JPS62170448A - Hyperfine aluminum wire - Google Patents

Abstract

PURPOSE:To obtain a hyperfine Al wire having superior tensile strength, elongation characteristics and improved cuttability at the tail part by adding specified amounts of Mg and Mn to Al and restricting the amounts of impurities to a specified value or below each. CONSTITUTION:The composition of an Al alloy is composed of 0.5-4wt% Mg, 0.002-0.2wt% Mn and the balance Al with inevitable impurities and the amounts of the inevitable impurities are restricted to <=0.001wt% each. The Al alloy is plastically worked into a hyperfine wire by drawing.

Description

[Detailed Description of the Invention] The present invention is directed to an ultra-fine wire made of aluminum 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. In particular, the present invention relates to ultrafine aluminum wires that have improved tensile strength and elongation properties, as well as cutting properties, particularly at the tail portion after bonding, when used as bonding wires.

Conventional technologyFor 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 also a desire to improve productivity by increasing the speed of wiring work.

By the way, when an ultrafine aluminum wire is used, for example, as a bonding wire, the cuttability of the ultrafine wire, in addition to its tensile strength and elongation characteristics, 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 ultra-fine wire at the tail section. Any unevenness on this cut surface may cause electrical shorts, and it also ensures a stable connection area for the next connection operation. This may cause problems such as not being able to 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 there will be a high risk of softening and deformation due to Joule heat generated during use of the semiconductor, resulting in a tab short.

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 canting properties.

The ultrafine wire made of Al-Mg alloy that has been proposed so far is S
Impurities such as i, Fe, Mn, etc. are each 0.005 to 0.06
This is an At-0.5-5χMg alloy containing about 0.1% of
/mm2, elongation is about 2.5% and tensile strength is 10k.
g f 7 mm", and the elongation is about 1%. Here, the elongation is small because conventional ultrafine wires are manufactured by wire drawing an ingot with an equiaxed structure cast in a mold, The wire is work hardened by wire drawing, and in order to make subsequent wire drawing difficult, it is annealed and softened at an 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 unidirectional solidification casting of molten Al or ^1 alloy to form a cast body having a columnar crystal structure, solution treatment of the cast body, and final annealing treatment without annealing at an intermediate stage. It is characterized by plastic working to the wire rod of the wire diameter. In other words, by using an Al-based material with a columnar Mn weave oriented in one direction, it is possible to perform plastic working without annealing the wire up to the final wire diameter, and by omitting annealing at an intermediate stage. This made it possible to produce ultrafine aluminum wires with excellent strength by avoiding an overall decrease in tensile strength with respect to elongation properties.

As a result of research into this manufacturing method, the present applicant has developed a type of 41 alloy material consisting of a columnar crystal structure oriented in one direction, which can be produced into ultra-fine wires with a final wire diameter without annealing in the intermediate stage of wire drawing. We have discovered that when wire drawing is performed, annealing at a temperature of about 350°C or lower, where the decrease in tensile strength due to annealing is not so great, results in a characteristic in which the elongation increases significantly to a peak on the softening curve. Based on this, if an aluminum alloy material with such elongation characteristics is used and the 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 has been discovered that production is possible, and that an Al-Mg alloy in which the content of each unavoidable impurity is limited to 0.001% or less can sufficiently exhibit such 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 is It has been found that this is undesirable because a protrusion in the shape of a bulge or sag is formed in 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 when an appropriate amount of Mn is added to an Al-Mg alloy in which the content of each unavoidable impurity is limited to 0°001% 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, an 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 present invention contains 0.5 to 4% by weight of Mg and 0.002 to 0.0% by weight.
Contains 2% by weight of Mn, the balance is Al and each 0.0
This is an ultrafine aluminum wire containing 0.1% by weight or less of unavoidable impurities.

The old alloy, in which an appropriate amount of Mn was added to an Al-Mg alloy in which the content of unavoidable impurities was limited to 0.001% or less, was manufactured using the manufacturing method proposed by the applicant, that is, a columnar crystal structure oriented in one direction. Particularly favorable effects (excellent strength, elongation characteristics, and cuttability) are exhibited when manufactured from materials 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, thereby improving the force and knotting properties without impairing the elongation properties.

Here, the aluminum ultrafine wire according to the present invention is manufactured ^
1 To explain the polymerization composition in more detail, ^1 preferably has high purity (99.99% or more). This is because even a very small amount of crystallization of intermetallic compounds caused by impurity elements inhibits the drawing of ultra-fine wires having a wire diameter 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.

Moreover, the reason why Mg is contained in the alloy of the present invention is that the tensile strength is not reduced so much by the addition of Mg at a temperature of about 350°C.
This is based on the knowledge that the final annealing treatment at the following temperatures can exhibit a property that significantly increases the elongation to a peak shape, and that when the Mg content is 0.5% by weight or less, the wire has sufficient strength. Based on the knowledge that Mg
The range of content of

Furthermore, the range of Mn content related to cutting properties is
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 is more than 0.2% 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 of Da Chung Coal (inevitable impurities are o and oo respectively)
t% 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 (450°C x 24 hours), then wire-drawn and plastic-processed into an ultra-fine wire with a diameter of 30 μm.

No annealing treatment was performed during this plastic working stage. That is, it was possible to draw a wire up to an ultra-fine wire with a diameter of 30 μm without annealing and without causing defects 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 H shown in Table 1, A to E are examples of the present invention.

As a comparative example, F-H is a material with a columnar crystal structure oriented in one direction, but a simple Al-Mg alloy that does not contain Mn, which is a feature of the present invention, was used in the same manner as Examples A-H. This is a manufactured ultra-fine aluminum wire.

Examples Ingredients Annealing temperature Tensile strength Elongation Cuttability A Al-1χMg-0,003χMn 20
0℃ 23kgf/mm” IIX Good B
Al-lXMg-0,003?4Mn 175℃26
kgf/mm” 6χGood CAl-1χMg-0,15χ
Mn 200℃25kgf/mm” 11χ Good D Al
-1,5χMg-0,OIXMn 200℃24kgf
/mm” 12χ Good E Al-3χMg-0,15χM
n 200℃32kgf/mm” IIZ RyouF At-
IZMg 200°C22kgf/mm212Z Evil G
Al-1,1χMg 200℃
24kgf/mm” 13χ Evil 11^1
-1.5χMg 175°C26kgf/mm” 7
χ Table 1 Here, the cutting property is judged by actually bonding the test piece 2 with these ultra-thin aluminum wires 1 using a bonding machine as shown in Figure 1, and then The end portion, that is, the cut end at the tail IA, was visually inspected using a microscope, and the case where almost no firmness or sagging was observed at this end was designated as “good”, and the case where clear crispness or sagging was observed was designated as “bad”. .

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.

Effects of the Invention ■ This is an ultra-fine aluminum wire that has significantly greater elongation characteristics than conventional ultra-fine aluminum wires and excellent cutting properties.

■ 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 short circuits.

■ 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 reliability of semiconductor devices and the like can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a state in which ultra-fine aluminum wires are connected as bonding wires, particularly showing an unfavorable shape due to cutting at the tail. 1... Bonding wire lA... Tail 2... Piece

Claims (1)

[Claims] 0.5-4 wt% Mg and 0.002-0.2 wt%
An ultra-fine aluminum wire containing Mn of 100% and the balance consisting of Al and unavoidable impurities of 0.001% by weight or less.