JP2957087B2 - Low temperature sealing composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a low-temperature sealing composition, and more particularly to a low-temperature sealing composition suitable for hermetically sealing IC ceramic packages using alumina.

[0002]

2. Description of the Related Art Conventionally, glass has been used as a sealing material for IC ceramic packages because of its excellent airtightness, lack of moisture permeability and high mechanical strength. As sealing glass for such applications, PbO-B ₂ O
₃ system, PbO-B ₂ O ₃ low-melting glass are known in -ZnO system, normally, when used for sealing a ceramic package, for matching the ceramic package and the thermal expansion coefficient between these sealing glass, filler It is used by adding a metal oxide powder or the like referred to. Examples of the sealing composition containing a filler include JP-A-60-204637,
There is one disclosed in JP-A-59-18132.

[0003] However, Japanese Patent Application Laid-Open No. 60-204637,
The one disclosed in Japanese Patent Application Laid-Open No. Sho 59-18132 has a high sealing operation temperature of 400 to 450 ° C. In recent years, the degree of integration of semiconductor elements has been remarkably increased, and characteristics may be degraded under the influence of heat at the time of sealing. Therefore, sealing at a lower temperature has been desired. In addition, a low-temperature sealing material that can be sealed without causing thermal deterioration is also required for various display devices and the like that have been rapidly spread in recent years.

The above-mentioned PbO-B ₂ O ₃ system, PbO-B ₂ O
For low melting point glass ₃ -ZnO system, generally, increasing the PbO content, by reducing the content of B ₂ O _3, can be a low melting point, reduction of the amount of B ₂ O ₃ is a glass lost Increases the tendency to permeability and makes the glass unstable. Therefore B
It is said that the amount of ₂ O ₃ is required to be at least 6 to 7%.
As a result, JP-A-60-204637 and JP-A-59-1
In the composition disclosed in Japanese Patent No. 8132, the PbO content is already close to 90%, and it is difficult to stably and significantly reduce the melting point by this method.

A low-temperature sealing frit disclosed in Japanese Patent Application Laid-Open No. 63-315536 is one in which other components are introduced to lower the melting point. According to this, by adding Tl ₂ O to the PbO—B ₂ O ₃ -based glass, sealing at a temperature of 380 ° C. or less became possible.

[0006]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
The low-melting glass disclosed in JP-A-63-315536 has a thermal expansion coefficient of 1 as shown in Table 1.
It is extremely large at 50 to 167 × 10 ⁻⁷ / ° C. JP-A-63-3
In No. 15536, a large amount of Ca-substituted lead titanate having a negative expansion coefficient is used to make the thermal expansion coefficient close to that of alumina, and low expansion ceramic powder is added to suppress the occurrence of cracks. However, as pointed out in JP-A-63-315536, when a glass and a filler having significantly different coefficients of thermal expansion are mixed with each other, fine cracks are easily generated in the glass, and the mechanical strength and airtightness are reduced. If possible, it is desired that the low-melting glass itself has a low thermal expansion coefficient.

Further, if the matching of the thermal expansion coefficient is dependent on the introduction of a large amount of low expansion filler, there is a problem that the fluidity is reduced and the airtightness and the sealing strength are reduced, or the heat treatment time during sealing is prolonged. . The extension of the heat treatment time should be suppressed in a short time as much as possible in consideration of not only an increase in the processing cost but also an influence on the sealed object.

The present invention has been made in view of the above circumstances, and provides a low-temperature sealing glass which can be hermetically sealed at a low temperature of 350 ° C. or less in a short time and has a relatively low coefficient of thermal expansion. Aim. It is another object of the present invention to provide a low-temperature sealing composition having a thermal expansion coefficient similar to that of an IC ceramic package without deterioration in fluidity even when a filler is introduced.

[0009]

SUMMARY OF THE INVENTION The present invention, in order to achieve the above object, F to _{PbO-B 2 O 3 -Tl 2} O -based glass
To lower the softening point and to contain SnO ₂ to suppress an increase in the coefficient of thermal expansion.

That is, the present invention relates to a method for producing PbO
_{20~55%, PbF 2 3~20%,} Tl 2 O 30
_{~50%, B 2 O 3 6~14} %, SnO 2 2~10%,
ZnF ₂ 0-10%, ZnO 0.5-3%, Al ₂ O
₃ has 0.5 to 3% of the composition, a cold sealing glass, wherein the molar ratio of B ₂ O ₃ / SnO ₂ is 3 or more.

The low-temperature sealing glass (55 to 80% by volume) may have low expansion of at least one of lead titanate, niobium pentoxide, β-eucryptite, cordierite, and zircon. Ceramic filler 20 ~
It is a low-temperature sealing composition mixed with 45%.

[0012]

Next, the operation of the present invention will be described. In general, low-melting glass tends to have a high expansion as it becomes low-melting, and the addition of a large amount of low-expansion ceramic filler to match the thermal expansion coefficient with the ceramic package lowers the fluidity of the sealing glass. Low melting of glass
It is important to lower the softening point without increasing the coefficient of thermal expansion. In the present invention, by setting the glass composition within the above range, a low-melting glass with a reduced thermal expansion coefficient could be obtained.

That is, Tl ₂ O, PbF ₂ , ZnF ₂
, The softening point was lowered, and the addition of SnO ₂ suppressed an increase in the coefficient of thermal expansion. SnO ₂ has the effect of suppressing the coefficient of thermal expansion of the glass. However, increasing the amount of SnO ₂ gives the glass a tendency to devitrify. Therefore, in the present invention, by setting the molar ratio of B ₂ O ₃ / SnO ₂ to 3 or more, the tendency of devitrification is suppressed, and the amorphous state can be maintained.

The reasons for limiting each component of the low-temperature sealing glass to the above range are as follows.

[0015] PbO is a main component constituting the low melting point glass, but if it is less than 20%, the melting point becomes high and the glass becomes unstable, and if it exceeds 55%, the water resistance deteriorates. Preferably it is 25-45%. However, PbF ₂
May change to PbO and be present in the glass, so that the amount of PbO in the analytical composition is also expected to slightly exceed the upper limit.

PbF ₂ is a component effective for lowering the melting point of glass. However, if it is less than 3%, it has no effect, and if it exceeds 20%, the glass tends to be devitrified. Preferably 5 to 1
5%.

Tl ₂ O has a remarkable effect on lowering the melting point of glass, but if it is less than 30%, the contents of B ₂ O ₃ , ZnO and Al ₂ O ₃ added for stabilizing the glass are reduced. When the amount is increased to the upper limit, low meltability cannot be maintained.
If it exceeds 50%, the coefficient of thermal expansion becomes too high, which is not preferable. Preferably it is 35 to 45%.

B ₂ O ₃ is a glass stabilizing component.
If it is less than 6%, the glass is crystallized, and if it exceeds 14%, the sealing temperature becomes too high. Preferably 7 to 12%
It is.

SnO ₂ has the effect of lowering the coefficient of thermal expansion of the glass, but if it is less than 2%, the effect is small, and if it exceeds 10%, the glass tends to be devitrified, and the viscosity increases, and the fluidity is impaired. . Preferably it is 3 to 8%.

ZnF ₂ lowers the yield point of glass,
If it exceeds 0%, crystallization of the glass is caused. Preferably 5%
It is as follows. Further, if a large amount of F is present in the glass, crystallization is promoted. Therefore, the total amount of fluoride is preferably 5% or less.

ZnO and Al ₂ O ₃ are each 0.5%
If it is less than 3%, the glass becomes unstable, and if it exceeds 3%, the sealing temperature rises. Preferably, the upper limit of Al ₂ O ₃ is 2%.

The reason why the molar ratio of B ₂ O ₃ / SnO ₂ is set to 3 or more is to suppress the tendency of the glass to devitrify as described above. It has a tendency to be transparent, which is not preferable.

The low expansion ceramic filler in the present invention may be any one or two of lead titanate, niobium pentoxide, β-eucryptite, cordierite and zircon.
One or more powders are added to the low temperature sealing glass in the range of 20-45% by volume to approximate the thermal expansion coefficient of the material to be sealed. At this time, it is preferable that the addition amount is as small as possible in consideration of the fluidity at the time of sealing. In this regard, it is preferable to use minus-expanded lead titanate and niobium pentoxide. Liquidity,
In consideration of airtightness, sealing strength, etc., the filler having a particle size of 100 mesh is used. Further, it is more effective to use one that has passed through a 300-mesh sieve.

When the mixing ratio of the low-expansion ceramic filler to the low-temperature sealing glass is less than 20% by volume, it is difficult to approximate the thermal expansion coefficient of the ceramic package, and when it exceeds 45% by volume, the fluidity deteriorates and the airtightness is deteriorated. Or the sealing strength is reduced, or the heat treatment time during sealing is prolonged.
Assuming the sealing of the alumina ceramic package,
Although it depends on the filler to be combined, it is preferably in the range of 30 to 45% by volume.

The low-temperature sealing glass of the present invention comprises, in addition to the above components, TeO ₂ , V ₂ O ₅ , Sb ₂ O ₃ , Bi ₂ O ₃ , C
aO, MgO, Cu ₂ O, As ₂ O ₃ , BaO, GeO
_2. AlF ₃ can be added as needed, for example, to stabilize the glass or improve the water resistance. However, the amount of addition is limited to about 5% in total so as not to impair the properties of the glass for sealing at low temperatures.

Also, if the low expansion ceramic filler has a coefficient of thermal expansion of 50 × 10 ⁻⁷ / ° C. or less,
It does not prevent use within the above range. Other fillers that can be used include willemite, tin oxide,
There are mullite, quartz glass, and the like.

[0027]

Embodiments of the present invention will be described below. Table 1 shows examples of the present invention. In Table 1, No. 1 to
No. 24 shows an example of the present invention, and Nos. 25 to 27 are comparative examples. The compositions in the table are shown by mass percentage, and "B ₂
“O ₃ / SnO ₂ ” represents the molar ratio, and “α” represents (× 10 ^−7).
/ C), and the thermal expansion coefficient, “Tc”, represents the yield point of DTA.

[0028]

[Table 1]

[0029]

[Table 1]

[0030]

[Table 1]

[0031]

[Table 1]

[0032]

[Table 1]

[0033]

[Table 1]

A mixture of lead red, lead fluoride, thallium nitrate, stannic oxide, zinc white, aluminum hydroxide, etc. was prepared so as to have the composition shown in Table 1, placed in a platinum crucible, placed in an electric furnace, and placed at 700 ° C. For 30 minutes to obtain a sample. The glass obtained as a molded product was ground with a ball mill and used for sealing.

As is clear from the results shown in Table 1, the glass of the present invention has a coefficient of thermal expansion of 120 to 140 (× 10
^-7 / ° C) and its yield point is low. In contrast, Comparative Examples Nos. 25 and 26 containing no SnO ₂
Has a sag point equal to or lower than that of the examples of the present invention, but has a very high coefficient of thermal expansion. Also N
The glass of o.27 contains SnO _2, but B ₂ O ₃ / S
In this example, the molar ratio of nO ₂ was less than 3, and the glass was devitrified as a result of melting.

Next, a low-expansion ceramic filler was mixed using the above-mentioned glass so as to have a thermal expansion coefficient equivalent to that of alumina ceramic to prepare a sample of a low-temperature sealing composition. This example is shown in Table 2. In Table 2, the mixing ratio of the glass and the filler is indicated by volume percentage, and “α” is 30 to 20.
The coefficient of thermal expansion at 0 ° C., “sealing state”, was determined by processing each composition powder into a paste, applying it between alumina ceramic test pieces, drying and solidifying, and then heating at a temperature of about 350 ° C. for 15 minutes. The result of observing the sealing state after cooling is shown. The “sealing temperature” was obtained by molding a sample into a pellet having a thickness of 3 mm and a diameter of 20 mm, and measuring the temperature at which the diameter of the pellet expanded to 23 mm or more when heated for 15 minutes.

Samples Nos. 1 to 14 according to the examples of the present invention were all capable of sealing at a temperature of 350 ° C. or less, had no cracks or gaps on the sealing surface, and had a good sealing state. In contrast, Sample No. 1 using the glass of Comparative Example No. 26 above
In No. 5, 50% by volume of lead titanate was required to make the thermal expansion coefficient equal to that of alumina ceramics. Therefore, the fluidity was poor, and sufficient heat treatment at 350 ° C. for 15 minutes could not provide sufficient sealing strength. . When the sealing surface was observed by increasing the heat treatment temperature, fine cracks were observed in the glass, and it was judged that both the strength and the airtightness were insufficient.

[0038]

[Table 2]

[0039]

[Table 2]

[0040]

As described above, the present invention provides a PbO-PbF
_{By using 2-} B ₂ O ₃ —Tl ₂ O—SnO ₂ glass, the softening point was successfully reduced while suppressing an increase in the coefficient of thermal expansion. Thereby, sealing at 350 ° C. or lower can be performed, and adverse effects due to the heat treatment of the sealed object can be suppressed.

Further, since the thermal expansion coefficient of the glass itself is small, it is possible to use only a small amount of filler to be mixed and used to match the thermal expansion coefficient with the object to be sealed. Improves the airtightness and sealing strength of the joint.

Furthermore, since the difference in the thermal expansion coefficient between the filler and the glass mixed and used becomes small, cracks do not occur in the glass after sealing, and extremely reliable sealing can be performed.

As described above, the low-temperature sealing composition of the present invention comprises:
It is a member that is easily affected by heat and requires high reliability in airtightness and the like, for example, a material suitable as a sealing material for a semiconductor ceramic package.

Claims (3)

(57) [Claims] 1. PbO 20 to 55% by mass percentage,
PbF ₂ 3-20%, Tl ₂ O 30-50%, B ₂ O
_{3 6~14%, SnO 2 2~10%} , ZnF 2 0~10
%, 0.5% to 3% ZnO, Al ₂ O ₃ have a 0.5% to 3% of the composition, a low temperature sealing glass, wherein the molar ratio of B ₂ O ₃ / SnO ₂ is 3 or more . 2. The low-expansion ceramic filler 20 in 55 to 80% of the low-temperature sealing glass according to claim 1, in a volume percentage.
A low-temperature sealing composition comprising a mixture of about 45%. 3. The low-expansion ceramic filler is one or more of lead titanate, niobium pentoxide, β-eucryptite, cordierite, and zircon. Low temperature sealing composition.