JP5591055B2 - Glass ceramic board and glass ceramic wiring board with built-in coil - Google Patents

Description

  The present invention relates to a glass ceramic substrate in which a ferrite layer and an insulating layer are laminated, and a glass ceramic wiring substrate with a built-in coil in which a coil is built in a ferrite layer and a wiring conductor is formed in the insulating layer.

  Conventionally, a large number of electronic devices have been incorporated in electronic devices such as mobile communication devices such as mobile phones, and various electronic devices have become smaller as electronic devices have become increasingly smaller. There is a demand for reduction in thickness and thickness. For example, an LC filter has conventionally been formed by mounting a relatively large chip coil or chip capacitor on a substrate, but recently, a ferrite layer having a high magnetic permeability is formed inside a ceramic substrate. It has been proposed to embed a coil conductor in a ferrite layer (see, for example, Patent Document 1).

Such a ceramic substrate is composed of, for example, a pair of insulating layers on which wiring layers are formed, and a ferrite layer sandwiched between the pair of insulating layers and embedded with a planar coil conductor. Yes. In order to suppress electrical loss due to resistance, it is necessary to use a low resistance metal such as low resistance Cu or Ag for the wiring layer or planar coil conductor, and such a low resistance metal has a relatively low melting point. Thus, a glass ceramic substrate is manufactured by simultaneously firing glass ceramics and ferrite having FeFe ₂ O ₄ as a main phase, respectively, as an insulating layer and a ferrite layer that can be fired at a low temperature. In addition, in order to increase the bonding strength between the glass ceramic layer and the ferrite layer of such a glass ceramic substrate, an intermediate layer having the components of the glass ceramic layer and the ferrite layer is formed between the glass ceramic layer and the ferrite layer. What has been known is also known.

JP-A-6-20839

However, in order to satisfy the mechanical characteristics and electrical characteristics of the glass ceramic substrate, crystallized glass is often used as the glass ceramic glass of the insulating layer. voids or gaps occur at the interface between the ferrite layer, there problem that led to lower under the bonding strength at the interface as a result.

  In addition, even if an intermediate layer is formed between the glass ceramic layer and the ferrite layer, if the crystal structure of the crystal contained in the glass ceramic layer and the ferrite crystal contained in the ferrite layer are different, the crystals are difficult to bond. . Therefore, when the glass ceramic substrate is sintered, the glass ceramic layer and the ferrite layer are peeled off from the interface during shrinkage, and gaps and voids may be generated between the glass ceramic layer and the ferrite layer. If there is a portion where such gaps or voids are connected, moisture is transferred to the inside of the substrate through the gaps or voids, resulting in insulation degradation due to ion migration.

  Therefore, there is a demand for a glass ceramic substrate that further improves the bonding strength between the insulating layer and the ferrite layer.

The glass ceramic substrate of the present invention is disposed between a ferrite layer having a ferrite crystal, an insulating layer having a glass ceramic containing a first crystal having the same crystal structure as the ferrite crystal, and the insulating layer and the ferrite layer. In the glass ceramic substrate in which the glass ceramic containing the first crystal and the intermediate layer having the ferrite crystal are laminated, some of the plurality of ferrite crystals in the intermediate layer protrude toward the insulating layer , A part of the ferrite crystal protruding to the insulating layer side is bonded to the first crystal contained in the insulating layer .

The coil built glass ceramic substrate of the present invention, a glass ceramic substrate having the above structure, together with the wiring conductors are arranged, the coil conductors the wiring conductor electrically connected between the layers of the ferrite layer of the multiple Is arranged.

According to the glass ceramic substrate of the present invention, the ferrite layer having the ferrite crystal, the insulating layer having the glass ceramic containing the first crystal having the same crystal structure as the ferrite crystal, and the insulating layer and the ferrite layer are disposed. In a glass ceramic substrate in which a glass ceramic including a first crystal and an intermediate layer having a ferrite crystal are laminated, some of the ferrite crystals of the intermediate layer protrude toward the insulating layer and protrude toward the insulating layer since the first and crystal contained in the part with the insulating layer of the ferrite crystal is bonded, the bond strength to the insulating layer of the ferrites layer becomes high, at the interface between the insulating layer and the intermediate layer A glass ceramic substrate having high bonding strength can be obtained.

  According to the glass-ceramic wiring board with a built-in coil of the present invention, since the glass-ceramic board of the present invention having the above configuration, a wiring conductor formed in an insulating layer, and a coil conductor built in a ferrite layer are provided, Since the bonding strength between the layer and the intermediate layer is high, the substrate strength is high and the glass-ceramic wiring board with a built-in coil is highly reliable.

It is sectional drawing which shows an example of embodiment of the glass ceramic substrate of this invention. It is a principal part expanded sectional view in the A section of FIG. It is sectional drawing which shows an example of embodiment of the glass-ceramic wiring board with a built-in coil of this invention.

  The glass ceramic substrate and the glass ceramic wiring substrate with a built-in coil according to the present invention will be described in detail below with reference to the accompanying drawings. 1 to 3, 1 is an insulating layer, 1a is a first crystal, 2 is a ferrite layer, 2a is a ferrite crystal, 3 is an intermediate layer formed between the insulating layer 1 and the ferrite layer 2, and 4 is a wiring. Conductors 5 are coil conductors.

  As shown in FIGS. 1 and 2, the glass ceramic substrate of the present invention includes a ferrite layer 2 having a ferrite crystal 2a and an insulating layer having glass ceramics including a first crystal 1a having the same crystal structure as the ferrite crystal 2a. 1 and a glass ceramic substrate in which a glass ceramic including a first crystal 1 a disposed between an insulating layer 1 and a ferrite layer 2 and an intermediate layer 3 having a ferrite crystal 2 a are laminated, Since a part of the ferrite crystal 2a protrudes to the insulating layer 1 side, a part of the ferrite crystal 2a protruding to the insulating layer 1 side and the first crystal 1a included in the insulating layer 1 are combined, Since there is an amorphous glass component around the bonded ferrite crystal 2a and the first crystal 1a, the crystals are bonded to each other and the bonding strength at the interface between the insulating layer 1 and the intermediate layer 3 is increased. It can be a high glass ceramic substrate having.

The ferrite layer 2 is a ferromagnetic ferrite that is a solid solution having a spinel structure, and is X-Fe _2.
Ni—Zn-based ferrite represented as O ₄ (X is Cu, Ni, Zn), Mn—Zn-based ferrite represented as Y—Fe ₂ O ₄ (Y is Mn, Zn), Z—Fe ₂ O ₄ (Z Mg—Zn-based ferrite represented as Mg, Zn), Ni—Co-based ferrite represented as U—Fe ₂ O ₄ (U is Ni, Co), and the like. Among these, FeFe ₂ O ₄ is a main component of the spinel structure. Among the ferromagnetic ferrites having the above spinel structure, Ni—Zn ferrite can obtain a sufficiently high magnetic permeability in a high frequency band, and thus is preferably used in applications using a high frequency of 100 kHz or more.

In the case of Ni—Zn ferrite, the composition ratio is 63 to 73 mass% of FeFe ₂ O ₄ as a sintered body, 5 to 10 mass% of CuO, 5 to 12 mass% of NiO, and 10 to 10 of ZnO. When the content is 23% by mass, high-density firing with a sintered density of 5.0 g / cm ³ or more is possible at a temperature of 800 ° C. to 1000 ° C. or less at which the glass ceramic of the insulating layer 1 is fired, and sufficiently high permeability in the high-frequency band This is preferable because magnetic susceptibility can be obtained. FeFe ₂ O ₄ is a main component of ferrite, and a sufficient magnetic permeability can be obtained when the ratio is 63% by mass or more. Further, when FeFe ₂ O ₄ is 73 mass% or less, it is possible to retain the mechanical strength without lowering the sintering density. CuO is an important factor for lowering the sintering temperature, and CuO promotes sintering by forming a liquid phase at a low temperature, and the low temperature of 800 to 1000 ° C. without damaging the magnetic properties. Can be fired. When the proportion of CuO is 5% by mass or more, the sintering density can be increased when firing at 800 to 1000 ° C. simultaneously with the wiring layer and the planar coil conductor, so that the mechanical strength is maintained. When the content is 10% by mass or less, the ratio of CuFe ₂ O ₄ having a low magnetic property can be kept low, so that the magnetic property is easily maintained. NiO is contained in order to ensure the magnetic permeability of the ferrite layer 2 in the high frequency range. NiFe ₂ O ₄ does not cause the attenuation of the magnetic permeability due to resonance up to the high frequency range, and can maintain the magnetic permeability in the high frequency range at a relatively high value. % Or higher, the magnetic permeability in a high frequency range of 100 MHz or higher can be maintained without being lowered, and the initial magnetic permeability can be kept high if it is 12% by mass or lower. ZnO is an important element for improving the magnetic permeability of the ferrite layer 2. If the ferrite composition is 10% by mass or more, the magnetic permeability can be kept high. It can be maintained well.

The ferrite layer 2 is produced by firing a ferrite green sheet for the ferrite layer 2. The ferromagnetic ferrite powder used for the ferrite green sheet is a ferrite powder prepared by pre-calcining FeFe ₂ O ₄ and CuO, ZnO or NiO, for example, and has an average particle size of 0.1 μm to 0.9 μm. It is uniform in the range, and the grain shape is preferably close to a spherical shape. This is because when the average particle size is 0.1 μm or more, uniform dispersion of the ferrite powder is facilitated in the production of the ferrite green sheet, and when the average particle size is 0.9 μm or less, the sintering temperature of the ferrite green sheet is kept low. Because it can. Moreover, a uniform sintered state can be obtained because the particle diameter is uniform and nearly spherical. If the particle size of the ferrite powder is uniform, the growth of crystal grains does not decrease locally, and the permeability of the ferrite layer 2 obtained after sintering tends to be stable.

The insulating layer 1 is made of glass ceramics having a glass containing a glass phase and a first crystal 1a. As the glass phase, SiO ₂ system, SiO ₂ —B ₂ O ₃ system, SiO ₂ —Al ₂ O ₃ system, SiO ₂ —MO system (where M represents Ca, Sr, Mg, Ba or Zn), SiO ₂ —B ₂ O ₃ system—MO system, SiO ₂ —M ¹ O—M ² O system (provided that M ¹ and M ² are the same or different and represent Ca, Sr, Mg, Ba or Zn), SiO _2- B ₂ O ₃ -M ¹ O-M ² O system, SiO ₂ -M ³ ₂ O system (where M ³ represents Li, Na or K), SiO ₂ -B ₂ O ₃ -M ³ ₂ O-type glass etc. are mentioned. In addition to the above, Co, Cd, In and oxides thereof may be included.

The first crystal 1a is a crystal formed by crystallization of the glass in the green sheet for the insulating layer 1 by baking a green sheet for the insulating layer 1 containing glass powder and filler powder, or a glass component and filler. A crystal generated from the component or a crystal contained in the green sheet for the insulating layer 1. Examples of the glass that crystallizes into a spinel structure include SiO ₂ —Al ₂ O ₃ —MgO glass (provided that the molar ratio of MgO to Al ₂ O ₃ is 0.8 to 1.2), SiO ₂ —MgO glass (provided that SiO ₂ MgO to molar ratio of 1.8 to 2.2), SiO ₂ —Al ₂ O ₃ —ZnO glass (provided that the molar ratio of ZnO to Al ₂ O ₃ is 0.8 to 1.2), SiO ₂ —CoO—MnO ₂ glass (provided that The molar ratio of CoO to MnO ₂ is 1.8 to 2.2), and the SiO ₂ —CdO—InO ₂ glass (however, the molar ratio of CdO to InO _{2 is} 1.8 to 2.2). If MgO is included as the glass component and SiO ₂ is included as the filler component, Mg ₂ SiO ₄ may be generated as the first crystal 1a. Alternatively, if ZnO is included as the glass component and Al ₂ O ₃ is included as the filler component, ZnAl ₂ O ₄ may be generated as the first crystal 1a. Or, if Al ₂ O ₃ is included as a glass component and Fe ₂ O ₃ is included as a filler component, FeAl ₂ O ₄ may be generated. 1st crystal 1a
Is contained as a filler in the green sheet, for example, forsterite (Mg ₂ SiO ₄ ) or garnite (ZnAl ₂ O ₄ ) may be used. The first crystal 1a is not particularly limited as long as it has the same crystal structure as the ferrite crystal 2a.

Each of the first crystals 1a has the same crystal structure as that of the ferrite crystal 2a, and the difference in lattice constant between the first crystal 1a and the ferrite crystal 2a is within 10% of the lattice constant of the ferrite crystal 2a. It is preferable.

  The intermediate layer 3 is made of the glass ceramic material contained in the insulating layer 1, the ferrite material contained in the ferrite layer 2, and the filler contained in the insulating layer 1. Such an intermediate layer 3 is produced by disposing a ceramic paste, which is a mixture of a glass ceramic material containing a filler, and a ferrite material of the ferrite layer 2 between the insulating layer 1 and the ferrite layer 2 and firing.

By forming the intermediate layer 3 using such a ceramic paste, the glass in the ceramic paste for the intermediate layer 3 is softened during sintering, and the ferrite crystals 2a or the ferrite crystals 2a and the first crystal 1a are softened. Is filled with glass, and the interface between the insulating layer 1 made of glass ceramics and the intermediate layer 3 is filled with no gap. Then, as in the example shown in FIG. 2 , a part of the ferrite crystal 2 a in the ceramic paste for the intermediate layer 3 protrudes into the insulating layer 1 when it crystallizes. The length of the ferrite crystal 2a protruding to the insulating layer 1 is 2 to 3 μm. Also, the 1 ZnFe ₂ O ₄ which is a crystalline 1a, FeAl ₂ O ₄ and ZnAl ₂ O ₄ or the like is crystallized when crystallized glass crystallization of the insulating layer 1, as in the example shown in FIG. 2, the Such a first crystal 1a and a part of the ferrite crystal 2a protruding to the insulating layer 1 are combined. In this way, a glass ceramic substrate in which the intermediate layer 3 is formed between the insulating layer 1 and the ferrite layer 2 is obtained. Further, when the ferrite material and the glass ceramic material have the same particle size and the respective particle sizes are reduced, the bond between the ferrite crystal 2a and the first crystal becomes stronger.

In addition, since the ferrite layer 2 is sintered from the portion where the powder particles of the ferrite material are in contact with each other, if the ferrite material is contained in a large amount of 85 parts by weight to 95 parts by weight, the portion where the ferrite materials are in contact with each other Will increase. When the portions where the ferrite materials are in contact with each other increase in this way, the ferrite crystal 2a is likely to grow, and a part of the ferrite crystal 2a is likely to protrude into the insulating layer 1, and a part of the ferrite crystal 2a is formed on the insulating layer 1. The protruding portion increases, and the portion where the ferrite crystal 2a of the intermediate layer 3 and the first crystal 1a of the insulating layer 1 are combined increases. Accordingly, the bonding between the insulating layer 1 and the intermediate layer 3 is strengthened, and delamination between the insulating layer 1 and the intermediate layer 3 is suppressed, so that a glass ceramic substrate that is hardly deteriorated in insulation can be obtained.

It is preferable that the intermediate layer 3 further includes a second crystal. The second crystal includes, for example, ZnFe ₂ O ₄ , FeFe ₂ O ₄ , FeAl ₂ O ₄ , ZnAl ₂ O ₄ , Co ₂ MnO _4, or CdIn ₂ O ₄ , and the interface between the intermediate layer 3 and the ferrite layer 2 Exist throughout. For example, the insulating layer 1 is formed by sintering a green sheet containing SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —ZnO—MgO-based glass, and the ferrite layer 2 is made of X—Fe ₂ O ₄ (X In the case of Ni—Zn-based ferrite expressed as Cu, Ni, Zn), ZnFe ₂ O ₄ , FeAl ₂ O ₄ and ZnAl ₂ O ₄ are generated as the second crystal. By firing the glass ceramic green sheet, the glass component in the glass ceramic softens and flows in the firing temperature region, and ZnFe ₂ O ₄ , FeAl ₂ O ₄ and ZnAl are formed at the interface between the insulating layer 1 and the intermediate layer 3. Sintering while depositing ₂ O ₄ . Therefore, the bond between ZnFe ₂ O ₄ , FeAl ₂ O ₄ and ZnAl ₂ O ₄ and the insulating layer 1 becomes strong.

The first crystal 1a, the second crystal, and the ferrite crystal 2a have the same crystal structure, and the second crystal
The difference between the lattice constant of the crystal and the lattice constant of the ferrite crystal 2a, and the difference between the lattice constant of the second crystal and the lattice constant of the first crystal 1a are preferably within 10% of the lattice constant of the second crystal. .
Thus, the second crystal has the same crystal structure as the first crystal 1a, and the difference between the lattice constant of the second crystal and the lattice constant of the first crystal 1a is within 10% of the lattice constant of the second crystal. Since the insulating layer 1 and the intermediate layer 3 can be bonded at the atomic level, the bonding strength between the insulating layer 1 and the intermediate layer 3 can be increased. Moreover, since generation | occurrence | production of the lattice defect between the insulating layer 1 and the intermediate | middle layer 3 can be suppressed, generation | occurrence | production of a void and a clearance gap can be reduced in the interface of a 2nd crystal | crystallization and the 1st crystal | crystallization 1a. Similarly, the second crystal has the same crystal structure as the ferrite crystal 2a, and the difference between the lattice constant of the second crystal and the ferrite crystal 2a is within 10% of the lattice constant of the second crystal. If it exists, since the ferrite layer 2 and the intermediate | middle layer 3 can be joined at an atomic level, the joining strength of the ferrite layer 2 and the intermediate | middle layer 3 can be made high. Moreover, since generation | occurrence | production of the lattice defect between the ferrite layer 2 and the intermediate | middle layer 3 can be suppressed, generation | occurrence | production of a void and a clearance gap can be reduced in the interface of a 2nd crystal | crystallization and the ferrite crystal 2a.

When the second crystal has a part of the element contained in the first crystal 1a and a part of the element contained in the ferrite crystal 2a, for example, the ferrite crystal 2a is FeFe ₂ O ₄ and the first crystal 1a is ZnAl _2. When it is O ₄ and the second crystal is ZnFe ₂ O ₄ , the bond strength between the same elements is higher than the bond between the different elements, so that the second strength in the intermediate layer 3 is higher. The bond strength between the crystal and the first crystal 1a in the insulating layer 1 and the ferrite crystal 2a in the ferrite layer 2 is increased, and the bonding strength between the insulating layer 1 and the intermediate layer 3 and the bonding between the intermediate layer 3 and the ferrite layer 2 are increased. The strength becomes higher.

The first crystal 1a has forsterite (Mg ₂ SiO ₄ ) as the main phase, and the ferrite crystal 2a
Preferably, FeFe ₂ O ₄ is the main phase, and the second crystal is any one of ZnFe ₂ O ₄ , FeAl ₂ O _4, and ZnAl ₂ O ₄ . Thus, the second crystal has the same crystal structure as the ferrite crystal 2a and the first crystal 1a, the difference in lattice constant between the second crystal and the ferrite crystal 2a, and the second crystal and the first crystal 1a The difference in lattice constants of
Since each of them is smaller than 5% of the lattice constant of the second crystal, voids and gaps are less generated, so that a glass ceramic substrate with higher bonding strength can be obtained. Specifically, the bond between the insulating layer 1 and the intermediate layer 3 is the first crystal 1 a of the insulating layer 1.
Forsterite crystal and the second crystal ZnFe ₂ O ₄ , FeAl ₂ O _4, and ZnAl ₂ O ₄ in the intermediate layer 3 have the same crystal structure, and the difference in lattice constant between them is Since it is within 5% of the lattice constant, both atoms can be bonded at the atomic level. Further, when the glass ceramic of the insulating layer 1 has forsterite (Mg ₂ SiO ₄ ) as the main phase and the ferrite crystal 2a of the ferrite layer 2 has FeFe ₂ O ₄ as the main phase, the thermal expansion coefficients of both become close. Therefore, it is possible to suppress the occurrence of cracks due to the stress caused by the difference in thermal expansion in the firing step, the subsequent heating step, or the reliability evaluation step.

Here, as a method for confirming the crystal structures of the first crystal 1a, the second crystal, and the ferrite crystal 2a, there is a method using a transmission electron microscope. According to this method, first, the ceramic substrate is cut and the cut surface is polished, and the layer whose crystal structure is to be confirmed, that is, any one of the insulating layer 1, the intermediate layer 3, and the ferrite layer 2 is transmitted. Prepare for observation under a microscope. Thereafter, the crystal structure of the desired layer can be identified by observing the diffraction grating image at the cut surface of the layer. The crystal phase can be identified by referring to the JPCDS card for known ones. For example, the crystal structures and diffraction grating images of ZnFe ₂ O ₄ , FeAl ₂ O ₄ and ZnAl ₂ O ₄ are JPCDS cards (ZnFe ₂ O ₄ : JPCDS No. 22-1012, FeAl ₂ O ₄ : JPCDS No. 34- 0192, ZnAl ₂ O ₄ : JPCDS No. 5-669), it can be easily confirmed whether or not the crystal phase is precipitated.

The difference in the lattice constant between the first crystal 1a and the second crystal and the difference between the lattice constant between the second crystal and the ferrite crystal 2a are within 10% of the lattice constant of the second crystal, respectively. Crystal 1a
, The second crystal and the ferrite crystal 2a can be confirmed by measuring the distance from the origin of the diffraction grating image to the point corresponding to the same plane orientation. After confirming that the first crystal 1a, the second crystal, and the ferrite crystal 2a have the same crystal structure with the JPCDS card or the like, the distance from the origin of the diffraction grating image to the point corresponding to the same plane orientation is measured. Of the first crystal 1a, the second crystal and the ferrite crystal 2a,
If the distances from the origin of the diffraction grating image to the points corresponding to the same plane orientation are d1, d2 and d3, the ratio of the difference in lattice constant between the first crystal 1a and the second crystal to the lattice constant of the second crystal Can be calculated from (1 / d1-1 / d2) × d2, and the ratio of the difference in lattice constant between the second crystal and the ferrite crystal 2a to the lattice constant of the second crystal is (1 / d2− 1 / d3) × d2.

  As a method for confirming the crystal structures of the insulating layer 1, the ferrite layer 2, and the intermediate layer 3 other than the method using the transmission electron microscope, there is a method using an X-ray diffraction method. According to this method, first, the ceramic substrate is cut and the cut surface is polished so that a desired layer can be observed by X-ray diffraction. Thereafter, a diffraction grating image can be obtained by irradiating the cross section of the layer with X-rays. The X-ray irradiation is performed on an area of about 10 μm square so that only a desired layer portion is irradiated. Thereafter, the crystal structure of the insulating layer 1, the ferrite layer 2, and the intermediate layer 3 can be specified by the same procedure as the identification of the crystal structure by the transmission electron microscope.

  Such a glass ceramic substrate of the present invention includes a first preparation step of preparing a ceramic green sheet for the insulating layer 1, a second preparation step of preparing a ferrite green sheet for the ferrite layer 2, and a ferrite of the ceramic green sheet. Third preparatory step of applying ceramic paste for intermediate layer 3 to at least one of the green sheet side surface and the ceramic green sheet side surface of the ferrite green sheet by a coating method such as a doctor blade method or a printing method such as a screen printing method And a green body laminate manufacturing step in which a ceramic green sheet and a ferrite green sheet are laminated to produce a green sheet laminate, and a firing step in which the green sheet laminate is fired.

The ceramic green sheet for the insulating layer 1 is mainly composed of an insulator powder composed of glass powder and filler powder and an organic binder. The glass powder is a glass-phase glass powder as described above. In addition to the filler powder described above, the filler powder may be, for example, a composite oxide of Al ₂ O ₃ , SiO ₂ , ZrO ₂ and an alkaline earth metal oxide, depending on the electrical characteristics and mechanical characteristics of the insulating layer 1, A ceramic oxide such as a composite oxide of TiO ₂ and an alkaline earth metal oxide, a composite oxide containing at least one selected from Al ₂ O ₃ and SiO ₂ (for example, spinel, mullite, cordierite); Also good.

The ferrite green sheet for the ferrite layer 2 is a ferrite powder that is a powder of the ferrite crystal 2a as described above, or, for example, a ferrite powder prepared by pre-calcining FeFe ₂ O ₄ and CuO, ZnO, or NiO. , And an organic binder as a main component.

  As the organic binder contained in the ceramic green sheet for the insulating layer 1 and the ferrite green sheet for the ferrite layer 2, those conventionally used for ceramic green sheets can be used, for example, acrylic (acrylic acid, methacrylic acid) Or homopolymers or copolymers of these esters, specifically acrylic ester copolymers, methacrylic ester copolymers, acrylic ester-methacrylic ester copolymers, etc.), polyvinyl butyral , Polyvinyl alcohol-based, acrylic-styrene-based, polypropylene carbonate-based, cellulose-based homopolymers or copolymers. In view of decomposability and volatility in the firing step, an acrylic binder is more preferable.

The ceramic green sheet for the insulating layer 1 and the ferrite green sheet for the ferrite layer 2 are prepared by preparing a slurry, applying the slurry by a coating method such as a doctor blade method, and drying the solvent in the slurry. The slurry for producing the green sheet is 5 to 20 parts by mass of an organic binder and 15 to 50 parts by mass of an organic solvent with respect to 100 parts by mass of the insulator powder or ferrite powder, and mixed by a mixing means such as a ball mill. To a viscosity of 3 to 100 cps. The organic solvent at this time should just be a thing which can disperse | distribute and mix | blend an insulator powder or a ferrite powder, and an organic binder favorably, and an organic solvent, water, etc. of toluene, ketones, or alcohols are mentioned. Among these, a solvent having a high evaporation coefficient such as toluene, methyl ethyl ketone or isopropyl alcohol is preferable because the drying step after slurry application can be performed in a short time.

  The intermediate layer 3 is a mixture of 5 to 15 parts by weight of a glass ceramic material containing a filler and 85 to 95 parts by weight of a ferrite material of the ferrite layer 2, and an organic binder, an organic solvent, and a dispersant as required. And a ceramic paste prepared by mixing and kneading with a kneading means such as a ball mill, a three-roll mill, or a planetary mixer is printed between the insulating layer 1 and the ferrite layer 2 and fired. Here, as a glass-ceramic material contained in the ceramic paste used as the intermediate layer 3, for example, a mixture of 80 parts by weight of glass and 20 parts by weight of filler is used. As the organic binder of the ceramic paste used as the intermediate layer 3, the above-mentioned ones that have been conventionally used in ceramic green sheets, conductor pastes, and the like can be used. In view of decomposition and volatility in the firing step, acrylic and alkyd organic binders are more preferable.

  The organic solvent used in the ceramic paste for the intermediate layer 3 may be any material that can disperse and mix the material for the intermediate layer 3 and the organic binder, such as terpineol or butyl carbitol acetate. And phthalic acid can be used.

A method for producing a green sheet laminate includes a method in which heat and pressure are applied to the stacked ceramic green sheet for the insulating layer 1 and ferrite green sheet for the ferrite layer 2 by thermocompression bonding, an organic binder, a plasticizer, and For example, a method of applying an adhesive made of a solvent or the like between ceramic green sheets and between ferrite green sheets and thermocompression bonding can be employed. The conditions of heating and pressurization during lamination vary depending on the type and amount of the organic binder used, but are generally 30 to 100 ° C. and 2 to 30 MPa. The ceramic green sheets and ferrite green sheets at this time may be laminated in a necessary number depending on the thickness of the green sheets so as to have a thickness according to the characteristics required for the glass ceramic substrate.

Calcination of the green sheet laminate is 800-1000 after debinding at a temperature of 300-600 ° C.
It is performed by baking at a temperature of ° C.

In the method for producing a glass-ceramic substrate of the present invention, the insulator powder of the ceramic green sheet for the insulating layer 1 is 10 to 40% by mass filler made of forsterite, 22 to 52% by mass of SiO ₂ , and B _2. O ₃ 2-12 wt%, the _Al 2 _{O 3} 9 to 29 wt%, the ZnO 9 to 29 wt%, including 7-21 wt% 1-9 wt% and MgO and CaO, with respect to _Al 2 _{O 3} The ferrite green sheet of the ferrite layer 2 has a ferrite crystal 2a whose main phase is FeFe ₂ O _4. .

  FIG. 3 is a cross-sectional view showing an example of an embodiment of the glass-ceramic wiring board with a built-in coil according to the present invention. Since the glass-ceramic wiring board with a built-in coil of the present invention comprises the above-described glass-ceramic board of the present invention, a wiring conductor 4 formed in the insulating layer 1, and a coil conductor 5 built in the ferrite layer 2, Since the bonding strength between the insulating layer 1 and the ferrite layer 2 is high, the substrate strength is high and the glass-ceramic wiring board with a built-in coil is highly reliable.

  The glass ceramic substrate in the coil-embedded glass ceramic substrate of the example shown in FIG. 3 includes two insulating layers 1, a ferrite layer 2 having a ferrite crystal 2a provided between these insulating layers 1, and each insulating layer 1 And an intermediate layer 3 provided between the ferrite layer 2. In the case of such a configuration, since the front and back surfaces of the glass ceramic substrate are constituted by the insulating layer 1 made of glass ceramics, the insulation resistance is generally higher than that of ferrite, and the wiring conductor 4 and Since glass ceramics with high bonding strength are located on the surface of the glass ceramic substrate, insulation reliability is high, and components are mounted on the wiring conductor 4 or mounted on an external circuit board via the wiring conductor 4 This is a glass ceramic wiring board with a built-in coil with high mounting reliability.

  The wiring conductor 4 is made of a metallized metal that is a sintered body of a low resistance metal powder such as Cu, Ag, Au, Pt, Ag—Pd alloy, and Ag—Pt alloy, and is used as a green sheet for the insulating layer 1. A wiring conductor pattern to be the wiring conductor 4 is formed by printing a conductive paste for the wiring conductor 4, and this is formed by simultaneous firing with the green sheet for the insulating layer 1. The wiring conductor 4 is formed on the outer surface of the glass-ceramic substrate with a built-in coil, and an external wiring conductor for mounting an electronic component thereon or mounting on an external circuit board via a brazing material or the like, Internal wiring conductors for connecting external wirings of the internal wiring layer, and the internal wiring conductors include an internal wiring layer for routing in the planar direction in the insulating layer 1, and the internal wiring layers or between the internal wiring layers and the external wiring conductor. And a through conductor that penetrates the insulating layer 1 in the thickness direction.

The planar coil conductor 5 is made of a metallized metal layer, which is a sintered body of metal powder, like the wiring conductor 4, and by printing a conductor paste for the planar coil conductor 5 on the surface of the ferrite layer 2 green sheet. A coil pattern is formed, and a green sheet for ferrite layer 2 is further laminated thereon and fired at the same time, thereby being embedded in ferrite layer 2 (incorporated in ferrite layer 2). In the example shown in FIG. 3, the three-layered planar coil conductor 5 is formed so as to overlap two above and below, but when the plurality of coil conductors 5 are formed so as to overlap each other in this way, A plurality of green sheets for the ferrite layer 2 formed with a coil conductor pattern to be 5 and a through conductor pattern to be a through conductor for connecting the coil conductors to each other or between the coil conductor and the internal wiring layer; The green sheet for 2 may be laminated.

  The metal powder used for the production of the planar coil conductor 5 is a low-resistance metal powder similar to the wiring conductor 4 described above. Thereby, the electrical resistance of the planar coil conductor 5 can be reduced.

  The glass-ceramic wiring board with a built-in coil is formed by forming a wiring conductor pattern and a coil conductor pattern on the ceramic green sheet for the insulating layer 1 and the ferrite green sheet for the ferrite layer 2 in the above-described method for manufacturing a glass ceramic board. Can be produced. In the case of the glass-ceramic wiring board with a built-in coil as in the example shown in FIG. 3, a predetermined number of wiring patterns formed on the upper and lower sides of a predetermined number of green sheets for the ferrite layer 2 including those on which coil conductor patterns are formed. A ceramic substrate is produced by arranging a green sheet for insulating layer 1 to produce a laminate and firing the laminate.

  The wiring conductor pattern to be the wiring conductor 4 is formed by printing a conductive paste for the wiring conductor 4 on the surface of the green sheet for the insulating layer 1 in a predetermined pattern by a printing method such as a screen printing method or a gravure printing method. Prior to the formation of the wiring conductor pattern, the through conductors to be the wiring conductors 4 are formed in the green sheet for the insulating layer 1 by punching or laser processing, and embedded in the through holes by printing or press filling. It is formed by filling a conductor paste for the wiring conductor 4.

  Similarly, the coil conductor pattern to be the planar coil conductor 5 is formed by printing a conductor paste for the planar coil conductor 5 on the surface of the ferrite layer 2 green sheet in a predetermined pattern by a printing method such as a screen printing method or a gravure printing method. And the wiring pattern used as the penetration conductor in the ferrite layer 2 is formed similarly to the wiring conductor pattern used as the said penetration conductor. The conductor paste for the planar coil conductor 5 may be the same as the conductor paste for the wiring conductor 4. The coil conductor pattern to be the planar coil conductor 5 depends on the required inductance value and size, but when formed by printing as described above, the line width and the distance between adjacent outer and inner conductors is 0.1 mm. If it is more than about, it can be formed easily.

  The conductor paste for the wiring conductor 4 and the planar coil conductor 5 is a kneading means such as a ball mill, a three-roll mill, a planetary mixer, etc. by adding an organic binder, an organic solvent, and a dispersant as required to the main component metal powder. By mixing and kneading.

  As the organic binder of the conductor paste, the above-mentioned ones conventionally used for ceramic green sheets and conductor pastes can be used. In view of decomposition and volatility in the firing step, acrylic and alkyd organic binders are more preferable.

  The organic solvent for the conductor paste is not particularly limited as long as the above-described metal powder and organic binder can be well dispersed and mixed, and terpineol, butyl carbitol acetate, phthalic acid, and the like can be used.

The conductor paste for the wiring conductor 4 and the conductor paste for the planar coil conductor 5 are kneaded by adding 3 to 15 parts by mass of an organic binder and 10 to 30 parts by mass of an organic solvent to 100 parts by mass of the metal conductor powder. It is desirable that the viscosity be such that a pattern having a predetermined shape can be satisfactorily formed without causing problems such as bleeding or fading of the conductor paste by printing.

The conductive paste for forming a wiring pattern to be a through conductor is a paste having a relatively low fluidity with respect to the conductive paste for the wiring conductor 4 and the conductive paste for the planar coil conductor 5 depending on the amount of solvent and the amount of organic binder. It is preferable that the through hole is easily filled and heated and cured. Further, an inorganic component obtained by adding glass or ceramic powder to the metal conductor powder may be included for adjusting the sintering behavior.

  As the firing atmosphere, when the planar coil conductor 5 and the other wiring conductors 4 are made of a material that is difficult to oxidize such as Ag, the firing atmosphere is performed in the atmosphere, and when made of a material that is easily oxidized such as Cu, a nitrogen atmosphere is used. And is moistened so that it can be easily removed.

  The wiring conductor 4 formed on the surface of the glass-ceramic wiring board with a built-in coil after the firing is nickel-plated on the surface in order to strengthen the bonding with a semiconductor chip, a chip component, or an external electric circuit by soldering or the like. The layer and the gold layer may be sequentially deposited by a plating method.

  In addition, this invention is not limited to the example of the above embodiment, A various change may be added in the range which does not deviate from the summary of this invention. For example, in the above example, a laminate in which the ceramic green sheets for the insulating layer 1 are arranged above and below the ferrite green sheets for the ferrite layer 2 via the ceramic paste for the intermediate layer 3 is produced, and the laminate is fired. In this example, the glass ceramic substrate is manufactured. However, after the laminate is first prepared and fired only with the ferrite green sheet, the ceramic for the insulating layer 1 is interposed between the ceramic paste for the intermediate layer 3 above and below the laminate. A glass ceramic substrate may be produced by laminating green sheets and firing the laminate.

  Examples of the glass-ceramic substrate with a built-in coil according to the above embodiment will be described in detail below.

First, a SiO ₂ 37 _wt% as a glass _powder, B 2 _{O 3} to 7 wt%, _Al 2 _{O 3} of 19 wt%, ZnO of 17% by weight, of glass containing 15 wt% 5 wt% and MgO and CaO 80% by mass of powder and 20% by mass of forsterite powder as filler powder are mixed to make an insulator powder, and 12% by mass of acrylic resin as an organic binder with respect to 100% by mass of this insulator powder.
Add 6% by mass of phthalic acid plasticizer as plasticizer and 30% by mass of toluene as solvent, mix by ball mill method to prepare slurry, and use this slurry to have an insulating layer with a thickness of 160μm by doctor blade method A ceramic green sheet to be 1 was formed.

A through hole with a diameter of 150 μm for a through conductor was formed in this ceramic green sheet by punching with a mold. This through hole was filled with a through conductor paste to be the wiring conductor 4 by a screen printing method and dried at 70 ° C. for 30 minutes. As a penetrating conductor paste, 100% by mass of Ag powder, 10% by mass of glass powder as a sintering aid, 12% by mass of acrylic resin and 2% by mass of α-terpineol as an organic solvent are added, and a stirring deaerator Then, the mixture was sufficiently kneaded with three rolls after being sufficiently mixed.

  Next, a conductive paste to be the wiring conductor 4 was applied to the ceramic green sheet by a screen printing method to a thickness of 2 μm and a thickness of 20 μm, and dried at 70 ° C. for 30 minutes to form a wiring conductor pattern.

As the conductive paste, 100% by mass of Ag powder as metal powder, 12% by mass of acrylic resin
And 2% by mass of α-terpineol as an organic solvent were added, and the mixture was sufficiently mixed with a stirring deaerator and then sufficiently kneaded with three rolls.

Next, 700 g of FeFe ₂ O ₄ powder, 60 g of CuO powder, 60 g of NiO powder, 180 g of ZnO powder
Then, 4000 cm ³ of pure water and zirconia balls are put into a pot having a capacity of 7000 cm ³ and mixed for 24 hours in a ball mill by rotating the pot. Then, the dried mixed powder is put in a zirconia crucible and 730 ° C. in the atmosphere. Was then heated for 1 hour to prepare a ferromagnetic ferrite powder. 300 g of this ferrite powder was put in 600 g of pure water, stirred, and then pulverized by a bead mill having a capacity of 1000 cm ³ containing 200 g of zirconia beads until the particle size became 0.5 μm. To 100% by mass of the ferrite powder, 10% by mass of butyral resin as an organic binder and 45% by mass of IPA as an organic solvent were added and mixed by the same ball mill method to obtain a slurry. Using this slurry, a ferrite green sheet having a thickness of 100 μm was formed by a doctor blade method.

Through holes with a diameter of 150 μm for through conductors were formed in this ferrite green sheet by punching with a mold. This through hole was filled with a through conductor paste to be the coil conductor 5 by screen printing and dried at 70 ° C. for 30 minutes to form a through conductor composition to be a through conductor. As the through conductor paste, the same one as described above was used.

Subsequently, a conductor paste was applied to each of the two ferrite green sheets by screen printing to a thickness of 30 μm and dried at 70 ° C. for 30 minutes to form a planar coil conductor pattern. As the conductor paste, 100% by mass of Ag powder, 10% by mass of acrylic resin and 1% by mass of α-terpineol as an organic solvent, and sufficiently mixed by a stirring deaerator were used.

Next, 300 g of forsterite powder was put in 600 g of pure water, stirred, and then pulverized by a bead mill having a capacity of 1000 cm ³ containing 200 g of zirconia beads until the particle size became about 0.5 μm. This forsterite powder 20 wt%, a SiO ₂ 37 _wt% as a glass _powder, B 2 _{O 3} to 7 wt%, _Al 2 _{O 3} of 19 wt%, ZnO 17 wt%, 5 wt% and MgO and CaO 80% by mass of glass powder containing 15% by mass of glass ceramic powder is prepared. 5 mass% of the glass ceramic powder thus produced, 95 mass% of the above ferrite powder, 12 mass% of acrylic resin, and 2 mass% of α-terpineol as an organic solvent were added, and a stirring deaerator was added. After that, a ceramic paste was prepared which became an intermediate layer that was sufficiently kneaded with three rolls after sufficiently mixing.

  Next, three ceramic green sheets for the insulating layer 1 are laminated, and a ceramic paste for the intermediate layer 3 is printed on the uppermost surface of the ceramic green sheet by a screen printing method. Thereafter, a ferrite green sheet in which a planar coil pattern is formed between the two sheets is laminated on the uppermost surface of the ceramic green sheet laminate through a ceramic paste. Then, a ceramic paste is printed on the uppermost surface of the ferrite green sheet, and the laminated ceramic green sheets are stacked through this ceramic paste. Then, the laminated body in which the ceramic green sheet for the insulating layer 1 is located on the surface layer is manufactured by thermocompression bonding under conditions of 55 ° C. and 20 MPa.

Next, this laminate is heated in the atmosphere at 500 ° C. for 3 hours to remove organic components, and then fired in the atmosphere at 900 ° C. for 1 hour to form a glass-ceramic wiring board with a built-in coil. Was made. An Ni plating film and an Au plating film were sequentially formed on the wiring conductor formed on the outer surface of the glass-ceramic wiring board with a built-in coil by using an electroless plating method.

  A glass-ceramic wiring board with a built-in coil manufactured in this manner is referred to as Example 1. Further, Examples 2 to 7 and Comparative Examples 1 to 6 were produced by changing the glass ceramic powder of the ceramic paste for the intermediate layer used in Example 1 and the ferrite powder of the ceramic paste by 1% by mass, respectively.

  Five samples each of Examples 1 to 7 and Comparative Examples 1 to 6 shown in Table 1 obtained as described above were prepared and observed by the penetration test of the fluorescent flaw detection liquid.

In the penetration test of the fluorescent flaw detection liquid, immerse the glass ceramic substrate in the fluorescent flaw detection liquid, 0.5
After leaving for 2 hours under a pressure of MPa and taking out from the fluorescent flaw detection liquid, the side surface of the glass-ceramic wiring board with a built-in coil is polished to penetrate the fluorescent flaw detection liquid between the insulating layer 1 and the ferrite layer. We confirmed whether there was. It was determined that voids or gaps were formed at the interface between the insulating layer 1 and the ferrite layer for those that had permeated.

  0/5 shown in the penetration test results of the fluorescent flaw detection liquid in Table 1 indicates that there was no penetration of the fluorescent flaw detection liquid in all of the five samples, and 5/5 indicates that the flaw detection liquid was in all of the five samples. It shows that there was penetration. In addition, the determination result when there was no penetration of the fluorescent flaw detection liquid in all of the five samples was OK, and the determination result when even one of the five flaw detection liquids permeated was NG.

  As shown in Table 1, the glass-ceramic wiring boards with built-in coils of Examples 1 to 7 having the intermediate layer 3 in which the glass ceramic powder is 5% by mass to 15% by mass and the ferrite powder is 85% by mass to 95% by mass. It was confirmed that there was no penetration of the fluorescence flaw detection liquid.

  On the other hand, when the glass ceramic powder is 4% by mass or less and the ferrite powder is 96% by mass or more, and when the glass ceramic powder is 16% by mass or more and the ferrite powder is 84% by mass or less. It was confirmed that the glass-ceramic wiring board with a built-in coil of Comparative Examples 1 to 6 having the intermediate layer 3 has penetration of the fluorescent flaw detection liquid. This is because when the glass ceramic powder is 4% by mass or less, the glass does not flow sufficiently around the ferrite crystal 2a during the sintering, and when the glass ceramic powder is 16% by mass or more, the glass flows during the sintering. This is probably because the grain growth of the ferrite particles is suppressed and a part of the ferrite crystal 2a does not protrude into the insulating layer.

From the above results, 5 to 15% by weight of glass ceramic powder and 85% of ferrite powder were obtained.
It was confirmed that the glass-ceramic wiring boards with built-in coils of Examples 1 to 7 having the intermediate layer used by mass% to 95 mass% were highly reliable glass ceramic substrates.

DESCRIPTION OF SYMBOLS 1 ... Insulating layer 1a ... 1st crystal 2 ... Ferrite layer 2a ... Ferrite crystal 3 ... Intermediate layer 4 ... Wiring conductor 5 ... Planar coil conductor

Claims (2)

A ferrite layer having a ferrite crystal, an insulating layer having a glass ceramic containing a first crystal having the same crystal structure as the ferrite crystal, and a glass ceramic containing the first crystal disposed between the insulating layer and the ferrite layer And a glass ceramic substrate in which the intermediate layer having the ferrite crystal is laminated,
A part of the plurality of ferrite crystals of the intermediate layer protrudes toward the insulating layer, a part of the ferrite crystals protruding toward the insulating layer, and the first crystal included in the insulating layer A glass-ceramic substrate characterized by being bonded . A glass ceramic substrate according to claim 1, together with the wiring conductors are arranged, and characterized in that electrically connected to coil conductor is disposed on the wiring conductors between the layers of the ferrite layer of the multiple A glass ceramic wiring board with a built-in coil.

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