JPH06244051A - Structure of electrode in electronic part - Google Patents

Abstract

PURPOSE:To prevent cracking due to thermal stress exerted on substrates and chip portions during a mounting process in surface mounted electronic parts such as laminated ceramic chip capacitor. CONSTITUTION:The title electronic part is surface mounted electronic parts 10, such as laminated ceramic chip capacitor, having external electrodes 12 along both its end faces. In such an electronic part the surface of the chip portion between the external electrodes 12 and the ends B of the external electrodes 12 is covered with a solder resist member 13 such as over glass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure for mounting a surface mount type electronic component on a circuit board, and more particularly to an electrode structure for preventing internal damage of the component due to solder connection during mounting.

[0002]

2. Description of the Related Art A conventional surface mount type electronic component such as a monolithic ceramic chip capacitor has been surface mounted on a substrate as shown in FIG. The figure is a sectional side view of a main portion showing the mounting state. In the figure, reference numeral 1 denotes a surface mount electronic component, and as an example, a multilayer ceramic chip capacitor (hereinafter referred to as a chip capacitor) is shown, but it may be a resistor.
Reference numeral 2 is an external electrode provided on both sides of the chip capacitor 1 along the surface thereof, 3 is a dummy dielectric layer, and 4 is an opposing internal electrode connected to the external electrode 2. Reference numeral 5 denotes a circuit board (hereinafter referred to as a substrate), 6 denotes a pad provided on the substrate 5 so as to face the external electrode 2, and the chip component 1 mounts the external electrode 2 on the pad 6 and solders 7 to the substrate 5. Soldered.

[0003]

However, in the conventional chip capacitor mounting structure having the above-described structure, when the chip capacitor 1 is mounted on the substrate 5 by the solder 7, if the temperature changes in the actual use environment, the substrate is 5 and the chip capacitor 1 have different linear expansion coefficients, the thermal stress generated by the difference is concentrated at the boundary A between the end 2a of the external electrode 2 and the dummy dielectric layer 3, and in the worst case, A crack 3a is generated in the arrow direction. Therefore, there is a problem that the chip capacitor 1 has a reduced capacity or the capacitor is peeled off.

The present invention has been made in order to solve the problems of the prior art, and is generated by thermal stress from the interface between the external electrode 2 of the chip capacitor 1 and the dummy dielectric layer 3. It is an object of the present invention to provide an excellent monolithic ceramic chip capacitor having a structure for preventing the cracks 3a.

[0005]

The structure of the present invention for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. The present invention has external electrodes 12 along both surfaces at both ends. In the electrode structure of the monolithic ceramic chip capacitor 10, the surface between the external electrodes 12, 12 including the boundary portion B of the chip portion 11 of the chip capacitor 10 with the end 12a of the external electrode 12 is covered with a solder resist member overglass 13. Is coated with.

[0006]

With the above construction, according to the present invention,
When the laminated ceramic chip capacitor 10 is mounted on the pad 6 of the substrate 5 by soldering, the boundary B between the end 12a of the external electrode 12 and the surface of the dielectric dummy layer 11a is protected by the solder resist member 13 made of overglass. Therefore, it is not soldered. Therefore, since no thermal stress is generated in the boundary portion B and no thermal stress is applied to the inside, no crack is generated and the dielectric 11a is prevented from peeling from the external electrode 12. This eliminates the problem.

[0007]

Embodiments will be described below with reference to the drawings. Figure 1
FIG. 3 is a side sectional view showing an example of an electrode structure of a laminated ceramic chip capacitor used as an example of a surface mount electronic component having electrodes along the surfaces at both ends according to the present invention. In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals, and 10 denotes external electrodes 12, 1 on both ends of the chip part 11.
2 is a monolithic ceramic chip capacitor having substantially the same structure as the chip component 1 described with reference to FIG. 1
Reference numeral 3 denotes a solder resist member made of overglass, and this overglass is used for the external electrodes 12, 12 in the chip portion 11.
The surface between them and the upper surface of the end 12 a of the external electrode 12 are covered. Therefore, when both electrodes 12, 12 of the multilayer ceramic chip capacitor 10 are placed on the pads 6, 6 of the substrate 5 and soldered, the end portions (blank portions) B of the external electrodes 12 are solder resist members as shown in the figure. Since it is covered with the overglass 13, it is not soldered as in the conventional case (see FIG. 2). In other words, the metal compound generation layer formed of Sn of the solder 7 and Ag of the external electrode 12 is not formed here.
Therefore, the tip metal portion of the external electrode 12 related to the thermal stress shifts from the B portion to the C portion, so that the thermal stress generated between the multilayer ceramic chip capacitor 10 and the substrate 5 is concentrated in the arrow C portion and directly. No stress is applied to the ceramic portion of the chip portion 11, and the dummy dielectric layer 11
Since the adhesion strength between a and the external electrode 12 does not decrease,
The end face of the external electrode does not peel off from the dummy dielectric layer 11a. The electrode structure according to the present invention can also be applied to an electrode structure such as a chip type resistor which is also a surface mount type electronic component.

[0008]

As described above, according to the present invention,
Since the end of the electrode of the chip component and its vicinity are covered with the solder resist member, the solder does not adhere to the end of the electrode and the intermetallic compound layer with Sn in the solder is not formed. Therefore, the adhesive force between the dielectric and the electrode end portion of the surface-mounted electronic component body does not decrease. After mounting by soldering, the connection end between the solder and the electrode end moves to the inside rather than the conventional position, so the thermal stress caused by the difference in temperature coefficient between the substrate and the electronic component dielectric is not applied to the electrode end. The effect of not being focused occurs. Therefore, according to this, it can be expected that the thermal shock life of the surface-mounted electronic component, for example, the laminated ceramic chip capacitor is extended and improved. Further, the present invention can be applied to a surface mount type electronic component having a structure in which an electrode end portion and a solder connection end portion coincide with each other.

[Brief description of drawings]

FIG. 1 is a side sectional view of an essential part of an embodiment of the present invention.

FIG. 2 is a side sectional view of a main part of a conventional example.

[Explanation of Codes] 3 Dummy Dielectric Layer 4 Internal Electrode 5 Substrate 6 Pad 7 Solder 10 Multilayer Ceramic Chip Capacitor 11 Chip Part 12 External Electrode 13 Solder Resist Member

Claims (1)

[Claims] 1. In an electrode structure of a surface mount type electronic component having electrodes along both sides of the surface, a surface of the surface mount type electronic component including a boundary portion with the electrode is covered with a solder resist member. Electrode structure of electronic parts characterized by the above.