JP2012004480A - Method for manufacturing electronic component and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electronic component which prevents moisture such as a plating liquid from entering an element body, also prevents a mounting defect of the electronic component and increase of a product dimension, and can enhance reliability of the electronic component, and to provide the electronic component.SOLUTION: The method for manufacturing an electronic component 1 includes, in an element body 2 having a curved surface 9a of which the corner part 9 between end faces 2a and 2b and principal faces 2c and 2d is curved: a step S3 of forming a first paste layer which forms the first paste layer 16 by screen-printing a first conductive paste on the end faces 2a and 2b and the curved surface 9a so as not to impart the first conductive paste 52 on the principal faces 2c and 2d; and a step S5 of forming a second paste layer which forms the second paste layer 17 by screen-printing a second conductive paste on the principal faces 2c and 2d so as not to impart the second conductive paste 56 on the end faces 2a and 2b. The first paste layer 16 and the second paste layer 17 are joined at the curved surface 9a.

Description

  The present invention relates to an electronic component manufacturing method and an electronic component manufactured by the manufacturing method.

  As a conventional multilayer capacitor manufacturing method, the end face of the element body formed by alternately laminating and firing green sheets and internal electrode materials is immersed in a conductive paste to form a paste layer, and formed on one end face It is known that an external electrode is formed by drying the paste layer and the paste layer formed on the other end face so as to be close to each other and then firing the paste layer (see, for example, Patent Document 1).

JP 2006-13315 A

  In the above-described method for manufacturing an electronic component, after forming an element body, the external electrode is formed by immersing the end portion in a conductive paste and baking it. However, in this manufacturing method, when the element body is pulled away after immersion, the conductive paste is pulled near the center position of the end face, thereby increasing the thickness near the center position of the paste film, while the end face and side surfaces of the element body are increased. The thickness near the corners between them was thin. As a result, the thickness of the external electrode is reduced in the vicinity of the curved corner portion, and in the plating step after the firing step, there is a possibility that moisture such as a plating solution may enter the element body from the thinned portion. Therefore, in the electronic component manufactured by the conventional manufacturing method, the characteristic of the electronic component may be deteriorated due to the influence of moisture that has entered the element body during the plating process.

  In this regard, if it is attempted to secure a thickness near the corner portion of the paste film in the method of manufacturing the electronic component, the paste film near the center position of the end surface and the side surface portion of the element body is further increased accordingly. As a result, the outer dimensions of the product increase due to the increase in the external electrodes. Therefore, when the product dimensions are determined, there is a problem that it is difficult to achieve product characteristics by pressing the effective volume of the element body that secures the effective function of the electronic component.

  In the conventional manufacturing method, the paste layer is formed by immersing the end face of the element body in the conductive paste. In the element body that forms a rectangular parallelepiped, external electrodes are formed on the five faces of the end face, the pair of main faces, and the pair of side faces. For this reason, when mounting on the substrate, the solder goes around the external electrode formed on the side surface of the electronic component, so that the self-alignment property at the time of reflow is deteriorated. As a result, when electronic components are mounted at a high density, there is a problem in that mounting defects such as mounting position shift and chip standing occur.

  The present invention has been made to solve the above-described problems, and prevents moisture such as plating solution from entering the element body and prevents mounting failure of electronic components and increase in product dimensions. An object of the present invention is to provide an electronic component manufacturing method and an electronic component capable of improving reliability.

  In order to solve the above problems, an electronic component manufacturing method according to the present invention includes a pair of opposed end surfaces, a pair of main surfaces extending so as to connect between the pair of end surfaces, and a pair of main surfaces. A method for manufacturing an electronic component, comprising: an element body including a pair of side surfaces extending so as to connect the surfaces and facing each other; and an external electrode formed on an end surface side of the element body, wherein the end surface, the main surface, and the side surface Forming a first paste layer by screen-printing a first conductive paste on an end surface and a curved surface; One paste layer forming step, and forming a second paste layer by screen-printing a second conductive paste on one or both of the main surface and the side surface and the curved surface And having a process In the one paste layer forming step or the second paste layer forming step, the first paste layer or the second paste layer is formed so that the first paste layer and the second paste layer are joined on a curved surface. And

  In this method of manufacturing an electronic component, a first paste that forms a first paste layer by screen printing on an end surface and a curved surface of an element body having a curved surface with curved corner portions between the end surface, the main surface, and the side surface A layer forming step, and a second paste layer forming step of forming a second paste layer by screen printing on one side or both sides of the side surface or the main surface, wherein the first paste layer and the second paste layer are curved surfaces It is joined with. By forming the first paste layer by screen printing, compared with the case of being formed by the dipping method, the thickness near the corner portion is sufficiently secured and the increase in the thickness near the center position of the end face is prevented. be able to. Moreover, the thickness of the 2nd paste layer in the main surface or side surface of an element | base_body can be made small by forming a 2nd paste layer by screen printing. Then, by joining the first paste layer and the second paste layer with a curved surface, the conductive paste is prevented from entering the surface other than the surface to which the conductive paste is to be applied. The increase in the thickness of the external electrode can be suppressed, and the thickness of the external electrode on the end face can be reduced. As described above, since the thickness near the corner portion is secured by the first paste layer, it is possible to prevent moisture such as plating solution from entering the element body, and to suppress an increase in the thickness of the external electrode. Since the increase in dimensions can be prevented, the effective volume of the element body can be secured, and the product characteristics can be sufficiently achieved.

  Furthermore, since the second paste layer is formed on one surface or both surfaces of one of the main surface and the side surface and the curved surface, the second paste layer is formed only on one surface of the main surface or the side surface. In other words, since the external electrode is not formed on one of the main surface or the side surface, it is possible to suppress the solder from flowing from the electrode on the mounting surface of the electronic component to the electrode on the side surface adjacent to the mounting surface on the substrate. Therefore, the self-alignment property at the time of reflow can be ensured, and mounting failure of electronic parts can be prevented. As described above, the thickness of the external electrode on the main surface or side surface of the element body can be reduced, and an increase in the thickness in the vicinity of the center position of the end surface can be prevented, so that an increase in the external dimension of the electronic component can be suppressed. In addition, since the thickness of the external electrode in the vicinity of the corner portion can be secured by the first paste layer, it is possible to prevent moisture such as a plating solution from entering the element body from the vicinity of the corner portion when performing plating. . Furthermore, mounting failure of electronic components can be prevented, and as a result, reliability can be improved.

  Here, in the first paste layer forming step, the first paste layer is formed so that the first conductive paste is not applied to the main surface and the side surface, and in the second paste layer forming step, the second conductive paste is formed on the end surface. It is preferable to form the second paste layer so as not to be applied. In this case, since the conductive paste is not applied to the surface other than the surface to which the conductive paste is to be applied, the increase in the product dimension can be suppressed by reliably suppressing the increase in the thickness of the external electrode. The effective volume of the body can be secured.

  Of the first paste layer forming step and the second paste layer forming step, after the paste layer forming step in which the paste layer is formed first, the first baking step of baking the paste layer to form the first baking electrode, It is preferable to further include a second baking step of baking the paste layer formed in the next paste layer forming step to form a second baking electrode after the baking step. In this case, since the previously formed paste layer is baked twice, the strength is greatly improved. In addition, since the paste layer previously formed is baked, it is possible to prevent occurrence of defects in the previously formed paste layer due to mechanical impact or the like when aligning and arranging the element body in forming the next paste layer. .

  It is preferable to further include a plating layer forming step for forming a metal plating layer so as to cover the entire first baking electrode and the second baking electrode, and a heat treatment step for heat-treating the metal plating layer. In this way, by forming a metal plating layer and performing heat treatment, it is possible to volatilize residues such as moisture and plating solution in the plating film when the metal plating layer is formed. It is possible to prevent a decrease in reliability. Further, the first and second baked electrodes and the metal plating layer can be firmly bonded. Furthermore, the electrical and mechanical joints between the first and second baked electrodes are completely formed, and a dense external electrode can be formed.

  The heat treatment step preferably includes a first heat treatment step in which the metal plating layer is heat-treated in an oxygen atmosphere, and a second heat treatment step in which the metal plating layer is heat-treated in a reducing atmosphere after the first heat treatment step. . As a result, the metal plating layer is oxidized by heat treatment in an oxygen atmosphere, and residues such as moisture and plating solution are separated by oxidative decomposition, combustion decomposition, and the like. Further, voids and voids formed in the metal plating layer can be eliminated by volume expansion accompanying heat treatment in an oxygen atmosphere. Then, by performing heat treatment in a reducing atmosphere, the metal plating layer can be reduced to a metal in a densified state, and the first and second baking electrodes and the metal plating layer can be firmly bonded. Therefore, since a dense external electrode can be formed, the plating solution or the like can be prevented from entering the element without forming a baked electrode thickly in order to prevent the plating solution from entering the element as in the prior art. Can be prevented. Therefore, the thickness of the baked electrode on the main surface or side surface of the element body and the thickness of the baked electrode near the center position of the end surface of the element body can be made smaller than before, and the external dimensions of the external electrode can be reduced accordingly. Can do.

  It is preferable to further include a third baking step of baking the metal plating layer after the second heat treatment step. The metal plating layer is oxidized in the first heat treatment step, and in the process of returning to the original metal in the second heat treatment step, the crystal structure of the initial layer is reconstructed and densified. In this state, by further baking, sintering of the metal plating layer proceeds, so that the external electrode can be further densified.

  The electronic component according to the present invention is an electronic component manufactured by any one of the above-described electronic component manufacturing methods. By manufacturing an electronic component by the above-described method, moisture such as plating solution can be prevented from entering the element body, mounting failure of the electronic component and an increase in product size can be prevented, and the reliability of the electronic component can be improved. be able to.

  ADVANTAGE OF THE INVENTION According to this invention, while preventing moisture, such as plating solution, permeating into a body, the mounting defect of an electronic component and the increase in a product dimension can be prevented, and the reliability of an electronic component can be improved.

It is a perspective view which shows the electronic component manufactured by the manufacturing method of the electronic component which concerns on one Embodiment of this invention. It is sectional drawing of the electronic component shown in FIG. It is a flowchart which shows the manufacturing method of an electronic component. It is a figure which shows the process content of an element body holding process and a 1st paste layer formation process. It is a figure which shows the process content of a 1st paste layer formation process, Comprising: It is an expanded sectional view which shows a mode that a squeegee is pressed on the end surface of an element | base_body. It is a figure which shows the process content of a 2nd paste layer formation process. It is a figure which shows the process content of a 1st baking process and a 2nd baking process. It is a figure which shows the process content of a plating layer formation process and a 3rd baking process. It is a figure which expands and shows the element after a 1st baking process and a plating layer formation process. It is a figure which expands and shows the element body after an oxidation heat treatment process and the third baking process. It is a table | surface which shows the result of a dimension measurement. It is a table | surface which shows a test result. It is sectional drawing which shows the electronic component manufactured by the manufacturing method of the electronic component which concerns on a modification.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  With reference to FIG.1 and FIG.2, the structure of the electronic component manufactured by the manufacturing method of the electronic component which concerns on embodiment of this invention is demonstrated. FIG. 1 is a perspective view showing an electronic component manufactured by an electronic component manufacturing method according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the electronic component shown in FIG.

  As shown in FIGS. 1 and 2, the electronic component 1 is an electronic component such as a ceramic capacitor, for example, and is configured in a substantially rectangular parallelepiped shape by stacking and integrating a plurality of plate-shaped ceramic green sheets. The element body 2 is provided with external electrodes 3 and 4 formed on both end face sides of the element body 2. The element body 2 has a pair of end faces 2a, 2b facing the longitudinal direction of the element body 2 and parallel to each other, and a pair of main faces 2c, 2d extending so as to connect the pair of end faces 2a, 2b and facing each other. And a pair of side surfaces 2e and 2f extending so as to connect the pair of main surfaces 2c and 2d and facing each other. The external electrode 3 is formed so as to cover one end surface 2a and part of each edge of the two main surfaces 2c, 2d orthogonal to the end surface 2a. The size of the portion covering these two main surfaces 2c, 2d, that is, the dimension between the position where the thickness in the portion covering the end surface 2a of the external electrode 3 is maximum and the end portion in the portion covering the main surface 2c (see FIG. 2) (referred to as B in FIG. 2). The dimension B is set to about 0.5 mm to 0.6 mm, for example. Further, the external electrode 4 is formed so as to cover a part of each of the edge portions of the other end surface 2b and the two main surfaces 2c, 2d orthogonal to the end surface 2b. For example, the electronic component 1 is set to have a length of about 1.9 mm to 2.2 mm, a width of about 1.1 mm to 1.3 mm, and a thickness of about 1.1 mm to 1.3 mm. .

  As shown in FIG. 2, the element body 2 is configured as a laminated body in which a plurality of rectangular plate-like dielectric layers 6, a plurality of internal electrodes 7, and internal electrodes 8 are stacked. The internal electrodes 7 and the internal electrodes 8 are arranged one by one in the element body 2 along the stacking direction of the dielectric layers 6 (hereinafter simply referred to as “stacking direction”). The internal electrode 7 and the internal electrode 8 are disposed so as to face each other with at least one dielectric layer 6 interposed therebetween. In the actual electronic component 1, the plurality of dielectric layers 6 are integrated to such an extent that the boundary between them cannot be visually recognized. The element body 2 includes a first region 2A that is a region in which a plurality of internal electrodes 7 and 8 and dielectric layers 6 are alternately stacked, and a pair of dielectric layers 6 that sandwich the first region 2A in the stacking direction. And a second region 2B which is a region. The second region 2B may be formed of two or more pairs of dielectric layers 6.

  The element body 2 is chamfered so that the corner portions 9 between the end surfaces 2a, 2b and the main surfaces 2c, 2d and the side surfaces 2e, 2f are curved into a curved surface 9a having a predetermined radius of curvature. ing. The corner portions between the main surfaces 2c and 2d and the side surfaces 2e and 2f are also chamfered so as to be curved to form a curved surface 9b having a radius of curvature. The curvature radii of the curved surfaces 9a and 9b of the element body 2 are, for example, about 0.05 mm to 0.15 mm. The curved surface 9a is a corner chamfered portion provided to prevent cornering 9 on the corner portion 9 of the element body 2, and each of the curved surfaces 9a from the maximum height surface of the adjacent end surfaces 2a and 2b and the main surface 2c. This is a shape part of a dimensional difference between an intersection point drawn with a tangent line parallel to the surface and a corner portion of the actual element body 2.

  The internal electrodes 7 and 8 include a conductive material such as Ni or Cu. The thickness of the internal electrodes 7 and 8 is, for example, about 1 μm to 5 μm. The shape of the internal electrodes 7 and 8 is not particularly limited as long as the internal electrodes 7 and 8 have shapes that overlap with each other when viewed from the stacking direction. For example, the internal electrodes 7 and 8 have a rectangular shape or the like. The internal electrodes 7 and 8 are configured as a sintered body of a conductive paste containing the conductive material. The internal electrode 7 is electrically connected to the external electrode 3, and the internal electrode 8 is electrically connected to the external electrode 4.

  The external electrodes 3 and 4 have a U-shaped cross section, and are formed across both the end surfaces 2a and 2b of the element body 2 and a pair of main surfaces 2c and 2d facing each other in the stacking direction. That is, the external electrodes 3 and 4 are not formed on the side surfaces 2e and 2f, but are three-surface electrodes. The external electrodes 3 and 4 are formed at a predetermined temperature (for example, about 700 ° C.) after a conductive paste mainly composed of Cu, Ni, Ag, Pd or the like is attached to the outer surface of the element body 2 by a method described later. It is formed by baking and further electroplating. For electroplating, Cu, Ni, Sn, or the like can be used.

  As shown in FIG. 2, in the electronic component 1, the boundary portions of the first region 2A and the second region 2B of the element body 2, that is, the outer electrodes 3 and 4 at the position of the outermost inner electrode 8 in the stacking direction. The dimension (indicated by F in FIG. 2) is hereinafter referred to as F dimension, and the dimension of the external electrodes 3 and 4 (indicated by H in FIG. 2) on the main surfaces 2c and 2d of the element body 2 is hereinafter referred to as H dimension. The dimension (indicated by T in FIG. 2) of the external electrodes 3 and 4 in the vicinity of the center position of the two end faces 2a and 2b is hereinafter referred to as T dimension.

  Then, the manufacturing method of the electronic component 1 which concerns on embodiment of this invention with reference to FIGS. 3-8 is demonstrated. FIG. 3 is a flowchart showing a method for manufacturing an electronic component.

  As shown in FIG. 3, the manufacturing process of the electronic component 1 starts from the element body preparation process S1. In this element body preparation step S1, the following processing is performed. That is, after a ceramic green sheet to be the dielectric layer 6 is formed, the pattern of the internal electrodes 7 and 8 is printed on the ceramic green sheet with a conductive paste and dried to form an electrode pattern. A plurality of ceramic green sheets on which electrode patterns are formed in this way are stacked, and the laminate of the ceramic green sheets is cut into chips each having the size of the element body 2. Subsequently, chamfering of the corner portion 9 of the chip is performed by putting water, a plurality of chips, and a polishing medium into a sealed rotating pot made of a material such as polyethylene, and rotating the sealed rotating pot. The corner portion 9 is curved to be curved surfaces 9a and 9b having a predetermined radius of curvature (barrel polishing). The binder is removed by subjecting the chamfered chip to heat treatment at a predetermined temperature for a predetermined time. After the binder removal, the element body 2 is obtained by further firing. The element body preparation step S1 is completed by the above processing.

  After the element body preparation step S1, an element body holding step S2 is performed. FIG. 4 is a diagram showing process contents of the element body holding step S2 and the first paste layer forming step S3. This element body holding step S2 is a process of holding a plurality of element bodies 2 prepared in the element body preparing step S1 side by side. In the element body holding step S2, the main surfaces 2c and 2d are held on the other end face 2b side by using a known holding jig 50 such as a carrier plate so that one end face 2a of the element body 2 faces upward.

  After the element body holding step S2, a first paste layer forming step S3 is performed. In this first paste layer forming step S3, the end surface 2a and the corner portion 9 are covered with a screen mesh (plate making) 51 and screen-printed to form the first paste layer 16 on the end surface 2a and the corner portion 9 on the end surface 2a side. It is a process to do. In the first paste layer forming step S3, specifically, as shown in FIG. 4, the end surface 2a of the element body 2 fixed to the holding jig 50 is covered with a screen mesh 51 from above, and on the upper surface side of the screen mesh 51. Then, the squeegee 53 is moved so as to scrape the first conductive paste 52 in the one direction D1. 5 (a) and 5 (b), when the screen mesh 51 is pressed against the end surface 2a of the element body 2 by the squeegee 53, the end surface 2a and the curved surface 9a on the end surface 2a side, that is, the end surface The first conductive paste 52 is printed on the curved surface 9a that does not go around the main surface 2d from the 2a side, and the first paste layer 16 is formed so that the first conductive paste 52 is not applied to the main surface 2d. . The first conductive paste 52 is made of a metal powder containing Cu as a main component and contains glass.

  After the first paste layer 16 is formed, a drying process is performed, and the first paste layer 16 is cured. After the drying process of the first paste layer 16 on the end face 2a side, the first paste layer 16 is also formed on the end face 2b side by performing the above-described element holding process S2 and the first paste layer forming process S3. Formed and cured by drying. After the first paste layer forming step S3, a first baking step S4 is performed. In the first baking step S4, the first paste layer 16 is heat-treated at, for example, 780 ° C., thereby forming the first baking electrode 16a as shown in FIG.

  After the first baking step S4 is performed, a second paste layer forming step S5 is performed. In the second paste layer forming step S5, the main surface 2c and the corner portion 9 are covered with a screen mesh 55 and screen-printed to form the second paste layer 17 on the main surface 2c and the corner portion 9 on the main surface 2c side. It is a process to do. Specifically, in the second paste layer forming step S5, as shown in FIG. 6, the main surface 2c of the element body 2 arranged on the base is covered with a screen mesh 55 from above, and on the upper surface side of the screen mesh 55, Then, the squeegee 57 is moved so as to scrape the second conductive paste 56 toward the one direction D2. Thus, when the screen mesh 55 is pressed against the main surface 2c of the element body 2 by the squeegee 57, the main surface 2c and the curved surface 9a on the main surface 2c side, that is, the portion that does not go into the end surface 2a from the main surface 2c side. The second conductive paste 56 is printed on the curved surface 9a, and the second paste layer 17 is formed so that the second conductive paste 56 is not applied to the end surface 2a side. At this time, the 2nd paste layer 17 is formed so that it may join with the 1st baking electrode 16a and the curved surface 9a (corner part 9). The second conductive paste 56 may be the same as the first conductive paste 52 or may have a different composition.

  After the second paste layer 17 is formed, a drying process is performed, and the second paste layer 17 is cured. After the drying process of the second paste layer 17 on the main surface 2c side, the second paste layer 17 is also formed on the main surface 2d side by performing the process contents of the second paste layer forming process S5 described above, and drying. Curing is performed by. After the second paste layer forming step S5, a second baking step S6 is performed. In the second baking step S6, the second paste layer 17 is heat-treated at, for example, 780 ° C., thereby forming a second baking electrode 17a as shown in FIG.

  After the second baking step S6 is performed, a plating layer forming step S7 is performed. The plating layer forming step S7 is a step of forming a plating layer (metal plating layer) 18 by depositing a plating film so as to cover the entire first and second baking electrodes 16a and 17a by a wet plating method. In the plating layer forming step S7, a plating bath is formed with copper cyanide, copper sulfate, copper pyrophosphate, or the like to form the plating layer 18 as shown in FIG. At this time, the thickness of the plating layer 18 should just be the thickness which covers the 1st and 2nd baking electrodes 16a and 17a, for example, is 3 micrometers-20 micrometers. After the plating layer forming step S7 is performed, an oxidation heat treatment step (first heat treatment step) S8 is performed. The oxidation heat treatment step S8 is a step of performing a heat treatment of the plating layer 18 in an oxygen atmosphere. In this oxidation heat treatment step S8, the element body 2 on which the plating layer 18 is formed is heated at, for example, 500 ° C. in a heat treatment furnace in an oxygen atmosphere to oxidize the plating layer 18 and to form a CuO layer on the surface of the plating layer 18. 19 is formed. If the temperature in this oxidation heat treatment step S8 is low, the sublimation, oxidative decomposition, and combustion decomposition of the residue in the plating layer forming step S7 will be insufficient, and the CuO of the plating layer 18 will be insufficient. Is too high, the first and second baking electrodes 16a and 17a are excessively oxidized, and the glass component and CuO react with each other. Therefore, the temperature is preferably 300 ° C to 700 ° C, more preferably 400 ° C to 600 ° C. ° C.

  After the oxidation heat treatment step S8 is performed, a reduction heat treatment step (second heat treatment step) S9 is performed. The reduction heat treatment step S9 is a step of reducing the oxidized plating layer 18 (CuO) to Cu metal by heat-treating the plating layer 18 subjected to the oxidation heat treatment in a reducing atmosphere. In this reduction heat treatment step S9, the element body 2 on which the plating layer 18 is formed is heated, for example, at 500 ° C. in a heat treatment furnace in a nitrogen atmosphere (in a reduction atmosphere) to which hydrogen is added, for example, to thereby oxidize the plating layer. 18 is reduced to Cu metal, and the CuO layer 19 formed on the surface of the plating layer 18 is a continuous Cu metal layer. If the temperature is too low, the reduction of the plating layer 18 becomes insufficient. On the other hand, if the temperature is too high, the dielectric layer 6 of the element body 2 is reduced. It is 600 degreeC, More preferably, it is 350 to 550 degreeC.

  When the reduction heat treatment step S9 is completed, a third baking step S10 is performed. In the third baking step S10, for example, heat treatment is performed at 700 ° C., thereby forming the external electrodes 3 and 4 as shown in FIG. If the temperature in the third baking step S10 is too low, a sufficient sintering effect cannot be obtained. However, if the temperature is too high, the heat load applied to the element body 2 becomes large, and preferably 500 ° C to 850 ° C. More preferably, it is 550 degreeC-800 degreeC. After the third baking step S10 is performed, a plating step S11 is performed. The plating step S11 is a step of forming a Ni plating layer or a Sn plating layer on the surface of the electronic component 1. Specifically, in this plating step S11, after the electronic component 1 is immersed in the plating solution in the barrel, the surface of the electronic component 1 is plated while rotating the barrel. The process shown in FIG. 3 is complete | finished by the above, and the electronic component 1 can be obtained.

  Next, operations and effects of the method for manufacturing the electronic component 1 according to the embodiment of the present invention will be described.

  In the conventional method for manufacturing an electronic component, after forming an element body, the external electrode is formed by immersing the end portion in a conductive paste and baking it. However, in this manufacturing method, when the element body is pulled away after immersion, the conductive paste is pulled near the center position of the end face, so that the thickness near the center position of the paste film is increased, while the thickness near the corner portion of the element body is increased. It was thin. As a result, the thickness of the external electrode is reduced in the vicinity of the corner portion having the radius of curvature, and in the plating step after the baking step, moisture such as a plating solution may enter the element body from the thinned portion. Therefore, in the electronic component manufactured by the conventional manufacturing method, the characteristic of the electronic component may be deteriorated due to the influence of moisture that has entered the base body during the plating process. In particular, in MLCC (Multi-Layer Ceramic Capacitor), if a plating solution or the like penetrates into the element body and remains, reliability, particularly moisture resistance, may be significantly reduced.

  Further, in the conventional method for manufacturing an electronic component, since the paste layer is formed by immersing the end portion of the element body in the conductive paste, the element body forming a rectangular parallelepiped has an end face, a pair of main surfaces, and a pair of elements. External electrodes (five-side electrodes) are formed on the five sides. For this reason, the solder also wraps around the external electrode formed on the side surface of the electronic component when mounted on the substrate, and the self-alignment property during reflow deteriorates. For this reason, when electronic components are mounted at a high density, there is a problem that mounting defects such as a shift in mounting position and chip standing occur.

  On the other hand, in the manufacturing method of the electronic component 1 according to this embodiment, the end surface 2a of the element body 2 having the curved surface 9a in which the corner portion 9 between the end surfaces 2a, 2b and the main surfaces 2c, 2d is curved. , 2b and the curved surface 9a and a first paste layer forming step S3 for forming the first paste layer 16 so that the first conductive paste 52 is not applied to the main surfaces 2c, 2d, and the main surfaces 2c, 2d. And a second paste layer forming step S5 for forming the second paste layer 17 so that the second conductive paste 56 is not applied to the end faces 2a and 2b. By forming the first paste layer 16 by screen printing, the thickness in the vicinity of the center position of the end faces 2a and 2b is secured while ensuring a sufficient thickness in the vicinity of the corner portion 9 as compared with the case of being formed by the dipping method. Can be prevented from increasing. Further, by preventing the first conductive paste 52 from being applied to the main surfaces 2c and 2d, an increase in the thickness (H dimension) of the external electrodes 3 and 4 on the main surfaces 2c and 2d can be suppressed. Further, by forming the second paste layer 17 by screen printing, the thickness of the second paste layer 17 on the main surfaces 2c and 2d of the element body 2 can be reduced, and the second conductive paste 56 is applied to the end surfaces 2a and 2b. Is not provided, the thickness (T dimension) of the external electrodes 3 and 4 on the end faces 2a and 2b can be reduced.

  Then, by joining the first paste layer 16 and the second paste layer 17 with the curved surface 9a, the conductive paste can be prevented from entering the surface other than the surface to which the conductive paste is to be applied. While the increase in the thickness of the external electrodes 3 and 4 on the surfaces 2c and 2d can be suppressed, the thickness of the external electrodes 3 and 4 on the end surfaces 2a and 2b can be reduced. As described above, since the thickness near the corner portion 9 is secured by the first paste layer 16, it is possible to prevent moisture such as a plating solution from entering the element body 2 and the thickness of the external electrodes 3 and 4. By suppressing the increase, it is possible to prevent an increase in product dimensions, so that the effective volume of the element body 2 can be secured and the product characteristics can be sufficiently achieved.

  Further, in the electronic component 1 manufactured by the method of manufacturing the electronic component 1 of the present embodiment, the U-shaped external electrodes 3 and 4 are formed across the three surfaces of the end surfaces 2a and 2b and the main surfaces 2c and 2d. For this reason, the side electrodes which are adjacent to the external electrodes 3 and 4 on the lower surface (mounting surface) and which are not necessary for bonding at the time of conventional solder mounting are eliminated. Therefore, the width of the element body 2 can be expanded to the maximum of the width dimension of the product. Thereby, the effective volume of the element | base_body 2 can be expanded significantly. Further, since the first paste layer 16 and the second paste layer 17 are formed by screen printing, they can be formed uniformly and thinly over the entire end surfaces 2a and 2b and the main surface 2c. Like the external electrode formed by the construction method, the central part is thick and does not rise. Therefore, since the length dimension of the product is not compressed, the effective volume of the element body 2 can be further expanded.

  The first paste layer 16 is formed by screen printing on the end faces 2a and 2b of the element body 2 having the lead portions for the internal electrodes 7 and 8 which are important for ensuring reliability. Therefore, the thickness (F dimension) of the external electrodes 3 and 4 in the vicinity of the corner portions 9 of the end faces 2a and 2b is significantly smaller than the thickness of the center portions of the end faces 2a and 2b, as in the case of forming by the conventional dipping method. Is avoided. Further, when the thickness (T dimension) of the external electrodes 3 and 4 on the end faces 2a and 2b of the element body 2 is uniform, a thick F dimension can be obtained as compared with the dipping method. Intrusion of the plating solution into the element body 2 in the plating step S11 subsequent to the above can be effectively suppressed, and the reliability of the electronic component 1 can be remarkably improved.

  Further, in the electronic component 1, external electrodes are not formed on the side surfaces 2e and 2f adjacent to the main surfaces 2c and 2d on which mounting electrodes to be mounted on the substrate are formed. Therefore, in the electronic component 1, the solder fillet is not formed on the side surfaces 2e and 2f, and the self-alignment property at the time of mounting is greatly improved, and the occurrence of solder bridge with the adjacent component at the time of narrow adjacent mounting is greatly suppressed. be able to. Further, since the external electrodes 3 and 4 are formed with a uniform thickness in the surface by screen printing, the central portion does not have a convex shape unlike the external electrode formed by the dipping method, and the side surfaces 2e and 2f are further formed. There is no chip standing defect during mounting in which no electrode is formed.

  Here, as shown in FIG. 9A, the first and second baking electrodes 16a and 17a formed by baking the first paste layer 16 and the second paste layer 17 are formed by sintering conductive metal particles. Therefore, irregularities are generated on the surface. At this time, as shown in FIG. 9B, since the plating layer 18 is formed on the first and second baking electrodes 16a and 17a so as to cover the unevenness, the first and second baking electrodes 16a and 17a are formed. The effect of repairing the defect by filling the minute unevenness of the film can be obtained. Further, when the plating layer 18 is formed, the water resulting from the plating solution and the plating layer forming step S7 remains in the gaps and the element body 2 of the first and second baking electrodes 16a and 17a and in the plating layer 18 itself. Sometimes. Since this residual component S is an electrolyte, it remains in the element body 2 and the external electrodes 3 and 4 as in the case of Ni and Sn plating, thereby reducing the reliability of the electronic component 1 and particularly degrading the resistance to moisture load. Let

  On the other hand, in the manufacturing method of the electronic component 1 of this embodiment, as shown in FIG. 10A, by performing the oxidation heat treatment step S8 in which the heat treatment is performed in an acidic atmosphere after the plating layer formation step S7. In addition to the volatilization of moisture, the residual component S such as a plating solution that reduces the reliability of the electronic component 1 is separated from the element body 2 by oxidative decomposition and combustion decomposition, and the non-sublimable residue is stabilized. Oxide. The plated layer 18 is also formed into a CuO layer by heat treatment in an oxygen atmosphere. At this time, an effect of eliminating voids and voids formed in the layer by volume expansion can be obtained. Then, by performing the reduction heat treatment step S9, as shown in FIG. 10B, the CuO layer 19 formed on the surface of the plating layer 18 becomes a Cu metal layer having a continuous structure. The second baked electrodes 16a and 17a and the plated layer 18 that has been subjected to oxidation treatment are more firmly bonded through a reduction process to metal. Thereby, since the external electrodes 3 and 4 are densified, the penetration of a plating solution or the like into the element body 2 is reliably prevented.

  Furthermore, the external electrodes 3 and 4 are further densified by baking at a higher temperature after heat treatment in a reducing atmosphere, and the aforementioned uneven shape is relaxed and flattened. The part it has is modified. Thereby, the product dimension of the electronic component 1 can be made small. Note that the baking temperature in the third baking step S10 is determined from the first and second baking electrodes 16a, 17a and the like because a dense and continuous Cu layer is formed on the surfaces of the external electrodes 3 and 4 in the reduction heat treatment step S9. The glass float does not occur and heat treatment is possible at a higher temperature than before. As a result, the external electrodes 3 and 4 can be further densified.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

  The present inventors produced an electronic component by the manufacturing method described above. As the element body, a C1005 shape product having a length of 910 μm, a width of 456 μm, and a height of 460 μm was used. The corner portion between the end face and the main surface of the element body is curved, and the radius of curvature is R = 30 μm. Moreover, in order to form an external electrode, electrode paste A was prepared as a conductive paste. The electrode paste A is a Cu average particle diameter of 2 μm, a solid content of 70 wt%, a viscosity of 25 Pas, and an ethyl cellulose binder paste.

(Comparative Example 1)
First, a uniform paste film is formed on a flat plate (metalizer) by a doctor blade method so as to have a thickness of about 200 μm, and an element body held on a carrier plate is immersed in the paste film to form an electrode paste A Was applied to the end face side of the element body. And after apply | coating the electrode paste A, it was made to dry at predetermined temperature and baked at 800 degreeC. Thereafter, a 4 μm Ni plating film and a 4 μm Sn plating film were formed by barrel plating to form external electrodes, and Comparative Example 1 was obtained.

Example 1
Next, electrode paste A was applied to the end face of the element body by screen printing to form a first paste layer. For the formation of the first paste layer, printing was performed by applying a printing pressure of 10 kg to 20 kg to a squeegee using a screen mesh of # 260 Tetron. Subsequently, the first paste layer was formed and then dried, and electrode paste A was applied to one (one side) of the main surface of the element body by screen printing to form a second paste layer. For forming the second paste layer, a # 360 Tetron screen mesh was used. The screen mesh used for forming the second paste layer was slightly larger than the width and length dimensions of the element body. And after forming the 2nd paste layer, it was made to dry and the 1st paste layer and the 2nd paste layer were baked at 800 degreeC, and the 1st baked electrode and the 2nd baked electrode were formed. Thereafter, a 4 μm Ni plating film and a 4 μm Sn plating film were formed by barrel plating to form external electrodes, and Example 1 was obtained.

(Example 2)
Moreover, in the process of Example 1, printing and drying of the first paste layer were performed twice, and Example 2 was obtained.

(Example 3)
Moreover, in the process of Example 2, after printing and drying the first paste layer twice, the first paste layer is baked to form a first baking electrode, and then the second paste layer is printed and baked. A second baked electrode was formed. Then, after forming the first and second baking electrodes, a 4 μm Ni plating film and a 4 μm Sn plating film were formed by barrel plating to form an external electrode, and Example 3 was obtained.

Example 4
Moreover, after forming the 1st baking electrode and the 2nd baking electrode similarly to Example 1, the Cu plating layer was formed using the plating bath by pyrophosphoric acid. At this time, a Cu plating film (layer) was deposited at a target value of 5 μm. Then, after baking at a baking temperature of 600 ° C. in a heat treatment furnace in a nitrogen atmosphere, a 4 μm Ni plating film and a 4 μm Sn plating film were formed by barrel plating to form an external electrode, and Example 4 was obtained. .

(Example 5)
Further, after forming a Cu plating layer by the process of Example 4, an oxidation heat treatment was performed at 500 ° C. in a heat treatment furnace in an oxygen atmosphere, and a reduction heat treatment was further performed at 500 ° C. in a heat treatment furnace in a nitrogen atmosphere. Thereafter, a 4 μm Ni plating film and a 4 μm Sn plating film were formed by barrel plating to form external electrodes, and Example 5 was obtained.

(Example 6)
In addition, after performing reduction heat treatment at 500 ° C. in a heat treatment furnace in a nitrogen atmosphere in the process of Example 5, and further baking at a baking temperature of 700 ° C. in a heat treatment furnace in a nitrogen atmosphere, 4 μm Ni plating is performed by barrel plating. An external electrode was formed by forming a film and a 4 μm Sn plating film, and Example 6 was obtained.

(Example 7)
Moreover, after forming a 1st paste layer similarly to Example 1, electrode paste A was provided by screen printing on both surfaces of the main surface of an element | base_body, a 2nd paste layer was formed, and it dried at 800 degreeC. The first paste layer and the second paste layer were baked to form a first baked electrode and a second baked electrode. Thereafter, a 4 μm Ni plating film and a 4 μm Sn plating film were formed by barrel plating to form external electrodes, and Example 7 was obtained.

  And the dimension in each process step of the electronic component of the comparative example 1 and Examples 1-7 was measured. The measurement results are shown in FIG. Further, prior to the formation of Ni plating and Sn plating, it was confirmed by using a stereomicroscope and a metal microscope whether the appearance of the surface of the external electrode was abnormal.

  Moreover, the comparative example 1 and Examples 1-7 were thrown into the pressure cooker tank, and the accelerated moisture-proof load test (PCBT test) which performs a voltage application in the atmosphere of 121 degreeC-humidity 95% was implemented. The results obtained by these tests are shown in FIG.

  As shown in FIG. 11, in each of Examples 1 to 7 of the present invention, the product dimensions are greatly reduced compared to the comparative example, and the product volume calculated from the product maximum outer shape is the comparative example 1. On the other hand, it is greatly reduced to 82% to 84%. This reduced volume can be allocated to an increase in the effective volume of the element body that ensures the effective function (capacitance) of the electronic component, and depends on the design method of the internal structure, but is approximately 15 in terms of capacitance. It is possible to increase the capacity by ~ 20%.

  As shown in FIG. 12, all of the electronic components of Comparative Example 1 were in a state in which the external electrodes were swollen near the corners of the end faces of the electronic components, and abnormalities were confirmed. This is presumably because a reaction layer in which Cu of the external electrode and Ni of the internal electrode of the base body reacted when the paste layer was baked was detected as an abnormal appearance in a thin portion of the external electrode. Further, in the super accelerated moisture resistance load test, insulation resistance failure was confirmed in 35% of the comparative examples.

  On the other hand, the electronic component of Example 1 had a terminal appearance abnormality rate reduced to 26%, and the NG rate was also improved to 5% in the super accelerated moisture resistance load test result. Furthermore, in the electronic component of Example 2 in which the end face was screen-printed twice, as a result of the appearance of the terminal, the electrode was not bent near the corner of the element end face that occurred in Comparative Example 1 and Example 1. . The detected 1% appearance abnormality is the occurrence of minute electrode peeling at the corners. This is because when the first paste layer is printed and dried, the second paste layer is subsequently printed. It is considered that a defect occurred due to mechanical impact on the dried coating film having low mechanical strength before firing due to contact with a jig or the like when aligning the bodies. The electronic component of Example 2 has a super accelerated moisture resistance load test NG ratio of 333 ppm, which is significantly improved compared to the comparative example.

  In addition, regarding Example 3 in which the first paste layer was printed and then fired, and further, the second paste layer was printed and fired, both the terminal appearance and the super accelerated moisture resistance load test were detected as NG products. It was confirmed that the reliability was remarkably improved by the present invention.

  Further, in the electronic component plated with Cu of Example 4, as a result of the terminal appearance, the occurrence of abnormality such as the electrode near the corner of the end face of the element observed in Example 1 disappeared, and the terminal surface 3% of crystalline fine precipitate residue was generated. In the super accelerated moisture resistance load test of this electronic component, the NG rate was 2666 ppm, which was confirmed to be significantly improved from 5% of Example 1. Precipitates on the surface of the terminal are considered to be those that remain as a residue because the plating residue during Cu plating is deposited from the inside of the element body during the sintering heat treatment and cannot be decomposed by the heat treatment in a nitrogen atmosphere.

  In Example 5 in which the oxidation-reduction heat treatment was performed after Cu plating and in Example 6 in which the heat treatment was further performed thereafter, there was no abnormality in the appearance of the terminal, and the plating residue was completely decomposed and volatilized by the oxidation-reduction heat treatment. It is thought that It was also found that the results of the super accelerated moisture resistance load test were significantly improved to 666 ppm and 0 ppm.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the external electrodes 3 and 4 are formed on the main surfaces 2c and 2d, but the external electrodes 3 and 4 may be formed on the side surfaces 2e and 2f.

  In the above embodiment, the second paste layer 17 is formed after the first paste layer 16 is formed. However, the first paste layer 16 may be formed after the second paste layer 17 is formed. Alternatively, the first paste layer 16 may be formed and dried, then the second paste may be formed and dried, and the first paste layer 16 and the second paste layer 17 may be baked together.

  Moreover, in the said embodiment, although the external electrodes 3 and 4 are formed ranging over three surfaces of end surface 2a, 2b and a pair of main surface 2c, 2d, for example, end surface 2a, 2b and one main surface 2c are formed. It may be formed across two surfaces. Specifically, as shown in FIG. 13, in the electronic component 1 </ b> A, the external electrodes 3 </ b> A and 4 </ b> A have an L-shaped cross section, and are formed on two surfaces of the end surfaces 2 a and 2 b and one main surface 2 c (one surface). It is formed straddling.

  DESCRIPTION OF SYMBOLS 1 ... Electronic component, 2 ... Element body, 2a, 2b ... End surface, 2c, 2d ... Main surface, 2e, 2f ... Side surface, 3, 4 ... External electrode, 9 ... Corner | angular part, 9a ... Curved surface, 16 ... First Paste layer, 16a ... first baking electrode, 17 ... second paste layer, 17a ... second baking electrode, 18 ... plating layer, 52 ... first conductive paste, 56 ... second conductive paste, S3 ... first paste Layer forming step, S4 ... first baking step, S5 ... second paste layer forming step, S6 ... second baking step, S7 ... plating layer forming step (metal plating layer forming step), S8 ... oxidation heat treatment step (first heat treatment) Step, heat treatment step), S9 ... reduction heat treatment step (second heat treatment step, heat treatment step), S10 ... third baking step.

Claims (7)

A pair of end surfaces facing each other, a pair of main surfaces extending so as to connect the pair of end surfaces and facing each other, and a pair of side surfaces extending so as to connect the pair of main surfaces and facing each other With the body,
A method of manufacturing an electronic component comprising an external electrode formed on the end face side of the element body,
An element body preparing step of preparing the element body having a curved surface in which a corner portion between the end surface and the main surface and the side surface is curved;
A first paste layer forming step of forming a first paste layer by screen-printing a first conductive paste on the end surface and the curved surface;
A second paste layer forming step of forming a second paste layer by screen-printing a second conductive paste on one or both of the main surface and the side surface and the curved surface; Have
In the first paste layer forming step or the second paste layer forming step, the first paste layer or the second paste so that the first paste layer and the second paste layer are joined at the curved surface. A method of manufacturing an electronic component, wherein a layer is formed. In the first paste layer forming step, the first paste layer is formed so that the first conductive paste is not applied to the main surface and the side surface,
2. The method of manufacturing an electronic component according to claim 1, wherein in the second paste layer forming step, the second paste layer is formed so that the second conductive paste is not applied to the end face. Of the first paste layer forming step and the second paste layer forming step, a first baking step of baking the paste layer to form a first baking electrode after the paste layer forming step of previously forming the paste layer; ,
After the first baking step, a second baking step of baking the paste layer formed in the next paste layer forming step to form a second baking electrode;
The method of manufacturing an electronic component according to claim 1, further comprising: A plating layer forming step of forming a metal plating layer so as to cover the whole of the first baking electrode and the second baking electrode;
A heat treatment step for heat-treating the metal plating layer;
The method of manufacturing an electronic component according to claim 3, further comprising: The heat treatment step includes
A first heat treatment step of heat-treating the metal plating layer in an oxygen atmosphere;
After the first heat treatment step, a second heat treatment step of heat-treating the metal plating layer in a reducing atmosphere;
The manufacturing method of the electronic component of Claim 4 characterized by the above-mentioned.   6. The method of manufacturing an electronic component according to claim 5, further comprising a third baking step of baking the metal plating layer after the second heat treatment step.   The electronic component manufactured by the manufacturing method of the electronic component as described in any one of Claims 1-6.

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