JP3082475B2 - Method for manufacturing multilayer ceramic substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic multilayer wiring board for mounting electronic parts such as semiconductor LSIs and chip parts and interconnecting them, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the development of a low-temperature sintered glass / ceramic multilayer substrate, usable conductor materials include gold, silver, and silver.
Copper, palladium or mixtures thereof have been used. These metals have lower conductor resistance than conventionally used tungsten, molybdenum, and the like, and can be used with safe equipment at low cost.

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

Here, an example of a typical method for producing such a low-temperature sintered multilayer substrate will be described. There are three main types of low-temperature sintered multilayer substrates. Firstly, silver is used for the inner layer electrode of the multilayer substrate, a desired number of green sheets of the low-temperature sintering substrate are laminated and fired in the air, and then silver and palladium paste are printed and fired on the uppermost layer to obtain a green sheet. Things. This uses silver having a small impedance inside and silver / palladium having solder heat resistance as the uppermost layer. The second method is to use silver for the internal electrodes as in the former and use copper for the uppermost layer. By using copper for the uppermost layer wiring, the impedance and the solder wettability are lower than those of the former silver and palladium. It is valid. But,
Copper used for the uppermost layer has a low eutectic temperature with silver and is 600 ° C.
A low temperature fired copper paste 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 using copper electrodes for the inner layer and the uppermost layer. It is best in terms of conductor resistance, solder wettability, and cost, but all must be fired in a neutral atmosphere such as nitrogen, and its fabrication is difficult. Generally, in order to use a copper electrode, a wiring pattern is formed on a substrate by screen printing a Cu paste, dried, and then dried at a temperature lower than the melting point of Cu (85% or less).
(About 0 to 950 ° C.) and firing in a nitrogen atmosphere in which the oxygen partial pressure is controlled so that Cu is not oxidized and organic components in the conductor paste are sufficiently burned. In the case of forming a multilayer, the insulating layer is obtained by printing and firing under the same conditions.
However, it is difficult to control the atmosphere in the firing step under an appropriate partial pressure of oxygen, and in the case of multilayering, it is necessary to repeat firing each time after printing each paste, leading to a longer lead time and a longer equipment time. It has problems such as cost increase. Thus, Japanese Patent Application No. 59-147833 has already disclosed a method of producing a ceramic multi-layer substrate using a cupric oxide paste and performing three steps of a binder removal step, a reduction step, and a firing step. It produces a multilayer body using cupric oxide as a starting material for a conductor, and performs a heat treatment in a binder removing step in an oxygen atmosphere sufficient for carbon and at a temperature sufficient to thermally decompose the internal organic binder. Next, a reduction step for reducing cupric oxide to copper and a firing step for sintering the substrate are established. As a result, the atmosphere can be easily controlled during firing, and a dense sintered body can be obtained.

[0005] The ceramic multilayer substrate undergoes shrinkage due to sintering during firing. The shrinkage due to sintering differs depending on the substrate material, green sheet composition, powder lot, and the like used. This causes several problems in the fabrication of a multilayer substrate. First, in the production of a multilayer ceramic substrate, the inner layer wiring is fired as described above, and then the uppermost layer wiring is formed. Therefore, if the substrate material has a large shrinkage error, the inner layer wiring pattern and the dimensional error will cause the inner layer wiring to fail. Connection with the electrode cannot be made. As a result, a land with an unnecessarily large area must be formed in the uppermost layer electrode portion so as to allow a shrinkage error in advance, and it cannot be used for a circuit requiring 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 used according to the shrinkage ratio of the substrate. In this method, a large number of screen plates must be prepared, which is uneconomical.

On the other hand, if the uppermost layer wiring is performed simultaneously with 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. In some cases, printing cannot be performed on a required portion due to the error.
Also, in component mounting, there is a shift from a predetermined component position.

Second, the shrinkage of the multilayer substrate formed by the green sheet laminating method differs depending on the film forming direction of the green sheet depending on the width direction and the longitudinal direction. This also hinders the production of the ceramic multilayer substrate.

In order to minimize these shrinkage errors, it is necessary to manage not only the substrate material and the composition of the green sheet, but also the difference between powder lots and the laminating conditions (press pressure and temperature) in the manufacturing process. There is.
However, it is generally said that an error of the shrinkage ratio exists about ± 0.5%.

This is a problem common to ceramics and glass ceramics sintering irrespective of the multilayer substrate, and sintering of the substrate material occurs only in the thickness direction.
If a substrate with zero shrinkage in the plane direction can be manufactured, the above-mentioned problems can be solved, which is extremely effective industrially.

In order to solve the above problems, a green sheet containing at least an organic binder and a plasticizer is prepared on a glass / ceramic low-temperature sintered substrate material, and an electrode pattern is formed with a conductive paste composition. A desired number of the green sheets having the electrode pattern formed thereon are laminated, and thereafter, the glass sheet is laminated on both sides or one side of the green sheet laminate made of the low-temperature sintered glass / ceramic.
The ceramics are laminated so as to be sandwiched by green sheets made of an inorganic composition that does not sinter at the firing temperature of the ceramic low-temperature sintering substrate material, and the laminate is fired. Thereafter, a method of manufacturing a glass-ceramic substrate in which shrinkage during firing does not occur in a planar direction by removing an inorganic composition that does not sinter has been proposed in Japanese Patent Application No. 3-257553.

[0011]

However, the following problems have been clarified in the above-mentioned method of manufacturing a glass / ceramic substrate in which shrinkage during firing does not occur in a plane direction.

The glass-ceramic substrate is usually manufactured in the form of a square (square, rectangle) in many cases. However, both sides or one side of the glass-ceramic green sheet laminate are formed of an inorganic composition that does not sinter at the firing temperature. When firing treatment is performed after laminating the green sheets, the corner portions of the ceramic substrate may warp upward as shown in FIG. This is because the shrinkage of the glass-ceramic substrate in the planar direction is suppressed by the inorganic composition layer that does not sinter at the firing temperature of the glass-ceramic bonded to one or both surfaces of the glass-ceramic substrate.
It is considered that there is no inorganic composition layer on the side surface of the ceramic substrate, and the shrinkage stress of the glass / ceramic substrate tends to concentrate on the corner portion of the substrate. When the corner portion of the glass / ceramic substrate is warped, when the conductor paste is screen-printed to form the uppermost layer pattern on the substrate after firing, not only the printing becomes difficult but also the screen plate may be damaged. Therefore, a step of removing the warped corner portion of the substrate after the substrate is fired is required, which is uneconomical.

[0013] There is also a method of preventing the substrate warpage by placing an alumina sintered substrate or the like and firing while applying pressure. However, since the alumina sintered substrate covers the surface of the ceramic green sheet, a binder contained in the ceramic green sheet is used.
Since the decomposition and scattering of organic substances such as plasticizers are prevented, it is difficult to control the firing conditions.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a method of manufacturing a ceramic substrate which does not shrink in a planar direction and which easily prevents warping of a corner portion of the substrate during firing.

[0015]

In order to solve the above problems, a green sheet containing at least an organic binder and a plasticizer on a glass / ceramic low-temperature sintering substrate material is prepared.
An electrode pattern is formed with the conductive paste composition, a desired number of the green sheets and another green sheet on which an electrode pattern is formed are laminated, and the glass / ceramic green sheet laminate is fired at the firing temperature of the glass / ceramic. The layers are laminated so as to be sandwiched between green sheets made of an inorganic composition that is not bonded. After cutting the green sheet laminate so as to round the corners, the laminate is fired. Thereafter, by removing the inorganic composition that does not sinter, a glass-ceramic substrate is produced in which the corners of the substrate do not warp and shrinkage during firing does not occur in the planar direction.

[0016]

According to the present invention, by performing the above-described steps, a glass-ceramic substrate that shrinks only in the thickness direction during firing and does not shrink in the plane direction is prevented from warping at the corners of the substrate. Hereinafter, the operation of the present invention will be described.

First, in the production method of the present invention, a green sheet containing at least an organic binder and a plasticizer is prepared on a glass / ceramic low-temperature sintered substrate material, and an electrode pattern and a via electrode are formed with a conductive paste composition. A desired number of sheets and another green sheet on which an electrode pattern is formed are laminated to form a multilayer, and a green sheet made of an inorganic composition that does not sinter at the firing temperature of the substrate material is formed on both sides or one side of the glass-ceramic green sheet laminate To be laminated. Thereafter, a cutting process is performed so as to round the corners of the green sheet laminate. Thereby, even if the laminated body is fired, no shrinkage occurs except in the thickness direction. This is presumably because the sheet is sandwiched between non-sintered materials laminated on both sides or one side, so that contraction in the planar direction is prevented. Further, since the corners of the green sheet laminate are rounded, the concentration of the firing shrinkage stress of the glass ceramic on the corners of the substrate is reduced, and the corners of the substrate can be prevented from warping.
After sintering, a desired substrate can be obtained by removing unnecessary unsintered materials.

In the method of manufacturing a ceramic substrate according to the present invention, the corners of the ceramic green sheet laminate are cut so that the corners are rounded. This is because the shape of the green sheet has corners (squares). It is clear that the same effect can be obtained by using a green sheet having no corner from the beginning, for example, a circular shape or a shape close to a circular shape, without particularly dropping the corner of the laminate after lamination.

The firing of the glass-ceramic laminate is usually performed at a temperature in the range of 800 ° C. to 1000 ° C. Copper electrode,
When a silver electrode is used, it is performed at 900 ° C.

The inorganic components of the green sheet which are not sintered at the firing temperature of the glass / ceramic low-temperature sintering substrate material include Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ ,
At least one of BeO and BN is included. 900 ° C
Al ₂ O ₃ is most effective as a low-temperature sintering substrate material performed at the sintering temperature.

[0021]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a green sheet laminate according to one embodiment of the present invention.

Example 1 First, a 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 a weight ratio of alumina powder as a ceramic material to lead borosilicate glass powder was 50:50. This glass-ceramic powder was used as an inorganic component, polyvinyl butyral as an organic binder, ヂ -n-butyl phthalate as a plasticizer, and a mixed solution of toluene and isopropyl alcohol (30
(Weight ratio to 70 weight ratio) to obtain a slurry.

The slurry was formed into a sheet having a thickness of about 200 μm on an organic film by a doctor blade method. At this time, a system for continuously performing each step of drying, punching, and, if necessary, performing via hole processing from the film formation was used. Using a silver paste, a conductor pattern was formed on the green sheet and via-hole filling printing was performed by screen printing. The conductive paste is obtained by adding 5 wt% of a glass frit (GA-9 glass powder, Nippon Electric Glass Co., Ltd., average particle size of 2.5 μm) for obtaining an adhesive strength to Ag powder (average particle size of 1 μm) as an inorganic component. ,
Ethyl cellulose as an organic binder was added together with a vehicle dissolved in terpineol, and the mixture was mixed with a three-stage roll so as to obtain an appropriate viscosity. The Ag paste for filling vias was prepared by further adding 15% by weight of the above glass / ceramic powder as an inorganic component.

Next, a green sheet without sintering is manufactured by using alumina (A Sumitomo Chemical Co., Ltd.) as an inorganic component.
(LM-41, average particle size: 1.9 μm) Using only the powder, a green sheet was prepared by the same method with the same green sheet composition as that of the green sheet for a glass / ceramic substrate. The thickness of the alumina green sheet is about 300 μm.

A predetermined number of the green sheets on which the conductors have been formed are stacked, and the alumina green sheets are further stacked on both surfaces thereof. In this state, the laminate was formed by thermocompression bonding. The thermocompression bonding conditions are as follows: temperature is 80 ° C, pressure is 200
It was Kg / cm ² . FIG. 2A shows the configuration.
1 is a green sheet layer made of the substrate material, 2 is an inner layer electrode layer, 3 is a via electrode, and 4 is a green sheet layer made of alumina. The size of the laminate is 110 mm x 140 m
m and a thickness of 1.5 mm.

Next, in order to remove a corner portion of the laminate, the laminate was cut so as to make the corner round (R = 10 mm). FIG. 2B shows the green sheet laminate after processing. The laminate having the corners removed is placed on a 96% alumina substrate and fired. The firing was performed in a belt furnace at 900 ° C. in air for 1 hour.
(The holding time at 900 ° C. is about 12 minutes.) Since an unsintered alumina layer is present on the surface of the fired laminate, the alumina layer was cleaned by ultrasonic cleaning in a butyl acetate solvent. I was able to get rid of it.

After the firing, the shrinkage of the substrate was 0.1% or less, no shrinkage in the plane direction occurred, and no warping of the corners of the substrate. Further, the uppermost layer pattern was screen-printed on the multi-layer substrate using a silver / palladium paste, dried, and fired in the same manner as described above.

(Example 2) The same glass / ceramic green sheet as the substrate material was used in the same composition as in Example 1. After forming a via hole in a green sheet having a thickness of 200 μm, a conductor pattern was formed using CuO paste and printing for filling the via hole was performed by a screen printing method. The conductor paste is CuO powder (average particle size 3μ).
m) glass frit (LS-0803 glass powder, manufactured by NEC Corporation, average particle size 2.5
μm) was added as an inorganic component, ethyl cellulose as an organic binder was added together with a vehicle dissolved in terpineol, and the mixture was mixed with a three-stage roll so as to have an appropriate viscosity. The CuO paste for filling the via was prepared by adding 15% by weight of the glass / ceramic powder as an inorganic component.

Next, a green sheet without sintering is produced by using beryllium oxide (manufactured by Kanto Chemical Co., Ltd.) as an inorganic component.
A green sheet was prepared using only the powder and having the same green sheet composition as the green sheet for a glass-ceramic substrate and the same method using only the powder. The thickness of the beryllium oxide green sheet is about 300 μm.

A predetermined number of the green sheets on which the conductors have been formed are stacked, and the beryllium oxide green sheets are further stacked on both surfaces thereof. In this state, the laminate was formed by thermocompression bonding. The thermocompression bonding conditions were a temperature of 80 ° C. and a pressure of 200 kg / cm ² . The size of the laminate is 11
It was a square of 0 mm × 110 mm and the thickness was 1.3 mm.

Next, the laminate was cut so as to make the corners round (R = 8 mm) in order to remove the corners. The laminate having the corners removed is placed on a 96% alumina substrate and fired.

Next, the firing step will be described. The first is a binder removal process. The organic binder of the green sheet and the CuO paste used in the present invention is polyvinyl butyral and ethyl cellulose. Therefore, the decomposition temperature in air may be at least 500 ° C.
The laminate was degreased at a temperature of 0 ° C. Thereafter, the laminate is placed at 200 ° C.-5 in a 100% hydrogen gas atmosphere.
Reduced in time. When the Cu layer at this time was analyzed by X-ray diffraction, it was confirmed that the Cu layer was 100% Cu.

Next, in the firing step, firing was performed in pure nitrogen at 900 ° C. in a mesh belt furnace. When the beryllium oxide layer on the surface of the laminated body manufactured as described above was removed by ultrasonic cleaning in the same manner as in Example 1, the shrinkage was evaluated. There was no warping. Further, the uppermost layer pattern was screen-printed on this multilayer substrate with a commercially available Cu paste (QP153 manufactured by DuPont), dried, and fired in nitrogen in the same manner as described above.

In this embodiment, Al ₂ O ₃ and BeO are used as the unsintered materials, but other materials such as MgO, Zr
Similar effects were obtained by using O ₂ , TiO ₂ , and BN.

[0036]

According to the present invention, by performing the above-described steps, in a multilayer glass / ceramic substrate which shrinks only in the thickness direction during firing and does not shrink in the plane direction, the warpage of the corner portion of the substrate generated during firing. A ceramic substrate free of defects can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a warp generated at a corner portion of a ceramic substrate during firing.

FIG. 2 is a configuration diagram of a green sheet laminate according to one embodiment of the present invention.

[Explanation of symbols]

 1 Glass / Ceramic Green Sheet Layer 2 Internal Electrode Layer 3 Via Electrode 4 Alumina Green Sheet Layer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minehiro Itagaki 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Kazuhiro Miura 1006 Kazama Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Inside the company (72) Inventor Yoshifumi Nakamura 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Seiji Moriguchi 1006 Odaka Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) Reference Document JP-A-4-17394 (JP, A) JP-A-2-25094 (JP, A) JP-A-4-196391 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 3/46

Claims (10)

(57) [Claims] 1. An inorganic composition which does not sinter at a firing temperature of said glass / ceramic after laminating a desired number of green sheets made of glass / ceramic containing at least an organic binder and a plasticizer having an electrode pattern formed of a conductive paste composition. The green sheet made of a material is laminated on both sides or one side of the glass-ceramic laminate, cut and processed so as to round the corners of the laminate, and then fired, and then the non-sintered inorganic composition A method for manufacturing a multilayer ceramic substrate, comprising removing an object. 2. The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein the firing treatment is performed at a temperature in the range of 800 ° C. to 1000 ° C. 3. A green sheet made of an inorganic composition which is not sintered by a baking treatment is made of Al ₂ O ₃ , MgO, ZrO ₂ , Ti
_{2. The} method according to claim 1, comprising a green sheet containing at least one of O2, BeO, and BN. 4. The method for producing a multilayer ceramic substrate according to claim 1, wherein the inorganic composition which is not sintered in the firing treatment is removed by an ultrasonic cleaning method. 5. The conductive paste is made of Ag, Ag / Pd, Ag / Pd.
2. The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein one of Pt and Cu is a main component. 6. A green sheet comprising at least an organic binder having an electrode pattern formed of a conductive paste composition containing cupric oxide as a main component and glass ceramic containing a plasticizer is laminated in a desired number. Green sheets made of an inorganic composition that does not sinter at the sintering temperature are laminated on both sides or one side of the glass / ceramic laminate, and cut into round corners of the laminate, and then air-cooled. In the heat treatment at a temperature at which the organic binder inside the multilayer body is decomposed and scattered, and thereafter, a reduction heat treatment is performed in an atmosphere of hydrogen or a mixed gas of hydrogen and nitrogen. A method for producing a multilayer ceramic substrate, comprising sintering and then removing an inorganic composition that does not sinter. 7. The multilayer according to claim 6, wherein after removing the inorganic composition that is not sintered by the firing treatment, a wiring pattern is further formed on the uppermost layer portion with a Cu paste, and firing is performed in a nitrogen atmosphere. A method for manufacturing a ceramic substrate. 8. The method for manufacturing a multilayer ceramic substrate according to claim 6, wherein the firing treatment is performed at a temperature in the range of 800 ° C. to 1000 ° C. 9. An inorganic composition green sheet which is not sintered by the sintering treatment is made of Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , B
7. The method for manufacturing a multilayer ceramic substrate according to claim 6, comprising a green sheet containing at least one of eO and BN. 10. The method for manufacturing a multilayer ceramic substrate according to claim 6, wherein the inorganic composition that is not sintered in the firing treatment is removed by an ultrasonic cleaning method.