JPS62246890A - Metallized layer of non-oxide base ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is effective for, for example, bonding electrode parts of ceramic heaters made of non-oxide ceramics, forming conductive paths on non-oxide ceramic substrates, etc. The present invention relates to a non-oxide ceramic metallized layer used for.

[Conventional technology]

Generally, ceramics are stronger and more heat resistant than metals.

BACKGROUND ART In recent years, non-oxide ceramics such as silicon nitride and silicon carbide have excellent corrosion resistance, and in addition to the above properties, they also have high thermal shock resistance, so their applications have been widely expected in recent years. As an example, T i N that takes advantage of these characteristics
-S 1xNa-based composite non-oxide ceramic heaters and ceramic substrates made of SiC, AlN, and the like that take advantage of their high thermal conductivity are known.

In the ceramic heater and ceramic substrate described above, it is essential to form a metallized layer on the surface of the non-oxide ceramic in order to connect electrodes to the heater and form a conductive path on the substrate. Furthermore, in general, a metallized layer is often formed when non-oxide ceramic parts and metal parts are joined together.

As such a metallized layer, 1, for example, JP-A-59-
A method such as Ni plating followed by aging as disclosed in Japanese Patent No. 91684 is known.

[Problem that the invention seeks to solve]

However, conventional metallized layers, including the method described in the above-mentioned publication, have a problem in that they do not have sufficient adhesion strength to non-oxide ceramics and tend to peel off. Furthermore, the surface of conventional metallized layers is easily oxidized, especially at high temperatures.For example, in a structure in which a metalized layer is applied to the electrode part of a ceramic heater and the metal electrode is pressed against it to maintain conductivity, this oxidation can cause damage to the conductivity. This causes a problem in that it gradually becomes difficult to apply electricity to the ceramic heater over a long period of use.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of conventional metallized layers as described above, and to provide a novel metallized layer that has high adhesion strength and excellent conductivity.

[Means for solving problems]

In order to achieve the above object, the present invention provides at least Pt, Pt.
d, Rh, Ir, Ru, and Os; one or more metals selected from Cr, Ni, Fe, and Co; and one or more metals selected from C, B, Si, and P. a first coating layer coated on the non-oxide ceramic, the first coating layer containing the elements Au, Ag;

A second material containing one or more metals selected from Cu and Al.
A metallized layer with a covering layer is employed as a technical means.

[Effect]

According to the above means, the first coating layer coated on the non-oxide ceramic mainly contains Pt, Pd,
Due to the catalyst [action] of one or more metals selected from Rh, Ir, Ru, and Os, it bonds with the non-oxide ceramic with good wettability, and the second coating layer coated on the first coating layer has a large Ensure conductivity.

〔Effect of the invention〕

Therefore, according to the present invention, a metallized layer having high adhesion strength and conductivity can be formed on non-oxide ceramics.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings. FIG. 1 is a cross-sectional view illustrating a non-oxide ceramic metallized layer according to the present invention, where l is silicon nitride (St: +N
4) A non-oxide conductive ceramic test piece whose main component is titanium nitride (T i N), which was manufactured by the process described below.

The required amounts of silicon nitride with an average particle size of 0.8μ and titanium nitride with an average particle size of 0.5μ were weighed, and 41 mol% of silicon nitride,
A mixed powder having a composition of 55.4 mol% titanium nitride was prepared. Moreover, this mixed powder is MgAlgo.

Contains 2.2n+o1%, Y, and 0.1.4mol% sintering aid. This mixed powder was added to water as a solvent, and 1
Mixed for 2 hours. The mixed powder whose composition was mixed in this way was dried and granulated. Next, press mold to the specified size,
Thereafter, it was fired at 1750° C. for 4 hours in a nitrogen atmosphere to form a sintered body. Thereafter, the surface of the sintered body was polished to obtain a non-oxide ceramic test piece 1 for metallization.

Reference numeral 2 in FIG. 1 denotes the first coating layer constituting the metallized rrJ4 of the present invention, which was manufactured by the following steps.

From the transition metal group consisting of Pt, Pd, Rh, Ir, Ru, and Os (hereinafter referred to as element group I), Pt, Cr, and Ni
, Fe, and Co (hereinafter referred to as element group ■), select Ni-Cr, and from the element group consisting of B, C, Si, and P (hereinafter referred to as element group ■), select P. 1st
Weigh the combined ratio using the arrangement shown in the table, and dissolve 3 wt% of ethyl cellulose.
It was mixed with dissolved turpentine to form a paste.

This paste was then screen printed on one side of the specimen, and after drying, it was applied to
The first coating layer 2 was formed by heat treatment at 00° C. 10 minutes.

3 in FIG. 1 is a second coating layer constituting the metallized layer 4 of the present invention, and in order to form this second coating layer on the first coating layer, it is necessary to form a part other than the first coating layer 2 forming part of the test piece l. After masking the portion with tape, a second coating layer 3 made of Ag was formed by a commonly used known chemical plating method.

Note that the first coating layer 2. The thickness of the second coating 11i3 is 10μ.

Next, Table 1 shows the measurement results of the adhesion strength and specific resistance of the metallized layer 4 formed as described above.

As shown in Figure 2, the adhesion strength was determined by Kovar (F
e-Co-Ni alloy) 5 is bonded onto the metallized N4 using a silver solder 6, and a tensile force is applied in the direction of the arrow in the figure.
The force at the time of breakage was measured.

In addition, to measure the specific resistance of the metallized Ji4, as shown in FIG.
．． The resistance value between 8 and 8 was measured. Here, the specific resistance of the ceramic test piece l, which is the substrate, is approximately 2XlO-3Ω (up to), which is sufficiently large compared to the specific resistance of the metallized layer 4, so in this case, the resistance value is equal to that of the test piece l. It can be regarded as the value of the formed metallized layer 4.

Table 1 also shows the second example of the present invention for comparison with this example.
A sample lacking the coating layer 3 is shown as a comparative example (Sample N
12, 4.8.10.13).

(The following is a blank space) Based on the results of Table 1 obtained from the above experiment, the effects among the respective constituent elements in the two-layer metallized layer 4 according to the present invention will be explained.

The role of the first coating layer 2 of the present invention is mainly to ensure strong bonding with the non-oxide ceramic. The joining principle is thought to be as follows. For example, non-oxide ceramics such as silicon nitride generally have strong covalent bonds, and in order to bond with other materials, these covalent bonds must be broken to ensure sufficient fusion of the bonding agent.
The research conducted by the present inventors has revealed that the bonding strength does not increase. In the present invention, metal group I
First, PT selected from the following acts as a catalyst for the covalent bonds of the non-oxide ceramic, and plays the role of cleaving these covalent bonds. Next, N is a metallic element selected from element group ■
i-Cr diffuses into the decomposed ceramic after the covalent bond is broken, forming a diffusion layer. Furthermore, the element P selected from element group (2) functions to lower the melting point of the metal composition and to increase the fluidity when the metal element is melted, thereby lowering the viscosity.

The effects of the above three factors work together to create sample Kan 2.4 in Table 1.
, 8, 10.13, it is possible to form a metallized layer 4 with high adhesion based on a strong bond between a non-oxide ceramic and a metal.

The specific resistance value of the first coating layer 2 formed in this manner was as follows for sample 11h2. 4. 8. 10. As can be seen from 13, the lowest value is 1.3X10-'Ω-cm,
The high one has a value on the order of 9.2 x 10-5 Ω-■ and 10-5. Although this resistivity value is quite low compared to the resistivity 2X10-'Ω-CII of test specimen 1, it is still sufficient to be used as a press-contact type heater electrode, as will be shown in detail in the application example below. It's not a low value.

On the other hand, Au, Ag, Cu, A1, etc. have the lowest resistivity values among metal elements, each with a resistivity of 2.2 × 10-b,
1.62X 10-b, 1.72X 10-b,
2.65×10-'Ω-cffi. However, as is clear from the experiment with sample No. 16, it is almost impossible to adhere to non-oxide ceramics using only this method. It will peel off. Moreover, it is not only that (even if it looks like it is attached, its resistivity value is 1.5X10-4Ω-1, which is two orders of magnitude higher than the resistivity of Ag itself. This is due to the relationship between Ag and ceramic. This is due to poor wettability, which causes the formed Ag metallized layer to become porous.

In contrast, sample 11m3,5,9゜11 in Table 1
．． 14, a second coat of Ago is applied on top of the first coating 752.
By providing the coating layer 3, the specific resistance value of the metallized layer can be increased to 10 without significantly lowering the adhesion strength of the metallized layer 4.
It has become clear that it is possible to significantly lower the resistance by nearly one digit to -6Ω-■ order. In particular, in sample No. 9, the specific resistance could be reduced to approximately twice that of Ag itself.

In order to obtain such a low resistivity value of 10-6 Ω·low order, the composition range of the first coating N2 is important; pt of element group I is 5 to 60 mol%, Ni, C of element group
r is 38 to 93 mol%, P of element group ■ is 2 to 24 mol%
It is possible to obtain specific resistance values as low as 10-bΩ・(2) in the range of 1% (sample floors 3.5, 9, 11.14)
. This is especially true for the first coating layer 2 formed in the above composition range.
Because of its good wettability and adhesion to non-oxide ceramics, the first coating N2 itself becomes dense, and as a result, the second coating layer 3 formed thereon also becomes dense. This is thought to be the result of this. If the first coating layer 2 is outside the above composition range, sample N
A dense Ag layer is not formed as in 11, 6, 7, and 12.15, and the specific resistance does not decrease.

The TiN Si:+N4 composite ceramic used in the above embodiment has appropriate conductivity and can be used as a ceramic heater, and the metallized N4 in the above embodiment is still effective when used as an electrode of this heater. Figure 4 shows a ceramic heater used as an amphibious heater for an automobile exhaust gas purification filter.
The composition of sample 9 in the above example was used for the electrode parts 11.12 at both ends of the N4 ceramic heater 10, and the first coating layer 2. A Kovar electrode 13 on which a second coating layer 3 is formed and whose surface is plated with silver is pressed into contact with the structure shown in FIG. 5, which is a cross section taken along line AA in FIG. That is, the bolt-shaped electrode 13a is inserted into the through hole 10a of the ceramic heater 10, and the nut 15 is welded from the opposite side via the spacer 14, and the electrode 13 is held so as to be pressed from both sides.

In order to further confirm the specific resistance reduction effect of the metallized layer 4 according to the present invention, the contact resistance of Ra in the figure was measured for the heater described above and one without the second coating layer 3. By providing 2 coating layers 2, the initial contact resistance could be lowered to 1/3. The reason for this decrease in contact resistance is thought to be as follows. In other words, the conductivity at the contact surface between metals is related to the specific resistance of the metals in contact with each other and the contact area since each contact surface is uneven. This is thought to be because the specific resistance of the contact portion decreases and the Ag on the surface is soft, so the contact area increases when the electrodes are pressed together.

Furthermore, in order to check the heat resistance of this metallized layer 4,
Durability tests were conducted in a furnace at ℃. As shown in Table 2, the results show that in the case of the case without the second coating layer 3, the surface becomes black and oxidized and the resistance increases significantly, whereas in the case of the case with the second cover layer 3, there is almost no increase in resistance. Ta. This is because without the second coating N3, the surface of the first coating layer 2, which is the contact surface, is easily oxidized and the oxidation gradually progresses to the inside, whereas with the second coating layer 3, Ag is difficult to oxidize and is protected. This is thought to be because the Ag layer functions as a layer to prevent oxidation of the first coating layer 2, and also because the Ag layer maintains considerable electrical conductivity even when oxidation progresses and becomes silver oxide.

(Left below) As described above, the metallized layer 4 of the present invention has extremely high heat resistance. Therefore, the present invention can be used, for example, in a heater for regenerating a diesel particulate filter that removes carbon particulates from exhaust gas discharged from a diesel engine. It is extremely effective when used in electrode parts. That is, this type of heater uses a non-oxide ceramic containing silicon nitride and titanium nitride, and is used in a region exposed to exhaust gas and exposed to extremely high temperatures.

Next, the non-oxide ceramic according to the present invention is TiN-3i
It is applicable not only to zN4 composite ceramics but also to other non-oxide ceramics having covalent bonds such as SiC and AlN. In addition to Ag, the second coating layer 3 includes Cu, Au,
Even with Al, a similar resistivity reduction effect can be obtained. Third
The table shows the results of these experiments. In addition, in the experiment shown in Table 3, Al brazing material was used for the AlJi adhesion strength test.

As described above, it is possible to form a low resistivity metallized layer not only on conductive non-oxide ceramics but also on insulating AlN, etc., and these are suitable for forming non-oxide ceramics.

(Hereinafter, blank space) In addition, the first coating layer 2 of the present invention is not limited to those in Table 1,
Element group I includes Pd and Rh in addition to pt.

(2) r, Ru, and Os can be used, and the element group (2) includes Ni, Cr, and Fe in addition to Ni-Cr alloy.

Co can be used, and Si in addition to P can be used as the element group ■.
, B, and C are available. The results of these experiments are shown in Table 4.

(Margin below)

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional diagram showing the structure of the metallized layer of the present invention, FIGS. 2 and 3 are schematic diagrams showing the method for measuring the adhesion strength and specific resistance of this metallized layer, respectively, and FIG. 4 is a schematic cross-sectional diagram showing the structure of the metallized layer of the present invention. FIG. 5 is a sectional view taken along line AA in FIG. 4. ■...Non-oxide ceramic, 2...First coating layer. 3...Second coating layer.

Claims (2)

[Claims] (1) At least one or more metals selected from Pt, Pd, Rh, Ir, Ru, and Os, one or more metals selected from Cr, Ni, Fe, and Co, and C, B, Si, and P. a first coating layer containing one or more elements selected from Au, Ag, Cu, and Al and coated on the non-oxide ceramic; and a second coating layer containing one or more metals. (2) The content of one or more metals selected from the above Pt, Pd, Rh, Ir, Ru, and Os is 5 to 60 mol%, and the content of one or more metals selected from the above Cr, Ni, Fe, and Co. 38 to 93 mol%, and the content of one or more elements selected from B, C, Si, and P is in the range of 2 to 24 mol%. Metallized layer of oxide ceramic.