JP5670924B2 - Conductive bonding material, method of bonding ceramic electronic material using the same, and ceramic electronic device - Google Patents

Description

  The present invention relates to a conductive bonding material used for bonding ceramic electronic materials such as power semiconductors, a method for bonding ceramic electronic materials using the same, and a ceramic electronic device.

  The next generation power semiconductor module using SiC (silicon carbide), GaN (gallium nitride), C (diamond), etc. is attracting attention as a measure against global environment and power consumption reduction through power control technology represented by inverters. There is a lot of research on the practical application of. As a ceramic electronic material such as a power semiconductor module, an insulating semiconductor device 100 as shown in FIG. 2 is known, for example.

  The insulating semiconductor device 100 includes, as a basic component, a ceramic insulating substrate 104 on a base material (cooling plate) 102 made of copper (Cu) or the like via a bonding portion 101, and on its surface. Typically, a circuit wiring pattern of a metal film formed by a screen printing method or the like is drawn. A plurality of power semiconductor devices 106 such as IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), or diodes are provided on the ceramic insulating substrate 104 with a circuit via the joint portion 101. Yes. These semiconductor devices 106 are connected to each other (or with electrodes) in accordance with the purpose of use, and are sealed with a resin and packaged, so that it is possible to reduce the size and weight, simplify the manufacturing process, and the like. It is said.

In such a conventional insulating semiconductor device 100, generally, the electronic materials such as the semiconductor device 106, the ceramic insulating substrate 104, and the base material 102 are first heated at a high temperature (for example, 800 ° C.) with high-temperature solder. After joining, they are joined at a low temperature (for example, 500 ° C. or less) with a medium temperature or low temperature solder.
On the other hand, with further miniaturization, higher functionality, and higher integration of semiconductor materials for next-generation power semiconductor modules, it has been proposed to integrate a substrate and a semiconductor chip, for example, at a low temperature of 500 ° C. or lower. It has been studied to integrate power semiconductor modules by firing and bonding together.

  And as a material to join each semiconductor material in such next-generation power semiconductor module, low temperature sintering phenomenon and high surface activity due to quantum size effect of nanometer-sized conductive particles (typically metal nanoparticles) It has been proposed to use a low-temperature firing type conductive bonding material. Since the bonding interface by the conductive bonding material containing metal nanoparticles is bonded by metal bonding, it has high heat resistance, reliability and high heat dissipation, so conductive bonding of next-generation power semiconductor modules It is desirable as a material.

JP 2008-208442 A JP 2008-161907 A JP 2010-257880 A

  However, very fine metal nanoparticles with an average particle size of 100 nm or less are likely to agglomerate. In order to stabilize the metal nanoparticles, it is necessary to form an organic protective film on the surface of the metal nanoparticles. It was. This organic protective film must be removed at the time of bonding, but it is difficult to completely remove the protective film by heating at a low temperature, and it has been difficult to obtain sufficient bonding strength. In addition, it has been proposed to perform molecular design so that the organic protective film of the metal particles is decomposed at a low temperature, but when such metal particles are produced at room temperature of 20 ° C. to 30 ° C., the metal is immediately used. Since nanoparticle aggregation occurs, it has been difficult to produce metal nanoparticles that can be sintered at low temperatures. And for such metal nanoparticles that do not have an organic protective film, agglomeration occurs immediately, and for example, when forming joints by printing or the like, the compact density tends to be low. There was a problem that it tends to be low. Note that when the sintered body density is low, there are many voids, which causes problems such as a decrease in heat dissipation, an increase in electrical resistance, and a decrease in bonding strength.

On the other hand, in Patent Document 1, by adding a reducing agent made of an organic substance to metal compound particles (metal microparticles) having an average particle diameter of 1 nm to 50 μm, the metal compound particles are thermally decomposed. In addition, it is disclosed that metal compound particles are reduced at a low temperature to produce metal particles (metal nanoparticles) having an average particle size of 100 nm or less and used as a bonding material. However, according to this method, it is necessary to generate an oxide layer on the bonding surface in advance before bonding, and perform an oxidation treatment on the layer to generate an oxide layer with a thickness greater than the natural oxide film thickness. The joining method has become complicated.
In addition, due to the difficulty in handling such nanoparticles, a conductive bonding material using metal particles having an average particle size of 100 μm or less has been proposed (see, for example, Patent Documents 2 and 3).

  This invention is made | formed in view of this point, and it aims at providing the electroconductive joining material which can suppress the aggregation of electroconductive particle of nanometer size, and can maintain the state disperse | distributed stably. Another object of the present invention is to provide a ceramic electronic device such as a power semiconductor module formed using such a conductive bonding material.

As a result of intensive studies to achieve the above object, the present inventors have adjusted the solvent itself to a stable good solvent state in order to suppress aggregation of nanometer-sized particles and stably disperse them in the solvent. It is extremely important that a good solvent for the nanometer-sized particles is found to be extremely effective when a resin as a binder and a solvent are combined and formulated in a special combination. This is what I came up with.
That is, the conductive bonding material provided by the present invention is a conductive bonding material for bonding ceramic electronic materials, the conductive particles having an average particle size of 100 nm or less, a resin as a binder, and at least two kinds of solvents. These are prepared in the form of a paste (including slurry and ink. The same shall apply hereinafter). Here, the resin is a cellulose resin, and the mixed solvent contains at least an alcohol solvent and an ether solvent. The alcohol solvent and the ether solvent are characterized in that the alcohol solvent is blended in a proportion of 20% by mass to 80% by mass and the ether solvent is blended in a proportion of 80% by mass to 20% by mass.
Moreover, it is preferable that the ratio which comprises alcohol solvent> ether solvent, ie, alcohol solvent is 50 mass% or more of the whole.

  According to various studies by the present inventors, the cellulose resin has a good compatibility with a mixed solvent containing at least an alcohol solvent and an ether solvent, and dissolves well in the mixed solvent to form a uniform solvent system. Can do. In other words, alcohol-based solvents or ether-based solvents are unlikely to be one of the best good solvents alone for cellulosic resins, but alcohol-based solvents and ether-based solvents are combined at an appropriate blending ratio. By preparing it, it can be converted to a good solvent with higher solubility. A solvent system in which a resin is dissolved in a mixed solvent having good compatibility as described above is used for conductive particles having an average particle size of 100 nm or less (hereinafter, sometimes simply referred to as “nanoconductive particles”). Can also be a good good solvent. Therefore, even when the conductive bonding material is prepared in a paste form, it is possible to suppress the aggregation of the nanoconductive particles and maintain a stably dispersed state. By using such a conductive bonding material, there is no unevenness in density, and a high-density molded body (bonding layer) can be formed. In addition, by firing the molded body, a dense and uniform high-strength joint can be obtained, and at the same time, a joint having high heat resistance, reliability, and high heat dissipation can be formed.

Moreover, in one preferable aspect of the conductive bonding material disclosed herein, the resin and the alcohol-based resin are mixed so that the Hansen solubility parameter distance between the resin and the mixed solvent is 5.0 MPa ^0.5 or less. The solvent, the ether solvent and the blending ratio thereof are determined.
Hansen's solubility parameter (HSP) is an index representing the solubility of how much a certain substance dissolves in another certain substance. This HSP has a different concept from the Hildebrand SP value employed in solvent handbooks and the like, and represents solubility as a multi-dimensional (typically three-dimensional) vector. This vector can typically be represented by a dispersion term, a polar term, and a hydrogen bond term. Those having similar vectors can be determined to have high solubility, and the similarity of vectors can be determined by the Hansen solubility parameter distance (HSP distance). In addition, Hansen's solubility parameter can be used not only as a judgment of solubility, but also as an index for judging how easily a certain substance is present in another certain substance, that is, how good the dispersibility is.
Therefore, in the invention disclosed herein, the combination of the resin, the alcohol solvent, and the ether solvent, and its combination so that the HSP distance between the resin and the mixed solvent is 5.0 MPa ^0.5 or less. The mixing ratio is determined. When the HSP distance is 5.0 MPa ^0.5 or less, this solvent system is sufficiently stable, and nano-conductive particles can be dispersed stably. Thus, a paste-like conductive bonding material in which conductive particles having an average particle diameter of 100 nm or less are highly dispersed can be easily configured with a clear index of HSP distance.

  In a preferred embodiment of the conductive bonding material disclosed herein, as the nano conductive particles, silver (Ag) particles, copper (Cu) particles, aluminum (Al) particles, or particles of any metal belonging to the platinum group including. According to such a configuration, it is possible to form a joint portion by metal bonding of the nano-conductive particles by firing, and it is possible to form a joint portion that is more excellent in conductivity and the like.

  In a preferred embodiment of the conductive bonding material disclosed herein, the ether solvent is dipropylene glycol methyl-n-propyl ether (DPMNP). The DPMNP HSP is an ether solvent that is easy to guide the HSP of the mixed solvent closer to the HSP of the cellulose resin (that is, a good solvent) when mixed with an alcohol solvent (vector) ). Further, DPMNP is suitable as a solvent in the conductive bonding material because of characteristics such as boiling point and viscosity other than HSP. Therefore, by using such DPMNP as an ether solvent, a conductive bonding material in which nano conductive particles are well dispersed can be realized.

  In a preferred embodiment of the conductive bonding material disclosed herein, the cellulosic resin is ethyl cellulose. Ethyl cellulose is excellent in solubility in a high boiling point solvent, and is excellent in dispersibility and combustion decomposition characteristics of various materials, and has properties suitable as a binder for a baked paste. This provides a high-quality conductive bonding material that is excellent in dispersibility of conductive particles and has little residual resin component after firing.

  In a preferred embodiment of the conductive bonding material disclosed herein, the cellulose resin is ethyl cellulose, the alcohol solvent is terpineol, and the ether solvent is dipropylene glycol methyl-n-propyl ether. The combination of these resins, alcohol solvents and ether solvents has a good compatibility with respect to solubility, and can build a very good good solvent. Therefore, by dispersing nano conductive particles in such a solvent system, a conductive bonding material in which nano conductive particles are stably highly dispersed is provided.

In such a conductive bonding material, the mass ratio of terpineol and dipropylene glycol methyl-n-propyl ether is preferably 50:50 to 70:30 as terpineol: dipropylene glycol methyl-n-propyl ether. By setting the mixed solvent to the above composition, for example, the HSP distance between ethyl cellulose as the resin component and the mixed solvent can be set to 5.0 MPa ^0.5 or less, and a good solvent system can be prepared.

  As another aspect for solving the above object, the invention disclosed herein provides a ceramic electronic device. Such a ceramic electronic device is characterized in that at least two electronic materials including a ceramic electronic material are bonded to each other by the fired product (bonded portion) of the conductive bonding material according to any one of the above. . According to the conductive bonding material including the nano conductive particles, an organic protective film or the like hardly remains in the bonding portion. Typically, the nano conductive particles are bonded to each other by a metal bond. It has high conductivity and can have high heat resistance and high heat dissipation. In addition, the nano-conductive particles in the conductive bonding material can be closely aligned with a specific orientation on the surface of the electronic material that is the material to be bonded because the aggregation of each other is suppressed. Can be. Furthermore, depending on the constituent material of the electronic material that is the material to be joined, for example, an epitaxial joint interface can be formed with respect to the constituent material, so that higher joint strength and conductive characteristics can be provided.

Furthermore, as another aspect for solving the above object, the invention disclosed herein provides a method for joining ceramic electronic materials. Such a bonding method includes bonding at least two electronic materials including a ceramic electronic material to each other via the conductive bonding material according to any one of the above, and firing at a temperature range of 500 ° C. or less. The at least two electronic materials are joined by a joining member made of a fired product of a conductive joining material.
It is known that nano-conductive particles can lower their sintering temperature due to their high surface activity. In the conductive bonding material, aggregation of the conductive nanoparticles is suppressed, and sintering at a lower temperature than that of the aggregated conductive nanoparticles becomes possible. Therefore, in such a bonding method, firing is performed at a temperature range of 500 ° C. or lower (preferably 400 ° C. or lower, for example, 300 ° C. or lower), and the influence on other electronic materials other than the bonded portion is minimized. It is possible to stay.

It is sectional drawing which shows typically an example of the structure of the ceramic electronic device which concerns on embodiment of this invention. It is sectional drawing which shows typically an example of the structure of the conventional ceramic electronic device.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than those specifically mentioned in the present specification and matters necessary for carrying out the present invention (for example, a method for producing conductive particles, a method for mixing conductive particles and a solvent, conductive bonding) The method for supplying the material to the substrate, etc.) can be grasped as a design matter of those skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

<Ceramic electronic devices>
In addition, the ceramic electronic device manufactured using the electroconductive joining material disclosed here may be the same as that of the conventional ceramic electronic device, and does not include a configuration that makes it particularly different. An insulating semiconductor device 10 as an embodiment of such a ceramic electronic device is shown in FIG. The structure itself of the insulated semiconductor device 10 shown in FIG. 1 is the same as that of the conventional insulated semiconductor device 100 shown in FIG. 2, and there is no difference in the structure itself. That is, the ceramic electronic device according to the present embodiment may typically be an insulating semiconductor device 10 having the configuration illustrated in FIG.

  The insulating semiconductor device 10 includes a ceramic insulating substrate (typically, typically a cooling plate made of copper (Cu)) 2 as a basic component. , Alumina, aluminum nitride, silicon nitride) 4, and a circuit wiring pattern of a metal film typically formed by a screen printing method or the like is drawn on the surface thereof. A plurality of power semiconductor devices 6 are provided on the ceramic insulating substrate 4 with circuit. In FIG. 1, the display of wiring between the power semiconductor devices 6 is omitted, but the semiconductor devices 6 are connected to each other (or with electrodes) according to the purpose of use, sealed with resin, and packaged. It can be.

<Conductive bonding material>
The conductive bonding material disclosed herein is a conductive bonding material used for bonding ceramic electronic materials to each other or between an electronic material made of a ceramic electronic material and another material. The electronic materials are joined to each other by a joint 1 composed of a fired product obtained by firing a conductive joining material. Here, the electronic material is typified by, for example, the ceramic insulating substrate 4 described above, and various power semiconductor devices 6 such as an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or a diode. For example, a conductive bonding material for bonding a ceramic electronic material and an electronic material typified by the above-described base material 2 or the like.

Thus, in the invention disclosed herein, the ceramic electronic material is an electronic material in which at least a part of the electronic material constituting the electronic element or the like is made of ceramic. In addition, the term “ceramic” includes both oxide ceramics whose basic component is a metal oxide, or non-oxide ceramics whose basic component is a metal carbide, nitride, boride or fluoride. Can do. As ceramics constituting such a ceramic electronic material, for example, typically, alumina (Al ₂ O ₃ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), and sialon (Sialon, Si ₃ N) are used. _4- AlN—Al ₂ O ₃ solid solution), silicon carbide (SiC), boron nitride (BN), GaN (gallium nitride), and the like.

<Nano conductive particles>
The conductive bonding material is mainly composed of conductive particles having an average particle diameter of 100 nm or less, that is, so-called nano conductive particles, which are dispersed in a solvent so as to be supplied in an optimum state for an electronic material, and paste It is provided as a prepared product. Here, the solvent typically wraps a resin as a binder and a mixed solvent composed of at least two kinds of solvents. In the solvent composed of these resins and a mixed solvent (hereinafter, the solvent composed of the resin and the mixed solvent may be referred to as a “solvent system” in consideration of the correlation of the materials here), the resin is a cellulosic resin. The mixed solvent is characterized in that it is a mixed solvent in which an alcohol-based solvent is blended in an amount of 20% by mass to 80% by mass and an ether-based solvent is blended in an amount of 80% by mass to 20% by mass.

  As described above, the nano conductive particles contained as the main component of such a conductive bonding material are those having an average particle diameter (primary particles) of 100 nm or less. More specifically, the average particle diameter is preferably, for example, 1 nm to 50 nm, more preferably 2 nm to 30 nm, for example, 20 nm ± 5 nm. When the conductive bonding material is baked, the nano conductive particles are sintered to form a bonding portion for bonding the electronic material. By using the conductive particles of such a size, the temperature is lower. Thus, a conductive bonding material that can be fired and sintered is realized.

In the present specification, the average particle size is, for example, a particle size D ₅₀ value corresponding to 50% cumulative in a volume-based particle size distribution measured by particle size distribution measurement based on dynamic light scattering (DLS) ( Median diameter).

  As such nano-conductive particles, powders of various materials exhibiting conductivity can be used. About such electroconductive particle, there is no restriction | limiting in particular in the composition etc., You may be comprised from various electroconductive materials. For example, typically, gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), platinum group elements represented by iridium (Ir), titanium (Ti), Various metals such as tin (Sn), nickel (Ni), aluminum (Al), cobalt (Co) and the like, and intermetallic compounds or composites thereof, or a mixture thereof may be used. Among them, the conductive nanoparticles disclosed herein are preferably composed of silver (Ag), copper (Cu), aluminum (Al), or a platinum group element, and may be composed of any one of these, for example. preferable. In addition, even if such nano-conductive particles contain a small amount of impurities other than the material exhibiting the above conductivity, as long as it is a powder of a material exhibiting conductivity as a whole, the conductive particles referred to here are used. be able to. Moreover, since the nano electroconductive particle which consists of such a metal material mutually metal-bonds by baking, it becomes possible to form the junction part more excellent in electroconductivity etc. In addition, depending on the combination of the nano-conductive particles and the electronic material that is the material to be joined, the nano-conductive particles can be densely arranged with a specific orientation on the surface of the electronic material. An epitaxial structure can be obtained, a bonding interface is good, and bonding with excellent bonding strength and conductivity can be realized.

  The shape of the particles constituting the nano conductive particles is not particularly limited. Although it is typically spherical, it is not limited to a so-called true spherical shape. Other than spherical shapes, for example, flake shapes and irregular shapes can be mentioned. Such nano-conductive particles may be composed of particles of these various shapes. When such nano-conductive particles are composed of particles having a small average particle size (for example, several tens of nm size), it is preferable that 70% by mass or more of the particles (primary particles) have a spherical shape or a similar shape. For example, 70% by mass or more of the particles constituting the nanoconductive particles may be nanoconductive particles having an aspect ratio (that is, the ratio of the major axis to the minor axis) of 1 to 1.5. preferable.

  Although there is no restriction | limiting in particular about the content rate of the said nanoelectroconductive particle in the electroconductive joining material disclosed here, It is preferable that it is 90 mass% or more by making the whole this electroconductive joining material into 100 mass%. More preferably, the content is 92% by mass or more, and further 95% by mass or more (for example, 97% by mass). In this conductive bonding material, even when the nano-conductive material is made into such a high-concentration (high content) paste, aggregation of the nano-conductive particles is suppressed. And when the content rate of the nano electroconductive particle in the manufactured electroconductive joining material exists in the said range, the junction part in which the compactness and the electrical conductivity were improved more can be formed.

<Solvent system>
In the conductive bonding material disclosed herein, the preparation of the solvent system is extremely important in that it enables a high degree of dispersion of the nanoconductive particles. By making this solvent system a stable good solvent, the nano-conductive particles can be stably dispersed.
Therefore, a cellulose resin is used as the resin contained in the solvent system. Such a cellulose-based resin can impart good viscosity and coating film forming ability (adhesiveness) to the conductive bonding material prepared in a paste form. Examples of such cellulose-based resins include polymers made of cellulose such as cotton, hemp, and pulp, polymers in which some hydroxyl groups of cellulose such as chitin and chitosan are substituted with other functional groups, and some cellulose Polymers with substituted structures are included. Specific examples include ethyl cellulose, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, alcohol-solubilized cellulose butyrate, and the like. In particular, ethyl cellulose is preferable because it has excellent solubility in a high-boiling solvent, has excellent dispersibility of various materials and combustion decomposition characteristics, and has properties suitable as a binder in a conductive bonding material.

  Although not particularly limited, the proportion of the resin in the conductive bonding material is suitably 0.1% by mass to 10% by mass, preferably 1% by mass to 7% by mass. It is below, More preferably, they are 1 mass% or more and 5 mass% or less.

A mixed solvent is used as a solvent constituting the solvent system, and the mixed solvent includes at least two kinds of solvents, an alcohol solvent and an ether solvent. Alcohol solvents or ether solvents are unlikely to be one of the best good solvents for cellulose resins, which are solvent-based resin components, but alcohol solvents and ether solvents are mixed in an appropriate combination. Thus, a good solvent with higher solubility can be prepared.
Examples of alcoholic solvents that can form such good solvents include methanol, ethanol, n-propanol, i-propanol, butanol, isobutanol, tertiary butanol (TBA), butanediol, ethylhexanol, cyclohexanol, Various alcohol solvents such as benzyl alcohol and terpineol can be suitably used.

  Examples of ether solvents include diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, anisole, butyl phenyl ether, pentyl phenyl ether, methoxy toluene, benzyl ethyl ether, diphenyl ether. , Dibenzyl ether, dioxane, furan, tetrahydrofuran, diethylene glycol ethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, diethylene glycol Methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol propyl ether acetate, diethylene glycol isopropyl ether acetate, diethylene glycol butyl ether acetate, diethylene glycol-t-butyl ether acetate, triethylene glycol methyl ether acetate, triethylene glycol ethyl ether acetate, triethylene glycol propyl Ether solvents such as ether acetate, triethylene glycol isopropyl ether acetate, triethylene glycol butyl ether acetate, triethylene glycol-t-butyl ether acetate, dipropylene glycol dimethyl ether, dipropylene glycol monobutyl ether It can be exemplified. Of these, glycol ethers typified by propylene glycol monomethyl ether and the like are preferably used, and more preferably dipropylene glycol methyl-n-propyl ether (DPMNP) is preferably used. The DPMNP HSP is an ether-based solvent that is easy to guide each HSP closer to the HSP of the cellulosic resin (ie, a good solvent) when mixed with an alcohol solvent (vector). It has become. Moreover, characteristics such as boiling point and viscosity other than HSP are also suitable as a solvent in the conductive bonding material. Therefore, by using such DPMNP as an ether solvent, a conductive bonding material in which nano conductive particles are well dispersed can be realized. These may be used alone or in combination of two or more.

  These alcohol solvents and ether solvents are preferably mixed solvents in which, for example, ether solvents are mixed in a proportion of 20% by mass to 80% by mass and ether solvents are mixed in a proportion of 80% by mass to 20% by mass. More preferably, the alcoholic solvent ≧ the etheric solvent, that is, the alcoholic solvent is 50% by mass or more. Thereby, the solubility of the cellulose resin with respect to the mixed solvent is enhanced, and the cellulose resin can be well dissolved in the mixed solvent to form a uniform solvent system. As a result, the state of the solvent system can be stably adjusted, and a good solvent (dispersion medium) can be obtained for the nano conductive particles.

In one preferred embodiment of the conductive bonding material disclosed herein, the solubility of the resin and the mixed solvent is determined based on the distance from the Hansen solubility parameter, the resin, the alcohol solvent, and the ether solvent. In addition, the mixing ratio is determined.
Hansen ’s solubility parameter (HSP) is based on the idea that “similar things dissolve similar things” and “similar things want to be in the same place”. It is an index that expresses the solubility. This HSP is completely different in concept from the Hildebrand SP value employed in solvent handbooks and the like, and the solubility is represented by a multi-dimensional (typically three-dimensional) vector. This vector can typically be represented by a dispersion term, a polar term, and a hydrogen bond term. This dispersion term reflects van der Waals force, the polarity term reflects the dipole moment, and the hydrogen bond term reflects the action of water, alcohol, and the like. Those having similar vectors by HSP can be determined to have high solubility, and the similarity of vectors can be determined by the distance of the Hansen solubility parameter (HSP distance). In addition, Hansen's solubility parameter can be used not only as a judgment of solubility, but also as an index for judging how easily a certain substance is present in another certain substance, that is, how good the dispersibility is. Such HSPs are described, for example, in Wesley L. Reference may be made to the values disclosed by Archer, Industrial Solvents Handbook, et al. The HSP distance can be calculated by the following equation (1), for example, where the solute HSP is (D1, P1, H1) and the solvent HSP is (D2, P2, H2).

Therefore, in the invention disclosed herein, the combination of the resin, the alcohol solvent, and the ether solvent, and its combination so that the HSP distance between the resin and the mixed solvent is 5.0 MPa ^0.5 or less. Determine the blend ratio. A solvent system suitable for dispersing nano-conductive particles can be easily prepared by setting the HSP distance to 5.0 MPa ^0.5 or less with a clear index of HSP distance. Further, when the HSP distance is set to 5.0 MPa ^0.5 or less, it is possible to form a high-density joint portion of, for example, 60% or more with this conductive bonding material.

There are no particular restrictions on the combination of such a resin with an HSP distance of 5.0 MPa ^0.5 or less, an alcohol solvent and an ether solvent, and various combinations can be employed. In the conductive bonding material disclosed herein, it is preferable to employ a solvent system composed of a mixed solvent using ethyl cellulose as the resin and DPMNP as the ether solvent and terpineol as the alcohol solvent. As shown. The combination of these resins, alcohol solvents and ether solvents has a good compatibility with respect to solubility, and can build a very good good solvent. Therefore, by dispersing nano conductive particles in such a solvent system, a conductive bonding material in which nano conductive particles are more stably dispersed can be realized.

In addition, HPS (dispersion term, polar term, hydrogen bond term) of these materials is ethyl cellulose (18.0, 4.8, 4.9), DPMNP (15.5, 3.3, 6.6), Terpineol (17.4, 5.9, 9.8). Moreover, the mass ratio of these terpineol and dipropylene glycol methyl-n-propyl ether is 80: 20-20 as above-mentioned as terpineol: dipropylene glycol methyl-n-propyl ether, when using ethylene carbonate as resin. : A solvent system with an HSP distance of 5.0 MPa ^0.5 or less can be realized by adjusting the ratio between 80. And, more specifically, by setting terpineol: dipropylene glycol methyl-n-propyl ether in a mass ratio of 50:50 to 70:30, the HSP distance is 4.7 MPa ^0.5 or less. A solvent system can be realized.

  Such a mixed solvent is not particularly limited, but the proportion of the mixed solvent in the conductive bonding material is suitably 0.1% by mass or more and 10% by mass or less, preferably 1% by mass or more. It is 7 mass% or less, More preferably, it is 1 mass% or more and 5 mass% or less.

As described in detail above, in the conductive bonding material disclosed herein, the cellulose resin is highly soluble in a mixed solvent containing at least an alcohol solvent and an ether solvent, and forms a good solvent system. . Therefore, this solvent system can be a good solvent that suppresses aggregation and enables uniform dispersion even for conductive particles (nanoconductive particles) having an average particle size of 100 nm or less. An electrically conductive bonding material in which particles are highly dispersed without aggregation is provided.
The nano conductive particles in such a conductive bonding material are typically sintered by forming metal bonds by firing. Therefore, it is possible to form a joint having excellent conductivity and bonding strength.

  The conductive bonding material disclosed here is typically the above-mentioned nano conductive particles, resin, and mixed solvent, similarly to the conventional conductive bonding material (for example, including conductive paste). Can be easily prepared by mixing. For example, using a three-roll mill or other kneader, the nano-conductive particles, resin and mixed solvent having a predetermined mixing ratio may be mixed and stirred.

<Join method>
In addition, the conductive bonding material disclosed herein can be handled in the same manner as a conventional conductive bonding material that has been typically used for bonding electronic materials. It can be employed without any particular limitation. Typically, a desired film is formed on the bonding surface of an electronic material (which may be a ceramic electronic material) as a base material by screen printing, dispenser coating, dip coating, ink jet, or the like. It is applied (applied) so as to have a thickness (for example, 30 μm or less) or a coating film pattern, and another electronic material (which may be a ceramic electronic material) is bonded to each other through the conductive bonding material. Here, as described above, the electronic material may be an electronic material that does not include ceramic as a constituent member, or is a ceramic electronic material in which at least a part of the electronic material is made of ceramic. Also good. However, at least one of the electronic materials to be joined is a ceramic electronic material. Moreover, the ceramic electronic materials may be joined together, or the ceramic electronic material and the electronic material not containing ceramic may be joined.

  Next, the molded product (coated product) of the conductive bonding material is dried at an appropriate temperature (for example, room temperature or higher, typically about 100 ° C.). The means for drying is not particularly limited. It may be naturally dried or dried by heating. For example, you may employ | adopt combining various means, such as a heating, suction | inhalation, and ventilation, 1 or 2 or more together. After drying, by heating for a predetermined time in an appropriate baking furnace (for example, a high-speed baking furnace) under an appropriate heating condition of 500 ° C. or less (for example, 450 ° C. or less, preferably 200 ° C. or more and 400 ° C. or less), Firing is performed. During this firing, pressure may be applied to enhance the sinterability of the nano-conductive particles. The pressure in this case is not particularly limited, but for example, a pressure of about 10 MPa or less but higher than atmospheric pressure can be used as a guide. More preferably, the pressure is set to 1 MPa or more and 5 MPa or less, more preferably 1 MPa or more and 3 MPa or less. As a result, the applied material of the conductive bonding material is baked onto the electronic material and the resin is burned out, and the nanoconductive particles contained in the conductive bonding material are sintered together, typically due to metal bonding. A joint is formed. As described above, since firing at a low temperature of 500 ° C. or lower is possible, the thermal influence on other electronic materials other than the joint can be minimized. Therefore, for example, the power semiconductor modules can be fired and bonded together at a low temperature of 500 ° C. or lower. Further, since aggregation of the conductive nanoparticles is suppressed, the joint portion is homogeneous and has a higher density, and a highly reliable joining method is provided.

  The materials and processes for manufacturing the ceramic electronic device other than forming the ceramic electronic device using the conductive bonding material disclosed herein may be exactly the same as in the past. And the ceramic electronic device provided with the junction part formed with the said electroconductive joining material can be manufactured, without performing each stage special process. A typical example of the configuration of such a ceramic electronic device is the configuration shown in FIG. As a process after joining the ceramic electronic material, for example, as in the conventional case, the ceramic electronic device is connected according to the purpose of use, and sealed with a resin to be packaged. In this way, the ceramic electronic device 10 is manufactured.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the following examples.

[Preparation of paste material]
As conductive particles, A: Ag powder having an average particle diameter (D50) of 80 nm and B: Pd powder having an average particle diameter (D50) of 70 nm were prepared.
The solvent was prepared as follows. That is, ethyl cellulose (EC) was prepared as a resin component. As the solvent, solvent X: terpineol and solvent Y: dipropylene glycol methyl-n-propyl ether (DPMNP) were prepared, and the mixing ratio thereof was as shown in Table 1, (1) 0: 100, (2) The mixed solvent was changed in six ways of 20:80, (3) 40:60, (4) 60:40, (5) 80:20, and (6) 100: 0. And the 6 types of solvents 1-6 were prepared by mixing the said resin component and 6 types of mixed solvents in the ratio of 90 mass parts of mixed solvents with respect to 10 mass parts of resin components, respectively.

The Hansen solubility parameter (HSP) of EC is (18.0, 4.8, 4.9), the HSP of terpineol is (17.4, 5.9, 9.8), and the HSP of DPMNP. Is (15.5, 3.3, 6.6). The HSP distances of the above solvents 1 to 6 were determined from the combination of these HSP vectors and the mixed solvent, and are shown in Table 1.
Next, the conductive particles A or B and the solvents 1 to 6 are mixed at a ratio of 90 parts by weight of the conductive particles and 10 parts by weight of the solvent, and kneaded with three rollers for 30 minutes. Sex bonding materials (samples 1 to 12) were prepared.

[Evaluation of compact density of conductive bonding material]
The conductive bonding material (samples 1 to 12) obtained above is screen-printed on a commercially available SiC substrate having a size of 10 mm × 10 mm, and dried at 60 ° C. for 5 minutes without applying pressure. A molded body was formed. Screen printing was performed so that a film thickness might be 10 micrometers-20 micrometers.
Table 1 shows the relative density of the molded body obtained by drying the coating film molded body of the conductive bonding material (samples 1 to 12). The relative density was calculated by the following formula (2).
Relative density (%) = particle density of the compact (g / cm ³ ) ÷ true density of particles (g / cm ³ ) × 100 (2)
In addition, the particle density of the molded body is obtained by calculating the printing height of the coating film molded body with a surface roughness meter, calculating the volume by multiplying the printing height by the coating area, and calculating the binder from the printed weight of the conductive bonding material. The value obtained by subtracting the weight was divided by the volume.

From Table 1, a good solvent having an HSP distance of 5.0 MPa ^0.5 or less is prepared by dissolving EC such that X: Y is 20:80 to 80:20 in the composition of solvent X and solvent Y. It was confirmed that it was possible. And the molded object obtained from the electroconductive joining material (samples 2-5 and 8-11) prepared using the good solvent from which this HSP distance is set to 5.0 MPa ^0.5 or less has a relative density of 60%. It was as high as above. Further, there is a correlation between the HSP distance and the relative density of the molded body, and the mixture of the solvent X and the solvent Y is a mixed solvent in which X: Y is in the range of 50:50 to 70:30. Was smaller, resulting in a higher density molded body. In addition, it was also confirmed that the molded object obtained from the conductive bonding material using the solvent having the smallest HSP distance has the highest density.

That is, it can be seen that even if the nanoconductive particles to be used and the constituent materials of the solvent in which they are dispersed are the same, the state of the solvent can be better adjusted to suppress aggregation of the nanoconductive particles and disperse in the solvent. In addition, according to the conductive bonding material prepared in this way, the nano-conductive particles are not agglomerated and thus are not biased, and when the molded body is formed, it is densely packed to obtain a high-density molded body. It is thought that
This tendency was confirmed not only when A: Ag powder and B: Pd powder were used as the conductive particles, but also with Cu, Pt, Ti, Sn, Al, Co, for example. .

[Evaluation of bonding]
The conductive bonding material (samples 1 to 12) obtained above is screen-printed on a commercially available SiC substrate having a size of 10 mm × 10 mm, and a Cu plate is arranged via the printed conductive bonding material to bond the materials. went. The bonding conditions were a temperature of 400 ° C., no pressure, and a bonding time of 3 minutes.

  The bonding strength of the SiC substrate-Cu plate bonding member of the sample thus obtained was measured using a universal bond tester (manufactured by Daisy Japan Co., Ltd., series 4000). The SiC substrate-Cu plate bonding members bonded using the conductive bonding materials of Samples 2 to 5 and 8 to 11 have a bonding strength of 5 MPa or more, and do not peel off after bonding, thereby realizing strong bonding. It was confirmed that That is, it was confirmed that a strong bonding of the ceramic electronic material can be realized at 400 ° C. by using the conductive bonding material having a relative density of the bonded portion of 60%. The SiC substrates bonded using the conductive bonding materials of the samples 1, 6, 7 and 12 had only a bonding strength of less than 5 MPa.

  According to the present invention, there is provided a conductive bonding material that can suppress aggregation of nano-conductive particles and maintain a stably dispersed state. Also provided are a ceramic electronic device bonded using such a conductive bonding material, and a bonding method for bonding at a low temperature using such a conductive bonding material.

DESCRIPTION OF SYMBOLS 1 Junction part 2 Base material 4 Ceramics insulating substrate 6 Semiconductor device 10 Insulation type semiconductor device 100 Insulation type semiconductor device 101 Joining part 102 Base material 104 Ceramics insulation substrate 106 Semiconductor device

Claims (8)

A conductive bonding material for bonding ceramic electronic materials,
Conductive particles having an average particle size of 100 nm or less, a resin as a binder, and a mixed solvent composed of at least two kinds of solvents,
The resin is a cellulosic resin;
The mixed solvent includes at least an alcohol solvent and an ether solvent,
The alcohol solvent and the ether solvent are blended in a proportion of 20% by mass to 80% by mass of the alcohol solvent and 80% by mass to 20% by mass of the ether solvent,
The resin, the alcohol solvent, the ether solvent, and the blending ratio thereof are determined so that the distance of the Hansen solubility parameter between the resin and the mixed solvent is 5.0 MPa ^0.5 or less. A conductive bonding material that has been prepared. 2. The conductive bonding material according to claim 1 , wherein the conductive particles include silver (Ag) particles, copper (Cu) particles, aluminum (Al) particles, or particles of any metal belonging to the platinum group. The ether solvent is dipropylene glycol methyl -n- propyl ether, conductive bonding material according to claim 1 or 2. The cellulose resin is cellulose, conductive bonding material according to any one of claims 1-3. The cellulosic resin is ethyl cellulose,
The alcohol solvent is terpineol,
It said ether solvent is dipropylene glycol methyl -n- propyl ether, conductive bonding material according to any one of claims 1-4. The conductive bonding material according to claim 5 , wherein a mass ratio of terpineol and dipropylene glycol methyl-n-propyl ether is 50:50 to 70:30 as terpineol: dipropylene glycol methyl-n-propyl ether. A ceramic electronic, wherein at least two electronic materials including the ceramic electronic material are bonded to each other by a bonding portion made of a fired product of the conductive bonding material according to any one of claims 1 to 6. device. The at least two electronic materials including a ceramic electronic material are bonded to each other through the conductive bonding material according to any one of claims 1 to 6 , and are fired at a temperature range of 500 ° C or lower to achieve the conductive property. A method for joining ceramic electronic materials, comprising joining the at least two electronic materials by a joining portion made of a fired product of a joining material.

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