JPH0368485B2 - - Google Patents

Description

[Detailed description of the invention]

Technical field to which the invention pertains The present invention relates to a thick film conductive composition used for forming electronic circuits on an insulating substrate or forming electrodes of electronic components, particularly a conductive composition suitable for aluminum nitride substrates. Regarding. Conventional technology In recent years, electronic components and circuits have become smaller and more sophisticated in the field of electronics technology, and as a result, more elements have been mounted on a single circuit board. As density increases, dissipation of heat generated from the device becomes an important issue. Alumina ceramics, which have traditionally been widely used as circuit boards, have low thermal conductivity and poor heat dissipation, so non-oxide ceramics such as aluminum nitride, silicon carbide, and silicon nitride have recently attracted attention. ing. These materials have high thermal conductivity and also have excellent properties such as mechanical strength and insulation properties required for circuit boards, and are very promising as substrates for electronic circuits that can replace alumina-based ceramics. However, conductive compositions made of conductive powder and inorganic binders such as glass, which have been commonly used to form conductor circuits, were developed primarily for alumina substrates, such as aluminum nitride (AlN). ) as a substrate,
Even if it is baked, it will not adhere at all or the adhesive strength will be very weak, making it impossible to put it to practical use. Japanese Patent Publication No. 178687
When using a conductive composition containing copper oxide,
It has been reported that good adhesion strength is exhibited to Al 2 N substrates, but although it can be improved to some extent by copper oxide, it cannot be said to be fully satisfactory. Problems to be Solved by the Invention The present invention provides a conductor circuit that adheres with sufficient adhesive strength when baked on an AlN substrate with excellent heat dissipation properties, and has excellent properties such as conductivity and solderability. The purpose is to obtain a conductive composition that can be formed. Means for Solving the Problems The present invention is a conductive composition for aluminum nitride substrates, which is characterized in that chromium oxide is added to a conductive composition mainly composed of conductive powder and glassy frit. . Function The present invention is characterized by the addition of chromium oxide to the conductive composition, which significantly improves the adhesion to the Al 2 N substrate. That is, by baking a conductive composition containing chromium oxide onto an AlN substrate, a conductive film that is firmly adhered to the substrate can be formed. Further, the obtained conductive film has high conductivity and good solder wettability. Chromium oxide is usually added in the form of Cr ₂ O ₃ , but it may also be in the form of other oxides such as CrO, CrO ₂ and Cr ₂ O ₅ . Alternatively, it may be contained in the form of a multicomponent oxide containing chromium, such as an oxide containing chromium and copper. Even a small amount of chromium oxide is effective in improving adhesive strength, and the amount to be added is appropriately determined depending on the composition and required electrode characteristics. If the amount added is too large, the sintering of the conductive powder will be inhibited, the film strength will be weakened, and the conductivity will also be reduced.
It is desirable that the content be 10 parts by weight or less in terms of Cr ₂ O ₃ .
Although the preferred amount varies depending on the type of conductive component, the best effect can be obtained within a range of about 0.1 to 5 parts by weight. As the conductive powder, any material conventionally used as a conductive material can be used, such as silver, palladium, gold, platinum, copper, nickel, or an alloy or mixture thereof. There are no particular restrictions on the type of glass frit; for example, PbO−B ₂ O ₃ −SiO ₂ type, PbO−B ₂ O ₃ −SiO ₂ −
ZnO system, PbO−B ₂ O ₃ −SiO ₂ −CaO−Al ₂ O ₃ system,
PbO−B ₂ O ₃ −SiO ₂ −CaO−Al ₂ O ₃ −ZnO system, CaO
Various types such as -BaO-SiO ₂ can be used. However, depending on the composition, it is highly reactive with AlN, which may cause prisms and cracks, so it is desirable to select and use a material that is unlikely to cause such a reaction with the substrate. Furthermore, the composition of the present invention contains bismuth oxide, copper oxide,
It may contain metal oxides such as cadmium oxide, metal organic compounds that decompose during firing to produce metal oxides, and the like. These metal oxides may be added in the form of a conductive powder and a composite powder, or may be included as a component of the glass. These components are dispersed in a suitable organic vehicle to form a paste, coated on a substrate by a known method such as screen printing, dried, and then fired in a conventional manner to form a conductor. Examples Example 1 Pd powder 20 parts by weight Ag powder 80 parts by weight Glass frit 4 parts by weight Bi ₂ O ₃ powder 4 parts by weight Cr ₂ O ₃ powder 2 parts by weight The above composition was mixed and mixed with an appropriate amount of organic vehicle. A conductive paste was produced by kneading. However, the glass frit is PbO−SiO ₂ −CaO−Al ₂ O ₃ −
It is a B ₂ O ₃ --ZnO-based amorphous glass, and the organic vehicle is a dibutyl phthalate/terpineol mixed solvent solution of ethyl cellulose and alkyd resin. This paste was screen-printed in a square pattern of 1.5 mm x 1.5 mm on an AlN substrate manufactured by Tokuyama Soda Co., Ltd., dried at 150°C for 10 minutes, and then fired in air at a peak temperature of 920°C for a 30-minute cycle. Ivy. A solder-plated copper lead wire with a diameter of 0.5 mm was soldered to the obtained conductor film, and the initial adhesion strength and temperature at 150℃ were
When the adhesive strengths were measured after aging for 48 hours, they were 1.63Kg and 1.14Kg, respectively. Note that the adhesive strength is the peel strength when the lead is pulled in a direction perpendicular to the substrate. In addition, we formed a 10 mm x 10 mm conductive film, placed a 2.5 mm diameter solder ball on it, and held it at 230°C for 30 seconds, and then determined the solder wettability from the spread of the solder.
It was %. Examples _{2 to 4 Al}
A conductive film was formed on the N substrate. Table 1 shows the results of measuring adhesive strength and solder wettability. Comparative Example 1 A paste with the same composition as in Example 1 was made except that Cr ₂ O ₃ powder was not mixed, and the paste was prepared in the same manner as in Example 1.
Baking was performed on an AlN substrate. The resulting conductive film had very low adhesion strength to the substrate and peeled off when the lead wires were soldered. Comparative Example 2 A conductive film was formed on an Al N substrate in the same manner as in Example 1, except that 2 parts by weight of Cu ₂ O powder was added instead of Cr ₂ O ₃ powder. The initial strength and the strength after aging were 0.77Kg and 0.45Kg, respectively.

[Table] An x mark indicates that the adhesive strength is weak and the lead wire peeled off during soldering.
Example 5 Pd powder 3 parts by weight Ag powder 97 parts by weight Glass frit 3 parts by weight Bi ₂ O ₃ powder 4 parts by weight Cr ₂ O ₃ powder 0.5 parts by weight The above composition was mixed and kneaded with an appropriate amount of organic vehicle. A conductive paste was obtained. However, the glass frit is a CaO--BaO--SiO ₂ -based amorphous glass, and the organic vehicle is a dibutyl phthalate/terpineol mixed solvent solution of ethyl cellulose and alkyd resin. This paste was screen printed in a square pattern of 1.5 mm x 1.5 mm on an Al N substrate manufactured by Tokuyama Soda Co., Ltd., dried at 150 °C for 10 minutes, and then baked in air at a peak temperature of 850 °C for 30 minutes. Ivy. A solder-plated copper lead wire with a diameter of 0.5 mm was soldered to the obtained conductor film, and the initial adhesion strength and temperature at 150℃ were
The adhesive strength was measured after aging for 48 hours, and the results are shown in Table 2. Furthermore, the solder wettability was examined in the same manner as in Example 1, and is also shown in Table 2. _{Examples 6 to} 8 _Al
A conductive film was formed on the N substrate. The adhesive strength and solder wettability of each were measured, and the results are shown in Table 2. Comparative Example 3 A paste with the same composition as in Example 5 was made except that Cr ₂ O ₃ powder was not mixed, and the paste was prepared in the same manner as in Example 5.
Baking was performed on an AlN substrate. The resulting conductive film had very low adhesion strength to the substrate and peeled off when the lead wires were soldered. Comparative Example 4 A conductive film was formed on an AlN substrate in the same manner as in Example 1 except that 2 parts by weight of Cu ₂ O powder was added instead of Cr ₂ O ₃ powder, and the strength and solder wettability were shown in Table 2. Indicated.

[Table] Example 9 Cu powder 100 parts by weight Glass frit 4 parts by weight Cr ₂ O ₃ powder 4 parts by weight The above compositions were mixed and kneaded with an organic vehicle to produce a conductive paste. However, the glass frit is a PbO-B ₂ O ₃ -ZnO-SnO ₂ -SiO ₂ -based crystalline glass, and the organic vehicle is a solution of ethyl cellulose in 2,2,4-trimethyl 1,3-pentanediol monoisobutyrate. be. This paste was screen-printed in a square pattern of 1.5 mm x 1.5 mm on an AlN substrate manufactured by Tokuyama Soda Co., Ltd., dried at 120°C for 5 minutes, and then baked in a nitrogen atmosphere at a peak temperature of 900°C for 60 minutes. Ivy. A solder-plated copper lead wire with a diameter of 0.5 mm was soldered to the obtained conductor film, and the initial adhesion strength and temperature at 150℃ were
When the adhesive strengths were measured after aging for 48 hours, they were 2.28 Kg and 2.21 Kg, respectively. Comparative Example 5 A paste with the same composition as in Example 9 was made except that Cr ₂ O ₃ powder was not mixed, and the paste was prepared in the same manner as in Example 9.
Baking was performed on an AlN substrate. The initial and aging strengths of the obtained conductor coating were 1.26Kg and 1.26Kg, respectively.
It weighed 0.73Kg. Effects As is clear from the examples, by adding chromium oxide to a conventional conductive composition, it is possible to form an excellent conductive film that firmly adheres to the AlN substrate. Therefore, Al 2 N ceramics with good heat dissipation properties can be put to practical use as circuit boards, which makes it possible to further increase the packaging density, which is extremely advantageous industrially.

Claims (1)

[Scope of Claims] 1. A conductive composition for an aluminum nitride substrate, characterized in that chromium oxide is added to a conductive composition containing conductive powder and glassy frit as main components. 2. The conductive composition according to claim 1, wherein the amount of chromium oxide added is 10 parts by weight or less (excluding 0) in terms of Cr ₂ O ₃ based on 100 parts by weight of the conductive powder. 3 The conductive powder is one or two selected from the group consisting of silver, palladium, gold, platinum, copper, and nickel.
3. The conductive composition according to claim 1 or 2, which is a type or more.