JPH03248595A - Ceramic board for high-speed electronic part and manufacture thereof - Google Patents

Abstract

PURPOSE:To transmit a high-frequency signal at high speed while increasing mechanical strength by using ceramics having high mechanical strength as an external ceramic member on the outside of a ground wall while employing ceramics having a low dielectric constant as an internal ceramic member in the periphery of a signal line on the inside of the ground wall. CONSTITUTION:Since ceramics having a low dielectric constant are used as an internal ceramic member 30 surrounding the periphery of a signal line 20 on the inside of a ground wall 40, the propagation delay-time of a high-frequency signal transmitted on the signal line surrounded by the internal ceramic member 30 having the low dielectric constant is inhibited at a low value, thus quickly transmitting the high-frequency signal on the signal line. Ceramics having high mechanical strength are employed as an external ceramic member 10 covering the periphery of the internal ceramic member 30 through the ground wall 40. Accordingly, the external ceramic member 10 having high mechanical strength compensates the mechanical strength of the internal ceramic member 30 having low mechanical strength and the low dielectric constant in the periphery of the signal line 20, thus increasing the mechanical strength of a ceramic board.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a ceramic substrate for high-speed electronic components that is equipped with a signal line that can transmit high-frequency signals with less propagation delay time and less noise.

[Prior art] With the recent miniaturization and higher performance of electronic devices, it is becoming increasingly important to use ceramic substrates for mounting electronic components to transmit high-frequency signals with less propagation delay time (and less noise). The demand for ceramic substrates with high density is increasing.

Ceramic substrates equipped with signal lines for transmitting high-frequency signals have recently been developed using ceramics with a low dielectric constant such as mullite or silica, or alumina.
Ceramic substrates made of composite ceramics mainly composed of borosilicate glass and the like have been developed and are in use. In other words, the dielectric constant of conventionally widely used ceramics whose main component is alumina is 9.4 at 1 MHz.
For example, ceramics whose main component is mullite have a 1MH
The dielectric constant at z is as low as 7.3.

The propagation delay time T pd of a high-frequency signal transmitted through a signal line provided on a ceramic substrate is expressed by the following equation, where ε is the dielectric constant of the ceramic forming the substrate, and C is the speed of light.

Tpd=(ε/C... (1) From this equation, if the ceramic substrate is made of the above-mentioned ceramic with a low dielectric constant ε, the propagation delay time T pd of the high frequency signal transmitted through the signal line provided on the substrate can be calculated as follows: It turns out that less is said.

By the way, if the ceramic substrate is formed from the above-mentioned ceramic with a low dielectric constant, the above-mentioned ceramic with a low dielectric constant will be interposed between the signal lines provided in a high density on the substrate, resulting in tight capacitive coupling between the signal lines. Therefore, crosstalk occurs between the signal lines, and noise mixes into one signal line from the other signal line.

Therefore, recently, ceramic substrates have been proposed in which the signal line is surrounded by a ground wall in the form of a film or a grid, as described in JP-A-1227492 and JP-A-1-239995. ing. That is, according to this ceramic substrate, the signal line can be formed into a coaxial structure or a quasi-coaxial structure using the ground wall, and it is possible to prevent noise from entering the signal line from other signal lines.

Here, the coaxial structure refers to one in which the signal line is surrounded by a membrane-like ground wall with no gaps, and the pseudo-coaxial structure refers to
A ground wall that surrounds a signal line in the form of a lattice with gaps, a net, or a ground wall that is partly lattice-like and partly membrane-like.

[Problems to be Solved by the Invention] However, the above-mentioned ceramic having a low dielectric constant is inferior in mechanical strength to a widely used ceramic mainly composed of alumina.

That is, a ceramic whose main component is alumina has a refractive strength of 35 kg/mm', whereas a ceramic whose main component is mullite, which has a low dielectric constant, has a refractive strength of 20 to 3.
0 kg/mm"L. Therefore, when a ceramic substrate is formed from the above-mentioned ceramic having a low dielectric constant, there is a problem that cracks are likely to occur in the substrate and its reliability is reduced.

The present invention has been made in view of these problems, and is equipped with a signal line that can transmit signals of high frequency in recent years with less propagation delay time and without introducing noise.
It is an object of the present invention to provide a highly reliable ceramic substrate with high mechanical strength and a method of manufacturing the ceramic substrate that allows the substrate to be formed easily and quickly without any trouble.

[Means for Solving the Problems] For the above purpose, the ceramic substrate of the present invention provides a signal having a coaxial structure or pseudo-coaxial structure in which a ceramic member is surrounded by a ground wall in the form of a membrane, a grid, or a net. In the ceramic substrate equipped with a line, a ceramic with high mechanical strength is used for the external ceramic member outside the ground wall, and a low dielectric constant ceramic is used for the internal ceramic member around the signal line inside the ground wall. It is characterized by

Furthermore, the method for manufacturing a ceramic substrate of the present invention is characterized in that the ceramic substrate is formed by the following method.

a0 A metallizing paste for forming a ground wall is applied in a film, lattice, or net shape on the surface of a lower green sheet for forming an external ceramic member with high mechanical strength and is dried.

51 Next, a ceramic paste for forming an internal ceramic member having a low dielectric constant is applied in a belt shape to the surface of the dried metallization paste and dried.

C0 Next, a metallization paste for forming a signal line is linearly applied to the surface of the dried ceramic paste and dried.

61 Next, a ceramic paste for forming an internal ceramic member having a low dielectric constant is applied to the surface of the ceramic paste applied in the above step, including the surface of the dried metallization paste, and dried.

e. Next, a metallization paste for forming a ground wall is applied to the surface of the metallization paste applied in step a, including the surface of the dried ceramic paste, in the form of a film, lattice, or net, and is dried.

f. After that, an upper green sheet for forming an external ceramic member with high mechanical strength is laminated on the surface of the dried metallized paste, and the metallized paste and ceramic paste applied in steps a, bSc, d, and e are combined. The sandwiched upper and lower green sheets are heated while being pressed inside to bring the upper and lower green sheets, metallized paste, and ceramic paste into close contact with each other. Then, the upper and lower green sheets, metallized paste, and ceramic paste are fired together.

Further, in the method for manufacturing a ceramic substrate of the present invention, steps c, d, and e are provided before or in addition to step f.
Before at least one or more steps, the previously applied metallized paste or ceramic paste surface is heated while being pressed with a smooth metal plate through a protective film, so that the metallized paste or ceramic paste is applied to the lower part. It is preferable to bury it inside the green sheet, or to soften the surface of the upper green sheet by applying an organic solvent to the surface of the upper green sheet before step f.

Further, in the method for manufacturing the ceramic substrate of the present invention, ceramic green sheets containing alumina as a main component are used as the upper and lower green sheets for forming the external ceramic member, and the internal ceramic m phase [iJE ceramic paste and mullite] are used. Use a ceramic paste whose main component is tungsten or molybdenum as the metallization paste for forming signal lines and ground walls, or use mullite as the upper and lower green sheets for forming external ceramic members. Ceramic and tag green sheets are used as the main ingredients, ceramic paste with silica as the main ingredient is used to form internal ceramic members, and tungsten or molybdenum is used as the main ingredient of metallization paste for forming signal lines and ground walls. Alternatively, use a ceramic green sheet containing aluminum nitride as the main component for the upper and lower green sheets for forming the external ceramic member, and use a ceramic green sheet containing boron nitride as the main ingredient for the ceramic paste for forming the internal ceramic member. Either use a tungsten- or molybdenum-based metallization paste for the signal line and ground wall formation, or use alumina-borosilicate glass for the upper and lower green sheets for forming the external ceramic parts. Using a composite ceramic green sheet whose main component is silica-borosilicate glass as the ceramic paste for forming the internal ceramic member,
It is preferable to use a metallization paste containing gold, silver, or copper as a main component as the metallization paste for forming the signal line and the ground wall.

[Function] In the ceramic substrate having the above configuration, the internal ceramic member surrounding the signal line on the inside of the ground wall is made of a low dielectric constant ceramic such as mullite or ceramic whose main component is mullite, silica borosilicate glass, etc. A composite ceramic whose main component is Therefore, the propagation delay time Tpd of the high frequency signal transmitted through the signal line surrounded by the internal ceramic member having a low dielectric constant is suppressed to a small value, and the high frequency signal is quickly transmitted through the signal line.

This is because in a signal line with a coaxial structure or a quasi-coaxial structure, the electric field generated around the line is confined inside the ground wall, and the propagation delay time T, , 6 of the signal traveling through the signal line is This is because, as shown in equation (1), the length is shortened in proportion to the square root of the dielectric constant ε of the internal ceramic member inside the ground wall.

In addition, the external ceramic member that surrounds the internal ceramic member via a ground wall is made of a ceramic with high mechanical strength such as alumina, mullite, or aluminum nitride as a main component, or alumina-borosilicate as a main component. A composite ceramic is used. Therefore, the external ceramic member with high mechanical strength supplements the mechanical strength of the internal ceramic member with a low dielectric constant and low mechanical strength around the signal line, thereby increasing the mechanical strength of the ceramic substrate.

In the method for manufacturing a ceramic substrate of the present invention comprising the above steps, the metallized paste for forming the signal line is coated on the surface of the lower green sheet through the ceramic paste for forming the internal ceramic member, and the metallized paste for forming the ground wall is coated on the surface of the lower green sheet. When forming a signal line forming body with a coaxial structure or pseudo-coaxial structure surrounded by metallized paste, apply the ceramic paste for forming the internal ceramic member on both sides of the linear metallized paste for forming the signal line and on its top surface at once. At the same time, the metallization paste for ground wall formation on the surface of the lower green sheet applied in step a, including the surface of the applied ceramic paste, is simultaneously applied in the form of a film, lattice, or net. It is also applied to other areas. Therefore, it becomes possible to easily and quickly form a signal line forming body by applying the ceramic paste and metallization paste to the surface of the lower green belt.

In the method for manufacturing a ceramic substrate of the present invention, the metallization paste or ceramic paste applied before the fT step may be buried inside the lower green sheet, or the surface of the upper green sheet may be softened before the fT step. In the manufacturing method, when the upper and lower green sheets are heated while being pressed inward in step f,
A state in which the metallized paste or ceramic paste sandwiched between the upper and lower green sheets is firmly buried inside the upper and lower green sheets without crushing the metallized paste or ceramic paste sandwiched between them and destroying their shape. It can be brought into close contact with the And when they are fired together,
Delamination (peeling) between them can be accurately prevented.

In the method for manufacturing a ceramic substrate of the present invention, the upper and lower green sheets, the ceramic paste, and the metallized paste each contain a ceramic green sheet containing alumina as a main component, a ceramic paste containing mullite as a main component, and tungsten or molybdenum as a main component. In the manufacturing method using the above-mentioned combinations of metallized pastes etc. as ingredients, the combinations of green root, ceramic paste, etc.
When a ceramic substrate is formed by firing the metallized paste together, the substrate may crack due to thermal stress due to the difference in thermal expansion coefficients when they are sintered.
These interactions allow foreign substances to enter or diffuse into the external ceramic member, internal ceramic member, or signal line, reducing the mechanical strength of the external ceramic member and reducing the dielectric constant of the internal ceramic member. without reducing the signal line conductor resistance or increasing the conductor resistance of the signal line.
A ceramic substrate of the present invention can be formed.

[Example] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a preferred embodiment of the ceramic substrate of the present invention, and specifically shows a side sectional view thereof.

The embodiment shown in this figure will be described below.

In the figure, 10 is an external ceramic member forming the ceramic substrate body. This external ceramic member 10 is made of ceramic having high mechanical strength, such as alumina,
Ceramics whose main components are mullite or aluminum nitride, or composite ceramics whose main components are alumina-borosilicate glass are used.

20 is a signal line provided inside the external ceramic member 10 and transmits a high frequency signal. For this signal line 20, metallization whose main component is tungsten or molybdenum, which has a high conductor resistance value, or metallization whose main component is gold, silver, or copper, which has a low conductor resistance value, is used.

Reference numeral 30 denotes an internal ceramic member that surrounds the signal line 20 inside the external ceramic member 10 without any gap.

This internal ceramic member 30 is made of a low dielectric constant ceramic, such as a ceramic whose main component is mullite, silica, boron nitride, or silicon nitride, or a composite ceramic whose main component is silica-borosilicate glass.

40 is an internal ceramic member 3 surrounding the signal line 20.
A ground wall that covers the surrounding area and has a membrane, grid, or net shape. For this ground wall 40, metallization whose main component is tungsten or molybdenum, or metallization whose main component is gold, silver, or copper is used.

The ceramic substrate shown in FIG. 1 is constructed as described above, and according to this ceramic substrate, the signal line 2
0 is surrounded by the internal ceramic member 30 made of the above-mentioned ceramic with a low dielectric constant, and the internal ceramic member 30 is covered with a ground wall 40 made of metallized material, so that high-frequency signals pass through the signal line 20 with a propagation delay. The signal is transmitted quickly in a short amount of time, and no noise is mixed into the signal line 20 from other signal lines. Also,
Since the inner ceramic member 30 made of the ceramic with low dielectric constant and low mechanical strength around the signal line 20 is reinforced with the outer ceramic member 10 made of the ceramic with high mechanical strength, the ceramic substrate machine The strength of the objective increases.

In the illustrated embodiment, the periphery of the signal line 20 is cylindrically covered with a ground wall 40 via the internal ceramic member 30; 40 may be covered in a rectangular cylindrical shape, an elliptical cylindrical shape, etc., and even in such a case, a ceramic substrate having the same effect as the above-mentioned embodiment can be formed.

FIGS. 2 to 7 show preferred embodiments of the method of manufacturing a ceramic substrate of the present invention, and in detail, show diagrams explaining the manufacturing process. The embodiment shown in this figure will be described below.

a9 Prepare a lower green sheet 100 for forming an external ceramic member with high mechanical strength. The lower green sheet 100 is made of a ceramic paste whose main component is alumina or mullite for forming ceramics with high mechanical strength, or a composite ceramic paste whose main component is alumina-borosilicate glass. . And the second
As shown in the figure, a metallized paste 400 for forming a ground wall is applied to the surface of the lower green sheet 100 in a film, lattice, or net shape (in the figure, it is shown as a film), and the metallized paste 400 The organic solvent etc. inside it is scattered into the outside air by heating it, etc., and drying it. This metallization paste 400 uses a metallization paste whose main component is tungsten, molybdenum, gold, silver, or copper.

b. Next, as shown in FIG. 3, a ceramic paste 300 for forming an internal ceramic member with a low dielectric constant is applied in a strip shape on the surface of the dried metallizing paste 400, and the ceramic paste is 300 is heated or the like to scatter the organic solvent and the like inside it into the outside air and dry it.

As the ceramic paste 300, a ceramic paste mainly composed of mullite or silica for forming a low dielectric constant ceramic, or a composite ceramic paste mainly composed of phosphoric borosilicate glass or the like is used.

C1 Next, as shown in FIG. 4, in the center vertical direction of the surface of the dried band-shaped ceramic paste 300
A metallization paste 200 for forming a signal line is applied in a linear manner, and the metallization paste 200 is heated to scatter the organic solvent and the like inside it into the outside air and is dried. This metallizing paste 200 may include a metallizing paste containing tungsten or molybdenum as a main component for forming metallization with high conductor resistance value, similar to that used in step a, and metallization paste containing gold or silver for forming metallization with low conductor resistance value. Alternatively, a metallization paste containing copper as a main component is used.

68 Next, as shown in FIG. 5, a layer of material for forming a low dielectric constant internal ceramic member is applied to the surface of the band-shaped ceramic paste 3°0 applied in the previous step, including the surface of the metallized paste 200 applied in step C. ceramic paste 300
is applied, and the ceramic paste 300 is heated or the like to scatter the organic solvent and the like inside it into the outside air and dry it.

This ceramic paste 300 is the same as that used in step b, and is used for forming a low dielectric constant ceramic.

In steps b, c, and d, ceramic paste 3
00 and the metallizing paste 200 are prepared by using a screen b. with band-shaped or linear slits 52 on the surface, as shown by broken lines in FIGS. 3, 4, and 5. It is best to apply it in strips or lines using screen printing techniques.

e Next, as shown in FIG. 6, metallization paste 400 for forming a ground wall is spread (film-like, The metallizing paste 400 is applied in the form of a lattice or net (in the figure, it is shown as a film), etc., and the organic solvent, etc. inside it is scattered into the outside air by heating the metallizing paste 400 and drying it. In this step, the same metallizing paste as that used in step a is used.

In addition, in the aSe process, metallizing paste 400
When applying in the form of a grid or net, it is preferable to use a screen (not shown) with grid or net slits on the surface and apply by screen printing technique.

f. Then, as shown in FIG. 7, an upper green sheet 100 for forming an external ceramic member having high mechanical strength is laminated on the surface of the metallization paste 400 applied in step C. For this upper green root 100, the above-mentioned green IJ root for forming a ceramic having high mechanical strength, similar to that used in step a, is used. And a, b, c
Metallized paste 400.2 applied in SdSe process
The upper and lower green sheets 100 sandwiching 00 and ceramic paste 300 are heated while being pressed inside to form the upper and lower green sheets 1o01 for forming the external ceramic member 1oO1 ceramic paste 3001 for forming the internal ceramic member signal line The metallized pastes 200 and 400 for forming the ground wall and the ground wall are brought into close contact with each other without any gaps. In that case, please be sure to use the upper and lower green sheets (100, 400, 200, 400, 200, and ceramic paste).
It is preferable to heat the 300 for a predetermined period of time to remove organic components that would be a hindrance when sintering them by scattering them from the inside into the outside air. And those upper and lower green sheets 100, metallization paste 400, 2
00, the ceramic paste 300 is placed in a furnace, etc., and fired together.

In addition, the above a s b s C% d s e s
In step f, the upper and lower green sheets 100
When using a ceramic green sheet whose main component is alumina, etc., which is sintered at a high temperature, metallization paste whose main component is tungsten or molybdenum, which is sintered at a high temperature, is added to the metallization paste 400.200 and the ceramic paste 300. When a ceramic paste whose main components are paste and mullite is used, and conversely, when a composite ceramic, a tag green sheet, whose main components are alumina-borosilicate glass, which is sintered at a low temperature, is used for the upper and lower green sheets 100. In accordance with this, metallizing paste 400, 200 and ceramic paste l-300 are respectively sintered at low temperatures. A metallizing paste mainly consisting of gold, silver or copper and a composite ceramic paste mainly consisting of silica-borosilicate glass etc. It is necessary to use This is because, otherwise, the upper and lower green sheets 100, metallized pastes 400, 200, and ceramic paste 300 cannot be fired simultaneously at high or low temperatures.

In addition, the thickness of the ceramic paste 300 applied in steps b and d is equal to or greater than the thickness of the metallization paste 200 applied in step C, and the width of the metallization paste 200 applied in step C It is preferable that the width be 1/3 or less of the width of the ceramic paste 300. By doing so, when the upper and lower green sheets 100 are heated while being pressed inside in step f, the metallized paste 200, 400 and ceramic paste 300 sandwiched between them are removed.
Accurately prevents the metallized paste 200 for forming the signal line from leaking outside the ceramic paste 300 for forming the internal ceramic part due to the shape of the metallized paste 200 collapsing, causing a short circuit with the metallized paste 400 for forming the ground wall. Because you can.

In addition, the upper and lower green sheets 100 used in steps a and f do not have very high density, and the organic components can be contained by changing the inorganic component powder distribution, the inorganic/organic component ratio, and the crosstalk conditions. It is preferable that the relative density of all components to the theoretical density be about 70 to 80%. This is because if the upper and lower green sheets 100 are too dense, as shown in FIG. However, the metallized paste 200, 400 or ceramic paste 300 may be crushed and lose its shape, or the metallized paste 400, 200 or ceramic paste 300 sandwiched between the upper and lower green sheets 100 may be buried without any gaps. The upper and lower green sheets 100, metallizing pastes 400, 200, . This is because when the ceramic pastes 300 are fired together, gaps may be created between them, causing delamination (peeling).

In addition, in order to prevent such delamination, cSd is applied before or before the step f.

Even before step e, the surface of the metallized paste 400, 200 or ceramic paste 300 applied previously is coated with a smooth metal plate (not shown) from above through a protective film (not shown) made of plastic or the like. The metallized paste 400,
200 or ceramic paste 300 is reliably buried inside the lower green sheet 100, or before step f, an organic solvent such as phthalate ester that dissolves the binder in the green sheet is applied to the surface of the upper green sheet 100. If the surface of the upper Green Note 100 is softened, the upper and lower surfaces of the Green Note 100 can be softened in step f.
The metallized pastes 400, 200 and the ceramic paste 300 sandwiched between them are brought into close contact with the inside of the notebook 100 in a state where they are reliably buried without losing their shape and without any gaps, and the upper and lower green sheets 100 are
When the metallized pastes 400, 200 and the ceramic paste 300 are fired together, it is possible to accurately prevent delamination between them.

In addition, before step f, as shown in FIG.
(ceramic paste is used in the figure) and fill the valleys 402 with the paste, or as shown in FIG. Provide the groove l
If the metallized paste 400, 200 or ceramic paste 300 sandwiched between the upper and lower green sheets 100 is buried in O2, the metallized paste 400, 200 or ceramic paste sandwiched between them will be buried inside the upper and lower green sheets 100 in step f. 300 without changing its shape, and when they were baked together,
It is good to be able to more accurately prevent delamination caused by gaps between them.

In addition, in order to prevent delamination and deformation of the metallized pastes 400, 200 and the ceramic paste 300, pressure is applied to press the upper and lower green sheets 100 inward in step f, and heat is applied at that time. It is important to set the pressure and heating temperature to the upper and lower green sheets 100,
It is necessary to adjust depending on the type of combination of metallizing paste 400, 200 and ceramic paste 300.

In addition, when the metallizing paste 400 for forming the ground wall is applied in a grid or net shape in steps a and e, the metallizing paste 400 for forming the ground wall is applied to the surfaces of the upper and lower green sheets 100 for forming the external ceramic member. The ceramic paste 300 for forming the internal ceramic member is in direct contact with each other through the grid or mesh, and the barrier effect of the metallized paste 400 for forming the ground wall is weakened, and the upper and lower green sheets 100 and the ceramic paste are in direct contact with each other. 300, when the metallized paste 400 is fired together, the upper and lower green sheets 100 and the ceramic paste 30
0, the dielectric constant of the internal ceramic member 30 formed by sintering the ceramic paste 300 may decrease, and the external ceramic member 30 formed by sintering the upper and lower green sheets 100 may decrease. There is a possibility that the mechanical strength of the ceramic member 10 may be reduced. Therefore, when applying the metallized paste 400 for forming the ground wall in a grid or net shape as described above, the upper and lower green roots 100 and the ceramic paste 300
In particular, it is necessary to use a combination that does not cause the above-mentioned mutual reactions and diffusion effects when fired into a body.

In addition, in the f process, the upper and lower green sheets 1001
When the metallized pastes 400, 200 and the ceramic paste 300 are fired together, upper and lower green sheets 10 are used to prevent cracks from occurring in the substrate due to thermal stress caused by the difference in thermal expansion coefficients when they are sintered.
It is preferable to add a sintering aid to the metallized pastes 400, 200, and the ceramic paste 300, if necessary, to adjust the densification start time and shrinkage rate when they are sintered.

The method for manufacturing the ceramic substrate shown in FIGS. 1 to 7 consists of the above-mentioned steps. Through the above steps, a low dielectric constant internal ceramic member 30 is formed around the signal line 20 as shown in FIG. The ceramic substrate of the present invention can be formed in which the ground wall 40 is covered with a film-like, lattice-like, or net-like ground wall 40 through the ground wall 40, and the ground wall 40 is reinforced with an external ceramic member 10.

Below, preferred examples and unsuitable comparative examples of ceramic substrates formed by the above manufacturing method will be described.

Fruit 11'' Green sheets containing alumina as the main component are used for the upper and lower green sheets for forming the external ceramic member,
A ceramic paste containing mullite as the main component was used as the ceramic paste for forming the internal ceramic member, and a metallization paste containing tungsten or molybdenum as the main component was used as the metallization paste for forming the signal line and ground wall. Then, the upper and lower green sheets sandwiching the metallized paste and ceramic paste are placed inside them at a weight of, for example, 200 kg/c.
While pressing with m' d. They were heated at ℃ for about 10 minutes to bring them into close contact with each other. At that time, just to be sure, the upper and lower green sheets, ceramic paste, and metallized paste were washed in a humid nitrogen atmosphere under 7b. They were heated for about 5 hours at a temperature of 0.degree. and those upper and lower green sheets 100. metallize paste 40
0.200 and ceramic paste 300 in a weakly reducing atmosphere. 0-1d. A ceramic substrate was formed by integrally firing at a high temperature of 0°C. Here, firing the ceramic substrate in a weakly reducing atmosphere as described above is
This is to prevent the metallization paste from undergoing an oxidation reaction during firing. In addition, in order to match the sintering behavior of the upper and lower green sheets and the ceramic paste, that is, their sintering temperatures, we used alumina ceramic green sheets with a purity of 92 to 96% for the upper and lower green sheets, and A 95-99% mullite ceramic paste was used and a sintering aid was added to the upper and lower green sheets and the ceramic paste, respectively. Then, the area around the signal line is
In H2, it is surrounded by an internal ceramic member made of ceramic mainly composed of mullite, which has a low dielectric constant of 7.3, and the periphery of the internal ceramic member is surrounded by a ground wall made of metallization, so that the bending strength is increased. 35K
A ceramic substrate with high mechanical strength and high heat dissipation properties is obtained, which is reinforced with an external ceramic member made of ceramic mainly composed of alumina and has a high thermal conductivity of 15 W/mK (15 W/mK). The coefficient of thermal expansion of ceramic whose main component is mullite is 4.5X10-"/℃
The coefficient of thermal expansion of ceramic whose main component is alumina is 7.2X10-'/'C, and when they are sintered, thermal stress acts between them, but the coefficient of thermal expansion for the entire ceramic substrate is Since the volume ratio of the ceramic mainly composed of mullite was small, the thermal stress was small, and no cracks were generated in the ceramic substrate during firing.

Ceramic green sheets containing mullite as the main component are used as the upper and lower green sheets for forming the external ceramic members, and ceramic paste containing silica as the main component is used as the ceramic paste for forming the internal ceramic members. A metallizing paste containing tungsten or molybdenum as a main component was used as the metallizing paste for forming the ground wall. Then, in the same manner as in Example 1, the upper and lower green sheets sandwiching the metallized paste and the ceramic paste are heated while being pressed inside to bring them into close contact with each other. 1b. in a slightly acidic atmosphere. 0
~1d. A ceramic substrate was formed by integrally firing at a high temperature of 0°C.

In addition, since silica alone is difficult to densify during sintering, a sintering aid consisting of a combination of mullite, alumina, and a rare-earth group element MA compound was added to the ceramic paste whose main component is silica. . Then, the internal ceramic member is made of a ceramic whose main component is silica, which has a low dielectric constant of 3.5 at 1 MHz, and whose mechanical strength is extremely low when used alone. The bending strength is 20-30Kg/m for the 7-grid member.
m' and high thermal conductivity of 7 W/m K.
A ceramic substrate with high mechanical strength and high heat dissipation properties was obtained using ceramic containing mullite as a main component.

"Shioshiki Oki" Ceramic and 2K green sheets are used as the upper and lower green sheets for forming the external ceramic parts, and forsterite-based ceramic paste is used as the ceramic paste for forming the internal ceramic parts. A metallizing paste containing tungsten or molybdenum as a main component was used as the metallizing paste for forming the signal line and ground wall. Then, in the same manner as in Examples 1 and 2, the upper and lower green sheets sandwiching the metallized paste and ceramic paste are heated while being pressed inside.
They were brought into close contact with each other and fired together at high temperature to form a ceramic substrate. Then, the coefficient of thermal expansion of the ceramic whose main component is mullite is 4.5X 10-/''C, and the coefficient of thermal expansion of the ceramic whose main component is lusterite is 10.
5X10-@/"C, and there is a large difference in the coefficient of thermal expansion between the two, so the metallized paste for forming the ground wall is interposed between them due to the thermal stress that acts between them when firing the ceramic substrate. Although it acted as a buffer barrier to some extent, cracks occurred in the ceramic substrate.In addition, the ceramic green sheet containing mullite as a main component and the ceramic paste containing forsterite as a main component were mixed into 1b.0 to 1d. When they are simultaneously fired at a high temperature of 0°C, the metallized paste for forming the ground wall that is interposed between the two acts as a slight barrier, but the boundary between the two is caused by chemical interaction. They turned into a liquid phase and mixed with each other, increasing the dielectric constant of the internal ceramic member that surrounds the signal line and is made of ceramic whose main component is forsterite.

Daisatsuki 1 Ceramic green sheets containing aluminum nitride as the main component are used for the upper and lower green sheets for forming the external ceramic members, and ceramic paste containing hexagonal boron nitride as the main component for forming the internal ceramic members. A metallized paste containing tungsten or molybdenum as a main component was used for forming the signal line and ground wall. and,
The upper and lower green sheets sandwiching the metallized paste and ceramic paste are heated while being pressed inside to bring them into close contact with each other, and then heated at a high temperature of 1,700 to 1,800°C in a nitrogen-reducing atmosphere. A ceramic substrate was formed by firing the ceramic substrate. In addition, boron nitride does not become densified by itself when sintered, so the ceramic paste containing boron nitride as the main component may contain aluminum nitride, calcium carbonate, yttrium oxide, and other sintering aids. Compounds of group IVa and group Ila of the periodic table were added. Then, by using an internal ceramic member made of ceramic mainly composed of low dielectric constant boron nitride, which is difficult to use alone due to its low mechanical strength, it is possible to minimize the signal propagation delay time of the signal line, and to create a structure with high mechanical strength. A highly reliable ceramic substrate was obtained in which the mechanical strength of the substrate was increased by using an external ceramic member made of ceramic containing aluminum nitride as a main component. In this case, a good ceramic substrate can be formed even if the firing temperature of the substrate is 1800 to 1900°C, but in such a case, a ceramic paste mainly composed of boron nitride for forming internal ceramic members is used when firing the substrate. The metallization paste mainly composed of tungsten or molybdenum used to form signal lines interacts with each other to form tungsten boride, which significantly increases the conductor resistance of the signal line and reduces the resistance of the signal transmitted through the signal line. Since the conductor loss increases, the firing temperature of the substrate is preferably 1800° C. or lower.

Comparative Example 2 Ceramic green sheets containing aluminum nitride as the main component were used as the upper and lower green sheets for forming the external ceramic member, ceramic paste containing mullite as the main component was used as the ceramic paste for forming the internal ceramic member, and the signal line was A metallizing paste containing tungsten or molybdenum as a main component was used as the metallizing paste for forming the ground wall. Then, the upper and lower green sheets sandwiching the metallized paste and ceramic paste are heated while being pressed inside to bring them into close contact with each other, and sinter the ceramic whose main component is mullite. A ceramic substrate was formed by firing the two pieces together at high temperature in the same humid reducing atmosphere as in the process. As a result, the external ceramic member made of ceramic containing aluminum nitride as a main component undergoes an oxidation reaction in the humid reducing atmosphere, making it impossible to obtain a good ceramic substrate. Next, we fired the upper and lower green sheets, ceramic paste, and metallized paste together at high temperatures in the same nitrogen-neutral atmosphere that is used to sinter ceramics whose main component is aluminum nitride. A ceramic substrate was formed. Then, due to the residual carbon present in the furnace etc. during the firing of the substrate and the nitrogen in the nitrogen-neutral atmosphere, the internal ceramic member made of ceramic whose main component is mullite is nitrided, causing cracks on its surface and inside. or the mullite-based ceramic may diffuse into the external ceramic member made of the aluminum nitride-based ceramic, causing the external ceramic member to blacken, resulting in a defective ceramic substrate. I couldn't get it. In other words, ceramics whose main component is mullite and ceramics whose main component is aluminum nitride are
Since their thermal expansion coefficients are approximately the same, around 4.5 x 10-"/°C, it seems to be a good combination as a member for forming a ceramic substrate of the present invention, but from the above points, it is unsuitable. There was found.

Isamu Hihana (A composite ceramic green sheet containing alumina-borosilicate glass as the main component is used for the upper and lower green sheets for forming the external ceramic member, and silica-borosilicate glass is used as the main component for the ceramic paste for forming the internal ceramic member.) A metallization paste containing gold, silver, or copper as a main component was used as a metallization paste for forming signal lines and ground walls.

And those metallized pastes and cerami.

In the case where the upper and lower green sheets sandwiching the paste are heated while being pressed inward to bring them into close contact with each other, and a metallizing paste containing gold or silver as the main component is used as the metallizing paste. 8b. in the air, or in a neutral or reducing atmosphere if a metallizing paste containing copper as a main component is used. A ceramic substrate was formed by integrally firing at a low temperature of ~1000°C. Furthermore, the thermal shrinkage behavior of the upper and lower green sheets, ceramic paste, and metallized paste during sintering was matched by controlling the particle size distribution of the powder components that constitute them. Then, since the matrix components of the composite ceramic mainly composed of alumina-borosilicate glass and the composite ceramic mainly composed of silica-borosilicate glass are the same, no interaction will occur between them ( However, it is difficult to use it alone due to its low mechanical strength (it is difficult to use as a signal line by using an internal ceramic member made of a composite ceramic mainly composed of silica-borosilicate glass, which has a low dielectric constant of 3.9 at 1 MHz). In addition to keeping the signal propagation delay time to a minimum, the bending strength is 20
A highly reliable ceramic substrate was obtained in which the mechanical strength of the substrate was increased by using an external ceramic member made of a composite ceramic mainly composed of alumina-borosilicate glass of ~25 K g/mm8. In addition, the signal line made of metallization mainly composed of gold, silver, or copper has a low conductor resistance value, and a ceramic substrate with a signal line capable of transmitting high-frequency signals with low conductor loss was obtained.

Note that the ceramic substrate of the present invention can also be manufactured by a method other than the aforementioned manufacturing method of the present invention. For example, as shown in FIG. 11(a), there is a signal line 20 on the axis
A low dielectric constant internal ceramic member 30 comprising:
A columnar internal ceramic member 30 whose periphery is covered with a ground wall 40 and a mechanically strong external ceramic member 10 forming a ceramic substrate body as shown in FIG. 11(b) are fired separately. Then, the ceramic substrate of the present invention can be formed by fitting the internal ceramic member 30 into the insertion hole 12 provided in the external ceramic member IO by press-fitting or using an adhesive. Furthermore, in such a case, the present invention can select the types of combinations of the ceramic paste for forming the internal ceramic member 30, the green sheet for forming the external ceramic member 10, and the metallizing paste for forming the signal line 20 and the ground wall 40. Compared to the above-mentioned manufacturing method in which ceramic substrates are fired as one piece, the process is significantly expanded without being limited to the interaction of the green sheet, metallized paste, and ceramic paste during firing or the difference in their thermal expansion coefficients. becomes possible.

Further, the ceramic substrate of the present invention is disclosed in Japanese Unexamined Patent Publication No. 1-2274
It can also be formed by the method for manufacturing an electronic component substrate described in Japanese Patent No. 92. That is, a ceramic paste for forming an internal ceramic member with a low dielectric constant is used as the ceramic paste for forming an internal ceramic member inside the metallized paste for forming the ground wall, and a ceramic paste for forming an external ceramic member outside the metallized paste for forming the ground wall is used. A ceramic paste or green sheet for forming ceramics with high mechanical strength may be used as the ceramic paste or green sheet. However, when this manufacturing method is used, compared to the ceramic substrate manufacturing method of the present invention, a signal line having a coaxial structure made of the metallized paste and ceramic paste is formed on the surface of the green sheet forming the substrate body. In order to form the body, these pastes must be applied in many layers many times, and the application process takes a great deal of effort and time.

[Effects of the Invention] As explained above, the ceramic substrate of the present invention is equipped with a signal line having a coaxial structure or a pseudo-coaxial structure that can transmit high-frequency signals with a reduced propagation delay time Tpd and without introducing noise. A highly reliable ceramic substrate with high mechanical strength can be provided.

In addition, according to the method for manufacturing a ceramic substrate of the present invention, the screen printing technology, which is commonly used in the past, for applying metallized paste or ceramic paste to the surface of a green sheet, etc. can be used to integrate the metallized paste or ceramic paste together with the green sheet. By using a firing technique, a ceramic substrate having a signal line for transmitting high-frequency signals having a coaxial structure or a quasi-coaxial structure according to the present invention can be easily and quickly formed without any trouble.

[Brief explanation of drawings]

FIG. 1 is a partial side sectional view of a ceramic substrate of the present invention, FIGS. 2 to 7 are explanatory diagrams of a method of manufacturing a ceramic substrate of the present invention, and FIG. A partial side sectional view of a ceramic substrate, FIGS. 9 and 10 are illustrations of a method for preventing delamination, and FIGS. 11(a) and 11(b) are illustrations of other methods of manufacturing a ceramic substrate of the present invention, respectively. FIG. 10... External ceramic member, 20... Signal line,
30... Internal ceramic member, 40... Ground wall, b. ... Screen, 100 ... Upper or lower green root, 200 ...
- Metallized paste, 300...Ceramic paste, 400...Metallized paste.

Claims (8)

[Claims] 1. In a ceramic substrate having a signal line having a coaxial structure or a quasi-coaxial structure surrounded by a ground wall in the form of a membrane, a lattice, or a net, the external ceramic member outside the ground wall has high mechanical strength. A ceramic substrate for high-speed electronic components, characterized in that ceramic is used and a low dielectric constant ceramic is used for an internal ceramic member around a signal line inside a ground wall. 2. A method for manufacturing a ceramic substrate for high-speed electronic components, comprising forming the ceramic substrate by the following method. a. A metallizing paste for forming a ground wall is applied in the form of a film, a grid, or a net on the surface of a lower green sheet for forming an external ceramic member with high mechanical strength, and is dried. b. Next, a ceramic paste for forming an internal ceramic member having a low dielectric constant is applied in a belt shape onto the surface of the dried metallization paste and dried. c. Next, a metallized paste for forming signal lines is linearly applied to the surface of the dried ceramic paste and dried. d. Next, a ceramic paste for forming an internal ceramic member having a low dielectric constant is applied to the surface of the ceramic paste applied in step b, including the surface of the dried metallization paste, and dried. e. Next, the metallized paste for forming the ground wall is applied in a film, grid, or net shape on the surface of the metallized paste for forming the ground wall applied in step a, including the surface of the dried ceramic paste, and is dried. f. After that, an upper green sheet for forming an external ceramic member with high mechanical strength is laminated on the surface of the dried metallization paste, and the metallization paste and ceramic paste applied in steps a, b, c, d, and e are combined. The sandwiched upper and lower green sheets are heated while being pressed inside to bring the upper and lower green sheets, metallized paste, and ceramic paste into close contact with each other. Then, the upper and lower green sheets, ceramic paste, and metallized paste are fired together. 3. b, c, d, e before or in addition to step f
Before at least one or more steps, the previously applied metallized paste or ceramic paste surface is heated while being pressed with a smooth metal plate through a protective film, so that the metallized paste or ceramic paste is applied to the lower part. The method for manufacturing a ceramic substrate for high-speed electronic components according to claim 2, wherein the ceramic substrate is embedded inside a green sheet. 4. 4. The method for manufacturing a ceramic substrate for high-speed electronic components according to claim 2, wherein before step f, an organic solvent is applied to the surface of the upper green sheet to soften the surface of the upper green sheet. 5. Ceramic green sheets containing alumina as the main component are used for the upper and lower green sheets for forming the external ceramic members, and ceramic paste containing mullite as the main component for forming the internal ceramic members is used to form signal lines and ground walls. 5. The method of manufacturing a ceramic substrate for high-speed electronic components according to claim 2, wherein a metallizing paste containing tungsten or molybdenum as a main component is used as the metallizing paste. 6. Ceramic green sheets containing mullite as the main component are used for the upper and lower green sheets for forming the external ceramic members, and ceramic paste containing silica as the main component for forming the internal ceramic members is used to form signal lines and ground walls. 5. The method of manufacturing a ceramic substrate for high-speed electronic components according to claim 2, wherein a metallizing paste containing tungsten or molybdenum as a main component is used as the metallizing paste. 7. Ceramic green sheets containing aluminum nitride as the main component are used for the upper and lower green sheets for forming the external ceramic members, and ceramic paste containing boron nitride as the main component for forming the internal ceramic members is used to form signal lines and ground. Claims 2 and 3 wherein the metallizing paste for forming the wall is a metallizing paste containing tungsten or molybdenum as a main component.
Alternatively, the method for manufacturing a ceramic substrate for high-speed electronic components according to 4. 8. Composite ceramic green sheets mainly composed of alumina-borosilicate glass are used for the upper and lower green sheets for forming the external ceramic members, and composite ceramics mainly composed of silica-borosilicate glass are used for the ceramic paste for forming the internal ceramic members. Using paste,
5. The method of manufacturing a ceramic substrate for high-speed electronic components according to claim 2, wherein a metallization paste containing gold, silver, or copper as a main component is used as the metallization paste for forming the signal line and the ground wall.