JPH10134695A - Chip fuse and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the insulating property after fusion, miniaturize a fuse, and improve mass productivity by sealing a fuse element made of a soluble fine wire conductor, suspended between two electrode pads on an insulating substrate, and having a space around it with a resin. SOLUTION: Conductive members are filled in recesses penetrated in the thickness direction on both long side faces of a heat-resistant insulating substrate 2 made of an alumina ceramic or the like to form terminal electrodes 4a, 4b, and they are suitable for surface packaging. Two electrode pads 3a, 3b are formed in both width directions on the surface of the substrate 2, and they are connected to the terminal electrodes 4a, 4b. The terminal electrodes 4a, 4b and the electrode pads 3a, 3b are formed by the baking of a silver paste. A fuse element 5 made of a fusible conductor fine wire of aluminum having the prescribed size is suspended astride the electrode pads 3a, 3b. A fusion space 6 is formed around the fuse element 5, and it is covered with a seal body 7 such as a thermosetting porous resin. The fused fuse element 5 is scattered in the space 6 for complete insulation, and it is unnecessary to connect two substrates 2 with the seal body 7.

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 a surface mount type and a method of manufacturing the same.

[0002]

2. Description of the Related Art Chip fuses are widely used as protection elements against abnormal currents in various electronic circuits.

In general, in a chip fuse, a fuse element is formed of a thin conductor wire or a conductive film, and in any case, the conductor of the fuse element is considered in consideration of an abnormal current to be blown and a melting point of a conductive material constituting the fuse element. The portion was set to have a predetermined resistance. That is, when an abnormal current is applied to the fuse element, the fuse element generates heat due to Joule heat, and the heat melts the conductor material of the fuse element itself.

[0004] In such a fuse, it is important to blow out an abnormal current for a rated time, maintain high insulation properties after blowing, and prevent the occurrence of sparks and the like. For example, when using a conductor film of a predetermined metal for the structure of the fuse element, it is necessary to cover the fuse element with a glass material having a melting point lower than the melting point of the conductor film. When a thin wire is used for the fuse element, it is necessary to form a sufficient space around the thin wire.

Recently, there has been a demand for a chip fuse having a structure corresponding to surface mounting so that it can be mounted on a predetermined printed wiring board by a solder reflow method together with other electronic components.

[0006] The structure of such a surface mount type chip fuse is similar to a conventional chip resistor when a conductor thin film is used for a fuse element, and 2 mm when a thin wire is used for a fuse element. A concave portion is formed at the center of the joining surface of the two substrates that can be divided, and a thin wire is sandwiched between the two substrates and joined, and then terminal electrodes are formed at the ends of the two substrates connected to both ends of the thin wire. Was.

[0007]

The surface mount type chip fuse using a fine wire for the fuse element does not make the space around the fine wire formed by the concave portion sufficiently large in order to maintain the insulation characteristics after fusing. At the same time, there is a demand for a smaller external shape and lower cost.

However, in the conventional structure in which two substrates are joined to each other, when a thin line is sandwiched between two substrates, the thin line is not positioned at the center of the space around the thin line depending on the positioning, and the melt is scattered. Insufficient spacing can be maintained between the conductive material and the remaining portion of the fine wire, and dielectric breakdown such as sparks may occur.

In addition, since a thin wire is sandwiched between two substrates, it is difficult to reduce the size.

Furthermore, the number of parts is large, and the production becomes very complicated, which is not suitable for mass production. As a result, low cost cannot be achieved.

The present invention has been devised in view of the above-mentioned problems, and has as its object the purpose of being able to reliably form a space around a fuse element, to stabilize insulation characteristics after fusing, and to reduce the size. Accordingly, it is an object of the present invention to provide a surface mounting chip fuse excellent in mass productivity and a method of manufacturing the chip fuse.

[0012]

According to a first aspect of the present invention, there is provided a chip fuse using a fusible conductor thin wire for a fuse element. The chip fuse includes two electrode pads formed on a surface of an insulating substrate, and is connected to the electrode pads. An insulating substrate having a terminal electrode formed in a concave portion extending in a thickness direction of a side surface, a fuse element bridged between the two electrode pads and formed of a fusible thin wire conductor, and a space provided around the fuse element. And a resin sealing body formed on the surface of the insulating substrate.

Further, a second invention is a method of manufacturing a chip fuse element according to the first invention, which has a plurality of insulating substrate regions, and has two electrode pads on a surface in each of the insulating substrate regions.
A step of preparing a large-sized insulating substrate having a via-hole conductor formed by filling a conductive member into a through-hole formed over an adjacent insulating edge substrate region and having a via-hole conductor connected to the electrode pad; Between the electrode pads of each of the insulating substrate regions,
A step of bridging a fuse element made of a fusible wire conductor by bonding connection, a step of coating the fuse element with wax, and a step of forming a thermosetting resin on the large-sized insulating substrate so as to cover the fuse element coated with wax. A step of applying a porous resin; a step of heating and curing the thermosetting porous resin; and a step of absorbing the wax into the thermosetting porous resin to form a space around a fuse element; Absorb the substrate and the wax,
Cutting the cured resin and dividing it into individual chip fuse elements.

[0014]

The chip fuse according to the first invention has a structure very suitable for surface mounting since terminal electrodes are formed on the side surfaces of the insulating substrate.

An electrode pad connected to the terminal electrode is formed on the surface of the substrate.
A fuse element composed of a fusible conductor thin wire is directly provided, and a fusing space is formed around the fuse element. Therefore,
When the fuse element is blown from the fusible conductive wire, the fuse element scatters in the blown space, and complete insulation characteristics are obtained.

Furthermore, since the resin sealing body is formed by applying and curing a resin on an insulating substrate, there is no need to join two substrates as in the conventional case, so that miniaturization is possible and very production is possible. Performance will be improved.

Accordingly, a chip fuse for surface mounting which has stable insulation characteristics after fusing, can be miniaturized, and has excellent mass productivity.

The second invention is a manufacturing method for achieving the first invention (chip fuse). In particular, since it can be manufactured based on a large substrate from which a plurality of insulating substrates are extracted, the production method The properties are very good.

Further, the terminal electrodes are formed in a state of a large-sized substrate, and appear on the side surface of the insulating substrate by being cut in the final step. Therefore, since the terminal electrodes appearing on the side surfaces of the substrate are not contaminated by the resin or the like, the reliability of surface mounting is greatly improved.

Further, the fuse element, which is a fusible conductor thin wire, has a stable structure and can be easily formed because the electrode pad on the substrate surface is erected by bonding.

Furthermore, since the fusing space around the fuse element is coated with wax and absorbed by the resin sealing body during thermosetting of the resin sealing body, the fusing space can be easily and reliably formed. Can be.

Further, since the resin sealing body can be applied on a large-sized substrate at a time and cured by heat, it can be formed with very high productivity and easily.

As described above, according to the manufacturing method of the present invention, a method for manufacturing a chip fuse which has stable insulation characteristics after fusing, can be miniaturized, and is compatible with surface mounting at low cost.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a chip fuse and a method of manufacturing the same according to the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of the chip fuse of the present invention. FIG. 2 is a plan view in a state where the resin sealing body is omitted.

In the chip fuse 1 shown in FIGS. 1 and 2,
Reference numeral 2 denotes a heat-resistant insulating substrate such as an alumina ceramic substrate, and reference numerals 3a and 3b denote electrode pads on the upper surface of the substrate 2,
4a and 4b are terminal electrodes, 5 is a fuse element made of a fusible conductive wire, 6 is a fusing space, and 7 is a resin sealing body. still,
On the back surface of the substrate 2, lower surface terminal electrodes 8a, 8b connected to the terminal electrodes 4a, 4b may be formed.

The insulating substrate 2 has concave portions 41 formed on both sides of the long side of the substrate 2 in the thickness direction of the substrate 2, and terminal electrodes 4 a, 4 b filled with a conductive material in the concave portions 41.
Are formed. On the surface of the substrate 1, two electrode pads 3a, 3b connected to the terminal electrodes 4a, 4b are formed.

The two electrode pads 3a and 3b are, for example,
It is formed so as to spread in both directions in the width direction of the substrate 2 and is connected to the terminal electrodes 4a and 4b. Although four terminals are formed on the substrate 2, terminal electrodes having the same function are denoted by the same reference numerals. The number of terminals may be at least two, and in this case, the terminals may be formed on the side surface in the longitudinal direction of the substrate 2.

The electrode pads 3a, 3b, the terminal electrodes 4a, 4
b is formed by baking a conductive paste such as silver (Ag). The surfaces of the terminal electrodes 4a and 4b are
Is the same as the side surface. For example, when the shape of the concave portion 41 is large, a conductive film such as Ag may be attached to the inner wall surface, and may be further filled with a conductive member such as solder.

The fuse element 5 composed of a fusible conductive wire is
It is made of a thin wire such as aluminum and has a thickness of, for example, 1
0 μm, which is selected according to the current capacity, and is provided so as to extend over the two electrode pads 3a and 3b. Specifically, it is installed using a wire bonding method. Further, the fuse element 5 which is a thin wire is 2
More than one electrode pad 3a, 3b may be provided.

A fusing space 6 is formed around the fuse element 5 composed of such a fusible conductor, and is covered with a resin sealing body 7. The fusing space 6 secures an area where the thin wire scatters when the fuse element 5 made of the fusible conductive wire is heated and blown. This fusing space 6
Is formed by applying wax around the fuse element 5 and absorbing it in the resin sealing body 7 during the manufacturing process.

The resin sealing body 7 is based on a thermosetting resin such as a phenolic resin, and has alumina ceramic powder added thereto so as to be porous. Thereby, the resin sealing body 7 becomes a thermosetting porous resin body.

The resin sealing body 7 will be described in detail in a later-described manufacturing method. However, since the resin sealing body 7 is applied collectively on a large substrate which can be divided and extracted so as to become the substrate 2 and is thermally cured, a fusing space is provided. 6 are adhered integrally to the surface of the substrate 2 except for the surface electrodes of the terminal electrodes 4a and 4b which appear on the surface of the substrate 2.

The chip fuse 1 having the above structure is
Since the fuse element 5 composed of the fusible conductor thin wire is covered with the resin sealing body 7 having the fusing space 6, stable insulation characteristics can be maintained even after the fuse element 5 is melted by heat and the thin wire scatters. . In addition, in the relationship between the fuse element 5 and the fusing space 6, since the resin sealing body 7 having the periphery of the fusing element 5 covers almost the center of the fusing space 6, the fusing element 5 is thermally blown (the fusing of the element 5). In the case of scattering, a region where the flying object scatters is secured.

Further, since the terminal electrodes 4a and 4b are well exposed from the side surfaces of the substrate 2 and are flush with the side surfaces, the chip fuses 1 can be stably mounted on the printed wiring board. Can be implemented.

In addition, instead of using a structure in which a fuse element formed of a thin line of a fusible conductor is sandwiched and two substrates are joined, a resin sealing body 7 formed directly by applying and curing a resin on the substrate 2 is used. Therefore, the number of components required for assembly is small, and the shape of the resin sealing body 7 can be approximated to the shape including the fuse element 5 made of a fusible conductor fine wire and the fusing space 6. Can be downsized.

In order to improve the reliability of surface mounting on the printed wiring board, the terminal electrodes 4
The lower surface terminal electrodes 8a and 8b connected to a and 4b may be formed. Further, the shape of the concave portion 41 on the side surface of the substrate 2 is not limited to a substantially semicircular shape in plan view, and may be a semi-elliptical shape, a rectangular shape, or the like. What is important in the terminal electrodes 4a and 4b is that the conductive member is filled and arranged in the concave portion 41,
The surface of the terminal electrodes 4a and 4b forms the same plane as the side surface of the substrate 2.

Next, a method for manufacturing the chip fuse of the present invention will be described.

The method for manufacturing a chip fuse of the present invention uses a large substrate as shown in FIG. 3 as a base.

In FIG. 3, reference numeral 100 denotes a large-sized substrate. The large-sized substrate 100 is formed so as to extract a plurality of insulating substrates 2. In addition, in the figure, while the dotted line part shows the part which is finally divided or cut,
The area (element area) of each chip fuse is partitioned.

The large-sized substrate 100 is, for example, a ceramic substrate made of alumina or the like having a through-hole serving as a concave portion 41 at a boundary portion of each region. A conductive paste such as Ag is printed and baked in the through-hole. Via hole conductor 4
0 is formed. At the same time, electrode pads 3
a, 3b, if necessary, the lower surface electrodes 8a, 8b are printed,
It is formed by baking. In addition, such a large substrate 100
FIG. 4A is a partial cross-sectional view of FIG. Here, the via-hole conductor 40 is a through-hole such that a conductive member such as Ag connects the electrode pads 3 a and 3 b formed on the upper surface of the substrate 100 to the lower electrodes 8 a and 8 b on the lower surface of the substrate 100. Refers to the state of being filled in. In addition, the terminal electrode 4
In order to obtain a relatively large exposed area on the side surfaces of the substrate 2a and 4b, it is advantageous to increase the opening diameter of the through hole. There is. In this case, the conductor member can be formed only on the inner wall surface of the through-hole, and further, the hollow portion of the through-hole is filled with a conductive member such as solder. As a result, the via-hole conductor 40 in the large-sized substrate 100 has the through-hole completely closed.

In addition, simultaneously with the formation of the electrode pads 3a and 3b, electrodes for mounting other circuit elements such as capacitors and resistors are formed in each element region of the large-sized substrate 100, and then the capacitor is formed by a thick film method. , A resistor may be formed.

Next, as shown in FIG. 4B, a fuse element 5 composed of a fusible conductive wire is arranged and bonded between the electrode pads 3a and 3b in each area of the large-sized substrate 100. Specifically, both ends of the fuse element 5 made of a fine soluble wire are bonded to the corresponding electrode pads 3a and 3b.

Next, as shown in FIG. 4C, the fuse element 5 composed of the fusible conductor thin wire in each region of the large substrate 100 is formed.
The wax 61 is supplied to at least the blown portion of the fuse element 5 made of a fine conductive wire. Specifically, the wax 61 is dropped and supplied using a dispenser or the like such that the wax 61 adheres to the periphery of the fusible conductor thin wire that is the fuse element 5.

Further, a jig (not shown) for collecting the resin is attached to the outer periphery of the large-sized substrate 100, and the resin 70 which becomes the resin sealing body 7 is collectively filled in each region on the upper surface of the large-sized substrate 100. Specifically, the resin 70 is filled to such an extent that at least the fuse element 5 to which the wax 61 is attached is completely buried. The resin 70 is obtained by adding a heat-resistant inorganic filler such as alumina to a phenolic resin having a thermosetting property, for example, to further impart a porous property.

Next, as shown in FIG. 4D, the filled resin 70 is heat-treated, for example, heated at 200.degree. As a result, the resin 70 is hardened, and at the same time, the wax 61 applied around the fuse element 5 composed of the fusible conductor thin wire is melted and absorbed by the porous micropores of the resin 70. As a result, the resin 70 becomes the resin 71 in a cured state, and the fusing space 6 is formed around the fuse element 5 formed of the fusible conductor thin wire.

Finally, as shown in FIG. 4E, the large substrate 100 and the cured resin are cut and separated by slicing or wire cutting according to the shape of the fuse 1 composed of individual soluble conductor fine wires. Do.

At this time, from the cut surface of the large substrate 100, 2
One of the divided via-hole conductors 40 appears, and the terminal electrodes 4a and 4b having the same plane as the side surface of the substrate 2 are formed. After cutting, terminal electrodes 4a, 4b, lower surface electrode 8
Electroless plating of Ni or Sn may be collectively applied to a and 8b as needed.

In the above-described manufacturing method, first, using the large substrate 100, the constituent members of the chip fuse 1 are
Since there is no need to hold the substrate between two substrates, and the substrates can be manufactured collectively, the productivity is extremely excellent.

The terminal electrodes 4a and 4b are in a state in which the conductive members are completely filled in the through holes in the large-sized flat substrate 100, and the terminal electrodes 4a and 4b appear by cutting in the final cutting step. Will be. Therefore,
As shown in FIG. 4C, even if the resin 70 or the like is applied to the entire large substrate 100, it does not adhere to the surfaces of the terminal electrodes 4a and 4b at all. In the case of surface mounting, the mounting reliability is dramatically improved, and the formation of the resin sealing body 7 can be particularly easily performed.

Further, since the resin sealing body 7 covering the fuse element 5 is formed by applying and curing the sealing resin and cutting the whole, the substrate having the concave portion formed at the center is joined as in the conventional case. There is no need for sealing, and the resin sealing body 7
Since the inside fusing space 6 and the terminal electrodes 4a and 4b are formed, there is no need to provide a marginal dimension for the substrate 2, and the overall shape of the chip fuse 1 can be made very small.

[0052]

As described above in detail, according to the chip fuse of the present invention, a concave portion is provided on the side surface of the substrate, and the conductive member serving as the terminal electrode is previously filled in the concave portion. Becomes unnecessary.

Further, since the resin sealing body has the same shape as the planar shape of the substrate, and the resin does not flow to the terminal electrodes of the substrate at all in accordance with the manufacturing method, the surface mounting on the printed wiring board is not performed. The reliability is greatly improved.

In addition, a small chip fuse can be obtained without requiring a dimensional margin for the formation of the terminal electrode, the formation of the fusing space, and the sealing structure.

Further, since a portion constituting a chip fuse can be formed in a plurality of chip fuse element regions in common and collectively on a large substrate before the resin sealing body is individually cut. This is a method of manufacturing a chip fuse element having high reliability.

In addition, a via-hole conductor which is a terminal electrode having a through-hole filled with a conductive material is already formed on a large-sized substrate, and becomes a terminal electrode for the first time when cut into the shape of an individual chip fuse element. This is a manufacturing method in which the formation of the electrodes is very easy, the manufacturing is easy, and the mounting reliability is greatly improved.

A chip fuse element having high reliability in sealing a fuse element made of a fusible conductor fine wire, high reliability in surface mounting on a printed wiring board, and extremely high productivity, and a method of manufacturing the same. Become.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a chip fuse element of the present invention.

FIG. 2 is a plan view of the chip fuse element of the present invention in a state where a resin sealing body is omitted.

FIG. 3 is a plan view of a large substrate used in the method for manufacturing a chip fuse element of the present invention.

FIGS. 4A to 4E are partial cross-sectional views illustrating a method for manufacturing a chip fuse element of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Chip fuse 2 ... Substrate 3a, 3b ... Electrode pad 4a, 4b ... Terminal electrode 5 ... Fuse element made of fusible conductor thin wire 6 ... Fusing Space 7 ···· Resin sealing body 8a, 8b · Lower electrode 100 ··· Large substrate

Claims (2)

[Claims] 1. An insulating substrate having two electrode pads formed on a surface thereof, a terminal electrode connected to the electrode pads, and a terminal electrode formed in a concave portion extending in a thickness direction of a side surface, and a bridge between the two electrode pads. A chip fuse comprising: a fuse element made of a fusible thin wire conductor; and a resin sealing body formed on the surface of the insulating substrate by providing a space around the fuse element. 2. A semiconductor device comprising a plurality of insulating substrate regions, two electrode pads on a surface in each of the insulating substrate regions, and a conductive member filled in a through hole formed over an adjacent insulating edge substrate region. Preparing a large-sized insulating substrate having a via-hole conductor connected to the electrode pad and formed, and bonding a fuse element made of a fusible thin-wire conductor between the electrode pads in each of the insulating substrate regions. Erection, a step of covering the fuse element with wax, a step of applying a thermosetting porous resin on the large-sized insulating substrate so as to cover the fuse element covered with the wax, A step of heating and curing the cured porous resin and absorbing the wax into the thermosetting porous resin to form a space around the fuse element; It absorbs wax, cured resin was cut, a manufacturing method of the chip fuse comprising a step of dividing into individual chips fuse element.