JPH07147205A - Surface mount electronic device - Google Patents

Abstract

PURPOSE:To obtain a terminal where solder fillet is easily formed and solderability is excellent, and prevent substrate crack at the time of terminal bending. CONSTITUTION:In a surface mount electronic device having a terminal 12 which protrudes from the side surface of the main body 11 of an electronic device and is bent from the side surface toward the bottom surface side, a narrow part 13 to make bending easy is formed at the position of the terminal 12 which corresponds with the side surface of the main body 11. The small bending strength part of the narrow part 3 is positioned on the side surface of the main body 11 or the outer part thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mounting electronic component used in a small or high density mounting electronic device or the like.

[0002]

2. Description of the Related Art A conventional surface mounting electronic component will be described with reference to FIGS. 6 and 7 by taking a surface mounting variable resistor as an example.

The variable resistor 1 comprises a substrate 2 which is a main body and a slider 3. The substrate 2 is made of an insulating resin in which fixed side terminals 4 and 5 and variable side terminals 6 which are terminals made of metal are integrally molded, and the upper surface of the substrate 2 is electrically connected to one end of the fixed side terminals 4 and 5. Thus, the arc-shaped resistance film R made of a carbon-based resistor is formed. Also, the variable side terminal 6
In order to hold the slider 3 rotatably on the substrate 2 by engaging with the slider 3 and caulking the portion located in the through hole 2a formed in the central portion of the substrate 2. The fitting portion 6a is formed.

The fixed-side terminals 4 and 5 and the variable-side terminal 6 are made of a metal having a good conductivity, for example, a copper alloy, and the surfaces of these terminals are surface-treated, for example, so as to be easily soldered to a printed circuit board. The lower layer is nickel or nickel alloy plated, and the upper layer is tin or tin alloy plated.
Then, these terminals have a substantially rectangular developed shape, extend from both side surfaces of the substrate 2, and are bent from the side surface of the substrate 2 to the bottom surface side.

The variable resistor 1 is formed by incorporating the slider 3 in the substrate 2 described above. That is, the variable resistor 1 engages the engagement portion 3a of the slider 3 with the engagement portion 6a of the variable-side terminal 6 and caulks the engagement portion 6a, so that the slider 3 is mounted on the substrate 2. It is rotatably attached to.

[0006]

However, as shown in FIG. 8, a crack C is formed on the surface of the surface-mounted electronic component having such a structure, for example, the bent portion of the variable-side terminal 6 of the variable resistor 1. Occurs a lot. That is, since the entire bent portion of the variable-side terminal 6 extending from the side surface of the substrate 2 is curved, the crack C is generated over the entire outer surface of the variable-side terminal 6. Particularly, in the surface treatment of the variable-side terminal 6, when the lower layer is plated with nickel or nickel alloy, the ductility of nickel or nickel alloy is poor and cracks C occur in the plated layer of nickel or nickel alloy.
Occurs, and along with this, cracks C also occur in the upper layer, for example, the tin-plated layer.

Due to the crack C, when the variable resistor 1 is reflow-soldered to the printed circuit board 7 by cream soldering or the like, as shown in FIG. 9, the variable side terminal 6 is attached to the outer surface of the bent portion. Solder wettability is poor, and the solder fillet 8 is not formed above the bent portion. So
There is a problem that the soldered variable resistor 1 is easily separated from the printed circuit board 7, that is, it is in a so-called solder state, and soldering reliability is poor.

Further, as the surface-mounting electronic component becomes smaller, the bottom portion 2b of the variable side terminal 6 of the substrate 2 becomes thinner. Therefore, the bottom portion 2b becomes weak in strength, and there is a problem that when the variable side terminal 6 is bent, the bottom portion 2b may be broken or broken.

8 and 9 show a part of the variable resistor 1 which is the variable side terminal 6 and a part of the substrate 2, the fixed side terminals 4 and 5 are the same as the variable side terminal 6. It has similar problems. Further, in FIGS. 8 and 9, hatching of the cross section of the variable-side terminal 6 is omitted so that the generation state of the crack C can be easily understood.

The object of the present invention is to solve the above-mentioned problems, and it is provided with a terminal which is easy to form a solder fillet and has good solderability, and which is capable of preventing the substrate from cracking when the terminal is bent. It is to provide electronic components for mounting.

[0011]

Therefore, according to the present invention, there is provided a surface mounting electronic component having a terminal extending from a side surface of a body of an electronic component and bent from the side face to a bottom surface side of the body. A narrow width portion for facilitating bending is provided at a position of the terminal corresponding to a side surface of the main body, and a portion of the narrow width portion having a weak bending strength is located outside the side surface or the side surface of the main body. It is characterized by doing.

[0012]

In other words, according to the present invention, as described above, the narrow width portion is provided at a predetermined position of the terminal, and the weak bending strength portion of the narrow width portion is positioned on the side surface or outside of the side surface. It is possible to easily bend the root portion of the terminal extending from the side surface of the component body. Therefore, since a flat portion that is not bent is formed on a part of the terminal, the occurrence of cracks that affect the wettability of the solder is suppressed, and the main body when bending the terminal due to the miniaturization and thinning of electronic components. It is possible to prevent cracks and chips at the bottom.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 5 attached, taking a variable resistor for surface mounting as an example. In addition, Japanese Patent Application No. 5 by the same applicant as the applicant
A similar proposal is made in No. 231779 report, but the present invention is further improved. The present embodiment is characterized in that the fixed-side terminal and the variable-side terminal are provided with a narrow width portion, and the position of the weak bending strength portion existing in the narrow width portion is provided on the side surface or outside the side surface of the electronic component body. I am trying.
Detailed description of the same parts as those of the above-described conventional example will be omitted, and only the variable-side terminals and the substrate will be illustrated and described.

In FIG. 1, a substrate 11, which is the main body of the variable resistor, is made of, for example, an insulating resin in which a fixed side terminal (not shown) made of metal and a variable side terminal 12 are integrally molded.

The variable-side terminal 12 is made of metal having good conductivity.
For example, it is made of a copper alloy, and its surface is surface-treated so as to be easily soldered to a printed circuit board. For example, the lower layer is nickel or nickel alloy plated, and the upper layer is tin or tin alloy plated, or gold plated. The variable-side terminal 12 is located on the side surface of the substrate 11, that is,
A circular through hole is formed as the narrow width portion 13 at a position where it can be easily bent, and the developed shape of the variable-side terminal 12 extending from the side surface of the substrate 11 is, for example, a substantially rectangular shape. Although not shown, the fixed terminal is also the variable terminal 12
Similarly to the above, it has a narrow width portion.

The variable terminal 12 of the substrate 11 is shown in FIG.
As shown in FIG. 5, the substrate 11 is bent from the side surface to a part of the bottom surface. At this time, the narrow portion 1 provided on the variable-side terminal 12
3, the root portion N of the variable-side terminal 12 has a weak bending strength, and the circular through-hole of the narrow width portion 13 does not have a bent portion in the lower portion to be substantially flat. 1
2 The underlying nickel or nickel alloy on the surface is not extended. As a result, cracks hardly occur on the surface of the variable-side terminal 12, and the solder wettability is improved.

Then, as shown in FIG. 3, when the variable resistor (partially shown) using the above-mentioned substrate 11 is reflow soldered to the printed circuit board 7 by cream soldering or the like, the variable side terminal 12 is folded. The solder wettability to the surface of the bent portion is good, and the solder fillet 14 is formed up to above the bent portion.

Next, a portion of the narrow portion 13 having a low bending strength will be described with reference to FIG. As shown in FIG. 4, when the narrow portion 13 is a circular through hole, the center T of the through hole
The weak point 15 which is the portion having the smallest terminal remaining due to the circular through-hole in the narrow width portion 13 and having a weak bending strength is the portion located on the line crossing the both ends of the variable side terminal 12 at right angles. become.

The relationship between the weak point 15 and the side surface of the substrate 11 will be described below. 4 (a) and 4
The substrate 1 in which the variable-side terminal 12 is extended in FIG.
The upper side surface and the lower side surface of the variable side terminal 12 of No. 1 are on the same plane, and the weak point 15 is on the same plane as the side surface of the substrate 11. Also, FIG. 4 (c) and FIG.
In (d), the substrate 1 on which the variable-side terminal 12 extends
The upper side surface and the lower side surface of the variable-side terminal 12 of No. 1 are on the same plane, and the weak point 15 is outside the side surface of the substrate 11. Also, FIG.
4E and FIG. 4F, when the upper side surface and the lower side surface of the variable side terminal 12 of the substrate 11 from which the variable side terminal 12 extends are not on the same plane, the weak point 15
Is outside the side surface with respect to the lower side surface of the substrate 11 in the bending direction H of the variable-side terminal 12.

The variable side terminal 12 of the variable resistor having such a configuration
When is bent in the bending direction H, it is bent at the weak point 15, which is the weakest part in terms of strength. Therefore, when the variable-side terminal 12 having the weak point 15 inside the substrate 11 is bent, the variable side terminal 12 tries to bend inside the substrate 11.
On the other hand, when the weak point 15 according to the present invention is on the side surface of the substrate 11 or on the outer side of the side surface, the variable-side terminal 12 tries to bend on the side surface of the substrate 11 or on the outer side of the side surface. The load is reduced, and damage to the lower portion 11a such as cracks and chips is reduced.

Now, another embodiment of the narrow portion 13 having a through hole or a notch in the variable terminal 12 in the width direction of the variable terminal 12 will be described with reference to FIG. However, the variable side terminal 12 of the same figure shows the developed state before bending, and the weak point 15 is a figure located on the side surface of the substrate 11.

In FIG. 5, FIG. 5A shows the narrow portion 13
Is an elliptical through-hole, and FIG.
Is a rectangular through hole rotated by 45 °. Further, FIG. 5C and FIG. 5D show the variable side terminal 1
The narrow width portion 13 is provided by forming semi-elliptical or semi-rectangular notches on both sides of the side end portion of 2.

The weak point 15 which is the portion with the smallest remaining portion of the narrow side portion 13 of the variable side terminal 12 and which is weakly bent is similar to the through hole in FIG. It suffices that the side surface of the substrate 11 with respect to the bending direction H or outside the side surface is not limited to the shapes of the above-described four types of embodiments. Similarly to the narrow width portion 13 of the variable side terminal 12, the narrow width portion (not shown) of the fixed side terminal is provided with the weak point 15 on the side surface or outside the side surface of the substrate 11.

Although the weak point 15 described above is provided with a through hole or a notch portion in the width direction of the terminal, it may be easily bent by providing a portion having a small plate thickness in the plate thickness direction. .

As the electronic component, the above embodiment has been described by taking the variable resistor for surface mounting as an example. However, the invention is not limited to this. For example, a variable capacitor, an IC.
And so on.

[0026]

As described above, in the surface mounting electronic component according to the present invention, the surface of the bent portion of the terminal extending from the side surface of the electronic component body is free from cracks due to the bending processing of the terminal. Almost none, ready for soldering. Therefore, when this electronic component is soldered to the printed circuit board by reflow soldering such as cream solder, the wettability of the solder to the surface of the bent portion of the terminal is good,
A solder fillet is formed up to the bent portion of the terminal. Along with this, in terms of solderability to a printed circuit board, a highly reliable electronic component having good solderability can be obtained.

Further, since the weak point, which is a portion having a small bending strength due to the narrow width portion, is provided on the same surface as the side surface of the electronic component or outside the side surface, the terminal is bent on the side surface or outside the side surface, and The load on the bottom of the component body has been reduced, and the bottom does not crack.

[Brief description of drawings]

FIG. 1 is a partial top view of a main body including terminals before bending in an embodiment of a surface-mounting electronic component according to the present invention.

2 is a cross-sectional view of the terminal in FIG. 1 after bending.

FIG. 3 is a partial cross-sectional side view after soldering the surface mounting electronic component according to the present invention to a printed circuit board.

FIG. 4 is a partial top view and a cross-sectional view showing a weak point of a narrow portion of a terminal according to the present invention. FIG. 6A is a top view showing a case where a weak point is on the side surface of the main body of the surface mounting electronic component. (B) is sectional drawing in the BB line of (a). (C) is a top view showing the case where the weak point is outside the main body side surface of the surface mounting electronic component. (D) is sectional drawing in the CC line | wire of (c). (E) is a top view showing a case where the main body side surface of the surface mount electronic component is not on the same plane and the weak point is outside the side surface with respect to the main body side surface in the bending direction of the terminal. (F) is a sectional view taken along the line DD of (e).

FIG. 5 is a partial top view showing another embodiment of the narrow portion of the terminal according to the present invention.

FIG. 6 is a top view of a conventional surface mount electronic component (variable resistor).

7 is a cross-sectional view taken along the line AA of FIG.

8 is a cross-sectional side view showing a crack generated in the variable side terminal of FIG.

FIG. 9 is a partial cross-sectional side view showing a state after soldering to a conventional surface mount electronic component printed circuit board.

[Explanation of symbols]

11 main body (board) 12 terminal (variable side terminal) 13 narrow part 15 weak point (part with weak bending strength)

Claims (3)

[Claims] 1. A surface mounting electronic component having a terminal extending from a side surface of a main body of an electronic component and bent from the side surface to a bottom surface side of the main body, which corresponds to a side surface of the main body of the terminal. A narrow width portion for facilitating bending is provided at a position to be bent, and a portion having a low bending strength of the narrow width portion is located on the side surface of the main body or outside the side surface. Electronic components. 2. The surface mounting electronic component according to claim 1, wherein a solderable metal layer is provided on a surface of the terminal. 3. The electronic component for surface mounting according to claim 1, wherein a nickel or nickel alloy metal layer is provided as a lower layer and a solderable metal layer is provided as an upper layer on the surface of the terminal.