TECHNICAL PAPER ON WIRE WOUND RESISTOR

NATIONAL INSTITUTE OF INDUSTRIAL ENGINEERING

PGDIE-42

Industrial Engineering

 

Assignment on Industrial Engineering:

Presented by:

Vikas Sakre(Roll no:103)

                                                                                           

Summary of Technical Paper on Wire wound Resistor Manufacturing

ABSTRACT

A wire wound electronic component of the present invention includes a bobbin having a core 1a having a substantially circular cross-section and rectangular flanges 1b formed at both ends of the core. A groove 2 is formed in each side of each flange 1b. A conductive film or external electrode 3 is formed on each flange 1b. A coil or wire 4 is wound round the core la and has a conductor protruding from opposite stripped ends thereof. The opposite ends 5 of the conductor are respectively received in the grooves 2 of the flanges 1b and connected to the conductive films 3. A coating or armor 6 is formed on the coil 4 and has a flat surface 6a. The coating 6 has a rectangular configuration complementary to the configuration of the flanges

Discription

The present invention relates to an inductor, transformer, choke coil or similar wire wound electronic component.
A wire wound electronic component has been put to practical use in various forms, and various improvements have been made in the past. Japanese Utility Model Laid-Open Publication No. 51-115547, for example, teaches a fixed inductance device having a bobbin made up of a core and flanges, conductive layers formed on the circumferential surfaces of the flanges, and a coil wound round the core. A conductor protruding from opposite stripped ends of the coil is connected to the conductive layers and to conductive portions provided on a printed circuit board. Japanese Utility Model Laid-Open Publication No. 56-110612 discloses an inductance device having flanges formed with grooves, and a coil whose conductor is received in the grooves at both ends thereof.
Japanese Patent Laid-Open Publication No. 57-73916 proposes a miniature inductor including a core, flanges formed at both ends of the core, conductive layers respectively formed on the flanges, and a coil wound round the center of the core. In this inductor, electrodes are formed after the assembly has been sealed with a resin. Further, Japanese Utility Model Laid-Open Publication No. 61-144616 discloses a chip coil in which a conductor protruding from opposite stripped ends of a coil is drawn out via grooves formed in rectangular flanges, and electrodes are also formed on the sides of the flanges.
As stated above, a wire wound electronic component has a coil wound round a core and has a conductor protruding from the coil bonded to the electrodes of flanges. Such a wire wound electronic component may be produced by a method shown in FIG. 27. As shown in FIG. 27, (A), in a section, a bobbin having a core 900 and flanges 902 formed at both ends of the bobbin 900 is prepared. Then, as shown in FIG. 27, (B), electrodes 904 are respectively formed on the sides and end faces of the flanges 902 by dipping or similar technology. Subsequently, as shown in FIG. 27, (C), a coil 906 is wound round the core 900 and has its outgoing conductor 908 connected to the electrodes 904 by, e.g., heat pressure welding.
As shown in FIG. 27, (D), a resin or a paint is applied to the core portion, which was wound the coil 906, in order to form a coating or armour 910. Then, as shown in FIG. 27, (E), a plating 912 of, e.g., Ni is formed on each electrode 904. Finally, as shown in FIG. 27, (F), the assembly is entirely trimmed into a column having a rectangular cross-section.
In parallel with advances in the small size, light weight configuration of an electronic apparatus, there is an increasing demand for small size, light weight wire wound electronic components. In addition, improvements in mounting efficiency and productivity are essential from the cost saving standpoint. It is an object of the present invention to reduce the size and weight of a wire wound type electronic component without degrading its performance or reliability. It is another object of the present invention to improve the mounting efficiency and productivity of a wire wound electronic component.
According to the present invention, there is provided a method of producing a wire wound electronic component, comprising the steps of: providing a bobbin comprising a core, one or more flanges wherein at least one flange is at one end of said core, and external electrodes on said one or more flanges; winding a sheathed conductor around said core to form a coil and electrically connecting the coil to said external electrodes, and forming a coating having a flat surface on said coil, characterised in that the step of forming the coating comprises pressing the coating towards the coil so that the coating penetrates gaps between the turns of the coil.

Advantages

1) An electronic part includes a coating having a flat surface and formed on a coil. The part can therefore be easily and surely sucked by the suction of an automatic mounting machine when it is to be transferred to a printed circuit board.

 (2) Because the entire part is rectangular, it does not roll on a printed circuit board and is therefore easy to mount. In this respect, this part is advantageous over a drum-like bobbin having circular flanges.

 (3) A block for forming a bobbin is formed with recesses or projections for centering. The block can therefore be machined with accuracy while facilitating machining work.

 (4) Electrodes are formed by being shaved and therefore highly accurate in configuration.

 (5) Caps are fitted on opposite ends of the above block, so that the part is desirably adaptive to various kinds of configurations.

 (6) A paint is forced into the coil so as to enhance insulation.

 (7) A core included in the bobbin has a rough surface, preventing the turns of the coil from being dislocated.

 (8) Each flange and the core merge into each other via a curved portion, achieving improved strength.

 (9) The number of steps for production is reduced. This enhances productivity and allows wire wound electronic parts each having a particular characteristic to be efficiently produced.

 (10) Opposite ends of a conductor protruding from the coil are connected to electrodes at positions deviated from each other with respect to the longitudinal direction of the bobbin, so that L and Q can be adjusted, as desired.

 (11) A protective coating is provided in order to obviate breakage and other troubles. This successfully improves quality and productivity.

 (12) Irregularities are formed on at least one of the surfaces of the conductor and electrodes contacting each other, enhancing rigid bond between the conductor and the electrodes. Grooves are formed in the flanges of the bobbin in order to allow the conductor and electrodes to be bonded over a broader area. This additionally enhances rigid bond and provides the flanges with flat surfaces.

 (13) When the electrodes are implemented by a paste, the content of a binder is selected such that it is high in the portions adjoining the flanges and low in the portions adjoining the conductor of the coil. Therefore, the bonding strength is increased between the flanges and the electrodes and between the electrodes and the conductor.

 (14) The grooves formed in the flanges are tapered toward the outside. Therefore, the conductor received in the grooves bite into the walls of the grooves, increasing the bonding strength. This prevents the conductor from coming off and provides the flanges with flat surfaces.

 (15) The conductor of the coil has its opposite ends inserted in through holes formed in the flanges. This prevents the conductor from coming off and allows the sides of each flange to remain flat.

 (16) The ends of the conductor received in the grooves of the flanges each is positioned slightly short of the end of the groove or turned round to the end face of the flange over the end of the groove. The conductor is therefore surely prevented from coming off at the time of plating or mounting.

 (17) A coating configured to bulge out from the electrodes is trimmed to have preselected shape. The coating can therefore be accurately provided with flat surfaces desirable for mounting. Even a desired gap can be formed with accuracy, if desired.

 (18) The coating is provided with a rough surface for reducing static electricity and dislocation, promoting desirable mounting.

 (19) Grooves are formed in the sides of electrodes and allow the electrodes to be rigidly bonded to a circuit board by a small amount of solder or conductive paste.

 (20) The flanges each has a rectangular configuration having an oblong end face. This reduces the height of the part or reduces the area which the part occupies.

 (21) A circuit element is formed between the end of the conductor of the coil and the electrode. This reduces the number of components in a circuit and thereby improves efficient mounting.

Inventors

Amada, Yoshihiro (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)
Aoba, Hideo (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)
Otsuka, Kazuhiko (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)
Umeyama, Nobuhiro (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)
Koizumi, Katsuo (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)
Mamada, Nobuo (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)
Fujikawa, Iwao (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)
Shiba, Nobuyasu (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)
Uehara, Takayuki (c/o Taiyo Yuden Co., Ltd., 16-20, Ueno 6-chome, Taito-ku, Tokyo, JP)