JPH0558673A - Highly swellable sealing material - Google Patents

Abstract

PURPOSE:To obtain a sealing material having a high thermal expansion coefficient of approximately 120-220 X 10<-7>/ deg.C, capable of sealing at low temperatures, and having a high mechanical strength. CONSTITUTION:The objective sealing material comprises 45-80vol.% of the powder of low temperature melting point glass having a transition point of <=350 deg.C, 5-50vol.% of the powder of cristobalite and/or tridymite, and 0-40vol.% of the powder of a ceramic. The powder of the cristobalite and the powder of the tridymite, each having the maximum particle diameter of <=45mum, are employed. The ceramic powder includes the oxide powder of alumina, zirconia, magnesia, calcia, zinc stannate, calcium stannate, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-expansion sealing material, and more particularly to a high-expansion sealing material suitable for hermetically sealing metal IC packages.

[0002]

2. Description of the Related Art Alumina ceramics are widely used for high reliability packages for mounting ICs. In this alumina ceramic package, a sealing material made by mixing low-melting glass and low expansion filler such as willemite, cordierite, zircon, and tin oxide is used as a material for airtight sealing. There is.
These sealing materials have a low thermal expansion coefficient of 60 to 70 × 10 ⁻⁷ / ° C. so that they are compatible with alumina ceramics, and 500 ° C. so as not to adversely affect the IC chip to be mounted.
It can be sealed at the following temperatures.

By the way, in recent years, with the increase in size of ICs, ICs
In order to efficiently dissipate the heat generated from the package, it is considered to manufacture a package using a material having a higher thermal conductivity. As such, for example, metal packages using aluminum, copper, and alloys based on these have been proposed.

However, this metal package has a high coefficient of thermal expansion of 140 to 230 × 10 ^-7 / ° C., and the above-mentioned sealing material for the alumina ceramic package cannot be used.

On the other hand, among low melting point glass known as a low melting point sealing material, 120 to 180 × 10 ⁻⁷ /
Some of them have a high coefficient of thermal expansion of about ° C.
However, all such glasses have very low mechanical strength and cannot be practically used as a sealing material for IC packages.

Further, PbO-B ₂ O ₃ system, PbO-Zn
U.S. Pat. No. 4,818,730 proposes a high-expansion sealing material in which a low melting glass powder such as OB ₂ O ₃ system is mixed with calcium fluoride powder or barium fluoride powder.

[0007]

However, the mechanical strength of the sealing material disclosed in the above-mentioned US Patent is still insufficient.

The object of the present invention is 120 to 220 × 10 ^-7.
Another object of the present invention is to provide a sealing material having a high coefficient of thermal expansion of about / ° C, capable of sealing at low temperature, and having high mechanical strength.

[0009]

As a result of various studies, the present inventor has found that the above object can be achieved by using cristobalite powder or tridymite powder as a filler, and proposes the present invention. ..

That is, the high-expansion sealing material of the present invention is a mixture of 45-80% low melting glass powder, 5-50% cristobalite powder and / or tridymite powder, and 0-40% ceramic powder in volume%. Cristobalite powder and tridymite powder have a maximum particle size of 45 μm
It is characterized by the following.

[0011]

The high-expansion sealing material of the present invention is a mixture of low-melting glass powder, cristobalite powder and / or tridymite powder, and ceramic powder, and is 30-250.
It has a coefficient of thermal expansion of 120 to 220 × 10 ⁻⁷ / ° C. at high temperature and high mechanical strength.

In the high expansion sealing material of the present invention, the cristobalite powder and the tridymite powder are 30 to 250 ° C.
Coefficient of thermal expansion at 340 × 10 ^-7 / ° C, 3
It has a very high value of 00 × 10 ⁻⁷ / ° C. and high mechanical strength.

In the present invention, the cristobalite powder or tridymite powder has a maximum particle size of 45 μm or less, preferably 35 μm or less. That is, when such a filler having an extremely high thermal expansion coefficient is used in combination with the low melting point glass powder, the thermal expansion difference between the filler and the low melting point glass is large, and therefore, a very large thermal stress is exerted in the low melting point glass after sealing. Occurs. As a result, a large number of microcracks are generated in the sealing material, which makes air-sealing difficult.
However, the smaller the particle size of the filler used, the less likely it is that cracks will occur, and the maximum particle size is 45 μm.
In the following case, it is possible to effectively prevent the occurrence of cracks.

The reason why the mixing ratio of the cristobalite powder and / or the tridymite powder is limited as described above is that if the ratio of these fillers is less than 5% by volume, a sealing material having a high coefficient of thermal expansion cannot be obtained and the mechanical strength is high. This is because the strength decreases, and when the amount of these fillers exceeds 50% by volume, the thermal expansion coefficient of the sealing material becomes too large.

The cristobalite powder and the tridymite powder are spherical in shape, and the surface thereof is Z-shaped.
By forming a film made of nO, it is possible to improve the fluidity of the sealing material.

In the high-expansion sealing material of the present invention, alumina, zirconia, magnesia,
Oxide powders such as calcia, zinc stannate, and calcium stannate can be mixed in an amount of 40 vol% or less. That is, since the cristobalite powder and the tridymite powder have extremely high thermal expansion coefficients as described above, the thermal expansion coefficient of the sealing material may be too high if only these fillers are used. In such a case, it is possible to adjust the thermal expansion coefficient to a desired value by mixing one or more of the above-mentioned ceramic powders.

The reason why the mixing ratio of the ceramic powder is limited as described above is that when the amount of these fillers exceeds 40% by volume, there is little room for adding cristobalite powder or tridymite powder, and a sealing material having a high thermal expansion coefficient is obtained. Because it will not be obtained.

As the low-melting glass powder to be used in the high expansion sealing material of the present invention, various kinds of glass can be used, but one having a transition point of 350 ° C. or lower is particularly used. Thereby, the sealing temperature can be set to 500 ° C. or lower. Examples of such low melting point glass, PbO-B ₂ O ₃ system, PbO-ZnO-B ₂ O
_{3 system, PbO-PbF 2 -B 2 O} 3 system, PbO-V ₂ O _{5
System, PbO-V 2 O 5 -TeO} 2 system, PbO-V ₂ O ₅
-P ₂ O _{5 based, PbO-Bi 2 O 3 -B} 2 O 3 -TeO
₂ type glass etc. can be used.

The reason why the mixing ratio of the low-melting glass powder is limited as described above is that if the low-melting glass powder is less than 45% by volume, the fluidity of the sealing material is lowered and air-sealing cannot be performed. This is because the mechanical strength of the sealing material becomes insufficient when the content is more than the volume%.

When the highly expansive sealing material of the present invention is used in the form of paste, the average particle size of cristobalite powder, tridymite powder, and various ceramic powders is adjusted to 7 μm or less in order to obtain good fluidity. Preferably.

[0021]

【Example】

(Example 1) A low melting glass powder was prepared as follows.

By weight%, PbO 78.7%, B ₂ O ₃
6.0%, ZnO 2.8%, SiO ₂ 1.0%, Bi
₂ O ₃ 10.0%, so that the Fe ₂ O ₃ 1.5% of the composition, red lead, boric acid, zinc white, silica powder, bismuth oxide, and iron oxide formulated, using a platinum crucible 900 After melting at 0 ° C. for 1 hour, it was formed into a thin plate with a water cooling roller. Next, this molded product is crushed with a ball mill to give 250
A low-melting glass powder was obtained by passing through a mesh sieve. This glass had a transition point of 285 ° C. and a thermal expansion coefficient of 127 × 10 ⁻⁷ / ° C. at 30 to 250 ° C.

As the filler, cristobalite powder and alumina powder were used.

Cristobalite powder was prepared as follows. First, a spherical silica glass powder having a maximum particle size of 35 μm and an average particle size of 7 μm was fired at 1480 ° C. for 16 hours to be cristobalite. The cristobalite powder has an average particle size of 0.
After adding 5% by volume of ZnO fine particles of 1 μm and dry-mixing, it was heat-treated at 1000 ° C. for 1 hour to form a ZnO coating on the surface.

As the alumina powder, a commercially available product having an average particle diameter of about 5 μm was used.

The low melting point glass powder, cristobalite powder, and alumina powder thus obtained were mixed at a volume ratio of 60%, 20%, and 20% to obtain a sealing material.

This sealing material has a coefficient of thermal expansion of 150 × 10 ⁻⁷ / ° C. at a temperature of 30 to 250 ° C. and a sealing temperature of 410.
℃, bending strength is 600kg / cm ² , dielectric constant is 1
It was 2.3.

Further, using this sealing material, Al 70
% By weight, 30% by weight of Si, 160 × 10 ⁻⁷ /
A metal package (18 leads) having a coefficient of thermal expansion of ° C was sealed. As for the sealing, the sealing material was made into a paste using a vehicle as usual, and screen-printed on the package, followed by heat treatment in air at 410 ° C. for 10 minutes. The sealed product thus obtained was highly airtight.

The coefficient of thermal expansion is 4 mm in outer diameter and 5 in length.
Using a sample heat-molded to 0 mm, it was measured by a quartz push rod thermal dilatometer, and the bending strength was measured using a sample cut into a size of 10 × 10 × 50 mm from a block produced by heating a sealing material. It was determined by a 3-point bending test. Further, the dielectric constant was measured by using an LCR meter (25 ° C., 1M, using a sample heat-formed into a disk shape having an outer diameter of 35 mm and a thickness of 1.5 mm.
Hz).

Example 2 A low melting point glass powder was prepared as follows.

% By weight of PbO 84.3%, B ₂ O ₃ 1
Mix lead tin, boric acid, zinc white, and silica stone powder so that the composition is 1.9%, ZnO 2.8%, and SiO ₂ 1.0%, and melt at 900 ° C. for 1 hour using a platinum crucible. After doing
A water-cooled roller was used to form a thin plate. Next, this molded product was crushed by a ball mill and passed through a 250-mesh sieve to obtain a low melting point glass powder. This glass has a transition point of 300 ° C. and a thermal expansion coefficient of 11 at 30 to 250 ° C.
It was 2 × 10 ⁻⁷ / ° C.

As the filler, tridymite powder and cubic zirconia powder were used.

The maximum particle size of tridymite powder is 35 μm.
The quartz powder having m and an average particle size of 6 μm was heated at 1450 ° C. for 16 hours to form tridymite, which was used.

Cubic zirconia was prepared as follows. First, a low α-ray type zirconia raw material and calcium carbonate were added to ZrO ₂ 80 mol% and CaO 20 mol%.
And the mixture was baked at 1550 ° C. for 16 hours. Then, the fired product was crushed with a ball mill and
It was passed through a 50-mesh sieve to obtain cubic zirconia having an average particle size of 5 μm.

The low-melting glass powder, tridymite powder and cubic zirconia powder thus obtained were mixed at a volume ratio of 60%, 25% and 15% to obtain a sealing material.

This sealing material has a coefficient of thermal expansion of 160 × 10 ⁻⁷ / ° C. at 30 to 250 ° C. and a sealing temperature of 430.
℃, flexural strength 580kg / cm ² , dielectric constant 1
It was 2.5. Further, using this sealing material, Example 1
When the metal package used in 1. was sealed by the same method, a hermetically sealed product was obtained.

Comparative Example 60% by volume of the low-melting glass powder used in Example 1 and 40 calcium fluoride powder
A volume% was mixed to obtain a sealing material.

This sealing material has a coefficient of thermal expansion of 150 × 10 ⁻⁷ / ° C. at 30 to 250 ° C. and a sealing temperature of 410.
The temperature was 0 ° C. and the dielectric constant was 12.0, which was almost the same value as that of the sealing material of Example 1. When the metal package used in Example 1 was sealed by the same method using this sealing material, a sealed product with high airtightness was obtained. However, the mechanical strength was 400 kg / cm ² , and Example 1
It was as low as 200 kg / cm ^{2 as} compared with that of the sealing material.

The calcium fluoride powder was obtained by firing the raw material powder at 1000 ° C. for 5 hours for grain growth, crushing it with a ball mill and passing it through a 350 mesh sieve to obtain a powder having an average particle size of 5 μm. I used what I did.

[0040]

As described above, the low melting point and high expansion sealing material of the present invention has a thermal expansion coefficient of 120 to 220 × 10 ^−7.
It is suitable for airtight sealing of metal packages because it has high mechanical strength as high as / ° C and can be sealed at low temperature.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C03C 14/00 6971-4G

Claims (1)

[Claims] 1. A low melting point glass powder in a volume percentage of 45 to 80.
%, Cristobalite powder and / or tridymite powder 5 to 50%, and ceramic powder 0 to 40% are mixed, and the maximum particle diameter of the cristobalite powder and tridymite powder is 45 μm or less. material.