Ceramic substrate, ceramic substrate assembly sheet, and method for manufacturing ceramic substrate

Abstract

A ceramic substrate 1 comprises: a substrate body 10 formed by laminating an insulating layer and a restraining layer and having a first main surface 11 and a second main surface 12; and a columnar conductor 50 provided on the first main surface 11 of the substrate main body 10. A wiring 21 and an interlayer connection conductor 22 are provided inside the substrate main body 10. A layer serving as the first main surface 11 of the substrate main body 10 is a restraining layer that is a first restraining layer 31, an insulating layer in contact with the inside of the first restraining layer 31 is a first insulating layer 41, a restraining layer in contact with the inside of the first insulating layer 41 is a third restraining layer 33, a layer serving as the second main surface 12 of the substrate body 10 is a restraining layer that is a second restraining layer 32, an insulating layer in contact with the inside of the second restraining layer 32 is a second insulating layer 42, a restraining layer in contact with the inside of the second insulating layer 42 is a fourth restraining layer 34, and the thickness of the first insulating layer 41 is less than the thickness of the second insulating layer 42.

Description

Ceramic substrate, ceramic substrate assembly sheet, and method for manufacturing ceramic substrate

[0001] The present invention relates to a ceramic substrate, a ceramic substrate assembly sheet, and a method for manufacturing a ceramic substrate.

[0002] Patent Document 1 describes a ceramic multilayer substrate and a manufacturing method thereof, and describes that warping of the substrate occurs when base layers of different thicknesses are stacked. It also describes that in order to solve the warping of the substrate, it is effective to match the ratio of the thickness of the base layer and the constraining layer of the thinnest base layer with the ratio of sheets of other thicknesses.

[0003] Patent Document 2 describes a structure that suppresses peeling at the interface between a metal post made of sintered copper and a resin. Specifically, it describes that the plating film and the resin layer are compatible with each other, resulting in good adhesion and suppressing peeling. Furthermore, it describes that providing a tapered shape to the metal post ensures a sufficient contact area with the resin layer, further suppressing peeling.

[0004] Patent No. 5724806 Patent No. 6791352

[0005] The technology described in Patent Document 1 does not take into account the stress of wiring and interlayer connection conductors formed inside the ceramic substrate. Therefore, it is insufficient as a solution to the substrate warpage caused by the influence of conductors, and improvement is desired. Furthermore, the technology described in Patent Document 2 causes problems such as warpage and cracking of the substrate when stress from the sintered metal columns is applied to the ceramic multilayer substrate. In recent years, ceramic substrates with a large number of sintered metal columns (hereinafter referred to as columnar conductors) have been developed, and a solution to the problem of warpage has been desired.

[0006] The present invention has been made to solve the above problems, and aims to provide a ceramic substrate in which warping due to the influence of wiring and interlayer connection conductors formed inside the substrate body and columnar conductors provided on the main surface of the substrate body is suppressed.

[0007] The ceramic substrate of the present invention is a ceramic substrate comprising a substrate body formed by stacking insulating layers and constraining layers, the substrate body having a first main surface and a second main surface, and a columnar conductor provided on the first main surface of the substrate body, wherein wiring and interlayer connection conductors are provided inside the substrate body, the constraining layer being a first constraining layer, the insulating layer in contact with the inside of the first constraining layer being a first insulating layer, the constraining layer in contact with the inside of the first insulating layer being a third constraining layer, the constraining layer being a second constraining layer, the insulating layer in contact with the inside of the second constraining layer being a second insulating layer, the constraining layer in contact with the inside of the second insulating layer being a fourth constraining layer, and the thickness of the first insulating layer being thinner than the thickness of the second insulating layer.

[0008] The ceramic substrate assembly sheet of the present invention is a ceramic substrate assembly sheet having multiple ceramic substrate units attached thereto, which can be cut to obtain multiple ceramic substrates, and each of the multiple ceramic substrates is a ceramic substrate of the present invention.

[0009] The method for manufacturing the ceramic substrate of the present invention includes the steps of obtaining a laminate sheet in which a columnar conductor formation sheet having via conductors is further laminated on a first main surface of a substrate main body sheet having an insulating layer sheet on which a conductor pattern is formed and a constraint layer sheet laminated thereon; pressing and firing the laminate sheet, removing material around the via conductors in the columnar conductor formation sheet to expose the via conductors and form columnar conductors, thereby obtaining a ceramic substrate assembly sheet in which ceramic substrate units are attached on multiple sides; and cutting the ceramic substrate assembly sheet to obtain a plurality of ceramic substrates.

[0010] According to the present invention, it is possible to provide a ceramic substrate in which warping due to the influence of wiring and interlayer connection conductors formed inside the substrate body, and columnar conductors provided on the main surface of the substrate body, is suppressed.

[0011] Fig. 1 is a cross-sectional view schematically showing an example of the configuration of the ceramic substrate of the present invention. Fig. 2 is a cross-sectional view schematically showing an example of a module in which electronic components are mounted on the ceramic substrate of the present invention. Fig. 3 is a top view schematically showing an example of a ceramic substrate aggregate sheet. Fig. 4 is a top view schematically showing an example of a ceramic substrate obtained by singulating the ceramic substrate aggregate sheet.

[0012] The ceramic substrate, ceramic substrate assembly sheet, and method for manufacturing a ceramic substrate of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual preferred configurations described below also falls within the scope of the present invention.

[0013] [Ceramic Substrate] Fig. 1 is a cross-sectional view schematically showing an example of the configuration of a ceramic substrate of the present invention. The ceramic substrate 1 shown in Fig. 1 has a substrate body 10 formed by laminating an insulating layer and a constraining layer. The substrate body 10 has a first main surface 11 and a second main surface 12, and columnar conductors 50 are provided on the first main surface 11 of the substrate body.

[0014] Wiring 21 and interlayer connection conductors 22 are provided inside the substrate body 10. The wiring conductors and interlayer connection conductors are preferably made of a material that can be co-fired with the low-temperature co-fired ceramic material, such as Cu, Ag, Au, and alloys thereof. Cu, Ag, and Au have low resistance and are therefore particularly suitable for use in high-frequency applications of the ceramic substrate. The patterns of the wiring and interlayer connection conductors are not particularly limited.

[0015] The insulating layer preferably contains a low-temperature co-fired ceramic material (LTCC material). The low-temperature co-fired ceramic material is a ceramic material that can be fired at a temperature of 1000°C or less and can be co-fired with Au, Ag, Cu, or the like, which have low resistivity. Specific examples of the low-temperature co-fired ceramic material include glass composite low-temperature co-fired ceramic materials obtained by mixing ceramic powder such as alumina, zirconia, magnesia, or forsterite with borosilicate glass; ZnO-MgO-Al ２ O３ -SiO ２ Glass-ceramic low-temperature fired ceramic material using BaO-Al ２ O ３ -SiO ２ Ceramic powder and Al ２ O ３ -CaO-SiO ２ -MgO-B ２ O ３ Examples of suitable ceramic materials include non-glass-based low-temperature fired ceramic materials using ceramic powders.

[0016] The constraining layer is a layer containing a metal oxide that does not substantially sinter at the sintering temperature of the low-temperature co-fired ceramic material and does not shrink or shrinks only slightly during firing. Examples of metal oxides that do not substantially sinter at the sintering temperature of the low-temperature co-fired ceramic material include alumina, silica, zirconia, titania, silica, niobium pentoxide, tantalum pentoxide, and magnesia, with alumina and silica being preferred. These metal oxides can be used alone or in combination, taking into account the high-frequency characteristics of the ceramic substrate.

[0017] The metal oxide contained in each of the plurality of constraining layers of the substrate body is preferably the same type, more preferably at least one of alumina and silica, and even more preferably alumina.

[0018] The constraining layer preferably contains glass in addition to the metal oxide. When the constraining layer contains glass, examples of the glass contained in the constraining layer include B—Si-M (M is an alkali metal or alkaline earth metal) based glasses.

[0019] The insulating layers and constraining layers that make up the substrate body are preferably stacked alternately, but in some parts, two or more insulating layers may be stacked continuously, or two or more constraining layers may be stacked continuously. In the substrate body 10 shown in Figure 1, the insulating layers and constraining layers are stacked alternately.

[0020] Among the insulating layers and constraining layers that constitute the substrate body 10, names are given to insulating layers and constraining layers at specific positions. The names of the insulating layers and constraining layers located on the first main surface 11 side of the substrate body 10 are as follows. The constraining layer that constitutes the substrate body 10 and that forms the first main surface 11 of the substrate body 10 is referred to as the first constraining layer 31. The insulating layer that constitutes the substrate body 10 and that contacts the inner side of the first constraining layer 31 is referred to as the first insulating layer 41. The constraining layer that constitutes the substrate body 10 and that contacts the inner side of the first insulating layer 41 is referred to as the third constraining layer 33. The insulating layer that constitutes the substrate body 10 and that contacts the inner side of the third constraining layer 33 is referred to as the third insulating layer 43. The constraining layer that constitutes the substrate body 10 and that contacts the inner side of the third insulating layer 43 is referred to as the fifth constraining layer 35.

[0021] The names of the insulating layer and constraining layer located on the second main surface 12 side of the substrate body 10 are as follows: The constraining layer that constitutes the substrate body 10 and that becomes the second main surface 12 of the substrate body 10 is referred to as the second constraining layer 32. The insulating layer that constitutes the substrate body 10 and that contacts the inner side of the second constraining layer 32 is referred to as the second insulating layer 42. The constraining layer that constitutes the substrate body 10 and that contacts the inner side of the second insulating layer 42 is referred to as the fourth constraining layer 34.

[0022] A columnar conductor 50 is provided on the first main surface 11 of the substrate body 10. The columnar conductor 50 penetrates the first constraining layer 31 on the first main surface 11 of the substrate body 10 and is connected to the interlayer connection conductor 22 within the substrate body 10.

[0023] The columnar conductor may have any shape, such as a cylindrical or polygonal column, or may have a tapered shape. Examples of materials that can be used to form the columnar conductor include Cu, Ag, Au, and alloys thereof.

[0024] When the columnar conductor is cylindrical, the diameter of the columnar conductor is preferably 100 μm or more and 300 μm or less, more preferably 150 μm or more and 250 μm or less, and the length (height) of the columnar conductor is preferably 50 μm or more and 100 μm or less.

[0025] The number of columnar conductors on the first main surface of the ceramic substrate is preferably 10 or more and 70 or less per ceramic substrate. The density of the columnar conductors per unit area on the first main surface of the ceramic substrate is preferably 0.08 / mm. ２ or more, 0.30 pieces / mm ２ It is preferable that:

[0026] Regarding the thickness relationship between the first insulating layer located on the first main surface 11 of the substrate body 10 on which the columnar conductors 50 are provided and the second insulating layer located on the second main surface of the substrate body 10, the thickness of the first insulating layer 41 is thinner than the thickness of the second insulating layer 42. This configuration makes it possible to provide a ceramic substrate in which warping due to the influence of the columnar conductors provided on the first main surface of the substrate body is suppressed. The reason for this will be explained.

[0027] In the vicinity of the first main surface 11 of the substrate body 10 where the columnar conductor 50 is provided, a region of thickness surrounding the first constraining layer 31, the first insulating layer 41, and the third constraining layer 33 is defined as a rectangular region A surrounded by a dotted line. Meanwhile, in the vicinity of the second main surface 12 of the substrate body 10, a region of the same size as the region A is defined as a rectangular region B surrounded by a dotted line. Thus, the region A near the first main surface 11 contains two constraining layers, the first constraining layer 31 and the third constraining layer 33, whereas the region B near the second main surface 12 contains one constraining layer, the second constraining layer 32. In other words, the density of the constraining layer is higher in the region near the first main surface 11 than in the region near the second main surface 12. This means that the constraining force exerted by the constraining layer is higher in the region near the first main surface 11 than in the region near the second main surface 12.

[0028] The columnar conductors 50 are made of metal or a component containing a large amount of metal, and have large thermal expansion, so the first main surface 11 on which the columnar conductors 50 are provided is more susceptible to warping than the second main surface 12. Therefore, by increasing the density of the constraining layer near the first main surface 11 and increasing the constraining force, the influence of warping due to the presence of the columnar conductors 50 is mitigated, resulting in a ceramic substrate with reduced warping overall.

[0029] Since the first insulating layer 41 is in contact with the first constraining layer 31 and the third constraining layer 33, by reducing the thickness of the first insulating layer 41, the distance from the first main surface 11 to the third constraining layer 33 can be shortened, and the constraining force of the multiple constraining layers can be exerted near the first main surface 11.

[0030] In a typical ceramic substrate design, the thickness of the first insulating layer on the first principal surface side and the second insulating layer on the second principal surface side are usually the same, so the density of the constraining layer near the first principal surface and the second principal surface side is the same, and the warpage suppression effect of the constraining layer is exerted to the same extent on the first principal surface and the second principal surface. Therefore, if the columnar conductor is present only on one surface (the first principal surface), the thermal expansion of the columnar conductor will affect the thermal expansion of the first principal surface side, causing the ceramic substrate to warp.

[0031] The present invention has discovered that in a normal substrate in which the thickness of the first insulating layer on the first main surface side and the thickness of the second insulating layer on the second main surface side are the same, the problem of warping occurs when columnar conductors are present only on one side (first main surface) of the substrate body, or when the amount of metal components near the first main surface of the substrate body is greater than near the second main surface.The present invention solves this problem by increasing the constraint force near the first main surface by making the density of the constraint layer different between near the first main surface and near the second main surface.

[0032] The thickness of the first insulating layer is not particularly limited as long as it is thinner than the thickness of the second insulating layer, but is preferably, for example, 5 μm or more and 15 μm or less. The thickness of the second insulating layer is also not particularly limited, but is preferably, for example, 15 μm or more and 25 μm or less. The ratio of the thickness of the first insulating layer to the thickness of the second insulating layer (thickness of the first insulating layer / thickness of the second insulating layer) is preferably 0.7 or less. Alternatively, it may be 0.3 or more.

[0033] In the ceramic substrate of the present invention, the first insulating layer is preferably the thinnest insulating layer among the insulating layers. As the thickness of the first insulating layer becomes thinner, the distance from the first main surface to the third constraining layer becomes shorter, and the density of the constraining layer near the first main surface becomes higher. From this viewpoint, it is preferable that the thickness of the first insulating layer be thinner than that of the other insulating layers.

[0034] In the ceramic substrate of the present invention, it is preferable to provide a third insulating layer that is in contact with the inside of the third constraining layer and is thinner than the second insulating layer, and a fifth constraining layer that is also in contact with the inside of the third insulating layer. Figure 1 shows the third insulating layer 43 and the fifth constraining layer 35. The third insulating layer 43 is a "thin" insulating layer like the first insulating layer 41, and its thinness is defined as being thinner than the second insulating layer 42.

[0035] 1 shows a rectangular region C surrounded by a dotted line, which is a region of thickness surrounding the first constraining layer 31, the first insulating layer 41, the third constraining layer 33, the third insulating layer 43, and the fifth constraining layer 35 near the first main surface 11 of the substrate body 10 where the columnar conductor 50 is provided. This region C includes three constraining layers: the first constraining layer 31, the third constraining layer 33, and the fifth constraining layer 35, and it can be seen that a region with a higher density of the constraining layers is provided near the first main surface 11. In other words, by providing the thin insulating layer, the third insulating layer 43, in addition to the thin insulating layer, the density of the constraining layers near the first main surface 11 can be increased, and the constraining force near the first main surface 11 can be further increased.

[0036] The thickness of the third insulating layer is not particularly limited, but is preferably, for example, 5 μm or more and 15 μm or less. The thickness of the third insulating layer may be the same as the thickness of the first insulating layer. The third insulating layer may have the same thickness as the first insulating layer and may be the thinnest layer of the insulating layers. The third insulating layer may be thinner than the first insulating layer, but a thinner first insulating layer is preferable because it can increase the binding force in a region closer to the first main surface.

[0037] Furthermore, a thin insulating layer (thinner than the second insulating layer) may be provided as an insulating layer other than the first insulating layer and the third insulating layer. Furthermore, of the insulating layers constituting the substrate body, only the second insulating layer may be thick, and the insulating layers other than the second insulating layer may be thinner than the second insulating layer. In this case, all the insulating layers other than the second insulating layer may have the same thickness.

[0038] The thickness of each constraining layer is not particularly limited, and the thickness of the first constraining layer and the second constraining layer may be the same or different. During manufacturing, it is common for a thin constraining layer to be in contact with a thin insulating layer, so from that perspective, it is preferable that the thickness of the first constraining layer be thinner than the thickness of the second constraining layer. Furthermore, from the perspective of increasing the constraining force of the constraining layer near the first main surface, it is preferable that the thickness of the first constraining layer be thicker than the thickness of the second constraining layer.

[0039] 1 is illustrated schematically so that the thickness of the first constraining layer 31 is thinner than the thickness of the second constraining layer 32. In addition, throughout FIG. 1, the constraining layer in contact with the thick insulating layer is drawn thick, and the constraining layer in contact with the thin insulating layer is drawn thin, but the relationship between the thickness of the insulating layer and the thickness of the constraining layer in contact with that insulating layer is not limited to this relationship.

[0040] 1, electrode pads 51 used for mounting electronic components on the ceramic substrate 1 are provided on the first main surface 11 and the second main surface 12. Furthermore, a plating layer 52 is provided on the surface of the columnar conductor 50, and a plating layer 53 is provided on the surface of the electrode pad 51. Examples of materials that can form the plating layer include Cu, Ag, Au, Ni, Sn, and Pd.

[0041] A module can be formed by mounting and sealing electronic components on the ceramic substrate of the present invention. The following modules are also included in the concept of the ceramic substrate of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a module in which electronic components are mounted on the ceramic substrate of the present invention. The orientation of the module 2 shown in FIG. 2 is upside down compared to the ceramic substrate 1 shown in FIG. 1, with the first main surface 11 of the ceramic substrate 1 facing downward and the second main surface 12 facing upward. When mounting the module 2 on another substrate, the columnar conductors 50 face downward, and the module 2 is used in the orientation shown in FIG. 2.

[0042] Electronic components 61 are mounted on electrode pads 51 on the first main surface 11 of the ceramic substrate 1 and sealed with a sealing material 60. The sealing material 60 is polished so that the columnar conductors 50 are exposed from the sealing material 60, and a plating layer 54 is provided on the portions where the columnar conductors 50 are exposed by polishing. The columnar conductors exposed from the sealing material 60 are used to mount the module 2 on another substrate.

[0043] An electronic component 71 is mounted on the electrode pads 51 on the second main surface 12 of the ceramic substrate 1, and is sealed with a sealing material 70. The sealing material 70 may or may not be polished.

[0044] The sealing material is made of a sealing resin, and either a thermosetting resin or a thermoplastic resin may be used as the sealing resin. Examples of thermosetting resins include phenolic resin, epoxy resin, polyester resin, silicone resin, and polyimide resin. Examples of thermoplastic resins include thermoplastic liquid crystal polymer (LCP), thermoplastic polyimide resin, polyether ether ketone resin (PEEK), and polyphenylene sulfide resin (PPS).

[0045] The sealing resin may contain additives such as fillers, for example, glass, silica, aluminum oxide, aluminum nitride, boron nitride, and the like.

[0046] [Ceramic substrate assembly sheet] The ceramic substrate assembly sheet of the present invention is a ceramic substrate assembly sheet having multiple ceramic substrate units attached thereto, which can be cut to obtain multiple ceramic substrates, and each of the multiple ceramic substrates is the ceramic substrate of the present invention.

[0047] FIG. 3 is a top view schematically showing an example of a ceramic substrate assembly sheet. FIG. 4 is a top view schematically showing an example of a ceramic substrate obtained by singulating the ceramic substrate assembly sheet. FIG. 3 shows the ceramic substrate assembly sheet 100 from the side of a first main surface 111 of a ceramic substrate unit 110 on which a columnar conductor 50 is provided. The ceramic substrate assembly sheet 100 has multiple ceramic substrate units 110 attached thereto. When the ceramic substrate assembly sheet 100 is cut along the dotted cutting lines V and H, each ceramic substrate unit 110 becomes a ceramic substrate 1 as shown in FIG. 4. The ceramic substrate assembly sheet 100 shown in FIG. 3 has a total of 20 ceramic substrate units 110 attached thereto, with a 5×4 matrix.

[0048] 3 illustrates that a large number of columnar conductors 50 (10 per unit) are provided on the first main surface 111 of each ceramic substrate unit 110. When such a large number of columnar conductors are provided, the ceramic substrate assembly sheet is prone to warping after firing. Therefore, by making the thickness of the first insulating layer thinner than the thickness of the second insulating layer, as in the configuration of the ceramic substrate of the present invention, and increasing the density of the constraining layer near the first main surface of the ceramic substrate unit, and thereby increasing the constraining force near the first main surface, it is possible to suppress warping of the ceramic substrate assembly sheet.

[0049] When the ceramic substrate assembly sheet is prevented from warping, the cutting workability when cutting the ceramic substrate assembly sheet into ceramic substrates is improved, the dimensional accuracy of the ceramic substrates obtained by singulation is improved, and warping of the ceramic substrates themselves after singulation is also suppressed.

[0050] While Fig. 3 shows a ceramic substrate assembly sheet 100 in which each ceramic substrate unit 110 becomes a ceramic substrate 1 before electronic components are mounted thereon, the ceramic substrate assembly sheet before cutting may have electronic components mounted thereon or may be sealed with a sealing material. In the module manufacturing process shown in Fig. 2, electronic components may be mounted on the ceramic substrate units before cutting the ceramic substrate assembly sheet, and the ceramic substrate assembly sheet may be sealed with a sealing material, polished, and plated to obtain a ceramic substrate assembly sheet from which multiple modules can be obtained by cutting. Multiple modules can be obtained by cutting this ceramic substrate assembly sheet. A ceramic substrate assembly sheet that can be cut to obtain multiple modules is also included in the ceramic substrate assembly sheet of the present invention.

[0051] [Method for manufacturing ceramic substrate] The method for manufacturing the ceramic substrate of the present invention includes the steps of obtaining a laminate sheet in which a columnar conductor formation sheet having via conductors is further laminated on a first main surface of a substrate main body sheet having an insulating layer sheet on which a conductor pattern is formed and a constraining layer sheet laminated thereon; pressing and firing the laminate sheet to remove material around the via conductors in the columnar conductor formation sheet to expose the via conductors and form columnar conductors, thereby obtaining a ceramic substrate assembly sheet in which ceramic substrate units are attached on multiple sides; and cutting the ceramic substrate assembly sheet to obtain a plurality of ceramic substrates.

[0052] In the step of obtaining the laminate sheet, a constraining layer sheet and an insulating layer sheet are prepared and laminated in a predetermined order to obtain a substrate main body sheet. Alternatively, instead of laminating pre-formed sheets, a constraining layer paste to become the constraining layer and an insulating layer paste to become the insulating layer may be stacked and successively applied to obtain a substrate main body sheet.

[0053] When obtaining the substrate body sheet, a first constraining layer sheet that will become the first constraining layer is placed on the first main surface of the substrate body sheet, which is the surface that will become the first main surface of the substrate body. Then, a first insulating layer sheet that will become the first insulating layer is placed in contact with the inside of the first constraining layer sheet. Furthermore, a third constraining layer sheet that will become the third constraining layer is placed in contact with the inside of the first insulating layer sheet. A second constraining layer sheet that will become the second constraining layer is placed on the second main surface of the substrate body sheet, which is the surface that will become the second main surface of the substrate body. Then, a second insulating layer sheet that will become the second insulating layer is placed in contact with the inside of the second constraining layer sheet. Furthermore, a fourth constraining layer sheet that will become the fourth constraining layer is placed in contact with the inside of the second insulating layer sheet. In this arrangement, the thickness of the first insulating layer sheet is made thinner than the thickness of the second insulating layer sheet. Furthermore, other insulating layer sheets and constraining layer sheets may be placed between the third constraining layer sheet and the fourth constraining layer sheet described above. For example, a third insulating layer sheet may be arranged in contact with the inside of the third constraining layer sheet, and a fifth constraining layer sheet may be arranged in contact with the inside of the third insulating layer sheet. The thickness of the third insulating layer sheet is preferably thinner than the thickness of the second insulating layer sheet. Alternatively, the thickness of the third insulating layer sheet may be the same as the thickness of the first insulating layer sheet.

[0054] The paste that will form the constraining layer can be a paste containing a metal oxide such as alumina that will form the constraining layer and glass. The paste can be formed into a sheet of a predetermined thickness to form the constraining layer sheet. A predetermined conductor pattern can be formed on the constraining layer sheet. The conductor pattern becomes the wiring and interlayer connection conductors that will be provided inside the substrate main body. The paste that will form the insulating layer can be a paste containing a low-temperature co-fired ceramic material that will form the insulating layer. The paste can be formed into a sheet of a predetermined thickness to form the insulating layer sheet. A predetermined conductor pattern is formed on the insulating layer sheet. The conductor pattern becomes the wiring and interlayer connection conductors that will be provided inside the substrate main body. Furthermore, the predetermined conductor pattern formed on the insulating layer sheet is formed so that the ceramic substrate units are attached on multiple surfaces.

[0055] A laminate sheet is obtained by laminating a columnar conductor formation sheet having via conductors on the first main surface of a substrate main body sheet. The columnar conductor formation sheet can be a sheet containing a metal oxide that does not substantially sinter at the sintering temperature of the low-temperature co-fired ceramic material. A sheet having a composition other than that of the constraining layer sheet, excluding glass, can also be used. By providing via conductors so that they penetrate the columnar conductor formation sheet in the thickness direction, and stacking multiple columnar conductor formation sheets while aligning the via conductors as necessary, the columnar conductors can be formed by arranging the via conductors continuously in the thickness direction. The via conductors provided in the columnar conductor formation sheet are arranged to correspond to the arrangement of the columnar conductors when the ceramic substrate units are mounted on multiple surfaces.

[0056] The laminate sheet is pressed and fired. The material surrounding the via conductors in the columnar conductor formation sheet is then removed to expose the via conductors and form columnar conductors. Since the material surrounding the via conductors in the columnar conductor formation sheet is not sintered, it can be removed by methods such as sandblasting. The above process allows for the production of a ceramic substrate assembly sheet with multiple ceramic substrate units. The specific configuration of the constraining layer and insulating layer, particularly the thickness of the first insulating layer sheet being thinner than the thickness of the second insulating layer sheet, can suppress warping of the ceramic substrate assembly sheet.

[0057] Furthermore, plating layers may be provided by plating the surfaces of the electrode pads and the surfaces of the columnar electrodes arranged on the first and second main surfaces of the ceramic substrate assembly sheet.

[0058] A plurality of ceramic substrates can be obtained by cutting the ceramic substrate assembly sheet. A dicing device or the like can be used to cut the ceramic substrate assembly sheet. If the ceramic substrate assembly sheet has reduced warping, the workability of cutting the ceramic substrate assembly sheet improves and misalignment in the cutting position is prevented, resulting in high dimensional accuracy of the ceramic substrates after singulation. As a result, the yield of ceramic substrate production can be increased.

[0059] Alternatively, electronic components may be mounted on the ceramic substrates before cutting the ceramic substrate assembly sheet, and then the ceramic substrates may be sealed with a sealing material, polished, and plated to obtain a ceramic substrate assembly sheet from which multiple modules can be obtained by cutting the ceramic substrate assembly sheet.

[0060] The method for producing the ceramic substrate of the present invention is not limited to a method for cutting a ceramic substrate aggregate sheet to produce a plurality of ceramic substrates at once, but may be a method for producing ceramic substrates one by one. Furthermore, after cutting a ceramic substrate aggregate sheet to obtain a plurality of ceramic substrates, the individual ceramic substrates may be subjected to processes such as mounting electronic components, sealing with a sealing material, polishing, plating, etc. to obtain a module.

[0061] A shielding layer may be provided on the ceramic substrate, module, and ceramic substrate assembly sheet (including the ceramic substrate assembly sheet from which a module is obtained by cutting) described above. An example of a shielding layer forming method will be described below. Note that this shielding layer forming method can also be performed on objects other than the ceramic substrates described above, and the objects are not particularly limited. In addition, it can also be performed on substrates other than those having columnar conductors. Examples of other objects include printed wiring boards, coreless substrates, Si substrates, and acoustic wave devices. Hereinafter, the object on which a shielding layer is formed will be referred to as the "object."

[0062] The shielding layer is a layer that is provided on the exterior of an object to provide an electromagnetic wave shielding effect, and is preferably formed by forming a metal film by sputtering. The metal film that becomes the shielding layer is preferably a low-frequency shielding layer that shields low-frequency electromagnetic waves.

[0063] A method for forming the shield layer includes attaching the object to tape and forming a metal film by sputtering. Specific examples include the following methods.

[0064] The objects are aligned and placed on single-sided or double-sided adhesive tape at a fixed interval so that the back surface (the surface on which the shielding layer is not formed) is in contact with the adhesive surface. Examples of adhesive tape include UV-release tape, heat-foaming tape, and pressure-sensitive adhesive tape. The substrate of the adhesive tape may be PET, polyimide, PEN, or the like. The adhesive may be selected from acrylic, silicone, and the like. The thickness of the adhesive tape substrate is preferably 25 μm or more and 100 μm or less. The thickness of the adhesive is preferably a thickness that can follow the irregularities on the back surface of the object.

[0065] When arranging the objects on the adhesive tape, the spacing between the objects is preferably 0.6 mm or more and 1.2 mm or less so that the metal film adheres to the side surfaces of the objects. Furthermore, by placing dummy members on the outside of the aligned objects, large variations in the metal film thickness on the outer side surfaces of the outermost objects can be prevented. Furthermore, large variations in conformity to the adhesive tape and the generation of burrs due to sputtering can be suppressed. The spacing between the dummy members and the objects is preferably the same as the spacing between the objects, and the thickness of the dummy members is preferably equal to or less than the thickness of the objects. The dummy members may be members of approximately the same size as the objects, or may be strip-shaped members that surround the objects arranged in an aligned manner on the adhesive tape. The dummy members may be made of resin (e.g., polyester, epoxy), and may have an adhesive layer on their surfaces.

[0066] By aligning the target object on the adhesive tape and then pressing it onto the tape, the adhesive of the adhesive tape can better conform to the irregularities on the back surface of the target object, preventing the metal film from adhering to the back surface of the target object. Heating the tape while pressing the target object onto the adhesive tape further improves conformability. When using thermal foaming tape, pressing is performed below the foaming initiation temperature. The pressing method is preferably performed under negative pressure (vacuum) to prevent air from remaining between the target object and the adhesive tape. Some sputtering devices use a tape with aligned targets attached to a support jig and then inserted. In this case, pressing under negative pressure (vacuum) or using a lamination method is preferable to prevent air from remaining between the adhesive tape and the support jig.

[0067] A three-layer structure film such as SUS-Cu-SUS or Ti-Cu-Ti can generally be used as the shield layer. If structural defects such as peeling occur due to stress in the metal film formed by sputtering, a means of lowering the gas pressure during sputtering (reducing the degree of vacuum in the chamber) may be used to reduce the film stress. The gas flow rate may be adjusted so that the gas pressure is between 1 / 6 and 2 / 3 of the normal pressure (0.2 Pa and 1.2 Pa). Since structural defects in the shield layer are often caused by the Cu layer, the gas pressure (gas flow rate) may be adjusted only when the Cu layer is formed, or may be adjusted when all layers are formed.

[0068] Furthermore, a low-frequency shield layer may be formed by using a magnetic material for the shield layer. In this case, the film may be formed to have the following laminated structure: (Example 1) A laminated structure of SUS, Cr, and FeSiB-based amorphous magnetic material (0.5 μm or more, 5 μm or less). (Example 2) A laminated structure of NiFe (50 nm or more, 300 nm or less) and Ta (5 nm or more, 50 nm or less), with a total thickness of 4 μm or more. (Example 3) A laminated structure of FeSi (50 nm or more, 300 nm or less) and NiFe (5 nm or more, 50 nm or less), with a total thickness of about 6 μm.

[0069] The present specification discloses the following:

[0070] The present disclosure (1) is a ceramic substrate comprising: a substrate body formed by stacking insulating layers and constraining layers and having a first main surface and a second main surface; and a columnar conductor provided on the first main surface of the substrate body, wherein wiring and interlayer connection conductors are provided inside the substrate body; the constraining layer, which is the first main surface of the substrate body, is a first constraining layer; the insulating layer in contact with the inside of the first constraining layer is a first insulating layer; the constraining layer in contact with the inside of the first insulating layer is a third constraining layer; the constraining layer, which is the second main surface of the substrate body, is a second constraining layer; the insulating layer in contact with the inside of the second constraining layer is a second insulating layer; the constraining layer in contact with the inside of the second insulating layer is a fourth constraining layer; and the thickness of the first insulating layer is thinner than the thickness of the second insulating layer.

[0071] The present disclosure (2) is the ceramic substrate according to the present disclosure (1), wherein the first insulating layer is the thinnest layer among the insulating layers.

[0072] The present disclosure (3) is the ceramic substrate according to the present disclosure (1) or (2), wherein the thickness of the first constraining layer is thinner than the thickness of the second constraining layer.

[0073] The present disclosure (4) is a ceramic substrate according to any one of the present disclosures (1) to (3), in which a third insulating layer that is in contact with the inside of the third constraining layer and is thinner than the second insulating layer, and a fifth constraining layer that is in contact with the inside of the third insulating layer are provided.

[0074] The present disclosure (5) is a ceramic substrate assembly sheet having multiple ceramic substrate units attached thereto, from which multiple ceramic substrates can be obtained by cutting, wherein each of the multiple ceramic substrates is the ceramic substrate described in any one of the present disclosures (1) to (4).

[0075] The present disclosure (6) is a method for producing a ceramic substrate according to any one of the present disclosures (1) to (4), which includes the steps of obtaining a laminate sheet in which a columnar conductor formation sheet having via conductors is further laminated on a first main surface of a substrate main body sheet in which a constraining layer sheet and an insulating layer sheet having a conductor pattern formed thereon are laminated; pressing and firing the laminate sheet, removing material around the via conductors in the columnar conductor formation sheet to expose the via conductors and form columnar conductors, thereby obtaining a ceramic substrate assembly sheet in which ceramic substrate units are attached on multiple sides; and cutting the ceramic substrate assembly sheet to obtain a plurality of ceramic substrates.

[0076] REFERENCE SIGNS LIST 1 ceramic substrate 2 module 10 substrate body 11 first main surface of substrate body 12 second main surface of substrate body 21 wiring 22 interlayer connection conductor 31 first constraining layer 32 second constraining layer 33 third constraining layer 34 fourth constraining layer 35 fifth constraining layer 41 first insulating layer 42 second insulating layer 43 third insulating layer 44 fourth insulating layer 50 columnar conductor 51 electrode pad 52 plating layer of columnar conductor 53 plating layer on electrode pad 54 plating layer of columnar conductor (portion exposed from sealing material) 60 sealing material on first main surface side 61 electronic component 70 sealing material on second main surface side 71 electronic component 100 ceramic substrate aggregate sheet 110 ceramic substrate unit 111 first main surface of ceramic substrate unit V cutting line (vertical) H cutting line (horizontal)

Claims

1. A ceramic substrate comprising: a substrate body formed by laminating insulating layers and constraining layers and having a first main surface and a second main surface; and columnar conductors provided on the first main surface of the substrate body, wherein wiring and interlayer connection conductors are provided inside the substrate body; the constraining layer, which is the first main surface of the substrate body, is a first constraining layer, the insulating layer in contact with the inside of the first constraining layer is a first insulating layer, the constraining layer in contact with the inside of the first insulating layer is a third constraining layer, the constraining layer, which is the second main surface of the substrate body, is a second constraining layer, the insulating layer in contact with the inside of the second constraining layer is a second insulating layer, and the constraining layer in contact with the inside of the second insulating layer is a fourth constraining layer, and the thickness of the first insulating layer is thinner than the thickness of the second insulating layer.

2. The ceramic substrate according to claim 1, wherein the first insulating layer is the thinnest of the insulating layers.

3. The ceramic substrate according to claim 1 or 2, wherein the thickness of the first constraining layer is thinner than the thickness of the second constraining layer.

4. A ceramic substrate according to any one of claims 1 to 3, further comprising a third insulating layer that is in contact with the inside of the third constraining layer and is thinner than the second insulating layer, and a fifth constraining layer that is in contact with the inside of the third insulating layer.

5. A ceramic substrate assembly sheet having multiple ceramic substrate units attached thereto, which can be cut to obtain multiple ceramic substrates, wherein each of the multiple ceramic substrates is a ceramic substrate according to any one of claims 1 to 4.

6. A method for producing a ceramic substrate according to any one of claims 1 to 4, comprising the steps of: obtaining a laminate sheet in which a columnar conductor formation sheet having via conductors is further laminated on a first main surface of a substrate main body sheet having a constraining layer sheet and an insulating layer sheet having a conductor pattern formed thereon; pressing and firing the laminate sheet to remove material around the via conductors in the columnar conductor formation sheet to expose the via conductors and form columnar conductors, thereby obtaining a ceramic substrate assembly sheet in which ceramic substrate units are attached on multiple surfaces; and cutting the ceramic substrate assembly sheet to obtain a plurality of ceramic substrates.

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