JP2020083676A - Joined body and manufacturing method of joined body - Google Patents

Abstract

To provide a joined body of ceramic and a metal member having high reliability.SOLUTION: The joined body of ceramic and a metal member includes a ceramic member, a first metal layer formed on the ceramic member and containing an active metal compound, a second metal layer formed on the first metal layer and containing an intermetallic compound consisting of two or more metals, and the metal member formed on the second metal layer.SELECTED DRAWING: Figure 2

Description

The present invention relates to a joined body of ceramic and metal used for an electronic component such as a power module and a method for manufacturing the joined body.

For example, in a circuit board used for a power module or the like, a metal member is joined to a ceramic member. In general, for joining ceramics and a metal member, for example, a brazing material is placed between the ceramic member and the metal member and heated and melted to join the ceramic and the metal member. As such a brazing material, Patent Literature 1 discloses a brazing material that can be easily processed at room temperature without forming an intermetallic compound and can be formed into a shape that is easy to use when brazing. ..

JP 8-52589 A

As described above, the joining of the ceramic and the metal is performed by heating and melting the brazing material. However, the coefficient of thermal expansion of the ceramic member is different from that of the metal member. Therefore, for example, when heat is applied when the brazing material is heated and melted, thermal stress is generated due to the difference in thermal expansion coefficient between the two materials. This thermal stress causes the ceramics to crack and causes residual stress.

If the residual stress of the ceramic member becomes large, it may cause cracks in the ceramic or warp of the ceramic. As a result, the joint strength between the ceramic and the metal member may be reduced.

Therefore, an object of the present invention is to provide a highly reliable bonded body of a ceramic member and a metal member.

In order to achieve the above object, a joined body of the present invention is formed on a ceramic member, a first metal layer containing an active metal compound, formed on the ceramic member, and formed on the first metal layer, and It is characterized by including a second metal layer containing an intermetallic compound composed of two or more kinds of metals, and a metal member formed on the second metal layer.

According to the bonded body of the present invention, the second metal layer is firmly bonded to the first metal layer and the metal member that are firmly bonded to the ceramic member. That is, it becomes possible to provide a bonded body of a ceramic member and a metal member having high bonding strength. As a result, the reliability of the bonded body can be improved.

In the joined body of the present invention, it is preferable that the intermetallic compound is composed of one metal and another metal having a melting point lower than that of the one metal.

According to the above aspect, the intermetallic compound is composed of one metal and another metal having a melting point lower than that of the one metal, so that the second metal layer is bonded to the metal member while the first metal is being bonded. It becomes possible to bond with layers.

In the joined body of the present invention, the one metal has a melting point higher than a reaction start temperature of the ceramic member and the active metal, and the other metal reacts with the ceramic member and the active metal. It is preferable to have a melting point below the starting temperature.

According to the above aspect, the melting point of one metal is higher than the reaction start temperature of the ceramic member and the active metal, and the melting point of the other metal is lower than the reaction start temperature of the ceramic member and the active metal, The second metal layer can be bonded to the first metal layer while being bonded to the metal member.

In the joined body of the present invention, the active metal contains Ti, Zr, Hf, V or Cr, and the active metal compound is any one of a nitride, an oxide or a carbide of the active metal. It is preferable that the intermetallic compound is composed of any one of Cu, Ag or Ni and Sn.

According to the above aspect, for example, when the active metal is Ti, any one of TiO ₂ , TiN, and TiC is contained in the first metal layer. The intermetallic compound is any of Cu-Sn, Ag-Sn, and Ni-Sn. The first metal layer and the second metal layer have high wettability with each other, and the bonded state between the first metal layer and the second metal layer can be made stronger.

In the joined body of the present invention, the metal member is preferably Cu.

According to the above aspect, the intermetallic compound whose main composition is any one of Cu-Sn, Ag-Sn, and Ni-Sn has high wettability with Cu, and the bonding state between the intermetallic compound and the metal layer is high. Can be made stronger. Therefore, it becomes possible to maintain a strong joined state of the joined body.

A power module of the present invention is characterized by including the above-mentioned joined body as a circuit component. According to the above aspect, it is possible to maintain a good joined state between the ceramic member and the metal member, so that it is possible to improve the reliability of the power module.

The method for manufacturing a joined body according to the present invention comprises a step of forming an active metal layer made of an active metal on a ceramic member, a step of forming a metal layer made of a metal on the active metal layer, Forming another metal layer made of another metal having a lower melting point than the one metal on the one metal layer, placing a metal member on the other metal layer, and the other metal And a temperature higher than the melting point of the one metal and lower than the melting point of the one metal.

According to the above invention, when the melting temperature of the other metal reaches the melting point in the heating step, the other metal diffuses into the one metal, whereby an intermetallic compound of the one metal and the other metal is generated. .. Further, at the heating temperature, the reaction between the compound forming the ceramic member and the active metal proceeds, and a reaction product of the active metal and the ceramic member is produced. The intermetallic compound has a good bonding state with the metal member and a good bonding state with the reaction product of the active metal and the ceramic member. Therefore, it becomes possible to bond the metal member to the ceramic member at a temperature sufficiently lower than the heating temperature for manufacturing the conventional bonded body. Therefore, it is possible to reduce the residual stress generated in the ceramic member. As a result, it is possible to prevent the ceramic member from being damaged by cracks or warpage.

In the method for manufacturing a joined body according to the present invention, the ceramic member is a compound containing any one of a nitride, an oxide and a carbide, and the active metal contains Ti, Zr, Hf, V or Cr, and It is preferable that the one metal is Cu, Ag, or Ni, the other metal is Sn, and the metal member is Cu.

According to the above aspect, Sn has a lower melting point than Cu and therefore melts before Cu. The melted Sn diffuses into one metal layer. As a result, one of Cu—Sn, Ag—Sn, and Ni—Sn is produced as the intermetallic compound of the one metal and the other metal.

Next, for example, when the active metal is Ti, the active metal reacts with the ceramic member to generate any one of TiO ₂ , TiN, and TiC.

The metal layer containing the intermetallic compound has high wettability with the metal layer containing the active metal. Therefore, the bonding of the metal layer containing the intermetallic compound with the metal layer containing the active metal can be strengthened. Further, the metal layer containing the intermetallic compound has high wettability with the metal member made of Cu. Therefore, the bonding of the metal layer containing the intermetallic compound to the metal member can be strengthened.

In the method for manufacturing a joined body according to the present invention, the one metal has a melting point higher than a reaction start temperature of the ceramic member and the active metal, and the other metal is the ceramic member and the active metal. It preferably has a melting point lower than the reaction initiation temperature with.

According to the above aspect, the melting point of one metal is higher than the reaction start temperature of the ceramic member and the active metal, and the melting point of the other metal is lower than the reaction start temperature of the ceramic member and the active metal. It becomes possible to join the active metal layer while the metal layer containing the above metal and the intermetallic compound of the other metal is joined to the metal member.

According to the present invention, the second metal layer is firmly bonded to the first metal layer and the metal member that are firmly bonded to the ceramic member. That is, it becomes possible to provide a bonded body of a ceramic member and a metal member having high bonding strength. As a result, the reliability of the bonded body can be improved.

FIG. 1 is a plan view showing the internal configuration of the power module according to the embodiment. It is sectional drawing of the internal structure of the power module along the AA line of FIG. It is sectional drawing which shows the one part aspect of the manufacturing process of the joined body of ceramics and a metal. It is sectional drawing which shows the one part aspect of the manufacturing process of the joined body of ceramics and a metal. It is sectional drawing which shows the one part aspect of the manufacturing process of the joined body of ceramics and a metal. It is sectional drawing which shows the one part aspect of the manufacturing process of the joined body of ceramics and a metal. 5 is a diagram illustrating a test piece used in Test Example 2. FIG. FIG. 9 is a diagram illustrating a test mode in Test Example 2.

An example in which the joined body of ceramics and metal of the present invention is adopted as a circuit component in a power module will be described. FIG. 1 shows a plane of the internal configuration of the power module 100. As shown in FIG. 1, the power module 100 has a circuit component 10.

Circuit patterns 10a, 10b, 10c and 10d are formed on the circuit component 10. On the circuit patterns 10a, 10b, IGBTs (Insulated Gate Bipolar Transistors) 1a, 1b as power semiconductor elements and FWDs (Free Wheeling Diodes) 2a, 2b which are three freewheeling diodes may be soldered or the like. It is attached. The semiconductor element mounted on the circuit component 10 is not limited to the IGBT 1a, and for example, a power semiconductor element that amplifies an electric signal may be mounted.

The emitter electrodes of the IGBTs 1a and 1b and the anode electrodes of the FWDs 2a and 2b are connected to a conductive wire 11a, and these and the circuit patterns 10a, 10b, 10c and 10d are connected to each other by a conductive wire 11b. ing.

The main terminal 3a of the power module is connected to the circuit pattern 10a. The main terminal 3b is connected to the circuit pattern 10c. The main terminal 3c is connected to the circuit pattern 10b. The auxiliary terminals 3d and 3e are connected to the circuit pattern 10d.

FIG. 2 shows a cross section of the internal configuration of the power module 100 taken along the line AA of FIG. As shown in FIG. 2, the circuit component 10 includes a rectangular plate-shaped ceramic substrate 20 as a ceramic member. The circuit component 10 includes a first metal layer 30 formed on the main surface S1 of the ceramic substrate 20 and a second metal layer 40 formed on the first metal layer 30. The circuit component 10 also includes a copper plate 50 as a metal member that is bonded onto the second metal layer 40. That is, the power module 100 includes the circuit component 10 having a joined body of a ceramic member and a metal member. The circuit pattern 10a is formed on the copper plate 50, and the IGBT 1a is joined thereto by an adhesive of a conductor. The metal member is not limited to copper as long as it is a conductor, and may be silver or gold, for example.

The ceramic substrate 20 is formed in a rectangular plate shape, for example. The ceramic substrate 20 is made of a compound containing any one of nitride, oxide and carbide. Examples of compounds forming the ceramic substrate 20 include SiC (silicon carbide), Si ₃ N ₄ (silicon nitride), AlN (aluminum nitride), and Al ₂ O ₃ (alumina). Of these, Si ₃ N ₄ (silicon nitride), AlN (aluminum nitride), and Al ₂ O ₃ (alumina) are preferable because they have excellent heat resistance and insulating properties, but the compound forming the ceramic substrate 20 is particularly preferable. Is not limited.

The first metal layer 30 contains an active metal compound. An active metal compound is a compound of a metal that has an ionization energy lower than that of hydrogen and easily reacts with water or an acid. The active metal compound is composed of one or more active metals selected from Ti (titanium), Zr (zirconium), Hf (hafnium), V (vanadium) or Cr (chromium).

A compound of the ceramic substrate 20 and the first metal layer 30 is contained in the interface between the ceramic substrate 20 and the first metal layer 30 and in the vicinity thereof. For example, when the active metal is Ti and the ceramic substrate 20 is an oxide, TiO ₂ (titanium oxide) is contained in the interface between the ceramic substrate 20 and the first metal layer 30 and in the vicinity thereof.

The second metal layer 40 contains an intermetallic compound composed of two or more kinds of metals. The intermetallic compound is composed of one metal and another metal having a melting point lower than that of the one metal. One metal has a melting point higher than the reaction start temperature between the ceramic member and the active metal (for example, the reaction start temperature at which TiO ₂ is produced by the reaction between the active metal and the ceramic component is 300° C.). For example, Cu (copper), Ag (silver), and Ni (nickel) can be used as the one metal. The melting point of Cu is 1085°C. The melting point of Ag is 961.8°C. The melting point of Ni is 1455°C.

Other metals have melting points lower than the reaction initiation temperature of the ceramic member and the active metal. For example, Sn (tin) can be used as the other metal. The melting point of Sn is 231.9°C.

That is, the intermetallic compound can include, for example, any of Cu—Sn, Ag—Sn, and Ni—Sn, which is formed of any one of Cu, Ag, and Ni and Sn.

The first metal layer and the second metal layer having the above-described structures have high wettability with each other, and the bonded state between the first metal layer 30 and the second metal layer 40 can be made stronger.

In addition, the intermetallic compound contained in the second metal layer 40 has high wettability with the copper plate 50 serving as a metal member, and can strengthen the bonding state between the second metal layer 40 and the copper plate 50. .. Therefore, it becomes possible to maintain a strong joined state of the joined body.

Since the intermetallic compound is composed of one metal and another metal having a melting point lower than that of the one metal, the second metal layer 40 is bonded to the copper plate 50 and the first metal layer 30 is bonded. It becomes possible to join with.

In the present embodiment, the circuit component 10 is formed on the main surface S1 of the ceramic substrate 20. However, the circuit component 10 may be formed on the surface S2 of the ceramic substrate 20 opposite to the main surface S1. Further, the circuit component 10 may be formed on the main surface S1 of the ceramic substrate 20 and the surface S2 opposite to the main surface S1.

As described above, according to the bonded body of the present invention, the ceramic substrate 20 and the first metal layer 30 are firmly bonded to each other via the reaction product of the active metal and the ceramic member, and the first intermetallic compound-containing compound is contained. Since the first metal layer 30 and the copper plate 50, which is a metal member, are strongly bonded via the second metal layer 40, a bonded body of the ceramic substrate 20 having high bonding strength and the copper plate 50, which is a metal member. Can be provided. As a result, the reliability of the bonded body can be improved. In addition, since it is possible to maintain a good bonding state between the ceramic substrate 20 and the copper plate 50, it is possible to improve the reliability of the power module.

A method of manufacturing the circuit component 10 as a bonded body of the ceramic and the metal member described above will be described. 3A to 3D show some aspects of the manufacturing process of the joined body of ceramics and metal.

As shown in FIG. 3A, an active metal layer 70 made of an active metal is formed on the ceramic substrate 20. When forming the active metal layer 70, the contamination adhering to the ceramic substrate 20 hinders the diffusion of the active metal, so the ceramic substrate 20 may be washed. For cleaning the ceramic substrate 20, it is desirable to remove contamination with an organic solvent such as ethanol or acetone.

The step of forming the active metal layer 70 on the ceramic substrate 20 is preferably performed in a low oxygen atmosphere in order to prevent oxidation of the active metal layer 70. The low oxygen atmosphere is, for example, an atmosphere filled with an inert gas such as nitrogen or a rare gas.

The step of forming the active metal layer 70 on the ceramic substrate 20 is performed by, for example, sputtering. The step of forming the active metal layer 70 may be performed by vapor deposition or plating other than sputtering. The active metal is one or more active metals selected from the above Ti, Zr, Hf, V or Cr.

As shown in FIG. 3B, one metal layer 80 made of one metal is formed on the active metal layer 70. The step of forming the one metal layer 80 made of one metal on the active metal layer 70 is performed, for example, by sputtering in a low oxygen atmosphere. The step of forming the one metal layer 80 may be performed by vapor deposition or plating other than sputtering. The first metal has a melting point higher than the reaction start temperature of the ceramic substrate 20 and the active metal. As one metal, for example, a metal selected from the above-mentioned Cu, Ag and Ni can be used.

As shown in FIG. 3C, another metal layer 90 made of another metal is formed on the one metal layer 80. The step of forming another metal layer 90 made of another metal on the one metal layer 80 is performed in a low oxygen atmosphere by, for example, sputtering. The step of forming the other metal layer 90 may be performed by vapor deposition or plating other than sputtering. The other metal has a melting point lower than that of the first metal and lower than the reaction initiation temperature of the ceramic member and the active metal. As the other metal, for example, the above-mentioned Sn can be used.

As shown in FIG. 3D, the copper plate 50 as a metal member is placed on the other metal layer 90. After the copper plate 50 is placed on the other metal layer 90, the copper plate 50 is bonded to the ceramic substrate 20 by heating.

In the heating step, the temperature is higher than the melting point of the other metal and lower than the melting point of the one metal. The heating step is performed in a low oxygen atmosphere. Moreover, it is desirable that the heating step be performed in a reducing atmosphere. The reducing atmosphere is an atmosphere filled with CO (carbon monoxide), H ₂ S (hydrogen sulfide), H ₂ (hydrogen), HCHO (formaldehyde), HCOOH (formic acid), and the like. By performing the heating process in the reducing atmosphere, the oxide film formed on the copper plate 50 or the like can be removed.

The heating step may be performed, for example, at a temperature at which the reaction between the active metal and the ceramic component starts, which is 300° C. or more and less than 600 degrees. This is because the residual stress of the ceramic substrate 20 can be reduced by performing the heating process at a temperature lower than 600°C. Further, since a higher bonding strength of the copper plate 50 to the ceramic substrate 20 can be obtained, it is preferable that the heating step is performed at 400° C. or higher and 500° C. or lower.

In this heating step, Sn (melting point 231.9° C.) has a lower melting point than Cu (melting point 1085° C.) and thus melts earlier than Cu. The melted Sn diffuses into the one metal layer 80. As a result, either Cu—Sn, Ag—Sn, or Ni—Sn is produced as the intermetallic compound of the one metal and the other metal. As a result, the second metal layer 40 is formed.

Next, for example, when the active metal is Ti, TiO ₂ , TiN, and TiC are produced by the reaction between the active metal and the ceramic member. As a result, the first metal layer 30 is formed.

The second metal layer 40 containing the intermetallic compound has high wettability with the first metal layer 30 containing the active metal. Therefore, the bonding of the second metal layer 40 and the first metal layer 30 can be strengthened. Further, the second metal layer 40 has high wettability with the copper plate 50 as a metal member made of Cu. Therefore, the bonding of the second metal layer to the copper plate 50 can be strengthened. Further, by utilizing the diffusion by the one metal for joining the ceramic substrate 20 and the copper plate 50, it is not necessary to completely melt the one metal and the other metal. Therefore, the temperature of the heating process can be lowered. Furthermore, the inclusion of the intermetallic compound in the second metal layer makes it possible to raise the melting point of the second metal layer. Therefore, the reliability of the circuit component 10 can be improved.

The low oxygen atmosphere may be a vacuum atmosphere in which a space filled with a gas having a pressure lower than the atmospheric pressure is used.

Further, the one metal and the other metal do not have to be composed of two layers, and may be composed of multiple layers to facilitate diffusion. For example, one metal and another metal may be alternately laminated. By configuring the one metal and the other metal in this manner, it becomes easy to adjust the film thickness of the second metal layer 40.

[Test Example 1]
(Example 1)
AlN (aluminum nitride) was used as the ceramic substrate 20. Ti was used as the active metal. Cu was used as the first metal. Sn was used as another metal. An active metal, one metal, and another metal were deposited on the ceramic substrate 20 using a sputtering device.

Specifically, the ceramic substrate 20 is washed with acetone, placed in a sputtering apparatus, vacuumed to 10 ^-4 Pa or less, and then in an argon atmosphere (3 Pa) in the order of Ti, Cu, Sn, Film formation was performed with a film thickness of Ti=1 μm, Cu=2 μm, Sn=2 μm. After the film formation, the copper plate 50 was placed on the other metal layer 90 and heated in a formic acid atmosphere (atmospheric pressure) at a joining temperature of 400° C. for a joining time of 10 minutes to obtain a joined body.

(Comparative example)
AlN (aluminum nitride) was used as the ceramic substrate 20. A metal braze and a copper plate 50 were stacked in this order on the ceramic substrate 20 washed with acetone. The ceramics substrate 20 including the metal braze and the copper plate 50 was placed in a heating furnace, vacuumed to 10 ⁻⁴ Pa or less, and then heated at a bonding temperature of 1000° C. for a bonding time of 10 minutes to obtain a bonded body.

The warpage of the joined body of Example 1 and the joined body of the comparative example were inspected from the side of the joined body. As a result, in the bonded bodies according to the examples, the ceramic substrate 20 was not visually observed to be deformed such as warped. On the other hand, in the joined body according to the comparative example, a warp that could be visually discerned was confirmed.

[Test Example 2]
(Example 2)
As shown in FIG. 4A, a rectangular copper plate substrate 20 having a side of 10 mm and a height of 1 mm is provided with a cylindrical copper pin 50 a having a diameter of 2 mm and a height of 5 mm as a copper plate 50 in the first embodiment. It joined by the process demonstrated and the joined body was obtained. That is, in the same manner as in Example 1, Ti, Cu, and Sn were formed in this order on the ceramics substrate 20 to have film thicknesses of Ti=1 μm, Cu=2 μm, and Sn=2 μm, and then copper pins were formed. One end of 50a was brought into contact with the Sn film and heated from above in a formic acid atmosphere (atmospheric pressure) at a bonding temperature of 400° C. for a bonding time of 10 minutes to obtain a bonded body.

(Joint strength test)
The bonding strength between the ceramic substrate 20 and the pin 50a of the bonded body obtained above was measured by the test method shown in FIG. 4B. In FIG. 4B, the first jig TL1 is a jig for fixing the ceramic substrate 20. The first jig TL1 is formed in a rectangular plate shape. A groove GV is formed on one surface of the first jig TL1 and is recessed from the one surface toward the opposite surface. The groove GV is formed in a square shape when viewed from one surface, and is formed so as to be fittable with the ceramic substrate 20.

The second jig TL2 is a jig for fixing the pin 50a. The second jig TL2 is formed in a rectangular plate shape. A through hole TH is formed in the center of the second jig TL2 as viewed from one surface of the second jig TL2 and penetrates from one surface to the opposite surface. The through hole TH has a diameter equal to that of the pin 50a, and the pin 50a can be inserted therethrough.

The ceramic substrate 20 was fitted into the groove GV of the first jig TL1, and the pin 50a was inserted into the through hole TH of the second jig TL2. By applying a load in the direction perpendicular to the joining direction of the pin 50a to the ceramic substrate 20 (the direction of the arrow in the drawing), the load when the pin 50a is separated from the ceramic substrate 20 is measured, and the pin 50a and the ceramic substrate 20 are measured. The bonding strength was 20.

As a result, the bonded body according to this example had a bonding strength sufficiently higher than the bonding strength required as a circuit component.

As described above, it becomes possible to provide a bonded body of the ceramic substrate 20 and the copper plate 50 having high bonding strength while reducing the warpage and other deformations of the ceramic substrate 20.

100 power module 10 circuit component 20 ceramics substrate 30 first metal layer 40 second metal layer 50 copper plate 70 active metal layer 80 one metal layer 90 another metal layer

Claims (9)

A ceramic member,
A first metal layer formed on the ceramic member and containing an active metal compound;
A second metal layer formed on the first metal layer and containing an intermetallic compound composed of two or more kinds of metals;
A metal member formed on the second metal layer;
A zygote characterized by containing. The joined body according to claim 1, wherein the intermetallic compound is composed of one metal and another metal having a melting point lower than that of the one metal. The one metal has a melting point higher than the reaction start temperature of the ceramic member and the active metal,
The bonded body according to claim 2, wherein the other metal has a melting point lower than a reaction start temperature of the ceramic member and the active metal. The active metal includes Ti, Zr, Hf, V or Cr,
The active metal compound is a nitride, oxide or carbide of the active metal,
The joined body according to any one of claims 1 to 3, wherein the intermetallic compound is composed of Cu, Ag, or Ni and Sn. The joined body according to claim 4, wherein the metal member is Cu. A power module comprising the joined body according to any one of claims 1 to 5 as a circuit component. A step of forming an active metal layer made of an active metal on the ceramic member,
Forming a metal layer of one metal on the active metal layer,
A step of forming another metal layer made of another metal having a lower melting point than the one metal on the one metal layer,
Placing a metal member on the other metal layer,
Heating to a temperature higher than the melting point of the other metal and lower than the melting point of the one metal;
A method for producing a joined body, comprising: The ceramic member is a compound containing any of nitride, oxide or carbide,
The active metal includes Ti, Zr, Hf, V or Cr,
The one metal is Cu, Ag or Ni,
The other metal is Sn,
The method for manufacturing a joined body according to claim 7, wherein the metal member is Cu. The one metal has a melting point higher than the reaction start temperature of the ceramic member and the active metal,
The method for manufacturing a joined body according to claim 7 or 8, wherein the other metal has a melting point lower than a reaction start temperature of the ceramic member and the active metal.

Images