JP2009206233A - Method of manufacturing ceramic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a ceramic substrate which can be fired by microwave heating without increasing the dielectric constant of a first insulating layer. <P>SOLUTION: The method of manufacturing the ceramic substrate is provided in which a laminate is formed with: a first unfired sheet containing a glass component having a first glass transition point; a second unfired sheet containing a glass component having a second glass transition point lower than that of the first glass transition point by 80°C or more and an additive; and an internal wiring conductor. The laminate is heated up to the second glass transition point by microwave having a first output intensity, and heated and fired up to the first glass transition point by irradiation with a microwave having an output intensity higher than the first output intensity. The dielectric constant of the additive is preferably not less than 7 and, specifically, one of SiC, Si<SB>3</SB>N<SB>4</SB>, Co<SB>2</SB>O<SB>3</SB>, Cr<SB>2</SB>O<SB>3</SB>, TiO<SB>2</SB>and ZrO<SB>2</SB>having high dielectric constants is used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a ceramic substrate, and more particularly to a method for manufacturing a ceramic substrate using heating and firing with microwaves.

  In recent years, the frequency band used is shifting to a high frequency band exceeding GHz. In order to transmit a high-frequency signal at a high speed, the resistance of the conductor forming the wiring layer is required to be small, and a lower relative dielectric constant is also required for the insulating layer. For this reason, a glass ceramic multilayer substrate using glass ceramics obtained by firing a mixture of glass and ceramics (inorganic filler) as an insulating layer has attracted attention.

  However, since the glass ceramic multilayer substrate shrinks due to sintering during firing, desired dimensional accuracy may not be obtained.

Therefore, in order to solve this, a method has been proposed in which two types of ceramic green sheets having different glass transition points of glass components are alternately laminated to form a green sheet laminate, and the green sheet laminate is fired. (For example, refer to Patent Document 1). According to this method, even if the first ceramic green sheet having a glass component having a low glass transition point starts to shrink, the second ceramic green sheet having a glass component having a high glass transition point has an original shape. Therefore, the shrinkage generated in the first ceramic green sheet is suppressed by the second ceramic green sheet. Conversely, even if the second ceramic green sheet starts to shrink, the first ceramic green sheet has a substantial shrinkage reaction. Therefore, the shrinkage generated in the first ceramic green sheet is supposed to be suppressed by the second ceramic sheet already in the stable state.
JP-A-6-97656

  However, in the conventional method, the shrinkage completion temperature of the second ceramic green sheet and the sintering start temperature of the first ceramic green sheet are close to each other and it is difficult to clearly separate them. Before the contraction of the sheet is completed, the first ceramic green sheet starts to contract, and there is a problem that a desired dimensional accuracy cannot be obtained in the manufactured ceramic substrate.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a ceramic substrate that can obtain a ceramic substrate with a higher dimensional system.

The present invention is a ceramic substrate manufacturing method for manufacturing a laminated glass ceramic substrate by heating and firing using a microwave,
A plurality of first unsintered sheets including a glass component having a first glass transition point; and at least one glass component having a second glass transition point lower than the first glass transition point by 80 ° C. and an additive. A preparation step of preparing a second unsintered sheet;
An application step of applying a conductor paste to the first green sheet;
A lamination step of laminating the first unsintered sheet and the second unsintered sheet to obtain an unsintered laminated substrate;
A firing step of firing the unsintered laminated substrate by irradiating the unsintered laminated substrate with microwaves, and
The firing step includes
A first heating step of heating the laminated substrate to the second glass transition point by irradiating a microwave of a first output intensity;
A second heating step of heating the laminated substrate to a first glass transition point by irradiating a microwave having an output intensity higher than the first output intensity;
Is provided.

  Preferably, the method for manufacturing a ceramic substrate includes an application step of applying a conductor paste to the first unsintered sheet before the laminating step.

  In the method for manufacturing a ceramic substrate, preferably, the additive has a relative dielectric constant of 7 or more.

In the method for producing a ceramic substrate, the additive is at least one of SiC, Si ₃ N ₄ , Co ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ and ZrO ₂ .

  In the method for manufacturing a ceramic substrate, preferably, the second unsintered sheet includes an inorganic filler, and the content of the additive in the second unsintered sheet is the second unsintered sheet. When the glass component of the sintered sheet and the inorganic filler are 100% by weight, it is 0.5 to 40% by weight.

  According to the method for manufacturing a ceramic substrate of the present invention, a ceramic substrate having a higher dimensional system can be obtained.

  Hereinafter, a method for producing a ceramic substrate of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing a configuration of a ceramic wiring substrate 1 manufactured by the method for manufacturing a ceramic substrate according to the present embodiment. The ceramic wiring substrate 1 is configured to include a multilayer substrate 3 in which a predetermined circuit is formed by a wiring conductor 2, and surface wiring conductors 4, 5 and thick film resistors are formed on the main surface of the multilayer substrate 3 as necessary. A body film, a protective film, and the like are formed, and further, various electronic components 6 joined to the surface wiring conductors 4 and 5 are formed.

  The laminated substrate 3 includes first ceramic insulating layers 3a to 3e formed by sintering the first unsintered sheet, second ceramic insulating layers 3p to 3s formed by sintering the second unsintered sheet, and internal wiring. A predetermined circuit including the conductor 2 is provided.

  As the first ceramic insulating layers 3 a to 3 e and the second ceramic insulating layers 3 p to 3 s, glass ceramic materials that can be fired at a relatively low temperature of, for example, about 800 to 1000 ° C. are used.

  The glass-ceramic material mainly contains an inorganic filler and a glass component, and examples of the inorganic filler include corundum (α alumina), cristobalite, quartz, mullite, and cordierite.

  Further, the glass component is made of low melting point crystallized glass containing a plurality of metal oxides, for example, cordierite, mullite, anorthite, serdian, by firing at a relatively low temperature of about 800 to 1000 ° C. At least one of crystal phases of spinel, garnite, willemite, dolomite, petalite, and substituted derivatives thereof is precipitated.

  The inner layer conductor 2a and the via-hole conductor 2b constituting the internal wiring conductor 2 are Ag-based (Ag simple substance, Ag alloy such as Ag-Pd), Cu-based (Cu simple substance, Cu alloy), Pd-based (Pd simple substance, Pd alloy). Or the inner conductor 2a has a thickness of about 8 to 15 μm, and the diameter of the via-hole conductor 2b can be set to an arbitrary value, for example, 50 to 250 μm. It is.

  The surface wiring conductors 4 and 5 are made of Ag-based (Ag simple substance, Ag alloy such as Ag-Pd), Cu-based (Cu simple substance, Cu alloy), Pd-based (Pd simple substance, Pd alloy), or Pt (Pt simple substance, Pt). For example, it is already formed on the laminate substrate 3 before being fired.

  A thick film resistor film or a protective film is formed on the surface wiring conductors 4 and 5 of the multilayer substrate 3, and various electronic devices such as a chip capacitor, a chip resistor, a transistor, or an IC (Integrated Circuit) are provided. The component 6 or the like is mounted so as to be conductive with the surface wiring conductors 4 and 5 by soldering or wire bonding.

  Below, the manufacturing method of the ceramic wiring board 1 is demonstrated.

(Preparation process of unsintered sheet and conductive paste)
First, the 1st green sheet used as the 1st ceramic insulating layers 3a-3e and the 2nd green sheet used as the 2nd ceramic insulating layers 3p-3s are prepared, inner layer conductor 2a, via-hole conductor 2b, or surface Low resistance metal material (Ag, Cu, Pd, Pt, or alloys thereof) for forming a conductor film or conductor to be the wiring conductors 4 and 5, an additive having a high relative dielectric constant (SiC, Si ₃ N ₄ , Conductive pastes made of Co ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ and ZrO ₂ ), glass frit, and organic vehicle are prepared.

  The above-mentioned first unsintered sheet and second unsintered sheet are kneaded with a low melting point crystallized glass frit, an inorganic filler, a binder, and a solvent and tape-molded by a doctor blade method or the like to a predetermined size. It is cut and formed.

  As described above, the low-melting crystallized glass frit is obtained by firing at a relatively low temperature of about 800 to 1000 ° C., so that cordierite, mullite, anorthite, serdian, spinel, garnite, willemite, dolomite, It consists of a glass composition in which at least one crystal phase of petalite and its substituted derivative is precipitated, and the average particle size is 1.0 to 6.0 μm, preferably 1.5 to 3.5 μm.

In particular, if a glass frit that precipitates anorthite or serdian is used, a laminate substrate 3 having higher strength can be obtained, and if a glass frit that precipitates cordierite or mullite is used, a laminate having a low thermal expansion coefficient can be obtained. The body substrate 3 can be obtained, and is effective as a laminate substrate for mounting a silicon chip such as an IC bare chip on the laminate substrate 3. In order to obtain a laminate substrate 3 having a high strength and a low coefficient of thermal expansion, for example, B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZnO, And alkaline earth metal oxides are effective.

  The inorganic filler serves as an aggregate of the laminate substrate 3 and can be exemplified by ceramics such as corundum (α-alumina), cristobalite, quartz, mullite, cordierite, and the particle size is 1.0 to 6.0 μm. And preferably 1.5 to 4.0 μm.

  The binder must have wettability with solid components (glass frit and inorganic filler) and must have good thermal decomposability. Since the viscosity of the slip is determined at the same time, an ethylenically unsaturated compound having a carboxyl group or an alcoholic hydroxyl group such as an acrylic acid or methacrylic acid polymer is preferable. As an addition amount, it is preferable that it is 25 wt% or less with respect to all the solid components.

  As the solvent, an organic solvent or an aqueous solvent can be used. When an aqueous solvent is used, the binder needs to be water-soluble. It is preferable that a hydrophilic functional group, for example, a carboxyl group is added to the water-soluble binder, and the addition amount is 2 to 300 mgKOH / g in terms of acid value, and preferably 5 to 100 mgKOH / g. .

  The above-mentioned binder and solvent must be completely thermally decomposed in the binder drying process of the thermal drying step by the doctor blade method and the firing step of the laminate substrate, and in particular, decompose at 600 ° C. or less, preferably 500 ° C. or less. Good material to do.

  The constituent ratio of the above-mentioned inorganic filler and glass component is such that the inorganic filler is 10 wt% to 50 wt%, preferably 20 wt% to 35 wt%, and the glass component is 90 wt% to 50 wt%, preferably 80 wt% to 65 wt%. .

  When the inorganic filler is 10 wt% or more, that is, the glass component is less than 90 wt%, the ratio of the glassy material in the insulating layer is not too large, the strength of the laminate substrate 3 is maintained well, and the inorganic filler is 50 wt% or less. That is, when the glass component is 50 wt% or more, the denseness of the multilayer substrate 3 is maintained well.

  Here, in the ceramic wiring substrate 1 according to the present embodiment, the glass frit contained in the first unsintered sheet serving as the first ceramic insulating layers 1a to 1e and the second uncoated steel serving as the second ceramic insulating layers 3p to 3s. The glass transition point differs from the glass frit contained in the sintered sheet by 80 ° C. or more. That is, the glass transition point in the glass component is controlled between the first green sheet and the second green sheet. For example, in the above glass composition, as a method of setting the glass transition point of the second unsintered sheet low, there is a method of increasing the composition ratio of B2O3, ZnO, or an alkaline earth metal oxide. Further, the glass transition point can be lowered by adding an oxide such as Pb, Bi, or Cd, or adding an oxide of an alkali metal.

For example, the first unsintered sheet to be the first ceramic insulating layers 3a to 3e is a crystallized glass mainly composed of B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZnO, and alkaline earth metal oxide. In addition, alumina ceramic powder is used as the inorganic filler, acrylic resin is used as the binder, and toluene is used as the solvent. The constituent ratio of the solid component is 70 wt% for the crystallized glass and 30 wt% for the inorganic filler. Thereby, the 1st non-sintered sheet containing the glass component whose glass transition point is 740 degreeC is obtained.

The second unsintered sheet to be the second ceramic insulating layers 3p to 3s is mainly composed of, for example, PbO, B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZnO, and alkaline earth metal oxide. Crystallized glass to be used, alumina ceramic powder as an inorganic filler, acrylic resin as a binder, and toluene as a solvent. The constituent ratio of the solid component is 50 wt% for the crystallized glass and 50 wt% for the inorganic filler.

  Here, in the ceramic wiring board 1 according to the present embodiment, the second unsintered sheet to be the second ceramic insulating layers 3p to 3s has a ratio higher than that of the first ceramic insulating layers 1a to e in addition to the solid components described above. Contains an additive made of a high dielectric constant material.

The relative dielectric constant of the additive is preferably 7 or more. Specifically, SiC (εr = 9 to 12), Si ₃ N ₄ (εr = 7 to 9), Co ₂ O ₃ having a high relative dielectric constant (εr). (Εr = 6-11), Cr ₂ O ₃ (εr = 10-14), TiO ₂ (εr = 80-180) and ZrO ₂ (εr = 20-30), or one or more selected from Can be used. Thereby, the 2nd non-sintered sheet containing the glass component whose glass transition point is 600 degreeC is obtained.

  As described above, when the second unsintered sheet contains an additive having a relative dielectric constant of 7 or more, the second unsintered sheet is preferentially heated by the microwave. The inside of the laminate substrate can be heated as well as the surface of the substrate.

  In addition, content of an additive is 0.5-40 weight% when the glass frit and an inorganic filler are 100 weight% with respect to the solid component mentioned above. Therefore, the content of the additive to the second ceramic insulating layer obtained by firing the second unsintered sheet is also 0.5 to 40% by weight.

  When the content is 0.5% by weight or more, a decrease in heat generation due to microwaves can be suppressed, and heating becomes possible. Further, when the content is 40% by weight or less, an increase in the relative dielectric constant (dielectric loss) of the second unsintered sheet can be suppressed, and the delay of the high frequency signal passing through the internal wiring conductor 2 can be suppressed.

(Drilling and paste printing process)
Next, in consideration of the position where the via-hole conductor 2b is formed in the first unsintered sheet to be the first ceramic insulating layers 1a to 1e and the second unsintered sheet to be the second ceramic insulating layers 3p to 3s. Then, a through hole is formed by an NC punch or the like, and subsequently, the conductive paste is filled into the through hole by filling the conductive paste described above. And the conductor film used as the inner-layer conductor 2a is printed on the surface of the 1st non-sintered sheet used as the 1st ceramic insulating layers 1a-e so that it may become a predetermined circuit shape.

(Lamination process)
The first unsintered sheet filled with the through holes and printed with the wiring and the second unsintered sheet filled with the through holes become the first ceramic insulating layers 1a to e and the second ceramic insulating layers 3p to 3s. In this way, the layers are laminated in consideration of the order of lamination, and thermocompression-bonded to obtain an unfired laminate substrate.

(Baking process)
FIG. 2 is a view showing a configuration of a microwave baking furnace used when baking an unfired laminated substrate, (a) is a plan view of the microwave baking furnace, and (b) is ( It is sectional drawing in cut surface line AA 'of a).

  As shown in FIG. 2, in the microwave baking furnace 11, a casing 14 covered with a heat insulating material 13 is disposed in the internal space of the furnace wall 12. In the internal space of the housing 14, a plurality of shelf boards 16 for mounting the unfired laminated body substrate 15 are provided at predetermined intervals in the vertical direction by columns 17. The internal space of the housing 14 communicates with the outside of the furnace wall 12 by the atmospheric gas supply nozzle 18 and the exhaust nozzle 19, and the atmospheric gas 20 passes from the outside through the atmospheric gas supply nozzle 18 to the housing 14. The exhaust gas 21 is supplied to the internal space, and discharged from the internal space of the housing 14 to the outside through the exhaust nozzle 19.

  As a firing method using microwaves, first, the unfired laminate substrate 15 itself self-heats by the microwave introduced into the microwave firing furnace 11 through the waveguide, and is provided in the microwave firing furnace 11. The case 14 and the shelf board 16 also self-heat at the same time, so that the laminated substrate 3 is obtained. At this time, the surface layer portion tends to have a higher temperature than the inside due to heat radiation from the housing 14 and the shelf board 16. In the present embodiment, since the second unsintered sheet to be the second ceramic insulating layers 3p to 3s of the multilayer substrate 3 contains an additive having high heat generation by microwaves, the inside of the multilayer substrate 3 And the temperature gradient between the surface layer portion becomes extremely small.

  Moreover, the housing | casing 14 and the shelf board 16 have a microwave absorptivity. As the material, a ceramic material having a large dielectric loss (tan δ) and high microwave absorption is preferable. As a ceramic material which comprises such a housing | casing 14 and the shelf board 16, a silicon carbide type material or an alumina type material etc. are mentioned, for example.

  In addition, by supplying the atmospheric gas 20 from the cylindrical atmospheric gas supply nozzle 18 into the housing 14, the decomposed gas generated by the thermal decomposition of the binder contained in the unfired laminate substrate by microwave irradiation. Are exhausted out of the furnace as exhaust gas 21 from exhaust nozzles 19 on the side surfaces that face each other without staying in the housing 14.

  The firing atmosphere is an air (oxidizing) atmosphere or a neutral atmosphere. For example, when a Cu-based conductor is used for the inner layer conductor 2a or the like, the firing atmosphere is performed in a reducing atmosphere or a neutral atmosphere.

  The firing process for firing the unfired laminate substrate includes a binder removal process and a sintering process.

  First, in the binder removal process, the first unsintered sheet to be the first ceramic insulating layers 3a to 3e, the second unsintered sheet to be the second ceramic insulating layers 3p to 3s, the conductor film to be the inner layer conductor 2a, and the via hole This is for burning off organic components contained in the paste to be the conductor 2b, and is performed in a temperature region of 600 ° C. or less, for example.

  Next, in the sintering process, the crystallized glass component contained in the first green sheet to be the first ceramic insulating layers 1a to 1e and the second green sheet to be the second ceramic insulating layers 3p to 3s is predetermined. Simultaneously with the precipitation reaction of the crystal phase, it is uniformly dispersed at the grain boundary of the inorganic filler. Thereby, the strong laminated substrate 3 is obtained.

  Specifically, first, as a 1st heating process, the unbaked laminated body board | substrate 15 is heated to the glass transition point of the glass component of a 2nd non-sintered sheet. Thereby, the glass component contained in a 2nd unsintered sheet performs precipitation reaction of a predetermined crystal phase. At this stage, even if the second unsintered sheet starts to shrink, the first unsintered sheet having a glass component having a high glass transition point is not sintered but has an original shape. For this reason, the shrinkage stress which generate | occur | produces in a 2nd unsintered sheet acts large on the lamination direction of the laminated body, and the effect | action with respect to the plane direction perpendicular | vertical to a lamination direction is reduced. That is, shrinkage generated in the second green sheet is suppressed by the first green sheet.

  Next, as a 2nd heating process, it heats to the glass transition point of the glass component of a 1st non-sintered sheet. Thereby, the glass component contained in a 1st unsintered sheet performs precipitation reaction of a predetermined crystal phase. At this stage, even if the first unsintered sheet starts to shrink, the second unsintered sheet is in a stable state with the shrinkage reaction substantially completed. For this reason, the shrinkage stress which generate | occur | produces in a 1st unsintered sheet acts large on the lamination direction of the laminated body, and the effect | action with respect to the plane direction perpendicular | vertical to a lamination direction is reduced. That is, the shrinkage that occurs in the first green sheet is suppressed by the second green sheet that is already in a stable state.

  In the method for manufacturing a ceramic substrate according to the present embodiment, the second output intensity of the microwave in the second heating step is set higher than the first output intensity of the microwave in the first heating step. Therefore, the temperature at which the shrinkage of the second green sheet is completed and the temperature at which the shrinkage stress of the first green sheet is generated can be reliably separated. Thereby, the laminated substrate 3 with a higher dimensional system can be obtained.

  Further, in the conductive film to be the inner layer conductor 2a and the paste to be the via hole conductor 2b, for example, Ag-based powder is grown to reduce the resistance and integrated with the insulating layers 3a to 3e. Such a sintering process is performed in a temperature range that reaches a peak temperature of 800 to 1000 ° C.

(Surface treatment process)
Next, surface treatment is performed on both main surfaces of the fired laminate substrate. Here, the surface wiring conductor is formed by, for example, printing, drying, and baking of a copper-based conductive paste so as to be connected to the via-hole conductor 2b formed in the insulating layers 1a and 1e on the upper surface side main surface of the multilayer substrate 3. 4 and 5 are formed. Here, the copper-based surface wiring conductors 4 and 5 and the silver-based via-hole conductor 2b are joined. Therefore, considering the eutectic temperature of silver and copper, select a copper-based conductive paste that can be fired at a low temperature (for example, 780 ° C. or lower), and reduce the copper paste to prevent copper oxidation. In a neutral or neutral atmosphere.

  Thereafter, if necessary, a thick film resistive film or a protective film is baked, and various electronic components 6 are surface-mounted.

  In addition, about the above-mentioned embodiment, the surface sheet | seat conductors 4 and 5 of the laminated body board 3 form the conductor film used as the surface wiring conductors 4 and 5 in a lamination process, for example, and the green sheet used as the laminated body board | substrate 3 You may form by baking simultaneously with a laminated body.

  In addition, if necessary, a division groove may be formed in an unfired laminated substrate, and the division treatment may be performed immediately after firing or after the surface treatment process.

  In the method for manufacturing a ceramic substrate according to the present embodiment, the unfired laminated substrate is heated to the second glass transition point by irradiating the microwave with the first output intensity, and then the first output. A microwave having an output intensity higher than the intensity is irradiated and heated to the first glass transition point. Thereby, the shrinkage start temperature of the second green sheet including the glass component having the second glass transition point and the additive moves to a relatively low temperature side, and the first including the glass component having the first glass transition point. The shrinkage start temperature of the unsintered sheet moves to the relatively high temperature side. This is because the shrinkage action generated by the softening flow of the glass component contained in the unsintered sheet varies depending on the sintering rate of the glass component, that is, the shrinkage start temperature fluctuates, that is, the higher the sintering rate of the glass component. It is considered that the shrinkage start temperature moves to the relatively high temperature side, and conversely, the shrinkage start temperature moves to the relatively low temperature side as the sintering speed decreases. Therefore, according to the method for manufacturing a ceramic substrate according to the present embodiment, the temperature at which the shrinkage stress of the second unsintered sheet and the first unsintered sheet can be reliably separated, and the variation in dimensions is suppressed. Thus, a ceramic substrate with high dimensional accuracy is obtained. In addition, warping of the ceramic substrate can be suppressed.

  In the above description, the first unsintered sheet and the second unsintered sheet are alternately laminated. However, if the laminate has at least one second unsintered sheet, it is more than conventional. A ceramic substrate with good dimensional accuracy can be obtained.

  Further, the arrangement of the wiring conductors on the ceramic wiring board is not limited to that described and illustrated above. However, when this ceramic wiring board is used for high frequency applications, it is preferable to provide the inner layer conductor on the first unsintered sheet not containing the additive. At this time, the additive added to the second unsintered sheet remains in the second unsintered sheet or remains at the interface between the second unsintered sheet and the first unsintered sheet. Since it does not diffuse into the sintered sheet, an increase in the relative dielectric constant (dielectric loss) of the first unsintered sheet can be suppressed.

Example 1
A first green sheet having a thickness of 80 μm and a second green sheet having a thickness of 10 μm are prepared, and a conductive film is screen-printed on the first green sheet using an Ag-based conductive paste. After the formation, the first unsintered sheet 5 layers and the first unsintered sheet 4 layers were alternately laminated and thermocompression bonded to produce a laminate substrate. At this time, the glass transition point of the glass component of the first unsintered sheet was controlled to be 740 ° C. Further, the glass transition point of the glass component of the second unsintered sheet was controlled to be 635 ° C., and TiO ₂ added at 8 wt% as an additive was used.

The manufactured laminate substrate is placed in a case of SiC-based material that self-heats by microwaves, air is supplied into the case, and 2.45 GHz microwaves are continuously irradiated to remove organic components. Baking to 900 ° C. The shelf board in a baking furnace used what was produced with SiC type material. The microwave output intensity in the first heating step was 5.0 kW, and the microwave output intensity in the second heating step was 7.5 kW.
After firing, the resulting ceramic substrate had a good shrinkage of 10.1%, a warp of 35 μm, and no delamination or cracks between layers. The dimensional accuracy (shrinkage variation) was as good as ± 0.07%. Furthermore, the capacitance value between the internal wiring conductors was also appropriate.

(Example 2)
A laminate substrate was produced in the same manner as in Example 1 except that ZrO ₂ was used as an additive.
The produced laminate substrate was fired by microwaves in the same manner as in Example 1.
After firing, the resulting ceramic substrate had a good shrinkage rate of 10.1%, warpage of 40 μm, and no delamination or cracks between layers. Further, the dimensional accuracy was as good as ± 0.07%. Furthermore, the capacitance value between the internal wiring conductors was also appropriate.

(Example 3)
A laminate substrate was produced in the same manner as in Example 1 except that Co ₂ O ₃ was used as an additive.
The produced laminate substrate was fired by microwaves in the same manner as in Example 1.
After firing, the resulting ceramic substrate had a good shrinkage rate of 10.1%, warpage of 45 μm, and no delamination or cracks between layers. The dimensional accuracy was good at ± 0.08%. Furthermore, the capacitance value between the inner layer conductors was also appropriate.

Example 4
A laminate substrate was produced in the same manner as in Example 1 except that Cr ₂ O ₃ was used as an additive.
The produced laminate substrate was fired by microwaves in the same manner as in Example 1.
After firing, the resulting ceramic substrate had a good shrinkage rate of 10.1%, a warp of 55 μm, and no delamination or cracks between layers. Further, the dimensional accuracy was as good as ± 0.09%. Furthermore, the conduction resistance of the internal wiring conductor was satisfactory, and the capacitance value between the internal wiring conductors was appropriate.

(Comparative Example 1)
A laminate substrate was produced in the same manner as in Example 1 except that the glass transition point of the glass component of the second unsintered sheet was controlled to be 685 ° C.

  The produced laminate substrate was fired by microwaves in the same manner as in Example 1.

  After firing, the obtained ceramic substrate had no delamination or cracks between layers, and the capacitance value between the internal wiring conductors was appropriate. However, the shrinkage was 14.3%, the warpage was relatively large at 100 μm, and the dimensional accuracy was relatively large at ± 0.18%.

(Comparative Example 2)
A laminate substrate was produced in the same manner as in Example 1 except that the glass transition point of the glass component of the second unsintered sheet was controlled to be 740 ° C.
The produced laminate substrate was baked by microwaves in the same manner as in Example 1.
After firing, the obtained ceramic substrate had no delamination or cracks between layers, and the capacitance value between the internal wiring conductors was appropriate. However, the shrinkage was 15.3%, the warp was relatively large at 120 μm, and the dimensional accuracy was relatively large at ± 0.23%.

(Comparative Example 3)
A laminate substrate was produced in the same manner as in Example 1 except that no additive was used.
The produced laminate substrate was fired by microwaves in the same manner as in Example 1.
After firing, the shrinkage rate of the obtained ceramic substrate was relatively small at 14.3%, there was no delamination or crack between layers, and the capacitance value between the internal wiring conductors was also appropriate. However, the warpage was relatively large at 125 μm, and the dimensional accuracy was relatively large at ± 0.16%.

(Comparative Example 4)
A laminate substrate was produced in the same manner as in Example 1.
The produced laminate substrate was subjected to the same method as in Example 1 except that the microwave output intensity in the first heating step was 5.0 kW and the microwave output intensity in the second heating step was 5.0 kW. Baked by microwave.
After firing, the shrinkage rate of the obtained ceramic substrate was relatively small at 14.3%, there was no delamination or crack between layers, and the capacitance value between the internal wiring conductors was also appropriate. However, the warpage was relatively large at 120 μm and the dimensional accuracy was relatively large at ± 0.17%.

  The above results are summarized in Table 1.

  As in Examples 1 to 4, the glass transition point of the glass component of the second unsintered sheet is lower by 80 degrees or more than the glass transition point of the glass component of the first unsintered sheet, and the second unsintered sheet By adding an additive to the sintered sheet and further increasing the microwave output intensity of the second heating step compared to the first heating step, the shrinkage rate and warpage of the substrate were reduced, and the dimensional accuracy was also improved.

  In Comparative Examples 1 and 2, because the difference between the glass transition point of the glass component of the first unsintered sheet and the glass transition point of the glass component of the second unsintered sheet is not appropriate, shrinkage rate, increase in warpage, There was a decline in the dimension system. Since Comparative Example 3 did not contain an additive, the warpage of the substrate was large and the dimensional accuracy was also poor. In Comparative Example 4, since the microwave output intensity in the first heating process and the microwave output intensity in the second heating process were not appropriate, the warpage of the substrate was large and the dimensional accuracy was also poor.

It is sectional drawing which shows the structure of the ceramic wiring board produced by the manufacturing method of the ceramic substrate by this Embodiment. It is a figure which shows the structure of the microwave baking furnace used when baking the laminated body board | substrate of an unbaking state, (a) is a top view of a microwave baking furnace, (b) is the cutting | disconnection of (a). It is sectional drawing in surface line AA '.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic wiring board 2 Internal wiring conductor 2a Inner layer conductor 2b Via-hole conductor 3 Laminated body board 3a-3e 1st ceramic insulating layer 3p-3s 2nd ceramic insulating layer 4,5 Surface wiring conductor 6 Electronic component

Claims (5)

A method of manufacturing a ceramic substrate for manufacturing a laminated glass ceramic substrate by heating and firing using a microwave,
A plurality of first unsintered sheets containing a glass component having a first glass transition point, and at least one glass component having a second glass transition point that is 80 ° C. or more lower than the additive and the first glass transition point A preparation step of preparing a second unsintered sheet;
A lamination step of laminating the first unsintered sheet and the second unsintered sheet to obtain an unsintered laminated substrate;
A firing step of firing the unsintered laminated substrate by irradiating the unsintered laminated substrate with microwaves, and
The firing step includes
A first heating step of heating the laminated substrate to the second glass transition point by irradiating a microwave of a first output intensity;
A second heating step of heating the laminated substrate to a first glass transition point by irradiating a microwave having an output intensity higher than the first output intensity;
A method for producing a ceramic substrate comprising:   The method for producing a ceramic substrate according to claim 1, further comprising an application step of applying a conductive paste to the first unsintered sheet before the laminating step.   2. The method of manufacturing a ceramic substrate according to claim 1, wherein the additive has a relative dielectric constant of 7 or more. The _{additive, SiC, Si 3 N 4,} Co 2 O 3, Cr 2 O 3, wherein the at least one of TiO ₂ and ZrO ₂ from claim 1, wherein in any one of claims 3 Ceramic substrate manufacturing method. The second unsintered sheet includes an inorganic filler,
The content of the additive in the second unsintered sheet is 0.5 to 40% by weight when the glass component and the inorganic filler in the second unsintered sheet are 100% by weight. The method for producing a ceramic substrate according to any one of claims 1 to 4, wherein: