JP2017118061A - Circuit board production method, circuit board, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a warp caused by mutually bonding different materials, which are different from each other in thermal expansion coefficient, to prevent a damage attributed to the bending of an insulator layer, and to enhance the bondability of a semiconductor device.SOLUTION: A circuit board production method comprises: a coating step for coating a circuit layer with a glass-containing Ag paste; and a sintering step for sintering the coated Ag paste to form an Ag sintered layer composed of a sintered product of the glass-containing Ag paste. In the sintering step, the sintering temperature of the Ag paste is equal to or higher than 250°C and lower than 350°C. The glass that the Ag paste contains has a composition as described below on the supposition that the total amount of the glass is 100 mol%: POis 30-65 mol%; SnO is 30-65 mol%; SiOis 0.1-10 mol%; AlOis 0.1-10 mol%; and BOis 0.1-10 mol%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a circuit board in which a circuit layer and a metal layer are formed on an insulating layer, a circuit board, and a semiconductor device.

Among various semiconductor elements, for example, a power element for high power control used for controlling an electric vehicle or an electric vehicle has a large amount of heat generation. As a substrate on which such a power element for high power control is mounted, for example, a power module substrate (circuit substrate) in which a metal plate having excellent conductivity is bonded as a circuit layer on a ceramic substrate made of AlN (aluminum nitride) or the like. 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 the circuit layer made of aluminum, since a natural oxide film of aluminum is formed on the surface, it is difficult to perform good bonding with the solder material. Further, in the circuit layer made of copper, there has been a problem that the molten solder material reacts with copper and the components of the solder material penetrate into the circuit layer to deteriorate the conductivity of the circuit layer.

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.
Further, for example, Patent Documents 3 and 4 propose a technique for joining semiconductor elements using an oxide paste containing metal oxide particles and a reducing agent made of an organic substance without using a solder material.

  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 fired layer 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, whereby the oxide film formed on the surface of the circuit layer is removed by reacting with the glass to bak the Ag. A layer is formed, and a semiconductor element is joined via a solder material on the circuit layer on which the Ag fired layer is formed.

  Here, the Ag fired layer 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

  However, when a conventional glass-containing Ag paste is fired to form an Ag fired layer, the temperature zone necessary for firing is relatively high (for example, about 350 ° C. to 650 ° C.), so the circuit board is configured. The difference in coefficient of thermal expansion between different types of materials increases, and the warping (curving) of the circuit board tends to increase. If the warp of the circuit board becomes too large, the insulating layer may be damaged, and the bondability between the circuit layer and the semiconductor element may be reduced.

  When circuit layers and metal layers are formed symmetrically on both sides of an insulating layer, warping may occur due to variations in heating, cooling, load, etc. during bonding. In addition, in the case of a circuit board (integrated circuit board) in which a cooler or the like is further joined to one side of the insulating layer, both sides of the insulating layer have an asymmetric shape, so that warpage is particularly large, and damage to the insulating layer There is a problem that a bonding failure of a semiconductor element mounted on the Ag fired layer is likely to occur. The above problem is not limited to a circuit board provided with a cooler, but also applies to a circuit board in which a circuit layer and a metal layer are formed asymmetrically on both sides of an insulating layer.

  The present invention has been made in view of the above-described circumstances, and reduces the warpage caused by joining different types of materials having different thermal expansion coefficients, prevents damage due to the bending of the insulating layer, and improves the bondability of the semiconductor element. It is an object of the present invention to provide a circuit board manufacturing method, a circuit board, and a semiconductor device that can be improved.

In order to solve the above-described problems, a circuit board manufacturing method according to an embodiment of the present invention includes a circuit layer made of Al or an Al alloy formed on one surface of an insulating layer, and formed on the circuit layer. A method of manufacturing a circuit board comprising at least an Ag fired layer, wherein an application step of applying an Ag paste containing glass on the circuit layer, and firing the applied Ag paste to form an Ag paste containing glass A firing step of forming the Ag fired layer made of the fired body, wherein the firing temperature of the Ag paste in the firing step is 250 ° C. or higher and lower than 350 ° C., and the glass contained in the Ag paste is When the total amount of glass is 100 mol%, P ₂ O ₅ is 30 mol% or more and 65 mol% or less, SnO is 30 mol% or more and 65 mol% or less, and SiO ₂ is 0.00. The composition is characterized by having a composition of 1 mol% or more and 10 mol% or less, Al ₂ O ₃ of 0.1 mol% or more and 10 mol% or less, and B ₂ O ₃ of 0.1 mol% or more and 10 mol% or less.

  According to the circuit board manufacturing method of one embodiment of the present invention, the glass contained in the Ag paste has the above-described composition, whereby the Ag fired layer is formed at a firing temperature as low as 250 ° C. or higher and lower than 350 ° C. be able to. Such low-temperature firing can suppress thermal strain that occurs between different materials constituting the circuit board when the Ag fired layer is formed. Therefore, it is possible to prevent the insulating layer from being damaged due to a large warp during the manufacturing process. Further, when the semiconductor element is mounted on the circuit layer, it is possible to reliably prevent the semiconductor element from being peeled off due to the curvature of the circuit board or causing a conduction failure.

Here, when P ₂ O ₅ is less than 30 mol%, vitrification becomes difficult, and when an Ag paste containing glass is baked, the reaction between the glass component and the circuit layer becomes insufficient, and the circuit layer and the Ag baked layer Adhesion decreases. On the other hand, when it exceeds 65 mol%, the water resistance and weather resistance are deteriorated, so that the properties of the Ag fired layer surface change and cause a poor bonding when the semiconductor element is joined to the Ag fired layer.
When SnO is less than 30 mol%, the glass transition temperature becomes high, and when the Ag paste is fired, the reaction between the glass component and the circuit layer becomes insufficient, and the adhesion between the circuit layer and the Ag fired layer is lowered. Moreover, when it exceeds 65 mol%, vitrification will become difficult.
SiO ₂ and Al ₂ O ₃ impart water resistance and weather resistance, but if they are less than 0.1 mol%, there is no effect, and water resistance and weather resistance deteriorate, and the properties of the Ag fired layer surface change. When the semiconductor element is bonded to the Ag fired layer, a bonding failure is caused. Moreover, when it exceeds 10 mol%, a glass transition temperature will rise.
B ₂ O ₃ improves crystallization resistance, but if it is less than 0.1 mol%, it is ineffective and vitrification becomes difficult. Therefore, when an Ag paste containing glass is fired, the glass component and the circuit layer Reaction becomes insufficient, and the adhesion between the circuit layer and the Ag fired layer is lowered. If it exceeds 10 mol%, phase separation tends to occur, and when the Ag paste is baked, the reaction between the glass component and the circuit layer becomes non-uniform, resulting in a decrease in adhesion.

In one embodiment of the present invention, a cooler forming step of forming a cooler on the other surface side of the insulating layer is further provided before the applying step.
The circuit board on which the cooler is formed has an asymmetric configuration on both sides centering on the insulating layer, but since the firing temperature when forming the Ag fired layer can be lowered, an increase in thermal strain due to the asymmetric configuration is suppressed. Thus, damage to the insulating layer due to the occurrence of large warpage can be reliably prevented. Then, when forming the cooler over the other side of the insulating layer in the cooler forming step, for example, when the cooler is joined at a high temperature of 350 ° C. or higher by brazing or the like, Since the Ag fired layer can be formed at a low temperature, it is possible to reliably prevent the cooler bonded in the previous step from being exposed to a high temperature of 350 ° C. or more and peeling or increasing warpage.

According to another embodiment of the present invention, there is provided a circuit board manufacturing method comprising: a circuit layer made of Al or an Al alloy formed on one surface of an insulating layer; a metal layer formed on the other surface of the insulating layer; A method of manufacturing a circuit board comprising at least an Ag fired layer formed on a metal layer, wherein an application step of applying an Ag paste containing glass on the metal layer, and firing the applied Ag paste And a firing step of forming the Ag fired layer composed of a fired body of an Ag paste containing glass, and the firing temperature of the Ag paste in the firing step is 250 ° C. or higher and lower than 350 ° C., glass contained in the Ag paste, the total amount of the glass when the _100mol%, P 2 _{O 5} is 30 mol% or more, 65 mol% or less, SnO is 30 mol% or more, less 65 mol% SiO ₂ is 0.1 mol% or more, 10 mol% or less, _Al 2 _{O 3} is 0.1 mol% or more, 10 mol% or _less, B 2 _{O 3} is 0.1 mol% or more, characterized by having a composition of 10 mol% or less, And

  According to the circuit board manufacturing method of another embodiment of the present invention, the glass contained in the Ag paste has the above-described composition, thereby forming an Ag fired layer at a low firing temperature of 250 ° C. or higher and lower than 350 ° C. can do. Such low-temperature firing can suppress thermal strain that occurs between different materials constituting the circuit board when the Ag fired layer is formed. Therefore, it is possible to prevent the insulating layer from being damaged due to a large warp during the manufacturing process. Further, when the semiconductor element is mounted on the circuit layer, it is possible to reliably prevent the semiconductor element from being peeled off due to the curvature of the circuit board or causing a conduction failure.

In one embodiment of the present invention, a cooler forming step of forming a cooler on the Ag fired layer is further provided.
The circuit board on which the cooler is formed has an asymmetric configuration on both sides centering on the insulating layer, but since the firing temperature when forming the Ag fired layer can be lowered, an increase in thermal strain due to the asymmetric configuration is suppressed. Thus, damage to the insulating layer due to the occurrence of large warpage can be reliably prevented.

A circuit board according to an embodiment of the present invention is a circuit board including at least a circuit layer made of Al or an Al alloy formed on one surface of an insulating layer, and an Ag fired layer formed on the circuit layer. The Ag fired layer is a fired body of an Ag paste containing glass, and includes a glass layer formed on the circuit layer and an Ag layer formed on the glass layer. Contains 25 mol% or more and 57 mol% or less of P ₂ O _{5 and} 25 mol% or more and 57 mol% or less of SnO, and the warpage amount of the circuit board is 50 μm / 10 mm or less.

According to the circuit board of one embodiment of the present invention, an Ag fired layer can be formed at a low temperature using an Ag paste that can be fired at a low temperature, so that the warpage of the entire circuit board is suppressed to 50 μm / 10 mm or less. It is possible to prevent the insulating layer from being damaged by the curvature. In addition, when a semiconductor element is mounted on a circuit layer, a circuit board with less warpage can reliably prevent the semiconductor element from being peeled off due to warpage or causing a conduction failure.
Here, when P ₂ O ₅ is less than 25 mol%, Ag paste with insufficient vitrification is fired, so that the reaction between the glass component and the circuit layer becomes insufficient, and the adhesiveness between the circuit layer and the Ag fired layer is low. Decreases. On the other hand, if it exceeds 57 mol%, the water resistance and weather resistance deteriorate, the properties of the Ag fired layer surface change, and when the semiconductor element is joined to the Ag fired layer, poor bonding is caused.
If SnO is less than 25 mol%, an Ag paste having a glass component having a high glass transition temperature is fired, and the reaction between the glass component and the circuit layer becomes insufficient, and the adhesion between the circuit layer and the Ag fired layer is lowered. On the other hand, if it exceeds 57 mol%, Ag paste with insufficient vitrification is fired, so that the reaction between the glass component and the circuit layer becomes insufficient, and the adhesion between the circuit layer and the Ag fired layer decreases.

A circuit board according to another embodiment of the present invention includes a circuit layer made of Al or an Al alloy formed on one surface of an insulating layer, a metal layer formed on the other surface of the insulating layer, and the metal layer A circuit board manufacturing method comprising at least an Ag fired layer formed on the glass substrate, wherein the Ag fired layer is a fired body of an Ag paste containing glass, and a glass layer formed on the metal layer And an Ag layer formed on the glass layer, wherein the glass layer contains P ₂ O ₅ of 25 mol% or more and 57 mol% or less, SnO of 25 mol% or more and 57 mol% or less, The warping amount of the circuit board is 50 μm / 10 mm or less.

  According to the circuit board of another embodiment of the present invention, an Ag fired layer can be formed at a low temperature using an Ag paste that can be fired at a low temperature, so that the warpage of the entire circuit board is suppressed to 50 μm / 10 mm or less. It is possible to prevent the insulating layer from being damaged by bending. In addition, when a semiconductor element is mounted on a circuit layer, a circuit board with less warpage can reliably prevent the semiconductor element from being peeled off due to warpage or causing a conduction failure.

In one embodiment of the present invention, a cooler is further formed on the other surface of the insulating layer.
An integrated circuit board provided with a cooler can form an Ag fired layer at a low firing temperature even if it has an asymmetrical structure on both sides with an insulating layer as the center, so the amount of warping of the circuit board is 50 μm / 10 mm or less. To suppress. Thereby, the damage by the curvature of an insulating layer can be prevented reliably. In addition, when a semiconductor element is mounted, it is possible to reliably prevent the semiconductor element from being peeled off or poorly connected due to warping.

In one embodiment of the present invention, the Ag fired layer has an electrical resistance value in the thickness direction of 7.5 × 10 ⁻⁴ Ω · m or less.
Accordingly, it is possible to reliably conduct electricity between the semiconductor element and the circuit layer through the Ag fired layer and the solder layer, and an electrically reliable circuit board can be formed.

In one embodiment of the present invention, an insulating substrate selected from AlN, Si ₃ N ₄ or Al ₂ O ₃ is used as the insulating layer.
A ceramic substrate selected from AlN, Si ₃ N ₄ or Al ₂ O ₃ is excellent in insulation and strength. By using such a ceramic substrate, the reliability of the circuit substrate can be improved. In addition, it is possible to easily form a circuit layer by bonding a metal plate made of aluminum or an aluminum alloy on the ceramic substrate.

A semiconductor device according to an embodiment of the present invention includes the circuit board described in each of the above items and a semiconductor element that is overlapped and bonded to the circuit layer of the circuit board.
According to the semiconductor device of one embodiment of the present invention, the Ag fired layer is formed at a firing temperature as low as 250 ° C. or higher and lower than 350 ° C., and the semiconductor element mounted on the circuit layer is peeled off by the curvature of the circuit board. Or the occurrence of poor conduction can be reliably prevented.

  According to the present invention, a method for manufacturing a circuit board, which enables formation of an Ag fired layer at a low temperature, prevents damage to an insulating layer due to warpage reduction, and improves the bondability of a semiconductor element, In addition, a semiconductor device can be provided.

It is sectional drawing which shows the semiconductor device using the circuit board of this invention. It is sectional drawing which shows the circuit board in 1st embodiment of this invention. It is a principal part expanded sectional view which shows the junction part of an Ag baking layer and a circuit layer. It is sectional drawing which shows the circuit board in 2nd embodiment of this invention. It is a flowchart which shows the manufacturing method of Ag paste. It is a flowchart which shows the manufacturing method of the circuit board in 1st embodiment of this invention. It is a flowchart which shows the manufacturing method of the circuit board in 2nd embodiment of this invention. It is a flowchart which shows the manufacturing method of the circuit board in 3rd embodiment of this invention.

  Hereinafter, a method for manufacturing a circuit board, a circuit board, and a semiconductor device of the present invention will be described with reference to the drawings. Each embodiment described below is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

(Circuit board: First embodiment)
FIG. 1 is a cross-sectional view showing a semiconductor device including a circuit board according to a first embodiment of the present invention.
In the present embodiment, as an example of the semiconductor device, a power module on which a semiconductor element including a power element for high power control is mounted is illustrated.
A power module (semiconductor device) 1 includes a circuit board 12 provided with a circuit layer 12 and a semiconductor element (power module element) bonded to the surface of the circuit layer 12 via a solder layer 2. 3 is provided.

  The circuit board 10 includes a ceramic substrate (insulating layer) 11 constituting an insulating layer, a circuit layer 12 disposed on one surface side 11a (upper surface in FIG. 1) of the ceramic substrate 11, and the other surface side of the ceramic substrate 11. 11b (the lower surface in FIG. 1).

The ceramic substrate (insulating layer) 11 prevents electrical connection between the circuit layer 12 and the metal layer 13. For example, AlN (aluminum nitride) having high insulating properties or Al ₂ O ₃ (oxidized) is used. Aluminum), Si ₃ N ₄ (silicon nitride) or the like may be used. In this embodiment, AlN is used. Moreover, the thickness of the ceramic substrate 11 is set within a range of 0.2 to 1.5 mm, for example, and as an example, is set to 0.635 mm in the present embodiment.

  The circuit layer 12 is formed by bonding a conductive metal plate to one surface 11 a of the ceramic substrate 11. The circuit layer 12 is made of Al or an alloy containing Al. For example, aluminum (2N—Al) having a purity of 99 mass% or more, aluminum (3N—Al) having a purity of 99.9 mass% or more, aluminum (4N—Al) having a purity of 99.99 mass% or more, or the like can be used. Moreover, the thickness of the circuit layer 12 is set within a range of 0.1 to 2.0 mm, for example, and is set to 0.6 mm in the present embodiment as an example. Furthermore, 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 metal layer 13 is formed by bonding a metal plate to the other surface side 11 b of the ceramic substrate 11. In the present embodiment, the metal layer 13 is formed by bonding 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, as with the circuit layer 12. Has been. Moreover, the thickness of the metal layer 13 is set, for example in the range of 0.1-3.0 mm, and is set to 0.6 mm in this embodiment as an example.

  The cooler 40 is for cooling the entire power module 1 by propagating the heat generated in the circuit board 10 and dissipating it. Such a cooler 40 includes a top plate portion 41, radiating fins 42, 42... Hanged downward from the top plate portion 41, and a flow path 43 for circulating a cooling medium (for example, cooling water). It has. The cooler 40 (top plate portion 41) is preferably made of a material having good thermal conductivity. In the present embodiment, it is made of, for example, A6063 (aluminum alloy).

  In addition, even if the top plate portion 41 and the heat radiation fins 42, 42,... Of the cooler 40 are formed as an integral member, the plurality of fins 42, 42,. It may be the configuration. When the top plate portion 41 and the plurality of fins 42, 42... Are configured as separate members, the top plate portion 41 and the plurality of fins 42, 42.

The cooler 40 is not limited to a water-cooled cooler that allows cooling water to flow through the flow path 43 as a cooling medium. For example, the cooler 40 allows air to flow through the flow path 43 or exposes the flow path 43 to outside air. A so-called air-cooled cooler may be used.
The cooler 40 can also be formed of a simple plate made of a material having excellent thermal conductivity, and does not have to have a shape in which a cooling medium flow path is formed.

  Further, a buffer layer made of aluminum, an aluminum alloy, or a composite material containing aluminum (for example, AlSiC) may be provided between the top plate portion 41 of the cooler 40 and the metal layer 13. As the buffer layer, for example, a plate material made of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more can be used.

  On one side (upper surface in FIG. 1) 12a of the circuit layer 12, an Ag fired layer 30 obtained by firing a glass-filled Ag paste described later at 250 ° C. or higher and lower than 350 ° C. is formed. The semiconductor element 3 is mounted on the surface of the layer 30 via the solder layer 2.

Examples of the solder material for forming the solder layer 2 include Sn—Ag solder, Sn—In solder, Sn—Ag—Cu solder, and the like.
As shown in FIG. 1, the Ag fired layer 30 is not formed on the entire surface 12 a of the circuit layer 12, but is selectively formed at least in a portion where the semiconductor element 3 is disposed. The aluminum plate which comprises the circuit layer 12 is exposed to the periphery.

FIG. 2 is a cross-sectional view showing a circuit board before mounting a semiconductor element. FIG. 3 is an enlarged cross-sectional view of a main part showing a joint portion between the Ag fired layer and the circuit layer.
In the circuit board 10, the aforementioned Ag fired layer 30 is formed on one surface side (the upper surface in FIGS. 2 and 3) 12 a of the circuit layer 12. As shown in FIG. 3, the Ag fired layer 30 includes a glass layer 31 formed on the circuit layer 12 side, and an Ag layer 32 formed on the glass layer 31. And in this glass layer 31, the fine electroconductive particle 33 whose particle size is about several nanometers is disperse | distributing, for example. The conductive particles 33 are, for example, crystalline particles containing at least one of Ag or Al.

The circuit layer 12 is made of aluminum having a purity of 99.99 mass%, but the one surface side 12a of the circuit layer 12 is covered with an aluminum oxide film (natural oxide film: Al ₂ O ₃ ) 12A naturally generated in the atmosphere. Is called. However, in the portion where the Ag fired layer 30 is formed, the aluminum oxide film 12A is removed by the reaction with the glass when the Ag fired layer 30 is formed.

  Therefore, in this portion (the portion of the circuit layer 12 that overlaps with the Ag fired layer 30), the Ag fired layer 30 is formed directly on the circuit layer 12 without the aluminum oxide film 12A interposed therebetween. That is, the aluminum constituting the circuit layer 12 and the glass layer 31 are directly bonded.

The glass layer 31 constituting the Ag fired layer 30 contains P ₂ O _{5 in} a range of 25 mol% or more and 57 mol% or less, and SnO in a range of 25 mol% or more and 57 mol% or less. The composition of the glass-filled Ag paste for bringing the content ratio of P ₂ O ₅ and SnO contained in the glass layer 31 into the above-described range will be described in detail in the manufacturing method.
Further, the amount of warpage of the entire power module substrate 10 is set to 50 μm / 10 mm or less. By setting the amount of warpage of the power module substrate 10 to 50 μm / 10 mm or less, the circuit layer 12 and the semiconductor element 3 are firmly bonded without being separated through the solder layer 2, and the ceramic substrate 11 is bent. Prevent damage.

  The thickness of the aluminum oxide film 12A that naturally occurs on the circuit layer 12 is set to 4 nm ≦ to ≦ 6 nm. In this embodiment, the thickness tg of the glass layer 31 is 0.01 μm ≦ tg ≦ 5 μm, the thickness ta of the Ag layer 32 is 1 μm ≦ ta ≦ 100 μm, and the total thickness tg + ta of the Ag fired layer 30 is 1. It is preferable to be configured so that 01 μm ≦ tg + ta ≦ 105 μm.

Next, an Ag paste containing glass (Ag paste containing glass) for forming the Ag fired layer 30 will be described.
The Ag paste with glass contains Ag powder, glass powder, resin, and solvent, and the content of the powder component consisting of Ag powder and glass powder is 60% by mass of the total Ag paste with glass. The content is 90% by mass or less, and the balance is resin and solvent. Moreover, you may contain a dispersing agent as needed. In addition, in this embodiment, content of the powder component which consists of Ag powder and glass powder is 85 mass% of the whole Ag paste containing glass.
The viscosity of the Ag paste containing glass 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, lead oxide, zinc oxide, silicon oxide, boric acid, phosphoric acid, and bismuth oxide.

The composition of the glass powder, when the total amount of the glass powder and _100mol%, P 2 _{O 5} is 30 mol% or more, 65 mol% or less, SnO is 30 mol% or more, 65 mol% or less, SiO ₂ is 0.1 mol% or more, 10 mol% or less, Al ₂ O ₃ is 0.1 mol% or more and 10 mol% or less, and B ₂ O ₃ is 0.1 mol% or more and 10 mol% or less. By using the glass powder having such a composition, the Ag paste can be obtained by baking the Ag paste at a low temperature of 250 ° C. or higher and lower than 350 ° C.

  In the conventional Ag paste containing glass, it was difficult to sufficiently adhere the Ag fired layer to the circuit layer at such a low firing temperature of 250 ° C. or more and less than 350 ° C. By setting the composition of the glass powder constituting the Ag paste within the above-described range, the Ag fired layer 30 that can sufficiently adhere to the circuit layer 12 even at a low firing temperature of 250 ° C. or higher and lower than 350 ° C. Can be obtained. Then, by forming the Ag fired layer 30 at a firing temperature as low as 250 ° C. or higher and lower than 350 ° C., the warpage amount of the circuit board 10 can be suppressed to 50 μm / 10 mm or less.

The average particle diameter of the glass powder may be 0.1 μm or more and 1.0 μm. In the present embodiment, for example, glass powder having an average particle size of 0.5 μm is 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 Ag paste, and a resin that decomposes at 500 ° C. or higher is suitable. In this embodiment, ethyl cellulose is used.
In this embodiment, a dicarboxylic acid-based dispersant is added. In addition, you may comprise Ag paste containing glass, without adding a dispersing agent.

  Next, the manufacturing method of glass-containing Ag paste is demonstrated with reference to the flowchart shown in FIG. First, the above-mentioned Ag powder and the glass powder having the composition range described above are mixed to produce a mixed powder (mixed powder forming step S1). Moreover, a solvent and resin are mixed and an organic mixture is produced | generated (organic substance mixing process S2).

  Then, the mixed powder, the organic mixture, and the dispersant are premixed by a mixer (preliminary mixing step S3). Next, the preliminary mixture is mixed while being kneaded using a roll mill (kneading step S4). The obtained kneading is filtered with a paste filter (filtration step S5). In this way, the above-mentioned Ag paste with glass is produced.

  According to the circuit board 10 having the above-described configuration, the Ag fired layer 30 is formed using the glass-filled Ag paste having a composition suitable for a firing temperature as low as 250 ° C. or higher and lower than 350 ° C. Therefore, Ag There is little curvature of the circuit board 10 in which the baking layer 30 was formed. Thereby, the amount of warping of the circuit board 10 becomes 50 μm / 10 mm or less. Therefore, the flatness of the ceramic substrate (insulating layer) 11 is maintained, and when the semiconductor element 3 is mounted on the Ag fired layer 30, the semiconductor element 3 is peeled off due to the curvature of the Ag fired layer 30, or a conduction failure occurs. Can be reliably prevented.

  Further, in the integrated circuit board 10 in which the cooler 40 is formed, even if the structure is asymmetrical on both sides of the ceramic substrate (insulating layer) 11, the warp is caused by the Ag fired layer 30 formed at a low firing temperature. Therefore, it is possible to reliably prevent damage due to the curvature of the ceramic substrate (insulating layer) 11 and peeling or conduction failure of the semiconductor element 3 due to the curvature of the Ag fired layer 30.

(Circuit board: Second embodiment)
FIG. 5 is a cross-sectional view showing a semiconductor device including a circuit board according to the second embodiment of the present invention.
In the present embodiment, as an example of a semiconductor device, an LED module on which a semiconductor element made of an LED element is mounted is illustrated. In addition, about the structure similar to 1st embodiment, the same number is provided and the detailed description is abbreviate | omitted.
The LED module (semiconductor device) 5 is provided with a circuit layer 12 and joined to the circuit board 20 provided with a cooler 50 and the surface of the circuit layer 12 via, for example, a solder layer (not shown). And a semiconductor element (LED element) 6.

  The circuit board 20 includes a ceramic substrate (insulating layer) 11 constituting an insulating layer, a circuit layer 12 disposed on one surface side 11a (upper surface in FIG. 5) of the ceramic substrate 11, and the other surface side of the ceramic substrate 11. 11b (the lower surface in FIG. 5).

The ceramic substrate (insulating layer) 11 prevents electrical connection between the circuit layer 12 and the metal layer 13. For example, AlN (aluminum nitride) having high insulating properties or Al ₂ O ₃ (oxidized) is used. Aluminum), Si ₃ N ₄ (silicon nitride), and the like.

  The circuit layer 12 is formed by bonding a conductive metal plate to one surface 11 a of the ceramic substrate 11. The circuit layer 12 is made of Al or an alloy containing Al.

The metal layer 13 is formed by bonding a metal plate to the other surface side 11 b of the ceramic substrate 11.
In the present embodiment, the thickness t2 along the stacking direction of the metal layer 13 is formed to be thicker than the thickness t1 of the circuit layer 12.

  The cooler 50 is for cooling the entire LED module (semiconductor device) 5 by propagating the heat generated in the circuit board 20 and dissipating it. The cooler 50 in the present embodiment is configured by a flat plate made of a material having good thermal conductivity, for example, A6063 (aluminum alloy). The flat cooler 50 efficiently dissipates heat generated by lighting the semiconductor element (LED element) 6.

  Between the metal layer 13 and the cooler 50, two Ag fired layers 30A and 30B obtained by firing the above-described glass-filled Ag paste at 250 ° C. or higher and lower than 350 ° C. are formed. A bonding layer 52 is formed between the two Ag fired layers 30A and 30B.

  The Ag fired layers 30 </ b> A and 30 </ b> B each include a glass layer 31 formed on the metal layer 13 side and an Ag layer 32 formed on the glass layer 31. And in this glass layer 31, the fine electroconductive particle with a particle size of about several nanometers is disperse | distributing, for example. The conductive particles are, for example, crystalline particles containing at least one of Ag or Al.

The glass layers 31 constituting the Ag fired layers 30A and 30B each contain P ₂ O _{5 in} a range of 25 mol% to 57 mol% and SnO in a range of 25 mol% to 57 mol%.
Further, the warpage amount of the circuit board 20 is set to 50 μm / 10 mm or less. By setting the amount of warping of the circuit board 20 to 50 μm / 10 mm or less, the circuit layer 12 and the semiconductor element (LED element) 6 are firmly bonded without being separated by the warping, and the ceramic substrate 11 is not damaged due to bending. To prevent.

  In the present embodiment, the bonding layer 52 is made of a nano-sized or sub-micron-sized Ag sintered body obtained by reducing silver oxide, and is a sintered body of a silver oxide paste containing silver oxide and a reducing agent. . Here, an Ag sintered body is formed by reducing silver oxide, and the Ag fired layer 30A and the Ag fired layer 30B are joined by the Ag sintered body. This makes it possible to bond at a low temperature of about 350 ° C. or lower. Moreover, fine metal Ag particles are generated by reduction of silver oxide, and the particle diameter thereof is very fine, for example, 10 nm to 1 μm, so that the metal layer 13 and the cooler 50 can be formed even in a high temperature environment. Sufficient bonding strength and bonding reliability can be maintained.

  In applying the silver oxide paste when forming the bonding layer 52, various means such as a screen printing method, an offset printing method, and a photosensitive process can be employed. In this embodiment, the silver oxide paste was printed by the screen printing method.

This silver oxide paste contains silver oxide powder, a reducing agent, and a solvent.
The content of the silver oxide powder is 60% by mass or more and 92% by mass or less of the entire silver oxide paste, the content of the reducing agent is 5% by mass or more and 15% by mass or less of the entire silver oxide paste, and the remainder is a solvent. It is said that.
The silver oxide paste has a viscosity adjusted to 10 Pa · s to 100 Pa · s, more preferably 30 Pa · s to 80 Pa · s.

The bonding layer 52 may be, for example, a solder bonding layer other than the above-described Ag sintered body. When the bonding layer 52 is formed of solder, for example, Sn—Ag solder, Sn—In solder, Sn—Ag—Cu solder, or the like can be used.
In addition to the silver oxide paste, a silver paste having nano-sized or submicron-sized silver particles can also be used.

  According to the circuit board 20 having the above-described configuration, the Ag fired layer 30A and the Ag fired layer 30B are formed using a glass-filled Ag paste having a composition suitable for a low firing temperature of 250 ° C. or higher and lower than 350 ° C. Therefore, warpage of the Ag fired layer 30A and the Ag fired layer 30B is small. Thereby, the curvature amount of the circuit board 20 becomes 50 μm / 10 mm or less. Therefore, the flatness of the ceramic substrate (insulating layer) 11 is maintained, and when the semiconductor element (LED element) 6 is mounted on the circuit layer 12, the semiconductor element 6 is peeled off due to the curvature of the Ag fired layer 30. The occurrence of defects can be reliably prevented.

In particular, when the thickness t2 of the metal layer 13 is thicker than the thickness t1 of the circuit layer 12 as in this embodiment, that is, when the shape is asymmetric in the vertical direction in the stacking direction around the ceramic substrate (insulating layer) 11, However, such warpage can be reliably prevented by forming the Ag fired layer 30A and the Ag fired layer 30B using a glass-filled Ag paste having a composition suitable for a low firing temperature.
Moreover, it can prevent that the light emission characteristic of the semiconductor element (LED element) 6 changes with curvature.

  Moreover, in the integrated circuit board 20 in which the flat cooler 50 is formed, the Ag fired layer formed at a low firing temperature, even if the structure is asymmetric on both sides with the ceramic substrate (insulating layer) 11 as the center. Since warpage is suppressed by 30A and 30B, damage due to the bending of the ceramic substrate (insulating layer) 11, and peeling and conduction failure of the semiconductor element (LED element) 6 due to the bending of the Ag fired layers 30A and 30B are surely prevented. can do.

  In the first embodiment and the second embodiment described above, the power module element and the LED element are exemplified as the semiconductor element. However, the type of the semiconductor element to be mounted on the circuit board of the present invention is not particularly limited. Various semiconductor elements can be mounted.

(Circuit board manufacturing method: first embodiment)
Next, a circuit board manufacturing method (first embodiment) according to the first embodiment shown in FIGS. 1 to 3 will be described with reference to a flowchart shown in FIG.
First, an aluminum plate to be the circuit layer 12 and an aluminum plate to be the metal layer 13 are prepared. As the aluminum plate used for the circuit layer 12 and the metal layer 13, for example, a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more is used. The thickness of such a rolled plate is, for example, about 0.6 mm.

  These aluminum plates are laminated on one surface side 11a and the other surface side 11b of the ceramic substrate (insulating layer) 11 via brazing materials, respectively, and cooled after being pressurized, heated, and thereby the aluminum plate and the ceramic substrate 11 are bonded. Bonding (circuit layer bonding step S11). The bonding temperature is set to 640 ° C to 650 ° C.

  Examples of the brazing material used in the circuit layer bonding step S11 include an Al—Cu based brazing material and an Al—Si based brazing material. In this embodiment, an Al—Si brazing material is used. After the circuit layer 12 is bonded to the ceramic substrate (insulating layer) 11 with a brazing material, a predetermined circuit pattern can be formed by, for example, etching.

As the ceramic substrate (insulating layer) 11, a ceramic thin plate such as Si ₃ N ₄ (silicon nitride), AlN (aluminum nitride), Al ₂ O ₃ (alumina) having excellent insulating properties and heat dissipation can be used. . In the present embodiment, the ceramic substrate (insulating layer) 11 is made of AlN. Moreover, the thickness of the ceramic substrate (insulating layer) 11 should just be in the range of 0.2-1.5 mm, for example, and the thickness of 0.635 mm is used in this embodiment.

  Next, the cooler 40 (top plate portion 41) is joined to the other surface side of the metal layer 13 via a brazing material (cooler joining step S12). Note that the brazing temperature of the cooler 40 is set to 590 ° C to 610 ° C. Examples of the brazing material used in the cooler joining step S12 include an Al—Cu brazing material and an Al—Si brazing material. In this embodiment, an Al—Si brazing material is used.

  In the cooler joining step S12, it is also preferable to form a buffer layer between the other surface side of the metal layer 13 and the cooler 40 (top plate portion 41). The buffer layer may be aluminum, an aluminum alloy, or a composite material containing aluminum (for example, AlSiC). As an example, a plate-like member made of high-purity Al having a purity of 99.98 mass% or more can be used. . The thickness of the buffer layer may be 0.4 mm or more and 2.5 mm or less, for example. If such a buffer layer is formed between the metal layer 13 and the cooler 40, the buffer layer functions as a stress buffer.

  Next, a glass-filled Ag paste is applied to one surface side 12a of the circuit layer 12 (glass-filled Ag paste coating step S13). In addition, when apply | coating Ag paste containing glass, various means, such as a screen printing method, an offset printing method, and a photosensitive process, are employable. In the present embodiment, an Ag paste containing glass is formed on the circuit layer 12 by a screen printing method.

As described above, the glass-filled Ag paste includes Ag powder and glass powder, and the composition of the glass powder is such that P ₂ O ₅ is 30 mol% or more and 65 mol% or less when the total amount of the glass powder is 100 mol%. , SnO is 30 mol% or more, 65 mol% or less, SiO ₂ is 0.1 mol% or more, 10 mol% or less, _Al 2 _{O 3} is 0.1 mol% or more, 10 mol% or _less, B 2 _{O 3} is 0.1 mol% or more, 10 mol% or less. Depending on the composition of the glass powder, the Ag paste containing glass can be fired at a low temperature of 250 ° C. or higher and lower than 350 ° C.

In a state where the glass-filled Ag paste is applied to the one surface side 12a of the circuit layer 12, the glass-layered Ag paste is fired by being placed in a heating furnace (firing step S14). The firing temperature at this time is set to 250 ° C. or more and less than 350 ° C. (low temperature firing).
By this firing step S14, the Ag fired layer 30 including the glass layer 31 and the Ag layer 32 is formed. In the firing step S14, the glass-filled Ag paste is fired at a low temperature of 250 ° C. or higher and lower than 350 ° C., so that an Ag fired layer is formed by conventional high-temperature baking (for example, about 350 ° C. to 650 ° C.). Compared to the case, the amount of warping of the circuit board 10 due to heating can be reduced. The amount of warping of the circuit board 10 can be 50 μm / 10 mm or less.

  Further, in the circuit board 10 to which the cooler 40 is bonded, both sides of the insulating layer 11 are asymmetrical. However, since the Ag fired layer 30 can be formed by low-temperature firing, the amount of warping of the circuit board 10 due to heating can be kept small. . Therefore, damage due to the bending of the insulating layer 11 and peeling of the cooler 40 can be prevented.

  Further, in this firing step S14, the formation of the glass layer 31 melts and removes the aluminum oxide film 12A naturally generated on the surface of the circuit layer 12, and the glass layer 31 is directly formed on the circuit layer 12. The Further, fine Ag particles 33 having a particle size of about several nanometers are dispersed inside the glass layer 31.

  Through the above steps, the circuit board 10 in which the Ag fired layer 30 is formed on the surface of the circuit layer 12 can be manufactured.

  In the present embodiment, the cooler joining step S12 is performed as a pre-process of the firing step S14, and the cooler 40 is joined. Thereby, even if the cooler 40 is joined at a high temperature of 350 ° C. or higher in the cooler forming step S12, for example, the Ag fired layer 30 is formed at a low temperature (less than 350 ° C.) in the subsequent firing step S14. Further, it is possible to prevent the cooler 40 from being peeled off by heat or the circuit board 10 from being exposed to a high temperature of 350 ° C. or higher to increase warpage due to thermal strain.

  Thereafter, when the semiconductor element 3 is mounted, for example, the semiconductor element 3 is placed on the surface of the Ag fired layer 30 via a solder material and soldered in a reduction furnace (solder joining step S15). Thereby, the power module (semiconductor device) 1 in which the semiconductor element 3 is bonded onto the circuit layer 12 via the solder layer 2 can be manufactured.

(Circuit board manufacturing method: second embodiment)
Next, another manufacturing method (second embodiment) of the circuit board of the first embodiment shown in FIGS. 1 to 3 will be described with reference to the flowchart shown in FIG.
In addition, detailed description is abbreviate | omitted about the structure similar to the manufacturing method of the circuit board of 1st embodiment.
First, an aluminum plate to be the circuit layer 12 and an aluminum plate to be the metal layer 13 are prepared. These aluminum plates are laminated on one side 11a and the other side 11b of the ceramic substrate (insulating layer) 11 via brazing materials, and are cooled after being pressurized and heated, whereby the aluminum plate and the ceramic substrate 11 Are joined (circuit layer joining step S21).

  Next, a glass-filled Ag paste is applied to one side 12a of the circuit layer 12 (glass-filled Ag paste coating step S22). The glass-filled Ag paste is the same as the glass-filled Ag paste of the first embodiment described above.

In a state where the glass paste Ag paste is applied to the one surface side 12a of the circuit layer 12, the Ag paste is placed in a heating furnace and the Ag paste is fired (firing step S23). The firing temperature at this time is set to 250 ° C. or more and less than 350 ° C. (low temperature firing).
By this firing step S23, the Ag fired layer 30 including the glass layer 31 and the Ag layer 32 is formed. In the firing step S23, the glass-filled Ag paste is fired at a low temperature of 250 ° C. or higher and lower than 350 ° C., so an Ag fired layer is formed by conventional high-temperature baking (for example, about 350 ° C. to 650 ° C.). Compared to the case, the amount of warping of the circuit board 10 due to heating can be reduced. The amount of warping of the circuit board 10 can be 50 μm / 10 mm or less.

  Next, the cooler 40 (top plate portion 41) is joined to the other surface side of the metal layer 13 by soldering (cooler joining step S24). At this time, a buffer layer may be formed between the other surface side of the metal layer 13 and the cooler 40 (top plate portion 41). The soldering temperature of the cooler 40 is preferably less than 350 ° C. Thus, even when the cooler joining step S24 is performed as a subsequent step of the firing step S23, the Ag fired layer 30 already formed in the previous step is not exposed to a high temperature of 350 ° C. or higher, and the circuit board The amount of warpage of 10 can be 50 μm / 10 mm or less.

  Also in the circuit board manufacturing method of the second embodiment as described above, the circuit board 10 in which the Ag fired layer 30 is formed on the surface of the circuit layer 12 can be manufactured.

(Circuit board manufacturing method: third embodiment)
Next, a circuit board manufacturing method (third embodiment) according to the second embodiment shown in FIG. 5 will be described with reference to the flowchart shown in FIG.
First, an aluminum plate to be the circuit layer 12 and an aluminum plate to be the metal layer 13 are prepared. As the aluminum plate used for the circuit layer 12 and the metal layer 13, for example, a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more is used. The thickness of the rolled plate is such that the circuit layer 12 is about 0.1 mm, for example, and the metal layer 13 is about 0.2 mm, for example, so that the metal layer 13 is thicker than the circuit layer 12.

  These aluminum plates are laminated on one surface side 11a and the other surface side 11b of the ceramic substrate (insulating layer) 11 via brazing materials, respectively, and cooled after being pressurized, heated, and thereby the aluminum plate and the ceramic substrate 11 are bonded. Bonding (circuit layer and metal layer bonding step S31). The bonding temperature is set to 640 ° C to 650 ° C.

  Examples of the brazing material used in the circuit layer and metal layer joining step S31 include an Al—Cu based brazing material and an Al—Si based brazing material. In this embodiment, an Al—Si brazing material is used. After the circuit layer 12 is bonded to the ceramic substrate (insulating layer) 11 with a brazing material, a predetermined circuit pattern can be formed by, for example, etching.

As the ceramic substrate (insulating layer) 11, a ceramic thin plate such as Si ₃ N ₄ (silicon nitride), AlN (aluminum nitride), Al ₂ O ₃ (alumina) having excellent insulating properties and heat dissipation can be used. . In the present embodiment, the ceramic substrate (insulating layer) 11 is made of AlN. Moreover, the thickness of the ceramic substrate (insulating layer) 11 should just be in the range of 0.2-1.5 mm, for example, and the thickness of 0.635 mm is used in this embodiment.

  Next, a flat plate cooler 50 made of, for example, A6063 (aluminum alloy) is prepared. And Ag paste containing glass is apply | coated on the metal layer 13 and the cooler 50, respectively (Ag paste application process S32 with glass). In addition, when apply | coating Ag paste containing glass, various means, such as a screen printing method, an offset printing method, and a photosensitive process, are employable. In the present embodiment, glass-filled Ag paste was formed on the metal layer 13 and the cooler 50 by screen printing. The glass-filled Ag paste is the same as in the first embodiment described above.

  Next, the laminate in which the glass-containing Ag paste is applied on the metal layer 13 and the cooler 50 in which the glass-containing Ag paste is applied are respectively placed in a heating furnace to fire the glass-containing Ag paste (firing). Step S33). The firing temperature at this time is set to 250 ° C. or more and less than 350 ° C. (low temperature firing).

  In this firing step S33, an Ag fired layer provided with a glass layer 31 and an Ag layer 32 on each of the laminate obtained by applying the glass-filled Ag paste on the metal layer 13 and the cooler 50 applied with the glass-filled Ag paste. 30A and 30B are formed. In the firing step S33, the glass-filled Ag paste is fired at a low temperature of 250 ° C. or higher and lower than 350 ° C., and thus an Ag fired layer is formed by conventional high temperature firing (for example, about 350 ° C. to 650 ° C.). Compared to the case, the amount of warping of the circuit board 20 due to heating can be suppressed to be small. The warpage amount of the circuit board 20 can be 50 μm / 10 mm or less.

  Next, a silver oxide paste containing silver oxide powder, a reducing agent, and a solvent is applied between the Ag fired layer 30A and the Ag fired layer 30B formed in the firing step S33, for example, at a low temperature of about 350 ° C. Heat with. As a result, a bonding layer 52 made of a nano-sized or sub-micron-sized Ag sintered body is formed between the Ag fired layer 30A and the Ag fired layer 30B, and the metal layer 13 and the cooler 50 are connected to the Ag fired layer 30A. , Bonding layer 52 and Ag fired layer 30B are bonded (cooler forming step S34).

Through the above steps, the circuit board 20 in which the metal layer 13 and the cooler 50 are bonded through the Ag fired layer 30A, the bonding layer 52, and the Ag fired layer 30B can be manufactured.
Thereafter, when the semiconductor element (LED element) 6 is mounted, for example, the semiconductor element 6 is placed on the circuit layer 12 via, for example, a solder material, and soldered in a reduction furnace, thereby the LED. A module (semiconductor device) 5 can be manufactured.

In the above embodiment, the semiconductor element is mounted on the circuit layer (on the Ag fired layer) by solder bonding. However, the present invention is not limited thereto, and a silver paste containing nano-sized or submicron-sized silver particles is used. The joining by Ag sintering used can also be used.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

Hereinafter, verification examples for verifying the effects of the present embodiment will be shown.
(Experimental Examples 1-25)
By the method described in the above embodiment, a 4N-Al aluminum plate is used and a glass-filled Ag paste having the glass components shown in Table 1 is used. The firing temperature is 320 ° C., the firing time is 30 minutes, and the 10 μm thick Ag fired layer ( 10 mm × 10 mm). The weight ratio A / G between the weight A of the Ag powder and the weight G of the glass powder was A / G = 80/5. And the semiconductor element was joined on the Ag baking layer by the method of Table 1. When the joining method was solder, 96.5Sn-3Ag-0.5Cu solder was used, and in the case of Ag sintering, the semiconductor element was joined using the silver oxide paste described in the embodiment.
Adhesion was evaluated with respect to the circuit board in which the obtained Ag baking layer was formed. Further, the amount of P ₂ O ₅ and SnO in the glass layer and the adhesion strength between the circuit layer and the semiconductor element were evaluated for the semiconductor device to which the semiconductor element was bonded.

(Adhesion evaluation between Ag fired layer and circuit layer)
The adhesion between the Ag fired layer and the circuit layer was evaluated by the method defined in JIS K 5600-5-6 (cross cut method). However, as an evaluation method, it was set as the number of squares of the Ag fired layer remaining after the tape peeling. That is, the larger the number, the higher the adhesion. Note that the squares were 100 升 (10 升 x 10 升).
(Evaluation of adhesion strength between circuit layer and semiconductor element and amount of P ₂ O ₅ and SnO in glass layer)
The cross section of the glass layer was subjected to quantitative analysis of P and Sn by EDS (Ultra-55 manufactured by Carl Zeiss). P was converted to P ₂ O ₅ , Sn was converted to SnO, and the amounts were P ₂ O ₅ and SnO.
The adhesion strength between the circuit layer and the semiconductor element was the shear strength (shear strength) required by a shear test. The circuit layer was fixed horizontally with the semiconductor element facing upward, and the semiconductor element was pressed horizontally with a shear tool to confirm the strength when the junction between the circuit layer and the semiconductor element was broken. In addition, the shear strength test of 3 times was implemented and it was set as the average value.
The evaluation results are shown in Table 1.

From the results of Table 1, in Experimental Examples 1, 6, 10, 11, 15, 16, 20, 21, and 25 in which the glass component was outside the scope of the present invention, the adhesion of the Ag fired layer was poor, and the Experimental Example In No. 5, although the adhesion was good, the shear strength after bonding the semiconductor element was low.
In Experimental Examples 1, 6, 10, 11, 15, 16, 20, 21, and 25, which had low adhesion, the amount of P ₂ O ₅ and SnO in the glass layer and the circuit were reduced because the Ag fired layer was peeled off. The adhesion strength between the layer and the semiconductor element is not evaluated.
On the other hand, in Experimental Examples 2 to 4, 7 to 9, 12 to 14, 17 to 19, and 22 to 24 according to the present invention, it was found that a power module (semiconductor device) having high adhesion and adhesion strength can be obtained.

(Experimental examples 30 to 34, conventional example)
A 4N-Al plate having a thickness of 0.6 mm serving as a circuit layer is formed on one surface of a ceramic substrate made of AlN, and a 4N-Al plate having a thickness of 0.6 mm serving as a metal layer is formed on the other surface using an Al-Si solder. The materials were joined. An Ag fired layer was formed on the circuit layer using an Ag paste containing glass having the glass components shown in Table 1. The weight ratio A / G between the weight A of the Ag powder and the weight G of the glass powder was A / G = 80/5, and the firing temperature was as shown in Table 1. And the adhesiveness and curvature of Ag baking layer and a circuit layer were evaluated with respect to the circuit board in which Ag baking layer was formed. The evaluation of adhesion was the same as that described above.
(Evaluation of warpage)
Warpage was measured using a surface roughness meter (SV-414 manufactured by Mitutoyo Corporation) at a distance of 10 mm on the circuit surface with a warp roughness meter, and the difference between the minimum and maximum values was calculated as the amount of warpage. did.
The results are shown in Table 2.

From the results in Table 2, the adhesion was poor in Experimental Example 30 where the firing temperature was as low as 200 ° C. Moreover, it turned out that curvature becomes large in Experimental example 34 whose baking temperature is as high as 400 degreeC. Also, it was found that the adhesion was low when a conventional glass component was used.
On the other hand, in Experimental Examples 31 to 33 according to the present invention, it was found that a power module (semiconductor device) having high adhesion and low warpage could be obtained.

1 Power module (semiconductor device)
2 Solder layer 3 Semiconductor element (power module element)
5 LED module (semiconductor device)
6 Semiconductor elements (LED elements)
10 Circuit board 11 Ceramic board (insulating layer)
DESCRIPTION OF SYMBOLS 12 Circuit layer 12A Aluminum oxide film 20 Circuit board 30,30A, 30B Ag baking layer 31 Glass layer 32 Ag layer 33 Ag particle 40 Cooler 50 Cooler

Claims (10)

A circuit board manufacturing method comprising at least a circuit layer made of Al or an Al alloy formed on one surface of an insulating layer and an Ag fired layer formed on the circuit layer,
An application step of applying an Ag paste containing glass on the circuit layer;
Firing the applied Ag paste and forming the Ag fired layer made of a fired body of Ag paste containing glass, and
The firing temperature of the Ag paste in the firing step is 250 ° C. or more and less than 350 ° C.,
When the total amount of glass is 100 mol%, the glass contained in the Ag paste is
P ₂ O ₅ is 30 mol% or more and 65 mol% or less,
SnO is 30 mol% or more and 65 mol% or less,
SiO ₂ is 0.1 mol% or more and 10 mol% or less,
Al ₂ O ₃ is 0.1 mol% or more and 10 mol% or less,
B ₂ O ₃ is 0.1 mol% or more, less 10 mol%,
A circuit board manufacturing method characterized by having the following composition:   2. The method of manufacturing a circuit board according to claim 1, further comprising a cooler forming step of forming a cooler on the other surface side of the insulating layer before the applying step. A circuit layer made of Al or Al alloy formed on one surface of the insulating layer, a metal layer formed on the other surface of the insulating layer, and an Ag fired layer formed on the metal layer A circuit board manufacturing method comprising:
An application step of applying an Ag paste containing glass on the metal layer;
Firing the applied Ag paste and forming the Ag fired layer made of a fired body of Ag paste containing glass, and
The firing temperature of the Ag paste in the firing step is 250 ° C. or more and less than 350 ° C.,
When the total amount of glass is 100 mol%, the glass contained in the Ag paste is
P ₂ O ₅ is 30 mol% or more and 65 mol% or less,
SnO is 30 mol% or more and 65 mol% or less,
SiO ₂ is 0.1 mol% or more and 10 mol% or less,
Al ₂ O ₃ is 0.1 mol% or more and 10 mol% or less,
B ₂ O ₃ is 0.1 mol% or more, less 10 mol%,
A circuit board manufacturing method characterized by having the following composition:   4. The method of manufacturing a circuit board according to claim 3, further comprising a cooler forming step of forming a cooler on the Ag fired layer. A circuit board comprising at least a circuit layer made of Al or an Al alloy formed on one surface of an insulating layer, and an Ag fired layer formed on the circuit layer,
The Ag fired layer is a fired body of an Ag paste containing glass, and includes a glass layer formed on the circuit layer and an Ag layer formed on the glass layer.
In the glass layer, P ₂ O ₅ is contained in an amount of 25 mol% or more and 57 mol% or less, and SnO is contained in an amount of 25 mol% or more and 57 mol% or less,
A circuit board, wherein the amount of warping of the circuit board is 50 μm / 10 mm or less. A circuit layer made of Al or Al alloy formed on one surface of the insulating layer, a metal layer formed on the other surface of the insulating layer, and an Ag fired layer formed on the metal layer A circuit board manufacturing method comprising:
The Ag fired layer is a fired body of an Ag paste containing glass, and includes a glass layer formed on the metal layer and an Ag layer formed on the glass layer.
In the glass layer, P ₂ O ₅ is contained in an amount of 25 mol% or more and 57 mol% or less, and SnO is contained in an amount of 25 mol% or more and 57 mol% or less,
A circuit board, wherein the amount of warping of the circuit board is 50 μm / 10 mm or less.   7. The circuit board according to claim 5, further comprising a cooler formed on the other surface of the insulating layer. The circuit board according to claim 5, wherein the Ag fired layer has an electric resistance value in the thickness direction of 7.5 × 10 ⁻⁴ Ω · m or less. The circuit board according to claim 5, wherein an insulating substrate selected from AlN, Si ₃ N _4, or Al ₂ O ₃ is used as the insulating layer.   10. A semiconductor device comprising: the circuit board according to claim 5; and a semiconductor element bonded to the circuit layer of the circuit board.

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