TWI598175B - Brass welding wire and its manufacturing method - Google Patents

Description

Copper welding wire and manufacturing method thereof

The present invention relates to a copper bonding wire and a method of manufacturing the same.

Conventionally, a gold (Au) wire is used for a bonding wire for connecting an electrode pad of a semiconductor element and a wiring pad of a circuit board, and in particular, in a resin package type semiconductor element, a diameter is often used from the viewpoint of connection reliability. Au line of 0.02~0.03mm.

In recent years, in the case of the high price of Au, in the wire welding of power modules for vehicles such as automobiles, aluminum wires having a material cost significantly lower than the Au line and having a diameter of about 0.1 to 0.3 mm have been used.

However, in a power module such as an automobile, a material having a higher thermal conductivity and electrical conductivity (conductivity) than an aluminum wire is required from the viewpoint of miniaturization of the device and increase in current density.

Therefore, a bonding wire in which copper (Cu) or a Cu alloy is used as a core material and palladium (Pd) or a Pd alloy is coated on the outer periphery thereof or via an intermediate layer is proposed (see Patent Document 1). This welding wire has an advantage of being excellent in oxidation resistance when the surface is oxidized and the material is stored, but the technical problem is as follows.

That is, in the case of the Pd-coated bonding wire, when the ball is formed in the ball at the tip end of the ball bonding and Pd is dissolved in the Cu, even if it is extremely small, the hardness of the ball is harder than that of the copper, and the solid is not solid. The Pd which is dissolved and remains on the surface layer itself is also hard, so there is a problem that the fragile aluminum pad on the wafer is damaged during ball bonding. Further, there is a problem that the material cost of the Pd itself used as the covering material is also high.

On the other hand, a weld line in which a coating layer made of zinc or the like is formed on the surface of a core material formed of Cu or a Cu alloy has been proposed (see Patent Documents 2 and 3).

Conventional technical literature

Patent literature

Patent Document 1: Japanese Unexamined Publication No. Sho 60-160554

Patent Document 2: Japanese Laid-Open Patent Publication No. 60-207357

Patent Document 3: Japanese Laid-Open Patent Publication No. 62-287634

In the conventional welding line in which a coating layer containing Zn is formed on the surface of a core material formed of Cu or a Cu alloy, Zn is cheaper than Pd material, and further, even when the Zn component is dissolved in Cu, Pd is used. In contrast, there is a tendency that the ball is hard to harden, which is advantageous in these respects.

However, when storing the weld line, Cu in the core material spreads to the surface of the weld line, and the diffused Cu combines with oxygen to grow an oxide film. When the coating layer formed of Zn is formed thick, the Zn itself may be Oxygen bonding causes the Zn oxide film to grow thickly, and as a result, there is a problem that connection to the aluminum pad is poor during soldering.

Accordingly, an object of the present invention is to provide a copper bonding wire which can suppress the growth of an oxide film on the surface of a bonding wire during storage of a bonding wire, and can improve connection reliability at the time of soldering.

In order to achieve the above object, the present invention provides the copper bonding wire of the following [1] to [8] and a method of manufacturing the same.

[1] A copper bonding wire comprising a core material mainly composed of copper and a surface treatment layer formed on a surface of the core material, the surface treatment layer having a metal and oxygen having a higher affinity for oxygen than copper Amorphous layer.

[2] The copper bonding wire according to the above [1], wherein the amorphous layer further contains copper diffused from the core material.

[3] The copper bonding wire according to the above [1], wherein the surface treatment layer further has a diffusion layer under the amorphous layer, the diffusion layer containing copper and affinity for oxygen. A metal that is higher than copper, or a metal that contains copper, has a higher affinity for oxygen than copper, and oxygen.

[4] The copper bonding wire according to any one of [1] to [3] wherein the metal having a higher affinity for oxygen than copper is zinc.

[5] The copper bonding wire according to any one of [1] to [4] wherein the surface treatment layer has a thickness of 3 nm or more and 0.6 μm or less.

[6] A method for producing a copper bonding wire, comprising forming a coating layer containing a metal having a higher affinity for oxygen than copper on a surface of a core material containing copper as a main component, and forming the coating layer at 50 ° C or higher The surface treatment layer is formed by heat-treating at a temperature of 150 ° C or lower for 30 seconds or longer and 60 minutes or shorter.

[7] The method for producing a copper weld wire according to the above [6], wherein the metal having a higher affinity for oxygen than copper is zinc.

[8] The method for producing a copper bonding wire according to the above [6], wherein the surface treatment layer has a thickness of 3 nm or more and 0.6 μm or less.

According to the present invention, it is possible to provide a copper welding wire which can suppress the growth of an oxide film on the surface of the bonding wire during storage of the bonding wire, and can improve the connection reliability at the time of soldering.

1‧‧‧Bronze welding line

2‧‧‧ core material

3‧‧‧ surface treatment layer (amorphous layer)

4‧‧‧Bronze welding line

5‧‧‧Surface treatment layer

6‧‧‧Diffusion layer

7‧‧‧Amorphous layer

Fig. 1 is a cross-sectional view schematically showing a copper bonding wire according to an embodiment of the present invention; Figure 2 is a cross-sectional view schematically showing a copper bonding wire according to another embodiment of the present invention; Fig. 3 is a graph showing the results of the Auger element analysis in the depth direction of the test piece after repeated sputtering from the surface layer in the constant temperature (100 ° C) holding test of the copper bonding wire according to the third embodiment of the present invention; Fig. 4 is a graph showing temporal changes in oxygen intrusion depth (oxide thickness) from the surface layer in the constant temperature (100 ° C) holding test of the copper bonding wire according to Example 3, Comparative Example 1, and Conventional Example 1 of the present invention. ;as well as Fig. 5 is an electron beam diffraction image showing the results of RHEED analysis of the copper bonding wire according to the third embodiment of the present invention.

1. Composition of copper welding wire

Fig. 1 is a cross-sectional view schematically showing a copper bonding wire according to an embodiment of the present invention. this 2 is a cross-sectional view schematically showing a copper bonding wire according to another embodiment of the present invention.

The copper bonding wire 1 according to the embodiment of the present invention shown in Fig. 1 includes a core material 2 mainly composed of copper and a surface treatment layer 3 formed on the surface of the core material 2.

As the material mainly composed of copper constituting the core material 2, for example, oxygen-free copper, toughened copper, or the like can be used. Further, it is not necessarily required to be pure copper. In the range in which the effects of the present invention can be achieved, a copper alloy can be used. Specifically, it can be used with 3 to 15 ppm by mass of sulfur, 2 to 30 ppm by mass of oxygen, and 5 to 55 mass. Low concentration copper alloy of ppm Ti.

The surface treatment layer 3 has an amorphous layer containing a metal having a higher affinity for oxygen than copper and oxygen. Alternatively, the surface treatment layer 3 has an amorphous layer containing a metal having higher affinity for oxygen than copper, oxygen, and copper diffused from the core material 2.

Further, as shown in Fig. 2, as the copper bonding wire 4 according to another embodiment of the present invention, the surface treatment layer 5 may have an amorphous layer 7 and a diffusion layer 6 formed under the amorphous layer 7, the diffusion Layer 6 contains copper and a metal having a higher affinity for oxygen than copper, or a metal containing copper and having a higher affinity for oxygen than copper and oxygen. A diffusion layer 6 containing copper and a metal having a higher affinity for oxygen than copper and oxygen is preferred.

When the amorphous layer (surface-treated layer 3) and the diffusion layer 6 are provided, zinc is preferable as the metal constituting the amorphous layer 7 and having a higher affinity for oxygen than copper. Examples of the zinc other than Ti include Mg, Mg, Zr, Al, Fe, Sn, and Mn. In particular, from the viewpoint of recirculation, Ti, Mg, and Zr which are easily oxidized and removed when copper is produced are preferable. The metal constituting the diffusion layer 6 and having a higher affinity for oxygen than copper is preferably the same metal as the metal constituting the amorphous layer and having a higher affinity for oxygen than copper.

The amorphous layer in which the elements are randomly arranged is a structure denser than the crystal layer in which the elements are regularly arranged, so that the amorphous layer can suppress or even reduce the diffusion of copper to the surface of the surface treatment layer due to oxidation of the copper raw material and Intrusion of oxygen into the copper raw material. As a result, amorphous has a function as a barrier layer for preventing the combination of copper and oxygen.

In order to form the amorphous layer, it is necessary to preferentially bond oxygen to other metals than copper. In order to promote the formation of the amorphous layer, it is preferable to arrange the affinity for oxygen on the surface of the core material to be higher than that of the core material 2. Metal (for example, zinc).

For the surface treatment layers 3 and 5, since the dissimilar elements are in contact at the interface, a smooth concentration change is generally exhibited at the interface of the dissimilar elements, and it is difficult to define the thickness of the surface treatment layer. therefore, In the present invention, the thickness of the surface treatment layer is defined as "the thickness of the layer is a metal and oxygen having a higher affinity for oxygen than copper, and a thickness of a layer containing copper according to the occasion, and the thickness of the layer is either The atomic concentration (at%) of the element content ratio of the elements constituting the layer is 2 at% or more.

The thickness of the surface treatment layer 3 (the surface treatment layer 5 in the case of the copper bonding wire 4 having the diffusion layer 6) used in the copper bonding wire 1 according to the present embodiment also depends on the thickness of the diffusion layer 6 and the heat treatment conditions. However, it is preferably 3 nm or more and 0.6 μm or less. More preferably, it is 6 nm or more and 0.6 micrometer or less.

When the diffusion layer 6 is provided, the thickness of the diffusion layer 6 is not particularly limited as long as it is a copper core material. In practical terms, the lower limit of the coating thickness is preferably about 3 nm. Further, the upper limit of the thickness of the diffusion layer 6 is preferably 0.5 μm or less. When it exceeds 0.5 μm, it may become difficult to stably form the amorphous layer 7 which contributes to the development of high corrosion resistance. The thickness of the amorphous layer 7 is not particularly limited, but is preferably 3 nm or more.

2. Copper welding wire manufacturing method

In the copper bonding wire according to the present embodiment, when the metal having a higher affinity for oxygen than copper is, for example, zinc, it can be produced by forming Zn on the surface of the copper-based conductor by electroplating according to the size and shape of the final product. The layer (preferably having a thickness of 20 μm or less, more preferably 17 μm or less, further preferably 15 μm or less) is directly exposed to the atmosphere at a temperature of 50° C. or higher and 150° C. or lower for 30 seconds or longer and 60 minutes or shorter. heating. Thereby, a copper bonding wire having at least a surface treatment layer containing an amorphous layer of zinc and oxygen can be obtained. In other words, the amorphous layer can be formed by a simple method in which zinc is coated on the surface of the core material containing copper as a main component and a predetermined heat treatment is performed.

In the method for producing a copper weld line according to the present invention, as described above, the coating layer is preferably subjected to heat treatment under conditions of a temperature of 50 ° C to 150 ° C and a time of 30 seconds or longer and 60 minutes or shorter. Further, for the formation of the Zn layer, a plating method is preferably used. In addition to the plating method, a sputtering method, a vacuum evaporation method, a metal clad method, or the like can also be used.

Further, as another embodiment, a method of manufacturing by using a method in which zinc is plated before being processed into a final product size and shape, and then processed into a final product size and shape may be employed. The coating layer was set to 0.6 μm or less.

Further, the diffusion layer 6 can be produced by coating a surface of a core material mainly composed of copper with a temperature of 50 ° C or higher before forming the amorphous layer 7 of the surface treatment layer 5 . Heat in the atmosphere or keep in the oil bath or salt bath. In addition, it can also be used to generate resistance Heat to make. After the diffusion layer 6 is formed, the amorphous layer 7 is formed on the outer periphery in the same manner as the above method.

Further, the surface treatment layer may be formed on a wire as a weld line, and in the case of a flat core material such as a welded strip, it may be formed only on one surface or on both surfaces. In the present invention, the weld strip is included in the definition of the weld line.

Effect of the embodiment

According to the present embodiment, since the surface treatment layer 3 or 5 for suppressing or even reducing the diffusion of copper to the surface of the surface treatment layer and the barrier layer in which oxygen penetrates into the core material 2 is formed, it is possible to suppress welding during storage of the weld line. The oxide film grown on the surface of the wire has corrosion resistance (oxidation resistance), so that the connection reliability during soldering can be improved.

Hereinafter, the present invention will be specifically described by way of examples, but the invention is not limited to the examples.

Example

The structures of the copper bonding wires of Examples 1 to 8 and Comparative Examples 1 to 3 and Conventional Examples 1 to 4 of the present invention are shown in Table 1. In addition, the evaluation result of the evaluation item mentioned later is also shown in Table 1.

In Examples 1 to 8 and Comparative Examples 1 to 3 in Table 1, it is roughly produced by forming a zinc coating layer of various thicknesses by plating on a core material made of copper as a substrate.

That is, in the copper bonding wires of Examples 1 to 8, a coating layer which changed the thickness of the zinc plating layer was formed on the line formed of oxygen-free copper, and then it was produced by annealing in the atmosphere.

On the other hand, in the copper bonding wire of Comparative Example 1, in order to evaluate the influence of the thickness of the zinc layer on the characteristics of the copper-based material, a zinc layer having a changed thickness was formed, and then the same heat treatment as in Example 1 was carried out, and Comparative Example 2 was carried out. In order to evaluate the influence of the heat treatment conditions on the characteristics of the copper-based material, the copper bonding wires of 3 and 3 were not subjected to heat treatment (Comparative Example 2) or the heat treatment conditions were changed (Comparative Example 3).

Further, as a conventional example, oxygen-free copper (conventional example 1), high-purity copper (6N) (conventional example 2), and a weld line in which Pd plating was applied to the surface of oxygen-free copper were prepared (conventional example 3). ), Au line (conventional example 4).

Hereinafter, details of each of the examples, comparative examples, and conventional examples will be described.

[Example 1]

A Zn layer having a thickness of 0.07 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was carried out for 10 minutes at a temperature of 50 ° C to prepare a copper weld line having a surface treated layer. With respect to the produced copper bonding wire, it was confirmed that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.003 μm by analyzing the depth in the direction of the surface.

[Example 2]

A Zn layer having a thickness of 0.17 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was performed at a temperature of 50 ° C for 1 hour to prepare a copper weld line. With respect to the produced copper bonding wire, it was confirmed that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.006 μm by analyzing the depth in the direction of the surface.

[Example 3]

A Zn layer having a thickness of 0.27 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was performed for 5 minutes at a temperature of 100 ° C to prepare a copper weld line. For the fabricated copper wire, by self-surface The Oberhausen analysis in the depth direction confirmed that the surface treatment layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.01 μm.

[Example 4]

A Zn layer having a thickness of 0.60 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was performed for 5 minutes at a temperature of 100 ° C to prepare a copper weld line. With respect to the produced copper bonding wire, it was confirmed by the Oujie analysis in the depth direction from the surface that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.02 μm.

[Example 5]

A Zn layer having a thickness of 1.33 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was performed for 10 minutes at a temperature of 120 ° C to prepare a copper weld line. With respect to the produced copper bonding wire, it was confirmed that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.05 μm by analyzing the depth in the direction of the surface.

[Example 6]

A Zn layer having a thickness of 2.67 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was carried out for 30 seconds at a temperature of 150 ° C to prepare a copper weld line. With respect to the produced copper bonding wire, it was confirmed that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.1 μm by analyzing the depth in the direction of the surface.

[Example 7]

A Zn layer having a thickness of 17 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was carried out for 30 seconds at a temperature of 150 ° C to prepare a copper weld line. With respect to the produced copper bonding wire, it was confirmed that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.6 μm by analyzing the depth in the direction of the surface.

[Example 8]

A copper wire having a diameter of 1 mm formed of a low-concentration copper alloy having an oxygen concentration, a sulfur concentration, and a titanium concentration of 7 to 8 ppm by mass, 5 ppm by mass, and 13 ppm by mass was produced. A Zn layer having a thickness of 0.27 μm was formed by electroplating on the copper wire. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was carried out for 30 seconds at a temperature of 150 ° C to prepare a copper weld line. With respect to the produced copper bonding wire, it was confirmed that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.01 μm by analyzing the depth in the direction of the surface.

[Comparative Example 1]

A Zn layer having a thickness of 31.7 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was performed for 5 minutes at a temperature of 100 ° C to prepare a copper weld line. With respect to the produced copper bonding wire, it was confirmed that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 1 μm by analyzing the depth in the direction of the surface.

[Comparative Example 2]

A Zn layer having a thickness of 0.67 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. With respect to the produced copper bonding wire, it was confirmed by the Oujie analysis in the depth direction from the surface that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.02 μm.

[Comparative Example 3]

A Zn layer having a thickness of 0.33 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. Thereafter, heat treatment in the atmosphere was carried out for 30 seconds at a temperature of 400 ° C to prepare a copper weld line. With respect to the produced copper bonding wire, it was confirmed by the Oujie analysis in the depth direction from the surface that the surface-treated layer composed of zinc (Zn), oxygen (O), and copper (Cu) was formed to have a thickness of 0.02 μm.

[Conventional Example 1]

4N copper (purity 99.99% by weight) wire with a diameter of 1mm was wire-drawn to a diameter of 0.03 mm, and further, the copper core material was softened by electric conduction annealing.

[Conventional Example 2]

A 6N copper (purity of 99.9999% by weight) wire having a diameter of 1 mm was subjected to wire drawing to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing.

[Conventional Example 3]

A Pd (palladium) layer having a thickness of 1.67 μm was formed by electroplating on a 4N copper (purity 99.99% by weight) line having a diameter of 1 mm as the core material 2. Thereafter, wire drawing was performed to a diameter of 0.03 mm, and then, the copper core material was softened by electric conduction annealing. With respect to the produced copper bonding wire, it was confirmed by the Oujie analysis from the surface to the depth direction that the surface treatment layer composed of Pd was formed to have a thickness of 0.05 μm.

[Conventional Example 4]

A gold (purity of 99.99% by weight) wire having a diameter of 1 mm was subjected to wire drawing until the diameter was 0.03 mm, and then, the gold core material was softened by electric conduction annealing.

Evaluation method

The surface treatment layer formed on each of the copper bonding wires in Table 1 was obtained from the results of Oujie spectroscopic analysis.

The confirmation of the presence of the amorphous layer in Table 1 was carried out by RHEED analysis (Reflection High Energy Electron Diffraction). In the case where the halo pattern indicating the presence of the amorphous layer was confirmed, the case where the diffraction pattern of the electron beam indicating the crystal structure was confirmed was "none".

The ball hardness, the connection failure rate (%), and each evaluation of the ring shape and the overall evaluation of each of the copper bonding wires produced in Table 1 were carried out as follows.

For the ball hardness, the material hardness of the spherical section was measured by a Vickers hardness tester after forming a free air ball. 60 Hv or less is set to ◎, more than 60 Hv, and 70 Hv or less is set to ○, and more than 70 Hv and 80 Hv or less is set to Δ. Further, at the time of actual wire bonding, it was visually confirmed that the damage of the aluminum pad (aluminum splash) was large in proportion to the hardness thus measured.

The connection failure rate was evaluated by wire bonding and tensile test with the number of samples n=30. The case where the welding was not bonded and the joint strength measured by the tensile test was 70% or less of the conductor strength was judged to be bad, and the value of dividing the number of defects by the total number of tests was regarded as the connection failure rate.

For the ring shape, it is evaluated by the deviation of the ring height. Set the ring height deviation to within ±150μm ◎, it is more than ±150 μm and is set to ○ within ±300 μm, and the case of exceeding ±300 is Δ.

These items and costs were collectively evaluated, and it was judged that ◎ is the best, ○ is good, △ is insufficient, and × is not appropriate.

〔Evaluation results〕

Fig. 3 is a graph showing the results of the Auger element analysis in the depth direction while repeating sputtering from the surface layer in the 3600-hour test piece in the constant temperature (100 °C) holding test of the copper bonding wire according to the third embodiment of the present invention. The horizontal axis is the depth (nm) from the surface, the vertical axis represents the atomic concentration (at%), the solid line represents the atomic concentration (at%) as the content ratio of oxygen (O), and the long broken line represents the atomic concentration of zinc (Zn). The short dashed line indicates the atomic concentration of copper (Cu). The depth of penetration of oxygen is about 10 nm from the surface, and in particular, the average element content ratio of the surface layer portion having a depth of 0 to 3 nm is (the maximum atomic concentration of each element at a depth of 0 to 30 nm - the minimum atomic concentration) /2. In Example 3, zinc (Zn) was 60 at%, oxygen (O) was 33 at%, and copper (Cu) was 7 at%.

In addition, in the case of the other examples, the average element content ratio is such that zinc (Zn) is in the range of 35 to 68 at%, oxygen (O) is in the range of 30 to 60 at%, and copper (Cu) is 0 to 15 at. The range of %.

On the other hand, in the copper bonding wire of Comparative Example 1, zinc (Zn) was 33 at%, oxygen (O) was 41 at%, and copper (Cu) was 26 at%. For the copper bonding wire of Comparative Example 2, Zinc (Zn) is 5 at%, oxygen (O) is 46 at%, and copper (Cu) is 49 at%.

Fig. 4 is a graph showing temporal changes in oxygen intrusion depth (oxide thickness) from the surface layer in the constant temperature (100 ° C) holding test of the copper bonding wire according to Example 3, Comparative Example 1, and Conventional Example 1 of the present invention. . The oxygen intrusion depth was obtained by performing Oujie analysis in the depth direction while repeatedly sputtering from the surface of the sample held at each time. In Fig. 4, the horizontal axis represents the 100 °C isothermal holding time (h), the vertical axis represents the oxygen intrusion depth (nm), the solid line represents Example 3, and the broken line represents the oxygen intrusion depth of Conventional Example 1. Further, Comparative Example 1 is indicated by dots.

In the third embodiment, as shown in Fig. 3, the oxygen concentration in the vicinity of the surface is increased in the state after the holding for 3,600 hours, but the depth of invasion is almost unchanged from that before the test, and is about 0.01 μm or less. The copper bond wire of Example 3 showed high oxidation resistance.

On the other hand, as shown in Fig. 4, in the conventional example 1 before the constant temperature holding test, the thickness of the oxygen-containing layer was about 0.006 μm from the surface, which was the same level as Example 3 before the constant temperature holding test. Depth, but in the conventional example 1 after the test was maintained for 3,600 hours, the oxygen concentration near the surface was The temperature increase was significantly increased before the test, and the oxygen intrusion depth of the conventional example 1 was about 0.036 μm, which was more than 5 times that before the test. Further, the conventional example 1 after the test was also changed to a brown color in appearance, and it was judged that the oxygen-containing layer was formed to be thickly thick. Further, in Comparative Example 1 in which a 1 μm Zn layer was formed on oxygen-free copper, the oxygen intrusion depth had reached about 0.080 μm after the 1000-hour hold test.

The results of RHEED analysis of the surface of Example 3 excellent in corrosion resistance are shown in Fig. 5. For the diffracted image of the electron beam, a halo pattern was observed, and it was found that an amorphous layer was formed on the surface. On the other hand, in the conventional example 1 which is inferior in corrosion resistance, the crystal which consists of copper and oxygen was confirmed.

(ball hardness)

With respect to the ball hardness, the weld lines of Examples 1 to 8, Comparative Examples 1 to 3, and Conventional Examples 1, 2, and 4 all showed good characteristics. In Example 8, and Conventional Example 2 and Conventional Example 4 in which the overall purity of the raw material was high, a softer ball was formed. In the case of the ninth example, it is considered that the added titanium is trapped as sulfur as an impurity, and the copper base material (parent) is highly purified, and the soft properties of the raw material are improved.

On the other hand, in the Pd-coated solder wire shown in Conventional Example 3, the ball was hard. This shows that when Pd is dissolved in the core material Cu, the ball tends to be hard even if its value is extremely small. On the other hand, in the Zn coating shown in the examples, even if Zn is dissolved in Cu, the increase in hardness is small, and the reason is considered to be that the atomic radii of Cu and Zn are substantially equal, so that strain due to solid solution occurs. Less, the effect on hardness is small.

(connection reliability)

Regarding the connection reliability, in Examples 1 to 8, excellent characteristics of a defective ratio of 0 were exhibited. On the other hand, even in Comparative Examples 1 to 3 having the same Zn-based surface treatment layer, it was confirmed that good characteristics were not obtained. When the thickness of the zinc is thick as in the case of the comparative example 1, the case where the heat treatment after the plating is not performed as in the case of the comparative example 2, the case where the excess heat treatment is performed after plating as in the comparative example 3, etc. The evaluation results of the case of crystal quality were all bad. In Conventional Examples 1 and 2, adhesion failure due to oxidation of copper occurred. Further, in Conventional Example 2, neck fracture with insufficient strength occurred. This is because, since it is high-purity copper, crystal grains are coarsened, and strength is lowered. For the conventional examples 3 and 4, good characteristics were exhibited.

From the above results, it is confirmed that the heat treatment at the time of performing the Zn treatment is preferably 50° C. or more in an atmosphere containing 1% or more of oxygen.

(ring)

The ring shape was good except for the conventional example 2 in which the soft reverse ring was unstable. In particular, Example 8 showed more stable ring characteristics.

(cost)

Regarding the cost (economy), for the 4N copper (conventional example 1) and the inventive examples 1 to 8 and the comparative examples 1 to 3, the material itself is excellent in corrosion resistance and does not require a noble metal having a high material cost. Coating or the like uses inexpensive Zn, and its thickness is extremely thin, so that productivity and economy are extremely excellent. Although the high-purity copper of the conventional example 2 is cheaper than the Pd of the conventional example 3 and the Au of the conventional example 4, the manufacturing method is special, and therefore it has to be expensive compared with the material based on 4N copper.

Regarding the electrical conductivity and the thermal conductivity, it is needless to say that Examples 1 to 8 in which copper and copper were used as the core material were excellent.

When the results are comprehensively determined, the oxidative degradation is reduced by the surface treatment, the weld line characteristics are excellent, and the electrical conductivity and economy are high. As the weld line material, the examples of the examples 1 to 8 are proposed. Copper welding line.

Further, the present invention is not limited to the above-described embodiments and the above-described embodiments, and various changes can be made.

1‧‧‧Bronze welding line

2‧‧‧ core material

3‧‧‧ surface treatment layer (amorphous layer)

Claims (6)

A copper bonding wire comprising a core material mainly composed of copper and a surface treatment layer formed on a surface of the core material, the surface treatment layer having an amorphous layer containing oxygen Zinc and oxygen have higher affinity than copper. The copper bonding wire according to claim 1, wherein the amorphous layer further contains copper diffused from the core material. The copper bonding wire according to claim 1 or 2, wherein the surface treatment layer further has a diffusion layer under the amorphous layer, the diffusion layer containing copper and affinity for oxygen Zinc, which is higher than copper, or zinc and oxygen, which contain copper and have a higher affinity for oxygen than copper. The copper bonding wire according to the first or second aspect of the invention, wherein the surface treatment layer has a thickness of 3 nm or more and 0.6 μm or less. A method for producing a copper welding wire, wherein a coating layer formed of zinc having a higher affinity for oxygen than copper is formed on a surface of a core material containing copper as a main component, and the coating layer formed at 50 ° C or higher is formed. The surface treatment layer having an amorphous layer is formed by heat treatment at a temperature of 150 ° C or lower for 30 seconds or longer and 60 minutes or shorter. The method for producing a copper bonding wire according to claim 5, wherein the surface treatment layer has a thickness of 3 nm or more and 0.6 μm or less.