JPH07307539A - Circuit board and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a circuit board, having a the circuit wiring and excellent electric characteristics, and the manufacturing method thereof. CONSTITUTION:In a circuit substrate on which a circuit wiring is integrally formed on the surface of a ceramic board, a circuit wiring is formed by a composition consisting of a composite oxide of 1 to 50wt.% containing tungsten and rare-earth element. Also, the hole rate of the circuit wiring is set at 20wt.% or smaller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board in which circuit wiring is integrally formed on the surface of a ceramic substrate and a method for manufacturing the same, and more particularly to a circuit board having fine circuit wiring and excellent electrical characteristics and a method for manufacturing the same. .

[0002]

2. Description of the Related Art Ceramic circuit boards on which semiconductor elements such as LSI packages are mounted are widely used as electronic equipment parts. In recent years, demands for miniaturization and improvement of functions of electronic devices have further increased, and accordingly, semiconductor elements have rapidly progressed toward the aim of improvement in integration density, multifunction, speed, and output. There is. In particular, the reliability of semiconductor elements is also required to be at a high level, and the development of technology for preventing malfunction of semiconductor elements is underway. Corresponding to these, the amount of heat generated from the semiconductor element tends to further increase, and a circuit board for mounting a semiconductor element using an aluminum nitride (AlN) substrate, which has a large heat dissipation ability in place of the conventional Al ₂ O ₃ substrate, is widely used. is doing.

According to the circuit board using the AlN substrate, in addition to the high thermal conductivity peculiar to the AlN substrate, various characteristics such as coefficient of thermal expansion, airtightness, and electrical insulation are highly evaluated.

By the way, since a commonly used AlN substrate has a high sintering temperature, when a circuit board is manufactured by simultaneously firing an AlN compact and a circuit wiring, a refractory metal is used as a circuit wiring material. Tungsten (W) is used. Tungsten metal, due to its high melting point,
Even when the AlN compact is sintered at a high temperature at the same time, there is an advantage that defects such as electrical short circuits due to melting of circuit wiring are less likely to occur.

However, there is a problem that the densification and sintering temperature of the circuit wiring itself made of tungsten becomes higher. That is, since there is a large difference between the sintering temperature of AlN and the densification temperature of tungsten and the behavior of densification is different, there is a problem that pores tend to remain in the circuit wiring of the circuit board formed by simultaneous firing. It was As a means for solving this problem, the particle size of the tungsten raw material powder is made as small as possible,
Although attempts were made to promote densification, the difference in shrinkage ratio between the AlN substrate and the circuit wiring during simultaneous firing was large, and practical application was almost impossible.

The porous circuit wiring layer containing a large number of pores as described above has low airtightness, low corrosion resistance, and high volume resistance. In any case, the durability and operation reliability of the semiconductor element mounting circuit board are high. There is a drawback that reduces the sex.

As a measure for filling the above-mentioned pores, A has been conventionally used in a tungsten composition for forming circuit wiring by printing.
The 1N component and the sintering aid component are preliminarily blended to bring the circuit wiring and the substrate close to each other in sintering shrinkage, and
There has also been taken a measure to make the secondary generation phase (liquid phase) of N ceramics permeate the inside of the pores and embed it, resulting in densification.

[0008]

However, in the case where the liquid phase generated by previously blending the AlN component and the sintering aid component in the composition for forming a circuit wiring and filling the generated liquid phase in the pores as in the above-mentioned conventional method, AlN is used. The amount of liquid phase generated varies depending on the composition of the raw material mixture and the sintering conditions, and it is difficult to completely fill the pores.

There is also a problem that the electrical resistance of the circuit wiring is inevitably increased when the amount of the AlN component and the amount of the sintering aid compounded are increased. Further, segregation of the liquid phase component is likely to occur on or around the circuit wiring during sintering, and there is also a drawback that the appearance of the circuit board product or plating abnormality is likely to occur.

Further, when the pores do not disappear and the circuit wiring layer is not sufficiently densified, impurities easily enter the circuit wiring layer, and after the plating process or the thin film forming process is performed on the wiring layer, heating is performed. When the treatment is performed, the plating layer or the thin film layer is likely to have a bulge defect, and in any case, the production yield of the circuit board is significantly reduced.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a circuit board having fine circuit wiring and excellent electrical characteristics, and a method for manufacturing the same.

[0012]

In order to achieve the above-mentioned object, the present inventors have prepared various kinds of circuit boards by blending various additives with a composition for forming a circuit wiring and co-firing them. The effects of the type of material and the added amount on the characteristics of circuit wiring were compared and examined. As a result, it has been found that when a predetermined amount of a composite oxide containing tungsten and a rare earth element is added to a tungsten base material, a circuit wiring layer with few pores and high density can be obtained. The present invention has been completed based on the above findings.

That is, the circuit board according to the present invention is a circuit board in which circuit wiring is integrally formed on the surface of a ceramics substrate, containing 1 to 50% by weight of a complex oxide containing tungsten and a rare earth element, and the balance being tungsten. It is characterized in that the circuit wiring is formed of a product. The porosity of the circuit wiring is set to 20 vol% or less. Furthermore, the ceramic substrate is suitable for a co-firing circuit substrate which is an aluminum nitride substrate.

A method of manufacturing a circuit board according to the present invention is
1 to 50% by weight of a composite oxide powder containing tungsten and a rare earth element is added, an organic additive is added to a composition consisting of the balance tungsten powder to prepare a circuit wiring composition paste, and the composition paste is used as a ceramics. It is characterized in that it is applied to the surface of the molded body to form a wiring pattern of a predetermined shape, and thereafter the ceramic molded body and the wiring pattern are simultaneously fired.

Here, the composite oxide containing tungsten and a rare earth element has a lower melting point than the tungsten metal that is the base material of the circuit wiring, and the firing temperature of the AlN compact is 1780 to 1880 ° C. in a nitrogen gas atmosphere. When it is co-fired with the AlN compact, it melts and fills the pores in the circuit wiring, and at the same time decomposes by nitriding and pyrolysis into a dense layer of tungsten metal.

Specific examples of the above composite oxide include Y ₂ O.
₃ · WO ₃ (Y ₂ WO ₆ ), Y ₂ O ₃ · ₃ WO ₃ , Yb
₂ O ₃ · WO ₃ , Eu ₂ O ₃ · 3WO ₃ , La ₂ O ₃ ·
3WO ₃ , Sc ₂ O ₃ · 3WO ₃ , Pr ₂ O ₃ · W
O ₃ , Gd ₂ O ₃ · 3WO ₃ , Lu ₂ O ₃ · 3WO ₃ ,
Lu ₂ O ₃ · WO ₃ , Dy ₂ O ₃ · 3WO ₃ , Tb ₂ O
₃ · 3WO _3, and the like.

The composition for forming circuit wiring used in the method of the present invention is prepared by blending 1 to 50% by weight of the above composite oxide with respect to the tungsten powder as the base material. When the compounding amount of the composite oxide is less than 1% by weight, the action of filling the pores by the liquid phase generated from the oxide becomes insufficient, and it is difficult to form circuit wiring having a porosity of 20 vol% or less. Become. On the other hand, if the blending amount exceeds 50% by weight, the electrical resistance of the circuit wiring increases, so the blending amount of the complex oxide is set within the above range, but more preferably in the range of 10 to 30% by weight. Is desirable.

The composition paste for circuit wiring used in the method of the present invention comprises a binder, a dispersion medium, and, if necessary, an organic additive such as a plasticizer in a total amount of 20% by weight or less. It is prepared by uniformly kneading. Ethyl cellulose or acrylic resin is suitable as the binder, and is added in an amount of about 1 to 5% by weight based on the composition. In addition, terpineol and butyl carbitol are used as the dispersion medium, while dibutyl phthalate (DBP) and dioctyl phthalate (D) are used as the plasticizer.
OP) is used.

The composition paste for circuit wiring prepared as described above is applied to the surface of the ceramic molded body by a screen printing method or the like to form a predetermined wiring pattern, and then at a temperature of 400 to 800 ° C. The circuit wiring is integrally formed on the surface of the ceramic substrate by degreasing by heating for 2 hours to remove the organic additives, and by cofiring at a temperature of 1750 to 1850 ° C. for 2 to 5 hours in a non-oxidizing atmosphere such as a nitrogen gas atmosphere. The formed circuit board is formed.

In the case of producing a multilayer circuit board, a mixture of ceramic raw material powder and a sintering aid is made into a slurry to prepare a slurry, and the slurry is formed into a sheet or tape by a doctor blade method or the like. As a body, the composition paste is applied to the surface of each sheet-shaped molded body or the like to form a wiring pattern, and a plurality of sheet-shaped molded bodies having the wiring pattern formed thereon are thermocompression-bonded to obtain a laminated body. The body is similarly degreased and then co-fired to obtain a multilayer circuit board.

[0021]

In the circuit board and the method of manufacturing the same having the above structure, the tungsten base material for forming the circuit wiring is
Containing a composite oxide containing tungsten and a rare earth element, the composite oxide melts at a temperature at which the ceramic substrate and the circuit wiring pattern are fired,
The pores generated in the tungsten base material are filled, and at the same time, nitriding pyrolysis is performed to form a dense circuit wiring.

Therefore, since the electric resistance of the circuit wiring is reduced, the operation speed of the semiconductor element can be increased. In addition, since there are few pores in the circuit wiring, even when heat treatment is performed after forming the plating layer or thin film on the circuit wiring, there are few defects such as swelling of the plating layer or thin film The yield can be significantly improved.

[0023]

EXAMPLES Next, the present invention will be described based on the following examples.
This will be described more specifically.

Examples 1 to 11 and Comparative Example 1 Prepare metal oxides such as yttrium oxide (Y ₂ O ₃ ) shown in Table 1 as rare earth element oxides and tungsten oxide (WO ₃ ) as tungsten oxide, 60 mol% tungsten oxide, 40 mol% rare earth element oxide
Wet-mixing in ethanol so that the resulting mixture was heated to a temperature of 120 ° C. in the atmosphere to obtain dry powders.

Next, each of the dry powders obtained was filled in a small alumina crucible and an alumina lid was attached, and the entire small crucible was housed in a larger box-shaped alumina crucible for exclusive use. I put on the lid. In order to prevent the small crucible filled with the dry powder from falling, refractory bricks were spread around the small crucible to fix the small crucible. Then, the large box-shaped crucible was heated to a temperature of 1200 ° C. in the atmosphere, and then cooled to prepare complex oxide powders.

Next, for each of the prepared composite oxide powders,
Phase identification was performed using an X-ray diffractometer. as a result,
It was found that each of the composite oxide powders was composed of a single phase having a chemical composition shown in Table 1. Each composite oxide powder was pulverized and sieved to have a uniform particle size of 50 μm or less.

Further, the above-mentioned composite oxide powder having the adjusted particle size was added and blended into tungsten powder having an average particle size of 1 μm so as to have the content shown in Table 1, and each composition for circuit wiring was prepared. 3 organic polymers to the composition
% By weight, and terpionel as a dispersion medium was further added to form a mixture, and the mixture was kneaded by passing it through a three-roll mill to prepare a composition paste.

On the other hand, yttrium oxide (Y ₂ O) as a sintering aid is added to aluminum nitride (AlN) raw material powder.
₃ ) was added to 3% by weight of the raw material mixture, and the slurry prepared by slurring was prepared to have a thickness of 0.5 mm by the doctor blade method.
After being formed into a green sheet, the green sheet was punched out with a blank mold to manufacture a large number of square AlN formed bodies.

Next, the above composition pastes were screen-printed on the surface of the prepared sheet-shaped AlN molded body to form wiring portions such as predetermined wiring patterns, electrode pads, and wire bonding pads. Further, a plurality of sheet-shaped AlN compacts having wiring patterns and the like formed thereon were integrally laminated by a thermocompression bonding method to form a laminate having a thickness of 3 mm.

Further, each laminated body is heated at a temperature of 70 in a nitrogen atmosphere.
After degreasing at 0 ° C, also in a nitrogen atmosphere at a temperature of 180
Simultaneous firing was performed by heating at 0 ° C. for 6 hours to prepare the co-fired multilayer circuit boards according to Examples 1 to 11 in which the circuit wiring was integrally formed on the AlN substrate.

On the other hand, as Comparative Example 1, preparation of an AlN molded body, printing of a wiring pattern, and laminated body were carried out under the same conditions as in Examples 1 to 11 except that a paste containing only tungsten powder to which no complex oxide was added was used. Was formed, degreased and sintered to prepare a co-fired multilayer circuit board according to Comparative Example 1 having the same dimensions as those of Examples 1 to 11.

The volume resistance, densification degree and porosity of the circuit wiring of each of the multilayer circuit boards according to Examples 1 to 11 and Comparative Example 1 thus prepared were measured and the results shown in Table 1 below were obtained. The densification degree was obtained by image analysis of a cross-sectional photograph of circuit wiring. That is, five fracture surfaces of the circuit wiring were photographed with a scanning electron microscope (SEM), and in each photograph, the ratio of the dense region area excluding the pore portion to the total cross-sectional area was averaged and obtained. The porosity was calculated by the area ratio of the pores.

[0033]

[Table 1]

As is clear from the results shown in Table 1,
In the multilayer circuit boards according to Examples 1 to 11, since the circuit wiring was formed by the composition containing the composite oxide containing tungsten and the rare earth element, the dense circuit wiring with few pores was obtained. In addition, since the circuit wiring is dense, the wiring resistance is small and a circuit board that can cope with high speed is obtained. In particular, since pores are rarely generated in the circuit wiring, it is possible to provide a highly reliable circuit board in which liquid impurities and organic impurity components do not penetrate into the pores of the circuit wiring in the plating process and the thin film layer forming process. did it.

[0035]

As described above, in the circuit board and the method for manufacturing the same according to the present invention, the tungsten base material forming the circuit wiring contains the composite oxide containing tungsten and a rare earth element, At the temperature at which the ceramics substrate and the circuit wiring pattern are fired, the composite oxide melts and fills the pores generated in the tungsten base material, and at the same time decomposes by nitriding and pyrolysis to form a dense circuit wiring.

Therefore, since the electric resistance of the circuit wiring is greatly reduced, the operation speed of the semiconductor element can be increased.
In addition, since there are few pores in the circuit wiring, even when heat treatment is performed after forming the plating layer or thin film on the circuit wiring, there are few defects such as swelling of the plating layer or thin film The yield can be significantly improved.

Claims (5)

[Claims] 1. A circuit board integrally formed with circuit wiring on the surface of a ceramic substrate, wherein the circuit wiring is formed of a composition containing 1 to 50% by weight of a complex oxide containing tungsten and a rare earth element, and the balance being tungsten. A circuit board characterized by the above. 2. The circuit board according to claim 1, wherein the porosity of the circuit wiring is 20 vol% or less. 3. The circuit board according to claim 1, wherein the ceramics substrate is an aluminum nitride substrate. 4. A circuit wiring composition paste is prepared by adding 1 to 50% by weight of a composite oxide powder containing tungsten and a rare earth element, and adding an organic additive to a composition comprising the balance tungsten powder. A method for producing a circuit board, comprising applying the composition paste to the surface of a ceramic molded body to form a wiring pattern having a predetermined shape, and then simultaneously firing the ceramic molded body and the wiring pattern. 5. A circuit wiring composition comprising 1 to 50% by weight of a composite oxide powder containing tungsten and a rare earth element, and the balance being tungsten powder.