JPS61136653A - Hyperfine aluminum wire - Google Patents

Abstract

PURPOSE:To obtain a hyperfine Al wire having superior tensile strength, elongation and improved suitability to cutting at the tail by adding a proper amount of Si to an Al-Mg alloy contg. a specified reduced amount of inevitable impurities. CONSTITUTION:The composition of a hyperfine Al wire of about 10-60mum diameter is composed of 0.5-6wt% Mg, 0.002-1wt% Si and the balance Al with <=0.001wt% inevitable impurities. The Mg content is preferably regulated to 0.8-4wt% from the viewpoint of elongation and drawability. The hyperfine Al wire is especially suitable for use as a bonding wire.

Description

[Detailed Description of the Invention] The present invention is an ultra-fine wire made of ^1 alloy (hereinafter referred to as aluminum ultra-fine wire) for use in various wires, lead wires and bonding wires of electrical devices such as audio equipment and semiconductor devices. The present invention relates to ultrafine aluminum wires that have improved tensile strength and elongation properties, as well as improved cutting properties, particularly at the tail portion after bonding, when used as bonding wires.

For example, bonding wires used in semiconductor devices are
Usually, it is a very thin ultra-fine wire with a diameter of about 10 to 60 μm. Gold wire has been used as a bonding wire due to its conductivity and corrosion resistance, but in recent years aluminum wire has been used because of its low cost in addition to the above-mentioned properties.

On the other hand, semiconductor devices are improving reliability, making devices smaller,
In addition to increasing the density of wiring, there is a demand for improved productivity by increasing the speed of wiring work.

By the way, when an aluminum ultra-fine wire is used, for example, as a bonding wire, in addition to its tensile strength and elongation properties, the cuttability of the ultra-fine wire has a great influence on the reliability and productivity of semiconductor devices. Cutting performance here refers to the smoothness of the cut surface of the polar tR wire at the tail part. If unevenness occurs on this cut surface, it may cause an electrical short, and it also ensures a stable connection area for the next connection work. Problems such as not being able to obtain results may occur. Furthermore, if the above-mentioned tensile strength is too low, the wire will easily break due to stress during wiring work or during use, and the semiconductor will become soft and deformed due to Joule heat generated during use, increasing the risk of tab shorting.

If the elongation property is too small, the bonding force during connection work will be low, and the wire will be likely to break when subjected to stress during use. Furthermore, it becomes difficult to obtain a preferable loop shape after bonding, making high-speed, high-density wiring difficult. Therefore, it is required to have sufficiently high tensile strength and elongation properties, and also to have good cutting properties.

The ultrafine wire made of Al-Mg alloy that has been proposed so far is S
It is an Al-0.5~5χMg alloy containing about 0.005~0°01% of each of impurities such as i, Fe, and Mn, and the ultrafine wire with this composition has a tensile strength of 10 kg/
mm”, and the elongation is about 2.5%.The reason why the elongation is small is that conventional ultrafine wire is manufactured by wire drawing an ingot with an equiaxed crystal structure cast in a mold. , because it is work hardened by wire drawing, and in order to make subsequent wire drawing difficult, it is annealed and softened in the intermediate stage of processing. Therefore, it is desirable that the elongation be larger.

Therefore, the present applicant previously filed an application for a new method for manufacturing ultrafine aluminum wire (see Japanese Patent Application No. 1982-92994).

This manufacturing method involves unidirectionally solidifying and casting molten AI or Al alloy to form a cast body having a columnar crystal structure, and after solution treatment of the cast body, the final line is formed without annealing at an intermediate stage. This is characterized by the fact that it can be plastically worked into wire rods of the same diameter. That is, A of the columnar crystal structure oriented in one direction
By using I-series materials, it is possible to perform plastic working without annealing up to the final wire diameter, and by omitting the annealing treatment at an intermediate stage, an overall decrease in tensile strength relative to elongation properties can be avoided. This made it possible to manufacture aluminum wire with excellent strength.

As a result of conducting research on this manufacturing method, the present applicant has developed an ultra-fine wire with a final wire diameter of 2, without annealing in the intermediate stage of wire drawing, a type of Al alloy material consisting of a columnar crystal structure oriented in one direction. We have discovered that when wire-drawn to a temperature of about 400°C or lower, where the decrease in tensile strength due to annealing is not so great, the elongation significantly increases to a peak on the softening curve. Based on this, if an aluminum alloy material with such elongation characteristics is used and final annealing is performed at an appropriate temperature, it will not only have excellent tensile strength, but also an ultra-fine aluminum wire with significantly superior elongation characteristics. It was discovered that the At- and G alloys, in which the content of unavoidable impurities was limited to 0.001% or less, sufficiently exhibited these characteristics.

However, when wiring work is carried out using a normal bonding machine using a bonding wire with simply enhanced elongation properties, the loop shape after bonding can be obtained in a desirable shape, but the wire cut portion for the next bonding, i.e. It has been found that this is undesirable because a protrusion in the shape of a bulge or sag is formed on the tail portion and the smoothness of the cut surface is lost.

As a result of various studies to solve these drawbacks, the inventors have found that the above drawbacks can be overcome by adding an appropriate amount of Si to an Al-Mg alloy in which the amount of unavoidable impurities is limited to 0°0019A or less. It has been found that this problem can be solved and good cutting properties can be obtained.

In view of the above-mentioned problem of cuttability, the object of the present invention is to provide an ultrafine aluminum wire that has excellent tensile strength and elongation properties, and has improved cuttability at the tail portion.

The bottom of the light dish of the present invention contains 0.5 to 6 Mg, 0.002 to 1% by weight of Si, and the balance is At and 0.001% by weight, respectively.
This is an ultra-fine aluminum wire consisting of unavoidable impurities of less than % by weight.

Sakuji'l An alloy in which an appropriate amount of Si is added to an Al-Mg alloy in which the content of unavoidable impurities is limited to 0.001% or less, is produced by the manufacturing method proposed by the applicant, that is, unidirectionally oriented. It exhibits particularly favorable effects (excellent strength, elongation characteristics, and cutting properties) when manufactured from a material with a columnar crystal structure without intermediate annealing.

In other words, the deterioration of cutting performance at the tail, which occurs especially when the elongation properties are increased, can be improved by using the composition that is a feature of the present invention, without impairing the elongation properties.

Here, A for manufacturing ultrafine aluminum wire according to the present invention
To explain the t alloy composition in more detail, At is preferably of high purity (99.99% or more). This is because even a very small amount of crystallization of intermetallic compounds due to impurity elements inhibits the drawing of ultra-fine wires with wire diameters on the order of several tens of micrometers, which is the object of the present invention. This is because the presence of such crystallized substances significantly impedes bonding properties when the alloy of the present invention is used as a bonding wire.

According to the inventor's research, it has been found that in order to completely satisfy the above characteristics, the amount of each unavoidable impurity contained in the alloy of the present invention must be 0.001% or less.

In addition, Mg is contained in the alloy of the present invention at temperatures of about 400°C, where the decrease in tensile strength is not so large due to this inclusion.
This is based on the knowledge that the final annealing treatment at the following temperatures can exhibit a characteristic in which the elongation increases significantly in the form of a peak. Based on the knowledge that if the fg content is less than 0.5% by weight, it will not be possible to obtain sufficient elongation, and if it exceeds 6% by weight, solid solution formation will be incomplete and difficulty will arise in wire drawing processing. A range of Mg content was determined. Further, from the viewpoint of elongation and ease of wire drawing, the weight is preferably 0.8 to 4 times.

Furthermore, the range of Si content related to cutting properties is as follows:
The range was determined based on the knowledge that if it is less than 0.002% by weight, no effect can be obtained, and if it exceeds 1% by weight, elongation decreases and the solid solution temperature becomes high, making it difficult to form a solid solution.

Alloy composition shown in Table 1 (inevitable impurities are 0.00% each)
1% or less) into a heated mold (actual temperature 680°).
C) was used for unidirectional solidification, whereby a 20 mm wire bar was cast (casting speed 20 mm/min). This wire bar was subjected to solution treatment (520"CX for 4 hours), and then was drawn and plastic-processed to an ultra-fine wire with a diameter of 30 μm. No annealing treatment was performed in the middle of this plastic processing stage. It was possible to draw wires up to an ultra-fine wire with a diameter of 30 μm without annealing and without any problems such as wire breakage.

Next, the ultrafine wire with a diameter of 30 μm produced in this way
A final annealing treatment over a period of time was applied.

Ten test pieces were cut out from this ultra-fine wire and their tensile strength and elongation properties were measured. The measuring machine used was "Universal Tensile Testing Machine" manufactured by Toyo Baldwin Co., Ltd.

The tensile test conditions were a gage distance of 50 mm and a tensile speed of 10 mm/min. The measurement results are shown in Table 1.

Among Examples A to L shown in Table 1, A to J are examples of the present invention.

As a comparative example, L is an ultrafine aluminum wire manufactured in the same manner as in Examples A-J using a material with a columnar crystal structure oriented in one direction but with a composition not included in the present invention. .

A At-0,82Mg-0,2XSi 200℃24
kg/mm” 11χ Good B At-0, 82Mg-0,
22Si 175℃27kg/++n+” 6χ Good CA
l-0,82Mg-0,52Si 200℃28kg/
mm” 11! Good D At-0,8χMg-0,5χS
i 175℃30kg/+n+++” 7χ Good E At
-1χMg-0,003χSi 200℃22kg/m
m212χGoodF Al-1χMg-0,003χSi
175℃25kg/mn+27χGoodG At-3χMg
-0,003χSi 200℃25kg/mm” 12
X good HAl-3$Mg-0,0032Si 175℃2
9kg/IIIm” 7X Good I Al-3χMg-0,
2XSi 200℃27kg/mm” 11χ Good L A
l-lXMg 175℃25kg/nu++” 7χ
Table 1 Here, the cutting property is judged by actually bonding the test piece 2 with these ultra-fine aluminum wires 1 using a bonding machine as shown in Figure 1, and then measuring the wire end on the secondary side. The cut end at the tail IA is visually inspected using a microscope RL, and if there is almost no crack or sag at this end, it is judged as "good", and when there is clearly a break or sag, it is judged as "bad". displayed.

As a result, it is clear that the ultrafine aluminum wire of the present invention can be made into a wire with excellent tensile strength and elongation as well as good cutting properties by appropriately selecting the final annealing temperature. On the other hand, in the comparative example, when the composition of the material is different as shown in L, when manufactured using a manufacturing method that increases tensile strength and elongation, cutting performance may be inhibited by the improvement in elongation. I understand.

In other words, the ultrafine aluminum wire according to the present invention can clearly improve tensile strength and elongation, and in particular, the problem of deterioration in cuttability that accompanies improved elongation can be solved without sacrificing elongation (by having a sufficiently large elongation). What was achieved is understood.

In addition, it is an ultra-fine aluminum wire with excellent cutting properties and has significantly greater elongation characteristics than conventional ultra-fine aluminum wires.

■ Since it has excellent cutting properties, when used as a bonding wire, it can eliminate sagging and cracks in the tail, and prevent accidents such as cutting.

■ Since it has high elongation, the loop can be shaped into a desired shape after bonding.

(2) Therefore, when this is used, high-speed, high-density wiring becomes possible, productivity is improved, and the reliability of semiconductor devices and the like can be significantly improved.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the state in which ultra-fine aluminum wires are connected as bonding wires, especially the unfavorable shape caused by cutting at the tail 6 1...Bonding wire IA...Tail 2...Peace procedure amendment (Voluntary) December 28, 1980 ゛December 2, 1980 is the patent application filed @ (2) 2,
Name of the invention Aluminum Thin Line 3, Relationship to the case of the person making the amendment Patent applicant name (name) (474) Nippon Light Metal Co., Ltd. 4, Agent 164 Address 5-6-23 Yayoi-cho, Nakano-ku, Tokyo Column 6 of the detailed explanation of the invention in the specification, contents of the amendment (b) "The elongation is about 2.5%" on page 3, line 17 of the specification is amended as follows: rThe elongation is 2.5% Tensile strength from about 30kg/(3)
``Approx. (5) On page 9, line 4, “520℃ x 4 hours” was changed to “
Corrected to 450°C x 24 hours.

Claims (2)

[Claims] (1) Ultrafine aluminum wire containing 0.5 to 6% by weight of Mg, 0.002 to 1% by weight of Si, and the remainder consisting of Al and unavoidable impurities of 0.001% by weight or less each. (2) The ultrafine aluminum wire according to claim 1, wherein the Mg content is 0.8 to 4% by weight.