JP2801793B2 - Tin-plated copper alloy material 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-plated copper alloy material and a method for manufacturing the same, and more particularly, to a tin-plated copper alloy material and
The present invention relates to a tin-plated copper alloy material having excellent solderability, which is suitably used for an electronic material component such as a connector, and a method for producing the same.

[0002]

2. Description of the Related Art Tin-plated copper alloy materials are used for various electronic parts including terminals and connectors. The purpose of tin plating is to provide corrosion resistance and good solderability. Further, the contact material also has a purpose of keeping the contact resistance value low and stable.

Conventionally, most of these tin-plated copper alloy materials have been manufactured by directly tin-plating a copper alloy material or by plating a copper base between the copper alloy material and the tin plating. In brass containing Zn, a copper base plating is applied. This is because Zn diffuses at a grain boundary in tin plating in a short time,
This is to prevent the concentration on the surface of the tin plating layer from deteriorating the solderability.

However, tin plating is directly applied on copper base plating.
When tin is applied, tin and copper react and expand even at temperatures around room temperature.
Scattered, intermetallic compound Cu₆Sn_FiveΗ layer consisting of
You. When placed in an environment of about 80 ° C or more,
Thing Cu_Three An ε layer made of Sn also grows. These spreads
Very fast, at 100-200 ° C for several hours to tens of hours
Spread 1-2 μm.

[0005] These intermetallic compounds adversely affect the properties of the tin plated material. For example, when tin plating and Cu react and diffuse to form a brittle ε layer thick, this causes peeling of the plated layer during bending. In addition, if the entire tin plating layer becomes an intermetallic compound and the pure tin layer disappears, soldering becomes impossible, or Cu diffuses into the surface of the tin plating layer to form copper oxide, and the contact resistance value decreases. Or get higher.

[0006] Recent changes in soldering methods due to the introduction of miniaturization, thinning, and surface mounting of electric and electronic components have made the thermal effects on components more severe. Therefore, the conventional tin-plated copper alloy material has come to have a case where satisfactory solderability and low and stable contact resistance cannot be satisfied.

As a countermeasure to avoid this, there is a method in which tin plating is applied thickly to save time for diffusion.
There is a problem that the cost of the tin plating material is increased. Further, when the tin plating is thick, many burrs (stamps of stamping) of tin are generated on the end face during stamping, and there is a problem that the life of the mold is shortened.

Accordingly, there has been a demand for a tin-plated copper alloy material having a conventional thin tin-plated layer and having a small change in solderability and contact resistance value under the influence of heat.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tin-plated copper alloy material having excellent solderability after thermal influence and a method for producing the same.

[0010]

A first gist of the present invention for solving the above-mentioned problems is that a copper base plating layer having a thickness of 0.1 to 0.4 μm is formed on a surface by melting. Ni ₃ S
An intermediate layer made of n-intermetallic compound and a tin plating layer are sequentially formed, which is present in a tin-plated copper alloy material.

A second gist of the present invention is that a copper base plating layer is formed on a surface of a copper alloy material, and then a thickness of 0.08 to 0.3 μm.
m, a tin plating layer is further formed thereon, and then the tin plating layer is melted (reflowed) so that 0.1 to 0.1 mm is formed between the copper base plating layer and the tin plating layer. There is provided a method for manufacturing a tin-plated copper alloy material, comprising providing an intermediate layer made of a 0.4 μm Ni ₃ Sn intermetallic compound.

A third gist of the present invention resides in that a copper base plating layer is formed on a surface of a copper alloy material, and then a thickness of 0.08 to 0.3 μm.
m, the copper alloy material is immersed in molten tin to form a molten tin plating layer, and the thickness between the copper alloy material and the tin plating layer is 0.1 to 0.4μ
An intermediate layer made of m ₃ Ni ₃ Sn intermetallic compound is provided.

[0013]

The operation of the present invention will be described together with the detailed structure of the present invention.

In the present invention, a Ni ₃ Sn layer having a thickness of 0.1 to 0.4 μm is provided between the copper base plating and the tin plating layer. This Ni ₃ Sn layer prevents copper from diffusing into the tin plating layer, and further suppresses the tin plating layer from changing to an intermetallic compound. The inventors found that the diffusion rate of Cu in the Ni ₃ Sn intermetallic compound layer was extremely slower than the diffusion rate in the tin plating layer, and based on this finding, provided the Ni ₃ Sn intermetallic compound. Due to the presence of the Ni ₃ Sn intermetallic compound layer, the tin plating layer prevents the formation of an intermetallic compound with Cu and can preserve the pure tin portion for a long time. Then, leaving the pure tin layer for a long period of time will maintain good solderability and low contact resistance for a long period of time.

The operation will be clarified in more detail below together with the knowledge obtained in carrying out the present invention.

Conventionally, it has been said that when an intermetallic compound such as a Ni ₃ Sn layer is formed, the plating layer peels off from the interface between the intermetallic compound layer and the copper alloy material by bending. Therefore, it has been conventionally performed to minimize the generation of Ni ₃ Sn intermetallic compound. However, unlike intermetallic compounds formed by diffusion over time, intermetallic compounds formed by melting at or above the melting point of tin have fewer defects due to diffusion at the interface and have excellent adhesion. I found it.

However, even when the molten intermetallic compound is interposed between the copper base plating layer and the tin plating layer, the adhesion may not always be excellent, and the cause has been intensively investigated. However, they have also found that the thickness of the layer made of the intermetallic compound affects the adhesion.

As described above, when the layer made of the intermetallic compound of Ni ₃ Sn is formed at a temperature equal to or higher than the melting point of tin and its thickness is controlled within a certain range, it does not adversely affect the peeling of the plating. In addition, it was clarified that it has the feature of preventing alloying of the tin plating layer. This has led to the development of a tin-plated copper alloy material having stable solderability both thermally and over time, and a method for producing the same.

In order to obtain an intermetallic compound having excellent adhesion,
The thickness is set to 0.1 μm or more. The thickness of the Ni ₃ Sn layer is set to 0.1 μm because a Ni ₃ Sn layer of 0.1 μm or more is required to prevent copper from diffusing into tin. The reason why the thickness is set to 0.4 μm or less is that there is no great difference in the effect of preventing the diffusion of copper even if the thickness exceeds 0.4 μm. Also,
When the Ni ₃ Sn layer grows beyond 0.4 μm, bending stress increases during bending, and the Ni ₃ Sn layer peels off from the interface of the copper alloy. Furthermore, if the thickness of the tin plating layer exceeds 0.4 μm, most of the layer becomes an alloy layer, and the pure tin layer becomes thin, which results in poor solderability and contact resistance. It is presumed that this is because Ni diffuses into the tin plating layer by heating and reaches the tin plating surface to generate nickel oxide. In addition, the intermetallic compound layer is 0.4μ
When the thickness exceeds m, the life of the die is shortened when stamping the plating material. Therefore, N
The thickness of the i ₃ Sn layer was 0.1 to 0.4 μm.

Although the thickness of the tin plating on the copper base is not limited, in practice, it is preferably 0.3 to 1.0 μm. Z from material
This is because a 0.3 μm copper plating layer is sufficient to prevent n from diffusing into the tin plating layer and maintain good solderability. Also, even if the thickness of the copper plating layer is 1 μm or more, there is no great difference in the effect of preventing Zn from diffusing into the tin plating layer.

The thickness of the copper plating is desirably thin in consideration of cost and generation of burrs and scum at the time of stamping. However, on the other hand, from the viewpoints of heat-peelability and solderability, a thicker one is desirable. The details may be determined according to the use of the plating material. However, assuming that the period from plating to processing into parts and soldering when mounted on equipment is about one year, in order to maintain good solderability during that period, it is necessary to use 0.1 mm. It is preferable that the thickness be 3 μm or more.

Next, the manufacturing method will be described.

In the present invention, first, a copper base plating is applied to the surface of the copper alloy material, a nickel plating is applied on the copper base plating, and a tin plating is applied. The method of applying tin plating is
Either a reflow plating method in which a plating layer is melt-processed after electroplating a copper alloy material, or a hot-dip plating method in which a copper alloy material is immersed in molten tin to form a tin layer may be used. In the former, the tin plating and the nickel plating that are melted when the electroplating film is melted form a Ni ₃ Sn layer. In the case of hot-dip plating, a Ni ₃ Sn layer is similarly formed. That is, in the reflow plating, a reflow step of giving gloss and a step of changing nickel plating to a compound layer are performed simultaneously. In the hot-dip plating, the step of providing a tin layer and the step of changing nickel plating to a compound layer are performed simultaneously.

The reason why the thickness of the nickel plating is set to 0.08 μm or more is that if the thickness is smaller than that, the thickness of the Ni ₃ Sn layer formed becomes less than 0.1 μm, and the effect of preventing Cu from diffusing into the Sn plating. Is insufficient. Also, 0.
The reason why the thickness is set to 3 μm or less is that the Ni ₃ S
This is because the thickness of the n-layer exceeds 0.4 μm, and the above-described problem occurs. Furthermore, the nickel plating layer is completely Ni
_This is because there is a possibility that the Sn intermetallic compound layer remains without being formed, and the reaction and diffusion of tin and nickel proceed to form a brittle intermetallic compound layer having many defects. Therefore, the thickness of the Ni plating is set to 0.08 to 0.3 μm.

In the case of reflow plating, the thickness of the Ni ₃ Sn layer is controlled by controlling the thickness of the Ni plating or the reflow temperature and time. In the case of hot-dip plating, the thickness of the Ni plating is controlled. It may be performed by controlling the melting temperature of the plating solution and the plating time.

In the present invention, a particularly remarkable effect is obtained when a copper alloy containing Zn (for example, copper or brass) is used as a base material, but other copper or copper alloys may be used. It is possible.

[0027]

Embodiments of the present invention will be described below.

In this example, as a base material, C2100
(5.1 wt% Zn-Cu), C2600 (3
0.5 wt% Zn-Cu), C2680 (35.2 wt%)
% Zn-Cu).

On the surface of the copper alloy, a copper base plating was formed to a thickness of 0.8 μm by a conventional method.

Next, a nickel plating was formed on the copper base plating by a conventional method to a thickness shown in Table 1.

Next, in Table 1, No. 1, No. 6, No.
13-No. For No. 15, hot-dip plating was performed, and for others, reflow plating was performed.

The plating conditions are as follows.

[0033] With respect to the plating formed as described above, the thickness of the tin plating and the thickness of the Ni ₃ Sn layer were measured. Table 1 shows the results.

Further, these tin-plated copper alloy materials were
After performing heat treatment at 0 ° C. for 5 minutes and 10 minutes, contact resistance, solderability and adhesion were evaluated. The evaluation method is as follows. The above heat treatment conditions take into account the reflow soldering method that has been increasing with recent surface mounting of connectors.

(Soldering Test Conditions) Solder composition: Sn / Pb = 6/4 Solder temperature: 230 ± 5 ° C. Flux: rosin-based inactive flux The evaluation of soldering was that the solder adhesion area was 85 after soldering.
% Or more was regarded as “good” and less than or equal to “poor”.

(Contact resistance measurement conditions) Load: 50 gf (at the time of measurement) Current value: 20 mA The contact resistance was such that a pure gold probe was reciprocated on the sample surface while changing the load from 0 to 50 gf, and a load of 50 gf was applied. The time value was measured.

(Adhesion test) Adhesion was 500 at 150 ° C.
After heat treatment for 90 hours, these materials were repeatedly bent twice at 90 °, and the surface of the bent portion was observed with a stereoscopic microscope to confirm the presence or absence of peeling of the plating layer.

Table 1 shows the results of the evaluation of the solderability and the contact resistance and the results of the adhesion test.

As a result, the intermetallic compound Ni_ThreeSn layer thickness
Is 0.1 μm or more and 0.4 μm or less (NO.
No. 9, Example), good solderability, contact resistance
Was kept low. This is Ni_ThreeSn layer diffuses Cu
And suppress Cu₆Sn_FiveLayer composed of, Cu_Three Sn From
This is because the growth of the ε layer is prevented.

No. 10-No. 18 is Ni ₃
Since the thickness of the Sn layer exceeded 0.4 μm, peeling of the Ni ₃ Sn layer occurred in the adhesion test.

Further, as in the prior art, the intermetallic compound Ni_Three
When there is no Sn layer (No. 20, No. 21), or
However, when it is thinner than 0.1 μm (No. 19),
Cu in tin₆Sn_FiveLayer composed of, Cu_Three Sn Ε consisting of
The layer grows and the tin-plated layer quickly changes to an intermetallic compound.
The adhesion was poor.

From the results of the above examples, it can be seen that the intermetallic compound N
The thickness of the i ₃ Sn layer needs to be 0.1 to 0.4 μm,
In order to obtain an intermetallic compound layer of that thickness, it became clear that it is necessary to apply a Ni plating layer of 0.08 to 0.3 μm.

[0043]

According to the present invention, tin-plated brass or copper material having excellent solderability and thermally stable contact resistance can be produced. These tin-plated copper alloy materials improve the solderability and contact resistance characteristics of electric and electronic components such as terminals and connectors, and can contribute to increasing the reliability of equipment.

[0044]

[Table 1]

Continuation of the front page (56) References JP-A-4-323396 (JP, A) JP-A-61-166994 (JP, A) JP-A-4-235292 (JP, A) JP-A-61-198507 (JP, A) , A) JP-A-48-38247 (JP, A) JP-A-50-21272 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C25D 3/00-7/12

Claims (3)

(57) [Claims] 1. A copper base plating layer having a thickness of 0.1
A tin-plated copper alloy material comprising an intermediate layer made of a molten Ni ₃ Sn intermetallic compound having a thickness of up to 0.4 μm and a tin plating layer formed sequentially. 2. A copper base plating layer, a Ni intermediate plating layer having a thickness of 0.08 to 0.3 μm, and a tin plating layer thereon. By melting (reflowing) the plating layer, 0.1 to 0.4 μm of N is interposed between the copper base plating layer and the tin plating layer.
A method for producing a tin-plated copper alloy material, comprising providing an intermediate layer made of an i ₃ Sn intermetallic compound. 3. After applying a copper base plating layer and then a Ni intermediate plating layer having a thickness of 0.08 to 0.3 μm on the surface of the copper alloy material, the copper alloy material is immersed in molten tin, Forming a hot-dip tinned layer and, at the same time, providing an intermediate layer made of a Ni ₃ Sn intermetallic compound having a thickness of 0.1 to 0.4 μm between the copper alloy material and the tin plated layer; Manufacturing method of copper alloy material.