JP2005150669A - Method of manufacturing multilayer ceramic substrate, and multilayer ceramic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reasonable method of manufacturing with which surface contraction due to sintering is suppressed, variation of contraction in an X-Y plane is reduced even in a case in which dividing grooves are formed before sintering on a multilayer ceramic substrate which contracts only in the thickness direction. <P>SOLUTION: Dividing grooves are formed on an unsintered ceramic substrate which is composed of low-temperature-sintering ceramic grains. A binding material is manufactured, whose main component is a sintering-resistant ceramic grains in which sintering does not occur at the sintering temperature of the ceramic grains that compose the green sheets of the laminated substrate. The front and rear surfaces of the unsintered ceramic substrate are coated by printing with the binding material, which is then dried to form a first binding layer by printing. A green sheet composed of the binding material is stacked thereon to form a second binding layer of a sheet form, resulting to form a total binding layer of 50 μm thick. A member composed of the unsintered ceramic substrate and the binding layer is pressed, and is sintered. Then, the binding layer of the sintering-resistant ceramic grains adhering on the surface is removed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a multilayer ceramic substrate, and in particular, the sintering shrinkage rate of the substrate surface is close to zero, and is highly accurately matched with the conductor pattern or solder pattern formed on the surface, and the conductive adhesive formation pattern. The present invention relates to a method for producing a multilayer ceramic substrate and a multilayer ceramic substrate obtained by this method.

Today, multilayer ceramic substrates are widely used to configure various electronic components such as antenna switch modules, PA module substrates, filters, chip antennas, and various package components in the field of mobile communication terminal equipment such as cellular phones. It has been.
In order to mount electronic parts, semiconductor integrated circuits, etc. at a high density, multilayer ceramic substrates have via holes in ceramic green sheets, printed and filled with conductors, and printed with wiring patterns on the sheet surfaces. A plurality of sheets are laminated and pressure-bonded to form a green sheet laminate, and then fired. The green sheet is made of ceramic powder, a polymer binder, and a plasticizer, and most of the ceramic powder is made of a mixture of glass and ceramics such as alumina, mullite, cordierite, etc., so-called glass ceramics. The firing temperature of the green sheet laminate depends on the sintering temperature of the ceramic material constituting the green sheet.

  For example, when the green sheet is mainly made of a high-temperature sintered material such as alumina or mullite, the green sheet laminate is fired at a high temperature of about 1600 ° C., and the green sheet is mainly made of a low-temperature sintered material such as glass or glass ceramics. When it becomes, a green sheet laminated body is baked at the low temperature of 800 to 1000 degreeC. Since the conductor material printed on the green sheet is also fired at the above temperature, a low resistance metal conductor material having a melting point above that temperature is used. For example, tungsten, molybdenum, or the like is used as the conductor in the case of the high-temperature sintered material, and silver, silver-palladium, copper, gold, or the like is used in the case of the low-temperature sintered material.

  By sintering the green sheet laminate, its volume is reduced and densified. That is, the ratio of the bulk density to the theoretical density of the ceramic body, that is, the relative density is usually 45 to 65%, whereas the relative density is about 95% or more by sintering. is there. The green sheet laminate is usually placed on a ceramic floor and sintered in an electric furnace. The shrinkage rate of the green sheet laminate by sintering is generally in the range of 10 to 25% in terms of linear shrinkage rate, but there is usually a difference or variation in the linear shrinkage rate in each direction, which is a problem. There is a case.

  That is, when the XY coordinate is taken on the surface of the green sheet laminate and the Z coordinate is taken in the thickness direction, there is a difference between the shrinkage rate in the XY direction and the shrinkage rate in the Z direction. The difference is not a problem in most cases, but if there is a difference or variation in shrinkage in the XY plane of, for example, 0.5%, it is 250 μm at a distance of 50 mm from the reference point compared to the case where it is designed without it. This causes a problem that the circuit pattern does not match the design position of the wiring pattern formed thereon and the solder pattern for connecting the components to be mounted.

As means for solving the above problems, for example, there are the following patent documents.
In Patent Document 1 (Japanese Patent No. 2554415), a green sheet for a substrate composed of a mixture of a ceramic powder dispersed in a polymer binder and a sinterable inorganic binder, and sintering at the sintering temperature of the green sheet for a substrate. An unfired multilayer ceramic substrate formed by laminating a plurality of green sheets for a substrate is prepared, preferably comprising a mixture of inorganic materials (alumina or the like) dispersed in a polymer binder, preferably a constraining green sheet. Then, the constraining green sheet is brought into close contact with the upper surface and the lower surface, and then fired. Then, in the firing step, the sinterable inorganic binder contained in the base green sheet, that is, the glass component, permeates the constraining green sheet layer in a range of 50 μm or less and exhibits bonding strength. At this time, since the inorganic material contained in the constrained green sheet is not substantially sintered, the contraction is constrained, and the contraction is suppressed in the XY plane where the constrained green sheet is in close contact.

  Patent Document 2 (Japanese Patent No. 2617643) discloses a technique similar to that of Patent Document 1, except that the content of the polymer binder added to the inorganic material (alumina) needs to be 10% by volume or more. Disclosure.

  In Patent Document 3 (Japanese Patent Laid-Open No. 6-100377), green sheets made of an inorganic material that does not sinter at the sintering temperature of the glass ceramic material are laminated and pressed on both surfaces of the glass ceramic green sheet laminate. Then, a method for producing a glass ceramic substrate is disclosed in which the inorganic material that is fired and then not sintered is removed to prevent shrinkage during firing in the plane direction.

  In Patent Document 4 (Japanese Patent Laid-Open No. 5-327220), as a means for forming a constraining layer on the surface of an unfired multilayer ceramic substrate, a constraining layer is printed by screen printing using a paste-like mixture and dried. Later, it is disclosed to cut.

Japanese Patent No. 2554415 Japanese Patent No. 2617643 JP-A-6-1000037 JP-A-5-327220

  In the conventional non-shrink process, attention is paid to how to increase the bonding force between a glass ceramic green sheet made of a mixture of a sinterable inorganic binder (glass component) and ceramic powder and a constraining green sheet made of an inorganic material. It can be said that it has come. The green sheet for restraint after sintering is a porous powder-like sheet in which the polymer binder has been volatilized, so it can be removed relatively easily. May not be removed. That is, in a glass ceramic green sheet made of a mixture of glass powder and ceramic powder, the glass powders are sintered and densified by softening and flowing the glass powder at a high temperature. Accordingly, when the distance between the glass powders is increased, more remarkable softening and fluidity are required. In the mixture of glass and ceramic powder, ceramic particles are interposed between the glass powders, so the distance between the glass powders is relatively far away, and for sintering, fluidity is required to melt the glass powder. become. Therefore, the interface with the constraining green sheet is in a liquefied state of the glass component, and alumina enters the base green sheet side and is easily buried. It is difficult to remove the alumina that has bitten into the surface layer. Similarly, the electrode pattern of the surface layer conductor (hereinafter referred to as an external electrode) formed on the surface of the multilayer body also has an adverse effect. For example, alumina may remain scattered on the electrode. Further, it is conceivable that the glass component adheres to the surface of the external electrode. These cause poor formation of the metallized surface layer conductor film such as Ni plating or Au plating applied later on the electrode.

In the prior art, the substrate dividing means is not considered. For example, a multilayer ceramic substrate used for mobile phones and various electronic circuit components / substrates has a single substrate size of several mm to several tens of mm square. Normally, in the production of multilayer ceramic substrates, the starting green sheet is a large size of 100 mm to 200 mm square, and the above-mentioned drilling, printing, laminating, crimping and firing are performed, and the surface layer conductor (external electrode) is simultaneously with the substrate If it is fired, it is plated with Ni, Au, etc. If the surface conductor pattern is not fired simultaneously with the substrate, the surface conductors such as Ag / Pd, Ag / Pt, Au are printed and fired, and then Through processes such as solder paste printing, component mounting, and reflow, the wafer is finally divided into individual small board.
There are several methods for dividing the substrate. As for the dividing method, the processing differs depending on whether the processing such as dividing grooves is performed before or after the firing step. When it is performed after firing, a divided groove is formed with a diamond blade, a diamond pen, and a laser, and the substrate is divided into individual substrates by breaking the groove. Direct cutting with a diamond blade or laser is also performed. On the other hand, when forming the dividing groove before firing, the knife blade is pressed against the ceramic green body. After firing, the substrate is divided into individual substrates by breaking the grooves. Here, as processing, it is easier to form the dividing grooves before firing, and productivity is generally good. Conversely, the formation and cutting of the divided grooves after firing requires a hard substrate, takes time for processing, and consumes a diamond blade or the like, resulting in a relatively high production cost.

In the non-shrink process of each of the above-mentioned patent documents, the following problems arise when dividing grooves are provided on the surface of a glass ceramic green sheet laminate before firing (hereinafter referred to as an unfired multilayer ceramic substrate).
In other words, shrinkage and distortion starting from the dividing groove are likely to occur, and the variation in the shrinkage and the amount of warpage increase. This occurs even when a green sheet (hereinafter referred to as a constraining green sheet) made of an inorganic material that is not sintered at the sintering temperature of the glass ceramic material is in close contact with the laminate surface. This is because the constraining green sheet has a certain degree of flexibility, but its fluidity is poor, so it cannot penetrate into the dividing groove and the effect of suppressing shrinkage is incomplete. It is done. For this reason, there is a problem that the expansion of the dividing grooves and the shrinkage variation in the planar direction are particularly large.

  Furthermore, the decomposability of the polymer binder has not been considered in the conventional process. That is, the external electrode formed on the unfired multilayer ceramic substrate is fired after the constraining green sheet containing the polymer binder is in intimate contact, so that the polymer binder decomposition product contained in the constraining green sheet This causes a problem that the adhesion between the external electrode and the ceramic body is impaired.

  Accordingly, an object of the present invention is a method for manufacturing a multilayer ceramic substrate in which the surface shrinkage shrinkage is suppressed and shrinks only in the thickness direction, the influence on the external electrode formed on the surface layer is reduced, and the constraining layer It is an object of the present invention to provide a multilayer ceramic substrate manufacturing method capable of reducing shrinkage variation and warpage in the XY plane even when a dividing groove is formed before firing.

  The method for producing a multilayer ceramic substrate of the present invention includes a step of producing a green sheet for a substrate using a slurry of a low-temperature sintered ceramic material, and an internal electrode, a via electrode, and an external electrode are appropriately formed on the green sheet for the substrate, Laminating this to produce an unsintered multilayer ceramic substrate, producing a constrained material obtained by adding a flowable additive to a powder of an inorganic material that does not sinter at the sintering temperature of the low-temperature sintered ceramic material, Forming a constraining layer by applying and / or superimposing the constraining material to a thickness of 50 μm or more on the upper surface and / or the lower surface including the external electrodes of the unfired multilayer ceramic substrate; A step of sintering an unfired multilayer ceramic substrate having a constraining layer at 800 ° C. to 1000 ° C., and a step of removing the constraining layer from the multilayer ceramic substrate. And wherein the Rukoto. Thereby, the influence on the external electrode formed on the surface is reduced, the removal of the constraining layer can be performed relatively easily and cleanly, and a good external electrode can be obtained.

  The method for producing a multilayer ceramic substrate of the present invention includes a step of producing a green sheet for a substrate using a slurry of a low-temperature sintered ceramic material, and an internal electrode, a via electrode, and an external electrode are appropriately formed on the green sheet for the substrate. And laminating this to produce an unsintered multilayer ceramic substrate, forming a split groove in the unsintered multilayer ceramic substrate, and an inorganic material that does not sinter at the sintering temperature of the low-temperature sintered ceramic material. A step of producing a constraining material obtained by adding a flowable additive to powder, and applying and / or overlaying the constraining material to a thickness of 50 μm or more on the upper surface and / or the lower surface including external electrodes of the unfired multilayer ceramic substrate A step of forming a constraining layer, a step of pressure-bonding the constraining layer, and sintering an unsintered multilayer ceramic substrate provided with the constraining layer at 800 ° C. to 1000 ° C. And extent, characterized by a step of removing the constraining layer from the multilayer ceramic substrate. This suppresses shrinkage and warping even when dividing grooves are formed, reduces the effect on the external electrode formed on the surface, and removes the constraining layer relatively easily and neatly, resulting in a good external electrode. It is done.

  A constraining material for coating formation obtained by adding the above fluid additive to an inorganic material having an average particle size of 0.3 to 4 μm is coated and printed on the upper surface and / or the lower surface of the unfired multilayer ceramic substrate to a thickness of 10 μm or more, After drying and press-bonding to form a constrained layer, the fluidity of the printing paste is excellent, so that the paste spreads around the electrodes and into the dividing grooves and can be evenly adhered. When the constraining layer formed by printing is thinner than 50 μm, the constraining material formed in the form of a sheet is superposed thereon, and the total thickness of the constraining material is 50 μm or more. In the sintering process, in the XY plane, the presence of the alumina particle layer, which is the constraining material, becomes a resistance and cannot contract, and contracts exclusively in the z direction. In addition, since alumina particles are also filled in the dividing grooves, a resistance force of the alumina particle layer is generated including the dividing grooves, and the shrinkage rate in the XY plane is close to zero as described above, and the variation is extremely small. . Here, powder is used for inorganic materials (alumina etc.). The shape of the powder is classified into a spherical shape, a plate shape, and a rod shape. In the present invention, the average particle diameter is calculated from the powder shape observed with a scanning microscope (SEM). Approximate the length of the powder in the xyz direction. If the X, Y, Z ratio is within 1 / 3-3, the diameter is converted to a sphere, and if the X, Y ratio is within 1 / 3-3, If the ratio between the smaller value and Z exceeds 3, it is regarded as a plate-like powder, and the ratio between the larger X and Y values and Z is 1 when the X, Y ratio is within 1 / 3-3. Z was defined as the particle size so that it was a rod-like powder when it was smaller than / 3. If the average particle size is less than 0.3 μm, more fluid additives are required to obtain the viscosity characteristics necessary for printing, the filling rate of the inorganic material powder is reduced, and the binding force is reduced along with the flat surfaces and the dividing grooves. I can't show it. If it exceeds 4 μm, the binding force particularly at the dividing groove portion becomes weak. Further, if the thickness of the first constraining layer made of the constraining material paste is less than 10 μm, the constraining force cannot be exhibited when there are split grooves.

  In the present invention, the inorganic material used for the constraining layer is particularly preferably plate-shaped. It is desirable to use a flat plate having a circle equivalent diameter of 4 μm or less and a thickness of 1 μm or less, particularly a flat plate having a circle equivalent diameter of 1 μm or less and a thickness of 0.1 μm or less. This is because in the case of tabular grains, the flat surface is oriented parallel to the surface of the multilayer ceramic substrate and closely adhered to the multilayer ceramic substrate, and the effect of suppressing the shrinkage in the XY direction is high. On the other hand, there are irregularities on the surface of the multilayer ceramic substrate, and when a flat powder is used, the substantial contact portion with the surface of the multilayer ceramic substrate is less than that of the spherical powder. Is easier to remove. Therefore, when a flat powder is used, it can be removed relatively cleanly by ultrasonic cleaning or the like.

  In the present invention, a first constraining layer of 10 μm or more is formed by applying the constraining material on the upper surface and / or the lower surface including external electrodes of the unfired multilayer ceramic substrate, and a green sheet made of the constraining material is formed thereon. It is desirable to adopt a method for manufacturing a multilayer ceramic substrate in which a second constraining layer is formed by superimposing layers and a constraining layer of 50 μm or more is formed in total.

  A second green sheet method is formed by coating and molding so as to be in close contact with the upper surface and / or lower surface of the unfired multilayer ceramic substrate, that is, typically by providing a first constraining layer by a printing method and stacking green sheets thereon. By providing this constraining layer, the effect of reducing the shrinkage rate as described above, and the shortening and simplification of the constraining layer forming step can be achieved. That is, if the constraining layer is formed by a printing method, the paste has high fluidity, so that the paste reaches the unevenness of the unfired ceramic body, minute step portions of the electrode, and the like, and a high constraining effect is obtained. The greater the constraining layer thickness, the greater the constraining effect. That is, the larger the constraining layer thickness, the smaller the shrinkage rate in the XY plane and the less the variation tends to be. When the thickness of the unfired multilayer ceramic substrate is large, a thicker constraining layer is required. The thickness formed by printing is affected by the viscosity characteristics, solid content, screen thickness, screen aperture, printing conditions, etc. of the printing paste. When the viscosity is relatively high, the solid content is high, the screen is thick, and the screen opening is large, a larger printed film thickness is obtained. By optimizing the printing conditions, the film thickness that can be printed at one time can be changed to 10 to 300 μm.

  A mesh screen is generally used for printing an electrode pattern or the like on a green sheet. A mesh screen in which emulsion is patterned on a mesh knitted with stainless steel wire has good film thickness uniformity even when printing over a large area, but it is difficult to increase the aperture ratio, and the appropriate film thickness that can be printed is About 10-50 micrometers. On the other hand, when a metal mask in which a stainless steel plate is pierced in a printing pattern is used, a film thickness corresponding to the stainless steel plate thickness is formed, so that printing can be performed relatively thickly. However, when the pattern on the metal mask is large, there is a problem that the printed film thickness in the pattern varies, and formation up to 300 μm is appropriate. In addition, when the printing film thickness is large, the drying time becomes long, and the printing film may be cracked depending on the drying method, and it is necessary to use an appropriate drying temperature profile. The film thickness that can be formed by printing including overprinting is 500 μm.

As described above, when the thickness of the unfired multilayer ceramic substrate is large, a thicker constraining layer is required. For example, when the thickness of the unfired multilayer ceramic substrate is 3 mm or more, the constraining layer thickness needs to exceed 500 μm. In such a case, the first constraining layer is formed on the unfired multilayer ceramic substrate by a constraining material paste printing method, and then a constraining material green sheet is laminated thereon as a second constraining layer. Can be made. This method is also effective when the thickness of the constraining layer is 500 μm or less. That is, the first constraining layer is formed on the unfired multilayer ceramic substrate by using a mesh screen with a printing method of 10 to 50 μm, and the necessary remaining constraining layer thickness is compensated by stacking constraining material green sheets. Can do. In this case, 10-50 μm printing of the constraining material paste can form a uniform film thickness even with a large area pattern, can be easily dried, and can be overlaid with a green sheet. Therefore, productivity is good.
Here, the first constraining layer is formed by the constraining material paste printing method, and then, when the constraining material green sheet is laminated thereon as the second constraining layer, the first constraining layer is pressure-bonded. It is more preferable to form the second constraining layer. A more constraining constraining layer can be formed on the second constraining layer by laminating a constraining material green sheet and then pressing again.

In the present invention, in the production of a constraining material composed of an inorganic material and a flowable additive, the selection conditions for the binder material are less strict and the amount added is smaller than in the production of a green sheet for a substrate.
The green sheet for a base is formed from a slurry in which a low-temperature sintered ceramic material, a polymer binder, a plasticizer, and a solvent are mixed. Here, the binder is required to have a green sheet strength, a punching ability to the green sheet, a pressure-bonding property between the green sheets, a dimensional stability of the green sheet, and the like, and a polymer binder having characteristics suitable for it is selected. Typical polymer binders include polyvinyl butyral resin and polymethacrylic resin, and the amount added is at least 10% by volume, preferably 20 to 30% by volume. On the other hand, when forming a constrained layer by application and / or superposition, it has been found that the binder to be added to the inorganic material may be at least fluidity. That is, the polymer binder used in the green sheet for a substrate is generally thermally decomposed at 300 ° C. or higher and produces various decomposition byproducts. Some by-products are difficult to decompose, and considerable residual carbon is still analyzed in the ceramic material of the multilayer ceramic substrate heat treated at 500 ° C. (debinder treatment). Ag used for the external electrode starts sintering between Ag particles at about 400 ° C. The polymer binder residue is undesirable because it adversely affects the sintering of Ag particles. Therefore, it is more desirable to add a binder having good decomposability to the inorganic material as the constraining material.
And in order to implement | achieve the said, it discovered that it was suitable to form a constrained layer by application | coating and / or superimposition. For example, when the constraining layer is formed by a printing method, a fluid additive is added to the powder of the inorganic material to prepare a paste. As the fluid additive, there are used hydrocarbons, fatty acid esters, that is, fats and oils, and synthetic resins or natural resins having a good polymerization degree of 2000 or less and a mixture thereof in a solvent. Paraffin is used as the hydrocarbon type, linseed oil, drill oil as the fat and oil, polyvinyl butyral resin, polymethacrylic resin, cellulosic resin as the synthetic resin, and rosin as the natural resin.

  Since the synthetic resin tends to generate a decomposition reaction product during the firing process, the amount thereof can be reduced to 4% by volume or more and less than 10% by volume. For example, among the synthetic resins, a cellulose resin that has good thermal decomposability and is easy to adjust the viscosity is preferable. That is, as an inorganic material (hardly sinterable ceramic particles), for example, alumina is prepared, a vehicle in which ethyl cellulose as a synthetic resin is separately dissolved in terpineol as an organic solvent is prepared, and the alumina and the vehicle are mixed with a mortar and a pestle. After premixing, the paste is prepared by mixing with three rolls. The amount of ethyl cellulose at this time may be usually less than 10% by volume. Here, the binder used for the printing paste may be less than 10% by volume as long as it has a viscosity characteristic necessary for printing, adhesion between the powders constituting the paste, and adhesion to the substrate. Addition of more binder increases the strength of the printed film alone and can improve the adhesion to the substrate, but the filling rate of the inorganic material powder decreases and the degradation product has an adverse effect on the external electrode . A higher filling rate of the inorganic material particles is effective in reducing the shrinkage rate and reducing the variation thereof, and the printed inorganic material particle film and the substrate can be brought into close contact with each other by pressure bonding. Therefore, the preferred binder amount varies depending on the average particle size of the inorganic material powder used, but is in the range of 4% by volume or more and less than 10% by volume.

The low-temperature sintered ceramic material used in the method for producing a multilayer ceramic substrate of the present invention is a mixture of at least SiO ₂ and an oxide of Al ₂ O ₃ and at least one carbonate at 700 ° C. to 850 ° C. It is desirable that the calcined powder is composed of a pulverized powder of a calcined composite having at least a glass phase and an alumina crystal phase. For example, when Al, Si, Sr, and Ti, which are main components, are converted into Al ₂ O ₃ , SiO ₂ , SrO, and TiO ₂ , respectively, 10 to 60 mass% in terms of Al ₂ O ₃ and 25 to 25 in terms of SiO _2. 60% by mass, 7.5 to 50% by mass in terms of SrO, 20% by mass or less (including 0) in terms of TiO ₂ , Bi, Na, K as subcomponents with respect to 100% by mass of the main component At least one of the Co groups is 0.1 to 10% by mass in terms of Bi ₂ O ₃ , 0.1 to 5% by mass in terms of Na ₂ O, and 0.1 to 5% by mass in terms of K ₂ O. And 0.1 to 5% by mass in terms of CoO, and at least one of the group of Cu, Mn and Ag is 0.01 to 5% by mass in terms of CuO and 0.01 to 5 in terms of MnO ₂ Containing 0.01% to 5% by mass of Ag and other inevitable impurities And that the mixture was calcined at 700 ° C. to 850 ° C., it is desirable to use it was triturated consisting milled particles having an average particle diameter of 0.6~2μm calcined composite. It may also contain Zr of 0.01 to 2 mass% in terms of ZrO ₂ to the secondary component.

When the mixture of the main component and the subcomponent is calcined, vitrification proceeds except for Al ₂ O ₃ and TiO ₂ . Some amounts of Al ₂ O ₃ and TiO ₂ can enter the glass. In order to achieve uniform and complete vitrification containing SiO ₂ as a main component, it is necessary to melt the composition at a firing temperature of 1300 ° C. or higher. For calcined materials at 700 ° C. to 850 ° C., the glass phase is determined by X-ray diffraction analysis. But still has a SiO ₂ phase remaining and is considered a non-uniform glass phase. Particles obtained by finely pulverizing a calcined material that is a solidified product of ceramic particles and a partial glass phase are particles in which glass is partially or entirely covered with ceramic particles. Compared to the conventional raw material in which glass particles and ceramic particles that are generally melted and mixed are mixed, the glass component of the calcined composite of the present invention is in a state where the vitrification reaction is insufficient and it is difficult to flow. Since the calcined composite having such characteristics is used, the reactivity of the glass component is low even in the main sintering, and the interface between the unfired multilayer ceramic substrate and the constrained layer is in a state of high viscosity where the glass component is inactive. is there. That is, when compared with the sintering behavior of a conventional mixture of single glass particles and ceramic particles, the flow of glass is suppressed and the glass component is difficult to penetrate. Therefore, it can be said that the glass component is in a stable state without adhering to the external electrode. Further, it is possible to prevent an inorganic material such as alumina from being buried on the green sheet side for the substrate.

Further, in a conventional glass ceramic green sheet made of a mixture of glass powder and ceramic powder, the glass powders are sintered and densified by softening and flow of the glass powder at a high temperature. When the distance between the glass powders is increased, more remarkable softening and fluidity are required. However, the calcined composite according to the present invention is a particle in which glass is partially or wholly covered with ceramic particles. The degree of contact between the glass portions is large. That is, the distance between the glass powders is short, and the glass powder can be densely sintered by heat treatment that imparts relatively small softening and fluidity.
If the calcining temperature is less than 700 ° C., the degree of vitrification is insufficient, and if it exceeds 850 ° C., it becomes difficult to finely grind the calcined product. If the average particle size of the finely pulverized particles is less than 0.6 μm, it is difficult to form a green sheet, and if it exceeds 2 μm, it is difficult to produce a thin green sheet, particularly a sheet having a thickness of 20 μm or less.

According to the non-shrinkage process of the present invention, it is possible to easily form a constraining layer that has little influence on the external electrode. A multilayer ceramic substrate in which the shrinkage rate in the XY plane direction is 1% or less, the variation 3σ is 0.07% or less, and the warp in the XY plane is 30 μm or less per 50 mm even if the substrate has divided grooves. Can be obtained.
In addition, when using a calcined composite once calcined with a mixture of low-temperature sintered ceramic materials, it can be sintered in a state where the flowability of the glass component is low, so that inorganic materials such as alumina are difficult to embed, The glass component does not adhere to the electrode, and the quality of the external electrode is stabilized. In addition, an inorganic material such as alumina can be in a form that does not easily enter the substrate side, and the constraining layer can be easily and cleanly removed.

  Hereinafter, the multilayer ceramic substrate of the present invention will be further described with reference to the drawings following the manufacturing method. FIG. 1 is a cross-sectional view showing a large unfired multilayer ceramic substrate before the non-shrink process, and FIG. 2 is a top view of the unfired multilayer ceramic substrate before providing a constraining layer. FIG. 3 is a cross-sectional view of an unfired multilayer ceramic substrate showing the situation after the constraining layer is formed. FIG. 4 is a cross-sectional view showing a small multilayer ceramic substrate on which mounting components are placed and divided. FIG. 5 is a flowchart showing the manufacturing process of the present invention. FIG. 6 is an X-ray diffraction pattern diagram of each of the mixed powder, the calcined composite powder, and the sintered body. FIG. 7 shows SEM images of the calcined composite before (a) and after (b) pulverization.

[Material of green sheet for substrate]
The green sheet for a substrate is made of a low-temperature sintered ceramic material. The use of this material in the present invention is useful and will be described here.
The material composition used in the present invention is composed mainly of oxides of Al, Si, Sr, and Ti, and is 10 to 60% by mass in terms of Al ₂ O ₃ , 25 to 60% by mass in terms of SiO ₂ , and SrO equivalent. 10 to 50% by mass and 20% by mass or less (including 0) in terms of TiO ₂ , and can be fired at a temperature of 900 ° C. or less. Thereby, integral simultaneous sintering can be performed using a metal material having high conductivity such as silver, copper, and gold as a conductor for an electrode.

Further, with respect to 100% by mass of the main component, 0.1 to 10% by mass in terms of Bi ₂ O ₃ and 0.1 to 5 in terms of Na ₂ O among the groups of Bi, Na, K, and Co as subcomponents. It is preferable to contain at least one mass%, 0.1 to 5 mass% in terms of K ₂ O, and 0.1 to 5 mass% in terms of CoO. These subcomponents act as a sintering aid when components other than Al ₂ O ₃ and TiO ₂ are vitrified in the calcination step, and have an effect of lowering the softening point of the glass, and start shrinking at a lower temperature. A material is obtained.
Furthermore, among Cu, Mn, and Ag as subcomponents, 0.01 to 5% by mass in terms of CuO, 0.01 to 5% by mass in terms of MnO ₂ , and at least one of 0.01 to 5% by mass of Ag. It is preferable to contain seeds or more. These subcomponents have an effect of mainly promoting crystallization in the firing step, and can obtain a high Q dielectric property at a firing temperature of 1000 ° C. or less in the firing step.

The reason for specifying each component range is as follows. Since this material has a feature as a dielectric material for microwaves, the characteristics of the side are also described.
When Si is less than 25% by mass in terms of SiO ₂ and Sr is less than 10% by mass in terms of SrO, the sintering density does not rise sufficiently at low temperature firing at 1000 ° C. or lower, so the porcelain becomes porous. Good characteristics cannot be obtained due to moisture absorption or the like. When Al is less than 10% by mass in terms of Al ₂ O ₃ , good high strength cannot be obtained. Also, when Al is more than 60% by mass in terms of Al ₂ O ₃ , Si is more than 60% by mass in terms of SiO ₂ , Sr is more than 50% by mass in terms of SrO, Since the sintered density does not increase sufficiently, the porcelain becomes porous, and good characteristics cannot be obtained due to moisture absorption or the like.
On the other hand, when Ti is more than 20% by mass in terms of TiO ₂ , the sintering density is not sufficiently increased by low-temperature firing at 1000 ° C. or lower, so that the porcelain becomes porous, and good characteristics cannot be obtained due to moisture absorption or the like. At the same time, the temperature coefficient of the resonance frequency of the porcelain increases with the Ti content, and good characteristics cannot be obtained. The temperature coefficient τf of the resonance frequency of the porcelain when Ti is not contained increases with increasing amount of Ti with respect to −20 to −40 ppm / ° C., and τf may be adjusted to 0 ppm / ° C. Easy.

Bi is added to achieve low temperature sintering. In other words, by adding this Bi, when components other than Al ₂ O ₃ and TiO ₂ try to vitrify in the calcination step, there is an effect of lowering the softening point of this glass, and shrinkage starts at a lower temperature. It is possible to obtain a material to be obtained and to obtain a high Q dielectric property at a firing temperature of 1000 ° C. or lower in the firing step. However, when it is more than 10% by mass in terms of Bi ₂ O ₃ , the Q value becomes small. For this reason, 10 mass% or less is desirable. More preferably, it is 5 mass% or less. On the other hand, if it is less than 0.1% by mass, the effect of addition is small, and crystallization at a lower temperature becomes difficult. More preferably, it is 0.2 mass% or more.

When Na, K, and Co are less than 0.1% by mass in terms of Na ₂ O, less than 0.1% by mass in terms of K ₂ O, and less than 0.1% by mass in terms of CoO, The softening point becomes high and sintering at low temperature becomes difficult. For this reason, a dense material cannot be obtained by firing at 1000 ° C. or lower. On the other hand, if it exceeds 5% by mass, the dielectric loss becomes too large and the practicality is lost. Therefore, 0.1 to 5 mass% in terms of Na ₂ O, 0.1 to 5 mass% in _{K 2} O in terms of, 0.1 to 5 mass% in terms of CoO is preferable.

Cu and Mn have the effect of promoting crystallization of the dielectric ceramic composition in the firing step, and are added to achieve low-temperature sintering, but when less than 0.01% by mass in terms of CuO, MnO ₂ When the amount is less than 0.01% by mass, the effect of addition is small, and it becomes difficult to obtain a material having a high Q by firing at 900 ° C. or lower. Moreover, since low temperature sinterability will be impaired when it exceeds 5 mass%, 0.01-5 mass% is preferable in conversion of CuO.
Ag has the effect of lowering the softening point of the glass and at the same time promoting crystallization, and is added to achieve low-temperature sintering, but if it exceeds 5% by mass, the dielectric loss becomes too large, and practicality is increased. There is no. For this reason, Ag is preferably added in an amount of 5% by mass or less. More preferably, it is 2 mass% or less.

In addition, it is desirable to contain 0.01 to ₂ % by mass of Zr in terms of ZrO ₂ because the mechanical strength is improved. Further, this low-temperature sintered ceramic material does not contain Pb and B contained in conventional materials. PbO is a hazardous substance, and it costs money to treat wastes and the like generated in the manufacturing process, and attention should be paid to the handling of PbO in the manufacturing process. In addition, B ₂ O ₃ dissolves in water and alcohol during the manufacturing process, segregates during drying, reacts with the electrode material during firing, reacts with the polymer binder used, and degrades the performance of the binder. There is. Since it does not contain such harmful elements, it is also useful in terms of environment.

[Preparation of green sheet for substrate]
Starting materials are selected from the above main components and subcomponents, and oxide powders or carbonate compound powders as raw materials are weighed. These powders are put into a polyethylene ball mill, and media balls made of zirconium oxide and pure water are put into it and wet mixed for 20 hours. The mixed slurry is dried by heating to evaporate water, and then pulverized with a lycra machine, placed in an alumina crucible, and calcined at 700 to 900 ° C., for example, 800 ° C. for 2 hours. The calcined solid is put into the aforementioned ball mill, wet pulverized for 20 to 40 hours, and dried to obtain finely pulverized particles having an average particle diameter of 0.6 to 2 μm, for example, 1 μm. Particles obtained by pulverizing the calcined product are particles in which ceramic particles are partially or wholly coated with glass. To the obtained calcined powder, ethanol, butanol, polyvinyl butyral resin as a polymer binder, and butyl butylphthalyl glycolate (abbreviation: BPBG) as a plasticizer were mixed with a ball mill to prepare a slurry. For example, polymethacrylic resin can be used as the polymer binder, di-n-butyl phthalate can be used as the plasticizer, and alcohols such as toluene and isopropyl alcohol can be used as the solvent.
Next, this slurry was formed into a sheet on an organic film (polyethylene terephthalate PET) by a doctor blade method and dried to obtain a ceramic green sheet having a thickness of 0.15 mm. The ceramic green sheet was cut into 180 mm square together with the organic film.

[Production of unfired multilayer ceramic substrate]
A via hole 3 is provided in the above ceramic green sheet, the via hole is filled with a conductor paste mainly composed of Ag, the internal electrode pattern 2 is printed and formed with a conductor paste mainly composed of Ag, and the circuit is formed by drying. An electrode pattern to be formed is formed. Also, electrode patterns 4 of external electrodes are formed on the green sheets located on the upper and lower surfaces. A plurality of, for example, 10 to 20 sheets of these green sheets were stacked while temporarily pressing one by one. Temporary pressure bonding conditions were a temperature of 60 ° C. and a pressure of 2.8 MPa, and then thermocompression bonded to obtain an unfired multilayer ceramic substrate 10. The thermocompression bonding conditions at this time were a temperature of 85 ° C. and a pressure of 10.8 MPa. Thereafter, the dividing grooves 5 were put into 10 × 15 mm squares, which are substrate sizes of product pieces 1A to 4A, 1B to 4B, 1C to 4C (all symbols are not shown). In the division grooving, a knife blade was pressed against the green body to a depth of 0.1 mm. The thickness of the knife blade was 0.15 mm. The cross-sectional shape of the dividing groove was a substantially isosceles triangle having a base of about 0.15 mm and a depth of about 0.1 mm.

[Preparation of constrained layer paste]
The constraining layer 6 is made of an inorganic material that does not sinter at the sintering temperature of the low-temperature sintered ceramic material described above. As this inorganic material, for example, alumina powder or zirconia powder can be used. The average particle size of the inorganic material powder is desirably 0.3 to 4 μm. This is because, as described above, the restraining force can be controlled to some extent by the particle size. That is, if the average particle size of the inorganic material (alumina, etc.) is less than 0.3 μm, the amount of binder necessary for obtaining the viscosity characteristics necessary for printing increases, and the filling rate of the inorganic material powder decreases, resulting in a flat surface. The restraining force cannot be exhibited together with the dividing groove, and if it exceeds 4 μm, the restraining force particularly at the dividing groove portion becomes weak. Furthermore, it is desirable to use a flat inorganic material having a flat circle equivalent diameter of 4 μm or less and a thickness of 1 μm or less. In particular, it is desirable to use a flat plate having a circle equivalent diameter of 0.3 to 1.0 μm and a thickness of 0.1 μm or less. In the case of tabular grains, the flat surface is oriented parallel to the surface of the multilayer ceramic substrate and is brought into close contact with the surface, so that the effect of suppressing shrinkage in the XY direction is high. On the other hand, the surface of the multilayer ceramic substrate has irregularities, and when a flat powder is used, the substantial contact with the surface is less than that of the spherical powder, and the removal is easier after firing. That is, when a flat powder is used, it can be removed relatively cleanly by ultrasonic cleaning or the like.

Alumina having the above particle diameter is prepared as a hardly sinterable inorganic material powder, and separately mixed and kneaded with a fluid additive to prepare a paste. As shown in FIG. 5, the fluidity additives include hydrocarbons (example (B)), fatty acid esters, that is, fats and oils (example (C)), and an average degree of polymerization of 2000 or less with good degradability. Synthetic resin or natural resin (example of (A)) A substance obtained by dissolving a mixture of any of these examples in a solvent is used. As petroleum hydrocarbons, petroleum jelly and paraffin, as fats and oils, citrus oil and drill oil, as synthetic resins, polyvinyl butyral resins, polymethacrylic resins, cellulose resins, and as natural resins, rosin can be used. The fluidity additive is added so as to have a printable viscosity of 10 to 1000 PaS.
As the fluidity additive, a vehicle in which ethyl cellulose, which is a typical example of a cellulose resin as a synthetic resin, is dissolved in α-terpineol as an organic solvent is preferable. This is because it has excellent thermal decomposability and is easy to adjust the viscosity characteristics suitable for printing. The amount of ethyl cellulose dissolved in the solvent is small. Here, the dissolution amount is 5 wt%. Alumina and the vehicle are premixed with a mortar and pestle and then kneaded with three rolls to produce a paste. The amount of ethyl cellulose relative to alumina may be 4% by volume or more and less than 10% by volume. More fluid additives can increase the strength of the printed film alone and improve the adhesion to the substrate, but the filling rate of the inorganic material powder is reduced. A higher filling rate of the inorganic material particles is effective in reducing the shrinkage rate and reducing its variation. Furthermore, since decomposition products in the firing process are reduced, there is little adverse effect on the external electrode, and a good external electrode can be obtained.

[Preparation of green sheet for constraining layer]
In addition to the paste described above, the constraining layer 6 is also formed in the form of a green sheet. Similarly to the above, alumina having an average particle size of 0.3 to 4 μm is prepared as a hardly sinterable inorganic material powder, and the powder, ethanol, butanol, a polyvinyl butyral resin as a polymer binder, and butylphthalyl glycol as a plasticizer A slurry was prepared by mixing butyl acid (abbreviation: BPBG) with a media ball made of zirconium oxide by a ball mill made of polyethylene. For example, polymethacrylic resin can be used as the polymer binder, di-n-butyl phthalate can be used as the plasticizer, and alcohols such as toluene and isopropyl alcohol can be used as the solvent. It is not always necessary to use flat alumina for the constraining green sheet.
Next, this slurry was formed into a sheet on an organic film (polyethylene terephthalate PET) by the doctor blade method and dried to obtain a ceramic green sheet. Three types of green sheets with thicknesses of 0.04 mm, 0.10 mm, and 0.20 mm were prepared by changing the gap of the doctor blade. The ceramic green sheet was cut into 180 mm square together with the organic film.

[Formation of constraining layer on unfired multilayer ceramic substrate]
Next, when forming the constraining layer 6 on the upper surface and / or the lower surface of the unfired multilayer ceramic substrate 10, first, the paste prepared above is directly applied onto the unfired multilayer ceramic substrate by a printing means. When using a mesh screen, print with a film thickness of 10 to 50 μm, and when using a metal mask with a stainless steel plate piercing the print pattern, print to a film thickness of 300 μm and use an ethylcellulose vehicle. In some cases, the film was dried at 80 ° C. for 30 minutes to 2 hours to form a first constraining layer. At this time, when flat alumina is used as the inorganic material, printing is performed using a squeegee, so that the effect of aligning the flat surface parallel to the surface of the unfired multilayer ceramic substrate is obtained. Thereafter, one or more of the constraining layer green sheets described above as the second constraining layer were appropriately stacked thereon. Next, thermocompression bonding was performed at a temperature of 85 ° C. and a pressure of 10.8 MPa.
In the above, when hydrocarbon type or fatty acid ester type is used as the flow additive, heat treatment for drying is not particularly performed. In addition, when the printed film thickness is 50 μm or more, the constraining layer green sheets need not be overlapped.

[Main sintering of unfired multilayer ceramic substrate with constraining layer]
Firing was performed in the air in a batch furnace, held at 500 ° C. for 4 hours to remove the binder, and then held at 900 ° C. for 2 hours for sintering. The temperature rising rate was 3 ° C./min, and cooling was natural cooling in the furnace. The sintering temperature is 800 to 1000 [deg.] C., similar to the sintering of a substrate made of a conventional low-temperature sintered ceramic material. When the temperature is lower than 800 ° C., there is a problem that densification becomes difficult. When the temperature is higher than 1000 ° C., formation of an Ag-based electrode material becomes difficult, and preferable dielectric characteristics cannot be obtained.

[Removal of constrained layer]
After sintering, alumina particles adhering to the surface are removed. This is performed by driving the ultrasonic wave by placing the fired substrate in the water of an ultrasonic cleaning tank. In particular, when tabular alumina particles are used, they are easily removed. When other alumina particles are used, most of the alumina particles are removed. However, the alumina particles on the external electrode, for example, the Ag pad, are difficult to remove by ultrasonic cleaning, and are supplementarily removed by sandblasting. As the sand material, alumina, glass, zircon particles or the like can be used. Thereby, metallization such as Ni plating and Au plating can be formed on the Ag pad with high quality. A known electroless plating can be applied to the metallization.

[Division of multilayer ceramic substrate]
A solder pattern is formed by screen printing on the metallized electrode on the upper surface of the substrate. Then, components such as individual semiconductor elements and chip elements are mounted and connected by reflow. Then, the wire bonding semiconductor element performs wire bonding connection. Thereafter, a small multilayer ceramic substrate is obtained by breaking along the dividing groove from the large substrate.

Starting materials shown in Table 1 were prepared for the main component and subcomponents of the low-temperature sintered ceramic material described above. At this time, an Al ₂ O ₃ powder having a purity of 99.9% and an average particle diameter of 0.5 μm, an SiO ₂ powder having a purity of 99.9% or more and an average particle diameter of 0.5 μm or less, a purity of 99.9% and an average particle diameter 0.5 μm SrCO ₃ powder, purity 99.9%, average particle size 0.5 μm TiO ₂ powder, purity 99.9%, average particle size 0.5-5 μm Bi ₂ O ₃ powder, Na ₂ CO ₃ The powder, K ₂ CO ₃ powder, CuO powder, Ag powder, MnO ₂ powder, and Co ₃ O ₄ powder were weighed.
Next, a test substrate was manufactured according to the method for manufacturing a multilayer ceramic substrate described above. In addition, it has shown that it is a comparative example that * was attached to sample No. of Table 1. Here, the calcining temperature is 800 ° C. × 2 hours, the average particle size of the finely pulverized particles is 1 μm, the number of laminated sheets of the unfired multilayer ceramic substrate is 10, and the average particle size of the alumina particles for the constrained layer is 0. 4 to 0.5 μm, the thickness of the constraining layer was about 300 μm, and the flow additive was a vehicle in which ethyl cellulose was dissolved in α terpineol at 5 wt%. The temperature of the main sintering is shown in Table 1 for each sample. Other conditions were performed according to the above-described example. Further, the dividing grooves were formed in the same manner as described above. After sintering, the alumina layer of the constraining layer on the surface was removed by ultrasonic cleaning, and the shrinkage rate was evaluated from the pattern formed in the uppermost layer. The degree of densification was evaluated by the shrinkage rate in the Z direction, the high frequency characteristics were evaluated by electrical characteristics, and the quality of the external electrodes was evaluated by plating ability. The results are also shown in Table 1.

  From Table 1, the multilayer ceramic substrate according to the present invention has an X-Y direction shrinkage rate of 1% or less and a shrinkage rate variation 3σ of 0.07% or less. In addition, good results can be obtained with respect to the denseness, the high-frequency characteristics, and the state of the external electrodes.

As a representative composition of the low-temperature sintered ceramic material described above, the main component is composed of oxides of Al, Si, Sr, and Ti, and each is 48% by mass in terms of Al ₂ O ₃ , 38% by mass in terms of SiO _{2, and in} terms of SrO. 10% by mass, 4% by mass in terms of TiO ₂ , and Bi, Na, K as secondary components are 2.5% by mass in terms of Bi ₂ O _{3 with} respect to 100% by mass of the main component, Na ₂ O 2% by mass in terms of conversion, 0.5% by mass in terms of K ₂ O, Cu, 0.3% by mass in terms of CuO, and Mn, 0.5% by mass in terms of MnO ₂ (sample No. 29 in Table 1) The starting material was weighed. At this time, an Al ₂ O ₃ powder having a purity of 99.9% and an average particle diameter of 0.5 μm, an SiO ₂ powder having a purity of 99.9% or more and an average particle diameter of 0.5 μm or less, a purity of 99.9% and an average particle diameter 0.5 μm SrCO ₃ powder, purity 99.9%, Bi ₂ O ₃ powder having an average particle size of 0.5 to 5 μm, Na ₂ CO ₃ powder, K ₂ CO ₃ powder, CuO powder, MnO ₂ powder were used. .
Next, it manufactured along the manufacturing method of the above-mentioned multilayer ceramic substrate. Here, the calcining conditions were 800 ° C. × 2 hours, the average particle size of the finely pulverized particles of the calcined solid was about 1 μm, and a ceramic green sheet for a substrate was produced.
Moreover, the alumina particle | grains as an inorganic material for restraint changed the average particle diameter into 0.2-5 micrometers, and changed the thickness of one side of a restraint layer into 30-600 micrometers, and also evaluated the presence or absence of division | segmentation groove | channel formation. Here, as shown in Table 2, the constraining layer was formed by combining a first constraining layer by a printing method and a second constraining layer by sheet lamination. The temperature of the main sintering was constant at 900 ° C. × 2 hours. The other conditions were the same as described above. After sintering, the alumina layer of the constrained layer on the surface is removed by ultrasonic cleaning, and the distance between specific positions of the electrode pattern formed on the uppermost layer is calculated from the XY coordinates measured by a three-dimensional coordinate measuring instrument. The shrinkage rate and its variation were evaluated from the distance between the same positions measured before layer printing. The shrinkage in 16 directions was evaluated per substrate sample. Also, the amount of warpage per small piece was evaluated with the difference in height of the Z coordinate as the warp. The evaluation results are also shown in Table 2. Samples having no * in the sample number are examples of the present invention, and samples having a sample number appended with * are comparative examples outside the scope of the present invention.

From the results in Table 2, the constraining layer paste made of alumina having an average particle size of 0.3 to 4 μm is printed on one side to a film thickness of 50 μm or less, and the constraining layer green sheet is overlaid on the constraining layer thickness. When the split groove is formed on the unfired low-temperature fired ceramic substrate, the shrinkage rate in the XY direction is suppressed to 1% or less, the shrinkage variation 3σ is 0.07% or less, and in the XY plane. A highly accurate substrate with a warpage of 30 μm or less per 50 mm is manufactured. These effects are due to the provision of the constraining layer. In particular, with regard to warping, the constraining layer made of the first paste uniformly covers the electrode step portion and the split groove portion, thereby causing local warping. This is considered to be due to effective suppression of shrinkage unevenness. In addition, the preferable range of a printing film thickness is 10-50 micrometers. By setting the amount of ethyl cellulose as a polymer binder to 4% by volume or more and less than 10% by volume, a first constraining layer having no defects can be formed after printing and drying.
For samples whose sample numbers are not marked with an asterisk (*), the front and back surfaces of the substrate were subjected to blasting with a projection pressure of 0.4 Mpa using zircon sand, and then Ni plating with an average film thickness of 5 μm on the Ag conductor on the surface A film and an Au plating film having an average film thickness of 0.4 μm were formed by an electroless method. As a result, no defective plating film was observed, which was good.
Similar results were obtained even when at least one material of magnesia, zirconia, titania and mullite was used as the ceramic particles instead of alumina.

Next, the example which changed the fluidity additive was performed. Alumina particles with an average particle size of 0.5 μm are used as the restraining inorganic material, and a paste using hydrocarbon-based petroleum jelly, fatty acid ester (oil) oil, and natural resin rosin as fluid additives. did. In preparing the paste, a solvent was added as necessary.
In the same manner as in Example 2, a constraining paste was applied to the upper and lower surfaces of the unfired multilayer ceramic substrate by a printing method, and pressure bonding was performed at room temperature at a pressure of 10.8 MPa. When the thickness of the first constraining layer is less than 50 μm, the constraining layer green sheets prepared by the above method are stacked and thermocompression bonded at a temperature of 85 ° C. and a pressure of 10.8 MPa to obtain a thickness of the constraining layer. The thickness was set to 50 μm or more. The evaluation results are shown in Table 3 in the same manner as in Example 2.

  A highly accurate substrate is obtained in which the thickness of all constraining layers is 50 μm or more, the XY direction shrinkage is suppressed to 1% or less, the shrinkage variation 3σ is 0.07% or less, and the warp in the XY plane is 30 μm or less per 50 mm. I was able to. In addition, no pores having a diameter of 0.5 μm or more were found on the surface of the external electrode from which the alumina in the constrained layer was removed, and a very good external electrode was obtained.

Next, the low temperature fired ceramic material was investigated. First, the crystal phase of this material was examined by X-ray diffraction analysis. The target was Cu, and the Kα ray was used as a diffracted X-ray source. FIG. 6 shows powder X-ray diffraction pattern diagrams of the mixed powder, calcined composite powder, and sintered body. In the mixed powder, the crystal phase of the raw material is observed, and in the calcined composite powder, the presence of the glass phase is recognized from the crystal phase of Al ₂ O ₃ , TiO ₂ and SiO ₂ and the halo pattern from 20 degrees to 30 degrees. Further, it was confirmed that SrAl ₂ Si ₂ O ₈ (strontium feldspar) was newly deposited in the sintered body.

Furthermore, the observation photograph by the scanning electron microscope of the said calcined composite and its ground material is shown in FIG. In FIG. 7 (a), Al ₂ O ₃ is a calcined composite and white particles appear. Black spots are pores. Moreover, the part which is a continuous phase is a glass phase. This is a state in which the liquid phase is solidified. In the calcined composite, it is recognized that the Al ₂ O ₃ particles are partially or entirely covered with the glass phase. This by being calcined, the vitrification proceeds except _Al 2 _{O 3} and TiO _2, a slight amount of _Al 2 _{O 3} and TiO ₂ is for entering into the glass. In order to achieve uniform and complete vitrification containing SiO ₂ as a main component, it is necessary to melt the composition at a firing temperature of 1300 ° C. or higher. Although the SiO ₂ phase still remains, such a state is regarded as a non-uniform glass phase.
FIG. 7B shows particles obtained by pulverizing the calcined product, and similarly, a state in which the glass phase is partially or entirely covered with Al ₂ O ₃ particles can be seen. That is, particles obtained by finely pulverizing a calcined product that is a solidified product of ceramic particles and a partial glass phase are particles in which glass is partially or entirely covered with ceramic particles.
As described above, the glass component of the calcined composite of the present invention is in a state in which the vitrification reaction is insufficient and difficult to flow as compared with the raw material in which glass particles and ceramic particles that are generally melted and manufactured are mixed. . Since the calcined composite having such characteristics is used, the reactivity of the glass component is low even in the main sintering, and the interface between the unfired multilayer ceramic substrate and the constrained layer is in a state of high viscosity where the glass component is inactive. is there. Therefore, the flow of the glass is suppressed and the glass component is difficult to penetrate.

  In the present invention, since the sintering shrinkage rate of the surface of the multilayer ceramic substrate is close to zero and the pattern variation is small, the multilayer ceramic that matches the conductor pattern or solder pattern formed thereon and the conductive adhesive formation pattern with high accuracy. This is a substrate manufacturing method, and can be used for mobile phones, automobile electronic control circuit boards, semiconductor packages, and opto-electric circuit boards that require high-density ceramic substrates.

It is a sectional structure figure showing an unfired multilayer ceramic substrate (before constraining layer formation) by a large sized substrate of the present invention. FIG. 2 is a top perspective view of FIG. 1. It is a cross-sectional structure which shows the non-baking multilayer ceramic substrate (after constraining layer formation) by the large sized board | substrate of this invention. It is a cross-sectional structure diagram showing a module substrate in which chip components such as semiconductor elements are mounted on a multilayer ceramic substrate. It is a flowchart of the manufacturing process of the multilayer ceramic substrate of this invention. It is a powder X-ray diffraction pattern figure of each of the mixed powder, calcined powder, and sintered body of the low-temperature fired ceramic material of the present invention. It is the observation photograph by the scanning electron microscope of the calcined material of the low-temperature baking ceramic material of this invention, and its pulverized powder.

Explanation of symbols

1 (1A to 4A, 1B to 4B, 1C to 4C): multilayer ceramic substrate 2: internal electrode 3: via electrode 4: external electrode 5: dividing groove 6: constraining layer 7: mounting component 8: green sheet 10 for substrate: Unfired multilayer ceramic substrate

Claims (13)

Producing a green sheet for a substrate using a slurry of a low-temperature sintered ceramic material;
Forming an internal electrode, a via electrode, and an external electrode as appropriate on the green sheet for the substrate, and laminating this to produce an unfired multilayer ceramic substrate;
Producing a constrained material in which a fluid additive is added to a powder of an inorganic material that is not sintered at the sintering temperature of the low-temperature sintered ceramic material;
Applying and / or overlaying the constraining material to a thickness of 50 μm or more on the upper surface and / or the lower surface including external electrodes of the unfired multilayer ceramic substrate, and bonding the pressure layer;
Sintering the unfired multilayer ceramic substrate having the constraining layer at 800 ° C. to 1000 ° C .;
Removing the constraining layer from the multilayer ceramic substrate;
A method for producing a multilayer ceramic substrate, comprising: Producing a green sheet for a substrate using a slurry of a low-temperature sintered ceramic material;
Forming an internal electrode, a via electrode, and an external electrode as appropriate on the green sheet for the substrate, and laminating this to produce an unfired multilayer ceramic substrate;
Forming split grooves in the green multilayer ceramic substrate;
Producing a constrained material in which a fluid additive is added to a powder of an inorganic material that is not sintered at the sintering temperature of the low-temperature sintered ceramic material;
Applying and / or overlaying the constraining material to a thickness of 50 μm or more on the upper surface and / or the lower surface including external electrodes of the unfired multilayer ceramic substrate, and bonding the pressure layer;
Sintering the unfired multilayer ceramic substrate having the constraining layer at 800 ° C. to 1000 ° C .;
Removing the constraining layer from the multilayer ceramic substrate;
A method for producing a multilayer ceramic substrate, comprising: A first constraining layer of 10 μm or more is formed by applying the constraining material on the upper surface and / or the lower surface including external electrodes of the unfired multilayer ceramic substrate, and a green sheet made of the constraining material is overlaid thereon. The method for producing a multilayer ceramic substrate according to claim 1, wherein the second constraining layer is formed by the step of forming a constraining layer of 50 μm or more. The method for producing a multilayer ceramic substrate according to any one of claims 1 to 3, wherein the fluidity additive is a synthetic resin having an average degree of polymerization of 2000 or less or a substance obtained by adding a solvent thereto. The method for producing a multilayer ceramic substrate according to any one of claims 1 to 3, wherein the fluidity additive is a natural resin or a substance obtained by adding a solvent thereto. The method for producing a multilayer ceramic substrate according to claim 1, wherein the fluidity additive is a hydrocarbon-based material. The method for producing a multilayer ceramic substrate according to any one of claims 1 to 3, wherein the fluidity additive comprises an ester of a fatty acid. The method for producing a multilayer ceramic substrate according to any one of claims 1 to 3, wherein the amount of the synthetic resin contained in the constraining material for coating formation is 4% by volume or more and less than 10% by volume. . The said inorganic material is plate shape, The manufacturing method of the multilayer ceramic substrate in any one of Claims 1-3 characterized by the above-mentioned. The low-temperature sintered ceramic material is obtained by calcining a mixture of at least SiO ₂ and Al ₂ O ₃ oxide and at least one carbonate at 700 ° C. to 850 ° C., and at least a glass phase and an alumina crystal phase. The method for producing a multilayer ceramic substrate according to claim 1, comprising a pulverized powder of a calcined composite. When the low-temperature sintered ceramic material is converted into Al ₂ O ₃ , SiO ₂ , SrO, and TiO ₂ , respectively, the main components Al, Si, Sr, and Ti are 10 to 60% by mass in terms of Al ₂ O ₃ , 25-60 wt% in terms of SiO _2, from 7.5 to 50 mass% in terms of SrO is less than 20 wt% in terms of TiO ₂ (including 0), as a sub-component for the main component of 100 wt%, Bi, Na, K, at least one selected from the group of Co 0.1 to 10 mass% in terms _{of Bi} 2 _{O 3,} 0.1 to 5 mass% in terms of Na ₂ O, with _{K 2} O in terms of 0. 1 to 5% by mass, 0.1 to 5% by mass in terms of CoO,
Further, at least one of the group of Cu, Mn, and Ag contains 0.01 to 5% by mass in terms of CuO, 0.01 to 5% by mass in terms of MnO ₂ , and 0.01 to 5% by mass of Ag. 7. A mixture containing other inevitable impurities is calcined at 700 ° C. to 850 ° C. and pulverized to form finely pulverized particles having an average particle size of 0.6 to 2 μm. A method for producing a multilayer ceramic substrate according to any one of the above. 12. A multilayer ceramic substrate obtained by the manufacturing method according to claim 1, wherein the shrinkage ratio in the plane of the substrate is 1% or less and the variation 3σ is 0.07% or less. A multilayer ceramic substrate having a warpage in a substrate plane obtained by the production method according to claim 1 of 30 μm or less per 50 mm.

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