Patent Application
20230416142
The present invention relates to a glass ceramic material, a laminate, and an electronic component.
In recent years, sintered products of dielectric materials that can be co-fired with conductor materials at a temperature of 1000° C. or lower have been used for multilayer ceramic substrates. For example, Patent Literature 1 discloses a glass-ceramic composite material containing borosilicate glass (50 to 90%) containing SiO2 (70 to 85%), B2O3 (10 to 25%), K2O (0.5 to 5%), and Al2O3 (0.01 to 1%) and at least one SiO2 filler (10 to 50%) selected from the group consisting of α-quartz, α-cristobalite, and β-tridymite.
Patent Literature 1: JP 2002-187768 A
At the time of firing of a glass-ceramic composite material (hereinafter also referred to as a “glass ceramic material”), densification proceeds due to viscous flow of the glass while the maximum temperature is retained. When a certain amount of materials subjected to firing is introduced into a firing furnace, variation will occur in the time taken to reach the maximum temperature among the materials subjected to firing. This requires adjustment for extension of the retention time so that a material subjected to firing which is behind in reaching the maximum temperature will be sufficiently densified.
However, when the retention time at the maximum temperature is extended at the time of firing, pores will be generated due to gasification of a carbon component remaining in a trace amount at a more quickly densified portion. When the pores are enclosed in a sintered product obtained after firing, the pores will not be discharged to the outside but will remain as voids. This causes problems in the resulting sintered product such as low density and poor insulation. In particular, a glass ceramic material containing a large amount of SiO2 component as in Patent Literature 1 has a relatively high glass viscosity at the maximum temperature at the time of firing. This requires extension of the retention time at the maximum temperature at the time of firing, which accentuates the problems described above.
The present invention is made to solve the above problems. The present invention aims to provide a glass ceramic material capable of producing a dense sintered product even when the retention time at the maximum temperature is extended at the time of firing; a laminate including a stack of multiple glass ceramic layers made of a sintered product of the glass ceramic material; and an electronic component including the laminate.
The glass ceramic material of the present invention contains: glass containing SiO2, B2O3, and M2O, where M is an alkali metal; filler containing quartz; and at least one metal oxide selected from the group consisting of MnO, NiO, CuO, and ZnO, wherein an amount of the metal oxide is 0.05 parts by weight to 2 parts by weight relative to a total 100 parts by weight of the glass and the filler.
The laminate of the present invention includes a stack of multiple glass ceramic layers made of a sintered product of the glass ceramic material.
The electronic component of the present invention includes the laminate.
The present invention can provide a glass ceramic material capable of producing a dense sintered product even when the retention time at the maximum temperature is extended at the time of firing; a laminate including a stack of multiple glass ceramic layers made of a sintered product of the glass ceramic material; and an electronic component including the laminate.
Hereinafter, the glass ceramic material, the laminate, and the electronic component of the present invention are described. The present invention is not limited to the following preferred embodiments, and may be suitably modified without departing from the gist of the present invention. Combinations of two or more preferred features described in the following preferred embodiments are also within the scope of the present invention.
The glass ceramic material of the present invention is a low temperature co-fired ceramic (LTCC) material. Herein, the term “low temperature co-fired ceramic material” refers to a glass ceramic material capable of being sintered at a firing temperature of 1000° C. or lower.
The glass ceramic material of the present invention contains glass containing SiO2, B2O3, and M2O, where M is an alkali metal; filler containing quartz; and at least one metal oxide selected from the group consisting of MnO, NiO, CuO, and ZnO, wherein an amount of the metal oxide is 0.05 parts by weight to 2 parts by weight relative to a total 100 parts by weight of the glass and the filler.
Since the glass ceramic material of the present invention contains a specific amount of the metal oxide, densification proceeds uniformly even when the retention time at the maximum temperature is extended at the time of firing. Thus, a dense sintered product can be obtained.
In the glass ceramic material of the present invention, the glass contains SiO2, B2O3, and M2O, where M is an alkali metal.
SiO2 in the glass contributes to a decrease in dielectric constant when the glass ceramic material is fired. This, as a result, reduces or prevents stray capacitance associated with an increase in frequency of electric signals, for example.
B2O3 in the glass contributes to a decrease in glass viscosity. Thus, a sintered product of the glass ceramic material is rendered dense.
M2O in the glass contributes to a decrease in glass viscosity. Thus, a sintered product of the glass ceramic material is rendered dense. M2O is not limited as long as it is an alkali metal oxide but is preferably Li2O, K2O, or Na2O, more preferably K2O. One type of M2O may be used, or several types thereof may be used.
The amount of SiO2 in the glass is preferably 65 wt % to 90 wt % in terms of oxide. The amount is more preferably 70 wt % to 85 wt %.
The amount of B2O3 in the glass is preferably 5 wt % to 30 wt % in terms of oxide. The amount is more preferably 10 wt % to 25 wt %.
The amount of M2O in the glass is preferably 1 wt % to 5 wt % in terms of oxide. The amount is more preferably 1.5 wt % to 4.5 wt %. When several alkali metal oxides are used as M2O, the total amount thereof is regarded as the amount of M2O.
The glass may further contain Al2O3. Al2O3 in the glass contributes to an improvement in chemical stability of the glass.
When the glass contains Al2O3, the amount of Al2O3 in the glass is preferably 0.1 wt % to 2 wt % in terms of oxide. The amount is more preferably 0.5 wt % to 1 wt %.
The glass may further contain an alkaline earth metal oxide such as CaO. However, from a viewpoint of reducing the dielectric constant and dielectric loss by increasing the amount of SiO2 in the glass, preferably, the glass contains no alkaline earth metal oxide. Even when the glass contains an alkaline earth metal oxide, the amount thereof in the glass is preferably less than 15 wt %, more preferably less than 5 wt %, still more preferably less than 1 wt %.
The glass may contain impurities in addition to the above components. The amount of impurities in the glass is preferably less than 5 wt %, more preferably less than 1 wt %.
In the glass ceramic material of the present invention, the filler contains quartz. The filler contributes to an improvement in mechanical strength when the glass ceramic material is fired. Herein, the term “filler” refers to an inorganic additive not contained in the glass.
The quartz in the filler contributes to an increase in thermal expansion coefficient when the glass ceramic material is fired. While the glass has a thermal expansion coefficient of about 6 ppm/K, the quartz has a thermal expansion coefficient of about 15 ppm/K. Thus, the presence of the quartz in the glass ceramic material results in a high thermal expansion coefficient when the glass ceramic material is fired. Thus, compressive stress is generated during cooling after firing, which increases the mechanical strength (e.g., bending strength) and which also increases the reliability at the time of mounting of the laminate onto a board (e.g., a resin board).
The filler may contain only quartz but may further contain SiO2 other than quartz. The filler may further contain Al2O3 and/or ZrO2.
The presence of Al2O3 and ZrO2 as the filler in the glass ceramic material prevents precipitation of cristobalite crystals when the glass ceramic material is fired. Cristobalite crystals, which are a type of SiO2 crystals, undergo a phase transition at about 280° C. Thus, precipitation of cristobalite crystals during firing of the glass ceramic material will significantly change the volume of the glass ceramic material in a high temperature environment, decreasing the reliability. Al2O3 and ZrO2 in the filler also contribute to a decrease in dielectric loss, an increase in thermal expansion coefficient, and an increase in mechanical strength when the glass ceramic material is fired.
When the filler contains Al2O3 and Zr2, the amount of each is preferably 1 wt % to 5 wt %.
More preferably, the filler contains only quartz.
Preferably, the glass ceramic material of the present invention contains the glass in an amount of 50 parts by weight to 90 parts by weight and the filler in an amount of parts by weight to 50 parts by weight relative to a total 100 parts by weight of the glass and the filler. More preferably, the amount of the glass is 60 parts by weight to parts by weight, and the amount of the filler is 20 parts by weight to 40 parts by weight.
The glass ceramic material of the present invention contains at least one metal oxide selected from the group consisting of MnO, NiO, CuO, and ZnO, and the metal oxide is contained in an amount of 0.05 parts by weight to 2 parts by weight relative to a total 100 parts by weight of the glass and the filler. When several metal oxides are used, the total of all the metal oxides used is adjusted to 0.05 parts by weight to 2 parts by weight relative to a total 100 parts by weight of the glass and the filler.
A dense sintered product having a high relative density can be obtained even when the firing time is extended, owing to the presence of the metal oxide(s) in an amount in the above range in the glass ceramic material of the present invention. Such a sintered product is excellent in terms of dielectric constant and Q factor (reciprocal of dielectric loss). The metal oxide is preferably CuO.
As described above, densification of the glass ceramic material of the present invention proceeds uniformly even when the firing time is extended, so that a dense sintered product can be obtained. The glass and the filler in a sintered product of the glass ceramic material can be discriminated from each other by analyzing electron diffraction patterns under a transmission electron microscope (TEM).
The actual compositional makeup of a sintered product of the glass ceramic material (described later) may be used as the compositional makeup of the glass ceramic material of the present invention. For example, a glass ceramic material containing a large amount of SiO2 component as in Patent Literature 1 has a relatively high glass viscosity at the maximum temperature at the time of firing as described above. Thus, precipitation of crystals from the glass, for example, is less likely to occur during firing. In this case, there is no problem in considering that the compositional makeup of the glass ceramic material of the present invention is substantially the same as the compositional makeup of a sintered product of the glass ceramic material.
The laminate of the present invention includes a stack of multiple glass ceramic layers made of a sintered product of the glass ceramic material of the present invention. The multiple glass ceramic layers may each have the same compositional makeup or a different compositional makeup, but preferably, these glass ceramic layers have the same compositional makeup.
The relative density of the laminate is preferably 90% or more, more preferably 95% or more. The relative density is the quotient of the apparent density determined by the Archimedes method divided by the true density. The true density is the density of powder obtained by grinding the laminate. The apparent density is the density including voids. The volume ratio of voids in the laminate can be calculated by dividing the apparent density by the true density. When the relative density is 100%, it means that the laminate includes no voids.
The dielectric constant of the laminate is preferably 4.5 or less. The dielectric constant is measured at 3 GHz by the perturbation method.
Q factor which is the reciprocal of the dielectric loss of the laminate is preferably 250 or more. Q factor is calculated as the reciprocal of the dielectric loss at 3 GHz by the perturbation method.
The laminate of the present invention may further include a conductor layer. The conductor layer is disposed between the glass ceramic layers adjacent to each other in a stacking direction and/or on a surface of the glass ceramic layer.
The laminate of the present invention may further include a via conductor. The via conductor is disposed to penetrate the glass ceramic layer.
The conductor layer and the via conductor can be formed by screen printing, photolithography, or the like using a conductive paste containing Ag or Cu.
The laminate 1 may include conductor layers 9, 10, and 11 and via conductors 12. For example, these conductor layers and via conductors may define passive elements such as capacitors and inductors or may define connecting wires for electric connection between elements.
Preferably, the conductor layers 9, 10, and 11 and the via conductors 12 each contain Ag or Cu as a main component. Use of such a low-resistance metal prevents the occurrence of signal propagation delay associated with an increase in frequency of electric signals. The glass ceramic layers 3 are made of the glass ceramic material of the present invention, i.e., a low temperature co-fired ceramic material, and thus can be co-fired with Ag or Cu.
The conductor layers 9 are inside the laminate 1. Specifically, each conductor layer 9 is between two glass ceramic layers 3 adjacent to each other in the stacking direction.
The conductor layers 10 are on one of main surfaces of the laminate 1.
The conductor layers 11 are on the other main surface of the laminate 1.
Each via conductor 12 is disposed to penetrate the glass ceramic layer 3 and plays a role in electrically connecting the conductor layers 9 at different levels to each other, electrically connecting the conductor layers 9 and 10 to each other, or electrically connecting the conductor layers 9 and 11 to each other.
A multilayer ceramic substrate, which is as an example of the laminate of the present invention, is produced as described below, for example.
The glass ceramic material of the present invention is prepared by mixing glass, filler, and a metal oxide at a predetermined compositional makeup.
The glass ceramic material of the present invention is mixed with a binder, a plasticizer, and the like to prepare a ceramic slurry. Then, the ceramic slurry is applied to a base film (e.g., a polyethylene terephthalate (PET) film) and dried, whereby a green sheet is produced.
The green sheets are stacked to produce unfired laminated green sheets. The laminated green sheets may include conductor layers and via conductors formed therein.
The laminated green sheets are fired. As a result, the laminate (multilayer ceramic substrate) 1 shown in
The firing temperature of the laminated green sheets is not limited as long as it is a temperature at which the glass ceramic material of the present invention defining the green sheets can be sintered. For example, the firing temperature may be 1000° C. or lower.
The firing atmosphere of the laminated green sheets is not limited. Yet, when the conductor layers and the via conductors are made of a material resistant to oxidation, such as Ag, an air atmosphere is preferred; while when the conductor layers and the via conductors are made of a material prone to oxidation, such as Cu, a hypoxic atmosphere such as a nitrogen atmosphere is preferred. The firing atmosphere of the laminated green sheets may be a reducing atmosphere.
The laminated green sheets may be fired in a state of being sandwiched by restraint green sheets. The restraint green sheets contain, as a main component, an inorganic material (e.g., Al2O3)that is not substantially sintered at a sintering temperature of the glass ceramic material of the present invention defining the green sheets. Thus, the restraint green sheets do not shrink at the time of firing of the laminated green sheets but act to reduce or prevent shrinkage in the main surface direction of the laminated green sheets. This, as a result, improves the dimensional accuracy of the resulting laminate 1 (in particular, the conductor layers 9, 10, and 11, and the via conductors 12).
When the laminate of the present invention includes conductor layers, preferably, the main component of the conductor layers is Cu, and the metal oxide in the glass ceramic layer includes at least CuO.
In the case of conventional laminated green sheets, when the main component of the conductor layers is Cu, diffusion of Cu occurs from the conductor layers to the laminated green sheets at the time of firing, resulting in non-uniform and slow sintering. Presumedly, such problems occur because the amount of Cu diffused is large at portions near the conductor layers so that sintering proceeds slowly there, while the amount of Cu diffused at portions away from the conductor layers is small so that sintering proceeds quickly there. In contrast, in the case of laminated green sheets produced by adding CuO as a metal oxide to a glass ceramic material, presumably, non-uniform sintering is unlikely to occur because CuO is already diffused in the laminated green sheets before firing.
Herein, that the main component of the conductor layers is Cu means that at least 90 vol % of the conductor layers is made of Cu. Preferably, the conductor layers are made of a mixture of Cu, glass, and an aluminum oxide. The glass for use in forming the conductor layers can be the same as the glass in the glass ceramic material of the present invention, for example.
That the metal oxide includes at least CuO means that the metal oxide includes only CuO or that the metal oxide includes CuO and one or more additional metal oxides other than CuO. More preferably, the metal oxide includes only CuO.
When the laminate of the present invention includes via conductors, preferably, the main component of the via conductors is Cu, and the metal oxide in the glass ceramic layer includes at least CuO.
The electronic component of the present invention includes the laminate of the present invention.
The electronic component of the present invention includes, for example, a multilayer ceramic substrate, which is an example of the laminate of the present invention, and a chip component mounted on the multilayer ceramic substrate. Examples of the chip component include LC filters, capacitors, and inductors.
The electronic component 2 may be mounted on a mounting board (e.g., motherboard) in an electrically connected manner via the conductor layers 11.
An example has been described in which the laminate of the present invention is used as a multilayer ceramic substrate, but the laminate of the present invention may also be used as a chip component to be mounted on a multilayer ceramic substrate. In other words, the laminate of the present invention may be used as an LC filter, a capacitor, an inductor, or the like. For example, when the laminate of the present invention is used as a capacitor, the laminate includes a conductor layer between the glass ceramic layers adjacent to each other in the stacking direction.
The laminate of the present invention may be used as a product other than the multilayer ceramic substrate and the chip component.
Hereinafter, examples that more specifically disclose the present invention are described. The present invention is not limited to these examples.
Frit powders G1 to G4 each having a compositional makeup shown in Table 1 were mixed and placed in a crucible made of Pt and melted in an air atmosphere at 1600° C. for 30 minutes or longer. Subsequently, the resulting molten product was quenched to obtain cullet. Here, a carbonate was used as a raw material of K2O (an alkali metal oxide) in Table 1. In Table 1, the amount of K2O indicates the percentage of the carbonate in terms of oxide. The cullet was coarsely ground and then placed in a container together with ethanol and PSZ balls (diameter: 5 mm) and mixed in a ball mill. When mixing in the ball mill, the grinding time was adjusted, whereby a glass powder having a median particle size of 1 μm was obtained. Here, the term “median particle size” refers to the median particle size D50 determined by the laser diffraction scattering method.
A glass powder, a quartz powder as filler, and a metal oxide were placed in ethanol and mixed in a ball mill according to the compositional makeup shown in Table 2, whereby a glass ceramic material was prepared. The quartz powder and the metal oxide each had a median particle size of 1 μm.
The glass ceramic material prepared above, a solution of polyvinyl butyral in ethanol as a binder solution, and a dioctyl phthalate (DOP) solution as a plasticizer were mixed, whereby a ceramic slurry was prepared. Then, the ceramic slurry was applied to a polyethylene terephthalate film using a doctor blade and dried at 40° C., whereby green sheets S1 to S29 each having a thickness of 50 μm were produced.
Each of the green sheets S1 to S29 was cut into 50-mm square pieces, and 20 of these pieces of the same type were stacked, placed in a mold, and subjected to compression bonding using a pressing machine. The resulting laminated green sheets were fired in an air atmosphere at 900° C. for 30 to 180 minutes. The firing time is as shown in Table 2. After firing, the apparent density of the resulting laminate was determined by the Archimedes method, and the dielectric constant at 3 GHz and Q factor (reciprocal of dielectric loss) thereof were determined by the perturbation method. Subsequently, the laminate was ground, and the true density of the powder was determined.
The relative density as the quotient of the apparent density determined by the Archimedes method divided by the true density was calculated in percent as shown in the following formula.
(Apparent density)/(true density)×100=relative density (%)
Table 2 shows the evaluation results.
The laminate was determined as being dense when the relative density was 95% or more. The laminate was determined as having a low dielectric constant when the dielectric constant was 4.5 or less and was determined as having a low dielectric loss when the Q factor was 250 or more.
The laminates of Examples 1 to 14 each had a relative density of 95% or more, a dielectric constant of 4.5 or less, and a Q factor of 250 or more.
Among the laminates of Comparative Examples 1 to 3 in which no metal oxide such as MnO was used, the laminate in Comparative Example 1 with a short firing time had an appropriate relative density, an appropriate dielectric constant, and an appropriate Q factor, while the laminates in Comparative Examples 2 and 3 with a firing time of 120 minutes or longer each had a relative density of 90% or less. The Q factor was also low in Comparative Example 3.
The laminates of Comparative Examples 4 to 7 each had a low Q factor, with the amount of the metal oxide being more than 2 parts by weight.
The laminates of Comparative Examples 8 to 15 each had a low relative density, with the amount of the metal oxide being less than 0.05 parts by weight. The Q factor was also low in Comparative Examples 10 and 11.
1 laminate (multilayer ceramic substrate)
2 electronic component
3 glass ceramic layer
9, 10, 11 conductor layer
12 via conductor
13, 14 chip component
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-040275 | Mar 2021 | JP | national |
The present application is a continuation of International application No. PCT/JP2022/009046, filed Mar. 3, 2022, which claims priority to Japanese Patent Application No. 2021-040275, Mar. 12, 2021, the entire contents of each of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/009046 | Mar 2022 | US |
| Child | 18463703 | US |
