JP7453288B2 - Manufacturing method of bonded substrate - Google Patents

Description

The present invention relates to a method for manufacturing a bonded substrate.

Silicon nitride ceramics have high thermal conductivity and high insulation properties. Therefore, a bonded substrate in which a copper plate is bonded to a silicon nitride ceramic substrate is suitably used as an insulated heat dissipation substrate on which a power semiconductor element is mounted.

The bonded substrate is often manufactured by producing an intermediate product in which the brazing material layer is between a copper plate and a silicon nitride ceramic substrate, and heat-treating the produced intermediate product. When the intermediate product is heat treated, the braze layer transforms into a bonding layer that joins the copper plate to the silicon nitride ceramic substrate. Further, the intermediate product changes to a bonded substrate in which a copper plate is bonded to a silicon nitride ceramic substrate via a bonding layer.

It has also been proposed to hot press the intermediate product when heat treating the intermediate product. For example, in the technique described in Patent Document 1, the bonded substrate has a configuration in which a copper plate is bonded to one principal surface of a silicon nitride substrate via a bonding layer (paragraphs 0024-0025). The bonded substrate is obtained by applying a brazing material on one main surface of a silicon nitride substrate, overlapping a copper plate on the surface to which the brazing material is applied, and applying heat and pressure (paragraphs 0024-0025).

Japanese Patent Application Publication No. 2018-506496

If hot pressing is performed on an intermediate product when the bonded substrate is manufactured, it may be difficult to separate the copper plate from other objects after the copper plate is hot press bonded to the silicon nitride ceramic substrate. be. For example, the copper plate may stick to the punch that presses the intermediate product, making it difficult to separate the copper plate from the punch. In addition, if hot pressing is performed on multiple intermediate products with multiple intermediate products stacked in the thickness direction of the silicon nitride ceramic substrate, two copper plates each provided on two adjacent intermediate products may be difficult to separate from each other.

The present invention has been made with this problem in mind. The problem to be solved by the present invention is to provide a method for manufacturing a bonded substrate that makes it easy to separate the copper plate from other objects after the copper plate is hot-press bonded to the silicon nitride ceramic substrate.

In order to solve the above problems, a first aspect of the present invention is a method for manufacturing a bonded substrate, comprising: a) a silicon nitride ceramic substrate each having a first main surface and a second main surface; first and second copper plates each having one main surface and the other main surface, and between the one main surface of the first copper plate and the first main surface of the silicon nitride ceramic substrate. and a second brazing material layer between the one main surface of the second copper plate and the second main surface of the silicon nitride ceramic substrate. a step of preparing a plurality of intermediate products, and b) a step of forming a coating with a thickness of 5 μm or more containing a mold release agent so as to cover the other main surface of each of the first and second copper plates; c) stacking the plurality of intermediate products on which the coating has been formed in the thickness direction of the silicon nitride ceramic substrate, and d) upper punching the plurality of intermediate products stacked in step c) while heating them. The plurality of intermediate products are hot pressed by applying pressure with a lower punch, and the first brazing material layer and the second brazing material layer of each of the plurality of intermediate products are a step of changing the copper plate into first and second bonding layers that bond the second copper plate and the silicon nitride ceramic substrate; and e) removing the coating, and in the step a) , the first brazing material layer and the second brazing material layer apply a brazing material paste containing at least an active metal and a solvent prepared in advance to the first main surface and the second main surface of the silicon nitride ceramic substrate. It is formed by screen printing on the surface, and in step d), the plurality of intermediate products are applied in the thickness direction of the silicon nitride ceramic substrate according to a surface pressure profile such that the maximum surface pressure is 5 MPa or more and 25 MPa or less. The first and second bonding layers are formed to have a thickness of 0.1 μm or more and 5 μm or less by pressing and heating according to a temperature profile with a maximum temperature of 800° C. or more and 1000° C. or less.

A second aspect of the present invention is a method for manufacturing a bonded substrate according to the first aspect, characterized in that the mold release agent includes crystals having a network layered structure.

A third aspect of the present invention is a method for manufacturing a bonded substrate according to the first or second aspect, wherein the mold release agent is made of boron nitride powder, graphite powder, molybdenum disulfide powder, and molybdenum dioxide powder. It is characterized by containing at least one kind selected from the group.

A fourth aspect of the present invention is a method for manufacturing a bonded substrate according to any one of the first to third aspects, wherein the first brazing material layer and the second brazing material layer contain silver. It is characterized by containing at least one member selected from the group consisting of metal powder, titanium hydride powder, and zirconium hydride powder.

A fifth aspect of the present invention is a method for manufacturing a bonded substrate according to any one of the first to fourth aspects, wherein the first and second brazing filler metal layers have an average size of 0.1 μm or more and 10 μm or less. It is characterized in that it contains an active metal brazing material made of powder having a particle size.

A sixth aspect of the present invention is a method for manufacturing a bonded substrate according to any one of the first to fifth aspects, wherein the first bonding layer and the second bonding layer have a thickness of 0.1 μm or more and 5 μm. It is characterized by having the following thickness:

A seventh aspect of the present invention is a method for manufacturing a bonded substrate according to any one of the first to sixth aspects, comprising: f) the first copper plate from which the coating has been removed after the step e); The method is characterized by further comprising a step of patterning the second copper plate.
An eighth aspect of the present invention is a method for manufacturing a bonded substrate according to any one of the first to seventh aspects, characterized in that the thickness of the coating is 30 μm or less.
A ninth aspect of the present invention is a method for manufacturing a bonded substrate according to any one of the first to eighth aspects, wherein the release agent has an average particle diameter of 0.1 μm or more and 10 μm or less, and the coating The thickness is less than or equal to .

According to the first to ninth aspects of the present invention, the copper plate is hot-press bonded to the silicon nitride ceramic substrate while the other main surface of the copper plate is covered with a coating containing a mold release agent. This makes it easy to separate the copper plate from other objects after the copper plate is hot-press bonded to the silicon nitride ceramic substrate. Thereby, productivity of bonded substrates can be improved.

FIG. 2 is a cross-sectional view schematically illustrating a bonded substrate. 2 is a flowchart showing the flow of manufacturing a bonded substrate. FIG. 2 is a cross-sectional view schematically illustrating a workpiece obtained during manufacturing of a bonded substrate and a hot press apparatus used for manufacturing the bonded substrate.

1 Bonded Substrate FIG. 1 is a cross-sectional view schematically illustrating a bonded substrate 100 of this embodiment.

The bonding substrate 100 illustrated in FIG. 1 includes a silicon nitride ceramic substrate 110, a copper plate 111, a bonding layer 112, a copper plate 113, and a bonding layer 114. The bonded substrate 100 may include elements other than these elements. One of the pair of copper plate 111 and bonding layer 112 and the pair of copper plate 113 and bonding layer 114 may be omitted.

Copper plates 111 and 113 are bonded to silicon nitride ceramic substrate 110 via bonding layers 112 and 114, respectively. Copper plates 111 and 113 are brazed to first main surface 1101 and second main surface 1102 facing in opposite directions of silicon nitride ceramic substrate 110 by bonding layers 112 and 114, respectively.

Although the bonding substrate 100 may be used in any manner, it is used, for example, as an insulating heat dissipation substrate on which a power semiconductor element is mounted.

2 Method for Manufacturing Bonded Substrate FIG. 2 is a flowchart showing the flow of manufacturing the bonded substrate 100. FIG. 3 is a cross-sectional view schematically illustrating a workpiece obtained during manufacturing of the bonded substrate 100 and a hot press apparatus used for manufacturing the bonded substrate 100.

In manufacturing the bonded substrate 100, steps S11 to S16 illustrated in FIG. 2 are sequentially performed.

In step S11, a plurality of intermediate products 150 to be included in the workpiece 140 illustrated in FIG. 3 are prepared.

Each intermediate product 150 included in the plurality of intermediate products 150 includes a silicon nitride ceramic substrate 110, a copper plate 111, a brazing material layer 162, a copper plate 113, and a brazing material layer 164. When the copper plate 111 and the bonding layer 112 are omitted from the bonded substrate 100, the copper plate 111 and the brazing material layer 162 are omitted from the intermediate product 150. When the copper plate 113 and the bonding layer 114 are omitted from the bonded substrate 100, the copper plate 113 and the brazing material layer 164 are omitted from the intermediate product 150.

The brazing material layer 162 is between one main surface 111A of the copper plate 111 and the first main surface 1101 of the silicon nitride ceramic substrate 110. The brazing material layer 164 is between one main surface 113A of the copper plate 113 and the second main surface 1102 of the silicon nitride ceramic substrate 110.

When forming braze layers 162 and 164, a paste containing an active metal braze and a solvent is prepared. The paste may further contain a binder, a dispersant, an antifoaming agent, and the like. Subsequently, the prepared paste is screen printed on the first main surface 1101 and the second main surface 1102 of the silicon nitride ceramic substrate 110, and the paste is screen printed on the first main surface 1101 and the second main surface 1102 of the silicon nitride ceramic substrate 110. First and second screen printed films are formed on the main surface 1102 of the screen, respectively. Subsequently, the solvent contained in the formed first and second screen printed films is evaporated. This transforms the first and second screen printed films into brazing material layers 162 and 164, respectively. Braze layers 162 and 164 include active metal braze materials. The brazing material layers 162 and 164 may be formed by a method different from this method.

The active metal brazing material consists of powder. The active metal brazing material is, for example, at least one metal element selected from the group consisting of silver (Ag) and copper (Cu), and at least one metal element selected from the group consisting of titanium (Ti) and zirconium (Zr). Contains several active metal elements. The active metal brazing material desirably consists of at least one selected from the group consisting of metal powder containing silver, titanium hydride (TiH ₂ ) powder, and zirconium hydride (ZrH ₂ ) powder. The active metal brazing material can be atomized at low cost, such as when the active metal brazing material is made of at least one selected from the group consisting of a metal powder containing silver, and a titanium hydride powder and a zirconium hydride powder. If it does not contain difficult alloy powders, it becomes easy to atomize the active metal brazing material at low cost.

The active metal brazing material desirably consists of powder having an average particle size of 0.1 μm or more and 10 μm or less. The average particle diameter can be obtained by measuring the particle size distribution using a commercially available laser diffraction particle size distribution analyzer and calculating D50 from the measured particle size distribution. Having such a small average particle size of the active metal brazing material allows the brazing material layers 162 and 164 to be thin.

In step S12, the coating 165 is formed in the workpiece 140 so that the other main surface 111B of the copper plate 111 and the other main surface 113B of the copper plate 113 are covered with the coating 165.

When coating 165 is formed, a coating liquid containing a mold release agent and a solvent is prepared. The coating liquid may further contain a binder, a dispersant, an antifoaming agent, and the like. Solvents include isopropyl alcohol and the like. Subsequently, the prepared coating liquid is sprayed toward the surface to be formed, which is the other main surface 111B of the copper plate 111 or the other main surface 113B of the copper plate 113, to form a spray film on the surface to be formed. When a spray film is formed on a surface to be formed, a coating liquid is desirably applied electrostatically to the surface to be formed. Thereby, it is possible to suppress the coating liquid from going around to areas other than the surface to be formed, and it is possible to reduce the loss of the coating liquid. Subsequently, the solvent contained in the formed spray film is evaporated. This transforms the spray film into a coating 165. Coating 165 includes a mold release agent. Coating 165 may be formed by a method different from this method. For example, instead of spraying a coating liquid containing a mold release agent toward the surface to be formed, a paste containing a mold release agent may be screen-printed onto the surface to be formed.

The thickness of the coating 165 is arbitrary, but is preferably 5 μm or more and 30 μm or less. If the thickness of the coating 165 is thinner than this range, the other main surface 111B of the copper plate 111 and the other main surface 113B of the copper plate 113 tend to be exposed easily. Therefore, in step S14 described below, it is difficult to separate the copper plate 111 provided in the uppermost intermediate product 150U and the copper plate 113 provided in the lowermost intermediate product 150L from the upper punch 180 and the lower punch 181, respectively. This tends to make it difficult to separate the copper plate 111 provided in the lower intermediate product 150 from the copper plate 113 provided in the upper intermediate product 150. On the other hand, if the thickness of the coating 165 is thicker than this range, it tends to take a long time to remove the coating 165 in step S15 described below.

The mold release agent consists of powder. The mold release agent preferably contains crystals having a network layered structure, and more preferably contains a group consisting of boron nitride (BN) powder, graphite powder, molybdenum disulfide (MoS ₂ ) powder, and molybdenum dioxide (MoO ₂ ) powder. The boron nitride powder contains at least one selected from the group consisting of boron nitride powder and preferably has high heat resistance.

The mold release agent desirably has an average particle diameter of 0.1 μm or more and 10 μm or less. The average particle diameter can be obtained by measuring the particle size distribution using a commercially available laser diffraction particle size distribution analyzer and calculating D50 from the measured particle size distribution. If the average particle size is larger than this range, when the copper plates 111 and 113 are hot-press bonded to the silicon nitride ceramic substrate 110, the other main surface 111B of the copper plate 111 and the other main surface 113B of the copper plate 113 are released. The shape of the powder of the agent is transferred, and the surface roughness of the other main surface 111B of the copper plate 111 and the other main surface 113B of the copper plate 113 tends to deteriorate.

In step S13, a plurality of intermediate products 150 are stacked in the thickness direction of silicon nitride ceramic substrate 110. As a result, the object to be processed 140 is obtained.

In step S14, the workpiece 140 is heated by the heater 182 provided in the hot press device 170 while being pressurized by the upper punch 180 and the lower punch 181 provided in the hot press device 170. As a result, hot pressing is performed on the plurality of intermediate products 150 provided on the workpiece 140. As a result, the brazing material layer 162 changes into a bonding layer 112 that bonds the copper plate 111 to the silicon nitride ceramic substrate 110, and the copper plate 111 is hot press bonded to the silicon nitride ceramic substrate 110. Furthermore, the brazing material layer 164 changes into a bonding layer 114 that bonds the copper plate 113 to the silicon nitride ceramic substrate 110, and the copper plate 113 is hot press bonded to the silicon nitride ceramic substrate 110. Each intermediate product 150 includes a copper plate 111, a bonding layer 112, a copper plate 113, and a bonding layer 114, and a bonding substrate in which the copper plates 111 and 113 are bonded to the silicon nitride ceramic substrate 110 via the bonding layers 112 and 114, respectively. Changes to 100.

In step S14, the workpiece 140 is preferably pressurized in the thickness direction of the silicon nitride ceramic substrate 110 in a vacuum or in an inert gas according to a surface pressure profile with a maximum surface pressure of 5 MPa or more and 25 MPa or less. and is heated according to a temperature profile with a maximum temperature of 800°C or more and 1000°C or less, preferably a maximum temperature of 800°C or more and 900°C or less.

The bonding layers 112 and 114 obtained in step S14 desirably have a thickness of 0.1 μm or more and 5 μm or less.

By hot press bonding the copper plates 111 and 113 to the silicon nitride ceramic substrate 110, defects in the bonding layer 112, the bonding layer 114, and the silicon nitride ceramic substrate 110 can be reduced. Thereby, poor insulation of the bonded substrate 100 due to defects can be suppressed.

Furthermore, the brazing layers 162 and 164 are made thinner, and the copper plates 111 and 113 are hot-press bonded to the silicon nitride ceramic substrate 110, so that the bonding layers 112 and 114 can be made thinner. Thereby, the stress caused by the presence of the bonding layers 112 and 114 can be reduced, and a decrease in the durability of the bonded substrate 100 against thermal cycles caused by the stress can be suppressed.

Further, by hot press bonding the copper plates 111 and 113 to the silicon nitride ceramic substrate 110, the copper plates 111 and 113 can be plastically deformed so as to cancel out the warpage that occurs in the bonded substrate 100. Thereby, the flatness of the bonded substrate 100 can be improved.

By performing step S12 before performing step S14, the other main surface 111B of the copper plate 111 provided in the uppermost intermediate product 150U and the other main surface 111B of the copper plate 113 provided in the lowermost intermediate product 150L. Copper plates 111 and 113 are hot-press bonded to silicon nitride ceramic substrate 110 with main surface 113B covered with coating 165 containing a mold release agent. Therefore, when the copper plates 111 and 113 are hot-press bonded to the silicon nitride ceramic substrate 110, the other main surface 111B of the copper plate 111 provided in the uppermost intermediate product 150U and the lowermost intermediate product 150L The other main surface 113B of the copper plate 113 indirectly contacts the upper punch 180 and the lower punch 181 via the coating 165, but does not directly contact the upper punch 180 and the lower punch 181. As a result, after the copper plates 111 and 113 are hot-press bonded to the silicon nitride ceramic substrate 110, the copper plate 111 provided in the uppermost intermediate product 150U and the copper plate 113 provided in the lowermost intermediate product 150L are punched, respectively. 180 and the lower punch 181 becomes easy. Thereby, productivity of the bonded substrate 100 can be improved.

Moreover, by performing step S12 before performing step S14, the other main surface 111B of the copper plate 111 provided in the lower intermediate product 150 among the two adjacent intermediate products 150 contains the mold release agent. Copper plates 111 and 113 are hot press bonded to silicon nitride ceramic substrate 110 while covered with coating 165 . Therefore, when the copper plates 111 and 113 are hot-press bonded to the silicon nitride ceramic substrate 110, the other main surface 111B of the copper plate 111 provided in the lower intermediate product 150 is attached to the two intermediate products through the coating 165. It indirectly contacts the copper plate 113 provided in the upper intermediate product 150 in 150 and does not directly contact the copper plate 113 provided in the upper intermediate product 150. Thereby, after the copper plates 111 and 113 are hot-press bonded to the silicon nitride ceramic substrate 110, it becomes easy to separate the copper plate 111 provided in the lower intermediate product 150 from the copper plate 113 provided in the upper intermediate product 150. . Thereby, productivity of the bonded substrate 100 can be improved.

By performing step S13 before performing step S14, a plurality of bonded substrates 100 can be obtained at the same time. Thereby, productivity of the bonded substrate 100 can be improved. However, the workpiece 140 may include only one intermediate product 150. In that case, step S13 is not executed.

In step S15, coating 165 is removed. Removal of coating 165 may be performed by sandblasting, scrubbing, rinsing, ultrasonic cleaning, polishing, or the like.

In step S16, the copper plate 111, bonding layer 112, copper plate 113, and bonding layer 114 are patterned as necessary. Patterning of the copper plate 111, bonding layer 112, copper plate 113, and bonding layer 114 is performed, for example, by etching.

Although this invention has been described in detail, the above description is illustrative in all aspects, and the invention is not limited thereto. It is understood that countless variations not illustrated can be envisaged without departing from the scope of the invention.

100 Bonding substrate 110 Silicon nitride ceramic substrate 111 Copper plate 112 Bonding layer 113 Copper plate 114 Bonding layer 150 Intermediate product 162 Brazing metal layer 164 Brazing metal layer 165 Coating

Claims (9)

A method for manufacturing a bonded substrate, the method comprising:
a) Each
a silicon nitride ceramic substrate having a first main surface and a second main surface;
first and second copper plates each having one main surface and the other main surface;
a first brazing material layer between the one main surface of the first copper plate and the first main surface of the silicon nitride ceramic substrate;
a second brazing material layer between the one main surface of the second copper plate and the second main surface of the silicon nitride ceramic substrate;
preparing a plurality of intermediate products,
b) forming a coating with a thickness of 5 μm or more containing a mold release agent so as to cover the other main surface of each of the first and second copper plates;
c) stacking the plurality of intermediate products on which the coating has been formed in the thickness direction of the silicon nitride ceramic substrate;
d) The plurality of intermediate products stacked in step c) are heated and pressurized with an upper punch and a lower punch to hot press the plurality of intermediate products, and the plurality of intermediate products are heated. The first brazing material layer and the second brazing material layer are respectively changed into first and second bonding layers that bond the first copper plate and the second copper plate to the silicon nitride ceramic substrate. a step of causing
e) removing said coating;
Equipped with
In step a), the first brazing material layer and the second brazing material layer are formed by applying a brazing material paste containing at least an active metal and a solvent prepared in advance to the first main surface of the silicon nitride ceramic substrate. formed by screen printing on the second main surface,
In step d), the plurality of intermediate products are pressurized in the thickness direction of the silicon nitride ceramic substrate according to a surface pressure profile such that the maximum surface pressure is 5 MPa or more and 25 MPa or less, and the maximum temperature is 800° C. or more and 1000° C. Forming the first and second bonding layers to a thickness of 0.1 μm or more and 5 μm or less by heating according to the following temperature profile,
A method for manufacturing a bonded substrate, characterized in that: A method for manufacturing a bonded substrate according to claim 1, comprising:
The mold release agent includes crystals having a network layered structure.
A method for manufacturing a bonded substrate, characterized in that: A method for manufacturing a bonded substrate according to claim 1 or 2, comprising:
The mold release agent includes at least one selected from the group consisting of boron nitride powder, graphite powder, molybdenum disulfide powder, and molybdenum dioxide powder.
A method for manufacturing a bonded substrate, characterized in that: A method for manufacturing a bonded substrate according to any one of claims 1 to 3,
The first brazing material layer and the second brazing material layer contain a metal powder containing silver, and at least one selected from the group consisting of titanium hydride powder and zirconium hydride powder.
A method for manufacturing a bonded substrate, characterized in that: A method for manufacturing a bonded substrate according to any one of claims 1 to 4, comprising:
The first brazing material layer and the second brazing material layer contain an active metal brazing material made of powder having an average particle size of 0.1 μm or more and 10 μm or less.
A method for manufacturing a bonded substrate, characterized in that: A method for manufacturing a bonded substrate according to any one of claims 1 to 5,
The first bonding layer and the second bonding layer have a thickness of 0.1 μm or more and 5 μm or less,
A method for manufacturing a bonded substrate, characterized in that: A method for manufacturing a bonded substrate according to any one of claims 1 to 6,
f) patterning the first copper plate and the second copper plate from which the coating has been removed after step e);
A method for manufacturing a bonded substrate, further comprising: A method for manufacturing a bonded substrate according to any one of claims 1 to 7,
The thickness of the coating is 30 μm or less,
A method for manufacturing a bonded substrate, characterized in that: A method for manufacturing a bonded substrate according to any one of claims 1 to 8, comprising:
The average particle diameter of the release agent is 0.1 μm or more and 10 μm or less and less than or equal to the thickness of the coating,
A method for manufacturing a bonded substrate, characterized in that:

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