JPS63230839A - Extra fine wire made of al-mn-mg alloy and its production - Google Patents

Abstract

PURPOSE:To manufacture an extra fine wire for ball bonding excellent in heat resistance and corrosion resistance, by preparing a crude wire having a columnar-crystal structure oriented in one longitudinal direction from an Al-Mn- Mg alloy with a specific composition, applying homogenizing treatment and cold wire drawing to the above and then subjecting the resulting extra fine wire to annealing at a specific temp. CONSTITUTION:A wire bar of about 6-20mm wire diameter composed of columnar-crystal structure is prepared from a molten Al-Mn-Mg alloy containing, by weight, 0.5-3.0% Mn, 0.05-0.5% Mg, and <0.001% inevitable impurities by means of unidirectional-solidification casting using a heated mold, which is heated to 350-550 deg.C for >=15min to undergo homogenizing and then subjected to cold wire drawing so as to be formed into an extra fine wire of 15-70mum diameter. This extra fine Al-Mn-Mg alloy wire is heated to 250-500 deg.C in a vacuum annealing furnace to undergo annealing, so that extra fine wire of Al-Mn-Mg alloy suitable for ball bonding wire can be manufactured.

Description

[Detailed Description of the Invention] The present invention provides a wire with particularly excellent heat resistance and corrosion resistance that is suitable as a pole bonding wire for bonding semiconductor elements such as ICs and LSIs to external lead terminals. Al-Mn-Mg
This article relates to an ultrafine alloy wire and its manufacturing method.

■Pole bonding wires used to bond semiconductor devices and external lead terminals are basically required to have the following characteristics in terms of manufacturing and performance. That is, (a) Medium conductivity) Tensile strength (C1 elongation/wire drawing workability (d) Ball forming property (e) Pounding strength (f) Loop forming property (g) Tail cutting property However, it depends on the usage environment. Sealing treatment is performed to prevent characteristic deterioration, but when applying pole bonding wires to resin-molded semiconductor devices that are resin-sealed, it is important to avoid the heat received during the resin-sealing process. There have been problems in that the strength of the pole bonding wire decreases due to negative effects, the high temperature strength against the heat generated during use is insufficient, and there is a risk of corrosion due to reaction with resin-containing substances.

More specifically, resin sealing treatment (affected by temperatures of approximately 200 to 300°C) after pole bonding,
When ceramic sealing treatment (which is affected by temperatures of approximately 400 to 450 degrees Celsius) is performed, the pole bonding wire used becomes work-hardened aluminum (AJ).
If it is an alloy-based wire, the required strength (approximately 5 to 7 kg/
The strength decreases to a level inferior to that of 10 mm (mm").

In addition, the pole bonding wire is softened by the heat received during these treatments and by Joule heat during use, increasing the risk of tab shorting.

On the other hand, epoxy resin, which is a thermosetting resin, is widely used as a synthetic resin encapsulant, but melanin resin, polyimide resin, silicone resin, etc. are also used, and thermoplastic resins include Polyethylene, polyamide, and fluororesin are also used. It is known that chlorine, amine, etc. contained in these resins react with water vapor in the air and are liberated, which causes corrosion of Al.

Therefore, bonding wires made of AE have generally been rarely applied to resin-molded semiconductor devices and the like that have such problems.

雛] Meiyo Maruyo Various types of ultra-fine bonding wires made by Alfi have been developed and provided. Among these examples, those containing only manganese (Mn>) are described in, for example, JP-A-51-142988, and those containing Mn and/or magnesium (Mg) are described in, for example, JP-A-57-164542. In the former, MEI
The content of I is proposed to be 0.05 to 6% by weight (the remainder being AE). In addition, in the latter case, the Mn content is 1.
0 to 3.0% by weight and/or 0 as Mg content
．． 5 to 3.0% by weight, respectively, has been proposed.

Ultrafine wires made of AI-Mn alloys containing such amounts of Mn or Al-Mn-Mg alloys containing Mn and Mg have better characteristics as bonding wires than conventional wires. However, as mentioned above, when used in resin-molded semiconductor devices, there are problems such as a decrease in high-temperature strength due to the influence of Joule heat, and problems related to corrosion over time. The solution was still not satisfactory.

The present invention also provides an ultra-fine wire, particularly an ultra-fine wire made of Al-Mn-Mg alloy, which can solve the above-mentioned problems regarding thermal influence and corrosion resistance.
The purpose of this invention is to propose a manufacturing method that can exhibit the desired characteristics of an ultra-fine Mg alloy wire for pole bonding, and also as a wire that can be subjected to ultrasonic bonding.

1 Ri■A! The ultrafine wire proposed by the present invention contains 0.5-3.0% by weight of Mn, 0.05-0.5% by weight of Mg, and the balance is AN and a total of 0.001% by weight or less. This is an ultra-fine wire made of an Al-Mn-Mg alloy characterized by containing unavoidable impurities.

Here, in the composition according to the present invention, the Mn content is much higher than the Mg content. This is JP-A-57-
This is significantly different from the fil-Mn-Mg alloy ultrafine wire described in No. 164542, in which the contents of Mn and Mg are approximately the same.

To explain this point, in conventional alloys with a high Mg content, which is involved in sphericity in the pole bonding method, heat during device assembly (for example, heat during resin sealing) Since there is a problem with corrosion resistance, as the wire surface becomes cloudy due to oxidation, we reduced the Mg content and added a sufficient amount of Mn to ensure high-temperature strength. This provides a favorable balance between heat resistance and corrosion resistance, ensuring excellent properties in terms of heat resistance and corrosion resistance, even when bonding is performed not only by pole bonding, but also by ultrasonic bonding. They discovered that it is possible to produce ultra-fine wires that can

Here, the limitation on the content of Mn in the present invention is that if the content is less than 0.5% by weight, the required strength (approximately 7% by weight)
kg/mm''), and if the content exceeds 3.0% by weight, the elongation will drop significantly and the solution heat treatment time will become longer, which is undesirable. Therefore, in the present invention, the Mn content The amount is set at 0.5-3.0% by weight, preferably 1-2% by weight.

Furthermore, the limitation on the content of Mg is that if the content is less than 0.05% by weight, the required elongation will not be obtained, and the flow during pole bonding will deteriorate, resulting in deterioration of sphericity.
Moreover, if the content exceeds 0.5% by weight, the wire surface becomes defective due to surface oxidation, which impairs the integrity of the pole. Therefore, in the present invention, the Mg content is reduced to 0.
．． The content is set at 0.05 to 0.5% by weight, preferably 0.1 to 0.5% by weight.

Furthermore, the reason why we have suppressed the total amount of unavoidable impurities to 0.001% by weight or less is to keep it within a range that can be controlled at present, and it is desirable to keep it at this level in order not to deteriorate the basic characteristics of an ultra-fine wire. .

Furthermore, the purity of kl, Mn, and Mg used is 99.9.
The content is 9% by weight or more.

In the present invention, in order to manufacture ultrafine wires having such a composition and desired characteristics, first, a braided wire consisting of a columnar crystal structure oriented in one direction of the long grains is formed, and then this wire is homogenized. After the chemical treatment, an ultra-fine wire having a final wire diameter is formed by cold wire drawing, and then b.

Here, the method for producing ultrafine wires from wires having a unidirectional columnar crystal structure is well known as it is described in Japanese Patent Application Laid-Open No. 60-238079, which has already been filed and published by the applicant. Also, by using this method, it is possible to produce a braided wire having a columnar crystal structure oriented in one longitudinal direction. Of course, other methods are also possible. Therefore,
Examples of methods that can be used in the present invention to produce such braided wires are listed below.

(al) A braided wire (wire bar) having a columnar crystal structure is manufactured from molten metal using unidirectional solidification casting using a heated mold.

fb) After producing a braided wire from the molten metal using a Properch type continuous casting rolling mill or the like, it is converted into a columnar crystal structure using a zone melting device.

Further, the manufacturing process according to the present invention will be briefly explained as shown in FIG. That is, as shown in FIG. 1, in the manufacturing process according to the present invention, a braided wire having a columnar crystal structure is first manufactured by any of the methods described above. The wire diameter of such braided wires is approximately 6~
It is said to be about 20mm.

Next, this wire assembly is subjected to a homogenization treatment, for example, an electric furnace can be used as such a homogenization treatment. Moreover, as processing conditions, heating is performed for 15 minutes to 48 hours at a temperature range of 350 to 550°C, for example.

Thereafter, the homogenized wire assembly is cold-worked and drawn to a required wire diameter. Here, the required wire diameter means the final wire diameter to be made into a product, and is usually 15 to 70 I1 mφ. In such a wire drawing process, for example, a process of single head wire drawing--small diameter medium wire--precision wire drawing can be used.

The ultra-fine wire of the final wire diameter produced in this way is annealed and made into a product. This annealing treatment is intended to transform the steel into an equiaxed structure through recrystallization and improve the elongation properties. In order to obtain such effects, the present invention uses a temperature range of 300 to 500°C, preferably 320°C.
It has been found to be preferable to anneal at a temperature range of -450<0>C. The reason for this is that it has been found that when annealing is performed at a temperature exceeding 500°C, the elongation and strength do not increase but rather decrease. Of course, a sufficient annealing effect cannot be obtained at a temperature lower than 300°C.

The annealing time is preferably about 0.1 minute to 12 hours. In such annealing treatment, it is preferable to use a vacuum annealing furnace to prevent oxidation, and approximately I
An annealing furnace capable of ensuring a vacuum degree of 0-' to IXIO-'Torr is used. In this annealing treatment, the obtained polar ++a wire is naturally cooled to room temperature in an annealing furnace.

Examples of the present invention will be described below.

1旌■ Al, Mn and Mg with guaranteed purity of 99.99% by weight
Using metal, three types of alloy A with the composition shown in Table 1
, B, and C were melted. Here, alloys A and B match the composition proposed by the present invention, and alloy C has a composition conventionally used as a comparative example.

Based on these three types of alloys A-C, ultrafine wires were manufactured according to the following steps.

[Manufacture of braided wire with unidirectional columnar crystal structure]

20mm using a heated mold (actual temperature 680℃)
A braided wire with a wire diameter of 20 mm was manufactured by a unidirectional solidification casting method in which the wire was drawn upward at a casting speed of 7 minutes.

[Homogenization treatment]

This braided wire was subjected to homogenization treatment by heating at 400° C. for 24 hours.

[Cold wire drawing processing]

From braided wires with a wire diameter of 20mm to ultra-fine wires with a wire diameter of 30μm,
Wire drawing was performed continuously in the cold.

[Annealing treatment]

The ultrafine wires of each alloy A-C were divided into two groups and subjected to two types of annealing treatment, namely, 300° C. x 4 hours and 400° C. x 4 hours, respectively.

The tensile strength and elongation of each of the ultrafine wires of alloys A to C finally manufactured in this manner were measured to examine mechanical properties, and a corrosion resistance test was also conducted.

(2) The measured mechanical properties are shown in Table 2.

■Also, as an evaluation of loop formability, we observed the shape of the loop when bonded using the pole bonding method.
If it is within 30% of the setting height of the welding machine, 7
0% or less was determined to be defective.

In addition, as high temperature strength, after heating at 450° C. for 4 hours, tensile strength was measured using a room temperature tensile tester. This result is the third
Shown in the table.

■ Corrosion resistance test was performed by immersing the manufactured ultrafine wire in a test tube containing 3% by weight of saline in a constant temperature and humidity chamber at a room temperature of 85°C and humidity of 80%. water surface position)
Corrosion resistance was evaluated based on the length of time required until the surface of the ultrafine wire became cloudy by visual observation. The results are shown in Table 4.

Considering the mechanical properties of the ultrafine wires shown in Tables 2 and 3 and the corrosion resistance evaluation shown in Table 4, it can be seen that the ultrafine wires A and B with the composition according to the present invention are different from those with the conventional composition. Compared to ultra-thin wire C, the mechanical properties are the same or better,
It is recognized that it has excellent high-temperature strength, and it is also clear that it is significantly superior in terms of corrosion resistance. Similarly,
It is also clear that the ultrafine wire produced according to the manufacturing method according to the invention can provide better properties than conventional ultrafine wires.

As explained above, it is clear that the aluminum ultrafine wire produced by the composition and manufacturing method of the present invention is significantly superior to conventional wires in terms of strength, elongation, and corrosion resistance. Therefore, it is possible to expand the range of applications, such as making it possible to apply the wire for pole bonding to resin-molded semiconductor devices, and to obtain sufficiently high reliability in use.

In addition, since it has excellent high-temperature strength, it becomes possible to apply ultrasonic bonding by adjusting the final annealing conditions, and the applicable technology can be expanded.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the steps of the method for manufacturing ultrafine wire according to the present invention.

Claims (2)

[Claims] (1) 0.5-3.0 wt% Mn, 0.05-0.5
Contains % by weight of Mg, the balance being Al and a total of 0.00
An ultrafine wire made of an Al-Mn-Mg alloy, characterized by containing 1% by weight or less of unavoidable impurities. (2) 0.5-3.0 wt% Mn, 0.05-0.5
Contains % by weight of Mg, the balance being Al and a total of 0.00
After homogenizing a coarse wire consisting of a columnar crystal structure oriented in one longitudinal direction and containing unavoidable impurities of 1% by weight or less, an ultra-fine wire with a final wire diameter is formed by cold wire drawing, and then, A method for producing an ultrafine wire made of an Al-Mn-Mg alloy, characterized by annealing within a temperature range of 250°C to 500°C.