JPH08129950A - Chip fuse - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a chip fuse that does not generate an arc after fusing and has high insulation characteristics. A glass glaze layer 2, a fuse conductor film 3 having a blowout fine detail 3a, and a glass coating layer 4 covering the fuse conductor film 3 are formed on a ceramic substrate 1, and a pair of opposing ends of the ceramic substrate 1 are formed. Terminal electrode 5a,
In the chip fuse formed by forming 5b, the fusing electrode details 3a of the fuse conductor film 3 are formed such that the central width thereof is large and both ends thereof are narrow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip fuse suitable for surface mounting, and more particularly to a chip fuse having excellent insulation characteristics after the fuse conductor film is blown.

[0002]

2. Description of the Related Art Conventionally, a chip fuse having a structure suitable for surface mounting has been proposed as a fuse element used in electronic devices, communication devices and the like.

For example, the chip fuse disclosed in Japanese Patent Laid-Open No. 4-65046 is composed of a ceramic substrate, a fuse conductor film, and two layers of thick film glass formed above and below the fuse conductor film. Has been done. In the above-mentioned chip fuse, the thick glass layer prevents heat from being dissipated, improves the heat storage effect, and has a structure in which the fuse conductor film is blown at a high speed.

Further, as a planar structure, as shown in FIG. 3, terminal electrodes 5a and 5b are formed on both ends of the ceramic substrate 1 on which the glass glaze layer 2 is formed and connected to the terminal electrodes 5a and 5b. As described above, the fuse conductor film 30 having the blowout electrode details 30a was formed, and the fuse conductor film 30 was covered with the glass coating layer 4. Here, the fuse conductor film 30 is formed with a fusing electrode detail 30a having a uniform width that is fused by heat generated by an overcurrent.

What is important about this type of chip fuse is that the fuse conductor film is naturally blown at a high speed, and further, complete insulation characteristics can be maintained after the fuse is blown.

[0006]

However, due to the heat generated by the fuse conductor film 30 due to the overcurrent, the fusing electrode details 30a are formed.
Even if the metal component of the fuse conductor film 30 is gasified or melted out when a part of the fuse is melted, and the surrounding glass 2, 4 or the like reacts or remains, and even after melting. , A slight voltage may cause an arc.

When the distribution of heat generated by the overcurrent in the fusing electrode details 30a having a uniform width is examined, the heat is concentrated in the center of the fusing electrode details 30a of the fuse conductor film 30 and is separated from this central part like ripples. The distribution gradually decreases on concentric circles. Further, since the width of the fusing electrode details 30a that is blown by the heat generation of the overcurrent is uniform, the fusing portion occurs near the central portion of the fusing electrode details 30a where the heat is concentrated, and the heat is concentrated. Fusing groove width is about 5μ
The width becomes extremely narrow as m.

Therefore, due to the fact that the width of the fusing groove is narrow and the like, the metal component of the melted fuse conductor film 30 has an effect, and the arc cannot be completely prevented.

The present invention has been devised in view of the above-mentioned problems, and an object thereof is to sufficiently widen the width of the fusing groove to be fused at the fusing electrode details and to sufficiently fill the fusing portion with glass. The present invention provides a chip fuse that can be filled and that has stable insulation characteristics.

[0010]

In the chip fuse of the present invention, a glass glaze layer, a fuse conductor film having blown electrode details, and a glass coating layer for covering the fuse conductor film are formed on a ceramic substrate, and at the same time, a ceramic is formed. In a chip fuse formed by forming a terminal electrode to which the fuse conductor film is electrically connected at a pair of opposing end portions of a substrate, the fusing conductor film of the fuse conductor film has a wide central portion and wide ends. The chip fuse is formed so as to be narrow.

[0011]

As described above, in the present invention, the details of the fusing conductor film of the fusing conductor film have such a shape that the central width is wide and both end sides are narrow.

That is, the shape of the fusing electrode details is similar to the shape of the heat generation distribution generated in the fusing electrode details.

Therefore, when the fusing electrode details are blown, not only the center of the fusing electrode details but also the heat generation amount of the fusing electrode details is made uniform, and the heat generation amount is uniformly high in the fusing part and its surroundings. Occurs, and the width of the melted fusing groove becomes wider.

As a result, the fusing groove is filled with a sufficient amount of the glass component, high insulation characteristics can be obtained, and the occurrence of arc or the like can be effectively suppressed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The chip fuse of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a plan view of a chip fuse of the present invention, and FIG. 2 is a view showing a cross section taken along the line AA in FIG.

The chip fuse 10 of the present invention comprises a ceramic substrate 1, a glass glaze layer 2, a fuse conductor film 3, a glass coating layer 4, and terminal electrodes 5a and 5b.

The ceramic substrate 1 has a substrate thickness of 0.4 mm.
Made of ceramics such as alumina.

The glass glaze layer 2 is made of PbO.ZnO.
Glass such as lead borosilicate containing B ₂ O ₃ · SiO ₂ can be exemplified, and the surface of the ceramic substrate 1 is 20 to 50 μm.
Is formed with a thickness of. The thermal conductivity of the glass glaze layer 2 is required to be smaller than that of the ceramic substrate 1.

Specifically, the above glass paste is printed and dried using a thick film technique, and then baked at about 1200.degree.

The fuse conductor film 3 is made of, for example, a conductor material such as gold or silver. After printing and drying a metalloorganic paste containing such conductor material (for example, E-3610 manufactured by NE Chemcat), For example, about 80
After forming a conductor film by baking at 0 ° C. for about 1 hour,
Further, after applying an anti-etching resist film by a spin coating method or the like, an exposure process is performed by applying a mask, an unnecessary pattern portion is removed, and then an etching process is performed to form a predetermined shape.

The fuse conductor film 3 has a film thickness of 0.5 to 2 μm.
The length is about m, and the shape is formed so as to extend in the longitudinal direction of the substrate 1 so as to be connected to the terminal electrodes 5a and 5b formed at both ends in the longitudinal direction of the ceramic substrate 1, and the central portion thereof is , Fusing electrode details 3a with uneven width
Are formed. Specifically, the width of the central portion of the fusing electrode details 3a is wide, and the width becomes narrower toward both ends. For example, the width of the central portion of the fusing electrode details 3a is 0.1 to
The width is 0.2 mm, the width of the narrowest portion on both end sides is 0.1 mm or less, and the one side has an arc shape expanding to the outside, and has a substantially elliptical shape as a whole.

The glass coating layer 4 completely covers at least the fused ultrafine portion 3a of the fuse conductor film 3, and is a low melting point glass such as lead borosilicate containing PbO.ZnO.B ₂ O ₃ .SiO _2. Can be illustrated. In particular,
The above glass paste is printed and dried using a thick film technique, and then baked at about 600 ° C. The film thickness is 3
It is about 0 μm.

A plating resistant coating layer may be formed on the surface of the glass coating layer 4. This anti-plating coating layer is
When a plating film is formed in order to suppress solder erosion on the surface of terminal electrodes 5a and 5b, which will be described later, and to improve solder wettability, the fuse conductor film 3 and the glass coating film 4 are formed by a plating solution. This is to prevent deterioration, and for example, overglass mainly containing resin or silica can be exemplified.

The terminal electrodes 5a and 5b are made of Ag or Ag-Pd.
Etc., and is formed over the three surfaces of the ceramic substrate 1 at both ends in the longitudinal direction of the front surface, the end surface, and the back surface. Further, if necessary, a Ni plating layer, a solder plating layer, or the like is formed on the surfaces of the terminal electrodes 5a, 5b for reliability of solder joint (prevention of solder erosion, improvement of solder wettability). .

The conductor films on the surface side of the terminal electrodes 5a and 5b are connected to the fuse conductor film 3. Since the fuse conductor film 3 connected to the conductor film on the front surface side is very thin, it is formed so as to overlap the fuse conductor film 3 after the fuse conductor film 3 is formed, for example.

The back-side conductor film may be formed at the same time when the front-side conductor film is formed, that is, after the fuse conductor film is formed, and may be baked at the same time as the front-side conductor film. Alternatively, before forming the fuse conductor film 3, the conductor film on the back surface side may be formed independently.

When the ceramic substrate 1 is divided and extracted from a large-sized substrate, for example, the conductor film on the end face side is formed by, for example, dividing into strips and then printing and baking the end faces of the conductive paste.

In the chip fuse of the present invention having the above-mentioned structure, when an overcurrent flows in the fuse conductor film 3,
When the fuse conductor film 3 is heated by Joule heat and exceeds the melting point temperature of the fuse conductor film 3, the fuse conductor film 3 is melted and cut.
The shape of the fusing electrode details 3a is similar to the distribution of heat generation, that is, the width of the central portion is wide and both ends are narrow. For this reason, although the heat is concentrated in the central portion of the fusing electrode details 3a, a sufficient heat generating action is generated even in a portion away from the central portion, and the width of the fusing groove is blown. It can be wide enough.

The inventor conducted various experiments under various conditions, that is, various combinations of the thermal conductivity of the substrate, the thermal conductivity of the glass glaze layer, the softening points of the glass glaze layer 2 and the glass coating layer 4, and the like. When the width of the fusing electrode details 3a was made uniform as in the conventional case, the fusing width was 5 μm at the maximum, but in the case where the shape of the fusing electrode details 3a was as described above as in the present invention, It was confirmed that the width of the fusing groove of 10 μm or more could be secured.

Therefore, in the fusing groove of 10 μm or more,
The glass component constituting the glass coating layer 4 is sufficiently softened and flows in, a high insulating property, for example, 10 ¹⁴ Ω or more can be secured, and even if a high voltage such as 500 V is applied after melting, no arc is generated. No chip fuse is obtained.

In forming the fuse conductor film 3 on the glass glaze layer 2, for example, a conductor material made of a conductor material such as gold or silver is used, and the conductor film is formed almost entirely on a metal organic paste containing such conductor material. After that, it is subjected to etching treatment, but this is to prevent the film thickness of the edge portion of the print coating film from being sharply reduced when printed and formed to a predetermined shape with a metal organic paste, A print coating film is formed on almost the entire surface including a predetermined shape to stabilize the film thickness, and the shape accuracy is increased by an etching process.

Therefore, if the film thickness can be made uniform and the printing shape can be made highly accurate only by printing the metal organic paste, the etching process can be omitted.

[0034]

As described above, according to the chip fuse of the present invention, the shape of the blowout electrode details of the fuse conductor film is formed such that the width of the central portion is wide and the widths of both end sides are narrow. However, even if an overcurrent flows and heat is generated, for example, a sufficient amount of heat generation is obtained at both ends of the fusing electrode, and a sufficient amount of heat generation is also generated in the fusing part and its surroundings. Therefore, the width of the blown fusing groove can be sufficiently widened.

For this reason, a glass component and the like can sufficiently enter into the fusing groove, and high insulation characteristics can be maintained, so that the chip fuse does not generate an arc or the like.

[Brief description of drawings]

FIG. 1 is a plan view of a chip fuse of the present invention.

FIG. 2 is a view showing a cross section taken along the line AA in FIG.

FIG. 3 is a plan view of a conventional chip fuse.

[Explanation of symbols]

 10 ... Chip fuse 1 ... Ceramic substrate 2 ... Glass glaze layer 3 ... Fuse conductor film 3a ... Fusing details 4 ... Glass coating layer 5a, 5b ...

Claims (1)

[Claims] 1. A glass glaze layer, a fuse conductor film having fusing details, and a glass coating layer for covering the fuse conductor film are sequentially formed on a ceramic substrate, and a pair of opposing end portions of the ceramic substrate are formed. In a chip fuse formed by forming a terminal electrode to which the fuse conductor film is electrically connected, the blowout electrode details of the fuse conductor film are formed such that the width at the center thereof is wider than the width at both ends. Chip fuse characterized by.