JP2699919B2 - Multilayer wiring board, method for manufacturing the same, and method for manufacturing sintered silica used therefor - 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 multilayer wiring board used for a microwave integrated circuit which requires a particularly low dielectric constant and a low dielectric loss factor, a method for manufacturing the same, and a silica sintered body used for the same.

[0002]

2. Description of the Related Art Conventionally, a ceramic multilayer wiring board can easily mount a fine circuit pattern therein.
When a plurality of elements and the like are mounted at high density, the wiring length can be reduced, and it has been widely applied to fields requiring high-speed transmission. In order to further increase the speed, the signal propagation delay time is proportional to the square root of the dielectric constant of the insulating material around the wiring. Therefore, studies have been made on lowering the dielectric constant of the substrate material. For example, an alumina substrate, which is well known as a ceramic multilayer wiring substrate, has been put into practical use in many cases (glass-ceramic multilayer wiring substrate) in which the dielectric constant is lowered by a composite of glass and alumina. Substrate materials such as quartz, forsterite, and steatite are also known.

In addition to low dielectric constants, there are fields (such as microwave integrated circuits) that require suppression of an increase in dielectric loss in a high frequency band . The above-mentioned glass ceramic multilayer wiring board has a dielectric constant of at least about 3.9, but does not sufficiently meet the demand for low dielectric loss of the multilayer wiring board.

[0004]

As an insulating material satisfying both a low dielectric constant and a low dielectric loss, silica represented by quartz or the like can be considered. However, silica is used as a low-loss conductor material because of its high sintering temperature.
It is difficult to incorporate a low-resistance conductor such as silver or copper, and when it is used for a multilayer wiring board, a plurality of materials such as B ₂ O ₃ and borosilicate glass are added in an amount of about 10 to 20% by weight to form a glass phase. The sintering temperature must be reduced by producing

As a method of lowering the sintering temperature by means of an additive, Japanese Patent Application Laid-Open No. 2-302362 discloses a technique in which BPO ₄ is added in an amount of 5% by weight or more to raise the sintering temperature to 950 to 1100 ° C. When firing at 1000 ° C. or less, which is required when copper or silver is used as a conductor, the amount added is 20.
% By weight or more.

Japanese Patent Application Laid-Open No. 2-26862 discloses an example of a method for producing a silica sintered body at a low temperature. As an example, ultrafine silica powder having a mean particle size of 50 nm or less, preferably 5 to 20 nm is used. A technique for obtaining a silica sintered body by hot pressing at 500 to 800 ° C. is disclosed. It is also described that a rare earth oxide is added to this ultrafine powder at about 5% by weight as needed. But,
Applying high pressure during firing is not desirable as a method for manufacturing a multilayer wiring board.

An object of the present invention is to provide a multilayer wiring board having low dielectric constant and low dielectric loss by enabling low-temperature firing of silica, and a method of manufacturing the same.

[0008]

A feature of the multilayer wiring board according to the present invention is that the insulating layer contains 95% by weight or more of a silica sintered body and the conductive layer is made of a conductive material having a melting point of 800 to 1200 ° C. .

Further, such a silica sintered body is obtained by adding a fine silica powder having an average particle size of 5 to 500 nm to a binder,
A slurry is formed by mixing with a solvent, and after forming the slurry, 800-1 atm. In an atmosphere containing steam having a partial pressure of 0.005 atm or more and 0.85 atm or less and nitrogen or air.
By firing at 200 ° C., a dense sintered body can be formed.

When this is used as a multilayer wiring board, a green sheet is prepared using a slurry prepared from a fine powder of silica having an average particle diameter of 5 to 500 nm, a binder and a solvent, and a conductive layer is formed on the green sheet. And laminating them, and then integrally firing at 800 to 1200 ° C. in an atmosphere containing water vapor having a partial pressure of 0.005 to 0.85 atm and nitrogen or air. Alternatively, it can be manufactured by forming a wiring board in which a conductor layer is provided on the above-described silica sintered body, laminating at least two or more wiring boards, and integrally firing.

[0011]

The multilayer wiring board according to the present invention includes Au, Ag,
It is desirable to use a conductive material selected from at least one of Ag-Pd and Cu. This is because these metals have particularly good high-frequency characteristics. Further, such a silica sintered body may be crystalline or amorphous, but it is desirable that 50% by weight or more of the entire silica sintered body is amorphous silica in terms of thermal expansion and transition temperature. .

What is important in the production of a silica sintered body is that the average particle size of the fine silica powder is in the range of 5 to 500 nm, and that the water vapor has a partial pressure of 0.005 to 0.85 atm. 800 to 1200 in an atmosphere containing
C. and sintering. This means that the average particle size is 5 nm
This is because it is difficult to obtain a silica powder having a particle size of less than 500 nm, and when the average particle size is larger than 500 nm, sintering at 1200 ° C. or less is unsuitable.
A range of 0 nm is preferred. Regarding the firing atmosphere, sintering becomes difficult if the partial pressure of water vapor is less than 0.005 atm. Although the sinterability improves as the amount of water vapor increases, it is difficult to create an atmosphere having a partial pressure of 0.85 atm or less. Therefore, it is preferable to bake at a pressure of 0.005 to 0.85 atm, more preferably 0.3 to 0.7 atm. With these conditions, the firing temperature can be controlled between 800 and 1200 ° C.

Further, it is more preferable that amorphous silica account for 50% by weight or more of the fine silica powder, since the effect of the change in volume at the transition point is smaller than that when the amount is less than 50% by weight. In this case, since the amorphous silica powder has a good sinterability when it is spherical, the specific surface area is 5 to 450 m ² / g.
Is preferably within the range.

Further, when the silica powder is a mixed powder of a fine powder of 5 to 500 nm and a crystallized quartz powder having an average particle diameter of 1 μm to 10 μm in an amount of 1% to 20% by volume, It is possible to improve strength and toughness. The crystallized quartz referred to here is preferably composed of at least one of α-quartz, cristobalite and tridymite. If the average particle size is smaller than 1 μm, the toughness is not improved, and if it is larger than 20 μm, the sinterability is reduced. The same applies to the amount of addition, and if less than 1% by volume is added, the toughness is not improved, and if more than 20% by volume is added, sinterability is reduced, which is not preferable.

In the case of manufacturing a multilayer wiring board, it is most preferable to form a conductive layer on a green sheet and fire it after integrating it, since the process can be simplified. However, wiring with a conductive layer provided on pre-sintered silica
Easier substrate, stacking at least two layers of the wiring substrate
After that, integrated firing may be performed.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited to the following Examples without departing from the scope of the invention.

(Example 1) As a raw material powder, the average particle size was 5
Amorphous silica powder having a nm was used. A solution obtained by dissolving polyvinyl butyral with a solvent containing ethanol as a main component and a predetermined amount of the raw material powder are uniformly mixed to give a viscosity of 30.
A slurry with a viscosity of 00 to 10,000 cps is prepared.
This is formed into a green sheet by a slip casting film forming method so as to have a thickness of 50 μm to 200 μm. A green laminate was obtained by hot pressing the produced green sheet. The green laminate was fired at 800 ° C. for 24 hours in an atmosphere containing water vapor at a partial pressure of 0.5 atm, oxygen and nitrogen (Table 1, sample number 1).

[0018]

[Table 1]

The thus-obtained silica sintered body was transparent white and had a density of 2.20 g / cm ³ . X
When the crystal phase was identified by the line diffraction method, it was found that the crystal phase was amorphous (FIG. 3). In addition, observation of the fracture surface of the sample with a scanning electron microscope showed that 1 μm
Although the following voids were observed to be slightly present, it was observed that the sintered body was dense. When the dielectric constant of this sintered body was measured, εr = 3.8 at 1 MHz.

Example 2 A coarse powder of amorphous silica was made into a fine powder by a dry pulverizer. The average particle size of the powder was measured by a laser diffraction type particle size analyzer, and was found to be 0.5 μm. Using this fine powder as a raw material powder, a green laminate was obtained in the same process as in Example 1. This green laminate was fired at 1200 ° C. for 48 hours in an atmosphere containing 0.85 atm of water vapor, oxygen and nitrogen at a partial pressure (Table 2, Sample No. 12).

[0021]

[Table 2]

The silica sintered body thus obtained was white, showing translucency, and had a density of 2.20 g / cm ³ , similarly to the sample obtained in Example 1. Although the identification of the crystal phase by the X-ray diffraction method includes a slight cristobalite phase,
Most were in the amorphous phase (FIG. 3). Also, when the dielectric constant of this sintered body was measured, at 1 MHz, εr =
3.9.

(Example 3) Using an amorphous silica powder having an average particle size of 7 nm, a green laminate was produced in the same process as in Example 1, and baked at 1200 ° C for 48 hours. At this time, as the firing atmosphere, steam having a partial pressure of 0.005 atm, and oxygen and nitrogen were used (Table 2, sample number 1).
0).

The obtained sample had a sintered body density of 2.20 g / cm ³ as in the case of Examples 1 and 2, and had the same translucent white appearance in appearance. The identification of the crystal phase by the X-ray diffraction method confirmed that it contained a slight cristobalite phase as in Example 2, but the others were confirmed to be amorphous phases.

Example 4 A mixed powder composed of 50% by weight of the above-mentioned amorphous silica powder having an average particle diameter of 7 nm and 50% by weight of crystalline quartz powder having an average particle diameter of 1 μm was dispersed in ethanol using a homogenizer. To prepare a dispersion. A solution obtained by dissolving polyvinyl butyral in a solvent containing ethanol as a main component is mixed with a predetermined amount of the above-mentioned dispersion to prepare a slurry whose viscosity is adjusted to 3,000 to 10,000 cps. This is formed into a green sheet by a slip casting method so as to have a thickness of 50 to 200 μm. A green laminate is obtained by hot pressing the produced green sheet. This green laminate was fired in an electric furnace at 1200 ° C. for 24 hours in an atmosphere containing water vapor at a partial pressure of 0.5 atm and oxygen and nitrogen (Table 3, Sample No. 16).

[0026]

[Table 3]

The sample thus obtained was white with the same light transmittance as the sintered body of the amorphous silica alone, and the sintered body temperature was 2.35 g / cm ³ . When the crystal phase was identified by the X-ray diffraction method, quartz was confirmed, and a slight cristobalite phase and an amorphous phase were confirmed.

Example 5 A mixed powder consisting of 80% by weight of amorphous silica powder having an average particle diameter of 7 nm and 20% by weight of crystalline quartz powder having an average particle diameter of 1 μm was produced by the same process as in Example 4. A laminate was prepared and fired (Table 3, Sample No. 17). The sample thus obtained was white with the same light transmittance as the sintered body of the amorphous silica alone, and the density of the sintered body was 2.22 g / cm ³ . In the identification of the crystal phase by the X-ray diffraction method, a broad pattern indicating an amorphous phase and a quartz peak were confirmed.

Example 6 A mixed powder composed of 95% by weight of amorphous silica powder having an average particle diameter of 7 nm and 5% by weight of borosilicate glass powder having an average particle diameter of 1 μm, and amorphous silica having an average particle diameter of 7 nm Using a mixed powder consisting of 97% by weight of the powder and 3% by weight of a borosilicate glass powder having an average particle size of 1 μm, green laminates were prepared in the same manner as in Example 4, and the partial pressure was adjusted to 0.5 atm. Baking was performed at 1000 ° C. for 24 hours in an atmosphere composed of steam, nitrogen and oxygen. The obtained sample has the same appearance as the sample obtained in Example 1, and has a sintered body density of 2.19 g / cm ³ and 2.20, respectively.
g / cm ³ . The borosilicate glass used has a dielectric constant of 5.0, and the dielectric constant of the sintered body is 4.0, respectively.
3.9.

Example 7 A green sheet having a thickness of 100 μm was produced in the same manner as in Example 1 using the above-mentioned amorphous silica powder having an average particle diameter of 7 nm as a silica raw material.
A via hole having a diameter of 200 μm was formed therein and Cu paste was embedded therein. Further, 20 sheets on which a conductor pattern is printed with a Cu paste are laminated, and 90 ° C., 50MP
a) Isostatic pressing was performed for 30 minutes to form a green laminate. This raw laminate is subjected to a partial pressure of 0.5 atm of steam,
Under an atmosphere composed of nitrogen and a trace amount of oxygen, binder removal and firing were performed under the conditions shown in FIG. The insulating layer of the obtained multilayer substrate (FIG. 2) showed the same performance as the sintered body obtained in Example 1. The specific resistance of the Cu conductor is 3 μΩ · cm.
And was good as a low resistance conductor.

Example 8 The raw material powder had an average particle size of 5
80% by volume of amorphous quartz powder having an average particle diameter of 20% by volume and α-quartz powder having an average particle diameter of 1 μm and 99% by volume of amorphous quartz powder having an average particle diameter of 5 nm and α-quartz powder having an average particle diameter of 10 μm. A mixed powder consisting of 1% by volume was used. This mixed powder was subjected to ball mill mixing using ethyl cellosolve as a dispersion medium. After adding polyvinyl butyral, a plasticizer, and the like to the obtained dispersion, the binder was dissolved and mixed while heating to about 80 ° C. with a homogenizer to prepare a slurry having a viscosity of 3,000 to 10,000 cps. The obtained slurry was formed into a green sheet having a thickness of 50 μm to 200 μm by a slip casting method. A green laminate was obtained by hot pressing the produced green sheet. This green laminate was baked at 1000 ° C. for 10 hours in an atmosphere containing water vapor at a partial pressure of 0.5 atm and oxygen and nitrogen.

The silica sintered body thus obtained exhibited a translucent white color, and had a density of 2.40 g / cm ³ .
Observation of the fractured surface with a scanning electron microscope showed that almost no pores were observed, and that the sintered body was a dense sintered body. Also, cut out prism test piece from the sintered body, a K _IC = 3.5MPa / m ^1/2 and 3.0 MPa / m ^1/2 was subjected to fracture toughness measurement be reliable enough to obtain confirmed.

In addition, when cristobalite and tridymite are used as the α-quartz powder as the raw material powder, the fracture toughness is 3.0 MPa / m ^1/2 or more, and sufficient reliability can be obtained.

Example 9 A coarse powder of amorphous quartz was made into a fine powder by a dry pulverizer. When the particle size of this powder was measured with a laser diffraction particle size analyzer, the average particle size was 500 nm. 80% by volume of this fine powder, 20% by volume of α-quartz powder having an average particle size of 1 μm, 99% by volume of the fine powder and 1
A raw laminate was prepared by the same process as in Example 1 using a mixed powder consisting of 0% of α-quartz powder of 1% by volume as a raw material powder. The green laminate was fired at 1200 ° C. for 50 hours in an atmosphere containing 0.5 atm of water vapor, oxygen and nitrogen at a partial pressure.

When the fracture toughness value of the obtained silica sintered body was measured, K _IC = 3.5 MPa / m ^1/2 and 3.0 M
Pa / m ^1/2 .

(Comparative Example 1) A sample prepared by the same process as in Example 1 was placed in an electric furnace at 750 ° C. in an atmosphere containing water vapor at a partial pressure of 0.85 atm and oxygen and nitrogen.
The firing was performed for 8 hours (Table 2, Sample No. 13). The obtained sample showed a large shrinkage as compared with the dimensions of the green laminate, but exhibited a white color with no translucency. Observation of the fracture surface with a scanning electron microscope revealed that it was not sintered. Therefore, regarding the firing temperature, 750
C is considered insufficient.

On the other hand, when sintering is performed in a temperature range of 1200 ° C. or more, sufficient sintering is possible, but simultaneous sintering becomes impossible because the temperature exceeds the melting point of the low-resistance conductor, which is not practical.

(Comparative Example 2) A green laminate produced by the same steps as in Example 1 was subjected to a partial pressure of 0.004 atm in an atmosphere containing water vapor, nitrogen and oxygen, and a maximum temperature of 1%.
Baking was performed at 200 ° C. for 48 hours (Table 2, Sample No. 9). The obtained sample does not show translucency and is not sintered at all. The amount of water vapor in the firing atmosphere is 0.0
If the pressure is not more than 04 atm, a sufficient sintered body cannot be obtained by firing in the temperature range shown in the present invention.

The partial pressure of the water vapor is 0.85
It is difficult to achieve a pressure higher than the atmospheric pressure, which is not practical.

Comparative Example 3 45 wt% of amorphous silica powder having an average particle size of 5 nm and crystalline quartz powder 55 w having an average particle size of 1 μm
Using t% as a raw material, a green laminate was obtained in the same manner as in Example 4. This is divided at a partial pressure of 0.5 atm into water vapor and an atmosphere containing oxygen and nitrogen at 1200 ° C. for 24 hours.
Time calcination was performed (Table 3, Sample No. 15). The sample thus obtained showed a large shrinkage as compared with the size of the green laminate, but exhibited brittleness that could be easily broken, and sintering was insufficient. Therefore, when the amount of the amorphous silica is 45 wt% or less, a sufficient sintered body cannot be obtained under the firing conditions in the range of the present invention.

Comparative Example 4 A coarse powder of crystalline quartz was made into a fine powder having an average particle size of 0.5 μm by a dry pulverizer. The crystal phase of this powder was identified by an X-ray diffraction method, and it was confirmed that the powder was quartz. Using this powder as a raw material powder, a green laminate was obtained in the same steps as in Example 1. This green laminate was fired at 1200 ° C. for 24 hours in an atmosphere containing 0.5 atm of water vapor, oxygen and nitrogen at a partial pressure (Table 3, sample number 14). The calcined silica body thus obtained was white and very brittle. Observation of the fracture surface with a scanning electron microscope confirmed that many microcracks had occurred. This is considered to be caused by a transition point from a high-temperature type crystal to a low-temperature type crystal during cooling. Therefore, it is not suitable to make a strong sample if all is made of crystalline quartz.

Comparative Example 5 A mixed powder composed of 90% by weight of amorphous silica powder having an average particle diameter of 7 nm and 10% by weight of borosilicate glass powder having an average particle diameter of 1 μm was prepared in the same manner as in Example 4. A green laminate was prepared, and a partial pressure of 0.5 atm water vapor and 100 atmospheres of nitrogen and oxygen were used.
The firing was performed at 0 ° C. for 24 hours. The obtained sample has the same appearance as that of the sample obtained in Example 6, but its dielectric constant is 4.1 at 1 MHz, which is 4.0 or more. When a dense silica sintered body having a SiO ₂ content of less than 95% by weight on a weight basis is manufactured, the low dielectric constant is not significant and is not practical.

[0043]

As described above, according to the present invention, a multilayer wiring board having a very low dielectric constant can be obtained. In particular, in the case of amorphous silica, the dielectric constant is 3.5 to 3.5.
4.0, thereby further reducing the signal propagation delay time. In addition, since sintering can be performed at a temperature equal to or lower than the melting point of a low-resistance conductor such as Au, Ag, or Ag-Pd, the inner conductor can be formed by simultaneous firing. In particular, when α-quartz powder or the like is added, the fracture toughness value is K _IC = 3.5 to
It was 3.6 (MPa / m ^1/2 ), and a highly reliable silica sintered body was obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of firing conditions in the present invention.

FIG. 2 is a diagram showing a configuration of a multilayer wiring board according to the present invention using Cu as a low-resistance conductor.

FIG. 3 is an XRD pattern showing a crystal phase when firing at 900 ° C., 1200 ° C., and 1400 ° C.

FIG. 4 is a view schematically showing a silica sintered body.

[Explanation of symbols]

 Reference Signs List 1 silica sintered body 2 copper conductor pattern 3 via copper conductor 4 quartz matrix 5 crystallized quartz particle

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-83674 (JP, A) JP-A-60-11781 (JP, A) JP-A-61-186259 (JP, A) JP-A-61-186259 247660 (JP, A) JP-A-54-111511 (JP, A)

Claims (10)

(57) [Claims] 1. A dielectric layer is a silica sintered body 95 wt% or more free
A multilayer wiring board comprising a dense layer having a sintered body density of 2.19 g / cm ³ or more , and a conductive layer made of a conductive material having a melting point of 800 to 1200 ° C. 2. The multilayer wiring board according to claim 1, wherein 50% by weight or more of the silica sintered body is amorphous silica. 3. The method according to claim 1, wherein the conductive layer is made of at least one of Au, Ag, Ag-Pd, and Cu.
3. The multilayer wiring board according to any one of claims 2 to 3. 4. A fine powder of silica having an average particle size of 5 to 500 nm is mixed with a binder and a solvent to form a slurry.
5 atm and less steam, depending on firing at 800 to 1200 ° C. in an atmosphere including nitrogen or air
A method for producing a silica sintered body, comprising forming a sintered body. 5. A fine silica powder having an average particle size of 5 to 500 nm and a crystallized quartz powder having an average particle size of 1 μm or more and 10 μm or less, wherein the crystallized quartz powder is 1% by volume to 20% by volume of the whole powder. %, And then weighed so as to be less than 10%, and then mixed with a binder and a solvent to form a slurry.
In an atmosphere containing water vapor having a partial pressure of 0.005 to 0.85 atm and nitrogen or air , 800 to
The method for producing a silica sintered body and forming a the firing Therefore sintered body at 1200 ° C.. 6. The method for producing a silica sintered body according to claim 4, wherein 50% by weight or more of the fine silica powder is amorphous silica. 7. The specific surface area of the amorphous silica powder is 5 m ²
/ Method for producing a silica sintered body according to claim 6, wherein the g or more 450m ² / g or less. 8. The method according to claim 5, wherein the crystallized quartz powder comprises at least one of α-quartz, cristobalite, and tridymite. 9. A green sheet is prepared by using a slurry prepared from a fine powder of silica having an average particle diameter of 5 to 500 nm, a binder and a solvent, a conductor layer is formed on the green sheet, and these are laminated. After that, the partial pressure was set to 0.1.
Steam between 005 and 0.85 atm and nitrogen
Or a method of manufacturing a multilayer wiring board, comprising integrally firing at 800 to 1200 ° C. in an atmosphere containing air.
Law . 10. A multilayer wiring, comprising: forming a wiring substrate in which a conductor layer is provided on a silica sintered body according to any one of claims 4 to 8, laminating at least two wiring substrates, and integrally firing. Substrate manufacturing method.