Method of manufacturing electronic components

Abstract: Disclosed herein is a method of efficiently forming external electrodes on chip electronic components such as multilayer ceramic capacitors in desired thicknesses. Cutting grooves (5) are formed in a block (1) along surfaces (3, 4) to be provided with external electrodes for dividing the block (1) into individual chips (6) while metal paste (7) for forming external electrodes is cast into the cutting grooves (5) and dried, so that the metal paste (7) filling up each of the cutting grooves (5) is cut with a blade (8) to be divided in two. Parts of the metal paste (7) thus being divided with the blade (8) define external electrodes.

Description: The present invention relates to a method of manufacturing plural electronic components such as chip capacitors or chip resistors and to a method of manufacturing an electronic component array such as a capacitor array. Japanese Patent Laying-Open No. 60-109204 (1985) describes a conventional method of forming external electrodes on chip components, which is of interest to the present invention. According to this known method, external electrodes are formed on chip components in the following procedure: (1) First prepared are first and second holding plates, each of which is formed by an elastic body provided with a plurality of receiving holes passing therethrough across its front and rear surfaces. (2) Second ends of chip components are pushed into the receiving holes of the first holding plate from the front side thereof, so that first ends of the chip components are exposed on the front surface of the first holding plate. (3) Metal paste is applied to the first ends of the chip components which are exposed on the front surface of the first holding plate, and then the as-formed metal paste films are dried. (4) The front surface of the first holding plate is opposed to that of the second holding plate, and the first ends, being provided with the metal paste films, of the chip components which are held by the first holding plate are pushed into the receiving holes of the second holding plate so that the second ends of the chip components, being provided with no metal paste films, are exposed on the front surface of the second holding plate, thereby transferring the chip components from the first holding plate to the second holding plate. (5) Metal paste is applied to the second ends of the chip components which are exposed on the front surface of the second holding plate, and then the as-formed metal films are dried. (6) The chip components are taken out from the second holding plate. (7) The chip components treated in the aforementioned manner are heat treated in a heat treat furnace so that the metal paste films are fired, thereby forming external electrodes. In the aforementioned conventional method, however, it is necessary to handle separate chip components for forming external electrodes thereon, and hence equipment is required for orienting the chip components along a constant direction. Such equipment includes the aforementioned first and second holding plates, and a device for pushing the chip components into the receiving holes of the first holding plate along a constant direction, for example. Further, a relatively large number of steps must be carried out in order to form the external electrodes through the equipment. In addition, thicknesses of the as-formed metal paste films tend to disperse in the aforementioned conventional method. The invention aims to provide a method of manufacturing chip electronic components, which can reduce the number of steps for forming external electrodes with simplified equipment, while reducing dispersion in thickness of the external electrodes. According to one aspect of the invention there is provided a method of manufacturing plural electronic components in order to provide an external electrode on at least one end surface of each component, the method comprising the steps of: preparing a block comprising said plural electronic components; cutting one or more grooves in said block in order to separate said plural components from each other and to form on each component said at least one end surface to be provided with external electrodes; applying metal paste into said one or more grooves; and cutting said metal paste filling up each said groove so as to divide the same in two and thereby form on said at least one end surface of each said component an external electrode comprising a metal paste film of desired thickness. The practice of this one aspect of the invention is directed to a method of manufacturing chip electronic components, each of which is provided with external electrodes on both end surfaces thereof. The metal paste for forming external electrodes can be applied into the cutting grooves provided in the block, which is still maintained in its original shape. Further, the metal paste filling up each of the cutting grooves is divided in two, to define external electrodes for an adjacent pair of chip electronic components. The block is easier to handle as compared with the chip components being separately handled in the conventional method. Thus, the metal paste can be easily applied to prescribed positions. Further, it is not necessary to orient separate chip components along a constant direction dissimilarly to the conventional method, whereby at least a step for such an operation can be omitted. In addition, the thicknesses of the external electrodes are determined by spaces provided by the cutting grooves and the thickness of a blade which is employed for cutting the metal paste filling up each of the cutting grooves and dividing the same in two. Thus, it is possible to reduce dispersion in thickness of the external electrodes, while the thicknesses of the external electrodes can be easily controlled. The present invention can advantageously be applied to manufacturing of chip-type ceramic electronic components such as multilayer ceramic capacitors, for example. In this case, the block may be prepared in a state containing a green ceramic material, i.e., in an unfired state, so that a step of cofiring the metal paste with the green ceramic material is carried out after the step of cutting the metal paste. Such a specific method is usefully applied to manufacturing of chip-type ceramic electronic components such as multilayer ceramic capacitors which are provided therein with internal electrodes of a base metal such as nickel, in particular. In this case, it is hard to attain mutual dissolution of the nickel, forming the internal electrodes, with silver, forming external electrodes. Therefore, nickel paste is first applied onto the block as a first layer for forming external electrodes and cofired with the ceramic material contained in the block, so that paste containing silver is then applied as a second layer onto the as-obtained nickel film, and baked. In this case, a step can be advantageously applied to formation of the first layer for forming external electrodes. The present invention can also be effectively applied to manufacturing of an electronic component array comprising a plurality of electronic component elements, each of which is provided with external electrodes on both ends surfaces thereof, and a carrier part holding the electronic component elements in common with spaces defined therebetween. Therefore in another aspect the invention provides a method of manufacturing an electronic component array comprising a plurality of electronic component elements each being provided with external electrodes on two ends thereof, and a carrier part holding said electronic component elements in common with spaces defined therebetween, said method comprising the steps of: preparing a block comprising said electronic component elements and said carrier part; cutting grooves in said block between said electronic component elements so as not to extend into the carrier part in order to form surfaces on said electronic component elements which surfaces are to be provided with external electrodes; applying metal paste into said grooves; and cutting said metal paste filling up each said groove so as to divide the same in two and thereby form on said surfaces of said electronic component elements an external electrode comprising a metal paste film of desired thickness. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1(1) to 1(4) are sectional views showing steps included in an embodiment of the present invention. Fig. 2 is a perspective view showing a block 1a employed in another embodiment of the present invention; and Fig. 3 is a perspective view showing a capacitor array 11 obtained by still another embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figs. 1(1) to 1(4) illustrate steps included in an embodiment of the present invention, which is directed to manufacturing of multilayer ceramic capacitors. As shown in Fig. 1(1), a block 1 is prepared from a layered product of green ceramic sheets. This block 1 is provided therein with layers of a plurality of internal electrodes 2 for forming electrostatic capacitance. The block 1 provides a plurality of chip-type multilayer ceramic capacitors when the same is cut along surfaces 3 and 4 to be provided with external electrodes. Then, cutting grooves 5 are formed in the block 1 along the surfaces 3 and 4 to be provided with external electrodes, as shown in Fig. 1(1). Due to formation of the cutting grooves 5, the block 1 is divided into a plurality of chips 6 for defining individual multilayer ceramic capacitors respectively. The cutting grooves 5 are formed with a dicing saw, for example. Then, metal paste 7 for forming external electrodes is applied into the cutting grooves 5 by casting, for example, as shown in Fig. 1(2). Then, the metal paste 7 is dried as shown in Fig. 1(3). Then, the metal paste 7 filling up each of the cutting grooves 5 is cut with a blade 8, for example, to be divided in two, as shown in Fig. 1(4). Thus, metal paste films 7 are defined on the surfaces 3 and 4 of the chips 6 in desired thicknesses. The blade 8 is smaller in thickness than that employed for forming the cutting grooves 5 in the step shown in Fig. 1(1). It is possible to freely control the thicknesses of the metal paste films 7 which are defined on the surfaces 3 and 4 of the chips 6 to be provided with external electrodes, by appropriately selecting thicknesses of the blade for forming the cutting grooves 5 and the blade 8 shown in Fig. 1(4) respectively. The chips 6 thus provided with the metal paste films 7 on the surfaces 3 and 4 respectively are then fired. At this time, the green ceramic materials contained in the chips 6 are cofired with the metal paste films 7. Thus, desired multilayer ceramic capacitors are obtained. Fig. 2 shows another embodiment of the present invention. Referring to Fig. 2, elements corresponding to those shown in Figs. 1(1) to 1(4) are denoted by similar reference numerals, to omit redundant description. In the embodiment shown in Fig. 2, a larger block 1a is prepared so that individual chips 6 are obtained when the same is cut along plural cutting lines 9 and 10 which are perpendicular to each other. Such a block 1a is first provided with cutting grooves 5, so that metal paste 7 is cast into the same and then dried. Thereafter the block 1a is cut along the cutting lines 9 and 10 with a dicing saw, for example. The block 1a may be successively cut along the cutting lines 9 and 10 in this order, or vice versa. According to the embodiment shown in Fig. 2, formation of the cutting grooves 5 and application of the metal paste 7 can be simultaneously performed in relation to a number of chips 6, whereby mass productivity is improved, in particular. Experimental Example carried out according to the present invention is now described. First, ceramic slurry was formed by a doctor blade coater, to obtain sheets of 20 µm in thickness, 150 mm in width and 10 m in length. Then, conductive films for defining internal electrodes were formed on these sheets in desired patterns, and the sheets were stacked with each other and pressed to obtain the block 1a shown in Fig. 2. Then, a dicing saw having a blade of 100 µm in thickness was applied to the block 1a, to form the cutting grooves 5. Then, nickel paste which was adjusted to 4 to 5 poises in viscosity was cast into the cutting grooves 5 with a spatula. Then the block 1a was dried in an oven at 70°C for 30 minutes, and cut along the cutting lines 9 and 10 shown in Fig. 2 with a dicing saw. A blade employed in this step was smaller in thickness than that for forming the cutting grooves 5. Then, the as-obtained chips 6 were debindered and fired. Thus, multilayer ceramic capacitors were obtained with nickel films provided as first layers for external electrodes. Then, silver films were formed by baking as second layers for external electrodes, and plated with Ni/Sn for improving solderability. Thus, the multilayer ceramic capacitors were completed. In the aforementioned Experimental Example, the time required for forming the first layers for external electrodes was only 0.3 minutes as to 1000 multilayer ceramic capacitors, although the conventional method required 1 minute for such an operation. Further, it was possible to suppress deviation in thickness of the first layers, which was 120 % in the conventional method, to 15 % in the aforementioned Experimental Example. While each embodiment has been described in relation to a method of manufacturing multilayer ceramic capacitors, the present invention is also applicable to chip-type ceramic electronic components other than multilayer ceramic capacitors, as well as to chip electronic components containing no ceramic material. When the present invention is applied to chip-type ceramic electronic components, for example, the block to be provided with cutting grooves may not necessarily be unfired as hereinabove described, but a block formed by a sintered body may be provided with cutting grooves, to be subjected to subsequent steps. The present invention is also applicable to manufacturing of a capacitor array 11 shown in Fig. 3. Referring to Fig. 3, a capacitor array 11 comprises a plurality of capacitor elements 14, each of which is provided with external electrodes 12 and 13 on both end surfaces thereof. These capacitor elements 14 are held by a carrier part 15 in common, with spaces 16 defined therebetween. Each of the capacitor element 14 forms a multilayer capacitor comprising a plurality of internal electrodes 17, as shown expediently in the leftmost one appearing in Fig. 3. Actually, the internal electrodes 17 are not visible from the outside. In order to obtain the aforementioned capacitor array 11, a block 18 is prepared for providing the capacitor elements 14 and the carrier part 15. In this stage, the block 18 is not yet provided with grooves corresponding to the spaces 16. This block 18 is formed by a layered product of a plurality of ceramic green sheets, which are provided with the internal electrodes 17 on desired positions. Then, grooves for defining the spaces 16 are formed in the block 18, not to reach the carrier part 15. Then, metal paste for forming the external electrodes 12 and 13 is applied into the aforementioned grooves. The metal paste filling up each groove is dried and then cut to be divided in two. Thereafter the block 18 is fired, whereby the capacitor array 11 is obtained. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

Claims: A method of manufacturing plural electronic components in order to provide an external electrode on at least one end surface of each component, the method comprising the steps of: preparing a block (1, 1a) comprising said plural electronic components; cutting one or more grooves (5) in said block (1, 1a) in order to separate said plural components from each other and to form on each component said at least one end surface (3, 4) to be provided with external electrodes; applying metal paste (7) into said one or more grooves (5); and cutting said metal paste (7) filling up each said groove (5) so as to divide the same in two and thereby form on said at least one end surface (3, 4) of each said component an external electrode comprising a metal paste film of desired thickness. A method of manufacturing plural electronic components in accordance with claim 1, wherein said electronic components are chip-type ceramic electronic components and said block (1, 1a) comprises a green ceramic material, said method further comprising a step of cofiring said metal paste (7) with said green ceramic material after said step of cutting said metal paste (7). A method of manufacturing chip electronic components in accordance with claim 1, wherein said chip electronic components are chip-type ceramic electronic components and said block (1, 1a) comprising a green ceramic material, said method further comprising a step of firing said green ceramic material before said step of cutting said grooves (5) in said block. A method of manufacturing chip electronic components in accordance with any preceding claim, wherein said step of cutting said grooves (5) in said block (1, 1a) is carried out with a dicing saw. A method of manufacturing chip electronic components in accordance with claim 1, further comprising a step of drying said metal paste (7) between said step of applying metal paste (7) and said step of cutting said metal paste (7). A method of manufacturing chip electronic components in accordance with claim 1, further comprising a step of preparing a first blade for cutting said grooves (5) in said block (1, 1a) and a second blade (8) for cutting said metal paste (7) respectively, and a step of selecting a difference in thickness between said first and second blades in order to determine the thickness of the external electrodes to be formed. A method of manufacturing electronic components in accordance with claim 1, wherein said block (1a) is cut along plural cutting lines (9, 10) being perpendicular to each other for providing a plurality of chip electronic components and said grooves (5) are cut along said first cutting lines (9), said method further comprising a step of cutting said block (1a) along said second cutting lines (10). A method of manufacturing an electronic component array (11) comprising a plurality of electronic component elements (14) each being provided with external electrodes (12, 13) on two ends thereof, and a carrier part (15) holding said electronic component elements (14) in common with spaces (16) defined therebetween, said method comprising the steps of: preparing a block (18) comprising said electronic component elements (14) and said carrier part (15); cutting grooves in said block (18) between said electronic component elements so as not to extend into the carrier part (15) in order to form surfaces on said electronic component elements which surfaces are to be provided with external electrodes (12, 13); applying metal paste into said grooves; and cutting said metal paste filling up each said groove so as to divide the same in two and thereby form on said surfaces of said electronic component elements an external electrode comprising a metal paste film of desired thickness. A method of manufacturing an electronic component array in accordance with claim 8, wherein each of said electronic component elements forms a capacitor. A method of manufacturing an electronic component array in accordance with claim 8, wherein said block (18) contains a green ceramic material, said method further comprising a step of cofiring said metal paste with said green ceramic material after said step of cutting said metal paste. A method of manufacturing an electronic component array in accordance with claim 8, wherein said block (18) contains a green ceramic material, said method further comprising a step of firing said green ceramic material before said step of forming grooves.

Inventors: INAGAKI YASUTO C O MURATA MANU, KOHNO YOSHIAKI C O MURATA MANU, INAGAKI, YASUTO, C/O MURATA MANUFACTURING CO.,LTD., KOHNO, YOSHIAKI, C/O MURATA MANUFACTURING CO.,LTD.
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1992
Main classification: H01G4
IPC codes: H01G4, H01C17, H01G13