JP2000357554A - Contact spring structure of electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such contact spring structure that distance to a mating conductor is narrowed, the thickness of a substrate for supporting a spring is reduced (to make the size compact and thin), the center axis of the spring is hardly bent and interposed, and the contact area with the mating conductor is increased (to enhance reliability). SOLUTION: In contact spring structure of an electronic apparatus, a metal wire having elasticity is spirally wound so that the outer shape becomes almost conical, the bottom of the metal wire whose outer shape is almost conical is conductively connected to one conductor, and the top of the conical shape is elastically brought into contact with the surface of the other conductor to form a contact spring. The plane overlap of the metal wires on the inside and outside of the spiral is prevented, and pitch in the axial direction of the spiral is changed, or the bottom of the contact spring is stored in a shallow recessed part 3a of a substrate 3 to enhance effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device,
The present invention relates to a structure of a contact spring used for connecting parts.

[0002]

2. Description of the Related Art In recent years, relatively small electronic information devices such as cellular phones have been greatly developed. Their internal structure is complicated, and various types of components incorporated in a housing or a circuit board are electrically connected to each other. In many cases, these connection means are by spring contact after soldering.
Although the reliability and miniaturization of the connection means are small in their cost ratio, they are important in controlling the function and quality of the electronic device in which they are incorporated.

[0003] The connection means using elastic contact by a spring, that is, a contact spring structure is roughly classified into a means using a leaf spring and a means using a coil spring. Since the present invention improves the latter contact spring structure, it will be described below. Conventionally, as a coil spring, an elastic metal wire wound in a cylindrical coil shape has been used. 3 (a) and 3 (b) show a conventional contact spring structure, which is represented by a cross-sectional view including a center axis of a cylindrical coil.
(A) shows a normal structure. FIG. 2A is a similar cross-sectional view, but showing a state where the coil spring is extremely compressed.

[0004] Reference numeral 2 denotes a cylindrical spring, such as a buzzer.
It is a terminal for electrical components independent of the integrated circuit board. Reference numeral 3 denotes an insulating substrate (or housing or the like) unique to the electric component, and a cylindrical spring 2 is provided in the cylindrical concave portion 3a.
The bottom is housed. Reference numeral 4 denotes a lead plate embedded in the substrate 3 by means such as insert molding or the like, which is a conductor on the fixed end side of the cylindrical spring 2 and is connected to an internal circuit of an electric component. The fixed end 2a of the cylindrical spring 2 is a line bent parallel to the cylindrical axis,
And is securely and electrically conductively fixed to the lead plate 4 by the solder 5 on the outside. Further, a hard brazing material may be used instead of solder, or resistance welding may be performed with a lead plate. Reference numeral 6 denotes a mating conductor, which is, for example, a conductive pattern provided on an integrated circuit board (not shown) of the electronic information device main body.
The cylindrical spring 2 is appropriately compressed, and the distal end is pressed against the counter conductor 6 with a predetermined contact pressure.

There are several problems with this conventional structure. First, since the strands of the cylindrical spring 2 overlap in the axial direction as shown in FIG. 2A, the distance D2 between the lead plate 4 and the counter conductor 6 cannot be sufficiently reduced. In addition, since the cylindrical spring 2 is easily buckled, the concave portion 3 supporting the base of the spring needs a certain depth to be compressed in a straight manner, so that the substrate 3 needs a considerable thickness T2. These circumstances can be a constraint on the demand for thinner and smaller electronic devices incorporating the contact spring structure. Further, the contact length between the cylindrical spring 2 and the counter conductor 6 is shorter than the length of the wire for one turn of the coil, so that a large contact area cannot be obtained, and the contact resistance increases and becomes unstable. There may be a difference in performance when incorporated into the product.

FIG. 3B shows a state where another problem appears. That is, when assembling the electronic information device by bringing the substrate 3 and the opposing conductor 6 close to each other, the two move relatively to each other in the lateral direction, or when a strong shock is applied after the product is completed and the interval between the two temporarily increases. In this state, the cylindrical spring 2 is bent, and a number of turns of the tip end are sandwiched between the outer surface of the concave portion 3 a of the substrate 3 and the counter conductor 6. In this case, the contact pressure is not reduced to a predetermined value, but an excessive force acts to deform the substrate 3, the mating conductor 6, or the cylindrical spring itself.
In the case where is small, there is a possibility that the surface may come off.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned problems of the prior art. In particular,
(1) A contact spring structure capable of shortening the distance from the counter conductor, (2) a contact spring structure capable of reducing the thickness of the substrate supporting the spring or omitting the substrate, (3) An object of the present invention is to provide a contact spring structure in which the center axis of the spring is unlikely to bend during assembly or impact, and (4) a contact spring structure capable of increasing a contact area with a counter conductor.

[0008]

In order to achieve the above object, the contact spring structure of the present invention has the following features. (1) A metal wire having elasticity is spirally wound so as to have a substantially conical outer shape, the bottom of the metal wire having the substantially conical shape is conductively fixed to one conductor, and the top of the conical shape is formed. Elastically contact the other conductor surface.

The contact spring structure of the present invention may further have the following features. (2) When the metal wire having the substantially conical outer shape is viewed from the substantially conical axial direction, the inner and outer metal wires that are spirally wound and adjacent to each other have a planar shape such that they do not overlap with each other.

(3) The pitch of the spirally wound metal wire along the substantially conical axis becomes smaller toward the tip of the substantially conical shape, so that the substantially conical shape becomes slightly domed. Being close.

(4) A contact in which the conical bottom is placed in the concave portion of the insulating substrate having the concave portion and the one conductor at the bottom of the concave portion, and the conical top is projected from the substrate. In the spring structure, the depth of the concave portion is about 1 to 5 times the diameter of the metal wire at the bottom.

[0012]

FIG. 1 shows a contact spring structure according to an embodiment of the present invention. FIG. 1 (a) is a plan view (with the mating conductor removed), and FIG. 1 (b) is an A including a spring axis. It is -A sectional drawing. In the present invention, a conical spring 1 is used as a contact spring instead of a conventional cylindrical spring 2. 1a is its fixed end and 1b is its tip. Other parts are given the same names and symbols as in the conventional example, and the description thereof will not be repeated.

The conical spring 1 is formed by spirally winding a metal wire so that the outer shape is substantially conical. The conical bottom (thick) spring end 1a is fixed to the lead plate 4 by solder 5 and the thinner 1b is pressed against the mating conductor 6. Conical springs have the property of being extremely difficult to fall. Therefore, even if the concave portion 3a is provided in the substrate 3, its main purpose is only the positioning of the spring, and the required depth is smaller than that of the conventional example. In many cases, the thickness T1 of the substrate 3 can be reduced. Alternatively, if there is no problem in the positioning of the conical spring, the substrate 3 or the concave portion 3a
May be omitted, and the lead plate 4 to which the conical spring 1 is fixed may be naked.

The apex angle of the cone of the conical spring 1 is arbitrary, and various types are conceivable, from a shape close to a cylindrical spring to a flat shape. However, as shown in the plan view of FIG. 1 (a), those having a spiral shape such that the inner and outer adjacent wires do not overlap with each other can be extremely compressed in the axial direction, for example, to the diameter of the wires. is there. If this is utilized, the lead plate 4
As shown in FIG. 2 (b), the distance D1 between the conductor 6 and the opposing conductor 6 can be made extremely small so that the two can approach each other. This is advantageous for reducing the size and thickness of the electronic device.

Further, according to the present invention, the contact area between the conical spring 1 and the counter conductor 6 can be increased as compared with the case where a cylindrical spring is used. When the opposing conductor 6 is pressed in the direction of the lead plate with a strong force, the spiral of the conical spring 1 is finally crushed (assuming that there is no substrate 3), and the side surface extending over several turns (excluding the solid end 1a) of the conical spring 1 It comes into contact with the surface of the conductor 6. Since the contact length in the case of using a cylindrical spring is less than one turn of the coil, if the maximum diameter of the contact portion of the conical spring is equal to the diameter of the cylindrical spring, the contact length of the conical spring is longer. And the contact area increases.

Consider a case where the mating conductor 6 is brought close enough to not completely crush the conical spring 1. FIG. 2B shows the ideal state. Although the conical spring 1 is crushed only halfway, the contact with the mating conductor 6 progresses from the center to the outside. Actually, this does not occur when the spiral pitches in the axial direction are equal as shown in FIG. Since the rigidity of the deformation in the axial direction becomes higher as the winding diameter of the wire becomes smaller, if the pitch is equal in the axial direction, the conical spring 1
This is because the ring having the larger diameter at the bottom portion contacts the lead plate 4 (in the case of a flat surface) instead of the mating conductor sequentially.

FIG. 2 shows a case where a wire having a uniform diameter is used.
In order to realize the state of (b), the smaller the winding diameter, the smaller the pitch in the axial direction, and the outer shape of the spring may be shaped like a dome. Alternatively, although not shown, several turns at the tip end are wound in a plane spiral, and after securing a predetermined contact area with the counter conductor, the outside is wound in a conical shape,
The outer shape may be a truncated cone. In the present invention, these dome-shaped and frusto-conical outer shapes are also regarded as substantially conical.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above range. For example, selection of wire diameter and number of windings, non-circular cross section of the wire (for example, punching a spring from a plate material), making the cross section non-uniform (for example, making it thinner as it approaches the tip, making the bending force uniform at each winding diameter Measure), number of spiral wire turns, radial pitch, axial pitch and its change, shape and material of conductor on the spring bottom side, fixing condition of spring bottom (not only soldering and welding, but also caulking) It may be used, or the fixed end 1a may be simply inserted into the hole 4a of the lead plate and positioned, and may be frictionally fixed by the contact pressure of the spring), the shape of the spring tip or the fixed end, the shape of the mating conductor The present invention can be implemented by adding various devices to the state of the contact portion, the state of the contact portion, and the like.

[0019]

(1) The line of action of the contact pressure substantially coincides with the center axis of the spring body, and there is no bias in the force, and the contact is stable and reliable.

(2) Compared with the conventional cylindrical coil spring, the degree of freedom in designing stroke-to-contact pressure is greater, and the stroke is deeper because the wires do not overlap.

(3) The thickness of the spring in use or the thickness of the substrate that houses the base of the spring can be reduced.

(4) The insulating substrate surrounding the base of the spring may be omitted.

(5) Whether the wires do not overlap when compressed
Since there is little overlap, the distance to the partner conductor can be designed to be small, which can contribute to miniaturization and thinning of electronic devices.

(6) The contact area between the spring and the mating conductor can be increased, and the reliability of the connection can be improved.

(7) It is extremely unlikely that the contact spring will be pinched when the electronic device is assembled or when an impact is received.

[Brief description of the drawings]

FIG. 1 shows a contact spring structure according to a first embodiment of the present invention, wherein (a) is a plan view and (b) is a side view.

FIGS. 2A and 2B are cross-sectional views showing a state where a contact spring is compressed. FIG. 2A shows a conventional example, and FIG. 2B shows a case of the present invention.

FIG. 3 is a cross-sectional view showing a contact spring structure of a conventional example, and FIG.
Shows a normal state, and (b) shows a state in which a spring is pinched.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conical spring 1a Fixed end 1b Tip part 2 Cylindrical spring 2a Fixed end 3 Substrate 3a Depression 4 Lead plate 5 Solder 6 Mating conductor D1, D2 Distance from mating conductor T1, T2 Substrate thickness

Claims (4)

[Claims] 1. A metal wire having elasticity is spirally wound so that its outer shape is substantially conical, and the bottom of the metal wire whose outer shape is substantially conical is fixed conductively to one conductor.
A contact spring structure for an electronic device, wherein the top of the conical shape is elastically contacted with another conductor surface. 2. When the metal wire whose outer shape is substantially conical is viewed from the substantially conical axial direction, the inner and outer metal wires that are spirally wound and adjacent to each other have a planar shape such that they do not overlap with each other. The contact spring structure for an electronic device according to claim 1, wherein 3. The pitch of the spirally wound metal wire along the substantially conical axis decreases toward the substantially conical tip, so that the substantially conical shape is slightly closer to a dome. The contact spring structure for an electronic device according to claim 1, wherein the contact spring structure is provided. 4. A contact spring having a concave portion, wherein the conical bottom is accommodated in the concave portion of an insulating substrate having the one conductor at the bottom of the concave portion, and the conical top is projected from the substrate. 4. The contact spring structure for an electronic device according to claim 1, wherein the depth of the concave portion is about 1 to 5 times the diameter of the metal wire at the bottom.