JP2010108917A - Copper conductive paste to be filled in through-hole, method of manufacturing substrate with copper conductor filled in through-hole, substrate with copper conductor filled in through-hole, circuit board, electronic component, semiconductor package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper conductive paste to be filled in through-holes for preventing the fall-off or continuity failure of a copper conductor by reducing the occurrence of shrinkage when filled in the through-holes and fired. <P>SOLUTION: The copper conductive paste to be filled in the through-holes is of such a type that it is filled in the through-holes of a heat resistant substrate and fired under a non-oxidizing atmosphere. It has a volume change rate of 8% or lower during firing, wherein the copper conductor has an electric resistivity of 10 μΩcm or smaller after firing. It contains at least copper powder, glass powder, and organic vehicle. The copper powder is a mixed powder consisting of one having particle sizes of smaller than 1 μm and accounting for 10-30 mass% and one having particle sizes of 1-50 μm and accounting for 70-90 mass%. It has a tap density of 6.0 g/cc or more. The copper conductive paste contains organic components accounting for 8.5 mass% or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a copper conductor paste used by filling and firing through holes to obtain conduction of a wiring circuit formed in a plurality of layers on a substrate, and high-temperature firing after filling the copper conductor paste into the through holes. The present invention relates to a method for manufacturing a copper conductor through-hole filling substrate, and also relates to a copper conductor through-hole filling substrate, a circuit board, an electronic component, and a semiconductor package.

  Multi-layer circuit boards such as front and back double-sided wiring are used for high-density mounting of electrical and electronic components. In this multilayer circuit board, the conductive connection of a plurality of layers of conductor circuits formed on the board is performed by through holes provided in the board. In particular, when a heat resistant substrate such as a ceramic substrate is used as the substrate, the connection of the conductor circuit by the through hole is generally performed by filling the through hole with a conductor paste.

  This high-temperature firing type conductive paste is prepared, for example, containing conductive metal powder, glass powder, organic vehicle, etc., and after filling the through-hole formed in the substrate with the conductive paste, this is heated to high temperature. By baking, the paste filled in the through hole becomes a conductor, and the conductor circuit can be connected.

  However, when the conductor paste is filled into the through hole and fired, the conductive metal powder shrinks during firing, causing the conductor filled in the through hole to shrink, causing the conductor to fall out of the through hole, or to connect with the conductor circuit. There was a problem of poor continuity.

  Therefore, in Patent Document 1, an expansion agent is added to the conductor paste, and the expansion agent is expanded when the conductor paste is filled in the through hole and fired, so that the conductor filled in the through hole is prevented from shrinking. I have to.

  However, when the expanding agent is contained in the conductor paste as described above, there is a problem that the conductivity of the conductor filled in the through hole may be lowered. In addition, the expansion agent expands by being oxidized at the time of firing, and it is necessary to perform firing in an oxidizing atmosphere. In the case of a base metal paste such as a copper conductor paste, the conductor metal is also oxidized and the conductivity is remarkably high. Since it falls, it cannot be applied.

  In Patent Document 2, firing shrinkage is reduced by adding ruthenium oxide powder to the conductor paste. However, in the case of silver conductor paste, the effect of reducing shrinkage is recognized, but in the case of copper conductor paste, as seen in FIG. The effect of reducing the firing shrinkage of the copper conductor paste by adding ruthenium powder is small.

Japanese Patent Laid-Open No. 9-46013 JP-A-7-94840

  The present invention has been made in view of the above points, and reduces shrinkage when filling through holes and firing, and prevents copper conductors from dropping or poor conduction. The purpose of the present invention is to provide a copper conductor paste for filling through-holes, and the copper conductor can fall off by preventing shrinkage when filling the through-holes with copper conductor paste and firing. An object of the present invention is to provide a method for producing a copper conductor through-hole-filled substrate capable of preventing the occurrence of poor conduction, and a copper conductor through-hole-filled substrate using such a copper conductor paste, An object of the present invention is to provide a circuit board, an electronic component, and a semiconductor package.

  The copper conductor paste for filling through-holes according to the present invention is a copper conductor paste for filling through-holes that is filled in through-holes of a heat-resistant substrate and fired in a non-oxidizing atmosphere, and the volume change due to firing The rate is 8% or less, and the electrical resistivity of the fired copper conductor is 10 μΩ · cm or less.

  According to the present invention, the volume change rate during firing of the copper conductor paste is 8% or less, that is, as small as + 8% to -8%, and shrinkage occurs when the copper conductor paste is filled in the through holes and fired. The copper conductor can be prevented from falling out of the through-hole and the conduction failure with the conductor circuit of the through-hole can be prevented, and the electrical resistivity of the copper conductor after firing is 10 μΩ. -It is as small as cm or less and has good conductive properties.

  The through-hole filling copper conductor paste according to the present invention contains at least a copper powder, a glass powder, and an organic vehicle. The copper powder has a particle size of less than 1 μm and a particle size of 10 to 30% by mass and a particle size of 1 to 50 μm. The mixture is a mixed powder composed of 70 to 90% by mass, the tap density is 6.0 g / cc or more, and the organic content in the copper conductor paste is 8.5% by mass or less. To do.

  Thus, the copper powder is a mixed powder composed of 10 to 30% by mass with a particle size of less than 1 μm, 70 to 90% by mass with a particle size of 1 to 50 μm, and a tap density of 6.0 g / cc or more. And a copper conductor paste having a high copper powder content while maintaining good filling properties by using a copper conductor paste having an organic content of 8.5% by mass or less. And can be fired into a copper conductor having a low electrical resistivity as described above. Further, this copper conductor paste can greatly reduce shrinkage due to solvent drying and high-temperature firing after filling the through hole, and the volume change rate of the copper conductor can be reduced as described above.

In the present invention, the mixed powder of copper has an average specific surface area of 0.3 to 0.6 m ² / g.

  Copper oxidizes when heated in an oxidizing atmosphere such as in the air, but the copper conductor paste made of mixed copper powder having such an average specific surface area oxidizes the surface of the copper powder when heated in air, As copper becomes copper oxide, the volume expands moderately, and volume shrinkage due to solvent removal of the paste can be compensated. In addition, the surface-oxidized copper powder is reduced to metallic copper during subsequent firing under an inert atmosphere, but the copper oxide layer on the surface of the copper powder inhibits (slows) the sintering of the copper powder in the firing process, It is possible to reduce the sintering shrinkage of the copper powder.

  Moreover, this invention contains 0.5-10 mass% of copper oxide powder, It is characterized by the above-mentioned.

  By containing copper oxide powder as a part of the copper mixed powder in the copper conductor paste in this way, the sinterability of the copper conductor paste is moderately suppressed, and the shrinkage of the copper conductor during firing is suppressed to change the volume. Can be reduced.

  The method for manufacturing a copper conductor paste through-hole-filled substrate according to the present invention includes a step of filling the through-hole formed in the heat-resistant substrate with the copper conductor paste, and the copper conductor paste filled in the through-hole with an oxidizing atmosphere. And a step of partially oxidizing the copper powder and a step of baking the oxidized copper conductor paste at a temperature of 700 ° C. or higher in an inert atmosphere.

  According to the present invention, when the copper conductor paste filled in the through hole is heated in an oxidizing atmosphere to oxidize the surface of the copper powder and further fired in an inactive atmosphere, the surface oxidized copper powder is Sinterability is suppressed by the oxide layer on the surface, and it is reduced to metallic copper without greatly shrinking, and it is sintered, and shrinkage that occurs when filling the through hole with copper conductor paste and firing This can be reduced as described above. In the present invention, to partially oxidize copper powder means to oxidize the entire surface without oxidizing the inside of the copper powder.

  Moreover, in this invention, the process of heating and oxidizing the copper conductor paste with which said through hole was filled is performed by the heating of the temperature of 200-300 degreeC.

  By setting the heating temperature within this range, the copper powder of the copper conductor paste can be appropriately oxidized without breaking the shape of the copper conductor paste filled in the through hole.

  In the present invention, the heat-resistant substrate is a ceramic substrate.

  The ceramic substrate is excellent in heat resistance and widely used in the manufacture of circuits and electronic components, and therefore, a great effect can be obtained by applying the present invention.

  In the present invention, the ceramic substrate is an aluminum nitride substrate.

  Aluminum nitride is particularly preferable because it is excellent in mechanical properties, electrical properties, thermal conductivity, and the like.

  And a circuit board, an electronic component, and a semiconductor package can be manufactured using the copper conductor through-hole filling board | substrate produced using the copper conductor paste of this invention as mentioned above.

  According to the present invention, when the copper conductor paste filled in the through-hole is heated in an oxidizing atmosphere to oxidize the surface of the copper powder and then fired in an inert atmosphere, the surface-oxidized copper powder is It is reduced to metallic copper without being greatly shrunk and sintered, and it can prevent shrinkage from occurring when the copper conductor paste is filled into a through hole and fired. It is possible to prevent the copper conductor from dropping from the hole or causing poor conduction.

  And the copper conductor whose volume change rate by baking is 8% or less and whose electrical resistivity after baking is 10 microhm * cm or less can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The copper conductor paste of the present invention is prepared by blending at least copper powder, glass powder, and an organic vehicle.

  In the present invention, the copper powder includes 10 to 30% by mass of the powder having a particle size of less than 1 μm, 70 to 90% by mass (100% by mass in total) having a particle size of 1 to 50 μm, and a tap density of 6. While using the mixed powder which is 0 g / cc or more, the one whose organic content in the copper conductor paste is 8.5% by mass or less is used. In the present invention, the particle size means the center particle size.

In the present invention, the copper mixed powder having an average specific surface area of 0.3 to 0.6 m ² / g is used.

  In the present invention, the glass powder is blended for the purpose of improving the wettability with respect to the substrate and the like and improving the adhesion, and is not particularly limited, but the softening point is in the range of about 400 to 750 ° C. Are preferred. The type of glass is not particularly limited, but a low-melting glass that does not contain harmful substances such as lead and cadmium, such as borosilicate glass, zinc borosilicate glass, and bismuth glass, is preferable. When the substrate after filling the through hole requires a plating process, it is preferable to use glass having chemical resistance. The particle size and shape of the glass powder are not particularly limited, but those having a particle size in the range of 0.1 to 10 μm are preferable, and more preferable for minimizing shrinkage due to melting of the glass. Is 0.1 to 5 μm, more preferably 0.1 to 3 μm.

  In the present invention, as the organic vehicle, an organic binder dissolved in an organic solvent can be used. The organic binder is not particularly limited, but is an organic compound that is easily burned off during the baking process and has a low ash content, for example, acrylics such as polybutyl methacrylate and polymethyl methacrylate, nitrocellulose, ethyl cellulose, cellulose acetate, Celluloses such as butyl cellulose, polyethers such as polyoxymethylene, polyvinyls such as polybutadiene and polyisoprene can be used, and these are used alone or in combination of two or more. It can also be used.

  Although it does not specifically limit as an organic solvent, The organic compound which gives moderate viscosity to a copper conductor paste, and is easily volatilized by a drying process after apply | coating a copper conductor paste to a board | substrate, for example, carbitol, carbitol High boiling organic solvents such as acetate, terpineol, metacresol, dimethylimidazole, dimethylimidazolidinone, dimethylformamide, diacetone alcohol, triethylene glycol, paraxylene, ethyl lactate, isophorone can be used, These may be used alone or in combination of two or more.

  A copper conductor paste is prepared by blending the above-mentioned copper powder, glass powder, organic vehicle and, if necessary, sintering inhibitors such as oxides, surface active agents, antioxidants, etc., and mixing them. It is something that can be done. The blending ratio of each material is not particularly limited, but is 1 to 6 parts by weight of glass powder, 0.5 to 3 parts by weight of organic binder, and 4 to 9 parts by weight of organic solvent with respect to 100 parts by weight of copper powder. It is preferable to set the range. Here, in the copper conductor paste of the present invention, the total amount of the organic content of the organic binder, organic solvent, and other organic additives in the paste is set to 8.5% by mass or less. Is.

  The glass powder improves the denseness of the fired copper conductor and improves the adhesion between the copper conductor and the substrate. When the blending amount of the glass powder is less than 1 part by mass, the denseness of the fired copper conductor is lowered and the adhesive strength with the substrate is also lowered, so that the copper conductor may drop from the through hole after firing. On the other hand, the glass powder melts and shrinks during high-temperature firing of the copper conductor. If the blending amount is 6 parts by mass or more, the firing shrinkage of the copper conductor paste becomes large, and the target low shrinkage rate cannot be obtained. There is a fear.

  The organic binder has a role such as imparting an appropriate viscosity to the copper conductor paste and maintaining the shape after the solvent is removed and dried. When the blending amount of the organic binder is less than 0.5 parts by mass, the stability and printability of the copper conductor paste are lowered, and satisfactory through hole filling becomes difficult. On the other hand, when it exceeds 3 parts by mass, the viscosity of the copper conductor paste is increased, and the filling property to the through hole may be lowered.

  Moreover, since all the organic components in the copper conductor paste are evaporated and decomposed during drying or firing, there is a tendency that the firing shrinkage of the copper conductor paste increases as the amount increases. In order to achieve the low shrinkage rate of the present invention, the organic content in the copper conductor paste is set to 8.5% by mass or less. The smaller the organic content, the smaller the shrinkage due to removal by burning. However, if the amount is too small, the fluidity (fillability) of the paste is lowered, so it is preferably 6.0% by mass or more.

  The copper conductor paste of the present invention prepared as described above is used by filling a through hole in order to obtain conduction of a wiring circuit formed in a plurality of layers on a heat resistant substrate.

  The heat-resistant substrate is not particularly limited as long as it can withstand the high temperature of baking after filling the copper conductor paste into the through hole. For example, a ceramic substrate, a glass substrate, a silicon substrate, an enamel substrate, and the like can be given. Ceramics include non-oxidized ceramics such as alumina, zirconia, beryllia, mullite, holsterite, cordierite, lead titanate, barium titanate, lead zirconate titanate, silicon nitride, aluminum nitride, silicon carbide, etc. Among these, aluminum nitride is particularly preferable because aluminum nitride is excellent in mechanical characteristics, electrical characteristics, thermal conductivity, and the like.

  The heat-resistant substrate has through holes penetrating the substrate at locations where wiring circuits are formed on both sides, and the through holes are filled with a copper conductor paste. Filling the through holes with the copper conductor paste can be performed by any method, for example, by screen printing.

  After filling the through hole with the copper conductor paste in this way, the solvent is first removed by heating to remove the solvent in the copper conductor paste. 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.

  Thereafter, a copper conductor having a small firing shrinkage ratio can be obtained by firing the substrate filled with the copper conductor paste in a through hole in an inert atmosphere at a temperature of 700 ° C. or higher. However, it is preferable to heat-oxidize the copper conductor paste in order to further reduce the firing shrinkage rate. This thermal oxidation is for thermally decomposing part of the organic binder in the copper conductor paste filled in the through hole and oxidizing the surface of the copper powder, and in an active atmosphere (oxidizing atmosphere) such as in the air. It is done. When the surface of the copper powder is oxidized, the volume of the copper powder increases, so that the volume decrease due to the volatilization of the solvent and the decomposition of the organic binder is compensated. The heating temperature is set to 200 ° C. or higher. Although the upper limit of heating temperature is not specifically limited, It is desirable that it is the temperature of 300 degrees C or less. If the temperature at which the copper conductor paste is heated is less than 200 ° C., the copper powder cannot be sufficiently oxidized, so that a sufficient shrinkage suppressing effect cannot be obtained. Moreover, when the temperature which heats a copper conductor paste exceeds 300 degreeC, an organic binder will be decomposed | disassembled completely and there exists a possibility that the shape of the copper conductor paste with which the through hole was filled may collapse, or it may fall out from a board | substrate. In addition, the copper powder is excessively oxidized and cannot be sufficiently reduced in the subsequent firing step, and the conductivity may be greatly reduced. In addition, although the time of a heating is not specifically limited, About 30 to 180 minutes are generally preferable.

  Next, after the copper powder of the copper conductor paste is partially oxidized by heating in this way, the substrate is heated in an inert atmosphere, and the copper conductor paste filled in the through holes is fired. The heating temperature for this baking is set to 700 ° C. or higher. Here, as the non-active atmosphere (non-oxidizing atmosphere, reducing atmosphere), for example, a nitrogen atmosphere or the like can be used. In this way, by heating the copper conductor paste to 700 ° C. or higher in an inert atmosphere, the copper powder whose surface is made of copper oxide as described above is reduced, returned to the original metallic copper and sintered. And the organic vehicle is decomposed and removed.

  If the heating temperature during firing is less than 700 ° C., the effect of reducing the copper oxide to metallic copper becomes insufficient, and the sintering is also insufficient, so that sufficient conductivity and adhesion cannot be obtained. There is a fear. The upper limit of the heating temperature is not particularly set, but firing is preferably performed at a temperature of 950 ° C. or lower. 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.

  In this way, by firing at 700 ° C. or higher in an inert atmosphere, the copper oxide is sintered while being reduced to metallic copper, but the copper oxide layer on the surface of the copper powder inhibits the sintering of the copper powder. Then, sintering shrinkage is reduced by lowering the sinterability. Accordingly, it is possible to prevent the conductor formed in the through hole from being contracted by firing the copper conductor paste, and the conductor may be dropped from the through hole or the conductor may be chipped. This eliminates problems such as the occurrence of poor conduction.

Here, in the present invention, the copper conductor paste can be easily partially oxidized by heating the copper conductor paste at a temperature of 200 ° C. or higher, and the oxidized copper conductor paste is further subjected to an inert atmosphere. As the copper powder that can be easily reduced to metallic copper without shrinking the surface-oxidized copper powder by firing at a temperature of 700 ° C. or higher, those having a particle size of less than 1 μm as described above are 10 to 10. 30% by mass, mixed powder consisting of 70-90% by mass with a particle size of 1-50 μm, tap density of 6.0 g / cc or more, and average specific surface area of 0.3-0.6 m ² / g The one that is is used.

  In this mixed powder of copper, if the particle size is less than 1% by mass, the effect of preventing the copper powder from being oxidized and preventing shrinkage when fired in an inert atmosphere. Becomes insufficient. On the other hand, when the particle size is less than 1 μm and exceeds 30% by mass, the oxidized copper powder cannot be sufficiently reduced when fired in an inert atmosphere, and the conductivity may be lowered.

  On the other hand, when the tap density of the copper powder is less than 6.0 g / cc, the filling density of the copper powder is low, and a large amount of solvent is required when forming a paste. Such a copper conductor paste shrinks greatly due to the removal of the solvent during drying and firing, and thus the purpose of reducing the volume change rate cannot be achieved. The tap density is preferably as high as possible, and the upper limit is not particularly set. However, in practice, the upper limit is about 7.0 g / cc.

Further, when the average specific surface area of the copper powder is less than 0.3 m ² / g, the copper powder is insufficiently oxidized, and has an effect of preventing shrinkage and reducing the volume change when firing in an inert atmosphere. It becomes insufficient. On the other hand, if the average specific surface area exceeds 0.6 m ² / g, the oxidized copper powder cannot be sufficiently reduced when fired in an inert atmosphere, and the conductivity may be lowered.

  Moreover, in this invention, copper oxide powder can be mix | blended and used for copper conductor paste other than said each component. Thus, when copper oxide powder is blended into the copper conductor paste as a part of the copper mixed powder, the copper oxide powder expands when the copper conductor paste filled in the through hole as described above is heated in an oxidizing atmosphere. Thus, the volume decrease can be compensated for, and the volume change can be reduced by suppressing the shrinkage of the copper conductor. The compounding amount of the copper oxide powder is preferably in the range of 0.5 to 10% by mass in the copper conductor paste. The effect by mix | blending copper oxide powder cannot be fully acquired as it is less than 0.5 mass%. Conversely, when it exceeds 10 mass%, a copper conductor will expand | swell excessively by expansion | swelling of a copper oxide powder, and the volume change of a copper conductor will become large on the contrary with this expansion | swelling. The particle size of the copper oxide powder is not particularly limited, but the center particle size is preferably in the range of 0.5 to 20 μm.

  Then, by using the copper conductor paste having the above composition and filling the through hole of the substrate with the copper conductor paste by the above method and firing, the shrinkage during firing is suppressed and the volume change rate is reduced. A copper conductor having a volume change rate by firing of 8% or less, that is, a volume change rate in the range of -8% to + 8% can be obtained. When the volume change rate shrinks beyond -8%, the copper conductor may fall out of the through hole or a conduction failure with the conductor circuit of the through hole may occur. Conversely, if the copper conductor expands and the volume expansion coefficient exceeds + 8%, the copper conductor may protrude greatly from the through hole, or the through hole may be broken by the copper conductor.

  In addition, the copper oxide can be reduced by firing in an inert atmosphere to obtain high conductivity of the copper conductor, and a copper conductor having an electrical resistivity of 10 μΩ · cm or less can be obtained. It can be done. If the electrical resistivity exceeds 10 μΩ · cm, sufficient conductivity cannot be ensured in the through hole, and there is a possibility that it cannot be used in high current applications. The lower the electrical resistivity, the better. The lower limit is not particularly set, but 1.69 μΩ · cm, which is the electrical resistivity of pure copper, is the practical lower limit.

  A circuit board can be obtained by forming a circuit on a heat-resistant substrate using the copper conductor through-hole-filled substrate 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.

  The present invention will now be illustrated by examples and comparative examples.

  As shown in Table 1, copper powders 1 to 5 having a center particle size of 7.3 μm, 4.8 μm, 1.2 μm, 0.83 μm, and 0.52 μm (all manufactured by Mitsui Kinzoku Mining Co., Ltd.) are used as the copper powder. In addition, cuprous oxide powder having a center particle size of 4.2 μm (manufactured by High Purity Chemical Research Laboratory) was used as the copper oxide powder, and these were mixed in the blending amounts shown in Table 2 and used as a mixed powder. In the present invention, the center particle size (D50) is a value measured by a laser diffraction / scattering particle size distribution measuring apparatus, and the values disclosed by the manufacturer are adopted. Moreover, in this invention, an average specific surface area is the value measured by BET method, and the numerical value of Table 1 is a manufacturer disclosure value. Further, in the present invention, the tap density of the mixed copper powder is a value measured with a graduated cylinder type tap density measuring device (tap density meter “PT-DTI” manufactured by Pharmatest, Germany). In addition, the numerical value of the tap density of various copper powder or copper oxide powder of Table 1 is a manufacturer disclosure value.

  As the glass frit, zinc borosilicate glass powder having a softening point of 565 ° C. and an average particle diameter of 3 μm was used.

  Further, as the organic vehicle, an organic binder acrylic resin and an organic solvent carbitol / terpineol (= 1: 1) mixed at a mass ratio of 1: 2 were used.

  And after mix | blending these with the compounding quantity of Table 2, and mixing with a mixer, the copper conductor paste of Examples 1-4 and Comparative Examples 1-8 was obtained by knead | mixing uniformly with a three roll.

  About this copper conductor paste, the shrinkage | contraction rate and resistivity after baking were measured. Since it is difficult to measure the shrinkage rate and resistivity with the through-hole filled with the copper conductor paste, the measurement was performed by printing the copper conductor paste on the surface of the aluminum nitride substrate.

  First, using a 250-mesh screen on the surface of the aluminum nitride substrate, the copper conductor pastes of Examples 1 to 4 and Comparative Examples 1 to 8 were screen-printed in pattern shapes, and heated at 150 ° C. for 10 minutes to obtain copper. The organic solvent in the conductor paste was removed. Next, oxidation treatment was performed by heating for 60 minutes at a temperature shown in Table 2 in air using a continuous drying furnace. Then, it baked by heating at 900 degreeC for 60 minute (s) in nitrogen atmosphere using the continuous baking furnace.

  The volume change rate is determined by measuring the thickness of the pattern before firing and the thickness of the pattern after firing with a stylus thickness meter, and comparing the film thickness values before and after firing with the following formula. Calculated as a rate.

Shrinkage rate (%) = [(film thickness before firing−film thickness after firing) / film thickness before firing] × 100
If the shrinkage rate (%) is a positive value, the volume is decreasing, so the volume change rate is a negative value. On the other hand, if the shrinkage rate (%) is a negative value, the volume has increased, so the volume change rate is a positive value. The results are shown in Table 2.

  Further, the resistivity was obtained as a volume resistivity by measuring a resistance value of a 10 mm square pattern formed on the substrate after firing using a four-terminal resistivity meter. The results are shown in Table 2.

  Next, about the copper conductor paste of Examples 1-4 and Comparative Examples 1-8, the filling property to a through hole and adhesiveness were evaluated.

  First, an aluminum nitride substrate (3 inches x 3 inches x thickness 0.635 mm) provided with a large number of two types of through holes with a hole diameter of 0.15 mm and 0.3 mm was used, and copper conductor paste was manually printed on the through holes. Filled with. Next, this was put into a 150 ° C. blower dryer and heated for 20 minutes to dry the solvent, and then the copper conductor paste remaining on the substrate surface was completely removed by buffing. Thereafter, this substrate was put in a continuous drying furnace at 220 ° C. and heated in air for 60 minutes, and then the substrate was put in a continuous baking furnace and baked at 900 ° C. for 60 minutes in a nitrogen atmosphere.

  For the substrate after firing in this manner, the filling state of the through hole is observed with a stereomicroscope to confirm whether or not the conductor is dropped (first time), and the substrate is further placed in an ultrasonic device and subjected to ultrasonic vibration. After adding for 20 minutes, the through-hole filling state was again observed with a stereomicroscope to confirm whether or not the conductor was dropped (second time). The results are shown in Table 2. In Table 2, “* 1” indicates that it dropped out at the first time, and “* 2” indicates that it dropped out at the second time.

  As seen in Table 2, the copper conductor pastes of Examples 1 to 4 had a low volume change rate of 8% or less by firing. Then, the volume change rate was further reduced and the electrical resistivity was sufficiently small by oxidizing with heating at a temperature of 200 ° C. or higher. Regarding the through-hole filling properties, those in Examples 1 to 4 were good, and the conductor was not dropped or chipped even after ultrasonic vibration was applied. When the through-hole portion of the substrate was cut and observed in cross section, the wall surface of the through-hole and the filled conductor were adhered without any gap, and there were no defects such as voids.

  In Example 4, a part of the copper powder of Example 3 was replaced with copper oxide powder, and thus the generation of shrinkage can be further suppressed by blending the copper oxide powder at 180 ° C. Even when the oxidation treatment was performed at this temperature, almost no shrinkage could be achieved.

  On the other hand, the copper conductor paste of Comparative Example 1 has a high ratio of fine copper powder having a particle size of less than 1 μm, and it is possible to reduce shrinkage during firing by oxidizing at a temperature of 200 ° C. or higher. The oxidized copper powder could not be sufficiently reduced during firing, and the conductivity was greatly reduced and the resistivity increased.

  Moreover, since the copper conductor paste of the comparative example 2 had a low tap density of the copper powder, the shrinkage during firing was large, and the conductor dropped out from the through hole. Further, since the average specific surface area of the copper powder is large, when the copper powder is oxidized, blisters are generated and the conductivity is greatly reduced.

  In addition, the copper conductor pastes of Comparative Example 3 and Comparative Example 4 do not contain fine copper powder having a particle diameter of less than 1 μm, and the tap density is low, so that a large shrinkage occurs during firing, and the conductor is dropped from the through hole. It was something to do.

  In addition, since the copper conductor paste of Comparative Example 5 had a low tap density, the shrinkage during firing was large, and the conductor dropped out of the through hole.

  Further, the copper conductor pastes of Comparative Example 6 and Comparative Example 7 have a high ratio of fine copper powder having a particle size of less than 1 μm, a small tap density and a large average specific surface area, so that blisters are easily generated during oxidation treatment. However, the conductivity was greatly reduced.

  Further, the copper conductor paste of Comparative Example 8 had a large shrinkage despite the oxidation treatment because of the large amount of organic vehicle.

Claims (13)

  A copper conductor paste for filling through-holes that fills through-holes in a heat-resistant substrate and is fired in a non-oxidizing atmosphere, and has a volume change rate of 8% or less due to firing, and copper after firing A copper conductor paste for filling through-holes, wherein the electrical resistivity of the conductor is 10 μΩ · cm or less.   It contains at least a copper powder, a glass powder, and an organic vehicle, and the copper powder is a mixed powder composed of 10 to 30% by mass with a particle size of less than 1 μm and 70 to 90% by mass with a particle size of 1 to 50 μm. The copper conductor paste for filling a through hole according to claim 1, wherein the tap density is 6.0 g / cc or more and the organic content in the copper conductor paste is 8.5% by mass or less. . The mixed powder of copper, the average specific surface area of 0.3~0.6m 2 / ^g characterized in that it is a claim 1 or 2 through hole for filling copper conductor paste according to.   The copper conductor paste for filling through-holes according to any one of claims 1 to 3, comprising 0.5 to 10% by mass of copper oxide powder.   A step of filling the through-hole formed in the heat-resistant substrate with the copper conductor paste according to any one of claims 1 to 4, and heating the copper conductor paste filled in the through-hole in an oxidizing atmosphere to obtain a copper powder. A method for producing a copper conductor through-hole-filled substrate, comprising: a step of partially oxidizing, and a step of firing an oxidized copper conductor paste at a temperature of 700 ° C. or higher in an inert atmosphere.   The method for producing a copper conductor through-hole-filled substrate according to claim 5, wherein the step of heating and oxidizing the copper conductor paste filled in the through-hole is performed at a temperature of 200 to 300 ° C.   7. The method for manufacturing a copper conductor through-hole-filled substrate according to claim 5, wherein the heat-resistant substrate is a ceramic substrate.   The method for manufacturing a copper conductor through-hole-filled substrate according to claim 7, wherein the ceramic substrate is an aluminum nitride substrate.   A copper conductor through-hole-filled substrate, wherein a copper conductor made of a fired product of the copper conductor paste according to any one of claims 1 to 4 is filled in a through-hole of a heat-resistant substrate.   A copper conductor through-hole-filled board manufactured by the method according to claim 5.   The circuit board provided with the copper conductor through-hole filling board of Claim 9 or 10.   The electronic component provided with the copper conductor through-hole filling board | substrate of Claim 9 or 10.   The semiconductor package provided with the copper conductor through-hole filling board | substrate of Claim 9 or 10.