JPH07282698A - Proximity sensor - Google Patents

Abstract

PURPOSE:To eliminate effects of a lead frame, etc., in a proximity sensor in which an electronic part including a coil is mounted on the lead frame. CONSTITUTION:A chip coil 2 having a core, and spools 4a, 4b above and under it is disposed on a lead frame 1. The lead frame 1 is formed in such a way that the core 3 and a coil winding are not positioned just above the lead frame 1. Detection of these can thus be eliminated, thereby the deterioration of detection sensitivity can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proximity sensor for detecting the proximity of an object.

[0002]

2. Description of the Related Art Conventionally, a high frequency oscillation type proximity sensor has been used which has a coil facing a detection surface and an oscillation circuit together with this coil, and detects the proximity of an object by the change of the oscillation state accompanying the proximity of the object. Has been. In order to reduce the size of such a proximity sensor, a proximity sensor has been proposed in which a coil as a detection element and an electronic circuit section are mounted on a lead frame and integrally molded by resin molding.

When manufacturing this proximity sensor, as shown in FIG.
As shown in (a), the hatched portion of the lead frame is punched to form an opening. Then, the lead frame main body 100 to which the chip coil and the chip component are attached, and the fishing lead portion 10 for connecting the lead frame to the outer frame.
1 and are provided. Then, after mounting the electronic component including the coil on the lead frame main body 100, the portion indicated by the chain double-dashed line in the figure is molded by the resin mold 102 as shown in FIG. 8B. Then, the fishing lead portion 101 is cut in the vicinity of the resin mold 102 to form a proximity sensor. Therefore, as shown in FIG. 8C, a part of the fishing lead is exposed to the outside.

[0004]

According to such a conventional proximity sensor arranged on a lead frame, it is necessary to arrange a coil as a detection element on the lead frame. Therefore, there is a drawback that the coil may detect the lead frame, the electrode for connecting the coil wire, the solder, etc., and the detection sensitivity may decrease. Further, as shown in FIG. 8C, the fishing lead is exposed to the outside of the resin mold 102 even after a part of the fishing lead is cut, so that the circuit may malfunction when it comes into contact with another circuit or a metal body. . In addition, there is a drawback that it is easily affected by static electricity, and the electrostatic resistance may decrease.

The inventions of claims 1 to 3 of the present application have been made in view of such conventional problems, and provide a proximity sensor having a structure in which the sensitivity is not lowered without detecting a lead frame or solder. The purpose is to provide. In addition to this problem, an object of the invention of claim 3 of the present application is to prevent the fishing lead from being exposed on the outer surface of the resin mold.

[0006]

According to a first aspect of the present invention, a coil and an electronic component are mounted on a lead frame, and the electronic circuit portion is integrally molded with the lead frame by resin molding. A proximity sensor comprising an oscillation circuit including a coil and a circuit unit for detecting an object by a change in an oscillation state of the coil, wherein the coil has at least the core and the coil winding portion removed from the lead frame. It is characterized by being placed in a position.

According to the invention of claim 2 of the present application, the coil is a chip coil in which a coil winding is wound around a core having upper and lower spools, and an electrode portion is formed at both ends of one spool, and both ends of the coil winding are formed. Are connected to the electrode portions, respectively.

According to the invention of claim 3 of the present application, the lead frame is characterized in that a narrow portion having a narrow width is provided in the resin mold of the fishing lead for connecting the lead frame body and the outer frame.

[0009]

According to the inventions of claims 1 to 3 having the above characteristics, the coil is arranged on the lead frame, and the coil has a position in which the core and the coil winding portion are separated from the lead frame. Therefore, it is possible to oscillate without being affected by the lead frame even when oscillating. For this reason, it is difficult to be affected by the lead frame and the sensitivity does not decrease. Further, according to the invention of claim 3, since the narrow portion is provided in the resin mold of the fishing lead, when the fishing lead is cut after the resin molding, the fishing lead is cut at the narrow portion. The part is not exposed to the outside of the resin mold.

[0010]

1 is a front view showing a punched lead frame used in a high-frequency oscillation type proximity sensor according to an embodiment of the present invention. In this figure, it is assumed that the lead frame 1 is punched out into a substantially square shape with the substantially square portion 2c on which the coil 2 is arranged leaving only the four corners. A normal lead frame pattern for mounting electronic components, IC chips, etc. is formed on the right side of the coil arrangement position. 2A is a side view of the chip coil used in the present embodiment, FIG. 2B is a perspective view thereof, and FIG. 2C is a bottom view of the chip coil placed on the lead frame. As shown in these figures,
The chip coil 2 is provided with a cylindrical core 3 in the center, and upper and lower sides of the core 3 have a substantially square upper spool 4a and a lower spool 4 respectively.
b is formed, and the coil winding 5 is wound between them. As shown in FIGS. 2A and 2C, electrode surfaces 4c are formed on the left and right sides of the lower spool 4b and are connected to both ends of the coil winding 5. Then, the core 3 and the coil winding 5 are separated from directly above the lead frame 1, that is, only the four corners of the lower spool 4b are connected to the lead frame 1a,
The lead frames 1a and 1b so as to be mounted on the lead frame
Is configured.

Now, the chip coil 2 constructed in this way
FIG. 3 shows a block diagram of a proximity sensor having a detection coil. The proximity sensor shown in FIG. 3 has an oscillation circuit 11 using the chip coil 2 as a detection coil, and a change in oscillation output is detected by the comparison circuit 12 and output to the outside via the output circuit 13. If this proximity sensor is a two-wire proximity sensor, a load and a power supply are connected in series between the pair of terminals 14a and 14b. And one terminal 14
A constant voltage circuit 15 is connected to a and is configured to supply power to each unit. In this proximity sensor, most of the circuit including the oscillation circuit 11, the comparison circuit 12, the output circuit 13, and the constant voltage circuit 15 is composed of the IC chip 16.

The IC chip 16 is mounted on the lead frame 1 shown in FIG. 1 and wire bonding or the like is performed to mount the chip coil 2 and necessary electronic components. FIG. 4A is a perspective view showing a state in which electronic components are mounted on the lead frame, and is shown by removing the outer frame of the lead frame. After that, by covering the area shown by the chain double-dashed line in FIG. 1 with the resin mold 20, the proximity sensor can be configured using the chip coil as the detection coil. Figure 4
(B) is a perspective view showing this proximity sensor.

When the resin molding is performed, the resin shrinks, so that the chip coil 2 may be stressed and damaged. In order to avoid this, as shown in FIG. 5A, the resin coil 20 may cover only the lower portion of the chip coil 2 excluding the upper spool 4a. See also FIG.
As shown in (b), a protective cover 21 made of resin for enclosing the chip coil 2 is provided, and the resin mold 20 including the protective cover 21 is provided.
It can also be integrally molded by. In this case, the stress applied to the chip coil 2 can be reduced, and damage to the chip coil 2 during molding can be prevented in advance.

FIG. 6 is a top view and a side view showing another example of the chip coil. This chip coil 2A has a core 3 in the center, an upper spool 4a at the top and bottom, and a lower spool 4 at the bottom.
It is similar to the first embodiment that d is attached and the coil winding 5 is wound between them. The chip coil 2A has a lower spool 4d extending downward as shown in the drawing to have a rectangular shape, and both ends thereof are electrodes 4e. By separating the electrode 4e from the coil portion in this way, the influence of the electrode during oscillation can be reduced, and a decrease in sensitivity can be prevented.

Further, as described above, when a part of the lead frame is exposed to the outside, there is a possibility that the electrostatic resistance may be lowered or the circuit may malfunction. Therefore, as shown in FIG. 7A, a part that is easily cut is provided on a part of the fishing lead exposed from the resin mold. That is, the fishing lead portion is processed to be thinner and thinner slightly inside the resin mold portion, and this is used as the narrow portion 1c. In this way, if the cutting is performed after the resin molding, the lead frame is cut at the narrow portion 1c, so that the fishing lead is not exposed from the outside of the resin molding as shown in FIG. 8C.
Therefore, malfunctions and damages caused by the voltage of the external circuit applied to the proximity sensor, and malfunctions caused by static electricity can be prevented in advance. Further, as shown in FIG. 7B, if the narrow portion 1e provided on the ground line 1d of the lead frame is brought close to the end of the resin mold 20, electrostatic noise from the outside will easily fly to the grant line, and the signal line will be easily discharged. It is possible to prevent the electrostatic breakdown of.

[0016]

As described in detail above, according to the invention of claim 1 or 2, when the coil is arranged on the lead frame, the core and the winding portion of the coil are separated from the lead frame. By arranging it in the position, the lead frame, the connecting electrode of the coil, the solder, etc. are not detected, and the detection sensitivity is not reduced. Further, according to the invention of claim 3 of the present application, the fishing lead for connecting the lead frame body and the outer frame is not exposed to the outside at the time of manufacturing the lead frame. Therefore, the electrostatic resistance does not decrease, and the internal circuit can be prevented from being damaged by the voltage applied to the internal circuit.

[Brief description of drawings]

FIG. 1 is a front view showing a punched state of a lead frame according to an embodiment of the present invention.

2A is a side view of the chip coil, FIG. 2B is a perspective view thereof, and FIG. 2C is a bottom view of the chip coil connected to the lead frame.

FIG. 3 is a block diagram showing an example of a proximity sensor according to the present invention.

4A is a perspective view showing a state where a chip coil and an electronic circuit component are mounted on a lead frame, and FIG. 4B is a perspective view of a proximity sensor after resin molding.

5A is a side view showing a different example when the chip coil is covered with a resin mold, and FIG. 5B is a side view showing still another example.

6A is a top view showing the structure of a chip coil according to another embodiment of the present invention, and FIG. 6B is a side view thereof.

FIG. 7 is a front view showing a processed state of a fishing lead portion of a lead frame according to another embodiment of the present invention.

FIG. 8 is a diagram showing a lead frame showing an example of a conventional detection sensor in which an electronic circuit section is mounted on a lead frame, and a process of processing the lead frame.

[Explanation of symbols]

 1, 1a, 1b Lead frame 2, 2A Chip coil 4a Upper spool 4b, 4d Lower spool 4c, 4e Electrode surface 5 Coil winding 11 Oscillation circuit 12 Comparison circuit 13 Output circuit 14a, 14b Terminal 15 Constant voltage circuit 16 IC chip 20 Resin mold 21 Protective cover

Claims (3)

[Claims] 1. A coil and an electronic component are mounted on a lead frame, and the electronic circuit portion is integrally molded with the lead frame by resin molding.
The electronic circuit unit is a proximity sensor having an oscillating circuit including a coil and a circuit unit that detects an object by a change in an oscillating state of the oscillating circuit. At least the core and the coil winding portion of the coil are separated from the lead frame. Proximity sensor characterized by being placed in a position. 2. The coil is a chip coil in which a coil winding is wound on a core having upper and lower spools, electrode portions are formed at both ends of the one spool, and both ends of the coil winding are connected to the electrode portion. The proximity sensor according to claim 1, wherein the proximity sensor is connected to each of the. 3. The proximity sensor according to claim 1, wherein the lead frame has a narrow narrow portion provided in a resin mold of a fishing lead that connects the lead frame main body and an outer frame.