JP2014141397A - Glass and sheath tube for semiconductor sealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass for semiconductor sealing which satisfies conditions necessary for a glass for semiconductor sealing, specifically, a sealing temperature of 650°C or lower and a coefficient of linear expansion in a temperature range of 30 to 380°C of 85 to 100×10/°C, and is excellent in acid resistance, regardless of a glass having a low content of a lead, and to provide a sheath tube for semiconductor sealing.SOLUTION: A glass for semiconductor sealing contains, as a glass composition, by mass%, 5 to 35% of PbO, 40 to 55% of SiO, and 5 to 20% of LiO+NaO+KO; and preferably contains 5 to 35% of PbO, 40 to 55% of SiO, 0 to 5% of AlO, 0 to 15% of BO, 0 to 5% of MgO, 0 to 5% of CaO, 0 to 5% of BaO, 0 to 5% of SrO, 0 to 10% of ZnO, 1 to 5% of LiO, 0 to 10% of NaO, 0 to 10% of KO, 5 to 20% of LiO+NaO+KO, 0 to 10% of TiO, and 0 to 3% of ZrO.

Description

  The present invention relates to a glass for semiconductor encapsulation, that is, a glass that hermetically seals an element such as a silicon diode, a light emitting diode, or a thermistor and an electrode material such as a jumet wire electrically connected thereto.

The following methods are widely used for manufacturing small electronic components such as diodes, LEDs, thermistors, and the like. First, an electrode material such as a semiconductor element and a dumet wire is inserted and held in a glass sheath tube in a state where the semiconductor element is sandwiched between the electrode materials from both sides. Subsequently, the semiconductor element is hermetically sealed in the glass tube by heating in this state to soften and deform the glass tube. The temperature at which the glass tube is heated is generally the temperature at which the viscosity of the glass is 10 ⁶ dPa · s, and is called the sealing temperature. Here, the condition required for the encapsulation temperature of the glass is that the electrical characteristics of the semiconductor are not higher than the heat resistance temperature of the semiconductor to be encapsulated so as not to be lost at the encapsulation temperature. Although the heat resistance temperature of semiconductors varies widely depending on the type and design, since the heat resistance of semiconductors with high versatility is about 650 ° C., it is important that the sealing temperature is 650 ° C. or lower. Further, as a characteristic required for glass, there is a thermal expansion coefficient. This is to match the coefficient of thermal expansion of the most commonly used jumet wire as an electrode material, specifically within the range of 85 to 100 × 10 ⁻⁷ / ° C. (between 30 to 380 ° C.). The thermal expansion coefficient is required. Furthermore, after heat sealing the semiconductor element, the metal wire exposed outside the glass tube is subjected to an acid treatment or a plating treatment for the purpose of removing the oxide film. At this time, depending on the specifications of the parts, a part of the glass tube (leaded type) or the entire surface (surface mount type) is immersed in these chemicals and processed. For this reason, the glass is required to have sufficient chemical resistance, particularly acid resistance.

  Conventionally, lead silicate glass containing PbO in a large amount of 45 to 75% by mass is used as a glass for semiconductor encapsulation that satisfies such conditions. The reason why lead silicate glass is widely used includes, for example, the following advantages. PbO has a large effect of reducing the viscosity of glass in silicate glass, and can enclose a semiconductor element at a low temperature. In addition, since the thermal expansion coefficient can be adjusted by adjusting the amount of PbO, it is easy to match the thermal expansion coefficient of various commonly used jumet wires.

JP 2002-37641 A Japanese Patent Application Laid-Open No. 08-067534

  In recent years, environmental pollution due to harmful components such as lead, cadmium and arsenic has been regarded as a problem, and industrial products are required to reduce these harmful components. Also in electronic parts, first, lead reduction of solder has been actively pursued, and then the PbO content reduction is also desired in the glass for semiconductor encapsulation.

  By the way, when the temperature at the time of encapsulating the semiconductor element is high, the element deteriorates, or the contact of the metal wire is lost due to loss of elasticity beyond the yield point of the metal. In order to improve this, it is desirable to lower the glass sealing temperature. In the conventional lead silicate glass, it can be said that the reason why PbO is contained in a large amount is to lower the sealing temperature. However, PbO has a property of being easily eluted in an acid solution, and the more PbO is contained, the greater the amount of elution and the lowering of sealing properties may occur.

  In addition, if the acid resistance is not sufficient, fine cracks due to deterioration of the glass surface occur, and various stains and moisture are liable to adhere, resulting in a decrease in the surface resistance of the device, which may cause problems in electrical products.

The present invention has been made in order to solve the above-mentioned problems. Despite being a glass having a low content of lead, the conditions necessary for glass for semiconductor encapsulation, that is, an encapsulation temperature of 650 ° C. or lower, 30 A linear expansion coefficient in a temperature range of ˜380 ° C. satisfies 85 to 100 × 10 ⁻⁷ / ° C., and further provides a glass for semiconductor encapsulation and an outer tube for semiconductor encapsulation excellent in acid resistance.

Even if the inventors reduce the PbO content to 5-35% by mass, the alkali metal oxide R ′ ₂ O (Li ₂ O, Na ₂ O, K, while maintaining the content of SiO _2, etc. It has been found that by increasing the amount of ₂ O), it is possible to obtain a glass that can achieve both a reduction in the sealing temperature and prevention of a decrease in acid resistance.

That is, the glass for semiconductor encapsulation of the present invention is characterized by containing, as a glass composition, 5% to 35% PbO, 40% to 55% SiO ₂ , and 5% to 20% Li ₂ O + Na ₂ O + K ₂ O by mass%. . Here, “Li ₂ O + Na ₂ O + K ₂ O” refers to the total content of Li ₂ O, Na ₂ O and K ₂ O.
According to the above configuration, the encapsulation temperature is 650 ° C. or less, the linear expansion coefficient in the temperature range of 30 to 380 ° C. is 85 to 100 × 10 ^{−7 /} ° C., and the semiconductor encapsulation sheath has excellent acid resistance. Tubes can be made.

In the present invention, as a glass composition, by mass%, PbO 5 to 35%, SiO ₂ 40 to 55%, Al ₂ O ₃ 0 to 5%, B ₂ O ₃ 0 to 15%, MgO 0 to 5%, _{CaO 0~5%, BaO 0~5%,} SrO 0~5%, 0~10% ZnO, Li 2 O 1~5%, Na 2 O 0~10%, K 2 O 0~10%, Li 2 _{O + Na 2 O + K 2} O 5~20%, TiO 2 0~10%, preferably contains ZrO 2 0 to 3%.

According to the above configuration, the encapsulation temperature is 650 ° C. or less, the linear expansion coefficient in the temperature range of 30 to 380 ° C. is 85 to 100 × 10 ^{−7 /} ° C., and the semiconductor encapsulation sheath has excellent acid resistance. Tubes can be made easily.

In the present invention, in _mass%, it is preferable that SiO ₂ + TiO ₂ 45~60%. Here, “SiO ₂ + TiO ₂ ” refers to the total content of SiO ₂ and TiO ₂ .

  According to the said structure, the glass excellent in acid resistance can be obtained.

In the present invention, the temperature corresponding to a viscosity of 10 ⁶ dPa · s is preferably 650 ° C. or lower. In the present invention, “temperature corresponding to a viscosity of 10 ⁶ dPa · s” means a temperature determined as follows. First, the softening point of glass is measured by a fiber method conforming to ASTM C338. Next, a temperature corresponding to the viscosity of the working point region is obtained by a platinum ball pulling method. Finally, these viscosities and temperatures are applied to the Fulcher equation to calculate the temperature at 10 ⁶ dPa · s.

  The outer tube for semiconductor encapsulation of the present invention is characterized by being made of the above glass.

  The glass for semiconductor encapsulation of the present invention can encapsulate a semiconductor element at a low temperature. Moreover, since it is excellent in acid resistance, even if an acid treatment or a plating treatment is performed after the element is encapsulated, a crack is not generated on the surface, so that a highly reliable semiconductor encapsulated part can be produced. In addition, since it is difficult for crystals to precipitate during glass tube forming, it is possible to stably produce a large amount of outer tube.

  The reason for limiting the glass composition range as described above in the lead-free glass for semiconductor encapsulation of the present invention will be described below. In addition, the following% display points out the mass%.

  PbO is an important component for lowering the sealing temperature and adjusting to a desired thermal expansion coefficient. However, when the PbO content increases, the acid resistance deteriorates. For this reason, the content of PbO is 5 to 35%, preferably 10 to 35%, and more preferably 10 to 30%. When there is too little content of PbO, it will become difficult to enjoy the above-mentioned effect. On the other hand, when there is too much content of PbO, the glass surface will deteriorate easily by acid treatment, and as a result, the sealing property of a product will fall.

SiO ₂ is a main component and an important component for stabilizing the glass. It also has a great effect on improving acid resistance. On the other hand, SiO ₂ is also a component that raises the sealing temperature. The content of SiO ₂ is 40 to 55%, preferably 40 to 52%, more preferably 43 to 52%. When the content of SiO ₂ is too small it becomes difficult to enjoy the effects described above. On the other hand, if the SiO ₂ content is too large, low-temperature encapsulation becomes difficult.

Al ₂ O ₃ is a component that suppresses precipitation of crystals containing Si and increases water resistance and acid resistance. On the other hand, Al ₂ O ₃ is also a component that increases the viscosity of the glass. The content of Al ₂ O ₃ is preferably 0 to 5%, particularly preferably 0.5 to 4.5%. When the content of Al ₂ O ₃ is too large tends to decrease. Viscosity becomes too high formability of the glass, it is difficult to cold sealed. Further, the composition balance is lost, and crystals containing Li are likely to precipitate.

B ₂ O ₃ is a component that stabilizes the glass and lowers the viscosity of the glass. On the other hand, B ₂ O ₃ is also a component that lowers chemical resistance. The content of B ₂ O ₃ is preferably 0 to 15%, 3 to 11%, particularly preferably 5 to 10%. If the content of B ₂ O ₃ is too small it becomes difficult to enjoy the effects described above. On the other hand, if the content of B ₂ O ₃ is too large, the chemical resistance is deteriorated.

Alkaline earth metal oxides RO (MgO, CaO, SrO, BaO) have a high effect of stabilizing the glass. On the other hand, in a glass having a temperature corresponding to a viscosity of 10 ⁶ dPa · s of 650 ° C. or lower, the effect of lowering the glass temperature by RO cannot be expected, but rather the encapsulation temperature may be increased. For this reason, it is preferable that the content of RO is small, and the content is preferably 0 to 5%, particularly preferably 0 to 3%. Further, the total amount of these components is desirably 10% or less, particularly 7% or less.

  ZnO is a component that can lower the viscosity of the glass without increasing the expansion and without deteriorating the acid resistance as compared with the alkali metal oxide. The content of ZnO is preferably 0 to 10%, 0.5 to 8%, particularly 3 to 7%. If the amount of ZnO is too small, the above-mentioned effects cannot be enjoyed. Conversely, if the amount is excessive, crystals are likely to precipitate.

Alkali metal oxide R ′ ₂ O (Li ₂ O, Na ₂ O, K ₂ O) has an effect of lowering the viscosity of glass or increasing the expansion. In particular, Li ₂ O is preferably used as an essential component in the glass having the above composition because it has a great effect of reducing the viscosity of the glass. On the other hand, when R ₂ O becomes excessive, expansion becomes too high and cracks are generated between metal wires such as dumet. Therefore, the total amount of R ₂ O (Li ₂ O, Na ₂ O, K ₂ O) is 5 to 20%, preferably 6 to 15%, and more preferably 9 to 13%. Each alkali metal oxide component will be described below.

Li ₂ O has a large effect of reducing the viscosity of the glass as described above. However, when the content of Li ₂ O increases, crystals containing Li tend to be generated. For this reason, it is desirable that the content of Li ₂ O is 1 to 5%, 1.5 to 4.5%, and particularly 2.5 to 4.0%. On the other hand, when the content of Li ₂ O is too large, devitrification tends to occur, and crystals of Li ₂ O—ZnO—SiO ₂ or Li ₂ O—TiO ₂ —SiO ₂ tend to precipitate. Moreover, acid resistance tends to deteriorate.

Na ₂ O has the effect of stabilizing the glass and preventing devitrification in addition to the effects common to the alkali metals described above. On the other hand, Na ₂ O deteriorates the acid resistance of the glass. In the present invention, it is desirable to introduce in consideration of stabilization of the glass. The content of Na ₂ O is preferably 0 to 10%, 2 to 7%, particularly 3 to 6%. When the Na 2 _O content is too small it becomes difficult to enjoy the effects described above. On the other hand, when the content of Na 2 _O is too large, easily devitrified.

K ₂ O has the effect of stabilizing the glass and preventing devitrification in addition to the effects common to the alkali metals described above. On the other hand, K ₂ O worsens the acid resistance of the glass. The content of K ₂ O is preferably 0 to 10%, 2 to 7%, particularly 3 to 6%. When the content of K 2 _O is too large easily devitrified.

In order to stabilize the glass, it is desirable to contain one or both of Na ₂ O and K ₂ O.

TiO ₂ is a component added to increase acid resistance. On the other hand, TiO ₂ tends to induce crystals and tends to deteriorate the devitrification resistance of the glass. For this reason, if TiO ₂ is contained excessively, the glass is easily devitrified by contact with a metal or a refractory, and there is a possibility that the dimensional accuracy of the glass obtained due to the influence of the devitrified material is lowered. The content of TiO ₂ is preferably 0 to 10%, 0.5 to 6%, particularly preferably 1.5 to 4%.

ZrO ₂ is a component that improves chemical resistance. On the other hand, when the content of ZrO ₂ is too large too high the viscosity of the glass, it is difficult to cold sealed. The content of ZrO ₂ is preferably 0 to 3%, particularly preferably 0 to 2%.

In the glass of the present invention, by strictly controlling the SiO ₂ and the total amount of TiO _2, it is easy to achieve both acid resistance and low temperature (sealing temperature). By increasing the total amount of SiO ₂ and TiO ₂ , it is possible to efficiently improve acid resistance. The total content of SiO ₂ and TiO ₂ is 45 to 60%, particularly 47 to 52%. If the total amount of SiO ₂ and TiO ₂ is 45% or more, the acid resistance is further improved, which is preferable. If the total amount of SiO ₂ and TiO ₂ is 60% or less, the glass is hard to be hardened, and encapsulation at a low temperature becomes easier.

The glass for semiconductor encapsulation of the present invention can contain various components in addition to the above components as long as the properties of the glass are not impaired. For example, in order to reduce the viscosity of glass, F can be added to 0.5%, and Sb ₂ O ₃ can be added to 0.5% as a fining agent. However, environmentally undesirable components such as As ₂ O ₃ should not be added. Specifically, the content of As ₂ O ₃ is limited to 0.1% or less.

The glass for semiconductor encapsulation of the present invention having the above composition has a temperature corresponding to a viscosity of 10 ⁶ dPa · s, preferably 650 ° C. or less, more preferably 620 to 640 ° C., and further preferably 620 to 635 ° C. The viscosity temperature of 10 ⁶ dPa · s generally corresponds to the sealing temperature of the semiconductor element. Therefore, the glass of the present invention can encapsulate a semiconductor element at 650 ° C. or lower.

Moreover, the glass for semiconductor encapsulation of the present invention preferably has a thermal expansion coefficient in the range of 30 ° C. to 380 ° C. of the glass, preferably 85 to 100 × 10 ⁻⁷ / ° C., more preferably 85 to 95 ×, for sealing with dumet. 10 ⁻⁷ / ° C., more preferably 90 to 95 × 10 ⁻⁷ / ° C.

  The glass for semiconductor encapsulation of the present invention preferably has a weight loss rate of 500 ppm or less, more preferably 400 ppm or less, and even more preferably 300 ppm or less when immersed in a 5% by mass solution of 30 ° C.-36N sulfuric acid for 60 minutes. . A smaller weight reduction rate is preferable because cracks and the like are less likely to occur on the glass surface in the plating process.

  Moreover, it is preferable that the glass for semiconductor encapsulation of the present invention has as high a volume resistance as possible. Specifically, the volume resistance value at 150 ° C. is preferably 7 or more, particularly 9 or more, and more preferably 11 or more in Logρ (Ω · cm). If the volume resistance of glass is low, for example, in the case of a diode, a slight amount of electricity flows between the electrodes, resulting in a circuit as if a resistor was installed in parallel with the diode.

  Next, the manufacturing method of the outer tube for semiconductor encapsulation made of the glass for semiconductor encapsulation of the present invention will be described. However, the method for producing the outer tube for semiconductor encapsulation of the present invention is not limited to the following method.

  In one aspect of the manufacturing method of the outer tube for semiconductor encapsulation on an industrial scale, a mixing and mixing step of measuring and mixing minerals and refined crystal powder containing components constituting glass and preparing raw materials to be introduced into a furnace, and raw materials A melting step of forming a molten glass, a forming step of forming the molten glass into a tube shape, and a processing step of cutting the tube into predetermined dimensions.

  First, glass raw materials are prepared and mixed so as to be in the above composition range. The raw materials are composed of minerals and impurities composed of a plurality of components such as oxides and carbonates, and may be prepared in consideration of the analytical values, and the raw materials are not limited. These are measured in terms of weight and mixed with an appropriate mixer according to the scale, such as a V mixer, a rocking mixer, or a mixer equipped with stirring blades, to obtain an input raw material.

Next, the raw material is put into a glass melting furnace and vitrified. The melting furnace is for melting a glass raw material into a vitrification tank, a clarification tank for raising and removing bubbles in the glass, and lowering the clarified glass to a viscosity suitable for molding and leading it to a molding apparatus. It is common to have a passage (feeder). As the melting furnace, a refractory material or a furnace covered with platinum is used, and it is heated by heating with a burner or electric current to glass. The charged raw materials are usually vitrified in a melting tank at 1100 ° C. to 1400 ° C., and further enter a clarification tank at 1200 ° C. to 1500 ° C. Here, bubbles in the glass are lifted to remove the bubbles. The glass that comes out of the clarified rice cake has a viscosity of 10 ^3.5 to 10 ⁶ dPa · s, which is suitable for forming the glass, as it moves to the forming device through the feeder.

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

  Then, the outer tube for semiconductor encapsulation of the present invention can be obtained by cutting the glass tube into a predetermined size. The glass tube can be cut one by one with a diamond cutter. However, as a method suitable for mass production, a large number of tube glasses are bound together and then cut with a diamond wheel cutter. A method of cutting a large number of tube glasses at a time is generally used.

  The lead-free glass for encapsulating a semiconductor of the present invention is not only molded into a glass tube and used as a mantle tube, but also encapsulates a semiconductor element by, for example, forming a powder into a paste, winding it around a semiconductor element and firing it. You can also.

  Next, an example of a method for encapsulating a semiconductor element using the outer tube for semiconductor encapsulation of the present invention will be described.

  First, a jig is used so that an electrode material such as a dumet wire sandwiches the semiconductor element from both sides in the outer tube. Thereafter, the whole is heated to a temperature of 650 ° C. or lower, the outer tube is softened and deformed, and the semiconductor element is hermetically sealed. By such a method, a small electronic component such as a silicon diode, a light emitting diode, or a thermistor can be manufactured.

  Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited to the following Example.

  Table 1 shows examples of the present invention (sample Nos. 1 to 11) and comparative examples (samples No. 12 and 13). No. No. 12 is a glass described in Patent Document 2, No. 12; 13 is a general lead silicate glass conventionally used as a glass for semiconductor encapsulation.

  Each sample was prepared as follows. First, glass raw materials were prepared so as to have the glass composition described in the table, melted at 1300 ° C. for 3 hours using a platinum pot, molded, and subjected to various evaluations. As the glass raw material, silica powder, aluminum oxide, boric acid, calcium carbonate, barium carbonate, zinc oxide, lithium carbonate, sodium nitrate, potassium carbonate, titanium oxide and the like were used.

Next, the thermal expansion coefficient, temperature at 10 ⁶ dPa · s, acid resistance (weight reduction rate, presence or absence of cracks), volume resistance, and crystal precipitation viscosity were evaluated for the obtained samples.

As is apparent from Table 1, sample No. which is an example of the present invention. 1 to 11 had a temperature at 10 ⁶ dPa · s of 647 ° C. or lower, and could be sealed at a low temperature. The coefficient of thermal expansion was 86.2-99.3 × 10 ⁻⁷ / ° C., indicating a coefficient of thermal expansion consistent with the Jumet line. Further, the volume reduction rate was 420 ppm or less, no crack was generated, and the acid resistance was good. Furthermore, it was confirmed that the crystal precipitation viscosity is high and devitrification hardly occurs.

  The thermal expansion coefficient is a value obtained by measuring an average linear thermal expansion coefficient in a temperature range of 30 to 380 ° C. with a self-recording differential thermal dilatometer using a cylindrical measurement sample having a diameter of about 5 mm and a length of about 20 mm.

The enclosure temperature was determined as follows. First, the softening point was measured by a fiber method conforming to ASTM C338. Next, a temperature corresponding to the viscosity of the working point region was determined by a platinum ball pulling method. Finally, these viscosities and temperatures were applied to the Fulcher equation to calculate the temperature at 10 ⁶ dPa · s, which was used as the sealing temperature.

  The acid resistance was determined as follows. A 30 × 30 × 5 mm glass plate is prepared, mirror-polished, washed with water and dried to measure the original weight. Then, after dipping in a 5% by mass solution of 30 ° C.-36N sulfuric acid for 60 minutes, washing with pure water for 90 seconds, drying at 100 ° C. for 30 minutes or more, measuring the weight after treatment, and (initial weight−weight after treatment) ) / (Initial weight) × 100, the weight reduction rate was calculated. The unit is expressed in ppm. In addition, the presence or absence of cracks was observed on the treated glass surface with an episcopic microscope.

  The volume resistivity at 150 ° C. is a value measured by a method based on ASTM C-657.

  The crystal precipitation viscosity is determined by crushing the sample and aligning the particle size with a sieve, then transferring it to a platinum boat, treating it for 3 hours in a furnace with a temperature gradient, and using a polarizing microscope to determine the highest temperature at which crystals have precipitated. Read this, convert this temperature into viscosity, and set it as crystal precipitation viscosity

  The glass for semiconductor encapsulation of the present invention is suitable as a glass envelope material used for encapsulation of semiconductor elements such as silicon diodes, light emitting diodes, and thermistors.

Claims (5)

A glass for semiconductor encapsulation, containing 5 to 35% of PbO, 40 to 55% of SiO ₂ , and 5 to 20% of Li ₂ O + Na ₂ O + K ₂ O as a glass composition. As a glass composition, in _{weight%, PbO 5~35%, SiO 2} 40~55%, Al 2 O 3 0~5%, B 2 O 3 0~15%, 0~5% MgO, CaO 0~5% _{, BaO 0~5%, SrO 0~5%} , 0~10% ZnO, Li 2 O 1~5%, Na 2 O 0~10%, K 2 O 0~10%, Li 2 O + Na 2 O + K 2 O The glass for semiconductor encapsulation according to claim 1, comprising 5 to 20%, TiO ₂ 0 to 10%, and ZrO ₂ 0 to 3%. The glass for semiconductor encapsulation according to claim 1, wherein SiO ₂ + TiO ₂ is 45% to 60% by mass. The temperature corresponding to a viscosity of 10 ⁶ dPa · s is 650 ° C. or lower, and the glass for semiconductor encapsulation according to claim 1,   A sheath tube for semiconductor encapsulation, comprising the glass according to claim 1.