JP2014179564A - Method for manufacturing substrate for power module and method for manufacturing power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a substrate for a power module capable of forming an Ag base layer having a small electric resistance value on a surface of a circuit layer using a glass-containing Ag paste, and a method for manufacturing a power module in which a semiconductor element is bonded onto the circuit layer.SOLUTION: A method for manufacturing a substrate for a power module comprises the steps of: forming a circuit layer 12 by bonding a metal plate to one surface of an insulating layer 11; applying a glass-containing Ag paste containing a glass component to the one surface of the circuit layer; forming an Ag base layer 31 including a glass layer by burning the glass-containing Ag paste applied to the one surface of the circuit layer by heat treatment; and energizing the Ag base layer before a semiconductor element 3 is bonded onto the circuit layer.

Description

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

Among various semiconductor elements, a power element for high power control used for controlling an electric vehicle or an electric vehicle has a large amount of heat generation. Therefore, as a substrate on which the power element is mounted, for example, AlN (aluminum nitride) 2. Description of the Related Art Conventionally, a power module substrate in which a metal plate having excellent conductivity is bonded as a circuit layer on a ceramic substrate made of, for example, has been widely used.
In such a power module substrate, a semiconductor element as a power element is mounted on the circuit layer via a solder material (see Patent Document 1).

As the metal constituting the circuit layer, aluminum or an aluminum alloy, or copper or a copper alloy is used.
Here, since the aluminum oxide film is formed on the surface of the circuit layer made of aluminum, it cannot be satisfactorily bonded to the solder material. Further, in the circuit layer made of copper, there is a problem that the molten solder material reacts with the copper and the components of the solder material enter the inside of the circuit layer to deteriorate the conductivity of the circuit layer.

As a joining method that does not use the solder material described above, Patent Document 2 proposes a technique for joining semiconductor elements using Ag nanopaste.
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 is thinner than the solder material. Therefore, 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 the cycle load tends to act on the semiconductor element, and the performance of the power module may be deteriorated.

Therefore, in Patent Documents 5 to 7, after an Ag underlayer is formed 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. Technology has 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 to remove the oxide film formed on the surface of the circuit layer by reacting with glass to remove the Ag underlayer. The semiconductor element is joined to the circuit layer on which the Ag underlayer is formed by 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 ensured 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 JP2013-12706A

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 is formed thicker in the Ag underlayer and the electric resistance value tends to increase, and both the bonding reliability and the electric resistance value are balanced. It was difficult. 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 or the like, electricity is supplied between the circuit layer and the semiconductor element. The problem that it cannot flow well arises.

  The present invention has been made in view of the above-described circumstances, and manufacturing a power module substrate capable of forming an Ag underlayer having a small electric resistance value on the surface of a circuit layer using a glass-containing Ag paste. It is an object of the present invention to provide a method and a manufacturing method of a power module in which a semiconductor element is bonded on the circuit layer.

  In order to solve the above-described problems, a power module substrate manufacturing method according to the present invention includes a power module in which a circuit layer made of metal is formed on one surface of an insulating layer, and a semiconductor element is bonded on the circuit layer. A method for manufacturing a circuit board, comprising: a circuit layer forming step of bonding a metal plate to one surface of the insulating layer to form the circuit layer; and a glass-containing Ag containing a glass component on one surface of the circuit layer. An application step of applying a paste, an Ag underlayer forming step of forming an Ag underlayer having a glass layer by baking the glass-containing Ag paste by heat-treating the glass-containing Ag paste, and the circuit. An energization step of energizing the Ag underlayer before the semiconductor element is bonded onto the layer.

According to the method for manufacturing a power module substrate of the present invention, a coating process for applying a glass-containing Ag paste containing a glass component to one surface of a circuit layer, and a heat treatment in a state where the glass-containing Ag paste is applied. Since it comprises an Ag underlayer forming step of firing a glass-containing Ag paste and forming an Ag underlayer having a glass layer, the surface of the circuit layer is formed by the glass contained in the glass-containing Ag paste when the glass-containing Ag paste is fired. In this way, the oxide film formed in (1) can be removed, and the Ag underlayer can be satisfactorily formed on the circuit layer.
Furthermore, since an energization step of energizing the Ag underlayer before the semiconductor element is bonded onto the circuit layer is provided, an Ag underlayer having a low electrical resistance value can be formed. That is, since the Ag underlayer includes a glass layer, the electrical resistance value may be high. However, when the current is applied as described above, the electrical resistance value can be reduced and an Ag underlayer having a low electrical resistance value can be formed. . Moreover, the electrical resistance value of the Ag underlayer can be stabilized by performing the energization process.

The power module manufacturing method of the present invention is characterized in that, in the power module substrate described above, the Ag base layer and the semiconductor element are bonded by a bonding layer.
According to the method for manufacturing a power module of the present invention, in the power module substrate described above, the Ag base layer and the semiconductor element are bonded by the bonding layer. Can be bonded together, and electrical conduction between the circuit layer and the semiconductor element can be ensured with certainty.

  According to the present invention, a method for manufacturing a power module substrate capable of forming an Ag underlayer having a small electrical resistance value on the surface of a circuit layer using a glass-containing Ag paste, and a semiconductor element bonded on the circuit layer It is an object of the present invention to provide a method for manufacturing a power module.

It is a schematic explanatory drawing of the power module which concerns on one Embodiment of this invention. It is a schematic explanatory drawing of the board | substrate for power modules which concerns on one Embodiment of this invention. FIG. 2 is an enlarged explanatory view of a bonding interface between a circuit layer and a semiconductor element in FIG. 1. It is a flowchart which shows the manufacturing method of the board | substrate for power modules shown in FIG. 1, and a power module. It is a schematic explanatory drawing of the manufacturing method of the board | substrate for power modules shown in FIG. In one Embodiment of this invention, it is upper surface explanatory drawing which shows the electricity supply method which sends an electric current to Ag base layer, and the measuring method of the electrical resistance value of the thickness direction of Ag base layer. In one Embodiment of this invention, it is side explanatory drawing which shows the electricity supply method which sends an electric current to Ag base layer, and 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.
As shown in FIG. 1, the power module 1 according to the present embodiment includes a power module substrate 10 on which a circuit layer 12 is disposed, and a semiconductor bonded to one surface (upper surface in FIG. 1) of the circuit layer 12. The element 3 and a cooler 40 disposed on the other side of the power module substrate 10 are provided.

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

The ceramic substrate 11 prevents electrical connection between the circuit layer 12 and the metal layer 13, and has high insulating properties such as AlN (aluminum nitride), Si ₃ N ₄ (silicon nitride), and Al ₂ O _3. (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.

The circuit layer 12 is formed by bonding a conductive metal plate such as aluminum or aluminum alloy, copper or copper alloy to one surface of the ceramic substrate 11. In the present embodiment, the circuit layer 12 is formed by joining rolled aluminum sheets having a purity of 99.99% by mass or more. Note that the thickness of the circuit layer 12 is set in a range of 0.1 mm or more and 1.0 mm or less, and is set to 0.6 mm in the present embodiment. Further, a circuit pattern is formed on the circuit layer 12, and one surface (the upper surface in FIG. 1) is a bonding surface to which the semiconductor element 3 is bonded.
On one surface of the circuit layer 12, an Ag underlayer 31 made of a sintered body of a glass-containing Ag paste described later is formed.

  The metal layer 13 is formed by bonding a metal plate such as aluminum or aluminum alloy, copper or copper alloy to the other surface of the ceramic substrate 11. In this embodiment, the metal plate (metal layer 13) is a rolled plate of aluminum or aluminum alloy having a purity of 99% by mass or more, more specifically, a purity of 99.99% by mass or more. It is a rolled plate of aluminum (so-called 4N aluminum). Here, the thickness of the metal layer 13 is set within a range of 0.2 mm to 3.0 mm, and is set to 1.6 mm in the present embodiment.

  The cooler 40 is for cooling the power module substrate 10 described above. The top plate portion 41 joined to the power module substrate 10 and the top plate portion 41 are suspended downward. The heat radiation fin 42 and the flow path 43 for distribute | circulating a cooling medium (for example, cooling water) are provided. The cooler 40 (top plate portion 41) is preferably made of a material having good thermal conductivity, and is made of A6063 (aluminum alloy) in the present embodiment.

  The semiconductor element 3 is made of a semiconductor material such as Si, and a surface treatment film 3 a made of Ni, Au, or the like is formed on the joint surface with the circuit layer 12.

In the power module 1 shown in FIG. 1, the Ag underlayer 31 and the bonding layer 38 described above are formed between the circuit layer 12 and the semiconductor element 3.
As shown in FIG. 1, the Ag base layer 31 and the bonding layer 38 are not formed on the entire surface of the circuit layer 12, and the portion where the semiconductor element 3 is disposed, that is, the contact with the semiconductor element 3. It is selectively formed only on the joint surface.

Here, the Ag underlayer 31 is a fired body of a glass-containing Ag paste containing a glass component. As shown in FIG. 3, the Ag base layer 31 includes a glass layer 32 formed on the circuit layer 12 side and an Ag layer 33 formed on the glass layer 32.
In the glass layer 32, fine conductive particles having a particle size of about several nanometers are dispersed. In addition, the electroconductive particle in the glass layer 32 is observed by using a transmission electron microscope (TEM), for example.
In addition, fine glass particles having a particle diameter of about several micrometers are dispersed inside the Ag layer 33.

The glass-containing Ag paste constituting the Ag underlayer 31 contains Ag powder, lead-free glass powder containing ZnO, a resin, a solvent, and a dispersant. From the Ag powder and the lead-free glass powder, The content of the resulting powder component is 60% by mass or more and 90% by mass or less of the entire glass-containing Ag paste, 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 a lead-free glass powder is 85 mass% of the whole glass containing Ag paste.
The lead-free glass powder contains Bi ₂ O ₃ , ZnO, and B ₂ O ₃ as main components, and has a glass transition temperature of 300 ° C. or higher and 450 ° C. or lower, a softening temperature of 600 ° C. or lower, and a crystallization temperature. 450 ° C. or higher.
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 bonding layer 38 formed on the Ag base layer 31, that is, on the Ag layer 33, is a fired body of a silver oxide paste containing silver oxide and a reducing agent. That is, the bonding layer 38 is an Ag fired body obtained by reducing silver oxide. Here, since the particles precipitated on the surface of the Ag layer 33 generated by reducing silver oxide are very fine, for example, with a particle diameter of 10 nm to 1 μm, a dense Ag bonding layer is formed. Become. In the bonding layer 38, the glass particles observed in the Ag layer 33 of the Ag underlayer 31 are not present or very few.

The silver oxide paste constituting the bonding layer 38 contains a silver oxide powder, a reducing agent, a resin, and a solvent. In this embodiment, in addition to these, an organic metal compound powder is contained. Yes.
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, 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 0% by mass or more and 10% by mass or less of the entire silver oxide paste, and the remainder is a solvent. In this silver oxide paste, a dispersant and a resin are not added in order to suppress the unreacted organic matter from remaining in the bonding layer 38 obtained by sintering.
The reducing agent is an organic substance having reducibility, and for example, alcohol and organic acid can be used.
The organometallic compound has an action of promoting the reduction reaction of silver oxide and the decomposition reaction of organic substances by the organic acid generated by thermal decomposition, for example, formic acid Ag, acetic acid Ag, propionic acid Ag, benzoic acid Ag, oxalic acid. A carboxylic acid metal salt such as Ag is applied.
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.

Next, a method for manufacturing the power module substrate 10 and the power module 1 according to the present embodiment will be described with reference to FIGS.
First, as shown in FIG. 5, an aluminum plate 22 having a thickness of 0.6 mm that becomes the circuit layer 12 on the upper surface of the ceramic substrate 11, and an aluminum plate 23 having a thickness of 1.6 mm that becomes the metal layer 13 on the lower surface. The aluminum plates 22 and 23 are bonded to the ceramic substrate 11 by laminating via the material 25 and cooling after pressurization / heating (circuit layer forming step S01, metal layer forming step S02). In addition, the temperature of this brazing is set to 620-650 degreeC.

  Next, the cooler 40 is joined to the other surface side of the metal layer 13 via a brazing material (cooler joining step S03). Note that the brazing temperature of the cooler 40 is set to 590 to 610 ° C.

Next, the glass containing Ag paste used as the Ag base layer 31 is apply | coated to the surface of the circuit layer 12 (glass containing Ag paste application | coating process S04).
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 is formed on the bonding surface to which the semiconductor element 3 of the circuit layer 12 is bonded by a screen printing method.

  Next, after drying with the glass-containing Ag paste applied to the surface of the circuit layer 12, the glass-containing Ag paste is placed in a heating furnace and baked (heat treatment) to form an Ag underlayer 31 ( Ag underlayer forming step S05). Here, the Ag base layer 31 includes a glass layer 32 formed on one surface of the circuit layer 12 and an Ag layer 33 formed on the glass layer 32. In addition, the firing temperature at this time is set to 350-645 degreeC.

  Next, the Ag underlayer 31 is energized (energization step S06). Specifically, as shown in FIGS. 6 and 7, a current is passed between the upper surface of the Ag base layer 31 and the circuit layer 12. When energized, as shown in FIGS. 6 and 7, the upper surface center point of the Ag underlayer 31 and the distance H from the upper surface center point of the Ag underlayer 31 to the edge of the Ag underlayer 31 are the same distance. Electricity is supplied between a point on the circuit layer 12 that is a distance H away from the end of the Ag base layer 31.

Here, the current value and the energization time for energization in the energization step S06 are preferably 0.1 A or more and 5 seconds or more. More preferably, it is 1.0 A or more and 10.0 A or less and 10 seconds or more.
Furthermore, in the energization step S06, it is desirable to conduct energization so that the current (A) × time (seconds) is 10.0 or more.
In this way, the power module substrate 10 in which the Ag base layer 31 is formed on one surface of the circuit layer 12 is manufactured.

Next, a silver oxide paste to be the bonding layer 38 is applied to the surface of the Ag base layer 31 (silver oxide paste application step S07).
In addition, when apply | coating a silver oxide paste, various means, such as a screen printing method, an offset printing method, and a photosensitive process, are employable. In this embodiment, the silver oxide paste was applied by screen printing.

Next, after the silver oxide paste is applied and dried (for example, stored at room temperature in an air atmosphere for 24 hours), the semiconductor element 3 is stacked on the silver oxide paste (semiconductor element stacking step S08).
Then, the semiconductor element 3 and the power module substrate 10 are stacked in a heating furnace, and the silver oxide paste is baked to form the bonding layer 38 (bonding layer forming step S09). At this time, the pressurizing pressure is set to 0 to 10 MPa, and the firing temperature is set to 150 to 400 ° C.
Desirably, the semiconductor element 3 and the power module substrate 10 can be bonded more reliably by heating them while being pressed in the stacking direction. In this case, the pressurizing pressure is desirably 0.5 to 10 MPa.

  In this manner, the semiconductor element 3 and the circuit layer 12 on which the Ag base layer 31 is formed are bonded by the bonding layer 38. Thereby, the power module 1 which is this embodiment is manufactured.

  According to the present embodiment configured as described above, the glass-containing Ag paste application step S04 for applying the glass-containing Ag paste to one surface of the circuit layer 12, and the glass-containing Ag paste are baked to form an Ag underlayer. And an Ag underlayer forming step S05 for forming 31, the oxide film formed on the surface of the circuit layer 12 by the glass contained in the glass-containing Ag paste can be removed when the glass-containing Ag paste is baked. The Ag underlayer 31 can be satisfactorily formed on the circuit layer 12.

Since the Ag underlayer 31 formed in the Ag underlayer forming step S05 includes the energization step S06 for energizing, the Ag underlayer 31 having a low electric resistance value is reduced by reducing the electrical resistance value of the Ag underlayer 31. Can be formed. The Ag underlayer 31 formed in the Ag underlayer forming step S05 includes the glass layer 32, and thus may have a high electric resistance value. However, the Ag underlayer 31 includes the glass layer 32 in which the electric resistance value is reduced by performing the energization step S06. The Ag underlayer 31 can be formed. Furthermore, the electrical resistance value of the Ag underlayer 31 can be stabilized by performing the energization step S06.
The mechanism by which the electric resistance value decreases by energizing the Ag underlayer 31 is not clear, but a migration phenomenon occurs in the Ag underlayer 31 and an electric conduction path is formed in the glass layer 32 of the Ag underlayer 31. This is thought to be due to

Since electricity is supplied in the electricity supply step S06, the electrical resistance value of the Ag underlayer 31 can be reduced.
Furthermore, since a current of 0.1 A or more is applied for 5 seconds or more, the electrical resistance value of the Ag base layer 31 can be reliably reduced. In addition, when a current of 1.0 A or more and 10.0 A or less is passed for 10 seconds or longer, the Ag underlayer 31 having a low electrical resistance value can be reliably formed. 0.0 A or less and 10 seconds or more.
In addition, in the energization step S06, the electrical resistance value of the Ag base layer 31 can be more reliably reduced by performing energization such that current (A) × time (seconds) is 10.0 or more.

  In the power module substrate 10 of the present embodiment, the circuit layer 12 and the semiconductor element 3 can be reliably bonded by the bonding layer 38 via the Ag base layer 31 formed as described above. Electrical conduction between the circuit layer 12 and the semiconductor element 3 can also be ensured. Therefore, the highly reliable power module 1 can be configured.

  In this embodiment, since the bonding layer 38 is a fired body of silver oxide paste containing silver oxide and a reducing agent, the silver oxide is reduced by the reducing agent when the silver oxide paste is fired. It becomes fine silver particles, and the bonding layer 38 can have a dense structure. Further, since the reducing agent is decomposed when the silver oxide is reduced, it is difficult to remain in the bonding layer 38 and the conductivity and strength in the bonding layer 38 can be ensured. Furthermore, since firing can be performed under a relatively low temperature condition such as 300 ° C., the junction temperature of the semiconductor element 3 can be kept low, and the thermal load on the semiconductor element 3 can be reduced.

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 above-described embodiment, the case where the circuit layer on which the Ag base layer is formed and the semiconductor element are bonded using a silver oxide paste as a bonding material has been described. You may join using a solder material as a joining material. Alternatively, the circuit layer and the semiconductor element may be bonded using an Ag paste containing Ag particles and an organic substance as a bonding material.

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 copper plate, by applying a direct bonding method (DBC method), an active metal brazing method, a casting method, etc., A ceramic substrate and a copper plate can be joined.

Moreover, about the raw material of a glass containing Ag paste, and a compounding quantity, it is not limited to what was described in embodiment. For example, although it demonstrated as using lead-free glass powder, the glass containing lead may be sufficient.
Furthermore, the raw material and blending amount of the silver oxide paste are not limited to those described in the embodiment. For example, it may not contain an organometallic compound.

  Moreover, although it demonstrated as what forms an Ag base layer on a circuit layer after joining a cooler, it is not limited to this, Before joining an aluminum plate to a ceramic substrate, or joining a cooler Prior to this, an Ag underlayer may be formed.

Furthermore, although demonstrated as what comprised the top-plate part of the cooler with aluminum, you may be comprised with the composite material etc. which contain aluminum alloy or aluminum. Furthermore, although it demonstrated as a cooler having the radiation fin and the flow path of a cooling medium, there is no limitation in particular in the structure of a cooler.
Moreover, although the case where the board | substrate for power modules was equipped with a cooler was demonstrated, it does not need to be equipped with a cooler.
Moreover, although the case where the board | substrate for power modules was provided with the metal layer was demonstrated, it does not need to be provided with the metal layer.

Below, the result of the confirmation experiment performed in order to confirm the effect of this invention is demonstrated.
The power module substrates of Samples 1 and 2 were produced as follows.
For sample 1, first, an aluminum plate (28 mm × 28 mm × 0.6 mmt) having a purity of 99.99% or more and a ceramic substrate (30 mm × 30 mm × 0.635 mmt) were placed at 650 ° C. through an Al—Si brazing material. To form a circuit layer on the ceramic substrate.
Next, after applying the glass-containing Ag paste on the circuit layer, it was placed in a heating furnace and baked at 600 ° C. to form an Ag underlayer on the circuit layer. Here, the glass-containing Ag paste used in Sample 1 is a cellulose resin, a Bi ₂ O ₃ —ZnO—B ₂ O ₃ lead-free glass frit, a glass-containing Ag paste containing α-terpineol and Ag as solvents. did.
For sample 2, a copper plate (28 mm × 28 mm × 0.3 mmt) made of oxygen-free copper and a ceramic substrate (30 mm × 30 mm × 0.635 mmt) were heated to 800 ° C. via an Ag—Cu—Ti based active brazing material. Thus, a circuit layer was formed on the ceramic substrate.
Next, after applying the glass-containing Ag paste on the circuit layer, it was placed in a heating furnace and baked in a nitrogen atmosphere at 700 ° C. to form an Ag underlayer on the circuit layer. Here, the glass-containing Ag paste used in Sample 2 was an acrylic resin, a PbO—ZnO—B ₂ O ₃ glass frit, and a glass-containing Ag paste containing α-terpineol and Ag as solvents.

Next, electricity was applied to the Ag underlayer of the power module substrates of Samples 1 and 2 to form an Ag underlayer. As shown in FIGS. 6 and 7 in the above embodiment, the energization is performed by the same distance as the distance of 1 mm from the center point of the upper surface of the Ag base layer to the edge of the Ag base layer from the upper surface center point of the Ag base layer. A current of 5 A was passed between a point on the circuit layer 12 that was a distance of 1 mm from the edge of the underlying layer. The energization time was 10 seconds. And the electrical resistance value before electricity supply and the electrical resistance value after electricity supply were calculated | required. Note that an E3640A single-output DC power supply (manufactured by Agilent Technologies) was used as a power source for supplying current.
Table 1 shows the electrical resistance values before and after energization.

  From the results of Table 1, it was confirmed that an Ag underlayer having a small electrical resistance value can be obtained by energizing the Ag underlayer.

3 Semiconductor element 10 Power module substrate 11 Ceramic substrate (insulating layer)
12 circuit layer 31 Ag base layer 32 glass layer

Claims (2)

A method for manufacturing a power module substrate, wherein a circuit layer made of metal is formed on one surface of an insulating layer, and a semiconductor element is bonded on the circuit layer,
A circuit layer forming step in which a metal plate is bonded to one surface of the insulating layer to form the circuit layer;
An application step of applying a glass-containing Ag paste containing a glass component on one surface of the circuit layer;
An Ag underlayer forming step of forming an Ag underlayer having a glass layer by baking the glass-containing Ag paste by heat treatment in a state where the glass-containing Ag paste is applied;
An energizing step of energizing the Ag base layer before the semiconductor element is bonded onto the circuit layer.   The power module manufacturing method according to claim 1, wherein the Ag base layer and the semiconductor element are bonded together by a bonding layer.

Images