KR101059487B1 - Tin whisker inhibitor and manufacturing method of whisker-resistant tin plating material using the same - Google Patents

Abstract

The present invention relates to a tin whisker inhibitor capable of sufficiently smoothing the surface of a material to be tin plated even with a small amount of etching, and effectively preventing the occurrence of tin whiskers, and a method for producing a whisker resistant tin plated product using the same.

The tin whisker inhibitor of the present invention has a pH of 5 or less, and is preferably an iron compound-based oxidizing agent, preferably ferric chloride, ferric sulfate and / or ferric nitrate, or a nonionic surfactant. 1) and / or a compound represented by the general formula (2), and an aqueous solution containing copper ions:

A [(C ₃ H ₆ O) _n (C ₂ H ₄ O) _m H] _k (1)

A [(C ₂ H ₄ O) _m (C ₃ H ₆ O) _n H] _k (2)

(In the formulas (1) and (2), A is a k-valent active hydrogen-containing compound residue, k is a number of 1 to 4, n is a number of 3 to 35, and m is 1 to Number of 70).

Tin plating, whiskers, inhibitors, ferrous oxidizers, nonionic surfactants, copper ions

Description

TIN WHISKER GENERATION-PREVENTING AGENT AND METHOD OF PRODUCING A WHISKERLESS TIN-PLATED PRODUCT BY USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tin whisker inhibitor for preventing tin whiskers in a tin plated product and a method for producing a whisker resistant tin plated product using the same.

Tin plating is good in solderability and corrosion resistance, and is suitable for plating of electric and electronic components (for example, the terminal of an electrical component, a printed wiring board, etc.), and is used widely.

However, it is known that tin-plated tin crystals, called whiskers, occur on the surface of the plating after tin plating. Since this tin whisker causes a short circuit especially in electrical and electronic components, it is necessary to prevent tin whiskers from occurring in the tin plating material.

The occurrence of such tin whiskers is thought to be due to the unevenness of the surface of the material to be tin-plated, and an attempt has been made to smooth the surface of the material to be tin-plated, and Japanese Unexamined Patent Application Publication No. 5-148658 (claims, etc.). A method of smoothing the surface of a material to be tin-plated by treating it with a treatment liquid containing an acid, a peroxide, and an organic high molecular compound containing a sulfate or phosphoric acid group as a hydrophilic group and a linear or cyclic hydrocarbon group as a hydrophobic group is proposed.

However, in the case of using the treatment liquid described in the patent document, in order to smooth the surface of the material to be tin plated, the surface of the material to be tin plated had to be etched to a thickness of 2 µm or more. For this reason, there is a problem in that the shape stability of the material to be tin-plated is not maintained when the above-described treatment liquid is used for the material to be tin-plated such as circuit copper having a thin line width in electronic parts which are highly integrated each year.

It is therefore an object of the present invention to provide a whisker inhibitor that can smoothly smooth the surface of a material to be tin plated even with a slight etching amount, thereby effectively preventing the occurrence of tin whiskers.

Further, another object of the present invention is to provide a method for producing a whisker-proof tin plated product, which is tin plated even with a fine etching amount while maintaining the shape stability of the material to be tin plated.

MEANS TO SOLVE THE PROBLEM The present inventors completed this invention as a result of earnestly researching in order to solve the said subject.

That is, the present invention relates to a whisker inhibitor, wherein the pH is 5 or less and an aqueous solution containing an iron compound oxidant, a nonionic surfactant, and copper ions.                     

In the tin whisker inhibitor of the present invention, the nonionic surfactant is preferably a compound represented by the following general formula (1) and / or general formula (2), and the iron compound-based oxidizing agent is ferric chloride. At least one member selected from the group consisting of ferrous sulfate and ferric nitrate:

A [(C ₃ H ₆ O) _n (C ₂ H ₄ O) _m H] _k (1)

A [(C ₂ H ₄ O) _m (C ₃ H ₆ O) _n H] _k (2)

(In the formulas (1) and (2), A is a k-valent active hydrogen-containing compound residue, k is a number of 1 to 4, n is a number of 3 to 35, and m is 1 to Number of 70).

The present invention also relates to a method for producing a whisker-resistant tin plated product characterized by subjecting the surface of the material to be tin-plated with the tin whisker inhibitor of the present invention, followed by tin plating.

In the manufacturing method of the present invention, it is preferable that the material to be tin plated is wiring copper of an electronic device.

(Embodiment of the Invention)

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely.

The tin whisker inhibitor of this invention is an acidic aqueous solution of pH 5 or less, Preferably pH 4 or less. When the pH of the aqueous solution exceeds 5, the etching property of the material to be tin plated, especially copper, is deteriorated, and sludge is also likely to occur. On the other hand, the lower limit of the pH of the aqueous solution is not particularly limited, and the lower limit within the limit suitable for industrialization is preferable.

The method of adjusting the said aqueous solution to pH of the said range is not specifically limited, What is necessary is just a well-known method, For example, pH can be adjusted by containing an acid. The acid at this time may be an organic acid or an inorganic acid, and examples of such acids may include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, and the like, or may be used alone. Preference is given to hydrochloric acid, phosphoric acid or formic acid.

The tin whisker inhibitor of this invention contains an iron compound type oxidizing agent. The iron compound oxidizing agent is used in the present invention because it does not intensively etch the surface of the material to be tin plated, especially the surface of copper, but also etches uniformly. The iron compound-based oxidizing agent that can be used in this respect is not particularly limited, and any iron compound known as an oxidizing agent can be used. Examples of such iron compounds include ferric chloride, ferric sulfate, and ferric nitrate. Etc. can be mentioned.

The amount of the iron compound-based oxidizing agent used in the present invention is not particularly limited, but may be any amount that can etch the surface of the material to be tin plated, especially the surface of copper, to about 1.0 µm / min to 5.0 µm / min. It can use suitably if it is 0.5 to 10 weight%, Preferably it is about 1 to 5 weight%.

In addition, the tin whisker inhibitor of the present invention includes a nonionic surfactant. The nonionic surfactant may be any nonionic surfactant, but considering the fact that the effects of the present invention can be obtained satisfactorily, the compounds represented by the following general formula (1) and / or general formula (2) desirable:

A [(C ₃ H ₆ O) _n (C ₂ H ₄ O) _m H] _k (1)

A [(C ₂ H ₄ O) _m (C ₃ H ₆ O) _n H] _k (2)

(In the formulas (1) and (2), A is a k-valent active hydrogen-containing compound residue, k is a number of 1 to 4, n is a number of 3 to 35, and m is 1 to Number of 70).

In the above general formulas (1) and (2), examples of the active hydrogen-containing compound corresponding to A include alkylphenols having 3 to 18 carbon atoms and alkyl groups having 3 to 18 carbon atoms, ethylene glycol and propylene glycol. And hydroxyl group-containing compounds such as glycols such as butylene glycol, polyols such as trimetholpropane, glycerin, pentaerythritol, and sorbitol, or alkyleneamines such as ethylenediamine and diethylenetriamine. And alkylamines, such as ethylenediamine, are especially preferable.

In addition, in the above formulas, polyoxyethylene chain, polyoxypropylene chain can be obtained by adding ethylene oxide or propylene oxide to the active hydrogen-containing compound described above according to a conventional method. As the added mole number (n and m in the general formula), in the present invention, the desired n is 3 to 35, more preferably 6 to 15, and m is 1 to 70. More preferably, it is the number of 2-20. In addition, these are shown by the average value.                     

Although the usage-amount of the nonionic surfactant used for this invention is not specifically limited, either, If it is about 0.1-7 weight%, Preferably it is about 0.5-3 weight%, it can use suitably.

In addition, the tin whisker inhibitor of the present invention contains copper ions. Copper ions used in the present invention may be obtained by dissolving copper salts such as copper chloride, copper sulfate, and copper nitrate, or may be obtained by dissolving metal copper in a step in which an oxidant is present in the system. In addition, when dissolving a copper salt, it is preferable to use it as an anion salt similar to the said iron compound, an acid, etc. in handling.

Such copper ions can be suitably used at a copper concentration of 0.05 to 10 g / l, more preferably 0.5 to 5 g / l, and most preferably 1.5 to 5 g / l.

In addition to the above-mentioned compound, a solubilizer, a wettability improving agent, etc. can be mix | blended with the tin whisker prevention agent of this invention in the range which does not impair the objective of this invention as needed.

Next, the manufacturing method of the tin plating material of this invention is demonstrated. The method for producing a tin plated product of the present invention is characterized by subjecting the surface of the material to be tin plated with the tin whisker inhibitor of the present invention, followed by tin plating.

The material to be tin-plated may be a metal and is not particularly limited. However, if the material to be tin-plated is particularly copper or a copper alloy, a significant effect is obtained. In addition, when the material to be tin-plated is copper, etc. of the fine wiring of the electronic device can be obtained a significant effect is preferable.

The method for treating the surface of the material to be tin plated using the tin whisker inhibitor of the present invention is not particularly limited. For example, the tin whisker of the present invention may be applied to the surface of the material to be tin plated according to a known method such as dipping or spraying. What is necessary is just to contact an inhibitor.

Further, the treatment conditions are not particularly limited, but from the viewpoint that a significant effect can be obtained in sufficiently smoothing the surface of the material to be tinned even with a slight etching amount, the surface of the material to be tin plated by the tin whisker inhibitor of the present invention. What is necessary is just to process 10 to 120 second, Preferably it is about 20 to 60 second at 10-40 degreeC so that etching amount may be 0.1-1.5 micrometers, Preferably it is about 0.3-1 micrometer.

(Example)

Although an Example is given to the following and this invention is demonstrated in detail, this invention is not limited to this.

EXAMPLE 1

82.1 parts by weight of 40% by weight ferric chloride, 117.4 parts by weight of 20% by weight hydrochloric acid, 10.5 parts by weight of 76% by weight formic acid, 10.8 parts by weight of 85% by weight phosphoric acid, 10.7 parts by weight of dipropylene glycol monomethyl ether as a wettability enhancer In the formula (1), A is an ethylenediamine residue, n = 11.6, m = 10.5, 11.0 parts by weight of a compound having k = 4, in formula (1), A is an ethylenediamine residue, 1.1 parts by weight of a compound having n = 11.6, m = 4.0, and k = 4, and 856.4 parts by weight of pure water were mixed, 3.8 parts by weight of copper chip was dissolved in the mixture, and a tin whisker inhibitor of the present invention (1 )

The tin whisker inhibitor (1) thus obtained had a pH of 0.12, a ferric chloride content of 3.0 wt%, a total content of nonionic surfactant of 1.1 wt%, and a copper concentration of 3.0 g / l.

On the other hand, using a polyimide film having a thickness of 170 μm at 10 cm × 10 cm as an insulating substrate, the lead width is 25 μm and the lead space width is 25 μm on the substrate by a semi-additive method. The copper wiring circuit whose lead thickness is 8 micrometers was formed, and the test piece was obtained.

Subsequently, the test piece thus obtained was immersed in the tin whisker inhibitor (1) at 25 ° C. for 30 seconds, and then washed with water and dried. Then, an electroless tin plating process was performed, and a 0.5 micrometer thick tin plating film was formed on the copper wiring circuit.

The test specimens thus treated were left in the air, and the conditions of whiskers after 60 days and 90 days were observed under a microscope. As a result, no whiskers were observed in any of the specimens. It remained well. In addition, in the said test piece, the lead thickness of the said copper wiring circuit reduced by the process using the tin whisker inhibitor 1 was 0.7 micrometer.

EXAMPLE 2

82.1 parts by weight of 40% by weight ferric chloride, 117.4 parts by weight of 20% by weight hydrochloric acid, 10.5 parts by weight of 76% by weight formic acid, 10.8 parts by weight of 85% by weight phosphoric acid, 10.7 parts by weight of dipropylene glycol monomethyl ether as a wettability enhancer In addition, in Formula (2), A is an ethylenediamine residue, n = 11.6, m = 10.5, 11.0 parts by weight of a compound having k = 4, in Formula (2), A is an ethylenediamine residue, 1.1 parts by weight of a compound having n = 11.6, m = 4.0 and k = 4, and 856.4 parts by weight of pure water were mixed, and 3.8 parts by weight of a copper chip was dissolved in the mixture to obtain a tin whisker inhibitor (2) of the present invention.

The tin whisker inhibitor 2 had a pH of 0.12, a ferric chloride content of 3.0 wt%, a total content of nonionic surfactant of 1.1 wt%, and a copper concentration of 3.0 g / l.

Using the same specimen as in Example 1 and performing the same test as in Example 1, whiskers were not observed at all in the specimen after 60 days and 90 days after it was left unattended. It remained well. In addition, in the said test piece, the lead thickness of the said copper wiring circuit reduced by the process using the tin whisker inhibitor 2 was 0.7 micrometer.

EXAMPLE 3

82.1 parts by weight of 40% by weight ferric chloride, 117.4 parts by weight of 20% by weight hydrochloric acid, 10.5 parts by weight of 76% by weight formic acid, 10.8 parts by weight of 85% by weight phosphoric acid, 10.7 parts by weight of dipropylene glycol monomethyl ether as a wettability enhancer In the formula (1), A is an ethylenediamine residue, n = 11.6, m = 10.5, 11.0 parts by weight of a compound having k = 4, in formula (2), A is an ethylenediamine residue, 1.1 parts by weight of a compound having n = 11.6, m = 4.0 and k = 4, and 856.4 parts by weight of pure water were mixed, and 3.8 parts by weight of a copper chip was dissolved in the mixture to obtain a tin whisker inhibitor (3) of the present invention.

The tin whisker inhibitor (3) had a pH of 0.12, a ferric chloride content of 3.0 wt%, a total content of nonionic surfactant of 1.1 wt%, and a copper concentration of 3.0 g / l.

Using the same specimen as in Example 1 and performing the same test as in Example 1, whiskers were not observed at all in the specimen after 60 days and 90 days after it was left unattended. It remained well. Moreover, in the said test piece, the lead thickness of the said copper wiring circuit reduced by the process using the tin whisker inhibitor 3 was 0.7 micrometer.

As described above, by using the tin whisker inhibitor of the present invention, it is possible to effectively smooth the surface of the material to be tin-plated even with a slight etching amount to effectively prevent the occurrence of tin whiskers. Further, according to the method for producing a whisker-resistant tin plated product of the present invention, tin plating can be performed while maintaining the shape stability of the material to be tin-plated even with a slight etching amount in the fine tin-plated material.

Claims (5)

pH is below 5, A tin whisker inhibitor comprising an aqueous solution containing an iron compound-based oxidant, a nonionic surfactant represented by the following general formulas (1) and / or (2), and copper ions: A [(C ₃ H ₆ O) _n (C ₂ H ₄ O) _m H] _k (1) A [(C ₂ H ₄ O) _m (C ₃ H ₆ O) _n H] _k (2) (In Formulas (1) and (2), A is an ethylene diamine residue, k is 4, n is a number from 3 to 35, and m is a number from 1 to 70.) . delete The method of claim 1, The iron compound-based oxidizing agent is at least one member selected from the group consisting of ferric chloride, ferric sulfate and ferric nitrate. A method for producing a whisker-proof tin plated product, characterized by subjecting the surface of the material to be tin-plated with the tin whisker inhibitor of any one of claims 1 to 3 to tin plating. 5. The method of claim 4, And the material to be tin plated is wiring copper of an electronic device.