JP5767435B2 - Conductive paste for hole filling, conductor hole filling board, method for manufacturing conductor hole filling board, circuit board, electronic component, semiconductor package - Google Patents

Description

  The present invention provides a conductive paste for filling a hole used to fill a hole in a substrate in order to obtain conduction of a wiring circuit formed in a plurality of layers on the substrate or to obtain a thermal via as a high-speed heat transfer path, In addition, the present invention relates to a conductor hole-filled substrate in which holes in the substrate are filled with this hole-filling conductor paste and a method for manufacturing the same, and to a circuit board, an electronic component, and a semiconductor package using the conductor hole-filled substrate.

  With the downsizing and higher functionality of electronic components, the demand for multilayer boards and front and back double-sided wiring boards is increasing. In these substrates, holes are formed in the substrate and conductors are provided in the holes for electrical conduction between the front and back surfaces or between the surface and the inner layer conductor circuit. In recent years, the output and processing speed of semiconductor elements and semiconductor integrated circuits have greatly increased, and a large amount of heat generated from semiconductor elements and semiconductor integrated circuits (hereinafter referred to as semiconductor elements) in use can be quickly dissipated, thereby providing a semiconductor. If the elements and the like are not kept below a certain temperature, the function and life of the semiconductor elements and the like may be significantly reduced. Since a substrate on which a semiconductor element or the like is mounted does not usually have sufficient thermal conductivity, by providing a through hole directly under or near the semiconductor element or the like and filling the hole with a highly thermally conductive conductor, the semiconductor element It is widely known to use thermal vias that transmit heat generated from the like to the opposite side of the substrate through a highly thermally conductive conductor.

There are several methods for providing a conductor in a hole provided in a substrate. That is, (1) a plating method for filling a hole in a substrate with electrolysis or electroless plating, (2) a dry method for filling a hole in a substrate with sputtering or vapor deposition, (3) liquid A non-firing type conductive paste method in which a paste made of a metal powder dispersed in a high content in a resin solution such as an epoxy resin is filled in a hole in a substrate and the resin is cured at a temperature of 300 ° C. or lower; (4) metal powder , ceramic powder, glass powder, baking type conductive paste made of resin solution, was packed into a hole drilled in the ceramic green sheet, co-firing the conductive paste method on so that forming baked together with the ceramic green sheet, (5 ) Fill a hole in the ceramic substrate with a firing type conductive paste made of metal powder, glass powder, resin solution, etc., and fire it at a temperature of 300 ° C or higher. To decompose the firing paste method after the metallic powder to be sintered, and the like.

  In the above method (1), filling only the holes of the substrate, which is an insulator, with a metal by plating requires a very complicated process and is expensive. The method (2) is very expensive because the process is complicated and expensive vacuum equipment is required. There is also a limitation on the substrate size. The method (3) is inexpensive but has insufficient conductivity and thermal conductivity because a polymer exists between the metal powders. In addition, it has poor reliability such as heat resistance. Although the method (4) is excellent in heat resistance and reliability, it is necessary to match the firing behavior (sintering temperature, shrinkage rate, etc.) of the ceramic green sheet. It is necessary to add powder. As a result, the conductivity and thermal conductivity of the fired via conductor are reduced. In addition, since ceramics shrink greatly during firing, there is a problem that this simultaneous firing method has poor dimensional accuracy of the fired product, and it is difficult to meet the demand for high precision and downsizing.

  The post-baking paste method (5) has some problems, but is excellent in terms of reliability, cost, dimensional accuracy, and miniaturization. The post-baking paste method includes the following methods.

  That is, there is a method of forming a conductor layer on the inner wall surface of the through hole by applying a conductive paste to the inner wall surface of the through hole of the substrate and firing it, and the conductor layer is thus formed on the inner wall surface of the through hole. Connection between circuits can be established.

  However, since the conductor layer formed on the inner wall surface of the through hole has a small cross-sectional area, there is a problem that a large current cannot flow and the effect of releasing heat is low. For example, in a board for electric power steering of a large vehicle, it is necessary to pass a current of about 50 to 60 A, but in a through hole conductor layer, an allowable current value is about 1 A at most, and the application is limited. .

  For this reason, a conductor is completely placed in a through hole such as a through hole or a non-through hole so that a large current can be used with a low electrical resistance and heat generated from the element can be released. A method of filling is performed.

  In this complete filling method, a conductor paste with a large cross-sectional area is formed by completely filling a conductor paste into a hole that has not penetrated or penetrated a substrate and then firing it, and then firing it. Therefore, it is possible to flow a large current and to obtain high heat dissipation.

  However, in this way, in the case where the inside or non-through hole of the substrate is filled with the conductor made of the conductive paste, the solvent in the conductive paste is volatilized in the process of filling the hole with the conductive paste, then drying and firing. Volume shrinkage occurs due to sintering of metal powder. For this reason, the surface of the conductor filled in the hole may be dented, the conductor may fall out of the hole, or the conductor may peel off from the inner periphery of the hole until it does not fall off. Reliability may be significantly reduced.

  Therefore, in order to solve such a shrinkage problem, the content of the metal powder in the conductor paste has been increased. However, when the metal content exceeds 90%, the paste viscosity rapidly rises and fills. Since workability is significantly reduced, there is a limit to increasing the metal content.

  For this reason, conventionally, it has been proposed to use a metal powder having low sinterability for the conductor paste and to blend an expanding agent into the conductor paste (see Patent Documents 1 to 3, etc.). That is, when the conductive paste is filled into a through-hole or non-through-hole in the substrate and fired, the expansion agent expands to prevent the conductor filled in the hole from shrinking.

  However, when the expansion agent is contained in the conductor paste as described above, the conductor filled in the hole is less dense due to expansion, and voids are likely to be generated. Therefore, the conductivity, thermal conductivity, and airtightness of the conductor are increased. Etc. significantly decreased, causing a problem in reliability.

JP 09-046013 A Japanese Patent Laid-Open No. 07-094840 JP 2007-087712 A

  The present invention has been made in view of the above points, and an object of the present invention is to provide a conductor paste for filling holes that can form a conductor having a small volume change due to firing and having high conductivity and thermal conductivity. Therefore, it is an object of the present invention to provide a conductor hole-filling substrate, a conductor hole-filling substrate manufacturing method, a circuit board, an electronic component, and a semiconductor package using the hole-filling conductor paste.

The conductive paste for hole filling according to the present invention is formed by containing conductive metal particles mainly composed of silver, at least one of glass and inorganic oxide, and an organic vehicle, and is provided in a heat-resistant substrate. Alternatively, a conductive paste for filling a hole with a conductor by filling a non-through hole and firing, the content of the conductive metal particles being 93 to 97% by mass, the glass and the inorganic oxide The total content of 0.05 to 5% by mass, the content of at least one of the glass and the inorganic oxide is 0.05 to 5% by mass, and the content of the organic vehicle is 2 to 6.9% by mass The conductive metal particles include a metal powder having a center particle size of 0.25 μm or more and metal nanoparticles having a center particle size of 10 to 100 nm, and the conductor paste has an inorganic content including the metal in the conductor paste. 93 in total And a quantity% or more, relative to the volume of the dry, is characterized in that a range change ratio of the volume after firing is -1.2～ + 10% at 600 ° C..

  By setting the configuration of the conductive metal particles in this way, it is possible to obtain a conductor paste with good fluidity, good filling into small holes, and small volume change due to firing, A highly conductive conductor can be formed. And since a volume change is small, it is not necessary to mix | blend an expansion agent and a sintering inhibitor in a conductor paste, and a conductor with high electroconductivity and heat conductivity can be formed.

If the volume change due to shrinkage or expansion of the conductor formed by firing the conductor paste is so small, dents and blisters on the surface of the conductor filled in the hole in the board, and the gap between the inner wall of the hole and the conductor It is possible to eliminate problems such as occurrence and to obtain high reliability such as conduction. In addition, by having a high content of conductive metal particles in the conductor paste and a low content of non-conductive inorganic components such as glass and inorganic oxide, the conductive paste has higher conductivity. A conductor can be obtained.

  Further, the present invention is characterized in that the electrical resistivity of the conductor after firing at 600 ° C. is 10 μΩ · cm or less, and further, the electrical resistivity of the conductor after firing at 600 ° C. is 4 μΩ · cm. cm or less.

  Thus, a low electrical resistivity makes it possible to form a highly conductive and highly reliable conductor.

  The present invention is also characterized in that the conductor has a thermal conductivity of 150 W / m · K or more after firing at 600 ° C.

  Thus, by high heat conductivity, a conductor with high heat dissipation can be formed, and it can be used for the use for which heat dissipation is requested | required.

  In the present invention, the metal powder having a center particle size of 0.25 μm or more is characterized in that two or more kinds of metal powders having a center particle diameter of 3 times or more are used in combination.

  Thus, as metal powder having a center particle diameter of 0.25 μm or more, by using metal powders having different center particle diameters in combination, the filling ability of the metal powder can be improved and the air permeability inside the conductor paste at the time of firing is increased. It is possible to prevent the occurrence of defects such as blisters at the time of firing, and a highly dense and highly conductive conductor can be formed.

  In the present invention, the metal powder having a center particle size of 0.25 μm or more is characterized in that the content of the metal powder having a center particle size of 1 μm or more is 50 to 80% by mass.

  By using such a metal powder, defects such as voids and blisters during firing can be reduced, and a highly conductive conductor with high density can be formed.

In the present invention, the conductive metal particles contain 50 to 90% by mass of metal powder having a center particle size of 0.25 μm or more, and 10 to 50% by mass of metal nanoparticles having a center particle size of 10 to 100 nm . It is characterized by this.

  By using such conductive metal particles, it is possible to obtain a conductor paste that can form a conductor having good filling properties and a small volume change rate after firing.

In the present invention, the metal nanoparticles having a central particle size of 10 to 100 nm are nanoparticles having a particle size distribution within a range of 1 to 200 nm , and the center particle size is It is in the range of 10 to 50 nm.

  When the particle size of the metal nanoparticles is within this range, the filling property of the metal nanoparticles is more remarkably exhibited, and a highly conductive and low shrinkage conductor can be easily obtained.

  Further, the present invention has a protective colloid for stabilizing the dispersibility of the metal nanoparticles on the surface of the metal nanoparticles in an amount of 0.5 to 15% by mass with respect to the metal nanoparticles. It is what.

  Thus, by having a protective colloid on the surface of the metal nanoparticles, it is possible to obtain both high concentration of the conductive metal particles in the conductor paste and fluidity of the conductor paste.

  In the present invention, the metal nanoparticles include at least silver nanoparticles.

  Silver nanoparticles can be obtained at a lower cost, and can easily form a conductor having high electrical properties and thermal conductivity.

  Moreover, in this invention, said glass is a bismuth-type glass with a softening point of 550 degrees C or less, It is characterized by the above-mentioned.

  By using such a glass frit, a conductor can be formed while suppressing shrinkage during firing.

  In the present invention, the bismuth-based glass has a bismuth oxide content of 70% by mass or more in terms of oxide.

  Thus, by being bismuth-type glass with much content of bismuth oxide, the effect which can form a conductor, suppressing the shrinkage | contraction at the time of baking can be acquired notably.

  Moreover, the conductor paste of this invention is baked at the temperature of 400-950 degreeC, It is characterized by the above-mentioned.

  By firing at this temperature, a sintered conductor having a smaller volume change rate after firing can be obtained.

  The method for manufacturing a conductor hole-filled substrate according to the present invention includes a step of filling the through-hole or non-through hole provided in the heat-resistant substrate with the above-mentioned conductor paste, a step of drying the conductor paste filled in the hole, and a method of drying And baking the conductive paste at a temperature of 400 to 950 ° C. in an air atmosphere.

  According to the present invention, it is possible to obtain a conductor-filled substrate in which the volume change due to firing is small, the filling property into the hole is good, and the hole is filled with a highly conductive conductor with high conductivity and high thermal conductivity. Is.

  In the present invention, the heat-resistant substrate is selected from a ceramic substrate, a glass substrate, a silicon substrate, and an enamel substrate.

  By using such a high heat resistant substrate, a more reliable conductor hole-filled substrate can be obtained.

  The conductor hole-filled substrate according to the present invention is characterized in that a through-hole or a non-through-hole provided in the heat-resistant substrate is filled with a conductor obtained by firing the above-described conductor paste.

  According to the present invention, it is possible to obtain a conductor-filled substrate in which the volume change due to firing is small, the filling property into the hole is good, and the hole is filled with a highly conductive conductor with high conductivity and high thermal conductivity. Is.

  A circuit board, an electronic component, and a semiconductor package can be manufactured by using the conductor hole-filled substrate as described above.

  According to the present invention, it is possible to obtain a conductor paste that has good fluidity and good filling properties in small holes, and that can form a highly conductive conductor with a small volume change due to firing. A paste can be obtained. Therefore, a highly reliable conductor hole-filled substrate can be obtained by embedding a conductor having a small volume change due to firing into a through-hole or non-through-hole of the heat-resistant substrate and having high conductivity and heat conductivity.

  Embodiments of the present invention will be described below.

  The conductor paste of the present invention is prepared by blending at least conductive metal particles, powder of at least one of glass and inorganic oxide, and an organic vehicle.

  The conductive metal particles contain silver as a main component, but the silver ratio and the type and amount of other conductive metals are not particularly limited, and the required sinterability, electrical characteristics, It can be set according to physical and chemical characteristics. From the viewpoint of cost, sinterability, electrical characteristics, etc., it is preferable that the conductive metal particles contain 60% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more. More preferably. All of the conductive metal particles may be silver. In the conductive metal particles, a metal other than silver is appropriately selected for the purpose of improving migration resistance, improving reliability, improving adhesion, adjusting sinterability, adjusting electric resistance, etc. Can be blended. Examples of the metal species include palladium (Pd), platinum (Pt), gold (Au), ruthenium (Ru), indium (In), and the like, and the blending amount is appropriately determined according to each purpose. Can be set.

  In the present invention, the conductive metal particles are composed of metal powder having a center particle size of 0.25 μm or more and metal nanoparticles having a center particle size of 150 nm or less. In the metal powder having a center particle size of 0.25 μm or more, the upper limit of the center particle size is not particularly limited, but the center particle size may be 100 μm or less in consideration of the filling property and workability of the conductor paste. Preferably, it is 50 μm or less, and more preferably 20 μm or less.

  As described above, the conductive metal particles are composed of the metal powder having a center particle size of 0.25 μm or more and the metal nanoparticles having a center particle size of 150 nm or less. A metal paste having a central particle diameter of 150 nm or less and capable of increasing the packing density of conductive metal particles, and a conductive paste capable of forming a conductor that is dense, highly conductive, and has a small volume change upon firing. It can be obtained.

  Here, the metal powder having a center particle size of 0.25 μm or more is preferably used in combination of two or more kinds of metal powders having a center particle diameter of 3 times or more different. In the conductor paste of the present invention, it is necessary to increase the packing density of the metal powder in the conductor paste in order to suppress the drying shrinkage and firing shrinkage to the maximum. By using together the metal powder of a seed | species or more, the packing density of metal powder can be raised. The upper limit of the difference in the center particle size is not particularly set, but practically the center particle size is preferably in the range of 3 to 30 times. Further, the metal powders having different center particle diameters may be at least two kinds, and the upper limit is not particularly set, but about four kinds are practically the upper limit.

  Moreover, it is preferable that 50-80 mass% of metal powder with a center particle diameter of 1 micrometer or more occupies among metal powders with a center particle diameter of 0.25 micrometers or more. By setting in this way, the conductor paste has an appropriate sinterability, and it is possible to reduce inconveniences such as generation of voids and blisters during firing. When the content of the metal powder having a center particle size of 1 μm or more is less than 50% by mass, the sinterability becomes too high, and the shrinkage during drying and firing of the conductor paste tends to increase, and the degassing is likely to occur. This makes it difficult to generate voids and blisters. As a result, the variation in the volume change rate of the fired conductor becomes large, and voids may be generated inside the conductor. On the other hand, when the content of the metal powder having a center particle size of 1 μm or more exceeds 80% by mass, the packing property at the time of firing the conductor paste is lowered, and it becomes difficult to form pores in the fired conductor. There is a risk of shrinkage.

  The shape of the metal powder having a center particle size of 0.25 μm or more may be any conventionally known shape such as a spherical shape, a flake shape, a polygonal shape, and a fiber shape, but is not particularly limited. From the viewpoint of the packing density of the conductive metal particles therein and the filling workability of the conductor paste, it is preferable to use mainly spherical ones. Also, the method for producing the metal powder is not particularly limited, and a metal powder produced by any known method such as a wet reduction method, a dry reduction method, an electrolysis method, an atomization method, or a mechanical grinding method can be used. .

On the other hand, the metal nanoparticles having a central particle size of 150 nm or less are one of the essential components of the conductive metal particles to be blended in the conductor paste of the present invention, and at least the following two effects are obtained by using the metal nanoparticles. Things can be mentioned. First, since the metal nanoparticles present in the conductor paste have a very small particle size and excellent fluidity, the metal particles between the metal particles having a large particle size with a central particle size of 0.25 μm or more are large. It is possible to increase the metal content in the conductor paste by reducing the amount of organic vehicle used by filling and filling. As a result, it is possible to reduce both drying shrinkage and firing shrinkage after filling the hole in the substrate with the conductive paste, and further improve the denseness, conductivity and thermal conductivity of the conductor obtained by firing. It can be done. The second is that the metal nanoparticles interact with glass and inorganic oxide during firing to form fine pores in the sintered conductor obtained by firing and further reduce shrinkage due to firing. Although the formation mechanism of pores due to the addition of metal nanoparticles is not clear, the formation of pores tends to become prominent in the case of a combination of noble metal nanoparticles and low-melting glass. Is trapped in the sintered body of metal nanoparticles, and the glass melts under a certain temperature condition, thereby releasing the gas present in the glass, thereby forming pores in the sintered conductor. Guessed.

  The type of the metal nanoparticles is not particularly limited, but is preferably a noble metal when a conductor paste is formed for firing in air. Examples of the noble metal nanoparticles include nanoparticles such as Ag, Au, Pt, and Pd. Among these, Ag nanoparticles are particularly excellent in terms of cost, conductivity, thermal conductivity, and the like. preferable.

  The method for producing the metal nanoparticles is not particularly limited, and those produced by any known method such as a wet reduction method or a vapor phase precipitation method can be used. The surface of the metal nanoparticles is stabilized with a stabilizer such as protective colloid because the metal nanoparticles are stably dispersed in the conductor paste until the conductor paste is dried and fired. It is preferable to coat it. The amount of the protective colloid for protecting the metal nanoparticles is not particularly limited, but is preferably set in the range of 0.5 to 15% by mass with respect to the metal nanoparticles. If the coating amount of the protective colloid is less than 0.5% by mass with respect to the metal nanoparticles, the stabilization effect is insufficient, and the metal nanoparticles aggregate while the conductor paste is being stored. There is a risk of sintering. On the contrary, if the amount of the protective colloid exceeds 15% by mass, the organic content in the conductor paste increases, so that shrinkage due to firing may increase. The amount of the protective colloid is more preferably in the range of 0.5 to 5% by mass with respect to the metal nanoparticles.

As the protective colloid, but are not particularly limited, and may be an organic compound having a carboxyl group, a shall be composed of a polymeric dispersing agent.

  Representative organic compounds include carboxylic acids. Examples of such carboxylic acid include monocarboxylic acid, polycarboxylic acid, and hydroxycarboxylic acid (or oxycarboxylic acid). Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, caprylic acid, caproic acid, hexanoic acid, capric acid, lauric acid, myristic acid, stearic acid, cyclohexanecarboxylic acid, dehydrocholic acid, and colanic acid. Can be mentioned. Examples of the polycarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and cyclohexanedicarboxylic acid. Examples of the hydroxycarboxylic acid include glycolic acid, lactic acid, oxybutyric acid, glyceric acid, 6-hydroxyhexanoic acid, cholic acid, deoxycholic acid, chenodeoxycholic acid, 12-oxochenodeoxycholic acid, glycocholic acid, lithocholic acid, and hyodeoxyl. Examples include cholic acid, ursodeoxycholic acid, apocholic acid, taurocholic acid and the like.

  Typical polymer dispersants include resins (or water-soluble resins and water-dispersible resins) containing hydrophilic units (or hydrophilic blocks) composed of hydrophilic monomers. Examples of hydrophilic monomers include carboxyl group or acid anhydride group-containing monomers ((meth) acrylic monomers such as acrylic acid and methacrylic acid, unsaturated polycarboxylic acids such as maleic acid, and maleic anhydride. Etc.), addition group monomers such as hydroxyl group-containing monomers (hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, vinylphenol), condensation monomers such as alkylene oxide (ethylene oxide, etc.), etc. Can be illustrated. The condensed monomer may form a hydrophilic unit by a reaction with an active group such as a hydroxyl group (for example, the hydroxyl group-containing monomer).

  Examples of the resin include styrene resin (styrene- (meth) acrylic acid copolymer, styrene-maleic anhydride copolymer, etc.), acrylic resin (methyl (meth) acrylate- (meth) acrylic acid copolymer, (Meth) acrylic acid resins such as poly (meth) acrylic acid), water-soluble urethane resins, water-soluble acrylic urethane resins, water-soluble epoxy resins, water-soluble polyester resins, and the like.

  The polymer dispersant may be a synthesized one or a commercially available product. Specific examples of commercially available polymer dispersants (or dispersants composed of at least an amphiphilic dispersant) include Solsperse 13240, Solsperse 13940, Solsperse 32550, Solsperse 31845, Solsperse 24000, Solsperse 26000, Solsperse series such as Solsperse 27000, Solsperse 28000, Solsperse 41090, etc. [manufactured by Avicia Co., Ltd.]; Big 180, Dispersic 182, Dispersic 184, Dispersic 190, Dispersic 191, Dispersic 92, Disperbic 193, Disperbic 194, Disperbic 2001, Disperbic 2050, etc. Disperbic series [manufactured by Big Chemie Co., Ltd.]; EFKA-46, EFKA-47, EFKA-48, EFKA-49, EFKA-1501, EFKA-1502, EFKA-4540, EFKA-4550, polymer 100, polymer 120, polymer 150, polymer 400, polymer 401, polymer 402, polymer 403, polymer 450, polymer 451, polymer 452, polymer 453 [EFKA Chemical Co., Ltd.] Manufactured by Ajisper PB711, Azisper PAl11, Azisper PB811, Azisper PB821, Azisper PW911, etc. [Ajinomoto Co., Ltd.]; Lorne series such as Len DOPA-158, Floren DOPA-22, Floren DOPA-17, Floren TG-700, Floren TG-720W, Floren-730W, Floren-740W, Floren-745W [manufactured by Kyoeisha Chemical Co., Ltd.]; John Examples include John Crill series such as Kuril 678, John Crill 679, and John Crill 62 [manufactured by Johnson Polymer Co., Ltd.].

  In the present invention, metal nanoparticles having a central particle size of 150 nm or less are used, but the smaller the particle size, the lower the storage stability and the greater the amount of protective colloid required for stabilizing the metal nanoparticles. When the amount of the protective colloid is increased, the organic content in the conductor paste is increased, and shrinkage due to firing may be increased. Therefore, the metal nanoparticles preferably have a center particle size of 10 nm or more. Further, when the metal nanoparticle has a central particle diameter exceeding 150 nm, the properties such as high filling property, low shrinkage, high conductivity, and high thermal conductivity derived from the nanoparticle may be deteriorated. The central particle size of the metal nanoparticles is more preferably 100 nm or less, and even more preferably 50 nm or less.

  Moreover, as a result of analyzing the particle size distribution of the metal nanoparticles obtained under various synthesis conditions so that the center particle size of the metal nanoparticles is in a preferable range of 10 to 50 nm as described above, The diameter distribution is preferably in the range of 1 to 200 nm. It suffices if it is substantially within the range of 1 to 200 nm, and it may contain a minute amount of less than 1 nm or more than 200 nm so as not to affect the performance.

  In the present invention, the conductive metal particles are composed of metal powder having a center particle size of 0.25 μm or more and metal nanoparticles having a center particle size of 150 nm or less, as described above. It is preferable to set the blending ratio so that the content of metal powder of 25 μm or more is 50 to 90% by mass and the content of metal nanoparticles having a central particle size of 150 nm or less is 10 to 50% by mass (the sum of both). 100% by mass). If the blending ratio of the metal powder having a center particle size of 0.25 μm or more and the metal nanoparticles having a center particle size of 150 nm or less is out of this range, firing shrinkage when firing the conductor paste tends to increase.

  In the present invention, the blending ratio of the conductive metal particles, at least one of glass and inorganic oxide, and the organic vehicle is not particularly limited, but the content of the conductive metal particles is 93 to 97% by mass. It is preferable that the glass and inorganic oxide content is 0.05 to 5% by mass and the organic vehicle content is 2 to 6.9% by mass. When the content of the conductive metal particles is less than 93% by mass, the volume shrinkage during drying and firing of the conductor paste tends to increase. On the other hand, when the content of the conductive metal particles exceeds 97% by mass, the viscosity of the conductor paste becomes too high, and workability such as filling the holes in the substrate is lowered.

  As described above, in the conductor paste of the present invention, it is necessary to blend at least one of glass and inorganic oxide. This glass or inorganic oxide not only has a role of increasing the bonding force between the fired conductor and the substrate, but also acts to foam the fired conductor in a small amount to reduce firing shrinkage. The kind of glass or inorganic oxide is not particularly limited as long as it has foamability in combination with metal nanoparticles.

  Examples of the glass include bismuth glass containing bismuth oxide, zinc glass containing zinc oxide, zinc borosilicate glass, and lead glass containing lead oxide. Among these, it is preferable to use a bismuth glass frit from the viewpoint of wettability with a metal component, solder wettability of a fired conductor, effectiveness and stability of micropore formation, and the like. More preferred is a bismuth glass having a softening point of 550 ° C. or lower, and even more preferred is a bismuth glass having a bismuth oxide content of 70% by mass or more in terms of oxide.

  Here, the glass melts at an appropriate temperature during the firing of the conductor paste, forms fine pores in the fired conductor by the action of the metal component in the firing process, and compensates for the sintering shrinkage of the metal. Although it plays a role of reducing shrinkage due to firing, by using a glass having a softening point of 550 ° C. or lower as described above, it matches the sintering temperature of metal particles mainly composed of silver, It can contribute to the promotion of sintering and the formation of pores. In addition, the bismuth component has good compatibility with silver, diffuses as a flux into the silver powder being sintered, has the effect of further promoting the sintering, and bismuth oxide incorporated into the sintered silver metal phase. Is reduced during firing to generate a small amount of oxygen, which can further contribute to pore formation and shrinkage reduction. The lower limit of the softening point of the bismuth glass is not particularly set, but about 300 ° C. is practically the lower limit of the softening point of the bismuth glass.

  Moreover, when the content of bismuth oxide is 70% by mass or more and the content of bismuth oxide is large, the above-described shrinkage control effect can be obtained more remarkably. In the bismuth-based glass, the upper limit of the bismuth oxide content is not particularly set, but about 90% by mass is practically the upper limit of the bismuth oxide content.

  Examples of the inorganic oxide include bismuth oxide, zinc oxide, lead oxide and the like.

  As for said glass and inorganic oxide, you may make it use only 1 type, but may use 2 or more types together. In particular, glass and inorganic oxides that are effective for other purposes such as improvement of sinterability and adhesion may be used in combination with the above-mentioned pore formation.

The glass or inorganic oxide preferably has a particle size of 20 μm or less so that a sufficient effect can be obtained even with a small amount. It is more preferably 10 μm or less, further preferably 5 μm or less, and most preferably 3 μm or less. The lower limit of the particle size of the glass or inorganic oxide particles is not particularly limited. In the present invention, the particle size means the center particle size.

The blending amount of glass or inorganic oxide is not particularly limited, but in order to obtain high conductivity and thermal conductivity, the total amount of glass and inorganic oxide is 0.02 in the conductor paste as described above. It is preferable to set it within the range of ˜5 mass%, more preferably within the range of 0.05 to 2 mass%, and most preferably within the range of 0.1 to 1 mass%. When the blending amount is less than 0.02% by mass, formation of pores of the fired conductor becomes insufficient, and shrinkage due to firing tends to increase. On the other hand, if the blending amount exceeds 5% by mass, voids are generated due to the foaming of the glass itself, the conductor after firing expands more than necessary, the volume change rate increases, and the electrical resistance and thermal resistance increase. May cause problems.

  In the conductor paste of the present invention, as described above, an organic vehicle that acts as an organic medium in which conductive metal particles and the like are dispersed is required as a subcomponent. Any organic vehicle may be used as long as it can disperse the conductive metal powder satisfactorily, and those conventionally used for conductive pastes can be used without any particular limitation. Examples thereof include petroleum hydrocarbons such as mineral spirits (particularly aliphatic hydrocarbons), ethylene glycol, diethylene glycol, and triethylene glycol or their derivatives, high-boiling organic solvents such as terpineol, and the like. Alternatively, a plurality of types can be used in combination. Also, these organic solvents include acrylics such as polybutyl methacrylate and polymethyl methacrylate, celluloses such as nitrocellulose, ethyl cellulose, cellulose acetate and butyl cellulose, polyethers such as polyoxymethylene, polyvinyls such as polybutadiene and polyisoprene. It is also possible to use a polymer in which a polymer such as a phenol resin or an epoxy resin is dissolved. Although content of an organic vehicle is not specifically limited, It is preferable that it is the range of 2-6.9 mass% in the whole conductor paste as mentioned above.

  The conductive metal particles mainly composed of the above silver, glass or inorganic oxide powder, organic vehicle, and, if necessary, a surface active agent, an antioxidant, etc. are blended, and these are mixed to obtain the present invention. A conductor paste for filling holes can be prepared.

  The conductor paste of the present invention prepared in this way is used by completely filling the through or non-through holes provided in the heat-resistant substrate. Thus, after filling the hole of a heat-resistant board | substrate with a conductor paste, it heats first and removes the solvent in a conductor paste, It dries. The heating for removing the solvent can be performed at a temperature of less than 200 ° C., for example, a temperature of about 150 ° C.

When the shrinkage (dry shrinkage) of the conductor paste due to the solvent removal is large, the conductor paste may be filled again after drying. The conductor paste of the present invention has a very small volume change due to firing, but the drying shrinkage may be large depending on the amount of solvent in the conductor paste. In that case, the hole can be completely filled with the conductor paste in a desired filling amount by repeatedly filling after drying .
Next, it is fired in an oxidizing atmosphere such as in the air to burn off the organic matter in the conductor paste filled in the holes and to sinter the metal component, thereby obtaining a highly conductive and highly thermally conductive conductor material. The holes of the heat-resistant substrate can be filled with the conductor thus formed. By completely filling conductors in the through or non-through holes of the board, it is possible to achieve electrical continuity between the front and back of the board and the wiring between layers, and heat conduction by the conductor filled in this hole realizes heat dissipation Is something that can be done.

  The firing temperature is not particularly limited, but is preferably in the range of 400 to 950 ° C, more preferably in the range of 500 to 800 ° C. When the firing temperature is less than 400 ° C., the formation of pores in the conductor obtained by firing is insufficient, and the shrinkage rate after firing tends to increase. Conversely, when the firing temperature exceeds 950 ° C., oversintering occurs in the conductive metal particles containing silver as a main component, and the variation in the volume change rate due to firing tends to increase. Although the firing time is not particularly limited, it is generally preferable to hold it at the above temperature for about 10 to 60 minutes.

  The heat-resistant substrate used in the present invention is not particularly limited as long as it can withstand the high temperature of baking after the conductor paste is filled in the holes provided in the substrate. For example, a ceramic substrate, a glass substrate, a silicon substrate, a hollow substrate, and the like can be given. Ceramics include alumina, zirconia, beryllia, mullite, holsterite, cordierite, oxide ceramics such as lead titanate, barium titanate, lead zirconate titanate, and non-oxidized silicon nitride, aluminum nitride, silicon carbide, etc. Examples thereof include physical ceramics.

  Further, the filling of the through-hole or non-through-hole provided in the heat-resistant substrate can be performed by any method, for example, screen printing, dispenser filling, press injection, or the like.

  As described above, a conductive paste-filled substrate in which a conductor formed by firing is filled in a hole is manufactured by filling a conductive paste in a through-hole or non-through-hole in a heat-resistant substrate, drying the paste, and firing it. It is something that can be done. And it is preferable that the rate of change of the volume after baking the conductor with which the hole was filled in this way is the range of -5%-+ 10% with respect to the dry volume of a conductor paste. When the volume change rate is within such a small range, dents and blisters on the surface of the conductor filled in the hole of the heat-resistant substrate are reduced, and defects such as a gap between the inner wall of the hole and the conductor are generated. Therefore, it is possible to obtain high reliability such as conduction reliability.

  The conductor filled in the hole of the heat-resistant substrate preferably has an electrical resistivity of 10 μΩ · cm or less, more preferably 6 μΩ · cm or less after firing at 600 ° C. for 10 minutes. More preferably, it is 4 μΩ · cm or less. Thus, a low electrical resistivity makes it possible to form a highly conductive and highly reliable conductor. The lower the electrical resistivity, the better, and no lower limit is set.

  The conductor filled in the hole of the heat-resistant substrate preferably has a thermal conductivity of 150 W / m · K or more after firing at 600 ° C. for 10 minutes, and more than 200 W / m · K. It is more preferable. Thus, by high heat conductivity, a conductor with high heat dissipation can be formed, and it can be used for the use for which heat dissipation is requested | required. The higher the thermal conductivity, the better, and no upper limit is set.

  A circuit board can be obtained by forming a circuit such as an electronic circuit on a heat-resistant board using the conductor hole-filled board produced as described above. An electronic component can be obtained by mounting an electronic element on the heat-resistant substrate of the circuit board. Furthermore, a semiconductor package can be obtained by mounting and sealing a semiconductor element on the heat-resistant substrate of this circuit board.

  Next, the present invention will be specifically described with reference to examples.

(Synthesis of silver nanoparticles with a central particle size of 30 nm)
66.8 g of silver nitrate, 10 g of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.), a polymer dispersant (“Dispervic 190” manufactured by Big Chemie), a polyethylene oxide chain which is a hydrophilic unit, and an alkyl group which is a hydrophobic unit 2 g of amphiphilic dispersant, solvent: water, 40% by mass of a non-volatile component, an acid value of 10 mg KOH / g, and an amine value of 0) were added to 1000 g of ion-exchanged water and vigorously stirred. To this was added 100 g of 2-dimethylaminoethanol (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was heated and stirred at 70 ° C. for 2 hours. This reaction product was centrifuged at 7000 rpm for 1 hour using a high-speed centrifuge (“Kusan“ H-200 SERIES ”), and a precipitate in which silver nanoparticles protected by the protective colloid were aggregated was collected. According to the measurement with a transmission electron microscope (TEM), the central particle diameter of the obtained silver nanoparticles was 30 nm.

  Further, when the content of the protective colloid was measured with a thermogravimetric measuring device (TG / DTA, “EXSTAR6000” manufactured by Seiko Instruments Inc.), the content was 3 parts by mass with respect to 100 parts by mass of silver. The measurement by TG / DTA was performed under the condition that the sample was heated from 30 ° C. to 550 ° C. at a rate of 10 ° C. per minute, and the content of the protective colloid was calculated from the mass decrease at this time.

(Synthesis of silver nanoparticles with a central particle size of 4 nm)
2.5 g of silver nitrate, 4.9 g of n-octylamine and 4.9 g of linoleic acid were added to 1.0 L of trimethylpentane, and the mixture was stirred and dissolved. To this mixed solution, 1.0 L of a propanol solution containing 0.03 mol / L sodium borohydride was dropped over 1 hour to reduce silver. Further, this was stirred for 3 hours to obtain a black liquid. After the obtained black liquid was concentrated by an evaporator, 2.0 L of methanol was added thereto to produce a brown precipitate, and then the precipitate was collected by suction filtration. The resulting precipitate was redispersed in trimethylpentane, further filtered, and dried to obtain silver nanoparticles protected by the protective colloid as a black solid. According to a transmission electron microscope (TEM), the central particle diameter of the obtained silver nanoparticles was 4 nm.

  Moreover, when content of the protective colloid was measured with the thermogravimetry apparatus similarly to the above, it was a content rate of 25 mass parts with respect to 100 mass parts of silver.

(Preparation of conductor paste for hole filling)
The above silver nanoparticles, silver powder, and palladium powder are used as the conductive metal particles, the glass has a low melting point (bismuth glass (Bi ₂ O ₃ —ZnO—B ₂ O ₃ )), and the bismuth content is 81 in terms of bismuth oxide. Example 1 by using a pentanediol as a solvent of an organic vehicle, mixing them with a mixer in a blending amount shown in Table 1, and then kneading them uniformly with a three roll. To 10 and Comparative Examples 1 to 7 were obtained.

  About the said conductor paste for hole filling, the filling property to a hole was evaluated. That is, the conductor paste was filled and printed on an alumina substrate having a thickness of 0.635 mm on which many through holes having a diameter of 0.15 mm were formed under the conditions of a squeegee angle of 30 degrees, a squeegee speed of 15 mm / second, and a printing pressure of 0.25 MPa. And, when the hole can be completely filled by printing within 3 times, “◯”, when it can be completely filled by printing 4 times to 10 times, “△”, 10 times or more The case where printing was necessary was determined as “×”.

  Next, after the substrate filled with the conductive paste in the hole as described above is dried by a blow dryer at 150 ° C. for 20 minutes, the conductive paste protruding from the substrate surface or remaining on the substrate surface is removed. It was completely removed by buffing. Next, this substrate was placed in a continuous firing furnace, and was fired in an air atmosphere at a peak temperature of 600 ° C. for 10 minutes. The residence time of the substrate from the firing furnace inlet to the outlet was 60 minutes. The firing strength of the filled conductor was evaluated for the substrate after firing in this manner. In other words, after observing the hole filled with the conductor with the actual microscope and confirming the presence or absence of the conductor, the substrate was put into an ultrasonic device, treated for 20 minutes, and then again confirmed with the actual microscope for the presence or absence of the conductor. did. The case where there was no dropout of the conductor or chipping of 5 μm or more was judged as “◯”, the case of chipping of 5 μm or more and less than 10 μm was judged as “Δ”, and the case of dropping or chipping of 10 μm or more was judged as “X”.

  Moreover, about the conductor paste for hole filling, the baking volume change rate, the baking conductor electrical resistivity, and the baking conductor thermal conductivity were measured. Since it is difficult to perform these measurements in a state where the hole is filled with the conductive paste, the conductive paste was printed on the surface of the alumina substrate under the following conditions and evaluated.

  First, using a 250 mesh screen on the surface of a 96% alumina substrate, the conductor paste is printed in a 5 × 5 mm, 10 × 10 mm pattern shape, and heated at 150 ° C. for 10 minutes to remove the organic solvent in the conductor paste. Drying was performed. Next, this was placed in a continuous firing furnace and fired in air at a peak temperature of 600 ° C. for 10 minutes. The residence time of the substrate from the firing furnace inlet to the outlet was 60 minutes.

  The firing volume change rate was measured with a stylus type film thickness meter ("Dektak 6m" manufactured by Beaco) using a 5 x 5 mm pattern and measuring the thickness of the pattern before firing and the thickness of the pattern after firing. The film thickness was obtained by comparing the film thickness values before and after firing with the following formula.

Volume change rate (%) = [(film thickness after firing−film thickness before firing) / film thickness before firing] × 100
The fired conductor electrical resistivity was obtained as a volume resistivity by measuring a resistance value of a 10 × 10 mm pattern using a four-terminal resistivity meter (“2002 MULTITIMER” manufactured by Toyo Technica Co., Ltd.).

  The evaluation of the thermal conductivity of the fired conductor was performed as follows. First, using a 250 mesh screen on the surface of a 96% alumina substrate, the conductor paste was printed in a 10 mm square pattern, dried at 150 ° C. for 10 minutes to remove the organic solvent, A conductor film having a thickness of 1 mm was prepared by repeatedly drying and overprinting, and thereafter fired under the same conditions as described above. The conductor film thus obtained was peeled from the substrate, and the thermal conductivity was measured by a laser flash method. Then, 200 W / m · K or more was judged as “◯”, 150 W / m · K or more, less than 200 W / m · K as “Δ”, and less than 150 W / m · k as “x”.

  Table 1 shows the above measurement results and evaluation results. Note that the present invention targets at a value of determination “Δ” or higher.

  As seen in Table 1, all of the conductor pastes for filling holes of Examples 1 to 10 satisfying the requirements of the present invention have good filling properties, and have high conductor strength, small volume change rate, It was possible to form a conductor having a low electrical resistivity and high thermal conductivity.

  On the other hand, Comparative Example 1 is the same as Example 1 except that the low-melting glass was not blended, but the firing volume change rate was -9.6%, and the filled conductor was fired. Was easily dropped from the hole.

  In Comparative Example 2, the metal nanoparticles were not blended, the firing volume change rate was -18.3%, and the shrinkage was greatly contracted, and the filled conductor after firing easily dropped out of the hole. . Moreover, the filling property was also inferior to the thing of each Example which mix | blended the metal nanoparticle.

  In Comparative Example 3, silver particles having a small particle diameter with a central particle diameter of 0.25 μm are used instead of metal nanoparticles, but there is no expansion effect like metal nanoparticles, and the firing volume change rate is − It contracted greatly to 22.1%, and the filled conductor after firing easily dropped out of the hole. Moreover, the filling property was also inferior to the thing of each Example which mix | blended the metal nanoparticle.

  In Comparative Example 4, metal particles having a center particle size of 0.25 μm or more were not blended, and only metal nanoparticles were blended as conductive metal particles, but the firing volume change rate was as large as −16.9%. The filled conductor after shrinkage and firing was easily removed from the hole. Further, the filling property was also inferior to that of each Example in which metal particles having a center particle size of 0.25 μm or more were blended.

  Comparative Example 5 has the same composition as Example 1 except that the amount of the organic solvent serving as the organic vehicle is excessive. However, as a result of the increase in the amount of the organic solvent used, the metal concentration in the conductor paste was 92.1. The mass was low. For this reason, although the filling property of the conductor paste is good, the shrinkage due to the solvent drying greatly occurs, and the firing volume change rate is as large as -8.8%, and the filled conductor after firing easily falls out of the hole. It was something to do.

  Comparative Example 6 has the same composition as Example 3 except that silver nanoparticles having a small center particle diameter of 4 nm are used, but the amount of protective colloid contained in the silver nanoparticles is too large. The metal concentration of was reduced to 90.9% by mass. For this reason, firing shrinkage occurred greatly, and the filled conductor easily dropped from the hole. Although not shown as data in Table 1, when trying to reduce the amount of solvent in order to increase the metal concentration, the fluidity of the conductor paste was significantly reduced, making it difficult to fill the holes. .

  In Comparative Example 7, as in the conventionally known technique, a large amount of glass component is blended to expand the conductive paste being fired to eliminate firing shrinkage. In this case, the volume change rate by firing can be satisfied as 6.4%, but the electrical resistivity of the fired conductor is as high as 14.9 μΩ · cm, and there is a problem in conductivity, Further, when treated with ultrasonic waves, a part of the silver conductor was chipped and dropped off.

  Next, in addition to firing at a firing temperature of 600 ° C. as described above using the conductor paste of Example 1, firing was performed at temperatures of 500 ° C., 700 ° C., and 800 ° C. by changing the firing temperature. . In the same manner as described above, the firing volume change rate, the fired conductor electrical resistivity, and the strength after firing the fired conductor were measured. The results are shown in Table 2.

  As can be seen in Table 2, the conductor paste blended in Example 1 according to the present invention exhibits a stable volume change rate and conductor strength even when fired in a wide temperature range, and has high conductivity. there were.

Claims (21)

Filled with through or non-through holes provided in a heat-resistant substrate and fired, containing conductive metal particles mainly composed of silver, at least one of glass and inorganic oxides, and an organic vehicle A conductive paste for filling a hole with a conductor, wherein the content of the conductive metal particles is 93 to 97% by mass, and the total amount of the glass and the inorganic oxide is 0.05 to 5% by mass. , at least one of the content of 0.05 to 5% by weight of the above glass and an inorganic oxide, content of the organic vehicle is from 2 to 6.9 wt%, said conductive metal particles, It contains metal powder with a center particle size of 0.25 μm or more and metal nanoparticles with a center particle size of 10 to 100 nm, and the inorganic substance content including the metal in the conductor paste is 93% by mass or more of the total amount of the conductor paste, and is dried. Vs. state volume That, 600 ° C. in filling a conductive paste, wherein the rate of change of volume after firing is in the range of -1.2～ + 10%.   The conductor paste for filling holes according to claim 1, wherein the electrical resistivity of the conductor after firing at 600 ° C is 10 µΩ · cm or less.   The conductor paste for filling holes according to claim 1, wherein the electrical resistivity of the conductor after firing at 600 ° C is 4 µΩ · cm or less.   The conductor paste for filling holes according to any one of claims 1 to 3, wherein the conductor has a thermal conductivity of 150 W / m · K or higher after firing at 600 ° C.   5. The metal powder having a center particle diameter of 0.25 μm or more is a combination of two or more kinds of metal powders having a center particle diameter of three or more times different from each other. The conductor paste for filling holes described.   6. The metal powder having a center particle size of 0.25 μm or more has a content of metal powder having a center particle size of 1 μm or more of 50 to 80% by mass, according to claim 1. Conductive paste for filling holes.   Among the above conductive metal particles, the metal powder having a center particle size of 0.25 μm or more is contained in 50 to 90% by mass, and the metal nanoparticles having a center particle size of 10 to 100 nm are contained in 10 to 50% by mass. The conductive paste for hole filling according to any one of claims 1 to 6.   The metal nanoparticle having a central particle size of 10 to 100 nm is a nanoparticle having a particle size distribution within a range of 1 to 200 nm, for filling a hole according to any one of claims 1 to 7. Conductor paste.   9. The conductive paste for filling holes according to claim 1, wherein the metal nanoparticles having a central particle size of 10 to 100 nm have a central particle size in the range of 10 to 50 nm.   2. A protective colloid for stabilizing the dispersibility of the metal nanoparticles is provided on the surface of the metal nanoparticles in an amount of 0.5 to 15% by mass with respect to the metal nanoparticles. The conductor paste for hole filling as described in any one of thru | or 9.   11. The conductive paste for filling a hole according to claim 1, wherein the metal nanoparticles include at least silver nanoparticles.   The conductive paste for hole filling according to any one of claims 1 to 11, wherein the glass is a bismuth glass having a softening point of 550 ° C or lower.   13. The conductive paste for filling holes according to claim 12, wherein the bismuth-based glass has a bismuth oxide content of 70% by mass or more in terms of oxide.   14. The conductive paste for filling holes according to claim 1, wherein the paste is fired at a temperature of 400 to 950 ° C. 15.   A step of filling the conductive paste according to any one of claims 1 to 14 into a through or non-through hole provided in the heat-resistant substrate, a step of drying the conductive paste filled in the hole, and a drying And a step of firing the conductive paste at a temperature of 400 to 950 ° C. in an air atmosphere.   The method of manufacturing a conductor hole-filled substrate according to claim 15, wherein the heat-resistant substrate is selected from a ceramic substrate, a glass substrate, a silicon substrate, and an enamel substrate.   A conductive hole-filled substrate, wherein a through-hole or a non-through-hole provided in the heat-resistant substrate is filled with a conductor obtained by firing the conductive paste according to any one of claims 1 to 14.   A conductor hole-filled substrate manufactured by the method according to claim 15 or 16.   A circuit board comprising the conductor hole-filling board according to claim 17.   An electronic component comprising the conductor hole-filling substrate according to claim 17.   A semiconductor package comprising the conductor hole-filling substrate according to claim 17.