JPH06132632A - Manufacture of ceramic board - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a ceramic board having excellent connecting reliability of a viahole to a conductor pattern. CONSTITUTION:Viaholes 90 are opened at a green sheet 81 for forming a ceramic board. Conductor films 11 are formed on wall of the viaholes 90 with their centers kept empty. Conductor patterns 12, 13 are formed at the sheet 81. Then, the green sheet 81 is covered with a sheet 2 on each side, compressed, and sintered at a given temperature, at which the sheets 2 cannot be sintered. Thereafter, the unsintered sheets 2 are removed by the baked element.

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 ceramic substrate having excellent connection reliability between via holes and conductor patterns.

[0002]

2. Description of the Related Art A ceramic substrate has excellent mechanical properties, high insulation resistance, and resistance to environments such as temperature and humidity, which are peculiar to ceramics. Utilizing this property, a ceramic substrate has been conventionally used as a substrate for mounting electronic components. As such a multilayer ceramic substrate 9, for example, as shown in FIG. 9, there is one in which ceramic substrates 97 to 99 in which via holes 90 and conductor patterns 58 and 59 are formed are laminated. The via hole conductor 5 is filled in the via hole 90.

In manufacturing the multilayer ceramic substrate, first, a green sheet for forming the ceramic substrate is prepared. Next, a via hole is formed in the green sheet, and the via hole conductor is filled therein. Then, a conductor pattern is printed on the surface of the green sheet. Then, the green sheet is sintered to obtain the multilayer ceramic substrate.

However, at the time of firing the green sheet, the green sheet is 10 to 30 in each of the three directions of length, width and thickness.
Shrinks with a dimensional error of about%. This shrinkage causes a problem that the formation position of the outer layer circuit formed on the ceramic substrate is displaced.

Therefore, in order to make the shrinkage rate constant, the applicant, as shown in FIG. 10, in a state where the green sheet 87 to 89 is press-bonded to the outermost layer of the green sheets 87 to 89 during the firing. I applied for a method of removing the unsintered sheet 2 after that (Japanese Patent Application No. 4-223190).
issue).

The unsintered sheet 2 is made of an alumina material and does not sinter at the sintering temperature of the green sheet. According to this method, the green sheet is restrained from shrinking in the vertical and horizontal directions by the unsintered sheet and shrinks only in the thickness direction. Therefore, the green sheet should be shrunk to a uniform thickness of 0.1% or less. You can

[0007]

[Problems to be Solved] However, according to the above conventional manufacturing method, when firing the green sheet,
As shown in FIG. 10, the wall surface of the via hole 90 is curved,
The gap 8 is formed in the via hole 90. Therefore, the connection reliability between the via hole 90 and the conductor patterns 58 and 59 deteriorates.

It is assumed that the via hole 90 is curved for the following reason. That is, during firing, the green sheets 87 to 89 are the green sheets 87 that have been thermocompression bonded.
This suppresses contraction in the vertical and horizontal directions, and contracts only in the thickness direction. However, the thickness direction of the green sheet is free from any constraint. Therefore, the via hole 90
The contraction in the vicinity of the center of the is large, causing a curving deformation. This shrinkage and bending increase as the overall thickness of the green sheet increases. In view of the above problems, the present invention aims to provide a method of manufacturing a ceramic substrate having excellent connection reliability between a via hole and a conductor pattern.

[0009]

According to the present invention, in a method of manufacturing a ceramic substrate having a via hole, a green sheet for forming the ceramic substrate and an unsintered sheet that does not sinter at the sintering temperature of the green sheet are prepared. First
Steps, a second step of forming a via hole in the green sheet, a third step of forming a conductor film on the wall surface of the via hole, and a third step of forming a void in the center thereof, and forming a conductor pattern on the green sheet And a fifth step of obtaining the pressure-bonded body by placing the green sheet above and below the green sheet and pressure-bonding it, and firing the pressure-bonded body at the sintering temperature of the green sheet. And a seventh step of removing the green sheet from the fired body, and a seventh step of removing the unsintered sheet from the fired body.

What is most noticeable in the present invention is that the conductor film is formed on the wall surface of the via hole and the central portion thereof is in a void state. In forming the conductor film, for example, the via hole conductor is filled into the via hole from the upper side of the ceramic substrate by screen printing, and at the same time, the conductor in the central portion of the via hole is sucked and removed from the lower side by a suction device. The via hole conductor is Ag
A system paste or the like is used.

The green sheet for forming the ceramics substrate is preferably a low temperature firing substrate material that can be sintered at 1000 ° C. or lower. The unsintered sheet does not sinter at the sintering temperature of the green sheet, and alumina, zirconia or the like is used. A multilayer body of ceramic substrates can be formed by stacking a plurality of the green sheets. In this case, the conductor pattern is
It can be formed inside or on the surface of the multilayer ceramic substrate.

[0012]

In the present invention, the conductor film is formed in advance on the wall surface of the via hole formed in the green sheet, and the central portion thereof is in a void state. Therefore, the conductor film is in close contact with the wall surface of the via hole, and even if the via hole is curved during firing of the green sheet, the conductor film is curved along with the wall surface of the via hole, and no gap is formed between the two.

Therefore, the conductor film is excellent in connection reliability with the conductor pattern formed on the surface of the ceramic substrate. Therefore, according to the present invention, it is possible to provide a method of manufacturing a ceramic substrate having excellent connection reliability between the via hole and the conductor pattern.

[0014]

EXAMPLES Example 1 An example according to the present invention will be described with reference to FIGS. This example is a method of manufacturing a multilayer ceramic substrate 9 including ceramic substrates 91 and 92 having via holes 90 as shown in FIG. Conductor patterns 12 and 13 are formed above and below the ceramic substrate 91. As shown in FIGS. 2 to 4, the ceramic substrate 91
The conductor patterns 12 and 13 are alternately electrically connected via the conductor film 11 filled in the via hole 90.

A method of manufacturing the above ceramic substrate will be described. First, in the first step, as shown in FIG. 5A, a green sheet 81 for forming a ceramic substrate 91 that can be sintered at 800 ° C. to 1000 ° C. is prepared. The green sheet is obtained by mixing ceramic powder, a binder, and a solvent and forming a sheet by the doctor blade method. The thickness of the green sheet is 0.
It is 36 mm.

The above ceramic powder is CaO--Al ₂ O.
It is a mixture of 60 parts by weight of _3- SiO ₂ --B ₂ O ₃ glass and 40 parts by weight of α-alumina, and is a powder having an average particle size of 2 μm. Butyral resin is used as the binder. As the solvent, for example, toluene, ethanol and dibutyl phthalate are used.

Next, as shown in FIG.
A 4 mm green sheet 2 is prepared. The green sheet 2
Is obtained by mixing α-alumina powder that is sintered at 1000 ° C. or higher in the same manner as the above green sheet to form a sheet. Average particle size of α-alumina powder is 1
μm. Then, in the second step, as shown in FIG. 5C, the green sheet 81 is formed by using a mold.
Then, a via hole 90 having a diameter of 0.3 mm is formed.

Next, in the third step, as shown in FIG. 5D, the conductor film 11 is formed on the wall surface of the via hole 90, and the central portion thereof is in a void state. In forming the conductor film 11, as shown in FIG. 8, the via hole conductor 10 is filled into the via hole 90 from the upper side of the green sheet 81 by the screen printing machine 3 and, at the same time, the via hole 90 of the via hole 90 is formed from the lower side thereof. Attract the via-hole conductor in the center.

The screen printing machine 3 has a pattern 31 having holes 310 of the same shape as the via holes 90 of the green sheet 81. The via-hole conductor 10 is placed on the pattern 31, and this is pushed out from the hole 310 by the squeegee 32. As a result, the via hole conductor 10 is filled in the via hole 90.

The suction device 4 has a vacuum chamber 40 and a chuck plate 41 provided at the upper opening of the vacuum chamber 40. The chuck plate 41 has a hole 410 having the same shape as the via hole 90 of the green sheet 81. Then, the green sheet 81 is placed on the chuck plate 41 to reduce the pressure in the vacuum chamber 40. As a result, the via hole conductor 10 at the center of the via hole 90 is sucked into the vacuum chamber 40, and the conductor film 11 remains only on the wall surface of the via hole 90.

The via-hole conductor 10 is in a paste form, and is obtained by mixing a mixed powder of Ag powder and ethyl cellulose as a binder with terpineol as a solvent. At the time of mixing, the above-mentioned mixed powder is uniformly dispersed by using a three-roll mixer. The average particle size of the mixed powder is 1 μm.

Next, in the fourth step, as shown in FIG. 5E, the conductor patterns 12 and 13 are printed on the front and back surfaces of the green sheet 81. The conductor pattern 12 is an outer layer pattern, and the conductor pattern 13 is an inner layer pattern. Further, the green sheet 82 for forming the ceramic substrate 92 is formed in the same manner as in the first step.

Next, the green sheet 81 processed by the first to fourth steps and the green sheet 82 formed by the first step are used to obtain an outer dimension 12 using a mold.
Punching into a 0 mm x 120 mm square shape. Next, in the fifth step, as shown in FIG.
2, 81 are laminated in order from the bottom, and the green sheet 2 is placed on the uppermost layer and the lowermost layer. Next, set these to 1
Thermocompression bonding is performed at 00 ° C. and a pressure of 100 Kg / cm ² to obtain a pressure bonded body 99.

Next, in a sixth step, the pressure-bonded body 99 is
Is baked at 900 ° C. for 20 minutes to bake the pressure-bonded body 99 to obtain a fired body. Next, in the seventh step, as shown in FIG. 7, the unsintered sheet 2 is removed from the fired body 98. As a result, the multilayer ceramic substrate 9 shown in FIGS. 1 to 4 is obtained.

Next, the conductivity of the conductor film 11 in the via hole 90 of the multilayer ceramic substrate manufactured as described above was evaluated. For comparison, a ceramic substrate (comparative example) as shown in FIG. 9 was prepared by filling the entire inside of the via hole with a via hole conductor and by the same method as described above. When measuring the electrical continuity of the conductor, a tester was used. When the resistance value was 100Ω or more, the electrical continuity was determined, and when it was less than 100Ω, the electrical conductivity was determined.

As a result, all the via holes of the examples according to the present invention were conductive. In the comparative example, the via hole was curved and a gap was formed between the via hole conductor and the conductor pattern connected to the via hole, so that there was no conductivity. As is known from the above, in the ceramic substrate of this example, the conductor film 11 is formed on the inner wall of the via hole 90 formed in the green sheets 81 and 82, and the central portion of the via hole 90 is in a void state.

Therefore, the conductor film 11 is in close contact with the wall surface of the via hole, and even if the via hole 90 is curved during firing of the green sheet, the conductor film 11 is curved along with the wall surface of the via hole 90, and a gap is generated between the two. do not do. Therefore, the ceramic substrate of this example has excellent connection reliability between the via hole and the conductor pattern.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multilayer ceramic substrate of Example 1.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a plan view of the multilayer ceramic substrate shown in FIG.

FIG. 4 is a sectional view taken along the line BB of FIG.

FIG. 5 is an explanatory view of the manufacturing process of the ceramic substrate of the first embodiment.

FIG. 6 is an explanatory view of the manufacturing process following FIG.

FIG. 7 is an explanatory view of the manufacturing process following FIG. 6;

FIG. 8 is an explanatory view showing a method of forming a conductor film in a via hole in the first embodiment.

FIG. 9 is a sectional view of a conventional ceramic substrate.

FIG. 10 is an explanatory diagram of a problem in the conventional example.

[Explanation of symbols]

 10. ． ． Via-hole conductor, 11. ． ． Conductor film, 12, 13. ． ． Conductor pattern, 2. ． ． Unsintered sheet, 9. ． ． Multi-layer ceramics substrate, 90. ． ． Beer hall, 91,92. ． ． Ceramic substrate, 81, 82. ． ． Green sheet, 98. ． ． Fired body, 99. ． ． Crimp body,

Claims (1)

[Claims] 1. A method of manufacturing a ceramic substrate having a via hole, comprising: a green sheet for forming the ceramic substrate;
A first step of preparing an unsintered sheet that does not sinter at the sintering temperature of the green sheet; a second step of forming a via hole in the green sheet; and forming a conductor film on the wall surface of the via hole, and A third step of forming a void in the central portion, a fourth step of forming a conductor pattern on the green sheet, and placing the unsintered sheet above and below the green sheet and crimping them Of the green sheet, a sixth step of firing the pressure-bonded body at a sintering temperature of the green sheet to obtain a fired body, and a seventh step of removing the unsintered sheet from the fired body. A method for manufacturing a ceramic substrate, comprising: