JP2007201346A - Ceramics circuit board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramics circuit board excellent in a heat radiation property, conductivity, joining reliability of a ceramics substrate and a conductor circuit and durability without interposing a solder layer, and to provide its manufacturing method. <P>SOLUTION: (A) An application layer 2 is formed by applying first paste on the surface of the ceramics substrate B, (B) a first metallization layer 3 highly adhesive to the substrate B is formed by calcining the application layer 2, (C) an application layer 4 is formed by applying second paste to the metallization layer 3, (D) a second metallization layer 5 of a high heat radiation property is formed by calcining the application layer 4, and the circuit board is manufactured having the heat radiating conductor circuit 1 of a thick film selectively. By using the second paste in which the ratio of glass components to metal particle components such as copper powder is small compared to the first paste, the heat radiating conductor circuit 1 is formed as highly adhesive to the substrate and having the high heat radiation property. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ceramic circuit board excellent in heat dissipation, conductivity, etc., and suitable for mounting a semiconductor, and a method for manufacturing the same.

  In recent years, semiconductor devices used in electronic devices and the like have a tendency to increase heat generation and current. On the other hand, a metal film with a thickness of several hundred μm is placed on a ceramic substrate to improve heat dissipation. Attempts have been made to use it as a conductor circuit through which a large current flows.

  As a specific means for improving the heat dissipation, there is a method in which a metallized layer is provided on a ceramic substrate, and a semiconductor is mounted on the upper part via a metal heat dissipation plate called a heat spreader. As the heat spreader, a member made of a material such as copper or aluminum having a high thermal conductivity is preferably used, and the heat spreader and the metallized layer are joined via solder. For example, a method of forming a thick conductor circuit by bonding a metal foil to a ceramic substrate is known. Specifically, Japanese Patent Laid-Open No. 03-18087 (Patent Document 1) discloses a paste prepared by adding an organic solvent to silver powder, copper powder and titanium hydride powder, and then nitriding it by screen printing. The step of applying to the surface of the aluminum sintered body, the step of arranging a copper plate at the paste application location, the aluminum nitride sintered body having the copper plate arranged thereon is heat-treated at a temperature of 800 ° C. or higher and 950 ° C. or lower in an inert atmosphere and then cooled. A method of manufacturing a circuit board with good heat dissipation has been proposed.

  On the other hand, when using a metal film as a high-current conductor circuit, the copper foil surface is oxidized in advance in an oxygen / nitrogen mixed atmosphere with a minute oxygen partial pressure, and then the oxidized copper foil and an alumina or aluminum nitride substrate Are bonded at 1065 to 1083 ° C. in an oxygen / nitrogen mixed atmosphere with a small oxygen partial pressure, etching is performed using iron chloride or copper chloride, and a circuit is formed while leaving a necessary portion protected by a mask. A method of manufacturing a circuit board by a circuit forming process is known.

  However, in the method using the heat spreader, since the solder layer having a low thermal conductivity exists between the metallized layer and the heat spreader, the heat radiation characteristic inherent to the material constituting the heat spreader cannot be sufficiently obtained. In addition, since the solder component diffuses to the interface between the metallized layer and the substrate, the bonding interface between the conductor circuit and the substrate is deteriorated, resulting in poor bonding reliability.

  In the method of forming a thick conductor circuit by laminating a metal foil on an insulating substrate, the thickness of the metal foil at a predetermined portion cannot be selectively changed, and all have the same thickness within the substrate surface. For this reason, the thickness of the other part is governed by the thickness of the part that should be made the thickest, and it is impossible to efficiently form conductor circuits having different thicknesses. Moreover, in order to form a circuit pattern, it is common to perform an etching process after bonding a metal foil to a substrate. However, when a circuit is formed by etching a thick metal foil, a fine circuit pattern is formed. It is difficult to form and the substrate area cannot be used effectively.

In addition, when a metal foil is bonded to a ceramic substrate, the thermal expansion coefficients of the ceramic and the metal are greatly different. Therefore, thermal stress is concentrated on the bonding interface and the ceramic substrate is destroyed near the bonding surface, resulting in poor reliability. There was a problem. In addition, it is not efficient from the viewpoint of cost and space that it is necessary to apply metal foils having the same thickness on both sides in order to avoid warping of the substrate that occurs when the substrate and the metal foil are joined.
Japanese Patent Laid-Open No. 03-18087 (Claims)

  Accordingly, an object of the present invention is to provide a ceramic circuit board having not only excellent heat dissipation and conductivity without interposition of a solder layer, but also having high bonding durability between the ceramic board and the conductor circuit and high durability against thermal stress. It is in providing the manufacturing method.

  Another object of the present invention is to provide a ceramic circuit board capable of efficiently forming conductor circuits having different thicknesses and effectively utilizing the board area, and a method for manufacturing the same.

  Still another object of the present invention is to provide a ceramic circuit board capable of forming a fine conductor circuit pattern even when the thickness is large, and a method for manufacturing the same.

  Another object of the present invention is to provide a ceramic circuit board that does not warp even when a conductor circuit is formed on one surface of the board, and a method for manufacturing the same.

  As a result of intensive studies to achieve the above-mentioned problems, the inventors have selectively formed a heat dissipating conductor circuit with a thick metal particle component sintered body having high conductivity and heat conductivity, in particular, Using a screen printing method, etc., the first metallized layer composed of a sintered particle having high adhesion to the ceramic substrate and having high conductivity and thermal conductivity, and bonding to the metallized layer And forming a heat dissipating conductor circuit with at least one second metallized layer composed of a sintered body of particles having a small amount of glass component and a high conductivity and heat conductivity. The present invention has been completed by finding that it has bonding reliability with a heat-dissipating conductor circuit, high durability, and that a fine conductor circuit pattern can be formed even when the thickness is large.

  That is, in the ceramic circuit board of the present invention, a thick heat dissipation conductive circuit is selectively formed on the surface of the ceramic board. The circuit board has a portion (heat dissipating conductor circuit) that is selectively thick with respect to the surface of the board. The heat dissipating conductor circuit is composed of a sintered body of metal particle components having electrical conductivity and thermal conductivity, and usually forms a metallized layer.

  The heat dissipating conductor circuit may be composed of a first conductor layer laminated on a ceramic substrate and at least one second conductor layer laminated at least partially on the first conductor layer. . In the heat dissipating conductor circuit having such a laminated structure, the glass component content of the second conductor layer is usually smaller than that of the first conductor layer (in other words, the metal particle component content is high). In such a ceramic circuit board, since the heat dissipating conductor circuit can be selectively formed in a thick film without interposing solder, it is excellent in heat dissipation, conductivity, bonding reliability and durability. Moreover, since it is not necessary to attach a conductor such as a copper foil, material cost and space can be reduced.

  The metal particle component may be a particle having high conductivity and thermal conductivity, and may be at least one selected from components having high heat dissipation properties, for example, copper and copper oxide. The thickness of the heat dissipating conductor circuit may be 105 to 1200 μm, the thickness of the first conductor layer may be about 5 to 200 μm, and the thickness of the second conductor layer is about 100 to 1000 μm. There may be. In order to improve adhesion and adhesion reliability, a complex oxide (such as an intermetallic complex oxide) may be present at the interface between the substrate and the conductor circuit.

  The structure of the heat dissipating conductor circuit is not particularly limited. For example, the conductor circuit is formed on the surface of the ceramic substrate, the first conductor layer, the first conductor layer, and the first conductor layer. You may comprise a conductor circuit with the 2nd conductor layer (or heat radiating conductor layer) whose area is smaller than this. Further, conductor circuits having different thicknesses (heat dissipating conductor circuits having different thicknesses depending on portions) may be formed on the surface of the ceramic substrate.

  The present invention also includes a method for manufacturing a ceramic circuit board in which a heat dissipating conductor circuit is formed on the surface of the ceramic board. In this method, the heat dissipating conductor circuit can be formed by applying a paste containing the metal particle component, drying it, and then firing it. The manufacturing method of the present invention includes a step of applying a paste to the surface of a ceramic substrate to form a coating layer, and a step of firing the coating layer formed in this coating step to form a fired layer, To form a plurality of layers that at least partially overlap, and at least after the final coating step, the coating layer is fired to form a heat-dissipating conductor circuit (firing layer), and a ceramic circuit board is manufactured. Also good.

  The method of the present invention also includes a step of applying a first paste to the surface of a ceramic substrate to form a first coating layer, and at least partially overlapping the coating layer formed in this coating step. It comprises a step of applying a second paste to form a second coating layer and a step of firing the formed first and second coating layers to form a heat dissipating conductor layer (firing layer). May be.

  The coating layer can be formed by applying a paste by various methods, for example, a screen printing method. When the screen printing method is used, a layer having a fine pattern with high accuracy can be easily formed.

  Further, in order to form a uniform fine particle sintered body firmly adhered to the ceramic substrate, a paste containing a metal particle component having an average primary particle diameter of 0.003 to 0.3 μm is applied to the ceramic substrate in the first coating step. It may be applied to the surface. In addition, when a paste having a smaller glass component to particle component ratio than the paste in the first application step is applied in the final application step, the glass component in the surface layer portion of the conductor layer is less, so the surface layer surface solder Since the wettability is high, solder mounting is possible, and since the content of the metal component is large, a high heat dissipation property derived from metal can be obtained. Note that the paste used in the final coating step may be a paste that does not include a glass component or that has a glass component ratio of 5 parts by weight or less with respect to 100 parts by weight of a metal particle component.

  In the present specification, the “metal particle component” means particles having high conductivity and heat conductivity. In addition, the conductor layer formed by firing may be simply referred to as “metallized layer” or “fired layer”. Furthermore, the “heat dissipating conductor circuit” means a circuit in which a heat dissipating conductor layer having a large heat dissipating property and conductivity is formed on at least the surface layer of the conductor circuit, and the entire conductor circuit is formed of the heat dissipating conductor layer. May be. Furthermore, unless otherwise specified, the “coating step” means a step of forming a coating layer and may be referred to as a coating step including a drying step.

  In the present invention, since the heat dissipating conductor circuit formed in a thick film on the ceramic substrate is composed of the particle sintered body, the heat dissipating property and the conductivity are excellent without using a solder layer. Reliability of joining to the circuit and durability against thermal stress can be improved. Moreover, since a conductor circuit can be formed in the application | coating process and a baking process, while being able to form the conductor circuit from which thickness differs efficiently, a board | substrate area can be utilized effectively. Furthermore, a fine conductor circuit pattern can be formed even if the thickness is large. Furthermore, even if a conductor circuit is formed on one surface of the substrate, the occurrence of warpage can be suppressed.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as necessary.

  FIG. 1 is a process diagram for explaining a method of manufacturing a ceramic circuit board according to the present invention. In this method, (A) a first coating step for forming a coating layer 2 (dry film) by coating and drying a first paste containing a metal particle component on the surface of a ceramic substrate B; (B) a coating layer 2 (dry film) is fired to form a metallized layer 3 (fired layer or adhesive conductor layer), (C) a metal particle component on a part of the surface of the metallized layer (fired layer) 3 A second coating step of forming a coating layer 4 (dry film) by coating and drying a second paste containing, and (D) firing the coating layer 4 (dry film) to form a metallized layer 5 (firing layer). Or a heat-dissipating conductor layer having a metallized layer 5 (heat-dissipating conductor layer) on the ceramic substrate B.

  In the heat-dissipating conductor circuit 1, the metallized layer 3 and the metallized layer 5 formed by firing may not be substantially distinguished or distinguished from each other, but in this example, in order to help the understanding of the present invention, the metallized layer is used for convenience. Described as layer 3 and metallization layer 5. In some cases, the metallized layer 3 may have heat dissipation (high heat dissipation), and the metallized layer 3 and the metallized layer 5 may not be clearly distinguished from the viewpoint of heat dissipation. 5 are described as an adhesive conductor layer and a heat-dissipating conductor layer, respectively. Note that at least the surface layer portion of the heat dissipating conductor circuit is composed of a heat dissipating conductor layer.

[First application step]
The coating step (A) includes a step of forming the coating layer 2 (dry film) by coating and drying the first paste. The coating layer 2 forms a metallized layer 3 by firing, and plays a role as a conductor circuit and a bonding between the substrate and the conductor circuit. Therefore, the metallized layer 3 can be referred to as an “adhesive conductor layer” or a highly conductive “conductor layer”.

  The ceramic substrate B used in the present invention is not particularly limited, and examples thereof include metal oxides (silicon oxide, quartz, alumina or aluminum oxide, zirconia, sapphire, ferrite, titania or titanium oxide, zinc oxide, niobium oxide, mullite, and beryllia. Metal nitride (aluminum nitride, silicon nitride, boron nitride, carbon nitride, titanium nitride, etc.), metal carbide (silicon carbide, boron carbide, titanium carbide, tungsten carbide, etc.), metal boride (titanium boride, boron, etc.) Zirconate, etc.), metal double oxides [metal titanate (barium titanate, strontium titanate, lead titanate, niobium titanate, calcium titanate, magnesium titanate, etc.), metal zirconate (barium zirconate, Calcium zirconate, lead zirconate, etc.) ] Ceramics such as; metal salt (lithium niobate, lithium tantalate, etc.) can be fired single crystal and the like; and low-temperature sintered glasses, such as borosilicate glass may be used. It does not matter whether the shape of the ceramic substrate or the surface is physically or chemically treated.

  Of these ceramic substrates, a sintered substrate made of aluminum oxide or aluminum nitride is preferable. Aluminum oxide substrates can be obtained as 96% alumina substrates from companies such as Kyocera Corporation, Nikko Corporation, and Nippon Carbide Industries. Aluminum nitride substrates with different thermal conductivity are commercially available from Toshiba Fine Ceramics Co., Ltd., Asahi Techno Glass Co., Ltd., Tokuyama Co., Ltd., Maruwa Co., Ltd., etc. Can be used.

  The metal particle component is not particularly limited as long as it is a component having high thermal conductivity and high conductivity and can be sintered, and is usually at least one particle component selected from metals and metal compounds (oxides, etc.). Can be used. Examples of the metal species of the metal particle component include periodic table group 1B elements (gold, silver, copper, etc.), periodic table group 2B elements, periodic table group 3B elements (aluminum, gallium, indium, etc.), periodic table group 4B elements. (Lead, tin, etc.), periodic table group 2A elements (magnesium), periodic table group 3A elements, periodic table group 4A elements (zirconium, titanium, etc.), periodic table group 5A elements (vanadium, niobium, tantalum, etc.), periodic table Examples include 6A group elements (tungsten, molybdenum, chromium, etc.), periodic table 7A group elements, periodic table 8 group elements (iron, cobalt, rhodium, iridium, nickel, palladium, platinum, etc.). These metal particle components are not limited to metals such as tough pitch copper, oxygen-free copper, silver, and aluminum as long as a metallized layer can be formed by firing, and metal compounds (for example, alloys containing silver, copper and zirconium copper, metals, etc. Oxides such as metal oxides can also be used. Further, the metal compound may be a hydride such as titanium hydride. The volume resistivity (μΩ · cm, 20 ° C.) of the metal particle component is, for example, 50 or less (for example, about 1 to 20, preferably about 1.5 to 10, more preferably about 1.5 to 5). About 1.5-3. The thermal conductivity (cal / s · cm · ° C.) of the metal particle component is, for example, 0.2 to 1, preferably 0.4 to 1, and more preferably 0.5 to 1 (for example, 0.55 to 1). ) These metal particle components can be used alone or in combination of two or more. Among these metal particle components, silver, copper, aluminum or a compound thereof is preferable from the viewpoint of thermal conductivity and electric resistance, and copper or copper oxide particles are preferable from the viewpoint of price.

The average primary particle diameter of the metal particle component can be selected from the range of about 0.001 to 10 μm, and is usually 0.003 to 1 μm, preferably 0.005 to 0.5 μm, more preferably 0.01 to 0.3 μm. Degree. A metal particle component having a small average primary particle size of nanometer size (for example, a particle component having a diameter of about 0.003 to 0.3 μm, preferably about 0.005 to 0.25 μm, more preferably about 0.01 to 0.2 μm). If used, the adhesive strength with the ceramic substrate can be improved and the bonding reliability can be increased. Fine particles having such an extremely small particle size can impart high uniformity to the coating layer and the fired layer, and have extremely high reactivity as the specific surface area increases, compared to particles having a large particle size. It is possible to form a sintered body composed of metal particle components on the ceramic substrate surface by the firing process without roughening or sensitizing the ceramic substrate surface, and also uniform fine particle sintering firmly adhered to the ceramic substrate The body can be formed. That is, when a minute metal particle component is used, it reacts at the interface between the substrate and the metallized layer to form a complex oxide (such as an intermetallic complex oxide), and the adhesion strength between the two can be greatly improved. For example, when copper particles are selected as the metal particle component and the ceramic substrate is aluminum oxide or aluminum nitride, a composite such as CuAl ₂ O ₄ or CuAlO ₂ is formed at the interface between the substrate and the metallized layer by appropriate heat treatment. An oxide can be formed, and the metallized layer 3 having high bonding reliability can be formed over a long period of time due to its chemical bonding strength. When the average particle size of the metal particle component is increased, the reactivity with the ceramic substrate becomes poor, and there is a possibility that high adhesion cannot be obtained. In addition, since the metal particle component having a large average particle size has a small specific surface area, when a plating layer (especially electroless plating layer) is formed in a subsequent process, the ability as a catalyst nucleus of plating (especially electroless plating) is sufficient. There is a problem that cannot be obtained. On the other hand, it is often difficult to prepare metal fine particles having an average particle size that is too small. If necessary, the metal particle component having an average primary particle size of the nanometer size and a metal particle component having a size larger than the average primary particle size may be used in combination.

  The metal particle component, particularly a fine metal particle component (fine particles) can be obtained, for example, by a method called precipitation method, that is, a method of directly depositing metal particles from a metal salt solution using a reducing agent. For example, copper fine particles can be obtained by adding a reducing agent such as formalin, hydrazine, sodium hypophosphite, borohydride, etc. to an aqueous solution containing copper ions under appropriate conditions. If necessary, these metal particle components may be surface treated with a surface treatment agent such as an organic fatty acid or a coupling agent to prevent aggregation of the metal particles and improve dispersibility.

  The paste only needs to contain a metal particle component as a main ingredient and be capable of forming a coating film by coating, and is usually composed of a metal particle component and an auxiliary agent. Examples of the auxiliary agent include a binder component, a solvent, and a glass component.

  The binder component is not particularly limited as long as it has a film-forming property and decomposes in the baking step, and may be a low molecular compound such as starch or saccharide, but a resin is often used. The binder component may be a water-soluble or water-dispersible component or an oil-soluble component that is soluble in an organic solvent. The binder component may be an aromatic component having an aromatic ring, but is usually a non-aromatic component in many cases. Examples of binder resins include acrylic resins (polybutyl methacrylate, polymethyl methacrylate, and (meth) acrylic monomers such as methyl methacrylate- (meth) acrylic acid copolymer) or cellulose. Derivatives [cellulose esters (nitrocellulose, cellulose acetate, etc.), cellulose ethers (alkylcelluloses such as methylcellulose, ethylcellulose, butylcellulose, hydroxyalkylcelluloses such as hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, etc. ), Etc.], polyethers (polyoxyalkylenes such as polyoxymethylene resins, polyethylene glycol and polypropylene glycol) Olefins such as recall), polyvinyls (polydienes such as polybutadiene and polyisoprene), ethylene-vinyl acetate copolymers, ethylene- (meth) acrylic acid ester copolymers, ethylene- (meth) acrylic acid copolymers, etc. Polymers), polyamide resins (polyamide 6, polyamide 66, aliphatic polyamides such as polyamide 11 and alicyclic polyamides), vinyl alcohol resins or derivatives thereof (polyvinyl alcohol, polyvinyl acetal, polyvinyl butyral, etc.), polyvinyl Examples include ether resins (polyalkyl vinyl ether resins, alkyl vinyl ether-maleic anhydride copolymers, etc.). These binder components can be used alone or in combination of two or more.

  The amount of the binder component used is about 0.1 to 70 parts by weight, preferably 1 to 50 parts by weight, more preferably 2 to 30 parts by weight (for example, 5 to 15 parts by weight) with respect to 100 parts by weight of the metal particle component. It is.

  The type of the solvent is not particularly limited, and an aqueous solvent (water, water / water / water) may be used as long as it has dispersibility of the particles and stability over time of the dispersion, can dissolve the binder component, and has wettability to the ceramic substrate. It may be a mixed solvent of water such as alcohol and a water-soluble organic solvent) or may be an oil-based solvent (non-water-soluble organic solvent). Examples of the organic solvent include various solvents such as alcohols, hydrocarbons, ketones, esters, ethers and amides. As the solvent, an oily solvent is usually used in many cases. The solvent may be a low boiling point solvent, but usually a high boiling point solvent (especially a high boiling point organic solvent) is often used. The boiling point of the high boiling point solvent may be about 125 ° C. or higher (for example, 130 to 300 ° C.), preferably about 150 ° C. or higher (for example, 170 to 250 ° C.) at normal pressure. Specific examples of the high boiling point solvent include cellosolves (such as ethyl cellosolve and butyl cellosolve), cellosolve acetates (such as ethyl cellosolve acetate and butyl cellosolve acetate), carbitols (such as ethyl carbitol and butyl carbitol), and carbitol. Acetates (such as ethyl carbitol acetate and butyl carbitol acetate), monohydric alcohols [aliphatic alcohols (such as diacetone alcohol), terpene alcohols (such as terpineol), aromatic alcohols (cresols such as metacresol) Aralkyl alcohols such as benzyl alcohol)], polyhydric alcohols (diols such as diethylene glycol, triethylene glycol, tetraethylene glycol, etc.) Polyols such as phosphorus), hydrocarbons [xylenes (such as paraxylene), aromatic hydrocarbons such as ethylbenzene], esters (such as methyl lactate, ethyl lactate, butyl lactate), ketones (isophorone, Examples include homocyclic ketones such as acetophenone, heterocyclic ketones such as dimethylimidazolidinone), amides (such as dimethylformamide and dimethylacetamide), and sulfoxides (such as dimethylsulfoxide). These solvents can be used alone or in admixture of two or more.

  The amount of the solvent used is not particularly limited as long as the viscosity can be adjusted so that the paste can be applied, and is 1 to 500 parts by weight, preferably 5 to 300 parts by weight with respect to 100 parts by weight of the total amount of the metal particle component, the glass component and the binder component. Parts, more preferably about 10 to 250 parts by weight, and may be about 10 to 100 parts by weight (for example, 15 to 25 parts by weight).

  The glass component contributes to smoothing the film formed by firing, improving the adhesion between the ceramic substrate B and the conductor circuit (metallized layer 3), and is important for maintaining high adhesion reliability. . The softening point of the glass component is desirably lower than the firing temperature of the metal particle component and higher than the thermal decomposition temperature of the binder component. Therefore, the softening point of the glass component can be selected from the range of about 200 to 1000 ° C. depending on the type of the metal particle component, the type of the binder component, etc., and is usually 250 to 900 ° C., preferably 300 to 800 ° C., more preferably. Is about 350-700 degreeC. When at least one kind of particle selected from copper fine particles and copper oxide fine particles is selected as the particles, the glass component preferably has a softening point of about 300 to 600 ° C. (for example, 400 to 500 ° C.).

  The glass component is often used in a powdery form, and the average primary particle size of the powdery glass component is usually in the range of about 0.1 to 10 μm (for example, 1 to 10 μm). In addition, when screen printing is used as the paste applying means, those having a mesh pass particle size of 200 mesh or more (particle size of 0.074 mm or less) are preferable.

The composition of the glass component is preferable from the viewpoint that no lead is used, and there is an advantage that there is no risk of attacking the plating solution when electroless plating is performed in a subsequent process. The glass component contains at least network-forming oxides (oxides with strong single bond strength such as SiO ₂ , B ₂ O ₃ , GeO ₂ , V ₂ O ₅ ), and the single bond strength is small and glass forming ability alone. Network modified oxides (CaO, MgO, SrO, BaO, La ₂ O ₃ , SnO ₂ , Li ₂ O, etc.) without an intermediate oxide (ZnO, Bi ₂ O ₃ , TiO ₂ , ZrO ₂ , Al ₂ O _3, etc.) may be included. The glass component often contains SiO ₂ and / or B ₂ O ₃ . Specific examples of the composition of typical glass components include SiO ₂ —B ₂ O ₃ —ZnO, SiO ₂ —B ₂ O ₃ —Bi ₂ O ₃ , and SiO ₂ —B ₂ O ₃ —TiO _2. , SiO ₂ —B ₂ O ₃ —ZrO system, SiO ₂ —B ₂ O ₃ —CaO system, SiO ₂ —B ₂ O ₃ —MgO system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system, B ₂ Examples thereof include an O ₃ —ZnO—Bi ₂ O ₃ system and a B ₂ O ₃ —Bi ₂ O ₃ system. These glass components can be used alone or in combination of two or more.

  In 1st and 2nd paste, content of a glass component can be selected from the range of about 0-10 weight part with respect to 100 weight part of metal particle components, Usually, 1-8 weight part, Preferably it is 2-2 weight part. About 6 parts by weight. When the added amount of the glass component exceeds 10 parts by weight, the amount of the glass component remaining in the metallized layer 3 after firing increases, and the electrical resistance value of the conductor circuit tends to increase.

  In the first paste, the glass component content is 0.25 to 10 parts by weight (for example, 1 to 10 parts by weight) with respect to 100 parts by weight of the metal particle component in order to improve the adhesion of the fired layer to the ceramic substrate. Part), preferably about 3 to 9 parts by weight (for example, 4 to 8 parts by weight), and usually about 3 to 7 parts by weight. When there is too little content of a glass component, it will be difficult to improve adhesiveness with a ceramic substrate.

  The paste may further contain additives such as a viscosity modifier, a dispersant, a dispersion stabilizer, and a leveling agent, if necessary.

  A paste is prepared by mixing (or mixing and dispersing) each of the above components, and is applied to at least one surface (one side or both sides) of the ceramic substrate over the entire surface or a pattern shape (predetermined region or line shape, etc.). The coating layer 2 can be formed by drying at a temperature of. The paste application method is not particularly limited, and various methods such as a screen printing method, a flexographic printing method, a gravure printing method, a stamping method, a casting method, a dipping method, a spin coating method, an electrophoresis method, a spray method, and an ink jet method are used. Can be adopted.

  When the screen printing method is selected as the paste application method, a fine pattern can be easily formed, which is preferable from the viewpoint of workability and economy. In other words, by using an appropriate mesh screen or metal mask, the thickness of the film that can be formed by one printing can be adjusted, and the wiring pattern can be densified, so the pattern is set in consideration of economy and workability. It is possible and is very useful in the present invention. In addition, a fine circuit can be formed as compared with a method of forming a circuit by etching a metal foil.

  The drying conditions of the coating film are not particularly limited, and may be, for example, a drying temperature of 100 to 180 ° C. (for example, 130 to 170 ° C.) and a drying time of about 10 to 30 minutes.

[First firing step]
After forming the coating layer 2 (dry film), (B) the coating layer 2 (dry film) is fired to form the metallized layer 3 (fired layer). By this firing step, the metallized layer 3 (fired layer or adhesive conductor layer) made of a sintered body of metal particle components can be formed on the surface of the ceramic substrate B.

  The firing atmosphere can be selected according to the firing temperature, etc., and can be selected from an air atmosphere, an oxidizing gas atmosphere, an inert gas atmosphere (nitrogen, helium gas, argon, etc.), a reducing gas atmosphere, or a combination of these atmospheres as desired. Can be selected. Firing is performed at a temperature below the melting point of the metal particle component. Moreover, when the coating layer 2 contains a glass component, it is baked at a temperature higher than the softening point of the glass component. The firing temperature can be selected from the range of about 500 to 1500 ° C., for example, depending on the type of the metal particle component, and is usually about 600 to 1300 ° C., preferably about 700 to 1200 ° C. By such firing, the metal particle component is firmly bonded to the ceramic substrate B. In particular, as described above, by performing an appropriate heat treatment, a composite oxide can be formed at the interface with the ceramic substrate, and the metallized layer 3 having excellent long-term bonding reliability is formed by its chemical bonding force. can do.

  Specifically, when at least one kind of particles selected from copper and copper oxide is used as the metal particle component, the heating temperature is 600 or more and less than 1083 ° C. (for example, 750 to 1050 ° C., preferably 800 to 1000 ° C.) in a nitrogen atmosphere. ), And can be baked under conditions of heating time of about 1 to 2 hours including temperature rising / falling time.

  The thickness of the metallized layer 3 after firing can be selected from a range of about 1 to 250 μm, and is usually about 5 to 200 μm, preferably 10 to 150 μm, and more preferably about 15 to 100 μm (for example, 15 to 50 μm). May be. When the metallized layer 3 having such a thickness is formed, a fine pattern can be formed and the substrate area can be effectively utilized.

[Second application step]
After the metallized layer (fired layer) 3 is formed, (C) a second paste containing a metal particle component is applied and dried in the same manner as described above so as to overlap at least part of the surface of the metallized layer 3. A second coating layer (dry film) 4 is formed. The second coating layer 4 forms a metallized layer 5 that serves as a conductor circuit and radiates heat generated from a semiconductor or the like. Therefore, the metallized layer 5 can be referred to as a “heat dissipating conductor layer”.

  As the metal particle component of the second paste, particles having high conductivity and heat conductivity similar to those described above can be used. Moreover, the component of the paste may contain auxiliary agents and additives such as a binder component, a solvent, and a glass component as described above. In addition, when there is much content of a glass component in a 2nd paste, solder wettability may be inhibited or heat dissipation may be impaired. Therefore, the second paste often has a smaller ratio to the metal particle component than the first paste. For example, the second paste does not contain a glass component, or 5 parts by weight or less (for example, 0 to 5 parts by weight, preferably 0.5 to 4.5 parts by weight) of the glass component with respect to 100 parts by weight of the metal particle component. Parts, more preferably about 1 to 3.5 parts by weight). By reducing the content of the glass component, the solder wettability of the surface of the metallized layer 5 can be improved, the semiconductor can be mounted by soldering, and a high heat dissipation characteristic can be realized because the content of the metal particle component is increased. .

[Second firing step]
After forming the second coating layer, (D) the coating layer (dry film) 4 is fired to form a metallized layer (fired film or heat-dissipating conductor layer) 5. By this firing, the heat dissipating conductor circuit 1 in which the metallizing layer (or heat dissipating conductor layer) 5 made of a sintered body of the metal particle component is integrated with at least a part of the surface of the metallizing layer 3 can be formed. For example, by firing, there is no clear interface between the metallized layer 3 and the metallized layer 5, and the heat dissipating conductor circuit 1 in which the metallized layer 3 and the metallized layer 5 are integrated can be formed. Since the metallized layer 3 and the metallized layer 5 are integrated without interposing a solder layer, it is possible to provide a ceramic circuit board having high heat dissipation and electrical conductivity and excellent bonding reliability. Note that the firing can be performed in the same manner as in the first firing step. Specifically, when at least one kind of particles selected from copper and copper oxide is used as the metal particle component, the heating temperature is 600 or more and less than 1083 ° C. (for example, 750 to 1050 ° C., preferably 800 to 1000 ° C.) in a nitrogen atmosphere. ), And can be baked under conditions of heating time of about 1 to 2 hours including temperature rising / falling time.

  The thickness of the metallized layer (heat dissipating conductor layer) 5 after firing may be about 100 to 1000 μm, preferably 120 to 800 μm (for example, 150 to 750 μm), more preferably about 200 to 500 μm. When the metallized layer 5 having such a thickness is formed, heat dissipation and conductivity are high, and it can be used for large current applications.

  The total thickness of the heat dissipating conductor circuit 1 composed of the metallized layer 3 and the metallized layer 5 may be a thick film that does not impair the heat dissipating property, and is, for example, about 100 to 2000 μm (for example, 105 to 1200 μm). It can be selected from the range, and is usually 120 to 1500 μm, preferably 150 to 1000 μm (for example, 175 to 800 μm), more preferably about 200 to 750 μm (for example, 250 to 500 μm). Such a heat dissipating conductor circuit has high heat dissipation and conductivity, and can supply a large current. Furthermore, since the surface of the heat dissipating conductor circuit has high affinity with solder, solder mounting is possible, and a plating layer can be formed, so that semiconductor chips can be mounted efficiently.

  In the example shown in FIG. 1, the heat-dissipating conductor circuit 1 is formed by repeating the coating process and the baking process, but (B) the first baking process is not necessarily (A) the first coating process and (C ) There is no need to carry out between the second coating step, for example, (B) the first baking step and (D) the second baking step by baking after (C) the second coating step. Can be performed simultaneously. For example, as shown in FIG. 2, (A) a first application process in which a first paste is applied to the surface of a ceramic substrate B to form a first application layer 2; (C) a first application process. (B) (D) first after passing through the 2nd application process which forms the 2nd application layer by applying the 2nd paste at least partially overlapping with application layer 2 formed by (1) The heat-dissipating conductor circuit 1 may be formed by going through a firing step of firing a laminated coating layer composed of the coating layer 2 and the second coating layer 4. In this method, since a conductor layer (an adhesive conductor layer and a heat dissipating conductor layer) can be formed by a single firing step, a heat dissipating conductor circuit can be easily formed.

  By such a manufacturing method, a ceramic circuit board having a selectively thick portion (thick film portion) and having a heat radiating conductor circuit 1 made of a sintered body of metal particle components can be obtained. Specifically, on the surface of the ceramic substrate B, there is no clear interface between the metallized layer 3 and the metallized layer 5, and the heat dissipating conductor circuit 1 in which both are integrated is formed. A complex oxide (intermetallic complex oxide) exists at the interface between the conductor circuit (metallized layer) 3 and the conductor circuit (metallized layer) 3 and is intimately bonded by a chemical bonding force. Therefore, it is possible to selectively form a thick-film heat-dissipating conductor circuit 1 without interposing solder, and the heat-dissipation and conductivity can be improved, and the bonding reliability and durability are high and have a fine pattern. The heat dissipating conductor circuit 1 can be formed. Furthermore, by adjusting the composition of the paste that forms the first coating layer 2 and the second coating layer 4, various functions can be imparted to the heat dissipating conductor circuit 1. For example, the metallized layer (adhesive conductor layer) 3 having high adhesion to the ceramic substrate B is formed by the first coating layer 2, the adhesiveness to the metallized layer 3 is high by the second coating layer 4, and heat dissipation. When the highly metallized layer (heat dissipating conductor layer) 5 is formed, the heat dissipating conductor circuit 1 having high adhesion to the ceramic substrate B and excellent in heat dissipation can be formed. In particular, when the thickness of the metallized layer 5 is increased, heat dissipation can be improved. Furthermore, since the heat dissipating conductor circuit 1 having a thick film only at a desired portion of the substrate B can be formed, unnecessary thickness portions can be reduced, and the material cost can be reduced.

  In the method of the present invention, the paste may be applied to the surface of the ceramic substrate, dried, and then fired to selectively form a thick film heat-dissipating conductor circuit. In this method, a thick film heat dissipating conductor circuit is obtained by applying paste once to the surface of a ceramic substrate and firing the formed thick film coating layer once to form a fired layer (heat dissipating conductor circuit). Alternatively, as shown in FIG. 1, the heat dissipating conductor circuit may be formed by repeating a cycle composed of a coating process and a baking process. Furthermore, as shown in FIG. 2, from the viewpoint of productivity and economy, when forming a coating layer in a plurality of coating steps, after the final coating step, the coating layer is baked to provide a heat-dissipating conductor circuit. It may be formed. For example, the coating process is repeated to form a plurality of layers that overlap at least partially (such as a plurality of coating layers or a plurality of layers composed of a fired layer and a coating layer), and are applied after at least the final coating process. A thick film heat dissipating conductor circuit may be formed by firing the layer.

  Furthermore, the coating layer for forming each metallized layer may be formed by a plurality of coating steps instead of a single coating step. For example, when forming the metallized layer 3 having a large thickness, the step of applying and drying the paste may be repeated a plurality of times to form the coating layer 2 having a required thickness, and then fired. In addition, by performing firing one or more times during the lamination of the coating layers (for example, during the formation of a plurality of coating layers), it is possible to form a metallized layer having a high thickness while ensuring bonding with the ceramic substrate. it can. For example, a metallized layer having a desired thickness can be formed by repeating a process of applying a paste, drying, and baking a plurality of times. In addition, when forming a some application layer using a 1st paste, you may reduce in steps or continuously as the ratio of the glass component with respect to a metal particle component goes to the application layer of the surface layer side.

  Moreover, when forming the metallized layer 5 with a large thickness, the process of applying and drying the paste is repeated a plurality of times to form the coating layer 4 with a desired thickness, and then fired. Similarly to the metallized layer 3, firing is performed one or more times during the lamination of the coating layer (for example, while the coating layer is formed), thereby ensuring the bonding property with the ceramic substrate or the metallized layer 3. A metallized layer having a large thickness can be formed. For example, a metallized layer having a large thickness can be formed by repeating a process of applying a paste, drying, and baking a plurality of times. In addition, when forming a some coating layer using a 2nd paste, you may reduce in steps or continuously as the ratio of the glass component with respect to a metal particle component goes to the surface layer side coating layer.

  Furthermore, in the method of forming a plurality of coating layers, by adjusting the composition of the paste, for example, it is possible to form a conductor layer (adhesive conductor layer) excellent in bondability with a ceramic substrate at least in the first coating step. It is possible to form a coating layer or to form a coating layer capable of forming a conductor layer having excellent heat dissipation (heat dissipating conductor layer) at least in the final coating step. For example, in the final coating step, a paste having a smaller ratio of glass component to particle component than the paste in the first coating step (containing no glass component or having a glass component ratio of 5 to 100 parts by weight of the particle component). By applying a weight part or less paste), a circuit board having excellent heat dissipation can be formed.

  The structure of the heat dissipating conductor circuit can be variously designed according to the adhesiveness to the ceramic substrate, the durability, the heat dissipating property, etc. For example, various structures as shown in FIGS. 3 (a), (b) and (c) are possible. A structure or a pattern can be illustrated. Moreover, it is also possible to combine the structures and patterns of these conductor circuits and mix them on the same ceramic substrate.

  The structure of the heat dissipating conductor circuit 1 shown in FIG. 3A includes a metallized layer (first conductor layer having a wide line width) 3 formed on the surface of the ceramic substrate B with a predetermined line width, and the metallized layer 3. And a metallized layer (second conductor layer or heat dissipating conductor layer having a small line width) 5 having a smaller line width and a larger thickness than the metallized layer 3. That is, in the ceramic circuit board, the bonding area between the ceramic substrate B and the metallized layer 3 is larger than the bonding area between the metallized layer 5 and the metallized layer 3. 1 and part of the same wiring in the heat dissipating conductor circuit 1 is a thick film.

  In a ceramic circuit board, concentration of thermal stress generally tends to occur at a portion where the conductor circuit 1 is thick, specifically, at a thickness of 100 μm or more. However, in the ceramic circuit board having the structure described above, since the bonding area between the ceramic substrate B and the metallized layer 3 is larger than the bonding area between the metallized layer 5 and the metallized layer 3, concentration of thermal stress can be avoided. There are advantages. It is difficult to form the heat dissipating conductor circuit 1 having such a structure by etching a conventional metal foil.

  The thickness and formation site of the heat dissipating conductor layer are not particularly limited as long as the heat dissipating property is not impaired, but in order to improve the heat dissipating property, it is advantageous to increase the thickness of the heat dissipating conductor layer. Moreover, it is advantageous to form the heat dissipating conductor layer having a high heat dissipating property at a predetermined portion where heat dissipating property is required. The structure of the heat dissipating conductor circuit 1 shown in FIG. 3B includes a conductor circuit 1a having only the metallized layer 3 on the same ceramic substrate B, and a conductor circuit 1b in which the metallized layer 5 is laminated on the surface of the metallized layer 3. In the conductor circuit 1 b configured by laminating the metallized layer 3 and the metallized layer 5, the line width of the metallized layer 3 is equal to the line width of the metallized layer 5. That is, in the ceramic circuit board, the conductor circuits 1a and 1b having different thicknesses are arranged side by side. In such a ceramic circuit board, in the case where the conductor circuit 1 having a different calorific value is provided depending on the part, the metallized layer 5 can be formed only in a part having a large calorific value, if necessary. Note that at least one of the conductor circuit 1a and the conductor circuit 1b may form a heat dissipating conductor circuit. For example, the conductor circuit 1a and the conductor circuit 1b are formed of heat dissipating conductor circuits having different thicknesses from each other. One conductor circuit 1a may form a connection conductor circuit or the like according to the use of the circuit board.

  In the structure of the heat dissipating conductor circuit 1 shown in FIG. 3 (c), a plurality of heat dissipating conductor circuits in which the conductor circuit 1a having only the metallized layer 3, the metallized layer 3, and the metallized layer 5 are laminated on the same ceramic substrate B. In the plurality of heat dissipating conductor circuits 1b and 1c having a laminated structure, the metallized layers (heat dissipating conductor layers) 5 are formed in different thicknesses. That is, in the ceramic circuit board, conductor circuits 1a, 1b, and 1c having different thicknesses are arranged side by side. In such a ceramic circuit board, when the conductor circuit 1 having a different calorific value is provided depending on the part, the metallized layer 5 can be formed only in a part where the calorific value is large as necessary, Different metallized layers 5 can be formed. It is sufficient that at least one of the conductor circuits 1a, 1b, and 1c forms a heat dissipating conductor circuit. For example, each of the conductor circuits 1a, 1b, and 1c has a thick film having a relatively different thickness. A conductor circuit may be formed, the conductor circuit 1a may form a connection conductor circuit or the like according to the use of the circuit board, and the conductor circuits 1b and 1c are heat radiation properties of thick films having relatively different thicknesses. A conductor circuit may be formed.

  In addition, what is necessary is just to form the thickness of the coating layer of a single or laminated structure into predetermined thickness in consideration of the reduction | decrease in the film thickness accompanying baking.

  In the ceramic circuit board of the present invention, the thick heat dissipation conductor circuit may be selectively formed on the surface of the ceramic substrate. That is, the ceramic circuit board has a portion (heat dissipating conductor circuit portion) that is selectively thick with respect to the surface of the substrate, corresponding to the formation portion of the plating layer, the mounting portion of the semiconductor chip, and the like. The heat dissipating conductor circuit may be formed of at least a surface layer of the conductor circuit and a heat dissipating conductor layer having a large heat dissipating property and conductivity, and the entire heat dissipating conductor circuit may be formed of the heat dissipating conductor layer. Also good.

  Note that it is not always necessary to interpose a complex oxide (such as intermetallic complex oxide) at the interface between the ceramic substrate and the conductor circuit, but in order to improve the adhesion and adhesion reliability between the ceramic substrate and the conductor circuit. It is preferable that a complex oxide intervenes between them.

  The structure of the heat dissipating conductor circuit is not particularly limited, and may be a single layer structure or a laminated structure as long as each layer constituting the heat dissipating conductor circuit can be distinguished or identified. As described above, it is often difficult to identify each layer constituting the heat dissipating conductor circuit. When each layer is identifiable by physical or chemical characteristics, heat dissipation is improved with an adhesive conductor layer (metallized layer 3) for improving adhesion to the substrate in the entire thickness of the heat dissipation conductor circuit. The thickness ratio with the heat dissipating conductor layer (the metallized layer 5) is, for example, the former / the latter = 1/99 to 50/50, preferably 2/98 to 30/70, more preferably 5/95 to It may be about 20/80.

  The surface of the heat-dissipating conductor circuit may be flat, may be formed with the same thickness, and has a continuous or stepped step structure in the cross-sectional shape (for example, in the form of a pyramid or a convex, the bottom Or a structure having a narrower top than the other. The heat dissipating conductor circuit includes a first conductor layer laminated on the surface of the ceramic substrate, and a second conductor layer formed on the first conductor layer and having a smaller area than the first conductor layer. You may comprise. For example, as shown in FIGS. 1 and 2, the heat dissipating conductor circuit includes a first conductor layer (for example, a first conductor layer having a wide line width) laminated on the surface of the ceramic substrate with a predetermined width; You may comprise with the 2nd conductor layer (or heat radiating conductor layer, for example, 2nd conductor layer with a narrow line | wire width) formed with the predetermined | prescribed line | wire width on this 1st conductor layer. Furthermore, in a heat dissipating conductor circuit having a laminated structure or a step structure, each conductor layer is often laminated at least partially on top of each other, for example, a first conductor layer laminated on a ceramic substrate, The heat dissipating conductor circuit may be constituted by at least one second conductor layer laminated at least partially on the first conductor layer. Further, as described above, the second conductor layer having a smaller area than the first conductor layer may have a smaller area ratio due to the line width in the cross-sectional shape, and the predetermined shape of the first conductor layer in the planar shape may be small. The area ratio of a predetermined pattern (polygonal shape such as a planar quadrilateral shape, circular shape, dot shape, etc.) formed in a part (or region) may be small. For example, in a laminated structure of a plurality of conductor layers, the line width of the upper layer may be smaller stepwise or continuously than the bottom layer, and stepwise or continuous in a pyramidal or convex form. The area may be small.

  Further, heat dissipating conductor circuits having different thicknesses may be formed on the surface of the ceramic substrate, and the thickness of the heat dissipating conductor layer (or heat dissipating conductor circuit) may vary depending on the portion of the ceramic substrate. For example, as shown in FIG. 3C, a plurality of heat dissipating conductor layers having high heat dissipation and conductivity and different thicknesses may be formed in the conductor circuit.

  In the heat dissipating conductor circuit having such a structure, the content of the glass component in the second conductor layer is smaller than that in the first conductor layer in order to achieve both high adhesion and heat dissipation to the ceramic substrate ( In other words, the content of the metal particle component is often high).

  Since the ceramic circuit board of the present invention has high heat dissipation and can flow a large current, it is useful for mounting a semiconductor (semiconductor chip) and using it as a board for electrical / electronic devices. The semiconductor mounting form is not particularly limited, and the semiconductor (semiconductor chip) can be mounted in various forms according to the structure of the ceramic circuit board, the circuit pattern, and the like. FIG. 4 is a schematic view showing an example of a mounting form in which the ceramic circuit board of the present invention is applied to a large current application.

  In this example, the ceramic circuit board has a laminated structure in which a single-layer conductor circuit 1a composed of the metallized layer 3 and the metallized layer 5 are laminated on the metallized layer 3 on one surface of the same ceramic substrate B. A plurality of conductor circuits 1b and 1c are formed, and the plurality of conductor circuits 1b and 1c having a laminated structure include a heat dissipating conductor circuit 1b having a small metallized layer 5 thickness and a plurality of metallized layer 5 having a large thickness. It is comprised with the heat-radiating conductor circuit 1c. That is, on the surface of the ceramic substrate B, conductor circuits 1a, 1b, and 1c having different thicknesses in which the metallized layer 3 and the metallized layer 5 are laminated as desired are formed. In such a circuit board, conductor circuits 1a, 1b, and 1c having different thicknesses can be formed according to the amount of heat generated and the amount of current, and the heat radiating conductor circuit 1c is plated to form the plating layer 13 or the solder 12 The semiconductor (semiconductor chip) 11 can be mounted by using it. The conductor circuit 1a may also form a heat dissipating conductor circuit, and the conductor circuit 1a may constitute a conductor circuit for wiring or the like depending on the use of the circuit board.

  In this example, the semiconductor chip 11 is mounted on the surface of the metallized layer 5 of the heat dissipation conductor circuit 1c having a large thickness via the solder 12, and the heat dissipation conductor circuit 1c having a large thickness adjacent to the heat dissipation conductor circuit 1c. The metallized layer 5 is plated (for example, Ni plated) to form a plated layer 13, and the semiconductor chip 11 and the plated layer 13 are connected by a bonding wire 14. Since the metallized layer 5 is excellent in wettability with the solder 12, the semiconductor chip 11 is excellent in mountability. In addition, although a plating process is not necessarily required, the metallized layer 5 is also excellent in plating properties, so that the plated layer 13 can be easily formed on the surface of the conductor circuit 1. The plating layer is often formed by an electroless plating method.

  The ceramic circuit board of the present invention is useful for mounting a semiconductor (semiconductor chip) and using it as a board of an electric / electronic device.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
As a copper paste for forming the metallized layer 3, 8 parts by weight of an acrylic binder resin and terpineol with respect to 100 parts by weight of copper powder (particle size distribution width: 0.01 to 5 μm) containing copper fine particles having an average primary particle size of 0.1 μm A copper paste containing 16 parts by weight and 6 parts by weight of glass powder was prepared. Further, as a copper paste for forming the metallized layer 5, a copper paste containing 6 parts by weight of an acrylic binder resin, 12 parts by weight of terpineol, and 3 parts by weight of glass powder with respect to 100 parts by weight of copper powder having an average primary particle diameter of 5 μm. Prepared. As the ceramic substrate, an aluminum nitride substrate (thickness t = 0.635 mm, 170 W / m · K) was used.

[Evaluation of heat dissipation]
A copper paste for forming the metallized layer 3 is applied to the surface of the aluminum nitride substrate by screen printing, dried at 150 ° C. for 20 minutes, and then fired at 900 ° C. for 60 minutes in a nitrogen atmosphere, thereby forming a metallized layer comprising a copper particle sintered body. Layer 3 (12 mm × 12 mm, thickness 20 μm) was formed. Next, a copper paste for forming the metallized layer 5 is applied by screen printing so as to overlap with a part of the metallized layer 3, dried at 150 ° C. for 20 minutes, and then fired at 900 ° C. for 60 minutes in a nitrogen atmosphere to burn copper particles. By forming a metallized layer 5 (10 mm × 10 mm, thickness 280 μm) made of a bonded body, a ceramic circuit board on which a conductor circuit having a thickness of 300 μm at the thickest part was formed.

Using this ceramic circuit board as a sample, the heat dissipation was evaluated using a laser flash method. And when the laser beam was irradiated to the board | substrate surface in which the conductor circuit is not formed and the heat conduction to the conductor circuit surface of the other side was measured, the thermal diffusivity was 0.85 cm < ² > / sec.

[Reliability evaluation]
A copper paste for forming the metallized layer 3 is applied to the surface of the aluminum nitride substrate by screen printing, dried at 150 ° C. for 20 minutes, and then fired at 900 ° C. for 60 minutes in a nitrogen atmosphere, thereby forming a metallized layer comprising a copper particle sintered body. Layer 3 (2.2 mm × 2.2 mm, thickness 20 μm) was formed. Next, a copper paste for forming the metallized layer 5 is applied by screen printing so as to overlap with a part of the metallized layer 3, dried at 150 ° C. for 20 minutes, and then fired at 900 ° C. for 60 minutes in a nitrogen atmosphere to burn copper particles. By forming a metallized layer 5 (2 mm × 2 mm, thickness 280 μm) made of a bonded body, a ceramic circuit board on which a conductor circuit having a thickness of 300 μm at the thickest part was obtained. Subsequently, tin-lead eutectic cream solder is applied to the surface of the conductor circuit (metallized layer 5) to a thickness of 150 μm, and the tin-plated annealed copper wire is soldered so as to be in contact with the surface of the conductor circuit (metalized layer 5). A sample for sex evaluation was prepared.

  The sample was subjected to 1000 cycles of a thermal shock test comprising 1 cycle of cooling to −40 ° C. and heating to 125 ° C. When the sample after the test was cut with a diamond cutter and observed in cross section, no crack was generated at the interface between the conductor circuit and the substrate and inside the substrate.

Example 2
A sample was prepared in the same manner as in Example 1 except that the aluminum nitride substrate was replaced with a 96% alumina substrate, and the heat dissipation evaluation and reliability evaluation were performed. The thermal diffusivity was 0.099 cm ² / sec. As for the result of the thermal shock test, the occurrence of cracks was not observed as in Example 1.

Comparative Example 1
A copper paste for forming metallized layer 3 is applied to the surface of a 96% alumina substrate (thickness t = 0.635 mm) by screen printing, dried at 150 ° C. for 20 minutes, and then baked at 900 ° C. for 60 minutes in a nitrogen atmosphere. Then, a metallized layer 3 (12 mm × 12 mm, thickness 20 μm) made of a copper particle sintered body was formed. Next, a sample in which a copper foil (thickness: 300 μm, 10 mm × 10 mm) was joined to the upper portion of the metallized layer 3 via solder was used as a sample for heat dissipation evaluation. When the thermal diffusivity was measured in the same manner as in Example 1, it was 0.089 cm ² / sec.

Comparative Example 2
A copper-plated aluminum nitride substrate bonded with a copper foil having a thickness of 300 μm is etched into a 2 mm width pattern using ferric chloride, a tin-lead eutectic cream solder is applied to a thickness of 150 μm, and tin-plated annealed copper A sample was prepared by soldering the wire so as to be in contact with the surface of the metallized layer. About this sample, the thermal shock test which comprises 1 cycle by cooling to -40 degreeC and heating to 125 degreeC was repeated 1000 cycles. After the test, the sample was cut with a diamond cutter, and the cross section was observed. As a result, cracks were observed inside the substrate due to stress concentration.

  As described above, the samples obtained in Examples 1 and 2 not only have higher heat dissipation than Comparative Example 1, but also have better bonding reliability than Comparative Example 2. Thus, it was confirmed that the ceramic circuit board of the present invention was excellent in both heat dissipation and bonding reliability.

FIG. 1 is a process diagram for explaining a method of manufacturing a ceramic circuit board according to the present invention. FIG. 2 is a process diagram showing another example of the method for manufacturing a ceramic circuit board according to the present invention. FIGS. 3A, 3B and 3C are schematic views showing examples of the structure of the conductor circuit. FIG. 4 is a schematic view showing an example of a mounting form on a ceramic circuit board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heat-radiating conductor circuit 1a, 1b, 1c ... Conductor circuit 2 ... 1st coating layer 3 ... 1st metallization layer 4 ... 2nd coating layer 5 ... 2nd metallization layer

Claims (18)

  A circuit board in which a thick heat dissipation conductor circuit is selectively formed on the surface of a ceramic substrate, wherein the heat dissipation conductor circuit is composed of a sintered body of metal particle components having electrical conductivity and thermal conductivity Ceramic circuit board.   The ceramic circuit board according to claim 1, wherein the metal particle component is composed of at least one particle component selected from a metal and a metal oxide.   The ceramic circuit board according to claim 1, wherein the metal particle component is at least one selected from copper and copper oxide.   The heat dissipating conductor circuit is composed of a first conductor layer laminated on a ceramic substrate and at least one second conductor layer laminated at least partially on the first conductor layer. The ceramic circuit board according to Item 1.   The ceramic circuit board according to claim 4, wherein the content of the glass component in the second conductor layer is less than that in the first conductor layer.   The ceramic circuit board according to claim 1, wherein the thickness of the heat dissipating conductor circuit is 105 to 1200 μm.   The ceramic circuit board according to claim 4 or 5, wherein the first conductor layer has a thickness of 5 to 200 µm.   The ceramic circuit board according to claim 4 or 5, wherein the thickness of the second conductor layer is 100 to 1000 µm.   The ceramic circuit board according to claim 1, wherein a complex oxide is present at an interface between the board and the conductor circuit.   A heat dissipating conductor circuit is composed of a first conductor layer laminated on the surface of the ceramic substrate, and a second conductor layer formed on the first conductor layer and having a smaller area than the first conductor layer. The ceramic circuit board according to claim 1, which is configured.   The ceramic circuit board according to claim 1, wherein heat-radiating conductor circuits having different thicknesses are formed on the surface of the ceramic board.   A method of manufacturing a circuit board in which a thick heat dissipation conductor circuit is selectively formed on a surface of a ceramic substrate, wherein the heat dissipation conductor circuit includes a metal particle component having electrical conductivity and thermal conductivity. A method for producing a ceramic circuit board, wherein a paste is applied, dried, and then fired.   Including a step of applying a paste to the surface of the ceramic substrate to form a coating layer, and a step of firing the coating layer formed in this coating step to form a fired layer, and at least partially repeating the coating step The manufacturing method according to claim 12, wherein a plurality of overlapping layers are formed and the coating layer is baked at least after the final coating step.   Applying a first paste on the surface of the ceramic substrate to form a first application layer, and applying a second paste at least partially overlapping the application layer formed in the application process; The manufacturing method of Claim 12 comprised by the process of forming a 2nd coating layer, and the process of baking the formed 1st and 2nd coating layer and forming a heat-radiating conductor layer.   The manufacturing method according to claim 12, wherein the paste is applied by a screen printing method.   The manufacturing method of Claim 13 or 14 which apply | coats the paste containing a metal particle component with an average primary particle diameter of 0.003-0.3 micrometer at the first application | coating process.   The manufacturing method of Claim 13 or 14 which apply | coats the paste with a smaller ratio of the glass component with respect to a metal particle component in the last application | coating process than the paste in the first application | coating process.   The manufacturing method of Claim 13 or 14 which apply | coats the paste which does not contain a glass component in the last application | coating process, or the ratio of a glass component is 5 weight part or less with respect to 100 weight part of metal particle components.

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