JP2009111184A - Multilayer ceramic substrate and method of manufacturing multilayer ceramic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayer ceramic substrate whose curvature can be suppressed while preventing interlayer peeling. <P>SOLUTION: The method of manufacturing the multilayer ceramic substrate includes: a first press-fitting stage of forming a plurality of first green sheet stacks 10 and 11 by stacking and press-fitting ceramic green sheets 1 to 4; a second press-fitting stage of forming a second green sheet stack 20 by stacking and press-fitting the plurality of first green sheet stacks 10 and 11; and a baking stage of baking the second green sheet stack 20. Press-fitting strengths of the plurality of first green sheet stacks 10 and 11 formed in the first press-fitting stage are so defined that contraction coefficients of the first green sheet stacks 10 and 11 after the baking stage are equal to each other, and the press-fitting strength of the second green sheet stack formed in the second press-fitting stage is a predetermined press-fitting strength so determined as to prevent the baked multilayer ceramic substrate from peeling. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a multilayer ceramic substrate. More specifically, the present invention relates to a method for manufacturing a multilayer ceramic substrate that can suppress warping during firing. The present invention also relates to a multilayer ceramic substrate.

  In recent years, the demand for miniaturization of electronic devices has been increasing. Therefore, a multilayer ceramic substrate having a built-in electronic circuit such as a capacitor or an inductor is also used in the ceramic substrate. This multilayer ceramic substrate is made of a sheet (ceramic green sheet) that is a mixture of raw materials of low temperature co-fired ceramics, and the necessary wiring pattern is printed on the surface using a conductive material such as silver. A plurality of ceramic green sheets are laminated and pressure-bonded, dried, and fired. Since the low-temperature co-fired ceramic can be fired at a temperature lower than the melting point of the conductive material such as silver, the circuit pattern formed in the multilayer ceramic substrate by the printing is not damaged.

  However, since the ceramic green sheet is formed of a ceramic raw material, it shrinks upon firing. On the other hand, printed conductors such as silver have different shrinkage rates than ceramic raw materials and exhibit different shrinkage behaviors. Therefore, the shrinkage rate of ceramic green sheets depends on the conductor area printed on each ceramic green sheet. Shrinkage is different. Therefore, due to the difference in the compression rate of each ceramic green sheet, peeling may occur in the fired multilayer ceramic substrate, or cracks in the substrate and warpage of the multilayer ceramic substrate may occur. It was.

In order to deal with such a problem, a technique for preventing warpage and peeling by devising a method of pressing the laminated ceramic green sheets has been proposed (for example, Patent Document 1). In this technology, the ceramic green sheets to be laminated are roughly divided into two blocks, and the first step is applied to each block with the compression strength at which warpage is most unlikely to occur. Further, the second stage of pressure bonding is performed. At this time, the second-stage crimping is performed with a lower crimping strength than any of the first-stage crimping so as not to break the crimping balance in which warpage is unlikely to occur in the first-stage crimping.
Japanese Patent Laid-Open No. 2005-19718

  Here, according to the technique disclosed in Patent Document 1, it is a requirement that the second-stage crimping is performed with a lower crimping strength than any of the first-stage crimping. However, both blocks are brought into close contact with each other only by the second-stage crimping, and if the second-stage crimping is performed with a small crimping strength, peeling is likely to occur at the interface between the two blocks. .

  The present invention has been made to solve such a problem, and an object of the present invention is to supply a method for manufacturing a multilayer ceramic substrate that can suppress warpage while preventing delamination.

  The method for manufacturing a multilayer ceramic substrate according to the present invention includes a printing step of forming a wiring by printing a conductor on a ceramic green sheet, and a first green sheet laminate formed by stacking and pressing the ceramic green sheets. A first pressure-bonding step for creating a plurality of first green sheet laminates, a second pressure-bonding step for creating a second green sheet laminate formed by crimping a plurality of the first green sheet laminates, and the second green sheet laminate A method for producing a ceramic laminated part having a firing step. In addition, the compression strength of each of the first green sheet laminates produced in the first crimping step is determined so that the shrinkage rate of each first green sheet laminate after the firing step is equal, The pressure-bonding strength of the second green sheet laminate produced in the second pressure-bonding step is a predetermined pressure-bonding strength determined to prevent the fired laminated ceramic substrate from peeling off.

  According to the above configuration, the compression strength of each of the first green sheet laminates produced in the first crimping step is determined so that the contraction rate of each first green sheet laminate after the firing step is equal. Warpage of the manufactured multilayer ceramic substrate can be suppressed. As shown in FIG. 1, the warpage of the multilayer ceramic substrate 100 is such that a green sheet laminate 60 having a larger shrinkage ratio than the laminated green sheet laminate 50 is laminated and fired. It occurs so that the body 60 side is concave. Therefore, warping can be prevented if there is no difference in shrinkage.

  In addition, according to the above configuration, the second green sheet laminate produced in the second crimping step is fired because it has a predetermined crimp strength determined to prevent peeling of the fired laminated ceramic substrate. Peeling of the multilayer ceramic substrate can be prevented. In the prior art, the pressure bonding strength in the second pressure bonding step is performed at a pressure strength lower than the first pressure bonding strength. In this method, since the pressure bonding strength in the second pressure bonding step is small, the pressure bonding strength balance in the first pressure bonding step can be maintained, but sufficient strength to prevent peeling of the fired multilayer ceramic substrate may not be obtained. There is sex. In the present invention, regardless of the pressure bonding strength in the first pressure bonding step, the fired laminated ceramic substrate is always peeled at a predetermined pressure strength determined to prevent peeling of the fired laminated ceramic substrate. Can be prevented. In addition, the predetermined | prescribed crimping | compression-bonding intensity | strength in this 2nd crimping | compression-bonding process can be defined objectively. For example, a correlation between the pressure bonding strength and the occurrence probability of peeling may be taken and determined to be a pressure bonding strength that is less than or equal to a practically allowable peeling occurrence rate.

  In the method for manufacturing a multilayer ceramic substrate according to the present invention, the respective crimping strengths in the first crimping step are the ratio of the area of the printed conductor to the surface area of the ceramic green sheet and the respective crimping in the first crimping step. It is preferably determined based on one selected from the group consisting of a graph, a table, and a relational expression showing the relationship between the strength and the shrinkage ratio after firing.

  Further, according to the above configuration, each crimping strength in the first crimping step is a ratio of the area of the printed conductor to the surface area of the ceramic green sheet, each crimping strength in the first crimping step, and a shrinkage ratio after firing. Since it is determined based on one selected from the group consisting of a graph, a table, and a relational expression showing the relationship, the crimping strength can be easily obtained.

  The ceramic substrate manufactured by the method for manufacturing a multilayer ceramic substrate according to the present invention can suppress warpage while preventing delamination.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a method for manufacturing a multilayer ceramic substrate and a multilayer ceramic substrate embodying the present invention will be described with reference to the drawings.

First, a raw material powder composed of dielectric ceramics and a sintering aid, an organic binder, a plasticizer and a solvent are mixed to form a slurry-like mixture, which is formed into a sheet having a thickness of about 130 μm by a doctor blade molding machine. The ceramic green sheets 1, 2, 3, and 4 are produced as shown in FIG. Next, vias (through holes) for connecting up and down are opened as necessary. Next, in the printing step, circuit patterns 6 and 7 are formed by printing a paste containing a conductor on the surfaces of the ceramic green sheets 1 and 2 by a screen printing method. The via is filled with a conductor paste by screen printing or the like. As a conductor to be printed, silver having a high conductivity is optimal. Further, since it is necessary to sinter at or below the melting point of silver which is a conductor, a glass raw material such as SiO ₂ or MgO is used as a sintering aid.

  Next, a 1st crimping | compression-bonding process is performed. As shown in FIG.2 (b), after laminating | stacking the ceramic green sheet 1 and the ceramic green sheet 2, it crimps | bonds and forms the 1st green sheet laminated body 10 (for upper layers). The pressure bonding strength at this time was 18 MPa. Similarly, as shown in FIG. 2C, the ceramic green sheet 3 and the ceramic green sheet 4 are laminated and then pressed to form another laminated body 11 (for the lower layer) of the first green sheet. The pressure bonding strength at this time was 30 MPa.

  Further, a second pressure bonding process is performed. As shown in FIG. 2 (d), the first green sheet laminate 10 and the other first green sheet laminate 11 are laminated and then pressed to form a second green sheet laminate 20. At this time, the pressure bonding strength was set to 35 MPa. The second green sheet laminate 20 thus produced is cut into a desired size and fired to produce a multilayer ceramic substrate.

  In the manufacturing method of the multilayer ceramic substrate in the present embodiment, the pressure bonding strength is determined as follows.

  It is practical to determine the pressure bonding strength in the second pressure bonding step to a pressure bonding strength that is equal to or lower than a practically allowable peeling occurrence rate by correlating the pressure bonding strength with the occurrence probability of peeling. Here, since the interface between the first green sheet laminate 10 and the other first green sheet laminate 11 is crimped only by the second crimping step, peeling after firing occurs most at the interface. Cheap. In the prior art, the crimping strength in the second crimping step is limited to the smallest one of the crimping strengths in the first crimping step. Although it is a measure for preventing the pressure-bonding force balance in the first pressure-bonding step from being lost as much as possible, there is no support that can prevent peeling after firing with such pressure-bonding strength, and peeling after firing may occur. In the present embodiment, since the second pressure bonding strength is set to a pressure bonding strength that is equal to or less than a practically allowable peeling occurrence rate, peeling after firing can be prevented.

  Next, the pressure bonding strength in the first pressure bonding step will be described. As shown in FIG. 3, if the pressure bonding strength is constant, the shrinkage rate after firing becomes smaller as the area ratio of the printed conductor to the area of the ceramic green sheet (hereinafter referred to as conductor area ratio) is larger. FIG. 3 is a graph when conductor printing is performed on a ceramic green sheet having a thickness of 130 μm so as to have a thickness of 8 μm after firing. In addition, the shrinkage ratio is as follows. In the 25 mm square rectangular ceramic green sheet 1 as shown in FIG. 4, nine via holes 2 are provided at 10 mm intervals so as to be positioned at the apexes of the lattice shape. Measurement was performed before firing and after firing, and the ratio was calculated.

  In addition, as shown in FIG. 5, when the second press pressure, that is, the crimping strength in the second crimping step is constant, the shrinkage after firing becomes higher as the first press pressure, that is, the crimping strength in the first crimping step increases. Get smaller. Further, as described above, in order to obtain the same shrinkage rate, the smaller the conductor area ratio, the greater the pressure bonding strength required. In the present embodiment, the shrinkage rate is 11.3%. Then, the crimping strength required for the first green sheet laminate 10 having a conductor area ratio of 5% is about 18 MPa, as derived from the graph of FIG. 5, and the conductor area ratio is 0%, that is, no conductor printing is performed. The compression strength required for the two green sheet laminate 20 is about 30 MPa.

  According to the method for manufacturing a multilayer ceramic substrate of the above embodiment, the following effects can be obtained.

  (1) According to the manufacturing method of the multilayer ceramic substrate of the above embodiment, the compression strength of the first green sheet laminate 10 and the first green sheet laminate 11 that are created in the first crimping step is the same as that after the firing step. Since the shrinkage rates of the first green sheet laminate 10 and the first green sheet laminate 11 are determined to be equal, warpage of the produced multilayer ceramic substrate can be suppressed.

  (2) According to the method for manufacturing a multilayer ceramic substrate of the above embodiment, the pressure-bonding strength of the second green sheet laminate 20 created in the second pressure-bonding step is determined to prevent peeling of the fired multilayer ceramic substrate. Because of the predetermined compression strength, peeling of the fired multilayer ceramic substrate can be prevented.

  (3) According to the method for manufacturing a multilayer ceramic substrate of the above embodiment, the pressure-bonding strength of the first green sheet laminate 10 and the first green sheet laminate 11 in the first crimping step is printed with respect to the surface area of the ceramic green sheet. Since it is determined based on a graph showing the relationship between the area ratio of the conductors, the respective crimping strengths in the first crimping step, and the shrinkage ratio after firing, the crimping strength can be easily obtained.

  In addition, you may change the said embodiment as follows.

  -In the manufacturing method of the multilayer ceramic substrate concerning the said embodiment, the 1st crimping | compression-bonding process is 1st in a 1st crimping | compression-bonding process so that the shrinkage rate of the 1st green sheet laminated body 10 and the 1st green sheet laminated body 11 may become 11.3%. Although the pressure bonding strength of the green sheet laminate 10 and the first green sheet laminate 11 is determined, it may be determined so as to have another shrinkage rate. For example, when the crimping strength of the first green sheet laminate 10 and the first green sheet laminate 11 in the first crimping step is determined so that the shrinkage rate is 12.7%, the crimp strength of the first green sheet laminate 10 is determined. Is 0 MPa, and the pressure bonding strength of the first green sheet laminate 11 is 11 MPa. That is, the first pressure bonding step can be omitted for the first green sheet laminate 10. Therefore, after forming ceramic green sheets 1 to 4 as shown in FIG. 6A and conducting conductor printing on the ceramic green sheets 1 and 2, the ceramic green sheets as shown in FIG. The first green sheet laminate 11 is formed by pressure bonding 3 and 4. On the other hand, since the ceramic green sheets 1 and 2 are not formed, the first green sheet laminate 10 is not formed by pressure bonding. As shown in FIGS. 6C and 6D, the ceramic green sheets 1 and 2 (corresponding to the first green sheet laminate 10) and the first green sheet laminate 11 are laminated to form a second crimping step. Pressurize at 35 MPa. In this case, part of the crimping in the first step can be omitted, which contributes to cost reduction.

  -In the manufacturing method of the multilayer ceramic substrate concerning the said embodiment, the crimping | compression-bonding strength of the 1st green sheet laminated body 10 in the 1st crimping | compression-bonding process and the 1st green sheet laminated body 11 is the printed conductor with respect to the surface area of a ceramic green sheet. Although it is determined based on a graph showing the relationship between the area ratio, each crimping strength in the first crimping step, and the shrinkage ratio after firing, other configurations may be used. For example, each of the pressure bonding strengths in the first pressure bonding step includes the ratio of the area of the printed conductor to the surface area of the ceramic green sheet, each pressure bonding strength in the first pressure bonding step, and the shrinkage ratio after the firing. It may be determined based on a table or a relational expression indicating the relationship. Whichever method is used, the crimping strength of the first green sheet laminate 10 and the first green sheet laminate 11 can be easily obtained.

  -In the manufacturing method of the multilayer ceramic substrate concerning the said embodiment, the crimping | compression-bonding strength of the 2nd green sheet laminated body 20 in a 2nd crimping | compression-bonding process correlates the crimping | compression-bonding strength in the 2nd crimping | compression-bonding process with the probability of occurrence of peeling. The pressure-bonding strength is set to be equal to or lower than the practically allowable peeling occurrence rate, but other methods may be used. For example, if a pressure bonding strength that does not cause peeling of the multilayer ceramic substrate is obtained empirically, the value may be applied as it is. According to the manufacturing method according to the present embodiment, the pressure bonding strength in the second pressure bonding step does not need to be particularly weak, so that the pressure bonding strength can be increased as long as other adverse effects do not occur. According to this method, it is not necessary to perform a special experiment in order to determine the crimping strength in the second crimping step, which contributes to cost reduction.

  In the multilayer ceramic substrate according to the above embodiment, each of the first green sheet laminate 10 and the first green sheet laminate 11 is composed of two ceramic green sheets, but each has three or more ceramics. You may be comprised with the green sheet. A multilayer ceramic substrate having a highly integrated circuit can be formed by using many ceramic green sheets.

  In the multilayer ceramic substrate according to the above embodiment, two sets of first green sheet laminates composed of the first green sheet laminate 10 and the first green sheet laminate 11 are created in the first pressure bonding step. Three or more sets of first green sheet laminates may be created. That is, the number of first green sheet laminates is not particularly limited as long as warpage of the fired multilayer ceramic substrate can be suppressed.

  A multilayer ceramic substrate was prepared using 8 ceramic green sheets having a thickness of 138 μm, a long side of 25 mm, and a short side of 20 mm, and the amount of warpage was measured.

(First crimping process)
As shown in FIG. 7, after laminating the ceramic green sheet subjected to conductor printing, which is the uppermost layer after stacking, and three ceramic green sheets not subjected to conductor printing, pressure bonding was performed at 35 MPa as shown in Table 1, A first green sheet laminate for the upper layer was prepared. Further, after laminating four ceramic green sheets that were not subjected to conductor printing, pressure bonding was performed at 45 MPa as shown in Table 1 to prepare a first green sheet laminate for the lower layer.

(Second crimping process)
The first green sheet laminate for the upper layer and the first green sheet laminate for the lower layer were laminated and pressure-bonded at 45 MPa as shown in Table 1 to prepare a second green sheet laminate.

(Baking process)
The produced 2nd green sheet laminated body was baked with the temperature profile which hold | maintains maximum temperature 850 degreeC for 1 hour, and the multilayer ceramic substrate was manufactured.

(Measurement of warpage)
As shown in FIG. 8, the manufactured multilayer ceramic substrate 100 was placed on a horizontal table with a concave surface facing downward, and the height of the central portion was measured with a height gauge 72. The warpage amount of the multilayer ceramic substrate 100 was calculated by subtracting the measured value of the film thickness of the multilayer ceramic substrate 100 measured by the micrometer 71 as shown in FIG.

  A multilayer ceramic substrate was prepared using 8 ceramic green sheets in the same manner as in Example 1, and the amount of warpage was measured.

(First crimping process)
After laminating four ceramic green sheets that were not subjected to conductor printing, pressure bonding was performed at 35 MPa as shown in Table 2 to prepare a first green sheet laminate for the lower layer. On the other hand, the structure of the first green sheet laminate for the upper layer is the same as that in Example 1, but no particular pressure bonding was performed.

(Second crimping process)
The same treatment as in Example 1 was performed except that the pressure bonding strength was 35 MPa.

(Baking process)
The same treatment as in Example 1 was performed to manufacture a multilayer ceramic substrate.

(Measurement of warpage)
The same measurement as in Example 1 was performed, and the amount of warpage of the multilayer ceramic substrate 100 was calculated.

[Comparative example]
A multilayer ceramic substrate was prepared using 8 ceramic green sheets in the same manner as in Example 1, and the amount of warpage was measured.

(First crimping process)
The point that conductor printing was performed on the ceramic green sheet as the uppermost layer after stacking was the same as in Example 1, but no particular pressure bonding was performed.

(Second crimping process)
The same treatment as in Example 1 was performed except that the pressure bonding strength was 35 MPa.

(Baking process)
The same treatment as in Example 1 was performed to manufacture a multilayer ceramic substrate.

(Measurement of warpage)
The same measurement as in Example 1 was performed, and the amount of warpage of the multilayer ceramic substrate 100 was calculated.

[Result comparison]
As shown in FIG. 10, the warpage amount of Example 1 and Example 2 was ½ or less compared to the comparative example, and it was confirmed that the warpage of the multilayer ceramic substrate 100 was suppressed. In addition, since the pressure bonding of 35 MPa or more is performed in the second pressure bonding step, peeling of the multilayer ceramic substrate is prevented.

  Since the method for manufacturing a multilayer ceramic substrate according to the present invention is a method for manufacturing a multilayer ceramic substrate that can suppress warping during firing, it can be widely used industrially.

It is a schematic diagram for demonstrating the state of the curvature of a laminated ceramic substrate. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an oblique projection for explaining an embodiment of a method for producing a multilayer ceramic substrate to which the present invention is applied, wherein (a) is a schematic view of a green sheet and (b) is a first green sheet laminate (for upper layer). (C) is a figure explaining the production method of a 1st green sheet laminated body (for lower layers), (d) is a figure explaining the production method of a 2nd green sheet laminated body. It is a figure to do. It is a graph which shows the relationship between printing area ratio and shrinkage | contraction rate. It is a top view of the ceramic green sheet for demonstrating the measuring method of shrinkage rate. It is a graph which shows the relationship between a 1st crimping | compression-bonding intensity | strength and shrinkage | contraction rate. It is the oblique projection for demonstrating the modification of the manufacturing method of the multilayer ceramic substrate to which this invention is applied, Comprising: (a) is a schematic diagram of a green sheet, (b) is the 1st green sheet laminated body (for lower layers) (C) and (d) is a figure explaining the production method of a 2nd green sheet laminated body. It is a cross-sectional schematic diagram for demonstrating the Example of the manufacturing method of the laminated ceramic substrate to which this invention is applied. It is a schematic diagram for demonstrating the measuring method of the curvature amount of a multilayer ceramic substrate. It is a schematic diagram for demonstrating the measuring method of the thickness of a laminated ceramic substrate. It is a graph which compares the result of an Example and a comparative example.

Explanation of symbols

  1, 2, 3, 4 ... ceramic green sheets, 6, 7 ... circuit pattern, 10 ... first green sheet laminate (for upper layer), 11 ... first green sheet laminate (lower layer) 20) second green sheet laminate, 50 ... green sheet laminate, 60 ... green sheet laminate, 71 ... micrometer, 72 ... height gauge, 100 ... laminate. Ceramic substrate.

Claims (3)

A printing process for forming wiring by printing a conductor on a ceramic green sheet;
A first crimping step of creating a plurality of first green sheet laminates formed by stacking and crimping the ceramic green sheets;
A second crimping step of creating a second green sheet laminate formed by stacking and crimping the first green sheet laminate;
In the method for producing a ceramic laminated part having a firing step of firing the second green sheet laminate,
The pressure-bonding strength of each of the first green sheet laminates created in the first crimping step is determined so that the shrinkage rate of each of the first green sheet laminates after the firing step is equal,
The multilayer ceramic substrate, wherein the second green sheet laminate produced in the second crimping step has a predetermined crimp strength determined to prevent peeling of the fired multilayer ceramic substrate. Manufacturing method.   The crimping strength of each of the first green sheet laminates is the ratio of the printed conductor area to the surface area of the ceramic green sheet, the crimping strength in the first crimping step, and the shrinkage ratio after firing. 2. The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein the method is determined based on one selected from the group consisting of a graph, a table, and a relational expression.   A ceramic substrate manufactured by the method for manufacturing a multilayer ceramic substrate according to claim 1.

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