JP2002338338A - Low temperature burned ceramics substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramics substrate which has low transmission loss in high frequency, is burnable at <=930 deg.C, and has high reliability in the connection parts of FC(flip chip) and BGA(ball grid array). SOLUTION: The low temperature burned ceramics substrate in which Qf is >=3,000 GHz, deflective strength is >=180 MPa, and the coefficient of linear expansion at room temperature to 300 deg.C is 9 to 12 ppm/ deg.C consists of a sintered compact of, by mass, a 35 to 40% filler (wherein, 30 to 39.5% quartz, and Al2 O3 and/or Fe2 O3 of 0.5 to 5% in total can be contained), and 60 to 65% glass. The composition of the glass consists of 40 to 46% SrO, 35 to 40% SiO2 , 9 to 11% B2 O3 , 1.5 to 5.8% SnO2 , 2 to 4% ZnO, 0.6 to 2.8% Al2 O3 +AlN, 0.1 to 2% Na2 +K2 O and 0.1 to 1.5% MgO, and the balance impurities of <=2% in total.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass-ceramic type low-temperature fired ceramic substrate having high linear thermal expansion, high Qf value and sufficient strength.

[0002]

2. Description of the Related Art With the recent high performance and miniaturization of IC chips (LSIs), increasing the wiring density of circuit boards on which IC chips are mounted has become an important issue. As this circuit board, a multilayer circuit board having an inner conductor wiring inside is generally used. Circuit boards are roughly classified into a plastic substrate in which the insulating material is plastic and a ceramic substrate in which the insulating material is ceramic.

[0003] Ceramic substrates are excellent in heat resistance and therefore in reliability, and are characterized in that the manufacturing process of a multilayer circuit substrate is simpler than that of a plastic substrate.
In applications such as RF module substrates, ceramic substrates have become mainstream.

A typical example of the ceramic substrate is an alumina substrate. The alumina substrate has excellent insulating properties and a very high mechanical strength of 300 MPa or more in bending strength. However, since the alumina substrate has a high firing temperature of 1500 to 1600 ° C., in the case of multilayering, a high melting point metal such as W or Mo is used as a wiring material. However, since these metals have relatively high electrical resistance, signal transmission loss and power loss increase. Alumina has a relatively high relative dielectric constant of about 9, and the signal delay speed increases as the frequency of the transmission signal increases. From the above points, the alumina substrate is not suitable for increasing the speed of an IC chip.

In order to solve this problem, 850 ° C. to 1050 ° C.
A low-temperature fired ceramic substrate that can be fired at a low temperature has been developed.
When the firing temperature is low, low-resistance metals such as Cu and Ag can be used as wiring materials, and signal transmission loss and power loss are significantly reduced. Many low-temperature fired ceramic substrates are
It is composed of a glass composite material (glass ceramic) consisting of a mixture of glass and a crystalline filler (ceramic) of aggregate. This type of ceramic substrate generally has a lower dielectric constant than an alumina substrate, and can suppress signal delay at high frequencies.

On the other hand, as a method of mounting an IC chip on a circuit board, flip chip (FC) mounting, which is high in density and excellent in electrical connection, is increasingly used instead of conventional wire bonding. Regarding the method of mounting a package in which an IC chip is mounted on a circuit board on a printed wiring board, a BGA (b) is used instead of the conventional PGA (pin grid array).
all grid array) is becoming mainstream.

[0007]

The connection by FC and BGA can be performed at a high density, and can meet the demands for downsizing the package and increasing the mounting density. But,
Since the connecting portion between the chip and the circuit board or the package and the printed wiring board is shortened, a larger thermal stress is applied to the connecting portion per unit volume. The thermal stress is generated by heat generated in the operation of the LSI because the chip and the substrate, or the package (circuit board) and the printed wiring board have different thermal expansion coefficients.

As the degree of integration and miniaturization of LSIs increase, the amount of heat generated by the package is increasing, and the thermal stress applied to the connection is increasing. FC with short connection distance
In the case of the BGA or the BGA, if the thermal stress is not sufficiently absorbed, the connection portion may be peeled off, resulting in a loss of connection reliability. Therefore, for FC or BGA connection, it is required to prevent a decrease in connection reliability due to thermal stress. Thermal stress is FC
And the smaller the difference between the coefficients of thermal expansion of the members on both sides of the BGA, the smaller the difference.

For FC connection, a ceramic substrate material having a coefficient of thermal expansion close to that of silicon as a chip material has been developed, and high connection reliability can be secured. Also, by injecting the reinforcing resin between the chip and the circuit board, there is no problem in connection reliability even if there is a certain difference in the coefficient of thermal expansion.

However, in the BGA connection between the package and the printed wiring board, when the circuit board is a ceramic package in which the circuit board is a ceramic substrate, the thermal expansion coefficient of the ceramic substrate is larger than that of the printed wiring board made of resin and glass fiber. It is difficult to obtain high connection reliability because it is quite small and has a large difference in thermal expansion coefficient. In the BGA mounting of a package on a printed wiring board, it is difficult to adopt a method of injecting a reinforcing resin that makes it impossible to replace the package. Therefore, in order to improve the reliability of the BGA connection, a ceramic circuit board having a thermal expansion coefficient close to that of a printed wiring board is required.

The operating temperature of electronic equipment is usually 100 ° C. or less, but since the BGA is mounted by reflow soldering, the package and printed wiring board must be 30 ° C during reflow mounting.
Exposure to temperatures close to 0 ° C. Therefore, in the temperature range from room temperature to 300 ° C., the thermal expansion coefficients of the ceramic substrate and the printed wiring board must be matched.

In particular, in a circuit board for an RF (high-frequency) module for a cellular phone, in order to cope with a higher frequency,
Substrate with low transmission loss, ie, Qf value given by Q × f
(Q is the reciprocal of the dielectric loss, that is, Q = 1 / tan δ <tan δ = dielectric loss>, and f is the frequency).

A glass-ceramic low-temperature fired ceramic substrate is inevitably lower in strength than an alumina substrate, but it cannot cope with the miniaturization (thinning) of the substrate unless the bending strength is high to some extent.

The present invention focuses on these points, and has a high Qf value (Qf = 3000 GHz or more) and can be fired at a low temperature to lower the resistance of the inner conductor (fired at 930 ° C. or less where Ag wiring is possible). ), Moderately high coefficient of thermal expansion (9 between room temperature and 300 ° C)
It is an object of the present invention to provide a ceramic substrate satisfying characteristics of high bending strength (≧ 180 Mpa).

[0015]

According to the present invention, there is provided a glass ceramic type low-temperature fired ceramic substrate comprising a sintered body of an aggregate mainly composed of quartz and a glass containing SrO and SiO _2. Can be solved.

Here, the present invention relates to a ceramic substrate comprising a sintered body of an aggregate mainly composed of quartz and a glass containing SrO and SiO ₂ , wherein the ceramic substrate has a temperature range from room temperature to 300 ° C. Linear thermal expansion coefficient 9-12 ppm / ° C, flexural strength 18
A ceramic substrate characterized by having a pressure of 0 MPa or more and a Qf value of 3000 GHz or more.

In one embodiment, the ceramic substrate is 35 to 40% by mass of aggregate (including 30 to 39.5% of quartz).
%), 60-65% of glass, and the composition of glass is SrO
_{: 40~46%, SiO 2: 35~40} %, B 2 0 3: 9~11%, Sn
_{O 2: 1.5~5.8%, ZnO:} 2~4%, Al 2 0 3 + AlN:
_{0.6~2.8%, Na 2 0 + K} 2 0: 0.1~2%, MgO: 0.1~
1.5%, other impurities: 2% or less in total.

The aggregate is preferably an alumina, at least one aluminum compound selected from aluminum nitride and aluminum hydroxide, and / or ferric oxide to (Fe ₂ 0 _3), total 0.5 to 5 wt% (However, Fe ₂ O ₃
Is 2% by mass).

The above-mentioned ceramic substrate can constitute a multilayer ceramic circuit board having an inner conductor wiring therein.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The glass-ceramic type low-temperature fired ceramic substrate of the present invention is characterized in that both the coefficient of thermal expansion and the Qf value are larger than those of a conventional glass-ceramic substrate. This large coefficient of thermal expansion and Qf value can be achieved by the choice of glass and aggregate composition, as described below.

As the aggregate, quartz which is one of the silica crystals is used. Quartz has a high thermal expansion coefficient of about 14 ppm / ° C. When amorphous silica or another silica crystal such as cristobalite or tridymite is used as an aggregate, the thermal expansion coefficient is low, or there is a phase transition at 300 ° C. or less, and the thermal expansion coefficient changes. Also, when using aggregates other than silica such as alumina and mullite,
At least one property of thermal expansion coefficient, Qf value, and strength decreases.

Glass also contains SrO and SiO ₂ as main components and a small amount of Na ₂ O and / or so as to increase the coefficient of thermal expansion.
Alternatively, a glass composition containing K ₂ O is selected. Thereby, SrO-SiO ₂ -Al ₂ O ₃ , SrO-
Crystals such as SiO ₂ -Fe ₂ O ₃ precipitate from the inside of the glass, resulting in crystallized glass having a high coefficient of thermal expansion.

In order to lower the resistance of the internal wiring and to improve the dielectric properties and strength, sintering is densely promoted by firing at a low temperature of 930 ° C. or less, which is required for Ag wiring, and many crystals are precipitated inside the glass. Need to be done. For this, B ₂ O ₃ , SnO ₂ , ZnO,
Add Al ₂ O ₃ .

The aggregate may be only quartz, and further, at least one aluminum compound selected from alumina, aluminum nitride and aluminum hydroxide, and Fe ₂ O
_The addition of one or both of ₃ is preferable because the precipitation of the crystal having a high thermal expansion coefficient is promoted.

If the ratio of the aggregate to the glass is too large, the sinterability becomes poor and a dense sintered body cannot be obtained. On the other hand, if there is too much glass, the mechanical strength of the ceramic substrate will decrease.

For the above reasons, according to the present invention, the linear thermal expansion coefficient in the temperature range from room temperature to 300 ° C. is 9 to 12 ppm.
/ ° C, flexural strength of 180 MPa or more, Qf value of 3000 GHz or more, low-temperature fired ceramic substrate that can be fired at a temperature of 930 ° C or less is 35% to 40% of aggregate by mass% (of which,
Quartz 30 to 39.5%), made from 60 to 65% glass, the composition of the _{glass, SrO: 40~46%, SiO 2} : 35~40%, B 2 0 3: 9~
_{11%, SnO 2: 1.5~5.8%} , ZnO: 2~4%, Al 2 0 3 +
_{AlN: 0.6~2.8%, Na 2 0} + K 2 0: 0.1~2%, MgO:
Achieved by a composition of 0.1-1.5% and other impurities: 2% or less in total.

The aggregate is preferably an alumina, at least one aluminum compound selected from aluminum nitride and aluminum hydroxide, and / or ferric oxide to (Fe ₂ 0 _3), total 0.5 to 5 wt% (However, Fe ₂ O ₃
Is 2% by mass). Of these, aluminum hydroxide changes to alumina during firing. These compounds, when fired, are SrO-SiO ₂ -Al ₂ O ₃ , SrO-SiO ₂ -F
Crystals having a high coefficient of thermal expansion such as e ₂ O ₃ are promoted to precipitate in glass. However, even if the aggregate does not contain these compounds at all, Al ₂ O ₃ contained in the glass causes precipitation of the glass. However, in that case,
The upper limit of quartz is 39.5%.
(Eg, 40%), the thermal expansion coefficient or Qf value cannot be satisfied.

When the aggregate contains at least one of the above-mentioned aluminum compounds, the composition of the whole substrate including the aggregate and the glass after firing is generally expressed by mass% of SiO ₂ : 65.5%.
~51%, SrO: 24~29.9%, Na 2 O + K 2 O: 0.06~1.3%, B 2
O ₃ : 5.4 to 7.2%, Al ₂ O ₃ + AlN: 0.9 to 6.8%, SnO ₂ : 0.9
-3.8%, MgO: 0.06-1.0%, ZnO: 1.2-2.6%, and other impurities 2% or less.

On the other hand, when the aggregate contains ₂ % by mass or less of Fe ₂ O ₃ , the composition of the whole substrate after firing is generally in mass%, SiO ₂ : 65.5 to 51%, SrO: 24 to 29.9%, Na ₂ O + K ₂ O:
_{0.06~1.3%, B 2 O: 5.4} ~7.2%, Al 2 O 3 + AlN: 0.4~1.
_{8%, SnO 2: 0.9~3.8%} , MgO: 0.06~1.0%, ZnO: 1.2
_{~2.6%, Fe 2 O 3:} 0.5~2%, would be 2% other impurities less.

The SiO _{2 in} the composition of the entire substrate is an amount containing quartz as an aggregate and SiO ₂ in the glass. However, since the crystal form of quartz does not change even after firing, the crystal content in the substrate is determined by X-ray diffraction. Can be quantified.

Basically, the ceramic substrate of the present invention is obtained by mixing the respective powders of the aggregate and glass, forming the mixture as required, and then firing the glass to at least partially melt the glass to form a sintered body. Can be manufactured. The production method is not particularly limited, and may be the same as the conventional method. The mixing and molding of the powder can be carried out by using a suitable binder and a solvent for the binder, for example, by sheet molding by slip casting. As in the case of the thick film printing method, a paste prepared from a binder, a small amount of a solvent, and a powder mixture may be screen-printed and fired to produce a ceramic substrate. In the case of a single-layer substrate, molding is possible without using a binder.

The firing temperature is not limited as long as a dense sintered body can be obtained, but is usually 850 ° C. or higher. In the case of firing together with the wiring material as in a multilayer circuit board having an inner conductor, the firing is performed at a temperature sufficiently lower than the melting point of the wiring material. For example, when the wiring material is Ag, the temperature is 930 ° C or less,
In the case of Cu, the temperature is preferably 1050 ° C. or less. The firing atmosphere is also selected according to the wiring material. For example, in the case of Cu, the atmosphere is a non-oxidizing atmosphere (eg, a vacuum or an inert gas atmosphere), whereas in the case of a noble metal such as Ag, the atmosphere may be an atmosphere. In addition, Ag-Pd, Au, and the like can be used as the wiring material.

The ceramic substrate of the present invention is preferably formed into a multilayer ceramic circuit board having internal conductor wiring inside by a well-known green sheet laminating method or a thick film multilayer printing method. Since the firing is performed at a low temperature, a low-resistance wiring material such as Ag described above can be used for the inner conductor, and signal transmission loss is reduced. Transmission loss is further reduced due to the high Qf value of the substrate itself.

The ceramic substrate of the present invention can be used at room temperature to 30
The coefficient of linear thermal expansion in the temperature range up to 0 ° C is 9 to 12 ppm / ° C,
It shows properties such as flexural strength of 180 MPa or more and Qf value of 3000 GHz or more.

The linear thermal expansion coefficient of a general printed wiring board material, glass-epoxy material, in the same temperature range is about 14 to
Since it is 15 ppm / ° C, the ceramic substrate of the present invention
Small difference in thermal expansion coefficient from printed wiring board. Therefore, for example, even if the substrate is heated to approximately 300 ° C. during the reflow mounting, the thermal stress generated in the BGA connection portion is small, and the connection reliability can be ensured. The thermal expansion coefficient of silicon, which is the material for IC chips, is about ppm / ° C.
The thermal stress when the chip side is connected by FC is not so large. The coefficient of thermal expansion is less than 9 ppm / ° C or 12 ppm /
If the temperature is higher than ° C, the difference in the coefficient of thermal expansion between the printed wiring board and the chip becomes too large.

The ceramic substrate of the present invention has a Qf value of 30.
Transmission loss at high frequencies is very small because it is extremely large at 00 GHz or more. Therefore, good signal responsiveness can be maintained even when an LSI whose operating frequency is increased for high-speed processing is mounted. Also, the operating frequency is very high,
Even when used as an F module substrate, transmission loss can be suppressed low.

[0037]

EXAMPLES Four kinds of glasses A to D having the compositions shown in Table 1 were prepared by a usual melting and quenching method and pulverized to have an average particle size of about 10 μm. Glass A is a comparative glass having a composition outside the above range, and the remaining glasses B to D
Is a glass having a composition within the above range.

To the glass powder selected from these, a quartz powder of an aggregate (average particle size of about 2 μm) was added at a mixing ratio shown in Table 2, and in some cases, Al ₂ O ₃ or Fe was further added as a part of the aggregate.
₂ O ₃ powder was added. This powder mixture was mixed and pulverized in a ball mill for 30 minutes using an organic solvent as a pulverizing solvent. Here, an acrylic binder and a plasticizer were added, and mixing in a ball mill was continued for another 18 hours to form a slurry. The slurry was formed into a sheet by a doctor blade method and dried to produce a green sheet having a thickness of 0.1 mm.

(1) Measurement of Linear Thermal Expansion Coefficient 35 green sheets were laminated, bonded by a hot press, and cut into 3.5 mm × 17.5 mm. The laminated sample was held at a firing temperature of 930 ° C. lower than the melting point of Ag for a holding time of 30 minutes.
And fired in air. The sintered sample obtained by firing was heated from room temperature to 300 ° C. at a rate of 10 ° C./min, and the elongation of the sample at that time was measured by TMA (thermomechanical analysis) to calculate the linear thermal expansion coefficient.

(2) Flexural strength measurement Twelve green sheets were laminated and bonded by hot pressing.
It was cut to 10.0 mm x 50.0 mm. The laminated sample was fired in the atmosphere at 930 ° C. for a holding time of 30 minutes. A bending test was performed using the obtained sintered sample, and the bending strength was measured.

(3) Measurement of Qf value The above glass powder and quartz powder were mixed and pulverized using an organic solvent in a ball mill, and then dried at 100 ° C. for 24 hours. The obtained powder mixture was formed into a cylindrical shape having a diameter of 15 mm by a die press, and the obtained formed body was fired in the atmosphere at 930 ° C. for 30 minutes to obtain a sintered body. Using the obtained cylindrical sintered sample, the Q value and the resonance frequency f were measured by the dielectric resonance method, and the Qf value was calculated.

In the above firings (1) to (3), if a dense sintered body was not obtained and the shrinkage of the sintered body was less than 10%, it was determined that the sintering was poor, and Each measurement was not performed. Table 2 summarizes the above measurement results.

[0043]

[Table 1]

[0044]

[Table 2]

As can be seen from Table 2, when the amount of aggregate is more than 40% on a mass basis, sintering becomes poor. The amount of aggregate
If it is 40% or less, a dense sintered body can be obtained, but if the amount of the aggregate is less than 35%, the strength of the sintered ceramic substrate decreases. When the amount of the aggregate is in the range of 35 to 40%, a ceramic substrate made of a sintered body that is dense and has sufficient strength can be obtained.

Regarding the thermal expansion coefficient and the Qf value of the ceramic substrate, if the quartz in the aggregate is 39.5% or less and the glass composition is within the above range, the linear thermal expansion coefficient is 9 to 12 ppm / ° C.
Within this range, a substrate having a Qf value of 3000 GHz or more, with high reliability of the connection portion even with reflow mounting, low transmission loss at high frequencies, and excellent signal responsiveness can be obtained.

[0047]

According to the present invention, Qf is as high as 3000 GHz or more, sintering can be performed at 930 ° C. or less, linear thermal expansion coefficient from room temperature to 300 ° C. is in the range of 9 to 12 ppm / ° C. A ceramic substrate having a bending strength of 180 MPa or more is provided.

The ceramic substrate of the present invention is made of a low-resistance Ag
Can be used as an inner conductor for the multilayer ceramic circuit board. In addition to reducing the resistance of the wiring, the Qf of the substrate itself
Since the value is high, the substrate has a low transmission loss even when the operating frequency is high. Therefore, the ceramic substrate of the present invention can cope with a higher frequency, and is particularly useful as an RF module substrate of a mobile phone or an LSI substrate having a high operating frequency.

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Claims (4)

[Claims] An aggregate mainly composed of quartz, SrO and
A ceramic substrate comprising a sintered body of glass containing SiO _{2 and} having a linear thermal expansion coefficient of 9 to 12 in a temperature range from room temperature to 300 ° C.
A ceramic substrate having a ppm / ° C, a flexural strength of 180 MPa or more, and a Qf value of 3000 GHz or more. 2. 35% to 40% of aggregate (including 30% by weight of quartz)
～39.5%), consists from 60 to 65% glass, the composition of the _{glass, SrO: 40~46%, SiO 2} : 35~40%, B 2 0 3: 9~11%, SnO 2: 1.5~5.8% _{, ZnO: 2~4%, Al 2} 0 3 + AlN: 0.6~2.8%, Na 2 0 + K 2 0: 0.1~2%, MgO: 0.1~1.5%, other impurities: total of 2% or less, The ceramic substrate according to claim 1. 3. An aggregate comprising at least one aluminum compound selected from alumina, aluminum nitride and aluminum hydroxide, and / or ferric oxide (Fe ₂
0 ₃ ) to a total of 0.5 to 5% by mass (however, the upper limit of Fe ₂ O ₃ is 2
The ceramic substrate according to claim 2, wherein the ceramic substrate is contained at a ratio of (% by mass). 4. The ceramic substrate according to claim 1, which constitutes a multilayer ceramic circuit board having an inner conductor wiring therein.