KR20140050630A - Copper strand for bonding wire and method for producing copper strand for bonding wire - Google Patents

Abstract

This copper wire for bonding wire is copper wire for forming the bonding wire of 180 micrometers or less of wire diameters. The wire diameter of copper wire is 0.15 mm or more and 3.0 mm or less. The copper element wire contains at least one additive element selected from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and rare earth elements in a range of 0.0001% by mass or more and 0.01% by mass or less, with the balance being copper and inevitable. It has a composition which is an impurity. In the copper element wire, the special grain boundary ratio (Lσ / L) which is the ratio of the length Lσ of the special grain boundary to the length L of all the grain boundaries measured by the EBSD method is 50% or more.

Description

Copper wire for bonding wire and manufacturing method of copper wire for bonding wire {COPPER STRAND FOR BONDING WIRE AND METHOD FOR PRODUCING COPPER STRAND FOR BONDING WIRE}

TECHNICAL FIELD This invention relates to the copper wire for bonding wires used when submitting the bonding wire of 180 micrometers or less of wire diameters, and the manufacturing method of the copper wire for bonding wires.

This application claims priority based on Japanese Patent Application No. 2011-161036 for which it applied to Japan on July 22, 2011, and uses the content here.

Generally, in the semiconductor device in which the semiconductor element is mounted, the semiconductor element and the lead are connected by the above-mentioned bonding wires. Conventionally, Au wire is mainly used as a bonding wire from a viewpoint of freshness, electroconductivity, etc. However, since Au is expensive, a bonding wire made of Cu is provided as a bonding wire to replace the Au line.

Since Cu is harder than Au, the ball formed at the tip of the wire at the time of bonding, for example, might destroy the Al wiring film formed on the surface of the Si semiconductor element. Moreover, since Cu has low elongation compared with Au, there existed a problem of being unable to maintain an appropriate wire loop shape.

Therefore, for example, in Patent Documents 1 and 2, a bonding wire made of Cu using ultra high purity copper (6NCu) having a purity of 99.9999% by mass or more is proposed. In addition, Patent Document 3 proposes a bonding wire made of Cu in which trace amounts of Ti, Zr, Hf, V, Cr, and B are added.

By the way, as described in patent documents 1 and 2, when using ultra high purity copper 6NCu whose purity is 99.9999 mass% or more, the refinement | purification process process is needed in order to obtain ultra high purity copper 6NCu. For this reason, there existed a problem that manufacturing cost drastically increased.

Moreover, in the bonding wire of patent document 3, compared with Au, it is still hard and elongation is low. For this reason, the characteristic was inadequate for the substitution of Au wire.

Moreover, in recent years, thinning of the bonding wire which consists of Cu wires is calculated | required, and the workability which is not disconnected is also required for the copper wire for bonding wires.

Japanese Laid-Open Patent Publication No. 62-111455 Japanese Patent Application Laid-Open No. 04-247630 Japanese Patent Publication No. 04-012623

This invention is made | formed in view of the above-mentioned situation, and an object of this invention is to provide the manufacturing method of the copper wire for bonding wires and the copper wire for bonding wires which are low in hardness, high in elongation, and also excellent in workability.

In order to solve the said subject, the copper wire for bonding wire which concerns on one aspect of this invention is a copper wire for forming the bonding wire of 180 micrometers or less of wire diameters, and an element diameter is 0.15 mm or more and 3.0 mm or less, Mg, At least one additive element selected from Ca, Sr, Ba, Ra, Zr, Ti and rare earth elements is contained in the range of 0.0001 mass% or more and 0.01 mass% or less in total, and remainder has the composition which is copper and an unavoidable impurity, EBSD The special grain boundary ratio (Lσ / L), which is the ratio of the length Lσ of the special grain boundary to the length L of all the grain boundaries measured by the method, is 50% or more.

In the copper element wire for this bonding wire, 1 or more types of additional elements selected from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and rare earth elements are contained in 0.0001 mass% or more and 0.01 mass% or less in total, The balance has a composition that is copper and unavoidable impurities. For this reason, S contained in copper reacts with the element mentioned above, and forms a compound. Thereby, the influence of S becomes small, recrystallization temperature can be made low, and hardness can be made low.

Moreover, the special grain boundary ratio (Lσ / L) which is the ratio of the length Lσ of the special grain boundary with respect to the length L of all the grain boundaries measured by the EBSD method is 50% or more. For this reason, it becomes possible to improve elongation and workability in the state which kept hardness low.

In addition, by using an EBSD measuring apparatus using a field emission scanning electron microscope, grain boundaries and special grain boundaries are specified, and the length L of all grain boundaries and the length Lσ of the special grain boundaries are calculated. From these lengths, the special grain boundary ratio (Lσ / L) in this aspect is obtained.

The grain boundary is defined as the boundary between the crystals when the orientation orientation difference between two neighboring crystals is 15 ° or more as a result of two-dimensional cross-sectional observation.

In addition, the special grain boundary is a crystallographically corresponding grain boundary satisfying 3 ≦ Σ ≦ 29, which is defined on the basis of the CSL theory (Kronberg et al: Trans. Met. Soc. In addition, the inherent corresponding site lattice orientation defect (Dq) at the corresponding grain boundary satisfies Dq ≤ 15 ° / Σ ^1/2 (DG Brandon: Acta. Metallurgica. Vol. 14, p. 1479, (1966)). It is defined as being a grain boundary.

In the copper element wire for bonding wire which concerns on one aspect of this invention, it is preferable that the sum total of content of the said additional element is 0.0003 mass% or more and 0.002 mass% or less.

In this case, recrystallization temperature can be surely suppressed low and hardness can be made low.

Moreover, content of Fe, Pb, and S which are said inevitable impurities is Fe; 0.0001 mass% or less, Pb; 0.0001 mass% or less and S; It is preferable that it is 0.005 mass% or less.

By defining the content of the impurity as described above, the recrystallization temperature can be surely lowered and the hardness can be lowered.

It is preferable that the number of acid-insoluble residues of 30 micrometers or more of particle diameters obtained by heat-dissolving 100 g of said copper wires for bonding wires in a nitric acid solution is 1000 or less.

In this case, the particle size of the acid-insoluble residue which exists in the inside of the copper wire for bonding wires is small, and its number is small. For this reason, it becomes possible to suppress generation | occurrence | production of the disconnection at the time of wire drawing at the time of manufacturing a bonding wire.

It is preferable that the quantity of the acid insoluble residue obtained by heat-dissolving the said copper wire for bonding wires in a nitric acid solution is 0.00015 mass% or less.

In this case, the ratio of the acid insoluble residue which exists in the inside of the copper wire for bonding wires is small. For this reason, it becomes possible to suppress generation | occurrence | production of the disconnection at the time of wire drawing at the time of manufacturing a bonding wire.

The manufacturing method of the copper wire for bonding wire which concerns on one aspect of this invention is a manufacturing method of the copper wire for bonding wire mentioned above, Mg, Ca, Sr, Ba, in a copper raw material of purity 99.99 mass% or more and 99.998 mass% or less; A copper molten metal production process which adds 1 or more types of additional elements chosen from Ra, Zr, Ti, and a rare earth element, produces | generates the copper molten metal, and supplies the said copper molten metal to a belt-wheel continuous casting machine, and continuously submits an ingot. The continuous casting process and the continuous rolling process of rolling the submitted ingot continuously on the conditions of the initial temperature 800 degreeC or more are provided.

According to the manufacturing method of this copper wire for bonding wires, the so-called 4NCu copper raw material is used for purity 99.99 mass% or more and 99.998 mass% or less. For this reason, compared with the case of using 6NCu, the manufacturing cost of the copper wire for bonding wires can be reduced significantly.

Moreover, it is equipped with the continuous rolling process which continuously rolls the submitted ingot on conditions with an initial temperature of 800 degreeC or more. For this reason, the special grain boundary ratio (Lσ / L) in the copper element wire for bonding wire can be 50% or more.

Moreover, the manufacturing method of the copper wire for bonding wire which concerns on another aspect of this invention is a manufacturing method of the copper wire for bonding wire mentioned above, Mg, Ca, Sr, in a copper raw material of purity 99.99 mass% or more and 99.998 mass% or less; A copper molten metal forming step of adding at least one additional element selected from Ba, Ra, Zr, Ti, and rare earth elements and producing a copper molten metal, a casting process of injecting the copper molten metal into a mold and submitting an ingot; An extrusion process in which the ingot is extruded under conditions of an initial temperature of 800 ° C. or higher to submit an extrusion wire, a processing / annealing step of repeatedly annealing with any of rolling processing or wire drawing, and a reduction ratio of 5% with respect to the obtained extrusion wire. Rolling is carried out to 25% or more of the above, and the pressure reduction step is performed so that the final wire diameter may be 0.15 mm or more and 3.0 mm or less.

According to the manufacturing method of this copper wire for bonding wires, the so-called 4NCu copper raw material is used for purity 99.99 mass% or more and 99.998 mass% or less. For this reason, compared with the case of using 6NCu, the manufacturing cost of the copper wire for bonding wires can be reduced significantly.

Moreover, the process and annealing process which repeats annealing with any of a rolling process or a wire drawing with respect to an extrusion element wire, and the low pressure process which rolls by 5% or more and 25% or less of a reduction ratio, and makes final wire diameter 0.15mm or more and 3.0mm or less. Equipped with. For this reason, the special grain boundary ratio (Lσ / L) in the copper element wire for bonding wire can be 50% or more.

According to one aspect of the present invention, it is possible to provide a method for producing a copper wire for a bonding wire and a copper wire for a bonding wire having low hardness, high elongation, and further excellent workability.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the continuous casting rolling apparatus used when manufacturing the copper wire for bonding wire which is one Embodiment of this invention.
It is a flowchart of the manufacturing method of the copper element wire for bonding wires which is one Embodiment of this invention.
It is a flowchart of the manufacturing method of the copper wire for bonding wire which is another embodiment of this invention.
It is a graph which shows the evaluation result of the acid insoluble residue in Example 1 of this invention.

Below, the manufacturing method of the copper wire for bonding wires and the copper wire for bonding wire which concerns on one Embodiment of this invention is demonstrated.

The copper element wire for bonding wire which concerns on this embodiment is used as a raw material at the time of manufacturing the bonding wire of 180 micrometers or less of wire diameters, More preferably, 20 micrometers or more and 180 micrometers or less of wire diameters.

Moreover, the wire diameter of the copper element wire for bonding wires which concerns on this embodiment is 0.15 mm or more and 3.0 mm or less.

This copper wire for bonding wire contains in total at least 0.0001 mass% or more 0.01 mass% of 1 or more types of addition elements chosen from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and a rare earth element, It has a composition that is added copper and unavoidable impurities. Preferably, the sum total of content of 1 or more types of addition element chosen from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and a rare earth element is 0.0003 mass% or more and 0.002 mass% or less.

Moreover, content of Fe, Pb, S which is the said unavoidable impurity is Fe; 0.0001 mass% or less, Pb; 0.0001 mass% or less, S; It is 0.005 mass% or less.

Here, the rare earth elements are Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

The special grain boundary ratio (Lσ / L) of the copper wire for bonding wires is 50% or more. Here, the special grain boundary ratio is the ratio of the length Lσ of the special grain boundary to the length L of all the grain boundaries. Grain boundaries and special grain boundaries are specified by an EBSD measuring apparatus using a field emission scanning electron microscope, and the length L of all grain boundaries and the length Lσ of the special grain boundaries are calculated. From this calculated length, a special grain boundary ratio is obtained. That is, in the copper element wire for bonding wire which is this embodiment, more special grain boundaries exist than a normal crystal grain boundary.

The grain boundary is defined as the boundary between the crystals when the orientation orientation difference between two neighboring crystals is 15 ° or more as a result of two-dimensional cross-sectional observation.

In addition, the special grain boundary is a crystallographically corresponding grain boundary satisfying 3 ≦ Σ ≦ 29, which is defined on the basis of the CSL theory (Kronberg et al: Trans. Met. Soc. AIME, 185, 501 (1949)). In addition, the intrinsic corresponding site lattice orientation defect (Dq) at the corresponding grain boundary satisfies Dq ≦ 15 ° / Σ ^1/2 (DG Brandon: Acta. Metallurgica. Vol. 14, p. 1479, (1966)). It is defined as being a grain boundary.

Moreover, the number of acid-insoluble residues of 30 micrometers or more of particle diameters obtained by heat-dissolving 100 g of copper wires for bonding wires of this embodiment in nitric acid solution is 1000 or less. Moreover, the ratio of the acid insoluble residue mentioned above is 0.00015 mass% or less.

Evaluation of acid insoluble residue is performed in the following procedure.

First, a predetermined amount (100 g) of a sample is sampled from the copper element wire for bonding wire which wash | cleaned the surface, and it heat-dissolves in the heated nitric acid solution. The solution is cooled to room temperature, filtered through a filter, and the residue is collected.

The filter which collected the residue is weighed, and the residue mass of the residue is measured. And the ratio (mass%) of the quantity (residual mass) of the residue with respect to the quantity of a sample (copper wire for bonding wires) is computed. By the above, the quantity (presence ratio) of the acid insoluble residue obtained by heat-dissolving the copper wire for bonding wires in nitric acid solution is measured.

Next, the filter which collected the residue is observed with the scanning electron microscope, and SEM photograph is taken. The SEM photographs are image analyzed and the size and number of residues are measured. Then, the number of residues having a particle diameter of 30 µm or more is obtained. By the above, the number of the acid insoluble residue of particle size 30 micrometers or more obtained by heat-dissolving 100 g of copper wires for bonding wires in a nitric acid solution is measured.

Next, the manufacturing method of the copper wire for bonding wire which is this embodiment is demonstrated.

The copper wire for bonding wire whose ratio (Lσ / L) of the total special grain boundary length (Lσ) of the special grain boundary to the total grain boundary length (L) of the grain boundary is 50% or more can be obtained by the continuous casting rolling method or the extrusion processing method of the ingot. Are manufactured.

In this embodiment, it demonstrates as an example using the continuous casting-rolling apparatus 10 shown in FIG.

The continuous casting rolling apparatus 10 shown in FIG. 1 includes the melting furnace 11, the holding furnace 12, the casting cylinder 13, the belt-wheel continuous casting machine 30, the continuous rolling apparatus 15, And a coiler 18.

In this embodiment, the shaft furnace which has a cylindrical furnace main body is used as the melting furnace 11. In the lower part of the furnace main body, a plurality of burners (not shown) are arranged in the circumferential direction, and are arranged in multiple stages in the vertical direction. And electric copper which is a raw material is charged from the upper part of a furnace main body. By burning the burner, the electric copper is dissolved, and the molten copper is continuously made.

The fat and oil furnace 12 stores the pure copper molten metal produced by the melting furnace 11 in the state hold | maintained at predetermined temperature once, and sends a fixed amount of molten copper to the casting cylinder 13.

The casting cylinder 13 transfers the molten copper sent from the holding furnace 12 to the tundish 20 arranged above the belt-wheel continuous casting machine 30. This casting cylinder 13 is sealed with inert gas or reducing gas, such as Ar, for example. Moreover, stirring means (not shown) which stirs a molten copper with an inert gas is provided in this casting cylinder 13.

In the tundish 20, an element adding means 21 for adding an element to the transferred molten copper is formed. Moreover, the pouring nozzle 22 is arrange | positioned at the flow direction terminal side of the molten copper of the tundish 20. As shown in FIG. The molten copper in the tundish 20 is supplied to the belt-wheel continuous casting machine 30 through this pouring nozzle 22.

The belt-wheel continuous casting machine 30 has a casting wheel 31 with a groove formed on its outer circumferential surface, and an endless belt 32 that is circumferentially moved so as to contact a part of the outer circumferential surface of the casting wheel 31. In the space formed between the groove and the endless belt 32, the molten copper supplied through the pouring nozzle 22 is injected and cooled, and the rod-shaped ingot 40 is continuously cast.

And this belt-wheel continuous casting machine 30 is connected to the continuous rolling apparatus 15. This continuous rolling apparatus 15 continuously rolls the rod-shaped ingot 40 submitted from the belt-wheel continuous casting machine 30, and submits the copper-sulfur cutting edge 50 of a predetermined outer diameter. The copper-sulfur cutting wire 50 submitted from the continuous rolling apparatus 15 is wound up by the coiler 18 via the washing | cleaning cooling apparatus 16 and the flaw detector 17. FIG.

Next, the manufacturing method of the copper wire for bonding wires using this belt-wheel continuous casting machine 30 is demonstrated using FIG. 1, FIG.

First, the copper raw material (so-called 4NCu) of purity 99.99 mass% or more and 99.998 mass% or less is thrown into the melting furnace 11, and it melt | dissolves and obtains a molten copper (melting process (S01)). In this melting process (S01), the air-fuel ratio of the some burner to a shaft is adjusted and the inside of the melting furnace 11 is made into a reducing atmosphere.

The molten copper obtained by the melting furnace 11 is transferred to the tundish 20 via the holding furnace 12 and the casting cylinder 13.

Here, the molten copper passing through the casting cylinder 13 sealed with an inert gas or a reducing gas is stirred by the above-described stirring means. As a result, the reaction between the molten copper and the inert gas or the reducing gas is promoted.

Next, one or more elements selected from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and rare earth elements are continuously connected to the molten copper in the tundish 20 by the element addition means (apparatus) 21. (Element addition step (S02)). Thereby, content of 1 or more types of elements chosen from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and a rare earth element totals 0.0001 mass% or more and 0.01 mass% or less, More preferably, it is 0.0003 mass% or more and 0.002 mass The molten copper adjusted to% or less is produced.

The molten copper thus adjusted is supplied to the belt-wheel continuous casting machine 30 through the pouring nozzle 22, and the rod-shaped ingot 40 is continuously submitted (continuous casting step S03). Here, in the continuous casting step (S03), the space formed between the groove of the cast ring 31 and the endless belt 32 is trapezoidal. For this reason, the rod-shaped ingot 40 whose cross section becomes substantially trapezoidal is submitted.

This rod-shaped ingot 40 is supplied to the continuous rolling apparatus 15, and a roll rolling process is performed, and the copper-sulfur cutting wire 50 of a predetermined outer diameter (8 mm in diameter in this embodiment) is submitted (continuous rolling process (S04) )). In this continuous rolling process (S04), rolling is performed in 400-900 degreeC. In this embodiment, the initial temperature of rolling is made 800 degreeC or more. The initial temperature of rolling becomes like this. Preferably it is 800 degreeC or more and 1050 degrees C or less.

The copper-sulfur cutting wire 50 submitted from the continuous rolling apparatus 15 is wound up by the coiler 18 via the washing | cleaning cooling apparatus 16 and the flaw detector 17. FIG. The cleaning cooling device 16 cools the surface of the copper-sulfur cutting wire 50 submitted from the continuous rolling device 15 with a cleaning agent such as alcohol. Moreover, the flaw detector 17 detects the flaw of the copper-sulfur cutting ship 50 sent from the washing | cleaning cooling apparatus 16. FIG.

Next, wire drawing is performed to the obtained copper-sulfur cutting wire 50, and it is set as final wire diameter 0.15 mm or more and 3.0 mm or less (in this embodiment, diameter 0.9mm) (drawing process (S05)).

And after re-crystallization heat processing process (S05) mentioned above, recrystallization heat treatment is performed at 150 degreeC or more and 250 degrees C or less (finishing heat processing process (S06)). In this embodiment, atmospheric heat treatment is performed at 220 degreeC for 2 hours.

By the above procedure, the copper wire for bonding wire which is this embodiment is submitted.

The copper wire for the bonding wire according to the present embodiment is further subjected to drawing processing to become a thin wire having a diameter of 180 μm or less, and used as a bonding wire.

According to the copper element wire for bonding wires of this embodiment which has such a characteristic, 0.0001 mass% or more and 0.01 mass in total of 1 or more types of additional elements chosen from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and a rare earth element in total It contains in the range of% or less, and has a composition whose remainder is copper and an unavoidable impurity. More preferably, the sum total of content of the said additional element is 0.0003 mass% or more and 0.002 mass% or less. For this reason, S contained in copper forms the above-mentioned addition element and a compound. Therefore, since the influence of S becomes small, recrystallization temperature can be made low and hardness can be made low.

Moreover, the special grain boundary ratio (Lσ / L) of the copper element wire for bonding wires which is this embodiment is 50% or more. In addition, by using an EBSD measuring apparatus using a field emission scanning electron microscope, grain boundaries and special grain boundaries are specified, and the length L of all grain boundaries and the length Lσ of the special grain boundaries are calculated. And a special grain boundary ratio is obtained from this calculated length. When this special grain boundary ratio is high, the match of the grain boundaries of the whole structure improves, and dislocations become difficult to accumulate. Therefore, it becomes possible to improve elongation and workability in the state which kept hardness low.

Moreover, the number of acid-insoluble residues of 30 micrometers or more of particle diameters obtained by heat-dissolving 100 g of copper wires for bonding wires of this embodiment in nitric acid solution is 1000 or less. In addition, the amount (existence ratio) of an acid insoluble residue is 0.00015 mass% or less.

Thus, the particle size of an acid insoluble residue is small, the number is small, and also the existence ratio is suppressed. For this reason, it becomes possible to suppress the disconnection at the time of carrying out wire drawing of the copper wire for bonding wires with a bonding wire.

Moreover, according to the manufacturing method of the copper element wire for bonding wires of this embodiment, purity 99.99 mass% or more and 99.998 mass% or less, so-called 4NCu copper raw material is used. For this reason, compared with the case where 6NCu is used, the manufacturing cost of the copper element wire for bonding wires can be reduced significantly.

Moreover, the continuous casting process S03 which continuously submits the rod-shaped ingot 40 using the belt-wheel continuous casting machine 30, and continuously rolling the submitted rod-shaped ingot 40 on conditions of the initial temperature 800 degreeC or more are carried out. Continuous rolling process (S04) is provided. For this reason, the special grain boundary ratio (Lσ / L) of the copper wire for bonding wires submitted can be 50% or more.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.

In this embodiment, although demonstrated as what manufactures the copper wire for a bonding wire using a belt-wheel continuous casting machine, it is not limited to this.

For example, as shown in FIG. 3, the molten copper production process (S11), the casting process (S12), the hot extrusion process (S13), the processing and annealing process (S14), and the low pressure process (S15) By carrying out, the copper wire for bonding wires having a special grain boundary ratio (Lσ / L) of 50% or more may be submitted.

In the molten copper production step (S11), at least one kind selected from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and rare earth elements to a copper raw material (so-called 4NCu) having a purity of 99.99% by mass or more and 99.998% by mass or less. The element is added to obtain a molten copper.

In the casting step (S12), molten copper is poured into a mold to obtain an ingot having a diameter of 200 mm to 400 mm.

In a hot extrusion process (S13), an ingot is extruded on conditions of 800 degreeC or more of initial stages, and an extrusion element wire is obtained. The initial temperature of extrusion processing becomes like this. Preferably it is 800 degreeC or more and 1050 degrees C or less.

In work and annealing process (S14), annealing is repeated with either a rolling process or a wire drawing process with respect to an extrusion element wire. Annealing is performed whenever the cross-sectional reduction rate is 80% or more.

In the pressure reduction step (S15), rolling is performed at a reduction ratio of 5% or more and 25% or less, and the final wire diameter is 0.15 mm or more and 3.0 mm or less.

Example

(Example 1)

Below, the result of the evaluation test evaluated about the copper wire for bonding wire which is this embodiment mentioned above is demonstrated.

By the method shown in the flowchart of FIG. 2, the copper wire for bonding wires of Examples 1-5 of this invention and Comparative Examples 1, 2 were submitted. In detail, the addition element of Table 1 was added to 4NCu, and the molten copper was obtained. The molten copper was poured into a belt-wheel continuous casting machine, and continuous casting rolling was performed. Furthermore, wire drawing and finishing heat treatment were performed, and the copper wire for bonding wires of 0.9 mm in diameter was submitted.

By the method shown in the flowchart of FIG. 3, the copper wire for bonding wires of Examples 6-10 of this invention and Comparative Examples 3, 4 were submitted. In detail, the addition element of Table 1 was added to 4NCu, and the molten copper was obtained. Ingot of 240 mm diameter was submitted using the molten copper. This ingot was hot-extruded at 800 degreeC, and the extrusion wire of 8 mm in diameter was submitted. Rolling and annealing were repeated about this extruded element wire, and the copper element wire of 1 mm of wire diameter was submitted. Then, rolling of 10% of the rolling rate was performed with respect to this copper element wire. Subsequently, finish heat treatment was performed at 220 degreeC, and the copper wire for bonding wires of diameter 0.9mm was submitted.

The copper wire for the bonding wire of the prior art example was submitted by the following method. First, 0.0030 mass% Zr was added to 4NCu, and the molten copper was obtained. Ingot of 240 mm diameter was submitted using the molten copper. This ingot was hot-extruded at 800 degreeC, and the extrusion wire of 8 mm in diameter was submitted. The extrusion process was performed for the extrusion wire. Subsequently, finish heat treatment was performed at 220 degreeC, and the copper wire for bonding wires of diameter 0.9mm was submitted.

Moreover, about the copper wire for bonding wires of obtained invention examples 1-10, comparative examples 1-4, and a prior art example, wire drawing was performed and the bonding wire of 180 micrometers in diameter was submitted.

(Special grain boundary ratio)

About the obtained copper wire for bonding wires of Examples 1-10, Comparative Examples 1-4, and a prior art example, the special grain boundary ratio (Lσ / L) was measured by the following method.

Each sample was subjected to mechanical polishing using a domestic abrasive paper and diamond abrasive grains. Subsequently, finish polishing was performed using a colloidal silica solution.

The grain boundaries and special grain boundaries are specified by an EBSB measuring device (S4300-SEM manufactured by HITACHI, OIM Data Collection manufactured by EDAX / TSL) and analysis software (OIM Data Analysis ver. 5.2 manufactured by EDAX / TSL). The length L and the length Lσ of the special grain boundary were calculated. Thereby, the average grain size and the special grain boundary length ratio were analyzed. The detail of a measuring method is shown below.

First, using a scanning electron microscope, the electron beam was irradiated to the individual measurement points within the measurement range of a sample surface, and the electron beam was scanned in two dimensions on the sample surface. By azimuth analysis by backscattered electron beam diffraction, the grain boundary was set between the measurement points which the orientation difference between adjacent measurement points becomes 15 degrees or more.

The total grain boundary length (length of all grain boundaries) L of the grain boundaries in the measurement range was measured. Moreover, while determining the position of the grain boundary whose interface between adjacent grains is a special grain boundary, the total grain boundary length (length of all the special grain boundaries) (Lσ) of the special grain boundary was measured. And the ratio (Lσ / L) of the length Lσ of the special grain boundary with respect to the total grain boundary length L of the said measured grain boundary was calculated | required, and it was set as the special grain boundary ratio (Lσ / L).

(Hardness test)

Next, the hardness was measured about the copper wire for bonding wires of this invention example 1-10, comparative examples 1-4, and a prior art example, and the bonding wire submitted from the copper wire for these bonding wires.

In addition, the hardness test was performed based on JISZ22241 using the Micro Vickers tester MVK-700 made from AKASHI.

(Elongation)

Next, with respect to the bonding wires submitted from the copper wires for the bonding wires of the invention examples 1 to 10, the comparative examples 1 to 4, and the conventional examples, and the copper wires for the bonding wires thereof, Amsler-type male tensile made by AKASHI. The tensile test was done using the test machine, and the elongation was evaluated.

(Processability)

Further, wire drawing was performed on the obtained copper wires for bonding wires of the inventive examples 1 to 10, the comparative examples 1 to 4, and the conventional example to produce wires having a diameter of 87 µm, 50 µm, or 20 µm. The number of disconnections at the time of drawing was evaluated.

Table 1 shows the results of the evaluation of the special grain boundary ratio (Lσ / L), hardness and elongation of the bonding wire for bonding wire, hardness and elongation of the bonding wire, and the number of disconnections at the time of drawing.

In Examples 1 to 10 of the present invention, it is confirmed that the special grain boundary ratio (Lσ / L) is 50% or more. On the other hand, in Comparative Examples 1-4 and the prior art example, the special grain boundary ratio (Lσ / L) was less than 50%. In contrast to Examples 6 to 10 of the present invention and the prior art, it is possible to increase the special grain boundary ratio (Lσ / L) by processing the rolling rate of 10% before performing the final heat treatment on the element wire having the final wire diameter. It is confirmed that it is possible.

In Examples 1 to 10 of the present invention, in which the special grain boundary ratio (Lσ / L) is 50% or more, it is confirmed that the hardness is lowered to 40 Hv or less in the state of a bonding wire having a wire diameter of 180 µm.

Moreover, in Examples 1-10 of this invention, compared with the comparative example, the disconnection at the time of drawing is suppressed and it can be confirmed that it can be drawn to narrow diameter.

(Example 2)

Next, the residue amount and particle size distribution of the acid insoluble residue were evaluated using the copper wire for bonding wires of Examples 1-10 of this invention.

The sample was etched with nitric acid to remove impurities adhering to the surface. Next, 100 g of sample was weighed. This sample was dissolved in a nitric acid solution by heating. Heating temperature was 60 degreeC. This work was repeated.

Next, it cooled to room temperature, and filtered with a filter to collect the residue.

Here, filtration was performed using the polycarbonate filter (pore size 0.4 micrometer). The polycarbonate filter which collected the residue was precisely weighed in a clean room, and the residue mass of the residue was measured.

In addition, the particle size distribution of the acid insoluble residue was measured. The filter which collected the above-mentioned residue was observed with the scanning electron microscope, and the SEM image was taken. The image was input to a computer, and the image was binarized by the software for image analysis (WinRoof software). And the projection area of the residue was measured, and the diameter (circle equivalent diameter) of the circle which has the area same as this projection area was computed. This circle equivalent diameter was used as a particle size of a residue. The size (circle equivalent diameter) and the number of residues were measured. Moreover, the graph of particle size distribution was created from the data of Example 1 of this invention. The results are shown in Fig.

As a result of image analysis of WinRoof software, when 100 g of samples (copper wire for bonding wire) of Examples 1 to 10 of the present invention were dissolved in a nitric acid solution, all of the acid-insoluble residues having a particle diameter of 30 µm or more were 1000 or less. It was confirmed. Moreover, as a result of measuring the residue mass of the residue by the method mentioned above, it was confirmed that the mass ratio of the acid insoluble residue in the sample of this invention Examples 1-10 is 0.00015 mass% or less.

Industrial availability

The copper element wire for bonding wires of this embodiment is low in hardness, high in elongation, and also excellent in workability. For this reason, the copper element wire of this embodiment can be preferably applied to the manufacturing process of Cu bonding wire used instead of Au wire.

30: belt-wheel continuous casting machine

Claims (7)

As a copper element wire for forming the bonding wire of the wire diameter of 180 micrometers or less,
The wire diameter is 0.15 mm or more and 3.0 mm or less,
At least one additive element selected from Mg, Ca, Sr, Ba, Ra, Zr, Ti and rare earth elements is contained in a range of 0.0001% by mass to 0.01% by mass in total, and the balance has a composition of copper and unavoidable impurities ,
A special grain boundary ratio (Lσ / L), which is a ratio of the length Lσ of the special grain boundary to the length L of all the grain boundaries measured by the EBSD method, is 50% or more. The method of claim 1,
The sum total of content of the said additional element is 0.0003 mass% or more and 0.002 mass% or less, The copper wire for bonding wires characterized by the above-mentioned. 3. The method according to claim 1 or 2,
Fe, Pb, and S which are said unavoidable impurities are Fe; 0.0001 mass% or less, Pb; 0.0001 mass% or less and S; It is 0.005 mass% or less, The copper wire for bonding wires characterized by the above-mentioned. 4. The method according to any one of claims 1 to 3,
The number of acid-insoluble residues of 30 micrometers or more of particle diameters obtained by heat-dissolving 100 g of said copper wires for bonding wires in a nitric acid solution is 1000 or less, The copper wires for bonding wires characterized by the above-mentioned. 5. The method according to any one of claims 1 to 4,
The amount of the acid insoluble residue obtained by heat-dissolving the said copper wire for bonding wires in a nitric acid solution is 0.00015 mass% or less, The copper wire for bonding wires characterized by the above-mentioned. As a manufacturing method of the copper wire for bonding wires in any one of Claims 1-5,
Copper molten metal production process which adds 1 or more types of additional elements chosen from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and rare earth elements to the copper raw material of purity 99.99 mass% or more and 99.998 mass% or less, and produces copper molten metal. and,
A continuous casting step of supplying the molten copper to a belt-wheel continuous casting machine and continuously submitting an ingot;
A method of producing a copper wire for bonding wire, comprising a continuous rolling step of continuously rolling the submitted ingot under the conditions of an initial temperature of 800 ° C. or more. As a manufacturing method of the copper wire for bonding wires in any one of Claims 1-5,
Copper molten metal production process which adds 1 or more types of additional elements chosen from Mg, Ca, Sr, Ba, Ra, Zr, Ti, and rare earth elements to the copper raw material of purity 99.99 mass% or more and 99.998 mass% or less, and produces copper molten metal. and,
A casting process of injecting the molten copper into a mold and submitting an ingot;
An extrusion process of extruding the obtained ingot under conditions of an initial temperature of 800 ° C. or more and submitting an extrusion wire;
Process and annealing process which repeats annealing with either a rolling process or a wire process with respect to the obtained extrusion element wire,
A rolling method for producing a copper wire for bonding wire, comprising: a rolling reduction step of rolling at a reduction ratio of 5% or more and 25% or less to a final wire diameter of 0.15 mm or more and 3.0 mm or less.

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