JP3149613B2 - Ceramic substrate and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate and a method of manufacturing the same, and more particularly, to a ceramic substrate often used as a multilayer wiring board for mounting electronic components and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, ceramics have been increasingly used as a substrate material in multilayer wiring boards on which highly integrated LSIs and various electronic components are mounted due to requirements for miniaturization, reliability, and the like. Alumina has advantages such as high strength, so that it accounts for a large proportion of the ceramics for the substrate material. However, on the other hand, the alumina has a large relative dielectric constant, which causes a delay in transmission signals, and the thermal expansion coefficient is much larger than that of silicon, so that reliability cannot be ensured when mounting components. have. Further, since alumina has a high firing temperature of about 1500 ° C. or more, it is necessary to use W or Mo having a high melting point and a high electric resistivity for the wiring in the inner layer. Also have.

In order to solve such a problem, the relative dielectric constant is reduced, the thermal expansion coefficient is brought close to that of silicon, and a metal material having a low melting point such as Cu, Ag or Ag-Pd is used as an inner layer conductor. Research and development of a low-temperature fired ceramic substrate that can be fired as a substrate has been advanced.

[0004] Generally, a low-temperature fired ceramic substrate is manufactured by mixing a glass material and a crystal material called an aggregate and firing the mixture. However, the number of combinations of glass materials and crystal materials is extremely large, and the combination of the two provides a synergistic effect during firing, resulting in the properties of the resulting ceramic substrate (relative permittivity, coefficient of thermal expansion, firing temperature,
Flexural strength). Therefore, it has been difficult to find the best combination and to produce a ceramic substrate having a stable composition and structure so as to always exhibit certain characteristics.

In such a background, the strength is improved without deteriorating the characteristic that the relative dielectric constant is low and the coefficient of thermal expansion is close to that of silicon, and the speed of signal transmission and the size of the mounted element are increased. As a low-temperature fired ceramic substrate that can be used, cordierite (2MgO.2Al ₂ O ₃ .5SiO) as disclosed in JP-A-2-225338 is used.
₂ ) System-crystallized glass has attracted attention.

[0006]

However, the above-mentioned Japanese Patent Application Laid-Open
The cordierite-based crystallized glass used in JP-A-225338 has a high softening temperature and a high viscosity at a high temperature, and thus has a problem that it is difficult to densify the substrate.

[0007] From such a point, firing at a temperature of 950 ° C or less required for forming an inner layer of Ag or at a temperature of 1000 ° C or less required for forming an inner layer of Cu or the like so as to precipitate a cordierite-based crystallized glass. In the case of performing the above, the obtained ceramic substrate does not have a sufficiently small porosity, does not have sufficient bending strength and moisture resistance, and is liable to generate oxidation and migration of the inner layer conductor and has low reliability. There was a problem of becoming.

[0008] The present invention has been made in view of the above-mentioned problems, and is sufficiently densified by firing at 1000 ° C or lower, and even 950 ° C or lower, has a low relative dielectric constant, flexural strength, moisture resistance, and water resistance. It is an object of the present invention to provide a ceramic substrate excellent in the above and a manufacturing method thereof.

[0009]

Means for Solving the Problems] ceramic substrate according to the present invention in order to achieve the above _{object, MgO: 10~30wt% Al 2 O} 3: 5~20wt% SiO 2: 40~55wt% B 2 O 3 _{: 10~20wt% R 2 O: 0~} 5wt% ( where, R represents an alkali metal, 0
(Excluding glass powder) and Al ₂ O ₃ crystal grains, and a glass powder obtained by calcining a mixture obtained by mixing glass powder: 60 to 80 wt% crystal grains: 20 to 40 wt%. A ceramic substrate , wherein the crystal contains a cordierite crystal.

The method of manufacturing a ceramic substrate according to the present invention is the above-described method of manufacturing a ceramic substrate, wherein : MgO: 10 to 30 wt% Al ₂ O ₃ : 5 to 20 wt% SiO ₂ : 40 to 55 wt% B ₂ O ₃ : 10 to 20 wt % R ₂ O: 0 to 5 wt% (where R is an alkali metal and 0 is
(Excluding glass powder) and Al ₂ O ₃ crystal grains in a temperature range from 800 ° C. to less than 1000 ° C. by mixing a mixture obtained by mixing glass powder: 60 to 80 wt% crystal grains: 20 to 40 wt%. It is characterized by firing.

[0011]

In the ceramic substrate according to the above-mentioned structure, comprising glass and crystal, the glass is made of MgO-Al ₂
It is composed of an O ₃ —SiO ₂ —B ₂ O ₃ —R ₂ O-based glass (R represents an alkali metal), the crystal contains cordierite, the softening temperature of the glass is 720 ° C. or less, and the pores are The ceramic substrate has a low coefficient of thermal expansion, a thermal expansion coefficient close to that of a silicon substrate, a small relative dielectric constant, and excellent burrow strength, moisture resistance, water resistance, and the like. Further, since the ceramic substrate has a low softening point, the temperature is 800 ° C.
A material having the above characteristics can be obtained even by firing at 000 ° C. or less, and a ceramic substrate in which Ag, Cu, or the like can be used for circuit wiring is obtained.

[0012] According to the method of manufacturing a ceramic substrate as described above, the glass powder consisting of _{MgO, Al 2 O 3, SiO} 2, B 2 O 3 and R ₂ O (R is an alkali metal), Al ₂ O Mix ₃ crystal grains, 800 ℃ or more 10
Since firing is performed in a temperature range of less than 00 ° C., cordierite precipitates in the ceramic substrate, the porosity of the glass ceramic decreases, and the glass ceramic becomes denser, and the ceramic substrate having the above various excellent characteristics is manufactured.

[0013] Incidentally, the terms composition of the glass powder in the manufacture of the ceramic substrate, MgO becomes insufficient high becomes densification is the softening temperature exceeds 30 wt%, also
If MgO is less than 10 wt%, cordierite does not precipitate and the coefficient of thermal expansion increases. If the Al ₂ O ₃ content exceeds 20 wt%, the softening temperature becomes high, and if the firing temperature is less than 1000 ° C., the densification becomes insufficient and the flexural strength decreases, and if the Al ₂ O ₃ content is less than 5 wt%, cordierite precipitates. Without this, the coefficient of thermal expansion increases. If the content of SiO ₂ exceeds 55% by weight, the softening temperature increases,
If the sintering temperature is lower than 0 ° C., the densification becomes insufficient and the transverse rupture strength becomes small. If the SiO ₂ content is less than 40% by weight, the relative dielectric constant and the thermal expansion coefficient become large. If B ₂ O ₃ exceeds 20 wt%, the water resistance of the glass decreases, and the composition becomes uneven due to phase separation in the glass manufacturing process. If B ₂ O ₃ is less than 10 wt%, the softening strength is high. At a sintering temperature of 1000 ° C. or less, the densification is insufficient and the bending strength is reduced. Alkali metal is MgO
, Al ₂ O ₃ , SiO ₂ and B ₂ O _3, and in particular, the softening temperature decreases due to the synergistic action with B ₂ O ₃ , but if it exceeds 5 wt%, the water resistance deteriorates.

Therefore, the composition of the glass powder material is as follows:
MgO 10 ~ 30wt%, Al ₂ O _{3 5} ~ 20wt%, SiO ₂ 40 ~ 55
wt%, B ₂ O ₃ is 10-20 wt%, alkali metal oxide 0-5
range of wt% (0 is not included), more is MgO 10-20 wt%,
Al ₂ O ₃ is 10-20 wt%, SiO ₂ is 40~55wt%, B ₂ O ₃ is 10 to 20
wt%, alkali metal oxides in the range of 1-5 wt% good better <br/> physician.

In the method of manufacturing a ceramic substrate, Al ₂ O ₃ is selected as the crystal of the aggregate because:
Cordierite is precipitated by the interaction between glass and aggregate, and has good properties as a ceramic substrate (specific permittivity is 7.0 or less, coefficient of thermal expansion is around 5.0 to 6.0, firing temperature is Less than 1000 ° C, bending strength is 20kgf / mm
² or more).

Regarding the mixing ratio of glass and crystal in the raw material, the bending strength of the obtained ceramic substrate was set to 20 kg.
f / mm ² or more, glass is 60 to 80 wt.
% And the crystals are preferably mixed in the range of 40 to 20 wt%.

Here, the term "water resistance" means a property that glass does not dissolve in water, and the term "moisture resistance" means that a liquid permeated into a porous portion of glass affects an inner layer conductor (oxidation and migration). Means that it does not give

[0018]

EXAMPLES Examples and comparative examples of a ceramic substrate and a method of manufacturing the same according to the present invention will be described below. MgO, A
It is composed of l ₂ O ₃ , SiO ₂ , B ₂ O ₃ and R ₂ O (R represents an alkali metal) and has an average particle size of 0.1 to 10
A glass powder of μm and crystal grains of Al ₂ O _{3 having} an average particle diameter of 0.1 to 10 μm were mixed at a ratio shown in Table 1.

Next, an appropriate amount of an organic binder, a plasticizer and a solvent are added to the mixture, and the mixture is kneaded to obtain a mixture of about 10,000 cps.
Of the slurry.

Next, the slurry was formed into a sheet having a thickness of 0.2 mm by a doctor blade method and dried at 80 ° C. for about 10 minutes. Thereafter, the sheet is heated at 10 ° C./m
The temperature is raised at a rate of in, and baked at about 900 ° C. for 30 minutes.
The manufacture of the sintered body of the ceramic substrate was completed.

Next, it was confirmed that cordierite crystals had precipitated on the ceramic substrate manufactured by the above method.
It was confirmed by line diffraction. Further, the porosity, the relative dielectric constant at a frequency of 1 MHz, the coefficient of thermal expansion, the value of the transverse rupture strength and the water resistance of the ceramic substrate were measured. The porosity was measured by the Archimedes method, and the relative permittivity was measured by an impedance analyzer. The average coefficient of thermal expansion was measured from room temperature to 350 ° C. using a contact linear dilatometer. The flexural strength was measured by a three-point bending test, and the water resistance was evaluated by keeping the test piece in boiling water for a certain period of time and reducing its weight. Moisture resistance was evaluated by contacting water or steam from one side of the thin plate sample and increasing the humidity on the other side.

[0022]

[Table 1]

[0023]

[Table 2]

As is clear from Table 1, Examples 1 to 25
It can be seen that the ceramic substrate can be sufficiently densified even at a sintering temperature of 1000 ° C. or lower, has a low relative dielectric constant, and has excellent flexural strength, moisture resistance, water resistance and the like.

In the temperature range where the inner conductor is not melted, the higher the firing temperature of the ceramic substrate, the more dense and crystallized the ceramic substrate, so that a large bending strength and a small thermal expansion coefficient can be obtained.

FIG. 1 shows that the sample obtained in Example 6
It is data of X-ray diffraction intensity at the time of X-ray diffraction. From FIG. 1, it was confirmed that cordierite was precipitated.
Further, observation with a TEM (transmission electron microscope) revealed that cordierite was precipitated from the surface of the alumina.

Comparative Example 1 is a comparative example made on the basis of the contents disclosed in JP-A-2-225338,
900 which is the temperature range required for inner layer of Cu and Cu etc.
It can be seen that the porosity does not become sufficiently small and the densification does not occur when firing at a temperature of not more than ℃, so that the transverse rupture strength is low. In Comparative Example 2, since the amount of MgO in the glass material was small, cordierite did not precipitate, the porosity was large, the transverse rupture strength was small, and the moisture resistance was poor. Comparative Example 3
It can be seen that, since the amount of Al ₂ O _{3 in} the glass material was small, cordierite did not precipitate, the porosity was large, the transverse rupture strength was small, and the moisture resistance was poor. In Comparative Example 4, since the mixing ratio of the aggregate to the glass was small, the transverse rupture strength was low. In Comparative Example 5, since the amount of K ₂ O in the glass material was large, the substrate was deformed, and the water resistance was poor. In Comparative Example 6, since the amount of B ₂ O _{3 in} the glass material was small, the porosity was large, the bending strength was small, and the moisture resistance was poor. In Comparative Example 7, since the amount of B ₂ O _{3 in} the glass material was large, the substrate was deformed and the water resistance was poor. Comparative Example 8
It can be seen that since the mixing ratio of the aggregate to glass is large, the porosity is large, the bending strength is small, and the moisture resistance is poor.

[0028]

In the ceramic substrate made of glass and crystal according to the present invention as described in detail above, according to the present invention, the glass is _{MgO-Al 2 O 3 -SiO 2} -B 2 O 3 -R 2
It is composed of an O-based glass (R represents an alkali metal), the crystal contains cordierite, the softening temperature of the glass becomes 720 ° C. or less, the porosity decreases, and the glass becomes denser, and the thermal expansion coefficient increases. Is close to a silicon substrate, has a low relative dielectric constant, and is a ceramic substrate excellent in bending strength, moisture resistance, water resistance, and the like. In addition, since the ceramic substrate has a low softening point, it is possible to produce a substrate having the above characteristics even by firing at 800 ° C. or higher and 1000 ° C. or lower, and use a low melting point, low electric resistance Ag, Cu, or the like for circuit wiring. Can be manufactured.

According to the method of manufacturing a ceramic substrate according to the present invention, MgO, Al ₂ O ₃ , SiO ₂ , B ₂
A glass powder composed of O ₃ and R ₂ O (R represents an alkali metal) and Al ₂ O ₃ crystal grains are mixed,
By firing in a temperature range of at least 1000 ° C.,
Precipitating cordierite in the ceramic substrate,
Reduce the porosity of glass ceramics and make it denser,
Thermal expansion coefficient is close to silicon substrate, relative dielectric constant is small,
A ceramic substrate having excellent bending strength, moisture resistance, water resistance and the like can be manufactured.

[Brief description of the drawings]

FIG. 1 shows X-ray diffraction intensity data when the sample obtained in Example 6 was subjected to X-ray diffraction.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C04B 35/16

Claims (2)

(57) [Claims] 1. A _{MgO: 10~30wt% Al 2 O 3} : 5~20wt% SiO 2: 40~55wt% B 2 O 3: 10~20wt% R 2 O: 0~ 5wt% ( where, R represents an alkali A mixture of a glass powder having a composition of metal (excluding 0) and Al ₂ O ₃ crystal grains, such that glass powder: 60 to 80 wt% and crystal grains: 20 to 40 wt%. A ceramic substrate comprising glass and a crystal, wherein the crystal contains a cordierite crystal. 2. MgO: 10 to 30 wt% Al ₂ O ₃ : 5 to 20 wt% SiO ₂ : 40 to 55 wt% B ₂ O ₃ : 10 to 20 wt% R ₂ O: 0 to 5 wt% (where R is an alkali) A mixture of glass powder having a composition of metal (excluding 0) and Al ₂ O ₃ crystal grains mixed with glass powder: 60 to 80 wt% crystal grains: 20 to 40 wt% is 800 ° C. to 1000 ° C. 2. The method for producing a ceramic substrate according to claim 1, wherein the firing is performed in a temperature range of less than.