JP4219360B2 - Manufacturing method of multilayer ceramic substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a multilayer ceramic substrate, and more particularly to a technique for preventing shrinkage and deformation during firing.

  In the field of electronic equipment and the like, substrates for mounting electronic devices are widely used. However, in recent years, as a substrate having high reliability in response to demands for reduction in size and weight of electronic devices and multifunctional functions. A multilayer ceramic substrate has been proposed and put into practical use. The multilayer ceramic substrate is configured by laminating a plurality of ceramic layers, and high density mounting is possible by integrally forming a wiring conductor (conductor pattern), an electronic element, and the like in each ceramic layer.

  The multilayer ceramic substrate is formed by laminating a plurality of green sheets to form a laminate and then firing the laminate. The green sheet is surely shrunk with the sintering in the firing step, which is a major factor for reducing the dimensional accuracy of the multilayer ceramic substrate. Specifically, shrinkage variation occurs with the shrinkage, and the finally obtained multilayer ceramic substrate has a dimensional accuracy of only about 0.5%.

Under such circumstances, a so-called non-shrinkage firing method that suppresses shrinkage in the in-plane direction of the green sheet and shrinks only in the thickness direction in the firing process of the multilayer ceramic substrate has been proposed (for example, Patent Document 1). And Patent Document 2). As described in these patent documents, when a sheet that does not shrink even at the firing temperature is attached to a laminate of green sheets and firing is performed in this state, shrinkage in the in-plane direction is suppressed, and the thickness direction Only shrinks. As a result, the dimensional accuracy in the in-plane direction of the multilayer ceramic substrate can be improved to about 0.05%.
JP-A-62-260777 JP-A-10-75060

  By the way, in a multilayer ceramic substrate, via holes, variously shaped conductor patterns, etc. are usually formed in each ceramic layer constituting this, and conduction between the electrodes installed in each ceramic layer can be obtained, It plays the role of connecting the parts that make up. Or as above-mentioned, electronic elements, such as an inductor and a capacitor, may be formed in each ceramic layer.

  In such a case, even if an attempt is made to produce a multilayer ceramic substrate using the above-described non-shrinkage firing method, a phenomenon occurs in which the fired multilayer ceramic substrate is deformed. This is presumed to be due to various factors such as non-uniform distribution of each conductor pattern in the substrate, for example, temperature variations on the front and back of the substrate and before and after the firing in a firing belt furnace, etc. In any case, the situation remains that the multilayer ceramic substrate obtained after firing is likely to suffer from inconveniences such as warping and bending.

  In order to eliminate the inconveniences as described above, the laminated body in which the green sheet for substrate and the green sheet for shrinkage suppression are laminated at the time of firing is fired while pressing from both sides, or when passing through the belt furnace for firing. In order to reduce the temperature difference between the upper and lower surfaces, it may be possible to cover and fire with a setter or the like, but in the former case, it cannot be continuously fired. Problems such as the need for capital investment arise and it is difficult to reduce the production cost.

  The present invention has been proposed in view of such a conventional situation, has high dimensional accuracy due to being formed by a non-shrinkage firing method, and is free from deformation such as warpage and deflection, and is reliable. It aims at providing the manufacturing method which can manufacture a highly reliable multilayer ceramic substrate. The present invention also provides a method for producing a multilayer ceramic substrate that does not require pressurization during firing, is excellent in productivity, can reduce capital investment, and can reduce production costs. Objective.

  In order to achieve the above-mentioned object, a method for manufacturing a multilayer ceramic substrate according to the present invention includes stacking a plurality of green sheets for a substrate, placing a green sheet for suppressing shrinkage on both sides of the stacked green sheets for a substrate, and firing. A method for producing a multilayer ceramic substrate, characterized in that at least one shrinkage-suppressing green sheet is placed on an outer side of a shrinking green sheet that shrinks during firing, and the firing is performed.

  When the shrinkage-suppressing green sheets are stacked on both sides of the substrate green sheet and fired, the sheet cannot be shrunk basically in the surface direction, but shrinks only in the thickness direction. As a result, dimensional accuracy in the in-plane direction is ensured. However, due to the formation of via holes, conductor patterns, and the like in each ceramic layer, warpage, deflection, and the like may occur in the obtained multilayer ceramic substrate.

  Therefore, in the present invention, in addition to the contraction-suppressing green sheet, the contraction green sheet is arranged on the outer side to eliminate the warpage and the bending. When the contraction green sheet is provided outside the contraction suppression green sheet, the contraction force of the contraction green sheet is applied to the back side of the contraction suppression sheet in a form against the contraction force of the substrate green sheet. As a result, deformations such as warping and bending caused by the contraction force of the substrate green sheet are suppressed. Moreover, although the said shrinkage | contraction green sheet densifies by baking, this is also considered to have contributed to suppression of the said deformation | transformation.

  In the firing, it is only necessary to arrange the contracted green sheet. For example, it is not necessary to pressurize or cover with a setter during firing. Therefore, continuous firing is possible, and ordinary equipment for firing can be used, so that there is no particular large scale, and there is no disadvantage such as an increase in production cost.

  As a technique for eliminating the warp of the multilayer ceramic substrate, as described in Japanese Patent No. 3687484, there is also known a method in which constraining layers having different rigidity are pressure-bonded to both main surfaces. There is a possibility that the restraining force cannot be applied evenly to both surfaces of the laminate of the green sheets, and anxiety remains in terms of dimensional accuracy of the multilayer ceramic substrate after firing. In the present invention, since the same shrinkage-suppressing green sheets are stacked and fired on both sides of the substrate green sheet, it is possible to apply a binding force evenly on both sides of the substrate green sheet laminate, This is advantageous in terms of dimensional accuracy. In addition, the correction of the warp is performed by arranging a contraction green sheet. In this case, the contraction force of the contraction green sheet is applied to the back side of the contraction suppression green sheet, and the contraction force of the substrate green sheet is canceled. Exerts a great correction force. Even if the rigidity of the constraining layer is changed as described in the above-mentioned patent publication, the correction force that cancels the contraction force of the green sheet for substrate does not work.

  As described above, in the production method of the present invention, the shrinkage-suppressing green sheets are disposed on both sides of the laminated substrate green sheet, and the shrinkable green shrinks upon firing outside of at least one of the shrinkage-preventing green sheets. Since a sheet is provided, the shrinkage in the in-plane direction of the resulting multilayer ceramic substrate can be suppressed to improve dimensional accuracy, and at the same time, deformation such as warpage or deflection of the multilayer ceramic substrate that occurs during firing can be suppressed. Can do. In addition, according to the present invention, it is not necessary to perform pressure firing, use of a setter that covers the substrate, etc., so that productivity can be improved and capital investment can be minimized, and production cost can be reduced. Is possible.

  Hereinafter, a method for producing a multilayer ceramic substrate to which the present invention is applied will be described in detail with reference to the drawings.

(First embodiment)
In order to produce a multilayer ceramic substrate, first, a green sheet for a substrate that becomes each ceramic layer after firing is prepared. The green sheet for a substrate forms a slurry-like dielectric paste obtained by mixing ceramic powder and an organic vehicle, and forms the film on a support such as a polyethylene terephthalate (PET) sheet by a doctor blade method or the like. To form. Any known ceramic powder and organic vehicle can be used.

  Via holes, conductor patterns (electrode pads, etc.), and electronic elements (inductors, capacitors, etc.) are formed in the green sheet for substrates as necessary. For example, when forming a via hole, a through hole is formed at a predetermined position after the green sheet for a substrate is formed. The through holes communicate with each other after stacking to form via holes, and are usually formed as circular holes. Of course, the present invention is not limited to this, and as described above, any shape such as an ellipse, an oval, a square or a rectangle with round corners, or a combination of these may be used. In addition, for example, when the thickness of the green sheet is about 125 μm, the diameter of the through hole is set to about 0.1 mm in diameter considering the filling property of the conductive paste into the through hole. By performing pressure filling or the like, it is possible to cope with a smaller hole diameter, and conversely, a larger hole diameter may be used.

  The electrode pad is formed as an annular conductive pattern with a conductive paste around the through hole corresponding to the through hole. When the through hole is circular, the electrode pad is also formed concentrically around the through hole. However, when the through hole is not circular, the shape of the electrode pad may be matched to the shape of the through hole. Further, when forming the electrode pad with the conductive paste, the inside of the through hole is also filled with the conductive paste.

  The conductive paste is prepared by kneading a conductive material made of various conductive metals and alloys such as Ag, Ag—Pd alloy, Cu, and Ni and an organic vehicle. The organic vehicle has a binder and a solvent as main components, and the mixing ratio of the conductive material is arbitrary, but usually the binder is 1 to 15% by mass, and the solvent is 10 to 50% by mass. It is blended with the conductive material. Additives selected from various dispersants, plasticizers, and the like may be added to the conductive paste as necessary.

  After preparing the said board | substrate green sheet, as shown in FIG. 1, this is piled up and it is set as a laminated body. In the case of this embodiment, the laminated body 1 is configured by laminating eight green sheets 1a to 1h for a substrate.

  This is fired to obtain a multilayer ceramic substrate. In firing, as shown in FIG. 1A, after the shrinkage green sheet 2 and the shrinkage suppression green sheet 3 are placed in this order on the base in this order, The substrate green sheets 1a to 1h are placed thereon. Furthermore, the shrinkage-suppressing green sheet 4 and the shrinking green sheet 5 are overlaid in this order. The stacked state is shown in FIG. As shown in FIG. 1B, at the time of firing, the shrinkage-suppressing green sheets 3 and 4 are arranged on both sides of the laminate 1 in which the substrate green sheets 1a to 1h are laminated, and the shrinkage greens are respectively provided on the outer sides thereof. Sheets 2 and 5 are arranged.

  Here, first, the shrinkage-suppressing green sheets 3 and 4 are made of materials that do not shrink at the firing temperature of the substrate green sheets 1a to 1h, such as tridymite and cristobalite, and also quartz, fused quartz, alumina, mullite, zirconia. A composition containing aluminum nitride, boron nitride, magnesium oxide, silicon carbide, or the like is used. By sandwiching the laminate 1 between the shrinkage-suppressing green sheets 3 and 4 and firing, the shrinkage in the in-plane direction is suppressed, and the shrinkage occurs only in the thickness direction.

  On the other hand, the shrinkage green sheets 2 and 5 arranged outside the shrinkage suppression green sheets 3 and 4 are layers that shrink at the firing temperature of the laminate 1, unlike the shrinkage suppression green sheets 3 and 4. is there. Therefore, although the material which satisfy | fills this is used, it is preferable to form with the same material as the said green sheets 1a-1h for board | substrates, for example. The substrate green sheets 1a to 1h are shrunk by firing. By using the same material as the shrink green sheets 2 and 5, the shrinkage degree of the shrink green sheets 2 and 5 and the substrate green sheets 1a to 1h is reduced. It has the same advantage that it is easy to balance when canceling the contraction forces. Further, by diverting the substrate green sheets 1a to 1h as the contracted green sheets 2 and 5, it is not necessary to prepare the contracted green sheets 2 and 5 in a separate process, which is advantageous in reducing the manufacturing cost. .

  As described above, the shrinkage-suppressing green sheets 3 and 4 and the shrinking green sheets 2 and 5 are disposed on both sides of the laminated body 1 and fired. However, the fired multilayer ceramic substrate has excellent dimensional accuracy, warping and bending. Etc. are less deformed. Specifically, first, the contraction in the in-plane direction of each of the substrate green sheets 1a to 1h constituting the laminated body 1 is suppressed by the action of the shrinkage suppressing green sheets 3 and 4, and dimensional accuracy is ensured. . On the other hand, stress is applied to the laminated body 1 due to the shrinkage force of the substrate green sheets 1a to 1h during firing, which causes deformation such as warping and bending, but is offset by the shrinkage force of the shrinkage green sheets 2 and 5, The stress is relaxed and the deformation is suppressed. In addition, the contracted green sheets 2 and 5 are densified after firing, which is presumed to contribute to the suppression of the deformation.

  In the present embodiment, the shrinkage suppressing green sheets 3 and 4 and the shrinking green sheets 2 and 5 are disposed on both sides of the laminated body 1 and fired. Depending on the state of warping, firing can be performed by stacking the shrinkage green sheet on only one of the shrinkage suppression sheets 3 (or the shrinkage suppression sheet 4). For example, when the laminate 1 is curved after firing, the shrinking green sheets are stacked only on the convex side. Thereby, the said curvature can be eliminated. Furthermore, the thickness of the contracted green sheets 2 and 5 can be adjusted according to the warp.

(Second Embodiment)
In the above example, the shrinkage green sheets 2 and 5 and the shrinkage suppression green sheets 3 and 4 are formed separately and overlapped with each other. However, the shrinkage green sheet and the shrinkage suppression green sheet are integrally formed in advance. You may make it pile this up. Thereby, the shrinkage green sheet and the shrinkage suppression green sheet can be collectively disposed on the laminate 1.

  FIG. 2 shows an example using a shrinkage suppression material in which the shrinkage green sheet and the shrinkage suppression green sheet are integrally formed. Basically, it is the same as in the previous embodiment. In this example, as shown in FIG. 2A, first, the shrinkage-suppressing green sheet 3 is overlaid on the shrinking green sheet 2. The first shrinkage suppression material 11 formed in this manner is prepared, and the substrate green sheets 1a to 1h are stacked thereon. Next, the second shrinkage suppression material 12 formed by overlapping the shrinkage green sheet 5 on the shrinkage suppression green sheet 4 is placed thereon.

  As shown in FIG. 3, the first shrinkage suppression material 11 and the second shrinkage suppression material 12 are formed by applying a shrinkage material or a shrinkage suppression material on a film serving as a support and drying it. it can. FIG. 3A shows an example of a method for producing the first shrinkage suppression material 11. First, a shrinkage suppression material 17 is supplied from a coater 16 onto a base film 13 that is a support film, and then dried. Thus, the shrinkage-suppressing green sheet 3 is formed. After the formation of the shrinkage-suppressing green sheet 3, the shrinkage material 15 is supplied from the coater 14 thereon and dried to form the shrinkage green sheet 2. As the base film 13, a polyethylene terephthalate film (PET film) or the like can be used.

  The same applies to the second shrinkage suppression material 12. When the second shrinkage suppression material 12 is formed, the shrinkage material 15 is first formed on the base film 13 as shown in FIG. 3B, contrary to the formation of the first shrinkage suppression material 11. Is supplied from the coater 14 and dried to form the contracted green sheet 5. After the formation of the shrinkage green sheet 5, the shrinkage suppression material 17 is supplied from the coater 16 thereon and dried to form the shrinkage suppression green sheet 4.

  The reason why the first and second shrinkage suppression materials 11 and 12 are used as the shrinkage suppression material is that the layers are usually stacked by sequentially stacking each layer on a base that is a support. by. That is, when laminating the above-described layers on the base, first, the base and the shrinkage green sheet 2 of the first shrinkage suppression material 11 face each other (that is, the shrinkage green sheet 2 faces downward). The first shrinkage suppression material 11 is stacked on the base, and the base film 13 is peeled off. As a result, the contraction green sheet 2 and the contraction suppression green sheet 3 are placed in this order on the base. Next, the substrate green sheets 1a to 1h are sequentially stacked thereon. Usually, the substrate green sheets 1a to 1h are also provided in a form formed on the base film, respectively, but in that case, the substrate green sheets are overlapped downward and the base film is peeled off, The substrate green sheets 1a to 1h are sequentially stacked. Lastly, the second shrinkage suppression material 12 is stacked, but also when the second shrinkage suppression material 12 is stacked, the uppermost substrate green sheet 1 h and the second shrinkage suppression material 12 are used for shrinkage suppression. 4, the second shrinkage suppression material 12 is stacked so that the shrinkage-suppressing green sheet 4 faces downward. After the second shrinkage suppression material 12 is stacked, the base film 13 of the second shrinkage suppression material 12 is peeled off.

  By providing the first shrinkage-suppressing material 11 and the second shrinkage-suppressing material 12 and further the substrate green sheets 1a to 1h on the base film, by superimposing and peeling the base film, A predetermined laminated structure can be easily obtained, and productivity can be greatly improved.

(Third embodiment)
In the production of a multilayer ceramic substrate, when a green sheet in which conductors are extremely unevenly distributed, a green sheet composed of different materials with different shrinkage behavior, a green sheet containing a dielectric and ferrite, etc. are used, Even if the shrinkage green sheets are stacked on the entire surface of the shrinkage-suppressing green sheet as in the first embodiment and fired, it may be difficult to fire evenly. In such a case, it is effective to partially dispose the contracted green sheet.

  FIG. 4 shows an example in which contracted green sheets are partially arranged according to the electrode pattern formed on the substrate green sheet. In the case of this example, ten substrate green sheets 21a to 21j are laminated to form a laminate 21, and this is fired to produce a multilayer ceramic substrate. The uppermost substrate green sheet 21j has an electrode pattern 22 formed on the surface thereof, but when the shrinkage-suppressing green sheets 23 and 24 are stacked on both sides and fired, the electrode pattern 22 portion is partially covered. It may rise or reverse. The portion where the electrode pattern 22 is formed has a relatively small degree of shrinkage compared to other portions. Therefore, when the shrinkage green sheet is uniformly arranged, the bulge and the depression are generated due to the difference in the degree of shrinkage. To do.

  Therefore, in the present embodiment, the contracted green sheet pieces 25 patterned corresponding to the electrode pattern 22 are formed in an array on the back side of the contraction suppressing green sheet 24 on which the electrode pattern 22 is formed. The contracted green sheet piece 25 may be formed by, for example, a printing method, or may be formed by pasting it into a predetermined shape by punching or the like.

  5 and 6 show a laminated structure when the contracted green sheet pieces 25 are formed in an array. Shrinking green sheet pieces 25 are arranged at positions facing the electrode pattern 22. In this way, by forming the contracted green sheet pieces 25 patterned corresponding to the electrode patterns 22 and performing firing, deformation such as partial rise or partial depression corresponding to the electrode patterns 22 is performed. Can be eliminated.

  In the present embodiment, the case where the electrode pattern is formed on the green sheet for the substrate has been described as an example. However, the present invention is not limited to this, and the present invention is not limited to this. The present invention can also be applied to a case where a green sheet or the like containing is combined in an unbalanced manner. In the above example, the contraction green sheet piece 25 is disposed only on one surface, but the contraction green sheet piece may be disposed on the back of both the contraction suppression green sheets 23 and 24. In any case, it is only necessary to apply a shrinking green sheet to an appropriate part depending on the occurrence of warping or deformation, and the shape, size, thickness, etc. of the shrinking green sheet piece 25 can be arbitrarily set. . In particular, regarding the thickness, the thickness may be changed depending on the portion, or the thickness may be changed on the front and back of the laminate.

(Fourth embodiment)
In each of the above-described embodiments, the case where only the contraction green sheet is disposed on the back surface of the contraction suppression green sheet has been described. However, not only the contraction green sheet but also the second contraction suppression green sheet may be disposed in combination. Is possible. The second shrinkage suppressing green sheet may be formed on the entire surface or may be partially added.

  FIG. 7 shows an example in which a shrinkage green sheet is disposed on one surface of the laminate and a second shrinkage suppression green sheet is disposed on the other surface. In the case of this example, ten substrate green sheets 31a to 31j are laminated to form a laminate 31, and this is fired to produce a multilayer ceramic substrate. A rectangular electrode pattern 32 is formed on the surface of the uppermost substrate green sheet 31j. When the shrinkage-suppressing green sheets 33 and 34 are stacked on both sides and fired, the rectangular electrode pattern 32 is formed. Are directed in the same direction, so that they curve in the x direction as shown in FIG.

  Therefore, in order to eliminate such a curvature, in the present embodiment, a belt-like second shrinkage-suppressing green sheet piece 35 is superimposed on the shrinkage-suppressing green sheet 33 on the concave surface (the lower surface in the figure). The strip-shaped contracted green sheet piece 36 is disposed on the contraction-suppressing green sheet 34 on the convex surface (the upper surface in the drawing). The laminated state is shown in FIG. Thereby, contraction force works only on the convex surface, and warping is eliminated. In particular, by making the green sheet piece 35 for shrinkage suppression and the shrinkable green sheet 36 into a strip shape, it is possible to impart directionality to the correction force and effectively eliminate the curvature in the x direction.

  The usage form of the second shrinkage suppression green sheet can be arbitrarily changed. For example, the second shrinkage suppression green sheet can be arranged on the back surface of both of the shrinkage suppression green sheets 33 and 34, and warpage or deformation occurs. What is necessary is just to provide the 2nd green sheet for shrinkage | contraction suppression to a suitable site | part according to a condition. Further, the shape, size, thickness, and the like of the second shrinkage suppression green sheet can be arbitrarily set.

  In addition, when the shrinkage green sheet and the second shrinkage suppression green sheet are used in combination for correcting deformation such as warpage, the advantage is that the laminate can be easily pressed if they are used in combination in the same layer. Also have. For example, if the shrinkage green sheet is incorporated so as to be fitted to the second shrinkage suppression green sheet, it can be handled as one sheet (correction composite green sheet). If this straightening composite sheet is used, the thickness of the final laminate becomes uniform. For example, instead of an isostatic press, a press using a normal flat die can be used. Can be greatly reduced.

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results.

Example 1
In this example, the shrinkage green sheet and the shrinkage suppression green sheet were formed separately, and these were laminated to suppress shrinkage and deformation in the in-plane direction. Specifically, an alumina-glass dielectric material is prepared as a ceramic material for a substrate, mixed with an organic binder and an organic solvent, and then formed into a sheet by a doctor blade method to form a ceramic green sheet having a thickness of 125 μm (green for substrate). Sheet).

  On the other hand, a tridymite-silica-based material prepared as a shrinkage-suppressing material is mixed with an organic binder and an organic solvent in the same way as a ceramic material, and is formed into a sheet by the doctor blade method to give a 125 μm-thick forced layer green sheet (shrinkage-preventing green sheet) Was made. Further, in order to form a composite compulsory layer together with the compulsory layer green sheet, a sheet made of the same material as the ceramic green sheet for a substrate and having a thickness of only 64 μm was prepared, and this was used as a contracted green sheet.

  The ceramic green sheet that forms each layer of the multilayer ceramic substrate is drilled with through-holes that form through-holes and filled with conductive paste, and if necessary, elements such as inductors and capacitors are formed and connected to each other. A conductor pattern portion to be provided was provided, and a total of eight ceramic green sheets were laminated to form a laminate. And the said forced layer green sheet was piled up on both surfaces of this laminated body, and the shrinkage | contraction green sheet for forming a composite forced layer was further laminated | stacked on the outer side. A composite compulsory layer is formed by overlapping the compulsory layer green sheet and the contracted green sheet.

The laminated body thus obtained was put into a mold having a flat upper and lower punch and pressurized at 700 kg / cm ^{2 for} 7 minutes, then placed on a setter and fired at 900 ° C. without installing a cover. did. After passing through the furnace, the composite forced layer (fired product of forced layer green sheet and contracted green sheet) could be easily removed manually. This is because the substrate-material alumina-glass-based dielectric material and the tridymite-silica-based material that suppresses shrinkage have a large difference in coefficient of thermal expansion and contain strong stress when cooled to room temperature. . In addition, since the residue from the forced layer is slightly present in the multilayer ceramic substrate after the removal, it was removed by washing.

  The fired multilayer ceramic substrate generally expanded by about 0.2% in the plane direction and contracted only in the thickness direction. The reason for the expansion of the plane direction is that in this example, the forced layer green sheet is relatively thick, so the forced layer is strongly thermally expanded during firing, and the ceramic substrate expands as it is pulled by this forced layer. This is probably due to sintering. In this example, although a cover for preventing radiant heat in the furnace directly irradiated during firing was not installed, the warpage was less than 50 μm with a substrate approximately 60 mm square.

Example 2
In this example, a forced layer green sheet (shrinkage suppressing green sheet) and a contracted green sheet were previously formed on a film and laminated on a ceramic green sheet as a substrate green sheet in a state of a composite forced layer.

  Also in this example, an alumina-glass dielectric material was prepared as the substrate ceramic material. This dielectric material was mixed with an organic binder and an organic solvent, and formed into a sheet by a doctor blade method to produce a ceramic green sheet having a thickness of 125 μm.

  On the other hand, for the composite forced layer, first, as shown in FIG. 3A, the tridymite-silica-based material prepared as a shrinkage-suppressing material is mixed with an organic binder and an organic solvent, and the PET film is coated on the PET film by the doctor blade method. A compulsory layer green sheet was formed by coating and drying to a thickness of 40 μm. Thereafter, the same alumina-glass dielectric material as the ceramic material for the substrate is mixed with the organic binder and the organic solvent, and is applied to the thickness of 65 μm by a doctor blade method so as to have a thickness of 65 μm. A composite forced layer green sheet A having a total thickness of 105 μm was produced.

  Similarly, as shown in FIG. 3B, an alumina-glass-based dielectric material similar to the substrate ceramic material is mixed with an organic binder and an organic solvent, and a thickness of 65 μm is formed on the PET film by a doctor blade method. This was coated and dried to form a contracted green sheet. Further, the tridymite-silica-based material prepared as a material for suppressing shrinkage is similarly mixed with an organic binder and an organic solvent, and is applied to the thickness of 40 μm by a doctor blade method so as to form a forced layer green sheet. The composite forced layer green sheet B having a total thickness of 105 μm was formed. In preparing the composite compulsory layer green sheets A and B, the drying conditions were determined so as not to increase the degree of dissolution of the lower layer by the organic solvent.

  The ceramic green sheet that forms each layer of the multilayer ceramic substrate is drilled with through-holes that form through-holes and filled with conductive paste, and if necessary, elements such as inductors and capacitors are formed and connected to each other. In this example, a total of 10 ceramic green sheets were laminated to form a laminate. Then, the composite compulsory layer green sheets A and B were stacked on both sides of the laminate so that the contracted green sheets were on the outside, and the PET film was peeled off.

The laminated body thus obtained was put in a mold having a normal upper and lower punch and pressed at 700 kg / cm ^{2 for} 7 minutes, and then placed on a setter and baked at 900 ° C. without installing a cover. The fired multilayer ceramic substrate was not shrunk as much as 1% in the plane direction as a whole, and was greatly shrunk only in the thickness direction. Moreover, despite the fact that no cover was installed to prevent radiant heat in the furnace that was directly irradiated during firing, the substrate was approximately 60 mm square and the warp was less than 50 μm.

Example 3
In this example, the contracted green sheet was partially applied according to the electrode pattern formed on the substrate green sheet.

  An alumina-glass dielectric material was prepared as a ceramic material for the substrate. This was mixed with an organic binder and an organic solvent to form a sheet having a thickness of 125 μm by a doctor blade method, and a ceramic green sheet (a green sheet for a substrate) was produced. On the other hand, an alumina-glass-based material was used as a shrinkage-suppressing material, and this was mixed with an organic binder and an organic solvent in the same manner as the ceramic material.

  Drilling through holes to form through holes in the ceramic green sheets that form each layer of the multilayer ceramic substrate, filling with conductor paste, forming inductors and capacitors, and providing conductor pattern parts to connect each element A total of 10 sheets were laminated as shown in FIG. 4, and green sheets for suppressing shrinkage were laminated on both sides. In the multilayer ceramic substrate manufactured in this way, the portion where the relatively large conductor pattern is arranged on the surface is relatively less likely to shrink than the other portions. Printed and partially placed shrink green sheets. The dry film thickness of this partially installed shrinkage green sheet was 20 μm.

The laminated body thus obtained was sealed in a polyethylene bag while being heated to 75 ° C., and pressurized at 700 kg / cm ² under a hydrostatic pressure of 75 ° C. for 7 minutes, and then placed on a setter and a cover was installed. It fired at 900 degreeC, without doing. The fired multilayer ceramic substrate was not shrunk as much as 1% in the plane direction as a whole, and was greatly shrunk only in the thickness direction. In addition, the bulge at the center of the electrode pattern was improved from a little less than 40 μm when the contracted green sheet was not installed to a little less than 30 μm.

Example 4
In this example, an attempt was made to eliminate the warpage by combining the contraction green sheet and the second contraction suppression green sheet.

  As in Example 3, an alumina-glass dielectric material was prepared as the substrate ceramic material. This was mixed with an organic binder and an organic solvent to form a sheet having a thickness of 125 μm by a doctor blade method, and a ceramic green sheet (a green sheet for a substrate) was produced. On the other hand, an alumina-glass-based material was used as a shrinkage-suppressing material, and this was mixed with an organic binder and an organic solvent in the same manner as the ceramic material.

  Drilling through holes to form through holes in the ceramic green sheets that form each layer of the multilayer ceramic substrate, filling with conductor paste, forming inductors and capacitors, and providing conductor pattern parts to connect each element A total of 10 sheets were laminated as shown in FIG. 7, and green sheets for shrinkage suppression were laminated on both sides. Since this laminated body has many rectangular electrode patterns installed in the same direction on a ceramic green sheet immediately below one surface, it has a warp as shown in FIG.

  Therefore, the second shrinkage suppression green sheet is rectangular on the outer side of the warp, and the second shrinkage green sheet is on the outer side of the warp. And then overlaid. If you try to adjust the warpage by adding a second shrinkage-suppressing green sheet or shrinkage green sheet that is not formed into a rectangle, the direction of the warp will be perpendicular or the opposite side will be inside. May become warped. By forming the second shrinkage-suppressing green sheet or the shrinking green sheet into a rectangular shape, it is possible to give directionality to the correction of the warp.

The laminated body thus obtained was sealed in a polyethylene bag in a state heated to 75 ° C., and pressurized at 700 kg / cm ² under a hydrostatic pressure of 75 ° C. for 7 minutes, and then placed on a setter. Firing was performed at 900 ° C. without installing a cover. The multilayer ceramic substrate after firing did not shrink as much as 1% in the plane direction as a whole, and was greatly shrunk only in the thickness direction. Even in this example, the warpage is reduced from about 80 μm to 40 μm or less when compared with a substrate having a size of about 60 mm square, although a cover for preventing radiant heat in the furnace that is directly irradiated during firing is not installed. Improved. Since there is little variation in the amount of warpage, it is presumed that the warpage can be further improved by further setting the shape of the shrinkage green sheet added to the outside of the shrinkage suppression green sheet or the second shrinkage suppression green sheet.

BRIEF DESCRIPTION OF THE DRAWINGS It shows an example of the lamination | stacking state of the green sheet for shrinkage | contraction suppression to the laminated body of the green sheet for board | substrates, and a shrinkage | contraction green sheet, (A) is a schematic sectional drawing which shows the state laminated | stacked partially, (B) is a lamination | stacking state It is a schematic sectional drawing which shows. The other example of the lamination | stacking state of the green sheet for shrinkage | contraction suppression to the laminated body of the green sheet for board | substrates and a shrinkage | contraction green sheet is shown, (A) is a schematic sectional drawing which shows the state laminated | stacked partially, (B) It is a schematic sectional drawing which shows a lamination state. It shows an example of the formation method of a shrinkage | contraction suppression material, (A) is a schematic diagram which shows the formation method of a 1st shrinkage | contraction suppression material, (B) is a schematic diagram which shows the formation method of a 2nd shrinkage | contraction suppression material. is there. It is a disassembled perspective view which shows the example which added the shrinkage | contraction green sheet partially. It is a schematic perspective view which shows the lamination | stacking state at the time of adding a shrinkage | contraction green sheet partially. It is a schematic sectional drawing which shows the lamination | stacking state at the time of adding a shrinkage | contraction green sheet partially. It is a disassembled perspective view which shows the example which added the strip | belt-shaped shrinkage | contraction green sheet and the 2nd green sheet for shrinkage | contraction suppression. It is a schematic perspective view which shows the mode of the curvature of a laminated body. It is a schematic perspective view which shows the lamination | stacking state at the time of adding a strip | belt-shaped contraction green sheet and the 2nd contraction suppression green sheet.

Explanation of symbols

1, 21, 31 Laminate, 1a to 1h, 21a to 21j, 31a to 31j Green sheet for substrate, 2,5 Shrinkage green sheet, 3, 4, 23, 24, 33, 34 Shrinkage suppression green sheet, 11th 1 shrinkage suppression material, 12 second shrinkage suppression material, 13 base film, 14, 16 coater, 15 shrinkage material, 17 shrinkage suppression material, 25 shrinkage green sheet piece, 35 second shrinkage suppression green sheet

Claims (15)

A method for producing a multilayer ceramic substrate in which a plurality of green sheets for a substrate are laminated, and a green sheet for suppressing shrinkage is disposed on both sides of the laminated green sheets for a substrate.
A method for producing a multilayer ceramic substrate, comprising: placing at least one shrinkage green sheet that shrinks during firing on an outer side of at least one shrinkage suppression green sheet, and performing the firing.   2. The method of manufacturing a multilayer ceramic substrate according to claim 1, wherein the contracted green sheet is formed of the same material as the substrate green sheet.   3. The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein the shrinkage green sheets are arranged so as to overlap each other on both sides of the shrinkage-suppressing green sheets on both sides of the green sheet for substrates.   4. The method for producing a multilayer ceramic substrate according to claim 3, wherein the shrinkage-suppressing green sheet and the shrinking green sheet are provided in a state where they are previously laminated on a support film. A shrinkage-suppressing green sheet provided on the support film, and a first shrinkage-suppressing material sheet provided with the shrinkage green sheet thereon;
5. The method for producing a multilayer ceramic substrate according to claim 4, wherein a shrinkage green sheet is provided on the support film, and a second shrinkage suppression material sheet provided with a shrinkage suppression green sheet thereon is prepared. On the support, the shrinkage green sheet and the shrinkage suppression green sheet were placed in this order using the first shrinkage suppression material sheet, and the support film of the first shrinkage suppression material sheet was peeled off,
A predetermined number of substrate green sheets are stacked on the shrinkage-suppressing green sheet,
Furthermore, the green sheet for shrinkage and the green sheet for shrinkage are placed in this order on the green sheet for substrate using the second shrinkage suppressing material sheet,
The method for producing a multilayer ceramic substrate according to claim 5, wherein the support film of the second shrinkage suppression material sheet is peeled and then fired.   The method for producing a multilayer ceramic substrate according to claim 1, wherein the contracted green sheet is partially arranged.   The method for producing a multilayer ceramic substrate according to claim 7, wherein the contracted green sheet is formed by a printing method.   8. The method for producing a multilayer ceramic substrate according to claim 7, wherein the shrinkage green sheet is formed into a predetermined shape and is superposed on the shrinkage suppression green sheet.   The method for producing a multilayer ceramic substrate according to any one of claims 7 to 9, wherein the thickness of the contracted green sheet varies depending on a part.   The method for producing a multilayer ceramic substrate according to any one of claims 1 to 3, wherein a second shrinkage-suppressing green sheet is further stacked on the outside of at least one of the shrinkage-preventing green sheets.   The method for producing a multilayer ceramic substrate according to claim 11, wherein the second shrinkage suppressing green sheet is partially disposed.   13. The method for producing a multilayer ceramic substrate according to claim 12, wherein the second shrinkage suppressing green sheet is formed by a printing method.   13. The method for producing a multilayer ceramic substrate according to claim 12, wherein the second shrinkage-suppressing green sheet is formed into a predetermined shape and is superposed on the shrinkage-suppressing green sheet.   The method of manufacturing a multilayer ceramic substrate according to any one of claims 11 to 14, wherein the thickness of the second shrinkage suppressing green sheet varies depending on a part.

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