JPH10275548A - Electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent heating of a protective component itself from being influ enced by an operating temperature by constituting an external electrode exposed to the outside by a material free of solder eating and constituting the external electrode and an internal electrode connecting an internal electronic element of a chip body with each other by a material of its electric resistance rate smaller than the external electrode. SOLUTION: Solder eating is prevented by mounting an external electrode 3a by a re-flow solder or using an Ag-Pd alloy for the external electrode 3a. Since an end exposed to the outside of an internal electrode 2a formed of Ag or Cu is covered with an Ag-Pd alloy film 3b, Ag or Cu is never directly contacts a solder, and this part is never solder eaten. A majority of the external terminal 3a is covered with a solder during mounting to a substrate, an Ag-Pd alloy is not almost useful, a specific resistance is high through connection with the outside of an electronic part 1, and there is no problem. Since the internal electrode 2a is lowly resistive, even a protective part of a temperature sensor such as thermal fuse itself does not influence an operating temperature by heating itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component to be soldered to a printed circuit board, and more particularly to an electronic component free from solder erosion.
The present invention relates to an electronic component having an electrode structure with a small electric resistivity.

[0002]

2. Description of the Related Art A conventional electronic component will be described with reference to the drawings. FIG. 5 is a cross-sectional view of a thermal fuse as one of the conventional electronic components 10. On both surfaces of the ceramic chip substrate 10a, a pair of metal thin films 20, 20 are adhered from both sides in the longitudinal direction in a U-shaped cross section, and one end of one surface is connected to the internal electrodes 20a, 20a. One end of the surface is an external electrode 20b. The material of the metal thin films 20, 20 is made of an Ag-Pd alloy. Then, the substrate chip 10a and the frame-shaped substrate 10
b are stacked and fired into a box shape, and internal electrodes 20a, 20a are formed on the inner bottom surface of the box from both sides of the frame-shaped substrate 10b.
Is exposed. A fusible alloy, which is the electronic element 50, is bridged and fixed to the internal electrodes 20a, 20a. The periphery of the fusible alloy in the box is filled with the flux 60, and the lid 70 of the insulator is bonded with an adhesive.

This thermal fuse is connected to external electrodes 20b and 20b.
b is soldered to a printed circuit board of an electronic device and connected in series to a current circuit. When heat generation abnormality occurs in the electronic device to which the thermal fuse is attached, the heat is transmitted to the thermal fuse, and the viscosity of the flux 60 surrounding the fusible alloy 50 in the box is reduced and fluidized. In addition, the fusible alloy 50 heated by the heat reacts with the flux 60 to promote melting, and becomes spherical due to surface tension in the liquid of the flux 60 in the box. And cut off the circuit.

To mount an electronic component on a printed circuit board or the like, external electrodes are soldered by reflow soldering, and an Ag-Pd alloy is generally used as an electrode material of the electronic component. The specific resistance of this Ag-Pd alloy is large, and the total resistance of the protection component reaches 100 mΩ or more. on the other hand,
When Ag or Cu alone is used, the specific resistance is low and the total resistance of the protective component is less than 10 mΩ. It is not used because it causes poor attachment.

[0005]

However, the Ag-Pd alloy conventionally used has a high specific resistance when used as an electrode material for a protective component for sensing temperature such as a temperature fuse. It is not preferable because the heat generated by the protection component itself affects the sensed temperature. However, the use of Ag alone or Cu alone is problematic in that the solder is easily eroded and oxidized as described above, and is difficult to use.

In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a semiconductor device, in which, among the electrodes of the chip body, the external electrodes exposed to the outside are made of a material which is not eroded by solder. The internal electrode electrically connecting the electronic element provides an electronic component made of a material having a lower electrical resistivity than the external electrode.

In addition, the connection between the external electrode and the internal electrode provides an electronic component in which the internal electrode is covered with the external electrode and connected at the upper end of the chip substrate on which the electronic element is mounted. Further, the present invention provides an electronic component, wherein the electronic element is a fusible alloy that melts at a specific temperature and cuts off a current supplied to the electronic component. Also, the present invention provides an electronic component in which the external electrode is an Ag-Pd alloy and the internal electrode is Ag or Cu.

[0007]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a thermal fuse according to an embodiment of the electronic component 1 of the present invention. A pair of metal thin films 2 and 2 made of a single metal of Ag or Cu are deposited on both sides of the upper end of the ceramic chip substrate 1a, and Ag-Pd alloy is formed on both sides and side surfaces of the lower end of the chip substrate 1a. Metal thin films 3, 3 are applied. The contact portion between the metal thin film 2 and the metal thin film 3 at both ends of the upper end of the chip substrate 1a is shown in FIG.
As shown in the figure, the metal thin film 3b is further coated with the same Ag-Pd alloy.

A chip substrate 1a and a frame-shaped substrate 1b on which these metal thin films are applied in a U-shaped cross section from both sides are superposed and fired to form a box-shaped chip body 4. The portions where the metal thin films 2 and 2 are exposed inside the chip body 4 become the internal electrodes 2a and 2a, and the fusible alloy as the electronic element 5 is cross-linked and connected. The periphery of the fusible alloy 5 is filled with a flux 6, and the chip body 4 is sealed with an insulator lid 7. The metal thin film 3 exposed to the outside of the chip body 4 is soldered to a printed board or the like as external electrodes 3a, 3a.

FIG. 3 is a perspective view of the chip substrate 1a before being divided. In manufacturing the chip substrate 1a, as shown in step (a) of FIG. 4, first, a connecting plate of a ceramic green sheet is formed, and a dividing groove 8a and a through hole 8 are formed at the boundary.
b is formed. As shown in step (b), a paste of Ag-Pd to be the external terminals 3b is applied to one surface and lower end of the green sheet by screen printing, and further formed on the chip substrate 1a as shown in step (c). Through the through hole 8b from the opposite side
Is applied with Ag-Pd paste. A ceramic green sheet coated with this paste is heated to 120 ° C.
And solidify the paste. Next, a paste of Ag or Cu to be the internal electrodes 2a is applied to the other surface of the green sheet by screen printing, and dried at 120 ° C. to solidify the paste. By this application, the Ag-Pd paste and the Ag or Cu paste are brought into contact with each other, and conduction is established.

Further, as shown in the step (e), a paste of Ag-Pd is applied by screen printing from the end of the through hole of the chip substrate 1a on this surface to about 3 mm,
The Ag or Cu paste and the Ag-Pd paste at the end of the side surface of the through hole are further contacted with Ag.
-Pd paste is applied repeatedly to ensure conduction. Next, this was fired in an oven at 880 ° C. for about 1 hour,
A metal thin film having a thickness of 0 to 20 μm is formed. In the steps up to this point, the chip substrate 1a has the Ag or Cu metal thin film 2 on one surface, the Ag-Pd alloy metal thin film 3 on one surface,
Further, a metal thin film having a U-shaped cross section is formed by the portion 3b in which Ag or Cu is covered with the Ag-Pd alloy thin film.

The connecting plate of the chip substrate 1a and the frame-shaped substrate 1
The connecting plate b is stacked and fired, and a connecting plate of a box-shaped ceramic substrate is completed. Chip substrate 1a in the box
The fusible alloy 5 is cross-linked to the upper internal electrodes 2a, 2a and fixed with solder or a conductive adhesive. And this fusible alloy 5
Is filled with a flux 6 and an insulating lid 7 is bonded with an adhesive. Next, these are divided into the dividing groove 8a and the through hole 8
The electronic component 1 is completed by dividing by b.

When the electronic component 1, which is a protective component such as a thermal fuse, is mounted on the printed circuit board 9, the external electrodes 3a and 3a are soldered by reflow soldering. Since the Pd alloy is used, no solder erosion occurs. Ag or C
Since the ends of the internal electrodes 2a, 2a formed of u which may be exposed to the outside are covered with the Ag-Pd alloy metal thin film 3b as shown in FIG. 2, Ag or Cu directly contacts the solder. And solder erosion does not occur in this portion. In addition, as shown in FIG. 4, most of the external terminals 3a of the electronic component are covered with the solder 11, and the high resistance A
Since the g-Pd alloy hardly contributes, the electronic component 1
There is no problem because the specific resistance is high due to the connection with the outside. Since the internal electrodes 2a and 2a are formed of Ag or Cu, the specific resistance is low and the total resistance of the protection component is 10m.
Even if it is a protection component that works by sensing the temperature, such as a thermal fuse, it does not affect the operating temperature due to the heat generated by the protection component itself.

[0013]

As described above, when the electronic component of the present invention is mounted on a printed circuit board, the portion that comes into contact with the solder is formed of an Ag-Pd alloy thin film, so that solder erosion does not occur. , And the internal terminal is Ag or Cu
, The specific resistance is low and good connection with the electronic element is possible, and the operating temperature is not affected by the heat generated by the protection component itself.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electronic component according to the present invention.

FIG. 2 is an enlarged view of an electrode part of the present invention.

FIG. 3 is a perspective view of the connecting board of the chip substrate 1a of the present invention before being divided.

FIG. 4 is a manufacturing process diagram of the connecting plate of the chip substrate 1a of the present invention.

FIG. 5 is a sectional view of mounting the electronic component of the present invention on a printed circuit board.

FIG. 6 is a sectional view of a conventional electronic component.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electronic component 1a chip substrate 2a internal electrode 3a external electrode 3b part of internal electrode covered with external electrode 4 chip body 5 electronic element (soluble alloy)

Claims (4)

[Claims] An external electrode which is exposed to the outside among the electrodes of the chip body is made of a material which is not eroded by solder, and an internal electrode for electrically connecting the external electrode and an electronic element inside the chip body is formed of the external electrode. An electronic component made of a material having a lower electrical resistivity than an electrode. 2. The electronic component according to claim 1, wherein the connection between the external electrode and the internal electrode is made by covering the external electrode with the internal electrode at an end on the chip substrate on which the electronic element is mounted. . 3. The electronic component according to claim 1, wherein the electronic element is a fusible alloy that melts at a specific temperature and cuts off a current supplied to the electronic component. 4. The electronic component according to claim 1, wherein the external electrode is an Ag—Pd alloy, and the internal electrode is Ag or Cu.