JP2002266095A - Copper alloy material for electronic-electrical parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the whisker resistance of a copper alloy material for electrical-electronic parts without damaging the advantages of the excellent press blanking properties and low friction coefficient of bright electrotinning. SOLUTION: Bright electrotinning having a plating thickness of 0.5 to 2 μm, and in which the reflectivity of the surface is <=30%, the content of C in the plating is 0.05 to 1 mass%, and the crystal grain size of the plating is 0.1 to 1 μm, and the orientation index of the (101) plane in the plating is <=2.0 is applied to a copper alloy containing 0.1 to 10 mass% Zn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a terminal, a connector,
Electronics used for switches, relays, lead frames, etc.
The present invention relates to a copper alloy material for electric parts.

[0002]

2. Description of the Related Art Sn plating techniques include electroplating, reflow plating, and a method of mechanically or air immersing a material in a molten Sn bath to control the thickness of the plated film. Since it is difficult to control the plating film thickness in the method of immersion in a molten Sn bath, electroplating and reflow plating, which are excellent in quality stability, are frequently used for electronic and electric components.

[0003] In general, electroplating is carried out by using electrobright Sn plating using a brightener in order to suppress the deterioration of solder wettability with time and improve the appearance. However, it is difficult to suppress the generation of whiskers (needle-shaped Sn single crystal) in the electro-bright Sn plating, and it is often replaced with reflow Sn plating from the viewpoint of electrical reliability. Note that Sn
When whiskers are generated in plating, a short circuit failure such as a short circuit in a circuit or between terminals, insulation failure, or the like may occur, or noise may be generated. On the other hand, reflow Sn plating has disadvantages in that press punching properties are inferior (generation of burrs) and the friction coefficient is high. Beard burr refers to a state in which plating has dropped or is about to fall off in a layered manner in the vicinity of a shearing surface of press punching, and may cause breakage of a press die or a pressing flaw, or a short circuit during use. Also, the high coefficient of friction is an obstacle to increasing the number of poles of connectors in recent years with the progress of electrical equipment such as automobiles.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to improve whisker resistance in electronic and electric parts applications without impairing the advantages of electro-gloss Sn plating such as excellent press punching properties and low friction coefficient. It is what it was.

[0005]

Means for Solving the Problems The present inventor has limited the Zn content of a copper alloy material, and at the same time, controlled the thickness, reflectivity, and C content of electro-gloss Sn plating, and further improved the crystal grain size of the Sn plating. The above object was achieved by controlling the diameter and the orientation index. That is, the copper alloy material for electronic / electric parts according to the present invention is obtained by plating a copper alloy containing 0.1 to 10 mass% of Zn with a plating thickness of 0.5 to 2 μm and a surface reflectance of 30% or more. The amount of C inside is 0.05-1 mass
%, The crystal grain size of the plating is 0.1 to 1 μm,
It is characterized by being subjected to electro-gloss Sn plating having an orientation index of the (01) plane of 2.0 or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The chemical components of the copper alloy material according to the present invention and the reasons for limiting the thickness, reflectance, C content, crystal grain size, and orientation index of Sn plating will be described below. (Zn: 0.1 to 10 mass%) Whisker resistance is improved by containing Zn in the copper alloy material. However, if the Zn content is less than 0.1 mass%, the effect is small. Also one
If it exceeds 0 mass%, the whisker resistance is rather reduced.
Therefore, the Zn content of the material is set to 0.1 to 10 mass%. Note that the effect of Zn is dominant on whisker suppression, and the same effect can be obtained when the copper alloy material appropriately contains an element other than Zn.

Although various theories have been described as to the cause of whiskers, the predominant one is the oxide film theory on the Sn plating surface. The present inventors have found that, since the generation of whiskers is strongly suppressed when the Zn content is in the range of 0.1 to 10 mass%, in a copper alloy having a large Zn content such as brass, Zn which is more easily oxidized than Cu is plated with Sn. Whisker is generated by reaching the surface and forming a thick Zn oxide film. In a copper alloy containing no Zn, whisker is generated when Cu reaches the Sn plating surface and forms an oxide film. In a copper alloy containing Zn in a relatively small amount of 0.1 to 10 mass%, it is speculated that a small amount of Zn reaching the plating surface may suppress the oxidation of Cu.

(Sn plating thickness: 0.5-2 μm) Sn
If the plating thickness is less than 0.5 μm, the contact resistance degradation after the high temperature storage test becomes large. Further, the solder wettability after aging is also reduced. On the other hand, when it exceeds 2 μm, the press punching property is reduced (the generation of burrs) and the friction coefficient is increased.
Therefore, the Sn plating thickness is set to 0.5 to 2 μm. Note that Cu plating may be applied to the Sn plating underlayer for the purpose of suppressing deterioration over time. The Sn plating thickness is the same in this case.

(Reflectance of Sn plating: 30% or more) Sn
If the plating has a surface reflectance of less than 30%, the appearance is deteriorated and the solder wettability after aging is reduced. Therefore,
The reflectance of Sn plating is 30% or more. (C content of Sn plating: 0.05 to 1 mass%) If the C content contained in the Sn plating is less than 0.05 mass%, the press punching property is reduced (the occurrence of burrs) and the friction coefficient is increased. On the other hand, if the C content exceeds 1 mass%, the whisker resistance decreases. Therefore, the C content of Sn plating is set to 0.05 to 1 mass%.

(Grain size of Sn plating) The crystal grain boundary of Sn plating is a main route for diffusing elements constituting the copper alloy material to the plating surface, and when the crystal grain size is small, the area of the crystal grain boundary is large and diffuses. The reverse is true for higher speeds and larger grain sizes. Therefore, assuming the oxide film theory as a mechanism of whisker generation, in order to control the diffusion of Zn, it is necessary to control not only the Zn content of the copper alloy material but also the crystal grain size of Sn plating which controls the diffusion. Should be important. As a result of study based on the presumption, the crystal grain size of the Sn plating was 0.1 μm at the Zn content.
When it is less than m or more than 1 μm, whiskers are easily generated, and it has been found that whisker generation is suppressed when the crystal grain size is in the range of 0.1 to 1 μm. This is because the crystal grain size is 1μ.
If it exceeds m, Zn diffusion tends to occur, Zn forms an oxide film on the Sn plating surface, and if the crystal grain size is less than 0.1 μm, Zn diffusion hardly occurs, and the amount of Zn necessary to suppress whiskers is reduced. It is presumed that it did not reach the Sn plating surface.

(Orientation Index of Sn Plating) The crystal orientation in which whiskers grow from the Sn plating surface is <101>.
Therefore, the possibility that whisker growth can be suppressed by controlling the orientation index of the (101) plane of the Sn plating is recalled. As a result of repeated experiments, it can be suppressed by controlling the orientation index to 2.0 or less. I found Therefore, the orientation index of the (101) plane of Sn plating is set to 2.0 or less.

A copper alloy material having the above composition is electroplated with an electroluminescent Sn plating having a thickness of 0.5 to 2 μm, the reflectance of the Sn plating surface is 30% or more, and the C content in the plating is 0.05 to 1 μm.
mass%, the crystal grain size of Sn plating is 0.1-1 μm, and the orientation index of the (101) plane of Sn plating is 2.0 or less at the same time.
Using a plating bath to which 0 ml / l of a brightener (a reaction precipitate of acetaldehyde and orthotoluidine was dissolved in isopropyl alcohol) and 20 g / l of a dispersant, the current density of plating was 1 to 5 A / dm ^2. The Sn plating may be performed under the plating conditions of a plating bath temperature of 5 to 15 ° C. This plating condition is characterized in that the bath temperature is controlled to be lower than in the conventional condition. Conventionally, with respect to the plating bath having the above composition, the bath temperature is usually controlled to about 17 to 40 ° C.
n plating was performed. When plating is performed on such a high temperature side, the orientation index of the (101) plane of Sn plating in particular exceeds 2.0, making it difficult to obtain the orientation index of the present invention.

[0013]

EXAMPLES Examples of the copper alloy material for electronic / electric parts according to the present invention will be described below together with comparative examples.
The ingots having different Zn contents having the compositions shown in Table 1 were hot-rolled, and cold rolling and annealing were appropriately repeated to obtain 0.25 mm
The thickness of the plate was adjusted, and the plate was electroplated with Sn in a sulfuric acid Sn bath. Surface reflectance of Sn plating,
In order to control C content, crystal grain size and crystal orientation,
The plating bath composition, brightener concentration, plating bath temperature, and current density were appropriately adjusted as described above. In addition, No. Reference numeral 16 denotes reflow Sn plating. With respect to each copper alloy sheet material after the Sn plating, the plating thickness, the reflectance, the C content, the crystal grain size, and the (101) orientation index of the electroluminescent Sn plating were measured. The results are shown in Table 1.

[0014]

[Table 1]

The measurement of the reflectance of the Sn plating is performed according to JI
It carried out by the method described in SZ8722. The C content in the Sn plating was determined by using the same plating solution as used for plating each plate material, applying a 10 μm-thick Sn plating on a 50 × 100 mm titanium plate at the same current density, and then peeling off the film. After ultrasonic cleaning in the inside, it was quantitatively analyzed by a combustion infrared absorption method. The crystal grain size of the Sn plating was determined by subjecting the cut surface of the plating with a microtome to Ar etching to produce crystal grains, and the size was determined according to the comparison method described in JIS H0501. However, since the crystal grain size was small, the observation was performed using a SEM with a magnification of 10,000 times.

The orientation index of Sn plating is 10 × 10 mm
Were sampled and measured using an X-ray diffractometer. X
CuKα radiation was used as the radiation source. The calculation method of the orientation index is based on the following equation. Orientation index = {A / B} / {C / D} where: A: peak intensity value (cps) of desired orientation plane ((101) plane in this case) B: sum of peak intensity of orientation plane considered (cps) C) Orientation plane determined by powder X-ray diffraction (in this case, (10
1) Peak intensity of surface) (csp) D: Sum of peak intensities of oriented surfaces taken into account by powder X-ray diffraction (csp) Excluding the peak intensity of the base material, a peak due to the plating film was observed (200). (101), (220),
Peak intensity was measured for eight types of planes (301), (112), (400), (321) and (312). These correspond to the orientation planes considered above.

A test piece was taken from each of the above copper alloy sheets, and whisker resistance (whisker length), contact resistance after leaving at high temperature,
Solder wettability, press punching property (with or without burrs) and coefficient of friction were measured as follows. Table 2 shows the results. To measure the whisker resistance, a test piece with a width of 50 mm and a length of 100 mm is sampled and fixed to a U-shaped jig with an inner width of 94 mm in a state of being bent in the longitudinal direction, and a bending stress is applied. To promote the generation of whiskers.
After standing at room temperature for 3 months, an area of 30 mm × 20 mm was observed with a magnifying glass, and the maximum length of the generated whisker was recorded.

Measurement of contact resistance after leaving at high temperature was 120 ° C.
The plating surface after holding for 120 hours was subjected to a four-terminal method under the conditions of an open voltage of 20 mv, a current of 10 mA, and a contact load of 9.8 N. The probe used was Au. Solder wettability was 96 at 40 ° C. and 80% RH as conditions for promoting aging.
After holding, the solder checker ATS-2000 manufactured by Resca
Performed using a mold. Solder composition is 60 mass% Sn-40
The mass% Pb was set to 245 ° C., and the flux used was a rosin-based inactive type (α100). Test piece size is 10m
Under the conditions of m width, 30 mm length, immersion speed of 25 mm / s, immersion depth of 8 mm, and immersion time of 5 s, the time until the wetting force changes from the rebound side to the retraction side (so-called zero cross time) was measured.

The burrs after press punching were performed by setting the mold clearance to 5% of the plate thickness, the punch diameter to 10 mm, and the punching speed to 5 mm.
S near the shear surface when punching without lubrication at 0 mm / min
The state of n-plating was observed with a stereoscopic microscope, and the presence or absence of mustache was determined. The coefficient of friction was measured as follows. In order to simulate the shape of the contact part of the actual terminal,
After cutting out a material having a size of × 10 mm, it was processed into a hemispherical shape having an inner radius of 1.5 mm and a height of 1 mm using a molding die and a press, and the male terminal was left as a plate. As shown in FIG. 1, the measurement was performed by sandwiching the male test piece 1 between two female test pieces 2 and then setting the male test piece 1 to 80 mm / min. In the horizontal direction at a speed of 2 mm, and the pull-out force after sliding 2 mm is measured by a horizontal load measuring device 3 (Model-
301 type). The contact load is 300 g
f. The maximum pulling force was divided by twice the contact load, and this value was defined as the friction coefficient. The reason for dividing by twice the contact load is that
This is because there are two upper and lower contact portions.

[0020]

[Table 2]

As shown in Table 2, as shown in FIG. 1 to 5 are all good. On the other hand, No. Nos. 6 and 7 have poor whisker resistance due to the low Zn content of the copper alloy material.
o. Conversely, Nos. 8 and 9 have an excessively high Zn content and have poor whisker resistance. No. No. 10 has a small plating thickness and is inferior in contact resistance and solder wettability. No. Sample No. 11 has a large plating thickness, generates burrs, and has a poor coefficient of friction. No. 12
And 13 have poor reflectivity and therefore poor solder wettability. N
o. 14 has a low reflectance and a low C content, and thus has poor solder wettability, press punching properties, and friction coefficient. No. 1
Sample No. 5 has a low C content because of its high C content. No. 1
Reference numeral 6 denotes reflow Sn plating, which is inferior in press punching properties and friction coefficient. No. No. 17 has a too small grain size of Sn plating. No. 18 is inferior in whisker resistance because the crystal grain size is too large. No. 19 is Sn plating (10
1) Since the orientation index of the plane is large, the whisker resistance is poor.

[0022]

The copper alloy material for electronic and electric parts according to the present invention has excellent whisker resistance of electro-gloss plating, and at the same time, press punching property, friction coefficient, solder wettability after aging and contact resistance after standing at high temperature. It also has excellent electrical reliability. Therefore, the present invention greatly contributes to improvement in productivity and reliability of electric / electronic parts.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for measuring a friction coefficient.

[Explanation of symbols]

 1 Female terminal 2 Male terminal

Claims (1)

[Claims] 1. A copper alloy containing Zn of 0.1 to 10 mass% has a plating thickness of 0.5 to 2 μm and a surface reflectance of 3%.
0% or more, the amount of C in the plating is 0.05 to 1 mass%, the crystal grain size of the plating is 0.1 to 1 μm, and the orientation index of the (101) plane of the plating is 2.0 or less. A copper alloy material for electronic and electrical parts, characterized in that: