JPH07307570A - Manufacture of multilayered ceramic board - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a multilayered ceramic board, wherein a time required for a laminating process can be lessened by restraining delamination. CONSTITUTION:Ceramic powder, binder, solvent, plasticizer and the like are mixed well and molded into green sheets 1 and 1a. The green sheets 1 and 1a are sandwiched in between laminating jigs 4, and then a laminating process wherein a laminating device is exhausted and the green sheets 1 and 1a are pressed is carried out. The plasticizer contained in the green sheets 1 and 1a is reduced to less than 20% by weight of its initial loadings. Silicone rubbers 6 are interposed between the green sheets 1 and 1a and the jigs 4 as buffer when the sheets 1 and 1a are pressed. Thereafter, a green sheet laminate 7 is pre-burned and then fully burned.

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, and more particularly to a method for manufacturing a multilayer ceramic substrate characterized by a green sheet laminating step.

[0002]

2. Description of the Related Art As a multilayer substrate for mounting electronic components such as IC and LSI chips, various types have been proposed so far. Especially in recent years, high integration
In order to protect highly functional electronic components from thermal destruction, multilayer ceramic substrates using a ceramic material having good thermal conductivity have been manufactured.

A multilayer ceramic substrate is produced by using a slurry obtained by adding and kneading a binder, a sintering aid, a plasticizer, etc. to ceramic powder as a starting material. The slurry is formed into a sheet by a doctor blade method or the like. The obtained green sheet is provided with through-hole forming holes, positioning holes, etc., if necessary,
Further, pattern printing is performed with the conductor paste. A plurality of green sheets printed with the conductor paste are stacked on a jig and thermocompression-bonded by a laminating process for about 30 minutes (a process mainly consisting of evacuation in the laminating apparatus and pressurization to the green sheets). . Laminated green sheet (green sheet laminate)
Is further subjected to degreasing, calcination, and main calcination to be a sintered body.

[0004]

However, in the case of the green sheet laminate obtained by the conventional method, since the laminating step is carried out in a state in which a large amount of the plasticizer is contained, volatile gas is easily generated and swelling occurs between the layers ( So-called delamination) was easy to occur. And this has been a cause of deterioration of dimensional accuracy and lot out.
In addition, the adhesion strength between layers may be deteriorated due to the progress of delamination.

Therefore, in the prior art, the time for the laminating process (especially the time for vacuuming) is secured to some extent,
It was obliged to remove the volatile gas sufficiently.
Therefore, there is a problem that the operating efficiency of the equipment is inevitably reduced and the amount that can be laminated per day is reduced.

Further, in the case of the conventional method, the positioning hole is gradually deformed while the green sheet having plasticity is flowing, and the thickness around the positioning hole tends to be thicker than other portions. Then, if pressure is applied in this state, there is a problem that the press pressure is concentrated around the guide pins and a sufficient pressure cannot be applied to the central portion of the green sheet. In addition, such uneven pressurization has been a cause of delamination.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a multilayer ceramic substrate capable of suppressing delamination and shortening the time required for the laminating step. is there.

[0008]

In order to solve the above problems, according to the invention of claim 1, a ceramic powder,
A laminating process in which a plurality of green sheets formed by mixing and molding a binder, a solvent, a plasticizer, etc. are placed between laminating jigs, and then a vacuum is drawn in the laminating apparatus and the green sheets are pressed. In the method for manufacturing a multilayer ceramic substrate in which the green sheet laminate is pre-fired and then main-fired, the plasticizer in the green sheet is initially mixed in the amount before the evacuation performed in the laminating step. The main point is to remove less than 20% by weight.

According to the second aspect of the invention, a plurality of green sheets formed by mixing and molding ceramic powder, binder, solvent, plasticizer and the like are arranged between the jigs for lamination, and then the green sheets are placed in the laminating apparatus. In a method for manufacturing a multilayer ceramic substrate, which comprises performing a laminating step of performing vacuuming and pressurizing the green sheet, and further performing preliminary firing and main firing of the green sheet laminate, The gist is to apply pressure with a cushioning material placed between them.

According to a third aspect of the invention, the gist of the invention of the first aspect is that the pressure is applied in a state in which a cushioning material is arranged between the green sheet and the jig.

The gist of the invention according to claim 4 is that the cushioning material according to claim 2 or 3 is a rubber plate having elasticity.

[0012]

According to the method of the present invention as set forth in claim 1, since the plasticizer, which is a source of residual gas, is sufficiently removed from the green sheet, the vacuuming time is shorter than that in the normal lamination. I will be done. Moreover, delamination of the green sheet due to the escape of residual gas is extremely reduced.

According to the method of the second aspect of the present invention, the buffering material interposed uniformly applies pressure to the green sheet, so that the pressurizing time is shorter than that in the normal lamination. Moreover, delamination of the green sheet due to uneven pressure is extremely reduced.

According to the method of the third aspect of the present invention, the plasticizer, which is the source of the residual gas, is sufficiently removed from the green sheet, and the cushioning material interposed uniformly applies pressure to the green sheet. It will be. therefore,
The vacuuming time and the pressurizing time can be shortened as compared with the normal laminating. Moreover, the delamination of the green sheet due to the escape of residual gas and uneven pressure is extremely reduced.

According to the method of the invention described in claim 4, it is possible to more surely realize the uniform pressurization as compared with the case where, for example, a paperboard having no elasticity is used as the cushioning material. Moreover, since it is a rubber plate having elasticity, it can be repeatedly used.

The method for manufacturing a multilayer ceramic substrate of the present invention will be described in detail below in the order of steps. As a ceramic material for forming the green sheet, for example, Al
N, Al ₂ O ₃ (alumina), 3Al ₂ O ₃・ 2SiO
₂ (mullite), boron nitride (BN), silicon carbide (Si
Powders such as C) and silicon nitride (Si ₃ N ₄ ) are used.
Among them, it is desirable to select AlN powder that can obtain a substrate having excellent electric insulation and thermal conductivity. Next, a predetermined amount of binder, sintering aid, plasticizer, solvent, and the like are added to the ceramic powder selected from those listed above.

Among the above substances, the plasticizer and the solvent are volatile components, and the ceramic powder, the sintering aid and the binder are solid contents. Usually, the content of the volatile component is about 20 to 30% by weight of the solid content. The main component of the volatile component is the solvent. The content of the plasticizer is a fraction to one tenth of the content of the solvent. Further, the plasticizer used generally has a high boiling point as compared with the boiling point of the solvent in many cases.

By uniformly kneading the mixture,
A raw material slurry for making a green sheet is obtained. Then, a green sheet is continuously formed from the raw material slurry by, for example, a doctor blade method. Here, drying is performed to such an extent that the raw material slurry loses fluidity and can retain the sheet shape, that is, about 80% of the volatile components (mainly solvent) in the green sheet are removed.

Hereinafter, the drying performed at this stage is referred to as "primary drying" for convenience of explanation. In addition, hereinafter, the term "green sheet" refers to a sheet-shaped ceramic molded body that has undergone primary drying. At this time, while the solvent is removed by the primary drying, the plasticizer is hardly removed. Therefore, the green sheet after the primary drying still has plasticity.

The green sheet that has undergone the primary drying is dried again after the contour cutting. Drying at this stage removes the solvent but little plasticizer.
Hereinafter, the drying performed at this stage is referred to as "secondary drying" for convenience of description. About 8 green sheets in the secondary drying process
It is dried at 0 ° C. for several hours.

The green sheet which has been subjected to the secondary drying is provided with through-hole forming holes and positioning holes. Further, a paste containing a refractory metal as a main component is printed on the green sheet. With this paste,
Conductor patterns are formed inside the through holes and on the surface of the green sheet. In this case, as the conductive metal, for example, tungsten, molybdenum, tantalum, niobium or the like is used. Among them, it is desirable to select tungsten powder which is particularly excellent in cost performance.

After that, drying is carried out for the purpose of removing the solvent in the printed paste. Hereinafter, the drying performed at this stage is referred to as “tertiary drying” for convenience of description.
However, the plasticizer in the green sheet is hardly removed even after the third drying. In the third drying step, the green sheet is dried at about 70 ° C. for about 10 to 30 hours.

A plurality of green sheets having the conductor pattern formed thereon are placed on a laminating jig in a state of being superposed. It should be noted that another green sheet that does not contain a sintering aid is arranged in the outermost layer of the green sheet. Before or after stacking the green sheets, the green sheets are dried. Hereinafter, the drying performed at this stage is referred to as “quaternary drying” for convenience of description.
The plasticizer remaining in the green sheet is removed up to about 2/3 or less of the initial blending amount by passing through the fourth drying step. Therefore, the residual amount of the plasticizer in the green sheet at this point is 60% by weight or less. In the fourth drying process, the green sheet has a temperature of 80 ° C to 120 ° C for 20
It is dried for about 80 hours. In the present invention, it is required to remove the plasticizer in the green sheet to less than 20% by weight, preferably less than 10% by weight of the initial blending amount, by the primary drying to the fourth drying. If the plasticizer is not removed sufficiently, the amount of volatile gas generated will increase,
This is because shortening of the laminating time cannot be achieved.

The green sheets that have undergone the quaternary drying are thermocompression-bonded to each other in the subsequent laminating process. The laminating step in the present invention mainly consists of vacuuming the inside of the laminating apparatus and pressing the green sheet. More specifically, in this laminating step, preheating of the apparatus, setting of a jig in the laminating apparatus, evacuation in the laminating apparatus, aging, pressurization to the green sheet and removal of the jig are performed. However, the time required for preheating, setting, aging and removal is
Both are less than 1 minute.

In the present invention, it is required that a cushioning material be arranged between the green sheet and the jig when the green sheet is pressed. In the present invention, a plate material having a certain thickness and made of a material that is at least softer than a jig made of metal or a green sheet made of ceramics (for example, a resin plate or paperboard) is used as the cushioning material.

The substance used as the cushioning material is at least the temperature at the time of lamination (about 100 ° C.
It is preferably capable of withstanding a predetermined time for 150 ° C.) or pressure (70 kg / cm ^{2 to} 90 kg / cm ² ).

As the rubber plate, for example, natural rubber, silicone rubber, urethane rubber, polysulfide rubber, fluororubber,
There are elastic rubber sheets such as synthetic rubbers such as diene rubber, olefin rubber, and vinyl rubber.
Examples of paperboard include corrugated cardboard, white paperboard, yellow paperboard,
There are papers that are somewhat thicker than Western paper, such as colored balls and construction paper. In this case, it is preferable to select a rubber plate having elasticity rather than paperboard having no elasticity, and it is also preferable to select a silicone rubber having excellent heat resistance among the rubber plates.

The thickness of the cushioning material is preferably 0.1 mm to 5 mm, more preferably 1 mm to 3 mm. If the cushioning material is too thin, pressure equalization may not be sufficiently achieved. On the other hand, if the cushioning material is too thick,
It may be difficult to transfer heat from the jig side. It should be noted that a release paper having a thickness of several tens of μm, which is commonly used, does not satisfy the condition of the thickness, and therefore is not included in the concept of the cushioning material here.

After that, the green sheet laminate obtained by the laminating step is further degreased under predetermined conditions,
A calcinated body is obtained through preliminary calcination and main calcination.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a method for manufacturing a multilayer aluminum nitride substrate will be described in detail below with reference to FIGS. Here, 8 kinds of samples are prepared by 8 methods (5 of which correspond to the examples).
Were prepared and evaluated for them.

First, 100 g of AlN powder having an average particle size of 1.7 μm, 11 g of an acrylic binder, 4.0 g of Y ₂ O ₃ as a sintering aid, 30 g of butanol and ethanol as a solvent in total, and DO as a plasticizer
A [Dioctyl adipate, boiling point = 215 ° C (5 mmHg)]
4.2g was added. Then, by uniformly kneading this mixture with a ball mill, a uniform raw material slurry for producing the green sheet 1 was produced. Further, a raw material slurry was prepared by removing only Y ₂ O ₃ from the raw material slurry and used as the raw material slurry for producing the outermost green sheet 1a.

Then, a green sheet 1 having a thickness of 0.3 mm and an outermost green sheet 1a were continuously formed from the two kinds of raw material slurry by a doctor blade method. About 80% of the solvent in the green sheets 1 and 1a was removed by the primary drying performed in the drying furnace of the sheet forming machine.

Further, the obtained green sheets 1, 1a
After cutting the outer shape into 250mm square, green sheet 1,
Secondary drying was performed on 1a at 80 ° C. for 5 hours. By this secondary drying, the solvent in the green sheets 1 and 1a was almost completely removed, and the plasticizer DOA was reduced to about 90% by weight of the initial blending amount.

Then, the through holes 2 and the positioning holes 2a were formed by punching predetermined coordinates on the green sheet 1 by punching. Similarly, positioning holes 2a were formed in the outermost green sheet 1a.

Next, a tungsten paste P was screen-printed on a predetermined portion of the green sheet 1. Then, as shown in FIG. 1, the conductor patterns 3 are formed inside the through-hole forming holes 2 and on the surface of the green sheet 1, respectively.
a and 3b were formed.

Further, by screen-printing the same tungsten paste P, as shown in FIG.
A solid pattern 3c for preventing tungsten carbonization was formed on the entire one surface of the outermost green sheet 1a. Then, the green sheets 1 and 1a were subjected to tertiary drying at 70 ° C. for 20 hours to mainly remove the solvent in the tungsten paste P.

Next, some of the guide pins 4
After performing the fourth drying (100 ° C., 30 hours to 40 hours) on the green sheets 1 and 1a on the jig 4 having a, a laminating step was performed under predetermined conditions. However, the sample, (that is, the comparative example) green sheet 1,
About 1a, the predetermined laminating step was performed without performing the fourth drying.

At this time, in some of the laminates (samples, ...), as shown in FIGS. 3 and 4, the silicone rubber 6 having a thickness of 2 mm and the thickness of 50 μm are used as a cushioning material.
m of release paper 5 was interposed between the jig 4 and the green sheet 1a. On the other hand, in the other laminates, as shown in FIG. 6, only the release paper 5 having a thickness of 50 μm was interposed between the jig 4 and the green sheet 1a as in the conventional case. In Table 1, each sample immediately before the laminating step
Shows the residual amount (% by weight) of the plasticizer. In addition, in the laminating step, the surface pressure during pressurization was set to 80 kg / cm ² , and the temperature during pressurization was uniformly set to 130 ° C. On the other hand, the vacuuming time (minutes) and pressurizing time (minutes) were set as shown in Table 1. Then, the total required time (minutes) was obtained by adding the time required for preheating, setting, aging, and removal (here, 3 minutes) to the evacuation time and pressurization time.

After carrying out the above-mentioned laminating step, the green sheet laminated body 7 was degreased in an inert atmosphere and further calcined. Then, at this point, the incidence (%) of delamination was investigated by touch and sight. The results are shown in Table 1.

Next, the obtained calcined body was subjected to main firing under predetermined conditions to obtain a sintered body 8. By cutting the outer shape of this sintered body 8 and subjecting it to surface grinding, a multilayer AlN substrate 9 as a final product was obtained as shown in FIG. Then, a tensile test is conducted using the obtained samples to determine the adhesion strength (kgf / kgf) between the layers of the green sheet 1.
cm ² ) was measured. The results are also shown in Table 1.

[0041]

[Table 1]

Each method was evaluated in four grades (extremely excellent, excellent, good, and poor) based on the three results of the time required for the laminating step, the occurrence rate of delamination and the adhesion strength. As a result, the effectiveness of setting the residual amount of the plasticizer to less than 20% by weight and interposing the silicone rubber 6 was clarified as in Examples. In addition, the residual amount of plasticizer is 1
It was also clear that if the content is less than 0% by weight, the adhesion strength can be improved. Furthermore, it was also revealed that both the reduction of the residual amount of the plasticizer and the use of the silicone rubber 6 give better results than the case where either one is performed alone.

Summarizing the above results, the method for producing the sample is the best, the method for producing the sample is the second best, and the sample ,,,
It is concluded that the method of making the is the second best after the two. In particular, according to the method for producing the sample, although the laminating time is about ⅙ of the conventional time, there is no delamination and the adhesion strength is good. Therefore, according to the method of the above-described embodiment, the operating efficiency of the equipment is improved and the amount that can be laminated per day is increased as compared with the conventional method.

On the other hand, a sample as a comparative example,
In the method for producing, it was not possible to obtain good results comparable to those in the above-mentioned examples. In addition, even if the evacuation time and the pressurization time are long as in the method for producing a sample, it is not possible to suppress delamination that frequently occurs.

The present invention is not limited to the above embodiment, but can be modified as follows. For example, (a) the ceramic powder may be other than the aluminum nitride powder. Also, green sheets 1, 1a
The number of stacked layers is also arbitrary.

(B) The release paper 5 arranged between the green sheet 1a and the silicone rubber 6 is not particularly essential. Instead of the above method, the surface of the silicone rubber 6 may be coated with a release agent or the like.

(C) When performing the fourth drying, the green sheets 1 and 1a do not necessarily have to be dried on the jig 4. However, when it is desired to reduce the residual rate of the plasticizer to less than 10% by weight in the fourth drying, there is an advantage that the handling property is not impaired if the drying is performed on the jig 4.

(D) Predetermined conditions (eg hardness, thickness,
Not only rubber plates and paperboards, but also soft resin materials, metal plate materials, natural products typified by cotton and leather, and ceramic fiber papers are used as cushioning materials as long as they satisfy the conditions (such as heat resistance). It is also possible.

Here, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments and other examples will be listed below together with their effects. (1) In the invention described in claims 1, 3 and 4, the residual amount of the plasticizer is less than 10% by weight of the initial compounding amount. With this method, higher adhesion strength can be secured.

(2) Claims 2, 3 and 4, technical idea 1
In the invention described in any of 1, the cushioning material has a thickness of 1 mm to
Must be 3 mm silicone rubber 6. According to this method, it is possible to sufficiently achieve equalization of pressure, it is difficult for heat to be transferred from the jig side, and there is no fear that the cushioning material is deteriorated by heat during lamination.

(3) Claims 2 and 3, technical ideas 1 and 2
In the invention described in any one of 1., vacuuming and pressurizing are performed at the same time. With this method, the time required for the laminating step can be further shortened.

[0052]

As described above in detail, according to the method for producing a multilayer ceramic substrate of the present invention as defined in claim 1, the depressurization time can be shortened by removing the plasticizer, so that the delamination can be performed. This has the excellent effect of suppressing the occurrence of heat and shortening the time required for the laminating step.

Further, according to the method of the invention described in claim 2, since the pressing time can be shortened by equalizing the pressure, delamination can be suppressed and the time required for the laminating step can be shortened. It has an excellent effect that

Further, according to the method of the present invention as defined in claim 3, both depressurization time and pressurization time can be shortened by removing the plasticizer and equalizing the pressure. It has an excellent effect that the time required for the laminating step can be further shortened.

Further, according to the method of the invention described in claim 4, it is excellent in that the uniform pressurization can be realized more surely as compared with the case where, for example, a paperboard having no elasticity is used as the cushioning material. Produce the effect. Moreover, since it is a resin plate having elasticity, it has an excellent effect that it can be repeatedly used.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional view showing a state in which a conductor pattern is printed on a green sheet.

FIG. 2 is a partially enlarged cross-sectional view showing a state in which a solid pattern is printed on the outermost green sheet.

FIG. 3 is a cross-sectional view showing a state in which a plurality of green sheets are fixed on a laminating jig.

FIG. 4 is a cross-sectional view showing a state in which a green sheet is pressed in a laminating step.

FIG. 5 is a cross-sectional view showing a multilayer AlN substrate.

FIG. 6 is a cross-sectional view showing a state where a green sheet is pressed without using silicone rubber in a laminating step.

[Explanation of symbols]

1 ... Green sheet, 1a ... (Outermost layer) green sheet, 4 ... Jig, 6 ... Silicone rubber as cushioning material, 7
... green sheet laminate, 9 ... multilayer AlN substrate as multilayer ceramic substrate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B28B 11/04

Claims (4)

[Claims] 1. A plurality of green sheets formed by mixing and molding ceramic powder, a binder, a solvent, a plasticizer and the like are arranged between jigs for laminating, and then a vacuum is drawn in the laminating apparatus and the green sheets are transferred to the green sheets. In the method for manufacturing a multilayer ceramic substrate, which comprises performing a laminating step of applying pressure and further performing a preliminary firing and a main firing of the green sheet laminate, in the green sheet before vacuuming performed in the laminating step. A method for producing a multilayer ceramic substrate, characterized in that the plasticizer is removed to less than 20% by weight of the initial blending amount. 2. A plurality of green sheets formed by mixing and molding ceramic powder, a binder, a solvent, a plasticizer and the like are arranged between jigs for laminating, and then a vacuum is drawn in the laminating apparatus and the green sheets are transferred to the green sheets. In the method for manufacturing a multilayer ceramic substrate, the cushioning material is arranged between the green sheet and the jig in the method for manufacturing a multi-layer ceramics substrate, in which the laminating step of performing the pressurization of A method for manufacturing a multilayer ceramic substrate, which comprises applying pressure in a state. 3. The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein pressure is applied in a state where a cushioning material is arranged between the green sheet and the jig. 4. The method for manufacturing a multilayer ceramic substrate according to claim 2, wherein the cushioning material is a rubber plate having elasticity.