Patent Application
20240336532
The disclosed embodiment relates to a ceramic sintered body, a ceramic substrate, a mounting substrate, an electronic device, and a method for manufacturing a ceramic sintered body.
In the known art, since a ceramic substrate using a ceramic sintered body as a substrate has excellent insulation properties and thermal conductivity, the ceramic substrate may be used as a mounting substrate for mounting an electronic component. For example, Patent Document 1 discloses a ceramic substrate containing Al2O3 (alumina) as a main component and TiO2 (titanium oxide) as an additive. Cited Document 1 also describes that an Al2O3 powder having a particle size from 120 nm to 500 nm is used and that the powder has a particle size of 1 μm or less.
Patent Document 2 describes a mounting substrate in which a copper plate and an alumina substrate in contact with each other are heated in an inert atmosphere to dispose the copper plate on the alumina substrate. The method disclosed in Patent Document 2 is referred to as an active metal bonding (AMB) method. In addition, Patent Document 3 describes a mounting substrate prepared using a direct bonding method of ceramic and copper. The method disclosed in Patent Document 3 is referred to as a direct copper bonding (DCB) method. Cited Document 4 describes a method of manufacturing a circuit board in which a metal plate including copper or a copper alloy is bonded to a surface of a substrate made of alumina or the like using a hot pressing process.
Patent Document 1: JP 2017-218368 A
Patent Document 2: JP S63-166774 A
Patent Document 3: JP H5-243725 A
Patent Document 4: JP 2020-145335 A
In an aspect of an embodiment, a ceramic sintered body contains Al2O3 (alumina) and an additive, in which a content of Al2O3 is 94 mass % or greater. The additive contains SiO2 (silica), CaO (calcia), MgO (magnesia), TiO2 (titanium oxide), and Fe2O3 (iron oxide). In the ceramic sintered body, a content of Ti (titanium) in terms of TiO2 is 120 ppm or greater, and a content of Fe (iron) in terms of Fe2O3 is 180 ppm or greater.
Hereinafter, embodiments of a ceramic sintered body, a ceramic substrate, a mounting substrate, an electronic device, and a method for manufacturing a ceramic sintered body disclosed in the present application will be described with reference to the accompanying drawings. The present disclosure is not limited by the following embodiments. Note that the drawings are schematic and that the dimensional relationships between elements, the proportions of the elements, and the like may differ from the actual ones. There may be differences between the drawings in terms of dimensional relationships, proportions, and the like.
In the embodiments described below, expressions such as “constant”, “orthogonal”, “perpendicular”, and “parallel” may be used, but these expressions do not mean exactly “constant”, “orthogonal”, “perpendicular”, and “parallel”. In other words, it is assumed that the above expressions allow deviations in manufacturing accuracy, installation accuracy, or the like.
The ceramic substrate 2 is a plate-shaped member including a ceramic sintered body containing Al2O3 (alumina) and additives and having an Al2O3 content of 94 mass % or greater, and having a thickness of, for example, about from 0.2 to 1 mm. The additive contains SiO2 (silica), CaO (calcia), MgO (magnesia), TiO2 (titanium oxide), and Fe2O3 (iron oxide).
For the ceramic substrate 2 according to the embodiment, in the ceramic sintered body, a content of Ti (titanium) in terms of TiO2 is 120 ppm or greater, and a content of Fe (iron) in terms of Fe2O3 is 180 ppm or greater. Thus, when using the ceramic sintered body according to the embodiment, the ceramic substrate 2 has high mechanical strength. According to the embodiment, the ceramic sintered body has excellent thermal shock resistance.
In the ceramic sintered body, the content of Ti in terms of TiO2 and the content of Fe in terms of Fe2O3 can be determined by, for example, the following method. First, quantitative analysis of Ti and Fe in the ceramic sintered body is performed using an ICP emission spectrophotometer (ICP). Then, the content (ICP content) in terms of TiO2 as an oxide is determined from the content of Ti measured by ICP, and the content (ICP content) in terms of Fe2O3 as an oxide is determined from the content of Fe measured by ICP.
When using the ceramic sintered body according to the embodiment, the reason why the ceramic substrate 2 can improve the mechanical strength is considered as follows, for example. That is, when TiO2 is contained in the ceramic sintered body constituting the ceramic substrate 2, TiO2 is located at a crystal grain boundary of the ceramic sintered body. When the content of TiO2 in the ceramic sintered body is 120 ppm or greater, TiO2 located at the crystal grain boundary of the ceramic sintered body functions as a resistor that suppresses the progress of a crack that is likely to occur at the crystal grain boundary. Since TiO2 located at the crystal grain boundary of the ceramic sintered body serves as a crystal nucleus for a sintering aid component (for example, SiO2, CaO, and MgO), it is possible to polycrystallize and toughen the crystal grain boundary, and it is possible to suppress occurrence of a crack. Therefore, when the ceramic sintered body contains TiO2 at a suitable content, the mechanical strength of the ceramic substrate 2 can be improved.
When the ceramic sintered body constituting the ceramic substrate 2 contains Fe2O3, Fe2O3 is located at the crystal grain boundary of the ceramic sintered body. When the content of Fe2O3 in the ceramic sintered body is 180 ppm or greater, Fe2O3 located at the crystal grain boundary of the ceramic sintered body causes a phenomenon of moving the crystal grain boundary and moving TiO2 located at the crystal grain boundary. Therefore, when the ceramic sintered body contains Fe2O3 at a suitable content, the crystal grain boundaries and TiO2 can be suitably dispersed. The mechanical strength of the ceramic substrate 2 is improved as the crystal grain boundary and the dispersion of TiO2 proceed. Therefore, according to the ceramic substrate 2 of the embodiment, the mechanical strength of the ceramic substrate 2 can be improved.
For the ceramic sintered body constituting the ceramic substrate 2 according to the embodiment, the ceramic sintered body may contain 96 mass % or greater and 98 mass % or less of Al2O3. When the content of Al2O3 is less than 96 mass %, the proportion of sintering aid components (for example, SiO2, CaO, and MgO) in the ceramic sintered body increases, and therefore, sintering between aluminum oxides (Al2O3) as the main component may become insufficient. When the content of Al2O3 is greater than 98 mass %, the crystal of Al2O3 is hardly densified, and therefore, the mechanical strength of the ceramic substrate 2 may be reduced.
In the ceramic sintered body constituting the ceramic substrate 2 according to the embodiment, the content of Ti in terms of TiO2 is preferably 350 ppm or less. When the content of TiO2 is greater than 350 ppm, the distribution of TiO2 located at the crystal grain boundary of the ceramic sintered body is biased, and therefore, the mechanical strength of the ceramic substrate 2 may be reduced.
In the ceramic sintered body constituting the ceramic substrate 2 according to the embodiment, the content of Fe in terms of Fe2O3 is preferably greater than the content of Ti in terms of TiO2. When the content of TiO2 is greater than the content of Fe, the distribution of TiO2 located at the crystal grain boundary of the ceramic sintered body is biased, and therefore, the mechanical strength of the ceramic substrate 2 may be reduced. The content of Fe in terms of Fe2O3 in the ceramic sintered body constituting the ceramic substrate 2 is preferably 410 ppm or less.
For the ceramic sintered body constituting the ceramic substrate 2 according to the embodiment, the ceramic sintered body does not contain ZrO2 (zirconia). ZrO2 (zirconia) is relatively expensive. Thus, since the ceramic sintered body does not contain ZrO2, the raw material cost can be suppressed.
In addition, since ZrO2 is not contained in the ceramic substrate 2 according to the embodiment, thermal conductivity can be improved and a dielectric loss can be reduced. For example, in the ceramic substrate containing ZrO2 at a ratio of Al2O3: ZrO2 (including Y2O3 (yttria))=90:10, the thermal conductivity is 23 W/m·K, and the dielectric loss at 1 MHz is 2×10−4. On the other hand, in the ceramic substrate 2 according to the embodiment, for example, the thermal conductivity is 25 W/m·K, and the dielectric loss at 1 MHz is 0.4×10−4. According to the ceramic substrate 2 of the embodiment, effective characteristic values are obtained also from the viewpoint of the thermal conductivity and the dielectric loss.
In the ceramic sintered body constituting the ceramic substrate 2 according to the embodiment, TiO2 and Fe2O3 are located at the crystal grain boundary. The positions of TiO2 and Fe2O3 in the ceramic sintered body can be determined by, for example, observing the surface of the ceramic substrate 2 using a scanning electron microscope (SEM) or an energy dispersive X-ray analyzer (EDX) attached to a transmission electron microscope (TEM).
The observation by TEM and EDX was performed at a magnification of 500000 times. In the TEM photograph of
The EDX image of
From the TEM photograph of
When TiO2 and Fe2O3 are located at the crystal grain boundary of the ceramic sintered body as described above, the occurrence and progress of cracks at the crystal grain boundary can be suppressed. Therefore, according to the ceramic substrate 2 of the embodiment, the mechanical strength can be further improved.
Next, a configuration of an electronic device 10 including the above-described mounting substrate 1 will be described with reference to
As illustrated in
As the electronic component 4, for example, a semiconductor element such as a light emitting diode (LED) element, an insulated gate bipolar transistor (IGBT) element, an intelligent power module (IPM) element, a metal oxide film field-effect transistor (MOSFET) element, a freewheeling diode (FWD) element, a giant transistor (GTR) element, or a Schottky barrier diode (SBD), or a heating element such as a sublimation type thermal printer head element, a thermal ink jet printer head element, or a Peltier element can be used.
Next, a method of manufacturing the ceramic substrate 2 will be described, which is included in the mounting substrate 1 according to the embodiment.
An Al2O3 (aluminum) powder is prepared as a main raw material. As additives, powders of SiO2 (silica), CaO (calcia), MgO (magnesia), TiO2 (titanium oxide), and Fe2O3 (iron oxide) are prepared.
First, a powder of Al2O3 and a powder of an additive are blended such that the content of Al2O3 is 94 mass % or greater to produce a blended powder. A blending composition at this time is as follows. Al contained in the ceramic substrate 2 is 94 mass % or greater in terms of Al2O3. The sum of values obtained by converting Si into SiO2, Ca into CaO, Mg into MgO, Ti into TiO2, and Fe into Fe2O3 (i.e., the additive contained in the ceramic substrate 2) is 1.0 mass % or greater and 6.0 mass % or less. A mass ratio of SiO2 in the additive is, for example, 38 mass % or greater and 60 mass % or less. A mass ratio of CaO in the additive is, for example, 20 mass % or greater and 43 mass % or less. A mass ratio of MgO in the additive is, for example, 14 mass % or greater and 37 mass % or less. A content of Fe contained as an impurity in the powder of Al2O3 in terms of Fe2O3 is from 100 to 300 ppm.
It is preferable that, in the additive, a content (blended content) of Ti in terms of TiO2 be 0.48 mass % or greater and 1.18 mass % or less, and a content (blended content) of Fe in terms of Fe2O3 be 0.48 mass % or greater.
Next, a solvent and a binder are added to a blended powder produced by blending the powder of Al2O3 and the powder of the additive, and then they are mixed and pulverized by, for example, a ball mill or the like to prepare a slurry.
Next, the slurry is spray-dried using a spray dryer to produce granules.
Thereafter, the granules are molded by a press molding method, a roll compaction molding method, or the like to prepare a molded body having a desired shape. Instead of preparing granules, a slurry may be molded by a doctor blade method to prepare a sheet-shaped molded body. In addition, a cut-out, a hole, a recess, or the like may be formed in the prepared molded body by a drill, a laser, or the like as necessary.
Next, the molded body is subjected to heat treatment to perform degreasing, and then the molded body is fired. The firing temperature is, for example, in a range of 1500° C. or higher and 1600° C. or lower. The composition after firing is the same as the blended composition except for TiO2 and Fe2O3. The ceramic sintered body produced by firing the molded body may be subjected to polishing, grinding, drilling, laser processing, blasting, or the like as necessary. As described above, the ceramic substrate 2 is produced using the ceramic sintered body according to the embodiment.
Hereinafter, examples of the ceramic substrate 2 according to the embodiment will be specifically described.
A ceramic sintered body (Samples Nos. 3 to 8) of Example 1 was prepared as follows. A powder of Al2O3 and a powder of the additive were blended such that the contents (mass %) of Al2O3 and the additive contained in the ceramic sintered body were the contents shown in Table 1 to prepare a blended powder. Next, after a solvent and a binder were added to the blended powder, granules were prepared through a slurry, and the granules were reshaped as desired by press molding to prepare a molded body. Thereafter, the binder component was removed by degreasing, and then the molded body was fired to produce a ceramic sintered body (Samples Nos. 3 to 8).
Next, the content of the metal element (Ti, Fe) in the produced ceramic sintered body was measured by ICP, and the content (ICP content) in terms of oxide (TiO2, Fe2O3) was determined. The resulting value of each ICP content is shown in Table 1.
In the ICP contents shown in Table 1, the underlined numerical values of the ICP contents are values estimated using an approximate function indicating a relationship between a blended content (that is, in the additive, a content of Ti in terms of TiO2 and a content of Fe in terms of Fe2O3) and an ICP content.
Samples of the produced ceramic sintered bodies were each processed into a test piece of 3 mm×4 mm×40 mm (hereinafter also referred to as “JIS piece”). The JIS piece was prepared by a press molding method. Using this JIS piece, a three-point bending strength test and a thermal shock resistance test were performed. The results of the thermal shock resistance test will be described below.
The three-point bending strength of each sample was measured in accordance with JIS R 1601-2008. A crosshead speed used for measuring the three-point bending strength was 0.5 mm/min. The obtained results of the three-point bending strength test are as shown in Table 1. The thermal shock resistance test was performed in accordance with JIS R 1648-2002. The crosshead speed in the thermal shock resistance test was also 0.5 mm/min.
A ceramic sintered body of Comparative Example 1 (Sample No. 1) was prepared under the same conditions as in Example 1 except that the powder of TiO2 was not blended as an additive to the powder of Al2O3.
The ICP content for a metal element (Ti, Fe) in the produced ceramic sintered body was measured and estimated in the same manner as described above. The resulting value of each ICP content is shown in Table 1. In Table 1, the ICP content of TiO2 in the ceramic sintered body is not 0. This is because the powder of Al2O3 to be blended contains TiO2 as an impurity.
The produced ceramic sintered body was subjected to the same three-point bending strength test as in Example 1. The result of the three-point bending strength test is as shown in Table 1.
A ceramic sintered body of Comparative Example 2 (Sample No. 2) was prepared under the same conditions as in Example 1 except that the powder of Fe2O3 was not blended as an additive to the powder of Al2O3.
The ICP content for a metal element (Ti, Fe) in the produced ceramic sintered body was measured and estimated in the same manner as in Example 1. The resulting value of each ICP content is shown in Table 1. In Table 1, the ICP content of Fe2O3 in the ceramic sintered body is not 0. This is because the Al2O3 powder to be blended contains Fe2O3 as an impurity.
The produced ceramic sintered body was subjected to the same three-point bending strength test as in Example 1. The result of the three-point bending strength test is as shown in Table 1.
In Samples Nos. 1 and 2 in which the powder of TiO2 or the powder of Fe2O3 was not added as an additive to the powder of Al2O3, the three-point bending strength was less than 490 MPa. On the other hand, in Samples Nos. 3 to 8, which are the ceramic sintered bodies of Example 1, the three-point bending strength was 490 MPa or greater.
From the above results, it is preferable that, in the ceramic sintered body, the content of Ti (titanium) in terms of TiO2 be 120 ppm or greater, and the content of Fe (iron) in terms of Fe2O3 be 180 ppm or greater.
A ceramic sintered body (Samples Nos. 9 to 12) was prepared by changing the contents (mass %) of Al2O3 and the additive. The conditions were the same as in Example 1 except that the contents (mass %) of Al2O3 and the additive contained in the ceramic sintered body were changed to the contents shown in Table 2. Samples Nos. 9, 10, and 12 are the same as Samples Nos. 7, 5, and 8, respectively.
The same measurement and estimation of the ICP content as in Example 1 and the same three-point bending strength test as in Example 1 were performed. The resulting value of each ICP content is shown in Table 2. The obtained results of the three-point bending strength test are as shown in Table 2.
Samples Nos. 10 and 11 in which the content of Al2O3 was 96 mass % or greater and 98 mass % or less had higher three-point bending strength than Sample No. 9 in which the content of Al2O3 was less than 96 mass % and Sample No. 12 in which the content of Al2O3 was greater than 98 mass %.
From the above results, for the ceramic sintered body constituting the ceramic substrate 2 according to the embodiment, the ceramic sintered body preferably contains 96 mass % or greater and 98 mass % or less of Al2O3.
Samples Nos. 10 to 12 in which the ICP content of TiO2 was 350 ppm or less had higher three-point bending strength than Sample No. 9 in which the ICP content of TiO2 was greater than 350 ppm.
From the above results, in the ceramic sintered body constituting the ceramic substrate 2 according to the embodiment, the content of Ti in terms of TiO2 is preferably 350 ppm or less.
A ceramic sintered body (Samples Nos. 13 and 14) was prepared by changing the content of Fe in terms of Fe2O3 and the content of Ti in terms of TiO2 in the ceramic sintered body. The conditions were the same as in Example 1 except that the content of Fe in terms of Fe2O3 and the content of Ti in terms of TiO2 in the ceramic sintered body were changed to the ICP contents shown in Table 3, and the contents (mass %) of Al2O3 and the additive contained in the ceramic sintered body were changed to the contents shown in Table 3.
The ICP content was measured and estimated in the same manner as in Example 1. The resulting value of each ICP content is shown in Table 3.
Samples of the produced ceramic sintered bodies were each processed into a test piece of 24 mm×40 mm×0.32 mm (hereinafter referred to as “test substrate”). The test substrate was prepared by a roll compaction molding method.
The three-point bending strength of each sample was measured in accordance with JIS R 1601-2008. A crosshead speed used for measuring the three-point bending strength was 5 mm/min. The obtained results of the three-point bending strength test are as shown in Table 3.
Sample No. 14 in which the ICP content of Fe2O3 was greater than the ICP content of TiO2 by 200 ppm or greater had higher three-point bending strength than Sample No. 13 in which the difference between the ICP content of Fe2O3 and the ICP content of TiO2 was 20 ppm or less.
From the above results, in the ceramic sintered body constituting the ceramic substrate 2 according to the embodiment, the content of Fe in terms of Fe2O3 is preferably greater than the content of Ti in terms of TiO2.
A ceramic sintered body (Samples Nos. 18 to 20, 22, and 23) of Example 4 was prepared as follows. A powder of Al2O3 and a powder of the additive were blended such that the contents (mass %) of Al2O3 and the additive contained in the ceramic sintered body were the contents shown in Table 4 to prepare a blended powder. Here, the content of Ti in terms of TiO2 and the content of Fe in terms of Fe2O3 in the additive were the blended contents shown in Table 4. Next, after a solvent and a binder were added to the blended powder, granules were prepared through a slurry, and the granules were reshaped as desired by press molding to prepare a molded body. Thereafter, the binder component was removed by degreasing, and then the molded body was fired to produce ceramic sintered bodies (Samples Nos. 18 to 20, 22, and 23). Samples Nos. 18 to 20, 22, and 23 are the same as Samples Nos. 3, 5, 6, 7, and 11, respectively.
Each of the produced samples was subjected to the same three-point bending strength test as in Example 1. The results of the three-point bending strength test are as shown in Table 4.
A ceramic sintered body of Comparative Example 3 (Sample No. 16) was prepared under the same conditions as in Example 4 except that the powder of TiO2 was not blended as an additive to the powder of Al2O3. Sample No. 16 is the same sample as Sample No. 1.
The produced ceramic sintered body was subjected to the same three-point bending strength test as in Example 4. The result of the three-point bending strength test is as shown in Table 4.
A ceramic sintered body of Comparative Example 4 (Sample No. 17) was prepared under the same conditions as in Example 4 except that the powder of Fe2O3 was not blended as an additive to the powder of Al2O3. Sample No. 17 is the same sample as Sample No. 2.
The produced ceramic sintered body was subjected to the same three-point bending strength test as in Example 4. The result of the three-point bending strength test is as shown in Table 4.
A ceramic sintered body of Comparative Example 5 (Sample No. 21) was produced under the same conditions as in Example 4 except that the content of Ti in the additive in terms of TiO2 was changed to the blended content shown in Table 4.
The produced ceramic sintered body was subjected to the same three-point bending strength test as in Example 4. The result of the three-point bending strength test is as shown in Table 4.
Sample Nos. 16 and 17 in which the powder of TiO2 or the powder of Fe2O3 was not added as an additive to the powder of Al2O3 and Sample No. 21 in which the blended content of TiO2 was greater than 1.18 mass % had three-point bending strength less than 490 MPa. On the other hand, Samples Nos. 18 to 20, 22, and 23, which are the ceramic sintered bodies of Example 4, had a three-point bending strength of 490 MPa or greater.
From the above results, when the blended powder was prepared, it is preferable that, in the additive, the content of Ti in terms of TiO2 be 0.48 mass % or greater and 1.18 mass % or less, and the content of Fe in terms of Fe2O3 be 0.48 mass % or greater.
The thermal shock resistance test was performed using Samples Nos. 1, 2, and 8 in Example 1. The results of the thermal shock resistance test are as shown in Table 5. Samples Nos. 1 and 2 are comparative examples, and Sample No. 8 is an example. Table 5 also shows the results of evaluating the three-point bending strength of the JIS piece without performing the thermal shock resistance test. The three-point bending strength of the JIS piece that was not subjected to the thermal shock resistance test is provided without a description of temperature. Table 5 shows the three-point bending strength of the JIS piece measured by heating the JIS piece to 190° C., 240° C., 265° C., and 290° C., then dropping the JIS piece into water having a water temperature of 10° C. to rapidly cool the JIS piece, and then performing a three-point bending test.
In Samples Nos. 1 and 2 as Comparative Examples, the three-point bending strength was deteriorated by about 30% at 265° C., and the three-point bending strength was deteriorated by about 80% at 290° C. On the other hand, in Sample No. 8 as an Example, strength degradation at 265° C. was only about 4%, and the three-point bending strength was deteriorated by about 61% at 290° C. From the above, also from the viewpoint of the thermal shock resistance, it is preferable that, in the ceramic sintered body, the content of Ti (titanium) in terms of TiO2 is 120 ppm or greater, and the content of Fe (iron) in terms of Fe2O3 is 180 ppm or greater.
Further effects and variations can be readily derived by those skilled in the art. Thus, a wide variety of aspects of the present invention are not limited to the specific details and representative embodiments represented and described above. Accordingly, various changes are possible without departing from the spirit or scope of the general inventive concepts defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-127812 | Aug 2021 | JP | national |
| 2021-177914 | Oct 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/029822 | 8/3/2022 | WO |
