JPS61136654A - 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 or Mn to an Al-Cu ally contg. less than a specified amount of inevitable impurities. CONSTITUTION:The composition of a hyperfine Al wire of about 10-60mum diameter is composed of, by weight, 0.5-5.5% Cu, <=0.9% in total of 0.002-0.2% Si and/or 0.002-0.8% Mg and the balance Al with <=0.001% inevitable impurities. The Cu content is preferably regulated to 0.8-3.5% from the viewpoint of elongation and drawability.

Description

Detailed Description of the Invention The present invention relates to ultra-fine wires made of 41 alloy (hereinafter referred to as aluminum ultra-fine wires) 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 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 cutting properties.

The ultrafine wire made of ^1-Cu alloy that has been proposed so far is S
Impurities such as i, Fe, Mn, etc. are each 0.005 to 0
It is an Al-0.5~5χCu alloy containing about 0.01%, but the ultrafine wire with this composition has a tensile strength of 25 kg/
mm”, and the elongation is about 1%.The reason why the elongation is small is that conventional ultrafine wires are manufactured by wire drawing an ingot with an equiaxed hole structure cast in a mold, but wire drawing In order to make the subsequent wire drawing process difficult, it is annealed and softened in the intermediate stage of processing.Therefore, due to the balance with the tensile strength, only this level of strength can be obtained, and it is desirable that It is preferable that the elongation be greater.

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 a molten AI or At 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 ultrafine aluminum wires with excellent strength.

As a result of research into this manufacturing method, the applicant has found that A1 alloy material consisting of a columnar crystal structure oriented in one direction can be made into ultra-fine wire with the final wire diameter without annealing in the intermediate stage of wire drawing. It has been discovered that when wire drawing is performed, the elongation significantly increases to a peak on the softening curve by annealing at a temperature of about 400°C or lower, where the decrease in tensile strength due to annealing is not so large. 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-Cu 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, 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 inventor has developed an Al-Cu alloy in which the content of unavoidable impurities is limited to 0.001% or less.
It has been found that when an appropriate amount of n is added, the above drawbacks can be solved and good canting 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 5.5% by weight of Cu, and further contains 0.5% to 5.5% by weight of Cu.
．． 0.002 to 0.2 wt.% Si or 0.002 to 0.2 wt. 002~0
．． 8% by weight of any one type of Mn or a total of 0.9
This is an ultrafine aluminum wire containing Si and Mn in a weight percent or less, and the balance being A1 and unavoidable impurities in a weight percent or less each.

Production-1- The A1 alloy, which is made by adding an appropriate amount of Si or (and) Mn to an Al-Cu alloy in which the content of unavoidable impurities is limited to 0 and 00% or less, respectively, is produced by the manufacturing method proposed by the applicant, namely Particularly favorable effects (strength,
Excellent elongation and cutting properties). 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
1. To explain the alloy composition in more detail, AI preferably has high purity (99.99% or more). This is because even a small amount of impurity elements prevents the crystallization of intermetallic compounds, but the drawing of ultra-fine wires having a wire diameter on the order of tens of micrometers, which is the object of the present invention, is inhibited, and such crystallization This is because the presence of such substances significantly impairs the 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, the reason why Co is contained in the alloy of the present invention is that the tensile strength is not significantly reduced by the addition of Co at approximately 400°C.
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 a peak shape.When the CLI content is 0.5% by weight or less, sufficient elongation cannot be obtained. What you won't be able to do again 5.
The range of Cu content was determined based on the knowledge that if it exceeds 5% by weight, solid solution formation becomes incomplete and wire drawing becomes difficult. The content is preferably 0.8 to 3.5% by weight from the viewpoint of ease of elongation, wire drawing, and corrosion.

Furthermore, the content range of Si and Mn related to cutting properties is not effective under 0.002 gravity,
When Si exceeds 0.2% by weight, Mn exceeds 0.8% by weight, or the total of both exceeds 0.9% by weight, elongation decreases and the solid solution temperature becomes high, making it difficult to form a solid solution. The scope was determined based on knowledge of the matter.

The alloy composition shown in Table 1 of the main construction (each unavoidable impurity is 0.00
1% or less) into a heated mold (actual temperature 680°C).
) to cast a 20 mm wire bar (casting speed: 20 mm/min). After solution treatment (520°C x 4 hours), this wire bar was subjected to surface treatment and wire drawing to reduce the diameter. Plastic processing was performed to an ultra-fine wire 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- shown in Table 1, A-J are examples of the present invention.

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

A Al-LχCu-0,003χSi 245℃23
kg/nun” 8χ Good B Al-1χCu-0,00
3XSi 300℃20kg/mm” 12χ Medium Cali
-1χCu-0, LχSi 250℃28kg/mm”
7χGoodD ALIχCu-0,1χS+ 200℃2
4kg/mm25χ Good E Al-3χCu-0,003
χSi 250℃28kg/mm” 5.5χ Good F A
l-3χCu-0,003χSi 300℃25kg/
mm” 9.5χ Medium G Al-3χCu-0,003X
Si 350℃19kg/mm27.5χ Good 1 (Al-
3χCu-0,2χMn 250℃30kg/ms! 5
χGood I Al-3ZCu-0,2χMn 300℃26
kg/mad” 9χ Good K Al-1χCu 300
℃20kg/mn
As shown in the figure, these ultra-thin aluminum wires 1 are bonded to the test piece 2, and the end of the wire on the secondary side, that is, the cut end at the tail IA, is visually inspected using a microscope to confirm that there are no cracks or sag in this end. Cases in which almost no difference was observed were indicated as "good," cases in which there was clearly a difference or dullness were indicated as "bad," and cases in between these were indicated as "medium."

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, if the composition of the material is different as shown in Comparative Example K, it can be seen that when manufactured using a manufacturing method that provides high tensile strength and elongation, the cuttability is inhibited by the improvement in elongation. .

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.

This ultra-fine aluminum wire has a significantly thicker elongation property than conventional ultra-fine aluminum wire and has 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 the drawing]

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 IA...Tail 2...Spontaneous writing of peace procedure amendment) December 28, 1980 1, Incident display, -, f-2ζ, Q'=71=Showa 5
9 Showa 5 Blade 2, Name of the invention Aluminum ultra-fine wire 3, Relationship to the case of the person making the amendment Name of patent applicant (name) (474) Nippon Light Metal Co., Ltd. 4, Agent 164 Address Yayoi-cho, Nakano-ku, Tokyo Column 6 of Detailed Description of the Invention in Specification No. 5-6-23, Contents of Amendment (1) Page 3, line 17 of the specification: ``The elongation is about 1%.''
' shall be corrected as follows. (3) On page 9, line 11, change “520℃ x 4 hours” to “5
Corrected to 20°C x 24 hours.

Claims (2)

[Claims] (1) Contains 0.5 to 5.5% by weight of Cu, and further contains 0.5 to 5.5% by weight of Cu.
002-0.2 wt% Si or 0.002-0.8
An ultrafine aluminum wire containing any one type of Mn in the amount of % by weight, or Si and Mn in a total amount of 0.9% by weight or less, with the remainder being Al and unavoidable impurities of 0.001% by weight or less each. (2) The ultrafine aluminum wire according to claim 1, wherein the Cu content is 0.8 to 3.5% by weight.