JPS6037632A - Thick film fuse and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a thick film fuse and a method for manufacturing the same.

Generally, thick film fuses are made by printing conductive paste on an insulating substrate such as ceramic to form a connecting terminal layer and a fuse layer.
The conductive paste is then fired.

In the above-mentioned thick film fuse, since it is in close contact with the surface of the insulating substrate, there is a problem that even if an overcurrent flows, heat is dissipated and it is difficult to blow out. Furthermore, since the heat dissipation conditions change depending on the shape of the substrate, etc., there is a problem in that there is large variation in the fusing characteristics. Furthermore, the W film constituting the fuse is physically and chemically in close contact with the substrate, making it difficult to confirm the blown state.

To solve these problems, for example, it is possible to suppress heat radiation by interposing a heat insulating layer such as glass between the fuse layer and the substrate, or to locally increase the current density by creating a constriction in a part of the fuse layer. Although it is conceivable that the fusing characteristics can be improved by the following, in either case, the problem of difficulty in confirming the fusing state cannot be solved, and there is also the problem that the substrate temperature increases due to the heat generated during the fusing.

The present invention has been made in view of the above circumstances, and its object is to provide a thick film fuse that has excellent fusing characteristics, allows easy confirmation of the fusing state, and reduces substrate temperature rise during fusing, and a method for manufacturing the same. The goal is to provide the following.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an example of the thick film fuse of the present invention. Reference number 1 in the figure is an insulating substrate made of alumina (Aρ203).
, glass, etc.

Connection terminals 1i-i2v2 are formed on the insulating substrate 1, and a fuse N3 is provided between the connection terminal layers 2, 2.
is formed with a gap 4 between it and the surface of the insulating substrate 10, and the gap 4 serves as an air insulation layer.

The connection terminal layers 2, 2 are formed by laminating a metal layer 6 such as a solder alloy on a conductive base 5 formed on an insulating substrate 1, and have a total thickness of about 100 to 200 μm. Further, fuse N3 is formed only of metal R6, has a thickness of about 60 to 180μ, and a width of connection terminal layer 2,
It is set to approximately one-third of 2. Further, the height of the gap 4 is set to about 20 to 40μ.

Next, an example of the method for manufacturing the above-mentioned thick film fuse is shown in FIGS. 2a and 2b.
This will be explained with reference to FIGS. 6a and 6h.

First, as shown in FIGS. 2a and 2b, a layer of polyimide-based or cermet-based conductive paste is applied to the surface of the insulating substrate 1 at positions that will become the connection terminal layers 2, 2 (see FIG. 1) by means of screen printing. 5 is formed, and then fuse layer 3 (first
Similarly, an epoxy resin base layer 7 is formed at the position shown in FIG.

The pastes forming the conductive paste layer 5 and the resin paste I-kt 7 are both suitable for soldering (adhesion (coating, etc.) of fusible materials).

Furthermore, the paste used to form the resin paste layer 7 is one that can be easily removed by being dissolved with an organic solvent or the like in a subsequent process.

Next, the conductive paste layer 5 and the resin paste layer 7 are hacked together to cover a part of the upper surface and the entire side surface of the resin paste layer 7 (with the covers 8 and 8 attached), as shown in FIGS. 3a and 3b. .

After this, as shown in FIGS. 4a and 4b, the conductive paste layer 5
A metal layer 6 made of a solder alloy or the like is formed on the exposed portion of the resin paste layer 7 by printing, melting, dipping, or the like. As a result, the connection terminal layers 2, 2 formed by laminating the conductive paste layer 5 and the metal layer 6 and the metal 1) f
A fuse N3 consisting of 6 is formed.

After that, remove the covers 8, 8 (see Fig. 5 a, b),
Using a TA/8 agent such as acetone, only the resin paste layer 7 is removed due to the difference in solubility. As a result, Figure 6a
, b, a gap 4 having a shape corresponding to the resin paste N7 is formed between the fuse layer 3 and the surface of the insulating substrate 1.

Next, the action of the thick film fuse will be explained.

When an overcurrent flows through the fuse layer 3, the fuse layer 3 is heated by Joule heat, and thermal energy for blowing is sequentially accumulated. At this time, the fuse N3 uses air as a heat insulating layer, and the connection with the insulating substrate 1 is made through the connection terminal layer 2.
, 2, and there is little heat dissipation due to thermal conduction, so there is also little heat dissipation from the fuse layer 3, and the temperature rises rapidly with the passage of time. Note that the insulating substrate 1 is the fuse M3.
Since it hardly acts as a heat dissipation plate, it is not affected by differences in heat dissipation due to the shape and size of the insulating substrate 1.
＜There is no variation in temperature rise.

Then, when the temperature of the fuse layer 3 approaches the sub-point of the metal layer 6, it melts and becomes ball-shaped due to surface tension and aggregates on the connection terminal layers 2, 2 side.

Therefore, thermal energy for blowing is more likely to be concentrated in the fuse layer 3 than when a constriction is provided to locally increase the current density (the insulating substrate acts as a heat sink). Further, since there is little heat dissipation due to thermal conduction and the insulating substrate 1 is made of alumina or the like, it has a non-combustible structure.

In the present invention, the fusing characteristics can be further improved by providing a constriction in the fuse layer 3 to locally increase the current density.

As explained above, according to the thick film fuse of the present invention, a gap is provided between the fuse layer and the insulating substrate, and the gap is used as an air insulating layer, so it has excellent fusing characteristics and L9 heat dissipation.
It is easy to control the fusing conditions even if the structure has localized current density concentration.In addition, there is little heat dissipation due to thermal conduction, and the temperature rise of the insulating substrate itself can be suppressed, and the circuit The fuse layer can be formed on the same substrate as the circuit as part of the circuit.Furthermore, since the fuse layer aggregates into a ball shape on the connection terminal layer side when blown, the blown can be easily confirmed visually.

Further, according to the method for manufacturing a thick film fuse of the present invention, the resin paste layer is melted and removed by utilizing the difference in solvent resistance of the resin, and an air insulation layer is formed between the fuse layer and the insulating substrate. It is easy to manufacture and does not require high costs. Furthermore, the air insulation layer can be easily changed by changing the thickness of the resin paste layer.

Furthermore, the connection terminal layer has a double structure of a conductive paste layer and a metal layer, and as compared to the case where five metal layers are directly formed on an insulating substrate, adhesive strength is obtained and reliability is improved.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, with FIG. 1 being a perspective view and FIG.
Figures a, b to 6 are process explanatory diagrams consisting of a side view and a plan view illustrating the manufacturing process. G... Insulating board, 2... Connection end 4 layers, 3...
...Used layer, 4...Gap (air insulation layer), 5...Conductive paste 1 layer, 7...
resin paste layer. Patent Applicant Yazaki Sogyo Co., Ltd. Figure 1 Figure 2 (a) (b) Figure 3 Figure 4 8 Procedure Neif↑Author (spontaneous) October 13, 1980 Commissioner of the Patent Office Wakaichisugi 1 Kuchi Husband■, Indication of the case 1982 Patent Application No. 1444.85 34 Relationship with the person making the amendment Patent applicant Address 1-4-28, Mikuchi, Minato-ku, Tokyo Name (68
9) Power 11 Xun Sogyo Co., Ltd. 4, Agent 5, Date of amendment order: Showa, Month, Day 6, Number of inventions increased by amendment

Claims (2)

[Claims] (1) At least one pair of connecting terminal layers provided on an insulating substrate, and a fuse layer provided so as to create a gap between the connecting terminal layers and the insulating substrate, and the gap is filled with air. E(
ltA Hughes. (2) Form a conductive paste layer on the insulating substrate at a position that will become a connecting terminal layer, and also form a resin paste layer that can be removed with a solvent in a subsequent process at a position that will become a fuse layer between the connecting terminal layers, and then A metal layer such as a solder alloy is laminated at a predetermined position on the surface excluding the conductive paste shoulders and the side surfaces of the resin paste layer to form a connection terminal layer and a fuse layer, and then the resin paste layer is dissolved and removed using a solvent. A method for manufacturing a thick film fuse, comprising: forming an air heat insulating layer between the fuse layer and the insulating substrate.