JP4992776B2 - Multilayer electronic component and manufacturing method thereof - Google Patents

Description

  The present invention relates to a laminated electronic component having a laminated structure of an element body made of ceramics and internal electrodes, and a method for manufacturing the same.

  Generally, thermistors, capacitors, inductors, LTCCs (Low Temperature Co-fired Ceramics), varistors and their composites, which have ceramic bodies, internal electrodes and external electrodes, are printed circuit boards such as printed circuit boards. The external electrode is soldered to a predetermined connection position. In that case, for example, if the external electrode (base electrode) made of Ag and the terminal electrode made of Ni layer and Sn layer are formed by plating, the bondability to the substrate by solder is improved and the productivity is improved. Can be.

  For example, Patent Document 1 discloses that in the plating process for forming such terminal electrodes, the electrical characteristics of the laminated electronic component are prevented from deteriorating due to the plating electrolyte entering the component element body. Therefore, an electronic component has been proposed in which all pores present on the surface portion of the ceramic body of the electronic component are impregnated with a silicone resin or a phenol resin.

Japanese Patent No. 270097

  By the way, the present inventor examined the physical properties and electrical characteristics of the above-mentioned various laminated electronic components in which terminal electrodes are plated on external electrodes. For example, a porous ceramic such as a PTC (Positive Temperature Coefficient) thermistor is used. In a multilayer electronic component having an element body, the terminal electrode metal may be plated up to the surface of the element body, the surface layer portion, and even the inside of the element body. It has been found that, sometimes, the plating reaches the internal electrodes, which can cause problems such as loss of product function.

  Specifically, external electrodes (underlying electrodes) were formed on both ends of the PTC thermistor, and Ni / Sn terminal electrodes were formed by electroplating with bereel plating. As a result, plating adhered to the entire surface of the ceramic body. As a result of inspecting the elemental distribution of Ni and Sn in the element cross section with EPMA (Electron-Probe Microanalyzer), it was found that a large amount of Ni adhered to the surface layer and Ni also adhered to a deeper part. did. From this, it is estimated that the plating solution infiltrates into the open holes that reach the internal electrodes and power is supplied from the internal electrodes, so that the plating adheres and grows from inside the element body. The Such plating adhesion phenomenon to the element body is similarly seen when electroless plating using a catalyst and when electroless plating is started by a contact method without using a catalyst. It is estimated that the plating adheres and grows from the inside of the opening (open pore) that reaches the internal electrode. On the other hand, when the entire surface of the ceramic body is impregnated with a silicone resin using the conventional method disclosed in Patent Document 1, depending on the type of resin and the resin impregnation conditions, the ceramic body may be plated. It was confirmed that the adhesion could not be sufficiently suppressed.

  Therefore, the present invention has been made in view of such circumstances, and even when a terminal electrode is formed by plating on an external electrode, plating adhesion to the surface of a porous body made of ceramics can be sufficiently suppressed. Accordingly, an object of the present invention is to provide a multilayer electronic component capable of preventing a decrease in product reliability and a method for manufacturing the same.

  In order to solve the above-mentioned problems, the present inventor has made a physical property of an element material that can cause plating adhesion on the surface of a porous ceramic element of a multilayer electronic component, conditions at that time, and a resin that fills the pores of the element As a result of diligent research focusing on the relationship between the type and properties of the present invention, the present invention has been completed. That is, the multilayer electronic component according to the present invention includes a porous element body (porous ceramic element body) mainly made of ceramics and including a plurality of pores, and at least one internal electrode provided in the porous element body. The porous body has an addition polymerization type in at least a part of the plurality of pores. The porous body has a laminate, an external electrode connected to the internal electrode, and a terminal electrode formed by plating on the external electrode. (Addition polymerizable) resin is filled. The “pores” contained in the porous element body in the present invention are equivalent to “pores” defined in Japanese Industrial Standards JIS Z2500 and 2501.

Further, the “filling rate” of the resin in the porous body described later is a value measured as follows. That is, first, the weight of the laminated electronic component in a state before the terminal electrode is formed by plating is dried at 150 ° C. for 1 hour under atmospheric pressure to evaporate the moisture (weight m1). Next, the weight of the impregnated water is measured by holding the laminated electronic component in a state of being immersed in water for 30 minutes in a vacuum (weight m2). Further, after drying the laminated electronic component at 200 ° C. for 1 hour under atmospheric pressure, the porous body is impregnated with an uncured resin (a monomer in the case of a polymerizable material) so that the resin does not adhere to the external electrode, The weight of the resin obtained by drying and curing (heat curing, polymerization) is measured (weight m3). And the following formula (1);
Filling rate (%) = 100 × (m3−m1) / {(m2−m1) × ρ} (1),
Substituting the weights m1, m2, and m3 and the density ρ of the resin in a dry and cured state into the relational expression represented by the following equation, the “filling rate” of the resin is calculated.

  In the multilayer electronic component configured in this way, the pores of the porous body are filled with resin, and the pores (open pores) opened in the porous body are closed by the resin. When forming a terminal electrode on the electrode by plating, the plating solution enters the inside of the porous body through such openings, thereby preventing the plating solution from reaching the internal electrode and depositing / growing the plating. Is done. At this time, it is assumed that the higher the filling rate of the pores with the resin, the more the plating solution can be prevented from entering the porous body, but if a resin such as a dehydration condensation type is used, a reaction is generated during polymerization. Water is generated as an object, and the water is released from the inside of the pores of the porous element body 2 to generate voids. In this case, filling of the pores of the porous element body with the resin is suppressed, and the resin filling It becomes difficult to increase the rate sufficiently. On the other hand, when an addition polymerization type resin is used, water is not generated at the time of polymerization and curing. Therefore, void formation is suppressed, and the pore filling rate of the porous element body 2 is lower than when a dehydration condensation type resin is used. Can be further increased.

  Further, the porous element body is preferably such that a plurality of pores are filled with an addition polymerization type resin at a filling rate of 60% or more.

  According to the knowledge of the present inventor, when the filling rate of the resin into the porous element body is 60% or more, the plating adhesion rate (ratio of the plating adhesion area to the exposed area) on the surface of the porous element body is approximately 5%. It was confirmed that it was kept low enough so that Further, by using an addition polymerization type resin as in the laminated electronic component according to the present invention, it becomes easy to reliably and reliably achieve a resin filling rate of 60% or more. Productivity can also be improved while preventing intrusion more reliably. In addition, it is preferable that the resin layer is formed on the exposed surface of the porous element body, preferably almost entirely, since the barrier effect is further enhanced.

  In addition, the PTC thermistor obtained by using the same method as that disclosed in the above-mentioned Patent Document 1 is subjected to a heat treatment such as reflow, or is heated to a high temperature environment by heating during mounting or heat up during operation. It has been confirmed that when exposed, the PTC characteristics may be deteriorated depending on the impregnation conditions of the resin, such that the resistance value at a high temperature is significantly reduced. This is probably because the flux used for soldering electronic components such as PTC thermistors flows into the pores of the porous body during heating, and the ceramic body is reduced by the residual flux. Presumed to be.

  On the other hand, in particular, when the resin filling rate in the porous element body is 70% or more, the flux flows into the porous element body when the laminated electronic component is mounted on the wiring board or the like or thereafter. It was found that the occurrence rate (frequency) of characteristic defects can be significantly reduced. If an addition polymerization type resin is used as in the laminated electronic component according to the present invention, there is an advantage that it can be easily and reliably achieved even with such a high resin filling rate.

  Furthermore, when the temperature characteristics of the PTC thermistor obtained by using the above conventional method were evaluated, depending on the resin impregnation conditions, a significant amount of individuals that generate foam (so-called “explosion”) from the ceramic body was generated. Was also confirmed. In the conventional method, although the pores on the surface of the ceramic body are blocked, the air inside the pores expands when exposed to high temperatures due to the remaining pores inside the body. Presumed to be caused by rupture.

  On the other hand, it has also been found that when the filling rate of the resin in the porous element body is 80% or more, the occurrence rate (frequency) of “explosion” can be significantly reduced. When an addition polymerization type resin is used as in the laminated electronic component according to the present invention, such a higher resin filling rate can be easily and surely achieved, which is extremely useful.

  Further, the present invention is further useful when the porous body is fired (sintered body) and the sintered density (measured density / theoretical density × 100%) is 90% or less. . That is, according to the research of the present inventors, when a porous element having a sintered density exceeding 90% is used, the adhesion of plating to the surface of the porous element is almost recognized at the time of forming the terminal electrode. In other words, it was confirmed that when the sintered density was 90% or less, the adhesion rate of plating to the surface of the porous element body rapidly increased as the sintered density decreased. This is because when the sintered density of the porous element body exceeds 90%, almost no open pores are generated, and even if voids are formed, many are closed pores and the plating solution is Although it does not penetrate, when the sintered density becomes 90% or less, it is presumed that the number of holes and the ratio to all the holes rapidly increase. Therefore, when applied to a laminated electronic component including a porous element body having a sintered density of 90% or less in which such a large amount of openings can be formed, the operational effects of the present invention are more suitably realized.

  In addition, it is preferable to further include an overcoat layer that covers the external electrode, because when the terminal electrode is plated on the surface of the external electrode, corrosion of the external electrode by the plating solution can be surely prevented.

  Furthermore, the method for manufacturing a multilayer electronic component according to the present invention is a method for effectively manufacturing the multilayer electronic component according to the present invention, which is mainly made of ceramics and includes at least a porous body including a plurality of pores. A step of forming a laminated structure by providing one internal electrode, a step of firing the laminated structure to form a laminated body (sintered body), and electrically connecting the conductive paste to the internal electrode of the laminated body A step of applying to the laminate so as to connect, a step of firing the conductive paste to form the external electrode, and impregnating the porous element with a monomer for obtaining an addition-polymerization type resin. A step of polymerizing a polymer and filling an addition polymerization type resin into a plurality of pores at a filling rate of preferably 60% or more, more preferably 70% or more, and particularly preferably 80% or more, and plating on an external electrode And a step of forming a more terminal electrodes.

  In this case, the internal electrode mainly containing Ni, Cu, or Al is used as the metal component, and the external electrode is preferably 1 part by mass or more and 60 parts by mass with respect to Ag as the metal component and 100 parts by mass of Ag. When the following conductive paste containing Al or the like is used, since the conductive paste does not contain Cu that is easily oxidized, it can be fired in the atmosphere. This simplifies the atmosphere control during firing and eliminates the need for firing in a reducing atmosphere and subsequent re-baking in an oxidizing atmosphere that are required when Cu is included as a metal component. An increase in cost can also be prevented.

  According to the multilayer electronic component and the method of manufacturing the same of the present invention, since the plurality of pores included in the porous element body are filled with the addition polymerization type resin, the porosity filling rate of the porous element body can be easily increased. Therefore, even if the terminal electrode is formed by plating, the plating solution is prevented from intruding through the pores of the porous element body and flowing into the internal electrode, so that the adhesion of the plating to the porous element body is sufficiently suppressed. Therefore, it is possible to eliminate the inconvenience that the reliability of the product is reduced, and to effectively prevent the occurrence of characteristic failure when high temperature is applied and the occurrence of “explosion” under high temperature. be able to.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios. Further, the following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention only to the embodiments. Furthermore, the present invention can be variously modified without departing from the gist thereof.

<First Embodiment>
FIG. 1 is a sectional view showing a schematic structure of a first embodiment of a multilayer electronic component according to the present invention. The multilayer electronic component 1 is a PTC thermistor having a multilayer body 4 including a porous element body 2 made of ceramics and having a plurality of pores, and a plurality of internal electrodes 3 formed in the porous element body 2. For example, at least one unit structure 10 in which the porous body 2 and the internal electrode 3 are laminated is provided. More specifically, the internal electrodes 3 having end portions exposed on one side surface of the multilayer body 4 and the internal electrodes 3 having end portions exposed on the other side surface of the multilayer body 4 are alternately stacked. .

  External electrodes 5 and 5 are provided on both side surfaces of the laminate 4 so as to cover the side surfaces, and each external electrode 5 is a group of internal electrodes 3 exposed from one side surface of the laminate 4 or It is electrically connected to the group of internal electrodes 3 exposed from the other surface of the laminate 4.

Further, terminal electrodes 7 and 7 are formed on the outside of the external electrodes 5 and 5 by plating. These terminal electrodes 7 and 7 are joined to, for example, electrodes on a wiring board (not shown) by solder or the like. Each terminal electrode 7 has, for example, a two-layer structure including a Ni layer 7a and a Sn layer 7b that are stacked from the external electrode 5 side. The Ni layer 7a functions as a barrier metal which prevents the Sn layer 7b and the external electrode 5 from contacting each other and prevents corrosion of the external electrode 5 due to Sn, and has a thickness of about 2 μm, for example. Further, the Sn layer 7b has a function of improving the wettability of the solder, and the thickness thereof is, for example, about 4 μm.

When a PTC thermistor is manufactured as the multilayer electronic component 1 as in the present embodiment, the porous element body 2 needs to be made of ceramics, specifically, semiconductor ceramics as described above, and more specifically, For example, it is made of a barium titanate ceramic. In this barium titanate ceramic, part of Ba may be replaced with Ca, Sr, Pb, or the like, or part of Ti may be replaced with Sn, Zr, or the like as necessary. As donor elements to be added to obtain barium titanate semiconductor ceramics, rare earth elements such as La, Y, Sm, Ce, Dy, and Gd, and transition elements such as Nb, Ta, Bi, Sb, and W are used. Can be used. Further, if necessary, SiO ₂ , Mn or the like may be added to the barium titanate semiconductor ceramics.

  Thus, by forming the porous element body 2 of barium titanate semiconductor ceramics, the PTC thermistor characteristic (PTC characteristic) that the electric resistance rapidly increases at the Curie temperature can be obtained satisfactorily. Applications of such PTC thermistors include overcurrent protection, constant temperature heating elements, overheat detection and the like.

  The method for synthesizing the barium titanate-based ceramic powder used to form the porous element body 2 is not particularly limited. For example, a hydrothermal method, a hydrolysis method, a coprecipitation method, a solid phase method, A sol-gel method or the like can be used, and calcining may be performed as necessary.

  Further, the porous element body 2 is formed by filling a plurality of pores with a resin with a filling rate of preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. When the filling ratio of the resin is 60% or more, when the terminal electrode 7 is formed by plating, the plating solution enters the inside of the porous element body 2 from the openings (open pores) included in the porous element body 2. As a result, it is possible to sufficiently prevent the plating solution from reaching the internal electrode and causing the plating to adhere and grow. Further, when the filling rate of the resin in the porous element body 70 is 70% or more, the occurrence ratio of characteristic defects due to the inflow / residue of the flux into the porous element, which is a concern when mounting the laminated electronic component 1 or the like In particular, when the filling rate of the resin is 80% or more, when the laminated electronic component 1 is exposed to a high temperature, the air inside the pores may expand and burst. It is possible to keep the occurrence of “explosion” extremely low.

  In addition, it is preferable that the porous element body 2 has a resin layer formed on the exposed surface, preferably substantially the entire surface, because the barrier effect is further enhanced. In addition, the coverage with the resin layer on the surface of the porous element body 2 is preferably higher if the handling is not particularly inconvenient because the plating solution can be prevented from entering the opening (open pore).

  Here, FIG. 2 is an enlarged photograph showing a surface layer cross section of an example of a real porous element body 2 filled with a resin at a filling rate of 60% or more. A plurality of pores are formed inside the porous element body 2, and it is confirmed that many apertures communicate with the internal pores. It can be seen that a resin layer is formed on the surface of the element body 2.

  The type of resin used for filling the pores of the porous element body 2 is not particularly limited, and various kinds of resins can be appropriately selected as long as they are addition polymerization type resins that can be impregnated into the porous element body 2. Can be used. The type of the monomer or prepolymer (oligomer) for obtaining the addition polymerization type resin is not limited, for example, preferably having an unsaturated reactive group, particularly preferably a (meth) acryloyl group, a vinyl group, an epoxy group. Or those having a derivative group thereof. An example of the addition polymerization type resin is polydimethylsiloxane. Polydimethylsiloxane is preferable in view of mass productivity because it has a simple structure, stable characteristics, and is inexpensive.

  As described above, when a dehydration-condensation type resin is used, water is generated as a reaction product during polymerization, and voids can be generated by releasing the water from the pores of the porous element body 2. On the other hand, when an addition polymerization type resin is used, water is not generated at the time of polymerization and curing, so that the generation of voids is suppressed, and the porosity filling rate of the porous element body 2 is further increased as compared with the case of using a dehydration condensation type resin. Can be increased.

  The porous body 2 is a sintered body, and the sintered density is not particularly limited. However, when the sintered density is 90% or less, the above-described effects due to the resin filling are remarkably exhibited. That is, when the sintered density of the porous element body 2 exceeds 90%, the amount of plating attached to the surface of the porous element body 2 when the terminal electrode 7 is plated is not significant, whereas the sintered density is 90%. When the ratio is less than or equal to%, the amount and ratio of the pores of the porous element body 2 increase as the sintered density decreases, and the adhesion rate of plating to the surface of the porous element body 2 tends to increase rapidly. . Therefore, when the porous element body 2 has a sintered density of 90% or less at which such a large amount of openings can be formed, it is possible to fill the openings with a high filling rate by using an addition polymerization type resin. The plating adhesion to the surface of the porous element body 2 can be effectively suppressed.

  On the other hand, for the internal electrode 3, for example, a material mainly composed of Ni, Cu, or Al is used from the viewpoint of enabling reliable ohmic contact with the porous body 2. It may be a composite material, and by using a porous body 2 that can be fired at a low temperature, Cu (melting point 1083 ° C.) and Al (melting point 660 ° C.) having a melting point lower than Ni (melting point: 1450 ° C.) should be used. Can do.

  On the other hand, the external electrode 5 is obtained, for example, by applying and baking a conductive paste on the side surface of the laminate 4. Examples of the conductive paste for forming the external electrode 5 mainly include glass powder, an organic vehicle (binder), and a metal powder. By firing the conductive paste, the organic vehicle is volatilized, Finally, the external electrode 5 containing a glass component and a metal component is formed. In addition, you may add various additives, such as a viscosity modifier, an inorganic binder, and an oxidizing agent, to an electrically conductive paste as needed.

  In the present embodiment, the external electrode 5 includes, for example, Ag and Al as metal components, and the Al or the like is a constituent component of the internal electrode 3 such as Ni, Cu, or Al, and the external electrode. 5, the bonding area between the internal electrode 3 and the external electrode 5 is increased, whereby the connection resistance can be sufficiently reduced, and the internal electrode 3. It is also possible to increase the mechanical bonding strength between the external electrode 5 and the external electrode 5.

  Next, a method for manufacturing the multilayer electronic component 1 according to the present embodiment will be described with reference to FIGS. 3-7 is process drawing which shows an example of the procedure which manufactures the multilayer electronic component 1. FIG.

First, as a starting material, a predetermined amount of BaCO ₃ , TiO ₂ and Sm nitrate solution are mixed, put into a polyethylene pot together with pure water and zirconia balls, pulverized and mixed for 5 hours, and then the mixture is evaporated and dried. The mixed powder was calcined at 1100 degrees.

Next, the calcined powder is again pulverized with a ball mill for 5 to 30 hours using pure water and zirconia balls, and then evaporated and dried to obtain a barium titanate semiconductor ceramic powder. For example, a barium titanate semiconductor ceramic powder having a composition of (Ba _0.9985 Gd _0.0015 ) _0.995 (Ti _0.9985 Nb _0.0015 ) O ₃ is obtained.

  Next, an organic solvent, an organic binder, a plasticizer, and the like are added to the obtained powder to form a ceramic slurry, which is then molded by a doctor blade method to form a sheet-like porous body 2 shown in FIG. Get a green sheet.

  Furthermore, as shown in FIG. 4, the pattern of the internal electrode 3 is formed on the sheet-like porous body 2 by screen printing a conductive paste containing Ni, Cu, or Al as a metal component.

  Next, as shown in FIG. 5, a plurality of porous element bodies 2 on which internal electrodes 3 are formed and a plurality of porous element bodies 2 on which no internal electrodes 3 are formed are alternately laminated, and further pressurized. Thus, the laminated structure 40 is obtained.

  Then, as shown in FIG. 6, the laminated structure 40 is cut to be divided into individual laminated structures 41. The end of the internal electrode 3 is exposed from the side surface of the laminated structure 41 after cutting.

Next, the laminated structure 41 is subjected to a binder removal treatment in the air, and then fired at 1300 ° C. for 2 hours in a strong reducing atmosphere of H ₂ / N ₂ = 3/100, whereby the laminated body 4 is sintered. obtain. Thereafter, reoxidation treatment is performed in the air at a temperature of 600 ° C. to 1000 ° C. for 1 hour.

  Next, as shown in FIG. 7, a conductive paste containing Ag, Al, and the like is applied to the side surface of the laminate 4 and fired in the air at a temperature of 600 ° C. to 1000 ° C. for 1 hour to several hours. The external electrode 5 is formed.

  Next, the porous element body 2 is filled with an addition polymerization type resin. The filling method is not particularly limited, and (1) a monomer or prepolymer liquid for obtaining an addition polymerization type resin over the entire porous body 2 with the external electrodes 5 and 5 covered with appropriate members. (A known additive such as a polymerization initiator or a stabilizer may be added as appropriate.) By dipping in a predetermined time and maintaining for a predetermined time, the pores of the porous body 2 are impregnated with the monomer or prepolymer. (2) The whole porous element body 2 is immersed in a monomer or prepolymer solution for obtaining an addition polymerization type resin without covering the external electrodes 5 and 5 part. A method of impregnating the pores of the porous element body 2 with the monomer or prepolymer, removing the liquid adhering to the external electrodes 5 and 5 with a solvent, and then heating and polymerizing and curing; (3) Porous element body 2 From the exposed surface After press-fitting the monomer or prepolymer solution to obtain a pressurized polymerization type resins can be exemplified by a method of heat curing and polymerization.

  The filling rate of the addition polymerization type resin into the porous body 2 is adjusted by repeating the impregnation of the monomer or prepolymer solution for obtaining the resin once or a plurality of times, and adjusting the number of times appropriately. The higher the number of impregnations, the higher the filling rate of the resin. Alternatively, the filling rate of the resin into the porous element body 2 can also be adjusted by adjusting the viscosity of the monomer or prepolymer liquid. Although depending on the type of resin, for example, in the case of a silicone resin, examples of the heat polymerization curing condition include a method of heating at 70 ° C. for 30 minutes and further heating at 180 ° C. for 1 hour. Further, when the monomer or prepolymer is polymerized and cured, ultraviolet irradiation and heating may be performed simultaneously as long as the resin also serves as an ultraviolet curing type in order to promote crosslinking of the resin layer on the surface of the porous body 2.

  Further, as shown in FIG. 2, in order to form a resin layer on the surface of the porous element body 2, the porous element body 2 is impregnated with a monomer or prepolymer for obtaining an addition polymerization type resin, and then the porous element body 2 is impregnated. The body 2 may be polymerized and cured without washing or not sufficiently washed.

  Further, as shown in FIG. 1, a terminal electrode 7 is formed by sequentially depositing a Ni layer 7a and a Sn layer 7b on the surface of the external electrode 5 by electroplating. For example, in the formation of the Ni layer 7a, a barrel plating method is adopted, and Ni of 2 μm is deposited using a watt bath. Further, in forming the Sn layer 7b, a barrel plating method is adopted, and Sn is deposited by 4 μm using a neutral tin plating bath. Then, solder is formed on the terminal electrode 7 or an electrode of a wiring board (not shown), and the solder is melted to electrically connect the terminal electrode 7 and the electrode of the board.

  According to the method for manufacturing the multilayer electronic component 1, the conductive paste for the external electrode 5 can be fired in the air atmosphere. Thereby, compared with the case where it bakes in a reducing atmosphere, atmosphere control becomes simple and can reduce manufacturing cost. In addition, as described above, in particular, when a PTC thermistor is manufactured, if the conductive paste for forming the external electrode is baked in a reducing atmosphere, the laminate does not exhibit the PTC characteristics. Since the external electrode 5 can be formed while maintaining the PTC characteristics of the body 4, for example, mass productivity can be improved as compared with the case where the terminal electrode is formed by a thin film method.

Second Embodiment
FIG. 8 is a sectional view showing a schematic structure of a second embodiment of the multilayer electronic component according to the present invention. The multilayer electronic component 9 is the same as the multilayer electronic component 1 shown in FIG. 1 except that an overcoat layer 8 containing Ag as a metal component is formed on the surface of the external electrode 5 so as to cover the external electrode 5. It is configured. The overcoat layer 8 can be formed, for example, by printing and baking a conductive paste containing Ag. Although illustration is omitted, in FIG. 8, terminal electrodes 7 and 7 are laminated on the outside of the overcoat layers 8 and 8.

  According to the multilayer electronic component 9 having such a structure, since the overcoat layer 8 is formed on the surface of the external electrode 5, Al or the like contained in the external electrode 5 forms the terminal electrode 7 as shown in FIG. It can prevent more reliably that it is corroded by the plating solution for doing.

  In addition, as above-mentioned, this invention is not limited to said each embodiment, In the range which does not deviate from the summary, it can add suitably. For example, the monomer or polymer of the addition polymerization type resin impregnated into the porous body 2 may be used by mixing a plurality of types, or both the monomer and the prepolymer may be used. In the multilayer electronic component 1, the porous element body 2 may be impregnated with a monomer or a prepolymer before the external electrode 5 is formed. In the multilayer electronic component 9, before or after the external electrode 5 is formed. Alternatively, after the overcoat layer 8 is formed, the porous element body 2 may be impregnated with a monomer or a prepolymer. Furthermore, the porous element body 2 may be a ceramic and need not be a semiconductor ceramic. For example, when a multilayer ceramic capacitor is manufactured as the multilayer electronic component 1, 9, the porous element body 2 can be made of an insulating ceramic. Furthermore, at least one internal electrode 3 may be formed.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1-8)
In the same manner as the manufacturing procedure described above, the composition has a porous element body 2 made of (Ba _0.9985 Gd _0.0015 ) _0.995 (Ti _0.9985 Nb _0.0015 ) O ₃ and a plurality of internal electrodes 3 made of Ni of 3.2 mm × 1. A laminated body 4 having a size of 6 mm × 0.5 mm was prepared, and conductive pastes having different contents of Al and Ag were applied to the side surfaces of the laminated body 4 and fired at 600 ° C. in an air atmosphere to external electrodes. 5 was formed. After impregnating this porous element body 2 with an addition polymerization type silicone monomer, the resin was polymerized and cured under heating conditions of heating at 70 ° C. for 30 minutes and further heating at 180 ° C. for 1 hour. Further, the terminal electrodes 7 and 7 are formed on the external electrodes 5 and 5 by using a watt bath by barrel plating with a Ni thickness of 2 μm and a neutral tin plating bath with a thickness of 4 μm. A plurality of PTC thermistors as laminated electronic components were manufactured. It should be noted that a porous element body 2 having a sintering density of 80% is used, and the impregnation of the monomer is repeated once or a plurality of times, and the number of impregnations is appropriately adjusted, whereby various filling rates of the resin to the porous element body 2 are achieved. Changed.

(Comparative Example 1)
A plurality of PTC thermistors having a resin filling rate of 0% were produced in the same manner as in the above example except that the porous polymer was not impregnated with the addition polymerization type silicone monomer and was not filled with the addition polymerization type resin. .

(Test evaluation 1)
About the PTC thermistors obtained in Examples 1 to 8 and Comparative Example 1, the plating adhesion rate (%) on the surface of the porous body, the occurrence rate of characteristic defects after mounting the PTC thermistor on the wiring board (%), and the explosion test The defect occurrence rate (%) was measured and evaluated. The plating adhesion rate (%) on the surface was calculated from the area of the plated region with respect to the exposed area of the porous body of the PTC thermistor. Also, the characteristic failure rate (%) after mounting is 10% higher than the resistance value before reflow after mounting 100 samples for each PTC thermistor on the wiring board by reflow processing. It was calculated from the ratio of the number of individuals that decreased. Furthermore, the defect occurrence rate (%) in the explosion test was calculated from the ratio of the number of individuals in which 100 samples for each PTC thermistor were immersed in silicon oil at 260 ° C. and foamed from the porous body. The results are summarized in Table 1. FIG. 9 is a graph of the data in Table 1.

  From Table 1 and FIG. 9, in the PTC thermistor of the example, the plating adhesion rate on the surface of the porous element body, the characteristic defect occurrence rate after mounting the PTC thermistor on the wiring board, and the defect occurrence rate in the explosion test, Compared to the PTC thermistor of Comparative Example 1, it is sufficiently reduced. In particular, when the filling rate of the resin into the porous element body 2 is 60% or more, the plating adhesion rate on the surface of the porous element body can be further sufficiently suppressed. In addition, if the filling rate is 70% or more, the characteristic defect occurrence rate after mounting the PTC thermistor on the wiring board can be further sufficiently improved, and if the filling rate is 80% or more, an explosion test is performed. It has been confirmed that the defect occurrence rate in can be further sufficiently reduced.

  FIG. 10 and FIG. 11 are a plane external view photograph of a porous body of a PTC thermistor of a comparative example having a resin filling rate of 0% (plating adhesion rate of 100%), and a cross-sectional enlarged photograph of the surface layer portion, respectively. 12 and 13 are diagrams showing element distributions of Ni and Sn, respectively, when the cross section is observed with EPMA. From these results, in the PTC thermistor in which the porous element body is not impregnated / filled with resin, the surface of the porous element body has a metallic luster, and Ni penetrates into a deep region inside the porous element body. Turned out to be.

  14 and 15, FIG. 16 and FIG. 17, FIG. 18 and FIG. 19, FIG. 20 and FIG. 21 respectively show a resin filling rate of 42% (plating adhesion rate of 31%) and a resin filling rate of 56% (plating adhesion). Each of the PTC thermistors of the comparative example with a rate of 9.1%), the resin filling rate of 82% (plating adhesion rate of 3.2%), and the resin filling rate of 98% (plating adhesion rate of 0.5%). It is the plane external appearance photograph of a porous element | base_body, and the cross-sectional enlarged photograph of those surface layer parts.

(Reference Examples 1-6)
The PTC thermistor was manufactured in the same procedure as in Comparative Example 1 by changing the sintered density of the porous element body 2, and the relationship between the sintered density and the plating adhesion rate to the surface of the porous element body was evaluated. The results are summarized in Table 2. FIG. 22 is a graph of the data in Table 1.

  From Table 2 and FIG. 22, when the sintered density of the porous element body is 90% or less, the adhesion of the plating is remarkable to the extent that the plating adhesion rate exceeds 80%, whereas the sintering density is 90%. When the percentage exceeds 50%, the plating adhesion rate decreases rapidly, and it has been found that the adhesion of the plating is almost inconvenient.

  The present invention relates to a thermistor, a capacitor, an inductor, a LTCC (Low Temperature Co-fired Ceramics), a varistor, a laminated electronic component composed of a composite part thereof, and a device, an apparatus, a system, a facility, and the like including them, and Can be widely used in the manufacture of

It is sectional drawing which shows schematic structure of 1st Embodiment of the multilayer electronic component by this invention. It is an enlarged photograph which shows the surface layer cross section of an example of the real thing of the porous element | base_body 2 with which the resin was filled with the filling rate of 60% or more. It is process drawing which shows an example of the procedure which manufactures a laminated electronic component. It is process drawing which shows an example of the procedure which manufactures a laminated electronic component. It is process drawing which shows an example of the procedure which manufactures a laminated electronic component. It is process drawing which shows an example of the procedure which manufactures a laminated electronic component. It is process drawing which shows an example of the procedure which manufactures a laminated electronic component. It is sectional drawing which shows schematic structure of 2nd Embodiment of the multilayer electronic component by this invention. It is a graph which shows the plating adhesion rate of the surface with respect to the filling rate of the resin to a porous element body, the characteristic defect occurrence rate after mounting, and the defect occurrence rate in the explosion test. It is a plane external appearance photograph of the porous element body of the PTC thermistor of the comparative example with a resin filling rate of 0% (plating adhesion rate of 100%). It is a cross-sectional enlarged photograph of the surface layer part of the porous element body of the PTC thermistor of the comparative example of 0% of resin filling rate (plating adhesion rate 100%). It is a figure which shows element distribution of Ni when the cross section of the surface layer part of the porous body of the PTC thermistor of the comparative example of 0% of resin filling rate (plating adhesion rate 100%) is observed by EPMA. It is a figure which shows element distribution of Sn when the cross section of the surface layer part of the porous element body of the PTC thermistor of the comparative example of 0% of resin filling rate (plating adhesion rate 100%) is observed by EPMA. It is a plane external appearance photograph of the porous element body of the PTC thermistor of the comparative example of resin filling rate 42% (plating adhesion rate 31%). It is a cross-sectional enlarged photograph of the surface layer part of the porous element body of the PTC thermistor of the comparative example with a resin filling rate of 42% (plating adhesion rate of 31%). It is a plane external appearance photograph of the porous element body of the PTC thermistor of the comparative example of 56% of resin filling rate (plating adhesion rate 9.1%). It is a cross-sectional enlarged photograph of the surface layer part of the porous element body of the PTC thermistor of the comparative example of 56% of resin filling rate (plating adhesion rate 9.1%). It is a plane external appearance photograph of the porous element body of the PTC thermistor of the comparative example of resin filling rate 82% (plating adhesion rate 3.2%). It is a cross-sectional enlarged photograph of the surface layer part of the porous element body of the PTC thermistor of the comparative example of resin filling rate 82% (plating adhesion rate 3.2%). It is a plane external appearance photograph of the porous element body of the PTC thermistor of the comparative example of resin filling rate 98% (plating adhesion rate 0.5%). It is a cross-sectional enlarged photograph of the surface layer part of the porous body of the PTC thermistor of the comparative example with a resin filling rate of 98% (plating adhesion rate of 0.5%). It is a graph which shows the plating adhesion rate to the surface of a porous element with respect to the sintered density of a porous element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,9 ... Laminated electronic component, 2 ... Porous element body, 3 ... Internal electrode, 4 ... Laminated body (sintered body), 5 ... External electrode, 7 ... Terminal electrode, 7a ... Ni layer, 7b ... Sn layer, 8 ... overcoat layer, 10 ... unit structure, 40, 41 ... laminated structure.

Claims (1)

A step of forming a laminated structure by providing at least one internal electrode in a porous body mainly made of ceramics and including a plurality of pores;
Firing the laminated structure to form a laminated body;
Applying a conductive paste to the laminate so as to be electrically connected to an internal electrode of the laminate;
Firing the conductive paste to form external electrodes;
A step of impregnating the porous element with a monomer or prepolymer for obtaining an addition polymerization type resin, polymerizing the monomer or prepolymer, and filling at least a part of the plurality of pores with the addition polymerization type resin; When,
Forming a terminal electrode on the external electrode by plating;
A method of manufacturing a laminated electronic component having