JP6835645B2 - Ceramic sintered body and wiring board using it - Google Patents

Description

The present disclosure relates to a ceramic sintered body and a wiring board using the same.

Conventionally, semiconductor devices have been used as active elements for communication in electronic devices such as optical communication and wireless communication. In this case, the wiring board for mounting the semiconductor element for communication is also required to support high frequencies. As a wiring board for meeting such a demand, a wiring board using mullite as an insulating substrate has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2010-93197

However, mullite has problems that the mechanical strength is originally low and the chemical resistance is low depending on the composition of the insulating substrate.

Therefore, it is an object of the present disclosure to provide a ceramic sintered body having high mechanical strength and chemical resistance and excellent high frequency characteristics, and a wiring board using the same.

The ceramic sintered body of the present disclosure has a composite phase of an alumina crystal phase and a mullite crystal phase as a main crystal phase, and contains a canoeite-based crystal phase in the grain boundary of the main crystal phase and the mullite crystal phase.

The wiring board of the present disclosure includes an insulating substrate made of the above-mentioned ceramic sintered body and a conductor layer provided on at least the surface of the insulating substrate.

According to the present invention, it is possible to obtain a ceramic sintered body having high mechanical strength and chemical resistance and excellent high frequency characteristics, and a wiring board using the same.

It is sectional drawing of the ceramic sintered body of this embodiment.

FIG. 1 is a schematic cross-sectional view of the ceramic sintered body of the present embodiment. In the ceramic sintered body of the present embodiment, the alumina crystal phase 1a and the Murite crystal phase 1b are set as the main crystal phase 1, and the grain boundary 3 of the main crystal phase 1 contains the canoeite-based crystal phase 5. Here, the main crystal phase 1 refers to a case where the total ratio of the alumina crystal phase 1a and the mullite crystal phase 1b is 60% by mass or more.

According to the ceramic sintered body of the present embodiment, since the main crystal phase 1 is a composite of the alumina crystal phase 1a and the mullite crystal phase 1b, the alumina crystal phase 1a exists alone in the main crystal phase 1. By including the mullite crystal phase 1b as compared with the case of the above, the relative dielectric constant, which is one of the dielectric characteristics governing the high frequency characteristics, can be lowered.

Further, in this ceramic sintered body, as described above, the main crystal phase 1 is a composite phase in which the alumina crystal phase 1a and the mullite crystal phase 1b coexist, so that the mullite crystal phase 1b is contained in the main crystal phase 1. The mechanical strength can be increased as compared with the case where it exists alone.

That is, this ceramic sintered body is mainly composed of an alumina crystal phase 1a that contributes to mechanical strength and a mullite crystal phase 1b that contributes to a decrease in relative permittivity.

Further, since this ceramic sintered body contains the canoeite-based crystal phase 5 in the grain boundary 3 between the main crystal phases 1, the proportion of glass contained in the grain boundary 3 is reduced, and an amorphous phase such as glass is formed. It is possible to improve the chemical resistance of the grain boundaries 3 as compared with the ceramic sintered body as the main phase. The canoeite-based crystal phase 5 is also partially present in the mullite crystal phase 1b.

Further, in the above-mentioned ceramic sintered body, the average particle size of the alumina crystal phase 1a existing in the mullite crystal phase 1b is preferably 0.8 to 5.5 μm, particularly 0.8 to 3.8 μm. .. Thereby, the various characteristics described above can be balanced and enhanced.

For example, when the ratio of each crystal phase contained in this ceramic sintered body is the ratio shown below, all the characteristics such as mechanical properties, dielectric properties and chemical resistance are balanced to provide insulation for a wiring board described later. It can be useful as a substrate. For example, when the alumina crystal phase 1a is 15 to 82% by mass, the mulite crystal phase 1b is 20 to 82% by mass, and the canoeite crystal phase 5 is 1 to 15% by mass, the mechanical strength (three-point bending strength). Is 232 MPa or more, the relative permittivity at 60 GHz is 8.2 or less, the dielectric loss tangent (tan δ) at the same frequency is 46 × 10 ^-4 or less, and the weight loss rate when the chemical resistance is evaluated is 0.12 mass% or less. A ceramic sintered body can be obtained.

As shown in FIG. 1, such a ceramic sintered body has a structure in which the mullite crystal phase 1b forms a matrix and the alumina crystal phase 1a exists in the mullite crystal phase 1b via the grain boundary 3. Since the alumina crystal phase 1a having a high relative permittivity has a structure structure surrounded by the mullite crystal phase 1b spread in a matrix, an increase in the relative permittivity can be suppressed even if a large amount of the alumina crystal phase 1a is present. Here, the matrix shape refers to a matrix structure having no clear grain boundary.

Further, this ceramic sintered body has a structure in which an alumina crystal phase 1a and a mullite crystal phase 1b, which are crystal phases, are bonded via a canoeite crystal phase 5. That is, since the structure is such that the three types of crystal phases are bonded to each other, the mechanical strength of the ceramic sintered body can be increased.

Therefore, even if the glass phase 7 is present at the grain boundary 3 of the ceramic sintered body, the glass phase 7 is in a state of being separated by the canoeite-based crystal phase 5, so that the glass phase 7 is also in the chemical resistance test. Is less likely to elute, which can improve chemical resistance.

Here, the canoeite-based crystal phase contains manganese, magnesium, and silicon as elements, and has _{a metal oxide represented by (Mn, Mg) 2} (Si ₂ O ₆ ) as a main constituent mineral. That is, the canoeite-based crystal phase in the present embodiment means that the canoeite crystal phase includes a crystal phase in which Mn, Mg, and Si constituting the canoeite have an indefinite ratio composition.

Further, when the ratio of each crystal phase contained in the ceramic sintered body is limited as follows, the mechanical properties can be improved, and the relative permittivity and the dielectric loss tangent can be lowered. In addition, the weight loss rate when the chemical resistance is evaluated can be reduced. For example, if the alumina crystal phase 1a is limited to 31 to 66% by mass, the mulite crystal phase 1b is limited to 30 to 65% by mass, and the canoeite crystal phase 5 is limited to 2 to 10% by mass, the mechanical strength (three-point bending strength) is 327 MPa. As described above, a ceramic having a relative permittivity of 7.9 or less at 60 GHz, a dielectric loss tangent (tan δ) of 28 × 10 ^-4 or less at the same frequency, and a weight loss rate of 0.09 mass% or less when chemical resistance is evaluated. A sintered body can be obtained.

Furthermore, when the proportion of the canoeite-based crystal phase is limited to 2 to 7% by mass, the relative permittivity at 60 GHz is 7 while maintaining the above-mentioned mechanical strength (three-point bending strength) and chemical resistance. The dielectric loss tangent can be 18 × 10 ^-4 or less.

The ceramic sintered body described above has high mechanical strength, excellent dielectric properties in a high frequency region, and high chemical resistance, and thus is suitable as a wiring board for high frequencies. Specifically, when this ceramic sintered body is used as an insulating substrate and a wiring board having a conductor layer is formed on at least the surface of the insulating substrate, in a high frequency region as compared with a general-purpose alumina wiring board. In addition to having high transmission characteristics, it is possible to obtain a circuit board that is comparable to a general-purpose alumina wiring board in terms of metal fittings and airtight sealing.

Next, the ceramic sintered body of the present embodiment was specifically produced and its characteristics were evaluated. First, as raw material powder, alumina powder having a purity of 99.5% by mass and an average particle size of 1.5 μm, Murite powder having a purity of 99% by mass and an average particle size of 2.4 μm, purity of 99.7% by mass, and an average particle size. A 1.5 μm SiO ₂ powder, 99% by mass purity, Mn ₂ O _{3 powder having an average particle size of 1.5 μm, and an MgCO 3} powder having a purity of 99.5 mass% and an average particle size of 5.0 μm were prepared.

Next, each of the above-mentioned raw material powders was mixed so as to have the ratio shown in Table 1. A ball mill was used to mix the raw material powders. Alumina balls were used as the medium.

Next, an organic vehicle (an acrylic binder dissolved in toluene) was added to the mixed powder to prepare a slurry. After that, a green sheet having a thickness of 300 μm was prepared by the doctor blade method.

Next, a predetermined number of the prepared green sheets were laminated and heated under pressure, and then cut into a desired shape to prepare a molded product as a base of the ceramic sintered body. Next, the produced molded product was fired under the following conditions. The calcination was carried out at a temperature of room temperature to 600 ° C. in a nitrogen-hydrogen mixed atmosphere with a dew point of + 30 ° C., and then the dew point was changed to + 20 ° C. and held at 1400 ° C. for 1 hour. The size of the sample of the produced ceramic sintered body was 40 mm in length, 5 mm in width, and 3.6 mm in thickness.

Next, the produced ceramic sintered body was evaluated as follows. The ratio of the alumina crystal phase, the mullite crystal phase, and the canoeite-based crystal phase was determined by crushing the produced ceramic sintered body, performing X-ray diffraction, and performing Rietveld analysis. The number of samples was one. In this case, for those whose crystal structure has an uninflected word of canoeite, those whose lattice constant deviates from the original canoeite are also identified as the canoeite-based crystal phase.

The average particle size of the alumina crystal phase was determined from a photograph of a cross section of the ceramic sintered body. Specifically, a sample cut from the produced ceramic sintered body was embedded in a resin, the cross section was polished, the crystal structure was observed using a scanning electron microscope, and a photograph was taken. ^{Next, the alumina crystal phase existing in the region of about 7,000 μm 2} was extracted from the photographed photograph, the particle size was measured by image analysis, and the average value was obtained. In the image analysis in this case, first, the contours of the individual alumina crystal phases were captured, and the area formed by the contours was once converted into a circle. After that, the diameter was obtained from the circle, the diameter was used as the particle size of the alumina crystal phase, and the average value was obtained from a plurality of samples to obtain the average particle size.

The anti-folding strength was processed by polishing the produced ceramic sintered body so as to have a size of 40 mm in length, 4 mm in width, and 3 mm in thickness. Also. The C surface of the edge of the sample was also processed. Next, the prepared sample was set in an autograph and a three-point bending test was performed at room temperature (25 ° C.). The number of samples was 25, and the average value was calculated.

The dielectric properties were determined by the cavity resonator method. As a sample, a ceramic sintered body was processed to prepare a sample having a length of 50 mm, a width of 50 mm, and a thickness of 0.5 mm. Next, the relative permittivity and the dielectric loss (tan δ) of the prepared sample were measured in the frequency range of 55 to 60 GHz, and the dielectric characteristics near 60 GHz were calculated. The number of samples was three.

For chemical resistance, 5 ceramic sintered bodies with a length of 40 mm, a width of 5 mm, and a thickness of 3.6 mm are prepared, and the weight changes before and after immersion in an aqueous solution of acidic ammonium fluoride having a concentration of 10 g / L for 5 minutes. I asked for it. The calculation method of the mass reduction rate shown in Table 2 is "mass reduction rate = (" mass before immersion of sintered body "-" mass after immersion of sintered body ") /" mass before immersion of sintered body "x 100. ) ”.

As is clear from the results in Table 2, a sample in which the alumina crystal phase is 15 to 82% by mass, the mulite crystal phase is 20 to 82% by mass, and the canoeite crystal phase is 1 to 15% by mass (Sample Nos. 1 to 7). , 9-14, 16 and 18-20), the mechanical strength (three-point bending strength) is 232 MPa or more, the relative permittivity at 60 GHz is 8.2 or less, and the dielectric loss tangent (tan δ) at the same frequency is 46 × 10 ^{−. 4} or less, the weight change rate when the chemical resistance was evaluated was 0.12% by mass or less. In each of these samples, the alumina crystal phase formed a crystal structure surrounded by a mullite crystal phase in which the alumina crystal phase spread in a matrix.

Further, regarding this ceramic sintered body, a sample in which the alumina crystal phase was limited to 31 to 66% by mass, the mullite crystal phase was limited to 30 to 65% by mass, and the canoeite crystal phase was limited to 2 to 10% by mass (Sample Nos. 3 to 5). , 9, 12, 13 and 18-20), the mechanical strength (three-point bending strength) is 327 MPa or more, the relative permittivity at 60 GHz is 7.9 or less, and the dielectric loss tangent (tan δ) at the same frequency is 28 × 10 ^{−. 4} or less, the weight change rate when the chemical resistance was evaluated was 0.09% by mass or less.

Further, in the samples (Sample Nos. 3 to 5, 9, 13 and 18 to 20) in which the ratio of the canoeite crystal phase was limited to 2 to 7% by mass, the mechanical strength (three-point bending strength) was 327 MPa or more and the resistance was The relative permittivity at 60 GHz was 7.8 or less, and the dielectric loss tangent was 18 × 10 ^-4 or less, while the weight change rate when the chemical properties were evaluated was maintained at 0.09 mass% or less.

On the other hand, the samples containing no mullite crystal phase or no canoeite crystal phase (samples Nos. 8, 15 and 17) had a relative permittivity of 9.3 at 60 GHz and were evaluated for chemical resistance. The rate of change in weight was 0.16% by mass or more.

1 ... Main crystal phase 1a ... Alumina crystal phase 1b ... Murite crystal phase 3 ... Grain boundary 5 ... Kanoite-based crystal phase 7 ... Glass phase

Claims (4)

A ceramic sintered body in which a composite phase of an alumina crystal phase and a mullite crystal phase is used as a main crystal phase, and a canoeite-based crystal phase is contained in the grain boundary of the main crystal phase and the mullite crystal phase. The ceramic sintered body according to claim 1, wherein the alumina crystal phase is 31 to 66% by mass, the mullite crystal phase is 30 to 65% by mass, and the canoeite crystal phase is 2 to 10% by mass. The ceramic sintered body according to claim 1 or 2, wherein the alumina crystal phase is surrounded by the mullite crystal phase spread in a matrix. A wiring board comprising an insulating substrate made of the ceramic sintered body according to any one of claims 1 to 3 and a conductor layer provided on at least the surface of the insulating substrate.

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