Electronic devices, method for forming end terminations thereof and paste material for forming same

Abstract: An improved electronic device has metal-grazing type end terminations comprising a surface metal phase which is made of Cu and/or Ni alloy containing at least one of Pb, Su and Zn, by sintering a paste material containing a matrix metal powder (Cu and/or Ni), a fluxing metal powder (Pb, Sn and/or Zn), an inorganic bonding material powder and an organic binding material, so that the surface portion serves to improve a wettabilty and a solderability of the end termination owing to its composition similar to a solder.

Description: This invention generally relates to electronic devices or components comprising a ceramic body and end terminations having a good absorbant effect against heat shock on soldering as well as a good solderability on connecting a conducting wire, and particularly relates to ones having an end termination comprising a metal phase as an electrical conducting component and an inorganic glass phase as a bonding component for adhesion to the ceramic body. This invention also relates to a method for forming an end termination with much low cost as well as a paste composition for forming same. Recently, with development on the miniaturization and high densification of circuit, most of electronic devices and components have been generally mounted on the surfaces of base plates. Among these devices and components, electronic components such as solid resistant elements and multi-layer ceramic capacitors are provided with end terminations, which are mounted on ends of ceramic bodies by bonding a sintered metallic powder product thereto with glass frit. This arrangement is called a metal grazing type one. As this end termination portion is soldered direactly on a patching metal surface of circuit base plate, it is required to have a good wettability with solder and prevent from occurring an absorbing phenomenon by solder wherein a metal phase of the end termination portion can be absorbed and swept away by means of contacting a melting solder. As the end termination, there has been coventionally used a silver electrode which can be sintered in air. For solving the above problems, there are now proposed to use an Ag-Pd alloy electrode in place of the silver electrode and also to cover a sintered silver end termination at outer surface by a Ni coating and further cover it by a Sn-Pb coating (solder plating). However, it is disadvantageous that use of this method makes a productivity of the end termination worse and thus makes a production cost thereof high. Furthermore, when a solder melt contacts an end termination of an electronic component on soldering it on a patch board, cracks have been sometimes occurred at the end termination owing to a bigger tension thereon caused by a temperature difference between a ceramic body of the component and the end termination adhered thereto and thus by a heat expand difference therebetween. According to demand, therefore, it has been required to preheat the component in order to avoid generation of such a big temperature difference on soldering. Meanwhile, for decreasing the cost of production, it is requested to use a base metal such as Cu, Ni and so on as end termination materials in place of silver. In multi-layered capacitors, provided with internal electrodes made of the base metal, which is subjected to a sintering treatment under an atmosphere containing a low partial oxygen pressure, it has been already proposed as described in U.S.P No.3,920,781 to use an end termination made of a base metal such as Ni and Cu. These base metals have a poor absorption phenomenon as above, but have a problem in solderability, especially in a lowering of wettability owing to surface oxidation of the end termination. Therefore, it has been proposed to subject outer surface of the end termination to a solder plating. Also, according to demand, it has been tried to subject the component to a preheat treatment in order to avoid generation of cracks as in the conventional case. The above plating method is not advantageous since requirement of additional steps for plating make a manufacturing process complicated and also the electronic components expensive. Furthermore, in some case, dipping treatment of the component in a plating liquid may make its chemical and physical properties changed and worsen. The plating method also has no effect for avoiding generation of crack in the component under soldering. DE-A-31 48 778 defining the closest prior art from which the invention proceeds discloses an electronic chip having a substrate and a pair of end terminations for electrical conducting comprising conducting layers made of Ni, Cu or silver and connecting layers made of silver. The known chip further comprises an electrically effective layer consisting of resistance material. The connecting layers are overlaped by the electrically effective layer as well as by the contacting layers. The electrically effective layer is covered by a protecting layer consisting of e.g. glass. From EP-A-0 163 478, there is known a process of manufacturing a ceramic circuit board involving co-firing at least a dielectric ceramics and a conductor paste of base metal. To protect the metal from oxidation while avoiding formation of blisters on the board, the known process comprises preparing the conductor paste so that it contains an organic material which is thermally decomposed at a temperature higher than a decomposition point of an organic binder contained in the dielectric ceramics, and forming a circuit pattern of the conductor paste containing the organic material. Alternatively, the known process comprises the steps of forming the circuit pattern of the conductor paste and covering the circuit pattern with the organic material. The process then in either case further comprises the steps of thermally decomposing the organic binder in an oxidizing atmosphere at a temperature lower than the decomposition point of the organic material, and thermally decomposing the organic material in an atmosphere having a partial oxygen pressure lower than that of the oxidizing atmosphere. DE-A-35 28 906 describes a monolithic ceramic capacitor having a ceramic body. SUMMERY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide an improved electronic device or component having metal-grazing type end terminations which can be manufactured in low cost and provided with a good solderability and also a less deterioration property owing to oxidation as well as a superior shock absorption effect on soldering. Another object of the present invention is to provide a paste material for forming the end termination having the above superior properties by means of sintering treatment. A further object of the present invention is to provide a method for forming the end termination having the above superior properties by means of sintering treatment. In accordance with one aspect of this invention, there is provided an electronic device having a ceramic body and at least one pair of end terminations thereof comprising a surface metal phase for electrical conducting and a bottom inorganic glass phase adhered to a ceramic body, wherein the metal phase is composed of an alloy containing Cu and/or Ni as well as one or more of alloying metal components selected from the group consisting of Pb, Sn and Zn. In these inventive devices and components, a wettability on soldering can be improved because Cu and/or Ni alloy with Pb, Sn and/or Zn can be easily wetted by solder melt made of Pb-Sn alloy and a lowering of solderability can be supressed owing to an improved inhibitory action against oxidation reaction at the end termination. As will be seen from the following disclosure, the expression "alloy" means that any metal phases can be composed of a matrix metal and metals such as Cu and/or Ni and a fluxing metal and metals such as Pb, Sn and/or Zn and includes a metal mixture phase, an intermetallic compound phase and a solid solution phase. In the Cu alloys, the metal phase is preferably composed of Cu with 0.3 to 70 wt% of Pb, 0.8 to 65 wt% of Sn or 0.5 to 80 wt% of Zn based on the weight of the Cu matrix, while in the Ni alloys, the metal phase is preferably composed of Ni with 1.5 to 45 wt% of Pb, 1.5 to 55 wt% of Sn or 1.5 to 65 wt% of Zn based on the weight of the Ni matrix because a good improvement on the above effect can be not obtained out of the above alloying metal content range. It is allowable to add two or more of the alloying metal in combination and to add a third component or components such as Bi and any other components which is conventionally used for solder so long as the above inventive desired effects are not dereased This invention is especially suitable for a multi-layer capacitor made up of ceramic dielectric layers and internal electrode layers, for instance made of a base metal, extending between the ceramic dielectric layers. In the preferred embodiments of the invention, there is provided an end termination for electronic devices or components made by directly sintering an electrode metal material on a ceramic dielectric body, which comprises: (A) a bottom portion at least partially made of an inorganic glass phase adhered to the ceramic body; (B) a main portion made of at least one selected from the group consisting of (B₁) metal mixture phases, which can be made up of at least two phases selected from (1) a matrix metal phase mainly composed of Cu or Ni, (2) a fluxing metal phase mainly composed of Pb, Sn and/or Zn and (3) an intermetallic compound phase composed of one of the matrix metals and one or more of the fluxing metals, and (B₂) solid solution phases composed of one of the matrix metals and one or more of the fluxing metals; (C) a surface portion at least partially made of a phase which contains higher average content of the fluxing metal than that of the main portion. The bottom portion must at least partially, preferably mainly contains an inorganic glass phase, since the end termination can be adhered to the ceramic body mainly by the glass phase. However, the adhesion surface need not to be all covered by a layer made of the inorganic glass phase to keep an electrical conductivity through the end termination. The main portion of the end termination may comprise a matrix metal such as Cu and Ni and various matrix metal rich alloys including a metal mixture, an intermetallic compound and solid solution as well as alloys having different content ratio between a matrix metal and an alloying metal. The main portion may contain a fluxing metal such as Pb, Sn and Zn which remains between sintered matrix particle-particle boundaries as shown in Fig.8(b). The main portion thus formed serves to alleviate a heat shock occurring on soldering owing to lowering a heat conductivity of the end termination. The surface portion may be formed by the fluxing metal which is melt out from the main portion to the surface during a sintering process and solidified thereon as shown in Fig.8 (a)∼(c) . The surface portion may be completely or partially covered by the fluxing metal or fluxing metal rich alloys. The surface portion thus formed serves to improve a wettability and a solderability of the end termination owing to similar composition as that of solder. In a further preferred embodiment of this invention, there is provided a paste material for forming an end termination of an electronic device and component by a direct sintering treatment on a ceramic body, which comprises (a) a matrix metal powder which can not be melt by itself during the sintering treatment of the paste material, (b) incongruently melt to be a liquid phase by itself or by an electric reaction thereof with the matrix metal during the sintering treatment, (c) an inorganic bonding material powder which can be melt and adhered to the ceramic body under the sintering treatment, (d) an organic binding material which make the other powder mixture into a paste and tends to volatilize out during the sintering treatment of the paste material. The matrix metal powder is preferably selected from Cu metal powder, Ni metal powder and alloy powder thereof. The fluxing metal powder is preferably selected from Pb metal powder, Sn metal powder, Zn metal powder and alloy thereof such as Pb-Sn alloy powder, Pb-Zn alloy powder, Sn-Zn alloy powder, Pb-Sn-Zn alloy powder, Pb-Bi alloy powder, Sn-Bi alloy powder, Zn-Bi alloy powder, Pb-Sn-Bi alloy powder, Pb-Zn-Bi alloy powder, Sn-Zn-Bi alloy powder, Pb-Sn-Zn-Bi alloy powder. The inorganic bonding material powder may be selected from a conventional glass frit and any other same material powders which can be melt and adhered to a ceramic body, for example a mixture of ZnO powder (30 mol%), B₂O₃ powder(30 mol%) and SiO₂ powder(40 mol%) and a powder, made by melting a mixture at 1200°C and subjecting the melt to a water fraction by dropping it into a water and then to a grinding treatment by a ball-mill, are suitable for use. The organic binding materials may comprise an organic binding resin such as ethyl cellulose and acryl resins and an organic solvent such as Carbitol acetate, α-terpineol, toluene and any other solvent or dipersant by which the binding resin materials can be disolubed and be swelled to control a viscosity and a drying speed etc. The paste composition may be prepared by a metal component containing a matrix metal and a fluxing metal (70∼80 wt%), a glass frit(1∼6 wt%) and an organic binding material (15∼30%). The matrix metal powder and the fluxing metal powder may be added as a solid solution metal powder between Cu and/or Ni matrix metal and Pb, Sn and/or Zn metal and also may be added as an alloy powder between Cu and/or Ni matrix metal and Pb, Sn and/or Zn metal. For example, preferred compositions may comprise (1) a Cu powder, a Pb powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Cu to Pb weight ratio is between 99.7 to 0.3 and 30 to 70; (2) a Cu powder, a Sn powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Cu to Sn weight ratio is between 99.2 to 0.8 and 35 to 65; (3) a Cu powder, a Zn powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Cu to Zn weight ratio is between 99.5 to 0.5 and 20 to 80; (4) a Ni powder, a Pb powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Ni to Pb weight ratio is between 98.5 to 1.5 and 55 to 45; (5) a Ni powder, a Sn powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Ni to Sn weight ratio is between 98.5 to 1.5 and 45 to 55; (6) a Ni powder, a Zn powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Ni to Zn weight ratio is between 98.5 to 1.5 and 35 to 65. In accordance with further aspect of this invention, there is provided a method for making end terminations of electronic devices or components by direct sintering the above paste material on a ceramic body thereof. In the method, it is important to control a sintering temperature in order that the fluxing metal can be congruently melt or incongruently melt to be a liquid phase by itself or by an eutectic reaction with the matrix metal, while the matrix metal can not be melt by itself. Thereby, the fluxing metal can be seeped to the surface of a metal mixture as a sintering process proceeds, and then the melt is to be solidified thereon in layers, so that the resulting end termination comes to have a good wettability and solderability and can be made much more easily in comparison with a conventional plating method. This process is shown in Fig.8(a) to Fig.8(c). Other objects and features of the present invention will be more apparent to those skilled in the art on consideration of the accompanying drawings and following specification wherein are disclosed several exemplary embodiments of the invention with the understanding that such variations, modifications and elimination of parts may be made therein as fall within the scope of the appended claims without departing the spirit of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 and Fig.2 are sectional views of an end termination of a fixed resistor element according to empodiments of this invention. Fig.3 to 7 are sectional views of various end terminations of a multi-layer dielectric capacitor according to empodiments of this invention. Fig.8 (a) to 8 (c) are process diagrams of an end termination according to this invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 (Fixed resistor element) A fixed resistor is provided from a grazing resistance body made of rhenium oxide-zinc borosilicate glass sintered on an alumina base plate at 850°C. A paste material for an end termination of the resistor is composed of the following composition: a metal powder 100 weight parts (composed of Cu or Ni metal powder and Pb, Sn or Zn metal powder having a grain diameter of 0.5 ∼ 1.5 µm with a predetermined mixture ratio shown in Table 1), a glass frit (average particle size 0.8µm) 12 weight parts, a binder(made of an acryl resin and an petroleum solvent). An end termination is made by the following steps: The resistance body is coated at the both ends by dipping it in the paste material and is dried in air at 80°C. Then, it is subjected to a heatinq treatment in an electric oven with an oxygen content lowered to 2 ppm by means of flowing a nitrogen gas wherein an atmosphere temperature is controlled so that it is raised to 280°C over 5 hours and then to 550 ∼ 600°C over 30 minutes and thereafter maintained thereto during 15 minutes and lowered to a room temperature. A resulting element thus manufactured is tested by placing it in the following conditions (A) and (B). (A) Under an air during 14 hours. (B) Under an atmosphere containing a 60% moisture at 40°C during 60 hours. Thereafter, the element is tacked to a glass epoxy base plate provided with a Cu wiring layer by an organic bonding material, then is soldered at 230°C by a reflow soldering. 50 products thus soldered are subjected to a visual examination, and in some case there were found some defective ones which are observed to have an clearly non-soldered portion. As apparent from the below Table 1, an end termination made of Cu or Ni metal containing Pb, Sn or Zn was superior in a solderability, especially after placing in an oxidizable condition, in comparison with ones not containing the above fluxing metal such as Pb, Sn and Zn. It is preferred that Cu metal contains 0.3 ∼ 70 wt% of Pb, 0.8 ∼ 65 wt% of Sn or 0.5 ∼ 80 wt% of Zn, while Ni metal contains 1.5 ∼ 45 wt% of Pb, 1.5 ∼ 55 wt% of Sn or 1.5 ∼ 65 wt% of Zn. If the above fluxing metal content is below the preferred range, no improvement on a solderability can be obtained. If the content is above the preferred range, separation of the end termination from the body occurs and thus the defective numbers increases because adhesion power between the end termination and the body decreases before soldering owing to partially melting of the end termination metal, although the solderability is not lowered. Example 2 (Multi-layer ceramic capacitor including Cu internal electrodes) An multi-layer ceramic capacitor is manufactured form the following steps: The dielectric body is made by forming a Pb composite perovskite dielectric material into a sheet, forming an internal electrode layer thereon, laminating multi-layers, burning out it in air and then metalizing it into only the internal electrodes layer in a hydrogen gas atmosphere below a sintering temperature and finally sintering it. An end termination is formed and treated in a similar manner as Example 1 and then is subjected to a visual examination in a similar manner as Example 1. The result is shown in the below Table 2. As apparent from the Table 2, end terminations of Cu or Ni alloy containing at least Pb, Sn or Zn come to have a more improved solderability in comparison with ones made of Cu or Ni metal without Pb, Sn or Zn. Example 3 (Fixed resistor element) A fixed resistor is based on a graizing resistance body made of rhenium oxide-zinc borosilicate glass sintered on an alumina base plate at 950°C. A paste material for an end termination of the resistor is prepared by mixing the following composition and controlling a solvent amount to have a viscosty of about 8000 cps at 20°C: An end termination is made by the following steps: The resistance body is coated at the both ends by dipping it in the paste material and is dried in air at 80°C. Then, it is subjected to a heatinq treatment in a tubular type electric oven with an oxygen content lowered to 2 ppm by means of flowing a nitrogen gas wherein an atmosphere temperature is controlled so that it is raised to 280°C over 5 hours and then to 550 ∼ 600°C over 30 minutes and thereafter maintained thereto during 5 minutes and lowered to a room temperature over 30 minutes. A resulting element thus manufactured is subjected to a X-ray microanalyzer and a X-ray microdiffraction analyzer to estimate a component distribution. As shown in the accompanying Fig. 1, the end termination comprises an underlying layer 12 containing an inorganic frit which is melt and partially adhered to a ceramic body 11; an intermediate layer 13 having a thickness of about 700 µm and made of a 2 ∼ 40 µm particle sized mixture phase composed of about Cu metal phase and Pb metal phase; and a surface layer 14 having a thickness of 0.3 ∼ 60 µm and consisting of Pb metal phase. If the Pb content is below 0.1 wt%, there is scarcely observed a Pb metal phase in the intermediate layer. The resulting element thus manufactured is tested by placing it in the following conditions (A) and (B). (A) Under an air during 14 hours. (B) Under an atmosphere containing a 60% moisture at 40°C during 60 hours. Thereafter, the element is tacked to a glass epoxy base plate provided with a Cu wiring layer by an organic bonding material, then is soldered at 230°C by a reflow soldering. 50 products thus soldered are subjected to a visual examination, and in some case there were found some defective ones which is observed to have an clearly non-soldered portion (See below Table 3). In the below Table 3 and 4, there is scarcely observed a Pb metal phase in the intermediate layer (See below comparative sample No.63 in Table 3). In order to compared with a prior method, comparative sample No. 62 is coated with a solder plating layer by subjecting it to a barrel plating treatment in a solder plating liquid (pH:1.0) mainly containing alkanol sulfonic acid. It is judged to be the defective when an resistant value to be measured varies to a more than 50 % extent of the initial value. In the below Table 4, there are shown the defective numbers per 100 artcles of sample No.62 and No. 66. In the sample No.62 with a solder plating except initial defective articles, no soldering defective is found even after the above treatment (A) and (B). As apparent from the below Tables 3 and 4, the products according to this invention are superior in a solderability even after the treatment under an oxidizable condition in comparison with ones made of Cu single metal phase and also have little variation and degradation of the initial properties in comparison with ones provided with a solder plating. The paste material according to this invention preferably contains 0.3 ∼ 70 wt% of Pb based on the weight of the matrix metal. If the content is below the preferred range, only a little improvement on a solderability can be obtained. If the content is above the preferred range, separation of the end termination from the body occurs and thus the defective numbers increases because adhesion power between the end termination and the body decreases before soldering owing to partially melting of the end termination metal, although the solderability is not lowered. Example 4 (Fixed resistor element) A fixed resistor is based on a grazing resistance body made of rhenium oxide-zinc borosilicate glass sintered on an alumina base plate at 1050°C. A paste material for an end termination of the resistor is prepared by mixing the following composition and controlling a solvent amount to have a viscosity of about 10000 cps at 20°C : An end termination is made by the following steps: The resistance body is coated at the both ends by dipping it in the paste material and is dried in air at 80°C. Then, it is subjected to a heating treatment in an tubular type electric oven with an oxygen content lowered to 2 ppm by means of flowing a nitrogen gas wherein an atmosphere temperature is controlled so that it is raised to 280°C over 5 hours and then to 550 ∼ 600°C over 30 minutes and thereafter maintained thereto during 5 minutes and lowered to a room temperature over 30 minutes. A resulting element thus manufactured is subjected to a X-ray microanalyzer and a X-ray microdiffraction analyzer to estimate a component distribution. As shown in the accompanying Fig.2, the end termination comprises the most lower portion partially made of an underlayer 22 containing an inorganic frit melt and adhered to a ceramic body 21; an intermediate layer 23 having a thickness of about 700 µm and made of a about 20 µm grain sized mixture phase (in which Sn is partially occluded ) composed of Cu metal phase, Sn metal phase Cu₃Sn and Cu₆Sn₅ intermetallic compound phases; and a surface layer 24 having a thickness of 2 ∼ 60 µm and consisting of Sn metal phase. If the Sn content is below 0.1 wt%, there is scarcely observed a Sn metal phase in the intermediate layer. If the Sn content is about 0.8 wt%, the intermediate layer is made of a Sn solid solution Cu phase. If Cu₃Sn is used as the starting material, no surface Sn metal layer is observed The resulting element thus manufactured is tested by placing it in the following conditions (A) and (B). (A) Under an air during 14 hours. (B) Under an atmosphere containing a 60% moisture at 40°C during 60 hours. Thereafter, the element is tacked to a glass epoxy base plate provided with a Cu wiring layer by an organic material, then is adhered at 230°C by a reflow soldering. 50 products thus soldered are subjected to a visual examination, and in some case there were found some defective ones which is observed to have an clearly non-soldered portion (See below Table 5). In the below Table 5, there is scarcely observed a Sn metal phase in the intermediate layer (See below comparative sample No.70 in Table 5). In sample No.73, no formation of Sn matal phase is observed in the surface layer and no formation of liquid phase is observed by an eutectic reaction or partially melting of metal powder in the sintering temperature. As apparent from the below Table 5, the products according to this invention are superior in a solderability, especially after the treatment under an oxidizable condition in comparison with ones made of Cu single metal phase. The paste material according to this invention preferably contains 0.8 ∼ 65 wt% of Sn based on the weight of the matrix metal. If the content is below the preferred range, only a small improvement on a solderability can be obtained. If the content is above the preferred range, separation of the end termination from the body occurs and thus the defective numbers increases because adhesion power between the end termination.and the body decreases owing to a larger melting amount of the end termination metal. However, even within the preferred range, sample No.73 can form no liquid phase during the sintering process and thus no Sn phase is found on the surface so that no improvement on a solderability after preservation under an oxidazable condition is attained in comparison with sample No.72 which can form a liquid phase during the sintering process. From the data of Table 5, therefore, it is necessary to form a liquid phase during the sintering process in order to obtain a sufficient improvement effect. Example 5 (Multi-layer ceramic capacitor) A multi-layer ceramic capacitor (size:3.2 x 1.6 x 0.7 mm) is made by laminating alternatively ceramic layers of barium titanate 29 having a 20µm thickness through Ni internal electrode layers 30 having a 2.1µm thickness and also laminating a pair of invalid layers at the top and bottom thereof. A paste material for an end termination of the resistor is prepared by mixing the following composition and controlling a solvent amount to have a viscosity of about 8000 cps at 20°C: An end termination is made by the following steps: The resistance body is coated at the both ends by dipping it in the paste material and is dried in air at 80°C. Then, it is subjected to a heatinq treatment in an tubular type electric oven with an oxygen content lowered to 0.5 ppm by means of flowing a nitrogen gas wherein an atmosphere temperature is controlled so that it is raised to 280°C over 5 hours and then to 550 ∼ 600°C over 30 minutes and thereafter maintained thereto during 5 minutes and is lowered to a room temperature over 30 minutes. A resulting element thus manufactured is subjected to a X-ray microanalyzer and a X-ray microdiffraction analyzer to estimate a component distribution. The model figures of the end terminations containing Pb, Sn and Zn are shown in the accompanying Figs.3, 4 and 5. Each of the end terminations comprises the most lower portion partially made of each underlayer 32, 42 and 52 containing an inorganic frit which is melt and adhered to each ceramic body 31, 41 and 51. In Fig.3, there exists an intermediate layer 33 made of a about 30 µm grain sized mixture phase composed of Cu metal phase and Ni metal phase. It is confirmed in the Pb content of 1.5 wt% that an intermediate layer 33 is a single metal phase wherein a very small amount of Pb is occluded in Ni matrix metal. In Fig.4, there exists an intermediate layer 43 having an average grain size of 20µm and made of a mixture phase composed of a metal phase mainly containing Ni (in which less than 10 wt% of Sn is occluded ), Sn metal phase and an intermetallic compound phase. If the Sn content is below 5 wt%, it is confirmed that an intermediate layer is a single metal phase wherein Sn is occluded in Ni matrix metal. In Fig.5, there exists an intermediate layer 53 having a grain size of 2 ∼ 30µm and made of a mixture phase composed of a metal phase mainly containing Ni (in which less than 30 wt% of Zn is occluded ), Zn metal phase and an intermetallic compound phase. If the Zn content is below 5 wt%, it is confirmed that an intermediate layer is a single metal phase wherein Zn is occluded in Ni matrix metal. In any cases, intermediate layers have a thickness of about 700µm. Further, in Fig.3, the surface layer 34 comprises Pb metal phase. In Fig.4, the surface layer 44 comprises Sn metal phase. In Fig.5, the surface layer 54 comprises a single Zn metal phase or a metal mixture phase made of a Zn metal phase and a intermetallic compound phase od Zn and Cu. In any cases, the surface layers have a thickness of about 0.5 ∼ 60 µm. There is found no surface layer in samples containing nothing or less than 0.1 wt% of Pb, Sn and Zn. The resulting element thus manufactured is tested by placing it in the following conditions (A) and (B). (A) Under an air during 14 hours. (B) Under an atmosphere containing a 60% moisture at 40°C during 60 hours. Thereafter, the element is tacked to a glass epoxy base plate provided with a Cu wiring layer by an organic bonding material, then is adhered thereto at 230°C by a reflow soldering. 50 products thus soldered are subjected to a visual examination, and in some case there were found some defective ones which is observed to have an clearly non-soldered portion (See below Table 6). For comparison with a conventional method, sample No.76 is subjected to a solder plating in a plating liquid (pH 1.0) mainly containing alkanol sulfonic acid by a barrel method. Samples No.77 to No.88 are dipped in a soldering barrel without preheating and then are subjected to a grinding from an end to a centerline and among 50 samples, a number of the defective having a crack or cracks is counted. The result is indicated in the below Table 7. As apparent from the below Table 6, an end termination made by carrying out the present invention, is superior in a solderability, especially after the treatment under an oxidazable condition in comparison with one made of Ni single metal phase. The paste material according to this invention preferably contains 1.5 to 45 wt% of Pb, 1.5 to 55 wt% of Sn or 1.5 to 65 wt% of Zn based on the weight of the matrix metal Ni. If the content is below the preferred range, only a little improvement on a solderability can be obtained. If the content is above the preferred range, separation of the end termination from the body occurs and thus the defective nummber increases because adhesion power between the end termination and the body decreases owing to a larger melting amount of the end termination metal. As apparent from Table 7, all samples except Nos.95, 96, 102 and 108, comprise an intermediate layer made of a mixture phase composed of Ni metal, Pb, Sn and/or Zn metal and their intermetallic compounds and are hard to be cracked owing to a heat shock, while sample Nos. 95, 96, 102 and 108 comprise an intermediate layer made of Ni single metal phase and, therefore, are easy to be cracked. For attaining this effect, it is preferred that each content of Pb, Sn and Zn is within the above preferred range. This is apparent from the fact that an intermediate layer made of a mixture phase of Ni metal and Pb metal according to this invention, gives an improvement on a heat shock absorption effect. Example 6 (Multi-layer ceramic capacitor) A multi-layer ceramic capacitor (size:3.2 x 1.6 x 0.7 mm) is made by laminating alternatively ceramic layers of Pb composite perovskite 29 having a 20µm thickness Ni internal electrode layers 30 having a 1.8µm thickness and also laminating a pair of invalid layers having a thickness of 62µm at the top and bottom thereof. A paste material for an end termination of the resistor is prepared by mixing the following composition and controlling a solvent amount to have a viscosity of about 8000 cps at 20°C: An end termination is made by the following steps: The resistance body is coated at the both ends by dipping it in the paste material and is dried in air at 80°C. Then, it is subjected to a heating treatment in an tubular type electric oven with an oxygen content lowered to 0.5 ppm by means of flowing a nitrogen gas wherein an atmosphere temperature is controlled so that it is raised to 280°C over 5 hours and then to 550 ∼ 600°C over 30 minutes and thereafter maintained thereto during 5 minutes and lowered to a room temperature over 30 minutes. A resulting element thus manufactured is subjected to a X-ray microanalyzer and a X-ray microdiffraction analyzer to estimate a component distribution. The model figures of the end terminations containing Pb and containing Zn and CuZn₄ are shown in the accompanying Figs. 7 and 6. Each of the end terminations comprise the most lower portion partially made of each underlayer 62 and 72 containing an inorganic frit which is melt and adhered to each ceramic body 61 or 71. In Fig.6, there exists an intermediate layer 63 made of an about 2 ∼ 30 µm grain sized mixture phase composed of Cu metal phase and Zn metal phase or made of a solid solution phase. It is confirmed in the Zn content of 1.5 wt% that an intermediate layer is a single metal phase wherein a very small amount of Zn is occluded in Cu matrix metal. In Fig.7, there exists an intermediate layer 73 having an average grain size of 30µm and made of a mixture phase composed of a Cu metal phase and Pb metal phase. If the Pb content is below 0.1 wt%, it is confirmed that an intermediate layer is a single metal phase. In any cases, intermediate layers have a thickness of about 500µm. Further, in Fig.6, the surface layer 64 comprises Zn metal phase or a mixture phase composed of Zn metal phase and Pb-Zn intermetallic compound phase. In Fig.7, the surface layer 74 comprises Pb metal phase. In any cases, the surface layers have a thickness of about 0.3 ∼ 80 µm. There is found no surface layer in samples containing less than 0.1 wt% of Pb, Sn and Zn. The resulting element thus manufactured is tested by placing it in the following conditions (A) and (B) . (A) Under an air during 14 hours. (B) Under an atmosphere containing a 60% moisture at 40°C during 60 hours. Thereafter, the element is tacked to a glass epoxy base plate provided with a Cu wiring layer by an organic bonding material, then is adhered thereto at 230°C by a reflow soldering. 50 products thus soldered are subjected to a visual examination, and in some case there were found some defective ones which is observed to have an clearly non-soldered portion (See below Table 8). For comparison with a conventional method, sample No.114 is subjected to a solder plating in a plating liquid (pH 2.5) mainly containing alkanol sulfonic acid by a barrel method. Samples No.115 to No.126 are dipped in a soldering barrel without preheating and then are subjected to a grinding from an end to a centerline and among 50 samples, a number of the defective having a crack or cracks is counted. The result is indicated in the below Table 9. As apparent from the below Table 8, an end termination made by carrying out the present invention, is superior in a solderability, especially after the treatment under an oxidizable condition in comparison with one made of Ni single metal phase. The paste material according to this invention preferably contains 0.3 to 70 wt% of Pb, or 1.5 to 80 wt% of Zn based on the weight of the matrix metal. If the content is below the prefered range, only a little improvement on a solderability can be obtained. If the content is above the preferred range, separation of the end termination from the body occurs and thus the defective number increases because adhesion power between the end termination and the body decreases owing to a larger melting amount of the end termination metal. As apparent from Table 9, all samples Nos.129 ∼ 133 and Nos.135 ∼ 139, comprise an intermeditate layer made of a mixture phase composed of Cu metal, Zn metal and thier intermetallic compounds or a mixture phase of Cu metal and Pb metal and are hard to be cracked owing to a heat shock, while sample Nos. 127, 128 and 134 comprise an intermediate layer made of Cu single metal phase and, therefore, are easy to be cracked. For attaining this effect, it is preferred that each content of Pb and Zn is within the above preferred range. This is apparent from the fact that an intermediate layer made of a mixture phase of Cu metal, Zn metal and their intermetallic compound, or made of a mixture phase of Cu metal and Pb metal according to this invention, gives an improvement on a heat shock absorption effect. Example 7 (Multi-layer seramic capacitor) Multi-layer ceramic capacitors comprising a same Cu internal electrode as Example 6 are tested. An end termination is prepared by mixing a Cu metal powder having a grain diameter of 1.0 ∼ 3.0µm and one or more alloy powders having a grain size of about 5µm selected from 80wt%Pb-20wt%Zn, 80wt%Pb-20wt%Sn and 75wt%Pb-20wt%Sn-5wt%Bi with a predetermined mixture ratio shown in Tables 10 and 11. A resulting element thus manufactured is subjected to a X-ray microanalyzer and a X-ray microdiffraction analyzer to estimate a component distribution. The model sectional figures of the end terminations are same as the accompanying Figs.6 and 7. The intermediate layer is made of a mixture phase having a grain size of about 2 ∼ 60µm and composed of a metal phase mainly containing Cu metal and an intermetallic compound between Pb, Sn and/or Zn metal and Cu metal to have a total thickness of about 500µm. The surface layer is made of a metal phase mainly containing Pb-Sn, Pb-Zn or Pb-Sn-Bi to have a thickness of 0.3 ∼ 80µm. The above elements are subjected to a solderability test and a heat shock test. The results are indicated in the below Tables 10 and 11. As apparent from the below Table 10, an end termination according to this invention, is improving in a solderability, especially after the treatment under an oxidazable condition in comparison with one made of Cu single metal phase. As apparent from Table 11, samples Nos.145 ∼ 147 comprise an intermediate layer metal mixture phase composed of a metal phase mainly containing Cu metal, a metal phase mainly containing Pb, Sn and/or Zn metal and also their intermetallic compound phase, so that they are hard and to be cracked owing to a heat shock, while sample No.144 comprises an intermediate phase made of a Cu single metal phase, so that it is easy to be cracked. Further, samples Nos.143 and 147 show a possibility that the end termination may contain a third component other than Pb, Sn and Zn and also are expected to exhibit some effects as above.

Claims: An electronic device having a body and at least one pair of end terminations thereof comprising a surface metal phase for electrical conducting, wherein the metal phase comprises Cu and/or Ni, characterized in that the body is a ceramic body (11; 21; 31; 41; 51; 61; 71), the end terminations further comprise a bottom inorganic glass phase (12; 22; 32; 42; 52; 62; 72) adhered to the ceramic body, and the metal phase (13, 14; 23, 24; 33, 34; 43, 44; 53, 54; 63, 64; 73, 74) is composed of an alloy containing Cu and/or Ni as well as one or more of alloying metal components selected from the group consisting of Pb, Sn and Zn. The electronic device according to claim 1, wherein the metal phase (13,14; 73,74) is composed of Cu alloy with 0.3 to 70 wt% of Pb based on the weight of the matrix Cu. The electronic device according to claim 1, wherein the metal phase (23,24) is made of Cu alloy with 0.8 to 65 wt% of Sn based on the weight of the matrix Cu. The electronic device according to claim 1, wherein the metal phase (63,64) is composed of Cu alloy with 0.5 to 80 wt% of Zn based on the weight of the matrix Cu. The electronic device according to claim 1, wherein the metal phase (33,34) is composed of Ni alloy with 1.5 to 45 wt% of Pb based on the weight of the matrix Ni. The electronic device according to claim 1, wherein the metal phase (43,44) is composed of Ni alloy with 1.5 to 55 wt% of Sn based on the weight of the matrix Ni. The electronic device according to claim 1, wherein the metal phase (53,54) is composed of Ni alloy with 1.5 to 65 wt% of Zn based on the weight of the matrix Ni. The electronic device according to at least anyone of the previous claims, wherein the ceramic body comprises ceramic dielectric layers (31; 41; 51; 61; 71) laminated with base metal internal electrode layers. The electronic device according to at least anyone of the previous claims, wherein an end termination comprises: (A) a bottom portion (12; 22; 32; 42; 52; 62; 72) at least partially made of an inorganic glass phase adhered to the ceramic body; (B) an main portion (13; 23; 33; 43; 53; 63; 73) made of at least one selected from the group consisting of metal mixture phases, which can be made up of at least two phases selected from (1) a matrix metal phase mainly composed of Cu or Ni, (2) a fluxing metal phase mainly composed of Pb, Sn and/or Zn and (3) an intermetallic compound phase composed of one of the matrix metals and one or more of the fluxing metals, and solid solution phases composed of one of the matrix metals and one or more of the fluxing metals; (C) a surface portion (14; 24; 34; 44; 54; 64; 74) at least partially made of a phase which contains higher average content of the fluxing metal than that of the main portion. The electronic device according to claim 9, wherein the main portion (13; 73) is one containing a metal mixture phase of the matrix phase mainly composed of Cu metal and the fluxing phase mainly composed of Pb metal, while the surface layer (14; 74) is one mainly or partially composed of Pb metal. The electronic device according to claim 9, wherein the main portion (23) is comprised of solid solution phase composed of Cu including at least Sn metal or metal mixture phase made up of at least two phases selected from (1) a matrix metal phase mainly composed of Cu, (2) a fluxing metal phase mainly composed of Sn and (3) an intermetallic compound phase composed of Cu and Sn, while the surface layer (24) is a phase mainly or partially made of Sn metal single phase or a mixture phase made of an intermetallic compound phase of Cu and Sn mixed with a Sn metal single phase. The electronic device according to claim 9, wherein the main portion (63) is comprised of solid solution phase composed of Cu including at least Zn metal or a metal mixture phase made up of at least two phases selected from (1) a matrix metal phase mainly composed of Cu, (2) a fluxing metal phase mainly composed of Zn and (3) an intermetallic compound phase made of Cu and Zn, while the surface layer (64) is a phase mainly or partially made of Zn metal single phase or a mixture phase made of an intermetallic compound phase of Cu and Zn mixed with a Zn metal single phase The electronic device according to claim 9, wherein the main portion (33) is comprised of a solid solution phase composed of Ni including Pb or a metal mixture phase of the matrix phase composed of Ni metal and the fluxing phase mainly composed of Pb metal, while the surface layer (34) is one mainly or partially composed of Pb metal. The electronic device according to claim 9, wherein the main portion (43) is comprised of solid solution phase composed of Ni including at least Sn metal or metal mixture phase made up of at least two phases selected from (1) a matrix metal phase mainly composed of Ni, (2) a fluxing metal phase mainly composed of Sn and (3) an intermetallic compound phase composed of Ni and Sn, while the surface layer (44) is a phase mainly or partially made of Sn metal single phase or a mixture phase made of an intermetallic compound.phase of Ni and Sn mixed with a Sn metal single phase. The electronic device according to claim 9, wherein the main portion (53) is comprised of solid solution phase composed of Ni including at least Zn metal or metal mixture phase made up of at least two phases selected from (1) a matrix metal phase mainly composed of Ni, (2) a fluxing metal phase mainly composed of Zn and (3) an intermetallic compound phase composed of Ni and Zn, while the surface layer (54) is a phase mainly or partially made of Zn metal single phase or a mixture phase made of an intermetallic compound phase of Ni and Zn mixed with Zn metal single phase The electronic device according to at least anyone of the previous claims, wherein a paste material forms an end termination, which paste material comprises (a) a matrix metal powder which consists of the metall phase and can not be melt by itself during sintering treatment, (b) a fluxing metal powder which can be congruently melt or incongruently melt to be a liquid phase by itself or by an eutectic reaction thereof with the matrix metal during the sintering treatment, (c) an inorganic bonding material powder which can be melt and adhered to the ceramic body under the sintering treatment, and (d) organic binding material which make the other powder mixture into a paste and tends to volatilize out during the sintering treatment of the paste material. The electronic device according to claim 16, wherein the matrix metal and the fluxing metal is added as a solid solution metal powder or an alloy metal powder between Cu and/or Ni metal and Pb, Sn and/or Zn metal. The electronic device according to claim 16, wherein the paste material comprises a Cu metal powder, a Pb metal powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Cu to Pb weight ratio is between 99.7 to 0.3 and 30 to 70. The electronic device according to claim 16, wherein the paste material comprises a Cu metal powder, a Sn metal powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Cu to Sn weight ratio is between 99.2 to 0.8 and 35 to 65. The electronic device according to claim 16, wherein the paste material comprises a Cu metal powder, a Zn metal powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Cu to Zn weight ratio is between 99.5 to 0.5 and 20 to 80. The electronic device according to claim 16, wherein the paste material comprises a Ni metal powder, a Pb metal powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Ni to Pb weight ratio is between 98.5 to 1.5 and 55 to 45. The electronic device according to claim 16, wherein the paste material comprises a Ni metal powder, a Sn metal powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Ni to Pb weight ratio is between 98.5 to 1.5 and 45 to 55. The electronic device according to claim 16, wherein the paste material comprises a Ni metal powder, a Zn metal powder, an inorganic frit powder, an organic binder and an organic solvent, wherein Ni to Zn weight ratio is between 98.5 to 1.5 and 35 to 65. A method for making end terminations of electric devices or components by directly sintering a paste material containing at least a matrix metal powder on a ceramic body, wherein the paste material contains a fluxing metal powder which can be congruently melt or incongruently melt to be a liquid phase by itself or by an eutectic reaction with the matrix metal during the sintering treatment and the sintering treatment is carried out within a temperature range wherein the fluxing metal which can be congruently melt or incongruently melt to be a liquid phase by itself or by an eutectic reaction with the matrix metal, but the matrix metal powder can not be melt by itself, characterized in that the matrix metal is a metal powder selected from the group consisting of Cu metal powder, Ni metal powder and alloy powders thereof, and the fluxing metal is a metal powder selected from the group consisting of Pb, Sn and Zn metal powders as well as alloy powders thereof.

Inventors: KUGIMIYA KOICHI, NAKATANI SEIICHI, YOKOTANI YOICHIRO, KUGIMIYA, KOICHI, NAKATANI, SEIICHI, YOKOTANI, YOICHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1990
Main classification: H01R13
IPC codes: H01R13, H01C1, H01G4