Surface mounting type electronic component

THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCT INTERNATIONAL APPLICATION PCT/JP02/03464.

The present invention relates to a surface mounted electronic component mounted on a surface of a printed circuit board in various electronic instruments and having a function, such as an encoder, a variable resistor, or a switch.

Electronic instruments have recently been downsized and thinned, and this requires downsizing and thinning of electronic components used for them strongly. A surface mounted electronic component (it is called electronic component hereinafter) has been preferably used.

The electronic component is mainly a chip type electronic component, but is an electronic component having a function, such as an encoder, a variable resistor, or a switch, which is utilized with an operation knob mounted to an operating shaft.

The electronic component has an output terminal out of a case and a board mounting part, such as a leg, mounted to the case. The board mounting part is soldered to a land of a component-soldered part on the printed circuit board, thereby assuring mounting strength of the electronic component.

A material used for the board mounting part of the electronic component is thinned or narrowed, thereby downsizing and thinning the electronic component and reducing its material.

Such a conventional surface mounted electronic component having a board mounting part will be described hereinafter with reference to the accompanying drawings. FIG. 8 is a front view of the conventional surface mounted electronic component. FIG. 9 is a side view of the component. FIG. 10 is a top view of the component. The surface mounted electronic component 1 includes a resin case 2 and a leg 3 as the board mounting part.

The leg 3 made of metallic flat plate projects outward from a side of the case 2 , is bent toward the bottom side of the case 2 at a predetermined position, and extends along a side wall of the case 2 . The leg 3 has a soldering part 3 A projecting outward from a bottom surface position of the case 2 . The soldering part 3 A is bent near the case 2 laterally by approximately 90°. The leg 3 is disposed on each sides of the case 2 opposite to each other of the electronic component 1 .

The case 2 accommodates a functioning component, such as an encoder, a variable resistor, or a switch, and the output terminal is guided out of the case 2 (not shown).

A printed circuit board 11 for accepting the electronic component 1 has two lands 12 soldered to the soldering parts 3 A of the legs 3 , as shown in a perspective view of FIG. 11 .

The electronic component 1 is mounted through having the output terminals (not shown) soldered to a predetermined pattern (not shown) on the printed circuit board 11 and through having the soldering parts 3 A as the board mounting parts soldered to the lands 12 on the board 11 . While being mounted, even if an external force P is applied to the side of the electronic component 1 , the electronic component 1 absorbs the external force P with connection between the board mounting parts (the legs 3 ) and the board 11 .

If the conventional surface mounted electronic component 1 having the legs 3 as the board mounting part is downsized and thinned, the leg 3 must be narrowed, shortened, and thinned. This structure accordingly reduces the soldering strength of the soldering part 3 A to the board 11 and the strength of the leg 3 itself, so that shortage of the strength against the external force P is concerned.

A surface mounted electronic component includes a case, a leg extending from the case, and a board mounting part at a tip of the leg. The leg includes a projection extending in an extending direction of the leg from the case, and an outer frame formed perpendicularly to the projection away from the case.

The surface mounted electronic component keeps to be mounted tightly to a circuit board even when an external force is applied to the electronic component.

FIG. 1 is a front view of a surface mounted electronic component in accordance with an exemplary embodiment of the present invention.

FIG. 2 is a side view of the surface mounted electronic component in accordance with the embodiment.

FIG. 3 is a top view of the surface mounted electronic component in accordance with the embodiment.

FIG. 4 is a side view for illustrating a method of forming a board mounting part of the surface mounted electronic component in accordance with the embodiment.

FIG. 5 is a perspective view of a printed circuit board for accepting the surface mounted electronic component in accordance with the embodiment.

FIG. 6 shows the board including the surface mounted electronic component mounted thereon in accordance with the embodiment.

FIG. 7 shows another printed circuit board including the surface mounted electronic component mounted thereon in accordance with the embodiment.

FIG. 8 is a front view of a conventional surface mounted electronic component.

FIG. 9 is a side view of the conventional surface mounted electronic component.

FIG. 10 is a top view of the conventional surface mounted electronic component.

FIG. 11 is a perspective view of a printed board for receiving the conventional surface mounted electronic component.

FIG. 12 shows the printed circuit board including the conventional surface mounted electronic component mounted thereon.

FIG. 1 is a front view of a surface mounted electronic component in accordance with an exemplary embodiment of the present invention. FIG. 2 is a side view of the component, and FIG. 3 is a top view of the component. A surface mounted electronic component 21 includes a resin case 22 substantially square in its top view and fixtures made of metal plate fixed to the case 22 . A tip of the leg 23 of each fixture extends downward along a side surface of the case 22 functions as a board mounting part 51 .

The leg 23 may extend integrally on the side surface of a fixture mounted as to cover the case 22 .

Detailed configurations of a fixing part between the case 22 and the fixture, an operating shaft projecting upward from the case 22 , and the like are complicated, and thus, these are considered integrally as the case 22 in the drawings for simple explanation.

The tip of the leg 23 includes an outer frame 23 A having the same width as that of the leg 23 . The outer frame 23 A is bent outward by approximately 90° from the leg 23 at a height equal to a bottom surface of the case 22 . The outer frame 23 A is perpendicular to the leg 23 , as shown in FIG. 3 . The outer frame 23 A has a substantially square U-shaped tip having its opening towards the case 22 . The tip of the outer frame 23 A is integrally connected to the leg 23 , and the integrated structure has a penetration hole 25 at a center from top view.

A central position of a portion of the leg 23 connected with the opening of the outer frame 23 A is provided with a projection 23 B. As shown in FIG. 2, the projection 23 B projects under the bottom of the case 22 , and is formed unitarily with the leg 23 in its extending direction.

The board mounting part 51 of the present embodiment includes the outer frame 23 A and the projection 23 B that are orthogonal to each other.

The board mounting parts 51 are disposed on facing edges of the four edges constituting the outer periphery of the case 22 , respectively. The facing edges are different from the edges having an output terminal (not shown).

For forming the board mounting part 51 , a tip of the leg 23 formed at a predetermined width, as shown in the side view in FIG. 4, is punched to form an upward square U-shaped opening. The opening corresponds to the through hole 25 . The remaining part of the tip of the leg 23 is machined in a frame shape with the predetermined width. Then, the remaining part is bent perpendicularly at broken lines of FIG. 4 so as to separate the tip from the case 22 to form the outer frame 23 A. The outer frame 23 A has a frame shape, and thus, a deviation of the lateral bending position is small, thus allowing the frame to be bent easily and accurately. Therefore, the projection 23 B from the leg 23 is consequently positioned accurately.

Thus, the board mounting part 51 is simply and accurately formed of a part coaxial with the leg 23 without material loss.

A printed circuit board 31 for accepting the electronic component 21 including the board mounting parts 51 has a substantially quadrangular lands 32 A at positions corresponding to the outer frames 23 A of the legs 23 , as shown in FIG. 5 . The lands 32 A are used as mounted parts 32 for the board mounting parts 51 , and are larger than the outer frames 23 A. A central part at an edge of each land 32 A includes a hole 32 B, where the projection 23 B passes, disposed on the leg 23 .

Since the electronic component 21 includes the board mounting parts 51 facing each other, the mounted parts 32 corresponding to them faces each other on the printed board 31 with the edges having the holes 32 B as inner edges.

The board 31 includes a land corresponding to an output terminal and a pattern connected to the land (not shown).

For mounting the electronic component 21 on the board 31 , cream solder is applied to the land corresponding to the output terminal on the board 31 , and cream solder is also applied to the lands 32 A of the mounted parts 32 , as shown in FIG. 6 . The projections 23 B are inserted into the holes 32 B to mount the electronic component 21 on the board 31 .

At this moment, entire lower surfaces of the outer frames 23 A are securely butted on the lands 32 A. That is because the outer frames 23 A orthogonal to the projections 23 B are parallel with an upper surface of the board 31 , and the outer frames 23 A themselves are bent accurately with little deviation of the lateral bending position,

Then, the cream solder, upon being melted, connects the outer frames 23 A to the land parts 32 A of the mounted parts 32 and simultaneously, connects the output terminal to the land.

If a clearance between the projection 23 B of each board mounting parts 51 and the hole 32 B in the board 31 is small, the electronic component 21 is easily supported by itself even when the electronic component 21 is placed on the printed board 31 . Additionally, a displacement of the electronic component 21 due to a movement in a manufacturing process until the soldering, and the vibration can be reduced. The clearance, if being such a size that the projection 23 B is inserted into the hole 32 B slightly press-fittingly, prevents the displacement and allows the electronic component 21 to be soldered accurately.

Since the entire lower surface of each outer frame 23 A contacts with the cream solder, as discussed above, the inner end surface of the outer frame 23 A including the penetration hole 25 as well as its outer end surface is certainly soldered, and is connected to the landts 32 A on the board 31 at high connecting strength.

The electronic component 21 has the outer frames 23 A thus tightly soldered to the lands 32 A is soldered to the printed board 31 . Therefore, even when an external force Q to tilt the electronic component 21 is applied to the electronic component 21 from a side direction or the like (FIG. 6 ), the projections 23 B inserted into the holes 32 B abut on side walls of the holes 32 B to generate large resistance.

Additionally, the accurately formed outer frames 23 A are certainly soldered to the lands 32 A having the edges parallel with the side surface of the case 22 , and the penetration holes 25 in the outer frames 23 A are filled with the solder in soldering. This reinforces the legs 23 of the electronic component 21 . Even when the external force Q is applied, the electronic component 21 can be kept to be mounted normally for a long time. Even if fixtures forming the board mounting parts 51 is thin, for example, the electronic component 21 is tightly mounted.

If the output terminal and the board mounting parts 51 are arranged so as to solder four edges on the outer periphery of the case 22 , the board mounting parts 51 is tightly mounted regardless of the direction of the external force Q.

The projections 23 B of the board mounting parts 51 are inserted into the holes 32 B in the board 31 in the above example. As shown in FIG. 7, a printed circuit board 41 including mounted parts 43 having side walls processed into solderable as a through hole 43 B may be used. In this case, the output terminal of the electronic component 21 are soldered to the land, and the outer frames 23 A are soldered to lands 43 A of the mounted parts 43 . The projections 23 B are also soldered to the through holes 43 B, where the projections pass. This allows the electronic component 21 to be more tightly soldered and mounted to the printed board 41 . In other words, the side surfaces of the projections 23 B are soldered and fixed to the side wall of the through holes 43 B. This arrangement increases resistance to an undesired external force R transversely applied to the electronic component 21 . Therefore, the electronic component 21 is kept to be mounted stably for a long time.

Even when solder is not previously applied to the side walls of the through holes 43 B in the former case, cream solder may be pressed into the holes 32 B using the projections 23 B when the projections 23 B is inserted into the holes 32 B, thus allowing the component to be mounted similarly.

In either case, patterns (not shown) connected to the mounted parts 32 and 43 for the board mounting parts 51 of the printed boards 31 and 41 accepting the electronic component 21 may be connected to a ground in a working instrument. Static electricity from an operation part of the instrument into the electronic component 21 flows to the ground via the legs 23 (the board mounting parts 51 ) and the patterns connected to the board mounting parts 51 of the boards 31 and 41 . This prevents noise caused by the static electricity, thereby allowing a predetermined functional element accommodated in the case 22 of the electronic component 21 to output normally, for example, an encoder, a variable resistor, or a switch.

The board mounting parts 51 may be formed of a member other than fixtures, and provides similar advantageousness.

According to the present invention, a surface mounted electronic component including a simplified board mounting part including an outer frame and a projection. The outer frame and the projection can be formed accurately without material loss.