Solder material, method for producing solder sheet, and method for producing semiconductor device

Abstract

To provide a solder material that is capable of joining at 250°C or below and that has a heat resistance of at least 180°C.　The solder material (14) has Sn, Zn, and Al as its main components; has two endothermic peaks in measurement by differential scanning calorimetry; and contains a first alloy phase (11) having an endothermic peak at from 190°C to less than 230°C mixed with a second alloy phase (12) having an endothermic peak at from 240°C to less than 380°C.

Description

Solder material, solder sheet manufacturing method, and semiconductor device manufacturing method

[0001] The present application relates to a solder material, a method for manufacturing a solder sheet, and a method for manufacturing a semiconductor device.

[0002] In recent years, the demand for reliability in semiconductor devices has been increasing, and in particular, semiconductor devices using wide bandgap semiconductor elements such as SiC and GaN, which have higher breakdown voltage and lower loss than conventional Si semiconductor elements, have been developed. While the operating temperature of conventional semiconductor devices using Si is approximately 125°C, the operating temperature of semiconductor devices using SiC, GaN, etc. is 175°C or higher. Therefore, solder materials used to join semiconductor elements to workpieces are required to have high heat resistance. Furthermore, to reduce environmental impact, the adoption of Pb-free solder materials, which do not contain Pb, a substance subject to environmental regulations, is being promoted.

[0003] The melting point of Sn-3Ag-0.5Cu (values ​​represent weight percent, hereafter referred to as SAC305), a typical composition of conventional Pb-free solder, is 220°C. Therefore, SAC305 softens at temperatures above 175°C, and sufficient bonding strength cannot be obtained. An alternative to SAC305 is a sintered Ag bonding material that uses nanosilver particles, although it is not a solder material. However, nanosilver particles are expensive, and sintered Ag bonding materials require pressure bonding at high pressure, which presents significant disadvantages in terms of cost and bonding process.

[0004] As a method for improving the heat resistance of Sn-based solders, Zn-based solders have been developed in which a portion of the Sn, the main component, has been replaced with Zn. For example, a solder material has been disclosed that, when the total is taken as 100 wt%, consists of 10 to 70 wt% Sn, 2 to 10 wt% Al, and the remainder being Zn and unavoidable impurities (see, for example, Patent Document 1). Another solder material has been disclosed that, when the total components are taken as 100 mol%, consists of 82 to 94 mol% Sn, 5 to 15 mol% Zn, and 1 to 3 mol% Al. The composition of this solder material, when rewritten in weight ratio, is 2.84 to 9.09 wt% Zn, 0.23 to 0.75 wt% Al, and the remainder being Sn (see, for example, Patent Document 2).

[0005] Japanese Patent Laid-Open No. 6-226489 Japanese Patent Laid-Open No. 2002-1575

[0006] The solder material described in Patent Document 1 requires a bonding temperature of 350 to 410°C. However, when semiconductor elements are bonded by reflow soldering at temperatures above 350°C, the semiconductor elements may soften and warp. Warping of the semiconductor elements reduces bonding reliability due to the large residual stresses that remain at the bonded portions. Furthermore, copper alloy electrode films, polyimide insulating films, and other films are formed on the surfaces of semiconductor elements, and heating at temperatures above 350°C can alter the electrical properties of these films. Changes in the electrical properties of the electrode films, insulating films, and other films can alter the characteristics of the semiconductor device. The solder material described in Patent Document 2 requires a bonding temperature of 250 to 255°C. However, because the melting point of this solder material is approximately 200°C, it is difficult to apply it to semiconductor devices using wide-bandgap semiconductor elements that locally or momentarily reach temperatures above 180°C during operation. Therefore, conventional Zn-based solder materials have difficulty being bonded at temperatures below 250°C and having heat resistance above 180°C.

[0007] The present application has been made to solve the above-mentioned problems, and has as its object to provide a solder material that can be bonded at 250°C or less and has heat resistance of 180°C or more.

[0008] The solder material of the present application is a solder material whose main components are Sn, Zn, and Al, and has two endothermic peaks in differential scanning calorimetry, including a first alloy phase having an endothermic peak at 190°C or higher and lower than 230°C, and a second alloy phase having an endothermic peak at 240°C or higher and lower than 380°C.

[0009] The solder material of the present application has two endothermic peaks in differential scanning calorimetry, and is a mixture of a first alloy phase having an endothermic peak at 190°C or higher but lower than 230°C and a second alloy phase having an endothermic peak at 240°C or higher but lower than 380°C, and therefore can be bonded at 250°C or lower and has heat resistance of 180°C or higher.

[0010] 1 is a flowchart of a manufacturing process of a solder sheet according to embodiment 1. FIG. 2 is a schematic diagram of a manufacturing process of a solder sheet according to embodiment 1. FIG. 3 is a schematic diagram of a manufacturing process of a solder sheet according to embodiment 1. FIG. 4 is a schematic diagram of a manufacturing process of a solder sheet according to embodiment 1. FIG. 5 is a cross-sectional schematic diagram of a solder material according to embodiment 1. FIG. 6 is a diagram showing measurement results of differential scanning calorimetry of the solder material according to embodiment 1. FIG. 7 is a flowchart of a manufacturing process of a semiconductor device according to embodiment 1. FIG. 8 is a schematic diagram of a manufacturing process of a semiconductor device according to embodiment 1. FIG. 9 is a schematic diagram of a manufacturing process of a semiconductor device according to embodiment 1. FIG. 10 is a schematic diagram of a die shear strength test according to embodiment 1. FIG. 11 is a table showing test results of the composition of the solder material and the bonding strength according to embodiment 1.

[0011] Hereinafter, a solder material, a method for manufacturing a solder sheet, and a method for manufacturing a semiconductor device according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the same reference numerals in each drawing indicate the same or corresponding parts.

[0012] Embodiment 1. Figure 1 is a flowchart of the manufacturing process of a solder sheet according to embodiment 1. In step S01, raw material powders of solder material are mixed. Specifically, 10 g of Zn powder, 5 g of Al powder, and 85 g of Sn powder are mixed. The average particle size of the raw material powder is preferably 10 to 100 μm. The average particle size of the raw material powder is the average particle size measured using, for example, a laser diffraction particle size distribution analyzer.

[0013] Next, in step S02, the mixed raw material powders are melted in a melting furnace to form molten solder. The melting temperature is set to 700°C. As long as the melting temperature is equal to or higher than the melting point of Al, which has the highest melting point among the raw material powders Zn (melting point 420°C), Al (melting point 660°C), and Sn (melting point 232°C), the powders can be melted and mixed uniformly. Next, in step S03, the molten solder is dropped onto a flat stage. Then, in step S04, the molten solder dropped onto the stage is formed into a sheet using a squeegee before solidifying.

[0014] 2 is a schematic diagram showing the state in which molten solder 1 has been dropped onto a flat stage 2 in step S03. Stage 2 is, for example, a flat stainless steel plate with a temperature adjustment function. The temperature of stage 2 when molten solder 1 is dropped in step S03 is set to approximately 300° C. As shown in FIG. 2, the thickness of molten solder 1 when dropped onto stage 2 is non-uniform.

[0015] 3 and 4 are schematic diagrams showing the state when the molten solder 1 is formed into a sheet by the squeegee 3 in step S04. The distance between the squeegee 3 and the stage 2 is set to, for example, 100 μm, which is the thickness of the solder sheet. The squeegee 3 moves parallel to the surface of the stage 2. At this time, the distance between the squeegee 3 and the stage 2 is always kept constant. As shown in FIGS. 3 and 4, before the molten solder 1 dropped onto the stage 2 solidifies, the squeegee 3 is moved to form the molten solder 1 into a sheet, thereby producing a solder sheet 4.

[0016] Finally, in step S05, the sheet-shaped solder sheet 4 is cooled. The atmosphere in steps S03 to S05 may be an oxidizing atmosphere such as air, an inert atmosphere such as nitrogen or argon, or a reducing atmosphere such as formic acid or hydrogen. In the cooling step of step S05, the temperature of the stage 2 is adjusted to cool from 300°C to 100°C in a cooling time of more than 20 seconds but not more than 200 seconds. The cooling rate at this time is, in absolute value, 1°C / second or more and less than 10°C / second.

[0017] The solder sheet 4 formed in this manner is cut to a predetermined size. For example, it is cut to a 5 mm square to fit the joining surface of the semiconductor element. The thickness of the solder sheet 4 is preferably 0.05 mm or more and less than 1 mm. The thickness of the solder sheet 4 can be adjusted by the distance between the squeegee 3 and the stage 2.

[0018] If cracks or other defects occur in the solder sheet, the solder sheet can be returned to step S02 to reduce loss of raw materials. While Zn powder, Al powder, and Sn powder are simultaneously mixed and melted in steps S01 and S02, other methods may be used. For example, Zn powder and Sn powder may be mixed and melted to first produce a bulk of Sn and Zn, and then the bulk may be remelted and Al powder may be added. Furthermore, although molten solder is dropped and formed into a sheet before solidifying in steps S03 and S04, other methods may be used. For example, the molten solder may be first formed into small ball-shaped solids. These small ball-shaped solids may then be dispersed on a stage. Finally, the ball-shaped solids dispersed on the stage may be heated and compressed at 700°C to form a sheet. The solder sheet formed into a sheet by heating and compression molding at 700°C is cooled from 300°C to 100°C in a cooling time of more than 20 seconds but not more than 200 seconds. The cooling rate at this time is, in absolute value, 1° C. / sec or more and less than 10° C. / sec.

[0019] Fig. 5 is a cross-sectional schematic diagram of a solder material constituting the solder sheet according to this embodiment. Fig. 5 is a diagram illustrating the composition when the cross section of the solder material is observed under magnification with a scanning electron microscope. As shown in Fig. 5, the solder material 14 constituting the solder sheet 4 of this embodiment is separated into two phases. In the solder material 14, a second alloy phase 12 is dispersed within a first alloy phase 11. When the cross-sectional shape of the second alloy phase 12 is approximated as a circle, its diameter is 20 µm or less.

[0020] FIG. 6 shows the results of differential scanning calorimetry of the solder material according to this embodiment. Differential scanning calorimetry (hereinafter referred to as DSC) is a method of measuring the temperature difference between a reference material and a measurement material while applying a constant amount of heat, and then measuring the endothermic and exothermic reactions of the measurement material from the temperature difference. In FIG. 6, the horizontal axis represents temperature, and the vertical axis represents the calorific value (hereinafter referred to as DSC value) calculated from the temperature difference between the reference material and the measurement material. The vertical axis is expressed in logarithm. In the DSC curve shown in FIG. 6, the direction in which the DSC value decreases represents an endothermic reaction, and the direction in which the DSC value increases represents an exothermic reaction. As shown in FIG. 6, two endothermic peaks are observed in the DSC curve of the solder material according to this embodiment. The two endothermic peaks are endothermic peak A, which appears at approximately 210°C, and endothermic peak B, which appears at approximately 340°C.

[0021] Composition analysis and detailed DSC measurements have revealed the following relationship between the first and second alloy phases shown in Figure 5 and the two endothermic peaks shown in Figure 6: the endothermic reaction in the first alloy phase 11 corresponds to endothermic peak A, and the endothermic reaction in the second alloy phase 12 corresponds to endothermic peak B. The first alloy phase 11 is a phase containing Sn as the main component and Al and Zn therein, and the second alloy phase 12 is a phase containing Zn as the main component and Al and Sn therein.

[0022] Next, the specific heat capacities of the first alloy phase and the second alloy phase were compared. The specific heat capacities of the first alloy phase and the second alloy phase were measured in accordance with Japanese Industrial Standard JIS K 7123, which allows specific heat capacity to be calculated using DSC. As a result, it was found that the specific heat capacity of the first alloy phase was larger than that of the second alloy phase. Specific heat capacity is the amount of heat required to raise the temperature of a substance of unit mass by a unit, and its unit is J / (kg K).

[0023] Generally, when preparing a solder material such as SAC305, which is an alloy of Sn, Ag, and Cu, the solder material is rapidly cooled to prevent phase separation. Specifically, the absolute value of the cooling rate of the molten solder material is, for example, 50°C / sec or more. In the method for preparing a solder material according to this embodiment, the absolute value of the cooling rate from 300°C to 100°C is set to 1°C / sec or more and less than 10°C / sec, so that a solder material separated into two phases, a first alloy phase and a second alloy phase, is obtained, as shown in FIG.

[0024] Next, a method for manufacturing a semiconductor device according to this embodiment will be described. FIG. 7 is a flowchart of the manufacturing process of a semiconductor device according to this embodiment. In step S11, a solder sheet 4 is placed on a substrate 5, which is a member to be joined. FIG. 8 is a schematic diagram showing the state in which the solder sheet 4 has been placed on the substrate 5 in step S11. The substrate 5 is, for example, a copper plate such as tough pitch copper, having a thickness of 1 mm and a size of 10 mm square. The solder sheet 4 is, for example, 100 μm thick and a size of 5 mm square.

[0025] The outermost surface of the substrate 5 is made of solid copper and is not plated. However, the outermost surface of the substrate 5 may be coated with a rust inhibitor having a decomposition temperature of 100°C or less, as long as it does not affect the solder joint. Furthermore, the surface of the substrate 5 may be coated with an adhesive that thermally decomposes at 100°C or higher to prevent the solder sheet 4 from shifting when placed on it. The viscosity of the adhesive is preferably 200 Pa·s or higher. Alternatively, a resist film may be coated on the surface of the substrate 5 in areas other than the joining surface to prevent the solder sheet 4 from shifting when placed on it.

[0026] The solder sheet 4 may be slightly curved. This is because the initial shape of the solder sheet 4 has little effect on the solder sheet 4, as it melts when heated. However, if the solder sheet 4 is curved to the extent that it causes the semiconductor element to be misaligned when it is placed on the solder sheet 4 in the next process, the curvature of the solder sheet 4 must be corrected.

[0027] Next, in step S12, the semiconductor element 6 is placed on the solder sheet 4. FIG. 9 is a schematic diagram showing the state in which the semiconductor element 6 is placed on the solder sheet 4 in step S12. The semiconductor element 6 is, for example, a semiconductor element using SiC, and is 100 μm thick and 5 mm square. A Ni film may be formed on the joining surface of the semiconductor element 6 facing the solder sheet 4 to improve wettability with the solder material. In addition, an adhesive may be applied to the joining surface of either the semiconductor element 6 or the solder sheet 4 to prevent the semiconductor element 6 from shifting when placed.

[0028] Next, as shown in Figure 10, the substrate 5, solder sheet 4, and semiconductor element 6 are placed in this order on a hot plate 7 and then placed in a sealed furnace 8. The interior of the sealed furnace 8 is adjusted to an atmosphere of 3% by volume hydrogen, which can reduce oxide films, with the remainder being nitrogen. In step S13, the hot plate 7 is used to heat the solder sheet 4 at 250°C for 10 minutes to melt it. In this way, the substrate 5 and the semiconductor element 6 are bonded together with the solder material 14. Although not shown, it is preferable to apply pressure from above the semiconductor element 6 to strengthen the bond between the substrate 5 and the semiconductor element 6 with the solder material 14.

[0029] Next, as shown in FIG. 11 , the semiconductor device 13, in which the substrate 5 and the semiconductor element 6 are bonded with the solder material 14, is transferred to the cooling stage 9 in the sealed furnace 8. The interior of the sealed furnace 8 is adjusted to an atmosphere of 3% by volume hydrogen, which can reduce oxide films, with the remainder being nitrogen. In step S14, the solder material 14 is cooled from 250°C to 100°C over 500 seconds using the cooling stage 9. The absolute value of the cooling rate is 0.3°C / sec. Such a slow cooling rate is not adopted in the manufacturing process of general-purpose semiconductor devices because it would increase the takt time. In this embodiment, the cooling rate (absolute value) of 0.3°C / sec can suppress the occurrence of warping, undulation, and other problems in the semiconductor element 6 due to thermal contraction of the solder material 14. Note that when proceeding from step S13 to step S14, the semiconductor device 13 is transferred from the hot plate 7 to the cooling stage 9. However, a temperature adjustment stage having both the functions of a hot plate and a cooling stage may also be used. This temperature adjustment stage can adjust the temperature of the substance on the stage within a temperature range of, for example, 20° C. to 400° C. By using such a temperature adjustment stage, the process of transferring the semiconductor device 13 from the hot plate 7 to the cooling stage 9 is not required.

[0030] In the cooling step of step S14, the cooling time from 250° C. to 100° C. is preferably 300 seconds or more. That is, the cooling rate from 250° C. to 100° C. is preferably 0.5° C. / second or less in absolute value. If the cooling time from 250° C. to 100° C. is 300 seconds or more, it is possible to suppress the occurrence of warping, undulation, etc. of the semiconductor element 6 due to thermal contraction of the solder material 14.

[0031] In the semiconductor device 13 manufactured by this method, the solder material 14 that joins the substrate 5 and the semiconductor element 6 can be bonded at temperatures of 250° C. or less and has heat resistance of 180° C. or more. The reason for this will be explained below.

[0032] As shown in FIG. 6 , the solder material of this embodiment has two alloy phases: a first alloy phase corresponding to endothermic peak A appearing at approximately 210°C, and a second alloy phase corresponding to endothermic peak B appearing at approximately 340°C. In the 250°C heating step in step S13 of the semiconductor device manufacturing process, the first alloy phase having an endothermic peak at approximately 210°C melts, allowing the substrate and semiconductor element to be bonded. On the other hand, when the semiconductor device is heated to 180°C or higher, the first alloy phase having an endothermic peak at approximately 210°C softens, but the second alloy phase having an endothermic peak at approximately 340°C does not soften. As a result, the solder material of the semiconductor device of this embodiment does not soften more than necessary even at temperatures above 180°C, and has heat resistance above 180°C.

[0033] In the above description of this embodiment, the composition of the solder material is 10 wt % Zn, 5 wt % Al, and 85 wt % Sn. Hereinafter, the characteristics of solder materials with different composition ratios will be described. The solder material of this embodiment may contain inevitable impurities other than the main components.

[0034] In step S01 of the flowchart of the solder sheet manufacturing process shown in Figure 1, when mixing the raw material powder of the solder material, the mixing ratio of Zn powder, Al powder, and Sn powder was changed to manufacture multiple types of solder sheets. Using these solder sheets, multiple semiconductor devices with different solder material compositions were manufactured based on the flowchart of the semiconductor device manufacturing process shown in Figure 7. A die shear strength test was performed on the multiple semiconductor devices manufactured in this manner.

[0035] 12 is a schematic diagram of a die shear strength test in this embodiment. As shown in FIG. 12, a die 10 is brought into contact with the side of a semiconductor element 6 of a semiconductor device 13 in which a substrate 5 and a semiconductor element 6 are joined with solder material 14, and a load is applied to the die 10 in a direction parallel to the joining surface. The load applied to the die 10 is gradually increased, and the load value at which the semiconductor element 6 cannot withstand the load from the die 10 and moves laterally is defined as the joining strength of the joining surface. The joining strength of the semiconductor device 13 was measured at 20°C.

[0036] FIG. 13 is a table showing the composition of the solder material and the test results of the joint strength in this embodiment. In the table shown in FIG. 13, the vertical rows represent the Zn weight percentage of the solder material, and the horizontal columns represent the Al weight percentage of the solder material. The Sn weight percentage of the solder material is calculated by subtracting the Zn weight percentage and the Al weight percentage from 100 weight percent. In FIG. 13, "○" and "×" indicate the evaluation results of the joint strength. The minimum joint strength was set to 40 MPa, and a joint strength of 40 MPa or more at 20°C was defined as "○," while a joint strength of less than 40 MPa at 20°C was defined as "×." The reason for setting the minimum joint strength at 40 MPa is that the joint strength of SAC305, a general-purpose solder material, at 20°C is approximately 40 MPa.

[0037] As shown in the table of FIG. 13, when the total weight is taken as 100%, a solder material containing Zn of 5 wt % or more but less than 20 wt % and Al of 3.5 wt % or more but less than 10 wt % exhibited a bonding strength of 40 MPa or more at 20° C.

[0038] In solder materials with a Zn content of less than 5 wt%, the ratio of Sn in the solder material is high, resulting in a low strength of the solder material itself. As a result, the joint strength at 20°C for solder materials with a Zn content of less than 5 wt% was less than 40 MPa. On the other hand, in solder materials with a Zn content of 20 wt% or more, the strength of the solder material itself is high, but the ratio of Sn in the solder material is low. As a result, the solder material does not melt completely at a joining temperature of 250°C, resulting in a low initial joint strength. As a result, the joint strength at 20°C was less than 40 MPa. Furthermore, it is thought that a high Zn content makes the solder material more susceptible to oxidation, and this oxidation may have contributed to the low initial joint strength.

[0039] Even in solder materials with an Al content of less than 3.5 wt%, the Sn content in the solder material is high, resulting in a low strength of the solder material itself. Therefore, even in solder materials with an Al content of less than 3.5 wt%, the joint strength at 20°C was less than 40 MPa. On the other hand, in solder materials with an Al content of 10 wt% or more, the strength of the solder material itself is high, but the Sn content in the solder material is low. Therefore, at a joining temperature of 250°C, the solder material does not melt completely, resulting in a low initial joint strength. As a result, the joint strength was less than 40 MPa. Note that when the Al content is high, the joint strength can be improved by setting the joining temperature to 250°C or higher. However, setting the joining temperature to 250°C or higher is not preferable because it may cause warping of the semiconductor element.

[0040] From the above results, it can be seen that when the total is taken as 100% by weight, a solder material containing 5% by weight or more but less than 20% by weight of Zn, 3.5% by weight or more but less than 10% by weight of Al, and the remainder being Sn can be bonded at 250°C or less and has heat resistance of 180°C or more.

[0041] Next, DSC measurement was performed on the solder materials that were evaluated as "○" in the table of FIG. 13. As a result, two endothermic peaks were observed in all solder materials, as shown in FIG. 6. In this case, the peak temperature of endothermic peak A on the low-temperature side was in the range of 190°C or higher and lower than 230°C. Furthermore, the peak temperature of endothermic peak B on the high-temperature side was in the range of 240°C or higher and lower than 380°C. Therefore, it can be seen that a solder material that has two endothermic peaks in DSC measurement, and that contains a first alloy phase having an endothermic peak at 190°C or higher and lower than 230°C, and a second alloy phase having an endothermic peak at 240°C or higher and lower than 380°C, can be bonded at 250°C or lower and has heat resistance of 180°C or higher.

[0042] In solder materials with 20% or more by weight of Zn, the height of the endothermic peak on the low-temperature side decreases. The peak temperatures of the two endothermic peaks shift toward the high-temperature side as the proportion of Al increases. Therefore, it is estimated that when the Al content is 10% or more by weight, the solder material becomes difficult to melt at a joining temperature of 250°C.

[0043] In the semiconductor device manufacturing process of this embodiment, the atmosphere during bonding and cooling is 3% hydrogen by volume with the remainder being nitrogen. However, if safety concerns are not a concern, a 100% hydrogen by volume atmosphere may also be used. In addition to hydrogen, an organic acid atmosphere, such as formic acid, may also be used. Examples of organic acids that can be used include formic acid, acetic acid, lauric acid, caprylic acid, pelargonic acid, heptyl acid, and caproic acid. Furthermore, the solder sheet may be immersed in an organic acid before being introduced into the semiconductor device manufacturing process, thereby forming a coating of an organic acid salt on the surface of the solder sheet.

[0044] Although exemplary embodiments are described in this application, the various features, aspects, and functions described in the embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are anticipated within the scope of the technology disclosed in this specification. For example, variations in, addition to, or omission of at least one component are included.

[0045] 1 Molten solder, 2 Stage, 3 Squeegee, 4 Solder sheet, 5 Substrate, 6 Semiconductor element, 7 Hot plate, 8 Sealed furnace, 9 Cooling stage, 10 Die, 11 First alloy phase, 12 Second alloy phase, 13 Semiconductor device, 14 Solder material.

Claims

Claim 1: A solder material in which, when the whole is 100% by weight, Zn is 5% by weight or more and less than 20% by weight, Al is 3.5% by weight or more and less than 10% by weight, and the balance is Sn, which has two endothermic peaks in differential scanning calorimetry measurement, and a first alloy phase having an endothermic peak at 190°C or more and less than 230°C and a second alloy phase having an endothermic peak at 240°C or more and less than 380°C are mixed, characterized solder material. Claim 2: A solder material mainly composed of Sn, Zn and Al, which has two endothermic peaks in differential scanning calorimetry measurement, and a first alloy phase having an endothermic peak at 190°C or more and less than 230°C and a second alloy phase having an endothermic peak at 240°C or more and less than 380°C are mixed, and in the specific heat capacity calculated by differential scanning calorimetry measurement, the specific heat capacity of the first alloy phase is larger than the specific heat capacity of the second alloy phase, characterized solder material. Claim 3: In the specific heat capacity calculated by differential scanning calorimetry measurement, the specific heat capacity of the first alloy phase is larger than the specific heat capacity of the second alloy phase, characterized solder material according to claim 1. Claim 4: A step of disposing a solder sheet composed of the solder material according to any one of claims 1 to 3 on the surface of a member to be joined; A step of disposing a semiconductor element on the surface of the solder sheet; A step of heating and melting the solder sheet while applying pressure between the member to be joined and the semiconductor element; A method for manufacturing a semiconductor device, comprising a cooling step of cooling the member to be joined, the solder material, and the semiconductor element. Claim 5: The absolute value of the cooling rate from 250°C to 100°C in the cooling step is 0.5°C / second or less, characterized method for manufacturing a semiconductor device according to claim 4. Claim 6: A heating and melting step of heating and melting a solder material in which, when the whole is 100% by weight, Zn is 5% by weight or more and less than 20% by weight, Al is 3.5% by weight or more and less than 10% by weight, and the balance is Sn; A forming step of dropping the molten solder material onto the surface of a flat base material and spreading the solder material on the surface of the base material in a molten state to form a sheet shape; A method for manufacturing a solder sheet, comprising a cooling step of cooling the solder material formed into a sheet shape, wherein the absolute value of the cooling rate from 300°C to 100°C in the cooling step is 1°C / second or more and less than 10°C / second, characterized method for manufacturing a solder sheet.