbic acid, pyrocatechol, phenol sulfonic acid, catechol sulfonic acid, hydroquinone sulfonic acid, resorcin sulfonic acid, and pyrogallol sulfonic acid is 0 to 0.01 mol.
The electroless plating method according to claim 1, wherein an electroless plating bath containing 1 / L is used. 3. The inert gas according to claim 1, which is at least one selected from nitrogen, argon, helium, hydrogen and carbon dioxide, and has a flow rate of 10 to 500 ml / min / L. The electroless plating method according to claim 1. 4. The complexing agent according to claim 1, wherein citric acid is 0.0
5 to 0.5 mol / L, ethylenediaminetetraacetic acid of 0.
04-0.2 mol / L, nitrilotriacetic acid 0.05-
The electroless plating method according to claim 1, wherein an electroless plating bath having a concentration of 0.3 mol / L is used. 5. The reducing agent according to claim 1, wherein at least one selected from titanium trichloride, titanium sulfate, titanium oxalate and titanium iodide, which is composed of trivalent titanium ions, is used in an amount of 0.02 to 0. The electroless plating method according to claim 1, wherein an electroless plating bath containing 1 mol / L is used. 6. The pH adjusting agent according to claim 1 comprises at least one selected from an aqueous solution of sodium carbonate, aqueous ammonia and hydrochloric acid, and an electroless plating bath having a pH adjusted to 6.5 to 11 is used. The electroless plating method according to claim 1, wherein