JPH0480982B2 - - Google Patents

Description

[Detailed description of the invention]

Technical field: Ultra-fine wires made of aluminum alloy (hereinafter collectively referred to as ultra-fine aluminum wires) with a diameter of approximately 10 to 300 μm for use in various wires, lead wires and bonding wires for electrical devices such as audio equipment and semiconductor devices. Regarding the manufacturing method. Prior Art For example, bonding wires used in semiconductor devices are usually very thin wires with a diameter of about 10 to 60 μm. Gold wire has been used as a bonding wire because of its conductivity and corrosion resistance, but in recent years aluminum wire has come to be used because of its low cost in addition to the above-mentioned properties. The ultra-fine aluminum wires that have been proposed so far are
Al alloy containing 0.5-2% by weight of Si, Al alloy containing 1-4% by weight of Cu, 0.5-2% by weight of Cu.
Al alloy containing Mg or 0.4
The material is an alloy to which approximately % by weight of Mn, Cr, etc. can be added. As described above, ultrafine aluminum wires having a diameter of approximately 10 to 60 μm have been conventionally manufactured in the following manner. That is, a wire bar with a diameter of about 50 mm is cast from an Al alloy material and subjected to solution treatment. This wire bar is rolled to form a rough wire, which is then wire-drawn to form an ultra-fine aluminum wire of a predetermined wire diameter. At an intermediate stage, the wire is drawn while being appropriately annealed, thereby producing an ultrafine aluminum wire with a predetermined wire diameter. By the way, when ultrafine aluminum wire is used, for example, as a bonding wire, its tensile strength and elongation characteristics have a great influence on the reliability and productivity of semiconductor devices. That is, if the tensile strength is too low, it will be easy to break during wiring work, and there will be a high risk of softening and deformation due to the heat generated during use of the semiconductor, resulting in tubshot. If the elongation property is too small, the bonding force between the semiconductor chip and external wiring due to ultrasonic bonding will be small.
Furthermore, it becomes difficult to obtain a preferable loop shape, making high-speed, high-density wiring difficult. Therefore, it is required that the tensile strength and elongation properties are sufficiently high. However, when manufacturing using the conventional method described above, increasing the degree of processing by wire drawing to increase the tensile strength of the wire leads to a significant decrease in elongation properties. It is necessary to carry out an appropriate annealing treatment at an intermediate stage. On the other hand, if this annealing treatment is performed, even if the elongation properties can be improved, a decrease in tensile strength is unavoidable. That is, the annealing treatment has contradictory effects on the tensile strength and elongation properties required for the manufactured ultrafine aluminum wire. For this reason, with the conventional technology that requires intermediate annealing treatment to produce ultra-fine aluminum wires, it is not possible to obtain ultra-fine wires with excellent tensile strength and elongation properties. Due to these considerations, we had no choice but to be satisfied with a somewhat compromised tensile strength. In order to produce ultra-fine aluminum wire with excellent strength without sacrificing elongation properties, the applicant has developed a method for producing ultra-fine aluminum wire (Japanese Patent Application Laid-Open No. 1986-6001).
-Refer to No. 238079). This manufacturing method is
Molten Al or Al alloy is unidirectionally solidified and cast to form a cast body with a columnar crystal structure, and after the cast body is solution-treated, it is made into a wire rod of the final diameter without annealing at an intermediate stage. It is characterized by plastic working. In other words, by using an Al-based material with a columnar crystal structure oriented in one direction, it is possible to plastically work the wire up to the final wire diameter without annealing, and by omitting the annealing at an intermediate stage, the elongation properties can be improved. This made it possible to produce ultrafine aluminum wires with excellent strength by avoiding an overall decrease in tensile strength. As a result of research into the manufacturing method of the above-mentioned aluminum ultrafine wire, the present applicant has discovered that an appropriate amount of Cu is added to Al to create a columnar crystal structure that is oriented in one direction.
It has been shown that ultrafine wires made from alloy materials develop a characteristic in which their elongation properties significantly increase to a peak by annealing at a certain temperature of about 400°C or less, where the decrease in tensile strength due to annealing is not so large. heading,
Based on this, by using an aluminum alloy material that exhibits such elongation characteristics and performing a final annealing treatment at an appropriate temperature, it is possible to not only have excellent tensile strength but also significantly superior elongation characteristics. They discovered that it is possible to produce ultra-fine aluminum wires. Purpose of the Invention The purpose of the present invention, based on the above-mentioned findings, is to provide a method that makes it possible to produce ultrafine aluminum wires that have not only high tensile strength but also excellent elongation characteristics. Structure of the invention Al-Cu consisting of a columnar crystal structure oriented in one direction
After solution treatment of the base alloy material, plastic working is performed to the final wire diameter without annealing at an intermediate stage of plastic working, and then annealing is performed at a temperature range of 170℃ to 400℃. Features. Function The Al-Mg-based alloy used in the present invention is
Refers to an Al alloy containing 0.5 to 5.5% by weight of Cu. When melting this alloy, Al is preferably of high purity (99.99% by weight 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 with wire diameters on the order of several tens of micrometers, and the presence of such crystallized compounds This is because, when the alloy of the present invention is used as, for example, a bonding wire, the bonding properties are significantly impaired. According to the study of the present invention, it has been found that in order to completely satisfy the above characteristics, the amount of each unavoidable impurity contained in the alloy according to the present invention must be 0.001% by weight or less. In addition, the inclusion of Cu in the alloy according to the present invention does not cause a significant decrease in tensile strength, but the final annealing treatment at a temperature of about 400°C or lower causes the elongation to peak. This is due to the knowledge that it is possible to express significantly increased characteristics.
If the Cu content is less than 0.5% by weight, it will not be possible to obtain sufficient elongation and sufficient strength, and if it exceeds 5.5% by weight, the strength of the workpiece will increase and it will be annealed at an intermediate stage of the plastic working process. It has been found that unless the elongation properties are recovered by applying the process, plastic working to the final wire diameter cannot be performed, and as a result, the remarkable increase in elongation properties that is a feature of the present invention cannot be obtained. In particular, the preferred Cu content to fully express the above characteristic values is 0.8 to 3.5% by weight.
It is. Specific elements can be added to the Al--Cu based alloy according to the present invention at an intermediate stage of plastic working within a range that allows wire drawing to an ultra-fine wire with a final wire diameter without annealing. For example, 0.2% by weight or less of Si,
Mn up to 0.8% by weight, preferably up to 2.0% by weight
0.5% by weight or less of Mg can be added. Next, when the above-mentioned Al-Cu-based alloy, which has a columnar crystal structure oriented in one direction, is plastic-worked without annealing at an intermediate stage of the plastic-forming process, the workpiece obtained in this way has a specific shape. The mechanism of why the elongation properties significantly increase when the final annealing treatment is performed in a temperature range is not clear, but this fact was obtained as a result of the inventor's numerous experiments. Here, it has a columnar crystal structure oriented in one direction.
Unlike Al materials, which have a columnar crystal structure that is not oriented in one direction, Al materials exhibit specificity in subsequent plastic working. In other words, it is necessary for the Al material, which has a columnar crystal structure that is not oriented in one direction, to be annealed at an intermediate stage in the plastic working process to recover its elongation properties (the (The structure recrystallizes to become an equiaxed crystal structure), whereas Al material with a columnar crystal structure oriented in one direction can be plastic-worked to the final shape without annealing at an intermediate stage in the plastic-forming process. can. Although the elucidation of this specificity is unclear,
The grain boundaries, where the processing strain caused by plastic working is thought to concentrate, have a general equiaxed crystal structure.
The crystal grains are present in large quantities in Al materials, causing intensive work hardening and making subsequent plastic working difficult. In addition to the small number of fields,
This is thought to be because the direction of plastic working matches the growth direction of columnar crystals. Now, an Al alloy material with the above composition and a columnar crystal structure oriented in one direction is subjected to solution treatment, which creates a solid solution that eliminates casting strain and segregation of alloying elements, and then This is to ensure that the workpiece is plastically worked into the final shape without breaking during the processing process, and the temperature of this solution treatment is in the solid solution range, for example, 450°C to 580°C. Appropriately selected from general temperature ranges. The treatment time is also 15 minutes or more, and can be appropriately selected from the range of about 48 hours or less for reasons of thermoeconomics and productivity. The Al alloy material having the composition according to the present invention having a columnar crystal structure oriented in one direction and subjected to solution treatment in this way is plastically worked to the final shape without intermediate annealing. The workpiece material plastically worked at 170℃ to 400℃ shows a remarkable increase in elongation properties, although the temperature is determined by the composition.
A final annealing treatment is carried out at a temperature selected from a temperature range of 100 to 100%, which imparts excellent elongation properties and suitable strength. Here, the temperature above 170℃ is
At temperatures below this, remarkable elongation properties cannot be obtained,
The reason why we set the temperature below 400°C is that if the temperature is higher than this, the elongation will increase to some extent due to the growth of recrystallized particles, but on the other hand, the strength will drop significantly and the wire will lack the characteristics required for ultra-fine wire. This is because it will happen. It also has a columnar crystal structure oriented in one direction.
Al alloy material can be manufactured as follows. That is, a method in which molten Al alloy is cast in a heated mold and simultaneously cooled and solidified continuously from one side;
Alternatively, it can be manufactured by a general method such as a method in which an Al alloy material is partially melted and continuously cooled and solidified from one side. The Al alloy material produced in this way is plastically worked and drawn into an ultra-fine wire of any diameter, for example, 10 to 300 μm. This wire drawing process is performed by continuously or semi-continuously ( It can be carried out in a general manner, meaning that it passes through (including interruptions). Example

[Table] Using metals with the purity shown in Table 1, an alloy was melted using a conventional method, and unidirectionally solidified using a heated mold (actual temperature 680°C), thereby casting a wire bar with a diameter of 20 mm. After solution treatment, this wire bar is milled and then drawn to a diameter of 3 mm using an ordinary single-head wire drawing machine.
The wire was then drawn to a diameter of 0.8 mm using a continuous wire drawing machine. This was then wire-drawn using a precision wire-drawing machine, and plastically worked 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 an ultra-fine wire with a diameter of 30 μm without annealing and without causing defects such as wire breakage. These examples are designated in Table 2 by test numbers AC. Also, as a comparative example,
Using an alloy with a composition that does not contain Cu, ultrafine wires with a diameter of 30 μm were formed in the same manner as described above. This example is designated by test code D in Table 2. As another comparative example, a wire bar with a diameter of 50 mm was cast by mold casting a molten alloy containing Cu by a conventional method different from the method of the present invention. After solution treatment, this wire bar is face milled and rolled to form a rough drawn wire, and in order to avoid problems such as wire breakage during wire drawing, it is annealed several times during the plastic working stage to reduce the wire diameter. 200℃ after making 0.195mm wire
Then, an intermediate annealing treatment was performed at a temperature of 300°C for 30 minutes, and the wire was then drawn into an ultra-fine wire with a wire diameter of 30 μm.
Examples in which intermediate annealing treatment was performed at 200°C are shown in Table 2 with test code E, and examples in which intermediate annealing treatment was performed at 300°C are shown in Table 2 with test code F.

[Table] Next, the thus produced ultrafine wires with a diameter of 30 μm were subjected to a final annealing treatment for 2 hours at various temperatures within the temperature range of 100 to 550°C by a conventional method. Ten test pieces were cut out from each ultrafine wire, tensile tests and elongation properties were measured, and softening curves were created. The measuring device used was a "universal tensile testing machine manufactured by Toyo Baldwin." The tensile test conditions were a gage distance of 50 mm and a tensile speed of 10 mm/min. The softening curves thus obtained are shown in FIG. 1 for test codes A to C of the present invention, and in FIG. 2 for test codes D to F as comparative examples. According to Figure 1, the present invention (test code: It can be seen that due to the characteristics A to C), a remarkable peak-like increase in elongation properties can be expressed in the annealing temperature range of 170°C to 400°C. Therefore, it is clear that if the annealing temperature is selected to be at or around the temperature at which these peak elongations occur, a very large elongation property can be obtained without sacrificing strength. On the other hand, as shown in Figure 2, the Al alloy containing Mn (test code D) does not exhibit such large elongation properties, and therefore it is not possible to obtain large elongation properties even if the annealing temperature is selected. It is clear that this is not possible. Furthermore, as shown in Figure 2, aluminum alloys containing Cu produced by the conventional method (test codes E and F) also did not exhibit such large elongation properties, and therefore the annealing temperature was not selected. It becomes clear that it is not possible to obtain ultrafine wires with large elongation properties even if the As described above, since the aluminum ultrafine wire manufactured by the manufacturing method of the present invention has excellent tensile strength, it has a high It has been confirmed that the tensile strength and high elongation characteristics desired for forming a preferable loop shape can be fully satisfied. In actual production of ultrafine aluminum wires, the final annealing temperature can be appropriately selected based on such a softening curve to obtain the desired elongation and strength characteristics. Effects of the Invention It is possible to easily produce an ultra-fine wire having significantly greater elongation characteristics than ultra-fine aluminum wires obtained by conventional manufacturing methods. In order to obtain such high elongation properties, strength is not sacrificed. Due to its high elongation properties, when used as a bonding wire, the wire loop can be formed into a desirable shape during wiring work. Therefore, the quality of the aluminum ultrafine wire itself can be improved, and as a result, the reliability of products using it can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing a softening curve effective for selecting the final annealing temperature of the ultrafine aluminum wire manufactured by the manufacturing method of the present invention. FIG. 2 is a graph showing a softening curve of an ultrafine aluminum wire manufactured by a conventional method as a comparative example.

Claims (1)

[Claims] 1 Al− consisting of a columnar crystal structure oriented in one direction
After solution treatment of a Cu-based alloy material, plastic working is performed to the final wire diameter without annealing at an intermediate stage of plastic working, and then annealing is performed at a temperature range of 170°C to 400°C. A method for manufacturing ultrafine aluminum wire with excellent elongation properties.