JPH05327220A - Manufacture of multilayer ceramic base - Google Patents

Abstract

PURPOSE:To settle problems of a slippage of a component mounting position and deterioration of connection reliability due to shrinkage of a green sheet laminate at the time of baking and to obtain a multilayer ceramic base which shrinks only in the direction of thickness and does not shrink in the direction of plane, in a method for manufacture of the multilayer ceramic base to be used for an electronic apparatus or the like. CONSTITUTION:A green sheet 1 on which a wiring is patterned by a conductor paste composition and which is constituted of glass-ceramic containing an organic binder and a plasticizer at least is laminated in desired numbers. On a part or the whole of the surface of a green sheet laminate thus prepared, an alumina layer 2 is formed by using a paste composition of which the main constituent is alumina which is not sintered at the baking temperature of a base material constituted of glass-ceramic, and then baking is made. Thereafter the alumina layer 2 is removed.

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 multi-layer ceramic substrate for mounting semiconductor LSIs, chip parts, etc. and interconnecting them.

[0002]

2. Description of the Related Art In recent years, low-temperature sintered glass / ceramic multilayer substrates have been developed, and conductive materials that can be used include gold, silver, copper,
Palladium or mixtures thereof have come to be used. These metals have a lower conductor resistance than the conventionally used tungsten, molybdenum, etc., and since the equipment that can be used is safe, they can be manufactured at low cost.

On the other hand, among these metals, noble metals such as gold, silver, and palladium are expensive and have large price fluctuations. Therefore, it is desired to use a copper electrode material which is inexpensive and has little price fluctuations.

Here, an example of a typical method for producing such a low temperature sintered multilayer ceramic substrate will be described. There are roughly three types of methods for manufacturing low-temperature sintered multilayer ceramic substrates. First of all, silver is used for the inner layer electrodes of the multilayer substrate,
It is obtained by stacking a desired number of green sheets of low-temperature sintered substrates, firing in air, and then printing and firing silver and palladium paste on the uppermost layer. This uses silver with low impedance inside and silver / palladium having solder heat resistance as the uppermost layer. The second is a method in which silver is used for the internal electrodes as in the former and copper is used for the uppermost layer. By using copper for the uppermost layer wiring, it is effective in terms of lower impedance and solder wetting than the former silver / palladium. (For example, Japanese Patent Publication No. 03-78798). However, since the copper used for the uppermost layer has a low eutectic temperature with silver, a low temperature fired copper paste of about 600 ° C. must be used. As a result, there are many problems in terms of adhesive strength and solder wetting. Finally, as a third method, there is a method of using copper electrodes for the inner layer and the uppermost layer (JP-A-55-128899). This method is the best in terms of conductor resistance, solder wettability, and cost, but it must be fired in a neutral atmosphere such as nitrogen, and its manufacture is difficult. Generally, in order to use a copper electrode, a wiring pattern is formed by screen-printing a copper paste on a substrate, and after drying, the temperature is below the melting point of copper (850 to 950 ° C.) and the conductor paste is not oxidized. Firing is performed in a nitrogen atmosphere in which the oxygen partial pressure is controlled so that the organic components therein are sufficiently burned. When laminated in multiple layers, it is obtained by printing and baking the insulating layer under the same conditions. However, it is difficult to control the atmosphere in the firing process under an appropriate oxygen partial pressure, and when multilayering, it is necessary to repeat firing each time after printing each paste, which leads to a long lead time and cost of equipment. It has issues such as improvement. Therefore, Japanese Patent Publication No. 03-20914 has already disclosed a method of producing a ceramic multilayer substrate by using a cupric oxide paste in three steps of a binder removal step, a reduction step and a firing step. It uses cupric oxide as the starting material of the conductor to make a multilayer body, and in the binder removal step, heat treatment is performed in a sufficient oxygen atmosphere for carbon and at a temperature sufficient to thermally decompose the organic binder inside. Then, it is established by the reduction step of reducing cupric oxide to copper and the firing step of sintering the substrate. This facilitated the control of the atmosphere during firing and made it possible to obtain a dense sintered body.

[0005]

However, the products produced by the conventional method for manufacturing a multilayer ceramic substrate described above have the following problems.

That is, shrinkage occurs due to sintering when firing a multilayer ceramic substrate. The shrinkage due to the sintering depends on the substrate material used, the green sheet composition, the powder lot, and the like. This causes some problems in the production of multilayer ceramic substrates. First, in manufacturing a multilayer ceramic substrate, the inner layer wiring is fired as described above and then the uppermost layer wiring is formed. Therefore, if the shrinkage error of the substrate material is large, the inner layer electrode is dimensional error due to the uppermost layer wiring pattern. Cannot connect with. As a result, a land having an unnecessarily large area has to be formed in the uppermost wiring portion so as to allow the shrinkage error in advance, and it cannot be used in a circuit that requires high-density wiring. In addition, a method is used in which several screen plates for the uppermost layer wiring are prepared according to the shrinkage error and are used according to the shrinkage rate of the substrate. This method is uneconomical because many screen versions must be prepared.

However, if the uppermost layer wiring can be performed at the same time as the inner layer firing, a large land is not required. However, even with this simultaneous firing method, the shrinkage error of the substrate itself still exists, so the cream solder printing at the time of the last component mounting. In the above, there occurs a case where the necessary portion cannot be printed due to the error. Also, when mounting components, a deviation from a predetermined component position occurs.

Secondly, the multilayer ceramic substrate produced by the green sheet laminating method has different shrinkage rates in the width direction and the longitudinal direction depending on the film forming direction of the green sheet. This is also an obstacle to the production of the multilayer ceramic substrate.

In order to reduce these shrinkage errors as much as possible, it is necessary to sufficiently control the substrate material and the green sheet composition, the difference in powder lot, and the lamination conditions (pressing pressure, temperature) in the manufacturing process. However, it is generally said that the shrinkage ratio error is about ± 0.5%.

This is a common problem with ceramics and glass-ceramics, regardless of the multilayer ceramic substrate.

The present invention is intended to solve such a problem, and an object of the present invention is to provide an excellent method for producing a multilayer ceramic substrate in which sintering of the substrate material occurs only in the thickness direction and shrinkage in the plane direction does not occur. To do.

[0012]

In order to achieve the above object, the present invention laminates a required number of green sheets made of a glass / ceramic containing at least an organic binder and a plasticizer which are patterned with a conductor paste composition. Green sheet A green sheet is formed on both sides of the laminate by using a paste composition whose main component is an inorganic component that does not sinter at the sintering temperature of the glass / ceramic substrate material. After firing the laminate, the non-sintered inorganic component layer is removed.

[0013]

Therefore, according to the present invention, when the laminated body of the green sheets made of glass / ceramic is fired, it shrinks only in the thickness direction and does not shrink in the plane direction.
It is possible to obtain a multilayer ceramic substrate having excellent dimensional accuracy.

The operation of the present invention will be described below. First, in the manufacturing method of the present invention, a green sheet containing at least an organic binder and a plasticizer is prepared on a low temperature sintered substrate material made of glass / ceramic, and an electrode pattern is formed with a conductor paste composition. The desired green multilayer body is obtained by laminating a desired number of the electrode pattern-formed green sheets of (1) to form a multilayer. Then, a paste composition containing an inorganic component as a main component which does not sinter at the firing temperature of the glass / ceramic low-temperature sintering substrate material is formed on a part of the surface of the laminate or on both surfaces of the glass / ceramic green sheet laminate. It is applied over the entire surface to form an inorganic component layer. As a result, the inorganic component layer that does not sinter even if the laminate is fired suppresses shrinkage in the plane direction of the green sheet laminate, and does not shrink except in the thickness direction. Since it is sandwiched by the non-sinterable materials formed on both sides, contraction in the plane direction is prevented, and contraction occurs only in the thickness direction due to softening of the glass in the green sheet laminate made of glass-ceramic. After that, the unnecessary non-sintering inorganic component layer is removed to obtain a desired multilayer ceramic substrate.

The firing of the green sheet laminate made of the above glass / ceramic is usually performed in the range of 800 ° C to 1000 ° C. 90 when using copper or silver electrodes
It is desirable to carry out at 0 ° C. The inorganic components of the paste composition that do not sinter at the firing temperature of the glass / ceramic substrate material are Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , and Be.
It is composed of a component containing at least one of O and BN. 90
Al ₂ O ₃ is most effective for the glass-ceramic substrate material that is performed at a firing temperature of 0 ° C.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view when a coating film is formed on a green sheet laminate by a paste composition that does not sinter in a method for manufacturing a multilayer ceramic substrate according to an embodiment of the present invention. The inorganic component layers 3 are internal electrodes.

(Embodiment 1) Next, a first embodiment of the method for manufacturing a multilayer ceramic substrate will be described.

As the glass / ceramic of the substrate material, a composition (MLS-19 manufactured by Nippon Electric Glass Co., Ltd.) was used in which lead borosilicate glass powder and alumina powder as a ceramic material were mixed in a weight ratio of 50:50. This glass / ceramic powder as an inorganic component, polyvinyl butyral as an organic binder, di-n-butyl phthalate as a plasticizer, and a mixed solution of toluene and isopropyl alcohol (30
(70 weight ratio), and these were mixed into a slurry.

This slurry was formed into a sheet on an organic film by the doctor blade method. At this time, a system was used in which the steps of drying, punching, and if necessary, via hole processing were continuously performed from the film formation.
On the green sheet 1 thus obtained, the internal electrodes 3 were formed and the via hole filling printing was performed by a screen printing method using a conductor paste. The conductor paste was made by adding 5 wt% of glass frit (GA-9 glass powder manufactured by Nippon Electric Glass Co., Ltd., average particle size 2.5 μm) for obtaining adhesive strength to Ag powder (average particle size 1 μm) as an inorganic component, As the organic binder, polyvinyl butyral dissolved in terpineol was used, and the inorganic component and the organic binder were mixed with a three-stage roll so as to have an appropriate viscosity. The Ag paste for filling the via was used by adding 15% by weight of the above-mentioned glass-ceramic powder as an inorganic component to the above-mentioned conductor paste.

Next, the paste composition which does not cause sintering does not contain alumina as an inorganic component (ALM-4 manufactured by Sumitomo Aluminum Co., Ltd.).
1 average particle size 1.9 μm) using only powder, and dissolving ethyl cellulose in terpineol as an organic binder,
This was added to alumina powder and mixed using a three-stage roll so as to have an appropriate viscosity.

First, a predetermined number of printed sheets of the internal electrodes 3 were stacked on the green sheet 1 for a substrate, and thermocompression bonding was performed in this state to form a green sheet laminate. The thermocompression bonding conditions were a temperature of 80 ° C. and a pressure of 200 kg / cm ² . The thickness of the green sheet 1 for the substrate was set to about 200 μm. Next, a paste composition made of alumina was applied to both surfaces of the green sheet laminate to obtain a mesh number of 200 mesh,
Print twice using a screen plate with an emulsion thickness of 30 μm. As a result, the thickness of the coating layer of the paste composition was about 10
It became 0 μm. This green sheet laminate is
The laminate is dried for 10 minutes, and then the laminate is cut in order to remove the portion where the surface of the green sheet laminate is not covered with the alumina paste.

Next, the green sheet laminated body was treated with alumina 9
It was placed on a substrate containing 6% and baked in a belt furnace in air at 900 ° C. for 1 hour (holding time at 900 ° C. is about 12 minutes).

Since the unsintered alumina layer 2 exists on the surface of the obtained multilayer ceramic substrate after firing, the alumina layer 2 could be removed cleanly by ultrasonic cleaning in a butyl acetate solvent. .. The shrinkage rate of the multilayer ceramic substrate after firing was 0.1% or less.

The thickness of the alumina layer 2 is 10 μm to 3 μm.
A multilayer ceramic substrate was prepared by changing the thickness to 00 μm, and the shrinkage rate was measured for each. As a result, the shrinkage is about 5% at 10 μm, about 1% at 15 μm, and about 0.6 at 20 μm.
%, About 0.2% at 50 μm, about 0.0 at 100 μm
It was about 0.05% at 8% and 200 μm, about 0.05% at 300 μm, and about 0.05% at 400 μm. From these results, it was possible to produce a multilayer ceramic substrate in which the thickness of the alumina layer 2 was 15 μm or more and the shrinkage rate was 1% or less, and shrinkage in the planar direction hardly occurred. However, in terms of cost, the thickness of the alumina layer 2 is 400 μm.
However, those having a layer thickness in the range of 15 μm to 300 μm are desirable. Further, considering the production cost of the screen plate for printing and the like, the alumina layer 2 having the thickness of 50 μm to 300 μm is optimal.

When the uppermost wiring pattern was screen-printed on the thus-prepared multilayer ceramic substrate using silver / palladium paste and dried and fired, print misalignment hardly occurred.

Although Al ₂ O ₃ is used as the inorganic component layer in this embodiment, other components such as MgO, ZrO ₂ and Ti are used.
Similar effects were obtained also in the paste composition using O ₂ , BeO, and BN.

(Embodiment 2) Next, a second embodiment of the present invention will be described. FIG. 2 shows a cross section of the multilayer ceramic substrate in one stage of the manufacturing method of this embodiment.
Description will be given using the same numbers as in the first embodiment.

This example differs from the first example in that the paste composition which does not sinter is applied to the surface of the green sheet laminate by dip coating instead of screen printing. The other steps and materials used were the same as those in the first embodiment.

That is, the green sheet laminate produced in the same manner as in the first embodiment was dipped in a tank filled with the paste composition and then dried at 50 ° C. for 10 minutes. FIG. 2 shows the green sheet laminated body after the dipping, but the difference from FIG. 1 is that the alumina layer 2 is formed on the side surface of the green sheet 1 because the coating is performed by the dipping method.

The step of firing the green sheet laminate is also the same as in the case of the first embodiment.

The shrinkage rate of the multilayer ceramic substrate after firing was 0.1% or less as in the case of the first embodiment.
In addition, silver
When the uppermost wiring pattern was screen-printed using a palladium paste and dried and fired, print misalignment hardly occurred.

(Embodiment 3) Next, a third embodiment of the present invention will be described. Also in this embodiment, the green sheet 1 is manufactured in the same manner as in the first embodiment, and the conductor paste using CuO instead of Ag in the first embodiment is used for the formation of the internal electrode 3 and the via hole. The pad printing was performed by the screen printing method. The conductor paste is a glass frit (LS-made by Nippon Electric Glass Co., Ltd.) for obtaining adhesive strength to CuO powder (average particle size 3 μm).
0803 glass powder, average particle size 2.5 μm) 3 wt%
The added component was used as an inorganic component, and ethyl cellulose was dissolved in terpineol as an organic binder, and the inorganic component and the organic binder were mixed with a three-stage roll so as to have an appropriate viscosity. The CuO paste for filling the via was used by adding 15% by weight of the above glass-ceramic powder as an inorganic component to the above conductor paste.

Next, for the paste composition that does not sinter, only beryllium oxide (average particle size: 1 μm, manufactured by Kanto Chemical Co., Inc.) powder was used as an inorganic component, and polyvinyl butyral resin (PVB) was dissolved in terpineol as an organic binder. In addition to the beryllium oxide powder, it was prepared by mixing with a three-stage roll so as to have an appropriate viscosity (150 Pa.s).

First, a predetermined number of sheets of the substrate green sheet 1 on which the internal electrodes 3 were printed were stacked and thermocompression bonded in this state to form a green sheet laminate. The thermocompression bonding conditions were a temperature of 80 ° C. and a pressure of 200 kg / cm ² . The thickness of the green sheet 1 for the substrate was set to about 200 μm. Next, the paste composition made of beryllium oxide was printed on both sides of the green sheet laminate twice using a screen plate having a mesh number of 200 mesh and an emulsion thickness of 30 μm. As a result, the thickness of the coating layer of the paste composition was about 100 μm. The green sheet laminate was dried at 50 ° C. for 10 minutes, and then the laminate was cut so that the surface of the green sheet laminate was covered with the beryllium oxide paste.

Next, the firing process will be described. The first is a binder removal process. The organic binder of the green sheet, CuO paste, and beryllium oxide paste used in the invention is polyvinyl butyral or ethyl cellulose, so that the decomposition temperature in air is 500 ° C.
Since the above conditions are sufficient, the temperature was set to 600 ° C. Thereafter, the green sheet laminate was reduced at 200 ° C. for 5 hours in a 100% hydrogen gas atmosphere. The Cu layer at this time is X
An analysis by line diffraction confirmed that it was 100% Cu. Next, in the firing step, firing was carried out in a mesh belt furnace at 900 ° C. in pure nitrogen gas.

The beryllium oxide layer on the surface of the multilayer ceramic substrate produced as described above was removed by ultrasonic cleaning in the same manner as in Example 1, and the shrinkage rate was evaluated to be 0.05%.
The shrinkage was as follows.

Also in this example, when the uppermost layer of the multilayer ceramic substrate was printed and fired using the copper paste, no printing misalignment occurred.

In this example, BeO was used as the material of the inorganic component layer, but other materials such as Al ₂ O ₃ , MgO and Zr were used.
Similar effects were obtained with a paste composition using O ₂ , TiO ₂ , and BN. The same effect was obtained even when the paste composition was formed on both sides and a load was applied during firing.
However, when the paste compositions applied to both surfaces are formed to have different thicknesses on the front and back surfaces, the warp of the substrate is likely to occur.

Further, the wiring pattern of the uppermost layer was formed after firing the substrate, but it is needless to say that the same effect can be obtained by printing the conductor paste for the uppermost layer wiring on the green sheet in advance and simultaneously firing it. Nor.

As described above, according to the present invention, when a layer of a coating film made of an inorganic component that does not sinter in the manufacturing process of a multilayer ceramic substrate is provided and the substrate is fired, shrinkage due to sintering does not occur in the plane direction at all. A multilayer ceramic substrate is obtained. It goes without saying that this method can be applied not only to a ceramic multilayer wiring board, but also to a laminated ceramic capacitor, a ceramic structural material that requires stability of shrinkage, and the like.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. In this embodiment, the green sheet 1 is manufactured by using the same materials and processes as those in the first embodiment.
The formation of the internal electrode 3 and the via hole filling printing were carried out by using a conductor paste using CuO as in the case of the third embodiment.

Further, the production of a paste composition which does not cause sintering is also carried out according to the third embodiment.

First, a predetermined number of printed sheets of the internal electrodes 3 were stacked on the green sheet 1 for the substrate, and thermocompression bonding was performed in this state to form a green sheet laminate. The thermocompression bonding conditions were a temperature of 80 ° C. and a pressure of 200 kg / cm ² . The thickness of the green sheet 1 for the substrate was set to about 200 μm. Further, a paste composition made of beryllium oxide was applied to both surfaces of the green sheet laminate so as to leave the electrode portions exposed on the surface thereof, the number of meshes was 200 mesh, and the emulsion thickness was 3
Printing was performed twice using a 0 μm screen plate. As a result, the thickness of the coating layer of the paste composition was about 100 μm. The green sheet laminate was dried at 50 ° C. for 10 minutes, and then the laminate was cut so that the surface of the green sheet laminate was covered with the beryllium oxide paste. The subsequent firing step was performed according to the case of the third embodiment.

The beryllium oxide layer on the surface of the multilayer ceramic substrate produced as described above was removed by ultrasonic cleaning in the same manner as in Example 1, and the shrinkage rate was evaluated to be 0.05%.
The shrinkage was as follows.

Further, the uppermost layer of the multilayer ceramic substrate was printed and baked using a copper paste. In this example, the paste composition was printed so as to leave the electrode portion exposed on the surface, so that the paste composition did not adhere to the electrode portion. Therefore, it was possible to obtain a multilayer ceramic substrate in which the copper paste printed on the uppermost layer and the electrode portion were joined well.

Although the wiring pattern of the uppermost layer is formed after firing the substrate, even in the case of simultaneous firing in which the conductor paste for the uppermost wiring is printed on the green sheet in advance, the pattern can be mounted from the aspect of component mounting. The method of printing the inorganic composition while avoiding a part of the above is effective.

[0047]

As is apparent from the above examples, the present invention forms an inorganic component layer on the surface of a green sheet laminate by using a paste composition containing an inorganic component that is not sintered as a main component, and after firing this inorganic component layer. Since the ceramic substrate shrinks only in the thickness direction and does not shrink in the planar direction when it is fired because it has undergone the process of removing the component layers, it depends on the substrate material, green sheet composition, powder lot, etc. used for the ceramic substrate. It is possible to always obtain a ceramic substrate having the same size. Similarly, also in the production of the multilayer ceramic substrate, the innermost layer wiring is baked and the uppermost layer wiring is formed as described above, whereby the uppermost layer wiring pattern and the inner layer wiring can be completely connected.
As a result, it is possible to obtain a multilayer ceramic substrate in which the land area for connection can be reduced and which enables high-density mounting of components. Further, the number of screen plates is small, and it is economical because there is no need to expand the inner layer pattern in consideration of shrinkage in the board design.

As described above, it is possible to very effectively solve the problem of shrinkage error, which is the greatest drawback in the method for manufacturing a multilayer ceramic substrate by the green sheet laminating method.

[Brief description of drawings]

FIG. 1 is a sectional view of a green sheet laminate according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a green sheet laminate after formation of an inorganic component layer by dip coating in the second embodiment of the present invention.

[Explanation of symbols]

 1 Green sheet 2 Alumina layer (inorganic component layer) 3 Internal electrode (wiring)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Hakotani 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kazuhiro Miura, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. A required number of green sheets made of glass / ceramic containing at least an organic binder and a plasticizer in which wiring is patterned with a conductor paste composition are laminated, and the glass / ceramic substrate material of the glass / ceramic substrate material is provided on both sides of the green sheet laminate. An inorganic component layer is formed on a part or the whole of the surface of the green sheet laminate by using a paste composition containing an inorganic component as a main component which is not sintered at a sintering temperature, and the green sheet laminate is fired and then sintered. A method for manufacturing a multilayer ceramic substrate, characterized in that the inorganic component layer is removed. 2. A paste composition containing an inorganic component as a main component, which does not sinter at a sintering temperature of a glass / ceramic substrate material, is printed on a green sheet laminate by a screen printing method, and after drying, a predetermined size is obtained. The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein the green sheet laminate is cut. 3. A paste composition containing an inorganic component as a main component, which does not sinter at the sintering temperature of the glass / ceramic substrate material, is formed on the entire surface of the green sheet laminate by dip coating. A method for manufacturing the multilayer ceramic substrate described. 4. A coating film of a paste composition whose main component is an inorganic component which does not sinter at the sintering temperature of a glass / ceramic substrate material, is formed on the surface of the green sheet laminate in a thickness of 15 μm to 3 μm.
The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein the multilayer ceramic substrate is formed in a range of 00 μm. 5. A coating film of a paste composition whose main component is an inorganic component that does not sinter at the sintering temperature of the glass / ceramic substrate material, leaving a part of the electrode portion formed on the surface of the green sheet laminate. The method of manufacturing a multilayer ceramic substrate according to claim 1, wherein the multilayer ceramic substrate is formed. 6. The method for producing a multilayer ceramic substrate according to claim 1, wherein the firing temperature is 800 ° C. to 1000 ° C. 7. The paste composition comprises Al ₂ O ₃ , MgO, Z.
The method for producing a multilayer ceramic substrate according to claim 1, wherein the paste composition is a paste composition containing at least one of rO ₂ , TiO ₂ , BeO, and BN. 8. The method for producing a multilayer ceramic substrate according to claim 1, wherein the inorganic component layer is removed by an ultrasonic cleaning method. 9. A conductor paste composition comprising Ag, Ag / Pd,
2. The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein any one of Ag / Pt, Cu, and CuO is a main component.