JP2008080392A - Joining body and joining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joining body which can keep excellent mechanical strength even under high temperature conditions using joining material which does not substantially contain lead, and further to provide a semiconductor device. <P>SOLUTION: A joining layer composed of Sn formed by the physical vapor deposition method and a metallic material having a melting point higher than the melting point of Sn and higher than 260°C is used as a joining material instead of a metallic alloy containing lead and gold as principal components. The joining layer provided on one portion to be joined is joined on the other portion to be joined. As a result, excellent joining conditions can be achieved, and high strength at a high temperature can be kept within the temperature range from 300°C to 450°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

In particular, the present invention relates to a joined body and a joining method that are preferably used for joining electronic device components, and more particularly to a joined body and a joining method having improved heat resistance.

  Solder bonding technology, which is a bonding technology using a certain object and a material having a lower melting point than that object, has been used for a long time, and semiconductors such as microprocessors, memories, resistors, and capacitors have also been used for bonding electronic devices. Widely used for joining devices and electronic components to mounting boards. Solder bonding not only mechanically fixes a component to a substrate, but also has an advantage of being electrically bonded by including a conductive metal in the solder.

  Today, as personal devices such as personal computers and mobile phones are rapidly spreading, the selection of bonding materials and bonding methods in electronic component mounting technology is becoming increasingly important.

  Conventionally, tin-lead eutectic solder has been frequently used because it is extremely suitable for practical use. However, since the lead contained in the tin-lead eutectic solder is harmful to the human body, there is an urgent need to develop a so-called lead-free solder that does not contain lead.

  On the other hand, among the current semiconductor devices, for example, power device bonding materials are mainly low-temperature solder (Sn—Pb eutectic solder) having a melting point of 183 ° C. and high-temperature solder (Pb—) having a melting point of about 300 ° C. 5Sn solder) is widely used, and is used properly according to the process.

  Among these, for low-temperature solders, those centered on tin-silver-copper alloys have reached the stage of practical application, and in the next few years, many set manufacturers will replace lead-free eutectic solders. It is scheduled to be completed.

  However, for a high-temperature solder, that is, a bonding material that forms a bonding portion that maintains good mechanical strength even at a high temperature condition of 260 ° C., for example, a gold-based alloy containing gold as a main component other than a high-lead-containing material is used. Although it is mentioned, it is a difficult material to use for general purposes because it uses a precious metal gold, and the material price increases significantly. Further, metal alloys mainly composed of metal materials other than lead and gold have not yet been put into practical use as high-temperature solders.

  Up to now, Zn-based alloys have been cited as candidates as one of the bonding materials that form a bonding portion that has a metal material other than lead and gold as a main component and maintains good mechanical strength even at a high temperature of 260 ° C. (See Patent Documents 1 and 2). Since this bonding material is a metal material made of Zn element, it is inexpensive and is a bonding material that is environmentally friendly. However, since it has poor wettability with copper and is hard as a bonding material, it has not been put into practical use.

Further, an attempt has been made to apply a high temperature solder to a Sn-based alloy containing Sn as a main component (see Patent Documents 3 and 4), but in the case of a Sn-based alloy, the bondability and hardness with a material to be bonded such as Cu. However, since liquefaction starts at a low melting point, it is difficult to satisfy the heat resistance as a high-temperature solder.

JP 2004-237357 A JP 2001-121285 A JP 2003-364363 A JP 2001-284792 A

The present invention uses a bonding material that does not substantially contain lead and gold, and a bonding method, a bonded body, and a material that can form a bonded portion capable of maintaining good mechanical strength even under high temperature conditions in a short time. Bonding method, bonded body, and bonding method capable of maintaining good mechanical strength at the bonding portion between the semiconductor element and the lead frame using a bonding material that does not contain lead in general An object of the present invention is to provide a semiconductor device manufactured by the above method.

  1st this invention contains the metal material which has 1st to-be-joined member, Sn, and the melting | fusing point more than said Sn, and said Sn is 35 to 70% by mass ratio, and solid phase A joined body having a joining layer having a line temperature of 260 ° C. or higher and a second member to be joined.

  According to a second aspect of the present invention, a thin film is formed on a surface of a first member to be bonded, which is a metallic material having a melting point of Sn and the Sn or more and having a composition of Sn of 35% to 70%. It is formed by the method, and then brought into contact with the second member to be joined, heated under a temperature condition of 300 ° C. or higher and 450 ° C., and pressurized and joined if necessary.

The bonding layer obtained by the bonding preferably has a solidus temperature of 260 ° C. or higher.

  The joined body of the present invention has sufficient joint strength without substantially using harmful lead and expensive gold, and can maintain mechanical strength even under high temperature conditions.

According to the bonding method of the present invention, it is possible to ensure a good bonding state under a bonding temperature condition of 300 ° C. or higher and 450 ° C. or lower, substantially using no harmful lead and expensive gold, and A joint having high heat resistance is formed in a joining time equivalent to that of a conventional high-temperature solder.

[Principle of the Invention]
In the present invention, when bonding is performed using a bonding material composed of Sn and a metal element having a higher melting point than this, the bonding material is applied to the surface of the member to be bonded in a thin film form and added to Sn. In addition to enabling bonding at a temperature lower than the melting temperature of the refractory metal, the resulting bonding layer is improved in heat resistance in order to form a refractory alloy.
That is, among the components constituting the bonding material, Sn, which is a low melting point metal, and an additive metal component having a higher melting point contact each other in the thin film, and are heated to a temperature higher than the melting temperature of the low melting point metal. The high melting point metal is dissolved in the molten low melting point metal and alloyed to form a high melting point alloy.

[First embodiment: joined body]
As shown in FIG. 1 which is a schematic cross-sectional view of a joined body, the joined body 4 of this embodiment includes a first joined member 1 and a second joined member 3 that are Sn and Sn or more. A metal material having a melting point is contained, and the Sn is bonded by the bonding layer 2 having a mass ratio of 35% to 70%.
In the joined body, the joining layer 2 is preferably made of a material having a solidus temperature of 260 ° C. or higher. When the solidus temperature is below 260 ° C., if this bonded body is heated to 260 ° C. or higher, the bonded portion is melted and the high temperature strength is not maintained.

  The thin film-like bonding layer of the present embodiment is made of a first component made of Sn and a metal material added to the first component. As the second component to be added, at least a refractory metal element is used rather than the first component metal element. Specific examples of the refractory metal element include Ag, Cu, Ni, Au, Sb, Bi, Co, and Al. Two or more kinds of elements used as the second component may be selected from the elements described above. Further, when an element having a melting point lower than that of Sn is contained, the content is preferably several percent or less with respect to the bonding layer.

  As the bonding layer material of the present invention, an AgCuSn-based alloy is preferably used, and more specifically, Ag22Cu25Sn53, Ag13Cu35Sn52, Ag13Cu40Sn47, Ag13Cu45Sn42, and the like are preferable, but not limited thereto.

  When the second member to be bonded is a high thermal expansion material such as Cu, it is preferable to select a bonding material that can be bonded at a bonding temperature of 400 ° C. or lower. When the second bonding member is a low expansion material such as an Fe-42Ni alloy (hereinafter referred to as 42 alloy), it is desirable to select a bonding material that can be bonded at a bonding temperature of 450 ° C. or lower. Further, it is desirable to select a bonding material that can be bonded at a bonding temperature of 450 ° C. or lower even when the second member to be bonded is coated with a high expansion material such as Cu on the surface of a low expansion material such as 42 alloy. Joining at a temperature equal to or higher than the joining temperature is not preferable because thermal stress due to the difference in thermal expansion coefficient between the first member to be joined and the second member to be joined increases to cause joining strain. In particular, when the second member to be joined does not contain Cu, Ag, Au, or Sb, the Sn mass ratio of the joining material is desirably 50% or less.

  Further, the bonding layer may contain an intermetallic compound generated by dissolving and diffusing at least one constituent metal element of the first bonded member and the second bonded member.

  Depending on the joining conditions, as shown in FIG. 2 which is a cross-sectional view of the joined body, Sn and the first to-be-bonded material may be present at the interface between the first to-be-joined member 1 and the second to-be-joined member 3 and the joining layer 7. The intermetallic compound layer 8 made of the constituent elements of the joining member 1 and the intermetallic compound layer 9 made of the constituent elements of the Sn and the second joined member 3 may be formed. Even in such a joined body, the effects of the present invention can be achieved.

  The joined body of the said embodiment can be manufactured with the joining method demonstrated below.

[Second Embodiment: Joining Method]
Hereinafter, the bonding method according to the present embodiment will be described.
In the bonding method of the present embodiment, a thin bonding material containing Sn and a metal material having a higher melting point than Sn is contained on the surface of the first member to be bonded, and the Sn content is 35% to 70%. Forming into a shape,
A bonding method including a step of bonding the thin film bonding material formed on the surface of the first member to be bonded and the second member to be bonded to each other by heating at 300 ° C. or higher, more preferably 350 ° C. or higher. It is. The upper limit temperature of the bonding temperature differs depending on the second member to be bonded, and when having a low expansion material such as 42 alloy, the bonding temperature is characterized by bonding at a bonding temperature of 450 ° C. or lower. The bonding is performed at a bonding temperature of 400 ° C. or lower.

In the joining step in this joining method, the heating of the first member to be joined, the thin film joining material and the second member to be joined, and the close contact thereof may be performed at the same time, or one of them may be preceded. You may go. Moreover, it can also carry out by pressurizing, when making it closely_contact | adhere.
In the joining step, the heating time is desirably 0.1 seconds or more, and it is more preferable if heating is performed so that the heating time at the peak temperature is 0.5 seconds or more. The heating time may be 30 seconds or less at the longest, and the heating may be performed so that the heating time at the peak temperature is 10 seconds or less.
The soldering process may be performed in an atmosphere in the air, but when a bonding material containing a metal that is easily oxidized is used, it is preferable to perform heating in a non-oxidizing atmosphere such as nitrogen. Furthermore, it is more preferable to perform heating in a reducing atmosphere containing hydrogen.

(Joining material and joining layer)
The bonding material used in the bonding layer 2 shown in the first embodiment can be used for the thin-film bonding material of the present embodiment. That is, in the bonding material composed of the first component composed of Sn and the additive component composed of the metal element added thereto, a refractory metal element is used as the second component rather than the first component metal element. Two or more kinds of elements used as the second component may be selected from the elements described above.

As a means for forming the bonding material as a thin film on the surface of the first member to be bonded, a physical film forming method, in particular, vacuum deposition, ion plating, electron beam treatment, etc. can be adopted. In addition to the physical film forming method, a plating method or a chemical film forming method can also be employed.
In the bonding material of the present embodiment, all components may be formed into a thin film at the same time, or each component may be formed sequentially. In the case of sequentially depositing each component, a single element layer may be divided into a plurality of layers. Specifically, if the A metal and the B metal are formed, the film can be divided into four layers such as an A layer, a B layer, an A layer, and a B layer. Such a film forming method is preferable because the alloying of the A metal and the B metal proceeds rapidly.
The thickness of the thin film bonding material is preferably in the range of 1 μm or more and 50 μm or less. When thinning over a plurality of layers, the total film thickness is preferably in the above range. When the metal layer is thinner than 1 μm, it is difficult to ensure good bonding properties. When the metal layer is 50 μm or more, when the bonding layer is formed by a physical film forming method, the production efficiency may be hindered. This is not preferable.

The material of the bonding layer obtained by the bonding step is an alloy of the elements constituting the bonding material, and the bonding layer includes constituent metal elements of the first member to be bonded and the second member to be bonded. An intermetallic compound formed by dissolving and diffusing may exist.
The solidus temperature of the bonding layer material is preferably 260 ° C. or higher. When the liquidus temperature exceeds 260 ° C., the joint is melted and the high temperature strength is not maintained.

(Members to be joined)
In this embodiment, a metal material can be used for the first member to be joined and the second member to be joined. Although the metal material to be used can be selected according to a use and is not specifically limited, It is desirable that it is a material with favorable joining property with molten Sn. Specifically, Au, Ni, Ag, Cu, Pd, Pt, Al, Ge, Be, Nb, Mn, or alloys thereof are preferable.

(effect)
According to the present embodiment, even if an alloy material having a high melting point is used for solder joining, the joining time does not extremely increase, so that the production efficiency of the joined body is not lowered. For example, in an actual semiconductor device mounting process, it is possible to set a manufacturing speed comparable to the current manufacturing speed using lead-containing solder, and the manufacturing efficiency is not reduced.

  Further, according to the bonding method of the present embodiment, since the bonding layer having a heat resistance of 260 ° C. or higher is formed, the heat resistance of the bonding layer can be maintained even under a high temperature condition of 260 ° C. It is possible to sufficiently meet the demand for heat resistance at 260 ° C., which is required as a system mount material. Further, in the bonding material, the phase in which the constituent elements of the first bonded member or the second bonded member are dissolved in the bonding layer, or the bonding material constituting elements in the bonding layer and each bonded member configuration An intermetallic compound phase composed of elements may be generated. As a result, a bonded body with good mechanical strength can be obtained in a short time even under high temperature conditions.

  The joined body and joining method according to the present invention may be used in any field where solder joining can be performed, but in particular, an electronic equipment component, a semiconductor device, especially power, which is placed under high temperature conditions during the manufacturing process or product use. It is suitably used for joining components in a semiconductor device. In particular, it is particularly preferably used for joining a semiconductor element and a lead frame.

[Third Embodiment: Modification of Joining Method]
In the said 1st Embodiment, although the example which forms a joining material in one surface of a to-be-joined member was shown, a joining material was shown on both surfaces of the 1st to-be-joined member and the 2nd to-be-joined member. It may be formed.
In this case, the two bonding materials may be layers having the same composition, or layers having different compositions. The solder joint of the present invention can be formed by adjusting the composition of each layer so that the joint layer material after the final solder joint has the composition of the joint layer of the present invention.
Moreover, the thickness of the thin film formed on each substrate surface can be set so that the total amount thereof is in the range of 1 μm or more and 50 μm or less.

[Fourth Embodiment: Another Modification of Joining Method]
In the bonding method of this embodiment, at least one of the first member to be bonded and the second member to be bonded is formed by forming a metallized layer on the surface of a base material made of metal, ceramics, or semiconductor. is there. This method is suitable when a material that is not suitable for soldering is used as a member to be joined.

  As described above, the first member or the second member is composed of a base material made of a material such as metal, ceramics, or semiconductor, and a metallized layer formed on the surface thereof. The metallized layer is preferably a material selected from the group consisting of Au, Ni, Ag, Cu, Pd, Pt, Al, Ge, Be, Nb, Mn, or a metal alloy using these metal materials. It can be selected according to the application and is not particularly limited. This metallized layer may be a single material layer, or may be composed of a plurality of metallized layers made of different materials. As means for metallizing on the surface of the base material, physical or chemical film formation methods such as vapor deposition, sputtering, plating treatment, and electron beam treatment can be employed.

  The thickness (average thickness) of the metallized layer is not particularly limited, but is preferably in the range of 0.1 μm or more and 500 μm or less. If this thickness is 0.1 μm or less, sufficient solder joint strength cannot be obtained. In addition, forming a metallized layer of 500 μm or more requires a long time to form a thin film and is not practical.

  In the present embodiment, a bonding material layer can be formed on the surface of the metallized layer by applying the film forming method, and bonding can be performed in the same manner as in the method in the first embodiment. Further, a bonding material layer can be formed on the surface of the bonding member not provided with the metallized layer, and bonded to the base material provided with the metallized layer.

[Fifth Embodiment: Semiconductor Device Applying the Joining Technique]
The solder joining technique can be applied to the manufacture of semiconductor devices.

Hereinafter, a semiconductor device to which the present invention can be applied will be described with reference to the drawings.
FIG. 3 is a cross-sectional view showing an example of a semiconductor device to which the bonding technique of the present invention is applied. The semiconductor device according to this embodiment includes a lead frame 34 having a lead portion 37 serving as an external terminal, a semiconductor element 36 disposed on the surface of the lead frame 34, and the lead frame 34 and the semiconductor element 36. It has the joining layer 35 which has joined, and the sealing resin 32 which surrounds these.
The lead frame 34 may be subjected to, for example, silver plating or copper plating on a metal surface of a low thermal expansion material such as 42 alloy or a high thermal expansion material such as copper. Examples of the semiconductor device of this embodiment include a diode, a transistor, a capacitor, and a thyristor.

  In the semiconductor device of the present embodiment, the surface of the semiconductor element is made of a material selected from the group consisting of Au, Ni, Ag, Cu, Pd, Pt and Al, or a metal alloy using these metal materials. The metal thin film of the semiconductor element and the metal lead frame on which the semiconductor element is mounted are bonded to each other by a bonding material composed of Sn and a metal element having a higher melting point. To do.

  In the semiconductor device, the metal frame may be made of Au, Ni, Ag, Cu, Pd, Pt, and Al, or a material selected from the group consisting of metal alloys using these metal materials. The surface of any metal matrix is metallized with a metal thin film using a material selected from the group consisting of Au, Ni, Ag, Cu, Pd, Pt and Al, or a metal alloy using these metal materials. May be.

  In the present embodiment, the metal material having a melting point equal to or higher than Sn constituting the bonding material is selected from the group consisting of Ag, Cu, Ni, Pd, Pt and Al, or a metal alloy using these metal materials. It is preferable to use a material. Even if a trace amount of other metal elements is added, the effect of the present invention does not change.

(effect)
According to the method of manufacturing a semiconductor device and the semiconductor device of the present embodiment, the semiconductor element and the lead frame are not exposed to a high lead-containing bonding material, which is harmful in the manufacturing process of the semiconductor device, even when exposed to high temperature conditions. Therefore, a highly reliable semiconductor device can be provided in a short time.

  Hereinafter, the present invention will be described in detail by way of examples.

(Example 1)
The semiconductor element and the lead frame in the power semiconductor device were joined. FIG. 3 is a cross-sectional view showing a bonding form between a 2.5 × 3.0 × 0.6 mm semiconductor element and a lead frame. In this power semiconductor module, a metalized layer 1 made of gold having a thickness of 0.1 μm is formed on a 10 mm square silicon semiconductor element 11 by depositing gold as a first bonded member by vapor deposition of gold. . Further, on the surface of the metallized layer 1, a 10 μm-thick bonding material 5 containing substantially 25% Sn and 22% Cu with the balance being Ag was formed by vapor deposition.
Further, the metallized layer 3 made of Cu as the second member to be joined was applied to the surface of the lead frame 12 made of 42 alloy by electroless plating.
Further, the bonding material 5 and the metallized layer 3 were laminated so as to be in contact with each other, and then heated to perform bonding. The heating was performed on a hot plate in a forming gas (nitrogen + hydrogen) atmosphere having an oxygen concentration of 100 ppm or less. The heating conditions were 450 ° C. and 5 seconds.

  From the SEM observation of the cross section of the bonded interface after bonding, no significant voids were observed, indicating good bonding properties.

  Finally, the joined lead frame and the semiconductor element were sealed with a resin to obtain a power semiconductor device having heat resistance of 260 ° C.

(Example 2)
The power semiconductor and the lead frame were bonded in the same manner as in Example 1 except that Ag13Cu35Sn52 was used as the bonding material.
When a cross section of the bonded interface after bonding was observed with an SEM, no significant voids were observed, indicating good bonding properties.

(Example 3)
The power semiconductor and the lead frame were bonded in the same manner as in Example 1 except that Ag13Cu40Sn47 was used as the bonding material.
When a cross section of the bonded interface after bonding was observed with an SEM, no significant voids were observed, indicating good bonding properties.

(Evaluation)
A high temperature shear test was performed on the joined bodies prepared in the above Examples. An outline of the test apparatus is shown in FIG. As shown in FIG. 4, a test body in which the semiconductor element 43 is bonded to the surface of the lead frame 41 via the bonding layer 42 is applied with a force in the direction of the arrow using the pressure piece 44, The strength was measured. This measurement was performed on each test piece for 10 samples each at room temperature and at 275 ° C. heating. The result is shown in FIG.
FIG. 5 is an example of the shear strength test result for the sample provided by the embodiment of the present application, and the shear strength at room temperature and 275 ° C. is measured. In each example, 3 to 5 samples were prepared, the shear strength of each sample was measured, and the average value was calculated.
As can be seen from FIG. 5, in each result, even when heated at 275 ° C., the shear strength was comparable to that at room temperature, indicating that it had heat resistance.

Example 4
In this example, a power semiconductor device was obtained in the same manner as in Example 1 except that a metallized layer made of Ag was formed on a lead frame made of 42 alloy as the second member to be joined.

  From the SEM observation of the cross section of the bonded interface after bonding, no conspicuous voids were generated and good bonding property was exhibited, and the bonding property at high temperature was also good.

  Finally, the joined lead frame and the semiconductor element were sealed with a resin to obtain a power semiconductor device having heat resistance of 260 ° C.

(Example 5)
In this example, on the surface of the 0.1 μm-thick gold layer 1 and the 10 μm-thick Sn layer 5 formed by vacuum deposition on the semiconductor element 13 of 2.5 × 3.0 × 0.6 mm size, A power semiconductor device was obtained in the same manner as in Example 1 except that a 10 μm thick Zn—Sn bonding layer 6 was formed by vacuum deposition. The Zn—Sn bonding layer 6 formed by vapor deposition uses a Zn—Sn alloy composed of 50.0% by mass of Sn and the balance of Zn. This bonding layer 6 was mounted on a tin layer 8 provided on a lead frame 7 made of Cu, and heated on a hot plate in a forming gas (nitrogen + hydrogen) atmosphere having an oxygen concentration of 100 ppm. The heating conditions were 400 ° C. and 5 seconds.

  From the SEM observation of the cross section of the bonded interface after bonding, no conspicuous voids were generated and good bonding property was exhibited, and the bonding property at high temperature was also good.

  Finally, the joined lead frame and the semiconductor element were sealed with resin to obtain a power semiconductor device.

(Examples 6-11 and Comparative Examples 1-3)
In Example 6, as a first member to be bonded, a member to be bonded that was copper-plated to 42 alloy, in Examples 7 to 11, copper was used as the member to be bonded, and the AgCuSn-based bonding material was in a ratio as shown in Table 1. In this example, each element is formed into a film by vapor deposition. In the case of Example 6, the heating was evaluated at 450 ° C., and in the case of Examples 7 to 11, the bonding property was evaluated at 400 ° C. in an N ₂ atmosphere.
On the other hand, 42 alloys were used as the materials to be joined in Comparative Examples 1 and 2, and each element was formed by vapor deposition in the same manner as in Example 6 so that the ratios shown in Table 1 were obtained. In Comparative Example 3, copper was used as the member to be joined. Each element was formed into a film by vapor deposition and evaluated so as to be Ag13Cu75Sn12. Example,
Table 1 shows the results. The evaluation was performed based on the bondability of each bonding material and the bonding strength at 265 ° C. As in Example 1, the bonding interface was observed by SEM, and “Good” indicates that the bonding is good, “V” indicates that a void is generated at the bonding interface, and “X” indicates that the bonding is not bonded. Moreover, the measurement of joining strength produced the test body to which the semiconductor element was joined similarly to Example 4, and measured the shear strength in 260 degreeC of each test body. The specimens that were not joined and for which the shear strength could not be measured were indicated by “-”, and the specimens that could be measured for the specimens showed the strength at break (kg · f).
All of Examples 6 to 11 of the present invention were sufficiently joined, whereas Comparative Example 1 was not joined. In addition, each of Examples 6 to 11 had a bonding strength greater than 10 kg · f and showed a sufficient bonding strength, while Comparative Examples 2 and 3 had a bonding strength at 265 ° C. of 10 kgf or less (in Table 1, “×”). It was not practically sufficient.

It is sectional drawing of the conjugate | zygote of this-application embodiment. It is sectional drawing which shows the other example of the conjugate | zygote of embodiment of this application. It is sectional drawing of the semiconductor device to which this invention is applied. It is a conceptual diagram of the apparatus which measures the heat resistance of a joined body. It is a graph which shows the effect of the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st to-be-joined member 2 ... Joining layer 3 ... 2nd to-be-joined member 4 ... Joined body 7 ... Joining layer 8, 9 ... Intermetallic compound layer 10 ... Joined body 32 ... Sealing resin 34 ... Lead frame 35 ... Junction layer 36 ... Semiconductor element 37 ... Lead wire

Claims (5)

  It includes a first member to be bonded, Sn formed on the member to be bonded, and a metal material having a melting point higher than Sn, and the Sn is made of a material having a mass ratio of 35% to 70%. A joined body comprising a joining layer and a second joined member.   2. The joined body according to claim 1, wherein the joining layer is made of a material having a solidus temperature of 260 ° C. or higher. Forming a thin film bonding material containing Sn and a metal material having a melting point equal to or higher than Sn and containing Sn in a range of 35% to 70% on the surface of the first member to be bonded;
A step of heating the thin film bonding material formed on the surface of the first member to be bonded and the second member to be bonded to a temperature of 300 ° C. or higher and 450 ° C. or lower and bonding them to each other. Joining method.   The bonding method according to claim 3, wherein the bonding layer formed by the bonding step is made of a material having a solidus temperature of 260 ° C. or higher. 5. The bonding method according to claim 3, wherein the thin film bonding material is formed on the surface of the first bonded member by a physical or chemical film forming method.

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