JP2633879B2 - Conductive paste composition for non-oxide ceramics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductive paste composition, particularly to a conductive paste composition suitable for metallization of non-oxide ceramics or wiring.

[Conventional technology]

Non-oxide ceramics, in particular, aluminum nitride and silicon carbide have been receiving attention as substrate materials for electronic components with the improvement of sintering technology and purification technology in recent years.

For example, (1) IEEE Trans on C. by Y. Kurokawa et al.
In a paper entitled "AlN Substrates with High Thernal Conductivity" in HMT, CHMT -8 , No. 2, pp. 247-252 (1985), pressure-sintering of high-density, high-purity aluminum nitride powder was performed. Thermal conductivity 160W / m · K (room temperature), electric resistivity 5 × 10 ¹³ Ω · cm (room temperature), dielectric constant 8.9
(1MHz) Flexural strength 50kg / mm ² , coefficient of thermal expansion 4.3 × 10 ^-6 / ℃
(Room temperature to 400 ° C.). Also, (2) Japanese Patent Publication No. 58-15953 discloses that a pressurized sintered body of silicon carbide to which beryllia is added has a thermal conductivity of 0.1.
Disclosed is a substrate for an electric device which has a property of not less than 25 cal / cm · sec · ° C., a resistivity of not less than 10 ⁷ Ω · cm (room temperature) and a thermal expansion coefficient of not more than 4 × 10 ⁻⁶ / ° C.

Non-oxide ceramic sintered bodies such as aluminum nitride and silicon carbide are expected to contribute to the improvement of the properties of electronic devices. In order to realize this expectation, a metallization layer for integrally joining a semiconductor substrate such as silicon or another member made of metal or ceramic material or a metallization layer as a conductor wiring between functional elements is formed by the above-described firing. It must be formed on the body.

As a typical example of a metallization technique for a conventional aluminum nitride sintered body, (3) Japanese Patent Application Laid-Open No.
A method of metallizing an aluminum nitride sintered body by printing and firing a chemical bond type paste in which copper oxide is added in an amount of 0.1 wt% or more (in terms of Cu ₂ O) to a silver paste mainly composed of platinum, silver-palladium, etc. (4) Proceedi by N. Kuramoto et al.
ngs of 36th Electronic Component Conference Seattl
e "Translucent AlN Cera" on May 5-7 (1986)
The paper entitled mic Substrate ", silver, palladium bismuth oxide, glass frit _{(PbO-SiO 2 -CaO-Al} 2 O 3
-B ₂ O ₃ -ZnO) printed Furitsuto type paste containing, a method of metallizing a sintered aluminum nitride by firing is disclosed, respectively. Similar metallization techniques are also being studied for silicon carbide sintered bodies.

(5) JP-A-60-32343 discloses a power semiconductor module substrate in which an aluminum nitride member and a copper member are joined via an alloy layer of Ti, Zr and copper as active metals. And (6) a brazing filler metal paste obtained by adding titanium to a silver-copper-based metal, such as an active metal brazing filler for ceramics (SP641) manufactured by Tanaka Metal Industry Co., Ltd.

[Problems to be solved by the invention]

In the above (3), a composite oxide layer such as CuAlO ₂ or CuAl ₂ O ₄ is formed between the metallized conductor and the aluminum nitride sintered body, which is said to contribute to maintaining the bonding strength of the conductor. However, according to the experimental results of the present inventors, the bonding strength that can be realized by applying this technology is at most 2 kg / mm.
^Second , it is not enough to provide the advantage of a high heat conductive substrate on which power elements with a large amount of heat can be mounted at high density. This is because the bonding between the composite oxide and the conductive metal layer is not always strong, and the composite oxide layer itself has a porous and brittle property. This, of course, is also a major cause of failure to withstand thermal stress such as temperature cycling. In addition, the metallized conductor is significantly corroded by metal solder, particularly lead-60% by weight tin solder. According to experiments by the present inventors, a silver-palladium conductor layer having a thickness of 12 μm (palladium 20% by weight) has a temperature of 250 ° C. After 2 to 3 seconds of immersion in the above solder bath, the conductor layer completely disappeared, and only the composite oxide layer remained on the sintered body. This is because there is no carrier that suppresses the erosion of the metal solder in the conductor layer.

On the other hand, according to (4), a glassy substance mainly composed of bismuth oxide, oxides of zinc, silver and lead remains between the metallized conductor and the sintered body of aluminum nitride in a layered state. These substances penetrate into the sintered body along the grain boundaries when the ceramic material is alumina and contribute to the maintenance of the adhesive force by the anchor effect. However, when aluminum nitride is used, the same penetrating action does not occur. Since residual Gallus electrolyte layer forms a localized layer of porous qualitative and is and brittle zinc oxide and bismuth oxide, the bonding strength is at most 2 kg / mm ² obtained only, yet resulted in strength reduction to thermal stress ing.

The above-described problems of the prior art are common to circuit boards using other non-oxide ceramics as a base material such as silicon carbide, boron nitride, silicon nitride, and titanium nitride.

From the situation described above, circuit devices that require advanced performance and reliability, such as hybrid integrated circuit devices that combine a power element that handles a large current and a signal circuit that controls the power element, are not compatible with conventional metallization technology. It has been extremely difficult to achieve with a circuit board based on this.

In the prior art based on the above (5) and (6),
The heat treatment at the time of joining must be performed in a specially controlled atmosphere, such as in a vacuum, an inert gas, or a reducing atmosphere. Further, it is difficult to match a conductor formed by such a method with a process that requires firing in an oxidizing atmosphere, such as a subsequent formation of a resistor and a dielectric.

Therefore, the present invention does not compensate for the drawbacks of the conventional technology described above, and has a strong bonding strength to non-oxide ceramics.
It is an object of the present invention to provide a conductive paste composition capable of providing a metallized layer having excellent heat conduction function and excellent reliability.

[Means for solving the problem]

The present invention relates to a conductive paste composition,
A conductive powder made of at least one metal selected from the group consisting of silver, gold, platinum and palladium, and preferably a first glass powder having a density (g / cm ³ ) of 4.0 to 6.3, or chromium, It is characterized by containing an oxide powder of at least one metal selected from the group consisting of titanium and zirconium, and an organic vehicle.

In the present invention, the conductive powder in the paste is for imparting electrical conductivity to the metallized layer or the conductive layer and for imparting wettability to the metal solder. In addition, the first glass powder in the paste serves at the bonding interface between the metallized layer or the conductive layer and the substrate to strengthen the bonding strength between the two, and the first glass powder is dispersed in the metallized layer or the conductive layer to form a metal solder. It has a role in preventing erosion by ash. That is,
During the firing process, the glass powder chemically reacts with the surface of the ceramic substrate to form a bonding carrier with the substrate.
Of course, this bonding carrier also serves as a bonding carrier for the metal layer or the conductor layer. In addition, the vitreous substance is dispersed in the metallization layer or the conductor layer, and effectively reduces the contact area (reaction area) with the metal solder, thereby preventing erosion by the metal solder.

In the present invention, the metal oxide dissolves in the molten glass to promote the flow of the glass itself, and also chemically activates the surface of the non-oxide-based ceramic to enhance the wettability of the flowing glass. In addition, metal oxides have a high affinity for non-oxide ceramics, and themselves chemically bond to ceramic constituents. Further, a part of the metal oxide added to the paste is dispersed in the metal layer together with the glass component, thereby suppressing the erosion of the metal solder. On the other hand, since the metal oxide promotes the flow of the glass, it also functions to suppress (promote the sedimentation) of the glass component on the surface of the metal layer and to enhance the wettability of the metal solder. Further, the metal oxide has a remarkable effect to stably increase the bonding strength at the interface between the conductor metal layer and the ceramics substrate.

In the present invention, the reason why the density of the vitreous substance is selected to be 4.0 or more and 6.3 or less (g · cm ³ ) is to promote the flow of the molten vitreous substance to the interface and at the same time to appropriately disperse the molten vitreous substance in the sintered conductor. It is suitable for When the density of the vitreous substance is smaller than the above range, the floating of the vitreous substance on the surface of the metallized layer or the conductor layer is promoted, and when the density exceeds the above range, dispersion in the conductor becomes difficult.
The former case affects the wettability of the metal solder and the latter case affects the resistance of the metal solder to erosion.

In the conductor paste composition of the present invention, a density of 4.0 to 6.3
Preferably, the weight of the first glass powder of g / cm ³ is 0.01 to 0.1 based on the total weight of the conductor powder, the first glass powder and the metal oxide, and the weight of the metal oxide powder is the above total weight. It is preferably 0.001 to 0.05 based on

Further, in the conductor paste composition of the present invention, the density
Even if the second glass powder has a value smaller than 4.0 g / cm ^3, the first glass powder having a density (g / cm ³ ) of 4.0 or more and 6.3 or less or a metal oxide as long as the wettability to the metal solder is not impaired. May be added together with the material powder. in this case,
The second glass powder is preferably 0.001 to 0.03 based on the total weight of the conductor powder, the first and second glass powders, and the metal oxide powder.

Under a particularly preferred form of the invention, the conductor consists of silver and palladium and the vitreous material is SiO ₂
—B ₂ O ₃ —Al ₂ O ₃ —PbO—ZnO system having a density in the above range and a softening point of 550 ° C. or less.

It is important that the paste of the present invention containing no chromium or titanium group does not contain bismuth oxide. Bismuth oxide reduces strength.

The substrate material is non-oxide ceramics such as aluminum nitride and silicon carbide, as well as mixed ceramics of these non-oxide compounds including, for example, boron nitride, silicon nitride or aluminum nitride and silicon carbide, and composites in which these are laminated. Even with ceramics, the effects of the present invention can be obtained. Further, the same effect can be obtained by using a mixture or a composite ceramic of the above-mentioned non-oxide ceramic and an oxide ceramic represented by aluminum oxide or beryllia.

Further, the aluminum nitride is not limited to a high-purity sintered pressure-resistant sintered body, for example, Y ₂
Contains sintered materials with other additives such as O ₅ , CaO, alkaline earth oxides, and rare earth oxides that do not significantly impair the thermal conductivity, and naturally contained impurities It may be one that has been sintered under normal pressure.

Further, in applying the conductor paste composition of the present invention, there is no problem in that the non-oxide-based ceramic surface is oxidized before or before the conductor firing process. This is because the surface oxides coexist with the vitreous substances and metal oxides unevenly distributed at the interface to help keep the bonding interface strong and to improve the water resistance.

Organic vehicles that can be used in the present invention include aliphatic alcohols, esters of such alcohols such as acetate and propionate, terpenes such as pine oil α- and β-terpineol, and solvents such as pine oil and polymethacrylate of ethylene glycol monoacetate. Or a solution of ethylcellulose. The vehicle may contain a volatile liquid to facilitate rapid drying.

Example 1 By weight ratio, 56% of silver powder (average particle diameter 1 μm) as a conductive metal powder, 15% of palladium powder (average particle diameter 1 μm),
A mixture composed of 5% of the first glass powder or 1.5% of the chromium oxide powder (average particle size of 2.5 μm) and the remainder of an organic vehicle composed of ethylcellulose resin and α-terpineol is sufficiently kneaded with a three-roll mill. Thus, a conductor paste composition was obtained. The first glass powder has a main component composition of SiO ₂ (14.5%)-B ₂ O ₃ (4.2%)-Al ₂ O ₃ (1.5%) by weight.
-Has PbO (70.0%)-ZnO (9.1%), density 5.2g / c
It is a powder having an average particle size of 2 μm having physical properties such as m ³ , a coefficient of thermal expansion of 7.3 × 10 ⁻⁶ / ° C. and a softening point of 500 ° C.

The glass powder in the conductor paste composition contains 0.065 based on the total weight of the conductor metal powder and the glass powder or further the chromium oxide powder, and the chromium oxide powder contains 0.019 based on the total weight.

In order to confirm the effect of the above composition, a circuit board having a conductor layer provided on a ceramics substrate was prepared, and various evaluations were made.

The circuit board is prepared by subjecting the above-mentioned conductor paste composition to pressure sintering of high-purity synthetic aluminum nitride powder (particle size: 1 μm or less), calcium carbonate as an additive, etc. in a nitrogen atmosphere (2 × 10 ⁴ P
a, 2000 ° C.) and a green compact made of silicon carbide powder under pressure (2 × 10 ⁴ Pa) in vacuum with beryllia powder (1.5% by weight) as an additive. , 200
0 ° C) is applied on a non-oxide-based ceramics substrate, which is a sintered silicon carbide obtained by screen printing, and then dried at 120 ° C for 60 minutes in the air.
The conductor layer was obtained by baking at 850 ° C for 10 minutes in a tunnel furnace with forced air flowing.

FIG. 1-1 is a schematic sectional view of a circuit board 10 having a conductor layer 2 provided on a ceramics substrate 1 obtained through the above steps.
FIGS. -2 and 1-4 are line analysis results of the X-ray microanalyzer in the normal direction of the conductor layer 2 forming portion on the aluminum nitride substrate 1, and FIGS. 1-3 and 1-5 are results on the silicon carbide substrate 1. 5 is a graph showing the results of analysis of a conductor layer 2 forming portion in a relationship between a distance from the surface side (horizontal axis) and X-ray intensity (vertical axis). Figures 1-2 and 1-3 do not include chromium oxide powder. Focusing on Pb, which is the main component of the vitreous substance, in the line analysis results, it can be seen that Pb is distributed at a high concentration at the bonding interface between the substrate 1 and the conductive layer 2 and also penetrates into the inside of the substrate 1. In contrast, the concentration decreases toward the surface of the conductor layer 2. Pb is also locally distributed in the conductor layer 2. In addition, it is a major component of chromium oxide
Focusing on Cr, it has a distribution similar to the main components of glass. The fact that the surface of the conductor layer 2 has a low concentration and is highly eroded into the substrate 1 is a characteristic advantage when chromium oxide is added. According to the X-ray diffraction results of the joint interface, Cr and
An intermetallic compound of Al or Cr and Si is formed. Al and Si, which are main components of the substrate 1, are also found in a region where glass is distributed at a high concentration. The vitreous or high-concentration region of chromium oxide keeps the bonding between the substrate 1 and the conductor layer 2 strong, and the vitreous substance and chromium oxide dispersed in the conductor layer 2 prevent erosion by metal solder. (Described later). In addition, the low vitreous and chromium oxide concentration on the surface contributes to enhancing the wettability to metal solder.

FIG. 2 and FIG. 3 show that silver-plated copper pins having a diameter of 2.5 mm are joined on the conductor layer 2 with Pb-60% by weight Sn solder.
The results of tracking the strength in the direction perpendicular to the joint surface while giving a temperature cycle of ℃ are shown as the relationship between the number of temperature cycles (times, horizontal axis) and the joint strength (kg / mm ² , vertical axis). It is a graph. FIG. 2 does not contain chromium oxide powder. It has an initial strength of 4 kg / mm ² regardless of whether the substrate 1 is made of aluminum nitride or silicon carbide.
In addition, the chromium oxide containing chromium oxide shown in FIG. Both are 1000
The level is almost the same as the initial level even after the passage.
The value of the above-mentioned initial strength is twice as large as ² kg / mm ² in the case of applying the chemical bond type paste based on the prior art example (3) and the frit type paste based on the same (4). In addition, in the case of these prior art examples, the conductor layer 2 is peeled off in about 500 temperature cycles, whereas in the case of the embodiment, the long-term reliability against thermal stress is sufficiently ensured. It suggests.

FIG. 4 is a frequency distribution of the bonding strength (kg / mm ² ). FIG. 3A shows the distribution of the present embodiment, and FIG. 3B shows a comparative example in which chromium oxide is not added in the configuration of the present embodiment. For this embodiment have a small distribution of variation has a peak at about 4 kg / mm ^2, with a high-duty distribution in the region of but lower strength than that having a same peak at 4 kg / mm ² Higher strength is obtained more stably than the comparative example. This is a characteristic point when chromium oxide is added.

The conductor layer 2 is formed so as to have a thickness of 11 μm, and has a sheet resistance of 19.8 mΩ / □, which is sufficiently conductive as a wiring for a hybrid integrated circuit.
No increase in sheet resistance is observed even after a temperature cycle test of 1000 times and a high-temperature storage test in air at 150 ° C. (1000 hours). When a 6 mm × 6 mm silicon power transistor chip is mounted on the conductor layer 2 by Pb-5 wt% Sn solder, the thermal resistance between the chip and the substrate 1 is 0.8.
° C / W (aluminum nitride substrate) and 0.7 ° C / W (silicon carbide substrate), ensuring sufficient heat dissipation. This thermal resistance maintained the same value as the initial value even after 1000 temperature cycles.

Next, the circuit board 10 was placed in a Pb-60 wt% Sn solder bath (250
C.) and the wettability (wet area / metallized area) ratio of the solder was measured. This result is compared with the prior art example (3),
The results are shown in Table 1 together with other comparative examples based on (4). ()
The inside contains chromium oxide powder. Both of them have the same value.

The initial wettability (5 seconds immersion) of the example is slightly inferior to the chemical bond type of the comparative example, but shows the same wettability as the frit type, and does not hinder practical use. Also, good wettability is maintained even when immersed for a long time. On the other hand, in the case of the comparative example, the chemical bond type is superior in initial wettability, but the wettability is easily lost by long-time immersion. This is because it has no carrier to resist solder erosion. Further, in the case of the frit type of the comparative example, the wettability to long-term immersion is improved as compared with the chemical bond type, but is inferior to the result of the example. As described above, the circuit boards of the examples are excellent in wettability to metal solder and erosion resistance.

As described above, the first vitreous material and chromium oxide play an important role in obtaining an excellent circuit board.

Example 2 Instead of the glass powder used in Example 1, pastes were added in the same manner as above, in which various glass powders having the compositions and properties shown in Table 2 were added in equal amounts (5% by weight). The table also shows the glass powder used for the comparative example.

These pastes were printed and fired in the same manner as described above (the firing temperature was 900 ° C.) to obtain a circuit board 10.

Tables 3-1 and 3-2 summarize the results. The numbers in the table correspond to the numbers in Table 2,
No. 1 to No. 6 show the results of this example, and No. 7 to No. 16 show the results of the comparative example. Table 3-1 shows the case where the substrate 1 is made of aluminum nitride, and Table 3-2 shows the case where the substrate 1 is made of silicon carbide. () Includes chromium oxide powder, and the other values are the same.

The circuit board 10 (No. 1 to No. 6) of this embodiment has a sheet resistance,
The joint strength, heat resistance, and wettability (corrosion resistance) are almost the same as those of Example 1. The glass materials No. 1 to No. 6 are substitutes for the first glass material of Example 1. Indicates that it can be These glass substances including the glass substance of Example 1 may be added alone, or may be added in an appropriate combination of these glass substances. According to the line analysis result of the conductor layer by the X-ray microanalyzer, similarly to the case of the paste of Example 1, the vitreous substance and the chromium oxide are distributed at a high concentration at the boundary with the ceramics substrate 1 and are deeply distributed in the substrate 1. It was confirmed that they were diffused and dispersed in the conductor layer 2 and were distributed at a low concentration on the surface of the conductor layer 2.

Also, from the results of this example, it is found that the density of the glass material needs to be 4.2 to 4.0 in order to obtain a circuit board having excellent electrical conductivity, bonding strength, heat dissipation, solder wettability (erosion resistance) and reliability.
It is recognized that it is important to be 6.2 g / cm ³ .
Even when glass materials having densities of 4.0 g / cm ³ and 6.3 g / cm ³ were used, performance almost equivalent to that of the present example was obtained.

Example 3 In this example, the amounts of the vitreous material and chromium oxide added will be described. In this example, a conductive paste composition was prepared in the same manner as in Example 1 except that the amount of chromium oxide added was adjusted variously. In preparing the paste composition, the types and amounts of the conductive metal powder and the organic vehicle, and the types and amounts of the first vitreous substance were based on Example 1. Further, a circuit board 10 was prepared using the same paste and through the same procedure as described above. The amount of the chromium oxide powder described below in the present embodiment means the weight of the chromium oxide based on the total weight of the conductive metal, the first vitreous substance, and the chromium oxide, expressed as% by weight.

5 and 6 show the relationship between the amount of glass and chromium oxide powder added (% by weight, horizontal axis), sheet resistance (mΩ / □, vertical axis), and thermal resistance (° C./W, vertical axis). It is a graph. The sheet resistance naturally depends on the dispersion density of the first vitreous substance and chromium oxide dispersed in the conductor layer 2 mainly composed of Ag and Pb, but when the addition amount is 5% by weight or less, the addition amount is 0% by weight. Is obtained. When the resistance is 10% by weight or less, a value close to 0% by weight is obtained. This is because the shared thermal resistance of the chip mounting solder material controls the overall thermal resistance. FIG. 5 does not contain chromium oxide powder.

FIGS. 7 and 8, the glassy material and chromium oxide powder amount (wt%, abscissa) and the bonding strength (kg / mm ^2, the vertical axis)
6 is a graph showing a relationship with the graph. 1% by weight of glass
Above, the amount of chromium oxide added is about 5 times or more compared to the case of no addition
In the range of 0.1 to 10% by weight, a high strength of about 4 kg / mm ² is obtained.

FIG. 9 and FIG. 10 are graphs showing the relationship between the added amount of glassy substance and chromium oxide (% by weight, horizontal axis) and wettability (%, vertical axis). At the initial stage of immersion, the wettability decreases in a region exceeding about 10% by weight, but when the amount is less than 10% by weight, good wettability is obtained. Also, after 60 seconds of immersion, good wettability is maintained even with 1 to 10% by weight of the vitreous substance and 10% by weight or more of the latter, indicating that the erosion by solder is small. In the range of less than 1% by weight and more than 10% by weight, the wettability is poor. When the amount is less than 1% by weight, the conductor layer 2 is lost due to the erosion by the solder, and when it exceeds 10% by weight, the spread of the solder is slow.

If the chromium oxide powder exceeds 10% by weight in the initial stage, the solder wettability is reduced because the excess of chromium oxide inhibits the contact between the solder and the conductor, resulting in improved wetting after 60 seconds of immersion This is because contact is promoted.

Based on the above results, the preferable addition amount of vitreous and chromium oxide, which is comprehensively selected, is [vitreous or chromium oxide / metal conductor + first vitreous substance + chromium oxide] × 10
0] for the former, 1-10% by weight for the former, and
0.1 to 5% by weight.

In this example, the case of the first vitreous substance used in Example 1 was described.
Even when the first vitreous substance of o.6 is added, the preferable range of the addition amount described above does not change.

Embodiment 4 In this embodiment, an example will be described in which two types of vitreous substances having a density of 5.2 g / cm ³ and a density of 3.5 g / cm ³ are added together with a metal conductor.

By weight ratio, 56% silver powder (average particle diameter 1 μm) as a conductive metal powder, 15% palladium powder (average particle diameter 1 μm),
Conductive paste composition comprising 5% of the first glass powder of the same type as in Example 1, 1.5% of the second glass powder of the same type as No. 13 in Example 2, and the remainder being an organic vehicle composed of ethyl cellulose resin and α-terpineol. Example 1
Created in the same way as The paste composition thus obtained contains 0.065 of the first glass powder and 0.019, based on the total weight of the conductive metal powder, the first glass powder, and the second glass powder.
Of the second glass powder.

Further, using the same paste, a circuit board 10 having the same wirings as the first embodiment was formed on an aluminum nitride substrate through the same procedure as in the first embodiment.

Table 4 summarizes the performance of the obtained circuit board 10.

Sheet resistance, bonding strength, heat resistance, and wettability (corrosion resistance) were all lower than those in Example 1. In particular, in this example, even if the solder immersion (60 min) was repeated three times, no decrease in wettability due to solder erosion was observed. This is because the second vitreous substance was uniformly dispersed in the conductor layer 2 and the diffusion of solder, especially tin, was suppressed. This advantage extends to a point that the degree of decrease in bonding strength after leaving at high temperature is reduced.

Than this, the present invention is a basic that it comprises a first vitreous material comprising a density 4.0~6.3g / cm ^3, glassy substance is added in an appropriate amount less than the density in addition to these 4.0 g / cm ³ It can be seen that even in this case, the object of the present invention is sufficiently achieved. In order to obtain sufficient initial solder wettability and erosion resistance, the added second vitreous material should be 0.001 to 0.001% based on the total weight of the conductive metal, the first glass, the chromium oxide, and the second glass. Desirably 0.03. This point is the same as in Example 2 except that No. 7 to No.
The same applies to the case where the 16 glassy substances are the second glass.

Note that even when such a paste containing a vitreous substance is applied to the silicon carbide substrate 1, a circuit board 10 having similar performance can be obtained.

Example 5 In this example, the conductive metal of the paste in Example 1 was changed to silver alone (71% by weight), silver-platinum (71% by weight),
Alternatively, the same paste composition was prepared in which silver-gold (71% by weight) was used. At this time, the vitreous substance, chromium oxide, and organic vehicle were the same type and the same amount as in Example 1, and the manufacturing procedure was the same. The paste was applied to an aluminum nitride substrate 1
After application on the upper surface, the substrate was dried at 120 ° C. for 60 minutes in the air, and then subjected to a baking process at 850 ° C. for 10 minutes in forced air to form a circuit board 10.

Table 5 summarizes the performance of the obtained circuit board 10. Figures in parentheses are those containing chromium oxide. Everything else is the same.

The sheet resistance, the bonding strength, the heat resistance, and the wettability (corrosion resistance) are all practically acceptable. Even when a silicon carbide substrate is used, performance equivalent to this is obtained.

The effect of the present invention does not change even if the conductor metal is made of any combination and any composition of silver, platinum, gold, and palladium.

Example 6 In this example, the effect of an additive other than chromium oxide will be described. In the same manner as in Example 2, a conductor paste composition was prepared in which the addition amount of titanium oxide or zirconium oxide, which is a substitute for chromium oxide, was variously adjusted. In preparing the paste composition, the types and amounts of the conductive metal powder and the organic vehicle, and the types and amounts of the first glass material were based on Example 1. Further, a circuit board 10 having a conductor formed on aluminum nitride was prepared using the paste and the same procedure as described above. In addition, the metal oxide addition amount described below in the present embodiment is expressed by weight% of the weight of the metal oxide based on the total weight of the conductive metal, the first vitreous substance, and the metal oxide.

FIG. 11 is a graph showing the relationship between the amount of metal oxide powder added (% by weight, horizontal axis), sheet resistance (mΩ / □, vertical axis), and thermal resistance (° C./W, vertical axis). As for the sheet resistance, a value close to no addition is obtained when the addition amount is 5% by weight or less. Also, the thermal resistance shows a value close to no addition when the addition amount is 10% by weight or less.

FIG. 12 is a graph showing the relationship between the amount of metal oxide powder added (% by weight, horizontal axis) and bonding strength (kg / mm ² , vertical axis). About 4 kg in the range of 0.1 to 10% by weight of metal oxide powder
/ mm ² and high strength. Note that, when these metal oxides are added, stable high strength is easily obtained as compared with the case where no metal oxide is added, similarly to the case where chromium oxide is added.

FIG. 13 is a graph showing the relationship between the amount of metal oxide powder added (% by weight, horizontal axis) and wettability (%, vertical axis). At the initial stage of immersion, the wettability decreases in a region exceeding about 10% by weight, but good wettability is maintained at 10% by weight or less. Also, after 60 seconds of immersion, good wettability is maintained even at 10% by weight or less, and even with 10% by weight or less, it resists erosion by solder.

From the above results, it is apparent that the same effect as when chromium oxide is added can be obtained even when the metal oxide is titanium oxide or zirconium oxide. This effect does not change even when the substrate is made of silicon carbide.

Further, the preferable addition amount of the metal oxide, which is selected in view of the above results comprehensively, is 0.1 in terms of [metal oxide / metal conductor + first glassy substance + metal oxide] × 100].
~ 5% by weight.

In this example, the case of the first vitreous substance used in Example 1 was described.
Even when the first vitreous material of No. 6 is added, or when the second vitreous material having a density of 4 g / cm ³ or less is added as in the case of Example 4, the range of the preferable addition amount described above is not changed. Absent.

The effect of the present invention does not change even if the conductor metal is made of any combination and any composition of silver, platinum, gold, and palladium.

〔The invention's effect〕

As described above in detail, according to the present invention, it has a strong bonding strength and erosion resistance to metal solder, has a conductive region imparted with excellent heat dissipation and electrical conductivity, and has a It is possible to provide a conductive paste composition that is advantageous for obtaining a circuit board made of non-oxide ceramics that can maintain stable performance.

[Brief description of the drawings]

FIG. 1-1 is a schematic cross-sectional view of one example of a circuit board of the present invention, and FIGS. 1-2 to 1-5 are concentration distributions in cross sections of components of the circuit board of the present invention, FIGS. 2 and 3. FIG. 4 is a graph showing the relationship between the number of temperature cycles and the bonding strength of the circuit board of the present invention. FIG. 4 is a graph showing the bonding strength of the circuit board; FIGS. 7, 8 and 12 are diagrams showing the relationship between the amount and the sheet resistance and the thermal resistance, and FIGS. 7, 8 and 12 are diagrams showing the relationship between the amount of the vitreous substance added to the circuit board of the present invention and the bonding strength. 10 and 13 are diagrams showing the relationship between the amount of the vitreous substance additive and the solder wettability of the circuit board of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadahiko San ▲ 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. In the Komoro factory of Hitachi, Ltd. (56) References JP-A-61-87397 (JP, A) JP-A-62-86602 (JP, A) JP-A-58-68918 (JP, A)

Claims (1)

(57) [Claims] 1. A silver, gold, and conductive powder made of at least one metal selected from platinum and palladium, density _{SiO 2 -B 2 O 3 -Al 2} O 3 -PbO-ZnO system 4.0~6.3g / cm ³
A glass powder having a softening point of 550 ° C. or less, an oxide powder of at least one metal selected from the group consisting of chromium, titanium and zirconium, and an organic vehicle. Conductive paste composition for ceramics.