JPH10269928A - Micro-fuse for auto mounting of printed wiring board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable fusion characteristics and obtain high yields with an assembling method suitable to mass-production by bonding fuse elements to lead-frame shaped terminals simultaneously in plurality, sandwiching it between cases of ceramic rectangular insulator of same type at the top and bottom, and bonding them simultaneously through a nitrogen atmosphere furnace. SOLUTION: In a pair of upper and lower ceramic made rectangular insulators 1, a recess for sealing a fuse element at the center is formed, a cutout for lead protrusion of a terminal is left around the periphery, and rims are formed. A terminal 5-1 bends a terminal lead protruded from a rectangular insulator 1 by a gal wing shaped terminal for board mounting. A terminal packaged by emboss taping is temporarily fixed onto a cream solder print- applied in this shape onto a pad of the board surface by means of auto mounting machine, then is mounted by re-flow soldering device or the like. Thereby, heat discharge at a terminal joint part is improved, and workability is improved by an assembling method suitable to mass-production independent of skilled workmanship.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microfuse, and more particularly to a microfuse for automatic mounting of a printed circuit board which can be mounted on a printed circuit board or the like by surface mounting or insertion mounting.

[0002]

2. Description of the Related Art A conventional fuse is manufactured by passing a fuse element through a glass tube and soldering a metal cap one by one to a metal cap, or by heating and melting the solder in the cap and quickly inserting the same into a glass tube and joining them. ing. However, in the former case, the hole for passing the element opened in the base is closed with solder, so the strength at the time of breaking may be insufficient.In the latter, the glass tube and the fuse element are inserted simultaneously into the molten solder in the base. To
Cooling started immediately, and in some cases, the element and the terminal were incompletely joined. In addition, variations in the fusing characteristics were caused by the bonding state of the elements in the base, and the influence of heat generated in other than the center of the element was observed. These products are mounted on a printed circuit board by manual insertion or continuous taping.However, when mounting errors occur during automatic mounting, or when soldering to a through-hole board, heat is applied during soldering. In some cases, the solder joining the base and the fuse element is melted inside the base, causing troubles such as the element being eroded.

[0003] On the other hand, surface mount products of fuses are commercialized by various companies under the names of circuit protectors and thin film chip fuses, but most of these products use a single metal wire such as a bonding wire for a fuse element. Only the fast-blow type fuse has the fusing characteristics,
If the rated current of the fuse is selected at a normal steady-state current value in applications such as printer printing or paper feed motor drive circuits where current fluctuations occur frequently, the wire will break prematurely due to metal fatigue caused by expansion and contraction of the element, which is necessary. A fuse having a rated current value with the above margin is selected. In the above-described usage method, an abnormal current continues to flow, for example, when the motor control circuit (CPU) runs out of control for one reason or one or two phases are locked, thereby causing burnout of the motor driver or the motor. Thus, there has been a demand for a microfuse for surface mounting having a semi-time lag characteristic. Also, some commercial products have large variations in fusing characteristics, and because of excessive size reduction or flow after automatic mounting, reflow soldering,
Problems such as damage to the junction between the fuse element and the terminal and damage to the fuse element due to thermal deformation of the printed circuit board have occurred.

[0004]

For this purpose, the fuse element is provided with a fuse element suspended diagonally between terminals bonded to hollow recesses of a ceramic square insulator, and a lid is provided on the upper surface. Is molded so that a ceramic square insulator of the same shape is adhesively coated. Both ends of the terminal are led out from both ends of the ceramic square insulator and bent to form a gull wing for surface mounting or a DIP shape for insertion mounting. Since the fuse element thus configured is a thin metal wire suspended in a hollow portion similar to a conventional tubular fuse, when a constant current according to the wire diameter flows, the fuse element is blown in the atmosphere, and is blown. The capacity and blowing characteristics have substantially the same effects as the conventional tubular fuse.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a plurality of fuse elements are simultaneously joined to a lead frame-shaped terminal and sandwiched between upper and lower same type ceramic square insulator cases. in the structure to be joined as to improve the heat dissipation of the terminal connection region by uniform bonding ceramic Rectangular insulator elements and terminals by the bonding of the fuse element and the terminal to a plurality simultaneously solder bonded through N ₂ atmosphere furnace It is an object of the present invention to provide a microfuse for automatic mounting of a printed circuit board which has stable fusing characteristics, has a good yield by an assembling method suitable for mass production which does not depend on skilled work, and has easy fusing characteristics and easy switching of mounting form. .

In molding, the yield is improved by an assembling method suitable for mass production that does not depend on skilled work, and the switching of fusing characteristics and mounting forms is facilitated. The case and lid of the ceramic square insulator are formed in the same shape, and a part of the lead frame terminal mold is used in common to reduce the cost.

[0007]

As a connection method of the embodiment of the invention The fuse element and the terminal, N ₂ atmosphere to affect the corrosion and fusing characteristics of the element permeates into inorganic fibers flux is a core wire in a normal soldering when the winding element Bonding was possible with the minimum amount of flux inside. For metal single wire element, the solder joint in the N ₂ atmosphere furnace, can use the flux of solder low activity, can prevent erosion of the fuse element. Also,
By selecting the solder and setting the temperature conditions, evaluate the solder joint condition between the terminal and the fuse element by observing the appearance, measuring the resistance value, fusing characteristics, and breaking test, and it is more variable than soldering using flux in the atmosphere. Could be reduced. Furthermore, it is used as a lead frame terminal for mass production, and a fuse element and a terminal can be joined at the same time. In addition, a rectangular insulator made of ceramic having the same shape as the top and bottom is sandwiched between the terminals as a case and a lid.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, FIG. 2 and FIG.
FIG. 1 is a plan view of a pair of upper and lower ceramic square insulators (1), (1). The insulator has a concave portion (2) for enclosing the element in the center and a peripheral portion (3) except for a notch (4) for projecting the lead of the terminal.

FIGS. 2 and 3 show the shape of a pair of terminals. The terminal (5-1) of FIG. 2 shows a gull-wing-shaped terminal for mounting a substrate, which will be described later, and the terminal (5) of FIG. Reference numeral -2) denotes a terminal for inserting a substrate, which will also be described later, and a tongue piece (5-3) for fixing a fuse element is provided at the tip of each of the terminals.

FIGS. 4 and 5 are views showing an embodiment of the manufacturing method according to the third aspect, in which a plurality of continuous terminals are shown. FIG. 4 shows the board mounting terminal (5-1) shown in FIG. 2, and FIG. 5 shows the board insertion terminal (5-2) shown in FIG. Both continuous terminals are provided to face each other with an interval for inserting the fuse element, and the fuse element is fixed diagonally across the fuse element.

FIG. 6, FIG. 7, and FIG. 8 are views showing an embodiment showing a joining process of the fuse element (6) and the terminal (5).
First, as shown in FIG. 6, the fuse element (6) is placed diagonally on the opposite terminal (5), and the tongue piece (5-3) is bent and temporarily fixed. (See FIG. 7) Thereafter which _{N 2}
Bonding is performed by a chip solder (7) in an atmosphere furnace (not shown).

The fuse element thus combined has the lead portion of the terminal (5) in the central recess (2) of the ceramic rectangular insulator (1) having the same shape as the upper and lower portions shown in FIG. The microfuse is formed by protruding from the notch (4) of the portion and storing it, covering and bonding one of the rectangular insulators (1) serving as a lid from above.

FIGS. 9 and 10 show the thus formed microfuse of the present invention. FIG. 9 shows a microfuse using the terminal (5-1) shown in FIG. 2 described above, in which a terminal lead protruding from the rectangular insulator (1) is bent as shown in the figure, and the package is embossed and taped. The obtained product is temporarily fixed on a cream solder printed and coated in this shape on a pad on the substrate surface by an automatic mounting machine, and then mounted by a reflow soldering device or the like. Also,
The fuse shown in FIG. 10 uses the terminal (5-2) shown in FIG. 3 and bends a protruding lead as shown in the figure. The fuse having this shape is mounted on a stick or the like formed of resin or the like. The lead is inserted into a hole provided in the substrate by an automatic mounting machine and mounted by a flow soldering device or the like. In the microfuse of the present invention, the size of the rectangular insulator (the size of the fuse itself) is actually 4 × 9 × 4 m.
m or about 3 × 6 × 3 mm.

The fuse element used is a fuse element characterized in that inorganic fiber is used as a core wire and silver-plated copper fine wires are wound at regular intervals, and is used in a control circuit of a printer or the like in which this fuse is mounted. In a circuit where an inrush current flows, such as when starting a pulse motor, heat is released from the element to the core wire while an abnormal current flows to the circuit due to a CPU runaway, etc. It is used to obtain semi-time lag fusing characteristics for preventing and protecting the like. Then, the junction with the fuse terminal reliably performs the electrical junction with the element and the thermal junction with the inorganic fiber serving as the core wire.

Ceramic Square Insulator Ceramics are used because they have excellent heat resistance, heat conduction characteristics, and insulation properties for radiating the heat generated by the terminals and for supporting various mounting forms on a printed circuit board. Also, by making the upper and lower parts have the same shape, the cost of the mold was reduced and the variety of parts could be reduced.

Terminal Shape The side surface constituting the solder reservoir serves also for positioning the element, and the tongue on the front surface serves to temporarily fix the winding element and to prevent the flow of solder. Also, since only the shape of the lead part corresponding to each mounting form was changed,
The terminal type can be shared, and the cost can be reduced. And, for mass production, the supply of terminals is made to be a continuous lead frame, and by facing each other at a certain distance, the electrical and thermal lengths of the elements between the terminal joints can be made constant.

Method of Connecting Winding Element to Terminal Since a metal wire is wound around the inorganic fiber, in the case of soldering using ordinary atmospheric flux, the corrosion and fusing characteristics of the element penetrate into the inorganic fiber whose flux is the core wire. Therefore, a method of soldering in a N ₂ atmosphere with a minimum amount of flux is used. In addition, the selection of appropriate solder and temperature conditions were found, and in addition to the state of electrical connection between the element and the terminal, the fusing characteristics, the state of thermal coupling, and the like, the unevenness of the solder due to observation of the appearance was eliminated.

[0018]

As described above, in the microfuse for automatic mounting of a printed circuit board according to the present invention, a plurality of fuse elements are simultaneously joined to a lead frame-shaped terminal and sandwiched between upper and lower same type ceramic square insulator cases. The junction between the fuse element and the terminal is N ₂
By soldering multiple pieces simultaneously through an atmosphere furnace, the uniform joining of elements and terminals and the ceramic square insulator improve heat dissipation at the terminal joints, achieve stable fusing characteristics and enable mass production independent of skilled work. A microfuse for automatic mounting of a printed circuit board with a good yield by a suitable assembling method and easy switching of a fusing characteristic mounting mode could be provided.

[Brief description of the drawings]

FIG. 1 is an exploded plan view of a rectangular insulator to be coated.

FIG. 2 is an exploded plan view of a gull wing terminal.

FIG. 3 is an exploded plan view of a lead insertion terminal (DIP).

FIG. 4 is an embodiment view of a lead frame terminal for a gull wing.

FIG. 5 is an embodiment view of an insertion lead terminal.

FIG. 6 is a first process diagram of joining the fuse element and the terminal.

FIG. 7 is a diagram showing the second process.

FIG. 8 is a diagram showing a third process.

FIG. 9 is a side view of a micro fuse having a gull wing terminal shape.

FIG. 10 is a side view of a micro fuse having a lead insertion terminal shape.

[Explanation of symbols]

 (1). . . Ceramic square insulator (2). . . Recess (3). . . Edge (4). . . Notch (5). . . Terminal (5-1). . . Gull wing type terminal (5-2). . . Lead insertion terminal (5-3). . . Tongue piece (6). . . Fuse element (7). . . Chip solder

Claims (3)

[Claims] 1. A fuse element is sandwiched and adhered between upper and lower identical ceramic square insulator cases, and lead ends for mounting a substrate are protruded from both ends of the case, and the lead ends are formed into gull-wing shapes for surface mounting. Or DI for insertion mounting
A microfuse for automatic mounting of a printed circuit board, which is formed in a P shape. 2. A method for producing a micro-fuse PCB automatic mounting was characterized by joining the chip solder bonding of the fuse element and the terminal in an N ₂ atmosphere at micro fuse according to claim 1. 3. A method in which two sets of terminals stamped and pressed into a plurality of continuous lead frame shapes are opposed to each other at predetermined intervals, and fuse elements are mounted diagonally and are simultaneously joined in an N ₂ atmosphere. The method for manufacturing a microfuse for automatic mounting of a printed circuit board according to claim 2.