JP5768272B2 - Chip component and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electronic component, and more particularly to a chip component having a ceramic body.

  In recent years, applications of electronic parts have been diversified, such as automobiles and industrial equipment. As a result, the demand for electronic components that protect electronic circuits from unexpected noise and large pulses has become extremely demanding. In addition, it is necessary to fully consider the effects of temperature / humidity changes, sulfurization, condensation, vibration, etc. when using electronic components, and to provide reliable products for continuous use, not just the initial functions. There is.

  Against this background, chip components, especially multilayer chip varistors, are used to protect circuits from high-voltage pulses in a wide range of fields such as ESD and lightning surges. In order to protect, the products are also increased in proportion. However, increasing the size of the product makes it difficult to ensure mounting reliability, which is an issue for surface mounting. In particular, in automotive applications, it is difficult to ensure high performance, high quality, and high reliability in a mounted state in a large product due to severe requirements such as resistance to thermal history, vibration, impact, and deflection.

  Various proposals have been made in the field of the above-mentioned chip parts from the demand for high performance and high reliability. Patent Document 1 proposes covering the ceramic fired body and the tip of the external electrode with an epoxy resin layer. Accordingly, an object of the present invention is to provide an excellent ceramic electronic component that reduces the influence of external stress applied to the ceramic fired body and does not cause cracks in the ceramic fired body. However, this epoxy resin is formed to prevent the soldering layer from being formed around the lower portion of the ceramic fired body, and serves to strengthen the bonding between the ceramic fired body and the external electrode. In other words, the surface of the ceramic fired body is not sufficiently bonded to the external electrode, and the external electrode may peel from the ceramic fired body.

  In this regard, in the fifth and sixth examples of Patent Document 1, even if the external electrode is cracked and partly peels off and deforms, the deformation occurs only in part. There is a description that conduction between external electrodes is still ensured. However, when a further external force is applied to the component, there is a high possibility that the deformed electrode is broken and the component is dropped from the circuit board. For this reason, it is necessary that the ceramic fired body and the external electrode layer are strongly bonded.

  Patent Document 2 proposes forming a coating film having a higher resistance than that of a varistor element body such as resin or glass on the varistor element body. This coating film is formed only on a partial surface of the element body. Regarding the bonding strength, there is a description that since the resin in the resin electrode enters the recesses on the surface of the varistor element body, it is easy to ensure the bonding strength between the resin electrode and the varistor element body. However, the unevenness of the varistor element surface is small, and it is difficult to ensure sufficient bonding strength.

  In Patent Document 2, a coating film is partially formed on the varistor element body. However, when the external electrode is formed by immersing the element body in a resin paste, the formation region of the external electrode varies and the formation position Therefore, the external electrode may be formed in a portion where the coating film is not formed. In this case, since the varistor element body is eroded by the plating solution, the reliability of the components is lowered.

JP-A-8-162357 JP-A-11-297507

  The present invention has been made based on the above-described circumstances, and provides a multilayer chip component capable of ensuring high reliability in a mounted state with high performance and high quality even with a large chip component, and a method for manufacturing the same. For the purpose.

In the chip component of the present invention, the entire surface of the dielectric element (ceramic fired body) is covered with a glass layer. And the external electrode layer is composed of a base electrode containing a metal component and a resin electrode, the surface of the glass layer is formed with irregularities due to glass particles, the base electrode is formed on both end faces of the dielectric element, The resin electrode covers the base electrode and is bonded to the dielectric element through a glass layer.

  Concavities and convexities are formed on the surface of the glass layer, and the glass layer on the surface of the dielectric element (ceramic fired body) plays a role of linking, and the external electrode layer to the strong and reliable ceramic body Connection can be secured. In particular, by using crystallized glass in which irregularities are easily formed, stronger bonding can be ensured between the glass layer and the external electrode layer due to the anchor effect. In addition, since the glass layer covers the entire surface of the dielectric element, the dielectric element is prevented from being damaged during the manufacture and use of the component, and moisture and the like are prevented from entering the dielectric element. It is also possible to prevent plating from adhering to the element and reducing the reliability of the component.

  Furthermore, by forming the outer layer of the external electrode layer with a resin electrode, the influence of external stress applied to the chip component due to the elasticity of the resin electrode is reduced, and cracks are less likely to occur in the dielectric element. Note that the electrical connection between the internal electrode and the external electrode layer is that the glass particles of the glass layer are not densely attached to the surface of the dielectric element, but are loosely attached, and the metal component is fluidized when the base electrode is fired. It is ensured by mixing the material and glass.

It is sectional drawing of the multilayer chip varistor of one Example of this invention. It is an enlarged view of the A part of FIG. It is a partial see-through perspective view of the varistor. It is sectional drawing which shows the outline of the manufacturing process of the said varistor. It is a flowchart which shows the example of a manufacturing process of the said varistor.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 5, taking a multilayer chip varistor as an example. In addition, in each figure, the same code | symbol is attached | subjected and demonstrated to the same or equivalent member or element.

  As shown in FIGS. 1 to 3, the multilayer chip varistor according to the present invention includes a dielectric element 11 that is a ceramic fired body laminated with an internal electrode 11a sandwiched between ceramic sheets 11b, and the entire surface of the dielectric element. The glass layer 12 to cover and the external electrode layer 15 which consists of the base electrode 13 containing a metal component, and the resin electrode 14 are provided. The dielectric element 11 is arranged such that a plurality of internal electrodes 11a are opposed to each other via the ceramic sheet 11b, and one end side thereof is alternately drawn out to an end face on a different side.

  The external electrode layer 15 includes a base electrode 13 and a resin electrode 14 formed thereon. The base electrode 13 is formed by depositing and baking a silver paste, and contains glass containing silver as a main component. The resin electrode 14 is formed by applying a resin silver paste and heating and curing, and is mainly composed of silver containing a resin.

  The resin electrode 14 completely covers the base electrode 13, and the base electrode 13 is bonded to the internal electrode 11 a on the end face of the dielectric element 11 through the glass layer 12. The electrical connection between the internal electrode 11a and the external electrode layer 15 is that the glass layer is not densely adhered to the surface of the dielectric element 11, but is loosely adhered, and the metal component is not formed when the base electrode 14 is fired. It is ensured by fluidization and mixing of the base electrode material and glass.

  Since the surface of the glass layer 12 has sparse glass particles, irregularities rougher than the surface of the dielectric element are formed. Further, as shown in FIG. The both ends extend to the surface of the glass layer 12 more than the base electrode 13 and enter the unevenness, whereby the surface of the dielectric element 11 and the external electrode layer 15 are strongly connected by the anchor effect. Further, since the resin electrode 14 is more elastic than an electrode made of only a metal component, the stress generated between the mounting substrate and the dielectric element 11 is relieved.

  As shown in FIG. 3, at both ends of the dielectric element 11, the base electrode 13 is bonded to both end faces C of the dielectric element 11 through the glass layer 12, the resin electrode 14 covers the base electrode 13, and the dielectric The body element 11 is directly bonded to the dielectric element 11 through the glass layer 12 at both end portions B on the four side surfaces. Therefore, since the resin electrode 14 includes the base electrode 13 at the end face and is bonded to the both end portions B on the four side surfaces of the dielectric element 11 via the glass layer 12, the glass layer 12 serves as a connection, and the external electrode layer A strong connection to both ends of the 15 dielectric elements 11 is obtained.

  When the mounting direction is limited, the resin electrode 14 can be bonded only to the lower portion of the dielectric element 11 when manufacturing the component. This is because peeling of the external electrode layer from the element body is likely to occur in the lower part when the component is mounted. It is also possible to form the Ni plating layer 16 on the external electrode layer 15 and further the Sn plating layer 17 thereon. The Ni plating layer 16 prevents solder erosion, and the Sn plating layer 17 improves solder bonding with the mounting substrate.

  A glass layer 12 made of glass, particularly crystallized glass, is formed on the entire surface of the dielectric element 11. Since this glass layer is in a state in which glass particles remain, irregularities are formed on the surface, and it provides a strong bondability to the external electrode layer 15. Further, by setting the thickness of the glass layer to 10 μm or less, the metal component of the base electrode 13 is fluidized at the time of firing, and conduction between the internal electrode 11 a exposed on the end face of the dielectric element 11 and the external electrode layer 15 is ensured. Is done.

  The composition of the glass layer 12 is B2O3-Bi2O3, B2O3-SiO2, B2O3-Bi2O3-SiO2, B2O3-ZnO-SiO2, B2O3-Bi2O3-SiO2-ZnO, B2O3-Bi2O3-SiO2-ZnO-Sb2O3, B2O3-SiO2-PbO Bi2O3-SnO2, Bi2O3-B2O3, etc. are conceivable. The glass layer is preferably crystallized in order to improve bondability.

  The glass layer is particularly preferably bismuth borosilicate glass represented by ZnO—Bi 2 O 3 —SiO 2 —B 2 O 3 —Sb 2 O 3. This glass can be crystallized by baking at 700 ° C. or higher. The composition of bismuth borosilicate glass consists of 1 to 2 wt% zinc oxide (ZnO), 50 to 70 wt% bismuth oxide (Bi2O3), 10 to 20 wt% silicon oxide (SiO2), and boron oxide (B2O3). ) 8 to 13 wt% and antimony oxide (Sb2O3) 0.1 to 1 wt%. Bi2O3 is added to improve the wettability of the dielectric element, ZnO is added to improve the bonding strength between the dielectric element and the resin electrode, and Sb2O3 is added to improve the acid resistance.

  Here, two or more of calcium oxide, magnesium oxide, aluminum oxide, zirconium oxide, barium oxide, strontium oxide, sodium oxide, lithium oxide, and potassium oxide may be contained in an amount of 5 wt% or less.

  Since bismuth borosilicate glass has a basic composition of SiO 2 -B 2 O 3, and SiO 2 alone has a high melting point and is difficult to use, B 2 O 3 can be added to lower the firing to make it easier to use. Add Bi2O3 to lower the temperature further. Thereby, wettability improves with the low temperature of baking. However, in this state, it becomes amorphous glass and may be eroded by the plating solution. Therefore, ZnO and Sb2O3 are added for crystallization, and the acid resistance is improved by crystallization. In addition, when calcium oxide, magnesium oxide, aluminum oxide, zirconium oxide, barium oxide, barium oxide, strontium oxide, sodium oxide, lithium oxide, or potassium oxide is added to ZnO-Bi2O3-SiO2-B2O3-Sb2O3, Low temperature can be promoted.

  Table 1 shows the results of examining the firing temperature of the glass layer when the glass composition is used. In examining the firing temperature, the thermal behavior of the glass was ascertained using a thermal analyzer. As a result, it can be seen that by using the above glass composition and baking at 700 ° C. or higher, a crystalline material can be obtained and crystallized.

  Here, the plating resistance (%) indicates the ratio of the plating extending to the surface of the dielectric element when electrolytic plating is performed on the surface of the external electrode layer. When the plating extends to the surface of the dielectric element, the glass layer is dissolved by the plating solution, and the plating solution also dissolves the glass layer that joins the external electrode layer and the surface of the dielectric element. Deterioration of bonding strength on the element surface is brought about. Confirming that the firing temperature of the glass layer is 700 ° C. or higher, the crystal phase of the glass layer becomes crystalline and the plating resistance is improved, thereby maintaining the bonding strength between the dielectric element and the external electrode layer. it can.

  Next, the manufacturing process of the chip component according to the present invention will be described with reference to FIGS. As shown in FIG. 4, the outline of this manufacturing process is as follows: a ceramic green sheet is prepared, a ceramic green sheet is sandwiched between internal electrodes and fired to form a dielectric element; A glass layer forming step (b) for forming a glass layer covering the entire surface of the device with a glass solution, and a base electrode formation for forming a base electrode electrically connected to the internal electrode by applying a paste mainly composed of silver A step (c) and a resin electrode formation step (d) for covering the base electrode and forming a resin electrode so as to reach the surface of the dielectric element through the glass layer. Further, a Ni plating layer forming step (e) and a Sn plating layer forming step (f) may be provided.

  Next, each step will be specifically described. As shown in FIG. 5, in the lamination process, varistor materials such as ZnO, Bi2O3, CoO, MnO, and NiO are prepared (S1), and the calcination, pulverization, and sizing steps are repeated (S2-S4). An organic binder, a plasticizer, etc. are added and mixed to produce a slurry (S5), and a ceramic green sheet is produced by a doctor blade method or the like (S6). Then, a conductive paste such as Ag-Pd is screen-printed on the green sheet to arrange the internal electrodes, laminate them, and dice them to produce ceramic chips (S6-S8).

  Then, a binder removal process by heat treatment is performed (S9), and firing is performed at a high temperature to produce a dielectric element which is a ceramic fired body laminated with an internal electrode sandwiched between ceramic sheets (S10). In order to further improve the reliability of the varistor, annealing, which is a second heat treatment, is performed (S11), and the corners of the ceramic chip are removed by barrel processing (S12), thereby completing the dielectric element 11.

  Next, in the glass layer forming step (S 13), the glass layer 12 is formed on the entire surface of the dielectric element 11 with a uniform thickness by depositing a glass solution on the dielectric element and performing heat treatment. The glass solution is preferably formed by mixing 9 wt% of bismuth borosilicate glass with 1 wt% of polyethylene glycol and 90 wt% of ion exchange water.

  Then, 100 g of the obtained glass solution is mixed with the dielectric element 11 described above, then transferred to a cylindrical metal container, placed on a hermetically sealed ball mill frame, and rotated for 1 hr at a rotation speed of 60 rpm while applying 40 ° C. heat. dry. Then, it bakes at the glass transition temperature or more of each composition. By firing at 700 ° C. or higher as described above, the crystallized glass layer 12 can be uniformly formed on the entire surface of the dielectric element 11 with a thickness of 10 μm or less. The solid content of the glass solution used in this example is optimally 5 to 15 wt%.

  Next, in the base electrode forming step (S14), both end surfaces of the dielectric element 11 are immersed in a paste in which 70 wt% of silver powder, 10 to 15 wt% of glass and other solvent are mixed, and fired at 600 to 800 ° C. A base electrode 13 is formed. At the time of firing, the silver component in the base electrode is fluidized and diffuses in the glass layer, and comes into contact with the internal electrode 11a exposed on the end face of the dielectric element 11, thereby electrically connecting the internal electrode 11a and the base electrode 13 to each other. Continuity is ensured.

  Further, in the resin electrode forming step (S15), both end surfaces of the dielectric element 11 are immersed so as to cover the base electrode 13 in a paste prepared by mixing 70 wt% of silver powder with 30 wt% of thermosetting resin and mixing a solvent. To do. Then, the resin electrode 14 is formed by curing at 150 to 300 ° C. Thereby, the multilayer chip varistor provided with the external electrode layer 15 composed of the base electrode 13 and the resin electrode 14 is completed.

  Further, after this, it is possible to form the Ni plating layer 16 and the Sn plating layer 17 on the external electrode layer 15 (S16). The Ni plating layer 16 and the Sn plating layer 17 can be easily formed by electrolytic plating. As a result, the solderability can be improved when mounted on the mounting board.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

  INDUSTRIAL APPLICABILITY The present invention can be used for a chip component having a ceramic body such as a multilayer capacitor, a multilayer varistor, a thermistor, and a resistor.

Claims (4)

A dielectric element;
An internal electrode provided inside the dielectric element;
An external electrode layer electrically connected to the internal electrode,
A glass layer covering the entire surface of the dielectric element between the dielectric element and the external electrode layer;
The external electrode layer is composed of a base electrode containing a metal component and a resin electrode,
Unevenness due to glass particles is formed on the surface of the glass layer,
The chip electrode characterized in that the resin electrode covers the base electrode and is bonded to the dielectric element through the glass layer.   2. The chip part according to claim 1, wherein the glass layer is made of crystallized glass.   The resin electrode covers the base electrode at both end faces of the dielectric element, and is joined to the dielectric element through the glass layer at both end parts of four side faces of the dielectric element. Item 2. The chip component according to Item 1. Preparing a ceramic green sheet, laminating and sandwiching an internal electrode on the ceramic green sheet, and firing to form a dielectric element;
Covering the entire surface of the dielectric element and forming a glass layer having irregularities due to glass particles on the surface;
Forming a base electrode electrically connected to the internal electrode through the glass layer;
A method of manufacturing a chip component, comprising a step of forming a resin electrode that covers the base electrode and covers the surface of the dielectric element.

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