JPH1050190A - Manufacturing method of chip fuse element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a chip fuse element excellent in surface smoothness. SOLUTION: In the manufacturing method of the chip fuse lelement, a fuse conductor film and terminal electrodes 2a and 2b are formed in the respective element areas of a large sized substrate, after over-coat resin 61 has been formed, which crosses over a dividing groove 12 extended in the longitudinal direction so as to ride across adjacent element areas 10 and 10, the over-coat resin 61 is separated along the dividing groove 12, after that, the large sized substrate is divided so as to be processed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a chip fuse element for protecting a circuit against abnormal current of a predetermined circuit.

[0002]

2. Description of the Related Art As shown in FIG. 7, a chip fuse element has a glass glaze layer formed on a main surface of an insulating substrate 1 and, at the same time, terminal electrodes 2a, 2a and 2b on opposite ends of the insulating substrate 1.
b, a fuse conductor film 3 made of a metal material such as aluminum is formed on the glass glaze layer between the terminal electrodes 2a and 2b, and a glass film 5 is further formed on the fuse conductor film 3. And the overcoat resin 60.

In such a chip fuse element, a blown portion of the fuse conductor film 3 generates heat due to an abnormal current applied between the terminal electrodes 2a and 2b. At this time, the thermal conductivity of the glaze layer is appropriately set so that the generated heat does not excessively escape to the insulating substrate side. Then, due to this heat generation, the fuse conductor film 3 is melted and acts as a fuse. Furthermore, the softened glass film 5 was filled in the blown portion, and high insulation after the blow was maintained.

The chip fuse element is, for example, 1.6 mm
Since it has a chip shape of × 3.2 mm or the like, it is mounted on an automatic mounting apparatus on a printed wiring board, like other chip-shaped electronic components. Specifically, the surface of the element is brought into contact with a suction nozzle of an automatic mounting apparatus, sucked, conveyed to a predetermined position on a printed wiring board, suction is released, and a chip fuse element is arranged.

[0005]

However, in the chip fuse element, it is very important that the fuse conductor film is blown and that the insulating property is stably maintained, especially against an abnormal current. For example, when an excessive abnormal current of several tens of amperes is applied between the terminal electrodes, the energy becomes large, and the fuse conductor film ruptures instead of fusing. In order to prepare for such a situation, the thickness of the odor coat resin 60 is increased, or an elastic film is formed between the glass film 5 and the overcoat resin 60.

For this reason, the flatness of the surface of the overcoat resin 60 is greatly reduced, and as a result, poor suction often occurs when the overcoat resin 60 is mounted on a printed wiring board.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a method for manufacturing a chip fuse element having an excellent overcoat resin surface flatness. is there.

[0008]

According to the present invention, a plurality of square-shaped chip fuse elements are formed in a plurality of square-shaped chip fuse elements by a plurality of vertically extending divided grooves and a laterally extending divided groove. A step of preparing a partitioned large substrate; a step of forming a fuse conductor film extending in a longitudinal direction in each element region of the large substrate; and a step of forming the fuse at both ends in a vertical direction of each element region of the large substrate. Forming a terminal electrode to be connected to the conductive film, and forming an overcoat resin continuously so as to expose the terminal electrode of each element region in parallel with the dividing groove extending in the lateral direction of the large substrate. And separating the overcoat resin on the vertically extending dividing groove, and dividing the large-sized insulating substrate into a laterally extending dividing groove, a vertically extending dividing groove, and a longitudinal direction. Preparative, a method of manufacturing a chip fuse element which comprises.

[0009]

In the chip fuse element of the present invention, the overcoat resin is formed in a series on the large-sized substrate on the side where the terminal electrode is not formed (in the width direction of the insulating substrate) in the adjacent element region. Is done. That is, in the chip fuse element after the division, the overcoat resin is formed over the entire width in the width direction of the insulating substrate.

Accordingly, there is no sagging of the overcoat resin in the width direction, so that the overcoat resin has excellent flatness as a whole, and the adsorption reliability of the element is greatly improved.

In the manufacturing process, particularly in the case of dividing a large substrate, an overcoat resin is formed so as to cover a dividing groove extending in one direction. Is performed, there is no peeling of the overcoat resin in the element region on one side due to the stress at the time of division.

The overcoat resin is preferably separated completely from the overcoat resin, but does not necessarily have to reach the substrate from the surface of the overcoat resin.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a chip fuse element according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a chip fuse element according to the present invention, FIG. 2 is a sectional structural view in a vertical direction (longitudinal direction of a substrate), and FIG. 3 is a sectional view in a horizontal direction (width direction). FIG.

In the figure, 1 is an insulating substrate, 2a and 2b are terminal electrodes, 3 is a fuse conductor film, 4a and 4b are end electrodes, 5 is a low melting point glass film, and 6 is an overcoat resin.

The insulating substrate 1 is made of, for example, alumina ceramic and has a shape of, for example, 1.6 mm × 3.2 m.
m. A glass glaze layer 15 is formed on the surface of the insulating substrate 1. The glass glaze layer 15 usually has a thickness of 10 to 20 μm.
It may be a thickness such as μm.

The fuse conductor film 3 is made of a metal thin film such as Al, extends in the longitudinal direction (one direction) of the insulating substrate 1 and has a very thin central portion to form a fusing portion 3a. The terminal electrodes 2 a and 2 b are connected to each other so as to be connected to both ends of the fuse conductor film 3. The terminal electrodes 2a and 2b are made of an Ag-based thick conductor film, and a part of the surface thereof is plated with Ni, solder or tin as needed.

A low-melting glass film 5 is formed on the fuse conductor film 3, especially on the blown portion 3a, and an overcoat resin 6 is formed on the fuse conductor film 3 including the low-melting glass film 5. Coated.

The low-melting glass film 5 is made of lead borosilicate glass and softens and fills a fusing groove formed by fusing the fuse conductor film 3, thereby providing a high insulating property after fusing. To achieve.

The overcoat resin 6 is made of, for example, an epoxy resin, and is mainly used for improving moisture resistance reliability.
On the insulating substrate 1, on one side (longitudinal direction) side, the end portions of the terminal electrodes 2a and 2b are exposed, and on the other direction (width direction) side, it is formed over the entire width of the insulating substrate 1. ing.

If necessary, an excessive abnormal current may cause the fuse conductor film 3 to rupture between the low-melting glass film 5 and the overcoat resin 6, causing the low-melting glass film 5 to blow off. In order to prevent this, an elastic layer 7 having elasticity such as silicon is disposed.

Further, end face electrodes 4a and 4b connected to the terminal electrodes 2a and 2b are formed on a pair of opposed end face portions in the longitudinal direction of the insulating substrate 1. This end face electrode 4a,
4b is formed by curing a conductive resin containing a conductive metal powder such as Ag, for example.

Next, a method of manufacturing the above-described chip fuse element will be described.

First, a large substrate is prepared in which a dividing groove for dividing a region to be a plurality of chip fuse elements is formed.
The dividing groove is formed such that the dividing groove extending in the vertical direction and the dividing groove extending in the lateral direction cross each other. still,
In order to improve the dividing property, it is desirable to form dividing grooves on both main surfaces of the large-sized substrate. A region formed by two vertically extending divided grooves and two horizontally extending divided grooves is called an element region.

Next, a glass glaze layer 15 is formed on the surface of each element region of the large substrate. Specifically, it is formed by printing and firing a lead borosilicate glass paste, and its film thickness is 10 to 20 μm.

Next, on the surface of each element region of the large substrate, A
1 is formed.

Specifically, deposition of a metal thin film, application of a photoresist film, selective exposure, selective development of a photoresist film, selective etching of an Al thin film, and photolithography by peeling the photoresist film It is formed in a predetermined pattern by a technique.

Next, terminal electrodes 2a and 2b are formed at both ends in the longitudinal direction of the surface of each element region of the large substrate. Specifically, it has a shape that overlaps with the end of the fuse conductor film 3 and reaches the vertically extending dividing groove, and is formed by printing and firing an Ag-based conductive paste. Note that the conductor film may also be formed by burning both end portions in the longitudinal direction on the back surface side of each element region so as to face the terminal electrodes 2a and 2b on the front surface side.

Next, a low-melting glass film 5 is formed so as to cover the fusing portion 3a of the fuse conductor film 3 in each element region of the large substrate. Specifically, it is formed by printing and firing a low melting point glass paste such as lead borosilicate glass. Its film thickness is 10 to 20 μm.

Next, a silicon elastic layer 7 is formed so as to cover the fuse conductor film 3 in each element region of the large substrate.
That is, the silicon elastic film 7 is formed so as to completely cover the low melting point glass film 5. The silicon elastic film 7 is formed, for example, by applying a silicon paste of # 8130 manufactured by Shin-Etsu Co., Ltd., and curing it by heat treatment at 120 ° C. for 1 hour. Its film thickness is 10 to 30 μm.

FIG. 4 shows the large substrate thus far. In FIG. 4, 100 is a large-sized substrate, 11... Are horizontally extending dividing grooves, 12.
.. denotes each element region.

Next, as shown in FIG.
The overcoat resin 61 is formed so as to completely cover the fuse conductor film 3 in each element region and to straddle the adjacent element regions 10 and 10 with the dividing groove 12 extending in the vertical direction as a boundary. That is, the overcoat resin 61 is formed in parallel with the dividing groove 11 extending in the lateral direction so as to expose the terminal electrodes 2a and 2b of each element region 10.

The overcoat resin 6 can be, for example, a thermosetting resin such as an epoxy resin or an ultraviolet curable resin. The overcoat resin 6 is formed by application of an epoxy resin and a predetermined method such as heat treatment or ultraviolet irradiation. This thickness is
For example, it has a thickness of 20 to 50 μm.

Next, as shown in FIG.
Along the dividing groove 12 extending in the vertical direction of the resin, the resin is separated into a continuous overcoat resin 61 formed on the surface thereof.
Specifically, the cutting is performed using a cutting jig (cutter) 13 that matches the shape of the dividing groove 12 extending in the vertical direction.
When the substrate 100 is divided along the division grooves 12 extending in the vertical direction, the continuous overcoat resin 61 is intended to be divided stably.
The overcoat resin 6 is prevented from being excessively removed on one element side adjacent to the boundary 2. Therefore, the cutting depth of this separation is the overcoat resin 6
It is not necessary to separate the overcoat resin 6 over its entire thickness, and a depth sufficient to prevent the above-mentioned overcoat resin 6 from being excessively removed is sufficient.

Next, the primary division processing is performed along the division grooves 11 extending in the lateral direction which divide each element region of the large substrate.
Thus, the large-sized substrate becomes a strip-shaped substrate, and the surfaces on which the end surface electrodes 4a and 4b are formed appear by division.

Next, the end face electrodes 4a and 4b are formed on the divided surface of each element region of the strip-shaped substrate. Thereby, the terminal electrode 2a, the end face electrode 4a, and the terminal electrode 2b in each element region are formed.
And the end face electrode 4b are connected to each other.

Next, secondary division processing is performed along division grooves extending in the vertical direction that divide each element region of the strip-shaped substrate. As a result, each element region is completely divided individually. At this time, since the overcoat resin 6 applied on the vertically extending divisional grooves is already separated along the vertically extending divisional grooves, the overcoat resin 6 is stable along the shape of the element region. Will be divided.

Finally, if necessary, the terminal electrodes 2a, 2a
b and the surfaces of the end face electrodes 4a and 4b
Apply plating, tin or solder plating.

In the above embodiment, the terminal electrode 2
a and 2b are formed immediately after the fuse conductor film 3 is formed. However, after the glass film 5 and the overcoat resin 6 are formed, a conductive resin is applied and cured by heat (about 200 ° C.). No problem.

Further, the overcoat resin 6 is cut before the primary division. This is because it is effective to cut in the state of a large substrate from the viewpoint of productivity. For example, the overcoat resin 6 may be cut after forming a strip-shaped substrate by a primary division process, The overcoat resin 6 may be cut at the same time as the dividing process.

In the chip fuse element manufactured in this manner, the overcoat resin 6 is formed over the entire width of the insulating substrate 1 in the width direction. Accordingly, as compared with the case where the overcoat resin is formed in an island shape in one element region (FIG. 7), there is no sagging around when the overcoat resin 6 is applied. The surface flatness of No. 6 is greatly improved. And
When mounted on a printed wiring board by suction, suction reliability is greatly improved.

[0042]

EXPERIMENTAL EXAMPLE The inventor measured the flatness of the overcoat resin 6 according to the present invention. In the comparative product, an overcoat resin was formed in an island shape on an insulating substrate (element region). In addition, the thickness of the overcoat resin 6 is 40 μm.
And

As shown in FIG. 3, when the width (l) of the region within 4 μm (Δh) from the maximum height of the overcoat resin in the width direction of the substrate (total width L) as shown in FIG. It was represented by L (flatness). In addition, L = 3.2 mm.

As a result, in the product of the present invention, l = 1.4 mm
And the flatness was 0.87. On the other hand, the comparative product had l = 0.3 mm and the flatness was 0.19.

The degree of adsorption (the number of normal mountings / the total number of mountings) in the automatic mounting apparatus on the printed wiring board was 99.9999% for the product of the present invention and 99.7% for the comparative product.

Normally, the degree of adsorption in an automatic mounting apparatus for a printed wiring board is required to be 99.99% or more, but it is much lower than that of a comparative product.

Incidentally, as a result of various studies by the present inventors, in order to achieve 99.99% or more of the adsorption degree, the flatness must be:
It was found that 0.25 or more was required, but it was confirmed that the manufacturing method of the present invention could provide a flatness of 0.25 or more regardless of the thickness of the overcoat resin 6 no matter how the thickness was changed.

In the above-mentioned manufacturing method, Al of the fuse conductor film 3 is a material which is easily oxidized, and the terminal electrode 2
Before the formation of the terminal electrodes 2a and 2b, and during the formation of the terminal electrodes 2a and 2b, an oxide film is formed on the surface of the fuse conductor film 3, so that the terminal electrodes 2a and 2b and the fuse conductor film 3 The connection reliability is reduced.

For this reason, the overcoat resin 6 of the present invention
Are cut by the separation jig, the terminal electrodes 2a, 2b
Of the fuse conductor film 3 and the terminal electrode 2a by pressing the overlapped portion of the fuse conductor film 3 and the terminal electrode 2a. It is important to improve the connection reliability with the second and second wires.

Therefore, if the jig for cutting the overcoat resin 6 of the present invention is used as a jig-shaped cutting / pressing jig having a sharp edge, the cutting of the overcoat resin 6 and the fuse conductor film 3 can be performed. Destruction of the oxide film on the surface can be performed simultaneously.

[0051]

As described above, according to the method for manufacturing a chip fuse element of the present invention, the overcoat resin can be formed with improved smoothness, so that the efficiency of mounting on a printed wiring board is greatly improved. I do.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional structural view of a chip fuse element according to the present invention.

FIG. 3 is a cross-sectional structural view in the width direction of the chip fuse element according to the present invention.

FIG. 4 is a plan view showing main steps of the manufacturing method of the present invention.

FIG. 5 is a plan view showing main steps of the manufacturing method of the present invention.

FIG. 6 is a sectional structural view showing main steps of the manufacturing method of the present invention.

FIG. 7 is a plan view of a conventional chip fuse element.

[Explanation of symbols]

 1 ... Insulating substrate 15 ... Glaze layer 2a, 2b ... Terminal electrode 3 ... Fuse conductor film 4a, 4b ... End face electrode 5 ... .... Low melting point glass film 6 ..... Overcoat resin

Claims (1)

[Claims] A step of preparing a large-sized substrate partitioned into a plurality of quadrangular chip fuse elements by a plurality of vertically extending divisional grooves and a plurality of laterally extending divisional grooves orthogonal to each other; Forming a vertically extending fuse conductor film in each element region of the large substrate; and forming terminal electrodes connected to the fuse conductor film at both longitudinal ends of each element region of the large substrate. A step of forming an overcoat resin continuously so as to expose terminal electrodes of each element region in parallel with the laterally extending divisional groove of the large-sized substrate; and Separating the overcoat resin, and dividing the large-sized insulating substrate into a laterally extending dividing groove, a longitudinally extending dividing groove, and a vertical direction. A method for manufacturing a fuse element.