JP2000096164A - Copper alloy for electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a copper alloy to sufficiently be applied even to a multipin lead frame or the like by controlling the crystal grain size of an alloy contg. specified ratios of Zn and Si, moreover contg. at least one kind among Bi, Se, Ca, Sr and rare earth elements by specified ratios in total, and the balance Cu with inevitable impurities to the specified one. SOLUTION: The crystal grain size of a copper alloy contg., by weight, 5 to 35% Zn and 0.5 to 3% Si, furthermore contg. at least one kind among Bi, Se, Ca, Sr and rare earth elements by 0.001 to 0.5% in total, and the balance Cu with inevitable impurities is preferably controlled to 5 to 35 μm. This copper alloy uses a Cu-Zn alloy as a base, and stress corrosion cracking as its weak point is improved by adding a suitable amt. of Si and optimumly controlling the crystal grain size therein. Zn improves its punching workability. Bi, Se, Ca, Sr and rare earth elements moreover improve the punching workability. Furthermore, Si contributes to the improvement of its strength, and the optimization of the crystal grain size improves its bending workability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy for electronic equipment which can be sufficiently applied to a multi-pin lead frame and the like.

[0002]

2. Description of the Related Art Conventionally, lead frames and terminals of semiconductor devices have been used in addition to iron-based materials, as well as Cu-Sn-based and Cu-based materials.
Copper-based materials such as Fe-based are widely used. The lead frame material and the like are required to have strength, heat resistance, electric conductivity, heat conductivity, and the like. In addition, plating properties of noble metals and solders, solder bonding properties, surface smoothness, and the like are also important. Also,
Etching properties and punching workability that can form a lead frame from strips and plates with high precision are also required, and it is also important that the cost is lower. By the way, in recent years, high integration, miniaturization, and high functionality of semiconductor devices have been advanced, and accordingly, for example,
Leadframes have become smaller, thinner, have more pins, and have finer pitches. In addition, matrix leadframes having a small number of pins arranged in multiple rows have been developed. And these are mainly manufactured by the punching method with low processing cost.

[0003]

SUMMARY OF THE INVENTION
A Cu-Zn based copper alloy having excellent punching workability has been proposed (Japanese Patent Application Laid-Open Nos. 1-162737 and 5-36878).
However, one copper alloy (Japanese Patent Application Laid-Open No. 1-162737) is susceptible to stress corrosion cracking, and has insufficient punching workability for a multi-pin lead frame having 100 pins or more. (Japanese Patent Application Laid-Open No. 5-36878) is a plating method in which Ni / Pd is plated on the surface of a Cu—Zn-based alloy.
In any case, it has been difficult to apply the method to increasing the number of pins and fine pitch of the lead frame. An object of the present invention is to provide a copper alloy for electronic devices that can be sufficiently applied to a multi-pin lead frame and the like.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for producing Zn by using 5 to 3 Zn.
5 wt%, containing 0.5 to 3 wt% of Si, Bi, Se,
A copper alloy containing at least one of Ca, Sr, and rare earth elements in total of 0.001 to 0.5 wt%, with the balance being Cu and unavoidable impurities, and having a crystal grain size of 5 to 35 μm;
m, which is a copper alloy for electronic equipment.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The copper alloy of the present invention is based on a Cu--Zn alloy, and its stress corrosion cracking, which is a defect of
It is improved by adding an appropriate amount of i and by appropriately controlling the crystal grain size. Further, the Si contributes to the improvement of the strength, and the optimization of the crystal grain size improves the bending workability. In the present invention, Zn added to Cu significantly reduces the occurrence of burrs and the twisting of leads during punching, thereby improving punching workability. The reason why the content is specified in the range of 5 to 35% by weight is that if the content is less than 5% by weight, the effect cannot be sufficiently obtained, and if the content exceeds 35% by weight, a β phase appears to deteriorate cold workability. Si contributes to the improvement of the stress corrosion cracking resistance and the strength as described above. The reason for defining the Si content to be 0.5 to 3 wt% is that if the content is less than 0.5 wt%, the effect cannot be sufficiently obtained, and if it exceeds 3 wt%, the conductivity and castability are reduced. The reason why the grain size is specified to be 5 to 35 μm in the present invention is that even if the grain size is less than 5 μm or more than 35 μm, the bending workability and the stress corrosion cracking resistance are not sufficiently improved. Here, the crystal grain size is determined in accordance with JIS H0501.

In the copper alloy of the present invention, in addition to Zn and Si,
Further, when at least one of Bi, Se, Ca, Sr and rare earth elements is contained, the punching workability is further improved.
The reason for defining the total content of these elements to be 0.001 to 0.5 wt% is that if the content is less than 0.001 wt%, the effect of the content cannot be sufficiently obtained. Is to be reduced. The rare earth elements include La, C
Misch metal may be used in addition to elements such as e, Pr, Nd, and Sm. Misch metal is Ce45-50wt
%, La 20 to 40 wt%, and the balance of Pr, Nd, Sm and the like is inexpensive and economically advantageous.

In the copper alloy of the present invention, in addition to the above elements,
By adding In, Ba, Sb, Hf, Be, Nb, Pd, B, C, etc., the strength and heat resistance required for the lead frame material and the terminal material can be further improved. It is recommended that the amount of these elements be added so that the conductivity is not significantly reduced. In addition, in the copper alloy of the present invention, O
When the content of S and S is 50 ppm or less, the plating property,
Surface properties such as solder jointability and solder wettability are improved.

[0008]

The present invention will be described below in detail with reference to examples. (Example 1) Copper alloys having compositions Nos. 1 to 16 shown in Table 1 were melted by a high-frequency melting furnace and cast at a cooling rate of 6 ° C./sec. To have a thickness of 30 mm, a width of 100 mm and a length of 150 mm. Was obtained. In Table 1, MM of the selected element is misch metal. Next, the ingot was heated at 850 ° C. to a thickness of 12 mm.
Hot-rolled, cut both sides to a thickness of 9 mm to remove the oxide film, cold-rolled to a thickness of 1.2 mm, and then annealed at 530 ° C. for 1 hour in an inert gas atmosphere. Next, after cold-rolling to a thickness of 0.21 mm, the sheet was annealed at 530 ° C. for 1 hour in an inert gas, and then finish-rolled to produce a 0.15 mm-thick plate.

Comparative Example 1 A plate having a thickness of 0.15 mm was produced in the same manner as in Example 1 except that copper alloys having compositions Nos. 17 to 27 shown in Table 1 were used. In some cases, the annealing conditions were changed to change the crystal grain size of the sheet material.

The grain size, tensile strength (TS), electrical conductivity (EC), bending workability, punching workability, and stress corrosion cracking resistance of each of the sheet materials obtained in Example 1 and Comparative Example 1 were as follows. The method was investigated. The results are shown in Tables 2 to 4. Crystal grain size: The crystal structure was observed with an optical microscope (200 times), and measured according to the cutting method of JIS H0501. Tensile strength (TS): Measured according to JISZ2241. Conductivity (EC): Measured according to the cutting method of JIS H0501. Bending workability: A plate material is cut out to a width of 10 mm and a length of 50 mm (the length direction and the rolling direction are parallel), and is subjected to W-bending at a bending radius of 0.1 mm.
It was visually observed with an optical microscope of 0 magnification. Good for those without cracks and rough skin, good for those with rough skin,
Those having cracks were judged to be defective. Punching workability: 1mm x 5m with SKD11 mold for plate material
Then, 20 square samples were randomly extracted from the 5001st to 10000th punchings, and the ratio of the fractured part thickness a to the sample thickness b [(a / b)
× 100%]. Breakage ratio (fracture surface ratio)
Is regarded as one of the standards of punching workability. It is evaluated that the larger this ratio is, the better the punching workability is, the higher the yield in punching is, and the processing can be performed precisely. Stress corrosion cracking resistance (SCC resistance): width 8m from plate
m, a tensile test piece having a length of 50 mm (the length direction and the rolling direction were parallel) was cut out and exposed to an ammonia atmosphere according to JISC8306. 20 at each end of this sample
A constant load of kgf / mm ² was applied to measure the time until breakage.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

[Table 3]

[0014]

[Table 4]

As is clear from Tables 2 to 4, the present invention
Nos. 1 to 16 all have excellent properties. On the other hand, in Comparative Example No. 17, the amount of Zn was small.
Since i was not added, the tensile strength and the punching workability decreased in all cases. In No. 18, since there was much Zn, the manufacturing workability, conductivity, and bending workability were reduced. In No. 20, since a large amount of Si was present, a large amount of oxide was generated during melting and casting, and the workability and bending workability were reduced. No. 21 contained a large amount of Bi and generated large cracks during hot working, and could not be manufactured normally. No.22 has many misch metal (MM),
Since o.23 contained a large amount of Ca, cracking occurred during bending work and cold rolling in all cases, resulting in reduced workability. In Nos. 24 and 25, the annealing conditions were not appropriate and the crystal grain size was fine and mixed. Therefore, the bending workability was reduced, and the SCC resistance was also reduced. In Nos. 26 and 27, the annealing conditions were not appropriate and the crystal grain size was large, so that the bending workability was slightly lowered, and the punching workability and SCC resistance were lowered.

[0016]

As described above, the copper alloy for electronic equipment of the present invention has a Zn content of 5 to 35 wt% and a Si content of 0.5 to 3 wt%.
%, And at least one of Bi, Se, Ca, Sr, and rare earth elements is contained in an amount of 0.001 to 0.5 wt%, and has a crystal grain size of 5 to 35 μm. Excellent in properties, strength, electrical and thermal conductivity, bending workability, punching workability, stress corrosion cracking resistance, manufacturing workability, etc. To play.

Claims (1)

[Claims] 1. A Zn content of 5 to 35% by weight and a Si content of 0.5 to 3%.
wt%, and at least one of Bi, Se, Ca, Sr, and rare earth elements is 0.001 to 0.5 wt% in total.
A copper alloy for electronic equipment, the balance being a copper alloy comprising Cu and inevitable impurities and having a crystal grain size of 5 to 35 μm.