Al BONDING MATERIAL

Abstract

To provide an Al bonding material which may enable suppression of internal cracking during production and exhibits superior temperature cycle reliability.SOLUTION: An Al bonding material contains 3.0 mass% or more and 12.0 mass% or less of Si, and contains one or more of Sr, Na, Eu, and Ca in a total amount of 5 mass ppm or more and 800 mass ppm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an Al connection material.

Background Art

[0002] In a semiconductor device, the electrodes formed on a semiconductor chip are connected to the electrodes on a lead frame or a substrate by bonding wires (wires) or bonding ribbons (strips). In a power semiconductor device, bonding wires and bonding ribbons mainly made of aluminum (Al) are used. The wire diameter of the Al bonding wire is mainly in the range of 100 μm to 600 μm, and for the Al bonding ribbon, the width is mainly in the range of 100 μm to 3000 μm and the thickness is in the range of 50 μm to 600 μm. Here, the Al bonding wire and the Al bonding ribbon are collectively referred to as an Al connection material.

[0003] In a power semiconductor device, silicon (Si) is often used as the material of the semiconductor chip, and Al-Si alloy or Al-Cu alloy is often used as the material of the electrodes formed on the semiconductor chip. In addition, a power semiconductor device using an Al connection material is often used as a high-power device such as an air conditioner or a solar power generation system, or as an in-vehicle semiconductor device.

[0004] Regarding the joining method of the Al connection material, there are a first joining with the electrodes on the semiconductor chip and a second joining with the electrodes on the lead frame or the substrate, and in both cases, wedge joining is used. Wedge joining is a method in which ultrasonic vibration and a load are applied to the Al connection material through a metal jig (tool) to break the surface oxide film of the Al connection material and the electrode material and expose a fresh surface, and solid-phase diffusion joining is performed. This joining method is characterized in that the connection material is joined in a solid state without melting, and it is a joining technique different from welding techniques that melt the connection material.

[0005] In next-generation power semiconductor devices, it is required to operate stably for a long time compared to general-purpose power semiconductor devices. The power semiconductor device operates by repeatedly turning on and off the current. When current is supplied to the Si semiconductor chip through the Al connection material, the temperature of the 1st junction rises. On the other hand, when the supply of current is stopped, the temperature of the 1st junction drops. In this way, during the operation of the power semiconductor, the 1st junction repeatedly undergoes temperature increase and decrease. Then, thermal stress caused by the difference in thermal expansion between the Al connection material and the semiconductor chip is repeatedly applied to the 1st junction. When a connection material made only of high-purity Al is used, it was difficult to satisfy the performance required for next-generation power semiconductor devices because the Al connection material was destroyed in a relatively short time due to thermal stress. Therefore, in next-generation power semiconductors, improvement in the joint life of the 1st junction (hereinafter also referred to as "temperature cycle reliability") accompanying temperature increase and decrease of the 1st junction is required.

[0006] In response to the requirement for temperature cycle reliability, an Al connection material with the main focus on improving mechanical strength has been proposed. As a method for improving the mechanical properties of the Al connection material, a technique of adding a specific element to Al has been proposed.

[0007] Patent Document 1 discloses a bonding wire made of an Al alloy containing at least magnesium (Mg) and silicon (Si), and the total content of Mg and Si is 0.03 mass% or more and 0.3 mass% or less. This patent document discloses that due to the effect of strengthening by solid solution of Mg and Si and the effect of suppressing crack propagation by precipitated magnesium silicide (Mg2Si), the decrease in the bonding strength of the 1st junction in the cold temperature cycle test in the temperature range of 70°C to 120°C is delayed.

[0008] Patent Document 2 discloses a bonding wire made of an alloy containing 0.01 to 0.2% by mass of iron (Fe), 1 to 20 ppm by mass of silicon (Si), and the balance being Al with a purity of 99.997% by mass or more. The solid solution amount of Fe is 0.01 to 0.06%, the precipitation amount of Fe is 7 times or less the solid solution amount of Fe, and the microstructure has an average crystal grain diameter of 6 to 12 μm. This patent document discloses that by uniformly dispersing intermetallic compound particles of Fe and Al in Al to improve the mechanical strength of the matrix and further refining the recrystallized grains, a decrease in the bonding strength of the first joint in a thermal shock test in the temperature range from -50°C to 200°C can be suppressed.

[0009] Patent Document 3 discloses a bonding wire formed by melting an Al - Si alloy containing 0.1 to 5% by mass of silicon (Si) and the balance being Al and impurities, and then ejecting and rapidly cooling it to form a fine wire. This patent document discloses that by rapidly cooling the molten Al - Si alloy to disperse Si finely and uniformly, the mechanical strength is improved.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0011] As described above, in next-generation power semiconductor devices, it is required to withstand longer use compared to general-purpose power semiconductor devices. During the operation of a power semiconductor device, the temperature of the first joint repeats heating and cooling. As a result, since the Al connecting material has a larger coefficient of linear expansion than the semiconductor chip, thermal stress due to the difference in the coefficients of linear expansion between the two occurs at the first joint, and ultimately the Al connecting material may undergo fatigue failure. One of the tests for accelerating the evaluation of the life (temperature cycle reliability) of the joint accompanying the heating and cooling of such a first joint is the temperature cycle test. The Al connecting material used for next-generation power semiconductors is required to exhibit excellent temperature cycle reliability in the temperature cycle test. However, when using an Al connecting material strengthened by adding Si or the like as disclosed in Patent Documents 1 to 3, in the temperature cycle test assuming use in next-generation power semiconductor devices, cracks progress relatively rapidly in the Al alloy electrode having a lower strength than the Al connecting material, and it has been confirmed that there is a problem that it is difficult to stably obtain good temperature cycle reliability.

[0012] In addition, regarding Al alloys containing a high concentration of alloying elements, due to hardening, a decrease in workability, a deterioration in manufacturing yield, a decrease in quality, etc. occur, which becomes an obstacle to practical application. It has been found that cracks (hereinafter referred to as "internal cracks") may occur in the Al connecting material during wire drawing when using an Al connecting material strengthened by adding Si or the like. This is considered to be caused by the formation of coarse Si precipitates, non-uniform plastic deformation of the Al phase, etc. Since internal cracks may induce defects such as a decrease in temperature cycle reliability and melting fracture when a large current is applied, it is required to suppress the occurrence of internal cracks.

[0013] An object of the present invention is to provide an Al connecting material that can suppress the occurrence of internal cracks during manufacturing and exhibits excellent temperature cycle reliability.

Means for Solving the Problems

[0014] As a result of intensive studies on the above problems, the inventors have found that an Al connecting material containing 3.0% by mass or more and 12.0% by mass or less of Si and a total of 5 ppm by mass or more and 800 ppm by mass or less of any one or more of Sr, Na, Eu, and Ca can solve the above problems. Based on such findings, the present invention has been completed through further repeated studies.

[0015] That is, the present invention includes the following contents. <1> An Al connecting material containing 3.0% by mass or more and 12.0% by mass or less of Si and a total of 5 ppm by mass or more and 800 ppm by mass or less of any one or more of Sr, Na, Eu, and Ca. <2> The Al connecting material according to <1>, wherein when measuring the crystal orientation of the Si phase in the L cross-section (the cross-section in the central axis direction including the central axis) of the Al connecting material, the total of the orientation ratios of the <111> crystal orientation and the <110> crystal orientation with an angular difference of 15° or less with respect to the central axis direction is 20% or more and 70% or less. <3> The Al connecting material according to <1> or <2>, wherein the average diameter of the Si phase in the L cross-section is 0.8 μm or more and 4 μm or less. <4> The Al connecting material according to any one of <1> to <3>, further containing a total of 10 ppm by mass or more and 500 ppm by mass or less of any one or more of Ti, B, and Zr. <5> The Al connecting material according to any one of <1> to <4>, further containing a total of 5 ppm by mass or more and 500 ppm by mass or less of any one or more of Ni, Y, Yb, and Sc.

Advantages of the Invention

[0016] According to the present invention, it is possible to provide an Al connecting material that can suppress the generation of internal cracks during manufacturing and exhibits excellent temperature cycle reliability.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the present invention will be described in detail with reference to its preferred embodiments. Although reference may be made to the drawings in the description, each drawing only schematically shows the shape, size, and arrangement of the components to the extent that the invention can be understood. The present invention is not limited to the following embodiments and examples, and can be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and its equivalent scope.

[0019] [Al Connection Material] The Al connection material of the present invention is characterized by containing 3.0 mass% or more and 12.0 mass% or less of Si, and containing 5 mass ppm or more and 800 mass ppm or less in total of any one or more of Sr, Na, Eu, and Ca.

[0020] As described above, in the temperature cycle test (TCT), when using a connection material composed only of high-purity Al, it was difficult to obtain good temperature cycle reliability because cracks propagated relatively quickly inside the connection material. On the other hand, when using an Al connection material strengthened by adding Si or the like, since cracks propagated inside the Al alloy electrode with relatively low strength, it was confirmed that it was difficult to obtain the temperature cycle reliability required for next-generation power semiconductor devices. Furthermore, for Al connection materials strengthened by adding Si or the like, internal cracks sometimes occurred during their manufacture.

[0021] As a result of intensive research to solve the above problems, the inventors have found that an Al connecting material containing 3.0 mass% to 12.0 mass% Si and 5 mass ppm to 800 mass ppm in total of at least one of Sr, Na, Eu, and Ca can suppress the occurrence of internal cracks during its manufacture and can provide excellent temperature cycle reliability. Such an Al connecting material of the present invention significantly contributes to realizing the temperature cycle reliability required for next-generation power semiconductor devices.

[0022] The Al connecting material of the present invention contains 3.0 mass% to 12.0 mass% of Si, and is composed of an Al phase in which Si is dissolved in Al, and a Si phase formed by crystallization or precipitation of Si. Here, the Al phase may contain other additive elements in addition to Si. The Si phase is a general term for Si crystallized particles and Si precipitates. The Si crystallized particles are formed from the melt during solidification and are coarse with a size of about 1 to 20 μm, while the Si precipitates are formed from the solid state and are small with a size of about 0.1 to several μm.

[0023] The reason why the Al connecting material of the present invention can suppress the occurrence of internal cracks during manufacturing and can also provide excellent temperature cycle reliability is presumed to be as follows.

[0024] With regard to temperature cycle reliability, it is believed that the Si phase has a smaller linear expansion coefficient than Al, which contributes to reducing the difference in linear expansion coefficient between the Al connecting material and the semiconductor chip, thereby reducing the thermal stress that occurs. It is also believed that the particulate Si phase can suppress the growth of cracks that occur at the bonding interface into the Al connecting material.

[0025] Regarding internal cracks, it is considered that on the surface of the Si phase composed of coarse Si precipitates, a decrease in adhesion to the Al phase or peeling from the Al phase occurs, which serves as a crack initiation point. In this regard, when containing a high concentration of Si and a predetermined amount of any one or more of Sr, Na, Eu, and Ca (hereinafter also referred to as the "first element group"), it is considered that the effect of improving the adhesion at the interface between the Si phase and the Al phase can be obtained, and the generation of internal cracks can be suppressed. As a cause of this, it is considered that a part of the first element group is concentrated on the surface of the Si phase to improve the adhesion, or the shape of the Si phase becomes closer to granular or spherical due to the addition of the first element group, thereby improving the adhesion.

[0026] As described above, as a result of appropriately controlling the factors contributing to the suppression of internal cracks and the improvement of temperature cycle reliability in the Al connecting material of the present invention, it is inferred that the generation of internal cracks during manufacturing can be suppressed as described above, and excellent temperature cycle reliability can also be achieved.

[0027] -Si concentration- When the Si concentration is in the range of 3.0 mass% or more and 12.0 mass% or less, it helps to reduce the thermal strain at the joint and improve the temperature cycle characteristics. If it is less than 3.0 mass%, the improvement effect is small, and if it exceeds 12.0 mass%, problems such as a decrease in the initial joint strength due to hardening and damage to the semiconductor chip will occur. From the viewpoint of obtaining good temperature cycle reliability, the concentration of Si in the Al connection material of the present invention is 3.0 mass% or more, preferably 3.5 mass% or more, more preferably 3.6 mass% or more, 3.8 mass% or more, 4.0 mass% or more, 4.2 mass% or more, 4.4 mass% or more, 4.5 mass% or more, 4.6 mass% or more, 4.8 mass% or more, or 5.0 mass% or more. On the other hand, when the hardness of the Al connection material becomes excessive, damage to the semiconductor chip is likely to occur during the first bonding under the bonding conditions of ultrasonic vibration and load generally used. From the viewpoint of obtaining good bonding strength when performing the first bonding under general bonding conditions, the Si concentration in the Al connection material of the present invention is 12.0 mass% or less, preferably 11.5 mass% or less or 11.0 mass% or less, more preferably 10.8 mass% or less, 10.6 mass% or less, 10.5 mass% or less, 10.4 mass% or less, 10.2 mass% or less, or 10.0 mass% or less.

[0028] For the concentration analysis of the elements contained in the Al connection material of the present invention, for example, an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer or an ICP mass spectrometer can be used. When elements derived from contaminants in the atmosphere such as oxygen and carbon are adsorbed on the surface of the Al connection material, it is effective to perform cleaning with an acid or an alkali according to the adsorbed substance before analysis.

[0029] -Concentration of the first element group- From the perspective of suppressing the generation of internal cracks during manufacturing and obtaining good temperature cycle reliability, the total concentration of the first element group in the Al connection material of the present invention is 5 mass ppm or more, preferably 10 mass ppm or more, more preferably 20 mass ppm or more, 30 mass ppm or more, 40 mass ppm or more, or 50 mass ppm or more, still more preferably 60 mass ppm or more, 80 mass ppm or more, or 100 mass ppm or more, and the upper limit thereof is 800 mass ppm or less, preferably 750 mass ppm or less or 700 mass ppm or less, more preferably 650 mass ppm or less or 600 mass ppm or less, still more preferably 580 mass ppm or less, 560 mass ppm or less, or 550 mass ppm or less. When the total concentration of the first element group is within the above preferred range, it is also beneficial from the perspective of easily achieving good 1st bonding strength while suppressing damage to the semiconductor chip.

[0030] -Crystal Orientation of Si Phase in L Cross-Section From the perspective of obtaining even better temperature cycle reliability and reducing the occurrence frequency of wire breakage during wire drawing, when measuring the crystal orientation of the Si phase in the L cross-section of the Al connection material, the total of the orientation ratios of the <111> crystal orientation and the <110> crystal orientation with an angular difference of 15° or less with respect to the central axis direction (hereinafter, also referred to as the "total <111>+<110> ratio of the Si phase") is preferably in the range of 20% or more and 70% or less. In the present invention, the L cross-section of the Al connection material, that is, the cross-section in the central axis direction including the central axis of the Al connection material, is as described with reference to FIG. 1 in the column of "(Method for Measuring Crystal Orientation of Si Phase)" below.

[0031] In addition to the control of the above-described Al alloy composition, when the total ratio of <111> + <110> of the Si phase is within such a range, effects such as an increase in the number of test cycles until the occurrence of a defect in which the bonding strength decreases and an adaptation to an increase in the temperature difference in the temperature cycle test can be obtained, and better temperature cycle reliability can be achieved. This is considered to be because, by aligning the <111> crystal orientation and the <110> crystal orientation of the Si phase, the adhesion at the interface between the Si phase and the Al phase is improved, and the deformation in the central axis direction of the Al connection material is reduced, etc., so that the effect of suppressing defects such as crack propagation at the joint due to thermal strain in the temperature cycle test appears. In addition, an Al alloy containing Si at a high concentration of 3.0 mass% or more and 12.0 mass% or less has a tendency to increase the frequency of wire breakage during the wire drawing process. It is considered that the particles of the Si phase crystallized during solidification cause stress concentration during wire drawing and induce wire breakage. In this regard, when a predetermined amount of the first element group is contained and the total ratio of <111> + <110> of the Si phase is adjusted to the above-mentioned preferred range, it is presumed that wire breakage can be reduced by an action such as relaxing stress concentration during wire drawing. The total ratio of <111> + <110> of the Si phase is more preferably 25% or more, further preferably 26% or more, 28% or more, or 30% or more from the viewpoint of obtaining even better temperature cycle reliability and reducing the occurrence frequency of wire breakage during wire drawing, and the upper limit is more preferably 65% or less, further preferably 60% or less, 58% or less, 56% or less, 55% or less, 54% or less, 52% or less, or 50% or less.

[0032] For measuring the total ratio of <111> + <110> of Si phase in the L cross-section of the Al connection material, a method can be used that combines the information on Al concentration and Si concentration obtained by SEM-EDS and the information on crystal orientation obtained by electron backscatter diffraction (EBSD). Specifically, in the measurement region with the L cross-section of the Al connection material as the inspection surface, the concentration measurement of Al and Si using EDS and the crystal orientation analysis using EBSD are performed simultaneously. Subsequently, the Al phase and Si phase are separated and extracted from the measurement results of EDS using the analysis software attached to the device. Specifically, it is preferable to use the Chi Scan function, which is a function of the analysis software OIM Data Collection or OIM Anaysis (both manufactured by TSL Solutions) attached to the FE-SEM device. Then, for the region identified as the Si phase, the orientation ratios of the <111> crystal orientation and <110> crystal orientation of the Si phase can be calculated by using the analysis software attached to the device. When calculating the orientation ratio, the partial ratio calculated with the area of only the crystal orientations that can be identified based on a certain reliability within the measurement area as the population is used. Therefore, in one embodiment, the orientation ratio of the crystal orientation of the Si phase in the L cross-section of the Al connection material of the present invention is calculated by the following procedures (1) to (3). (1) In the measurement region with the L cross-section of the Al connection material as the inspection surface, the concentration measurement of Al and Si using EDS and the crystal orientation measurement using EBSD are performed simultaneously. (2) The Al and Si are separated and extracted using the Chi Scan function. Specifically, by setting the Tolerance corresponding to the threshold value of Si from the measurement results of Si EDS, the Al and Si can be separated and identified. The crystal orientation can be analyzed using the crystal information of Al and Si from the material file. (3) For the region identified as the Si phase, the crystal orientation is analyzed, and the orientation ratios of the <111> crystal orientation and <110> crystal orientation of the Si phase are calculated.

[0033] In the procedure of (2) above, the setting of Tolerance(%) can be selected in the range of 20 - 40%, and in the standard analysis of the L cross-section of the Al connection material, it is preferable to compare at about 30%. A supplementary explanation of the procedure for adjusting this Tolerance will be given. It is preferable to select or confirm the numerical value of Tolerance so that the shape and size of the Si phase extracted and identified by the Chi Scan function are equivalent to those of the Si phase identified from the EDS map that two-dimensionally displays the Si element concentration in the EDS analysis.

[0034] In the present invention, the orientation ratio of the <111> crystal orientation and the orientation ratio of the <110> crystal orientation of the Si phase in the L cross-section were taken as the average values of the respective values obtained by measuring three or more points. When selecting the measurement region, from the viewpoint of ensuring the objectivity of the measurement data, it is preferable to obtain a measurement sample from the Al connection material to be measured at intervals of 50 cm or more in the central axis direction of the Al connection material and use it for measurement. Also, in the present invention, the measurement region of the crystal orientation by the EBSD method has a length in the central axis direction of the Al connection material of 300 μm or more and less than 800 μm, and it is desirable that the entire Al connection material enters in the direction perpendicular to the central axis of the Al connection material. However, when the size is large and it is difficult to measure the whole, it may be adjusted within a range of less than 600 μm.

[0035] -Average diameter of Si phase in L cross-section- In the Al connection material of the present invention, it is preferable that the average diameter of the Si phase in its L cross-section is 0.8 μm or more and 4 μm or less.

[0036] Regarding an Al connection material whose strength is increased by adding Si or the like, it is easy to damage the semiconductor chip during the first bonding. When adjusting the ultrasonic vibration or load to reduce such damage, a phenomenon (hereinafter also referred to as "mid-hole") where a portion with insufficient metal bonding is formed near the center of the bonding region between the Al connection material and the electrode may occur. The part where the mid-hole occurs has insufficient metal bonding, which leads to a decrease in the bonding strength and becomes the starting point of defects in the temperature cycle test.

[0037] When the average diameter of the Si phase in the L cross-section is in the range of 0.8 μm or more and 4 μm or less, it is possible to suppress the void formation in the 1st joint part. By controlling the average diameter of the Si phase, effects such as promoting the deformation of the Al phase contributing to the joining and enhancing the transmission efficiency of ultrasonic vibration to the central part of the joining region can be obtained, and it is considered that void formation can be suppressed.

[0038] From the viewpoint of further suppressing the void formation in the 1st joint part, the average diameter of the Si phase in the L cross-section of the Al connection material of the present invention is more preferably 3.5 μm or less, still more preferably 3.4 μm or less, 3.2 μm or less, or 3 μm or less, and the lower limit thereof is more preferably 1 μm or more, still more preferably 1.2 μm or more.

[0039] A method for measuring the average diameter of the Si phase in the L cross-section of the Al connection material will be described. For measuring the average diameter of the Si phase in the L cross-section, a method of combining the information on the Al concentration and Si concentration obtained by SEM-EDS and the information on the crystal orientation obtained by EBSD can be used, similar to the measurement of the total ratio of <111> + <110> of the Si phase described above. The detailed procedure may be the same as that described above in relation to the measurement of the total ratio of <111> + <110> of the Si phase, that is, for the region identified as the Si phase, the crystal orientation can be analyzed by using the analysis software attached to the apparatus. If the orientation difference between the measurement points is 15° or more, it is determined as a grain boundary and the equivalent circle diameter is calculated. The average value of the equivalent circle diameters of each Si phase is defined as the average diameter of the Si phase. In the process of obtaining the average diameter of the Si phase, parts where the crystal orientation cannot be measured or parts where the reliability of the orientation analysis is low even if it can be measured are excluded from the calculation. Therefore, in one embodiment, the average diameter of the Si phase in the L cross-section of the Al connection material of the present invention is calculated by the following procedures (1) to (3). (1) Using the L cross-section of the Al connection material as the inspection surface, simultaneously perform the concentration measurement of Al and Si using EDS and the crystal orientation measurement using EBSD. (2) Use the Chi Scan function to separate and extract Al and Si. Specifically, by setting the Tolerance corresponding to the threshold value of Si from the measurement results of the EDS of Si, Al and Si can be separated and identified. The crystal orientation can be analyzed using the crystal information of Al and Si from the material file. (3) For the region identified as the Si phase, analyze the crystal orientation. If the orientation difference between the measurement points is 15° or more, it is determined as a grain boundary, and the equivalent circle diameter of each crystal grain is obtained. Then, the equivalent circle diameters of each crystal grain are averaged to calculate the average diameter of the Si phase. Here, for the average calculation, the average value obtained by the Area average that can be selected by the software attached to the device is adopted. By adopting the average value obtained by the Area average, it is possible to accurately measure and determine whether the conditions regarding the average diameter of the Si phase, which are suitable for suppressing the void in the 1st joint, are met. In the calculation of the Area average, it is calculated from the average of the values obtained by multiplying the ratio of each particle area to the total area of all particles by each particle area value, and the software automatically performs the calculation.

[0040] In the present invention, when calculating the average diameter of the Si phase in the L cross-section, only Si phases with a diameter (equivalent circle diameter) of 0.5 μm or more are targeted. Thereby, it is possible to accurately determine whether the requirements regarding the average diameter of the Si phase in the L cross-section, which are suitable for suppressing the void in the 1st joint, are met.

[0041] When measuring the average diameter of the Si phase in the L cross-section, the setting range of the Tolerance in the procedure of (2) above, the method of obtaining the sample for measurement, and the measurement region of the crystal orientation by the EBSD method are as described above for the measurement of the total ratio of <111> + <110> of the Si phase.

[0042] In addition to the above, there are several methods for measuring the average diameter of the Si phase, including binarization processing from the observation image of the L cross-section. In the present invention, however, since it is equipped with many measurement functions and can obtain a plurality of characteristics such as the total ratio of <111> + <110> of the Si phase and the average diameter of the Si phase in one measurement, can be automatically analyzed, and is a popular device and analysis technology that is easy to measure, for the reasons described above, a method of combining the information on the Al concentration and Si concentration obtained by SEM-EDS and the information on the crystal orientation obtained by EBSD is used.

[0043] -Average diameter of the Al phase in the L cross-section- It is preferable that the average diameter of the Al phase in the L cross-section of the Al connecting material of the present invention is 5 μm or more and 40 μm or less.

[0044] When the average diameter of the Al phase in the L cross-section is in the range of 5 μm or more and 40 μm or less, a high effect can be obtained in reducing the variation in the bonding strength in the second bonding. That is, by containing Si at a predetermined concentration and containing any one or more of Sr, Na, Eu, and Ca, which are the first element group, in a predetermined amount, the effect of promoting the deformation of the Al connecting material by ultrasonic vibration and the effect of making the average diameter of the Al phase 5 μm or more and 40 μm or less are considered to act synergistically to equalize the deformation of the Al connecting material in two directions parallel and perpendicular to the central axis of the Al connecting material.

[0045] For measuring the average diameter of the Al phase in the L cross-section of the Al connecting material, similar to the measurement of the average diameter of the Si phase, a method of combining the information on the Al concentration and Si concentration obtained by SEM-EDS and the information on the crystal orientation obtained by EBSD can be used. Therefore, in one embodiment, the average diameter of the Al phase in the L cross-section of the Al connecting material of the present invention is calculated according to the following procedure (3) after performing the procedures (1) and (2) above. (3) For the region identified as the Al phase, analyze the crystal orientation. If the orientation difference between measurement points is 15° or more, it is determined as a grain boundary, and the equivalent circle diameter of each grain is obtained. Then, calculate the average of the equivalent circle diameters of each grain to calculate the average diameter of the Al phase. Regarding the average calculation, similar to the measurement of the average diameter of the Si phase, adopt the average value obtained by the Area average that can be selected by the software attached to the device.

[0046] When calculating the average diameter of the Al phase in the L cross-section, only the Al phase with a diameter (equivalent circle diameter) of 0.5 μm or more is targeted. Also, when measuring the average diameter of the Al phase in the L cross-section, the setting range of Tolerance, the method of obtaining the sample for measurement, and the measurement region of the crystal orientation by the EBSD method in the procedure of (2) above are the same as those described above for the measurement of the total ratio of <111> + <110> of the Si phase.

[0047] - Addition of Ti, B, Zr - The Al connecting material of the present invention may further contain any one or more of Ti, B, and Zr (hereinafter, also referred to as the "second element group") in a total amount of 10 mass ppm or more and 500 mass ppm or less.

[0048] When joining the Al connecting material by applying ultrasonic vibration and load, it is important to control the joining shape. The joining shape of the Al connecting material can be evaluated by the indentation length in the central axis direction of the Al connecting material (hereinafter, referred to as the "joining length") at the indentation of the fracture part when performing the shear strength test of the joint part. Reducing and stabilizing the variation in this joining length contributes to improving the temperature cycle reliability. In this regard, for an Al connecting material strengthened by adding Si or the like, in order to enhance the joinability, it is effective to join under the condition of a large ultrasonic output at the initial stage of the joining time. However, under such joining conditions, there is a concern that the slippage between the joining tool and the Al connecting material becomes unstable due to the application of strong ultrasonic vibration at the initial stage of deformation, increasing the variation in the joining length.

[0049] In the process of further studying Al connection materials containing 3.0 mass% or more and 12.0 mass% or less of Si and containing a predetermined amount of the first element group, the inventors have found that by further containing a total of 10 mass ppm or more and 500 mass ppm or less of the second element group, when joining the Al connection material by applying ultrasonic vibration and load, the variation in the joining length of the Al connection material can be reduced. It is considered that the second element group acts to control the surface friction, crystal structure, hardness, etc. of the Al connection material by concentrating on the surface of the Al connection material or affecting the oxide film on the surface of the Al connection material.

[0050] From the viewpoint of reducing the variation in the joining length during joining and further improving the temperature cycle reliability required for next-generation power semiconductor devices, the total concentration of the second element group in the Al connection material of the present invention is more preferably 20 mass ppm or more, still more preferably 30 mass ppm or more, 40 mass ppm or more, or 50 mass ppm or more, and the upper limit thereof is preferably 450 mass ppm or less, more preferably 440 mass ppm or less, 420 mass ppm or less, or 400 mass ppm or less from the viewpoint of easily achieving good first joining strength while suppressing damage to the semiconductor chip.

[0051] - Addition of Ni, Y, Yb, Sc - The Al connection material of the present invention may further contain any one or more of Ni, Y, Yb, Sc (hereinafter, also referred to as the "third element group") in a total amount of 5 mass ppm or more and 500 mass ppm or less.

[0052] Furthermore, by containing one or more of Ni, Y, Yb, and Sc in a total amount of 5 mass ppm or more and 500 mass ppm or less, it is possible to suppress the generation of scratches and chips on the surface of the Al connecting material and form a smooth surface. In an Al alloy containing Si at a high concentration of 3.0 mass% or more and 12.0 mass% or less, hardening of the surface, peeling of the Si phase and Al oxide present on the surface, etc. occur, resulting in scratches and chips on the surface during wire drawing processing, which may lead to an Al connecting material with large surface irregularities. It is presumed that by adding the third element group, stabilization of the Al oxide on the surface of the Al connecting material, reduction of friction between the Al connecting material and the die, etc. are promoted, thereby reducing scratches and chips during wire drawing processing. It is considered that by adding the third element group in combination with the first element group, the effect of suppressing the generation of scratches and chips on the surface of the Al connecting material and forming a smooth surface is enhanced.

[0053] From the viewpoint of forming an Al connecting material that suppresses the generation of scratches and chips on the surface and has a smooth surface, the total concentration of the third element group in the Al connecting material of the present invention is more preferably 10 mass ppm or more, even more preferably 20 mass ppm or more, 30 mass ppm or more, 40 mass ppm or more, or 50 mass ppm or more. The upper limit is more preferably 450 mass ppm or less, even more preferably 440 mass ppm or less, 420 mass ppm or less, or 400 mass ppm or less from the viewpoint of easily achieving good first bonding strength while suppressing damage to the semiconductor chip.

[0054] As the aluminum raw material for manufacturing the Al connecting material of the present invention, it is preferable to use Al with a purity of 4N (Al: 99.99 mass% or more), and it is more preferable to use Al with a purity of 5N (Al: 99.999 mass% or more) or higher with less impurity content.

[0055] Within the range that does not inhibit the effects of the present invention, the Al connecting material of the present invention may further contain elements other than Al, Si, the first element group, the second element group, and the third element group (hereinafter also referred to as "other elements"). The total concentration of other elements in the Al connecting material is not particularly limited within the range that does not inhibit the effects of the present invention. The total concentration of the other elements may be, for example, 0.5% by mass or less, 0.4% by mass or less, 0.3% by mass or less, 0.2% by mass or less, 0.15% by mass or less, 0.1% by mass or less, 0.08% by mass or less, 0.06% by mass or less, 0.05% by mass or less, 0.04% by mass or less, 0.03% by mass or less, 0.025% by mass or less, 0.02% by mass or less, 0.018% by mass or less, 0.016% by mass or less, 0.015% by mass or less, 0.014% by mass or less, 0.012% by mass or less, or 0.01% by mass or less. The lower limit of the total concentration of the other elements is not particularly limited and may be 0% by mass.

[0056] In one embodiment, the balance of the Al connecting material of the present invention consists of Al and unavoidable impurities. Therefore, in a preferred embodiment, the Al connecting material of the present invention consists of Al, Si, any one or more of the first element group, and unavoidable impurities. In another preferred embodiment, the Al connecting material of the present invention consists of Al, Si, any one or more of the first element group, any one or more of the second element group, and unavoidable impurities. In still another preferred embodiment, the Al connecting material of the present invention consists of Al, Si, any one or more of the first element group, any one or more of the third element group, and unavoidable impurities. In still another preferred embodiment, the Al connecting material of the present invention consists of Al, Si, any one or more of the first element group, any one or more of the second element group, any one or more of the third element group, and unavoidable impurities.

[0057] In a preferred embodiment, the Al connecting material of the present invention does not have a coating mainly composed of a metal other than Al on the outer periphery of the Al connecting material. Here, the "coating mainly composed of a metal other than Al" refers to a coating in which the content of a metal other than Al is 50% by mass or more.

[0058] The Al connection material of the present invention may be an Al bonding wire or an Al bonding ribbon. When the Al connection material of the present invention is an Al bonding wire, its wire diameter is not particularly limited and may be, for example, in the range of 100 to 600 μm. When the Al connection material of the present invention is an Al bonding ribbon, the dimensions (W×T) of its rectangular or substantially rectangular cross-section are not particularly limited. For example, W may be 100 to 3000 μm and T may be 50 to 600 μm.

[0059] The Al connection material of the present invention can suppress the generation of internal cracks during manufacturing and can provide excellent temperature cycle reliability. Therefore, the Al connection material of the present invention can be suitably used as an Al connection material for semiconductor devices, particularly for power semiconductor devices.

[0060] - Manufacturing method of Al connection material - An example of the manufacturing method of the Al connection material of the present invention will be described. Hereinafter, an example will be described in accordance with the manufacture of an Al bonding wire having a wire diameter of 200 to 400 μm.

[0061] It is preferable that the raw material Al and alloying elements have high purity. Al is preferably one having a purity of 99.99 mass% or more and the balance being composed of inevitable impurities. Si, the first element group, the second element group, and the third element group used as alloying elements are preferably ones having a purity of 99.9 mass% or more and the balance being composed of inevitable impurities. The Al alloy used for the bonding wire can be manufactured by loading the raw material of Al and the raw material of alloying elements into a graphite or alumina crucible processed so as to obtain a cylindrical ingot, and melting using an electric furnace or a high-frequency heating furnace. The diameter of the cylindrical ingot is preferably Φ6 mm or more and less than 8 mm in consideration of the workability in the subsequent processing steps. The atmosphere in the furnace during melting is preferably an inert atmosphere or a reducing atmosphere in order to prevent excessive oxidation of Al and other elements constituting the wire. The maximum temperature reached by the molten metal during melting is preferably in the range of 800°C or more and less than 1050°C in consideration of ensuring the fluidity of the molten metal and making it easy to control the shape and size of the Si phase during solidification. As the cooling method after melting, water cooling, furnace cooling, air cooling, etc. can be used.

[0062] For the cylindrical ingot obtained by melting, after performing a solution treatment of heating at a high temperature, the wire having the target wire diameter can be manufactured by repeatedly performing wire drawing using a die. The wire after wire drawing can be used as an Al alloy bonding wire by performing a final heat treatment using an electric furnace.

[0063] In order to control the crystal orientation and particle size of the Si phase in the L cross-section, it is effective to control heat treatment conditions such as solution treatment, homogenization treatment, and final heat treatment, and wire drawing conditions. When performing wire drawing, it is effective to use a lubricating fluid in order to ensure the lubricity at the contact interface between the wire and the die.

[0064] Regarding the Al connecting material of the present invention containing the first element group (Sr, Na, Eu, Ca), there is a tendency that the particle size of the Si phase is easily controlled. Since the first element group affects the form of the Si phase, the appropriate range of manufacturing conditions may vary depending on the type and concentration of the first element group.

[0065] An example of manufacturing conditions for controlling the total ratio of <111> + <110> of the Si phase in the L cross-section within the range of 20% or more and 70% or less is shown below.

[0066] In order to adjust the crystal orientation of the Si phase, it is effective to perform a two-step heat treatment on the ingot and control the area reduction rate of wire drawing.

[0067] It is effective that the temperature range of the solution treatment is 400 °C or more and less than 550 °C, and the time is 1 hour or more and less than 6 hours. After this solution treatment, it is effective to perform a homogenization treatment in the range of 250 °C or more and less than 350 °C for 2 hours or more and less than 10 hours. By promoting the fragmentation and growth of the Si phase crystallized during the solidification process in this way, the orientations of <111> and <110> with respect to the crystal orientation of the Si phase can be promoted.

[0068] Regarding the wire drawing conditions, it is effective that the wire area reduction rate per die used during wire drawing is in the range of 10% or more and less than 30%. Here, if the wire area reduction rate per die is P1, P1 is expressed by the following formula.

[0069] P1 = {(R2 2 - R1 2 ) / R2 2} × 100 In the formula, R2 represents the diameter (mm) of the wire before processing, and R1 represents the diameter (mm) of the wire after processing.

[0070] By adjusting the wire area reduction rate in the above high range (high area reduction rate) compared with normal wire drawing conditions, the entire wire is greatly deformed during die processing, the processing strain increases up to the inside of the wire, the Si phase arranges in the wire central axis direction, and at the same time, the processing strain within the Si phase is adjusted. From such a wire drawing state, by performing a subsequent heat treatment, it becomes possible to increase the orientation ratios of the <111> crystal orientation and the <110> crystal orientation with high atomic density.

[0071] In order to adjust the average diameter of the Si phase in the L cross-section to a range of 0.8 μm or more and 4 μm or less, it is effective to adjust the temperature during melting to a range of 800 °C or more and less than 1000 °C, the casting temperature to a range of 700 °C or more and less than 780 °C, and control the temperature of the solution treatment to a range of 400 °C or more and less than 550 °C and the time to a range of 1 hour or more and less than 6 hours. The casting temperature is the temperature at which the molten metal is cast into a mold or the like and corresponds to the solidification start temperature. When the casting temperature is high, the Si phase crystallized during solidification tends to become coarser and columnar, and the average diameter of the Si phase tends to increase. When the temperature of the solution treatment is high, the columnar Si phase tends to be fragmented and granulated, resulting in a decrease in the average diameter of the Si phase. In order to further reduce the average diameter of the Si phase, it is effective to increase the cooling rate during solidification, for example, water cooling is also effective.

[0072] In order to control the average diameter of the Al phase in the L cross-section to a range of 5 μm or more and 40 μm or less, it is effective to adjust the temperature and time of the heat treatment at the final wire diameter to control the growth of crystal grains due to recrystallization of the Al phase.

[0073] As described above, the above is an example described in accordance with the production of Al bonding wire, which is a wire, as a representative example of the Al connection material. The Al bonding ribbon, which is a strip material, can basically be manufactured by the same procedure. The temperature and time of the heat treatment can use conditions that are approximately the same as the above. Also, when manufacturing the Al bonding ribbon by rolling, the reduction ratio of the die can be replaced with the rolling reduction ratio and adjusted.

[0074] [Semiconductor device] Using the Al connection material of the present invention, a semiconductor device can be manufactured by connecting an electrode on a semiconductor chip and an external electrode on a lead frame or a substrate. As described above, wedge bonding is used for both the first bonding with the electrode on the semiconductor chip and the second bonding with the electrode on the lead frame or the substrate.

[0075] In one embodiment, the semiconductor device of the present invention includes a circuit board, a semiconductor chip, and an Al connection material for electrically connecting the circuit board and the semiconductor chip, and is characterized in that the Al connection material is the Al connection material of the present invention.

[0076] In the semiconductor device of the present invention, the circuit board and the semiconductor chip are not particularly limited, and known circuit boards and semiconductor chips that can be used to configure the semiconductor device may be used. Alternatively, a lead frame may be used instead of the circuit board. For example, a semiconductor device configuration including a lead frame and a semiconductor chip mounted on the lead frame may be used, as in the semiconductor device described in JP-A-2020-150116.

[0077] Examples of the semiconductor device include various semiconductor devices used in electrical products (e.g., computers, mobile phones, digital cameras, televisions, air conditioners, solar power generation systems, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, and airplanes, etc.). Among them, power semiconductor devices (power semiconductor devices) are preferred.

Examples

[0078] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples shown below.

[0079] (Sample) A method for preparing a sample will be described. Al as a raw material was used with a purity of 4N (99.99 mass% or more), and the balance was composed of inevitable impurities. Si, the first element group (Sr, Na, Eu, Ca), the second element group (Ti, B, Zr), and the third element group (Ni, Y, Yb, Sc) used as alloying elements were used with a purity of 99.99 mass% or more and the balance was composed of inevitable impurities. The Al alloy used for the Al connecting material was manufactured by charging the raw materials of Al and alloying elements into an alumina crucible and melting them using a high-frequency heating furnace. The atmosphere in the furnace during melting was an Ar atmosphere, the maximum temperature reached by the molten metal during melting was 800 °C or more and less than 1000 °C, and the casting temperature was 700 °C or more and less than 780 °C. The cooling method after melting was air cooling by cooling in the air or water cooling by cooling in water.

[0080] A cylindrical ingot with a diameter of Φ6 mm was obtained by melting, and after solution treatment and homogenization treatment were performed on the ingot, wire drawing using a die and intermediate heat treatment were performed to produce an Al connecting material (Al bonding wire) with a diameter of Φ300 μm. The temperature range of the solution treatment was 400 °C or more and less than 550 °C, and the time was 1 hour or more and less than 4 hours. Continuously during cooling after the solution treatment, homogenization treatment was carried out. The temperature range of the homogenization treatment was 250 °C or more and less than 350 °C, and the time was 4 hours or more and less than 10 hours. The cooling method after the homogenization treatment was air cooling by cooling in the air.

[0081] A commercially available lubricant was used during wire drawing, and the wire area reduction rate per die during wire drawing was 14% or more and less than 30%. The temperature range of the final heat treatment was 250 °C or more and less than 350 °C, and the time of the final heat treatment was 4 hours or more and less than 18 hours.

[0082] (Method for measuring element content) The concentration analysis of the elements contained in the Al connecting material was measured using an ICP-OES ("PS3520UVDDII" manufactured by Hitachi High-Technologies Corporation) or an ICP-MS ("Agilent 7700x ICP-MS" manufactured by Agilent Technologies, Inc.) as an analytical device.

[0083] (Method for Measuring Crystal Orientation of Si Phase) The L cross-section (cross-section in the central axis direction including the central axis) of the Al connecting material was used as the inspection surface, and the crystal orientation of the Si phase was measured. In the present invention, the central axis of the Al connecting material and the cross-section in the central axis direction including the central axis (L cross-section) are as shown in FIG. 1. FIG. 1 shows the case where the Al connecting material is an Al bonding wire having a circular cross-sectional shape. However, when the Al connecting material is an Al bonding ribbon having a rectangular or substantially rectangular cross-sectional shape with a width W and a thickness T, the central axis refers to the axis passing through the center of the width W and the center of the thickness T, and the L cross-section refers to the cross-section in the central axis direction including the central axis and the cross-section in the direction of the thickness T. When performing cross-section processing to expose the L cross-section of the Al connecting material, it may deviate from the central axis of the Al connecting material. At this time, if the length in the direction perpendicular to the central axis of the L cross-section is 90% or more of the wire diameter of the Al connecting material (thickness T in the case of a ribbon), it can be regarded as a cross-section including the central axis.

[0084] In addition, FE-SEM (SU-70 manufactured by Hitachi High-Tech Corporation) was used for measurement, and APEX (for data collection), OIM Data Collection (for Kikuchi scan), and OIM Anaysis (for data analysis) manufactured by TSL Solutions were used for analysis software. Three measurement regions were randomly selected at intervals of 50 cm or more in the central axis direction of the Al connecting material, and measurements were performed on the three regions. The measurement region was determined to be 300 μm or more and less than 800 μm in the central axis direction of the Al connecting material, and the entire Al connecting material was included in the direction perpendicular to the central axis. Also, regarding the main conditions of EDS and EBSD measurements, the acceleration voltage was 15 kV, the measurement magnification was 350 times, the scan speed was 30 to 120 points / second, and the measurement interval was in the range of 0.1 to 0.3 μm. Here, when the scan speed is high, the measurement time can be shortened, but there is a concern that the measurement accuracy of EDS may decrease. It is desirable to select an appropriate scan speed within the above range.

[0085] For the measurement of the orientation ratio of the crystal orientation of the Si phase in the L cross-section of the Al connection material, a method combining the information on the Al concentration and Si concentration obtained by SEM-EDS and the information on the crystal orientation obtained by EBSD was used. Specifically, the measurement was carried out according to the following procedures (1) to (3). (1) In the measurement region with the L cross-section of the Al connection material as the inspection surface, the concentration measurement of Al and Si using EDS and the crystal orientation measurement using EBSD were performed simultaneously. (2) The Chi Scan function, which is a function of the EBSD analysis software, was used to separate and extract Al and Si. Specifically, Al and Si were separated and identified by setting the Tolerance corresponding to the threshold value of Si from the measurement results of the EDS of Si. The crystal orientation analysis was performed using the crystal information of Al and Si from the material file. Here, the condition of Tolerance was mainly set to 30% and can be adjusted as necessary. (3) For the region identified as the Si phase, the crystal orientation was analyzed, and the orientation ratio of the <111> crystal orientation and the orientation ratio of the <110> crystal orientation of the Si phase were calculated. The partial ratio was used for the orientation ratio of the crystal orientation.

[0086] The orientation ratio of the <111> crystal orientation and the orientation ratio of the <110> crystal orientation of the Si phase were taken as the average values of the respective values obtained by the above procedures (1) to (3) for three measurement regions.

[0087] (Method for measuring the average diameter of the Si phase) For the measurement of the average diameter of the Si phase in the L cross-section of the Al connection material, a method combining the information on the Al concentration and Si concentration obtained by SEM-EDS and the information on the crystal orientation obtained by EBSD was used, similar to the measurement of the crystal orientation of the Si phase. Specifically, after performing the above procedures (1) and (2), the measurement was carried out according to the following procedure (3). (3) For the regions identified as the Si phase, the crystal orientation was analyzed. If the orientation difference between the measurement points was 15° or more, it was determined to be a grain boundary, and the equivalent circle diameter of each crystal grain was obtained. Then, the equivalent circle diameters of each crystal grain were averaged to calculate the average diameter of the Si phase. Here, in the average calculation, the average value obtained by Area averaging was used. Also, when calculating the average diameter of the Si phase in the L cross-section, only Si phases with a diameter (equivalent circle diameter) of 0.5 μm or more were targeted.

[0088] The average diameter of the Si phase was taken as the average value of the values obtained by the above procedures (1) to (3) for three measurement regions. Also, by the same procedure, the average diameter of the Al phase in the L cross-section of the Al connection material was measured.

[0089] (Evaluation method for Al connection material) The evaluation method for the Al connection material will be described. The wire diameter of the Al connection material (Al bonding wire) used for evaluation was Φ300 μm. A semiconductor chip made of Si was used, and for the electrodes on the semiconductor chip, an alloy with a composition of Al - 0.5% Cu was deposited with a thickness of 4 μm. For the substrate, an Al alloy with 15 μm of Ni deposited on it was used. For the bonding of the Al connection material, a commercially available wire bonder (manufactured by Ultrasonic Industry Co., Ltd.) was used, and both the 1st bonding and the 2nd bonding were wedge bonds.

[0090] (Evaluation method for temperature cycle reliability) A commercially available thermal shock test device was used for the evaluation of the temperature cycle test. In the temperature cycle test, the sample chamber moves between the low-temperature bath and the high-temperature bath to repeat heating and cooling. The temperature of the low-temperature bath was set at -40°C, and the temperature of the high-temperature bath was set at 175°C. The test was started from the state where the sample chamber was in the high-temperature bath, and one cycle was defined as the period from when the sample chamber moved to the low-temperature bath and then returned to the high-temperature bath. The time for the sample chamber to stay in the low-temperature bath and the high-temperature bath was set at 20 minutes each. The sample for the temperature cycle test had a structure in which a semiconductor chip was mounted on a substrate, and the electrodes on the semiconductor chip and the electrodes on the substrate were connected with an Al connecting material. After the start of the test, the sample was taken out every 250 cycles, and a shear test of the 1st joint was performed. As the value of the shear strength of the 1st joint used for the evaluation of the temperature cycle reliability, the average value of the shear strengths of 5 randomly extracted 1st joints was used. The number of cycles at the time when the shear strength decreased to 70% or less of the value before the temperature cycle test was defined as the joint life. If the joint life was less than 500 cycles, it was judged that there was a practical problem and marked as "0". If the joint life was 500 cycles or more and less than 750 cycles, it was judged that there was no practical problem and marked as "1". If the joint life was 750 cycles or more and less than 1000 cycles, it was judged that it was excellent and marked as "2". If the joint life was 1000 cycles or more, it was judged that it was particularly excellent and marked as "3". "0" was considered a failure, and "1", "2", and "3" were considered passes. The evaluation results were described in the column of "Temperature Cycle Reliability" in the table.

[0091] (Method for Evaluating Internal Cracks) A method for evaluating internal cracks in Al connection materials will be described. For the manufactured Al connection materials, evaluation was performed by observation using a soft X-ray projection inspection device (manufactured by Matsusada Precision, μB2600) (hereinafter referred to as X-ray observation). The measurement conditions for X-ray observation can be appropriately determined according to the wire diameter of the Al connection material. In the case of the Al connection material with a wire diameter of 300 μm manufactured in this example, the voltage was adjusted in the range of 50 to 80 kV and the current was adjusted in the range of 60 to 90 μA. Three locations were randomly selected at intervals of 1 m or more in the central axis direction of the Al connection material, and three samples with a length of about 8 cm were selected at each of the three locations, for a total of nine samples as measurement samples. Fig. 3 shows an example of X-ray observation of an Al connection material with a wire diameter of 300 μm, and internal cracks were observed. If the length of the internal crack is 0.3 mm or more, it is judged as a defective defect and scored "2". If it is 0.1 mm or more and less than 0.3 mm, it is judged as something to be noted and scored "0.5". The sum of the scores at the measurement locations was set as the "crack index". For the crack index of the entire measurement sample, if it is zero, it is judged as good and scored "3". If it is in the range of 0.1 to 2.0, it is judged as no problem in practical use and scored "2". If it is in the range of 2.0 to 5.0, it is judged that improvement is necessary and scored "1". If it exceeds 6.0, it is judged as difficult to use in practice and scored "0". The evaluation results were described in the column of "Internal Cracks" in the table.

[0092] (Evaluation method for wire breakage during processing) A method for evaluating wire breakage during processing will be described. Drawing was performed from a wire diameter of 6 mmφ to a wire diameter of 0.3 mmφ, and the number of times of wire breakage was confirmed. The processing conditions for drawing, such as the feed rate and the area reduction rate, were selected from the above-mentioned conditions, and the appropriate manufacturing conditions were adjusted and changed for each wire. The length of the drawn Al connection material was in the range of 100 to 200 m, and the number of wire breakages was calculated in terms of per 100 m. If the number of wire breakages is 0, it is judged as good and scored "3". If it is 1, it is judged that it can be dealt with by improving the manufacturing conditions and scored "2". If it is 2 to 4, the decrease in productivity is regarded as a problem and scored "1". If it is 5 or more, it is judged as difficult to use in practice and scored "0". The evaluation results were described in the column of "Wire Breakage During Processing" in the table.

[0093] (Evaluation method for voids in the 1st joint) A method for evaluating the voiding defect of the 1st joint will be described. After performing the shear strength test of the 1st joint described above, the indentation on the fracture surface on the electrode side was observed with an optical microscope or SEM, and the portion where no metal joint was obtained within the fracture region was determined as voiding. The portion where voiding occurred was the portion that did not join even when the electrode was deformed, and could be distinguished from the region where the joint was a metal joint. The shear strength test was under the conditions described above, and the fracture surfaces of 10 1st joints were observed. Then, the ratio of the total length (K) in the joint width direction of the voiding region to the joint length (J) in the direction perpendicular to the central axis of the Al connection material (joint width direction) was obtained as the voiding ratio (K / J) (Figure 2). The voiding ratio was confirmed at the fracture surfaces of 10 locations, and the maximum value was defined as the "voiding defect rate". If the voiding defect rate was less than 5%, it was judged to be good and rated as "3"; if it was 5% or more and less than 15%, it was judged to be practically problem-free and rated as "2"; if it was 15% or more and less than 25%, it was judged that improvement was necessary and rated as "1"; if it exceeded 25%, it was judged to be an obstacle to mass production and rated as "0". The evaluation results were described in the column of "voiding of the 1st joint" in the table.

[0094] (Evaluation method for stability of joint length) A method for evaluating the stability of the joint length will be described. After performing the shear strength test of the 1st joint described above, it was evaluated based on the indentation length (joint length) at the indentation on the fracture surface on the electrode side. Specifically, for the indentation on the fracture surface, the joint length (μm) in the central axis direction of the Al connection material was measured, and the population standard deviation (σ) was calculated. If σ was 15 or more, it was judged that there was a problem in practical use and rated as "1"; if σ was 5 or more and less than 15, it was judged to be good and rated as "2"; if σ was less than 5, it was judged to be excellent and rated as "3". "1" was unqualified, and "2" and "3" were qualified. The evaluation results were described in the column of "stability of joint length" in the table.

[0095] (Evaluation method for surface scratches and abrasions) Regarding the surface properties of the Al connection material, attention was paid to scratches and shaving, and evaluation was carried out. The wire diameter of the Al connection material was 0.3 mmφ. Three measurement regions were randomly selected at intervals of 1 m or more in the central axis direction of the Al connection material, and three samples with a length of about 2 cm were collected at each of the three locations, and a total of nine samples were observed. The surface was observed at a magnification in the range of 50 to 500 times of SEM. Scratches with a length of 50 μm or more and shaving with a length of 30 μm or more were judged as defective. The number of locations with scratches and shaving was counted. If there were 0 locations, it was judged as good and passed, and rated as "3"; if there were 2 locations or less, it was judged as having no problem in practical use and rated as "2"; if there were 3 to 7 locations, it was judged that the surface properties were not good and rated as "1"; if there were 8 locations or more, it was judged that it was difficult to use in practice and rated as "0". The evaluation results were described in the column of "Surface Properties" in the table.

[0096] The evaluation results of the examples and comparative examples are shown in Tables 1 to 3.

[0097]

Table 1

[0098]

Table 2

[0099]

Table 3

[0100] All of the Al connection materials of Examples No. 1 to 47 contain 3.0 mass% or more and 12.0 mass% or less of Si, and contain one or more of the first element group (Sr, Na, Eu, Ca) in a total amount of 5 mass ppm or more and 800 mass ppm or less. It was confirmed that the generation of internal cracks can be suppressed during manufacturing, and good temperature cycle reliability can be exhibited. In addition, it was confirmed that the Al connection materials of Examples Nos. 1 to 3, 5 to 24, 26 to 37, and 39 to 47, in which the total ratio of <111> + <110> of the Si phase in the L cross section is 20% or more and 70% or less, tend to obtain even better temperature cycle reliability and can reduce the occurrence frequency of wire breakage during processing. It was confirmed that the Al connection materials of Examples Nos. 1 to 11, 13, 14, 16 to 27, and 29 to 47, in which the average diameter of the Si phase in the L cross section is 0.8 μm or more and 4 μm or less, can suppress the inner escape of the 1st joint. Also, it was confirmed that the Al connection materials in which the average diameter of the Al phase in the L cross section is 5 μm or more and 40 μm or less tend to result in better results in terms of the bonding strength stability of the 2nd joint. Furthermore, it was confirmed that the Al connection materials of Examples Nos. 20 to 23, 25 to 27, and 41 to 47, which contain one or more of the second element group (Ti, B, Zr) in a total amount of 10 mass ppm or more and 500 mass ppm or less, can reduce the variation in the bonding length during bonding and stabilize the bonding length. It was confirmed that the Al connection materials of Examples Nos. 29 to 36, 38, 39, and 41 to 47, which contain one or more of the third element group (Ni, Y, Yb, Sc) in a total amount of 5 mass ppm or more and 500 mass ppm or less, suppress the occurrence of surface scratches and chipping and have a smooth surface. On the other hand, for the Al connection materials of Comparative Examples Nos. 1 to 7, either the Si concentration or the concentration of the first element group is outside the scope of the present invention, and it was confirmed that either the suppression effect of internal crack generation during manufacturing or the temperature cycle reliability cannot be sufficiently obtained.

Claims

1. An Al connecting material containing 3.0 mass% or more and 12.0 mass% or less of Si, and containing 5 mass ppm or more and 800 mass ppm or less in total of any one or more of Sr, Na, Eu, and Ca.

2. When measuring the crystal orientation of the Si phase in the L cross-section (cross-section in the central axis direction including the central axis) of the Al connecting material, the total of the orientation ratios of the <111> crystal orientation and the <110> crystal orientation with an angular difference of 15° or less with respect to the central axis direction is 20% or more and 70% or less. The Al connecting material according to Claim 1.

3. The Al connecting material according to Claim 1, wherein the average diameter of the Si phase in the L cross-section is 0.8 μm or more and 4 μm or less.

4. The Al connecting material according to Claim 1, further containing 10 mass ppm or more and 500 mass ppm or less in total of any one or more of Ti, B, and Zr.

5. The Al connecting material according to any one of Claims 1 to 4, further containing 5 mass ppm or more and 500 mass ppm or less in total of any one or more of Ni, Y, Yb, and Sc.

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