WO2022153891A1

WO2022153891A1 - Laminate, method for manufacturing same, and power module

Info

Publication number: WO2022153891A1
Application number: PCT/JP2022/000041
Authority: WO
Inventors: 優也弓場; 篤士酒井; 賢久上島; 賢太郎中山; 佳孝谷口
Original assignee: デンカ株式会社
Priority date: 2021-01-12
Filing date: 2022-01-04
Publication date: 2022-07-21
Also published as: JPWO2022153891A1; JP2023026431A; JP7538845B2; JP7186929B1

Abstract

According to one aspect of the present disclosure, there is provided a laminate comprising a ceramic plate, a stress-relieving layer formed on the ceramic plate, and a metal circuit layer formed on the stress-relieving layer, the stress-relieving layer having: an alloy layer in which the magnesium content is 7.5 mass% or less and which has an average thickness of less than 0.2 mm, the alloy layer being in contact with the ceramic plate; and a metal layer in which the magnesium content is lower than that in the alloy layer, the metal layer being in contact with the metal circuit layer.

Description

Laminates, their manufacturing methods, and power modules

This disclosure relates to a laminate, a method for manufacturing the laminate, and a power module.

Power modules that control large currents are used in fields such as automobiles, electric railways, industrial equipment, and power generation. A ceramic substrate is used as the insulating substrate mounted on the power module. The ceramic substrate has a ceramic plate and a metal circuit layer provided on the ceramic plate.

In recent years, there has been a tendency to increase the thickness of the metal circuit layer in order to increase the current density. Therefore, the thermal stress caused by the difference in thermal expansion between the ceramic plate and the metal circuit layer is large. Therefore, the ceramic substrate is required to have further improved durability against heat cycles. From the viewpoint of improving the durability of the ceramic substrate against the heat cycle, it is said that it is effective to provide an intermediate layer for reducing the thermal stress caused by the difference in thermal expansion between the ceramic plate and the metal circuit layer.

Further, from the viewpoint of improving the productivity and reliability of the ceramic substrate, it is possible to form a circuit without requiring an etching process or the like, and a method of manufacturing a ceramic substrate by suppressing oxidation of the material due to heating has been studied. There is. As an example, a method of forming a metal circuit layer by a cold spray method has been studied (for example, Patent Documents 1, 2, etc.).

Japanese Unexamined Patent Publication No. 2013-018190 International Publication No. 2018/135490

The advantage of the method for manufacturing a ceramic substrate by the cold spray method is that a metal circuit can be formed on the ceramic plate without using a brazing material. However, on the other hand, by forming the metal circuit layer without using a brazing material, the bonding between the ceramic plate and the metal circuit layer may be weaker than that of the ceramic substrate obtained by the conventional manufacturing method. .. It would be useful if a ceramic substrate could be manufactured by the cold spray method, which suppresses a decrease in bondability between the ceramic plate and the metal circuit layer and has excellent durability against heat cycles.

An object of the present disclosure is to provide a laminate having excellent durability against a heat cycle and a method for producing the same. The present disclosure is also intended to provide a reliable power module.

One aspect of the present disclosure includes a ceramic plate, a stress relaxation layer formed on the ceramic plate, and a metal circuit layer formed on the stress relaxation layer, and the stress relaxation layer contains magnesium. The alloy layer in contact with the ceramic plate having an amount of 7.5% by mass or less and an average thickness of less than 0.2 mm has a lower magnesium content than the alloy layer and contacts the metal circuit layer. Provided is a laminate having a metal layer and a metal layer.

In the above laminated body, the stress relaxation layer has an alloy layer and a metal layer, and the alloy layer in contact with the ceramic plate contains magnesium, so that the adhesion between the ceramic plate and the metal circuit is strong. The laminate also has a low magnesium content in the metal layer in contact with the metal circuit layer, and the alloy layer is provided so as to have a thickness less than a predetermined thickness, so that the stress relaxation layer becomes too hard. Since it can be suppressed and the metal layer side of the stress relaxation layer can be appropriately thermally expanded, the durability against the heat cycle is excellent as a whole.

The average thickness of the alloy layer may be 0.02 mm or more and less than 0.2 mm.

The coefficient of thermal expansion of the stress relaxation layer may be larger than the coefficient of thermal expansion of the ceramic plate and may be larger than the coefficient of thermal expansion of the metal circuit layer. When the coefficient of thermal expansion of the stress relaxation layer satisfies the above conditions, the thermal stress from the metal circuit layer having a larger coefficient of thermal expansion than the ceramic plate can be more sufficiently relaxed, and the durability against the heat cycle is further improved. It can be further improved.

The metal layer may contain aluminum.

The average thickness of the metal layer may be more than 0.1 mm.

The ceramic plate may be a silicon nitride plate, an aluminum nitride plate, or an aluminum oxide plate material.

One aspect of the present disclosure is a circuit board, a semiconductor element electrically connected on one main surface of the circuit board, and a heat radiating member connected on the other main surface of the circuit board. Provided is a power module in which the circuit board is the above-mentioned laminate.

The power module is excellent in reliability because the circuit board is the above-mentioned laminated body.

One aspect of the present disclosure is a step of forming a first deposited layer in contact with a ceramic plate by spraying a first metal powder containing magnesium together with an inert gas from a nozzle onto the surface of the ceramic plate, and the above. A step of heat-treating the first deposited layer in an inert gas atmosphere to form an alloy layer, and a second metal powder having a magnesium content smaller than that of the first metal powder are combined with the inert gas to form the alloy. A step of forming a second deposited layer in contact with the alloy layer by spraying on the surface of the layer, and a step of heat-treating the second deposited layer in an inert gas atmosphere to form a metal layer. A step of forming a third deposited layer in contact with the metal layer by spraying a third metal powder containing metal particles from a nozzle together with an inert gas onto the surface of the metal layer, and the third Provided is a method for producing a laminated body, comprising a step of heat-treating the deposited layer of the above in an inert gas atmosphere to form a metal circuit layer.

The above-mentioned method for producing a laminate can produce a laminate having an alloy layer, a metal layer, and a metal circuit layer on a ceramic plate from the ceramic plate side by spraying metal powder. Then, according to the manufacturing method, it is possible to form an alloy layer and a metal layer so that the magnesium content gradually decreases from the ceramic plate side, and a laminate having excellent durability against a heat cycle is manufactured. be able to.

The first metal powder may be a gas atomizing powder containing aluminum-magnesium alloy particles.

According to the present disclosure, it is possible to provide a laminate having excellent durability against heat cycles and a method for producing the same. According to the present disclosure, it is also possible to provide a power module having excellent reliability.

FIG. 1 is a schematic cross-sectional view showing an example of a laminated body. FIG. 2 is a schematic cross-sectional view showing an example of the laminated body. FIG. 3 is a schematic view showing an example of a process of forming an alloy layer on a ceramic plate. FIG. 4 is a schematic cross-sectional view showing an example of the power module.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings in some cases. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents. In the description, the same reference numerals are used for the same elements or elements having the same function, and duplicate description may be omitted in some cases. In addition, the positional relationship such as up, down, left, and right shall be based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratio of each element is not limited to the ratio shown in the figure.

One embodiment of the laminate includes a ceramic plate, a stress relaxation layer formed on the ceramic plate, and a metal circuit layer formed on the stress relaxation layer. Here, the stress relaxation layer has an alloy layer in contact with the ceramic plate having a magnesium content of 7.5% by mass or less and an average thickness of less than 0.2 mm, and magnesium more than the alloy layer. It has a metal layer having a small content of and in contact with the metal circuit layer.

FIG. 1 is a schematic cross-sectional view showing an example of the laminated body. The laminate 100 shown in FIG. 1 has a ceramic plate 1 and

metal circuits

2a and 2b provided on both sides thereof. The metal circuit 2a includes a stress relaxation layer 20a and a metal circuit layer 23a. The metal circuit layer 23a is joined to the ceramic plate 1 via a stress relaxation layer 20a. The stress relaxation layer 20a is composed of an alloy layer 21a in contact with the ceramic plate 1 and a metal layer 22a provided on the alloy layer 21a and in contact with the metal circuit layer 23a. The metal circuit 2b includes a stress relaxation layer 20b and a metal circuit layer 23b. The metal circuit layer 23b is joined to the ceramic plate 1 via a stress relaxation layer 20b. The stress relaxation layer 20b is composed of an alloy layer 21b in contact with the ceramic plate 1 and a metal layer 22b provided on the alloy layer 21b and in contact with the metal circuit layer 23b. Although the

metal circuit layers

23a and 23b shown in FIG. 1 are described as examples of uniform layers, they may have a pattern such as wiring. The metal circuit 2a and the metal circuit 2b are electrically insulated by the ceramic plate 1. As described above, the metal circuit layer and the stress relaxation layer or the metal circuit layer are in direct contact with each other, and the laminate 100 does not have a brazing material layer.

The types of ceramic components constituting the ceramic plate 1 may be, for example, carbides, oxides, nitrides, and the like. Specifically, the type of ceramic component may be silicon carbide (SiC), aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (Al N ₃ ), or the like. The ceramic plate 1 may be, for example, an aluminum oxide plate, a silicon nitride plate, and an aluminum nitride plate. Since the silicon nitride plate has few oxide layers on the surface, the effect of the present disclosure is more remarkable when the ceramic plate 1 is a silicon nitride plate. The oxide layer improves the adhesive force with other layers. In the laminate according to the present disclosure, the adhesive strength is improved by containing a predetermined amount of magnesium in the alloy layer. As a result, sufficient adhesive strength can be exhibited even when a ceramic plate having a small oxide layer is used.

The average thickness of the ceramic plate 1 may be, for example, 0.2 to 1.5 mm or 0.25 to 1.0 mm.

The average thickness of the plates and layers in the present specification means the average value of the thickness measured by a micrometer. The average value is the arithmetic mean value obtained by measuring at 10 points.

The stress relaxation layers 20a and 20b are layers for relaxing the stress generated due to the difference in thermal expansion during the heat cycle between the ceramic plate 1 and the

metal circuit layers

23a and 23b, respectively. The coefficient of thermal expansion of the stress relaxation layers 20a and 20b may be larger than the coefficient of thermal expansion of the ceramic plate 1 and may be larger than the coefficient of thermal expansion of the

metal circuit layers

23a and 23b.

The stress relaxation layers 20a and 20b are shown in the example of being composed of two layers of

alloy layers

21a and 21b and metal layers 22a and 22b, respectively, but may be composed of, for example, three or more layers. The magnesium content in the stress relaxation layers 20a and 20b is set so as to be large on the ceramic plate 1 side and small on the

metal circuit layers

23a and 23b. The metal layers 22a and 22b in contact with the

metal circuit layers

23a and 23b do not have to contain magnesium. Since the metal layers 22a and 22b do not contain magnesium, they are softer than the alloy layers 21a and 21b, and the stress relaxation performance can be further improved.

The alloy layers 21a and 21b contain magnesium. By containing magnesium having an excellent oxygen affinity, the bonding between the alloy layers 21a and 21b and the ceramic plate 1 becomes stronger. This effect is more remarkable when the oxide layer on the surface of the ceramic plate is small. Here, the alloy layers 21a and 21b may be alloys containing magnesium and aluminum. The composition of the alloy layers 21a and 21b can be selected according to the metal composition of the metal layers 22a and 22b. The alloy layers 21a and 21b may be an aluminum-magnesium-based alloy or may be an aluminum-magnesium alloy.

The alloy layers 21a and 21b may contain components other than aluminum and magnesium as long as the effects of the present invention are not impaired. The total content of other components is, for example, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.1% by mass or less. , 0.05% by mass or less, or 0.01% by mass or less. Here, the term "other components" includes impurities unintentionally contained in addition to the components to be arbitrarily added. Other components include, for example, O, C, Si, Mn, P, S, N, Ca, Cr, Ti, Nb, V, B, Mo, Cu, Ni, Sb, Sn, Ta, Mg, Zn, Examples thereof include Co, Zr, REM (Rare-earth element), and compounds thereof (for example, oxides, nitrides, sulfides, etc.).

The upper limit of the magnesium content in the alloy layer 21a is 7.5% by mass or less based on the total amount of the alloy layer 21a, but for example, 7.0% by mass or less, 6.5% by mass or less, or 6 It may be 0.0% by mass or less. When the upper limit of the magnesium content is within the above range, the stress relaxation layer 20a is more sufficiently suppressed from becoming too hard, and the durability against the heat cycle is more excellent as a whole. The lower limit of the magnesium content in the alloy layer 21a may be, for example, more than 0% by mass, based on the total amount of the alloy layer 21a, for example, 0.001% by mass or more, 0.01% by mass or more, 0. It may be 0.05% by mass or more, 0.1% by mass or more, or 0.3% by mass or more. When the lower limit of the magnesium content is within the above range, a chemical bond is generated via an oxygen atom, and the bond between the stress relaxation layer 20a and the ceramic plate 1 can be further strengthened. The magnesium content in the alloy layer 21a may be adjusted within the above range, and may be, for example, 0.001 to 7.5% by mass based on the total amount of the alloy layer 21a.

The magnesium content in the present specification means a value measured by inductively coupled plasma (ICP) emission spectrometry.

The upper limit of the average thickness of the alloy layer 21a is less than 0.2 mm, but may be, for example, 0.1 mm or less. Since the alloy layer 21a contains magnesium, it is a relatively hard layer. Therefore, if the upper limit of the average thickness of the alloy layer 21a is within the above range, the stress relaxation layer 20a is more sufficiently hardened. Suppresses and is more durable against heat cycles. The lower limit of the average thickness of the alloy layer 21a may be, for example, 0.02 mm or more, 0.03 mm or more, 0.04 mm or more, or 0.05 mm or more. When the lower limit of the average thickness of the alloy layer 21a is within the above range, the bond between the stress relaxation layer 20a and the ceramic plate 1 can be made stronger. The average thickness of the alloy layer 21a may be adjusted within the above range, and may be, for example, 0.02 mm or more and less than 0.2 mm, 0.02 mm to 0.1 mm, or 0.03 to 0.1 mm.

The magnesium content in the alloy layer 21b may be the same as that described above for the alloy layer 21a. The magnesium content in the alloy layer 21b and the magnesium content in the alloy layer 21a may be the same or different. It may be adjusted according to the type and thickness of the metal of the

metal circuit layers

23a and 23b.

The average thickness of the alloy layer 21b may be the same as that described above for the alloy layer 21a. The average thickness of the alloy layer 21b and the average thickness of the alloy layer 21a may be the same or different. The average thickness of the alloy layers 21a and 21b can be adjusted according to the composition of the alloy layer, the difference in the coefficient of thermal expansion between the ceramic plate 1 and the

metal circuit layers

23a and 23b, and the like.

The metal layers 22a and 22b are layers having a lower magnesium content than the alloy layers 21a and 21b, and may not contain magnesium. The metal layers 22a and 22b may include, for example, at least one selected from the group consisting of aluminum and aluminum alloys, may be composed of aluminum or an aluminum alloy, or may be composed of aluminum. The metal layers 22a and 22b preferably do not contain magnesium and are more preferably composed only of aluminum and the metals constituting the

metal circuit layers

23a and 23b. When the metal layers 22a and 22b contain a metal constituting the

metal circuit layers

23a and 23b, the metal may form an alloy with aluminum, and in this case, the alloy may form the metal circuit layers 23a and the metal circuit layers 23a and 22b of the metal layers 22a and 22b. It may be scattered on the surface on the 23b side.

The metal layers 22a and 22b may contain components other than aluminum and magnesium as long as the effects of the present invention are not impaired. The total content of other components is, for example, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.1% by mass or less. , 0.05% by mass or less, or 0.01% by mass or less. Here, the term "other components" includes impurities unintentionally contained in addition to the components to be arbitrarily added. Other components include, for example, O, C, Si, Mn, P, S, N, Ca, Cr, Ti, Nb, V, B, Mo, Cu, Ni, Sb, Sn, Ta, Mg, Zn, Examples thereof include Co, Zr, REM, and compounds thereof (for example, oxides, nitrides, sulfides, etc.).

The average thickness of the metal layer 22a is larger than the average thickness of the alloy layer 21a, and is, for example, 1.0 times or more, 1.5 times or more, or 2 times or more based on the average thickness of the alloy layer 21a. You can do it. Since the average thickness of the metal layer 22a and the average thickness of the alloy layer 21a have the above relationship, the stress relaxation layer 20a is more sufficiently suppressed from becoming too hard, and the durability against the heat cycle is more excellent. The average thickness of the metal layer 22a may be, for example, 20 times or less, 17 times or less, or 15 times or less based on the average thickness of the alloy layer 21a. When the average thickness of the metal layer 22a and the average thickness of the alloy layer 21a have the above relationship, the thermal resistance of the ceramic substrate can be reduced. The average thickness of the metal layer 22a may be adjusted within the above range, and may be, for example, 1.0 to 20 times based on the average thickness of the alloy layer 21a.

The lower limit of the average thickness of the metal layer 22a may be, for example, more than 0.1 mm, 0.15 mm or more, or 0.2 mm or more. When the lower limit of the average thickness of the metal layer 22a is within the above range, the durability against the heat cycle is more excellent. The upper limit of the average thickness of the metal layer 22a may be, for example, 0.4 mm or less, 0.35 mm or less, or 0.3 mm or less. When the upper limit of the average thickness of the metal layer 22a is within the above range, the thermal resistance of the ceramic substrate can be reduced.

The average thickness of the metal layer 22b may be the same as that described above for the metal layer 22a. The average thickness of the metal layer 22b and the average thickness of the metal layer 22a may be the same or different. The average thickness of the metal layers 22a and 22b can be adjusted according to the difference in the coefficient of thermal expansion between the ceramic plate 1 and the

metal circuit layers

23a and 23b.

The

metal circuit layers

23a and 23b may contain metals such as gold, platinum, silver, copper, nickel, and chromium, may contain gold, silver, copper, and the like, and may be made of copper. The

metal circuit layers

23a and 23b may be, for example, a wiring pattern made of copper, a wiring pattern made of a copper alloy, or the like.

The lower limit of the average thickness of the

metal circuit layers

23a and 23b may be, for example, 0.3 mm or more, 0.35 mm or more, or 0.4 mm or more. The upper limit of the average thickness of the

metal circuit layers

23a and 23b may be, for example, 4 mm or less, 3 mm or less, or 2 mm or less.

The laminate 100 of FIG. 1 shows an example in which the end face 21E of the alloy layer 21a, the end face 22E of the metal layer 22a, and the end face 23E of the metal circuit layer 23a are the same surface, but the end face 21E of the alloy layer 21a and the metal The surface composed of the end surface 22E of the layer 22a and the surface composed of the end surface 23E of the metal circuit layer 23a do not necessarily have to be the same surface. The laminate 101 shown in FIG. 2 is an example in which the surface composed of the end surface 21E of the alloy layer 21a and the end surface 22E of the metal layer 22a and the surface composed of the end surface 23E of the metal circuit layer 23a are different surfaces. Indicated. By setting the widths of the stress relaxation layers 20a and 20b to be larger than the widths of the

metal circuit layers

23a and 23b as in the laminated body 101, the laminated body is more excellent in durability against heat cycle. It can be a thing. The difference between the widths of the

metal circuit layers

23a and 23b and the widths of the stress relaxation layers 20a and 20b may be, for example, 1 to 1000 μm or 10 to 100 μm.

The above-mentioned

laminates

100 and 101 can be manufactured by a method of sequentially forming an alloy layer, a stress relaxation layer including a metal layer, and a metal circuit layer on a ceramic plate by using a so-called cold spray method. When a stress relaxation layer having an alloy layer and a metal layer and a metal circuit layer are formed on a ceramic plate by a spraying operation such as cold spraying or thermal spraying, irregularities derived from the spraying operation may be formed at the interface of each layer. .. Therefore, the above-mentioned

laminated bodies

100 and 101 have characteristics different from those manufactured by sequentially laminating metal thin films and the like formed in layers in advance.

In one embodiment of the method for producing a laminate, a first metal powder containing magnesium is sprayed together with an inert gas from a nozzle onto the surface of the ceramic plate to form a first deposited layer in contact with the ceramic plate. The step, the step of heat-treating the first deposited layer in an inert gas atmosphere to form an alloy layer, and the step of inactivating the second metal powder having a magnesium content smaller than that of the first metal powder. A step of forming a second deposited layer in contact with the alloy layer by spraying the gas together with the surface of the alloy layer, and a metal layer by heat-treating the second deposited layer in an inert gas atmosphere. And a step of forming a third deposited layer in contact with the metal layer by spraying a third metal powder containing metal particles together with an inert gas from a nozzle onto the surface of the metal layer. The third layer is heat-treated in an inert gas atmosphere to form a metal circuit layer.

FIG. 3 is a schematic view showing an example of a process of forming an alloy layer on a ceramic plate. In the method shown in FIG. 3, the first deposited layer is formed on the ceramic plate 1 by spraying the metal powder onto the surface of the ceramic plate 1 using the powder spray device 3. The alloy layer 21a is formed by heat-treating the first sedimentary layer. After forming the alloy layer 21a, the alloy layer 21b on the back side thereof may be formed.

The powder spray device 3 shown in FIG. 3 is mainly composed of a high-pressure gas cylinder 4, a heater 6, a powder supply device 7, a nozzle 10 of a spray gun having a tapered tapered shape, and a pipe connecting them. A first pressure regulator 5a is provided on the downstream side of the plurality of high-pressure gas cylinders 4, and the pipe branches into two circuits on the downstream side of the first pressure regulator 5a. A second pressure regulator 5b and a heater 6 and a third pressure regulator 5c and a powder supply device 7 are connected to each of the two branched circuits. The pipes from the heater 6 and the powder supply device 7 are connected to the nozzle 10.

In the powder spray device 3, the high-pressure gas cylinder 4 is filled with an inert gas used as a working gas, for example, at a pressure of 1 MPa or more. The inert gas may be, for example, a single gas of helium or nitrogen, or a mixed gas thereof. The working gas OG supplied from the high-pressure gas cylinder 4 is heated by the heater 6 after being adjusted in pressure by the second pressure regulator 5b on one circuit, and then supplied to the nozzle 10 of the spray gun. .. The working gas OG is also supplied to the powder supply device 7 after the pressure is adjusted by the third pressure regulator 5c on the other circuit. From the powder supply device 7, metal powder for film formation is supplied to the nozzle 10 of the spray gun together with the working gas OG.

The gauge pressure of the working gas OG is adjusted to be, for example, 1.5 to 5.0 MPa or 2.0 to 4.0 MPa at the inlet 10a of the nozzle 10. When the gauge pressure of the working gas OG is within the above range, a sedimentary layer (a layer that is later heat-treated to become an alloy layer) or the like can be efficiently formed. The gauge pressure at the inlet of the nozzle of the working gas OG can be measured at the connection portion between the nozzle and the pipe.

The heating temperature by the heater 6 is usually set lower than the melting point or softening point of the metal powder to be formed. The heater 6 can be arbitrarily selected from ordinary heating devices.

The working gas supplied to the nozzle 10 of the spray gun is compressed by passing through the tapered portion, and is accelerated by being expanded at once in the divergent portion on the downstream side thereof. The metal powder is heated to a predetermined temperature, accelerated to a predetermined speed, and then ejected from the outlet of the nozzle 10. The metal powder ejected from the nozzle 10 is sprayed onto the surface of the ceramic plate 1. As a result, the metal powder is deposited on the surface of the ceramic plate 1 while colliding with each other in a solid phase state to form the first deposition layer. The first sedimentary layer is then heat treated to form an alloy layer 21a. By adjusting the amount of the first metal powder sprayed, the thickness of the alloy layer formed later can be controlled.

The first metal powder may be, for example, magnesium alloy particles containing magnesium and other metal elements, or aluminum-magnesium alloy particles. The aluminum-magnesium alloy particles may be gas atomizing powder in which magnesium is dissolved in aluminum. Since the composition of the first metal powder (for example, the content of magnesium) is reflected in the composition of the alloy layer formed later (for example, the content of magnesium), the composition of the first metal powder is adjusted. , The composition of the alloy layer can be controlled.

In the formation of the first sedimentary layer, the first metal powder may be heated to, for example, 10 to 270 ° C. or 20 to 260 ° C. By setting the heating temperature of the first metal powder within this range, the first body lamination can be efficiently formed. In the present specification, the temperature at which the metal powder is heated means the maximum temperature reached by the metal powder. The temperature of the inert gas at the outlet of the nozzle 10 can also be regarded as the temperature at which the metal powder is heated. Here, the term "heating" is used in the present specification to include adjusting the temperature to a predetermined temperature below room temperature.

By arranging a mask material covering a part of the surface of the ceramic plate 1 on the ceramic plate 1, a first sedimentary layer or the like having a pattern (circuit pattern) may be formed on the ceramic base material. According to this method, after forming the alloy layer or the like, a metal circuit having a desired pattern can be easily formed without performing an additional process such as etching. The method according to the present embodiment is more advantageous than the conventional molten metal method and brazing method, which require etching for pattern formation, from the viewpoint of simplifying the process and controlling the quality of the obtained product. I can say.

The first metal powder may be accelerated to 250 to 1050 m / sec in the nozzle 10. As used herein, the rate at which the metal powder is accelerated means the maximum speed that the accelerated metal powder can reach. If the speed at which the accelerated metal powder arrives is less than 250 m / sec, it is difficult for the metal powder to be sufficiently plastically deformed at the moment when the metal powder collides with a ceramic base material or the like, so that it is difficult to form a deposited layer. Or, the adhesion of the formed sedimentary layer tends to decrease. If the speed at which the accelerated metal powder reaches exceeds 1050 m / sec, when the metal powder collides with a ceramic base material or the like, the metal powder tends to be crushed and scattered, making it difficult to form a deposited layer. be.

The first body laminate formed on the ceramic plate is heat-treated in an inert gas atmosphere. The temperature of the heat treatment may be, for example, 400 to 600 ° C. By heating the first sedimentary layer at a temperature of 400 ° C. or higher, the reaction between magnesium and the oxide layer on the surface of the ceramic plate can be further promoted, and a strong bond can be formed. Further, by heating the first sedimentary layer at a temperature of 600 ° C. or lower, the influence of softening of the first sedimentary layer can be reduced.

After forming the alloy layer, a second deposited layer is formed by spraying the second metal powder onto the surface of the alloy layer by the same method as the above-mentioned formation of the alloy layer, and the metal layer is formed by the subsequent heat treatment. Form. When the stress relaxation layer is composed of three or more layers, for example, the layers can be sequentially formed by repeating the same means as the formation of the alloy layer described above. The composition and thickness of the metal layer can be controlled by the composition and the amount of spraying of the second metal powder, respectively. At this time, the composition of the alloy or metal constituting each layer can be changed by adjusting the composition of the metal powder sprayed on the surface of each layer. For example, the content of magnesium in the metal powder may be adjusted to be gradually reduced. The metal powder to be finally sprayed to form a layer to be bonded to the metal circuit layer to be formed later preferably does not contain magnesium, and from the viewpoint of improving stress relaxation performance, for example, it is an aluminum powder. Is preferable.

After forming the metal layer, a third metal powder containing copper or the like as a main component is sprayed from the nozzle to the surface of the metal layer together with an inert gas to form a third deposited layer, followed by heat treatment to form a metal circuit. Form a layer.

In the formation of the third sedimentary layer, the third metal powder may be heated to, for example, 10 to 650 ° C or 20 to 640 ° C. By setting the heating temperature of the third metal powder within the above range, the third sedimentary layer can be efficiently formed. By setting the heating temperature of the third metal powder to 650 ° C. or lower, it is possible to prevent softened metal particles such as copper from adhering to the inner wall of the nozzle and clogging the nozzle, and the metal circuit. The formation of layers can be made easier. By setting the heating temperature of the third metal powder to 10 ° C. or higher, the plastic deformation of the metal particles such as copper can be made easier, and the formation of the third sedimentary layer can be made easier.

Also in the formation of the third sedimentary layer, the gauge pressure of the working gas OG may be, for example, 1.5 to 5.0 MPa or 2.0 to 4.0 MPa at the inlet 10a of the nozzle 10. By setting the gauge pressure of the working gas OG within the above range, the third sedimentary layer can be efficiently formed. By setting the working gas gauge pressure at the inlet of the nozzle to 1.5 MPa or more, it is possible to prevent the third metal powder from becoming difficult to adhere to the metal layer, and to make it easier to form the third sedimentary layer. can do. By setting the gauge pressure of the working gas at the inlet of the nozzle to 5.0 MPa or less, the tertiary metal powder sprayed on the metal layer together with the inert gas is crushed, and the efficiency of forming the third deposited layer is reduced. It can be more suppressed.

In addition, the conditions for forming the third sedimentary layer by spraying the third metal powder may be adjusted in the same manner as for the formation of the alloy layer and the metal layer described above. When forming the third sedimentary layer, as in the case of forming the alloy layer and the metal layer, by arranging the mask material on the ceramic plate 1, a third sedimentary layer having a pattern is formed and heated. By processing, a metal circuit layer having a pattern may be formed.

The third sedimentary layer is heat-treated in an inert gas atmosphere. For this heat treatment, the temperature may be, for example, 250 to 350 ° C. By heating the third sedimentary layer at a temperature of 250 ° C. or higher, strain in the alloy layer and the metal layer due to work hardening can be reduced. By heating the third sedimentary layer at a relatively low temperature of 350 ° C. or lower, it is possible to suppress the formation of intermetallic compounds and the diffusion of metal components by the reaction between the metal layer and the third sedimentary layer. ..

In order to suppress the formation of pores in the alloy layer, the metal layer and the metal circuit layer, the first metal powder, the second metal powder, and / or the third metal powder may each be composed of spherical particles. The first metal powder, the second metal powder, and / or the third metal powder may each have a small variation in particle size. The average particle size of the metal powder may be, for example, 10 to 70 μm or 20 to 60 μm. By setting the average particle size of the metal powder to 10 μm or more, it is possible to further prevent the metal powder from clogging the tapered portion of the nozzle. By setting the average particle size of the metal powder to 70 μm or less, the speed of the metal powder can be sufficiently increased.

The average particle size in the present specification is the particle size (D50) when the integrated value from the small particle size reaches 50% of the total in the volume-based particle size distribution curve measured by the laser diffraction / scattering method. To say. D50 is also called a median diameter and is known as the average particle size of the target particles.

Since the above-mentioned laminated body has excellent durability against heat cycles, it can be suitably used as, for example, a member (for example, a circuit board or the like) constituting a power module or the like. One embodiment of the power module comprises a circuit board, a semiconductor element electrically connected on one main surface of the circuit board, and a heat dissipation member connected on the other main surface of the circuit board. To be equipped. The circuit board is the above-mentioned laminated body.

FIG. 4 is a schematic cross-sectional view showing an example of a power module. The power module 300 includes a base plate 70 and a circuit board 102 that is joined to one surface of the base plate 70 via a solder 32. The metal circuit 2b (alloy layer, metal layer and metal circuit layer) of the circuit board 102 is joined to the solder 32. The circuit board 102 may be the above-mentioned

laminates

100, 101, or the like.

A semiconductor element 60 is attached to the metal circuit 2a of the circuit board 102 via a solder 31. The semiconductor element 60 is connected to a predetermined position in the metal circuit 2a by a metal wire 34 such as an aluminum wire (aluminum wire). In order to electrically connect the outside of the housing 36 to the metal circuit 2a, a predetermined portion of the metal circuit 2a is connected to an electrode 33 provided through the housing 36 via a solder 35.

A housing 36 is arranged on one surface of the base plate 70 so as to accommodate the circuit board 102. The accommodation space formed by one surface of the base plate 70 and the housing 36 is filled with a resin 30 such as silicone gel.

Cooling fins 72 forming a heat radiating member are joined to the other surface of the base plate 70 via grease 74. A screw 73 for fixing the cooling fin 72 to the base plate 70 is attached to the end of the base plate 70. The base plate 70 and the cooling fins 72 may be made of aluminum. The base plate 70 and the cooling fins 72 have high thermal conductivity and thus function well as heat radiating portions.

The power module 300 includes

metal circuits

2a and 2b of the circuit board 102 and a semiconductor element 60 that is electrically connected to the metal circuit 2a. The semiconductor element 60 is sealed with the resin 30 together with the circuit board 102. Such a power module 300 can maintain the adhesion between the resin 30 and the ceramic plate 1 even if the semiconductor element 60 generates heat.

Although some embodiments have been described above, the present disclosure is not limited to the above embodiments. In addition, the contents of the description of the above-described embodiments can be applied to each other.

Hereinafter, the contents of the present disclosure will be described in more detail with reference to Examples and Comparative Examples. However, the present disclosure is not limited to the following examples.

<Preparation of aluminum nitride plate (AlN)>
A commercially available aluminum nitride plate (manufactured by MARUWA Co., Ltd.) was used as the ceramic plate.

<Manufacturing of silicon nitride plate (Si ₃ N ₄ plate)>
Silicon nitride powder, magnesium oxide powder, and yttrium oxide powder were prepared as sintering aids. These were blended in a ratio of Si ₃ N ₄ : Y ₂ O ₃ : MgO = 94.0: 3.0: 3.0 (mass ratio) to obtain a raw material powder. This raw material powder was uniaxially pressure-molded to prepare a molded product. This molded body was placed in an electric furnace equipped with a carbon heater and fired at 1800 ° C. for 12 hours in an atmosphere of nitrogen gas to obtain a flat plate-shaped silicon nitride plate. The obtained silicon nitride plate was used as a ceramic plate.

<Preparation of aluminum oxide plate (Al ₂ O ₃ )>
A commercially available aluminum oxide plate (manufactured by MARUWA Co., Ltd.) was used as the ceramic plate.

(Example 1)
<Formation of alloy layer (layer made of aluminum-magnesium alloy)>
Using an aluminum-magnesium alloy powder (manufactured by High Purity Chemical Laboratory Co., Ltd., gas atomized powder, median diameter: 24 μm), using a powder spraying device having the same configuration as in FIG. 3, length: 56 mm, width: 46 mm, A deposit layer (first deposit layer) of aluminum-magnesium alloy powder having a thickness of 0.1 mm was formed on each of the front and back surfaces of the aluminum nitride plate within a range of 2 mm inside from the end face of the base material. The formation of the first deposited layer was carried out under the conditions that nitrogen was used as the working gas, the temperature of the aluminum-magnesium alloy powder (gas atomized powder) was 260 ° C., and the pressure of the working gas at the nozzle inlet was 3 MPa. The first sedimentary layer was heat-treated by holding it at a temperature of 550 ° C. for 3 hours in a nitrogen atmosphere to form an aluminum-magnesium alloy layer (alloy layer).

<Formation of metal layer (layer made of aluminum)>
Next, using an aluminum powder (manufactured by High Purity Chemical Laboratory Co., Ltd., gas atomized powder, median diameter: 24 μm), a powder spraying device having the same configuration as in FIG. A 0.2 mm aluminum powder deposit layer (second deposit layer) is formed on the surfaces of the two alloy layers formed as described above so that the length is 56 mm and the width is 46 mm, similarly to the alloy layer. did. The formation of the second sedimentary layer was carried out under the conditions that nitrogen was used as the working gas, the temperature of the aluminum powder was 260 ° C., and the pressure of the working gas at the nozzle inlet was 3 MPa. The second sedimentary layer was heat-treated by holding it at a temperature of 550 ° C. for 3 hours in a nitrogen atmosphere to form an aluminum layer (metal layer).

<Formation of metal circuit layer (layer made of copper)>
Further, a part of the aluminum layer is masked with an iron masking material, and copper powder (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., water atomized powder, median diameter: 17 μm) is used, and the powder has the same structure as that of FIG. By the spraying device, the copper powder deposit layer (third deposit layer) is placed in the range 50 μm inside from the end face of the aluminum layer so that the length is 55.9 mm, the width is 45.9 mm, and the thickness is 0.4 mm. Formed. The third sedimentary layer was carried out under the conditions that nitrogen was used as the working gas, the temperature of the copper powder was 640 ° C., and the pressure of the working gas at the nozzle inlet was 3 MPa. The end face of the aluminum layer protruded outward with a width of 50 μm from the end face of the copper layer. The third sedimentary layer was heat-treated by holding it at a temperature of 300 ° C. for 1 hour in a nitrogen atmosphere to form a copper layer (metal circuit layer).

By the above procedure, a laminate in which a metal circuit composed of an aluminum-magnesium alloy layer, an aluminum layer and a copper layer was formed on both sides of a silicon nitride plate was obtained.

(Examples 2 to 9)
Lamination in the same manner as in Example 1 except that the type and thickness of the ceramic plate, the magnesium content in the alloy layer, the thickness of the alloy layer, and the thickness of the metal layer were changed as shown in Table 1. The body was prepared.

(Comparative Examples 1 to 3)
A laminate was prepared in the same manner as in Example 1 except that the type and thickness of the ceramic plate and the magnesium content in the alloy layer were changed as shown in Table 2 without providing the metal layer.

(Comparative Examples 4 to 5)
A laminate was prepared in the same manner as in Example 1 except that the type and thickness of the ceramic plate and the thickness of the metal layer were changed as shown in Table 2 without providing the alloy layer.

(Comparative Examples 7-14)
Lamination in the same manner as in Example 2 except that the type and thickness of the ceramic plate, the magnesium content in the alloy layer, the thickness of the alloy layer, and the thickness of the metal layer were changed as shown in Table 1. The body was prepared.

<Evaluation of durability against heat cycle: heat cycle test>
A heat cycle test was conducted on each of the laminates prepared in Examples 1 to 9 and Comparative Examples 1 to 17, and the durability against the heat cycle was evaluated. Specifically, a heat cycle test was conducted in which the laminate was left in an environment of 180 ° C. for 30 minutes and then left in an environment of −55 ° C. for 30 minutes as one cycle, and this was carried out for 3000 cycles. From the cross-sectional observation of the laminated body after the test, it was evaluated according to the following criteria. The results are shown in Tables 1 and 2.
A: No abnormalities such as peeling were observed even after 3000 cycles.
B: Peeling was observed in more than 1500 cycles and less than 3000 cycles.
C: Peeling was observed in more than 1000 cycles and less than 1500 cycles.
D: Peeling was observed in 1000 cycles or less.

According to the present disclosure, it is possible to provide a laminate having excellent durability against heat cycles. According to the present disclosure, it is also possible to provide a power module having excellent reliability.

1 ... Ceramic plate, 2a, 2b ... Metal circuit, 3 ... Powder spray device, 4 ... High pressure gas cylinder, 5a ... First pressure regulator, 5b ... Second pressure regulator, 5c ... Third pressure regulator , 6 ... heater, 7 ... powder supply device, 10 ... nozzle, 10a ... inlet, 20a, 20b ... stress relaxation layer, 21a, 21b ... alloy layer, 22a, 22b ... metal layer, 23a, 23b ... metal circuit layer, 30 ... Resin, 31, 32, 35 ... Solder, 33 ... Electrode, 34 ... Metal wire, 36 ... Housing, 60 ... Semiconductor element, 70 ... Base plate, 72 ... Cooling fin, 73 ... Screw, 74 ... Grease, 100, 101 ... Laminate, 102 ... Circuit board, 300 ... Power module.

Claims

With a ceramic plate
The stress relaxation layer formed on the ceramic plate and
A metal circuit layer formed on the stress relaxation layer is provided.
The stress relaxation layer is
An alloy layer in contact with the ceramic plate having a magnesium content of 7.5% by mass or less and an average thickness of less than 0.2 mm.
A laminate having a metal layer having a magnesium content lower than that of the alloy layer and in contact with the metal circuit layer.
The laminate according to claim 1, wherein the average thickness of the alloy layer is 0.02 mm or more and less than 0.2 mm.
The laminate according to claim 1 or 2, wherein the coefficient of thermal expansion of the stress relaxation layer is larger than the coefficient of thermal expansion of the ceramic plate and larger than the coefficient of thermal expansion of the metal circuit layer.
The laminate according to any one of claims 1 to 3, wherein the metal layer contains aluminum.
The laminate according to any one of claims 1 to 4, wherein the metal layer has an average thickness of more than 0.1 mm.
The laminate according to any one of claims 1 to 5, wherein the ceramic plate is a silicon nitride plate, an aluminum nitride plate, or an aluminum oxide plate.
With the circuit board
A semiconductor element electrically connected on one main surface of the circuit board,
A heat radiating member connected to the other main surface of the circuit board.
A power module in which the circuit board is the laminate according to any one of claims 1 to 6.
The process of forming the first deposited layer in contact with the ceramic plate by spraying the first metal powder containing magnesium together with the inert gas from the nozzle onto the surface of the ceramic plate.
A step of heat-treating the first sedimentary layer in an atmosphere of an inert gas to form an alloy layer, and
A second deposited layer in contact with the alloy layer is formed by spraying the second metal powder having a magnesium content lower than that of the first metal powder on the surface of the alloy layer together with the inert gas. Process and
A step of heat-treating the second sedimentary layer in an atmosphere of an inert gas to form a metal layer, and
A step of forming a third deposited layer in contact with the metal layer by spraying a third metal powder containing metal particles from a nozzle together with an inert gas onto the surface of the metal layer.
A method for producing a laminate, comprising a step of heat-treating the third sedimentary layer in an atmosphere of an inert gas to form a metal circuit layer.
The method for producing a laminate according to claim 8, wherein the first metal powder is a gas atomized powder containing aluminum-magnesium alloy particles.