JPH08259335A - Production of ceramic substrate - Google Patents

Abstract

PURPOSE: To provide a method for producing ceramic substrate, capable of making density of laminated green sheet uniform and surely reducing peeling and warp of each green sheet in baking a ceramic substrate. CONSTITUTION: In this method for producing ceramic substrate by laminating and baking a ceramic green sheet composed of raw material powder, a sintering additive, a binder, a plasticizer and a solvent, the ratio of readily volatile solvent in the solvent is made large when the ceramic green sheet is thick and the radio of readily volatile solvent is made small when the ceramic green sheet is thin and these ceramic green sheets are combined and laminated and then baked.

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 substrate, and more particularly to a semiconductor device (LSI, IC, etc.) or the like mounted thereon to form a small electronic component, which is used for communication equipment, computers, etc. The present invention relates to a method for manufacturing a ceramic substrate.

[0002]

2. Description of the Related Art In recent years, semiconductor devices (LSI, IC, etc.) are mounted on a ceramic substrate containing alumina particles as a main component to form small electronic components, which are used in communication devices, computers, etc. Higher speed, higher performance, smaller size and thinner products have been rapidly promoted.
In addition, with the increase in speed, improvement in performance, reduction in size, and reduction in thickness,
There is a demand for miniaturization of conductor patterns on ceramic substrates and improvement in dimensional accuracy of conductor patterns.

An outline of a conventional method for manufacturing a ceramic substrate of this type will be described. First, a ceramic raw material powder such as alumina is mixed with an additive such as a sintering aid, a butyral resin, a plasticizer, and an organic solvent (such as xylene) to form a slurry, and the slurry is used to form a green by a doctor blade method. Make a sheet. In order to process the green sheet obtained by the above method into a form according to each purpose and application, processing such as formation of through holes and printing of conductive paste for wiring, etc. are performed, and the ceramics are obtained by firing the laminated product. Produce a substrate.

FIG. 1 is a schematic perspective view showing a doctor blade method in the manufacturing process of the ceramic substrate. According to the doctor blade method, the defoamed slurry 61 is transferred from the slurry tank to the carrier film 62.
Pour on top, carrier film 62 and doctor blade 6
The slurry thickness is controlled by changing the face-to-face distance of 3 (hereinafter referred to as a gap), and usually the tape thickness is 1/2 to 1/3 of the gap.

[0005]

The electrical characteristics of the ceramic substrate depend on the thickness of the green sheets to be laminated and the wiring length, and in the case of a PGA (Pinglit Array) type package, the pins are brazed. In order to improve the strength of the green sheet, it is necessary to increase the thickness of the green sheet. As described above, in a ceramic substrate used for a package or the like, it is necessary to improve electric characteristics, strength, and the like, so that the thickness of each laminated green sheet generally varies. The thickness of the green sheet is selected in the range of about 30 μm to 1000 μm and laminated according to the purpose.

Here, the thicker the green sheet,
The green sheet density is high. This is for the following reason. That is, the thickness of the green sheet is equal to
It is controlled by a gap (not shown) on the surface through which the carrier film 62 is passed. If the gap is large, the degree of freedom of movement of the alumina particles is increased, the raw material particles are easily clogged, and the density is increased.

On the other hand, the green sheet density is inversely proportional to the shrinkage rate during firing, and the higher the green sheet density, the lower the shrinkage rate during firing. This is for the following reason. That is, the higher the density of the green sheet and the smaller the number of pores contained therein, the less easily the acrylic resin and the plasticizer contained in the green sheet are decomposed in the degreasing step, and the more difficult it is to be discharged to the outside. Get lower.

As described above, the green sheets stacked in the package or the like have different densities for each thickness. Therefore, there is a problem in that there is a difference in shrinkage rate between each of the firings, which causes "warping" and "peeling" of each green sheet. This "sledding" and "peeling" cannot be solved in the subsequent process. Therefore, it becomes necessary to unify the density of each green sheet even when stacking green sheets having different thicknesses.

A method using a press can be considered as a method for making the green sheet densities the same. However, when the press treatment is performed, the thickness shrinks, which may cause delamination during lamination.

However, conventionally, the green sheet density has been unified to some extent by the pressing. As a result, the slight difference in density depends on the one having a smaller shrinkage ratio after firing, so that the "warping" and "peeling" can be overcome. However, for example, when a green sheet having a density of 2.3 g / cm ³ and a green sheet having a density of 2.4 g / cm ³ are laminated, the shrinkage rate after firing is about 16% each.
And about 15%, and the difference is 1%. For example, 4 cm
If there is a difference in the shrinkage ratio in the corner package, the difference is 400 μm only in the uniaxial direction. Wire bond wire spacing is 200μ in normal package
Since it is less than or equal to m, the difference in shrinkage becomes fatal in forming the wiring pattern.

It is also conceivable to prepare only one type of green sheet thickness and to form a desired thickness by laminating a portion requiring a larger thickness, but depending on the thickness, it is necessary to laminate 10 or more sheets. In some cases, the yield may be poor and the cost may be high.

[0012] The present invention has been made in view of the above problems, and manufactures a ceramic green sheet which can make the density of the laminated green sheets uniform and reduce the "peeling" and "warping" of each green sheet during firing. It is intended to provide a way.

[0013]

In order to achieve the above object, a method of manufacturing a ceramic substrate according to the present invention comprises laminating a ceramic green sheet composed of raw material powder, a sintering aid, a binder, a plasticizer and a solvent. In the method of manufacturing a ceramic substrate to be fired, the ratio of the volatile solvent in the solvent is increased for the ceramic green sheet having a large thickness, while the volatile solvent ratio in the solvent is increased for the ceramic green sheet having a small thickness. The method is characterized by including a step of reducing the volatile solvent ratio, combining and stacking these ceramic green sheets, and then firing.

[0014]

The present inventor has found the action of the solvent described below and devised the present invention. When the slurry (FIG. 1, 61) is taped and the solvent in the taped green sheet is evaporated to dryness, the drying begins from the front and sides. Once the surface and the side surface are dried and fixed, the inside of the green sheet is less likely to be dried thereafter, and hence the shrinkage of the thickness of the green sheet is less likely to occur. When the shrinkage rate of the green sheet thickness is small, the green sheet density is low as compared with the case where the shrinkage rate is large. Thus, the drying speed of the surface of the green sheet affects the density of the green sheet. That is, the larger the ratio of the easily volatile solvent in the solvent, the faster the evaporation rate of the solvent and the faster the drying and fixing of the surface of the green sheet. Therefore, the shrinkage rate of the green sheet is reduced, and as a result, the green sheet density is reduced. On the other hand, the smaller the ratio of the easily volatile solvent in the solvent, the slower the evaporation rate of the solvent and the slower the drying and fixing of the surface of the green sheet. Therefore, the shrinkage rate of the green sheet becomes high, and as a result, the green sheet density becomes high.

According to the method for producing a ceramic substrate according to the present invention, in the method for producing a ceramic substrate, a ceramic green sheet composed of raw material powder, a sintering aid, a binder, a plasticizer and a solvent is laminated and fired,
As for the ceramic green sheet having a large thickness, while increasing the ratio of the volatile solvent in the solvent,
For thin ceramic green sheets, the ratio of easily volatile solvents in the solvent is reduced, and a step of firing after combining these ceramic green sheets is included, so that the density of the laminated green sheets is uniform. As a result, “warping” and “peeling” of each green sheet during firing are reduced.

[0016]

EXAMPLES Examples of the method for manufacturing a ceramic substrate according to the present invention will be described below.

5 parts by weight of a sintering aid (SiO ₂ , MgO, etc.) is added to 95 parts by weight of alumina powder, water is further added, and the mixture is pulverized and mixed in a ball mill for 24 hours and dried. After that, it was crushed, and 12 parts by weight of an acrylic resin and a plasticizer (DO
4 parts by weight of P and the like and 28 parts by weight of a solvent (toluene and / or xylene) are added and mixed by a ball mill to form a slurry.

Thereafter, the defoaming of the slurry is carried out, for example, for about 5 minutes, and the slurry is tape-formed into a desired thickness by using a doctor blade method, and thereafter, 60 to 12 are formed.
A green sheet is produced by drying in a temperature range of 0 ° C. At this time, the green sheet density is measured, for example, by the Archimedes method.

Next, these green sheets are, for example, 4 ×
Cut into 4 cm squares and then stack, for example, about 50 kg /
After thermocompression bonding under the conditions of cm ² and about 90 ° C., the above green at a temperature of about 1600 ° C. under a reducing atmosphere of, for example, H ₂ : N ₂ = 2: 8 and dew point = 30 ° C. The laminated body of sheets is fired for about 2 hours to produce a ceramic substrate.

Then, the MAX of the warped part of each sample
The height is measured as the amount of "sliding". In measuring the amount of warp, ten ceramic substrates under each sample condition of Table 1 to 3 were prepared and measured.

In this embodiment, the green sheet thickness is 50 μm, 100 μm, 200 μm, 400 μm, 8
Each green sheet having a thickness of 00 μm was produced, and the density was measured. Then, five required green sheets were laminated to form a ceramic substrate, and the warpage and peeling were measured. Further, in this example, toluene was used as the easily volatile solvent and xylene was used as the other solvent.

Table 1 is a table showing the green sheet density when the thickness of the green sheet used in this example and the mixing ratio of the solvent are changed.

[0023]

[Table 1]

For example, No. 1 to No. 5 and No. 6 to No. 1 in Table 1
0, No11-15, No16-20, No21-25
In each case, the thicker the green sheet, the higher the green sheet density.

Further, for example, No1, No6, No11,
Comparing No. 16 and No. 21 green sheets having the same thickness, the green sheet density becomes lower as the ratio of the easily volatile solvent in the solvent increases.

As is clear from Table 1, the thick green sheet makes the ratio of the easily volatile solvent in the solvent large to reduce the density of the green sheet, while the thin green sheet makes the solvent in the solvent. By increasing the density of the green sheets by decreasing the ratio of the easily volatile solvent of the above, even if the thickness of each green sheet combined and laminated on the ceramic substrate is different, the density of each green sheet is unified. You can

Table 2 shows the results of measuring the amount of warp and peeling rate after the green sheets shown in Table 1 were laminated and fired to form a ceramic substrate. Sample 1 is a laminate of five green sheets No. 1 to 5 in Table 1 one by one, and Sample 2 is No. 11 to 15 in Table 1
No. 5, No. 9, No. 13 in Table 1,
No. 17 and No. 21 green sheets are laminated one by one, five sheets in total. Ten ceramic substrates were prepared for each of Samples 1 to 3, and the warpage rate in the table shows the rate of warpage in all 10 ceramic substrates. The warpage amount and the rate of peeling caused warpage and peeling, respectively. The average value in the ceramic substrate is shown.
At this time, when the warp generated was 50 μm or less, it was considered that the warp did not occur.

[0028]

[Table 2]

As is clear from Tables 1 and 2, in Sample 1, the laminated green sheet density was 2.08 to
In the range of 2.32 g / cm ^2, since between the maximum value and the minimum value is a density difference of 0.24 g / cm ^2, the difference becomes a difference in shrinkage after firing the formed ceramic substrate 70% of the ceramic substrate is warped,
The amount of warpage was 2580 μm. The peeling rate was 60%. In the sample 2 in the range green sheet density laminated is 2.20~2.46g / cm ^2, since between the maximum value and the minimum value is a density difference of 0.26 g / cm ^2, the The difference becomes the difference in shrinkage ratio after firing, warpage occurs on all ceramic substrates, and the warp amount is 300
It became 0 μm. The peeling rate was 80%.

On the other hand, in the sample 3 in the range green sheet density laminated is 2.29~2.32g / cm ^2, the density feed of 0.03 g / cm ² between the maximum and minimum values Therefore, even if the difference resulted in a difference in shrinkage ratio after firing, only 10% of the samples had warped ceramic substrates. The amount of sled is only 8
It was 0 μm, and the peeling rate was 0%.

As described above, according to the method for manufacturing a ceramic substrate according to the embodiment, the ceramic substrate is formed by stacking and firing the ceramic green sheets composed of the raw material powder, the sintering aid, the binder, the plasticizer and the solvent. In the manufacturing method, the ceramic green sheet thickness is increased while increasing the volatile solvent ratio in the solvent, while the ceramic green sheet thickness is decreased, the volatile solvent ratio in the solvent is decreased. However, since it includes a step of firing after combining and stacking these ceramic green sheets, the density of the green sheets to be laminated is made uniform, and the "peeling" and "warping" of each green sheet during firing is surely reduced. be able to.

Alumina powder was used as the ceramic raw material powder in the above-mentioned embodiments, but the present invention is not limited to this, and it can be similarly applied to alumina nitride powder or the like in another embodiment.

Although xylene and toluene were used as the solvent in the above embodiment, the solvent is not limited to them. In another embodiment, MEK, methyl butyl ketone, MI.
The same application is possible even in combination with other easily volatile solvents such as BK and ethylbenzene.

[0034]

As described above in detail, according to the method for manufacturing a ceramic substrate of the present invention, the raw material powder, the sintering aid,
In a method for manufacturing a ceramic substrate in which a ceramic green sheet composed of a binder, a plasticizer, and a solvent is laminated and fired, while the ceramic green sheet is thick, the volatile solvent ratio in the solvent is increased, As for the ceramic green sheet having a small thickness, the ratio of the easily volatile solvent in the solvent is reduced, and a step of firing after combining these ceramic green sheets is included,
The density of the laminated green sheets can be made uniform, and the "peeling" and "warping" of each green sheet during firing can be reliably reduced.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a state in which a slurry is made into a tape by a doctor blade method.

Claims (1)

[Claims] 1. A method of manufacturing a ceramic substrate in which ceramic green sheets composed of raw material powder, a sintering aid, a binder, a plasticizer, and a solvent are laminated and fired, and the ceramic green sheet having a large thickness is as described above. While increasing the ratio of the easily volatile solvent in the solvent, for the thin ceramic green sheet, the ratio of the easily volatile solvent in the solvent is reduced, and a step of firing after laminating these ceramic green sheets in combination is performed. A method of manufacturing a ceramic substrate, which comprises: