JPH0822763B2 - Low melting point sealing composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low melting point sealing composition, and more specifically, an IC made of a low expansion ceramic such as aluminum nitride, silicon nitride, silicon carbide or mullite. The present invention relates to a low melting point sealing composition suitable for machine-sealing a package.

[Prior Art and its Problems] The main characteristics required for a sealing material used for hermetically sealing an IC package made of a low expansion ceramic such as aluminum nitride are the thermal expansion coefficient of a low expansion ceramic ( (30 to 50 × 10 ^-7 / ℃), having a thermal expansion coefficient close to it, high mechanical strength so that cracks do not occur when shocked after sealing, and mounted in the package
To protect the IC element, it is necessary to seal it at the lowest temperature possible.

As sealing for conventionally IC package, but PbO-B ₂ O ₃ -based or PbO-B ₂ O ₃ -SiO ₂ based glass powder is used, mechanical strength, there is insufficient points in the thermal expansion coefficient Therefore, in recent years, many sealing materials have been proposed in which various low expansion filler powders are added to these glasses.

As described above, the sealing material for the low expansion ceramic package is required to have a coefficient of thermal expansion similar to that of the low expansion ceramic, and generally, the particle size of the low expansion filler is increased or the addition amount is increased. It is possible to lower the coefficient of thermal expansion of the sealing material by doing so, but on the other hand, increasing the particle size of the low expansion filler or increasing the addition amount deteriorates the fluidity of the sealing material and seals at low temperature. The problem arises that you cannot wear it.

[Object of the Invention] The present invention has been made in view of the above circumstances, and has a coefficient of thermal expansion similar to that of a low expansion ceramic, high mechanical strength, and sealing at a low temperature, specifically 450 ° C or lower. It is possible, and other characteristics required for the IC package sealing material, that is, the IC package sealing material has a high insulation resistance so that the signal current does not leak, and the IC element is irradiated with α rays. Since a soft error occurs, the substance that emits α-rays should not be included as much as possible, and the lead wires are electrically connected to each other if tin adheres to the glass in the tinning process of the lead wire after sealing, so there is no tin adhesion. That is, it is an object of the present invention to provide a low melting point sealing composition which also satisfies characteristics such as not causing a plating bridge.

[Structure of the Invention] The present invention achieves the above object by limiting the composition of the low melting point glass powder, the specific low expansion filler and the mixing ratio thereof, that is, the low melting point sealing composition of the present invention , The yield point is 350 ℃ or less, the coefficient of thermal expansion is 130 ×
Consists of a 10 ^-7 / ° C. or less of amorphous PbO-B ₂ O ₃ -based low melting glass powder and the lead titanate-based ceramic powder and a low-expansion ceramic powder, PbO-B These proportions are by weight ₂ O ₃ system low melting glass powder 45-80% Lead titanate ceramic powder 3 53% Low expansion ceramic powder 1-45%, the above amorphous PbO-B ₂ O ₃ system low melting point glass powder, PbO 78.0 to 87.0% by weight, B ₂ O ₃ 8.0~15.0
%, ZnO 0.5-3.0%, Bi ₂ O ₃ 1.0-4.0%, V ₂ O ₅ 0.1-1.
5%, SiO ₂ 0~1.0%, consists Al ₂ O ₃ 0~2.0%, the lead titanate-based ceramic powder, PbO by weight 60.0 to 75.
0%, TiO ₂ 10.0 to 35.0%, Fe ₂ O _{3 0 to} 10.0%, WO ₃
0-12.0%, CaO 0-10%, Fe ₂ O ₃ + WO ₃ + CaO 1.0-2
It consists of 0.0%.

The reason for limiting the mixing ratio of the PbO—B ₂ O ₃ based low melting point glass powder, the lead titanate based ceramic powder, and the low expansion ceramic powder in the present invention as described above is as follows.

That is, when the content of the low melting point glass powder is less than 45%, the fluidity of the composition for sealing becomes poor and the sealing becomes impossible at 450 ° C. or lower. If it exceeds 80%, the coefficient of thermal expansion becomes too large and the thermal shock resistance becomes small.

The lead titanate-based ceramic powder used in the present invention is PbTi
This is a solid solution of Fe ₂ O ₃ , WO ₃ or CaO in O ₃ crystal, and when the content of each component is in the above range, the effect of lowering the thermal expansion coefficient becomes larger than that of ordinary titanic acid powder. However, if the content of lead titanate-based ceramic powder is less than 3%, this effect cannot be obtained. If the content of lead titanate-based ceramic powder is more than 53%, the fluidity of the glass deteriorates and sealing cannot be performed at low temperature.

The low-expansion ceramic powder used in the present invention is one or more of willemite-based ceramic powder, β-eucryptite powder, cordierite powder, zircon-based ceramic powder, and tin solid solution powder. However, if the low-expansion ceramic powder is less than 1%, high mechanical strength cannot be obtained, and if it is more than 45%, the amount of lead titanate-based ceramic powder added is limited and the thermal expansion coefficient cannot be lowered sufficiently. .

Next, the reason why each composition of the PbO—B ₂ O ₃ based low melting point glass powder used in the present invention is limited as described above will be shown.

If the PbO content is less than 78.0%, the glass becomes too viscous, and if it is more than 87.0%, the glass tends to devitrify.

If B ₂ O ₃ is less than 8.0%, the glass tends to devitrify, and if it exceeds 15.0%, the viscosity of the glass becomes too large.

When ZnO is less than 0.5%, the glass tends to devitrify, and when it is more than 3.0%, the viscosity of the glass becomes too large.

When Bi ₂ O ₃ is less than 1.0%, the glass tends to devitrify, and when it exceeds 4.0%, the viscosity of the glass becomes too large.

V ₂ O ₅ is effective in stabilizing the glass, but 0.1
If less than 1.5%, the effect cannot be obtained, and if more than 1.5%, the glass tends to devitrify.

SiO ₂ and Al ₂ O ₃ are effective in stabilizing the glass, but when SiO ₂ is more than 1.0% and Al ₂ O ₃ is more than 2.0%, the viscosity becomes too large.

The low melting point glass powder of the present invention contains PbO, B ₂ O
₃ , ZnO, Bi ₂ O ₃ , V ₂ O ₅ , SiO ₂ , Al ₂ O ₃ as well as PbF ₂ , Sn
It is possible to contain other components such as O ₂ , BaO and TeO ₂ up to 3.0%.

[Examples] The present invention will be described below based on Examples.

Glasses A to D in Table 1 are amorphous PbO used in the present invention.
-B ₂ O ₃ system is an example of a low-melting glass powder.

The low-melting glass powder shown in Table 1 is prepared by mixing Komeitan, boric acid, zinc white, bismuth oxide, vanadium pentoxide, silica powder, aluminum hydroxide, and lead fluoride so as to have the composition shown in Table 1. Then, put it in a platinum crucible and about 900 in an electric furnace
After melting at 30 ° C. for 30 minutes, it was molded into a thin plate, pulverized with an alumina ball mill, and passed through a 150-mesh stainless sieve.

Since each glass has a yield point of 315 ° C or less, it has good sealing properties, and since the coefficient of thermal expansion is 122 × 10 ^-7 / ° C or less, it lowers the coefficient of thermal expansion as a sealing material. It is easy to do.

Table 2 shows the low-melting glass powder obtained as described above with lead titanate-based ceramic powder and low-expansion ceramic powder such as willemite-based ceramic powder, β-eucryptite powder, zircon-based ceramic powder or tin solid solution powder. It shows an example of mixing.

The lead titanate-based ceramic powder and each low expansion ceramic powder shown in Table 2 will be described below.

First, as described above, the lead titanate-based ceramic powder used in the present invention contains Fe ₂ O ₃ , WO ₃ or Ca in PbTiO ₃ crystals.
It is a solid solution of O, and was manufactured as follows in this example. Resurge, titanium oxide, calcium carbonate PbO 70
%, TiO ₂ 20%, CaO 10%.
After mixing, the mixture was fired at 1100 ° C. for 5 hours, and then the fired product was pulverized and passed through a 350-mesh stainless sieve to obtain a powder having an average particle size of about 5 μm.

Willemite ceramic powder is composed of zinc white, optical stone powder and aluminum oxide in a weight ratio of ZrO ₂ 70.0%, SiO ₂ 2
The mixture was prepared to have a composition of 5.0% and Al ₂ O ₃ 5.0%, mixed, baked at 1440 ° C. for 15 hours, ground with an alumina ball mill, and passed through a 250 mesh stainless sieve.

The β-eucryptite powder is prepared by mixing lithium carbonate, alumina, and stone powder for optical glass so as to have a composition of Li ₂ O · Al ₂ O ₃ · 2SiO ₂ , and after mixing, firing at 1250 ° C for 5 hours, and then What was crushed with a ball mill and passed through a 250-mesh stainless sieve was used.

Zircon-based ceramic powder is obtained by decomposing natural zircon sand with soda, dissolving it in hydrochloric acid, and repeating concentration crystallization to make zirconium oxychloride, which has extremely low U- and α-ray emitting substances, and after neutralization with alkali. ,
Heat to obtain purified ZrO ₂ , which contains high-purity silica powder and oxidized second
Iron was blended to have a composition of ZrO ₂ 66%, SiO ₂ 32%, and Fe ₂ O ₃ 2% by weight ratio, mixed and then fired at 1400 ° C. for 16 hours, and then the fired product was crushed to 250 The one passed through a stainless steel mesh sieve was used.

Tin solid solution is SnO ₂ 93%, TiO ₂ 2%, MnO ₂ by weight.
Prepare and mix tin oxide, titanium oxide, and manganese dioxide to 5%, and burn for 16 hours at 1400 ℃, then crush and
The one passed through a 0 mesh stainless sieve was used.

The above-mentioned low-melting glass powder, lead titanate powder and low-expansion ceramic powder were mixed in the proportions shown in Table 2 and then fired into a predetermined shape, and the thermal expansion coefficient and flexural strength were measured using this. However, the coefficient of thermal expansion was 40 to 55 × 10 ^-7 / ° C, and the bending strength was 610 kg / cm ² or more, indicating good properties.

Also, the mixture is added to the above-mentioned mixture by adding a vehicle to form a paste, and the coefficient of thermal expansion is 44 × 10 ^-7 /
When printed on a package made of aluminum nitride at ℃ and sealed, and the sealing temperature was measured, it was possible to seal at a low temperature of 440 ° C or lower.

In addition to the above, other characteristics required for IC packages, namely insulation resistance, α-ray emission, and tin deposition rate, were also measured. The insulation resistance (logarithmic value) was 1
It was 3.2 or more, the amount of α-ray emission was 0.21 count / cm ² · hr or less, and the occurrence rate of tin adhesion was 0%.

The coefficient of thermal expansion was measured for the fired product using a push rod type thermal expansion measuring device, and the bending strength was 10 × 10 × 50 mm for the fired product.
It was molded into a rectangular column and measured by a well-known three-point load measuring method. The insulation resistance is 150 ° C using a mega ohm meter.
The value of α-ray emission was measured using a ZnS scintillation counter.
This is a result of observing the glass surface with a microscope of 28 times after forming a 28-lead package, tin-plating this lead.

[Effects of the Invention] As described above, the low melting point sealing composition of the present invention is suitable for hermetically sealing an IC package made of a low expansion ceramic, specifically, aluminum nitride, silicon carbide, silicon nitride. It is suitable as a sealing material for packages made of ceramics having low expansion and high thermal conductivity.

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Claims (2)

[Claims] 1. A yield point of 350 ° C. or less and a thermal expansion coefficient of 130 × 10.
Consists of a ^-7 / ° C. or less of amorphous PbO-B ₂ O ₃ -based low melting glass powder and lead titanate-based ceramic powder and the low expansion ceramic powders, PbO-B ₂ O ₃ these proportions by weight system is in the range of the low-melting glass powder 45-80% lead titanate-based ceramic powder 3-53% low expansion ceramic powders _{1~45%, PbO-B 2 O} 3 based low-melting glass powder of the amorphous , PbO 78.0 to 87.0% by weight, B ₂ O ₃ 8.0 to 15.0
%, ZnO 0.5 to 3.0%, Bi ₂ O ₃ 1.0 to 4.0%, V ₂ O ₅ 0.1
.About.1.5%, SiO ₂ 0 to 1.0%, Al ₂ O ₃ 0 to 2.0%, and the lead titanate-based ceramic powder is PbO 6 in weight ratio.
0.0 to 75.0%, TiO ₂ 10.0 to 35.0%, Fe ₂ O _{3 0 to} 10.0
%, WO ₃ 0 to 12.0%, CaO 0 to 10%, Fe ₂ O ₃ + WO ₃ + Ca
A low melting point sealing composition comprising O 1.0 to 20.0%. 2. The low-expansion ceramic powder is one or more of willemite-based ceramic powder, β-eucryptite powder, cordierite powder, zircon-based ceramic powder, and tin solid solution powder. The low melting point sealing composition according to item 1.