JPH0653652A - Multilayer ceramic wiring board and manufacture of the same - Google Patents

Abstract

PURPOSE:To improve signal propagation speed while maintaining a mechanical strength by selectively forming a cavity only in the proximity to an internal layer conductor wiring. CONSTITUTION:A multilayer ceramic wiring substrate produced by a green sheet multilayer forming method which allows three dimensional conductor wirings has a structure that a ground layer 2, a signal layer 3 and a power supply layer 4 are provided in the form of three-dimension within an insulated ceramic 1, a high speed LSI element 6 is provided on the upper surface of the ceramic 1 and input/output pins 7 are provided at the lower surface through via holes 5. Moreover, cavities 8 are selectively provided only in the proximity to conductor wiring within the multilayer ceramic wiring substrate by a cavity forming technology utilizing photolithographic method. Thereby, it becomes possible to obtain a high speed LSI 6 element loading substrate, contributing to the improvement of high density packaging and high transmission speed, because only the dielectric constant of the medium in the vicinity of wiring required for high transmission speed is low, sudden drop of mechanical characteristic such as strength is never generated and design of wirings can be realized very easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic wiring board for mounting a high speed LSI device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, semiconductor elements such as IC and LSI are
It was mounted on a printed circuit board such as glass epoxy or an alumina ceramic board, but with the high integration, miniaturization, and speedup of semiconductor elements, high-density fine wiring, high-speed transmission, and high-speed transmission were also achieved for the mounting board. There has been an increasing demand for higher frequencies and higher heat dissipation.

The conventional printed circuit board has problems such as through-hole plating property, workability, multi-layered adhesion, and thermal deformation at high temperature, so that there is a limit to high density. Therefore, it has not yet been put to practical use as a high-density mounting board, and a ceramic board has more potential.

However, since the alumina substrate also has to be sintered at a high temperature of 1500 ° C. or higher, the wiring conductor materials to be co-fired are limited to high melting point metals such as W and Mo having a relatively high specific resistance. . Therefore, if the transmission loss of the pulse signal is taken into consideration, there is a limit to the miniaturization of the wiring pattern.

On the other hand, even for high-speed transmission, since the propagation delay time of the pulse signal is proportional to the square root of the dielectric constant of the substrate material, it is essential to reduce the dielectric constant of the substrate material. However, the alumina substrate has a relatively high dielectric constant of about 10.

Therefore, a low temperature sinterable multilayer ceramic substrate has been developed. As the insulating material, there are a composite material system of ceramic and glass, a crystallized glass system, and the like, but since both are sintered at 1000 ° C. or less, Au, Ag—Pd, Cu, etc. having a low specific resistance are used as the wiring conductor material. Low melting point metals can be used. Further, it is possible to reduce the dielectric constant of the insulating material to 5 or less by selecting low dielectric constant ceramic or glass. Furthermore, since the green sheet multi-layering method can be used, three-dimensional wiring is possible, which is very advantageous for increasing the density.

[0007]

However, in order to efficiently increase the signal propagation speed, that is, to effectively reduce the distributed capacitance of the inner layer conductor, it is sufficient to lower the relative permittivity of only the peripheral dielectric. , There is no need to lower the relative permittivity of the entire dielectric. Among the current ceramics, no one has a relative permittivity superior to that of quartz glass, and is at most about 3.8.

On the other hand, Japanese Patent Application No. 63-269766, 24
As described in Nos. 5066 and 269766,
The uniform introduction of voids containing air or gas with a relative permittivity of 1 into the ceramic is very effective in lowering the relative permittivity of the matrix, but the reduction rate is limited and reliability is maintained. On top of that, I can only lower it to around 3. Also, with the introduction of many voids, mechanical properties, particularly bending strength, are severely deteriorated, and there are many practical problems.

Therefore, an object of the present invention is to provide a multilayer ceramic wiring board and a method for manufacturing the same, which solves the conventional problems.

[0010]

In order to achieve the above object, in a multilayer ceramic wiring board according to the present invention,
A multilayer ceramic wiring substrate in which conductor wiring is three-dimensionally formed in a ceramic substrate, and a cavity is selectively formed only in the vicinity of the inner layer conductor wiring.

In the method for manufacturing a multilayer ceramic wiring board according to the present invention, a method for manufacturing a multilayer ceramic wiring board having a conductor wiring pattern forming step, a cavity pattern forming step, a laminated body manufacturing step, and a processing step. In the step of forming the conductor wiring pattern, the through holes are formed in the green sheet in which the ceramic powder and the organic additive such as the binder are uniformly dispersed in the solvent, the conductor is filled, and the conductor wiring pattern is formed on the green sheet. The step of forming a cavity pattern, the step of forming a cavity pattern is a step of forming a desired cavity pattern using a photosensitive resin on a support, and the step of forming a laminate is a step of forming a cavity pattern made of the photosensitive resin and a ceramic green. It is a step of producing a laminate including sheets, and the treatment step is a step of debinding and firing the laminate. A.

[0012]

[Function] A step of forming through holes in a green sheet in which a ceramic powder and an organic additive such as a binder are uniformly dispersed in a solvent to fill a conductor and form a conductor wiring pattern on the green sheet; And a step of forming a required cavity forming pattern using a photosensitive resin,
A cavity is selectively formed only in the vicinity of the inner-layer conductor wiring by a step of producing a laminate including a cavity forming pattern made of the photosensitive resin and a ceramic green sheet, and a step of debinding and firing the laminate. By reducing only the effective relative permittivity in the periphery as much as possible, the signal propagation speed is efficiently increased and the mechanical strength is maintained.

[0013]

Next, the present invention will be described in detail with reference to the drawings.

(Example 1) In FIG. 1, a multilayer ceramic wiring board of the present invention is manufactured by a green sheet multilayering method capable of three-dimensional conductor wiring, and three-dimensionally grounded in the insulating ceramic portion 1. The layer 2, the signal layer 3 and the power supply layer 4 are formed, and the high speed LSI element 6 is formed on the upper surface of the ceramic portion 1.
Is installed, and the input / output pin 7 is placed on the bottom surface through the via hole 5.
Is a multilayer ceramic wiring board provided with,
Only near the conductor wiring inside the multilayer ceramic wiring board,
The cavities 8 are selectively provided by the hole forming technique using the photolithography method.

As Example 1 of the present invention, 55% by weight of alumina as a ceramic material and 45% by weight of borosilicate lead glass were used.
A case where a two-component composite containing wt% is used as a ceramic will be described. This composition is used in Japanese Patent Application No. 59-22.
It is described in the publication No. 399. This composite is 900 ℃
Sintered at about low temperature, dielectric constant 7.8, bending strength 3000
Indicates kg / cm ² . Further, a conductor material having low resistance such as gold or silver or a silver-palladium system can be applied.

Generally, a multilayer ceramic wiring board is manufactured by the following method. That is, a mixed powder of the above composition and an organic additive such as a binder are uniformly dispersed in a solvent using a high speed mixer or a ball mill to prepare a slurry, which is then formed into an insulating layer by a slip casting method or a docker blade method. A green sheet having a film thickness suitable for forming is prepared. In addition, the components of the organic vehicle such as the binder and the solvent are not particularly limited.

Next, through holes for connecting the upper and lower conductors are formed in the green sheet, the conductors are filled, and a conductor wiring pattern is formed on the green sheet. Further, these are laminated and thermocompression-bonded so as to have a required multilayer structure to produce a laminated body. Next, the organic vehicles added at the time of formation are sufficiently removed, that is, the binder is removed, and then baked under optimum conditions to obtain a multilayer ceramic wiring board.

Further, in the present invention, a step of forming a highly precise fine hole pattern using a photosensitive resin and laminating / thermocompression bonding with a green sheet including the above-mentioned green sheet on which conductor wiring is formed is added. FIG. 2 shows an example of a manufacturing process of the multilayer ceramic wiring board of the present invention, and FIG. 3 shows an example of a process system diagram. For details, see Japanese Patent Application No. 60-2.
No. 43218, 243219, 61-186427.

As the photosensitive resin, there are photocrosslinking type, photodegrading type, photopolymerizing type and the like which are generally used for photoresists, and acrylic type, nylon type, epoxy type, polyurethane type, polybutadiene type, etc. Various materials such as the above can be applied. For details, see Japanese Patent Application No. 61-1062.
67, 106268, 106269, 18642
No. 7 publication.

The following characteristics are required for these photosensitive resins. (1) A uniform film can be formed in a wide range of film thickness. (2) The fine pattern can be formed regardless of the film thickness. (3) There is little pattern deformation in the stacking / press bonding process. (4) Phenomena such as rapid decomposition, melting, expansion and deformation in the binder removal process do not occur. (5) There is no residue after decomposition. In particular, in designing wiring with high accuracy, it is considered that the film thickness of the photosensitive resin, that is, the cavity forming agent, is required to be about 10 μm to 1 mm and the film thickness accuracy is ± 10% or less.
Further, even at the level of practical use at present, a pattern width of 10 μm and a pitch width of 20 μm are possible.

Now, in order to form a highly precise fine cavity pattern using the above-mentioned photosensitive resin, first, referring to FIG.
As shown in (a), the support 10 is uniformly coated with the photosensitive resin 9 to a predetermined thickness. The support 10
Examples thereof include a carrier film such as polyester, a glass plate, a metal sheet, and a ceramic green sheet.

A photomask pattern 11 on which a desired pattern is formed is brought into close contact with the photosensitive resin 9 applied in this manner, and after light irradiation and exposure, development processing is performed to form a predetermined cavity pattern 12. Form (FIG. 3 (b),
(C)). In addition, in this embodiment, as the photosensitive resin 9,
The copolymer of methyl methacrylate and butyl methacrylate was 52.2% by weight, tetraethylene glycol diacrylate was 13% by weight, trimethylolpropane triacrylate was 2.6% by weight, benzophenone was 2.6% by weight, and Michler's ketone was 0. 5% by weight, 2-ethyl 4
0.05% by weight of -tert-butylphenol, 0.25% by weight of methylene blue, 21% by weight of ethylene glycol monoethyl ether acetate, 5.2% by weight of diethylene glycol monoethyl ether and 2.6% by weight of xylene. A photopolymerization type was used. The exposure conditions were that ultraviolet rays were selectively irradiated for 1 minute by a 3 kW ultra-high pressure mercury lamp. The developing conditions were such that methyl chloroform was sprayed at a pressure of 1 kg / cm ² .

Next, when the support 10 is other than the ceramic green sheet, it is necessary to form the cavity patterns 12 and then peel them off from the support 10 and transfer them onto the green sheet. For example, from the carrier film 110
If the resin is pressed under the conditions of ° C and a pressure of 250 kgf / cm ² , it can be easily peeled off, and the resin of the cavity forming pattern is embedded in the green sheet while maintaining its ideal shape.

In this way, the highly precise and fine cavity pattern 12 has the conductor wirings 2, 3, 3 so that it has a desired structure.
5 is laminated together with a green sheet including the ceramic green sheet 13 in which the ceramic green sheet 5 has been formed into a die for thermocompression bonding, and is integrated by applying pressure and temperature (FIG. 3 (d),
(E)).

Further, this laminated body is treated under a debinding condition so that the resin of the hollow pattern and the organic vehicles contained in the ceramic green sheet 13 are sufficiently decomposed and scattered. Usually, these organic substances are 500 to 600
Up to ℃, it decomposes and oxidizes completely in an oxidizing atmosphere, but if the temperature is rapidly raised to the decomposition temperature, cracks, deformation, delamination, etc. occur in the laminate. Therefore, it is preferable to raise the temperature at a slow rate of temperature increase of, for example, about 25 ° C./hour, and hold the temperature at 500 to 600 ° C. for a sufficiently long time.

Since the laminated body from which the organic substances have been sufficiently removed in the binder removal step is subsequently sintered at a predetermined temperature, the cavity pattern portion remains as a cavity 8 inside the sintered body (FIG. 3 (f)). )). In particular, if the cavity 8 having a desired size is formed at a predetermined position in the vicinity of the inner-layer conductor wiring, it is possible to selectively form the cavity inside the substrate by considering the lamination.

For example, when the cavity 8 having a size as shown in FIG. 4 is formed in the vicinity of the inner layer conductor wiring of the substrate and the signal propagation delay time is measured, it becomes 5.7 ns / m, and 9.5 ns when the cavity is not formed. It can be shortened by about 40% as compared with / m, which can greatly contribute to speeding up.

Also, using the volume logarithmic mixing rule (equation (1) below), which is a typical equation for calculating the composite relative permittivity, the relative permittivity of the medium existing between the signal layer and the ground layer is calculated as follows. become that way.

LogK = V ₁ · logK ₁ + V ₂ · logK ₂ (1) (K: relative permittivity of complex, V ₁ , K ₁ : volume fraction and relative permittivity of substance I, V ₂ , K ₂ : volume fraction and relative permittivity of substance II) If substance I is used as a ceramic in Example 1 of the present invention as a composite of alumina and borosilicate lead glass, and substance II is a cavity, K ₁ Is 7.8 and K ₂ is 1. Further, if the ratio V ₂ occupied by the cavity 8 between the signal layer 3 and the ground layer ₂ is simply calculated from the thickness in the cross-sectional direction,
It becomes 0.5. By substituting the above numerical values into the above formula (1) and determining the relative permittivity of the composite, it becomes approximately 2.8.

Further, when a theoretical value is obtained from a theoretical formula (see the following formula (2)) showing the relationship between the relative permittivity and the propagation delay time,
Since it becomes 5.6 ns / m as shown below, which is not much different from the above experimental value, it seems that it is sufficiently possible to predict the signal propagation delay time at the time of wiring design.

Tpd = √K / c (2) (Tpd: signal propagation delay time, c: speed of light) Similarly, basic pulse transmission characteristics such as characteristic impedance and crosstalk noise can be sufficiently designed. Is.

On the other hand, with respect to bending strength, a value required for practical use can be cleared as long as the cavity has a sufficient thickness.

(Example 2) As Example 2 of the present invention, a three-component composite containing 15% by weight of quartz glass as a ceramic material, 20% by weight of cordierite and 65% by weight of borosilicate glass was used. The case of using as a ceramic will be described. In addition, this composition is Japanese Patent Application No. 01-218707.
It is described in Japanese Patent Publication No. This composite was sintered at a low temperature of about 900 ° C. and had a dielectric constant of 4.4 and a flexural strength of 1600 kg /
In addition to showing cm ² , the thermal expansion coefficient is close to that of the Si element, and bare chip mounting is possible. Further, a conductor material having low resistance such as gold, silver, copper, or silver-palladium system can be applied. The manufacturing method is the same as that of the first embodiment.

As in Example 1, when a cavity having a size as shown in FIG. 4 was formed near the inner conductor wiring of the substrate and the signal propagation delay time was measured, it was 4.7 ns / m. It can be shortened by about 35% as compared with 7.0 ns / m, which can contribute to further speeding up compared with the first embodiment.
Further, the wiring design and the strength can be maintained sufficiently as in the first embodiment.

FIG. 4 of the present invention is merely an example, and the feature of the method for producing a multilayer ceramic wiring board of the present invention is that the position of the cavity can be controlled arbitrarily.
Another important point. Further, the present invention is not limited to the above embodiments unless the gist thereof is changed.

[0036]

As described above, in the multilayer ceramic wiring board of the present invention, the cavity effective for reducing the dielectric constant is provided only in the vicinity of the inner layer conductor on which the three-dimensional wiring is formed by the green sheet multilayer method. In addition, it can be selectively formed by using a photosensitive resin. Therefore, only the dielectric constant of the medium around the wiring required for high-speed transmission is low, the mechanical characteristics such as strength do not drop sharply, and the wiring design is relatively easy. Therefore, it is possible to provide a substrate for mounting a high-speed LSI element. This makes it possible to greatly contribute to higher packaging density and higher transmission speed.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view showing a multilayer ceramic wiring board of the present invention.

FIG. 2 is a diagram showing an example of a substrate manufacturing process of the present invention.

FIG. 3 is a diagram showing an example of a process system of the present invention.

FIG. 4 is a structural cross-sectional view showing a specific example of the present invention.

[Explanation of symbols]

 1 Insulation Ceramic Part 2 Ground Layer 3 Signal Layer 4 Power Layer 5 Via Hole 6 High Speed LSI Element 7 Input / Output Pin 8 Cavity 9 Photosensitive Resin for Cavity Formation 10 Support 11 Photomask Pattern 12 Cavity Formation Pattern 13 Ceramic Green Sheet

Claims (2)

[Claims] 1. A multilayer ceramic wiring board in which conductor wiring is three-dimensionally formed in a ceramic substrate, wherein a cavity is selectively formed only in the vicinity of the inner layer conductor wiring. Multilayer ceramic wiring board. 2. A method for manufacturing a multilayer ceramic wiring board, comprising: a conductor wiring pattern forming step, a cavity pattern forming step, a laminated body manufacturing step, and a treating step, wherein the conductor wiring pattern forming step comprises a ceramic powder. This is the process of forming through holes in a green sheet in which organic additives such as binders are uniformly dispersed in a solvent, filling conductors, and forming a conductor wiring pattern on the green sheet. A step of forming a desired cavity pattern using a photosensitive resin on the top, and a laminate producing step is a step of producing a laminate including the cavity pattern made of the photosensitive resin and a ceramic green sheet, Is a step of debinding and firing the laminate, a method for manufacturing a multilayer ceramic wiring board.