JPH08157234A - Composition for sealing - Google Patents

Abstract

PURPOSE: To obtain a compsn. satisfying various conditions required by the sealing material of a ceramic package for IC, a display device, etc., and hardly causing a plating bridge because the compsn. is almost independent of plating conditions. CONSTITUTION: This compsn. for sealing consists of 45-85vol.% glass powder and 15-55vol.% refractory filler powder. The glass powder has a compsn. consisting of, by weight, 25-88% PbO, 1-20% B2 O3 , 0 1-20% GeO2 , 0-70% Bi2 O3 , 0.1-10% in total, of 0-5% V2 O5 , 0-5% Fe2 O3 and 0-5% CuO, 0-20% ZnO, 0-3% TiO2 , 0-5% Al2 O3 and 0-9% F2 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing composition, and more particularly to a sealing composition suitable for sealing electronic parts such as IC ceramic packages and display devices.

[0002]

_2. Description of the Related Art Conventionally, PbO-B _{2 has been} used as a sealing material for electronic parts such as ceramic packages for ICs and display devices.
A sealing material using O ₃ —SiO ₂ glass powder is known.

Electronic components such as ceramic packages for ICs and display devices are mounted on a wiring board with lead-tin alloy solder. However, if an oxide film is formed on a metal surface such as leads, solder wettability deteriorates. Therefore, the electrical connection between the wiring board and the electronic component and the adhesive strength are deteriorated, and the connection reliability of the solder mounting is lowered. However, when these electronic components are sealed with the above-mentioned sealing material, there is a problem that the metal surface of the signal or power supply lead is oxidized by heating during sealing. Therefore, it is common practice to remove the oxide film of the leads and perform tin plating before mounting the electronic component.

Under these circumstances, the sealing material is required to have stability in a tin plating bath, that is, tin metal does not adhere to the sealing material even when plated, and good insulation between leads can be maintained.

[0005]

As a method of tin-plating electronic parts, a method of applying a current to a lead in a tin-plating bath has been used. A commonly used curmo tin plating bath is a 10% aqueous solution of sulfuric acid containing 3% tin sulfate and a brightening agent and is plated at a current density of 2 A / dm ² . According to this method, since the glass as the sealing material is an insulator, it is selectively plated only on the metal leads.

However, tin metal may adhere to the glass in contact with the leads, causing a problem of shorting between the leads, which must maintain the insulating property by the glass. The phenomenon in which tin metal adheres to the glass is called a plating bridge and is regarded as a problem that reduces the reliability of electronic components.

The cause of the plating bridge is considered as follows. That is, a plating bridge does not occur under a predetermined plating condition, and a commonly used sealing material has sufficiently high reliability. However, in the actual production line, the cleaning water from the pretreatment process that adheres to the leads may mix into the plating bath and reduce the sulfuric acid concentration.
It is not always possible to plate with a predetermined sulfuric acid concentration. Also,
Since the higher the current density is, the higher the plating efficiency is, the plating may be performed at a higher current density than the standard. In this way, plating under conditions other than the prescribed plating conditions
This is considered to be the cause of the plating bridge phenomenon.

Further, the sealing material used for sealing ceramic packages for ICs, display devices, etc. is not likely to cause the above-mentioned plating bridge, and is sealed at a low temperature so as not to adversely affect the ICs. It is required that the thermal expansion coefficient be compatible with that of ceramics and window glass, and that weather resistance such as water resistance be good. Also especially IC
In addition to these conditions, the sealing material for the package has high mechanical strength, good insulation characteristics so that the signal current does not leak, and soft error occurs when the IC element is irradiated with α-rays. Since it is generated, it is necessary to satisfy the condition that the substance that emits α rays is not included as much as possible.

The present invention has been made in view of the above circumstances.
It is an object of the present invention to provide a sealing composition that satisfies various conditions required for a sealing material such as a ceramic package for IC and a display device, and is particularly hard to be influenced by a plating condition and thus is unlikely to cause a plating bridge.

[0010]

The present inventors have SUMMARY OF THE INVENTION As a result of various experiments, the plating bridge SiO ₂ is present to be likely to occur in the glass composition, and GeO ₂ instead of SiO ₂ It has been found that the inclusion of the compound makes it difficult for plating bridges to occur, and is proposed as the present invention.

That is, the sealing composition of the present invention contains PbO 25-88%, B ₂ O ₃ 1-20%, Ge by weight percentage.
O ₂ 0.1 to 20%, Bi ₂ O ₃ 0 to 70%, V ₂ O _{5
0~5%, Fe 2 O 3 0~5} %, 0~5% CuO, V
₂ O ₅ + Fe ₂ O ₃ + CuO 0.1-10%, ZnO
_{0~20%, TiO 2 0~3%,} Al 2 O 3 0~5%,
It is characterized by comprising glass powder having a composition of F ₂ 0 to 9%.

The composition for sealing of the present invention has a weight percentage of PbO 25-88%, B ₂ O ₃ 1-20% and GeO _{2.
0.1~20%, Bi 2 O 3 0~70} %, V 2 O 5 0
_{~5%, Fe 2 O 3 0~5} %, 0~5% CuO, V 2
O ₅ + Fe ₂ O ₃ + CuO 0.1-10%, ZnO 0
_{~20%, TiO 2 0~3%,} Al 2 O 3 0~5%, F
₂ glass powder 45-85 vol% with 0-9% of the composition
And a refractory filler powder of 15 to 55% by volume.

[0013]

When the SiO ₂ is present in the glass composition, a plating bridge is likely to occur. However, PbO-B ₂ O
_{In a 3-} SiO ₂ type glass, if the content of SiO ₂ is extremely reduced, crystals are precipitated in the composition during sealing and the fluidity deteriorates, and low temperature sealing required as a sealing material. I can't wear it. On the other hand, in the present invention, SiO ₂
Since it contains GeO ₂ instead of, the stability of the glass is greatly improved and it becomes difficult for crystals to precipitate. For this reason, the sealing composition of the present invention can be sealed without causing a plating bridge and at a temperature equal to or lower than that of the conventional SiO ₂ -containing glass.

The reason why the composition of the glass powder in the sealing composition of the present invention is limited as described above will be described below.

The content of PbO is 25 to 88%, preferably 30 to 85.5%. If PbO is less than 30%, the viscosity tends to be high, and if it is less than 25%, the viscosity becomes too high and the glass does not flow sufficiently at low temperature. On the other hand, if it exceeds 85.5%, a crystallization tendency appears, and if it exceeds 88%, crystal precipitation becomes remarkable and low-temperature sealing becomes difficult.

The content of B ₂ O ₃ is 1 to 20%, preferably 1 to 15.5%. B ₂ O ₃ has the effect of stabilizing the glass. When the content of B ₂ O ₃ is less than 1%, crystals are deposited and low temperature sealing becomes impossible. On the other hand, 15.
If it exceeds 5%, the viscosity of the glass tends to be high, and 2
If it exceeds 0%, sealing at low temperature becomes difficult.

The content of GeO ₂ is 0.1 to 20%, preferably 0.1 to 10%. GeO ₂ is known as a glass-forming component like SiO _2, and by incorporating this component, a glass having excellent stability can be obtained. Moreover, the glass is stable with a smaller content than SiO ₂ , and the melting point can be lowered with the same content. GeO ₂
If the content is less than 0.1%, the glass tends to be more likely to crystallize and cannot be sealed at a sufficiently low temperature. On the other hand, if it exceeds 10%, the viscosity of the glass tends to be high, and
If it exceeds 0%, sealing cannot be performed at low temperatures.

The Bi ₂ O ₃ content is 0 to 70%, preferably 0.1 to 55%. Bi ₂ O ₃ has the effect of stabilizing the glass without increasing the viscosity and expanding the vitrification range. Bi ₂ O ₃ is not an essential component, but its effect appears when it is contained in an amount of 0.1% or more. On the other hand, if it exceeds 55%, the viscosity of the glass tends to be high, and if it exceeds 70%, the viscosity of the glass is further increased, and sealing cannot be performed at a sufficiently low temperature.

The content of V ₂ O ₅ is 0 to 5%, preferably 0.1% to 5%. V ₂ O ₅ has the effects of stabilizing the glass and lowering the surface tension of the glass to lower the melting point. V ₂ O ₅ is not an essential component, but when it is contained in an amount of 0.1% or more, the effect of lowering the melting point appears. On the other hand, if it exceeds 5%, it will be crystallized and cannot be sealed at a low temperature.

The contents of Fe ₂ O ₃ and CuO are 0 to 5 respectively.
%, Preferably 0 to 3% each. These components have the effect of stabilizing the glass, but if they are more than 3%, the viscosity of the glass tends to be high, and if they exceed 5%, they do not flow at a low temperature.

Further, in the present invention, in order to stabilize the glass, V ₂ O ₅ , Fe ₂ O ₃ and CuO are added in a total amount of 0.
1 to 10%, preferably 0.4 to 6%. If the total amount of these components is less than 0.4%, a crystallization tendency appears, and if it is less than 0.1%, precipitation of crystals becomes remarkable and low-temperature sealing becomes difficult. On the other hand, the total amount of these is 6%
If it is more than 10%, the viscosity of the glass tends to be high, and 10%.
If it exceeds, the viscosity becomes too high and it becomes difficult to seal at low temperature.

The content of ZnO is 0 to 20%, preferably 0 to 10%. ZnO has the effect of stabilizing the glass and improving the water resistance, but if it exceeds 10%, the vitrification range becomes narrow, and if it exceeds 20%, the glass crystallizes and does not flow sufficiently.

The content of TiO ₂ is 0 to 3%, preferably 0 to 2%. TiO ₂ has the effect of stabilizing the glass, but if it exceeds 2%, it tends to crystallize, and 3%.
If it exceeds, the tendency of crystallization becomes remarkable and the fluidization is stopped.

The content of Al ₂ O ₃ is 0 to 5%, preferably 0 to 2%. Al ₂ O ₃ has the effect of stabilizing the glass. If Al ₂ O ₃ is more than 2%, the viscosity of the glass tends to be high, and if it exceeds 5%, crystals precipitate and do not flow.

The content of F ₂ is 0 to 9%, preferably 0 to
8%. When F ₂ is added to a composition system containing a large amount of Bi ₂ O _3, the effect of reducing the viscosity of glass and suppressing the tendency of crystallization can be obtained. If F ₂ is more than 8%, crystallization tends to occur, and if it exceeds 9%, the stability of the glass is impaired, and crystallization becomes remarkable and the glass does not flow.

In the present invention, since SiO ₂ is a component that easily causes plating bridge, it is basically preferable not to contain it, but if the content is less than 0.5%, desired characteristics can be maintained. It doesn't matter.

In addition to the above components, Ag of 5% or less
O, SrO, P ₂ O ₅ , Co ₂ O ₃ , TeO ₂ , and 3
% Or less of Mo ₂ O ₃ , Rb ₂ O, Cs ₂ O, Nb ₂ O
₅ , Ta ₂ O ₃ , CeO ₂ , NiO, Cr ₂ O ₃ , As
Rare earths such as ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ and La ₂ O ₃ can be contained as other components. However, Tl ₂
The addition of highly toxic components such as O and CdO is environmentally unfavorable and should be avoided.

The glass having the above composition is amorphous and has good flowability because it is difficult for crystals to precipitate during sealing. Moreover, the glass transition point is as low as 320 ° C. or lower, and the viscosity of the glass is also low, so that it is a sealing composition suitable for low temperature sealing. Further, the thermal expansion coefficient at 30 to 250 ° C. is 110 × 10 ^−7.
/ ° C or higher, and it is possible to seal a high expansion material compatible therewith.

On the other hand, alumina (70 × 10 ⁻⁷ / ° C.), aluminum nitride (45 × 10 ⁻⁷ / ° C.), window glass (85
When sealing an IC package or display device made of a material that does not conform to the thermal expansion coefficient, such as × 10 ^-7 / ° C), mix refractory filler powder for the purpose of correcting the expansion difference with the adherend. It is possible to use.

When the refractory filler powder is mixed, the mixing ratio is preferably 45 to 85% by volume of glass powder and 15 to 55% by volume of refractory filler powder. The reason why the ratio of the two is limited in this way is that when the content of the refractory filler powder is less than 15% by volume, the effect is not exhibited, and 55% by volume.
This is because if the amount is larger, the fluidity becomes poor and the sealing becomes difficult.

As the refractory filler powder, lead titanate-based ceramics, willemite-based ceramics, cordierite, zircon-based ceramics, tin oxide solid solution,
Alumina is particularly suitable, and it is preferable to use these alone or in combination. Other than these, titanium oxide, niobium pentoxide, mullite and the like can be used. Note that β-eucryptite has a poor compatibility with glass and significantly reduces the fluidity. Further, it is preferable not to use it because it contains an alkali metal element (Li) as a constituent component and reduces the insulation resistance.

[0032]

EXAMPLES The sealing composition of the present invention will be described below based on examples.

Example 1 Table 1 shows SiO ₂ and GeO ₂
Of the effect on the plating bridge,
Sample a is an example of PbO—B ₂ O ₃ —Bi ₂ O ₃ —SiO ₂ -based glass, and sample b is SiO _{2 based on} the composition of sample a.
_{PbO-B 2 O 3 -Bi 2} O 3 based glass, excluding the sample c shows the sealing composition of the present invention with the addition of GeO ₂ in 1% sample b, respectively.

[0034]

[Table 1]

The samples in Table 1 were prepared as follows.

The raw material powders are blended so as to have the composition shown in the table,
The mixture was mixed, put in a platinum crucible, melted at 900 ° C. for 1 hour, molded into a thin plate, crushed, and passed through a 350-mesh stainless sieve to obtain a glass powder sample having an average particle diameter of 4 μm.

The glass powder samples obtained were evaluated for glass transition point, fluidity, glass stability, and stability in tin plating bath (hereinafter abbreviated as tin plating property). Regarding the tin plating property, 60% by volume of glass powder was used.
And 40% by volume of willemite-based ceramic powder are mixed, and the coefficient of thermal expansion at 30 to 250 ° C. is adjusted to 69 × 70 ⁻⁷ / ° C. of alumina so as to be 69 to 70
The one adjusted to × 10 ^-7 / ° C was used. The results are shown in Table 1.

As is clear from Table 1, sample a had a glass transition point of 315 ° C. and was excellent in fluidity and stability, but a plating bridge was generated in the tin plating property evaluation. Further, the sample b obtained by removing SiO ₂ from the composition of the sample a is
The tin plating property was improved, and the glass transition point was 305 ° C., which was lower than that of the sample a. However, crystal precipitation was remarkable, and the fluidity and stability were poor. on the other hand,
Sample c containing GeO ₂ has a glass transition point of 307 ° C.
And a lower value than Sample a, and no generation of plating bridge was observed. The fluidity and stability were also good.

These facts indicate that Ge ₂ instead of SiO ₂
Addition of O ₂ can prevent the occurrence of plating bridges,
Moreover, it is shown that a sealing composition having good fluidity and stability and capable of low-temperature sealing can be obtained.

The glass transition point is measured by a differential thermal analyzer (DT
Determined according to A). Moreover, the fluidity is 20m from the sample.
After making a button of m, height 5mm, 420 ℃, 10
Heated under the condition of minutes, the diameter of the button at this time is 23 mm
20m is acceptable, 20 to 23mm is acceptable.
Those less than m were disqualified. The stability was evaluated by visually observing the surface of the sample after the fluidity test, in which no crystals were observed at all, and when it was observed, it was judged as unsatisfactory. The tin plating property was evaluated as follows. First, an alumina package (28L C-DI was used by using each sample whose thermal expansion coefficient was adjusted.
After P) is sealed, the lead oxide film is removed and tin plating is performed. Then, the interface between the lead and the sealing composition was observed under a microscope of 50 times, and the sealing material having no metal tin adhered was good, the metal tin adhered, and the size of the adhered portion was 1
Those with a size of less than 00 μm were acceptable, and those with more than 100 μm were not acceptable. Note that tin plating is performed under conditions in which a plating bridge is likely to occur (a bath having a sulfuric acid concentration of 5% by volume, a current density of 5 A / dm
² , the plating time was 20 minutes).

(Example 2) Tables 2 and 3 show examples of a sealing composition made of glass powder according to the present invention.

[0042]

[Table 2]

[0043]

[Table 3]

As is clear from Tables 2 and 3, sample A
~ I has a glass transition point of 214 to 312 ° C, 30 to 250
The coefficient of thermal expansion at 10 ° C was 106 to 162 × 10 ^-7 / ° C, and both the fluidity and the stability were good.

Each sample in the table was prepared and evaluated in the same manner as in Example 1. The thermal expansion coefficient was measured using a push rod thermal expansion measuring device.

(Example 3) Tables 4 to 6 are prepared by mixing refractory filler powder with each sample of Tables 2 and I.
Examples of compositions for sealing C packages (Sample Nos. 1 to 1
12).

[0047]

[Table 4]

[0048]

[Table 5]

[0049]

[Table 6]

As is clear from Tables 4 to 6, sample N
o. 1 to 12 have a sealing temperature of 430 ° C. or less, a package strength of 230 lbf · in or more, and an α-ray emission amount of 0.18.
It was less than count / cm ² · hr and was excellent in tin plating property and insulation property. The coefficient of thermal expansion at 30 to 250 ° C. is the same as that of Sample No. 1 to 9 is 65 to 78 × 10
^-7 / ° C, sample No. 10-12 is 52-53 × 10 ^-7 /
The temperature was 0 ° C, and values corresponding to alumina (70 x 10 ^-7 / ° C) and aluminum nitride (45 x 10 ^-7 / ° C) were shown.

Table 7 shows examples (Sample Nos. 13 to 15) of sealing compositions for fluorescent display tubes, which were prepared by mixing the samples of Table 2 with refractory filler powder.

[0052]

[Table 7]

As is clear from Table 7, the sample No. Thirteen
In Nos. 15 to 15, the sealing temperature was 400 ° C. or lower, and the tin plating property and the insulating property were excellent. Further, the coefficient of thermal expansion at 30 to 250 ° C. was 76 × 10 ⁻⁷ / ° C., which was a value suitable for that of window glass (85 × 10 ⁻⁷ / ° C.).

These facts indicate that the sealing composition of the present invention satisfies various conditions required for a sealing material for IC packages and display devices, and in particular, it is difficult for plating bridges to occur.
Also, by containing an appropriate amount of refractory filler powder,
It is shown that the coefficient of thermal expansion can be adjusted so as to be compatible with the material to be sealed such as alumina, aluminum nitride and window glass.

The sealing temperature is the minimum temperature at which the paste prepared by adding a vehicle to each sample is printed on each package part and then graded, and then baked at various temperatures to achieve sealing. I asked. Package strength is 28 leads
It was determined by the torque test of the LSI C-DIP package. In the torque test, a rotational force is applied to the C-DIP base ceramic and the cap ceramic, and the strength at which the sealing material portion breaks is measured with a torque meter.
The α-ray emission amount was measured using a ZnS scintillation counter. For insulation, the resistance value between the leads of the electronic component is measured using a mega ohm meter, and the resistance value is 1 × 1.
Those having a resistance of more than 0 ⁹ Ω were evaluated as good, and those having a resistance of less than ⁹ Ω were evaluated as defective. The tin plating property was evaluated in the same manner as in Example 1. Sample No. Aluminum nitride for 10-12,
Sample No. For 13 to 15, evaluation was performed using a package made of window glass.

The refractory filler powders shown in Tables 4 to 7 were prepared as follows.

Lead titanate-based ceramic powder is PbT
It is a solid solution of CaO in iO ₃ crystal and contains litharge, titanium oxide, and calcium carbonate in a weight percentage of PbO70.
%, TiO ₂ 20%, CaO 10%, and after mixing, calcination is performed at 1100 ° C. for 5 hours, and the calcination product is crushed with alumina balls and passed through a 350-mesh stainless sieve. A powder having an average particle size of 4 μm was used.

The willemite-based ceramic powder includes zinc white, optical stone powder, and aluminum oxide in a weight percentage of ZnO 7.
It was prepared to have a composition of 0%, SiO ₂ 25%, and Al ₂ O ₃ 5%, and after mixing, it was fired at 1440 ° C. for 15 hours, then this fired product was crushed and passed through a 250 mesh stainless sieve. Then, a powder having an average particle diameter of 5 μm was used.

As the cordierite powder, magnesium oxide, aluminum oxide and optical stone powder are used as 2MgO.2Al ₂
Prepare so that the ratio of O ₃ · 5SiO ₂ is, and after mixing,
It was fired at 1400 ° C. for 10 hours, then the fired product was crushed and passed through a 250-mesh stainless sieve.

The zircon ceramic powder was produced as follows. First, natural zircon sand is once decomposed with soda, dissolved in hydrochloric acid, and then repeatedly concentrated and crystallized to obtain zirconium oxychloride having extremely small amounts of U and Th which are α-ray emitting substances, neutralized with an alkali, and then heated. Purified ZrO ₂ was obtained. Furthermore, high-purity silica stone powder and ferric oxide were added to this purified ZrO ₂ in a weight percentage of ZrO ₂ 66%, Si
O ₂ 32% and Fe ₂ O ₃ 2% were mixed and mixed, and after the mixture was fired at 1400 ° C. for 16 hours, the fired product was crushed and passed through a 250 mesh stainless sieve. used.

The tin oxide solid solution powder was made of SnO ₂ 9 by weight%.
A mixture of tin oxide and manganese dioxide having a composition of 9% and MnO ₂ 1%, mixed and fired at 1400 ° C. for 16 hours, then the fired product was crushed and passed through a 250 mesh stainless sieve. It was used.

As the alumina powder, a commercially available 350 mesh pass product was used.

[0063]

As described above, the sealing composition of the present invention satisfies various characteristics required for a sealing material such as an IC package and a display device, and is particularly hard to be influenced by plating conditions. Bridges are hard to happen. Therefore, it has high reliability and is suitable as a sealing material for electronic parts.

Claims (2)

[Claims] 1. PbO 25-88%, B by weight percentage
₂ O ₃ 1-20%, GeO ₂ 0.1-20%, Bi ₂ O
_{3 0~70%, V 2 O 5} 0~5%, Fe 2 O 3 0~5
%, CuO 0-5%, V ₂ O ₅ + Fe ₂ O ₃ + CuO
0.1~10%, 0~20% ZnO, TiO 2 0~
A sealing composition comprising a glass powder having a composition of 3%, Al ₂ O ₃ 0 to 5%, and F ₂ 0 to 9%. 2. PbO 25-88%, B by weight percentage
₂ O ₃ 1-20%, GeO ₂ 0.1-20%, Bi ₂ O
_{3 0~70%, V 2 O 5} 0~5%, Fe 2 O 3 0~5
%, CuO 0-5%, V ₂ O ₅ + Fe ₂ O ₃ + CuO
0.1~10%, 0~20% ZnO, TiO 2 0~
3%, Al ₂ O ₃ 0-5%, F ₂ 0-9% 45-85% by volume of glass powder and 15-55% by volume of refractory filler powder for sealing. Composition.