JPS62260769A - Mullite ceramic material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

This mullite ceramic material is used for ceramic insulating substrates suitable for attaching pins for inputting and outputting Wi multiplier signals and for mounting semiconductor components to form functional modules, and is also used for sealing parts of semiconductor packages. It is also used as a buffer material (spacer) for thermal expansion.

[Conventional technology]

In recent years, as integrated circuits such as LSIs have become faster and more densely packed, a method of mounting chips directly on a circuit board has come into use 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 problems such as cracking do not occur when attaching pins and the like.

However, the above mounting method has the problem that as the size of integrated circuits such as LSIs increases, the stress generated between the integrated circuit materials such as LSIs and the circuit board materials due to temperature changes during mounting increases. there were. In other words, alumina (AuzOs), which is the mainstream of current ceramic multilayer circuit boards, has a thermal expansion coefficient of 3 that is lower than that of silicon, which is a material for integrated circuits such as LSI.
Compared to 0X10-7/'C (room temperature to 500℃), approximately 2
It shows a value more than twice as large. For this reason.

When a silicon semiconductor chip such as an LSI is directly connected to an alumina-based multilayer circuit board using a handheld cloth, thermal stress due to the difference in coefficient of thermal expansion occurs at the solder joint, causing cracks and other defects in the solder joint, resulting in long mounting times. There is a problem with not being able to obtain a long life. 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.

Furthermore, alumina has a high dielectric constant, which causes the problem that the propagation speed of electrical signals is slow.

In order to solve these problems, the coefficient of thermal expansion of the multilayer circuit board should be brought closer to that of silicon.

In order to increase the propagation speed of electrical signals in multilayer circuits,
There is a need to develop substrate materials with low dielectric constant and high strength.

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/''C (room temperature to 500℃), which is close to the coefficient of thermal expansion of silicon, and a relative dielectric constant of approximately 6.7 (IMIL
This is because it is small.

However, when making a multilayer circuit board using only mullite,
Firing temperature 16 used for alumina multilayer circuit boards
There is a problem that at temperatures near oO°C, sintering is insufficient and the material becomes porous, resulting in a sintered body with low strength. Therefore, in order to obtain an aSa mullite sintered body, it is necessary to fire it at a higher temperature, but the current firing temperature is about 1650°C at maximum, and r be.

Therefore, it was necessary to develop a mullite-based material that can be sintered at the same firing temperature as alumina-based ceramics and has high strength. Composite materials consisting of mullite and glass exist as such mullite-based materials (Japanese Patent Laid-Open No. 57-11
5895). In this conventional example, the glass composition is, for example, cordierite C2MgO, 2AAxOδ.
5 S i 02).

The above-mentioned conventional mullite-based material is one in which mullite crystals are bonded by glass or crystals produced from glass. The strength of the material therefore depends on the glass or crystals produced from the glass that binds the mullite crystals.

[Problem that the invention seeks to solve]

However, the strength of the conventional material is up to 150M, P
There are about a. In other words, the above-mentioned conventional technology uses mullite, develops a glass composition that enables sintering at a temperature equivalent to that of alumina, and mullite itself has a low dielectric constant and a coefficient of thermal expansion close to that of silicon. It was developed with a focus on the high 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, the difference in thermal expansion coefficient between the brazing material and the multilayer circuit board when input/output pins for electrical signals are connected to the multilayer circuit board by brazing, etc. The stress generated by this process causes defects such as cracks in the wiring board, and the problem remains that a highly reliable wiring board cannot be obtained.

In order to solve these problems, the present invention aims to provide a high-strength mullite-based ceramic material.

[Means for solving problems]

Regarding materials in which glass composition is added to conventional mullite, we investigated the amount of glass added, the composition of the glass material, etc., and found that they did not have a significant effect on improving strength. Next, as a result of examining two types of oxide systems, it was found that the mullite-based ceramic material to which oxides belonging to the Ma group of the periodic table were added could be sufficiently sintered at the firing temperature of 1600'C, which is used for alumina-based materials. That's what's happening.

This was determined from the shrinkage rate of the sintered body. .

The present invention was made based on this knowledge, and its composition includes 0.1 to 10% by weight of at least one type of oxide of the Ma group.
, remaining mullite (AIlzOs・Syu02~2 A Q
208.5ift) and unavoidable impurities. Further, one or more of magnesia and calcia is added to this by 0.1 to 5.
It is characterized by containing 0% by weight. In the case of these two types, 0.1 to 5.0% by weight is preferable.

[Effect]

A mullite-based ceramic material containing 0.1 to 10% by weight of an oxide belonging to group MA of the periodic table added to a ceramic material containing mullite as a main component has a higher concentration than a conventional mullite-based material with 30% by weight of a glass component added. , there is almost no glass phase binding the mullite particles, and sintering occurs in the same phase, so the grain growth of the mullite particles is small, and the addition amount is 0.
Since the amount is as small as 1 to 10% by weight, the reaction product generated by the reaction with the mullite system is the least. Therefore, the reaction product interposed between the mullite particles is composed of a stable crystalline phase, so it is highly It is thought that the strength has been improved.

Next, the reason why the amount of the oxide of group 111a of the periodic table added as a sintering aid is limited to 0.1 to 10% by weight in total of one or more types will be explained.

If the amount of oxide is less than 0.1% by weight, the material becomes porous at a firing temperature of 1600° C., which is equivalent to that of an alumina ceramic material, and a dense sintered body cannot be obtained, so that sufficient strength cannot be obtained. In this case, it is conceivable that a denser sintered body could be obtained by increasing the firing temperature, but this would result in a practically suitable sintered body.
The problem is that there is no.

Next, the reason why the weight is set to 10% by weight or less is that if it exceeds 10% by weight, grain growth of mullite will occur, and the 1 strength will decrease. The amount of ittria is preferably 0.1 to 3.0% by weight.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that the present invention is not limited to these Examples.

Below, "parts" indicate parts by weight, and "%" indicate weight %.

(Example 1) Table 1 (1) and (2) show the composition of the mullite ceramic material. The composition is shown in weight%.

Also, actunium-based oxides are excluded. This is because actunium is a radioactive element.

Mullite powder (average particle size 2 μm) is used as the mullite.

The composition shown in Table 1 includes 5.9 parts of polyvinyl butyral with a degree of polymerization of 100o, 124 parts of trichlorethylene, 32 parts of tetrachlorethylene, 44 parts of n-butyl alcohol,
Add 2 parts of butyl phthalyl glycolate and mix in a ball mill for 20 hours to make a slurry. Air bubbles are removed from the slurry by vacuum degassing. Next, the slurry is coated on a polyester film to a thickness of approximately 0.2 m using a doctor blade, and dried through an oven to form a green sheet (green molded product). make. green sheet 5
After cutting into zero angles and laminating 30 layers, they were bonded by hot pressing. The pressure bonding conditions were a temperature of 120° C., held for 10 minutes, and a pressure of 40 kg/d. After the pressure bonding, the green sheet laminate was held at a temperature of 1200° C. for 1 hour to remove the resin and degrease the green sheet laminate. Thereafter, the temperature was maintained at 1600° C. for 1 hour to perform firing, thereby obtaining a sintered body. The reason for firing at 1600° C. is that the wiring conductor materials such as W and Mo must be sintered at the same time.

Next, the sintered body was cut into test pieces for measuring dielectric constant and bending strength, and polished using a diamond trap grindstone. Table 2 shows the properties of the materials shown in (1) and (2) in Table 1. In Table 2, the overall evaluation is whether the mullite-based ceramic material to which I[Ia group oxide is added has applicability as a multilayer wiring board,
A mark of 0 in the overall evaluation indicates a dielectric constant of 9.5 (IM& ) or less and a bending strength of 150 MPa or more, and an x mark indicates a non-permittance. J4 Indicates that the electrical constant is greater than 9.5 and the bending strength is less than 150 MPa.For materials used for spacers etc., ratio, % [not limited to ratio value,
It is sufficient if the bending strength is 150 M, P a or more.

In addition, for comparison, Table 3 shows the composition and properties of mullite-based ceramics made by adding 30% of a glass component to form nigerite to general mullite, and alumina-based materials.

The characteristics shown in Tables 2 and 3 will be explained below.

In Table 1, those in which more than 10% of Laz and s were added had a low bending strength of 120 to 140 MPa. Also, Nα20 and Nα3 in Table 2
3. &40, in which the 111a group oxide is not added as a sintering aid, the sintered body is porous and not densified, so the specific 1N electric rate is 6.0 ~
Although it is low at 6.5 (LM7), the bending strength is 50 to 110.
It is unsuitable for use due to its small MPa.

On the other hand, the other material systems listed in Table 1 have a dielectric constant of 9.5 C.
LM7) Below, a bending strength of 150 to 280 MPa is obtained, and the material can be sufficiently used as a multilayer wiring board material. At this time, the relative dielectric constant is 9.5 at maximum even if 1O 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 oxide of group 111a of the periodic law; conversely, in order to obtain a material system with a high bending strength It can be seen that it is sufficient to increase the amount of oxide added.

Next, the results in Table 3 will be explained. As can be seen from Table 3, the comparative material, alumina, has a dielectric constant of 10.
(IMHz), the flexural strength is 300 MPa, and a mullite material with 30% cordierite added has a dielectric constant of 5.9 (IMI(z)) and a flexural strength of 150 MPa. Therefore, alumina has a large value of 300 MPa, which is a sufficiently satisfactory strength, but 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 added has a good dielectric constant as low as 5.9, but a bending strength of 100 to 150 MPaL,
The strength is insufficient because it has not been obtained.

On the other hand, in the material of the present invention in Table 3, which is a mullite-based material to which yttria oxide is added, the dielectric constant is 7.
．． 5 (IMI (z '')) shows a slightly larger value than the system in which 30% glass is added to the mullite-based material, but the ratio is almost the same in the system in which 0.1% yttria oxide is added to the mullite-based material. In terms of strength, a transverse strength of 150 MPa was obtained.Therefore, the transverse strength is improved by more than 50% compared to a system in which 30% glass is added to a mullite-based material.Especially Regarding strength, when 3.0% yttrioxide is added to mullite-based material, 250 MPa is obtained, which is more than 80% of alumina's strength of 300 MPa, and has a low dielectric constant and high strength. It was confirmed that it is a strong mullite ceramic material.

(,, people ifa) Table 2 Next, the results of X-ray analysis of the sintered body will be explained.

In the X-ray analysis results of the sintered body shown in Nα8 in Table 1.

In addition to mullite, yztrium silicate (YzSiOs
) and aluminum yttrium oxide (A n z
It consisted of a stable single crystal with Y40e), and almost no amorphous material was observed.

On the other hand, the X-ray analysis results of the sintered body containing 30% glass (cordierite) in the mullite-based material shown in Table 3 show A Q z○a, 5iOz in addition to mullite.

Spinel (A
Q 2M g O4), Safarin (MggA Q
asiz, 502o) + cordierite (M gzA
Q 4S i 2+016), sillimanite (A Q
It consists of many complex phases such as zs i Oa). This is because the glass component contained for firing the mullite-based material reacts and generates at the mullite interface.

Therefore, this causes insufficient strength.

From the above examples, it was found that by manufacturing a sintered body by adding 0.1 to 10 gb of oxide of Group A of Periodic Table 111 as a sintering aid to Murai 1-based material, it has a low dielectric constant. Moreover, a high-strength multilayer circuit board material can be obtained.

Note that when the material of the present invention is used as a spacer material, the dielectric constant can be ignored.

Next, a multilayer circuit board was manufactured using the mullite-martA oxide ceramic. A vertical cross-sectional view of this multilayer circuit board is shown in FIG. 3 indicates a back layer made of the material of the present invention. External connection pins 4 are connected to this back layer 3 via gold-germanium solder joints 8. being touched. Furthermore, a Si chip 6 is connected to the 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.

The mullite-ma group oxide ceramic green sheet produced in Example 1 and its specific H electric rate of about 6 or less (IMH
Holes with a diameter of 100 μm were formed in the green sheet of the silica-based material of z) using a punching machine, tungsten paste was filled in, and conductor wiring was formed using the tungsten paste by screen printing. The surface layer 1 and the back layer 3 in FIG.
A silica-based material was used. After conductor wiring, a laminate was produced using a laminate press machine. After cutting this laminate into an external shape, it was set in a furnace. First, in order to remove fat from the oil, the temperature was increased at a heating rate of 50'C/8 in an atmosphere of Nz gas + H2 gas containing water vapor.
The temperature was raised to 1200°C in h.

Next, the temperature was increased at a rate of 100°C in an atmosphere of N2 gas and H2 gas.
/h and held at a maximum temperature of 1600'c for 1 hour,
A ceramic multilayer circuit board was fabricated.

After electroless nickel plating and gold plating were applied to the ceramic multilayer circuit board thus produced, Kovar pins 4 were connected in a gold-germanium furnace 8 using a conventional method using a carbon jig.

In addition, the Si chip 6 was directly mounted using solder 5.

In the multilayer circuit board obtained in this way, no cracks due to stress caused by the difference in thermal expansion coefficient with the furnace material were observed in the front layer 1 and back layer 3, and a healthy and highly reliable multilayer circuit board was obtained. Obtained. surface like this)? j1 and back layer 3
A multilayer circuit board that can prevent cracks that occur in the multilayer circuit board due to the expansion difference between the brazing material and the multilayer circuit board even when electrical signal output pins are connected by brazing, etc., and that the multilayer circuit board has a long life. It is.

〔Effect of the invention〕

As explained above, according to the mullite-based ceramic material according to the present invention, sintering is performed in an in-phase reaction state by adding 0.1 to 10% by weight of a Ma group oxide, so mullite The grain growth of the particles is also small, resulting in a sintered body with almost no glass phase at the mullite grain boundaries. Therefore, it is composed of a stable crystalline phase, and high strength can be achieved.

[Brief explanation of drawings]

FIG. 1 shows a vertical cross-sectional configuration diagram of a multilayer wiring circuit board formed by fIS using a mullite ceramic material according to the present invention. 1... Surface layer, 2... Insulating layer, 3... Back layer, 4
...External connection pin, 5...Solder connection part, 6...
- Si chip, 7... Conductor wiring, 8... Gold-germanium brazing connection part.

Claims (1)

[Scope of Claims] 1. A mullite-based ceramic material comprising 0.1 to 10% by weight of at least one group IIIa oxide, the balance being mullite and unavoidable impurities. 2. At least one group IIIa oxide 0.1 to 10
1. A mullite-based ceramic material comprising at least one of 0.1-5.0% by weight of magnesia and 0.1-5.0% by weight of calcia, and the balance being mullite and unavoidable dull material.