JPH0570262A - Brazing filler metal paste for joining aluminum nitride substrate to metallic plate - Google Patents

Abstract

PURPOSE:To surely join an AlN substrate to a metallic plate at the time of joining with a brazing filler metal contg. an active metal and to improve the reliability of the resulting joined body. CONSTITUTION:TiN powder is added to metal powders of Ti, Cu and Ag by about 1-10 pts.wt. per 100 pts.wt., in total, of the metal powders and an org. vehicle (org. substance) is further added to obtain brazing filler metal paste. When an AlN substrate is superposed on a metallic plate with the paste in-between and they are heat-treated, part of the TiN transfers to the interface between the metallic plate and the AlN substrate and the reaction of the Ti powder in the brazing filler metal with the AlN of the AlN substrate is accelerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing paste for joining an aluminum nitride substrate and a metal plate. More specifically, it relates to a soldering paste used for producing an aluminum nitride-metal bonded substrate used as a substrate for IC packages, power diodes and the like.

[0002]

2. Description of the Related Art In order to cope with an increase in the amount of heat generated by higher density, higher speed and higher output of semiconductor devices, a substrate material having excellent heat dissipation has been required. An alumina substrate has been conventionally used as a substrate material having excellent heat dissipation, but recently, an aluminum nitride (hereinafter referred to as AlN) substrate having a high thermal conductivity has been attracting attention. However, in order to improve the heat dissipation as a mounting board, a thickness of several hundred μm is used as a heat sink on the AlN board.
It is necessary to join a metal plate such as a copper plate of m. For this reason, conventionally, a metal plate is bonded to an AlN substrate using a brazing material to which an active metal such as Ti (titanium) is added.

FIG. 1 is a sectional view showing the structure of a bonded body of an AlN substrate and a metal plate. In this joined body 1, after the paste of the brazing material 3 to which Ti is added is printed on the metal plate 2 having a flat surface, the paste printing surface of the metal plate 2 is superposed on the AlN substrate 4.
A heat treatment is applied in a vacuum with a load applied from above to melt the paste of the brazing material 3, and then the metal plate 2 is firmly bonded to the surface of the AlN substrate 4 through the layer of the solidified brazing material 3. It is a thing. In this way, the metal plate 2 bonded to the AlN substrate 4 functions as a heat sink to improve heat dissipation as a mounting substrate. The metal plate 2 can also be used as a wiring pattern.

[0004]

In the above-mentioned bonded body, Ti contained in the brazing material reacts with AlN to generate TiN (titanium nitride) at the interface between the brazing material and the AlN substrate. As a result, the AlN substrate and the metal plate are more firmly bonded.

However, when the AlN substrate and the metal plate are joined with a paste of a brazing material made of, for example, a mixed powder of Ti-Ag-Cu, if the joining area between the AlN substrate and the metal plate becomes large, the TiN is entirely covered on the joining surface. It becomes difficult to form the reaction layer. As a result, in the conventional example, there was a problem that the TiN reaction layer was not sufficiently formed on the entire bonding surface, and the reliability of the bonding deteriorated. In addition, when the non-bonded portion is formed, the non-bonded portion has a thermal resistance, which hinders heat conduction from the AlN substrate to the metal plate, thereby impairing heat dissipation.

The present invention has been made in view of the problems of the above conventional examples, and an object thereof is to bond an AlN substrate and a metal plate when bonding is performed using a brazing material containing an active metal. To secure the reliability of the bonded body.

[0007]

A brazing paste for joining an aluminum nitride substrate and a metal plate according to the present invention is a brazing paste for joining an aluminum nitride substrate and a metal plate. It is characterized by comprising titanium nitride powder added in an amount of approximately 1 part by weight or more and 10 parts by weight or less with respect to parts by weight, and an organic vehicle.

Further, typically, as the metal powder, one containing copper, silver and titanium elements can be used.

[0009]

In the bonding solder paste of the present invention, since TiN powder is added to the solder paste, when heat treatment is performed in a vacuum during brazing, part of this TiN becomes an aluminum nitride substrate. It moves to the interface with the brazing material and promotes the production of TiN by the reaction between Ti and AlN in the brazing material. As a result, Ti in the brazing material effectively reacts with AlN in the aluminum nitride substrate, and even if the bonding area becomes large, almost no non-bonded portion is formed. Therefore,
By joining the aluminum nitride substrate and the metal plate with the joining wax paste of the present invention, it is possible to obtain a joined body with small variations in joining strength and high joining reliability.

The addition amount of the TiN powder is equal to that of the metal powder 1.
When the amount is about 1 part by weight or less with respect to 00 parts by weight, TiN
The production area ratio of was decreased, and the joining property and the joining reliability were lowered. Further, when it was about 10 parts by weight or more, the peel strength of the joined body was lowered and the joining strength was low.

[0011]

EXAMPLE A brazing paste for joining according to an exemplary embodiment of the present invention is a metal powder composed of Ti, Cu and Ag and Ti.
N is added, and the balance consists of an organic vehicle (organic matter).

A metal plate such as a copper plate printed with a wax paste to which TiN has been added in advance is stacked on an AlN substrate,
When heat-treated while applying a load, a part of TiN moves to the interface between the metal plate and the AlN substrate, and Ti powder and A
The reaction of the AlN substrate with AlN is promoted, and the metal plate and AlN
The bonding with the substrate is surely performed.

In order to determine the optimum amount of TiN to be added to this wax paste, the following several samples were prepared and their bonding strength and bondability were evaluated. The results will be described below.

First, a metal powder was prepared by mixing Ti in an amount of 10% by weight, Ag in an amount of 65% by weight, and Cu in an amount of 25% by weight. As shown in column I of Table 1, the total amount of the metal powder was 100%.
0 parts by weight, 0.5 parts by weight, 1 part by weight, 3 parts by weight, 5 parts by weight, 10 parts by weight, and 15 parts by weight of TiN to parts by weight, respectively.
The wax pastes of Sample Nos. 1 to 7 were prepared by adding them in an amount of part by weight, and further adding organic substances to the rest. The samples marked with * in the sample numbers in Table 1 are samples outside the scope of the present invention.

[0015]

[Table 1]

Next, the bonding strength between the AlN substrate and the copper plate was measured using the wax pastes of Sample Nos. 1 to 7. That is, the wax paste 13 of sample No. 1 to 7 is 2 m
Printed on 10 copper plates 12 each with m-square and thickness of 0.3 mm,
As shown in FIG. 2, the paste printing surfaces were brought into contact with each other, and five copper plates 12 were stacked in two rows on the AlN substrate 14 having a 25.4 mm square and a thickness of 0.635 mm. This is the load (eg 1
g / mm ² ) in a vacuum (10 ⁻⁵ to 10 ⁻⁴ T)
After heat treatment at 850 ° C. for 10 minutes at orr), it was cooled at a cooling rate of 1 ° C./min to produce a bonded body 11 of the AlN substrate 14 and the copper plate 12. Then, as shown in FIG. 3, a copper wire 1 having a diameter of 0.8 mm is formed on each copper plate 12 bonded to the AlN substrate 14 by each of the wax pastes of Sample Nos. 1 to 7.
5 was brazed, the copper wire 15 was bent into an L shape, and the peel strength (peel strength) was measured. Thus each sample
The peel strength (average value) of the joined body was determined for each of Nos. 1 to 7. The results are shown in column II of Table 1. According to column II of Table 1, sample No. 7 containing 15 parts by weight of TiN powder was added.
Peel strength is 2.6k in the joint using the wax paste of
gf / (2 mm square), the peel strength was 3.7 kgf / (2 mm in the case of the joints using the wax pastes of Sample Nos. 1 to 6 in which the addition amount of TiN powder was 10 parts by weight or less.
It was as high as above.

Further, in order to evaluate the bondability in a large area,
The above sample No. 1 on a 25 mm square, 0.3 mm thick copper plate
Screen printing each wax paste of ~ 7, and contact the paste printing surface to make a copper plate 25.4mm square, thickness 0.635.
It was laminated on both sides of a mm AlN substrate. Then, heat treatment was performed under the same conditions as in the evaluation of the bonding strength, and copper plates were bonded to both surfaces of the AlN substrate. After that, the bonded body was immersed in a nitric acid aqueous solution to melt and remove the metal parts (the copper plate and the metal part of the brazing material) to expose the TiN layer as a reaction product on the surface of the AlN substrate. Then, the generation area of the TiN layer was measured by an image analysis device, and the T
The ratio of the iN layer generation area (TiN generation area ratio) was obtained.
The results are shown in column III of Table 1. As is clear from column III of Table 1, sample No. 1 containing no TiN powder
Sample N containing less than 1 part by weight of TiN
In the case of o.2, the TiN production area ratio was 74.0% or less. The area ratio was obtained.

Therefore, the addition amount of TiN powder is 1
1 to 10 parts by weight of sample No. 3 to 00 parts by weight
When the wax paste of No. 6 was used, it was possible to obtain a bonded body having good characteristics in both peel strength and TiN generation area ratio.

[0019]

According to the joining wax paste of the present invention,
Ti due to the reaction between Ti in the brazing material and AlN during heat treatment
The generation of N can be promoted, and Ti in the brazing material effectively reacts with AlN in the aluminum nitride substrate, and almost no non-bonded portion is formed even if the bonded area becomes large.
Therefore, when the aluminum nitride substrate and the metal plate are bonded by the bonding wax paste of the present invention, it is possible to obtain a bonded body with small fluctuation in bonding strength and high reliability of bonding. Therefore, a bonded body suitable as a substrate of a semiconductor device or the like can be manufactured.

[Brief description of drawings]

FIG. 1 is a front view showing a joined body of a ceramic substrate and a metal plate joined by a conventional wax paste.

FIG. 2 is a plan view showing a bonded body for peel strength measurement.

FIG. 3 is a schematic cross-sectional view showing a method for measuring the peel strength of a joined body.

[Explanation of symbols]

 12 Copper plate 13 Raw paste 14 AlN substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Sakabe 2 26-10 Tenjin Tenjin, Nagaokakyo City, Kyoto Murata Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A wax paste for joining an aluminum nitride substrate and a metal plate, which is approximately 1 to 100 parts by weight of metal powder and a total of 100 parts by weight of metal powder.
A brazing paste for joining an aluminum nitride substrate and a metal plate, which comprises titanium nitride powder added in an amount of 10 parts by weight or more and 10 parts by weight or less, and an organic vehicle. 2. The brazing paste for joining an aluminum nitride substrate and a metal plate according to claim 1, wherein the metal powder contains copper, silver and titanium elements.