JP6443178B2 - Manufacturing method of power module substrate with Ag underlayer, power module substrate with Ag underlayer, and power module - Google Patents

Description

  The present invention relates to a method for manufacturing a power module substrate with an Ag underlayer in which a circuit layer is formed on one surface of an insulating layer, a power module substrate with an Ag underlayer, and a power module.

A semiconductor device such as an LED or a power module has a structure in which a semiconductor element is bonded on a circuit layer made of a conductive material.
In power semiconductor elements for large power control used to control wind power generation, electric vehicles, hybrid vehicles, etc., the amount of heat generated is large. Therefore, for example, AlN (aluminum nitride), Al A power module substrate comprising: an insulating layer made of a ceramic substrate such as ₂ O ₃ (alumina); and a circuit layer formed by disposing a metal having excellent conductivity on one surface of the insulating layer, Widely used in the past.
In such a power module substrate, a semiconductor element as a power element is mounted on the circuit layer via a solder material (see, for example, Patent Document 1).

As the metal constituting the circuit layer, aluminum or an aluminum alloy, or copper or a copper alloy is generally used.
Here, in a circuit layer made of aluminum or an aluminum alloy, since a natural oxide film of aluminum is formed on the surface, it is difficult to perform good bonding with a semiconductor element using a solder material.
Further, in a circuit layer made of copper or a copper alloy, there is a possibility that the molten solder material reacts with copper and the components of the solder material enter the inside of the circuit layer to deteriorate the characteristics of the circuit layer.
For this reason, conventionally, as shown in Patent Document 1, a Ni plating film is formed on the surface of a circuit layer, and then a semiconductor element is implemented by a solder material.

On the other hand, as a joining method that does not use a solder material, for example, Patent Document 2 proposes a technique for joining semiconductor elements using Ag nanopaste.
For example, Patent Documents 3 and 4 propose a technique for joining semiconductor elements using an oxide paste containing metal oxide particles and an organic reducing agent.

However, as disclosed in Patent Document 2, when a semiconductor element is bonded using an Ag nano paste without using a solder material, the bonding layer made of the Ag nano paste has a thickness larger than that of the solder material. Since it is formed thin, the stress at the time of thermal cycle load tends to act on the semiconductor element, and the semiconductor element itself may be damaged.
In addition, as disclosed in Patent Documents 3 and 4, when a semiconductor element is bonded using a metal oxide and a reducing agent, the fired layer of the oxide paste is still formed thinly. The stress at the time of thermal cycle load tends to act on the semiconductor element, and the performance of the power module may be deteriorated.

  Therefore, for example, in Patent Documents 5 to 7, after forming an Ag underlayer on a circuit layer made of aluminum or copper using a glass-containing Ag paste, the circuit layer and the semiconductor element are bonded via a solder material or an Ag paste. Techniques for joining have been proposed. In this technique, a glass-containing Ag paste is applied to the surface of a circuit layer made of aluminum or copper and baked, thereby removing the oxide film formed on the surface of the circuit layer by reacting with glass to remove the Ag layer. A ground layer is formed, and a semiconductor element is bonded to the circuit layer on which the Ag underlayer is formed via a solder material.

  Here, the Ag underlayer includes a glass layer formed by reacting glass with an oxide film of a circuit layer, and an Ag layer formed on the glass layer. Conductive particles are dispersed in the glass layer, and conduction of the glass layer is secured by the conductive particles.

JP 2004-172378 A JP 2008-208442 A JP 2009-267374 A JP 2006-202938 A JP 2010-287869 A JP 2012-109315 A JP 2013-012706 A

By the way, in order to improve the bonding reliability between the circuit layer and the Ag underlayer, it is effective to increase the glass content in the glass-containing Ag paste.
However, when the glass content in the glass-containing Ag paste is increased, the glass layer becomes thicker in the Ag underlayer. Even when conductive particles are dispersed, the glass layer has a higher electrical resistance than an Ag layer or the like. For this reason, as the glass layer becomes thicker, the electrical resistance value of the Ag underlayer tends to increase, and it is difficult to balance both the bonding reliability and the electrical resistance value. Thus, when the electrical resistance value of the Ag underlayer is high, when the circuit layer on which the Ag underlayer is formed and the semiconductor element are joined via a solder material, the circuit layer and the electronic component such as the semiconductor element are There was a risk that the conductivity could not be ensured.

  The present invention has been made in view of the above-described circumstances, and even when an Ag underlayer having a glass layer and an Ag layer is formed on a circuit layer, the electrical resistance value in the Ag underlayer is sufficient. An object of the present invention is to provide a method for manufacturing a substrate for a power module with an Ag underlayer, a substrate for a power module with an Ag underlayer, and a power module that can be reduced.

In order to solve such problems and achieve the above object, a method for manufacturing a substrate for a power module with an Ag underlayer of the present invention includes a circuit layer formed on one surface of an insulating layer, and the circuit layer. A method for producing a substrate for a power module with an Ag underlayer comprising an Ag underlayer formed on the substrate, wherein a glass-containing Ag paste is applied to one surface of the circuit layer; and the glass-containing Ag A baking step of baking a paste to form an Ag underlayer composed of a glass layer formed on the circuit layer side and an Ag layer laminated on the glass layer, and the glass layer of the Ag layer is opposite to the glass layer An ultrasonic treatment step of bringing a horn of an ultrasonic wave application device into contact with the side surface, applying ultrasonic waves to the Ag layer, and forming a portion where the Ag layer and the circuit layer are in direct contact with each other. It is characterized by.

According to the method for manufacturing a power module substrate with an Ag underlayer having this configuration, an Ag underlayer in which an Ag layer is laminated on a glass layer is formed by firing a glass-containing Ag paste, and the glass is included in the Ag layer. Since the ultrasonic treatment step of applying ultrasonic waves to the Ag layer is provided by bringing the horn of the ultrasonic wave application device into contact with the surface opposite to the layer, the electrical resistance value in the Ag underlayer is greatly reduced. It becomes possible. That is, by applying ultrasonic waves to the Ag layer by bringing the horn of the ultrasonic wave application device into contact, the pores formed in the Ag layer at the time of firing are crushed and the density of the Ag layer is improved, and part of the Ag layer It is considered that a portion in direct contact with the circuit layer is formed, and the electrical resistance value in the Ag underlayer is significantly reduced.
In addition, since the ultrasonic wave is applied by directly contacting the Ag layer with the Ag layer, the ultrasonic wave is applied only to a necessary portion of the Ag layer without masking or the like, and the electric resistance value is locally applied. It can be reduced.

Here, in the method for manufacturing a power module substrate with an Ag underlayer of the present invention, in the ultrasonic treatment step, the horn is brought into contact with the Ag layer in a state where ultrasonic waves are oscillated in advance in the horn. Is preferred.
When an ultrasonic wave is oscillated in a state where the horn is in contact with the Ag underlayer, wrinkles may occur in the Ag underlayer due to an impact at the time of oscillation. Therefore, the generation of wrinkles in the Ag underlayer can be suppressed by making the horn contact the Ag underlayer in a state where ultrasonic waves are oscillated in advance in the horn.

A power module substrate with an Ag underlayer of the present invention is a power module substrate with an Ag underlayer comprising a circuit layer formed on one surface of an insulating layer and an Ag underlayer formed on the circuit layer. The Ag underlayer is composed of a glass layer formed on the circuit layer side and an Ag layer laminated on the glass layer, and a portion where the Ag layer and the circuit layer are in direct contact is formed. It is characterized by having.
According to the power module substrate with an Ag underlayer having this configuration, the Ag underlayer includes a glass layer formed on the circuit layer side and an Ag layer laminated on the glass layer, and the Ag layer Since the portion where the circuit layer and the circuit layer are in direct contact with each other is formed , the electric resistance value in the Ag underlayer can be greatly reduced even if the glass layer is provided.

Here, in the power module substrate with an Ag underlayer of the present invention, it is preferable that the electrical resistance value in the thickness direction at the place where the Ag layer and the circuit layer are in direct contact is 10 mΩ or less.
In this case, since the electrical resistance value in the thickness direction at the portion where the Ag layer and the circuit layer are in direct contact with each other is 10 mΩ or less in the Ag underlayer, the conductivity in the Ag underlayer is ensured. By mounting a semiconductor element on the base layer, a power module with less current loss can be obtained.

The power module of the present invention includes the above power module substrate with an Ag underlayer and a semiconductor element, and the semiconductor element is bonded to the Ag underlayer through a bonding layer. It is said.
According to the power module having this configuration, since ultrasonic waves are applied to at least a part of the Ag layer, the electrical resistance value in the Ag underlayer can be greatly reduced even if the glass layer is provided. Therefore, it is possible to provide a power module that is excellent in bonding reliability and in which the circuit layer and the semiconductor element are securely bonded.

  According to the present invention, even when an Ag underlayer having a glass layer and an Ag layer is formed on a circuit layer, the electrical resistance value in the Ag underlayer can be sufficiently reduced. It becomes possible to provide a method for manufacturing a power module substrate, a power module substrate with an Ag underlayer, and a power module.

It is a schematic explanatory drawing of the power module which is embodiment of this invention. It is a schematic explanatory drawing of the board | substrate for power modules with an Ag base layer which is embodiment of this invention. It is a principal part expanded sectional view which shows the junction part of Ag base layer and a circuit layer. It is a flowchart of the manufacturing method of the board | substrate for power modules with an Ag base layer which is embodiment of this invention. It is a schematic explanatory drawing of the manufacturing method of the board | substrate for power modules with an Ag base layer which is embodiment of this invention. It is upper surface explanatory drawing which shows the measuring method of the electrical resistance value of the thickness direction of Ag base layer. It is side surface explanatory drawing which shows the measuring method of the electrical resistance value of the thickness direction of Ag base layer.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a power module 1 according to an embodiment of the present invention. The power module 1 includes a power module substrate 10 with an Ag underlayer, and a semiconductor element 3 bonded to one surface (the upper surface in FIG. 1) of the power module substrate 10 with an Ag underlayer via a bonding layer 2. And a heat sink 41 disposed on the other surface (lower side in FIG. 1) of the power module substrate 10 with an Ag underlayer.

  As shown in FIG. 2, a power module substrate 10 with an Ag underlayer includes a ceramic substrate 11 constituting an insulating layer, and a circuit layer 12 disposed on one surface (the upper surface in FIG. 2) of the ceramic substrate 11. And a metal layer 13 disposed on the other surface (lower surface in FIG. 2) of the ceramic substrate 11 and an Ag underlayer 30 formed on one surface of the circuit layer 12.

The ceramic substrate 11 prevents electrical connection between the circuit layer 12 and the metal layer 13. For example, AlN (aluminum nitride), Si ₃ N ₄ (silicon nitride), Al ₂ having a high insulating property is used. O ₃ is composed of (alumina) or the like. In this embodiment, it is comprised with AlN (aluminum nitride) excellent in heat dissipation. In addition, the thickness of the ceramic substrate 11 is set within a range of 0.2 to 1.5 mm, and in this embodiment is set to 0.635 mm.

  As shown in FIG. 5, the circuit layer 12 is formed by bonding a conductive metal plate 22 to one surface of the ceramic substrate 11. In the present embodiment, the circuit layer 12 is formed by joining an aluminum plate made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more to the ceramic substrate 11. The circuit layer 12 is formed with a circuit pattern, and one surface (the upper surface in FIG. 1) is a mounting surface on which the semiconductor element 3 is mounted. Here, the thickness of the circuit layer 12 (metal plate 22) is set within a range of 0.2 mm to 3.0 mm, and is set to 0.6 mm in the present embodiment.

  As shown in FIG. 5, the metal layer 13 is formed by bonding a metal plate 23 to the other surface of the ceramic substrate 11. In this embodiment, the metal layer 13 is formed by joining an aluminum plate made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more to the ceramic substrate 11. Here, the thickness of the metal layer 13 (metal plate 23) is set within a range of 0.2 mm to 3.0 mm, and is set to 1.6 mm in the present embodiment.

As will be described later, the Ag base layer 30 is a fired body of a glass-containing Ag paste containing a glass component. The Ag underlayer 30 was formed on the glass layer 31 and the glass layer 31 formed on the circuit layer 12 side as shown in FIGS. 2 and 3 before the semiconductor element 3 is bonded. And an Ag layer 32.
In the glass layer 31, fine conductive particles 33 having a particle diameter of about several nanometers are dispersed. The conductive particles 33 are crystalline particles containing at least one of Ag and Al. In addition, the electroconductive particle 33 in the glass layer 31 is observed by using a transmission electron microscope (TEM), for example.
In addition, fine glass particles (not shown) having a particle size of about several nanometers are dispersed inside the Ag layer 32.

  In the present embodiment, since the circuit layer 12 is made of aluminum having a purity of 99.99 mass% or more, an aluminum oxide film 12A that is naturally generated in the atmosphere is formed on the surface of the circuit layer 12. . Here, in the portion where the Ag underlayer 30 is formed, the aluminum oxide film 12A is removed, and the Ag underlayer 30 is directly formed on the circuit layer 12. That is, as shown in FIG. 3, the aluminum constituting the circuit layer 12 and the glass layer 31 are directly bonded.

  In the present embodiment, as shown in FIG. 3, the thickness to of the aluminum oxide film 12A that naturally occurs on the circuit layer 12 is 4 nm ≦ to ≦ 6 nm. Further, the thickness tg of the glass layer 31 is 0.01 μm ≦ tg ≦ 5 μm, the thickness ta of the Ag layer 32 before ultrasonic treatment described later is 1 μm ≦ ta ≦ 100 μm, and the total thickness of the Ag underlayer 30 is 1. It is configured to satisfy 01 μm ≦ t1 ≦ 105 μm.

  In the present embodiment, the surface of the Ag base layer 30 (upper surface in FIG. 3) is subjected to ultrasonic treatment. Pressure is applied to the Ag layer 32 by this ultrasonic treatment, and pores inside the Ag layer 32 are crushed. Further, a portion where a part of the Ag layer 32 is in direct contact with the circuit layer 12 is formed.

  Further, in the present embodiment, the electrical resistance value P in the thickness direction at a portion where the ultrasonic treatment is performed in the Ag underlayer 30 is set to 10 mΩ or less. Here, in the present embodiment, the electrical resistance value in the thickness direction of the Ag base layer 30 is the electrical resistance value between the upper surface of the Ag base layer 30 and the upper surface of the circuit layer 12. This is because the electrical resistance of 4N aluminum constituting the circuit layer 12 is very small compared to the electrical resistance in the thickness direction of the Ag base layer 30. When measuring the electrical resistance, as shown in FIGS. 6 and 7, the Ag base layer 30 has an upper surface center point (a location subjected to ultrasonic treatment) and the Ag base layer 30 from the upper surface center point to Ag. The electrical resistance between the point on the circuit layer 12 that is separated from the end of the Ag base layer 30 by the same distance as the distance to the end of the base layer 30 is measured.

  In the power module 1 according to the present embodiment, the bonding layer 2 is provided between the semiconductor element 3 and the Ag base layer 30. An example of the bonding layer 2 is a solder layer. Examples of the solder material for forming the solder layer include Sn—Ag, Sn—In, and Sn—Ag—Cu.

  The heat sink 41 is for cooling the above-described power module substrate 10 with an Ag underlayer, and includes a flow path 42 for circulating a cooling medium (for example, cooling water). In the present embodiment, the heat sink 41 is a multi-hole tube made of aluminum or an aluminum alloy. In the present embodiment, the metal layer 13 and the heat sink 41 are joined via a brazing material such as Al—Si.

Next, the glass-containing Ag paste for forming the Ag underlayer 30 will be described.
This glass-containing Ag paste contains Ag powder, glass powder, resin, solvent, and dispersant, and the content of the powder component composed of Ag powder and glass powder is the glass-containing Ag paste. The total content is 60% by mass or more and 90% by mass or less, and the remainder is a resin, a solvent, and a dispersant.

In addition, in this embodiment, content of the powder component which consists of Ag powder and glass powder is 85 mass% of the whole glass containing Ag paste.
Further, the viscosity of the glass-containing Ag paste is adjusted to 10 Pa · s or more and 500 Pa · s or less, more preferably 50 Pa · s or more and 300 Pa · s or less.

The Ag powder has a particle size of 0.05 μm or more and 1.0 μm or less. In this embodiment, an Ag powder having an average particle size of 0.8 μm was used.
The glass powder contains, for example, any one or more of lead oxide, zinc oxide, silicon oxide, boron oxide, phosphorus oxide and bismuth oxide, and the softening temperature is 600 ° C. or less. In the present embodiment, glass powder made of lead oxide, zinc oxide and boron oxide and having an average particle size of 0.5 μm was used.
The weight ratio A / G between the weight A of the Ag powder and the weight G of the glass powder is adjusted within the range of 80/20 to 99/1. In this embodiment, A / G = 80/5 It was.

A solvent having a boiling point of 200 ° C. or higher is suitable. In this embodiment, diethylene glycol dibutyl ether is used.
The resin is used to adjust the viscosity of the glass-containing Ag paste, and those that decompose at 500 ° C. or higher are suitable. In this embodiment, ethyl cellulose is used.
In this embodiment, a dicarboxylic acid-based dispersant is added. In addition, you may comprise a glass containing Ag paste, without adding a dispersing agent.

  This glass-containing Ag paste is prepared by premixing a mixed powder obtained by mixing Ag powder and glass powder and an organic mixture obtained by mixing a solvent and a resin together with a dispersing agent using a mixer, and then using the roll mill machine. After mixing while kneading, the resulting kneaded product is produced by filtering with a paste filter.

Next, the manufacturing method of the board | substrate 10 for power modules with an Ag base layer which is this embodiment is demonstrated with reference to FIG.4 and FIG.5.
First, a metal plate 22 to be the circuit layer 12 and a metal plate 23 to be the metal layer 13 are prepared, and these metal plates 22 and 23 are respectively placed on one surface and the other surface of the ceramic substrate 11 with a brazing material 26 interposed therebetween. Then, the metal plates 22 and 23 and the ceramic substrate 11 are joined by cooling after pressurizing and heating (circuit layer and metal layer forming step S01).
In the circuit layer and metal layer forming step S01, an Al-7.5 mass% Si brazing foil was used as the brazing material 26, and the brazing temperature was set to 640 ° C to 650 ° C.

Next, an Ag underlayer 30 is formed on one surface of the circuit layer 12 (Ag underlayer formation step S02).
In this Ag underlayer forming step S02, first, a glass-containing Ag paste is applied to one surface of the circuit layer 12 (application step S21). In addition, when apply | coating a glass containing Ag paste, various means, such as a screen printing method, an offset printing method, and a photosensitive process, are employable. In this embodiment, the glass-containing Ag paste was formed in a pattern by a screen printing method.

In a state in which the glass-containing Ag paste is applied to one surface of the circuit layer 12, the glass-containing Ag paste is fired by being placed in a heating furnace (firing step S22). In addition, the baking temperature at this time is set to 350 to 645 degreeC, for example.
By this firing step S <b> 22, the Ag base layer 30 including the glass layer 31 and the Ag layer 32 is formed. At this time, the aluminum oxide film 12A naturally generated on the surface of the circuit layer 12 is melted and removed by the glass layer 31, and the glass layer 31 is directly formed on the circuit layer 12. In addition, fine conductive particles 33 having a particle size of about several nanometers are dispersed inside the glass layer 31. The conductive particles 33 are crystalline particles containing at least one of Ag or Al, and are presumed to have precipitated in the glass layer 31 during firing.

Next, the horn 51 of the ultrasonic wave applicator 50 is brought into contact with the surface of the Ag underlayer 30 opposite to the circuit layer 12 (surface opposite to the glass layer 31 of the Ag layer 32). A sound wave is applied (ultrasonic treatment step S23).
In this ultrasonic treatment step S23, it is preferable to use a horn 51 having a contact area in the range of 20 mm ² or more and 200 mm ² or less. Ultrasonic waves are oscillated in advance in the horn 51, and the horn 51 is brought into contact with the Ag layer 32 and slid so as to stroke the surface of the Ag layer 32, whereby ultrasonic waves are applied to the Ag layer 32. .
In the ultrasonic treatment step S23, the output is preferably in the range of 100 W to 200 W.

  Thus, the substrate 10 for power modules with an Ag underlayer according to the present embodiment is manufactured.

Next, a heat sink 41 is laminated on the other surface side of the metal layer 13 via a brazing material, and the heat sink 41 and the metal layer 13 are joined by cooling after pressurization and heating (heat sink cooler joining step). S03).
In addition, in this heat sink cooler joining process S03, the brazing temperature was set to 590 degreeC-610 degreeC using Al-10mass% Si brazing foil as a brazing material.

Then, the semiconductor element 3 is placed on the Ag layer 32 of the Ag base layer 30 via a solder material, and solder-bonded in a reduction furnace (semiconductor element bonding step S04).
At this time, part or all of the Ag layer 32 constituting the Ag underlayer 30 is melted in the bonding layer 2 formed of the solder material.
Thereby, the power module 1 in which the semiconductor element 3 is bonded onto the circuit layer 12 via the bonding layer 2 is produced.

  According to the power module 1 and the power module substrate with an Ag base layer 10 according to the present embodiment configured as described above, the glass layer 31 and the glass layer 31 are laminated on one surface of the circuit layer 12. An Ag underlayer 30 composed of the Ag layer 32 is formed, and the surface of the Ag underlayer 30 opposite to the circuit layer 12 (the surface of the Ag layer 32 opposite to the glass layer 31) is super Since ultrasonic waves are applied by the horn 51 of the sonic wave applying device 50, pressure can be applied to the Ag layer 32, the pores inside the Ag layer 32 are crushed, and the circuit layer 12 is partially formed on the Ag layer 32. As a result, a portion in direct contact with the Ag underlayer 30 can be greatly reduced.

Here, in the present embodiment, in the ultrasonic treatment step S23, ultrasonic waves are oscillated in advance on the horn 51 of the ultrasonic wave application device 50, and this horn 51 is brought into contact with the Ag layer 32 so that the surface of the Ag layer 32 is covered. Since the ultrasonic wave is applied to the Ag layer 32 by sliding it like stroking, it is possible to suppress wrinkles from being generated in the Ag layer 32 due to an impact when the ultrasonic wave is oscillated.
In addition, since ultrasonic waves can be selectively applied to the Ag layer 32 where the horn 51 is brought into contact, pressure is applied only to necessary portions of the Ag layer 32 without performing masking or the like, thereby reducing the electrical resistance value. can do.

  In addition, since the electrical resistance value P in the thickness direction at the portion subjected to the ultrasonic treatment in the Ag underlayer 30 is set to 10 mΩ or less, the conductivity in the Ag underlayer 30 is ensured, and the Ag underlayer 30 By bonding the semiconductor element 3 to 30 via the bonding layer 2, the power module 1 with less current loss can be obtained.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, in the present embodiment, the metal plate constituting the circuit layer and the metal layer has been described as a rolled plate of pure aluminum (4N aluminum) having a purity of 99.99 mass%, but the present invention is not limited to this. You may be comprised with the other aluminum or aluminum alloy. Moreover, the metal plate which comprises a circuit layer and a metal layer is good also as what was comprised with copper or copper alloy. Furthermore, it is good also as a thing of the structure which solid-phase diffusion-bonded the copper plate and the aluminum plate.

Moreover, although it demonstrated as what joins an aluminum plate and a ceramic substrate by brazing, it is not limited to this, Even if it applies a transient liquid phase bonding method (Transient Liquid Phase Bonding), a casting method, etc. Good.
Furthermore, when the metal plate constituting the circuit layer and the metal layer is made of copper or a copper alloy, when joining the metal plate made of copper or copper alloy to the ceramic substrate, the direct joining method (DBC method), the activity A metal brazing method, a casting method, or the like can be applied.

Also, have been described as using a ceramic substrate made of AlN as an insulating layer, is not limited thereto, it may be used a ceramic substrate made of Si ₃ N ₄ or Al ₂ O _3, or the like, insulating The insulating layer may be made of resin.

  Furthermore, in this embodiment, although demonstrated as what joins a semiconductor element via a solder material on Ag base layer, it is not limited to this, A silver oxide paste, the paste containing silver particle, Ag powder A semiconductor element may be bonded onto the Ag underlayer using a conductive adhesive containing bismuth. In this case, since Ag is bonded to each other, the bonding reliability between the semiconductor element and the Ag underlayer can be improved.

  In addition, as a silver oxide paste, what contains silver oxide powder, a reducing agent, resin, a solvent, and an organometallic compound powder can be used. The content of the silver oxide powder is 60% by mass or more and 80% by mass or less of the entire silver oxide paste, and the content of the reducing agent is 5% by mass or more and 15% by mass or less of the entire silver oxide paste. The content is preferably 0% by mass or more and 10% by mass or less of the entire silver oxide paste, and the remainder is preferably a solvent. Here, in the silver oxide paste, it is preferable not to add a dispersant or a resin in order to prevent unreacted organic matter from remaining after sintering.

Further, the heat sink is not limited to the one exemplified in this embodiment, and the structure of the heat sink is not particularly limited.
Further, a buffer layer may be provided between the heat sink and the metal layer. As the buffer layer, a plate made of aluminum, an aluminum alloy, or a composite material containing aluminum (for example, AlSiC) can be used.

  A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.

A metal plate was joined to one surface of the ceramic substrate to form a circuit layer. Here, the ceramic substrate was AlN, and the size was 27 mm × 17 mm × 0.6 mm. The metal plate used as the circuit layer was made of the material shown in Table 1, and the size was 25 mm × 15 mm × 0.3 mm.
When the metal plate was an aluminum plate, an Al—Si brazing material was used as the bonding material. Moreover, when the metal plate was a copper plate, an active metal brazing material (Ag—Cu—Ti brazing material) was used as the bonding material.

An Ag underlayer was formed by applying the glass-containing Ag paste described in the embodiment to the surface of the circuit layer and heat-treating it.
As the glass powder of the glass-containing Ag paste, a _Bi 2 _{O 3} 90.6 wt%, the ZnO 2.6 _wt%, the B 2 _{O 3} 6.8 wt%, with lead-free glass powder containing. Further, ethyl cellulose was used as the resin, and diethylene glycol dibutyl ether was used as the solvent. Furthermore, a dicarboxylic acid-based dispersant was added.
Here, the weight ratio A / G between the weight A of the Ag powder and the weight G of the glass powder in the glass-containing Ag paste and the coating amount were adjusted, and the thicknesses of the glass layer and the Ag layer were adjusted as shown in Table 1. It was adjusted.

And ultrasonic treatment was implemented on the conditions shown in Table 1 with respect to the whole surface of Ag layer among baking Ag base layers. In Comparative Example 1-3, no ultrasonic treatment was performed.
About the obtained substrate for power module with an Ag underlayer of the present invention example and the comparative example, the thickness of the Ag underlayer was measured by using the tester (manufactured by KEITHLEY: 2010 MULTITIMER) by the method described in FIGS. The electric resistance value in the direction was measured. The electrical resistance is measured on a circuit layer that is separated from the Ag base layer edge by H when the upper surface center point of the Ag base layer is a distance H from the top center point of the Ag base layer to the Ag base layer edge. And went between. The evaluation results are shown in Table 1.

In the present invention example in which the Ag underlayer was subjected to ultrasonic treatment, the electrical resistance value was lower than that of the comparative example having the glass layer and the Ag layer having the same thickness.
From the above, according to the present invention, it was confirmed that an Ag underlayer-provided power module substrate having an Ag underlayer with low electrical resistance can be provided.

1 Power Module 10 Ag Module Power Module Substrate 11 Ceramic Substrate (Insulating Layer)
12 circuit layer 30 Ag base layer 31 glass layer 32 Ag layer

Claims (5)

A method of manufacturing a power module substrate with an Ag underlayer comprising a circuit layer formed on one surface of an insulating layer and an Ag underlayer formed on the circuit layer,
An application step of applying a glass-containing Ag paste to one surface of the circuit layer;
A firing step of firing the glass-containing Ag paste to form an Ag underlayer composed of a glass layer formed on the circuit layer side and an Ag layer laminated on the glass layer;
In the Ag layer, a horn of an ultrasonic wave application device is brought into contact with the surface opposite to the glass layer, ultrasonic waves are applied to the Ag layer, and the Ag layer and the circuit layer are in direct contact with each other. A sonication process to be formed ;
The manufacturing method of the board | substrate for power modules with an Ag base layer characterized by having.   2. The manufacturing of a power module substrate with an Ag underlayer according to claim 1, wherein in the ultrasonic treatment step, the horn is brought into contact with the Ag layer in a state where ultrasonic waves are oscillated in advance in the horn. Method. A power module substrate with an Ag underlayer comprising a circuit layer formed on one surface of an insulating layer and an Ag underlayer formed on the circuit layer,
The Ag underlayer is composed of a glass layer formed on the circuit layer side and an Ag layer laminated on the glass layer, and a location where the Ag layer and the circuit layer are in direct contact is formed. A substrate for a power module with an Ag underlayer characterized by 4. The power module substrate with an Ag underlayer according to claim 3, wherein an electrical resistance value in a thickness direction at a portion where the Ag layer and the circuit layer are in direct contact with each other is 10 mΩ or less. A power module substrate with an Ag underlayer according to claim 3 or 4, and a semiconductor element,
The power module, wherein the semiconductor element is bonded to the Ag base layer through a bonding layer.

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