JPH0513112B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an aluminum nitride metallization paste composition, which has a practical adhesion strength of, for example, 2.5.
The aim is to obtain Kgf/2mm□ or more. (Prior Art) Up until now, ceramics have been mainly made of oxides, but due to the diversification of required physical properties, the uses of ceramics other than oxides are expanding. Particularly in the case of ceramic substrate materials for electronic components, the dissipation of heat generated as the density of elements increases has become an extremely important issue, and the use of highly thermally conductive materials to replace the conventional alumina is being considered. . Aluminum nitride is the most likely material for practical use as a highly thermally conductive substrate material. When using it as a substrate material, it is necessary to draw a circuit on its surface using conductive material.
In the case of alumina, there are the following technologies. A method in which a circuit is formed by printing molybdenum-manganese paste on a substrate and baking it at 1350 to 1450°C in wet hydrogen or a wet hydrogen/nitrogen mixed gas. A method of forming circuits by mixing fine metal powders of Ag/Pd, Ag/Pt, Au, and Cu with glass frit, organic binder, etc. to form a paste, printing it on a substrate, and firing it. A method of placing a copper plate on a ceramic substrate and heating it in a reactive atmosphere while applying pressure. However, these methods cannot be directly applied to aluminum nitride. This is because high adhesion, which is the most important property required of a wiring board, cannot be obtained. This is because the above methods all obtain sufficient adhesion strength through an adhesion mechanism that takes advantage of the characteristics of the alumina substrate being an oxide, whereas in the case of non-oxide ceramics such as aluminum nitride, This is because the bonding layer that is formed in the case of an alumina substrate is not formed. Therefore, various studies have been conducted on metallizing compositions and metallizing methods for non-oxide ceramics, and although some silicon carbide and silicon nitride have been put into practical use, aluminum nitride metallized products have no practical strength. The current situation is that a device equipped with this has not yet been put into practical use. (Problems to be Solved by the Invention) An object of the present invention is to provide a novel metallizing paste composition that has excellent adhesion to aluminum nitride and exhibits sufficient strength for practical use. (Means for solving the problem) The present inventor has discovered that tungsten, which is a high melting point metal,
We compared various metallization paste compositions based on molybdenum and combined them with metals such as titanium, zirconium, vanadium, niobium, tantalum, chromium, silicon, manganese, and hafnium. The present inventors have discovered that a dense metallized layer with high adhesion strength can be formed on an aluminum nitride substrate by using the above method, and have completed the present invention. That is, the present invention provides a method for aluminum nitride containing 78 to 95% by weight of tungsten (W) and/or molybdenum (Mo) powder, 4 to 21% by weight of manganese powder (Mn), and 1 to 10% by weight of niobium powder. This is a composition for metallizing paste. The present invention will be explained in more detail below. The effect of increasing adhesion strength using the metallizing paste composition of the present invention can be explained as follows. When manganese and niobium are heated to metallization processing temperatures, they react with aluminum nitride at the bonding interface to form a compound believed to be niobium-manganese nitride and a niobium-aluminum alloy, which forms a strong bonding layer. In addition, manganese and niobium each react with aluminum nitride, and manganese reacts with aluminum nitride.
Since Mn ₄ N and niobium produce compounds of Nb ₂ N and AlNb ₂ , it is expected that a metallized layer with excellent adhesion can be formed. Even when mixed with metal, it was not possible to form a metallized layer with practical adhesion strength. That is, as an example, using a paste containing 20% by weight of manganese and molybdenum, in hydrogen,
When heated to the metallization treatment _temperature , manganese reacts with aluminum nitride at the bonding interface to produce _{Mn 4 N} ;
→4Mn+1/ _2N2 A part of it decomposes and releases _N2 . This N ₂ creates voids at the bonding interface, making it impossible to obtain sufficient bonding strength. On the other hand, 10% by weight of niobium in molybdenum
When a blended paste is used, sintering is insufficient and only a metallized layer is obtained that easily peels off when rubbed with a knife. However, if a paste containing manganese and niobium is used at the same time, unstable Mn ₄ N will not be generated, and a highly adhesive metallized layer that does not create voids at the bonding interface can be obtained. It became very detailed. In the present invention, the reason why the proportions of molybdenum and/or tungsten, manganese and niobium are limited as described above is to fully exhibit the above effects. In other words, the reason why molybdenum and/or tungsten is 78 to 95% by weight is that if it is less than 78% by weight,
The total amount of niobium and manganese exceeds 22% by weight, and the thickness of the reaction product layer, which is difficult to sinter, becomes thick, creating voids due to insufficient sintering, and only a small adhesion strength can be obtained. On the other hand, if it exceeds 95% by weight, the amount of reaction products will be too small, resulting in a decrease in strength and insufficient sintering of the metallized layer. The manganese content of 4 to 21% by weight is 4% by weight.
If it is less than that, the sintering of the metallized layer is insufficient,
Furthermore, if the content exceeds 21% by weight, voids will appear at the bonding interface. The reason why niobium is set at 1 to 10% by weight is that if it is less than 1% by weight, there is almost no effect of improving adhesion strength, and if it exceeds 10% by weight, the effect does not increase, and the sintering of the metallized layer is not improved. This is due to a decrease in density. A particularly preferred proportion of niobium is 0.1 to 1 times the weight of manganese. The particle size of the metal powder is preferably as fine as possible in order to enhance the reaction at the joint surface and increase the density of the metallized layer. Specifically, for molybdenum and tungsten, the average particle size is 5μ.
Below, it is desirable that manganese and niobium be 44μ or less. In order to prepare a metallization paste using the above-mentioned metal powder, it may be mixed together with an organic binder such as ethyl cellulose or PMMA used in general metallization pastes, and a solvent such as terpineol or toluene. To give an example of the formulation, for 100 parts by volume of solvent,
30-60 parts by weight of metal powder and 30-60 parts by weight of organic binder
Parts by weight. The viscosity of the paste is 20,000~
It is about 150000CPS. To explain how to use the metallizing paste of the present invention, the paste is applied to the surface of an aluminum nitride substrate by a method such as screen printing, and then dried.
The metallizing temperature is 1000 to 1400, which is heated to the metallizing temperature for about 1 hour in a hydrogen atmosphere or an inert atmosphere such as nitrogen or argon.
℃ range is preferred, and particularly preferred is a temperature range in which niobium and manganese actively react with aluminum nitride and almost no decomposition of the reaction products occurs.
The temperature is 1150-1350℃. The metallized layer obtained as described above can be further plated with nickel or copper by electroless plating or electrolytic plating to create a structure that allows metal bodies to be joined by methods such as brazing. (Example) Examples of the present invention will be shown below. Example 1 A total of 2 g of the composition powder shown in Table 1 was weighed out, and 0.5 cc of a toluene solution containing 30% by weight of PMMA and 0.5 cc of terpineol were added thereto and thoroughly mixed.
A homogeneous paste was prepared. By screen printing this paste, 9 patterns of 2mm□ were printed on 25mm
Printed on a square, 0.65 mm thick aluminum nitride sintered substrate. This substrate was placed in an oven at 80℃ for 2 hours to dry the paste, and then placed in a molybdenum tube placed in a 50φ alumina furnace tube.Then, the metallization treatment was performed at a temperature of 1300 while flowing hydrogen at a rate of 1/min. The temperature was raised to ℃ and held for 60 minutes. After cooling, the inside of the furnace was replaced with N ₂ and the substrate was taken out.
Next, electroless nickel plating was applied to the metallized portion of this metallized substrate, and a 0.6φ tin plated copper wire was soldered to a 2 mm square metallized pad, and the peel strength was measured by L-shaped tension. Next, the substrate prepared in the same manner as above was heated to 150°C.
The sample was left in an oven for one week, and its peel strength was measured to determine whether there was a decrease in strength due to aging. These results are summarized in Table 1. Note that the values in Table 1 are the average values of 9 values. Experiment Nos. 1 to 27 are examples of the present invention, and Experiments Nos. 28 to 35 are comparative examples. The average particle size of the molybdenum powder used is 2μ, and that of manganese and niobium is less than 44μ.

【table】

[Table] Example 2 Table 2 shows the results obtained by varying the metallization treatment temperature for the metallization paste composition of Experiment No. 8.

[Table] Example 3 Regarding the composition of Experiment No. 8 shown in Example 1, when the atmosphere during firing was changed to argon, the peel strength was 4.1 Kgf/2 mm□ before aging treatment and 4.1 after aging treatment. It was Kgf/2mm□. Example 4 In Experiment No. 8 of Example 1, 88% by weight of W powder (average particle size: 0.75μ) was used instead of 88% by weight of Mo powder. As a result, the peel strength before the aging treatment was 4.5Kgf/2mm□, and that after the aging treatment was 4.5Kgf/2mm□. Example 5 In Experiment No. 8 of Example 1, 44% by weight of Mo powder (average particle size 2μ) and 44% by weight W powder (average particle size 0.75μ) were used instead of Mo powder. the result,
Peel strength before aging treatment is 4.3Kgf/2mm
□, and after aging process it is 4.0Kg
It was f/2mm□. Reference example Commercially available Pd/Ag paste, 25.4mm square, 0.65mm
2 by screen printing on a thick alumina substrate.
Print 9 patterns of mm□, and after drying,
Baked at 925℃, 2mm 0.6φ tin wire
□ After soldering to the pad, peel strength was measured. As a result, the weight before aging was 4.1Kg.
f/2mm□, 2.1Kgf/2mm after aging treatment
□ It was. (Effects of the Invention) According to the present invention, a metallized layer having sufficiently high adhesion strength can be formed on an aluminum nitride substrate, and the metallized layer can be dense.

Claims (1)

[Claims] 1 Tungsten and/or molybdenum powder 78~
A metallizing paste composition for aluminum nitride comprising 95% by weight of manganese powder, 4 to 21% by weight of manganese powder, and 1 to 10% by weight of niobium powder.