JPH02129997A - Manufacture of multilayer ceramic circuit substrate - Google Patents

Abstract

PURPOSE:To improve electrical connection between a high melting-point metal layer and a Cu thick-film conductor by printing a junction paste layer of a specific composition on the high melting-point metal layer, connecting a junction layer obtained by calcining it, printing a Cu thick-film conductor, a resistor, and a protection body in sequence, and forming calcination under non-oxidized environment repeatedly. CONSTITUTION:A junction paste layer 5 containing a metal mixture powder including a nickel of 0-80weight% (preferably 40-80weight%) and a palladium of 20-100weight% (preferably 20-60weight%) is printed on a high melting-point metal layer 2 and the high melting-point metal layer 2 obtained by calcining it is connected to the high melting-point metal layer 2. Then, a Cu thick-film conductor 6, a resistor 7, and a protection body 8 are printed on it in sequence and calcined under a non-oxidized environment repeatedly. Thus. electrical connection between the high melting-point metal layer 2 and the Cu thick-film conductor 6 can be maintained fully.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a multilayer ceramic circuit board,
In detail, Cu thick film conductors, resistors and protectors are printed on a ceramic multilayer substrate, fired in a non-oxidizing atmosphere,
The present invention relates to a method for manufacturing a multilayer ceramic circuit board by baking.

[Problems to be Solved by the Prior Art and the Invention 1] In order to miniaturize circuits and improve functionality, it is further desired to increase the density of hybrid thick film integrated circuit boards (hereinafter referred to as HIC boards). As one system that meets this demand, a multilayer ceramic circuit board is required in which a Cu thick film conductor is formed on a co-fired multilayer board that uses W, Mo, or the like as an internal conductor and alumina or the like as an insulator. Cu thick film conductors are less prone to migration and have high electrical conductivity, making it possible to use thin wires and conduct wiring with narrow intervals. Recently, improvements have been made in resistor pastes for firing in non-oxidizing atmospheres used in Cu thick film systems, and the formation of resistors by printing methods has reached a practical level. For this reason, high-performance HIC boards that mix digital and analog circuits also require high-performance Cu.
As the application of thick film systems becomes possible, there is an increasing need to form Cu thick film systems on multilayer substrates.

Until now, there has been no method of forming a Cu thick film conductor on the surface layer of a multilayer substrate using a high-melting point metal layer such as Mo5W as an internal conductor by electrically and mechanically connecting it to the internal conductor such as W. Several methods are also being considered.

The simplest method is to print a Cu thick film conductor paste directly on the internal conductor and bake it in a non-oxidizing atmosphere, but this method does not allow electrical contact between the internal conductor and the Cu thick film conductor. Mechanically, it is difficult to connect in a stable state.

As a method to solve this problem, for example,
-30194, on the W inner conductor, N l
A method has been disclosed in which a plating layer made of a conductive metal such as CO or Cu is formed and then a Cu thick film conductor is formed on the plating layer. There are problems such as an increase in resistance at the connection portion between the conductor and the Cu thick film conductor.

In addition, in Japanese Patent Publication No. 59-155995, M
o.

After applying Ni plating on the internal conductor such as W, further N
A method has been proposed in which the i-paste is printed and baked, and then a surface Cu thick film conductor is printed and baked. Additionally, a method has been proposed in which Ni plating is applied to the W internal conductor, followed by rough Cu plating, and then a Cu paste is printed and baked, but both methods require a wet plating process. The problem is that the plating is complicated as it requires two or more steps, and the plating tends to peel off due to thermal stress during firing in a non-oxidizing atmosphere in the subsequent Cu thick film conductor formation process. .

For HIC boards with resistors that have a Cu thick film conductor on the surface layer, it is necessary to perform firing in a non-oxidizing atmosphere at least twice: firing the Cu thick film conductor and firing the resistor. The mechanical and electrical connections must remain stable after this step. The methods proposed so far are insufficient in terms of stability and process simplicity, and there is a need for a more stable electrical connection and a simpler process.

An object of the present invention is to provide an inexpensive method for manufacturing a multilayer ceramic circuit board with excellent electrical and mechanical connections between internal conductors and Cu thick film conductors.

[Means and effects for solving the problem] In order to achieve the above object, the inventors of the present invention have made various studies and have developed the present invention by printing a paste of a certain composition on the high melting point metal layer which is the internal conductor. The invention was completed.

That is, the method for manufacturing a multilayer ceramic circuit board of the present invention is to form a Cu thick film conductor, a resistor, and a protector in a non-oxidizing manner on a multilayer wiring board composed of alumina ceramics as an insulator and a high melting point metal layer as an internal conductor. In a method for manufacturing a ceramic circuit board in which firing and baking is performed in an atmosphere, palladium powder or palladium is added to the high melting point metal layer.
After printing a bonding paste layer containing a mixed powder containing 0% by weight or more and 80% by weight or less of nickel, and connecting the bonding layer by firing this with a high melting point metal layer, a Cu thick film conductor and a resistor are placed on top of this. and a protective body are formed by sequentially repeating printing and firing in a non-oxidizing atmosphere.

The bonding paste used in the present invention contains 0 to 0 nickel.
Contains metal powder or metal mixed powder (hereinafter collectively referred to as metal powder) containing 80% by weight, preferably 40 to 80% by weight, and 20 to 100% by weight, preferably 20 to 60% by weight of palladium. .

If the Ni content exceeds 80% by weight, the bond between the high-melting point metal layer and the bonding layer obtained by firing the bonding paste will become weak, the bonding layer will easily peel off from the high-melting point metal layer, and the connection resistance will decrease. The rate of change becomes too high, and the resistance value increases quickly with respect to the number of firings. Therefore, under a non-oxidizing atmosphere, approximately 90
Repeated firing at 0°C results in loss of electrical connection.

In addition, when the Ni content is in the range of 0 to 40% by weight and the Pd content is in the range of 60 to 100% by weight, when the bonding paste contains glass powder or alumina powder, the bonding between the high melting point metal layer and the bonding layer is difficult. Before the high melting point metal layer is formed, the high melting point metal tends to aggregate into beads, making it difficult to form a bond between the high melting point metal layer and the bonding layer.

The particle size range of each of these components is NiO, 1 to 1 μm, 1 Pd
O, 2 to 1 μm is preferable.

In addition to the above-mentioned metal powder components, the paste used in the present invention also contains binders such as glass powder, alumina powder, ethyl cellulose resin, acrylic resin, butyl carpitol acetate, α-terpineol, petroleum-based high Organic solvents such as boiling point solvents are preferably contained.

As the glass powder, borosilicate glass powder, barium borosilicate glass powder, calcium aluminoborosilicate glass powder, etc. are preferably used, and the metal oxide in the glass is W.
It is preferable to use a material that cannot be reduced by, for example, a material containing a large amount of PbO or ZnO. If glass powder and alumina powder are present in the paste at the same time, SiO2 and Ca in the alumina powder and glass powder will be removed when the paste is heated.
O, etc. react, and a portion of the glass crystallizes to form anorthite, increasing its strength. The content of this glass powder is
It is preferably 10 to 20 parts by weight based on 100 parts by weight of the metal powder described above. If the glass powder content is less than 10 parts by weight, the periphery of the bonding layer will easily peel off from the alumina insulating layer during the production of the ceramic substrate, and if it exceeds 20 parts by weight, the thick film conductor formed on the bonding layer will peel off easily. There is an increased possibility that solder wettability will deteriorate. The softening point of glass powder is approximately 800
~900°C and an average particle size of 2 to 3 μm are preferred.

The alumina powder preferably has an average particle size of 2 to 4 μm. The content of this alumina powder is preferably 1 to 5 parts by weight based on 100 parts by weight of the metal powder.

If the alumina powder content is less than the ITII part unstructured part, the adhesive strength between the alumina insulating layer and the bonding layer will decrease, and if it exceeds 5 parts by weight, the glass will crystallize too much, and the bonding layer and high melting point metal layer will , stress relaxation with the alumina insulating layer cannot be achieved properly, and there is a possibility that the bonding layer may peel off or cracks may appear in the bonding layer.

Next, a method for manufacturing a multilayer ceramic circuit board according to the present invention will be explained in detail based on the drawings.

FIG. 1 shows a longitudinal cross-sectional view of a multilayer ceramic circuit board according to the present invention, and FIG. 2 shows a thick film conductor printed pattern.

In Fig. 1, 1 is an alumina green sheet, 2 is a high melting point metal layer, 3 is an alumina paste printed layer (becomes an alumina insulating layer after firing), 4 is an opening, and 15 is a bonding paste layer (becomes a bonding layer after baking). layer), 6 is Cu thick film conductor, 7
8 shows a resistor, 8 shows a protector, and BO shows a printed pattern of a thick film conductor.

In the manufacturing method of the present invention, first, a requisite number of high melting point metal layers 2 made of WlMo etc. and an alumina paste printed layer 3 are formed on a regular alumina green sheet 1, and then fired in a reducing atmosphere. , obtaining a multilayer substrate having multiple layers of conductors connected to each other inside.

Next, on the high melting point metal layer 2 exposed through the opening 4 of the alumina insulating layer 3 obtained by firing the multilayer substrate, a bonding paste having the above composition is applied by screen printing to a thickness of 10 mm after drying. Print so that it is about ~30μm, 9
The bonding layer 5 is formed by heat treatment at a temperature of 00 to 1100° C. for 3 to 15 minutes in N2 gas or a non-oxidizing atmosphere containing N2 gas as necessary.

The required amount of N2 gas varies depending on the structure of the kiln, etc.
It is necessary to have more N2 gas than reacts with the 02 gas mixed in the furnace to form H and O, and usually the volume ratio of N2 gas to N2 gas is 0 and a range of N2 gas/N2 gas ≦3 is adopted. be done. If N2 gas is used, Ni in high melting point metals and bonding layers can be removed.
Even if the surface is oxidized, it is reduced by N2 gas during heat treatment, and a good bond between the high melting point metal layer and the bonding layer is formed.

Further, when forming an atmosphere using only N2 gas, the oxygen concentration in the N2 gas is preferably 1Oppm or less.

If LQppi is exceeded, the surface of the high melting point metal and the Ni in the bonding layer will be oxidized, resulting in insufficient electrical connection between the high melting point metal layer and the bonding layer, and the connection may be lost during subsequent Cu thick film circuit formation. be.

The heat treatment temperature is preferably in the range of 900 to 1100°C,
If the temperature is less than 900°C, the bonding between the high-melting point metal layer and the bonding layer will be insufficient, and if it exceeds 1100°C, the high-melting point metal layer and the bonding layer will react too much, resulting in large changes in the body structure of the high-melting point metal layer. As a result, distortion occurs in the high melting point metal layer, and the bonding strength actually decreases.

Next, a Cu thick film conductor 6, a resistor 7 and a protector 8 are deposited on the bonding layer 5 formed in this way according to a normal method.
Form each layer.

Here, the Cu thick film conductor 6 is printed with the thick film conductor print pattern 60 and then fired at about 900° C. in a non-oxidizing atmosphere.

Further, the resistor 7 is made of a lanthanum boride paste or a tin oxide paste, and is fired at about 900°C.

The protector 8 is made of a low melting point glass paste or resin, and the low melting point glass paste is fired in a non-oxidizing atmosphere at about 500 to 700°C, and the resin is hardened at 80 to 180°C. or UV cured.

A multilayer ceramic circuit board is manufactured by such a manufacturing method.

[Examples] The present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1-13 Alumina (Ajll 203) 94% by weight and M
gO.

A total of 100% by weight of inorganic components including 6% by weight of a flux component consisting of Ca OSS io 2, polyvinyl butyral (binder), and dioctyl phthalate (plasticizer)
Using a slurry prepared and kneaded from an organic component consisting of sorbitan trioleate (dispersant) and a mixed solvent of ethanol and toluene, an alumina green sheet with a thickness of approximately 0.635 mm was formed on a carrier film using a doctor blade method. .

Next, a high melting point metal paste was prepared from W metal powder with a particle size of 1 to 5 μm and a vehicle mainly composed of ethyl cellulose, terpineol, etc., and screen printed onto an alumina green sheet to a thickness of about 20 μm after drying. I printed it to look like this.

After drying this high melting point metal layer paste, an alumina paste prepared from the same inorganic and organic components as the alumina green sheet is printed so that the thickness after drying is approximately 50 μm, and the high melting point metal layer and alumina insulating layer are separated. A laminate was obtained.

After drying the laminate, the volume ratio of N2 gas:N2 gas is 1.
: About 3, in a reducing atmosphere with a dew point of 40℃, about 155
A ceramic circuit board was obtained by firing at 0°C.

On the high melting point metal layer in the opening of this ceramic circuit board,
Print using a paste with the components shown in Table 1 so that the thickness of the bonding paste layer after drying is approximately 20 μm, and after drying, either in an N2 gas atmosphere or at a volume ratio of about 3 to 3. in a dry mixed gas atmosphere of 900-10
Heat treatment was performed at 00°C for 10 minutes.

The particle size of the Ni metal powder used in this paste was 0.1
~0.5 μm, Pd metal powder particle size is 0.3~0
．． 8μms glass powder (SL0255% by weight, B20,
9% by weight, AJ20, 14% by weight, Ca020% by weight
, Mg02% by weight, softened fish at 840°C) has an average particle size of 2
~3 μm and alumina powder having an average particle size of 2 to 4 μm, and acrylic resin and terpineol were used as vehicles.

A second Cu thick film conductor is placed on the substrate thus obtained.
The pattern shown in the figure was printed and baked in a non-oxidizing atmosphere at 900°C.

After this, the electrical resistance between terminals AB in FIG. 2 was measured. The electrical resistance after firing 2 to 5 times was also measured, and the results are shown in Table 1.

The purpose of the multilayer ceramic circuit board manufactured by the present invention is to achieve high density, so circuits are often formed on both sides of the board. After firing the resistors at approximately 900°C, the glasses (protectors) on both sides are fired simultaneously or separately at approximately 850°C. Therefore, the maximum number of firings is 4 times at 900℃.
A total of 6 times, 2 times at 650°C. For this reason, it would be sufficient to withstand firing at 900°C four times and 650°C twice, but since the test conditions lacked uniformity, the evaluation was made based on the number of times the product could withstand firing at 900°C. At this time, it was determined that it was necessary to endure more firing than four times at 900°C, so the evaluation was performed based on the electrical conductivity after firing at 900°C five times.

Further, using the bonding layer paste of Example 5, an adhesive strength evaluation test between the bonding layer and the alumina insulating layer was conducted. Approximately 100
When heat treated at 0° C., a bealling strength of usually LKg/an2 or more and at least 0.5'J/an2 or more was obtained.

Comparative Examples 1 to 3.

Test samples were prepared in the same manner as in Examples 1 to 13, except that the bonding layer paste having the composition shown in Table 1 was used, and the same measurements as in Examples 1 to 13 were performed. Shown in the table.

Comparative Example 4 After creating a ceramic circuit board consisting of a high melting point metal layer (tungsten) and an alumina insulating layer in the same manner as in Examples 1 to 13, commercially available boron-based Ni chemical plating was applied on the high melting point metal layer in the opening. N1 containing approximately 1% boron using liquid
-B film is formed, and the volume ratio of H2 gas and N2 gas is 1:3.
The sample was heat-treated at about 850° C. for 10 minutes in a high-temperature oven. Furthermore, a thick film circuit of Cu was formed on this, and Examples 1 to 13
The same measurements as above were carried out and the results are shown in Table 1.

As is clear from Table 1, under N2 gas atmosphere, 900
Even after repeating the firing at °C five times, the multilayer ceramic circuit boards formed using the pastes of Examples 1 to 13 exhibit good electrical conductivity.

However, Comparative Examples 1 to 3 in which the paste composition was outside the range of the present invention
After firing five times, the resistance value exceeded [kΩ] in all cases. Further, in Comparative Example 4 in which the N1-B film was formed, the resistance value exceeded 1Ω after one firing.

[Effects of the Invention] As explained above, by the manufacturing method of the present invention in which a paste with a certain composition is used as a bonding layer of a multilayer ceramic circuit board, the high melting point metal layer remains intact even after repeated firing in a non-oxidizing atmosphere. The electrical connection between the conductor and the Cu thick film conductor can be maintained in good condition.

Further, since only one layer is required between the high melting point metal layer and the Cu thick film conductor, the process is simple and an increase in cost can be suppressed.

Furthermore, it is possible to reliably and firmly adhere the bonding layer to the alumina insulating layer.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a multilayer ceramic circuit board according to the present invention, and FIG. 2 is a thick film conductor printed pattern. DESCRIPTION OF SYMBOLS 1... Alumina green sheet, 2... High melting point metal layer, 3... Alumina paste printing layer (alumina insulation layer), 4... Opening, 5... Bonding paste layer (bonding layer), 6... Cu thick film conductor, 7... Resistor, 8... Protector, 80... Thick film conductor layer printing pattern diagram. Patent applicant Noritake Co., Ltd.

Claims (1)

[Claims] 1. A method for manufacturing a ceramic circuit board, in which a Cu thick film conductor, a resistor, and a protector are fired and baked in a non-oxidizing atmosphere on a multilayer wiring board composed of alumina ceramics as an insulator and a high melting point metal layer as an internal conductor. , on the high melting point metal layer, palladium powder or palladium 2
After printing a bonding paste layer containing a mixed powder containing 0% by weight or more and 80% by weight or less of nickel, and connecting the bonding layer by firing this with a high melting point metal layer, a Cu thick film conductor and a resistor are placed on top of this. A method for manufacturing a multilayer ceramic circuit board, comprising sequentially forming a protective body by repeatedly printing and firing in a non-oxidizing atmosphere.