JPH0345027B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides ceramic compositions with good surface smoothness that are particularly suitable for electronic industrial parts and used for other heat-resistant industrial parts, tableware kitchen parts, decorative items, etc. Regarding the manufacturing method.

[Prior art] Thin film patterns such as conductors, resistors, and insulators are formed using thin film forming techniques such as vapor deposition and sputtering methods to form hybrid circuits, such as substrates for thin film hybrid circuits, and other materials. For applications that require a substrate with excellent surface smoothness, high-purity alumina substrates made from fine alumina powder or materials to which trace amounts of MgO or Cr ₂ O ₃ have been added have traditionally been used. .

These alumina substrates had excellent thermal and mechanical properties, and when expressed in terms of surface roughness Ra, had good planar smoothness of approximately Ra = 0.1 μm, making them suitable as substrates for thin films.

[Problems to be solved by the invention] The above-mentioned conventional substrates have excellent surface smoothness when viewed from a microscopic perspective expressed by Ra, but the undulations and warpage of the substrate are similar to those of other Ra. Masks that are similar to low-purity alumina substrates, which are not very good, and are used when forming thin film patterns directly on substrates by vapor deposition or sputtering, and masks used when forming patterns on formed thin films by photolithography processing. However, there were problems in that the adhesion with the substrate deteriorated, making it more likely to cause defects and making it difficult to form precise circuit patterns.

Other ways to obtain a substrate with a smooth surface include polishing the substrate or applying a glaze to the surface of the substrate, but polishing is expensive and internal pores come out to the surface. The method of applying glaze is also expensive, and in order to eliminate warpage and waviness, it is necessary to polish the substrate to be glazed, further increasing the cost.

[Means for Solving the Problems] In consideration of the above problems, the present invention has good mechanical properties, eliminates waviness, and eliminates undulations without polishing after firing.
Small warpage, excellent adhesion with thick film conductors, and
The present invention provides a substrate material composition having excellent surface smoothness with an Ra of about 0.1 μm.

That is, the present invention deals with MO (where M: Ca, Mg) which may contain up to 10% impurities on a weight basis.
4-35.75%, _SiO2 18-45.5%, _{Al2O3 35-72} %,
MO10~ with a composition consisting of 0~19.5% _B2O3 and may contain up to 10% impurities as starting _material
55%, _{Al2O3 0} ~30%, _SiO2 45~70%, _{B2O3 0} ~
Glass powder with a BET specific surface area of 3 m ² /g or more, with the balance being 40-65%.
A mixture of alumina with a BET specific surface area of 4.5 to 6 m ² /g, which may contain up to 10% impurities, was heated at 1100°C.
This is a method for producing a ceramic composition with good surface smoothness, which is characterized by firing at the following temperature.

A composition that meets the above purpose can be obtained by such a manufacturing method, but more specifically, a method of firing a green tape obtained by a doctor blade method, that is, a method in which a binder, a plasticizer, a solvent, and a dispersant are added to the raw material powder. It is preferable that after adding and mixing, the green tape formed into a sheet shape is punched out into a desired size using a knife coater or the like, and then fired. The reason is that the surface of the green tape obtained in this way has a very smooth surface compared to the pre-fired molded product obtained by other molding methods, and the smoothness of the fired product is This is to give good results.
When obtaining a molded body using other molding methods, such as dry powder pressing, the surface of the press mold must have a mirror surface or a surface roughness close to that, and the binder added to the raw materials must be used to prevent pores or In order to avoid leaving pinholes, care must be taken such as choosing a material that is as soft as possible.

The reason why the composition obtained in the present invention has less waviness and warp is due to the softening of the glass that occurs during firing because 40 to 65% glass is used as the starting material. In other words, the surface of the substrate whose starting material glass has been softened during firing and shrinkage will follow the surface of the setter that holds the substrate during firing, so if there is no undulation or warpage on the setter surface, No waviness or warping occurs on the board. Therefore, it is necessary for the setter to have no undulations or warps, and it is preferable to use a polished alumina substrate or crystallized glass.
Ra doesn't have to be that good. Due to this behavior, in order to eliminate waviness and warpage, the softening state of the glass immediately after the densification of the material is completed is important. If it softens too much, it will react with the setter, and if it is not softened enough, it will cause waviness. , the sled doesn't go away.
The composition of the present invention exhibits optimal glass softening behavior under the above conditions.

Since the above composition can be fired at a low temperature of 1100℃ or less, Ag, Ag
−Using wiring conductor materials such as Pd, Au, and Cu,
It can be a co-fired multilayer circuit board. Of course, thin film circuits can be formed on the surface of this multilayer circuit board and can be connected to internal wiring.

When the above conductor materials are co-fired, the softening of the glass causes the conductor wiring pattern to flow.
In the composition of the present invention, the alumina powder used as a starting material prevents the conductor pattern from flowing, and also prevents the precipitation of secondary crystals such as anorthite, mullite, and cordierite that occur immediately after the densification of the material is completed. It also prevents the conductor pattern from flowing. Similarly, when forming a thick film on a fired body, the pattern does not flow.

As described above, the composition of the present invention can be fired at temperatures below 1100°C, and therefore
Another major feature is the ability to use low-resistance conductor materials such as
Because the temperature is as high as 1,500 to 1,700°C, it was necessary to sinter relatively high-resistance conductor materials such as Mo and W in a reducing atmosphere. In addition, in order to use this type of circuit board, the dielectric constant of the board should be small in order to reduce the signal propagation delay, and the coefficient of thermal expansion should also be low considering that the silicon chip is directly mounted. , which is close to silicon's 3.5×10 ^-6 °C, is better, but conventional alumina substrates have a large dielectric constant ε=10 and a large coefficient of thermal expansion of 7×10 ^-6 /℃, but the substrate of the present invention has a high dielectric constant ε=10. = 6 to 9, and the coefficient of thermal expansion is also small, 3 to 7 x 10 ^-6 /°C.

Next, the composition of the glass powder used in the present invention, the ratio of the alumina powder to the glass powder, and the reason for limiting the BET specific surface area of the glass powder and the alumina powder will be described.

_SiO2 is limited to a range of 45-70%. If SiO ₂ decreases below the specified amount, the dielectric constant and coefficient of thermal expansion will increase, and the amount of anorthite, cordierite, and mullite that precipitates due to component crystallization will not be sufficient, causing conductor and resistance patterns to deteriorate during firing and reheating. It becomes easier to flow. If the amount exceeds the specified amount
It becomes difficult to fire at temperatures below 1100℃.

When Al ₂ O ₃ exceeds 30%, it becomes difficult to sinter at temperatures below 1100°C.

When MO is less than 10%, firing at temperatures below 1100°C is impossible, and when it exceeds 55%, the dielectric constant and coefficient of thermal expansion become large. The dielectric constant and coefficient of thermal expansion are smaller when MgO is used than CaO, but if it exceeds 55%, the amount of cordierite and mullite precipitated due to partial crystallization will not be sufficient.

B ₂ O ₃ melts glass at temperatures around 1300 to 1450℃, and has the effect of lowering the firing temperature of ceramics, so it can be used at a firing temperature of 1100℃ or lower without changing the electrical or mechanical properties. You will be able to do it. When the B ₂ O ₃ content exceeds 30%, resistance strength becomes weak, water resistance deteriorates, and reliability deteriorates. However, as B ₂ O ₃ increases, the dielectric constant and coefficient of thermal expansion tend to decrease.

This glass contains up to 0-5% impurities.
It may contain alkali metal oxides such as Na ₂ O or K ₂ O. These are contained as impurities in glass raw materials, or are added to improve solubility during vitrification, but if the amount exceeds 5%, it may deteriorate electrical properties and water resistance, leading to reliability problems. It gets worse and I don't like it.

Also, BaO, PbO, Fe ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ ,
It may contain up to 10% of impurities such as Cr ₂ O ₃ , NiO, Co ₂ O ₃ . These do not significantly deteriorate the properties, and when the material of the present invention is partially crystallized, there is basically no need to add a special nucleating substance to the glass component, but the impurities mentioned above impair crystallization. It is thought that this may be promoted in some cases.

The ratio of alumina powder and glass powder is 35-60%
It needs to be 65% to 40%. Alumina powder is 60
If it exceeds %, a dense sintered body cannot be obtained at temperatures below 1100°C, and the dielectric body also becomes large. If it is less than 35%, the strength will be low and the strength as a substrate will be insufficient.

Limiting the BET specific surface area of alumina powder and glass powder is very important in order for the surface roughness of the substrate obtained by the present invention to have a good surface smoothness of about Ra = 0.1 μm, that is, 0.2 μm Ra or less. be.

The reason why the BET specific surface area of the glass powder needs to be 3 m ² /g or more is that the BET specific surface area becomes large;
In other words, if the particle size becomes finer, there will be more viscous flowing parts of the glass during firing, and the surface will be smoother.
In addition, the surface roughness after firing due to the size of the glass particles of the starting material is reduced, and the surface roughness is improved, but in order to obtain Ra = approximately 0.1 μm due to these effects, the specific surface area must be 3 m ² /g. This is because glass powder having a fineness higher than that is required. However, when the proportion of glass is 40-50%, the glass powder
The BET specific surface area is required to be 4 cm ² /g or more. In this case, if it is less than 4 m ² /g, a dense sintered body cannot be obtained.

The reason why the BET specific surface area of alumina powder is required to be 4.5 m ² /g or more is that the surface roughness caused by the alumina particles located on the surface after firing becomes smaller if the alumina particles are finer, and the surface roughness is improved. Therefore, in order to obtain Ra=0.1μm, the specific surface must be
This is because fine alumina powder of 4.5 cm ² /g or more is required. However, if the alumina powder is 6 m ² /g or more, the material loses its sinterability, making it impossible to obtain a dense sintered body.

The limited range of BET specific surface area of alumina powder is
It can also be indicated by a limited range of particle sizes. In other words, in order to obtain Ra=0.1μm, the average particle size is
The thickness is required to be 1 μm or less, and if it is 0.5 μm or less, the material will not be sufficiently densified.

As an example of the embodiment of the method for producing the ceramic composition of the present invention, raw materials include CaO, MgO, SiO ₂ ,
Al ₂ O ₃ and B ₂ O ₃ are mixed to a predetermined composition, melted and rapidly cooled at 1300 to 1450°C, and vitrified.
The raw material may be in the form of carbonate, oxide, hydroxide, etc. This temperature range is a desirable range considering the furnace materials and the like.

Next, glass powder and alumina powder are mixed in a predetermined ratio to form a molded powder, which is then molded using normal ceramic molding methods such as cold pressing or tape casting, and fired at 800 to 1000°C. .

When applying the present invention to a multilayer board, for example, an Ag-based conductor is printed on a formed green sheet,
A necessary number of substrates can be stacked and fired at the same time, and through holes can be formed if necessary to form an integrated substrate.

In addition, we can print resistors such as RuO ₂ or SiC, as well as BaTiO ₃ , SrTiO ₃ , Pb (Fe _2/3
Print a capacitor paste such as W _1/3 ) O ₃ −Pb (Fe _1/2 Nb _1/2 ) O ₃ on a green sheet, and stack these or create a green sheet based on the capacitor composition. , these can be stacked and fired at the same time to form an integrated substrate with built-in resistance capacitors.

Furthermore, we printed a Cu powder paste with particle size adjustment and oxidation-resistant treatment as a conductor on a green sheet to create a multilayered structure, and then simultaneously fired it in an atmosphere mainly composed of _N2 . It is also possible to create fired multilayer substrates. In this case, since the atmosphere is _N2 inert, a resistance paste using a metal or intermetallic compound such as Ni-Cr molybdenum silicide or W-Ni is used to remove Cu.
It is also possible to create multilayer substrates with built-in conductors and resistors.

[Example] CaCO ₃ , Mg(OH) ₂ , SiO ₂ , Al ₂ O ₃ and H ₃ BO ₃ were used as starting materials for glass and were weighed according to predetermined composition ratios. After mixing thoroughly with the Raikai machine,
Glass was obtained by melting it at 1400℃ and dropping it into water. The obtained glass was put into an alumina pot together with water and alumina balls, mixed and pulverized, and after drying, a glass powder having a specific surface area of 3 to 4.5 m ² /g was obtained. 45 to 60% of this glass powder and 55 to 40% of alumina powder having a BET specific surface area of 5.7 m ² /g and an average particle size of 0.8 μm were placed in an alumina pot together with water and alumina balls, mixed for 3 hours, and then dried. 1000g of this dry powder, 100g of methacrylic binder, 50g of plasticizer (DOP),
After adding 450 g of solvent (toluene, xylene) to form a slip, a 1 mm thick green sheet was prepared using a doctor blade. This green sheet was fired at 900-1000°C and its physical properties were measured.

Table 1 shows the relationship between composition and physical properties as Examples 1 to 4. The Ra of the obtained substrate is 0.08 ~
At 0.12 μm, waviness and warpage were also very small.

FIG. 1 is a measurement chart when the surface roughness Ra of Example 1 was measured.

Figure 3 shows glass powder 2.5m ² /g, alumina 4
It has a specific surface area of m ² /g, and the glass composition is:
This is a measurement chart for measuring the surface roughness Ra of a substrate made using a material having the same composition as in Example 1 and using the same method as in Example. Ra=0.25μm
The difference from the example can also be seen from the measurement chart.

FIG. 2 is a cross-sectional curve of the substrate of Example 1. The size of the board was 60 x 50 mm, and we measured about 40 mm in the middle of the long side.

FIG. 4 shows a cross-sectional curve of a high-purity alumina substrate. The size of the board is 60 x 50mm, the thickness is 0.82mm
Measured about 40mm in the middle of the long side. As can be seen by comparing both, the substrate obtained by the present invention has much smaller waviness and warp than alumina powder.

Application Example A green sheet with a thickness of 0.3 mm was produced using the same material as in Example 2 in the same manner as in the above example. Add 1 g of ethyl cellulose and 12 g of terpineol to a mixture of 15 g of Ag powder and 5 g of Pd powder,
A conductor pattern was printed on a green sheet using a paste prepared by thoroughly kneading it with this roller. Four conductor pattern printed green sheets having different conductor patterns were obtained using the same procedure. These four green sheets were laminated under pressure at 120° C., 100 Kg/cm ² for 60 seconds to form an integral structure.
Connections between the four conductor layers were made by filling 0.4 mm diameter through holes with the Ag--Pd paste.
This green body was fired at 900°C and held for 20 minutes. The surface roughness of the obtained multilayer substrate is
It was 0.1μmRa. A thin film of Ta ₂ N was formed on the surface of this substrate by sputtering, and a resistor pattern was formed by lithography. Furthermore, Ti,
After forming a thin film of Pd by sputtering and forming a conductor pattern by lithography, the conductor pattern was plated with Au to construct a thin film hybrid circuit. The inner conductor and surface thin film circuit were connected by through holes. A thin film hybrid circuit was formed on a multilayer wiring board by the method described above.

[Effects of the Invention] The composition obtained by the present invention can form a substrate with good surface smoothness. This one is 0.1μm
It has a surface roughness on the order of Ra, and has very little waviness or warping compared to high-purity alumina substrates, so the adhesion between the mask used to form thin film patterns and the substrate is good, allowing precision circuits to be formed. Easy to form patterns. Additionally, since it can be fired at temperatures below 1100℃, it is possible to create co-fired multilayer substrates using conductors such as Au, Ag, Ag-Pd, and Cu. High-density three-dimensional circuits can be formed.

[Brief explanation of drawings]

Fig. 1 is a measurement graph of the surface roughness of Example 1, Fig. 2 is a cross-sectional curve of the same substrate, Fig. 3 is a measurement graph of the surface roughness of a conventional alumina substrate, and Fig. 4 is a cross-sectional curve of the same substrate. shows.

Claims (1)

[Claims] 1 MO (M: Ca, Mg) 4 to 35.75%, which may contain impurities up to 10% by weight,
_SiO2 18~45.5%, _Al2O3 35~72%, _{B2O3 0 ~} 19.5
% and may contain up to 10% impurities as starting material MO10-55%, Al ₂ O ₃ 0
-30%, SiO ₂ 45-70%, B ₂ O ₃ 0-30%, with a BET specific surface area of 3 m ² /g or more, 40-65% glass powder and the balance up to 10%. BET specific surface area that may contain impurities is 4.5 to 6 m ² /
A method for producing a ceramic composition with good surface smoothness, characterized by firing a mixture of g of alumina at a temperature of 1100°C or less.