JPH08307029A - Conductive paste - Google Patents

Abstract

PURPOSE: To provide conductive paste which becomes a very reliable and good- conditioned via electrode even if used on a very precise glass ceramic multilayer substrate which causes no contraction in the planar direction. CONSTITUTION: This paste includes an inorganic composition, a solvent, and an organic binder. The inorganic composition consists of 59.94-79.94wt.% of copper oxide, 0.05-0.10wt.% of oxide particles such as SiO2 , TiO2 , and a mixture of SiO2 and TiO2 , and glass. In the paste, the inorganic composition is dispersed. Preferably, an average grain diameter of the oxide particles of SiO2 , TiO2 , or the mixture of SiO2 and TiO2 is 0.5-1.0mm, that of the copper oxide is 2.0-5.0μm, and that of the glass, an inorganic binder, is 1.0-4.0μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste for mounting semiconductor LSIs, chip parts and the like, and for applying them to vias for connecting wiring electrodes of respective layers of a ceramic multilayer substrate for interconnecting them.

[0002]

2. Description of the Related Art In recent years, semiconductor LSIs, chip parts, etc. have been reduced in size and weight, and wiring boards for mounting them have also been desired to be reduced in size and weight. In order to meet such demands, the ceramic multilayer substrate has obtained the required high-density wiring, and since it can be thinned, it is regarded as important in today's electronics industry. The conductor composition as an electrode material used for the ceramic multilayer substrate is generally a paste composition in which a conductive metal, an inorganic oxide and glass powder are dispersed in an organic medium. In recent years, due to the development of a low-temperature sintered glass / ceramic multilayer substrate, copper is an inexpensive conductive material that can be used, and since the specific resistance is small and the solder wettability is excellent, use of a copper electrode material is desired. As a method of using copper for the low-temperature sintered glass-ceramic multilayer substrate, there is a method of using copper for the wiring of the inner layer and the uppermost layer. It is the best in terms of conductor resistance, solder wettability, and cost, but it is difficult to manufacture because it must be fired in a neutral atmosphere such as nitrogen. Therefore, Japanese Patent Application Laid-Open No. 3-20914 proposes a method of producing a ceramic multilayer substrate by using a copper oxide paste and using three steps, a binder removal step, a reduction step, and a firing step. It uses copper oxide as a starting material for a conductor to form a multilayer body, and in the binder removal step, heat treatment is performed in a sufficient oxygen atmosphere for carbon and at a temperature sufficient to thermally decompose the organic binder inside. Next, the reduction step of reducing copper oxide to copper and the firing step of sintering the substrate are established. As a result, it became easy to control the atmosphere during firing, and a dense sintered body could be obtained.

On the other hand, the ceramic multi-layer substrate shrinks due to sintering during firing. The shrinkage due to the sintering depends on the substrate material used, the green sheet composition, the powder lot, and the like. This has caused some problems in the fabrication of multilayer substrates. First of all, in the production of a multilayer ceramic substrate, the inner layer wiring is fired as described above before the uppermost layer wiring is formed. Therefore, when the shrinkage error of the substrate material is large, the inner layer wiring pattern and the dimensional error cause the inner layer wiring to have a large shrinkage error. Cannot connect to the electrode. As a result, a land having an unnecessarily large area has to be formed in the uppermost electrode portion so as to allow a shrinkage error in advance, which is difficult to use in a circuit that requires high-density wiring. Therefore, some screen plates may be prepared for the uppermost layer wiring according to the shrinkage error and used according to the shrinkage rate of the substrate.
This method is uneconomical because many screen versions must be prepared.

Also, if the uppermost layer wiring is fired at the same time as the inner layer, a large land is not required, but since the shrinkage error of the board itself is still present even by this simultaneous firing method, cream solder printing at the time of mounting components on the board. At
Due to that error, there may be cases where it is not possible to print on the required part,
Also, when mounting components, there is a deviation from the predetermined component position.

In order to reduce these shrinkage errors as much as possible, it is necessary to control not only the substrate material and the green sheet composition but also the difference in powder lot and the lamination conditions (pressing pressure, temperature) in the manufacturing process. is there. However, it is generally said that the error of the shrinkage ratio is about ± 0.5%. This is a common problem with ceramics, regardless of the multilayer substrate, and those involving the sintering of glass-ceramics. Therefore, in JP-A-5-102666,
A desired number of green sheets made of low temperature sintered glass / ceramic with electrode patterns are laminated, and an inorganic composition which does not sinter at the firing temperature of the low temperature sintered glass / ceramic substrate material is formed on both surfaces of this laminated body. Laminate so that it is sandwiched between green sheets, and fire the laminate,
After that, an invention has been proposed in which the inorganic composition on both surfaces of the multilayer substrate which is not sintered is removed. As a result, the substrate material is sintered only in the thickness direction, and a substrate having no shrinkage in the plane direction can be manufactured, and various problems as described above can be solved. From the above, a substrate that does not shrink in the planar direction has been created.

[0006]

However, there are some problems here. Since the substrate shrinkage during firing occurs only in the thickness direction, the electrode inside the via has a rough film structure after firing in the past electrode paste composition used in the conventional firing method, or It means that it becomes columnar and separates from the wall surface of the via. Therefore, there are problems that the wiring electrodes of each layer cannot be joined, the electrodes are easily oxidized due to the large contact area with the outside air, and the reliability is lowered. The cause of the above problems is that the sintering of the substrate and the sintering of the electrode are not matched, but even if the conductor composition is simply increased due to the densification of the via electrode, the glass-ceramic multilayer During firing of the substrate, the firing of the conductor material starts earlier than the firing of the substrate, so that the substrate cannot suppress the firing of the conductor, and cracks occur in the substrate around the via after firing.

In addition, since a substrate whose contraction in the plane direction is zero does not sinter the substrate material only in the thickness direction, in order to obtain a substrate having the same thickness as the conventional one, the starting glass-ceramic green sheet is more than the conventional 200 μm thick. Also needs to be thicker. However, at present, when the sheet thickness is thicker than 200 μm, via filling due to printing is deteriorated, and a dense via conductor film cannot be obtained after firing. For this reason, in order to use the above-mentioned glass-ceramic multi-layer substrate in which the highly precise shrinkage in the planar direction is suppressed, a conductive paste for vias adapted to the substrate is required.

In order to solve the above-mentioned problems, the present invention supplies a conductive paste which becomes a via electrode in a good state with high reliability even when used for a highly accurate glass-ceramic multilayer substrate which does not shrink in the plane direction. The purpose is to do.

[0009]

In order to achieve the above object, the conductive paste of the present invention contains copper oxide of 59.94-
79.97% by weight, SiO ₂ or TiO ₂ , or S
Oxide particles, which are a mixture of iO ₂ and TiO ₂ , are 0.05 to
It is characterized in that it contains 0.10% by weight of inorganic composition with the balance being glass, a solvent and an organic binder, and the inorganic component is dispersed therein.

In the above structure, SiO in the inorganic component
₂ or TiO ₂ , or a mixture of SiO ₂ and TiO ₂ preferably has an average particle diameter of 0.05 to 0.1 μm. Moreover, in the said structure, it is preferable that the average particle diameter of copper oxide is 2.0-5.0 micrometers and the average particle diameter of glass is 1.0-4.0 micrometers.

[0011]

According to the conductive paste of the present invention, the copper oxide content is 5%.
9.94 to 79.97% by weight, SiO ₂ or Ti
O ₂ or 0.05 to 0.10% by weight of oxide particles, which is a mixture of SiO ₂ and TiO ₂ , and an inorganic composition made of glass, the balance of which is an inorganic binder, containing a solvent and an organic binder, Even if it is used for a glass / ceramic multilayer substrate that does not shrink in the planar direction due to the dispersion of inorganic components, cracks do not occur in the substrate around the via electrode, and the via electrode has a dense film structure. As a result, a conductive paste can be achieved in which the wiring electrodes can be properly joined and the thick green sheet can be filled with vias.

According to a preferred embodiment of the present invention, the average particle size of the oxide particles, which are SiO ₂ or TiO ₂ or a mixture of SiO ₂ and TiO _{2 in} the inorganic component, is 0.05 to 0.1 μm. Due to the surface resistance of these fine particles, the viscosity characteristic of the conductor paste becomes low when a force is applied to the paste when filling the via, and when the paste fills the via and the force is no longer applied, the paste stays in the via with a high viscosity. Become. For this reason, it becomes possible to fill vias in a sheet thicker than the conventional 200 μm green sheet, and a dense conductor film is obtained even after firing. The average particle size of copper oxide is 2.
0-5.0 μm, average particle size of glass is 1.0-4.0 μm
According to the preferable example of the present invention that m, the sintering of copper during sintering is delayed, the sintering of the copper electrode is suppressed until the glass / ceramic substrate is sintered, and the sintering of the conductor is started after the substrate is sintered. .

As a result of the above, the via electrode has a dense film structure, the substrate around the via electrode is not cracked, and the reliability is improved.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. (Example 1) The paste used here had an inorganic composition of copper oxide: 65.0% by weight (average grain size: 5.0 μm), Ti.
O _2: 0.08 wt%, the glass: 34.92 wt% (manufactured by Nippon Electric Glass Co., Ltd. borosilicate lead glass, an average particle diameter 4.0μ
m) and the particle size of TiO ₂ is as shown in Table 1. The mill base of each of these compositions is mixed with a solvent (α-
Terpineol, 15.5 wt% with respect to the entire paste) and an organic binder (ethyl cellulose, 1.2 wt% with respect to the entire paste) are kneaded by a three-roll ceramic roll to an appropriate viscosity, and a copper oxide paste Was produced. Viscosity is 450000cps at 20 rpm, 20
The rpm was 280000 cps and the ratio of 10 rpm / 20 rpm was 1.60. The viscosity of the paste is particularly preferably 1.2 to 2.0 at a ratio of 10 rpm / 20 rpm.

Next, glass-ceramic green sheets for low temperature firing were prepared with different thicknesses, and via holes were formed in each with a diameter of 0.2 μm, and the copper oxide paste was used to fill the via holes. I went. The filling state of the via was evaluated.

[0016]

[Table 1]

As shown in Table 1, when the particle size of TiO ₂ is 0.05 μm, the sheet thickness is 800 μm when the particle size is 0.1 μm.
Even in m, the via paste was completely filled. From this, the paste in which even a thick sheet was completely filled was when the particle size of TiO ₂ was 0.05 to 0.1 μm.

(Embodiment 2) The paste composition used here is copper oxide (average particle diameter 3.5 μm), Si for the inorganic powder.
O ₂ (average particle size 0.08 μm), glass frit (borosilicate glass manufactured by Nippon Electric Glass Co., average particle size 2.5 μm)
used. The compounding ratio of the inorganic powder used is shown in Table 2.

[0019]

[Table 2]

The mill base having the above composition was mixed with a solvent (α-terpineol, 17.0% by weight based on the whole paste).
And an organic binder (ethyl cellulose, 2.5% by weight based on the total paste) were kneaded with a three-roll ceramic roll so as to have an appropriate viscosity to prepare a copper oxide paste. Viscosity is 50000cps at 20rpm, 20rpm
At 450000 cps, the ratio of 10 rpm / 20 rpm was 1.28.

A via hole having a diameter of 0.2 μm was formed in a glass / ceramic green sheet for low temperature firing (thickness: about 300 μm), and the copper oxide paste was used to fill the via hole. A required number of green sheets with the vias filled therein are laminated, and alumina green sheets are laminated on both sides. In this state, thermocompression bonding was performed to form a laminated body having a thickness of about 900 μm. The thermocompression bonding conditions are a temperature of 80 ° C. and a pressure of 20.
It was 0 Kg / cm ² . This laminated body is kept at 500 ° C. for 2 hours in air in a box furnace to remove the organic binder,
350 ° C in a mixed atmosphere of hydrogen and nitrogen in a reduction furnace,
It was held for 2 hours for reduction, and fired at 950 ° C. for 1 hour in pure nitrogen in a mesh belt furnace. With respect to the sample after firing, the performance was evaluated based on the denseness inside the via and the presence or absence of substrate cracks after firing.

As shown in Table 2, when the amount of SiO ₂ added was 0.02% by weight, there was no composition region of copper oxide and glass which satisfied the condition of good compactness and no cracking. When the amount of SiO ₂ added is 0.05% by weight, copper oxide: 59.97 to 79.97% by weight, glass: 19.
When the content was 98 to 39.98% by weight, the compactness was good and no crack was generated. Similarly, when the added amount of SiO ₂ is 0.07% by weight, copper oxide: 59.96 to 79.
94% by weight, glass: 19.99 to 39.97% by weight, when the SiO ₂ addition amount is 0.10% by weight, copper oxide:
59.94 to 79.92% by weight, glass: 19.98 to
When the content was 39.96% by weight, the compactness was good and no crack was generated. SiO ₂ addition amount is 0.15,
When the content was 0.20% by weight, none of them satisfied the denseness and the state where no cracks were generated. From this fact, the reason why the via has good density and is free from cracks is that copper oxide has an inorganic composition of 59.94 to 79.97.
%, SiO ₂ is 0.05 to 0.10 wt%, and the glass as the inorganic binder is 19.98 to 39.98 wt%. The best condition among them was that copper oxide was 69.95% by weight and Si
It was when O ₂ was 0.07% by weight and glass was 29.98% by weight.

(Embodiment 3) The paste composition used here is copper oxide: 72.56% by weight and Ti for the inorganic powder.
O ₂ : 0.06% by weight (particle diameter 0.06 μm), glass frit (borosilicate glass manufactured by Nippon Electric Glass Co., Ltd.) 27.
38% by weight was used. Table 3 shows the average particle diameters of the copper oxide and glass used.

[0024]

[Table 3]

Millbases having the respective compositions shown in Table 3 were mixed with a solvent (butyl carbitol acetate, 13.0% by weight based on the entire paste) and an organic binder (poly α-).
Methylstyrene, 1.6% by weight based on the total paste)
At the same time, the mixture was kneaded with a three-roll ceramic roll so as to have an appropriate viscosity to prepare a copper oxide paste. Viscosity: 580000cps at 10rpm, 400000cps at 20rpm, 10rpm /
The 20 rpm ratio was 1.45.

A via hole having a diameter of 0.2 μm was formed in a glass / ceramic green sheet for low temperature firing (thickness: about 400 μm), and the copper oxide paste was used to fill the via hole. A required number of green sheets with the vias filled therein are laminated, and alumina green sheets are laminated on both sides. In this state, thermocompression bonding was performed to form a laminated body having a thickness of about 800 μm. The thermocompression bonding conditions are a temperature of 80 ° C. and a pressure of 20.
It was 0 Kg / cm ² . This laminated body is kept at 500 ° C. for 2 hours in air in a box furnace to remove the organic binder,
350 ° C in a mixed atmosphere of hydrogen and nitrogen in a reduction furnace,
It was held for 2 hours for reduction, and fired at 950 ° C. for 1 hour in pure nitrogen in a mesh belt furnace. With respect to the sample after firing, the performance was evaluated based on the denseness inside the via and the presence or absence of substrate cracks after firing.

As shown in Table 3, when the average particle size of copper oxide was 1.5 μm, the electrode sintering did not proceed and the film structure of the electrode became rough. When the average particle diameter of the glass is 0.5 μm, cracks are generated in the substrate, 4.5 μm and 5.0 μm.
At that time, the via electrode film became rough. From this fact, it is configured that the average particle size of copper oxide is 2.0 to 5.0 μm and the average particle size of glass is 1.0 to 4.0 μm in that the substrate is not cracked and the electrode state is dense. It was time to be done.

In this example, the particle size of SiO ₂ used in the inorganic composition was 0.08 μm, and the compounding ratio of TiO _{2 to} the inorganic powder was 0.06% and 0.08%. When the particle size of SiO ₂ or TiO ₂ is 1 μm or less and the compounding ratio to the inorganic powder is 0.10 to 0.05% by weight,
Similar effects were obtained with both SiO ₂ and TiO ₂ .
Even when SiO ₂ and TiO ₂ were mixed and used, the same effect was obtained under the above conditions. The mixing ratio can be arbitrarily set as needed. SiO ₂ and TiO ₂
May have the same particle size or different from each other.

As the solvent and the organic binder of the conductive paste of this embodiment, any known material used for preparing a general conductive paste can be arbitrarily used.

[0030]

As described above, according to the conductive paste of the present invention, 59.94 to 79.97% by weight of copper oxide, SiO ₂ or TiO ₂ , or SiO ₂ and TiO _{2 is used.}
Oxide particles that are a mixture of 0.05 to 0.10% by weight, the balance contains an inorganic composition made of glass that is an inorganic binder, a solvent and an organic binder, and the inorganic components are dispersed. Even if it is used for a glass / ceramic multilayer substrate that does not shrink in the planar direction, cracks do not occur in the substrate around the via electrode, and the via electrode has a dense film structure, and the bonding between wiring electrodes is correct. Therefore, it is possible to provide a conductive paste that can be filled and can fill a thick green sheet with vias.

Therefore, the via electrode has a dense film structure, cracks do not occur in the substrate around the via electrode, and reliability is improved.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshihiro Bessho 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A copper oxide content of 59.94% by weight or more and 79.9.
7% by weight or less, SiO ₂Or TiO₂, Or SiO
₂And TiO₂0.05% by weight of oxide particles, which is a mixture of
Above 0.10% by weight, inorganic composition with the balance being glass
Substance, solvent and organic binder are contained, and inorganic components are dispersed
Conductive paste characterized in that 2. SiO ₂ or TiO ₂ in the inorganic component,
The conductive paste according to claim 1, wherein the oxide particles, which are a mixture of SiO ₂ and TiO ₂ , have an average particle diameter of 0.05 μm or more and 0.1 μm or less. 3. The average particle size of copper oxide in the inorganic component is 2.0.
The conductive paste according to claim 1, which has a thickness of not less than μm and not more than 5.0 μm. 4. The average particle size of glass in the inorganic component is 1.0.
The conductive paste according to claim 1, having a thickness of not less than μm and not more than 4.0 μm.