JP2681328B2 - Circuit board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a circuit board for accurately forming a wiring pattern on a ceramic substrate.

[0002]

2. Description of the Related Art Conventionally, VTR (video tape recorder)
Electronic components are mounted inside electronic devices such as computers and personal computers. As the electronic component, there is one using a ceramic substrate that can be fired at a low temperature of 800 to 1000 ° C. (Japanese Patent Publication No. 3-53269). The low temperature fired ceramics substrate has a smaller thermal expansion coefficient and dielectric constant than the alumina substrate, and is superior in heat resistance and mechanical strength to the resin substrate.

In order to manufacture a circuit board using a ceramics substrate, wiring patterns are formed on both sides of the circuit board, and a plurality of ceramics boards provided with via holes for electrical conduction on both sides are prepared. Laminate and join.
As a result, a circuit board having wiring patterns on both sides and inside of the ceramic substrate can be obtained.

Next, a method of manufacturing the above conventional circuit board will be described. First, a green sheet for forming a ceramics substrate containing glass is prepared. Next, a via hole is bored and a conductor is filled in the via hole. Next, the wiring pattern is printed on the green sheet.
In this way, a plurality of green sheets having a wiring pattern are produced. After that, these green sheets are laminated and fired at 800 to 1000 ° C. This gives
A circuit board is obtained.

[0005]

However, the above-mentioned method for manufacturing a circuit board has the following problems. That is, as shown in FIG. 10, a plurality of ceramic substrates 99, 98
In the case of stacking, the height difference of the wiring pattern 59 causes a height difference between the design substrate 980 and the ceramics substrate 98.

Therefore, when the wiring pattern 58 is formed on the ceramic substrate 98 as shown in FIG.
Due to the difference in height of the ceramic substrate 98, an error of ± 10 μm or more occurs in the width of the wiring pattern 58 with respect to the design pattern 580, and a blur 581 or a defect 582 may be formed. Further, when the wiring pattern is provided with a resistor, an error of ± 25% or more occurs in the resistance value, which may reduce the resistance trimming yield.

As another manufacturing method, there is a method of forming a circuit board in the same manner as the manufacturing method described above, using a fired ceramics substrate obtained by firing a green sheet in advance. However, in this case, since the solvent in the paste for forming the wiring pattern is not absorbed by the firing ceramics substrate on the front surface and the back surface of the firing ceramics substrate, the wiring pattern cannot be formed accurately. Besides, there are the same problems as described above. In view of the above problems, the present invention aims to provide a method of manufacturing a circuit board that can form a wiring pattern with high accuracy.

[0008]

According to a first aspect of the present invention, a green sheet for forming a low temperature sinterable ceramic substrate containing glass and a transfer sheet that does not sinter at the sintering temperature of the green sheet are prepared. A preparatory step for printing, a printing step for printing a wiring pattern such as a conductor or a resistor on the transfer sheet, and a sheet stacking step for stacking the transfer sheet on the green sheet and thermocompressing to obtain a laminate. By firing the laminated plate at the sintering temperature of the green sheet, the green sheet is sintered to obtain a ceramic substrate, and the wiring pattern on the transfer sheet is transferred to the ceramic substrate side to form a fired plate. It is characterized by comprising a sintering transfer step for obtaining and a removing step for obtaining a circuit board by removing the transfer sheet from the firing plate. In the manufacturing method of the circuit board to be.

What is most noticeable in the first invention is that the transfer sheet is laminated on the green sheet, fired to transfer the wiring pattern to the ceramic substrate, and then the transfer sheet is removed. The sintering temperature of the laminated plate is preferably 1000 ° C. or lower. 1000
If the temperature exceeds ℃, it is difficult to use noble metal for the material of the wiring pattern. The green sheet is a green sheet for forming a ceramic substrate containing glass and can be sintered at a low temperature of 800 ° C to 1000 ° C. The green sheet can be formed by the doctor blade method.

The transfer sheet does not sinter at the sintering temperature of the green sheet and has good printability. The transfer sheet is a green body formed by molding a mixture of a powder of alumina, zirconia, mullite or the like and a binder.
The transfer sheet preferably has a thickness of 100 μm to 1000 μm. If it is less than 100 μm, it is difficult to handle and the transfer sheet may be deformed. 1
If it exceeds 000 μm, there is a problem of debinding.

Further, in the above invention, the green sheet may be attached to a firing substrate that has been fired in advance, and a wiring pattern may be formed on the green sheet by using a transfer sheet. The firing substrate is fired at a temperature higher than the sintering temperature of the green sheet. An alumina substrate, a zirconia substrate, an aluminum nitride substrate or the like is used as the firing substrate.

A second aspect of the present invention is a preparatory step of preparing a green sheet for forming a low temperature sinterable ceramic substrate containing glass and a transfer sheet which is not sintered at the sintering temperature of the green sheet. And a printing step of printing a wiring pattern such as a conductor or a resistor on the transfer sheet, and firing the green sheet at a sintering temperature of the green sheet to sinter the green sheet to obtain a ceramic substrate. A sintering step, a sheet laminating step in which the transfer sheet is laminated on the ceramic substrate obtained in the sintering step, and a laminated plate is obtained by thermocompression bonding, and the lamination is performed at a sintering temperature of the green sheet. A transfer step of transferring the wiring pattern on the transfer sheet to the ceramic substrate side by baking the plate to obtain a baked plate; In the manufacturing method of the circuit board, characterized in that the more the removal step to obtain a circuit board by removing the transfer sheet from the plate.

According to the first aspect of the present invention, a ceramic substrate is prepared by firing the green sheet at a sintering temperature in advance, and then a transfer sheet is laminated on the ceramic substrate and thermocompression bonding is performed. Is. Others are the same as the first invention.

A third aspect of the invention is a printing step of printing a wiring pattern such as a conductor or a resistor on a transfer sheet,
An intermediate layer applying step of applying an intermediate layer containing a glassy material on a ceramic substrate that has been fired in advance and drying, and a laminated board by placing the transfer sheet on the intermediate layer and thermocompression bonding And a sheet baking step in which the intermediate layer is softened and the wiring pattern on the transfer sheet is transferred to the intermediate layer side by firing the laminated sheet at a temperature at which the intermediate layer softens. And a removing step of removing the transfer sheet from the firing plate to obtain a circuit board.

In the present invention, an intermediate layer containing glass is formed on a ceramic substrate that has been fired in advance.
After placing a transfer sheet on which a wiring pattern is printed, it is baked at a temperature at which the intermediate layer softens. The intermediate layer is in a paste form before coating and has a vitreous substance and a binder. The intermediate layer is applied by screen printing. The intermediate layer is preferably one that can be fired at a low temperature of 1000 ° C. or lower. If the temperature exceeds 1000 ° C, it is difficult to use a noble metal as a material for the wiring pattern. Others are the same as the first invention.

[0016]

In the first aspect of the invention, since the transfer sheet absorbs the solvent in the wiring pattern, the solvent does not flow out from the wiring pattern. Therefore, the wiring pattern can be accurately printed on the transfer sheet.
Therefore, according to the transfer sheet, the wiring pattern can be accurately transferred onto the surface of the circuit board.

In the sintering transfer process, the laminated plate is fired at the sintering temperature of the green sheet to obtain a fired plate.
Therefore, the glass material contained in the green sheet softens and joins with the wiring pattern on the transfer sheet. On the other hand, in the sintering transfer step, the transfer sheet is not sintered and the binder in the transfer sheet is decomposed. Therefore, the transfer sheet becomes brittle and easily peels off.

Therefore, in the next removing step, the transfer sheet can be easily removed by merely tapping the firing plate. Further, in the present invention, since the wiring pattern of the transfer sheet is transferred to the flexible green sheet, the wiring pattern can be accurately formed on the circuit board.

Further, in the second invention, since the wiring pattern is transferred by the flexible transfer sheet,
The wiring pattern can be accurately formed. In the third aspect of the invention, the intermediate layer is formed on the ceramic substrate, the transfer sheet on which the wiring pattern is printed is placed on the intermediate layer, and then the intermediate layer is fired at the softening temperature of the intermediate layer. Therefore, the softened intermediate layer adheres to the wiring pattern to form the wiring pattern on the surface of the ceramic substrate. Besides, the same effects as the first invention can be obtained. Therefore, according to the inventions of the first to third aspects, it is possible to provide a method of manufacturing a circuit board, which can easily form an accurate wiring pattern.

[0020]

EXAMPLES Example 1 An example according to the present invention will be described with reference to FIGS. The circuit board manufactured according to this example is obtained by stacking green sheets, integrating them, and firing them. As shown in FIG. 5, the circuit board 991 includes the ceramic boards 91, 92, 93 and the wiring patterns 51, 52.
And via hole 90. Ceramic substrate 9
Wiring patterns 51 are formed on the surfaces of the wires 1, 92. Wiring patterns 52 are formed on both surfaces of the circuit board 991.

A method of manufacturing the circuit board of this example will be described. First, in the preparation process, the ceramic substrate 9
Green sheets 910, 920, 9 for 1, 92, 93
Create 30. When making the green sheet 910, CaO—Al ₂ O ₃ --Si as glass is used.
O ₂ --B ₂ O ₃ based glass 60% by weight (hereinafter referred to as%)
A solvent, a binder, and a plasticizer are added to a mixed powder of a ceramic substrate material composed of 40% alumina and 40% alumina, and the mixture is kneaded to form a slurry.

Next, using a conventional doctor blade method, as shown in FIG. 1 (a), a green sheet 9 having a thickness of 0.25 mm is prepared. Next, as shown in FIG. 1B, the green sheet 9 is cut into a 150 mm square, and a via hole 90 having a diameter of 0.2 mm necessary for forming a wiring pattern is formed.
Drilling. Next, as shown in FIG. 1C, the via hole 90 is filled with the silver-based conductor 5.

Next, as shown in FIG. 1D, a wiring pattern 51 is formed on the surface of the green sheet 9 by screen printing. As a result, the ceramic substrate 91
A green sheet 910 is obtained. The green sheets 920 and 930 are also created in the same manner as above. No wiring pattern is formed on the surface of the green sheet 930.

On the other hand, a transfer sheet is prepared by a printing process. That is, a solvent, a binder, and a plasticizer are added to a powder of alumina having an average particle size of 0.5 μm and kneaded to form a slurry. Next, a transfer sheet having a thickness of 0.4 mm is formed by a conventional doctor blade method. Then, the transfer sheet is cut into 150 mm square. Next, as shown in FIG. 2, wiring patterns 52 to be formed on both surfaces of the circuit board are printed on the transfer sheet 1.

Next, in the sheet laminating step, as shown in FIG. 3, green sheets 910, 920 and 930 are laminated in order from the bottom. Then, the transfer sheet 1 is placed on the back surface of the green sheet 910 and the front surface of the green sheet 930. These are aligned and thermocompression-bonded using a mold under the conditions of 100 ° C., 50 kg / cm ² , and 20 seconds to be integrated to obtain a laminated plate.

Next, in the sintering transfer process, the laminated plate is fired in air at 900 ° C. for 20 minutes. This gives
As shown in FIG. 4, the green sheets 910, 920, 9
30 is sintered and the ceramic substrates 91, 92, 93 are integrated. At the same time, the wiring pattern 52 on the transfer sheet 1 is changed to the ceramic substrate 9
It is transferred to the back surface of No. 1 and the front surface of the ceramic substrate 93. At this time, the transfer sheet 1 is not sintered. In the removing step, the unsintered transfer sheet 1 is lightly tapped to remove the circuit board 991 shown in FIG.

Next, the operation and effect of this embodiment will be described. In this example, since the transfer sheet 1 absorbs the solvent in the wiring pattern 52, the solvent in the paste for the wiring pattern 52 does not flow out. Therefore, the wiring pattern 52 can be accurately printed on the transfer sheet 1. Therefore, according to the transfer sheet 1, the circuit board 99
The wiring pattern 52 can be accurately transferred to both surfaces of 1.

In the sintering transfer process, the laminated plate is fired at the sintering temperature of the green sheets 910, 920, 930 to obtain a fired plate. Therefore, the vitreous material contained in the green sheet is softened and bonded to the wiring pattern on the transfer sheet 1. On the other hand, in the above-mentioned sintering transfer process, the transfer sheet 1 is not sintered and the binder in the transfer sheet 1 is decomposed. Therefore, the transfer sheet 1 becomes brittle and easily peels off. Therefore, in the next removing step, the transfer sheet 1 can be easily removed by merely tapping the baking plate.

Example 2 In this example, the green sheet in Example 1 is formed by printing on a separately prepared firing substrate. As shown in FIG. 7, the circuit board 992 manufactured by this example is
A ceramic substrate 94 is integrally thermocompressed and laminated on the surface of a fired substrate 95. Ceramic substrate 94
A wiring pattern 52 transferred using a transfer sheet is formed on the surface of the.

Next, the manufacturing method of this example will be described.
First, in the preparation process, as shown in FIG.
The green sheet 9 for the ceramics substrate 94 is formed on the surface of an alumina substrate which has already been fired as the firing substrate 95.
40 is formed.

In forming the green sheet 940, a mixed powder of a ceramic substrate material composed of 75% CaO--Al ₂ O ₃ --SiO ₂ --B ₂ O ₃ glass and 25% alumina, a solvent, a binder, And a plasticizer are added and kneaded to form a slurry. Next, a green sheet 940 having a thickness of 0.25 mm is applied to the surface of the fired substrate 95 by using a conventional doctor blade method.

Next, in the sheet laminating step, as shown in FIG.
As shown in (b), on the surface of the green sheet 940,
The transfer sheet 1 similar to that in the first embodiment is placed. These are treated in the same manner as in Example 1 at 100 ° C., 50 kg / cm ² , 20
Thermocompression bonding is performed under the condition of second for integration to obtain a laminated plate. Next, in the transfer step, as shown in FIG. 6C, the laminated plate is baked in air at 900 ° C. for 20 minutes.

As a result, the green sheet 940 is sintered and the ceramic substrate 94 integrated with the fired substrate 95 is formed.
And the wiring pattern 5 on the transfer sheet 1 is obtained.
2 is transferred to the surface of the ceramic substrate 94. At this time, the transfer sheet 1 is not sintered.

Next, in the removing step, the unsintered transfer sheet 1 is removed to obtain the circuit board 992 shown in FIG. Others are the same as the first embodiment. In addition, the same effects as in the first embodiment can be obtained.

Embodiment 3 This embodiment is different from Embodiment 1 in that, as shown in FIG. 8, before the sheet laminating step, the green sheets 910, 920, 9 are formed.
Sintering step of obtaining ceramic substrates 91, 92, 93 by previously firing 30 (see FIG. 3 and the like hereinafter) is performed. That is, in the preparation process and the printing process, as in the first embodiment,
A green sheet and a transfer sheet that is not fired at the sintering temperature of the green sheet are prepared, and a wiring pattern is printed on the transfer sheet.

On the other hand, in the sintering process, as shown in FIG. 8A, the green sheets 910, 920, 930 are formed.
Only the layers are stacked in order from the bottom, aligned, and fired to form an integrated ceramic substrate 91, 92,
Get 93. As described in the first embodiment, the green sheet has a via hole 9 filled with the silver-based conductor 5.
0 and the wiring pattern 51 (see FIG. 1). At the time of the above firing, thermocompression bonding was performed under the conditions of 100 ° C., 50 kg / cm ² , and 20 seconds for integration, and further in air at 870 ° C. and 20 ° C.
Bake under the condition of minutes.

Next, in the sheet laminating step, as shown in FIG.
As shown in (b), the transfer sheet 1 is placed on the back surface of the ceramics substrate 91 and the front surface of the ceramics substrate 93 in the above-mentioned laminated plate to perform alignment. / Cm ² , 20 seconds, thermocompression bonding, ceramics substrate 91, 92, 93
And a transfer sheet 1 is obtained.

Next, in the transfer step, the laminated plate is baked in air at 900 ° C. for 20 minutes. As a result, the wiring pattern 52 on the transfer sheet 1 is transferred to the back surface of the ceramic substrate 91 and the front surface of the ceramic substrate 93. At this time, the transfer sheet 1 is not sintered.

Then, in the removing step, the unsintered transfer sheet 1 is removed (see FIG. 5) to obtain the circuit board of this example. The obtained circuit board is the same as in Example 1. In this example, since the wiring pattern 52 is transferred by the flexible transfer sheet 1, the wiring pattern 52 is accurately transferred.
Can be formed. In addition, the same effects as in the first embodiment can be obtained.

Example 4 In the circuit board according to this example, as shown in FIG. 9, an intermediate layer 96 containing glass is formed on a ceramic substrate 97 which has been fired in advance, and a wiring pattern 52 is printed on the intermediate layer 96. After the transfer sheet 1 is placed, it is baked at the softening temperature of the intermediate layer 96. The intermediate layer 96 is in paste form before coating and can be fired at a low temperature of 1000 ° C. or lower. The intermediate layer has a glass material and a binder. The intermediate layer 96 is applied by screen printing.

Next, the manufacturing method of this example will be described.
First, in a printing process, as shown in FIG. 9A, a wiring pattern 5 such as a conductor or a resistor is formed on the transfer sheet 1.
Print 2. In addition, in the intermediate layer coating step, as shown in FIG.
As shown in (b), a glass substrate-containing intermediate layer 96 is applied onto a pre-fired ceramics substrate 97 by a screen printing method and dried. The ceramics substrate 97 is a firing substrate of a ceramics substrate material composed of 75% CaO—Al ₂ O ₃ —SiO ₂ —B ₂ O ₃ based glass and 25% alumina. The intermediate layer 96 is obtained by adding a solvent and a binder to the mixed powder of the ceramic substrate material,
It is obtained by kneading. Then, similarly to the third embodiment, the stacking process, the transfer process, and the removing process are performed. As a result, the circuit board 994 shown in FIG. 9C is obtained.

Next, the function and effect of this example will be described. In this example, the intermediate layer 96 is formed on the ceramic substrate 97.
Is formed, and the transfer sheet 1 having the wiring pattern 52 printed thereon is placed thereon, and then baked at the softening temperature of the intermediate layer 96. Therefore, the softened intermediate layer 96 adheres to the wiring pattern 52, and the wiring pattern 52 is formed on the surface of the ceramic substrate 97. In addition, the same effects as in the first embodiment can be obtained.

Experimental Example 1 In this example, the difference between the wiring pattern width and the unevenness of the circuit board manufactured in Examples 1, 3 and 4 and the design pattern was measured. For comparison, Comparative Examples 1 to 3
The circuit board according to Example 1 was manufactured without using the transfer sheet 1, and the same measurement was performed as above. In Comparative Example 1, the green sheet 910, 920, 930 was printed with the random wiring patterns 51, 52 and then fired at 800 to 1000 ° C. to obtain ceramic substrates 91, 92, 93 (see FIG. 5). Others are the same as the first embodiment.

Comparative Example 2 differs from Example 3 in that the wiring pattern 52 is printed on the pre-sintered ceramic substrates 91, 92, 93, and the other points are the same as in Example 3 (see FIG. 5). In Comparative Example 3, the wiring pattern 52 was directly printed on the surface of the ceramic substrate 97 in Example 4.
Other than that, the other points are the same as in the fourth embodiment (see FIG. 9).

The results of the above measurements are shown in Table 1. In the table, the difference from the design pattern refers to the average increase in the width of the wiring pattern with respect to the design pattern. Further, the maximum blurring is the largest blurring 581. Also,
The largest defect is the largest defect 582 (see FIG. 11).

As is known from Table 1, the difference from the design pattern width is 2 μm in each of Examples 1, 3 and 4.
It was a little as m. On the other hand, in Comparative Examples 2 and 3, the width of the wiring pattern increased by 10 μm or more. The maximum bleeding was as small as 5 to 7 μm in Examples 1, 3, and 4.
On the other hand, in each of Comparative Examples 1 to 3, bleeding of 50 μm or more occurred. Regarding maximum loss, Examples 1 to 3 are 10
On the other hand, Comparative Examples 2 and 3 had defects of 40 μm or more.

Experimental Example 2 In this example, the above-mentioned Examples 1 and 3 and Comparative Examples 1 and 2 were used.
In addition, we measured the variation in resistance when a resistor was installed as a type of wiring pattern. Since the resistance value is proportional to the volume of the resistor, it is possible to know the change in the volume of the resistor when it is mounted by measuring the variation in the resistance value. This measurement was performed by a conventional method. Table 2 shows the results.

As is known from Table 2, the resistance values of Examples 1 and 3 were 20% or less, and the resistance values of Comparative Examples 1 and 3 were 30% or more. Therefore, also from this example, it is understood that according to Examples 1 and 3, the wiring pattern can be formed with high accuracy.

[0049]

[Table 1]

[Table 2]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a green sheet manufacturing process according to a first embodiment.

FIG. 2 is an explanatory diagram of a transfer sheet manufacturing process according to the first embodiment.

3 is an explanatory view of the manufacturing process at the time of stacking, following FIG. 1 and FIG.

FIG. 4 is an explanatory view of the manufacturing process after firing following FIG.

5 is a cross-sectional view of a circuit board manufactured by the manufacturing method of Example 1. FIG.

6A and 6B are manufacturing process explanatory diagrams illustrating the manufacturing method of the second embodiment.

FIG. 7 is a cross-sectional view of a circuit board manufactured by the manufacturing method according to the second embodiment.

FIG. 8 is a manufacturing process explanatory view showing the manufacturing method of Example 3;

FIG. 9 is a manufacturing process explanatory view showing the manufacturing method of Example 4;

FIG. 10 is a sectional view of a circuit board according to a conventional example.

FIG. 11 is a plan view of a circuit board according to a conventional example.

[Explanation of symbols]

1. . . Transfer sheet, 5. . . Silver-based conductor, 51, 52. . . Wiring pattern, 9, 910, 920, 930, 940. . . Green sheet, 91, 92, 93, 94, 97. . . Ceramics substrate, 95. . . Baked substrate, 96. . . Middle layer, 991, 992, 994. . . Circuit board,

Claims (3)

(57) [Claims] 1. A preparatory step of preparing a green sheet for forming a low temperature sinterable ceramics substrate containing glass and a transfer sheet which does not sinter at the sintering temperature of the green sheet, and the transfer sheet. A printing step of printing a wiring pattern such as a conductor or a resistor on the green sheet; a sheet laminating step of laminating the transfer sheet on the green sheet and thermocompression bonding to obtain a laminated plate; and a sintering temperature of the green sheet. A sintering transfer step of firing the laminated plate to sinter the green sheet to obtain a ceramics substrate, and also to transfer a wiring pattern on the transfer sheet to the ceramics substrate side to obtain a fired plate. A method of manufacturing a circuit board, comprising: a removal step of removing the transfer sheet from the plate to obtain a circuit board. 2. A preparatory step of preparing a green sheet for forming a low temperature sinterable ceramics substrate containing glass and a transfer sheet which is not sintered at the sintering temperature of the green sheet, and the transfer sheet. A printing step of printing a wiring pattern such as a conductor or a resistor on the green sheet, and a sintering step of firing the green sheet at a sintering temperature of the green sheet to sinter the green sheet to obtain a ceramic substrate. By laminating the transfer sheet on the ceramic substrate obtained in the sintering step and thermocompression-bonding the laminated sheet, a sheet laminating step is performed, and by firing the laminated sheet at the sintering temperature of the green sheet. A transfer step of transferring the wiring pattern on the transfer sheet to the ceramic substrate side to obtain a fired plate, and Method of manufacturing a circuit board, characterized in that the use sheet is removed becomes more and removing step to obtain a circuit board. 3. A printing step of printing a wiring pattern such as a conductor or a resistor on a transfer sheet, and an intermediate layer applying step of applying an intermediate layer containing glass on a ceramic substrate that has been fired in advance and drying it. A sheet laminating step of obtaining the laminated sheet by placing the transfer sheet on the intermediate layer and thermocompression bonding, and firing the laminated sheet at a temperature at which the intermediate layer softens A transfer process of softening the layer and transferring the wiring pattern on the transfer sheet to the intermediate layer side to obtain a fired plate, and a removing process of removing the transfer sheet from the fired plate to obtain a circuit board. A method of manufacturing a circuit board, comprising: