Solder joint member, semiconductor device, solder joint method, and method for manufacturing semiconductor device

Abstract

A solder joint member (4) for joining a first object (2) and a second object (3), the solder joint member (4) containing Sn as a main component, 3% by mass or more and less than 4% by mass of Ag, 0.5% by mass or more and less than 1.0% by mass of Cu, 2.5% by mass or more and less than 4% by mass of Bi, and 0.5% by mass or more and less than 3% by mass of Sb, the present invention is characterized by comprising: a main phase (12) that contains Sn, Ag, and Cu and has a melting point of 210 DEG C or more and less than 220 DEG C; a Sn-Bi alloy phase (10) that covers at least a portion of the main phase (12) and has a melting point of 135 DEG C or more and less than 145 DEG C; and a Sn-Bi-Sb alloy phase (11) that covers at least a portion of the Sn-Bi alloy phase (10) and has a melting point of 170 DEG C or more and less than 180 DEG C.

Description

Technical Field

[0001] The present disclosure relates to a solder bonding member, a semiconductor device, a solder bonding method, and a method for manufacturing a semiconductor device. Background Art

[0002] In recent years, the reliability requirements for semiconductor devices including semiconductor elements and circuit boards have become increasingly higher. In semiconductor devices, especially for the junction (joint body) between the semiconductor element and the circuit board, the difference in thermal expansion coefficients between the two is large and defects are easily generated, so it is necessary to improve the reliability.

[0003] On the other hand, in order to reduce the environmental load, the use of lead-free solders that do not contain lead (Pb), which is an environmentally regulated substance, as solders used for such joints is being promoted. As a representative lead-free solder in the past, a solder having a composition of Sn-3Ag-0.5Cu (wt%) (Sn-3Ag-0.5Cu solder) is known.

[0004] The melting point of Sn-3Ag-0.5Cu solder is 220°C. In order to melt the lead-free solder and improve its fluidity (wetting and spreading on the joint surface), the heating temperature needs to be increased to about 250°C, which is 30°C higher than the melting point. During the subsequent cooling, due to thermal contraction, the joined components warp or accumulate high residual stress. Therefore, in the joint reliability evaluation (thermal cycle test, power cycle test) after cooling, the stress is released, and cracks are likely to occur in the solder joint at an early stage.

[0005] In order to reduce the residual stress after such solder bonding, Bi, In, etc. having the effect of lowering the melting point are added to the above-mentioned Sn-3Ag-0.5Cu solder.

[0006] For example, in Patent Document 1 (Japanese Patent Publication No. 2002-120085), the following solder alloy is disclosed: the lead-free solder alloy has a melting temperature lower than 215°C and is substantially composed of 76-96% tin, 0.2-2.5% copper, 2.5-4.5% silver, and more than 0 and less than 12% indium. It is described that: Thus, it is possible to provide a lead-free solder having a moderate melting temperature range (175-210°C) that can be used in mainstream electronic manufacturing and having high strength and high fatigue resistance.

[0007] In addition, in Patent Document 2 (Japanese Patent Publication No. 2018-149558), the following lead-free solder alloy is disclosed: it contains Ag of 1 mass % or more and 4 mass % or less, Cu of 0.1 mass % or more and 1 mass % or less, Sb of 1.5 mass % or more and 5 mass % or less, and In of 1 mass % or more and 6 mass % or less, and the remainder is composed of Sn. In addition, it is also disclosed that in addition to the above composition, Bi is also contained in an amount of 1 mass % or more and 5.5 mass % or less.

[0008] It should be noted that in Patent Document 2, the specific reflow conditions (temperature distribution) are disclosed as follows: preheating is 170°C to 190°C, 110 seconds, the peak temperature is 245°C, the time above 200°C is 65 seconds, the time above 220°C is 45 seconds, and the cooling rate from the peak temperature to 200°C is 3 to 8°C / second.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2002-120085

[0012] Patent Document 2: Japanese Patent Application Publication No. 2018-149558 Summary of the invention

[0013] Problems to be solved by the invention

[0014] Patent Documents 1 and 2 do not pay attention to the structure (structure) of the joint portion after soldering, which causes problems in actual use.

[0015] Specifically, on the joined surface, Sn, which is the main component of the solder, forms an intermetallic compound. Near the interface between the intermetallic compound and its surroundings, other added elements are relatively concentrated relative to the main component Sn locally, forming a phase with a melting point different from the melting point of the solder single substance before use. For example, when the other added element is Bi, a Sn-Bi eutectic phase (melting point 140°C) is formed. Therefore, during solidification and shrinkage after solder joining, the main phase solidifies first, and then the phase with a lower melting point (such as the Sn-Bi phase) solidifies. Due to such deviations in the timing of solidification, shrinkage cavities (gaps such as cracks generated during the solidification process), stress caused by thermal shrinkage, etc. are generated, so the semiconductor element as the joined component may be damaged.

[0016] In addition, if warping, unevenness, etc. occur in the joined member (semiconductor element or substrate) after soldering, the electrical characteristics of the semiconductor element will change at each solder joint, causing problems in motor design. Furthermore, if unevenness occurs in the semiconductor element, the stress of wire bonding is applied to the semiconductor element during the subsequent wire bonding process (electrical wiring), which may cause cracks in the semiconductor element or poor wire bonding.

[0017] It should be noted that in Patent Documents 1 and 2, the addition of In has the effect of lowering the melting point of the solder. However, In is a metal that is easily oxidized, so if the solder contains a large amount of In, there is a possibility that voids will be generated during the initial bonding due to oxidation of In. Therefore, in practice, it is necessary to make the amount of In added less than the amount described in the above documents.

[0018] An object of the present disclosure is to provide a solder capable of suppressing the occurrence of defects caused by a joint formed using the solder.

[0019] Means for solving problems

[0020] The solder bonding member of this embodiment is a solder bonding member for bonding a first object and a second object.

[0021] The invention comprises: Sn as a main component, 3 mass % or more and less than 4 mass % of Ag, 0.5 mass % or more and less than 1.0 mass % of Cu, 2.5 mass % or more and less than 4 mass % of Bi, and 0.5 mass % or more and less than 3 mass % of Sb,

[0022] have:

[0023] A main phase comprising Sn, Ag and Cu and having a melting point of 210° C. or higher and lower than 220° C.;

[0024] A Sn-Bi alloy phase having a melting point of 135° C. or higher and lower than 145° C. covering at least a portion of the main phase; and

[0025] A Sn—Bi—Sb alloy phase having a melting point of 170° C. or higher and lower than 180° C. is provided to cover at least a portion of the Sn—Bi alloy phase.

[0026] Effects of the Invention

[0027] According to the present disclosure, it is possible to suppress the occurrence of defects caused by a joining portion formed using solder.

[0028] In the solder joint component disclosed in the present invention, since two phases having a lower melting point than the main phase inside are present near the joint interface with the object (joined object), the stress generated during thermal shrinkage (solidification shrinkage) is relieved, and the generation of defects caused by stress is suppressed. Therefore, a highly reliable joint (and a semiconductor device having the same) is provided.

[0029] Furthermore, since the stress generated after bonding is also alleviated by including the above-mentioned two phases, a bonding portion (and a semiconductor device including the same) capable of maintaining high reliability even after bonding is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart showing the manufacturing steps of a semiconductor device (semiconductor element assembly).

[0031] Figure 2 To express Figure 1 A schematic cross-sectional view of the first step of the process.

[0032] Figure 3 To express Figure 1 A schematic cross-sectional view of the second step.

[0033] Figure 4 To express Figure 1 A schematic cross-sectional view of the third step.

[0034] Figure 5 To express Figure 1 A schematic cross-sectional view of the fourth step.

[0035] Figure 6 To express Figure 1 A schematic cross-sectional view of the 5th step.

[0036] Figure 7 for Figure 1 A schematic cross-sectional view of the bonding interface after the fifth step.

[0037] Figure 8 The following are the DSC measurement results of the solder joint member of Example 1.

[0038] Fig. 9 It is the DSC measurement result of the solder joint member of Comparative Example 1.

[0039] Fig.10 The cross-sectional observation results of the solder joint member of Example 1 are shown.

[0040] Fig.11 1 and 2 are cross-sectional observation results of the solder joint member of Comparative Example 1.

[0041] Fig.12 It is a schematic cross-sectional view of the solder bonding member according to the first embodiment. DETAILED DESCRIPTION

[0042] It should be noted that in the drawings, the dimensional relationships of length, width, thickness, depth, etc. are appropriately changed for the sake of clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[0043] Implementation method 1.

[0044] <Solder-joined components>

[0045] The solder joint member 4 of the present embodiment is a member for joining a first object 2 (eg, a substrate) and a second object 3 (eg, a semiconductor element) (see Figure 6 ). It should be noted that the solder joint member 4 is different from the solder sheet 1 described later, and is a member composed of solder (solder alloy) that is melted and solidified by a heating process, and is a member that exists in a state of being joined to both the joined members (the first object and the second object).

[0046] The solder joint member 4 of the present embodiment contains Sn as a main component, 3 mass % or more and less than 4 mass % of Ag, 0.5 mass % or more and less than 1.0 mass % of Cu, 2.5 mass % or more and less than 4 mass % of Bi, and 0.5 mass % or more and less than 3 mass % of Sb.

[0047] In addition, the solder joint member 4 of the present embodiment has:

[0048] A main phase 12 (high melting point phase) containing Sn, Ag and Cu and having a melting point of 210° C. or higher and lower than 220° C.;

[0049] A Sn-Bi alloy phase 10 (low melting point phase) covering at least a portion of the main phase 12 and having a melting point of 135° C. or higher and lower than 145° C.; and

[0050] The Sn-Bi-Sb alloy phase 11 (intermediate melting point phase) having a melting point of 170° C. or more and less than 180° C. (see Figure 7 and Fig.12 ).

[0051] As described above, the solder bonding member 4 of the present embodiment has a multi-phase structure, and has a plurality of separate phases having different melting points.

[0052] It is to be noted that in the solder joint component 4, the Sn-Bi-Sb alloy phase 11 (medium melting point phase), the Sn-Bi alloy phase 10 (low melting point phase) and the main phase 12 (high melting point phase) basically exist in sequence from the side of the joined component (the first object 2 or the second object 3).

[0053] The solder joint member 4 of the present embodiment contains Sn as a main component. Here, the so-called "main component" refers to the component with the largest amount among the components contained in the solder joint member 4. The content of Sn in the solder joint member 4 is preferably 60% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more.

[0054] In the solder joint member 4 of the present embodiment, the Ag content is 3 mass % or more and less than 4 mass %, and the Cu content is 0.5 mass % or more and less than 1.0 mass %. When the Ag and Cu contents are within this range, the effects of the present disclosure are confirmed to be obtained.

[0055] It should be noted that the addition of Ag and Cu has a melting point lowering effect, such as the melting point of Sn single substance is 232°C and the melting point of Sn-Ag-Cu eutectic is 220°C. In addition, the addition of Ag has a high strength effect due to the enhanced fine dispersion of Ag-Sn compounds. The addition of Cu has an effect of preventing Sn from forming coarse interface compounds at the bonding interface. It should be noted that in the absence of Cu, the compound reaction at the bonding interface proceeds, Sn disappears, and Bi is easily concentrated, so it is preferred to make the Cu addition amount within the above range.

[0056] It should be noted that the solder joint member 4 may contain elements other than the above, for example, In having a melting point lowering effect may be contained in an amount of 0.1 mass % or more and less than 1 mass % as other added elements. Even in this case, the bonding properties will not be greatly affected, and the same effect as above can be obtained.

[0057] Implementation method 2.

[0058] <Semiconductor devices>

[0059] The semiconductor device according to the present embodiment includes a substrate 2 and a semiconductor element 3. The substrate 2 and the semiconductor element 3 are bonded together via the solder bonding member 4 described in the first embodiment. Thus, a semiconductor device with high reliability is provided.

[0060] Implementation method 3.

[0061] <Soldering method>

[0062] The solder joining method of the present embodiment is a solder joining method for joining a first object 2 (for example, a substrate) and a second object 3 (for example, a semiconductor element) (see Figure 1 to Figure 6 ).

[0063] The solder joining method of this embodiment includes the following heating step: heating a solder sheet 1 while being clamped between a first object 2 and a second object 3, wherein the solder sheet includes Sn as a main component, 3 mass % or more and less than 4 mass % of Ag, 0.5 mass % or more and less than 1.0 mass % of Cu, 2.5 mass % or more and less than 4 mass % of Bi, and 0.5 mass % or more and less than 3 mass % of Sb.

[0064] By going through the heating step, the solder sheet 1 becomes the solder bonding member 4, and the first object 2 and the second object 3 are bonded. In addition, the steps other than the heating step will be described later in the examples.

[0065] In the heating process, the heating temperature (maximum reached temperature) is preferably 220° C. or higher and lower than 230° C., and the heating time (time of maintaining the temperature at 220° C. or higher and lower than 230° C.) is 10 minutes or higher and lower than 20 minutes. In this case, the solder joint component of this embodiment can be more reliably formed, and the effect of the solder joint component described above can be obtained.

[0066] Furthermore, in the present disclosure, the oxygen concentration in the solder sheet 1 is also important. Bi is easily oxidized, and if Bi is added and not stored in a vacuum dryer or the like, the solder wettability is poor and good bonding cannot be obtained. The oxygen concentration contained in the solder sheet 1 is preferably greater than 0 ppm and less than 500 ppm. In this case, the same effect as above can be obtained more reliably.

[0067] Implementation method 4.

[0068] <Method for manufacturing semiconductor device>

[0069] The method for manufacturing a semiconductor device of the present embodiment is a method for manufacturing a semiconductor device having a substrate and a semiconductor element. The method for manufacturing a semiconductor device of the present embodiment includes: a step of bonding a substrate (substrate wiring such as a copper plate) and a semiconductor element using the solder bonding method of Embodiment 3. Thus, a semiconductor device with high reliability is provided.

[0070] Example

[0071] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0072] (Example 1)

[0073] Below, refer to Figure 1 The flowchart shown in FIG. 1 illustrates an example of steps for producing a semiconductor element bonded body (a bonded body of a semiconductor element and a substrate) in the method for manufacturing a semiconductor device according to the present embodiment.

[0074] First, as a first step (S1), the solder sheet 1 is cut into a predetermined size (see Figure 2 ).

[0075] Specifically, first, as a representative example of solder composition, each element is added and melted to form a composition represented by Sn-3.5Ag-0.7Cu-3.3Bi-2.0Sb (numerical values ​​represent mass %, Sn being the remainder of the composition ratio of other elements) to produce a bulk body.

[0076] Next, a roll-shaped solder sheet 1 was produced by a rolling process at 100° C. or less so as to have a thickness of 100 μm. Then, the roll-shaped solder sheet 1 was cut into a size of 5 mm×5 mm, which is the same size as the semiconductor element described below.

[0077] It should be noted that the manufacture of the solder sheet 1 is not only rolling, but also melting the block and casting the molten solder in sequence from a thin slit, thereby manufacturing the solder sheet 1. In addition, as mentioned above, when the combination of elements is 5 elements or more, sometimes the composition of the block becomes uneven due to the uneven temperature of the melting furnace. In this case, the solder composition can be adjusted by initially manufacturing a block of Sn-Ag-Cu, then melting it again, and adding a specified amount of remaining Bi and Sb. In addition, once the solder is spheroidized, the solder balls can be evenly spread on a flat plate and compression-molded to manufacture a sheet.

[0078] Next, as a second step (S2), a solder sheet 1 (see Figure 3 ).

[0079] A tough pitch copper plate (thickness: 1 mm, size: 10 mm×10 mm) was used as the substrate 2. The outermost surface of the substrate 2 was pure copper, and no plating treatment was performed on the outermost surface.

[0080] It is to be noted that, in order to prevent oxidation, a predetermined amount of rust inhibitor having a decomposition temperature of 100°C or less that does not affect the bonding property may be applied to the outermost surface of the CuMo alloy plate. In addition, when placing the solder sheet 1, an organic agent that is thermally decomposed at a high temperature of 100°C or more may be used as a viscous material in a manner that the solder sheet 1 does not deviate from the initial position. The viscosity of the viscous material is preferably 200 Pa·s or more. Alternatively, a resist film may be applied outside the bonding portion of the Cu plate in a manner that the solder sheet 1 does not deviate.

[0081] The solder sheet 1 may be slightly bent when being cut or handled. This is because the solder sheet 1 is completely melted by heating, so there is no influence of the initial shape of the solder sheet 1. However, since a semiconductor element is placed in the next step, if the solder sheet is bent to such an extent that the semiconductor element cannot be placed, it can be corrected to be parallel on another flat plate.

[0082] Next, as a third step (S3), the semiconductor element 3 is placed on the solder sheet 1 (see Figure 4 ). The semiconductor element 3 is made of Si, has a thickness of 100 μm, and a size of 5 mm×5 mm. On the bonding surface side, a Ni film is formed in a solder-wetting manner. In addition, the above-mentioned adhesive material can be applied between the semiconductor element 3 and the solder sheet 1 to fix the mounting position.

[0083] Next, as a fourth step, the stacked body of each member obtained in the above steps is placed on a hot plate 6 in a heating furnace 5 (see Figure 5 Then, formic acid, which is a typical organic acid capable of reducing the oxide film, is sealed in the heating furnace 5, and the solder sheet 1 is melted by heating at 180°C for 5 minutes and then at 230°C for 10 minutes to form the solder joint member 4.

[0084] Next, as a fifth step (S5), the sample (semiconductor element joint body) on which the solder joint member 4 is formed is placed on a cooling plate 7 and cooled (see Figure 6 ).

[0085] At this time, if the semiconductor element warps or undulates (produces unevenness) due to the thermal contraction of the solder, it becomes a cause of fluctuations in the electrical characteristics of the semiconductor element 3. Therefore, in the cooling process, it takes 360 seconds to cool slowly to 130°C (for a temperature drop of 100°C from 230°C to 130°C) when the sample is taken out.

[0086] It should be noted that such a cooling (slow cooling) process is not performed in the general solder manufacturing process. This is because the tact (operation time) of solder jointing is prolonged due to such a slow cooling process. However, considering the influence of the semiconductor element 3 mentioned above, the above-mentioned slow cooling is performed in order to reduce stress as much as possible.

[0087] Through the above steps, a semiconductor element bonded body is obtained.

[0088] Figure 7 The semiconductor element bonded body obtained after the fifth step (see Figure 6 ) is a schematic cross-sectional view of the bonding interface portion 8 (a portion of the solder bonding member 4 and the substrate 2 side, including the bonding interface of the two). Figure 7 As shown in the figure, in the bonding interface portion 8, there are, in order from the substrate 2 side, an interface compound 9 (a compound containing components of the substrate 2 and components of the solder sheet 1), a Sn-Bi alloy phase 10 (a low melting point phase), a Sn-Bi-Sb alloy phase 11 (a medium melting point phase), and a main phase 12.

[0089] In addition, regarding the constitution of each phase in the entire solder bonding member 4 including the substrate 2 side and the semiconductor element 3 side, as shown in FIG. Fig.12 as shown in .

[0090] <Evaluation>

[0091] The obtained sample (semiconductor element joint body) was removed from the semiconductor element 3 and a part of the solder joint member 4 was scraped off from the semiconductor element 3 side, so that only the joint interface portion 8 on the substrate (Cu plate) 2 side remained. It should be noted that since processing oil, grinding residue, water, etc. were mixed into the sample during production, the sample was washed with ethanol in advance and left at room temperature for 24 hours after washing.

[0092] Differential scanning calorimetry (DSC) was performed on the bonding interface 8 of the solder bonding member 4. Pt (platinum) was used for the pan in which the sample was placed. DSC measurement (device) is a method (device) for measuring the state change of the sample. By DSC measurement, the melting point of the solder bonding member 4 at the bonding interface 8 can be confirmed. The heating rate during DSC measurement is 2°C / min.

[0093] The DSC measurement results of the samples are shown in Figure 8 .exist Figure 8 In the figure, the horizontal axis is the heating temperature in the DSC measurement, and the vertical axis is the heat flow of the solder joint member 4. It should be noted that an endothermic reaction occurs when changing from a solid to a liquid, so the heat flow becomes a negative value. The vertical axis is a logarithmic axis, and the unit of heat flow is mW. Figure 8 The numerical values ​​shown in are relative values ​​(relative values ​​with respect to the Pt disk).

[0094] Depend on Figure 8 The results shown in , mainly three heat flow peaks (reverse peaks) were observed. These three peaks correspond to a phase having a melting point of 135°C or more and less than 145°C (low melting point phase: Sn-Bi alloy phase 10), a phase having a melting point of 170°C or more and less than 180°C (medium melting point phase: Sn-Bi-Sb alloy phase 11), and a phase having a melting point of 210°C or more and less than 220°C (main phase 12).

[0095] From this result, it can be confirmed that in this embodiment, due to the interface reaction during bonding, Figure 7 A plurality of phases are formed in the bonding interface portion 8 (a portion of the substrate side of the solder bonding member 4) after the fifth step shown in FIG.

[0096] Then, the bonding strength of the sample (semiconductor element joint body) was measured by a chip shear test. As a result, the bonding strength was 48MPa. This value is the target value, i.e., above 40MPa. It should be noted that the peel strength of the joint body when the same joint body is obtained using the general Sn-3Ag-0.5Cu solder is 40MPa, so the bonding strength higher than this is set as the target value. As for the reason for the high bonding strength, it is presumed that it is because: by adding Bi and Sb to the solder, the solid solution strengthening mechanism partially works.

[0097] In addition, the warpage (maximum distance from the substrate) of the semiconductor element in the sample (semiconductor element joint body) was measured. As a result, the warpage of the semiconductor element as a whole was less than 10 μm, achieving the target of less than 30 μm. On the other hand, when the general Sn-3Ag-0.5Cu solder was used, the warpage was 40 μm, which failed to achieve the target.

[0098] (Comparative Example 1)

[0099] In order to examine the effect of Sb addition, a sample (semiconductor element junction) was prepared in the same manner as in Example 1 except that the solder sheet 1 did not contain Sb (the solder sheet 1 had a composition of Sn-3.5Ag-0.7Cu-3.3Bi), and the same evaluation was performed.

[0100] exist Fig. 9 The DSC measurement results of Comparative Example 1 are shown in FIG. Fig. 9 As shown in , no intermediate melting point phase was found in Comparative Example 1, and the low melting point phase was also outside the range of "135°C or more and less than 145°C" in Example 1. This is believed to be because the added Sb has the effect of increasing the melting points of the low melting point phase and the intermediate melting point phase. In addition, for the main phase 12, similarly to Example 1, a peak corresponding to a phase having a melting point of 210°C or more and less than 220°C was found. This is believed to be more pronounced because Sb is concentrated at the bonding interface.

[0101] In order to clarify the above mechanism, an elemental scan of the solder joint member 4 of the sample of Example 1 prepared using the solder sheet 1 containing Sb (Sn-3.5Ag-0.7Cu-3.3Bi-2.0Sb) was performed. Fig.10 As shown in , Sb and Bi are concentrated particularly in the bonding interface, and they are low melting point phase and medium melting point phase.

[0102] Furthermore, if Fig.11As shown in the SEM photograph of , in the sample of Comparative Example 1 made using solder sheet 1 (Sn-3.5Ag-0.7Cu-3.3Bi) without Sb addition, shrinkage cavities due to solidification shrinkage were confirmed on the interface compound 9. It is believed that this is because if Sb is not added, the main phase 12 solidifies, and then the low melting point phase solidifies all at once, resulting in such shrinkage cavities. That is, it is believed that the addition of Sb has the following effect: in the slow cooling process for suppressing the residual stress of the joint in the present disclosure, the solidification shrinkage cracks of the low melting point phase caused by phase separation formed at the joint interface are suppressed.

[0103] (Example 2)

[0104] The addition amounts of Bi and Sb were changed as shown in Table 1. For the bonded samples obtained in the same manner as in Example 1, the presence or absence of solidification cracks was visually confirmed using SEM photographs. The confirmation results are shown in Table 1. In Table 1, "OK" indicates no solidification cracks, and "NG" indicates the presence of solidification cracks.

[0105] [Table 1]

[0106]

[0107] From the results shown in Table 1, it is known that when Bi of 2.5 mass % or more and less than 4 mass % and Sb of 0.5 mass % or more and less than 3 mass % are added, there is no solidification crack and good bonding can be performed. In addition, in this case, it is confirmed that the bonding strength of the bonded sample is more than 40 MPa. It is believed that this is because there is no solidification crack (shrinkage cavity), so high bonding strength is maintained. The warpage of the semiconductor element is also less than 10 μm, which is good.

[0108] When Bi is less than 2.5 mass%, sufficient solder wettability cannot be obtained and the bonding strength is insufficient (less than 40 MPa). When Bi is 4 mass% or more, the proportion of the low melting point phase increases, solidification cracks occur, and the bonding strength is insufficient (less than 40 MPa).

[0109] When Sb is less than 0.5 mass%, the sufficient effect of the intermediate melting point phase cannot be obtained, solidification cracks occur, and the bonding strength is insufficient (less than 40 MPa). When Sb is more than 3 mass%, the melting point of the main phase 12 also rises, sufficient solder wettability cannot be obtained, and the bonding strength is insufficient (less than 40 MPa).

[0110] The embodiments and examples disclosed this time should be considered as illustrative in all aspects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0111] Description of Reference Numerals

[0112] 1 solder sheet, 2 first object (substrate: copper plate), 3 second object (semiconductor element), 4 solder joint member, 5 heating furnace, 6 hot plate, 7 cooling plate, 8 joint interface, 9 interface compound, 10 Sn-Bi alloy phase (low melting point phase), 11 Sn-Bi-Sb alloy phase (medium melting point phase), 12 main phase.

Claims

1. A solder joint component for joining a first object and a second object, wherein: containing Sn as a main component, 3 mass % or more and less than 4 mass % of Ag, 0.5 mass % or more and less than 1.0 mass % of Cu, 2.5 mass % or more and less than 4 mass % of Bi, and 0.5 mass % or more and less than 3 mass % of Sb, have: A main phase comprising Sn, Ag and Cu and having a melting point of 210° C. or higher and lower than 220° C.; A Sn-Bi alloy phase having a melting point of 135° C. or higher and lower than 145° C. covering at least a portion of the main phase; and A Sn-Bi-Sb alloy phase having a melting point of 170° C. or higher and lower than 180° C. is provided to cover at least a portion of the Sn-Bi alloy phase. 2 . The solder joint member according to claim 1 , further comprising 0.1 mass % or more and less than 1 mass % of In.

3. The solder joint member according to claim 1 or 2, wherein: The first object is a substrate, and the second object is a semiconductor element.

4. A semiconductor device comprising a substrate and a semiconductor element, The substrate and the semiconductor element are joined via the solder joining member according to any one of claims 1 to 3.

5. A solder joining method for joining a first object and a second object, The method comprises a heating step, wherein: A solder sheet is heated while being sandwiched between the first object and the second object, the solder sheet containing Sn as a main component, 3 mass % or more and less than 4 mass % of Ag, 0.5 mass % or more and less than 1.0 mass % of Cu, 2.5 mass % or more and less than 4 mass % of Bi, and 0.5 mass % or more and less than 3 mass % of Sb, In the heating step, the heating temperature is 220° C. or higher and lower than 230° C., and the heating time is 10 minutes or higher and lower than 20 minutes.

6. The solder joining method according to claim 5, wherein: The total amount of oxygen contained in the solder sheet is greater than 0 ppm and less than 500 ppm.

7. The solder joining method according to claim 5 or 6, wherein: The first object is a substrate, and the second object is a semiconductor element.

8. A method for manufacturing a semiconductor device, comprising: a method for manufacturing a semiconductor device comprising a substrate and a semiconductor element; The method comprises the step of bonding the substrate and the semiconductor element using the solder bonding method according to claim 7.

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