Ceramic substrates, green sheets for ceramic substrates, and composite powders for ceramic substrates

Abstract

The ceramic substrate according to the present invention is characterized by containing at least a glass, a first ceramic filler, a second ceramic filler, and a third ceramic filler, and is characterized in that the first ceramic filler is alumina, the second ceramic filler is willemite, and the third ceramic filler is zirconia and / or zircon.

Description

[Technical Field]

[0001] This invention relates to a ceramic substrate, a green sheet for a ceramic substrate, and a composite powder for a ceramic substrate. [Background technology]

[0002] Conventionally, when inspecting semiconductor wafers, probe cards are placed on the semiconductor wafer, and the semiconductor wafer is electrically connected to a tester via the probe cards.

[0003] A probe card typically includes a test head that contacts a semiconductor wafer, a printed ceramic substrate connected to a tester, and a ceramic substrate called an interposer substrate that connects the printed ceramic substrate and the test head. For example, Patent Document 1 describes a ceramic substrate containing glass and ceramic filler as a ceramic substrate that can be fired at low temperatures. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-074823 [Overview of the project] [Problems that the invention aims to solve]

[0005] The distance between electrode pads on a printed ceramic substrate is greater than the distance between electrode pads on a test head. One main surface of the interposer substrate has electrode pads corresponding to those on the printed ceramic substrate, while the other main surface has electrode pads corresponding to those on the test head. These electrode pads on one main surface and the other main surface are connected by an internal conductor. Therefore, high positional accuracy of the electrode pads on both main surfaces is crucial for the interposer substrate.

[0006] Furthermore, testing using probe cards is performed over a wide temperature range, such as from -40°C to +125°C. Therefore, to prevent differences between the electrode pad distances of the interposer substrate and the electrode pad distances of the test head or printed ceramic substrate when the test temperature changes, it is preferable to approximate the thermal expansion coefficient of the interposer substrate to that of the test head or printed ceramic substrate. Thus, it is preferable that the interposer substrate be made of a material whose thermal expansion coefficient can be adjusted according to the operating environment.

[0007] Furthermore, the thermal expansion coefficient of the test head is usually close to that of the semiconductor wafer. For this reason, there is a demand to lower the thermal expansion coefficient of the interposer substrate (ceramic substrate) to about the same level as that of the semiconductor wafer. However, the ceramic substrate described in Patent Document 1 has the problem that it is difficult to achieve a low thermal expansion coefficient.

[0008] Furthermore, because via holes are formed in the interposer substrate and internal conductors are formed inside them, it is difficult to maintain mechanical strength. Therefore, there is a demand to increase the mechanical strength of the interposer substrate (ceramic substrate).

[0009] The object of the present invention is to provide a ceramic substrate that can be fired at low temperatures, has a low coefficient of thermal expansion, and has high mechanical strength. [Means for solving the problem]

[0010] As a result of diligent research, the inventors have found that the above technical problems can be solved by adding three specific ceramic fillers to glass to form a composite powder, and then using this as a ceramic substrate. This invention is proposed as the present invention. Specifically, the ceramic substrate of the present invention contains at least glass, a first ceramic filler, a second ceramic filler, and a third ceramic filler, wherein the first ceramic filler is alumina, the second ceramic filler is willemite, and the third ceramic filler is zirconia and / or zircon.

[0011] Furthermore, in the ceramic substrate of the present invention, it is preferable that the glass is borosilicate glass.

[0012] Furthermore, in the ceramic substrate of the present invention, it is preferable that the glass contains, as a glass composition, SiO2 60-80%, B2O3 10-30%, Li2O+Na2O+K2O 1-10%, and MgO+CaO+SrO+BaO 0-20% by mass%. Here, "Li2O+Na2O+K2O" refers to the combined amount of Li2O, Na2O, and K2O. "MgO+CaO+SrO+BaO" refers to the combined amount of MgO, CaO, SrO, and BaO.

[0013] Furthermore, the ceramic substrate of the present invention has a thermal expansion coefficient of 3.0 × 10 in the temperature range of -40 to +125°C. -6 ~4.6×10 -6 It is preferable that the coefficient of thermal expansion is / °C. Here, the "coefficient of thermal expansion in the temperature range of -40 to +125°C" can be measured, for example, with a dilatometer.

[0014] Furthermore, it is preferable that the ceramic substrate of the present invention has a three-point bending strength greater than 280 MPa. Here, "three-point bending strength" refers to the strength measured by a method compliant with JIS R1601 (2008) with a sample thickness of 3.0 mm.

[0015] The green sheet for a ceramic substrate of the present invention contains glass, a first ceramic filler, a second ceramic filler, and a third ceramic filler, wherein the first ceramic filler is alumina, the second ceramic filler is willemite, and the third ceramic filler is zirconia and / or zircon.

[0016] The composite powder for a ceramic substrate of the present invention contains glass, a first ceramic filler, a second ceramic filler, and a third ceramic filler, wherein the first ceramic filler is alumina, the second ceramic filler is willemite, and the third ceramic filler is zirconia and / or zircon.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a ceramic substrate that can be fired at a low temperature, has a low coefficient of thermal expansion, and has high mechanical strength.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a ceramic circuit board according to the present invention.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, an example of a preferred embodiment of the present invention will be described. However, the following embodiments are merely illustrative, and the present invention is not limited to the following embodiments in any way.

[0020] FIG. 1 is a schematic cross-sectional view showing an example of a ceramic circuit board according to the present invention. The ceramic circuit board 1 has a ceramic substrate 10 having first and second main surfaces 10a and 10b. The ceramic substrate 10 is composed of a laminate of a plurality of ceramic layers 11.

[0021] Multiple internal conductors 20 are arranged inside the ceramic substrate 10. Each internal conductor 20 has an interlayer electrode 21 located between adjacent ceramic layers 11, and a via-hole electrode 22 that penetrates the ceramic layer 11 and connects the interlayer electrodes 21 that are facing each other in the stacking direction of the ceramic layers 11 via the ceramic layer 11.

[0022] Multiple internal conductors 20 are provided spanning the first main surface 10a and the second main surface 10b of the ceramic substrate 10. The end of the internal conductor 20 on the first main surface 10a side is connected to an electrode pad 31 provided on the first main surface 10a. The end of the internal conductor 20 on the second main surface 10b side is connected to an electrode pad 32 provided on the second main surface 10b.

[0023] The distance between adjacent electrode pads 32 is longer than the distance between adjacent electrode pads 31. Therefore, when the ceramic substrate 10 is used as an interposer substrate, the test head is connected to the second main surface 10b side, and the ceramic substrate 10 is connected to the first main surface 10a side.

[0024] The internal conductor 20 and electrode pads 31 and 32 can be made of appropriate conductive materials. The internal conductor 20 and electrode pads 31 and 32 can each be made of at least one of the following metals: Pt, Au, Ag, Cu, Ni, Pd, etc.

[0025] In the ceramic substrate 10, the coefficient of thermal expansion in the temperature range of -40 to +125°C is preferably 3.0 × 10⁻⁶. -6 ~4.6×10 -6 / ℃, especially 3.2 × 10 -6 ~4.5×10 -6 The temperature is / °C. If the thermal expansion coefficient of the ceramic substrate 10 falls outside the above range, the difference with the thermal expansion coefficient of the semiconductor wafer becomes large, and when the inspection temperature changes, the difference between the electrode pads of the interposer substrate and the electrode pads of the test head or printed ceramic substrate tends to increase.

[0026] In the ceramic substrate 10, the three-point bending strength is preferably greater than 280 MPa, particularly 300 MPa or more. When the three-point bending strength of the ceramic substrate 10 is low, the mechanical strength of the ceramic substrate 10 tends to decrease.

[0027] In the ceramic substrate 10, the specific gravity is preferably 4.5 g / cm 3 or less, 4.4 g / cm 3 or less, 4.3 g / cm 3 or less, 4.2 g / cm 3 or less, 4.1 g / cm 3 or less, particularly 4.0 g / cm 3 or less. When the specific gravity of the ceramic substrate 10 increases, it becomes difficult to reduce the weight of the probe card.

[0028] The ceramic substrate 10 contains glass, a first ceramic filler, a second ceramic filler, and a third ceramic filler. The first ceramic filler is alumina, the second ceramic filler is willemite, and the third ceramic filler is zirconia and / or zircon.

[0029] Glass is a component that enhances the density (relative density) of the ceramic substrate 10. In the ceramic substrate 10, the content of glass is preferably 20 to 60% by mass, 30 to 60% by mass, 40 to 60% by mass, particularly 40 to 55% by mass. When the content of glass decreases, it becomes difficult to enjoy the above effects of glass. On the other hand, when the content of glass increases, the thermal expansion coefficient of the ceramic substrate 10 increases and the mechanical strength of the ceramic substrate 10 tends to decrease.

[0030] The glass in the ceramic substrate 10 is preferably borosilicate glass. By using borosilicate glass, it becomes easier to suppress the decrease in the thermal expansion coefficient of the ceramic substrate 10.

[0031] Borosilicate glass preferably contains, in terms of mass%, SiO2 60-80%, B2O3 10-30%, Li2O+Na2O+K2O 1-10%, and MgO+CaO+SrO+BaO 5-30% as a glass composition. In the following descriptions of the content ranges for each component, percentages refer to mass% unless otherwise specified.

[0032] SiO2 is a component that forms the framework of glass. The SiO2 content is preferably 60-80%, and particularly 65-75%. If the SiO2 content is too low, vitrification becomes difficult. On the other hand, if the SiO2 content is too high, the meltability tends to decrease.

[0033] B2O3 is a component that forms the framework of the glass, expands the vitrification range, and stabilizes the glass. The B2O3 content is preferably 10-30%, particularly 15-25%. If the B2O3 content is low, the meltability tends to decrease. On the other hand, if the B2O3 content is high, the thermal expansion coefficient of the ceramic substrate 10 tends to increase.

[0034] Alkali metal oxides (Li2O, Na2O, K2O) are components that reduce the viscosity of glass and increase its meltability. The content of Li2O + Na2O + K2O is preferably 1-10%, and particularly 2-6%. If the content of Li2O + Na2O + K2O is low, the effect of reducing the viscosity of the glass becomes weaker. On the other hand, if the content of Li2O + Na2O + K2O is high, the water resistance tends to decrease. The content of Li2O is preferably 0-4%, and particularly 0-2%. The content of Na2O is preferably 0-4%, and particularly 0-2%. The content of K2O is preferably 0-6%, and particularly 2-5%.

[0035] Alkaline earth metal oxides (MgO, CaO, SrO, BaO) are components that reduce the viscosity of glass and increase its meltability. The content of MgO + CaO + SrO + BaO is preferably 5-30%, and particularly 10-20%. If the content of MgO + CaO + SrO + BaO is high, the glass becomes unstable and more prone to devitrification during melting. The content of MgO is preferably 0-10%, and particularly 0-5%. The content of CaO is preferably 0-30%, 5-25%, and particularly 10-20%. The content of SrO is preferably 0-10%, and particularly 0-5%. The content of BaO is preferably 0-10%, and particularly 0-5%.

[0036] In addition to the components listed above, other components may be introduced into the glass composition.

[0037] Ceramic fillers are components that can adjust the coefficient of thermal expansion, mechanical strength, thermal conductivity, specific gravity, etc., in the temperature range of -40°C to +125°C. In particular, alumina, the first ceramic filler, is a component that increases both thermal conductivity and mechanical strength; willemite, the second ceramic filler, is a component that reduces the coefficient of thermal expansion in the temperature range of -40°C to +125°C; and zirconia and zircon, the third ceramic fillers, are components that significantly increase mechanical strength.

[0038] The first ceramic filler is alumina, which is a component that enhances both thermal conductivity and mechanical strength. In the ceramic substrate 10, the content of the first ceramic filler is preferably 10 to 40% by mass, and particularly 20 to 30% by mass. If the content of the first ceramic filler is low, it becomes difficult to enjoy the above effects. On the other hand, if the content of the first ceramic filler is high, the content of the second and third ceramic fillers decreases relatively, making it difficult to enjoy the effects of the second and third ceramic fillers.

[0039] The second ceramic filler is willemite, which is a component that reduces the coefficient of thermal expansion. In the ceramic substrate 10, the content of the second ceramic filler is preferably 1 to 45% by mass, particularly 5 to 40% by mass, and even more preferably 15 to 40% by mass. If the content of the second ceramic filler is low, it becomes difficult to enjoy the above effect. On the other hand, if the content of the second ceramic filler is high, the content of the first and third ceramic fillers decreases relatively, making it difficult to enjoy the effects of the first and third ceramic fillers. Willemite is a silicon-zinc composite oxide. Willemite is generally represented as Zn2SiO4.

[0040] The third ceramic filler is zirconia and / or zircon, and is a component that significantly increases mechanical strength. In the ceramic substrate 10, the content of the third ceramic filler is preferably 1 to 45% by mass, particularly 5 to 40% by mass, and even more preferably 5 to 25% by mass. If the content of the third ceramic filler is low, it becomes difficult to enjoy the above effects. On the other hand, if the content of the third ceramic filler is high, the content of the first and second ceramic fillers decreases relatively, making it difficult to enjoy the effects of the first and second ceramic fillers. Also, the specific gravity tends to increase.

[0041] The size of the first to third ceramic powders is not particularly limited, but if the average particle size of these powders is too large, the porosity of the ceramic substrate 10 will increase, and its mechanical strength will tend to decrease. On the other hand, if the average particle size of these powders is too small, they tend to be difficult to handle. Specifically, homogeneous mixing and dispersion becomes difficult, which may lead to fluctuations in the coefficient of thermal expansion and mechanical strength. Therefore, the average particle size of each powder (D 50 The particle size (D) is preferably 0.01 to 10 μm, 0.1 to 5 μm, and particularly 0.5 to 3 μm. Here, the average particle size (D) 50 ) refers to the value measured by laser diffraction scattering.

[0042] Preferably, the average particle size of the second ceramic filler is smaller than the average particle size of the first ceramic filler. In this case, the overall filling density of the ceramic filler increases, and the mechanical strength of the ceramic substrate 10 improves.

[0043] In addition to the first to third ceramic fillers, other ceramic fillers may be introduced, such as β-spodumene, mullite, or quartz.

[0044] Next, a method for manufacturing the ceramic substrate 10 will be described.

[0045] First, a composite powder containing the aforementioned glass powder, the first ceramic filler, the second ceramic filler, and the third ceramic filler is prepared. Next, a binder containing resin, plasticizer, solvent, etc. is added to this composite powder and kneaded to produce a slurry. This slurry is then formed into a sheet using a doctor blade method or the like to produce a green sheet for ceramic substrates.

[0046] Next, beer holes are formed in the green sheet. These beer holes can be formed, for example, by laser irradiation or mechanical punching.

[0047] Next, conductive paste is filled into the via holes to form via hole electrodes 22. Also, conductive paste is applied to the green sheet to form interlayer electrodes 21 and electrode pads 31 and 32.

[0048] Subsequently, the green sheets are stacked as needed to obtain a laminate. By firing this laminate, a ceramic circuit board 1 (ceramic substrate 10) can be manufactured. [Examples]

[0049] The present invention will be described in detail below based on the following examples. However, the present invention is not limited in any way to the following examples, and can be implemented with appropriate modifications without changing the essence of the invention.

[0050] Table 1 shows examples of the present invention (samples No. 1 to 6) and comparative examples (sample No. 7).

[0051] As a glass composition, glass raw materials were prepared with mass% SiO2 65%, B2O3 15%, CaO 16%, and K2O 4%. The glass raw materials were placed in a platinum crucible and melted at 1450°C to obtain molten glass. Next, the molten glass was supplied between two water-cooled rotating rolls and stretched to obtain a film-like glass. The glass thus obtained was crushed using a ball mill to obtain glass powder with an average particle size of 2.7 μm. Subsequently, the glass powder, alumina powder, willemite powder, and zirconia powder were mixed in the proportions shown in the table to prepare a composite powder. Furthermore, 2 mass% of methacrylic acid resin was added to the composite powder and mixed as an ethanol dispersion. The ethanol was dried and the resulting granules were uniaxially pressed to produce compacted powder in a fold-resistant shape. This was sintered at 880°C to obtain a sintered body. The CTE, specific gravity, and three-point bending strength were measured using this sintered body. The results are shown in Table 1.

[0052] [Table 1]

[0053] Table 2 shows examples of the present invention (samples No. 8 to 13) and comparative examples (samples No. 14 and 15).

[0054] As a glass composition, glass raw materials were prepared with mass% SiO2 65%, B2O3 15%, CaO 16%, and K2O 4%. The glass raw materials were placed in a platinum crucible and melted at 1450°C to obtain molten glass. Next, the molten glass was supplied between two water-cooled rotating rolls and stretch-formed to obtain a film-like glass. The glass thus obtained was crushed using a ball mill to obtain glass powder with an average particle size of 2.7 μm. Subsequently, the glass powder, alumina powder, willemite powder, and zircon powder were mixed in the proportions shown in the table to prepare a composite powder. Furthermore, 2 mass% of methacrylic acid resin was added to the composite powder and mixed as an ethanol dispersion. The ethanol was dried and the resulting granules were uniaxially pressed to produce compacted powder in a fold-resistant shape. This was sintered at 880°C to obtain a sintered body. The CTE, specific gravity, and three-point bending strength were measured using this sintered body. The results are shown in Table 2.

[0055] [Table 2]

[0056] CTE is the coefficient of thermal expansion in the temperature range of -40 to +125°C, and is measured using a dilatometer.

[0057] The specific gravity was measured using the well-known Archimedes method.

[0058] The three-point bending strength was measured using a method compliant with JIS R1601 (2008), with a sample thickness of 3.0 mm.

[0059] As can be seen from Table 1, samples No. 1 to 6 have a CTE of 4.3 × 10⁴. -6 The temperature was below / ℃ and the three-point bending strength was 290 MPa or higher. Therefore, samples No. 1 to 6 are suitable for use as ceramic substrates in probe cards. On the other hand, sample No. 7 did not contain willemite, so its CTE was higher than that of samples No. 1 to 6.

[0060] As can be seen from Table 2, samples No. 8-13 have a CTE of 4.4 × 10⁴. -6 The temperature was below / ℃ and the three-point bending strength was 285 MPa or higher. Therefore, samples No. 8 to 13 are suitable for use as ceramic substrates in probe cards. On the other hand, sample No. 14 did not contain willemite, so its CTE was higher than that of samples No. 8 to 13. Also, sample No. 15 did not contain zircon, so its three-point bending strength was lower than that of samples No. 8 to 13. [Explanation of Symbols]

[0061] 1 Ceramic circuit board, 10 Ceramic substrate, 10a First main surface, 10b Second main surface, 11 Ceramic layer, 20 Internal conductor, 21 Interlayer electrode, 22 Via hole electrode, 31, 32 Electrode pads

Claims

1. It contains glass, a first ceramic filler, a second ceramic filler, and a third ceramic filler. The glass is borosilicate glass, and its composition, in mass%, contains SiO₂ 60-80%, B₂O₃ 10-30%, Li₂O + Na₂O + K₂O 1-10%, and MgO + CaO + SrO + BaO 5-30%. The first ceramic filler is alumina, the second ceramic filler is willemite, and the third ceramic filler is zirconia and / or zircon. The glass content is 40 to 60% by mass. The content of the first ceramic filler is 20 to 40% by mass. The content of the second ceramic filler is 1 to 24% by mass. A ceramic substrate having a third ceramic filler content of 1 to 24% by mass.

2. The coefficient of thermal expansion in the temperature range of -40 to +125°C is 3.0 × 10⁻⁶. －６ ~4.6 x 10 －６ A ceramic substrate according to claim 1, wherein the temperature is / ℃.

3. A ceramic substrate according to claim 1 or claim 2, wherein the three-point bending strength is greater than 280 MPa.

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