JP2715686B2 - Method for manufacturing ceramic-metal joined body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic-metal joined body in which a ceramic substrate and a metal plate are joined. More specifically, the present invention relates to a method of manufacturing a ceramic-metal bonded body used as a substrate for mounting, for example, an IC package, a power diode, and the like.

[0002]

2. Description of the Related Art A ceramic-metal joined body is obtained by joining metal plates to both main surfaces of a ceramic substrate, and the metal plate is formed by using a brazing material to which an active metal such as titanium (Ti) is added. (See FIG. 2). This joined body is used as a substrate for mounting a semiconductor device such as an IC package or a power diode. Since the heat generated by semiconductor devices has been increasing due to their higher density, higher speed, and higher output, if such a joined body is used as a substrate, the metal plate acts as a heat sink, and the heat generated by the semiconductor device is increased. Can be efficiently radiated into the air.

[0003] In order to manufacture this joined body, first, a brazing material paste is printed on a ceramic substrate or a metal plate, and the metal plate and the ceramic substrate are laminated with the brazing material paste interposed therebetween.
Next, when heat treatment is performed in a vacuum, the brazing material is melted by the heat treatment. The molten brazing material is solidified by cooling, and the ceramic substrate and the metal plate are firmly joined by the solidified brazing material.

[0004]

However, the heat treatment of the ceramic substrate and the metal plate laminated with the brazing material paste interposed therebetween is performed in a vacuum so as not to oxidize active metals such as titanium in the brazing material. The metal in the material is scattered and easily adheres to the ceramic substrate. A region where the metal in the brazing material is not joined to the metal plate of the ceramic substrate (insulating region)
If it adheres, the insulation resistance between the metal plates decreases,
Further, when plating the surface of the metal plate, there is a problem that the plating metal adheres to the ceramic substrate and the reliability as a substrate material is reduced.

In the heat treatment step, the molten brazing material acts as a lubricating layer, so that the ceramic substrate and the metal plate are liable to shift and move.
The positioning accuracy of the metal plate with respect to the ceramic substrate was poor.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object to provide a bonded body which can easily position a metal plate and has high reliability as a substrate material. An object of the present invention is to provide a method for producing a ceramic-metal joined body that can be obtained.

[0007]

SUMMARY OF THE INVENTION A method of manufacturing a ceramic-metal bonded body according to the present invention is a method of manufacturing a ceramic-metal bonded body by brazing a circuit metal plate to a part of a ceramic substrate. A boron nitride paste is deposited on the surface of the ceramic substrate in a region other than the metal plate joining portion, a brazing material is applied to the metal joining portion on the ceramic substrate surface, the metal plates are stacked, and then a heat treatment is applied to the ceramic substrate and the metal plate. It is characterized by joining.

[0008]

According to the present invention, since the boron nitride paste formed in the region other than the metal plate joining portion on the surface of the ceramic substrate functions as a mask, the metal scattered from the brazing material is removed from the metal plate joining portion of the ceramic substrate. It can be prevented from adhering to other areas.

Further, if the thickness of the boron nitride paste made larger than the thickness of the brazing material layer, it serves as a positioning jig of the membrane metal plate boron nitride paste, ceramic in brazing time to the heat treatment The displacement between the substrate and the metal plate can be prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ceramic according to one embodiment of the present invention will now be described.
The method for manufacturing the metal joined body will be specifically described. FIG. 1 shows a state before heat treatment in a manufacturing process of a ceramic-metal joined body according to one embodiment of the present invention, and FIG. 2 is a front view of the ceramic-metal joined body manufactured by the method of this embodiment. .

First, a ceramic substrate 1 was prepared as follows. Aluminum nitride (AlN) was selected as a ceramic substrate material, and yttrium oxide (Y ₂ O ₃ ) powder was added and mixed at a ratio of 3% by weight as a sintering aid, and an organic binder was further added to form a sheet. did.
The dimensions after firing this green sheet are 2 inches long and 1 inch wide.
After punching out to be inches, heat treatment is performed at 850 ° C. for 5 hours in a nitrogen atmosphere to disperse the binder, and further baked at 1850 ° C. for 5 hours in a nitrogen atmosphere.
A ceramic substrate (aluminum nitride substrate) 1 was obtained.

Next, as the metal plate 2, thermal expansion → joining →
A copper (Cu) plate having a plane dimension in consideration of a dimensional change in the process of cooling shrinkage was prepared. The thickness of this copper plate is 30
It was set to 0 μm.

Further, titanium (Ti) 5% by weight, silver (A)
g) Ethyl cellulose (5% by weight) and an organic solvent were added to a mixed powder consisting of 69% by weight and 26% by weight of copper (Cu) to prepare a brazing material paste 3. Also, 5% by weight of ethylcellulose and an organic solvent are added to boron nitride (BN) powder to form a nitride.
A boron paste 4 was produced.

After the preparation is completed, first, the ceramic
Tsu nitrogen in a region other than the upper and lower surfaces of the metal plate joining portion click substrate 1
Boron fossil paste 4 is printed in advance to have a thickness of 100 μm, and then a metal plate 2 on which a brazing material paste 3 is printed on one side is sandwiched by the brazing material paste 3 so that the metal plate joining portion of the ceramic substrate 1 is Pressed against. Here, the thickness of the brazing material paste 3 is considerably smaller than the thickness of the boron nitride paste 4. Further, as shown in FIG. 1, a boron nitride plate 5 is stacked on the upper and lower surfaces of the metal plate 2 and a load is applied with a copper weight 6 of 500 g from above, and the metal plate 2 is evenly applied to the metal plate 2 via the boron nitride plate 5. Pressure was applied. In this state, 1 × 1
In 0 ^-5 Torr or more in a vacuum, 10 at 950 ° C.
Heat treatment was performed for minutes. After the heat treatment, the copper weight 6 and the nitrogen
The boron nitride plate 5 was removed, and the boron nitride paste 4 was removed by ultrasonic cleaning in an organic solvent to obtain a ceramic-metal bonded body 7 as shown in FIG.

In the ceramic -metal bonded body 7 manufactured as described above, no displacement between the ceramic substrate 1 and the metal plate 2 occurred. Before the removal of the boron nitride paste 4, the surface of the metal plate 2 was electrolessly plated with nickel (Ni), but the nickel plating did not adhere to the ceramic substrate 1.

Next, for comparison with the method for manufacturing a joined body according to the embodiment of the present invention, a joined body was also manufactured by the methods of Comparative Examples 1 and 2 as described below. Comparative Example 1 In Comparative Example 1, a ceramic -metal joined body was manufactured in the same manner as in Example except that the boron nitride paste was not applied to the ceramic substrate. In this case, Serra
A misalignment of several percent of the size of the metal plate with respect to the mic substrate occurred. Also, when nickel electroless plating was applied to this joined body, adhesion of nickel plating was observed on the ceramic substrate.

Comparative Example 2 In Comparative Example 2, a paste using aluminum nitride powder instead of boron nitride was prepared, and this aluminum nitride paste was applied to a region other than the metal plate joining portion of the ceramic substrate. In the same manner as in the above, a ceramic -metal joined body was produced. In this case, the aluminum nitride powder adhered to the edge of the brazing material, and a good joined body could not be obtained.

The ceramic-metal joined body of the above embodiment is a sample for comparing the effect with the comparative example, and the dimensions of the metal plate and the like do not represent actual product dimensions.

[0019]

According to the present invention, the scattered metal from the brazing material can be prevented from adhering to the area other than the metal plate joining portion of the ceramic substrate by the boron nitride paste. Therefore, it is possible to prevent a decrease in insulation resistance between the metal plates joined to the ceramic substrate, and also to prevent a plating metal from adhering to the ceramic substrate during plating on the metal plate, thereby improving reliability as a substrate material. Can be enhanced.

If the thickness of the boron nitride paste is made larger than the thickness of the brazing material layer, displacement of the ceramic substrate and the metal plate during brazing or heat treatment can be prevented, and And the positioning accuracy of the ceramic substrate can be improved.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a method for manufacturing a ceramic-metal joined body according to an embodiment of the present invention.

FIG. 2 is a front view of the ceramic-metal joined body manufactured by the above method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ceramic substrate 2 Metal plate 3 Brazing material paste 4 Boron nitride paste

Claims (1)

(57) [Claims] 1. A method of manufacturing a ceramic-metal bonded body by brazing a metal plate for a circuit to a part of a ceramic substrate, wherein a surface of the ceramic substrate is nitrided in a region other than a bonded portion of the metal plate.
A ceramic-metal joint characterized in that a boron paste is deposited, a brazing material is applied to a metal joint on the surface of the ceramic substrate, a metal plate is laminated, and then a heat treatment is applied to join the ceramic substrate and the metal plate. How to make the body.