JP6041201B2 - Lead-free glass for semiconductor encapsulation - Google Patents

Description

  The present invention relates to a lead-free glass for semiconductor encapsulation, and more particularly to a lead-free glass for semiconductor encapsulation used as an envelope material for encapsulation of semiconductor elements such as silicon diodes, light emitting diodes, and thermistors.

  Small electronic parts such as silicon diodes, light-emitting diodes, thermistors, etc. are sandwiched between metal semiconductors such as dumet wires from both sides, and surrounded by a glass-made semiconductor enclosure tube, and then heated to a predetermined temperature. A structure (DHD type) in which the outer tube is softly deformed and hermetically sealed is widely used. The thermistor also has a structure in which a lead wire is provided in one direction.

The glass for semiconductor encapsulation is required to be capable of being encapsulated at a temperature at which the semiconductor element is not thermally deteriorated. The heat-resistant temperature of a semiconductor element varies depending on the type and design, but tends to decrease as the semiconductor element becomes smaller. For this reason, it is preferable that the enclosure temperature is as low as possible, for example, 660 ° C. or lower, particularly 650 ° C. or lower. The sealing temperature generally refers to a temperature at which the viscosity of the glass is 10 ⁶ dPa · s.

  Conventionally, lead silicate glass containing a large amount of PbO has been used as a glass for semiconductor encapsulation capable of low-temperature encapsulation. The reason is that PbO in the glass composition has an extremely large effect of lowering the viscosity of the glass while stabilizing the glass skeleton. Specifically, the glass for semiconductor encapsulation containing 46% by mass of PbO has an encapsulation temperature of about 700 ° C., and the glass for semiconductor encapsulation containing 60% by mass of PbO has an encapsulation temperature of about 655 ° C.

  However, since lead is an environmentally unfavorable component, semiconductor encapsulating glass made of lead-free glass that does not substantially contain lead or other harmful components and is environmentally friendly has been proposed in recent years (for example, Patent Document 1). ~ 4).

JP 2002-37641 A Japanese Patent Laid-Open No. 2003-17632 JP 2011-116578 A JP 2012-31048 A

  However, the glass described in Patent Document 1 and Patent Document 2 has a high sealing temperature of 651 to 710 ° C., and the problem cannot be solved with respect to the current situation where further lowering of the sealing temperature is desired.

  By the way, it is desired that the glass for semiconductor encapsulation has a high volume resistivity. If the volume resistivity of the glass is low, a small amount of electricity flows between the electrodes, resulting in a hindrance to the electrical characteristics of the semiconductor product. However, lead-free glass tends to have a lower volume resistivity than conventional lead silicate glass.

Reference examples 3 and 4 disclose examples of glass having a relatively high volume resistivity while being lead-free glass. However, these glasses contain a large amount of TiO ₂ and are easily devitrified. Further, the invention of the cited document 3 uses expensive Bi ₂ O ₃ as an essential component, and there is a problem that the raw material cost is high.

An object of the present invention is a lead-free glass for encapsulating a semiconductor that can be sealed at a low temperature of 650 ° C. or lower, has a high volume resistivity of 10 ^12.5 Ω · cm or higher at 150 ° C., and has excellent devitrification resistance. Is to provide.

Encapsulating a semiconductor lead-free glass of the present invention has a glass composition, _SiO 2 24 to _46% by _{mass%, Al 2 O 3 0.1~4.0%} , B 2 O 3 16~35%, ZnO 6~22 %, Li ₂ O 1-5%, Na ₂ O 1-10%, K ₂ O 2-12%, TiO ₂ 0-2%, and the ratio of Na ₂ O / K ₂ O is ≦ 1.2 It is characterized by being. “Lead-free” means that PbO is not actively added as a glass raw material, and specifically refers to a case where the content of PbO in the glass composition is 2000 ppm or less.

In the present invention, it is preferable to contain substantially no Bi ₂ O _3. Note that "substantially free of Bi ₂ O _3" is a glass raw material is positively spirit not using Bi ₂ O _3, in particular the content of Bi ₂ O ₃ in the glass composition It refers to the case of 2000 ppm or less.

  According to the said structure, the raise of raw material cost can be suppressed.

  In the present invention, the volume resistivity at 150 ° C. is preferably 12.5 (Ω · cm) or more in terms of Log ρ.

  According to the above configuration, it becomes possible to more reliably manufacture a semiconductor product having excellent electrical characteristics.

Moreover, in this invention, it is preferable that enclosure temperature is 650 degrees C or less. The “encapsulation temperature” in the present invention means a temperature at which the viscosity of the glass is 10 ⁶ dPa · s.

  According to the said structure, the thermal degradation of the semiconductor element enclosed can be prevented appropriately.

  The glass of the present invention can be sealed at a low temperature, has a high volume resistivity, and is excellent in devitrification resistance. Therefore, it is suitable as an outer tube material used for manufacturing a small electronic component such as a silicon diode, a light emitting diode, or a thermistor.

  The reason why the composition range of the lead-free glass for semiconductor encapsulation of the present invention is limited as described above will be described. Hereinafter, “%” means mass% unless otherwise specified.

SiO ₂ is a main component necessary for constituting a glass skeleton, and its content is 24 to 46%, preferably 30 to 44%, and more preferably 36 to 42%. When the content of SiO ₂ is less than 24%, the weather resistance necessary for practical use becomes insufficient. When the content of SiO ₂ is more than 46%, the sealing temperature becomes high.

Al ₂ O ₃ is a component that enhances the weather resistance of the glass, and its content is 0.1 to 4.0%, preferably 0.2 to 3%, and more preferably 0.3 to 2%. When the content of Al ₂ O ₃ is less than 0.1%, the weather resistance is insufficient. When the content of Al ₂ O ₃ is more than 4.0%, the encapsulation temperature becomes high.

B ₂ O ₃ is a component that constitutes the skeleton of the glass and lowers the sealing temperature while lowering the thermal expansion coefficient, and its content is 16 to 35%, preferably 18 to 30%, more preferably 20 to 20%. 25%. When the content of B ₂ O ₃ is less than 16%, the sealing temperature becomes high. When the content of B ₂ O ₃ is more than 35%, the water resistance deteriorates.

  ZnO is a component that lowers the encapsulation temperature while lowering the thermal expansion coefficient, and its content is 6 to 22%, preferably 9 to 19%, and more preferably 12 to 17%. When the ZnO content is less than 6%, the encapsulation temperature becomes high. When the content of ZnO is more than 22%, devitrification is deteriorated.

Li ₂ O is a component having the largest effect of increasing the thermal expansion coefficient and the effect of decreasing the sealing temperature, and its content is 1 to 5%, preferably 1.5 to 4.5%, more preferably 2. 0 to 4.0%. When the content of Li ₂ O is less than 1%, the encapsulation temperature increases. When the content of Li ₂ O is more than 5%, the thermal expansion coefficient becomes too large.

Na ₂ O is a component that lowers the encapsulation temperature, and its content is 1 to 10%, preferably 2 to 9%, and more preferably 3 to 8%. When the content of Na ₂ O is less than 1%, the sealing temperature increases. When the content of Na ₂ O is more than 10%, the volume resistivity becomes too low.

K ₂ O is a component that increases the volume resistivity, and its content is 2 to 12%, preferably 4 to 11%, more preferably 6 to 10%, and particularly preferably 8.5 to 10%. If the content of K ₂ O is less than 2%, the volume resistivity becomes too low. When the content of K ₂ O is more than 12%, the thermal expansion coefficient becomes too high.

TiO ₂ is an effective component for enhancing acid resistance, and its content is 0 to 2%. When the content of TiO ₂ is more than 2%, devitrification tends to deteriorate.

Na ₂ ratio of O / _{K 2} O is an index to increase the volume resistivity, the ratio _{Na 2 O / K 2 O ≦} 1.2, preferably _{Na 2 O / K 2 O ≦} 1.1, more preferably Is Na ₂ O / K ₂ O ≦ 1.0. When the ratio is Na ₂ O / K ₂ O> 1.2, the volume resistivity decreases.

In addition to the above components, P ₂ O ₅ , SO ₃ , Sb ₂ O ₃ , F, Cl are used for the purpose of improving the meltability, lowering the sealing temperature, improving the chemical durability, improving the clarity. Etc. can be added in an appropriate amount. Incidentally, as described above, PbO and _Bi 2 _{O 3} is preferably not added.

  The lead-free glass for semiconductor elements of the present invention preferably has a volume resistivity at 150 ° C. of 12.5 or more, particularly 12.7 or more in terms of Log ρ (Ω · cm). When the volume resistivity at 150 ° C. becomes low, electricity flows between the electrodes, and a circuit in which a resistor is installed in parallel with a diode or the like is likely to be generated.

  The lead-free glass for semiconductor encapsulation of the present invention preferably has an encapsulation temperature of 650 ° C. or lower, particularly 640 ° C. or lower.

The lead-free glass for a semiconductor element of the present invention preferably has a thermal expansion coefficient at 30 to 380 ° C. of 85 to 105 × 10 ⁻⁷ / ° C., particularly 85 to 100 × 10 ⁻⁷ / ° C. If it does in this way, the thermal expansion coefficient of the glass for semiconductor encapsulation can be easily matched with the thermal expansion coefficient of a metal wire such as a dumet wire, and as a result, the reliability of the electronic component can be improved.

  Next, a lead-free glass for semiconductor encapsulation of the present invention and a method for producing a semiconductor encapsulation sheath tube using the same will be described.

  First, various glass raw materials are prepared and mixed. The glass raw material usually contains minerals and impurities composed of a plurality of components. In such a case, the glass raw material may be formulated so as to have a desired glass composition in consideration of the component analysis value of the glass raw material. Subsequently, various glass raw materials are mixed with a mixer such as a V mixer, a rocking mixer, and a mixer equipped with stirring blades to obtain input raw materials.

Next, the input raw material is charged into a glass melting furnace to obtain molten glass. The glass melting furnace is a melting tank for obtaining molten glass, a clarification tank for removing bubbles in the molten glass, and for lowering the clarified molten glass to a viscosity suitable for molding and leading it to a molding apparatus. It consists of a passage (feeder) and the like. The glass melting furnace is heated by a burner or electric conduction. The input raw material is usually melted in a dissolution tank at 1300 ° C. to 1600 ° C. and further enters a clarification tank at 1400 ° C. to 1600 ° C. In the process of moving the molten glass from the clarified rice cake through the feeder to the molding apparatus, the temperature is lowered and the viscosity becomes 10 ⁴ to 10 ⁶ dPa · s suitable for molding.

  Next, the molten glass is formed into a tubular shape with a forming apparatus. As a forming method, a Danner method, a tongue method, a downdraw method, an updraw method, or the like can be applied.

  If the obtained glass tube is cut into a predetermined dimension, a mantle tube for semiconductor encapsulation can be produced. When cutting a glass tube, it is possible to cut the glass tube individually with a diamond wheel cutter. However, a method in which a large number of glass tubes are bound and then cut with a diamond wheel cutter is suitable for mass production.

  Next, a method for encapsulating a semiconductor element using a semiconductor encapsulating tube will be described.

  First, a metal wire such as a dumet wire is fixed so that the semiconductor element is sandwiched from both sides in the outer tube for semiconductor encapsulation. Next, the semiconductor element is sealed by heating to a temperature of 650 ° C. or lower to soften and deform the outer tube. In this way, electronic components such as silicon diodes, light emitting diodes, thermistors, and the like can be manufactured.

  The lead-free glass for encapsulating a semiconductor of the present invention can be used as an outer tube, for example, by crushing it into a powder form and then pasting it, winding it around a semiconductor element and firing it to encapsulate the semiconductor element You can also.

  Hereinafter, the present invention will be described in detail based on examples.

Tables 1-2 show Examples (No. 1-12) and Comparative Examples (No. 13-14) of the present invention.
Is shown.

Glass raw materials were prepared so as to have the glass composition shown in the table, and after melting for 4 hours 30 minutes at 1200 ° C. using a platinum crucible, the molten glass was formed into a predetermined shape and processed for each evaluation. Each sample was evaluated for thermal expansion coefficient, strain point, annealing point, softening point, encapsulation temperature, molding temperature, volume resistivity at 150 ° C., and temperature and liquidus temperature at 10 ⁸ Ω · cm.

  The thermal expansion coefficient is a value obtained by measuring an average thermal expansion coefficient in a temperature range of 30 to 380 ° C. with a self-described differential thermal dilatometer using a cylindrical measurement sample having a diameter of about 3 mm and a length of about 50 mm.

The strain point, annealing point and the like were measured by a fiber method in accordance with ASTM C336. The softening point was measured by a fiber method conforming to ASTM C338. The molding temperature was determined as a temperature corresponding to a viscosity of 10 ⁴ dPa · s by a platinum ball pulling method.

The enclosure temperature was determined as follows. First, the temperature and viscosity of the strain point, annealing point, softening point and molding temperature obtained by the above method were applied to the Fulcher equation, and the temperature corresponding to 10 ⁶ dPa · s was taken as the sealing temperature.

  The volume resistivity at 150 ° C. is a value measured by a method based on ASTM C657.

The temperature at 10 ⁸ Ω · cm is an index indicating volume resistance, and the larger the value, the higher the volume resistivity. The temperature at 10 ⁸ Ω · cm is a reciprocal 1 / K of absolute temperature on the horizontal axis 1 / K (K is an absolute temperature) after obtaining volume resistivity of 150 ° C., 250 ° C. and 350 ° C. by a method according to ASTM C657, It calculated from the inclination of the graph which plotted volume resistivity (Log) ohm * cm on the vertical axis | shaft.

  The liquid phase temperature passed through a standard sieve 30 mesh (500 μm), the glass powder remaining in 50 mesh (300 μm) was placed in a platinum boat, held in a temperature gradient furnace for 24 hours, and then the temperature at which crystals precipitated was measured. Points to the value.

As is apparent from Tables 1 and 2, No. 1 is an example of the present invention. 1 to 12 had an enclosure temperature of 650 ° C. or lower and a volume resistivity at 150 ° C. of Log ρ of 12.5 (Ω · cm) or higher. Moreover, it was found that the thermal expansion coefficient is in the range of 88 to 99 × 10 ⁻⁷ / ° C., which is consistent with the jumet wire that is the encapsulated metal. Embodiments of the present invention that the content of TiO ₂ is 2% or less also, the liquidus temperature is low, it was confirmed to have excellent devitrification resistance.

On the other hand, sample No. which is a comparative example. 13 and 14, the ratio of Na ₂ O / K ₂ O was> 1.2, and the volume resistivity at 150 ° C. was as low as less than 12.5.

Claims (4)

A glass composition, _SiO 2 _24~46% by _{mass%, Al 2 O 3 0.1~4.0%} , B 2 O 3 16~35%, ZnO 6~22%, Li 2 O 1~5%, Lead free for semiconductor encapsulation, containing Na ₂ O 1-10%, K ₂ O 2-12%, TiO ₂ 0-2%, and a ratio of Na ₂ O / K ₂ O ≦ 1.0 Glass. The lead-free glass for semiconductor encapsulation according to claim 1, which contains substantially no Bi ₂ O ₃ .   The lead-free glass for semiconductor encapsulation according to claim 1, wherein the volume resistivity at 150 ° C. is 12.5 (Ω · cm) or more in terms of Log ρ. The lead-free glass for semiconductor encapsulation according to any one of claims 1 to 3, wherein the encapsulation temperature is 650 ° C or lower.