Bonding wire for semiconductor devices

Abstract

The objective of this invention is to ensure the reliability of primary bonding (also known as first bonding, FAB bonding, ball bonding) and secondary bonding (also known as second bonding, wedge bonding), improve the anti-deposition properties of the cutting edge, and maintain and improve the productivity of the bonding process. The aim is to provide an Ag bonding line that achieves the above objectives. The bonding line that achieves these objectives is an Ag bonding line composed of an Ag alloy comprising: In: 0.05% to 3.0% by mass; Pd, Pt, and Au: 0.010% to 5.0% by mass; Sc, Ti, and Mn: 0.0005% to 0.050% by mass; and P, Zn, Bi, and Cu: 0% to 0.030% by mass.

Description

Technical Field

[0001] The present invention relates to a bonding wire for semiconductor devices used for wiring of circuit wiring boards for connecting electrodes on semiconductor elements to external leads, etc. Background Technology

[0002] As bonding wires for semiconductor devices (hereinafter sometimes referred to as bonding wires, or simply wires) are used to bond electrodes on semiconductor elements to external leads, fine wires with a diameter of about 15 to 50 μm are mainly used. Excellent ball-forming properties, ball-joining properties, wedge-joining properties, and wire arc-forming properties are required for bonding wires. To comprehensively meet these requirements, Au (gold) bonding wires have traditionally been the primary material used. However, Au is expensive, so a low-cost wire material to replace Au is needed. One such material proposed is Ag (silver) bonding wires (hereinafter referred to as Ag bonding wires).

[0003] For example, in Patent Document 1, an Ag bonding wire is proposed that, in order to ensure bonding reliability under high temperature conditions and suppress chip damage during ball bonding, even with a molding resin with a high S (sulfur) content, the contents of Pd and Pt, as well as P, Cr, Zr, and Mo, are appropriate.

[0004] Patent documents 2 and 3 propose an Ag-Pd-Pt ternary Ag bonding wire for ultra-high frequency signals (several GHz band).

[0005] Patent document 4 proposes an Ag bonding wire that contains one or more of In, Ga, and Cd in order to meet the requirements of bonding reliability, warpage performance, and chip damage performance.

[0006] Patent document 5 proposes an Ag bonding wire that, in order to ensure bonding reliability and achieve the bonding strength of the ball joint required in high-density installation, improves the skew characteristics of the upright part of the ball, contains one or more of Be, B, P, Ca, Y, La, Ce, and one or more of In, Ga, Cd.

[0007] Prior technology documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2021 / 205931

[0010] Patent Document 2: Japanese Patent Application Publication No. 2014-201797

[0011] Patent Document 3: Japanese Patent Application Publication No. 2014-222725

[0012] Patent Document 4: Japanese Patent No. 5839763

[0013] Patent Document 5: International Publication No. 2017 / 187653 Summary of the Invention

[0014] In response to the trend of high integration in semiconductor devices and to cope with high-density mounting, improved stability and reliability of bonding wires are essential, not to mention control over wire arc shape. Especially in Ag bonding wires, it is known that during the process of melting the wire tip to form a Free Air Ball (FAB) for ball bonding of chip electrodes, some elements contained in the Ag wire accumulate and precipitate on the FAB surface. When this precipitation occurs on the FAB surface, even in minute quantities, it adheres to the cleaving tool and gradually accumulates, forming a build-up at the cleaving tool tip. It is known that this build-up at the cleaving tool tip can lead to wire non-adhesion or wire detachment, thus degrading the productivity of the bonding process.

[0015] The objective of this invention is to ensure the reliability of primary joints (also known as first joints, FAB joints, ball joints) and secondary joints (also known as second joints, wedge joints), and to improve the anti-deposition properties of the cutting edge, thereby maintaining and improving the productivity of the jointing process. The aim is to provide such an Ag joint line.

[0016] Technical means for solving technical problems

[0017] In order to achieve the above-mentioned goals, the inventors focused on development and gained the following understanding. (1)

[0019] Analysis of the deposits formed at the tip of the cleaver revealed that they contained elements found in the Ag line. This is attributed to the fact that elements (especially In) introduced to improve the properties of the bonding line are locally enriched on the surface of the FAB during its formation. During ball bonding (single bonding), when the FAB is pressed against the tip of the cleaver, these enriched elements adhere to the cleaver tip. It is evident that through tens or hundreds of thousands of repeated bonding processes, such precipitates accumulate at the tip of the cleaver, forming a deposit. (2)

[0021] It has been found that Sc, Ti, and Mn have the effect of suppressing the formation of deposits (especially In-based compounds) at the tip of the cleaver during the continuous improvement of Ag bonding lines by incorporating various elements. Furthermore, it has been confirmed that these elements do not degrade bonding line properties (first-time bonding reliability, second-time bonding (wedge bonding) reliability, FAB shape control, and line arc shape control).

[0022] This invention is based on this understanding, and its main points are as follows.

[0023] [1] A bonding wire for a semiconductor device, characterized in that,

[0024] Contains In at a concentration of 0.05% to 3.0% by mass.

[0025] Contains one or more of Pd, Pt, and Au, totaling 0.010% to 5.0% by mass.

[0026] Contains one or more of Sc, Ti, and Mn, totaling 0.0005% to 0.050% by mass.

[0027] Contains one or more of P, Zn, Bi, and Cu, totaling 0% to 0.030% by mass.

[0028] The remainder consists of Ag and unavoidable impurities.

[0029] [2] The bonding wire for the semiconductor device as described in [1] comprises one or more of P, Zn, Bi, and Cu, totaling 0.0001% to 0.030% by mass.

[0030] [3] A bonding wire for a semiconductor device as described in [1] or [2], wherein,

[0031] In a cross-section perpendicular to the axis of the junction line, the ratio of the total length of the twin grain boundaries to the total length of the grain boundaries is more than 40%.

[0032] Invention Effects

[0033] The Ag bonding line according to the present invention can ensure the bonding reliability of primary and secondary bonding, and suppress the formation of deposits at the tip of the cleaver to maintain and improve productivity in the bonding process. Detailed Implementation

[0034] The following description is based on one embodiment of the present invention (hereinafter referred to as the present invention). In particular, unless otherwise specified, "%" in relation to composition indicates the mass percentage in the line. In particular, the case where no lower limit is specified or the lower limit is 0% also includes the case where it is not contained (0%). Furthermore, as mentioned above, in this specification, the bonding wire for semiconductor devices is sometimes referred to as a bonding wire, or simply as a wire.

[0035] [In: 0.05% to 3.0%]

[0036] In improves the reliability of primary bonding (ball (FAB) bonding) of Ag bonding lines. For example, in the HAST test (high temperature and high humidity test) at 130°C and 85% humidity, lines without In and those containing In were evaluated. The results confirmed that the time it took for the shear strength (shear strength) of the ball joint to reach half of its initial strength was more than twice that of the lines without In. Therefore, the In content is set to 0.05% or more. The lower limit of the In content can be set to 0.10%, 0.15%, 0.20%, 0.30%, 0.40%, or 0.50%.

[0037] On the other hand, when the In content increases, stress concentration occurs during ball bonding in the bonding process, which can easily lead to chip damage. Furthermore, it is believed that In tends to accumulate on the FAB surface and easily forms an In-based precipitate buildup at the tip of the cleaver. Therefore, the In content is set to 3.0% or less. The upper limit of the In content can be set to 2.7%, 2.5%, 2.3%, 2.1%, or 1.9%.

[0038] [One or more of Pd, Pt, and Au: 0.010% to 5.0%]

[0039] Compared to Ag, Pd, Pt, and Au inhibit sulfur adsorption (exceptionally exhibiting resistance to sulfurization). Therefore, they can suppress sulfurization on the Ag bonding surface, extending the service life (lifespan of the bonding line). Furthermore, these elements have strong binding affinity to In and are contained in combination, thus effectively inhibiting degradation over time based on a synergistic effect. Therefore, the content of one or more of Pd, Pt, and Au is set to a total of 0.010% or more. The lower limit of the total content of these elements can be set to 0.030%, 0.050%, 0.070%, 0.100%, 0.200%, 0.300%, 0.400%, or 0.500%.

[0040] On the other hand, as the content of Pd, Pt, and Au increases, the resistivity rises while the electrical and thermal conductivity deteriorates, making it unsuitable for practical applications. Therefore, the content of one or more of Pd, Pt, and Au is set to a total of 5.0% or less. The upper limit of the content can be set to 4.5%, 4.0%, 3.5%, 3.0%, or 2.5%.

[0041] [0.0005% to 0.050% of one or more of Sc, Ti, and Mn]

[0042] It has been confirmed that the formation of deposits (especially In-based precipitates) at the tip of the cleaver is suppressed by the presence of Sc, Ti, and Mn. The mechanism is unclear, but it is believed that the enrichment of In onto the FAB surface is suppressed by the presence of Sc, Ti, and Mn. Therefore, it is believed that the adhesion of In-based precipitates to the tip of the cleaver is suppressed when the FAB is pressed using the tip of the cleaver during the bonding process. Therefore, the content of one or more of Sc, Ti, and Mn is set to a total of 0.0005% or more. The lower limit of the content can be set to 0.0010%, 0.0020%, 0.0040%, 0.0070%, or 0.010%.

[0043] On the other hand, as the content of Sc, Ti, and Mn increases, the strength of the wire itself increases; for example, the breaking strength during secondary bonding (wedge bonding) increases, but warping defects become more likely. Therefore, the content of one or more of Sc, Ti, and Mn is set to a total of 0.050% or less. The upper limit of the content can be set to 0.045%, 0.040%, 0.035%, or 0.030%.

[0044] [One or more of P, Zn, Bi, and Cu: 0% to 0.030%]

[0045] Alternatively, it can be free of P, Zn, Bi, and Cu (or 0%). However, the presence of P, Zn, Bi, and Cu can improve the true sphericity of the FAB shape. This is presumed to be because it affects the fluidity and wettability of the melt during FAB melting and spheroidization, thus improving the true sphericity.

[0046] On the other hand, as the contents of P, Zn, Bi, and Cu increase, the shape of the FAB deteriorates, and the primary bonding (spherical bonding) worsens. Therefore, the content of one or more of P, Zn, Bi, and Cu can be set to a total of 0.030% or less. The upper limit of the content can be set to 0.026%, 0.022%, 0.018%, or 0.015%.

[0047] To reliably obtain the effects of containing P, Zn, Bi, and Cu, the total content of one or more of P, Zn, Bi, and Cu can be set to 0.0001% or more. The lower limit of the content can be set to 0.0005%, 0.0010%, 0.0020%, 0.0030%, 0.0040%, or 0.0050%.

[0048] The remaining components are Ag and impurities. Here, "impurities" means components that may be mixed in during the industrial manufacturing of Ag bonding lines due to various factors in the manufacturing process, such as raw materials like silver ingots, and are permissible within a range that will not adversely affect the present invention.

[0049] [In a section perpendicular to the linear axis, the ratio of the total length of the twin grain boundary to the total length of the grain boundary is 40% or more.]

[0050] Compared to large-angle grain boundaries, the grain boundaries of twinned grains generally have lower interfacial energies and are more stable, making them less prone to movement at high temperatures. Therefore, even during solidification from a molten state of a single-joint (ball-joint) connection, it is easier to maintain the grain size of the line near the ball, making it difficult for the heat-affected zone (FAB) caused by dislocation overlap (FAB) to form, thus suppressing the reduction in line strength. This ensures the strength of the ball neck (upright portion) and improves the controllability of skew characteristics and line arc shape. Furthermore, twinned grain boundaries can prevent dislocation movement in the same way as typical large-angle grain boundaries. On this basis, because cross-slip occurs at their interface, materials with more twinned grain boundaries possess strength comparable to conventional materials and excellent ductility. Therefore, complex arc formation can also be performed as desired. In other words, a higher proportion of twinned grain boundaries is effective in controlling the line arc shape of complex arc formations such as low and high line arcs required for high-density semiconductor mounting, as well as in improving skew characteristics to avoid contact with adjacent lines. Therefore, it is preferred that, with respect to the Ag bonding line of the present invention, the ratio of the total twin grain boundary length (total twin grain boundary length) in the cross section perpendicular to the central axis of the line (central axis of the bonding line) to the total grain boundary length (total grain boundary length) is 40% or more. More preferably, the ratio of the twin grain boundary length to the grain boundary length is 50% or more, or it can be 60% or more.

[0051] The cross-section perpendicular to the line's central axis can be exposed through ion beam processing. The total length of twin grain boundaries and the total length of grain boundaries can be determined by measuring the entire cross-section using electron backscattered diffraction (EBSD). EBSD determines grain boundaries by calculating the crystal orientation difference between adjacent measurement points. For grain boundaries, an orientation difference of 15 degrees or more between adjacent grains is considered a large-angle grain boundary, and the region enclosed by a large-angle grain boundary is considered a single grain. Among these, those in a specific positional relationship (a positional relationship rotated 60 degrees around the <111> axis) are twin grain boundaries, and their total length, along with the total grain boundary length, is calculated using specialized analysis software (e.g., OIManalysis from TSL Solutions). Then, the total length of grain boundaries in the entire cross-section perpendicular to the line's central axis is taken as the total grain boundary length, and the total length of twin grain boundaries is taken as the total twin grain boundary length. The ratio of the total twin grain boundary length to the total grain boundary length is then calculated.

[0052] [Manufacturing method of bonding wire]

[0053] An example of a method for manufacturing a bonding wire according to the present invention will be described. The method for manufacturing a bonding wire according to the present invention is not limited to the method described below; any Ag bonding wire that satisfies the requirements specified in the present invention, even based on other manufacturing methods, is included in the bonding wires of the present invention.

[0054] Silver (Ag) with a purity of 4N to 5N (99.99% to 99.999%) is melted, and predetermined amounts of in and other predetermined elements are added. A cylindrical ingot is then obtained through continuous casting. Next, the ingot is continuously drawn into wire using a die. During this process, intermediate heat treatment at 350°C to 550°C is repeatedly performed followed by wire drawing until the final wire diameter is reached. The wire drawing process can be carried out using a continuous wire drawing device equipped with multiple diamond-coated dies.

[0055] During the wire drawing process, two heat treatments (intermediate heat treatments) can be performed. For example, the cross-sectional reduction rate in each stage of the wire drawing process (first wire drawing process) can be set to 18% to 30%, and intermediate annealing can be performed on each stage of wire drawing from stage 1 to stage 3, thereby increasing the grain boundary length of the twins (annealed twins) in the wire.

[0056] The section shrinkage rate for each grade is set to 18% or more, preferably 20% or more and 30% or less, and more preferably 28% or less.

[0057] The intermediate annealing temperature can be 350℃ to 550℃. Preferably, the first intermediate heat treatment temperature is within the range of 450℃ to 550℃, and the second temperature is within the range of 350℃ to 450℃. Furthermore, it is effective to set the next (second) heat treatment temperature lower than the previous (first) intermediate heat treatment temperature. This can increase the twin grain boundary length.

[0058] Furthermore, a final heat treatment can be performed after the final wire drawing process. Regarding the temperature conditions for the final heat treatment, for example, a heat treatment temperature can be set such that the elongation at break of the wire falls within a predetermined range. Regarding the final heat treatment temperature, for example, it can be performed within the range of 200–700°C for 5 seconds or less, preferably 3 seconds or less, or 2 seconds or less. Regarding the atmosphere for the heat treatment, it is preferable to use, for example, an inert gas such as nitrogen or Ar, or a non-oxidizing atmosphere such as a synthesis gas (5% H₂–N₂).

[0059] Example

[0060] The following description pertains to specific examples. Regarding the materials used, the purity of Ag, as a raw material, is 99.99% or higher, with the remainder consisting of unavoidable impurities. Similarly, the purity of added elements such as In is 99.9% or higher, with the remainder consisting of unavoidable impurities.

[0061] Ag bonding wires with the composition shown in Table 1 were manufactured. To obtain Ag alloys for each bonding wire, predetermined amounts of Ag and In were loaded into a cylindrical carbon crucible and heated to 1080°C–1600°C in a vacuum or in an inert atmosphere such as N2 or Ar gas in a high-frequency furnace to melt them. Then, Ag alloy ingots with a diameter of 4–6 mm were obtained through continuous casting.

[0062] The obtained Ag alloy ingot was continuously drawn using a die to produce wires with a diameter of φ200μm to φ600μm. This process is called a single wire drawing process.

[0063] Then, the wire drawing process is repeated to obtain a final wire diameter of φ15μm to φ25μm. For wire drawing, a commercially available lubricant is used, and the wire feed speed is set to 100m / min to 600m / min. This process is called the secondary wire drawing process. Between the secondary wire drawing processes, two intermediate heat treatments are performed (first: 450℃ to 550℃, second: 350℃ to 450℃). During the intermediate heat treatments, the wire is continuously passed through an Ar gas atmosphere. The wire feed speed during the intermediate heat treatments is set to 20m / min to 120m / min.

[0064] By adjusting the section reduction rate and wire feed speed in the secondary wire drawing process, as well as the wire diameter and intermediate heat treatment temperature, the grain size and the proportion of twin grains can be adjusted. As a result, the ratio of the total length of twin grain boundaries to the total length of grain boundaries is adjusted. When the section reduction rate is adjusted to a higher value, the wire feed speed to a faster value, the wire diameter to a thinner value during intermediate heat treatment, and the temperature to a higher value, there is a tendency for the proportion of twin grain boundaries to increase.

[0065] After the secondary drawing process, a final heat treatment was performed, resulting in a wire elongation at break of approximately 9–25%. The wire feed rate during the final heat treatment was set to 50 m / min–150 m / min, the final heat treatment temperature was 300℃–550℃, and the heat treatment time was set to 0.2 seconds–1.0 seconds.

[0066] By doing so, the line samples recorded in Table 1 were prepared.

[0067] [Reliability evaluation of primary connection]

[0068] The samples used for the first-time bonding reliability evaluation were manufactured as follows. Each wire sample was ball-bonded to an electrode forming a 1.0 μm thick aluminum (Al) film on a silicon substrate on a standard lead frame using a commercially available wire bonding machine, and then sealed with commercially available epoxy resin (a semiconductor sealant). Furthermore, N2 + 5% H2 gas was passed through the ball bonding process at a flow rate of 0.4–0.6 L / min. The ball diameter was adjusted to be 1.5–1.6 times the wire diameter.

[0069] The bonding reliability was evaluated using a high temperature and high humidity test (HAST). In the evaluation, the bonding reliability evaluation samples were exposed to a high temperature and high humidity environment of 130°C and 85% relative humidity using an unsaturated pressure cooker tester, with a 5V bias applied. Regarding the bonding life of the ball joints, shear tests were performed on the ball joints every 48 hours, with the time set at which the shear strength value reached half (1 / 2) of the initially obtained shear strength. The shear tests were conducted after removing the resin through acid treatment to expose the ball joints.

[0070] The shear testing machine used for the HAST evaluation was a DAGE company testing machine. The shear strength value was calculated by arithmetic averaging the measurements taken at 10 randomly selected ball joints. Results with a joint life of 288 hours or more were categorized as "Excellent," 144 hours or more but less than 288 hours as "Good," 96 hours or more but less than 144 hours as "Acceptable," and less than 96 hours as "Unacceptable." The evaluation results are shown in Table 1.

[0071] [Secondary joint reliability evaluation (wedge joint tensile strength)]

[0072] The samples used for secondary bonding reliability evaluation were manufactured as follows. Each wire sample was wedge-bonded onto an Ag-plated Cu alloy leadframe using a commercially available wire bonder. At this point, 80 wedge bonding operations were performed at each of the four directions (0° direction as the reference direction when viewing the leadframe from above, clockwise, 0°, 90°, 180°, and 270° directions), totaling 320 wires, to create evaluation samples. The secondary bonding reliability evaluation samples were manufactured using freshly manufactured wire, wire stored at room temperature in a cleanroom for one week, and wire stored at room temperature in a cleanroom for two weeks, and tensile tests were performed on the wedge bonding portions for each.

[0073] Regarding the tensile strength value, 15 samples were randomly selected from each direction, and the arithmetic mean of the measured values ​​from a total of 60 samples across the four directions was calculated. A tensile strength of 4gf or higher was categorized as "Excellent," 3gf or higher but less than 4gf as "Good," and less than 3gf as "Unqualified." The evaluation results are shown in Table 1.

[0074] [Productivity evaluation: continuous joint evaluation, observation of the cutting edge]

[0075] For the evaluation of continuous bonding performance, each wire sample was continuously bonded 200,000 times on an Ag-plated Cu alloy frame using a commercially available wire bonding machine. Continuous bonding performance was evaluated based on the number of times the machine stopped during the 200,000 bonding cycles. Zero stops were recorded as "Excellent," one or two stops as "Good," and three or more stops as "Unacceptable." The evaluation results are shown in Table 1.

[0076] Next, after 200,000 consecutive bonding cycles, the face of the cleaver tip was observed using SEM, and the adhesion of the build-up was visually evaluated. For the entire face of the cleaver tip, results where the build-up (attachment) could not be confirmed or where it was slightly scattered were marked "Excellent," results where less than 1 / 4 of the face was present were marked "Good," and results where more than 1 / 4 of the face was covered were marked "Unacceptable." The evaluation results are shown in the "Cleaver Observation" column of Table 1.

[0077] [FAB Shape Evaluation]

[0078] For the FAB shape, spheres (FABs) for ball bonding were formed using commercially available wire bonding machines from various wire samples, and the FAB shape was observed using SEM in this state. A total of 50 FABs were formed and evaluated. Perfectly spherical results were considered good, while eccentric or irregularly shaped results were considered poor. Among the 50 FABs, results with 0 defects were marked as "excellent," results with 1-2 defects as "good," and results with 3 or more defects as "unacceptable." The evaluation results are shown in Table 1.

[0079] [Evaluation of Linear Arc Shape Control]

[0080] The controllability of the arc shape was evaluated using low arc shape control and skew characteristics.

[0081] To assess the controllability of low-curve shape, 100 wire samples were joined using a commercially available wire bonding machine on an evaluation lead frame with a 1mm arc length and 60μm arc height. Next, SEM (scanning electron microscopy) was used to evaluate the presence of neck damage at the ball-and-socket joint. Cracks or deformation at the neck of the joint, resulting in wire thinning, were considered signs of neck damage. If three or more wires out of 100 showed neck damage, the result was deemed unacceptable; two were deemed acceptable; one was deemed good; and zero were deemed excellent. Good and excellent were considered acceptable.

[0082] To assess the skew characteristics, 100 wire samples were bonded to an evaluation lead frame using a commercially available wire connector, with a wire arc length of 5 mm and a wire arc height of 0.5 mm. As an evaluation method, the skew interval (the maximum distance between the vertical line passing through the center of the ball joint and the vertical portion of the wire) was used for evaluation when the skew interval was smaller than the wire diameter. If the skew interval was larger than the wire diameter, the skew was considered good; if it was larger, the vertical portion tilted, and therefore the skew was considered undesirable.

[0083] Regarding the control of arc shape, in the evaluation of 100 lines each for low arc shape control and deviation interval, the results of 0 lines with neck damage and 0 lines with poor deviation were recorded as "Excellent"; the results of 1 line with neck damage or 1 to 3 lines with poor deviation were recorded as "Good"; the results of 2 lines with neck damage or 4 to 5 lines with poor deviation were recorded as "Acceptable"; and all other results, i.e., more than 3 lines with neck damage or more than 6 lines with poor deviation, were recorded as "Unacceptable". The evaluation results are shown in Table 1.

[0084] As shown in Table 1, the Ag bonding wire of the present invention exhibits good reliability in both primary and secondary bonding, and the formation of deposits at the tip of the cleaver is suppressed, demonstrating excellent continuous bonding performance. Therefore, it can be confirmed that as long as the Ag bonding wire of the present invention is used, it will not hinder the productivity of the bonding process. Furthermore, it can be confirmed that as long as the Ag bonding wire of the present invention is used, the controllability of the FAB shape and the arc shape is excellent. In other words, it can be confirmed that as long as the Ag bonding wire of the present invention is used, bonding reliability can be maintained and productivity can be improved.

[0085] [Table 1]

[0086]

[0087] Industrial availability

[0088] This invention can be used in the semiconductor industry.

Claims

1. A bonding wire for a semiconductor device, characterized in that, Contains In at a concentration of 0.05% to 3.0% by mass. Contains one or more of Pd, Pt, and Au, totaling 0.010% to 5.0% by mass. Contains one or more of Sc, Ti, and Mn, totaling 0.0005% to 0.050% by mass. Contains one or more of P, Zn, Bi, and Cu, totaling 0% to 0.030% by mass. The remainder consists of Ag and unavoidable impurities.

2. The bonding wire for a semiconductor device as claimed in claim 1, comprising one or more of P, Zn, Bi, and Cu, totaling 0.0001% to 0.030% by mass.

3. The bonding wire for a semiconductor device as described in claim 1 or 2, wherein, In a cross-section perpendicular to the axis of the junction line, the ratio of the total length of the twin grain boundaries to the total length of the grain boundaries is more than 40%.

Images