JPH0283255A - Multi-layer circuit board using mullite-based ceramic material and semiconductor module - Google Patents

Abstract

PURPOSE:To form a high-strength ceramic material of mullite base suitable as multi-layer circuit board material of ceramics by blending mullite as a main component with a specific amount of at least one of Cr oxide, Mn oxide and compound oxide thereof. CONSTITUTION:This mullite-based ceramic material consists of 0.1-10wt.% at least one of Cr oxide, Nn oxide and compound oxide thereof and the rest of mullite and unavoidable impurities. A ceramic layer and a wiring conductor layer are alternately laminated, the wiring conductor layers are electrically connected by a through-hole conductor to give a ceramic multi-layer circuit board, which is loaded with a semiconductor element to give a semiconductor module. In the ceramic multi-layer circuit board and the semiconductor module, a sintered material of the abovementioned mullite-based ceramic material is used as the ceramic layer.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to mullite-based ceramic materials.

This mullite-based ceramic material is used for ceramic insulating substrates that are suitable for attaching pins for inputting and outputting electrical signals and for mounting semiconductor components to form functional modules, and is also used for the sealing part of semiconductor packages. It is also used as a buffer material (spacer) for thermal expansion.

[Conventional technology]

2. Description of the Related Art In recent years, as integrated circuits such as LSIs have become faster and more dense, a method of mounting chips directly on a circuit board has been used in order to dissipate heat and increase the speed of elements. This substrate has conventionally been made of alumina. This is because alumina has high strength, so when attaching pins etc.
This is because problems such as cracking do not occur.

However, this mounting method has a problem in that as the size of an integrated circuit such as an LSI increases, the stress generated between the integrated circuit material such as an LSI and the circuit board material due to temperature changes during mounting increases. In other words, alumina (AQ2), which is the mainstream of current ceramic multilayer circuit boards,
03), the thermal expansion coefficient of alumina itself is 30 x 10-
7/°C (from room temperature to 500°C), this value is more than twice as large. For this reason, the L
When silicon semiconductor chips such as SI are directly connected with solder, etc., thermal stress occurs at the solder joint due to the difference in coefficient of thermal expansion, which causes defects such as cracks and reduces the long life of the mounting. be.

In particular, the miniaturization of solder joints due to the increase in size and density of LSI chips tends to further worsen the mounting life. In addition, alumina has a high dielectric constant and has a problem in that the propagation speed of electrical signals is slow. To solve these problems, we need to develop substrate materials with low relative permittivity and high strength in order to bring the coefficient of thermal expansion of multilayer circuit boards closer to that of silicon and increase the propagation speed of electrical signals within multilayer circuits. There is a need.

Mullite ceramics can be considered as a material that satisfies this requirement. It is because the coefficient of thermal expansion of mullite is 40 to 5.
It has a coefficient of thermal expansion of 5X10''/'C (room temperature to 500'C), which is close to the coefficient of thermal expansion of silicon, and a relative permittivity of approximately 6.7 (LMHz
) and small.

However, when making a multilayer circuit board using only mullite, the firing temperature used for alumina multilayer circuit boards is 1600°C.
There is a problem in that the sintered body in the vicinity becomes porous due to insufficient sintering, and only a sintered body with low strength can be obtained. Therefore,
In order to obtain a dense mullite sintered body, it must be fired at a high temperature, but this poses various problems in terms of mass production.

Therefore, it was necessary to develop a high-strength mullite-based material that can be sintered at the same firing temperature as alumina-based ceramic materials. As such a mullite-based material, there is a composite material consisting of mullite and glass (Japanese Patent Application Laid-Open No. 115-1989)
(described in Publication No. 895). In this conventional example, the glass composition is, for example, cordierite (2MgO-ZAQz○a
・5sioz). In conventional mullite-based materials, mullite crystals are bonded by glass or crystals produced from glass.

Therefore, the strength of the material is the glass that binds the mullite crystals,
Or it depends on the crystals produced from the glass.

[Problem to be solved by the invention]

However, the strength of conventional materials is only about 150 MPa at maximum. In other words, the conventional technology uses mullite, develops a glass composition that enables sintering at a temperature equivalent to that of alumina, and focuses on the fact that mullite itself has a low dielectric constant and a coefficient of thermal expansion close to that of silicon. The purpose was not to increase the strength of mullite-based materials, and no studies have been conducted on that aspect.

Therefore, if a mullite-based material with low strength is applied to a multilayer circuit board, when electrical signal input/output pins are connected to the multilayer circuit board by brazing, etc., there will be a difference in the coefficient of thermal expansion between the brazing material and the multilayer circuit. The stress generated by this causes defects such as cracks in the wiring board, and the problem of not being able to obtain a highly reliable wiring board remains.

The object of the present invention is to provide a high-strength mullite ceramic material,
Another object of the present invention is to provide a semiconductor device using the same.

[Means to solve the problem]

We investigated the amount of glass added, the composition of the glass material, etc. for conventional materials in which glass composition is added to mullite, and found that they do not have a significant effect on strength improvement. Next, as a result of examining various oxide systems, it was found that mullite-based ceramic materials containing at least one of Cr oxide, Mn oxide, or their composite oxides are used in alumina-based materials. It was found from the shrinkage rate of the sintered body that sintering was sufficient at the firing temperature of 1600°C.

The present invention was made based on this knowledge, and its composition is 0.1 to 10% by weight of at least one of Cr oxide, Mn oxide, or their composite oxide, and the balance is mullite, and Consists of unavoidable impurities.

[Effect]

Cr added to ceramic materials whose main component is mullite
In a mullite-based ceramic material containing at least one of oxides, Mr, oxides, or composite oxides thereof in an amount of 0.1 to 10, compared to conventional mullite-based materials, 30
Compared to a system in which % by weight of glass is added, the mullite particles are sintered in a state where there is almost no glass phase binding them together, so the grain growth of the mullite particles is small. In addition, the amount added is 0.1 to 10
Since the weight percentage is small, the amount of reaction products produced by reaction with mullite is also small. Therefore, it is considered that the reaction product interposed between the mullite particles is composed of a stable crystalline phase, thereby achieving high strength.

Next, as a sintering aid, Cr oxide, Mn oxide, or
At least one of those composite oxides is 0.1 to 1
The reason why it is limited to 0% by weight will be explained. If the amount of oxide is less than 0.1% by weight, the material becomes porous and a dense sintered body cannot be obtained, so that sufficient strength cannot be obtained at a firing temperature of 1600° C., which is equivalent to that of an alumina ceramic material. In this case, it may be possible to obtain a sintered body with dense HL by increasing the firing temperature, but this poses problems in that there is no practically suitable furnace and in mass production. Next, the reason why it is set to 10% by weight or less is that if it exceeds 10% by weight, grain growth of mullite will occur, and the strength will decrease. An oxide amount of 1.0 to 360% by weight is good in terms of the dielectric constant and strength of the sintered body.

The ceramic material of the present invention is used as a ceramic layer material of a ceramic multilayer circuit board in which ceramic layers and wiring conductor layers are alternately laminated and each wiring conductor layer is electrically connected by a through-hole conductor. It is used as a ceramic layer material in a semiconductor module in which a semiconductor element is mounted on a plate via a ceramic carrier substrate and is equipped with a cooling means for cooling the back surface of the semiconductor element.

Further, in the semiconductor module according to the present invention, the ceramic carrier substrate and the semiconductor element are bonded by solder bumps, and the solder bumps are covered with an organic resin, and the organic resin includes 100 parts by weight of the resin and 5 to 10 parts by weight of rubber particles. 35 to 60% by volume of ceramic powder, the rubber particles are polybutadiene and one or more silicone rubbers, and the ceramic powder is a type of silicon carbide containing quartz, silicon carbide, silicon nitride, calcium carbonate, and beryllium. Preferably. The carrier substrate is preferably made of the above-described ceramic material of the present invention, has the same composition as the multilayer circuit board, or has a similar composition, and has a coefficient of thermal expansion similar to that of the multilayer circuit board.

The present invention can be used as a ceramic multilayer circuit board material in a computer-implemented structure in which the printed circuit board is electrically connected to a platter by pins provided thereon. The above-mentioned cooling means can be performed by indirectly cooling the semiconductor element with water. Therefore, the semiconductor element can be cooled through a heat transfer disk that is brought into contact with the semiconductor element and a heat transfer block that is cooled by a refrigerant. .

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Note that the present invention is not limited to these examples. Below, "1 part" indicates parts by weight, and "%" indicates weight %.

(Example 1) Table 1 shows the composition of the mullite ceramic material.

The composition is shown in weight%.

Mullite powder (average particle size 2 μm) is used as the mullite. The other elements have an average particle size of 1 to 3 μm.

The composition shown in Table 1 includes 5.9 parts of polyvinyl butyral with a degree of polymerization of 1000, 124 parts of trichlorethylene, 32 parts of tetrachlorethylene, 44 parts of n-butyl alcohol,
Add 2 parts of butyl phthalyl glycolate and wet mix in a ball mill for 20 hours to make a slurry. Air bubbles are removed from the slurry by vacuum degassing. The slurry is then applied onto a polyester film to a thickness of about 0.2 nynt using a doctor blade and dried through an oven to form a green sheet. Cut the green sheet into 50 square pieces,
After laminating 0 layers, they were bonded by hot pressing.

The crimping conditions were a temperature of 120°C, held for 10 minutes, and a pressure of 40°C.
kg/cd. After the pressure bonding, in order to remove the resin from the green sheet laminate, it was held at a temperature of 1200'C for one hour to perform degreasing. Thereafter, sintering was performed by holding the temperature at 1600'C for 1.5 hours to obtain a sintered body.

The wiring conductor materials, W and M, were fired at 1600°C.
This is because sintering such as o must be performed at the same time. Next, the sintered body was cut into test pieces for measuring relative dielectric constant and bending strength, and the test pieces were ground using a diamond lap grinding wheel. Table 2 shows the properties of the materials shown in Table 1.

In Table 2, a mark of 0 in the overall evaluation indicates a dielectric constant of 9.5 (IMHz) or less and a bending strength of 150 MPa or more, and a mark of X indicates a dielectric constant of 9.5. It is larger and the resistance strength is smaller than 150 MPa. For comparison, Table 3 shows the properties of mullite-based ceramics in which 30% of glass having a cordierite composition is added to mullite, and alumina-based materials.

In Table 2, the comprehensive evaluation is based on whether the material of the present invention has applicability as a multilayer wiring board.The characteristics shown in Tables 2 and 3 will be explained below. Nα in Table 1
1 to Nα3, Cr oxide, Mn oxide, or
Those to which at least one of these composite oxides is added in an amount exceeding 10% have a bending strength of 120 to 150 M.
The relative dielectric constant is as low as P a and 11.2-14 (LM
Hz). Mullite alone, such as N021, has a very low bending strength of 70 to 80 MPa. This is because densification is not achieved due to insufficient sintering. On the other hand, Nα4 to Nα20 in Table 1
With this material system, a dielectric constant of 9.5 (IMHz) or less and a bending strength of 150 to 290 MPa can be obtained, and the material can be sufficiently used as a multilayer wiring board material. The relative dielectric constant at this time is 9.4 at maximum even if 10 weight of oxide is added. From Tables 1 and 2, it can be seen that in order to obtain a material system with a low dielectric constant, it is sufficient to reduce the amount of the above-mentioned oxide added; conversely, in order to obtain a material system with a high flexural strength,
It can be seen that it is sufficient to increase the amount of oxide added.

Next, Table 3 will be explained. As can be seen from Table 3, the comparative material, alumina, has a dielectric constant of 7B, yl, 1
is 10 (IMHz) and the flexural strength is 300 MPa, and when 30% cordierite is added to the mullite material, the dielectric constant is 5.9 (IMHz) and the flexural strength is 150 MPa. It becomes. Therefore, although alumina exhibits a large strength value of 300 MPa, which is fully satisfactory, its relative dielectric constant is as large as 10, which causes a slowing of the signal propagation speed. On the other hand, a mullite-based material with 30% cordierite 1- added has a low dielectric constant of 5.9, which is good, but a flexural strength of 100 to 150 MPa, which is poor. It is enough. On the other hand, the mullite-based material shown in Table 3, which is the material of the present invention, has a dielectric constant of 9.5 (L M H
z) is larger than that of a system in which 30% glass is added to a mullite-based material, but a system in which 0.1% Cr oxide is added to mullite exhibits a similar dielectric constant and a lower bending strength. 150 to 160 MPa, and the bending strength is improved by 50% or more compared to the material system containing 30% glass. In particular, with regard to strength, when 3% of oxides were added, 240
~290 MPa was obtained, and the strength of alumina was 300
It was confirmed that this was a mullite-based ceramic material with a relatively low dielectric constant reaching more than 90% of MPa and high strength.

Next, the results of X-ray analysis of the sintered body will be explained. 1st
In the X-ray analysis results of the sintered body shown in Nα11 in the table, in addition to mullite, manganese aluminum oxide (MnSi0
3) and manganese silicate (MnSi03), and almost no amorphous material was observed. In contrast, the X-ray diffraction results of the sintered body containing 30% glass (cordierite) in the mullite-based material shown in Table 3 show that
In addition to mullite, spinel (A Q 2Mg04
), Safari (MgsAQ9Sit, t+0zo)
, Kozierai 1-(Mg2A Q 4si50t3)
, sillimanite (A Q zMgo5), and many other complex phases. This is because the glass component contained for firing the mullite-based material reacted with the glass component contained for firing the mullite-based material at the mullite interface.

Therefore, this is the cause of not being able to obtain sufficient strength.

In this way, from this example, mullite contains Cr oxide, M
By manufacturing a sintered body by adding 0.1 to 10% by weight to at least one of n-oxides or their composite oxides, a multilayer circuit with relatively low dielectric constant and high strength can be produced. A plate material is obtained.

Next, a multilayer circuit board was manufactured using a system in which 3% MnOz was added to mullite. A longitudinal cross-sectional view of this multilayer circuit board is shown in FIG. In FIG. 1, 1 indicates the surface layer;
2 indicates an insulating layer (an intermediate layer made of silica) close to the line wiring, and 3 indicates a back layer. External connection pins 4 are soldered to this back surface M3 via gold-germanium solder portions 8. Further, a Si chip 6 is connected to the first surface layer 1 via a solder connection portion 5 . 7 indicates conductor wiring.

Next, a method for manufacturing the multilayer circuit board shown in FIG. 1 will be explained. A hole with a diameter of 100 μm was formed using a puncher in the green sheet prepared by adding 3% MnO2 to mullite prepared in Example 1, and the green sheet made of a silica-based material with a dielectric constant of about 6 or less, and a conductor was formed using a commercially available tungsten paste. Wiring was formed by screen printing. The surface layer 1 and the back layer 3 in FIG. 1 are made of the material of the present invention, and the insulating layer 2 (
A silica-based material was used for the intermediate layer. After conductor wiring,
A laminate was produced using a laminate press.

After cutting this laminate into an external shape, it was placed in an electric furnace.

First, to remove the resin, use 10 H of N2 gas containing water vapor.
The temperature was raised to 1200°C at a temperature increase rate of 50°C/h in a two-gas atmosphere. Next, the temperature was raised at a rate of 100°C/h in a N2 gas atmosphere at 10 Hz, and the maximum temperature was 1.5°C at 1600°C.
h to produce a ceramic multilayer circuit board. After electroless Ni plating and gold plating were applied to the ceramic multilayer circuit board thus produced, Kovar pins 4 were connected with gold-germanium solder 8 using a conventional method using a carbon jig. In addition, the Si chip 6 was directly mounted using solder 5. In the thus obtained multilayer circuit board, the surface layer 1 and the back layer 3 are free from cracks due to stress caused by the difference in coefficient of thermal expansion with the brazing material, and are sound and highly reliable. A multilayer circuit board was obtained. Such a surface layer 1. Even when the electrical signal output pin is connected to the back layer 3 by brazing or the like, cracks that occur in the multilayer circuit board due to the difference in thermal expansion coefficient between the brazing material and the multilayer circuit board can be prevented, and This is a multilayer circuit board with a long lifespan.

Example 2 FIG. 2 shows the Nα10,11°12.
13, 17, and 18 are cross-sectional views of semiconductor modules using ceramic multilayer circuit boards.

The carrier board 12 was manufactured using the same composition and method as the ceramic multilayer circuit board. The differences are that the through hole position, the wiring pattern, the number of laminated sheets is seven, and the dimensions of the carrier substrate after firing are 11 mm square and 1 m thick. The ceramic layers of the multilayer board and the carrier substrate can have the same composition or can be combined with any of the compositions mentioned above.

95% of the 10 nn square semiconductor element 6 is placed on the carrier substrate 12.
Connection was made with lead-5% tin solder 5. The solder between the semiconductor element 6 and the carrier substrate 12 has a higher melting point than the solder 5 on the multilayer board side. Between the carrier substrate 12 and the semiconductor element 6, 100 parts of epoxy resin (EP-828) and polybutazine (C
TBNl 300x9) 5 to 10 parts of a mixed organic substance was mixed with 35 to 60 volume % of quartz terminals having an average particle size of 1 μm, and a resin having a coefficient of thermal expansion equivalent to that of the solder material was introduced.

next.

9×9=81 carrier substrates 12 (semiconductor elements are connected and materials mainly composed of organic materials are inserted) on a ceramic multilayer circuit board 13 in which Kovar pins 4 are connected with gold-germanium wax 8. were connected using 60% button-40% tin solder 5 to produce a semiconductor module. In this embodiment, the ceramic multilayer circuit board 13 has a layer of resin 14 using polyimide resin 14 and a circuit 15 on the upper layer. FIG. 3 shows a semiconductor device 6 mounted on the multilayer circuit board 13 produced in Example 1, a thermally conductive disk 11 brought into contact thereon, sealed with a metal housing 19, and He gas introduced inside. FIG. 2 is a partial cross-sectional view showing the structure of a semiconductor module. The heat conductive disk 11 is made of ceramics and has a thermal conductivity of 0.1 caQ/an-sec at room temperature.
・A sintered body having a temperature of ℃ or higher is preferable, and this sintered body is S
Those containing 0.1 to 3% by weight of Be in iC (BeO is particularly preferred) are preferred. Since the semiconductor element 6 generates a large amount of heat as an integrated circuit, water is directed back through the cooling port 20 to cool it. The structure shown in FIG. 2 can be similarly used as the semiconductor module structure.

FIG. 4 shows the semiconductor module 2 of FIG. 1 or 2.
4 has the structure shown in FIG. 3, and this is a multilayer printed circuit board 25.
FIG. 3 is a perspective view showing a computer mounting structure in which a semiconductor module 24 is three-dimensionally mounted, which is mounted on a connector 27 of a platter 26 via a terminal provided on a multilayer printed circuit board 25 and mounted on a connector 27 of a platter 26 via a terminal provided on a multilayer printed circuit board 25.

With this configuration, computer implementation can be made compact, and as mentioned above, the dielectric constant is low, so
Fast signal processing speed can be obtained.

〔Effect of the invention〕

According to the present invention, a multilayer circuit board with high signal processing speed can be obtained.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a semiconductor module according to an embodiment of the present invention, FIG. 3 is a cross-sectional view of a semiconductor module equipped with a cooling means of the present invention, and FIG. 4 is a cross-sectional view of a semiconductor module according to an embodiment of the present invention. FIG. 1... Surface layer, 2... Insulating layer, 3... Back layer, 4
...Pin, 5...Solder, 6...Semiconductor element.

Claims (3)

[Claims] 1. A mullite-based ceramic material comprising 0.1 to 10% by weight of at least one of Cr oxide, Mn oxide, or composite oxides thereof, and the remainder consisting of mullite and unavoidable impurities. 2. In a ceramic multilayer circuit board in which ceramic layers and wiring conductor layers are alternately laminated and each of the wiring conductor layers is electrically connected by a through-hole conductor, the ceramic layer is made of Cr oxide, Mn oxide, or
At least one of those composite oxides is 0.1 to 1
0% by weight, the balance being mullite and unavoidable impurities, the sintered body has a relative dielectric constant of 9.5 or less at 1 MHz, and a bending strength at room temperature of 150 MPa.
A ceramic multilayer circuit board characterized by the above. 3. A semiconductor module in which a semiconductor element is mounted on a ceramic multilayer circuit board in which ceramic layers and wiring conductor layers are alternately laminated and the wiring conductor layers are electrically connected by through-hole conductors, wherein the ceramic layer is made of Cr. oxide Mn oxide, or
The sintered body is composed of 0.1 to 10% by weight of one or more of these composite oxides, and the remainder is mullite and unavoidable impurities, and the relative permittivity of the sintered body at 1 MHz is 9.
．． 5 or less and a bending strength at room temperature of 150 MPa or more, the wiring conductor layer is made of Mo and/or W, and the ceramic multilayer circuit board is electrically connected to a printed circuit board. A semiconductor module characterized by being provided with pins.