JPH06132664A - Manufacture of ceramic multilayer board - Google Patents

Abstract

PURPOSE:To prevent a laminated body from warping, peeling, swelling, etc., when the laminated body is being dried and surely manufacture a large multilayer board which is 60-300mm in one side length L, 0.1-20mm in thickness T. CONSTITUTION:A speed of temperature increase for drying a green sheet laminated body 4 is set in a range of 0. 1-10 deg.C/min. Within the range of such temperature increase speed, lower temperature increase speed is set for the longer length of one side length L and the thicker T of the green sheet laminated body 4. The green sheet laminated body 4 is fired after it is dried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic multilayer substrate.

[0002]

2. Description of the Related Art Conventionally, a multilayer substrate of this type is manufactured by the following method. First, ceramic powder,
A green sheet is produced by molding a mixture of a sintering aid, a binder, a solvent and the like. A paste containing a conductive metal such as tungsten, a binder and a solvent is printed on the green sheet, and as a result, a conductor circuit in a through hole is formed on the green sheet. Further, the green sheets are laminated and pressure-bonded, and the obtained green sheet laminate is fired at a high temperature.

The green sheet and paste in the laminate contain the volatile solvent as described above. It is known that when a large amount of this type of solvent remains in the laminate, the solvent causes delamination, warpage, cracks and the like of the sheet during firing. Therefore, in order to avoid these disadvantages, it is necessary to sufficiently remove the volatile solvent from the laminate before firing.

Therefore, before the firing process,
A drying process is performed in which the green sheet laminate is kept at a temperature at which the volatile solvent vaporizes. For example, in the case of the conventional general size green sheet laminate (tens of mm
In the case of a square and a thickness of 5 mm), a method of drying the laminate for 24 hours at about a hundred and several tens of degrees Celsius is adopted. Further, it is said that the temperature rising rate at that time is preferably set to about 15 ° C./minute.

[0005]

By the way, in recent years, a technique of producing a large green sheet over 100 mm square and drying and firing a laminate using the green sheet has begun to appear. ing. The advantage of this method is that a plurality of multilayer substrates can be taken from one by cutting the sintered laminated body. Therefore, the method has been attracting attention as an effective method that can reduce the manufacturing cost of the multilayer substrate.

However, when a large green sheet laminate is dried under the same conditions as in the conventional case, the solvent vaporized in the laminate suddenly flows out and the laminate is warped. Further, peeling may occur at the outer edge portion of the green sheet due to the outflow of the solvent, or swelling may occur in the laminate due to peeling at the central portion of the green sheet.

When the delaminated and swollen laminate is subjected to degreasing and firing, cracks are generated from the portion,
As a result, the laminate is destroyed. Further, even if the laminated body is not destroyed, the shrinkage ratio varies in each part of the laminated body, so that it is extremely difficult to obtain a multilayer substrate with high dimensional accuracy.

On the other hand, it is known that the warp of the laminate can be corrected to some extent during degreasing and firing. However, if this type of correction work is performed, the number of steps increases, resulting in an increase in cost.
Further, even if the correction work is performed, the dimensional accuracy of the multilayer substrate may be adversely affected.

As a result of intensive studies conducted by the present inventors in view of the above circumstances, the conventional method was apt to cause peeling or the like of the laminate because the temperature rising rate during drying was inappropriately set. It turned out that Then, they have found that the temperature rising rate during drying may be set slower than the conventional one, and the temperature rising rate may be slowed down as the laminated body becomes larger. Then, the present inventors have completed the following inventions based on this knowledge.

It is an object of the present invention to prevent warp, peeling or swelling of a laminated body during drying and to reliably manufacture a large-sized multi-layer substrate capable of being taken in large numbers. Another object of the present invention is to improve the dimensional accuracy of the multilayer substrate.

[0011]

In the present invention, therefore, the length of one side is 60 mm to 300 mm and the thickness is 0.1 mm to 20.
A method for manufacturing a ceramic multi-layer substrate, comprising drying a green sheet laminate having a size of 10 mm and then firing the laminate, wherein a temperature rising rate during drying is in the range of 0.1 ° C / min to 10 ° C / min. Within the range of the temperature rising rate,
The heating rate is set slower as the length and thickness of one side of the green sheet laminate are larger.

More specifically, it is desirable that the temperature rising rate be set within the range shown in Table 1 below.

[0013]

[Table 1]

[0014]

According to this method, the rate of temperature rise during drying is set to be slower than in the prior art, so the amount of solvent volatilized per unit time in the laminate is also reduced. Therefore, unlike the conventional case, the vaporized solvent does not suddenly flow out of the laminate. Therefore, when dried, the laminate does not warp, peel off, or swell. Therefore, it becomes possible to reliably manufacture a large-sized multi-layer substrate capable of taking a large number of pieces.

Further, since the problems such as warp, peeling or swelling are solved, the dimensional accuracy of the multilayer substrate can be improved. In addition, as shown in the case of Table 1 above, the preferable range of the temperature rising rate is slightly different depending on the length and thickness of one side of the laminate. In each case, if the temperature rising rate is too fast, it becomes impossible to sufficiently prevent the warp, peeling and swelling of the substrate. On the other hand, if the temperature rising rate is too slow, the time until the drying step is completed will be long.

The method for manufacturing the ceramic multilayer substrate of the present invention will be described in detail below in the order of steps. Examples of the ceramic material used in the present invention include powders of aluminum nitride (AlN), alumina, silicon carbide, silicon nitride and the like. A predetermined amount of binder, sintering aid, solvent and the like are added to the ceramic powder. Examples of the solvent that can be used include ethanol, toluene, isopropyl alcohol, butanol, ethyl acetate and the like. By uniformly kneading the mixture, a raw material slurry for producing a green sheet is obtained. Then, the obtained green sheet is provided with a plurality of through-hole forming holes.

A conductive metal paste is printed on the green sheet, and the paste forms a conductor circuit on the surface of the green sheet and in the through-hole forming holes.
The paste is obtained by mixing and kneading a powder of a conductive metal such as tungsten, molybdenum, tantalum, and niobium, which is a main component, a binder, a solvent, and the like. Examples of the solvent that can be used include normal butyl methacrylate and α-terpineol.

The green sheet on which the conductor circuit is formed is
After being appropriately laminated, they are thermocompression bonded. Then, a large green sheet laminate having a side length of 60 mm to 300 mm and a thickness of 0.1 mm to 20 mm is manufactured.

Next, the laminate is set in a dryer and heated to a temperature at which the volatile solvent evaporates. At this time, the temperature inside the dryer is raised at a rate of 0.1 ° C / minute to 10 ° C / minute. Then, after reaching the evaporation temperature of the solvent, the laminate is kept at that temperature for about 10 to 40 hours.

After removing the volatile solvent from the green sheet laminated body, the laminated body is further degreased, pre-baked and main-baked according to a conventional method.

[0021]

EXAMPLE An example in which the present invention is embodied in a method for producing a multilayer substrate made of AlN will be described in detail with reference to FIG.

In Example 1, A having an average particle size of 1.4 μm was used.
220 g of an acrylic binder, 50 g of Y ₂ O ₃ as a sintering aid, and 400 ml of an alcohol solvent were mixed with 1 kg of 1N powder. By uniformly kneading this mixture with a ball mill, a highly viscous raw material slurry was prepared. Then, the green sheet 1 was formed into a sheet from the raw material slurry according to the doctor blade method (see FIG. 1 (a)). Further, by punching, a plurality of through-hole forming holes 2 are provided in the green sheet 1 (see FIG. 1 (b)).

Next, 100 g of tungsten powder having an average particle size of 3 μm was mixed with 2 g of an acrylic binder, 3 ml of an ether solvent, and 0.1 g of an ether dispersant. This mixture was uniformly kneaded with a three-roll mixer to obtain a tungsten paste P for forming a conductor circuit.

Then, the paste P was printed on the green sheet 1 using a screen printing machine. This paste P
As a result, as shown in FIG. 1C, the conductor circuits 3a, 3 are formed in the through-hole forming hole 2 and on the surface of the green sheet 1.
b was formed.

After stacking a plurality of the green sheets 1, a pressing force is applied in the thickness direction thereof so that the green sheets 1 are thermocompression-bonded to each other. Then, a large green sheet laminate 4 having a length L of 90 mm and a thickness T of 4.0 mm was produced (see FIG. 1 (d)).

Next, the green sheet laminate 4 was placed in a dryer, and the laminate 4 was heated at a temperature rising rate of 5.0 ° C./min. Then, after the temperature inside the dryer reached 150 ° C., the temperature was kept for about 24 hours to sufficiently dry the laminated body 4. Then, the laminated body 4 was stood to cool to room temperature.

Subsequently, the laminated body 4 is placed under an inert atmosphere for 1
Degreasing and calcination were performed at 600 ° C. for 5 hours. Further, the calcined laminated body 4 was main-baked at 1850 ° C. for 3 hours in the same atmosphere. The AlN multilayer substrate of Example 1 was manufactured through the series of steps described above.

Then, basically following the manufacturing method of Example 1, several AlN multilayer substrates similar to those of Example 1 were manufactured. However, in manufacturing these multilayer substrates, the length L (mm) and thickness T (mm) of one side of the green sheet laminate 4 and the temperature rising rate (° C / min) during drying were slightly changed.

That is, as shown in Table 2, in Example 2, the length L of one side, the thickness T, and the rate of temperature increase v are each 150
mm, 4.0 mm, and 2.0 ° C./min. And so on
In Example 3, L = 250 mm, T = 4.0 mm, v = 0.
5 ° C./minute, and in Example 4, L = 150 mm, T =
The setting was 1.0 mm and v = 5.0 ° C./min. In Example 5, L = 150 mm, T = 10 mm, and v = 0.5 ° C./minute. The composition of the green sheets and the paste, the drying time of the laminated body, the degreasing of the laminated body, the preliminary firing, the firing conditions, and the like are all in accordance with Example 1.

Further, for the purpose of determining the quality of the multilayer substrate of each of Examples 1 to 5, each laminate was observed after the drying step, and whether or not warp, peeling, bulge or the like had occurred. I investigated. Then, the quality of each multilayer substrate was judged based on the results of these investigations.

Further, multilayer substrates of Comparative Examples 1 to 3 corresponding to the above Examples 1 to 5 were manufactured. As shown in Table 2,
In each of Comparative Examples 1 to 3, according to the conventional manufacturing method, the temperature rising rate v was set to 15 ° C./min to dry the laminate. The length L and the thickness T of one side of the laminated body were 9 in Comparative Example 1.
0 mm and 1.0 mm, 150 mm and 1.0 mm in Comparative Example 2, and 250 mm and 1.0 mm in Comparative Example 3 (see Table 2). The same investigation was conducted on the multilayer substrate of each comparative example. The results are shown together in Table 2.

[0032]

[Table 2]

As is clear from Table 2, each of Examples 1 to 5 is
No particular physical change was observed in the laminated body of.
Furthermore, when the observation and investigation were conducted again after firing, no change was observed. Therefore, it was possible to obtain excellent dimensional accuracy despite the large-sized multilayer substrate.

On the contrary, in each of Comparative Examples 1 to 3, it was confirmed that warp, peeling, bulging, etc. occurred in all the laminated bodies. Then, as a result of observation and inspection after firing, cracks were observed particularly in many of the multi-layered substrates in which the sheet was peeled. Further, also in the laminates which did not cause the generation of cracks, very few laminates had the same dimensional accuracy as in the above-mentioned examples.

The present invention is not limited to the above embodiment, but can be modified as follows. For example, the atmosphere for drying the laminated body 4 may be either an oxidizing atmosphere such as air or a non-oxidizing atmosphere such as nitrogen.

In this case, when giving priority to the oxidation prevention of the conductive metal in the paste, it is preferable to select a non-oxidizing atmosphere. Further, when priority is given to reduction of manufacturing cost and simplification of equipment, it is preferable to select an oxidizing atmosphere.

[0037]

As described above in detail, according to the method for manufacturing a ceramic multilayer substrate of the present invention, warpage, peeling, swelling and the like of the laminate during drying can be prevented, so that a large number of large pieces can be taken. It has an excellent effect that the multilayer substrate can be reliably manufactured.

Further, according to the manufacturing method of the present invention, there is an excellent effect that the dimensional accuracy of the multilayer substrate can be improved.

[Brief description of drawings]

1A to 1D are Al of the present invention (Example 1).
FIG. 7 is a schematic front cross-sectional view for explaining the manufacturing process of the N-made multilayer substrate.

[Explanation of symbols]

4 Green sheet laminate, L side length, T thickness.

Claims (1)

[Claims] 1. The length (L) of one side is 60 mm to 300 mm,
A method for manufacturing a ceramic multilayer substrate, comprising: drying a green sheet laminate (4) having a thickness (T) of 0.1 mm to 20 mm, and then firing the laminate (4). The temperature rate is set within the range of 0.1 ° C./min to 10 ° C./min, and the length (L) and the thickness of one side of the green sheet laminate (4) within the range of the temperature raising rate. A method for manufacturing a ceramic multilayer substrate, wherein the heating rate is set slower as (T) is larger.