JPH04257211A - Chip type electronic component - Google Patents

Abstract

PURPOSE:To prevent an electronic component body from cracking by imparting mechanical and thermal buffer functions to an external electrodes. CONSTITUTION:The outer face of an extraction electrode 15 communicating with an internal electrode 11 of an electronic component body is overlaid with a buffer layer 16 using conductive paste: this buffer layer 16 coats the whole extraction electrode 15 and is overlaid externally with a plating layer 17 to form an external electrode 14. The mechanical buffer function of the buffer layer 16 relieves propagation of stress to the electronic component main body when a circuit board bends and prevents the component from being broken down; whereas, the thermal buffer function of the buffer layer 16 decreases thermal conductivity, reduces thermal propagation to the internal electrode when soldered, and prevents cracks due to thermal shock of the internal electrode and the ceramic interface.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to chip-type ceramic electronic components, particularly external electrodes.

0002

2. Description of the Related Art FIG. 3 shows a laminated LC filter block as an example of a chip-type ceramic electronic component, which is formed by providing a plurality of external electrodes 2 on both sides of a ceramic laminate 1 that are electrically connected to internal electrodes. While placed on the substrate 3, the external electrodes 2 are connected to the pattern by reflow soldering or flow soldering to be mounted.

Conventionally, as shown in FIG. 4, the external electrode 2 employed in the above-mentioned laminated LC chip filter block, etc. is made by baking a paste of silver, copper, etc. on the outside of the ceramic laminate 1 to form the internal electrode 4. It has a structure in which a lead electrode 5 is provided and a plating layer 6 is formed on the outer surface of the lead electrode 5, and this plating layer 6 is coated with Ni to prevent diffusion of the lead electrode 5 by solder during mounting. Sn or S for good soldering to the inner layer 7 and pattern used.
and an outer layer 8 made of n/Pb or the like, and the external electrode 2 is substantially formed in three layers.

0004

[Problems to be Solved by the Invention] By the way, since the conventional external electrode 2 as described above is entirely made of metal material, it has rigidity itself, and as shown in FIG. When the circuit board 3 is subjected to a deflection test with the circuit board 3 mounted by soldering, the mechanical stress due to the bending of the circuit board 3 acts directly on the ceramic laminate 1 through the external electrode 2, causing the ceramic laminate 1 to bend as shown in FIG. There is a problem in that a crack 9 occurs in a portion of the body 1 close to the external electrode 2.

Furthermore, since the external electrodes 2 are all made of metal materials, they have good thermal conductivity, and the heat of the solder during mounting is transferred to the external electrodes 2 and the internal electrodes 4 that are electrically connected to them, resulting in poor thermal conductivity. Applying a thermal shock to the ceramic laminate 1,
This causes the problem of cracks.

[0006] Therefore, an object of the present invention is to provide a chip-type electronic component that can buffer the mechanical stress caused by bending the circuit board and the thermal shock during mounting, and that does not cause cracks in the ceramic part. do.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides an extraction electrode that is electrically connected to an internal electrode on the outside of a chip-type electronic component body, and uses a conductive paste on the surface of this extraction electrode. The external electrode has a structure in which a buffer material layer is formed to cover the entire surface of the extraction electrode, and a plating layer is provided on the outer surface of the buffer material layer.

[0008]

[Function] A buffer layer made of conductive paste is provided between the lead electrode and the plating layer, so the buffer layer prevents deformation stress caused by deflection of the circuit board from propagating to the electronic component body when mounted on the circuit board. to prevent cracks from forming in the electronic component body.

[0009] In addition, the buffer material layer reduces heat propagation during soldering and prevents the plating solution from penetrating into the interior.
Thermal shock damage at the interface between the internal electrode and the electronic component body due to thermal shock can be suppressed.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to FIGS. 1 and 2 of the accompanying drawings.

The drawing illustrates a multilayer LC filter as a chip-type electronic component, in which a plurality of ceramic dielectrics 12 each having an internal electrode 11 on one side are stacked to form a ceramic laminate 13. External electrodes 14 that are electrically connected to the internal electrodes 11 are provided on both sides of the external electrodes 13 .

The external electrode 14 is made of ceramic laminate 1.
Internal electrode 11 is baked on the outside of 3 with a paste of silver, copper, etc.
an extraction electrode 15 electrically connected to the extraction electrode 15; a buffer material layer 16 provided on the surface of the extraction electrode 15 using conductive paste so as to cover the entire surface of the extraction electrode 15;
The plating layer 17 is formed on the outer surface of the plating layer 17.
is formed of an inner layer 18 made of Ni and an outer layer 19 made of Sn or Sn/Pb, etc. Therefore, the external electrode 14 has substantially four layers.

The material of the conductive paste used to form the buffer material layer 16 includes a metal component, a resin component, a solvent component, etc., and the metal components include Ag, Ni, Cu, and Ag/Cu.
etc.

[0014] The resin component may be epoxy, phenol, etc., but any resin may be used as long as it has heat resistance, plating resistance, and adhesion.

The above-mentioned method for forming the buffer material layer 16 may be selected as appropriate, such as a dipping method, a brush coating method, a roller method, etc., and the formed buffer material layer 16 is cured by a method suitable for the material. For example, the internal electrode 11 and the extraction electrode 1
If 5 is made of a base metal, a method that takes into account the oxidation prevention of the base metal may be used.

[0016] Also, a plating layer 17 to be provided on the surface in a later process.
In order to stabilize the plating adhesion of the resin, it is necessary to control the resin thickness and sufficiently suppress fluctuations in the curing conditions.

Further, by forming the buffer material layer 16 so as to cover the entire surface of the extraction electrode 15 so that it is not exposed, deterioration of the characteristics due to the plating layer 17 can be prevented.

The formation of the plating layer 17 described above can be carried out either wet or dry, but from the viewpoint of mass production, a wet method using a barrel or the like is preferable, and a two-layer structure as shown in the figure improves heat resistance and adhesion to solder. improves.

The external electrode of the present invention has the above-described structure, and the laminated LC filter is mounted on the circuit board by soldering the plating layer 17 of the external electrode 14 to the pattern, and in this mounted state, the circuit board is mounted. When a deflection test is performed, the buffer material layer 16 acts as a mechanical buffer and alleviates the propagation of deformation stress to the ceramic laminate 13 during deflection.
This prevents the laminate 13 from being destroyed.

Furthermore, since the buffer material layer 6 covers the entire surface of the extraction electrode 15, it is possible to prevent the plating solution from penetrating into the ceramic laminate 13 during the formation of the plating layer 17. Electrode 11 and ceramic dielectric 12
Poor adhesion can be suppressed, thereby improving reliability and preventing cracks in the ceramic dielectric 13 due to thermal shock.

Furthermore, since the buffer material layer 16 reduces the thermal conductivity of the external electrode 14 due to its heat insulating properties, heat propagation to the internal electrode 11 during solder immersion is reduced, and the internal electrode 1
It is possible to suppress destruction of the ceramic due to thermal shock at the interface between the ceramic dielectric 1 and the ceramic dielectric 12.

In the illustrated embodiment, a laminated LC filter block is shown in which a plurality of external electrodes 14 are provided on both sides, but the external electrodes 14 can be used not only for such electronic components but also for example, for It can also be used in single unit or block multilayer chip capacitors.

[0023]

As described above, according to the present invention, a buffer material layer using conductive paste is formed on the surface of the extraction electrode that is electrically connected to the internal electrode so as to cover the entire surface of the extraction electrode,
Since a plating layer is provided on the outer surface of this buffer material layer, the intermediate buffer material layer of the external electrode acts as a mechanical buffer layer, and prevents deformation stress caused by bending from being applied to the chip-type electronic component body during mounting on a circuit board. It is possible to alleviate the propagation and prevent the occurrence of destruction of the chip-type electronic component body.

[0024] Furthermore, since the thermal conductivity of the external electrode is reduced by the buffer material layer, heat propagation to the lead electrode and internal electrode during soldering is reduced, and thermal shock damage at the interface between the internal electrode and the ceramic can be suppressed. .

Furthermore, since the buffer material layer covers the entire surface of the extraction electrode, it is possible to suppress the plating solution from penetrating into the inside of the extraction electrode when forming the plating layer, and there is no occurrence of poor adhesion between the internal electrode and the ceramic, and heat is prevented. It can prevent cracks in ceramics due to impact and improve the reliability of chip-type electronic components.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing an external electrode according to the present invention.

FIG. 2 is a partially cutaway side view of an external electrode according to the present invention.

FIG. 3 is a perspective view showing a state in which chip-type electronic components are mounted.

FIG. 4 is a longitudinal sectional front view showing a conventional external electrode.

FIG. 5 is an explanatory diagram showing the state of a deflection test of a chip-type electronic component.

FIG. 6 is an explanatory diagram showing a state where a crack has appeared in ceramic.

[Explanation of symbols]

11 Internal electrode 12 Ceramic dielectric 13 Ceramic laminate 14 External electrode 15 Extraction electrode 16 Cushioning material layer 17 Plating layer 18 Inner layer 19 Outer layer

Claims (1)

[Claims] 1. An extraction electrode that is electrically connected to the internal electrode is provided on the outside of the chip-type electronic component body, and a buffer layer using conductive paste is formed on the surface of the extraction electrode so as to cover the entire surface of the extraction electrode, A chip-type electronic component characterized in that a plating layer is provided on the outer surface of the buffer material layer.