Conjugate and method for producing conjugate

Abstract

To provide a joint body in which an organic residue of a joint layer made of a sintered compact is sufficiently and securely reduced and the generation of defects such as deterioration in joint strength caused by the organic residue can be suppressed, and a method for producing the joint body.SOLUTION: A joint body 10 is obtained by joining a first member 11 and a second member 12 via a joint layer 13 made of a sintered compact of silver, and an ion residue amount obtained by immersing the joint body 10 into 2-propanol / pure water of 50% (v / v), thereafter extracting an ion residue and measuring the extract by ion chromatography is 2.5 μg / cm2 or less per joint area.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a joined body in which a first member and a second member are joined via a joining layer made of a silver sintered body, and a method for manufacturing the joined body.

Background Art

[0002] For example, in various devices such as LEDs and power modules, a structure is adopted in which electronic components such as semiconductor elements are joined on a circuit layer made of a metal member. Here, when joining an electronic component such as a semiconductor element onto a circuit layer, for example, as shown in Patent Documents 1 and 2, a method using a solder material is widely used. Recently, from the viewpoint of environmental protection, lead-free solders such as Sn-Ag-based, Sn-In-based, or Sn-Ag-Cu-based solders have become mainstream.

[0003] By the way, as described in Patent Documents 1 and 2, when joining an electronic component such as a semiconductor element and a circuit layer via a solder material, when used in a high-temperature environment, a part of the solder may melt, and there is a risk that the joining reliability between the electronic component such as a semiconductor element and the circuit layer may decrease. In particular, recently, the heat resistance of the semiconductor element itself has been improved, and the semiconductor device may be used in a high-temperature environment such as an engine room of an automobile. In addition, a large current is applied to the semiconductor element, and the heat generation amount of the semiconductor element itself has increased. For this reason, it has been difficult to cope with the conventional structure joined with a solder material.

[0004] Therefore, as an alternative to the solder material, for example, Patent Documents 3 and 4 propose a silver paste containing silver powder and an organic solvent. By applying the silver paste between the circuit layer and the semiconductor element and heating and sintering it, a joining layer made of a silver sintered body is formed, and the circuit layer and the semiconductor element are joined. The joining layer made of this silver sintered body is excellent in heat resistance and can be stably used even in a high-temperature environment or for high-current applications.

[0005] By the way, when a bonding layer made of a silver sintered body is formed, there are residues of organic components (organic residues) contained in the silver paste in the bonding layer, which may cause problems such as a decrease in bonding strength. In addition, there is concern that the organic residues may have an adverse effect on various devices such as LEDs and power modules. Therefore, in Patent Document 5, a silver paste composed only of Ag nanoparticles with an average particle size of 1 to 1000 nm and a dispersion solvent has been proposed. In the silver paste described in this Patent Document 5, the dispersibility of the silver powder is improved, and it does not contain additives such as rosin and thixotropic agents that cause organic residues, aiming to suppress the generation of organic residues in the bonding layer.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, in the silver paste described in Patent Document 5, since it contains an organic component as a solvent, depending on the shape and area of the bonding surface, etc., there is a possibility that the organic residues in the bonding layer made of the sintered body cannot be sufficiently reduced. For this reason, there is a possibility that problems such as a decrease in bonding strength caused by organic residues cannot be reliably reduced.

[0008] This invention has been made in view of the foregoing circumstances, and provides a joined body in which organic residues in a joining layer made of a sintered body are sufficiently and surely reduced, and it is possible to suppress the occurrence of problems such as a decrease in joining strength caused by the organic residues, and a method for manufacturing this joined body.

Means for Solving the Problems

[0009] In order to solve the above problems, the joined body of the present invention is a joined body in which a first member and a second member are joined via a joining layer made of a silver sintered body, and the joined body is immersed in 50% (v / v) 2-propanol / water to extract ionic residues, and then the amount of ionic residues determined by measuring the extract by ion chromatography is 2.5 μg / cm per joining area 2 or less, and is characterized by this.

[0010] According to the joined body of the present invention, since the amount of ionic residues is determined by immersing the joined body in 50% (v / v) 2-propanol / water to extract ionic residues and then measuring the extract by ion chromatography, it is possible to accurately evaluate the amount of organic residues present inside and around the joining layer. And since the amount of the ionic residues is limited to 2.5 μg / cm 2 or less per joining area, the amount of organic residues present inside and around the joining layer is sufficiently reduced, and it is possible to suppress the occurrence of problems such as a decrease in joining strength caused by the organic residues.

[0011] The method for manufacturing a joined body of the present invention is a method for manufacturing a joined body in which a first member and a second member are joined via a joining layer made of a silver sintered body, and includes a laminating step of laminating the first member and the second member via a silver paste containing silver powder and an organic solvent, a sintering step of firing the silver paste disposed between the first member and the second member to form the joining layer made of a silver sintered body, and washing the joining layer with a washing solvent as 20% - 80% (v / v) 2 - propanol / waterIt has a cleaning step of cleaning using [the cleaning agent], and after immersing the bonded body in 50% (v / v) 2-propanol / water to extract ionic residues, the amount of ionic residues determined by measuring the extract by ion chromatography is 2.5 μg / cm per bonded area. 2 It is characterized by being as follows.

[0012] According to the method for manufacturing a bonded body of the present invention, after the sintering step, it includes a cleaning step of cleaning the bonded layer using a cleaning solvent. After immersing the bonded body in 50% (v / v) 2-propanol / water to extract ionic residues, the amount of ionic residues determined by measuring the extract by ion chromatography is 2.5 μg / cm per bonded area. 2 Since it is as follows, organic residues inside and around the bonded layer are surely removed by the cleaning step. Therefore, it is possible to manufacture a bonded body in which problems such as a decrease in bonding strength caused by organic residues are suppressed.

[0013] Here, in the method for manufacturing a bonded body of the present invention, it is preferable that the cleaning solvent used in the cleaning step is a mixed solution of 20% - 80% (v / v) 2-propanol / water. In this case, in the above-mentioned cleaning step, organic residues inside and around the bonded layer can be more surely removed, and the amount of organic residues present inside and around the bonded layer can be further reduced.

[0014] Furthermore, in the method for manufacturing a bonded body of the present invention, it is preferable that the thermal decomposition temperature of the organic solvent contained in the silver paste is 300°C or lower, and the sintering temperature in the sintering step is 250°C or higher. In this case, the organic solvent contained in the silver paste can be sufficiently thermally decomposed in the sintering step, the amount of organic residues present inside and around the bonded layer can be reduced, and in the cleaning step, this organic residue can be more surely removed, and it becomes possible to further reduce the amount of ionic residues.

Advantages of the Invention

[0015] According to the present invention, an organic residue in a bonding layer made of a sintered body is sufficiently and surely reduced, and it is possible to provide a bonded body capable of suppressing the occurrence of problems such as a decrease in bonding strength due to the organic residue, and a method for manufacturing the bonded body.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0017] Hereinafter, a bonded body which is an embodiment of the present invention and a method for manufacturing the bonded body will be described with reference to the drawings.

[0018] As shown in FIG. 1, the bonded body 10 according to the present embodiment is obtained by bonding a first member 11 and a second member 12 via a bonding layer 13 made of a silver sintered body. In the present embodiment, the bonded body 10 is a semiconductor device in which a circuit layer (first member 11) of an insulating circuit board and a semiconductor element (second member 12) are bonded via a bonding layer 13.

[0019] And, in the bonded body 10 which is the present embodiment, after immersing the bonded body 10 in 50% (v / v) 2-propanol / water to extract ionic residues, the amount of ionic residues determined by measuring the extract by ion chromatography is 2.5 μg / cm per bonding area. 2 It is as follows.

[0020] By immersing the bonded body 10 in 50% (v / v) 2-propanol / water, organic residues inside and around the bonding layer 13 are extracted into 2-propanol / water as ionic residues. This extract is measured by ion chromatography, and the response value of the electrical conductivity detector of the ion chromatography is taken as the amount of ionic residue. In this embodiment, for calculating the amount of ionic residue, a standard value using an NaCl standard solution is used to obtain the amount of ionic residue (μg) by area conversion.

[0021] As described above, by measuring the amount of ionic residue, it becomes possible to accurately evaluate the amount of organic residues inside and around the bonding layer 13. And, by reducing the amount of the ionic residue in the bonded body 10 to 2.5 μg / cm per bonding area 2 as follows, the organic residues inside and around the bonding layer 13 are sufficiently reduced, and it becomes possible to improve the bonding strength between the first member 11 and the second member 12. Note that the amount of the ionic residue in the bonded body 10 is preferably 1.6 μg / cm or less per bonding area, more preferably 1.0 μg / cm 2 or less, and even more preferably 0.6 μg / cm 2 or less. 2 It is even more preferable to be as follows.

[0022] Next, a method for manufacturing the bonded body 10 according to this embodiment will be described with reference to FIGS. 2 and 3.

[0023] (Paste application step S01) As shown in FIG. 3, a silver paste 23 containing silver powder and an organic solvent is applied to one or both of the bonding surfaces of the first member 11 and the second member 12. The application method is not particularly limited, and for example, a metal mask method, a screen printing method, a dispensing method, etc. can be applied. Here, the organic solvent contained in the silver paste 23 preferably has a thermal decomposition temperature of 300°C or lower. The thermal decomposition temperature of the organic solvent is defined as the temperature at the intersection of the baseline and the tangent line of the heat generation rise at the peak of TG-DTA (extrapolation start temperature). When the organic solvent consists of a plurality of solvents, it is preferable that the thermal decomposition temperature of the solvent with the highest thermal decomposition temperature is 300°C or lower. There is no limitation on the Ag powder used in the silver paste 23, and commercially available Ag powder can be used.

[0024] (Lamination step S02) Next, as shown in FIG. 3, the first member 11 and the second member 12 are laminated via the above-described silver paste 23.

[0025] (Sintering step S03) Next, as shown in FIG. 3, the first member 11 and the second member 12 laminated via the silver paste 23 are heat-treated to sinter the silver paste 23, forming a bonding layer 13 made of a sintered body of silver and bonding the first member 11 and the second member 12. Here, during the heat treatment, organic components such as the solvent contained in the silver paste 23 will decompose and generate gas.

[0026] Note that the heating temperature in the sintering step S03 is not particularly limited, but it is preferably in the range of 150°C or higher and 400°C or lower. Furthermore, during the heat treatment, the laminate may be pressurized in the lamination direction at a pressure of 0.1 MPa or higher and 20 MPa or lower.

[0027] (Washing step S04) Next, as shown in FIG. 3, the first member 11 and the second member 12 joined via the bonding layer 13 are immersed in a cleaning solvent 25, and the bonding layer 13 is cleaned using this cleaning solvent 25. By this washing step S04, organic residues present inside and around the bonding layer 13 are removed, obtaining the joined body 10 which is the present embodiment. In the cleaning step S04, the bonded body 10 is immersed in 50% (v / v) 2-propanol / water to extract ionic residues, and then the amount of ionic residues determined by measuring the extract by ion chromatography is 2.5 μg / cm per bonding area. 2 Cleaning is performed until the following is achieved. It is preferable to use pure water with a conductivity of 1.0 μS / cm or less.

[0028] Here, as the cleaning solvent 25, it is preferable to use 20% - 80% (v / v) 2-propanol / water. Also, the cleaning method is not particularly limited, and immersion cleaning, shaking cleaning, ultrasonic cleaning, etc. can be applied. In this embodiment, ultrasonic cleaning is employed, and the cleaning time is set to 1 minute or more. By applying ultrasonic waves during cleaning, it is possible to sufficiently penetrate the cleaning solvent into the inside and periphery of the bonding layer 13, and efficiently remove organic residues.

[0029] According to the bonded body 10 of this embodiment configured as described above, after immersing the bonded body in 50% (v / v) 2-propanol / water to extract ionic residues, the amount of ionic residues is determined by measuring the extract by ion chromatography. Therefore, it is possible to accurately evaluate the amount of organic residues present inside and around the bonding layer 13. And since the amount of ionic residues is limited to 2.5 μg / cm or less per bonding area, the amount of organic residues present inside and around the bonding layer 13 is sufficiently reduced, and it is possible to suppress the occurrence of problems such as a decrease in bonding strength caused by organic residues. 2

[0030] According to the manufacturing method of the bonded body 10 of this embodiment, after the sintering step S03, it includes a cleaning step S04 for cleaning the bonding layer 13 using the cleaning solvent 25. By this cleaning step S04, the bonded body 10 is immersed in 50% (v / v) 2-propanol / water to extract ionic residues, and then the amount of ionic residues determined by measuring the extract by ion chromatography is 2.5 μg / cm per bonding area. 2Since it is as described below, the cleaning step S04 surely removes the organic residues inside and around the bonding layer 13. Therefore, it is possible to manufacture the bonded body 10 capable of suppressing the occurrence of problems such as a decrease in bonding strength due to organic residues.

[0031] In the present embodiment, when the cleaning solvent 25 used in the cleaning step S04 is 20% to 80% (v / v) of 2-propanol / water, in the above-described cleaning step S04, the organic residues inside and around the bonding layer 13 can be removed more surely, the amount of ionic residues can be further reduced, and the occurrence of problems such as a decrease in bonding strength due to organic residues can be further suppressed.

[0032] In the present embodiment, when the thermal decomposition temperature of the organic solvent contained in the silver paste 23 is 300°C or lower and the sintering temperature in the sintering step S03 is 250°C or higher, the organic solvent contained in the silver paste 23 can be sufficiently thermally decomposed in the sintering step S03, the amount of organic residues remaining inside and around the bonding layer 13 can be reduced, and in the cleaning step S04, this organic residue can be removed more surely, and the amount of ionic residues can be further reduced.

[0033] As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto, and can be appropriately changed without departing from the technical idea of the invention.

Example

[0034] Below, the results of the confirmation experiments conducted to confirm the effectiveness of the present invention will be described.

[0035] A circuit board (thickness: 2 mm) made of a copper plate with gold plating on the outermost surface was prepared as the first member, and a semiconductor element (thickness: 400 μm) made of SiC with gold plating on the outermost surface was prepared as the second member. Note that the bonding area between the semiconductor element and the circuit board was adjusted so as to be shown in Table 1 according to the size of the semiconductor element. Also, a silver paste containing silver powder and an organic solvent was prepared. The thermal decomposition temperature of the organic solvent contained in the silver paste is shown in Table 1.

[0036] The silver paste was applied to the first member with a coating thickness of 100 μm, and the second member was laminated via this silver paste. This laminate was heat-treated under the conditions shown in Table 1 in a nitrogen atmosphere to bake the silver paste and form a bonding layer composed of a sintered body of silver, thereby bonding the first member and the second member.

[0037] After sintering, in Examples 1 to 4 of the present invention, a cleaning step was performed by the cleaning method shown in Table 1. Note that in Comparative Examples 1 and 2, the cleaning step was not performed. Regarding the bonded body obtained as described above, the amount of ionic residues and the bonding strength were evaluated as follows.

[0038] (Amount of ionic residues) The obtained bonded body was immersed in 50% (v / v) 2-propanol / water for 1 minute to extract ionic residues, and then the extract was measured by an ion chromatography apparatus (ICS-5000+ manufactured by Dionex Corporation), and the response amount of the electrical conductivity detector was taken as the amount of ionic residues. In this example, the amount of ionic residues per bonding area was determined using the standard value with a NaCl standard solution. The evaluation results are shown in Table 1.

[0039] (Shear strength) The bonding strength of the bonded body was measured using a shear strength evaluation tester (Bonding Tester PTR-1101 manufactured by Resca Co., Ltd.). The measurement was performed by horizontally fixing the first member of the bonded body and using a shear tool at a position 50 μm above the surface of the bonding layer to push the second member horizontally from the side, and measuring the strength when the second member was broken. The moving speed of the shear tool was set to 0.1 mm / sec. The evaluation results are shown in Table 1.

[0040]

Table 1

[0041] In the comparative example, the amount of ionic residue was 6.7 μg / cm per bonding area 2 and the shear strength was as low as 8 MPa.

[0042] On the other hand, in Examples 1 to 6 of the present invention, the amount of ionic residue was 2.5 μg / cm per bonding area 2 or less, the shear strength was 10 MPa or more, and the bonding strength was excellent. In Examples 1 to 4 of the present invention, the cleaning solvent used in the cleaning step was 20% to 80% (v / v) 2-propanol / water, the thermal decomposition temperature of the organic solvent contained in the silver paste was 300°C or lower, and the sintering temperature in the sintering step was 250°C or higher. The amount of ionic residue was less than 0.6 μg / cm per bonding area 2 and the shear strength was 31 MPa or more, and the bonding strength was particularly excellent.

[0043] From the results of the above confirmation experiments, according to the examples of the present invention, it was confirmed that the organic residue of the bonding layer made of the sintered body was sufficiently and surely reduced, and it was possible to provide a bonded body capable of suppressing the occurrence of problems such as a decrease in bonding strength due to the organic residue, and a method for manufacturing this bonded body.

Claims

1. A joined body in which a first member and a second member are joined via a joining layer made of a silver sintered body, The amount of ionic residue determined by immersing the bonded body in 50% (v / v) 2-propanol / pure water to extract the ionic residue and then measuring the extract by ion chromatography is 2.5 μg / cm per bonding area ２ A bonded body, characterized in that it is as follows.

2. A method for manufacturing a joined body in which a first member and a second member are joined via a joining layer made of a silver sintered body, a laminating step of laminating the first member and the second member via a silver paste containing silver powder and an organic solvent; a sintering step of firing the silver paste disposed between the first member and the second member to form the joining layer made of a silver sintered body; and a cleaning step of cleaning the joining layer using 20% to 80% (v / v) 2-propanol / water as a cleaning solvent. The amount of ionic residue determined by immersing the conjugate in 50% (v / v) 2-propanol / pure water to extract the ionic residue and then measuring the extract by ion chromatography is 2.5 μg / cm per bonding area ２ A method for manufacturing a conjugate, characterized in that it is as follows.

3. The method for manufacturing a joined body according to claim 2, wherein a thermal decomposition temperature of the organic solvent contained in the silver paste is 300°C or lower, and a sintering temperature in the sintering step is 250°C or higher.

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