JP3070176B2 - Joining method of aluminum nitride substrate and copper plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for joining an aluminum nitride substrate and a copper plate. The joined body of the aluminum nitride substrate and the copper plate manufactured by the present invention is, for example, an IC
(Integrated circuit) This is used as a substrate for mounting a package, a power diode, and the like.

[0002]

2. Description of the Related Art In order to cope with an increase in the amount of heat generated by high density, high speed, and high output of a semiconductor device, a mounting board having an excellent heat radiation property is required. Conventionally, an alumina substrate has been used as a mounting substrate for this purpose, but recently, an aluminum nitride (hereinafter, referred to as AlN) substrate having a high thermal conductivity has attracted attention. However, in order to improve the heat dissipation as a mounting board,
It is necessary to join a copper plate (hereinafter, referred to as a Cu plate) having a thickness of several 100 μm as a heat sink to the AlN substrate.

For this reason, conventionally, an AlN substrate and a Cu plate are joined by using a brazing material to which an active metal such as Ti (titanium) is added. That is, C with a flat surface
After printing the paste of the brazing filler metal to which the active metal was added on the surface of the u-plate,
A heat treatment is performed in a vacuum with a load applied from both sides to the N substrate. At the time of this heat treatment, the paste of the brazing material melts and the AlN substrate reacts with the active metal,
The Cu plate is firmly joined to the surface of the AlN substrate via the brazing material layer. Thus, the Cu plate functions as a heat sink, improves the heat radiation of the AlN substrate, and can be used as a wiring pattern.

[0004]

However, in the joined body of the AlN substrate and the Cu plate joined by the above method, the residual thermal stress at the joint interface between the AlN substrate and the Cu plate was large. For this reason, the variation in the joining strength is relatively large, and there has been a concern about the reliability of the joining.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and has as its object to reduce the residual stress at the bonding interface and to provide a method of manufacturing a highly reliable bonded body. To provide.

[0006]

According to the present invention, there is provided a method for joining an aluminum nitride substrate and a copper plate using a brazing material containing an active metal. After brazing, the joined body is placed in an atmosphere containing hydrogen for 300 to 75
The heat treatment is performed at 0 ° C.

[0007]

In the present invention, the heat treatment of the joined body is performed in an atmosphere containing hydrogen after brazing the aluminum nitride substrate and the copper plate, so that oxygen dissolved in the copper plate or the brazing material is reduced. As a result, the yield stress of the copper plate or brazing material decreases. For this reason, the copper plate or the brazing material is easily plastically deformed, and the thermal stress at the joining interface is effectively reduced. Therefore, by manufacturing a joined body of an aluminum nitride substrate and a copper plate by the method of the present invention, it is possible to obtain a substrate material (joined body) with small variation in joining strength and high joining reliability.

[0008]

FIG. 1 is a front view showing a joined body manufactured by a method according to an embodiment of the present invention. A method for manufacturing the joined body 4 will be described. First, a brazing material 3 having a weight ratio of Ti: Ag: Cu of 10:65:25 and the balance of organic material was used.
Is printed on the entire surface of a plurality of Cu plates 1 and the paste printed surface is directed to the AlN substrate 2 side.
The Cu plate 1 is laminated on both upper and lower surfaces of the substrate 2. Thereafter, a load is applied to both sides of the laminate in this state, and 10 ^-5 to 10 ^-4 Torr is applied.
In a vacuum at 850 ° C. for 10 minutes.
At this time, Ti added to the paste of the brazing material 3 as an active metal reacts with the AlN substrate 2 to generate a TiN (titanium nitride) layer, and the AlN substrate 2 and the Cu plate 1 are joined. The cooling rate at this time is 1 ° C./min.

Next, the joined body 4 is heat-treated at 300 to 750 ° C. in an atmosphere of 80% nitrogen and 20% hydrogen. The cooling rate at this time is 1 ° C. as in the case of brazing.
/ Min. When heat treatment is performed on the joined body 4 in an atmosphere containing hydrogen in this manner, oxygen dissolved in the Cu plate 1 or the brazing material 3 is reduced and removed, and the Cu plate 1 or the brazing material 3 is removed.
Yield stress decreases. Therefore, the Cu plate 1 or the brazing material 3 is plastically deformed, and the thermal stress at the joining interface is reduced. In addition, metal Ti reacts with hydrogen, and fragile hydrogenated Ti
Since brazing cannot be performed in an atmosphere containing hydrogen, most of the Ti is TiN at the interface with the AlN substrate 2 after brazing is completed. Without this, there is no possibility that the joining surface becomes brittle.

Next, in order to measure the peel strength of the joined body, a sample according to an embodiment of the present invention and a sample according to a comparative example were prepared. First of all, C of 2 mm in length and width and 0.3 mm in thickness
The weight ratio of Ti: Ag: Cu is 10:65:
At 25, a paste of a brazing filler metal made of an organic material is printed, and the paste-printed surface is directed toward the AlN substrate side, and two rows of 10 Cu plates are arranged on an AlN substrate having a length of 25.4 mm in each direction and a thickness of 0.635 mm. Was. Then, a load was applied from above the Cu plate in this state, and heat treatment was performed at 850 ° C. for 10 minutes in a vacuum of 10 ⁻⁵ to 10 ⁻⁴ Torr to obtain a joined body of the AlN substrate and the Cu plate.

Next, this joined body is made up of 80% nitrogen and 20% hydrogen.
% Heat treatment at 300 ° C. in an atmosphere of 30% to produce 30 samples of Example 1.

Similarly, the bonded body subjected to the first heat treatment is placed in an atmosphere of 80% nitrogen and 20% hydrogen in an atmosphere of 5% each.
A second heat treatment was performed at 00 ° C., 700 ° C., and 750 ° C., and each of the samples of Example 2, Example 3, and Example 4 was
Made one by one.

On the other hand, 30 bonded bodies were produced as Comparative Example 1 only with the first heat treatment but without the second heat treatment. Further, the joined body subjected to the first heat treatment was subjected to a second heat treatment at 200 ° C. in an atmosphere of 80% nitrogen and 20% hydrogen, and 30 samples of Comparative Example 2 were manufactured.

Thereafter, a copper wire 6 having a diameter of 0.8 mm was soldered to the Cu plate 1 as shown in FIG. 2 to measure the bonding strength of each of the bonded bodies of Examples 1 to 4 and Comparative Examples 1 and 2. And the peel strength (peel strength) was measured. Table 1 shows the average value, the minimum value, and the standard deviation of the peel strength of each sample thus measured together with the heat treatment temperature conditions and the like.

[0015]

[Table 1]

Comparing the samples of Examples 1 to 4 with the samples of Comparative Examples 1 and 2 from Table 1, the joined body of the embodiment has a larger minimum and average peel strength than the joined body of the comparative example. Moreover, the variation (standard deviation) in the peel strength is small.

In the above embodiment, the heat treatment is performed in an atmosphere containing hydrogen after brazing in a vacuum, but the heat treatment may be performed by blowing a gas containing hydrogen into the joined body during cooling during brazing. Good.

[0018]

According to the present invention, it is possible to effectively reduce the thermal stress at the joining interface by plastic deformation of the copper plate or brazing material, to reduce the variation in joining strength, and to obtain a highly reliable joining material. (Joined body) can be manufactured.

[Brief description of the drawings]

FIG. 1 shows an Al manufactured by a method according to an embodiment of the present invention.
It is a front view which shows the joined body of N board and Cu board.

FIG. 2 is a diagram showing a method for measuring the peel strength of a joined body of an AlN substrate and a Cu plate.

[Explanation of symbols]

 Reference Signs List 1 Cu plate 2 AlN substrate 3 Brazing material

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukio Sakabe 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd. (56) References JP-A-2-46750 (JP, A) JP-A Heihei JP-A-2-174145 (JP, A) JP-A-2-149478 (JP, A) JP-A-1-155686 (JP, A) JP-A-62-289396 (JP, A) JP-A-3-114289 (JP, A A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 37/02 H01L 23/15 H05K 3/38

Claims (1)

(57) [Claims] In a method for joining an aluminum nitride substrate and a copper plate using a brazing material containing an active metal, the aluminum nitride substrate and the copper plate are brazed in a vacuum, and the joined body is placed in an atmosphere containing hydrogen. ~ 750
A method for bonding an aluminum nitride substrate and a copper plate, the method comprising heat-treating at a temperature of about 100 ° C.