Magnetic ceramic substrate, substrate manufacturing method, and circulator

Abstract

The magnetic ceramic substrate (1) comprises a base material (2) made of ferrite, a metal conductor (3) made of Ag, and 3 vol% to 12 vol% of amorphous glass (4), and has an apparent density of 7.3 g / cm 3 More than 9.0g / cm 3 The surface pattern conductor (6) described below is provided on the surface of the substrate (2).

Description

[Technical field]

[0001] The present disclosure relates to a magnetic ceramic substrate, a substrate manufacturing method, and a circulator. [Background technology]

[0002] The transmitting and receiving circuits of electronic devices use circulators to control the flow of transmitting and receiving signals and share antennas. In the ceramic circuit board used in these circulators, a circuit pattern is formed by metallizing the surface of a magnetic ceramic base material. A commonly used method for forming a circuit pattern using a thick-film printing method is a simple method that is excellent in mass productivity. However, this method for forming a circuit pattern has the problem that it is difficult to ensure adhesion between a ceramic substrate and a conductor pattern and to improve reliability during solder mounting. Furthermore, when a conductor paste containing a large amount of glass frit is used to improve the adhesion of the conductor pattern, there is a problem that plating adhesion deteriorates when plating is performed on the surface of the conductor.

[0003] Therefore, Patent Document 1 proposes a circuit board in which a first metallized layer with high adhesion is formed by applying a first paste to the surface of a ceramic substrate and firing the first paste, and a second metallized layer with high heat dissipation is formed by applying a second paste to the first metallized layer and firing the second paste. Here, the second paste has a lower ratio of glass components to metal particle components than the first paste. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-201346 A Summary of the Invention [Problem to be solved by the invention]

[0005] According to the circuit board proposed in Patent Document 1, the first paste contains a glass component, which improves adhesion between the ceramic substrate and the conductor. However, the circuit board has a problem in that the conductor may peel off when thermal stress is applied to the interface during baking of the paste or thermal stress due to a heat cycle or the like.

[0006] The present disclosure aims to provide a magnetic ceramic substrate having a surface pattern conductor formed on a base material made of ferrite, the surface pattern conductor having excellent adhesion and excellent plating adhesion. [Means for solving the problem]

[0007] The magnetic ceramic substrate according to the present disclosure comprises: A substrate made of ferrite, It contains a metal conductor made of Ag and 3 vol% to 12 vol% of amorphous glass, and has an apparent density of 7.3 g / cm 3 More than 9.0g / cm 3 The substrate is provided on its surface with a surface layer pattern conductor as described below. Effect of the Invention

[0008] According to the present disclosure, since the apparent density of the surface pattern conductor is smaller than the true density of Ag, the elastic modulus (apparent elastic modulus) of the surface pattern conductor is lower than the elastic modulus of Ag. Furthermore, since the surface pattern conductor contains amorphous glass, the thermal expansion coefficient of the entire surface pattern conductor is smaller than the thermal expansion coefficient of Ag. Therefore, the difference in thermal expansion coefficient between the substrate and the surface pattern conductor is relatively small. Therefore, in the magnetic ceramic substrate according to the present disclosure, the thermal stress at the interface between the substrate and the surface pattern conductor is relatively small. Furthermore, in the magnetic ceramic substrate according to the present disclosure, since the amount of amorphous glass is appropriate, glass floating on the surface of the surface pattern conductor can be reduced. Therefore, according to the present disclosure, a magnetic ceramic substrate can be provided in which a surface pattern conductor is formed on a base material made of ferrite, and the surface pattern conductor has excellent adhesion and excellent plating adhesion. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a magnetic ceramic substrate 1 according to a first embodiment. [Diagram 2] 1 is a cross-sectional view of a magnetic ceramic substrate having a dense surface layer pattern conductor according to the prior art. [Diagram 3] 3 is an enlarged view of a surface layer pattern conductor 6 according to the first embodiment. FIG. [Figure 4] An enlarged view of a surface pattern conductor that does not contain glass. [Diagram 5] 3 is an enlarged view of the interface between the substrate 2, the surface of which has been smoothed, and a surface layer pattern conductor 6 according to the first embodiment. FIG. [Figure 6] FIG. 2 is an enlarged view of the interface between a substrate whose surface has not been smoothed and a surface layer pattern conductor. [Figure 7] 1 is a cross-sectional view of a magnetic ceramic substrate 1 according to a first embodiment. [Figure 8] 1 is a cross-sectional view of a magnetic ceramic substrate 1 according to a first embodiment. [Figure 9] FIG. 11 is a cross-sectional view of a circulator 17 according to a second embodiment. [Figure 10] FIG. 11 is a cross-sectional view of a circulator 17 according to a second embodiment. [Figure 11] 3 is a table showing an overview of examples and comparative examples related to the magnetic ceramic substrate 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the description of the embodiments and the drawings, the same elements and corresponding elements are denoted by the same reference numerals. Descriptions of elements denoted by the same reference numerals will be omitted or simplified as appropriate.

[0011] Embodiment 1 Hereinafter, the present embodiment will be described in detail with reference to the drawings. As a method for forming a surface pattern conductor on the surface of a sintered magnetic ceramic substrate, a method is known in which a conductive paste containing glass as a binder is printed on the surface of the magnetic ceramic substrate and the printed conductive paste is baked. However, due to the difference in thermal expansion coefficient between the substrate and the surface pattern conductor, thermal stress may occur at the interface between the substrate and the surface pattern conductor, which may induce peeling of the surface pattern conductor. In particular, when ferrite with low mechanical strength is used as the substrate, there is a problem that fine cracks are likely to occur near the interface of the substrate, and the surface pattern conductor peels off from the generated fine cracks. In addition, when the amount of glass added is extremely increased in order to increase the effect of improving the adhesion of the surface pattern conductor, there is a problem that the plating adhesion on the surface of the conductor pattern deteriorates due to an increase in glass floating on the surface of the conductor pattern. Therefore, the inventors of the present disclosure conducted intensive research to solve the above problems and discovered the following in a magnetic ceramic substrate having a surface pattern conductor formed on a base material made of ferrite. 1. By reducing the apparent density of the surface layer pattern conductor, the elastic modulus of the surface layer pattern conductor can be reduced. 2. By incorporating amorphous glass, which has a lower thermal expansion coefficient than that of Ag, into the surface pattern conductor, the thermal expansion coefficient of the surface pattern conductor is reduced, thereby reducing the difference in thermal expansion coefficient between the substrate and the surface pattern conductor, thereby reducing the thermal stress generated at the interface between the substrate and the surface pattern conductor, and improving the adhesion between the substrate and the surface pattern conductor.

[0012] ***Configuration Description*** Fig. 1 shows an example of a schematic cross-sectional view of a magnetic ceramic substrate 1 according to the first embodiment. As shown in Fig. 1, the magnetic ceramic substrate 1 is composed of a substrate 2 made of ferrite and a surface pattern conductor 6 formed on the surface of the substrate 2. The magnetic ceramic substrate 1 is used in a circuit board that utilizes the magnetism of an electronic device. The surface of the substrate 2 is the surface of the substrate 2 that is in contact with the surface pattern conductor 6. Ferrite is also called magnetic ceramic. The surface layer pattern conductor 6 is composed of a metal conductor 3, amorphous glass 4, and voids 5, and is also called a conductor pattern. The metal conductor 3 is specifically a conductor made of Ag. The voids 5 are three-dimensional regions within the surface pattern conductor 6 that are not filled with the metal conductor 3. A plurality of voids 5 exist within the surface pattern conductor 6. At least a portion of the plurality of voids 5 is filled with amorphous glass 4.

[0013] Generally, in a ceramic substrate, the thermal expansion coefficients are different between the substrate and the surface pattern conductor, so that thermal stress occurs at the interface between the substrate and the surface pattern conductor when the surface pattern conductor is baked. If this thermal stress is excessively large, this thermal stress causes a decrease in adhesion in the surface pattern conductor. In particular, when a surface pattern conductor containing glass as a binder is used, the adhesive force of the glass at the interface between the substrate and the surface pattern conductor is strong, so that the thermal stress causes microcracks in the substrate near the interface, and the surface pattern conductor may peel off from the microcracks, as if scraping off the substrate. Such peeling of the surface pattern conductor starting from the microcracks in the substrate does not occur much when a ceramic substrate using a substrate with a relatively high strength, such as a substrate made of aluminum oxide or silicon nitride, is used, but tends to occur significantly when a substrate with a relatively low strength, such as a substrate made of ferrite, is used. Therefore, when the substrate 2 made of ferrite is used as in the magnetic ceramic substrate 1 according to the first embodiment, it is important to minimize the thermal stress occurring at the aforementioned interface in order to improve the adhesion between the substrate 2 and the surface pattern conductor 6. The thermal stress occurring at the interface tends to increase as the difference in thermal expansion coefficient between the materials facing each other at the interface increases and as the elastic modulus of each material increases. Therefore, in order to improve the adhesion between the substrate 2 and the surface pattern conductor 6, it is important to reduce the difference in thermal expansion coefficient between the substrate 2 and the surface pattern conductor 6 by lowering the elastic modulus and the thermal expansion coefficient of the surface pattern conductor 6. However, for the substrate 2, it is necessary to emphasize the electrical and magnetic properties, which are the basic performance of the substrate. Therefore, it is difficult to improve the elastic modulus and the thermal expansion coefficient of the substrate 2. Therefore, in the magnetic ceramic substrate 1 according to the first embodiment, the generation of thermal stress at the interface is reduced by improving the surface pattern conductor 6.

[0014] The apparent density of the surface layer pattern conductor 6 is the true density of Ag, which is the main component of the surface layer pattern conductor 6 (10.49 g / cm 3 ) The elastic modulus (apparent elastic modulus) of the surface layer pattern conductor 6 becomes lower than the elastic modulus of Ag (82.7 GPa) by reducing the apparent density. Therefore, the thermal stress generated at the interface can be reduced. On the other hand, as shown in Fig. 2, when the surface layer pattern conductor has a dense structure, the elastic modulus of the surface layer pattern conductor becomes high (equivalent to the elastic modulus of Ag). As a result, a large thermal stress occurs at the interface, which may reduce adhesion. Fig. 2 shows a cross-sectional view of a magnetic ceramic substrate according to the prior art, which has a dense surface layer pattern conductor.

[0015] The surface pattern conductor 6 also contains amorphous glass 4. In the surface pattern conductor 6, as shown in Fig. 3, some of the spaces between the partially sintered Ag particles are filled with amorphous glass 4 that was once melted and solidified. Among the spaces between the Ag particles, the spaces that are not filled with amorphous glass 4 are voids 5. In general, the thermal expansion coefficient of glass tends to be smaller than that of Ag. Therefore, as shown in Fig. 3, the presence of amorphous glass 4 with a relatively small thermal expansion coefficient between partially sintered Ag particles makes the thermal expansion coefficient of the entire surface pattern conductor 6 smaller than that of Ag. Therefore, the difference in the thermal expansion coefficient between the substrate 2 and the surface pattern conductor 6 can be kept relatively low, thereby reducing the thermal stress generated at the interface.

[0016] On the other hand, when the amorphous glass 4 does not exist between the partially sintered Ag particles as shown in Fig. 4, the thermal expansion coefficient of the surface pattern conductor 6 does not decrease, that is, the thermal expansion coefficient of the surface pattern conductor 6 is a relatively large value equivalent to the thermal expansion coefficient of Ag. Therefore, in this case, the effect of reducing the thermal stress generated at the interface cannot be obtained. For this reason, the magnetic ceramic substrate 1 according to the first embodiment, by having the above-mentioned configuration, has excellent adhesion of the surface layer pattern conductors 6 and excellent plating adhesion.

[0017] The material of the base material 2 may be any material that satisfies the magnetic properties required for the application of the magnetic ceramic substrate 1. A specific example of the material is garnet-type ferrite (YFeO 12 etc.), M-type hexagonal ferrite (BaFe 12 O 19 , SrFe 12 O 19 ), W-type hexagonal ferrite (BaFe 18 O 27 , SrFe 18 O 27 ), Z-type hexagonal ferrite (Ba3Co2Fe 24 O 41 , Sr3Co2Fe 24 O 41 ), Y-type hexagonal ferrite (BaZnFe 12 O 22), or spinel-type ferrite (AFe2O4: A=Mn, Co, Ni, Cu, Zn). In particular, garnet-type ferrite is suitable as the material for the substrate 2 because it has low magnetic loss in the high frequency range and is in high demand as a magnetic circuit board for microwaves. Furthermore, the surface of the substrate 2 is preferably smooth in order to suppress microcracks 8 in the substrate 2, which are a cause of reduced adhesion between the substrate 2 and the surface pattern conductor 6. With a smooth surface, even if thermal stress occurs at the interface due to a difference in thermal expansion coefficient between the substrate 2 and the surface pattern conductor 6, microcracks 8 are less likely to occur in the substrate 2 as shown in FIG.

[0018] On the other hand, as shown in Fig. 6, when the surface of the substrate 2 is not smooth, stress due to the difference in thermal expansion coefficient between the substrate 2 and the surface pattern conductor 6 is concentrated on the protrusions 7 on the surface of the substrate 2, and tensile stress is partially applied to the protrusions 7. As a result, as shown in Fig. 6, microcracks 8 tend to occur mainly in the portions of the protrusions 7, and the adhesion of the surface pattern conductor 6 may decrease from the microcracks 8 that occur as starting points. Therefore, it is more preferable to smooth the surface of the substrate 2. The smooth surface refers to a surface of the substrate 2 that has been subjected to mirror polishing treatment after the substrate 2 has been cut. Examples of the mirror polishing method include buff polishing, barrel polishing, and shot blast polishing. The surface smoothness is preferably 0.01 μm or more and 0.5 μm or less in terms of Ra, and more preferably 0.02 μm or more and 0.3 μm or less. When the surface smoothness exceeds 0.5 μm in terms of Ra, the stress concentrated on the surface protrusions 7 becomes large, and fine cracks 8 may rarely occur, and although it does not impair practical use, adhesion tends to decrease slightly. On the other hand, when the surface smoothness is less than 0.01 μm in terms of Ra, excessive mirror finishing is performed, and productivity decreases. Here, the arithmetic mean roughness (Ra) is a value calculated by [Equation 1] using the data of the surface unevenness of the substrate 2 measured in the line direction of a length of 10 mm and a width (l) using a contact roughness meter.

[0019]

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[0020] The surface layer pattern conductor 6 is composed of a metal conductor 3, amorphous glass 4, and voids 5. The apparent density of the surface layer pattern conductor 6 is 7.3 g / cm 3 More than 9.0g / cm 3 In this way, the apparent density of the surface layer pattern conductor 6 is adjusted to the true density of Ag (10.49 g / cm 3 ), the elastic modulus (apparent elastic modulus) of the surface layer pattern conductor 6 becomes lower than the elastic modulus of Ag (82.7 GPa). Therefore, the thermal stress generated at the interface can be reduced. Here, from the viewpoint of reducing the thermal stress occurring at the interface, the lower the apparent density of the surface layer pattern conductor 6, the more the thermal stress can be reduced. 3 If the temperature is too low, such as less than 100° C., the adhesion between the surface pattern conductor 6 and the substrate 2 becomes too sparse, reducing the adhesion. Furthermore, in this case, the volume resistivity is significantly deteriorated, and electrical loss increases, preventing the surface pattern conductor 6 from fulfilling its function. On the other hand, the apparent density is 9.0 g / cm 3 If the density exceeds this value, the effect of lowering the elastic modulus (apparent elastic modulus) becomes smaller, so that the thermal stress generated at the interface increases, and microcracks 8 become more likely to occur in the base material 2. Here, the apparent density is a value calculated by taking several photographs of the cross section of the surface layer pattern conductor 6 of the magnetic ceramic substrate 1 at a magnification of several hundred to several thousand times using a SEM (Scanning Electron Microscope), determining the areas occupied by the metal conductor 3, the amorphous glass 4, and the voids 5, respectively, by image analysis, and using the determined areas to calculate according to [Equation 2].

[0021]

number

[0022] Here, S Ag and S. g and S.p are the areas occupied by Ag, glass, and voids, respectively, determined by image analysis. Ag is the true density of Ag, 10.49 g / cm 3 ρ g is the true density of the glass, and ρ g A value according to the type of glass can be used as the true density of each glass. A known value can be used as the true density of each glass. As a specific example, the true density of borosilicate glass is 2.51 g / cm 3 The type of glass can also be identified from the composition ratio obtained from the results of elemental analysis using an EPMA (Electron Probe Micro Analyzer) or the like.

[0023] On the other hand, when the surface layer pattern conductor 6 has a dense structure as shown in Fig. 2, the elastic modulus of the surface layer pattern conductor 6 becomes relatively high (equivalent to the elastic modulus of Ag), which may cause a large thermal stress at the interface and reduce the adhesion. Furthermore, when the surface pattern conductor 6 has a dense structure, the proportion of the amorphous glass 4 contained in the surface pattern conductor 6 that protrudes to the surface of the dense surface pattern conductor 6 increases. Therefore, in this case, there is a problem that the plating deposition property on the surface pattern conductor 6 deteriorates. Therefore, from the viewpoint of plating the surface pattern conductor 6, it is preferable to set the apparent density low. In order not to inhibit plating deposition, the ratio of the exposed area of ​​the metal conductor 3 on the surface of the surface pattern conductor 6 opposite the substrate 2 is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. Here, the ratio of the exposed area of ​​the metal conductor 3 is a value calculated by taking several photographs of the surface of the surface pattern conductor 6 of the magnetic ceramic substrate 1 enlarged several hundred to several thousand times with an SEM, determining the areas occupied by the metal conductor 3, the amorphous glass 4, and the voids 5 by image analysis, and using the determined areas according to [Equation 3].

[0024]

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[0025] The surface pattern conductor 6 according to the present embodiment contains 3 vol% or more and 12 vol% or less of amorphous glass 4. The amorphous glass 4 contained in the surface pattern conductor 6 plays the role of a binder between the substrate 2 and the surface pattern conductor 6, and therefore contributes to improving the adhesion between the substrate 2 and the surface pattern conductor 6. In addition, since the thermal expansion coefficient of the amorphous glass 4 is smaller than that of the metal conductor 3, the thermal expansion coefficient of the surface pattern conductor 6 can be reduced by the surface pattern conductor 6 containing the amorphous glass 4. Therefore, it is possible to obtain an effect of suppressing thermal stress generated at the interface due to the difference in thermal expansion coefficient between the substrate 2 and the surface pattern conductor 6. However, when the content of the amorphous glass 4 is too high, the proportion of the amorphous glass 4 protruding on the surface of the surface pattern conductor 6 increases more than expected, causing problems in plating deposition. From this viewpoint, the content of the amorphous glass 4 in the surface pattern conductor 6 is preferably 3 vol% or more and 12 vol% or less. Here, when the content of amorphous glass 4 is less than 3 vol%, the effect as a binder is weakened, resulting in a decrease in the adhesive strength between the substrate 2 and the surface pattern conductor 6. When the content of amorphous glass 4 is more than 12 vol%, glass floating on the surface of the surface pattern conductor 6 increases, causing problems with plating deposition.

[0026] Considering the above-mentioned viewpoint, it is considered that the optimum content of the amorphous glass 4 in the surface pattern conductor 6 varies depending on the apparent density of the surface pattern conductor 6. Therefore, it is difficult to uniquely determine the optimum content. However, in order to reduce the elastic modulus of the surface layer pattern conductor 6 according to the present embodiment, the apparent density is set to 7.3 g / cm 3 More than 9.0g / cm 3 It has been found that within this apparent density range, the suitable content of the amorphous glass 4 is 3 vol % or more and 12 vol % or less. By setting the apparent density and the content of the amorphous glass 4 within the above ranges, the thermal expansion coefficient and elastic modulus of the surface layer pattern conductor 6 can be effectively reduced. Therefore, the thermal stress generated at the interface can be suppressed, and a remarkable effect of improving adhesion can be obtained. Furthermore, the glass floating on the surface can be reduced, which is also effective in improving plating adhesion.

[0027] In the magnetic ceramic substrate 1 according to the present embodiment, it is more preferable that the difference in thermal expansion coefficient between the substrate 2 and the surface pattern conductor 6 ((thermal expansion coefficient of surface pattern conductor 6)-(thermal expansion coefficient of substrate 2)) is 8.2 ppm / K or less. Here, the thermal expansion coefficient of the surface pattern conductor 6 varies depending on the content of the amorphous glass 4 (not less than 3 vol% and not more than 12 vol%). On the other hand, the thermal expansion coefficient of the base material 2 varies depending on the type of ferrite used. Therefore, the difference in thermal expansion coefficient between the two can be adjusted by combining the content of the amorphous glass 4 with the type of base material 2. It is more preferable to adjust the difference in thermal expansion coefficient to 8.2 ppm / K or less. When the difference in thermal expansion coefficient exceeds 8.2 ppm / K, the thermal stress generated at the interface is relatively large, and thus the adhesion may decrease, although not to the extent that it impairs practical use.

[0028] The surface pattern conductor 6 according to the present embodiment is formed by printing Ag paste in a desired shape on the surface of the base material 2 using a screen mask or a metal mask by a thick film printing method, and baking the printed Ag paste at a desired temperature. Baking the Ag paste is to bake the Ag paste. The Ag paste is an example of a conductor paste. At this time, the Ag paste contains coarse Ag particles having a particle size of 5 μm to 15 μm, fine Ag particles having a particle size of 1 μm to 3 μm, and amorphous glass powder made of amorphous glass 4. In addition, the firing shrinkage rate of the Ag paste is preferably 5% or less. Since the Ag paste contains coarse Ag particles and fine Ag particles and has a firing shrinkage rate of 5% or less, it becomes easier to adjust the apparent density of the surface pattern conductor 6 after firing the Ag paste to a desired value. The thickness of the surface pattern conductor 6 is 2 μm or more and 50 μm or less, preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 20 μm or less. When the thickness of the surface pattern conductor 6 is less than 2 μm, the pattern is likely to be blurred when printed in a thick film, resulting in reduced productivity. On the other hand, when the thickness of the surface pattern conductor 6 is more than 50 μm, the internal stress generated during baking is large, which may induce peeling of the surface pattern conductor 6. Here, the thickness of the surface pattern conductor 6 is, as a specific example, the average thickness of several photographs of the cross section of the magnetic ceramic substrate 1 enlarged several hundred to several thousand times by SEM, and the thickness of the surface pattern conductor 6 is measured at any 20 points. Furthermore, for the purpose of reducing electrical loss, the surface layer pattern conductor 6 preferably has a volume resistivity of 6.5 μΩ·cm or less, and more preferably has a volume resistivity of 5.5 μΩ·cm or less.

[0029] The metal conductor 3 may be any material as long as it can be fired at a temperature lower than the heat-resistant temperature of the base material 2 and satisfies the electrical conductivity required depending on the application of the magnetic ceramic substrate 1. Here, it is not preferable to bake the metal conductor 3 at a temperature equal to or higher than the sintering temperature of the base material 2, since this may cause distortion of the base material 2. Therefore, the baking temperature of the metal conductor 3 is preferably at least 300°C lower than the sintering temperature of the base material 2, and more preferably at least 400°C lower than the sintering temperature of the base material 2. Specific examples of such a metal conductor 3 include Ag, Ag-Pd, and Cu. Among these, Ag, which has a relatively low volume resistivity, is suitable for the purpose of reducing loss as a conductor.

[0030] The glass contained in the surface pattern conductor 6 of the magnetic ceramic substrate 1 according to the first embodiment is preferably amorphous glass 4. After being melted once during baking of the surface pattern conductor 6, the amorphous glass 4 maintains its amorphous state and does not crystallize even if it is solidified again. Therefore, the amorphous glass 4 is likely to fully exert its effect as a binder that improves the adhesion between the surface pattern conductor 6 and the substrate 2. Specific examples of the amorphous glass 4 include zinc-based glass, silica-based glass, bismuth-based glass, and borosilicate glass, which may be used alone or in combination of two or more. Regarding the melting temperature of the amorphous glass 4, when the softening point of the amorphous glass 4 is taken as the melting start temperature, it is preferable that the relationship between the softening point of the amorphous glass 4 and the sintering temperature of the metal conductor 3 satisfies the following. sof The sintering temperature of the metal conductor 3 constituting the surface pattern conductor 6 is T sin When 100℃≦T sin -T sof It is preferable that the temperature is ≦300° C. T sin -T sof When the sintering temperature is less than 100°C, the sintering temperature of the metal conductor 3 is too close to the softening temperature of the amorphous glass 4, so that the metal conductor 3 is sintered, and the amorphous glass 4 melts after the metal conductor 3 is densely sintered. Therefore, the dense metal conductor 3 acts as a lid, making it difficult for gas components such as water vapor contained in the amorphous glass 4 to escape. As a result, internal defects such as voids and blisters may occur in the surface pattern conductor 6. On the other hand, T sin -T sof When the temperature exceeds 300° C., the amorphous glass 4 is heated at a temperature excessively higher than the softening point of the amorphous glass 4. As a result, the viscosity of the molten amorphous glass 4 becomes excessively low, so that the amorphous glass 4 is likely to float on the surface of the surface pattern conductor 6, and the plating adhesion on the surface of the surface pattern conductor 6 may decrease. Therefore, it becomes difficult to stably improve the adhesion and plating adhesion. From the viewpoint of improving the adhesion at the interface between the surface pattern conductor 6 and the substrate 2, the dispersion state of the amorphous glass 4 in the surface pattern conductor 6 should not be such that the amount of amorphous glass 4 contributing to the adhesion at the interface is very small due to the amorphous glass 4 being unevenly dispersed near the surface other than the interface. Therefore, the amorphous glass 4 may be uniformly dispersed throughout the surface pattern conductor 6, or may be unevenly dispersed near the interface between the substrate 2 and the surface pattern conductor 6.

[0031] As shown in FIG. 7, the magnetic ceramic substrate 1 according to the first embodiment preferably has a glass layer 9 having a thermal expansion coefficient of 5 ppm / K or more and 10 ppm / K or less on a part of the surface of the substrate 2 and on the entire circumference of the end of the surface pattern conductor 6 in a plan view. The glass layer 9 is provided so as to press the end of the surface pattern conductor 6 in a plan view against the surface of the substrate 2. The end of the surface pattern conductor 6 is composed of the side of the surface pattern conductor 6 and the area around the side of the surface pattern conductor 6. The side of the surface pattern conductor 6 is a surface of the surface pattern conductor 6 excluding the surface in contact with the substrate 2 and the surface opposite to the surface in contact with the substrate 2. Specifically, the part of the surface of the substrate 2 is a region of the surface of the substrate 2 located outside the end of the surface pattern conductor 6 in a plan view. It is preferable that a part of the glass layer 9 is impregnated in a void portion present at the end of the surface pattern conductor 6 in a plan view. The void portion present at the end corresponds to a part of the multiple voids 5 present at the end among the multiple voids 5. Providing the glass layer 9 having such a configuration provides the effect of the glass layer 9 physically pressing down the ends of the surface pattern conductor 6, further improving the adhesion between the substrate 2 and the surface pattern conductor 6. In particular, the ends of the surface pattern conductor 6 tend to be thinner than the central portion of the surface pattern conductor 6, and tend to have a smaller content of amorphous glass 4. Therefore, by having the glass layer 9 physically press down the entire periphery of the ends of the surface pattern conductor 6, a more effective adhesion improvement effect is likely to be obtained.

[0032] The surface pattern conductor 6 of the magnetic ceramic substrate 1 of the first embodiment may have a two-layer structure by forming a second layer surface pattern conductor 10 on the surface of a first layer surface pattern conductor formed on the surface of the base material 2, as shown in Fig. 8. The second layer surface pattern conductor 10 does not contain glass. Since the second layer surface pattern conductor 10 does not contain glass, plating adhesion on the surface of the surface pattern conductor 6 is further improved.

[0033] The magnetic ceramic substrate 1 in the first embodiment having the above-mentioned configuration is a magnetic ceramic substrate in which the surface layer pattern conductors 6 have excellent adhesion.

[0034] ***Production Method Description*** An example of manufacturing steps will be described with respect to a manufacturing method for the magnetic ceramic substrate 1. The manufacturing method for the magnetic ceramic substrate 1 corresponds to a substrate manufacturing method. First, a block of sintered ferrite is cut to a desired size and thickness to produce a substrate 2 made of ferrite. The method for cutting the block is not particularly limited, and may be a method using a blade cutter, a wire machine, an electric discharge machine, a laser machine, or an NC (Numerical Control) machine.

[0035] Next, it is preferable to mirror-polish the surface of the cut substrate 2. The mirror-polishing is performed only on the surface of the substrate 2 on which the conductive paste is to be thick-film printed, and is specifically performed on one or both sides of the substrate 2. When mirror-polishing is performed on both sides, each side may be processed one at a time, or both sides may be processed simultaneously.

[0036] Next, a conductor paste is printed in a thick film on the surface of the substrate 2. The conductor paste used for the thick film printing preferably contains coarse Ag particles having a particle size of 5 μm to 15 μm, fine Ag particles having a particle size of 1 μm to 3 μm, and amorphous glass powder. The firing shrinkage rate of the conductor paste is preferably 5% or less. The amount of amorphous glass powder in the conductor paste is preferably 3 vol% to 12 vol% relative to the amount of inorganic solids. The printer for performing the thick-film printing is not particularly limited, and may be a manual printer or an automatic printer, etc. From the viewpoint of keeping the printing and printing speed constant, it is preferable to use an automatic printer. The mask used in thick film printing may be a screen mask, a metal mask, etc. When a conductor pattern having a more complicated shape is to be printed, it is preferable to use a screen mask. After the thick-film printing, the conductive paste is dried using a thermostatic chamber to remove the solvent component of the conductive paste. The drying temperature can be adjusted appropriately according to the boiling point of the solvent component contained in the conductive paste, and is generally in the range of 80°C to 200°C.

[0037] Next, the dried conductor paste is baked on the substrate 2 on which the conductor paste has been thick-film printed. The device used for baking is not particularly limited, and may be a box-type baking furnace, a tubular-type baking furnace, or a belt-conveying type baking furnace. The baking temperature may be appropriately adjusted depending on the type of metal conductor used, and is generally about 600°C to 1000°C. The magnetic ceramic substrate 1 is completed by baking the conductive paste onto the base material 2.

[0038] The magnetic ceramic substrate 1 manufactured as described above is a magnetic ceramic substrate having excellent adhesion to the surface layer pattern conductors 6 and excellent plating adhesion.

[0039] Next, a method for manufacturing the magnetic ceramic substrate 1 shown in Fig. 7 will be described. In this manufacturing method, the steps up to the step of drying the conductive paste are the same as those described above. Therefore, the steps after the step of drying the conductive paste will be described. First, a glass paste containing glass powder having a thermal expansion coefficient of 5 ppm / K or more and 10 ppm / K or less is thick-film printed on a part of the surface of the substrate 2 and on the entire circumference of the end portion in a planar view of the conductive paste that has been thick-film printed and dried on the surface of the substrate 2. Next, the thick-film printed glass paste is dried. Next, the dried glass paste and the dried conductor paste are baked onto the surface of the substrate 2 by co-firing.

[0040] ***Explanation of the Effects of the First Embodiment*** As described above, according to the present embodiment, it is possible to provide a magnetic ceramic substrate 1 having excellent adhesion to the surface layer pattern conductors 6 and excellent plating adhesion, and a manufacturing method thereof.

[0041] Embodiment 2 The following mainly describes the differences from the above-described embodiment with reference to the drawings.

[0042] ***Configuration Description*** The following mainly describes the differences from the above-described embodiments with reference to the drawings. The second embodiment relates to a circulator 17 including the magnetic ceramic substrate 1 according to the first embodiment.

[0043] Fig. 9 shows a specific example of a schematic cross-sectional view of a circulator 17 according to embodiment 2. As shown in Fig. 9, in the circulator 17, a permanent magnet 12 is mounted via a spacer 11 on the surface of the surface pattern conductor 6 of the magnetic ceramic substrate 1 according to embodiment 1. In the circulator 17, the magnetic ceramic substrate 1 is provided with a through-hole conductor 13a and a through-hole conductor 13b. In circulator 17, surface pattern conductor 6 and input / output terminal 14a are electrically connected by through-hole conductor 13a, and surface pattern conductor 6 and input / output terminal 14b are electrically connected by through-hole conductor 13b. Furthermore, the magnetic ceramic substrate 1 is provided with a ground conductor 15 .

[0044] The type of permanent magnet 12 is not particularly limited, and may be a metal magnet such as a neodymium-iron-boron, samarium-cobalt, alnico, or iron-chromium-cobalt magnet, or may be a ceramic magnet such as a hexagonal ferrite magnet. As a method for electrically connecting the surface layer pattern conductor 6 to each of the input / output terminals 14a and 14b, in addition to a method of connecting via through-hole conductors, a method of connecting via side conductors 16a and 16b formed on the side surfaces of the magnetic ceramic substrate 1 may be used, as shown in Fig. 10. The through-hole conductor is a general term for the through-hole conductors 13a and 13b. The method for mounting the permanent magnets 12 and the method for forming the through-hole conductors are not particularly limited, and may be any method known in the technical field relating to these methods.

[0045] ***Explanation of the effect of the second embodiment*** As described above, according to the second embodiment, it is possible to provide a circulator 17 having excellent adhesion between the surface layer pattern conductor 6 and the base material 2 and excellent mounting reliability.

[0046] The magnetic ceramic substrate 1 according to the present disclosure will be described below using examples and comparative examples. Fig. 11 is a table showing an overview of the examples and comparative examples. In Fig. 11, one table is divided into two.

[0047] [Example 1] Garnet-type ferrite (Y3Fe5O 12 A block of 1000 sintered bodies was cut to a thickness of 1 mm using a grinding wheel cutter to produce a substrate made of magnetic ceramic. Next, an Ag paste containing, as inorganic components, 60 vol% Ag powder with an average particle size of 13 μm, 34 vol% Ag powder with an average particle size of 2 μm, and 6 vol% borosilicate-based amorphous glass with a softening point 300°C lower than the sintering temperature of Ag, was screen printed on the surface of a substrate made of magnetic ceramic using an automatic printing machine. Next, the solvent was removed by drying for 20 minutes in a thermostatic chamber at 120°C. Next, a belt conveying type electric furnace was used to carry out a baking process at a top temperature of 800°C, with a speed of 60 minutes from loading to unloading, to obtain a magnetic ceramic substrate 1 for evaluation. Here, "from loading to unloading" refers to the period from loading into the furnace to unloading out of the furnace.

[0048] [Example 2] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that the top temperature was set to 850° C. and the baking process was carried out at a speed of 60 minutes from loading to unloading.

[0049] [Example 3] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that the top temperature was set to 890° C. and the baking process was carried out in 60 minutes from loading to unloading.

[0050] [Example 4] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that an Ag paste containing 61.9 vol.% Ag powder with an average particle size of 13 μm, 35.1 vol.% Ag powder with an average particle size of 2 μm, and 3 vol.% amorphous glass was used, the top temperature was set to 840° C., and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0051] [Example 5] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that an Ag paste containing 58.7 vol.% Ag powder with an average particle size of 13 μm, 33.3 vol.% Ag powder with an average particle size of 2 μm, and 8 vol.% amorphous glass was used, the top temperature was set to 840°C, and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0052] [Example 6] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that an Ag paste containing 56.2 vol.% Ag powder with an average particle size of 13 μm, 31.8 vol.% Ag powder with an average particle size of 2 μm, and 12 vol.% amorphous glass was used, the top temperature was set to 840° C., and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0053] [Example 7] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that spinel ferrite (Mn-Zn ferrite) with a thermal expansion coefficient of 11 ppm / K was used as the base material 2, the top temperature was set to 840°C, and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0054] [Example 8] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that spinel ferrite (Mn-Zn ferrite) with a thermal expansion coefficient of 10.7 ppm / K was used as the base material 2, the top temperature was set to 840°C, and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0055] [Example 9] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that spinel ferrite (Mn-Zn ferrite) with a thermal expansion coefficient of 10.6 ppm / K was used as the base material 2, the top temperature was set to 840°C, and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0056] [Example 10] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that the surface of the base material 2 was mirror-polished for 30 minutes using a buffing machine.

[0057] [Comparative Example 1] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that the top temperature was set to 790° C. and the baking process was carried out at a speed of 60 minutes from loading to unloading.

[0058] [Comparative Example 2] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that the top temperature was set to 900° C. and the baking process was carried out at a speed of 60 minutes from loading to unloading.

[0059] [Comparative Example 3] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that an Ag paste containing 62.6 vol.% Ag powder with an average particle size of 13 μm, 35.4 vol.% Ag powder with an average particle size of 2 μm, and 2 vol.% amorphous glass was used, the top temperature was set to 840° C., and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0060] [Comparative Example 4] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that an Ag paste containing 55.5 vol.% Ag powder with an average particle size of 13 μm, 31.5 vol.% Ag powder with an average particle size of 2 μm, and 13 vol.% amorphous glass was used, the top temperature was set to 840°C, and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0061] [Comparative Example 5] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that an Ag paste containing 62.6 vol.% Ag powder with an average particle size of 13 μm, 35.4 vol.% Ag powder with an average particle size of 2 μm, and 2 vol.% amorphous glass was used, the top temperature was set to 900° C., and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0062] [Comparative Example 6] A magnetic ceramic substrate 1 for evaluation was obtained in the same manner as in Example 1, except that an Ag paste containing 55.5 vol.% Ag powder with an average particle size of 13 μm, 31.5 vol.% Ag powder with an average particle size of 2 μm, and 13 vol.% amorphous glass was used, the top temperature was set to 900°C, and the baking process was performed at a speed of 60 minutes from loading to unloading.

[0063] The magnetic ceramic substrates 1 obtained in the above examples and comparative examples were evaluated for adhesion of the surface layer pattern conductors 6. The adhesion evaluation was performed by using the CYCUS method, in which a diamond blade was inserted horizontally into the interface between the surface pattern conductor 6 and the substrate 2, and the resistance force when cutting into the interface was measured. In Fig. 11, the results of the adhesion evaluation are shown as relative values ​​when the CYCUS strength value in Example 1 is set to 1. The plating adhesion was evaluated by visually observing the plating adhesion state when acidic electroless Ni plating was applied to the magnetic ceramic substrate 1. In the evaluation results shown in Fig. 11, "○" indicates that the plating is uniformly adhered to the entire surface of the surface pattern conductor 6, and "×" indicates that there are noticeable areas on the surface of the surface pattern conductor 6 where the plating is not adhered.

[0064] Figure 11 As shown in Fig. 1, the magnetic ceramic substrate 1 in each of Examples 1 to 10, in which the apparent density of the surface layer pattern conductor was 7.3 g / cm3 or more and 9 g / cm3 or less and the content of amorphous glass was 3 vol% or more and 12 vol% or less, had a relatively large relative value of CYCUS strength and improved adhesion of the surface layer pattern conductor 6. In addition, the plating adhesion was also good. In particular, in Examples 7 and 8, in which the difference in thermal expansion coefficient between the substrate 2 and the surface layer pattern conductor 6 is 8.2 ppm / K or less, the thermal stress generated at the interface is reduced, and thus the adhesion is further improved. Furthermore, when comparing samples having the same difference in thermal expansion coefficient, Example 10, in which the surface of the substrate 2 is mirror-polished, has improved adhesion compared to Examples 1, 3, and 5, which are not mirror-polished. On the other hand, in Comparative Example 1 and Comparative Example 2 in which the apparent densities of the surface layer pattern conductor 6 are 7.2 g / cm3 and 9.1 g / cm3, respectively, the adhesion is significantly low. Moreover, in Comparative Example 3 in which the amount of amorphous glass added was 2 vol %, the content of glass as a binder was too low, so that the adhesion was not improved. Conversely, in Comparative Example 4, in which the amount of amorphous glass added was 13 vol %, the adhesion was good, but there was a lot of glass floating on the surface of the surface layer pattern conductor 6, and the plating adhesion was deteriorated. Furthermore, in Comparative Example 5 in which the content of amorphous glass was 2 vol % and the apparent density of the surface layer pattern conductor 6 was 9.1 g / cm 3 , the adhesion was significantly low. In addition, in Comparative Example 6 in which the content of amorphous glass was 13 vol % and the apparent density of the surface layer pattern conductor 6 was 9.1 g / cm 3 , the adhesion was low and the plating adhesion was also poor.

[0065] As can be seen from the above results, according to the present disclosure, it is possible to provide a magnetic ceramic substrate 1 having excellent adhesion of the surface layer pattern conductors 6 and excellent plating adhesion on the surfaces of the surface layer pattern conductors 6.

[0066] ***Other embodiments*** The above-described embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted. Moreover, the embodiments are not limited to those shown in the first and second embodiments, and various modifications are possible as necessary. [Explanation of symbols]

[0067] 1 magnetic ceramic substrate, 2 base material, 3 metal conductor, 4 amorphous glass, 5 void, 6 surface pattern conductor, 7 protrusion, 8 microcrack, 9 glass layer, 10 second layer surface pattern conductor, 11 spacer, 12 permanent magnet, 13a, 13b through-hole conductors, 14a, 14b input / output terminals, 15 ground conductor, 16a, 16b side conductors, 17 circulator.

Claims

1. A substrate made of ferrite, A magnetic ceramic substrate comprising a metal conductor made of Ag and 3 vol% or more and 12 vol% or less of amorphous glass, and having a surface pattern conductor on the surface of the base material and having an apparent density of 7.3 g / cm3 or more and 9.0 g / cm3 or less.

2. Within the surface layer pattern conductor, there are a plurality of voids, each of which is a three-dimensional region not filled with the metal conductor; At least a portion of the plurality of voids is filled with the amorphous glass; 2. The magnetic ceramic substrate according to claim 1, wherein the difference in thermal expansion coefficient between said base material and said surface layer pattern conductor is 8.2 ppm / K or less.

3. 2. The magnetic ceramic substrate according to claim 1, wherein the arithmetic mean roughness of the surface of the base material that is in contact with the surface layer pattern conductor is 0.01 μm or more and 0.5 μm or less.

4. the surface layer pattern conductor is formed by firing a conductor paste containing coarse Ag particles having a particle size of 5 μm or more and 15 μm or less, fine Ag particles having a particle size of 1 μm or more and 3 μm or less, and amorphous glass powder made of the amorphous glass; 2. The magnetic ceramic substrate according to claim 1, wherein the conductor paste has a firing shrinkage rate of 5% or less.

5. The magnetic ceramic substrate further comprises: A glass layer having a thermal expansion coefficient of 5 ppm / K or more and 10 ppm / K or less is provided on a part of a surface of the substrate that is in contact with the surface pattern conductor and on an entire periphery of an end of the surface pattern conductor in a plan view. Equipped with the glass layer is provided so as to physically press an end portion of the surface pattern conductor in a plan view against a surface of the base material that is in contact with the surface pattern conductor, 2. The magnetic ceramic substrate according to claim 1, wherein a portion of the glass layer is impregnated into a portion of a plurality of voids present at the end portion.

6. 2. A magnetic ceramic substrate according to claim 1, wherein the surface layer pattern conductor has a volume resistivity of 6.5 μΩ·cm or less.

7. 7. The magnetic ceramic substrate according to claim 1, wherein the ferrite is a garnet-type ferrite.

8. A circulator comprising the magnetic ceramic substrate according to any one of claims 1 to 6.

9. The surface of the ferrite substrate is mirror-polished, A conductor paste containing coarse Ag particles having a particle size of 5 μm or more and 15 μm or less, fine Ag particles having a particle size of 1 μm or more and 3 μm or less, and amorphous glass powder having an amount of 3 vol % or more and 12 vol % or less with respect to the amount of inorganic solids is printed on the surface in a thick film form; The thick-film printed conductor paste is dried, A method for manufacturing a magnetic ceramic substrate by baking a dried conductive paste onto the surface.

10. A glass paste containing glass powder having a thermal expansion coefficient of 5 ppm / K or more and 10 ppm / K or less is thick-film-printed on a part of the surface and on an entire periphery of an end portion in a plan view of the conductor paste thick-film-printed on the surface and dried, The thick-film printed glass paste is dried, 10. The method of claim 9, wherein the dried glass paste and the dried conductor paste are baked onto the surface by co-firing.

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