JPH0344064A - Junction structure of aluminum nitride substrate and metal substrate - Google Patents

Abstract

PURPOSE:To eliminate the degradation of junction strength caused by low wettability, and improve the junction strength to a metal substrate, by forming a titanium nitride layer on an aluminum nitride substrate, forming a metal material layer on the surface thereof, and joining the metal substrate to said metal material layer by using wax material or solder. CONSTITUTION:On the surface of an aluminum nitride substrate 10 facing a copper substrate 11, a titanium nitride layer 12 is formed so as to cover the surface. Said titanium nitride layer 12 is formed by baking TiN paste. The lower surface of said layer 12 is coated with a metal layer 13 formed by Cu- plating. The metal layer 13 and the substrate 11 are joined by using wax material 14 composed of Ag-Cu. Thereby the junction strength between the aluminum nitride substrate 10 and the copper substrate 11 can be remarkably improved, and the stress caused by the difference between thermal expansion coefficients of both substrates can be relieved, so that the exfoliation caused by temperature change can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is applicable to a metal substrate, for example, when heat-generating components such as an IC package, a power diode, or a power transistor are bonded to a metal substrate via an aluminum nitride substrate. The present invention relates to a bonding structure with the aluminum trinium nitride substrate, and particularly relates to a structure that can improve bonding strength between the two and prevent peeling due to a difference in coefficient of thermal expansion.

[Conventional technology]

Generally, heat generating components such as power diodes must constantly radiate heat so that their internal temperature does not exceed a predetermined temperature limit. Therefore, a structure has conventionally been adopted in which an aluminum nitride substrate with high thermal conductivity is used as a heat sink, and this aluminum nitride substrate is bonded to a metal substrate, such as a copper substrate. As a structure in which such heat-generating components are bonded to a copper substrate via an aluminum nitride substrate,
Conventionally, there is one shown in FIG. This is constructed by connecting an aluminum nitride substrate 3 to a copper substrate 1 using a solder 2, and connecting a power diode 5 to the aluminum substrate 3 using a solder 4.

[Problem that the invention seeks to solve]

However, in the conventional structure in which the copper substrate 1 and the aluminum nitride substrate 3 are bonded together by the solder 2, since the aluminum substrate 3 has poor wettability with metal melt,
There is a problem that it is difficult to obtain a predetermined bonding strength. Further, since the aluminum nitride substrate 3 and the copper substrate 1 have a large difference in coefficient of thermal expansion, there is also the problem that they are likely to peel off due to changes in ambient temperature, resulting in low quality reliability.

The present invention has been made in view of the above-mentioned conventional situation, and it is possible to improve the bonding strength between an aluminum nitride substrate and a metal substrate, and to prevent peeling caused by the difference in coefficient of thermal expansion. The purpose is to provide a bonding structure between a substrate and a metal substrate.

[Means for solving problems]

Therefore, in the present invention, a titanium nitride layer is formed on the surface of an aluminum nitride substrate, a metal material layer is formed on the surface of the titanium layer, and a metal substrate is attached to the surface of the metal material layer using a brazing material or solder. This is a bonded structure of an aluminum nitride substrate and a metal substrate, which are bonded together.

Here, the reason why the above configuration is adopted in the present invention will be explained.

First, the reason why a titanium nitride layer was formed on an aluminum nitride substrate was to improve the wettability of the aluminum nitride plate. The titanium nitride layer can be formed by applying a TiN paste to the aluminum nitride substrate and baking it.

11. The reason why a metal layer was formed on the titanium nitride layer is that this metal layer is essential for improving the bonding strength between the aluminum nitride substrate and the metal substrate. In this case, it is desirable that the metal layer has a thickness of 1 μm or more; if the thickness is less than 1 μm, satisfactory strength cannot be obtained. In addition, the upper limit of the above thickness is not particularly specified, but is 10 μm.
About m is preferable. This is because even if it becomes thicker than this, the bonding strength will not improve. Furthermore, the metal layer includes Cu, A
Metals such as u, Ag, and Ni can be used, and as methods for forming this, electrolytic plating, two-thick film printing, sputtering, etc. can be used.

[Effect]

According to the bonding structure between an aluminum nitride substrate and a metal substrate according to the present invention, a titanium nitride layer is formed on the aluminum nitride substrate, and a metal material layer is formed on the surface of the titanium nitride layer,
Since the metal substrate is bonded to the metal material layer using a brazing material or solder, deterioration in bond strength due to low wettability can be eliminated, and the bond strength with the metal substrate can be significantly improved.
Stress caused by the difference in thermal expansion coefficient between the aluminum nitride substrate and the metal substrate can be alleviated, and the problem of peeling due to temperature changes can also be solved. Therefore, when the bonding structure of the present invention is adopted as a bonding substrate for heat-generating components such as IC packages and power diodes, it is possible to secure the necessary bonding strength and prevent peeling due to heat generation while bonding the aluminum substrate. It can be used efficiently as a heat sink, greatly improving reliability in terms of quality.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram for explaining a bonding structure between an aluminum nitride substrate and a metal substrate according to an embodiment of the present invention.

This embodiment will be explained by taking as an example a case where a heat generating electronic component such as a power diode is bonded onto a metal substrate.

In the figure, 10 is an aluminum nitride substrate on which heat generating electronic components such as power diodes (not shown) are mounted, and this is bonded to a copper substrate 11. The surface of the aluminum nitride substrate 10 facing the copper substrate 11 is coated with a titanium nitride layer 12 . This titanium nitride layer 1
2 is formed by baking TiN paste. Further, the lower surface of the titanium nitride layer 12 is coated with a metal layer 13 formed by Cu plating.
3 is formed to have a thickness of 1 μm or more.

The metal layer 13 and the copper substrate 11 are made of Ag.
They are joined by a brazing filler metal 14 made of Cu. In addition,
The metal layer 13 and the copper substrate 11 may be joined by solder.

Next, the effects of this embodiment will be explained.

In this embodiment, heat from the heat generating electronic components is constantly radiated through the highly thermally conductive aluminum nitride substrate 10, thereby preventing the internal temperature of the heat generating electronic components from exceeding a predetermined limit temperature. ing.

Here, since the conventional bonding structure is a structure in which a copper substrate and an aluminum nitride substrate are simply bonded by soldering,
There was a problem in that the bonding strength between the two was low, and furthermore, the two were easily peeled off due to the difference in their coefficient of thermal expansion. On the contrary,
In this embodiment, an aluminum nitride substrate 10 is formed with a titanium nitride layer 12. Since it is bonded to the copper substrate 11 with the Ag-Cu brazing material 14 through the copper plating metal layer 13, the bonding strength between the two can be greatly improved, and the difference in thermal expansion coefficient between the aluminum nitride substrate 10 and the copper substrate 11 can be Stress can be alleviated, peeling caused by temperature changes can be prevented, and quality reliability can be improved.

In addition, although the above embodiment describes the case where a heat generating component such as a power diode is bonded to a copper substrate via an aluminum nitride substrate, the bonding structure of the present invention is not limited to this, and may be used in other applications. Of course, it can also be applied.

Further, in the above embodiment, Cu is used for the metal layer, but other materials such as fi, u, Ag, Ni, etc. may also be used, and the bonding strength can also be improved in this case.

Furthermore, as a method for forming the metal layer, although electrolytic plating was used as an example in the above embodiments, other methods such as thick film printing, sputtering, etc. can be used.

Furthermore, in the above embodiments, a copper substrate was used as an example of the metal substrate, but this can also be applied to other metal plates.

Here, a specific example for realizing the joining structure of this example will be explained, and a test conducted to confirm the effect will be explained.

■ First, aluminum nitride (A#N) powder and yttrium oxide (yz○3) powder as a sintering agent were mixed at Y$.
Prepare. 3 wt % of Y2O3 powder is added and mixed with the above /'IN powder, and an organic binder is added thereto to form a sheet material. A7! A4N and TiN are mixed at a weight ratio of 1:1 on the surface of this sheet material! After applying the N-TiN paste, it is dried to form an aluminum nitride substrate.

■ Applying TiN paste on the top surface of the aluminum nitride substrate, debinding it in a nitrogen atmosphere at 800°C for 2 hours, and then burning it in a nitrogen atmosphere at 1850°C for 5 hours. Body sintering. As a result, a titanium nitride layer 1 is formed on the upper surface of the aluminum nitride substrate 10.
2 is formed.

■ The top surface of the titanium nitride layer 12 is coated with a Cu film with a thickness of 1 μm or more by electrolytic plating.
form 3. A copper substrate 1 with a thickness of 300 μm is formed on the upper surface of this metal layer I3 by a brazing filler metal 14 made of Ag-Cu.
1 is joined, thereby configuring the joining structure of this embodiment.

Next, the bonding strength between the aluminum nitride substrate 10 and the copper substrate 11 produced by the above manufacturing method was measured. This measurement is performed by connecting a lead wire to the copper substrate 1■ by soldering, and pulling the lead wire in a direction perpendicular to the bonding surface between the aluminum nitride substrate 10 and the copper substrate 11 until the bonding surface separates. Then, the bonding strength was measured.

The table shows the results. For sample size 1, when the thickness of the metal layer 13 was set to 0.5 μm, the thickness was as follows: m2. Nn3° level 4 shows the cases where the film thicknesses are 1.0 μm, 10 μm, and 50 μm, respectively.

As is clear from the table, the thickness of the metal layer 13 is 0.5
In the case of μm, the bonding strength is as low as 0.2 kg/vs2, and a satisfactory value cannot be obtained. On the other hand, when the film thickness is 1.0 μm or more, the bonding strength is as high as 3 to 6 kg/m”.On the other hand, even when the film thickness is 10 μm or more, the bonding strength is has not been improved, and from the viewpoint of cost, the thickness of the metal layer is 1 to 1.
It can be said that a range of 0 μm is preferable.

〔Effect of the invention〕

As described above, according to the bonding structure between an aluminum nitride substrate and a metal substrate according to the present invention, a titanium nitride layer and a metal material layer are sequentially formed on the surface of an aluminum nitride substrate, and a wax is applied to the surface of the metal material layer. Since the metal substrates are bonded using , or solder, the bonding strength between the aluminum nitride substrate and the metal substrate can be improved, and the problem of peeling due to the difference in coefficient of thermal expansion can be solved.

/Q /

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining a bonding structure between an aluminum nitride substrate and a metal substrate according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional bonding structure. In the figure, 10 is an aluminum nitride substrate, 11 is a copper substrate, 12 is a titanium nitride layer, 13 is a copper plating metal layer, 1
4 is an Ag-Cu brazing material.

Claims (1)

[Claims] (1) A titanium nitride layer is formed on the surface of an aluminum nitride substrate, a metal material layer is formed on the surface of the titanium layer, and a metal plate is bonded to the surface of the metal material layer using a brazing material or solder. Features a bonding structure between an aluminum nitride substrate and a metal plate.