JP3155139B2 - Tin or tin alloy plated material having excellent oxidation resistance and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tin or tin alloy plated material in which tin or a tin alloy is plated on a copper or copper alloy surface, and more particularly to a method for producing the same. The present invention relates to a tin or tin alloy plated material excellent in oxidation resistance with little deterioration in discoloration resistance, solder wettability and contact resistance, and a method for producing the same.

[0002]

2. Description of the Related Art In general, for electronic parts such as terminals, connectors, contacts and the like, plated materials obtained by plating tin or a tin alloy on a copper or copper alloy surface are widely used. recent years,
With miniaturization, weight reduction, and high performance of electronic devices and the like, terminals, connectors, which are a part of electronic components, are also required to be further reduced in size, thickness, and performance. Further, as terminals and connectors have become smaller and more sophisticated, the area of the soldered portion and the contact area between the terminals have become smaller, and requirements for solder wettability, contact resistance, and the like have become more stringent. Further, from the viewpoint of improving the productivity at the time of assembling an electronic component, it is necessary to shorten the solder wetting time. Therefore, even a slight oxidation of the plating surface has become a problem with respect to the solder wettability.

[0003] However, in the case of the conventional tin or tin alloy plating material, the plating surface is easily oxidized, so that the above-mentioned requirements cannot be sufficiently satisfied. For this reason, a tin or tin alloy plating material that maintains solder wettability and low contact resistance for a long time has been required.

On the other hand, a contact using a tin or tin alloy plating material has a low unit price and is excellent in solder wettability, workability, contact resistance, heat resistance, etc., but is left in a high temperature and high humidity state for a long time. Then, as mentioned above, the surface oxidizes, discolors,
There is a problem in that the contact resistance increases, and there is a problem in that the solderability before contact with the substrate deteriorates.

[0005] For this reason, especially for the contact, since it has excellent oxidation resistance and high reliability as a high-grade contact,
Gold-plated ones may be used instead of tin or tin alloy plating.

However, a contact using a gold-plated material is expensive and does not require the same characteristics as a gold-plated material in order to reduce the consumption of gold. On the other hand, there is a strong demand for the development of a tin or tin alloy plating material to be replaced.

[0007]

The following two factors are considered as causes of deterioration of properties such as solder wettability and contact resistance. The first is that the plating surface is oxidized and a tin oxide layer is formed on the plating surface. The second is,
This is because Cu diffuses from the raw material or the copper base plating during the tin or tin alloy plating, and the tin or tin alloy plating layer changes to an intermetallic compound of copper and tin.

That is, when the plating surface is oxidized and an oxide such as tin having a melting point higher than that of tin or tin alloy plating is formed thicker, the melting point of the plating surface becomes higher, and the melt bonding property with the solder, that is, the solder, Poor wettability. In addition, the electrical resistance of tin oxide (specific resistance 10 ² to 10 ³ Ωcm)
Electrical resistance of tin metal (specific resistance 1.1 × 10 ^-5 Ωcm)
When the tin oxide is formed thicker on the plating surface, the contact resistance becomes higher.

Further, as described above, when Cu diffuses during plating and the tin or tin alloy plating layer changes to an intermetallic compound of copper and tin, an oxide of Cu having a high resistance (specific resistance) is formed on the plating surface. Cu ₂ O: 10 ⁸ to 10 ⁹ Ωcm, CuO: 2.1 × 10 ⁶
Ωcm) and the contact resistance increases. Further, since the intermetallic compound of copper and tin has a higher melting point than the metal of tin and tin alloys, when the plating layer changes to an intermetallic compound of copper and tin, the solder wettability is reduced. Further, when the plating layer changes to an intermetallic compound of copper and tin, the discoloration resistance also deteriorates.

As a technique for preventing oxidation of the tin plating surface, a passivation treatment is used in tin plating of steel with tin. As the passivation treatment, a method of performing an electrolytic treatment in a sodium bichromate solution is widely used, but when this passivation treatment is performed, a hydrated oxide of Cr ³⁺ is formed on the tin plating surface, Tin oxidation is suppressed. However, if this technology is applied to tin or tin alloy plated material on copper alloy material surfaces for electronic components, the hydrated oxide of Cr ³⁺ formed on the plated surface will adversely affect solder wettability and contact resistance. Exert.

The application of a solution containing 0.5% by weight or more of a phosphate ester type surfactant to the surface of a tin plating is disclosed in Japanese Patent Publication No. 5-22322. Since the emphasis is not on the prevention of oxidation but on the improvement of the lubricity of the connector contacts, a phosphate ester having a relatively large carbon number and a polyphenyl ether base is used as the phosphate ester. In these phosphate esters, the alkyl group of the lipophilic group is decomposed by heat treatment at the time of assembling the terminal or left in a high-temperature, high-humidity factory, and the antioxidant effect cannot be expected. For this reason,
The phosphoric acid ester disclosed in the above publication cannot prevent oxidation of tin or tin alloy plating for terminals, connectors, and contacts.

As described above, tin or tin alloy plating materials for terminals, connectors, and contacts are poor in solder wettability and contact resistance due to oxidation of the tin and tin alloy plating surface, and the tin and tin alloy plating during tin and tin alloy plating. Discoloration due to Cu diffusion,
Deterioration of solder wettability and contact resistance becomes a problem. For this reason, development of a tin or tin alloy plating material with little deterioration such as discoloration due to oxidation of a plating surface, solder wettability, and contact resistance has been awaited.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a phosphate ester, a diphenyl phosphate, and a phosphoric acid ester contained in an antioxidant solution applied to a plating material surface.
By limiting the number of carbon atoms of phosphite and phosphite diphenyl ester, the surface of tin or tin alloy plating is less oxidized, and terminals, connectors and contacts with less discoloration, solder wettability, contact resistance, etc. It is an object of the present invention to provide a tin or tin alloy plated material for use and a method for producing the same.

[0014]

Means for Solving the Problems The surface of a plating material obtained by plating tin or a tin alloy on the surface of copper or a copper alloy is made of a phosphoric acid ester, a phosphite ester, or a mixture of a phosphoric acid ester and a phosphite ester. A tin or tin alloy plated material having an organic film and excellent oxidation resistance.

A terminal in which an organic film made of a phosphate ester, a phosphite ester, or a mixture of a phosphate ester and a phosphite ester is formed on the surface of a plating material obtained by plating tin or a tin alloy on the surface of copper or a copper alloy. It is a tin or tin alloy plating material with excellent oxidation resistance for connectors, connectors and contacts.

The solder wetting time according to the meniscograph method after steam aging at a temperature of 105 ° C. and a humidity of 100% RH for a period of 24 hours is the same as the solder wetting time before the steam aging.
The tin or tin alloy plated material having excellent oxidation resistance according to claim 1 or 2, which is 1.5 times or less. However, the solder wetting time was measured with a 6/4 solder at 230 ° C using a 0.3 mm thick plated material and an inert flux.

An antioxidant solution in which at least one of a phosphoric acid ester and a phosphite is dissolved in water or a solvent is sprayed or immersed on the surface of a plating material obtained by plating tin or a tin alloy on the surface of copper or a copper alloy. A method for producing a tin or tin alloy plated material having excellent oxidation resistance according to claim 3.

The antioxidant has the general formula (1), (2) or (3)
It is an antioxidant liquid containing at least one kind of phosphate represented by Where R ₁ , R ₂ , R ₃ ,
R ₄ , R ₅ , and R ₆ are substituents composed of aliphatic or aromatic.

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The antioxidant is an antioxidant containing at least one phosphite represented by the general formulas (4) and (5). However, R ₇ , R ₈ and R ₉ in the general formula are aliphatic or aromatic substituents.

Embedded image

The antioxidant liquid according to claim 5, wherein the phosphoric acid ester contains phosphoric acid diphenyl ester.

The antioxidant solution according to claim 6, wherein the phosphite comprises diphenyl phosphite.

An antioxidant solution comprising an aqueous solution containing 0.1 g / l or more of diphenyl phosphate, an aqueous solution containing 0.1 g / l or more of diphenyl phosphite, or a mixed aqueous solution thereof.

[0023]

[Action] An antioxidant solution consisting of a phosphoric acid ester or a phosphite or a mixture thereof is applied to the surface of a tin or tin alloy plating material to form an organic film. O ₂ or H ₂ 0
And is less likely to be oxidized. For this reason, the tin or tin alloy plating material according to the present invention has less deterioration in discoloration resistance, solder wettability, contact resistance and the like.

The phosphate ester used in the present invention is represented by the general formulas PO (OR ₁ ) (OH) ₂ , PO (OR ₂ ) (OR ₃ ) OH, PO (OR ₄ ) (O
R ₅ ) (OR ₆ ), and typical examples are diphenyl phosphate, dibutyl phosphate, diethyl phosphate and the like. However, R ₁ , R ₂ , R ₃ , R ₄ ,
R ₅ and R ₆ are substituents composed of aliphatic or aromatic. The phosphite is represented by the general formula PO (OR ₇ ) (OR ₈ ) H, P
It is represented by O (OR ₉ ) (OH) H 2, and typical examples are diphenyl phosphite, dibutyl phosphite, diethyl phosphite and the like. However, R ₇ , R ₈ ,
R ₉ is an aliphatic or aromatic substituent.

Here, R, which is a substituent of each phosphoric acid ester or phosphite, is aliphatic or aromatic, and the aliphatic is preferably one having 5 or less carbon atoms and a short molecular structure. In the case of an aliphatic having a long straight chain having 6 or more carbon atoms, if left at high temperature and high humidity for a long time, the straight chain of the alkyl group can be bonded in the child, and the alkyl group is phosphoric acid. Dissociate with the part. That is, the phosphoric acid ester and the phosphite ester are decomposed, and the antioxidant effect may be reduced.

Among phosphoric acid esters, those having a particularly large antioxidant effect are phosphoric acid diphenyl esters. The amount of diphenyl phosphate contained in the antioxidant solution is preferably 0.1 g / l or more. The reason for this is that when the content of phosphoric acid diphenyl ester is less than 0.1 g / l, the antioxidant effect of the tin or tin alloy plated material is reduced.

Further, among the phosphites,
One having a large antioxidant effect is diphenyl phosphite. Further, the amount of diphenyl phosphite contained in the antioxidant is 0.1 g / l or more, and the temperature is preferably 30 ° C. or more. The reason is that when the content of diphenyl phosphite is less than 0.1 g / l, the antioxidant effect of the tin or tin alloy plating material is reduced, and when the liquid temperature is less than 30 ° C., This is because they do not dissolve sufficiently and may precipitate.

The phosphate or phosphite applied to the plating surface is represented by the general formula:
Among them, it is presumed that O not bonded to R is bonded to tin or a tin alloy on the plating surface and covers the tin or tin alloy plating surface as a single thin film. For this reason, it is considered that the phosphoric acid ester or the phosphite organic film exerts an antioxidant effect.

The organic film composed of a phosphoric ester or a phosphite or a mixture thereof is close to a single-layer film and has a thin film, so that it does not adversely affect solder wettability and contact resistance. On the contrary, since the plating surface is not easily oxidized, the discoloration resistance, the solder wettability and the contact resistance are hardly deteriorated.

Examples of the tin or tin alloy plating material include an electroluminescent tin or tin alloy plating material using a brightener, a reflow tin or tin alloy plating material subjected to a melting treatment after tin or tin alloy plating, and a molten tin or tin alloy plating material. There is a hot-dip tin or tin alloy plating material to be plated through the material inside, a vapor-deposited tin or tin alloy-plated material plated by vapor deposition of a dry plating method, etc. It is effective for plated materials by any plating method.

The tin alloy plating material referred to in the present invention is Pb,
It is obtained by plating copper or a copper alloy with a tin alloy containing at least one of In, Zn, Sb, Cd, and Ag. Therefore, 6 /
4 (Sn / Pb) solder plated is also included in the tin alloy plating material.

As a method of applying an antioxidant solution of a phosphoric acid ester or a phosphite or a mixture thereof to a plating surface, spray or dip coating is preferable. The reason is that these coating methods can uniformly apply the antioxidant solution to the plating material surface without damaging the plating surface.

The procedure for applying the antioxidant solution is, for example, to apply the antioxidant solution after pressing, degreasing, washing, and drying in a contact that performs cleaning such as degreasing after pressing the plated material. Even if the antioxidant solution is applied before the degreasing cleaning, the organic film on the plating surface formed by the coating may be peeled off by the subsequent degreasing cleaning, and the antioxidant effect may be weakened. Also, if there is no degreasing and washing process after pressing,
An antioxidant solution may be applied before press working to form an organic film on the surface of the plating material.

As described above, tin or tin alloy plated materials for terminals, connectors, and contacts are exposed to a high-temperature and high-humidity environment between manufacturing and shipment and soldering on a board, as described above. May deteriorate. Therefore, it is important to secure the solder wettability at the time of assembling the electronic component from the viewpoint of improving the productivity at the time of assembling the electronic component. In order to ensure this solder wettability, temperature 105 ℃, humidity 100% RH, time
It is important to suppress the solder wetting time of the tin or tin alloy plated material by meniscography after steam aging for 24 hours to 1.5 times or less the solder wetting time before steam aging. This is because if the solder wetting time exceeds 1.5 times, the productivity will be significantly reduced. However, the solder wetting time was 6/4 at 230 ° C using a 0.3 mm thick plated material and an inert flux.
(Sn: Pb = 6: 4).

As described above, according to the present invention, the tin or tin for terminals, connectors and contacts is excellent in oxidation resistance, in which the plating surface is not easily oxidized, and which has excellent resistance to discoloration, solder wettability and little deterioration of contact resistance. An alloy plating material can be obtained.

[0036]

The present invention will be specifically described below with reference to examples. Example 1 Table 1 shows the main components of the antioxidant applied to the plating material surface. The plating material is phosphor bronze class 1 (C5111) Cu-4.0
% Sn-0.03% P, thickness 0.3mm, tin plating thickness 1.0
μm. After applying the antioxidant shown in Table 1 to the surface of the plated material by spraying, steam aging was performed as an oxidation acceleration test, and then the discoloration state was observed, the solder wetting time was measured, and the contact resistance was measured. Table 2 shows the results. Table 3 and Table 4 show the steam aging condition, the solder wettability test condition, and the contact resistance measurement condition, respectively.
It is shown in Table 5. FIG. 1 shows the solder wetting time (t ₁ ) and the solder pull-in force (PW). The solder wetting time is defined as the time (t ₁ ) until the wetting force recovers to zero.

Nos. 1 to 13 of the examples of the present invention exhibit an antioxidant effect. In particular, diphenyl phosphates of Nos. 1 and 2, 7-10 diphenyl phosphite, and a mixture of 13 diphenyl phosphate and phosphite have excellent antioxidant effects. On the other hand, in Comparative Examples Nos. 14 and 15, the antioxidant effect was small, and No. 16, which did not apply the antioxidant, was discolored, the solder wetting time, and the contact resistance were both increased, resulting in significant oxidation. You can see that there is.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

[Table 4]

[0042]

[Table 5]

Example 2 The plating material was phosphor bronze class 1 (C5111) Cu-4.0% Sn-
0.03% P, 0.3mm thickness, 0.1mm thickness on the surface of this material
μm copper base plating and a thickness of 1.0
This is a 6/4 (Sn / Pb) solder plating of μm. 0.1 g / l of diphenyl phosphate on this plating material surface
Aqueous solution containing 0.1 g / l of phosphite and 0.1 g / l of phosphite were individually applied by dip coating, and then subjected to steam aging under the steam aging conditions shown in Table 6 as an oxidation promotion test. Thereafter, observation of discoloration state, solder wettability Degradation was measured.

The solder wettability was evaluated by the solder wetting time (t ₁ ) and the solder pull-in force (PW) shown in FIG. The solder pull-in force (PW) was defined as the solder wetting force after 5 seconds. Table 7 shows the measurement results of the discoloration state, the solder wetting time (t ₁ ), and the solder pull-in force (PW).

In Examples 1 and 2 of the present invention, even after the steam aging was performed for 48 hours, the solder wetting time and the solder pull-in force did not change, and the solder wettability did not deteriorate. On the other hand, in Comparative Example 1, when steam aging was performed, the solder wetting time and the solder pull-in force changed with time, and the solder wettability deteriorated. In addition, in Examples 1 and 2 of the present invention, the surface did not discolor even when subjected to steam aging for 48 hours, whereas in Comparative Example 1, the surface was discolored by steam aging for 4 hours or more. In Table 7, the shorter the solder wetting time and the larger the solder pull-in force, the better the solder wettability.

[0046]

[Table 6]

[0047]

[Table 7]

[0048]

As is apparent from the above description,
According to the present invention, it is possible to obtain a tin or tin alloy plating material whose plating surface is difficult to be oxidized,
It is possible to obtain terminals, connectors and contacts excellent in oxidation resistance with little deterioration such as discoloration, solder wettability and contact resistance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a solder wetting time and a solder pull-in force in a solder wettability test.

[Explanation of symbols]

t ₁ : solder wetting time, PW: solder pull-in force.

Claims (9)

(57) [Claims] 1. An organic film comprising a phosphoric acid ester, a phosphite ester, or a mixture of a phosphoric acid ester and a phosphite ester is formed on the surface of a plating material obtained by plating tin or a tin alloy on the surface of copper or a copper alloy. A tin or tin alloy plated material having excellent oxidation resistance. 2. An organic film made of a phosphoric acid ester, a phosphite ester, or a mixture of a phosphoric acid ester and a phosphite ester is formed on the surface of a plating material obtained by plating tin or a tin alloy on the surface of copper or a copper alloy. A tin or tin alloy plated material having excellent oxidation resistance for terminals, connectors and contacts. 3. The solder wetting time according to the meniscograph method after steam aging at a temperature of 105 ° C. and a humidity of 100% RH for a period of 24 hours is the same as the solder wetting time before the steam aging.
3. A tin or tin alloy plated material having excellent oxidation resistance according to claim 1 or 2, which is 1.5 times or less. However, the solder wetting time was measured with a 6/4 solder at 230 ° C using a 0.3 mm thick plated material and an inert flux. 4. An antioxidant solution in which at least one of a phosphoric ester and a phosphite is dissolved in water or a solvent is sprayed or immersed on the surface of a plating material obtained by plating tin or a tin alloy on the surface of copper or a copper alloy. The method for producing a tin or tin alloy plated material having excellent oxidation resistance according to claim 3, wherein the coating is applied. 5. The antioxidant according to claim 1, wherein the antioxidant has the general formula (1), (2),
An antioxidant comprising at least one phosphoric ester represented by (3). However, in the general formula
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are aliphatic or aromatic substituents. 6. An antioxidant solution, wherein the antioxidant solution contains at least one phosphite represented by the general formulas (4) and (5). However, R ₇ in the general formula,
R ₈ and R ₉ are an aliphatic or aromatic substituent. 7. The antioxidant liquid according to claim 5, wherein the phosphoric acid ester contains phosphoric acid diphenyl ester. 8. The antioxidant solution according to claim 6, wherein the phosphite contains diphenyl phosphite. 9. An aqueous solution containing 0.1 g / l or more of diphenyl phosphate or 0.1 g / l of diphenyl phosphite
An antioxidant solution comprising an aqueous solution containing the above or a mixed aqueous solution thereof.