JP2000038628A - Copper alloy for semiconductor lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy for a semiconductor lead frame excellent in strength, electric conductivity, bending workability, punching workability, stress corrosion cracking resistance, production workability or the like. SOLUTION: This is a copper alloy contg., by weight, 5 to 35% Zn, 0.1 to 3% Sn, one or >= two kinds selected from the groups of Ni, Si, Cr, Ti, Zr, Fe, Co, Mn, Al, Ag and Mg by 0.01 to 1% in total, and the balance Cu with inevitable impurities, in which the grain size is controlled to 5 to 35 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy used for a lead material of an electronic device, and more particularly to a copper alloy suitable for a lead material (lead frame material) of a semiconductor device such as an IC.

[0002]

2. Description of the Related Art Conventionally, as lead frame materials for semiconductor devices, copper-based materials such as Cu-Sn-based and Cu-Fe-based materials having excellent electrical and thermal conductivity have been widely used in addition to iron-based materials. Used.

[0003] By the way, in addition to the strength, heat resistance, electric conductivity, and heat conductivity, the lead frame material and the like include
Since noble metal (Ag or the like) plating or solder plating is applied, characteristics such as plating properties, solder bonding properties, and surface smoothness are emphasized. In addition, in order to ensure dimensional accuracy when molding a lead frame from a strip and a plate, molding workability such as good etching or punching workability is required.
It is also important to be practical in terms of price.

[0004] These required characteristics have become more severe in response to the recent high integration, miniaturization, high functionality, and low cost of semiconductor devices. In particular, in recent years, the number of pins in the lead frame has been increased, the size has been reduced, the thickness has been reduced, and a material having good moldability has been strongly demanded in order to ensure high dimensional accuracy.

[0005] As a molding method of a lead frame, a punching method is predominant, and due to recent technological innovations, a multi-pin or fine-pitch lead frame, a matrix-shaped lead that has a small number of pins but is processed in multiple rows. Frames and the like have been manufactured by stamping, and the importance of stamping workability of materials has been particularly increasing. Punching is also a cost-effective processing method.

[0006]

The above-mentioned Cu-Sn-based alloy and Cu-Fe-based alloy are widely used as lead frame materials, but have a problem that punching workability is slightly inferior. As an improvement measure, Cu with excellent punching workability
-An alloy based on a Zn alloy is disclosed in
No. 37 and JP-A-5-36878.

However, the Cu-Zn alloy disclosed in the former JP-A-1-162737 is liable to cause stress corrosion cracking, and has sufficient punching workability with a multi-pin lead frame having 100 pins or more. However, there is a problem in that the C
The u-Zn-based alloy has a surface in which Ni / Pd plating is applied to improve stress corrosion cracking. However, when a lead is bent, the Ni plating layer is cracked and stress corrosion cracking occurs. .

[0008] The present invention has been made under such circumstances,
An object of the present invention is to provide a copper alloy for a semiconductor lead frame excellent in strength, conductivity, bending workability, punching workability, stress corrosion cracking resistance, manufacturing workability, and the like.

[0009]

In order to solve the above-mentioned problems, the present invention provides a method for preparing Zn in an amount of 5 to 35 wt% and Sn in an amount of 0.1 to 0.1 wt%.
3 wt%, Ni, Si, Cr, Ti, Zr, Fe, C
a copper alloy containing a total of 0.001 to 1 wt% of one or more selected from the group consisting of o, Mn, Al, Ag, and Mg, with the balance being Cu and unavoidable impurities; Is 5 to 35 μm.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The copper alloy according to the present invention is Cu-Z
It is based on an n-type alloy, and its stress corrosion cracking, which is a drawback, is improved by adding an appropriate amount of Sn and appropriately controlling the crystal grain size. In addition, Sn contributes to the improvement of the strength, and the optimization of the crystal grain size contributes to the improvement of the bending workability.

[0011] In the copper alloy according to the present invention, Zn has an effect of improving the punching workability by minimizing the occurrence of burrs and the twisting of the leads during the punching process. The reason why the Zn content is specified to be 5 to 35 wt% is that if the content is less than 5 wt%, the effect of the addition is not sufficiently obtained, and if it exceeds 35 wt%, a β phase appears and the cold workability deteriorates. . The preferred Zn content is 6 to 30 wt%.

Sn contributes to improvement in strength and resistance to stress corrosion cracking. The reason for defining the content to be 0.1 to 3 wt% is that if it is less than 0.1 wt%, the effect of its addition cannot be sufficiently obtained, and if it exceeds 3 wt%, the conductivity and hot workability deteriorate. .

The reason why the grain size of the copper alloy according to the present invention is specified to be 5 to 35 μm is that even if the grain size is less than 5 μm or more than 35 μm, the effect of improving bending workability and stress corrosion cracking resistance is sufficient. Because they cannot be obtained.
The preferred grain size is 5 to 20 μm. In the copper alloy according to the present invention, the crystal grain size is JIS-H050.
Determined according to 1.

In the copper alloy according to the present invention, Ni, S
i, Cr, Ti, Zr, Fe, Co, Mn, Al, Ag
And Mg improve the punching workability by increasing the alloy strength. The content of one or two or more of these elements is defined as a total of 0.001 to 1% by weight.
If it is less than 001 wt%, the effect cannot be sufficiently obtained, and 1 w
If the content exceeds t%, the conductivity and the hot workability are significantly reduced. The preferred content of these elements is 0.1.
005 to 0.8 wt%.

In the copper alloy according to the present invention, In, Ba, Sb, Hf, Be, Nb, and P are effective as additional elements for improving the strength and heat resistance of the lead frame material and the terminal material.
d, B, C and the like. The addition amount is in a range that does not significantly lower the conductivity, for example, 0.001 to 1 w.
It is desirably t%.

When the content of O and S mixed during melting and casting is set to 50 ppm or less, it is possible to maintain good surface properties such as plating property, solderability, solderability and the like.

[0017]

Next, examples of the present invention will be shown, and the present invention will be described more specifically. (Example 1) 22 kinds of alloys (N
o. 1 to 22) were melted by a high-frequency melting furnace.
Cast at a cooling rate of ° C./sec, thickness 30 mm, width 100
mm and a 150 mm long ingot were obtained. This ingot is 850
It hot-rolled at ° C, and set it as the hot-rolled material of thickness 12mm. Next, this hot-rolled material was cut on both sides to a thickness of 9 mm to remove an oxide film, then cold-rolled to a thickness of 1.2 mm, and then annealed at 530 ° C. for 1 hour in an inert gas atmosphere. did.
Then, after cold-rolling to a thickness of 0.21 mm, annealing at 530 ° C. for 1 hour in an inert gas,
Finish rolling was performed on a 5 mm plate to obtain 22 kinds of plate samples.

[0018]

[Table 1]

Comparative Example 1 Six kinds of alloys (Nos. 23 to 28) having the compositions shown in Table 2 below were processed into sheet materials in the same manner as in Example 1.

Comparative Example 2 Two alloys (Nos. 29 and 30) having the compositions shown in Table 2 below were used in Example 1 except for the annealing conditions.
It processed into the board | plate material by the same method as above.

(Conventional Example 1) An alloy (No. 31) having a composition shown in Table 2 below was processed into a sheet material in the same manner as in Example 1.

[0022]

[Table 2]

For each of the sheet material samples obtained as described above, (1) grain size, (2) tensile strength (TS),
(3) Conductivity (EC), (4) Bending workability, (5) Punching workability, and (6) Stress corrosion cracking resistance were examined by the following methods. The results are shown in Tables 3 and 4 below.

The measuring method of each characteristic is as follows. (1) Crystal grain size: The crystal structure was observed with an optical microscope (200 times) and measured according to the cutting method of JIS-H0501.

(2) Tensile strength (TS): JIS-Z22
41 was measured. (3) Conductivity (EC): Measured according to JIS-H0505. (4) Bendability: plate material is 10 mm wide and 50 mm long
(The length direction and the rolling direction were parallel to each other), and the sheet was bent in a W shape with a bending radius of 0.1 mm, and the presence or absence of cracks in the bent portion was visually observed with a 50-fold optical microscope. Those without cracks and rough skin were evaluated as ○, those with rough skin were evaluated as Δ, and those with cracks were evaluated as x.

(5) Punching property: A 1 mm × 5 mm square hole was made in a plate material using a SKD11 mold, and
Twenty samples were randomly extracted from the punching up to the 0000th time, and the ratio of the broken portion to the thickness b of the sample (a /
b) × 100% was determined. This broken portion ratio is regarded as one of the standards of the punching workability. It is evaluated that the larger the ratio is, the better the punching workability, the higher the yield in punching, and the more precise the processing.

(6) Stress corrosion cracking resistance (SCC resistance):
A tensile test piece having a width of 8 mm and a length of 50 mm (the length direction and the rolling direction are parallel) was cut out from the plate material, and this was cut out according to JIS-C83.
Exposure to an ammonia atmosphere according to C.06. A constant load of 20 kgf / mm ² was applied to both ends of the sample, and the time until breakage was measured.

[0028]

[Table 3]

[0029]

[Table 4]

As is apparent from Tables 3 and 4, the sample No. of the present invention example. All of Nos. 1 to 22 are excellent in all characteristics. On the other hand, the sample No. 23
Has a small amount of Zn. Sample No. 25 does not contain Sn, In No. 27, since no other element was added, the tensile strength was low and the punching workability was deteriorated. In addition, the sample No. of the comparative example. 24, 2
Samples Nos. 6 and 28 are inferior in manufacturing workability due to the large content of any of Zn, Sn and other elements. Sample No. 28 was severely hot-rolled and could not be produced.

The sample No. In Nos. 29 and 30, the annealing conditions were not appropriate, the crystal grain size was out of the standard value of the present invention, and the bending workability was lowered. Furthermore, the sample No. 25 and the sample No. of the conventional example. In No. 31, the SCC resistance was reduced because Sn was not added.

[0032]

As described above in detail, the copper alloy for a semiconductor lead frame according to the present invention has excellent punching workability.
Based on a u-Zn alloy, Sn and the like are added in an appropriate amount, and the grain size is controlled to improve stress corrosion cracking resistance and the like. Strength, conductivity, bending workability, punching work It has excellent properties, stress corrosion cracking resistance, manufacturing workability, etc., and has an industrially remarkable effect.

Claims (1)

[Claims] 1. A Zn content of 5 to 35 wt% and a Sn content of 0.1 to 3 wt.
wt%, Ni, Si, Cr, Ti, Zr, Fe, Co,
1 selected from the group consisting of Mn, Al, Ag and Mg
A copper alloy for a semiconductor lead frame, comprising a total of 0.001 to 1 wt% of a seed or two or more kinds, a balance of Cu and unavoidable impurities, and a crystal grain size of 5 to 35 μm.