JP3752755B2 - Manufacturing method of ceramic circuit board - Google Patents

Description

【００３２】
実施形態例３
本例においては，図４に示すごとく，第１焼成工程と第２焼成工程とを連続的に行った。
即ち，まず，加熱炉の中に，導体回路の表面に保護ガラス層を形成したセラミック基板を載置した。次いで，以下の第１，第２焼成工程を行なった。
即ち，第１焼成工程において，６００℃において保護ガラス層を焼成した。これにより，結晶化ガラスを溶融させた状態において，導体成分と結晶化ガラス成分との相互拡散を進行させた。
【００３３】
続いて，加熱炉の温度を連続的に昇温して，６６５℃とし，この温度で第２焼成工程を行い，保護ガラス層を焼成した。これにより，結晶化ガラスを結晶化させた。
その他は，実施形態例１と同様である。
本例のセラミック回路基板について，保護ガラス層の密着強度を測定したところ，実施形態例１と同様に１０ｋｇｆ／２ｍｍ□以上と高い値を示した。
【００３４】
実施形態例４
本例においては，第１焼成工程の焼成時間と保護ガラス層の密着強度との関係について測定した。
測定に際し，第１焼成工程の焼成温度は６００℃とし，焼成時間を種々に変化させた。また，第２焼成工程の焼成温度は６７５℃とし，焼成時間は５分間とした。その他は，実施形態例１と同様の条件でセラミック回路基板を製造した。
得られたセラミック回路基板について，保護ガラス層の密着強度を測定し，その結果を図５に示した。
【００３５】
その結果，第１焼成工程において，焼成時間が１分間の場合には，１．５ｋｇｆ／２ｍｍ□程度であった。１〜１０分と長くなるに連れて保護ガラス層の密着強度が高くなった。１０分間以上になると，密着強度は１０ｋｇｆ／２ｍｍ□以上と，高い値を維持した。このことから，第１焼成工程においては，１０分間以上焼成することにより，高い密着強度が得られることがわかる。
【００３６】
【発明の効果】
本発明によれば，導体抵抗が低く，かつ半田付着性が高い導体回路を有し，かつ導体回路と保護ガラス層との間の密着強度が高いセラミック回路基板の製造方法を提供することができる。
【図面の簡単な説明】
【図１】本発明における，導体回路と保護ガラス層との界面における，結晶化ガラス成分と導体成分との相互の拡散を示す説明図。
【図２】実施形態例１における，セラミック回路基板の断面図。
【図３】実施形態例２における，導体回路に対する保護ガラス層の密着強度を示す図。
【図４】実施形態例３における，保護ガラス層の焼成方法を示す説明図。
【図５】実施形態例４における，第１焼成工程の焼成時間と，導体回路に対する保護ガラス層の密着強度との関係を示す図。
【図６】従来例における，印刷法により導体回路を形成したセラミック回路基板の断面図。
【図７】従来例における，めっき法により導体回路を形成したセラミック回路基板の断面図。
【符号の説明】
１．．．保護ガラス層，
１１．．．結晶化ガラス成分，
２．．．導体回路，
２１．．．導体成分，
２２．．．界面，
２６．．．銅めっき，
２７．．．導体パターン，
３．．．拡散層．
５．．．セラミック基板，
７．．．セラミック回路基板，[0001]
【Technical field】
The present invention relates to a method for manufacturing a ceramic circuit board, and more particularly to a method for forming a protective glass layer on the surface of a conductor circuit on a ceramic substrate.
[0002]
[Prior art]
Conventionally, as shown in FIG. 6, there is a ceramic circuit board in which a conductor circuit 92 is provided on a ceramic substrate 91 and the surface of the conductor circuit 92 is covered with a protective glass layer 93. The protective glass layer 93 ensures the surface protection of the conductor circuit 92 and the electrical insulation between the adjacent conductor circuits 92, and also serves as a solder dam, and is essential for the ceramic circuit board 9.
[0003]
As a method for manufacturing the ceramic circuit board 9, for example, a conductor material mainly composed of a metal 922 and glass 921 is printed on the ceramic substrate 91 and fired to form the conductor circuit 92. Next, a protective glass layer 93 is formed by printing protective glass on the surface of the conductor circuit 92.
[0004]
Next, the protective glass layer 93 is fired. During the firing, a chemical bond is formed between the glass 921 and the protective glass layer 93 in the conductor circuit 92. Furthermore, the surface of the conductor circuit 92 is relatively porous, and a large number of pores 920 are observed.
Therefore, when the glass 931 of the protective glass layer 93 penetrates into the pores 920, the anchor effect of the glass 931 works, and mechanical coupling is obtained between the conductor circuit 92 and the protective glass layer 93. Therefore, the protective glass layer has a high adhesion to the conductor circuit.
[0005]
[Problems to be solved]
However, in the above-described conventional method of manufacturing a ceramic circuit board, the conductor circuit 92 contains the glass 921, so that the conductor resistance is high and the solder adhesion of the conductor circuit is low. Therefore, when the bonding wire is bonded to the conductor circuit 92 exposed from the protective glass layer, the bonding strength of the bonding wire is low.
[0006]
Therefore, as shown in FIG. 7, it is conceivable to form the conductor circuit 929 by metal plating. The conductor circuit 929 formed by metal plating is a pure metal containing no glass and is smooth. Therefore, the conductor circuit has a low conductor resistance and excellent solder adhesion.
[0007]
However, since the conductor circuit formed by metal plating is pure metal that does not contain glass as described above and is smooth, a protective glass layer is formed on the smooth surface despite good solder adhesion. Then, the adhesion of the protective glass layer becomes very weak. Therefore, when heat stress is applied to the protective glass layer, there is a problem that the protective glass layer easily peels from the conductor circuit.
[0008]
In view of the conventional problems, the present invention provides a method for producing a ceramic circuit board having a conductor circuit with low conductor resistance and high solder adhesion and high adhesion strength between the conductor circuit and the protective glass layer. It is something to be offered.
[0009]
[Means for solving problems]
The invention according to claim 1 forms a conductive circuit made of metal on a ceramic substrate, then forms a protective glass layer made of crystallized glass on the surface of the conductive circuit, and fires the protective glass layer A method for manufacturing a ceramic circuit board, comprising:
Firing the protective glass layer includes a first firing step of firing the protective glass layer at a temperature that is 50 ° C. lower than the softening point of the crystallized glass and less than the crystallizing point of the crystallized glass. Done,
Thereafter, a second firing step of firing the protective glass layer is performed within a temperature range necessary for crystallizing the crystallized glass.
[0010]
What is most remarkable in the present invention is that, when the protective glass layer is fired, once in the first firing step, the temperature is 50 ° C. lower than the softening point of the crystallized glass and within the range below the crystallization point. The protective glass layer is fired at a temperature to melt the crystallized glass of the protective glass layer, and then the protective glass layer is crystallized by firing at a temperature necessary for crystallization in the second firing step. .
[0011]
The present invention focuses on the softening point and crystallization point of crystallized glass. That is, first, in the first firing step, firing of the protective glass layer made of crystallized glass is maintained at a temperature of 50 ° C. lower than the softening point of the crystallized glass and below the crystallisation point. As a result, the crystallized glass is melted and the mutual diffusion of the conductor component and the crystallized glass component proceeds.
Next, in the second firing step, the protective glass layer is fired at a temperature necessary for crystallizing the crystallized glass to crystallize the protective glass layer. As a result, the adhesion strength between the protective glass layer and the conductor circuit can be increased and the electrical characteristics of the protective glass layer can be ensured.
[0012]
The present invention embodies the above points of interest. Hereinafter, the present invention will be described in detail.
First, in the first firing step, the firing temperature of the protective glass layer is at least 50 ° C. lower than the softening point of the crystallized glass and lower than the crystallisation point of the crystallized glass. When the protective glass layer is fired at such a firing temperature, as shown in FIG. 1, the crystallized glass component 11 in the protective glass layer 1 is melted, and the crystallized glass component 11 and the conductor component 21 of the conductor circuit 2 are mutually diffused. Then, the diffusion layer 3 is generated at the interface 22 between the protective glass layer 1 and the conductor circuit 2.
[0013]
In the first firing step, when the firing temperature is less than 50 ° C. lower than the softening point, the crystallized glass is not sufficiently melted, the crystallized glass has poor fluidity, and the conductor circuit is poorly wetted. Therefore, the adhesion of the protective glass layer to the conductor circuit is reduced. On the other hand, when the firing temperature is higher than the above crystallization point, the crystallized glass is crystallized, the fluidity of the crystallized glass is deteriorated, and the wettability with the conductor circuit is deteriorated. To do.
[0014]
Next, in the second firing step, the firing temperature of the protective glass layer is within the range of the temperature necessary to crystallize the crystallized glass. When the protective glass layer is fired at such a firing temperature, the crystallized glass component in the protective glass layer is crystallized, thereby ensuring the electrical characteristics of the protective glass layer.
[0015]
As described above, according to the present invention, it is possible to provide a method for producing a ceramic circuit board having a conductor circuit with low conductor resistance and high solder adhesion and between the conductor circuit and the protective glass layer. it can.
The softening point and crystallization point differ depending on the type of crystallized glass.
[0016]
Next, as described in claim 2, the firing time in the first firing step is preferably 10 minutes or more. The longer the firing time, the higher the adhesion of the protective glass layer. In the case of less than 10 minutes, the crystallized glass is not sufficiently melted, and the mutual diffusion between the crystallized glass component and the conductor component is insufficient, so that the crystallized glass reaches the interface between the metal grains of the conductor circuit. There is a possibility that the adhesion of the protective glass layer to the conductor circuit may be reduced without entering. However, the longer the firing time, the worse the productivity of the ceramic circuit board. Therefore, it is preferable to set the shortest time to ensure the strength.
[0017]
The first firing step and the second firing step may be performed separately. For example, a ceramic substrate having a protective glass layer formed on the surface of a conductor circuit is sequentially passed through a heating furnace that performs a first firing process and then a heating furnace that performs a second firing process.
Moreover, after performing a 1st baking process, it heats up continuously, it may be set as the baking temperature of a 2nd baking process, and a 2nd baking process may be performed. For example, after the ceramic substrate is placed in a heating furnace and the first firing process is performed, the temperature is adjusted in the same heating furnace and the second firing process is continuously performed.
[0018]
Next, as for the crystallized glass used for the protective glass layer, any glass system that can be crystallized can improve the strength by using the present invention. It is preferably a vitrified glass. As a result, it is possible to protect the surface of the conductor circuit, ensure electrical insulation between adjacent conductors, give the protective glass layer a role of a solder dam, and obtain a good protective film characteristic of the resistor.
[0019]
Next, as described in claim 4, it is preferable to form the conductor circuit on the ceramic substrate by metal plating. According to the metal plating process, a conductor circuit can be formed of pure metal.
For this reason, conductor circuits formed by metal plating have low conductor resistance and excellent electrical characteristics. Further, the plating surface is very smooth and dense with a surface roughness (Ra) of 2 μm or less. Therefore, the solder adhesion on the surface of the conductor circuit is high, and the bonding strength of the bonding wire is high.
[0020]
Further, the interface between the conductor circuit and the protective glass layer is fired at a temperature that is 50 ° C. lower than the softening point and lower than the crystallization point in the first firing step, so that the crystallized glass component of the protective glass layer is obtained. Diffuses into the conductor circuit and the conductor components of the conductor circuit mutually diffuse into the protective glass layer to form a diffusion layer. Thereafter, the crystallized glass component in the protective glass layer is crystallized by firing at a temperature necessary for crystallization in the second firing step. Thereby, while exhibiting the high adhesive strength of the protective glass layer with respect to a conductor circuit, the electrical property of a protective glass layer can be ensured.
[0021]
Next, as described in claim 5, when the conductor circuit is formed by metal plating on a metal mainly composed of W (tungsten) or Mo (molybdenum), the effect of the present invention is very large. It will be a thing.
This also increases the conductor characteristics of the conductor circuit. The metal plating process for forming the conductor circuit can be performed by either electroplating or electroless plating. Moreover, Cu (copper), Ni (nickel), Au (gold) can also be used for the said conductor circuit.
In addition, the conductor circuit formed from the plating process can be formed only from the metal plating process, but it can also be formed by performing metal plating on the surface of the conductor pattern formed by printing or etching the conductor foil. You can also.
[0022]
Next, the ceramic substrate may be any substrate that does not deform or deteriorate at the firing temperature in the second firing step. As such a ceramic substrate, for example, alumina is used as described in claim 6. Further, alumina nitride (AlN) or a glass substrate may be used.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
A method for manufacturing a ceramic circuit board according to an embodiment of the present invention will be described with reference to FIG.
This example is a method of manufacturing a ceramic circuit board in which a conductor circuit made of metal is formed on a ceramic substrate, and then a protective glass layer made of crystallized glass is formed on the surface of the conductor circuit and fired. This will be described in detail below.
[0024]
First, as shown in FIG. 2, a conductor pattern 27 made of W was formed on the surface of the ceramic substrate 5 by screen printing. The ceramic substrate 5 is composed of 96 wt% alumina and 4 wt% inorganic sintering aid. Next, the ceramic substrate 5 and the conductor pattern 27 were simultaneously fired at 1580 ° C. in a reducing atmosphere.
[0025]
Subsequently, a copper plating 26 having a thickness of 7 μm was deposited on the surface of the conductor pattern 27 by an electroless plating method. Next, the copper plating 26 was annealed by heating in a heating furnace for 60 minutes in a reducing atmosphere at a maximum temperature of 900 ° C. At this time, the surface roughness (Ra) of the copper plating 26 was 1 μm. Thereby, the conductor circuit 2 including the conductor pattern 27 and the copper plating 26 covering the conductor pattern 27 was formed.
[0026]
Next, the crystallized glass was screen-printed so as to cover the copper plating 26, dried and fired to form the protective glass layer 1. The crystallized glass is lead borosilicate crystallized glass having a softening point of about 550 ° C. and a crystallization point of about 655 ° C.
Next, the protective glass layer 1 was fired twice. First, in the first firing step, the protective glass layer 1 was fired at 550 to 600 ° C. for 20 minutes. Thereby, the mutual diffusion of the copper plating component and the protective glass layer was advanced. Next, in the second firing step, the protective glass layer 1 was fired at 655 to 665 ° C. for 5 minutes. As a result, the crystallized glass component was crystallized to obtain the ceramic circuit board 7.
[0027]
Next, the adhesion strength of the protective glass layer was measured by a peel method. As a specific measurement method, heat-resistant tape was attached to a protective glass layer formed on the copper plating surface. A central portion of the heat-resistant tape was cut out to form a window having a size of 2 mm × 2 mm. Next, an adhesive was applied to the surface of the protective glass layer from the window of the heat-resistant tape, and a hexagon nut was adhered thereto, followed by drying at 150 ° C. for 10 minutes. Thereafter, a U-shaped wire was passed through the hex nut, and the wire was pulled upward. The pulling force at this time was measured. Since the adhesion force of the protective glass layer increases as the pulling force increases, this pulling force is defined as the adhesion strength between the copper plating 26 and the protective glass layer 1.
As a result of the measurement, the adhesion strength between the protective glass layer and the conductor circuit was as high as 10 kgf / 2 mm □ (per square with a side of 2 mm) or more.
[0028]
Embodiment 2
In this example, the effect of the change in the firing temperature in the first and second firing steps on the relationship of the adhesion strength between the protective glass layer and the conductor circuit was measured.
In the measurement, as shown in Table 1, the firing temperature in the first firing step was varied between 400 and 675 ° C., and the firing temperature in the second firing step was varied between 655 and 675 ° C. At this time, the firing temperature in the first firing step was set to be lower than the firing temperature in the second firing step.
The firing time in the first firing step was 20 minutes, and the firing time in the second firing step was 5 minutes.
[0029]
The measurement of the adhesion strength between the protective glass layer and the conductor circuit was performed by the same measurement method as in the first embodiment.
As a result of the measurement, as shown in Table 1 and FIG. 3, the adhesion strength was as high as 10 kgf / 2 mm □ or more. That is, (first firing step, second firing step) = (550 ° C., 655 ° C.), (550 ° C., 665 ° C.), (600 ° C., 655 ° C.), (600 ° C., 665 ° C.), (600 ° C., In the case of a temperature condition of 675 ° C., excellent adhesion strength was obtained.
[0030]
In these temperature conditions, the protective glass layer exhibited excellent adhesion strength, as shown in FIG. 1, in the first firing step, the crystallized glass component 11 of the protective glass layer 1 is transferred to the conductor circuit 2, This is because the protective glass layer 1 and the conductor circuit 2 are bonded to each other through the diffusion layer 3 by the diffusion of the conductor component 21 of the conductor circuit 2 to the protective glass layer 1 to form the diffusion layer 3. .
[0031]
[Table 1]

[0032]
Embodiment 3
In this example, as shown in FIG. 4, the first firing step and the second firing step were continuously performed.
That is, first, a ceramic substrate having a protective glass layer formed on the surface of a conductor circuit was placed in a heating furnace. Next, the following first and second firing steps were performed.
That is, in the first firing step, the protective glass layer was fired at 600 ° C. As a result, the interdiffusion between the conductor component and the crystallized glass component proceeded in the state where the crystallized glass was melted.
[0033]
Subsequently, the temperature of the heating furnace was continuously raised to 665 ° C., and the second firing step was performed at this temperature to fire the protective glass layer. Thereby, the crystallized glass was crystallized.
Others are the same as in the first embodiment.
When the adhesion strength of the protective glass layer was measured for the ceramic circuit board of this example, it showed a high value of 10 kgf / 2 mm □ or more as in Example 1.
[0034]
Embodiment 4
In this example, the relationship between the firing time of the first firing step and the adhesion strength of the protective glass layer was measured.
In the measurement, the firing temperature in the first firing step was 600 ° C., and the firing time was variously changed. The firing temperature in the second firing step was 675 ° C., and the firing time was 5 minutes. Otherwise, a ceramic circuit board was manufactured under the same conditions as in the first embodiment.
With respect to the obtained ceramic circuit board, the adhesion strength of the protective glass layer was measured, and the result is shown in FIG.
[0035]
As a result, in the first firing step, when the firing time was 1 minute, it was about 1.5 kgf / 2 mm □. The adhesion strength of the protective glass layer was increased as the length increased from 1 to 10 minutes. After 10 minutes or more, the adhesion strength maintained a high value of 10 kgf / 2 mm □ or more. From this, it can be seen that in the first firing step, high adhesion strength can be obtained by firing for 10 minutes or more.
[0036]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it can provide the manufacturing method of a ceramic circuit board which has a conductor circuit with low conductor resistance and high solder adhesiveness, and high adhesive strength between a conductor circuit and a protective glass layer. .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing mutual diffusion of a crystallized glass component and a conductor component at an interface between a conductor circuit and a protective glass layer in the present invention.
2 is a cross-sectional view of a ceramic circuit board in Embodiment 1. FIG.
FIG. 3 is a view showing the adhesion strength of a protective glass layer to a conductor circuit in Embodiment 2;
4 is an explanatory view showing a method for firing a protective glass layer in Embodiment 3. FIG.
5 is a graph showing the relationship between the firing time of the first firing step and the adhesion strength of the protective glass layer to the conductor circuit in Embodiment Example 4. FIG.
FIG. 6 is a cross-sectional view of a ceramic circuit board on which a conductor circuit is formed by a printing method in a conventional example.
FIG. 7 is a cross-sectional view of a ceramic circuit board on which a conductor circuit is formed by plating in a conventional example.
[Explanation of symbols]
1. . . Protective glass layer,
11. . . Crystallized glass component,
2. . . Conductor circuit,
21. . . Conductor component,
22. . . interface,
26. . . Copper plating,
27. . . Conductor pattern,
3. . . Diffusion layer.
5. . . Ceramic substrate,
7). . . Ceramic circuit board,

Claims (6)

A conductor circuit made of metal is formed on a ceramic substrate,
Next, a method for producing a ceramic circuit board comprising forming a protective glass layer made of crystallized glass on the surface of the conductor circuit, and firing the protective glass layer,
Firing the protective glass layer includes a first firing step of firing the protective glass layer at a temperature that is 50 ° C. lower than the softening point of the crystallized glass and less than the crystallizing point of the crystallized glass. Done,
Then, the manufacturing method of the ceramic circuit board characterized by performing the 2nd baking process which bakes the said protective glass layer within the range of the temperature required to crystallize the said crystallized glass. 2. The method of manufacturing a ceramic circuit board according to claim 1, wherein the firing time of the first firing step is 10 minutes or more. 3. The method of manufacturing a ceramic circuit board according to claim 1, wherein the crystallized glass used for the protective glass layer is a lead borosilicate crystallized glass. 4. The method for manufacturing a ceramic circuit board according to claim 1, wherein the conductor circuit is formed on the ceramic substrate by metal plating. 5. The method of manufacturing a ceramic circuit board according to claim 1, wherein the conductor circuit is formed by metal plating on a metal containing W or Mo as a main component. 6. The method of manufacturing a ceramic circuit board according to claim 1, wherein the ceramic substrate is alumina.

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