JPH0672272B2 - Method for producing composite copper alloy for lead frame - Google Patents

Description

The present invention relates to an improvement in a method for producing a copper alloy for a lead frame used in a device having a semiconductor as an element.

Devices such as ICs, LSIs, etc., which have semiconductors as elements, are made up of semiconductor pellets, leads, bonding wires, and sealed with a hermetic seal, ceramic seal, or plastic seal technology. Is used.

Generally, the following characteristics are required for lead frame materials for semiconductor devices.

(1) Good thermal and electrical conductivity (2) High strength (3) Good heat resistance (4) Good plating property Conventional lead frame materials include Kovar, Fe-Ni alloy,
Phosphor bronze (CA501), Cu-Fe-Zn-P (CA194), Cu-Fe-Co-Sn
-P (CA195) etc. are used.

However, in general, when the strength is increased, the conductivity tends to decrease, and it is not possible to obtain one having sufficient characteristics. On the other hand, recently, there has been a demand for a material having high strength and high conductivity in response to demands for downsizing and high performance of equipment.

As a result of intensive studies in view of the present circumstances, the present invention has found a method for producing a copper alloy for a lead frame, which is excellent in strength and conductivity, heat resistance, and plating property. That is, Cu-Al alloy billet is made into powder by chatter vibration (self-excited vibration) tool, and then it is made into Cu-0.2 to 1.2wt% Al ₂ O ₃ alloy that can oxidize Al by internal oxidation method, and then this is sintered. This is characterized in that the surface of the caulking is coated with Cu or a Cu alloy.

The reason why the Cu-Al alloy powder is produced by the chatter vibration tool in the method of the present invention is that the Cu-Al alloy ingot is mechanically crushed by using a ball mill or the like as in the conventional method and necessary for internal oxidation.
In order to obtain a particle size of about 50μ, it takes a long time for pulverization and enormous cost for equipment such as a ball mill. On the other hand, in the case of crushing with an anti-numb vibration tool, the equipment cost is not a small cost, and the powder can be pulverized in a short time in a short time, so that the production cost of the powder is significantly reduced. In addition, the size of the powder becomes uniform and the strength is improved. That is, as shown in FIG. 1, the cutting blade portion 2 is housed in the chatter tool body 1 via the roller member 3, and the tip of the cutting blade portion contacts the surface of the rotating Cu-Al alloy billet 4 at a constant speed. Install as you would. A spring 5 is attached to the rear end of the cutting edge portion 2, and the cutting edge portion is vibrated to give a reciprocating motion back and forth.

A strong impact force is applied to the rotating billet when the tip of the cutting edge portion 2 comes into contact with or separates from the surface of the Cu-Al alloy billet 4, and this force causes the Cu-Al alloy billet 4 to have an ultrafine fibrous shape. The powder is easily cut.

Therefore, in order to manufacture ultrafine short fiber powder by chatter vibration, the tool is required to have predetermined conditions. That is, it is necessary to reduce the rigidity of the tool to increase the natural frequency, keep the cutting speed V within a predetermined range according to the material, and reduce the feed speed f of the tool. V = 50 to 300 m / min , f = 0.001 to 0.01 mm / rev is preferable.

The reason for covering the Cu or Cu alloy Cu-Al ₂ O ₃ alloy of the substrate surface in the process of the present invention, with only Cu-Al ₂ O ₃ alloy high strength, has a high conductivity, Al ₂ O _{Since 3} is finely dispersed, it hinders plating and solderability and is unsuitable as a lead frame material. Therefore, tough pitch copper,
Pure copper such as phosphorus-deoxidized copper, oxygen-free copper or Cu-Sn system, Cu-Fe system, Cu
-A Zn-based or Cu-Ni-based copper alloy is coated to improve the plating property and solderability.

The thickness of the Cu-Cu alloy coating layer is not particularly limited, but if it is too thin, the coating layer may be damaged during processing such as extrusion, and if it is too thick, the Cu-Al ₂ O ₃ alloy The excellent high strength and high conductivity cannot be fully utilized. Therefore, it is usually preferable that the thickness of the Cu—Al ₂ O ₃ alloy is about 4 to 15%.

Further, in the method of the present invention, the content of Al ₂ O ₃ is 0.2 to 1.2 wt%
The reason for limiting the content to (1) is that if it is less than 0.2 wt%, the heat resistance and strength are poor, and if it exceeds 1.2 wt%, the electrical conductivity decreases.

Next, examples of the present invention will be described.

Examples (1) to (8) and Comparative Examples (1) to (12) After melting Cu in a high frequency furnace, 0.1 to 0.6% Al was added thereto to cast a billet having a diameter of 150 mm.

Using a low-vibration chatter vibration tool with low rigidity shown in Fig. 1, this was cut under the condition of self-excited vibration at a cutting speed of 100 m / min and a tool feed speed of 0.005 mm / rev.
A short fiber powder having a size of 50 μm and a length of about 5 mm was obtained.

Only Al is selectively oxidized by the internal oxidation method into a Cu-Al ₂ O ₃ alloy powder having the composition shown in Table 1 and sintered to produce a billet (base material) with a diameter of 95 mm and a length of 30 mm. did. Then, as shown in FIG. 2, the billet 7 is inserted into a Cu or Cu alloy tube 6 having an outer diameter of 120 mm and an inner diameter of 96 mm, and plugs 8 are closely attached to both ends.
The inside of the tube was evacuated and sealed to a diameter of 12 mm and a length of 300.
mm extrusion billets were produced. In addition, 9 is a welded part. After that, it was heated at 900 ° C. for 1 hour and extruded to a thickness of 12 mm and a width of 60 mn. In the meantime, 700 ° C. × 1 Hr intermediate refining was performed at 3 mm and 1.75 mm, and cold rolling was performed to 0.3 mm to obtain a composite copper alloy by the method of the present invention.

Incidentally, in order to compare with the composite copper alloy according to the method of the present invention,
Al ₂ O ₃ content outside the range of the present invention and Cu-Al
_{About 2} O ₃ alloy powder manufactured by a ball mill,
A comparative example composite copper alloy was obtained in the same manner as in the other examples except for the above.

The properties and powder production costs of the thus obtained composite copper alloy were measured. The results are as shown in Table 1.

The plate thickness was 0.3 mm (coating material thickness was 15μ) and the final rolling rate was 60%.

As is clear from the above table, the method of the present invention is excellent in properties as a lead frame material and can be manufactured at a large cost at a low cost, so it is extremely useful when used in a device having a semiconductor as an element. .

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of a chatter vibration tool for obtaining a Cu—Al alloy powder in the method of the present invention, and FIG. 2 is a manufacturing method of a Cu—Al ₂ O ₃ sintered billet in the method of the present invention. 1
It is a schematic explanatory drawing which shows an example. 1 ... Tool body, 2 ... Cutting edge part, 3 ... Roller member, 4 ...
... Cu-Al alloy billet, 5 ... spring, 6 ... Cu or Cu alloy tube, 7 ... Cu-Al ₂ O ₃ billet, 8 ... plug, 9 ... welded part.

Claims (1)

[Claims] 1. A Cu-Al alloy billet is powdered by a chatter vibration (self-excited vibration) tool, and then Al is oxidized by an internal oxidation method to form a Cu-0.2 to 1.2 wt% Al ₂ O ₃ alloy powder. rear,
A method for producing a composite copper alloy for a lead frame, which comprises sintering this and coating the surface thereof with Cu or a Cu alloy.