JP5953537B2 - Low softening point glass powder - Google Patents

Description

The present invention relates to a glass powder used for sealing electronic parts.

  In recent years, sealing using a paste containing glass powder has been performed in various electronic component manufacturing processes. Sealing is mainly to protect electronic parts from gas and moisture, so that the electronic parts are covered with a protective member and sealed with a paste containing glass powder for stable operation of the electronic parts. It is an important process.

For glass powder used for sealing, in order to prevent deterioration of electronic components to be sealed, it is desired that the glass powder is melted at a low temperature, specifically, the softening point is 600 ° C. or less. Yes. Currently, glass powder containing lead oxide is used as such a low softening point glass powder.

  In recent years, however, the toxicity of lead has become a problem. Lead is less likely to be excreted when ingested by the human body and tends to accumulate in the body. It is also known to cause lead poisoning when ingested in large amounts. In addition, it has been pointed out that lead from the discarded electronic components is eluted by acid rain and penetrates underground, causing soil contamination and groundwater contamination. For this reason, environmental regulations are often applied, and in Europe, the use of lead in electronic components is regulated. Against this background, development of a low softening point glass powder that can be sealed at a low temperature with a lead-free composition is strongly demanded.

  In addition, when using a glass powder material whose viscosity changes rapidly due to temperature changes even when the softening point is low, strict temperature control is required to control the viscosity range with good workability in the sealing process. -ing

Bismuth glass (Patent Documents 1 and 2) and vanadium glass (Patent Documents 3 and 4) have been proposed as practical lead-free low softening point glass powder materials used for such sealing. Bi ₂ O ₃ —B ₂ O ₃ glass, Bi ₂ O ₃ —ZnO—B ₂ O ₃ glass and V ₂ O ₅ —BaO—ZnO—B ₂ O ₃ glass that have been put into practical use are softened. The difference between the point and the glass transition temperature is about 20 ° C. to 80 ° C., and the material has a viscosity that suddenly changes due to temperature change. Further, even in lead borosilicate glass such as PbO—B ₂ O ₃ —SiO ₂ that has a relatively slow viscosity change, the difference between the softening point and the glass transition temperature is 80 ° C. to 100 ° C. In the composition adjusted so that a difference exceeds 100 degreeC, since the softening point exceeds 600 degreeC, the use used will be limited (patent document 5).

Next, the thermal expansion coefficient of the sealing glass can be kept low by adding a low expansion ceramic filler or the like, but by adding a ceramic filler, the softening point is increased and the softening flow is not uniform. Since it affects the thermophysical properties, it cannot be added in large quantities. Therefore, it is desired that the thermal expansion coefficient of the glass powder is 100 × 10 ⁻⁷ or less, and further 80 × 10 ⁻⁷ or less.

  In addition, when the particle size of the glass frit is small, the surface area of the powder is increased and aggregation is likely to occur. Such agglomeration causes a bridging phenomenon (a phenomenon in which powders agglomerate and a tube used as a conveyance path is blocked) in the manufacturing process. On the other hand, if the average particle size is too large, the thermal conductivity of the particles becomes uneven, which tends to cause non-uniformity of the softening flow.

Japanese Patent No. 3172592 Japanese Patent No. 4766444 Japanese Patent No. 4299021 JP-A-8-59295 JP-A-5-282951

First, the glass transition temperature and the softening point will be described. Glass becomes liquid when heated to a temperature above its melting point. Conversely, when the glass melt is slowly cooled from a molten state at high temperatures, atoms and molecules are regularly arranged and crystallization occurs. However, when the glass melt is cooled relatively quickly, the viscosity is low. Since it is high, the arrangement of atoms and molecules hardly occurs even when the melting point is reached, and as a result, the liquid is cooled without being crystallized. This state is called supercooled liquid. As the liquid cools, the viscosity increases, and as the liquid cools, it becomes a solid state. This temperature is called the glass transition temperature (Tg).

As described above, the glass transition temperature is a temperature at which the supercooled liquid changes to a glass state, and is generally obtained from analysis of a thermal expansion curve. That is, the tangent of the thermal expansion coefficient curve in the low-temperature solid state and the tangent of the thermal expansion coefficient curve in the high-temperature supercooled liquid are extrapolated, and the temperature at which they intersect is obtained as the glass transition temperature. Since this temperature corresponds to about 10 ¹³ to 10 ¹⁴ poise in terms of viscosity coefficient, the glass transition temperature can also be obtained from viscosity measurement.

On the other hand, the softening point (Ts) is a temperature at which the glass becomes significantly soft due to its own weight and starts to deform, and the viscosity coefficient is considered to be a temperature corresponding to about 10 ⁷ to 10 ⁸ poise, and is also obtained from viscosity measurement. be able to.

More simply, the glass transition temperature and the softening point can be obtained by a method using differential thermal analysis (DTA). DTA is a technique for detecting the temperature difference between a sample and a reference material. When the sample melts or reacts as the temperature changes, the temperature difference from the reference material changes, and this is detected. Is. In general, when performing differential thermal analysis of a glass material, when the temperature is increased from the low temperature side to the high temperature side, a first endothermic peak corresponding to the glass transition temperature, a second endothermic peak corresponding to the glass softening point, and A first exothermic peak corresponding to the crystallization temperature appears. From the temperature corresponding to these peaks, the glass transition temperature and the softening point can be determined.

As can be seen from the relationship between these temperatures and the viscosity coefficient, the larger the temperature difference between the softening point Ts and the glass transition temperature Tg, the slower the viscosity change, and such glass powder can be used for sealing. If possible, it is not necessary to strictly control the temperature in the sealing process, and the workability of the sealing process is improved.

In view of such problems, an object of the present invention is to provide a glass powder having viscosity and viscosity controllability suitable for a sealing material. More specifically, the softening point is 600 ° C. or less. In addition, the temperature difference between the softening point and the glass transition temperature is 100 ° C. or more, the viscosity changes gradually with respect to the temperature change, and the average thermal expansion coefficient in the temperature range of 30 to 250 ° C. is 80 × 10 ^{− The} present invention provides a glass powder having a low softening point of ⁷ / ° C. or lower.

In order to achieve the above object, the present invention contains V ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Li ₂ O, and when the content is expressed by weight%, V ₂ O ₅ is 24 to 48 wt%. , _B 2 _{O 3} is 20~28wt%, SiO ₂ is 5~14wt%, a range Li ₂ O is 1~7wt%, the total content of these four components be 50wt% or less than 75 wt% And it is a glass powder whose average particle diameter exists in the range of 0.5-10 micrometers.

Here, V ₂ O ₅ is a component that forms a glass skeleton, and is an important component for achieving a low melting point and thermal stability. The optimum content is in the range of 24-48 wt%. If the content is less than 24 wt%, crystals are likely to precipitate during glass melting, and vitrification becomes difficult. This is because even if it exceeds 48 wt%, crystals are likely to precipitate during glass melting, and vitrification becomes difficult.

B ₂ O ₃ is an essential component for achieving low melting point and low expansion coefficient in the present invention, and is preferably contained in an amount of 20 to 28 wt%. If it exceeds 28 wt%, vitrification becomes difficult, and if it is less than 20 wt%, crystals tend to precipitate during glass melting, and vitrification becomes difficult.

SiO ₂ is a component that suppresses the crystallization tendency of glass, stabilizes the glass, and lowers the expansion coefficient, and is an essential component. The optimum content is 5-14 wt%. When SiO ₂ is less than 5 wt%, crystals tend to precipitate during glass melting, and vitrification becomes difficult. This is because if it exceeds 14 wt%, the temperature difference between the softening point and the glass transition temperature cannot be made 100 ° C. or more.

Li ₂ O is a component that lowers the softening point and moderates a viscosity change due to a temperature change, and is an essential component. By adding in an appropriate range, the glass is stabilized and has an effect of suppressing the crystallization tendency. In the present invention, when the content of Li ₂ O is less than 1 wt%, the effect of addition is small, and the temperature difference between the softening point and the glass transition temperature cannot be made 100 ° C. or more. When the content of Li ₂ O exceeds 7 wt%, glass phase separation occurs, and stable glass cannot be obtained.

The total content of the four components, which are essential components in the present invention, is at least 50 wt% or more, but is preferably 75 wt% or less. And by containing 25 wt% or more of two or more selected from the group consisting of ZnO, Al ₂ O ₃ , MgO, CaO and SrO, the glass can be further stabilized and the precipitation of crystals can be suppressed. is there. That is, these five components such as ZnO have a great effect of suppressing the phase separation of glass that is easily caused by the addition of Li ₂ O, and it becomes possible to obtain glass more stably. Here, if only one of these components is added, the amount of the component added becomes too large and the glass tends to become unstable. In order to achieve a lower expansion coefficient, it is preferable to add ZnO and Al ₂ O ₃ .

  In addition, in the range which achieves the objective of this invention, it is also possible to contain a small amount of components other than 5 components such as the essential 4 components and ZnO for stabilizing the glass.

In the present invention, the glass powder has a composition range specified in the present invention, so that the softening point can be made 600 ° C. or lower, the viscosity change due to the temperature change is gentle, and the temperature control is easy. A low-melting glass powder suitable for a wearing application can be obtained, and the thermal expansion coefficient can be set to 80 × 10 ⁻⁷ / ° C. or less suitable as a glass powder for sealing. And the favorable fluidity | liquidity suitable as a glass powder for sealing can also be achieved by making the average particle diameter of glass powder into the range of 0.5-10 micrometers.

It is explanatory drawing which showed how to take the general differential thermal analysis curve and softening point which glass shows. It is explanatory drawing which showed how to take a glass transition point from a differential thermal analysis curve. It is explanatory drawing which showed the DTA curve obtained about Example 3 of this invention, and Tg and Ts.

  The mode for carrying out the present invention has been described in detail in the means for solving the problem, and will be specifically described below with reference to examples and comparative examples. The present invention is not limited to these examples.

A raw material batch in which V ₂ O ₅ , boric acid, silica and lithium carbonate were mixed as raw material oxides in the ratios (% by weight) shown in the seven examples in Table 1 was filled in a platinum crucible. After melting in an electric furnace at 1000 ° C. to 1200 ° C. for 60 to 120 minutes, the melt was poured onto a stainless steel plate to obtain glass. The obtained glass was pulverized by a hammer mill and classified by a sieve having an opening of 100 μm. The glass powder that passed through the sieve was pulverized for 48 hours with a pot mill to obtain glass powder with an average particle size of 0.5 to 10 μm.

About the obtained glass powder, JIS
According to K 0129: 2005, differential thermal analysis (DTA) measurement was performed using a thermal analyzer Thermo Plus TG8120 manufactured by Rigaku Corporation. The measurement was performed by using α-alumina as a reference, putting 30 mg of a sample in a platinum pan, and increasing the temperature from room temperature to 700 ° C. at a temperature increase rate of 10 ° C./min.

The temperature at the center of the first endothermic peak of the differential curve of the obtained DTA curve (intersection of tangents at the first inflection point and the second inflection point) is the glass transition temperature Tg, the bottom end of the second endothermic peak ( The temperature at the fourth inflection point) was the softening point Ts, and the temperature at the center of the first exothermic peak was the crystallization temperature. ΔT was calculated by subtracting the glass transition temperature from the softening point. Such reading methods are (1) JP 2012-46825 A, (2) Paragraph 0017 of JP 2010-254540 A, (3) Asahi Glass Co., Ltd. AGC powder glass product catalog (revised 2012.04) P. 3 and (4) As described in Yamagata University, Faculty of Engineering, Organic Device Engineering, Mori Laboratory Materials Collection, “Basics of DSC” (http://polyeb.yz.yamagata-u.ac.jp/~morilab/) Moreover, it is a general method in the technical field of the present invention. FIG. 1 illustrates how to obtain the softening point Ts described in (1), and FIG. 2 illustrates how to obtain the glass transition point Tg described in (4) (implementation in Table 1). The DTA curve, Tg and Ts obtained for Example 3) are shown in FIG.

The thermal expansion coefficient is obtained by placing the obtained glass powder in a mold, heating it for 10 minutes at a temperature of softening point + 50 ° C., and creating a sintered body. Thermomechanical analyzer manufactured by Rigaku Corporation (TMA8310) Was measured by a push rod type thermal expansion measurement method. The average particle size was measured using a laser diffraction particle size distribution analyzer (Laser diffraction / scattering particle size distribution measuring apparatus LA-950V2 manufactured by Horiba, Ltd.).

As can be seen from the examples shown in Table 1, within the range of the glass composition of the present invention, the softening point can be 600 ° C. or lower, and the temperature difference between the softening point and the glass transition temperature is 100 ° C. or higher. Furthermore, the expansion coefficient could be 80 × 10 ⁻⁷ or less.

Nine comparative examples shown in Table 2 were prepared using the same method as in the example, and evaluated in the same manner as in the example. As can be seen from Table 2, when the glass composition is out of the range of the present invention, the glass is devitrified during melting or cooling, and it is difficult to stably obtain the glass. In addition, even when glass was obtained, the temperature difference between the glass transition temperature and the softening point was 100 ° C. or less, and a glass powder showing a gradual viscosity change could not be obtained or the fluidity was lowered. The reason why stable vitrification is difficult is considered to be due to crystallization due to phase separation of glass.

Thus, by setting the composition of the glass powder to the composition range of the present invention, it is possible to realize the characteristics of the glass powder suitable for the sealing step while keeping the phase separation suppressing effect high. Conceivable.

  In addition, as shown in Comparative Examples 8 and 9, even when the glass composition is within the composition range of the present invention, when the average particle diameter of the glass powder is less than 0.5 μm or more than 10 μm, the inter-particle It was confirmed that aggregation became remarkable and fluidity deteriorated.

The fluidity was evaluated by forming the sample into a button shape having an outer diameter of 10 mm and a height of 5 mm and then heating at 600 ° C. for 10 minutes. In the observation after the heating, the button diameter was judged to be good when the diameter exceeded 13 mm, acceptable when it was 10 to 13 mm, and impossible when the diameter was less than 10 mm.

Claims (2)

When V ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Li ₂ O are contained and the content is expressed by weight%, V ₂ O ₅ is 24 to 48 wt%, B ₂ O ₃ is 20 to 28 wt%. , SiO ₂ is in the range of 5 to 14 wt%, Li ₂ O is in the range of 1 to 7 wt%, the total content of these four components is 50 wt% or more and 75 wt% or less, and the average particle diameter is 0.5 A low softening point glass powder characterized by being in the range of 10 μm to 10 μm. _2. The low softening point glass powder according to claim 1, comprising at least 25 wt% of two or more components selected from the group consisting of ZnO, Al ₂ O ₃ , MgO, CaO and SrO.