Al bonding wire

Abstract

Provided is an Al wire bond, which is capable of sufficiently obtaining the bonding reliability of a bonding portion of the wire bond in a high-temperature state in which a semiconductor device using the Al wire bond is operated. The Al wire bond is characterized by containing 0.02 to 1% of Fe in mass%, and further containing at least one or more of 0.05 to 0.5% of Mn and Cr in total, with the remainder being Al and inevitable impurities, and the total solid solution amount of Fe, Mn, and Cr being 0.01 to 1%. Since Mn and Cr are contained in addition to Fe, the solid solution of Fe, Mn, and Cr can be promoted in a quenching process after a solid solution treatment, and thus the solid solution strengthening effect of the wire and the effect of preventing recrystallization progression in the semiconductor device in long-term use at high temperature can be exerted due to the increase in the total solid solution amount of Fe, Mn, and Cr.

Description

Technical Field

[0001] This invention relates to an Al bonding wire. Background Technology

[0002] In semiconductor devices, bonding wires connect electrodes formed on semiconductor elements to electrodes on lead frames or substrates. As materials for bonding wires, gold (Au) or copper (Cu) are used in integrated circuit semiconductor devices such as super LSIs, while aluminum (Al) is primarily used in power semiconductor devices. For example, Patent Document 1 shows the use of... Examples of aluminum bonding wires (hereinafter referred to as "Al bonding wires"). Furthermore, in power semiconductor devices using Al bonding wires, wedge bonding is used as a bonding method for connections to electrodes on the semiconductor element and to electrodes on the lead frame or substrate.

[0003] Power semiconductor devices using Al bonding wires are often used in high-power equipment such as air conditioning or solar power systems, as well as automotive semiconductor devices. In these semiconductor devices, the junction of the Al bonding wires is exposed to high temperatures of 100–150°C. When using materials composed solely of high-purity Al as Al bonding wires, the wires tend to soften in such high-temperature environments, making them difficult to use in high-temperature environments.

[0004] Patent document 2 discloses Al wire containing 0.02 to 1% by weight of Fe. In Al wire without Fe, recrystallization occurs directly above the wire bonding interface at the high temperatures used in semiconductor applications, forming small grains that can cause cracks. To address this, the recrystallization temperature can be increased by containing 0.02% or more Fe. Through annealing after wire drawing, the wire grain size before bonding is set to 50 μm or more. The larger grain size prevents recrystallization even at the high temperatures used in semiconductor applications, thus preventing crack formation.

[0005] In Patent Document 3, Invention 3 discloses a wire with a diameter of 300 μm, which is obtained as follows: a 99.99 wt% (4N) high-purity Al-0.2 wt% Fe alloy ingot is produced, drawn, annealed at 300°C for 30 minutes, and then slowly cooled to remove processing strain and soften it. When subjected to intermittent aging at 100–200°C for 1 minute to 1 hour after joining, even at the maximum operating temperature of 200°C, the propagation of cracks generated at the joint due to repeated high current during use is suppressed.

[0006] Patent document 4 discloses a bonding wire composed of 0.2–2.0% iron (Fe) by mass, with the remainder being aluminum (Al) of 99.99% or higher purity. In this wire, 0.01–0.05% Fe is dissolved in the Al matrix, and the Fe-Al intermetallic compound particles are uniformly crystallized in a homogeneous, fine recrystallized structure on the order of several μm in the drawn matrix. By adding a solution treatment and rapid cooling before tempering, the amount of Fe dissolved is increased to the solubility limit of 0.052% at 650°C. Subsequent wire drawing and tempering further refine the crystal grain size and increase the purity of Al, resulting in dynamic recrystallization during bonding and preventing chip damage. Furthermore, Patent Document 5 discloses an aluminum alloy fine wire containing 0.01–0.2% Fe by mass, 1–20 ppm Si by mass, and the remainder composed of Al with a purity of 99.997% by mass or higher. The Fe solid solution content is 0.01–0.06%, the Fe precipitation is less than 7 times the Fe solid solution content, and the average crystal grain size is 6–12 μm, forming a fine microstructure. By suppressing the Fe content and maintaining the ratio of Fe precipitation to Fe solid solution within a certain range, the recrystallization temperature is stabilized. Furthermore, the strength is improved by adding trace amounts of Si, resulting in stable thermal shock test results.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2002-314038

[0010] Patent Document 2: Japanese Patent Application Publication No. 8-8288

[0011] Patent Document 3: Japanese Patent Application Publication No. 2008-311383

[0012] Patent Document 4: Japanese Patent Application Publication No. 2013-258324

[0013] Patent Document 5: Japanese Patent Application Publication No. 2014-129578 Summary of the Invention

[0014] The technical problem that the invention aims to solve

[0015] Sometimes, even when using a semiconductor device with an Al bonding wire containing Fe, as described in Patent Documents 2-5, the bonding reliability of the bonding wire joint is not sufficiently obtained under the high temperature conditions that enable the semiconductor device to operate.

[0016] The object of the present invention is to provide an Al bonding wire that provides sufficient bonding reliability of the bonding portion of the bonding wire when the semiconductor device using the Al bonding wire is operating at high temperature.

[0017] Technical means for solving technical problems

[0018] That is, the essence of the present invention is as follows.

[0019] [1] An Al bonding wire, characterized in that, by mass%, it contains 0.02 to 1% Fe, and also contains 0.05 to 0.5% of at least one of Mn and Cr, the remainder being composed of Al and unavoidable impurities, and the total solid solution content of Fe, Mn and Cr is 0.01 to 1%.

[0020] [2] The Al bonding wire as described in [1] is characterized in that the average crystal grain size in the cross section perpendicular to the wire length direction is 0.1 to 50 μm.

[0021] [3] The Al bonding line as described in [1] or [2] is characterized in that, in a cross section perpendicular to the line length direction, the area ratio of crystals with an angle difference of less than 15° between the crystal <111> orientation and the line length direction is 30 to 90%.

[0022] [4] The Al bonding wire as described in any one of [1] to [3] is characterized in that the Vickers hardness is in the range of Hv20 to 40.

[0023] [5] The Al bonding wire as described in any one of [1] to [4] is characterized in that the wire diameter is 50 to 600 μm.

[0024] Invention Effects

[0025] Regarding the Al bonding wire of the present invention, it contains 0.02 to 1% Fe by mass, and also contains at least one of Mn and Cr by mass of ... Detailed Implementation

[0026] In the invention described in Patent Documents 4 and 5, Fe is contained in the Al bonding wire, and the amount of Fe dissolved in the wire is increased by solution heat treatment and subsequent rapid cooling during wire manufacturing. As a result, the strength of the wire is increased and the recrystallization temperature is increased. In order to prevent the progress of recrystallization during use at high temperature, the wire strength is maintained.

[0027] However, it was determined that even in semiconductor devices using Al bonding wires containing Fe and with an increased amount of dissolved Fe, a decrease in bonding strength at the bonding joints was observed when the semiconductor device operated at high temperatures for extended periods, meaning that sufficient bonding reliability could not be achieved. It is presumed that when observing the cross-section of the bonding wires of the semiconductor device after prolonged high-temperature operation, compared to when the bonding was initiated, the crystal grain size of the wires increased, and recrystallization of the wires progressed further due to the prolonged high-temperature operation. Consequently, the wire strength decreased, and the reliability of the bonding joints decreased.

[0028] In this invention, the Al bonding wire is incorporating a predetermined amount of one or both of Mn and Cr in addition to Fe, thereby ensuring that the total amount of Fe, Mn, and Cr dissolved in the solution during heat treatment and subsequent quenching is 0.01% to 1%. This increases the recrystallization temperature of the wire, effectively suppressing recrystallization even during prolonged use of the semiconductor device at high-temperature arc conditions, and preventing a decrease in wire strength. This will be explained in detail below.

[0029] The following describes the reliability evaluation test of the joint after prolonged exposure to high temperatures.

[0030] The bonding wires used were Al bonding wires of the comparative example containing only 0.5% by mass of Fe, and Al bonding wires of the present invention containing 0.5% Fe and 0.5% Mn. The wire diameter after drawing was 200 μm. During the drawing process, solution heat treatment and subsequent rapid cooling were performed to increase the Fe and Mn solid solution content, and tempering heat treatment was performed on the drawn wire to adjust the Vickers hardness of the bonding wire to below Hv40. The average crystal grain size of the wires was approximately 10 μm.

[0031] The total (mass%) of Fe, Mn, and Cr dissolved in the wire was evaluated using the residual resistivity ratio (RRR). The residual resistivity ratio refers to the resistance ρ at room temperature (293 K). 293K Resistance ρ at liquid helium temperature (4K) 4K The ratio ρ 293K / ρ 4K The fewer impurities in the solid solution, the lower the resistivity ρ at the liquid helium temperature (4K). 4KThe lower the concentration of impurities, the higher the residual resistivity (RRR). Thus, the resistance in the superconducting state varies depending on the amount of impurities. By setting a value that reflects the solid solution content, the total solid solution content (mass%) of Fe, Mn, and Cr in aluminum can be calculated. In the comparative example Al bond wire, the solid solution content of Fe is 0.005–0.009%, while in the Al bond wire of the present invention, the total solid solution content of Fe and Mn is 0.02–0.94%. Furthermore, the residual resistivity (RRR) can be used to measure the resistance ρ at room temperature (293 K) using a four-terminal method. 293K and the resistance ρ at liquid helium temperature (4K) 4K The result is calculated by conducting measurements.

[0032] In a semiconductor device, the first joint between the semiconductor chip and the bonding wire, and the second joint between the external terminal and the bonding wire are together configured as a wedge joint.

[0033] High-temperature long-term exposure was conducted through power cycling tests. In these tests, a semiconductor device with Al bonding wires was subjected to repeated heating and cooling cycles. During heating, the temperature of the bonding wire junction in the semiconductor device was raised to 140°C over 2 seconds, and then cooled to 30°C over 5 seconds. This heating and cooling cycle was repeated 200,000 times.

[0034] After prolonged exposure to the aforementioned high temperature, the shear strength of the first joint was measured, and the reliability of the joint was evaluated. The results showed that for the Al joint line of the comparative example containing only 0.5% by mass Fe, the shear strength of the joint was less than 50% compared to the initial value, indicating insufficient reliability of the joint. In contrast, for the Al joint line of the present invention containing 0.5% Fe and 0.5% Mn, the shear strength of the joint was over 90% compared to the initial value, sufficiently ensuring the reliability of the joint.

[0035] After prolonged exposure to high temperatures, crystal observation of the cross-section was performed. The results showed that in the Al bonding line of the present invention containing 0.5% Fe and 0.5% Mn, the average crystal grain size remained below 50 μm. In contrast, the Al bonding line of the comparative example containing only 0.5% Fe by mass had an average crystal grain size exceeding 50 μm. The bonding line of the present invention, containing both Fe and Mn, with a combined Fe and Mn solid solution content of 0.01% or more, was considered to have a higher recrystallization temperature, and recrystallization did not progress even after prolonged exposure to high temperatures. In contrast, the bonding line of the comparative example, containing only Fe, with a Fe solid solution content of less than 0.01%, was considered to have a lower recrystallization temperature. During prolonged exposure to high temperatures, recrystallization progressed, resulting in reduced strength, and therefore, the reliability of the bonding could not be adequately ensured.

[0036] The composition of the bonding wire of the present invention will be described. "%" means % by mass.

[0037] Fe: 0.02-1%

[0038] Since the Al bonding wire contains 0.02% or more Fe, combined with the effects of its composite addition with Mn and Cr described below, it can achieve a solid solution strengthening effect on the wire due to the increased total solid solution content of Fe, Mn, and Cr, as well as an effect of preventing recrystallization during long-term high-temperature use of semiconductor devices. Fe content of 0.1% or more is more preferred, 0.3% or more is even more preferred, and 0.5% or more is even more preferred. On the other hand, when the Fe content exceeds 1%, the wire hardness becomes excessively high, which can lead to chip cracking, deterioration of bonding properties, and reduced reliability of the bonding joint; therefore, the upper limit is set to 1%. Fe content of 0.8% or less is more preferred.

[0039] At least one of Mn and Cr: 0.05% to 0.5% in total

[0040] Since the wire contains at least 0.05% of either Mn or Cr, combined with the aforementioned effect of Fe, it can achieve a solid solution strengthening effect due to the increased total solid solution content of Fe, Mn, and Cr, as well as an effect of preventing recrystallization during long-term high-temperature use of semiconductor devices. Either Mn or Cr will exert its effect in the same way. A total Mn and Cr content of 0.1% or more is more preferred. A total Mn and Cr content of 0.3% or more is even more preferred. On the other hand, when the total Mn and Cr content exceeds 0.5%, the wire hardness becomes excessively high, which can lead to chip cracking, deterioration of bonding, and reduced bonding reliability. Therefore, the upper limit is set at 0.5%. A total Mn and Cr content of 0.4% or less is more preferred.

[0041] For the concentration analysis of Fe, Mn, and Cr in the bonding line, an ICP emission spectrometer or an ICP mass spectrometer can be used. The Fe, Mn, and Cr contents shown in this invention are based on concentrations determined by ICP emission spectrometry or ICP mass spectrometry.

[0042] The remaining portion of the bonding line consists of Al and unavoidable impurities. Examples of unavoidable impurity elements include Si and Cu. The lower the total content of unavoidable impurities, the smaller the deviation in material properties can be suppressed, which is preferable. As the aluminum raw material for manufacturing the line, using aluminum with a purity of 4N (Al: 99.99% or higher) yields the best results.

[0043] The total solid solubility of Fe, Mn, and Cr is 0.01% to 1%.

[0044] By setting the total solid solution content of Fe, Mn, and Cr to 0.01% or more, the recrystallization temperature of the wire can be sufficiently increased. As a result, the effect of preventing recrystallization progression during long-term high-temperature use of semiconductor devices can be achieved. It is more preferable if the total solid solution content of Fe, Mn, and Cr is 0.02% or more, even more preferable if it is 0.03% or more or 0.05% or more, and even more preferable if it is 0.1%, 0.3%, or 0.5% or more. On the other hand, when the total solid solution content of Fe, Mn, and Cr exceeds 1%, the wire hardness becomes excessively high, causing chip cracks and deterioration of bonding properties; therefore, the upper limit is set to 1%. It is more preferable if the total solid solution content of Fe, Mn, and Cr is 0.9% or less. It is even more preferable if it is 0.8% or less. Furthermore, the amount of Fe precipitation can be calculated by subtracting the Fe solid solution content from the Fe content.

[0045] Average crystal grain size of the line

[0046] In this invention, it is preferable that the average crystal grain size in the cross-section (C-section) perpendicular to the length direction of the bonding line is 0.1 to 50 μm. As a method for measuring the average crystal grain size, the area of ​​each grain is obtained using methods such as EBSD (Electron Back Scatter Diffraction Patterns), and the area of ​​each grain is converted into the area of ​​a circle as the average diameter. When the average crystal grain size is 0.1 μm or more, recrystallization caused by the tempering heat treatment during wire drawing progresses moderately. Combined with the solution heat treatment performed during wire manufacturing to force the components contained in the wire into a solid solution, the wire softens, preventing chip cracking during bonding and reducing the bonding strength of the bonding joint. On the other hand, when the average crystal grain size exceeds 50 μm, it indicates that the recrystallization of the wire has progressed too much, making it difficult to obtain sufficient strength. By performing tempering heat treatment during wire drawing, the average crystal grain size in the C-section of the wire can be set to 0.1 to 50 μm.

[0047] <111> Orientation Area Ratio of Lines

[0048] In this invention, it is preferable that the area ratio (<111> orientation area ratio) of crystals in a cross section (C section) perpendicular to the length direction of the bonding line, where the angle difference between the <111> orientation and the line length direction is within 15°, is 30% to 90%. EBSD can be used to measure the <111> orientation area ratio. By setting the cross section perpendicular to the length direction of the bonding line as the inspection surface and using the analysis software attached to the device, the <111> orientation area ratio can be calculated. During the calculation of the <111> orientation area ratio, areas where crystal orientation cannot be measured, or areas where the reliability of orientation analysis is low even if it can be measured, are excluded. When the <111> orientation area ratio is below 90%, recrystallization caused by the tempering heat treatment during wire drawing will progress moderately, the wire will soften, and the generation of chip cracks during bonding and a decrease in the bonding strength of the bonding joint can be prevented. On the other hand, when the <111> orientation area ratio is less than 30%, it indicates that the recrystallization of the wire has progressed too much, making it difficult to obtain sufficient strength. By performing tempering heat treatment during the online wire drawing process, the <111> orientation area ratio in the cross section perpendicular to the wire length direction can be set to 30-90%.

[0049] Vickers Hardness of Lines

[0050] In this invention, it is preferable that the Vickers hardness in the cross-section (C-section) perpendicular to the length direction of the bonding line is in the range of Hv20 to 40. By setting it to Hv40 or below, good bonding performance can be achieved without chip cracking during bonding, and wire arcs can be easily formed for wiring of semiconductor devices. On the other hand, when the Vickers hardness decreases to less than Hv20, it indicates that the recrystallization of the wire has progressed too much, which may reduce the reliability of the bonding joint. Therefore, the lower limit of the Vickers hardness is preferably set to Hv20. As mentioned above, the Vickers hardness of the wire can be set to the range of Hv20 to 40 by performing solution heat treatment and quenching treatment during the in-line manufacturing process to increase the total amount of Fe, Mn, and Cr dissolved in the solution, and then performing tempering heat treatment during the wire drawing process.

[0051] Line Diameter

[0052] In this invention, it is preferred that the diameter of the bonding wire is 50 to 600 μm. For power devices, where large currents flow, wires with a diameter of 50 μm or more are generally used. However, wires with a diameter of 600 μm or more become difficult to operate or are not compatible with the wire bonder. Therefore, wires with a diameter of 600 μm or less are used.

[0053] Manufacturing Method of Joint Lines

[0054] The bonding wire of the present invention is manufactured by the following method: based on obtaining an Al alloy containing a predetermined composition, it is rolled and drawn using conventional methods.

[0055] During manufacturing, a solution heat treatment and subsequent rapid quenching are performed. The solution heat treatment can be carried out in a stage with a wire diameter of about 1 mm. The solution heat treatment conditions are preferably set at 570–640°C for 1–3 hours. The rapid quenching after the solution heat treatment is preferably performed by rapid quenching in water. Thus, combined with the presence of Fe and one or both of Mn and Cr in Al within the scope of this invention, the total amount of Fe, Mn, and Cr dissolved in the solution can be included within the scope of this invention.

[0056] Tempering heat treatment is performed during or after wire drawing, or in both cases. Higher temperatures and longer treatment times result in larger average crystal grain sizes, leading to a lower <111> orientation ratio and consequently, a decrease in Vickers hardness. Tempering heat treatment conditions can be selected within a temperature range of 250–350°C and a time range of 2–4 hours to achieve optimal average crystal grain size, <111> orientation ratio, and Vickers hardness.

[0057]

Example

[0058] Aluminum with a purity of 99.99% by mass (4N) was melted with Fe, Mn, and Cr with a purity of 99.9% by mass or higher to obtain an Al alloy with the composition shown in Table 1. This alloy was used as an ingot, which was then subjected to grooved roll rolling and wire drawing. At a wire diameter of 800 μm, a solution heat treatment was performed at 620°C for 3 hours, followed by cooling. Two cooling conditions were used: rapid cooling (water cooling) and slow cooling (air cooling). Then, with a final wire diameter of 200 μm, wire drawing was performed using a die. After wire drawing, a tempering heat treatment was performed at 270°C for 10 seconds.

[0059] The contents of Fe, Mn, and Cr in the line were analyzed using ICP (inductively coupled plasma atomic emission spectrometry). Furthermore, the total solid solution content (mass%) of Fe, Mn, and Cr in the line was evaluated based on the residual resistivity ratio (RRR).

[0060] Using this line, the average crystal grain size in a cross section perpendicular to the line length direction, the area ratio of crystals with an angle difference of less than 15° from the line length direction (<111> orientation area ratio), and Vickers hardness were measured.

[0061] Regarding the determination of the average crystal grain size, the area of ​​each grain is obtained using EBSD, and this area is used as the average diameter when the area of ​​each grain is considered as a circle.

[0062] Regarding the determination of the <111> orientation area ratio, an EBSD-based measurement was performed in a cross section perpendicular to the length of the joint line, and the <111> orientation area ratio was calculated using analysis software attached to the device.

[0063] Regarding the determination of Vickers hardness, the hardness of the C-section was measured at the center of the radial direction within the C-section.

[0064] In a semiconductor device, the semiconductor chip electrode is Al-Cu, and the external terminal is Ag. The first junction between the semiconductor chip electrode and the bonding wire, and the second junction between the external terminal and the bonding wire, are together configured as a wedge joint.

[0065] The bonding performance of bonding wires in semiconductor devices was judged based on the presence or absence of initial bonding defects (non-bonding) at the first bonding portion (before prolonged exposure to high temperature). The first bonding portion to be bonded was marked as "○", and the first bonding portion not bonded was marked as "×", and the results were recorded in the "Bondability" column of Table 1.

[0066] For the evaluation of chip cracks in semiconductor devices, acid was used to dissolve the metal on the surface of the solder pads, and the presence or absence of chip cracks under the solder pads was observed under a microscope and evaluated. No cracks were marked as "○", and cracks were marked as "×", and recorded in the "Chip Cracks" column of Table 1.

[0067] High-temperature long-term exposure was conducted through power cycling tests. In these tests, a semiconductor device with Al bonding wires was subjected to repeated heating and cooling cycles. During heating, the temperature of the bonding wire junction in the semiconductor device was raised to 140°C over 2 seconds, and then cooled to 30°C over 5 seconds. This heating and cooling cycle was repeated 200,000 times.

[0068] After the aforementioned prolonged high-temperature treatment, the shear strength of the first joint was measured, and the reliability of the joint was evaluated. The shear strength measurement was performed by comparing it with the initial shear strength of the joint. A value of 95% or more of the initial joint strength was marked as "◎", 90% or more but less than 95% as "○", 50% or more but less than 90% as "△", and less than 50% as "×", and these values ​​were recorded in the "Reliability Test" column of Table 1.

[0069] The manufacturing conditions and results are shown in Table 1. Mn and Cr are referred to as "second component". In Table 1, values ​​for component contents that deviate from the scope of the present invention, and values ​​for evaluation results that deviate from the preferred scope of the present invention, are underlined.

[0070] Table 1

[0071]

[0072] Table 1 lists Examples No. 1 to 18 of this invention. After solution treatment, rapid quenching was performed. The composition content of the wire and the total amount of Fe, Mn, and Cr dissolved in the solution are within the range of this invention. Furthermore, the average crystal grain size, <111> orientation area ratio, and Vickers hardness of the wire are all within the preferred range of this invention. The evaluation results for bonding and chip cracking are all "○". This is the result of containing the components specified in this invention, undergoing solution heat treatment and rapid quenching to reduce the Fe / solid Fe ratio, and then undergoing appropriate recrystallization through tempering heat treatment.

[0073] In the evaluation of the reliability of the joints after prolonged high-temperature exposure in Examples No. 1 to 18 of this invention, all results were marked with "○" or "◎". This is because the combined amount of the components specified in this invention and the solid solution of Fe, Mn, and Cr results in solid solution strengthening of the line and increases the recrystallization temperature, thus preventing the progression of recrystallization during prolonged high-temperature exposure. In particular, for Examples No. 7 to 12 of this invention, where the Fe content is within the preferred range of this invention, the joint reliability evaluation results were all marked with "◎".

[0074] Table 1 shows comparative examples No. 1 to 13. Regarding the cooling conditions after solution treatment, comparative examples 1 to 10 were subjected to rapid cooling, while comparative examples 11 to 13 were subjected to slow cooling.

[0075] In Comparative Examples No. 1 to 3, the Fe content was less than the lower limit of the present invention. In Comparative Example No. 1, the combined Mn and Cr content was further less than the lower limit of the present invention. In Comparative Example No. 3, the combined Mn and Cr content exceeded the upper limit of the present invention. The reliability evaluation results were all "×". Furthermore, the internal properties of the wire after prolonged exposure to high temperature were evaluated, and the average crystal grain size of Comparative Examples No. 1 to 3 all exceeded 50 μm. This is presumed to be because insufficient Fe in the wire prevented the recrystallization temperature from rising sufficiently, leading to excessive recrystallization during prolonged exposure to high temperature.

[0076] In Comparative Examples No. 4 and 5, the total content of Mn and Cr was less than the lower limit of this invention, and the total solid solution content of Fe, Mn, and Cr was less than 0.01%. The reliability evaluation results were all "×". The internal composition of the wire after prolonged high-temperature exposure was evaluated, and the average crystal grain size exceeded 50 μm. This is presumed to be because the total content of Mn and Cr in the wire was insufficient; even with solution treatment and rapid cooling, the total solid solution content of Fe, Mn, and Cr could not be set above 0.01%, and the recrystallization temperature would not rise sufficiently. During prolonged high-temperature exposure, excessive recrystallization occurred.

[0077] In Comparative Example No. 6, the combined content of Mn and Cr exceeded the upper limit of the present invention. As a result, the Vickers hardness of the wire deviated from the upper limit of the preferred range. Furthermore, the bonding performance and chip cracking after bonding were both "×", and the reliability evaluation result was also "×".

[0078] In Comparative Examples No. 7-10, the Fe content exceeds the upper limit of the present invention. Furthermore, in Comparative Examples No. 7 and 8, the combined Mn and Cr content is less than the lower limit of the present invention, while in Comparative Example No. 10, the combined Mn and Cr content exceeds the upper limit of the present invention. In Comparative Examples No. 7-10, the Fe content all exceeds the upper limit of the present invention, therefore the Vickers hardness deviates from the preferred upper limit of the present invention. In Comparative Example No. 10, the combined Mn and Cr content also exceeds the upper limit, therefore even with forced solid solution, incomplete solid solution will occur and precipitation will occur, the average crystal grain size is less than the preferred lower limit of the present invention, and the <111> orientation area ratio deviates from the preferred upper limit of the present invention. As a result, any of Comparative Examples No. 7-10 has an "×" rating for bonding and chip cracking, and the reliability evaluation result of the bonding after long-term high-temperature exposure is also "×".

[0079] In Comparative Examples No. 11-13, the composition range was within the scope of this invention, but the cooling condition after solution treatment during manufacturing was "slow cooling." As a result, the solid solution of Fe and Mn in the wire was not sufficiently achieved, and the total amount of Fe, Mn, and Cr dissolved was less than 0.01%. The hardness of the wire was also less than the lower limit of the preferred range. The reliability evaluation results were all "×". Furthermore, the internal quality of the wire after long-term high-temperature exposure was evaluated, and the average crystal grain size exceeded 50 μm. It is presumed that the reason is that because the total amount of Fe, Mn, and Cr dissolved could not be set to more than 0.01%, the recrystallization temperature was not sufficiently increased, and excessive recrystallization occurred during long-term high-temperature exposure.

Claims

1. An Al bonding wire, characterized in that, It consists of at least one of Fe, Mn and Cr, and the remainder, and contains 0.02 to 1% Fe by mass, and at least one of Mn and Cr totaling 0.05 to 0.5%, the remainder consisting of more than 99.99% Al by mass, and the total solid solution content of Fe, Mn and Cr is 0.01 to 1%.

2. The Al bonding wire as claimed in claim 1, characterized in that, It contains more than 0.3% Fe.

3. The Al bonding wire as described in claim 1, characterized in that, It contains more than 0.5% Fe.

4. The Al bonding wire as claimed in claim 1, characterized in that, It contains less than 0.8% Fe.

5. The Al bonding wire as claimed in claim 1, characterized in that, It contains at least one of Mn and Cr, totaling more than 0.1%.

6. The Al bonding wire as claimed in claim 1, characterized in that, It contains at least one of Mn and Cr, with a total content of 0.3% or more.

7. The Al bonding wire as claimed in claim 1, characterized in that, It contains at least one of Mn and Cr, with a total content of less than 0.4%.

8. The Al bonding wire as claimed in claim 1, characterized in that, The total solid solution content of Fe, Mn, and Cr is above 0.03%.

9. The Al bonding wire as claimed in claim 1, characterized in that, The total solid solution content of Fe, Mn, and Cr is 0.05% or more.

10. The Al bonding wire as claimed in claim 1, characterized in that, The total solid solubility of Fe, Mn, and Cr is above 0.1%.

11. The Al bonding wire as claimed in claim 1, characterized in that, The total solid solubility of Fe, Mn, and Cr is more than 0.3%.

12. The Al bonding wire as claimed in claim 1, characterized in that, The total solid solution content of Fe, Mn, and Cr is more than 0.5%.

13. The Al bonding wire as claimed in claim 1, characterized in that, The total solid solubility of Fe, Mn, and Cr is less than 0.8%.

14. The Al bonding wire as claimed in claim 1, characterized in that, The average crystal grain size in the cross section perpendicular to the line length direction is 0.1–50 μm.

15. The Al bonding wire as claimed in claim 1, characterized in that, In a cross-section perpendicular to the line length direction, the area ratio of crystals with an angular difference of less than 15° from the line length direction is 30-90%.

16. The Al bonding wire as claimed in claim 1, characterized in that, The Vickers hardness ranges from Hv20 to 40.

17. The Al bonding wire as claimed in any one of claims 1 to 16, characterized in that, The wire diameter is 50–600 μm.

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