JPH04254478A - Production of multilayered ceramic substrate - Google Patents

Abstract

PURPOSE:To suppress a change in shrinkage coefft. between products by piling up plural green sheets belonging to different production lots in a prescribed order and firing them. CONSTITUTION:Green sheets 1a belonging to a production lot A, green sheets 1b belonging to a production lot B and green sheets 1c belonging to a production lot C are alternately piled up and fired to produce a multilayered ceramic substrate 2. Since the effect of characteristics of green sheets belonging to the same production lot is eliminated, a change in shrinkage coefft. between products is suppressed and high dimensional accuracy of through holes can easily be ensured.

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 multilayer ceramic substrate manufactured by a green sheet method, which suppresses fluctuations in shrinkage rate during firing.

0002

[Common Technology] In recent years, as computers have become faster and smaller, it has become necessary to increase the density and capacity of substrates on which LSIs are mounted. However, in conventional printed wiring boards, the wiring connecting each element is in a planar direction, and there is a restriction on the through hole pitch, so there is a limit to realizing the above-mentioned high-density mounting board.

[0003] For this reason, multilayer ceramic substrates that have vertically expanded wiring to increase the density and have excellent thermal conductivity are attracting attention. This multilayer ceramic substrate is
Generally manufactured using the green sheet method.

0004

BACKGROUND OF THE INVENTION Conventional methods for manufacturing multilayer ceramic substrates include laminating and firing a single lot of green sheets.

Next, a conventional method for manufacturing a multilayer ceramic substrate will be explained with reference to the drawings.

FIG. 3 is a perspective sectional view showing an example of a conventional method for manufacturing a multilayer ceramic substrate, and FIG. 4 is a manufacturing process diagram illustrating an example of a conventional method for manufacturing a multilayer ceramic substrate.

The method for manufacturing a multilayer ceramic substrate shown in FIG. 3 includes laminating green sheets 1d of a single production lot and firing them to manufacture a multilayer ceramic substrate 2.

Next, a conventional method for manufacturing a multilayer ceramic substrate will be explained in detail.

In FIG. 4, step mixing 21 involves stirring and mixing ceramic material 11, which will become the base of multilayer ceramic substrate 2, with binder 12, solvent 13, and plasticizer 14.
This is a step of forming slurry 15 in the form of slurry. Process film formation 22
This is a process in which the slurry 15 produced in process mixing 21 is coated onto a carrier film to a uniform thickness using a doctor blade or the like, and dried with a dryer to produce a sheet-shaped ceramic tape. In the multilayer ceramic substrate 2, it is the basic unit that constitutes the layers.

[0010] Process through hole formation 23 is performed in process film formation 2.
In this step, a plurality of through holes for circuit connection are formed at predetermined positions in the green sheet 1d manufactured in step 2 using a punch or the like. Process printing 24 is green sheet 1
A circuit pattern is printed with conductor paste 16 on
This is the process of filling a through hole to connect the upper and lower layers.

The process lamination 25 consists of the conductive paste 1 described above.
This is a step of stacking a plurality of green sheets 1d of a single production lot on which 6 is printed so as to constitute a predetermined circuit. The thermocompression bonding process 26 is a process of fixing and bonding the laminate of the green sheets 1d using a hot press. The step firing 27 is a step in which the green sheet laminate produced in the thermocompression bonding step 26 is fired in a furnace to form a ceramic substrate. By the main firing, the ceramic substrate shrinks compared to the laminate before firing, and its shape becomes smaller. The amount of dimensional change before and after firing is called the shrinkage rate. Then, the step contour processing 28 is a step in which the ceramic substrate is cut and polished and processed into a final shape to form the multilayer ceramic substrate 2.

0012

[Problems to be Solved by the Invention] In the conventional method for manufacturing multilayer ceramic substrates described above, green sheets from a single production lot are laminated and fired, so that the characteristics of the green sheets themselves from the production lot vary depending on the firing process. This has the disadvantage that the shrinkage rate of the product varies from production lot to production lot.

For this reason, it is difficult to ensure the dimensional accuracy of the through holes, which is important in multilayer ceramic substrates, and the final substrate becomes expensive.

[0014]

Means for Solving the Problems The method for manufacturing a multilayer ceramic substrate of the present invention is characterized in that a plurality of green sheets from different production lots are laminated in a predetermined order and fired. Further, the plurality of green sheets may be manufactured from a plurality of ceramic materials of different production lots.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective sectional view showing an embodiment of the present invention.

The method for manufacturing the multilayer ceramic substrate shown in FIG. 1 is to laminate a green sheet 1a of production lot A, a green sheet 1b of production lot B, and a green sheet 1c of production lot C, and then sinter them to form a multilayer ceramic substrate. It includes manufacturing a substrate 2.

Next, this embodiment will be explained in more detail.

FIG. 2 is a manufacturing process diagram for explaining this embodiment. In FIG. 2, process mixing 21 involves mixing ceramic material 11, which will become the matrix of multilayer ceramic substrate 2, with binder 1.
2. This is a step of stirring and mixing with a solvent 13 and a plasticizer 14 to form a slurry 15 in the form of a slurry. Process film formation 22 is a process in which the slurry 15 produced in process mixing 21 is coated onto a carrier film to a uniform thickness with a doctor blade or the like, and dried with a dryer to produce a sheet-shaped ceramic tape. The green sheet 1 is called a green sheet 1 and serves as a basic unit constituting layers in the multilayer ceramic substrate 2. Further, this green sheet 1 is generally in a metastable state and can be stored.

In the method for manufacturing the multilayer ceramic substrate 2 of this embodiment, a required number of green sheets 1a, 1b, and 1c of different production lots (three production lots in this embodiment) are prepared. The process of forming through holes 23 is a process of forming a plurality of through holes for circuit connection at predetermined positions in the green sheets 1a, 1b, and 1c using a punch. Process printing 24 is a process in which a circuit pattern is printed on the green sheet 1 using conductive paste 16, and at this time, the previously formed through holes are filled with conductive paste 16 to form through holes that connect the upper and lower layers. be.

The process lamination 25 consists of the conductive paste 1 described above.
This is a step of laminating a plurality of green sheets 1a, 1b, 1c from a plurality of different production lots on which numerals 6 are printed so as to constitute a circuit having a desired performance. The process thermocompression bonding 26 is
This is a step of fixing and joining the laminate of green sheets 1 by heat pressing. In the firing step 27, the green sheet laminate produced in the thermocompression bonding step 26 is fired in a furnace to form a ceramic substrate. Process firing 27 generally has two functions. That is, in the early stage, the binder 12, which is an organic binder component, is burned and scattered, and in the latter stage, the sintering of the ceramic material 11 is promoted. Then, the process outline processing 28 is a step in which the ceramic substrate is cut and polished and processed into a final shape to form the multilayer ceramic substrate 2.

[0022] By firing, the ceramic substrate shrinks more than the laminate before firing, and its shape becomes smaller. The amount of dimensional change before and after firing is called the shrinkage rate. As a structural function, it is necessary for the multilayer ceramic substrate 2 to mount an LSI on the upper surface and a connector for extracting signals on the lower surface. For this reason, it is necessary to ensure the dimensional accuracy of the through holes, and as the density and capacity of substrates increase, the required accuracy is becoming stricter, and stabilizing the shrinkage rate mentioned above has become an important issue. There is. This shrinkage rate depends on the particle shape (particle size, particle size distribution, specific surface area, etc.) of the ceramic material 11 contained in the green sheet 1, the component ratio of the binder 12, solvent 13, and plasticizer 14 contained in the green sheet 1, thickness, printing conditions in process printing 24 (conductor paste 16 composition, content), thermocompression bonding conditions in process thermocompression bonding 26 (press temperature, press pressure), firing conditions in process baking 27 (firing profile, firing atmosphere), etc. varies depending on, and
These conditions are used to control the shrinkage rate to a predetermined value. However, the characteristic values related to the green sheet 1 described above are difficult to control. In other words, other conditions can be controlled by setting values, but the characteristic values related to the green sheet 1 are determined by the setting conditions of the process mixing 21 and the process film formation 22. The various characteristic values related to the ceramic material 11 vary from manufacturing lot to manufacturing lot, so they lack controllability and are difficult to obtain stable characteristic values. Therefore, each manufacturing lot of the green sheet 1 has its own central value of shrinkage rate, and the shrinkage rate changes around this value. When viewed from a large number of production lots, these are distributed with a certain degree of spread relative to the desired shrinkage rate. Therefore, as disclosed in the method for manufacturing the multilayer ceramic substrate 2, by stacking and firing a plurality of green sheets 1 from different manufacturing lots, the shrinkage of the green sheets 1 from different manufacturing lots interacts with each other. Shrinks around the desired shrinkage rate as the center value, suppressing variations from production lot to production lot.

More specifically, when the green sheet 1 is manufactured by setting the shrinkage rate of the multilayer ceramic substrate 2 to, for example, 15%, due to variations depending on the manufacturing lot, the The center value of the shrinkage rate is 15.2% for green sheet 1a;
Assume that b is 14.9% and green sheet 1c is 15.1%. At this time, if the multilayer ceramic substrate 2 is manufactured according to the conventional manufacturing method, each multilayer ceramic substrate 2 will shrink around the specific contraction rate of each green sheet 1a, 1b, 1c. Therefore, 0.1% (2 sheets) and 0.2% (1 sheet) against the setting of 15%.
Each board will be manufactured with an opening of . However, as disclosed in the manufacturing method of the present multilayer ceramic substrate 2, by stacking and firing green sheets 1a, 1b, 1c from different manufacturing lots, the unique shrinkage of each green sheet 1a, 1b, 1c is achieved. interact with each other and shrink around the average shrinkage rate of 15.07%, resulting in a substrate that has been improved to a difference of 0.07% (3 sheets) from the set value of 15%. It becomes possible to manufacture. Moreover, when laminating a large number of green sheets, green sheets from different production lots may be alternately laminated.

Furthermore, each of these green sheets 1a,
If 1b and 1c are each manufactured using different ceramic materials from a plurality of manufacturing lots, this variation in shrinkage rate can be further suppressed.

[0025]

Effects of the Invention The method for manufacturing a multilayer ceramic substrate of the present invention uses different green sheets from multiple manufacturing lots instead of using green sheets from a single manufacturing lot, or uses different ceramic materials from multiple manufacturing lots. By using a green sheet using green sheets, it is possible to reduce the influence of the characteristics of each manufacturing lot of green sheets, which has the effect of suppressing fluctuations in shrinkage rate from product to product.

Therefore, the dimensional accuracy of the through holes, which is important in multilayer ceramic substrates, can be easily ensured.
This has the effect of making the final board cheaper.

[Brief explanation of the drawing]

FIG. 1 is a perspective cross-sectional view showing one embodiment of the present invention.

FIG. 2 is a manufacturing process diagram illustrating this example.

FIG. 3 is a perspective sectional view showing a conventional example.

FIG. 4 is a manufacturing process diagram illustrating a method of manufacturing a conventional example of a multilayer ceramic substrate.

[Explanation of symbols]

1, 1a to 1d Green sheet 2 Multilayer ceramic substrate 11 Ceramic material 12 Binder 13 Solvent 14 Plasticizer 15 Slurry 16 Conductive paste 21 Process mixing 22 Process film formation 23 Process through hole formation 24 Process printing 25 Process lamination 26 Process thermocompression bonding 27 Process Firing 28 Process external shape processing

Claims (2)

[Claims] 1. A method for manufacturing a multilayer ceramic substrate, comprising stacking a plurality of green sheets from different production lots in a predetermined order and firing the stack. 2. The method of manufacturing a multilayer ceramic substrate according to claim 1, wherein the plurality of green sheets are each manufactured from a plurality of ceramic materials from different production lots.