JPH08253345A - Composition for low-temperature sealing - Google Patents

Abstract

PURPOSE: To improve water resistance, insulating characteristics and fluidity in sealing of a composition for low-temperature sealing, incorporating a glass powder having a specific composition and a low-expansion ceramic filler powder. CONSTITUTION: Raw materials are blended so as to give a composition having 50-75wt.% of PbO, 1-20wt.% of PbF2 , 6-12wt.% of B2 O3 , 1-10wt.% of TeO2 , 1-5wt.% of ZnO, 0.5-2wt.% of SiO2 , 0.5-2wt.% of Al2 O3 and 0-10wt.% of Bi2 O3 . The raw materials are heated melted, deaerated, stirred, made to flow, annealed and ground to give glass powder. The glass powder in an amount of 5-90vol.% is mixed with 10-50vol.% of low-expansion ceramic filler powder to give the objective composition for low-temperature sealing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing composition which can be sealed at a temperature of 380 ° C. or lower, and more particularly to a low temperature sealing composition suitable for sealing an IC ceramic package.

[0002]

2. Description of the Related Art Low-melting-point glass frits are widely used for sealing or coating glass, ceramics and metals. It is also used in the semiconductor field when hermetically sealing a semiconductor chip in a ceramic package such as alumina. The main conditions required for the low melting point glass frit used for sealing the IC ceramic package are as follows. Capable of sealing at low temperature so as not to adversely affect the IC. Good water resistance to maintain good insulation properties for a long period of time. The coefficient of thermal expansion should match that of the ceramic package.

Of these, the lowering of the sealing temperature is strongly desired for the protection of the circuit, which is becoming more integrated and finer year by year.
A sealing composition obtained by adding a low expansion filler powder to a B ₂ O ₃ based or PbO—B ₂ O ₃ —Bi ₂ O ₃ based glass has a limit to lowering the melting point, and sealing at 400 ° C. or lower is not possible. It was difficult. The present inventors Besides this there is also one using the proposed PbO-B ₂ O ₃ -TeO ₂ based glass as Japanese Patent Application No. 5-219180, the also sealing requires temperatures of about 450 ° C. And

For this reason, the development of a composition capable of sealing at 400 ° C. or lower has been promoted, and a PbO-B ₂ O ₃ -Tl ₂ O-based composition represented by JP-A-63-315536 and a composition of JP-A No. -9747
Described in 0 JP _{PbO-B 2 O 3 -Bi 2} O 3 -F 2
System compositions and the like have been developed.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention JP-A-63-315536
_{PbO-B 2 O 3 -Tl 2} O based cold sealing frit described in JP, although can be lowered sealing temperature by the action of Tl ₂ O, since thallium is toxic substances, during manufacture, the sealing It is necessary to introduce equipment to prevent dust scattering in each process during work, which is not preferable from the viewpoint of environmental measures such as disposal of used products in the future. Further, the glass constituting the frit for low temperature sealing has a very large coefficient of thermal expansion as compared with ceramics such as alumina,
A large amount of low expansion filler must be mixed in order to match the coefficient of thermal expansion, and there is a drawback that the fluidity during sealing is impaired.

The PbO described in the above-mentioned JP-A-5-97470.
The -B ₂ O ₃ -Bi ₂ O ₃ -F ₂ type composition can be sealed at a temperature of 400 ° C or lower, but this composition has poor water resistance, and thus it can be used as an insulating material for long-term use. There is concern that defects may occur.

The present invention has been made in consideration of such circumstances, and it is substantially free of thallium and can be hermetically sealed at a temperature of 380 ° C. or less in a short time, and has water resistance. An object is to provide an excellent low-temperature sealing composition.

[0008]

In order to achieve the above object, the present invention reduces the softening point by substituting a part of PbO with PbF ₂ in a PbO-B ₂ O ₃ -Bi ₂ O ₃ system glass. , TeO ₂ are contained to improve water resistance.

That is, according to the present invention, PbO is used in terms of mass percentage.
_{50~75%, PbF 2 1~20%,} B 2 O 3 6~1
2%, TeO ₂ 1-10%, ZnO 1-5%, SiO
₂ 0.5-2%, Al ₂ O ₃ 0.5-2%, Bi ₂ O ₃
Glass powder 50-9 having a composition of 0-10%
0% by volume and low expansion ceramic filler powder 10-50
It is a low-temperature sealing composition composed of volume%.

As the low expansion ceramic filler powder, one or more selected from lead titanate, β-eucryptite, cordierite and zircon is used.

[0011]

The function of each component of the glass constituting the present invention and the reason for limiting the composition range as described above will be described below.

PbO is a main component for constituting a low melting point glass, but if it is less than 50%, a sufficiently low melting property cannot be maintained, and if it exceeds 75%, the glass becomes unstable.
It is preferably in the range of 55 to 75%. However, it is possible that F ₂ volatilizes in the melting stage, and PbF _{2 corresponding} to that amount is changed to PbO and is present in the glass. Therefore, it is also predicted that the amount of PbO slightly exceeds the upper limit value in the analytical composition. To be done.

PbF ₂ is an essential component in the present invention as a component for lowering the sealing temperature, but if it is less than 1%, its effect is small, and if it exceeds 20%, the glass becomes unstable.
It is preferably 3 to 15%. Since this composition range is a value when the raw material composition is vitrified as it is, it is expected that the amount of PbF ₂ will be rather low in the analytical composition, contrary to the above. In the present invention, the F component detected by the analysis is assumed to exist as PbF ₂ .

B ₂ O ₃ has an effect of stabilizing the glass, but if it is less than 6%, the glass is crystallized, and if it exceeds 12%, the softening point becomes too high and the initial purpose cannot be achieved. It is preferably in the range of 7 to 10%.

TeO ₂ has a remarkable effect on improving the water resistance of the glass, and is an essential component of the present invention as a component for stabilizing the glass, but if it is less than 1%, its effect is small, and if it exceeds 10%, it softens. This is not practical because the coefficient of thermal expansion increases as the point increases. Preferably 2-8
It is within the range of%.

ZnO has the effect of reducing the coefficient of thermal expansion of glass by the addition thereof in the glass of the present invention.
If it is less than 1%, the effect is not sufficient, and if it exceeds 5%, the softening point becomes high. It is preferably in the range of 2 to 4%.

SiO ₂ suppresses the tendency of glass to crystallize,
Al ₂ O ₃ has the effect of stabilizing the glass and improving the water resistance of the glass, but if it is less than 0.5%, the effect is small, and if it exceeds 2%, the softening point becomes too high, which is not preferable.

Bi ₂ O ₃ has the effect of improving the wettability and meltability of glass and stabilizing the glass, but it is 10%.
If it is contained in an amount exceeding the above range, the viscosity of the glass becomes too high and the fluidity is lowered.

The low-melting glass having the above composition has a large thermal expansion coefficient by itself as compared with ceramics such as alumina. Therefore, a low-expansion ceramic filler is mixed and used to approximate the thermal expansion coefficient of the adherend. . As the low expansion ceramic filler, one or more selected from lead titanate, β-eucryptite, cordierite and zircon is used, and 10 to 50% by volume is added to the low melting point glass. The particle size of these low expansion ceramic fillers can be used without any particular problem as long as they pass through a 60-mesh screen, but it is preferable to select and use the particle size appropriately depending on the object to be sealed. For example, when the material to be sealed has a small coefficient of thermal expansion such as alumina or aluminum nitride, it is possible to reduce the amount of filler added by using a material having a particle size between 60 mesh and 100 mesh sieve. It has the advantage of not increasing the sealing temperature. However, if a filler with a coarse particle size is used, the mechanical strength of the frit may decrease, so the particle size of the filler depends on various characteristics such as the coefficient of thermal expansion and mechanical strength required for sealing. It is desirable to select.

In the present invention, if the addition amount of the low expansion ceramic filler is less than 10% by volume, the effect of lowering the coefficient of thermal expansion is small and the desired value cannot be adjusted.
If it exceeds 0% by volume, the fluidity at the time of sealing may be deteriorated, and the airtightness and the sealing strength may be deteriorated, which is not preferable. The preferred range is 20 to 45% by volume, more preferably 25 to
40% by volume.

[0021]

Embodiments of the present invention will be described below. Table 1 shows examples of the present invention, and Table 2 shows comparative examples.

Red lead, lead fluoride, boric acid, tellurium oxide, zinc oxide, silica powder, aluminum hydroxide, and bismuth oxide were compounded so as to have the compositions shown in Tables 1 and 2 and housed in platinum crucibles. It heated at 1000 degreeC in the electric furnace for 1 hour. The melt was sufficiently stirred for defoaming and homogenization, poured onto an iron plate, and then gradually cooled at an appropriate temperature. Then, the low melting glass was pulverized and finely pulverized to 45 μm or less by a ball mill or the like. Next, in order to match the coefficient of thermal expansion with that of the alumina ceramic, ceramic fillers were mixed at the mixing ratio shown in each table to obtain a sealing composition. The particle size of the mixed ceramic filler used was one that passed through a 100-mesh sieve.

For each of the obtained sealing compositions,
The thermal expansion coefficient in the range of 30 to 250 ° C was measured by thermomechanical analysis (TMA), and α (× 10 -7 / ° C) was recorded in the table.
Indicated as. The sealing temperature (° C.) in the table is the temperature at which a button having a diameter of 20 mm was prepared from the composition powder for sealing and the button was heated to soften the button and the diameter thereof exceeded 23 mm. Further, the glass transition point and the water resistance of the low melting point glass in which the ceramic filler was not mixed were measured, and this is also shown in the table. The glass transition point is determined by a differential thermal analysis method (DTA method), and the water resistance is shown by the weight loss rate before and after boiling an intermediate particle size sample in boiling water for 1 hour according to the Japan Optical Glass Industry Association method. It was

[0024]

[Table 1]

[Table 1]

[Table 2]

The water resistance of the example samples shown in Table 1 shows a very good value because TeO ₂ was contained in the low melting point glass composition. As a result, the insulating property is kept good for a long time. The coefficient of thermal expansion of the sealing composition mixed with the ceramic filler was 67 to 70 × 10 −7 / ° C., which was in good agreement with that of alumina ceramics, and the sealing temperature in this state was 380 ° C. or less for all the example samples. Met.

Next, these sealing compositions were processed into a paste, applied between two alumina plates, heated and held at a temperature of 380 ° C. for 15 minutes, and the sealed state after cooling was observed. As shown in Table 1, in the examples of the present invention, the alumina plates were firmly sealed to each other in any of the samples, no cracks or bubbles were observed in the sealed portion, and the sealed state was good. It was decided.

On the other hand, Comparative Example No. 1 shown in Table 2 1
Had a high glass transition point (Tg) because it did not contain PbF ₂ in the glass composition, and as a result, the sealing temperature of the mixture with the ceramic filler also showed a high value. Comparative Example No. Two
Is an example in which PbF ₂ was excessively added, but the glass became unstable and crystallization occurred, and the fluidity was poor and the sealing temperature was high. Comparative Example No. In Nos. 3 and 5, the sealing temperature became high as a result of excessive addition of B ₂ O ₃ and TeO ₂ , respectively. Comparative Example No. In No. 4, the sealing temperature was the same as that of the example, but the water resistance was extremely poor, and the reliability of the insulation characteristics was low.

Also in these comparative examples, similarly to the examples, they were processed into a paste and applied between two alumina plates to form a paste.
The mixture was heated and held at a temperature of 80 ° C. for 15 minutes, and the sealed state after cooling was observed. As a result, Comparative Example No. Since the fluidity of samples 1, 2, 3 and 5 is poor and the adhesive surface is not wet enough,
It came off easily. Comparative Example No. Since the sealing temperature of the samples 6, 7, and 8 was 390 ° C, sufficient adhesive strength could not be obtained under the temperature condition of 380 ° C.

In the above embodiment, an example was shown in which the mixing ratio of the ceramic filler was selected so as to match the coefficient of thermal expansion with that of alumina ceramic, but the present invention is not limited to this.
It can be used by adjusting within the above range so that the coefficient of thermal expansion can be approximated to that of the adherend. Further, the present invention can be applied not only to semiconductor ceramic packages but also to various applications that require sealing at low temperatures. In particular, the low-temperature sealing composition of the present invention has high reliability with respect to insulation properties, and is therefore suitable for sealing various display device packages and other electronic components as well as semiconductor packages.

[0030]

As described above, the low-temperature sealing composition of the present invention contains substantially no thallium, so that
It is not necessary to install equipment to prevent dust scattering in each process of use, and the product is easy to handle.

Further, since it is excellent in water resistance, it has a high reliability with respect to insulation characteristics, can be sealed at a low temperature of 380 ° C. or less, and has excellent fluidity at the time of sealing. And no leaks will occur. Therefore, it is extremely suitable for sealing electronic components that require high reliability.

Claims (2)

[Claims] 1. PbO 50-75% by mass percentage,
PbF ₂ 1 to 20%, B ₂ O ₃ 6 to 12%, TeO ₂ 1
-10%, ZnO 1-5%, SiO ₂ 0.5-2%,
50 to 90% by volume of glass powder having a composition of 0.5 to 2% of Al ₂ O _{3 and} 0 to 10% of Bi ₂ O ₃ and 10 to 50% by volume of low expansion ceramic filler powder. A composition for low-temperature sealing. 2. The low expansion ceramic filler powder comprises:
Lead titanate, β-eucryptite, cordierite,
The low-temperature sealing composition according to claim 1, which is one kind or two or more kinds selected from zircon.